Abstract:

Objective To investigate the effect of Toll-like receptor 2 （TLR2） on the proliferation of human keratinocytes. Methods Keratinocytes were isolated from the foreskin of children, and subjected to primary culture. After 3-5 passages, the keratinocytes were incubated with various concentrations of peptidoglycan （PGN）, a TLR2 agonist. Cell proliferation was detected by MTT colorimetric assay and the suitable concentrations of PGN were determined. The mRNA and protein expressions of Ki67, TLR2, NF-κB p65 and TGF-α were detected by real-time quantitative PCR and Western blot, respectively, in keratinocytes treated with PGN of 0, 1.25, 2.5 and 5 μg/mL. Antibody blocking test was utilized to evaluate the effect of blocking TLR2 with specific anti-TLR2 neutralizing monoclonal antibody before incubation with PGN on the expressions of Ki67, TLR2, NF-κB p65 and TGF-α by keratinocytes. Results The proliferation of keratinocytes was significantly promoted by the incubation with PGN of 1.25, 2.5 and 5 μg/mL for 24 hours （all P < 0.05）, which also increased the expression of Ki67 protein, TLR2 mRNA and protein, and NF-κB p65 protein. Further more, the mRNA expression of Ki67 in keratinocytes was elevated by PGN of 1.25 and 2.5 μg/mL, the mRNA expression of NF-κB p65 elevated by PGN of 1.25 μg/mL, and the expressions of TGF-α protein and mRNA elevated by PGN of 1.25 and 5 μg/mL （P < 0.05）. The mRNA and protein expressions of Ki67, TLR2, NF-κB p65 and TGF-α were all inhibited by the blocking of TLR2 before incubation with PGN （all P < 0.05）. Conclusion Activation of TLR2 by PGN could induce the over-proliferation of human keratinocytes, likely through promoting NF-κB activation and TGF-α expression.