Macrophage-mediated IL-6 signaling drives ryanodine receptor–2 calcium leak in postoperative atrial fibrillation
Joshua A. Keefe, … , Dobromir Dobrev, Xander H.T. Wehrens
Joshua A. Keefe, … , Dobromir Dobrev, Xander H.T. Wehrens
Published March 6, 2025
Citation Information: J Clin Invest. 2025;135(9):e187711. https://doi.org/10.1172/JCI187711.
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Research Article Cardiology Immunology

Macrophage-mediated IL-6 signaling drives ryanodine receptor–2 calcium leak in postoperative atrial fibrillation

Abstract

Postoperative atrial fibrillation (poAF) is AF occurring days after surgery, with a prevalence of 33% among patients undergoing open-heart surgery. The degree of postoperative inflammation correlates with poAF risk, but less is known about the cellular and molecular mechanisms driving postoperative atrial arrhythmogenesis. We performed single-cell RNA-seq comparing atrial nonmyocytes from mice with and without poAF, which revealed infiltrating CCR2+ macrophages to be the most altered cell type. Pseudotime trajectory analyses identified Il-6 as a gene of interest driving in macrophages, which we confirmed in pericardial fluid collected from human patients after cardiac surgery. Indeed, macrophage depletion and macrophage-specific Il6ra conditional knockout (cKO) prevented poAF in mice. Downstream STAT3 inhibition with TTI-101 and cardiomyocyte-specific Stat3 cKO rescued poAF, indicating a proarrhythmogenic role of STAT3 in poAF development. Confocal imaging in isolated atrial cardiomyocytes (ACMs) uncovered what we believe to be a novel link between STAT3 and CaMKII-mediated ryanodine receptor–2 (RyR2)-Ser(S)2814 phosphorylation. Indeed, nonphosphorylatable RyR2S2814A mice were protected from poAF, and CaMKII inhibition prevented arrhythmogenic Ca2+ mishandling in ACMs from mice with poAF. Altogether, we provide multiomic, biochemical, and functional evidence from mice and humans that IL-6-STAT3-CaMKII signaling driven by infiltrating atrial macrophages is a pivotal driver of poAF, which portends therapeutic utility for poAF prevention.

Authors

Joshua A. Keefe, Yuriana Aguilar-Sanchez, J. Alberto Navarro-Garcia, Isabelle Ong, Luge Li, Amelie Paasche, Issam Abu-Taha, Marcel A. Tekook, Florian Bruns, Shuai Zhao, Markus Kamler, Ying H. Shen, Mihail G. Chelu, Na Li, Dobromir Dobrev, Xander H.T. Wehrens

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Figure 6

Optical mapping of mouse hearts in sham and thoracotomy mice.

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Optical mapping of mouse hearts in sham and thoracotomy mice. Langendorf...
Langendorff-perfused mouse hearts from sham (n = 5) and thoracotomy (n = 8) mice were paced at 10 Hz, and conduction velocity and coefficient of variation were assessed in the (A–C) right and (D–F) left atria. Induction of atrial arrhythmias was assessed using an S1-S2 pacing protocol (see Supplemental Materials). Representative atrial electrograms and corresponding voltage-sensitive dye oscillations during and after S1-S2 pacing in (G) Sham and (H) thoracotomy mice. Blue arrows in G and H denote S1 pacing at 10 Hz while red arrows denote premature stimulus (S2). Red arrowheads in G and H denote time stamps at which the images below were taken. White asterisks in paced beat image denotes location of pacing electrode (right atrium) while yellow asterisks in H denote triggered activity. (I) Atrial arrhythmia incidence, defined as ≥ 2 positive atrial tachyarrhythmia events after S1-S2 pacing, and (J) the incidence of triggered activity, defined as the percent of total S1-S2 protocols that led to triggered activity, were significantly greater in thoracotomy versus sham mice. (K) AERP did not differ between groups. Please note that these data show that triggered activity is the primary arrhythmia mechanism in our murine poAF mouse model given the lack of reentry-driving substrate alterations. P values in B, C, E, F, J, and K were derived from 2-sample 2-tailed t tests. P value in I was derived from Fisher’s exact test. AERP, atrial effective refractory period; CoV, coefficient of variation; CV, conduction velocity; DADs, delayed afterdepolarizations; Sh, sham; SR, sinus rhythm; Th, thoracotomy.