ABSTRACT
OBJECTIVE: The aim of the present study was to investigate the effect of adipokine NAMPT (nicotinamide phosphoribosyltransferase) silencing on the expression of genes encoding IRS1 (insulin receptor substrate 1) and some other proliferation related proteins in U87 glioma cells for evaluation of the possible significance of this adipokine in intergenic interactions. METHODS: The silencing of NAMPT mRNA was introduced by NAMPT specific siRNA. The expression level of NAMPT, IGFBP3, IRS1, HK2, PER2, CLU, BNIP3, TPD52, GADD45A, and MKI67 genes was studied in U87 glioma cells by quantitative polymerase chain reaction. Anti-visfatin antibody was used for detection of NAMPT protein by Western-blot analysis. RESULTS: It was shown that the silencing of NAMPT mRNA led to a strong down-regulation of NAMPT protein and significant modification of the expression of IRS1, IGFBP3, CLU, HK2, BNIP3, and MKI67 genes in glioma cells and a strong up-regulation of IGFBP3 and IRS1 and down-regulation of CLU, BNIP3, HK2, and MKI67 gene expressions. At the same time, no significant changes were detected in the expression of GADD45A, PER2, and TPD52 genes in glioma cells treated by siRNA specific to NAMPT. Furthermore, the silencing of NAMPT mRNA suppressed the glioma cell proliferation. CONCLUSIONS: Results of this investigation demonstrated that silencing of NAMPT mRNA with corresponding down-regulation of NAMPT protein and suppression of the glioma cell proliferation affected the expression of IRS1 gene as well as many other genes encoding the proliferation related proteins. It is possible that dysregulation of most of the studied genes in glioma cells after silencing of NAMPT is reflected by a complex of intergenic interactions and that NAMPT is an important factor for genome stability and regulatory mechanisms contributing to the control of glioma cell metabolism and proliferation.
Subject(s)
Cytokines/genetics , Gene Expression Regulation, Neoplastic/genetics , Gene Expression/genetics , Glioma/genetics , Insulin Receptor Substrate Proteins/genetics , Nicotinamide Phosphoribosyltransferase/genetics , Cell Cycle Proteins/genetics , Cell Line, Tumor , Cell Proliferation/genetics , Clusterin/genetics , Down-Regulation , Humans , Insulin-Like Growth Factor Binding Protein 3/genetics , Membrane Proteins/genetics , Neoplasm Proteins/genetics , Period Circadian Proteins/genetics , Proto-Oncogene Proteins/genetics , RNA, Messenger , RNA, Small Interfering , Up-RegulationABSTRACT
OBJECTIVE: The aim of the present investigation was to study the effect of hypoxia on the expression of genes encoding endothelin-1 (EDN1) and its cognate receptors (EDNRA and EDNRB) as well as endothelin converting enzyme 1 (ECE1) in U87 glioma cells in response to inhibition of endoplasmic reticulum stress signaling mediated by ERN1/IRE1 (endoplasmic reticulum to nucleus signaling 1) for evaluation of their possible significance in the control of glioma growth through ERN1 and hypoxia. METHODS: The expression level of EDN1, EDNRA, EDNRB, and ECE1 genes as well as micro-RNA miR-19, miR-96, and miR-206 was studied in control and ERN1 knockdown U87 glioma cells under hypoxia by quantitative polymerase chain reaction. RESULTS: It was shown that the expression level of EDN1, EDNRA, EDNRB, and ECE1 genes was up-regulated in ERN1 knockdown glioma cells in comparison with the control glioma cells, being more significant for endothelin-1. We also observed down-regulation of microRNA miR-206, miR-96, and miR-19a, which have specific binding sites in mRNA EDN1, EDNRA, and EDNRB, correspondingly, and can participate in posttranscriptional regulation of these mRNA expressions. Furthermore, inhibition of ERN1 endoribonuclease lead to up-regulation of EDNRA and ECE1 gene expressions and down-regulation of the expression level of EDN1 and EDNRB genes in glioma cells. Thus, the expression of EDNRA and ECE1 genes is regulated by ERN1 endoribonuclease, but EDN1 and EDNRB genes preferentially by ERN1 protein kinase. We have also shown that hypoxia enhanced the expression of EDN1, EDNRA, and ECE1 genes and that knockdown of ERN1 signaling enzyme function significantly modified the response of all studied gene expressions to hypoxia. Thus, effect of hypoxia on the expression level of EDN1 and ECE1 genes was significantly or completely reduced in ERN1 knockdown glioma cells since the expression of EDNRA gene was down-regulated under hypoxia. Moreover, hypoxia is induced the expression of EDNRB gene in ERN1 knockdown glioma cells. CONCLUSIONS: Results of this investigation demonstrate that ERN1 knockdown significantly increased the expression of endothelin-1 and its receptors as well as ECE1 genes by different mechanisms and that all studied gene expressions were sensitive to hypoxia. It is possible that hypoxic regulation of the expression of these genes is a result of complex interaction of variable ERN1 related transcription and regulatory factors with HIF1A and possibly contributed to the control of glioma growth.
