Contribution of caveolin protein abundance to augmented nitric oxide signaling in conscious dogs with pacing-induced heart failure.
Myocardial NO signaling appears elevated in heart failure (HF). Whether this results from increased NO production, induction of the high-output NO synthase (NOS)2 isoform, or changes in NOS regulatory pathways (such as caveolae) remains controversial. We tested the hypothesis that increased abundance of caveolin-3 and/or sarcolemmal caveolae contribute to increased NO signaling in pacing-induced HF. Abundance of caveolin-3 (0.59+/-0.08 versus 0.29+/-0.08 arbitrary units, P = 0.01) but not caveolin-1 was increased in HF compared with control conditions, assessed by Western blot. Additionally, transmission electron microscopy revealed increased caveolae (2. 7+/-0.4 versus 1.3+/-0.3 per micrometer myocyte membrane, P<0.005). The association between caveolin-3 and NOS3 at the sarcolemma and T tubules was unchanged in HF compared with control myocytes. The impact of NOS inhibition with L-N(G)-methylarginine hydrochloride (L-NMMA) on beta-adrenergic inotropy was assessed in conscious dogs before and after HF. In control dogs, dobutamine (5 microg. kg(-1) x min(-1)) increased +dP/dt by 36+/-7%, and this was augmented to 66+/-24% by 20 mg/kg L-NMMA (P = 0.04 versus without L-NMMA, n = 8) but not affected by 10 mg/kg L-NMMA (34+/-10%, P = NS; n = 8). In HF, dobutamine +dP/dt response was depressed (P<0.001 versus control), and increased concentrations were required to match control inotropic responses (10 to 15 microg. kg(-1) x min(-1), 48+/-7%). L-NMMA enhanced +dP/dt responses similarly at 10 mg/kg (61+/-17%, P = 0.02; n = 4) and 20 mg/kg (54+/-7%, P = 0.04; n = 7). Caveolin-3 abundance positively correlated with L-NMMA augmentation of dobutamine inotropic responses in HF (r = 0.9, P = 0.03; n = 4). Thus, in canine pacing-induced HF, expression of caveolin-3 and of sarcolemmal caveolae is increased. This increase is associated with augmented agonist-stimulated NO signaling, likely via a compartmentation effect.
Hare
J M
JM
Department of Medicine, Cardiology Division, Johns Hopkins Medical Institutions, Baltimore, MD 21287-6568, USA. jhare@mail.jhmi.edu
Lofthouse
R A
RA
Juang
G J
GJ
Colman
L
L
Ricker
K M
KM
Kim
B
B
Senzaki
H
H
Cao
S
S
Tunin
R S
RS
Kass
D A
DA
D000818:Animals; D002303:Cardiac Output, Low / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial; D051242:Caveolin 1; D051244:Caveolin 3; D022461:Caveolins; D004285:Dogs; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006439:Hemodynamics; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism* / Q000648:ultrastructure; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction; D019323:omega-N-Methylarginine / Q000494:pharmacology
D051242:Caveolin 1; D051244:Caveolin 3; D022461:Caveolins; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase