Role of oxidative stress, inflammation and fibrosis in promoting vasculopathy in systemic sclerosis related pulmonary arterial hypertension
Grzegorzewska, Agnieszka Paulina
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Systemic sclerosis (SSc) is a rare connective tissue disease affecting skin and internal organs. The pathogenesis of SSc is multifactorial and includes autoimmunity, inflammation and vasculopathy. Pulmonary arterial hypertension (PAH) is among the most serious of SSc complications and is characterized by augmented vasoconstriction, neointimal remodeling and occlusion of small arteries in lung. Elevated pulmonary arterial blood pressure and volume overload in the right heart eventually lead to death from heart failure. Pre-existing elevated pro-fibrotic signaling, systemic vasculopathy and chronic inflammation are additional factors that likely contribute to the more severe PAH manifestation in SSc patients, whose response to existing therapies is suboptimal. The aim of my thesis research was to investigate the pathological role of altered transcriptional regulation of endothelium in pulmonary vasculature, as well as testing potential novel therapies for SSc-PAH in vivo. I found that endothelial downregulation of GATA6 promotes increased production of reactive oxygen species (ROS) by suppressing enzymatic machinery responsible for ROS clearance. Increased ROS production triggered ER stress and inflammation, exacerbating endothelial dysfunction and vascular injury both in vitro and in vivo. Another discovery is that simultaneous depletion of two ETS-family factors, ERG and FLI1 synergistically activates interferon signaling in pulmonary endothelial cells and promotes inflammation in lung in vivo. Based on observed pathological contribution of oxidative stress and inflammation to vasculopathy and fibrosis I tested an anti-oxidative and anti-inflammatory agent- dimethyl fumarate (DMF) in mouse models of PAH, as well as lung and skin fibrosis. DMF efficiently ameliorated increased pulmonary artery pressure and vascular remodeling, as well as fibrotic changes in lung and skin. Mechanistically, I found that DMF promotes a proteasomal, βTRCP-dependent degradation of pro-fibrotic mediators TAZ/YAP, β-catenin and Sp1. In conclusion, I characterized new elements of pathological mechanism that promote vasculopathy and fibrosis, as well as provided an insight into anti-inflammatory and anti-fibrotic DMF therapy. Importantly, elucidating the novel mechanism of DMF action and recognizing the pathological role of Hippo and Wnt signaling in fibrosis might help to design more specific and effective pharmacological intervention in SSc-PAH patients.