Isoproterenol induces primary loss of dystrophin in rat hearts: correlation with myocardial injury

Single-molecule imaging of aquaporin-4 array dynamics in astrocytes

Aquaporin-4 (AQP4) facilitates water transport across astrocytic membranes in the brain, forming highly structured nanometric arrays. AQP4 has a central role in regulating cerebrospinal fluid (CSF) circulation and facilitating the clearance of solutes from the extracellular space of the brain. Adrenergic signaling has been shown to modulate the volume of the extracellular space of the brain via AQP4 localized at the end-feet of astrocytes, but the mechanisms by which AQP4 regulates CSF inflow and outflow in the brain remain elusive. Using advanced imaging techniques, including super-resolution microscopy and single-molecule tracking, we investigated the hypothesis that β-adrenergic receptor activation induces cellular changes that regulate AQP4 array size and mobility, thus influencing water transport in the brain. We report that the β-adrenergic agonist, isoproterenol hydrochloride, decreases AQP4 array size and enhances its membrane mobility, while hyperosmotic conditions induce the formation of larger, less mobile arrays. These findings reveal that AQP4 arrays are dynamic structures, responsive to adrenergic signals and osmotic changes, highlighting a novel regulatory mechanism of water transport in the brain. Our results provide insights into the molecular control of CSF circulation and extracellular brain space volume, laying the groundwork for understanding the relationship between astrocyte water transport, sleep physiology, and neurodegeneration.

Sesamol Supplementation Mitigates Isoproterenol-Induced Cardiac Toxicity in Rats by Stabilizing Cardiac Mitochondrial and Lysosomal Enzymes

The current investigation was intended to evaluate the antimyocardial ischemic effects of sesamol on lactate dehydrogenase (LDH) isoenzymes, DNA damage, and mitochondrial and lysosomal enzyme activities in isoproterenol (ISO)-induced myocardial infarction (MI) in male albino Wistar strain rats. Rats that received ISO (85 mg/kg body weight (B.W) subcutaneously) for the first 2 consecutive days showed significant reduction in the activities of tricarboxylic acid (TCA) cycle enzymes (isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, malate dehydrogenase, and succinate dehydrogenase) and respiratory chain enzymes (cytochrome c oxidase and nicotinamide adenine dinucleotide hydrogen (NADH) dehydrogenase) in the heart mitochondria. The activities of the lysosomal enzymes (α-and β-glucosidases, α and β-galactosidases, β-glucuronidase and β-N-acetyl glucosaminidase and cathepsin-B and cathepsin-D) were increased significantly in the heart homogenate of ISO-induced MI rats. ISO injection also increased the % of tail DNA, tail length, and tail moment and decreased the % of head DNA. Pretreatment with sesamol (50 mg/kg B.W) every day for a period of 9 days prevented the above abnormalities induced by ISO. In conclusion, it can be inferred that administration of sesamol has a potent beneficial role against ISO-induced damage to the mitochondria, lysosomes, and DNA, thereby preventing MI.

Effect of chronic alcohol consumption on myocardial apoptosis in the rat model of isoproterenol-induced myocardial injury and investigation on the cardioprotective role of calpain inhibitor 1

We investigated the presence of myocardial apoptosis on isoproterenol (ISO)-induced myocardial injury (MI) after long-term high dose alcohol consumption and examined the antiapoptotic role of calpain inhibitor 1. Male Wistar Albino rats (n = 108) were divided into six groups: Control, alcohol (ethanol was given during 30 days for chronic alcohol consumption), MI (150 mg/kg ISO injection at last two days of alcohol consumption), alcohol + MI, alcohol + MI + calpain inhibitor 1 (10 mg/kg inhibitor was injected at 15 min before ISO injections) and Dimethyl Sulfoxide (DMSO) groups. Biochemical, histological, and morphometric methods determined apoptosis levels in the heart tissue of rats. Cytochrome c, caspase 3, and calpain levels were significantly high in alcohol, MI, and alcohol + MI groups. In contrast, mitochondrial cardiolipin content was found to be low in alcohol, MI, and alcohol + MI groups. These parameters were close to the control group in the therapy group. Histological and morphometric data have supported biochemical results. As a result of our biochemical data, myocardial apoptosis was seen in the alcohol, MI, and especially alcohol after MI groups. Calpain inhibitor 1 reduced apoptotic cell death and prevented myocardial tissue injury in these groups. The efficiency of calpain inhibitor was very marked in MI after long-term high dose alcohol consumption.

