Brain dysfunction associated with an induction of nitric oxide synthase following an intracerebral injection of lipopolysaccharide in rats

Effects of ortho-eugenol on anxiety, working memory and oxidative stress in mice

Ortho-eugenol is a synthetic derivative from eugenol, the major compound of clove essential oil, which has demonstrated antidepressant and antinociceptive effects in pioneering studies. Additionally, its effects appear to be dependent on the noradrenergic and dopaminergic systems. Depression and anxiety disorders are known to share a great overlap in their pathophysiology, and many drugs are effective in the treatment of both diseases. Furthermore, high levels of anxiety are related to working memory deficits and increased oxidative stress. Thus, in this study we investigated the effects of acute treatment of ortho-eugenol, at 50, 75 and 100 mg/kg, on anxiety, working memory and oxidative stress in male Swiss mice. Our results show that the 100 mg/kg dose increased the number of head-dips and reduced the latency in the hole-board test. The 50 mg/kg dose reduced malondialdehyde levels in the prefrontal cortex and the number of Y-maze entries compared to the MK-801-induced hyperlocomotion group. All doses reduced nitrite levels in the hippocampus. It was also possible to assess a statistical correlation between the reduction of oxidative stress and hyperlocomotion after the administration of ortho-eugenol. However, acute treatment was not able to prevent working memory deficits. Therefore, the present study shows that ortho-eugenol has an anxiolytic and antioxidant effect, and was able to prevent substance-induced hyperlocomotion. Our results contribute to the elucidation of the pharmacological profile of ortho-eugenol, as well as to direct further studies that seek to investigate its possible clinical applications.

Neuromodulatory role of L-arginine: nitric oxide precursor against thioacetamide-induced-hepatic encephalopathy in rats via downregulation of NF-κB-mediated apoptosis

The aim of the present study was to investigate the impact of arginine (ARG), a nitric oxide (NO) precursor, on thioacetamide (TAA)-induced hepatic encephalopathy (HE) in rats by injection of TAA (100 mg/kg, i.p) three times per week for six consecutive weeks. TAA-injected rats were administered ARG (100 mg/kg; p.o.) concurrently with TAA for the six consecutive weeks. Blood samples were withdrawn, and rats were sacrificed; liver and brain tissues were isolated. Results of the present study demonstrated that ARG administration to TAA-injected rats revealed a restoration in the serum and brain ammonia levels as well as serum aspartate transaminase, alanine transaminase, and alkaline phosphatase and total bilirubin levels as well as behavioral alterations evidenced by restoration in locomotor activity, motor skill performance, and memory impairment. ARG showed also improvement in the hepatic and neuro-biochemical values, pro-inflammatory cytokines, and oxidative stress biomarkers. All these results were confirmed by histopathological evaluation as well as ultrastructural imaging of the cerebellum using a transmission electron microscope. Furthermore, treatment with ARG could ameliorate the immunological reactivity of nuclear factor erythroid-2-related factor 2 (Nrf2) and cleaved caspase-3 proteins in the cerebellum and hepatic tissues. From all the previous results, it can be fulfilled that ARG showed a beneficial role in modulating the adverse complications associated with TAA-induced HE in rats via reducing hyperammonemia and downregulating nuclear factor kappa B (NF-κB)-mediated apoptosis.

Vitamin B12 administration prevents ethanol-induced learning and memory impairment through re-establishment of the brain oxidant/antioxidant balance, enhancement of BDNF and suppression of GFAP

There are growing evidence indicating that the adolescent brain is persistently affected by the use of psychostimulant agents. In this regard, alcohol drinking has become rather common among the adolescents in many societies during the last decade. It is currently well known that long-term ethanol exposure deteriorates various cognitive functions such as learning and memory. Mechanistically, these adverse effects have been shown to be mediated by oxidative damage to central nervous system. On the other hand, Vit-B12 is known to improve cognitive performance by suppression of oxidative parameters. Thus, in the present study we aimed to test whether treatment by Vit-B12 could prevent ethanol-induced complications in mice using behavioral and biochemical methods. Different groups of male Syrian mice received ethanol, ethanol+Vit-B12, Vit-B12 alone, or saline during adolescence and then learning and memory functions were assessed by Morris water maze (MWM) and Passive Avoidance (PA) tests. Finally, mice were sacrificed for measurement of biochemical factors. Results indicated that, adolescent ethanol intake impairs learning and memory function through exacerbation of oxidative stress and Vit-B12 treatment improves these complications by re-establishment of oxidant/anti-oxidant balance in CNS. Moreover, we found that Vit-B12 prevents ethanol-induced reduction of BDNF and enhancement of GFAP and acetylcholinesterase (AChE) activity. In conclusion, it seems that Vit-B12 supplementation could be used as an effective therapeutic strategy to prevent learning and memory defects induced by chronic alcohol intake during adolescence.

PlexinA1 deficiency in BALB/cAJ mice leads to excessive self-grooming and reduced prepulse inhibition

PlexinA1 (PlxnA1) is a transmembrane receptor for semaphorins, a large family of proteins that act as axonal guidance cues during nervous system development. However, there are limited studies on PlxnA1 function in neurobehavior. The present study examined if PlxnA1 deficiency leads to behavioral abnormalities in BALB/cAJ mice. PlxnA1 knockout (KO) mice were generated by homologous recombination and compared to wild type (WT) littermates on a comprehensive battery of behavioral tests, including open field assessment of spontaneous ambulation, state anxiety, and grooming, home cage grooming, the wire hang test of muscle strength, motor coordination on the rotarod task, working memory on the Y maze alternation task, cued and contextual fear conditioning, anxiety on the elevated plus maze, sociability to intruders, and sensory processing as measured by prepulse inhibition (PPI). Measures of motor performance, working memory, fear memory, and sociability did not differ significantly between genotypes, while PlxnA1 KO mice displayed excessive self-grooming, impaired PPI, and slightly lower anxiety. These results suggest a crucial role for PlxnA1 in the development and function of brain regions controlling self-grooming and sensory gating. PlxnA1 KO mice may be a valuable model to investigate the repetitive behaviors and information processing deficits characteristic of many neurodevelopmental and psychiatric disorders.

The effects of hydro-ethanolic extract of Capparis spinosa (C. spinosa) on lipopolysaccharide (LPS)-induced inflammation and cognitive impairment: Evidence from in vivo and in vitro studies

ETHNOPHARMACOLOGICAL RELEVANCE

Capparis spinose (C. spinosa) belonging to Capparaeae, originates from dry areas in the west or central Asia and Mediterranean basin. For thousands of years, C. spinosa has been reported to be used as a therapeutic traditional medicine to relieve various ailments including rheumatism, pain and inflammatory diseases.

AIM OF THE STUDY

There are several studies mentioning that systemic inflammation results in learning and memory impairments through the activation of microglia. The objective of this study was to investigate the effect of C. spinosa on both in vivo and in vitro models of neuroinflammation and cognitive impairment using lipopolysaccharide (LPS).

MATERIALS AND METHODS

In vivo: 40 male rats were used in the present study. Cognitive impairment was induced using LPS (1 mg/kg/d; i.p.) for 4 weeks. Treatment with C. spinosa (100 and 300 mg/kg/d; p.o.) was performed 1 h before LPS administration. At the end of the experiment, rats were undergone for behavioral and biochemical analysis. In vitro: Primary microglia isolated from mouse was used in the present study. The cells were pretreated with C. spinosa extract (10-300 μg/ml) and then stimulated with LPS (1 μg/ml). The expression levels of inflammatory and anti-inflammatory cytokines were elucidated using Real-Time PCR and ELISA methods.

RESULTS

The escape latency in the Morris water maze test in the LPS group was significantly greater than the control group (p < 0.001), while, in extract-treated groups, it was less than the LPS group (p < 0.001). Additionally, we found that the levels of IL-1β, TNF-α, and iNOS/Arg-1 ratio was also significantly lower in extract-treated groups than the LPS group (p < 0.001). The results revealed that C. spinosa extract significantly reduced the levels of TNF-α, iNOS, COX-2, IL-1β, IL-6, NO and PGE2, and the ratios of iNOS/Arg-1 and NO/urea, following the LPS-induced inflammation in microglia (p < 0.001).

