Amina S. Attia

Hypericum perforatum extract demonstrates antioxidant properties against elevated rat brain oxidative status induced by amnestic dose of scopolamine

This study was designed to investigate if the impairment of learning and memory induced by acute administration of scopolamine (1.4 mg/kg ip) in rats is associated with altered brain oxidative stress status. The passive avoidance paradigm was used to assess retrieval memory of rats after scopolamine treatment. Following retrieval testing, biochemical assessments of malondialdehyde (MDA), glutathione peroxidase (GSHPx), glutathione (GSH), and superoxide dismutase (SOD) levels/activities as oxidative stress indices were performed. This study also investigated the effect of acute administration of Hypericum perforatum extract (4.0, 8.0, 12.0, and 25.0 mg/kg ip), containing flavonoids with documented antioxidant activity, on brain oxidative status of nai;ve rats treated with amnestic dose of scopolamine. Results showed that administration of 1.4 mg/kg of scopolamine impaired retrieval memory of rats and that such amnesia was associated with elevated MDA and reduced GSH brain levels. In nai;ve rats, which have not been exposed to conditioned fear, scopolamine administration also increased MDA and reduced GSH levels, although with an increase in brain GSHPx activity. Pretreatment of the animals with Hypericum extract (4, 8, and 12 mg/kg) resulted in an antioxidant effect through altering brain MDA, GSHPx, and/or GSH level/activity. Since oxidative stress is implicated in the pathophysiology of dementia, the findings of this study may substantiate the value of scopolamine-induced amnesia in rats as a valid animal model to screen for drugs with potential therapeutic benefit in dementia. Exposure of animals to conditioned fear may be suggested to impair the balance between the rate of lipid peroxidation and the activation of GSHPx as a compensatory antioxidant protective mechanism. It is also concluded that low doses of Hypericum extract, demonstrating antioxidant activity, may be of value for demented patients exhibiting elevated brain oxidative status. Since depression commonly coexists with dementia, Hypericum extract as a drug with documented antidepressant action may also be a better alternative than several other antidepressant medications that have not been evaluated to test their effect on brain oxidative status during amnesia.

Pharmacological preconditioning with nicorandil and pioglitazone attenuates myocardial ischemia/reperfusion injury in rats.

The present investigation was designed to study the cardioprotective effects of nicorandil and pioglitazone preconditioning in myocardial ischemia/reperfusion-induced hemodynamic, biochemical and histological changes in rats. Oral doses of nicorandil (3 or 6 mg/kg) and pioglitazone (10 or 20mg/kg) were administered once daily for 5 consecutive days. Rats were then subjected to myocardial ischemia/reperfusion (40 min/10 min). Heart rate and ventricular arrhythmias were recorded during ischemia/reperfusion progress. At the end of reperfusion, plasma creatine kinase-MB activity and total nitrate/nitrite were determined. In addition, lactate, adenine nucleotides, thiobarbituric acid reactive substances, reduced glutathione and myeloperoxidase activity were estimated in the heart left ventricle. Finally, histological examination was performed to visualize the protective cellular effects of different pretreatments. Nicorandil (3 or 6 mg/kg) was effective in attenuating the ischemia/reperfusion-induced ventricular arrhythmias, creatine kinase-MB release, lactate accumulation and oxidative stress. Nicorandil (3 mg/kg) was more effective in improving the energy production and lowering the elevated myeloperoxidase activity. Both doses of pioglitazone (10 or 20 mg/kg) were equally effective in reducing lactate accumulation and completely counteracting the oxidative stress. Pioglitazone (10 mg/kg) was more effective in improving energy production and reducing ventricular arrhythmias, plasma creatine kinase-MB release and total nitrate/nitrite. It seems that selective mitochondrial K(ATP) channel opening by lower doses of nicorandil and pioglitazone in the present study provided more cardioprotection against ventricular arrhythmias and biochemical changes induced by ischemia/reperfusion. Histological examination revealed also better improvement by the lower dose of nicorandil than that of pioglitazone.

