calpain and Ventricular-Dysfunction--Left

To explore the effects of captopril on calpain‑mediated apoptosis of myocardial cells and cardiac function in diabetic rats, 30 adult male Sprague‑Dawley rats were randomly divided into three groups: Negative control (NC group), untreated diabetic rats (DM group) and diabetic rats treated with captopril (Cap group). Diabetes was induced by streptozotocin injection. Captopril was intragastrically administered at a daily dose of 50 mg/kg for 12 weeks; the NC and DM groups received an equivalent volume of saline. After 12 weeks of treatment, left ventricular systolic pressure (LVSP), left ventricular end‑diastolic pressure (LVDEP), maximal rate of left ventricular pressure increase (+dp/dtmax), maximal rate of left ventricular pressure decrease (‑dp/dtmax) and left ventricular mass index (LVMI) were measured. The levels of calpain‑1, calpain‑2, B‑cell lymphoma (Bcl)‑2, Bcl‑2 associated protein X (Bax) and total caspase‑3 were detected in cardiac tissue by western blot analysis. The apoptotic index (AI) was assessed with a terminal deoxynucleotidyl transferase‑mediated dUTP nick‑end labeling assay. The ultrastructure of cardiac tissue was determined by transmission electron microscopy. Compared with the NC group, LVDEP and LVMI were increased, whereas LVSP, +dp/dtmax and ‑dp/dtmax were decreased in the DM group. In the Cap group, LVDEP and LVMI were decreased, whereas LVSP, +dp/dtmax and ‑dp/dtmax were increased compared with the DM group. Bcl‑2 protein expression was decreased, whereas the levels of calpain‑1, calpain‑2, Bax and total caspase‑3 protein were increased in the DM group, compared with the NC group. Cap treatment increased Bcl‑2 protein expression and decreased calpain‑1, calpain‑2, Bax and total caspase‑3 protein expression compared with the DM group. Additionally, the AI was increased in the DM group compared with the NC group, and decreased in the Cap group compared with the DM group. Furthermore, ultrastructural examination demonstrated that myocardial cell injury was reduced in the Cap group compared with the DM group. Therefore, captopril improved myocardial structure and ventricular function, by inhibiting calpain‑1 and calpain‑2 activation, increasing Bcl‑2 expression, reducing Bax expression and subsequently inhibiting caspase‑3‑dependent apoptosis.

Topics: Animals; Apoptosis; bcl-2-Associated X Protein; Calpain; Captopril; Caspase 3; Diabetes Mellitus, Experimental; Disease Models, Animal; Gene Expression Regulation; Heart; Humans; Myocytes, Cardiac; Proto-Oncogene Proteins c-bcl-2; Rats; Ventricular Dysfunction, Left

The activation of the calpain system is involved in the repair process following myocardial infarction (MI). However, the impact of the inhibition of calpain by calpastatin, its natural inhibitor, on scar healing and left ventricular (LV) remodeling is elusive. Male mice ubiquitously overexpressing calpastatin (TG) and wild-type (WT) controls were subjected to an anterior coronary artery ligation. Mortality at 6 wk was higher in TG mice (24% in WT vs. 44% in TG, P < 0.05) driven by a significantly higher incidence of cardiac rupture during the first week post-MI, despite comparable infarct size and LV dysfunction and dilatation. Calpain activation post-MI was blunted in TG myocardium. In TG mice, inflammatory cell infiltration and activation were reduced in the infarct zone (IZ), particularly affecting M2 macrophages and CD4(+) T cells, which are crucial for scar healing. To elucidate the role of calpastatin overexpression in macrophages, we stimulated peritoneal macrophages obtained from TG and WT mice in vitro with IL-4, yielding an abrogated M2 polarization in TG but not in WT cells. Lymphopenic Rag1(-/-) mice receiving TG splenocytes before MI demonstrated decreased T-cell recruitment and M2 macrophage activation in the IZ day 5 after MI compared with those receiving WT splenocytes. Calpastatin overexpression prevented the activation of the calpain system after MI. It also impaired scar healing, promoted LV rupture, and increased mortality. Defective scar formation was associated with blunted CD4(+) T-cell and M2-macrophage recruitment.

