Dietary green tea extract increases phase 2 enzyme activities in protecting against myocardial ischemia-reperfusion

Abstract 

Green tea catechins are dietary antioxidant compounds that have been shown to protect against myocardial ischemia-reperfusion (IR) injury. Considering reports that catechins can induce phase 2 enzymes in cultured cells and some organs, we hypothesized that part of the protection to heart against IR injury may involve elevation of phase 2 enzyme activities. Rats were fed for 10 days with either control diet (sham and control groups) or the diet mixed with 0.25% green tea extract. At the end of 10 days, hearts were excised and subjected to global ischemia for 20 min followed by reperfusion for 2 hours. The hearts were compared for indices of cell death, oxidative stress, and phase 2 enzyme activities. Hearts from the green tea group had a 65% to 85% decrease in markers of apoptosis, a tendency to higher total glutathione, and higher activities of the phase 2 enzymes glutamate cysteine ligase and quinone reductase. The results support a possible involvement of phase 2 enzymes in the protection by green tea catechins against myocardial IR injury.

Abbreviations: DCIP, 2,6-dichloroindophenol, GCL, glutamate cysteine ligase, GSH, reduced glutathione, GSSG, oxidized glutathione, IR, ischemia-reperfusion, LDH, lactate dehydrogenase, PMSF, phenylmethylsulfonyl fluoride, QR, quinone reductase, TBARS, thiobarbituric acid reactive substances

Keywords: Cell death, Glutamate cysteine ligase, Green tea, Heart, Ischemia-reperfusion, Phase 2 enzymes, Quinone reductase, Rat