Targeting cytosolic phospholipase A2 by arachidonyl trifluoromethyl ketone prevents chronic inflammation in mice

Development of Calcium-Dependent Phospholipase A2 Inhibitors to Target Cellular Senescence and Oxidative Stress in Neurodegenerative Diseases

Significance: Cellular senescence is a critical process underlying aging and is associated with age-related diseases such as Alzheimer's disease. Lipids are implicated in cellular senescence. Fatty acids, particularly eicosanoids, have been associated with various forms of senescence and inflammation, and the associated reactive oxygen species production has been proposed as a therapeutic target for mitigating senescence. When overactivated, calcium-dependent phospholipase A2 (cPLA2) catalyzes the conversion of arachidonic acid into eicosanoids such as leukotrienes and prostaglandins. Recent Advances: With a growing understanding of the importance of lipids as mediators and modulators of senescence, cPLA2 has emerged as a compelling drug target. cPLA2 overactivation plays a significant role in several pathways associated with senescence, including neuroinflammation and oxidative stress. Critical Issues: Previous cPLA2 inhibitors have shown potential in ameliorating inflammation and oxidative stress, but the dominant hurdles in the central nervous system-targeting drug discovery are specificity and blood-brain barrier penetrance. Future Directions: With the need for more effective drugs against neurological diseases, we emphasize the significance of discovering new brain-penetrant, potent, and specific cPLA2 inhibitors. We discuss how the recently developed Virtual Synthon Hierarchical Enumeration Screening, an iterative synthon-based approach for fast structure-based virtual screening of billions of compounds, provides an efficient exploration of large chemical spaces for the discovery of brain-penetrant cPLA2 small-molecule inhibitors. Antioxid. Redox Signal. 41, 1100-1116.

Discovery of novel NSAID hybrids as cPLA2/COX-2 dual inhibitors alleviating rheumatoid arthritis via inhibiting p38 MAPK pathway

A series of NSAIDs hybrid molecules were synthesized and characterized, and their ability to inhibit NO release in LPS-induced RAW264.7 macrophages was evaluated. Most of the compounds showed significant anti-inflammatory activity in vitro, of which (2E,6Z,9Z,12Z,15Z)-1,1,1-trifluorohenicosa-2,6,9,12,15-pentaen-2-yl 2-(4-benzoylphenyl) propanoate (VI-60) was the most optimal (IC50 = 3.85 ± 0.25 μΜ) and had no cytotoxicity. In addition, VI-60 notably reduced the production of PGE2 in LPS-stimulated RAW264.7 cells compared to ketoprofen. Futhur more, VI-60 significantly inhibited the expression of iNOS, cPLA2, and COX-2 and the phosphorylation of p38 MAPK in LPS-stimulated RAW264.7 cells. The binding of VI-60 to cPLA2 and COX-2 was directly verified by the CETSA technique. In vivo studies illustrated that VI-60 exerted an excellent therapeutic effect on adjuvant-induced arthritis in rats by regulating the balance between Th17 and Treg through inhibiting the p38 MAPK/cPLA2/COX-2/PGE2 pathway. Encouragingly, VI-60 showed a lower ulcerative potential in rats at a dose of 50 mg/kg compared to ketoprofen. In conclusion, the hybrid molecules of NSAIDs and trifluoromethyl enols are promising candidates worthy of further investigation for the treatment of inflammation, pain, and other symptoms in which cPLA2 and COX-2 play a role in their etiology.

In vitro Anti-hemolytic Effect, in vivo Anti-inflammatory and in vitro Anti-oxidant Activity of Anchusa azurea Mill

BACKGROUND

Anchusa azurea Mill. (AA) is a medicinal plant largely used traditionally in folk medicine in Algeria; it is locally named hamham. It is effective in the treatment of various diseases.

OBJECTIVES

The aim of the present study is to determine the antioxidant, anti-inflammatory, and anti- hemolytic effects of phenolic fractions from Anchusa azurea Mill.

