Broccoli: a unique vegetable that protects mammalian hearts through the redox cycling of the thioredoxin superfamily

Epidemiological evidence indicates several health benefits of the consumption of broccoli, especially related to chemoprevention. Because broccoli contains high amounts of selenium and glucosinolates (particularly glucoraphanin and isothiocyanate sulforaphane), which can produce redox-regulated cardioprotective protein thioredoxin (Trx), it was reasoned that consumption of broccoli could be beneficial to the heart. To test this hypothesis, a group of rats were fed broccoli (slurry made with water) through gavaging; control animals were gavaged water only. After 30 days, the rats were sacrificed; isolated hearts perfused via working mode were made ischemic for 30 min followed by 2 h of reperfusion. The results demonstrated significant cardioprotection with broccoli as evidenced by improved postischemic ventricular function, reduced myocardial infarct size, and decreased cardiomyocyte apoptosis accompanied by reduced cytochrome c release and increased pro-caspase 3 activities. Ischemia/reperfusion reduced both RNA transcripts and protein levels of the thioredoxin superfamily including Trx1, Trx2, glutaredoxin Grx1, Grx2, and peroxiredoxin (Prdx), which were either restored or enhanced with broccoli. Broccoli enhanced the expression of Nrf2, a cytosolic suppressor of Keap1, suggesting a role of antioxidant response element (ARE) in the induction of Trx. Additionally, broccoli induced the expression of another cardioprotective protein, heme oxygenase (HO)-1, which could be transactivated during the activation of Trx. Examination of the survival signal revealed that broccoli caused the phosphorylation of Akt and the induction of Bcl2 in concert with the activation of redox-sensitive transcription factor NF kappa B and Src kinase, indicating a role of Akt, Bcl2, and cSrc in the generation of survival signal. Taken together, the results of the present study indicate that the consumption of broccoli triggers cardioprotection by generating a survival signal through the activation of several survival proteins and by redox cycling of thioredoxins.