Endothelial C-type natriuretic peptide/guanylyl cyclase-B signaling prevents pulmonary arterial hypertension.

Mice developing pulmonary hypertension show reduced pulmonary NPPC and NPR2 expression compared to mice without PH.

• NPPC encodes C-type natriuretic peptide (CNP) and NPR2 encodes guanylyl cyclase-B (GC-B)
• Reduced expression was observed at the pulmonary level in PH-developing mice
• This finding paralleled observations in human disease, establishing translational relevance

Endothelial cells from patients with idiopathic PAH exhibit lower NPPC and NPR2 expression than control endothelial cells.

• Expression of both NPPC and NPR2 was reduced in idiopathic PAH patient-derived endothelial cells
• This finding mirrors the mouse model data, supporting a conserved role of endothelial CNP/GC-B signaling in PAH pathogenesis
• The comparison was made between idiopathic PAH endothelial cells and control endothelial cells

Endothelial cell-specific CNP or GC-B conditional knockout mice develop more severe PH than genetic controls in PAH models.

• Both CNP ecKO and GC-B ecKO mice showed more severe PH compared to their respective genetic controls
• These mice also showed greater expression of Edn1, Il6, Ccl2, and Tgfb1 mRNAs than genetic controls
• The worsened phenotype was specific to endothelial knockout, as smooth muscle cell-specific GC-B conditional knockout (GC-B smcKO) mice did not show the same severity

Smooth muscle cell-specific GC-B conditional knockout mice do not show more severe PH than genetic controls in PAH models.

• GC-B smcKO mice showed no significant difference in PH severity compared to genetic controls
• This contrasts with endothelial-specific knockouts, indicating the protective role of CNP/GC-B signaling is endothelium-dependent rather than smooth muscle-dependent
• The finding localizes the critical signaling to the endothelial compartment

CNP suppresses hypoxia-induced increases in expression of Edn1, Il6, Ccl2, and Tgfb1 mRNAs in cultured human pulmonary arterial endothelial cells.

• Hypoxia-induced upregulation of Edn1 (endothelin-1), Il6 (interleukin-6), Ccl2 (monocyte chemoattractant protein-1), and Tgfb1 (TGF-β1) was attenuated by CNP treatment
• These experiments were performed in cultured human pulmonary arterial endothelial cells
• CNP also restored the SMAD2/3–SMAD1/5/9 balance disrupted by hypoxia in these cells

CNP administration prevents PH in genetic control and GC-B smcKO mice but not in GC-B ecKO mice.

• The preventive effect of exogenous CNP administration was abolished in endothelial-specific GC-B knockout mice
• CNP was protective in smooth muscle cell-specific GC-B knockout mice, confirming that the therapeutic target is endothelial GC-B
• This demonstrates that the protective effect of CNP requires endothelial GC-B signaling

CNP administration has therapeutic effects in Sugen5416-hypoxia PAH models and provides additive benefits when combined with established therapies.

• The Sugen5416-hypoxia model is a severe preclinical model of PAH
• CNP administration showed therapeutic efficacy in this model
• Additive benefits were observed when CNP was combined with established PAH therapies, suggesting potential for combination treatment strategies

CNP acts as an autocrine/paracrine mediator in endothelial cells, regulating systemic blood pressure and vascular remodeling via GC-B and natriuretic peptide receptor-C.

• CNP is released from endothelial cells and signals through two receptors: guanylyl cyclase-B (GC-B, encoded by NPR2) and natriuretic peptide receptor-C (NPR-C)
• This autocrine/paracrine mechanism positions CNP as an endothelium-derived vasoprotective factor
• The study builds on this known biology to investigate its specific role in pulmonary arterial hypertension