Cytosolic phospholipase A2 modulates TLR2 signaling in synoviocytes

Inhibition of DYRK1B BY C81 impedes inflammatory processes in leukocytes by reducing STAT3 activity

Chronic inflammatory diseases are a significant global burden and are associated with dysregulated resolution of inflammation. Therefore, promoting the process of resolution is a promising therapeutic approach. This study presents the potent anti-inflammatory and pro-resolving effects of a natural product-derived compound called C81. Administration of C81 in a therapeutic window resolved inflammation in the murine imiquimod-induced psoriasis model, and reduced microglial infiltration in a laser-induced choroidal neovascularisation model. Investigations into the underlying mechanisms of C81 identified the DYRK1B/STAT3 axis as a new regulator of inflammatory processes in leukocytes. The inhibition of DYRK1B by C81 resulted in attenuated STAT3 phosphorylation. The depletion of STAT3-regulated gene expression led to the inhibition of leukocyte adhesion and migration due to reduced integrin activation, and in addition to the inhibition of the release of pro-inflammatory mediators such as cytokines and eicosanoids. Importantly, the pro-resolving effects of C81 included the cell type-specific induction of apoptosis in neutrophils and a subsequent increase in efferocytosis. In conclusion, we report the DYRK1B/STAT3 axis as a novel and promising therapeutic target for activating the resolution of inflammation.

Maximal Information Coefficient-Based Testing to Identify Epistasis in Case-Control Association Studies

Interactions between genetic variants (epistasis) are ubiquitous in the model system and can significantly affect evolutionary adaptation, genetic mapping, and precision medical efforts. In this paper, we proposed a method for epistasis detection, called EpiMIC (epistasis detection through a maximal information coefficient (MIC)). MIC is a promising bivariate dependence measure explicitly designed for rapidly exploring various function types equally and for interpreting and comparing them on the same scale. Most epistasis detection approaches make assumptions about the form of the association between genetic variants, resulting in limited statistical performance. Based on the notion that if two SNPs do not interact, their joint distribution in all samples and in only cases should not be substantially different. We developed a statistic that utilizes the difference of MIC as a signal of epistasis and combined it with a permutation resampling strategy to estimate the empirical distribution of our statistic. Results of simulation and real-world data set showed that EpiMIC outperformed previous approaches for identifying epistasis at varying degrees of heredity.

Inhibition of Cytosolic Phospholipase A2α Induces Apoptosis in Multiple Myeloma Cells

Cytosolic phospholipase A2α (cPLA2α) is the rate-limiting enzyme in releasing arachidonic acid and biosynthesis of its derivative eicosanoids. Thus, the catalytic activity of cPLA2α plays an important role in cellular metabolism in healthy as well as cancer cells. There is mounting evidence suggesting that cPLA2α is an interesting target for cancer treatment; however, it is unclear which cancers are most relevant for further investigation. Here we report the relative expression of cPLA2α in a variety of cancers and cancer cell lines using publicly available datasets. The profiling of a panel of cancer cell lines representing different tissue origins suggests that hematological malignancies are particularly sensitive to the growth inhibitory effect of cPLA2α inhibition. Several hematological cancers and cancer cell lines overexpressed cPLA2α, including multiple myeloma. Multiple myeloma is an incurable hematological cancer of plasma cells in the bone marrow with an emerging requirement of therapeutic approaches. We show here that two cPLA2α inhibitors AVX420 and AVX002, significantly and dose-dependently reduced the viability of multiple myeloma cells and induced apoptosis in vitro. Our findings implicate cPLA2α activity in the survival of multiple myeloma cells and support further studies into cPLA2α as a potential target for treating hematological cancers, including multiple myeloma.