CONCLUSIONS

Our finding provides evidence that C. spinosa has a neuroprotective effect, and might be considered as an effective therapeutic agent for the treatment of neurodegenerative diseases that are accompanied by microglial activation, such as AD.

Dietary Intake of Green Nut Oil or DHA Ameliorates DHA Distribution in the Brain of a Mouse Model of Dementia Accompanied by Memory Recovery

Docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid, has significant healthbenefits. Previous studies reported decreased levels of DHA and DHA-containing phosphatidylcholines inthe brain of animals suffering from Alzheimer's disease, the most common type of dementia; furthermore,DHA supplementation has been found to improve brain DHA levels and memory efficiency in dementia. Oilextracted from the seeds of Plukenetia volubilis (green nut oil; GNO) is also expected to have DHA like effectsas it contains approximately 50% α-linolenic acid, a precursor of DHA. Despite this, changes in the spatialdistribution of DHA in the brain of animals with dementia following GNO or DHA supplementation remainunexplored. In this study, desorption electrospray ionization imaging mass spectrometry (DESI-IMS) wasapplied to observe the effects of GNO or DHA supplementation upon the distribution of DHA in the brain ofmale senescence-accelerated mouse-prone 8 (SAMP8) mice, a mouse model of dementia. DESI-IMS revealedthat brain DHA distribution increased 1.85-fold and 3.67-fold in GNO-fed and DHA-fed SAMP8 mice,respectively, compared to corn oil-fed SAMP8 mice. Memory efficiency in SAMP8 mice was also improvedby GNO or DHA supplementation. In summary, this study suggests the possibility of GNO or DHAsupplementation for the prevention of dementia.

Synaptic and memory dysfunction induced by tau oligomers is rescued by up-regulation of the nitric oxide cascade

BACKGROUND

Soluble aggregates of oligomeric forms of tau protein (oTau) have been associated with impairment of synaptic plasticity and memory in Alzheimer's disease. However, the molecular mechanisms underlying the synaptic and memory dysfunction induced by elevation of oTau are still unknown.

METHODS

This work used a combination of biochemical, electrophysiological and behavioral techniques. Biochemical methods included analysis of phosphorylation of the cAMP-responsive element binding (CREB) protein, a transcriptional factor involved in memory, histone acetylation, and expression immediate early genes c-Fos and Arc. Electrophysiological methods included assessment of long-term potentiation (LTP), a type of synaptic plasticity thought to underlie memory formation. Behavioral studies investigated both short-term spatial memory and associative memory. These phenomena were examined following oTau elevation.

RESULTS

Levels of phospho-CREB, histone 3 acetylation at lysine 27, and immediate early genes c-Fos and Arc, were found to be reduced after oTau elevation during memory formation. These findings led us to explore whether up-regulation of various components of the nitric oxide (NO) signaling pathway impinging onto CREB is capable of rescuing oTau-induced impairment of plasticity, memory, and CREB phosphorylation. The increase of NO levels protected against oTau-induced impairment of LTP through activation of soluble guanylyl cyclase. Similarly, the elevation of cGMP levels and stimulation of the cGMP-dependent protein kinases (PKG) re-established normal LTP after exposure to oTau. Pharmacological inhibition of cGMP degradation through inhibition of phosphodiesterase 5 (PDE5), rescued oTau-induced LTP reduction. These findings could be extrapolated to memory because PKG activation and PDE5 inhibition rescued oTau-induced memory impairment. Finally, PDE5 inhibition re-established normal elevation of CREB phosphorylation and cGMP levels after memory induction in the presence of oTau.

CONCLUSIONS

Up-regulation of CREB activation through agents acting on the NO cascade might be beneficial against tau-induced synaptic and memory dysfunctions.

Insulin treatment protects the brain against neuroinflammation by reducing cerebral cytokines and modulating mitochondrial function

In the central nervous system, glial cells protect the brain against neuronal stress by inducing inflammatory responses; namely, intracellular signaling and cytokine production. However, chronic inflammation is often associated with degenerative diseases that can damage hormone signaling and mitochondrial function. Lipopolysaccharide (LPS) induces neuroinflammation by stimulating the production of interleukin-1beta (IL-1β) and tumor necrosis factor-alpha (TNF-α); moreover, it generates oxidative stress and impairs cognitive functions. The aim of the present study was to assess the therapeutic efficacy of intracerebroventricular (i.c.v.) injections of insulin against neuroinflammation. Inflammation was first induced in male Wistar rats (60 days old, n = 12/group) through an intraperitoneal injection of 0.1 mg/kg LPS. The i.c.v. insulin treatment at a 0.5 mU dose was initiated 4 h later and administered once a day for 5 days. Thereafter, the spatial memory of the rats was assessed, and the hippocampus and cortex were later dissected for biochemical analyses. Our results showed that LPS induced cognitive function impairments, but the insulin treatment reversed these effects. Whereas the levels of brain-derived neurotrophic factor and beta-nerve growth factor in the hippocampus were not altered by LPS, they were decreased in the cortex by insulin. The IL-1β and TNF-α levels were increased in the cortex and hippocampus following exposure to LPS, but insulin reversed these effects. Evaluation of the H₂O₂levels and mitochondrial membrane potential revealed that LPS modulated mitochondrial function, an effect that was also reversed by insulin. Moreover, LPS induced oxidative stress by decreasing the superoxide dismutase and catalase activities and glutathione and sulfhydryl levels. Furthermore, the levels of oxidative stress probes/markers (i.e.,2',7'-dichlorodihydrofluoresceindiacetateand nitrite) were higher in the LPS-treated rats. These effects were all reversed in the cortex and hippocampus by insulin treatment. Our results suggest a potential role for insulin as a therapeutic drug against inflammatory diseases associated with mitochondrial dysfunction in the brain.

Intraischemic Modest Hypothermia Does Not Prevent Onset of Locomotor Inactivity After Transient Forebrain Ischemia in Rats

Although modest hypothermia of 35°C has been demonstrated to provide histological neuroprotection in a rodent model of cerebral ischemia, the long-term behavioral outcome is still not clear. This study was designed to investigate whether modest hypothermia of 35°C provides sustained histological and behavioral neuroprotection following transient forebrain ischemia in rats. Male Sprague-Dawley rats were randomly assigned to one of three groups: sham, control, and modest hypothermia group. Each group contained eight rats. Ten-minute transient forebrain ischemia was produced by bilateral carotid artery occlusion plus hemorrhagic hypotension (mean arterial pressure = 40 mmHg). The hypothermic group was cooled to 35°C in preischemic period, and the cooling was continued for 1 hour postischemia. To evaluate behavioral outcome, spontaneous alternation behavior and locomotor activity were assessed using Y-maze test on a weekly basis. The rats were sacrificed after 28 days, and the number of intact neurons per 1 mm in the hippocampal CA1 subfield was counted microscopically. There was significant difference between the control [19(24.5)/mm: median (interquartile range)] and hypothermia groups [116(24)/mm; p < 0.01] in the intact CA1 neuron count. In the control and modest hypothermia groups, the locomotor activities were gradually decreased, and reached significantly lower levels in comparison with the sham group at 14 days postischemia. This study indicates that intraischemic modest hypothermia provided long-term histological neuroprotection, but did not reverse the onset of locomotor inactivity in a rat transient forebrain ischemia model.

The effects of aminoguanidine on hippocampal cytokines, amyloid beta, brain-derived neurotrophic factor, memory and oxidative stress status in chronically lipopolysaccharide-treated rats

INTRODUCTION

In the present study, the effects of aminoguanidine (AMG) on hippocampal cytokines, amyloid beta (Aβ), brain-derived neurotrophic factor, oxidative stress status and memory in chronically lipopolysaccharide (LPS) treated rats were investigated.

