Rapid mitogen－activated protein kinase by basic fibroblast growth factor in rat intestine after ischemia／reperfusion injury

AIM: Previous studies showed that exogenous basic fibroblast growth factor (bFGF or FGF-2) could improve physiological dysfunction after intestinal ischemia/ reperfusion (I/R) injury. However, the mechanisms of this protective effect of bFGF are still unclear. The present study was to detect the effect of bFGF on the activities of mitogen-activated protein kinase (MAPK) signaling pathway in rat intestine after I/R injury, and to investigate the protective mechanisms of bFGF on intestinal ischemia injury. METHODS: Rat intestinal I/R injury was produced by clamping the superior mesenteric artery (SMA) for 45 minutes and followed by reperfusion for 48 hours. Seventy-eight Wistar rats were used and divided randomly into sham-operated group (A), normal saline control group (B), bFGF antibody pre-treated group (C), and bFGF treated group (D). In group A, SMA was separated without occlusion. In groups B, C and D, SMA was separated and occluded for 45 minutes, then, released for reperfusion for 48 hours. After the animals were sacrificed, blood and tissue samples were taken from the intestine 45 minutes after ischemia in group A and 2, 6, 24, and 48 hours after reperfusion in the other groups. Phosphorylated forms of p42/p44 MAPK, p38 MAPK and stress activated protein kinase/C-Jun N-terminal kinase (SAPK/JNK) were measured by immunohistochemistry. Plasma levels of D-lactate were examined and histological changes were observed under the light microscope. RESULTS: Intestinal I/R injury induced the expression of p42/p44 MAPK, p38 MAPK, and SAPK/JNK pathways and exogenous bFGF stimulated the early activation of p42/p44 MAPK and p38 MAPK pathways. The expression of phosphorylated forms of p42/p44 MAPK was primarily localized in the nuclei of crypt cells and in the cytoplasm and nuclei of villus cells. The positive expression of p38 MAPK was localized mainly in the nuclei of crypt cells, very few in villus cells. The activities of p42/p44 MAPK and p38 MAPK peaked 6 hours after reperfusion in groups B and C, while SAPK/JNK peaked 24 hours after reperfusion. The activities of p42/p44 MAPK and p38 MAPK peaked 2 hours after reperfusion in group D and those of SAPK/JNK were not changed in group B. D-lactate levels and HE staining showed that the intestinal barrier was damaged severely 6 hours after reperfusion; however, histological structures were much improved 48 hours after reperfusion in group D than in the other groups. CONCLUSION: The results indicate that intestinal I/R injury stimulates the activities of MAPK pathways, and that p42/p44 MAPK and p38MAPK activities are necessary for the protective effect of exogenous bFGF on intestinal I/R injury. The protective effect of bFGF on intestinal dysfunction may be mediated by the early activation of p42/p44 MAPK and p38 MAPK signaling pathways.     

Rapid mitogen-activated protein kinase by basic fibroblast growth factor in rat intestin after ischemia/reperfusion injury

AIM: Previous studies showed that exogenous basic fibroblast growth factor (bFGF or FGF-2) could improve physiological dysfunction after intestinal ischemia/reperfusion (I/R) injury. However, the mechanisms of this protective effect of bFGF are still unclear. The present study was to detect the effect of bFGF on the activities of mitogen-activated protein kinase (MlAPK) signaling pathway in rat intestine after I/R injury, and to investigate the protective mechanisms of bFGF on intestinal ischemia injury. METttODS: Rat intestinal I/R injury was produced by clamping the superior mesenteric artery (SMA) for 45minutes and followed by repeffusion for 48 hours. Seventyeight Wistar rats were used and divided randomly into sham-operated group (A), normal saline control group (B),bFGF antibody pre-treated group (C), and bFGF treated group (D). Tn group A, SMA was separated without occlusion. In groups B, C and D, SMA was separated and occluded for 45 minutes, then, released for reperfusion for 48 hours. After the animals were sacrificed, blood and tissue samples were taken from the intestine 45 minutes after ischemia in group A and 2, 6, 24, and 48 hours after reperfusion in the other groups. Phosphorylated forms of p42/p44 MAPK, p38 MAPK and stress activated protein kinase/C-Jun N-terminal kinase (SAPK/JNK) were measured by immunohistochemistry. Plasma levels of D-lactate were examined and histological changes were observed under the light microscope. RESULTS: Intestinal I/R injury induced the expression of p42/p44 MAPK, p38 MAPK, and SAPK/JNK pathways and exogenous bFGF stimulated the early activation of p42/p44 MAPK and p38 MlAPK pathways. The expression of phosphorylated forms of p42/p44 MAPK was primarily localized in the nuclei of crypt cells and in the cytoplasm and nuclei of villus cells. The positive expression of p38MAPK was localized mainly in the nuclei of crypt cells, very few in villus cells. The activities of p42/p44 MAPK and p38MAPK peaked 6 hours after reperfusion in groups B and C,while SAPK/JNK peaked 24 hours after reperfusion. The activities of p42/p44 MAPK and p38 MAPK peaked 2 hours after reperfusion in group D and those of SAPK/JNK were not changed in group B. D-lactate levels and HE staining showed that the intestinal barrier was damaged severely 6hours after reperfusion; however, histological structures were much improved 48 hours after reperfusion in group D than in the other groups. CONCLUSION: The results indicate that intestinal I/R injury stimulates the activities of MAPK pathways, and that p42/p44 MAPK and p38MAPK activities are necessary for the protective effect of exogenous bFGF on intestinal I/R injury.The protective effect of bFGF on intestinal dysfunction may be mediated by the early activation of p42/p44 MAPK and p38 MAPK signaling pathways.     