Activation of the cytosolic calcium-independent phospholipase A2 β isoform contributes to TRPC6 externalization via release of arachidonic acid

During vascular interventions, oxidized low-density lipoprotein and lysophosphatidylcholine (lysoPC) accumulate at the site of arterial injury, inhibiting endothelial cell (EC) migration and arterial healing. LysoPC activates canonical transient receptor potential 6 (TRPC6) channels, leading to a prolonged increase in intracellular calcium ion concentration that inhibits EC migration. However, an initial increase in intracellular calcium ion concentration is required to activate TRPC6, and this mechanism remains elusive. We hypothesized that lysoPC activates the lipid-cleaving enzyme phospholipase A₂ (PLA₂), which releases arachidonic acid (AA) from the cellular membrane to open arachidonate-regulated calcium channels, allowing calcium influx that promotes externalization and activation of TRPC6 channels. The focus of this study was to identify the roles of calcium-dependent and/or calcium-independent PLA₂ in lysoPC-induced TRPC6 externalization. We show that lysoPC induced PLA₂ enzymatic activity and caused AA release in bovine aortic ECs. To identify the specific subgroup and the isoform(s) of PLA₂ involved in lysoPC-induced TRPC6 activation, transient knockdown studies were performed in the human endothelial cell line EA.hy926 using siRNA to inhibit the expression of genes encoding cPLA₂α, cPLA₂γ, iPLA₂β, or iPLA₂γ. Downregulation of the β isoform of iPLA₂ blocked lysoPC-induced release of AA from EC membranes and TRPC6 externalization, as well as preserved EC migration in the presence of lysoPC. We propose that blocking TRPC6 activation and promoting endothelial healing could improve the outcomes for patients undergoing cardiovascular interventions.

Targeting Toll-like Receptor (TLR) Pathways in Inflammatory Arthritis: Two Better Than One?

Inflammatory arthritis is a cluster of diseases caused by unregulated activity of the immune system. The lost homeostasis is followed by the immune attack of one’s self, what damages healthy cells and tissues and leads to chronic inflammation of various tissues and organs (e.g., joints, lungs, heart, eyes). Different medications to control the excessive immune response are in use, however, drug resistances, flare-reactions and adverse effects to the current therapies are common in the affected patients. Thus, it is essential to broaden the spectrum of alternative treatments and to develop disease-modifying drugs. In the last 20 years, the involvement of the innate immune receptors TLRs in inflammatory arthritis has been widely investigated and targeting either the receptor itself or the proteins in the downstream signalling cascades has emerged as a promising therapeutic strategy. Yet, concerns about the use of pharmacological agents that inhibit TLR activity and may leave the host unprotected against invading pathogens and toxicity issues amid inhibition of downstream kinases crucial in various cellular functions have arisen. This review summarizes the existing knowledge on the role of TLRs in inflammatory arthritis; in addition, the likely druggable related targets and the developed inhibitors, and discusses the pros and cons of their potential clinical use.

TLRs Play Crucial Roles in Regulating RA Synoviocyte

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease comparing the inflammation of synovium. Macrophage-like synoviocytes and fibroblast-like synoviocytes (synoviocytes) are crucial ingredients of synovium. Therein, a lot of research has focused on synoviocytes. Researches demonstrated that TLR1, TLR2, TLR3, TLR4, TLR5, TLR6 TLR7 and TLR9 are expressed in synoviocyte. Additionally, the expression of TLR2, TLR3, TLR4 and TLR5 is increased in RA synoviocyte. In this paper, we review the exact role of TLR2, TLR3, TLR4 and TLR5 participate in regulating the production of inflammatory factors in RA synoviocyte. Furthermore, we discuss the role of vasoactive intestinal peptide (VIP), MicroRNA, Monome of Chinese herb and other cells (Monocyte and T cell) influence the function of synoviocyte by regulating TLRs. The activation of toll-like receptors (TLRs) in synoviocyte leads to the aggravation of arthritis, comparing with angiogenesis and bone destruction. Above all, TLRs are promising targets for managing RA.

