The cardiac TRPA1 channel drives calcium-mediated mechano-arrhythmogenesis

Abstract

SUMMARY PARAGRAPHPhysiological systems require feedback to maintain normal function. In the heart, electrical excitation causes mechanical contraction1, with feedback of mechanics to electrics occurring through ‘mechano-electric coupling’ processes2. In diseases that affect cardiac mechanics, this feedback can result in deadly mechanically-induced arrythmias (‘mechano-arrhythmogenicity’)3. However, the molecular identity of the specific factor(s) driving mechano-arrhythmogenicity are unknown4. Here we show that mechano-sensitive5–10 transient receptor potential kinase ankyrin 1 (TRPA1) channels11 are a source of cardiac mechano-arrhythmogenicity through a calcium (Ca2+)-driven mechanism. Using a cell-level approach involving stretch of single ventricular myocytes combined with simultaneous voltage-Ca2+ imaging, we found that activation of TRPA1 channels resulted in an increase in diastolic Ca2+ load and the appearance of stretch-induced arrhythmias, which were driven by trans-sarcolemmal fluxes and intracellular oscillations of Ca2+, and prevented by pharmacological TRPA1 channel block or Ca2+ buffering. Our results demonstrate that TRPA1 channels act as a trigger for stretch-induced excitation (via Ca2+-influx) and create a substrate for complex arrhythmic activity (via Ca2+-overload), and thus may represent a novel anti-arrhythmic target in cardiac diseases in which TRPA1 channel expression and activity are augmented12–16.

Mechano-arrhythmogenicity is enhanced during late repolarisation in ischemia and driven by a TRPA1-, calcium-, and reactive oxygen species-dependent mechanism

“…Rabbit ventricular myocytes were enzymatically isolated as previously described. 15 Details are available in the supplemental methods.…”

“…Cells were subjected to axial stretch using the carbon fibre (CF) method previously described for stretch of ventricular myocytes. 15,21 Figure shows a schematic for the stretch protocol. Contractile function and characteristics of stretch were assessed by monitoring sarcomere length and piezo-electric translators (PZT) and CF tip positions to determine incidence and classification of mechano-arrhythmogenicity (Fig.…”

“…Fluorescence imaging. Figure 1 shows a schematic of the single-excitation/dual-emission fluorescence imaging technique to monitor voltage-Ca 2+ dynamics in isolated ventricular myocytes, adapted from our previous work 15 . Ratiometric Ca 2+ levels were assessed using Fura Red-AM (5 µM; AAT Bioquest).…”

“…We next sought to determine mechanisms underlying the observed increase in mechanoarrhythmogenicity during the ischemic VP. As we previously showed that TRPA1 channels can act as a source for mechano-arrhythmogenicity, 15 and as it is known that TRPA1 channel activity is increased in ischemia, 17 we tested the effects of a specific TRPA1 blocker on arrythmia incidence. Pre-incubating ischemic cells with HC-030031 reduced arrhythmia incidence in the VP (0.9 vs 6.8%; p<0.005;), with no change in diastolic incidence (Fig.…”

“…10,11 Further work showed that the mechano-sensitive, 12 Ca 2+ -permeable 13 transient receptor potential ankyrin 1 (TRPA1) channel 14 can act as a source for Ca 2+ -mediated mechano-arrhythmogenicity in ventricular myocytes by triggering premature excitation and creating a substrate for more complex arrhythmic activity. 15 Since the response of TRPA1 to mechanical stimulation is dependent on its baseline activity, 16 which is increased in ischemia 17 as it is agonised by multiple ischemic factors (e.g., increased cytosolic Ca 2+ and ROS), 18,19 TRPA1 may be involved in ischemic mechano-arrhythmogenicity.…”