Objective To observe the inhibitory effect of doxycycline (Doxy) on oxidative stress injury after corneal alkali burn in rats.

Methods A total of 204 healthy SD rats were randomly divided into normal group, model group and Doxy group, with 68 rats in each group. The rats in the normal group received no treatment, and the corneal alkali burn model of the left eye was established in the rats of the model group and the Doxy group. After successful modeling, no treatment was given to the rats in the normal group, the rats in the Doxy group were given 5.0 g/L Doxy eye drops, and those in the model group were given menstruum eye drops. Corneal inflammation index, neovascular area and corneal turbidity score were observed and calculated on day 3, day 7, day 14 and day 21 after alkali burn, respectively. Pathological sections were taken after corneal sampling, and pathological changes of corneal tissue were observed after hematoxylin-eosin (HE) staining. The contents of reactive oxygen species (ROS), malondialdehyde (MDA) and 8-hydroxydeoxyguanosine (8-OHdG) in corneal tissue were detected by chemical fluorescence, thiobarbituric acid (TBA) and enzymolinked immunosorbent assay (ELISA).

Results On day 3, day 7, day 14 and day 21 after alkali burn, corneal inflammation index and neovascular area and corneal turbidity score in the Doxy group were significantly lower than those in the model group, and all the differences were statistically significant (all P < 0.05). On day 3, day 7, day 14 and day 21 after alkali burn, the degree of corneal edema, inflammatory cell infiltration and the number of neovasculation in the Doxy group were significantly lower than those in the model group, and the arrangement of collagen fibers was more orderly. On day 3, day 7 and day 14 after alkali burn, the contents of ROS, MDA and 8-OHdG in the Doxy group were significantly lower than those in the model group, but higher than those in the normal group, and the differences were all statistically significant (all P < 0.05). On day 21 after alkali burn, the contents of ROS, MDA and 8-OHdG in the Doxy group were significantly lower than those in the model group. Among them, the ROS content was higher than that in the normal group, and all the differences were statistically significant (all P < 0.05). There were no significant differences in MDA and 8-OHdG contents between the Doxy group and the normal group (all P > 0.05).

Conclusion Doxy can effectively inhibit oxidative stress injury after corneal alkali burn in rats, and may be related to inhibiting corneal inflammation and the formation of neovascularization.