Selective inhibitors of Kv11.1 regulate IL-6 expression by macrophages in response to TLR/IL-1R ligands

• Published in: TheScientificWorld 2010-01, Vol.10, p.1580-1596
• Main Authors: Hunter, Cheryl, Kadakia, Tejas B, Cooper, Dianne, Perretti, Mauro, Schwartz, Richard C, Brown, Simon B
• Format: Article
• Language: English
• Subjects: Animals; Blotting, Western; CCAAT-Enhancer-Binding Protein-beta - metabolism; Cells, Cultured; ERG1 Potassium Channel; Ether-A-Go-Go Potassium Channels - antagonists & inhibitors; Ether-A-Go-Go Potassium Channels - metabolism; Female; Gene expression; Genetic aspects; Health aspects; Interleukin-6 - genetics; Interleukin-6 - metabolism; Interleukins; Ligands; Ligands (Biochemistry); Macrophages; Macrophages - cytology; Macrophages - drug effects; Macrophages - metabolism; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Neutrophils - drug effects; Neutrophils - metabolism; Peritonitis - metabolism; Peritonitis - prevention & control; Phenethylamines - pharmacology; Physiological aspects; Platelet Endothelial Cell Adhesion Molecule-1 - genetics; Platelet Endothelial Cell Adhesion Molecule-1 - metabolism; Potassium Channel Blockers - pharmacology; Receptors, Interleukin-1 - metabolism; Sulfonamides - pharmacology; Toll-Like Receptors - metabolism
• ISSN: 1537-744X; 2356-6140; 1537-744X
• DOI: 10.1100/tsw.2010.155

The mechanism by which the platelet-endothelial cell adhesion molecule PECAM-1 regulates leukodiapedesis, vascular endothelial integrity, and proinflammatory cytokine expression in vivo is not known. We recently identified PECAM-1 as a negative regulator of Kv11.1, a specific voltage-gated potassium channel that functioned in human macrophages to reset a resting membrane potential following depolarization. We demonstrate here that dofetilide (DOF), a selective inhibitor of the Kv11.1 current, had a profound inhibitory effect on neutrophil recruitment in mice following TLR/IL-1R-elicited peritonitis or intrascrotal injection of IL-1 Beta, but had no effect on responses seen with TNF alpha. Furthermore, inhibitors of Kv11.1 (DOF, E4031, and astemizole), but not Kv1.3 (margatoxin), suppressed the expression of IL-6 and MCP-1 cytokines by murine resident peritoneal macrophages, while again having no effect on TNF alpha. In contrast, IL-6 expression by peritoneal mesothelial cells was unaffected. Using murine P388 cells, which lack endogenous C/EBP Beta expression and are unresponsive to LPS for the expression of both IL-6 and MCP-1, we observed that DOF inhibited LPS-induced expression of IL-6 mRNA following ectopic expression of wild-type C/EBP Beta, but not a serine-64 point mutant. Finally, DOF inhibited the constitutive activation of cdk2 in murine peritoneal macrophages; cdk2 is known to phosphorylate C/EBP Beta at serine-64. Taken together, our results implicate a potential role for Kv11.1 in regulating cdk2 and C/EBP Beta activity, where robust transactivation of both IL-6 and MCP-1 transcription is known to be dependent on serine-64 of C/EBP Beta. Our data might also explain the altered phenotypes displayed by PECAM-1 knockout mice in several disease models.