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.     

Inhibitors of mitogen-activated protein kinases differentially regulate eosinophil-activating cytokine release from human airway smooth muscle

Airway smooth muscle (ASM) is a potential source of multiple proinflammatory cytokines during airway inflammation. In the present study, we examined a requirement for mitogen-activated protein (MAP) kinase activation for interleukin (IL)-1beta-stimulated GM-CSF, RANTES, and eotaxin release. IL-1beta induced concentration-dependent phosphorylation of p42/p44 extracellular signal-regulated kinases (ERKs), p38 MAP kinase, and c-Jun amino-terminal kinase (SAPK/JNK). p42/p44 ERK and p38 MAP kinase phosphorylation peaked at 15 min and remained elevated up to 4 h. SAPK/JNK phosphorylation also peaked at 15 min but fell to baseline within 60 min. SB 203580 selectively inhibited IL-1beta-stimulated activation of p38 MAP kinase; U 0126 was selective against p42/p44 ERK activity. SB 202474, an inactive analog, had no effect on p42/p44 ERK, p38 MAP kinase, or SAPK/JNK activation, or on eotaxin or RANTES release. Eotaxin release was inhibited by SB 203580 and U 0126, whereas RANTES release was prevented by U 0126 only. GM-CSF release was inhibited by U 0126 but enhanced by SB 203580. These data indicate that RANTES release is dependent on p42/p44 ERK activation but occurs independently of p38 MAP kinase activity. Eotaxin release, however, is dependent on both p38 MAP kinase- and p42/p44 ERK-dependent mechanisms. GM-CSF release is p42/p44 ERK dependent and is tonically suppressed by a mechanism that is partially dependent on p38 MAP kinase, though direct inhibition of cyclooxygenase (COX) activity due to poor inhibitor selectivity may also contribute.     

Cytochrome P4502E1 sensitizes to tumor necrosis factor alpha-induced liver injury through activation of mitogen-activated protein kinases in mice

The goal of this study was to evaluate the role of mitogen-activated protein kinase (MAPK) in cytochrome P4502E1 (CYP2E1) potentiation of lipopolysaccharide or tumor necrosis factor alpha (TNF-alpha)-induced liver injury. Treatment of C57/BL/6 mice with pyrazole (PY) plus lipopolysaccharide (LPS) induced liver injury compared with mice treated with PY or LPS alone. The c-Jun N-terminal kinase (JNK) inhibitor SP600125 or p38 MAPK inhibitor SB203580 prevented this liver injury. PY plus LPS treatment activated p38 MAPK and JNK but not extracellular signal-regulated kinase (ERK). PY plus LPS treatment triggered oxidative stress in the liver with increases in lipid peroxidation, decrease of glutathione (GSH) levels, and increased production of 3-nitrotyrosine adducts and protein carbonyl formation. This oxidative stress was blocked by SP600125 or SB203580. PY plus LPS treatment elevated TNF-alpha production, and this was blocked by SP600125 or SB203580. Neither SP600125 nor SB203580 affected CYP2E1 activity or protein levels. Treating C57/BL/6 mice with PY plus TNF-alpha also induced liver injury and increased lipid peroxidation and decreased GSH levels. Prolonged activation of JNK and p38 MAPK was observed. All of these effects were blocked by SP600125 or SB203580. In contrast to wild-type SV 129 mice, treating CYP2E1 knockout mice with PY plus TNF-alpha did not induce liver injury, thus validating the role of CYP21E1 in this potentiated liver injury. Liver mitochondria from PY plus LPS or PY plus TNF-alpha treated mice underwent calcium-dependent, cyclosporine A-sensitive swelling, which was prevented by SB203580 or SP600125. CONCLUSION: These results show that CYP2E1 sensitizes liver hepatocytes to LPS or TNF-alpha and that the CYP2E1-enhanced LPS or TNF-alpha injury, oxidant stress, and mitochondrial injury is JNK or p38 MAPK dependent.     

