Effects of Nitric Oxide on Voltage-Gated K+ Currents in Human Cardiac Fibroblasts through the Protein Kinase G and Protein Kinase A Pathways but Not through S-Nitrosylation

Abstract

This study investigated the expression of voltage-gated K+ (KV) channels in human cardiac fibroblasts (HCFs), and the effect of nitric oxide (NO) on the KV currents, and the underlying phosphorylation mechanisms. In reverse transcription polymerase chain reaction, two types of KV channels were detected in HCFs: delayed rectifier K+ channel and transient outward K+ channel. In whole-cell patch-clamp technique, delayed rectifier K+ current (IK) exhibited fast activation and slow inactivation, while transient outward K+ current (Ito) showed fast activation and inactivation kinetics. Both currents were blocked by 4-aminopyridine. An NO donor, S-nitroso-N-acetylpenicillamine (SNAP), increased the amplitude of IK in a concentration-dependent manner with an EC50 value of 26.4 µM, but did not affect Ito. The stimulating effect of SNAP on IK was blocked by pretreatment with 1H-(1,2,4)oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) or by KT5823. 8-bromo-cyclic GMP stimulated the IK. The stimulating effect of SNAP on IK was also blocked by pretreatment with KT5720 or by SQ22536. Forskolin and 8-bromo-cyclic AMP each stimulated IK. On the other hand, the stimulating effect of SNAP on IK was not blocked by pretreatment of N-ethylmaleimide or by DL-dithiothreitol. Our data suggest that NO enhances IK, but not Ito, among KV currents of HCFs, and the stimulating effect of NO on IK is through the PKG and PKA pathways, not through S-nitrosylation.

Carbon monoxide activation of delayed rectifier potassium currents of human cardiac fibroblasts through diverse pathways

“…However, the strong mRNA expression of Kv1.5 for the Kv channels is also in HCFs [ 32 , 51 ] and ventricular cardiomyocytes [ 52 ]. These findings may indicate a functional role of these ion channel subunits in action potential formation in the human atrium and ventricle.…”

“…Tissue and species–specific Kv gene expression contributes to the current heterogeneity [ 45 ]. HCFs also showed strong gene expression of Kv1.1, Kv1.2, and Kv3.1 in the Kv channels of these cells [ 51 ].…”

“…NO also showed a similar difference for I K . NO inhibited the hKv1.5 channel current, which activates I K in transfected Chinese hamster ovary cells and mouse ventricular myocytes [ 47 ] but also activated the current in HCFs [ 51 ], cardiomyocytes [ 58 ] and the sino-atrial node cells of guinea-pigs [ 59 ]. Considering the differing CO effects for I K , the importance of HCFs in the heart cell population, and the connection between other cell types of the myocardium, more research is required on CO as a therapeutic agent for cardiovascular disease.…”

“…DPO-1 also increases action potential duration in atrial but not ventricular myocytes and prevents atrial arrhythmias [50]. However, the strong mRNA expression of Kv1.5 for the Kv channels is also in HCFs [32,51] and ventricular cardiomyocytes [52]. These findings may indicate a functional role of these ion channel subunits in action potential formation in the human atrium and ventricle.…”

Kv1.3 Current Voltage Dependence in Lymphocytes is Modulated by Co-Culture with Bone Marrow-Derived Stromal Cells: B and T Cells Respond Differentially

“…Different mechanisms of action were reported for BMSC-related immunosuppression, including requirement of direct contact with immune cells and/or secretion of soluble factors, such as nitric oxide (NO), tumor growth factor (TGF-β), prostaglandin E2 (PGE2) [1][2][3][4]. Modulatory effects of aforementioned bioactive compounds on ion channel expression/function were reported for different cellular models [5][6][7][8][9]. Ion channels are important players in signaling events during lymphocyte proliferation, but possible BMSC effects on the expression and biophysical properties of lymphocyte plasma membrane ion channels were not addressed, except a single study where no significant difference in Kv1.3 current between human B cells in monoculture and co-culture with BMSC was reported, whereas possible modulation of the Kv1.3 voltage dependence by a co-culture with BMSC was not explored [10].…”