IL-6/gp130 signaling in CD4+ T cells drives the pathogenesis of pulmonary hypertension

Pulmonary arterial hypertension (PAH) is characterized by stenosis and occlusions of small pulmonary arteries, leading to elevated pulmonary arterial pressure and right heart failure. Although accumulating evidence shows the importance of interleukin (IL)-6 in the pathogenesis of PAH, the target cells of IL-6 are poorly understood. Using mice harboring the floxed allele of gp130, a subunit of IL-6 receptor, we found substantial Cre recombination in all hematopoietic cell lineages from the primitive hematopoietic stem cell level in SM22α-Cre mice. We also revealed that a CD4+ cell-specific gp130 deletion ameliorated the phenotype of hypoxia-induced pulmonary hypertension in mice. Disruption of IL-6 signaling via deletion of gp130 in CD4+ T cells inhibited phosphorylation of signal transducer and activator of transcription 3 (STAT3) and suppressed the hypoxia-induced increase in T helper 17 cells. To further examine the role of IL-6/gp130 signaling in more severe PH models, we developed Il6 knockout (KO) rats using the CRISPR/Cas9 system and showed that IL-6 deficiency could improve the pathophysiology in hypoxia-, monocrotaline-, and Sugen5416/hypoxia (SuHx)-induced rat PH models. Phosphorylation of STAT3 in CD4+ cells was also observed around the vascular lesions in the lungs of SuHx rat model, but not in Il6 KO rats. Blockade of IL-6 signaling had an additive effect on conventional PAH therapeutics, such as endothelin receptor antagonist (macitentan) and soluble guanylyl cyclase stimulator (BAY41-2272). These findings suggest that IL-6/gp130 signaling in CD4+ cells plays a critical role in the pathogenesis of PAH.肺动脉高压（Pulmonary arterial hypertension, PAH）以肺小动脉狭窄及闭塞为特征，可导致肺动脉压升高与右心衰竭。尽管日益增多的证据表明白细胞介素（interleukin, IL）-6在PAH的发病机制中具有重要作用，但目前对IL-6的靶细胞仍知之甚少。本研究使用携带IL-6受体亚单位gp130的floxed等位基因的小鼠，发现SM22α-Cre小鼠中，从原始造血干细胞层级起的所有造血细胞谱系均存在显著的Cre重组事件。本研究还证实，CD4阳性细胞特异性gp130缺失可改善小鼠低氧诱导性肺动脉高压表型。在CD4阳性T细胞中敲除gp130以阻断IL-6信号通路，可抑制信号转导与转录激活因子3（signal transducer and activator of transcription 3, STAT3）的磷酸化，并抑制低氧诱导的辅助性T细胞17（T helper 17 cells, Th17）细胞比例升高。为进一步在更严重的PH模型中探究IL-6/gp130信号通路的作用，本研究通过CRISPR/Cas9系统构建了IL-6基因敲除（knockout, KO）大鼠，证实IL-6缺失可改善低氧、野百合碱以及Sugen5416/低氧（SuHx）诱导的大鼠PH模型的病理生理改变。在SuHx大鼠模型的肺部血管病变周围，可检测到CD4阳性细胞中STAT3的磷酸化，但在IL-6 KO大鼠中未观察到此现象。IL-6信号通路阻断与常规PAH治疗药物，如内皮素受体拮抗剂（macitentan，马西替坦）及可溶性鸟苷酸环化酶激动剂（BAY41-2272）联合使用时，具有协同增效作用。上述研究结果表明，CD4阳性细胞中的IL-6/gp130信号通路在PAH的发病机制中发挥关键作用。