Targeting Macrophage Crosstalk to PASMC by Blunting Inflammatory Phenotype Via SerpinB1 Protects Against Hypoxia-Induced Pulmonary Hypertension

BACKGROUND: Perivascular macrophages play a significant role in the pathogenesis of hypoxia-induced pulmonary hypertension via crosstalk to pulmonary artery smooth muscle cells (PASMCs) to stimulate their proliferation and pulmonary vascular remodeling. However, whether hypoxia exposure of macrophages affects cellular crosstalk remains entirely unclear. This study aimed to decipher the effects of hypoxia on macrophages' crosstalk to PASMCs and elucidate the underlying molecular mechanisms. METHODS: Conditioned medium obtained from bone marrow-derived macrophages under normoxia or hypoxia was transferred for hypoxic culture of primary mouse PASMCs, followed by RNA sequencing analysis. Myeloid-specific SerpinB1-overexpressing mice were generated to explore SerpinB1's role in macrophage inflammatory phenotype, PASMC proliferation, and pulmonary vascular remodeling. RESULTS: Hypoxia-exposure of macrophages produced a conspicuous augmentation to the pro-proliferative effect of the conditioned medium on PASMCs. Hypoxia exposure aggravated macrophage inflammatory phenotype, as indicated by marked enrichment of multiple inflammatory pathways and elevated levels of inflammatory cytokines. SerpinB1 (serpin family B member 1) was identified as the key downstream mediator of hypoxia to regulate macrophage inflammatory phenotype because hypoxia induced its drastic downregulation and subsequent NLRP3 (NOD [nucleotide oligomerization domain]-, LRR [leucine-rich repeat]-, and PYD [pyrin domain]-containing protein 3)-independent inflammatory caspase-1 activation. Myeloid-specific overexpression of SerpinB1 largely blunted hypoxia-induced macrophage inflammatory phenotype and amplified the pro-proliferative effect on PASMCs. Myeloid SerpinB1-overexpressing mice exhibited lower right ventricular systolic pressure, milder right ventricular hypertrophy, and pulmonary vascular remodeling after chronic hypoxia exposure. CONCLUSIONS: Hypoxia exposure directly amplifies the pro-proliferative crosstalk of macrophages to PASMCs via downregulating SerpinB1 to induce caspase-1 activation and inflammatory phenotype. Targeting macrophage SerpinB1 may hold promise for treating pulmonary hypertension.