Abstract
Heart failure (HF) is characterized by exaggerated systemic and myocardial pro-inflammatory responses, which impede myocardial healing and promote pathological remodeling and dysfunction. Currently, there are no strategies available to restrain and/or modulate immune cell responses triggered by myocardial injury. 4F, an apolipoprotein A-I mimetic, exhibits anti-inflammatory properties and influences macrophage polarity. We hypothesized that 4F treatment following reperfused myocardial infarction (MI) in mice would attenuate post-MI cardiac remodeling by inducing an anti-inflammatory and tissue healing monocyte polarity. C57BL/6 mice (6-8/group) were intravenously injected with either PBS or L-4F (100 μg/day) for 5 d starting at day 3 after reperfused MI (60 min ischemia). Flow cytometry revealed that compared to PBS injected MI mice, 4F significantly (p < 0.05) decreased levels of pro-inflammatory monocytes (CD45+Cd11b+Ly6Chigh) in blood (20.4 ± 4.6 vs 9.4 ± 1.7%), spleen (25.5 ± 7.4 vs 8.0 ± 6.0%), and heart (0.9 ± 0.4 vs 0.2 ± 0.1%); and decreased myocardial macrophage (CD45+CD11b+F4/80+) infiltration (1.6 ± 0.8 vs 0.28 ± 0.2%). The levels of anti-inflammatory monocytes, however, were unchanged. Echocardiography revealed that these changes in immune cell profiles in 4F-injected mice were also accompanied by improvements in cardiac function. Compared to PBS injected MI mice, 4F treatment attenuated post-MI LV chamber dilatation (84.1 ± 16 vs 65.0 ± 8.5 uL and 59.15 ± 16.6 vs 38.4 ± 11.8 uL; end-diastolic and systolic volumes, respectively), and improved LV ejection fraction (28.4 ± 10.8 vs 41.7 ± 12.8%). In addition, in vitro studies using mouse peritoneal macrophages indicated that 4F promotes an anti-inflammatory macrophage phenotype potentially by inhibiting the glycolytic metabolic profile typical of pro-inflammatory macrophages. These effects on macrophage polarity by 4F were associated with parallel alterations in the expression of hypoxia inducible factor isoforms 1 and 2α, known markers of macrophage polarity. We conclude that 4F could be used therapeutically after MI to augment reparative immune responses and thereby limit the long-term maladaptive effects of exaggerated inflammation on adverse post-MI cardiac remodeling.
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