Melatonin inhibits lipopolysaccharide-induced CC chemokine subfamily gene expression in human peripheral blood mononuclear cells in a microarray analysis

Melatonin possesses a number of important biologic activities including oncostatic, anti-oxidant, and immunostimulatory actions. This study was designed to assess the effects of melatonin on inflammation-related gene expression in lipopolysaccharide (LPS)-stimulated human peripheral blood mononuclear cells (PBMCs), using CombiMatrix 2K Human Inflammation chip. After pretreatment with melatonin (100 mu M) for 4 hr, cells were incubated with LPS (I mu g/mL) for 24 hr. We compared gene expression profiles between LPS-treated, melatonin-treated. LSP/melatonin-treated. and control groups. LPS induced the upregulation of 95 genes, compared with controls. Melatonin pretreatment in LPS-stimulated PBMCs suppressed the expression of 23 genes more than twofold. Interestingly, melatonin showed a suppressive effect on the expression of CC chemokine subfamily genes, including CCL2/MCP1, CCL3/MIP1 alpha, CCL4/MIP1 beta, CCL5/RANTES, CCL8/MCP2, CCL20/MDC, and CCL22/MIP3 alpha, in LPS-stimulated PBMCs. This result was confirmed by reverse transcriptase polymerase chain reaction. Among the CC chemokine subfamily genes, particularly, the expression of CCL2 and CCL5 was markedly downregulated by melatonin in LPS-stimulated PBMCs. The secretion levels of CCL2 and CCL5 were measured using enzyme-linked immunosorbent assay. Stimulation of PBMCs by LPS induced the secretion of CCL2 (2334.3 +/- 161.4 pg/mL, mean +/- S.E.M.) whereas melatonin pretreatment, (153.0 +/- 3.8 pg/mL) inhibited the LPS-induced secretion of CCL2. Melatonin pretreatment (2696.2 +/- 385.3 pg/mL) also inhibited the LPS-induced secretion of CCL5 (4679.6 +/- 107.5 pg/mL). Taken together, these results suggest that melatonin may have a suppressive effect on LPS-induced expression of CC chemokine genes, especially CCL2 and CCL5, which may explain its beneficial effects in the treatment of various inflammatory conditions.