Glycated human serum albumin enhances macrophage inflammatory protein-1β mRNA expression through protein kinase C-δ and NADPH oxidase in macrophage-like differentiated U937 cells

Background: In a previous report (Higai K et al, Biol Pharm Bull, 2007), glycated human serum albumin (Glc-HSA) was found to induce interleukin-8 (IL-8) mRNA expression in human monocyte-derived U937 cells through a reactive oxygen species (ROS)-dependent pathway; however, Glc-HSA signaling has not been elucidated in macrophages. Methods: U937 cells were differentiated by treatment with 50 ng/mL phorbol 12-myristate 13-acetate (PMA) for 2 days and the macrophage-like differentiated U937 (differentiated U937) cells were stimulated with Glc-HSA and glycolaldehyde dimer-modified HSA (GA-HSA) in the presence of various signaling inhibitors. Macrophage inflammatory protein-1 beta (MIP-1 beta) mRNA expression was determined by real-time PCR. Intracellular ROS generation was estimated by confocal laser microscopy. Results: Glc-HSA and GA-HSA markedly enhanced MIP-1 beta mRNA expression in differentiated U937 cells. Enhanced MIP-1 beta mRNA expression was completely suppressed by the ROS scavenger N-acetyl-L-Cysteine, the NADPH oxidase inhibitors diphenylene iodonium and apocynin, and the protein kinase C (PKC)-delta inhibitor rottlerin. Furthermore, ROS generation was suppressed completely by rottlerin but not by the PKC-gamma inhibitor Ro318425 or the PKC-alpha, -beta 1 and -mu inhibitor Go6976. Conclusion: Glc-HSA and GA-HSA enhance MIP-1 beta mRNA expression in differentiated U937 cells through PKC-delta-dependent activation of NADPH oxidase. (c) 2007 Elsevier B.V All rights reserved.