METHODS

The rats were divided into five groups and were treated: (1) Control (Saline), (2) LPS (1 mg/kg), (3-5) LPS- AMG50, LPS-AMG100, and LPS-AMG150 (AMG 50, 100 and 150 mg/kg 30 min before LPS injection). The treatment started five weeks prior to the behavioral experiments and continued during the behavioral tests (LPS injection two hours before each behavioral evaluation). Finally, the tissue was removed for biochemical measurements.

RESULTS

The escape latency in Morris water maze test and the latency to enter the dark compartment in passive avoidance test in LPS group were significantly greater than the control group (P < 0.001), while, in LPS-AMG 100 and LPS-AMG150 groups they were less than LPS group (P < 0.001). Malondialdehyde (MDA), NO metabolites of hippocampal and cortical tissues and interleukin-6 (IL-6), Aβ and tumor necrosis factor-α (TNFα) concentration in the hippocampus of LPS group were higher than control group (P < 0.001-P < 0.05). However, in LPS-AMG 100 and LPS-AMG150 group they were lower than LPS group (P < 0.001-P < 0.05). The thiol content and the activities of catalase (CAT) and superoxide dismutase (SOD) in both cortical and hippocampal tissues of LPS group were reduced compared to the control group (P < 0.001-P < 0.05). These factors enhanced in LPS-AMG 100 and LPS-AMG150 groups compared to LPS (P < 0.001-P < 0.05). The hippocampal content of brain-derived neurotrophic factor (BDNF) in LPS group was significantly lower compared to the control group (P < 0.001). All treated groups had higher BDNF content in comparison to LPS group (P < 0.01-P < 0.001).

CONCLUSION

The findings indicated that the protective effects of AMG against LPS-induced memory were accompanied by decreasing of inflammatory cytokines, Aβ, oxidative stress and increasing of anti-inflammatory mediators and BDNF.

Lipopolysaccharide-induced memory impairment in rats: a model of Alzheimer's disease

Alzheimer's disease (AD) is a primary cause of dementia in the middle-aged and elderly worldwide. Animal models for AD are widely used to study the disease mechanisms as well as to test potential therapeutic agents for disease modification. Among the non-genetically manipulated neuroinflammation models for AD, lipopolysaccharide (LPS)-induced animal model is commonly used. This review paper aims to discuss the possible factors that influence rats' response following LPS injection. Factors such as dose of LPS, route of administration, nature and duration of exposure as well as age and gender of animal used should be taken into account when designing a study using LPS-induced memory impairment as model for AD.

Hepato- and neuro-protective influences of biopropolis on thioacetamide-induced acute hepatic encephalopathy in rats

Hepatic encephalopathy (HE) is a neuropsychiatric syndrome that ultimately occurs as a complication of acute or chronic liver failure; accompanied by hyperammonemia. This study aimed to evaluate the potential of biopropolis as a hepato- and neuro-protective agent using thioacetamide (TAA)-induced acute HE in rats as a model. Sixty Wistar rats were divided into 5 groups: Group 1 (normal control) received only saline and paraffin oil. Group 2 (hepatotoxic control) received TAA (300 mg/kg, once). Groups 3, 4, and 5 received TAA followed by vitamin E (100 mg/kg) and biopropolis (100 and 200 mg/kg), respectively, daily for 30 days. Evidences of HE were clearly detected in TAA-hepatotoxic group including significant elevation in the serum level of ammonia, liver functions, increased oxidative stress in liver and brain, apoptotic DNA fragmentation and overexpression of iNOS gene in brain tissue. The findings for groups administered biopropolis, highlighted its efficacy as a hepato- and neuro-protectant through improving the liver functions, oxidative status and DNA fragmentation as well as suppressing the brain expression of iNOS gene. In conclusion, biopropolis, at a dose of 200 mg/kg per day protected against TAA-induced HE through its antioxidant and antiapoptotic influence; therefore, it can be used as a protective natural product.

Effects of the inducible nitric oxide synthase inhibitor aminoguanidine in two different rat models of schizophrenia

Several lines evidence indicate that the non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist ketamine and the mixed dopamine (DA) D1/D2 receptor agonist apomorphine induce schizophrenia-like symptoms in rodents, including memory impairments and social withdrawal. Nitric oxide (NO) has been proposed to act as an intracellular messenger in the brain and its overproduction is associated with schizophrenia. The current study was designed to investigate the ability of the inducible NO synthase (iNOS) inhibitor aminoguanidine (AG) to counteract schizophrenia-like behavioural deficits produced by ketamine and apomorphine in rats. The efficacy of AG to antagonize extinction of recognition memory, ketamine and apomorphine-induced recognition memory impairments was tested utilizing the novel object recognition task (NORT). Further, the efficacy of AG to attenuate ketamine-induced social withdrawal was examined in the social interaction test. AG (25 and 50mg/kg) antagonized extinction of recognition memory and reversed ketamine (3mg/kg) and apomorphine (1mg/kg)-induced recognition memory deficits. In contrast, AG (50 and 100mg/kg) did not counteract the ketamine (8mg/kg)-induced social isolation. The present data show that the iNOS inhibitor AG counteracted extinction of recognition memory and reversed recognition memory deficits produced by dysfunction of the glutamatergic and the dopaminergic (DAergic) system in rats. Therefore, AG may be efficacious in attenuating memory impairments often observed in schizophrenia patients.

TLR4-activated microglia require IFN-γ to induce severe neuronal dysfunction and death in situ

Microglia (tissue-resident macrophages) represent the main cell type of the innate immune system in the CNS; however, the mechanisms that control the activation of microglia are widely unknown. We systematically explored microglial activation and functional microglia-neuron interactions in organotypic hippocampal slice cultures, i.e., postnatal cortical tissue that lacks adaptive immunity. We applied electrophysiological recordings of local field potential and extracellular K(+) concentration, immunohistochemistry, design-based stereology, morphometry, Sholl analysis, and biochemical analyses. We show that chronic activation with either bacterial lipopolysaccharide through Toll-like receptor 4 (TLR4) or leukocyte cytokine IFN-γ induces reactive phenotypes in microglia associated with morphological changes, population expansion, CD11b and CD68 up-regulation, and proinflammatory cytokine (IL-1β, TNF-α, IL-6) and nitric oxide (NO) release. Notably, these reactive phenotypes only moderately alter intrinsic neuronal excitability and gamma oscillations (30-100 Hz), which emerge from precise synaptic communication of glutamatergic pyramidal cells and fast-spiking, parvalbumin-positive GABAergic interneurons, in local hippocampal networks. Short-term synaptic plasticity and extracellular potassium homeostasis during neural excitation, also reflecting astrocyte function, are unaffected. In contrast, the coactivation of TLR4 and IFN-γ receptors results in neuronal dysfunction and death, caused mainly by enhanced microglial inducible nitric oxide synthase (iNOS) expression and NO release, because iNOS inhibition is neuroprotective. Thus, activation of TLR4 in microglia in situ requires concomitant IFN-γ receptor signaling from peripheral immune cells, such as T helper type 1 and natural killer cells, to unleash neurotoxicity and inflammation-induced neurodegeneration. Our findings provide crucial mechanistic insight into the complex process of microglia activation, with relevance to several neurologic and psychiatric disorders.

Effect of chronic intraperitoneal aminoguanidine on memory and expression of Bcl-2 family genes in diabetic rats

Long-term hyperglycemia associates with memory defects via hippocampal cells damaging. The aim of the present study was to examine the effect of 1 month of i.p. injections of AG on passive avoidance learning (PAL) and hippocampal apoptosis in rat. Eighty male rats were divided into 10 groups: control, nondiabetics and STZ-induced diabetics treated with AG (50, 100, 200, and 400 mg/kg, i.p.). PAL and the Bcl-2 family gene expressions were determined. Diabetes resulted in memory and Bcl-2 family gene expression deficits. AG (50 and 100 mg/kg) significantly improved the learning and Bcl-2, Bcl-xl, Bax, and Bak impairment in diabetic rats. However, negative effects were indicated by higher doses of the drug (200 and 400 mg/kg). Present study suggests that 1 month of i.p. injections of lower doses of AG, may improve the impaired cognitive tasks in STZ-induced diabetic rats possibly by modulating Bcl-2 family gene expressions.