Extracellular signal-regulated protein kinase, but not c-Jun N-terminal kinase, is activated by type II gonadotropin-releasing hormone involved in the inhibition of ovarian cancer cell proliferation

Although a novel second form of GnRH (GnRH-II) has been reported to have an antiproliferative effect on gynecologic cancer cells, its biological mechanism remains to be elucidated. We have previously demonstrated that GnRH-II activates p38 MAPK. There is accumulating evidence that activation of MAPKs by GnRH-I and -II is important for cell proliferation, differentiation, and apoptosis. In the present study, we further investigated the involvement of GnRH-II in the inhibition of cell proliferation and activation of ERK1/2 and c-Jun N-terminal protein kinase/stress-activated protein kinase (JNK/SAPK) in ovarian cancer cells, OVCAR-3. The [(3)H]thymidine incorporation and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays revealed that treatment with GnRH-II suppresses cell proliferation of ovarian cancer cells. Western blot analysis demonstrated that ERK1/2 was activated by GnRH-II (100 nm). Moreover, PD98059 (10 mum), an inhibitor of a MAPK/ERK kinase, reversed the activation of ERK1/2 induced by GnRH-II. The activation of ERK1/2 by GnRH-II subsequently phosphorylated Elk-1 as a downstream pathway, which was blocked by PD98059. On the other hand, it is not likely that GnRH-II activates the JNK/SAPK pathway. Taken together, these results indicate that the ERK1/2 pathway is involved in the effect of GnRH-II on antiproliferation and may be an important target for ovarian cancer therapy.     

Expression of mitogen-activated protein kinase phosphatase 1, a negative regulator of the mitogen-activated protein kinases, in rheumatoid arthritis: up-regulation by interleukin-1beta and glucocorticoids

OBJECTIVE: Mitogen-activated protein kinases (MAPKs) are activated by proinflammatory stimuli. MAPK phosphatases (MKPs), in particular MKP-1, have been identified as endogenous negative regulators of MAPK activation. Since MAPKs are known to be important in rheumatoid arthritis (RA) synoviocyte activation, this study assessed the expression, regulation, and function of MKP-1 in RA. METHODS: MKP-1 expression was measured by Western blotting (WB) and real-time polymerase chain reaction (PCR). RA fibroblast-like synoviocytes (FLS) were treated with interleukin-1beta (IL-1beta), tumor necrosis factor alpha, fetal calf serum, and dexamethasone. Expression of MAPKs in RA FLS was analyzed by WB using phosphospecific antibodies, while IL-6 expression was assessed by real-time PCR. RESULTS: MKP-1 protein and messenger RNA were detected in cultured RA FLS. IL-1beta rapidly up-regulated MKP-1, coinciding with reciprocal down-regulation of ERK, JNK, and p38 MAPK phosphorylation. Dexamethasone rapidly and sustainably up-regulated MKP-1, and this also coincided with down-regulation of ERK, JNK, and p38 MAPK phosphorylation. In addition, dexamethasone augmented IL-1beta-induced up-regulation of MKP-1, and this was associated with inhibition of ERK, JNK, and p38 MAPK phosphorylation and IL-6 expression. Dexamethasone had no effect on the phosphorylation of upstream kinases such as MEKK-3/6. In the presence of glucocorticoid (GC) receptor antagonist RU 486, the dexamethasone-mediated up-regulation of MKP-1 was impaired. Moreover, inhibition of MKP-1 expression impaired dexamethasone-mediated inhibition of MAPK phosphorylation. CONCLUSION: This study demonstrates the expression of MKP-1 in RA FLS. Cytokine and GC regulation of MKP-1 may be important in determining the magnitude of the inflammatory response in RA that is mediated via MAPKs. The effects of GCs in RA may be mediated, in part, via GC receptor-dependent up-regulation of MKP-1.     

