Prostacyclin-IP signaling and prostaglandin E2-EP2/EP4 signaling both mediate joint inflammation in mouse collagen-induced arthritis

Revisiting prostaglandin E2: A promising therapeutic target for osteoarthritis

Osteoarthritis (OA) is a complex disease characterized by cartilage degeneration and persistent pain. Prostaglandin E2 (PGE2) plays a significant role in OA inflammation and pain. Recent studies have revealed the significant role of PGE2-mediated skeletal interoception in the progression of OA, providing new insights into the pathogenesis and treatment of OA. This aspect also deserves special attention in this review. Additionally, PGE2 is directly involved in pathologic processes including aberrant subchondral bone remodeling, cartilage degeneration, and synovial inflammation. Therefore, celecoxib, a commonly used drug to alleviate inflammatory pain through inhibiting PGE2, serves not only as an analgesic for OA but also as a potential disease-modifying drug. This review provides a comprehensive overview of the discovery history, synthesis and release pathways, and common physiological roles of PGE2. We discuss the roles of PGE2 and celecoxib in OA and pain from skeletal interoception and multiple perspectives. The purpose of this review is to highlight PGE2-mediated skeletal interoception and refresh our understanding of celecoxib in the pathogenesis and treatment of OA.

Exploring the roles of prostanoids, leukotriens, and dietary fatty acids in cutaneous inflammatory diseases: Insights from pharmacological and genetic approaches

Prostanoids and leukotrienes (LTs) are representative of ω6 fatty acid-derived metabolites that exert their actions through specific receptors on the cell surface. These lipid mediators, being unstable in vivo, act locally at their production sites; thus, their physiological functions remain unclear. However, recent pharmacological and genetic approaches using experimental murine models have provided significant insights into the roles of these lipid mediators in various pathophysiological conditions, including cutaneous inflammatory diseases. These lipid mediators act not only through signaling by themselves but also by potentiating the signaling of other chemical mediators, such as cytokines and chemokines. For instance, prostaglandin E2 -EP4 and LTB4 -BLT1 signaling on cutaneous dendritic cells substantially facilitate their chemokine-induced migration ability into the skin and play critical roles in the priming and/or activation of antigen-specific effector T cells in the skin. In addition to these ω6 fatty acid-derived metabolites, various ω3 fatty acid-derived metabolites regulate skin immune cell functions, and some exert potent anti-inflammatory functions. Lipid mediators act as modulators of cutaneous immune responses, and manipulating the signaling from lipid mediators has the potential as a novel therapeutic approach for human skin diseases.

EP2 inhibition restores myeloid metabolism and reverses cognitive decline

Nonsteroidal anti-inflammatory drugs alleviate pain and inflammation by inhibiting the cyclooxygenase pathway. This pathway has various downstream effects, some of which are beneficial. Prostaglandin E2 is a key downstream product in the cyclooxygenase pathway that modulates inflammation. A correlation between aging and increased expression of the prostaglandin E2 receptor, EP2, has been associated with inflammatory processes, cognitive aging, angiogenesis, and tumorigenesis. Therefore, inhibition of EP2 could lead to therapeutic effects and be more selective than inhibiting cyclooxygenase-2. Studies suggest that inhibition of EP2 restores age-associated spatial memory deficits and synaptic proteins and impairs tumorigenesis. The data indicate that EP2 signaling is important in myeloid cell metabolism and support its candidacy as a therapeutic target.

The phospholipase A2 superfamily as a central hub of bioactive lipids and beyond

In essence, "phospholipase A₂" (PLA₂) means a group of enzymes that release fatty acids and lysophospholipids by hydrolyzing the sn-2 position of glycerophospholipids. To date, more than 50 enzymes possessing PLA₂ or related lipid-metabolizing activities have been identified in mammals, and these are subdivided into several families in terms of their structures, catalytic mechanisms, tissue/cellular localizations, and evolutionary relationships. From a general viewpoint, the PLA₂ superfamily has mainly been implicated in signal transduction, driving the production of a wide variety of bioactive lipid mediators. However, a growing body of evidence indicates that PLA₂s also contribute to phospholipid remodeling or recycling for membrane homeostasis, fatty acid β-oxidation for energy production, and barrier lipid formation on the body surface. Accordingly, PLA₂ enzymes are considered one of the key regulators of a broad range of lipid metabolism, and perturbation of specific PLA₂-driven lipid pathways often disrupts tissue and cellular homeostasis and may be associated with a variety of diseases. This review covers current understanding of the physiological functions of the PLA₂ superfamily, focusing particularly on the two major intracellular PLA₂ families (Ca²⁺-dependent cytosolic PLA₂s and Ca²⁺-independent patatin-like PLA₂s) as well as other PLA₂ families, based on studies using gene-manipulated mice and human diseases in combination with comprehensive lipidomics.

The emerging role for metabolism in fueling neutrophilic inflammation

Neutrophils are a critical element of host defense and are rapidly recruited to inflammatory sites. Such sites are frequently limited in oxygen and/or nutrient availability, presenting a metabolic challenge for infiltrating cells. Long believed to be uniquely dependent on glycolysis, it is now clear that neutrophils possess far greater metabolic plasticity than previously thought, with the capacity to generate energy stores and utilize extracellular proteins to fuel central carbon metabolism and biosynthetic activity. Out-with cellular energetics, metabolic programs have also been implicated in the production of neutrophils and their progenitors in the bone marrow compartment, activation of neutrophil antimicrobial responses, inflammatory and cell survival signaling cascades, and training of the innate immune response. Thus, understanding the mechanisms by which metabolic processes sustain changes in neutrophil effector functions and how these are subverted in disease states provides exciting new avenues for the treatment of dysfunctional neutrophilic inflammation which are lacking in clinical practice to date.

Remodeling articular immune homeostasis with an efferocytosis-informed nanoimitator mitigates rheumatoid arthritis in mice

Massive intra-articular infiltration of proinflammatory macrophages is a prominent feature of rheumatoid arthritis (RA) lesions, which are thought to underlie articular immune dysfunction, severe synovitis and ultimately joint erosion. Here we report an efferocytosis-informed nanoimitator (EINI) for in situ targeted reprogramming of synovial inflammatory macrophages (SIMs) that thwarts their autoimmune attack and reestablishes articular immune homeostasis, which mitigates RA. The EINI consists of a drug-based core with an oxidative stress-responsive phosphatidylserine (PtdSer) corona and a shell composed of a P-selectin-blocking motif, low molecular weight heparin (LMWH). When systemically administered, the LMWH on the EINI first binds to P-selectin overexpressed on the endothelium in subsynovial capillaries, which functions as an antagonist, disrupting neutrophil synovial trafficking. Due to the strong dysregulation of the synovial microvasculature, the EINI is subsequently enriched in the joint synovium where the shell is disassembled upon the reactive oxygen species stimulation, and PtdSer corona is then exposed. In an efferocytosis-like manner, the PtdSer-coroneted core is in turn phagocytosed by SIMs, which synergistically terminate SIM-initiated pathological cascades and serially reestablish intra-articular immune homeostasis, conferring a chondroprotective effect. These findings demonstrate that SIMs can be precisely remodeled via the efferocytosis-mimetic strategy, which holds potential for RA treatment.

Wounds under diabetic milieu: The role of immune cellar components and signaling pathways

A major challenge in the field of diabetic wound healing is to confirm the body's intrinsic mechanism that could sense the immune system damage promptly and protect the wound from non-healing. Accumulating literature indicates that macrophage, a contributor to prolonged inflammation occurring at the wound site, might play such a role in hindering wound healing. Likewise, other immune cell dysfunctions, such as persistent neutrophils and T cell infection, may also lead to persistent oxidative stress and inflammatory reaction during diabetic wound healing. In this article, we discuss recent advances in the immune cellular components in wounds under the diabetic milieu, and the role of key signaling mechanisms that compromise the function of immune cells leading to persistent wound non-healing.