METHODS

In this study, various extracts from Anchusa azurea Mill. (AA) using solvents with increasing polarity were prepared. The quantification of polyphenols and flavonoids was determined. The anti-radical activity of the different extracts was evaluated using DPPH and by measuring the inhibition of the oxidative degradation of β-carotene. The In-vitro antihemolytic effect of the plant extracts is determined (CrE, ChE, AcE, and AqE). For each extract, four concentrations were tested: 10.59, 21.18, 42.37, 84.74 μg/ml. Vitamin C is used as a standard. The free-radical attack was measured by measuring the HT₅₀ (Half-Hemolysis Time). The anti-inflammatory effect using PMA on mice of the methanolic extract (CrE) was evaluated.

RESULTS

The quantification of polyphenols and flavonoids showed that ethyl acetate extract (AcE) contains a higher amount of polyphenols. However, chloroform extract (ChE) presents a higher amount of flavonoids. AcE showed an important scavenging activity using the DPPH radical (IC₅₀= 68.35 μg/ml). The results showed that AcE also exhibited a significant inhibition effect on the oxidation of β-carotene/linoleic acid (84.33 %). All extracts increased the HT50 values (Half-Hemolysis Time) in a dose-dependent manner. The three highest concentrations (21.18, 42.37, and 84.74 μg / ml) of ChE caused a very significant delay (p ≤ 0.001) of hemolysis compared to the negative control and the positive control "VIT C". The anti-inflammatory effect of using PMA on mice showed that the methanolic extract (CrE) of AA reduced the weight of the ear edema.

CONCLUSION

This plant has a strong pharmacological power, which supports its traditional medicinal use.

Phospholipase A2 enzymes represent a shared pathogenic pathway in psoriasis and pityriasis rubra pilaris

Altered epidermal differentiation along with increased keratinocyte proliferation is a characteristic feature of psoriasis and pityriasis rubra pilaris (PRP). However, despite this large degree of overlapping clinical and histologic features, the molecular signatures these skin disorders share are unknown. Using global transcriptomic profiling, we demonstrate that plaque psoriasis and PRP skin lesions have high overlap, with all differentially expressed genes in PRP relative to normal skin having complete overlap with those in psoriasis. The major common pathway shared between psoriasis and PRP involves the phospholipases PLA2G2F, PLA2G4D, and PLA2G4E, which were found to be primarily expressed in the epidermis. Gene silencing each of the 3 PLA2s led to reduction in immune responses and epidermal thickness both in vitro and in vivo in a mouse model of psoriasis, establishing their proinflammatory roles. Lipidomic analyses demonstrated that PLA2s affect mobilization of a phospholipid-eicosanoid pool, which is altered in psoriatic lesions and functions to promote immune responses in keratinocytes. Taken together, our results highlight the important role of PLA2s as regulators of epidermal barrier homeostasis and inflammation, identify PLA2s as a shared pathogenic mechanism between PRP and psoriasis, and as potential therapeutic targets for both diseases.

Research Progress of Therapeutic Enzymes and Their Derivatives: Based on Herbal Medicinal Products in Rheumatoid Arthritis

Rheumatoid arthritis (RA) acts as one of the most common, agnogenic and chronic inflammatory-autoimmune disorder which is characterized by persistent synovitis, cartilage destruction, and joint deformities, leads to a wide range of disabilities, and increased mortality, thus imposing enormous burdens. Several drugs with anti-inflammatory and immunomodulatory properties such as celecoxib, diclofenac and methotrexate are being selected as conventional drugs in the allopathic system of medicine for the treatment of RA in clinic. However, there are some serious side effects more or less when using these drugs because of their short poor bioavailability and biological half-life for a long time. These shortcomings greatly promote the exploration and application of new low- or no-toxicity drugs for treating the RA. Meanwhile, a growing number of studies demonstrate that several herbs present certain anti-inflammatory and anti-arthritic activities through different enzymes and their derivatives, which indicate that they are promising therapeutic strategies when targeting these mediators based on herbal medicinal products in RA research. This review article summarizes the roles of the main enzymes and their derivatives during the pathogenesis of RA, and clearly clarifies the explicit and potential targeted actions of herbal medicinal products that have anti-RA activity. Our review provides timely and critical reference for the scientific rationale use of herbal medicinal products, with the increasing basic research and clinical application of herbal medicinal products by patients with RA.

