Stimulation of MAPK cascades by insulin and osmotic shock: lack of an involvement of p38 mitogen-activated protein kinase in glucose transport in 3T3-L1 adipocytes

Osmotic shock and insulin stimulate GLUT4 translocation and glucose transport via mechanisms that are for the most part distinct yet convergent. In this article, we investigated the effect of osmotic shock and insulin on the activation of the mitogen-activated protein kinase (MAPK) cascades in differentiated 3T3-L1 adipocytes. The MAPKs are activated by phosphorylation on conserved tyrosine and threonine residues. Both sorbitol and insulin strongly stimulated extracellular regulated kinase (ERK) 1 and 2 phosphorylation (8- and 18-fold, respectively). In contrast, c-jun-NH2-terminal kinase (JNK)/stress-activated protein kinase (SAPK) phosphorylation was stimulated only by sorbitol (sevenfold) and not by insulin. Phosphorylation of p38 MAPK was stimulated strongly by sorbitol (22-fold) but weakly by insulin (2.7-fold). Measurement of intrinsic JNK and p38 MAPK activity confirmed the phosphorylation studies. JNK and p38 MAPK were activated only significantly by sorbitol. The MAPKs are phosphorylated by dual-specificity kinases (mitogen-activated ERK-activating kinase [MEK] or MAPK kinase [MKK]). As expected, sorbitol and insulin both stimulated MEK phosphorylation. MKK4 was phosphorylated only in response to sorbitol, and neither of the stimuli caused phosphorylation of MKK3 or 6. To determine the functional significance of the observed activation of p38 MAPK in response to insulin and osmotic shock, we used three pyridinyl imidazole p38 MAPK inhibitors, SB203580, SB202190, and PD169316. Insulin and osmotic shock-stimulated glucose transport was not inhibited by any inhibitor at concentrations that were shown to block p38 MAPK activity. Furthermore, activation of the p38 MAPK pathway by treatment of cells with anisomycin did not stimulate glucose transport. These results suggest that activation of the p38 MAPK pathway is not involved in the stimulation of glucose transport.     

Involvement of the mitogen-activated protein kinase family in tetracaine-induced PC12 cell death

BACKGROUND: To explore whether cytotoxicity of local anesthetics is related to apoptosis, the authors examined how local anesthetics affect mitogen-activated protein kinase (MAPK) family members, extracellular signal-regulated kinases (ERKs), c-Jun N-terminal kinases (JNKs)-stress-activated protein kinases, and p38 kinase, which are known to play important roles in apoptosis. METHODS: Cell death was evaluated using PC12 cells. Morphologic changes of cells, cellular membrane, and nuclei were observed. DNA fragmentation was electrophoretically assayed. Western blot analysis was performed to analyze phosphorylation of the MAPK family, cleavage of caspase-3 and poly(adenosine diphosphate-ribose) polymerase. Intracellular Ca2+ concentration was measured using a calcium indicator dye. RESULTS: Tetracaine-induced cell death was shown in a time- and concentration-dependent manner and characterized by nuclear condensation or fragmentation, membrane blebbing, and internucleosomal DNA fragmentation. Caspase-3 activation and phosphorylation of ERK, JNK, and p38 occurred in the cell death. PD98059, an inhibitor of ERK, enhanced tetracaine-induced cell death and JNK phosphorylation, whereas ERK phosphorylation was inhibited. Curcumin, an inhibitor of JNK pathway, attenuated the cell death. Increase of intracellular Ca2+ concentration was detected. In addition to the increase of ERK phosphorylation and the decrease of JNK phosphorylation, two Ca2+ chelators protected cells from death. Neither cell death nor phosphorylation of the MAPK family was caused by tetrodotoxin. Nifedipine did not affect tetracaine-induced apoptosis. CONCLUSIONS: Tetracaine induces apoptosis of PC12 cells via the MAPK family. ERK activation protects cells from death, but JNK plays the opposite role. Toxic Ca2+ influx caused by tetracaine seems to be responsible for the cell death, but blocking of Na+ channels or L-type Ca2+ channels is unlikely involved in the tetracaine's action for apoptosis.     

