Abstract 18631: Mechanistic Insight on the Protective Role of Microbiome-Derived Butyrate in Pulmonary Hypertension

Abstract

Introduction: Endothelial cell (EC) dysfunction is increasingly recognized as a precipitating event in Pulmonary hypertension (PH), a progressive, severe disease characterized by high blood pressure in the pulmonary circulation and excessive pulmonary vascular remodeling and inflammation. Microbiome-derived metabolites are altered in PH but their role in this disease remains poorly understood. Butyrate, a microbiome-derived short-chain fatty acid (SCFA) with biological activity, has been associated with benefit in cardiovascular diseases such as atherosclerosis. We aimed to test whether and how butyrate plays a protective role in PH. Results: PH-related inflammatory cytokine IL1β (10 ng/ml) increased expression of mesenchymal markers fibronectin, N-cadherin and transgelin (SM22) in human pulmonary arterial EC (HPAEC), consistent with induction of endothelial-to-mesenchymal transdifferentiation (EndMT). Butyrate (given as sodium butyrate, NaB; 2mM) attenuated this IL1β -induced upregulation (p<0.01, p<0.001, p<0.001 for each gene, respectively). Likewise, butyrate inhibited IL1β-induced upregulation of b-catenin (p<0.001), an important mediator of EndoMT. We previously showed that butyrate reversed IL1 β-induced downregulation of the PDZ protein EBP50, which we showed as a critical modulator of EndMT. In vivo, butyrate (NaB, 150mM) reversed PH phenotypes in wildtype mice (WT) following hypoxia exposure. In contrast, this reversal was attenuated in EBP50 heterozygous mice (Het, 50% EBP50 expression vs. WT) under hypoxia supplemented with butyrate. Similarly, butyrate reduced the number of circulating monocytes in hypoxia exposed WT but not Het mice. Conclusions: Collectively our results demonstrate that butyrate attenuates PH potentially via protecting against pulmonary vascular endothelial reprogramming and myeloid cell induction, through a mechanism that involves EBP50. These findings support the possible therapeutic benefits of butyrate in PH and shed mechanistic insight on the underlying cellular pathways propagating butyrate protection.