p38 MAPK plays a distinct role in sulforaphane-induced up-regulation of ARE-dependent enzymes and down-regulation of COX-2 in human bladder cancer cells

Abstract

Sulforaphane, a well-characterised dietary isothiocyanate, has been demonstrated to be a potent anti-carcinogenic agent in numerous cancer models, including in bladder cancer cells. In the present study, sulforaphane upregulated the expression of two Nrf2-dependent enzymes, glutathione transferase (GSTA1-1) and thioredoxin reductase (TR-1), and down-regulated cyclooxygenase 2 (COX-2) in human bladder cancer T24 cells. This action of sulforaphane was associated with the p38 MAPK activity. When a specific p38 MAPK inhibitor, SB202190, was used, both sulforaphaneinduced up-regulation of GSTA1-1 and TR-1 and downregulation of COX-2 were eliminated; in contrast, an activator of p38 MAPK, anisomycin, enhanced the effect of sulforaphane on modulation of GST, TR-1 and COX-2 expression. Moreover, it was established that anisomycin increased nuclear translocation of Nrf2, whereas SB202190 abrogated sulforaphane-induced Nrf2 translocation into the nucleus. In summary, these data suggest that p38 MAPK activation can regulate Nrf2-antioxidant response element (ARE)-driven enzymes and COX-2 expression, thereby facilitating the role of sulforaphane in cancer prevention. This study strongly supports the contention that p38 MAPK is a pivotal and efficient target of sulforaphane in the chemoprevention of bladder cancer.