Native Plateau Tibetan Umbilical Vein Endothelial Cells To Hypoxia Inducible Factor-1¦Á Gene And Hypoxia-inducible Gene Expression Studies

Hypoxia inducible factor 1 (HIF-l), a nuclear protein that activates hypoxia inducible genes (HIG5) transcription, which include inducible nitric oxide synthase (iNOS), vascular endothelial growth factor (VEGF) and erythropoietin (EPO), specifically in response to reduced cellular oxygen concentration, plays a central role in essential adaptive responses to hypoxia. High altitude living produces physiological changes for adaptation to chronic hypobaric-hypoxia conditions. Living the longest at high altitude, Tibetan exhibit the best adaptation to high altitude and thus a valuable source for studying of mechanisms of adaptation to high altitude. Although a number of studies on physiological responses to hypoxia in Tibetan have been presented, little has been known about gene expression of Tibetan by now. To investigate how hypoxia affects the expression of HIF- 1 and HIGs, we cultured native Tibetan neonatal umbilical venous endothelial cells (UVEC5), sequenced Tibetan cDNA with PCR, investigated expression of HIF-1 a , iNOS, endothelial nitric oxide synthase (eNOS), VEGF and EPO mRNA with RT-PCR and HJF- 1 a protein with Western blot in Tibetan UVECs, detected nitric oxide (NO) and endothelin (ET) with colorimetry and radioimmunoassay methods in culture medium and plasma of healthy adults respectively, as well as blood gas in native Tibetan. The main results and conclusions are as following: 1. Tibetan UVECs cultured in vitro displayed similar cell morphology and ?Iv. growth characteristics with migrant Han. 2. The HIF-1 a cDNA sequence was almost the same as formerly reported lowlander HIF- 1 a mRNA sequence, except for substitutions of T by A at 3360nt and T by A at 3383nt. 3. HIF- 1 a mRNA was detected in Tibetan and Han UVECs cultured under normoxic conditions and remained unchanged following hypoxic exposure. HIF- 1 a protein was undetectable in Tibetan UVECs cultured under normoxic conditions and after exposed to 0.5% oxygen for 2h. After hypoxic exposure for 4h, HIF-1 a protein was detected and kept increasing as hypoxia being prolonged to 12h and 24h. These findings indicate that the regulation of HIF 1 a protein accumulation by hypoxia is independent of the regulation of mRNA expression and confirm the theory that HJF 1 a is post-transcriptionally activated by hypoxia. 4. VEGF, iNOS, and EPO mRNA were up-regulated while eNOS mRNA depressed by hypoxia similarly in Tibetan and Han UVECs, which suggests that these changes are common passways in mechanisms of hypoxic responses. EPO can also be expressed by UVECs, which probably contributes to hypoxic responses other than erythropoiesis. 5. ET excretion from UVECs was elevated while NO decreased in Tibetan and Han after exposed to hypoxia. ET released by UVECs was higher in Tibetan than in Han after 12h and 24h hypoxic exposure, which may be in favor of lower vascular resistance and better fetal blood supply in Tibetan, and thus plays a role in the mechanisms of less intrauterine growth restriction (IUGR) throughout pregnancy and heavier birth weight of Tibetan newborns. 6. The highland residents showed poorer blood oxygen parameters than lowlanders. Arterial oxygen saturation and content were lower in Tibetan than in Han, while arteriovenous difference of oxygen content consistent in both groups of highland residents, indicatin...