Joe E K, Schussheim A E, Longrois D, Mäki T, Kelly R A, Smith T W, Balligand J L
Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA USA.
J Mol Cell Cardiol. 1998 Feb;30(2):303-15. doi: 10.1006/jmcc.1997.0593.
Inflammatory cytokines have been implicated in the reversible depression of cardiac contractile function accompanying local or systemic immune stimulation. Incubation of cardiac myocytes with soluble components in the supernatant from cultured rat lung macrophages activated with endotoxin decreases their contractile response to beta-adrenergic stimulation through the induction of iNOS and the subsequent production of nitric oxide by these cells. In the present study, we characterize the mechanisms underlying NO's attenuation of adrenergic responsiveness in cardiac myocytes. iNOS was induced in cultured ventricular myocytes from adult rats by incubation for 20 h with conditioned medium from lipopolysaccharide (LPS)-activated macrophages. iNOS induction did not induce any alteration in beta-adrenergic receptor density or affinity, Galphai protein abundance, or adenylyl cyclase activity in cultured myocytes. Myocyte exposure to activated macrophage-conditioned medium markedly attenuated the elevation of cAMP in response to isoproterenol (Iso, 2 nM). Induction of iNOS with the macrophage-conditioned medium also potentiated the Iso-induced increase in myocyte cGMP. This cGMP increase was totally abolished by NOS inhibitors. NOS inhibition also returned the attenuated cAMP response to 2 nM Iso to levels observed in control cells. Pre-incubation of the cells in isobutylmethylxanthine (IBMX), a phosphodiesterase inhibitor, also partly reversed the attenuation of cAMP increase with 2 nM Iso in cells expressing iNOS. Brief (15 min) exposure of myocytes to the NO donor, S-nitrosoacetylcysteine (SNAC, 100 micro M) which produced a three-fold increase in intracellular cGMP, also decreased by half the contractile response of cardiac myocytes to Iso (2 nM). We conclude that NO endogenously produced by iNOS decreases the intracellular levels of cAMP in response to beta-adrenergic stimulation in isolated cardiac myocytes, in part through a cGMP-mediated mechanism. This effect may participate in the NO-dependent depression of cardiac function following cytokine exposure.
炎症细胞因子与局部或全身免疫刺激后出现的心脏收缩功能可逆性降低有关。用内毒素激活的培养大鼠肺巨噬细胞上清液中的可溶性成分孵育心肌细胞，可通过诱导诱导型一氧化氮合酶（iNOS）以及这些细胞随后产生一氧化氮，降低其对β-肾上腺素能刺激的收缩反应。在本研究中，我们阐述了一氧化氮（NO）减弱心肌细胞肾上腺素能反应性的潜在机制。通过用脂多糖（LPS）激活的巨噬细胞的条件培养基孵育成年大鼠培养的心室肌细胞20小时，可诱导iNOS。iNOS的诱导并未引起培养心肌细胞中β-肾上腺素能受体密度或亲和力、Gαi蛋白丰度或腺苷酸环化酶活性的任何改变。心肌细胞暴露于活化巨噬细胞条件培养基中，显著减弱了对异丙肾上腺素（Iso，2 nM）的反应中cAMP的升高。用巨噬细胞条件培养基诱导iNOS也增强了Iso诱导的心肌细胞cGMP增加。这种cGMP增加被一氧化氮合酶抑制剂完全消除。一氧化氮合酶抑制也使对2 nM Iso减弱的cAMP反应恢复到对照细胞中观察到的水平。在磷酸二酯酶抑制剂异丁基甲基黄嘌呤（IBMX）中预孵育细胞，也部分逆转了表达iNOS的细胞中2 nM Iso引起的cAMP增加的减弱。心肌细胞短暂（15分钟）暴露于一氧化氮供体S-亚硝基乙酰半胱氨酸（SNAC，100 μM），使细胞内cGMP增加了三倍，但也使心肌细胞对Iso（2 nM）的收缩反应减半。我们得出结论，iNOS内源性产生的NO部分通过cGMP介导的机制，降低了分离心肌细胞对β-肾上腺素能刺激的细胞内cAMP水平。这种效应可能参与了细胞因子暴露后NO依赖性的心脏功能降低。
