Sulforaphane-induced transcription of thioredoxin reductase in lens: possible significance against cataract formation

Abstract

PurposeSulforaphane is a phytochemically derived organic isothiocyanate 1-isothiocyanato-4-methylsulfinyl-butane present naturally in crucifers, including broccoli and cauliflower. Biochemically, it has been reported to induce the transcription of several antioxidant enzymes. Since such enzymes have been implicated in preventing cataract formation triggered by the intraocular generation of oxy-radical species, the purpose of this investigation was to examine whether it could induce the formation of antioxidant enzymes in the eye lens. Thioredoxin reductase (TrxR) was used as the target of such induction.MethodsMice lenses were cultured for an overnight period of 17 hours in medium 199 fortified with 10% fetal calf serum. Incubation was conducted in the absence and presence of sulforaphane (5 μM). Subsequently, the lenses were homogenized in phosphate-buffered saline (PBS), followed by centrifugation. TrxR activity was determined in the supernatant by measuring the nicotinamide adenine dinucleotide phosphate (reduced) (NADPH)-dependent reduction of 5,5′-dithiobis-2-nitrobenzoic acid (DTNB). Non-specific reduction of DTNB was corrected for by conducting parallel determinations in the presence of aurothiomalate. The reduction of DTNB was followed spectrophotometrically at 410 nm.ResultsThe activity of TrxR in the lenses incubated with sulforaphane was found to be elevated to 18 times of that observed in lenses incubated without sulforaphane. It was also noticeably higher in the lenses incubated without sulforaphane than in the un-incubated fresh lenses. However, this increase was much lower than that observed for lenses incubated with sulforaphane.ConclusionSulforaphane has been found to enhance TrxR activity in the mouse lens in culture. In view of the protective effect of the antioxidant enzymes and certain nutrients against cataract formation, the findings suggest that it would, by virtue of its ability to enhance the activity of such enzymes, prevent the tissue against oxidative stress that leads to cataract formation. Additional studies with the activities of other antioxidant enzymes such as quinone oxidoreductase and the levels of Nrf2 are in progress.

Nrf2 as a target for prevention of age‐related and diabetic cataracts by against oxidative stress

“…Recently, SFN has been detected to increase the activity of TrxR in the mouse lens, and prevents the tissue against oxidative stress that contributes to cataract formation. Further researches on the behaviors of other antioxidant enzymes like quinone oxidoreductase are still in progress (Varma et al ., ). SFN was found to significantly inhibit the increased cytotoxicity/apoptosis induced by H 2 O 2 in the human lens epithelial cell line FHL124 (Liu et al ., ).…”

Mechanisms of activation of the transcription factor Nrf2 by redox stressors, nutrient cues, and energy status and the pathways through which it attenuates degenerative disease

“…Treatment of human K562 erythroleukemia cells with tBHQ and human K-1034 RPE cells with SFN has been reported to induce TXN [340, 341], and the increase in TXN protects mice against light-induced retinal damage [341]. Importantly, the increase in GSH and TXN upon activation of Nrf2 is associated with upregulation of reductases, GSR1, TXNRD1, and SRXN1 [35, 342, 343], which along with the increase in expression of enzymes involved in NADPH regeneration ensures these thiol-based antioxidant systems are kept reduced [61]. …”

A Glance at… Broccoli, glucoraphanin, and sulforaphane

“…Nrf2 activation and the indirect antioxidant effects of sulforaphane appear to be ubiquitous; they have been observed in the liver [30][31][32]41,59,60], kidney [60], lungs [60][61][62][63], lens [58], central nervous system [49,60], immune system [50], choroid plexus [51], small intestine [9], large intestine [60], prostate [60], retinal pigment epithelial cells [34,39,64], corneal epithelial cells [55], astroglial cells [54], fetal neural crest cells [52], neuroblastoma cells [36], insulin-secreting pancreatic cells [65], differentiated peripheral blood neutrophils [53], endothelial cells [40], osteoblasts [37], and keratinocytes [33][34][35].…”