Conditional neuronal nitric oxide synthase overexpression impairs myocardial contractility

TY - JOUR

T1 - Conditional neuronal nitric oxide synthase overexpression impairs myocardial contractility

AU - Burkard, Natalie

AU - Rokita, Adam G

AU - Kaufmann, Susann G

AU - Hallhuber, Matthias

AU - Wu, Rongxue

AU - Hu, Kai

AU - Hofmann, Ulrich

AU - Bonz, Andreas

AU - Frantz, Stefan

AU - Cartwright, Elizabeth J

AU - Neyses, Ludwig

AU - Maier, Lars S

AU - Maier, Sebastian K G

AU - Renné, Thomas

AU - Schuh, Kai

AU - Ritter, Oliver

PY - 2007/2/16

Y1 - 2007/2/16

N2 - The role of the neuronal NO synthase (nNOS or NOS1) enzyme in the control of cardiac function still remains unclear. Results from nNOS(-/-) mice or from pharmacological inhibition of nNOS are contradictory and do not pay tribute to the fact that probably spatial confinement of the nNOS enzyme is of major importance. We hypothesize that the close proximity of nNOS and certain effector molecules like L-type Ca(2+)-channels has an impact on myocardial contractility. To test this, we generated a new transgenic mouse model allowing conditional, myocardial specific nNOS overexpression. Western blot analysis of transgenic nNOS overexpression showed a 6-fold increase in nNOS protein expression compared with noninduced littermates (n=12; P<0.01). Measuring of total NOS activity by conversion of [(3)H]-l-arginine to [(3)H]-l-citrulline showed a 30% increase in nNOS overexpressing mice (n=18; P<0.05). After a 2 week induction, nNOS overexpression mice showed reduced myocardial contractility. In vivo examinations of the nNOS overexpressing mice revealed a 17+/-3% decrease of +dp/dt(max) compared with noninduced mice (P<0.05). Likewise, ejection fraction was reduced significantly (42% versus 65%; n=15; P<0.05). Interestingly, coimmunoprecipitation experiments indicated interaction of nNOS with SR Ca(2+)ATPase and additionally with L-type Ca(2+)- channels in nNOS overexpressing animals. Accordingly, in adult isolated cardiac myocytes, I(Ca,L) density was significantly decreased in the nNOS overexpressing cells. Intracellular Ca(2+)-transients and fractional shortening in cardiomyocytes were also clearly impaired in nNOS overexpressing mice versus noninduced littermates. In conclusion, conditional myocardial specific overexpression of nNOS in a transgenic animal model reduced myocardial contractility. We suggest that nNOS might suppress the function of L-type Ca(2+)-channels and in turn reduces Ca(2+)-transients which accounts for the negative inotropic effect.

AB - The role of the neuronal NO synthase (nNOS or NOS1) enzyme in the control of cardiac function still remains unclear. Results from nNOS(-/-) mice or from pharmacological inhibition of nNOS are contradictory and do not pay tribute to the fact that probably spatial confinement of the nNOS enzyme is of major importance. We hypothesize that the close proximity of nNOS and certain effector molecules like L-type Ca(2+)-channels has an impact on myocardial contractility. To test this, we generated a new transgenic mouse model allowing conditional, myocardial specific nNOS overexpression. Western blot analysis of transgenic nNOS overexpression showed a 6-fold increase in nNOS protein expression compared with noninduced littermates (n=12; P<0.01). Measuring of total NOS activity by conversion of [(3)H]-l-arginine to [(3)H]-l-citrulline showed a 30% increase in nNOS overexpressing mice (n=18; P<0.05). After a 2 week induction, nNOS overexpression mice showed reduced myocardial contractility. In vivo examinations of the nNOS overexpressing mice revealed a 17+/-3% decrease of +dp/dt(max) compared with noninduced mice (P<0.05). Likewise, ejection fraction was reduced significantly (42% versus 65%; n=15; P<0.05). Interestingly, coimmunoprecipitation experiments indicated interaction of nNOS with SR Ca(2+)ATPase and additionally with L-type Ca(2+)- channels in nNOS overexpressing animals. Accordingly, in adult isolated cardiac myocytes, I(Ca,L) density was significantly decreased in the nNOS overexpressing cells. Intracellular Ca(2+)-transients and fractional shortening in cardiomyocytes were also clearly impaired in nNOS overexpressing mice versus noninduced littermates. In conclusion, conditional myocardial specific overexpression of nNOS in a transgenic animal model reduced myocardial contractility. We suggest that nNOS might suppress the function of L-type Ca(2+)-channels and in turn reduces Ca(2+)-transients which accounts for the negative inotropic effect.

KW - Animals

KW - Arginine

KW - Caffeine

KW - Calcium

KW - Calcium Channels, L-Type

KW - Calcium Signaling

KW - Cell Size

KW - Cells, Cultured

KW - Citrulline

KW - Cyclic GMP

KW - Doxycycline

KW - Enzyme Induction

KW - Ion Channel Gating

KW - Mice

KW - Mice, Transgenic

KW - Myocardial Contraction

KW - Myocytes, Cardiac

KW - Nitric Oxide Synthase Type I

KW - Ornithine

KW - Protein Interaction Mapping

KW - Recombinant Fusion Proteins

KW - Sarcoplasmic Reticulum Calcium-Transporting ATPases

KW - Stroke Volume

KW - Ventricular Dysfunction, Left

U2 - 10.1161/01.RES.0000259042.04576.6a

DO - 10.1161/01.RES.0000259042.04576.6a

M3 - SCORING: Journal article

C2 - 17272813

VL - 100

SP - e32-44

JO - CIRC RES

JF - CIRC RES

SN - 0009-7330

IS - 3

ER -