Essential role for vascular gelatinase activity in relaxin-induced renal vasodilation, hyperfiltration, and reduced myogenic reactivity of small arteries.
During pregnancy, relaxin stimulates nitric oxide (NO)-dependent renal vasodilation, hyperfiltration and reduced myogenic reactivity of small renal arteries via the endothelial ETB receptor subtype. Our objective in this study was to elucidate the mechanisms by which relaxin stimulates the endothelial ETB receptor/NO vasodilatory pathway. Using chronically instrumented conscious rats, we demonstrated that a specific peptide inhibitor of the gelatinases MMP-2 and -9, cyclic CTTHWGFTLC (cyclic CTT), but not the control peptide, STTHWGFTLS (STT), completely reversed renal vasodilation and hyperfiltration in relaxin-treated rats. Comparable findings were observed with a structurally different and well-established, general antagonist of MMPs, GM6001. In contrast, phosphoramidon, an inhibitor of endothelin-converting enzyme, did not significantly change the renal vasodilatory response to relaxin administration. When small renal arteries were incubated with either of the general MMP inhibitors, GM6001 or TIMP-2 (tissue inhibitor of MMP), or with the specific gelatinase inhibitor, cyclic CTT, the reduced myogenic reactivity of these blood vessels from relaxin-treated nonpregnant and midterm pregnant rats was totally abolished. Moreover, a neutralizing antibody specific for MMP-2 completely abrogated the reduced myogenic reactivity of small renal arteries from relaxin-treated nonpregnant and midterm pregnant rats. In contrast, phosphoramidon did not significantly affect the reduction in myogenic reactivity. Using gelatin zymography, we showed increased pro and active MMP-2 activity in small renal arteries from relaxin-treated nonpregnant and midterm pregnant rats relative to the control animals. Thus, inhibitors of MMPs in general and of gelatinases in particular reverse the renal vascular changes induced by pregnancy or relaxin administration to nonpregnant rats. Finally, the typical reduction in myogenic reactivity of small renal arteries from relaxin-treated nonpregnant rats was absent in ETB receptor-deficient rats, despite an increase in vascular MMP-2 activity. These results indicate an essential role for vascular gelatinase, which is in series with, and upstream of, the endothelial ETB receptor/NO signaling pathway in the renal vasodilatory response to relaxin and pregnancy.
Jeyabalan
Arundhathi
A
Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh School of Medicine and Magee-Women's Research Institute, 204 Craft Ave, Pittsburgh, Pa 15213, USA.
Novak
Jacqueline
J
Danielson
Lee A
LA
Kerchner
Laurie J
LJ
Opett
Shannon L
SL
Conrad
Kirk P
KP
D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004151:Dipeptides / Q000494:pharmacology; D000072396:Endothelin-Converting Enzymes; D005260:Female; D018093:Gelatinases / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D005919:Glomerular Filtration Rate / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D007668:Kidney / Q000187:drug effects* / Q000502:physiology; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism / Q000502:physiology; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism / Q000502:physiology; D061965:Matrix Metalloproteinase Inhibitors; D008666:Metalloendopeptidases; D009842:Oligopeptides / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D011247:Pregnancy; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats; D020318:Rats, Long-Evans; D011994:Recombinant Proteins / Q000494:pharmacology; D012065:Relaxin / Q000494:pharmacology*; D012077:Renal Artery / Q000187:drug effects* / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects
D004151:Dipeptides; D061965:Matrix Metalloproteinase Inhibitors; C078131:N-(2(R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl)-L-tryptophan methylamide; D009842:Oligopeptides; D010456:Peptides, Cyclic; D011480:Protease Inhibitors; D011994:Recombinant Proteins; D012065:Relaxin; D016282:Aspartic Acid Endopeptidases; D018093:Gelatinases; D008666:Metalloendopeptidases; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D000072396:Endothelin-Converting Enzymes