Cyclooxygenase-1 and -2 enzymes differentially regulate the brain upstream NF-kappa B pathway and downstream enzymes involved in prostaglandin biosynthesis

Pharmacological mechanisms of sinomenine in anti-inflammatory immunity and osteoprotection in rheumatoid arthritis: A systematic review

BACKGROUND

Sinomenine (SIN) is the main pharmacologically active component of Sinomenii Caulis and protects against rheumatoid arthritis (RA). In recent years, many studies have been conducted to elucidate the pharmacological mechanisms of SIN in the treatment of RA. However, the molecular mechanism of SIN in RA has not been fully elucidated.

PURPOSE

To summarize the pharmacological effects and molecular mechanisms of SIN in RA and clarify the most valuable regulatory mechanisms of SIN to provide clues and a basis for basic research and clinical applications.

METHODS

We systematically searched SciFinder, Web of Science, PubMed, China National Knowledge Internet (CNKI), the Wanfang Databases, and the Chinese Scientific Journal Database (VIP). We organized our work based on the PRISMA statement and selected studies for review based on predefined selection criteria.

OUTCOME

After screening, we identified 201 relevant studies, including 88 clinical trials and 113 in vivo and in vitro studies on molecular mechanisms. Among these studies, we selected key results for reporting and analysis.

CONCLUSIONS

We found that most of the known pharmacological mechanisms of SIN are indirect effects on certain signaling pathways or proteins. SIN was manifested to reduce the release of inflammatory cytokines such as Tumor necrosis factor-α (TNF-α), Interleukin-6 (IL-6), and IL-1β, thereby reducing the inflammatory response, and apparently blocking the destruction of bone and cartilage. The regulatory effects on inflammation and bone destruction make SIN a promising drug to treat RA. More notably, we believe that the modulation of α7nAChR and the regulation of methylation levels at specific GCG sites in the mPGES-1 promoter by SIN, and its mechanism of directly targeting GBP5, certainly enriches the possibilities and the underlying rationale for SIN in the treatment of inflammatory immune-related diseases.

Inflammatory mechanisms of Ginkgo Biloba extract in improving memory functions through lncRNA-COX2/NF-κB pathway in mice with status epilepticus

PURPOSE

This study was to explore whether Ginkgo biloba extract (GBE) improve memory impairment by alleviating neuroinflammation signaling in mice with status epilepticus.

METHODS

The status epilepticus (SE) mice model was established by pilocarpine and treated with 100 mg / kg of GBE for 14 days. Spontaneous alternation of Y-maze and new object recognition were used to explore memory impairment. To examine glial cell activation, we performed immunohistochemistry and immunofluorescence staining. The activation of NF-κB signaling and the expression level of lncRNA-COX2 were detected by Western blot and qRT-PCR, respectively. Adeno-associated virus lncRNA-COX2 was injected into mice for overexpression of lncRNA-COX2.

RESULTS

After GBE treatment, the spontaneous alternation rate and the recognition coefficient in SE mice were both increased. Moreover, activation of glial cells, NF-κB signaling and lncRNA-COX2 were significantly decreased in SE mice. In the GBE-treated SE mice with lncRNA-COX2 overexpression, NF-κB signaling was up-regulated again; the reduced level of inflammation factors was reversed; the GBE-rescued spontaneous alternation rate of Y-maze was eliminated.

CONCLUSION

Our results suggested that GBE reduces the hippocampal inflammation by down-regulating lncRNA-COX2 / NF-κB signaling in the SE mice, leading to the decrease of neuronal damage and the improvement of memory functions.

Dietary n-9, n-6 and n-3 fatty acids modulate the oxidative stress in brain and liver of mice. Effect of trans fatty acids supplementation

BACKGROUND: Arachidonic (20:4n-6) and docosahexaenoic (22:6n-3) acids interaction affects brain structure and function. Unsaturated fatty acids (UFAs) generate oxygenated lipid-derived eicosanoids which modulate the inflammatory response. The presence of trans fatty acids (TFA) in neuronal membranes can favor to generation of pro-oxidant metabolites. OBJECTIVE: This study evaluated the effect of supplementation with TFA to diets containing different proportions of FA, on the oxidative stress (OS) generation and the inflammatory response in mice brain and liver. METHODS: CF1 mice were fed diets (16 weeks) with olive (O), corn (C) or rapeseed (R) oils. OS parameters and gene expression of some key liver and brain enzymes involved in OS production were evaluated. RESULTS: In brain and liver, lipoperoxidation was increased and catalase activity was decreased in C. In brain, glutathione was diminished by supplementation with TFA in all diets and histological sections showed lymphocytes in O and C. In liver, decreased amount of lipid vacuoles and increased of cyclooxygenase-1 (COX-1) and PPARγ mRNA levels were observed in R and Rt. IL-1b and IL-6 in serum were augmented in O and Ot. CONCLUSIONS: Rapeseed oil could have protective effects on the development of OS and inflammation, while TFA supplementation did not showed marked effects on these parameters.

Inflammation and JNK's Role in Niacin-GPR109A Diminished Flushed Effect in Microglial and Neuronal Cells With Relevance to Schizophrenia

Schizophrenia is a neuropsychiatric illness with no single definitive aetiology, making its treatment difficult. Antipsychotics are not fully effective because they treat psychosis rather than the cognitive or negative symptoms. Antipsychotics fail to alleviate symptoms when patients enter the chronic stage of illness. Topical application of niacin showed diminished skin flush in the majority of patients with schizophrenia compared to the general population who showed flushing. The niacin skin flush test is useful for identifying patients with schizophrenia at their ultra-high-risk stage, and understanding this pathology may introduce an effective treatment. This review aims to understand the pathology behind the diminished skin flush response, while linking it back to neurons and microglia. First, it suggests that there are altered proteins in the GPR109A-COX-prostaglandin pathway, inflammatory imbalance, and kinase signalling pathway, c-Jun N-terminal kinase (JNK), which are associated with diminished flush. Second, genes from the GPR109A-COX-prostaglandin pathway were matched against the 128-loci genome wide association study (GWAS) for schizophrenia using GeneCards, suggesting that G-coupled receptor-109A (GPR109A) may have a genetic mutation, resulting in diminished flush. This review also suggests that there may be increased pro-inflammatory mediators in the GPR109A-COX-prostaglandin pathway, which contributes to the diminished flush pathology. Increased levels of pro-inflammatory markers may induce microglial-activated neuronal death. Lastly, this review explores the role of JNK on pro-inflammatory mediators, proteins in the GPR109A-COX-prostaglandin pathway, microglial activation, and neuronal death. Inhibiting JNK may reverse the changes observed in the diminished flush response, which might make it a good therapeutic target.

Tissue pretreatment for LC-MS/MS analysis of PUFA and eicosanoid distribution in mouse brain and liver

Polyunsaturated fatty acids (PUFAs) and eicosanoids are important mediators of inflammation. The functional role of eicosanoids in metabolic-syndrome-related diseases has been extensively studied. However, their role in neuroinflammation and the development of neurodegenerative diseases is still unclear. The aim of this study was the development of a sample pretreatment protocol for the simultaneous analysis of PUFAs and eicosanoids in mouse liver and brain. Liver and brain samples of male wild-type C57BL/6J mice (11-122 mg) were used to investigate conditions for tissue rinsing, homogenization, extraction, and storage. A targeted liquid chromatography-negative electrospray ionization tandem mass spectrometry method was applied to quantify 7 PUFAs and 94 eicosanoids. The final pretreatment protocol consisted of a 5-min homogenization step by sonication in 650 μL n-hexane/2-propanol (60:40 v/v) containing 2,6-di-tert-butyl-4-methylphenol at 50 μg/mL. Homogenates representing 1 mg tissue were extracted in a single step with n-hexane/2-propanol (60:40 v/v) containing 0.1% formic acid. Autoxidation was prevented by addition of 2,6-di-tert-butyl-4-methylphenol at 50 μg/mL and keeping the samples at 4 °C during sample preparation. Extracts were dried under nitrogen and reconstituted in liquid chromatography eluent before analysis. Recovery was determined to range from 45% to 149% for both liver and brain tissue. Within-run and between-run variability ranged between 7% and 18% for PUFAs and between 1% and 24% for eicosanoids. In liver, 7 PUFAs and 15 eicosanoids were quantified; in brain, 6 PUFAs and 21 eicosanoids had significant differences within the brain substructures. In conclusion, a robust and reproducible sample preparation protocol for the multiplexed analysis of PUFAs and eicosanoids by liquid chromatography-tandem mass spectrometry in liver and discrete brain substructures was developed.

