Ziolo Mark T, Maier Lars S, Piacentino Valentino, Bossuyt Julie, Houser Steven R, Bers Donald M
Department of Physiology, Loyola University Medical Center, Maywood, Ill 60153, USA.
Circulation. 2004 Apr 20;109(15):1886-91. doi: 10.1161/01.CIR.0000124231.98250.A8. Epub 2004 Mar 22.
Human heart failure (HF) usually exhibits blunted response to beta-adrenergic receptor (AR) stimulation. Here, we examined whether expression of nitric oxide synthase-2 (NOS2, or inducible NOS) contributes to this loss of inotropic reserve in human HF.
Failing human hearts were obtained at transplantation. Contraction and [Ca2+]i measurements were performed in isolated cardiac myocytes and trabeculae. In HF myocytes and muscle, isoproterenol (ISO), a beta-AR agonist, led to small inotropic and lusitropic responses. Specific inhibition of NOS2 by aminoguanidine (AG) or L-NIL dramatically increased the ISO-induced inotropy and lusitropy, such that the ISO+AG response in HF approached that seen with ISO alone in nonfailing human myocytes or muscles. Ca2+ transient data directly paralleled these results, indicating that altered cellular Ca2+ handling is responsible. In nonfailing human hearts, NOS2 inhibition had no effects. In addition, NOS2 inhibition also had no effect in 30% of failing hearts, but in these myocytes and muscles, the ISO response alone was similar to that of nonfailing hearts. In line with these functional findings, NOS2 protein expression measured by Western blotting was induced in HF when AG/L-NIL had a functional effect but not when AG/L-NIL had no effect on contractility and Ca2+ transients.
NOS2 expression strongly limited ISO-induced increases in contraction, twitch Delta[Ca2+]i, and lusitropy in trabeculae and isolated myocytes from failing human hearts. Thus, the beta-AR hyporesponsiveness in human HF is mediated in large part by NO (or related congeners) produced within cardiac myocytes via NOS2.
人类心力衰竭（HF）通常对β-肾上腺素能受体（AR）刺激表现出反应迟钝。在此，我们研究了一氧化氮合酶2（NOS2，即诱导型NOS）的表达是否导致人类HF中这种变力性储备的丧失。
在心脏移植时获取衰竭的人类心脏。在分离的心肌细胞和小梁中进行收缩和[Ca2+]i测量。在HF心肌细胞和肌肉中，β-AR激动剂异丙肾上腺素（ISO）导致较小的变力性和变时性反应。用氨基胍（AG）或L-NIL特异性抑制NOS2可显著增加ISO诱导的变力性和变时性，使得HF中ISO+AG反应接近非衰竭人类心肌细胞或肌肉中单独使用ISO时的反应。Ca2+瞬变数据直接与这些结果平行，表明细胞Ca2+处理改变是原因所在。在非衰竭人类心脏中，抑制NOS2没有影响。此外，抑制NOS2在30%的衰竭心脏中也没有作用，但在这些心肌细胞和肌肉中，单独的ISO反应与非衰竭心脏相似。与这些功能发现一致，当AG/L-NIL有功能作用时，通过蛋白质印迹法测量的HF中NOS2蛋白表达被诱导，而当AG/L-NIL对收缩性和Ca2+瞬变没有影响时则未被诱导。
NOS2表达强烈限制了ISO诱导的衰竭人类心脏小梁和分离心肌细胞收缩、单次收缩Δ[Ca2+]i和变时性的增加。因此，人类HF中的β-AR低反应性在很大程度上是由心肌细胞内通过NOS2产生的NO（或相关同系物）介导的。
