Heterogeneous Nuclear Ribonucleoprotein A1 as a Key Regulator in Pulmonary Arterial Hypertension Development

ABSTRACT Background Although plexiform lesion (PL) formation in severe pulmonary arterial hypertension (PAH) is a therapeutic target, the mechanisms underlying their formation have not been fully elucidated. This study aimed to identify candidate proteins involved in PL formation by examining differentially expressed proteins (DEPs) in PAH lesions. Methods Proteomic remodeling was assessed before and after the formation of PLs in a SU5416 combined with hypoxia (SuHx) rat model of severe PAH using laser-capture microdissection coupled with mass spectrometry. Unobstructed pulmonary arteries with medial hypertrophy (UMHPAs) and PLs from SuHx rats were subjected to qualitative and quantitative proteomics, revealing DEPs between these structures. Results We identified 718 proteins with 58 DEPs, of which 31 were upregulated in UMHPAs and 27 were upregulated in PLs. Immunostaining confirmed that DEPs detected in our proteomic analysis were differentially expressed between UMHPAs and PLs. Among them, we focused on heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) as a candidate protein that may be strongly associated with PL formation because of its strong association with cell proliferation. siRNA knockdown of hnRNPA1 in hypoxia-treated pulmonary artery smooth muscle cells reduced pyruvate kinase M2 expression and significantly decreased proliferative capacity. Treatment of SuHx rats with hnRNPA1 inhibitors also suppressed pulmonary artery remodeling in PAH and PL formation. Conclusions Several DEPs associated with PL formation but with unclear relevance to pulmonary artery remodeling in PAH were discovered. Among these, hnRNPA1, which was not detected in transcriptome analysis, may be important in PL formation. What are the Clinical Implications? The prognosis for pulmonary arterial hypertension (PAH) with plexiform lesions (PLs) is poor. Although PLs are therapeutic targets, the mechanisms of PL formation have not been fully elucidated, and there have been no direct examinations of proteomic remodeling before and after their formation. We identified several differentially expressed proteins (DEPs) that may be strongly associated with PL formation. Of these, heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) was examined as a candidate protein involved in PA remodeling in PAH and PLs. Inhibition of hnRNPA1 in a severe PAH model not only suppressed pulmonary artery remodeling in PAH but also reduced PL formation. Several DEPs involved in pulmonary artery remodeling in PAH may be of significant value in the search for new therapeutic targets.