7 research outputs found
Stimulation of neuronal KATP channels by cGMP-dependent protein kinase: involvement of ROS and 5-hydroxydecanoate-sensitive factors in signal transduction
The ATP-sensitive potassium (KATP) channel couples intracellular metabolic state to membrane excitability. Recently, we demonstrated that neuronal KATP channels are functionally enhanced by activation of a nitric oxide (NO)/cGMP/cGMP-dependent protein kinase (PKG) signaling cascade. In this study, we further investigated the intracellular mechanism underlying PKG stimulation of neuronal KATP channels. By performing single-channel recordings in transfected HEK293 and neuroblastoma SH-SY5Y cells, we found that the increase of Kir6.2/SUR1 (i.e., the neuronal-type KATP) channel currents by PKG activation in cell-attached patches was diminished by 5-hydroxydecanoate (5-HD), an inhibitor of the putative mitochondrial KATP channel; N-(2-mercaptopropionyl)glycine, a reactive oxygen species (ROS) scavenger, and catalase, a hydrogen peroxide (H2O2)-decomposing enzyme. These reagents also ablated NO-induced KATP channel stimulation and prevented the shifts in the single-channel open- and closed-time distributions resulting from PKG activation and NO induction. Bath application of H2O2 reproduced PKG stimulation of Kir6.2/SUR1 but did not activate tetrameric Kir6.2LRKR368/369/370/371AAAA channels. Moreover, neither the PKG activator nor exogenous H2O2 was able to enhance the function of KATP channels in the presence of Ca2+ chelators and calmodulin antagonists, whereas the stimulatory effect of H2O2 was unaffected by 5-HD. Altogether, in this report we provide novel evidence that activation of PKG stimulates neuronal KATP channels by modulating intrinsic channel gating via a 5-HD-sensitive factor(s)/ROS/Ca2+/calmodulin signaling pathway that requires the presence of the SUR1 subunit. This signaling pathway may contribute to neuroprotection against ischemic injury and regulation of neuronal excitability and neurotransmitter release by modulating the function of neuronal KATP channels
Antiarrhythmic activity of a new spiro-cyclic benzopyran activator of the cardiac mitochondrial ATP dependent potassium channels
‘Compound A’ (4ı-(N-(4-acetamidobenzyl))-2,2-
dimethyl-2,3-dihydro-5ıH-spiro[chromene-4,2ı-[1,4]oxazinan]-
5ı-one) is a new spiro-cyclic benzopyran activator of
the mitochondrial ATP-dependent potassium channels
(mitoKATP). We researched the effect of compound A on
ischemia/reperfusion (I/R)-induced ventricular arrhythmias.
We also tested the hypothesis that the application of
the activation of mitoKATP in combination with the inhibition
of sarcolemmal ATP-dependent potassium channels
(sarcKATP) may produce a stronger antiarrhythmic effect.
In anesthetized rats, myocardial ischemia was performed
by ligating the left main coronary artery followed by
reperfusion. At a dose of 10 mg/kg, compound A significantly
decreased arrhythmia scores and the total length of
arrhythmias, whereas this was found to be ineffective at a
dose of 3 mg/kg. Pre-treatment with 5-HD, a selective
mitoKATP blocker, abolished the antiarrhythmic effect of
compound A. Both diazoxide, a selective mitoKATP opener
and HMR 1098, a selective sarcKATP blocker, significantly
decreased the total length of arrhythmias. However, the
combination of neither diazoxide nor compound A with
HMR 1098 showed no additional therapeutic benefit. These
results reveal that compound A may have a dose-dependent
antiarrythmic effect, which is more pronounced than the
antiarrhythmic effect of diazoxide. The antiarrhythmic effect of compound A may possibly depend on mitoKATP
activation