Mechanisms of newborn pulmonary hypertension caused by chronic intrauterine hypoxia

PROJECT SUMMARY
Chronic intrauterine hypoxia is common amongst not only the 140 million people in the
world living at high altitudes but also in many complications of pregnancy such as preeclampsia,
cigarette smoking, and placental insufficiency. Adaptation of the fetus to chronic hypoxia results
in many adverse developmental outcomes, including pulmonary hypertension of the newborn.
The BKCa channel is critical to the relaxation of the pulmonary vasculature of the newborn at
birth. Recent results from our well-established fetal lamb model of chronic hypoxia during
pregnancy points to BKCa channel dysfunction as a causal factor in pulmonary hypertension. The
work in this proposal will investigate the mechanistic link between cellular hypoxia and BKCa
channel dysfunction. Recent work by others indicates that the ‘master hypoxamir’ miR210, a
micro-RNA that is upregulated by HIF-1?, orchestrates pulmonary hypertension by suppressing
translation of the iron-sulfur cluster assembly protein ISCU. The resulting lack of iron-sulfur
clusters results in mitochondrial dysfunction. We hypothesize that chronic intrauterine hypoxia
leads to pulmonary hypertension by activation of the HIF-1? → miR210 → ISCU axis,
resulting in increased mitochondrial-derived reactive oxygen species that lead to BKCa channel
dysfunction.
We propose three specific aims. Each specific aim is designed to integrate in vitro and in
vivo approaches in order to better ascertain the relevance of the in vitro results to pulmonary
function of the intact animal. Aim 1 will focus on determining the mechanism underlying BKCa
channel dysfunction, and on establishing whether loss of BKCa channel function alone is
adequate to result in pulmonary hypertension in intact lambs. Aim 2 will focus on the effects of
hypoxia-induced increases in miR210 on ISCU activity, iron-sulfur cluster levels, and
mitochondrial function and reactive oxygen species production. In intact lambs, we will
establish whether activation of this pathway in the absence of hypoxia results in pulmonary
hypertension, and whether suppression of this pathway in the presence of hypoxia prevents BKCa
channel function and pulmonary hypertension. Aim 3 will investigate whether the increased
reactive oxygen species levels in response to chronic hypoxia play a causative role in BKCa
channel function and pulmonary hypertension. Using both in vitro and in vivo methods, we will
determine whether the global antioxidant Vitamin C or mitochondria-specific antioxidant MitoQ
will prevent pulmonary hypertension caused by chronic intrauterine hypoxia.

Grant Number: 5R01HL155295-04
NIH Institute/Center: NIH
Principal Investigator: Arlin Blood