Background: Stimulation of sGC (soluble guanylate cyclase) or inhibition of PDE5 (phosphodiesterase type 5) activates PKG (protein kinase G)-1α to counteract cardiac hypertrophy and failure. PKG1α acts within localized intracellular domains; however, its oxidation at cysteine 42, linking homomonomers, alters this localization, impairing suppression of pathological cardiac stress. Because PDE5 and sGC reside in separate microdomains, we speculated that PKG1α oxidation might also differentially influence the effects from their pharmacological modulation.

Methods and Results: Knock-in mice expressing a redox-dead PKG1α (PKG1α^C42S) or littermate controls (PKG1α^WT) were subjected to transaortic constriction to induce pressure overload and treated with a PDE5 inhibitor (sildenafil), sGC activator (BAY602770 [BAY]), or vehicle. In PKG1α^WT controls, sildenafil and BAY similarly enhanced PKG activity and reduced pathological hypertrophy/fibrosis and cardiac dysfunction after transaortic constriction. However, sildenafil failed to protect the heart in PKG1α^C42S, unlike BAY, which activated PKG and thereby facilitated protective effects. This corresponded with minimal PDE5 activation in PKG1α^C42S exposed to transaortic constriction versus higher activity in controls and little colocalization of PDE5 with PKG1α^C42S (versus colocalization with PKG1α^WT) in stressed myocytes.

Conclusions: In the stressed heart and myocytes, PKG1α C42-disulfide formation contributes to PDE5 activation. This augments the pathological role of PDE5 and so in turn enhances the therapeutic impact from its inhibition. PKG1α oxidation does not change the benefits from sGC activation. This finding favors the use of sGC activators regardless of PKG1α oxidation and may help guide precision therapy leveraging the cyclic GMP/PKG pathway to treat heart disease.

中文翻译：

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预防PKG-1α氧化可抑制PDE5抑制而非sGC刺激的抗肥大/抗纤维化作用

背景：刺激sGC（可溶性鸟苷酸环化酶）或抑制PDE5（5型磷酸二酯酶）可激活PKG（蛋白激酶G）-1α，以抵消心脏肥大和衰竭。PKG1α在局部细胞内结构域内起作用；然而，其在半胱氨酸42处的氧化将同分异构体连接起来，改变了这种定位，削弱了对病理性心脏压力的抑制作用。由于PDE5和sGC位于不同的微区中，我们推测PKG1α的氧化作用也可能会不同地影响它们的药理作用。

方法和结果：敲入小鼠表达氧化还原死PKG1α（PKG1α ^C42S）或同窝对照（PKG1α ^WT）进行transaortic收缩诱导的压力过载，并与PDE5抑制剂（西地那非），的sGC活化剂（BAY602770 [BAY处理]）或车辆。在PKG1α ^WT对照，西地那非和BAY同样增强的PKG活性和降低的病理性肥大/纤维化和心脏功能障碍transaortic收缩后。然而，西地那非未能保护在PKG1α的心脏^C42S，不像BAY，其中激活PKG，从而促进了保护作用。这相当于以最小的PDE5激活PKG1α ^C42S暴露于transaortic收缩相对于在对照和PDE5的小共定位PKG1α更高活性^C42S（相对于共定位PKG1α ^WT在强调肌细胞）。

结论：在紧张的心脏和心肌细胞中，PKG1αC42-二硫键的形成有助于PDE5的活化。这增强了PDE5的病理作用，因此反过来又增强了其抑制作用的治疗效果。PKG1α氧化不会改变sGC激活的好处。这一发现有利于使用sGC激活剂，而与PKG1α的氧化无关，并可能有助于利用循环GMP / PKG途径治疗心脏病的精确疗法。