cPLA2α Enzyme Inhibition Attenuates Inflammation and Keratinocyte Proliferation

As a regulator of cellular inflammation and proliferation, cytosolic phospholipase A₂ α (cPLA₂α) is a promising therapeutic target for psoriasis; indeed, the cPLA₂α inhibitor AVX001 has shown efficacy against plaque psoriasis in a phase I/IIa clinical trial. To improve our understanding of the anti-psoriatic properties of AVX001, we sought to determine how the compound modulates inflammation and keratinocyte hyperproliferation, key characteristics of the psoriatic epidermis. We measured eicosanoid release from human peripheral blood mononuclear cells (PBMC) and immortalized keratinocytes (HaCaT) and studied proliferation in HaCaT grown as monolayers and stratified cultures. We demonstrated that inhibition of cPLA₂α using AVX001 produced a balanced reduction of prostaglandins and leukotrienes; significantly limited prostaglandin E₂ (PGE₂) release from both PBMC and HaCaT in response to pro-inflammatory stimuli; attenuated growth factor-induced arachidonic acid and PGE₂ release from HaCaT; and inhibited keratinocyte proliferation in the absence and presence of exogenous growth factors, as well as in stratified cultures. These data suggest that the anti-psoriatic properties of AVX001 could result from a combination of anti-inflammatory and anti-proliferative effects, probably due to reduced local eicosanoid availability.

Cytosolic group IVA phospholipase A2 inhibitors, AVX001 and AVX002, ameliorate collagen-induced arthritis

Background

Cytosolic phospholipase A2 group IVA (cPLA2α)-deficient mice are resistant to collagen-induced arthritis, suggesting that cPLA2α is an important therapeutic target. Here, the anti-inflammatory effects of the AVX001 and AVX002 cPLA2α inhibitors were investigated.

Methods

In vitro enzyme activity was assessed by a modified Dole assay. Effects on inhibiting IL-1β-induced release of arachidonic acid (AA) and prostaglandin E2 (PGE2) were measured using SW982 synoviocyte cells. In vivo effects were studied in prophylactic and therapetic murine collagen-induced arthritis models and compared to methotrexate (MTX) and Enbrel, commonly used anti-rheumatic drugs. The in vivo response to treatment was evaluated in terms of the arthritis index (AI), histopathology scores and by plasma levels of PGE2 following 14 and 21 days of treatment.

Results

Both cPLA2α inhibitors are potent inhibitors of cPLA2α in vitro. In synoviocytes, AVX001 and AVX002 reduce, but do not block, release of AA or PGE2 synthesis. In both CIA models, the AI and progression of arthritis were significantly lower in the mice treated with AVX001, AVX002, Enbrel and MTX than in non- treated mice. Several histopathology parameters of joint damage were found to be significantly reduced by AVX001 and AVX002 in both prophylactic and therapeutic study modes; namely articular cavity and peripheral tissue inflammatory cell infiltration; capillary and synovial hyperplasia; articular cartilage surface damage; and periostal and endochondral ossification. In comparison, MTX did not significantly improve any histopathology parameters and Enbrel only improved ossification. Finally, as a biomarker of inflammation and as an indication that AVX001 and AVX002 blocked the cPLA2α target, we determined that plasma levels of PGE2 were significantly reduced in response to the AVX inhibitors and MTX, but not Enbrel.

Conclusions

AVX001 and AVX002 display potent anti-inflammatory activity and disease-modifying properties in cellular and in vivo models. The in vivo effects of AVX001 and AVX002 were comparable to, or superior, to those of MTX and Enbrel. Taken together, this study suggests that cPLA2α inhibitors AVX001 and AVX002 are promising small molecule disease-modifying anti-rheumatic therapies.