The effects of L-arginine on spatial memory and synaptic plasticity impairments induced by lipopolysaccharide

Background:

An important role of nitric oxide (NO) in neuroinflammation has been suggested. It is also suggested that NO has a critical role in learning and memory. Neuro-inflammation induced by lipopolysaccharide (LPS) has been reported that deteriorates learning and memory. The effect of L-arginine (LA) as a precursor of NO on LPS-induced spatial learning and memory and neuronal plasticity impairment was evaluated.

Materials and Methods:

The animals were grouped into: (1) Control, (2) LPS, (3) LA-LPS, and (4) LA. The rats received intraperitoneally LPS (1 mg/kg) 2 h before experiments and LA (200 mg/kg) 30 min before LPS. The animals were examined in Morris water maze (MWM). Long-term potentiation (LTP) from CA₁ area of the hippocampus was also assessed by 100 Hz stimulation in the ipsilateral Schaffer collateral pathway.

Results:

In MWM, time latency and traveled path were higher in LPS group than the control group (P < 0.001) whereas in LA-LPS group they were shorter than LPS group (P < 0.001). The amplitude and slope of field excitatory postsynaptic potential (fEPSP) decreased in LPS group compared to control group (P < 0.05 and P < 0.01) whereas, there was not any significant difference in these parameters between LPS and LA-LPS groups.

Conclusion:

Administration of LPS impaired spatial memory and synaptic plasticity. Although LA ameliorated deleterious effects of LPS on learning of spatial tasks, it could not restore LPS-induced LTP impairment.

Lipopolysaccharide-induced memory impairment in rats is preventable using 7-nitroindazole

Inflammation and oxidative stress have important roles in memory impairment. The effect of 7-nitroindazole (7NI) on lipopolysaccharide (LPS)-induced memory impairment was investigated. Rats were used, divided into four groups that were treated as follows: (1) control (saline); (2) LPS; (3) 7NI-LPS; and (4) 7NI before passive avoidance (PA). In the LPS group, the latency for entering the dark compartment was shorter than in the controls (p < 0.01 and p < 0.001); while in the 7NI-LPS group, it was longer than in the LPS group (p < 0.01 and p < 0.001). Malondialdehyde (MDA) and nitric oxide (NO) metabolite concentrations in the brain tissues of the LPS group were higher than in the controls (p < 0.001 and p < 0.05); while in the 7NI-LPS group, they were lower than in the LPS group (p < 0.001 and p < 0.05, respectively). The thiol content in the brain of the LPS group was lower than in the controls (p < 0.001); while in the 7NI-LPS group, it was higher than in the LPS group (p < 0.001). It is suggested that brain tissue oxidative damage and NO elevation have a role in the deleterious effects of LPS on memory retention that are preventable using 7NI.

Effect of Ca2EDTA on zinc mediated inflammation and neuronal apoptosis in hippocampus of an in vivo mouse model of hypobaric hypoxia

Background

Calcium overload has been implicated as a critical event in glutamate excitotoxicity associated neurodegeneration. Recently, zinc accumulation and its neurotoxic role similar to calcium has been proposed. Earlier, we reported that free chelatable zinc released during hypobaric hypoxia mediates neuronal damage and memory impairment. The molecular mechanism behind hypobaric hypoxia mediated neuronal damage is obscure. The role of free zinc in such neuropathological condition has not been elucidated. In the present study, we investigated the underlying role of free chelatable zinc in hypobaric hypoxia-induced neuronal inflammation and apoptosis resulting in hippocampal damage.

Methods

Adult male Balb/c mice were exposed to hypobaric hypoxia and treated with saline or Ca₂EDTA (1.25 mM/kg i.p) daily for four days. The effects of Ca₂EDTA on apoptosis (caspases activity and DNA fragmentation), pro-inflammatory markers (iNOS, TNF-α and COX-2), NADPH oxidase activity, poly(ADP ribose) polymerase (PARP) activity and expressions of Bax, Bcl-2, HIF-1α, metallothionein-3, ZnT-1 and ZIP-6 were examined in the hippocampal region of brain.

Results

Hypobaric hypoxia resulted in increased expression of metallothionein-3 and zinc transporters (ZnT-1 and ZIP-6). Hypobaric hypoxia elicited an oxidative stress and inflammatory response characterized by elevated NADPH oxidase activity and up-regulation of iNOS, COX-2 and TNF-α. Furthermore, hypobaric hypoxia induced HIF-1α protein expression, PARP activation and apoptosis in the hippocampus. Administration of Ca₂EDTA significantly attenuated the hypobaric hypoxia induced oxidative stress, inflammation and apoptosis in the hippocampus.

Conclusion

We propose that hypobaric hypoxia/reperfusion instigates free chelatable zinc imbalance in brain associated with neuroinflammation and neuronal apoptosis. Therefore, zinc chelating strategies which block zinc mediated neuronal damage linked with cerebral hypoxia and other neurodegenerative conditions can be designed in future.

Long-term effects of post-ischaemic oestrogen on brain injury in a rat transient forebrain ischaemia model

BACKGROUND

The current study was conducted to compare the effects of post-treatment with oestrogen on histological and neurological outcomes after short (7-day) and long (28-day) recovery periods in rats subjected to transient forebrain ischaemia.

METHODS

Male Sprague-Dawley rats were randomly assigned to one of five groups: vehicle (7-day recovery period), vehicle (28-day recovery period), oestrogen (17β-estradiol 200 μg/kg, 7-day), oestrogen (17β-estradiol 200 μg /kg, 28-day), or sham surgical (n = 8 in each group). After forebrain ischaemia was induced with bilateral carotid artery occlusion and haemorrhagic hypotension (mean arterial pressure = 40 mmHg) for 10 min, the brain was reperfused for 7 or 28 days. Either 17β-estradiol or vehicle was injected intravenously during the initial 2 min of reperfusion. To evaluate histological damage, the number of intact neurons per 1 mm in the hippocampal CA1 subfield was counted at 7 or 28 days after transient forebrain ischaemia.

RESULTS

At 7 days after ischaemia, the number of intact neurons in the hippocampal CA1 subfield was significantly greater in the oestrogen group [57.5 (46.5)/mm: median (interquartile range)] than in the vehicle group [10 (19.5) /mm; P = 0.014]. However, there was no difference between groups at 28 days after ischaemia [vehicle: 11 (20)/mm vs. oestrogen: 6 (11)/mm]. The neurological deficit scores in the oestrogen and vehicle groups were not different from the sham group at any point post-ischaemia.

CONCLUSION

The current study indicates that post-ischaemic administration of oestrogen provided short-term but not long-term neuroprotective effects in transient forebrain ischaemia in rats.

Combretum mucronatum and Capparis thonningii prevent scopolamine-induced memory deficit in mice

CONTEXT

Roots of Combretum mucronatum Schumach. & Thonn. (Combretaceae) and Capparis thonningii Schum. (Capparaceae) are used in southwest Nigeria in the treatment of inflammatory disorders and mental illness.

OBJECTIVE

This study evaluated the antidementic effect of the methanol root extracts of C. mucronatum and C. thonningii on scopolamine (3 mg/kg, i.p.) induced memory impairment in mice.

MATERIALS AND METHODS

The effect of C. mucronatum and C. thonningii (50-200 mg/kg) administered orally for 3 days on memory impairments induced in mice by scopolamine was assessed in the passive avoidance and Morris water maze test and compared with that of tacrine (5 mg/kg, i.p.). The activities of acetylcholinesterase (AchE) and antioxidant enzymes were estimated in the brain after the completion of behavioral studies.