Essential roles of the dystrophin-glycoprotein complex in different cardiac pathologies

The dystrophin-glycoprotein complex (DGC), situated at the sarcolemma dynamically remodels during cardiac disease. This review examines DGC remodeling as a common denominator in diseases affecting heart function and health. Dystrophin and the DGC serve as broad cytoskeletal integrators that are critical for maintaining stability of muscle membranes. The presence of pathogenic variants in genes encoding proteins of the DGC can cause absence of the protein and/or alterations in other complex members leading to muscular dystrophies. Targeted studies have allowed the individual functions of affected proteins to be defined. The DGC has demonstrated its dynamic function, remodeling under a number of conditions that stress the heart. Beyond genetic causes, pathogenic processes also impinge on the DGC, causing alterations in the abundance of dystrophin and associated proteins during cardiac insult such as ischemia-reperfusion injury, mechanical unloading, and myocarditis. When considering new therapeutic strategies, it is important to assess DGC remodeling as a common factor in various heart diseases. The DGC connects the internal F-actin-based cytoskeleton to laminin-211 of the extracellular space, playing an important role in the transmission of mechanical force to the extracellular matrix. The essential functions of dystrophin and the DGC have been long recognized. DGC based therapeutic approaches have been primarily focused on muscular dystrophies, however it may be a beneficial target in a number of disorders that affect the heart. This review provides an account of what we now know, and discusses how this knowledge can benefit persistent health conditions in the clinic.

Regenerative Potential of a Suspension and Spheroids of Multipotent Mesenchymal Stromal Cells from Human Umbilical Cord on the Model of Myocardial Infarction in Rats

Regenerative potential of multipotent mesenchymal stromal cells from the human umbilical cord (MMSC-UC) in the suspension and spheroid form was revealed during the progression of experimental small focal myocardial infarction in rats. In isoproterenol-induced myocardial infarction, foci of necrosis and inflammatory infiltrate and at later terms fibrosis foci were found mainly in the left ventricle of rat heart. In rats receiving MMSC-UC, destructive changes in the myocardium, fibrous scars, and inflammatory process were less pronounced. MMSC-UC also contributed to normalization of the morphofunctional parameters of the heart. Spheroids exhibited higher efficiency in comparison with cell suspension.

Protective Effects of Rocuronium Bromide on Ischemia-Reperfusion Injury in Skeletal Muscle Induced by Tourniquet in Patients Undergoing Elective Unilateral Total Knee Arthroplasty: A Prospective, Double Blind, Randomized, Controlled Study

Purpose

To investigate the effects of different doses of rocuronium on ischemia-reperfusion injury in skeletal muscle induced by tourniquet in patients undergoing elective unilateral total knee arthroplasty.

Patients and Methods

A total of 90 patients undergoing elective unilateral knee arthroplasty under general anesthesia combined with femoral nerve block were randomly divided into 3 groups: normal saline group (group S), rocuronium 0.6 mg/kg group (group L), and rocuronium 1.2 mg/kg group (group H). The primary outcome was the expression of dystrophin in skeletal muscle at 60 min after ischemia. Secondary outcomes included the concentration of malondialdehyde (MDA) and neuronal nitric oxide synthase (nNOS) in blood at 5 min and 30 min after reperfusion. In addition, thigh girth at 24 h and 48 h after operation, the leaving bed time, the incidence of tourniquet-related hypertension and short-term (3 days after operation) complications (nausea and vomiting, swelling, blister, wound infection) and long-term (3 months after operation) complications (joint instability, stiffness, nerve paralysis, pain) were recorded.

Main Results

The expression of dystrophin in the rocuronium group was higher than that in group S after ischemia (P <0.05). The concentration of MDA in the rocuronium 1.2 mg/kg group was lower at 30 min after reperfusion (P < 0.05). There was no significant difference in nNOS among groups at each time point (P > 0.05). The change of thigh girth was the smallest in the rocuronium 1.2 mg/kg group after operation (P<0.05). The leaving bed time was significantly earlier after operation in the rocuronium group than that in group S (P <0.05).

Conclusion

Rocuronium can protect skeletal muscle from ischemia-reperfusion injury induced by tourniquet. The mechanism may be related to the fact that rocuronium can reduce the loss of dystrophin in skeletal muscle and have the effects of anti-oxidation and anti-stress.

