Anti-Inflammatory Effects of Progesterone in Lipopolysaccharide-Stimulated BV-2 Microglia

Female sex is associated with improved outcome in experimental brain injury models, such as traumatic brain injury, ischemic stroke, and intracerebral hemorrhage. This implies female gonadal steroids may be neuroprotective. A mechanism for this may involve modulation of post-injury neuroinflammation. As the resident immunomodulatory cells in central nervous system, microglia are activated during acute brain injury and produce inflammatory mediators which contribute to secondary injury including proinflammatory cytokines, and nitric oxide (NO) and prostaglandin E₂ (PGE₂), mediated by inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2), respectively. We hypothesized that female gonadal steroids reduce microglia mediated neuroinflammation. In this study, the progesterone’s effects on tumor necrosis factor alpha (TNF-α), iNOS, and COX-2 expression were investigated in lipopolysaccharide (LPS)-stimulated BV-2 microglia. Further, investigation included nuclear factor kappa B (NF-κB) and mitogen activated protein kinase (MAPK) pathways. LPS (30 ng/ml) upregulated TNF-α, iNOS, and COX-2 protein expression in BV-2 cells. Progesterone pretreatment attenuated LPS-stimulated TNF-α, iNOS, and COX-2 expression in a dose-dependent fashion. Progesterone suppressed LPS-induced NF-κB activation by decreasing inhibitory κBα and NF-κB p65 phosphorylation and p65 nuclear translocation. Progesterone decreased LPS-mediated phosphorylation of p38, c-Jun N-terminal kinase and extracellular regulated kinase MAPKs. These progesterone effects were inhibited by its antagonist mifepristone. In conclusion, progesterone exhibits pleiotropic anti-inflammatory effects in LPS-stimulated BV-2 microglia by down-regulating proinflammatory mediators corresponding to suppression of NF-κB and MAPK activation. This suggests progesterone may be used as a potential neurotherapeutic to treat inflammatory components of acute brain injury.     

Induction of COX-2/PGE2/IL-6 is crucial for cigarette smoke extract-induced airway inflammation: Role of TLR4-dependent NADPH oxidase activation

Exposure to cigarette smoke extract (CSE) leads to airway and lung inflammation through an oxidant-antioxidant imbalance. Cyclooxygenase-2 (COX-2) and prostaglandin E₂ (PGE₂) have been shown to play critical roles in respiratory inflammation. Here, we show that COX-2/PGE₂/IL-6 induction is dependent on Toll-like receptor 4 (TLR4)/NADPH oxidase signaling in human tracheal smooth muscle cells (HTSMCs). CSE induced COX-2 expression in vitro in HTSMCs and in vivo in the airways of mice. CSE also directly caused an increase in TLR4. Moreover, CSE-regulated COX-2, PGE₂, and IL-6 generation was inhibited by pretreatment with TLR4 Ab; inhibitors of c-Src (PP1), NADPH oxidase (diphenylene iodonium chloride and apocynin), p38 MAPK (SB202190), MEK1/2 (U0126), JNK1/2 (SP600125), and NF-κB (helenalin); a ROS scavenger (N-acetyl-l-cysteine); and transfection with siRNA of TLR4, MyD88, TRAF6, Src, p47^phox, p38, p42, JNK2, or p65. CSE-induced leukocyte numbers in BAL fluid were also reduced by pretreatment with these inhibitors. Furthermore, CSE induced p47^phox translocation and TLR4/MyD88/TRAF6 and c-Src/p47^phox complex formation. We found that PGE₂ enhanced IL-6 production in HTSMCs and leukocyte count in BAL fluid. In addition, treatment with nicotine could induce COX-2, PGE₂, and IL-6 generation in in vivo and in vitro studies. These results demonstrate that CSE-induced ROS generation was mediated through the TLR4/MyD88/TRAF6/c-Src/NADPH oxidase pathway, in turn initiated the activation of MAPKs and NF-κB, and ultimately induced COX-2/PGE₂/IL-6-dependent airway inflammation.     

