EFFECT OF LANSOPRAZOLE ON RESPIRATION AND SOME ANTIOXIDANT ENZYMEES OF ORAL BACTERIA

Abstract

Benzimidazoles such as lansoprazole (LAN) or omeprazole (OM) are widely used asproton-pump inhibitors to control stomach hyperacidity and have been found also to haveantimicrobial actions against Helicobacter pylori and oral streptococci. We found that it actsalso to suppress respiration of oral streptococci and of Fusobacterium nucieatum, an org,nismassociated with development of gingivitis. LAN was a potent inhibitor of respiration of the oralstreptococci Streptococcus mutans GS-5 or UA 159 and S. sanguis NCTC 10904. 50%inhibitory concentrations for intact cells in suspensions were about 0.20 mM with nearlycomplete inhibition of O2 metabolism at higher LAN levels. 0.5 mM LAN inhibited O2 utilization by F. nucleatum ATCC 25586 by some 50%, but almost 50% of O2 metabolism bythe anaerobe was not LAN sensitive. NADH oxidase plays the major role on O2 utilization byoral streptococci and is also important for F. nucleatum. In cell extracts of S. mutans, the 50% inhibitory concentration (IC50) of LAN for NADH oxidase activity was ca. 0.1 mM. LAN wasinhibitory also for the protective enzyme SOD with IC50 of 0.1 mM. However, the enzymescatalase of Actenomyces naeslundii and pseudocatalase of Lactobacillus plantarum were notsensitive to LAN. Mechanism of action of LAN on oral bacteria seems to be complicated andneeds further work to understand fully the role of this antimicrobial agent on oxidativephysiology of oral bacteria.