Targeting apoptosis in the heart of streptozotocin-induced diabetic rats

To address the issue of cardiomyocyte apoptosis as a possible cause of diabetic cardiomyopathy and whether it would be possible to suppress this apoptosis by the use of PPAR gamma agonists [glitazones] and PPAR alpha agonists [fibrates], versus insulin. forty male rats were made diabetic by intraperitoneal [i.p.] streptozotocin [STZ] injection and were divided into four groups: group II [STZ-injected rats], groups III, IV and V [STZ-injected rats treated with insulin, PPAR gamma agonist [rosiglitazone] and PPAR alpha agonist [bezafirate] respectively, for twelve weeks starting one week following STZ injection]. Additionally, ten rats were injected i.p. by a single dose of saline and served as a control for group II. At the end of the experimental period, plasma glucose was measured. Left ventricular [LV] papillary muscles isometric force [developed tension [DT]] was determined. Oxidative stress as assessed by cardiac malondialdehyde [MDA] and reduced glutathione [GSH] concentrations as well as caspase-3 activity as an index of apoptosis were determined. STZ-injection induced diabetes, evidenced by significant higher mean value in plasma glucose concentration in group II compared to that of the control group I. Significant cardiomyopathy could be observed, in the form of significantly decreased DT of LV papillary muscles in group II compared to the control group I. STZ-injection resulted in oxidative stress evidenced by significant higher mean value in cardiac MDA concentration and significant lower mean value in cardiac GSH concentration in group II compared to the control group I. STZ-injection resulted in cardiac apoptosis evidenced by significant higher mean value in cardiac caspase-3 activity in group II compared to the control group I. The use of insulin, rosiglitazone as well as bezafibrate caused a significant decrease in plasma glucose concentration as well as a significant increase in body weight compared to group II. The use of insulin as well as rosiglitazone, but not bezafibrate, decreased cardiac caspase-3 activity and improved oxidative stress parameters evidenced by significant lower mean value in cardiac MDA concentration and significant higher mean value in cardiac GSH concentration compared to group II. Rosigitazone but neither insulin nor bezafibrate resulted in significant improvement of LV papillary muscle DT compared to group II. The results of the present study support the hypothesis that apoptosis plays a key role in the pathophysiology of diabetic cardiomyopathy and demonstrate that the use of PPAR gamma agonists might have a protective role against diabetic cardiomyopathy. We recommend further human studies to evaluate the role of the addition of PPAR gamma agonists to the treatment regimen of diabetes, from the onset of the disease, in protection against diabetic cardiomyopathy. Although the use of PPAR-alpha agonists seems counterintuitive in light of the current findings, the benefit of reduced delivery of fatty acids to the myocardium may outweigh the effects of activating the cardiac PPARalpha pathway in the diabetic patient

protective effect of nigella sativa oil and the derived thymoquinone and nigellone against thioacetamide induced liver fibrosis in rats

The present study examined the effect of oral administration of Nigella saliva oil [NSO], thymoquinone [TQ], the main active principle of the volatile oil of NSO and nigellone [NG], the less toxic carbonyl polymer of TQ, on progress of thioacetamide [TAA] -induced liver fibrosis in rats. Sixty male albino rats weighing 150-200 g/rat were classified into 6 groups as follows: group I, [saline-control], group II [TAA-induced liver injury], group III [NSO-treated], group IV [TQ-treated], group V [NG-treated] and group VI [propylene glycol - treated]. NSO, TQ, NG and propylene glycol were given daily orally for 6 weeks starting with TAA administration. Propylene glycol was the vehicle of TQ and NG. TAA-injury [group II] caused a significant rise in the portal pressure and serum concentrations of tumor necrosis factor -alpha, transforming growth factor - beta[1] and malondialdehyde. Moreover, liver function tests [serum aspartate and alanine aminotransferases, alkaline phosphatase and gamma-glutamyl transferase activities and serum albumin concentration] were significantly impaired in group II as compared to group I. Liver tissues obtained from rats treated by TAA had higher hydroxyproline and lower reduced glutathione contents as compared to saline-control [group I]. Administration NSO, TQ or NG caused significant and similar protective effects against all TAA-induced haemodynamic and biochemical impairments. This study suggests that NSO, TQ and NG are significantly and probably equally effective against TAA-induced liver injury and fibrosis. Inhibition of synthesis and/or release of TNF-alpha and TGF-beta[1] as well as inhibition of tissue oxidative stress may be of particular importance

Possible neuroprotective effect of some drugs modulating Nitric Oxide apoptotic pathway in L-2 chloropropionic acid-induced neuronal injury in rats

