Intracellular angiotensin II fusion protein alters AT1 receptor fusion protein distribution and activates CREB

In recently published studies, we show that angiotensin II (AII) generated from an engineered rat angiotensinogen cDNA, and maintained intracellularly, is growth stimulatory for a rat hepatoma cell line. In the present study, we report that co-expression of AII fused to cyan fluorescent protein (ECFP/AII) and angiotensin type I receptor fused to yellow fluorescent protein (AT1R/EYFP) enhances proliferation of COS-7 and CHO-K1 cells by 59% and 64%, respectively, compared to cells expressing the corresponding independent proteins (P < 0.001 for both). This effect is inhibited by losartan, suggesting (as in our previous published studies) that losartan is internalized by the cells, via receptor-mediated endocytosis, and thus inhibits intracellular receptor-ligand interaction. The growth effect is independent of anti-AII antibodies suggesting that it does not reflect AII secretion into the culture media; AII is also undetectable in the media. Expression of AT1R/EYFP with ECFP/AIIC (control scrambled sequence AII fused to ECFP) has no effect upon cell proliferation. ECFP/AII also alters the cellular localization of AT1R/EYFP. ECFP/AII is concentrated in the nucleus, but shows diffuse cytoplasmic fluorescence as well. AT1R/EYFP, expressed independently, is visible in the endoplasmic reticulum and Golgi apparatus of COS-7 and CHO-K1 cells as early as 24-h post-transfection. At 72 h, it is visibly associated with the plasma membrane. By 144 h, 85% of the cells show detectable circumferential fluorescence. In contrast, in cells that express AT1R/EYFP and ECFP/AII, both proteins accumulate in the nucleus and only 13% of the cells show visible plasma membrane-associated yellow fluorescence at 144 h (P < 0.001). Furthermore, co-expression of ECFP/AII with AT1R/EYFP stimulates cAMP response element-binding protein (CREB) activity in CHO-K1 and COS-7 cells. Exogenous AII similarly significantly increases CREB activation in AT1R/EYFP-stably transfected CHO-K1 and COS-7 cells.     

Meat hydrolysate and essential amino acid-induced glucagon-like peptide-1 secretion, in the human NCI-H716 enteroendocrine cell line, is regulated by extracellular signal-regulated kinase1/2 and p38 mitogen-activated protein kinases

Glucagon-like peptide-1 (GLP-1) is a potent insulin secretagogue released from L-cells in the intestine. Meat hydrolysate (MH) is a powerful activator of GLP-1 secretion in the human enteroendocrine NCI-H716 cell line, but the mechanisms involved in nutrient-stimulated GLP-1 secretion are poorly understood. The objective of this study was to characterize the intracellular signalling pathways regulating MH- and amino acid-induced GLP-1 secretion. Individually, the pharmacological inhibitors, SB203580 (inhibitor of p38 mitogen-activated protein kinase (MAPK)), wortmannin (inhibitor of phosphatidyl inositol 3-kinase) and U0126 (inhibitor of mitogen activated or extracellular signal-regulated protein kinase (MEK1/2) upstream of extracellular signal-regulated kinase (ERK)1/2) all inhibited MH-induced GLP-1 secretion. Further examination of the MAPK pathway showed that MH increased the phosphorylation of ERK1/2, but not p38 or c-Jun N-terminal kinase over 2-15 min. Incubation with SB203580 resulted in a decrease in phosphorylated p38 MAPK and a concomitant increase in the phosphorylation of ERK1/2. Phosphorylation of ERK1/2 was augmented by co-incubation of MH with SB203580. Inhibitors of protein kinase A and protein kinase C did not inhibit MH-induced GLP-1 secretion. In contrast to non-essential amino acids, essential amino acids (EAAs) increased GLP-1 secretion and similar to MH, activated ERK1/2. However, they also activated p38-suggesting type of protein may affect GLP-1 secretion. In conclusion, there appears to be a crosstalk between p38 and ERK1/2 MAPK in the human enteroendocrine cell with the activation of ERK1/2 common to both MH and EAA. Understanding the cellular pathways involved in nutrient-stimulated GLP-1 secretion has important implications for the design of new treatments aimed at increasing endogenous GLP-1 release in type-2 diabetes and obesity.     

