N-acetylcysteine attenuates myocardial dysfunction and postischemic injury by restoring caveolin-3/eNOS signaling in diabetic rats

Abstract

BackgroundPatients with diabetes are prone to develop cardiac hypertrophy and more susceptible to myocardial ischemia–reperfusion (I/R) injury, which are concomitant with hyperglycemia-induced oxidative stress and impaired endothelial nitric oxide (NO) synthase (eNOS)/NO signaling. Caveolae are critical in the transduction of eNOS/NO signaling in cardiovascular system. Caveolin (Cav)-3, the cardiomyocytes-specific caveolae structural protein, is decreased in the diabetic heart in which production of reactive oxygen species are increased. We hypothesized that treatment with antioxidant N-acetylcysteine (NAC) could enhance cardiac Cav-3 expression and attenuate caveolae dysfunction and the accompanying eNOS/NO signaling abnormalities in diabetes.MethodsControl or streptozotocin-induced diabetic rats were either untreated or treated with NAC (1.5 g/kg/day, NAC) by oral gavage for 4 weeks. Rats in subgroup were randomly assigned to receive 30 min of left anterior descending artery ligation followed by 2 h of reperfusion. Isolated rat cardiomyocytes or H9C2 cells were exposed to low glucose (LG, 5.5 mmol/L) or high glucose (HG, 25 mmol/L) for 36 h before being subjected to 4 h of hypoxia followed by 4 h of reoxygenation (H/R).ResultsNAC treatment ameliorated myocardial dysfunction and cardiac hypertrophy, and attenuated myocardial I/R injury and post-ischemic cardiac dysfunction in diabetic rats. NAC attenuated the reductions of NO, Cav-3 and phosphorylated eNOS and mitigated the augmentation of O2 −, nitrotyrosine and 15-F2t-isoprostane in diabetic myocardium. Immunofluorescence analysis demonstrated the colocalization of Cav-3 and eNOS in isolated cardiomyocytes. Immunoprecipitation analysis revealed that diabetic conditions decreased the association of Cav-3 and eNOS in isolated cardiomyocytes, which was enhanced by treatment with NAC. Disruption of caveolae by methyl-β-cyclodextrin or Cav-3 siRNA transfection reduced eNOS phosphorylation. NAC treatment attenuated the reductions of Cav-3 expression and eNOS phosphorylation in HG-treated cardiomyocytes or H9C2 cells. NAC treatment attenuated HG and H/R induced cell injury, which was abolished during concomitant treatment with Cav-3 siRNA or eNOS siRNA.ConclusionsHyperglycemia-induced inhibition of eNOS activity might be consequences of caveolae dysfunction and reduced Cav-3 expression. Antioxidant NAC attenuated myocardial dysfunction and myocardial I/R injury by improving Cav-3/eNOS signaling.

Nicorandil alleviates apoptosis in diabetic cardiomyopathy through PI3K/Akt pathway

“…It is known that the production of NO is reduced and eNOS activity is weakened in the environment of hyperglycaemia. 28 These changes can cause endoplasmic reticulum stress and inflammatory reaction in cardiomyocytes, which promote hypertrophy of cardiomyocyte and apoptosis in the heart and accelerate the process of DCM. 29 As a NO donor, nicorandil can not only increase NO.…”

Myocyte membrane and microdomain modifications in diabetes: determinants of ischemic tolerance and cardioprotection

“…While there are few analyses of cardiac caveolar architecture and density in DM, significant changes in constituent caveolins and cavins are observed and likely disrupt caveolae function and formation. Hyperglycemia may suppress myocardial caveolin-3 in a PKCβ2 dependent manner [ 250 ] and H9c2 cardiomyoblast caveolin-3 in an oxidant-dependent manner [ 275 ], while hyperinsulinemia also depresses caveolar caveolin-3 in H9c2 cells [ 254 ]. Moreover, saturated fats reduce cardiac caveolin-3 [ 276 ], as does aging [ 277 ], whereas PUFA supplementation can up-regulate caveolin-3 expression [ 278 ].…”

“…Nonetheless, the acuteness of STZ-induced hyperglycemia and variable ischemic tolerance in these T1DM models raise questions regarding relevance: paradoxical cardioprotection in the initial weeks in rat T1DM models [ 2 , 84 , 293 ] is not relevant to the ischemic intolerance observed in chronic disease and T2DM. Hyperglycemia also acutely depresses caveolin-3 expression in cardiac myoblasts [ 275 ], and hyperinsulinemia suppresses caveolar levels of caveolin-3 in H9c2 myoblasts, which may dysregulate Akt-dependent InsR signaling [ 254 ]. No study has comprehensively assessed mechanistic involvement of caveolin-3 in the cardiac sequelae of T2DM, with only a single report of an insignificant fall in cardiac Cav3 mRNA in the non-obese GK rat model [ 294 ].…”

Topical combination of meldonium and N‐acetyl cysteine relieves allodynia in rat models of CRPS‐1 and peripheral neuropathic pain by enhancing NO‐mediated tissue oxygenation

“…Meldonium also has an acute, carnitine‐independent effect of increasing vascular NO levels (Sesti et al, ; Sjakste et al, , ; Zhu et al, ). N‐acetyl cysteine (NAC) is a precursor of the potent anti‐oxidant glutathione that also stimulates endothelial NO production and sustains its level by neutralizing NO‐consuming oxidative free radicals (Bavarsad Shahripour, Harrigan, & Alexandrov, ; Millea, ; Su et al, ; Xia, Liu, et al, ; Xia, Nagareddy, Guo, Zhang, & McNeill, ). By replenishing glutathione, it alleviates oxidative stress in different tissues including vascular endothelial and smooth muscle cells (Rodrigues et al, ).…”

“…Meldonium also has an acute, carnitine-independent effect of increasing vascular NO levels (Sesti et al, 2006;Sjakste et al, 2005Sjakste et al, , 2004Zhu et al, 2013). N-acetyl cysteine (NAC) is a precursor of the potent anti-oxidant glutathione that also stimulates endothelial NO production and sustains its level by neutralizing NO-consuming oxidative free radicals (Bavarsad Shahripour, Harrigan, & Alexandrov, 2014;Millea, 2009;Su et al, 2016;Xia, Liu, et al, 2006a;Xia, Nagareddy, Guo, Zhang, & McNeill, CRPS and peripheral neuropathic pain, this work showcases the analgesic potential of locally targeting microvascular dysfunction and tissue ischemia/hypoxia in these conditions, with emphasis on the role of NO.…”