Hypoxia increases AP-1 binding activity by enhancing capacitative Ca2+ entry in human pulmonary artery endothelial cells.

Abstract

Activating protein (AP)-1 transcription factors modulate expression of genes involved in cell proliferation and migration. Chronic hypoxia increases pulmonary artery smooth muscle cell proliferation by upregulating AP-1-responsive genes encoding for endothelium-derived vasoactive and mitogenic factors implicated in pulmonary hypertension development. The expression of AP-1 transcription factors is sensitive to changes in cytosolic free [Ca2+] ([Ca2+]cyt). Capacitative Ca2+ entry (CCE) via store-operated Ca2+ channels (SOC) is an important mechanism for raising [Ca2+]cyt in pulmonary artery endothelial cells (PAEC). Using combined molecular biological, fluorescence microscopy, and biophysical approaches, we examined the effect of chronic hypoxia (3% O2, 72 h) on AP-1 DNA binding activity, CCE, and transient receptor potential (TRP) gene expression in human (h) PAEC. EMSA showed that AP-1 binding to hPAEC nuclear protein extracts was significantly enhanced by hypoxia, the increase being dependent on store-operated Ca2+ influx and sensitive to La3+, an SOC inhibitor. Hypoxia also increased basal [Ca2+]cyt, the amount of CCE produced by store depletion with cyclopiazonic acid, and the amplitude of SOC-mediated currents (ISOC). The increases of CCE amplitude and ISOC current density by hypoxia were paralleled by enhanced TRPC4 mRNA and protein expression. Hypoxia-enhanced CCE and TRPC4 expression were also attenuated by La3+. These data suggest that hypoxia increases AP-1 binding activity by enhancing Ca2+ influx via La3+-sensitive TRP-encoded SOC channels in hPAEC. The Ca2+-mediated increase in AP-1 binding may play an important role in upregulating AP-1-responsive gene expression, in stimulating pulmonary vascular cell proliferation and, ultimately, in pulmonary vascular remodeling in patients with hypoxia-mediated pulmonary hypertension.

• Authors: Ivana Fantozzi, Shen Zhang, Oleksandr Platoshyn, Carmelle V Remillard, Randy T Cowling, Jason X-J Yuan
• Journal: American journal of physiology. Lung cellular and molecular physiology (Am J Physiol Lung Cell Mol Physiol) Vol. 285 Issue 6 Pg. L1233-45 (Dec 2003) ISSN: 1040-0605 [Print] United States
• PMID: 12909593 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Calcium Channels
• Enzyme Inhibitors
• Indoles
• Nuclear Proteins
• RNA, Small Interfering
• TRPC Cation Channels
• Transcription Factor AP-1
• Calcium
• cyclopiazonic acid

Topics

• Calcium (metabolism)
• Calcium Channels (genetics, metabolism)
• Cells, Cultured
• Chronic Disease
• Endothelium, Vascular (cytology, metabolism)
• Enzyme Inhibitors (pharmacology)
• Gene Silencing
• Humans
• Hypertension, Pulmonary (metabolism)
• Hypoxia (metabolism)
• Indoles (pharmacology)
• Nuclear Proteins (metabolism)
• Pulmonary Artery (cytology, metabolism)
• RNA, Small Interfering
• TRPC Cation Channels
• Transcription Factor AP-1 (metabolism)