肾病综合征氧化低密度脂蛋白脂质肾损伤的实验研究

目的 通过观察氧化低密度脂蛋白（oxidized low-density lipoprotein,ox-LDL）对系膜细胞（Mesangial Cells,MCs）分泌炎症介质功能的影响及MAPK信号通路和核因子-κB（nuclear factor kappa B,NF-κB）活性的改变,进一步阐明脂质在肾损伤中的作用机制.方法 利用ox-LDL诱导大鼠系膜细胞增殖,分别采用ELISA、real-time PCR、western blot技术检测MCs炎症介质、MAPK通路相关蛋白（p38、JNK、ERK）及NF-κB的表达水平.结果 利用ox-LDL诱导大鼠系膜细胞增殖并加入CXCR6受体后,其表面炎症因子[CXCL16、CD36、ADAM10、ADAM17、干扰素（IFN）、白细胞介素（IL6）、肿瘤坏死因子（TNF-α）]的表达水平以及MAPK信号通路（p38、JNK、ERK）、NF-κB的磷酸化水平显著升高（P〈0.01）.结论 ox-LDL可促使系膜细胞释放CXCL16、CD36、ADAM10、ADAM17、IFN、IL6、TNF-α等炎症介质,CXCR6可介导这一途径.ox-LDL激活MAPK信号转导通路,使p38、ERK1/2、SAPK/JNK的磷酸化水平升高,激活了NF-κB p65的活性,CXCR6-CXCL16介导MAPK信号途径.     

细胞外信号调节激酶和p38丝裂原活化蛋白激酶的表达水平对人精子活动力的影响

目的:比较细胞外信号调节激酶(ERK)、P38丝裂原活化蛋白激酶(P38MAPK)的磷酸化和蛋白表达水平在正常精子和弱精子症患者精子中的差异,旨在探讨ERK和P38MAPK表达水平与精子活动力的相关性。方法:收集正常精液(精子浓度≥20×106/ml,a级精子≥25%或a+b级精子≥50%)和弱精子症患者精液(精子浓度≥20×106/ml,a级精子<25%或a+b级精子≤40%)各20份,洗涤后提取精子总蛋白,采用Western印迹方法分别检测ERK、P38MAPK的磷酸化和蛋白表达水平。结果:ERK和P38MAPK在正常精子和弱精子症患者精子中均有表达,ERK、P38MAPK蛋白表达水平和P38MAPK磷酸化水平在弱精子症患者组显著升高(P<0.05),而两组间ERK磷酸化水平差异无统计学意义(P>0.05)。结论:人精子ERK、P38MAPK蛋白表达水平和P38MAPK磷酸化水平升高可能是精子活动力低下的原因之一。     

Effects of insulin, contraction, and phorbol esters on mitogen-activated protein kinase signaling in skeletal muscle from lean and ob/ob mice

Effects of diverse stimuli, including insulin, muscle contraction, and phorbol 12-myristate-13-acetate (PMA), were determined on phosphorylation of mitogen-activated protein kinase (MAPK) signaling modules (c-Jun NH(2)-terminal kinase [JNK], p38 MAPK, and extracellular signal-related kinase [ERK1/2]) in skeletal muscle from lean and ob/ob mice. Insulin increased phosphorylation of JNK, p38 MAPK, and ERK1/2 in isolated extensor digitorum longus (EDL) and soleus muscle from lean mice in a time- and dose-dependent manner. Muscle contraction and PMA also elicited robust effects on these parallel MAPK modules. Insulin action on JNK, p38 MAPK, and ERK1/2 phosphorylation was significantly impaired in EDL and soleus muscle from ob/ob mice. In contrast, muscle contraction-mediated JNK, p38 MAPK, and ERK1/2 phosphorylation was preserved. PMA effects on phosphorylation of JNK and ERK1/2 were normal in ob/ob mice, whereas effects on p38 MAPK were abolished. In conclusion, insulin, contraction, and PMA activate MAPK signaling in skeletal muscle. Insulin-mediated responses on MAPK signaling are impaired in skeletal muscle from ob/ob mice, whereas the effect of contraction is generally well preserved. In addition, PMA-induced phosphorylation of JNK and ERK1/2 are preserved, whereas p38 MAPK pathways are impaired in skeletal muscle from ob/ob mice. Thus, appropriate MAPK responses can be elicited in insulin-resistant skeletal muscle via an insulin-independent mechanism.     

Involvement of the Mitogen-activated Protein Kinase Family in Tetracaine-induced PC12 Cell Death

Background: To explore whether cytotoxicity of local anesthetics is related to apoptosis, the authors examined how local anesthetics affect mitogen-activated protein kinase (MAPK) family members, extracellular signal-regulated kinases (ERKs), c-Jun N-terminal kinases (JNKs)-stress-activated protein kinases, and p38 kinase, which are known to play important roles in apoptosis.

