Differential Activation of Mitogen-activated Protein Kinases in Ischemic and Anesthetic Preconditioning

Background: Accumulating evidence pinpoints to the pivotal role of mitogen-activated protein kinases (MAPKs) in the signal transduction underlying cardiac preconditioning.

Methods: PD98059, an inhibitor of extracellular signal-regulated protein kinase (MEK-ERK1/2), and SB203580, an inhibitor of p38 MAPK, were used to evaluate the role of MAPKs with respect to postischemic functional recovery in isolated perfused rat hearts subjected to ischemic preconditioning (IPC) and anesthetic preconditioning (APC). Western blot analyses were used to determine the degree of ERK1/2 and p38 MAPK activation after the application of the preconditioning stimulus and after ischemia-reperfusion. Immunohistochemical staining served to visualize subcellular localization of activated MAPKs.

Results: PD98059 and SB203580 abolished postischemic functional recovery in IPC but not in APC. IPC but not APC markedly activated ERK1/2 and p38 MAPK, which were abrogated by coadministration of the specific blockers. Conversely, IPC and APC enhanced ERK1/2 activity after ischemia-reperfusion as compared to nonpreconditioned hearts, and IPC in addition enhanced p38 MAPK activity. Coadministration of PD98059 and SB203580 during IPC but not during APC inhibited postischemically enhanced MAPK activities. Moreover, chelerythrine and 5-hydroxydecanoate, effective blockers of IPC and APC, annihilated IPC- and APC-induced enhanced postischemic responses of MAPKs. Finally, administration of PD98059 during ischemia-reperfusion diminished the protective effects of IPC and APC. Immunohistochemistry revealed increased ERK1/2 activity primarily in intercalated discs and nuclei and increased p38 MAPK activity in the sarcolemma and nuclei of IPC-treated hearts.     

Differential activation of mitogen-activated protein kinases in ischemic and anesthetic preconditioning

BACKGROUND: Accumulating evidence pinpoints to the pivotal role of mitogen-activated protein kinases (MAPKs) in the signal transduction underlying cardiac preconditioning. METHODS: PD98059, an inhibitor of extracellular signal-regulated protein kinase (MEK-ERK1/2), and SB203580, an inhibitor of p38 MAPK, were used to evaluate the role of MAPKs with respect to postischemic functional recovery in isolated perfused rat hearts subjected to ischemic preconditioning (IPC) and anesthetic preconditioning (APC). Western blot analyses were used to determine the degree of ERK1/2 and p38 MAPK activation after the application of the preconditioning stimulus and after ischemia-reperfusion. Immunohistochemical staining served to visualize subcellular localization of activated MAPKs. RESULTS: PD98059 and SB203580 abolished postischemic functional recovery in IPC but not in APC. IPC but not APC markedly activated ERK1/2 and p38 MAPK, which were abrogated by coadministration of the specific blockers. Conversely, IPC and APC enhanced ERK1/2 activity after ischemia-reperfusion as compared to nonpreconditioned hearts, and IPC in addition enhanced p38 MAPK activity. Coadministration of PD98059 and SB203580 during IPC but not during APC inhibited postischemically enhanced MAPK activities. Moreover, chelerythrine and 5-hydroxydecanoate, effective blockers of IPC and APC, annihilated IPC- and APC-induced enhanced postischemic responses of MAPKs. Finally, administration of PD98059 during ischemia-reperfusion diminished the protective effects of IPC and APC. Immunohistochemistry revealed increased ERK1/2 activity primarily in intercalated discs and nuclei and increased p38 MAPK activity in the sarcolemma and nuclei of IPC-treated hearts. CONCLUSIONS: Although MAPKs may orchestrate cardioprotection as triggers and mediators in IPC, they are devoid of triggering, but they may have mediator effects in APC.     