Pre- and Neonatal Exposure to Lead (Pb) Induces Neuroinflammation in the Forebrain Cortex, Hippocampus and Cerebellum of Rat Pups

Lead (Pb) is a heavy metal with a proven neurotoxic effect. Exposure is particularly dangerous to the developing brain in the pre- and neonatal periods. One postulated mechanism of its neurotoxicity is induction of inflammation. This study analyzed the effect of exposure of rat pups to Pb during periods of brain development on the concentrations of selected cytokines and prostanoids in the forebrain cortex, hippocampus and cerebellum. Methods: Administration of 0.1% lead acetate (PbAc) in drinking water ad libitum, from the first day of gestation to postnatal day 21, resulted in blood Pb in rat pups reaching levels below the threshold considered safe for humans by the Centers for Disease Control and Prevention (10 µg/dL). Enzyme-linked immunosorbent assay (ELISA) method was used to determine the levels of interleukins IL-1β, IL-6, transforming growth factor-β (TGF-β), prostaglandin E2 (PGE2) and thromboxane B2 (TXB2). Western blot and quantitative real-time PCR were used to determine the expression levels of cyclooxygenases COX-1 and COX-2. Finally, Western blot was used to determine the level of nuclear factor kappa B (NF-κB). Results: In all studied brain structures (forebrain cortex, hippocampus and cerebellum), the administration of Pb caused a significant increase in all studied cytokines and prostanoids (IL-1β, IL-6, TGF-β, PGE2 and TXB2). The protein and mRNA expression of COX-1 and COX-2 increased in all studied brain structures, as did NF-κB expression. Conclusions: Chronic pre- and neonatal exposure to Pb induces neuroinflammation in the forebrain cortex, hippocampus and cerebellum of rat pups.

Neurobiology and Therapeutic Potential of Cyclooxygenase-2 (COX-2) Inhibitors for Inflammation in Neuropsychiatric Disorders

Neuropsychiatric disorders, such as depression, bipolar disorder, schizophrenia, obsessive-compulsive disorder, and neurodevelopmental disorders such as autism spectrum disorder, are associated with significant illness burden. Accumulating evidence supports an association between these disorders and inflammation. Consequently, anti-inflammatory agents, such as the cyclooxygenase-2 inhibitors, represent a novel avenue to prevent and treat neuropsychiatric illness. In this paper, we first review the role of inflammation in psychiatric pathophysiology including inflammatory cytokines' influence on neurotransmitters, the hypothalamic-pituitary-adrenal axis, and microglial mechanisms. We then discuss how cyclooxygenase-2-inhibitors influence these pathways with potential therapeutic benefit, with a focus on celecoxib, due to its superior safety profile. A search was conducted in PubMed, Embase, and PsychINFO databases, in addition to Clinicaltrials.gov and the Stanley Medical Research Institute trial registries. The results were presented as a narrative review. Currently available outcomes for randomized controlled trials up to November 2017 are also discussed. The evidence reviewed here suggests cyclooxygenase-2 inhibitors, and in particular celecoxib, may indeed assist in treating the symptoms of neuropsychiatric disorders; however, further studies are required to assess appropriate illness stage-related indication.

Autism-related behaviors in the cyclooxygenase-2-deficient mouse model

Prostaglandin E2 (PGE2) is an endogenous lipid molecule involved in normal brain development. Cyclooxygenase-2 (COX2) is the main regulator of PGE2 synthesis. Emerging clinical and molecular research provides compelling evidence that abnormal COX2/PGE2 signaling is associated with autism spectrum disorder (ASD). We previously found that COX2 knockout mice had dysregulated expression of many ASD genes belonging to important biological pathways for neurodevelopment. The present study is the first to show the connection between irregular COX2/PGE2 signaling and autism-related behaviors in male and female COX2-deficient knockin, (COX)-2^- , mice at young (4-6 weeks) or adult (8-11 weeks) ages. Autism-related behaviors were prominent in male (COX)-2^- mice for most behavioral tests. In the open field test, (COX)-2^- mice traveled more than controls and adult male (COX)-2^- mice spent less time in the center indicating elevated hyperactive and anxiety-linked behaviors. (COX)-2^- mice also buried more marbles, with males burying more than females, suggesting increased anxiety and repetitive behaviors. Young male (COX)-2^- mice fell more frequently in the inverted screen test revealing motor deficits. The three-chamber sociability test found that adult female (COX)-2^- mice spent less time in the novel mouse chamber indicative of social abnormalities. In addition, male (COX)-2^- mice showed altered expression of several autism-linked genes: Wnt2, Glo1, Grm5 and Mmp9. Overall, our findings offer new insight into the involvement of disrupted COX2/PGE2 signaling in ASD pathology with age-related differences and greater impact on males. We propose that (COX)-2^- mice might serve as a novel model system to study specific types of autism.

Cerebrovascular Injury After Serial Exposure to Chronic Stress and Abstinence from Methamphetamine Self-Administration

Cerebrovascular damage caused by either exposure to stress or the widely abused drug, methamphetamine (Meth) is known but stress and drug abuse frequently occur in tandem that may impact their individual cerebrovascular effects. This study examined their co-morbid cerebrovascular effects during abstinence from self-administered Meth after the exposure to chronic unpredictable stress (CUS). Exposure to CUS prior to unrestricted Meth self-administration had no effect on Meth intake in rats; however, the pro-inflammatory mediator cyclooxygenase-2 (COX-2) and the breakdown of cell-matrix adhesion protein β-dystroglycan in isolated cerebral cortical capillaries were increased after 3 days of abstinence and persisted for 7 days. These changes preceded decreases in occludin, a key structural protein component of the blood-brain barrier. The decrease in occludin was blocked by the COX-2 specific inhibitor nimesulide treatment during abstinence from Meth. The changes in COX-2, β-dystroglycan, and occludin were only evident following the serial exposure to stress and Meth but not after either one alone. These results suggest that stress and voluntary Meth intake can synergize and disrupt cerebrovasculature in a time-dependent manner during abstinence from chronic stress and Meth. Furthermore, COX-2 inhibition may be a viable pharmacological intervention to block vascular changes after Meth exposure.

AH6809 decreases production of inflammatory mediators by PGE2 - EP2 - cAMP signaling pathway in an experimentally induced pure cerebral concussion in rats

Increasing evidence suggests that PGE₂ metabolic pathway is involved in pathological changes of the secondary brain injury after traumatic brain injury. However, the underlying mechanisms, in particular, the correlation between various key enzymes and the brain injury, has remained to be fully explored. More specifically, it remains to be ascertained whether AH6809 (an EP2 receptor antagonist) would interfere with the downstream of the PGE₂, regulate the inflammatory mediators and improve neuronal damage in the hippocampus by PGE₂ - EP2 - cAMP signaling pathway. The expression and pathological changes of cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), microsomal prostaglandin-E synthase-1 (mPGES-1), E-prostanoid receptor 2 (EP2), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and inducible nitricoxide synthase (iNOS) in the CA1 area of hippocampus were evaluated by immunohistochemistry, Western blot and RT-PCR after pure cerebral concussion (PCC) induced by a metal pendulum closed brain injury in rats followed by AH6809 treatment. The morphology and number of neurons in CA1 region were analyzed by cresyl violet staining. The concentration of prostaglandin E₂ (PGE₂) and cyclic adenosine monophosphate (cAMP) was assayed by ELISA. Many neurons in hippocampal CA1 area appeared to undergo necrosis and the number of neurons was concomitantly reduced after PCC injury. With the passage of time, the protein and mRNA expression of various key enzymes including COX-1, COX-2 and mPGES-1, EP2 receptor, and inflammatory mediators including TNF-α, IL-1β and iNOS was increased; meanwhile, the concentration of PGE₂ and cAMP was enhanced. After PCC injury given AH6809 intervention, injury of neurons in hippocampal CA1 area was attenuated. The protein and mRNA expression of COX-1, COX-2, mPGES-1, EP2, TNF-α, IL-1β and iNOS was decreased, this was coupled with reduction of PGE₂ and cAMP. The results suggest that PGE₂ metabolic pathway is involved in secondary pathological changes of PCC. AH6809 improves the recovery of injured neurons in the hippocampal CA1 area and downregulates the inflammatory mediators by PGE₂ - EP2 - cAMP signaling pathway.