Potential role of bioactive lipids in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease, which involves a pathological inflammatory response against articular cartilage in multiple joints throughout the body. It is a complex disorder associated with comorbidities such as depression, lymphoma, osteoporosis and cardiovascular disease (CVD), which significantly deteriorate patients' quality of life and prognosis. This has ignited a large initiative to elucidate the physiopathology of RA, aiming to identify new therapeutic targets and approaches in its multidisciplinary management. Recently, various lipid bioactive products have been proposed to have an essential role in this process; including eicosanoids, specialized pro-resolving mediators, phospholipids/sphingolipids, and endocannabinoids. Dietary interventions using omega-3 polyunsaturated fatty acids or treatment with synthetic endocannabinoids agonists have been shown to significantly ameliorate RA symptoms. Indeed, the modulation of lipid metabolism may be crucial in the pathophysiology and treatment of autoimmune diseases.

Skeletal muscle redox signaling in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by synovitis and the presence of serum autoantibodies. In addition, skeletal muscle weakness is a common comorbidity that contributes to inability to work and reduced quality of life. Loss in muscle mass cannot alone account for the muscle weakness induced by RA, but instead intramuscular dysfunction appears as a critical factor underlying the decreased force generating capacity for patients afflicted by arthritis. Oxidative stress and associated oxidative post-translational modifications have been shown to contribute to RA-induced muscle weakness in animal models of arthritis and patients with RA. However, it is still unclear how and which sources of reactive oxygen and nitrogen species (ROS/RNS) that are involved in the oxidative stress that drives the progression toward decreased muscle function in RA. Nevertheless, mitochondria, NADPH oxidases (NOX), nitric oxide synthases (NOS) and phospholipases (PLA) have all been associated with increased ROS/RNS production in RA-induced muscle weakness. In this review, we aim to cover potential ROS sources and underlying mechanisms of oxidative stress and loss of force production in RA. We also addressed the use of antioxidants and exercise as potential tools to counteract oxidative stress and skeletal muscle weakness.

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.

MicroRNA-146a as a Prognostic Biomarker for Esophageal Squamous Cell Carcinoma

Background and Aims

MicroRNAs including miR146a have a regulatory role on the expression of genes and act with binding to 3'-UTR region of the genes. Cyclooxygenase-2 (COX-2) is involved in carcinogenesis as an inflammatory marker, and microRNA-146a (miR-146a) as a negative regulatory factor. We aimed to evaluate miR146a expression as a prognostic or diagnostic biomarker for esophageal squamous cell carcinoma (ESCC) and also an association between miR146a and COX2 expression.

Materials and Methods

We quantified the level of miR-146a and COX-2 expression in cancerous and adjacent normal tissue samples obtained from 34 patients with ESCC, using real-time-PCR. Statistical analyses were conducted using one-sample t-test. Receiver-operating characteristic (ROC) curve and Kaplan-Meier analysis were applied to assay miR146a as a diagnostic and prognostic marker, respectively, during 4 years of the study. Furthermore, the Cox regression model was performed to assay the hazard ratio (HR). The association between miR-146a and COX2 expression level in ESCC patients was evaluated by nonparametric Spearman's rho analysis.

Results

The results revealed a reduction of miR-146a expression in 50% of cancerous tissue when compared with adjacent normal regions (P-value=0.127). COX-2 expression in 80% of ESCC patients was higher than in the controls (P-value=0.001). Overall, in 60% of cases, direct association was seen between microRNA-146a and COX-2 expression level (correlation coefficient= 0.438, P-value=0.011). COX2 can be considered as a diagnostic biomarker (AUC=0.834, sensitivity=72%, specificity =83%, P-value<0.0001) but miR146a cannot be considered as a diagnostic biomarker (AUC=0.553, sensitivity=88%, specificity =28%, P-value=0.453). Survival analysis by Kaplan-Meier method showed miR146a and COX2 expression can be probably considered as prognostic biomarkers for ESCC because patients with high expression of miR146a had 7 months shorter life span and patients with low expression of COX2 had 8 months shorter life span.

Conclusion

COX2 expression is a diagnostic biomarker. MiR-146a and COX2 expression can probably be considered as prognostic biomarkers for survival in ESCC.