p38MAPK与 ERK1/2的协同效应及对成骨细胞分化的调控

 目的探讨骨髓间质干细胞(bone marrow mesenchymal stem cells,BMSCs)向成骨细胞分化过程中 p38MAPK与 ERK1/2的协同效应及其机制。方法以成骨细胞分化添加剂诱导小鼠 BMSCs向成骨细胞分化,测定碱性磷酸酶活性和钙沉积量。检测磷酸化 p38MAPK和磷酸化 ERK1/2(p-ERK1/2)的表达水平评估通路的激活状况。以 SB203580或 PD98059阻断 p38MAPK或 ERK1/2通路,观察对成骨细胞分化的影响。以 SB203580或亚砷酸钠阻断或激活 p38MAPK通路,观察 p-ERK1/2的变化。以冈田酸抑制蛋白磷酸酯酶 2A(protein phosphatases type 2A,PP2A)活性,观察 p-ERK1/2的变化及对成骨细胞分化的影响。通过免疫共沉淀实验观察 PP2A和 ERK1/2间的结合及 SB203580对结合的影响。结果成骨细胞分化添加剂诱导 BMSCs向成骨细胞分化的过程伴有 ERK1/2和 p38MAPK通路的激活, SB203580剂量±赖性抑制成骨细胞分化,PD98059剂量±赖性增强成骨细胞分化。 SB203580使 p-ERK1/2表达增加,亚砷酸钠减弱其表达。冈田酸使 p-ERK1/2表达增加,并使成骨细胞分化受到抑制。 PP2A可直接与 ERK1/2结合,SB203580使 PP2A与 ERK1/2的结合减弱。结论 p38MAPK可通过 PP2A与 ERK1/2产生协同效应,并调节 BMSCs向成骨细胞分化。     

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.     

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。     

P38 mitogen-activated protein kinase inhibition attenuates pulmonary inflammatory response in a rat cardiopulmonary bypass model.

OBJECTIVE: Cardiopulmonary bypass (CPB) produces an inflammatory response associated with pulmonary dysfunction. P38 mitogen-activated protein kinase (P38MAPK) have been shown to mediate pulmonary inflammatory response after CPB, we examined the effect of SB203580, a specific p38 MAPK inhibitor, on CPB-induced pulmonary inflammatory response. METHODS: Sprague-Dawley rats (n=54) were randomized into three groups (each n=18): (1) S group, rats underwent sham CPB; (2) CPB group, rats underwent CPB; (3) SB group, rats underwent CPB plus pretreatment with SB203580 (10 mg/kg, i.v., 30 min before CPB). The lung samples were collected after 10 min, 60 min, and 150 min lung reperfusion (each n=6) in CPB group and SB group, and after 70 min, 120 min, and 210 min observation in S group as the control. RESULTS: The level of lung phospho-IkappaBalpha, nuclear factor (NF)-kappaB activity and activating protein (AP)-1 activity in CPB group was increased than S group. CPB resulted in increased pulmonary tissue tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta expression and production, increased pulmonary inflammatory response. The in vivo administration of SB203580 prevented up-regulation of lung-phosphorylated p38 MAP kinase, decreased pulmonary tissue level of proinflammatory cytokines expression and production, and reduced lung inflammation. CONCLUSIONS: These findings suggested that (1) p38 MAP kinase activation is one of the important aspects of the signaling event that mediate the release of TNF-alpha and IL-1beta and contributes to CPB-induced pulmonary inflammatory response, (2) SB203580 selectively inhibiting p38 MAP kinase activation efficaciously reduces pulmonary inflammatory response after CPB, and (3) p38 MAP kinase influence the activation of NF-kappaB in the lung during and after CPB.     

Modulation of phorbol ester-induced regulation of matrix metalloproteinases and tissue inhibitors of metalloproteinases by SB203580, a specific inhibitor of p38 mitogen-activated protein kinase