Methods: Cell death was evaluated using PC12 cells. Morphologic changes of cells, cellular membrane, and nuclei were observed. DNA fragmentation was electrophoretically assayed. Western blot analysis was performed to analyze phosphorylation of the MAPK family, cleavage of caspase-3 and poly(adenosine diphosphate-ribose) polymerase. Intracellular Ca2+ concentration was measured using a calcium indicator dye.

Results: Tetracaine-induced cell death was shown in a time- and concentration-dependent manner and characterized by nuclear condensation or fragmentation, membrane blebbing, and internucleosomal DNA fragmentation. Casepase-3 activation and phosphorylation of ERK, JNK, and p38 occurred in the cell death. PD98059, an inhibitor of ERK, enhanced tetracaine-induced cell death and JNK phosphorylation, whereas ERK phosphorylation was inhibited. Curcumin, an inhibitor of JNK pathway, attenuated the cell death. Increase of intracellular Ca2+ concentration was detected. In addition to the increase of ERK phosphorylation and the decrease of JNK phosphorylation, two Ca2+ chelators protected cells from death. Neither cell death nor phosphorylation of the MAPK family was caused by tetrodotoxin. Nifedipine did not affect tetracaine-induced apoptosis.     

活化蛋白激酶在骨肉瘤中的表达及其意义

[目的]探讨细胞分裂素活化蛋白激酶（MAPK）中细胞外信号调节蛋白激酶（ERK）、c-jun氨基末端激酶（JNK）、P38三条通路在骨肉瘤发生中的作用。[方法]用免疫组织化学技术EnVision^TM法检测48例骨肉瘤标本及25例成骨性良性肿瘤标本中ERK、JNK、P38蛋白的表达，并比较他们的差异。[结果]ERK、JNK、P38三种蛋白在骨肉瘤组的阳性率分别为83．3％（40／48），72．9％（35／48）和85．4％（41／48），在成骨性良性肿瘤组中的阳性率分别为16．0％（4／25），12．0％（3／25）和20．0％（5／25），骨肉瘤组织中ERK、JNK、P38蛋白阳性率及阳性强度均明显高于成骨性良性肿瘤（P〈0．01）。[结论]MAPK中ERK、JNK、P38三条通路在骨肉瘤发生中均发挥了重要作用，用免疫组织化学方法检测MAPK，可为临床骨肉瘤与良性骨肿瘤的诊断与鉴别诊断提供参考指标。     

Expression and phosphorylation of mitogen-activated protein kinases during spermatogenesis and epididymal sperm maturation in mice.

The expression and phosphorylation/dephosphorylation of mitogen-activated protein (MAP) kinases during mouse spermatogenesis and epididymal sperm maturation have been investigated by immunoblotting and immunohistochemical staining with commercially available anti-ERK2 and anti-Active MAPK antibodies. Two forms of MAP kinases, p42ERK2 and p44ERK1, were expressed in a similar amount in spermatogenic cells at different stages. ERK1 and ERK2 were phosphorylated (activated) in early spermatogenic cells from primitive spermatogonia to zygotene primary spermatocytes, while only a small quantity of phosphorylated MAP kinases could be detected in pachytene primary spermatocytes and spermatids. MAP kinase activity in primative spermatogonia and preleptotene primary spermatocytes was the highest among spermatogenic cells. ERK1 and ERK2 were also present in epididymal spermatozoa, and their phosphorylation was increased while spermatozoa pass through epididymis and vas deferens for maturation. It would appear that MAP kinase activation may contribute to the mitotic proliferation of primative spermatogonia, an early phase of spermatogenic meiosis, and, later, sperm motility acquirement.     

p38 MAP kinase mediates endotoxin-induced expression of cyclooxygenase-2 in enterocytes

