2017 Fiscal Year Research-status Report
Quantitative investigation of CaMKII-mediated TRPM4 regulation in atrial remodeling-associated arrhythmias
| Project/Area Number |
17K15566
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| Research Institution | Fukuoka University |
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Principal Investigator |
フ ヤオペン 福岡大学, 医学部, 助教 (40708476)
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| Project Period (FY) |
2017-04-01 – 2019-03-31
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| Keywords | TRPM4 / CaMKII / arrhythmia |
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| Outline of Annual Research Achievements |
In the first year of our study, cellular experiments were performed to explore the regulation of TRPM4 channel under oxidative stresses. The results are summarized as follows: (1) CaMKII inhibitor KN-62 effectively suppressed Ca2+-activated TRPM4-mediated currents in expressed HEK293 cells. (2) Hydrogen peroxide which is a well-known metabolite agent of oxidative stresses modulated and changed the gating kinetics of TRPM4 channel. (3) In a beating monolayer of cultured atrial cardiomyocyte cell line HL-1, the rate of action potential (AP) firing was dramatically increased by hydrogen peroxide, and this change was counteracted by the application of KN-62. CaMKII activation of HL-1 cells expressing a novel CaMKII biosensor Camui was also assessed by fluorescence resonance energy transfer (FRET) measurements simultaneously. (4) A 2D-simulation model incorporating TRPM4 channel gating was constructed, which could reveal altered conduction.
These results suggest that hydrogen peroxide-enhanced automaticity, which often leads to tachyarrhythmias, is accompanied with increased CaMKII activation. Under this oxidative stresses, TRPM4 channel activity might contribute to the arrhythmogenicity by CaMKII-mediated regulation. A 2D-numerical model incorporating TRPM4 channel makes in silico analysis of altered spatial electrophysiological parameters become possible.
During the first year, we presented some of our research findings at domestic and international conferences. The results of the arrhythmogenic potential of TRPM4 channel were published in Cardiovascular Research.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Cellular experiments have elucidated important mechanism underlying CaMKII-mediated TRPM4 regulation and their kinetic relationships under oxidative stresses. Successful utilization of a novel CaMKII biosensor Camui into HL-1 cells will facilitate us to get more kinetic parameters describing how altered activation of CaMKII modulate TRPM4 channel activity during AP cycles in next step. 2D-simulation model which could be incorporated with wet experimental data may help us predict arrhythmic propensity under pathophysiological conditions in the future.
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| Strategy for Future Research Activity |
To further develop numerical simulation models faithfully reproducing the wet experimental data, validation of present data by animal experiments is necessary. We are going to quantify the temporal correlation between AP changes due to increased TRPM4 activity and CaMKII activation from beating monolayer of cultured HL-1 cells and remodeling heart of animal model. Both electrophysiological and biochemical differences will be investigated. Simulation model will continue being improved by the data from cellular to organ levels. Further extension of this theoretical approach to two-dimensional sheet and whole-heart model will promise to facilitate our understanding about more complex, multi-hierarchical nature of acquired arrthythmias associated with kinetic changes of the TRPM4 channel in different background of pathological conditions.
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| Causes of Carryover |
Research costs will predominately concentrate on animal feeding as well as consumables for cell culture, molecular biological, biochemical and functional experiments. To present the outcome of our study, we plan to attend some domestic and international conferences and submit experimental results to some academic journals.
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