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

In vivo treatment with NAC reduces oxidative stress within pancreatic β cells.                                            (A) Atg7F/+:Rip2-Cre                                            or Atg7F/F:Rip2-Cre mice that were untreated or treated with the                                            antioxidant NAC for 12 weeks.  At 16 weeks of age, mice were sacrificed and                                            serial sections of pancreatic tissue were analyzed for p62 and insulin or (B)                                            nitrotyrosine and insulin. (C) Quantification of nitrotyrosine                                            staining in islets of control mice, Atg7-deficient animals or                                            Atg7-deficient mice treated for 12 weeks with NAC (n=3 animals per group).                                            Graph represents the mean+/- SEM. **; p≤0.01.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: In vivo treatment with NAC reduces oxidative stress within pancreatic β cells. (A) Atg7F/+:Rip2-Cre or Atg7F/F:Rip2-Cre mice that were untreated or treated with the antioxidant NAC for 12 weeks. At 16 weeks of age, mice were sacrificed and serial sections of pancreatic tissue were analyzed for p62 and insulin or (B) nitrotyrosine and insulin. (C) Quantification of nitrotyrosine staining in islets of control mice, Atg7-deficient animals or Atg7-deficient mice treated for 12 weeks with NAC (n=3 animals per group). Graph represents the mean+/- SEM. **; p≤0.01.

Mentions: We next asked what the role of continuous oxidative stress was in this model of β cell dysfunction. We randomized knockout or control mice beginning at age 4 weeks to treatment with or without NAC. As expected, when compared to control animals, mice with conditional ablation of Atg7 accumulated increased levels of p62 within their islets (Figure 6A). Treatment with NAC did not noticeably affect this accumulation in conditionally ablated animals (0/18 islets p62 positive in Atg7F/+:RIP2-Cre mice; 22/24 islets p62 positive in Atg7F/F:RIP2-Cre mice and 17/17 islets p62 positive in Atg7F/F: RIP2-Cre mice treated with NAC; in random slides obtained from n=3 mice per condition). In addition, as an in situ marker of oxidative stress, we measured nitrotyrosine levels which are known to increase and contribute to the diabetic phenotype [20]. As noted, levels of nitrotyrosine were markedly elevated in Atg7 deficient islets and in contrast to our observations with p62, treatment with NAC was very effective in reducing the observed increase (Figure 6 B, C).


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)

In vivo treatment with NAC reduces oxidative stress within pancreatic β cells.                                            (A) Atg7F/+:Rip2-Cre                                            or Atg7F/F:Rip2-Cre mice that were untreated or treated with the                                            antioxidant NAC for 12 weeks.  At 16 weeks of age, mice were sacrificed and                                            serial sections of pancreatic tissue were analyzed for p62 and insulin or (B)                                            nitrotyrosine and insulin. (C) Quantification of nitrotyrosine                                            staining in islets of control mice, Atg7-deficient animals or                                            Atg7-deficient mice treated for 12 weeks with NAC (n=3 animals per group).                                            Graph represents the mean+/- SEM. **; p≤0.01.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: In vivo treatment with NAC reduces oxidative stress within pancreatic β cells. (A) Atg7F/+:Rip2-Cre or Atg7F/F:Rip2-Cre mice that were untreated or treated with the antioxidant NAC for 12 weeks. At 16 weeks of age, mice were sacrificed and serial sections of pancreatic tissue were analyzed for p62 and insulin or (B) nitrotyrosine and insulin. (C) Quantification of nitrotyrosine staining in islets of control mice, Atg7-deficient animals or Atg7-deficient mice treated for 12 weeks with NAC (n=3 animals per group). Graph represents the mean+/- SEM. **; p≤0.01.
Mentions: We next asked what the role of continuous oxidative stress was in this model of β cell dysfunction. We randomized knockout or control mice beginning at age 4 weeks to treatment with or without NAC. As expected, when compared to control animals, mice with conditional ablation of Atg7 accumulated increased levels of p62 within their islets (Figure 6A). Treatment with NAC did not noticeably affect this accumulation in conditionally ablated animals (0/18 islets p62 positive in Atg7F/+:RIP2-Cre mice; 22/24 islets p62 positive in Atg7F/F:RIP2-Cre mice and 17/17 islets p62 positive in Atg7F/F: RIP2-Cre mice treated with NAC; in random slides obtained from n=3 mice per condition). In addition, as an in situ marker of oxidative stress, we measured nitrotyrosine levels which are known to increase and contribute to the diabetic phenotype [20]. As noted, levels of nitrotyrosine were markedly elevated in Atg7 deficient islets and in contrast to our observations with p62, treatment with NAC was very effective in reducing the observed increase (Figure 6 B, C).

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