Decline of shear stress-induced activation of extracellular signal-regulated kinases,but not stress-activated protein kinases,in in vitro propagated endothelial cells

We investigated the involvement of mitogen-activated protein kinase (MAPK) signal transduction pathways in human endothelial cells in response to shear stress and alterations of these kinases in in vitro-propagated endothelial cells (ECs). Potent activation (10-fold) of extracellular signal-regulated kinase (ERK2), a member of the MAPK family, occurred within 10 min of shear stress (5 dynes/cm²), whereupon rapid inactivation ensued. Shear stress also induced activation of stress-activated protein kinase (SAPK) or c-Jun NH₂-terminal protein kinase (JNK) in ECs. Suramin pretreatment completely inhibited shear stress stimulation of ERK2, but not SAPK/JNK, highlighting a role for growth factor receptors in ERK activation. Translocation of ERK₂ from the cytoplasm to the nucleus was observed in shear-stressed endothelial cells. In addition, we compared activities of MAPKs in shear-stressed cells derived from passages 4 and 10 (older). The magnitude of ERK2 activation was significantly lower in aged ECs compared to those of passage 4, while SAPK/JNK was not altered in the in vitro aged ECs. A similar level of ERK2 activation was found in both young and older cells stimulated with phorbol-12-myristate-13-acetate (PMA), indicating an age-related alteration of the plasma membrane. Taken together, these findings suggest that MAP kinase activation may be crucial for the expression of many genes in ECs stimulated by shear stress, and that an alteration in MAPK activities could contribute to the age-related decline in proliferative capacity.     

Abrupt reoxygenation of microvascular endothelial cells after hypoxia activates ERK1/2 and JNK1, leading to NADPH oxidase-dependent oxidant production

OBJECTIVE: Mitogen-activated protein kinases (MAPK) in microvascular endothelial cells (EC) may participate in organ pathophysiology following hypoxia/reoxygenation (H/R). The authors aimed to determine the role of MAPK in H/R-induced reactive oxygen species (ROS) generation in mouse microvascular EC. METHODS: Cultured EC derived from skeletal muscle of male wild-type (WT), gp91phox-/- or p47phox-/- mice were subjected to hypoxia (0.1% O2, 1 h) followed by abrupt reoxygenation, H/RA (hypoxic medium quickly replaced by normoxic medium), or slow reoxygenation, H/RS (O2 diffused to cells through hypoxic medium). Cells were analyzed for ERK, JNK, and p38 MAPK phosphorylation, NADPH oxidase activation, and ROS generation. RESULTS: In WT cells, H/RA but not H/RS rapidly phosphorylated ERK1/2 and JNK1 and subsequently increased ROS production. H/RA did not affect p38. MAPK phosphorylation persisted despite inhibition of NADPH oxidase, mitochondrial respiration, protein tyrosine kinase, or PKC. ROS increase during H/RA was prevented by deletion of gp91phox or p47phox, or MAPK inhibition. CONCLUSIONS: Abrupt reoxygenation after hypoxia activates ERK1/2 and JNK1 in mouse microvascular endothelial cells via a tyrosine kinase-, PKC-, and NADPH oxidase-insensitive mechanism, leading to increased NADPH oxidase-dependent ROS production. The results suggest that MAPK activation in the microvascular endothelium is O2-sensitive, contributing critically to tissue pathophysiology after H/R.     