BACKGROUND: Necrotizing enterocolitis (NEC) occurs only after bacterial colonization of the intestine, suggesting that bacterial products, including lipopolysaccharide (endotoxin,) interact with enterocytes in the pathogenesis of this disease. Inflammatory molecules such as cyclooxygenase-2 (COX-2) are important mediators of the septic response leading to NEC. We therefore hypothesized that endotoxin activates production of COX-2 in enterocytes and explored the relative contributions of known mitogen-activated protein kinases (MAPK) pathways in this process. METHODS: IEC-6 enterocytes were treated with 5 microg/mL endotoxin, or various stresses, or media alone, and COX-2 protein levels were assayed by immunoblots with anti-COX-2 antibodies. Activation of MAPK was examined by immunoblots with phospho-MAPK antibodies. MAPK activity was blocked by treatment with pharmacologic inhibitors or transfection with dominant-negative MAPK constructs. RESULTS: Endotoxin treatment caused increased expression of the COX-2 protein 24 hours after treatment. This was preceded by rapid and transient activation of the 3 major MAPKs: extracellular-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38. SB203580, a specific inhibitor of p38, but not U0126 (ERK inhibitor) or SP600125 (JNK inhibitor), blocked endotoxin-induced accumulation of COX-2 protein. This response was also blocked by expression of dominant-negative p38 but not by the dominant-negative ERK construct. Genotoxic stress that activated p38 but not ERK was an effective inducer of COX-2, whereas stresses that activated both p38 and ERK were not effective. ERK inhibition by U1026 enhanced endotoxin-induced production of COX-2, consistent with negative regulation of COX-2 by ERK. These data point to p38 as the MAPK that mediates endotoxin-induced production of COX-2 in enterocytes. CONCLUSIONS: Endotoxin may be capable of inducing the production of COX-2 in enterocytes via the p38 MAPK pathway, which may be relevant to the development of NEC.     

Arachidonic acid directly activates members of the mitogen-activated protein kinase superfamily in rabbit proximal tubule cells

BACKGROUND: To explore the roles of eicosanoids in arachidonic acid-induced mitogen-activated protein kinase (MAPK) signal transduction, we have shown that exposure of proximal tubular cells to arachidonic acid induces phosphorylation of c-Jun NH2-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK), two members of the MAPK superfamily. We observed that ketoconazole, an inhibitor of the cytochrome P450 pathway, blocked ERK but not JNK activation. METHODS: Direct regulation of arachidonic acid on mitogen-activated protein kinase (MAPK) signaling pathways was evaluated more directly by utilizing specific enzyme inhibitors of the cytochrome P450 metabolic pathway and by comparing the relative efficacy of arachidonic acid versus its cytochrome P450 metabolites (exogenous and endogenous), eicosatetraynoic acid (ETYA), and other fatty acids on the phosphorylation of members of the MAPK superfamily (ERKs, JNK, and p38(MAPK)), by utilizing early passage rabbit proximal tubular epithelial cells. RESULTS: Arachidonic acid activated p38(MAPK), a third member of the MAPK superfamily, in a time- and concentration-dependent manner. Studies designed to evaluate the ability of arachidonic acid and its cytochrome P450 metabolites (endogenously and exogenously) to stimulate ERKs, JNK, and p38(MAPK) found four conclusions. First, the metabolites of arachidonic acid generated endogenously by cytochrome P450 2C1 significantly augmented basal ERK activity, whereas the metabolites generated by the 2C2 isozyme significantly augmented basal p38(MAPK) activity. However, their effects were less profound than arachidonic acid itself. In contrast, there were no significant effects with transfection of either isozyme on basal JNK activity. Second, a variety of exogenous cytochrome P450 products were less potent than arachidonic acid on a molar basis in stimulating the activity of all three MAPKs. Third, ketoconazole and 17-octadecynoic acid, inhibitors of the cytochrome P450 pathway, as well as PPOH and DDMS, inhibitors of the epoxygenase and omega-hydroxylase pathways, respectively, failed to significantly reduce the effects of arachidonic acid to activate ERK and p38(MAPK) (JNK was not evaluated). Finally, arachidonic acid, its inactive analog ETYA, and other fatty acids with differing chain lengths and degrees of saturation stimulated the activity of all three MAPKs. CONCLUSIONS: These observations substantiate a role for arachidonic acid and other fatty acids in signaling linked to the MAPK superfamily in rabbit proximal tubular epithelium without the necessity of conversion to cytochrome P450 metabolites.     