Genetic and Histological Alterations Reveal Key Role of Prostaglandin Synthase and Cyclooxygenase 1 and 2 in Traumatic Brain Injury-Induced Neuroinflammation in the Cerebral Cortex of Rats Exposed to Moderate Fluid Percussion Injury

After the initial insult in traumatic brain injury (TBI), secondary neurodegeneration occurs that is intimately associated with neuroinflammation. Prostaglandin (PG) synthases and cyclooxygenase (COX) 1 and 2 may contribute to inflammation in the brain. Temporal and spatial expression features of PG and COX1 and 2 following trauma may guide the development of antineuroinflammation strategies. Here, we examined PG synthase signaling and COX1 and 2 gene expression levels and COX-1- and 2-positive cell types and their temporal localization in TBI-induced brain in an effort to reveal their participation in the disease’s evolving neuroinflammation. Using brain samples from the cerebral cortex of rats subjected to TBI model of lateral moderate fluid percussion injury (FPI), we sought to characterize the temporal (subacute TBI) and spatial (lateral cortical lesion) brain alterations accompanying the disease progression. Temporal gene expression changes of PG synthase signaling were compared between sham-operated and TBI-treated rats using microarray pathway analysis. Moreover, we examined COX1 and 2 expression patterns and their intracellular distribution in sham-operated and TBI-treated rats by immunohistochemistry. After FPI, COX1 and 2 gene expression levels, and PGE₂ synthase increased while PGD₂ synthase decreased, suggesting that PGE₂ and PGD₂ afforded contraindicative effects of inflammation and anti-inflammation, respectively. Immunohistochemical analyses showed that both COX1 and COX2 increased in a time-dependent manner in the brain, specifically in degenerating neurons of the cortex. Interestingly, the expression of COX cell type was cell-specific, in that COX1 was particularly increased in degenerating neurons while COX2 was expressed in macrophages. In view of the dynamic temporal and spatial expression of PG, COX1 and 2 gene expression and localization in the injured brain regulating PG synthase and COX1 and 2 activity will require a careful disease-specific tailoring of treatments to abrogate the neuroinflammation-plagued secondary cell death due to TBI.

COX-1 and COX-2 polymorphisms in susceptibility to cerebral palsy in very preterm infants

Cerebral palsy (CP) is a nonprogressive motor disorder caused by white matter damage in the developing brain. Recent epidemiological and clinical data suggest intrauterine infection/inflammation as the most common cause of preterm delivery and neonatal complications, including CP. Cyclooxygenases are key enzymes in the conversion of arachidonic acid to prostaglandins. The COX family consists of two isoforms, COX-1 and COX-2. In the brain, COX-2 is constitutively expressed at high levels on pyramidal neurons, while COX-1 is predominantly expressed by microglia and can be upregulated in pathological conditions, such as infection, ischemia and traumatic brain injury. Single nucleotide polymorphisms in the COX-1 and COX-2 gene could have profound effects on COX-1 and COX-2 expression and, directly or indirectly, influence the pathogenesis, development and severity of CP. In this study we investigated the association between single nucleotide polymorphisms of the COX-1 and COX-2 gene and susceptibility to cerebral palsy in very preterm infants. The results of our study showed the association between COX-1 high expression genotype (-842 AA) and COX-1 high expression allele -842A and risk of CP in infants with cystic periventricular leucomalacia (cPVL). Our results support an important role of COX-1 enzyme on microglial activation during neuroinflammation resulting in huge neuroinflammatory response and the proinflammatory mediator overproduction, with the serious white matter damage and CP development as a consequence.

Acute restraint stress induces endothelial dysfunction: role of vasoconstrictor prostanoids and oxidative stress

We hypothesized that acute stress would induce endothelial dysfunction. Male Wistar rats were restrained for 2 h within wire mesh. Functional and biochemical analyses were conducted 24 h after the 2-h period of restraint. Stressed rats showed decreased exploration on the open arms of an elevated-plus maze (EPM) and increased plasma corticosterone concentration. Acute restraint stress did not alter systolic blood pressure, whereas it increased the in vitro contractile response to phenylephrine and serotonin in endothelium-intact rat aortas. NG-nitro-l-arginine methyl ester (l-NAME; nitric oxide synthase, NOS, inhibitor) did not alter the contraction induced by phenylephrine in aortic rings from stressed rats. Tiron, indomethacin and SQ29548 reversed the increase in the contractile response to phenylephrine induced by restraint stress. Increased systemic and vascular oxidative stress was evident in stressed rats. Restraint stress decreased plasma and vascular nitrate/nitrite (NOx) concentration and increased aortic expression of inducible (i) NOS, but not endothelial (e) NOS. Reduced expression of cyclooxygenase (COX)-1, but not COX-2, was observed in aortas from stressed rats. Restraint stress increased thromboxane (TX)B(2) (stable TXA(2) metabolite) concentration but did not affect prostaglandin (PG)F2α concentration in the aorta. Restraint reduced superoxide dismutase (SOD) activity, whereas concentrations of hydrogen peroxide (H(2)O(2)) and reduced glutathione (GSH) were not affected. The major new finding of our study is that restraint stress increases vascular contraction by an endothelium-dependent mechanism that involves increased oxidative stress and the generation of COX-derived vasoconstrictor prostanoids. Such stress-induced endothelial dysfunction could predispose to the development of cardiovascular diseases.

Polyunsaturated fatty acids and their metabolites in brain function and disease

The brain is highly enriched with fatty acids. These include the polyunsaturated fatty acids (PUFAs) arachidonic acid and docosahexaenoic acid, which are largely esterified to the phospholipid cell membrane. Once PUFAs are released from the membrane, they can participate in signal transduction, either directly or after enzymatic conversion to a variety of bioactive derivatives ('mediators'). PUFAs and their mediators regulate several processes within the brain, such as neurotransmission, cell survival and neuroinflammation, and thereby mood and cognition. PUFA levels and the signalling pathways that they regulate are altered in various neurological disorders, including Alzheimer's disease and major depression. Diet and drugs targeting PUFAs may lead to novel therapeutic approaches for the prevention and treatment of brain disorders.

Lithium and the other mood stabilizers effective in bipolar disorder target the rat brain arachidonic acid cascade

This Review evaluates the arachidonic acid (AA, 20:4n-6) cascade hypothesis for the actions of lithium and other FDA-approved mood stabilizers in bipolar disorder (BD). The hypothesis is based on evidence in unanesthetized rats that chronically administered lithium, carbamazepine, valproate, or lamotrigine each downregulated brain AA metabolism, and it is consistent with reported upregulated AA cascade markers in post-mortem BD brain. In the rats, each mood stabilizer reduced AA turnover in brain phospholipids, cyclooxygenase-2 expression, and prostaglandin E2 concentration. Lithium and carbamazepine also reduced expression of cytosolic phospholipase A2 (cPLA2) IVA, which releases AA from membrane phospholipids, whereas valproate uncompetitively inhibited in vitro acyl-CoA synthetase-4, which recycles AA into phospholipid. Topiramate and gabapentin, proven ineffective in BD, changed rat brain AA metabolism minimally. On the other hand, the atypical antipsychotics olanzapine and clozapine, which show efficacy in BD, decreased rat brain AA metabolism by reducing plasma AA availability. Each of the four approved mood stabilizers also dampened brain AA signaling during glutamatergic NMDA and dopaminergic D2 receptor activation, while lithium enhanced the signal during cholinergic muscarinic receptor activation. In BD patients, such signaling effects might normalize the neurotransmission imbalance proposed to cause disease symptoms. Additionally, the antidepressants fluoxetine and imipramine, which tend to switch BD depression to mania, each increased AA turnover and cPLA2 IVA expression in rat brain, suggesting that brain AA metabolism is higher in BD mania than depression. The AA hypothesis for mood stabilizer action is consistent with reports that low-dose aspirin reduced morbidity in patients taking lithium, and that high n-3 and/or low n-6 polyunsaturated fatty acid diets, which in rats reduce brain AA metabolism, were effective in BD and migraine patients.

Lack of Microsomal Prostaglandin E 2 Synthase-1 in Bone Marrow–Derived Myeloid Cells Impairs Left Ventricular Function and Increases Mortality After Acute Myocardial Infarction

Background—

Microsomal prostaglandin E 2 synthase-1 (mPGES-1), encoded by the Ptges gene, catalyzes prostaglandin E 2 biosynthesis and is expressed by leukocytes, cardiac myocytes, and cardiac fibroblasts. Ptges −/− mice develop more left ventricle (LV) dilation, worse LV contractile function, and higher LV end-diastolic pressure than Ptges +/+ mice after myocardial infarction. In this study, we define the role of mPGES-1 in bone marrow–derived leukocytes in the recovery of LV function after coronary ligation.

