Characterization of long-term interleukin-33 administration as an animal model of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by the severe obstruction of the small pulmonary arteries and concomitant high pulmonary arterial pressure, resulting in progressive right ventricular failure. Previously, we demonstrated that long-term interleukin (IL)-33 administration in mice induces severe occlusive medial hypertrophy of pulmonary arteries (PA) in the lungs, which is mediated by group 2 innate lymphoid cells (ILC2s). In response to IL-33, ILC2s accumulate around the blood vessels and produce IL-5, leading to perivascular eosinophil recruitment. In this study, we characterized IL-33-induced medial hypertrophy of PA. We demonstrated that long-term IL-33 administration causes an increase in right ventricular pressure. In IL-33-deficient mice, medial hypertrophy of PA mediated by eggs of Schistosoma mansoni was attenuated, accompanied by a partial reduction in ILC2s, eosinophils, and CD4⁺ T cells. In addition, proteomic analysis revealed dramatic changes in the urine samples from mice treated with IL-33 or S. mansoni eggs. Resistin-like alpha (RELMα), a pulmonary hypertension-related molecule, was commonly detected in the urine in both treatments. Large amounts of RELMα were observed in the lungs of the IL-33-treated mice. These observations suggest that IL-33-induced medial hypertrophy of PA is a useful model for studying the mechanism underlying the development of PAH and finding biomarkers to indicate the onset of PAH.