RESULTS

C. mucronatum and C. thonningii root extracts (50-200 mg/kg) reversed scopolamine-induced memory deficit with significant (p < 0.05) increase in transfer latency in passive avoidance test. Similarly, the extracts (200 mg/kg) ameliorated memory deficit as a result of significant (p < 0.001) decrease in escape latency and path length in Morris water maze test. The increased AChE activity induced by scopolamine was significantly (p < 0.05) inhibited by C. mucronatum and C. thonningii (100 and 200 mg/kg) treatment which was similar to the effect of tacrine. Both extracts significantly (p < 0.05) attenuated scopolamine-induced increase in oxidative stress parameters as well as restoration of glutathione activity.

DISCUSSION AND CONCLUSION

C. mucronatum and C. thonningii extracts possess significant anticholinesterase, antioxidant and antidementic properties, which may be useful in the management of Alzheimer's disease.

Pharmacological inhibition of inducible nitric oxide synthase (iNOS) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, convalesce behavior and biochemistry of hypertension induced vascular dementia in rats

Cognitive disorders are likely to increase over the coming years (5-10). Vascular dementia (VaD) has heterogeneous pathology and is a challenge for clinicians. Current Alzheimer's disease drugs have had limited clinical efficacy in treating VaD and none have been approved by major regulatory authorities specifically for this disease. Role of iNOS and NADPH-oxidase has been reported in various pathological conditions but there role in hypertension (Hypt) induced VaD is still unclear. This research work investigates the salutiferous effect of aminoguanidine (AG), an iNOS inhibitor and 4'-hydroxy-3'-methoxyacetophenone (HMAP), a NADPH oxidase inhibitor in Hypt induced VaD in rats. Deoxycorticosterone acetate-salt (DOCA-S) hypertension has been used for development of VaD in rats. Morris water-maze was used for testing learning and memory. Vascular system assessment was done by testing endothelial function. Mean arterial blood pressure (MABP), oxidative stress [aortic superoxide anion, serum and brain thiobarbituric acid reactive species (TBARS) and brain glutathione (GSH)], nitric oxide levels (serum nitrite/nitrate) and cholinergic activity (brain acetyl cholinesterase activity-AChE) were also measured. DOCA-S treated rats have shown increased MABP with impairment of endothelial function, learning and memory, reduction in serum nitrite/nitrate & brain GSH levels along with increase in serum & brain TBARS, and brain AChE activity. AG as well as HMAP significantly convalesce Hypt induced impairment of learning, memory, endothelial function, and alterations in various biochemical parameters. It may be concluded that AG, an iNOS inhibitor and HMAP, a NADPH-oxidase inhibitor may be considered as potential agents for the management of Hypt induced VaD.

Lipopolysaccharide induces paired immunoglobulin-like receptor B (PirB) expression, synaptic alteration, and learning-memory deficit in rats

Some typical immune proteins are expressed in the nervous system, among which the paired-immunoglobulin-like receptor B (PirB) is a receptor for major histocompatibility complex class I antigen (MHC-I), but may play a physiological role in the brain for neuronal circuitry stability by inhibiting synaptic plasticity. Chronic neuroinflammation is common to many neurodegenerative diseases and is often associated with neuronal/synaptic damage and dysfunction. Here we examined the expression of PirB in the rat brain following intracerebral application of lipopolysaccharide (LPS), which has been shown to induce proinflammatory changes and cognitive deficits in rodents. One month after unilateral intrahippocampal LPS injection (10 μg in 4 μl phosphate-buffered saline, PBS), increased protein levels and immunoreactivity of PirB were detected in the ipsilateral hippocampal formation and cortex of the experimental group relative to vehicle (PBS) control. The increased PirB labeling was localized to astrocytes and neurons. Reduced synaptophysin protein levels and immunoreactivity were also found in the ipsilateral hippocampal formation and cortex in LPS-treated rats relative to controls. Morris water maze tests indicated that hippocampus-dependent spatial learning and memory were impaired in LPS-treated animals. Our findings add new experimental data for an upregulation of immune proteins in neuronal and glial cells in the brain in a model of endotoxin-induced neuroinflammation, synaptic alteration, and cognitive decline. The results suggest that PirB modulation may be involved in the pathological process under neurodegenerative conditions.

Effects of betaine on lipopolysaccharide-induced memory impairment in mice and the involvement of GABA transporter 2

Background

Betaine (glycine betaine or trimethylglycine) plays important roles as an osmolyte and a methyl donor in animals. While betaine is reported to suppress expression of proinflammatory molecules and reduce oxidative stress in aged rat kidney, the effects of betaine on the central nervous system are not well known. In this study, we investigated the effects of betaine on lipopolysaccharide (LPS)-induced memory impairment and on mRNA expression levels of proinflammatory molecules, glial markers, and GABA transporter 2 (GAT2), a betaine/GABA transporter.

Methods

Mice were continuously treated with betaine for 13 days starting 1 day before they were injected with LPS, or received subacute or acute administration of betaine shortly before or after LPS injection. Then, their memory function was evaluated using Y-maze and novel object recognition tests 7 and 10-12 days after LPS injection (30 μg/mouse, i.c.v.), respectively. In addition, mRNA expression levels in hippocampus were measured by real-time RT-PCR at different time points.

Results

Repeated administration of betaine (0.163 mmol/kg, s.c.) prevented LPS-induced memory impairment. GAT2 mRNA levels were significantly increased in hippocampus 24 hr after LPS injection, and administration of betaine blocked this increase. However, betaine did not affect LPS-induced increases in levels of mRNA related to inflammatory responses. Both subacute administration (1 hr before, and 1 and 24 hr after LPS injection) and acute administration (1 hr after LPS injection) of betaine also prevented LPS-induced memory impairment in the Y-maze test.

Conclusions

These data suggest that betaine has protective effects against LPS-induced memory impairment and that prevention of LPS-induced changes in GAT2 mRNA expression is crucial to this ameliorating effect.

Molecular and behavioral aspects of the actions of alcohol on the adult and developing brain

The brain is one of the major target organs of alcohol actions. Alcohol abuse can lead to alterations in brain structure and functions and, in some cases, to neurodegeneration. Cognitive deficits and alcohol dependence are highly damaging consequences of alcohol abuse. Clinical and experimental studies have demonstrated that the developing brain is particularly vulnerable to alcohol, and that drinking during gestation can lead to a range of physical, learning and behavioral defects (fetal alcohol spectrum disorders), with the most dramatic presentation corresponding to fetal alcohol syndrome. Recent findings also indicate that adolescence is a stage of brain maturation and that heavy drinking at this stage can have a negative impact on brain structure and functions causing important short- and long-term cognitive and behavioral consequences. The effects of alcohol on the brain are not uniform; some brain areas or cell populations are more vulnerable than others. The prefrontal cortex, the hippocampus, the cerebellum, the white matter and glial cells are particularly susceptible to the effects of ethanol. The molecular actions of alcohol on the brain are complex and involve numerous mechanisms and signaling pathways. Some of the mechanisms involved are common for the adult brain and for the developing brain, while others depend on the developmental stage. During brain ontogeny, alcohol causes irreversible alterations to the brain structure. It also impairs several molecular, neurochemical and cellular events taking place during normal brain development, including alterations in both gene expression regulation and the molecules involved in cell-cell interactions, interference with the mitogenic and growth factor response, enhancement of free radical formation and derangements of glial cell functions. However, in both adult and adolescent brains, alcohol damages specific brain areas through mechanisms involving excitotoxicity, free radical formation and neuroinflammatory damage resulting from activation of the innate immune system mediated by TLR4 receptors. Alcohol also acts on specific membrane proteins, such as neurotransmitter receptors (e.g. NMDA, GABA-A), ion channels (e.g. L-type Ca²⁺ channels, GIRKs), and signaling pathways (e.g. PKA and PKC signaling). These effects might underlie the wide variety of behavioral effects induced by ethanol drinking. The neuroadaptive changes affecting neurotransmission systems which are more sensitive to the acute effects of alcohol occur after long-term alcohol consumption. Alcohol-induced maladaptations in the dopaminergic mesolimbic system, abnormal plastic changes in the reward-related brain areas and genetic and epigenetic factors may all contribute to alcohol reinforcement and alcohol addiction. This manuscript reviews the mechanisms by which ethanol impacts the adult and the developing brain, and causes both neural impairments and cognitive and behavioral dysfunctions. The identification and the understanding of the cellular and molecular mechanisms involved in ethanol toxicity might contribute to the development of treatments and/or therapeutic agents that could reduce or eliminate the deleterious effects of alcohol on the brain.

