| Background Our country has the largest area of plateau and population in the world, a quarter of the size is the plateau which above 3000 m and mainly distributed in Tibet, Qinghai and Xinjiang. These regions are important for western development, with the opening of Qinghai-Tibet Railway, the development of the plateau area and the prosperity of tourism, the number of people who go to the plateau is increasing. Other than flat area, the atmospheric pressure, partial pressure of oxygen, temperature, humidity are different on plateau, these factors have an big influence on people’s body, such as the cardiovascular system, nervous system, digestive system and so on. Hypoxia is a assignable factor of all, the researches were more about people who rush to the plateau or the native residents, while the study about people to and from plateau and plan is few. IH means the body discontinuous under the hypoxia environment and the rest time is in the normal environment. A large number of studies have shown that the impact of IH on body is depend on the extent of hypoxia, the duration of hypoxia and the alternately way of hypoxia and normoxia. Choline,known as an essential water-soluble nutrient belonging to B vitamins. To date, it was found gradually that choline played a significant role in many physiological processes such as signaling transduction, biosynthesis and integrity of cell membranes, DNA and histones methylation, and neurotransmitter Acetylcholine(ACh) synthesis. It has been found that choline metabolism changed under hypoxic exposure,but there is no idea in the effect of choline on hypoxic injury.Objective This study is about the impact of IH on the system of oxidative stress and endothelial,as to provide basic theory for drug of prevention.It also explore the role of choline in the injury of hypoxia in vascular endothelial cell(VEC).Method 1.The effect of IH on oxidative stress and endothelial function of rat Forty-eight Wistar rats weighing 180-200 g were divided into eight groups of sixanimals each.Four groups were housed in an experimental hypobaric-hypoxia chamber and exposed to conditions equivalent to 6000 m for a period of 6h or 7,14,21,28 days.The other four groups were kept in a sea-level-altitude in 7,14,21,28 days.At the end of the experiment,the rats were decapitated and the serum,heart,liver,brain and kidney removed.Then the samples were measured of MDA,SOD,T-AOC,NO,ET and VEGF. 2.The effect of IH on oxidative stress and endothelial function in VEC The cells were randomly divided into two groups,control(21%O2,37℃,48h) and IH(hypoxia 30 h,reoxygen 18h),then detect the level of MDA,SOD,NO and ET in the cell supernatant. We set control group, different concentration of H2O2 groups,hypoxia group and the complex group to investigate the injury of oxidative stress on VEC. 3. The effects of choline on VEC against damage under hypoxic conditions We set control, hypoxia, choline and choline+MLA groups, the cell survival rate,the releasing of LDH and VEGF were measured.Result 1. The effect of IH on oxidative stress and endothelial function of rat(1)The effect of CIH on oxidative stress of rat Serum:Compared with the control group,the content of MDA and SOD in IH have no significance in 1,2,3 week;while after 4 weeks of IH,the content of MDA was obviously increased and SOD was obviously decreased(P<0.05);The content of T-AOC was elevated in different time of IH after intervention, while there was a significant difference after 2nd, 3rd, 4th week(P<0.01). Heart: Compared with the control group, the content of MDA in IH has a significant increase in after 1st, 2nd, 3rd, 4th week(P<0.01); The content of SOD was decreased after different time of hypoxia after intervention, while there was significantly decreased after the 2nd,4th week(P<0.05);The content of T-AOC in each week was decreased in different degree, while there was no significant difference. Brain: Compared with the control group, the content of MDA in IH wasdecreased after the 1st, 2nd, 3rd, 4th week, and there was a significant differences after the 4th week(P<0.05); The content of SOD was decreased after different time of hypoxia, while there was obviously decreased after the 2nd week(P<0.05); T-AOC in each week has a significant increase in different degree, but has no statistical significance. Liver: Compared with the control group, the content of MDA in IH was decreased after the 1st, 3rd, 4th week, while there was a significant differences in the 4th week later(P<0.05); The content of SOD showed decreasing trend after different time of hypoxia, but has no significant differences; T-AOC in each week has a significant decrease in different degree, while there was such a significant difference after the4 th week(P<0.05). Kidney: Compared with the control group, the content of MDA in IH was increased after each week, while there was such a significant difference after the 2nd, 3rd, 4th week(P<0.01); 4 weeks later, the content of SOD in IH was significantly decreased after intervention(P<0.05); T-AOC in each week was increased in different degree, while there was no significant difference.(2) The effect of CIH on endothelial function in rats Compared with the control group, the content of NO began to decrease at 2nd week, while there was a significant difference in the later of 2nd and 4th week(P<0.05); The content of serum ET showed decreasing trend in different time of HI after intervention, and there was a significant difference in the later of 2nd week(P<0.05); The content of VEGF showed decreasing trend in1 st, 2nd, 4th week, but has no statistical significance. 2.The effect of IH on oxidative stress and endothelial function in VEC(1)The effect of IH on oxidative stress in VEC The group of 27 hours of IH, compared with the control group, has no significant differences between hypoxia and reoxygenation endothelial cell MDA level; Compared with control group, the content of MDA in vascular endothelial cells after 18 h reoxygenation of IH group was significantly increased, so the group of 30 hours of IH has statistical significance(P< 0.01). Therefore, we choose 30 h of hypoxia, 18hreoxygenation to study the effects of IH on vascular endothelial cell. The content of SOD in the cells of 30 hours of IH has a tendency to decrease after reoxygenation, but no statistical significant. Compared with the control group, the survival rate of the cell in hypoxia group, H2O2 group and hypoxic group H2O2 decreased significantly(P<0.05); the release of LDH between H2O2 group and compound group was significant increased(P<0.01).(2) The effect of IH on endothelial function of endothelial cells. Compared with the control group, the content of NO of IH was decreased after exposure to hypoxia and the content of ET were significant increased(P<0.05); After reoxygenation of 18 hours, the content of NO in hypoxia group were significantly increased, while the release of ET decreased significantly(P<0.01). 3. The effects of choline on VEC against hypoxic damage Under normoxic conditions, treated RAECs for 24-48 hours with choline, the survival rate of cell is increased, while the level of LDH had no significant difference(P>0.05); Under hypoxic condition, treated the RAECs for 24-48 hours with choline, 0.1-10μmol/L of choline made the survival rate of RAECs increasing, and the level of LDH is decreased(P<0.05). The content of VEGF in endothelial cells was significantly increased after hypoxia of 24 hours(P<0.05), 10μmol/L of the choline can further increase endothelial cells secreting of VEGF(P<0.01); Under hypoxic condition, compared with the group of choline, the survival rate of the cell in the group using MLA was decreased significantly(P<0.01).Conclusion 1.CIH may stimulate the oxidative stress system of rat after different weeks,while the extent of oxidative stress in serum,heart,brain,liver and kidney are different.CIH may have effects on endothelial function,one of which is the decreasing content of NO.CIH also have an influence on the level of ET,but have no significance in VEGF,which indicate that CIH dose not affect the vascular permeability. 2.IH may cause the oxidative damage of endothelial cell.The injury of different extent of oxidative stress on cell is distinctive,while the 800 u M H2O2 take for 30 h isthe most serious.The injury of complex is more than the single.CIH may have a repair effect of endothelial dysfunction. 3. Under both normoxic and hypoxic conditions, choline could significantly promote the proliferation of RAECs, choline only played a protective role to the endothelial cells subjected to hypoxic injuries,and this may by increase the secretion of VEGF in endothelial cells.Furthermore, choline might be through activating the target α7 n Ach R to achieve the goal. |
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