Sameer N. Goyal

Preventive effect of crocin of Crocus sativus on hemodynamic, biochemical, histopathological and ultrastuctural alterations in isoproterenol-induced cardiotoxicity in rats

We investigated the effects of crocin, a pharmacologically active constituent of Crocus sativus L., in isoproterenol (ISO)-induced cardiotoxicity with reference to hemodynamic, antioxidant, histopathological and ultrastructural parameters. Rats were administered crocin (5, 10 and 20mg/kg/day) or vehicle orally for 21 days along with ISO (85mg/kg, subcutaneously, at 24h interval) on 20th and 21st day. On 22nd day ISO-control rats showed cardiac dysfunction as indicated by lowering of systolic, diastolic and mean arterial blood pressures. In addition, a significant decrease in maximum positive and negative rate of developed left ventricular pressure (+/-LVdp/dt(max)) and an increase in left ventricular end-diastolic pressure (LVEDP) were observed. Furthermore, a marked reduction in the activities of myocardial creatine kinase-MB (CK-MB) isoenzyme, lactate dehydrogenase (LDH), superoxide dismutase (SOD), catalase (CAT), and reduced glutathione (GSH) levels along with an increase in content of malondialdehyde (MDA) were observed. Myocardial necrosis, edema and inflammation were evident from the light microscopic and ultrastructural changes. Crocin at the dose of 20mg/kg/day significantly modulated hemodynamic and antioxidant derangements. The preventive role of crocin on ISO-induced MI was reconfirmed by histopathological and ultrastructural examinations. The effect at the dose of 20mg/kg/day of crocin was more pronounced than that of other two doses (5 and 10mg/kg/day). The results suggest that crocin may have cardioprotective effect in ISO-induced cardiac toxicity through modulation of oxidative stress in such a way that maintains the redox status of the cell.

Telmisartan, a dual ARB/partial PPAR-γ agonist, protects myocardium from ischaemic reperfusion injury in experimental diabetes.

Aim: Apart from its angiotensin receptor blocker (ARB) activity, telmisartan is also a partial agonist of peroxisome proliferator‐activated receptor gamma (PPAR‐γ). Therefore, we assessed whether telmisartan treatment attenuates myocardial ischaemia/reperfusion (I/R) injury in diabetic rats through PPAR‐γ pathway.

Challenges and issues with streptozotocin-induced diabetes – A clinically relevant animal model to understand the diabetes pathogenesis and evaluate therapeutics

Streptozotocin (STZ) has been extensively used over the last three decades to induce diabetes in various animal species and to help screen for hypoglycemic drugs. STZ induces clinical features in animals that resemble those associated with diabetes in humans. For this reason STZ treated animals have been used to study diabetogenic mechanisms and for preclinical evaluation of novel antidiabetic therapies. However, the physiochemical characteristics and associated toxicities of STZ are still major obstacles for researchers using STZ treated animals to investigate diabetes. Another major challenges in STZ-induced diabetes are sustaining uniformity, suitability, reproducibility and induction of diabetes with minimal animal lethality. Lack of appropriate use of STZ was found to be associated with increased mortality and animal suffering. During STZ use in animals, attention should be paid to several factors such as method of preparation of STZ, stability, suitable dose, route of administration, diet regimen, animal species with respect to age, body weight, gender and the target blood glucose level used to represent hyperglycemia. Therefore, protocol for STZ-induced diabetes in experimental animals must be meticulously planned. This review highlights specific skills and strategies involved in the execution of STZ-induced diabetes model. The present review aims to provide insight into diabetogenic mechanisms of STZ, specific toxicity of STZ with its significance and factors responsible for variations in diabetogenic effects of STZ. Further this review also addresses ways to minimize STZ-induced mortality, suggests methods to improve STZ-based experimental models and best utilize them for experimental studies purported to understand diabetes pathogenesis and preclinical evaluation of drugs.

