title: Effects of hydrogen peroxide on voltage-dependent K(+) currents in human cardiac fibroblasts through protein kinase pathways.
abstract: Human cardiac fibroblasts (HCFs) have various voltage-dependent K(+) channels (VDKCs) that can induce apoptosis. Hydrogen peroxide (H2O2) modulates VDKCs and induces oxidative stress, which is the main contributor to cardiac injury and cardiac remodeling. We investigated whether H2O2 could modulate VDKCs in HCFs and induce cell injury through this process. In whole-cell mode patch-clamp recordings, application of H2O2 stimulated Ca(2+)-activated K(+) (KCa) currents but not delayed rectifier K(+) or transient outward K(+) currents, all of which are VDKCs. H2O2-stimulated KCa currents were blocked by iberiotoxin (IbTX, a large conductance KCa blocker). The H2O2-stimulating effect on large-conductance KCa (BKCa) currents was also blocked by KT5823 (a protein kinase G inhibitor) and 1 H-[1, 2, 4] oxadiazolo-[4, 3-a] quinoxalin-1-one (ODQ, a soluble guanylate cyclase inhibitor). In addition, 8-bromo-cyclic guanosine 3', 5'-monophosphate (8-Br-cGMP) stimulated BKCa currents. In contrast, KT5720 and H-89 (protein kinase A inhibitors) did not block the H2O2-stimulating effect on BKCa currents. Using RT-PCR and western blot analysis, three subtypes of KCa channels were detected in HCFs: BKCa channels, small-conductance KCa (SKCa) channels, and intermediate-conductance KCa (IKCa) channels. In the annexin V/propidium iodide assay, apoptotic changes in HCFs increased in response to H2O2, but IbTX decreased H2O2-induced apoptosis. These data suggest that among the VDKCs of HCFs, H2O2 only enhances BKCa currents through the protein kinase G pathway but not the protein kinase A pathway, and is involved in cell injury through BKCa channels.
authors.affiliation: Department of Physiology, College of Medicine, Chung-Ang University, Seoul 06974, Korea.
authors.forename: Hyemi
authors.initials: H
authors.lastname: Bae
authors.affiliation: Department of Physiology, College of Medicine, Chung-Ang University, Seoul 06974, Korea.
authors.forename: Donghee
authors.initials: D
authors.lastname: Lee
authors.affiliation: Department of Physiology, College of Medicine, Chung-Ang University, Seoul 06974, Korea.
authors.forename: Young-Won
authors.initials: YW
authors.lastname: Kim
authors.affiliation: Department of Physiology, College of Medicine, Chung-Ang University, Seoul 06974, Korea.
authors.forename: Jeongyoon
authors.initials: J
authors.lastname: Choi
authors.affiliation: Biomedical Research Institute, College of Medicine, Chung-Ang University, Seoul 06974, Korea.
authors.forename: Hong Jun
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine, College of Medicine, Chung-Ang University, Seoul 06974, Korea.
authors.forename: Sang-Wook
authors.initials: SW
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, College of Medicine, Chung-Ang University, Seoul 06974, Korea.
authors.forename: Taeho
authors.initials: T
authors.lastname: Kim
authors.affiliation: Department of Biochemistry, School of Medicine, Konkuk University, Seoul 05029, Korea.
authors.forename: Yun-Hee
authors.initials: YH
authors.lastname: Noh
authors.affiliation: Department of Physiology, College of Medicine, Chung-Ang University, Seoul 06974, Korea.
authors.forename: Jae-Hong
authors.initials: JH
authors.lastname: Ko
authors.affiliation: Department of Physiology, College of Medicine, Chung-Ang University, Seoul 06974, Korea.
authors.forename: Hyoweon
authors.initials: H
authors.lastname: Bang
authors.affiliation: Department of Physiology, College of Medicine, Chung-Ang University, Seoul 06974, Korea.
authors.forename: Inja
authors.initials: I
authors.lastname: Lim
keywords: Ca2+-activated K+ channels; Human cardiac fi broblasts; Hydrogen peroxide; K+ currents; Protein kinase