Inhibition of MAP kinase in synovium by treatment with tocilizumab in rheumatoid arthritis

To investigate the histological changes of mitogen-activated protein kinase (MAPK) in synovium with tocilizumab in rheumatoid arthritis (RA), synovial tissue samples were assessed from ten methotrexate (MTX)-treated RA patients for control and ten tocilizumab with MTX-treated RA patients. The synovium was observed using hematoxylin and eosin (H&E) stain and analyzed immunohistochemically for the expression of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), matrix metalloproteinase-3 (MMP-3), CD4 (T cell), CD20 (B cell), CD68 (macrophage), vascular endothelial growth factor (VEGF), CD29 (β-1 integrin), phospho-p38 MAPK (Tyr180/Tyr182), phospho-p44/42 MAPK [extracellular signal-regulated kinase (ERK) 1/ERK2], and phospho-c-Jun N-terminal kinase (JNK). H&E staining showed that there is a significant difference of cell proliferation; however, there is no change of hypervascularity in the synovium between both groups. An immunohistochemical examination showed that the decrease of CD29 (β-1 integrin) and JNK was found significant, while ERK was increased in the tocilizumab group. CD20, B-lymphocyte, was decreased in the tocilizumab group compared with the MTX group significantly. IL-6 was completely blocked in the patients who received tocilizumab. TNF-α was similarly expressed in the interstitial cells of synovium of patients in both groups. MMP-3 and CD68 were similarly expressed on the surface of synovium. VEGF was less expressed in both groups. These findings indicate that the inhibition of CD20, CD29, and JNK in MAPK may be involved in the efficacy of tocilizumab compared with MTX treatment in RA.     

Angiotensin II-induced cardiac hypertrophy is associated with different mitogen-activated protein kinase activation in normotensive and hypertensive mice

OBJECTIVE: In addition to its haemodynamic effects, angiotensin II (AngII) is thought to contribute to the development of cardiac hypertrophy via its growth factor properties. The activation of mitogen-activated protein kinases (MAPK) is crucial for stimulating cardiac growth. Therefore, the present study aimed to determine whether the trophic effects of AngII and the AngII-induced haemodynamic load were associated with specific cardiac MAPK pathways during the development of hypertrophy. Methods The activation of the extracellular-signal-regulated kinase (ERK), the c-jun N-terminal kinase (JNK) and the p38 kinase was followed in the heart of normotensive and hypertensive transgenic mice with AngII-mediated cardiac hypertrophy. Secondly, we used physiological models of AngII-dependent and AngII-independent renovascular hypertension to study the activation of cardiac MAPK pathways during the development of hypertrophy. RESULTS: In normotensive transgenic animals with AngII-induced cardiac hypertrophy, p38 activation is associated with the development of hypertrophy while ERK and JNK are modestly stimulated. In hypertensive transgenic mice, further activation of ERK and JNK is observed. Moreover, in the AngII-independent model of renovascular hypertension and cardiac hypertrophy, p38 is not activated while ERK and JNK are strongly stimulated. In contrast, in the AngII-dependent model, all three kinases are stimulated. CONCLUSIONS: These data suggest that p38 activation is preferentially associated with the direct effects of AngII on cardiac cells, whereas stimulation of ERK and JNK occurs in association with AngII-induced mechanical stress.     

Upregulation of urokinase-type plasminogen activator and inhibitor and gelatinase expression via 3 mitogen-activated protein kinases and PI3K pathways during the early development of osteoarthritis

OBJECTIVE: To examine whether upregulation of urokinase-type plasminogen activator (u-PA), PA inhibitor-1 (PAI-1), and gelatinases [matrix metalloproteinase (MMP)-2 and MMP-9] in early knee osteoarthritis (OA) of humans occurs through 3 major mitogen-activated protein kinases (MAPK): extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK) and p38 kinase signaling pathways, and the phosphatidylinositol 3-kinase (PI3K) signaling pathway. METHODS: Enzyme linked immunosorbent assay and gelatin zymography were used to investigate the effects of ERK 1/2 inhibitor U0126, JNK and p38 inhibitor SB203580, and PI3K inhibitor LY294002 on the secretion of u-PA, PAI-1, MMP-2, and MMP-9 in early osteoarthritic tissue cultures, with or without interleukin 1alpha (IL-1alpha) and lipopolysaccharide (LPS) induction. RESULTS: Our findings were: (1) latent and active forms of MMP-9 secretion in synovial and some meniscal cultures were inhibited significantly by U0126, SB203580, and LY294002; (2) latent and active forms of MMP-2 secretion were also inhibited significantly by U0126 and LY294002, but not by SB203580, except for active MMP-2 in synovial cultures; (3) a similar observation was seen in IL-1alpha- and LPS-treated cultures; and (4) U0126, SB203580, and LY294002 significantly decreased u-PA and PAI-1 levels in all cultures in the presence or absence of IL-1alpha and LPS. CONCLUSION: MAPK ERK, JNK, and p38 signaling pathways and the PI3K signaling pathway are involved in upregulation of u-PA, PAI-1, and gelatinase expression during early development of knee OA. Thus, blocking PA/plasmin and gelatinase expression by novel physiologic and pharmacological inhibitors could be an important therapeutic or preventive approach for early OA.     

