Dopaminergic neurotoxicity by 6-OHDA and MPP+: Differential requirement for neuronal cyclooxygenase activity

The effect of acetic acid-induced pain in Parkinson's disease model in zebrafish

Parkinson's disease (PD) is the second most common neurodegenerative disease caused by the degeneration of dopaminergic neurons and the accumulation of Lewy bodies. Pain is one of the most common non-motor symptoms in PD, but the molecular mechanism of pain in PD is not fully understood, which prevents early diagnosis of PD. We aimed to determine the changes in opioidergic pathways when external pain is inflicted by inducing pain intraperitoneally in zebrafish, for which we generated a rotenone-induced PD model. After behavioural analyses in control(C), acetic acid (AA), rotenone (ROT), and rotenone+ acetic acid (ROT+AA) groups, catecholamine levels in brain tissue were determined by LC-MS/MS, expression of opioid peptides and their receptors by RT-PCR, expression of tyrosine hydroxylase by immunohistochemical method, and analyses of oxidant-antioxidant parameters by spectrophotometric methods. In the ROT group, distance travelled, average speed, and brain dopamine levels decreased, while LPO (lipid peroxidation) and NO (nitric oxide) increased as indicators of oxidative damage, and the SOD activity decreased. The mRNA expression of lrrk, pink1, and park7 genes associated with PD increased, while the mRNA expression of park2 decreased. This indicates that rotenone exposure is a suitable means to induce PD in zebrafish. The fact that body curvature was higher in the AA group than in the ROT and ROT+AA groups, as well as the decreased expression of penka, pdyn, and ion channels associated with the perception of peripheral pain in the ROT+AA group, suggest that mechanisms associated with pain are impaired in the rotenone-induced PD model in zebrafish.

Emphasizing the Crosstalk Between Inflammatory and Neural Signaling in Post-traumatic Stress Disorder (PTSD)

Post-traumatic stress disorder (PTSD) is a chronic incapacitating condition with recurrent experience of trauma-related memories, negative mood, altered cognition, and hypervigilance. Agglomeration of preclinical and clinical evidence in recent years specified that alterations in neural networks favor certain characteristics of PTSD. Besides the disruption of hypothalamus-pituitary-axis (HPA) axis, intensified immune status with elevated pro-inflammatory cytokines and arachidonic metabolites of COX-2 such as PGE2 creates a putative scenario in worsening the neurobehavioral facet of PTSD. This review aims to link the Diagnostic and Statistical Manual of mental disorders (DSM-V) symptomology to major neural mechanisms that are supposed to underpin the transition from acute stress reactions to the development of PTSD. Also, to demonstrate how these intertwined processes can be applied to probable early intervention strategies followed by a description of the evidence supporting the proposed mechanisms. Hence in this review, several neural network mechanisms were postulated concerning the HPA axis, COX-2, PGE2, NLRP3, and sirtuins to unravel possible complex neuroinflammatory mechanisms that are obscured in PTSD condition.

A story of the potential effect of non-steroidal anti-inflammatory drugs (NSAIDs) in Parkinson's disease: beneficial or detrimental effects

Parkinson's disease (PD) is an advanced neurodegenerative disease (NDD) caused by the degeneration of dopaminergic neurons (DNs) in the substantia nigra (SN). As PD is an age-related disorder, the majority of PD patients are associated with musculoskeletal disorders with prolonged use of analgesic and anti-inflammatory agents, such as non-steroidal anti-inflammatory drugs (NSAIDs). Therefore, NSAIDs can affect PD neuropathology in different ways. Thus, the objective of the present narrative review was to clarify the potential role of NSAIDs in PD according to the assorted view of preponderance. Inhibition of neuroinflammation and modulation of immune response by NSAIDs could be an effective way in preventing the development of NDD. NSAIDs affect PD neuropathology in different manners could be beneficial or detrimental effects. Inhibition of cyclooxygenase 2 (COX2) by NSAIDs may prevent the development of PD. NSAIDs afforded a neuroprotective role against the development and progression of PD neuropathology through the  modulation of neuroinflammation. Though, NSAIDs may lead to neutral or harmful effects by inhibiting neuroprotective prostacyclin (PGI2) and accentuation of pro-inflammatory leukotrienes (LTs). In conclusion, there is still a potential conflict regarding the effect of NSAIDs on PD neuropathology.

Promising biomarkers and therapeutic targets for the management of Parkinson's disease: recent advancements and contemporary research

Parkinson's disease (PD) is one of the progressive neurological diseases which affect around 10 million population worldwide. The clinical manifestation of motor symptoms in PD patients appears later when most dopaminergic neurons have degenerated. Thus, for better management of PD, the development of accurate biomarkers for the early prognosis of PD is imperative. The present work will discuss the potential biomarkers from various attributes covering biochemical, microRNA, and neuroimaging aspects (α-synuclein, DJ-1, UCH-L1, β-glucocerebrosidase, BDNF, etc.) for diagnosis, recent development in PD management, and major limitations with current and conventional anti-Parkinson therapy. This manuscript summarizes potential biomarkers and therapeutic targets, based on available preclinical and clinical evidence, for better management of PD.

Biological Activity of Novel Pyrrole Derivatives as Antioxidant Agents Against 6-OHDA Induced Neurotoxicity in PC12 Cells

Background

Neuroinflammation and oxidative stress are critical factors involved in the pathogenesis of Parkinson's disease (PD), the second most common progressive neurodegenerative disease. Additionally, lipid peroxidation end products contribute to inflammatory responses by activating pro-inflammatory genes. Lipid peroxidation occurs as a result of either the overproduction of intracellular reactive oxygen species (ROS) or the reaction of cyclooxygenases (COXs).

Objectives

In this study, we examined the role of 1,5-diaryl pyrrole derivatives against the neurotoxic effects of 6-hydroxydopamine (6-OHDA) in a cellular model of PD.

Methods

PC12 cells were pre-treated with compounds 2-(4-chlorophenyl)-5-methyl-1-(4-(trifluoromethoxy)phenyl)-1H-pyrrole (A), 2-(4-chlorophenyl)-1-(4-methoxyphenyl)-5-methyl-1H-pyrrole (B), and 1-(2-chlorophenyl)-2-(4-chlorophenyl)-5-methyl-1H-pyrrole (C), respectively, 24 h before exposure to 6-OHDA. We conducted various assays, including 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide (MTT), ROS, and lipid peroxidation assays, Hoechst staining, Annexin V/PI, Western blotting analysis and ELISA method, to assess the neuroprotective effects of pyrrole derivatives on 6-OHDA-induced neurotoxicity.

