Second Affiliated Hospital, Zhejiang Chinese Medical University, Hangzhou 310005, China.
Zhejiang Respiratory Drugs Research Laboratory, School of Basic Medical Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China.
Biomed Pharmacother. 2017 Dec;96:1127-1136. doi: 10.1016/j.biopha.2017.11.110. Epub 2017 Nov 27.
Exchange protein directly activated by cAMP (Epac) is an important molecule in cAMP signal transduction, but the effect of Epac on lipopolysaccharide (LPS)-induced acute lung injury (ALI) is unclear. In this study, we treated in vitro and in vivo models with the Epac activator 8CPT to determine the effect and related mechanisms of Epac. The in vitro results indicate that 8CPT inhibits lipopolysaccharide (LPS)-induced tumor necrosis factor-α (TNF-α) release from mouse macrophages (MH-S), whereas the protein kinase A (PKA) activator 6BnZ has no effect. Furthermore, Epac over-expression can significantly suppress TNF-α release from LPS induced MH-S cell, while Epac siRNA can slightly increase TNF-α release. Moreover, 8CPT reduces LPS-induced microvascular permeability in human pulmonary microvascular endothelial cells (HPMVECs), whereas the PKA activator 6BnZ has no effect. In mice with LPS-induced ALI, 8CPT significantly reduces LPS-induced inflammatory cytokine release, neutrophil recruitment, and albumin leakage. LPS simultaneously decreases the Epac but not the PKA levels. However, 8CPT reverses the decreased Epac levels. Furthermore, the mechanism involves the small GTPase Rac1/2 but not the mitogen-activated protein kinase (MAPK) pathway. Thus, Epac activation reduces inflammation and microvascular permeability in LPS-induced lung injury and an Epac activator represents a novel choice for the early therapy of ALI.
环磷酸腺苷（cAMP）直接激活蛋白（Epac）是 cAMP 信号转导中的重要分子，但 Epac 对脂多糖（LPS）诱导的急性肺损伤（ALI）的影响尚不清楚。在本研究中，我们用 Epac 激活剂 8CPT 处理体外和体内模型，以确定 Epac 的作用及相关机制。体外结果表明，8CPT 抑制脂多糖（LPS）诱导的小鼠巨噬细胞（MH-S）肿瘤坏死因子-α（TNF-α）释放，而蛋白激酶 A（PKA）激活剂 6BnZ 则没有作用。此外，Epac 过表达可显著抑制 LPS 诱导的 MH-S 细胞中 TNF-α的释放，而 Epac siRNA 则可轻微增加 TNF-α的释放。此外，8CPT 降低 LPS 诱导的人肺微血管内皮细胞（HPMVEC）中微血管通透性，而 PKA 激活剂 6BnZ 则没有作用。在 LPS 诱导的 ALI 小鼠中，8CPT 显著降低 LPS 诱导的炎症细胞因子释放、中性粒细胞募集和白蛋白漏出。LPS 同时降低 Epac 但不降低 PKA 水平。然而，8CPT 逆转了 Epac 水平的降低。此外，其机制涉及小 GTPase Rac1/2，而不是丝裂原活化蛋白激酶（MAPK）途径。因此，Epac 的激活可减轻 LPS 诱导的肺损伤中的炎症和微血管通透性，Epac 激活剂代表了 ALI 早期治疗的一种新选择。
