The effects of NMDA receptor antagonist MK-801 on lipid peroxidation during focal cerebral ischemia in rats

Application of nanostructured lipid carriers: the prolonged protective effects for sesamol in in vitro and in vivo models of ischemic stroke via activation of PI3K signalling pathway

BACKGROUND

Treatment of the ischemic stroke has remained a major healthcare challenge. The phenolic compound, sesamol, has shown promising antioxidant and neuroprotective effects, however, fast clearance may negatively affect its efficiency. This, prompted us to incorporate sesamol into the nanostructured lipid carriers (S-NLCs) and evaluate its therapeutic potential in in vitro and in vivo models of ischemic stroke.

METHODS

S-NLCs formulations were prepared by high-pressure homogenization followed by physicochemical characterization, evaluation of the bioactivity of the optimal formulation in oxygen-glucose deprivation (OGD) and global cerebral ischemia/reperfusion (I/R) injury and implication of phosphatidylinositol 3-kinase (PI3K) pathway in this regard. Two- or three-way ANOVA, Mann-Whitney U test, and Student's t-test were used for data analysis.

RESULTS

Formation of S-NLCs which exhibited a controlled release profile, was confirmed by scanning electron microscope and differential scanning calorimetry. 1- and 8-h OGD followed by 24 h re-oxygenation significantly reduced PC12 cell viability, increased lactate dehydrogenase activity and the number of condensed nuclei, and induced oxidative stress as revealed by increased malondialdehyde level and decreased glutathione content and superoxide dismutase and catalase activities. Sesamol (80 and 100 μM) reduced the cytotoxicity, oxidative stress, and cellular damage only after 1-h OGD, while, S-NLCs (containing 80 and 100 μM of sesamol) were effective at both time points. Intravenous injections of S-NLCs (20 and 25 mg/kg) into rats markedly attenuated I/R-induced neurobehavioural deficits, cellular damage, and oxidative stress, while, free sesamol failed. Pre-treatment with PI3K inhibitor, LY294002, abolished the protective effects against OGD or I/R.

CONCLUSIONS

S-NLCs improve the pharmacological profile of sesamol and provide longer lasting protective effects for this phenolic phytochemical. This nanoformulation by activating PI3K pathway may serve as a promising candidate for neuroprotection against the cerebral stroke or other neurodegenerative disorders. Sesamol-loaded NLCs, a promising nanoformulation against the ischemic stroke.

Ferulic acid-loaded nanostructured lipid carriers: A promising nanoformulation against the ischemic neural injuries

AIMS

Treatment of the ischemic stroke has remained a major healthcare challenge. The phenolic compound, ferulic acid (FA), has shown promising antioxidant and neuroprotective effects, however, low bioavailability may negatively affect its efficiency. This, prompted us to incorporate FA into the nanostructured lipid carriers (FA-NLCs) and evaluate its therapeutic potential in in vitro and in vivo models of ischemic stroke.

MAIN METHODS

FA-NLCs were prepared by high-pressure homogenization followed by physicochemical characterization, evaluation of the bioactivity of FA-NLCs in oxygen-glucose deprivation (OGD) and global cerebral ischemia/reperfusion (I/R) injury and implication of phosphatidylinositol 3-kinase (PI3K) pathway in this regard.

KEY FINDINGS

Formation of FA-NLCs which exhibited a controlled release profile, was confirmed by scanning electron microscope and differential scanning calorimetry. 1- and 8-h OGD followed by 24h re-oxygenation significantly reduced PC12 cell viability, increased lactate dehydrogenase activity and number of condensed nuclei, and induced oxidative stress as revealed by increased malondialdehyde and decreased glutathione content and superoxide dismutase and catalase activities. FA (80 and 100μM) reduced the cytotoxicity, oxidative stress, and cellular damage only after 1-h OGD, while, FA-NLCs (containing 80 and 100μM of FA) were effective at both time points. Intravenous injections of FA-NLCs (20 and 25mg/kg) into rats significantly attenuated I/R-induced neurobehavioural deficits, cellular damage, and oxidative stress, while, FA failed. Pre-treatment with PI3K inhibitor, LY294002, abolished the protective effects against OGD or I/R.

SIGNIFICANCE

FA-NLCs by improving the pharmacological profile of FA and activating PI3K pathway might be of therapeutic value in cerebral stroke.

