Role of innate immunity and oxidative stress in steroid-induced cataracts in developing chick embryos

The exact etiopathogenesis of steroid-induced cataracts (SIC) is not known. Although oxidative stress is one of the most acceptable hypotheses, the exact molecular events in steroid-induced oxidative events in the lens need to be clarified. In addition, to the best of our knowledge, the innate immune system components in SIC formation have not been studied previously. The aim of the present study was to study the oxidative system and the innate immune system components in the cataractous lenses of a developing chick embryo SIC model.

The study included 20 specific pathogen-free (SPF) fertilized eggs divided into two groups, with one hydrocortisone (HC)-treated group (G1) and one non-HC-treated control group (G2). On the 15th day of incubation, the SPF eggs in the two groups were removed from the incubator; HC was injected into G1, and phosphate-buffered saline (PBS) was injected into G2 using insulin injectors into the chorioallantoic membrane. On day 17, all of the chick embryos were removed from the eggs, and all lens and liver tissues were dissected from the embryos. Cataract formation was evaluated in all lenses, and total antioxidant status (TAS), total oxidant status (TOS), reduced glutathione (GSH), oxidized glutathione (GSSG), interleukin-6 (IL-6), and interleukin-1β (IL-1β) levels were measured in all lens and liver tissues.

The lenses in the SIC group had lower levels of GSH, GSSG, TAS, and IL-6 (p = 0.016, 0.022, 0.000, 0.000, respectively), and higher levels of TOS (p = 0.000) than the control group. Furthermore, the liver tissues in the SIC group had decreased levels of TAS and IL-6, and increased levels of TOS compared to the control tissues (p = 0.000). Although the IL-1β levels in the lens and liver tissues in the HC-induced cataract group were lower than in the control group, these differences were not statistically significant. In addition, the GSH levels in the liver tissues did not statistically differ between the two groups despite the significant GSH difference in the lens tissues.

Steroid therapy causes a decrease in GSH, GSSG, and TAS levels and an increase in TOS levels in lens tissues, which means there is increased oxidative stress and decreased antioxidant defence. Furthermore, lenses with SIC have lower IL-6 levels compared to non-cataractous lenses. The interaction between lenticular IL-6 and antioxidant defence needs to be further studied.