过氧化物酶增殖物激活受体-γ在舒林酸干预治疗大鼠结直肠癌前病变中的作用

Role of peroxisome proliferators-activated receptor-γ in the chemical prevention therapy of sulindac for precancerous lesions of rats

目的:明确过氧化物酶增殖物激活受体-γ(peroxisome proliferators-activated receptor-γ,PPAR-γ)在舒林酸干预治疗大鼠结直肠癌前病变——异型隐窝灶(aberrant crypt foci,ACF)中的作用。方法:选用SPF级SD雄性大鼠64只,观察药物为舒林酸,结直肠肿瘤诱导剂为二甲肼(1,2-dimethylhydrazine,DMH),PPAR-γ激动剂选用吡格列酮,PPAR-γ拮抗剂为GW9662,进行ACF模型诱导。实验共分7组,分别为阴性对照组、DMH组、舒林酸组、舒林酸+GW9662组、吡格列酮组、吡格列酮+GW9662组和GW9662组,其中DMH组10只,余每组9只。阴性对照组不进行任何干预用药,其他各组均用DMH进行ACF诱导,观察12周。结果:(1)舒林酸与PPAR-γ激动剂均可显著抑制DMH诱导的大鼠ACF,从(137.8±59.4)个降低到(73.9±32.1)个和(96.4±32.6)个,分别减少了45.7%和30.0%,P<0.01和P<0.05;PPAR-γ拮抗剂可拮抗舒林酸的这一作用,ACF由(73.9±32.1)个上升至(106.3±33.9)个,P>0.05;(2)在DMH诱导肿瘤的过程中,结直肠黏膜PPAR-γ表达量较正常显著升高,相对灰度值分别为(0.304±0.288)和(2.292±1.380),P<0.01;而舒林酸和吡格列酮则可显著降低PPAR-γ的表达,相对灰度值分别为(1.023±1.115)和(0.352±0.187),与DMH组相比,P<0.01,应用PPAR-γ拮抗剂GW9662后PPAR-γ表达量又有所升高,相对灰度值分别为(1.279±0.303)和(0.998±0.295),与阴性对照组相比,P>0.05。结论:PPAR-γ在DMH诱导的大鼠结直肠ACF中出现异常高表达;舒林酸和PPAR-γ激动剂(吡格列酮)可抑制ACF的形成,同时PPAR-γ的表达量也随之下降,PPAR-γ拮抗剂可拮抗舒林酸的这一作用。由此推测PPAR-γ在舒林酸干预治疗大鼠ACF中发挥着重要作用,激活PPAR-γ可抑制DMH诱导的大鼠癌前病变ACF的产生。

Objective：To understand whether peroxisome proliferators-activated receptor-γ （PPAR-γ） plays an important role in the chemopreventive effect of sulindac on precancerous lesions （aberrant crypt loci, 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- γ and GW9662 used as a specific complete antagonist of PPAR-γ. 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℃ 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-γ 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% （P 〈0.05） compared with DMH group. Antagonist of PPAR-γ could counteract the chemopreventive effect of sulindae with an increase from 73.9 ± 32. 1 to 106.3 ± 33.9 ; （ 2 ） The expression of PPAR-γ 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-γ 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-γ/could promote the expression of PPAR-γ/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-γ had risen in DMH-induced ACFs of rats signifieantly. Sulindae and agonist of PPAR-γ （pioglitazone） could inhibit the formation of ACF, and followed by a decrease of PPAR-γ. Antagonist of PPAR-γ could interfere with the effect of sulindac. PPAR-γ might play an important role in the chemopreventive effect of sulindac on colorectal pre-caneerous lesions of rats and activation of PPAR-γ , pathway could inhibit the initiation and evolvement of ACF induced by DMH.