Z-ligustilide attenuates lipopolysaccharide-induced proinflammatory response via inhibiting NF-kappaB pathway in primary rat microglia

AIM

To investigate the anti-inflammatory effect of Z-ligustilide (LIG) on lipopolysaccharide (LPS)-activated primary rat microglia.

METHODS

Microglia were pretreated with LIG 1 h prior to stimulation with LPS (1 microg/mL). After 24 h, cell viability was tested with MTT, nitric oxide (NO) production was assayed with Griess reagent, and the content of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and monocyte chemoattractant protein (MCP-1) was measured with ELISA. Protein expression of the nuclear factor-kappaB (NF-kappaB) p65 subunit, cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) was detected with immunocytochemistry 1 h or 24 h after LPS treatment.

RESULTS

LIG showed a concentration-dependent anti-inflammatory effect in LPS-activated microglia, without causing cytotoxicity. Pretreatment with LIG at 2.5, 5, 10, and 20 micromol/L decreased LPS-induced NO production to 75.9%, 54.4%, 43.1%, and 47.6% (P<0.05 or P< 0.01), TNF-alpha content to 86.2%, 68.3%, 40.1%, and 39.9% (P<0.01, with the exception of 86.2% for 2.5 micromol/L LIG), IL-1beta content to 31.5%, 27.7%, 0.6%, and 0% (P<0.01), and MCP-1 content to 84.4%, 50.3%, 45.1%, and 42.2% (P<0.05 or P<0.01), respectively, compared with LPS treatment alone. LIG (10 micromol/L) significantly inhibited LPS-stimulated immunoreactivity of activated NF-kappaB, COX-2, and iNOS (P<0.01 vs LPS group).

CONCLUSION

LIG exerted a potent anti-inflammatory effect on microglia through inhibition of NF-kappaB pathway. The data provide direct evidence of the neuroprotective effects of LIG and the potential application of LIG for the treatment of the neuroinflammatory diseases characterized by excessive microglial activation.

Agmatine prevents LPS-induced spatial memory impairment and hippocampal apoptosis

Neuroinflammation is associated with a number of neurodegenerative diseases. It is known that lipopolysaccharide (LPS) treatment induces neuroinflammation and memory deterioration. Agmatine, the metabolite of arginine by arginine decarboxylase, is suggested to be a neuroprotective agent. The aim of this study was to explore if agmatine can prevent LPS-induced spatial memory impairment and hippocampal apoptosis. Adult male Wistar rats (200-250 g) were trained in water maze for 4 days (3 days in hidden platform and the last day in visible platform task). Saline, LPS (250 microg/kg/ip) or (and) agmatine (5 or 10 mg/kg) were administered 4h before every training session. LPS treatment impaired water maze place learning while agmatine co-administration prevented it. Also western blot studies revealed that LPS induces hippocampal caspase-3 activation while agmatine treatment prevented it.

Mechanisms involved in the neurotoxic, cognitive, and neurobehavioral effects of alcohol consumption during adolescence

Studies over the last decade demonstrate that adolescence is a brain maturation period from childhood to adulthood. Plastic and dynamic processes drive adolescent brain development, creating flexibility that allows the brain to refine itself, specialize, and sharpen its functions for specific demands. Maturing connections enable increased communication among brain regions, allowing greater integration and complexity. Compelling evidence has shown that the developing brain is vulnerable to the damaging effects of ethanol. It is possible to infer, therefore, that alcohol exposure during the critical adolescent developmental stages could disrupt the brain plasticity and maturation processes, resulting in behavioral and cognitive deficits. Recent neuroimaging studies have provided evidence of the impact of human adolescent drinking in brain structure and functions. Findings in experimental animals have also given new insight into the potential mechanisms of the toxic effects of ethanol on both adolescent brain maturation and the short- and long-term cognitive consequences of adolescent drinking. Adolescence is also characterized by the rapid maturation of brain systems mediating reward and by changes in the secretion of stress-related hormones, events that might participate in the increasing in anxiety and the initiation pattern of alcohol and drug consumption. Studies in human adolescents demonstrate that drinking at early ages can enhance the likelihood of developing alcohol-related problems. Experimental evidence suggests that early exposure to alcohol sensitizes the neurocircuitry of addiction and affects chromatin remodeling, events that could induce abnormal plasticity in reward-related learning processes that contribute to adolescents' vulnerability to drug addiction. In this article, we review the potential mechanisms by which ethanol impacts brain development and lead to brain impairments and cognitive and behavioral dysfunctions as well as the neurobiological and neurochemical processes underlying the adolescent-specific vulnerability to drug addiction.

Cholinergic protection via alpha7 nicotinic acetylcholine receptors and PI3K-Akt pathway in LPS-induced neuroinflammation

The present study was planned to investigate the effect of anti-cholinesterase drugs donepezil and neostigmine on neuroinflammation induced by intracerebroventricular administration of lipopolysaccharide (LPS, 50 microg) in rat. Proinflammatory cytokines (TNF-alpha and IL-1beta), expressions of iNOS and COX-2, acetylcholinesterase activity, malondialdehyde and reduced glutathione were studied in different brain regions at 24h of LPS injection. Donepezil was found to decrease the LPS-induced AChE activity and oxidative stress in all the brain regions. It also inhibited the LPS-induced proinflammatory cytokines and iNOS expression but did not affect the increased COX-2 expression whereas neostigmine treatment had no effect on LPS-induced proinflammatory cytokines. Methyllycaconitine (MLA), a alpha7 nicotinic acetylcholine receptor antagonist, significantly antagonized the donepezil mediated inhibition of LPS-induced proinflammatory cytokines, indicating that alpha7 nicotinic acetylcholine receptor subunit was playing a role in regulation of neuroinflammation. The phosphorylation of Akt, an effector of PI3K, increased with donepezil treatment. These results suggest that increased cholinergic activity in brain by donepezil prevents LPS-induced neuroinflammation via alpha7-nAChRs, followed by the PI3K-Akt pathway and this system may form the basis for the development of novel agents for reversing neuroinflammation or provide new indications for existing drugs.

Ameliorative effects of lotus seedpod proanthocyanidins on cognitive deficits and oxidative damage in senescence-accelerated mice

We investigated the effects of lotus seedpod proanthocyanidins (LSPC) administration by oral gavage for 3 months on body weight, learning and memory deficits using Y-maze test, oxidative stress and antioxidative enzyme activity in brain and serum of the senescence-accelerated mice (SAMP8) and the senescence-resistant mice (SAMR1). Mice of each group were weighed weekly. Brain was obtained from SAMP8 and SAMR1 (the control mouse for SAMP8) at 6 months of age and serum was available from SAMP8 and SAMR1 at 3, 4, 5 and 6 months of age. The results of body weight showed that 90mg/kg LSPC administration significantly increased body weight at 5.5 and 6 months of age in SAMP8 when compared with control SAMP8 of the same age. Y-maze test indicated that learning and memory abilities of mice were deteriorated significantly at 6 months of age in SAMP8 compared with age-matched SAMR1, but were remarkably improved after LSPC (60, 90, 120mg/kg body weight) administration beginning at 3 months of ages. Malondialdehyde (MDA), nitric oxide (NO) and nitric oxide synthase (NOS) exhibited significant increases mostly at 5 and 6 months of age in SAMP8. Glutathione (GSH), glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities decreased significantly mostly at 5 and 6 months of age in SAMP8. LSPC (60, 90, 120mg/kg body weight) administration beginning at 3 months of ages decreased MDA, NO content and lowered NOS activity in the brain and serum of SAMP8. Furthermore, LSPC significantly increased GSH level and augmented GPx, SOD activity in the brain and serum of SAMP8. These results suggest that an age-related increase in brain tissue vulnerability to oxidation and deterioration in learning and memory abilities in SAM that can be modified by LSPC, most likely through the ability of LSPC to scavenge oxygen free radicals and to stimulate antioxidant enzyme activity.