OBJECT: Expression of matrix metalloproteinases (MMPs) has been postulated to play a central role in brain tumor invasion; however, its underlying mechanism is not yet fully understood. In the present study, by assessing the effect of a specific p38 mitogen-activated protein kinase (MAPK) inhibitor, SB203580, on the secretion of MMPs and in vitro invasion of various glioma cells, the authors attempt to define the role of the p38 MAPK pathway in the regulation of MMPs and tissue inhibitors of metalloproteinases (TIMPs) activated by phorbol ester (phorbol-12-myristate-13-acetate [PMA]) in the D54 human glioblastoma cell line. METHODS: The activation of MAPKs was determined using Western blot analysis after addition of phospho-specific antibodies against these kinases, the status of MMPs and TIMPs was analyzed using gelatin zymography and Western blot analysis, and the invasion rate of D54 cells and other glioma cells was analyzed using a modified Boyden chamber assay. Treatment of D54 cells with PMA activated two distinct MAPKs, extracellular signal-regulated kinase (ERK) 1/2 and p38 MAPK, but not c-Jun N-terminal kinase/stress-activated protein kinase. Induction of MMP-9 production and MMP-2 activation by PMA were blocked by SB203580, a specific inhibitor of p38 MAPK, but not by PD98059, a specific inhibitor of ERK 1/2. In addition, PMA-induced downregulation of TIMP-1 and TIMP-2 secretion and upregulation of the membrane type I MMP, a major activator of MMP-2 on the cell surface, were reversed by SB203580 in these cells; the PMA-induced increase of invasion in vitro decreased when SB203580 was added to the top compartment of a modified Boyden chamber; and the inhibitor also reduced the MMP secretion and PMA-induced in vitro invasion in various glioma cell lines. CONCLUSIONS: These results indicate that activation of p38 MAPK by PMA plays a central role in the regulation of MMPs and TIMPs in D54 cells, which has a major influence in tumor invasion and metastasis. Furthermore, inhibition of p38 MAPK by SB203580 blocked the secretion of MMPs and in vitro invasion of various glioma cells, underscoring a possible role of p38 MAPK inhibitors as antiinvasive and/or antimetastatic agents of malignant gliomas.     

beta1-integrin-ligand disengagement induces in vitro capillary tube disruption mediated by p38 MAPK activity

BACKGROUND: Disrupting cell-matrix interactions may lead to capillary injury as seen in sepsis and transplant rejection. Previously, we demonstrated capillary disruption mediated by beta1-integrin-ligand disengagement. We now determine whether p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) pathways are involved in this capillary injury. METHODS: Endothelial capillaries on Matrigel were preincubated with a p38 MAPK inhibitor (SB203580), ERK pathway inhibitor (PD98059), or dimethyl sulfoxide. Subsequently, a beta1-integrin blocking (P5D2) or an irrelevant antibody was added. After 24 hours, capillary integrity was quantified as capillary intersections/well. Antibody-treated cell lysates then were immunoprecipitated with either a phospho-p38 MAPK or phospho-ERK1/2 antibody. Kinase activity was measured with ATF-2 and Elk-1 fusion proteins as substrates for p38 MAPK and ERK, respectively, followed by Western blotting. RESULTS: P5D2 disrupted capillary tubes. Increased p38 MAPK activity at 8 hours and ERK activity at 2 and 8 hours were seen in P5D2-treated lysates. Preincubation with SB203580, but not with PD98059 or DSMO, significantly reduced capillary tube disruption. CONCLUSIONS: The beta1-integrin-ligand disengagement resulted in capillary disruption and stimulated p38 MAPK and ERK activity. In spite of activation of both pathways, the p38 MAPK but not the ERK pathway inhibitor prevented beta1-integrin antibody effects. Inhibiting p38 MAPK may mitigate capillary injury associated with sepsis and transplant rejection.     

