Neuroinflammatory processes are important in neurodegenerative diseases: an hypothesis to explain the increased formation of reactive oxygen and nitrogen species as major factors involved in neurodegenerative disease development

Peripheral biomarkers of oxidative stress in aging and Alzheimer's disease

Aging is associated with a greatly increased incidence of a number of neurodegenerative disorders, including Alzheimer’s disease (AD), Parkinson’s disease (PD) and amyotrophic lateral sclerosis (ALS). These conditions are associated with chronic inflammation, which generates oxygen reactive species, ultimately responsible for a process known as oxidative stress. It is well established that this process is the culprit of neurodegeneration, and there are also mounting evidences that it is not restricted to the central nervous system. Indeed, several studies, including some by our group, have demonstrated that increased peripheral oxidative stress markers are associated to aging and, more specifically, to AD. Therefore, it is very instigating to regard aging and AD as systemic conditions that might be determined by studying peripheral markers of oxidative stress.

Pharmacological properties of BN82451: a novel multitargeting neuroprotective agent

BN82451 belongs to a new family of small molecules designated as multitargeting or hybrid molecules. BN82451 is orally active, has good central nervous system penetration, and elicits potent neuronal protection and antiinflammatory properties. Neuronal protection is due to Na+ channel blockade, antioxidant properties, and mitochondria-protecting activity, whereas inhibition of cyclooxygenases is mostly responsible for its antiinflammatory activity. BN82451 has been shown to exert a potent neuroprotective effect in various in vitro and in vivo animal models. BN82451 was found to exert a significant protection in experimental animal models mimicking aspects of cerebral ischemia, Parkinson disease, Huntington disease, and more particularly amyotrophic lateral sclerosis. Collectively, its pharmacological properties designate BN82451 as a promising neuroprotective agent.

Mechanisms of inflammatory neurodegeneration: iNOS and NADPH oxidase

Inflammation contributes to a wide variety of brain pathologies, apparently via glia killing neurons. A number of mechanisms by which inflammatory-activated microglia and astrocytes kill neurons have been identified in culture. These include iNOS (inducible nitric oxide synthase), which is expressed in glia only during inflammation, and PHOX (phagocytic NADPH oxidase) found in microglia and acutely activated by inflammation. High levels of iNOS expression in glia cause (i) NO (nitric oxide) inhibition of neuronal respiration, resulting in neuronal depolarization and glutamate release, followed by excitotoxicity, and (ii) glutamate release from astrocytes via calcium-dependent vesicular release. Hypoxia strongly synergizes with iNOS expression to induce neuronal death via mechanism (i), because NO inhibits cytochrome oxidase in competition with oxygen. Activation of PHOX (by cytokines, beta-amyloid, prion protein, ATP or arachidonate) causes microglial proliferation and inflammatory activation; thus PHOX is a key regulator of inflammation. Activation of PHOX alone causes no death, but when combined with expressed iNOS results in extensive neuronal death via peroxynitrite production.

Increased expression and localization of cyclooxygenase-2 in astrocytes of scrapie-infected mice

A number of aspects of the pathogenesis of scrapie, the archetype disease of the transmissible spongiform encephalopathies (prion disorders), remain to be elucidated. There is increasing evidence that there are cerebral based inflammatory processes that may contribute to the pathogenesis and to the progression of a number of neurodegenerative disorders, including prion diseases. In peripheral tissues, a key element that controls the generation of proinflammatory mediators is the highly inducible protein cyclooxygenase-2 (COX-2). In this study, in order to examine the possible association of COX-2 with the pathogenesis of scrapie, we analyzed the expression level and the cellular localization of COX-2 in the brains of control and scrapie-infected mice. The COX-2 mRNA and protein levels were increased significantly compared to the control group of mice. By immunohistological analysis, intense immunoreactivity of COX-2 was localized primarily in reactive astrocytes, with virtually no staining in sections from control mice. The staining for COX-2 was co-localized with the pathological form of the prion protein (PrP(Sc)) and with nuclear factor-kappa B (NF-kappaB). These results suggest that the upregulation of COX-2 expression in astrocytes may be related to the accumulation of PrP(Sc), and that COX-2 may then lead to the progression of scrapie, possibly by propagation of a cerebral inflammatory response.

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.

Increased catechol-O-methyltransferase activity and protein expression in OX-42-positive cells in the substantia nigra after lipopolysaccharide microinfusion

Activated microglial cells are found in the substantia nigra and the striatum of Parkinson's disease patients. These cells have been shown to express catechol-O-methyltransferase activity which may increase during pathological conditions. Lipopolysaccharides are potent activators of microglial cells. After paranigral lipopolysaccharide infusion to rats we observed intense microglial activation around the lesion area followed by a delayed injury in nigrostriatal pathway in 2 weeks. Simultaneously, catechol-O-methyltransferase activity in the substantia nigra was gradually increased up to 213%. In the Western blot the amount of soluble COMT and membrane bound COMT proteins were increased by 255% and 86%, respectively. Increased catechol-O-methyltransferase immunoreactivity was located primarily into the activated microglial cells in the lesion area. Interestingly, catechol-O-methyltransferase and OX-42 stained also intensively microglia/macrophage-like cells which surrounded the adjacent blood vessels. Inhibition of catechol-O-methyltransferase activity by tolcapone or entacapone did not increase lipopolysaccharide-induced neurotoxicity. We conclude that catechol-O-methyltransferase activity and protein expression were increased in the substantia nigra after inflammation induced by lipopolysaccharides. These changes in glial and perivascular catechol-O-methyltransferase activity may have clinical relevance for Parkinson's disease drug treatment due to increased metabolism of levodopa in the brain.

Anesthetic-mediated protection/preconditioning during cerebral ischemia

Cerebral ischemia is a multi-faceted neurodegenerative pathology that causes cellular injury to neurons within the central nervous system. In light of the underlying mechanisms being elucidated, clinical trials to find possible neuroprotectants to date have failed, thus highlighting the need for new putative targets to offer protection. Recent evidence has clearly shown that anesthetics can confer significant protection and or induce a preconditioning effect against cerebral ischemia-induced injury. This review will focus on the putative protection/preconditioning that is afforded by anesthetics, their possible interaction with GABA(A) and glutamate receptors and two-pore potassium channels. In addition, the interaction with inflammatory, apoptotic and underlying molecular (particularly immediately early genes and inducible nitric oxide synthase etc) pathways, the activation of K(ATP) channels and the ability to provide lasting protection will also be addressed.

