l-Arginine Attenuates Cardiac Dysfunction, But Further Down-Regulates α-Myosin Heavy Chain Expression in Isoproterenol-Induced Cardiomyopathy

Effect of Secreted Frizzled-Related Protein 5 in Mice with Heart Failure

Although some progress has been made in its treatment, heart failure is still one of the most important health problems that endanger public health. This study aims to explore the myocardial protective effect of secreted frizzled-related protein 5 (SFRP5) on mice with heart failure. The mouse model of heart failure was established by using the isoproterenol (ISO) hydrochloride gradient modeling method. The treatment group was injected with 0.02 mg/kg/24 h SFRP5 recombinant protein intraperitoneally 30 minutes after the injection of isoproterenol, and the ISO + phosphate-buffered saline (PBS) group was injected with the same amount of PBS. After intraperitoneal injection of SFRP5 recombinant protein in mice with heart failure, the inflammatory response was reduced, and the left ventricular systolic and diastolic function of heart failure mice and the pathological structure of the myocardial tissue were improved. Compared with the ISO group, the expression level of SFRP5 protein in the ISO + SFRP5 group was increased significantly, the expression levels of Wnt5a and JNK protein were decreased markedly, and the enzyme activities of SOD and GSH-Px in the serum were observably increased, but they were lower than those parameters in the normal group. The SFRP5 recombinant protein has a protective effect on isoproterenol-induced heart failure in mice. The mechanism of action may be related to inhibiting the Wnt5A/JNK signaling pathway and reducing oxidative stress and inflammation. SFRP5 may be one of the therapeutic targets of heart failure.

The tyrosine kinase inhibitor crizotinib influences blood glucose and mRNA expression of GLUT4 and PPARs in the heart of rats with experimental diabetes

Tyrosine kinases inhibitors (TKIs) may alter glycaemia and may be cardiotoxic with importance in the diabetic heart. We investigated the effect of multi-TKI crizotinib after short-term administration on metabolic modulators of the heart of diabetic rats. Experimental diabetes mellitus (DM) was induced by streptozotocin (STZ; 80 mg·kg^-1, i.p.), and controls (C) received vehicle. Three days after STZ, crizotinib (STZ+CRI; 25 mg·kg^-1 per day p.o.) or vehicle was administered for 7 days. Blood glucose, C-peptide, and glucagon were assessed in plasma samples. Receptor tyrosine kinases (RTKs), cardiac glucose transporters, and peroxisome proliferator-activated receptors (PPARs) were determined in rat left ventricle by RT-qPCR method. Crizotinib moderately reduced blood glucose (by 25%, P < 0.05) when compared to STZ rats. The drug did not affect levels of C-peptide, an indicator of insulin secretion, suggesting altered tissue glucose utilization. Crizotinib had no impact on cardiac RTKs. However, an mRNA downregulation of insulin-dependent glucose transporter Glut4 in the hearts of STZ rats was attenuated after crizotinib treatment. Moreover, crizotinib normalized Ppard and reduced Pparg mRNA expression in diabetic hearts. Crizotinib decreased blood glucose independently of insulin and glucagon. This could be related to changes in regulators of cardiac metabolism such as GLUT4 and PPARs.

Aliskiren attenuates cardiac dysfunction by modulation of the mTOR and apoptosis pathways