ERK and p38 MAP kinase are required for rat renal development

BACKGROUND: We previously demonstrated that extracellular signal-regulated protein kinase (ERK) and p38 mitogen-activated protein (MAP) kinase (p38) are strongly expressed in the embryonic kidney. In the present study, we investigated the role of ERK and p38 during kidney development. METHODS: Rat metanephroi were cultured from 15-day-old embryos, and exposed to inhibitors of MEK, an activator of ERK, PD98059 (300 micromol/L), U0126 (10 micromol/L), or a p38 inhibitor SB203580 (30 micromol/L) 24 to 120 hours after the start of culture. Growth of metanephroi was measured by surface area and thymidine incorporation. Ureteric buds and glomeruli were identified by labeling with Dolichos biflorus lectin and peanut agglutinin, respectively. PCNA staining and TUNEL assay were performed on kidney sections. The level of apoptosis was evaluated by examining DNA ladder formation. RESULTS: Growth of metanephroi was significantly inhibited by SB203580 but not by PD98059 or U0126. Ureteric bud branching was not affected by SB203580 or MEK inhibitors. Glomerular number was markedly reduced by SB203580 and to a lesser extent by U0126 (14 +/- 2 and 48 +/- 10% of controls, respectively). On histological examination, the number of tubuloglomerular structures was reduced in MEK inhibitor-treated metanephroi compared to controls. Very few mesenchymal condensates were observed in kidneys incubated with SB203580. PCNA-positive cells were reduced in SB203580-treated metanephroi compared to control and PD98059-treated kidneys. Apoptosis was increased in SB203580-treated kidneys and to a lesser extent in PD98059-treated cultures. CONCLUSIONS: Both ERK and p38 are required for renal development. ERK appears to play a role in nephrogenesis and p38 for kidney growth and nephrogenesis.     

Sphingosine-1-phosphate stimulates smooth muscle cell migration through galpha(i)- and pi3-kinase-dependent p38(MAPK) activation

BACKGROUND: Sphingosine-1-phosphate (S-1-P) is an extracellular mediator released in response to vessel injury. S-1-P binds to G-protein-coupled receptors, which can be Galpha(i)-, Galpha(q)-, or G(12/13)-linked. This study examines the role of p38 mitogen-activated protein kinase (p38(MAPK)) in vascular smooth muscle cell migration after stimulation with S-1-P, and pathways leading to p38(MAPK) activation. S-1-P has previously been shown to stimulate migration of vascular smooth muscle cells (VSMCs) in vitro through ERK1/2 and G(i). We hypothesized that S-1-P-induced VSMC migration is also dependent on p38(MAPK) activation through a G(i)-coupled extracellular receptor and phosphoinositide 3-kinase (PI3-K). METHODS: VSMCs were cultured in vitro. A linear wound assay was performed in the presence of S-1-P and inhibitors of p38(MAPK) (SB203580) or epidermal growth factor (EGF) receptor kinase (AG1478). Chemotaxis stimulated by S-1-P was also assayed in a modified Boyden chamber with and without SB203580 pretreatment. Western blotting was performed to examine p38(MAPK) activation in response to S-1-P with and without SB203580, AG1478, or inhibitors of G(i) (pertussis toxin), PI3-K (Wortmannin and LY294002), or MEK1 (PD98059). Western blotting and immunoprecipitation for targets of p38(MAPK) (MAPKAP kinase-2) and PI3-K (Akt) were also performed.S-1-P stimulated migration of VSMCs in both wound and Boyden transwell assays. This migration was inhibited by SB203580 to the level of control, whereas AG478 had no effect. RESULTS: S-1-P stimulated activation of p38(MAPK) that peaked at 10 min, as well as activation of MAPKAP kinase-2. Activation of p38(MAPK) was significantly inhibited by SB203580, pertussis toxin, Wortmannin, and LY294002, but not by PD98059 or AG1478; MAPKAP kinase-2 activation was inhibited by SB203580. Akt was activated by S-1-P at 3 to 5 min; this response was inhibited by Wortmannin and LY294002, but not by SB203580 or pertussis toxin. CONCLUSIONS: S-1-P induced VSMC migration through a G(i)-linked and a PI3-K coupled, p38(MAPK)- dependent process. PI3-K appears to function upstream of p38(MAPK), but was not G(i)-dependent. S-1-P-stimulated activation of p38(MAPK) does not signal via transactivation of the EGF receptor. Understanding signal transduction will allow targeted molecular interventions to treat the response of a vessel to injury.     

Mitogen-activated protein kinases signal inhibition of apoptosis in lipopolysaccharide-stimulated neutrophils.

