Purpose:
Previous studies have demonstrated that caffeine is a highly effective scavenger of various reactive oxygen species (ROS) known to be involved in cataract formation. We have previously shown that it inhibits oxidative damage and apoptosis in the lens in vitro. The objective of the present investigations was to examine the possibility of its effectiveness against apoptotic cell death and cataract formation in vivo using the galactose cataract model, by its topical administration.
Methods:
Rats maintained on a 24% galactose diet were treated either with 20 µl of an aqueous eye drop (ED) preparation containing 1.4 µmoles caffeine or with the placebo ED, 5 times/day for 25 days. The ED contained 0.9% hydroxypropyl methyl cellulose as a wetting agent and 0.001% benzalkonium chloride as an antiseptic. Cataract development was followed ophthalmoscopically, and recorded photographically after its isolation. Biochemical assessment was done by determining GSH levels. Morphology was studied by H&E histology. Apoptotic cells were detected by TUNEL staining. DAPI staining was done for nuclear localization.
Results:
Cataract formation was significantly thwarted by caffeine ED. At the end of the experiments, the relative opacity index of the lenses of the galactosemic animals treated with placebo was ~140 X of the normal vs. only 10X in the caffeine treated group. The protective effect was also evident by the maintenance of tissue morphology. Significant numbers of cells in the lenses of galactosemic animals were apoptotic as noted by fluorescence with TUNEL, migrating aberrantly towards the nucleus. These effects were also prevented by caffeine.
Conclusions:
Micromolar amounts of topical caffeine have been found to be significantly effective in inhibiting the formation of galactose cataract, strongly suggesting its possible usefulness against diabetic cataracts. The effects are attributed to its ability to prevent oxidative stress and consequent maintenance of tissue metabolic and transport functions, in addition to preventing the induction of apoptosis.
Keywords: antioxidants • cataract • apoptosis/cell death