Department of Pediatrics (Neonatology), Lung Biology and Disease Program, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA.
Cells. 2023 Dec 19;13(1):5. doi: 10.3390/cells13010005.
Earlier studies from our lab identified endoplasmic reticulum (ER) chaperone BiP/GRP78, an important component of MAM, to be a novel determinant of endothelial cell (EC) dysfunction associated with acute lung injury (ALI). Sigma1R (Sig1R) is another unique ER receptor chaperone that has been identified to associate with BiP/GRP78 at the MAM and is known to be a pluripotent modulator of cellular homeostasis. However, it is unclear if Sig1R also plays a role in regulating the EC inflammation and permeability associated with ALI. Our data using human pulmonary artery endothelial cells (HPAECs) showed that siRNA-mediated knockdown of Sig1R potentiated LPS-induced the expression of proinflammatory molecules ICAM-1, VCAM-1 and IL-8. Consistent with this, Sig1R agonist, PRE-084, known to activate Sig1R by inducing its dissociation from BiP/GRP78, blunted the above response. Notably, PRE-084 failed to blunt LPS-induced inflammatory responses in Sig1R-depleted cells, confirming that the effect of PRE-084 is driven by Sig1R. Furthermore, Sig1R antagonist, NE-100, known to inactivate Sig1R by blocking its dissociation from BiP/GRP78, failed to block LPS-induced inflammatory responses, establishing that dissociation from BiP/GRP78 is required for Sig1R to exert its anti-inflammatory action. Unlike Sig1R, the siRNA-mediated knockdown or Subtilase AB-mediated inactivation of BiP/GRP78 protected against LPS-induced EC inflammation. Interestingly, the protective effect of BiP/GRP78 knockdown or inactivation was abolished in cells that were depleted of Sig1R, confirming that BiP/GRP78 knockdown/inactivation-mediated suppression of EC inflammation is mediated via Sig1R. In view of these findings, we determined the in vivo relevance of Sig1R in a mouse model of sepsis-induced ALI. The intraperitoneal injection of PRE-084 mitigated sepsis-induced ALI, as evidenced by a decrease in ICAM-1, IL-6 levels, lung PMN infiltration, and lung vascular leakage. Together, these data evidence a protective role of Sig1R against endothelial dysfunction associated with ALI and identify it as a viable target in terms of controlling ALI in sepsis.
早期我们实验室的研究发现内质网伴侣蛋白 BiP/GRP78（MAM 的重要组成部分）是与急性肺损伤（ALI）相关的内皮细胞（EC）功能障碍的新型决定因素。Sigma1R（Sig1R）是另一种独特的内质网受体伴侣蛋白，已被鉴定与 MAM 上的 BiP/GRP78 相关，并且已知是细胞内稳态的多功能调节剂。然而，目前尚不清楚 Sig1R 是否也在调节与 ALI 相关的 EC 炎症和通透性中发挥作用。我们使用人肺动脉内皮细胞（HPAEC）的数据表明，Sig1R 的 siRNA 介导的敲低增强了 LPS 诱导的促炎分子 ICAM-1、VCAM-1 和 IL-8 的表达。与此一致的是，Sig1R 激动剂 PRE-084 通过诱导其与 BiP/GRP78 分离来激活 Sig1R，从而减弱了上述反应。值得注意的是，PRE-084 未能在 Sig1R 耗尽的细胞中减弱 LPS 诱导的炎症反应，证实了 PRE-084 的作用是由 Sig1R 驱动的。此外，Sig1R 拮抗剂 NE-100 通过阻断其与 BiP/GRP78 的分离来使 Sig1R 失活，未能阻断 LPS 诱导的炎症反应，这表明与 BiP/GRP78 的分离是 Sig1R 发挥抗炎作用所必需的。与 Sig1R 不同，BiP/GRP78 的 siRNA 介导的敲低或枯草溶菌素 AB 介导的失活可防止 LPS 诱导的 EC 炎症。有趣的是，在耗尽 Sig1R 的细胞中，BiP/GRP78 敲低或失活的保护作用被消除，这证实了 BiP/GRP78 敲低/失活介导的 EC 炎症抑制是通过 Sig1R 介导的。鉴于这些发现，我们在脓毒症诱导的 ALI 小鼠模型中确定了 Sig1R 的体内相关性。腹腔内注射 PRE-084 减轻了脓毒症诱导的 ALI，这表现在 ICAM-1、IL-6 水平降低、肺中性粒细胞浸润和肺血管渗漏减少。总之，这些数据表明 Sig1R 在与 ALI 相关的内皮功能障碍中具有保护作用，并将其确定为控制脓毒症中 ALI 的可行靶点。