The Roles of the Secreted Phospholipase A2 Gene Family in Immunology

Within the phospholipase A₂ (PLA₂) family that hydrolyzes phospholipids to yield fatty acids and lysophospholipids, secreted PLA₂ (sPLA₂) enzymes comprise the largest group containing 11 isoforms in mammals. Individual sPLA₂s exhibit unique tissue or cellular distributions and enzymatic properties, suggesting their distinct biological roles. Although PLA₂ enzymes, particularly cytosolic PLA₂ (cPLA₂α), have long been implicated in inflammation by driving arachidonic acid metabolism, the precise biological roles of sPLA₂s have remained a mystery over the last few decades. Recent studies employing mice gene-manipulated for individual sPLA₂s, in combination with mass spectrometric lipidomics to identify their target substrates and products in vivo, have revealed their roles in diverse biological events, including immunity and associated disorders, through lipid mediator-dependent or -independent processes in given microenvironments. In this review, we summarize our current knowledge of the roles of sPLA₂s in various immune responses and associated diseases.

Cytosolic phospholipase A2 modulates TLR2 signaling in synoviocytes

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic synovitis leading to destruction of cartilage and bone. PLA2 enzymes are key players in inflammation regulating the release of unsaturated fatty acids such as arachidonic acid (AA), a precursor of pro-inflammatory eicosanoids. Several lines of evidence point to toll-like receptors (TLRs) as drivers of synovitis and joint destruction in RA. However, few studies have addressed the implication of PLA2 activity downstream TLR activation in the synovium. Here, we aimed to characterize PLA2 enzyme involvement in TLR2-induced signaling in synovial fibroblast-like cells. TLRs1-7 and a range of sPLA2, iPLA2 and cPLA2 enzymes were found to be transcriptionally expressed in cultured synoviocytes. Activation of TLR2/1 and TLR2/6 led to phosphorylation of cPLA2α at Ser⁵⁰⁵, and induced AA release and PGE₂ production; effects that were attenuated by cPLA2α inhibitors. In contrast, sPLA2 inhibitors did not affect AA or PGE₂ release. cPLA2α inhibitors furthermore attenuated TLR-induced expression of IL-6, IL-8 and COX2. COX1/2 inhibitors attenuated TLR2/6-induced IL-6 transcription and protein production comparable to cPLA2α inhibition. Moreover, exogenously PGE₂ added alone induced IL-6 production and completely rescued IL-6 transcription when added simultaneously with FSL-1 in the presence of a cPLA2α inhibitor. Our results demonstrate for the first time that cPLA2α is involved in TLR2/1- and TLR2/6-induced AA release, PGE₂ production and pro-inflammatory cytokine expression in synoviocytes, possibly through COX/PGE₂-dependent pathways. These findings expand our understanding of cPLA2α as a modulator of inflammatory molecular mechanisms in chronic diseases such as RA.

Cytosolic phospholipase A2 regulates TNF-induced production of joint destructive effectors in synoviocytes

INTRODUCTION

Rheumatoid arthritis (RA) is an inflammatory disease of the joint characterized by chronic synovitis causing pain, swelling and loss of function due to destruction of cartilage and bone. The complex series of pathological events occurring in RA is largely regulated via excessive production of pro-inflammatory cytokines, the most prominent being tumor necrosis factor (TNF). The objective of this work was to elucidate possible involvement of group IVA cytosolic phospholipase A2 (cPLA2α) in TNF-induced regulation of synovitis and joint destructive effectors in RA, to evaluate the potential of cPLA2α as a future therapeutic target.

METHODS

The involvement of cPLA2α in tumor necrosis factor (TNF)-induced intracellular signaling cascades in synoviocytes (synovial fibroblast-like cells) was analyzed by arachidonic acid (AA) release assay, synoviocyte enzyme activity assay, gene expression analysis by real-time PCR and ELISA immunoassay for the detection of prostaglandin E2 (PGE2), interleukin 8 (IL8) and stromelysin-1 (MMP3), respectively.

RESULTS

Inhibitors of cPLA2α enzyme activity (AVX002, ATK) significantly reduced TNF-induced cellular release of AA, PGE2, IL8 and MMP3. This reduction was evident both at transcriptional, protein or metabolite levels. Interestingly, cPLA2α inhibition affected several key points of the arachidonyl cascade; AA-release, cyclooxygenase-2 (COX2) expression and PGE2 production. Furthermore, the results suggest that cPLA2α is subject to transcriptional auto-regulation as inhibition of cPLA2α resulted in reduced PLA2G4A gene expression in TNF-stimulated synoviocytes.

