Down-regulation of interleukin-8 gene expression in HL60 cell line by human Kunitz-type trypsin inhibitor

Urinary trypsin inhibitor (UTI) is one of the Kunitz-type protease inhibitors in human. Little is known about its anti-inflammatory functions other than protease inhibition. We studied the effect of UTI on gene expression of interleukin-8 (IL-8), an inflammatory cytokine. UTI inhibited IL-8 gene expression induced by lipopolysaccharide (LPS) in HL60 cells. The IL-8 concentrations in the cells and medium after LPS stimulation increased time-dependently in the absence of UTI, but did not increase in the presence of UTI. On the other hand, UTI did not inhibit either the synthesis or the release of IL-8 induced by the calcium ionophore A23187. UTI inhibited increase of cytosolic Ca2+ stimulated by LPS but not by A23187. Our results suggest that the inhibition by UTI is due to its effect on the cell membrane involved in regulating Ca2+ influx.