Trial Registration

The study was registered at http://www.chictr.org.cn (ChiCTR1800019221, registered on 2018-10-31).

Experimental model of acute myocardial infarction for evaluation of prevention and rehabilitation strategies in cardiovascular diseases – a pilot study

Introduction: Acute myocardial infarction (AMI) is an important acute disease of myocardial tissue, that occurs as a result of an imbalance between coronary blood supply and myocardial demand. Isoproterenol (ISO) is a synthetic catecholamine, a beta-adrenergic agonist that produces extensive biochemical, functional, and histological alterations in the heart, characteristic for AMI. The present study has been designed to identify the best dose of ISO that induces electrocardiogram (ECG) alterations, enzymatic reaction, and histopathological changes characteristic of AMI. Material and method: AMI was induced to Wistar-Bratislava white male rats, using three different subcutaneous doses of ISO (85 mg/kg bw, 100 mg/kg bw, and 150 mg/kg bw). ISO was administrated twice, with the second dose at 24h after the initial one. The ECGs were recorded at 24 hours after the last dose of ISO. Blood samples were collected for measurement of creatine kinase (CK), and CK-MB serum levels, and the hearts were excised and prepared for histopathologic examination. Results and discussions: All doses of ISO induced alterations in the ECG patterns such as increased heart rate and prolongation of QT and QTc intervals. Depression of the ST segment coupled with marked T wave inversion were observed at the doses of 100 mg/kg bw and 150 mg/kg bw of ISO. All doses of ISO induced an elevation of CK and CK-MB with highest levels observed for the dose of 150 mg/kg bw. Histopathologic examination revealed subendocardial AMI lesions for all doses tested. Conclusions: ISO in doses of 100 mg/kg and 150 mg/kg is useful for induction of infarct-like lesion on ECG, increased levels of myocardial necrosis enzymes and morphological changes characteristic for AMI.

Early dystrophin loss is coincident with the transition of compensated cardiac hypertrophy to heart failure

Hypertension causes cardiac hypertrophy, one of the most important risk factors for heart failure (HF). Despite the importance of cardiac hypertrophy as a risk factor for the development of HF, not all hypertrophied hearts will ultimately fail. Alterations of cytoskeletal and sarcolemma-associated proteins are considered markers cardiac remodeling during HF. Dystrophin provides mechanical stability to the plasma membrane through its interactions with the actin cytoskeleton and, indirectly, to extracellular matrix proteins. This study was undertaken to evaluate dystrophin and calpain-1 in the transition from compensated cardiac hypertrophy to HF. Wistar rats were subjected to abdominal aorta constriction and killed at 30, 60 and 90 days post surgery (dps). Cardiac function and blood pressure were evaluated. The hearts were collected and Western blotting and immunofluorescence performed for dystrophin, calpain-1, alpha-fodrin and calpastatin. Statistical analyses were performed and considered significant when p<0.05. After 90 dps, 70% of the animals showed hypertrophic hearts (HH) and 30% hypertrophic+dilated hearts (HD). Systolic and diastolic functions were preserved at 30 and 60 dps, however, decreased in the HD group. Blood pressure, cardiomyocyte diameter and collagen content were increased at all time points. Dystrophin expression was lightly increased at 30 and 60 dps and HH group. HD group showed decreased expression of dystrophin and calpastatin and increased expression of calpain-1 and alpha-fodrin fragments. The first signals of dystrophin reduction were observed as early as 60 dps. In conclusion, some hearts present a distinct molecular pattern at an early stage of the disease; this pattern could provide an opportunity to identify these failure-prone hearts during the development of the cardiac disease. We showed that decreased expression of dystrophin and increased expression of calpains are coincident and could work as possible therapeutic targets to prevent heart failure as a consequence of cardiac hypertrophy.

Sarcospan Regulates Cardiac Isoproterenol Response and Prevents Duchenne Muscular Dystrophy-Associated Cardiomyopathy

Background

Duchenne muscular dystrophy is a fatal cardiac and skeletal muscle disease resulting from mutations in the dystrophin gene. We have previously demonstrated that a dystrophin‐associated protein, sarcospan (SSPN), ameliorated Duchenne muscular dystrophy skeletal muscle degeneration by activating compensatory pathways that regulate muscle cell adhesion (laminin‐binding) to the extracellular matrix. Conversely, loss of SSPN destabilized skeletal muscle adhesion, hampered muscle regeneration, and reduced force properties. Given the importance of SSPN to skeletal muscle, we investigated the consequences of SSPN ablation in cardiac muscle and determined whether overexpression of SSPN into mdx mice ameliorates cardiac disease symptoms associated with Duchenne muscular dystrophy cardiomyopathy.