CONCLUSIONS

cPLA2α appears to be an important regulator of central effectors of inflammation and joint destruction, namely MMP3, IL8, COX2, and PGE2. Decreased transcription of the PLA2G4A and COX2 genes in response to cPLA2α enzyme inhibition further suggest a self-reinforcing effect of cPLA2α inhibition in response to TNF. Collectively, these results support that cPLA2α is an attractive therapeutic target candidate as its inhibition reduces the production of multiple key pro-inflammatory factors involved in RA pathogenesis.

The involvement of phospholipases A2 in asthma and chronic obstructive pulmonary disease

The increased morbidity, mortality, and ineffective treatment associated with the pathogenesis of chronic inflammatory diseases such as asthma and chronic obstructive pulmonary disease (COPD) have generated much research interest. The key role is played by phospholipases from the A2 superfamily: enzymes which are involved in inflammation through participation in pro- and anti-inflammatory mediators production and have an impact on many immunocompetent cells. The 30 members of the A2 superfamily are divided into 7 groups. Their role in asthma and COPD has been studied in vitro and in vivo (animal models, cell cultures, and patients). This paper contains complete and updated information about the involvement of particular enzymes in the etiology and course of asthma and COPD.

The ω3-polyunsaturated fatty acid derivatives AVX001 and AVX002 directly inhibit cytosolic phospholipase A(2) and suppress PGE(2) formation in mesangial cells

BACKGROUND AND PURPOSE

ω3-polyunsaturated fatty acids (ω3-PUFAs) are known to exert anti-inflammatory effects in various disease models although their direct targets are only poorly characterized.

EXPERIMENTAL APPROACH

Here we report on two new cPLA(2) inhibitors, the ω3-derivatives AVX001 and AVX002, and their effects on inflammatory PGE(2) production in cultures of renal mesangial cells.

KEY RESULTS

AVX001 and AVX002 dose-dependently inhibited the group IVA cytosolic phospholipase A(2) (cPLA(2) ) in an in vitro activity assay with similar IC(50) values for AVX001 and AVX002, whereas the known cPLA(2) inhibitor AACOCF(3) was less potent and docosahexaenoic acid (DHA) was inactive. In renal mesangial cells, AVX001 and AVX002 suppressed IL-1β-induced PGE(2) synthesis. Mechanistically, this effect occurred by a down-regulation of IL-1β-induced group IIA-sPLA(2) protein expression, mRNA expression and promoter activity. A similar but less potent effect was seen with AACOCF(3) and no effect was seen with DHA. As gene expression of sPLA(2) is known to be regulated by the transcription factor NF-κB, we further investigated NF-κB activation. Both compounds prevented NF-κB activation by blocking degradation of the inhibitor of κB.

CONCLUSIONS AND IMPLICATIONS

These data show for the first time that the novel cPLA(2) inhibitors AVX001 and AVX002 exert an anti-inflammatory effect in cultures of renal mesangial cells and reduce the pro-inflammatory mediator PGE(2) through an inhibitory effect on NF-κB activation. Therefore, these compounds may represent promising novel drugs for the treatment of inflammatory disorders.

Leukotrienes and airway inflammation

BACKGROUND

Asthma is a common chronic inflammatory disease of the airways characterized by airway obstruction and hyperresponsiveness. Leukotrienes (LTs) are lipid mediators that contribute to many aspects of asthma pathogenesis. As the LT pathway is relatively steroid-resistant, its blockade by alternative strategies is a desirable component of asthma management. Cysteinyl LT (cysLT) receptor 1 antagonists (LTRAs) have been utilized worldwide for more than 10years, and while their efficacy in asthma is well accepted, their limitations are also evident.

SCOPE OF REVIEW

In this review, we summarize the biological effects of LTs in asthma, review recent advances in LT receptors, and consider possible new therapeutic targets in the LT pathway that offer the potential to achieve better control of asthma in the future.

MAJOR CONCLUSIONS

CysLTs play pathogenetic roles in many aspects of asthma, and blockade of cysLT receptor 1 by currently available LTRAs is certainly beneficial in disease management. On the other hand, the limitations of LTRAs are also apparent. Recent studies have revealed new receptors for cysLTs other than classical cysLT receptors 1 and 2, as well as the potential importance of LTB(4) in asthma.

