Phospholipid Mediator Research Articles

Of rodents, research and relationships: a pharmacological odyssey.

This article is an autobiographical account of a research career in inflammatory diseases, mechanisms and pharmacotherapy, drug research and development, in academia and industry in various European countries spanning the last 55years. The author describes how tenacity and independent thought, learned in formative years, and tempered later by the development of good relationships with colleagues have guided his career. This has spanned research, among other fields, on prostaglandins as pro-and anti-inflammatory mediators, oxidative stress and antioxidants, phospholipid mediators, cytokines, innate and adaptive immune responses and the establishment of various inflammatory and immunological models. The author has helped discover and develop novel therapeutic approaches to pain, arthritic, dermatological, respiratory, and autoimmune disorders and contributed to bringing eight drug candidates to clinical trials. He has helped establish new research labs in four different centres and been involved in teaching undergraduate and mature students in three different universities. With extensive experience in scientific publishing and several international awards, he emphasises that without good teamwork, little can be achieved in scientific research.

A Review of Cyclic Phosphatidic Acid and Other Potential Therapeutic Targets for Treating Osteoarthritis.

Osteoarthritis (OA), a chronic degenerative joint disease, is the most common form of arthritis. OA occurs when the protective cartilage that cushions the ends of bones gradually breaks down. This leads to the rubbing of bones against each other, resulting in pain and stiffness. Cyclic phosphatidic acid (cPA) shows promise as a treatment for OA. In this article, we review the most recent findings regarding the biological functions of cPA signaling in mammalian systems, specifically in relation to OA. cPA is a naturally occurring phospholipid mediator with unique cyclic phosphate rings at the sn-2 and sn-3 positions in the glycerol backbone. cPA promotes various responses, including cell proliferation, migration, and survival. cPA possesses physiological activities that are distinct from those elicited by lysophosphatidic acid; however, its biochemical origin has rarely been studied. Although there is currently no cure for OA, advances in medical research may lead to new therapies or strategies in the future, and cPA has potential therapeutic applications.

A dual role of lysophosphatidic acid type 2 receptor (LPAR2) in nonsteroidal anti-inflammatory drug-induced mouse enteropathy

Lysophosphatidic acid (LPA) is a bioactive phospholipid mediator that has been found to ameliorate nonsteroidal anti-inflammatory drug (NSAID)-induced gastric injury by acting on lysophosphatidic acid type 2 receptor (LPAR2). In this study, we investigated whether LPAR2 signaling was implicated in the development of NSAID-induced small intestinal injury (enteropathy), another major complication of NSAID use. Wild-type (WT) and Lpar2 deficient (Lpar2−/−) mice were treated with a single, large dose (20 or 30 mg/kg, i.g.) of indomethacin (IND). The mice were euthanized at 6 or 24 h after IND treatment. We showed that IND-induced mucosal enteropathy and neutrophil recruitment occurred much earlier (at 6 h after IND treatment) in Lpar2−/− mice compared to WT mice, but the tissue levels of inflammatory mediators (IL-1β, TNF-α, inducible COX-2, CAMP) remained at much lower levels. Administration of a selective LPAR2 agonist DBIBB (1, 10 mg/kg, i.g., twice at 24 h and 30 min before IND treatment) dose-dependently reduced mucosal injury and neutrophil activation in enteropathy, but it also enhanced IND-induced elevation of several proinflammatory chemokines and cytokines. By assessing caspase-3 activation, we found significantly increased intestinal apoptosis in IND-treated Lpar2−/− mice, but it was attenuated after DBIBB administration, especially in non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice. Finally, we showed that IND treatment reduced the plasma activity and expression of autotaxin (ATX), the main LPA-producing enzyme, and also reduced the intestinal expression of Lpar2 mRNA, which preceded the development of mucosal damage. We conclude that LPAR2 has a dual role in NSAID enteropathy, as it contributes to the maintenance of mucosal integrity after NSAID exposure, but also orchestrates the inflammatory responses associated with ulceration. Our study suggests that IND-induced inhibition of the ATX-LPAR2 axis is an early event in the pathogenesis of enteropathy.