Tyrosine phosphatase STEP is a key regulator of glutamate-induced prostaglandin E2 release from neurons

The neuron-specific tyrosine phosphatase striatal-enriched phosphatase (STEP) is emerging as a key regulator of excitotoxicity, which is involved in the pathogenesis of both acute and chronic neurological diseases. However, the intracellular mechanisms that are regulated by STEP to confer neuroprotection against excitotoxic insults are not well understood. The present study investigates the role of STEP in regulating neuronal release of the proinflammatory prostanoid prostaglandin E₂ (PGE₂), which is associated with a wide range of pathological conditions. The findings show that glutamate-mediated activation of the N-methyl-D-aspartic acid receptor in STEP-deficient neurons leads to rapid and sustained increase in the phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK), a signaling molecule involved in the production of inflammatory mediators. Such sustained p38 MAPK activation increases the activity of cytosolic phospholipase A₂, which catalyzes the release of arachidonic acid, the initial substrate for PGE₂ biosynthesis. Sustained p38 MAPK activation also induces nuclear factor-κB–mediated increase in expression of cyclooxygenase-2 that is involved in the conversion of arachidonic acid to prostanoids, resulting in enhanced biosynthesis and release of PGE₂ from neurons. Restoration of STEP function with a STEP mimetic (TAT-STEP-myc peptide) significantly decreases the activation of p38 MAPK–mediated cytosolic phospholipase A₂/cyclooxygenase-2/PGE₂ signaling cascade. This study identifies an important mechanism involved in the neuronal release of the proinflammatory mediator PGE₂ after excitotoxic insult and highlights for the first time the immunomodulatory ability of a neuronal tyrosine phosphatase.     

Aspirin inhibits lipopolysaccharide-induced COX-2 expression and PGE2 production in porcine alveolar macrophages by modulating protein kinase C and protein tyrosine phosphatase activity

Aspirin has been demonstrated to be effective in inhibiting COX-2 and PGE₂ in Alveolar macrophages (AMs). However, the mechanisms have not been fully understood. In the present study, we found that pretreatment with aspirin inhibited LPS-induced COX-2 and PGE₂ upregulation, IκBα degradation, NFκB activation and the increase of PKC activity, but elevated LPS-induced the decrease of PTP activity. The PKC inhibitor calphostin C dramatically reduced the COX-2 mRNA and PGE₂ levels, but the PTP inhibitor peroxovanadium (POV) significantly increased the COX-2 mRNA and PGE₂ levels. Furthermore, the PTP inhibitor mitigated the inhibitory effect of aspirin on COX-2 and PGE₂ upregulation and NF-κB activation, whereas the PKC inhibitor enhanced the inhibitory effects of aspirin on the production of COX-2 and PGE₂. Our data indicate a novel mechanism by which aspirin acts as a potent anti-inflammatory agent in alveolus macrophages and ALI. [BMB Reports 2014; 47(1): 45-50]     

Prostaglandin E2/EP1 Signaling Pathway Enhances Intercellular Adhesion Molecule 1 (ICAM-1) Expression and Cell Motility in Oral Cancer Cells

Oral squamous cell carcinoma has a striking tendency to migrate and metastasize. Cyclooxygenase (COX)-2, the inducible isoform of prostaglandin (PG) synthase, has been implicated in tumor metastasis. However, the effects of COX-2 on human oral cancer cells are largely unknown. We found that overexpression of COX-2 or exogenous PGE₂ increased migration and intercellular adhesion molecule 1 (ICAM)-1 expression in human oral cancer cells. Using pharmacological inhibitors, activators, and genetic inhibition of EP receptors, we discovered that the EP1 receptor, but not other PGE receptors, is involved in PGE₂-mediated cell migration and ICAM-1 expression. PGE₂-mediated migration and ICAM-1 up-regulation were attenuated by inhibitors of protein kinase C (PKC)δ, and c-Src. Activation of the PKCδ, c-Src, and AP-1 signaling pathway occurred after PGE₂ treatment. PGE₂-induced expression of ICAM-1 and migration activity were inhibited by a specific inhibitor, siRNA, and mutants of PKCδ, c-Src, and AP-1. In addition, migration-prone sublines demonstrated that cells with increased migration ability had higher expression of COX-2 and ICAM-1. Taken together, these results indicate that the PGE₂ and EP1 interaction enhanced migration of oral cancer cells through an increase in ICAM-1 production.     