Sitagliptin attenuates transient cerebral ischemia/reperfusion injury in diabetic rats: Implication of the oxidative–inflammatory–apoptotic pathway

AIMS Ischemic stroke is a major macrovascular complication of diabetes mellitus. Sitagliptin, a dipeptidyl peptidase-IV inhibitor, was recently shown to improve cognitive functions in diabetic rats; hence the present study was conducted to evaluate its protective effect against transient ischemia-reperfusion (I/R) in diabetic animals. MAIN METHODS Diabetes was induced by streptozotocin (40 mg/kg). Six weeks later, cerebral I/R was induced by bicommon carotid occlusion for 15 min followed by 1h reperfusion. Sitagliptin (250 mg/kg; p.o.) was administered daily during the last 2 weeks before I/R. KEY FINDINGS The drug alleviated hippocampal injury inflicted by diabetes and/or I/R injury where it suppressed nuclear factor kappa (NF-κ)B, and consequently the downstream inflammatory cytokines tumor necrosis factor-α and interleukin-6. In parallel, the anti-inflammatory cytokine interleukin-10 was elevated. Antioxidant potential of sitagliptin was depicted, where it reduced neutrophil infiltration, lipid peroxides and nitric oxide associated with replenished reduced glutathione. Decline of excitatory amino acid glutamate content is a main finding which is probably mediated by the NF-κB signaling pathway as well as improved oxidant status. Sitagliptin exerted an anti-apoptotic effect as reflected by the reduction of the mitochondrial matrix component cytochrome -C and the key downstream executioner caspase-3. Histopathological examination corroborated the biochemical data. SIGNIFICANCE These findings suggest that sitagliptin is endowed with neuroprotective properties which are probably mediated by its antioxidant, anti-inflammatory, and anti-apoptotic mechanisms and hence may provide a novel agent for the management of ischemic stroke in diabetics.

Pinocembrin attenuates hippocampal inflammation, oxidative perturbations and apoptosis in a rat model of global cerebral ischemia reperfusion

BACKGROUND Pinocembrin is a major flavonoid molecule isolated from honey and propolis. It has versatile pharmacological and biological activities including antimicrobial, anti-inflammatory, antioxidant, and anticancer activities as well as neuroprotective effects against cerebral ischemic injury. The purpose of the current study was to determine the possible mechanisms of neuroprotection elicited by pinocembrin with specific emphasis on chronic prophylactic use before the induction of global cerebral ischemia reperfusion. METHODS Global cerebral ischemia-reperfusion (I/R) was induced by bilateral carotid artery occlusion for 15min followed by 60min reperfusion period. Animals were randomly allocated into 3 groups (n=28): Sham operated, I/R control and rats treated with pinocembrin (10mg/kg, po) daily for 7 days then I/R was induced 1h after the last dose of pinocembrin. After reperfusion rats were killed by decapitation, brains were removed and both hippocampi separated and the following biochemical parameters were estimated; lactate dehydrogenase activity, oxidative stress markers (lipid peroxides, nitric oxide and reduced glutathione), inflammatory markers (myeloperoxidase, tumor necrosis factor-alpha, nuclear factor kappa-B, interleukin-6 and interleukin-10), apoptotic biomarkers (caspase 3 and cytochrome C), neurotransmitters (glutamate, gamma aminobutyric acid) and infarct size were assessed. RESULTS Pinocembrin ameliorated damage induced by I/R through suppressing oxidative stress, inflammatory and apoptotic markers as well as mitigating glutamate and lactate dehydrogenase activity. One of the more significant findings to emerge from this study is that pinocembrin normalized the infarct size elevated by I/R. CONCLUSIONS Pinocembrin showed a neuroprotective effects through antioxidant, anti-inflammatory and antiapoptotic mechanisms.

Enhancement of amlodipine cardioprotection by quercetin in ischaemia/reperfusion injury in rats

Objectives To investigate the possible modification of the cardioprotective effect of amlodipine when co‐administered with quercetin in myocardial ischaemia/reperfusion‐induced functional, metabolic and cellular alterations in rats.