Upregulation of PPARγ by Aegle marmelos ameliorates insulin resistance and β-cell dysfunction in high fat diet fed-streptozotocin induced type 2 diabetic rats.

The global epidemic of type 2 diabetes demands the rapid evaluation of new and accessible interventions. This study investigated whether Aegle marmelos fruit aqueous extract (AMF; 250, 500 and 1000 mg/kg) improves insulin resistance, dyslipidemia and β‐cell dysfunction in high fat diet fed‐streptozotocin (HFD‐STZ)‐induced diabetic rats by modulating peroxisome proliferator‐activated receptor‐γ (PPARγ) expression. The serum levels of glucose, insulin, homeostasis model assessment of insulin resistance (HOMA‐IR), homeostasis model assessment of β‐cell function (HOMA‐B), lipid profile, TNF‐α and IL‐6 were evaluated. Further, the TBARS level and SOD activity in pancreatic tissue and PPARγ protein expression in liver were assessed. In addition, histopathological and ultrastructural studies were performed to validate the effect of AMF on β‐cells. The HFD‐STZ treated rats showed a significant increase in the serum levels of glucose, insulin, HOMA‐IR, TNF‐α, IL‐6, dyslipidemia with a concomitant decrease in HOMA‐B and PPARγ expression. Treatment with AMF for 21 days in diabetic rats positively modulated the altered parameters in a dose‐dependent manner. Furthermore, AMF prevented inflammatory changes and β‐cell damage along with a reduction in mitochondrial and endoplasmic reticulum swelling. These findings suggest that the protective effect of AMF in type 2 diabetic rats is due to the preservation of β‐cell function and insulin‐sensitivity through increased PPARγ expression. Copyright

Seabuckthorn Pulp Oil Protects against Myocardial Ischemia–Reperfusion Injury in Rats through Activation of Akt/eNOS

Seabuckthorn (SBT) pulp oil obtained from the fruits of seabuckthorn [Hippophae rhamnoides L. (Elaeagnaceae)] has been used traditionally for its medicinal and nutritional properties. However, its role in ischemia–reperfusion (IR) injury of myocardium in rats has not been elucidated so far. The present study reports the cardioprotective effect of SBT pulp oil in IR-induced model of myocardial infarction in rats and underlying mechanism mediating activation of Akt/eNOS signaling pathway. Male albino Wistar rats were orally administered SBT pulp oil (5, 10, and 20 ml/kg/day) or saline for 30 days. On the day 31, ischemia was induced by one-stage ligation of left anterior descending coronary artery for 45 min followed by reperfusion for 60 min. SBT pulp oil pretreatment at the dose of 20 ml/kg observed to stabilize cardiac function and myocardial antioxidants such as glutathione, superoxide dismutase, catalase, and inhibited lipid peroxidation evidenced by reduced malondialdehyde levels as compared to IR-control group. SBT pulp oil also improved hemodynamic and contractile function and decreased tumor necrosis factor and activities of myocyte injury marker enzymes; lactate dehydrogenase and creatine kinase-MB. Additionally, a remarkable rise in expression of pAkt–eNOS, Bcl-2 and decline in expression of IKKβ/NF-κB and Bax was observed in the myocardium. The histopathological and ultrastructural salvage of cardiomyocytes further supports the cardioprotective effect of SBT pulp oil. Based on findings, it can be concluded that SBT pulp oil protects against myocardial IR injury mediating favorable modulation of Akt-eNOS and IKKβ/NF-κB expression.

