EFFECT OF INTERLEUKIN-1β ON GROWTH HORMONE GENE EXPRESSION AND ITS POSSIBLE MOLECULAR MECHANISM IN RAT MtT/S SOMATOTROPH CELLS

Objective To elucidate the effect of interleukin-1β (IL-1β) on human growth hormone (hGH) gene expression in a rat somatotropic pituitary cell line MtT/S. Methods Stably transfected MtT/S cells were firstly established by transfecting 484-Luc1 plasmid which contained hGH gene promoter -484 to 30 bp and luciferase reporter gene. The effect of IL-1β on hGH gene expression was determined by assaying the luciferase activities. RT-PCR method was also used to determine whether IL-1 recepor mRNA was expressed in MtT/S cells. Results The 103 U/mL IL-1β stimulated secretion and synthesis of GH, and promoted the 5’-promoter activity of GH gene in stably transfected MtT/SGL cells with the action of 1.38 times above the control. Among inhibitors of signaling transduction pathways, mitogen-activated protein kinase kinase (MAPKK/MEK) inhibitor PD98059 (40 μmol/L) and p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 (5 μmol/L) completely blocked the stimulatory effect of IL-1β, and phosphatidylinositol-3-kinase (PI3-K) inhibitor LY294002 partly abolished the effect of IL-1β. Western blot analysis further confirmed the activation of phosphorylated MEK and p38 MAPK in MtT/SGL cells. Neither over-expression of Pit-1 nor inhibition of Pit-1 expression affected induction of hGH promoter activity by IL-1β. A series of deletion constructs of hGH promoter were created to identify the DNA sequence that mediated the effect of IL-1β, and results showed that the stimulatory effect of IL-1β was abolished following deletion of the -196 to -132 bp fragment. Conclusions IL-1β promotes GH secretion and synthesis in rat MtT/S somatotroph cells. The stimulatory effect of IL-1β on hGH gene promoter appears to require the activation of MEK, p38 MAPK, PI3-K, and a fragment of promoter sequence that spans the –196 to –132 bp of the gene, but it may be unlinked with Pit-1 protein.     

MEK AND p38 MAPK-DEPENDANT PATHWAYS ARE INVOLOVED IN THE POSITIVE EFFECT OF INTERLEUKIN-6 ON HUMAN GROWTH HORMONE GENE EXPRESSION IN RAT MtT/S SOMATOTROPH CELLS

Objective To investigate the effect of interleukin-6（IL-6） on the human growth hormone （hGH） gene expression in a rat somatotropic pituitary cell line MtT/S. Methods The plasmids containing various lengths of hGH gene 5＇-promoter fragments were constructed. Stably transfected MtT/S cells were created by cotransfecting the above plasmids and pcDNA3.1 （＋） with DMRIE-C transfection reagent. After the administration of these cells with IL-6 and/or various inhibitors of signaling transduction path-ways, the luciferase activities in MtT/S cells lysis were assayed to demonstrate the effects of IL-6 on hGH gene promoter activity and possibly involved mechanism. Results The 10^3U/mL IL-6 stimulated GH secretion and synthesis, and promoted the 5＇-promoter activity of GH gene in stably transfected MtT/SGL cells with the action of 1.69 times above the control. Among inhibitors of signaling transduction pathways, mitogen-activated protein kinase kinase （MAPKK/MEK） inhibitor PD98059 （40μmol/L） and p38 mitogen-activated protein kinase （MAPK） inhibitor SB203580 （5μmol/L） completely blocked the stimulatory effect of IL-6. Western blot analysis further confirmed the activation of phosphorylated MEK and p38 MAPK in MtT/SGL cells. Neither over-expression of Pit-1 nor inhibition of Pit-1 expression affected IL-6 induction of hGH promoter activity. A series of deletion constructs of hGH promoter were created to identify the DNA sequence that mediated the effect of IL-6. The results showed that the stimulatory effect of IL-6 was abolished following deletion of the - 196 to - 132 bp fragment. Conclusions IL-6 promotes GH secretion and synthesis by rat MtT/S somatotroph cells. The stimulatory effect of IL-6 on hGH gene promoter appears to require the activation of MEK and p38 MAPK, and a fragment of promoter se- quence that spans the - 196 to - 132 bp of the gene, but may be unlinked with Pit-1 protein.     

