Macrophage depletion in stellate ganglia attenuates cardiac sympathetic overactivation and ventricular arrhythmogenesis by inhibiting neuroinflammation in heart failure

Abstract

Cardiac sympathetic overactivation is a key trigger for ventricular arrhythmogenesis in patients with chronic heart failure (CHF). Inflammatory infiltration in the stellate ganglion (SG) is a critical factor for cardiac sympathetic hyperactivation in patients with ventricular arrhythmias. This study aims to investigate if macrophage depletion in SG decreases cardiac sympathetic overactivation and ventricular arrhythmogenesis by reducing neuroinflammation in CHF. RatCHF was induced by surgical ligation of left anterior descending coronary artery (LAD). Clodronate liposomes (2µl, 20mg/ml) was microinjected into bilateral SGs in CHF rats. CHF rats treated with PBS liposomes served as control. Final experiments were performed at 1 week after drug treatment (13 weeks of LAD ligation). Data from cytokine protein array demonstrated that nine inflammatory cytokines were detectable, among which the levels of only proinflammatory cytokines including TNFα and IL-1β were elevated in SGs from CHF rats. Using immunofluorescence staining and western blot analysis, we found that macrophage infiltration and expression of TNFα and IL-1β in SG were markedly increased in CHF rats, compared with age matched sham rats. Flow cytometry data further confirmed that percentage of macrophages (defined as CD45+/CD11b+ cells) in SG was much higher in CHF rats than sham rats. Treatment with clodronate liposomes significantly reduced CHF-elevated expression of TNFα and IL-1β as well as macrophage expansion in SGs. Our patch-clamp data demonstrated that clodronate liposomes treatment in SGs significantly reduced N-type (Cav2.2) Ca2+ currents (28.6±2.6 pA/pF in CHF+Clodronate liposomes group vs. 49.1±1.9 pA/pF in CHF group) and excitability of cardiac sympathetic postganglionic (CSP) neurons in CHF rats. In addition, CHF-induced increase in cardiac sympathetic nerve activity (CSNA) was markedly inhibited by clodronate liposomes treatment. ECG data obtained from 24-hour continuous telemetry recording in conscious rats demonstrated that treatment with clodronate liposomes in SGs not only restored CHF-increased heterogeneity of ventricular electical activities, but also reduced the incidence and duration of ventricular tachycardia/fibrillation in CHF. However, clodronate liposomes failed to improve CHF-induced cardiac contractile dysfunction. PBS liposomes had no effects on expression of TNFα and IL-1β and macrophage expansion in SG, Cav2.2 currents and cell excitability of CSP neurons, CSNA, and ventricular arrhythmogenesis in CHF rats. These data suggested that macrophage depletion with clodronate liposomes attenuated CHF-induced cardiac sympathetic overactivation and ventricular arrhythmias through reduction of macrophage expansion and proinflammatory cytokine levels in SGs. The present study suggests that macrophage depletion or anti-inflammatory treatment in SGs might be an effective therapeutic strategy to suppress lethal ventricular arrhythmia in patients with CHF.