Quantitative tests reveal that microtubules tune the healthy heart but underlie arrhythmias in pathology
J. Physiol​ 2020 Apr;598(7):1327-1338. doi: 10.1113/JP277083. Epub 2019 Jan 24.
Humberto C Joca 1, Andrew K Coleman 1, Chris W Ward 2, George S B Williams
Key points: Our group previously discovered and characterized the microtubule mechanotransduction pathway linking diastolic stretch to NADPH oxidase 2-derived reactive oxygen species signals that regulate calcium sparks and calcium influx pathways. Here we used focused experimental tests to constrain and expand our existing computational models of calcium signalling in heart. Mechanistic and quantitative modelling revealed new insights in disease including: changes in microtubule network density and properties, elevated NOX2 expression, altered calcium release dynamics, how NADPH oxidase 2 is activated by and responds to stretch, and finally the degree to which normalizing mechano-activated reactive oxygen species signals can prevent calcium-dependent arrhythmias.
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Abstract: Microtubule (MT) mechanotransduction links diastolic stretch to generation of NADPH oxidase 2 (NOX2)-dependent reactive oxygen species (ROS), signals we term X-ROS. While stretch-elicited X-ROS primes intracellular calcium (Ca2+ ) channels for synchronized activation in the healthy heart, the dysregulated excess in this pathway underscores asynchronous Ca2+ release and arrhythmia. Here, we expanded our existing computational models of Ca2+ signalling in heart to include MT-dependent mechanotransduction through X-ROS. Informed by new focused experimental tests to properly constrain our model, we quantify the role of X-ROS on excitation-contraction coupling in healthy and pathological conditions. This approach allowed for a mechanistic investigation that revealed new insights into X-ROS signalling in disease including changes in MT network density and post-translational modifications (PTMs), elevated NOX2 expression, altered Ca2+ release dynamics (i.e. Ca2+ sparks and Ca2+ waves), how NOX2 is activated by and responds to stretch, and finally the degree to which normalizing X-ROS can prevent Ca2+ -dependent arrhythmias.
Keywords: Calcium imaging; Cardiomyocyte; Excitation-contraction coupling; Mathematical model; mechanosensitivity.
