Wawaimuli Arozal

Curcumin attenuates diabetic nephropathy by inhibiting PKC‐α and PKC‐β1 activity in streptozotocin‐induced type I diabetic rats

SCOPE We hypothesized that curcumin, a potent anti-oxidant, might be beneficial in ameliorating the development of diabetic nephropathy through inhibition of PKC-α and PKC-β1 activity-ERK1/2 pathway. METHODS AND RESULTS Diabetes was induced by a single intraperitoneal injection of streptozotocin (STZ) (55 mg/kg) in rats. Three weeks after STZ injection, rats were divided into three groups, namely, normal, diabetic and diabetic treated with curcumin at 100 mg/kg/day, p.o., for 8 wk. At 11 wk after STZ injection, diabetic rats exhibited renal dysfunction, as evidenced by reduced creatinine clearance, increased blood urea nitrogen (BUN) and proteinuria, marked increases in lipid peroxidation, NOX4 and p67phox and decrease in anti-oxidant enzyme. All of these abnormalities were significantly reversed by curcumin. Furthermore, the high-glucose-induced PKC-α and PKC-β1 activities and phosphorylated ERK1/2 was significantly diminished by curcumin. Curcumin also attenuated the expression of TGF-β1, CTGF, osteopontin, p300 and ECM proteins such as fibronectin and type IV collagen. The high-glucose-induced expression of VEGF and its receptor VEGF receptor II (flk-1) was also ameliorated by curcumin. CONCLUSION These results prove that curcumin produces dual blockade of both PKC-α and PKC-β1 activities, which suggests that curcumin is a potential adjuvant therapy for the prevention and treatment of diabetic nephropathy.

Role of differential signaling pathways and oxidative stress in diabetic cardiomyopathy.

Diabetes mellitus increases the risk of heart failure independently of underlying coronary artery disease, and many believe that diabetes leads to cardiomyopathy. The underlying pathogenesis is partially understood. Several factors may contribute to the development of cardiac dysfunction in the absence of coronary artery disease in diabetes mellitus. There is growing evidence that excess generation of highly reactive free radicals, largely due to hyperglycemia, causes oxidative stress, which further exacerbates the development and progression of diabetes and its complications. Hyperglycemia-induced oxidative stress is a major risk factor for the development of micro-vascular pathogenesis in the diabetic myocardium, which results in myocardial cell death, hypertrophy, fibrosis, abnormalities of calcium homeostasis and endothelial dysfunction. Diabetes-mediated biochemical changes show cross-interaction and complex interplay culminating in the activation of several intracellular signaling molecules. Diabetic cardiomyopathy is characterized by morphologic and structural changes in the myocardium and coronary vasculature mediated by the activation of various signaling pathways. This review focuses on the oxidative stress and signaling pathways in the pathogenesis of the cardiovascular complications of diabetes, which underlie the development and progression of diabetic cardiomyopathy.

Protective effect of carvedilol on daunorubicin-induced cardiotoxicity and nephrotoxicity in rats

Daunorubicin (DNR) is one of the anthracycline anti-tumor agents widely used in the treatment of acute myeloid leukemia. However, the clinical use of DNR has been limited by its undesirable systemic toxicity, especially in the heart and kidney. This study was designed to test the effectiveness of carvedilol, a nonselective beta-blocker against DNR-induced cardiotoxicity and nephrotoxicity. Rats were treated with a cumulative dose of 9 mg/kg body weight DNR (i.v.). Carvedilol was administered orally every day for 6 weeks. DNR rats showed cardiac and nephrotoxicities as evidenced by worsening cardiac and kidney functions, which were evaluated by hemodynamic and echocardiographic studies, and by measuring protein in urine, levels of urea and creatinine in serum, lipid profiles, malondialdeyde level and the total level of glutathione peroxidase activity in both heart and kidney tissues. These changes were reversed by treatment with carvedilol, which resulted in significant improvement in the cardio-renal function. Furthermore, carvedilol down-regulated matrix metalloproteinase-2 expression in the heart, increased nephrin expression in the kidney, and attenuated the increased protein expression of NADPH oxidase subunits in heart and kidney. Moreover, carvedilol reduced myocardial and renal apoptosis and improved the histopathological changes in heart and kidney induced by DNR. In conclusion, the present study demonstrated a beneficial effect of carvedilol treatment in the prevention of DNR-induced cardiotoxicity and nephrotoxicity by reversing the oxidative stress and apoptosis.