Mitochondrial involvement in transhemispheric diaschisis following hypoxia-ischemia: Clomethiazole-mediated amelioration

Mitochondria play a central role in both the physiological and pathophysiological regulation of cell survival/death. Increasing evidence places mitochondrial dysfunction at the center of many neuropathological conditions. The present study investigates the extent of mitochondrial dysfunction in cortical, hippocampal and cerebellar tissues in a rat model of hypoxia-ischemia (HI). We hypothesized that; mitochondrial dysfunction in situ may be prevented by treatment with clomethiazole (CMZ), a GABA(A) receptor agonist. Assessment of mitochondrial FAD-linked respiration at both 1- and 3-day post-HI revealed a marked decrease in activity from ipsilateral cortical and hippocampal regions (P<0.001). In addition, small changes were seen in contralateral cortical and hippocampal tissues as well as in the cerebellum at 3-days (P<0.05). Assessment of the mitochondrial electron transport chain (complexes I-V), and mitochondrial markers of integrity (citrate synthase) and oxidative stress (aconitase) confirmed mitochondrial impairment in ipsilateral regions following HI. Complexes I, II-III, V and citrate synthase were also impaired in contralateral regions and cerebellum 3-days post-HI. Treatment with CMZ (414 mg/kg/day via minipumps) provided marked protection to all aspects of neuronal tissue assessed. Circulating cytokine (interleukin [IL]-1alpha, IL-1beta, tumor necrosis factor [TNF]-alpha, granulocyte macrophage colony-stimulating factor [GM-CSF], IL-4 and IL-10) levels were also assessed in these animals 3-days post-HI. Plasma IL-1alpha, IL-1beta, TNF-alpha and GM-CSF levels were significantly increased post-HI. Treatment with CMZ ameliorated the increases in IL-1alpha, IL-1beta, TNF-alpha and GM-CSF levels while increasing plasma IL-4 and IL-10 levels. This study provides evidence of the extent of mitochondrial damage following an HI-insult. In addition, we have shown that protection afforded by CMZ extends to preservation of mitochondrial function and integrity via anti-inflammatory mediated pathways.

AUF-1 mediates inhibition by nitric oxide of lipopolysaccharide-induced matrix metalloproteinase-9 expression in cultured astrocytes

Neuroinflammatory diseases are associated with increased production of matrix metalloproteinase-9 (MMP-9) and excessive generation of nitric oxide (NO). NO has been reported to have variable effects on MMP-9 gene expression and activation in various cell types. In the present study, we investigated the effect of NOon MMP-9 expression in primary cortical astrocytes. Zymography and real-time PCR showed that lipopolysaccharide (LPS) dramatically increased latent MMP-9 gelatinolytic activity and MMP-9 mRNA expression. By using the NO donor DETA NONOate, we observed a dose-dependent inhibition of MMP-9 induction by LPS. Active forms of MMP-9 were not found by zymography after NO treatment. The MEK1/2 inhibitor U0126 completely inhibited LPS-induced MMP-9, which was partially inhibited by the p38 MAPK inhibitor SB203580. NO had no effect on LPS-stimulated ERK1/2 and p38 MAPK activation, suggesting that the inhibitory action of NO occurs downstream of MAPK cascades. Real-time PCR analysis showed that NO accelerated the degradation of MMP-9 mRNA after LPS induction. Western blotting and pull-down assay demonstrated that NO increased AUF-1 expression as well as its specific binding to the MMP-9 gene 3'-untranslated region. Knockdown of AUF-1 with siRNA partially reversed the inhibitory action of NO on LPS-stimulated MMP-9 induction. We conclude that NO does not activate MMP-9 in astrocyte cultures but reduces LPS-induced MMP-9 expression via accelerating MMP-9 mRNA degradation, which is partially mediated by AUF-1. Our results suggest that elevated NO concentrations may suppress MMP-9 and restrict the inflammatory response in neurodegenerative diseases.

Mitogenic Responses of Vascular Smooth Muscle Cells to Lipid Peroxidation-derived Aldehyde 4-Hydroxy-trans-2-nonenal (HNE)

Products of lipid peroxidation such as 4-hydroxy-trans-2-nonenal (HNE) trigger multiple signaling cascades that variably affect cell growth, differentiation, and apoptosis. Because glutathiolation is a significant metabolic fate of these aldehydes, we tested the possibility that the bioactivity of HNE depends upon its conjugation with glutathione. Addition of HNE or the cell-permeable esters of glutathionyl-4-hydroxynonenal (GS-HNE) or glutathionyl-1,4-dihydroxynonene (GS-DHN) to cultures of rat aortic smooth muscle cells stimulated protein kinase C, NF-kappaB, and AP-1, and increased cell growth. The mitogenic effects of HNE, but not GS-HNE or GS-DHN, were abolished by glutathione depletion. Pharmacological inhibition or antisense ablation of aldose reductase (which catalyzes the reduction of GS-HNE to GS-DHN) prevented protein kinase C, NF-kappaB, and AP-1 stimulation and the increase in cell growth caused by HNE and GS-HNE, but not GS-DHN. The growth stimulating effect of GS-DHN was enhanced in cells treated with antibodies directed against the glutathione conjugate transporters RLIP76 (Ral-binding protein) or the multidrug resistance protein-2. Overexpression of RLIP76 abolished the mitogenic effects of HNE and its glutathione conjugates, whereas ablation of RLIP76 using RNA interference promoted the mitogenic effects. Collectively, our findings suggest that the mitogenic effects of HNE are mediated by its glutathione conjugate, which has to be reduced by aldose reductase to stimulate cell growth. These results raise the possibility that the glutathione conjugates of lipid peroxidation products are novel mediators of cell signaling and growth.

Increased brain levels of 4-hydroxy-2-nonenal glutathione conjugates in severe Alzheimer's disease

In the last decade an important role for the progression of neuronal cell death in Alzheimer's disease (AD) has been ascribed to oxidative stress. trans-4-Hydroxy-2-nonenal, a product of lipid peroxidation, forms conjugates with a variety of nucleophilic groups such as thiols or amino moieties. Here we report for the first time the quantitation of glutathione conjugates of trans-4-hydroxy-2-nonenal (HNEGSH) in the human postmortem brain using the specific and very sensitive method of electrospray ionization triple quadrupole mass spectrometry (ESI-MS-MS). Levels of HNEGSH conjugates calculated as the sum of three chromatographically separated diastereomers were determined in hippocampus, entorhinal cortex, substantia innominata, frontal and temporal cortex, as well as cerebellum from patients with AD and controls matched for age, gender, postmortem delay and storage time. Neither age, nor postmortem delay, nor storage time did correlate with levels of HNEGSH conjugates which ranged between 1 and 500 pmol/g fresh weight in the brain areas examined. The brain specimen from patients with clinically and neuropathologically probable AD diagnosed according to criteria of the consortium to establish a registry for AD (CERAD) show increased levels of HNEGSH in the temporal and frontal cortex, as well as in the substantia innominata. Classification of disease severity according to Braak and Braak, which takes into consideration the amount of neurofibrillary tangles and neuritic plaques, revealed highest levels of HNEGSH in the substantia innominata and the hippocampus, two brain regions known to be preferentially affected in AD. These results substantiate the link between conjugates of glutathione with a product of lipid peroxidation and Alzheimer's disease and justify further studies to evaluate the role of HNE metabolites as potential biomarkers for disease progression in AD.

Chronic unpredictable stress exacerbates lipopolysaccharide-induced activation of nuclear factor-kappaB in the frontal cortex and hippocampus via glucocorticoid secretion

Although the anti-inflammatory actions of glucocorticoids (GCs) are well established in the periphery, these stress hormones can increase inflammation under some circumstances in the brain. The transcription factor nuclear factor-kappaB (NF-kappaB), which is inhibited by GCs, regulates numerous genes central to inflammation. In this study, the effects of stress, GCs, and NMDA receptors on lipopolysaccharide (LPS)-induced activation of NF-kappaB in the brain were investigated. One day after chronic unpredictable stress (CUS), nonstressed and CUS rats were treated with saline or LPS and killed 2 h later. CUS potentiated the increase in LPS-induced activation of NF-kappaB in frontal cortex and hippocampus but not in the hypothalamus. This stress effect was blocked by pretreatment of rats with RU-486, an antagonist of the GC receptor. MK-801 [(+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine maleate], an NMDA receptor antagonist, also reduced the effect of LPS in all three brain regions. However, the combined antagonism of both GC and NMDA receptors produced no further reduction in NF-kappaB activation when compared with the effect of each treatment alone. Our results indicate that stress, via GC secretion, can increase LPS-induced NF-kappaB activation in the frontal cortex and hippocampus, agreeing with a growing literature demonstrating proinflammatory effects of GCs.