Ischemic preconditioning involves dual cardio-protective axes with p38MAPK as upstream target

The existing literature indicates a crucial role of p38 MAP (mitogen-activated protein) kinase (p38MAPK) and its downstream target MAPKAP kinase 2 (MK2) in ischemic preconditioning (IPC). Accordingly, deletion of MK2 gene should abolish the cardioprotective ability of IPC. Interestingly, we were able to partially precondition the hearts from MK2(-/-) knockout mice suggesting the existence of an as yet unknown alternative downstream target of p38MAPK. A recent study from our laboratory also determined a crucial role of CREB (cyclic AMP response element binding protein) in IPC. Since CREB is a downstream target of MSK-1 (mitogen- and stress-activated protein kinase-1) situated at the crossroad of ERK (extracellular receptor kinase) and p38MAPK signaling pathways, we reasoned that MSK-1 could be a downstream molecular target for p38MAPK and ERK signaling in the IPC hearts. To test this hypothesis, the rat hearts were subjected to IPC by four cyclic episodes of 5 min ischemia and 10 min reperfusion. As expected, IPC induced the activation of ERK1/2, p38MAPK, MK2 and HSP (heat shock protein) 27 as evidenced by their increased phosphorylation; and the inhibition of p38MAPK with SB203580 almost completely, and the inhibition of ERK1/2 with PD098059 partially, abolished cardioprotective effects of IPC. Inhibition of MSK-1 with short hairpin RNA (shRNA) also abolished the IPC-induced cardioprotection. SB203580 partially blocked the effects of MSK-1 suggesting that MSK-1 sits downstream of p38MAPK. shRNA-MSK-1 blocked the contribution of both p38MAPK and ERK1/2 as it is uniquely situated at the downstream crossroad of both of these MAP kinases. Although MSK-1 sits downstream of both ERK1/2 and p38MAPK, ERK1/2 activation appears to play less significant role compared to p38MAPK, since its inhibition blocked MSK activation only partially. Consistent with these results, shRNA-MSK-1 blocked the partial PC in MK2(-/-) hearts, and in combination with SB203580, completely abolished the PC effects in the wild-type hearts. The IPC-induced survival signaling was almost completely inhibited with SB203580, and only partially with PD 098059 as evidenced from the inhibition patterns of IPC induced activation of CREB, Akt and Bcl-2. Again SB203580 alone or in combination with shRNA-MSK-1 inhibited IPC induced survival signal comparatively, suggesting that MSK-1 exists downstream of p38MAPK. Taken together, these results indicate for the first time MSK-1 as an alternative (other than MK2) downstream target for p38MAPK, which also transmits survival signal through the activation of CREB.     

Cadmium-induced apoptosis and necrosis in human osteoblasts: role of caspases and mitogen-activated protein kinases pathways

Cadmium is a widespread environmental pollutant which induces severe toxic alterations, including osteomalacia and osteoporosis, likely by estrogen receptor-dependent mechanisms. Indeed, cadmium has been described to act as an endocrine disruptor and its toxicity is exerted both in vivo and in vitro through induction of apoptosis and/or necrosis by not fully clarified intracellular mechanism(s) of action. Aim of the present study was to further investigate the molecular mechanism by which cadmium might alter homeostasis of estrogen target cells, such as osteoblast homeostasis, inducing cell apoptosis and/or necrosis. Human osteoblastic cells (hFOB 1.19) in culture were used as an in vitro model to characterize the intracellular mechanisms induced by this heavy metal. Cells were incubated in the presence/ absence of 10-50 μM cadmium chloride at different times and DNA fragmentation and activation of procaspases- 8 and -3 were induced upon CdCl(2) treatment triggering apoptotic and necrotic pathways. Addition of caspase-8 and -3 inhibitors (Z-IETD-FMK and Z-DQMD-FMK) partially blocked these effects. No activation of procaspase-9 was observed. To determine the role of mitogen-activated protein kinases (MAPK) in these events, we investigated c-jun N-terminal kinase (JNK), p38 and extracellular signal-regulated protein kinase (ERK1/2) phosphorylation which were activated by 10 μM CdCl(2). Chemical inhibitors of JNK, p38, and ERK1/2, SP600125, SB202190, and PD98059, significantly reduced the phosphorylation of the kinases and blunted apoptosis. In contrast, caspase inhibitors did not reduce the cadmium-induced MAPK phosphorylation, suggesting an independent activation of these pathways. In conclusion, at least 2 pathways appear activated by cadmium in osteoblasts: a direct induction of caspase-8 followed by activation of caspase-3 and an indirect induction by phosphorylation of ERK1/2, p38, and JNK MAPK triggering activation of caspase-8 and -3.     