BACKGROUND: Neutrophil (PMN) apoptosis is critical to the resolution of infection and the limitation of inflammation. Bacterial endotoxin (lipopolysaccharide [LPS]) inhibits PMN apoptosis and activates the p38 mitogen-activated protein kinase (MAPK) signal cascade. The role of p38 and other MAPKs (ERK and SAPK/JNK) in regulating PMN apoptosis after LPS stimulation is unknown. We hypothesize that MAPK activation by LPS signals inhibition of PMN apoptosis. METHODS: PMNs were isolated from the blood of healthy human volunteers and incubated with PD98059 (ERK inhibitor), SB203580 (p38 inhibitor), or 0.1% dimethyl sulfoxide (vehicle) for 1 hour before treatment with LPS (0, 10, or 1000 ng/mL). Neutrophil MAPK activation was determined by Western blot analysis for phosphorylated p38, ERK, and SAPK/JNK. Apoptosis was quantified by flow cytometry with use of propidium iodide and annexin V. RESULTS: LPS inhibited PMN apoptosis and activated p38 and ERK in a dose- and time-dependent fashion. SAPK/JNK was not activated by LPS. Treatment of cells with ERK inhibitor before LPS stimulation abrogated LPS signaled inhibition of PMN apoptosis. Conversely, p38 inhibition with SB203580 augmented inhibition of apoptosis by LPS. CONCLUSIONS: These data demonstrate opposing roles of MAPKs in mediating PMN apoptosis after LPS stimulation. We conclude that LPS signal transduction by ERK inhibits PMN apoptosis while activation of p38 promotes apoptosis.     

丝裂原活化蛋白激酶类和蛋白激酶C在转化生长因子β1诱导肾小管细胞结缔组织生长因子表达中的作用

目的了解转化生长因子β1（TGF-β1）诱导肾小管细胞结缔组织生长因子（CTGF）表达的机制，特别是蛋白激酶C（PKC）和丝裂原活化蛋白激酶（MAPK）在CTGF基因表达中的作用及其对Smad磷酸化的影响。方法分别应用PKC抑制剂G06850以及MAPK的3个组成成分ERK、JNK和p38MAPK的抑制剂PD98059、U0126、SP600125和SB203580阻断相应通路，观察其对TGF．131诱导的CTGF表达以及Smad2／Smad3磷酸化的影响。结果TGF-β1（5μg／L）以时间依赖方式诱导HK-2细胞中Smad2／Smad3的磷酸化，从基础值0．87±0．09上升至2h时高峰2．350±0.11。PKC抑制剂G06850（5μmol／L）和ERK抑制剂PD98059（10μmol／L）、U0126（10μmol／L）可部分抑制TGF-β1诱导的CTGF表达，而p38MAPK抑制剂SB203580（20μmol／L）和JNK抑制剂SP600125（10μmol／L）对TGF-β1诱导的CTGF的表达无影响。PKC抑制剂G06850（5μmol／L）可减少TGF-β1诱导的Smad2／Smad3磷酸化，而ERK抑制剂PD98059（10μmol／L）和U0126（10μmol／L）对Smad2／Smad3的磷酸化没有影响。结论在肾小管上皮细胞中，TGF-β1诱导CTGF的表达需要PKC和Ras／MEK／ERK的参与。PKC以Smad依赖的方式参与肾小管上皮细胞中TGF-β1诱导的CTGF的表达，而Ras／MEK／ERK对CTGF表达的调节不依赖于Smads。     

Role of MAP kinase pathways in mediating IL-6 production in human primary mesangial and proximal tubular cells.

