BACKGROUND AND PURPOSE C‐type natriuretic peptide (CNP) is an endothelium‐derived vasorelaxant, exerting anti‐atherogenic actions in the vasculature and salvaging the myocardium from ischaemic injury. The cytoprotective effects of CNP are mediated in part via the G_i‐coupled natriuretic peptide receptor (NPR)3. As GPCRs are well‐known to control cell proliferation, we investigated if NPR3 activation underlies effects of CNP on endothelial and vascular smooth muscle cell mitogenesis.

EXPERIMENTAL APPROACH Proliferation of human umbilical vein endothelial cells (HUVEC), rat aortic smooth muscle cells (RAoSMC) and endothelial and vascular smooth muscle cells from NPR3 knockout (KO) mice was investigated in vitro.

KEY RESULTS CNP (1 pM–1 µM) facilitated HUVEC proliferation and inhibited RAoSMC growth concentration‐dependently. The pro‐ and anti‐mitogenic effects of CNP were blocked by the NPR3 antagonist M372049 (10 µM) and the extracellular signal‐regulated kinase (ERK) 1/2 inhibitor PD98059 (30 µM) and were absent in cells from NPR3 KO mice. Activation of ERK 1/2 by CNP was inhibited by Pertussis toxin (100 ng·mL⁻¹) and M372049 (10 µM). In HUVEC, ERK 1/2 activation enhanced expression of the cell cycle promoter, cyclin D1, whereas in RAoSMC, ERK 1/2 activation increased expression of the cell cycle inhibitors p21^waf1/cip1 and p27^kip1.

CONCLUSIONS AND IMPLICATIONS A facet of the vasoprotective profile of CNP is mediated via NPR3‐dependent ERK 1/2 phosphorylation, resulting in augmented endothelial cell proliferation and inhibition of vascular smooth muscle growth. This pathway may offer an innovative approach to reversing the endothelial damage and vascular smooth muscle hyperplasia that characterize many vascular disorders.