Institute of Physiology, Charité-Universitätsmedizin Berlin, Corporate Member of the Freie Universität Berlin and Humboldt Universität zu Berlin, Berlin, Germany; Department of Pathology, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China.
Institute of Physiology, Charité-Universitätsmedizin Berlin, Corporate Member of the Freie Universität Berlin and Humboldt Universität zu Berlin, Berlin, Germany.
Anesthesiology. 2024 Nov 1;141(5):913-928. doi: 10.1097/ALN.0000000000005171.
As a mechanosensitive cation channel and key regulator of vascular barrier function, endothelial transient receptor potential vanilloid type 4 (TRPV4) contributes critically to ventilator-induced lung injury and edema formation. Ca2+ influx via TRPV4 can activate Ca2+-activated potassium (KCa) channels, categorized into small (SK1-3), intermediate (IK1), and big (BK) KCa, which may in turn amplify Ca2+ influx by increasing the electrochemical Ca2+ gradient and thus promote lung injury. The authors therefore hypothesized that endothelial KCa channels may contribute to the progression of TRPV4-mediated ventilator-induced lung injury.
Male C57Bl/6J mice were ventilated for 2 h with low or high tidal volumes in the presence or absence of the nonselective KCa antagonists apamin and charybdotoxin or the selective IK1 antagonist TRAM34. Lung injury was similarly assessed in overventilated, endothelial-specific TRPV4-deficient mice or TRAM34-treated C57Bl/6J mice challenged with intratracheal acid installation. Changes in intracellular calcium Ca2+ concentration ([Ca2+]i) were monitored by real-time imaging in isolated-perfused lungs in response to airway pressure elevation or in human pulmonary microvascular endothelial cells in response to TRPV4 activation with or without inhibition of KCa channels. Analogously, changes in intracellular potassium concentration ([K+]i) and membrane potential were imaged in vitro.
Endothelial TRPV4 deficiency or inhibition of KCa channels, and most prominently inhibition of IK1 by TRAM34, attenuated ventilator-induced lung injury as demonstrated by reduced lung edema, protein leak, and quantitative lung histology. All KCa antagonists reduced the [Ca2+]i response to mechanical stimulation or direct TRPV4 activation in isolated lungs. TRAM34 and charybdotoxin yet not apamin prevented TRPV4-induced potassium efflux and membrane hyperpolarization in human pulmonary microvascular endothelial cells. TRAM34 also attenuated the TRPV4 agonist-induced Ca2+ influx in vitro and reduced acid-induced lung injury in vivo.
KCa channels, specifically IK1, act as amplifiers of TRPV4-mediated Ca2+ influx and establish a detrimental feedback that promotes barrier failure and drives the progression of ventilator-induced lung injury.
作为一种机械敏感性阳离子通道和血管屏障功能的关键调节剂，内皮瞬态受体电位香草酸型 4（TRPV4）对呼吸机引起的肺损伤和水肿形成有重要贡献。通过 TRPV4 的 Ca2+内流可以激活 Ca2+-激活的钾（KCa）通道，分为小（SK1-3）、中间（IK1）和大（BK）KCa，这反过来又可以通过增加电化学 Ca2+梯度来放大 Ca2+内流，从而促进肺损伤。因此，作者假设内皮 KCa 通道可能有助于 TRPV4 介导的呼吸机引起的肺损伤的进展。
雄性 C57Bl/6J 小鼠在低或高潮气量通气 2 小时，同时存在或不存在非选择性 KCa 拮抗剂 apamin 和 charybdotoxin 或选择性 IK1 拮抗剂 TRAM34。在过度通气、内皮特异性 TRPV4 缺陷小鼠或 TRAM34 处理的 C57Bl/6J 小鼠中，通过气管内酸安装来评估类似的肺损伤。通过实时成像监测分离灌注肺对气道压力升高的反应或人肺微血管内皮细胞对 TRPV4 激活的反应，监测细胞内钙离子浓度（[Ca2+]i）的变化，同时抑制 KCa 通道。类似地，在体外成像细胞内钾浓度（[K+]i）和膜电位的变化。
内皮 TRPV4 缺陷或 KCa 通道抑制，特别是 TRAM34 抑制 IK1，可减轻呼吸机引起的肺损伤，表现为肺水肿、蛋白漏和定量肺组织学减少。所有 KCa 拮抗剂均降低了机械刺激或直接 TRPV4 激活对分离肺的[Ca2+]i 反应。TRAM34 和 charybdotoxin 而非 apamin 可防止 TRPV4 诱导的人肺微血管内皮细胞钾外流和膜超极化。TRAM34 还可减弱 TRPV4 激动剂在体外的 Ca2+内流，并减少体内酸诱导的肺损伤。
KCa 通道，特别是 IK1，作为 TRPV4 介导的 Ca2+内流的放大器，并建立一种有害的反馈，促进屏障失效并推动呼吸机引起的肺损伤的进展。
