Research On Pathogenesis And The Mechanism Of Steroid Resistance In Ulcerative Colitis Patients

AIMS:1. To study the role of food allergy in the pathogenesis of ulcerative colitis.2. To examine the expression of P-glycoprotein and MDR1-mRNA in ulcerative colitis patients before and after steroid therapy. We want to illustrate the mechanism of steroid resistance in UC patients through this experiment.METHODS:1. We selected 121 ulcerative colitis (UC) patients and 47 health controls as study subjects. The serum food specific IgG & IgE of UC patients and health controls were detected by ELISA (enzyme-linked immuno sorbent assay) kits. The patients who appeared positive in food sIgG tests were randomly divided into Diet-control group and Non Diet-control group. The patients in Diet-control group were eliminated allergic food from their daily diet, while the Non Diet-control group patients were not given any dietary intervention. The patients in two groups were treated with prednisone (1mg/kg/d) and 5-amino salicylic acid. All the patients were followed-up 2 months after therapy.2. The ulcerative colitis patients accepted colonscopy and bowel mucosa biopsy before and two months after prednisone treatment. All the patients' P-glycoprotein expression in bowel mucosa biopsy samples were examined using immunohistochemistry stain technique. RT-PCR was adopted to examine the mRNA expression of MDR1 gene in UC patients.We used Leica QwinV3 system to analyze the PCR band and calculated the ratio of MDR1 gray value with (32-MG gray value.The ratio of MDRl/(32-MG can stand for the level of MDR1 mRNA expression. We compared the expression level of MDRl-mRNA and P-glycoprotein in patients before treatment with 2 months after prednisone treatment. We also compared the expression level of MDRl-mRNA and P-glycoprotein in prednisone sensitive patients with prednisone resistance patients two months after treatment.RESULTS:1.The inspection results of serum food specific IgG & IgE and the impact of allergic food elimination on the curative effect.There were 79 UC patients appeared positive in food specific IgG tests; and the positive rate was 65.29%(79 positive patients in 121 patients).There were only 8 people appeared positive in food specific IgG tests in health control group; and the positive rate was 17.02%(8/47). The difference of positive rate between UC patients and health controls had statistical significance (P< 0.01).There were 19 UC patients appeared positive in one kind of food specific IgG; and 31 UC patients appeared positive in two kinds of food specific IgG. There were 29 UC patients appeared positive in three and more than three kinds of food specific IgG. In a word, there were 49.59% of UC patients appeared positive in two and more than two kinds of food specific IgG simultaneously. There were 49 UC patients appeared positive in food specific IgE tests; and the positive rate was 40.50%(49 positive patients in 121 patients).There were only 2 people appeared positive in food specific IgE tests in health control group.The effective rate of Diet-control group was higher than Non Diet-control group two months after prednisone treatment.2. Immunohistochemistry stain results:The positive expression rate of P-glycoprotein(P-gp) in all 121 UC patients was 8.26%(10/121)before prednisone treatment; while the positive expression rate of P-glycoprotein in health controls group was 43.33% (13/30). The positive expression rate of P-glycoprotein in UC patients before prednisone treatment was obviously inferior to health controls (P<0.05). The positive expression rate of P-gp in UC patients was 35.54%(43/121) eight weeks after prednisone treatment, which was higher than UC patients before prednisone treatment (P<0.05).The 121 UC patients were divided into prednisone sensitive patients (n=85) and prednisone resistance patients (n=36) accoding to their response to the two-months'treatment. The positive expression rate of P-gp in prednisone sensitive patients was 17.65%(15/85),which was lower than prednisone resistance patients (77.78%).The positive expression rate of P-gp in prednisone resistance patients was higher than that in prednisone sensitive patients (P<0.05)3.RT-PCR results:The expression level of MDR1-mRNA in UC patients was 0.12±0.03 before prednisone treatment; while the MDR1-mRNA level was 0.68±0.06 in health controls group. The expression of MDR1-mRNA in health controls was higher than that in initially treated UC patients before prednisone treatment (P< 0.05). The average expression level of MDR1-mRNA in UC patients was 0.57±0.04 eight weeks after prednisone treatment. So the average expression level of MDR1-mRNA in patients after eight weeks'treatment was higher than that in patients before treatment (P<0.05). After eight weeks'treatment, the expression level of MDR1-mRNA in prednisone sensitive patients was 0.46±0.05, which was 0.89±0.03 in prednisone resistance patients.The MDRl-mRNA expression in prednisone resistance patients was higher than that in prednisone sensitive patients (P<0.05) CONCLUSIONS:We can enhanced the curative effect of UC patients through eliminated the allergic food from patients'diet. Food allergy may play a role in the pathogenesis of ulcerative colitis. The low expression of P-gp in UC patients may also play a role in the pathogenesis of ulcerative colitis. The expression of P-gp and MDRl-mRNA in UC patients rised after steroid treament. The high expression of P-gp and MDRl-mRNA in UC patients is one of the reasons which cause the steroid resistance during treatment.