Aliskiren (ALS) is well known for its antihypertensive properties. However, the potential underlying the molecular mechanism and the anti-hypertrophic effect of ALS have not yet been fully elucidated. The aim of the present study was to investigate the role of ALS in mammalian target of rapamycin (mTOR) and apoptosis signaling using in vivo and in vitro models of cardiac hypertrophy. A rat model of cardiac hypertrophy was induced by isoproterenol treatment (5 mg·kg^-1·day^-1) for 4 weeks, with or without ALS treatment at 20 mg·kg^-1·day^-1. The expression of hypertrophic, fibrotic, and apoptotic markers was determined by RT-qPCR. The protein expression of apoptotic markers mTOR and p-mTOR was assessed by western blot analysis. The proliferation of H9C2 cells was monitored using the MTS assay. Cell apoptosis was analyzed using flow cytometry. In vivo, isoproterenol-treated rats exhibited worse cardiac function, whereas ALS treatment reversed these dysfunctions, which were associated with changes in p-mTOR, Bcl-2, Bax, and cleaved caspase-3 expression, as well as the number of apoptotic cells. In vitro, H9C2 cardiomyocyte viability was significantly inhibited and cardiac hypertrophy was induced by Ang II administration, but ALS reversed Ang II-induced H9C2 cardiomyocyte hypertrophy and death. Furthermore, Ang II triggered the activation of the mTOR and apoptosis pathways in hypertrophic cardiomyocytes that were inhibited by ALS treatment. These results indicated that ALS alleviated cardiac hypertrophy through inhibition of the mTOR and apoptosis pathways in cardiomyocytes.

Ginsenoside Re Improves Isoproterenol-Induced Myocardial Fibrosis and Heart Failure in Rats

Objective. Panax ginseng is used widely for treatment of cardiovascular disorders in China. Ginsenoside Re is the main chemical component of P. ginseng. We aimed to investigate the protective effect of ginsenoside Re on isoproterenol-induced myocardial fibrosis and heart failure in rats. Methods. A model of myocardial fibrosis and heart failure was established by once-daily subcutaneous injection of isoproterenol (5 mg/kg/day) to rats for 7 days. Simultaneously, rats were orally administrated ginsenoside Re (5 or 20 mg/kg) or vehicle daily for 4 weeks. Results. Isoproterenol enhanced the heart weight, myocardial fibrosis, and hydroxyproline content in rat hearts. Ginsenoside Re inhibited (at least in part) the isoproterenol-induced increase in heart weight, myocardial fibrosis, and hydroxyproline content. Compared with the isoproterenol group, treatment with ginsenoside Re ameliorated changes in left ventricular systolic pressure, left ventricular end diastolic pressure, and the positive and negative maximal values of the first derivative of left ventricular pressure. Ginsenoside Re administration also resulted in decreased expression of transforming growth factor (TGF)-β1 in serum and decreased expression of Smad3 and collagen I in heart tissue. Conclusion. Ginsenoside Re can improve isoproterenol-induced myocardial fibrosis and heart failure by regulation of the TGF-β1/Smad3 pathway.

Regulatory Lymphoid and Myeloid Cells Determine the Cardiac Immunopathogenesis of Trypanosoma cruzi Infection

Chagas disease is a multisystemic disorder caused by the protozoan parasite Trypanosoma cruzi, which affects ~8 million people in Latin America, killing 7,000 people annually. Chagas disease is one of the main causes of death in the endemic area and the leading cause of infectious myocarditis in the world. T. cruzi infection induces two phases, acute and chronic, where the infection is initially asymptomatic and the majority of patients will remain clinically indeterminate for life. However, over a period of 10–30 years, ~30% of infected individuals will develop irreversible, potentially fatal cardiac syndromes (chronic chagasic cardiomyopathy [CCC]), and/or dilatation of the gastro-intestinal tract (megacolon or megaesophagus). Myocarditis is the most serious and frequent manifestation of chronic Chagas heart disease and appears in about 30% of infected individuals several years after infection occurs. Myocarditis is characterized by a mononuclear cell infiltrate that includes different types of myeloid and lymphoid cells and it can occur also in the acute phase. T. cruzi infects and replicates in macrophages and cardiomyocytes as well as in other nucleated cells. The pathogenesis of the chronic phase is thought to be dependent on an immune-inflammatory reaction to a low-grade replicative infection. It is known that cytokines produced by type 1 helper CD4+ T cells are able to control infection. However, the role that infiltrating lymphoid and myeloid cells may play in experimental and natural Chagas disease pathogenesis has not been completely elucidated, and several reports indicate that it depends on the mouse genetic background and parasite strain and/or inoculum. Here, we review the role that T cell CD4+ subsets, myeloid subclasses including myeloid-derived suppressor cells may play in the immunopathogenesis of Chagas disease with special focus on myocarditis, by comparing results obtained with different experimental animal models.