Topics: Animals; Calcium-Binding Proteins; Calpain; CD4-Positive T-Lymphocytes; Chemotaxis, Leukocyte; Disease Models, Animal; Enzyme Activation; Genotype; Heart Rupture, Post-Infarction; Homeodomain Proteins; Lymphocyte Activation; Macrophage Activation; Macrophages; Male; Mice, Inbred C57BL; Mice, Knockout; Myocardial Infarction; Myocardium; Phenotype; Time Factors; Up-Regulation; Ventricular Dysfunction, Left; Ventricular Function, Left; Ventricular Remodeling; Wound Healing

We have previously indicated that a new soluble calpain inhibitor, SNJ-1945 (SNJ), attenuates cardiac dysfunction after cardioplegia arrest-reperfusion by inhibiting the proteolysis of α-fodrin in in vitro study. Nevertheless, the in vivo study design is indispensable to explore realistic therapeutic approaches for clinical use. The aim of the present in situ study was to investigate whether SNJ attenuated left ventricular (LV) dysfunction (stunning) after mild ischemic-reperfusion (mI-R) in rat hearts. SNJ (60 μmol/l, 5 ml i.p.) was injected 30 min before gradual and partial coronary occlusion at proximal left anterior descending artery. To investigate LV function, we obtained curvilinear end-systolic pressure-volume relationship by increasing afterload 60 min after reperfusion. In the mI-R group, specific LV functional indices at midrange LV volume (mLVV), end-systolic pressure (ESP(mLVV)), and pressure-volume area (PVA(mLVV): a total mechanical energy per beat, linearly related to oxygen consumption) significantly decreased, but SNJ reversed these decreases to time control level. Furthermore, SNJ prevented the α-fodrin degradation and attenuated degradation of Ca(2+) handling proteins after mI-R. Our results indicate that improvements in LV function following mI-R injury are associated with inhibition of the proteolysis of α-fodrin in in situ rat hearts. In conclusion, SNJ should be a promising tool to protect the heart from the stunning.

Topics: Animals; Biomechanical Phenomena; Blotting, Western; Calcium; Calpain; Carbamates; Cardiotonic Agents; Carrier Proteins; Cysteine Proteinase Inhibitors; Disease Models, Animal; Male; Microfilament Proteins; Myocardial Reperfusion Injury; Myocardium; Oxygen Consumption; Rats; Rats, Wistar; Stroke Volume; Time Factors; Ventricular Dysfunction, Left; Ventricular Function, Left; Ventricular Pressure

Fetal cardiac surgery might improve the prognosis of certain complex congenital heart defects that have significant associated mortality and morbidity in utero or after birth. An important step in translating fetal cardiac surgery is identifying potential mechanisms leading to myocardial dysfunction after bypass. The hypothesis was that fetal cardiac bypass results in myocardial dysfunction, possibly because of perturbation of calcium cycling and contractile proteins.. Midterm sheep fetuses (n = 6) underwent 30 minutes of cardiac bypass and 120 minutes of monitoring after bypass. Sonomicrometric and pressure catheters inserted in the left and right ventricles measured myocardial function. Cardiac contractile and calcium cycling proteins, along with calpain, were analyzed by means of immunoblotting.. Preload recruitable stroke work (slope of the regression line) was reduced at 120 minutes after bypass (right ventricle: baseline vs 120 minutes after bypass, 38.6 ± 6.8 vs 20.4 ± 4.8 [P = .01]; left ventricle: 37 ± 7.3 vs 20.6 ± 3.9, respectively [P = .01]). Tau (in milliseconds), a measure of diastolic relaxation, was increased in both ventricles (right ventricle: baseline vs 120 minutes after bypass, 32.7 ± 4.5 vs 67.8 ± 9.4 [P < .01]); left ventricle: 26.1 ± 3.2 vs 63.2 ± 11.2, respectively [P = .01]). Cardiac output was lower and end-diastolic pressures were higher in the right ventricle, but not in the left ventricle, after bypass compared with baseline values. Right ventricular troponin I was degraded by increased calpain activity, and protein levels of sarco(endo)plasmic reticulum calcium ATPase were reduced in both ventricles.. Fetal cardiac bypass was associated with myocardial dysfunction and disruption of calcium cycling and contractile proteins. Minimizing myocardial dysfunction after cardiac bypass is important for successful fetal surgery to repair complex congenital heart defects.

