| First Author | Zhang JC | Year | 2018 |
| Journal | Front Physiol | Volume | 9 |
| Pages | 1447 | PubMed ID | 30450052 |
| Mgi Jnum | J:277415 | Mgi Id | MGI:6316771 |
| Doi | 10.3389/fphys.2018.01447 | Citation | Zhang JC, et al. (2018) Calcium-Mediated Oscillation in Membrane Potentials and Atrial-Triggered Activity in Atrial Cells of Casq2(R33Q/R33Q) Mutation Mice. Front Physiol 9:1447 |
| abstractText | Aim: We investigated the underlying mechanisms in atrial fibrillation (AF) associated with R33Q mutation and Ca(2+)-triggered activity. Methods and Results: We examined AF susceptibility with intraesophageal burst pacing in the sarcoplasmic reticulum (SR) Ca(2+) leak model calsequestrin 2 R33Q (Casq2(R33Q/R33Q)) mice. Atrial trigger appeared in R33Q mice but not WT mice (17.24%, 5/29 vs. 0.00%, 0/32, P < 0.05). AF was induced by 25 Hz pacing in R33Q mice (48.27%, 14/29 vs. 6.25%, 2/32, P < 0.01). The mice were given 1.5 mg/kg isoproterenol (Iso), and the incidences of AF increased (65.51%, 19/29 vs. 9.21%, 3/32, P < 0.01). Electrophysiology experiments and the recording of intracellular Ca(2+) indicated significant increases in the Ca(2+) sparks (5.24 +/- 0.75 100 muM(-1).s(-1) vs. 0.29 +/- 0.04 100 muM(-1).s(-1), n = 20, P < 0.05), intracellular free Ca(2+) (0.238 +/- 0.009 muM vs. 0.172 +/- 0.006 muM, n = 20, P < 0.05), Ca(2+) wave (11.74% vs. 2.24%, n = 20, P < 0.05), transient inward current (ITi) (-0.56 +/- 0.02 pA/pF vs. -0.42 +/- 0.01 pA/pF, n = 10, P < 0.05), and oscillation in membrane potentials (10.71%, 3/28 vs. 4.16%, 1/24, P < 0.05) in the R33Q group, but there was no significant difference in the L-type calcium current. These effects were enhanced by Iso, and the inhibition of calmodulin-dependent protein kinase II (CaMKII) by 1 muM KN93 reversed the effects of Iso on Ca(2+) sparks (5.01 +/- 0.66 100 mum(-1).s(-1) vs. 11.33 +/- 1.63 100 mum(-1).s(-1), P < 0.05), intracellular Ca(2+) (0.245 +/- 0.005 muM vs. 0.324 +/- 0.008 muM, P < 0.05), Ca(2+) wave (12.35% vs. 17.83%, P < 0.05), ITi (-0.61 +/- 0.02 pA/pF vs. -0.78 +/- 0.03 pA/pF, n = 10, P < 0.05), and oscillation in membrane potential (17.85% 5/28 vs. 32.17% 9/28, P < 0.05). The reduction of ryanodine receptor 2 (RyR2) stable subunits (Casq2, triadin, and junctin) rather than RYR2 and the increase in CaMKII, phosphor-CaMKII, phosphor-RyR2 (Ser 2814), SERCA, and NCX1.1 was reflected in the R33Q group. Conclusion: This study demonstrates that the increase in spontaneous calcium elevations corresponding to ITi that may trigger the oscillation in membrane potentials in the R33Q group, thereby increasing the risk of AF. The occurrence of spontaneous calcium elevations in R33Q atrial myocytes is due to the dysfunction of RyR2 stable subunits, CaMKII hyperactivity, and CaMKII-mediated RyR phosphorylation. An effective therapeutic strategy to intervene in Ca(2+)-induced AF associated with the R33Q mutation may be through CaMKII inhibition. |
