Calorie Restriction and Calorie Restriction Mimetics Dampen Inflammation

Chronic inflammation is an important aspect of aging, a process that stems from low-level biochemical damage and cellular dysfunction, and that then contributes to the progression of age-related disease and tissue dysfunction. Chronic inflammation sustained over years accelerates all of the common fatal age-related conditions: it disrupts tissue maintenance, and leads to fibrosis, immune dysfunction, and many more issues. The chronic inflammation of aging is important enough that beneficial therapies have been built on the basis of suppressing inflammation directly, without addressing its causes. Treatments that actually address the causes should be very much better at the end of the day, of course.

Interventions that have been demonstrated to slow aging in laboratory species tend to act to suppress the age-related increase in inflammation - they would have to, in order to achieve the outcome of a longer, healthier life in these animals. Calorie restriction is the best studied of these interventions, and a wide range of calorie restriction mimetic drugs have arisen from this field of research, compounds that mimic a fraction of the overall metabolic response to a lower intake of calories. Today's open access paper reviews what is known of the way in which mechanisms of the calorie restriction response act to reduce chronic inflammation and its impact on age-related disease.

A sizable fraction of the inflammation of aging arises from the presence of senescent cells. These cells grow in number with age, and their signaling produces a range of detrimental effects on surrounding tissue, of which chronic inflammation is just one - though, as noted here, an important one. Calorie restriction adopted in later life doesn't impact the burden of cellular senescence to anywhere near as great a degree as the use of senolytic drugs can achieve by selectively destroying senescent cells. That point is worth keeping in mind while looking over the paper noted here.

Control of Inflammation by Calorie Restriction Mimetics: On the Crossroad of Autophagy and Mitochondria

Under certain circumstances such as aging, there is a failure in the resolution mechanisms leading to the chronic activation of immune cells and persistent inflammation. This state of low-grade but chronic inflammation is known as inflammaging, and is characterized by increased levels of pro-inflammatory cytokines in the circulation. Notably, inflammaging is considered a risk factor for many age-related diseases. Even in certain tissues like the brain, that possesses a privilege protection against inflammation, certain signs of inflammation appear gradually with age, and this neuroinflammation can anticipate the appearance of some neurodegenerative diseases. In addition, the integrity of the intestinal barrier is compromised due to inflammatory stress during aging and contributes to the development of several diseases. Finding drugs that protect against inflammaging, the disruption of the intestinal barrier, and neuroinflammation should be a priority for geroscience in the next years.

Mitochondrial metabolism and autophagy are two of the most metabolically active cellular processes, playing a crucial role in regulating organism longevity. It is well known that an intense crosstalk exists between mitochondria and autophagosomes, and the activity or stress status of either one of these organelles may affect the other. A mitochondrial or autophagy decline compromises cellular homeostasis and induces inflammation. Furthermore, mitochondrial function and autophagy are key pathways controlling the activation of both the innate and the adaptive immune system. In the last decade, it has become evident that mitochondria are essential organelles that direct the fate of immune cells, giving rise to a new scientific discipline that is called immunometabolism. Moreover, the outcome of the inflammatory response can be controlled by modulating the metabolism of immune cells.

Calorie restriction (CR) is the oldest strategy known to promote healthspan, and a plethora of CR mimetics have been used to emulate its beneficial effects. Herein, we discuss how CR and CR mimetics, by modulating mitochondrial metabolism or autophagic flux, prevent inflammatory processes, protect the intestinal barrier function, and dampen both inflammaging and neuroinflammation. We outline the effects of some compounds classically known as modulators of autophagy and mitochondrial function, such as NAD+ precursors, metformin, spermidine, rapamycin, and resveratrol, on the control of the inflammatory cascade and how these anti-inflammatory properties could be involved in their ability to increase resilience to age-associated diseases.

Premature Menopause Correlates with Greater Later Incidence of Chronic Disease

Undergoing earlier menopause is a sign of a greater burden of age-related damage and dysfunction, so it should not be surprising to see that this correlates with a greater incidence of chronic disease in the years thereafter. People with a greater burden of cell and tissue damage tend to exhibit all of the manifestations of aging earlier than their less damaged peers. These variations in damage burden and consequences from individual to individual are near all the results of lifestyle choices, particularly smoking, weight, and exercise, and environmental factors such as exposure to chronic viral infection. Genetics plays only a small role until very late life, and even then it is outweighed by the choices made and the level of stress that the immune system has suffered over the years.

As life expectancy is now more than 80 years for women in high income countries, a third of a woman's life is spent after the menopause. It is known already that premature menopause, occurring at the age of 40 or younger, is linked to a number of individual medical problems in later life, such as cardiovascular disease and diabetes. However, there is little information about whether there is also an association between the time of natural menopause and the development of multiple medical conditions - known as multimorbidity.

Researchers used data on women who had joined the prospective Australian Longitudinal Study on Women's Health between 1946 and 1951. The women responded to the first survey in 1996 and then answered questionnaires every three years (apart from a two-year interval between the first and second survey) until 2016. The women reported whether they had been diagnosed with or treated for any of 11 health problems in the past three years: diabetes, high blood pressure, heart disease, stroke, arthritis, osteoporosis, asthma, chronic obstructive pulmonary disease, depression, anxiety, or breast cancer. Women were considered to have multimorbidity if they had two or more of these conditions.