Chrysanthemum indicum linnéextracts attenuate the mitogenic effect of epinephrine on human HCC cells

Objective: To investigate the stimulatory effect of epinephrine(Epi) and the antagonistic effect of Chrysanthemum indicum Linné extracts (CILE) on Epi-induced growth of human hepatocellular carcinoma(HCC) cells. Methods: The stimulatory effect of Epi and inhibitory effect of CILE on the growth of HepG2 and MHCC97H cells were investigated using a proliferation assay in correlation with βadrenergic receptor(β 2-AR) blockade, a MEK1/MEK2 inhibitor, and assessment of MAPK/ERK1/2 intracellular activity. Results:...     

Parathyroid hormone-mitogen-activated protein kinase axis exerts fibrogenic effect of connective tissue growth factor on human renal proximal tubular cells

Background Enhanced and prolonged expression of connective tissue growth factor （CTGF） is associated with kidney fibrosis. Parathyroid hormone （PTH） is involved in the genesis of disturbed calcium/phosphate metabolism and ostitis fibrosa in renal failure. PTH activated mitogen-activated protein kinase （MAPK） signaling pathway is present in renal tubular cells. The aim of this study was to identify the mechanism how the signal is transduced to result in extracellular signal-regulated protein kinase （ERK） activation, leading to upregulation of CTGF.Methods The levels of CTGF mRNA and protein in human kidney proximal tubular cells （HK-2） treated with PTH in the presence or absence of the MAPK inhibitor PD98059 were analyzed by quantitative real-time polymerase chain reaction （RT-PCR） and immunoblotting assay. The activation of the CTGF promoter in HK-2 cells was determined by the dual-luciferase assay. The effects of the protein kinase A （PKA） activator 8-Br-cAMP and protein kinase C （PKC） activator phorbol 12-myristate 13-acetate （PMA） on MAPK phosphorylation, and the effects of the PKA inhibitor H89 and PKC inhibitor calphostin C on MAPK phosphorylation and CTGF expression were detected by immunoblotting assay.Results PD98059 inhibited the PTH stimulated expression of CTGF, which strongly suggested that the MAPK signaling pathway plays an important role in the PTH-induced CTGF upregulation in renal tubular cells. A PKA activator as well as PKC activators induced MAPK phosphorylation, and both PKA and PKC inhibitors antagonized PTH-induced MAPK phosphorylation and CTGF expression.Conclusion CTGF expression is upregulated by PTH through a PKC/PKA-ERK-dependent pathway.     

U0126 PREVENTS ERK PATHWAY PHOSPHORYLATION ANDINTERLEUKIN-1β mRNA PRODUCTION AFTER CEREBRAL ISCHEMIA

Objective To study the role of extracellular signal-regulated kinase (ERK) in cerebral ischemia and the mechanism of protective effects of U0126 (1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio] butadiene) on ischemic brain. Methods Mice under, vent left middle cerebral artery occlusion (MCAO) by introducing a suture in the lumen. U0126 was injected intravenously through the internal jugular vein. The immunoactivity of phosphorylated ERKI/2 (pERK 1/2), phosphorylated mitogen activated protein kinase kinase (pMEK), and phosphorylated Elk-1 (pE1k-1) was assessed by Western blot analysis and immunohistochemistry. Interleukin (IL)-1β mRNA level was measured by ribonuclease protection assay.Results Phosphorylated ERKI/2 in 2 hours MCAO mice was down-regulated after intravenous injection of U0126. The inhibition was dose dependent and treatment time related, pMEK and pElk-I were also reduced in a similar fashion after U0126 treatment. IL-1β mRNA increased after 1 and 2 hours of MCAO. After injection of U0126, it was down-regulated during 1 to 4 hours after MCAO. Conclusion Intravenous administration of the MEK inhibitor U0126 inhibits pMEK, pERK1/2, and pElk-1 up-regulation induced by cerebral ischemia. The protective effect of U0126 against ischemic injury is probably resulted from the reduction of IL-1β mRNA via the inhibition of ERK pathway.     

Proliferation of renal mesangial cells induced by very low density lipoprotein is mediated by p42/44 mitogen activated protein kinase

Background The plasma concentration of very low density lipoprotein （VLDL） is negatively correlated to renal function in glomerular diseases. Effects of VLDL on renal function have been partially attributed to the proliferation of mesangial cells. This study examined the potential role of the p42/44 mitogen activated protein kinase （MAPK） in mesangial cell proliferation induced by VLDL. Methods Mesangial cells were treated with VLDL at different concentrations or for different time. The cell cycle of the mesangial cells was analyzed by Xl-r assay and flow-cytometry; MAPK activity was also assayed. In some experiments, cells were treated with VLDL together with or without 0.1 pmol/L PD 98059. Results Ten to 500 μg/ml VLDL stimulated the proliferation of mesangial cells cultured in vitro in a concentration-dependent manner. The effect was associated with an increase in p42/44 MAPK activity. Increased proliferation of mesangial cells by VLDL was significantly attenuated by PD98059, a specific p42/44 MAPK inhibitor. Conclusion These results indicate that the p42/44 MAPK pathway is an important regulator of mesangial cell proliferation and of renal functions.     

