Comparison of the efficacy of a Tabernaemontana divaricata extract and of biosynthesized silver nanoparticles in preventing cataract formation in an in-vivo system of selenite-induced cataractogenesis

The putative anticataractogenic efficacy of silver nanoparticles (AgNPs), biosynthesized with a Tabernaemontana divaricata (T. divaricata) extract, was evaluated in-vivo in four groups of Wistar rat pups: Group I (normal [control]); Group II (selenite-challenged [19 mu mol/kg body weight], untreated); Group III (selenite-challenged, T. divaricata extract-treated [350 mg/kg body weight]); and Group IV (selenite-challenged, biosynthesized AgNPs-treated [200 mg/kg body weight]). Mean levels/activities of lenticular reduced glutathione (GSH), malondialdehyde (MDA), calcium, Ca2+ and Na+/K+-ATPase and total calpain were measured. The expression pattern of genes at mRNA transcript (by reverse transcription-PCR) and protein (by immunoblot analysis) levels for Ca2+ transporters, calpain isoforms and lenticular proteins (alpha A- and beta B1-crystallins, and vimentin) were evaluated. In extract-treated and AgNPs-treated rats, relatively higher mean lenticular levels/activities of GSH, Ca2+ and Na+/K+-ATPase, total calpain, and higher mRNA transcript and protein levels of calpain isoforms and lenticular proteins were observed. However, relatively lower mean lenticular levels of MDA, calcium and also mRNA transcript and protein levels of plasma membrane Ca2+-ATPase-1 (PMCA-1) and sarco/endoplasmic reticulum Ca2+-ATPase-2 (SERCA-2) were recorded. The prevention of such lenticular alterations was more pronounced in AgNPs-treated rats than in plain extract-treated rats. These observations suggest that AgNPs biosynthesized with T. divaricata extract have the potential to prevent selenite-induced cataractogenesis in-vivo by maintaining normal lenticular calcium homeostasis and calpain cascade activities and by preventing alterations in key lenticular proteins.