Leukotriene B4 enhances tumour necrosis factor-α-induced CCL27 production in human keratinocytes

Background A chemokine CCL27 recruits skin-homing T cells. CCL27 production by epidermal keratinocytes is dependent on nuclear factor-kappa B (NF-kappa B) activity and is enhanced in lesions with atopic dermatitis or allergic contact dermatitis. A lipid mediator leukotriene B-4 (LTB4) may be involved in the development of these allergic dermatoses. LTB4 acts on cell surface G-protein-coupled receptors, BLT1 and BLT2. Objective The aim of this study was to investigate the in vitro effects of LTB4 on CCL27 production in human keratinocytes. Methods Keratinocytes were incubated with TNF-alpha and LTB4. CCL27 secretion and mRNA levels were analysed by ELISA and RT-PCR, respectively. NF-kappa B activities were analysed by luciferase assays. Protein levels or phosphorylation status were analysed by cell-based ELISA. Results LTB4 alone did not enhance CCL27 production and modestly enhanced NF-kappa B activity in human keratinocytes. However, LTB4 potently enhanced TNF-alpha-induced CCL27 secretion and mRNA expression and NF-kappa B activity. LTB4 alone or together with TNF-alpha, induced phosphorylation and degradation of inhibitory NF-kappa B alpha (I kappa B alpha) and phosphorylation of NF-kappa B p65. These effects of LTB4 were suppressed by BLT1 antagonist U75302, pertussis toxin, phosphoinositide-3 kinase (PI3K) inhibitor LY294002 and extracellular signal-regulated kinase (ERK) kinase inhibitor U0126, but not by BLT2 antagonist LY255283. LTB4 induced phosphorylation of ERK and Akt, downstream kinase of PI3K; LY294002 suppressed phosphorylation of both kinases while U0126 suppressed only the former. Conclusions These results suggest that LTB4 may enhance TNF-alpha-induced CCL27 production by activating NF-kappa B via the BLT1/G(i/o)/PI3K/ERK pathway in human keratinocytes. LTB4 may contribute to the enhanced CCL27 production of keratinocytes in lesions with atopic dermatitis or allergic contact dermatitis.