Enhancing effect of DHEA ON DbcAMP-induced cell differentiation / 中国药理学通报

Aim To observe whether DHEA has enhancing effect on DbcAMP -induced differentiation of NG108-15 cells, including neurite outgrowth, and study its possible mechanisms. Methods NG108-15 cells (a h ybrid cell line of mouse neuroblastoma and rat glioma) were used as a substitute for primary culture neuron in vitro. The morphology of NG108-15 cells was o bserved and neurite outgrowth was determined in an inversed microscope after treatme nt with various drugs. Gelatin-substrate gel electrophoresis was used to detect gelatinases (MMP-9 and MMP-2). Results ① DHEA and DbcAMP inhibited NG108-15 proliferation.②DHEA had enhancing effect on the promoting activity of neuronal differentiation and neurite outgrowth by DbcAMP. DbcAMP could increase neurite elongation of NG108-15 cells. Compared with this, the combined treatment with DHEA and DbcAMP significantly enhanced the neurite outgrowth of NG108-15 cells, including neurite length and numbers of cells with neurite, in a DHEA dose-dependent manner. ③ MMPs were involved in neuronal differentiation. DbcAMP induced the increase in MMP-9 and MMP-2 activities and such elevation was enhanced by DHEA in a dose-dependent manner. Conclusion DHEA enhances the effect of DbcAMP in promoting the neurite outgrowth of NG108-15 cells, which might be related to the increase in MMP-9 and MMP-2 activities.

Cell Cylce Regulatory Effects of Cyclic AMP in Cancer Cells Which Lack Wild-type p53 / 대한암학회지

PURPOSE: The activator of protein kinase A, cyclic AMP, has been a recognized growth inhibitor of certain cell types. The present study aimed to investigate the effects of dibutyryl cAMP on the growth of cancer cells which lack wild-type p53 and to determine the mechanism of growth inhibition. MATERIALS AND METHODS: Prostate and breast cancer cells were treated with dibutyryl cAMP and compared with untreated cells. Growth patterns of cells were assessed by trypan blue-excluding method and western blot was done to determine protein levels of cell cycle regulatory proteins which govern G1 and G1/S phase. Northern blot and immunoprecipitation were done to determine the level of mRNA of p21 and the association between cell cycle regulatory proteins. In vitro immune complex kinase assay was done to assess the activity of cdk2. RESULTS: cAMP reduced cell growth by 48 h. Cyclin D3 level was downregulated and RB protein level was decreased and mostly unphosphorylated forms remained. The association of RB with E2F1 was increased. While cdk2 levels remained constant throughout cAMP treatment, the activity of cdk2/cyclin E complex, which is responsible for entry into S phase, was downregulated. Cdk inhibitors, p27 and p21 were induced with cAMP treatment. CONCLUSION: These observation suggest that the growth inhibitory effects of dibutyryl cAMP on prostate and breast cancer cells were mediated by induction of cdk inhibitors such as p21 and p27 and RB activation in accordance with downregulation of cdk2.

Cholera toxin mediated regulation of the expression of Gq alpha and G11 alpha GTP binding proteins

Previously it has been shown that persistent activation of the stimulatory adenylyl cyclase pathway with cholera toxin (CT) downregulates the Gs alpha polypeptide (80%) in a cAMP-independent manner in C6 glioma cells (Shah, 1997). This study was conducted to examine the short and long term effects of CT on the regulation of pertussis toxin-sensitive and -insensitive G proteins and their transcripts in C6 glioma cells. Treatment of C6 cells with CT (100 ng/ml) up to 16 h had no effect on either Gi or Gq/11 alpha proteins. However, prolonged exposure (24-48 h) caused increased expression of Gi (20-30%) and Gq/11 alpha proteins (40%). Urea gradient gels, which can separate Gq alpha and G11 alpha proteins, revealed that prolonged CT treatment increased the expression of both of these G proteins. The CT-mediated enhanced expression of Gq alpha and G11 alpha proteins was accompanied by increased mRNA levels of these proteins as determined by RT/PCR. Cyclic-AMP elevating agents like forskolin (10 microM) and db-cAMP (1 mM) mimicked the effect of CT on Gi but not Gq/11 alpha proteins. These studies show long term cAMP-dependent regulation of Gi and cAMP-independent expression of Gq/11 alpha proteins in C6 glioma cells.