Alterations in macrophage free radical and tumor necrosis factor production by a potassium channel activator

The potassium channel activator nicorandil, under evaluation for antianginal management, has been shown to decrease neutrophil respiratory burst. Since our laboratory has demonstrated that reactive oxygen species (ROS) increase tumor necrosis factor (TNF) production, we hypothesized that nicorandil might decrease TNF production from a lipopolysaccharide (LPS) challenge via reduction of respiratory burst. Macrophage viability and TNF production were determined after an 18-hr exposure to 5.0 micrograms/ml LPS and varying concentrations of nicorandil. Nicorandil was not toxic to macrophages below 12 mM (94 +/- 3% viability versus control) and decreased ROS and TNF production. Intracellular superoxide production decreased from 164 +/- 24 OD550 to 99 +/- 6 OD550 with 10 mM nicorandil and extracellular superoxide decreased from 3108 +/- 111 to 1760 +/- 210 nM. Hydrogen peroxide production was also decreased by 10 mM nicorandil. TNF production in response to 5 micrograms/ml LPS decreased from 6.8 +/- 0.6 to 2.7 +/- 0.4 ng/ml with 10 mM nicorandil. Northern and slot blot analyses demonstrate that nicorandil acts at a post-transcriptional site. These data imply that nicorandil decreases macrophage TNF production from an LPS challenge, possibly through a reduction in respiratory burst. Such compounds may prove useful in the treatment of conditions thought to be associated with free radical-lymphokine interactions such as ischemia-reperfusion injury, oxygen toxicity, adult respiratory distress syndrome, and septic shock.