Fruit polyphenols and their effects on neuronal signaling and behavior in senescence

The onset of age-related neurodegenerative diseases superimposed on a declining nervous system could exacerbate the motor and cognitive behavioral deficits that normally occur in senescence. It is likely that, in cases of severe deficits in memory or motor function, hospitalization and/or custodial care would be a likely outcome. This means that unless some way is found to reduce these age-related decrements in neuronal function, healthcare costs will continue to rise exponentially. Thus, it is extremely important to explore methods to retard or reverse the age-related neuronal deficits as well as their subsequent, behavioral manifestations. Applying molecular biological approaches to slow aging in the human condition may be years away. So it is important to determine what methods can be used today to increase healthy aging, forestall the onset of these diseases, and create conditions favorable to obtaining a "longevity dividend" in both financial and human terms. In this regard, epidemiological studies indicate that consumption of diets rich in antioxidants and anti-inflammatory compounds, such as those found in fruits and vegetables, may lower the risk of developing age-related neurodegenerative diseases, such as Alzheimer's or Parkinson's diseases (AD and PD). Research suggests that the polyphenolic compounds found in fruits, such as blueberries, may exert their beneficial effects by altering stress signaling and neuronal communication, suggesting that interventions may exert protection against age-related deficits in cognitive and motor function. The purpose of this article is to discuss the benefits of these interventions in rodent models and to describe the putative molecular mechanisms involved in their benefits.

Intermittent ethanol exposure induces inflammatory brain damage and causes long-term behavioural alterations in adolescent rats

Adolescent brain development seems to be important for the maturation of brain structures and behaviour. Intermittent binge ethanol drinking is common among adolescents, and this type of drinking can induce brain damage. Because we have demonstrated that chronic ethanol treatment induces inflammatory processes in the brain, we investigate whether intermittent ethanol intoxication enhances cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) in adolescent rats, and whether these mediators induce brain damage and cause permanent cognitive dysfunctions. Adolescent rats were exposed to ethanol (3.0 g/kg) for two consecutive days at 48-h intervals over 14 days. Levels of COX-2, iNOS and cell death were assessed in the neocortex, hippocampus and cerebellum 24 h after the final ethanol administration. The following day or 20 days after the final injection (adult stage), animals were tested for different behavioural tests (conditional discrimination learning, rotarod, object recognition, beam-walking performance) to assess cognitive and motor functions. Our results show that intermittent ethanol intoxication upregulates COX-2 and iNOS levels, and increases cell death in the neocortex, hippocampus and cerebellum. Furthermore, animals treated with ethanol during adolescence exhibited behavioural deficits that were evident at the end of ethanol treatments and at the adult stage. Administration of indomethacin, a COX-2 inhibitor, abolishes the induction of COX-2 and iNOS expression and cell death, preventing ethanol-induced behavioural deficits. These findings indicate that binge pattern exposure to ethanol during adolescence induces brain damage by inflammatory processes and causes long-lasting neurobehavioural consequences. Accordingly, administering indomethacin protects against ethanol-induced brain damage and prevents detrimental ethanol effects on cognitive and motor processes.

Nitric oxide donor-induced inhibition of pregnant rat uterine spontaneous contractile activity and release of nitric oxide from uterus measured by microdialysis

Our aim was to study whether nitric oxide (NO) donor-induced inhibition of pregnant rat myometrium contractility correlates with the release of NO. Uterine rings from mid-pregnant and late pregnant Sprague-Dawley rats were used for isometric tension recording. Concentration-response relationships to sodium nitroprusside (SNP), nitroglycerine (NTG) and diethylamine (DEA)/NO were assessed. The time course of NO release after addition to the organ chambers of the 3 NO-donors was assessed by the detection of NO products NOx (NO3+NO2) using the microdialysis probe by a HPLC-NO detector system. DEA/ NO induced greater inhibition of the spontaneous contractile activity of uterine rings from mid-pregnant rats than SNP or NTG. In uterine rings from late pregnant rats, however, the maximal inhibition of the contractility by all 3 NO-donors were significantly less. The NOx levels measured in the uterine ring walls from either mid-pregnant or late pregnant rats significantly increased after DEA/ NO as compared to the basal levels or the levels after NTG or SNP. The decrease of NO-donor-induced inhibition of rat myometrium contractility, with unchanged formation of NOx, at term, suggests that the changes in NO signaling are responsible for gestational age-dependent attenuation of the inhibitory effect.

Effects of 7-nitroindazole and N-nitro-l-arginine methyl ester on changes in cerebral blood flow and nitric oxide production preceding development of hyperbaric oxygen-induced seizures in rats

Hyperbaric oxygen (HBO(2)) exposure induces increases in cerebral blood flow (CBF) and extracellular concentrations of nitric oxide (NO) that precede the appearance of central nervous system toxicity, which may manifest as convulsions. To elucidate the origins of NO production during HBO(2) exposure, we examined the effects of the selective neuronal NO synthase (NOS) inhibitor, 7-nitroindazole (7-NI), and the non-selective NOS inhibitor, N-nitro-l-arginine methyl ester (l-NAME), on changes in CBF and NO metabolites (NO(x), nitrite and nitrate) using a laser Doppler flow probe and in vivo microdialysis techniques, respectively. Rats were anesthetized, artificially ventilated, and pressurized to 5 atmosphere absolute (ATA) with pure oxygen for 60 min. In rats treated with vehicle, CBF and NO(x) levels in the cortex increased to 201% and 239% of basal levels, respectively, before the onset of electrical discharges, measured by electroencephalogram. The increase in CBF and NO(x) was completely inhibited by 7-NI and l-NAME. Both drugs also inhibited the appearance of electrical discharges for 60 min. Dynamic changes in CBF and NO(x) were not significantly different between 7-NI and l-NAME. These findings suggest that neuronal NOS is the main mediator of NO production associated with increase in CBF leading to the appearance of electrical discharge during HBO(2) exposure.

Oxidative Stress and Inflammation in Brain Aging: Nutritional Considerations

Aging can be defined as the condition where stressors are not counteracted by protective functions, leading to a dysregulation in development. These changes can be translated into decrements in neuronal functioning accompanied by behavioral declines, such as decreases in motor and cognitive performance, in both humans and animals. When coupled with genetic alterations, the ultimate expression of these changes is seen in diseases such as Alzheimer disease (AD). This association will be discussed in the last section of this chapter. In this review we will describe motor and cognitive deficits in behavior due to aging, and show how these deficits are related to increased vulnerability to oxidative stress, inflammation or signaling. Importantly, using muscarinic receptors as examples, we will also try to show that the sensitivity to these insults may be differentially expressed among neurotransmitter receptor subtypes.