Cell-cell communication by endocannabinoids during immune surveillance of the central nervous system

The immune system is designed to defend the organism from hazardous infection. The way by which cells of the immune system perform this function can be dangerous for the survival and function of the neuronal network in the brain. An attack of immune cells inside the brain includes the potential for severe neuronal damage or cell death and therefore impairment of CNS function. To avoid such undesirable action of the immune system, the CNS harbours an impressive arsenal of cellular and molecular mechanisms enabling strict control of immune reactions--the so-called "immune privilege". Under inflammatory and pathological conditions, loss of control of the CNS immune system results in the activation of neuronal damage cascades frequently associated with neurological disease. On the other hand, processes of neuroprotection and neurorepair after neuronal damage depend on a steady and tightly controlled immune surveillance. Accordingly, the immune system serves a highly specialized function in the CNS including negative feedback mechanisms that control immune reactions. Recent studies have revealed that endocannabinoids participate in one of the most important ones of the brain's negative feedback system. The CNS endocannabinoid system consists of cannabinoid receptors, their endogenous ligands and enzymes for the synthesis and degradation of endocannabinoids. It participates crucially in neuronal cell-cell-communication and signal transduction, e.g., by modulating synaptic input and protecting neurons from excitotoxic damage. Over the last decade, it has also become evident that endocannabinoids play an important role in the communication between immune cells, and in the interaction between nerve and immune system during CNS damage. Thus, therapeutic intervention in the CNS endocannabinoid system may help to restore the well-controlled and finely tuned balance of immune reactions in pathological conditions.

Nitrones as therapeutics in age-related diseases

Age-related diseases deprive individuals of a higher quality of life and therefore therapeutics for their treatment provide significant potential. An overview of the observations of nitrones as potential therapeutics in several age-related diseases is presented. Treatment of acute ischemic stroke is one condition where a nitrone (NXY-059) is in late phase 3 clinical trials now. Also presented is a summary of the most recent work we have accomplished on the anticancer activity of the nitrones in a hepatocellular carcinoma. The mechanistic basis of action of these compounds in several animal models is not yet understood at the molecular levels; however, it does appear clear that their anti-inflammatory properties are central to their action, which is based on their ability to down-regulate exacerbated signal transduction processes.

Redox regulation of cytokine-mediated inhibition of myelin gene expression in human primary oligodendrocytes

Multiple sclerosis (MS) is a chronic autoimmune demyelinating disorder of the central nervous system (CNS) of unknown etiology. Several studies have shown that demyelination in MS is caused by proinflammatory mediators which are released by perivascular infiltrates and/or activated glial cells. To understand if proinflammatory mediators such as IL (interleukin)-1beta and TNF (tumor necrosis factor)-alpha are capable of modulating the expression of myelin-specific genes, we investigated the effect of these cytokines on the expression of myelin basic protein (MBP), 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase), myelin oligodendrocyte glycoprotein (MOG), and proteolipid protein (PLP) in human primary oligodendrocytes. Interestingly, both IL-1beta and TNF-alpha markedly inhibited the expression of MOG, CNPase, and PLP but not MBP, the effect that was blocked by antioxidants such as N-acetylcysteine (NAC) and pyrrolidine dithiocarbamate (PDTC). Consistently, oxidants and prooxidants like H(2)O(2) and diamide also markedly inhibited the expression of MOG, CNPase, and PLP. Furthermore, both IL-1beta and TNF-alpha induced the production of H(2)O(2). Taken together, these studies suggest that proinflammatory cytokines inhibit the expression of myelin genes in human primary oligodendrocytes through the alteration of cellular redox.

Signaling pathways mediating a selective induction of nitric oxide synthase II by tumor necrosis factor alpha in nerve growth factor-responsive cells

Background

Inflammation and oxidative stress play a critical role in neurodegeneration associated with acute and chronic insults of the nervous system. Notably, affected neurons are often responsive to and dependent on trophic factors such as nerve growth factor (NGF). We previously showed in NGF-responsive PC12 cells that tumor necrosis factor alpha (TNFα) and NGF synergistically induce the expression of the free-radical producing enzyme inducible nitric oxide synthase (iNOS). We proposed that NGF-responsive neurons might be selectively exposed to iNOS-mediated oxidative damage as a consequence of elevated TNFα levels. With the aim of identifying possible therapeutic targets, in the present study we investigated the signaling pathways involved in NGF/TNFα-promoted iNOS induction.

Methods

Western blotting, RT-PCR, transcription factor-specific reporter gene systems, mutant cells lacking the low affinity p75NTR NGF receptor and transfections of TNFα/NGF chimeric receptors were used to investigate signalling events associated with NGF/TNFα-promoted iNOS induction in PC12 cells.

Results

Our results show that iNOS expression resulting from NGF/TNFα combined treatment can be elicited in PC12 cells. Mutant PC12 cells lacking p75NTR did not respond, suggesting that p75NTR is required to mediate iNOS expression. Furthermore, cells transfected with chimeric TNFα/NGF receptors demonstrated that the simultaneous presence of both p75NTR and TrkA signaling is necessary to synergize with TNFα to mediate iNOS expression. Lastly, our data show that NGF/TNFα-promoted iNOS induction requires activation of the transcription factor nuclear factor kappa B (NF-κB).

Conclusion

Collectively, our in vitro model suggests that cells bearing both the high and low affinity NGF receptors may display increased sensitivity to TNFα in terms of iNOS expression and therefore be selectively at risk during acute (e.g. neurotrauma) or chronic (e.g. neurodegenerative diseases) conditions where high levels of pro-inflammatory cytokines in the nervous system occur pathologically. Our results also suggest that modulation of NFκB-promoted transcription of selective genes could serve as a potential therapeutic target to prevent neuroinflammation-induced neuronal damage.

Increased oxidative damage in nuclear and mitochondrial DNA in Alzheimer's disease

Increasing evidence suggests that oxidative stress is associated with normal aging and several neurodegenerative diseases, including Alzheimer's disease (AD). Here we quantified multiple oxidized bases in nuclear and mitochondrial DNA of frontal, parietal, and temporal lobes and cerebellum from short postmortem interval AD brain and age-matched control subjects using gas chromatography/mass spectrometry with selective ion monitoring (GC/MS-SIM) and stable labeled internal standards. Nuclear and mitochondrial DNA were extracted from eight AD and eight age-matched control subjects. We found that levels of multiple oxidized bases in AD brain specimens were significantly (p < 0.05) higher in frontal, parietal, and temporal lobes compared to control subjects and that mitochondrial DNA had approximately 10-fold higher levels of oxidized bases than nuclear DNA. These data are consistent with higher levels of oxidative stress in mitochondria. Eight-hydroxyguanine, a widely studied biomarker of DNA damage, was approximately 10-fold higher than other oxidized base adducts in both AD and control subjects. DNA from temporal lobe showed the most oxidative damage, whereas cerebellum was only slightly affected in AD brains. These results suggest that oxidative damage to mitochondrial DNA may contribute to the neurodegeneration of AD.

