Department of Physiology, Michigan State University, 3197 Biomedical and Physical Sciences Bldg., East Lansing, MI 48824, USA.
Am J Physiol Lung Cell Mol Physiol. 2013 Jul 1;305(1):L33-41. doi: 10.1152/ajplung.00001.2013. Epub 2013 Apr 26.
Earlier work showed that apoptosis of alveolar epithelial cells (AECs) in response to endogenous or xenobiotic factors is regulated by autocrine generation of angiotensin (ANG) II and its counterregulatory peptide ANG1-7. Mutations in surfactant protein C (SP-C) induce endoplasmic reticulum (ER) stress and apoptosis in AECs and cause lung fibrosis. This study tested the hypothesis that ER stress-induced apoptosis of AECs might also be regulated by the autocrine ANGII/ANG1-7 system of AECs. ER stress was induced in A549 cells or primary cultures of human AECs with the proteasome inhibitor MG132 or the SP-C BRICHOS domain mutant G100S. ER stress activated the ANGII-generating enzyme cathepsin D and simultaneously decreased the ANGII-degrading enzyme ACE-2, which normally generates the antiapoptotic peptide ANG1-7. TAPI-2, an inhibitor of ADAM17/TACE, significantly reduced both the activation of cathepsin D and the loss of ACE-2. Apoptosis of AECs induced by ER stress was measured by assays of mitochondrial function, JNK activation, caspase activation, and nuclear fragmentation. Apoptosis induced by either MG132 or the SP-C BRICHOS mutant G100S was significantly inhibited by the ANG receptor blocker saralasin and was completely abrogated by ANG1-7. Inhibition by ANG1-7 was blocked by the specific mas antagonist A779. These data show that ER stress-induced apoptosis is mediated by the autocrine ANGII/ANG1-7 system in human AECs and demonstrate effective blockade of SP-C mutation-induced apoptosis by ANG1-7. They also suggest that therapeutic strategies aimed at administering ANG1-7 or stimulating ACE-2 may hold potential for the management of ER stress-induced fibrotic lung disorders.
早期工作表明，肺泡上皮细胞（AEC）对内源性或外源性因子的凋亡反应受到自分泌血管紧张素（ANG）II及其拮抗肽 ANG1-7 的调节。表面活性剂蛋白 C（SP-C）的突变诱导 AEC 中的内质网（ER）应激和凋亡，并导致肺纤维化。本研究检验了以下假设：AEC 中 ER 应激诱导的凋亡也可能受到 AEC 自分泌 ANGII/ANG1-7 系统的调节。用蛋白酶体抑制剂 MG132 或 SP-C BRICHOS 结构域突变体 G100S 诱导 A549 细胞或原代人 AEC 中的 ER 应激。ER 应激激活了生成 ANGII 的酶组织蛋白酶 D，同时降低了 ANGII 降解酶 ACE-2 的活性，ACE-2 通常会产生抗凋亡肽 ANG1-7。ADAM17/TACE 的抑制剂 TAPI-2 显著减少了组织蛋白酶 D 的激活和 ACE-2 的丢失。通过线粒体功能、JNK 激活、半胱天冬酶激活和核片段化测定来测量 AEC 中 ER 应激诱导的凋亡。MG132 或 SP-C BRICHOS 突变体 G100S 诱导的凋亡均被 ANG 受体阻滞剂沙拉新显著抑制，而被 ANG1-7 完全阻断。ANG1-7 的抑制作用被特异性 mas 拮抗剂 A779 阻断。这些数据表明，ER 应激诱导的凋亡是由人 AEC 中的自分泌 ANGII/ANG1-7 系统介导的，并证明了 ANG1-7 有效阻断 SP-C 突变诱导的凋亡。它们还表明，旨在给予 ANG1-7 或刺激 ACE-2 的治疗策略可能为 ER 应激诱导的纤维化肺疾病的管理提供潜在的治疗方法。
