Acute mitogen-activated protein kinase 1/2 inhibition improves functional recovery and vascular changes after ischaemic stroke in rat-monitored by 9.4 T magnetic resonance imaging

AIM

The aim was to evaluate the beneficial effect of early mitogen-activated protein kinase (MEK)1/2 inhibition administered at a clinical relevant time-point using the transient middle cerebral artery occlusion model and a dedicated rodent magnetic resonance imaging system (9.4T) to monitor cerebrovascular changes non-invasively for 2 weeks.

METHOD

Transient middle cerebral artery occlusion was induced in male rats for two hours followed by reperfusion. The specific MEK1/2 inhibitor U0126 was administered ip at 6 and 24 hours post-reperfusion. Neurological functions were evaluated by 6- and 28-point tests. 9.4 T magnetic resonance imaging was used to monitor morphological infarct changes at day 2, 8 and 14 after stroke and to evaluate cerebral perfusion at day 14. Immunohistochemistry evaluation of Ki67 was performed 14 days post-stroke.

RESULTS

U0126 improved long-term behavioural outcome and significantly reduced infarct size. In addition, cerebral perfusion in U0126-treated animals was improved compared to the vehicle group. Immunohistochemistry showed a significant increase in Ki67⁺ cells in U0126-treated animals compared to the vehicle group.

CONCLUSION

Early MEK1/2 inhibition improves long-term functional outcome, promotes recovery processes after stroke and most importantly provides a realistic time window for therapy.

Inhibition of mitogen-activated protein kinase 1/2 in the acute phase of stroke improves long-term neurological outcome and promotes recovery processes in rats

AIM

Extracellular signal-regulated kinase (ERK) 1/2 is activated during acute phase of stroke and contributes to stroke pathology. We have found that acute treatment with MEK1/2 inhibitors decreases infarct size and neurological deficits 2 days after experimental stroke. However, it is not known whether benefits of this inhibition persist long-term. Therefore, the aim of this study was to assess neurological function, infarct size and recovery processes 14 days after stroke in male rats to determine long-term outcome following acute treatment with the MEK1/2 inhibitor U0126.

METHODS

Transient middle cerebral artery occlusion was induced in male rats. U0126 or vehicle was given at 0 and 24 h of reperfusion. Neurological function was assessed by staircase, 6-point and 28-point neuroscore tests up to 14 days after induction of stroke. At day 14, infarct volumes were determined and recovery processes were evaluated by measuring protein expression of the tyrosine kinase receptor Tie-2 and nestin. Levels of p-ERK1/2 protein were determined.

RESULTS

Acute treatment with U0126 significantly improved long-term functional recovery, reduced infarct size, and enhanced Tie-2 and nestin protein expression at 14 days post-stroke. There was no residual blockade of p-ERK1/2 at this time point.

CONCLUSION

It is demonstrated that benefits of early treatment with U0126 persist beyond subacute phase of ischaemic stroke in male rats. Prevention of ERK1/2 activation in the acute phase results in improved long-term functional outcome and enhances later-stage recovery processes. These results expand our understanding of the benefits and promise of using MEK1/2 inhibitors in stroke recovery.

Protective effect of diallylsulphide against mercuric chloride-induced hepatic injury in rats

The present study was undertaken to evaluate the effect of diallylsulphide (DAS) against mercuric chloride (HgCl₂)-induced oxidative stress in rat livers. Rats were randomly divided into four groups of six rats each and exposed to HgCl₂ (50 mg/kg/body weight (b.w.)) intraperitoneally and/or DAS (200 mg/kg/b.w.) by gavage. HgCl₂ administration enhanced alanine aminotransferase (AST) and aspartate aminotransferase (ALT) levels (p < 0.05) with reduction in the levels of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px). However, treatment with DAS markedly attenuated HgCl₂-induced biochemical alterations in liver and serum transaminases (AST and ALT; p < 0.05). Further, biochemical results were confirmed by histopathological changes as compared to HgCl₂-intoxicated rats. Histopathology of liver also showed that administration of DAS significantly reduced the damage generated by HgCl₂ The present study suggests that DAS shows antioxidant activity and plays a protective role against mercury-induced oxidative damage in the rat livers.

