Rapid and simple detection of gero-suppressive agents

The principal cause of organismal aging is erosion of telomeres at each cell division, which results in telomere dysfunction and leads to intrinsic (replicative) cellular senescence. Other factors, however, additionally contribute to aging [1]. Premature cellular senescence is one of them. The recent body of evidence indicates that constitutive activation of nutrient-and mitogen-signaling pathways is the primary mechanism causing cellular senescence and premature aging [2]. Activation of these pathways leads to enhanced translation, accumulation of proteins, cell growth in size and mass (hypertrophy), and cellular senescence. Particularly during the slowed down progression through the cell cycle, such as occurs during replication stress, the growth continues unabated, leading to imbalance when the ratio of protein to DNA content increases; cells grow in size and acquire the senescence (unbalanced growth) phenotype [2, 3]. The key players in this mechanism of aging are the insulin-like growth factors (IGFs) including growth hormone (GH; the " GH/IGFs axis "), AKT/PKB, and PI3K; activation along these pathways converges on mammalian target of rapamycin (mTOR) and its downstream substrate S6K that phosphorylates eIF-4B and rp-S6, the factors of initiation and continuation of translation. The evidence that inhibition of signaling along these pathways slows down the aging process and leads to increased longevity of different species organisms, including mice and rats, is undisputable [3]. Detection of anti-aging (gero-suppressive) drugs inhibiting these pathways that potentially may have application for human is of obvious importance. The quest for such modalities based on their administration to animals and an assessment of the effect on longevity, whereas the most direct, is expensive and time consuming [3]. It cannot be applied therefore for rapid screening of a variety of compounds that may have potential anti-aging properties. Attempts have been made therefore to develop assays based on the in vitro induction of cellular senescence (gero-conversion) and its reversion to quiescence. One such tactic involves cell treatment with the drugs perturbing DNA replication to induce replication stress and assessment of the degree (" depth ") of premature cellular senescence by analysis of the classical senescence phenotype, including morphology, expression of SA-β-gal, p21 WAF1 , cyclin D1 and ƴH2AX measured by imaging (laser scanning) cytometry [4-6]. The reversibility of gero-conversion by the investigated anti-aging modalities when tested in parallel with inducers of replication stress provided evidence of their potential anti-aging properties. Berberine, a natural alkaloid, that has a long history of medicinal use in both Ayurvedic …