Transforming growth factor-β (TGF-β) becomes rapidly activated in the infarcted heart. Hence, TGF-β-mediated persistent activation of cardiac fibroblasts (CFs) and exaggerated fibrotic responses may result in adverse cardiac remodelling and heart failure. Additionally, peptidylarginine deiminase 4 (PAD4) was described to be implicated in organ fibrosis. Here, we investigated the impact of PAD4 on CF function and myofibroblast transdifferentiation in vitro. The expression of fibrosis-related genes was largely similar in cultured WT and PAD4^-/- CFs of passage 3, although collagen III was reduced in PAD4^-/- CFs. Exposure to TGF-β inhibited proliferation and increased contractile activity and migration of WT CFs, but not of PAD4^-/- CFs. However, under baseline conditions, PAD4^−/− CFs showed comparable functional characteristics as TGF-β-stimulated WT CFs. Although the SMAD-dependent TGF-β pathway was not disturbed in PAD4^-/- CFs, TGF-β failed to activate protein kinase B (Akt) and signal transducer and activator of transcription 3 (STAT3) in these cells. Similar results were obtained in WT CFs treated with the PAD4 inhibitor Cl-amidine. Abrogated Akt activation was associated with diminished levels of phosphorylated, inactive glycogen synthase kinase-3β (GSK-3β). Consequently, PAD4^-/- CFs did not upregulate collagen I and α-smooth muscle actin (α-SMA) expression after TGF-β treatment. Thus, PAD4 is substantially involved in the regulation of non-canonical TGF-β signalling and may represent a therapeutic target for the treatment of adverse cardiac remodelling.

中文翻译：

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受损的非经典转化生长因子-β信号传导可防止培养的肽精氨酸脱亚氨酶 4 缺陷小鼠心脏成纤维细胞中的促纤维化表型

转化生长因子-β (TGF-β) 在梗塞的心脏中迅速激活。因此，TGF-β介导的心脏成纤维细胞（CFs）持续激活和过度的纤维化反应可能导致不良的心脏重塑和心力衰竭。此外，肽精氨酸脱亚氨酶 4 (PAD4) 被描述为与器官纤维化有关。在这里，我们在体外研究了 PAD4 对 CF 功能和肌成纤维细胞转分化的影响。纤维化相关基因的表达在培养的 WT 和第 3 代的 PAD4 ^{-/- CFs 中基本相似，尽管 PAD4 -} /- CFs 中胶原蛋白 III 减少。暴露于 TGF-β 可抑制 WT CFs 的增殖和增加的收缩活性和迁移，但不抑制 PAD4 ^-/-CF。然而，在基线条件下，PAD4 ^-/- CFs 显示出与 TGF-β 刺激的 WT CFs 相当的功能特征。尽管 SMAD 依赖性 TGF-β 通路在 PAD4 ^-/- CFs 中没有受到干扰，但 TGF-β 未能激活这些细胞中的蛋白激酶 B (Akt) 和信号转导和转录激活因子 3 (STAT3)。在用 PAD4 抑制剂 Cl-脒处理的 WT CF 中获得了类似的结果。消除的 Akt 激活与磷酸化、无活性的糖原合酶激酶 3β (GSK-3β) 水平降低有关。因此，PAD4 ^-/-在 TGF-β 处理后，CFs 没有上调胶原蛋白 I 和 α-平滑肌肌动蛋白 (α-SMA) 的表达。因此，PAD4 主要参与非经典 TGF-β 信号传导的调节，并且可能代表治疗不良心脏重塑的治疗靶点。