Generation of myocyte agonal Ca2+ waves and contraction bands in perfused rat hearts following irreversible membrane permeabilisation

• Published in: Scientific reports Vol. 13; no. 1; p. 803
• Main Authors: Morishita, Yuma, Tamura, Shoko, Mochizuki, Kentaro, Harada, Yoshinori, Takamatsu, Tetsuro, Hosoi, Hajime, Tanaka, Hideo
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 16.01.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 631/443; 692/4019; 692/420; Actin; Actinin; ATP; Calcium (intracellular); Calcium signalling; Calpain; Carbonyl compounds; Cardiomyocytes; Cyanides; Humanities and Social Sciences; Mitochondria; Morphology; multidisciplinary; Myocytes; Proteolysis; Ryanodine; Saponins; Science; Science (multidisciplinary); Thapsigargin
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-023-27807-w

Although irreversible cardiomyocyte injury provokes intracellular Ca 2+ ([Ca 2+ ] i ) overload, the underlying dynamics of this response and its effects on cellular morphology remain unknown. We therefore visualised rapid-scanning confocal fluo4-[Ca 2+ ] i dynamics and morphology of cardiomyocytes in Langendorff-perfused rat hearts following saponin-membrane permeabilisation. Our data demonstrate that 0.4% saponin-treated myocytes immediately exhibited high-frequency Ca 2+ waves (131.3 waves/min/cell) with asynchronous, oscillatory contractions having a mean propagation velocity of 117.8 μm/s. These waves slowly decreased in frequency, developed a prolonged decay phase, and disappeared in 10 min resulting in high-static, fluo4-fluorescence intensity. The myocytes showing these waves displayed contraction bands, i.e., band-like actin-fibre aggregates with disruption of sarcomeric α-actinin. The contraction bands were not attenuated by the abolition of Ca 2+ waves under pretreatment with ryanodine plus thapsigargin, but were partially attenuated by the calpain inhibitor MDL28170, while mechanical arrest of the myocytes by 2,3-butanedione monoxime completely attenuated contraction-band formation. The depletion of adenosine 5′-triphosphate by the mitochondrial electron uncoupler carbonyl cyanide 4-trifluoromethoxy phenylhydrazone also attenuated Ca 2+ waves and contraction bands. Overall, saponin-induced myocyte [Ca 2+ ] i overload provokes agonal Ca 2+ waves and contraction bands. Contraction bands are not the direct consequence of the waves but are caused by cross-bridge interactions of the myocytes under calpain-mediated proteolysis.