Diversified Effects of COVID-19 as a Consequence of the Differential Metabolism of Phospholipids and Lipid Peroxidation Evaluated in the Plasma of Survivors and Deceased Patients upon Admission to the Hospital

As a result of SARS-CoV-2 infection, inflammation develops, which promotes oxidative stress, leading to modification of phospholipid metabolism. Therefore, the aim of this study is to compare the effects of COVID-19 on the levels of phospholipid and free polyunsaturated fatty acids (PUFAs) and their metabolites produced in response to reactions with reactive oxygen species (ROS) and enzymes (cyclooxygenases-(COXs) and lipoxygenase-(LOX)) in the plasma of patients who either recovered or passed away within a week of hospitalization. In the plasma of COVID-19 patients, especially of the survivors, the actions of ROS and phospholipase A2 (PLA2) cause a decrease in phospholipid fatty acids level and an increase in free fatty acids (especially arachidonic acid) despite increased COXs and LOX activity. This is accompanied by an increased level in lipid peroxidation products (malondialdehyde and 8-isoprostaglandin F2α) and lipid mediators generated by enzymes. There is also an increase in eicosanoids, both pro-inflammatory as follows: thromboxane B2 and prostaglandin E2, and anti-inflammatory as follows: 15-deoxy-Δ-12,14-prostaglandin J2 and 12-hydroxyeicosatetraenoic acid, as well as endocannabinoids (anandamide-(AEA) and 2-arachidonylglycerol-(2-AG)) observed in the plasma of patients who recovered. Moreover, the expression of tumor necrosis factor α and interleukins (IL-6 and IL-10) is increased in patients who recovered. However, in the group of patients who died, elevated levels of N-oleoylethanolamine and N-palmitoylethanolamine are found. Since lipid mediators may have different functions depending on the onset of pathophysiological processes, a stronger pro-inflammatory response in patients who have recovered may be the result of the defensive response to SARS-CoV-2 in survivors associated with specific changes in the phospholipid metabolism, which could also be considered a prognostic factor.

Pharmacological antagonism of EP2 receptor does not modify basal cardiovascular and respiratory function, blood cell counts, and bone morphology in animal models

The EP2 receptor has emerged as a therapeutic target with exacerbating role in disease pathology for a variety of peripheral and central nervous system disorders. We and others have recently demonstrated beneficial effects of EP2 antagonists in preclinical models of neuroinflammation and peripheral inflammation. However, it was earlier reported that mice with global EP2 knockout (KO) display adverse phenotypes on fertility and blood pressure. Other studies indicated that EP2 activation with an agonist has a beneficial effect of healing fractured bone in animal models. These results impeded the development of EP2 antagonists, and EP2 antagonism as therapeutic strategy. To determine whether treatment with EP2 antagonist mimics the adverse phenotypes of the EP2 global KO mouse, we tested two EP2 antagonists TG11-77. HCl and TG6-10-1 in mice and rats while they are on normal or high-salt diet, and by two different administration protocols (acute and chronic). There were no adverse effects of the antagonists on systolic and diastolic blood pressure, heart rate, respiratory function in mice and rats regardless of rodents being on a regular or high salt diet. Furthermore, chronic exposure to TG11-77. HCl produced no adverse effects on blood cell counts, bone-volume and bone-mineral density in mice. Our findings argue against adverse effects on cardiovascular and respiratory systems, blood counts and bone structure in healthy rodents from the use of small molecule reversible antagonists for EP2, in contrast to the genetic ablation model. This study paves the way for advancing therapeutic applications of EP2 antagonists against diseases involving EP2 dysfunction.

A Metalloproteinase Induces an Inflammatory Response in Preadipocytes with the Activation of COX Signalling Pathways and Participation of Endogenous Phospholipases A2

Matrix metalloproteinases (MMPs) are proteolytic enzymes that have been associated with the pathogenesis of inflammatory diseases and obesity. Adipose tissue in turn is an active endocrine organ capable of secreting a range of proinflammatory mediators with autocrine and paracrine properties, which contribute to the inflammation of adipose tissue and adjacent tissues. However, the potential inflammatory effects of MMPs in adipose tissue cells are still unknown. This study investigates the effects of BmooMPα-I, a single-domain snake venom metalloproteinase (SVMP), in activating an inflammatory response by 3T3-L1 preadipocytes in culture, focusing on prostaglandins (PGs), cytokines, and adipocytokines biosynthesis and mechanisms involved in prostaglandin E₂ (PGE₂) release. The results show that BmooMPα-I induced the release of PGE₂, prostaglandin I₂ (PGI₂), monocyte chemoattractant protein-1 (MCP-1), and adiponectin by preadipocytes. BmooMPα-I-induced PGE₂ biosynthesis was dependent on group-IIA-secreted phospholipase A₂ (sPLA₂-IIA), cytosolic phospholipase A₂-α (cPLA₂-α), and cyclooxygenase (COX)-1 and -2 pathways. Moreover, BmooMPα-I upregulated COX-2 protein expression but not microsomal prostaglandin E synthase-1 (mPGES-1) expression. In addition, we demonstrate that the enzymatic activity of BmooMPα-I is essential for the activation of prostanoid synthesis pathways in preadipocytes. These data highlight preadipocytes as important targets for metalloproteinases and provide new insights into the contribution of these enzymes to the inflammation of adipose tissue and tissues adjacent to it.

Telomere Shortening and Psychiatric Disorders: A Systematic Review

Telomeres are aging biomarkers, as they shorten while cells undergo mitosis. The aim of this study was to evaluate whether psychiatric disorders marked by psychological distress lead to alterations to telomere length (TL), corroborating the hypothesis that mental disorders might have a deeper impact on our physiology and aging than it was previously thought. A systematic search of the literature using MeSH descriptors of psychological distress ("Traumatic Stress Disorder" or "Anxiety Disorder" or "depression") and telomere length ("cellular senescence", "oxidative stress" and "telomere") was conducted on PubMed, Cochrane Library and ScienceDirect databases. A total of 56 studies (113,699 patients) measured the TL from individuals diagnosed with anxiety, depression and posttraumatic disorders and compared them with those from healthy subjects. Overall, TL negatively associates with distress-related mental disorders. The possible underlying molecular mechanisms that underly psychiatric diseases to telomere shortening include oxidative stress, inflammation and mitochondrial dysfunction linking. It is still unclear whether psychological distress is either a cause or a consequence of telomere shortening.

Role of arachidonic cascade in COVID-19 infection: A review

The World Health Organization has described the 2019 Coronavirus disease caused by an influenza-like virus called SARS-CoV-2 as a pandemic. Millions of people worldwide are already infected by this virus, and severe infection causes hyper inflammation, thus disrupting lung function, exacerbating breath difficulties, and death. Various inflammatory mediators bio-synthesized through the arachidonic acid pathway play roles in developing cytokine storms, injuring virus-infected cells. Since pro-inflammatory eicosanoids, including prostaglandins, and leukotrienes, are key brokers for physiological processes such as inflammation, fever, allergy, and pain but, their function in COVID-19 is not well defined. This study addresses eicosanoid's crucial role through the arachidonic pathway in inflammatory cascading and recommends using bioactive lipids, NSAIDs, steroids, cell phospholipase A2 (cPLA2) inhibitors, and specialized pro-resolving mediators (SPMs) to treat COVID-19 disease. The role of soluble epoxide hydrolase inhibitors (SEHIs) in promoting the activity of epoxyeicosatrienoic acids (EETs) and 17-hydroxide-docosahexaenoic acid (17-HDHA) is also discussed. Additional research that assesses the eicosanoid profile in COVID-19 patients or preclinical models generates novel insights into coronavirus-host interaction and inflammation regulation.

ZhiJingSan Inhibits Osteoclastogenesis via Regulating RANKL/NF-κB Signaling Pathway and Ameliorates Bone Erosion in Collagen-Induced Mouse Arthritis

Bone erosion is the most evident pathological condition of rheumatoid arthritis (RA), which is the main cause of joint deformities and disability in RA patients. At present, the conventional RA drugs have not achieved satisfactory effect in improving bone erosion. ZhiJingSan (ZJS), which is a traditional Chinese prescription composed of scolopendra (dried body of Scolopendra subspinipes mutilans L. Koch, scolopendridae) and scorpion (dried body of Buthus martensii Karsch, Buthus), exhibits anti-rheumatism, analgesic and joint deformities improvement effects. This study aimed to assess the therapeutic effect of ZJS on RA bone erosion and to elucidate the underlying mechanism. The effect of ZJS on RA bone erosion was investigated in a murine model of bovine collagen-induced arthritis (CIA), and the underlying mechanism was investigated in vitro in an osteoclast differentiation cell model. Administration of ZJS delayed the onset of arthritis, alleviated joint inflammation, and attenuated bone erosion in the CIA mice. Meanwhile, ZJS decreased the serum levels of TNF-α, IL-6, and anti-bovine collagen II-specific antibodies. Furthermore, ZJS treatment reduced the number of osteoclasts and the expression of cathepsin K in the ankle joints of CIA mice. ZJS also inhibited receptor activator of NF-κB ligand (RANKL)-induced osteoclast differentiation and the expression of MMP9 and cathepsin K in vitro. Mechanistically, ZJS blocked RANKL-induced p65 phosphorylation, nucleation, and inhibited the expression of downstream NFATc1 and c-Fos in bone marrow-derived macrophages (BMMs). Taken together, ZJS exerts a therapeutic effect on bone erosion in CIA mice by inhibiting RANKL/NF-κB-mediated osteoclast differentiation, which suggested that ZJS is a promising prescription for treating RA bone erosion.