Platelet-activating factor receptor in GtoPdb v.2023.1

Platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is an ether phospholipid mediator associated with platelet coagulation, but also subserves inflammatory roles. The PAF receptor (provisional nomenclature recommended by NC-IUPHAR [38]) is activated by PAF and other suggested endogenous ligands are oxidized phosphatidylcholine [74] and lysophosphatidylcholine [98]. It may also be activated by bacterial lipopolysaccharide [91].

A53 FECAL BIOACTIVE PHOSPHOLIPIDS AS TRIGGERS OF INTESTINAL HYPERSENSITIVITY IN IRRITABLE BOWEL SYNDROME

Abstract Background Chronic abdominal pain is the most common complaint of patients with gastrointestinal disorders. Its treatment is of limited efficacy as the pathophysiology is poorly understood. The gut microbiome has been shown to affect host physiology, including the neural system function, and growing evidence suggests that it plays an important role in pain perception. Gut microbiota produces a large variety of molecules that can regulate pain perception, such as histamine or bioactive lipids. Phospholipid mediators (PLM) are signaling molecules linked to neurogenic pain as by-products of inflammatory processes in mammals. But it is unknown whether bacteria can produce PLM and whether they play any role in visceral hyperalgesia. Purpose To investigate whether PLM are present in stool of patients with chronic abdominal pain, and whether they have potential to induce visceral hypersensitivity. Method Stool samples from 27 patients with irritable bowel syndrome (IBS) were collected both during periods of severe and minimal/no pain. The fecal concentration of two PLM (lipid A and lipid B) was determined by ELISA. The passage of lipid A and lipid B through the intestinal barrier was determined ex vivo using Ussing chambers and in vivo by their intracolonic instillation, and their levels assessed in the serosal compartment and the serum, respectively, by ELISA. We used primary cultures of sensory neurons from the dorsal root ganglia (DRG) of conventional mice (SPF) to study the neuronal activation in vitro. Calcium mobilization in DRG sensory neurons was measured by an inverted fluorescence microscope using a fluorescent probe Fluo-4 (1mM) after stimulation with different concentration of lipid A or lipid B. Visceral sensitivity in vivo after intracolonic instillation of combined lipids A and B was evaluated by colorectal distension. Result(s) The concentration of lipid A (p=0.001) and lipid B (p=0.002) in stool was significantly higher in IBS patients when experiencing severe abdominal pain compared to periods of minimal pain. The concentration of lipid A (p=0.03; p=0.07) and lipid B (p=0.018; p=0.018) in the serosal compartment and in the serum, respectively, was higher compared to the control condition. The percentage of neurons responding to lipid A or lipid B was significantly higher compared to the control condition, at all tested concentrations. Finally, combined lipid A and lipid B induced visceral hypersensitivity within 10 minutes (p=0.0433) and 90 minutes (p=0.0020) after intracolonic instillation. Conclusion(s) Our data suggest that PLM can be found in stool of patients with abdominal pain, that they cross the colonic barrier and increase visceral sensitivity. Further studies are needed to ascertain whether gut bacteria produce these PLM and investigate the precise mechanisms by which PLM induce hyperalgesia. Please acknowledge all funding agencies by checking the applicable boxes below CIHR, Other Please indicate your source of funding; Weston Family Foundation Disclosure of Interest None Declared

Abstract TP212: Robust Neuroprotection With PAF-R Antagonist Plus AT-NPD1 In Experimental Ischemic Stroke: Dose-response And Therapeutic Window