Modulation of PPAR-γ by telmisartan protects the heart against myocardial infarction in experimental diabetes

Telmisartan, an angiotensin II-receptor blocker (ARB), is a partial agonist of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma). We investigated whether telmisartan improved the pathophysiology of myocardial infarction in diabetes partially through the PPAR-gamma pathway by assessing a variety of indices, e.g., hemodynamic, biochemical, histoarchitectural changes, and apoptosis. Diabetes was induced by a single dose of streptozotocin (70 mg/kg, IP). Diabetic rats received either telmisartan (10 mg/kg/day, orally), the PPAR-gamma antagonist GW9662 (1 mg/kg/day, IP), or both for 14 days with concurrent administration of isoproterenol (85 mg/kg, SC) on days 13 and 14. Compared with diabetic controls, diabetic rats with myocardial infarction exhibited altered hemodynamic profiles and reduction in the activities of creatine kinase-MB isoenzyme, lactate dehydrogenase, superoxide dismutase, catalase, and glutathione level along with increased level of malondialdehyde in the heart. Further, diabetic animals with myocardial infarction exhibited increased myonecrosis, edema, and apoptotic cell death. Treatment with telmisartan significantly improved the redox status of the myocardium with subsequent cardiac functional recovery. However, significant effects were lowered in animals treated with telmisartan plus GW9662. Telmisartan markedly inhibited Bax expression, TUNEL-positive cells, myonecrosis, and edema. On the other hand, administration of telmisartan plus GW9662 did not elicit the same effects, nor did they increase Bcl-2 protein expression in isoproterenol-induced myocardially infarcted diabetic rats when administered concomitantly or individually. Moreover, down-regulated PPAR-gamma expression in myocardially infarcted diabetic hearts was increased by telmisartan treatment. In addition to class effects of ARBs, telmisartan reduces oxidative stress and apoptosis and improves cardiac function via the PPAR-gamma pathway.

Neuropeptide Y modulates the antidepressant activity of imipramine in olfactory bulbectomized rats: Involvement of NPY Y1 receptors

Since long-term treatment with imipramine increases the neuropeptide Y (NPY) levels in the frontal cortex and hypothalamus, the possibility exists that the antidepressant action of imipramine may be mediated via the NPY Y1 receptors. Bilateral olfactory bulbectomy (OBX) resulted in hyperactivity (increased number of ambulation, rearing and grooming episodes) in open field test (OFT) suggesting a depression-like condition. Chronic (14 days) administration of NPY, NPY Y1/Y5 receptor agonist [Leu(31), Pro(34)]-NPY (intracerebroventricular, i.c.v.) or tricyclic antidepressant imipramine (intraperitoneal) to OBX rats dose-dependently resulted in decreased hyperactivity in OFT, while selective NPY Y1 receptor antagonist BIBP3226 (i.c.v.) produced opposite effects. The antidepressant actions of imipramine were enhanced by co-administration of NPY or [Leu(31), Pro(34)]-NPY, and antagonized by BIBP3226 given at sub-effective doses. The data suggest that NPY, acting via NPY Y1 receptors, may be involved in antidepressant action of imipramine in OBX rats.

Cardioprotective effect of 'Khamira Abresham Hakim Arshad Wala' a unani formulation in isoproterenol-induced myocardial necrosis in rats.

The present study was designed to investigate whether Khamira Abresham Hakim Arshad Wala (KAHAW), a preparation of Unani System of Medicine, is able to attenuate the isoproterenol (ISO)-induced myocardial necrosis on the basis of its effects on hemodynamic, antioxidant, histopathological and ultrastructural parameters. Male Wistar albino rats were administered KAHAW (200, 400 and 800mg/kg/day, orally) or vehicle for 14 days with concurrent ISO administration (85mg/kg, subcutaneously, 2 doses at 24h interval) on 13th and 14th day. On the 15th day, vehicle+ISO-treated rats exhibit cardiac dysfunctions as indicated by decrease in systolic, diastolic, and mean arterial pressures, reduction in both maximum positive and maximum negative rates of developed left ventricular pressure (+/-LVdp/dt) and an increase in left ventricular end-diastolic pressure (LVEDP). Biochemical analysis of their heart homogenate presented reduced levels of enzymes viz., superoxide dismutase (SOD), catalase (CAT), lactate dehydrogenase (LDH), creatine kinase-MB (CK-MB) isoenzyme. A marked reduction in reduced glutathione (GSH) levels along with increase in levels of thiobarbituric acid reactive substances (TBARS) was also observed in rat myocardium. Myocardial necrosis, edema and inflammation were evident from the light microscopic and ultrastructural changes. KAHAW at dose of 800mg/kg/day significantly reversed majority of hemodynamic and antioxidant derangements. The protective role of KAHAW on ISO-induced myocardial necrosis was further confirmed by histopathological and ultrastructural examination. There was no significant change in heart rate in all experimental groups. KAHAW per se groups showed no significant change when compared with vehicle control group. The study results thus demonstrated the cardioprotective potential of KAHAW against ISO-induced myocardial necrosis and associated oxidative stress.