SIRT1 and SIRT2 modulators reduce LPS-induced inflammation in HAPI microglial cells and protect SH-SY5Y neuronal cells in vitro

Neuroinflammation is associated with the development of depression. Deacetylases SIRT1 and SIRT2 are reported to exert neuroprotective effects in aging, neurogenesis, neurodegeneration and neuroinflammation. Therefore, this study aimed to investigate the effects of SIRT1 and SIRT2 modulators on LPS-induced neuroinflammation and neurodegeneration in vitro. To achieve this, HAPI rat microglial cells were pre-treated with the SIRT1 activator resveratrol (0.1-20 µM), the selective SIRT1 inhibitor EX527 (0.1; 1 µM), the dual SIRT1/SIRT2 inhibitor sirtinol (0.1-20 µM) and the SIRT2 inhibitor AGK2 (0.1; 1 µM), prior to exposure with LPS (5 ng/mL) for 20 h. The reference antidepressant drug fluoxetine and the nonsteroidal anti-inflammatory drug ibuprofen were also evaluated in the same paradigm, both at 1 μM. Resveratrol and sirtinol inhibited TNF-α production to a greater degree than either fluoxetine or ibuprofen. Resveratrol, sirtinol, EX527 and AGK2 significantly reduced PGE₂ production by up to 100% in microglia. Then, the supernatant was transferred to treat SH-SY5Y cells for 24 h. In all cases, SIRT modulator pretreatment significantly protected undifferentiated SH-SY5Y human neuroblastoma cells from the insult of LPS-stimulated HAPI supernatant by up to 40%. Moreover, resveratrol and sirtinol also showed significantly better neuroprotection than fluoxetine or ibuprofen by up to 83 and 69%, respectively. In differentiated SH-SY5Y cells, only sirtinol (20, 10 µM) and AGK2 (0.1 µM) pretreatment protected the cells from LPS-stimulated HAPI supernatant. This study suggests that SIRT1 and SIRT2 modulators are effective in inhibiting LPS-stimulated production of TNF-α and PGE₂ in HAPI microglial cells and protecting SH-SY5Y cells from inflammation. Thus, we provide proof of concept for further investigation of the therapeutic effect of SIRT1 and SIRT2 modulators and combination with current antidepressant medication as a treatment option.

Bioactive Lipids in MSCs Biology: State of the Art and Role in Inflammation

Lipidomics is a lipid-targeted metabolomics approach that aims to the comprehensive analysis of lipids in biological systems in order to highlight the specific functions of lipid species in health and disease. Lipids play pivotal roles as they are major structural components of the cellular membranes and energy storage molecules but also, as most recently shown, they act as functional and regulatory components of intra- and intercellular signaling. Herein, emphasis is given to the recently highlighted roles of specific bioactive lipids species, as polyunsaturated fatty acids (PUFA)-derived mediators (generally known as eicosanoids), endocannabinoids (eCBs), and lysophospholipids (LPLs), and their involvement in the mesenchymal stem cells (MSCs)-related inflammatory scenario. Indeed, MSCs are a heterogenous population of multipotent cells that have attracted much attention for their potential in regulating inflammation, immunomodulatory capabilities, and reparative roles. The lipidomics of the inflammatory disease osteoarthritis (OA) and the influence of MSCs-derived lipids have also been addressed.

Oxidative Stress and Lipid Mediators Modulate Immune Cell Functions in Autoimmune Diseases

Autoimmune diseases, including psoriasis, systemic lupus erythematosus (SLE), and rheumatic arthritis (RA), are caused by a combination of environmental and genetic factors that lead to overactivation of immune cells and chronic inflammation. Since oxidative stress is a common feature of these diseases, which activates leukocytes to intensify inflammation, antioxidants could reduce the severity of these diseases. In addition to activating leukocytes, oxidative stress increases the production of lipid mediators, notably of endocannabinoids and eicosanoids, which are products of enzymatic lipid metabolism that act through specific receptors. Because the anti-inflammatory CB2 receptors are the predominant cannabinoid receptors in leukocytes, endocannabinoids are believed to act as anti-inflammatory factors that regulate compensatory mechanisms in autoimmune diseases. While administration of eicosanoids in vitro leads to the differentiation of lymphocytes into T helper 2 (Th2) cells, eicosanoids are also necessary for the different0iation of Th1 and Th17 cells. Therefore, their antagonists and/or the genetic deletion of their receptors abolish inflammation in animal models of psoriasis—RA and SLE. On the other hand, products of non-enzymatic lipid peroxidation, especially acrolein and 4-hydroxynonenal-protein adducts, mostly generated by an oxidative burst of granulocytes, may enhance inflammation and even acting as autoantigens and extracellular signaling molecules in the vicious circle of autoimmune diseases.

Prostaglandins as potential targets for the treatment of polycystic kidney disease

Polycystic kidney disease (PKD) is characterized by the proliferation of fluid-filled kidney cysts that enlarge over time, causing damage to the surrounding kidney and ultimately resulting in kidney failure. Both increased cell proliferation and fluid secretion are stimulated by increased cyclic adenosine monophosphate (cAMP) in PKD kidneys, so many treatments for the disease target cAMP lowering. Prostaglandins (PG) levels are elevated in multiple animal models of PKD and mediate many of their effects by elevating cAMP levels. Inhibiting the production of PG with cyclooxygenase 2 (COX2) inhibitors reduces PG levels and reduces disease progression. However, COX inhibitors also block beneficial PG and can cause nephrotoxicity. In an orthologous model of the main form of PKD, PGD₂ and PGI₂ were the two PG highest in kidneys and most affected by a COX2 inhibitor. Future studies are needed to determine whether specific blockage of PGD₂ and/or PGI₂ activity would lead to more targeted and effective treatments with fewer undesirable side-effects.

Prostanoid Receptor Subtypes and Its Endogenous Ligands with Processing Enzymes within Various Types of Inflammatory Joint Diseases

A complex inflammatory process mediated by proinflammatory cytokines and prostaglandins commonly occurs in the synovial tissue of patients with joint trauma (JT), osteoarthritis (OA), and rheumatoid arthritis (RA). This study systematically investigated the distinct expression profile of prostaglandin E2 (PGE2), its processing enzymes (COX-2), and microsomal PGES-1 (mPGES-1) as well as the corresponding prostanoid receptor subtypes (EP1-4) in representative samples of synovial tissue from these patients (JT, OA, and RA). Quantitative TaqMan®-PCR and double immunofluorescence confocal microscopy of synovial tissue determined the abundance and exact immune cell types expressing these target molecules. Our results demonstrated that PGE2 and its processing enzymes COX-2 and mPGES-1 were highest in the synovial tissue of RA, followed by the synovial tissue of OA and JT patients. Corresponding prostanoid receptor, subtypes EP3 were highly expressed in the synovium of RA, followed by the synovial tissue of OA and JT patients. These proinflammatory target molecules were distinctly identified in JT patients mostly in synovial granulocytes, in OA patients predominantly in synovial macrophages and fibroblasts, whereas in RA patients mainly in synovial fibroblasts and plasma cells. Our findings show a distinct expression profile of EP receptor subtypes and PGE2 as well as the corresponding processing enzymes in human synovium that modulate the inflammatory process in JT, OA, and RA patients.