There is a recent evidence supporting that neuronal injury may be dependent upon the generation of the free radical nitric oxide [NO] with the subsequent induction of programmed cell death [apoptosis]. The aim of the present study was to assess the contribution of NO and the possible neuroprotective effect of two drugs modulating NO-apoptotic pathway, namely minocycline and ebselen, in L-2 chloropropionic acid [L-CPA] -induced neuronal injury in the rat. The present study was conducted on 40 male albino rats that were divided into: Group I; normal rats that served as control Group II; rats in which cerebellar neuronal injury was induced by L-CPA, Groups III and IV; rats with L-CPA -induced neuronal injury that received minocycline and ebselen respectively for 2 days starting half an hour before dosing with L-CPA. Forty-eight hours following L-CPA administration, signs characteristic of cerebellar ataxia, including hind limb weakness and abnormal gait were recorded, The ability of the rat to lift [retract] its hindlimbs was measured. Rats were then exsanguinated, cerebellum isolated for the determination of cerebellar: Nitric oxide synthase [NOS] activity, caspase-3 activity as an index of apoptosis, sodium concentration as a measure of cerebellar edema and glutamate concentration as a marker for cerebellar granule cell necrosis. The results of the present study demonstrated a significant increase in: the time taken by rats to retract hindlimbs, cerebellar NOS and caspase-3 activities as well as in sodium concentration, in group II compared to group I. A significant decrease in cerebellar glutamate concentration could be observed in group II compared to group I. Treatment with minocycline and ebselen resulted in significant decrease in cerebellar NOS activity and active caspase-3 and sodium concentrations together with a significant increase in cerebellar glutamate concentration compared to non-treated rats receiving L-CPA. In conclusion, the present work demonstrated that neuronal injury, induced by L-CPA, is associated with increased NOS activity resulting in increased NO production, which has been suggested to play a role in the mediation of that injury. We demonstrated that drugs that reduce the activity of NOS and caspases, like minocycline and ebselen are capable of blocking neurotoxicity. These results provide an experimental rationale for the evaluation of the role of NO-apoptotic pathway and the possible therapeutic potential of minocycline and ebselen in human neurological disorders

New insights into the modulatory role of serotonin reuptake inhibitors in myocardial ischemia reperfusion injury in rabbits

In view of the importance of serotonin in the pathogenesis of myocardial infarction [MI] and the reported decrease in platelet serotonin concentration associated with the treatment with selective serotonin reuptake inhibitors [SSRIs], the present study was planned to test the hypothesis of decreased risk of MI associated with the use of SSRIs in rabbits exposed to myocardial ischemia reperfusion injury [MIRI], with or without cigarette smoking. The present study was conducted on 50 New Zealand White male rabbits grouped into: group I [sham-operated], group II [coronary artery ligated and reperfused for induction of MIRI], group III [smoking for eight weeks and then coronary artery ligated and reperfused], group IV [treated with fluoxetine for three weeks before coronary artery ligation and reperfusion] and group V [smoking for eight weeks and treated with fluoxetin for three weeks, starting from the 6[th] week of smoking, before coronary artery ligation and reperfusion]. Six hours following coronary artery ligation and reperfusion, relaxation response of left anterior coronary artery [LACA] segments to acetylcholine [Ach] was assessed and plasma cardiac troponin T[cTnT], homocysteine [Hcy] and urinary cotinine concentrations as well as percentage of platelet aggregation in response to adenosine diphosphate [ADP] were measured. MIRI resulted in a significant attenuation of ACh-induced relaxation in LACA segments compared to normal sham-operated rabbits. A significant decrease in Ach-induced relaxation in smoking MIRI compared to non-smoking MIRI rabbits could be also detected. A significant increase in percentage of platelet aggregation in response to ADP and in plasma Hcy and cTnT concentrations could be detected in MIRI rabbits compared to sham-operated rabbits with a significant difference between smoking and non-smoking MIRI rabbits. Fluoxetine treatment significantly improved endothelium-dependent relaxation to ACh in LACA segments obtained from nonsmoking and smoking MIRI rabbits. Fluoxetine treatment also resulted in significant decrease in plasma Hyc and cTnT concentrations and in percent of platelet aggregation compared to non-treated smoking and non-smoking MIRI rabbits. The data of the present study support the notion that platelets play a role in MI. It could be concluded that SSRIs could be protective against MI by inhibiting serotonin-mediated platelet activation and exerting favorable effect on endothelial function. Future clinical trials, well designed and carefully conducted should elucidate the potential benefits of SSRIs in multiple thrombotic events like MI and unstable angina

possible renoprotective effect of angiotensin converting enzyme inhibitors and statins on renal ischemia reperfusion injury in rats

