In pulmonary arterial hypertension (PAH), progressive structural remodeling accounts for the pulmonary vasculopathy including the obliteration of the lung vasculature that causes an increase in vascular resistance and mean blood pressure in the pulmonary arteries ultimately leading to right heart failure–mediated death. Deciphering the molecular details of aberrant signaling of pulmonary vascular cells in PAH is fundamental for the development of new therapeutic strategies. We aimed to identify kinases as new potential drug targets that are dysregulated in PAH by means of a peptide-based kinase activity assay. We performed a tyrosine kinase–dependent phosphorylation assay using 144 selected microarrayed substrate peptides. The differential signature of phosphopeptides was used to predict alterations in tyrosine kinase activities in human pulmonary arterial smooth muscle cells (HPASMCs) from patients with idiopathic PAH (IPAH) compared with healthy control cells. Thereby, we observed an overactivation and an increased expression of Jak2 (Janus kinase 2) in HPASMCs from patients with IPAH as compared with controls. In vitro, IL-6–induced proliferation and migration of HPASMCs from healthy individuals as well as from patients with IPAH were reduced in a dose-dependent manner by the U.S. Food and Drug Administration–approved Jak1 and Jak2 inhibitor ruxolitinib. In vivo, ruxolitinib therapy in two experimental models of pulmonary arterial hypertension dose-dependently attenuated the elevation in pulmonary arterial pressure, partially reduced right ventricular hypertrophy, and almost completely restored cardiac index without signs of adverse events on cardiac function. Therefore, we propose that ruxolitinib may present a novel therapeutic option for patients with PAH by reducing pulmonary vascular remodeling through effectively blocking Jak2–Stat3 (signal transducer of activators of transcription)–mediated signaling pathways.

在肺动脉高压 (PAH) 中，进行性结构重塑导致肺血管病变，包括肺血管闭塞，导致血管阻力和肺动脉平均血压增加，最终导致右心衰竭介导的死亡。破译 PAH 中肺血管细胞异常信号的分子细节是开发新治疗策略的基础。我们旨在通过基于肽的激酶活性测定将激酶鉴定为在 PAH 中失调的新的潜在药物靶点。我们使用 144 种选定的微阵列底物肽进行了酪氨酸激酶依赖性磷酸化测定。磷酸肽的差异特征用于预测与健康对照细胞相比，特发性 PAH (IPAH) 患者的人肺动脉平滑肌细胞 (HPASMC) 中酪氨酸激酶活性的变化。因此，我们观察到与对照组相比，来自 IPAH 患者的 HPASMC 中 Jak2（Janus 激酶 2）的过度激活和表达增加。在体外，美国食品和药物管理局批准的 Jak1 和 Jak2 抑制剂鲁索替尼以剂量依赖性方式减少了 IL-6 诱导的健康个体和 IPAH 患者 HPASMC 的增殖和迁移。体内在肺动脉高压的两个实验模型中，ruxolitinib 治疗剂量依赖性地减弱了肺动脉压的升高，部分减少了右心室肥厚，并且几乎完全恢复了心脏指数，而没有出现心脏功能不良事件的迹象。因此，我们建议鲁索替尼可能通过有效阻断 Jak2-Stat3（转录激活因子的信号转导器）介导的信号通路来减少肺血管重塑，从而为 PAH 患者提供一种新的治疗选择。