Topics: Animals; Calpain; Cardiac Surgical Procedures; Cardiopulmonary Bypass; Excitation Contraction Coupling; Female; Fetal Heart; Models, Animal; Myocardial Contraction; Pregnancy; Sarcoplasmic Reticulum Calcium-Transporting ATPases; Sheep; Time Factors; Troponin I; Ventricular Dysfunction, Left; Ventricular Dysfunction, Right; Ventricular Function, Left; Ventricular Function, Right; Ventricular Pressure

We have previously indicated that calpain inhibitor-1 prevents the heart from ischemia- reperfusion injury associated with the impairment of total Ca(2+) handling by inhibiting the proteolysis of alpha-fodrin. However, this inhibitor is insoluble with water and inappropriate for clinical application. The aim of the present study was to investigate the protective effect of a newly developed calpain inhibitor, SNJ-1945 (SNJ), with good aqueous solubility on left ventricular (LV) mechanical work and energetics in the cross-circulated rat hearts. SNJ (150 microM) was added to KCl (30 meq) cardioplegia (CP). Mean end-systolic pressure at midrange LV volume (ESP(mLVV)) and systolic pressure-volume area (PVA) at mLVV (PVA(mLVV); a total mechanical energy per beat) were hardly changed after CP plus SNJ arrest-reperfusion (post-CP + SNJ), whereas ESP(mLVV) and PVA(mLVV) in post-CP group were significantly (P < 0.01) decreased. Mean myocardial oxygen consumption for the total Ca(2+) handling in excitation-contraction coupling did not significantly decrease in post-CP + SNJ group, whereas it was significantly (P < 0.01) decreased in post-CP group. The mean amounts of 145- and 150-kDa fragments of alpha-fodrin in the post-CP group were significantly larger than those in normal and post-CP + SNJ groups. In contrast, the mean amounts of L-type Ca(2+) channel and sarcoplasmic reticulum Ca(2+)-ATPase were not significantly different among normal, post-CP, and post-CP + SNJ groups. Our results indicate that soluble SNJ attenuates cardiac dysfunction due to CP arrest-reperfusion injury associated with the impairment of the total Ca(2+) handling in excitation-contraction coupling by inhibiting the proteolysis of alpha-fodrin.

Topics: Animals; Calcium; Calcium Channels, L-Type; Calpain; Carbamates; Cardiotonic Agents; Carrier Proteins; Disease Models, Animal; Heart Arrest, Induced; Male; Microfilament Proteins; Myocardial Reperfusion Injury; Oxygen Consumption; Rats; Rats, Wistar; Sarcoplasmic Reticulum Calcium-Transporting ATPases; Ventricular Dysfunction, Left

Calpains, a family of Ca2+-dependent cysteine proteases, are activated during myocardial ischemia and reperfusion. This study investigates the cardioprotective effects of calpain inhibition on infarct size and global hemodynamics in an ischemia/reperfusion model in pigs, using the calpain inhibitor A-705253. The left anterior descending coronary artery was occluded for 45 min and reperfused for 6 h. A bolus of 1.0 mg/kg A-705253 or distilled water was given intravenously 15 min prior to induction of ischemia and a constant plasma level of A-705253 was maintained by continuous infusion of 1.0 mg/kg A-705253 during reperfusion. Infarct size was assessed histochemically using triphenyltetrazolium chloride staining. Macromorphometric findings were verified by light microscopy on hematoxylin-eosin- and Tunel-stained serial sections. Global hemodynamics, including the first derivate of the left ventricular pressure (dP / dtmax), were measured continuously throughout the experiment. A-705253 reduced the infarct size by 35% compared to controls (P < 0.05). Hemodynamic alterations, including heart rate, aortic blood pressure, central venous pressure and left atrial pressure, were attenuated mainly during ischemia and the first 2 h during reperfusion by A-705253. Cardiac function improved, as determined by dP / dtmax, after 6 h of reperfusion (P < 0.003). Our results demonstrate that myocardial protection can be achieved by calpain inhibition, which decreases infarct size and improves left ventricular contractility and global hemodynamic function. Hence, the calpain-calpastatin system might play an important pathophysiological role in porcine myocardial ischemia and reperfusion damage and A-705253 could be a promising cardioprotective agent.

Topics: Animals; Benzamides; Blood Pressure; Calpain; Cardiotonic Agents; Disease Models, Animal; Heart Rate; Hemodynamics; Infusions, Intravenous; Injections, Intravenous; Myocardial Contraction; Myocardial Infarction; Myocardial Reperfusion Injury; Sus scrofa; Ventricular Dysfunction, Left