Effect of polysaccharide sulfate 916 on the production of nitric oxide in ECV3 04 cells induced by cytokines and H2O2

Objective To investigate the effect of polysaccharide sulfate 916 (PS916) on the productio n of nitric oxide (NO) in ECV304 cells induced by tumor necrosis factor-α (TNF α), interleukin-1β (IL-1β) and H(2)O(2) in vitro. Methods Production of NO in ECV304 cells was measured by the Griess method and the proli feration of cells was tested by the MTT method. The activity of NO synthase was detected spectrophotometrically.Results Production of NO in ECV304 cells decreased after treatment with 40 ng/ml IL-1 β and 40 ng/ml TNFα, but increased in the presence of H(2)O(2) 0.1 mmol/L . PS916 significantly enhanced NO production in ECV304 cells in a dose-depende nt manner in the TNFα and IL-1β treated groups and decreased it in the H2O 2 treated group. Proliferation of ECV304 cells was inhibited by TNFα and H 2O2 and no effect was found in the IL-1β treated group. PS916 increased the proliferation of cells treated with TNFα and H(2)O(2) dose-dependently. In vitro, PS916 has no effect on the activity of NO synthase. Conclusion PS916 has a protective effect on ECV304 cells exposed to IL-1β, TNFα and H2 O2.     

The Relationship between p38MAPK and Apoptosis during Paclitaxel Resistance of Ovarian Cancer Cells

To investigate the relationship between p38 mitogen-activated protein kinase (p38MAPK) and cell apoptosis during the paclitaxel resistance of ovarian carcinoma cell lines, flow cytometry (FCM) and PI staining were employed to determine the effect of p38MAPK inhibitor SB203580 on the apoptosis of A2780/Taxol cells, a drug-resistant human ovarian carcinoma cell line. p38MAPK protein expression in SB203580-treated cells was immunochemically measured. The 50% inhibition concentration (IC50) of paclitaxel on A2780/Taxol cells was determined by MTT assay. MDR-1 mRNA, and expression of p38MAPK and phospho-p53 protein were detected by RT-PCR and West- ern blotting, respectively. The apoptosis rate of A2780/Taxol cells was (19.7±1.04)% 24 h after SB203580 treatment. A significant difference in apoptosis rate was found among experiment group, control group and untreated group (P<0.05). The relative reversal rate of A2780/Taxol cells to pacli- taxel was (57.18±2.01)%. As compared with the control group and the untreated group, p38MAPK protein and MDR-1 mRNA in SB203580-treated cells was substantially decreased. The expression of p53 protein was significantly increased. It is concluded that p38MAPK pathway is related to pacli- taxel resistance of ovarian carcinoma, and blockade of this pathway can promote the apoptosis of the drug-resistant cells and reverse the drug-resistance. Moreover, p38MAPK-mediated apoptosis in pa- clitaxel-resistant ovarian carcinoma cells depends on the activation of p53.     

Retinoic acid receptor β is required for anti-activator protein-1 activity by retinoic acid in gastric cancer cells

Objective To investigate the role of retinoic acid receptor β (RARβ) in mediating inhibitory effect of all-trans retinoic acid (ATRA) on activator protein-1 (AP-1) activity in gastric cancer cells. Methods Transient transfection and chloramphenicol acetyltransferase (CAT) assay, Northern blot, gene transfection, 3-［4,5-dimethylthiazol-2-yl］-2,5-diphenyltetrazolium bromide (MTT) assay, and anchorage-independent growth assay were used.Results Transient transfection of RARβ expression vector into MKN-45 cells resulted in the RARβ concentration-dependent repression of AP-1 activity induced by 12-o-tetradecanoylphorbol-13-acetate (TPA), regardless of the presence of ATRA. When the c-jun and c-fos expression vectors were cotransfected with the RARβ expression vector into MKN-45 cells, AP-1 activity was also obviously repressed. The inhibitory effect, again, was RARβ-concentration-dependent. The stable transfection of the RARβ gene into MKN-45 cells led to cell growth inhibition and colony formation inhibition by ATRA. Furthermore, Cotransfection of both RARβ/DNA binding domain (DBD) and reporter gene could not alter AP-1 activity, even in the presence of ATRA. However, when the cotransfection was substituted with the RARβ/ligand binding domain (LBD), the inhibition was significantly enhanced by ATRA. Conclusion RARβ might be required for anti-AP-1 activity, and contribute to growth inhibition of gastric cancer cells by ATRA.     