Quercetin offers cardioprotection against progression of experimental autoimmune myocarditis by suppression of oxidative and endoplasmic reticulum stress via endothelin-1/MAPK signalling

In order to test the hypothesis that treatment with quercetin at a dose of 10 mg/kg protects from the progression of experimental autoimmune myocarditis (EAM) to dilated cardiomyopathy (DCM), we have used the rat model of EAM induced by porcine cardiac myosin. Our results identified that the post-myocarditis rats suffered from elevated endoplasmic reticulum (ER) stress and adverse cardiac remodelling in the form of myocardial fibrosis, whereas the rats treated with quercetin have been protected from these changes as evidenced by the decreased myocardial levels of ER stress and fibrosis markers when compared with the vehicle-treated DCM rats. In addition, the myocardial dimensions and cardiac function were preserved significantly in the quercetin-treated rats in comparison with the DCM rats treated with vehicle alone. Interestingly, the rats treated with quercetin showed significant suppression of the myocardial endothelin-1 and also the mitogen activated protein kinases (MAPK) suggesting that the protection offered by quercetin treatment against progression of EAM involves the modulation of MAPK signalling cascade. Collectively, the present study provides data to support the role of quercetin in protecting the hearts of the rats with post myocarditis DCM.

Regulation of inflammation and myocardial fibrosis in experimental autoimmune myocarditis.

Autoimmune responses and inflammation are involved in the pathogenesis of many cardiovascular diseases. There is compelling evidence that inflammatory mechanisms may contribute to progressive heart failure. Thus, myocardial infiltration of lymphocytes and mononuclear cells, increased expression of pro-inflammatory chemokines and cytokines and circulating autoantibodies are frequently observed in myocarditis and dilated cardiomyopathy (DCM). Experimental autoimmune myocarditis (EAM) in rodents may be elicited by immunization of cardiac myosin and EAM in rats mimics human fulminant myocarditis in the acute phase and human DCM in the chronic phase. Our animal model, EAM was demonstrated to progress into the clinicopathological state similar to DCM in the chronic phase, and was found to be characterized by the enlargement of the heart, dilatation of ventricles, diffuse and extensive myocardial fibrosis, besides being a cellular immunity and inflammation mediated disease. Severity of myocarditis was characterized by increased inflammation, cardiac fibrosis and decreased myocardial performance in rats with DCM. Pharmacological interventions such as angiotensin converting enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARBs) significantly attenuated the myosin-induced inflammation and cardiac fibrosis and thereby improving myocardial function in rats with DCM. A growing body of evidence shows that ACEI and ARBs contribute to the pharmaceutical management of patients with heart failure mediated by immune and inflammatory response. The purpose of this review is to emphasize the role of inflammation and myocardial fibrosis in rats with DCM after EAM and study the effects of pharmacological interventions such as ACEI, ARBs in the treatment of heart failure through the suppression of inflammatory cytokines and fibrosis.

The antioxidant edaravone attenuates ER-stress-mediated cardiac apoptosis and dysfunction in rats with autoimmune myocarditis.

Abstract Experimental autoimmune myocarditis (EAM) is mediated by myocardial infiltration by myosin-specific T-cells secreting inflammatory cytokines. In this study, rat models of EAM were prepared by injection with porcine cardiac myosin. One week after immunization, edaravone was administered intraperitoneally at 3 or 10 mg/kg/day to rats for 2 weeks. Cardiac function was measured by haemodynamic and echocardiographic studies and TUNEL assay was performed. Left ventricular (LV) expression of NADPH oxidase sub-units (p47phox and p67phox), pro-inflammatory cytokines (TNF-α), endoplasmic reticulum (ER) stress signalling proteins (GRP78, caspase-12 and GADD153) and mitogen-activated protein kinase (MAPK) family proteins (phospho-p38 MAPK and phospho-JNK) were measured by western blotting. Edaravone improved LV function in a dose-dependent manner. Central venous pressure was significantly low and LV ejection fraction and fractional shortening was significantly high in edaravone groups compared with those in the vehicle group. In addition, edaravone treatment down-regulated LV expressions of p47phox, TNF-α, GADD153, phospho-p38 MAPK and phospho-JNK. Furthermore, the LV expressions of p67phox, GRP78, caspase-12 and TUNEL-positive cells of rats with EAM treated with edaravone were significantly low compared with those of the vehicle group. These findings suggest that edaravone ameliorated the progression of EAM by inhibiting oxidative and ER stress and, subsequently, cardiac apoptosis.

Beneficial effects of edaravone, a novel antioxidant, in rats with dilated cardiomyopathy.

