Fight Aging!

Decades ago, the pineal gland was the focus of a great deal of ignorant hype regarding research into aging and the prospects for treating aging. The paper here is an interesting overview of what is known about possible connections between the thymus and the pineal gland, both of which atrophy with age, and both of which have sweeping effects on the immune system. It is perhaps of greatest interest as a catalog of things yet to be discovered - roads leading into the dark forest from the starting point of lists of molecules secreted by thymus and pineal gland, added to what is known of what goes on inside these two organs, and what those molecules are known to do elsewhere in the body. There is the suspicion that some of these roads may cross somewhere in the great expanse of metabolism that is yet to be well mapped, but a much work has yet to be accomplished in order to find out whether or not this is the case.

Mutual influences and bidirectional networks among the nervous system, endocrine system, and immune systems are mediated by hormones, cytokines/chemokines and their binding sites, contributing, in turn, to body homeostasis. Many interactions are mediated by the highly regulated release of several hormones and peptides into the vessels, which have direct effects on the immune system. In particular, many studies have reported interactions between the pineal gland (PG), thymus gland (TG), and other parts of the immune system owing to the widespread expression of receptors that detect the respective humoral signals.

The impairment of TG and PG functions, mainly related to neuroendocrine and immune systems, is associated with ageing, and unfortunately, the physiological deterioration is a precursor to pathologies. Moreover, the alterations of the TG-PG axis during ageing are already indicative of a close relationship between these two glands. In fact, the PG, certainly via melatonin, but perhaps also via additional factors such as thyroid-stimulating hormone (TSH) and other peptides, influences humoral and cellular immunity, immune cell proliferation and immune mediator production. The TG is central to many immunological functions, which are mediated by peptides. Moreover, these glands play an important role as a functional unit because they constitute a bidirectional system in which PG acts on TG and vice versa. Thus, they have a mutual complementarity in the maintenance of a normal immune and endocrine status, which becomes especially evident in ageing.

Researchers have reported an influence of thymic peptides on PG and pineal peptides on TG. Importantly, removal of the PG induces decreases in thymus weight, the number of thymic cells, and TG secretory functions. The blockage of PG, induced by pharmacological treatments, also resulted in a decrease of the thymic hormone, thymulin, in the blood. Moreover, thymectomy caused changes in biorhythms for several immune indicators of glucocorticoid synthesis by the adrenal cortex. The bidirectional communication between TG and PG is also due to the release of some cytokines that are secreted by these glands. One of them is tumour necrosis factor-α (TNF-α) which is produced, apart from other immune cells, in the thymic medulla.

According to our current knowledge, the mutual functional relationship of the TG-PG axis during the phases of life and, particularly, in ageing would benefit from and be worth of increasing research efforts. To date, the literature is still somewhat scanty and does not easily reveal the entire complexity of their relationships, in part because many findings are relatively old and often published in languages rarely used in science. The histological and functional losses of both the PG and TG are salient features of ageing. The message of this article is that they seem to be interrelated.

Link: https://doi.org/10.3390/ijms21228806