Institute for Anatomy and Cell Biology, Division of Medical Cell Biology, Justus Liebig University, Aulweg 123, 35392, Giessen, Germany.
Department of Medical Education, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, 43614, USA.
Respir Res. 2024 Sep 23;25(1):345. doi: 10.1186/s12931-024-02935-7.
Idiopathic pulmonary fibrosis (IPF) is characterized by aberrant lung epithelial phenotypes, fibroblast activation, and increased extracellular matrix deposition. Transforming growth factor-beta (TGF-β)1-induced Smad signaling and downregulation of peroxisomal genes are involved in the pathogenesis and can be inhibited by peroxisome proliferator-activated receptor (PPAR)-α activation. However, the three PPARs, that is PPAR-α, PPAR-β/δ, and PPAR-γ, are known to interact in a complex crosstalk.
To mimic the pathogenesis of lung fibrosis, primary lung fibroblasts from control and IPF patients with comparable levels of all three PPARs were treated with TGF-β1 for 24 h, followed by the addition of PPAR ligands either alone or in combination for another 24 h. Fibrosis markers (intra- and extracellular collagen levels, expression and activity of matrix metalloproteinases) and peroxisomal biogenesis and metabolism (gene expression of peroxisomal biogenesis and matrix proteins, protein levels of PEX13 and catalase, targeted and untargeted lipidomic profiles) were analyzed after TGF-β1 treatment and the effects of the PPAR ligands were investigated.
TGF-β1 induced the expected phenotype; e.g. it increased the intra- and extracellular collagen levels and decreased peroxisomal biogenesis and metabolism. Agonists of different PPARs reversed TGF-β1-induced fibrosis even when given 24 h after TGF-β1. The effects included the reversals of (1) the increase in collagen production by repressing COL1A2 promoter activity (through PPAR-β/δ activation); (2) the reduced activity of matrix metalloproteinases (through PPAR-β/δ activation); (3) the decrease in peroxisomal biogenesis and lipid metabolism (through PPAR-γ activation); and (4) the decrease in catalase protein levels in control (through PPAR-γ activation) and IPF (through a combined activation of PPAR-β/δ and PPAR-γ) fibroblasts. Further experiments to explore the role of catalase showed that an overexpression of catalase protein reduced collagen production. Additionally, the beneficial effect of PPAR-γ but not of PPAR-β/δ activation on collagen synthesis depended on catalase activity and was thus redox-sensitive.
Our data provide evidence that IPF patients may benefit from a combined activation of PPAR-β/δ and PPAR-γ.
特发性肺纤维化（IPF）的特征是肺上皮表型异常、成纤维细胞激活和细胞外基质沉积增加。转化生长因子-β（TGF-β）1 诱导的 Smad 信号转导和过氧化物酶体基因下调参与发病机制，并可被过氧化物酶体增殖物激活受体（PPAR）-α激活所抑制。然而，三种 PPAR（即 PPAR-α、PPAR-β/δ 和 PPAR-γ）已知以复杂的串扰相互作用。
为了模拟肺纤维化的发病机制，用 TGF-β1 处理来自对照和 IPF 患者的原代肺成纤维细胞 24 小时，然后单独或联合加入 PPAR 配体再处理 24 小时。在用 TGF-β1 处理后分析纤维化标志物（细胞内和细胞外胶原水平、基质金属蛋白酶的表达和活性）和过氧化物酶体生物发生和代谢（过氧化物酶体生物发生和基质蛋白的基因表达、PEX13 和过氧化氢酶的蛋白水平、靶向和非靶向脂质组学谱），并研究 PPAR 配体的作用。
TGF-β1 诱导了预期的表型；例如，它增加了细胞内和细胞外的胶原水平，并降低了过氧化物酶体的生物发生和代谢。不同 PPAR 的激动剂即使在 TGF-β1 后 24 小时给予，也能逆转 TGF-β1 诱导的纤维化。这些作用包括：（1）通过抑制 COL1A2 启动子活性（通过 PPAR-β/δ 激活）来逆转胶原产生的增加；（2）通过 PPAR-β/δ 激活来逆转基质金属蛋白酶活性的降低；（3）通过 PPAR-γ 激活来逆转过氧化物酶体生物发生和脂质代谢的减少；（4）通过 PPAR-γ 激活降低对照（通过 PPAR-β/δ 和 PPAR-γ 的联合激活降低 IPF）成纤维细胞中的过氧化氢酶蛋白水平。进一步探索过氧化氢酶作用的实验表明，过氧化氢酶蛋白的过表达减少了胶原的产生。此外，PPAR-γ 而不是 PPAR-β/δ 激活对胶原合成的有益作用取决于过氧化氢酶活性，因此是氧化还原敏感的。
我们的数据提供了证据，表明 IPF 患者可能受益于 PPAR-β/δ 和 PPAR-γ 的联合激活。
