Rafiee Parvaneh, Theriot Monica E, Nelson Victoria M, Heidemann Jan, Kanaa Yasmin, Horowitz Scott A, Rogaczewski Aaron, Johnson Christopher P, Ali Irshad, Shaker Reza, Binion David G
Dept. of Surgery, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Am J Physiol Cell Physiol. 2006 Nov;291(5):C931-45. doi: 10.1152/ajpcell.00474.2005. Epub 2006 Jun 21.
The heat shock response maintains cellular homeostasis following sublethal injury. Heat shock proteins (Hsps) are induced by thermal, oxyradical, and inflammatory stress, and they chaperone denatured intracellular proteins. Hsps also chaperone signal transduction proteins, modulating signaling cascades during repeated stress. Gastroesophageal reflux disease (GERD) affects 7% of the US population, and it is linked to prolonged esophageal acid exposure. GERD is characterized by enhanced and selective leukocyte recruitment from esophageal microvasculature, implying activation of microvascular endothelium. We investigated whether phosphatidylinositol 3-kinase (PI3K)/Akt and MAPK regulate Hsp induction in primary cultures of human esophageal microvascular endothelial cells (HEMEC) in response to acid exposure (pH 4.5). Inhibitors of signaling pathways were used to define the contribution of PI3K/Akt and MAPKs in the heat shock response and following acid exposure. Acid significantly enhanced phosphorylation of Akt and MAPKs in HEMEC as well as inducing Hsp27 and Hsp70. The PI3K inhibitor LY-294002, and Akt small interfering RNA inhibited Akt activation and Hsp70 expression in HEMEC. The p38 MAPK inhibitor (SB-203580) and p38 MAPK siRNA blocked Hsp27 and Hsp70 mRNA induction, suggesting a role for MAPKs in the HEMEC heat shock response. Thus acidic pH exposure protects HEMEC through induction of Hsps and activation of MAPK and PI3 kinase pathway. Acidic exposure increased HEMEC expression of VCAM-1 protein, but not ICAM-1, which may contribute to selective leukocyte (i.e., eosinophil) recruitment in esophagitis. Activation of esophageal endothelial cells exposed to acidic refluxate may contribute to GERD in the setting of a disturbed mucosal squamous epithelial barrier (i.e., erosive esophagitis, peptic ulceration).
热休克反应在亚致死性损伤后维持细胞内稳态。热休克蛋白（Hsps）由热、氧自由基和炎症应激诱导产生，它们作为伴侣蛋白协助变性的细胞内蛋白质复性。Hsps还可作为信号转导蛋白的伴侣蛋白，在反复应激期间调节信号级联反应。胃食管反流病（GERD）影响着7%的美国人口，且与食管长时间暴露于酸性环境有关。GERD的特征是食管微血管中白细胞募集增强且具有选择性，这意味着微血管内皮细胞被激活。我们研究了磷脂酰肌醇3激酶（PI3K）/Akt和丝裂原活化蛋白激酶（MAPK）是否在人食管微血管内皮细胞（HEMEC）原代培养物中响应酸暴露（pH 4.5）时调节Hsp的诱导。使用信号通路抑制剂来确定PI3K/Akt和MAPKs在热休克反应以及酸暴露后的作用。酸显著增强了HEMEC中Akt和MAPKs的磷酸化，并诱导了Hsp27和Hsp70的产生。PI3K抑制剂LY - 294002和Akt小干扰RNA抑制了HEMEC中Akt的激活和Hsp70的表达。p38 MAPK抑制剂（SB - 203580）和p38 MAPK小干扰RNA阻断了Hsp27和Hsp70 mRNA的诱导，表明MAPKs在HEMEC热休克反应中发挥作用。因此，酸性pH暴露通过诱导Hsps以及激活MAPK和PI3激酶途径来保护HEMEC。酸性暴露增加了HEMEC中血管细胞黏附分子 - 1（VCAM - 1）蛋白的表达，但未增加细胞间黏附分子 - 1（ICAM - 1）的表达，这可能有助于食管炎中白细胞（即嗜酸性粒细胞）的选择性募集。暴露于酸性反流物的食管内皮细胞的激活可能在黏膜鳞状上皮屏障受损（即糜烂性食管炎、消化性溃疡）的情况下导致GERD。
