背景：肺纤维化是一组由多种病因引起的间质性肺疾病，是许多慢性肺病的共同结局。其病理特点包括肺泡上皮损伤、肺成纤维细胞积聚以及细胞外基质的过度沉积，最终导致不可逆性损伤。成纤维细胞是肺纤维化发生、发展中的重要效应细胞。受到各种因素刺激后，成纤维细胞被激活发生迁移、大量增殖和向肌成纤维细胞表型转化，并促进合成细胞外基质，导致肺纤维化。过氧化物酶体增殖物激活受体γ(peroxisome proliferator-activated receptor γ，PPARγ)是一类依赖配体激活的转录因子，属于核激素受体超家族成员。早期研究认为，PPARγ的功能主要是调节脂肪细胞分化和糖脂代谢，现在证实也具有抗炎和免疫调节的效应，参与急性肺损伤、慢性阻塞性肺病和哮喘等肺部疾病发病的调节。但PPARγ在肺纤维化发病中的作用和机制目前尚不清楚。 目的：临床实验观察PPARγ在肺纤维化患者肺组织中的表达；体外实验观察PPARγ激动剂对人胚肺成纤维细胞迁移、增殖和表型转化的影响。旨在探讨PPARγ在肺纤维化发病中的作用和机制。 方法：(1)采用免疫组织化学法检测16例肺纤维化患者与10例正常对照肺组织标本中PPARγ、NF-κB的表达情况。(2)用PPARγ特异性激动剂罗格列酮(rosiglitazone，RSG)干预体外培养的人胚肺成纤维细胞(MRC-5)。应用划痕法测定细胞迁移能力，应用噻唑蓝(MTT)比色法、免疫细胞化学法和流式细胞术观察细胞增殖情况，应用免疫印迹(Western Blot)法分析细胞蛋白表达。 结果：(1)肺纤维化组PPARγ阳性计数低于正常对照组，NF-κB阳性计数高于正常对照组(P＜0.05)。纤维化组PPARγ和NF-κB表达成负相关(P＜0.05)。PPARγ和NF-κB表达在寻常性间质性肺炎和非特异性间质性肺炎组间差异无统计学意义(P＞0.05)。(2)罗格列酮孵育对基础状态下肺成纤维细胞的迁移、增殖和α-SMA表达均无明显影响(P＞0.05)。但罗格列酮(10～20umol/l)处理延迟10%胎牛血清(FBS)和20ng/ml碱性成纤维细胞生长因子(bFGF)刺激的细胞迁移，抑制10%FBS和20ng/ml血小板源性生长因子-BB(PDGF-BB)诱导的细胞增殖，减少10ng/ml转化生长因子-β1(TGF-β1)诱导的细胞α-SMA表达(P<0.05)。FBS、 PDGF-BB和TGF-β1可以刺激细胞p-ERK/ERK表达增加，罗格列酮预孵育则减弱血清和细胞因子诱导的p-ERK/ERK增加(P＜0.05)。 结论：纤维化肺组织PPARγ表达下调；PPARγ激动剂罗格列酮干预肺成纤维细胞，能够抑制血清和细胞因子刺激的细胞迁移、增殖及向肌成纤维细胞表型转化，抑制ERK〓磷酸化是罗格列酮发挥上述作用的途径之一。PPARγ通路参与肺纤维化的发病过程，激活PPARγ对肺纤维化有保护作用，为防治肺纤维化提供新思路。 【关键词】肺纤维化；过氧化物酶体增殖物激活受体(PPAR)；罗格列酮；人胚肺成纤维细胞

 Backgroud: Pulmonary fibrosis is the final common pathway of a diverse group of lung disorders known as a devastating disease. It's characterized by epithelial injury, the formation of distinctive fibroblast/myofibroblast foci, and excessive deposition of extracellular matrix accumulation. The fibroblast is now recognized as the key effector cell in the development of fibrosis. Some chemokines/cytokines may initiate fibroblast migration to the site of injury and promote their proliferation and differentiation into myofibroblasts, which modulates extracellular matrix production. Peroxisome proliferator-activated receptor γ (PPARγ) is a class of ligand-dependent transcription factor belonging to the nuclear hormone receptor superfamily. The actions of PPARγ were originally thought to be limited to the control of lipid and glucose metabolism. However, recent studies have shown that activation of PPARγ is associated with anti-inflammatory and immunomodulatory effects. The PPARγ pathway is involved in the pathogenesis of lung diseases such as acute lung injury, chronic obstructive pulmonary disease and asthma, et al. But to date, the role and mechanism of PPARγ in the pathogenesis of pulmonary fibrosis has not been clarified. Objective: The present study was undertaken to evaluate the expression of PPARγ on lungs in patients with pulmonary fibrosis in clinical study, and to investigate the effects of PPARγ ligand on migration, proliferation and phenotypic differentiation of human lung fibroblasts in vitro study. We aimed to explore the role and mechanism of PPARγ in the pathogenesis of pulmonary fibrosis. Methods: (1) Immunohistochemical technology was performed to investigate the PPARγ and NF-κB expression in lung specimens from 16 cases of pulmonary fibrosis and 10 cases of normal controls. (2) Human lung fibroblasts(MRC-5) were incubated with specific PPARγ agonist, rosiglitazone, in vitro.The cell migration potential was observed in a scratch wound model. Cell proliferation was determined by the MTT method, immunocytochemical staining and flow cytometry, and protein expression by western blot analysis. Results: (1) The positive score of PPARγ in fibrosis group was lower than that in control group (P＜0.05). The positive score of NF-κB in fibrosis group was higher than that in control group (P＜0.05). There was negative correlation between PPARγ and NF-κB expression in fibrosis group(P＜0.05). There was no significance of PPARγ and NF-κB expression between usual interstitial pneumonia and nonspecific interstitial pneumonia(P＞0.05). (2) Rosiglitazone alone had no significant effect on cell migration, proliferation and α-SMA expression as compared with control cells (P＞0.05). Rosiglitazone incubation slowed cell migration distance induced by 10% fetal bovine serum (FBS) and 20ng/ml basic fibroblast growth factor (bFGF), decreased cell proliferation initiated by 10% FBS and 20ng/ml platelet-derived growth factor-BB (PDGF-BB), and decreased α-SMA protein expression induced by 10ng/ml transforming growth factor-β1 (TGF-β1) (P＜0.05). In addition, rosiglitazone incubation reduced the ratio of p-ERK to ERK expression stimulated by FBS, PDGF-BB and TGF-β1(P＜0.05). Conclusion: The PPARγ expression decreased on lungs in pulmonary fibrosis. Pretreatment with specific PPARγ agonist, rosiglitazone, inhibited lung fibroblast migration, proliferation and myofibroblast transdifferentiation stimulated by FBS and growth factors in vitro, which may be achieved through decreasing ERK〓 phosphorylation. These findings suggests that PPARγ pathway is involved in the pathogenesis of pulmonary fibrosis, and PPARγ agonists could antagonize pulmonary fibrosis, which may provide a new idea for treating this disease. [Key words]: Pulmonary fibrosis; Peroxisome proliferator-activated receptor γ; Rosiglitazone; Human lung fibroblasts