Somasundaram Arumugam

Curcumin alleviates oxidative stress, inflammation, and renal fibrosis in remnant kidney through the Nrf2–keap1 pathway

SCOPE We hypothesized that curcumin, by increasing the expression of nuclear factor-erythroid-2-related factor 2 (Nrf2), could reduce oxidative stress, inflammation, and renal fibrosis in remnant kidney. METHODS AND RESULTS Sprague-Dawley rats were subjected to 5/6 nephrectomy and randomly assigned to untreated (Nx), curcumin-treated (75 mg/kg/day, orally), and telmisartan-treated groups (10 mg/kg/day, orally; as positive control). Sham-operated rats also served as controls. Five/sixth nephrectomy caused renal dysfunction, as evidenced by elevated proteinuria, blood urea nitrogen, and plasma creatinine, and decreased creatinine clearance that were ameliorated by curcumin or telmisartan treatment. The Nx rats demonstrated reduced Nrf2 protein expression, whereas the Kelch-like ECH-associated protein 1 was upregulated and heme oxygenase-1 level was significantly diminished. Consequently, Nx animals had significantly higher kidney malondialdehyde concentration and lower glutathione peroxidase activity, which was associated with the upregulation of nicotinamide adenine dinucleotide phosphatase oxidase subunit (p67(phox) and p22(phox) ), NF-kappaB p65, TNF-α, TGF-β1, cyclooxygenase-2, and fibronectin accumulation in remnant kidney. Interestingly, all of these changes were ameliorated by curcumin or telmisartan. CONCLUSION These findings demonstrate that, by modulating Nrf2-Keap1 pathway, the curcumin effectively attenuates oxidative stress, inflammation, and renal fibrosis, which suggest that curcumin hold promising potential for safe treatment of chronic kidney disease.

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.

Depletion of 14-3-3 Protein Exacerbates Cardiac Oxidative Stress, Inflammation and Remodeling Process via Modulation of MAPK/NF-ĸB Signaling Pathways after Streptozotocin-induced Diabetes Mellitus

Diabetic cardiomyopathy is associated with increased oxidative stress and inflammation. Mammalian 14-3-3 proteins are dimeric phosphoserine-binding proteins that participate in signal transduction and regulate several aspects of cellular biochemistry. The aim of the study presented here was to clarify the role of 14-3-3 protein in the mitogen activated protein kinase (MAPK) and nuclear factor-kB (NF-ĸB) signaling pathway after experimental diabetes by using transgenic mice with cardiac-specific expression of a dominant-negative 14-3-3 protein mutant (DN 14-3-3). Significant p-p38 MAPK activation in DN 14-3-3 mice compared to wild type mice (WT) after diabetes induction and with a corresponding up regulation of its downstream effectors, p-MAPK activated protein kinase 2 (MAPKAPK-2). Marked increases in cardiac hypertrophy, fibrosis and inflammation were observed with a corresponding up-regulation of atrial natriuretic peptide, osteopontin, connective tissue growth factor, tumor necrosis factor α, interleukin (IL)-1β, IL-6 and cellular adhesion molecules. Moreover, reactive oxygen species, left ventricular expression of NADPH oxidase subunits, p22 phox, p67 phox, and Nox4, and lipid peroxidation levels were significantly increased in diabetic DN 14-3-3mice compared to diabetic WT mice. Furthermore, myocardial NF-ĸB activation, inhibitor of kappa B-α degradation and mRNA expression of proinflammatory cytokines were significantly increased in DN 14-3-3 mice compared to WT mice after diabetes induction. In conclusion, our data suggests that depletion of 14-3-3 protein induces cardiac oxidative stress, inflammation and remodeling after experimental diabetes induction mediated through p38 MAPK, MAPKAPK-2 and NF-ĸB signaling.

Schisandrin B Prevents Doxorubicin Induced Cardiac Dysfunction by Modulation of DNA Damage, Oxidative Stress and Inflammation through Inhibition of MAPK/p53 Signaling

Doxorubicin (Dox) is a highly effective antineoplastic drug. However, Dox-induced apoptosis in cardiomyocytes leads to irreversible degenerative cardiomyopathy, which limits Dox clinical application. Schisandrin B (Sch B), a dibenzocyclooctadiene derivative isolated from the fruit of Schisandra chinensis, has been shown to protect against oxidative damage in liver, heart and brain tissues in rodents. In current study, we investigated possible protective effects of Sch B against Dox-induced cardiomyopathy in mice. Mice received a single injection of Dox (20 mg/kg IP). Five days after Dox administration, left ventricular (LV) performance was significantly depressed and was improved by Sch B treatment. Sch B prevented the Dox-induced increase in lipid peroxidation, nitrotyrosine formation, and metalloproteinase activation in the heart. In addition, the increased expression of phospho-p38 MAPK and phospho-MAPK activated mitogen kinase 2 levels by Dox were significantly suppressed by Sch B treatment. Sch B also attenuated Dox-induced higher expression of LV proinflammatory cytokines, cardiomyocyte DNA damage, myocardial apoptosis, caspase-3 positive cells and phopho-p53 levels in mice. Moreover, LV expression of NADPH oxidase subunits and reactive oxygen species were significantly less in Sch B treatment mice after Dox injection. These findings suggest that Sch B attenuates Dox-induced cardiotoxicity via antioxidative and anti-inflammatory effects.

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.