Modulation of vascular smooth muscle cell alignment by cyclic strain is dependent on reactive oxygen species and P38 mitogen-activated protein kinase

PURPOSE: The aim of this study was to investigate the molecular targets of reactive oxygen species (ROS) and to determine whether cyclic strain induces smooth muscle cell (SMC) alignment via the ROS system. We assessed stretch-induced nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase activation and the redox sensitivity of cyclic strain-stimulated activation of the mitogen-activated protein kinase (MAPK) family. METHODS: SMCs were seeded on flexible collagen I-coated plates and exposed to cyclic strain. NAD(P)H oxidase activation was measured with lucigenin-enhanced chemiluminescent detection of superoxide. Activation of MAPK was detected by determining phosphorylation of extracellular signal-regulated protein kinase (ERK1/2), c-jun N-terminal kinase (JNK1/2), and p38 MAPK with immunoblotting. In other experiments, SMCs were exposed to diphenylene iodonium (DPI), an NAD(P)H inhibitor, 30 minutes before stretch. MAPK activation and cell orientation were then assessed. RESULTS: Cyclic strain elicits a rapid increase in intracellular NADH/NADPH oxidase in SMCs. There was also a rapid and robust phosphorylation of ERK1/2, JNK1/2, and p38 MAPK. Cyclic strain-induced intracellular NAD(P)H generation was almost completely blocked with DPI. DPI also inhibited the strain-induced phosphorylation of ERK1/2, JNK1/2, and p38 MAPK. Both the p38 MAPK specific inhibitor, SB 202190, and DPI blocked cyclic strain-induced cell alignment, but PD98059, an ERK1/2-specific inhibitor, and SP600125, an anthrazolone inhibitor of JNK, did not. CONCLUSION: Our results provide evidence that p38 MAPK is a critical component of the oxidant stress ROS-sensitive signaling pathway and plays a crucial role in vascular alignment induced by cyclic stain.     

Hyaluronan inhibits matrix metalloproteinase‐13 in human arthritic chondrocytes via CD44 and P38

We investigated the effects of hyaluronan (HA) on interleukin‐1β (IL‐1β)‐stimulated matrix metalloproteinase (MMP)‐13 production in human chondrocytes from patients with osteoarthritis (OA) or rheumatoid arthritis (RA). Secreted levels of MMP‐13 in conditioned media were detected by immunoblotting, while intracellular MMP‐13 synthesis in articular cartilage was evaluated by immunofluorescence microscopic analysis. Mitogen‐activated protein kinases (MAPKs), p38, extracellular signal‐regulated kinases (ERK), and c‐jun NH2‐terminal kinase (JNK) were assessed by Western blotting. IL‐1β (2 ng/ml) stimulates the secretion of MMP‐13 in both OA and RA chondrocytes. Inhibition studies using specific MAPK inhibitors revealed that IL‐1β induced MMP‐13 via p38 in both OA and RA chondrocytes. HA down‐regulates IL‐1β‐stimulated MMP‐13 and phosphorylated p38 (p‐p38) in a dose‐dependent manner (0.1, 1, 2, and 4 mg/ml). When used at 4 mg/ml, HA inhibits p‐p38 phosphorylation by more than 60%. In response to IL‐1β, RA chondrocytes express a higher level of p‐p38 than that of OA chondrocytes. Inhibition of CD44, using a blocking antibody, significantly reversed the inhibitory effect of HA on both MMP‐13 and p‐p38. Our study clearly shows that HA inhibits IL‐1β‐induced MMP‐13 via its principal receptor, CD44, and subsequent intracellular p38 MAPK signaling in OA and RA chondrocytes. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:258–264, 2011     

Extracellular signal-related kinase 1/2 and p38 mitogen-activated protein kinase pathways serve opposite roles in neutrophil cytotoxicity.

BACKGROUND: Inflammatory stimuli rapidly activate mitogen-activated protein kinases (MAPKs) in neutrophils (PMNs). However, their role in cytotoxic function remains unknown. Elucidating the signals involved in release of cytotoxic agents from PMNs may provide new avenues for therapy in diseases of diminished or excessive PMN function. HYPOTHESIS: The p38 MAPK and extracellular signal-related kinase 1/2 (ERK1/2) modulate superoxide generation and elastase release in activated human PMNs. STUDY DESIGN: Isolated human PMNs were incubated with specific inhibitors of MAPK pathways, or vehicle control solution, before activation with the bacterial peptide f-Met-Leu-Phe. MAIN OUTCOME MEASURES: The rate of superoxide release from activated PMNs was measured by the superoxide dismutase-inhibitable reduction of cytochrome-c. Elastase release from PMNs was determined by cleavage of the substrate Ala-Ala-Pro-Val-pNA. RESULTS: Superoxide release from activated PMNs was inhibited by blockade of p38 MAPK activation but unaffected by blockade of ERK1/2. Conversely, elastase release was unaffected by p38 MAPK inhibition and increased by ERK1/2 inhibition. CONCLUSIONS: Activation of p38 MAPK promotes superoxide release from PMNs activated by f-Met-Leu-Phe. The ERK1/2 pathway may serve as a negative feedback mechanism for granule exocytosis.     

