These data suggest that hypoxia enhances the expression of MUC1 through the transcriptional regulation by HIF-1alpha in a human lung epithelial cell line.
Chromatin immunoprecipitation assay demonstrated that HIF-1 alpha directly bound to this region under normoxia, and this binding activity was significantly enhanced under hypoxia.
Transfection with specific siRNA duplexes knocked down HIF 1-alpha mRNA and protein expression in hypoxia-exposed cells by approximately 80%, whereas transfection with scrambled siRNA duplexes had no noticeable effect on HIF 1-alpha expression.
Treatment of cells under hypoxia with low concentrations of the superoxide generator 2,3-dimethoxy-1,4-naphthoquinone lowered HIF-1alpha protein stabilization.
In conclusion, our data demonstrate that hyperglycemia impairs hypoxia-dependent protection of HIF-1alpha against proteasomal degradation and suggest a mechanism by which diabetes interferes with cellular responses to hypoxia.
These results suggest that the hypoxia induces the migration of CASMCs, and that the migration is elicited by TSP-1 of which induction is fully dependent on the stabilization of HIF-1alpha, in autocrine regulation.
Chromatin immunoprecipitation identified a previously unappreciated binding site for the hypoxia inducible factor-1 (HIF-1), and promoter studies established its relevance by loss of repression following point mutation.
Dimethyloxallyl glycine, a stabilizer of hypoxia-inducible factor 1alpha (HIF1alpha), mimicked the hypoxia-mediated upregulation of visfatin, and YC1, an inhibitor of HIF1 cancelled the hypoxia-induced upregulation of visfatin mRNA.
HUVECs were transfected with specific 21-nt small interfering RNA (siRNA) duplexes targeting HIF-1 alpha mRNA sequences or scrambled RNA duplexes and subjected either to normoxia for 251/2 h or to anoxia for 11/2 h, and subsequently normoxia for 24 h (A/R).
We suggest a dual role for HIF-1alpha in providing a survival or death signal, based on hypoxia duration, and consider the nuclear transcription factor, CREB, to be a possible target for hypoxic therapy against leukemia disease.
In contrast, coexpression of HIF-1alpha and CAIX in the epithelium in phyllodes tumors points to epithelial hypoxia, most probably caused by relatively distant blood vessels.
Overexpression of HIF-1alpha and HIF-2alpha was demonstrated in three HNSCC cell lines under hypoxia and tumor tissue versus normal tissue (n = 20, HIF-1alpha, P = 0.023; HIF-2alpha, P = 0.013).
The results showed that, although hypoxia markedly increased ROS generation in HeEB1 cells but not in EB8 cells, EB8 cells showed essentially a normal response to hypoxia, as assessed by VEGF gene promoter activity, HIF-1alpha accumulation, and HIF-1 target gene expressions.
Cell density also correlated with increased staining for reductively activated pimonidazole (a marker for hypoxia), as well as with increased levels of the HIF-1alpha subunit and HIF transcriptional activity as determined by immunocytochemistry, Western blot, and luciferase reporter assays.