Endothelial exposure to hypoxia induces Egr-1 expression involving PKCalpha-mediated Ras/Raf-1/ERK1/2 pathway.

Abstract

Hypoxia induces endothelial dysfunction that results in a series of cardiovascular injuries. Early growth response-1 (Egr-1) has been indicated as a common theme in vascular injury. Here we demonstrates that in bovine aortic endothelial cells (ECs) subjected to hypoxia (PO(2) approximately 23 mmHg), rapidly increased Egr-1 mRNA expression which peaked within 30 min and decreased afterwards. Treatment of ECs with PD98059, a specific inhibitor to mitogen-activated protein kinase (MAPK/ERK), inhibited this hypoxia-induced Egr-1 expression. The involvement of ERK pathway was further substantiated by the inhibition of Egr-1 promoter activities when ECs were co-transfected with a dominant negative mutant of Ras (RasN17), Raf-1 (Raf 301), or a catalytically inactive mutant of ERK2 (mERK). In addition, the hypoxia-induced transcriptional activity of Elk-1, an ERK substrate, was abolished by administration of PD98059. Addition of calphostin C, a protein kinase C (PKC) inhibitor, completely blocked the hypoxia-augmented Egr-1 expression. The likewise occurred while exposing ECs to D609 to inhibit phospholipase C and BAPTA/AM to chelate intracellular calcium. Hypoxia to ECs increased ERK phosphorylation within 10 min and which was abolished by administration of PD98095, calphostin C, and BAPTA/AM. Hypoxia triggered a transient translocation of PKCalpha from cytosol to membrane fraction concurrent with the association of PKCalpha to Raf-1. Involvement of PKCalpha in mediating ERK activation was further confirmed by the inhibition of ERK and the subsequent Egr-1 gene induction with antisense oligonucleotides to PKCalpha. These results indicate that ECs under hypoxia induce Egr-1 expression and this induction requires calcium, phospholipase C activation, and PKCalpha-mediated Ras/Raf-1/ERK1/2 signaling pathway. Our finding support the importance of specific PKC isozyme linked to MAPK pathway in the regulation of endothelial responses to hypoxia.

• Authors: L W Lo, J J Cheng, J J Chiu, B S Wung, Y C Liu, D L Wang
• Journal: Journal of cellular physiology (J Cell Physiol) Vol. 188 Issue 3 Pg. 304-12 (Sep 2001) ISSN: 0021-9541 [Print] United States
• PMID: 11473356 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright 2001 Wiley-Liss, Inc.

Chemical References

• DNA-Binding Proteins
• Enzyme Inhibitors
• Isoenzymes
• Proto-Oncogene Proteins
• RNA, Messenger
• Transcription Factors
• ets-Domain Protein Elk-1
• Proto-Oncogene Proteins c-raf
• Protein Kinase C
• Protein Kinase C-alpha
• Mitogen-Activated Protein Kinase 1
• Mitogen-Activated Protein Kinase 3
• Mitogen-Activated Protein Kinases
• Type C Phospholipases
• ras Proteins
• Calcium

Topics

• Animals
• Calcium (metabolism)
• Cattle
• Cell Hypoxia (physiology)
• Cells, Cultured
• DNA-Binding Proteins (biosynthesis, genetics)
• Endothelium, Vascular (cytology, metabolism)
• Enzyme Inhibitors (pharmacology)
• Gene Expression Regulation (drug effects)
• Genes, Dominant
• Genes, Reporter
• Isoenzymes (metabolism)
• Mitogen-Activated Protein Kinase 1 (antagonists & inhibitors, genetics, metabolism)
• Mitogen-Activated Protein Kinase 3
• Mitogen-Activated Protein Kinases (antagonists & inhibitors, metabolism)
• Protein Kinase C (metabolism)
• Protein Kinase C-alpha
• Proto-Oncogene Proteins (metabolism)
• Proto-Oncogene Proteins c-raf (genetics, metabolism)
• RNA, Messenger (metabolism)
• Signal Transduction (drug effects, physiology)
• Transcription Factors (biosynthesis, genetics)
• Transcriptional Activation
• Transfection
• Type C Phospholipases (metabolism)
• ets-Domain Protein Elk-1
• ras Proteins (genetics, metabolism)