Effect of Selenium on the Levels of Cytokines and Trace Elements in Toxin-Mediated Oxidative Stress in Male Rats

Selenium is an essential cofactor in the key enzymes involved in cellular antioxidant defense. This study was designed to investigate the protective effects of selenium on mercury chloride (HgCl2)-induced toxicity. Male Wistar rats were randomly divided into four groups of six animals each. The first group was control; the second group was treated with mercuric chloride (HgCl2: 50 mg/kg/bw). The third group was treated with sodium selenite (Se 0.2 mg/kg/bw), and the fourth group received Se (0.2 mg/kg/bw) plus HgCl2 (50 mg/kg for 24 h). The influence of Se on mercury induced levels of malondialdehyde (MDA) and the activity of superoxide dismutase (SOD) and zinc, copper, and iron in serum of rats were observed. The serum MDA, SOD, zinc, and iron concentrations were found to be statistically different among the control and toxin-treated group. The serum levels of IL-6, IL-10, and TNF-α were also measured. There was a significant decrease in the levels of TNF-α, IL-6, and IL-10 in toxin-treated group II compared with that of the control group (p < 0.05). A significant increase in the serum levels of inflammatory cytokines IL-6, TNF-α, and IL-10 after administration of Se seemed to counteract some of the damage, as indicated by differences in the serum concentrations of major elements.

Antioxidant and nephroprotective potential of butylated hydroxyanisole against ferric nitrilotriacetate-induced oxidative stress and early tumor events

The present study was aimed to study protective effect of butylated hydroxyanisole (BHA), a phenolic antioxidant used in foods on ferric nitrilotriacetate (Fe-NTA)–induced nephrotoxicity. Male albino rats of Wistar strain (4–6 weeks old) weighing 125–150 g were used in this study. Animals were given a single dose of Fe-NTA (9 mg kg−1 body weight) after treatment with BHA (1 and 2 mg animal−1 day−1). Fe-NTA treatment enhanced ornithine decarboxylase (ODC) activity to 5.3-fold, and [3H]-thymidine incorporation in DNA to 2.5-fold in kidney compared with the corresponding saline-treated control, whereas glutathione (GSH) levels and the activities of antioxidant enzymes decreased to a range of 2- to 2.5-fold in kidney. These changes were reversed significantly in animals receiving a pretreatment of BHA. The enhanced ODC activity and DNA synthesis showed a reduction to 2.12-fold and 1.15-fold, respectively, at a higher dose of 2 mg BHA day−1 animal−1, compared with the Fe-NTA-treated groups. Pretreatment with BHA prior to Fe-NTA treatment increased GSH and the activities of antioxidant enzymes to a range of 1.5- to 2-fold in kidney. The results indicate that BHA suppresses Fe-NTA-induced nephrotoxicity in male Wistar rats.

Amelioration of ferric nitrilotriacetate-induced hepatotoxicity in Wistar rats by diallylsulfide

Garlic contains diallylsulfide (DAS) and other structurally related compounds that are widely believed to be active agents in preventing cancer. This study shows the effect of DAS (a phenolic antioxidant used in foods, cosmetics, and pharmaceutical products) on ferric nitrilotriacetate (Fe-NTA)-induced hepatotoxicity in rats. Male albino rats of Wistar strain weighing 125-150 g were given a single dose of Fe-NTA (9 mg kg(-1) body weight, intraperitoneally) after 1 week of treatment with 100 and 200 mg kg(-1) DAS in corn oil respectively administered through the gavage. Fe-NTA administration led to 2.5-fold increase in the values of both alanine transaminase and aspartate aminotransferase, respectively, and 3.2-fold increase in the activity of lactate dehydrogenase, microsomal lipid peroxidation to approximately 2.0-fold compared to saline-treated control. The activities of glutathione (GSH) and other antioxidant enzymes decreased to a range of 2.2-2.5-fold. These changes were reversed significantly (p < 0.001) in animals receiving a pretreatment of DAS. DAS protected against hepatic lipid peroxidation, hydrogen peroxide generation, preserved GSH levels, and GSH metabolizing enzymes to 60-80% as compared to Fe-NTA alone-treated group. Present data suggest that DAS can ameliorate the toxic effects of Fe-NTA and suppress oxidant-induced tissue injury and hepatotoxicity in rats.

