Niacin bound chromium treatment induces myocardial Glut-4 translocation and caveolar interaction via Akt,AMPK and eNOS phosphorylation in streptozotocin induced diabetic rats after ischemia-reperfusion injury

Diabetes, one of the major risk factors of metabolic syndrome culminates in the development of Ischemic Heart Disease (IHD). Refined diets that lack micronutrients, mainly trivalent chromium (Cr³⁺) have been identified as the contributor in the rising incidence of diabetes. We investigated the effect of niacin-bound chromium (NBC) during ischemia/reperfusion (IR) injury in streptozotocin induced diabetic rats. Rats were randomized into: Control (Con); Diabetic (Dia) and Diabetic rats fed with NBC (Dia + NBC). After 30 days of treatment, the isolated hearts were subjected to 30 min of global ischemia followed by 2 h of reperfusion. NBC treatment demonstrated significant increase in left ventricular functions and significant reduction in infarct size and cardiomyocyte apoptosis in Dia + NBC compared with Dia. Increased Glut-4 translocation to the lipid raft fractions was also observed in Dia + NBC compared to Dia. Reduced Cav-1 and increased Cav-3 expression along with phosphorylation of Akt, eNOS and AMPK might have resulted in increased Glut-4 translocation in Dia + NBC. Our results indicate that the cardioprotective effect of NBC is mediated by increased activation of AMPK, Akt and eNOS resulting in increased translocation of Glut-4 to the caveolar raft fractions thereby alleviating the effects of IR injury in the diabetic myocardium.     

Postischemic Deactivation of Cardiac Aldose Reductase: ROLE OF GLUTATHIONE S-TRANSFERASE P AND GLUTAREDOXIN IN REGENERATION OF REDUCED THIOLS FROM SULFENIC ACIDS*

Aldose reductase (AR) is a multifunctional enzyme that catalyzes the reduction of glucose and lipid peroxidation-derived aldehydes. During myocardial ischemia, the activity of AR is increased due to the oxidation of its cysteine residues to sulfenic acids. It is not known, however, whether the activated, sulfenic form of the protein (AR-SOH) is converted back to its reduced, unactivated state (AR-SH). We report here that in perfused mouse hearts activation of AR during 15 min of global ischemia is completely reversed by 30 min of reperfusion. During reperfusion, AR-SOH was converted to a mixed disulfide (AR-SSG). Deactivation of AR and the appearance of AR-SSG during reperfusion were delayed in hearts of mice lacking glutathione S-transferase P (GSTP). In vitro, GSTP accelerated glutathiolation and inactivation of AR-SOH. Reduction of AR-SSG to AR-SH was facilitated by glutaredoxin (GRX). Ischemic activation of AR was increased in GRX-null hearts but was attenuated in the hearts of cardiospecific GRX transgenic mice. Incubation of AR-SSG with GRX led to the regeneration of the reduced form of the enzyme. In ischemic cardiospecific AR transgenic hearts, AR was co-immunoprecipitated with GSTP, whereas in reperfused hearts, the association of AR with GRX was increased. These findings suggest that upon reperfusion of the ischemic heart AR-SOH is converted to AR-SSG via GSTP-assisted glutathiolation. AR-SSG is then reduced by GRX to AR-SH. Sequential catalysis by GSTP and GRX may be a general redox switching mechanism that regulates the reduction of protein sulfenic acids to cysteines.     

Resveratrol in cardioprotection: a therapeutic promise of alternative medicine

Resveratrol, a polyphenol phytoalexin, possesses diverse biochemical and physiological actions, including estrogenic, antiplatelet, and anti-inflammatory properties. Several recent studies determined the cardioprotective abilities of resveratrol. Both in experiments (acute) and in chronic models, resveratrol attenuates myocardial ischemic reperfusion injury, atherosclerosis, and reduces ventricular arrhythmias. It appears that resveratrol-mediated cardioprotection is achieved through the preconditioning effect (the best yet devised method of cardioprotection), rather than direct protection. Thus, resveratrol likely fulfills the definition of a pharmacological preconditioning compound and gives hope to the therapeutic promise of alternative medicine.     

Rapid plasma membrane-endosomal trafficking of the lymph node sinus and high endothelial venule scavenger receptor/homing receptor stabilin-1 (FEEL-1/CLEVER-1)

The sinusoidal endothelia of liver, spleen, and lymph node are major sites for uptake and recycling of waste macromolecules through promiscuous binding to a disparate family of scavenger receptors. Among the most complex is stabilin-1, a large multidomain protein containing tandem fasciclin domains, epidermal growth factor-like repeats, and a C-type lectin-like hyaluronan-binding Link module, which functions as an endocytic receptor for acetylated low density lipoprotein and advanced glycation end products. Intriguingly, stabilin-1 has also been reported to mediate both homing of leukocytes across lymph node high endothelial venules and adhesion of metastatic tumor cells to peritumoral lymphatic vessels. Currently, however, it is not clear how stabilin-1 mediates these distinct functions. To address the issue, we have investigated the tissue and subcellular localization of stabilin-1 in detail and assessed the functional status of its Link module. We show that stabilin-1 is almost entirely intracellular in lymph node high endothelial venules, lymphatic sinus endothelium, and cultured endothelial cells but that a finite population, detectable only by fluorescent antibody or fluorescein-labeled (Fl)-acetylated low density lipoprotein uptake, cycles rapidly between the plasma membrane and EEA-1+ve (early endosome antigen 1) early endosomes. In addition, we show using full-length stabilin-1 cDNA and a stabilin-1/CD44 chimera in HeLa cells that intracellular targeting is influenced by the transmembrane domain/cytoplasmic tail, which contains a putative dileucine (DXXLL) Golgi to endosomal sorting signal. Finally, we provide evidence that the stabilin-1 Link domain binds neither hyaluronan nor other glycosaminoglycans. These properties support a role for stabilin-1 as a rapidly recycling scavenger receptor and argue against a role in cell adhesion or lymphocyte homing.     