During the 20 years of follow-up, 2.3% of women experienced premature menopause and 55% developed multimorbidity. Compared with women who experienced menopause at the age of 50-51 years, women with premature menopause were twice as likely to develop multimorbidity by the age of 60, and three times as likely to develop multimorbidity from the age of 60 onwards. "We found that 71% of women with premature menopause had developed multimorbidity by the age of 60 compared with 55% of women who experienced menopause at the age of 50-51. In addition, 45% of women with premature menopause had developed multimorbidity in their 60s compared with 40% of women who experienced menopause at the age of 50-51."

Link: https://www.eshre.eu/Press-Room/Press-releases-2020/menopause-and-multimorbitity

Astrocyte Senescence Causes Death of Neurons in Cell Culture

With the caveat that the behavior of cells in culture is not necessarily all that relevant to their behavior amidst the full complexities of living tissue, this study is an interesting initial exploration of the ways in which the cellular senescence of supporting cells in the brain might contribute to the progression of neurodegeneration. Senescent cells secrete a potent mix of inflammatory and other signaling; while they serve a useful purpose when present for a short time, not all are successfully destroyed. Their numbers grow with age, and the presence of these errant cells and their signaling is very harmful over the long term. Thus the development of senolytic therapies to selectively destroy senescent cells is a very promising line of work in the treatment of aging as a medical condition.

Neurodegeneration is a major age-related pathology. Cognitive decline is characteristic of patients with Alzheimer's and related dementias and cancer patients after chemotherapy or radiotherapy. A recently emerged driver of these and other age-related pathologies is cellular senescence, a cell fate that entails a permanent cell cycle arrest and pro-inflammatory senescence-associated secretory phenotype (SASP). Although there is a link between inflammation and neurodegenerative diseases, there are many open questions regarding how cellular senescence affects neurodegenerative pathologies.

Among the essential cell types in the brain, astrocytes are the most abundant population. Astrocytes retain proliferative capacity, and their functions are crucial for neuron survival. Astrocytes are critical for mediating ion homeostasis, growth factor responses and neurotransmitter functions in the brain. Previous studies showed that astrocyte dysfunction is associated with multiple neurodegenerative diseases. Importantly, senescent astrocytes were identified in aged and Alzheimer's disease brain tissue, and other studies identified several factors that are responsible for inducing senescence in astrocytes. These studies reported a link between an inflammatory environment and neurodegenerative diseases, but how astrocyte senescence might alter brain function in general remains unclear.

Here, we investigated the phenotype of primary human astrocytes made senescent by irradiation, and identified genes encoding glutamate and potassium transporters as specifically downregulated upon senescence. This down regulation led to neuronal cell death in co-culture assays. Unbiased RNA sequencing of transcripts expressed by non-senescent and senescent astrocytes confirmed that glutamate homeostasis pathway declines upon senescence. Genes that regulate glutamate homeostasis as well as potassium ion and water transport are essential for normal astrocyte function. Our results suggest a key role for cellular senescence, particularly in astrocytes, in excitotoxicity, which may lead to neurodegeneration including Alzheimer's disease and related dementias.

Link: https://doi.org/10.1371/journal.pone.0227887

Hypoxia-Inducible Factors in Vascular Aging

Stress response mechanisms have been shown to be important in the way in which metabolism determines longevity in any given species. Short-lived species exhibit great plasticity of life span in response to stresses such as heat, cold, nutrient deprivation, and hypoxia. A mild or transient stress can trigger lasting upregulation of cell and tissue maintenance activities, leading to improved function and a slowed aging process. Most such stress responses converge on the processes of autophagy responsible for recycling unwanted or damaged protein machinery and cell structures.

One of numerous lines of inquiry in this part of the field of aging research is focused on hypoxia-inducible factors (HIFs), proteins that manage the response to hypoxia, the stress resulting from insufficient oxygen to supply cellular operations. HIFs are involved in many age-related conditions, but their relationship with aging and disease is a complicated one. In some cases inappropriate overactivation of HIFs is harmful, such as in cancerous tissue. In the case of aging as a whole, HIFs may be involved in a range of processes that are both helpful and harmful. Thus a more careful exploration is required in order to pick out possible points of intervention.

Hypoxia-Inducible Factor-1α: The Master Regulator of Endothelial Cell Senescence in Vascular Aging

Since the discovery of HIF-1α, several seminal works have identified the changes in HIF associated with age and the development of age-related disorders, including neurodegenerative diseases. Importantly, in 2009, researchers described HIF-1 as a longevity factor, demonstrating that HIF-1 stabilization is associated with a 30-50% increase in lifespan in nematodes. Several studies have shown that stabilization of HIF-1 increases longevity and healthspan through different pathways in Caenorhabditis elegans. These critical findings in worms yielded a new perspective on the study of HIF stabilization and lifespan among mammals. However, the stabilization of mammalian HIF-1α has been implicated in tumor growth and cancer development and may therefore be harmful. Consequently, a balance between the beneficial and detrimental effects of HIF is critical for homeostasis and depends on the involved components and their contribution to longevity.

Studies on skin, a tissue that is continuously exposed to intrinsic and extrinsic aging factors, have identified HIF-1α as a crucial determinant of skin homeostasis, especially in epidermal aging and wound healing. Results have reported that the loss of epidermal HIF-1α accelerates epidermal aging and affects re-epithelialization in humans and mice. Notably, significant elevations in both hypoxia-inducible transcription factors HIF-1α and HIF-1β gene expression have also been found in the gingival tissues of aged animals, even though these tissues were deemed clinically healthy. In a model of limb ischemia in mice, HIF-1 was found to mediate angiogenesis and, therefore, has been proposed to contribute to the pathological aging process.