Antinociceptive Effect of Tetrandrine on LPS-Induced Hyperalgesia via the Inhibition of IKKβ Phosphorylation and the COX-2/PGE2 Pathway in Mice

Tetrandrine (TET) is a bisbenzylisoquinoline alkaloid that is isolated from the Stephania Tetrandra. It is known to possess anti-inflammatory and immunomodulatory effects. We have shown that TET can effectively suppress the production of bacterial lipopolysaccharide (LPS)-induced inflammatory mediators, including cyclooxygenases (COXs), in macrophages. However, whether TET has an antinociceptive effect on LPS-induced hyperalgesia is unknown. In the present study, we investigated the potential antinociceptive effects of TET and the mechanisms by which it elicits its effects on LPS-induced hyperalgesia. LPS effectively evoked hyperalgesia and induced the production of PGE₂ in the sera, brain tissues, and cultured astroglia. TET pretreatment attenuated all of these effects. LPS also activated inhibitor of κB (IκB) kinase β (IKKβ) and its downstream components in the IκB/nuclear factor (NF)-κB signaling pathway, including COX-2; the increase in expression levels of these components was significantly abolished by TET. Furthermore, in primary astroglia, knockdown of IKKβ, but not IKKα, reversed the effects of TET on the LPS-induced increase in IκB phosphorylation, P65 phosphorylation, and COX-2. Our results suggest that TET can effectively exert antinociceptive effects on LPS-induced hyperalgesia in mice by inhibiting IKKβ phosphorylation, which leads to the reduction in the production of important pain mediators, such as PGE₂ and COX-2, via the IKKβ/IκB/NF-κB pathway.     

Hypertonic environment elicits cyclooxygenase-2-driven prostaglandin E2 generation by colon cancer cells: Role of cytosolic phospholipase A2-α and kinase signaling pathways

Cyclooxygenase (COX)-2-derived prostaglandin (PG)E₂ controls many aspects of colon cancer development, modulating from apoptosis resistance and cell proliferation to angiogenesis, invasion, and metastasis. Here, we investigated the role of different phospholipases (PL)A₂ in supplying arachidonic acid (AA) for COX-2-dependent PGE₂ generation and signaling pathways involved in activation of colon cancer cells by a physiologically relevant stimulus. To emulate the hypertonic environment found physiologically in colon, the human colon cancer cell line Caco-2 was maintained in hypertonic complete DMEM medium. Human colon cancer cell line Caco-2 exposed to a hypertonic environment responded with marked AA release, COX-2 induction and PGE₂ generation. Selective secretory (s)PLA₂ and calcium-independent (i)PLA₂ inhibitors did not modify PGE₂ generation, while either COX-2 or cytosolic (c)PLA₂ inhibitors completely inhibited PGE₂ generation. cPLA₂-α was responsible for AA supply for PGE₂ generation, but had no role in COX-2 induction. Mitogen-activated protein (MAP) kinases, ERK 1/2, p38, and JNK, participated in the signaling events that lead to PGE₂ generation by modulating AA release, but only ERK 1/2 was involved in COX-2 upregulation. Our results indicate that hypertonic stress activates PGE₂ generation by Caco-2 cells through a mechanism dependent on MAP kinase-regulated AA mobilization, increased cPLA₂-α activity, and COX-2 induction.     

Bothrops moojeni snake venom induces an inflammatory response in preadipocytes: Insights into a new aspect of envenomation

Bothrops envenomation is a public health problem in Brazil. Despite the advances in the knowledge of the pathogenesis of systemic and local effects induced by Bothrops venom, the target tissues to this venom are not completely characterised. As preadipocytes are important cells of the adipose tissue and synthesize inflammatory mediators, we investigated the ability of B. moojeni snake venom (Bmv) to stimulate an inflammatory response in 3T3-L1 preadipocytes in vitro, focusing on (1) the release of PGE₂, IL-6, TNF-α, MCP-1, KC, leptin and adiponectin; (2) the mechanisms involved in PGE₂ release and (3) differentiation of these cells. Cytotoxicity of Bmv was determined by MTT assay. The concentrations of PGE₂, cytokines and adipokines were quantified by EIA. Participation of the COX-1 and COX-2 enzymes, NF-κB and PGE₂ receptors (EP1-4) was assessed using a pharmacological approach, and protein expression of the COX enzymes and P-NF-κB was analysed by western blotting. Preadipocyte differentiation was quantified by Oil Red O staining. Bmv (1 μg/mL) induced release of PGE₂, IL-6 and KC and increased expression of COX-2 in preadipocytes. Basal levels of TNF-α, MCP-1, leptin and adiponectin were not modified. Treatment of cells with SC560 (COX-1 inhibitor) and NS398 (COX-2 inhibitor) inhibited Bmv-induced PGE₂ release. Bmv induced phosphorylation of NF-κB, and treatment of the cells with TPCK and SN50, which inhibit distinct NF-κB domains, significantly reduced Bmv-induced PGE₂ release, as did the treatment with an antagonist of PGE₂ receptor EP1, unlike treatment with antagonists of EP2, EP3 or EP4. Bmv also induced lipid accumulation in differentiating cells. These results demonstrate that Bmv can activate an inflammatory response in preadipocytes by inducing the release of inflammatory mediators; that PGE₂ production is mediated by the COX-1, COX-2 and NF-κB pathways; and that engagement of EP1 potentiates PGE₂ synthesis via a positive feedback mechanism. Our findings highlight the role of the adipose tissue as another target for Bmv and suggest that it contributes to Bothrops envenomation by producing inflammatory mediators.     