Kaempferol Attenuates Myocardial Ischemic Injury via Inhibition of MAPK Signaling Pathway in Experimental Model of Myocardial Ischemia-Reperfusion Injury.

Kaempferol (KMP), a dietary flavonoid, has antioxidant, anti-inflammatory, and antiapoptotic effects. Hence, we investigated the effect of KMP in ischemia-reperfusion (IR) model of myocardial injury in rats. We studied male albino Wistar rats that were divided into sham, IR-control, KMP-20 + IR, and KMP 20 per se groups. KMP (20 mg/kg; i.p.) was administered daily to rats for the period of 15 days, and, on the 15th day, ischemia was produced by one-stage ligation of left anterior descending coronary artery for 45 min followed by reperfusion for 60 min. After completion of surgery, rats were sacrificed; heart was removed and processed for biochemical, morphological, and molecular studies. KMP pretreatment significantly ameliorated IR injury by maintaining cardiac function, normalizing oxidative stress, and preserving morphological alterations. Furthermore, there was a decrease in the level of inflammatory markers (TNF-α, IL-6, and NFκB), inhibition of active JNK and p38 proteins, and activation of ERK1/ERK2, a prosurvival kinase. Additionally, it also attenuated apoptosis by reducing the expression of proapoptotic proteins (Bax and Caspase-3), TUNEL positive cells, and increased level of antiapoptotic proteins (Bcl-2). In conclusion, KMP protected against IR injury by attenuating inflammation and apoptosis through the modulation of MAPK pathway.

Myocardial salvaging effect of telmisartan in experimental model of myocardial infarction

Telmisartan is a unique angiotensin II receptor blocker with an additional peroxisome proliferator-activated receptor-gamma (PPAR-gamma) activity. The present study has been designed to investigate whether telmisartan treatment attenuates the development of acute myocardial infarction in isoproterenol-treated rats by restoring hemodynamic, biochemical, histopathological and ultrastructural changes. Isoproterenol-induced cardiotoxicity was evidenced by marked decrease in systolic, diastolic, mean arterial pressures, maximal positive rate of developed left ventricular pressure (+LVdP/dt(max), a marker of myocardial contraction), maximal negative rate of developed left ventricular pressure (-LVdP/dt(max), a marker of myocardial relaxation) and an increase in left ventricular end-diastolic pressure (LVEDP, a marker of pre-load). In addition, a significant reduction in activities of myocardial creatine kinase-MB (CK-MB) isoenzyme, lactate dehydrogenase (LDH), superoxide dismutase (SOD), catalase, and reduced glutathione (GSH) level along with increase in malondialdehyde (MDA) content were observed. Oral pretreatment with telmisartan (1, 5 and 10mg/kg body weight) daily for a period of 14 days, favourably modulated the studied parameters in isoproterenol-induced myocardial injury. In addition, the protective role of telmisartan on isoproterenol-induced myocardial damage was further confirmed by histopathological and ultrastructural examinations. Telmisartan at a dose of 10mg/kg produced more pronounced protective effects than the other two doses (1 and 5mg/kg body weight). Present study thus provides evidence for protective effects of telmisartan on myocardium in experimentally induced myocardial infarction.