Borderzone contractile dysfunction is transiently attenuated and left ventricular structural remodeling is markedly reduced following reperfused myocardial infarction in inducible nitric oxide synthase knockout mice.
OBJECTIVE
We sought to determine the effect of inducible nitric oxide synthase (iNOS) expression on regional contractile function and left ventricular (LV) remodeling after reperfused myocardial infarction (MI).


BACKGROUND
Inducible nitric oxide synthase is known to contribute to global LV dysfunction after a large MI, but the mechanisms underlying this dysfunction remain unclear.


METHODS
We used immunohistochemistry to investigate the distribution of iNOS expression in wild-type (WT) and iNOS knockout (KO) mice early (day 1) and late (day 28) after reperfused MI. We also used serial cardiac magnetic resonance imaging at baseline and at 1, 7, and 28 days after MI to assess LV volumes, ejection fraction (EF), regional circumferential strain (E(cc)), and day 1 infarct size.


RESULTS
At baseline, LV volumes and EF were similar between groups. Day 1 infarct size was also similar between groups. Immunohistochemistry revealed that iNOS expression was abundant throughout the heart in WT mice on day 1 after MI, particularly near the infarct borderzone. On day 7 after MI, E(cc) in KO mice was significantly improved in some borderzone sectors compared with WT. The LV volumes were significantly lower in KO mice at days 7 and 28 compared with WT. The EF on days 7 and 28 was significantly higher in KO mice compared with WT. The circumferential extent of wall thinning was also significantly reduced in KO versus WT mice at days 7 and 28.


CONCLUSIONS
Expression of iNOS contributes importantly to post-infarction contractile dysfunction and subsequent LV remodeling, suggesting new strategies to combat heart failure resulting from large MI.
Gilson
Wesley D
WD
Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia 22903, USA.
Epstein
Frederick H
FH
Yang
Zequan
Z
Xu
Yaqin
Y
Prasad
Konkal-Matt R
KM
Toufektsian
Marie-Claire
MC
Laubach
Victor E
VE
French
Brent A
BA
D000818:Animals; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009203:Myocardial Infarction / Q000150:complications* / Q000378:metabolism* / Q000628:therapy; D015425:Myocardial Reperfusion; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D013318:Stroke Volume / Q000502:physiology; D013997:Time Factors; D018487:Ventricular Dysfunction, Left / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D020257:Ventricular Remodeling / Q000502:physiology*
D052247:Nitric Oxide Synthase Type II