Impaired Expression of Prostaglandin E2 (PGE2) Synthesis and Degradation Enzymes during Differentiation of Immortalized Urothelial Cells from Patients with Interstitial Cystitis/Painful Bladder Syndrome

Purpose

The differentiated superficial cells of the urothelium restrict urine flow into the bladder wall. We have demonstrated that urothelial cells isolated from bladders of patients with interstitial cystitis/painful bladder syndrome (IC/PBS) fail to release PGE₂ in response to tryptase. This study examines the expression of PGE₂ synthesis and degradation enzymes in urothelial cells during differentiation.

Materials and Methods

We measured immunoprotein expression of cyclooxygenase-2 (COX-2), prostaglandin E₂ synthase (PGES) and 15-hydroxyprostaglandin dehydrogenase (PGDH) in human urothelial cells and in immortalized urothelial cells isolated from the bladders of IC/PBS patients or normal subjects during stratification and differentiation produced by increased calcium and fetal bovine serum (Ca/FBS) in the culture medium for 1, 3 and 7 days.

Results

PGES immunoprotein expression increased during differentiation in normal and IC/PBS urothelial cells. COX-2 expression also increased in cells from normal patients following differentiation. Remarkably, no COX-2 expression was detectable in urothelial cells isolated from 3 out of 4 IC/PBS patients. PGDH immunoprotein expression decreased in normal cells after 1 and 3 days of Ca/FBS addition, but returned to normal after 7 days. PGDH expression was unchanged during differentiation at 1 and 3 days, but was more than 2-fold higher at 7 days compared to day 0 in the IC/PBS cells. Urothelial cells isolated from IC/PBS patients demonstrated no PGE₂ release in response to tryptase under any of the experimental conditions studied.

Conclusions

Taken together, our results indicate that PGE₂ release is compromised during stratification and differentiation in IC/PBS urothelium and may contribute to impaired barrier function.     

Crosstalk of EGF-directed MAPK signalling pathways and its potential role on EGF-induced cell proliferation and COX-2 expression in human mesenchymal stem cells

Epidermal growth factor (EGF) promotes proliferation in human mesenchymal stem cells (hMSCs) during in vitro propagation. In this study, we investigated the effects of PI3K/AKT, ERK1/2, P38 and JNK on EGF signalling in hMSCs. The effects of EGF on MAPKs and PI3K/AKT crosstalk were investigated by immunoblotting; cyclooxygenase-2 (COX-2) expression was studied by real-time RT-PCR; and cell proliferation was evaluated by methylthiazolyl tetrazolium bromide assay. Our results showed that EGF immediately activated all four pathways, induced proliferation and increased COX-2 expression. Interestingly, inhibition of PI3K/AKT-enhanced EGF-stimulated ERK1/2 activity, and inhibition of ERK1/2 and JNK reduced AKT phosphorylation. Furthermore, EGF-induced proliferation as well as EGF-augmented COX2 expression was hindered by ERK1/2 and p38 inhibitors. The results of this study provide evidences to be used in extended proliferation of hMSCs for cell therapy.     

