Human esophageal microvascular endothelial cells respond to acidic pH stress by PI3K/AKT and p38 MAPK-regulated induction of Hsp70 and Hsp27.
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).
Rafiee
Parvaneh
P
Dept. of Surgery, Medical College of Wisconsin, Milwaukee, WI 53226, USA. prafiee@mcw.edu
Theriot
Monica E
ME
Nelson
Victoria M
VM
Heidemann
Jan
J
Kanaa
Yasmin
Y
Horowitz
Scott A
SA
Rogaczewski
Aaron
A
Johnson
Christopher P
CP
Ali
Irshad
I
Shaker
Reza
R
Binion
David G
DG
D000199:Actins / Q000378:metabolism; D000818:Animals; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002470:Cell Survival / Q000502:physiology; D058534:Class I Phosphatidylinositol 3-Kinases; D003599:Cytoskeleton / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D004947:Esophagus / Q000098:blood supply* / Q000166:cytology; D005786:Gene Expression Regulation / Q000235:genetics; D050883:HSC70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D050957:HSP110 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D055551:HSP27 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D018832:Molecular Chaperones; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000502:physiology; D013552:Swine; D014157:Transcription Factors / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D000199:Actins; D015815:Cell Adhesion Molecules; D058534:Class I Phosphatidylinositol 3-Kinases; D004268:DNA-Binding Proteins; D050883:HSC70 Heat-Shock Proteins; D050957:HSP110 Heat-Shock Proteins; D055551:HSP27 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D014157:Transcription Factors; D048051:p38 Mitogen-Activated Protein Kinases; C121993:HSPA4 protein, human; C494371:HSPA8 protein, human; C057725:HSPB1 protein, human; C484760:PIK3CA protein, human