Results

Our results demonstrated that apoptosis induction was inhibited by controlling the lipid peroxidation process in the in vitro model following pre-treatment with compounds A, B, and, somehow, C. Furthermore, compounds A and C likely act by suppressing the COX-2/PGE2 pathway, a mechanism not attributed to compound B.

Conclusions

These findings suggest that the novel synthetic pyrrolic derivatives may be considered promising neuroprotective agents that can potentially prevent the progression of PD.

Cyclooxygenase-2 activates the free radical-mediated apoptosis of polymorphonuclear leukocytes in the maneb- and paraquat-intoxicated rats

Overproduction of free radicals and inflammation could lead to maneb (MB)- and paraquat (PQ)-induced toxicity in the polymorphonuclear leukocytes (PMNs). Cyclooxygenase-2 (COX-2), an inducible COX, is imperative in the pesticides-induced pathological alterations. However, its role in MB- and PQ-induced toxicity in the PMNs is not yet clearly deciphered. The current study explored the contribution of COX-2 in MB- and PQ-induced toxicity in the PMNs and the mechanism involved therein. Combined MB and PQ augmented the production of free radicals, lipid peroxides and activity of superoxide dismutase (SOD) in the rat PMNs. While combined MB and PQ elevated the expression of COX-2 protein, activation of nuclear factor-kappa B (NF-κB) and phosphorylation of c-Jun N-terminal kinase (JNK), release of mitochondrial cytochrome c and levels of procaspase-3/9 were attenuated in the PMNs. Celecoxib (CXB), a COX-2 inhibitor, ameliorated the combined MB and PQ-induced modulations in the PMNs. MB and PQ augmented the free radical generation, COX-2 protein expression, NF-κB activation and JNK phosphorylation and reduced the cell viability of cultured rat PMNs and human leukemic HL60. MB and PQ elevated mitochondrial cytochrome c release and poly (ADP-ribose) polymerase cleavage whilst procaspase-3/9 levels were attenuated in the cultured PMNs. MB and PQ also increased the levels of phosphorylated c-jun and caspase-3 activity in the HL60 cells. CXB; SP600125, a JNK-inhibitor and pyrrolidine dithiocarbamate (PDTC), a NF-κB inhibitor, rescued from MB and PQ-induced changes in the PMNs and HL60 cells. However, CXB offered the maximum protection among the three. The results show that COX-2 activates apoptosis in the PMNs following MB and PQ intoxication, which could be linked to NF-κB and JNK signaling.

Role of p53 methylation in manganese-induced cyclooxygenase-2 expression in BV2 microglial cells

Manganese (Mn) is an essential cofactor for many enzymes and plays an important role in normal growth and development. However, excess exposure to manganese (Mn) may be an important environmental factor leading to neurodegeneration. The overexpression of microglial cyclooxygenase-2 (COX-2) plays a key role in neuroinflammation in neurodegenerative diseases. The existing data suggest that Mn can induce neuroinflammation by up-regulating COX-2 expression. However, the mechanisms involved in Mn-induced microglial COX-2 up-regulation remain to be determined. The aim of this study was to investigate the role of p53 in Mn-induced COX-2 expression in microglial cells. The results showed that Mn exposure induced the up-regulation of COX-2 and inhibited the expression of p53 in BV2 microglial cells. The addition of p53 activator and the over-expression of p53 blocked the expression of COX-2 and prostaglandin E2 (PGE2), a COX-2 downstream effector, induced by Mn. Further, Mn increased the methylation of p53 DNA in microglia, while the addition of demethylation reagent 5-Aza-dC enhanced the expression of p53 but decreased the expression of COX-2. These results suggested that Mn may inhibit p53 expression through induction of DNA methylation, which can further induce the expression of COX-2 in microglial cells.

Emerging Therapeutic Strategies for Parkinson’s Disease and Future Prospects: A 2021 Update

Parkinson’s disease (PD) is a neurodegenerative disorder pathologically distinguished by degeneration of dopaminergic neurons in the substantia nigra pars compacta. Muscle rigidity, tremor, and bradykinesia are all clinical motor hallmarks of PD. Several pathways have been implicated in PD etiology, including mitochondrial dysfunction, impaired protein clearance, and neuroinflammation, but how these factors interact remains incompletely understood. Although many breakthroughs in PD therapy have been accomplished, there is currently no cure for PD, only trials to alleviate the related motor symptoms. To reduce or stop the clinical progression and mobility impairment, a disease-modifying approach that can directly target the etiology rather than offering symptomatic alleviation remains a major unmet clinical need in the management of PD. In this review, we briefly introduce current treatments and pathophysiology of PD. In addition, we address the novel innovative therapeutic targets for PD therapy, including α-synuclein, autophagy, neurodegeneration, neuroinflammation, and others. Several immunomodulatory approaches and stem cell research currently in clinical trials with PD patients are also discussed. Moreover, preclinical studies and clinical trials evaluating the efficacy of novel and repurposed therapeutic agents and their pragmatic applications with encouraging outcomes are summarized. Finally, molecular biomarkers under active investigation are presented as potentially valuable tools for early PD diagnosis.

The protective effects of the native flavanone flavanomarein on neuronal cells damaged by 6-OHDA

BACKGROUND

Flavanomarein is the main component of Coreopsis tinctoria Nutt. (C. tinctoria), which is a globally well-known flower tea that has a distinct flavor and many beneficial health effects, such as antioxidant activities. We aimed to explore the effect of flavanomarein on a 6-hydroxydopamine (6-OHDA)-lesioned cell model of oxidative stress.

METHODS

In this study, we used 6-OHDA-lesioned PC12 cells and primary cortical neurons to investigate the protective effects of flavanomarein and its potential mechanism.

RESULTS

The results indicated that pretreatment with flavanomarein (25, 50, or 100 µM for 24 h) significantly increased the cell viability, reduced the lactate dehydrogenase (LDH) release and improved the mitochondrial membrane potential (∆Ψm) and mitochondrial impairment. Additionally, flavanomarein markedly reduced the gene expression of tumor necrosis factor (TNF)-α and protein kinase C ζ (PKC-ζ), the nuclear translocation of p65, and the levels of p-AMPK-α and acetyl-p53. Flavanomarein also elevated the gene expression of P85α, PKC-β1, and Bcl-2, the protein expression of Sirt1 and ICAD, and the phosphorylation level of AKT.

CONCLUSIONS

Together, these results suggest that flavanomarein protects PC12 cells and primary cortical neurons from 6-OHDA-induced neurotoxicity by upregulating the PI3K/AKT signaling pathway and attenuating the nuclear factor kappa B (NF-κB) signaling pathway. Therefore, our study provides evidence that may aid in the development of a potential compound against 6-OHDA toxicity.