Edaravone, a novel antioxidant, acts by trapping hydroxyl radicals, quenching active oxygen and so on. Its cardioprotective activity against experimental autoimmune myocarditis (EAM) was reported. Nevertheless, it remains to be determined whether edaravone protects against cardiac remodelling in dilated cardiomyopathy (DCM). The present study was undertaken to assess whether edaravone attenuates myocardial fibrosis, and examine the effect of edaravone on cardiac function in rats with DCM after EAM. Rat model of EAM was prepared by injection with porcine cardiac myosin 28 days after immunization, we administered edaravone intraperitoneally at 3 and 10 mg/kg/day to rats for 28 days. The results were compared with vehicle‐treated rats with DCM. Cardiac function, by haemodynamic and echocardiographic study and histopathology were performed. Left ventricular (LV) expression of NADPH oxidase subunits (p47phox, p67phox, gp91phox and Nox4), fibrosis markers (TGF‐β1 and OPN), endoplasmic reticulum (ER) stress markers (GRP78 and GADD 153) and apoptosis markers (cytochrome C and caspase‐3) were measured by Western blotting. Edaravone‐treated DCM rats showed better cardiac function compared with those of the vehicle‐treated rats. In addition, LV expressions of NADPH oxidase subunits levels were significantly down‐regulated in edaravone‐treated rats. Furthermore, the number of collagen‐III positive cells in the myocardium of edaravone‐treated rats was lower compared with those of the vehicle‐treated rats. Our results suggest that edaravone ameliorated the progression of DCM by modulating oxidative and ER stress‐mediated myocardial apoptosis and fibrosis.

Olmesartan protects against oxidative stress possibly through the Nrf2 signaling pathway and inhibits inflammation in daunorubicin-induced nephrotoxicity in rats.

Anthracycline anticancer drug daunorubicin (DNR) can induce chronic nephrotoxicity, which is believed to be based on oxidative injury. Olmesartan has significant blood pressure lowering effect via modulating renin-angiotensin system although its mechanism of action in DNR-induced renal injury is largely unknown. Transcription factor nuclear factor-erythroid 2-related factor 2 (Nrf2) is an important regulator of cellular oxidative stress. This study examined the role of Nrf2 in olmesartan-mediated antioxidant effects in DNR induced kidney cells. In addition, key factors involved in promoting inflammation and oxidative stress were studied. Sprague-Dawley rats were treated with a cumulative dose of 9 mg/kg DNR (i.v.). Olmesartan was administered orally every day for 6 weeks. DNR treated rats showed nephrotoxicity as evidenced by worsening renal function, which was evaluated by measuring total cholesterol, triglyceride levels in kidney tissue and histopathological approaches; treatment with olmesartan reversed these changes. Furthermore, olmesartan treatment down-regulated phospho-MAPKAPK-2, caspase-12, p47(phox), p67(phox), upregulated renal expression of PPAR-γ, Bcl-xL, glutathione peroxidase and Nrf2. Furthermore, olmesartan down-regulated matrix metalloproteinase-2 and angiotensin II type I receptor expression in the kidney. In conclusion, the result demonstrated that angiotensin II and oxidative stress play a key role in DNR-induced nephrotoxicity. The present results indicated that olmesartan protects against oxidative stress, which may be possibly via the induction of Nrf2 signaling pathways.

Effect of telmisartan in limiting the cardiotoxic effect of daunorubicin in rats

Objectives  Studies have suggested that angiotensin receptor blockers may exert a protective role towards doxorubicin‐induced cardiotoxicity, but they have not been extensively investigated in this area. We therefore investigated whether the co‐treatment of telmisartan, an angiotensin (Ang II) type‐1 receptor blocker, might offer protection against daunorubicin cardiotoxic properties in rats.

Candesartan cilexetil protects from cardiac myosin induced cardiotoxicity via reduction of endoplasmic reticulum stress and apoptosis in rats: involvement of ACE2-Ang (1-7)-mas axis.

Candesartan cilexetil, an angiotensin (Ang) II receptor 1 blocker was reported to suppress the myocardial damage in various cardiovascular complications but the mode by which it is effective in preventing the progression of dilated cardiomyopathy (DCM) is unknown. Emerging evidences suggest that, at least, part of the benefits observed with the use of AT1 receptor blockers could be attributed to the increased Ang (1-7) levels observed during administration of these agents. Identification of the novel components of the RAS, ACE2 and Ang (1-7) receptor mas, provided essential elements for considering the existence of a vasodilator arm of the RAS, represented by the ACE2-Ang (1-7)-mas axis. In this study, rat model of DCM was prepared by injection with porcine cardiac myosin. Twenty-eight days after immunization, candesartan cilexetil was administered intraperitoneally at 1 or 10mg/kg/day to rats for four weeks. Myocardial expression of Ang receptors and markers of calcium homeostasis, endoplasmic reticulum (ER) stress and apoptosis were measured by Western blotting and histopathological staining techniques. Candesartan improved the functional markers in a dose-dependent manner and also upregulated Ang (1-7), ACE2 and mas1 in the myocardium of DCM rats. Various ER stress and apoptosis markers were attenuated and the number apoptotic cells were significantly lower in the candesartan treated rats compared with those of the vehicle group. These findings suggest that candesartan treatment prevented the progression of DCM by activation of the counter regulatory arm of the RAS and possibly through modulation of ER stress and subsequently, cardiac apoptosis.