铁离子螯合剂去铁胺上调巨噬细胞、泡沫细胞细胞外基质金属蛋白酶诱导因子表达的机制探讨

目的: 探讨铁负荷过低上调巨噬细胞、泡沫细胞细胞外基质金属蛋白酶诱导因子(EMMPRIN)表达的机制。研究促分裂原活化的蛋白激酶(MAPK)信号通路、视黄醛x受体（RXR）及过氧化物酶体增殖剂活化受体γ（PPARγ）在此过程中的作用。方法: 将巨噬细胞和泡沫细胞给予MAPK（p38,ERK1/2）信号通路抑制剂及RXR的天然配体预处理,加入或不加入去铁胺继续培养24 h,用Western blot测定细胞中EMMPRIN蛋白的表达。于巨噬细胞和泡沫细胞中加入铁离子鳌合剂去铁胺刺激,用Western blot检测MAPK（p38,ERK1/2）的磷酸化及PPARγ的水平。结果: p38 MAPK通路抑制剂及RXR和配体在本身不影响EMMPRIN表达的同时,可抑制去铁胺对EMMPRIN表达的上调。去铁胺可促进p38 MAPK磷酸化,但不影响PPARγ蛋白表达。结论: p38 MAPK 参与了铁负荷过低上调巨噬细胞和泡沫细胞中EMMPRIN表达的过程;RXR可能参与了该过程。     

CREB Activation and Ischaemic Preconditioning

PURPOSE: Previous studies from our laboratory showed that activation of p38 MAPK is one of the triggers of ischaemic preconditioning. The signalling events downstream of p38 MAPK and their links to the putative final effectors of preconditioning are not clear. The cAMP responsive element-binding protein (CREB) is also phosphorylated by exposure to short episodes of ischaemia/reperfusion, suggesting a triggering action. The aim of this study was to systematically investigate (1) the signalling pathways leading to CREB phosphorylation during an ischaemic or beta-adrenergic preconditioning protocol (2) changes in CREB phosphorylation during sustained ischaemia and their significance in ischaemia/reperfusion injury. METHODS: The isolated perfused working rat heart was preconditioned by 1 x 5 min global ischaemia or 3 x 5 min global ischaemia and freeze-clamped. Drugs to manipulate CREB activation were added 5 min before onset of ischaemia. Non-preconditioned and preconditioned hearts were subjected to 25 min global or 35 min regional ischaemia, followed by 30 min reperfusion. Infarct sizes were determined using tetrazolium staining. Phosphorylation of CREB was determined by Western blots. RESULTS: Exposure of hearts to 5 min global ischaemia followed by reperfusion, significantly increased CREB phosphorylation This is mediated by, amongst others, release of endogenous catecholamines and adenosine, as indicated by the use of receptor blockers. Events downstream of receptor stimulation were evaluated using inhibitors for PKA (H89), MSK-1 (H89, Ro318220), PKC (bisindolylmaleimide), p38 MAPK (SB203580) and ERK (PD98059). Activation of PKA, PKC, ERK and p38 MAPK is involved in preconditioning-induced CREB phosphorylation. Ischaemia-induced activation of iPLA(2) and cPLA(2) also contribute to CREB phosphorylation as indicated by the use of the inhibitors 4-bromo-enol-lactone (BEL) and AACOF(3,) respectively. Inhibition of CREB phosphorylation by either BEL or AACOF(3) during a preconditioning protocol partially attenuated cardioprotection. CREB phosphorylation was attenuated during sustained global ischaemia of both non-preconditioned and preconditioned hearts. CONCLUSIONS: These data suggest that CREB phosphorylation during an ischaemic preconditioning protocol may contribute to triggering preconditioning, while reduced phosphorylation during sustained ischaemia does not appear to be associated with cardioprotection.     