Non-steroidal anti-inflammatory drugs and risk of Parkinson's disease in the elderly population: a meta-analysis

PURPOSE

Several studies have explored the impact of non-steroidal anti-inflammatory drugs (NSAIDs) and the risk of Parkinson disease (PD). However, the extent to which NSAIDs may increase or decrease the risk of PD remains unresolved. We, therefore, performed a meta-analysis of relevant studies to quantify the magnitude of the association between NSAID use and PD risk in the elderly population.

METHODS

The electronic databases such as PubMed, EMBASE, Scopus, Google Scholar, and Web of Science were used to search the relevant articles published between January 1990 and December 2017. Large (n ≥ 1000) observational design studies with a follow-up at least 1 year were considered. Two authors independently extracted information from the included studies. Random effect model was used to calculate risk ratios (RRs) with 95% confidence interval (Cl).

RESULTS

A total of 17 studies with 2,498,258 participants and nearly 14,713 PD patients were included in the final analysis. The overall pooled RR of PD was 0.95 (95%CI 0.860-1.048) with significant heterogeneity (I² = 63.093, Q = 43.352, p < 0.0001). In the subgroup analysis, the overall pooled RR of PD was 0.90 (95%CI 0.738-1.109), 0.96 (95%CI 0.882-1.055), and 0.99 (95%CI 0.841-0.982) from the studies of North America, Europe, and Asia. Additionally, long-term use, study design, individual NSAID use, and risk of PD were also evaluated.

CONCLUSION

Despite the neuroprotective potential of NSAIDs demonstrated in some experimental studies, our findings suggest that there is no association between NSAIDs and the risk of Parkinson disease at the population level. Until further evidence is established, clinicians need to be vigilant ensuring that the use of NSAIDs remains restricted to their approved anti-inflammatory and analgesic effect.

Peroxisome proliferator-activated receptors (PPARs) as therapeutic target in neurodegenerative disorders

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors and they serve to be a promising therapeutic target for several neurodegenerative disorders, which includes Parkinson disease, Alzheimer's disease, Huntington disease and Amyotrophic Lateral Sclerosis. PPARs play an important role in the downregulation of mitochondrial dysfunction, proteasomal dysfunction, oxidative stress, and neuroinflammation, which are the major causes of the pathogenesis of neurodegenerative disorders. In this review, we discuss about the role of PPARs as therapeutic targets in neurodegenerative disorders. Several experimental approaches suggest potential application of PPAR agonist as well as antagonist in the treatment of neurodegenerative disorders. Several epidemiological studies found that the regular usage of PPAR activating non-steroidal anti-inflammatory drugs is effective in decreasing the progression of neurodegenerative diseases including PD and AD. We also reviewed the neuroprotective effects of PPAR agonists and associated mechanism of action in several neurodegenerative disorders both in vitro as well as in vivo animal models.

Effects of Oxidative Stress and Testosterone on Pro-Inflammatory Signaling in a Female Rat Dopaminergic Neuronal Cell Line

Parkinson's disease, a progressive neurodegenerative disorder, is associated with oxidative stress and neuroinflammation. These pathological markers can contribute to the loss of dopamine neurons in the midbrain. Interestingly, men have a 2-fold increased incidence for Parkinson's disease than women. Although the mechanisms underlying this sex difference remain elusive, we propose that the primary male sex hormone, testosterone, is involved. Our previous studies show that testosterone, through a putative membrane androgen receptor, can increase oxidative stress-induced neurotoxicity in dopamine neurons. Based on these results, this study examines the role of nuclear factor κ B (NF-κB), cyclooxygenase-2 (COX2), and apoptosis in the deleterious effects of androgens in an oxidative stress environment. We hypothesize, under oxidative stress environment, testosterone via a putative membrane androgen receptor will exacerbate oxidative stress-induced NF-κB/COX2 signaling in N27 dopaminergic neurons, leading to apoptosis. Our data show that testosterone increased the expression of COX2 and apoptosis in dopamine neurons. Inhibiting the NF-κB and COX2 pathway with CAPE and ibuprofen, respectively, blocked testosterone's negative effects on cell viability, indicating that NF-κB/COX2 cascade plays a role in the negative interaction between testosterone and oxidative stress on neuroinflammation. These data further support the role of testosterone mediating the loss of dopamine neurons under oxidative stress conditions, which may be a key mechanism contributing to the increased incidence of Parkinson's disease in men compared with women.

Neurotoxin mechanisms and processes relevant to Parkinson's disease: an update

The molecular mechanism responsible for degenerative process in the nigrostriatal dopaminergic system in Parkinson's disease (PD) remains unknown. One major advance in this field has been the discovery of several genes associated to familial PD, including alpha synuclein, parkin, LRRK2, etc., thereby providing important insight toward basic research approaches. There is an consensus in neurodegenerative research that mitochon dria dysfunction, protein degradation dysfunction, aggregation of alpha synuclein to neurotoxic oligomers, oxidative and endoplasmic reticulum stress, and neuroinflammation are involved in degeneration of the neuromelanin-containing dopaminergic neurons that are lost in the disease. An update of the mechanisms relating to neurotoxins that are used to produce preclinical models of Parkinson´s disease is presented. 6-Hydroxydopamine, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, and rotenone have been the most wisely used neurotoxins to delve into mechanisms involved in the loss of dopaminergic neurons containing neuromelanin. Neurotoxins generated from dopamine oxidation during neuromelanin formation are likewise reviewed, as this pathway replicates neurotoxin-induced cellular oxidative stress, inactivation of key proteins related to mitochondria and protein degradation dysfunction, and formation of neurotoxic aggregates of alpha synuclein. This survey of neurotoxin modeling-highlighting newer technologies and implicating a variety of processes and pathways related to mechanisms attending PD-is focused on research studies from 2012 to 2014.

Potential neuroprotective effect of ibuprofen, insights from the mice model of Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is one of the most common neurodegenerative diseases. An inflammatory reaction seems to be involved in the pathological process in PD. Prospective clinical studies with various nonsteroidal anti-inflammatory drugs (NSAIDs) have shown that ibuprofen decreases the risk of PD. In the present study we investigated the influence of ibuprofen on dopaminergic neuron injury in the mice model of PD.

METHODS

Twelve-month-old male C57Bl mice were injected with MPTP together with various doses of ibuprofen (10, 30 or 50 mg/kg), administered 1 h before MPTP injection for 7 consecutive days. Evaluation concerned dopamine content in the striatum, tyrosine hydroxylase (TH) protein and α-synuclein expression measured 7 and 21 days post MPTP administration (dpa).

