eNOS deficient mice develop progressive cardiac hypertrophy with altered cytokine and calcium handling protein expression.
Although studies have shown that endothelial nitric oxide synthase (eNOS) homozygous knockout mice (eNOS-/-) develop left ventricular (LV) hypertrophy, well compensated at least to 24 wks, uncertainty still exists as to the cardiac functional and molecular mechanistic consequences of eNOS deficiency at later time-points. To bridge the gap in existent data, we examined whole hearts from eNOS-/- and age-matched wild-type (WT) control mice ranging in age from 18 to 52 wks for macroscopic and microscopic histopathology, LV mRNA and protein expression using RNA Dot blots and Western blots, respectively, and LV function using isolated perfused work-performing heart preparations. Heart weight to body weight (HW/BW in mg/g) ratio increased significantly as eNOS-/- mice aged (82.2%, P < 0.001). Multi-focal replacement fibrosis and myocyte degeneration/death were first apparent in eNOS-/- mouse hearts at 40 wks. Progressive increases in LV atrial natriuretic factor (ANF) and alpha-skeletal actin mRNA levels both correlated significantly with increasing HW/BW ratio in aged eNOS-/- mice (r = 0.722 and r = 0.648, respectively; P < 0.001). At 52 wks eNOS-/- mouse hearts exhibited basal LV hypercontractility yet blunted beta adrenergic receptor (betaAR) responsiveness that coincided with a significant reduction in the LV ratio of phospholamban to sarcoplasmic reticulum Ca2+-ATPase-2a protein levels and was preceded by a significant upregulation in LV steady-state mRNA and protein levels of the 28 kDa membrane-bound form of tumor necrosis factor-alpha. We conclude that absence of eNOS in eNOS-/- mice results in a progressive concentric hypertrophic cardiac phenotype that is functionally compensated with decreased betaAR responsiveness, and is associated with a potential cytokine-mediated alteration of calcium handling protein expression.
Flaherty
Michael P
MP
Department of Medicine, Division of Cardiology, University of Louisville, Louisville, KY 40292, USA.
Brown
Maria
M
Grupp
Ingrid L
IL
Schultz
Jo El
JE
Murphree
Sidney S
SS
Jones
W Keith
WK
D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000235:genetics / Q000378:metabolism; D001794:Blood Pressure / Q000235:genetics; D001835:Body Weight; D006332:Cardiomegaly / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D015971:Gene Expression Regulation, Enzymologic; D020868:Gene Silencing; D006339:Heart Rate / Q000235:genetics; D006352:Heart Ventricles / Q000378:metabolism / Q000473:pathology; D066298:In Vitro Techniques; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000473:pathology; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III; D009929:Organ Size; D010477:Perfusion; D012333:RNA, Messenger / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*; D018487:Ventricular Dysfunction, Left / Q000235:genetics / Q000378:metabolism / Q000473:pathology
D000199:Actins; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D009320:Atrial Natriuretic Factor; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; C506947:Atp2a2 protein, mouse