The roles of small-molecule inflammatory mediators in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovial inflammation and joint destruction. Although great progress has been made in the treatment of RA with antagonists of pro-inflammatory cytokines such as TNF-α, IL-6 and IL-1, the disease remains refractory in some patients. Previous studies have found that small-molecule inflammatory mediators, such as prostaglandins, leukotrienes, reactive oxygen species, nitric oxide, lipoxins and platelet-activating factor, play a significant role in the development of RA. Such compounds help to induce, maintain or reduce inflammation and could therefore be potential therapeutic targets. In this review, we describe the roles of various classes of small-molecule inflammatory mediators in RA and discuss the effects of some drugs that modulate their activity. Many drugs targeting these mediators have demonstrated good efficacy in mouse models of RA but not in patients. However, it is clear that many small-molecule inflammatory mediators play key roles in the pathogenesis of RA, and a better understanding of the underlying molecular pathways may assist in the development of targeted therapies that are efficacious in RA patients.

Non-steroidal anti-inflammatory drugs, prostaglandins, and COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of the novel coronavirus disease 2019 (COVID-19), a highly pathogenic and sometimes fatal respiratory disease responsible for the current 2020 global pandemic. Presently, there remains no effective vaccine or efficient treatment strategies against COVID-19. Non-steroidal anti-inflammatory drugs (NSAIDs) are medicines very widely used to alleviate fever, pain, and inflammation (common symptoms of COVID-19 patients) through effectively blocking production of prostaglandins (PGs) via inhibition of cyclooxyganase enzymes. PGs can exert either proinflammatory or anti-inflammatory effects depending on the inflammatory scenario. In this review, we survey the potential roles that NSAIDs and PGs may play during SARS-CoV-2 infection and the development and progression of COVID-19. LINKED ARTICLES: This article is part of a themed issue on The Pharmacology of COVID-19. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.21/issuetoc.

Transcriptome analysis of porcine endometrium after LPS-induced inflammation: effects of the PPAR-gamma ligands in vitro†

Female fertility depends greatly on the capacity of the uterus to recognize and eliminate microbial infections, a major reason of inflammation in the endometrium in many species. This study aimed to determine the in vitro effect of peroxisome proliferator-activated receptor gamma (PPARγ) ligands on the transcriptome genes expression and alternative splicing in the porcine endometrium in the mid-luteal phase of the estrous cycle during LPS-stimulated inflammation using RNA-seq technology. The endometrial slices were incubated in vitro in the presence of LPS and PPARγ agonists-PGJ2 or pioglitazone and antagonist-T0070907. We identified 222, 3, 4, and 62 differentially expressed genes after LPS, PGJ2, pioglitazone, or T0070907 treatment, respectively. In addition, we detected differentially alternative spliced events: after treatment with LPS-78, PGJ2-60, pioglitazone-52, or T0070907-134. These results should become a basis for further studies explaining the mechanism of PPARγ action in the reproductive system in pigs.

International Union of Basic and Clinical Pharmacology. CIX. Differences and Similarities between Human and Rodent Prostaglandin E2 Receptors (EP1-4) and Prostacyclin Receptor (IP): Specific Roles in Pathophysiologic Conditions

Prostaglandins are derived from arachidonic acid metabolism through cyclooxygenase activities. Among prostaglandins (PGs), prostacyclin (PGI2) and PGE2 are strongly involved in the regulation of homeostasis and main physiologic functions. In addition, the synthesis of these two prostaglandins is significantly increased during inflammation. PGI2 and PGE2 exert their biologic actions by binding to their respective receptors, namely prostacyclin receptor (IP) and prostaglandin E2 receptor (EP) 1-4, which belong to the family of G-protein-coupled receptors. IP and EP1-4 receptors are widely distributed in the body and thus play various physiologic and pathophysiologic roles. In this review, we discuss the recent advances in studies using pharmacological approaches, genetically modified animals, and genome-wide association studies regarding the roles of IP and EP1-4 receptors in the immune, cardiovascular, nervous, gastrointestinal, respiratory, genitourinary, and musculoskeletal systems. In particular, we highlight similarities and differences between human and rodents in terms of the specific roles of IP and EP1-4 receptors and their downstream signaling pathways, functions, and activities for each biologic system. We also highlight the potential novel therapeutic benefit of targeting IP and EP1-4 receptors in several diseases based on the scientific advances, animal models, and human studies. SIGNIFICANCE STATEMENT: In this review, we present an update of the pathophysiologic role of the prostacyclin receptor, prostaglandin E2 receptor (EP) 1, EP2, EP3, and EP4 receptors when activated by the two main prostaglandins, namely prostacyclin and prostaglandin E2, produced during inflammatory conditions in human and rodents. In addition, this comparison of the published results in each tissue and/or pathology should facilitate the choice of the most appropriate model for the future studies.

Epigenetic regulation of the PGE2 pathway modulates macrophage phenotype in normal and pathologic wound repair

Macrophages are a primary immune cell involved in inflammation, and their cell plasticity allows for transition from an inflammatory to a reparative phenotype and is critical for normal tissue repair following injury. Evidence suggests that epigenetic alterations play a critical role in establishing macrophage phenotype and function during normal and pathologic wound repair. Here, we find in human and murine wound macrophages that cyclooxygenase 2/prostaglandin E2 (COX-2/PGE2) is elevated in diabetes and regulates downstream macrophage-mediated inflammation and host defense. Using single-cell RNA sequencing of human wound tissue, we identify increased NF-κB-mediated inflammation in diabetic wounds and show increased COX-2/PGE2 in diabetic macrophages. Further, we identify that COX-2/PGE2 production in wound macrophages requires epigenetic regulation of 2 key enzymes in the cytosolic phospholipase A2/COX-2/PGE2 (cPLA2/COX-2/PGE2) pathway. We demonstrate that TGF-β-induced miRNA29b increases COX-2/PGE2 production via inhibition of DNA methyltransferase 3b-mediated hypermethylation of the Cox-2 promoter. Further, we find mixed-lineage leukemia 1 (MLL1) upregulates cPLA2 expression and drives COX-2/PGE2. Inhibition of the COX-2/PGE2 pathway genetically (Cox2fl/fl Lyz2Cre+) or with a macrophage-specific nanotherapy targeting COX-2 in tissue macrophages reverses the inflammatory macrophage phenotype and improves diabetic tissue repair. Our results indicate the epigenetically regulated PGE2 pathway controls wound macrophage function, and cell-targeted manipulation of this pathway is feasible to improve diabetic wound repair.

GC-MS analysis, antimicrobial, antioxidant, antilipoxygenase and cytotoxic activities of Jacaranda mimosifolia methanol leaf extracts and fractions

Jacaranda mimosifolia trees are grown in frost-free regions globally. The aim of this study was to evaluate the methanol crude extract and various fractions of increasing polarity of J. mimosifolia leaves for bioactive metabolites, as well as antimicrobial, antioxidant and anticancer activities. The anti-inflammatory potential of the various fractions of J. mimosifolia leaf extract was studied via the lipoxygenase (LOX) inhibitory assay. Methanol crude extract (ME), derived fractions extracted with chloroform (CF) and ethyl acetate (EAF), and residual aqueous extract (AE) of dried J. mimosifolia leaves were assayed for polyphenolic compounds, their antioxidant, antimicrobial and lipoxygenase (LOX) inhibitory activities, and anticancer properties. Polyphenolic compounds were determined via HPLC while phytochemicals (total phenolics, flavonoids, tannins and ortho-diphenol contents), antioxidant activities (DPPH, hydrogen peroxideperoxide, hydroxyl and superoxide radical anions) and LOX were measured via spectrophotometry. Methanol extracts and various fractions were evaluated for antibacterial activities against Bacillus subtilis, Klebsiella pneumonia, Pseudomonas aeruginosa and Staphylococcus aureus. Antifungal potential of the fractions was tested against three species: Aspergillus flavus, Aspergillus fumigatus and Fusarium oxysporum. The highest values for total phenolic content (TPC), total flavonoid content (TFC), flavonols, tannins and ortho-diphenols were in the ME, followed by CF > EAF > AE. ME also had the highest antioxidant activity with EC₅₀ values 48±1.3, 45±2.4, 42±1.3 and 46±1.3 μg/mL based on the DPPH, hydrogen peroxide, hydroxyl radical and superoxide radical assays, respectively. TPC and TFC showed a significant, strong and positive correlation with the values for each of these antioxidant activities. ME exhibited anti-inflammatory potential based on its LOX inhibitory activity (IC₅₀ = 1.3 μg/mL). ME also had the maximum antibacterial and antifungal potential, followed by EAF > CF > AE. Furthermore, ME showed the strongest cytotoxic effect (EC₅₀ = 10.7 and 17.3 μg/mL) against human hormone-dependent prostate carcinoma (LnCaP) and human lung carcinoma (LU-1) cell lines, respectively. Bioactive compounds present in leaf methanol extracts of J. mimosifolia were identified using gas chromatography–mass spectrometry (GC–MS). Fifteen compounds were identified including phenolic and alcoholic compounds, as well as fatty acids. Our results suggest that J. mimosifolia leaves are a good source of natural products with antioxidant, anti-inflammatory and anti-cancer properties for potential therapeutic, nutraceutical and functional food applications.

