Regulatory effects of hedgehog pathway on intestinal epithelial barrier function under hypoxia

Abstract

Objective To investigate the regulatory effects of hedgehog pathway on intestinal epithelial barrier function under hypoxia.Methods The IEC-6 cells of rats were divided into 3 groups:the normoxia group (21％ oxygen concentration),the hypoxia group (2％ oxygen concentration) and the hypoxia + cyclopamine group (cells pretreated by 5 mmol/L of cyclopamine,and then exposed in an atmosphere with 2％ oxygen concentration).The mRNA expressions of IHH,PTCH and GLI-1 were detected,and the transepithelial electrical resistance (TER) was determined.The protein expressions of tight junction proteins (ZO-1,Occludin,Claudin-1) and IHH were assayed by using the Western blot.All data were analyzed using the one-way analysis of variance or LSD-t test.Results The relative mRNA expressions of IHH,PTCH and GLI-1 were 0.056 ± 0.009,0.459 ± 0.087,0.142 ± 0.023 in the normoxia group,and 0.303 ± 0.052,0.678 ± 0.073,0.483 ± 0.061 in the hypoxia group,with significant difference between the 2 groups (t =-14.05,-11.85,-6.52,P ＜ 0.05).The relative protein expressions of IHH in the normoxia group and the hypoxia group were 0.39 ±0.06 and 0.91 ±0.15,with a significant difference between the 2 groups (t =-8.08,P ＜ 0.05).The TERs of the normoxia group,the hypoxia group and the hypoxia + cyclopamine group were (134 ± 5) Ohm/cm3,(100 ± 6) Ohm/cm3 and (118 ± 5) Ohm/cm3,with significant difference between the 3 groups (F =1.04,P ＜ 0.05).Compared with the normoxia group,the TER of the hypoxia group was decreased by 27.7％ (t =7.84,P ＜ 0.05) ; compared with the hypoxia group,the TER of the hypoxia + cyclopamine group were increased by 16.4％,but it was still significantly lower than the normoxia group (t =4.23,P ＜ 0.05).The expressions of ZO-1,Occludin and Claudin-1 were 1.18 ± 0.24,0.80 ±0.13 and 0.90 ±0.09 in the normoxia group,and 0.58 ±0.08,0.32 ±0.05 and 0.50 ±0.09 in the hypoxia group,and 0.92 ± 0.21,0.43 ± 0.10 and 0.82 ± 0.11 in the hypoxia + cyclopamine group,with significant difference between the 3 groups (F =4.95,2.88,10.09,P ＜0.05).The expressions of ZO-1,Occludin and Claudin-1 in hypoxia group were decreased by 48.7％,40.0％ and 55.6％ when compared with the normoxia group (t =12.86,9.35,18.90,P ＜0.05).The expressions of ZO-1,Occludin and Claudin-1 in the hypoxia + cyclopamine group were increased by 59.9％,35.2％ and 65.1％ when compared with the hypoxia group (t =5.63,2.92,6.66,P ＜ 0.05).Conclusion Hedgehog signal pathway could be activated under hypoxia,and then the expressions of tight junction proteins are decreased,which finally induces the injury of intestinal epithelial barrier function. Key words: Hedgehog signal pathway; Cyclopamine; Epithelial barrier function; Transepithelial electrical resistance; Tight junction proteins