RESULTS

MPTP caused injury to dopaminergic neuron endings in the striatum: dopamine content decreased by about 0% 7 dpa and by 85% 21 dpa; TH protein expression diminished by 21% 7 dpa; α-synuclein level decreased by 10 and 26% 7 and 21 dpa, respectively. Ibuprofen administration to mice treated with MPTP significantly increased the level of dopamine in the striatum 7 and 21 dpa. It also prevented TH protein decrease and increased α-synuclein level 21 dpa.

CONCLUSIONS

Ibuprofen was shown to protect neurons against MPTP-induced injury in the striatum. The possible mechanism of the neuroprotective effect of ibuprofen might be associated with decreased dopamine turnover and cyclooxygenases inhibition resulting in lower reactive oxygen species formation.

Death in the substantia nigra: a motor tragedy

It is well known that the death of dopaminergic neurons of the substantia nigra pars compacta (SNc) is the pathological hallmark of Parkinson's disease (PD), the second most common and disabling condition in the expanding elderly population. Nevertheless, the intracellular cascade of events leading to dopamine cell death is still unknown and, consequently, treatment is largely symptomatic rather than preventive. Moreover, the mechanisms whereby nigral dopaminergic neurons may degenerate still remain controversial. Hitherto, several data have shown that the earlier cellular disturbances occurring in dopaminergic neurons include oxidative stress, excitotoxicity, inflammation, mitochondrial dysfunction and altered proteolysis. These alterations, rather than killing neurons, trigger subsequent death-related molecular pathways, including elements of apoptosis. In rare incidences, PD may be inherited; this evidence has opened a new and exciting area of research, attempting to shed light on the nature of the more common idiopathic PD form. In this review, the characteristics of the SNc dopaminergic neurons and their lifecycle from birth to death are reviewed. In addition, of the mechanisms by which the aforementioned alterations cause neuronal dopaminergic death, particular emphasis will be given to the role played by inflammation, and the relevance of the possible use of anti-inflammatory drugs in the treatment of PD. Finally, new evidence of a possible de novo neurogenesis in the SNc of adult animals and in PD patients will also be examined.

Inhibition of glycogen synthase kinase-3β by lithium chloride suppresses 6-hydroxydopamine-induced inflammatory response in primary cultured astrocytes

An increasing amount of evidence has emerged to suggest that neuroinflammatory process is involved in the pathogenesis of Parkinson's disease (PD). Activated microglia and astrocytes are found in the substantia nigra (SN) of Parkinson's disease brains as well as in animal models of Parkinson's disease. Although reactive astrocytes are involved in the progression of PD, the role of reactive astrocytes in neuroinflammation of PD has received limited attention to date. Recently, Glycogen synthase kinase-3β (GSK-3β) was identified as a crucial regulator of the inflammatory response. The purpose of this study was to explore the mechanism by which 6-hydroxydopamine (6-OHDA) induces inflammatory response in astrocytes and observe the anti-inflammatory effect of lithium chloride (LiCl) on 6-OHDA-treated astrocytes. In the present study, we found that glial fibrillary acidic protein (GFAP) was markedly upregulated in the presence of 6-OHDA. Moreover, our results revealed that proinflammatory molecules including inducible nitric oxide synthase (iNOS), nitric oxide (NO), cyclooxygenase-2(COX-2), prostaglandins E2 (PGE2), and tumor necrosis factor-α (TNF-α) were obviously increased in astrocytes exposed to 6-OHDA. Western blot analysis revealed that 6-OHDA significantly increased dephosphorylation/activation of GSK-3β as well as the nuclear translocation of nuclear factor-κB (NF-κB) p65. Besides, GSK-3β inhibitor LiCl and SB415286 inhibited the GSK-3β/NF-κB signaling pathway, leading to the reduction of proinflammatory molecules in 6-OHDA-activated astrocytes. These results confirmed that GSK-3β inhibitor LiCl and SB415286 provide protection against neuroinflammation in 6-OHDA-treated astrocytes. Therefore, GSK-3β may be a potential therapeutic target for the treatment of PD.

Glial-mediated inflammation underlying parkinsonism

The interest in studying neuroimmune interactions is increasing in the scientific community, and for many researchers, immunity is becoming a crucial factor in the understanding of the physiology of the normal brain as well as the biology underlying neurodegenerative diseases. Mounting data over the last two decades point toward immune and inflammatory alterations as important mediators of the progressive dopaminergic degeneration in Parkinson's disease. The purpose of this review is to address, under a historical perspective, as well as in the light of recent reports, the glial-mediated inflammatory and immune responses that occur in Parkinsonism. In line with this, this review also evaluates and highlights available anti-inflammatory drugs and putative targets for Parkinson's disease therapy for the near future.

COX-2 in the neurodegenerative process of Parkinson's disease

The enzyme cyclooxygenase-2 (COX-2), responsible for the first committed step in the synthesis of several important mediators which are involved in both initiation and resolution of inflammation, and the subsequent generation of prostaglandins (PGs) upon activation has been shown to participate in the neurodegenerative processes of a variety of diseases. This review looks particular at the role of COX-2 in the pathogenesis of Parkinson's disease, involving the generation of PGs and the role of the two different parts of the cyclooxygenase-cyclooxygenase and peroxidase activity.

The promise of neuroprotective agents in Parkinson's disease

Parkinson’s disease (PD) is characterized by loss of dopamine neurons in the substantia nigra of the brain. Since there are limited treatment options for PD, neuroprotective agents are currently being tested as a means to slow disease progression. Agents targeting oxidative stress, mitochondrial dysfunction, and inflammation are prime candidates for neuroprotection. This review identifies Rasagiline, Minocycline, and creatine, as the most promising neuroprotective agents for PD, and they are all currently in phase III trials. Other agents possessing protective characteristics in delaying PD include stimulants, vitamins, supplements, and other drugs. Additionally, combination therapies also show benefits in slowing PD progression. The identification of neuroprotective agents for PD provides us with therapeutic opportunities for modifying the course of disease progression and, perhaps, reducing the risk of onset when preclinical biomarkers become available.

Cyclooxygenase and neuroinflammation in Parkinson's disease neurodegeneration

Cyclooxygenase (COX) expression in the brain is associated with pro-inflammatory activities, which are instrumental in neurodegenerative processes such as Parkinson’s disease (PD). It is discussed that drugs with the capacity to rescue dopaminergic neurons from microglia toxicity and neuroinflammatory processes may result in an amelioration of parkinsonian symptoms by delaying the onset or slowing progression. This article reviews the involvement of COX in neuroinflammation, specifically focussing at the role of selective COX-2 inhibition in neuroinflammation and neurodegeneration in Parkinson’s disease.