A hypothesis is presented that explains one of the mechanisms by which a heart starts to fail. The hypothesis is that myocardial function of an overloaded or otherwise stressed heart may become impaired by cellular troponin degradation in vital cardiomyocytes. The troponins (I, T and C) regulate actin-myosin interaction, thereby controlling contraction and relaxation. Troponins have been shown to be targets of activated calpain I. This enzyme, that is activated by elevated intracellular Ca2+ concentrations, such as occurs during ischemia, degrades troponins, leading to impaired interaction between actin and myosin and, thereby, less contractile force. Several reports about troponin degradation in viable myocardium support this hypothesis. Also, results are discussed that demonstrate the presence of immunoreactive troponin fragments in plasma under conditions in which myocardial necrosis can be excluded or is unlikely. The hypothesis implicates that release of troponin and/or troponin degradation products is not specific for necrotic myocardium but may occur from viable myocardium as well. To test this hypothesis, several lines of research are suggested. If the hypothesis is not rejected in the near future, the concept that a positive troponin test reflects 'even microscopic zones of myocardial necrosis' as used by the Joint ESC/ACC Committee for the Redefinition of Myocardial Infarction [The Joint European Society of Cardiology/American College of Cardiology Committee for the Redefinition of Myocardial Infarction. Myocardial infarction redefined-A consensus document of the Joint European Society of Cardiology/American College of Cardiology Committee for the Redefinition of Myocardial Infarction. Eur Heart J 2000;21:1502-1513], should be withdrawn.

Topics: Animals; Calcium; Calpain; Enzyme Activation; Heart Failure; Humans; Myocardial Stunning; Myocytes, Cardiac; Physical Endurance; Troponin; Ventricular Dysfunction, Left

Calpains are ubiquitous neutral cysteine proteases. Although their physiological role has yet to be clarified, calpains seem to be involved in the expression of cell adhesion molecules. Therefore, we hypothesized that a selective calpain inhibitor could attenuate polymorphonuclear (PMN) leukocyte-induced myocardial ischemia-reperfusion (I/R) injury. We examined the effects of the calpain inhibitor Z-Leu-Leu-CHO in isolated ischemic (20 min) and reperfused (45 min) rat hearts perfused with PMNs. Z-Leu-Leu-CHO (10 and 20 microM, respectively) significantly improved left ventricular developed pressure (LVDP) (P < 0.01) and the maximal rate of development of LVDP (P < 0.01) compared with I/R hearts perfused without Z-Leu-Leu-CHO. In addition, Z-Leu-Leu-CHO significantly reduced PMN adherence to the vascular endothelium and subsequent infiltration into the postischemic myocardium (P < 0.01). Moreover, Z-Leu-Leu-CHO significantly inhibited expression of P-selectin on the rat coronary microvascular endothelium (P < 0.01). These results provide evidence that Z-Leu-Leu-CHO significantly attenuates PMN-mediated I/R injury in the isolated perfused rat heart to a significant extent via downregulation of P-selectin expression.

Topics: Animals; Calpain; Cell Adhesion; Cysteine Proteinase Inhibitors; Enzyme Inhibitors; In Vitro Techniques; Myocardial Reperfusion Injury; Neutrophils; Rats; Rats, Sprague-Dawley; Ventricular Dysfunction, Left; Ventricular Function, Left

The aim of the present study was to examine the mechanisms of Ca2+ overload-induced contractile dysfunction in rat hearts independent of ischemia and acidosis. Experiments were performed on 30 excised cross-circulated rat heart preparations. After hearts were exposed to high Ca2+, there was a contractile failure associated with a parallel downward shift of the linear relation between myocardial O(2) consumption per beat and systolic pressure-volume area (index of a total mechanical energy per beat) in left ventricles from all seven hearts that underwent the protocol. This result suggested a decrease in O(2) consumption for total Ca2+ handling in excitation-contraction coupling. In the hearts that underwent the high Ca2+ protocol and had contractile failure, we found marked proteolysis of a cytoskeleton protein, alpha-fodrin, whereas other proteins were unaffected. A calpain inhibitor suppressed the contractile failure by high Ca2+, the decrease in O(2) consumption for total Ca2+ handling, and membrane alpha-fodrin degradation. We conclude that the exposure to high Ca2+ may induce contractile dysfunction possibly by suppressing total Ca2+ handling in excitation-contraction coupling and degradation of membrane alpha-fodrin via activation of calpain.

Topics: Animals; Ankyrins; Blood Pressure; Calcium; Calpain; Cardiac Volume; Carrier Proteins; Cell Membrane; Connexin 43; Disease Models, Animal; Electrocardiography; Enzyme Inhibitors; In Vitro Techniques; Male; Microfilament Proteins; Myocardial Contraction; Myocardium; Oxygen Consumption; Peptide Hydrolases; Rats; Rats, Wistar; Systole; Troponin I; Ventricular Dysfunction, Left