ABSTRACT
Objective To explore the effects of Na+ H-exchanger 1(NHE1) knockdown on ATP binding cassette transporter A1 (ABCA1) protein expression levels and cholesterol efflux in the hypoxic RAW264.7 cells.Methods The RAW264.7 cells were infected with lentiviral vectors expressing shRNA specific for NHE1(siNHE1) or scramble RNA (siNC).The expression of NHE1 at mRNA or protein level was detected by qRT-PCR and Western blotting respectively in the infected cells after 24 h in a hypoxia condition.In the meantime,the methods of SNARF-1,Fluo-4 NW andSuc-LLVY-aminoluciferin were employed to determine NHE1 activity,intracellular Ca2+ ([Ca2+]i) and calpain activity,respectively.Furthermore,ABCA1 protein levels were detected by Western blotting in the 24 h hypoxic cells.In parallel,the intracellular cholesterol content and cholesterol efflux were analyzed by the methods of combined enzymatic HLPC and 3 H-cholesterol.Results The hypoxia condition versus the normoxia condition up-regulated NHE1 mRNA and protein expression level and activity by 2.48 folds,1.28 folds and 61.96％ (all P＜0.05),and increased[Ca2+]i and calpain activity by 4.51 folds and 2.41 folds(all P＜0.05).Whereas the NHE1 mRNA and protein expression and activity at the presence of hypoxia were inhibited by siNHE1 with the inhibition ratio of 84.95％,60.75％ and 66.44％,respectively (all P＜0.05)and[Ca2+]i and calpain activity were reduced by 59.23％ and 54.66％ (P＜0.05).Furthermore,the ABCA1 protein level was 61.67％ lower in the hypoxic cells than in the normoxic cells (P＜0.05),and siNHE1 was increased by 56.52％ after treatment of Hypoxia.Hypoxia elevated intracellular total cholesterol and cholesterol ester by 74.57 ％ and 101.81％ (all P＜0.05).Treatment with siNHE1 in the hypoxia condition can reduce total cholesterol and cholesterol ester by 34.24 ％ 及 49.66 ％ (all P＜0.05).Hypoxia reduced the cholesterol efflux by 34.79％(P＜0.05),which were partially reversed by siNHE1.Conclusions NHE1 might play an important role in hypoxia-induced ABCA1 protein attenuation and reverse cholesterol transport dysfunction through[Ca2+]i/calpain pathway.
ABSTRACT
Objective To explore the myogenic basis of the increased excitability and contractile activity in detrusor instability (DI) and investigate the differences of spontaneous contractions by ryanodine receptor (RyR) channels regulation in sarcoplasmic reticulum (SR) between DI and normal bladder muscle and of the RyR channels protein expression. Methods DI model was confirmed by filling cystometry from rats that underwent partial bladder outlet obstruction (BOO) about 8 weeks ago. Muscle strips were dissected from fresh bladder under microscope and the isometric tension in DI and normal strips were detected. The contractions were recorded in these strips exposed to some agents. SR microsome protein was obtained from DI and normal bladder muscle preparations and was used for Western blot analysis to determinate RyR channels expression. Results Treated with RyR channels blocker ryanodine , the contractile frequence significantly increased in normal strips, but not in DI muscle. Western blot analysis showed that RyR channels expression in DI muscle was significantly less than that in normal preparations. Conclusion RyR channels act a negative role in spontaneous contractile activity and the presumed mechanism may involve in Ca 2+ release of RyR channels which causes activation of Ca 2+ -dependent K + channels to decrease contractility. But this crosstalk mechanism is weaken in DI muscle, which provides a chance for spontaneous contractile overactivity.