Ameliorative effect of butylated hydroxyanisole against ferric nitrilotriacetate-induced hepatotoxicity and oxidative stress in rats

Ferric nitrilotriacetate (Fe-NTA) is a known renal carcinogen and has been shown to adversely induce oxidative stress and tissue toxicity after both acute and chronic exposure. Present studies were designed to study the hepatoprotective and antioxidant potential of butylated hydroxyanisole (BHA), a phenolic antioxidant used in foods on ferric nitrilotriacetate (Fe-NTA) induced hepatotoxicity in rats. Male albino rats of Wistar strain (4–6 weeks old) weighing 125–150 g were used in this study. Animals were given a single dose of Fe-NTA (9 mg/kg body weight, intraperitoneal) after a week’s treatment with BHA. BHA was administered orally once daily for 7 days at doses of 1 and 2 mg/animal/day. The hepatoprotective activity was assessed using various biochemical parameters as serum transaminases (alanine transaminase (ALT), aspartate transaminase (AST)) and lactate dehydrogenase (LDH). Fe-NTA treatment increased ALT, AST, and LDH levels significantly when compared to the corresponding saline-treated group ( p < 0.001). Fe-NTA also depleted the levels of glutathione and the activities of antioxidant enzymes namely glutathione reductase and glutathione- S-tranferase ( p < 0.05). Pretreatment with BHA significantly decreased ALT, AST and LDH levels in a dose-dependent manner ( p < 0.05). BHA also increased antioxidant enzymes level and decreased lipid peroxidation and hydrogen peroxide generation to 1.3–1.5-fold as compared to Fe-NTA-treated group. The results show the strong hepatoprotective activity of BHA which could be due to its potent antioxidant effects.

Diallyl sulphide, a component of garlic, abrogates ferric nitrilotriacetate-induced oxidative stress and renal damage in rats

Ferric nitrilotriacetate (Fe-NTA) induces tissue necrosis as a result of lipid peroxidation (LPO) and oxidative damage that leads to high incidence of renal carcinomas. The present study was undertaken to evaluate the effect of diallyl sulphide (DAS) against Fe-NTA-induced nephrotoxicity. A total of 30 healthy male rats were randomly divided into 5 groups of 6 rats each: (1) control, (2) DAS (200 mg kg−1), (3) Fe-NTA (9 g Fe kg−1), (4) DAS (100 mg kg−1) + Fe-NTA (9 mg Fe kg−1) and (5) DAS (200 mg kg−1) + Fe-NTA (9 mg Fe kg−1). Fe-NTA + DAS-treated groups were given DAS for a period of 1 week before Fe-NTA administration. The intraperitoneal administration of Fe-NTA enhanced blood urea nitrogen and creatinine levels with reduction in levels of antioxidant enzymes. However, significant restoration of depleted renal glutathione and its dependent enzymes (glutathione reductase and glutathione- S-transferase) was observed in DAS pretreated groups. DAS also attenuated Fe-NTA-induced increase in LPO, hydrogen peroxide generation and protein carbonyl formation ( p < 0.05). The results indicate that DAS may be beneficial in ameliorating the Fe-NTA-induced renal oxidative damage in rats.

Role of ascorbic acid in counteracting ferric nitrilotriacetate-induced nephrotoxicity in rats

CONTEXT

Ascorbic acid (AA) is a naturally occurring organic compound with antioxidant properties. It is necessary for normal growth and development, and has been shown to protect against tissue toxicity and oxidative stress.

OBJECTIVE

The protective effect of AA against nephrotoxicity induced in albino rats by ferric nitrilotriacetate (Fe-NTA) was evaluated.

MATERIALS AND METHODS

Male albino rats of Wistar strain (4-6 weeks old) weighing 125-150 g were used in this study. Animals were given a single dose of Fe-NTA (9 mg/kg body weight, intraperitoneal) after a week of treatment with AA (1 and 2 mg/animal/day).

RESULTS

Fe-NTA treatment enhanced microsomal lipid peroxidation (LPO) and hydrogen peroxide (H2O2) generation to 1.7- to 2.2-fold, glutathione (GSH) levels were decreased by two-fold and the activities of GSH metabolizing enzymes decreased to a range of 2.2- to 2.5-fold in renal tissue. These changes were reversed significantly in animals receiving pretreatment of AA. Treatment of rats with AA prior to the treatment with Fe-NTA decreased microsomal LPO and H2O2 generation to 124 and 172%, and also resulted in the recovery of reduced levels of GSH, GSH-metabolizing enzymes to almost 92% at the higher dose level of AA.

DISCUSSION AND CONCLUSION

AA protects against Fe-NTA-induced nephrotoxicity and renal damage. AA has a beneficial impact on Fe-NTA-induced toxicity due to its scavenging and antioxidant effect in albino rats.