Activation of the p38 mitogen-activated protein kinase pathway by gonadotropin-releasing hormone

Previous studies have shown that interaction of GnRH with its serpentine, G protein-coupled receptor results in activation of the extracellular signal regulated protein kinase (ERK) and the Jun N-terminal protein kinase (JNK) pathways in pituitary gonadotropes. In the present study, we examined GnRH-stimulated activation of an additional member of the mitogen-activated protein kinase (MAPK) superfamily, p38 MAPK GnRH treatment of alphaT3-1 cells resulted in tyrosine phosphorylation of several intracellular proteins. Separation of phosphorylated proteins by ion exchange chromatography suggested that GnRH receptor stimulation can activate the p38 MAPK pathway. Immunoprecipitation studies using a phospho-tyrosine antibody resulted in increased amounts of immunoprecipitable p38 MAPK from alphaT3-1 cells treated with GnRH. Immunoblot analysis of whole cell lysates using a phospho-specific antibody directed against dual phosphorylated p38 kinase revealed that GnRH-induced phosphorylation of p38 kinase was dose and time dependent and was correlated with increased p38 kinase activity in vitro. Activation of p38 kinase was blocked by chronic phorbol ester treatment, which depletes protein kinase C isozymes alpha and epsilon. Overexpression of p38 MAPK and an activated form of MAPK kinase 6 resulted in activation of c-jun and c-fos reporter genes, but did not alter the expression of the glycoprotein hormone alpha-subunit reporter. Inhibition of p38 activity with SB203580 resulted in attenuation of GnRH-induced c-fos reporter gene expression, but was not sufficient to reduce GnRH-induced c-jun or glycoprotein hormone alpha-subunit promoter activity. These studies provide evidence that the GnRH signaling pathway in alphaT3-1 cells includes protein kinase C-dependent activation of the p38 MAPK pathway. GnRH integration of c-fos promoter activity may include regulation by p38 MAPK.     

Aberrant p38 mitogen-activated protein kinase signalling in skeletal muscle from Type 2 diabetic patients

Aims/hypothesis p38 mitogen activated protein kinase (MAPK) is generally thought to facilitate signal transduction to genomic, rather than metabolic responses. However, recent evidence implicates a role for p38 MAPK in the regulation of glucose transport; a site of insulin resistance in Type 2 diabetes. Thus we determined p38 MAPK protein expression and phosphorylation in skeletal muscle from Type 2 diabetic patients and non-diabetic subjects.Methods In vitro effects of insulin (120 nmol/l) or AICAR (1 mmol/l) on p38 MAPK expression and phosphorylation were determined in skeletal muscle from non-diabetic (n=6) and Type 2 diabetic (n=9) subjects.Results p38 MAPK protein expression was similar between Type 2 diabetic patients and non-diabetic subjects. Insulin exposure increased p38 MAPK phosphorylation in non-diabetic, but not in Type 2 diabetic patients. In contrast, basal phosphorylation of p38 MAPK was increased in skeletal muscle from Type 2 diabetic patients.Conclusion/interpretation Insulin increases p38 MAPK phosphorylation in skeletal muscle from non-diabetic subjects, but not in Type 2 diabetic patients. However, basal p38 MAPK phosphorylation is increased in skeletal muscle from Type 2 diabetic patients. Thus, aberrant p38 MAPK signalling might contribute to the pathogenesis of insulin resistance.Abbreviations AICAR 5-aminoimidazole-4-carboxamide ribonucleoside - AMPK 5-AMP activated protein kinase - ERK 1/2 extracellular regulated kinase - GIR glucose infusion rate - IRS-1 insulin receptor substrate 1 - MAPK mitogen-activated protein kinase - PI phosphatidylinositol - VO_2max maximal oxygen uptake     

NADPH oxidase-derived superoxide anion mediates angiotensin II-induced pressor effect via activation of p38 mitogen-activated protein kinase in the rostral ventrolateral medulla