Objective: We examined the neuroprotective efficacy, including dose-responses and therapeutic window of 1) LAU-0901, receptor antagonist of the bioactive phospholipid mediator platelet-activating factor (PAF-R) that downregulates pro-inflammatory signaling and has been shown efficacy in a stroke model and, 2) AT-NPD1 (Aspirin- triggered NPD1), its synthesis in the brain was discovered upon aspirin + DHA administration (Bazan et al. Exp Neurol., 2012) and induced cell-survival pathways, anti-inflammatory and neuroprotective activity in focal cerebral ischemia. Methods: Male SD rats underwent 2 hours of MCAo. Behavior testing (days 1-7) and ex vivo MRI on day 7 were conducted. In dose-response, rats were treated with LAU-0901 (45 and 60 mg/kg; IP), AT-NPD1 (111, 222, 333 μg/kg; IV), LAU-0901+AT-NPD1 (LAU-0901 at 3h and AT-NPD1 at 3.15h) or vehicle. In the therapeutic window, vehicle LAU-0901 (60 mg/kg), AT-NPD1 (222 μg/kg), and LAU-0901+AT-NPD1 were administered at 3, 4, 5, and 6h after onset of MCAo. Rats were perfused on day 7, and an ex vivo brain MRI was conducted using 11.7 T MRI. Hierarchal region splitting was used to distinguish the core from the penumbra. Results: LAU-0901 and AT-NPD1 treatments alone improved behavior by 40-42% and 20-30%, respectively, and LAU-0901+AT-NPD1 by 40% compared to the vehicle group. T2-weighted imaging (T2WI) volumes were reduced with all doses of LAU-0901 and AT-NPD1 by 73-90% and 67-83% and LAU-0901+AT-NPD1 by 94% compared to vehicle. In the therapeutic window, treatment with LAU-0901 and AT-NPD1 alone, when administered at 3h, improved behavior on day 7 by 35 and 28%. In contrast, LAU-0901+AT-NPD1, when administered at 3, 4, 5, and 6 hours, improved behavior by 50, 56, 33, and 26%. Ischemic core, penumbra, and total lesion volumes were dramatically reduced with LAU-0901+AT-NPD1 when administered at 3, 4, 5, and 6h by 93, 90, 82, and 84% compared to the vehicle. Conclusion: These data suggest that LAU-0901 and AT-NPD1 alone in low doses provide high-grade neuroprotection in the MCAo model. Combination therapy with LAU-0901 and AT-NPD1 is more effective than the single therapy, affording synergistic neuroprotection with improved neurological recovery when administered up to 6 h after focal cerebral ischemia in rats.

Astrocytic Neuroimmunological Roles Interacting with Microglial Cells in Neurodegenerative Diseases.

Both astrocytic and microglial functions have been extensively investigated in healthy subjects and neurodegenerative diseases. For astrocytes, not only various sub-types were identified but phagocytic activity was also clarified recently and is making dramatic progress. In this review paper, we mostly focus on the functional role of astrocytes in the extracellular matrix and on interactions between reactive astrocytes and reactive microglia in normal states and in neurodegenerative diseases, because the authors feel it is necessary to elucidate the mechanisms among activated glial cells in the pathology of neurological diseases in order to pave the way for drug discovery. Finally, we will review cyclic phosphatidic acid (cPA), a naturally occurring phospholipid mediator that induces a variety of biological activities in the brain both in vivo and in vitro. We propose that cPA may serve as a novel therapeutic molecule for the treatment of brain injury and neuroinflammation.

Effects of 2-carba-cyclic phosphatidic acid derivatives on IL-1β-stimulated human chondrocytes

Osteoarthritis (OA) is a common joint disease characterized by the breakdown of subchondral bone and cartilage damage, most often affecting middle-aged and elderly people. Although the etiology of OA is still unknown, some reports suggest that inflammatory factors such as interleukin (IL)− 1β mediate the progression of OA. To investigate the effect of IL-1β and the possibility of treatment for OA, we applied 2-carba-cyclic phosphatidic acid (2ccPA) and its derivatives on human chondrocytes. 2ccPA is a synthesized phospholipid derived from a bioactive phospholipid mediator: cyclic phosphatidic acid (cPA). It has been previously reported that 2ccPA exhibits anti-inflammatory and chondroprotective effects in an OA animal model. 2ccPA and its ring-opened body (ROB) derivative significantly suppressed IL-1β-induced upregulation of IL-6, matrix metalloproteinase-13, and cyclooxygenase-2, as well as the degradation of type II collagen and aggrecan. However, the other two derivatives, namely the deacylated and ring-opened deacylated bodies, showed little effect on an IL-1β-exposed human chondrosarcoma cell-line. These data suggest that the intactness of 2ccPA and ROB is essential for anti-inflammatory effects on OA. Collectively, this study provides evidence that 2ccPA and ROB would be novel therapeutic agents for OA.

Phospholipid Mediator Induced Transformation in Three-Dimensional Cultures

Phospholipid Mediator Induced Transformation in Three-Dimensional Cultures

Phospholipid Mediator Induced Transformation in Three-Dimensional Cultures.