Methods and Results—

Cardiac structure and function in Ptges +/+ mice with Ptges +/+ bone marrow ( BM +/+ ) and Ptges +/+ mice with Ptges −/− BM ( BM −/− ) were assessed by morphometric analysis, echocardiography, and invasive hemodynamics before and 7 and 28 days after myocardial infarction. Prostaglandin levels and prostaglandin biosynthetic enzyme gene expression were measured by liquid chromatography–tandem mass spectrometry and real-time polymerase chain reaction, immunoblotting, immunohistochemistry, and immunofluorescence microscopy, respectively. After myocardial infarction, BM −/− mice had more LV dilation, worse LV systolic and diastolic function, higher LV end-diastolic pressure, more cardiomyocyte hypertrophy, and higher mortality but similar infarct size and pulmonary edema compared with BM +/+ mice. BM −/− mice also had higher levels of COX-1 protein and more leukocytes in the infarct, but not the viable LV, than BM +/+ mice. Levels of prostaglandin E 2 were higher in the infarct and viable myocardium of BM −/− mice than in BM +/+ mice.

Conclusions—

Lack of mPGES-1 in bone marrow–derived leukocytes negatively regulates COX-1 expression, prostaglandin E 2 biosynthesis, and inflammation in the infarct and leads to impaired LV function, adverse LV remodeling, and decreased survival after acute myocardial infarction.

Disturbed brain phospholipid and docosahexaenoic acid metabolism in calcium-independent phospholipase A(2)-VIA (iPLA(2)β)-knockout mice

Calcium-independent phospholipase A(2) group VIA (iPLA(2)β) releases docosahexaenoic acid (DHA) from phospholipids in vitro. Mutations in the iPLA(2)β gene, PLA2G6, are associated with dystonia-parkinsonism and infantile neuroaxonal dystrophy. To understand the role of iPLA(2)β in brain, we applied our in vivo kinetic method using radiolabeled DHA in 4 to 5-month-old wild type (iPLA(2)β(+/+)) and knockout (iPLA(2)β(-/-)) mice, and measured brain DHA kinetics, lipid concentrations, and expression of PLA(2), cyclooxygenase (COX), and lipoxygenase (LOX) enzymes. Compared to iPLA(2)β(+/+) mice, iPLA(2)β(-/-) mice showed decreased rates of incorporation of unesterified DHA from plasma into brain phospholipids, reduced concentrations of several fatty acids (including DHA) esterified in ethanolamine- and serine-glycerophospholipids, and increased lysophospholipid fatty acid concentrations. DHA turnover in brain phospholipids did not differ between genotypes. In iPLA(2)β(-/-) mice, brain levels of iPLA(2)β mRNA, protein, and activity were decreased, as was the iPLA(2)γ (Group VIB PLA(2)) mRNA level, while levels of secretory sPLA(2)-V mRNA, protein, and activity and cytosolic cPLA(2)-IVA mRNA were increased. Levels of COX-1 protein were decreased in brain, while COX-2 protein and mRNA were increased. Levels of 5-, 12-, and 15-LOX proteins did not differ significantly between genotypes. Thus, a genetic iPLA(2)β deficiency in mice is associated with reduced DHA metabolism, profound changes in lipid-metabolizing enzyme expression (demonstrating lack of redundancy) and of phospholipid fatty acid content of brain (particularly of DHA), which may be relevant to neurologic abnormalities in humans with PLA2G6 mutations.

Involvement of PKCα-MAPK/ERK-phospholipase A(2) pathway in the Escherichia coli invasion of brain microvascular endothelial cells

Escherichia coli K1 is the most common Gram-negative organism that causes neonatal meningitis following penetration of the blood-brain barrier. In the present study we demonstrated the involvement of cytosolic (cPLA(2)) and calcium-independent phospholipase A(2) (iPLA(2)) and the contribution of cyclooxygenase-2 products in E. coli invasion of microvascular endothelial cells. The traversal of bacteria did not determine trans-endothelial electrical resistance (TEER) and ZO-1 expression changes and was reduced by PLA(2)s siRNA. cPLA(2) and iPLA(2) enzyme activities and cPLA(2) phosphorylation were stimulated after E. coli incubation and were attenuated by PLA(2), PI3-K, ERK 1/2 inhibitors. Our results demonstrate the role of PKCα/ERK/MAPK signaling pathways in governing the E. coli penetration into the brain.

Cyclooxygenase expression and prostaglandin levels in central nervous system tissues during the course of chronic relapsing experimental autoimmune encephalomyelitis (EAE)

OBJECTIVE

Multiple sclerosis (MS) and its animal counterpart experimental autoimmune encephalomyelitis (EAE) have a major inflammatory component that drives and orchestrates both diseases. One particular group of mediators are the prostaglandins (PGs), which we have previously shown, through quantitation and pharmacological intervention, to be closely involved in the pathology of MS and EAE. The aim of the current study was to determine the expression of the PG-generating cyclooxygenase (COX) enzymes and the profile of PGE(2) and PGD(2), in selected central nervous system (CNS) tissues, with the development of the chronic relapsing (CR) form of EAE. In particular, the work investigates the possible relationship between the expression of COX isoenzymes and PG levels during the neurological phases of CR EAE.

METHODS

CR EAE was induced in Biozzi mice with inoculum containing lyophilised, syngeneic spinal cord emulsified in complete Freund's adjuvant. The cerebral cortex, cerebellum and spinal cord were dissected from mice during the acute, remission and relapse stages of disease with a minimum of five animals per treatment. The expression of COX-1, COX-1b variant and COX-2, in pooled samples, was determined by Western blotting. PGE(2) and PGD(2) levels in extracted samples were measured using commercial enzyme immunoassay kits.

RESULTS

COX-2 expression in spinal cords during acute disease remained unaltered and was in contrast to an enhancement of the enzyme, together with COX-1 and COX-1b, in all other sampled areas. PGE(2) and PGD(2) levels remained unchanged during the acute phase and the subsequent remission of symptoms. COX-1 and COX-1b expression was elevated in tissues during the relapse stage of CR EAE and concentrations of the prostanoids were markedly increased.

CONCLUSIONS

The study examines the implications of COX isoenzyme expression over the course of CR EAE and discusses the reported relationship between PGE(2) and PGD(2) in the instigation and resolution of CNS inflammation. Consideration is also given to the treatment of CR EAE and suggests that drugs designed to limit the inflammatory effects of the PGs should be administered prior to or during the relapse phase of the disease.

Cyclooxygenase-1 mediates prostaglandin E(2) elevation and contextual memory impairment in a model of sustained hippocampal interleukin-1beta expression

Interleukin (IL)-1beta is a proinflammatory cytokine implicated in several neurodegenerative disorders. Downstream actions of IL-1beta include production of prostaglandin (PG) E(2) by increasing expression of cyclooxygenase (COX) enzymes and prostaglandin E synthase (PGES) isoforms. We recently developed a transgenic mouse carrying a dormant human IL-1beta eXcisional Activation Transgene (XAT) for conditional and chronic up-regulation of IL-1beta in selected brain regions. This model is characterized by regionally specific glial activation, immune cell recruitment, and induction of cytokines and chemokines. Here, we aimed to elucidate the effects of long-term IL-1beta expression on the PGE(2) synthetic pathway and to determine the effects of PGs on inflammation and memory in our model. As expected, PGE(2) levels were significantly elevated after IL-1beta up-regulation. Quantitative real-time PCR analysis indicated significant induction of mRNAs for COX-1 and membranous PGES-1, but not COX-2 or other PGES isoforms. Immunohistochemistry revealed elevation of COX-1 but no change in COX-2 following sustained IL-1beta production. Furthermore, pharmacological inhibition of COX-1 and use of COX-1 knockout mice abrogated IL-1beta-mediated PGE(2) increases. Although COX-1 deficient mice did not present a dramatically altered neuroinflammatory phenotype, they did exhibit improved contextual fear memory. This data suggests a unique role for COX-1 in mediating chronic neuroinflammatory effects through PGE(2) production.

Activation of liver X receptor reduces global ischemic brain injury by reduction of nuclear factor-kappaB

Recent studies have found that liver X receptors (LXRs) agonists decrease brain inflammation and exert neuroprotective effect. The aim of this study was to examine the mechanisms of action of liver X receptor agonist GW3965 against brain injury following global cerebral ischemia in the rat. The 48 male SD (Sprague-Dawley) rats were randomly partitioned into three groups: sham, global ischemia (4-vessel occlusion for 15 min; 4VO) treated with vehicle and global ischemia treated with GW3965 (20 mg/kg, via i.p. injection at 10 min after reperfusion). The functional outcome was determined by neurological evaluation at 24 h post ischemia and by testing rats in T maze at 3 and 7 days after reperfusion. The rats' daily body weight, incidence of seizures and 72 h mortality were also determined. After Nissl staining and TUNEL in coronal brain sections, the numbers of intact and damaged cells were counted in the CA1 sector of the hippocampus. The expression of phosphorylated inhibitor of kappaB (p-IkappaBalpha), nuclear factor-kappaB (NF-kappaB) subunit p65, and cyclo-oxygenase-2 (COX-2) were analyzed with Western blot at 12 h after reperfusion. GW3965 tended to reduce 72 h mortality and the incidence of post-ischemic seizures. GW3965-treated rats showed an improved neuronal survivability in CA1 and a significant increase in the percentage of spontaneous alternations detected in T-maze on day 7 after ischemia. GW3965-induced neuroprotection was associated with a significant reduction in nuclear translocation of NF-kB p65 subunit and a decrease in the hippocampal expression of NF-kB target gene, COX-2. LXR receptor agonist protects against neuronal damage following global cerebral ischemia. The mechanism of neuroprotection may include blockade of NF-kappaB activation and the subsequent suppression of COX-2 in the post ischemic brain.

