Rowan, Simon C.

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Rowan, Simon C.
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Rowan, Simon C.

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  • Publication
    Hypoxic pulmonary hypertension: the paradigm is changing
    (Wiley, 2014-06-01)
    Rowan, Simon C. 
    ;
    McLoughlin, Paul 
    We began in the early 2000s to explore the hypothesis that vasoconstrictor mechanisms, selectively altered in the lung, were significant contributors to the increase in pulmonary vascular resistance in pulmonary hypertension. We found that in the normal rat pulmonary circulation the RhoA-ROCK pathway is a greater contributor to vasoconstriction than it is in systemic vessels, demonstrating an important phenotypic difference in the regulation of vascular tone in the two circulations.
      211Scopus© Citations 5
  • Publication
    Gremlin Plays a Key Role in the Pathogenesis of Pulmonary Hypertension
    (Ovid Technologies Wolters Kluwer -American Heart Association, 2012-01-13)
    Cahill, Edwina 
    ;
    Costello, Christine M. 
    ;
    Rowan, Simon C. 
    ;
    et al. 
    Background—Pulmonary hypertension occurs in chronic hypoxic lung diseases, significantly worsening morbidity and mortality. The important role of altered bone morphogenetic protein (BMP) signaling in pulmonary hypertension was first suspected after the identification of heterozygous BMP receptor mutations as the underlying defect in the rare heritable form of pulmonary arterial hypertension. Subsequently, it was demonstrated that BMP signaling was also reduced in common forms of pulmonary hypertension, including hypoxic pulmonary hypertension; however, the mechanism of this reduction has not previously been elucidated. Methods and Results—Expression of 2 BMP antagonists, gremlin 1 and gremlin 2, was higher in the lung than in other organs, and gremlin 1 was further increased in the walls of small intrapulmonary vessels of mice during the development of hypoxic pulmonary hypertension. Hypoxia stimulated gremlin secretion from human pulmonary microvascular endothelial cells in vitro, which inhibited endothelial BMP signaling and BMP-stimulated endothelial repair. Haplodeficiency of gremlin 1 augmented BMP signaling in the hypoxic mouse lung and reduced pulmonary vascular resistance by attenuating vascular remodeling. Furthermore, gremlin was increased in the walls of small intrapulmonary vessels in idiopathic pulmonary arterial hypertension and the rare heritable form of pulmonary arterial hypertension in a distribution suggesting endothelial localization. Conclusions—These findings demonstrate a central role for increased gremlin in hypoxia-induced pulmonary vascular remodeling and the increased pulmonary vascular resistance in hypoxic pulmonary hypertension. High levels of basal gremlin expression in the lung may account for the unique vulnerability of the pulmonary circulation to heterozygous mutations of BMP type 2 receptor in pulmonary arterial hypertension.
      410Scopus© Citations 76
  • Publication
    Hypoxic pulmonary hypertension in chronic lung diseases: novel vasoconstrictor pathway
    (Elsevier, 2016-03)
    Rowan, Simon C. 
    ;
    Keane, M. P. 
    ;
    Gaine, Seán 
    ;
    McLoughlin, Paul 
    Pulmonary hypertension is a well recognised complication of chronic hypoxic lung diseases, which are among the most common causes of death and disability worldwide. Development of pulmonary hypertension independently predicts reduced life expectancy. In chronic obstructive pulmonary disease, long-term oxygen therapy ameliorates pulmonary hypertension and greatly improves survival, although the correction of alveolar hypoxia and pulmonary hypertension is only partial. Advances in understanding of the regulation of vascular smooth muscle tone show that chronic vasoconstriction plays a more important part in the pathogenesis of hypoxic pulmonary hypertension than previously thought, and that structural vascular changes contribute less. Trials of existing vasodilators show that pulmonary hypertension can be ameliorated and systemic oxygen delivery improved in carefully selected patients, although systemic hypotensive effects limit the doses used. Vasoconstrictor pathways that are selective for the pulmonary circulation can be blocked to reduce hypoxic pulmonary hypertension without causing systemic hypotension, and thus provide potential targets for novel therapeutic strategies.
      861Scopus© Citations 47