Ascorbic acid inhibits ferric nitrilotriacetate induction of ornithine decarboxylase, DNA synthesis, oxidative stress, and hepatotoxicity in rats

Ascorbic acid (AA) is a naturally occurring phenolic compound with antioxidant properties used in food, cosmetics, and pharmaceutical products. In this study, the effect of AA on ferric nitrilotriacetate (Fe-NTA)-induced hepatotoxicity in rats has been examined. Fe-NTA alone enhances ornithine decarboxylase activity to 4.5-fold and tritiated thymidine incorporation in DNA to 3.6-fold in livers compared with the corresponding saline-treated controls. The enhanced ornithine decarboxylase activity and DNA synthesis showed a reduction to 3.02- and 1.88-fold, respectively, at a higher dose of 2 mg AA per day per animal, compared with the Fe-NTA-treated groups. Fe-NTA treatment also enhanced the hepatic microsomal lipid peroxidation to 1.7-fold compared to saline-treated controls. These changes were reversed significantly in animals receiving pretreatment of AA. The present data shows that AA can reciprocate the toxic effects of Fe-NTA and can serve as a potent chemopreventive agent to suppress oxidant-induced tissue injury and hepatotoxicity in rats.

Protective effect of butylated hydroxytoluene on ferric nitrilotriacetate induced hepatotoxicity and oxidative stress in mice

The present study was undertaken to evaluate the possible ameliorating effect of butylated hydroxyl toluene (BHT), associated with ferric nitrilotriacetate (Fe-NTA)-induced oxidative stress and liver injury in mice. The treatment of mice with Fe-NTA alone enhances ornithine decarboxylase activity to 4.6 folds, protein carbonyl formation increased up to 2.9 folds and DNA synthesis expressed in terms of [3H] thymidine incorporation increased to 3.2 folds, and antioxidants and antioxidant enzymes decreased to 1.8–2.5 folds, compared with the corresponding saline-treated controls. These changes were reversed significantly ( p < 0.001) in animals receiving a pretreatment of BHT. Our data show that BHT can reciprocate the toxic effects of Fe-NTA and can serve as a potent chemopreventive agent.

Patients' own drugs and self-administration of medication schemes in the United Kingdom

Focal points

Cytoskeletal Integrity as a Drug Target

The cytoskeleton provides structural integrity and determines localization of proteins and organelles throughout the cell. The focus on structure and transport has overshadowed the role this ubiquitous network plays in cell signaling cascades, though it participates in transduction of signals from the plasma membrane to the nucleus. Clearly the discovery that neurofibrillary tangles (NFTs) in Alzheimer's disease (AD) brain are made up of the microtubule (MT)-associated protein tau and evidence that the toxic amyloid peptides in AD can lead to tau hyper-phosphorylation and cytoskeletal dystrophy support the assertion that disruption of the MT network is an early signaling event in neurodegenerative cascades. Thus we have been testing the hypothesis that drugs that can moderate such signals through interactions with MTs would protect neurons against Abeta toxicity. Drugs targeted to MTs are currently used as anti-cancer agents, due to their blockade of cell proliferation and induction of cell death. However, we and others have now found that low concentrations of compounds that help stabilize MTs do indeed protect post-mitotic neurons challenged with various toxic stimuli. Therefore we propose that the cytoskeletal network actually serves as a sensor for the overall state of the neurons and a first-line transducer of stress signals. Drugs that can moderate initiation of such early signaling events do protect against disruption of the cytoskeleton and neuritic dystrophy in neuronal cell cultures. In vivo proof-of-concept studies in animal models will require the development of agents that can protect cytoskeletal integrity and also cross the blood brain barrier.

β-Amyloid-Induced Neurodegeneration and Protection by Structurally Diverse Microtubule-Stabilizing Agents

Deposition of beta-amyloid peptide (Abeta) and hyperphosphorylation of the tau protein are associated with neuronal dysfunction and cell death in Alzheimer's disease. Although the relationship between these two processes is not yet understood, studies have shown that both in vitro and in vivo exposure of neurons to Abeta leads to tau hyperphosphorylation and neuronal dystrophy. We previously reported that the microtubule-stabilizing drug paclitaxel (Taxol) protects primary neurons against toxicity induced by the Abeta(25-35) peptide. The studies in this report were undertaken to characterize the actions of paclitaxel more fully, to assess the effectiveness of structurally diverse microtubulestabilizing agents in protecting neurons, and to determine the time course of the protective effects of the drugs. Primary neurons were exposed to Abeta in the presence or absence of several agents shown to interact with microtubules, and neuronal survival was monitored. Paclitaxel protected neurons against Abeta(1-42) toxicity, and paclitaxel-treated cultures exposed to Abeta showed enhanced survival over Abeta-only cultures for several days. Neuronal apoptosis induced by Abeta was blocked by paclitaxel. Other taxanes and three structurally diverse microtubule-stabilizing compounds also significantly increased survival of Abeta-treated cultures. At concentrations below 100 nM, the drugs that protected the neurons did not produce detectable toxicity when added to the cultures alone. Although multiple mechanisms are likely to contribute to the neuronal cell death induced by oligomeric or fibrillar forms of Abeta, low concentrations of drugs that preserve the integrity of the cytoskeletal network may help neurons survive the toxic cascades initiated by these peptides.

