N-Acetylcysteine Influence on Oxidative Stress and Cardiac Remodeling in Rats During Transition from Compensated Left Ventricular Hypertrophy to Heart Failure.

BACKGROUND/AIMS: To evaluate the effects of the antioxidant N-acetylcysteine (NAC) on cardiac structure and function in rats with long-term ascending aortic stenosis (AS). METHODS: Four months after inducing AS, Wistar rats were assigned into the groups Sham, AS, and AS treated with NAC (AS-NAC) and followed for eight weeks. Cardiac structure and function were evaluated by echocardiogram. Myocardial antioxidant enzymes activity was measured by spectrophotometry and malondialdehyde serum concentration by HPLC. Gene expression of NADPH oxidase subunits NOX2, NOX4, p22 phox, and p47 phox was assessed by real time RT-PCR and protein expression of MAPK proteins by Western blot. Statistical analyzes were performed with Goodman and ANOVA or Mann-Whitney Results: NAC restored myocardial total glutathione (Sham 20.8±3.00; AS 12.6±2.92; AS-NAC 17.6±2.45 nmol/g tissue; p<0.05 AS vs Sham and AS-NAC). Malondialdehyde serum concentration was lower in AS-NAC and myocardial lipid hydroperoxide was higher in AS (Sham 199±48.1; AS 301±36.0; AS-NAC 181±41.3 nmol/g tissue). Glutathione peroxidase activity was lower in AS than Sham. Echocardiogram showed LV concentric hypertrophy with systolic and diastolic dysfunction before and after treatment; no differences were observed between AS-NAC and AS groups. NAC reduced p-ERK and p-JNK protein expression, attenuated myocardial fibrosis, and decreased the frequency of right ventricular hypertrophy. CONCLUSION: N-acetylcysteine restores myocardial total glutathione, reduces systemic and myocardial oxidative stress, improves MAPK signaling, and attenuates myocardial fibrosis in aortic stenosis rats.

Modulation of MAPK and NF-954;B Signaling Pathways by Antioxidant Therapy in Skeletal Muscle of Heart Failure Rats.

BACKGROUND/AIMS: Although increased oxidative stress plays a role in heart failure (HF)-induced skeletal myopathy, signaling pathways involved in muscle changes and the role of antioxidant agents have been poorly addressed. We evaluated the effects of N-acetylcysteine (NAC) on intracellular signaling pathways potentially modulated by oxidative stress in soleus muscle from HF rats. METHODS AND RESULTS: Four months after surgery, rats were assigned to Sham, myocardial infarction (MI)-C (without treatment), and MI-NAC (treated with N-acetylcysteine) groups. Two months later, echocardiogram showed left ventricular dysfunction in MI-C; NAC attenuated diastolic dysfunction. Oxidative stress was evaluated in serum and soleus muscle; malondialdehyde was higher in MI-C than Sham and did not differ between MI-C and MI-NAC. Oxidized glutathione concentration in soleus muscle was similar in Sham and MI-C, and lower in MI-NAC than MI-C (Sham 0.168 ± 0.056; MI-C 0.223 ± 0.073; MI-NAC 0.136 ± 0.023 nmol/mg tissue; p = 0.014). Western blot showed increased p-JNK and decreased p38, ERK1/2, and p-ERK1/2 in infarcted rats. NAC restored ERK1/2. NF-954;B p65 subunit was reduced; p-Ser276 in p65 and I954;B was increased; and p-Ser536 unchanged in MI-C compared to Sham. NAC did not modify NF-954;B p65 subunit, but decreased p-Ser276 and p-Ser536. CONCLUSION: N-acetylcysteine modulates MAPK and NF-954;B signaling pathways in soleus muscle of HF rats.

Influence of N- acetylcysteine on oxidative stress in slow-twitch soleus muscle of heart failure rats.

BACKGROUND: Chronic heart failure is characterized by decreased exercise capacity with early exacerbation of fatigue and dyspnea. Intrinsic skeletal muscle abnormalities can play a role in exercise intolerance. Causal or contributing factors responsible for muscle alterations have not been completely defined. This study evaluated skeletal muscle oxidative stress and NADPH oxidase activity in rats with myocardial infarction (MI) induced heart failure. METHODS AND RESULTS: Four months after MI, rats were assigned to Sham, MI-C (without treatment), and MI-NAC (treated with N-acetylcysteine) groups. Two months later, echocardiogram showed left ventricular dysfunction in MI-C; NAC attenuated diastolic dysfunction. In soleus muscle, glutathione peroxidase and superoxide dismutase activity was decreased in MI-C and unchanged by NAC. 3-nitrotyrosine was similar in MI-C and Sham, and lower in MI-NAC than MI-C. Total reactive oxygen species (ROS) production was assessed by HPLC analysis of dihydroethidium (DHE) oxidation fluorescent products. The 2-hydroxyethidium (EOH)/DHE ratio did not differ between Sham and MI-C and was higher in MI-NAC. The ethidium/DHE ratio was higher in MI-C than Sham and unchanged by NAC. NADPH oxidase activity was similar in Sham and MI-C and lower in MI-NAC. Gene expression of p47(phox) was lower in MI-C than Sham. NAC decreased NOX4 and p22(phox) expression. CONCLUSIONS: We corroborate the case that oxidative stress is increased in skeletal muscle of heart failure rats and show for the first time that oxidative stress is not related to increased NADPH oxidase activity.

Chronic heart failure-induced skeletal muscle atrophy, necrosis, and changes in myogenic regulatory factors.

BACKGROUND: Although intrinsic skeletal muscle abnormalities can influence exercise intolerance during heart failure (HF), the factors responsible for muscle changes have not been elucidated. In this study we evaluated the expression of myogenic regulatory factors (MRF), myosin heavy chain (MyHC) isoforms, and fiber trophism in the soleus muscle of rats with myocardial infarction-induced heart failure. METHOD/RESULTS: Six months after surgery, 2 groups of rats were studied: sham, and infarcted rats with HF (MI/HF+, MI size: 41.1±6.3% of total left ventricular area). In the infarcted group, microscopic evaluation revealed scattered foci of fiber necrosis in combination with inflammatory cells, phagocytosis, and increased fibrous tissue. The frequency of necrotic fibers was significantly higher in the MI/HF+ group than in the sham. The MI/HF+ group had atrophy of type I, IC/IIC, and IIA fibers compared to the sham group (P<0.05). MyoD gene expression was higher in the MI/HF+ group (sham: 1.00±0.49; MI/HF+: 2.53±0.71 arbitrary units; P<0.001). Myogenin and MRF4 gene expression was similar in both groups. Myogenin protein levels were reduced in the MI/HF+ group (sham: 1.00±0.21; MI/HF+: 0.74±0.21 arbitrary units; P=0.026). MyoD and MRF4 protein levels, as well as the MyHC distribution, were not different between groups. The MI/HF+ group had higher TNF-α and IL-6 serum concentrations than the sham group. CONCLUSIONS: Heart failure-induced skeletal muscle atrophy is combined with fiber necrosis, increased MyoD gene expression and decreased myogenin protein levels.