Metalloproteinase ADAMTS-1 but not ADAMTS-5 is manifold overexpressed in neurodegenerative disorders as Down syndrome, Alzheimer's and Pick's disease

ADAMTS-1 is a disintegrin and metalloproteinase with thrombospondin 1 (TSP1)-like motifs with ubiquitous though variable expression. Natural substrates of this protease are proteoglycans as aggrecan and versican and null mutant mice propose a role for growth, fertility, organ structure and function. As the gene for this protein is encoded on chromosome 21 and maybe overexpressed due to the gene dosage hypothesis based upon the presence of a third chromosome in trisomy 21, we decided to study expression in Down syndrome (DS) brain and used brains of patients with Alzheimer's (AD) and Pick's disease (PD) as controls. Frontal cortex of controls, DS, AD and PD were homogenized and extracted proteins were used for immunoblotting using antibodies against ADAMTS-1 and ADAMTS-5. ADAMTS-1-immunoreactivity was manifold increased in brain with DS and neurodegeneration, whereas ADAMTS-5 levels were comparable. Overexpression of this metalloproteinase maybe specifically involved in proteoglycan degradation and handling in brain of patients with neurodegenerative disease which in turn may lead to or reflect pathological lesions in DS, AD and PD brain. The manifold overexpression of ADAMTS-1 may be used as marker protein for neurodegeneration.

Macrophage colony stimulating factor (M-CSF) protects spiral ganglion neurons following auditory nerve injury: morphological and functional evidence

Because hearing disturbance due to auditory nerve dysfunction imposes a formidable burden on human beings, intense efforts have been expended in experimental and clinical studies to discover ways to restore normal hearing. However, the great majority of these investigations have focused on the peripheral process side of bipolar auditory neurons, and very few trials have focused on ways to halt degenerative processes in auditory neurons from the central process side (in the cerebellopontine angle). In the present study, we investigated whether administration of macrophage colony-stimulating factor (M-CSF) could protect auditory neurons in a rat model of nerve injury. The electrophysiological and morphological results of our study indicated that M-CSF could ameliorate both anterograde (Wallerian) and retrograde degeneration in both the CNS and PNS portions of the auditory nerve. We attribute the success of M-CSF therapy to the reported functional dichotomy (having the potential to cause both neuroprotective and neurotoxic effects) of microglia and macrophages. Whether the activities of microglia/macrophages are neuroprotective or neurotoxic may depend upon the nature of the stimulus that activates the cells. In the present study, the neuroprotective effects of M-CSF that were observed could have been due to M-CSF we administered and to M-CSF released from endothelial cells, resident cells of the CNS parenchyma, or infiltrating macrophages. Another possibility is that M-CSF ameliorated apoptotic auditory neuronal death, although this hypothesis remains to be proved in future studies.

Macromolecular oxidation in anisotonic suspensions of mouse spleen cells

Macromolecular oxidative alterations have been analysed in vitro in anisotonic suspensions of mouse splenocytes. Both hypertonicity and hypotonicity induced the generation of thiobarbituric acid reactive species (TBARS) and carbonylation of the proteins, which took place along with cell death. Addition of antioxidants partially inhibited oxidative changes in isotonic and hypotonic suspensions. Anisotonic shock of mouse splenocytes proved to be an inducer of oxidative stress. The oxidative macromolecular alterations might contribute to pathogenesis of cell death caused by osmotic stress.

Nitrone-related therapeutics: potential of NXY-059 for the treatment of acute ischaemic stroke

At present, none of the neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease and stroke are treatable with compounds that slow or halt neuronal cell death. However, the prototype nitrone radical trap alpha-phenyl-tert-butylnitrone (PBN) has been shown to be an effective neuroprotective agent in various models of neurodegeneration. Some of these data are briefly reviewed as an introduction to an examination of the effect of the novel nitrone radical trapping agent disodium 2,4-disulfophenyl-N-tert-butylnitrone (NXY-059) in various animal models of stroke. NXY-059 has been shown to be an effective neuroprotective agent in both transient (reperfusion) and permanent focal ischaemia models in rats. In both types of model, NXY-059 has a large window of opportunity, providing effective neuroprotection when given up to 5 hours after the start of the occlusion in transient ischaemia and 4 hours after the start of permanent ischaemia. The compound is also effective in a marmoset permanent ischaemia model when administered up to 4 hours after the start of the occlusion. In this model it has been found to attenuate the problem of spatial neglect and maintain function to the paretic arm. NXY-059 administration also improves motor function in a rat haemorrhagic stroke model and has a neuroprotective effect in a rabbit thromboembolic stroke model. The compound is also well tolerated in stroke patients at plasma levels shown to provide a maximum neuroprotective effect in animal models of stroke.NXY-059, like PBN, is a nitrone with free radical trapping properties and this may be the basis of its neuroprotective action. However, experiments with PBN and NXY-059 suggest the possibility of other mechanisms being involved and these are also reviewed. Further experiments are required to fully elucidate the mechanism of action of these very effective neuroprotective agents.

The role of antioxidants in models of inflammation: Emphasis on l-arginine and arachidonic acid metabolism

Inflammatory processes are made up of a multitude of complex cascades. Under physiological conditions these processes aid in tissue repair. However, under pathophysiological environments, such as wound healing and hypoxia-ischaemia (HI), inflammatory mediators become imbalanced, resulting in tissue destruction. This review addresses the changes in reactive oxygen species (ROS), L-arginine and arachidonic acid metabolism in wound healing and HI and subsequent treatments with promising anti-oxidants. Even though these models may appear divergent, anti-oxidant treatments are nevertheless still having favourable effects. On the basis of recent findings, it is apparent that protection with anti-oxidants is not solely attributed to scavenging of ROS. In addition, the actions of anti-oxidants must be considered in light of the inflammatory process being assessed. To this end, there does not appear to be any universally applicable single mechanism to explain the actions of anti-oxidants.

Scavenging of reactive oxygen species by novel indolin-2-one and indoline-2-thione derivatives

The antioxidant behavior of a series of new synthesized substituted indoline-2-ones and indolin-2-thiones was investigated in this study using an oxygen radical absorbance capacity assay (ORAC(ROO*-) and 2,2'-azobis(2-amidino-propane) dihydrochloride (AAPH) as the radical generator; system generating superoxide anion radical, O2*- (18-crown-6/KO(2)/DMSO), and the Fenton-like reaction [Co(II) + H(2)O(2) --> Co(III) + HO(*) + HO(-)]. Measurements were done using fluorescence, chemiluminescence methods, and a deoxyribose assay based on the spectrophotometry method, respectively. The results obtained indicated that the examined indoline derivatives had effective activities as radical scavengers and may be considered as an effective source for combating oxidative damage.

Where is the blood-brain barrier ? really?

Few terms in the biomedical lexicon are as widely recognized as the phrase blood-brain barrier (BBB). Indeed, it immediately conjures up a "barricade" between the blood and the brain, a feature often considered more obstacle than safeguard. In truth, the BBB performs in both capacities, and it is precisely this duality that imparts such a vital role to the BBB in influencing physiological and pathophysiological processes in the CNS. Although the concept is more than a century old, the BBB continues to remain enigmatic in both substance and idea, with seemingly resolved issues once again beckoning for clarification. In this regard, recent technological advancements, such as sequencing of the human genome and development of microarray analysis, have illuminated novel aspects of vascular gene expression and provoked reconsideration of the cellular and biochemical makeup of the BBB. In light of the critical impact of the BBB in the realms of science and medicine, this Mini-Review will revisit the topic of the composition of the BBB, specifically highlighting how recent developments in endothelial biology have prompted a reevaluation of its precise vascular location. We have intentionally avoided discussing generalized features of the BBB, as these have been skillfully described elsewhere as noted.