BACKGROUND: Both interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) are pleiotropic cytokines that have been implicated in the development of glomerular and tubular injury in various forms of immune-mediated renal disease, including glomerulonephritis. Although TNF-alpha has been shown to stimulate IL-6 production in renal cells in culture, the signaling mechanisms that regulate IL-6 production are not fully understood. The aim of this study was to examine the role of the p38 and extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) pathways in regulating TNF-alpha-mediated IL-6 production from both primary human mesangial cells (HMCs) and human proximal tubular (HPT) cells. METHODS: Primary mesangial and proximal tubular cells were prepared from nephrectomized human kidney tissue. Cells were treated for 24 hours with TNF-alpha in the presence and absence of the specific p38 and ERK1,2 MAPK inhibitors SB203580 and PD98059, respectively, either alone or in combination. IL-6 levels in the cell culture media were measured by enzyme-linked immunosorbent assay. MAPK activation was demonstrated by immunoblot for the active kinase (tyrosine/threonine phosphorylated) in whole cell extracts using phospho-specific antibodies. p38 MAPK activity in HPT cells was measured using an in vitro immunokinase assay using ATF2 as the substrate. RESULTS: TNF-alpha (0.1 to 100 ng/ml) stimulated a dose-dependent increase in IL-6 production in both renal cell types. The activation of the p38 and the ERK1,2 MAPKs occurred following TNF-alpha stimulation. The role of these activations in IL-6 production was confirmed by the ability of both inhibitors SB203580 (1 to 30 microM) and PD98059 (0.01 to 10 microM) to inhibit basal and TNF-alpha-stimulated IL-6 production in both cell types. The addition of both inhibitors in combination caused greater decreases in IL-6 production compared with either inhibitor alone. Pretreatment with SB203580 (10 microM) had no effect on basal or TNF-alpha-stimulated phosphorylation of p38 MAPK but completely abolished TNF-alpha-stimulated p38 MAPK activity. PD98059 decreased both basal and TNF-alpha-stimulated phosphorylation of ERK1,2. CONCLUSIONS: This study provides evidence that both the p38 and ERK MAPK pathways are important for the regulation of the production of IL-6 from the proximal tubular and glomerular mesangial regions of the nephron. In response to TNF-alpha, the activation of both pathways leads to IL-6 production. These findings could aid in an understanding of the cellular mechanisms that regulate IL-6 production and could provide insights into possible pharmacological strategies in inflammatory renal disease.     

Immune suppression in polymicrobial sepsis: differential regulation of Th1 and Th2 responses by p38 MAPK

BACKGROUND: Studies have indicated that a shift from a Th1 to a Th2 response occurs that contributes to the late immunosuppression seen during sepsis. However, the mechanism by which this occurs is unknown. In this regard, mediators released in response to sepsis are thought to upregulate a family of stress-induced mitogen-activated protein kinases (MAPKs), such as JNK, ERK, and p38 MAPK, which may play a role in this process. MATERIALS AND METHODS: To determine the role of MAPK in immune suppression, we induced polymicrobial sepsis in C3H/HeN male mice using cecal ligation and puncture (CLP). Splenic lymphocytes were harvested 24 h post-CLP and stimulated with the T-cell mitogen concanavalin A, and the expression and activation of these MAPKs were assessed by Western analysis. To determine the extent to which these MAPKs may have an impact on splenic immune function, cells were pretreated with a 10 microM concentration of the p38 MAPK inhibitor SB203580 or the MEK inhibitor PD98059 or with DMSO vehicle. The cells were then stimulated with 2.5 microg/ml of the T-cell mitogen concanavalin A, and cytokine release was then determined (by ELISA). RESULTS: In the lymphocytes from CLP mice no JNK signal was detected, however, p38 expression and activation were markedly (P < 0.05, n = 6) increased. In contrast, the expression of activated ERK markedly decreased following septic challenge. The results indicate that p38 MAPK inhibition with SB203580 suppressed the sepsis-induced augmentation of interleukin-10 release while restoring the suppressed Th1 cytokine interleukin-2 release typically encountered following sepsis. Inhibition of ERK had no effect on cytokine release. Neither PD98059 nor SB203580 had an effect on interferon gamma release or on proliferative capacity. CONCLUSION: This would indicate that the induction of p38 MAPK activation in splenocytes contributes to the immunosuppression seen in late sepsis.     