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.     

Conditional expression of mitogen-activated protein kinase phosphatase-1, MKP-1, is cytoprotective against UV-induced apoptosis

UV irradiation induces apoptosis in U937 human leukemic cells that is accompanied by the activation of both the stress-activated protein kinase (SAPK) and p38 mitogen-activated protein kinase (MAPK) signal transduction pathways. The MAPK phosphatase, MKP-1, is capable of inactivating both SAPK and p38 MAPK in vivo. To determine whether MKP-1-mediated inhibition of SAPK and/or p38 MAPK activity provided cytoprotection against UV-induced apoptosis, a U937 cell line conditionally expressing MKP-1 from the human metallothionein IIa promoter was established. Conditional expression of MKP-1 was found to abolish UV-induced SAPK and p38 MAPK activity, and inhibit UV-induced apoptosis as judged by both morphological criteria and DNA fragmentation. MKP-1 was also found to inhibit other biochemical events associated with apoptosis, including activation of caspase-3 and the proteolytic cleavage of the caspase-3 substrate, poly(ADP ribose) polymerase. These findings demonstrate that MKP-1 acts at a site upstream of caspase activation within the apoptotic program. The cytoprotective properties of MKP-1 do not appear to be mediated by its ability to inhibit p38 MAPK because the p38 MAPK specific inhibitor SB203580 had no effect on UV-induced apoptosis in U937 cells. Furthermore, by titrating the level of MKP-1 expression it was found that MKP-1 inhibited UV-induced SAPK activity, DNA fragmentation, and caspase-3 activation in a similar dose-dependent manner. The dual-specificity phosphatase, PAC1, which does not inhibit UV-induced activation of SAPK, did not provide a similar cytoprotection against UV-induced apoptosis. These results are consistent with a model whereby MKP-1 provides cytoprotection against UV-induced apoptosis by inhibiting UV-induced SAPK activity.     

Involvement of stress-activated protein kinase/c-Jun N-terminal kinase in endothelin-1-induced heat shock protein 27 in osteoblasts

OBJECTIVE: We have reported that endothelin-1 (ET-1) activates p38 mitogen-activated protein (MAP) kinase through protein kinase C in osteoblast-like MC3T3-E1 cells, and that p38 MAP kinase plays a role in the ET-1-induced heat shock protein 27 (HSP27). Recently, we found that stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) is activated by ET-1 in these cells. In the present study, we have investigated the involvement of SAPK/JNK in ET-1-induced HSP27 in MC3T3-E1 cells. METHODS: The concentration of HSP27 in soluble extracts of the cells, the expression of mRNA for HSP27, and the phosphorylation of SAPK/JNK were determined by an enzyme immunoassay, Northern blot analysis, and Western blot analysis respectively. RESULTS: SP600125, a specific inhibitor of SAPK/JNK, markedly reduced ET-1-stimulated HSP27 accumulation. The inhibitory effect of SP600125 was dose dependent in the range between 1 and 50 microM. SP600125 reduced the ET-1-increased level of HSP27 mRNA. Calphostin C and Go 6976, inhibitors of protein kinase C, reduced the ET-1-induced phosphorylation of SAPK/JNK. 12-O-Tetradecanoylphorbol-13-acetate, a direct activator of protein kinase C, induced SAPK/JNK phosphorylation, which was suppressed by SP600125. A combination of SP600125 and p38 MAP kinase inhibitor such as SB203580 and PD169316 additively reduced the ET-1-stimulated accumulation of HSP27. CONCLUSIONS: These results strongly suggest that JNK plays a part in ET-1-induced HSP27 in addition to p38 MAP kinase in osteoblasts.     