Role of p38 mitogen-activated protein kinase activation in podocyte injury and proteinuria in experimental nephrotic syndrome

Podocytes play an important role in maintaining normal glomerular function and structure, and podocyte injury leads to proteinuria and glomerulosclerosis. The family of mitogen-activated protein kinases (MAPK; extracellular signal-regulated kinase [ERK], c-Jun N-terminal kinase, and p38) may be implicated in the progression of various glomerulopathies, but the role of MAPK in podocyte injury remains elusive. This study examined phosphorylation of p38 MAPK in clinical glomerulopathies with podocyte injury, as well as in rat puromycin aminonucleoside (PAN) nephropathy and mouse adriamycin (ADR) nephropathy. The effect of treatment with FR167653, an inhibitor of p38 MAPK, was also investigated in rodent models. In human podocyte injury diseases, the increased phosphorylation of p38 MAPK was observed at podocytes. In PAN and ADR nephropathy, the phosphorylation of p38 MAPK and ERK was marked but transient, preceding overt proteinuria. Pretreatment with FR167653 (day -2 to day 14, subcutaneously) to PAN or ADR nephropathy completely inhibited p38 MAPK activation and attenuated ERK phosphorylation, with complete suppression of proteinuria. Electron microscopy and immunohistochemistry for nephrin and connexin43 revealed that podocyte injury was markedly ameliorated by FR167653. Furthermore, early treatment with FR167653 effectively prevented glomerulosclerosis and renal dysfunction in the chronic phase of ADR nephropathy. In cultured podocytes, PAN or oxidative stress induced the phosphorylation of p38 MAPK along with actin reorganization, and FR167653 inhibited such changes. These findings indicate that the activation of MAPK is necessary for podocyte injury, suggesting that p38 MAPK and, possibly, ERK should become a potential target for therapeutic intervention in proteinuric glomerulopathies.     

三羟基异黄酮对增生性瘢痕成纤维细胞受体型酪氨酸蛋白激酶-丝裂原活化蛋白激酶信号通路的影响

目的 了解5,7,4'-三羟基异黄酮(genistein)对增生性瘢痕成纤维细胞(HSFb)内受体型酪氨酸蛋白激酶-丝裂原活化蛋白激酶(TPK-MAPK)信号转导通路的影响,探讨genistein抑制瘢痕增生的分子机制. 方法体外分离培养HSFb,以不同浓度genistein(25、50、100μmol/L)处理细胞,再加入10 μg/L碱性成纤维细胞生长因子(bFGF)刺激,用[γ-32P]腺苷三磷酸底物掺入法检测细胞TPK活性;用蛋白质印迹法检测TPK-MAPK通路中主要信号蛋白分子c-Raf、丝裂原激活蛋白激酶激酶(MEK)、细胞外信号调节激酶(ERK)、p38 MAPK、c-Jun氨基末端激酶(JNK)磷酸化蛋白的表达变化.以二甲亚砜溶剂处理的HSFb为对照组. 结果 25、50、100μmol/L genistein作用后,HSFb内TPK活性分别为(7.15±0.35)、(5.62±0.88)、(3.17±0.94)×105 pmol·min-1·mg-1,与对照组(8.92±0.28)×105 pmol·min-1·mg-1比较,差异有统计学意义(P<0.05或P<0.01);细胞内磷酸化c-Raf、MEK1/2、ERK1/2、p38蛋白的含量均有不同程度降低,与对照组比较,差异有统计学意义(P<0.05或P<0.01).genistein各剂量组磷酸化JNK蛋白含量与对照组近似.在genistein预处理前提下,加入bFGF刺激的细胞内TPK活性及各信号蛋白的表达亦呈下降趋势. 结论 genistein可通过抑制细胞受体TPK信号转导途径影响HSFb的增殖与活化,主要信号通路可能为TPK→Raf→MEK→ERK/p38途径.     

