Fu Jiaying, Cameron Breanne A, Schönleitner Patrick, Schiatti Teresa, Kuiper Marion, Kittel Anna-Sophia, Simon-Chica Ana, Madl Josef, Kreutz Clemens, Filgueiras-Rama David, Schotten Ulrich, Römer Winfried, Ravens Ursula, Kohl Peter, Rog-Zielinska Eva A, Antoons Gudrun, Peyronnet Rémi
Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Medical Faculty and Medical Center-University of Freiburg Freiburg im Breisgau Germany.
Department of Physiology, Cardiovascular Research Institute Maastricht Maastricht University Maastricht Netherlands.
J Am Heart Assoc. 2025 Sep 2;14(17):e040495. doi: 10.1161/JAHA.124.040495. Epub 2025 Aug 29.
Mechanical stretch of the myocardium is proarrhythmic and alters cellular Ca handling, potentially involving cation nonselective mechano-sensitive ion channels. This study aimed to assess the presence and mechanisms of stretch-induced increase in Ca-spark rate (SiS) in isolated atrial cardiomyocytes.
Freshly isolated rabbit, pig, and human left atrial cardiomyocytes were stretched axially using glass microrods. Free cytosolic Ca concentration was monitored using confocal microscopy at resting sarcomere length (≈1.79 μm) and during severe (≈12%) increase in sarcomere length.
Diastolic stretch provoked SiS, which was prevented by disrupting microtubules with colchicine, but unaffected by inhibition of NADPH oxidase 2 or scavenging of reactive oxygen species. SiS was absent in Na- and Ca-free external solution, suggesting that it requires transsarcolemmal influx of Na or Ca. Activation of Piezo1 increased baseline spark rate, which was further increased by stretch. TRPA1 (transient receptor potential ankyrin 1) activation also increased baseline spark rate, with no further change upon stretch. SiS was not detectable in the presence of streptomycin (a blocker of nonselective mechano-sensitive ion channels), and HC-030031 and A-967079 (selective blockers of TRPA1), even when Piezo1 was activated. SiS was also observed in pig and human atrial cardiomyocytes.
In atrial cardiomyocytes, diastolic stretch enhances Ca-spark rate through a mechanism that requires microtubular integrity and TRPA1 but that is independent of redox signaling. TRPA1 emerges as a key regulator of stretch-induced Ca handling in atrial cells, with potential implications for arrhythmogenesis.