Effects of non-steroidal anti-inflammatory drugs on prostaglandin E2 production by cyclooxygenase-2 from endogenous and exogenous arachidonic acid in rat peritoneal macrophages stimulated with lipopolysaccharide

Lipopolysaccharide (LPS) stimulated prostaglandin E₂ (PGE₂) formation and induction of cyclooxygenase-2 (COX-2) expression without changing the levels of COX-1 protein in rat peritoneal macrophages. Non-steroidal anti-inflammatory drugs (NSAIDs) (nimesulide, indomethacin and ibuprofen) strongly inhibited LPS-stimulated PGE₂ production without any effect on COX-2 protein expression, suggesting that NSAIDs are active in inhibiting the ability of COX-2 to convert arachidonic acid (AA) endogenously released in response to LPS stimulation. Exogenous AA can be converted to PGE₂ by both COX isoforms even in LPS-stimulated macrophages. NSAIDs inhibited PGE₂ production from exogenous AA mediated by both COX-1 and COX-2. However, the two isoforms interacted differentially with different NSAIDs. Furthermore, NSAIDs were distinctly more active in inhibiting PGE₂ production from endogenous AA than that from exogenous AA. These data suggest that PGE₂ production through COX-2 from exogenous AA may not be subject to the same regulatory processes as that from endogenous AA and the two metabolic processes may be differentially sensitive to different NSAIDs.     

Prostaglandin E2 Exerts Multiple Regulatory Actions on Human Obese Adipose Tissue Remodeling,Inflammation, Adaptive Thermogenesis and Lipolysis

Obesity induces white adipose tissue (WAT) dysfunction characterized by unremitting inflammation and fibrosis, impaired adaptive thermogenesis and increased lipolysis. Prostaglandins (PGs) are powerful lipid mediators that influence the homeostasis of several organs and tissues. The aim of the current study was to explore the regulatory actions of PGs in human omental WAT collected from obese patients undergoing laparoscopic bariatric surgery. In addition to adipocyte hypertrophy, obese WAT showed remarkable inflammation and total and pericellular fibrosis. In this tissue, a unique molecular signature characterized by altered expression of genes involved in inflammation, fibrosis and WAT browning was identified by microarray analysis. Targeted LC-MS/MS lipidomic analysis identified increased PGE₂ levels in obese fat in the context of a remarkable COX-2 induction and in the absence of changes in the expression of terminal prostaglandin E synthases (i.e. mPGES-1, mPGES-2 and cPGES). IPA analysis established PGE₂ as a common top regulator of the fibrogenic/inflammatory process present in this tissue. Exogenous addition of PGE₂ significantly reduced the expression of fibrogenic genes in human WAT explants and significantly down-regulated Col1α1, Col1α2 and αSMA in differentiated 3T3 adipocytes exposed to TGF-β. In addition, PGE₂ inhibited the expression of inflammatory genes (i.e. IL-6 and MCP-1) in WAT explants as well as in adipocytes challenged with LPS. PGE₂ anti-inflammatory actions were confirmed by microarray analysis of human pre-adipocytes incubated with this prostanoid. Moreover, PGE₂ induced expression of brown markers (UCP1 and PRDM16) in WAT and adipocytes, but not in pre-adipocytes, suggesting that PGE₂ might induce the trans-differentiation of adipocytes towards beige/brite cells. Finally, PGE₂ inhibited isoproterenol-induced adipocyte lipolysis. Taken together, these findings identify PGE₂ as a regulator of the complex network of interactions driving uncontrolled inflammation and fibrosis and impaired adaptive thermogenesis and lipolysis in human obese visceral WAT.     

Enterovirus 71 induces COX-2 expression via MAPKs,NF-κB,and AP-1 in SK–N–SH cells: Role of PGE2 in viral replication