HIF is not only a transcriptional factor that regulates tissue oxygenation (including angiogenesis and vascular remodeling) but also controls redox balance, inflammation, and glucose metabolism to eventually maintain cellular homeostasis. According to current knowledge, the age-dependent impairment of HIF-1α induction leads to diminished vascular responses to limb ischemia and less effective wound healing. Some evidence shows the functionally important expression of HIF-1α among ischemic limb mice. It has been demonstrated that the abundance of the HIF-1α protein is decreased in ischemic tissues from aged mice and has also been linked with the downregulation of genes encoding angiogenic growth factors. Another vital player of vascular aging, which is positively regulated by HIF-1, is vascular endothelial growth factor (VEGF), a central mediator of angiogenesis. During aging, there is a defect in HIF-1 activity, yielding VEGF expression reduction and leading to the impairment of angiogenesis in response to the ischemia model.

Recently, we found that HIF-1α is involved in p53, p16, cyclin D1, and lamin B1-mediated senescence in vascular endothelial cells (ECs). Moreover, senescent ECs failed to express HIF-1α, and the microvesicles released by these cells were unable to carry HIF-1α. In another study, HIF-1α was found to play a critical regulatory role in vascular inflammation among macrophages after intimal injury through limiting excessive vascular remodeling. The mechanism by which macrophage-derived HIF-1α mediated this effect is still unknown. Considering these findings, HIF-1α may represent a possible therapeutic target in vascular diseases, especially in vascular aging.

The Decline of Mitophagy in Age-Related Neurodegenerative Conditions

Mitochondria are the power plants of the cell. A herd of these bacteria-like organelles in every cell manufacture the chemical energy store molecules that are used to power cellular processes. Mitochondrial function declines with age throughout the body. Evidence suggests that this is due to changes in mitochondrial dynamics that inhibit the quality control mechanisms of mitophagy that are responsible for recycling worn and damaged mitochondria. This loss of miochondrial function is well known to contribute to the progression of neurodegenerative conditions, as the brain is an energy-hungry organ, making this an important aspect of aging to target for reversal.

Mitochondrial health is vital for cellular and organismal homeostasis, and mitochondrial defects have long been linked to the pathogenesis of neurodegenerative diseases such as Alzheimer's, Parkinson's, ALS, Huntington's, and others. However, it is still unclear whether cellular mechanisms required for the maintenance of mitochondrial integrity and function are deficient in these diseases, thus exacerbating mitochondrial pathology. The quality control of mitochondria involves multiple levels of strategies to protect against mitochondrial damage and maintain a healthy mitochondrial population within cells. In neurons, mitophagy serves as a major pathway of the quality control mechanisms for the removal of aged and defective mitochondria through lysosomal proteolysis. The molecular and cellular mechanisms that govern mitophagy have been extensively studied in the past decade. However, mitophagy deficit has only been recognized recently as a key player involved in aging and neurodegeneration.

Given the fact that mitochondrial deficit is clearly linked to neuronal dysfunction and the exacerbation of disease defects, protection of mitochondrial function could be a practical strategy to promote neuroprotection and modify disease pathology. Mitochondrially targeted antioxidants have been proposed. In particular, the antioxidant MitoQ, a redox active ubiquinone targeted to mitochondria, has been examined and demonstrated to have positive effects in multiple models of aging and neurodegenerative disorders. Importantly, mitophagy could be another promising target for drug discovery strategy. Therefore, further detailed studies to elucidate mitophagy mechanisms not only advance our understanding of the mitochondrial phenotypes and disease pathogenesis, but also suggest potential therapeutic strategies to combat neurodegenerative diseases.

Link: https://doi.org/10.3390/cells9010150

Immune Activity in Alzheimer's Disease as Both Friend and Foe

Chronic inflammation in brain tissue is thought to be important in the progression of neurodegenerative conditions such as Alzheimer's disease. Some factions within the research community theorize that chronic inflammation driven by dysfunctional microglia and other supporting cells in the brain is the important cause of Alzheimer's, not the early accumulation of amyloid-β. Even as it becomes inflammatory with advancing age, the immune system continues to perform necessary functions, however. So any approach to addressing the issue must be fairly selective. An example is the use of senolytic drugs capable of passing the blood-brain barrier in order to destroy senescent microglia and astrocytes, a strategy that, in mouse models, has been shown to reverse the tau pathology characteristic of the later stages of Alzheimer's disease.

While there is consensus that the immune system is intimately involved in Alzheimer's disease (AD), there is considerable debate over which aspects of inflammation are harmful and contribute to degeneration, and which are protective and may prevent cognitive decline. Furthermore, it has yet to be established which components of the immune system actively play a role in pathology and which are just a consequence of disease. Gliosis, or increased numbers of activated astrocytes and microglia are a hallmark feature of neuroinflammation. However, past descriptions of this phenomenon, namely just "reactive" or "increased gliosis" are vastly oversimplified. Recent evidence highlights altered glia-specific pathways in post-mortem AD tissue and in mouse models of AD, suggesting that glial responses are much more heterogeneous and complex than previously thought.

