Human esophageal microvascular endothelial cells respond to acidic pH stress by PI3K/AKT and p38 MAPK-regulated induction of Hsp70 and Hsp27

Am J Physiol Cell Physiol. 2006 Nov;291(5):C931-45. doi: 10.1152/ajpcell.00474.2005. Epub 2006 Jun 21.

Abstract

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).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Animals
  • Cell Adhesion Molecules / metabolism
  • Cell Survival / physiology
  • Class I Phosphatidylinositol 3-Kinases
  • Cytoskeleton / metabolism
  • DNA-Binding Proteins / metabolism
  • Electrophoresis, Gel, Two-Dimensional
  • Endothelial Cells / drug effects
  • Endothelial Cells / enzymology
  • Endothelial Cells / metabolism*
  • Esophagus / blood supply*
  • Esophagus / cytology
  • Gene Expression Regulation / genetics
  • HSC70 Heat-Shock Proteins / genetics
  • HSC70 Heat-Shock Proteins / metabolism
  • HSP110 Heat-Shock Proteins / genetics
  • HSP110 Heat-Shock Proteins / metabolism*
  • HSP27 Heat-Shock Proteins
  • Heat Shock Transcription Factors
  • Heat-Shock Proteins / genetics
  • Heat-Shock Proteins / metabolism*
  • Humans
  • Hydrogen-Ion Concentration
  • Molecular Chaperones
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphorylation
  • Protein Transport
  • Proto-Oncogene Proteins c-akt / metabolism*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • RNA, Small Interfering
  • Signal Transduction / physiology
  • Swine
  • Transcription Factors / metabolism
  • p38 Mitogen-Activated Protein Kinases / metabolism*

Substances

  • Actins
  • Cell Adhesion Molecules
  • DNA-Binding Proteins
  • HSC70 Heat-Shock Proteins
  • HSP110 Heat-Shock Proteins
  • HSP27 Heat-Shock Proteins
  • HSPA4 protein, human
  • HSPA8 protein, human
  • HSPB1 protein, human
  • Heat Shock Transcription Factors
  • Heat-Shock Proteins
  • Molecular Chaperones
  • Neoplasm Proteins
  • RNA, Messenger
  • RNA, Small Interfering
  • Transcription Factors
  • Class I Phosphatidylinositol 3-Kinases
  • PIK3CA protein, human
  • Proto-Oncogene Proteins c-akt
  • p38 Mitogen-Activated Protein Kinases