Department of Basic Medicine, Harbin Medical University (Daqing), Heilongjiang Province, China.
Department of Chest Surgery, the Fifth Affiliated Hospital of Harbin Medical University, Daqing, Heilongjiang Province, China.
Eur J Pharmacol. 2024 Nov 5;982:176944. doi: 10.1016/j.ejphar.2024.176944. Epub 2024 Aug 24.
Pulmonary hypertension (PH) is a serious pulmonary vascular disease characterized by vascular remodeling. Circular RNAs (CircRNAs) play important roles in pulmonary hypertension, but the mechanism of PH is not fully understood, particularly the roles of circRNAs located in the nucleus. Circ-calmodulin 4 (circ-calm4) is expressed in both the cytoplasm and the nucleus of pulmonary arterial smooth muscle cells (PASMCs). This study aimed to investigate the role of endonuclear circ-calm4 in PH and elucidate its underlying signaling pathway in ferroptosis. Immunoblotting, quantitative real-time polymerase chain reaction (PCR), malondialdehyde (MDA) assay, immunofluorescence, iron assay, dot blot, and chromatin immunoprecipitation (ChIP) were performed to investigate the role of endonuclear circ-calm4 in PASMC ferroptosis. Increased endonuclear circ-calm4 facilitated ferroptosis in PASMCs under hypoxic conditions. We further identified the cartilage oligomeric matrix protein (COMP) as a downstream effector of circ-calm4 that contributed to the occurrence of hypoxia-induced ferroptosis in PASMCs. Importantly, we confirmed that endonuclear circ-calm4 formed circR-loops with the promoter region of the COMP gene and negatively regulated its expression. Inhibition of COMP restored the phenotypes related to ferroptosis under hypoxia stimulation combined with antisense oligonucleotide (ASO)-circ-calm4 treatment. We conclude that the circ-calm4/COMP axis contributed to hypoxia-induced ferroptosis in PASMCs and that circ-calm4 formed circR-loops with the COMP promoter in the nucleus and negatively regulated its expression. The circ-calm4/COMP axis may be useful for the design of therapeutic strategies for protecting cellular functionality against ferroptosis and pulmonary hypertension.
肺动脉高压（PH）是一种以血管重构为特征的严重肺血管疾病。环状 RNA（CircRNAs）在肺动脉高压中发挥重要作用，但 PH 的机制尚不完全清楚，特别是位于核内的 circRNAs 的作用。环状钙调蛋白 4（circ-calm4）在肺动脉平滑肌细胞（PASMCs）的细胞质和细胞核中均有表达。本研究旨在探讨核内 circ-calm4 在 PH 中的作用，并阐明其在铁死亡中的潜在信号通路。采用免疫印迹、实时定量聚合酶链反应（PCR）、丙二醛（MDA）测定、免疫荧光、铁测定、斑点印迹和染色质免疫沉淀（ChIP）实验，研究核内 circ-calm4 在 PASMC 铁死亡中的作用。结果表明，在缺氧条件下，增加核内 circ-calm4 促进 PASMC 铁死亡。我们进一步发现软骨寡聚基质蛋白（COMP）是 circ-calm4 的下游效应物，有助于 PASMC 缺氧诱导的铁死亡。重要的是，我们证实核内 circ-calm4 与 COMP 基因启动子区域形成 circR-环，并负调控其表达。抑制 COMP 可恢复与缺氧刺激联合抗 sense 寡核苷酸（ASO）-circ-calm4 治疗相关的铁死亡表型。综上所述，circ-calm4/COMP 轴促进 PASMC 缺氧诱导的铁死亡，circ-calm4 在核内与 COMP 启动子形成 circR-环，并负调控其表达。circ-calm4/COMP 轴可能有助于设计针对铁死亡和肺动脉高压保护细胞功能的治疗策略。