Involvement of p38 MAPK,JNK, p42/p44 ERK and NF-kappaB in IL-1beta-induced chemokine release in human airway smooth muscle cells

Asthma is an inflammatory disease, in which eotaxin, MCP-1 and MCP-3 play a crucial role. These chemokines have been shown to be expressed and produced by IL-1beta-stimulated human airway smooth muscle cells (HASMC) in culture. In the present study we were interested to unravel the IL-1beta-induced signal transduction leading to chemokine production. Using Western blot, we observed an activation of p38 MAPK, JNK kinase and p42/p44 ERK when HASMC were stimulated with IL-1beta. We also observed a significant decrease in the expression and the release of eotaxin, MCP-1 and MCP-3 in the presence of SB203580, an inhibitor of p38 MAPK (71 +/- 6%, P < 0.05, n = 8 and 39 +/- 10% P < 0.01, n = 10 respectively), curcumin, an inhibitor of JNK kinase (83 +/- 4.9% and 88 +/- 3.4% respectively, P < 0.01, n = 4). U0126, an inhibitor of p42/p44 ERK, also produced a significant decrease in chemokine production (46.3 +/- 9%, P < 0.01 n = 10 and 67.8 +/- 12%, P < 0.01, n = 12). Pyrrolydine dithiocarbamate, an inhibitor of NF-kappaB was also able to reduce the eotaxin, MCP-1 and MCP-3 expression and production (50 +/- 13%, P < 0.05, n = 10 and 23 +/- 7%, P < 0.05, n = 12). We conclude that p38 MAPK, JNK kinase, ERK and NF-kappaB are involved in the IL-1beta-induced eotaxin, MCP-1, and MCP-3 expression and release in HASMC.     

PDGF-CC induces tissue factor expression: role of PDGF receptor α/β

Tissue factor (TF) is the principal trigger of the coagulation cascade and involved in arterial thrombus formation. Platelet-derived growth factor CC (PDGF-CC) is a recently discovered member of the PDGF family released upon platelet activation. This study assesses the impact of PDGF-CC on TF expression in human cells. PDGF-CC concentration-dependently induced TF expression by 2.5-fold in THP-1 cells, by 2.0-fold in human peripheral blood monocytes, by 1.4-fold in vascular smooth muscle cells, and by 2.6-fold in microvascular endothelial cells, but did not affect TF expression in aortic endothelial cells. A similar pattern was observed with PDGF-BB. In contrast, PDGF-AA did not alter TF expression in THP-1 cells. TF whole cell activity was induced following stimulation with PDGF-BB and PDGF-CC in THP-1 cells. Real-time polymerase chain reaction revealed that PDGF-CC induced TF mRNA. PDGF-CC transiently activated p42/44 MAP kinase [extracellular signal-regulated kinase (ERK)], while phosphorylation of the MAP kinases c-Jun NH₂-terminal kinase (JNK) and p38 remained unaffected. PD98059, a specific inhibitor of ERK phosphorylation, but not the p38 inhibitor SB203580 or the JNK inhibitor SP600125 prevented PDGF-CC induced TF expression in a concentration-dependent manner. The effect of PDGF-CC was antagonized by both PDGF receptor α and PDGF receptor β neutralizing antibodies; in contrast, PDGF-BB was only inhibited by PDGF receptor β blocking antibody. PDGF receptor α and PDGF receptor β inhibition prevented PDGF-CC-induced ERK phosphorylation. PDGF-CC induces TF expression via activation of α/β receptor heterodimers and an ERK-dependent signal transduction pathway.     

Differential roles of extracellular signal-regulated kinase 1/2 and p38MAPK in mechanical load-induced procollagen alpha1(I) gene expression in cardiac fibroblasts

OBJECTIVE AND METHODS: We have previously demonstrated that mechanical loading of cardiac fibroblasts leads to increased synthesis and gene expression of the extracellular matrix protein collagen. We hypothesised that the upregulation of procollagen gene expression in cardiac fibroblasts, in response to cyclic mechanical load, is mediated by one or more members of the MAP kinase family. To test this hypothesis, the effect of mechanical load on the activation of extracellular signal-regulated kinase (ERK) 1/2, p46/54JNK, and p38MAPK was examined in rat cardiac fibroblasts. RESULTS: Peak phosphorylation of ERK 1/2, p38MAPK kinases, and p46/54JNK was observed following 10-20 min of continuous cyclic mechanical load. Mechanical load significantly increased procollagen alpha1(I) mRNA levels up to twofold above static controls after 24 h. This increase was completely abolished by the MEK 1/2 inhibitor U0126, with no effect on basal levels. In contrast, SB203580, a specific inhibitor of p38MAPK, enhanced both basal and stretch-stimulated levels of procollagen mRNA. Consistent with this finding, selective activation of the p38MAPK signalling pathway by expression of MKK6(Glu), a constitutive activator of p38MAPK, significantly reduced procollagen alpha1(I) promoter activity. SB203580-dependent increase in procollagen alpha1(I) was accompanied by ERK 1/2 activation, and inhibition of this pathway completely prevented SB203580-induced procollagen alpha1(I) expression. CONCLUSIONS: These results suggest that mechanical load-induced procollagen alpha1(I) gene expression requires ERK 1/2 activation and that the p38MAPK pathway negatively regulates gene expression in cardiac fibroblasts. These pathways are likely to be key in events leading to matrix deposition during heart growth and remodelling induced by mechanical load.     