Bioactive lipids, inflammation and chronic diseases

Endogenous bioactive lipids are part of a complex network that modulates a plethora of cellular and molecular processes involved in health and disease, of which inflammation represents one of the most prominent examples. Inflammation serves as a well-conserved defence mechanism, triggered in the event of chemical, mechanical or microbial damage, that is meant to eradicate the source of damage and restore tissue function. However, excessive inflammatory signals, or impairment of pro-resolving/anti-inflammatory pathways leads to chronic inflammation, which is a hallmark of chronic pathologies. All main classes of endogenous bioactive lipids - namely eicosanoids, specialized pro-resolving lipid mediators, lysoglycerophopsholipids and endocannabinoids - have been consistently involved in the chronic inflammation that characterises pathologies such as cancer, diabetes, atherosclerosis, asthma, as well as autoimmune and neurodegenerative disorders and inflammatory bowel diseases. This review gathers the current knowledge concerning the involvement of endogenous bioactive lipids in the pathogenic processes of chronic inflammatory pathologies.

Functional Lipids in Autoimmune Inflammatory Diseases

Lipids are apolar small molecules known not only as components of cell membranes but also, in recent literature, as modulators of different biological functions. Herein, we focused on the bioactive lipids that can influence the immune responses and inflammatory processes regulating vascular hyperreactivity, pain, leukocyte trafficking, and clearance. In the case of excessive pro-inflammatory lipid activity, these lipids also contribute to the transition from acute to chronic inflammation. Based on their biochemical function, these lipids can be divided into different families, including eicosanoids, specialized pro-resolving mediators, lysoglycerophospholipids, sphingolipids, and endocannabinoids. These bioactive lipids are involved in all phases of the inflammatory process and the pathophysiology of different chronic autoimmune diseases such as rheumatoid arthritis, multiple sclerosis, type-1 diabetes, and systemic lupus erythematosus.

The role of autonomously secreted PGE2 and its autocrine/paracrine effect on bone matrix mineralization at the different stages of differentiating MC3T3-E1 cells

Bone is consisted of osteoblast-linage cells, bone-forming cells in various differentiation stages. However, it is not fully understood how communicate and interact these cells immigrated from bone marrow. In this study, we showed that prostaglandin E2 (PGE₂) had a role in autonomous modification of matrix mineralization in osteoblastic cell line, MC3T3-E1, and interactions across the cells in different differentiation stages. Analysis using LC-MS/MS and inhibitors showed the autonomous secretion of PGE₂ among the prostanoids in differentiation stages and that depend on COX-2, a key enzyme for production of PGE₂. Treatment with inhibitors of PGE₂ receptors and COX-2 indicated that secreted PGE₂ regulates matrix mineralization in an autocrine/paracrine manner. In addition, we showed that the expression profile of PGE₂ receptors (EP1-EP4) and PGE₂ effects on matrix mineralization derived from it changed during cell differentiation. Treatment with inhibitors of PGE₂ signaling in the early differentiation stage of MC3T3-E1 cells induced significant changes in matrix mineralization several days after. Stimulation with the extracts from culture medium of the matured cells including PGE₂ and co-culture with the matured cells secreting PGE₂ significantly promoted matrix mineralization of the early stage cells, in contrast, treatment with inhibitor of COX-2 and PGE₂ receptors failed to do so. These results support that PGE₂ plays important roles in the interaction system of osteoblast-linage cells in bone tissue to regulate matrix mineralization reflecting condition of bone-forming cells, that is, population and maturation.

Prostaglandins as the Agents That Modulate the Course of Brain Disorders

Neurologic and neuropsychiatric diseases are associated with great morbidity and mortality. Prostaglandins (PGs) are formed by sequential oxygenation of arachidonic acid in physiologic and pathologic conditions. For the production of PGs cyclooxygenase is a necessary enzyme that has two isoforms, that are named COX-1 and COX-2. COX-1 produces type 1 prostaglandins and on the other hand, COX-2 produces type 2 prostaglandins. Recent studies suggest PGs abnormalities are present in a variety of neurologic and psychiatric disorders. In a disease state, type 2 prostaglandins are mostly responsible and type 1 PGs are not so important in the disease state. In this review, the importance of prostaglandins especially type 2 in brain diseases has been discussed and their possible role in the initiation and outcome of brain diseases has been assessed. Overall the studies suggest prostaglandins are the agents that modulate the course of brain diseases in a positive or negative manner. Here in this review article, the various aspects of PGs in the disease state have discussed. It appears more studies must be done to understand the exact role of these agents in the pathophysiology of brain diseases. However, the suppression of prostaglandin production may confer the alleviation of some brain diseases.

Comparison of two inhibitors of E-type prostanoid receptor four and carprofen in dogs with experimentally induced acute synovitis

OBJECTIVE

To investigate the ability of a proprietary antagonist of E-type prostanoid receptor (EP) 4, grapiprant, and carprofen to attenuate lameness attributable to urate-induced synovitis in dogs.

ANIMALS

5 purpose-bred hound-cross dogs.

PROCEDURES

A blinded, 3-way crossover study was performed. Dogs received each of 3 treatments (L-766, a proprietary antagonist of EP4; 4.0 mg/kg), grapiprant (an antagonist of EP4; 2.0 mg/kg), and carprofen (4.4 mg/kg); dogs received 4 doses of each treatment (14 and 2 hours before and 22 and 46 hours after urate injection). Synovitis was induced by intra-articular injection of sodium urate. Measurements (vertical ground reaction forces and clinical lameness scores) were obtained immediately before (0 hours; baseline) and 6, 12, 24, 36, and 48 hours after sodium urate injection. All data were analyzed with repeated-measures ANOVA.

RESULTS

Lameness scores at 6 hours were significantly higher than baseline lameness scores for all treatments. Lameness scores for the grapiprant treatment remained significantly higher at 12 and 24 hours, compared with baseline lameness scores. Lameness scores for the carprofen treatment were significantly lower than lameness scores for the grapiprant treatment at 6, 12, and 24 hours. Analysis of peak vertical force and vertical impulse data revealed a pattern similar to that for lameness scores. Treatment with L-766 resulted in a significantly higher vertical impulse at 48 hours than did treatment with carprofen or grapiprant.

CONCLUSIONS AND CLINICAL RELEVANCE

In these dogs, carprofen was the most effective treatment for attenuating lameness induced by injection of sodium urate, and grapiprant was the least effective treatment.

