[Role of peroxisome proliferators-activated receptor-gamma in the chemical prevention therapy of sulindac for precancerous lesions of rats].

Objective: To understand whether peroxisome proliferators-activated receptor-gamma (PPAR-gamma) plays an important role in the chemopreventive effect of sulindac on precancerous lesions (aberrant crypt foci, ACF) of rats.

Methods: Male Sprague-Dawley rats were used in this study and raised in Special Pathogen Free room. Sulindac was the main research object. Carcinogenic agent, 1, 2-dimethylhydrazine (DMH), was used to induce colonic precancerous lesions. Pioglitazone was chosen as agonist of PPAR-gamma and GW9662 used as a specific complete antagonist of PPAR-gamma. ACFs were induced according to the protocol certified in prior experiments. There were 7 groups, named as Negative control group, DMH group, Sulindac group, Sulindac+GW9662 group, Pioglitazone group, Pioglitazone+GW9662 group and GW9662 group. The experiment period was 12 weeks. At the end of the experiment, all rats were sacrificed by euthanasia. Half of the colon including the rectum was taken and immersed in formalin at 4 degrees Celsius overnight, and then recorded the number and size of ACF with the help of anatomic microscope stained by methylene blue.

Results: (1) Sulindac and agonist of PPAR-gamma could significantly inhibit DMH-induced ACFs of rats from 137.8+/-59.4 to 73.9+/-32.1 and 96.4+/-32.6 with a decrease of 45.7% (P<0.01) and 30.0%(P<0.05) compared with DMH group. Antagonist of PPAR-gamma could counteract the chemopreventive effect of sulindac with an increase from 73.9+/-32.1 to 106.3+/-33.9; (2) The expression of PPAR-gamma in colorectal mucosa increased significantly during the DMH induction period compared with negative control group, the relative values of gray were 0.304+/-0.288 and 2.292+/-1.380 (P<0.01), sulindac and pioglitazone could decrease the expression of PPAR-gamma remarkably compared with DMH group, the relative values of gray were 1.023+/-1.115 and 0.352+/-0.187 (P<0.01), and the application of GW9662, antagonist of PPAR-gamma could promote the expression of PPAR-gamma in some degree, and the relative values of gray were 1.279+/-0.303 and 0.998+/-0.295 (P>0.05).

Conclusion: The expression of PPAR-gamma had risen in DMH-induced ACFs of rats significantly. Sulindac and agonist of PPAR-Gamma (pioglitazone) could inhibit the formation of ACF, and followed by a decrease of PPAR-gamma. Antagonist of PPAR-gamma could interfere with the effect of sulindac. PPAR-gamma might play an important role in the chemopreventive effect of sulindac on colorectal pre-cancerous lesions of rats and activation of PPAR-gamma pathway could inhibit the initiation and evolvement of ACF induced by DMH.