Requirement of mitogen-activated protein kinase for collagenase production by the fibronectin fragment in human articular chondrocytes in culture

Abstract

Fibronectin fragments have been shown to up-regulate matrix metalloproteinase production in chondrocytes. We investigated the roles of mitogen-activated protein kinase (MAPK) pathways activated by the COOH-terminal heparin-binding fibronectin fragment (HBFN-f) in collagenase production by human chondrocytes in culture. In articular cartilage explant culture, HBFN-f stimulated type II collagen cleavage by collagenase in association with increased secretion of MMP-1 and MMP-13. In human articular chondrocytes, HBFN-f induced the collagenases with activation of the extracellular signal-regulated kinase (ERK), p38, and the c-Jun NH₂-terminal kinase (JNK). PD98059 that inhibits the ERK pathway blocked HBFN-f-stimulated production of MMP-1 and MMP-13 in explant culture. SB203580 at 1?µM, the concentration that inhibits p38 only, partially suppressed HBFN-f-induced collagenase production, whereas at 10?µM, the inhibitor that blocks both p38 and JNK almost completely inhibited collagenase induction. PD98059 and SB203580 individually blocked HBFN-f-increased cleavage of type II collagen in the explant culture, although 10?µM SB203580 strongly inhibited the collagen cleavage compared with 1?µM of the inhibitor. These results indicate that collagenase production leading to type II collagen cleavage in cartilage explants requires ERK, p38, and JNK.     

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.     

Extracellular signal-regulated protein kinase signaling pathway negatively regulates the phenotypic and functional maturation of monocyte-derived human dendritic cells

Dendritic cells (DC) are highly specialized antigen-presenting cells that on activation by inflammatory stimuli (eg, tumor necrosis factor alpha [TNF-alpha] and interleukin-1beta [IL-1beta]) or infectious agents (eg, lipopolysaccharide [LPS]), mature and migrate into lymphoid organs. During maturation, DC acquire the capacity to prime and polarize resting naive T lymphocytes. Maturation of monocyte-derived DC (MDDC) is inhibited by the p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580. This study found that in the presence of the mitogen-activated protein kinase kinase 1-extracellular signal-regulated kinase (ERK) inhibitors PD98059 or U0126, TNF-alpha- and LPS-induced phenotypic and functional maturation is enhanced. ERK pathway inhibitors increased expression of major histocompatibility complex and costimulatory molecules; loss of mannose-receptor-mediated endocytic activity; nuclear factor-kappaB DNA-binding activity; release of IL-12 p40; and allogeneic T-cell proliferation induced by LPS or TNF-alpha. Moreover, PD98059 and U0126 enhanced LPS-triggered production of IL-12 p70. In agreement with the effect of ERK inhibitors, maturation of MDDC was delayed in the presence of serum, an effect that was reversed by U0126. These results indicate that the ERK and p38 MAPK signaling pathways differentially regulate maturation of MDDC and suggest that their relative levels of activation might modulate the initial commitment of naive T-helper (Th) cells toward Th1 or Th2 subsets. The findings also suggest that maturation of MDDC might be pharmacologically modified by altering the relative levels of activation of both intracellular signaling routes.     

软脂酸通过丝裂原活化蛋白激酶通路促进血管内皮细胞凋亡

目的探讨软脂酸(PA)诱导的血管内皮细胞凋亡中丝裂原活化蛋白激酶(MAPK)通路的作用。方法将人脐静脉内皮细胞(HUVEC)分对照组、PA组、MAPK通路干预组[分别先用p38抑制剂SB203580、氨基末端激酶(JNK)抑制剂PD98059、细胞外信号调节激酶(ERK)抑制剂SP600125干预]再分为PA+SB组、PA+PD组、PA+SP组。流式细胞仪检测细胞凋亡率;Western blot法检测caspase-3、磷酸化p38、JNK和ERK1/2表达水平;分光光度法检测caspase-3的活性。结果与对照组比较,PA组、PA+SB组、PA+PD组、PA+SP组HUVEC凋亡及caspase-3表达和活性明显增加,PA组磷酸化p38MAPK表达明显增加(P<0.05)。与PA组比较,PA+SB组HUVEC细胞凋亡率、caspase-3表达和活性明显降低(P<0.05);而PA+PD组和PA+SP组HUVEC凋亡率、caspase-3表达和活性无明显变化(P>0.05)。结论 PA通过p38MAPK通路促进内皮细胞凋亡。     

