Objective To investigate the effects of high-altitude hypoxic environment on the pharmacokinetic characteristics and brain tissue distribution of phenytoin sodium in epileptic rats.Methods A total of 70 male SPF-grade Wistar rats aged 2 months and weighing(200±20)g were used in the study.An epilepsy model was induced in the rats using the lithium chloride-pilocarpine method.The successfully modeled rats were randomly assigned to a normoxic treatment group and a high-altitude hypoxic treatment group.Phenytoin sodium was administered via intragastric gavage at a dose of 50 mg/kg in both groups.Blood samples were collected from the orbital venous plexus before treatment and 0.5,1,2,3,4,6,8,10,and 24 h post treatment.The animals were euthanized after the final blood collection,and samples of the liver and the whole brain tissue were collected.In the brain tissue distribution experiment,brain tissue samples were collected at 0.5,1,2,and 4 h after drug administration.The concentration of phenytoin sodium in rat plasma and brain tissue was determined by liquid chromatography-tandem mass spectrometry(LC-MS/MS),and the pharmacokinetic parameters were calculated using WinNolin 8.1 software.The expression levels of CYP2C9 in liver tissue and those of P-gp in brain tissue of epileptic rats were determined by Western blot.Results Compared with those in the normoxia group,the peak concentration,peak time,and half-life of phenytoin sodium in the high-altitude hypoxia group were significantly decreased by 46.0%,42.3%,and 55.5%,respectively(all P<0.05);the clearance rate was significantly increased by 162.0%(P<0.05);and the area under the curve of plasma concentration-time curve was decreased by 45.6%(P<0.01).At 0.5,1,and 2 hours after administration,compared with that in the normoxia treatment group,the concentration of phenytoin sodium in the brain tissue of the high-altitude hypoxia treatment group was significantly decreased by 78.1%,63.5%,and 32.5%,respectively(all P<0.05).Western blot results showed that the expression levels of CYP2C9 in the liver tissue and P-gp in the brain tissue of rats in the high-altitude hypoxia group were approximately 1.78 and 1.65 times higher than those in the normoxia group,respectively(both P<0.05).Conclusion The hypoxic environment at high altitudes can promote the metabolism of phenytoin sodium,reduce its absorption efficiency,and change the characteristics its distribution in the brain,which may be related to the up-regulation of the expression of CYP2C9 in the liver and that of P-gp in the brain.

Objective To investigate the protective effect of Lycium barbarum polysaccharide(LBP)on reproductive system damage induced by exposure to high-altitude hypoxic environment in female rats,and to explore the mechanisms involved.Methods After undergoing physiological synchronization,30 female Wistar rats were randomly and evenly assigned to 3 groups,including a plain control(C)group,a high-altitude hypoxia(H)group,and a high-altitude hypoxia+LBP(H-LBP)group.The C group was placed in a region at an altitude of 1500 m above sea level(with an oxygen volume fraction of 18.55％),while the H group and the H-LBP group were placed in a region at an altitude of 4 010 m above sea level(with an oxygen volume fraction of 12.70％).Rats in the H-LBP group were fed with LBP at 75 mg/kg via gastric gavage,while the C and H groups received normal saline once a day for 14 days in a row.Changes in estrous cycles were documented throughout the experiment.At the end of the experiment,the serum levels of reproductive hormones and the levels of oxidative stress in the ovarian and uterine tissues were measured.Morphological changes in the ovarian and uterine tissues were assessed using hematoxylin-eosin(HE)staining.A component-target-pathway network diagram was constructed using network pharmacology methods to analyze the key targets and pathways.Results Compared with the C group,rats in the H group had disrupted estrous cycles and significantly lower serum levels of reproductive hormones(all P＜0.05).In addition,rats in the H group had increased oxidative stress damage and experienced pathological damage in the ovarian and uterine tissues.However,compared with those of the H group,the estrous cycle in the H-LBP group became normalized after the administration of LBP and the serum levels of estradiol(E2),progesterone(P),luteinizing hormone(LH),and anti-Müllerian hormone(AMH)were significantly increased in H-LBP group(all P＜0.05).In the ovarian tissue,the malondialdehyde(MDA)content was significantly reduced,superoxide dismutase(SOD)activity was increased,and the content of reduced glutathione(GSH)was increased.In addition,in the uterine tissue,the MDA content was reduced and SOD activity was increased(all P＜0.05),with LBP significantly improving the pathological damage to the reproductive organs of female rats caused by high-altitude hypoxic environment.Through network pharmacology analysis,we identified 76 potential targets for the protective effect of LBP against high-altitude hypoxia-induced reproductive injury,and the targets were mainly involved in the signaling pathways such as calcium channels,PI3K-Akt,MAPK,and HIF-1.Conclusion LBP can ameliorate high-altitude hypoxia-induced reproductive damage in female rats.The mechanisms involved may be associated with the regulation of PI3K-Akt,MAPK,and HIF-1 pathways.