A survey shows Beijing has 295 000 overweight kids

Background Angiotensin Ⅱ （AngⅡ） and platelet-derived growth factor （PDGF）-BB can induce hypertrophy in the cultured rat cardiomyocytes through different signal transduction pathways. Angll stimulates growth through G protein coupled receptor （GPCR）, while PDGF-BB acts via receptor tyrosine kinase （RTK）. Although there has been much development on the individual Angll and PDGF-BB mediated signal pathways, little is known about the interactions between these two factors. Therefore, the crosstalk between Angll and PDGF-BB mediated signal pathways in the rat cardiomyocytes was investigated in this study.
Methods Primary culture of neonatal rat ventricular myocytes was prepared. The amount of tyrosine-phosphorylated and non-phosphorylated PDGF-β receptor, Goq/11, and phospholipase C （PLC） β3 were measured by immunoblotting analysis. The statistical analysis was done by one-way ANOVA.
Results Tyrosine-phosphorylated PDGF-β receptor was increased by 120.60% at 1 minute and recovered to the control level at 10 minutes after Angll stimulation. Phosphorylation of PDGF-β receptor triggered by Angll was blocked by Iosartan, a specific antagonist of AT1 receptor. PLC inhibitor U73122, protein kinase C （PKC） inhibitor staurosporine （STS） and mitogen-activated ERK activating kinase （MEK） inhibitor PD98059 also inhibited the Angll-induced phosphorylation of PDGF-β receptor. PDGF-BB slightly increased the expression of Gao/11 protein.
Conclusion Angll transactivates PDGF-β receptor via AT1 receptor-Gaq/11-PLC-PKC pathway in the rat cardiomyocytes. ERK also participates in the transactivation of PDGF-β receptor triggered by Angll.     

Growth and activation of PI-3K/PKB and Akt by stromal cell-derived factor 1α in endometrial carcinoma cells with expression of suppressor endoprotein PTEN

Background Mutation or deletion in the phosphatase and tensin homologue deleted on chromosome ten （PTEN） gene has been identified as an important cause of endometrial carcinoma; stromal cell derived factor-1α （SDF-1α） exerts growth-promoting effects on endometrial cancer cells through activation of the PI-3 kinase/Akt pathway and downstream effectors such as extracellular-responsive kinase （ERK）. In this study, a plasmid containing the PTEN gene was transfected into Ishikawa cells to investigate the difference in growth and signal transduction between Ishikawa-PTEN and Ishikawa cells after SDF-1α stimulation, and to study mechanisms of the involvement of PTEN protein in endometrial carcinoma development. Methods Ishikawa cells were transfected with a plasmid （pLXSN-PTEN） containing the PTEN gene and a plasmid （pLXSN-EGFP） with enhanced green fluorescent protein （EGFP）. Cells were then screened to obtain Ishikawa-PTEN cells and Ishikawa-neo cells that can both stably express PTEN protein and EGFP. Expression of PTEN protein, phosphorylation levels of AKT and ERK （pAKT and pERK） and growth differences in Ishikawa-PTEN, Ishikawa-neo and Ishikawa cells before and after SDF-1α stimulation were then determined by Western blots and MTT assays. Results Western blot analysis showed that Ishikawa cells produced PTEN after transfection with the PTEN gene. At 15 minutes after SDF-1α stimulation, the pAKT level of Ishikawa-PTEN cells was lower than that of Ishikawa-neo cells and Ishikawa cells. There was no significant difference in pERK levels among the three cell lines. The positive effect of SDF-1α on Ishikawa-PTEN cells growth was markedly less than the effect on Ishikawa-neo and Ishikawa cells. However, in the absence of SDF-1α stimulation （baseline）, the pAKT level in Ishikawa-PTEN cells was less than that in Ishikawa cells. There was a significant difference in growth between the Ishikawa-PTEN cells and the Ishikawa-neo cells. Conclusions PTEN gene transfection can regulate the level of pAKT but not pERK in Ishikawa-PTEN cells. PTEN protein may suppress the growth-promoting effect of SDF-1α on endometrial carcinoma by inhibiting the PI-3K/AKT signal transduction pathway.