Several models have been developed to study cancer, such as rodent models and established cell lines. Valuable insights into carcinogenesis have been provided by studies using these models. Cell lines have provided an understanding of the deregulation of molecular signaling associated with breast tumorigenesis, while rodent models are widely used to study cellular and molecular characteristics of breast cancer in vivo. The establishment of 3D cultures of breast epithelial and cancerous cells aids in bridging the gap between in vivo and in vitro models by mimicking the in vivo conditions in vitro. This model can be used to understand the deregulation of complex molecular signaling events and the cellular characteristics during breast carcinogenesis. Here, a 3D culture system is modified to study a phospholipid mediator-induced (Platelet Activating Factor, PAF) transformation. Immunomodulators and other secreted molecules play a major role in tumor initiation and progression in the breast. In the present study, 3D acinar cultures of breast epithelial cells are exposed to PAF exhibited transformation characteristics such as loss of polarity and altered cellular characteristics. This 3D culture system will assist in shedding light on genetic and/or epigenetic perturbations induced by various small molecule entities in the tumor microenvironment. Additionally, this system will also provide a platform for the identification of novel as well as known genes that may be involved in the process of transformation.

Changes in Lysophospholipid Components in Ulcerative Colitis and Colitis-associated Cancer.

In recent years, it has become clear that, in addition to normal cytokines, phospholipid mediators play an important role in the development, growth, infiltration, and metastasis of cancer and in the cancer microenvironment. A phospholipid analysis method using tandem mass spectrometry (LC-MS/MS) with high detection sensitivity has enabled quantification of phospholipids, even when using a very small sample. To date, we had applied this MS technology to colorectal cancer tissue. Therefore, in this study, this mass spectrometry technique was applied to ulcerative colitis (UC) and UC-related colorectal cancer, and an analysis was conducted with the aim of clarifying which lysophospholipids specifically change in each type of tissue. UC-associated colorectal cancer tissue and UC mucosa were collected from surgical specimens of colitic cancer (n=3). Cancerous and non-cancerous tissues were collected from surgical specimens from patients with sporadic colorectal cancer (n=11). After extraction from these tissues, the amounts of lysophospholipids were quantified by LC-MS/MS. In addition, lysophosphatidylserine (LPS) and lysophosphatidylinositol (LPI) were quantified for each molecular species of fatty acids. Compared to normal mucosa, LPI was increased 3.8-fold (p<0.001) and LPS 3.5-fold (p<0.001) in UC-related colorectal cancer. Molecular species of LPI which were increased in UC-related colorectal cancer were 18:0 (p=0.001), 16:0 (p=0.03) and 20:4 (p=0.004), and of LPS were 18:0 (p<0.001) and 22:6 (p=0.014). Lysophospholipids increased in colorectal cancer and in UC-associated colorectal cancer. In particular, LPI may have contributed significantly to colitis-associated carcinogenesis.

2-Carba-lysophosphatidic acid is a novel \u03b2-lysophosphatidic acid analogue with high potential for lysophosphatidic acid receptor activation and autotaxin inhibition

Cyclic phosphatidic acid (cPA) is a naturally occurring phospholipid mediator that, along with its chemically stabilized analogue 2-carba-cyclic phosphatidic acid (2ccPA), induces various biological activities in vitro and in vivo. Although cPA is similar to lysophosphatidic acid (LPA) in structure and synthetic pathway, some of cPA biological functions apparently differ from those reported for LPA. We previously investigated the pharmacokinetic profile of 2ccPA, which was found to be rapidly degraded, especially in acidic conditions, yielding an unidentified compound. Thus, not only cPA but also its degradation compound may contribute to the biological activity of cPA, at least for 2ccPA. In this study, we determined the structure and examined the biological activities of 2-carba-lysophosphatidic acid (2carbaLPA) as a 2ccPA degradation compound, which is a type of β-LPA analogue. Similar to LPA and cPA, 2carbaLPA induced the phosphorylation of the extracellular signal-regulated kinase and showed potent agonism for all known LPA receptors (LPA1–6) in the transforming growth factor-α (TGFα) shedding assay, in particular for LPA3 and LPA4. 2carbaLPA inhibited the lysophospholipase D activity of autotaxin (ATX) in vitro similar to other cPA analogues, such as 2ccPA, 3-carba-cPA, and 3-carba-LPA (α-LPA analogue). Our study shows that 2carbaLPA is a novel β-LPA analogue with high potential for the activation of some LPA receptors and ATX inhibition.

