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 4

Loss of IL-6Rα from macrophages is sufficient to rescue poAF.

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Loss of IL-6Rα from macrophages is sufficient to rescue poAF. (A) Il6ra ...
(A) Il6ra was conditionally knocked out from macrophages by expressing Cre under the LysM promoter in Il6rafl/fl mice. (B and C) Validation of Il6rα cKO in macrophages via flow cytometry on mouse splenocytes. Each dot represents 1 mouse. (D) Incidence of poAF was decreased in Il6rα cKO compared with WT mice after cardiac surgery, with decreased atrial (E) Il6rα mRNA and (F) protein levels. Atrial (G) Il-6 and (H and I) pY705-STAT3 were lower in Il6ra cKO compared with WT mice after thoracotomy, consistent with the hypothesis that IL-6Rα from macrophages is critical for IL-6 transsignaling in the atria. Each dot represents 1 mouse. Please note that these data show that selective inhibition of the IL-6 receptor in macrophages is sufficient to prevent poAF. The P value in C was obtained from a 2-sample 2-tailed t test. P values in D were obtained from χ2 tests comparing the proportion of positive poAF events. P values in E–I were obtained from 1-way ANOVA followed by Tukey’s post hoc test at α = 0.05. cKO, conditional knockout; IL-6Rα, interleukin 6 receptor α; Macs, macrophages; Th, thoracotomy; TAF, thoracotomy atrial fibrillation; LysM, lysozyme M; Sh, sham.