Prostanoid extraction and measurement

Prostanoids are involved in numerous physiological and pathophysiological processes in all body organs. Therefore, measurement of the concentration of the prostanoids has always been of importance for research and drug development purposes as a measure of cyclooxygenase (COX) activities. Techniques used for the measurement of prostanoids have been described decades ago. These techniques have come a long way and improvements have been reported, especially with the specificity in competition immunoassays that rely on the use of specific antibodies against a given prostanoid. These assays are relatively fast and do not involve the use of radioactive isotopes as radioimmunoassay. However, prior extraction is required in order to concentrate the prostanoids and remove interfering substances such as proteins. In this chapter, we describe two protocols for the extraction and measurement of prostanoids using C18 columns and commercial enzyme immunoassays, which do not require specialized equipments and can be performed in any laboratory with standard equipments.

Expression of cyclooxygenase-1/-2, microsomal prostaglandin-E synthase-1 and E-prostanoid receptor 2 and regulation of inflammatory mediators by PGE(2) in the amoeboid microglia in hypoxic postnatal rats and murine BV-2 cells

This study aimed to investigate the effect of hypoxia on the expression of cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), microsomal prostaglandin-E synthase (mPGES-1), E-prostanoid receptor 2 (EP2) in microglia; and the roles of EP2-cyclic adenosine monophosphate (cAMP) signaling pathway in the prostaglandin E(2) (PGE(2)) regulation of inflammatory mediators released by hypoxic BV-2 cells. Immunoexpression of COX-1, COX-2, mPGES-1 and EP2 was localized in the amoeboid microglial cells (AMC), a nascent brain macrophage in the developing brain, as confirmed by double labeling with OX-42 and lectin, specific markers of microglia. AMC emitted a more intense immunofluorescence in hypoxic rats when compared with the matching controls. In postnatal rats subjected to hypoxia, mRNA and protein expression levels of COX-1, COX-2 and mPGES-1 along with tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), inducible nitric-oxide synthase (iNOS) and PGE(2) product in the callosal tissue were significantly increased. The results were shared in the BV-2 cells except for COX-1 mRNA and protein whose levels remained unaltered. Interestingly, treatment with EP2 antagonist AH-6809 resulted in suppression of hypoxia induced EP2, IL-1beta and iNOS mRNA and protein expression, TNF-alpha protein expression and intracellular cAMP level in BV-2 cells. It is suggested that PGE(2) may regulate above inflammatory mediators in the activated microglia via EP2-cAMP signaling pathway in hypoxic conditions.

Prostaglandin E2 synthases in neurologic homeostasis and disease

Prostaglandin E(2) synthases (PGES) currently comprise a group of three structurally and biologically distinct molecules. These enzymes are part of an important and complex paracrine signaling system involved in a wide range of biological processes. This review focuses on the normal physiological and pathological roles of these enzymes in the nervous system. Specific topics include the role of PGES(s) in fever and sickness behavior, inflammatory pain, and neural disease. Although the field is in its early stages, ongoing development of selective PGES inhibitors for possible use in people creates a significant need for more fully understanding the biological roles of these important enzymes.

The distinct roles of cyclooxygenase-1 and -2 in neuroinflammation: implications for translational research

Cyclooxygenases (COX-1 and COX-2) are key enzymes in the conversion of arachidonic acid to prostaglandins and other lipid mediators. Because it can be induced by inflammatory stimuli, COX-2 has been classically considered as the most appropriate target for anti-inflammatory drugs. However, recent data indicate that COX-2 can mediate neuroprotection and that COX-1 is a major player in the neuroinflammatory process. We discuss the specific contributions of COX-1 and COX-2 in various neurodegenerative diseases and in models of neuroinflammation. We suggest that, owing to its predominant localization in microglia, COX-1 might be the major player in neuroinflammation, whereas COX-2, which is localized in neurons, might have a major role in models in which the neurons are directly challenged. Overall, the benefit of using COX-2 inhibitors should be carefully evaluated and COX-1 preferential inhibitors should be further investigated as a potential therapeutic approach in neurodegenerative diseases with an inflammatory component.

The brain expression of genes involved in inflammatory response, the ribosome, and learning and memory is altered by centrally injected lipopolysaccharide in mice

Neuroinflammation plays a role in the progression of several neurodegenerative disorders. We used a lipopolysaccharide (LPS) model of neuroinflammation to characterize the gene expression changes underlying the inflammatory and behavioral effects of neuroinflammation. A single intracerebroventricular injection of LPS (5 microg) was administered into the lateral ventricle of mice and, 24 h later, we examined gene expression in the cerebral cortex and hippocampus using microarray technology. Gene Ontology (GO) terms for inflammation and the ribosome were significantly enriched by LPS, whereas GO terms associated with learning and memory had decreased expression. We detected 224 changed transcripts in the cerebral cortex and 170 in the hippocampus. Expression of Egr1 (also known as Zif268) and Arc, two genes associated with learning and memory, was significantly lower in the cortex, but not in the hippocampus, of LPS-treated animals. Overall, altered expression of these genes may underlie some of the inflammatory and behavioral effects of neuroinflammation.

Neuroinflammatory response to lipopolysaccharide is exacerbated in mice genetically deficient in cyclooxygenase-2

Background

Cyclooxygenases (COX) -1 and -2 are key mediators of the inflammatory response in the central nervous system. Since COX-2 is inducible by inflammatory stimuli, it has been traditionally considered as the most appropriate target for anti-inflammatory drugs. However, the specific roles of COX-1 and COX-2 in modulating a neuroinflammatory response are unclear. Recently, we demonstrated that COX-1 deficient mice show decreased neuroinflammatory response and neuronal damage in response to lipopolysaccharide (LPS).

Methods

In this study, we investigated the role of COX-2 in the neuroinflammatory response to intracerebroventricular-injected LPS (5 μg), a model of direct activation of innate immunity, using COX-2 deficient (COX-2^-/-) and wild type (COX-2^+/+) mice, as well as COX-2^+/+ mice pretreated for 6 weeks with celecoxib, a COX-2 selective inhibitor.

Results

Twenty-four hours after LPS injection, COX-2^-/- mice showed increased neuronal damage, glial cell activation, mRNA and protein expression of markers of inflammation and oxidative stress, such as cytokines, chemokines, iNOS and NADPH oxidase. Brain protein levels of IL-1β, NADPH oxidase subunit p67^phox, and phosphorylated-signal transducer and activator of transcription 3 (STAT3) were higher in COX-2^-/- and in celecoxib-treated mice, compared to COX-2^+/+ mice. The increased neuroinflammatory response in COX-2^-/- mice was likely mediated by the upregulation of STAT3 and suppressor of cytokine signaling 3 (SOCS3).

Conclusion

These results show that inhibiting COX-2 activity can exacerbate the inflammatory response to LPS, possibly by increasing glial cells activation and upregulating the STAT3 and SOCS3 pathways in the brain.

Immunohistochemical increase in cyclooxygenase-2 without apoptosis in different brain areas of subchronic nicotine- and D-amphetamine-treated rats

Cyclooxygenase-2 (COX-2) upregulation has been related to both neurodegeneration and physiological processes. To clarify whether nicotine-induced upregulation of COX-2 occurs, and to analyse its significance, a comparative immunohistochemical and Western blot study was performed on the frontoparietal cortex, hippocampus and cerebellar cortex of rats treated (14 days) with nicotine, D(+)amphetamine (0.35 and 1.16 mg free base/kg/day, respectively), or both drugs simultaneously. None of these treatments promoted neuronal apoptosis. Lipid peroxidation increased in the hippocampus of the nicotine-treated rats and in all the brain regions examined in the D(+)amphetamine rats, but not in the double-treated animals. Both molecules increased the COX-2 content (as determined by the number of immunopositive neurons and the intensity of their immunodeposits) in an area-, layer- and neuron type-dependent manner, in all brain regions in which a large number of COX-2 immunopositive neurons were observed in controls (the somatosensory cortical areas, CA-1, CA-3, the gyrus dentatus, the ectorhinal/perirhinal areas, and the gyrus cingularis). No increase was seen in the motor cortical areas, while a reduction was recorded in the cerebellar cortex; these regions had only a few immunopositive neurons in controls. Western blot analysis revealed a 50-80% increase in COX-2 in the brain cortex and hippocampus of nicotine-treated rats, and similar increases (150-200%) in the cortex of the D(+)amphetamine- and nicotine + D(+)amphetamine-treated rats. Nicotine-induced upregulation of COX-2 seems to be related to neuronal plasticity rather than neurodegeneration. Nicotine agonists might be useful in the treatment of cognitive disorders.

