Exposure to chronic hypoxia (CH) occurs with many pulmonary diseases and results in the development of pulmonary hypertension. Studies from our lab and others demonstrated a key role for the transcription factor, hypoxia-inducible factor-1 (HIF-1) in the development of hypoxic pulmonary hypertension. It is well recognized that expression of HIF-1a, the oxygen-sensitive subunit of HIF-1, correlates with hypoxic induction of genes encoding factors implicated in development of pulmonary hypertension, including endothelin-1 (ET-1), a potent vasoconstrictive and mitogenic agent. During the previous funding period, we defined several mechanisms by which CH and ET-1 alter pulmonary vasomotor tone. Recently, our studies revealed a new paradigm where ET-1 regulates HIF-1 expression. Our preliminary data show that ET-1 increased expression of the oxygen-sensitive 1 subunit of HIF-1, HIF-1a, in pulmonary arterial smooth muscle cells (PASMCs), even under normoxic conditions, and reduced expression of prolyl hydroxylases, key enzymes that are responsible for targeting HIF-1a for rapid degradation. These data suggest that while activation of HIF-1 by hypoxia in endothelial cells might cause elevated ET-1 production, subsequent ET-1 signaling in PASMCs contributes to maintained upregulation of HIF-1, creating a positive feedback, or feed-forward, process. Conversely, an elevation in ET-1 levels, as occurs in numerous disease states, may result in increased HIF-1 expression in the absence of associated hypoxia. Based on these new findings, we hypothesize that during moderate hypoxia, increased pulmonary ET-1 production and activation of ET-1 receptors on PASMCs leads to a positive feedback, or feed- forward, mechanism of HIF-11 protein accumulation and enhanced HIF-1-dependent gene transcription. This results in alterations in PASMC function which contribute to the development of pulmonary hypertension. To test this hypothesis, we will use a combination of techniques including transgenic animals, microfluorescence measurements, whole-cell patch-clamp, and molecular biology, to accomplish the following Specific Aims: 1) determine whether ET-1 derived specifically from endothelial cells is required for and/or accelerates HIF-dependent pathophysiological effects of CH in the pulmonary circulation;2) elucidate the mechanism(s) by which ET-1 modulates HIF-1 expression and 3) determine whether HIF-1 is the downstream effector molecule mediating hypoxia- induced alterations in PASMC homeostasis.

Public Health Relevance

The experiments in this proposal will explore cellular mechanisms involved in the development of pulmonary hypertension, a devastating disease with limited treatment options. Understanding the cellular changes that occur in the pulmonary vasculature with development of pulmonary hypertension is key to advancing treatment and therapeutic options.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL067191-06
Application #
7851386
Study Section
Respiratory Integrative Biology and Translational Research Study Section (RIBT)
Program Officer
Moore, Timothy M
Project Start
2001-04-01
Project End
2012-06-30
Budget Start
2010-07-01
Budget End
2012-06-30
Support Year
6
Fiscal Year
2010
Total Cost
$409,134
Indirect Cost
Name
Johns Hopkins University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
001910777
City
Baltimore
State
MD
Country
United States
Zip Code
21218
Shimoda, Larissa A; Laurie, Steven S (2014) HIF and pulmonary vascular responses to hypoxia. J Appl Physiol (1985) 116:867-74
Shimoda, Larissa A; Laurie, Steven S (2013) Vascular remodeling in pulmonary hypertension. J Mol Med (Berl) 91:297-309
Pisarcik, Sarah; Maylor, Julie; Lu, Wenju et al. (2013) Activation of hypoxia-inducible factor-1 in pulmonary arterial smooth muscle cells by endothelin-1. Am J Physiol Lung Cell Mol Physiol 304:L549-61
Wang, Jian; Shimoda, Larissa A; Sylvester, J T (2012) Ca2+ responses of pulmonary arterial myocytes to acute hypoxia require release from ryanodine and inositol trisphosphate receptors in sarcoplasmic reticulum. Am J Physiol Lung Cell Mol Physiol 303:L161-8
Abud, Edsel M; Maylor, Julie; Undem, Clark et al. (2012) Digoxin inhibits development of hypoxic pulmonary hypertension in mice. Proc Natl Acad Sci U S A 109:1239-44
Luke, Trevor; Maylor, Julie; Undem, Clark et al. (2012) Kinase-dependent activation of voltage-gated Ca2+ channels by ET-1 in pulmonary arterial myocytes during chronic hypoxia. Am J Physiol Lung Cell Mol Physiol 302:L1128-39
Sylvester, J T; Shimoda, Larissa A; Aaronson, Philip I et al. (2012) Hypoxic pulmonary vasoconstriction. Physiol Rev 92:367-520
Shimoda, Larissa A; Polak, Jan (2011) Hypoxia. 4. Hypoxia and ion channel function. Am J Physiol Cell Physiol 300:C951-67
Weigand, Letitia; Shimoda, Larissa A; Sylvester, J T (2011) Enhancement of myofilament calcium sensitivity by acute hypoxia in rat distal pulmonary arteries. Am J Physiol Lung Cell Mol Physiol 301:L380-7
Shimoda, Larissa A; Undem, Clark (2010) Interactions between calcium and reactive oxygen species in pulmonary arterial smooth muscle responses to hypoxia. Respir Physiol Neurobiol 174:221-9

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