Nordihydroguairetic acid is a potent inhibitor of ferric-nitrilotriacetate-mediated hepatic and renal toxicity, and renal tumour promotion, in mice

Ferric-nitrilotriacetate (Fe-NTA) is a known renal carcinogen. In the present study, we report the effect of a potent lignin-derived herbal antioxidant, nordihydroguairetic acid (NDGA), against Fe-NTA-mediated tissue toxicity. Fe-NTA (alone) treatment of mice enhances ornithine decarboxylase activity to 259% in liver and 341% in kidney and increases [3H]thymidine incorporation in DNA to 250% in liver and 324% in kidney compared with the corresponding saline-treated controls. The enhanced ornithine decarboxylase activity and DNA synthesis showed a reduction to 138 and 123%, respectively, in liver at a higher dose of 2 mg NDGA/day/animal whereas in kidney the reduction was to 118 and 102%, respectively, compared with the corresponding saline-treated controls. In the Fe-NTA (alone)-treated group, a 12% renal tumour incidence was recorded whereas, in N-diethylnitrosamine (DEN)-initiated and Fe-NTA-promoted animals, the percentage tumour incidence was increased to 68% as compared with untreated controls. No tumour incidence was recorded in the DEN-initiated, non-promoted group. The administration of NDGA, afforded >80% protection against DEN- and Fe-NTA-mediated renal tissue injury in vivo. Fe-NTA treatment also enhanced hepatic and renal microsomal lipid peroxidation to 170 and 205% of saline-treated controls, respectively, and hydrogen peroxide generation by >2.5-fold in both tissues accompanied by a 51 and 21% decrease in the level of glutathione and 35-48 and 35-50% decrease in the activities of glutathione-metabolizing and antioxidant enzymes in liver and kidney, respectively. These changes were reversed significantly in animals receiving a pre-treatment of NDGA. Our data show that NDGA can abrogate the toxic and tumour-promoting effects of Fe-NTA in liver and kidney of mice and can serve as a potent chemopreventive agent to suppress oxidant-induced tissue injury and tumorigenesis.

alpha-Tocopherol (vitamin-E) ameliorates ferric nitrilotriacetate (Fe-NTA)-dependent renal proliferative response and toxicity: diminution of oxidative stress

Ferric nitrilotriacetate (Fe-NTA) is a potent nephrotoxic agent. In this communication, we show the modulatory effect of DL-alpha-tocopherol (Vitamin-E) on ferric nitrilotriacetate (Fe-NTA)-induced renal oxidative stress, toxicity and hyperproliferative response in rats. Fe-NTA-treatment enhances the susceptibility of renal microsomal membrane for iron-ascorbate-induced lipid peroxidation and hydrogen peroxide generation which are accompanied by a decrease in the activities of renal antioxidant enzymes, catalase, glutathione peroxidase, glutathione reductase and glutathione-S-transferase and depletion in the level of renal glutathione. Parallel to these changes, a sharp increase in blood urea nitrogen and serum creatinine has been observed. In addition, Fe-NTA-treatment also enhances renal ornithine decarboxylase activity (ODC) and increases [3H]thymidine incorporation in renal DNA. Prophylactic treatment of animals with Vit.E daily for 1 week prior to the administration of Fe-NTA resulted in the diminution of Fe-NTA-mediated damage. Enhanced susceptibility of renal microsomal membrane for lipid peroxidation induced by iron-ascorbate and hydrogen peroxide generation were significantly reduced (P < 0.05). In addition, the depleted level of glutathione and inhibited activities of antioxidant enzymes recovered to significant levels (P < 0.05). Similarly, the enhanced blood urea nitrogen and serum creatinine levels which are indicative of renal injury showed a reduction of about 50% at a higher dose of Vit.E. The pretreatment of rats with Vit.E reduced the Fe-NTA-mediated induction in ODC activity and enhancement in [3H]thymidine incorporation in DNA. The protective effect of Vit.E was dose dependent. In summary, our data suggest that Vit.E is an effective chemopreventive agent in kidney and may suppress Fe-NTA-induced renal toxicity.