Mitochondrial dysfunction and oxidative stress mediate the physiological impairment induced by the disruption of autophagy

Abstract

Impaired or deficient autophagy is believed to cause or contribute to aging, as well as a number of age-related pathologies. The exact mechanism through which alterations in autophagy induce these various pathologies is not well understood. Here we describe the creation of two in vivo mouse models that allow for the characterization of the alteration in mitochondrial function and the contribution of the corresponding oxidative stress following deletion of Atg7. Using these models we demonstrate that isolated mitochondria obtained from Atg7-/- skeletal muscle exhibit a significant defect in mitochondrial respiration. We further show that cells derived from Atg7-/- mice have an altered metabolic profile characterized by decreased resting mitochondrial oxygen consumption and a compensatory increase in basal glycolytic rates. Atg7-/-cells also exhibit evidence for increased steady state levels of reactive oxygen species. The observed mitochondrial dysfunction and oxidative stress is also evident in a mouse model where Atg7 is deleted within the pancreatic β cell. In this model, the simple administration of an antioxidant can significantly ameliorate the physiological impairment in glucose-stimulated insulin secretion. Taken together, these results demonstrate the potential role of mitochondrial dysfunction and oxidative stress in autophagy related pathology.

Autophagic deficiency is related to steroidogenic decline in aged rat Leydig cells

“…ROS have been linked to autophagy and ageing in several studies. Wu et al 18 reported that the intracellular ROS level of Atg7 2/2 cells was increased, but it could be decreased by the antioxidant NAC. Masiero et al 36 reported that deletion of Atg7 resulted in muscle atrophy and an age-dependent decrease in strength with accumulation of abnormal mitochondria and a swollen sarcoplasmic reticulum.…”

“…[13][14][15][16] Because mitochondria are the crucial sources of ROS in aerobic eukaryotic cells, androgen deficiency in aged males may be attributed to dysfunctional mitochondria owing to an accumulation of ROS. [17][18][19] Autophagy is a cellular degradative pathway that involves the delivery of cytoplasmic cargo to lysosomes, and it is essential for cell survival, differentiation, development and homeostasis. [19][20][21] Autophagy can be induced by inhibiting target of rapamycin with rapamycin or blocked by inhibiting the class III PI3K with 3-methyladenine, wortmannin or bafilomycin A1 which inhibits the autophagosome fusion.…”

Defects in calcium homeostasis and mitochondria can be reversed in Pompe disease

“…Mitochondria were isolated from freshly harvested skeletal muscle of KO and WT mice (> 7 mo of age) as described. 88 Briefly, isolated muscles were washed and minced in ice-cold medium containing 225 mM mannitol (Sigma, M9546), 75 mM sucrose (Sigma, S7903), 5 mM MOPS (Sigma, M3183), 0.5 mM EGTA, 2 mM taurine (Sigma, T0625), pH 7.25. The tissues were digested (10 min on ice) with Nagarse (1 U/ml; Sigma, P8038) which was added to the medium; samples were then washed with the medium containing 0.3% BSA (Sigma, A6003), resuspended in the same medium, and homogenized with a glass-Teflon homogenizer.…”

Signal Transduction by Mitochondrial Oxidants

“…In the absence of an effective autophagy network, there is an accumulation of damaged organelles, including dysfunctional mitochondria. Indeed, mitochondria isolated from autophagydeficient tissues have impaired respiratory function (30). Similarly, cells with impaired autophagy have high basal levels of ROS, which appears to emanate from the mitochondria (31).…”