Mitochondrial Oxidative Stress Promotes Cardiac Remodeling in Myocardial Infarction through the Activation of Endoplasmic Reticulum Stress.

We have evaluated cardiac function and fibrosis in infarcted male Wistar rats treated with MitoQ (50 mg/kg/day) or vehicle for 4 weeks. A cohort of patients admitted with a first episode of acute MI were also analyzed with cardiac magnetic resonance and T1 mapping during admission and at a 12-month follow-up. Infarcted animals presented cardiac hypertrophy and a reduction in the left ventricular ejection fraction (LVEF) and E- and A-waves (E/A) ratio when compared to controls. Myocardial infarction (MI) rats also showed cardiac fibrosis and endoplasmic reticulum (ER) stress activation. Binding immunoglobulin protein (BiP) levels, a marker of ER stress, were correlated with collagen I levels. MitoQ reduced oxidative stress and prevented all these changes without affecting the infarct size. The LVEF and E/A ratio in patients with MI were 57.6 ± 7.9% and 0.96 ± 0.34, respectively. No major changes in cardiac function, extracellular volume fraction (ECV), or LV mass were observed at follow-up. Interestingly, the myeloperoxidase (MPO) levels were associated with the ECV in basal conditions. BiP staining and collagen content were also higher in cardiac samples from autopsies of patients who had suffered an MI than in those who had died from other causes. These results show the interactions between mitochondrial oxidative stress and ER stress, which can result in the development of diffuse fibrosis in the context of MI.

The Interplay of Mitochondrial Oxidative Stress and Endoplasmic Reticulum Stress in Cardiovascular Fibrosis in Obese Rats.

We have evaluated the role of mitochondrial oxidative stress and its association with endoplasmic reticulum (ER) stress activation in the progression of obesity-related cardiovascular fibrosis. MitoQ (200 µM) was orally administered for 7 weeks to male Wistar rats that were fed a high-fat diet (HFD, 35% fat) or a control diet (CT, 3.5% fat). Obese animals presented cardiovascular fibrosis accompanied by increased levels of extracellular matrix proteins and profibrotic mediators. These alterations were associated with ER stress activation characterized by enhanced levels (in heart and aorta vs. CT group, respectively) of immunoglobulin binding protein (BiP; 2.1-and 2.6-fold, respectively), protein disulfide-isomerase A6 (PDIA6; 1.9-fold) and CCAAT-enhancer-binding homologous protein (CHOP; 1.5- and 1.8-fold, respectively). MitoQ treatment was able to prevent (p < 0.05) these modifications at cardiac and aortic levels. MitoQ (5 nM) and the ER stress inhibitor, 4-phenyl butyric acid (4 µM), were able to block the prooxidant and profibrotic effects of angiotensin II (Ang II, 10-6 M) in cardiac and vascular cells. Therefore, the data show a crosstalk between mitochondrial oxidative stress and ER stress activation, which mediates the development of cardiovascular fibrosis in the context of obesity and in which Ang II can play a relevant role.

Oxidative Stress and Vascular Damage in the Context of Obesity: The Hidden Guest.

The vascular system plays a central role in the transport of cells, oxygen and nutrients between different regions of the body, depending on the needs, as well as of metabolic waste products for their elimination. While the structure of different components of the vascular system varies, these structures, especially those of main arteries and arterioles, can be affected by the presence of different cardiovascular risk factors, including obesity. This vascular remodeling is mainly characterized by a thickening of the media layer as a consequence of changes in smooth muscle cells or excessive fibrosis accumulation. These vascular changes associated with obesity can trigger functional alterations, with endothelial dysfunction and vascular stiffness being especially common features of obese vessels. These changes can also lead to impaired tissue perfusion that may affect multiple tissues and organs. In this review, we focus on the role played by perivascular adipose tissue, the activation of the renin-angiotensin-aldosterone system and endoplasmic reticulum stress in the vascular dysfunction associated with obesity. In addition, the participation of oxidative stress in this vascular damage, which can be produced in the perivascular adipose tissue as well as in other components of the vascular wall, is updated.

The role of mitochondrial oxidative stress in the metabolic alterations in diet-induced obesity in rats.

The impact of the mitochondria-targeted antioxidant MitoQ was evaluated in the metabolic alterations and the adipose tissue remodeling associated with obesity. Male Wistar rats were fed either a high-fat diet (HFD; 35% fat) or a standard diet (3.5% fat) for 7 wk and treated with MitoQ (200 µM). A proteomic analysis of visceral adipose tissue from patients with obesity and patients without obesity was performed. MitoQ partially prevented the increase in body weight, adiposity, homeostasis model assessment index, and adipose tissue remodeling in HFD rats. It also ameliorated protein level changes of factors involved in insulin signaling observed in adipose tissue of obese rats: reductions in adiponectin and glucose transporter 4 (GLUT 4) and increases in dipeptidylpeptidase 4, suppressor of cytokine signaling 3 (SOCS3), and insulin receptor substrate 1 phosphorylation. MitoQ prevented down-regulation of adiponectin and GLUT 4 and increases in SOCS3 levels in a TNF-α-induced insulin-resistant 3T3-L1 adipocyte model. MitoQ also ameliorated alterations in mitochondrial proteins observed in obese rats: increases in cyclophylin F and carnitine palmitoyl transferase 1A and reductions in mitofusin1, peroxiredoxin 4, and fumarate hydratase. The proteomic analysis of the visceral adipose tissue from patients with obesity show alterations in mitochondrial proteins similar to those observed in obese rats. Therefore, the data show the beneficial effect of MitoQ in the metabolic dysfunction induced by obesity.-Marín-Royo, G., Rodríguez, C., Le Pape, A., Jurado-López, R., Luaces, M., Antequera, A., Martínez-González, J., Souza-Neto, F. V., Nieto, M. L., Martínez-Martínez, E., Cachofeiro, V. The role of mitochondrial oxidative stress in the metabolic alterations in diet-induced obesity in rats.