Effect of clarithromycin on the expression of UL16-Binding protein 2 in human cells

Background Clarithromycin is a macrolide antibiotic that possesses anti-inflammatory and immunomodulatory properties. Although recent data suggests that macro lide antibiotics enhance Pseudomonas aeruginosa clearance from the lung, involving natural killer (NK) T cells in this process by activating the NKG2D-NKG2D ligand system, the precise underlying mechanism is still unclear. In this study, we examined the effect of clarithromycin on a potent NKG2D ligand, UL16-binding protei n 2 (ULBP2), in the lung and its shedding mechanism. Methods The gene expressions of ULBP2 and the shredder proteinases of ULBP2, a disintegrin and metalloproteinase domain 10 (ADAM10) and ADAM17, were meas ured using real-time PCR. The cell surface ULBP2 expression was measured by flow cytometry. The amount of solubilized ULBP2 (sULBP2) was measured using an ELISA. The activity of ADAM17 was examined by measurement of fluorescence intensity from the fluor escence resonance energy transfer peptide substrate cleaved by ADAM17. Results Clarithromycin significantly induced transcription of ULBP2 and ADAM17 in both A549 and LCSC # 2 cells, which endogenously express minimal and abundant levels of ULBP2, respectively. However, there was no significant change on transcription of ADA M10. The same tendency was observed when LCSC #2 cells were treated with tumor necrosis factoralpha processing inhibitor-2 to inhibit ADAM17 activity. The amount of sULBP2 was significantly decreased in