Resistance to endotoxic shock in mice lacking natriuretic peptide receptor-A.
OBJECTIVE
Excessive production of nitric oxide (NO) by inducible NO synthase (iNOS) is thought to underlie the vascular dysfunction, systemic hypotension and organ failure that characterize endotoxic shock. Plasma levels of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) are raised in animal models and humans with endotoxic shock and correlate with the associated cardiovascular dysfunction. Since both NO and natriuretic peptides play important roles in cardiovascular homeostasis via activation of guanylate cyclase-linked receptors, we used mice lacking natriuretic peptide receptor (NPR)-A (NPR1) to establish if natriuretic peptides contribute to the cardiovascular dysfunction present in endotoxic shock.


METHODS
Wild-type (WT) and NPR-A knockout (KO) mice were exposed to lipopolysaccharide (LPS) and vascular dysfunction (in vitro and in vivo), production of pro-inflammatory cytokines, and iNOS expression and activity were evaluated.


RESULTS
LPS-treated WT animals exhibited a marked fall in mean arterial blood pressure (MABP) whereas NPR-A KO mice maintained MABP throughout. LPS administration caused a greater suppression of vascular responses to the thromboxane-mimetic U46619, ANP, acetylcholine and the NO-donor spermine-NONOate in WT versus NPR-A KO mice. This differential effect on vascular function was paralleled by reduced pro-inflammatory cytokine production, iNOS expression and activity (plasma [NO(x)] and cyclic GMP).


CONCLUSIONS
These observations suggest that NPR-A activation by natriuretic peptides facilitates iNOS expression and contributes to the vascular dysfunction characteristic of endotoxic shock. Pharmacological interventions that target the natriuretic peptide system may represent a novel approach to treat this life-threatening condition.
Panayiotou
Catherine M
CM
Pharmacology (NPP), University College London, Medical Sciences Building, London, UK.
Baliga
Reshma
R
Stidwill
Raymond
R
Taylor
Valerie
V
Singer
Mervyn
M
Hobbs
Adrian J
AJ
D000818:Animals; D001013:Aorta, Thoracic / Q000201:enzymology / Q000503:physiopathology; D001794:Blood Pressure; D006152:Cyclic GMP / Q000097:blood; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D006439:Hemodynamics / Q000187:drug effects; D018836:Inflammation Mediators / Q000378:metabolism; D008070:Lipopolysaccharides; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000097:blood; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D017461:Receptors, Atrial Natriuretic Factor / Q000172:deficiency* / Q000235:genetics; D012772:Shock, Septic / Q000139:chemically induced / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control*; D013997:Time Factors; D014661:Vasoconstriction; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation; D014665:Vasodilator Agents / Q000494:pharmacology
D016207:Cytokines; D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D017461:Receptors, Atrial Natriuretic Factor; C091715:atrial natriuretic factor receptor A; D006152:Cyclic GMP