Effect And Mechanism Of Total Glucosides Of Paeony On Experimental Colitis

Background: The cause and the nature of inflammation of inflammatory bowel disease (IBD) are not clear, it is probably related with a variety of factors and the immunity is one of the research hotspots of IBD currently. Because of the disordered immune regulation, pro-inflammatory cytokines interact synergy, resulting in the continued development of inflammation has played an important role in the pathogenesis of IBD. Mitogen-activated protein kinases (MAPK) family is a group of important protein kinases, studies have shown that, p38 MAPK signal transduction pathway play a pivotal role in a variety of pro-inflammatory cytokine production and activation, p38αMAPK is main subtype which involved in immune and inflammatory responses. Total glucosides of paeony(TGP) are active ingredients extracted from traditional Chinese medicine paeony, which the main ingredients are Paeoniflorin (PF). Study shows that, TGP has certain immunomodulatory and inhibiting inflammation function, but whether it has the therapeutical effect on inflammatory bowel disease is unclear.Objective:(1) To observe effects of TGP on TNBS-induced experimental colitis in rats, to analyse whether TGP have therapeutic effects on experimental colitis. (2) To observe the changes of p38MAPK, p-p38MAPK, IL-10 and TNF-αin experimental colitis in rats and analyse the relationships between these changes and pathogenesy of experimental colitis. (3) To analyse the relationship between the effects of TGP on the experimental colitis and the results of the laboratory, and then to further investigate the pharmacological mechanisms of TGP.Method: Colitis model was induced in fifty rats by rectal administration of trinitrobenzenesulfonic acid (TNBS) resolved in ethanol. Thirty model rats were treated with 25, 50 and 100 mg/kg TGP, respectively, while 10 were treated with 100 mg/kg olsalazine as drug controls. Ten rats received 0.9% NaCl solution were served as normal controls. Disease activity index (DAI) was evaluated during the intervention. After 2-week intervention, the colonic macroscopic damage index (CMDI) and tissue damage index (TDI) were evaluated, the serum levels of tumor necrosis factor-α(TNF-α) and interleukin-10 (IL-10) were determined by enzyme-linked immunosorbent assay (ELISA), and the colonic expressions of p38 mitogen-activated protein kinase (p38MAPK) and phosphorylated p38 mitogen-activated protein kinase (p-p38MAPK) was determined by immunohistochemical method.Results: Compared with normal control group , the DAI during the intervention ( 0.07±0.02 vs 2.20±0.72,t=8.422, P<0.01 ) , the CMDI ( 0.30±0.48 vs 5.63±1.41,t=10.227,P<0.01)and TDI(0.20±0.42 vs 7.63±1.69,t=12.163,P<0.01), the serum level of TNF-α(32.09±3.46 pg/ml vs 72.35±3.11 pg/ml,t=25.619,P<0.01), as well as the colonic expressions of p38MAPK ( 11502.04±1619.55 vs 13475.02±1590.38,t=2.589 , P<0.05 ) and p-p38MAPK ( 4029.75±1656.95 vs 16014.51±1753.68,t=14.863,P<0.01) was markedly increased, while the serum level of IL-10(40.36±6.14 pg/ml vs 27.90±5.04 pg/ml,t=4.622,P<0.01) was significantly decreased. Compared with colitis model group, the DAI during the intervention(2.20±0.72 vs 1.05±0.57,t=3.776,P<0.01) and the colonic expressions of p38MAPK(13475.02±1590.38 vs 11516.11±1783.15,t=2.427,P<0.05) in high dose TGP group decreased significantly; the CMDI(5.63±1.41 vs 2.10±1.20, t=5.745,P<0.01;5.63±1.41 vs 1.10±0.99,t=7.996,P<0.01) and TDI(7.63±1.69 vs 4.50±1.35,t=4.369,P<0.01;7.63±1.69 vs 1.30±1.16,t=9.432,P<0.01), as well as the serum level of TNF-α(72.35±3.11pg/ml vs 53.28±4.03 pg/ml,t=11.001,P<0.01;72.35±3.11pg/ml vs 37.02±4.72pg/ml,t=18.207,P<0.01) and the colonic expressions of p-p38MAPK(16014.51±1753.68 vs 13171.44±2329.48,t=2.858,P<0.05;16014.51±1753.68 vs 11887.81±1990.94,t=4.601,P<0.01) in moderate and high dose TGP groups were significantly decreased, while the serum level of IL-10 was markedly increased (27.90±5.04pg/ml vs 33.23±5.27pg/ml , t=-2.172 , P<0.05 ; 27.90±5.04pg/ml vs 36.87±4.04pg/ml,t=-4.198,P<0.01)). The DAI, CMDI and TDI are positive correlated with the serum level of tumor necrosis factor-α(r=0.803,P<0.01;r=0.925,P<0.01;r=0.954,P<0.01) and the colonic expressions of p38MAPK (r=0.706,P<0.01;r=0.667,P<0.01;r=0.663,P<0.01)and p-p38MAPK(r=0.864,P<0.01;r=0.731,P<0.01;r=0.767,P<0.01), while the serum levels of IL-10 are negative correlated(r=-0.729,P<0.01;r=-0.691,P<0.01;r=-0.714,P<0.01), the colonic expressions of p38MAPK and p-p38MAPK are positive correlated with the serum levels of tumor necrosis factor-α(r=0.558,P<0.01;r=0.766,P<0.01)and negative correlated with the serum levels of IL-10(r=-0.523,P<0.01;r=-0.651,P<0.01). No statistically difference was observed between the therapeutic effect of high dose TGP group and olsalazine group.Conclusion: The expression and activation of p38MAPK are increased in TNBS-induced colitis of rats, and participated in the pathogenesis of experimental colitis. The mechanism may be related to promotion synthesis of pro-inflammatory factor, inhibiting synthesis of anti-inflammatory factor, resulting in pro- and anti-inflammatory cytokines imbalance, aggravated the immunoregulation disorders and protracted inflammation conditions. TGP can significantly attenuate the symptoms and colonic inflammatory damage in TNBS-induced experimental colitis in rats. The mechanism may be related to the recovery of immunoregulation via inhibition of p38MAPK activation and subsequently proinflammatory factor down-regulation and antiinflammatory factor up-regulation.