Tacrolimus (FK506) inhibits interleukin-1β-induced angiopoietin-1, Tie-2 receptor, and vascular endothelial growth factor through down-regulation of JNK and p38 pathway in human rheumatoid fibroblast-like synoviocytes

ObjectThis study aimed to identify the regulatory effect of tacrolimus on the interleukin-1β (IL-1β)-induced expressions of angiopoietin-1 (Ang-1), Tie-2 receptor (Tie-2), and vascular endothelial growth factor (VEGF) in human rheumatoid fibroblast-like synoviocytes (FLS) and to determine the regulatory mechanism in the mitogen-activated protein kinases (MAPKs) signaling pathway.MethodsIL-1β-induced Ang-1, Tie-2, and VEGF expressions with and without tacrolimus were measured in cultured FLS using real time–polymerase chain reaction, enzyme-linked immunosorbent assay, Western blotting, and immunofluorescence staining. The effect of tacrolimus on the regulation of Ang-1, Tie-2 and VEGF expressions through the MAPK signaling pathway was identified by Western blotting and immunofluorescence staining.ResultsIL-1β appeared to induce marked expressions of Ang-1, Tie-2, and VEGF in cultured FLS. Tacrolimus significantly inhibited Ang-1, Tie-2, and VEGF mRNA and protein in cultured FLS treated with 10 ng/ml IL-1β. In addition, expressions of these angiogenic molecules were shown to involve all three of the studied MAPK signaling pathways, including ERK, JNK, and p38. However, the inhibitory effects of tacrolimus on Ang-1, Tie-2, and VEGF proteins were regulated by blocking the phosphorylations of JNK and p38 MAPK, but not that of ERK.ConclusionThis study demonstrates that tacrolimus inhibits the expressions of Ang-1, Tie-2, and VEGF by blocking the activations of the IL-1β-mediated JNK and p38 MAPK pathways in human FLS. This suggests that tacrolimus contributes to the suppression of angiogenesis in the pathogenesis of RA.     

Activation of pulmonary mitogen-activated protein kinases during cardiopulmonary bypass

PURPOSE: Cardiopulmonary bypass (CPB) produces an inflammatory response associated with pulmonary dysfunction. Mitogen-activated protein kinases (MAPK) have been shown to mediate pulmonary injury. We hypothesized that MAPK are activated during CPB and potentially contribute to lung injury. METHODS: Pigs were placed on CPB (n = 6) for 90 min, which included 80 min of cardioplegic arrest, followed by 180 min of post-CPB reperfusion. Control animals (n = 6) underwent sternotomy and heparinization only. Lung samples were collected at baseline, during CPB, and during post-CPB reperfusion. Activated forms of extracellular signal-regulated kinases 1/2 (ERK1/2) and p38 were measured by Western blot. Immunohistochemistry was used for tissue localization of activated MAPK. Pulmonary inflammation was determined by histology. Pulmonary edema was estimated by tissue water percentage. RESULTS: Activated ERK1/2 and p38 were increased after 90 min of CPB compared with controls (3.94 +/- 0.61- and 2.49 +/- 0.15-fold increase, respectively; both P < 0.01). At 180 min of post-CPB reperfusion, ERK1/2 activity was increased by nearly 5-fold compared with controls (P < 0.01), whereas p38 activity returned to baseline levels. By immunohistochemistry, activated ERK1/2 and p38 in the CPB group were localized to alveolar epithelial cells, vascular endothelial cells, and bronchial smooth muscle. Histologic signs of lung injury included leukocyte infiltration in the CPB group. Tissue water percentage was increased with CPB (89.9 +/- 1.5% versus 82.5 +/- 1.0%, CPB versus control, P < 0.05). CONCLUSIONS: The results of our study demonstrate that CPB increases pulmonary p38 activity and causes sustained activation of ERK1/2. MAPK activation thus may in part mediate the pulmonary inflammatory response and provide a potential site of intervention to prevent pulmonary dysfunction due to CPB.     

