Figure 3: Efsevin Acts Through Mitochondrial Ca

(A) Representative recordings of mitochondrial Ca2+ in permeabilized HL-1 cardiomyocytes. Superfusion with caffeine induced a rapid uptake of Ca2+ into mitochondria (black trace), which was enhanced by 15 μM efsevin and blocked by 10 μM RuR (gray trace). (B) Quantification of peak mitochondrial fluorescence showed a significant increase in mitochondrial Ca2+ uptake in cells treated with efsevin from ΔF/F0 = 0.14 ± 0.03 (n = 10) to 0.50 ± 0.07 (n = 19, p < 0.001, ANOVA). (C) 15 µM efsevin reduces spontaneous propagating waves in RyR2R4496C/WT cardiomyocytes under ISO influence from 0.36 ± 0.16 waves/min (n = 15) to 0 (black bars) (n = 21, p = 0.035, Kruskal-Wallis test). In the presence of 8 µM of the mitochondrial Ca2+ uptake blocker Ru360, vehicle-treated cells showed 0.07 ± 0.04 waves/min (n = 29), which increased to 0.63 ± 0.16 under ISO influence (n = 21, p < 0.001) but could not be blocked with efsevin as shown by an indistinguishable value of 0.62 ± 0.12 waves/min under ISO influence together with efsevin (gray bars) (n = 62, p = 0.354 compared to that with ISO). (D) 10 µM of the MCU activator kaempferol significantly increased mitochondrial Ca2+ uptake after SR Ca2+ release from ΔF/F0 = 0.16 ± 0.04 (n = 9) to 0.55 ± 0.05 (n = 10, p < 0.001, ANOVA) Ca2+ uptake was inhibited by 50 μM RuR (gray bars). (E) Treatment of RyR2R4496C/WT cardiomyocytes with 10 μM kaempferol completely eliminated ISO-induced spontaneous diastolic Ca2+ waves from 0.19 ± 0.04 waves/min (n = 49) to 0 (n = 45; p < 0.001, Mann-Whitney U test). *p < 0.05; ***p < 0.001. ΔF/F0 = change in fluorescence over baseline fluorescence; MCU = mitochondrial Ca2+ uniporter; RuR = ruthenium red; SR = sarcoplasmic reticulum.

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