Expression of c-FLIP and caspase-8 during the formation of canine benign biliary strictures after bile duct injury

AIM:To investigate the expression and localization of apoptosis-regulatory protein cellular FLICE-like inhibitory protein (cFLIP) and its downstream apoptotic factor caspase-8 in the formation of benign biliary strictures after bile duct injury.METHODS:An animal model of benign biliary strictures was established in dogs by inducing bile duct injury.Tissue specimens were taken from the anastomotic sites created in 15 model dogs (experimental group) and 15 matched sham-operated dogs (control group) at 2,3,4,5 and 6 months after injury induction.The expression and localization of c-FLIP and caspase-8 proteins in these specimens was detected by immunohistochemistry using the streptavidinbiotin complex (SABC) method.The average optical density for each slice was then calculated,and the differential expression of c-FLIP and caspase-8 proteins at different time points was compared between the two groups.RESULTS:Strong positive expression of c-FLIP protein was found in anastomotic tissue in the experimental group at all time points,mainly distributed in the cytoplasm of fibroblasts.Significant differences were noted in the expression levels of c-FLIP protein between the experimental group and the control group at all time points (22.33 ± 3.40 vs 3.41 ± 0.69,21.01 ± 5.43 vs 3.28 ± 0.95,18.93 ± 2.54 vs 3.11 ± 1.01,18.88 ± 3.40 vs 3.35 ± 0.74,and 17.23 ± 3.53 vs 3.19 ± 0.91,respectively;all P 0.05),but not among different time points in either of the two groups (all P 0.05).Weak expression of caspase-8 was observed in anastomotic tissue in the experimental group at all time points,mainly concentrated in glandular epithelium and less localized in stromal tissue,Significant differences were also noted in the expression levels of caspase-8 between the experimental group and the control group at all time points (3.20 ± 0.86 vs 11.66 ± 2.80,3.42 ± 1.17 vs 10.16 ± 3.08,3.65 ± 0.90 vs 10.03 ± 1.93,3.91 ± 0.71 vs 10.90 ± 4.02,and 4.01 ± 0.88 vs 11.23 ± 2.73,respectively;all P 0.05) but not among different time points in either of the two groups (all P 0.05).A negative correlation was noted between the expression of c-FLIP and caspase-8 (r=-0.94,P 0.05).CONCLUSION:cFLIP may exert anti-apoptotic effects during the formation of benign biliary stricture by down-regulating the expression of caspase-8.