Cytokine-induced nitric oxide production inhibits mitochondrial energy production and impairs contractile function in rat cardiac myocytes.
OBJECTIVE
The present study examined whether nitric oxide (NO) produced by inducible nitric oxide synthase (iNOS) can directly inhibit aerobic energy metabolism and impair cell function in interleukin (IL)-1beta,-stimulated cardiac myocytes.


BACKGROUND
Recent reports have indicated that excessive production of NO induced by cytokines can disrupt cellular energy balance through the inhibition of mitochondrial respiration in a variety of cells. However, it is still largely uncertain whether the NO-induced energy depletion affects myocardial contractility.


METHODS
Primary cultures of rat neonatal cardiac myocytes were prepared, and NO2-/NO3- (NOx) in the culture media was measured using Griess reagent.


RESULTS
Treatment with IL-1beta (10 ng/ml) increased myocyte production of NOx in a time-dependent manner. The myocytes showed a concomitant significant increase in glucose consumption, a marked increase in lactate production, and a significant decrease in cellular ATP (adenosine 5'-triphosphate). These metabolic changes were blocked by co-incubation with N(G)-monomethyl-L-arginine (L-NMMA), an inhibitor of NO synthesis. Sodium nitroprusside (SNP), a NO donor, induced similar metabolic changes in a dose-dependent manner, but 8-bromo-cyclic guanosine 3',5'-monophosphate (8-bromo-cGMP), a cGMP donor, had no effect on these parameters. The activities of the mitochondrial iron-sulfur enzymes, NADH-CoQreductase and succinate-CoQreductase, but not oligomycin-sensitive ATPase, were significantly inhibited in the IL-1beta, or SNP-treated myocytes. Both IL-1beta and SNP significantly elevated maximum diastolic potential, reduced peak calcium current (I(Ca)), and lowered contractility in the myocytes. KT5823, an inhibitor of cGMP-dependent protein kinase, did not block the electrophysiological and contractility effects.


CONCLUSIONS
These data suggest that IL-1beta-induced NO production in cardiac myocytes lowers energy production and myocardial contractility through a direct attack on the mitochondria, rather than through cGMP-mediated pathways.
Tatsumi
T
T
Second Department of Medicine, Kyoto Prefectural University of Medicine, Japan. tatsumi@koto.kpu-m.ac.jp
Matoba
S
S
Kawahara
A
A
Keira
N
N
Shiraishi
J
J
Akashi
K
K
Kobara
M
M
Tanaka
T
T
Katamura
M
M
Nakagawa
C
C
Ohta
B
B
Shirayama
T
T
Takeda
K
K
Asayama
J
J
Fliss
H
H
Nakagawa
M
M
D000255:Adenosine Triphosphate / Q000032:analysis / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured / Q000502:physiology; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism / Q000502:physiology*; D005947:Glucose / Q000032:analysis / Q000378:metabolism; D006019:Glycolysis; D007249:Inflammation; D007375:Interleukin-1 / Q000502:physiology*; D019344:Lactic Acid / Q000032:analysis / Q000378:metabolism; D008929:Mitochondria, Heart / Q000378:metabolism*; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism*; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000502:physiology*; D009599:Nitroprusside / Q000494:pharmacology; D051381:Rats; D019323:omega-N-Methylarginine / Q000494:pharmacology
D007375:Interleukin-1; D009599:Nitroprusside; D019323:omega-N-Methylarginine; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; D019344:Lactic Acid; D000255:Adenosine Triphosphate; D019001:Nitric Oxide Synthase; D006152:Cyclic GMP; D005947:Glucose