Osteoprotegerin:A Prospective Indicator On The Sensitivity Of Glucocorticoid Therapy In Rats Of Severe Ulcerative Colitis

Background:As the morbidity and mortality of severe ulcerative colitis is rising rapidly,its progress is urgent and fast,severe Ulcerative colitis(SUC)has gradually become the focus of clinical.At present the medical profession recognized glucocorticoid as the first-line therapy for SUC,but different patients of glucocorticoid therapy have different clinical drug reaction,we can find parts of them with glucocorticoid resistance.Relevant reports have showed that the total effective rate of Glucocorticoid therapy is about 70%,about 30% of the SUC patients cannot relief,they need to upgrade the drug therapy,even more in need of surgery.With the increasing mortality of SUC,effective treatment is particularly important.We need a reliable standard to predict the sensitivity of glucocorticoids therapy in advance,which can help clinicians to choose effective treatment.Researchers have pointed out that glucocorticoid resistance is related to the increase of glucocorticoid receptor(GR-?)and NF-KB p65.As a kind of receptor proteins,osteoprotegerin can react the lesion degree,position and type of inflammatory bowel disease,and predict the sensitivity of glucocorticoids therapy in child patient with UC.It is expected to become a new indicator to assist in the diagnosis of ulcerative colitis.Objective: We discussed that whether the OPG could predict the sensitivity of glucocorticoids therapy in SUC rats by detecting the serum OPG and the expression of GR-? and NF-KB p65 before and after glucocorticoids treatment.Methods : The 60 male Spragye-Dawley rats(250-280g)were fed separately,rats of 1-40 were in TNBS group,41-50 were in M group while 51-60 were in N group.The rats in TNBS and M group were induced by intracolonic administration of 5% TNBS in 50% ethanol(v/v)which could induce SUC in rats,corresponding doses of 50% ethanol was given using the same method.After making models on the 3rd day,dexamethasone(2mg/kg)were given with administration of interaperitonea injection 10 days.We injected normal saline to the rats of M and N at the same doses.Scored on the Disease Activity Index(DAI)of rats everyday.At 3rd and 13 th day,we took the orbital venous blood to test OPG by ELISA.At 13 th day,we killed all rats,collected the colonic tissue and scored on the colon injury index score(CMDI)and histological score(TDI)of each rat.The rats numbered 1to 40 were subdivided into I and S group based on its score.The expression of GR-? in colon mucosa were determined respectively by RT-PCR while NF-KB p65 were tested by Western Blot.The data of serum OPG on the 3rd day and 13th day were completed by paired t-test.Results:1?Compared with N group,the scores of DAI,CMDI and TDI in other groups increased significantly,there were significant differences between N and other groups.(P<0.05),the highest DAI score?CMDI score?TDIM score were all in the M group.We can see purulent blood,the decrease in the appetite and spirit,the edema and necrosis of different level in colonic mucosal,different levels of structure damage,the infiltration of inflammatory cell and the decrease of intestinal goblet cells in HE,so the colitis model was successfully established.2?ELISA:(“+”is on behalf of the OPG at day 3 while “-”is the OPG at day 13.)The highest OPG was in the “M+” group while the lowest was in N.There was a marked drop in the expression of OPG in “S-” compared with “ S+ ”,their difference was significant(P<0.01);Statistical significance was not found between “I+” and“I-”,“N+” and“N-”(p>0.05).3?RT-PCR: The highest expression of GR-?was in I group while the lowest was in N group.The expression of GR-? in I was much higher than in S group.Statistical significance was not found between N and S group(p > 0.05)while the expression levels between any other two groups,the difference was statistically significant.(P<0.05).4?Western:The highest expression of NF-KB p65 was in M group while the lowest was in N group.The expression of GR-?in I group was much higher than in S group.5?ROC:OPG receiver operator characteristic curve analysis yielded an area under the curve of 0.910 to predict outcome,cutoff point was1542.9360 pg/ml,GR-? receiver operator characteristic curve analysis yielded an area under the curve of 0.944 to predict outcome while NF-KB p65 yielded an area under the curve of 0.891.Conclusions:1 ? Ulcerative colitis induced by TNBS in rats is an ideal method for establishing animal models,this experiment showed that colitis can achieve SUC standards in SD rats by giving TNBS at a dose of 180mg/kg.2 ? This research showed that the GR-? receptors and NF-KB p65 can indirectly predict the sensitivity of glucocorticoids therapy in rats.3?OPG can indirectly predict the sensitivity of glucocorticoids therapy in rats.