Preptin对人成骨细胞增殖和分化的影响及机制研究

目的 探讨preptin对人成骨细胞增殖和分化的影响及其信号途径.方法 体外培养人成骨细胞,用10-10、10-9、10-8和10-7mol/L preptin干预24 h,以[3H]脱氧胸腺嘧啶苷掺入法分析细胞增殖,用分光光度计法测定细胞碱性磷酸酶(ALP)活性判断细胞分化程度.Western印迹法检测细胞外信号调节激酶(ERK)、p38丝裂原活化蛋白激酶(p38MAPK)和c-Jun氨基末端激酶(JNK)的磷酸化水平.并在preptin干预前以ERK抑制剂(PD98059)、p38 MAPK抑制剂(SB203580)和JNK抑制剂(SP600125)预处理,观察preptin诱导人成骨细胞增殖和分化的途径.结果 Preptin剂量依赖地增加人成骨细胞的增殖和ALP活性,10-9mol/L浓度时达最大效应(均P<0.01).Preptin刺激人成骨细胞ERK的磷酸化,对p38MAPK和JNK无作用.PD98059阻断preptin刺激的成骨细胞增殖及ALP活性增加(均P<0.05),而SP600125和SB203580无此效应.结论 Preptin通过ERK途径促进人成骨细胞的增殖和分化.     

p38 mitogen-activated protein kinase and c-Jun-NH2-terminal kinase regulate interleukin-8 and RANTES production in hyperosmolarity stimulated human bronchial epithelial cells

OBJECTIVE: We have previously shown that p38 mitogen-activated protein kinase (MAPK) regulates, at least in part, hyperosmolarity induced interleukin (IL)-8 expression in human bronchial epithelial cells (BEC). In the previous study, hyperosmolarity also activated c-Jun-NH2-terminal kinase (JNK); however, the role of the JNK signalling pathway has not been determined. In the present study, we examined the role of the JNK signalling pathway in hyperosmolarity induced IL-8 and RANTES production by BEC using the novel inhibitor of the JNK signalling pathway CEP 11004 in order to clarify these issues. METHODS: Bronchial epithelial cells that had been pre-incubated with SB 203580, CEP 11004 or a combination of these were exposed to a hyperosmolar medium and then the p38 MAPK and JNK phosphorylation activity in these cells and IL-8 and RANTES concentrations in the culture supernatants were determined. RESULTS: The results showed that: (i) hyperosmolarity induced the threonine and tyrosine phosphorylation of p38 MAPK and JNK; (ii) SB 203580, as the specific inhibitor of p38 MAPK activity, and CEP 11004 attenuated hyperosmolarity induced p38 MAPK and JNK activity, respectively; (iii) SB 203580 and CEP 11004, but not PD 98059, partially attenuated IL-8 and RANTES production; and (iv) a combination of SB 203580 and CEP 11004 attenuated IL-8 and RANTES production in an additive fashion. CONCLUSION: These results indicate that p38 MAPK and the JNK pathway regulate hyperosmolarity induced IL-8 and RANTES production by BEC.     

Syk contributes to PDGF-BB-mediated migration of rat aortic smooth muscle cells via MAPK pathways

OBJECTIVE: Here we investigated the role of spleen tyrosine kinase (Syk) in the migration induced by platelet-derived growth factor (PDGF) in rat aortic smooth muscle cells (RASMC). METHODS: Cell migration was determined using a Boyden chamber, by wound-healing, and by aortic ring assays. Activity of Syk, mitogen-activated protein kinase (MAPK), and heat shock protein 27 (HSP27) were tested using immunoblotting with kinase inhibitors and small interference RNAs. RESULTS: PDGF-BB induced binding of Syk to the PDGFbeta receptor and increased the phosphorylation of Syk and migration in RASMC. These effects of PDGF-BB were inhibited by piceatannol, an inhibitor of Syk. PDGF-BB increased the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2, p38 MAPK, and HSP27, which were significantly inhibited by piceatannol and in Syk-knockdown cells. The p38 MAPK inhibitor SB203580 and ERK1/2 inhibitor PD98059 inhibited the migration, which was further inhibited by the combination of these inhibitors. SB203580, but not PD98059, inhibited the phosphorylation of HSP27 induced by PDGF-BB in RASMC. PDGF-BB-induced migration was attenuated in HSP27-knockdown cells. Kinase inhibitors and Syk-knockdown diminished PDGF-BB-induced sprout outgrowth in the aortic ring assay. CONCLUSIONS: These results imply that Syk is an upstream signal of the p38 MAPK/HSP27 and ERK1/2 pathways that contributes to PDGF-BB-mediated migration in RASMC.     

