Hormetic effect of low doses of rapamycin triggers anti-aging cascades in WRL-68 cells by modulating an mTOR-mitochondria cross-talk.

BACKGROUND: Rapamycin is hormetic in nature-it demonstrates contrasting effects at high and low doses. It is toxic at moderate/high doses, while it can restrain aging and extend lifespan at low doses. However, it is not fully understood how rapamycin governs cellular aging. On the other hand, aging is putatively correlated to mitochondrial dysregulation. Although previous studies have suggested that hormetic (low) doses of rapamycin can cause partial/incomplete inhibition of mTOR, the actual modus operandi of how such partial mTOR inhibition might modulate the mTOR-mitochondria cross-talk remained to be deciphered in the context of cellular aging. The present study was designed to understand the hormetic effects of rapamycin on cellular factors that govern aging-associated changes in mitochondrial facets, such as functional and metabolic homeostases, sustenance of membrane potential, biogenesis, mitophagy, and oxidative injury to mitochondrial macromolecules. METHODS AND RESULTS: WRL-68 cells treated (24 h) with variable doses of rapamycin were studied for estimating their viability, apoptosis, senescence, mitochondrial density and Δψm. Expression levels of key functional proteins were estimated by immunofluorescence/immunoblots. Oxidative damage to mtDNA/mtRNA/proteins was measured in mitochondrial lysates. We demonstrated that hormetic doses (0.1 and 1 nM) of rapamycin can alleviate aging-associated mitochondrial dyshomeostasis in WRL-68 cells, such as oxidative injury to mitochondrial nucleic acids and proteins, as well as disequilibrium of mitochondrial density, membrane potential, biogenesis, mitophagy and overall metabolism. CONCLUSIONS: We established that low doses of rapamycin can hormetically amend the mTOR-mitochondria cross-talk, and can consequently promote anti-aging outcome in cells.

Microtubule motors in centrosome homeostasis: A target for cancer therapy?

Cancer is a grievous concern to human health, owing to a massive heterogeneity in its cause and impact. Dysregulation (numerical, positional and/or structural) of centrosomes is one of the notable factors among those that promote onset and progression of cancers. In a normal dividing cell, a pair of centrosomes forms two poles, thereby governing the formation of a bipolar spindle assembly. A large number of cancer cells, however, harbor supernumerary centrosomes, which mimic the bipolar arrangement in normal cells by centrosome clustering (CC) into two opposite poles, thus developing a pseudo-bipolar spindle assembly. Manipulation of centrosome homeostasis is the paramount pre-requisite for the evasive strategy of CC in cancers. Out of the varied factors that uphold centrosome integrity, microtubule motors (MiMos) play a critical role. Categorized as dyneins and kinesins, MiMos are involved in cohesion of centrosomes, and also facilitate the maintenance of the numerical, positional and structural integrity of centrosomes. Herein, we elucidate the decisive mechanisms undertaken by MiMos to mediate centrosome homeostasis, and how dysregulation of the same might lead to CC in cancer cells. Understanding the impact of MiMos on CC might open up avenues toward a credible therapeutic target against diverse cancers.

A novel indenone derivative selectively induces senescence in MDA-MB-231 (breast adenocarcinoma) cells.

Triple-negative breast cancer is the most aggressive form of breast cancer with limited intervention options. Moreover, a number of belligerent therapeutic strategies adopted to treat such aggressive forms of cancer have demonstrated detrimental side effects. This necessitates exploration of targeted chemotherapeutics. We assessed the efficacy of a novel indenone derivative (nID) [(±)-N-(2-(-5-methoxy-1-oxo-3-(2-oxo-2-phenylethyl)-2,3-dihydro-1H-inden-2-yl)ethyl)-4-methylbenzenesulfonamide], synthesized by a novel internal nucleophile-assisted palladium-catalyzed hydration-olefin insertion cascade; against triple-negative breast cancer cells (MDA-MB-231). On 24 h treatment, the nID caused decline in the viability of MDA-MB-231 and MDA-MB-468 cells, but did not significantly (P < 0.05) affect WRL-68 (epithelial-like) cells. In fact, the nID demonstrated augmentation of p53 expression, and consequent p53-dependent senescence in both MDA-MB-231 and MDA-MB-468 cells, but not in WRL-68 cells. The breast cancer cells also exhibited reduced proliferation, downregulated p65/NF-κB and survivin, along with augmented p21Cip1/WAF1 expression, on treatment with the nID. This ensued cell cycle arrest at G1 stage, which might have driven the MDA-MB-231 cells to senescence. We observed a selectivity of the nID to target MDA-MB-231 cells, whereas WRL-68 cells did not show any considerable effect. The results underscored that the nID has potential to be developed into a cancer therapeutic.

Hexavalent chromium-induced autophagic death of WRL-68 cells is mitigated by aqueous extract of Cuminum cyminum L. seeds.

In this study, we assessed the potential of aqueous extract (CSEaq) of Cuminum cyminum L. (cumin) seeds in protecting WRL-68 cells from hexavalent chromium [Cr(VI)]-induced oxidative injury. Cells exposed to Cr(VI) (10 µM CrO3) for 24 h demonstrated a twofold increase in ROS, which, in turn, led to extensive oxidative stress, consequently causing colossal decline in cell viability (by 58.82 ± 9.79%) and proliferation (as was evident from a reduced expression of Ki-67, a proliferation marker). Immunofluorescence studies showed that Cr(VI) diminished the expressions of mTOR and survivin in WRL-68 cells. It also led to a substantial elevation of BECN1 expression, which suggested autophagy. Overall, our results indicated that 24 h exposure of WRL-68 cells to Cr(VI) caused oxidative stress-induced autophagic cell death. CSEaq was found to protect WRL-68 cells from the same fate by refurbishing their viability and proliferation in a dose-dependent manner. The extract reduced ROS in these cells, which consequently decreased the degree of autophagic cell death by restoring expressions of mTOR, survivin and BECN1 to their respective normal levels. Biochemical assays revealed that CSEaq is rich in phenolic constituents. Total phenolic content of CSEaq demonstrated positive correlations with (i) its antioxidant potential, (ii) its alleviation of cellular oxidative stress and (iii) its cytoprotective efficacy in Cr(VI)-treated WRL-68 cells. We also identified the major phenolic constituents of CSEaq. Our study suggested that polyphenols in CSEaq might be responsible for protecting WRL-68 cells from Cr(VI)-governed oxidative assault that would have otherwise led to survivin/mTOR-mediated autophagic death.