Display Settings:

Format

Send to:

Choose Destination
We are sorry, but NCBI web applications do not support your browser and may not function properly. More information
Free Radic Biol Med. 2004 Nov 15;37(10):1578-90.

Induction of detoxifying enzymes by garlic organosulfur compounds through transcription factor Nrf2: effect of chemical structure and stress signals.

Author information

  • 1Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, 160 Frelinghuysen Road, Piscataway, NJ 08854, USA.

Abstract

Garlic organosulfur compounds (OSCs) are recognized as a group of potential chemopreventive compounds. It is known that garlic OSCs can modulate drug metabolism systems, especially various phase II detoxifying enzymes, though the mechanism underlying their inductive effect on these enzymes remains largely unknown. In the present study, we investigated the transcriptional levels of NAD(P)H:quinone oxidoreductase 1 (NQO1) and heme oxygenase 1 (HO1) genes, the reporter activity mediated by antioxidant response element (ARE), and the protein level of transcription factor nuclear factor E2-related factor 2 (Nrf2), after administration of three major garlic OSCs--diallyl sulfide (DAS), diallyl disulfide (DADS), and diallyl trisulfide (DATS)--in human hepatoma HepG2 cells. Our results showed that ARE activation and Nrf2 protein accumulation were well correlated with phase II gene expression induction. The structure-activity relationship study indicated that the third sulfur in the structure of OSCs contributed substantially to their bioactivities, and that allyl-containing OSCs were more potent than propyl-containing OSCs. To better understand the signaling events involved in the upregulation of detoxifying enzymes by DATS, ARE activity and Nrf2 protein levels were examined after transient transfection of HepG2 cells with mutant Nrf2, cotreatment with antioxidants, and pretreatment with protein kinase inhibitors. DATS-induced ARE activity was inhibited by dominant-negative Nrf2 Kelch-like ECH-associating protein 1 and constructs. Cotreatment with thiol antioxidants decreased the ARE activity and Nrf2 protein level induced by DATS. Three major mitogen-activated protein kinases (MAPKs)--extracellular signal-regulated protein kinase, c-Jun N-terminal kinase, and p38--were activated by DATS treatment. However, the inhibition of these MAPKs did not affect DATS-induced ARE activity. Pretreatment with various upstream protein kinase inhibitors showed that the protein kinase C pathway was not directly involved in DATS-induced ARE activity, but instead the calcium-dependent signaling pathway appeared to play a role in the DATS-induced cytoprotective effect.

PMID:
15477009
[PubMed - indexed for MEDLINE]
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Elsevier Science
    Loading ...
    Write to the Help Desk