Ischemia-reperfusion-induced renal injury is the most common cause of acute renal failure [ARF]. Angiogenesis is an important phenomenon associated with recovery from ischemia. The aim of the present study was to assess the possible renoprotective effect of manipulating angiogenesis by trandolapril [an angiotensin converting enzyme [ACE] inhibitor] and simvastatin [a 3-hydroxy-3-methylglutaryl-coenzyme A [HMG-CoA] reductase inhibitor] in ischemic ARF in rat. The present study was conducted on 40 male albino rats that were divided into four groups. Group I included normal Sham-operated rats that served as control for group II, Group II were rats in which renal ischemia reperfusion injury [RIRI] was induced and Group III and Group IV consisted of rats that received trandolapril and simvastatin respectively, orally daily starting two days before and continuing for two days after the induction of RIRI. At the end of the experimental period, serum urea and creatinine concentrations and creatinine clearance were assessed. Moreover, serum and renal vascular endothelial growth factor [VEGF] levels, renal caspase-3 activity [as an index of apoptosis], renal hemoglobin content [as an index of angiogenesis] and renal oxidative stress parameters [malondialdhyde [MDA] and reduced glutathione [GSH] concentrations] were assessed. A significant increase in serum urea, creatinine concentrations and in renal VEGF, MDA concentrations and caspase-3 activity together with a significant decrease in creatinine clearance and renal GSH concentration has been observed in non-treated rats killed two days after RIRI compared to Sham-operated rats. Administration of trandolapril or simvastatin resulted in a significant decrease in serum urea and creatinine concentrations and in renal caspase-3 activity and renal MDA concentration as well as a significant increase in creatinine clearance and renal hemoglobin and GSH concentrations in rats killed two days following RIRI compared to non-treated rats with RIRI. A significant increase in renal VEGF concentration could be observed in simvastatin-, but not in trandolapril-treated rats killed two days following RIRI compared to non-treated rats with RIRI. The present study demonstrated the proangiogenic effect and the possible renoprotective role of trandolapril and simvastatin in rats with RIRI. It has been found that the proangiogenic effect of trandolapril is independent of VEGF, while that of simvastatin might involve several factors including VEGF

Role of oxidative stress in streptozotocin-induced diabetic neuropathy in rats

To assess the contribution of oxidative stress in the pathophysiology of diabetic neuropathy and the possible protective effect of L-carnitine, coenzyme Q 10 [CoQ10] and acetylsalicylic acid [ASA] in streptozotocin-included diabetic neuropathy in rats. We also examined whether the studied drugs can promote satisfactory regeneration of sciatic nerve fibers following sciatic nerve crushing. Twenty rats were used as control and were divided into two groups. 10 rats each: Group I a was injected intraperitoneal [i.p.] by a single dose of saline and served as a control for group II a, group I b similar to group I a but with induced sciatic nerve crushing and served as control for group II b. Eighty rats were made diabetic by i.p streptozotocin [STZ] injection and were divided into: group II a [STZ-injected rats], group II b [STZ-injected rats with sciatic nerve crushing], groups III a, IV a and V a [STZ-injected rats treated with L-carnitine, CoQ1O and ASA respectively, for six weeks starting one week following STZ injection], groups III b, IV b and V b [STZ-injected rats,with sciatic nerve crushing, that received the same drugs as groups III a, IV a and V a]. At the end of the experimental period, distal motor latency [DL], maximum peak and peak to peak amplitude of compound muscle action potential [CMAP] were measured by percutaneous sciatic nerve stimulation. Blood samples were collected for measurement of plasma glucose and malondialdehyde [MDA] concentrations. The sciatic nerve was isolated for measuring reduced glutathione [GSH] concentration. STZ-injection induced diabetes, evidenced by significant higher mean value in plasma glucose concentration in groups IIa and IIb compared to that of the control groups Ia and Ib respectively. Significant sciatic nerve dysfunction could be observed, in the form of significantly prolonged DL and significantly decreased maximum peak and peak to peak amplitude of CMAP, in groups IIa and IIb compared to the control groups Ia and Ib respectively. STZ-injection resulted in oxidative stress evidenced by significant higher mean value in plasma MDA concentration and significant lower mean value in sciatic nerve GSH concentration in groups IIa and IIb compared to the control groups Ia and Ib respectively. Sciatic nerve crushing in group I b resulted in significant prolongation of DL and significant decrease in maximum peak and peak to peak amplitude of CMAP compared to group I a. Sciatic nerve crushing in group I b also resulted in significant lower mean value of sciatic nerve GSH concentration compared to group I a. The use of L-carnitine, CoQ10 as well as ASA, did not cause a significant change in plasma glucose concentration nor in body weight compared to groups IIa and IIb. The use of the above mentioned drugs improved oxidative stress parameters evidenced by significant lower mean value in plasma MDA concentration and significant higher mean value in sciatic nerve GSH concentration compared to groups IIa and IIb. The increase in sciatic nerve GSH concentration in groups III b and IV b that received L-carnitine and CoQ10 respectively, was significant compared to group Vb that received ASA as an antioxidant, whereas no significant difference in plasma MDA was found between different drug-treated groups. The use of the studied drugs resulted in significant improvement of DL as well as significant increase in maximum peak and peak to peak amplitude of CMAP compared to groups IIa and IIb. Group V a showed significant higher mean value in the maximum peak and peak to peak amplitude of CMAP compared to groups III a and IV a. Also group V b showed significant higher mean value in the maximum peak and peak to peak amplitude of CMAP compared to group III b. The results of the present study support the hypothesis that oxidative stress plays a key role in the pathophysiology of diabetic neuropathy and demonstrate that the use of antioxidants might have a protective role against diabetic neuropathy as well as a role in enhancing regeneration of functional nerve fibers. We recommend further human studies to evaluate the role of the addition of natural antioxidants, like L-carnitine or CoQ10, as well as ASA to the treatment regimen of diabetes, from the onset of the disease, in protection against diabetic neuropathy