Identification of hyperreactive cysteines within ryanodine receptor type 1 by mass spectrometry

The skeletal-type ryanodine receptor (RyR1) undergoes covalent adduction by nitric oxide (NO), redox-induced shifts in cation regulation, and non-covalent interactions driven by the transmembrane redox potential that enable redox sensing. Tight redox regulation of RyR1 is thought to be primarily mediated through highly reactive (hyperreactive) cysteines. Of the 100 cysteines per subunit of RyR1, approximately 25-50 are reduced, with 6-8 considered hyperreactive. Thus far, only Cys-3635, which undergoes selective adduction by NO, has been identified. In this report, RyR1-enriched junctional sarcoplasmic reticulum is labeled with 7-diethylamino-3-(4'-maleimidylphenyl)-4-methylcoumarin (CPM, 1 pmol/microg of protein) in the presence of 10 mm Mg(2+), conditions previously shown to selectively label hyperreactive sulfhydryls and eliminate redox sensing. The CPM-adducted RyR1 is separated by gel electrophoresis and subjected to in-gel tryptic digestion. Isolation of CPM-adducted peptides is achieved by analytical and microbore high-performance liquid chromatography utilizing fluorescence and UV detection. Subsequent analysis using two direct and one tandem mass spectrometry methods results in peptide masses and sequence data that, compared with the known primary sequence of RyR1, enable unequivocal identification of CPM-adducted cysteines. This work is the first to directly identify seven hyperreactive cysteines: 1040, 1303, 2436, 2565, 2606, 2611, and 3635 of RyR1. In addition to Cys-3635, the nitrosylation site, six additional cysteines may contribute toward redox regulation of the RyR1 complex.

Genetic ablation of tumor necrosis factor-alpha (TNF-alpha) and pharmacological inhibition of TNF-synthesis attenuates MPTP toxicity in mouse striatum

The impact of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) in the pathology of Parkinson's disease (PD) and in MPTP neurotoxicity remains unclear. Here, male TNF-alpha (-/-) deficient mice and C57bL/6 mice were treated with MPTP (4 x 15 mg/kg, 24 h intervals) and in one series, thalidomide was administered to inhibit TNF-alpha synthesis. Real-time RT-PCR revealed that the striatal mRNA levels of TNF-alpha, of the astrocytic marker glial fibrillary acidic protein (GFAP) and of the marker for activated microglia, macrophage antigen complex-1 (MAC-1), were significantly enhanced after MPTP administration. Thalidomide (50 mg/kg, p.o.) partly protected against the MPTP-induced dopamine (DA) depletion, and TNF-alpha (-/-) mice showed a significant attenuation of striatal DA and DA metabolite loss as well as striatal tyrosine hydroxylase (TH) fiber density, but no difference in nigral TH and DA transporter immunoreactivity. TNF-alpha deficient mice suffered a lower mortality (10%) compared to the high mortality (75%) seen in wild-type mice after acute MPTP treatment (4 x 20 mg/kg, 2 h interval). HPLC measurement of MPP(+) levels revealed no differences in TNF-alpha (-/-), wild-type and thalidomide treated mice. This study demonstrates that TNF-alpha is involved in MPTP toxicity and that inhibition of TNF-alpha response may be a promising target for extending beyond symptomatic treatment and developing anti-parkinsonian drugs for the treatment of the inflammatory processes in PD.

Triptolide, a Chinese herbal extract, protects dopaminergic neurons from inflammation-mediated damage through inhibition of microglial activation

Mounting lines of evidence have suggested that brain inflammation participates in the pathogenesis of Parkinson's disease. Triptolide is one of the major active components of Chinese herb Tripterygium wilfordii Hook F, which possesses potent anti-inflammatory and immunosuppressive properties. We found that triptolide concentration-dependently attenuated the lipopolysaccharide (LPS)-induced decrease in [3H]dopamine uptake and loss of tyrosine hydroxylase-immunoreactive neurons in primary mesencephalic neuron/glia mixed culture. Triptolide also blocked LPS-induced activation of microglia and excessive production of TNFalpha and NO. Our data suggests that triptolide may protect dopaminergic neurons from LPS-induced injury and its efficiency in inhibiting microglia activation may underlie the mechanism.

APOE genotype-specific differences in human and mouse macrophage nitric oxide production

Individuals expressing an APOE4 genotype demonstrate increased Alzheimer's disease (AD) neuropathology and a decreased onset age. The APOE4 gene may act by modulating the CNS immune response. Using human monocyte-derived macrophages (MDM), we show a significantly greater increase in NO production during immune activation in MDM from APOE4 AD patients compared to normal, age-matched individuals or to AD patients with an APOE 3/3 genotype. Microglia and peritoneal macrophages from APOE4 targeted replacement mice demonstrate a similar increase in NO compared to the APOE3 targeted replacement mice. The enhanced macrophage responsiveness and the increased production of NO in APOE4 AD patients may predispose the CNS to an increased potential for nitration and nitrosation, consistent with the redox imbalance and neuroinflammatory state seen in AD.

Metallothionein prevents neurodegeneration and central nervous system cell death after treatment with gliotoxin 6-aminonicotinamide

Transgenic expression of interleukin-6 (IL-6) in the CNS under the control of the glial fibrillary acidic protein (GFAP) gene promoter (GFAP-IL6 mice) induces significant inflammation and neurodegeneration but also affords neuroprotection against acute traumatic brain injury. This neuroprotection is likely mediated by the IL-6-induced protective factors metallothioneins-I and -II (MT-I+II). Here we evaluate the neuroprotective roles of IL-6 vs. MT-I+II during 6-aminonicotinamide (6-AN)-induced neurotoxicity, by using GFAP-IL6 mice and transgenic mice overexpressing MT-I (TgMT) as well as GFAP-IL6 mice crossed with TgMT mice (GFAP-IL6 x TgMT). 6-AN caused acute damage of brainstem gray matter areas identified by necrosis of astrocytes, followed by inflammatory responses. After 6-AN-induced toxicity, secondary damage was observed, consisting of oxidative stress, neurodegeneration, and apoptotic cell death. We hereby show that the primary injury caused by 6-AN was comparable in wild-type and GFAP-IL6 mice, but MT-I overexpression could significantly protect the brain tissue. As expected, GFAP-IL6 mice showed increased CNS inflammation with more gliosis, macrophages, and lymphocytes, including increased cytokine expression, relative to the other mice. However, GFAP-IL6 mice showed reduced oxidative stress (judged from nitrotyrosine, malondialdehyde, and 8-oxoguanine stainings), neurodegeneration (accumulation of neurofibrillary tangles), and apoptosis (determined from TUNEL and caspase-3). MT-I+II expression was significantly higher in GFAP-IL6 mice than in wild types, which may contribute to the IL-6-induced neuroprotection. In support of this, overexpression of MT-I in GFAP-IL6 x TgMT as well as TgMT mice protected the brainstem tissue significantly from 6-AN-induced toxicity and secondary brain tissue damage. Overall, the results demonstrate that brain MT-I+II proteins are fundamental neuroprotective factors, which in the future may become therapeutic agents.