Mutagenesis and homology modeling reveal a predicted pocket of lysophosphatidylcholine acyltransferase 2 to catch Acyl-CoA.

Platelet-activating factor (PAF) is a potent proinflammatory phospholipid mediator that elicits various cellular functions and promotes several pathological events, including anaphylaxis and neuropathic pain. PAF is biosynthesized by two types of lyso-PAF acetyltransferases: lysophosphatidylcholine acyltransferase 1 (LPCAT1) and LPCAT2, which are constitutive and inducible forms of lyso-PAF acetyltransferase, respectively. Because LPCAT2 mainly produces PAF under inflammatory stimuli, understanding the structure of LPCAT2 is important for developing specific drugs against PAF-related inflammatory diseases. Although the structure of LPCAT2 has not been determined, the crystal structure was reported for Thermotoga maritima PlsC, an enzyme in the same gene family as LPCAT2. Here, we identified residues in mouse LPCAT2 essential for its enzymatic activity and a potential acyl-coenzyme A (CoA)-binding pocket, based on homology modeling of mouse LPCAT2 with PlsC. We also found that Ala115 of mouse LPCAT2 was important for acyl-CoA selectivity. In conclusion, these results predict the three-dimensional (3D) structure of mouse LPCAT2. Our findings have implications for the future development of new drugs against PAF-related diseases.

Prolonged Exposure to Platelet Activating Factor Transforms Breast Epithelial Cells.

Lipid species are known to have various biological functions owing to their structural differences, and each of them possesses a specific role to play depending upon their location and distribution in the cell. Some of these lipids interact with proteins on the cell membrane and acts as second messengers. The level of lipid mediators is generally maintained in the cell by feedback mechanisms; however, their improper degradation or enhanced production leads to their accumulation in the tumor microenvironment and disturbs the homeostasis of the cell. Platelet activating factor (PAF) is a known phospholipid mediator secreted upon immunological challenges by platelets, neutrophils, basophils, and macrophages. PAF, as a potent inflammatory molecule, is well studied, and its role in various cancers and cardiovascular diseases has also been investigated. Interestingly, increased levels of PAF have been found in the blood plasma of smokers, and breast cancer cells have shown the accumulation of PAF in presence of cigarette smoke extract. This accumulation was found to increase tumor cell motility that in turn could promote metastasis. Beyond this, however, the effect of PAF on tumorigenesis has not yet been well explored. Here, we show that the continuous exposure of 3D breast acinar cultures to PAF resulted in the activation of various oncogenic signaling pathways leading to transformation. We also found that the presence of PAF in the micro-environment increased the expression of PAF receptor (PAF-R), which corroborated with the higher expression of PAF-R detected in some epithelial cancers, as per literature. Thus, this study impresses on the fact that the presence of PAF alters the cellular microenvironment and eventually triggers irreversible effects that can cumulatively lead to transformation.

Interplay Between EGFR and the Platelet-Activating Factor/PAF Receptor Signaling Axis Mediates Aggressive Behavior of Cervical Cancer.

Epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase widely expressed in cervical tumors, being correlated with adverse clinical outcomes. EGFR may be activated by a diversity of mechanisms, including transactivation by G-protein coupled receptors (GPCRs). Studies have also shown that platelet-activating factor (PAF), a pro-inflammatory phospholipid mediator, plays an important role in the cancer progression either by modulating the cancer cells or the tumor microenvironment. Most of the PAF effects seem to be mediated by the interaction with its receptor (PAFR), a member of the GPCRs family. PAFR- and EGFR-evoked signaling pathways contribute to tumor biology; however, the interplay between them remains uninvestigated in cervical cancer. In this study, we employed The Cancer Genome Atlas (TCGA) and cancer cell lines to evaluate possible cooperation between EGFR, PAFR, and lysophosphatidylcholine acyltransferases (LPCATs), enzymes involved in the PAF biosynthesis, in the context of cervical cancer. It was observed a strong positive correlation between the expression of EGFR × PAFR and EGFR × LPCAT2 in 306 cervical cancer samples. The increased expression of LPCAT2 was significantly correlated with poor overall survival. Activation of EGFR upregulated the expression of PAFR and LPCAT2 in a MAPK-dependent fashion. At the same time, PAF showed the ability to transactivate EGFR leading to ERK/MAPK activation, cyclooxygenase-2 (COX-2) induction, and cell migration. The positive crosstalk between the PAF-PAFR axis and EGFR demonstrates a relevant linkage between inflammatory and growth factor signaling in cervical cancer cells. Finally, combined PAFR and EGFR targeting treatment impaired clonogenic capacity and viability of aggressive cervical cancer cells more strongly than each treatment separately. Collectively, we proposed that EGFR, LPCAT2, and PAFR emerge as novel targets for cervical cancer therapy.