The enterovirus 71 (EV71) causes severe neurological diseases that were mediated through cyclooxygenase-2 (COX-2) expression in brain. However, the mechanisms underlying EV71-initiated intracellular signaling pathways leading to COX-2 expression remain unknown in neurons. Here we report that exposure of SK–N–SH cells to EV71 increased COX-2 expression and PGE₂ generation in a time- and virus titer-dependent manner, revealed by Western blot, real-time PCR, and PGE₂ analyses. These EV71-induced responses were mediated through activation of p42/p44 MAPK, p38 MAPK, JNK, NF-κB, and AP-1, revealed by using selective pharmacological inhibitors or transfection with respective siRNAs. Consistently, EV71-stimulated translocation of NF-κB into the nucleus and degradation of IκBα in the cytosol was blocked by pretreatment with the selective inhibitors of MEK1/2 (U0126) and NF-κB (Bay11-7085), respectively, suggesting that MEK1/2-p42/p44 MAPK cascade linking to NF-κB was involved in COX-2 expression. In addition, EV71-induced AP-1 subunits (c-jun and c-fos mRNA) expression was also attenuated by pretreatment with a selective JNK inhibitor SP600125, suggesting that JNK cascade linking to AP-1 was involved in COX-2 expression induced by EV71. These findings suggested that up-regulation of COX-2 associated with the release of PGE₂ from EV71-infected SK–N–SH cells which was mediated through activation of p38 MAPK, JNK, p42/p44 MAPK, NF-κB, and AP-1 pathways.     

Honokiol Inhibits Non-Small Cell Lung Cancer Cell Migration by Targeting PGE2-Mediated Activation of β-Catenin Signaling

Lung cancer remains a leading cause of death due to its metastasis to distant organs. We have examined the effect of honokiol, a bioactive constituent from the Magnolia plant, on human non-small cell lung cancer (NSCLC) cell migration and the molecular mechanisms underlying this effect. Using an in vitro cell migration assay, we found that treatment of A549, H1299, H460 and H226 NSCLC cells with honokiol resulted in inhibition of migration of these cells in a dose-dependent manner, which was associated with a reduction in the levels of cyclooxygenase-2 (COX-2) and prostaglandin E₂ (PGE₂). Celecoxib, a COX-2 inhibitor, also inhibited cell migration. Honokiol inhibited PGE₂-enhanced migration of NSCLC cells, inhibited the activation of NF-κB/p65, an upstream regulator of COX-2, in A549 and H1299 cells, and treatment of cells with caffeic acid phenethyl ester, an inhibitor of NF-κB, also inhibited migration of NSCLC cells. PGE₂ has been shown to activate β-catenin signaling, which contributes to cancer cell migration. Therefore, we checked the effect of honokiol on β-catenin signaling. It was observed that treatment of NSCLC cells with honokiol degraded cytosolic β-catenin, reduced nuclear accumulation of β-catenin and down-regulated matrix metalloproteinase (MMP)-2 and MMP-9, which are the down-stream targets of β-catenin and play a crucial role in cancer cell metastasis. Honokiol enhanced: (i) the levels of casein kinase-1α, glycogen synthase kinase-3β, and (ii) phosphorylation of β-catenin on critical residues Ser⁴⁵, Ser^33/37 and Thr⁴¹. These events play important roles in degradation or inactivation of β-catenin. Treatment of celecoxib also reduced nuclear accumulation of β-catenin in NSCLC cells. FH535, an inhibitor of Wnt/β-catenin pathway, inhibited PGE₂-enhanced cell migration of A549 and H1299 cells. These results indicate that honokiol inhibits non-small cell lung cancer cells migration by targeting PGE₂-mediated activation of β-catenin signaling.     

Resveratrol inhibits urban particulate matter-induced COX-2/PGE2 release in human fibroblast-like synoviocytes via the inhibition of activation of NADPH oxidase/ROS/NF-κB

Human fibroblast-like synoviocytes (FLSs) play a role in joint synovial inflammation in rheumatoid arthritis (RA). Some evidence indicates that particulate matter (PM) in air pollution could contribute to the progression of RA. However, more research is needed to clarify this relationship. Up-regulation of cyclooxygenase (COX)-2 and its metabolite prostaglandin E₂ (PGE₂) are implicated in various inflammatory diseases. Resveratrol, a polyphenol found mainly in grapes and red wine, has antioxidant and anti-inflammatory activities. In the present study, we demonstrated that resveratrol reduced PM-induced COX-2/PGE₂ expression in human FLSs, and attenuated PM-enhanced NADPH oxidase activity and ROS generation. In addition, PM induced Akt, ERK1/2, or p38 MAPK activation, which was inhibited by resveratrol. Finally, we demonstrated that PM enhanced NF-κB p65 phosphorylation and the NF-κB promoter activity, which were reduced by pretreatment with a ROS inhibitor or resveratrol. Thus, we concluded that resveratrol functions as a suppressor of PM-induced inflammatory signaling pathways by inhibiting COX-2/PGE₂ expression.