A comparative study of allitin and garlic on lipid turnover in a teleost, Anabas testudineus (Bloch)

Both allitin and garlic have anti-lipogenic properties substantiated by the activity of three lipogenic enzymes and lipid profiles. The rise in the HDL levels and simultaneous fall in the LDL upon garlic intake is the most convincing indicator of reduced lipid concentration. However, the administration of allitin recorded a decrease in the HDL and LDL levels, but when calculated on a percentage basis, there was a marginal increase in the HDL level. On the basis of results, it can be concluded that garlic or its derivatives have hypolipidaemic effect in submammalian vertebrates also. The cholesterol lowering effect of allitin and garlic can be commercially exploited for producing fish with low cholesterol for possible human consumption.     

Ischemic preconditioning attenuates apoptotic cell death associated with ischemia/reperfusion

Apoptosis or programmed cell death is a genetically controlled response for cells to commit suicide and is associated with DNA fragmentation or laddering. The common inducers of apoptosis include oxygen free radicals/oxidative stress and Ca2+ which are also implicated in the pathogenesis of myocardial ischemic reperfusion injury. To examine whether ischemic reperfusion injury is mediated by apoptotic cell death, isolated perfused rat hearts were subjected to 15, 30 or 60 min of ischemia as well as 15 min of ischemia followed by 30, 60, 90 or 120 min of reperfusion. At the end of each experiment, the heart was processed for the evaluation of apoptosis and DNA laddering. Apoptosis was studied by visualizing the apoptotic cardiomyocytes by direct fluorescence detection of digoxigenin-labeled genomic DNA using APOPTAG® in situ apoptosis detection kit. DNA laddering was evaluated by subjecting the DNA obtained from the hearts to 1.8% agarose gel electrophoresis and photographed under UV illumination. The results of our study revealed apoptotic cells only in the 90 and 120 min reperfused hearts as demonstrated by the intense fluorescence of the immunostained digoxigenin-labeled genomic DNA when observed under fluorescence microscopy. None of the ischemic hearts showed any evidence of apoptosis. These results were corroborated with the findings of DNA fragmentation which showed increased ladders of DNA bands in the same reperfused hearts representing integer multiples of the internucleosomal DNA length (about 180 bp). The presence of apoptotic cells and DNA fragmentation in the myocardium were completely abolished by subjecting the myocardium to repeated short-term ischemia and reperfusion which also reduced the ischemic reperfusion injury as evidenced by better recovery of left ventricular performance in the preconditioned myocardium. The results of this study indicate that reperfusion of ischemic heart, but not ischemia, induces apoptotic cell death and DNA fragmentation which can be inhibited by myocardial adaptation to ischemia.     

Expression and characterization of a parasite-specific antigen on macrophages after infection withLeishmania donovani

A rabbit polyclonal antibody to crude soluble antigen ofLeishmania donovani promastigotes recognized a determinant expressed on the surface membrane of mouse peritoneal macrophages and human monocyte derived macrophages infectedin vitro. The determinant was recognized on infected macrophage surface only when F (ab)₂ fragments of anti-leishmanial antiserum was employed in immunofluorescence. F(ab)₂ fragments of human patient sera also could recognize the determinant. The expression of this antigen was not stage-specific for the parasite. Immunochemical analyses revealed this antigen to be of 51 kDa protein. Specific leaching of membrane proteins by trypsin showed three bands of expressed antigens of 26, 11 and 10 kDa, which in all likelihood might be arising from the 51 kDa antigen. The antigen was not expressed until 12 h of post infection, reached a maximum level at 24 h and thereafter attained a steady state level as studied upto 96 h of post infection. This typc of antigen might have a great potential in immunodiagnostics and site-specific drug targeting.     

Improved postischemic ventricular functional recovery by amphetamine is linked with its ability to induce heat shock

Heat shock has been shown to increase the cellular tolerances to ischemic injury. In this study, we examined the effects of heat shock induced by amphetamine on postischemic myocardial functional recovery in a setting of coronary revascularization for acute myocardial infarction. Intramuscular injection of amphetamine (3 mg/kg, i.m.) to pigs increased the body temperature to 42.5°C within 1 h, and maintained this temperature for an additional 2 h. Fourty h after the amphetamine injection, the pigs were placed on by cardiopulmonary bypass and then isolated,in situ heart preparations were subjected to 1 h of global hypothermic cardioplegic arrest and 1 h of normothermic reperfusion. Postischemic myocardial performance was monitored by measuring left ventricular (LV) pressure, its dp/dt, myocardial segmental shortening (%SS), and coronary blood flow. Cellular injury was examined by measuring creatine kinase (CK) release. Biochemical measurements included quantification of plasma catecholamines and study of the induction of heat shock gene expression and antioxidative enzymes in the heart tissue. The results of this study indicated significantly greater recovery of LV contractile functions by amphetamine as demonstrated by improved recovery of LVDP (61% vs 52%), dp/dt_max (52% vs 44%), and segmental shortening (46.2% vs 10%). Myocardial CK release was significantly reduced in the amphetamine group. Furthermore, amphetamine pretreatment was associated with the induction of heat shock protein (HSP) 27 mRNA and stimulated Cu/Zn-superoxide dismutase and catalase levels, suggesting that amphetamine mediated improved postischemic ventricular recovery might be linked with its ability to induce heat shock and stimulate antioxidant enzymes.     

A new alkamide from Piper sylvaticum

Sylvamide, a new amide derivative, has been isolated from the petrol extract of the seeds of Piper sylvaticum (Roxb.). From spectral and chemical s