Exposure to Cigarette Smoke is Linked to Platelet‐Activating Factor Accumulation in Myocardial Tissue

Smoking is a lifestyle risk factor for heart disease and is responsible for one‐third of all cardiovascular deaths. Although many studies have investigated the correlation between smoking and coronary artery disease, there are few studies examining the direct effect of smoking on the myocardium. In this study, we examined the effect of smoking on myocardial accumulation of platelet‐activating factor (PAF), a phospholipid mediator that causes a negative inotropic effect, arrhythmias, apoptosis and is involved in inflammation and atherosclerosis. Ventricular samples from mice exposed up to six months of cigarette smoke (48 min/day, 5 days/week), and human right atrial samples from smokers and nonsmokers scheduled for coronary artery bypass graft surgery were analyzed for biochemical and histochemical changes using activity assays, ELISA, immunoblot, and immunohistochemistry. Mice exposed to cigarette smoke showed a decrease in PAF‐acetylhydrolase (PAF‐AH, the enzyme responsible for PAF metabolism) activity that was significant after 1 month and decreased progressively over the 6 month period (5.8 ± 0.3 to 3.2 ± 0.5 nmol/mg protein/min, p&lt;0.01, n=6). This inhibition in PAF‐AH activity was accompanied by increased myocardial PAF content (0.23 ± 0.04 to 0.35 ± 0.03 at 6 months smoking, p&lt;0.05, n=6). In humans, smoking was associated with an increase in PAF content (3.19 ± 0.28 vs 4.29 ± 0.37 nmol/mg protein, p&lt;0.05, n=18) and inhibition of PAF‐AH activity (30.7 ± 2.0 vs 23.2 ± 1.8 nmol/mg protein/min, p&lt;0.01, n=18) when comparing atrial tissue from never smokers to current smokers. We did not detect a change in phospholipase A2 activity (the enzyme responsible for PAF production) in human or mouse myocardium exposed to cigarette smoke or room air. Thus, we hypothesize that the increase in PAF content in the myocardium is likely a result of smoking‐induced inhibition of PAF‐AH activity. The inhibition of PAF‐AH and subsequent accumulation of PAF in the myocardium of cigarette smokers may play a role in the pathogenesis of heart disease in this population.Support or Funding InformationLottie Caroline Hardy Foundation (to J.McH.)

Forty Years Since the Structural Elucidation of Platelet-Activating Factor (PAF): Historical, Current, and Future Research Perspectives.

In the late 1960s, Barbaro and Zvaifler described a substance that caused antigen induced histamine release from rabbit platelets producing antibodies in passive cutaneous anaphylaxis. Henson described a ‘soluble factor’ released from leukocytes that induced vasoactive amine release in platelets. Later observations by Siraganuan and Osler observed the existence of a diluted substance that had the capacity to cause platelet activation. In 1972, the term platelet-activating factor (PAF) was coined by Benveniste, Henson, and Cochrane. The structure of PAF was later elucidated by Demopoulos, Pinckard, and Hanahan in 1979. These studies introduced the research world to PAF, which is now recognised as a potent phospholipid mediator. Since its introduction to the literature, research on PAF has grown due to interest in its vital cell signalling functions and more sinisterly its role as a pro-inflammatory molecule in several chronic diseases including cardiovascular disease and cancer. As it is forty years since the structural elucidation of PAF, the aim of this review is to provide a historical account of the discovery of PAF and to provide a general overview of current and future perspectives on PAF research in physiology and pathophysiology.

Platelet-activating factor receptor (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

Platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is an ether phospholipid mediator associated with platelet coagulation, but also subserves inflammatory roles. The PAF receptor (provisional nomenclature recommended by NC-IUPHAR [37]) is activated by PAF and other suggested endogenous ligands are oxidized phosphatidylcholine [73] and lysophosphatidylcholine [96]. It may also be activated by bacterial lipopolysaccharide [89].