Long-term air pollution exposure is associated with neuroinflammation, an altered innate immune response, disruption of the blood-brain barrier, ultrafine particulate deposition, and accumulation of amyloid beta-42 and alpha-synuclein in children and young adults

Air pollution is a serious environmental problem. We investigated whether residency in cities with high air pollution is associated with neuroinflammation/neurodegeneration in healthy children and young adults who died suddenly. We measured mRNA cyclooxygenase-2, interleukin-1beta, and CD14 in target brain regions from low (n = 12) or highly exposed residents (n = 35) aged 25.1 +/- 1.5 years. Upregulation of cyclooxygenase-2, interleukin-1beta, and CD14 in olfactory bulb, frontal cortex, substantia nigrae and vagus nerves; disruption of the blood-brain barrier; endothelial activation, oxidative stress, and inflammatory cell trafficking were seen in highly exposed subjects. Amyloid beta42 (Abeta42) immunoreactivity was observed in 58.8% of apolipoprotein E (APOE) 3/3 < 25 y, and 100% of the APOE 4 subjects, whereas alpha-synuclein was seen in 23.5% of < 25 y subjects. Particulate material (PM) was seen in olfactory bulb neurons, and PM < 100 nm were observed in intraluminal erythrocytes from lung, frontal, and trigeminal ganglia capillaries. Exposure to air pollution causes neuroinflammation, an altered brain innate immune response, and accumulation of Abeta42 and alpha-synuclein starting in childhood. Exposure to air pollution should be considered a risk factor for Alzheimer's and Parkinson's diseases, and carriers of the APOE 4 allele could have a higher risk of developing Alzheimer's disease if they reside in a polluted environment.

Alteration in the activation state of new inflammation-associated targets by phospholipase A2-activating protein (PLAA)

Phospholipase A(2) (PLA(2))-activating protein (PLAA) is a novel signaling molecule that regulates the production of prostaglandins (PGE(2)) and tumor necrosis factor (TNF)-alpha. To characterize the function of native PLAA in situ, we generated HeLa (Tet-off) cells overexpressing plaa (plaa(high)) and control (plaa(low)) cells, with the plaa gene in opposite orientation in the latter construct. The plaa(high) cells produced significantly more PGE(2) and interleukin (IL)-6 compared to plaa(low) cells in response to TNF-alpha. There was an increased activation and/or expression of cytosolic PLA(2), cyclooxgenase-2, and NF-kappaB after induction of plaa(high) cells with TNF-alpha compared to the respective plaa(low) cells. Microarray analysis of plaa(high) cells followed by functional assays revealed increased production of proinflammatory cytokine IL-32 and a decrease in the production of annexin A4 and clusterin compared to plaa(low) cells. We demonstrated the role of annexin A4 as an inhibitor of PLA(2) and showed that addition of exogeneous clusterin limited the production of PGE(2) from plaa(high) cells. To understand regulation of plaa gene expression, we used a luciferase reporter system in HeLa cells and identified one stimulatory element, with Sp1 binding sites, and one inhibitory element, in exon 1 of the plaa gene. By using decoy DNA oligonucleotides to Sp1 and competitive binding assays, we showed that Sp1 maintains basal expression of the plaa gene and binds to the above-mentioned stimulatory element. We demonstrated for the first time that the induction of native PLAA by TNF-alpha can perpetuate inflammation by enhancing activation of PLA(2) and NF-kappaB.

Genetic deletion or pharmacological inhibition of cyclooxygenase-1 attenuate lipopolysaccharide-induced inflammatory response and brain injury

Cyclooxygenase (COX) -1 and -2 metabolize arachidonic acid to prostanoids and reactive oxygen species, major players in the neuroinflammatory process. While most reports have focused on the inducible isoform, COX-2, the contribution of COX-1 to the inflammatory response is unclear. In the present study, the contribution of COX-1 in the neuroinflammatory response to intracerebroventricular lipopolysaccharide (LPS) was investigated using COX-1 deficient (COX-1(-/-)) mice or wild-type (COX-1(+/+)) mice pretreated with SC-560, a selective COX-1 inhibitor. Twenty-four hours after lipopolysaccharide (LPS) injection, COX-1(-/-) mice showed decreased protein oxidation and LPS-induced neuronal damage in the hippocampus compared with COX-1(+/+) mice. COX-1(-/-) mice showed a significant reduction of microglial activation, proinflammatory mediators, and expression of COX-2, inducible NOS, and NADPH oxidase. The transcriptional down-regulation of cytokines and other inflammatory markers in COX-1(-/-) mice was mediated by a reduced activation of NF-kappaB and signal transducer and activator of transcription 3. Administration of SC-560 prior to LPS injection also attenuated the neuroinflammatory response by decreasing brain levels of prostaglandin (PG)E(2), PGD(2), PGF(2alpha), and thromboxane B(2), as well as the expression of proinflammatory cytokines and chemokine. These findings suggest that COX-1 plays a previously unrecognized role in neuroinflammatory damage.

Altered GABAergic neurotransmission is associated with increased kainate-induced seizure in prostaglandin-endoperoxide synthase-2 deficient mice

Excitotoxicity involves over activation of brain excitatory glutamate receptors and has been implicated in neurological, neurodegenerative and neuropsychiatric diseases. Metabolism of arachidonic acid (AA) through the phospholipase A(2) (PLA(2))/prostaglandin-endoperoxide synthase (PTGS) pathway is increased after excitotoxic stimulation. However, the individual roles of the PTGS isoforms in this process are not well established. We assessed the role of the PTGS isoforms in the process of excitotoxicity by exposing mice deficient in either PTGS-1 (PTGS-1(-/-)) or PTGS-2 (PTGS-2(-/-)) to the prototypic excitotoxin, kainic acid (KA). Seizure intensity and neuronal damage were significantly elevated in KA-exposed PTGS-2(-/-), but not in PTGS-1(-/-), mice. The increased susceptibility was not associated with an alteration in KA receptor binding activity or mediated through the CB1 endocannabinoid receptor. The frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) was decreased in the CA1 pyramidal neurons of PTGS-2(-/-) mice, suggesting an alteration of GABAergic function. In wild-type mice, six weeks treatment with the PTGS-2 selective inhibitor celecoxib recapitulated the increased susceptibility to KA-induced excitotoxicity observed in PTGS-2(-/-) mice, further supporting the role of PTGS-2 in the excitotoxic process. The increased susceptibility to KA was also associated with decreased brain levels of PGE(2), a biomarker of PTGS-2 activity. Our results suggest that PTGS-2 activity and its specific products may modulate neuronal excitability by affecting GABAergic neurotransmission. Further, inhibition of PTGS-2, but not PTGS-1, may increase the susceptibility to seizures.

Brain metabolism of nutritionally essential polyunsaturated fatty acids depends on both the diet and the liver

Plasma alpha-linolenic acid (alpha-LNA, 18:3n-3) and linoleic acid (LA, 18:2n-6) do not contribute significantly to the brain content of docosahexaenoic acid (DHA, 22:6n-3) or arachidonic acid (AA, 20:4n-6), respectively, and neither DHA nor AA can be synthesized de novo in vertebrate tissue. Therefore, measured rates of incorporation of circulating DHA and AA into brain exactly represent their rates of consumption by brain. Positron emission tomography (PET) has been used to show, based on this information, that the adult human brain consumes AA and DHA at rates of 17.8 and 4.6 mg/day, respectively, and that AA consumption does not change significantly with age. In unanesthetized adult rats fed an n-3 PUFA "adequate" diet containing 4.6% alpha-LNA (of total fatty acids) as its only n-3 PUFA, the rate of liver synthesis of DHA was more than sufficient to maintain brain DHA, whereas the brain's rate of DHA synthesis is very low and unable to do so. Reducing dietary alpha-LNA in the DHA-free diet led to upregulation of liver but not brain coefficients of alpha-LNA conversion to DHA and of liver expression of elongases and desaturases that catalyze this conversion. Concurrently, brain DHA loss slowed due to downregulation of several of its DHA-metabolizing enzymes. Dietary alpha-LNA deficiency also promoted accumulation of brain docosapentaenoic acid (22:5n-6), and upregulated expression of AA-metabolizing enzymes, including cytosolic and secretory phospholipases A(2) and cyclooxygenase-2. These changes, plus reduced levels of brain derived neurotrophic factor (BDNF) and cAMP response element-binding protein (CREB) in n-3 PUFA diet deficient rats, likely render their brain more vulnerable to neuropathological insults.