While neuroinflammation can promote efficient clearance of amyloid-β and neuronal debris it can also accelerate disease by causing neuronal and glial cell death. This inflammatory balance is highly orchestrated and understanding how to regulate these responses is key to developing effective therapeutics for AD. The initiation of an immunological reaction can be beneficial and critical, allowing for a burst of glial activity to protect and repair the site of damage, and to clear toxic species or dysfunctional synapses. For example, in response to adverse conditions, microglia will undergo morphological changes, accompanied by the release of a storm of molecular mediators that increases clearances of amyloid-β. Furthermore, various types of non-neuronal cells are recruited to the site to assist in repairing the damage and consolidating excessive inflammation. These reparative processes are beneficial, yet may also have harmful consequences such as sustained cytokine release which can become toxic to neuronal cells. Therefore, understanding the specific cellular roles and inflammatory reactions in AD is of vital importance.

Link: https://doi.org/10.3389/fnagi.2019.00337

Inhibition of Autophagy in Mice Produces Signs of Accelerated Aging

One must always be careful in the interpretation of studies of aging in which essential biological processes are disrupted. There are any number of ways to disrupt essential biological functions to produce all sorts of consequent damage. But damage that isn't relevant to the normal processes of aging can nonetheless produce results that look very much like age-related conditions. Thus the details matter greatly. Here researchers suppress autophagy in mice in order to gain greater insight into its role in aging, and suggest that there might be reasons for caution in the development of therapies to boost autophagy in old people - though again, the details matter greatly in any interpretation of this work.

Autophagy is the name given to a collection of cellular maintenance processes that work to recycle damaged protein machinery and structures. Autophagy declines with age, and this loss may be of greatest relevance when it comes to removal of worn and dysfunctional mitochondria. Mitochondrial function falters with age, which causes issues throughout the body, particularly in energy-hungry tissues such as the brain and muscle. This appears to be connected to a reduced effectiveness of mitochondrial autophagy, though the causes of this issue are still being investigated.

It is well known that many of the interventions known to slow aging in mice involve upregulation of autophagy, and some, like calorie restriction, will only slow aging and extend life if autophagy is functional. It is at present reasonable to conclude that autophagy is an important portion of the way in which the operation of metabolism steers the outcome of aging, but data resulting from the practice of calorie restriction in humans strongly suggests that the magnitude of the benefits that would result from therapeutic upregulation of autophagy just isn't as large as we'd all like it to be - though perhaps the upregulation just needs to be larger. We shall see in the years ahead, as biotech startups such as Selphagy Therapeutics make progress on clinical development of this class of therapy.

Temporal inhibition of autophagy reveals segmental reversal of ageing with increased cancer risk

Autophagy is an evolutionarily conserved bulk cellular degradation system that functions to breakdown and recycle a wide array of cytoplasmic components from lipids, proteins, and inclusion bodies, to whole organelles (e.g. mitochondria). Importantly a reduction in autophagic flux (the rate at which autophagosomes form and breakdown cellular contents) is associated with increasing age in mammals. Evidence from lower organisms suggests that autophagy inhibition can negate the positive-effects of regimens that extend lifespan, such as calorie restriction, rapamycin supplementation, and mutations in insulin signalling pathways.

In mice, the constitutive promotion of autophagy throughout lifetime has been shown to extend health- and life-span in mammalian models. These studies have provided hitherto missing evidence that autophagic flux can impact on mammalian longevity and supports the notion that the pharmacological promotion of autophagy may extend health-, and potentially life-span, in humans. However, whether a reduction in autophagy is sufficient to induce phenotypes associated with ageing, and whether these effects can be reversed by restoring autophagy has to date not been addressed. Considering that the therapeutic window for pharmacological intervention to counteract ageing, and age-related diseases, will be later in life (as opposed to from conception), after autophagic flux has declined, it is critical to understand how the temporal modulation (inhibition and restoration) of autophagy may impact on longevity and health.

To address these questions, we use two doxycycline (dox) inducible shRNA mouse models that target the essential autophagy gene Atg5 to demonstrate that autophagy inhibition in young adult mice is able to drive the development of ageing-like phenotypes and reduce longevity. Importantly we confirm that the restoration of autophagy is associated with a substantial restoration of health- and life-span, however this recovery is incomplete. Notably the degree of recovery is segmental, being dependent on both the tissue and metric analysed. A striking consequence of this incomplete restoration is that autophagy restored mice succumb to spontaneous tumour formation earlier and at an increased frequency than control mice, a phenotype not observed during autophagy inhibition alone. As such our studies indicate that despite the significant benefit, autophagy reactivation may also promote tumorigenesis in advanced ageing context.

Aging Skin as a Significant Source of Systemic Chronic Inflammation

Researchers here propose that the skin is a significant source of the systemic chronic inflammation that is observed in older individuals. Setting aside the range of other mechanisms that contribute to inflammation to only consider the accumulation of senescent cells with age, and the fact that these errant cells are a potent source of inflammatory signaling, this proposition doesn't seem unreasonable. The skin is a sizable organ, after all, and even if it produces senescent cells at much the same pace as the rest of the body, it will still represent a large and quite distributed pool of such cells, positioned to delivery their inflammatory signals throughout the body.

Increasing evidence points to a provocative role of sustained, sub-clinical inflammation, often termed "inflammaging," in the development of these chronic disorders. In support of this notion, chronologically aged humans (≥50 years) display elevated circulating levels of pro-inflammatory cytokines, particularly IL-6, IL-1β, and TNFα. Moreover, subjects with chronic cutaneous inflammatory diseases, such as psoriasis and eczematous dermatitis, also display an increased prevalence of aging-associated disorders, including atherosclerotic cardiovascular disease, obesity, and type 2 diabetes. Though anti-inflammatory regimens, such as inhibitors of IL-1βα and TNFα, as well as methotrexate, have been deployed in the management of these aging-associated disorders, the outcomes of treatments with these agents have been inconclusive.

