Abstract 3546: Heart Failure-Derived Macrophages Induce Myocyte Oxidative Stress and Contractile Dysfunction in a Juxtacrine and iNOS-Dependent Manner
The failing heart exhibits low-level, but progressive, tissue macrophage infiltration. Although macrophages are sources of pro-oxidants, whether macrophage-myocyte interactions are of consequence in heart failure (HF) is unknown. We hypothesized that macrophage-myocyte juxtacrine interactions can induce myocyte dysfunction in HF. Wild-type (WT, C57BL/6) mice underwent coronary ligation (HF group) or sham operation. At 4 weeks in the HF group, echocardiography and hemodynamics confirmed LV dysfunction and remodeling. Flow cytometry showed a larger number of activated blood monocytes (F4/80+CD11b+: 11±2% vs. sham 7±2%, p <0.05), and cardiac MOMA-2 immunostaining revealed a 2-fold increase in tissue activated macrophages. To assess macrophage-myocyte interactions, thioglycollate-elicited peritoneal macrophages were collected from WT naíve and HF mice, macrophages were co-cultured with isolated adult WT myocytes, and myocyte contraction was assessed in the presence or absence of myocyte-macrophage physical contact. Also, as macrophages lacking inducible nitric oxide synthase (iNOS) exhibit blunted activation, to deconstruct the role of macrophage activation, peritoneal macrophages were collected from ligated iNOS−/− HF mice. In the absence of macrophage association, myocyte contraction (1 Hz) was 9.5±1.3%. Contraction was significantly (p < 0.05) depressed upon physical contact with either WT HF macrophages (4.6 ± 1.0%) or LPS-stimulated naíve WT macrophages, but not upon contact with unstimulated naíve WT macrophages. In contrast, physical contact with iNOS KO HF macrophages did not depress contraction (shortening 8.9±1%, p = NS), even with LPS pre-stimulation. Myocytes were loaded with the fluorescent indicators DCF-DA or HKGreen-2 to monitor reactive oxygen species (ROS) and peroxynitrite, respectively. Myocyte attachment to WT HF macrophages induced a 4-fold increase in myocyte ROS and peroxynitrite over baseline, events that did not occur with attachment to iNOS KO HF macrophages. We conclude that direct physical interaction with activated macrophages in HF is sufficient to induce myocyte oxidative and nitrative stress and contractile dysfunction, and this is dependent, at least in part, on macrophage-derived iNOS.
This research has received full or partial funding support from the American Heart Association, AHA Great Rivers Affiliate (Delaware, Kentucky, Ohio, Pennsylvania & West Virginia).