2-Carba cyclic phosphatidic acid inhibits lipopolysaccharide-induced prostaglandin E2 production in a human macrophage cell line

Cyclic phosphatidic acid (cPA) is a naturally occurring phospholipid mediator that contains a unique cyclic phosphate ring at the sn-2 and sn-3 positions of its glycerol backbone. Using mouse models for multiple sclerosis (cuprizone-induced demyelination and experimental autoimmune encephalomyelitis) and traumatic brain injury, we revealed that cPA and its metabolically stabilized cPA derivative, 2-carba-cPA (2ccPA), have potential to protect against neuroinflammation. In this study, we investigated whether 2ccPA has anti-inflammatory effect on peripheral immune function or not using inflammation-induced macrophages-like cell line, THP-1 monocytes differentiated by phorbol 12-myristate 13-acetate (PMA). Lipopolysaccharide (LPS)-stimulated THP-1 cells were found to have higher expression of the mRNAs of several inflammation-related cytokines and of the enzyme cyclooxygenase-2 (Cox-2); however, when THP-1 cells were stimulated by LPS in the presence of 2ccPA, the increase in the expression of pro-inflammatory cytokine and Cox-2 mRNA was attenuated. 2ccPA treatment also decreased the amount of prostaglandin E2 (PGE2) produced by LPS-stimulated THP-1 cells and decreased expression of the mRNA of prostaglandin E receptor 2 (EP2, PTGER2), a PGE2 receptor that mediates inflammation. These results indicate that 2ccPA has anti-inflammatory properties.

Regulation of platelet-activating factor-mediated interleukin-6 promoter activation by the 48\xa0kDa but not the 45\xa0kDa isoform of protein tyrosine phosphatase non-receptor type 2

BackgroundAn underlying state of inflammation is thought to be an important cause of cardiovascular disease. Among cells involved in the early steps of atherosclerosis, monocyte-derived dendritic cells (Mo-DCs) respond to inflammatory stimuli, including platelet-activating factor (PAF), by the induction of various cytokines, such as interleukin 6 (IL-6). PAF is a potent phospholipid mediator involved in both the onset and progression of atherosclerosis. It mediates its effects by binding to its cognate G-protein coupled receptor, PAFR. Activation of PAFR-induced signaling pathways is tightly coordinated to ensure specific cell responses.ResultsHere, we report that PAF stimulated the phosphatase activity of both the 45 and 48 kDa isoforms of the protein tyrosine phosphatase non-receptor type 2 (PTPN2). However, we found that only the 48 kDa PTPN2 isoform has a role in PAFR-induced signal transduction, leading to activation of the IL-6 promoter. In luciferase reporter assays, expression of the 48 kDa, but not the 45 kDa, PTPN2 isoform increased human IL-6 (hIL-6) promoter activity by 40% after PAF stimulation of HEK-293 cells, stably transfected with PAFR (HEK-PAFR). Our results suggest that the differential localization of the PTPN2 isoforms and the differences in PAF-induced phosphatase activation may contribute to the divergent modulation of PAF-induced IL-6 promoter activation. The involvement of PTPN2 in PAF-induced IL-6 expression was confirmed in immature Mo-DCs (iMo-DCs), using siRNAs targeting the two isoforms of PTPN2, where siRNAs against the 48 kDa PTPN2 significantly inhibited PAF-stimulated IL-6 mRNA expression. Pharmacological inhibition of several signaling pathways suggested a role for PTPN2 in early signaling events. Results obtained by Western blot confirmed that PTPN2 increased the activation of the PI3K/Akt pathway via the modulation of protein kinase D (PKD) activity. WT PKD expression counteracted the effect of PTPN2 on PAF-induced IL-6 promoter transactivation and phosphorylation of Akt. Using siRNAs targeting the individual isoforms of PTPN2, we confirmed that these pathways were also active in iMo-DCs.ConclusionTaken together, our data suggest that PTPN2, in an isoform-specific manner, could be involved in the positive regulation of PI3K/Akt activation, via the modulation of PKD activity, allowing for the maximal induction of PAF-stimulated IL-6 mRNA expression.