Bucillamine induces glutathione biosynthesis via activation of the transcription factor Nrf2.
The properties of bucillamine, a synthetic antioxidant, have been attributed mainly to the donation of thiol groups to glutathione (GSH). We recently demonstrated that glutamate-cysteine ligase catalytic subunit (GCLC), the rate-limiting enzyme of GSH biosynthesis, and the multidrug-resistance-associated protein 2 (Mrp2/MRP2) are coordinately induced in response to xenobiotic through the activation of the antioxidant-response element (ARE) by nuclear factor-erythroid 2 p45-related factor (Nrf2). We tested the hypothesis that bucillamine and its oxidized metabolite SA 981 also activate the Nrf2 pathway, thereby increasing glutathione biosynthesis in human HepG2 and murine Hepa 1-6 hepatoma cell lines, through the induction of the GCLC enzyme as well as the Mrp2/MRP2 transporter, which mediates the excretion of glutathione and its conjugates from hepatocytes. Both bucillamine and SA 981 produced a significant dose-dependent increase in the mRNA levels of Mrp2/MRP2 and GCLC after 24 h. The levels of the transcription factor Nrf2 in the nuclei were maximal at 3 h, remained elevated at 6 h, and decreased to control values at 24 h in both cell lines. Moreover, both bucillamine and SA 981 significantly increased the expressions of Mrp2/MRP2 and GCLC proteins in both cell lines. Finally, in both cell lines, bucillamine and SA 981 increased the GSH content two- to three-fold. These results demonstrate that bucillamine and SA 981 activate the ARE-ARE pathway increasing the expression of ARE-driven genes such as those of GCLC and Mrp2/MRP2. The role of bucillamine as a chemopreventive agent against cancer remains to be elucidated.
Wielandt
Ana M
AM
Department of Gastroenterology, School of Medicine, Catholic University of Chile, Casilla ll4-D, Santiago, Chile.
Vollrath
Valeska
V
Farias
Marcelo
M
Chianale
Jose
J
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D020134:Catalytic Domain / Q000235:genetics; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D003545:Cysteine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics; D005721:Glutamate-Cysteine Ligase / Q000235:genetics / Q000378:metabolism; D005978:Glutathione / Q000096:biosynthesis*; D006801:Humans; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D015394:Molecular Structure; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism; D050984:NF-E2 Transcription Factor, p45 Subunit / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
D003545:Cysteine; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D050984:NF-E2 Transcription Factor, p45 Subunit; D012333:RNA, Messenger; C000715087:ABCC2 protein, human; C513116:bucillamine disulfide; C026535:bucillamine