The rostral ventrolateral medulla (RVLM), where sympathetic premotor neurons are located, is a central site via which angiotensin II (Ang II) elicits its pressor effect. We tested the hypothesis that NADPH oxidase-derived superoxide anion (O2*-) in the RVLM mediates Ang II-induced pressor response via activation of mitogen-activated protein kinase (MAPK) signaling pathways. Bilateral microinjection of Ang II into the RVLM resulted in an angiotensin subtype 1 (AT1) receptor-dependent phosphorylation of p38 MAPK and extracellular signal-regulated protein kinase (ERK)1/2, but not stress-activated protein kinase/Jun N-terminal kinase (SAPK/JNK), in the ventrolateral medulla. The Ang II-induced p38 MAPK or ERK1/2 phosphorylation was attenuated by application into the RVLM of a NADPH oxidase inhibitor, diphenyleneiodonium chloride (DPI), an antisense oligonucleotide that targets against p22phox or p47phox subunit of NADPH oxidase mRNA, or the superoxide dismutase mimetic tempol. DPI or antisense p22phox or p47phox oligonucleotide treatment also attenuated the AT1 receptor-dependent increase in O2*- production in the ventrolateral medulla elicited by Ang II at the RVLM. Functionally, Ang II-elicited pressor response in the RVLM was attenuated by DPI, tempol, or a p38 MAPK inhibitor, SB203580. The AT1 receptor-mediated enhancement of the frequency of glutamate-sensitive spontaneous excitatory postsynaptic currents induced by Ang II in RVLM neurons was also abolished by SB203580. These results suggest that NADPH oxidase-derived O2*- underlies the activation of p38 MAPK or ERK1/2 by Ang II in the ventrolateral medulla. Furthermore, the p38 MAPK signaling pathway may mediate Ang II-induced pressor response via enhancement of presynaptic release of glutamate to RVLM neurons.     

Regulation of MAPK activity in response to dietary sodium in the rat adrenal gland

Stimulation of aldosterone biosynthesis by angiotensin II (AII) is thought to be mediated via the PLC, IP3 and intracellular calcium signalling pathway. MAPK (p42/p44) is involved in cell proliferation, and is also activated by AII, but its role in the adrenal response to dietary sodium is unclear. To study the relationship between AII receptor (ATR), MAPK and PKC isoforms, PKCalpha and PKCepsilon, mature Wistar rats were maintained on low or high sodium diets for 1 week. In adrenals from animals on a sodium deplete diet, total ligand binding to both ATR subtypes decreased in the zona glomerulosa (ZG). Under these conditions, active MAPK in the ZG decreased paralleling a decrease in active PKCalpha. In the inner zones (IZ), largely reflecting medullary events, low sodium did not affect MAPK activity. However active PKCalpha decreased. In adrenals from sodium-loaded animals, type 2 ATR (AT2R) binding was reduced in the ZG, while type 1 ATR (AT1R) increased in the IZ. Active MAPK increased in ZG, as did active PKCalpha and PKCepsilon. In IZ, ERK, PKCalpha and PKCepsilon were unchanged. These results suggest that in the ZG and IZ, two different modes of MAPK regulation may exist, utilising different PKC isoforms.     

Components of the mitogen-activated protein kinase cascade are activated in hepatic cells by Echinococcus multilocularis metacestode

AIM： To explore the effect of Echinococcusmultilocularis on the activation of mitogen-activated protein kinase （MAPK） signaling pathways and on livercell proliferation.METHODS： Changes in the phosphorylation of MAPKs and proliferating cell nuclear antigen （PCNA）expression were measured in the liver of patients withalveolar echinococcosis （AE）. MAPKs, MEK1/2 [MAPK/extracellular signal-regulated protein kinase （ERK）kinase] and ribosomal S6 kinase （RSK） phosphorylationwere detected in primary cultures of rat hepatocytesin contact in vitro with （1） E. multilocu/aris vesicle fluid（EmF）, （2）E. multilocularis-conditioned medium （EmCM）.RESULTS： In the liver of AE patients, ERK 1/2 andp38 MAPK were activated and PCNA expression wasincreased, especially in the vicinity of the metacestode.Upon exposure to EmF, p38, c-Jun N-terminal kinase（JNK） and ERK1/2 were also activated in hepatocytesin vitro, as well as MEK1/2 and RSK, in the absenceof any toxic effect. Upon exposure to EmCM, only JNKwas up-regulated.CONCLUSION： Previous studies have demonstratedan influence of the host on the MAPK cascade inE. multilocularis. Our data suggest that the reverse,i.e. parasite-derived signals efficiently acting onMAPK signaling pathways in host liver ceils, is actuallyoperating.     