Chronic carbamazepine administration reduces N-methyl-D-aspartate receptor-initiated signaling via arachidonic acid in rat brain

BACKGROUND

Lithium and carbamazepine (CBZ) are used to treat mania in bipolar disorder. When given chronically to rats, both agents reduce arachidonic acid (AA) turnover in brain phospholipids and downstream AA metabolism. Lithium in rats also attenuates brain N-methyl-D-aspartic acid receptor (NMDAR) signaling via AA. We hypothesized that, like chronic lithium, chronic CBZ administration to rats would reduce NMDAR-mediated signaling via AA.

METHODS

We used our fatty acid method with quantitative autoradiography to image the regional brain incorporation coefficient k* of AA, a marker of AA signaling, in unanesthetized rats that had been given 25 mg/kg/day I.P. CBZ or vehicle for 30 days, then injected with NMDA (25 mg/kg I.P.) or saline. We also measured brain concentrations of two AA metabolites, prostaglandin E(2) (PGE(2)) and thromboxane B(2) (TXB(2)).

RESULTS

In chronic vehicle-treated rats, NMDA compared with saline increased k* significantly in 69 of 82 brain regions examined, but did not change k* significantly in any region in CBZ-treated rats. In vehicle- but not CBZ-treated rats, NMDA also increased brain concentrations of PGE(2) and TXB(2).

CONCLUSIONS

Chronic CBZ administration to rats blocks increments in the AA signal k*, and in PGE(2) and TXB(2) concentrations that are produced by NMDA in vehicle-treated rats. The clinical action of antimanic drugs might involve inhibition of brain NMDAR-mediated signaling involving AA and its metabolites.

Regulation of prostaglandin E synthases: Effects of siRNA-mediated inhibition of microsomal prostaglandin E synthase-1

Prostaglandin E2 (PGE2) is a key mediator involved in several inflammatory conditions. In this study, we investigated the expression and regulation of the terminal PGE2 synthesizing enzyme prostaglandin E synthases (mPGES-1, mPGES-2 and cPGES) in gingival fibroblasts stimulated with pro-inflammatory cytokines. We used siRNA knockdown of mPGES-1 to elucidate the impact of mPGES-1 inhibition on mPGES-2 and cPGES expression, as well as on PGE2 production. The cytokines TNFalpha and IL-1beta increased protein expression and activity of mPGES-1, accompanied by increased COX-2 expression and PGE2 production. The isoenzymes mPGES-2 and cPGES, constitutively expressed at mRNA and protein levels, were unaffected by the pro-inflammatory cytokines. We show for the first time that treatment with mPGES-1 siRNA down-regulated the cytokine-induced mPGES-1 protein expression and activity. Interestingly, mPGES-1 siRNA did not affect the cytokine-stimulated PGE2 production, whereas PGF(2alpha) levels were enhanced. Neither mPGES-2 nor cPGES expression was affected by siRNA silencing of mPGES-1. Dexamethasone and MK-886 both inhibited the cytokine-induced mPGES-1 expression while mPGES-2 and cPGES expression remained unaffected. In conclusion, mPGES-1 siRNA down-regulates mPGES-1 expression, and neither mPGES-2 nor cPGES substituted for mPGES-1 in a knockdown setting in gingival fibroblasts. Moreover, mPGES-1 siRNA did not affect PGE2 levels, whereas PGF(2alpha) increased, suggesting a compensatory pathway of PGE2 synthesis when mPGES-1 is knocked down.

In search of cyclooxygenase inhibitors, anti-Mycobacterium tuberculosis and anti-malarial drugs from Thai flora and microbes

Malaria continues to be a major infectious disease of the developing world and the problem is compounded not only by the emergence of drug resistant strains but also from a lack of a vaccine. The situation for tuberculosis (TB) infection is equally problematic. Once considered a "treatable" disease for which eradication was predicted, TB has re-emerged as highly lethal, multi-drug resistant strains after the outbreak of AIDS. Worldwide, the disease causes millions of deaths annually. Similarly, treatments for chronic inflammatory diseases such as arthritis have been impeded due to the potentially lethal side effects of the new and widely prescribed non-steroidal anti-inflammatory compounds. Thais have utilized bioresources from plants and some microorganisms for medicine for thousands of years. Because of the need for new drugs to fight malaria and TB, with radically different chemical structures and mode of actions other than existing drugs, efforts have been directed towards searching for new drugs from bioresources. This is also true for anti-inflammatories. Although Thailand is considered species-rich, only a small number of potential bioresources has been investigated. This article briefly describes the pathogenesis of 2 infectious diseases, malaria and TB, and modern medicines employed in chemotherapy. Diversities of Thai flora and fungi and their chemical constituents with antagonistic properties against these 2 diseases are described in detail. Similarly, anti-inflammatory compounds, mostly cyclooxygenase (COX) inhibitors, are also described herein to demonstrate the potential of Thai bioresources to provide a wide array of compounds for treatment of diseases of a different nature.

Flurbiprofen, A Cyclooxygenase Inhibitor, Reduces the Brain Arachidonic Acid Signal in Response to the Cholinergic Muscarinic Agonist, Arecoline, in Awake Rats

Cholinergic muscarinic receptors, when stimulated by arecoline, can activate cytosolic phospholipase A(2) (cPLA(2)) to release arachidonic acid (AA) from membrane phospholipid. This signal can be imaged in the brain in vivo using quantitative autoradiography following the intravenous injection of radiolabeled AA, as an increment in a regional brain AA incorporation coefficient k*. Arecoline increases k* significantly in brain regions having muscarinic M(1,3,5) receptors in wild-type but not in cyclooxygenase (COX)-2 knockout mice. To further clarify the roles of COX enzymes in the AA signal, in this paper we imaged k* following arecoline (5 mg/kg i.p.) or saline in each of 81 brain regions of unanesthetized rats pretreated 6 h earlier with the non-selective COX inhibitor flurbiprofen (FB, 60 mg/kg s.c.) or with vehicle. Baseline values of k* were unaffected by FB treatment, which however reduced by 80% baseline brain concentrations of prostaglandin E(2) (PGE(2)) and thromboxane B(2) (TXB(2)), eicosanoids preferentially derived from AA via COX-2 and COX-1, respectively. In vehicle-pretreated rats, arecoline increased the brain PGE(2) but not TXB(2) concentration, as well as values for k* in 77 of the 81 brain regions. FB-pretreatment prevented these arecoline-provoked changes. These results and those reported in COX-2 knockout mice suggest that the AA released in brain following muscarinic receptor-mediated activation is lost via COX-2 to PGE(2) but not via COX-1 to TXB(2), and that increments in k* following arecoline largely represent replacement by unesterified plasma AA of this loss.

Acute systemic inflammation transiently synchronizes clock gene expression in equine peripheral blood

Peripheral clocks receive timing signals from the master mammalian pacemaker in the suprachiasmatic nucleus (SCN) and function to adaptively anticipate daily changes that influence local physiology. Evidence suggests that peripheral immune activation may act as a resetting signal for circadian clocks in peripheral tissues. We wished to investigate whether acute systemic inflammation could synchronize clock gene expression in equine peripheral blood, a tissue that does not normally oscillate in this species. We report that in vivo administration of lipopolysaccharide (LPS) results in significant upregulation of the core clock genes Per2 and Bmal1 in equine blood, in association with an acute rise in tumor necrosis factor (TNF) alpha and core body temperature compared to vehicle-treated control animals. Furthermore, co-administration of LPS and phenylbutazone, a non-steroidal anti-inflammatory drug (NSAID) known to inhibit prostaglandin (PG) E(2) synthesis in the horse, prevents both the febrile response and the synchronized increase in clock gene expression. However, the rise in Per2 and Bmal1 expression cannot be replicated in equine peripheral blood mononuclear cells (PBMCs) ex vivo by treatment with PGE(2), LPS or a heat shock mimicking the in vivo febrile response. These results may suggest an indirect communication pathway between immune modulators and the molecular machinery of cell clocks in peripheral blood. This potential immune feedback regulation of an equine peripheral clock implies a role for the circadian system in contributing to innate immune reactions and maintaining homeostasis in a tissue that acts as the first line of defense during an infectious challenge.

