Mitochondrial K(ATP) channel opening protects a human atrial-derived cell line by a mechanism involving free radical generation.

Abstract

OBJECTIVES:

The mechanism by which the mitochondrial K(ATP) channel openers confer protection against ischemia/reperfusion injury is debated. Evidence suggests that rather than solely being an end effector, opening of these channels may act by a trigger mechanism. We examined the effects of the mitochondrial K(ATP) channel opener, diazoxide on parameters of mitochondrial function with specific reference to reactive oxygen species (ROS) generation in a human atrial derived cell line model of simulated ischemia/reperfusion (LSI/R).

METHODS AND RESULTS:

Propidium iodide (PI) exclusion was used to assess survival. Diazoxide treatment conferred protection against LSI/R (13.9+/-0.9% vs. 36.9+/-4.5% controls) that was abolished by pre-treatment with the mitoK(ATP) channel blocker, 5-hydroxydecanoate (5-HD) (33.3+/-3.6%) and with the free radical scavenger, 2-mercaptopropionylglycine (MPG) (29+/-4.0%). Diazoxide caused increased oxidation of the ROS probe, reduced mitotracker orange (1.3 vs. 1.0 arbitrary units for control; P<0.01 vs. control) that was abrogated by either 5-HD or MPG (1.07 and 1.07 arbitrary units, respectively). At the same time there was no change in orange fluorescent signal from the membrane potential sensitive probe, JC-1 indicating no change in mitochondrial membrane potential. Changes in light scattering, reflecting changes in mitochondrial volume, occurred during treatment with diazoxide.

CONCLUSION:

These results demonstrate for the first time that the mitoK(ATP) channel opener diazoxide can act as a trigger of preconditioning by a mechanism involving mitochondrial swelling and the generation of ROS.

• Authors: R Carroll, V A Gant, D M Yellon
• Journal: Cardiovascular research (Cardiovasc Res) Vol. 51 Issue 4 Pg. 691-700 (Sep 2001) ISSN: 0008-6363 [Print] England
• PMID: 11530102 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Anti-Arrhythmia Agents
• Decanoic Acids
• Free Radical Scavengers
• Hydroxy Acids
• Potassium Channels
• Reactive Oxygen Species
• 5-hydroxydecanoic acid
• Tiopronin
• Diazoxide

Topics

• Analysis of Variance
• Anti-Arrhythmia Agents (pharmacology)
• Cell Line
• Decanoic Acids (pharmacology)
• Diazoxide (pharmacology)
• Flow Cytometry
• Free Radical Scavengers (pharmacology)
• Heart Atria
• Humans
• Hydroxy Acids (pharmacology)
• Ion Channel Gating
• Ischemic Preconditioning, Myocardial
• Membrane Potentials (drug effects)
• Microscopy, Fluorescence
• Mitochondria, Heart (drug effects, metabolism, ultrastructure)
• Potassium Channels (drug effects)
• Reactive Oxygen Species (metabolism)
• Tiopronin (pharmacology)