Low-Dose Spironolactone Prevents Apoptosis Repressor With Caspase Recruitment Domain Degradation During Myocardial Infarction

Abstract

Abstract-Low-dose mineralocorticoid receptor antagonists reduce morbidity and mortality in patients with heart failure and myocardial infarction, despite normal plasma aldosterone levels. Since apoptosis plays an important role in heart failure and postinfarction left ventricular remodeling, we examined whether low-dose mineralocorticoid receptor antagonists modulate cardiomyocyte death by regulating the apoptosis repressor protein apoptosis repressor with caspase recruitment domain to lessen the extent of apoptosis. Hearts from adult male Sprague-Dawley rats were subjected to regional ischemia followed by reperfusion ex vivo, with mineralocorticoid receptor antagonists added to perfusates before ischemia. Low-dose spironolactone (10 nmol/L) or eplerenone (100 nmol/L) significantly reduced infarct size. Spironolactone also prevented cleavage of the apoptotic chromatin condensation inducer in the nucleus and of the inhibitor of caspase-activated DNAse induced by ischemia-reperfusion, thereby abolishing chromatin condensation and internucleosomal cleavage. Ischemia-reperfusion-induced activation of caspases 2, 3, and 9, but not caspase 8, was prevented by spironolactone, suggesting targeted regulation of the intrinsic pathway. Low-dose spironolactone and eplerenone prevented loss of the apoptosis repressor with the caspase recruitment domain and reduced myocyte death. In H9c2 cells, mineralocorticoid receptor activation by aldosterone resulted in apoptosis repressor with caspase recruitment domain degradation and enhanced apoptosis; these actions were prevented by coadministration of spironolactone. Using a triple lysine mutant we identified that aldosterone enhances posttranscriptional degradation of the apoptosis repressor with a caspase recruitment domain via the ubiquitin-proteasomal pathway. Our data demonstrate that low-dose mineralocorticoid receptor antagonists reduce infarct size and apoptosis in the reperfused myocardium by preventing the apoptosis repressor with caspase recruitment domain degradation. Key Words: myocardial infarction Ⅲ apoptosis Ⅲ ischemia Ⅲ reperfusion injury Ⅲ heart failure Ⅲ cardiovascular disease M ortality and morbidity after acute myocardial infarction remain high, despite rapid reperfusion by percutaneous coronary intervention, and additional therapeutic strategies that reduce infarct size are needed.1 Ischemia alters redox state triggering apoptosis and progressive loss of cardiomyocytes during and after myocardial infarction, which, in turn, contributes to developing congestive cardiac failure.2 Lowdose mineralocorticoid receptor (MR) antagonists have been shown clinically to reduce blood pressure, 3,4 particularly in resistant hypertension, and to substantially increase survival in heart failure, 5 heart failure after myocardial infarction, 6 and chronic systolic heart failure with mild symptoms. 7Significant benefits follow when eplerenone is administered early (Ͻ7 days) after myocardial infarction 8 and experimentally at reperfusion. 9,10 Interestingly, MR antagonists add...

Nicotine plus a high-fat diet triggers cardiomyocyte apoptosis

“…It also indicates the involvement of the mitochondria-dependent death pathway in nicotine-plus-HFD-induced CM apoptosis. This is consistent with the previous report showing the involvement of the mitochondria-dependent pathway in I-R-induced CM apoptosis (Le et al 2012). The data reported herein also indicate that the nicotine-plus-HFD-induced CM apoptosis coincides with the increased expression of FGF21 and SIRT1.…”

“…One possibility is that caspase 2 is dispensable for nicotine-plus-HFD-induced CM apoptosis. A growing body of evidence indicates that an apoptosis repressor with caspase recruitment domain (ARC) is an endogenous apoptosis repressor protein that is highly expressed in cardiac tissue and that has the ability to inhibit ischemia-reperfusion (I-R)-induced CM apoptosis by targeting the activation of the intrinsic pathway at multiple points (Zhang and Herman 2006; Ludwig-Galezowski et al 2011; Le et al 2012). Conversely, the preservation of ARC levels is sufficient for CM viability after oxidative stress (Nam et al 2007) or infarction (Foo et al 2007).…”

“…Conversely, the preservation of ARC levels is sufficient for CM viability after oxidative stress (Nam et al 2007) or infarction (Foo et al 2007). Available evidence further suggests that, in addition to ARC, other anti-apoptotic proteins such as BCL-2 and XIAP must be decreased for CM apoptosis to proceed, at least during myocardial I-R injury (Le et al 2012). ARC activation also counteracts the pro-apoptotic protein BAX (Gustafsson et al 2002).…”

Aldosterone Blockade Reduces Mortality without Changing Cardiac Remodeling in Spontaneously Hypertensive Rats

“…In infarcted rodents, they have improved cardiac remodeling [14,15,19,53,54], whereas in dogs with rapid ventricular pacing-induced heart failure, eplerenone failed to prevent LV changes [55]. In SHR, the aldosterone blockade was evaluated during the cardiac remodeling process but not during heart failure development.…”

Mineralocorticoid receptor antagonists: emerging roles in cardiovascular medicine

“…The second question, ie, of the relatively low doses of spironolactone/eplerenone required for substantial effects on mortality and morbidity when added to conventional agents, also appears to be answered by studies using the same ischemia-perfusion experimental model 23,25. When spironolactone alone was used as a control in the aldosterone/cortisol studies cited above, it was noted that it lessened both the area at risk and infarct size, presumably by protecting cells in the infarct margins against apoptosis.…”