GENERAL SIGNIFICANCE

Recent findings provide clues to new approaches for targeting the LT pathway that may overcome the current limitations of LTRAs and achieve superior control of asthma. This article is part of a Special Issue entitled: Biochemistry of Asthma.

Ginger phenylpropanoids inhibit IL-1beta and prostanoid secretion and disrupt arachidonate-phospholipid remodeling by targeting phospholipases A2

The rhizome of ginger (Zingiber officinale) is employed in Asian traditional medicine to treat mild forms of rheumatoid arthritis and fever. We have profiled ginger constituents for robust effects on proinflammatory signaling and cytokine expression in a validated assay using human whole blood. Independent of the stimulus used (LPS, PMA, anti-CD28 Ab, anti-CD3 Ab, and thapsigargin), ginger constituents potently and specifically inhibited IL-1β expression in monocytes/macrophages. Both the calcium-independent phospholipase A(2) (iPLA(2))-triggered maturation and the cytosolic phospholipase A(2) (cPLA(2))-dependent secretion of IL-1β from isolated human monocytes were inhibited. In a fluorescence-coupled PLA(2) assay, most major ginger phenylpropanoids directly inhibited i/cPLA(2) from U937 macrophages, but not hog pancreas secretory phospholipase A(2). The effects of the ginger constituents were additive and the potency comparable to the mechanism-based inhibitor bromoenol lactone for iPLA(2) and methyl arachidonyl fluorophosphonate for cPLA(2), with 10-gingerol/-shogaol being most effective. Furthermore, a ginger extract (2 μg/ml) and 10-shogaol (2 μM) potently inhibited the release of PGE(2) and thromboxane B2 (>50%) and partially also leukotriene B(4) in LPS-stimulated macrophages. Intriguingly, the total cellular arachidonic acid was increased 2- to 3-fold in U937 cells under all experimental conditions. Our data show that the concurrent inhibition of iPLA(2) and prostanoid production causes an accumulation of free intracellular arachidonic acid by disrupting the phospholipid deacylation-reacylation cycle. The inhibition of i/cPLA(2), the resulting attenuation of IL-1β secretion, and the simultaneous inhibition of prostanoid production by common ginger phenylpropanoids uncover a new anti-inflammatory molecular mechanism of dietary ginger that may be exploited therapeutically.

Recent progress in phospholipase A₂ research: from cells to animals to humans

Mammalian genomes encode genes for more than 30 phospholipase A₂s (PLA₂s) or related enzymes, which are subdivided into several classes including low-molecular-weight secreted PLA₂s (sPLA₂s), Ca²+-dependent cytosolic PLA₂s (cPLA₂s), Ca²+-independent PLA₂s (iPLA₂s), platelet-activating factor acetylhydrolases (PAF-AHs), lysosomal PLA₂s, and a recently identified adipose-specific PLA. Of these, the intracellular cPLA₂ and iPLA₂ families and the extracellular sPLA₂ family are recognized as the "big three". From a general viewpoint, cPLA₂α (the prototypic cPLA₂ plays a major role in the initiation of arachidonic acid metabolism, the iPLA₂ family contributes to membrane homeostasis and energy metabolism, and the sPLA₂ family affects various biological events by modulating the extracellular phospholipid milieus. The cPLA₂ family evolved along with eicosanoid receptors when vertebrates first appeared, whereas the diverse branching of the iPLA₂ and sPLA₂ families during earlier eukaryote development suggests that they play fundamental roles in life-related processes. During the past decade, data concerning the unexplored roles of various PLA₂ enzymes in pathophysiology have emerged on the basis of studies using knockout and transgenic mice, the use of specific inhibitors, and information obtained from analysis of human diseases caused by mutations in PLA₂ genes. This review focuses on current understanding of the emerging biological functions of PLA₂s and related enzymes.