Methods and Results

SSPN‐null mice exhibited cardiac enlargement, exacerbated cardiomyocyte hypertrophy, and increased fibrosis in response to β‐adrenergic challenge (isoproterenol; 0.8 mg/day per 2 weeks). Biochemical analysis of SSPN‐null cardiac muscle revealed reduced sarcolemma localization of many proteins with a known role in cardiomyopathy pathogenesis: dystrophin, the sarcoglycans (α‐, δ‐, and γ‐subunits), and β1D integrin. Transgenic overexpression of SSPN in Duchenne muscular dystrophy mice (mdx^TG) improved cardiomyofiber cell adhesion, sarcolemma integrity, cardiac functional parameters, as well as increased expression of compensatory transmembrane proteins that mediate attachment to the extracellular matrix.

Conclusions

SSPN regulates sarcolemmal expression of laminin‐binding complexes that are critical to cardiac muscle function and protects against transient and chronic injury, including inherited cardiomyopathy.

Comparison of the specificity of cardiac troponin I and creatine kinase MB in isoproterenol-induced cardiotoxicity model in rats

The aim of this study was to implement the determination of cardiac markers in preclinical research at our department. For this purpose, the pathophysiological model of acute cardiotoxicity induced by high doses of isoproterenol was used. Isoproterenol hydrochloride was intraperitoneally administrated to 42 Wistar male rats at a dose of 50 mg/kg body weight. Cardiac injury was determined by assessing the concentrations of the cardiac markers (cTnI - cardiospecific troponin I and CKMB - cardiac isoenzyme creatine kinase) in the blood at predetermined time-intervals (2, 4, 6, 12, 24 and 36 h), and confirmed by ECG. Isoproterenol hydrochloride caused an elevation in the plasma concentrations of both markers. The results showed a significant difference (P< 0.01) in the concentrations of cTnI between the experimental and control groups at 2, 4, 6 and 24 h with a maximum peak between the fourth and sixth hour. However, the difference in the concentrations of CKMB between the experimental and control groups was non-significant. This experiment confirmed that cTnI is more cardiospecific than CKMB. It also revealed the possibility to use this marker in preclinical testing.

Oxidative stress markers are not associated with outcomes after pediatric heart surgery

OBJECTIVES

To investigate whether perioperative serum levels of oxidative stress markers, thiobarbituric acid reactive substances (TBARS), and carbonyl moieties are associated with outcomes in children after heart surgery.

BACKGROUND

Oxidative stress markers are increased following heart surgery with cardiopulmonary bypass (CPB) and can play a role in ischemia-reperfusion injury, but its associations with myocardial dysfunction, low cardiac output syndrome (LCOS), and outcomes are not proven.

METHODS

In a retrospective secondary analysis of a cohort study comprising 55 children (median age, 109 [2-611] days), we compared pre-, intra- and postoperative serum levels of TBARS and carbonyl moieties among patients with and without postoperative LCOS, cyanotic and acyanotic congenital heart disease (CHD), and survivors and nonsurvivors. We also assessed the independent effect of TBARS and carbonyl moieties peak levels on the mortality-adjusted hospital length of stay (aLOS).

RESULTS

Patients who developed postoperative LCOS (n = 36) were significantly younger, more frequently cyanotic, more severely ill, and underwent more complex procedures with longer CPB. However, TBARS and carbonyl moieties serum levels did not change significantly over time. Moreover, they were not significantly different in patients with or without LCOS, cyanotic and acyanotic CHD, or survivors and nonsurvivors. There was a significant correlation between TBARS and tumor necrosis factor alpha (TNF-α) peak serum levels. Neither TBARS nor carbonyl moieties peak serum levels were independently associated with aLOS.

CONCLUSIONS

In conclusion, oxidative stress markers TBARS and carbonyl moieties were not associated with the development of LCOS, the aLOS, or mortality in children after heart surgery with CPB.