Phenolic thiazoles as novel orally-active neuroprotective agents

Novel phenolic thiazoles compounds were prepared which demonstrated potent antioxidant activity and potent in vivo neuroprotection in mitochondrial toxin models and also possess good oral bioavailability.

The role of metallothionein II in neuronal differentiation and survival

Metallothionein I and II (MT-I+II) are antioxidant and tissue protective factors. We have previously shown that MT-I+II prevent oxidative stress and apoptotic cell death and are of therapeutic value in brain inflammation. However, MT-I+II are expressed in glia and it remains to be elucidated if MT-I+II can affect neurons directly. It is likely that MT isoforms could be beneficial also during neurodegenerative disorders. In this study, we have examined if MT-II affects survival and neurite extension of dopaminergic and hippocampal neurons. We show for the first time that MT-II treatment can significantly stimulate neurite extension from both dopaminergic and hippocampal neurons. Moreover, MT-II treatment significantly increases survival of dopaminergic neurons exposed to 6-hydroxydopamine (6-OHDA) and protects significantly hippocampal neurons from amyloid beta-peptide-induced neurotoxicity. Accordingly, treatment with MT-II may be of therapeutic value in neurodegenerative disorders.

General aspects of neurodegeneration

Neurodegenerative diseases are morphologically featured by progressive cell loss in specific vulnerable neuronal populations of the central nervous system, often associated with cytoskeletal protein aggregates forming intracytoplasmic and/or intranuclear inclusions in neurons and/or glial cells. Most neurodegenerative disorders are now classified either according to the hitherto known genetic mechanisms or to the major components of their cellular protein inclusions. The major basic processes inducing neurodegeneration are considered multifactorial ones caused by genetic, environmental, and endogenous factors. They include abnormal protein dynamics with defective protein degradation and aggregation, many of them related to the ubiquitin-proteasomal system, oxidative stress and free radical formation, impaired bioenergetics and mitochondrial dysfunctions, and "neuroinflammatory" processes. These mechanisms that are usually interrelated in complex vitious circles finally leading to programmed cell death cascades are briefly discussed with reference to their pathogenetic role in many, albeit diverse neurodegenerative diseases, like Alzheimer disease, synucleinopathies, tauopathies, and polyglutamine disorders. The impact of protein inclusions on cell dysfunction, activation or prevention of cell death cascades are discussed, but the molecular basis for the underlying disease mechanisms remains to be elucidated.

Dietary lipids in the aetiology of Alzheimer's disease: implications for therapy

Amyloid plaques and neurofibrillary tangles are the neuropathological hallmarks of Alzheimer's disease (AD), but no conclusive evidence has emerged showing that these hallmarks are the cause and not a product of the disease. Many studies have implicated oxidation and inflammation in the AD process, and there is growing evidence that abnormalities of lipid metabolism also play a role. Using epidemiology to elucidate risk factors and histological changes to suggest possible mechanisms, the hypothesis is advanced that dietary lipids are the principal risk factor for the development of late-onset sporadic AD. The degree of saturation of fatty acids and the position of the first double bond in essential fatty acids are the most critical factors determining the effect of dietary fats on the risk of AD, with unsaturated fats and n-3 double bonds conferring protection and an overabundance of saturated fats or n-6 double bonds increasing the risk. The interaction of dietary lipids and apolipoprotein E isoforms may determine the risk and rate of sustained autoperoxidation within cellular membranes and the efficacy of membrane repair. Interventions involving dietary lipids and lipid metabolism show great promise in slowing or possibly averting the development of AD, including dietary changes, cholesterol-modifying agents and antioxidants.

Treatment with metallothionein prevents demyelination and axonal damage and increases oligodendrocyte precursors and tissue repair during experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is an animal model for the human demyelinating disease multiple sclerosis (MS). EAE and MS are characterized by significant inflammation, demyelination, neuroglial damage, and cell death. Metallothionein-I and -II (MT-I + II) are antiinflammatory and neuroprotective proteins that are expressed during EAE and MS. We have shown recently that exogenous administration of Zn-MT-II to Lewis rats with EAE significantly reduced clinical symptoms and the inflammatory response, oxidative stress, and apoptosis of the infiltrated central nervous system areas. We show for the first time that Zn-MT-II treatment during EAE significantly prevents demyelination and axonal damage and transection, and stimulates oligodendroglial regeneration from precursor cells, as well as the expression of the growth factors basic fibroblast growth factor (bFGF), transforming growth factor (TGF)beta, neurotrophin-3 (NT-3), NT-4/5, and nerve growth factor (NGF). These beneficial effects of Zn-MT-II treatment could not be attributable to its zinc content per se. The present results support further the use of Zn-MT-II as a safe and successful therapy for multiple sclerosis.

Astrocyte-targeted expression of IL-6 protects the CNS against a focal brain injury

The effect of CNS-targeted IL-6 gene expression has been thoroughly investigated in the otherwise nonperturbed brain but not following brain injury. Here we examined the impact of astrocyte-targeted IL-6 production in a traumatic brain injury (cryolesion) model using GFAP-IL6 transgenic mice. This study demonstrated that transgenic IL-6 production significantly increased wound healing following the cryolesion. Thus, at 20 days postlesion (dpl) the GFAP-IL6 mice showed almost complete wound healing compared to litter mate nontransgenic controls. It seems likely that a reduced inflammatory response in the long term could be responsible for this IL-6-related effect. Thus, while in the acute phase following cryolesion (1-6 dpl) the recruitment of macrophages and T lymphocytes was higher in GFAP-IL6 mice, at 10-20 dpl it was significantly reduced compared to controls. Reactive astrogliosis was also significantly increased up to but not including 20 dpl in the GFAP-IL6 mice. Oxidative stress as well as apoptotic cell death was significantly decreased throughout the time period studied in the GFAP-IL6 mice compared to controls. This could be linked to the altered inflammatory response as well as to the transgenic IL-6-induced increase of the antioxidant, neuroprotective proteins metallothionein-I + II. These results indicate that although in the brain the chronic astrocyte-targeted expression of IL-6 spontaneously induces an inflammatory response causing significant damage, during an acute neuropathological insult such as following traumatic injury, a clear neuroprotective role is evident.

Quercetin attenuates oxygen-glucose deprivation- and excitotoxin-induced neurotoxicity in primary cortical cell cultures

The possible role of quercetin, a naturally occurring plant flavonoid, in protecting against oxygen-glucose deprivation (OGD)-, excitotoxins-, and free radical-induced neuronal injury in mouse cortical cell cultures was investigated. Pre- and co-treatment with quercetin (100 microM) inhibited 50 min OGD-, 20 microM N-methyl-D-aspartate (NMDA)-, and 50 microM kainate-induced neurotoxicity by 36, 22, and 61%, respectively. Quercetin significantly ameliorated free radical-induced neuronal injury caused by buthionine sulfoximine, sodium nitroprusside, ZnCl(2), and FeCl(2). These results suggest that quercetin may contribute a neuroprotective action against ischemic neural injury, partially via antioxidant actions.

