Cytokines increase neonatal cardiac myocyte calcium concentrations: the involvement of nitric oxide and cyclic nucleotides.
Neonatal rat cardiac myocytes were treated with cytokines, with or without the nitric oxide synthase (NOS) inhibitors N-monomethyl-L-arginine (LNMMA) and N-nitro-L-arginine methyl ester (LNAME), and systolic and diastolic calcium levels were measured by fluorescence spectrophotometry and confocal microscopy. Time-dependent changes following interferon-gamma (IFN-gamma) treatment revealed a continuing increase in intracellular calcium, which was reduced with LNMMA, but not with LNAME. Increases in calcium also occurred with interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), but not to the extent seen with IFN-gamma. Increased cyclic guanosine monophosphate (cGMP) was involved in the results described with short-term (2 hr) TNF-alpha and long-term (18 hr) IFN-gamma treatments. Short-term exposure to IFN-gamma produced an increase in cyclic adenosine monophosphate (cAMP) and also an initial increase in the myocyte-bearing rate, with calcium levels either (i) subsequently returning to control levels while maintaining a fast beating rate or (ii), retaining a high systolic calcium level, but beating at control rates. Treatment with both IL-1beta and IFN-gamma stabilized the beating rate of the cells on some occasions. Shortening of myocytes increased with isoproterenol and following treatment with IFN-gamma, while isoproterenol stimulation of IFN-gamma-treated cells revealed increased contractile activity after short, but not long, treatment. LNMMA, but not reduced the increased contractile response with short-term IFN-gamma treatment. Our findings suggest that TNF-alpha acts via a cGMP-dependent pathway, whereas the actions of IFN-gamma involve adenylate cyclase, and possibly a NO-forming mechanism and cGMP pathway as well. It is also apparent that the two NO inhibitors function via different mechanisms or that LNMMA has a direct effect on the calcium-signaling pathway.
Bick
R J
RJ
Department of Pathology and Laboratory Medicine, University of Texas Health Science Center, Houston 77030, USA. bick@casper.med.uth.tmc.edu
Wood
D E
DE
Poindexter
B
B
McMillin
J B
JB
Karoly
A
A
Wang
D
D
Bunting
R
R
McCann
T
T
Law
G J
GJ
Buja
L M
LM
D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism*; D016207:Cytokines / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006321:Heart / Q000187:drug effects*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D009712:Nucleotides, Cyclic / Q000502:physiology*; D051381:Rats; D019323:omega-N-Methylarginine / Q000494:pharmacology
D016207:Cytokines; D004791:Enzyme Inhibitors; D009712:Nucleotides, Cyclic; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D002118:Calcium; D019331:NG-Nitroarginine Methyl Ester