R Mahalakshmi1, J Priyanga1, Dipita Bhakta-Guha2, Gunjan Guha3. 1. Department of Biotechnology, School of Chemical and Bio Technology, Cellular Dyshomeostasis Laboratory, SASTRA University, Tamil Nadu, Thanjavur, 613401, India. 2. Department of Biotechnology, School of Chemical and Bio Technology, Cellular Dyshomeostasis Laboratory, SASTRA University, Tamil Nadu, Thanjavur, 613401, India. dipita2001@gmail.com. 3. Department of Biotechnology, School of Chemical and Bio Technology, Cellular Dyshomeostasis Laboratory, SASTRA University, Tamil Nadu, Thanjavur, 613401, India. gunjan.doc@gmail.com.
Abstract
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.
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.
Authors: Richard A Miller; David E Harrison; C M Astle; Joseph A Baur; Angela Rodriguez Boyd; Rafael de Cabo; Elizabeth Fernandez; Kevin Flurkey; Martin A Javors; James F Nelson; Carlos J Orihuela; Scott Pletcher; Zelton Dave Sharp; David Sinclair; Joseph W Starnes; J Erby Wilkinson; Nancy L Nadon; Randy Strong Journal: J Gerontol A Biol Sci Med Sci Date: 2010-10-25 Impact factor: 6.053