Activation of the c-Jun N-terminal kinase pathway by a novel protein kinase related to human germinal center kinase

The c-Jun N-terminal kinase (JNK), or stress-activated protein kinase plays a crucial role in cellular responses stimulated by environmental stress and proinflammatory cytokines. However, the mechanisms that lead to the activation of the JNK pathway have not been elucidated. We have isolated a cDNA encoding a novel protein kinase that has significant sequence similarities to human germinal center kinase (GCK) and human hematopoietic progenitor kinase 1. The novel GCK-like kinase (GLK) has a nucleotide sequence that encodes an ORF of 885 amino acids with 11 kinase subdomains. Endogenous GLK could be activated by UV radiation and proinflammatory cytokine tumor necrosis factor α. When transiently expressed in 293 cells, GLK specifically activated the JNK, but not the p42/44^MAPK/extracellular signal-regulated kinase or p38 kinase signaling pathways. Interestingly, deletion of amino acids 353–835 in the putative C-terminal regulatory region, or mutation of Lys-35 in the putative ATP-binding domain, markedly reduced the ability of GLK to activate JNK. This result indicates that both kinase activity and the C-terminal region of GLK are required for maximal activation of JNK. Furthermore, GLK-induced JNK activation could be inhibited by a dominant-negative mutant of mitogen-activated protein kinase kinase kinase 1 (MEKK1) or mitogen-activated protein kinase kinase 4/SAPK/ERK kinase 1 (SEK1), suggesting that GLK may function upstream of MEKK1 in the JNK signaling pathway.     

Preptin对成骨细胞结缔组织生长因子表达的影响及其机制研究

目的 探讨Preptin对成骨细胞结缔组织生长因子(CTGF)表达的影响及其机制.方法采用人重组preptin干预人原代成骨细胞,CTGF蛋白水平用Western印迹法检测.丝裂原活化蛋白激酶p38(p38MAPK)、细胞外信号调节激酶(ERK1/2)、c-Jun氨基端激酶(JNK)及其磷酸化水平用Western印迹法检测.在preptin干预前用细胞信号阻断剂(PD98059、SP600125或SB203580)预处理阻断人成骨细胞MAPK信号转导,以分析preptin诱导人成骨细胞CTGF表达的作用机制.结果 Preptin可呈时间和剂量依赖性地促进人成骨细胞CTGF的分泌,并且preptin可诱导人成骨细胞ERK的活化,对p38MAPK或JNK无激活作用;人成骨细胞用ERK抑制剂PD98059预处理可使preptin诱导的CTGF分泌降低.结论Preptin增加CTGF的表达,并通过ERK/MAPK信号途径来介导.     

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.     

Predominant activation of MAP kinases and pro-destructive/pro-inflammatory features by TNF alpha in early-passage synovial fibroblasts via TNF receptor-1: failure of p38 inhibition to suppress matrix metalloproteinase-1 in rheumatoid arthritis

OBJECTIVE: To examine the relative importance of tumour necrosis factor-receptor 1 (TNF-R1) and TNF-R2 and their signalling pathways for pro-inflammatory and pro-destructive features of early-passage synovial fibroblasts (SFB) from rheumatoid arthritis (RA) and osteoarthritis (OA). METHODS: Cells were stimulated with tumour necrosis factor (TNF)alpha or agonistic anti-TNF-R1/TNF-R2 monoclonal antibodies. Phosphorylation of p38, ERK and JNK kinases was assessed by western blot; proliferation by bromodesoxyuridine incorporation; interleukin (IL)6, IL8, prostaglandin E(2) (PGE(2)) and matrix metalloproteinase (MMP)-1 secretion by ELISA; and MMP-3 secretion by western blot. Functional assays were performed with or without inhibition of p38 (SB203580), ERK (U0126) or JNK (SP600125). RESULTS: In RA- and OA-SFB, TNFalpha-induced phosphorylation of p38, ERK or JNK was exclusively mediated by TNF-R1. Reduction of proliferation and induction of IL6, IL8 and MMP-1 were solely mediated by TNF-R1, whereas PGE(2) and MMP-3 secretion was mediated by both TNF-Rs. In general, inhibition of ERK or JNK did not significantly alter the TNFalpha influence on these effector molecules. In contrast, inhibition of p38 reversed TNFalpha effects on proliferation and IL6/PGE(2) secretion (but not on IL8 and MMP-3 secretion). The above effects were comparable in RA- and OA-SFB, except that TNFalpha-induced MMP-1 secretion was reversed by p38 inhibition only in OA-SFB. CONCLUSION: In early-passage RA/OA-SFB, activation of MAPK cascades and pro-inflammatory/pro-destructive features by TNFalpha is predominantly mediated by TNF-R1 and, for proliferation and IL6/PGE(2) secretion, exclusively regulated by p38. Strikingly, RA-SFB are insensitive to p38 inhibition of MMP-1 secretion. This indicates a resistance of RA-SFB to the inhibition of pro-destructive functions and suggests underlying structural/functional alterations of the p38 pathway, which may contribute to the pathogenesis or therapeutic sensitivity of RA, or both.