Dextromethorphan protects dopaminergic neurons against inflammation-mediated degeneration through inhibition of microglial activation

Inflammation in the brain has increasingly been recognized to play an important role in the pathogenesis of several neurodegenerative disorders, including Parkinson's disease and Alzheimer's disease. Inflammation-mediated neurodegeneration involves activation of the brain's resident immune cells, the microglia, which produce proinflammatory and neurotoxic factors, including cytokines, reactive oxygen intermediates, nitric oxide, and eicosanoids that impact on neurons to induce neurodegeneration. Hence, identification of compounds that prevent microglial activation may be highly desirable in the search for therapeutic agents for inflammation-mediated neurodegenerative diseases. In this study, we report that dextromethorphan (DM), an ingredient widely used in antitussive remedies, reduced the inflammation-mediated degeneration of dopaminergic neurons through inhibition of microglial activation. Pretreatment (30 min) of rat mesencephalic neuron-glia cultures with DM (1-10 micro M) reduced, in a dose-dependent manner, the microglia-mediated degeneration of dopaminergic neurons induced by lipopolysaccharide (LPS, 10 ng/ml). Significant neuroprotection by DM was also evident when DM was applied to cultures up to 60 min after the addition of LPS. The neuroprotective effect of DM was attributed to inhibition of LPS-stimulated microglial activation because DM significantly inhibited the LPS-induced production of tumor necrosis factor-alpha, nitric oxide, and superoxide free radicals. This conclusion was further supported by the finding that DM failed to prevent 1-methyl-4-phenylpyridinium- or beta-amyloid peptide (1-42)-induced dopaminergic neurotoxicity in neuron-enriched cultures. In addition, because LPS did not produce any significant increase in the release of excitatory amino acids from neuron-glia cultures and N-methyl-D-aspartate antagonist dizocilpine maleate failed to afford significant neuroprotection, it is unlikely that the neuroprotective effect of DM is mediated through N-methyl-D-aspartate receptors. These results suggest that DM may be a promising therapeutic agent for the treatment of Parkinson's disease.

Ibuprofen for Alzheimer's disease

BACKGROUND

Non-steroidal antiinflammatory drugs such as ibuprofen may have a role in the treatment of conditions characterized by inflammatory processes. Ibuprofen may attenuate the effects of modulators of inflammation that have been implicated in the pathogenesis of Alzheimer's disease.

OBJECTIVES

To investigate the efficacy of ibuprofen treatment for people with Alzheimer's disease.

SEARCH STRATEGY

The trials were identified from a search of the Specialized Register of the Cochrane Dementia and Cognitive Improvement Group on 10 December 2002 using the (many) terms listed in the main text of the review. The CDCIG Register is updated regularly and contains records from all major health care databases and many ongoing trials databases. In addition computerized databases and Internet sites pertaining to ibuprofen and Alzheimer's disease were systematically examined by two reviewers independently. Data on ongoing trials of ibuprofen for the treatment of people with AD were also sought.

SELECTION CRITERIA

Eligibility for this review included all single or multi centre placebo-controlled randomized trials examining the efficacy of ibuprofen in the treatment of people diagnosed with Alzheimer's disease according to internationally accepted criteria. Inclusion and exclusion criteria were specified to ensure lack of bias in selection and methodological quality of selected trials.

DATA COLLECTION AND ANALYSIS

The aim was for the two reviewers NT and HF to collect data independently. The data selected would reflect cognitive, behavioural, physical and psychological domains of AD.

MAIN RESULTS

A systematic search of all available databases and other sources failed to identify any completed randomized, double-blind and placebo-controlled trials, assessing the efficacy of ibuprofen in AD eligible for inclusion in the review. One double-blind placebo-controlled trial investigating ibuprofen treatment for age-associated memory impairment has been identified, but is yet unfinished and no data are yet available. Other trials assessing the effect of ibuprofen on CSF beta amyloid in cognitively unimpaired individuals and the effect of other NSAIDs such as naproxen and rofecoxib for people with AD are currently under way.

REVIEWER'S CONCLUSIONS

No evidence yet exists from randomized double-blind and placebo-controlled trials on whether ibuprofen is efficacious for patients diagnosed as having Alzheimer's disease. Ibuprofen, like other NSAIDs, has an identifiable and in some instances a significant side-effect profile which may include gastrointestinal bleeding. Therefore, it needs to be shown that the benefits of such a treatment outweighs the risk of side effects before ibuprofen can be recommended for people with Alzheimer's disease.

Ischemia-reperfusion-related repair deficit after oxidative stress: implications of faulty transcripts in neuronal sensitivity after brain injury

Diseases of the heart are the No. 1 killer in industrialized countries. Brain injury can develop as a result of cerebral ischemia-reperfusion due to stroke (brain attack) and other cardiovascular diseases. Learning about the disease is the best way to reduce disability and death. We present here whether gene repair activities are associated with neuronal death in an ischemia-reperfusion model that simulates stroke in male Long-Evans rats. This experimental stroke model is known to induce necrosis in the ischemic cortex. Cerebral ischemia causes overactivation of membrane receptors and accumulation of extracellur glutamate and intracellular calcium, which activates neuronal nitric oxide synthase, causing damage to lipids, proteins, and nucleic acids, and reduces energy sources with consequent functional deterioration, leading to cell death. Restoration processes normally repair genes with few errors. However, ischemia elevates oxidative DNA lesions despite these repair mechanisms. These episodes concurrently occur with the induction of immediate-early genes that critically activate other late genes in the signal transduction pathway. Damage, repair, and transcription of the c-FOS gene are presented here as examples, because Fos peptide, one of the components of activator protein 1, activates nerve growth factor and repair mechanisms. The results of our studies show that treatments with 7-nitroindazole, a specific inhibitor of nitric oxide synthase known to attenuate nitric oxide, oxidative DNA lesions, and necrosis, increase intact c-fos mRNA levels after stroke. This suggests that the accuracy of gene expression could be accounted for the recovery of cellular function after cerebral injury.

Transcripts of damaged genes in the brain during cerebral oxidative stress

Recent studies using ischemia/reperfusion models of brain injury suggest that there is a period of time during which the formation of oxidative DNA lesions (ODLs) exceeds removal. This interval is a window of opportunity in which to study the effect of gene damage on gene expression in the brain, because the presence of excessive ODLs mimics a deficiency in gene repair, which has been shown to be associated with neurological disorders. Evidence from studies using similar models indicates that expression of faulty transcripts from ODL-infested genes and non-sense mutation in repaired genes occur before the process of cell death. Preventing the formation of ODLs and enhancing ODL repair are shown to increase the expression of intact transcripts and attenuate cell death. Understanding this mechanism could lead to the development of therapeutic techniques (physiologic, pharmacological, and/or genomic) that can enhance recovery.

Pharmaco-redox regulation of cytokine-related pathways: from receptor signaling to pharmacogenomics

Cytokines represent a multi-diverse family of polypeptide regulators; they are relatively low molecular weight (< 30 kDa), pharmacologically active proteins that are secreted by one cell for the purpose of altering either its own functions (autocrine effect) or those of adjacent cells (paracrine effect). Cytokines are small, nonenzymatic glycoproteins whose actions are both diverse and overlapping (specificity/redundancy) and may affect diverse and overlapping target cell populations. In many instances, individual cytokines have multiple biological activities. Different cytokines can also have the same activity, which provides for functional redundancy (network) within the inflammatory and immune systems. As biological cofactors that are released by specific cells, cytokines have specific effects on cell-cell interaction, communication, and behavior of other cells. As a result, it is infrequent that loss or neutralization of one cytokine will markedly interfere with either of these systems. The biological effect of one cytokine is often modified or augmented by another. Because an interdigitating, redundant network of cytokines is involved in the production of most biological effects, both under physiologic and pathologic conditions, it usually requires more than a single defect in the network to alter drastically the outcome of the process. This fact, therefore, may have crucial significance in the development of therapeutic strategies for biopharmacologic intervention in cytokine-mediated inflammatory processes and infections.

