Age-related loss of mitochondrial glutathione exacerbates menadione-induced inhibition of Complex I

Nicholas O Thomas,Kate P Shay,Tory M Hagen

doi:10.1016/j.redox.2019.101155

Nicholas O Thomas, Kate P Shay + Show 1 more

Open Access

https://doi.org/10.1016/j.redox.2019.101155

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Journal: Redox Biology	Publication Date: Mar 2, 2019
Citations: 6	License type: cc-by

Affiliation: Oregon State University

Abstract

The role of mitochondrial GSH (mGSH) in the enhanced age-related susceptibility to xenobiotic toxicity is not well defined. We determined mGSH status and indices of mitochondrial bioenergetics in hepatocytes from young and old F344 rats treated with 300 μM menadione, a concentration that causes 50% cell death in old. At this concentration, mGSH was significantly lost only in hepatocytes from old rats, and with near total depletion due to lower basal mGSH in aged cells. In old hepatocytes, menadione caused mitochondrial membrane potential to collapse, as well as significant deficits in maximal O2 consumption and respiratory reserve capacity, indicators of cellular bioenergetic resiliency. Further examination revealed that the menadione-mediated loss of respiratory reserve capacity in aged hepatocytes was from significant inhibition of Complex I activity and increased proton leak, for which an increase in Complex II activity was not able to compensate. These data demonstrate an age-related increase in mitochondrial susceptibility to a redox-cycling challenge, particularly in regards to Complex I activity, and provide a plausible mechanism to link this vulnerability to mGSH perturbations.

Highlights

Aging is characterized by a decline in cellular redox homeostasis and detoxification capacity, which is coincident with an increased risk for age-related pathophysiologies [1,2,3,4,5,6,7,8,9]
To determine whether the enhanced toxicity from menadione insult was mediated at least in part through mitochondrial dysfunction, we treated hepatocytes isolated from young and old Fischer 344 rats (F344) rats with 300 μM menadione and assayed mitochondrial GSH (mGSH) levels over a 20 min time-course
These results suggest that menadione causes marked losses in mGSH regardless of age, but mitochondria from old rat hepatocytes are less resilient owing to significantly lower steady-state mGSH levels prior to menadione additions, and the lack of recovery following menadione treatment

Summary

Introduction

Aging is characterized by a decline in cellular redox homeostasis and detoxification capacity, which is coincident with an increased risk for age-related pathophysiologies [1,2,3,4,5,6,7,8,9]. Mitochondrial dysfunction and decay is an underlying factor that has been implicated in aging and agerelated diseases [10]. Characteristics of this decay include decreased mitochondrial membrane potential (Δψm), basal respiration rate, and respiratory reserve capacity (RRC), a measure of mitochondrial elasticity to respond to energy requirements. Mitochondria from aged tissues display increases in oxidant leakage, mitochondrial DNA damage, and susceptibility to the formation of the mitochondrial permeability transition pore (MPTP), leading to apoptotic initiation [11,12,13]. MGSH is critical to maintaining mitochondrial function and as such, significantly influences cell and tissue survival. The mGSH pool constitutes a unique subcellular fraction that must be maintained in a narrowly defined equilibrium for proper mitochondrial and cellular function

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