While many chronologically aged humans merely display marked evidence of inflammation, they nonetheless display elevated circulating levels of cytokines, suggesting that one or more, as yet identified organs, could account for the aging-associated increase in circulating cytokines. It seems reasonable to postulate that the responsible organs must be large enough to sustain such an increase in circulating cytokines, even without noticeable inflammation. Although the musculoskeletal system is the largest organ in humans, most chronologically aged humans display no evidence of musculoskeletal inflammation.

Other relatively large organs to be considered include the skin, intestines, lungs, and liver. The skin weighs about 20 lbs (with an additional, variable contribution from subcutaneous adipose tissues), while the weights of the intestines, lungs, and liver represent ≈7.5, 5.0 and 3.3 lbs, respectively. Because of their relatively lesser size, inflammation of the lungs, intestines, and liver likely would not only need to be apparent, but also sustained if any of these organs could account for the increase in circulating levels of cytokines. Yet again, the majority of otherwise normal aged humans display few clinical signs or symptoms of inflammation in these organs. Hence, it seems unlikely that they could contribute substantially to "inflammaging" unless multiple organs simultaneously exhibit mild inflammation. Notably, the aged skin commonly exhibits signs and symptoms of inflammation, such as pruritus and senile xerosis.

Because of its relatively large size, we hypothesized that the skin could be an important contributor to the elevated levels of circulating cytokines in chronologically aged humans, despite the fact that it typically displays little evidence of inflammation. Not only its size, but also its unique anatomic site, serving as the interface between the body and external environment, supports our hypothesis. In this site, it is continuously exposed to external physical and chemical stressors, which themselves can provoke inflammation, even as other less-exposed organs remain quiescent. In addition, chronologically aged humans display alterations in several key epidermal functions, each of which can provoke low-grade, chronic inflammation in the skin.

Link: https://doi.org/10.2147/CIA.S235595

Immunosenescence and Loss of Resistance to Viral Infection

The authors of this open access review paper discuss what is known of the age-related failure of the immune system, with a focus on the consequences for viral infection and vaccination effectiveness. The elderly suffer greatly because the immune system falters in its ability to protect against pathogens, a dysfunction that has numerous root causes. The atrophy of the thymus, reducing the supply of new T cells to a trickle; the disruption of hematopoietic stem cell function, reducing the pace of production of all immune cells; the fibrosis of lymph nodes, rendering it hard for immune cells to coordinate with one another; the accumulation of broken and harmful immune cell populations absent a supply of undamaged reinforcements. Potential strategies exist to address all of these issues; they must just be brought to realization by the research and development communities.

Immunosenescence is a major cause of increased incidence and severity of viral infections in the elderly, and contributes to impaired immunogenicity and efficacy of vaccines. Understanding the biological basis for age-associated alterations in viral immunity and vaccine immunogenicity is a challenge with substantial clinical importance. Subsequently, the use of systems biology approaches in combination with computational model systems will be crucial to understand the complexity of age-associated changes in the immune system by identifying molecular networks that orchestrate immunity to vaccinations in humans and potentially define correlates of protection.

Given the plastic nature of aging and rapidly growing field of systems biology, molecular profiling of the aging-related changes is increasingly being examined at a single cell level by high-throughput omics technologies, including genomics, metagenomics, transcriptomics, and metabolomics. Specially, aging of the immune cells is affected by changes in homeostasis via cytokine levels, and by modifications in the metabolic pathways. Caloric restrictions (CR) affected a marked improvement in the maintenance and/or production of naïve T cells and the consequent preservation of TCR repertoire diversity. Furthermore, CR also improved T cell function and reduced production of inflammatory cytokines by memory T cells, suggesting that CR can delay T cell senescence and potentially contribute to extended lifespan by reducing susceptibility to infectious diseases.

A key area for future exploration in the immunosenescence field is the role of the secondary lymphoid organs as a critical partner in the development and function of the aging human immune system. It will be important to analyze age-related changes in secondary lymphoid organs, lymph nodes and spleen, given the aging-associated decrease in the size of lymph nodes. Lymph nodes not only serve as the key initiating region of the immune response, but they also play an important role in maintaining naive lymphocytes.

Next, investigation of how extracellular vesicles (EVs) are linked to aging could be a promising area of interest. EVs are membrane-bound vesicles released by multiple cell types that include immune cells. Evidence from cellular models suggests that exosomes released by macrophages from older are more pro-inflammatory than those released by macrophage from younger. In particular, mRNA levels of IL-6 and IL-12, but not TNF-α, in macrophage-derived exosomes were significantly higher in serums of older subjects. Given that EVs play an important role in immune cell network and cellular senescence, the profiles of secretome and the function of senescent immune cells will soon be revealed as the EV research field progresses.

Link: https://doi.org/10.4110/in.2019.19.e37

We All Age in the Same Way, but with a Distribution of Outcomes

Today's research materials are representative of numerous initiatives aiming to produce taxonomies of the biochemistry of aging, to catalog the observed variations. Yet, with the exception of a very small number of unlucky souls bearing rare harmful mutations, we all age for the same underlying reasons. The same processes of metabolism produce the same forms of cell and tissue damage, leading to the same downstream dysfunctions and the same ultimately fatal age-related conditions. Yes, there is some variation in outcome. For all that aging is a universally similar process of multiple interacting forms of damage, some portions of its consequences progress modestly more rapidly or modestly more slowly from individual to individual, a distribution of outcomes that largely results from lifestyle choices and random happenstance, rather than from genetic variation.

