Global knockout of melanoma differentiation-associated protein 5 protects mice from chronic hypoxia/SU5416-induced pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a severe disease affecting the pulmonary arteries, causing increased blood pressure due to narrowing of the pulmonary artery lumen. Aberrant proliferation of endothelial cells (ECs) and smooth muscle cells (SMCs), along with a dysregulation of the immune response, contributes to arterial remodeling. We hypothesized that the cytosolic RNA receptor melanoma differentiation-associated protein 5 (MDA5) contributes to PAH by dysregulating pulmonary vascular cell function and immune cell response. In lung tissue from control patients and PAH patients, MDA5 immunoreactivity was widely distributed throughout the pulmonary artery wall. After exposing whole-body MDA5-/- mice to the chronic hypoxia/SU5416 (Hx/Su) protocol, we detected reduced right ventricular systolic pressure and pulmonary artery media wall thickness compared to wild-type mice. Pro-inflammatory mediators, interferon-regulated genes, and perivascular accumulation of CD11b+ myeloid cells were decreased in the lung tissue of Hx/Su-exposed MDA5-/- mice. In cultured human pulmonary artery ECs, MDA5 gene silencing disrupted DNA synthesis and angiogenic network formation. Bulk RNA sequencing analysis revealed the differential expression of 2,533 genes, affecting gene ontologies such as immune response, cell cycle, and cholesterol metabolism. Analysis of a publicly available single-cell RNA-sequence dataset indicates increased expression of MDA5 in monocytes/macrophages in pulmonary arteries from patients with PAH, which is associated with an interferon gene signature. Knockdown of MDA5 in macrophage-like cells reduced the type I interferon gene signature. Our data suggest a protective effect of whole-body MDA5 knockout in mice, which may be due to reduced immune dysregulation.