Schisandrin B Ameliorates ICV-Infused Amyloid β Induced Oxidative Stress and Neuronal Dysfunction through Inhibiting RAGE/NF-κB/MAPK and Up-Regulating HSP/Beclin Expression

Amyloid β (Aβ)-induced neurotoxicity is a major pathological mechanism of Alzheimer’s disease (AD). Our previous studies have demonstrated that schisandrin B (Sch B), an antioxidant lignan from Schisandra chinensis, could protect mouse brain against scopolamine- and cisplatin-induced neuronal dysfunction. In the present study, we examined the protective effect of Sch B against intracerebroventricular (ICV)-infused Aβ-induced neuronal dysfunction in rat cortex and explored the potential mechanism of its action. Our results showed that 26 days co-administration of Sch B significantly improved the behavioral performance of Aβ (1–40)-infused rats in step-through test. At the same time, Sch B attenuated Aβ-induced increases in oxidative and nitrosative stresses, inflammatory markers such as inducible nitric oxide syntheses, cyclooxygenase-2, interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α, and DNA damage. Several proteins such as receptor for advanced glycation end products (RAGE), nuclear factor-κB, mitogen-activated protein kinases, and apoptosis markers were over expressed in Aβ-infused rats but were significantly inhibited by Sch B treatment. Furthermore, Sch B negatively modulated the Aβ level with simultaneous up-regulation of HSP70 and beclin, autophagy markers in Aβ-infused rats. The aforementioned effects of Sch B suggest its protective role against Aβ-induced neurotoxicity through intervention in the negative cycle of RAGE-mediated Aβ accumulation during AD patho-physiology.

Modulation of HMGB1 translocation and RAGE/NFκB cascade by quercetin treatment mitigates atopic dermatitis in NC/Nga transgenic mice.

Quercetin, glycosylated form of flavonoid compound, has potent antioxidant and anti‐inflammatory properties. In this study, we have investigated the effects of quercetin on skin lesion, high‐mobility group box (HMGB)1 cascade signalling and inflammation in atopic dermatitis (AD) mouse model. AD‐like lesion was induced by the application of house dust mite extract to the dorsal skin of NC/Nga transgenic mouse. After AD induction, quercetin (50 mg/kg, p.o) was administered daily for 2 weeks. We evaluated dermatitis severity, histopathological changes and changes in protein expression by Western blotting for HMGB1, receptor for advanced glycation end products (RAGE), toll‐like receptor (TLR)4, nuclear factor (NF)κB, nuclear factor erythroid‐2‐related factor (Nrf)2, kelch‐like ECH‐associated protein (Keap)1, extracellular signal‐regulated kinase (ERK)1/2, cyclooxygenase (COX)2, tumor necrosis factor (TNF)α, interleukin (IL)‐1β, IL‐2Rα and other inflammatory markers in the skin of AD mice. In addition, serum levels of T helper (Th) cytokines (interferon (IFN)γ, IL‐4) were measured by enzyme‐linked immunosorbent assay. Quercetin treatment attenuated the development of AD‐like skin lesions. Histological analysis showed that quercetin inhibited hyperkeratosis, parakeratosis, acanthosis, mast cells and infiltration of inflammatory cells. Furthermore, quercetin treatment downregulated cytoplasmic HMGB1, RAGE, nuclear p‐NFκB, p‐ERK1/2, COX2, TNFα, IL‐1β, IL‐2Rα, IFNγ and IL‐4 and upregulated nuclear Nrf2. Our data demonstrated that the HMGB1/RAGE/NFκB signalling might play an important role in skin inflammation, and quercetin treatment could be a promising agent for AD by modulating the HMGB1/RAGE/NFκB signalling and induction of Nrf2 protein.

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.

Molecular understanding of curcumin in diabetic nephropathy.

Diabetic nephropathy is characterized by a plethora of signaling abnormalities. Recent trials have suggested that intensive glucose-lowering treatment leads to hypoglycemic events, which can be dangerous. Curcumin is the active ingredient of turmeric, which has been widely used in many countries for centuries to treat numerous diseases. The preventive and therapeutic properties of curcumin are associated with its antioxidant and anti-inflammatory properties. Here, we highlight the renoprotective role of curcumin in diabetes mellitus (DM) with an emphasis on the molecular basis of this effect. We also briefly discuss the numerous approaches that have been undertaken to improve the pharmacokinetics of curcumin.

Curcumin attenuates hyperglycaemia-mediated AMPK activation and oxidative stress in cerebrum of streptozotocin-induced diabetic rat

Abstract Oxidative stress has been strongly implicated in the pathogenesis of diabetic encephalopathy (DE). Numerous studies have demonstrated a close relationship between oxidative stress and AMPK activation in various disorders, including diabetes-related brain disorders. Since curcumin has powerful antioxidant properties, this study investigated its effects on hyperglycaemia-mediated oxidative stress and AMPK activation in rats with DE. Diabetes was induced by a single intraperitoneal injection of streptozotocin (STZ-55 mg/kg BW). The diabetic rats were then orally administered curcumin (100 mg/kg BW) or vehicle for 8 weeks. The cerebra of the diabetic rats displayed upregulated protein expression of AdipoR1, p-AMPKα1, Tak1, GLUT4, NADPH oxidase sub-units, caspase-12 and 3-NT and increased lipid peroxidation in comparison with the controls and all of these effects were significantly attenuated with curcumin treatment, except for the increase in AdipoR1 expressions. These results provide a new insight into the beneficial effects of curcumin on hyperglycaemia-mediated DE, which are produced through the down-regulation of AMPK-mediated gluconeogenesis associated with its anti-oxidant property.