Aims/hypothesis: Osmotic and oxidative stress is associated with the progression and advancement of diabetic cataract. In the present study, we used a cDNA microarray method to analyse gene expression patterns in streptozotocin-induced diabetic rats and galactose-fed cataractous lenses. In addition, we investigated the regulation and interaction(s) of anti-oxidant protein 2 and lens epithelium-derived growth factor in these models.
Methods: To identify differential gene expression patterns, one group of Sprague-Dawley rats was made diabetic with streptozotocin and a second group was made galactosaemic. Total RNA was extracted from the lenses of both groups and their controls. Labelled cDNA was hybridised to Atlas Rat Arrays. Changes in gene expression level were analysed. Real-time PCR and western analysis were used to validate the microarray results.
Results: The expression of 31 genes was significantly modulated in hyperglycaemic lenses compared with galactosaemic lenses. Notably, transcript and protein levels of B-cell leukaemia/lymphoma protein 2 and nuclear factor-kappaB were significantly elevated in rat lenses at 4 weeks after injection of streptozotocin. At a later stage, mRNA and protein levels of TGF-beta were elevated. However, levels of mRNA for IGF-1, lens epithelium-derived growth factor and anti-oxidant protein 2 were diminished in streptozotocin-induced diabetic cataract.
Conclusions/interpretations: These results provide evidence that progression of sugar cataract involves oxidative- and TGF-beta-mediated signalling. These pathways may promote abnormal gene expression in the hyperglycaemic and galactosaemic states and thus may contribute to the symptoms associated with these conditions. Since oxidative stress seems to be a major event in cataract formation, supply of anti-oxidant may postpone the progression of such disorders.