Differential gene expression patterns in cyclooxygenase-1 and cyclooxygenase-2 deficient mouse brain

Microarray analysis of gene expression in the cerebral cortex and hippocampus of mice deficient in cyclooxygenase-1 or cyclooxygenase-2 reveals that the two enzymes differentially modulate brain gene expression.

Background

Cyclooxygenase (COX)-1 and COX-2 produce prostanoids from arachidonic acid and are thought to have important yet distinct roles in normal brain function. Deletion of COX-1 or COX-2 results in profound differences both in brain levels of prostaglandin E₂ and in activation of the transcription factor nuclear factor-κB, suggesting that COX-1 and COX-2 play distinct roles in brain arachidonic acid metabolism and regulation of gene expression. To further elucidate the role of COX isoforms in the regulation of the brain transcriptome, microarray analysis of gene expression in the cerebral cortex and hippocampus of mice deficient in COX-1 (COX-1^-/-) or COX-2 (COX-2^-/-) was performed.

Results

A majority (>93%) of the differentially expressed genes in both the cortex and hippocampus were altered in one COX isoform knockout mouse but not the other. The major gene function affected in all genotype comparisons was 'transcriptional regulation'. Distinct biologic and metabolic pathways that were altered in COX^-/- mice included β oxidation, methionine metabolism, janus kinase signaling, and GABAergic neurotransmission.

Conclusion

Our findings suggest that COX-1 and COX-2 differentially modulate brain gene expression. Because certain anti-inflammatory and analgesic treatments are based on inhibition of COX activity, the specific alterations observed in this study further our understanding of the relationship of COX-1 and COX-2 with signaling pathways in brain and of the therapeutic and toxicologic consequences of COX inhibition.

Arachidonic acid metabolism in brain physiology and pathology: lessons from genetically altered mouse models

The arachidonic acid (AA) cascade involves the release of AA from the membrane phospholipids by a phospholipase A(2), followed by its subsequent metabolism to bioactive prostanoids by cyclooxygenases coupled with terminal synthases. Altered brain AA metabolism has been implicated in neurological, neurodegenerative, and psychiatric disorders. The development of genetically altered mice lacking specific enzymes of the AA cascade has helped to elucidate the individual roles of these enzymes in brain physiology and pathology. The roles of AA and its metabolites in brain physiology, with a particular emphasis on the phospholipase A(2)/cyclooxygenases pathway, are summarized, and the specific phenotypes of genetically altered mice relevant to brain physiology and neurotoxic models are discussed.

Chronic lithium administration attenuates up-regulated brain arachidonic acid metabolism in a rat model of neuroinflammation

Neuroinflammation, caused by a 6-day intracerebroventricular infusion of lipopolysaccharide (LPS) in rats, is associated with the up-regulation of brain arachidonic acid (AA) metabolism markers. Because chronic LiCl down-regulates markers of brain AA metabolism, we hypothesized that it would attenuate increments of these markers in LPS-infused rats. Incorporation coefficients k* of AA from plasma into brain, and other brain AA metabolic markers, were measured in rats that had been fed a LiCl or control diet for 6 weeks, and subjected in the last 6 days on the diet to intracerebroventricular infusion of artificial CSF or of LPS. In rats on the control diet, LPS compared with CSF infusion increased k* significantly in 28 regions, whereas the LiCl diet prevented k* increments in 18 of these regions. LiCl in CSF infused rats increased k* in 14 regions, largely belonging to auditory and visual systems. Brain cytoplasmic phospholipase A(2) activity, and prostaglandin E(2) and thromboxane B(2) concentrations, were increased significantly by LPS infusion in rats fed the control but not the LiCl diet. Chronic LiCl administration attenuates LPS-induced up-regulation of a number of brain AA metabolism markers. To the extent that this up-regulation has neuropathological consequences, lithium might be considered for treating human brain diseases accompanied by neuroinflammation.

Gene expression of cyclooxygenase-1 and Ca(2+)-independent phospholipase A(2) is altered in rat hippocampus during normal aging

Brain aging is associated with inflammatory changes. However, data on how the brain arachidonic acid (AA) metabolism is altered as a function of age are limited and discrepant. AA is released from membrane phospholipids by phospholipase A(2) (PLA(2)) and then further metabolized to bioactive prostaglandins and thromboxanes by cyclooxygenases (COX)-1 and -2. We examined the phospholipase A(2) (PLA(2))/COX-mediated AA metabolic pathway in the hippocampus and cerebral cortex of 4-, 12-, 24- and 30-month-old rats. A two-fold increase in brain thromboxane B(2) level in 24 and 30 months was accompanied by increased hippocampal COX-1 mRNA levels at 12, 24, and 30 months. COX-2 mRNA expression was significantly decreased only at 30 months. Hippocampal Ca(2+)-independent iPLA(2) mRNA levels were decreased at 24 and 30 months without any change in Ca(2+)-dependent PLA(2) expression. In the cerebral cortex, mRNA levels of COX and PLA(2) were not significantly changed. The specific changes in the AA cascade observed in the hippocampus may alter phospholipids homeostasis and possibly increase the susceptibility of the aging brain to neuroinflammation.

Inhibition of Aβ production by NF-κB inhibitors

The transcription factor nuclear factor kappaB (NF-kappaB) is widely expressed in the nervous system and increased NF-kappaB immunoreactivity has been observed in Alzheimer's disease (AD) brains in the nuclei of neurons within the vicinity of diffuse beta-amyloid plaques. Beta-amyloid (Abeta) peptides are the main constituent of senile plaques and are known to stimulate NF-kappaB activity. In the present study, we investigated the effect of various NF-kappaB inhibitors on the production of Abeta1-40, Abeta1-42, secreted APP (sAPPbeta and sAPPalpha) and APP C-terminal fragments (APP-CTF) using CHO cells overexpressing the beta-amyloid precursor protein (APP). Our data show that NF-kappaB inhibitors decrease both Abeta1-40 and Abeta1-42 production. In addition, we show that some NF-kappaB inhibitors decrease sAPPbeta and APP-CTFbeta suggesting that they reduce the beta-secretase cleavage of APP. Altogether our data suggest that NF-kappaB inhibitors may be of therapeutic importance for the treatment of AD pathology not only by blocking inflammatory processes but also by directly inhibiting the production of Abeta peptides.

Cyclooxygenase-1 Is Involved in Endothelial Dysfunction of Mesenteric Small Arteries From Angiotensin II–Infused Mice

Angiotensin II induces endothelial dysfunction by reducing NO availability and increasing reactive oxygen species. We assessed whether cyclooxygenase (COX)-1 or COX-2 participate in the angiotensin II–induced endothelial dysfunction in murine mesenteric small arteries and examined the role of reduced nicotinamide-adenine dinucleotide phosphate–dependent reactive oxygen species production. Mice received angiotensin II (600 ng/kg per minute, SC), saline (controls), angiotensin II + apocynin (reduced nicotinamide-adenine dinucleotide phosphate oxidase inhibitor, 2.5 mg/day), or apocynin alone for 2 weeks. Endothelial function of mesenteric arteries was assessed by pressurized myograph. In controls, acetylcholine-induced relaxation was inhibited by N G -monomethyl- l -arginine and unaffected by DFU (COX-2 inhibitor), SC-560 (COX-1 inhibitor), or ascorbic acid. In angiotensin II–infused animals, the attenuated response to acetylcholine was less sensitive to N G -monomethyl- l -arginine, unaffected by DFU, and enhanced by SC-560 and, similarly, by SQ-29548, a thromboxane–prostanoid receptor antagonist. Moreover, response to acetylcholine was unchanged by ozagrel, a thromboxane synthase inhibitor, and normalized by ascorbic acid. Apocynin prevented the angiotensin II–induced vascular dysfunctions. In angiotensin II–infused mice, RT-PCR analysis showed a significant COX-2 downregulation, whereas COX-1 expression was upregulated. These changes were unaffected by apocynin. Modulation of COX isoform by angiotensin II was also documented by immunohistochemistry. In small mesenteric vessels, the reduced NO availability and oxidant excess, which characterize endothelial dysfunction secondary to angiotensin II, are associated with a reduced COX-2 and an increased COX-1 function and expression. Angiotensin II causes an oxidative stress–independent COX-1 overexpression, whereas angiotensin II–mediated oxidant excess production stimulates COX-1 activity to produce a contracting prostanoid endowed with agonist activity on thromboxane–prostanoid receptors.