Thus many researchers are interested in this distribution, perhaps more so than in doing something about the challenge of aging, the death and suffering it causes. Given this view of the situation, I would say that somewhat more scientific effort goes into cataloging the differences between individuals than is merited. Examining long-lived people, with the goal of producing interventions that might make more people live incrementally longer in good health, is a terrible strategy, when compared with the alternative of directly addressing the common causes of aging, which might make everyone live considerably longer in good health. Nonetheless, despite the great potential of rejuvenation biotechnology based on repair of the damage that causes aging, there is a lot more funding and interest in the research community for far less promising lines of work.

'Ageotypes' provide window into how individuals age

Researchers profiled a group of 43 healthy men and women between the ages of 34 and 68, taking extensive measurements of their molecular biology at least five times over two years. The researchers determined that people generally age along certain biological pathways in the body: metabolic, immune, hepatic (liver) and nephrotic (kidney). People who are metabolic agers, for example, might be at a higher risk for diabetes or show signs of elevated hemoglobin A1c, a measure of blood-sugar levels, as they grow older. People with an immune ageotype, on the other hand, might generate higher levels of inflammatory markers or be more prone to immune-related diseases as they age. But the ageotypes are not mutually exclusive, and a metabolic ager could also be an immune ager, for example.

Just because an individual falls into one or more of the four ageotypes - metabolic, immune, hepatic and nephrotic - doesn't mean that they're not also aging along the other biological pathways. The ageotype signifies the pathways in which increases in aging biomarkers are most pronounced. Perhaps most exciting - and surprising - is that not everyone in the study showed an increase in ageotype markers over time. In some people, their markers decreased, at least for a short period, when they changed their behavior. They still aged, but the overall rate at which they did so declined, and in some cases aging markers decreased. In fact, the team saw this phenomenon occur in a handful of important clinical molecules, including hemoglobin A1c and creatine, a marker for kidney function, among a small subset of participants.

In that subset, there were individuals who made lifestyle changes to slow their aging rate. Among those who exhibited decreased levels of hemoglobin A1c, many had lost weight, and one made dietary changes. Some who saw a decrease in creatine, indicating improved kidney function, were taking statins. In other cases, exactly why rates of aging markers waned was unclear. For some people, there were no obvious behavioral changes, yet the team still saw a decreased rate of aging along their ageotype pathways. There was also a handful of people that maintained a slower-than-average aging rate throughout the entire study. How or why is still a mystery.

Personal aging markers and ageotypes revealed by deep longitudinal profiling

The molecular changes that occur with aging are not well understood. Here, we performed longitudinal and deep multiomics profiling of 106 healthy individuals from 29 to 75 years of age and examined how different types of 'omic' measurements, including transcripts, proteins, metabolites, cytokines, microbes, and clinical laboratory values, correlate with age. We identified both known and new markers that associated with age, as well as distinct molecular patterns of aging in insulin-resistant as compared to insulin-sensitive individuals. In a longitudinal setting, we identified personal aging markers whose levels changed over a short time frame of 2-3 years. Further, we defined different types of aging patterns in different individuals, termed 'ageotypes', on the basis of the types of molecular pathways that changed over time in a given individual. Ageotypes may provide a molecular assessment of personal aging, reflective of personal lifestyle and medical history, that may ultimately be useful in monitoring and intervening in the aging process.

Vascular Dysfunction as a Distinct Contribution to Cognitive Decline and Dementia

The decline of the vascular system with age takes numerous forms, such as a loss of capillary density, stiffening of blood vessel walls leading to raised blood pressure and increased rupturing of small vessels, and leakage of the blood-brain barrier that wraps blood vessels in the central nervous system. This vascular degeneration is a distinct process from the accumulation of metabolic waste, such as amyloid-β, that characterizes neurodegenerative diseases. Age-related conditions tend to have numerous distinct causes that interact over time to make one another worse, and this is certainly true of the aging of the brain.

Three new studies add to growing evidence that damaged blood vessels wreak havoc on the brain, but not by exacerbating amyloid-β (Aβ) deposition. One found no correlation between intracerebral atherosclerosis and overall amyloid plaque burden in cognitively normal older adults. Another reported that midlife atherosclerosis in the carotid artery upped future risk of vascular dementia, but not Alzheimer's disease (AD). A third found that white-matter hyperintensities - a proxy for damage to small vessels in the brain - had no bearing on future changes in AD biomarkers.

"These studies can all be interpreted to support the hypothesis that vascular risk influences the risk for development of cognitive impairment and dementia principally via non-amyloidogenic pathways. They provide further evidence for, and are compatible with, the growing body of evidence that the timing of vascular risk also matters, with midlife being the most sensitive period. They all suggest that cerebrovascular disease and AD affect cognitive decline through distinct pathways."

On their own, faulty blood vessels in the brain can cause cognitive impairment and dementia. Blood-vessel disease is also thought to contribute to the clinical symptoms of AD, since people with Alzheimer's often have vascular pathology along with amyloid plaques and neurofibrillary tangles. Regardless of whether vascular dysfunction has an additive or synergistic relationship with AD pathology in influencing cognitive decline, the crucial point is that good blood vessel health benefits the brain. A person's vascular risk is highly modifiable by way of lifestyle choices or, if need be, medication.

