A Conductive Polymer Restores Connexin43 Expression Through the Suppression of Mitogen-Activated Protein Kinases to Improve Intercellular Communication and Alleviate Atrial Fibrillation.

Conductive biomaterials have shown promising results for correcting pathological cardiac electrical signaling. However, their mechanisms of operation are still largely unclear. One reason behind disrupted cardiac intercellular communication, though, is lowered expression of the gap junction protein connexin43 (Cx43), which may be alleviated by conductive biomaterials. In this study, we aimed to test this hypothesis, using the self-doping conductive biomaterial poly-3-amino-4-methoxybenzoic acid-gelatin (PAMB-G). An in vitro model was established, in which cardiomyocytes (CMs) were treated with anisomycin, while the in vivo model involved anisomycin-treated mice subjected to electrical pacing to induce atrial fibrillation (AF). Cx43 expression, Ca2+ transient propagation, and CM electrical conduction in vitro, as well as the in vivo effects of PAMB-G on AF, were evaluated; additionally, the underlying molecular mechanisms were identified. We found that anisomycin, at different concentrations, down-regulated Cx43; this was counteracted by PAMB-G, which restored proper Cx43 expression, coupled with improved Ca2+ signal and electrical conduction. Cx43 restoration was due to PAMB-G suppressing anisomycin-induced activation of MAPKs P38 and JNK, which are involved in phosphorylating Cx43 for degradation. Similar observations were also found in vivo, where a PAMB-G patch acted against anisomycin-induced Cx43 downregulation and impaired atrial cell communication, subsequently alleviating pacing-induced AF. Therefore, PAMB-G suppresses MAPKs, in turn upregulating Cx43, leading to improved electrical signal transduction. As a result, modulating the MAPK-Cx43 pathway, such as with PAMB-G, could serve as a potential therapeutic strategy for cardiac arrhythmia. STATEMENT OF SIGNIFICANCE: Disruption of atrial intercellular gap junction channels, comprised of connexins, leads to atrial fibrillation (AF), the most prevalent arrhythmia, with poor clinical outcomes. Current AF treatments are associated with adverse effects, and only focus on managing symptoms, thereby necessitating innovative treatment strategies. One such strategy is conductive biomaterials, which show promising results for correcting pathological cardiac electrical signaling. We synthesized a self-doping conductive biomaterial, poly-3-amino-4-methoxybenzoic acid-gelatin (PAMB-G), and found that it counteracts against anisomycin-induced connexin43 (Cx43) downregulation, subsequently improving cardiac electrical conduction and alleviating pacing-induced AF. This is owed to PAMB-G suppressing anisomycin-associated activation of mitogen-activated kinases P38 and JNK, which are involved in phosphorylating Cx43 for degradation. Therefore, PAMB-G modulation of MAPK-Cx43 pathway could aid in cardiac arrhythmia treatment.