[Historical and current pathophysiological concepts of stress (Tako-Tsubo) cardiomyopathy]

Tako-Tsubo cardiomyopathy (TTC), also referred to as stress cardiomyopathy (SCM), was first described in the 1990s and is characterized by transient left ventricular dysfunction. Its incidence represents 1-2% of all acute coronary syndromes (ACS). In most cases extreme emotional or physical stress precedes this syndrome. The majority of patients affected are postmenopausal women. Since its first description, various hypotheses regarding the pathophysiology of TTC have been discussed. From a historical perspective, coronary vasospasm has often been proposed as a possible cause of this disorder. However, reviews from numerous registries were able to demonstrate that coronary vasospasm plays only a minor role in the pathogenesis of TTC. Several groups showed disturbances in myocardial microcirculation and energy metabolism in the acute phase of TTC. Nevertheless, with regard to the data currently available, it cannot be differentiated whether these changes are the cause or rather the result of TTC. However, recent concepts include an excessive catecholamine overload and morphological changes which are unequivocally documented in TTC. The relation between elevated catecholamine levels and myocardial dysfunction analogous to TTC could be confirmed in animal experiments.In summary, it can be assumed that TTC is caused by an excessive cardiotoxic release of catecholamines. Ventricular dysfunction can be explained by increased numbers of β-adrenergic receptors in the apex, leading to greater vulnerability to catecholamine overload. Individual anatomical differences in the sympathoadrenergic system and distribution from β-adrenergic receptors are presumably responsible for the interindividual occurrence of wall motion abnormalities in TTC.

Protection by endogenous FGF-2 against isoproterenol-induced cardiac dysfunction is attenuated by cyclosporine A

Fibroblast growth factor-2 (FGF-2) is implicated in cardioprotection. However, previously we found that chronic elevation in cardiac FGF-2 levels in transgenic mice was associated with exaggerated, cyclosporine A-preventable, cellular infiltration after isoproterenol-induced injury, suggestive of an adverse outcome, although this was not examined with functional studies. We have now used highly sensitive tissue Doppler imaging (TDI) to evaluate cardiac functional parameters after isoproterenol administration in transgenic mice overexpressing the 18 kDa FGF-2 in the heart in vivo. Cardiac function was assessed in conscious FGF-2 transgenic and non-transgenic mice at 24 h as well as 2 and 4 weeks after isoproterenol administration, and in the absence or presence of either cyclosporine A or anti-CD3ε treatments. Isoproterenol decreased left ventricular endocardial velocity and strain rate by 47-51% at 24 h in non-transgenic mice, but to a significantly lesser extent (by 24%) in transgenic mice. While additional decreases were seen in non-transgenic mice at 2 weeks, there was no further reduction in ventricular endocardial velocity or strain rate up to 4 weeks post-treatment in FGF-2 transgenic mice. Functional improvement at 2 and 4 weeks post-isoproterenol was reduced significantly by treatment with cyclosporine A but not anti-CD3ε; the latter targets T lymphocyte activation more specifically. TDI values in the presence of chronic FGF-2 overexpression are prognostic of an improved cardiac outcome and protection from isoproterenol induced cardiac dysfunction in vivo. Our data also suggest that cyclosporine A-sensitive infiltrating cell population(s) may contribute to the sustained beneficial effect of FGF-2 in vivo.

Disruption of sarcolemmal dystrophin and beta-dystroglycan may be a potential mechanism for myocardial dysfunction in severe sepsis

Evidence from our laboratory has shown alterations in myocardial structure in severe sepsis/septic shock. The morphological alterations are heralded by sarcolemmal damage, characterized by increased plasma membrane permeability caused by oxidative damage to lipids and proteins. The critical importance of the dystrophin-glycoprotein complex (DGC) in maintaining sarcolemmal stability led us to hypothesize that loss of dystrophin and associated glycoproteins could be involved in early increased sarcolemmal permeability in experimentally induced septic cardiomyopathy. Male C57Bl/6 mice were subjected to sham operation and moderate (MSI) or severe (SSI) septic injury induced by cecal ligation and puncture (CLP). Using western blot and immunofluorescence, a downregulation of dystrophin and beta-dystroglycan expression in both severe and moderate injury could be observed in septic hearts. The immunofluorescent and protein amount expressions of laminin-alpha2 were similar in SSI and sham-operated hearts. Consonantly, the evaluation of plasma membrane permeability by intracellular albumin staining provided evidence of severe injury of the sarcolemma in SSI hearts, whereas antioxidant treatment significantly attenuated the loss of sarcolemmal dystrophin expression and the increased membrane permeability. This study offers novel and mechanistic data to clarify subcellular events in the pathogenesis of cardiac dysfunction in severe sepsis. The main finding was that severe sepsis leads to a marked reduction in membrane localization of dystrophin and beta-dystroglycan in septic cardiomyocytes, a process that may constitute a structural basis of sepsis-induced cardiac depression. In addition, increased sarcolemmal permeability suggests functional impairment of the DGC complex in cardiac myofibers. In vivo observation that antioxidant treatment significantly abrogated the loss of dystrophin expression and plasma membrane increased permeability supports the hypothesis that oxidative damage may mediate the loss of dystrophin and beta-dystroglycan in septic mice. These abnormal parameters emerge as therapeutic targets and their modulation may provide beneficial effects on future cardiovascular outcomes and mortality in sepsis.