Arachidonyl trifluoromethyl ketone is neuroprotective after spinal cord injury

In spinal cord injury (SCI), neuronal and oligodendroglial loss occurs as a result of the initial trauma and the secondary damage that is triggered by excitotoxicity, free radicals, and inflammation. There is evidence that SCI ellicits increased cytosolic phospholipase A(2) (cPLA(2)) activity. The cleavage of phospholipids by cPLA(2) leads to release of fatty acids, and in particular arachidonic acid (AA), the metabolites of which have been associated with increased inflammation and oxidative stress. The aim of our study was to investigate whether the inhibition of cPLA(2) following SCI leads to tissue protection and an improved functional outcome. Adult rats received compression SCI and 30 min after injury they were treated intravenously with either saline or the cPLA(2) inhibitor arachidonyl trifluoromethyl ketone (AACOCF3) (7.13 mg/kg). The animals were sacrificed at 7 days post-injury and the lesioned tissue was labeled using markers for neurons, oligodendrocytes, and macrophages/activated microglia. We also assessed locomotor recovery using the Basso-Beattie-Bresnahan (BBB) score. The number of surviving neurons and oligodendrocytes was significantly increased in animals treated with the cPLA(2) inhibitor compared to saline controls. The behavioral analysis mirrored the neuroprotective effects and showed that the inhibitor-treated group had better locomotor recovery compared to saline controls. Our results show that AACOCF3 has neuroprotective potential, and support the idea that cPLA(2) is critically involved in acute spinal injury.

TLR4-dependent induction of vascular adhesion molecule-1 in rheumatoid arthritis synovial fibroblasts: Roles of cytosolic phospholipase A(2)alpha/cyclooxygenase-2

Lipopolysaccharide (LPS)/Toll-like receptor 4 (TLR4)-mediated signaling pathways have caught the attention of strategies designed for rheumatoid arthritis (RA). In this study, we identified that cPLA(2)alpha acted as a modulator of LPS-induced VCAM-1 expression and THP-1 (human acute monocytic leukemia cell line) adherence. Treatment of RA synovial fibroblasts (RASFs) with LPS, a TLR4 agonist, promoted the VCAM-1 expression and THP-1 adherence which were decreased by pretreatment with a selective cytosolic phospholipase A(2) (cPLA(2)) inhibitor (AACOCF(3)), implying the involvement of cPLA(2)alpha in these responses. This notion was further confirmed by knockdown of cPLA(2)alpha expression by transfection with cPLA(2)alpha small interfering RNA (siRNA) leading to a decrease in VCAM-1 expression and THP-1 adherence induced by LPS. Subsequently, the LPS-stimulated cPLA(2)alpha phosphorylation was attenuated by pretreatment with a MEK1/2 inhibitor (U0126), suggesting that LPS-stimulated cPLA(2)alpha phosphorylation and activity are mediated through an ERK-dependent mechanism. Moreover, COX-2-derived PGE(2) production appeared to involve in LPS-induced VCAM-1 expression which was attenuated by pretreatment with selective COX-2 inhibitors (NS-398 and celecoxib), transfection with COX-2 siRNA, or PGE(2) receptor antagonists. In addition, pretreatment with ecosapentaenoic acid (EPA), a substrate competitor of arachidonic acid (AA), also blocked LPS-induced VCAM-1 mRNA and protein expression, and THP-1 adherence. Collectively, these results suggest that LPS-induced VCAM-1 expression and adhesion of THP-1 cells are mediated through the TLR4/ERK/cPLA(2)alpha phosphorylation and COX-2 expression/PGE(2) synthesis in RASFs.

Ceramide 1-phosphate is required for the translocation of group IVA cytosolic phospholipase A2 and prostaglandin synthesis

Little is known about the regulation of eicosanoid synthesis proximal to the activation of cytosolic phospholipase A(2)alpha (cPLA(2)alpha), the initial rate-limiting step. The current view is that cPLA(2)alpha associates with intracellular/phosphatidylcholine-rich membranes strictly via hydrophobic interactions in response to an increase of intracellular calcium. In opposition to this accepted mechanism of two decades, ceramide 1-phosphate (C1P) has been shown to increase the membrane association of cPLA(2)alpha in vitro via a novel site in the cationic beta-groove of the C2 domain (Stahelin, R. V., Subramanian, P., Vora, M., Cho, W., and Chalfant, C. E. (2007) J. Biol. Chem. 282, 20467-204741). In this study we demonstrate that C1P is a proximal and required bioactive lipid for the translocation of cPLA(2)alpha to intracellular membranes in response to inflammatory agonists (e.g. calcium ionophore and ATP). Last, the absolute requirement of the C1P/cPLA(2)alpha interaction was demonstrated for the production of eicosanoids using murine embryonic fibroblasts (cPLA(2)alpha(-/-)) coupled to "rescue" studies. Therefore, this study provides a paradigm shift in how cPLA(2)alpha is activated during inflammation.

