奥曲肽调节隐孢子虫感染大鼠空肠生长抑素受体蛋白表达的研究

Octreotide modulates expression of somatostatin receptors in the jejunum at different stages of infection with Cryptosporidium parvumin a neonate rat model

目的观察隐孢子虫感染SD大鼠空肠生长抑素受体SSTRs各亚型蛋白表达水平的变化以及奥曲肽对SSTRs亚型蛋白表达水平的影响。方法取5d龄SD乳鼠每只灌胃0.1ml(2×106个/ml)隐孢子虫卵囊,感染第10~17d腹腔注射奥曲肽50μg/(kg·d),分别在感染14、37、50d取空肠组织,用Western blot检测空肠生长抑素受体亚型SSTR1、SSTR3、SSTR4和SSTR5蛋白的表达。Image Pro Plus 6.0软件测定Western blot条带A值,SSTRs各亚型蛋白相对表达量用目的蛋白与GAPDH蛋白比值表示。结果隐孢子虫感染组感染后第14、37d及50d,空肠SSTR1蛋白水平分别为0.107 8±0.006 4、0.087 9±0.007 1和0.1068±0.005 8,与非感染组比较,均显著降低(P<0.01或P<0.05);SSTR3蛋白在感染后14d、37d升高(P<0.01或P<0.05),分别为0.411 3±0.027 4和0.544 2±0.013 2;感染后50d下降(P<0.01),由0.321 1±0.017 3下降为0.052 5±0.004 7;SSTR4和SSTR5蛋白水平升高(P<0.01),分别为1.144 5±0.021 9和1.313 9±0.033 2。与感染组比较,奥曲肽治疗组空肠SSTR1蛋白表达水平显著升高(P<0.01),SSTR3蛋白水平在感染14d后下降(P<0.01),由0.411 3±0.027 4下降为0.168 1±0.006 1,在感染后37d、50d显著升高,分别为1.219 6±0.051 0和1.194 3±0.086 4。奥曲肽治疗组SSTR4和SSTR5蛋白表达水平下降(P<0.01)。结论隐孢子虫感染致大鼠空肠生长抑素受体SSTRs亚型蛋白表达水平发生显著变化,奥曲肽治疗能逆转这一变化。提示SSTRs参与肠道慢性炎症过程,奥曲肽可能通过影响SSTRs表达发挥肠道免疫调节和抗炎作用。

Objectives To observe changes in somatostatin receptor（SSTR）subtypes in the jejunum of SD rats infected with Cryptosporidium parvum and the effects of octreotide on expression of the subtypes. Methods Five-day old rat pups were gavaged with 0.1 ml（2×10^6/ml）of C.parvum oocysts while control rats were gavaged with 0.1 ml of PBS alone.From day 10 to day 17 post-infection,rats were intraperitoneally injected with octreotide at a dose of 50μg/（kg·day）.Western blotting was performed to analyze expression of SSTR1,SSTR3,SSTR4,and SSTR5 in the jejunum on day 14,37,and 50 post-infection.In Western blotting,absorption bands were analyzed using the software Image Pro Plus 6.0.The relative expression of SSTR subtypes was expressed as the ratio of the target protein to GAPDH.Results Expression of SSTR1 protein in the jejunum was 0.107 8±0.006 4 on day 14 post-infection,0.087 9±0.007 1 on day 37,and 0.106 8±0.005 on day 50.The level of SSTR1 expression decreased markedly（P0.01）in comparison to the level in uninfected rats.Expression of SSTR3 protein increased on day 14 and 37 post-infection（P0.01 and P0.05）.Expression of SSTR3 protein was 0.411 3±0.027 4 on day 14 post-infection and 0.544 2±0.013 2 on day 37.Expression of SSTR3 decreased from 0.321 1±0.017 3 to 0.052 5±0.004 7 on day 50 post-infection（P0.01）.Expression of SSTR4 protein and SSTR5 protein increased（P0.01,1.144 5±0.021 9 for the former,1.313 9±0.033 2 for the latter）.Octreotide treatment markedly increased the level of SSTR1 protein in the jejunum（P0.01）in comparison to the level in infected rats.On day 14 post-infection,expression of SSTR3 protein decreased from 0.411 3±0.027 4to 0.168 1±0.006 1（P0.01）.Expression of SSTR3 protein increased markedly day 37 and 50 post-infection（1.219 6±0.051 0 for the former,1.194 3±0.086 4 for the latter）.Octreotide treatment decreased the level of SSTR4 and SSTR5 protein expression（P0.01）. Conclusion The level of expression of SSTRs changed in the jejunum of rats infected with C.parvum,and octreotide treatment reversed that change.The results indicate that SSTRs are involved in chronic intestinal inflammation and that octreotide may modulate intestinal immunity and relieve inflammation by affecting the expression of SSTR proteins.