The ability to selectively destroy a sizable fraction of senescent cells in many tissues in old animals has led to the understanding that these errant cells and their secretions are an important cause of the chronic inflammation characteristic of old age. The accumulation of senescent cells is far from the only mechanism involved, but the contribution is sizable. Removing senescent cells can turn back numerous inflammatory age-related conditions in animal models. The open access paper here proposes a view of age-related chronic inflammation that pulls together this and all of the other discoveries of the past decade related to aging and inflammation into what they term "senoinflammation".
Age-associated chronic inflammation is characterized by unresolved and uncontrolled inflammation with multivariable low-grade, chronic and systemic responses that exacerbate the aging process and age-related chronic diseases. Currently, there are two major hypotheses related to the involvement of chronic inflammation in the aging process: molecular inflammation of aging and inflammaging. However, neither of these hypotheses satisfactorily addresses age-related chronic inflammation, considering the recent advances that have been made in inflammation research. A more comprehensive view of age-related inflammation, that has a scope beyond the conventional view, is therefore required.
Based on the available findings from biochemical, molecular, and systems analyses, we propose the senoinflammation concept. It provides not only a broader scope, but also creates an intricate network among many inflammatory mediators that can lead to systemic chronic inflammation. When gene regulation is impaired because of constant damage to the genomic DNA by augmented oxidative susceptibility during the aging progresses, several key inflammatory transcription factors, including p53, AP-1, STAT, and NF-κB, that are important in cell survival become over-activated.
The resulting aberrant gene regulation in senescent cells leads them into a proinflammatory state, thereby altering systemic chemokine or cytokine activities. The proinflammatory senescent cell secretome imposes further stresses on the intracellular organelles, as well as tissues, organs, and systems, thus influencing metabolic disorders such as insulin resistance. It seems plausible that a vicious cycle takes place between senescent cell secretome induction and metabolic dysregulation, as proposed in the senoinflammation concept, and this may well be the underpinning of the aging process and age-associated diseases.
It is hoped that a better understanding of the molecular mechanisms involved in senoinflammation will provide a basic platform for the identification of potential targets that can suppress age-related chronic inflammation and thereby lead to the development of effective interventions to delay aging and suppress age-associated diseases.