Transcriptional and translational regulation of calpain in the rat heart after myocardial infarction – effects of AT₁ and AT₂ receptor antagonists and ACE inhibitor

Abstract

1 Recent studies demonstrated that the cardiac calpain system is activated during ischaemic events and is involved in cardiomyocyte injury. The aim of this study was to investigate the contribution of AT 1 and AT 2 receptors in the regulation of calpain-mediated myocardial damage following myocardial infarction (MI). 2 Infarcted animals were treated either with placebo, the ACE inhibitor ramipril (1 mg kg 71 d 71 ), the AT 1 receptor antagonist valsartan (10 mg kg 71 d 71 ) or the AT 2 receptor antagonist PD 123319 (30 mg kg 71 d 71 ). Treatment was started 7 days prior to surgery. On day 1, 3, 7 and 14 after MI, gene expression and protein levels of calpain I, II and calpastatin were determined in left ventricular free wall (LVFW) and interventricular septum (IS). At day 3 and 14 post MI, morphological investigations were performed. 3 Calpain I mRNA expression and protein levels were increased in IS 14 days post MI, whereas mRNA expression and protein levels of calpain II were maximally increased in LVFW 3 days post MI. Ramipril and valsartan decreased mRNA and protein up-regulation of calpain I and II, and reduced infarct size and interstitial ®brosis. PD 123319 did not a ect calpain I or II up-regulation in the infarcted myocardium, but decreased interstitial ®brosis. Calpastatin expression and translation were not a ected by AT receptor antagonists or ACE inhibitor. 4 Our data demonstrate a distinct, temporary-spatial up-regulation of calpain I and II following MI confer with the hypothesis of calpain I being involved in cardiac remodelling in the late and calpain II contributing to cardiac tissue damage in the early phase of MI. The up-regulation of calpain I and II is partly mediated via the AT 1 receptor and can be reduced by ACE inhibitors and AT 1 receptor antagonists. British Journal of Pharmacology (2001) 132, 767 ± 777 Keywords: Myocardial infarction; renin-angiotensin-system; calpain-system Abbreviations: ACE, angiotensin converting enzyme; AT 1 , angiotensin type 1 receptor; AT 2 , angiotensin type 2 receptor; [Ca 2+ ] i , intracellular calcium concentration; Calp I, calpain isoform I or m-calpain; Calp II, calpain isoform II or m-calpain; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; IS, interventricular septum; LV, left ventricle; LVFW, left ventricular free wall; MAP, mean arterial blood pressure; MI, myocardial infarction; RAS, renin-angiotensin system; RV, right ventricle IntroductionThe calpain system is an intracellular, strongly Ca 2+ -dependent, neutral cysteine protease system existing in all mammalian and in some non-mammalian cells. The calpain family consists of ubiquitous and tissue speci®c isoforms of calpains and of the naturally occurring endogenous inhibitor, calpastatin. The best characterized calpains are the widely distributed isoenzymes, calpain I or m-calpain, which requires micromolar intracellular calcium ([Ca 2+ ] i )-concentrations for half-maximum activity, and calpain II or m-calpain, which requires millimolar [Ca 2+ ] i -concentrations for activation, respective...

Anthracyclines Induce Calpain-dependent Titin Proteolysis and Necrosis in Cardiomyocytes

“…Collectively, however, our observations that doxorubicin decreased the expression of calpain-I, induced autolysis of calpain-II to a more proteolytically active form, and that the calpain-II/calpastatin ratio was elevated early relative to calpain-I lead us to speculate that calpain-II may be predominantly responsible for the doxorubicin-induced increase in total calpain activity. This observation is similar to what has been observed early after ischemic cardiac injury, where increases in calpain-II activity, mRNA, and protein levels were much greater compared with those in calpain-I (56,57). Interestingly, a reduction in calpain-I activity and in the rate of calpain-I autolysis has been reported in a neuroblastoma cell line treated with doxorubicin (58).…”

Activity profile of calpains I and II in chronically infarcted rat myocardium – influence of the calpain inhibitor CAL 9961

“…The increase in calpain I activity 14 days post MI was accompanied by a compensated cardiac hypertrophy as evidenced by an increase in THW/BW. Our results are in agreement with ®ndings of previous studies showing a transcriptional and translational up-regulation of calpain I in the non-infarcted hypertrophied rat myocardium (Sandmann et al, 2001). Additionally, studies on rats demonstrated an increase in diastolic myocardial [Ca 2+ ] i in ventricular myocytes of the failing heart which were associated with cardiac hypertrophy following pressure overload (Gwathmey & Morgan, 1985;Steenbergen et al, 1987b) and MI (Sandmann et al, 1999).…”

“…The resulting Ca 2+ -overload might activate calpain II which, subsequently, induces myocyte injury and myocardial necrosis. Additionally, in previous experiments, we demonstrated an up-regulation of calpain II in the infarcted region (Sandmann et al, 2001) and Mellgren et al (1988) reported a disappearance of the endogenous calpain inhibitor, calpastatin, in the ischaemic area within the ®rst hours post MI. Thus, it can be speculated that the calpain-calpastatinratio might be shifted to more calpain II in the ischaemic myocardium, leading to abnormal protein degradation and increased myocardial damage following MI.…”

Angiotensin II Peptide Vaccine Protects Ischemic Brain Through Reducing Oxidative Stress

“…Ang II increased the intracellular Ca 2+ , 36 and Ang II may have directly regulated the calpain activity in the brain, as reported in other types of tissues, such as aorta, 37 kidney, 38 and cardiomyocyte. 39 In the present study, the cerebroprotective effects of Ang II vaccine lasted 15 days after the vaccination. Although we could not examine whether the effects were preserved >15 days because of the limitation of the stroke model, the preventive effects of Ang II peptide vaccine may have lasted up to several months because we observed the continuing existence of anti-Ang II antibody in serum at least ≤3 months after immunization.…”