Subject(s)
Brain Neoplasms/genetics , Endoribonucleases/genetics , Glioma/genetics , Protein Serine-Threonine Kinases/genetics , Tumor Hypoxia/genetics , Brain Neoplasms/metabolism , Brain Neoplasms/pathology , Cell Hypoxia/genetics , Cell Line, Tumor , Endoribonucleases/deficiency , Endothelin-1/genetics , Endothelin-Converting Enzymes/genetics , Gene Expression Regulation, Neoplastic , Gene Knockdown Techniques , Glioma/metabolism , Glioma/pathology , Humans , Hypoxia/genetics , Hypoxia/pathology , Protein Serine-Threonine Kinases/deficiency , Receptor, Endothelin A/genetics , Receptor, Endothelin B/geneticsABSTRACT
OBJECTIVE: The aim of the present study was to examine the effect of glucose deprivation on the expression of genes encoded glucocorticoid receptor (NR3C1) and some related proteins (NR3C2, AHR, NRIP1, NNT, ARHGAP35, SGK1, and SGK3) in U87 glioma cells in response to inhibition of endoplasmic reticulum stress signaling mediated by ERN1/IRE1 (endoplasmic reticulum to nucleus signaling 1/inositol requiring enzyme 1) for evaluation of their possible significance in the control of glioma growth through endoplasmic reticulum stress signaling mediated by IRE1 and glucose deprivation. METHODS: The expression of NR3C1, NR3C2, AHR, NRIP1, NNT, ARHGAP35, SGK1, and SGK3 genes in U87 glioma cells transfected by empty vector pcDNA3.1 (control cells) and cells without ERN1 signaling enzyme function (transfected by dnERN1) under glucose deprivation was studied by real time quantitative polymerase chain reaction. RESULTS: It was shown that the expression level of NR3C2, AHR, SGK1, SGK3, and NNT genes was up-regulated in control U87 glioma cells under glucose deprivation condition in comparison with the control cells growing with glucose. At the same time, the expression of NRIP1 gene is down-regulated in these glioma cells under glucose deprivation, but NR3C1 and ARHGAP35 genes was resistant to this experimental condition. We also showed that inhibition of ERN1 signaling enzyme function significantly modified the response of most studied gene expressions to glucose deprivation condition. Thus, effect of glucose deprivation on the expression level of NR3C2, AHR, and SGK1 genes was significantly stronger in ERN1 knockdown U87 glioma cells since the expression of NNT gene was resistant to glucose deprivation condition. Moreover, the inhibition of ERN1 enzymatic activities in U87 glioma cells led to up-regulation of ARHGAP35 gene expression and significant down-regulation of the expression of SGK3 gene in response to glucose deprivation condition. CONCLUSIONS: Results of this study demonstrated that glucose deprivation did not change the expression level of NR3C1 gene but it significantly affected the expression of NR3C2, AHR, NRIP, SGK1, SGK3, and NNT genes in vector-transfected U87 glioma cells in gene specific manner and possibly contributed to the control of glioma growth since the expression of most studied genes in glucose deprivation condition was significantly dependent on the functional activity of IRE1 signaling enzyme.
