Fabricating an electroactive injectable hydrogel based on pluronic-chitosan/aniline-pentamer containing angiogenic factor for functional repair of the hippocampus ischemia rat model.

The hippocampus, a critical cerebral region involved in learning and memory formation, is especially vulnerable to ischemic defect. Here, we developed an injectable electroactive hydrogel based on pluronic-chitosan/aniline-pentamer with proper conductivity around 10-4 S/cm to achieve the functional repair of the hippocampus following the ischemic defect. FTIR, DSC, and TGA measurements were performed to assess the chemical structure and thermal stability of the synthesized hydrogel. Aniline pentamer decreased the swelling capacity, degradation, and drug release rate. Further, contact angle, melting point, and gelation time of hydrogels were enhanced by addition of aniline oligomer. Moreover, it endowed the on-demand electro-responsive drug release. Injectability of hydrogel was evaluated by rheometry, exhibiting proper gelling time at the body temperature. The ionic/electrical conductivity and desired in vitro biocompatibility with PC12 cells were also achieved. Injection of VEGF-loaded electroactive hydrogel in the hippocampal ischemic animal model resulted in decreased infarction volume, improved hippocampal dependent learning, and memory performance. Taken all together, the results confirmed that fabricated injectable hydrogel would be a suitable candidate for ischemic defect treatment and can lead to new horizons to treat neurological disorders.

Triggering microglia through toll-like receptor 2 pathway induced interferon ß expression in cell and animal model of Alzheimer's disease.

Synaptic function and memory performance are disrupted by soluble form of ß-amyloid (Aß). In the previous study, we found that early activation of microglia by toll-like receptor 2 (TLR2) attenuated Alzheimer's disease-associated cognitive deficit. This study was designed to investigate whether pretreatment with the TLR2 receptor ligand can regulate microglia to produce interferon ß (INFß) in a rat model of Alzheimer's disease. For this purpose, the BV-2 cell line was cultured in a 24-well plate, treated with Pam3Cys (1 µg/ml), and then incubated with oligomeric Aß for 24 h. The expression of TRIF, IRF3, and INFß was measured by western blot technique. For in-vivo study, bilateral guide cannulas were streotaxically implanted in the right and left lateral ventricles. Pam3Cys/vehicle was microinjected into the right ventricle every 3 days. Two weeks later, an osmotic pump was inserted into the left ventricle to microinfuse oligomeric Aß/placebo over 14 days. In the meanwhile, treatment with Pam3Cys was continued every 3 days. Then, expression of TRIF, IRF3, and INFß was measured in the hippocampus. The results showed that although oligomeric Aß could not alter the expression of these proteins at the cell and tissue level, treatment with Pam3Cys resulted in enhanced expression of them at both cell culture and hippocampal tissue following treatment with oligomeric Aß. It is concluded that stimulation of microglia through TLR2 pathway induces INFß expression, which may in part mediate neuroprotection against oligomeric Aß.

Photothrombotically induced unilateral selective hippocampal ischemia in rat.

INTRODUCTION: The vulnerability of hippocampal formation to ischemic insult has been documented in both humans and animal models. Ischemic injury induction through photothrombosis is an invasive and reproducible model of ischemic stroke which provides the ability to induce ischemia selectively in any desired area. In this study, we describe a method to induce selective unilateral hippocampal ischemia in rat through modified photothrombotic model. METHODS: Male wistar rats (n = 66) were subjected to stereotaxic surgery to insert a guide cannula just above the ascending part of hippocampal fissure. After recovery femoral vein was cannulated and rats were mounted in stereotaxic frame to optical fiber insertion in guide cannula and illumination of hippocampal fissure for 25 min. Rose Bengal dye was slowly injected through femoral vein during the first two-minute of illumination. Twenty-four hours later, infarct volume and histological change were evaluated in rat hippocampus. Cognitive function was also evaluated 48 h after ischemia induction. RESULTS: This procedure caused significant neuronal necrosis and infarct formation in the right hemisphere hippocampus. The infarct size was consisted in different subjects and was paralleled to cognitive impairment. The mean volume of infarction was 6.5% which affected whole right hippocampus and caused significant cognitive impairment compared to sham group (P < 0.001). DISCUSSION: The method described in this study provides the ability of selective hippocampal ischemia induction and study of hippocampal injury consequences following ischemia or other neurodegenerative disease that affect hippocampus.

Neuroprotective effect of monophosphoryl lipid A, a detoxified lipid A derivative, in photothrombotic model of unilateral selective hippocampal ischemia in rat.

