Investigation Of Smad Expression In Ulcerative Colitis

Objectives:To observe the expression of Smad7, total Smad3/Smad2 and active Smad3/Smad2(phosphorylated P-Smad3/2) in oxazolone induced colitis of mice and find out the mechanism of the abnormality of Smad on pathogenesis of colitis. Investigation the expression of Smad7 and IκB a on colonic mucosa of Ulcerative Colitis (UC) and the relationship between them were studied for illuminating overexpression of I-Smad on disturbance of intestinal mucosa immunology.Materials and Methods:Induction of colitis: BALB/c mice were presensitized by skin painting with 0.2ml 3% oxazolone in 100% ethanol on 0 and 1 folowed by intrarectal administration of 0.15ml l%oxazolone in 50% ethanol on day 7. The mice were sacrificed after 2-3 days. Colitis was evaluated by macroscopic and microscopic score; the quantity of Smad7,total Smad3/Smad2 and phosphorylated Smad3/Smad2 were examined by Western blot (WB). All the results were compared with the controls.Colonic biopsy specimens were collected from active UC and normal controls.The expression of Smad7 and I k B a were analyzed by immunohistochemistry(IHC).Results:Western blot: the amounts of Smad7, Smad3/P-Smad3 and Smad2/P-Smad2 expression in experimental and control group were 23.17 + 8.07,9.58 + 5.74,7.74+1.51,13.78 + 6.7,7.90 + 2.88 and 5.70±2.86,10.23± 2.13,14.7 + 3.16,13.9 ± 5.6,10.04 + 2.72 respectively. There were no difference of total Smad3^ Smad2 and P-Smad2 between two groups (P>0.05 respectively), but significant difference of Smad7 and P-Smad3 between two groups(P<0.01 respectively), overexpression of Smad7 and decreased active Smad3(P-Smad3) were shown in oxazolone induced colitis.Immunohistochemistry observation: A significant increase of Smad7 antigen expression in colonic mucosa of UC compared with normal colonic mucosa(P<0.001), while the expression of kB a increase in normal colonic mucosa compared with colonic mucosa of UC.The expression of Smad7 is negatively related to the expression of kB a in colonic mucosa of UC.Conclusions:Overpression of Smad7 and reduced phosphorylation of Smad3 is associated with defective TGF-Bl signaling and compromises the ability of TGF-61 to downregulate immune responses in inflamed intestinal mucosa.of oxazolone induced colitis.The inhibitory Smad7 is also increased and negatively related to kB a in colonic mucosa of UC.So the defection of TGF-61 suppressing NF- k B activation.which play important in thepathogenesis of UC, due to overpression of inhibitory Smad7. These observations suggest that, despite enhanced TGF-61 production, defective TGF-61/Smad signaling contributes to maintaining the chronic inflammatory state in UC.