Cinepazide maleate protects PC12 cells against oxygen-glucose deprivation-induced injury

Our previous study showed that cinepazide maleate (CM) was as effective and safe as mildronate in the treatment of acute ischemic stroke in a randomized, double-blind, active-controlled phase II multicenter trial, but underlying mechanism(s) is not well understood. As an extending study, here we demonstrated that CM could protect neuronal cells by affecting mitochondrial functions. PC12 cells were exposed to 2.5 h oxygen-glucose deprivation (OGD) followed by a 24 h reoxygenation, and then treated with different concentrations (1, 10, 100 μM) of CM. Among various concentrations, 10 μM CM exhibited most significant protection on PC12 cells against OGD injury. CM was found to suppress OGD-induced oxidative stress, as supported by its capability of reducing intracellular reactive oxygen species and malondialdehyde production and enhancing superoxide dismutase activity. Importantly, our results showed that CM could preserve mitochondrial functions, as revealed by its capability of stabilizing mitochondrial membrane potential, improving OGD-induced suppression of mitochondrial respiratory complex activities and enhancing ATP production. In summary, our present study provides the first evidence that CM can protect neuronal cells against OGD injury by preserving mitochondrial functions.

Aquaporin-4 inhibition mediates piroxicam-induced neuroprotection against focal cerebral ischemia/reperfusion injury in rodents

BACKGROUND AND PURPOSE

Aquaporin-4(AQP4) is an abundant water channel protein in brain that regulates water transport to maintain homeostasis. Cerebral edema resulting from AQP4 over expression is considered to be one of the major determinants for progressive neuronal insult during cerebral ischemia. Although, both upregulation and downregulation of AQP4 expression is associated with brain pathology, over expression of AQP4 is one of the chief contributors of water imbalance in brain during ischemic pathology. We have found that Piroxicam binds to AQP4 with optimal binding energy value. Thus, we hypothesized that Piroxicam is neuroprotective in the rodent cerebral ischemic model by mitigating cerebral edema via AQP4 regulation.

METHODS

Rats were treated with Piroxicam OR placebo at 30 min prior, 2 h post and 4 h post 60 minutes of MCAO followed by 24 hour reperfusion. Rats were evaluated for neurological deficits and motor function just before sacrifice. Brains were harvested for infarct size estimation, water content measurement, biochemical analysis, RT-PCR and western blot experiments.

RESULTS

Piroxicam pretreatment thirty minutes prior to ischemia and four hour post reperfusion afforded neuroprotection as evident through significant reduction in cerebral infarct volume, improvement in motor behavior, neurological deficit and reduction in brain edema. Furthermore, ischemia induced surge in levels of nitrite and malondialdehyde were also found to be significantly reduced in ischemic brain regions in treated animals. This neuroprotection was found to be associated with inhibition of acid mediated rise in intracellular calcium levels and also downregulated AQP4 expression.

CONCLUSIONS

Findings of the present study provide significant evidence that Piroxicam acts as a potent AQP4 regulator and renders neuroprotection in focal cerebral ischemia. Piroxicam could be clinically exploited for the treatment of brain stroke along with other anti-stroke therapeutics in future.

N(1)-(quinolin-2-ylmethyl)butane-1,4-diamine, a polyamine analogue, attenuated injury in in vitro and in vivo models of cerebral ischemia

It has been widely recognized that glutamate (Glu)-induced cytotoxicity, intracellular calcium overload and excessive free radical production are the key players in the development and progression of ischemic brain injury. Since MK-801, an antagonist of N-methyl-d-aspartate (NMDA) receptor, showed many adverse reactions that hampered its clinical applications, development of safe and effective agent for the treatment of cerebral ischemia is eagerly required. This study was to investigate the effects of N(1)-(quinolin-2-ylmethyl)butane-1,4-diamine (QMA), a polyamine analogue, on the in vitro and in vivo models of cerebral ischemic damage. The results revealed that pretreatment with QMA could attenuate Glu, putrescine (Put) and oxygen-glucose deprivation (OGD)-induced cell death, lipid peroxidation as well as the elevation of reactive oxygen species (ROS) and intracellular [Ca(2+)](i) in pheochromocytoma (PC12) cells and in rat primary cortical neurons. The results also demonstrated that QMA could inhibit NMDA-mediated intracellular [Ca(2+)](i) accumulation in rat primary cortical neurons and reduce brain infarct volume in middle cerebral artery occlusion (MCAO) rats. The present report suggested that polyamines played a crucial role in the pathological processes of cerebral ischemic damage and that QMA or other novel polyamine analogues could be promising therapeutic candidates for stroke by virtue of their anti-hypoxia and antioxidation property.

