He Donghong, Su Yanlin, Usatyuk Peter V, Spannhake Ernst Wm, Kogut Paul, Solway Julian, Natarajan Viswanathan, Zhao Yutong
Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA.
J Biol Chem. 2009 Sep 4;284(36):24123-32. doi: 10.1074/jbc.M109.007393. Epub 2009 Jul 8.
Lysophosphatidic acid (LPA), a bioactive phospholipid, induces a wide range of cellular effects, including gene expression, cytoskeletal rearrangement, and cell survival. We have previously shown that LPA stimulates secretion of pro- and anti-inflammatory cytokines in bronchial epithelial cells. This study provides evidence that LPA enhances pulmonary epithelial barrier integrity through protein kinase C (PKC) delta- and zeta-mediated E-cadherin accumulation at cell-cell junctions. Treatment of human bronchial epithelial cells (HBEpCs) with LPA increased transepithelial electrical resistance (TER) by approximately 2.0-fold and enhanced accumulation of E-cadherin to the cell-cell junctions through Galpha(i)-coupled LPA receptors. Knockdown of E-cadherin with E-cadherin small interfering RNA or pretreatment with EGTA (0.1 mm) prior to LPA (1 microm) treatment attenuated LPA-induced increases in TER in HBEpCs. Furthermore, LPA induced tyrosine phosphorylation of focal adhesion kinase (FAK) and overexpression of the FAK inhibitor, and FAK-related non-kinase-attenuated LPA induced increases in TER and E-cadherin accumulation at cell-cell junctions. Overexpression of dominant negative protein kinase delta and zeta attenuated LPA-induced phosphorylation of FAK, accumulation of E-cadherin at cell-cell junctions, and an increase in TER. Additionally, lipopolysaccharide decreased TER and induced E-cadherin relocalization from cell-cell junctions to cytoplasm in a dose-dependent fashion, which was restored by LPA post-treatment in HBEpCs. Intratracheal post-treatment with LPA (5 microm) reduced LPS-induced neutrophil influx, protein leak, and E-cadherin shedding in bronchoalveolar lavage fluids in a murine model of acute lung injury. These data suggest a protective role of LPA in airway inflammation and remodeling.
溶血磷脂酸（LPA）是一种生物活性磷脂，可诱导多种细胞效应，包括基因表达、细胞骨架重排和细胞存活。我们之前已经表明，LPA可刺激支气管上皮细胞分泌促炎和抗炎细胞因子。本研究提供了证据表明，LPA通过蛋白激酶C（PKC）δ和ζ介导的E-钙黏蛋白在细胞间连接处的积累来增强肺上皮屏障的完整性。用LPA处理人支气管上皮细胞（HBEpCs）可使跨上皮电阻（TER）增加约2.0倍，并通过Gαi偶联的LPA受体增强E-钙黏蛋白在细胞间连接处的积累。用E-钙黏蛋白小干扰RNA敲低E-钙黏蛋白或在LPA（1微摩尔）处理前用EGTA（0.1毫摩尔）预处理可减弱LPA诱导的HBEpCs中TER的增加。此外，LPA诱导粘着斑激酶（FAK）的酪氨酸磷酸化以及FAK抑制剂的过表达，并且FAK相关非激酶减弱了LPA诱导的TER增加和E-钙黏蛋白在细胞间连接处的积累。显性负性蛋白激酶δ和ζ的过表达减弱了LPA诱导的FAK磷酸化、E-钙黏蛋白在细胞间连接处的积累以及TER的增加。此外，脂多糖以剂量依赖性方式降低TER并诱导E-钙黏蛋白从细胞间连接处重新定位到细胞质中，在HBEpCs中LPA后处理可恢复这一现象。在急性肺损伤小鼠模型中，气管内给予LPA（5微摩尔）后处理可减少脂多糖诱导的中性粒细胞流入、蛋白渗漏以及支气管肺泡灌洗液中E-钙黏蛋白的脱落。这些数据表明LPA在气道炎症和重塑中具有保护作用。
