Jeon Kye-Im, Kulkarni Ajit, Woeller Collynn F, Phipps Richard P, Sime Patricia J, Hindman Holly B, Huxlin Krystel R
Flaum Eye Institute, University of Rochester, Rochester, New York.
Department of Medicine, University of Rochester, Rochester, New York.
Am J Pathol. 2014 May;184(5):1429-45. doi: 10.1016/j.ajpath.2014.01.026. Epub 2014 Mar 17.
Corneal scarring, whether caused by trauma, laser refractive surgery, or infection, remains a significant problem for humans. Certain ligands for peroxisome proliferator-activated receptor gamma (PPARγ) have shown promise as antiscarring agents in a variety of body tissues. In the cornea, their relative effectiveness and mechanisms of action are still poorly understood. Here, we contrasted the antifibrotic effects of three different PPARγ ligands (15-deoxy-Δ12,14-prostaglandin J2, troglitazone, and rosiglitazone) in cat corneal fibroblasts. Western blot analyses revealed that all three compounds reduced transforming growth factor (TGF)-β1-driven myofibroblast differentiation and up-regulation of α-smooth muscle actin, type I collagen, and fibronectin expression. Because these effects were independent of PPARγ, we ascertained whether they occurred by altering phosphorylation of Smads 2/3, p38 mitogen-activated protein kinase, stress-activated protein kinase, protein kinase B, extracellular signal-regulated kinase, and/or myosin light chain 2. Only p38 mitogen-activated protein kinase phosphorylation was significantly inhibited by all three PPARγ ligands. Finally, we tested the antifibrotic potential of troglitazone in a cat model of photorefractive keratectomy-induced corneal injury. Topical application of troglitazone significantly reduced α-smooth muscle actin expression and haze in the stromal ablation zone. Thus, the PPARγ ligands tested here showed great promise as antifibrotics, both in vitro and in vivo. Our results also provided new evidence for the signaling pathways that may underlie these antifibrotic actions in corneal fibroblasts.
角膜瘢痕形成，无论由外伤、激光屈光手术还是感染引起，仍然是人类面临的一个重大问题。过氧化物酶体增殖物激活受体γ（PPARγ）的某些配体已显示出有望成为多种身体组织中的抗瘢痕形成剂。在角膜中，它们的相对有效性和作用机制仍知之甚少。在此，我们对比了三种不同的PPARγ配体（15-脱氧-Δ12,14-前列腺素J2、曲格列酮和罗格列酮）对猫角膜成纤维细胞的抗纤维化作用。蛋白质印迹分析显示，所有三种化合物均降低了转化生长因子（TGF）-β1驱动的肌成纤维细胞分化以及α-平滑肌肌动蛋白、I型胶原蛋白和纤连蛋白表达的上调。由于这些作用独立于PPARγ，我们确定它们是否通过改变Smads 2/3、p38丝裂原活化蛋白激酶、应激激活蛋白激酶、蛋白激酶B、细胞外信号调节激酶和/或肌球蛋白轻链2的磷酸化而发生。只有p38丝裂原活化蛋白激酶的磷酸化被所有三种PPARγ配体显著抑制。最后，我们在光性屈光性角膜切削术诱导的角膜损伤猫模型中测试了曲格列酮的抗纤维化潜力。局部应用曲格列酮可显著降低基质消融区的α-平滑肌肌动蛋白表达和混浊。因此，本文测试的PPARγ配体在体外和体内均显示出作为抗纤维化药物的巨大潜力。我们的结果还为角膜成纤维细胞中这些抗纤维化作用可能的信号通路提供了新证据。