The endotoxin-induced neuroinflammation model of Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by the progressive loss of dopaminergic (DA) neurons in the substantia nigra. Although the exact cause of the dopaminergic neurodegeneration remains elusive, recent postmortem and experimental studies have revealed an essential role for neuroinflammation that is initiated and driven by activated microglial and infiltrated peripheral immune cells and their neurotoxic products (such as proinflammatory cytokines, reactive oxygen species, and nitric oxide) in the pathogenesis of PD. A bacterial endotoxin-based experimental model of PD has been established, representing a purely inflammation-driven animal model for the induction of nigrostriatal dopaminergic neurodegeneration. This model, by itself or together with genetic and toxin-based animal models, provides an important tool to delineate the precise mechanisms of neuroinflammation-mediated dopaminergic neuron loss. Here, we review the characteristics of this model and the contribution of neuroinflammatory processes, induced by the in vivo administration of bacterial endotoxin, to neurodegeneration. Furthermore, we summarize the recent experimental therapeutic strategies targeting endotoxin-induced neuroinflammation to elicit neuroprotection in the nigrostriatal dopaminergic system. The potential of the endotoxin-based PD model in the development of an early-stage specific diagnostic biomarker is also emphasized.

Human prostaglandin H synthase (hPHS)-1- and hPHS-2-dependent bioactivation, oxidative macromolecular damage, and cytotoxicity of dopamine, its precursor, and its metabolites

The dopamine (DA) precursor l-dihydroxyphenylalanine (L-DOPA) and metabolites dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 3-methoxytyramine may serve as substrates for prostaglandin H synthase (PHS)-catalyzed bioactivation to free radical intermediates. We used CHO-K1 cells expressing human (h) PHS-1 or hPHS-2 to investigate hPHS isozyme-dependent oxidative damage and cytotoxicity. hPHS-1- and hPHS-2-expressing cells incubated with DA, L-DOPA, DOPAC, or HVA exhibited increased cytotoxicity compared to untransfected cells, and cytotoxicity was increased further by exogenous arachidonic acid (AA), which increased hPHS activity. Preincubation with catalase, which detoxifies reactive oxygen species, or acetylsalicylic acid, an inhibitor of hPHS-1 and -2, reduced the cytotoxicity caused by DA, L-DOPA, DOPAC, and HVA in hPHS-1 and -2 cells both with and without AA. Protein oxidation was increased in hPHS-1 and -2 cells exposed to DA or L-DOPA and further increased by AA addition. DNA oxidation was enhanced earlier and at lower substrate concentrations than protein oxidation in both hPHS-1 and -2 cells by DA, L-DOPA, DOPAC, and HVA and further enhanced by AA addition. hPHS-2 cells seemed more susceptible than hPHS-1 cells, whereas untransfected CHO-K1 cells were less susceptible. Thus, isozyme-specific, hPHS-dependent oxidative damage and cytotoxicity caused by neurotransmitters, their precursors, and their metabolites may contribute to neurodegeneration associated with aging.

An overview of clinical pharmacology of Ibuprofen

Ibuprofen was the first member of Propionic acid derivatives introduced in 1969. It is a popular domestic and over the counter analgesic and antipyretic for adults and children. Ibuprofen has been rated as the safest conventional NSAID by spontaneous adverse drug reaction reporting systems in the UK. This article summarizes the main pharmacological effects, therapeutical applications and adverse drug reactions, drug-drug interactions and food drug interactions of ibuprofen that have been reported especially during the last 10 years.

Non-Steroidal Anti-Inflammatory Drugs in Alzheimer's Disease and Parkinson's Disease: Reconsidering the Role of Neuroinflammation

Alzheimer's disease (AD) and Parkinson's disease (PD) are the most common neurodegenerative diseases with age as the greatest risk factor. As the general population experiences extended life span, preparation for the prevention and treatment of these and other age-associated neurological diseases are warranted. Since epidemiological studies suggested that non-steroidal anti-inflammatory drug (NSAID) use decreased risk for AD and PD, increasing attention has been devoted to understanding the costs and benefits of the innate neuroinflammatory response to functional recovery following pathology onset. This review will provide a general overview on the role of neuroinflammation in these neurodegenerative diseases and an update on NSAID treatment in recent experimental animal models, epidemiological analyses, and clinical trials.

Adaptive immune regulation of glial homeostasis as an immunization strategy for neurodegenerative diseases

Neurodegenerative diseases, notably Alzheimer's and Parkinson's diseases, are amongst the most devastating disorders afflicting the elderly. Currently, no curative treatments or treatments that interdict disease progression exist. Over the past decade, immunization strategies have been proposed to combat disease progression. Such strategies induce humoral immune responses against misfolded protein aggregates to facilitate their clearance. Robust adaptive immunity against misfolded proteins, however, accelerates disease progression, precipitated by induced effector T cell responses that lead to encephalitis and neuronal death. Since then, mechanisms that attenuate such adaptive neurotoxic immune responses have been sought. We propose that shifting the balance between effector and regulatory T cell activity can attenuate neurotoxic inflammatory events. This review summarizes advances in immune regulation to achieve a homeostatic glial response for therapeutic gain. Promising new ways to optimize immunization schemes and measure their clinical efficacy are also discussed.

Genome-wide microarray analysis of the differential neuroprotective effects of antioxidants in neuroblastoma cells overexpressing the familial Parkinson's disease alpha-synuclein A53T mutation

In Parkinson's disease substantia nigra neurons degenerate likely due to oxidative damage interacting with genetic risk factors. Here, SH-SY5Y cells expressing wild-type or A53T alpha-synuclein had increased sensitivity to methyl-4-phenylpyridinium iodide (MPP(+)), which induces mitochondrial dysfunction, and 6-hydroxydopamine (6-OHDA), which causes oxidative stress. Edaravone protected only against MPP(+), and EGCG ((-)-epigallocatechin-3-O-gallate) protected only against 6-OHDA. Thus genomic responses to MPP(+) and 6-OHDA in the presence of these antioxidants were analyzed using microarrays. Pathway analysis indicated that MPP(+) activated p53 (P < 0.001) while 6-OHDA induced the Nrf2 antioxidative stress response (P < 0.0001). EGCG was more effective at blocking 6-OHDA-mediated genomic responses, while edaravone was more effective against MPP(+). We identified 32 genes that responded to both toxins except in the presence of an effective anti-oxidant; eight are transcription factors and potentially constitute a stress-response transcriptional network. These data provide insights into the mechanisms of neurotoxicity and identifies genes that might mediate antioxidant efficacy.