Ischemic preconditioning and postconditioning alleviates hippocampal tissue damage through abrogation of apoptosis modulated by oxidative stress and inflammation during transient global cerebral ischemia–reperfusion in rats

INTRODUCTION It has been argued recently that ischemic preconditioning (IPre) and postconditioning (IPost) have beneficial effects in many ischemic disorders however; their effects on global ischemia/reperfusion (I/R) are poorly understood. Thus, the present work aimed to study the possible mechanisms underlying the neuroprotective effects of IPre and IPost. METHODS Animals were randomly allocated into 4 groups (n = 30): (1) Sham operated (SO); (2) I/R group, animals were subjected to 15 min global ischemia followed by 60 min reperfusion; (3) IPre, animals were subjected to 3 episodes of 5 min ischemia followed by 10 min reperfusion before I/R; (4) IPost, animals were subjected to three episodes of 10s of ischemia and 10s of reperfusion after the period of ischemia followed by a 60 min reperfusion period. Lactate dehydrogenase activity, oxidative stress, inflammatory and apoptotic biomarkers, as well as neurotransmitters, infarct size and histopathological examination were assessed. RESULTS I/R induced hippocampal damage through increasing oxidative stress, inflammatory, excitotoxic and apoptotic markers as well as lactate dehydrogenase activity and infarct size. Both, IPre and IPost attenuated most markers induced by I/R. CONCLUSIONS IPre and IPost neuroprotective effects can be explained through their anti-oxidant, anti-inflammatory and anti-apoptotic mechanisms.

Neuroprotective effects of pioglitazone against transient cerebral ischemic reperfusion injury in diabetic rats: Modulation of antioxidant, anti-inflammatory, and anti-apoptotic biomarkers

BACKGROUND Recent growing consensus introduced thiazolidinediones, agonists of the nuclear receptor peroxisome proliferator-activated receptor gamma as promising candidates in the management of ischemia in various organs. Thereby, interest was raised to investigate the neuroprotective effects of pioglitazone against transient ischemia/reperfusion (I/R) injury in diabetic rats targeting mainly the oxidative-inflammatory-apoptotic cascades which are involved in this insult. METHODS Forebrain ischemia was induced in streptozotocin-diabetic rats by occlusion of the bilateral common carotid arteries for 15min followed by 1h reperfusion. Pioglitazone (10mg/kg; po) was administered daily for 2 weeks prior to I/R. RESULTS The drug alleviated hippocampal injury inflicted by diabetes and/or I/R injury where it suppressed nuclear factor kappa (NFκB), and consequently the downstream inflammatory cytokines tumor necrosis factor-α and interleukin-6. In parallel, the anti-inflammatory cytokine interleukin-10 was elevated. Antioxidant potential of pioglitazone was depicted, where it reduced neutrophil infiltration, lipid peroxides, nitric oxide associated with replenished reduced glutathione. Decline of excitatory amino acid glutamate content is a main finding which is probably mediated by the NFκB signaling pathway as well as improved oxidant status. Pioglitazone exerted an anti-apoptotic effect as reflected by the reduction of the cytosolic cytochrome c and the key downstream executioner caspase-3. CONCLUSIONS Pioglitazone is endowed with neuroprotective properties which are probably mediated by its antioxidant, anti-inflammatory, and anti-apoptotic mechanisms hence may provide a successful agent for the management of ischemic stroke.