Ischemic myocardial injuries after cardiac malformation repair in infants may be associated with oxidative stress mechanisms

BACKGROUND

Despite advances in pediatric cardiac surgery, perioperative myocardial injury can be the major determinant of postoperative dysfunction after cardiac surgery. This study investigated the pathology-related differences in 29 infants with congenital heart disease that led to death. The infants were treated at the University Hospital of Ribeirão Preto, Brazil.

METHODS

The patients were divided into four groups: Group 1, 16 infants who underwent operations for congenital heart disease on cardiopulmonary bypass; Group 2, four infants who underwent off-cardiopulmonary bypass operations for congenital heart disease; Group 3, nine infants who died from congenital heart disease prior to surgical treatment; and Group 4 (control group), five infants with no congenital heart disease and who died from other causes. The myocardial injuries and oxidative stress mechanisms were assessed by histopathology and immunohistochemistry and were quantified by morphometrical analyses.

RESULTS

Contraction band necrosis and dystrophic calcification were found primarily in infants of Group 1. Coagulation necrosis and healing were prominent in Group 2, while infants without repair (Group 3) showed mainly colliquative myocytolysis. Apoptotic cells were more prominent in the operative groups. The control group showed no significant myocardial lesions. Lipid peroxidation was the principal mechanism of oxidative stress accounting for the myocardial lesions.

CONCLUSION

The diversity of the lesions observed in these hearts seemed to indicate a large spectrum of cell damage due to inadequate myocardial perfusion, especially when these infants underwent surgery. Oxidative mechanisms could be a common mediator in the pathogenesis of myocardial injuries, mediated by peroxidation of the membrane phospholipids and resulting in changes in the permeability of the cell membrane, cell death, and intracellular calcium overload. Furthermore, an immature and often hypertrophied myocardium may promote unfavorable conditions, leading to heart failure and a lethal outcome.

Chronic beta-AR activation-induced calpain activation and impaired eNOS-Akt signaling mediates cardiac injury in ovariectomized female rats

OBJECTIVE

To address the pathophysiological relevance of ovarian hormones in chronic beta-adrenergic stimulation-induced myocardial injury, we assessed impairments of Ca(2+)-mediated cell signaling in the left ventricle of ovariectomized female rats.

RESEARCH DESIGN/METHODS

Female Wistar rats were subjected to bilateral ovariectomy and sham operation. Six weeks after ovariectomy (OVX), both OVX and sham rats were treated with isoproterenol (5mg/kg, intraperitoneally), a nonselective beta-adrenergic agonist, once a day for 28 days.

RESULTS

We found that chronic beta-adrenergic stimulation caused enhanced breakdown of sarcolemmal proteins such as dystrophin and utrophin in OVX rats compared to sham-operated rats. Generation of calpain-mediated 150 kDa-breakdown product of spectrin confirmed calpain activation following isoproterenol treatment. Marked breakdown of endogenous calpain inhibitor, calpastatin, in OVX rats was consistent with the calpain activation following chronic beta-adrenergic stimulation. In addition to calpain activation, we also found marked reduction of endothelial nitric oxide synthase (eNOS) activity with concomitant deregulation by heat shock proteins 90 kDa and caveolin 3, both of which are eNOS-associated proteins. Finally, we documented decreased Akt phosphorylation with concomitant increased glycogen synthase kinase 3beta phosphorylation underlying cell injury following chronic beta-adrenergic stimulation.

CONCLUSION

Taken together chronic beta-adrenergic stimulation caused severe cardiac injury in OVX rats through calpain activation and impairments of Akt and eNOS signaling pathways.