Emerging roles of PGE2 receptors in models of neurological disease

This review presents an overview of the emerging field of prostaglandin signaling in neurological diseases, focusing on PGE(2) signaling through its four E-prostanoid (EP) receptors. A large number of studies have demonstrated a neurotoxic function of the inducible cyclooxygenase COX-2 in a broad spectrum of neurological disease models in the central nervous system (CNS), from models of cerebral ischemia to models of neurodegeneration and inflammation. Since COX-1 and COX-2 catalyze the first committed step in prostaglandin synthesis, an effort is underway to identify the downstream prostaglandin signaling pathways that mediate the toxic effect of COX-2. Recent epidemiologic studies demonstrate that chronic COX-2 inhibition can produce adverse cerebrovascular and cardiovascular effects, indicating that some prostaglandin signaling pathways are beneficial. Consistent with this concept, recent studies demonstrate that in the CNS, specific prostaglandin receptor signaling pathways mediate toxic effects in brain but a larger number appear to mediate paradoxically protective effects. Further complexity is emerging, as exemplified by the PGE(2) EP2 receptor, where cerebroprotective or toxic effects of a particular prostaglandin signaling pathway can differ depending on the context of cerebral injury, for example, in excitotoxicity/hypoxia paradigms versus inflammatory-mediated secondary neurotoxicity. The divergent effects of prostaglandin receptor signaling will likely depend on distinct patterns and dynamics of receptor expression in neurons, endothelial cells, and glia and the specific ways in which these cell types participate in particular models of neurological injury.

Epidemiology of non-alcoholic fatty liver disease in China

Fatty liver (steatosis) is highly prevalent in China and is more often linked to obesity than to alcoholism. Among more affluent regions of China, the community prevalence of non-alcoholic fatty liver disease (NAFLD) is approximately 15%. With the increasing pandemic of obesity, the prevalence of NAFLD has approximately doubled in the past decade. The risk factors resemble those in other ethnic populations, but it is important to note that ethnic-specific definitions of central obesity, obesity and metabolic syndrome are more useful in assessment of Chinese people. The full range of histological manifestations of NAFLD has been demonstrated in Chinese patients, but to date hepatic severity is generally mild. In contrast to chronic hepatitis C, steatosis is less common in patients with chronic hepatitis B; it is associated with metabolic, and not viral factors and does not appear to affect disease severity. Although long-term outcomes of NAFLD in Chinese populations remain unclear, it may be a predictor of metabolic disorders, diabetes and cardiovascular disease. Public health interventions are therefore indicated to halt or reverse the national trend of obesity in China so as to improve liver as well as metabolic health.

Inflammatory response in Parkinsonism

Inflammatory responses have been proposed as important factors in dopaminergic neuro-degeneration in Parkinsonism. Increasing evidence suggests that the alteration of the glial microenvironment induced by neuronal degeneration could be deleterious to the remaining neurons. The activation of microglia/macrophages and reactive astrocytes may have a negative effect on the surrounding parenchyma, perpetuating the neurodegenerative process. However, this alteration may also go beyond the brain parenchyma and stimulate other inflammatory changes in other systems, inducing the release of proinflammatory cytokines and probably Acute Phase Proteins (APP) and Glucocorticoids (GC). In this work we review the latest advances in the field to provide a picture of the state of the art of studies of inflammatory responses and Parkinsonism, hopefully opening up new therapeutic perspectives for patients with Parkinson's disease.

Interactions between CB(1) receptors and TRPV1 channels mediated by 12-HPETE are cytotoxic to mesencephalic dopaminergic neurons

BACKGROUND AND PURPOSES

We recently proposed the existence of neurotoxic interactions between the cannabinoid type 1 (CB(1)) receptor and transient receptor potential vanilloid 1 (TRPV1) channels in rat mesencephalic cultures. This study seeks evidence for the mediator(s) and mechanisms underlying the neurotoxic interactions between CB(1) receptors and TRPV1 in vitro and in vivo.

EXPERIMENTAL APPROACH

The mediator(s) and mechanism(s) for the interactions between CB(1) receptors and TRPV1 were evaluated by cell viability assays, immunocytochemistry, Fura-2 calcium imaging, mitochondrial morphology assay, ELISA and Western blot assay in vitro in neuron-enriched mesencephalic cultures. Injections into the substantia nigra and subsequent cell counts were also used to confirm these interactions in vivo.

KEY RESULTS

The neurotoxic interactions were mediated by 12(S)-hydroperoxyeicosatetraenoic acid (12(S)-HPETE), an endogenous TRPV1 agonist. CB(1) receptor agonists (HU210 and WIN55,212-2) increased the level of 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE), a downstream metabolite of 12(S)-HPETE, which stimulates TRPV1-mediated death of mesencephalic neurons, both in vitro and in vivo. The neurotoxicity was mediated by increased intracellular Ca(2+) concentration ([Ca(2+)](i)) through TRPV1, consequently leading to mitochondrial damage and was attenuated by baicalein, a 12-lipoxygenase inhibitor.

CONCLUSION AND IMPLICATIONS

Activation of CB(1) receptors in rat mesencephalic neurons was associated with biosynthesis of 12(S)-HPETE, which in turn stimulated TRPV1 activity, leading to increased [Ca(2+)](i), mitochondrial damage and neuronal death.

Phenidone protects the nigral dopaminergic neurons from LPS-induced neurotoxicity

Anti-inflammatory drugs such as ibuprofen appear to prevent the development of Parkinson's disease (PD); however, long-term use has undesirable side-effects. A new strategy for anti-inflammatory drug therapy is using a dual inhibitor of COX and lipooxygenase (LOX). Here, we compared the dopaminergic neuroprotective property of phenidone (a dual COX and LOX inhibitor) with COX or LOX inhibitors including SC-560 (a COX-1 inhibitor), aspirin (a COX-1/2 inhibitor), meloxicam (a preferential COX-2 inhibitor), caffeic acid (a 5-LOX inhibitor), and esculetin (a 5, 12-LOX inhibitor) in our lipopolysaccharide (LPS)-induced PD animal model. Our results show that COX-2 and 5-LOX play a major role in LPS-induced dopaminergic neurotoxicity, as meloxicam and phenidone attenuated LPS-induced oxidative stress and meloxicam, phenidone, and caffeic acid attenuated dopaminergic neurodegeneration, while SC-560, aspirin, and esculetin did not. In addition, phenidone was superior in attenuating LPS-induced dopaminergic neurodegeneration and microglia activation, probably as a result of dual inhibition of COX-2 and LOX. Therefore, dual inhibition of COX and LOX with phenidone represents a promising new candidate for anti-inflammatory drug therapy, and may provide a novel therapeutic approach for inflammation-related neurodegenerative diseases including PD.