Sphingosine-1-phosphate-induced smooth muscle cell migration involves the mammalian target of rapamycin

BACKGROUND: Vascular smooth muscle cell (SMC) migration is an important component of the development of intimal hyperplasia. Sphingosine-1-phosphate (S-1-P) is a lipid released from activated platelets with numerous cellular effects including the stimulation of SMC migration in vitro. We examined the role of the mammalian target of rapamycin and ribosomal p70S6 kinase (p70S6K) in S-1-P-induced SMC migration . METHODS: Rat arterial SMCs were cultured in vitro. Linear wound and Boyden microchemotaxis assays of migration were performed in the presence of S-1-P (0.01 to 100 micromol/L) with and without rapamycin (10 nmol/L). Western blotting was performed for phosphorylated and total p70S6K, ERK1/2, and p38(MAPK) after stimulation with S-1-P (0.1 micromol/L), with and without rapamycin pretreatment. Phosphorylation of p70S6K was also assayed after S-1-P treatment in the presence and absence of inhibitors of PI3 kinase (wortmannin, WN, and LY294002, LY), Akt (AktI), p38(MAPK) (SB203580), and MEK1 (PD98059). RESULTS: S-1-P stimulated migration of SMCs in both linear wound and Boyden chamber assays compared to control (P < .05); these responses were inhibited by rapamycin to below the level of control (P < .05 vs S-1-P alone for both assays) in a dose-dependent manner (inhibitory concentration of 50%, 10 nmol/L). S-1-P stimulated phosphorylation of ERK1/2, p38(MAPK), and p70S6K, which peaked at 5 minutes for ERK1/2 and p38(MAPK) and10 minutes for p70S6K (2-fold increase over control for each, P < .05). Rapamycin prevented the phosphorylation of p70S6K at the Thr 389 site (which correlates with enzyme activity), reduced ERK1/2 phosphorylation, but had no effect on the Thr 421/Ser 424 site or on p38(MAPK) phosphorylation. Wortmannin and LY294002 inhibited phosphorylation of the Thr 389 site of p70S6K. AktI and SB203580 had no effect on p70S6K, whereas PD98059 had a marginal effect. CONCLUSIONS: S-1-P-induced SMC migration was completely inhibited by rapamycin, indicating that the p70S6K pathway is involved. This mechanism likely involves modulation of the ERK1/2 pathway. S-1-P stimulates phosphorylation of p70S6K in a MEK1-dependent, PI3 kinase-dependent, but Akt-independent manner.     

Inhibition of p38 mitogen activated protein kinase increases lipopolysaccharide induced inhibition of apoptosis in neutrophils by activating extracellular signal-regulated kinase

BACKGROUND: Prolonged polymorphonuclear neutrophil (PMN) survival has been implicated in tissue injury after sepsis. Previously we reported that lipopolysaccharide (LPS) inhibits PMN apoptosis via the activation of the extracellular signal-regulated kinase (ERK). Conversely, the p38 mitogen activated protein kinase (MAPK) pathway is involved in the spontaneous apoptosis of PMNs. The interaction between these 2 pathways and their ability to regulate apoptosis during sepsis remain largely undefined. We hypothesize that there is interaction between the ERK and p38 pathways during sepsis. METHODS: PMNs were isolated from healthy volunteers by Ficoll gradient centrifugation and red blood cell sedimentation. Cells were then pretreated for 1 hour with the ERK inhibitor (PD98059, 10 micromol/L), p38 inhibitor (SB203580, 1 micromol/L), or vehicle. After treatment with LPS, apoptosis and MAPK activity were correlated. RESULTS: LPS stimulation significantly inhibits PMN apoptosis compared with unstimulated cells. Furthermore, inhibition of ERK significantly abrogates this effect, whereas inhibition of p38 augments LPS induced inhibition of apoptosis. Elk-1 phosphorylation (ERK target) is significantly increased by LPS alone and by inhibition of the p38 pathway during LPS stimulation. This correlates with ERK phosphorylation by Western blot. CONCLUSIONS: These data show that p38 inhibition enhances ERK activity during endotoxemia. Furthermore, these data suggest that cooperation between ERK and p38 MAPK pathways dictates the apoptotic potential of PMNs during inflammatory states.     