Cytosolic Phospholipase A2 Alpha Regulates TLR Signaling and Migration in Metastatic 4T1 Cells

Metastatic disease is the leading cause of death in breast cancer patients. Disrupting the cancer cell’s ability to migrate may be a strategy for hindering metastasis. Cytosolic phospholipase A2 α (cPLA2α), along with downstream proinflammatory and promigratory metabolites, has been implicated in several aspects of tumorigenesis, as well as metastasis, in various types of cancer. In this study, we aim to characterize the response to reduced cPLA2α activity in metastatic versus non-metastatic cells. We employ an isogenic murine cell line pair displaying metastatic (4T1) and non-metastatic (67NR) phenotype to investigate the role of cPLA2α on migration. Furthermore, we elucidate the effect of reduced cPLA2α activity on global gene expression in the metastatic cell line. Enzyme inhibition is achieved by using a competitive pharmacological inhibitor, cPLA2α inhibitor X (CIX). Our data show that 4T1 expresses significantly higher cPLA2α levels as compared to 67NR, and the two cell lines show different sensitivity to the CIX treatment with regards to metabolism and proliferation. Inhibition of cPLA2α at nontoxic concentrations attenuates migration of highly metastatic 4T1 cells, but not non-metastatic 67NR cells. Gene expression analysis indicates that processes such as interferon type I (IFN-I) signaling and cell cycle regulation are key processes regulated by cPLA2a in metastatic 4T1 cells, supporting the findings from the biological assays. This study demonstrates that two isogenic cancer cell lines with different metastatic potential respond differently to reduced cPLA2α activity. In conclusion, we argue that cPLA2α is a potential therapeutic target in cancer and that enzyme inhibition may inhibit metastasis through an anti-migratory mechanism, possibly involving Toll-like receptor signaling and type I interferons.

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.

Toll immune signal activates cellular immune response via eicosanoids

Upon immune challenge, insects recognize nonself. The recognition signal will propagate to nearby immune effectors. It is well-known that Toll signal pathway induces antimicrobial peptide (AMP) gene expression. Eicosanoids play crucial roles in mediating the recognition signal to immune effectors by enhancing humoral immune response through activation of AMP synthesis as well as cellular immune responses, suggesting a functional cross-talk between Toll and eicosanoid signals. This study tested a cross-talk between these two signals. Two signal transducing factors (MyD88 and Pelle) of Toll immune pathway were identified in Spodoptera exigua. RNA interference (RNAi) of either SeMyD88 or SePelle expression interfered with the expression of AMP genes under Toll signal pathway. Bacterial challenge induced PLA₂ enzyme activity. However, RNAi of these two immune factors significantly suppressed the induction of PLA₂ enzyme activity. Furthermore, RNAi treatment prevented gene expression of cellular PLA₂. Inhibition of PLA₂ activity reduced phenoloxidase activity and subsequent suppression in cellular immune response measured by hemocyte nodule formation. However, immunosuppression induced by RNAi of Toll signal molecules was significantly reversed by addition of arachidonic acid (AA), a catalytic product of PLA₂. The addition also significantly reduced the enhanced fungal susceptibility of S. exigua treated by RNAi against two Toll signal molecules. These results indicate that there is a cross-talk between Toll and eicosanoid signals in insect immunity.

A systematic review on the role of eicosanoid pathways in rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis is characterized by the production of eicosanoids, cytokines, adhesion molecules, infiltration of T and B lymphocytes in the synovium and oxygen reduction accompanied by the cartilage degradation. Eicosanoids are responsible for the progressive destruction of cartilage and bone, however neither steroids, nor the non steroidal anti-inflammatory drugs (NSAIDs), cannot slow down cartilage and bone destruction providing only symptomatic improvement. The current rheumatoid arthritis treatment options include mainly the use of disease-modifying anti-rheumatic drugs, the corticosteroids, the NSAIDs and biological agents.

METHODS

PubMed, Cochrane, and Embase electronic database were used as the main sources for extracting several articles, reviews, original papers in English for further review and analysis on the implication of arachidonic acid metabolites with rheumatoid arthritis and different strategies of targeting arachidonic acid metabolites, different enzymes or receptors for improving the treatment of rheumatoid arthritis patients.

