Biology subjects

Dasi, A.

Publications and source records attributed to Dasi, A..

3 recordsLinked to original sources

bioRxiv2026

Channelrhodopsin Ion Selectivity Determines Mechanisms and Efficacy of Optogenetic Defibrillation in Human Atria and Ventricles

Optogenetic defibrillation uses light-gated ion channels to terminate cardiac arrhythmias through targeted illumination. Previous studies assessed the feasibility of using either cation (e.g. ChR2) or anion (e.g. GtACR1) non-selective channels, both of which depolarise resting cardiomyocytes upon photoactivation. In contrast, recently identified light-gated K+-channels (e.g. WiChR) suppress cardiomyocyte activity while maintaining the membrane potential near its resting state. Here, we use biophysically detailed simulations to compare the defibrillation potential of ChR2, GtACR1, and WiChR. Single-cell simulations show that activation of ChR2 and GtACR1 markedly increase diastolic intracellular Ca2+ concentration (by 42.6% and 52.6%, respectively), whereas WiChR induces only minimal changes (4.0% increase), suggesting a lower pro-arrhythmogenic risk. WiChR activation, however, slightly increases intracellular Na+ levels (by 15.1% compared to 0.1% and 3.4% for ChR2 and GtACR), consistent with the residual Na+ permeability of all currently available K+-selective channelrhodopsins. Simulations of human ventricles and atria demonstrate that GtACR1 most effectively terminates re-entrant arrhythmias at low light intensities, while WiChR achieves comparable efficacy at light levels [≥]5 mW/mm2. Complementary tissue-scale simulations reveal that defibrillation is either based on depolarisation within the excitable gap, followed by fast Na+ channel inactivation (depolarising variants ChR2 and GtACR1), or based on a reduction in membrane resistance supporting arrhythmia termination at sufficiently high light levels (large-conductance ion channels GtACR1 and WiChR). Overall, our findings identify channelrhodopsin ion selectivity as a key determinant of both arrhythmia termination success and mechanisms underlying defibrillation. Key points summaryO_LIWe use computational simulations to compare non-selective cation (ChR2), anion (GtACR1), and K+-selective channelrhodopsins (WiChR) for optogenetic termination of re-entrant arrhythmia. C_LIO_LISingle-cardiomyocyte simulations suggest that ChR2 and GtACR1 activation can cause progressive accumulation of intracellular Ca2+, which is minimised when using WiChR. C_LIO_LISimulations of human left ventricles and atria indicate that GtACR1 is most effective in terminating re-entrant arrhythmia at low light intensities, while WiChR becomes similarly effective at higher intensities. C_LIO_LITissue-scale simulations indicate distinct defibrillation mechanisms: Excitable gap extinction by de-novo action potential initiation followed by inactivation of fast Na+ channels for depolarising channelrhodopsins (ChR2, GtACR1), and reduction in membrane resistance for the large-conductance channels (GtACR1, WiChR), effectively clamping the membrane potential at each channels reversal potential at high light levels. C_LI

physiology↗

bioRxiv2024

Early atrial remodelling drives arrhythmia in Fabry Disease

BackgroundFabry disease (FD) is an X-linked lysosomal storage disorder caused by -galactosidase A (-Gal A) deficiency, resulting in multi-organ accumulation of sphingolipid, namely globotriaosylceramide (Gb3). This triggers ventricular myocardial hypertrophy, fibrosis, and inflammation, driving arrhythmia and sudden death, a common cause of FD mortality. Atrial fibrillation (AF) is common in FD, yet the cellular mechanisms accounting for this are unknown. To address this, we conducted electrocardiography (ECG) analysis from a large cohort of adults with FD at varying stages of cardiomyopathy. Cellular contractile and electrophysiological function were examined in an atrial FD model, developed using gene-edited atrial cardiomyocytes and imputed into in-silico atrial models to provide insight into arrhythmia mechanisms. MethodsIn 115 adults with FD, ECG P-wave characteristics were compared with non-FD controls. Induced pluripotent stem cells (iPSCs) were genome-edited using CRISPR-Cas9 to introduce the GLA p. N215S variant and differentiated into atrial cardiomyocytes (iPSC-CMs). Contraction, calcium handling and electrophysiology experiments were conducted to explore proarrhythmic mechanisms. A bi-atrial in-silico model was developed with the cellular changes induced by GLA p. N215S iPSC-CMs. ResultsECG analysis demonstrated P-wave duration and PQ interval shortening in FD adults before onset of cardiomyopathy on imaging and biochemical criteria. FD patients exhibited a higher incidence of premature atrial contractions and increased risk of developing AF. In our cellular model, GLA p. N215S iPSC-CMs were deficient in -Gal A and exhibited Gb3 accumulation. Atrial GLA p. N215S iPSC-CMs demonstrated a more positive diastolic membrane potential, faster action potential upstroke velocity, greater burden of delayed afterdepolarizations, greater contraction force, slower beat rate and dysfunction in calcium handling compared to wildtype iPSC-CMs. Inputting these changes into the in-silico model resulted in similar P-wave morphology changes to those seen in early FD cardiomyopathy and increased the action potential duration (APD) restitution slope, causing APD alternans and inducing AF. ConclusionsThese findings enhance our understanding of atrial myopathy in FD by providing novel insights into underpinning mechanisms for atrial arrhythmia and a rationale for early P-wave changes. These may be targeted in future research to develop therapeutic strategies to reduce the arrhythmic burden in FD and other atrial cardiomyopathies.

pathology↗

bioRxiv2024

Towards prospective in-silico trials in atrial fibrillation: the case of polypharmacological SK and K2P channel block

BackgroundVirtual evaluation of medical therapy through human-based modelling and simulation can accelerate and augment clinical investigations. Treatment of the most common cardiac arrhythmia, atrial fibrillation (AF), requires novel approaches. ObjectivesTo prospectively evaluate and mechanistically explain novel pharmacological therapies for atrial fibrillation through in-silico trials, considering single and combined SK and K2P channel block. MethodsA large cohort of 1000 virtual patients was developed for simulations of AF and pharmacological action. Extensive calibration and validation with experimental and clinical data support their credibility. ResultsSustained AF was observed in 654 (65%) virtual patients. In this cohort, cardioversion efficacy increased to 82% (534 of 654) through combined SK+K2P channel block, from 33% (213 of 654) and 43% (278 of 654) for single SK and K2P blocks, respectively. Drug-induced prolongation of tissue refractoriness, dependent on the virtual patients ionic current profile, explained cardioversion efficacy (atrial refractory period increase: 133.0{+/-}48.4 ms for combined vs. 45.2{+/-}43.0 and 71.0{+/-}55.3 for single SK and K2P block, respectively). Virtual patients cardioverted by SK channel block presented lower K2P densities, while lower SK densities favoured the success of K2P channel inhibition. Both ionic currents had a crucial role on atrial repolarization, and thus, a synergism resulted from the polypharmacological approach. All three strategies, including the multi-channel block, preserved atrial electrophysiological function (i.e., conduction velocity and calcium transient dynamics) and thus, its contractile properties (safety). ConclusionIn-silico trials identify key factors determining efficacy of single vs combined SK+K2P channel block as effective and safe strategies for AF management.

bioengineering↗