EP2/4 Receptors Promote the Synthesis of PGE2 Increasing Tissue Damage in Bovine Endometrial Explants Induced by Escherichia coli

The bovine uterine is easily contaminated with bacteria during coitus or parturition. A previous study suggested that prostaglandin E₂ (PGE₂) promoted Escherichia coli-infected bovine endometrial tissue inflammatory damage via cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGES-1). However, it remains unclear which PGE₂ receptors regulate the proinflammatory effect of PGE₂ In this study, we evaluated the effect of PGE₂ and its mediated receptors on E. coli-infected endometrium explants isolated from the bovine uterus. The E. coli-infected bovine endometrial explants were cultured in vitro, and the study used EP2/4 receptor agonists to investigate the responses of COX-2, mPGES-1, PGE₂, proinflammatory factors, and damage-associated molecular patterns (DAMPs). The expression of COX-2, mPGES-1, PGE₂, proinflammatory factors, and DAMPs was significantly increased after infection with E. coli; however, the high expression levels caused by E. coli were reduced following treatment with COX-2 and mPGES-1 inhibitors. In addition, the expression levels of COX-2, mPGES-1, PGE₂, proinflammatory factors, and DAMPs were higher in treatment with EP2/4 receptor agonists in E. coli-infected endometrium explants, and their promotable effects were effectively blocked by EP2/4 receptor antagonists. These findings provide evidence that PGE₂ may promote the progress of inflammation in endometrial explants infected with E. coli in bovines. Furthermore, EP2/4 may be involved in a positive feedback loop for COX-2 and mPGES-1 expression, and this may be responsible for the proinflammatory reaction of PGE₂ in E. coli-infected uteri of bovines. SIGNIFICANCE STATEMENT: PGE₂ promoted E. coli-infected bovine endometrial tissue damage via COX-2 and mPGES-1. However, this proinflammatory effect of PGE₂ depends on which receptors are affected by PGE₂, and this remains unclear. In this study, it was investigated that EP2 and EP4 may be involved in a positive feedback loop for COX-2 and mPGES-1 expression, and this may be responsible for the proinflammatory reaction of PGE₂ in E. coli-infected uteri of bovines.

Prostaglandin regulation of T cell biology

Prostaglandins (PG) are pleiotropic bioactive lipids involved in the control of many physiological processes, including key roles in regulating inflammation. This links PG to the modulation of the quality and magnitude of immune responses. T cells, as a core part of the immune system, respond readily to inflammatory cues from their environment, and express a diverse array of PG receptors that contribute to their function and phenotype. Here we put in context our knowledge about how PG affect T cell biology, and review advances that bring light into how specific T cell functions that have been newly discovered are modulated through PG. We will also comment on drugs that target PG metabolism and sensing, their effect on T cell function during disease, and we will finally discuss how we can design new approaches that modulate PG in order to maximize desired therapeutic T cell effects.

Effects of Sustained-Release Beraprost in Patients With Primary Glomerular Disease or Nephrosclerosis: CASSIOPEIR Study Results

TRK-100STP, a sustained-release preparation of the orally active prostacyclin analogue beraprost sodium, targets renal hypoxia. This study aimed to show the superiority of TRK-100STP over placebos in patients with chronic kidney disease (with either primary glomerular disease or nephrosclerosis) to determine the recommended dose. CASSIOPEIR (Chronic Renal Failure Asian Study with Oral PGI₂ Derivative for Evaluating Improvement of Renal Function) was a randomized, double-blind, placebo-controlled study conducted at 160 sites in seven Asia-Pacific countries and regions. Eligible patients (n = 892) were randomized to TRK-100STP 120, 240 μg, or placebo for a treatment period of up to 4 years. The primary efficacy endpoint was time to first occurrence of a renal composite: doubling of serum creatinine or occurrence of end-stage renal disease. No significant differences were observed in composite endpoints between TRK-100STP and placebo (P = 0.5674). Hazard ratios (95% CI) in the TRK-100STP 120 and 240 μg vs. placebo groups were 0.98 (0.78, 1.22) and 0.91 (0.72, 1.14), respectively. The overall incidence of adverse events and adverse drug reactions was comparable between treatment arms.

Cysteinyl leukotriene receptor antagonism: a promising pharmacological strategy for lowering the severity of arthritis

BACKGROUND AND AIMS

Though cyclooxygenase inhibitors are employed in rheumatoid arthritis treatment, modulators of leukotrienes are underexplored. We investigated the therapeutic potential of montelukast, a known cysteinyl leukotriene receptor-1 (CysLT1) inhibitor in an experimental rat model of arthritis.

METHODS

Arthritis was induced in rats, and montelukast (5 mg/kg body wt.) was administered prophylactically (PAM) and therapeutically (TAM) through oral route.

RESULTS AND DISCUSSION

Blood and joint tissue markers of oxidative stress (lipid peroxidation, protein carbonyls, and nitric oxides) were significantly (p < 0.05) reduced in montelukast administered rats. Paw inflammation, RA markers (RF and CRP), eicosanoids (PGE₂, LTB₄, and LTC₄), cytokines (IL-1β and MCP-1), activity of hydrolytic enzymes (collagenase, elastase, and hyaluronidase), expression of matrix metalloproteinases (MMP), and EP-4 receptor were significantly (p < 0.05) reduced in montelukast administered rats. This study established that leukotriene inhibition through montelukast lowered the severity of arthritis and thus a potential strategy for reducing the severity of arthritis.

Respective contribution of cytosolic phospholipase A2α and secreted phospholipase A2 IIA to inflammation and eicosanoid production in arthritis

Phospholipase A₂s (PLA₂) play a key role in generation of eicosanoids. Cytosolic PLA₂α (cPLA₂α) is constitutively expressed in most cells, whereas IIA secreted PLA₂ (sPLA₂-IIA) is induced during inflammation and is present at high levels in the synovial fluid of rheumatoid arthritis patients. In mice, both cPLA₂α and sPLA₂-IIA have been implicated in autoimmune arthritis; however, the respective contribution of these two enzymes to the pathogenesis and production of eicosanoids is unknown. We evaluated the respective role of cPLA₂α and sPLA₂-IIA with regard to arthritis and eicosanoid profile in an in vivo model of arthritis. While arthritis was most severe in mice expressing both enzymes, it was abolished when both cPLA₂α and sPLA₂-IIA were lacking. cPLA₂α played a dominant role in the severity of arthritis, although sPLA₂-IIA sufficed to significantly contribute to the disease. Several eicosanoids were modulated during the course of arthritis and numerous species involved sPLA₂-IIA expression. This study confirms the critical role of PLA₂s in arthritis and unveils the distinct contribution of cPLA₂α and sPLA₂-IIA to the eicosanoid profile in arthritis.

Divergent roles of prostacyclin and PGE2 in human tendinopathy

BACKGROUND

Tendon disease is a significant global healthcare burden whereby patients experience pain and disability; however, the mechanisms that underlie inflammation and pain are poorly understood. Herein, we investigated the role of prostaglandins as important mediators of inflammation and pain in tissues and cells derived from patients with tendinopathy.

METHODS

We studied supraspinatus and Achilles tendon biopsies from symptomatic patients with tendinopathy or rupture. Tendon-derived stromal cells (CD45negCD34neg) isolated from tendons were cultured and treated with interleukin-1β (IL-1β) to investigate prostaglandin production.

RESULTS

Diseased tendon tissues showed increased expression of prostacyclin receptor (IP) and enzymes catalyzing the biosynthesis of prostaglandins, including cyclooxygenase-1 (COX-1), COX-2, prostacyclin synthase (PGIS), and microsomal prostaglandin E synthase-1 (mPGES-1). PGIS co-localized with cells expressing Podoplanin, a marker of stromal fibroblast activation, and the nociceptive neuromodulator NMDAR-1. Treatment with IL-1β induced release of the prostacyclin metabolite 6-keto PGF1α in tendon cells isolated from diseased supraspinatus and Achilles tendons but not in cells from healthy comparator tendons. The same treatment induced profound prostaglandin E2 (PGE2) release in tendon cells derived from patients with supraspinatus tendon tears. Incubation of IL-1β treated diseased tendon cells with selective mPGES-1 inhibitor Compound III, reduced PGE2, and simultaneously increased 6-keto PGF1α production. Conversely, COX blockade with naproxen or NS-398 inhibited both PGE2 and 6-keto PGF1α production. Tendon biopsies from patients in whom symptoms had resolved showed increased PTGIS compared to biopsies from patients with persistent tendinopathy.

CONCLUSIONS

Our results suggest that PGE2 sustains inflammation and pain while prostacyclin may have a protective role in human tendon disease.

