Abstract
L-type Ca(2+) channels, particularly Ca(V)1.2, 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 L-type Ca(2+) channels in rat ventricular cardiomyocytes, we used RNA sequencing to assess isoform expression and whole-cell patch-clamp recordings to measure L-type Ca(2+) current (I(Ca,L)) under controlled mechanical and pharmacological conditions. RNA sequencing revealed predominant expression of Ca(V)1.2 (TPM: 0.1170 ± 0.0075) compared to Ca(V)1.3 (0.0021 ± 0.0002) and Ca(V)1.1 (0.0002 ± 0.0002). Local axial stretch (6-10 μm) consistently reduced I(Ca,L) in proportion to stretch magnitude. The NO donor SNAP (200 μM) had variable effects on basal I(Ca,L) in unstretched cells (stimulatory, inhibitory, or biphasic) but consistently restored stretch-reduced I(Ca,L) to control levels. Ascorbic acid (10 μM), which reduces S-nitrosylation, increased basal 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(Ca,L) in both stretched and unstretched cells, indicating involvement of the NO-cGMP pathway. Mechanical stress modulates L-type Ca(2+) 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.