Erythromycin treatment suppresses myocardial injury in autoimmune myocarditis in rats via suppression of superoxide production

Cardioprotective effects of omega 3 fatty acids from fish oil and it enhances autoimmunity in porcine cardiac myosin-induced myocarditis in the rat model

This experiment proposed to investigate the efficiency of omega 3 fatty acids from fish that improves autoimmune against myocarditis in the rat. Fish oil was extracted from fresh Tuna fish and performed FAME analysis and mice bioassay. The autoimmune myocarditis was induced by subcutaneous injection of porcine cardiac myosin (PCM) into the footpads of rats on the first and seventh day. Rats were dissected on the 21st day to analyze the histopathological, hemodynamic, echocardiographic factors, and immunohistochemistry expressions. In the study, 73.90% of total fatty acids were recorded. Histological analysis revealed that omega 3 fatty acids administrated groups showed tremendous development in the multifocal myocardia hyaline degeneration and necrosis with inflammatory changes. Moreover, omega 3 fatty acids inhabited the expressions of inflammatory cells (CD4, CD8 and CD11b) and suppressed the level of NF-κB. The echocardiographic factors such as heartbeat, SBP, DBP, levels of LVDs, LVDd, LVPW percentage of LVFS, EF, expression levels of inflammatory cytokines (TNF, IL-1β, IFN-ɤ, IL-2, and IL-6) also significantly suppressed by omega 3 fatty acids. Hence, the present study proved that consuming fatty acid-enriched fish might be a successful therapy for improving the inflammatory profile, regenerates the heart tissues, and controlled the production of inflammatory cells.

Oleuropein prevents the development of experimental autoimmune myocarditis in rats

Oleuropein (OLE) is a natural secoiridoid that is derived from Olea europaea. OLE possesses cardioprotective effects in experimental models of hypertension, myocardial infarction, atherosclerosis and hyperlipidaemia. In the present study, the effects of OLE on experimental autoimmune myocarditis (EAM) were evaluated. EAM in rats were induced by subcutaneous injections of porcine cardiac myosin. Cardiac function parameters, myocardial pathology, myocardial inflammatory cell infiltration and nuclear factor kappa-B (NF-κB) expression were measured. Our data showed that the postmyocarditis rats exhibited increased left ventricular end systolic diameters, left ventricular end diastolic diameters, left ventricular end-diastolic pressures (LVEDP), and decreased ejection fractions. However, OLE significantly suppressed these changes in EAM rats. Histological analysis revealed that myosin induced miliary foci of discolouration on endocardial surfaces and extensive myocardial injuries with inflammatory cell infiltration were significantly improved by OLE therapy. A definitive positive correlation between the histological scores and LVEDP was observed. Moreover, OLE inhibited CD4⁺, CD8⁺ cells and macrophage infiltration in myocardium and decreased the serum production of tumour necrosis factor-a (TNF-a), interleukin-1β (IL-1β) and IL-6 in EAM rats. Expectedly, the myocardial levels of NF-κB p65, p-IκBa, IKKa were significantly attenuated by OLE, indicating the inhibitory effects of OLE on the NF-κB pathway. Furthermore, OLE decreased the myocardial expressions of phosphorylated-p38 MAPK, phosphorylated-ERK, and did not change the levels of p38 MAPK and ERK in EAM rats. Collectively, our results suggest that OLE effectively prevents the development of myocarditis, at least in part, by inhibiting the MAPKs and NF-κB mediated inflammatory responses.

Cardiomyocyte GTP Cyclohydrolase 1 Protects the Heart Against Diabetic Cardiomyopathy

Diabetic cardiomyopathy increases the risk of heart failure and death. At present, there are no effective approaches to preventing its development in the clinic. Here we report that reduction of cardiac GTP cyclohydrolase 1 (GCH1) degradation by genetic and pharmacological approaches protects the heart against diabetic cardiomyopathy. Diabetic cardiomyopathy was induced in C57BL/6 wild-type mice and transgenic mice with cardiomyocyte-specific overexpression of GCH1 with streptozotocin, and control animals were given citrate buffer. We found that diabetes-induced degradation of cardiac GCH1 proteins contributed to adverse cardiac remodeling and dysfunction in C57BL/6 mice, concomitant with decreases in tetrahydrobiopterin, dimeric and phosphorylated neuronal nitric oxide synthase, sarcoplasmic reticulum Ca(2+) handling proteins, intracellular [Ca(2+)]i, and sarcoplasmic reticulum Ca(2+) content and increases in phosphorylated p-38 mitogen-activated protein kinase and superoxide production. Interestingly, GCH-1 overexpression abrogated these detrimental effects of diabetes. Furthermore, we found that MG 132, an inhibitor for 26S proteasome, preserved cardiac GCH1 proteins and ameliorated cardiac remodeling and dysfunction during diabetes. This study deepens our understanding of impaired cardiac function in diabetes, identifies GCH1 as a modulator of cardiac remodeling and function, and reveals a new therapeutic target for diabetic cardiomyopathy.

Methods for Testing Immunological Factors

Hypersensitivity reactions can be elicited by various factors: either immunologically induced, i.e., allergic reactions to natural or synthetic compounds mediated by IgE, or non-immunologically induced, i.e., activation of mediator release from cells through direct contact, without the induction of, or the mediation through immune responses. Mediators responsible for hypersensitivity reactions are released from mast cells. An important preformed mediator of allergic reactions found in these cells is histamine. Specific allergens or the calcium ionophore 48/80 induce release of histamine from mast cells. The histamine concentration can be determined with the o-phthalaldehyde reaction.

Mortality and morbidity in different immunization protocols for experimental autoimmune myocarditis in rats

AIM

We aimed to investigate the histological and clinical presentations of experimental autoimmune myocarditis (EAM) induced by different immunization schemes.

METHODS

Male young Lewis rats were divided into five groups immunized by porcine myocardial myosin: subcutaneously (SC) 2 mg (in two 1-mg doses on day 0 and 7), 0 mg (sham group) subcutaneously into rear footpads (RF), 0.25 mg RF, 0.5 mg RF or 1 mg RF (all RF once on day 0). On day 21, left ventricular (LV) function was assessed by cardiac magnetic resonance imaging and cardiac catheterization. The type and degree of myocardial inflammatory infiltrates were determined by conventional histology and immunohistochemistry.

RESULTS

In the SC immunized rats and in the RF sham group, we observed 0% mortality, while in the actively RF immunized rats, mortality was 20, 20 and 44% for the 0.25 mg, 0.5 mg and 1 mg myosin doses respectively. Morbidity as defined by inflammatory infiltrates on haematoxylin and eosin (HE) staining was 22% in the SC immunized rats, 0% in the RF sham group and 100% in all actively RF immunized groups. We observed augmented relative ventricle weight and spleen weight, increased LV end-diastolic pressure, reduced LV developed pressure and reduced LV ejection fraction in all with myosin-immunized RF groups without any systematic dose effect.

CONCLUSION

Subcutaneous immunization to the neck and flanks did not induce a reproducible EAM, while RF myosin administration reliably led to EAM. Lower myosin doses seem to induce the complete histological and clinical picture of EAM while being associated with lower mortality, non-specific symptoms and animal distress.