Differential hepatic GSTA 2 expression of arylalkyl isothiocyanates in vivo and in vitro: The molecular mechanism of gene induction by phenethyl isothiocyanate

Scope Naturally occurring isothiocyanates ( ITC s) have been investigated for their chemopreventive actions. However, limited studies have determined the potential for regulation of hepatic glutathione S ‐transferase A 2 ( GSTA 2) by arylalkyl or alkyl ITC s. Methods and results The present study was designed to investigate the effects of ITC s on GSTA 2 expression and upstream signaling analyzed by N orthern blotting, RT‐PCR , immunoblotting, and promoter‐luciferase assay. A single dose of ethyl isothiocyanate and phenethyl isothiocyanate ( PEITC ) enhanced GSTA 2 m RNA levels in rats. The three consecutive injections of arylalkyl ITC s resulted in the gene induction. PEITC was the most potent and sustained inducer of GSTA 2 in vivo. PEITC induced GSTA 2 m RNA and protein expression in H 4 IIE cells. PEITC increased the levels of nuclear factor erythroid 2 related factor 2 and CCAAT /enhancer binding protein β ( C/EBP β). The cells transfected with a p GL ‐Δ ARE or p GL ‐Δ C/EBP ‐deleted promoter construct failed to increase GSTA 2 promoter activity by PEITC . These effects of PEITC were downstream of multiple cellular signaling, including phosphoinositide 3‐kinase (PI3K), c‐jun N‐terminal kinase (JNK), and/or protein kinase A (PKA). Conclusion These results demonstrated that PEITC is the most efficacious of the arylalkyl ITC s for the induction of GSTA 2 in vivo and in vitro, and that transactivation of C/EBP and nuclear factor erythroid 2 related factor 2 downstream of multiple signaling pathways is involved in this induction.