Oxidative stress in experimental rodent corneas infected with aflatoxigenic and nonaflatoxigenic Aspergillus flavus.

PURPOSE: To seek a possible association between aflatoxigenicity and oxidative stress in keratitis caused by Aspergillus flavus in an experimental rodent model.

METHODS

Wistar rats were divided into 3 groups of 6 each. Group 1 served as mock-inoculated controls. Experimental fungal keratitis was induced in group 2 and group 3 rats using aflatoxigenic and nonaflatoxigenic A. flavus conidial suspensions, respectively, and clinical features were scored for 5 days after inoculation. At this time, animals were killed, and test corneas were excised and examined histologically. Expression of IL-1β and TNF-α genes was sought in excised corneas. Levels of malondialdehyde (MDA) and reduced glutathione (GSH) and activities of key antioxidant enzymes were measured in excised corneas and fungal mycelial homogenates. Antioxidant enzyme isoforms were sought in mycelial homogenates by native polyacrylamide gel electrophoresis.

RESULTS

Mean levels of MDA and GSH and mean activities of catalase, superoxide dismutase, and glutathione peroxidase were significantly (P < 0.05) higher in a mycelial homogenate of aflatoxigenic A. flavus than in the nonaflatoxigenic mycelial homogenate. Increased numbers of well-stained isoforms were detected in aflatoxigenic mycelial homogenates. Significantly (P < 0.05) higher expression profiles of IL-1β and TNF-α genes, MDA and GSH levels, and antioxidant enzyme activities were noted in group 2 rat corneas than in group 3 rat corneas. Clinical and histological scores suggested a more severe keratitis in group 2 rat corneas than in group 1 and group 3 rat corneas.

CONCLUSIONS

Aflatoxigenicity is associated with more intense oxidative stress in experimental A. flavus keratitis.