Quercetin in hypoxia-induced oxidative stress: novel target for neuroprotection

Oxidative stress in the central nervous system is one of the key players for neurodegeneration. Thus, antioxidants could play important roles in treating several neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and aging-related brain disorders. This review is focused on the new developments in oxidative stress-induced neurodegeneration. Further, based on our own investigations, new roles of quercetin, an antioxidant compound in hypoxia and ischemia induced neuroprotection in relation to suppression of oxidative stress, improvement in behavioral function, reduction in infarct volume, brain swelling, and cellular injury in both in vivo and in vitro models are discussed. Our new findings clearly suggest that antioxidant compounds have potential role in therapeutic strategies to treat neurodegenerative diseases in clinical settings.

The role of ASIC1a in neuroprotection elicited by quercetin in focal cerebral ischemia

One of the major instigators to neuronal cell death and brain damage following cerebral ischemia is calcium dysregulation. The intracellular calcium overload resulting from glutamate excitotoxicity is considered a major determinant for neuronal loss during cerebral ischemia. Moreover, ASIC1a activation due to acidosis also promotes intracellular calcium overload during ischemic insult. Interestingly, ASIC1a was found to be inhibited by some flavonoids which carry an anti-inflammatory property particularly quercetin, which could be exploited in hypoxic conditions like cerebral ischemia. This encourages us to investigate the neuroprotective effect of quercetin besides its possible downstream signaling mechanism in focal cerebral ischemia. The treatment of quercetin 30min before ischemia and 4h after reperfusion shows significant protection from ischemic injury as noticed by reduction in cerebral infarct volume and neurobehavioral deficit. In addition to earlier calcium dependent rise in the levels of nitrite and MDA exhibited marked reduction (P<0.01) in their levels when given quercetin pretreatment in ischemic brain regions. The quercetin treatment also reduced the spectrin break down products (SBDP) caused by ischemic activation of calcium dependent protease calpain. In ex-vivo study, it was also observed that quercetin inhibited the acid mediated intracellular calcium levels in rat brain synaptoneurosomes. These studies suggest the neuroprotective role of quercetin in focal cerebral ischemia by regulation of ASIC1a.

Effects of MK-801 on nitrite and cGMP levels during focal cerebral ischemia in rats

Glutamate is a major excitatory neurotransmitter in the mammalian central nervous system and initiates the events leading to ischemic brain damage. Glutamate receptor antagonists are being used to reduce neuronal damage observed after hypoxia and ischemia. The glutamate receptor antagonist, (+)-5-methyl-10,11-dihydro-5H-dibenzo-(a,d)-cyclohepten-5,10-imine maleate (MK-801) crosses the blood-brain barrier readily and produces a non-competitive use-dependent blockade of the N-methyl-D-aspartate subtype of glutamate receptor. The aim of this study was to investigate effects of MK-801 administered before and just after the onset of ischemia in rats on nitrite and cyclic guanosine monophosphate (cGMP) levels. Focal cerebral ischemia in rats was produced by permanent occlusion of right middle cerebral artery (MCAO). Nitrite and cGMP levels were measured in both cortex and cerebellum at 0, 10, and 60 min following MCAO. The same parameters were measured in rats treated with MK-801 (0.5 mg/kg, i.p.) 30 min before or just after MCAO. Ipsilateral cortical nitrite levels were increased relative to contralateral cortex after MCAO. No significant changes were observed in cerebellum. The cGMP concentrations in both sides of the cortex and cerebellum were increased at 10 and 60 min compared with 0 min values. cGMP level in the ipsilateral cortex was higher than contralateral cortex, whereas the opposite was found for the cerebellum. MK-801 treatment before or just after MCAO decreased significantly nitrite and cGMP production. Our data indicate that MK-801 treatment before or just after focal ischemia prevents the increase in NO and cGMP production.