Objectives Stimulators of soluble guanylate cyclase (sGC) are currently investigated in clinical trials for the treatment of fibrosis in systemic sclerosis (SSc). In this study, we aim to investigate the role of protein kinases G (PKG) as downstream mediators of sGC–cyclic guanosine monophosphate (cGMP) in SSc. Methods Mice with combined knockout of PKG1 and 2 were challenged with bleomycin and treated with the sGC stimulator BAY 41-2272. Fibroblasts were treated with BAY 41-2272 and with the PKG inhibitor KT 5823. Results PKG1 and 2 are upregulated in SSc in a transforming growth factor-β1 (TGFβ1)-dependent manner, as an attempt to compensate for the decreased signalling through the sGC–cGMP–PKG pathway. Inhibition or knockout of PKG1 and 2 abrogates the inhibitory effects of sGC stimulation on fibroblast activation in a SMAD-independent, but extracellular signal-regulated kinase (ERK)-dependent manner. In vivo, sGC stimulation fails to prevent bleomycin-induced fibrosis in PKG1 and 2 knockout mice. Conclusions Our data provide evidence that PKGs are essential mediators of the antifibrotic effects of sGC stimulators through interfering with non-canonical TGFβ signalling. TGFβ1 promotes its profibrotic effects through inhibition of sGC–cGMP–PKG signalling, sGC stimulation exerts its antifibrotic effects by inhibition of TGFβ1-induced ERK phosphorylation.

中文翻译：

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蛋白激酶 G 是 sGC 刺激物抗纤维化作用的重要下游介质

目的 可溶性鸟苷酸环化酶 (sGC) 的刺激剂目前正在临床试验中进行研究，用于治疗系统性硬化症 (SSc) 中的纤维化。在本研究中，我们旨在研究蛋白激酶 G (PKG) 作为 SSc 中 sGC-环磷酸鸟苷 (cGMP) 下游介质的作用。方法 联合敲除 PKG1 和 2 的小鼠用博莱霉素激发并用 sGC 刺激剂 BAY 41-2272 治疗。成纤维细胞用 BAY 41-2272 和 PKG 抑制剂 KT 5823 处理。 结果 PKG1 和 2 在 SSc 中以转化生长因子-β1 (TGFβ1) 依赖性方式上调，以补偿通过 sGC 的信号减弱–cGMP–PKG 途径。抑制或敲除 PKG1 和 2 消除了 sGC 刺激对 SMAD 非依赖性成纤维细胞活化的抑制作用，但细胞外信号调节激酶（ERK）依赖方式。在体内，sGC 刺激未能防止 PKG1 和 2 基因敲除小鼠中博来霉素诱导的纤维化。结论 我们的数据提供证据表明，PKG 是 sGC 刺激物通过干扰非经典 TGFβ 信号传导的抗纤维化作用的重要介质。TGFβ1 通过抑制 sGC-cGMP-PKG 信号传导促进其促纤维化作用，sGC 刺激通过抑制 TGFβ1 诱导的 ERK 磷酸化发挥其抗纤维化作用。