title: Relaxin peptide hormones are protective during the early stages of ischemic stroke in male rats.
abstract: The pregnancy hormone relaxin protects tissue from ischemic damage. The ability of relaxin-3, a relaxin paralog, to do so has not been explored. The cerebral expression levels of these peptides and their receptors make them logical targets for study in the ischemic brain. We assessed relaxin peptide-mediated protection, relative relaxin family peptide receptor (RXFP) involvement, and protective mechanisms. Sprague-Dawley rats receiving permanent (pMCAO) or transient middle cerebral artery occlusions (tMCAO) were treated with relaxin peptides, and brains were collected for infarct analysis. Activation of the endothelial nitric oxide synthase pathway was evaluated as a potential protective mechanism. Primary cortical rat astrocytes were exposed to oxygen glucose deprivation and treated with relaxin peptides, and viability was examined. Receptor involvement was explored using RXFP3 antagonist or agonist treatment and real-time PCR. Relaxin and relaxin-3 reduced infarct size after pMCAO. Both peptides activated endothelial nitric oxide synthase. Because relaxin-3 has not previously been associated with this pathway and displays promiscuous RXFP binding, we explored the receptor contribution. Expression of rxfp1 was greater than that of rxfp3 in rat brain, although peptide binding at either receptor resulted in similar overall protection after pMCAO. Only RXFP3 activation reduced infarct size after tMCAO. In astrocytes, rxfp3 gene expression was greater than that of rxfp1. Selective activation of RXFP3 maintained astrocyte viability after oxygen glucose deprivation. Relaxin peptides are protective during the early stages of ischemic stroke. Differential responses among treatments and models suggest that RXFP1 and RXFP3 initiate different protective mechanisms. This preliminary work is a pivotal first step in identifying the clinical implications of relaxin peptides in ischemic stroke.
authors.affiliation: Department of Biomedical Sciences (L.H.B., J.M.W., F.J.A., A.J.S.S.), Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada N1G2W1; Department of Biomedical Sciences (B.J.C., T.M.S.), Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada C1A4P3; and Department of Biology (B.C.W.), Acadia University, Wolfville, Nova Scotia, Canada B4P2R6.
authors.forename: Lindsay H
authors.initials: LH
authors.lastname: Bergeron
authors.forename: Jordan M
authors.initials: JM
authors.lastname: Willcox
authors.forename: Faisal J
authors.initials: FJ
authors.lastname: Alibhai
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Connell
authors.forename: Tarek M
authors.initials: TM
authors.lastname: Saleh
authors.forename: Brian C
authors.initials: BC
authors.lastname: Wilson
authors.forename: Alastair J S
authors.initials: AJ
authors.lastname: Summerlee
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects; D001921:Brain / Q000473:pathology; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004353:Drug Evaluation, Preclinical; D020244:Infarction, Middle Cerebral Artery / Q000473:pathology / Q000517:prevention & control*; D008297:Male; D011897:Random Allocation; D017207:Rats, Sprague-Dawley; D043562:Receptors, G-Protein-Coupled / Q000819:agonists / Q000037:antagonists & inhibitors; D018000:Receptors, Peptide / Q000819:agonists / Q000037:antagonists & inhibitors; D011994:Recombinant Proteins / Q000627:therapeutic use; D012065:Relaxin / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: C577472:RXFP3 protein, rat; D043562:Receptors, G-Protein-Coupled; D018000:Receptors, Peptide; D011994:Recombinant Proteins; D012065:Relaxin