Prostaglandin receptor EP2 protects dopaminergic neurons against 6-OHDA-mediated low oxidative stress

Dopaminergic neurons in the substantia nigra (SN) selectively die in Parkinson's disease (PD), but it is unclear how and why this occurs. Recent findings implicate prostaglandin E(2) (PGE(2)) and two of its four receptors, namely EP1 and EP2, as mediators of degenerative and protective events in situations of acute and chronic neuronal death. EP1 activation can exacerbate excitotoxic damage in stroke models and our recent study showed that EP1 activation may explain the selective sensitivity of dopaminergic neurons to oxidative stress. Conversely, EP2 activation may be neuroprotective, although toxic effects have also been demonstrated. Here we investigated if and how EP2 activation might alter the survival of dopaminergic neurons following selective low-level oxidative injury evoked by the neurotoxin 6-hydroxydopamine (6-OHDA) in primary neuronal cultures prepared from embryonic rat midbrain. We found that cultured dopaminergic neurons displayed EP2 receptors. Butaprost, a selective EP2 agonist, significantly reduced 6-OHDA neurotoxicity. EP2 receptors are coupled to stimulatory G-proteins (Gs), which activate adenylate cyclase, increasing cAMP synthesis, which then activates protein kinase A (PKA). Both dibutyryl cAMP and forskolin reduced dopaminergic cell loss after 6-OHDA exposure. Conversely, KT5720 and H-89, two structurally distinct high-affinity PKA inhibitors, abolished the protective effect of butaprost, implicating cAMP-dependent PKA activity in the neuroprotection by EP2 activation. Finally, we show that melanized dopaminergic neurons in the human SN express EP2. This pathway warrants consideration as a neuroprotective strategy for PD.

Resveratrol and quercetin, two natural polyphenols, reduce apoptotic neuronal cell death induced by neuroinflammation

Parkinson's disease (PD) is a movement disorder characterized by a progressive loss of nigrostriatal dopaminergic neurons. Microglia activation and neuroinflammation have been associated with the pathogenesis of PD. Indeed, cytokines have been proposed as candidates that mediate the apoptotic cell death of dopaminergic neurons seen in PD. In this study, we investigated the effect of two natural polyphenols, resveratrol and quercetin, on neuroinflammation. For glial cells, we observed that lipopolysaccharide (LPS)-induced mRNA levels of two proinflammatory genes, interleukin 1-alpha and tumor necrosis factor-alpha, are strongly decreased by treatments with resveratrol or quercetin. We also undertook microglial-neuronal coculture to examine the influence of resveratrol and quercetin on dopaminergic neuronal cell death evoked by LPS-activated microglia. Cytotoxicity assays were performed to evaluate the percentage of cell death, with apoptotic cells identified by both the TdT-mediated dUTP nick end labeling technique and the detection of cleaved caspase-3. We report that treatment of N9 microglial cells with resveratrol or quercetin successfully reduced the inflammation-mediated apoptotic death of neuronal cells in our coculture system. Altogether our results demonstrate that resveratrol and quercetin diminished apoptotic neuronal cell death induced by microglial activation and suggest that these two phytoestrogens may be potent antiinflammatory compounds.

Combined effects of smoking, coffee, and NSAIDs on Parkinson's disease risk

Inverse associations of Parkinson's disease (PD) with cigarette smoking, coffee drinking, and nonsteroidal anti-inflammatory drug (NSAID) use have been reported individually, but their joint effects have not been examined. To quantify associations with PD for the individual, two-way and three-way combinations of these factors, a case-control association study with 1,186 PD patients and 928 controls was conducted. The study setting was the NeuroGenetics Research Consortium. Subjects completed a structured questionnaire regarding smoking, coffee, and NSAID consumption. Odds ratios were calculated using unconditional logistic regression. Smoking, coffee, and over the counter NSAID use as individual factors exhibited significantly reduced risks of 20% to 30%. The two-way and three-way combinations were associated with risk reduction of 37% to 49%, and 62%, respectively. Smoking and coffee exhibited significant inverse risk trends with increasing cumulative exposures, suggesting dose-response relations. With respect to the combination of all three exposures, persons who were at the highest exposure strata for smoking and coffee and used NSAIDs had an estimated 87% reduction in risk (OR = 0.13, 95% CI = 0.06-0.29). Whether this finding reflects true biologic protection needs to be investigated.

Neuroinflammation in the pathophysiology of Parkinson's disease: evidence from animal models to human in vivo studies with [11C]-PK11195 PET

Increasing evidence suggests that neuroinflammation is an active process in Parkinson's disease (PD) that contributes to ongoing neurodegeneration. PD brains and experimental PD models show elevated cytokine levels and up-regulation of inflammatory-associated factors as cyclo-oxygenase-2 and inducible nitric oxide oxidase. Antiinflammatory treatment reduced neuronal degeneration in experimental models. In this review, we summarize the place of neuroinflammation in the pathophysiology of PD. In vivo PET studies are discussed. These methods provide a means to monitor in vivo potential clinical relevance of antiinflammatory treatment strategies in PD.

Neuronal Cyclooxygenase-2 Activity and Prostaglandins PGE2, PGD2, and PGF2α Exacerbate Hypoxic Neuronal Injury in Neuron-enriched Primary Culture

Cyclooxygenase-2 (COX-2) activity has been implicated in the pathogenesis of cerebral ischemia. To determine whether COX-2 activity within the neuron itself exacerbates hypoxic neuronal injury, neuron-enriched cultures were subjected to anoxia. Treatment with COX-2 selective antagonists decreased cell death. Neurons cultured from homozygous COX-2 gene disrupted mice were resistant to hypoxia compared to those of heterozygotes. Infection of primary neurons with AAV expressing COX-2 exacerbated cell death compared to neurons infected with enhanced green fluorescent protein (EGFP) control vector. Addition of PGE2, PGD2 or PGF2 alpha to the medium exacerbated injury, suggesting that the deleterious effects of COX-2 overexpression in hypoxia could be mediated by direct receptor mediated effects of prostaglandins. Overexpression of COX-2 did not increase expression of cyclin D1 or phosphoretinoblastoma protein (pRb), or cleavage of caspase 3 suggesting that this cell cycle mechanism does not mediate COX-2 toxicity in this model.

