Mechanotransduction-Driven Modulation of L-Type Calcium Channels: Roles of Nitric Oxide, S-Nitrosylation, and cGMP in Rat Ventricular Cardiomyocytes

<i>L</i>-type Ca²⁺ channels, particularly Ca_V1.2, play a crucial role in cardiac excitation-contraction coupling and are known to exhibit mechanosensitivity. However, the mechanisms regulating their response to mechanical stress remain poorly understood. To investigate the mechanosensitivity and nitric oxide (NO)-dependent regulation of <i>L</i>-type Ca²⁺ channels in rat ventricular cardiomyocytes, we used RNA sequencing to assess isoform expression and whole-cell patch-clamp recordings to measure <i>L</i>-type Ca²⁺ current (<i>I</i>_Ca,L) under controlled mechanical and pharmacological conditions. RNA sequencing revealed predominant expression of Ca_V1.2 (TPM: 0.1170 ± 0.0075) compared to Ca_V1.3 (0.0021 ± 0.0002) and Ca_V1.1 (0.0002 ± 0.0002). Local axial stretch (6-10 μm) consistently reduced <i>I</i>_Ca,L in proportion to stretch magnitude. The NO donor SNAP (200 μM) had variable effects on basal <i>I</i>_Ca,L in unstretched cells (stimulatory, inhibitory, or biphasic) but consistently restored stretch-reduced <i>I</i>_Ca,L to control levels. Ascorbic acid (10 μM), which reduces S-nitrosylation, increased basal <i>I</i>_Ca,L and partially restored the reduction caused by stretch, implicating S-nitrosylation in channel regulation. The sGC inhibitor ODQ (5 μM) decreased <i>I</i>_Ca,L in both stretched and unstretched cells, indicating involvement of the NO-cGMP pathway. Mechanical stress modulates <i>L</i>-type Ca²⁺ channels through a complex interplay between S-nitrosylation and NO-cGMP signaling, with S-nitrosylation playing a predominant role in stretch-induced effects. This mechanism may represent a key component of cardiac mechanotransduction and could be relevant for therapeutic targeting in cardiac pathologies involving mechanically induced dysfunction.