缺氧时丝裂原激活蛋白激酶类对人肾小管上皮细胞富含半胱氨酸蛋白61基因转录活性的调控

目的 探讨丝裂原激活蛋白激酶类（MAPKs）对缺氧条件下人近端肾小管上皮细胞（HKC）中富含半胱氨酸蛋白61（Cyr61）基因转录活性的调控机制。方法 缺氧培养HKC，Northern印迹检测Cyr61mRNA表达；Western印迹检测Cyr61、p38、细胞外信号调节激酶（ERK1／2）、c—Jun—N末端蛋白激酶（JNK）以及缺氧诱导因子1c（HIF-1α）的表达。构建含有人Cyr61基因启动子的报告基因Cyr61-luc质粒，将其单独或者分别与表达活性MAPKs的质粒Ca—MEK1和Ca—MKK6共同瞬时转染HKC。通过荧光素酶活性检测观察缺氧、MAPKs抑制剂和MAPKs活性酶对Cyr61基因转录活性的调控。结果 缺氧时HKC表达cyr61、HIF-1α增高，ERK1／2、JNK、p38总量不变，而其各自的磷酸化形式均明显增加。HKC转染Cyr—luc后，p38通路抑制剂SB203580和ERK通路抑制剂PD98059显著抑制缺氧时Cyr61的转录活性，两者协同作用时抑制作用显著增强。Ca—MEK1与Cyr—luc共转染HKC后，Cyr61转录活性无改变；而Ca—MKK6与Cyr—luc共转染后，Cyr61转录活性显著增高。对缺氧培养的HKC，PD98059处理使HIF-1α和Cyr61蛋白表达显著降低；SB203580处理可显著降低Cyr61蛋白表达，但对HIF-1α无影响。结论 在HKC中，缺氧可通过p38通路直接上调Cyr61基因启动子活性，也可通过ERK1／2途径促进HIF-1α表达，间接调节Cyr61基因启动子活性。     

Modulation of renal epithelial barrier function by mitogen-activated protein kinases (MAPKs): mechanism of cyclosporine A-induced increase in transepithelial resistance

BACKGROUND: Cyclosporine A (CsA) has been shown to increase transepithelial resistance in Madin-Darby canine kidney (MDCK) cells, and the mechanism may involve altered phosphorylation of junctional proteins. In this study, we examine the effect of the extracellular signal-regulated protein kinase (ERK) 1/2 and p38 mitogen-activated protein kinase (MAPK) pathways on the basal transepithelial resistance (TER) and on the CsA-induced increase in TER across MDCK monolayers. Here we present evidence that CsA may be mediating some of its effects through activation of the ERK 1/2 MAPK pathway. METHODS: MDCK cells were treated with CsA (4.2 micromol/L) and paracellular permeability was assessed by measuring TER. The role of the ERK 1/2 and the p38 MAPK pathways in modulating TER was investigated using the inhibitors PD98059 and U0126 for ERK 1/2 and SB203580 for p38. ERK 1/2 and p38 phosphorylation/activation was also examined by Western blot analysis. RESULTS: CsA (4.2 micromol/L) increased the TER of MDCK monolayers. The ERK 1/2 inhibitor PD98059 decreased basal TER and also ameliorated the CsA-induced increase in TER. Similar results were found with the U0126 inhibitor of ERK 1/2. The p38 inhibitor SB203580 had no effect on the basal TER of the monolayers, however, SB203580 significantly augmented the CsA-induced increase in TER. CsA was shown to significantly activate ERK 1/2 and this activation by CsA was prevented by PD98059. Inhibition of the p38 pathway by SB203580 also resulted in activation of ERK 1/2 and this activation of ERK 1/2 was further enhanced by CsA. No effect of CsA or the inhibitors PD98059 or SB203580 on p38 phosphorylation was detected. CONCLUSION: The results presented here suggest that activation of the ERK 1/2 MAPK cascade is important in the regulation of the paracellular permeability in MDCK cells. Activation of this pathway appears to be pivotal to the CsA-induced increase in TER.     

Activation of extracellular signal-related kinases 1 and 2 in Sertoli cells in experimentally cryptorchid rhesus monkeys

目的:观察恒河猴隐睾(热刺激)模型中睾丸细胞外信号调节激酶1和2(ERK1/2),c-Jun N 末端激酶(JNKs)和 p38有丝分裂原激活蛋白激酶(MAPK)的时空表达变化并探讨其参与支持细胞去分化的可能调节作用。方法:通过免疫组化和 Western blot 方法观察 ERK1/2、p38以及 JNK 在处于隐睾不同时期的睾丸中的表达变化。结果:腹部温度没有明显改变隐睾的睾丸细胞中的 ERK1/2表达量,但明显活化了磷酸化 ERK1/2在支持细胞中的表达。腹腔内的热压明显增加睾丸细胞中 JNK 总体水平的表达,但没有活化磷酸化 JNK 的表达。睾丸细胞内磷酸化 p38以及非磷酸化的 p38的表达不受热刺激的影响。不成熟或未分化的支持细胞的标志分子(CK-18)的时空表达变化与 ERK1/2在隐睾睾丸内的活化存在一致性。结论:隐睾睾丸内 ERK1/2的活化可能参与支持细胞受热刺激后发生去分化的调节过程。