Enhanced serelaxin signalling in co-cultures of human primary endothelial and smooth muscle cells.
OBJECTIVE
In the phase III clinical trial, RELAX-AHF, serelaxin caused rapid and long-lasting haemodynamic changes. However, the cellular mechanisms involved are unclear in humans.


METHODS
This study examined the effects of serelaxin in co-cultures of human primary endothelial cells (ECs) and smooth muscle cells (SMCs) on cAMP and cGMP signalling.


RESULTS
Stimulation of HUVECs or human coronary artery endothelial cells (HCAECs) with serelaxin, concentration-dependently increased cGMP accumulation in co-cultured SMCs to a greater extent than in monocultures of either cell type. This was not observed in human umbilical artery endothelial cells (HUAECs) that do not express the relaxin receptor, RXFP1. Treatment of ECs with l-N(G) -nitro arginine (NOARG; 30 μM, 30 min) inhibited serelaxin-mediated (30 nM) cGMP accumulation in HUVECs, HCAECs and co-cultured SMCs. In HCAECs, but not HUVECs, pre-incubation with indomethacin (30 μM, 30 min) also inhibited cGMP accumulation in SMCs. Pre-incubation of SMCs with the guanylate cyclase inhibitor ODQ (1 μM, 30 min) had no effect on serelaxin-mediated (30 nM) cGMP accumulation in HUVECs and HCAECs but inhibited cGMP accumulation in SMCs. Serelaxin stimulation of HCAECs, but not HUVECs, increased cAMP accumulation concentration-dependently in SMCs. Pre-incubation of HCAECs with indomethacin, but not l-NOARG, abolished cAMP accumulation in co-cultured SMCs, suggesting involvement of prostanoids.


CONCLUSIONS
In co-cultures, treatment of ECs with serelaxin caused marked cGMP accumulation in SMCs and with HCAEC also cAMP accumulation. Responses involved EC-derived NO and with HCAEC prostanoid production. Thus, serelaxin differentially modulates vascular tone in different vascular beds.
Drug Discovery Biology, Monash Institute of Pharmacology, Monash University, Australia.
M
M
Sarwar
Department of Pharmacology, Monash University, Australia.
C S
CS
Samuel
The Florey Institute of Neuroscience and Mental Health and the Department of Biochemistry and Molecular Biology, University of Melbourne, Australia.
R A
RA
Bathgate
Corthera Inc., San Mateo, CA, USA.
D R
DR
Stewart
Drug Discovery Biology, Monash Institute of Pharmacology, Monash University, Australia.
R J
RJ
Summers
D018920:Coculture Techniques; D003331:Coronary Vessels / Q000166:cytology*; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism*; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D019335:Nitroarginine / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D018000:Receptors, Peptide / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D012065:Relaxin / Q000494:pharmacology*; D015398:Signal Transduction; D014469:Umbilical Arteries / Q000166:cytology*; D014471:Umbilical Veins / Q000166:cytology*
C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D010069:Oxadiazoles; D011810:Quinoxalines; C417543:RXFP1 protein, human; D043562:Receptors, G-Protein-Coupled; D018000:Receptors, Peptide; D011994:Recombinant Proteins; C577649:serelaxin protein, human; D019335:Nitroarginine; D012065:Relaxin; D000242:Cyclic AMP; D006152:Cyclic GMP; D007213:Indomethacin