OBJECTIVES: Hypoxia can alter the oral bioavailability of drugs, including various substrates (drugs) of P-glycoprotein (P-gp), suggesting that hypoxia may affect the function of P-gp in intestinal epithelial cells. Currently, Caco-2 monolayer model is the classic model for studying the function of intestinal epithelial P-gp. This study combines the Caco-2 monolayer model with hypoxia to investigate the effects of hypoxia on the expression and function of P-gp in Caco-2 cells, which helps to elucidate the mechanism of changes in drug transport on intestinal epithelial cells in high-altitude hypoxia environment. METHODS: Normally cultured Caco-2 cells were cultured in 1% oxygen concentration for 24, 48, and 72 h, respectively. After the extraction of the membrane proteins, the levels of P-gp were measured by Western blotting. The hypoxia time, with the most significant change of P-gp expression, was selected as the subsequent study condition. After culturing Caco-2 cells in transwell cells for 21 days and establishing a Caco-2 monolayer model, they were divided into a normoxic control group and a hypoxic group. The normoxic control group was continuously cultured in normal condition for 72 h, while the hypoxic group was incubated for 72 h in 1% oxygen concentration. The integrity and polarability of Caco-2 cells monolayer were evaluated by transepithelial electrical resistance (TEER), apparent permeability (Papp) of lucifer yellow, the activity of alkaline phosphatase (AKP), and microvilli morphology and tight junction structure under transmission electron microscope. Then, the Papp of rhodamine 123 (Rh123), a kind of P-gp specific substrate, was detected and the efflux rate was calculated. The Caco-2 cell monolayer, culturing at plastic flasks, was incubated for 72 h in 1% oxygen concentration, the expression level of P-gp was detected. RESULTS: P-gp was decreased in Caco-2 cells with 1% oxygen concentration, especially the duration of 72 h (P<0.01). In hypoxic group, the TEER of monolayer was more than 400 Ω·cm², the Papp of lucifer yellow was less than 5×10^-7 cm/s, and the ratio of AKP activity between apical side and basal side was greater than 3. The establishment of Caco-2 monolayer model was successful, and hypoxia treatment did not affect the integrity and polarization state of the model. Compared with the normoxic control group, the efflux rate of Rh123 was significantly reduced in Caco-2 cell monolayer of the hypoxic group (P<0.01). Hypoxia reduced the expression of P-gp in Caco-2 cell monolayer (P<0.01). CONCLUSIONS Hypoxia inhibits P-gp function in Caco-2 cells, which may be related to the decreased P-gp level.
Humans ; ATP Binding Cassette Transporter, Subfamily B, Member 1 ; Caco-2 Cells ; ATP Binding Cassette Transporter, Subfamily B ; Hypoxia ; Oxygen

Tibetan is a kind of medicine which extensively absorbed and fused the Chinese Traditional Medicine, Indian medicine and food through long-term practice and form the unique medical system. At the same time, the Qinghai Tibet plateau has characteristics of high altitude and lack of resources and oxygen, which has formed its unique geographical environment and grow a lot of rare medicinal plants. Tibetan medicine has a long history and is one of the relatively complete and influential ethnic medicines in China, which has played an important role in the treatment of plateau diseases. In recent years, with the increasing of economic activities in the plateau, the plateau anoxia had greatly affected the working capacity of the plateau. According to "Chinese medicine" through the literature, the pharmacological activities, active ingredients, growing environment of Tibetan medicine with good plateau hypoxia effect were reviewed and according to the site, which could be divided into the lung protection medicine, the cardiac protection medicine, the brain protection medicine, the liver protection medicine, the improvement of fatigue medicine and other medicine, which could provide theoretical basis for finding more potential anti-hypoxia drugs.