Finding a neuroprotective strategy to rescue patients suffering from acute brain damage is of great interest. Monophosphoryl lipid A (MPL) is a derivative of lipopolysaccharide (LPS) that lacks many of the endotoxic properties of the parent molecule, and yet has similar protective effect. Here, we report the first evidence that MPL preconditioning, similar to LPS preconditioning, can induce neuroprotection against cerebral ischemia. MPL (0.5, 1, 5 µg/rat) was injected unilaterally into the left cerebral ventricle of male rats, and 48 h later, rats were subjected to ipsilateral selective hippocampal ischemia using a modified version of the photothrombotic method. The neuroprotective effects of MPL and LPS were evaluated by measuring infarct size and assessing cognitive function. The expression level of some inflammatory and anti-inflammatory cytokines involving in TLR4 signaling pathway was also measured. Cognitive impairment and infarct size were obvious in control group receiving normal saline intracerebroventricularly and then selective hippocampal ischemia, compared to the sham group. Immunologic preconditioning with MPL or LPS significantly reduced infarct size and improved cognitive function. Additionally, immunologic preconditioning resulted in inflammatory mediators, NF-κB and TNF-α, down-regulation but anti-inflammatory mediators, IRF3, IFN-ß, and TGF-ß, up-regulation. Our data showed that both MPL and LPS preconditioning may reprogram the TLR4 signaling pathway to produce a cytokine profile which eventually leads to neuroprotection against ischemia injury. MPL, unlike LPS, is safe and well tolerated in clinic, thus it could be considered as a new approach in prevention or even treatment of cerebral ischemic insult consequences.

Protective effect of thymoquinone, the active constituent of Nigella sativa fixed oil, against ethanol toxicity in rats.

OBJECTIVES: Long term consumption of ethanol may induce damage to many organs. Ethanol induces its noxious effects through reactive oxygen species production, and lipid peroxidation and apoptosis induction in different tissues and cell types. Previous experiments have indicated the antioxidant characteristics of thymoquinone, the active constituent of Nigella sativa fixed oil, against biologically dangerous reactive oxygen species. This experiment was planned to evaluate the protective effect of thymoquinone against subchronic ethanol toxicity in rats. MATERIALS AND METHODS: Experiments were performed on six groups. Each group consisted of six animals, including control group (saline, gavage), ethanol-receiving group (3 g/kg/day, gavage), thymoquinone (2.5, 5, 10 mg/Kg/day, intraperitoneally (IP)) plus ethanol and thymoquinone (10 mg/Kg/day, IP) groups. Treatments were carried out in four weeks. RESULTS: Thymoquinone reduced the ethanol-induced increase in the lipid peroxidation and severity of histopathological alteration in liver and kidney tissues. In addition it improved the levels of proinflammatory cytokines in liver tissue. Furthermore, thymoquinone corrected the liver enzymes level including alanine transaminase, aspartate transaminase and alkaline phosphatase in serum and glutathione content in liver and kidney tissues. Other experiments such as Western blot analysis and quantitative real-time RT-PCR revealed that thymoquinone suppressed the expression of Bax/Bcl-2 ratio (both protein and mRNA level), and caspases activation pursuant to ethanol toxicity. CONCLUSION: This study indicates that thymoquinone may have preventive effects against ethanol toxicity in the liver and kidney tissue through reduction in lipid peroxidation and inflammation, and also interrupting apoptosis.

Effect of Nigella sativa fixed oil on ethanol toxicity in rats.

OBJECTIVES: This study was planned to appraise the protective effect of Nigella sativa fixed oil (NSO) against subchronic ethanol induced toxicity in rats. MATERIALS AND METHODS: Studies were carried out on six groups of six animals each, including control (normal saline, gavage), ethanol (3 g/kg/day, gavage), NSO (0.125, 0.25 and 0.5 ml/Kg/day, IP) plus ethanol and NSO (0.5 ml/Kg/day, IP) groups. Treatments were continued for 4 weeks. RESULTS: According to data, treatment with NSO attenuated ethanol-induced increased levels of malondialdehyde (MDA), tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6), as well as histopathological changes in liver and kidney tissues. Moreover, NSO improved the level of serum liver enzymes (including alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP) and glutathione (GSH) content in liver and kidney tissues in ethanol-treated rats. Western blot analysis and quantitative real time RT-PCR showed that NSO treatment inhibited apoptosis stimulated by ethanol through decreasing the Bax/Bcl-2 ratio (both protein and mRNA levels), cleaved caspase-3, cleaved caspase-8 and cleaved caspase-9 level in liver and kidney. CONCLUSION: This study showed that NSO may have protective effects against hepatotoxicity and renal toxicity of ethanol by decreasing lipid peroxidation and inflammation and preventing apoptosis.