Affiliation:
1. From the Department of Pediatrics, Stanford University Medical School, Stanford, CA.
Abstract
Rationale:
Hypoxia-inducible factor-1α (HIF-1α), an oxygen (O
2
)-sensitive transcription factor, mediates transcriptional responses to low-O
2
tension states. Although acute hypoxia causes pulmonary vasoconstriction and chronic hypoxia can cause vascular remodeling and pulmonary hypertension, conflicting data exist on the role of HIF-1α in modulating pulmonary vascular tone.
Objective:
To investigate the role of smooth muscle cell (SMC)–specific HIF-1α in regulating pulmonary vascular tone.
Methods and Results:
Mice with an SMC-specific deletion of HIF-1α (SM22α-HIF-1α
−/−
) were created to test the hypothesis that pulmonary artery SMC (PASMC) HIF-1α modulates pulmonary vascular tone and the response to hypoxia. SM22α-HIF-1α
−/−
mice exhibited significantly higher right ventricular systolic pressure compared with wild-type littermates under normoxia and with exposure to either acute or chronic hypoxia in the absence of histological evidence of accentuated vascular remodeling. Moreover, myosin light chain phosphorylation, a determinant of SMC tone, was higher in PASMCs isolated from SM22α-HIF-1α
−/−
mice compared with wild-type PASMCs, during both normoxia and after acute hypoxia. Further, overexpression of HIF-1α decreased myosin light chain phosphorylation in HIF-1α–null SMCs.
Conclusions:
In both normoxia and hypoxia, PASMC HIF-1α maintains low pulmonary vascular tone by decreasing myosin light chain phosphorylation. Compromised PASMC HIF-1α expression may contribute to the heightened vasoconstriction that characterizes pulmonary hypertension.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Cardiology and Cardiovascular Medicine,Physiology
Cited by
68 articles.
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