| First Author | Varma D | Year | 2022 |
| Journal | J Mol Cell Cardiol | Volume | 163 |
| Pages | 147-155 | PubMed ID | 34755642 |
| Mgi Jnum | J:319667 | Mgi Id | MGI:6865518 |
| Doi | 10.1016/j.yjmcc.2021.10.006 | Citation | Varma D, et al. (2022) Inositol 1,4,5-trisphosphate receptor - reactive oxygen signaling domain regulates excitation-contraction coupling in atrial myocytes. J Mol Cell Cardiol 163:147-155 |
| abstractText | The inositol 1,4,5-trisphosphate receptor (InsP3R) is up-regulated in patients with atrial fibrillation (AF) and InsP3-induced Ca(2+) release (IICR) is linked to pro-arrhythmic spontaneous Ca(2+) release events. Nevertheless, knowledge of the physiological relevance and regulation of InsP3Rs in atrial muscle is still limited. We hypothesize that InsP3R and NADPH oxidase 2 (NOX2) form a functional signaling domain where NOX2 derived reactive oxygen species (ROS) regulate InsP3R agonist affinity and thereby Ca(2+) release. To quantitate the contribution of IICR to atrial excitation-contraction coupling (ECC) atrial myocytes (AMs) were isolated from wild type and NOX2 deficient (Nox2(-/-)) mice and changes in the cytoplasmic Ca(2+) concentration ([Ca(2+)]i; fluo-4/AM, indo-1) or ROS (2',7'-dichlorofluorescein, DCF) were monitored by fluorescence microscopy. Superfusion of AMs with Angiotensin II (AngII: 1 mumol/L) significantly increased diastolic [Ca(2+)]i (F/F0, Ctrl: 1.00 +/- 0.01, AngII: 1.20 +/- 0.03; n = 7; p < 0.05), the field stimulation induced Ca(2+) transient (CaT) amplitude (DeltaF/F0, Ctrl: 2.00 +/- 0.17, AngII: 2.39 +/- 0.22, n = 7; p < 0.05), and let to the occurrence of spontaneous increases in [Ca(2+)]i. These changes in [Ca(2+)]i were suppressed by the InsP3R blocker 2-aminoethoxydiphenyl-borate (2-APB; 1 mumol/L). Concomitantly, AngII induced an increase in ROS production that was sensitive to the NOX2 specific inhibitor gp91ds-tat (1 mumol/L). In NOX2(-/-) AMs, AngII failed to increase diastolic [Ca(2+)]i, CaT amplitude, and the frequency of spontaneous Ca(2+) increases. Furthermore, the enhancement of CaTs by exposure to membrane permeant InsP3 was abolished by NOX inhibition with apocynin (1 muM). AngII induced IICR in Nox2(-/-) AMs could be restored by addition of exogenous ROS (tert-butyl hydroperoxide, tBHP: 5 mumol/L). In saponin permeabilized AMs InsP3 (5 mumol/L) induced Ca(2+) sparks that increased in frequency in the presence of ROS (InsP3: 9.65 +/- 1.44 sparks*s(-1)*(100mum)(-1); InsP3 + tBHP: 10.77 +/- 1.5 sparks*s(-1)*(100mum)(-1); n = 5; p < 0.05). The combined effect of InsP3 + tBHP was entirely suppressed by 2-APB and Xestospongine C (XeC). Changes in IICR due to InsP3R glutathionylation induced by diamide could be reversed by the reducing agent dithiothreitol (DTT: 1 mmol/L) and prevented by pretreatment with 2-APB, supporting that the ROS-dependent post-translational modification of the InsP3R plays a role in the regulation of ECC. Our data demonstrate that in AMs the InsP3R is under dual control of agonist induced InsP3 and ROS formation and suggest that InsP3 and NOX2-derived ROS co-regulate atrial IICR and ECC in a defined InsP3R/NOX2 signaling domain. |
