Lipoxin A4 inhibits proliferation and inflammatory cytokine/chemokine production of human epidermal keratinocytes associated with the ERK1/2 and NF-κB pathways

Background: Current in vitro studies show that lipoxin A4 (LXA4) has multiple biological functions including inhibiting cell proliferation and inflammatory cytokine production. Our previous studies showed LXA4 could inhibit the expression of IL-6 and IL-8 in normal human epidermal keratinocytes (NHEKs). However, more specific effects including regulation of cell proliferation and anti-inflammatory mechanisms of LXA4 in NHEKs have not been previously studied.

Objective: We proposed to investigate the effects of LXA4 on cell proliferation and inflammatory cytokine/chemokine production in NHEKs, and the possible molecular mechanisms of cell cycle and anti-inflammatory signal transduction pathway.

Methods: NHEKs were stimulated with LPS, with or without preincubation with LXA4. Cell proliferation and cell cycle of NHEKs were examined by WST-8, CFSE assay and DNA staining, respectively. The mRNA and protein levels of inflammatory cytokines were quantified by real-time quantitative PCR and ELISA. The expressions of signaling proteins cyclin D1, P16INK4A, ERK1/2 and NF-κB-p65 were analyzed using Western blotting.

Results: Cell proliferation and inflammatory cytokine/chemokine production of NHEKs were suppressed by LXA4, which caused G0/G1 phase cell cycle arrest in NHEKs. The expression of cyclin D1 was down-regulated by LXA4, contrary to the results of P16INK4A. The ERK1/2 phosphorylation and NF-κB-p65 nuclear translocation of NHEKs were both suppressed by LXA4.

Conclusion: Cell growth and inflammatory cytokine/chemokine production of NHEKs were inhibited by LXA4, and the inhibitory effects might be associated with the mechanisms of cyclin D1/P16INK4A, ERK1/2 and NF-κB signal transduction pathway.