Cyclooxygenase-2-deficient mice are resistant to 1-methyl-4-phenyl1, 2, 3, 6-tetrahydropyridine-induced damage of dopaminergic neurons in the substantia nigra

Cyclooxygenases (COX), key enzymes in prostanoid biosynthesis, may represent important therapeutic targets in various neurodegenerative diseases. In the present study, we explored the role of COX in Parkinson's disease (PD) by using 1-methyl-4-phenyl1, 2, 3, 6-tetrahydropyridine (MPTP) as a tool to create a rodent Parkinsonian model. MPTP (20 mg/kg, subcutaneously) was injected daily into COX-1- and COX-2-deficient mice and wild-type (WT) controls for five consecutive days. Immunocytochemical analysis of tissues collected 7 days after the final MPTP treatment showed that MPTP significantly decreased the number of tyrosine hydroxylase-immunoreactive (TH-ir) neurons in the substantia nigra pars compacta (SNc) of WT (40% decrease) and COX-1(-/-) (45% decrease) mutants. However, a much smaller loss of TH-ir neurons in COX-2(-/-) mutants (20% decrease) was observed. Furthermore, electrochemical analysis revealed a more than 70% decrease in the levels of dopamine and its metabolites (3,4-dihydroxyphenylacetic acid and homovanillic acid) in the striatum of the WT control COX-1(-/-) and COX-2(-/-) mutant mice. These results indicate that loss of COX-2 activity reduces MPTP-induced damage to the dopaminergic neurons of the SNc, but does not alter the levels of dopamine and its metabolites in the striatum. Interestingly, MPTP caused the same degree of loss of dopaminergic neurons in both COX-2(+/-) and COX-2(-/-) mice (20% loss). The results of this study indicate an important role of COX-2 in MPTP-induced neuronal degeneration and suggest the possibility that manipulation of the COX-2 could be an important target for therapeutic interventions in PD.

Mice lacking glutathione peroxidase-1 activity show increased TUNEL staining and an accelerated inflammatory response in brain following a cold-induced injury

The mechanisms leading to neurodegeneration are complex and multifactorial. Oxidative stress has been identified as an important constituent in this process and the use of transgenic and knockout mice has allowed the role of key components of the antioxidant pathway to be evaluated. In this study, we have used mice lacking the glutathione peroxidase-1 gene in order to determine the consequences of a reduced capacity to neutralize hydrogen peroxide toward the pathological outcomes following cold-induced brain injury. Analysis of brain cryosections using TUNEL staining revealed a significant increase in brain cell death in knockout mice compared to that seen in wild-type mice. Interestingly, cell death appeared to be uncoupled to a neuro-inflammatory response which was observed in both knockout and wild-type mice but which proceeded in an accelerated manner in glutathione peroxidase-1 knockout mice at 24 h, rapidly diminishing by 96 h postinjury. Our data suggest an important role for glutathione peroxidase-1 in modulating molecular pathways involved in both the level of cell death and inflammatory cascades in brain through its antioxidant capacity in regulating levels of oxygen species such as hydrogen peroxide.

M-CSF deficiency leads to reduced metallothioneins I and II expression and increased tissue damage in the brain stem after 6-aminonicotinamide treatment

6-Aminonicotinamide (6-AN) is a niacin antagonist, which leads to degeneration of gray-matter astrocytes followed by a vigorous inflammatory response. Macrophage colony stimulating factor (M-CSF) is important during inflammation, and in order to further clarify the roles for M-CSF in neurodegeneration and brain cell death, we have examined the effect of 6-AN on osteopetrotic mice with genetic M-CSF deficiency (op/op mice). The 6-AN-induced degeneration of gray-matter areas was comparable in control and op/op mice, but the numbers of reactive astrocytes, macrophages, and lymphocytes in the damaged areas were significantly decreased in op/op mice relative to controls. The levels of oxidative stress (as determined by using immunoreactivity for inducible nitric oxide synthase, nitrotyrosine, and malondialdehyde) and apoptotic cell death (as determined by using TUNEL and immunoreactivity for caspases and cytochrome c) were significantly increased in 6-AN-injected op/op mice relative to controls. From a number of antioxidant factors assayed, only metallothioneins I and II (MT-I+II) were decreased in op/op mice in comparison to controls. Thus, the present results indicate that M-CSF is an important growth factor for coping with 6-AN-induced central nervous system damage and suggest that MT-I+II are likely to have a significant role.

Role of nitric oxide in a progressive neurodegeneration model of Parkinson's disease in the rat

This study was undertaken to investigate the nitric oxide synthase (NOS) activity in the striatum following 6-hydroxydopamine (6-OHDA) induced neurodegeneration in rats. Constitutive NOS (cNOS) activity remained unaltered at 3, 7 and 14 days after lesion, while a 43% and 45% decrease was observed at 30 and 50 days, respectively. Inducible NOS (iNOS) activity was detected only on the 3rd day after lesion and not in subsequent days or the control striatum. N(G)-nitro-L-arginine methyl ester (L-NAME) pretreatment blocked the amphetamine-induced rotations and inhibited the iNOS activity at the 3rd day after the 6-OHDA injection. L-NAME pretreatment also significantly restored the striatal dopamine (DA), dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) levels in 6-OHDA treated rats. Thus a possible role of nitric oxide in 6-OHDA induced neurodegeneration is suggested.

Effects of malonate C60 derivatives on activated microglia

Activated microglia in acute and chronic neurodegenerative disease of the central nervous system (CNS) can produce large amounts of free radicals, such as reactive oxygen species (ROS), which subsequently contribute to neuropathogenesis. Thus, it is believed that the induction of microglial deactivation can reduce neuronal injury. Buckminsterfullerene (C60) derivatives that possess free radical scavenging properties have been demonstrated to prevent neuronal cell death caused by excitotoxic insult. In this study, we investigated the biological role of two malonic acid C60 derivatives referred as trans-2 and trans-3 on microglia in the presence of the endotoxin lipopolysaccharide (LPS). Treatment of LPS-activated microglia with trans-2 and trans-3 induced a significant degree of transformation of amoeboid microglia to the ramified phenotype. To understand the mechanism underlying this C60 mediated microglial morphological transformation, we examined the production of proinflammatory cytokines, interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), as well as the final NO products (nitrate and nitrite) in the microglial culture supernatant. Although inducible nitric oxide (iNOS) mRNA and protein expression in LPS-activated microglia were slightly decreased by trans-2 and trans-3, levels of nitrate and nitrite were unaffected. Paradoxically, trans-2 and trans-3 were found to increase the release of IL-1beta in the activated microglial culture. However, trans-2 and trans-3 improved the activity of the antioxidant enzyme, superoxide dismutase (SOD) in LPS-treated microglia. Therefore, our results suggest that the C60 derivatives might increase microglial SOD enzymatic activity which causes microglial morphological transformation from the activated amoeboid phenotype to the resting ramified form.