Pathological consequences of inducible nitric oxide synthase expression in hippocampal slice cultures

The generation of toxic concentrations of nitric oxide by the inducible nitric oxide synthase expressed in microglia and other brain cell types is frequently invoked as a causative factor in neurodegeneration. Experiments were carried out on slice cultures of rat hippocampus to test this hypothesis. Exposure of the slices to bacterial lipopolysaccharide plus interferon-gamma led to a time-dependent expression of functional inducible nitric oxide synthase that was found only in microglia. Microglial activation by other means, such as physical damage, was not associated with inducible nitric oxide synthase expression. Damage and cell death in slices expressing inducible nitric oxide synthase was evaluated over a period of 6 days, but none was found. Consistent with this result, cGMP measurements indicated that the average local nitric oxide concentration remained in the low nanomolar range. When the microglial population was expanded to a density three-fold above normal by applying granulocyte-macrophage colony stimulating factor, however, lipopolysaccharide plus interferon-gamma provoked neurodegeneration that could be blocked by an inducible nitric oxide synthase inhibitor. The associated nitric oxide concentration in the slices was saturating for guanylyl cyclase-coupled nitric oxide receptors, signifying at least 10 nM. It is concluded that inducible nitric oxide synthase is expressed in microglia only in response to specific stimuli involving the innate immune system, and that the resulting level of nitric oxide in intact brain tissue is normally too low to inflict damage directly. Quantities of nitric oxide sufficient to contribute directly or indirectly to pathology could be produced should the density of microglia become high enough, although caution must be exercised in extrapolating this finding to the human brain in vivo.

Reversing the deleterious effects of aging on neuronal communication and behavior: beneficial properties of fruit polyphenolic compounds

Despite elegant research involving molecular biology studies and determination of the genetic mechanisms of aging, practical information on how to forestall or reverse the deleterious effects of aging may be years away. If this is the case, then it is prudent to try to establish other methods that can be used now to alter the course of aging. Numerous epidemiologic studies have indicated that individuals who consume diets containing large amounts of fruits and vegetables may reduce their risk for developing age-related diseases such as Alzheimer disease. Research from our laboratory suggested that dietary supplementation with fruit or vegetable extracts high in antioxidants (eg, blueberry or spinach extracts) might decrease the enhanced vulnerability to oxidative stress that occurs in aging. These reductions might be expressed as improvements in motor and cognitive behavior. Additional research suggested that mechanisms in addition to antioxidant and antiinflammatory activities might be involved in the beneficial effects of these extracts; the most important of these might be their ability to increase cellular signaling and neuronal communication.

Characterization of a rat model to study acute neuroinflammation on histopathological, biochemical and functional outcomes

Neuroinflammation is one of the events occurring after acute brain injuries. The aim of the present report was to characterize a rat model to study acute neuroinflammation on the histopathological, biochemical and functional outcomes. Lipopolysaccharide (LPS), known as a strong immunostimulant, was directly injected into the hippocampus. The spatiotemporal evolution of inducible NOS (iNOS) and cell death was studied from 6 h to 7 days. A perfect time course correlation was observed between iNOS immunoreactivity and iNOS activity showing an acute, expansive and transient iNOS induction in the hippocampus with a peak at 24 h. It was associated with a marked increase in NO metabolite (NO(x)) levels, and a high level of myeloperoxidase (MPO) activity. This inflammation precedes a massive cellular loss including at least neurons and astrocytes, and a drop of constitutive NOS activity, restrictive to the ipsilateral hippocampus from 48 h after LPS injection. Moreover, sensorimotor function impairment occurred from 24 h to 7 days with a maximum at 24 h post-LPS injection. Therefore, we characterized an in vivo model of acute neuroinflammation and neurodegeneration, in relation with a neurological deficit, which may be a powerful tool for mechanistic studies and for further evaluation of the potential neuroprotective agents.

Cortical calcium increase following traumatic brain injury represents a pitfall in the evaluation of Ca2+-independent NOS activity

In this report, our findings highlighted the presence of a high level of calcium in the cortex following traumatic brain injury (TBI) in a rat model of fluid percussion-induced brain injury. This calcium increase represents a pitfall in the assessment of Ca2+-independent nitric oxide synthase (NOS) activity supposed to play a role in the secondary brain lesion following TBI. The so-called Ca2+-independent NOS activity measured in the injured cortex 72 h after TBI had the pharmacological profile of a Ca2+-dependent NOS and was therefore inhibited with a supplement of calcium chelator. The remaining activity was very low and iNOS protein was hardly immunodetected on the same sample used for NOS activity assay. The concentration of calcium chelator used in the assay should be revised and adjusted consequently to make sure that the calcium-free condition is achieved for the assay. Otherwise, the findings tend towards an overestimation of Ca2+-independent and underestimation of Ca2+-dependent NOS activities. The revised Ca2+-independent NOS activity assay was then tested, in relation with the amount of iNOS protein, in a model of LPS-induced neuroinflammation. Taken together, precautions should be taken when assessing the Ca2+-independent enzymatic activity in cerebral tissue after a brain insult.

Effects of peroxisome proliferator-activated receptor agonists on LPS-induced neuronal death in mixed cortical neurons: associated with iNOS and COX-2

In neurodegenerative disease, the use of non-steroidal anti-inflammatory drugs (NSAIDs) has been regarded as beneficial. The NSAID, an inhibitor of cyclooxygenase (COX), has been also suggested as a ligand of the peroxisome proliferator-activated receptor (PPAR). In cortical neuron-glial co-cultures, we examined the effect of PPAR agonists on lipopolysaccharide(LPS)-induced neuronal death, which has been known to be NO-dependent. LPS induced iNOS expression and the release of nitric oxide in microglia, and COX-2 expression in neurons. PPAR-gamma agonists such as 15d-PGJ(2), ciglitazone and troglitazone prevented LPS-induced neuronal death and abolished LPS-induced NO and PGE(2) release, however PPAR-alpha agonists such as clofibrate and WY14,643 did not produce the same results. PPAR-gamma agonists also reduced LPS-induced iNOS and COX-2 expression, which suggested by interfering with the NF-kappaB signal pathway.

Expression of inducible nitric oxide synthase and cyclooxygenase-2 after excitotoxic damage to the immature rat brain

It is well established that after adult brain damage the enzymes cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) play an important role in the inflammatory processes and oxidative stress, which are considered to be the leading factors contributing to delayed cell death. The contribution of these enzymes to postnatal brain damage, however, is poorly understood. In our study, excitotoxic lesions were induced by the injection of N-methyl-D-aspartate in the cortex of postnatal day 9 rats. After different survival times ranging from 4 hr to 7 days post-lesion, brain sections were processed for the immunocytochemical demonstration of COX-2 and iNOS and double labeling with neuronal, glial and neutrophil markers. First and maximal de novo induction of iNOS and COX-2 expression was found at 10 hr post-lesion. Expression of both enzymes started to diminish at 24 hr, reaching basal levels at day 3. iNOS-expressing cells were mainly identified as infiltrated neutrophils as well as highly ramified protoplasmic astrocytes closely associated with blood vessels. Moreover, scattered iNOS-positive neurons were found at the lesion borders. In contrast, COX-2 was mainly observed in reactive microglial cells and neuronal cells. COX-2-positive neurons were found within the degenerating area at 10 hr and at the borders of the lesion later on. This study shows that maximal iNOS and COX-2 expression precedes the period of massive neuronal death observed at 24 hr post-lesion, and may therefore contribute to the evolution of the inflammatory response and the neurodegenerative process after an excitotoxic lesion to the postnatal brain.

Deterioration of spatial learning performances in lipopolysaccharide-treated mice

It is well demonstrated that acute or chronic stress leads to reduction of learning ability. Lipopolysaccharide (LPS), a component of the outer membrane of gram-negative bacteria, induces profound physiological and behavioral changes, including fever, decrease in food motivation, and decrease in social behavior. These changes might be interpreted as an acute stress reaction to the LPS. In the present study, therefore, we investigated the effects of LPS (400-800 microg/kg, i.p.) on spatial learning performances using C57BL/6J male mice. In the Morris water-maze task, spatial learning performances were examined in six trials of training for two consecutive days. LPS-treated mice took a longer time to reach the hidden platform than control mice (F(1,60)=4.80801, P<0.05 at 600 microg/kg). In addition, injection of LPS decreased the percent of correct choices in the Y-maze test (P<0.05 at 800 microg/kg). LPS, however, did not alter the body weight, grip tone, motor activity or swimming speed. Taken together, these results indicate that LPS treatment specifically impaired spatial learning performances.