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

Wu JJ, Quijano C, Chen E, Liu H, Cao L, Fergusson MM, Rovira II, Gutkind S, Daniels MP, Komatsu M, Finkel T - Aging (Albany NY) (2009)

Bottom Line: Using these models we demonstrate that isolated mitochondria obtained from Atg7(-/-) skeletal muscle exhibit a significant defect in mitochondrial respiration.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.

View Article: PubMed Central - PubMed

Affiliation: Translational Medicine Branch, National Heart Lung and Blood Institute, NIH, Bethesda, MD 20892, USA.

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 beta 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.

Show MeSH

Related in: MedlinePlus

Atg7 deficient cells exhibit increased levels of ROS. (A)                                            Intracellular ROS levels as assessed by DCFDA fluorescence intensity                                            (arbitrary units) in WT and Atg7-/- MEFs. ROS measurements were                                            made from three independent WT or Atg7-/- MEF primary cell                                            isolates and the fluorescent intensity of more than 250 cells of each                                            genotype were assessed.  (B) NAC treatment reduces the levels of ROS                                            in MEFs lacking Atg7. Levels of ROS were assessed by DCFDA fluorescence in                                            Atg7-/- MEFs untreated or treated with NAC (500 μM) for 4 days                                            prior to imaging. Values represent the normalized fluorescent intensity                                            (arbitrary units) of approximately 300 cells per condition. Graphs                                            represent the mean +/- SEM.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2806022&req=5

Figure 3: Atg7 deficient cells exhibit increased levels of ROS. (A) Intracellular ROS levels as assessed by DCFDA fluorescence intensity (arbitrary units) in WT and Atg7-/- MEFs. ROS measurements were made from three independent WT or Atg7-/- MEF primary cell isolates and the fluorescent intensity of more than 250 cells of each genotype were assessed. (B) NAC treatment reduces the levels of ROS in MEFs lacking Atg7. Levels of ROS were assessed by DCFDA fluorescence in Atg7-/- MEFs untreated or treated with NAC (500 μM) for 4 days prior to imaging. Values represent the normalized fluorescent intensity (arbitrary units) of approximately 300 cells per condition. Graphs represent the mean +/- SEM.

Mentions: Damaged mitochondria often produce increased levels of reactive oxygen species (ROS). This increase in ROS can further increase mitochondrial damage leading in turn to more oxidant release and additional mitochondrial damage, in a process termed the ‘vicious cycle'[17]. In some circumstances, this perpetuating cycle of mitochondrial damage and oxidative stress is thought to contribute to normal aging as well as many age-related diseases [18]. Given the above observations, we next sought to assess whether continuous oxidative stress was evident in autophagy deficient cells. As noted in Figure 3A, Atg7-/- MEFs had increased levels of intracellular ROS. Culturing these cells in the presence of the antioxidant N-acetylcysteine (NAC) resulted in a reduction in ROS levels (Figure 3B).


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

Wu JJ, Quijano C, Chen E, Liu H, Cao L, Fergusson MM, Rovira II, Gutkind S, Daniels MP, Komatsu M, Finkel T - Aging (Albany NY) (2009)

Atg7 deficient cells exhibit increased levels of ROS. (A)                                            Intracellular ROS levels as assessed by DCFDA fluorescence intensity                                            (arbitrary units) in WT and Atg7-/- MEFs. ROS measurements were                                            made from three independent WT or Atg7-/- MEF primary cell                                            isolates and the fluorescent intensity of more than 250 cells of each                                            genotype were assessed.  (B) NAC treatment reduces the levels of ROS                                            in MEFs lacking Atg7. Levels of ROS were assessed by DCFDA fluorescence in                                            Atg7-/- MEFs untreated or treated with NAC (500 μM) for 4 days                                            prior to imaging. Values represent the normalized fluorescent intensity                                            (arbitrary units) of approximately 300 cells per condition. Graphs                                            represent the mean +/- SEM.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2806022&req=5

Figure 3: Atg7 deficient cells exhibit increased levels of ROS. (A) Intracellular ROS levels as assessed by DCFDA fluorescence intensity (arbitrary units) in WT and Atg7-/- MEFs. ROS measurements were made from three independent WT or Atg7-/- MEF primary cell isolates and the fluorescent intensity of more than 250 cells of each genotype were assessed. (B) NAC treatment reduces the levels of ROS in MEFs lacking Atg7. Levels of ROS were assessed by DCFDA fluorescence in Atg7-/- MEFs untreated or treated with NAC (500 μM) for 4 days prior to imaging. Values represent the normalized fluorescent intensity (arbitrary units) of approximately 300 cells per condition. Graphs represent the mean +/- SEM.
Mentions: Damaged mitochondria often produce increased levels of reactive oxygen species (ROS). This increase in ROS can further increase mitochondrial damage leading in turn to more oxidant release and additional mitochondrial damage, in a process termed the ‘vicious cycle'[17]. In some circumstances, this perpetuating cycle of mitochondrial damage and oxidative stress is thought to contribute to normal aging as well as many age-related diseases [18]. Given the above observations, we next sought to assess whether continuous oxidative stress was evident in autophagy deficient cells. As noted in Figure 3A, Atg7-/- MEFs had increased levels of intracellular ROS. Culturing these cells in the presence of the antioxidant N-acetylcysteine (NAC) resulted in a reduction in ROS levels (Figure 3B).

Bottom Line: Using these models we demonstrate that isolated mitochondria obtained from Atg7(-/-) skeletal muscle exhibit a significant defect in mitochondrial respiration.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.

View Article: PubMed Central - PubMed

Affiliation: Translational Medicine Branch, National Heart Lung and Blood Institute, NIH, Bethesda, MD 20892, USA.

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 beta 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.

Show MeSH
Related in: MedlinePlus