Non-steroidal anti-inflammatory drugs in Parkinson's disease

Parkinson's disease (PD) is known to be a chronic and progressive neurodegenerative disease caused by a selective degeneration of dopaminergic (DAergic) neurons in the substantia nigra pars compacta (SNc). A large body of experimental evidence indicates that the factors involved in the pathogenesis of this disease are several, occurring inside and outside the DAergic neuron. Recently, the role of the neuron-glia interaction and the inflammatory process, in particular, has been the object of intense study by the research community. It seems to represent a new therapeutic approach opportunity for this neurological disorder. Indeed, it has been demonstrated that the cyclooxygenase type 2 (COX-2) is up-regulated in SNc DAergic neurons in both PD patients and animal models of PD and, furthermore, non-steroidal anti-inflammatory drugs (NSAIDs) pre-treatment protects against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or 6 hydroxydopamine (6-OHDA)-induced nigro-striatal dopamine degeneration. Moreover, recent epidemiological studies have revealed that the risk of developing PD is reduced in humans who make therapeutical use of NSAIDs. Consequently, it is hypothesized that they might delay or prevent the onset of PD. However, whether or not these common drugs may also be of benefit to those individuals who already have Parkinson's disease has not as yet been shown. In this paper, evidence relating to the protective effects of aspirin or other NSAIDs on DAergic neurons in animal models of Parkinson's disease will be discussed. In addition, the pharmacological mechanisms by which these molecules can exert their neuroprotective effects will be reviewed. Finally, epidemiological data exploring the effectiveness of NSAIDs in the prevention of PD and their possible use as adjuvants in the therapy of this neurodegenerative disease will also be examined.

Neuroinflammation, Oxidative Stress and the Pathogenesis of Parkinson's Disease

Neuroinflammatory processes play a significant role in the pathogenesis of Parkinson's disease (PD). Epidemiologic, animal, human, and therapeutic studies all support the presence of an neuroinflammatory cascade in disease. This is highlighted by the neurotoxic potential of microglia . In steady state, microglia serve to protect the nervous system by acting as debris scavengers, killers of microbial pathogens, and regulators of innate and adaptive immune responses. In neurodegenerative diseases, activated microglia affect neuronal injury and death through production of glutamate, pro-inflammatory factors, reactive oxygen species, quinolinic acid amongst others and by mobilization of adaptive immune responses and cell chemotaxis leading to transendothelial migration of immunocytes across the blood-brain barrier and perpetuation of neural damage. As disease progresses, inflammatory secretions engage neighboring glial cells, including astrocytes and endothelial cells, resulting in a vicious cycle of autocrine and paracrine amplification of inflammation perpetuating tissue injury. Such pathogenic processes contribute to neurodegeneration in PD. Research from others and our own laboratories seek to harness such inflammatory processes with the singular goal of developing therapeutic interventions that positively affect the tempo and progression of human disease.

Nonsteroidal anti-inflammatory drugs in Parkinson's disease: possible involvement of quinone formation

It has been revealed that nonsteroidal anti-inflammatory drugs (NSAIDs) have neuroprotective properties based not only on their cyclooxygenase-inhibitory action, but also on other properties including their inhibitory effects on the synthesis of nitric oxide radicals and agonistic action for peroxisome proliferator-activated receptor gamma, in addition to some as yet unknown properties. Recently, a number of experimental and clinical studies have examined the neuroprotective effects of NSAIDs on the pathogenesis of several neurodegenerative diseases, including Parkinson's disease. In this article, various pharmacological effects of NSAIDs (except for their cyclooxygenase-inhibitory action) are reviewed, and possible neuroprotective effects of NSAIDs on Parkinson's disease are discussed. The neurotoxicity of dopamine quinones, or DOPA quinones, has recently received attention as a dopaminergic neuron-specific oxidative stress that is known to play a role in the pathogenesis of Parkinson's disease and neurotoxin-induced parkinsonism. NSAIDs inhibit prostaglandin H synthase, thus suppressing dopamine oxidation and subsequent dopamine quinone formation. Therefore, this article also reviews possible suppressive effects of some NSAIDs against dopamine quinone generation.

Cyclooxygenases, lipoxygenases, and epoxygenases in CNS: Their role and involvement in neurological disorders

Three enzyme systems, cyclooxygenases that generate prostaglandins, lipoxygenases that form hydroxy derivatives and leukotrienes, and epoxygenases that give rise to epoxyeicosatrienoic products, metabolize arachidonic acid after its release from neural membrane phospholipids by the action of phospholipase A(2). Lysophospholipids, the other products of phospholipase A(2) reactions, are either reacylated or metabolized to platelet-activating factor. Under normal conditions, these metabolites play important roles in synaptic function, cerebral blood flow regulation, apoptosis, angiogenesis, and gene expression. Increased activities of cyclooxygenases, lipoxygenases, and epoxygenases under pathological situations such as ischemia, epilepsy, Alzheimer's disease, Parkinson disease, amyotrophic lateral sclerosis, and Creutzfeldt-Jakob disease produce neuroinflammation involving vasodilation and vasoconstriction, platelet aggregation, leukocyte chemotaxis and release of cytokines, and oxidative stress. These are closely associated with the neural cell injury which occurs in these neurological conditions. The metabolic products of docosahexaenoic acid, through these enzymes, generate a new class of lipid mediators, namely docosatrienes and resolvins. These metabolites antagonize the effect of metabolites derived from arachidonic acid. Recent studies provide insight into how these arachidonic acid metabolites interact with each other and other bioactive mediators such as platelet-activating factor, endocannabinoids, and docosatrienes under normal and pathological conditions. Here, we review present knowledge of the functions of cyclooxygenases, lipoxygenases, and epoxygenases in brain and their association with neurodegenerative diseases.

Aspirin protects striatal dopaminergic neurons from neurotoxin-induced degeneration: An in vivo microdialysis study

The effect of aspirin on dopaminergic neuronal damage induced by in vivo infusion of 1-methyl-4-phenylpiridinium iodide (MPP(+)) and 6-hydroxydopamine (6-OHDA) was studied in rats, using microdialysis. Rat striata were perfused with 1 mM MPP(+) or 6-OHDA for 10 min, causing peak levels of dopamine (DA) in the dialytic fluid, after 40 min. After 24 h, 1 mM MPP(+) was perfused again for 10 min and DA levels measured in the dialytic fluid, as an index of neuronal cell integrity. Pretreatment with Aspidol (lysine acetylsalicylate), 180 mg/kg i.p., 1 h before MPP(+) or 6-OHDA perfusion, did not modify DA extracellular output, on day 1, but restored MPP(+)-induced DA release on day 2, indicating a neuroprotective effect of Aspidol. Conversion of 0.5 mM 4-hydroxybenzoic acid (4-HBA) to 3,4-dihydroxybenzoic acid (3,4-DHBA) was measured as an index of reactive oxygen species (ROS). 6-OHDA, but not MPP(+), significantly enhanced 3,4-DHBA levels in the perfusion fluid. Aspidol (180 mg/kg, i.p.) reduced 6-OHDA-dependent increase of 3,4-DHBA levels. Meloxicam (50 mg/kg, i.p.), a specific cyclooxygenase-2 (COX-2) inhibitor, was ineffective against both neurotoxins. These data suggest that the protective effect of aspirin is due to different mechanisms of action according to the neurotoxin used, and it is independent from COX-2 inhibition.