Regulatory effects of paeoniflorin-6'-O-benzene sulfonate (CP-25) on dendritic cells maturation and activation via PGE2-EP4 signaling in adjuvant-induced arthritic rats

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease. Dendritic cells (DCs) are one of the most powerful antigen-presenting cells, and they play an important role in RA pathogenesis. Prostaglandin E2 (PGE2) is a potent lipid mediator that can regulate the maturation and activation of DCs, but the molecular mechanisms have not been elucidated. In this study, both in vitro and in an RA rat model, we investigated the mechanisms involved by focusing on PGE2-mediated signaling and using a novel anti-inflammatory compound, paeoniflorin-6'-O-benzene sulfonate (CP-25). PGE2 combined with tumor necrosis factor-α promoted DC maturation and activation through EP4-cAMP signaling. Treatment with CP-25 increased the endocytic capacity of DCs induced by PGE2. CP-25 inhibited the potency of DCs induced by the EP4 receptor agonist, CAY10598, to stimulate allogeneic T cells. Consistent with these findings, the CAY10598-induced upregulation of DC surface activation markers and production of IL-23 was significantly inhibited by CP-25 in a concentration-dependent manner. In vivo administration of CP-25 alleviated adjuvant arthritis (AA) in rats through inhibition of DC maturation and activation. Our results indicate that PGE2-EP4-cAMP signal hyperfunction can lead to abnormal activation of DC functions, which correlates with the course of disease in AA rats and provides a possible treatment target. The inhibition of DC maturation and activation by CP-25 interference of the PGE2-EP4 pathway may significantly contribute to the immunoregulatory profile of CP-25 when used to treat RA and other immune cell-mediated disorders.

Prostaglandin-cytokine crosstalk in chronic inflammation

Chronic inflammation underlies various debilitating disorders including autoimmune, neurodegenerative, vascular and metabolic diseases as well as cancer, where aberrant activation of the innate and acquired immune systems is frequently seen. Since non-steroidal anti-inflammatory drugs exert their effects by inhibiting COX and suppressing PG biosynthesis, PGs have been traditionally thought to function mostly as mediators of acute inflammation. However, an inducible COX isoform, COX-2, is often highly expressed in tissues of the chronic disorders, suggesting an as yet unidentified role of PGs in chronic inflammation. Recent studies have shown that in addition to their short-lived actions in acute inflammation, PGs crosstalk with cytokines and amplify the cytokine actions on various types of inflammatory cells and drive pathogenic conversion of these cells by critically regulating their gene expression. One mode of such PG-mediated amplification is to induce the expression of relevant cytokine receptors, which is typically observed in Th1 cell differentiation and Th17 cell expansion, events leading to chronic immune inflammation. Another mode of amplification is cooperation of PGs with cytokines at the transcription level. Typically, PGs and cytokines synergistically activate NF-κB to induce the expression of inflammation-related genes, one being COX-2 itself, which makes PG-mediated positive feedback loops. This signalling consequently enhances the expression of various NF-κB-induced genes including chemokines to macrophages and neutrophils, which enables sustained infiltration of these cells and further amplifies chronic inflammation. In addition, PGs are also involved in tissue remodelling such as fibrosis and angiogenesis. In this article, we review these findings and discuss their relevance to human diseases.

Interleukin-6 Interweaves the Bone Marrow Microenvironment, Bone Loss, and Multiple Myeloma

The immune system is strongly linked to the maintenance of healthy bone. Inflammatory cytokines, specifically, are crucial to skeletal homeostasis and any dysregulation can result in detrimental health complications. Interleukins, such as interleukin 6 (IL-6), act as osteoclast differentiation modulators and as such, must be carefully monitored and regulated. IL-6 encourages osteoclastogenesis when bound to progenitors and can cause excessive osteoclastic activity and osteolysis when overly abundant. Numerous bone diseases are tied to IL-6 overexpression, including rheumatoid arthritis, osteoporosis, and bone-metastatic cancers. In the latter, IL-6 can be released with growth factors into the bone marrow microenvironment (BMM) during osteolysis from bone matrix or from cancer cells and osteoblasts in an inflammatory response to cancer cells. Thus, IL-6 helps create an ideal microenvironment for oncogenesis and metastasis. Multiple myeloma (MM) is a blood cancer that homes to the BMM and is strongly tied to overexpression of IL-6 and bone loss. The roles of IL-6 in the progression of MM are discussed in this review, including roles in bone homing, cancer-associated bone loss, disease progression and drug resistance. MM disease progression often includes the development of drug-resistant clones, and patients commonly struggle with reoccurrence. As such, therapeutics that specifically target the microenvironment, rather than the cancer itself, are ideal and IL-6, and its myriad of downstream signaling partners, are model targets. Lastly, current and potential therapeutic interventions involving IL-6 and connected signaling molecules are discussed in this review.

Identification of Seven Aberrantly Methylated and Expressed Genes in Adrenocortical Carcinoma

Background: Adrenocortical carcinoma (ACC) is a rare endocrine malignancy with an unfavorable prognosis and limited treatment options. Nevertheless, no clinically applicable molecular markers have been identified for the progression of ACCs. DNA methylation alterations were found to contribute to the development of ACC in recent decades. Material and Methods: The aims of the current study was to identify the abnormally methylated differentially expressed genes (DEGs) in ACCs, and to elucidate the mechanistic basis for these changes. Analyses were conducted on gene expression and gene methylation profile datasets to identify the aberrantly methylated DEGs. The DAVID software was used to conduct the analyses of functional enrichment on screened genes. Finally, expression was validated, and the relationship between abnormally methylated DEGs and clinical features was determined via the Oncomine database and The Cancer Genome Atlas (TCGA). To further verify the altered expression and methylation status of our identified genes we also validated these changes at the tissue and cellular levels. Results: We screened and identified 92 differentially expressed genes and 802 abnormally methylated genes. Furthermore, seven aberrantly methylated and dysregulated genes were identified and validated, along with a number of functional enriched pathways. Among these seven genes, the expression or methylation status is significantly correlated with different pathological stages and overall rates of survival. In validation, the expression of seven genes were significantly altered and five genes were hypermethylated in ACC. Conclusions: Our study identified abnormally methylated DEGs and potentially affected pathways in ACCs, from which we could begin to understand the basic molecular mechanisms of these alterations. Moreover, these abnormally methylated genes might serve as therapeutic targets and biomarkers to allow ACC patients to be more precisely diagnosed and effectively treated.

Immunomodulatory Effects of CP-25 on Splenic T Cells of Rats with Adjuvant Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease in which T cells play an important role. Paeoniflorin-6-oxy-benzenesulfonate (CP-25) shows a strong anti-inflammatory and immunomodulatory effect in the joint of adjuvant arthritis (AA) rats, but the role of the spleen function is still unclear. The aim of this study was to research how CP-25 regulated spleen function of AA rats. Male Sprague-Dawley rats were administered with CP-25 (50 mg/kg) orally from day 17 to 29 after immunization. The spleen histopathological changes were analyzed by hematoxylin-eosin staining. G protein-coupled receptor kinases (GRKs) and prostaglandin receptor subtypes (EPs) were screened by Western blot and immunohistochemistry. The co-expression of GRK2 and EP2 as well as GRK2 and EP4 was measured by immunofluorescence and co-immunoprecipitation. The expression of GRK2 and EP4 in splenic T cells was further detected by immunofluorescence. CP-25 was found to relieve the secondary paw swelling, attenuate histopathologic changes, and downregulate GRK2, EP2 and EP4 expression in AA rats. Additionally, CP-25 not only downregulated the co-expression of GRK2 and EP4 but also downregulated GRK2, EP4 expression in splenic T cells of AA rats. From these results, we can infer that CP-25 play an anti-inflammatory and immune function by affecting the function of the splenic T cells.

Raging the War Against Inflammation With Natural Products

Over the last few decade Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) are the drugs of choice for treating numerous inflammatory diseases including rheumatoid arthritis. The NSAIDs produces anti-inflammatory activity via inhibiting cyclooxygenase enzyme, responsible for the conversation of arachidonic acid to prostaglandins. Likewise, cyclooxegenase-2 inhibitors (COX-2) selectively inhibit the COX-2 enzyme and produces significant anti-inflammatory, analgesic, and anti-pyretic activity without producing COX-1 associated gastrointestinal and renal side effects. In last two decades numerous selective COX-2 inhibitors (COXIBs) have been developed and approved for various inflammatory conditions. However, data from clinical trials have suggested that the prolong use of COX-2 inhibitors are also associated with life threatening cardiovascular side effects including ischemic heart failure and myocardial infection. In these scenario secondary metabolites from natural product offers a great hope for the development of novel anti-inflammatory compounds. Although majority of the natural product based compounds exhibit more selectively toward COX-1. However, the data suggest that slight structural modification can be helpful in developing COX-2 selective secondary metabolites with comparative efficacy and limited side effects. This review is an effort to highlight the secondary metabolites from terrestrial and marine source with significant COX-2 and COX-2 mediated PGE2 inhibitory activity, since it is anticipated that isolates with ability to inhibit COX-2 mediated PGE2 production would be useful in suppressing the inflammation and its classical sign and symptoms. Moreover, this review has highlighted the potential lead compounds including berberine, kaurenoic acid, α-cyperone, curcumin, and zedoarondiol for further development with the help of structure-activity relationship (SAR) studies and their current status.