Link: https://www.alzforum.org/news/research-news/vascular-dysfunction-taxes-cognition-not-amyloid-ad

MR1 as a Broad Signature of Cancer, Suitable for T Cell Targeting

Meaningful progress towards the control of cancer, ending it as a major threat to life and health, will be led by programs that can produce very broadly applicable treatments. That means therapies that can be applied to many (or even all) cancers with minimal differences in configuration or need for further per-cancer development. There are hundreds of cancer subtypes, but only so many researchers, and only so much funding for research and development: development of highly specific therapies is just not an effective path forward.

Examples of the most promising lines of work with broad application include the OncoSenX suicide gene therapy targeting p53 expression, interference in telomere lengthening, and blocking immune inhibitors such as CD47 that cancer cells use to evade the immune system. Researchers here report on another possible approach, a very broad cell surface signature of cancer that might be used to build chimeric antigen receptor T cell immunotherapies that can be applied to a very wide range of cancers indeed.

T-cell therapies for cancer - where immune cells are removed, modified and returned to the patient's blood to seek and destroy cancer cells - are the latest paradigm in cancer treatments. The most widely-used therapy, known as CAR-T, is personalised to each patient but targets only a few types of cancers and has not been successful for solid tumours, which make up the vast majority of cancers. Researchers have now discovered T-cells equipped with a new type of T-cell receptor (TCR) which recognises and kills most human cancer types, while ignoring healthy cells. This TCR recognises a molecule present on the surface of a wide range of cancer cells as well as in many of the body's normal cells but, remarkably, is able to distinguish between healthy cells and cancerous ones, killing only the latter.

Conventional T-cells scan the surface of other cells to find anomalies and eliminate cancerous cells - which express abnormal proteins - but ignore cells that contain only "normal" proteins. The scanning system recognises small parts of cellular proteins that are bound to cell-surface molecules called human leukocyte antigen (HLA), allowing killer T-cells to see what's occurring inside cells by scanning their surface. HLA varies widely between individuals, which has previously prevented scientists from creating a single T-cell-based treatment that targets most cancers in all people. The new study describes a unique TCR that can recognise many types of cancer via a single HLA-like molecule called MR1. Unlike HLA, MR1 does not vary in the human population - meaning it is a hugely attractive new target for immunotherapies.

T-cells equipped with the new TCR were shown, in the lab, to kill lung, skin, blood, colon, breast, bone, prostate, ovarian, kidney and cervical cancer cells, while ignoring healthy cells. To test the therapeutic potential of these cells in vivo, the researchers injected T-cells able to recognise MR1 into mice bearing human cancer and with a human immune system. This showed "encouraging" cancer-clearing results which the researchers said was comparable to CAR-T therapy in a similar animal model.

Link: https://www.cardiff.ac.uk/news/view/1749599-discovery-of-new-t-cell-raises-prospect-of-universal-cancer-therapy

ELOVL2 Upregulation Reverses Age-Related Decline in Vision Loss in Mice

In today's open access research materials, the authors report that upregulation of the gene expression of an identified marker of aging, ELOVL2, can improve visual function in aging mice. Normally, expression of ELOVL2 declines with age, and consequent effects on visual function may involve the role of ELOVL2 in production of long-chain omega-3 and omega-6 polyunsaturated acids. These metabolites are in high demand in retinal cells, and lowered levels may well cause a sizable fraction of age-related dysfunction.

Any discussion of this change in ELOVL2 expression and visual function is interesting in the context of why degenerative aging takes place. It is clearly the case that considerable dysregulation of cellular metabolism takes place with age. The proximate cause of this degeneration of function is changes in the epigenetic regulation of gene expression, the pace of production of various proteins essential to cell function. In near all cases it is quite obscure as to why exactly these epigenetic changes take place - researchers are far more interested in identifying changes than in the much more arduous work of understanding the full context of any given change. The underlying damage of aging is well catalogued, such as in the SENS view of aging, but linking this damage through a long chain of downstream consequences to specific age-related functional consequences is a sizable project, still in its very earliest stages.

Researchers Identify Gene with Functional Role in Aging of Eye

A lengthy-named gene called Elongation of Very Long Chain Fatty Acids Protein 2 or ELOVL2 is an established biomarker of age. Researchers found that an age-related decrease in ELOVL2 gene expression was associated with increased DNA methylation of its promoter. Methylation is a simple biochemical process in which groups of carbon and hydrogen atoms are transferred from one substance to another. In the case of DNA, methylation of regulatory regions negatively impacts expression of the gene. When researchers reversed hypermethylation in vivo, they boosted ELOVL2 expression and rescued age-related decline in visual function in mice.

ELOVL2 is involved in production of long-chain omega-3 and omega-6 polyunsaturated fatty acids, which are used in several crucial biological functions, such as energy production, inflammation response, and maintenance of cell membrane integrity. The gene is found in humans as well as mice. In particular, ELOVL2 regulates levels of docosahexaenoic acid or DHA, a polyunsaturated omega-3 fatty acid abundantly found in the brain and retina. DHA is associated with a number of beneficial effects. Notably, its presence in photoreceptors in eyes promotes healthy retinal function, protects against damage from bright light or oxidative stress and has been linked to improving a variety of vision conditions, from age-related macular (AMD) degeneration to diabetic eye disease and dry eyes.

