Effects of different ratios of medicine dosage for isoflurane and propofol on GABAA receptor α1 subunit proteostasis during hypoxia injury to hippocampal neurons of rats

Abstract

Objective To evaluate the effects of different ratios of medicine dosage for isoflurane and propofol on GABAA receptor(GABAAR)α1 subunit proteostasis during hypoxia injury to hippocampal neurons of rats. Methods The hippocampal neurons isolated from fetal rats obtained from Wistar rats were primarily cultured and divided into 6 groups(n=60 each)using a random number table: control group(group C), hypoxia group(group H), isoflurane group(group I), propofol group(group P)and different ratios of medicine dosage for isoflurane and propofol groups(group IP1 and group IP2). The cells were subjected to hypoxia for 6 h in group H. Cells were incubated for 3 h with 1.9 % isoflurane and with 22.4 μmol/L propofol after being subjected to hypoxia for 6 h in I and P groups, respectively.Cells were incubated for 3 h with 1.0% isoflurane and 6.7 μmol/L propofol and with 1.4 % isoflurane and 3.4 μmol/L propofol after being subjected to hypoxia for 6 h in IP1 and IP2 groups, respectively.Then the culture medium was replaced with plain culture medium.At 24 h of incubation, the cells were collected for measurement of cell viability by CCK-8 assay, GABAAR α1 mRNA expression(by quantitative polymerase chain reaction), GABAAR α1 expression in the cytomembrane(by Western blot), level of GABAAR α1 subunit endoplasmic reticulum-associated degradation(ERAD) (by immunoprecipitation and Western blot)and CCAAT/enhancer-binding protein homologous protein(CHOP)expression (by immunofluorescence). Results Compared with group C, the cell viability was significantly decreased, the expression of GABAAR α1 mRNA and GABAAR α1 in cytomembrane was down-regulated, the expression of CHOP was up-regulated, and the level of GABAAR α1 subunit ERAD was increased in the other five groups(P<0.05). Compared with group H, the cell viability was significantly decreased, the expression of GABAAR α1 mRNA and GABAAR α1 in cytomembrane was down-regulated, the expression of CHOP was up-regulated, and the level of GABAAR α1 subunit ERAD was increased in I, P and IP2 groups(P <0.05), and no significant change was found in the parameters mentioned above in group IP1(P<0.05). Compared with group I or group P, the cell viability was significantly increased, the expression of GABAAR α1 mRNA and GABAAR α1 in cytomembrane was up-regulated, the expression of CHOP was down-regulated, and the level of GABAAR α1 subunit ERAD was decreased in IP1 and IP2 groups(P<0.05). Compared with group IP1, the cell viability was significantly decreased, the expression of GABAAR α1 mRNA and GABAAR α1 in cytomembrane was down-regulated, the expression of CHOP was up-regulated, and the level of GABAAR α1 subunit ERAD was increased in group IP2(P<0.05). Conclusion Combination of 1.0% isoflurane and 6.7 μmol/L propofol does not aggravate hypoxia-induced destruction of GABAAR α1 subunit proteostasis in hippocampal neurons of rats. Key words: Propofol; Isoflurane; Receptors, GABA-A; Hypoxia-ischemia, brain