Inhibition of cytochromes P-450 and induction of glutathione S-transferases by sulforaphane in primary human and rat hepatocytes.
Level 5 - mechanism / opinion, no new human data
In vitro bench study in primary cell cultures
What was done
Researchers investigated the effects of the dietary isothiocyanate sulforaphane on Phase I (cytochrome P-450) and Phase II (glutathione S-transferase) carcinogen-metabolizing enzymes in primary cell cultures of rat and human hepatocytes. Enzyme mRNA expression was evaluated by Northern blot, and catalytic activities were measured, including ethoxyresorufin-O-deethylase (CYP1A1) and pentoxyresorufin-O-dealkylase (CYP2B1/2) in rat hepatocytes, as well as CYP3A4 in human hepatocytes.
What was found
The abstract reports directional findings without numerical values: - Rat hepatocytes: Dose-dependent induction of mRNAs for GSTA1/A2 and P1 (not M1), increased levels of GSTA1, A2, A4, A5, P1, M1, and M2, and dose-dependent reductions in CYP1A1 and CYP2B1/2 activities. - Human hepatocytes: Induction of GSTA1/2 mRNA (not GSTM1), no effect on CYP1A2 expression, and a marked decrease in CYP3A4 expression at both the mRNA and catalytic activity levels.
Why it matters
This study provides cellular mechanistic evidence that sulforaphane simultaneously activates Phase II detoxification enzymes while suppressing select Phase I bioactivating enzymes, notably human CYP3A4.
Limits
The study is restricted to in vitro primary hepatocyte cultures and does not assess in vivo pharmacokinetics, effective tissue concentrations, or clinical outcomes. The abstract omits sample sizes (number of human/rat liver donors), tested concentration ranges, and quantitative effect sizes.
Cited by
- supports Sulforaphane deactivates phase I biotransformation enzymes that convert procarcinogens into active carcinogens, such as heterocyclic amines from charred meat.