Suppression of p38 mitogen-activated protein kinase inhibits hepatitis B virus replication in human hepatoma cell: the antiviral role of nitric oxide

Summary.  The role of the p38 mitogen-activated protein kinase (MAPK) pathway in hepatitis B virus (HBV) replication was investigated in this study. After transient transfection with HBV plasmid, p38 MAPK, but not JNK or ERK1/2, was significantly phosphorylated in human hepatoma cell Huh7. Interestingly, HBV proteins and RNA synthesis were significantly inhibited by a specific inhibitor of p38 MAPK, SB203580, in a dose-dependent manner. Intracellular core-associated DNA, extracellular virion-associated DNA and covalently closed circular DNA were also significantly inhibited by SB203580. Further results showed the antiviral role of nitric oxide (NO) on the suppression of HBV replication and downregulation of p38 MAPK phosphorylation. In conclusion, these results suggested that suppression of phosphorylation of p38 MAPK by inhibitor or NO could inhibit intracellular HBV replication.     

Tumor necrosis factor-alpha induces insulin resistance in endothelial cells via a p38 mitogen-activated protein kinase-dependent pathway

Chronic inflammation contributes to vascular insulin resistance and endothelial dysfunction. Systemic infusion of TNF-alpha abrogates insulin's action to enhance skeletal muscle microvascular perfusion. In skeletal muscle TNF-alpha induces insulin resistance via the p38 MAPK pathway. To examine whether p38 MAPK also regulates TNF-alpha-induced vascular insulin resistance, bovine aortic endothelial cells (bAECs) were incubated+/-TNF-alpha (5 ng/ml) for 6 h in the presence or absence of SB203580 (p38 MAPK specific inhibitor, 10 microM) after serum starvation for 10 h. For the last 30 min, cells were treated+/-1 nM insulin, and insulin receptor substrate (IRS)-1, Akt, endothelial nitric oxide synthase (eNOS), p38 MAPK, ERK1/2, c-Jun N-terminal kinase, and AMP-activated protein kinase (AMPK) phosphorylation, and eNOS activity were measured. TNF-alpha increased p38 MAPK phosphorylation, potently stimulated IRS-1 serine phosphorylation, and blunted insulin-stimulated IRS-1 tyrosine and Akt phosphorylation and eNOS activity. TNF-alpha also potently stimulated the phosphorylation of ERK1/2 and AMPK. Treatment with SB203580 decreased p38 MAPK phosphorylation back to the baseline and restored insulin sensitivity of IRS-1 tyrosine and Akt phosphorylation and eNOS activity in TNF-alpha-treated bAECs without affecting TNF-alpha-induced ERK1/2 and AMPK phosphorylation. We conclude that in cultured bAECs, TNF-alpha induces insulin resistance in the phosphatidylinositol 3-kinase/Akt/eNOS pathway via a p38 MAPK-dependent mechanism and enhances ERK1/2 and AMPK phosphorylation independent of the p38 MAPK pathway. This differential modulation of TNF-alpha's actions by p38 MAPK suggests that p38 MAPK plays a key role in TNF-alpha-mediated vascular insulin resistance and may contribute to the generalized endothelial dysfunction seen in type 2 diabetes mellitus and the cardiometabolic syndrome.     

Erythromycin suppresses the expression of cyclooxygenase-2 in rheumatoid synovial cells

OBJECTIVE: To investigate whether erythromycin (EM) can suppress the expression of cyclooxygenase-2 (COX-2) in rheumatoid synovial cells, and determine the mechanisms involved. Methods. Synovial tissues were obtained from 25 patients with rheumatoid arthritis (RA). Rheumatoid synovial cells were cultured with or without EM (0.1-1000 nM) in the presence of interleukin 1beta (IL-1beta) for various times. Protein expression of COX-2, and phosphorylation of extracellular signal regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (p38 MAPK) were detected by Western blot. COX-2 messenger RNA (mRNA) was detected by RT-PCR. DNA binding activity of nuclear factor kappa B (NF-kB) was detected by ELISA. Results. IL-1beta-stimulated synovial cells expressed COX-2 protein. EM suppressed the IL-1beta-induced COX-2 protein expression in a dose-dependent manner and inhibited IL-1beta-induced p38 MAPK phosphorylation, which was correlated with COX-2 expression in synovial cells. In contrast, EM had no effect on DNA binding activity of NF-kB and ERK1/2 expression. CONCLUSION: Our results indicated that EM downregulated COX-2 expression by inhibiting the p38 MAPK cascade, but had no effect on NF-kB or ERK1/2, in rheumatoid synovial cells.