The lipid elongation enzyme ELOVL2 is a molecular regulator of aging in the retina

Methylation of the regulatory region of the elongation of very-long-chain fatty acids-like 2 (ELOVL2) gene, an enzyme involved in elongation of long-chain polyunsaturated fatty acids, is one of the most robust biomarkers of human age, but the critical question of whether ELOVL2 plays a functional role in molecular aging has not been resolved. Here, we report that Elovl2 regulates age-associated functional and anatomical aging in vivo, focusing on mouse retina, with direct relevance to age-related eye diseases.

We show that an age-related decrease in Elovl2 expression is associated with increased DNA methylation of its promoter. Reversal of Elovl2 promoter hypermethylation in vivo through intravitreal injection of 5-Aza-2'-deoxycytidine (5-Aza-dc) leads to increased Elovl2 expression and rescue of age-related decline in visual function. Mice carrying a point mutation C234W that disrupts Elovl2-specific enzymatic activity show electrophysiological characteristics of premature visual decline, as well as early appearance of autofluorescent deposits, well-established markers of aging in the mouse retina. Finally, we find deposits underneath the retinal pigment epithelium in Elovl2 mutant mice, containing components found in human drusen, a pathologic hallmark of age related macular degeneration.

These findings indicate that ELOVL2 activity regulates aging in mouse retina, provide a molecular link between polyunsaturated fatty acids elongation and visual function, and suggest novel therapeutic strategies for the treatment of age-related eye diseases.

Neural Stem Cell Derived Exosomes Improves Functional Recovery from Stroke in Pigs

Delivery of exosomes derived from stem cell populations has been demonstrated to improve recovery from injury in numerous studies and human applications. The interesting aspect of this demonstration in stroke recovery in pigs is that exosomes from neural stem cells provoke greater functional recovery without improving some of the structural changes that are normally associated with greater mortality and loss of function.

Researchers have presented brain imaging data for a new stroke treatment that supported full recovery in swine, modeled with the same pattern of neurodegeneration as seen in humans with severe stroke. The researchers report the first observational evidence during a midline shift - when the brain is being pushed to one side - to suggest that a minimally invasive and non-operative exosome treatment can now influence the repair and damage that follow a severe stroke.

Exosomes are considered to be powerful mediators of long-distance cell-to-cell communication that can change the behavior of tumor and neighboring cells. The results of the study echo findings from other recent studies using exosome technology. Many patients who suffer stroke exhibit a shift of the brain past its center line-the valley between the left and right part of the brain. Lesions or tumors will induce pressure or inflammation in the brain, causing what typically appears as a straight line to shift. "Based on results of the exosome treatment in swine, it doesn't look like lesion volume or the effects of a midline shift matter nearly as much as one would think. This suggests that, even in some extremely severe cases caused by stroke, you're still going to recover just as well."

Trauma from an acute stroke can happen quickly and can cause irreversible damage almost immediately. Data from the team's research showed that non-treated brain cells near the site of the stroke injury quickly starved from lack of oxygen and died - triggering a lethal action of damage signals throughout the brain network and potentially compromising millions of healthy cells. However, in brain areas treated with exosomes that were taken directly from cold storage and administered intravenously, these cells were able to penetrate the brain and interrupt the process of cell death.

Link: https://news.uga.edu/exosomes-promote-remarkable-recovery-in-severe-stroke/

Sticky Exosomes Can Worsen the Outcome of Stroke

Researchers here note a novel mechanism by which exosomes might cause issues following a stroke. Exosomes are a form of intracellular communication, membrane-bound packages of molecules that are released and taken up by cells in large numbers. Researchers are usually concerned with the way in which exosome cargo affects the behavior of cells once the exosomes are taken up, but here they note changes in exosome structure following a stroke that leads them to clump and block blood vessels. This is an interesting mechanism, and it will be equally interesting to see how the research community chooses to try to address it.

Researchers have found that after stroke, exosomes - nanosized biological suitcases packed with an assortment of cargo that cells swap, like proteins and fats - traveling in the blood get activated and sticky and start accumulating on the lining of blood vessels. Like a catastrophic freeway pileup, platelets, also tiny cells that enable our blood to clot after an injury, start adhering to the now-sticky exosomes, causing a buildup that can effectively form another clot, further obstruct blood flow to the brain and cause additional destruction.

One thing traveling exosomes typically aren't is sticky. Rather, much like our real suitcases, they have a smooth label that marks their intended destination. But when these external destination tags become inexplicably sticky following a stroke, not only do exosomes not reach their destination, they can worsen stroke outcome. In a bit of a perfect storm, the scientists have shown in both stroke models and human blood vessels that exosomes cruising through the blood then pick up RGD, the unique and normally sticky peptide sequence, arginine-glycine-aspartate, which is key to the pileup that can cause additional brain damage.

More typically, exosomes carry a negligible amount of RGD, a protein that's important in holding together the extracellular matrix that helps cells connect and form tissue. In the aftermath of a stroke, cells and the extracellular matrix both get damaged, and sticky RGD is effectively set free. Platelets normally aren't exposed to RGD, which should mostly be sequestered in the extracellular matrix, so they become angry, activated and also sticky in response.

Another piece of this sticky situation is that a receptor called αvβ3. Avβ3 also is found on the lining of blood vessels and naturally binds to sticky RGD as part of its role with the extracellular matrix. The new stroke study shows the RGD carrying exosomes also target these receptors. In fact, when scientists gave antibodies to αvβ3, the binding to the blood vessel lining was blocked. A bottom line of the new work is that RGD sequences are a key contributor to the secondary damage from stroke.

Link: https://jagwire.augusta.edu/sticky-situation-inside-blood-vessels-can-worsen-stroke-damage/