Comparative study of the cardioprotective effects of local and remote preconditioning in ischemia/reperfusion injury

AIMS Though the cardioprotective effects of local or remote preconditioning have been estimated, it is still unclear which of them is more reliable and provides more cardioprotection. The present investigation was directed to compare, in one study, the cardioprotective effects of different cycles of local or remote preconditioning in ischemia/reperfusion (I/R)-induced electrophysiological, biochemical and histological changes in rats. MAIN METHODS Rats were randomly assigned into 10 groups. Groups 1 and 2 were normal and I/R groups, respectively. Other groups were subjected to 1, 2, 3, 4 cycles of local or remote preconditioning before myocardial I/R (40 min/10 min). Heart rate and ventricular arrhythmias were recorded during I/R progress. At the end of reperfusion, plasma creatine kinase-MB (CK-MB) activity and total nitrate/nitrite (NO(x)) were determined. In addition, lactate, adenine nucleotides, thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH) and myeloperoxidase (MPO) activity were estimated in the heart left ventricle. Histological examination was also performed to visualize the protective cellular effects of the effective cycle of local or remote preconditioning. KEY FINDINGS In general, local preconditioning was more effective than remote preconditioning in reducing ventricular arrhythmias, CK-MB release, lactate accumulation and elevated MPO activity as well as preserving adenine nucleotides. Concerning the most effective group in each therapy, 3 cycles of local preconditioning provided more cardioprotection than that of remote preconditioning in the histological examination. SIGNIFICANCE Despite being invasive, local preconditioning provided more effective cardioprotection than remote preconditioning in ameliorating the overall electrophysiological, biochemical and histological changes.

Behavioral effects of acute and chronic triazolam treatments in albino rats

Previous behavioral studies on triazolam (TZ), which are small in number, could only speculate about tolerance to the anxiolytic effect of TZ, as the experiments did not cover sufficient time (of 4 to 7 days) for tolerance to develop. Therefore longer time for chronic TZ administration is used. We investigated the effects of TZ on motor activity and exploratory behavior using plus maze and open field. Three experiments were conducted. In the first, five groups of rats were acutely treated with different doses of TZ (0.25 mg/kg-4.0 mg/kg). In the second set of experiments, rats were treated chronically with a single daily dose of TZ (started with 0.25 mg/kg and increased by time to 1.0 mg/kg) for 5 weeks (representing clinical use). In the third, rats were treated chronically with three daily doses of TZ (started with 0.25 mg/kg and increased by time to 0.5 mg/kg) for 20 days (mimicking drug abuse). Acute TZ administration produced dose dependent anxiolytic effects and a decrease in motor activity with higher doses. Chronically treated rats, either once daily or three times daily doses, showed tolerance to both anxiolytic and sedative effects of TZ. It may be concluded that tolerance to the anxiolytic and sedative effects of TZ would develop after chronic administration either with clinical use or its abuse.

Pretreatment with magnesium ameliorates lipopolysaccharide-induced liver injury in mice

BACKGROUND Lipopolysaccharide (LPS), a component of the outer membrane of Gram-negative bacteria, is involved in the pathogenesis of sepsis. LPS administration induces systemic inflammation that mimics many of the initial clinical features of sepsis and has deleterious effects on several organs including the liver and eventually leading to septic shock and death. The present study aimed to investigate the protective effect of magnesium (Mg), a well known cofactor in many enzymatic reactions and a critical component of the antioxidant system, on hepatic damage associated with LPS-induced endotoxima in mice. METHODS Mg (20 and 40mg/kg, po) was administered for 7 consecutive days. Systemic inflammation was induced 1h after the last dose of Mg by a single dose of LPS (2mg/kg, ip) and 3h thereafter plasma was separated, animals were sacrificed and their livers were isolated. RESULTS LPS-treated mice suffered from hepatic dysfunction revealed by histological observation, elevation in plasma transaminases activities, C-reactive protein content and caspase-3, a critical marker of apoptosis. Liver inflammation was evident by elevation in liver cytokines contents (TNF-α and IL-10) and MPO activity. Additionally, oxidative stress was manifested by increased liver lipoperoxidation, glutathione depletion, elevated total nitrate/nitrite (NOx) content and glutathione peroxidase (GPx) activity. Pretreatment with Mg largely mitigated these alternations. CONCLUSION Pretreatment with Mg protects the liver from the acute injury which occurs shortly after septicemia.