转化生长因子β1对肾小管上皮细胞中结缔组织生长因子基因启动子活性的影响

目的探讨转化生长因子[β1（TCF-β1）对人近端肾小管上皮细胞系HK-2中结缔组织生长因子（CTGF）基因启动子活性的调控作用，以及丝裂原激活蛋白激酶（MAPK）途径对该生长因子作用的影响。方法构建含有人类CTGF基因启动子的报告基因pCTGF-luc，将其瞬时转染HK-2细胞。通过检测荧光素酶的活性观察TGF-β1和MAPK途径抑制剂对CTGF基因启动子活性的影响。结果TGF-β1以剂量和时间依赖方式上调HK-2中CTGF基因启动子的活性。最佳刺激浓度是5ng／ml，最佳刺激时间为12h，荧光素酶相对活性分别为对照组的1．82倍和2．10倍（P〈0．05）。应用PD98059、SB203580和SP600125分别特异性抑制MAPK途径的胞外信号调节蛋白激酶（ERK）、蛋白激酶p38（p38MAPK）和c-Jun-氨基末端激酶（JNK）通路，对TGF-β1上调CTGF启动子活性的作用有不同影响。PD98059显著增加HK-2中pCTGF-luc的基础活性．并在一定浓度范围内（0．5～10μmol／L）促进TGF-β1的上调作用。SB203580对pCTGF-luc基础活性无影响，但以剂量依赖方式显著抑制TGF-β1的激活效应。而SP600125对基础状态和TGF-β1刺激下CTGF基因启动子活性无影响。结论TGF-β1以剂量和时间依赖方式上调HK-2中CTGF基因启动子活性，在转录水平调节CTGF表达。MAPK途径的ERK和p38MAPK通路可影响TGF-β1的这一调控作用。     

丝裂原活化蛋白激酶对大鼠成骨细胞TRPV6表达的影响

目的探讨丝裂原活化蛋白激酶对大鼠成骨细胞瞬时性受体电位香草精受体6（transient receptor poten-tial vanilloid receptor 6,TRPV6）表达的影响。方法采用Wistar大鼠乳鼠,连续酶消化法提取成骨细胞并培养。根据组织形态学、改良Kaplow氏成骨细胞碱性磷酸酶染色、矿化结节茜素红染等方法进行鉴定。实验分组：a）正常对照组;b）PD组（PD98059 5μmol/L;PD98059 10μmol/L;PD98059 20μmol/L）;c）SB组（SB203580 5μmol/L;SB20358010μmol/L;SB203580 20μmol/L）;d）PD＋SB组（PD98059 5μmol/L＋SB203580 5μmol/L;PD98059 10μmol/L＋SB203580 10μmol/L;PD98059 20μmol/L＋SB203580 20μmol/L）。细胞计数法、MTT法检测细胞活性,RT-PCR检测成骨细胞TRPV6 mRNA。所得数据用x-±s表示,采用t检验进行统计学分析。结果随着PD98059和/或SB203580浓度的增加,细胞增殖活性有下降的趋势,二者联合作用时细胞活性低于二者单独作用。细胞计数法检测显示,PD98059与SB203580联合作用时,三种组合中细胞数均显著低于空白对照组,P〈0.01;同时也明显低于二者单独作用组细胞数量。碱性磷酸酶染色显示,联合用药组较单独用药细胞数明显减少,细胞体积变小,突起狭长,ALP染色阳性颗粒减少,随药物作用浓度增加上述变化更加显著。茜素红染色显示,钙结节与对照组比较数量少、体积小;10、20μmol/L联合作用组,细胞数减少更加明显,无钙结节形成。SB203580与PD98059二者联合应用显著抑制TR-PV6 mRNA的表达,5 mmol/L联合作用组即可明显抑制,随着作用浓度增加TRPV6 mRNA的表达量逐渐减少。结论 p44/42途径阻断剂PD98059能抑制成骨细胞增殖,明显降低成骨细胞TRPV6 mRNA表达,减少钙结节形成。p38途径阻断剂SB203580能抑制成骨细胞增殖,明显降低成骨细胞TRPV6 mRNA表达,减少钙结节形成。PD98059与SB203580在抑制成骨细胞增殖、降低成骨细胞TRPV6 mRNA表达、减少钙结节形成的作用方面存在协同作用。