Department of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA.
Department of Medicine, University of Wisconsin, Madison, WI 53792, USA.
Int J Mol Sci. 2022 Apr 26;23(9):4763. doi: 10.3390/ijms23094763.
Pulmonary hypertension in sickle cell disease is an independent predictor of mortality, yet the pathogenesis of pulmonary vascular disease in chronic hemolytic disorders remains incompletely understood and treatment options are limited primarily to supportive care. The release of extracellular hemoglobin has been implicated in the development of pulmonary hypertension, and in this study we explored the direct effects of hemin, the oxidized moiety of heme, on the pulmonary artery endothelium. We found that low dose hemin exposure leads to significantly increased endothelial cell proliferation, migration, and cytokine release as markers of endothelial dysfunction. Protein expression changes in our pulmonary artery endothelial cells showed upregulation of mesenchymal markers after hemin treatment in conjunction with a decrease in endothelial markers. Endothelial to mesenchymal transition (EndoMT) resulting from hemin exposure was further confirmed by showing upregulation of the transcription factors SNAI1 and SLUG, known to regulate EndoMT. Lastly, given the endothelial dysfunction and phenotypic transition observed, the endothelial cytoskeleton was considered a potential novel target. Inhibiting myosin light chain kinase, to prevent phosphorylation of myosin light chain and cytoskeletal contraction, attenuated hemin-induced endothelial hyper-proliferation, migration, and cytokine release. The findings in this study implicate hemin as a key inducer of endothelial dysfunction through EndoMT, which may play an important role in pulmonary vascular remodeling during the development of pulmonary hypertension in chronic hemolytic states.
镰状细胞病中的肺动脉高压是死亡的独立预测因子，但慢性溶血性疾病中肺血管疾病的发病机制仍不完全清楚，治疗选择主要限于支持性治疗。细胞外血红蛋白的释放与肺动脉高压的发展有关，在这项研究中，我们探讨了血红素的氧化部分——血红素卟啉对肺动脉内皮细胞的直接作用。我们发现，低剂量血红素暴露会导致内皮细胞增殖、迁移和细胞因子释放显著增加，这些都是内皮功能障碍的标志物。我们的肺动脉内皮细胞中蛋白表达的变化表明，血红素处理后间质标志物上调，同时内皮标志物下调。血红素暴露导致的内皮到间充质转化（EndoMT）进一步通过显示转录因子 SNAI1 和 SLUG 的上调得到证实，这两个转录因子已知调节 EndoMT。最后，鉴于观察到的内皮功能障碍和表型转变，内皮细胞骨架被认为是一个潜在的新靶点。抑制肌球蛋白轻链激酶以防止肌球蛋白轻链磷酸化和细胞骨架收缩，可减轻血红素诱导的内皮细胞过度增殖、迁移和细胞因子释放。这项研究的结果表明，血红素通过 EndoMT 作为内皮功能障碍的关键诱导剂，可能在慢性溶血性疾病中肺动脉高压发展过程中的肺血管重塑中起重要作用。