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.     

Sphingosine kinase 1 enhances colon cancer cell proliferation and invasion by upregulating the production of MMP-2/9 and uPA via MAPK pathways

Purpose

Sphingosine kinase (SphK) 1 is an oncogenic enzyme promoting transformation, proliferation, and survival of a number of human tumor cells. However, its effect on colon cancer cell behavior has not been fully clarified.

Methods

SphK1 plasmid or SphK1 shRNA transfection and N,N-dimethylsphingosine (DMS) was used to regulate the expression and activity of SphK1 in colon cancer line LOVO. Cell proliferation, apoptosis, invasion, and protein expression were detected by MTT, flow cytometry, transwell chambers model, and western blot. The levels of metalloproteinases-2/9 (MMP-2/9) and urokinase plasminogen activator (uPA) were detected by ELISA.

Results

Overexpression of SphK1 after plasmid transfection markedly enhanced LOVO cell viability and invasiveness and reduced cell apoptosis. In contrast, inhibition of SphK1 by DMS and shRNA significantly suppressed cell viability and invasiveness but promoted cell apoptosis. SphK1 increased the constitutive expression of extracellular signal-regulated kinase1/2 (ERK1/2) but reduced the constitutive expression of p38 mitogen-activated protein kinase (MAPK). Blocking ERK1/2 pathway inhibited the biological effects induced by overexpression of SphK1. Blocking p38 MAPK pathway reversed the effects of DMS and SphK1 shRNA. Moreover, SphK1 was required for the production of MMP-2/9 and uPA in tumor cells, which was suppressed by ERK1/2 inhibitor U0126, but enhanced by the p38 MAPK inhibitor SB203580.

Conclusions

SphK1 enhances colon cancer cell proliferation and invasiveness, meanwhile suppressing cell apoptosis. SphK1 promoting the secretion of MMP-2/9 and uPA via activation of ERK1/2 and suppression of p38 MAPK pathways maybe the molecular mechanisms for its regulation of the malignant behavior of colon cancer cell.     

PGE1 inhibits the expression of PAI-1 mRNA induced by TNF-alpha in human mesangial cells.

We examined the effect of PGE1 on the expression of plasminogen activator inhibitor-1 (PAI-1) mRNA induced by tumor necrosis factor-alpha (TNF-alpha) in human mesangial cells, because PAI-1 is one of major factors for the progression of glomerulosclerosis. The expression of PAI-1 mRNA was increased after stimulation with TNF-alpha, and it was diminished by pre-incubation with PGE1. Next, we examined the effect of PGE1 on the phosphorylation of mitogen activated protein kinase (MAPK) family and Akt. TNF-alpha activated the phosphorylation of p44/42 MAPK, p38 MAPK, SAPK/JNK and Akt in mesangial cells. PGE1 inhibited the TNF-alpha induced phosphorylation of SAPK/JNK and Akt, but not p44/42 MAPK and p38 MAPK. The TNF-alpha induced expression of PAI-1 mRNA was not affected by PD98059, an inhibitor of MEK, SB203580, an inhibitor of p38 MAPK, nor LY294002, an inhibitor of PI3 K. However, DMAP, an inhibitor of SAPK/JNK, inhibited the expression of PAI-1 mRNA, suggesting that the TNF-alpha induced expression of PAI-1 mRNA is regulated by the SAPK/JNK dependent pathway in human mesangial cells. By the incubation with H8, an inhibitor of PKA, the inhibitory effect of PGE1 on the expression of PAI-1 mRNA was abolished, suggesting that PGE1 inhibited the PAI-1 mRNA expression via the PKA pathway. Our results suggest that the inhibition of PAI-1 synthesis by PGE1 in human mesangial cells may have therapeutic implications for glomerulosclerosis such as occurs in diabetic nephropathy.