Glycyrrhizin restores impaired antimicrobial peptide production by human skin tissues cultured with immature myeloid suppressor cells (162.13)

Abstract

Abstract We have previously demonstrated that CD34+ CD31+ immature myeloid cells (IMC) appearing in burn patients suppress antimicrobial peptide production by cultured human skin keratinocytes. In the present study, the effect of glycyrrhizin (GL) on the peptide production by unburned patient skin (skin removed for the auto-grafting surgery) transwell-cultured with CD34+ CD31+ IMC was examined. Using a lineage cell depletion kit and flow cytometry, CD34+ CD31+ IMC were isolated from peripheral blood of burn patients. Unburned patient skin tissues (4 x 4 mm) were transwell-cultured with various numbers of IMC for 1 to 7 days in the presence or absence of GL (Minophagen Pharmaceutical Co., Ltd., Tokyo, Japan). Culture fluids obtained were assayed for human β-defensin-1 (HBD-1) by ELISA. In the results, 1-5 ng/ml of HBD-1 were produced by unburned patient skin tissues 2 to 7 days after cultivation. When skin tissues were transwell-cultured with 1 x 104 cells/ml of IMC syngeneic to the skin donors, 86% of HBD-1 production was suppressed. However, HBD-1 was produced by unburned patient skin tissues transwell-cultured with syngeneic IMC and GL. Similarly, HBD-1 was produced by unburned skin tissues transwell-cultured with allogeneic IMC and GL. These results indicate that GL is inhibitory on the IMC suppressor cell activity in HBD-1 production by unburned patient skin tissues.