RESULTS

We first focused on the role of individual prostaglandins and leukotrienes, in the inflammatory process of arthritis, concluding with an outline of the current clinical situation of rheumatoid arthritis and novel treatment strategies targeting the arachidonic acid pathway.

CONCLUSIONS

Extended research is necessary for the development of these novel compounds targeting the eicosanoid pathway, by increasing the levels of anti-inflammatory eicosanoids (PGD₂,15dPGJ₂), by inhibiting the production of pro-inflammatory eicosanoids (PGE₂, LTB₄, PGI₂) involved in rheumatoid arthritis or also by developing dual compounds displaying both the COX-2 inhibitor/TP antagonist activity within a single compound.

Deposition and hydrolysis of serine dipeptide lipids of Bacteroidetes bacteria in human arteries: relationship to atherosclerosis

Multiple reaction monitoring-MS analysis of lipid extracts from human carotid endarterectomy and carotid artery samples from young individuals consistently demonstrated the presence of bacterial serine dipeptide lipid classes, including Lipid 654, an agonist for human and mouse Toll-like receptor (TLR)2, and Lipid 430, the deacylated product of Lipid 654. The relative levels of Lipid 654 and Lipid 430 were also determined in common oral and intestinal bacteria from the phylum Bacteroidetes and human serum and brain samples from healthy adults. The median Lipid 430/Lipid 654 ratio observed in carotid endarterectomy samples was significantly higher than the median ratio in lipid extracts of common oral and intestinal Bacteroidetes bacteria, and serum and brain samples from healthy subjects. More importantly, the median Lipid 430/Lipid 654 ratio was significantly elevated in carotid endarterectomies when compared with control artery samples. Our results indicate that deacylation of Lipid 654 to Lipid 430 likely occurs in diseased artery walls due to phospholipase A2 enzyme activity. These results suggest that commensal Bacteriodetes bacteria of the gut and the oral cavity may contribute to the pathogenesis of TLR2-dependent atherosclerosis through serine dipeptide lipid deposition and metabolism in artery walls.

ROCK/actin/MRTF signaling promotes the fibrogenic phenotype of fibroblast-like synoviocytes derived from the temporomandibular joint

Malocclusion caused by abnormal jaw development or muscle overuse during mastication results in abnormal mechanical stress to the tissues surrounding the temporomandibular joint (TMJ). Excessive mechanical stress against soft and hard tissues around the TMJ is involved in the pathogenesis of inflammatory diseases, including osteoarthritis (OA). OA-related fibrosis is a possible cause of joint stiffness in OA. However, cellular and molecular mechanisms underlying fibrosis around the TMJ remain to be clarified. Here, we established a cell line of fibroblast‑like synoviocytes (FLSs) derived from the mouse TMJ. Then, we examined whether the Rho‑associated coiled‑coil forming kinase (ROCK)/actin/myocardin-related transcription factor (MRTF) gene regulatory axis positively regulates the myofibroblast (MF) differentiation status of FLSs. We found that i) FLSs extensively expressed the MF markers α‑smooth muscle actin (α‑SMA) and type I collagen; and ii) an inhibitor against the actin‑polymerizing agent ROCK, Y‑27632; iii) an actin-depolymerizing agent cytochalasin B; iv) an inhibitor of the MRTF/serum response factor‑regulated transcription, CCG‑100602, clearly suppressed the mRNA levels of α‑SMA and type I collagen in FLSs; and v) an MF differentiation attenuator fibroblast growth factor‑1 suppressed filamentous actin formation and clearly suppressed the mRNA levels of α-SMA and type I collagen in FLSs. These results strongly suggest that the ROCK/actin/MRTF axis promotes the fibrogenic activity of synoviocytes around the TMJ. Our findings partially clarify the molecular mechanisms underlying the emergence of TMJ‑OA and may aid in identifying drug targets for treating this condition at the molecular level.

