Therapeutic Effects Of Selective COX-2 Inhibitor PC407 On TNBS Induced Ulcerative Colitis In Rats

Background:Ulcerative Colitis has been classified by WHO as refractoriness in modern times, and it is always a popular study field to investigate its etiopathogenisis and medication. Recent researches concludes that multiple factors contributing to UC, including heredity, environment, diet and psychological state, might trigger a continual chronic immunologic process, in which neurophil, macrophage, T&B leukocytes are involved. The adhesion molecules, antibodies, inflammatory mediators and cytokines, mediate or cause histoclasia and inflammation. Aminosaicylic acids drugs are extensively used for UC treatment in clinic and their non-selective inhibition of COX leads to severe side effects. Based on recent studies of UC pathogen and safty evaluation of drugs for UC treatment, selective COX-2 inhibitor steps into the treatment for experimental UC. However, reports about selecive COX-2 inhibitors on market for experimental UC treatment showed unpleasant inconsistency, and the researches intending to investigate the mechanism lied behind this phenomenon are confined in the prostaglandins products of COX downstream and their protective function. The possible interaction between COX and UC related adhesion molecule receptors showed unlimited investigatory potential.This study was aimed to study the therapeutic effects of PC407, [4-[5-nap- hthyl-3-(trifluoromethyl)]-1H-pyrazol-1-yl]benzenesulfonamide], a new selective COX-2 inhibitor on TNBS-induced colitis in rats and evaluate its feasibility and efficacy. We also discuss the change in expression of UC related adhesion molecule receptor galectin-3 and cytokine TNF-αafter COX-2 inhibition, with the purpose of elucidating the healing mechanism of PC407 for UC rats. This would probably provide rationale for future UC treatment by selective COX-2 inhibitors.Methods:(1) the target compound was synthesized as reported and the chemical structure was determined by MS and 1HNMS; (2) Rat colitis model was induced by TNBS and 40% ethanol. 60 male rats were randomly divided into 5 groups, normal group, model group, Celecoxib group(17.6mg·kg^-1) and PC407 group(9.6,19.2,38.4 mg·kg^-1); Celecoxib and PC407 were administraterd intragastricly once per day for 6 days ; (3) death, body weight and the loose stool situation were recorded everyday; dead rat was sectionded immediately after observed; on the 7th day all rats were anesthetized to death to collect macrophages in abdominal cavity for in vitro culture; colon, thymus gland and spleen were separated; macroscopical and pathological changes of the colon were observed and studied by Hematoxylin-Eosin staining; the therapeutic effect of treatment groups was evaluated by loose stool rate, colon index, ulcer rate, thymus index and spleen index; the expression and distribution of COX-2, galectin-3, TNF-αin mucosa were examined by immunohistochemistry and western-blotting; the TNF-αsecretion of macrphages were examined by Enzyme linked immunosorbent essay.Results:(1) PC407 was sufficiently synthesized; the structure was confirmed by MS and 1HNMR, and consisted with that of the target molecule. (2) The model of ulcerative colitis was successfully induced by introcolonic TNBS and 40% ethanol. Mucosa defects, penetrating into submucosa area could be seen with infiltrations of inflammatory cells, mainly neutrophils and lymphocytes; Tissue damage could also be clearly observed. (3) Compared with model group, PC407 (9.6 mg·kg^-1)could significantly ameliorate the lession and pathological change in colon caused by TNBS, it could decrease colon index and ulcer rate, also prevent body weight drop and loose stool rate increasing; the activity of COX-2 was inhibited and the expression of TNF-αand galectin-3 in mocusa were lower and higher than model group, respectively; the TNF-αsecretion of macrphages in rat's abdominal cavity was inhibited; Celecoxb (17.6 mg·kg^-1) showed equivalent therapeutic effects to PC407 (9.6 mg·kg^-1); PC407 (19.2,38.4 mg·kg^-1) could significantly decrease the severity of lesion and inflammation; it could decrease colon index and ulcer rate, also prevent body weight dropand loose stool rate increasing; it could reverse the atrophy of thymus gland and intumescence of spleen; furthermore, it could significantly inhibit COX-2 activity, decrease TNF-αexpression and increase galectin-3 expression in mocusa compared to model group; the TNF-αsecretion of macrphages in rat's abdominal cavity was significantly decreased; PC407 group (38.4 mg·kg^-1) showed equivalent therapeutic effects campared to PC407 group (19.2 mg·kg^-1). Conclusion:PC407 has significant therapeutic effects on TNBS/ethanol induced colitis in rats. PC407 group (9.6 mg·kg^-1) and Celecoxb group (17.6 mg·kg^-1) showed equivalent therapeutic effects; PC407 group (19.2 mg·kg^-1) and PC407 group (38.4 mg·kg^-1) showed apparently better therapeutic effects, though the latter 2 groups showed no statistical variance when compared. In general, the mechanism of inflammatory remission may relate to the down regulation of TNF-αexpression and up regulation of galectin-3 after inhibition of COX-2 activity in UC rats'mocusa, as well as decreasing TNF-αsecretion by macrophages in UC rats'abdominal cavity; it is quite possible that PC407 group (38.4 mg·kg^-1) showed equivalent therapeutic effects campared to PC407 group (19.2 mg·kg^-1) because over inhibition of COX-2 activity leads to impaired protective effect of PG, which probably failed to result in any statistically meaningful difference in the regulatory levels of all index tested above.