Azithromycin and ciprofloxacin have a chloroquine-like effect on respiratory epithelial cells

Vojo Deretic; Graham S Timmins

Clinical studies have shown that adherence of P. aeruginosa to the epithelia of CF patients undergoing AZT therapy is reduced 38 . Based on our findings that AZT corrects acidification of TGN in CF cells, we investigated whether AZT affected the undersialylation of aGM1 and reduced bacterial adherence to CF lung epithelial cells. It has been proposed that undersialylation and reduced binding of cholera toxin was one of the evolutionary drivers for the emergence of CFTR mutations in human populations, and that this can be explained at least in part by hyperacidification of the TGN and the resulting suboptimal distribution or activity of sialyltransferases and other glycosylating enzymes in this organelle 29, 39 . CF and normal cells were grown for 14 days postconfluency, followed by 48 h treatment of the monolayers with 1-100 µM AZT. The monolayers were assayed for binding of cholera toxin subunit B (CTB) conjugated to fluorophore FITC (CTB binds preferentially to sialylated glycoconjugates) (Fig. 3A ). Using binding of CTB to S9 cells (CFTR-corrected IB3-1 cells) as 100%, and binding to IB3-1 cells (CF) as 0%, treatment of IB3-1 monolayers with 1-100 µM AZT increased CTB-FITC binding to levels that approached that of the non-CF S9 cells (Fig. 3A) . As with the TGN-38 pH correction, the effect of AZT on the correction of CTB binding was concentration independent, as expected from accumulation of an acidotropic agent and its intraorganellar trapping once it is protonated.