Fibroblast-like synoviocytes-dependent effector molecules as a critical mediator for rheumatoid arthritis: Current status and future directions

Rheumatoid arthritis (RA) is a systemic-autoimmune-mediated disease characterized by synovial hyperplasia and progressive destruction of joint. Currently available biological agents and inhibitor therapy that specifically target tumor necrosis factor-α, interleukin 1β (IL-1β), IL-6, T cells, B cells, and subcellular molecules (p38 mitogen-activated protein kinase and janus kinase) cannot facilitate complete remission in all patients and are unable to cure the disease. Therefore, further potent therapeutic targets need to be identified for effective treatment and successful clinical outcomes in patients with RA. Scientific breakthroughs have brought new insights regarding fibroblast-like synoviocytes (FLS), a major constituent of the synovial hyperplasia. These play a pivotal role in RA invading cartilage and bone tissue. Currently there are no effective therapies available that specifically target these aggressive cells. Recent evidences indicate that FLS-dependent effector molecules (toll-like receptors, nodal effector molecules, hypoxia-inducible factor, and IL-17) have emerged as important mediators of RA. In this review, we discuss the pathological features and recent advances in understanding the role of FLS-dependent effector molecules in the disease onset of RA. Pharmacological inhibition of FLS-dependent effector molecules might be a promising option for FLS-targeted therapy in RA.

Leptin suppresses adenosine triphosphate-induced impairment of spinal cord astrocytes

Spinal cord injury (SCI) causes long-term disability and has no clinically effective treatment. After SCI, adenosine triphosphate (ATP) may be released from neuronal cells and astrocytes in large amounts. Our previous studies have shown that the extracellular release of ATP increases the phosphorylation of cytosolic phospholipase A2 (cPLA2 ) and triggers the rapid release of arachidonic acid (AA) and prostaglandin E2 (PGE2) via the stimulation of epidermal growth factor receptor (EGFR) and the downstream phosphorylation of extracellular-regulated protein kinases 1 and 2. Leptin, a glycoprotein, induces the activation of the Janus kinase (JAK2)/signal transducers and activators of transcription-3 (Stat3) pathway via the leptin receptor. In this study, we found that 1) prolonged leptin treatment suppressed the ATP-stimulated release of AA and PGE2 from cultured spinal cord astrocytes; 2) leptin elevated the expression of caveolin-1 (Cav-1) via the JAK2/Stat3 signaling pathway; 3) Cav-1 blocked the interaction between Src and EGFR, thereby inhibiting the phosphorylation of EGFR and cPLA2 and attenuating the release of AA or PGE2; 4) pretreatment with leptin decreased ;he level of apoptosis and the release of interleukin-6 from cocultured neurons and astrocytes; and 5) leptin improved the recovery of locomotion in mice after SCI. Our results highlight leptin as a promising therapeutic agent for SCI. © 2016 Wiley Periodicals, Inc.

Emergence of a metalloproteinase / phospholipase A2 axis of systemic inflammation

We review select aspects of the biology of matrix metalloproteinases (MMPs) with a focus on the modulation of inflammatory responses by MMP-2. MMP-2 is a zinc- and calcium-dependent endoprotease with substrates including extracellular matrix proteins, vasoactive peptides and chemokines. Humans and mice with MMP-2 deficiency exhibit a predominantly inflammatory phenotype. Recent research shows that MMP-2 deficient mice display elevated activity of a secreted phospholipase A₂ in the heart. Additionally, MMP-2 deficient mice exhibit abnormally high prostaglandin E₂ levels in various organs (i.e., the heart, brain and liver), signs of inflammation and exacerbated lipopolysaccharide-induced fever. We briefly review the biology of sPLA₂ enzymes to propose the existence of a heart-centric MMP-2/sPLA₂ axis of systemic inflammation. Moreover, we postulate that PLA₂ activation is induced by chemokines, whose ability to signal inflammation is regulated in a tissue-specific fashion by MMPs. Thus, genetic and pharmacologically induced MMP-deficiencies can be expected to perturb PLA₂-mediated inflammatory mechanisms.