Lipids as targets for novel anti-inflammatory therapies

Lipids serve important functions as membrane constituents and also as energy storing molecules. Besides these functions certain lipid species have now been recognized as signalling molecules that regulate a multitude of cellular responses including cell growth and death, and also inflammatory reactions. Bioactive lipids are generated by hydrolysis from membrane lipids mainly by phospholipases giving rise to fatty acids and lysophospholipids that either directly exert their function or are further converted to active mediators. This review will summarize the present knowledge about bioactive lipids that either promote or attenuate inflammatory reactions. These lipids include polyunsaturated fatty acids (PUFA), eicosanoids including the epoxyeicosatrienoic acids (EET), peroxisome proliferation activating receptor (PPAR) activators, cannabinoids and the sphingolipids ceramide, sphingosine 1-phosphate and sphingosylphosphorylcholine.

Structure-activity relationship of 2-oxoamide inhibition of group IVA cytosolic phospholipase A2 and group V secreted phospholipase A2

The Group IVA cytosolic phospholipase A2 (GIVA cPLA2) is a key provider of substrates for the production of eicosanoids and platelet-activating factor. We explored the structure-activity relationship of 2-oxoamide-based compounds and GIVA cPLA2 inhibition. The most potent inhibitors are derived from delta- and gamma-amino acid-based 2-oxoamides. The optimal side-chain moiety is a short nonpolar aliphatic chain. All of the newly developed 2-oxoamides as well as those previously described have now been tested with the human Group V secreted PLA2 (GV sPLA2) and the human Group VIA calcium-independent PLA2 (GVIA iPLA2). Only one 2-oxoamide compound had appreciable inhibition of GV sPLA2, and none of the potent GIVA cPLA2 inhibitors inhibited either GV sPLA2 or GVIA iPLA2. Two of these specific GIVA cPLA2 inhibitors were also found to have potent therapeutic effects in animal models of pain and inflammation at dosages well below the control nonsteroidal anti-inflammatory drugs.

Interactions between neural membrane glycerophospholipid and sphingolipid mediators: A recipe for neural cell survival or suicide

The neural membranes contain phospholipids, sphingolipids, cholesterol, and proteins. Glycerophospholipids and sphingolipids are precursors for lipid mediators involved in signal transduction processes. Degradation of glycerophospholipids by phospholipase A(2) (PLA(2)) generates arachidonic acid (AA) and docosahexaenoic acids (DHA). Arachidonic acid is metabolized to eicosanoids and DHA is metabolized to docosanoids. The catabolism of glycosphingolipids generates ceramide, ceramide 1-phosphate, sphingosine, and sphingosine 1-phosphate. These metabolites modulate PLA(2) activity. Arachidonic acid, a product derived from glycerophospholipid catabolism by PLA(2), modulates sphingomyelinase (SMase), the enzyme that generates ceramide and phosphocholine. Furthermore, sphingosine 1-phosphate modulates cyclooxygenase, an enzyme responsible for eicosanoid production in brain. This suggests that an interplay and cross talk occurs between lipid mediators of glycerophospholipid and glycosphingolipid metabolism in brain tissue. This interplay between metabolites of glycerophospholipid and sphingolipid metabolism may play an important role in initiation and maintenance of oxidative stress associated with neurologic disorders as well as in neural cell proliferation, differentiation, and apoptosis. Recent studies indicate that PLA(2) and SMase inhibitors can be used as neuroprotective and anti-apoptotic agents. Development of novel inhibitors of PLA(2) and SMase may be useful for the treatment of oxidative stress, and apoptosis associated with neurologic disorders such as stroke, Alzheimer disease, Parkinson disease, and head and spinal cord injuries.