Inhibition of Acanthamoeba polyphaga by chlorhexidine-mediated oxidative stress response.

OBJECTIVES: Acanthamoeba keratitis is a severe corneal infection caused by a ubiquitous opportunistic protozoan pathogen known as acanthamoeba. For the last decade, the approach to treating this infection typically includes the use of polyhexamethylene biguanide (0.02%) and/or chlorhexidine (Chx) (0.02%). Although chlorhexidine is reportedly effective, its mode of action towards this type of cell is not clear. The aim of this work was to study the effect of chlorhexidine on the oxidative status of Acanthamoeba polyphaga.

METHODS: The effect of chlorhexidine (Chx) on the oxidative state of Acanthamoeba polyphaga was studied using different antiradical methods including ABTS, DPPH and FRAP and measuring the activity of a couple of antioxidant enzyme namely SOD, NADH-FRD and SDH.

RESULTS: The chlorhexidine was able to induce oxidative imbalance in cells by over expression of reactive oxygen species and/or inhibiting the antioxidant enzymes. In addition to enhancing the antiradical activity in response to oxidative stress, the present drug was able to reduce the activity of two antioxidant enzymes, superoxide dismutase (SOD) and reduced flavin adenine dinucleotide-fumarate reductase (NADH-FRD), to 30% and 40%, respectively.

CONCLUSIONS: We could observe an increase of the antiradical capacity of cell's lysate supernatant, to cope with the overproduction of ROS. The imbalance state The inhibition of both SOD and NADH-FRD activities could have a major role in cell oxidative imbalance.