PGE2 stimulates COX-2 expression via EP2/4 receptors and acts in synergy with IL-1β in human follicular dendritic cell-like cells

PGE2 is the major lipid mediator of inflammation produced by multiple cell types including follicular dendritic cells (FDCs) of the lymphoid tissue. We have investigated the immunoregulatory function of PGE2 and its production mechanism using FDC-like cells isolated from human tonsil. Our recent observation of COX-2-inducing effect of PGE2 prompted us to identify the responsible receptor in this study. Pharmacologic approaches were adopted and Western blotting was utilized to measure protein expression levels. Agonists selective for EP2 and EP4 significantly stimulated COX-2 expression, while antagonists for these receptors prevented PGE2 from triggering COX-2 induction. The combined addition of EP2 and EP4 antagonists resulted in further inhibition of PGE2. In contrast, EP1 and EP3 antagonists failed to exhibit the inhibitory effect on PGE2-induced COX-2 expression. Since PGE2 achieves COX-2 induction by repressing Akt activation in FDC-like cells, we confirmed EP2 and EP4 being the targets of PGE2 by examining the effects of E-prostanoid (EP) agonists and antagonists on the level of Akt phosphorylation. After the identification of PGE2 receptor, we examined the effect of PGE2 on IL-1β-induced COX-2 expression. PGE2 and IL-1β brought about a synergistic induction of COX-2 expression. Taken together, this study implies the impact of the combined role of eicosanoids and cytokines in inflammatory milieu.

Down-regulation of microsomal prostaglandin E2 synthase-1 in the infrapatellar fat pad of osteoarthritis patients with hypercholesterolemia

BACKGROUND

While epidemiological studies have reported a potential role for hypercholesterolemia (HCE) in osteoarthritis (OA), the association between HCE and OA has yet to be clarified. Adipose tissue is a primary locus for cholesterol metabolism and the presence of HCE reportedly causes adipose dysfunction. The knee joint contains adipose tissue in the form of the infrapatellar fat pad (IPFP), which has been shown to contribute to the pathophysiology of OA in the knee via the secretion of inflammatory mediators. However, the effect of HCE on the expression of inflammatory mediators in the IPFP has not been elucidated.

METHODS

IPFP and synovial tissues (ST) were extracted from 145 subjects with OA, diagnosed by radiography, during total knee arthroplasty. OA patients were divided into three groups according to their total cholesterol levels (Desirable, Borderline high and High) based on the National Cholesterol Education Program Adult Treatment Panel III (NCEPATP III). We examined the expression of cyclooxygenase-2 (COX-2), microsomal prostaglandin E synthase-1 (mPGES1), tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 using real-time polymerase chain reaction and compared results among the Desirable, Borderline high and High groups.

RESULTS

The mRNA expression levels of TNF-α, IL-1β, and IL-6 in ST and the IPFP were not significantly different among the three groups. COX-2 mRNA expression in ST and IPFP was likewise not different among the three groups. While the mRNA expression level of mPGES1 in ST was also not significantly different, that of mPGES1 in the IPFP was significantly lower in the High group than in the Desirable and Borderline high groups.

CONCLUSION

mRNA levels of mPGES-1 are reduced in the IPFP of knee OA patients with HCE. Additional studies are need to clarify the effect of mPGES-1 down-regulation in OA pathology.

A novel diindolylmethane analog, 1,1-bis(3'-indolyl)-1-(p-chlorophenyl) methane, inhibits the tumor necrosis factor-induced inflammatory response in primary murine synovial fibroblasts through a Nurr1-dependent mechanism

The progression of rheumatoid arthritis involves the thickening of the synovial lining due to the proliferation of fibroblast-like synoviocytes (FLS) and infiltration by inflammatory cells. Tumor necrosis factor alpha (TNFα) is a pro-inflammatory cytokine involved in progression of the disease. Under rheumatoid conditions, FLS express the tumor necrosis factor (TNF)-recognition complex (TNFR1, TNFR2, VCAM-1 and ICAM-1), which induces local macrophage activation and leads to downstream nuclear factor κB (NF-κB) signaling. The NF-κB-regulated inflammatory gene, cyclooxygenase (COX), increases synthesis of prostaglandins that contribute to the propagation of inflammatory damage within the joint. Because the nuclear orphan receptor, NR4A2 (Nurr1), can negatively regulate NF-κB-dependent inflammatory gene expression in macrophages, we postulated that activation of this receptor by the Nurr1 ligand 1,1-bis(3'-indolyl)-1-(p-chlorophenyl) methane (C-DIM12) would modulate inflammatory gene expression in synovial fibroblasts by inhibiting NF-κB. Treatment with C-DIM12 suppressed TNFα-induced expression of adhesion molecules and NF-κB regulated genes in primary synovial fibroblasts including vascular adhesion molecule 1 (VCAM-1), PGE2 and COX-2. Immunofluorescence studies indicated that C-DIM12 did not prevent translocation of p65 and stabilized nuclear localization of Nurr1 in synovial fibroblasts. Knockdown of Nurr1 expression by RNA interference prevented the inhibitory effects of C-DIM12 on inflammatory gene expression, indicating that the anti-inflammatory effects of this compound are Nurr1-dependent. Collectively, these data suggest that this receptor may be a viable therapeutic target in RA.

Prostaglandin E2 and IL-23 interconnects STAT3 and RoRγ pathways to initiate Th17 CD4+ T-cell development during rheumatoid arthritis

BACKGROUND

The chronic inflammation associated with rheumatoid arthritis (RA) leads to focal and systemic bone erosion of the joints resulting in a crippling disability. Recent reports indicate an increase in the incidence of RA in the coming years, placing a significant burden on healthcare resources. The incidence of RA is observed to be increasing with age and a significant proportion of those new cases will be aggressively erosive.

FINDINGS

The altered physiology, due to immune disturbances, contributes towards RA pathogenesis. The imbalance of inflammatory cytokines and non-cytokine immune modulators such as prostaglandin E2 (PGE2) and IL-23-induced pathogenic IL-17, plays a crucial role in persistent inflammation and bone degradation during RA. However, the molecular mechanism of IL-23, a key cytokine, and PGE2 in the development and perpetuation of IL-17 producing effector Th17 cells is poorly understood.

CONCLUSION

This review focuses on research findings that provide insight into the contribution of PGE2 and IL-23 during the development of pathogenic Th17 cells. We also highlight the key transcriptional factors required for Th17 development and therapeutic strategies to disrupt the interaction between IL-23 and IL-17 to prevent the end-organ damage in RA.

CD36 Shunts Eicosanoid Metabolism to Repress CD14 Licensed Interleukin-1β Release and Inflammation

Interleukin (IL)-1β is a potential target for treatment of several inflammatory diseases, including envenomation by the scorpion Tityus serrulatus. In this context, bioactive lipids such as prostaglandin (PG)E₂ and leukotriene (LT)B₄ modulate the production of IL-1β by innate immune cells. Pattern recognition receptors (PRRs) that perceive T. serrulatus venom (TsV), and orchestrate LTB₄, PGE₂, and cyclic adenosine monophosphate (cAMP) production to regulate IL-1β release are unknown. Furthermore, molecular mechanisms driving human cell responses to TsV remain uncharacterized. Here, we identified that both CD14 and CD36 control the synthesis of bioactive lipids, inflammatory cytokines, and mortality mediated by TsV. CD14 induces PGE₂/cAMP/IL-1β release and inflammation. By contrast, CD36 shunts eicosanoid metabolism toward production of LTB₄, which represses the PGE₂/cAMP/IL-1β axis and mortality. Of importance, the molecular mechanisms observed in mice strongly correlate with those of human cell responses to TsV. Overall, this study provides major insights into molecular mechanisms connecting CD14 and CD36 with differential eicosanoid metabolism and inflammation mediated by IL-1β.