Potential anti-aging agents suppress the level of constitutive mTOR- and DNA damage- signaling

Abstract

Two different mechanisms are considered to be the primary cause of aging. Cumulative DNA damage caused by reactive oxygen species (ROS), the by-products of oxidative phosphorylation, is one of these mechanisms (ROS concept). Constitutive stimulation of mitogen- and nutrient-sensing mTOR/S6 signaling is the second mechanism (TOR concept). The flow- and laser scanning- cytometric methods were developed to measure the level of the constitutive DNA damage/ROS- as well as of mTOR/S6- signaling in individual cells. Specifically, persistent activation of ATM and expression of γH2AX in untreated cells appears to report constitutive DNA damage induced by endogenous ROS. The level of phosphorylation of Ser235/236-ribosomal protein (RP), of Ser2448-mTOR and of Ser65-4EBP1, informs on constitutive signaling along the mTOR/S6 pathway. Potential gero-suppressive agents rapamycin, metformin, 2-deoxyglucose, berberine, resveratrol, vitamin D3 and aspirin, all decreased the level of constitutive DNA damage signaling as seen by the reduced expression of γH2AX in proliferating A549, TK6, WI-38 cells and in mitogenically stimulated human lymphocytes. They all also decreased the level of intracellular ROS and mitochondrial trans-membrane potential ΔΨm, the marker of mitochondrial energizing as well as reduced phosphorylation of mTOR, RP-S6 and 4EBP1. The most effective was rapamycin. Although the primary target of each on these agents may be different the data are consistent with the downstream mechanism in which the decline in mTOR/S6K signaling and translation rate is coupled with a decrease in oxidative phosphorylation, (revealed by ΔΨm) that leads to reduction of ROS and oxidative DNA damage. The decreased rate of translation induced by these agents may slow down cells hypertrophy and alleviate other features of cell aging/senescence. Reduction of oxidative DNA damage may lower predisposition to neoplastic transformation which otherwise may result from errors in repair of DNA sites coding for oncogenes or tumor suppressor genes. The data suggest that combined assessment of constitutive γH2AX expression, mitochondrial activity (ROS, ΔΨm) and mTOR signaling provides an adequate gamut of cell responses to evaluate effectiveness of gero-suppressive agents.

HIF-1α and rapamycin act as gerosuppressant in multiple myeloma cells upon genotoxic stress

“…Halicka et al have shown that gerosuppressive agents, including rapamycin, reduced the level of expression of gH2AX, in various cell types. 49 It is of interest to examine if RAD50 is involved in this decreased expression of gH2AX. DNA damages are able to decelerate, and even arrest, cell cycle so that they can be repaired.…”

Healthy Aging

“…), hormones (GH, thyroid hormones, adrenal and sexual hormones, melatonin [50]), bioregulatory peptides (timalin, epithalmin), biguanides (metformin, fenformin) [77], adaptogens (ginseng [48]). Sirolimus or rapamycin, described as immunosuppressive and antitumoral drug has been shown to be also an anti-ageing drug [41] whose goal is the TOR gene in yeast [43] and mTOR gene, its mammalian correspondent, also known as FK506 factor or FRAP1, a serine/threonine kinase that regulates cell growth, viability, mobility, protein synthesis and gene transcription [31,45,78]. Rapamycin, according to recent studies, may act preventively in atherosclerosis, hypertonia and hypercoagulation, thus preventing myocardial infarction, cardiovascular accidents, osteoporosis, cancer, autoimmune diseases, arthritis, fat diabetes, Alzheimer and Parkinson diseases [31,42,45].…”

“…2 deoxyglucose [78] is a glucose analog that absorbed by cells determine glucose inhibition resulting in decreased cellular energetic metabolism, situation that mimics calorie restriction. Data concerning the geroprotectection of this substance is not yet relevant.…”

Comparison of rapamycin schedules in mice on high-fat diet

“…[62][63][64][65][66][67][68][69][70] In the organism, suppression of geroconversion prevents age-related diseases in mammals [70][71][72][73][74][75][76][77][78] and pathological conditions in invertebrates, 79,80 extending healthy lifespan.…”