L-arginine supplementation reduces mortality and improves disease outcome in mice infected with Trypanosoma cruzi

Chagas disease caused by Trypanosoma cruzi is a neglected disease that affects about 7 million people in Latin America, recently emerging on other continents due to migration. As infection in mice is characterized by depletion of plasma L-arginine, the effect on infection outcome was tested in mice with or without L-arginine supplementation and treatment with 1400W, a specific inhibitor of inducible nitric oxide synthase (iNOS). We found that levels of L-arginine and citrulline were reduced in the heart and plasma of infected mice, whereas levels of asymmetric dimethylarginine, an endogenous iNOS inhibitor, were higher. Moreover, L-arginine supplementation decreased parasitemia and heart parasite burden, improving clinical score and survival. Nitric oxide production in heart tissue and plasma was increased by L-arginine supplementation, while pharmacological inhibition of iNOS yielded an increase in parasitemia and worse clinical score. Interestingly, electrocardiograms improved in mice supplemented with L-arginine, suggesting that it modulates infection and heart function and is thus a potential biomarker of pathology. More importantly, L-arginine may be useful for treating T. cruzi infection, either alone or in combination with other antiparasitic drugs.

Trypanosoma cruzi is the causative agent of the neglected Chagas disease in humans. During infection in mice, depletion of plasma L-arginine is correlated with mortality. L-arginine is a semi-essential amino acid needed for cell proliferation, and is the substrate of arginase 1 (Arg-1) and inducible nitric oxide synthase (iNOS), which is involved in the immune response against infections. Observed L-arginine depletion is likely caused by increased Arg-1 activity, but the effect on immune response are still unknown. Our hypothesis is that L-arginine depletion may block nitric oxide (NO) production by iNOS, which is needed for parasite killing. To test this hypothesis, mice were supplemented with and without L-arginine, and the differential effect of treatment with an iNOS inhibitor was determined. L-arginine supplement was beneficial to the mice, lowering mortality and improving disease outcome and heart function. The beneficial effect was associated with increased levels of NO, thus low levels of L-arginine and NO are considered candidate markers of pathology. Finally, as L-arginine is a common dietary supplement, it may be useful for treatment of Chagas patients, either alone or in combination with antiparasitic drugs.

Maternal inflammation activated ROS-p38 MAPK predisposes offspring to heart damages caused by isoproterenol via augmenting ROS generation

Maternal inflammation contributes to the increased incidence of adult cardiovascular disease. The current study investigated the susceptibility of cardiac damage responding to isoproterenol (ISO) in adult offspring that underwent maternal inflammation (modeled by pregnant Sprague-Dawley rats with lipopolysaccharides (LPS) challenge). We found that 2 weeks of ISO treatment in adult offspring of LPS-treated mothers led to augmented heart damage, characterized by left-ventricular systolic dysfunction, cardiac hypertrophy and myocardial fibrosis. Mechanistically, prenatal exposure to LPS led to up-regulated expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, antioxidant enzymes, and p38 MAPK activity in left ventricular of adult offspring at resting state. ISO treatment exaggerated ROS generation, p38 MAPK activation but down-regulated reactive oxygen species (ROS) elimination capacity in the left ventricular of offspring from LPS-treated mothers, while antioxidant N-acetyl-L-cysteine (NAC) reversed these changes together with improved cardiac functions. The p38 inhibitor SB202190 alleviated the heart damage only via inhibiting the expression of NADPH oxidases. Collectively, our data demonstrated that prenatal inflammation programs pre-existed ROS activation in the heart tissue, which switches on the early process of oxidative damages on heart rapidly through a ROS-p38 MAPK-NADPH oxidase-ROS positive feedback loop in response to a myocardial hypertrophic challenge in adulthood.