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Human CYP1B1 enzyme-mediated, AhR enhanced activation of aflatoxin B1 for its genotoxicity in human cells

Aflatoxin B1 (AFB1) is a human procarcinogen known to be activated by cytochrome P450 (CYP) 1A2 and 3A4. In a previous study AFB1 caused chromosomal rearrangement in a yeast strain genetically engineered for stably expressing human CYP1B1. Yet, further verification of the effect of AFB1 in human cells, a potential role of the aryl hydrocarbon receptor (AhR), and CYP1B1-catalyzed AFB1 metabolism remain unidentified. In this study, a human hepatocyte (L-02) line and a human lymphoblastoid (TK6) cell line were genetically engineered for the expression of human CYP1B1, producing L-02-hCYP1B1 and TK6-hCYP1B1, respectively. They were exposed to AFB1 and analyzed for the formation of micronucleus and elevation of γ-H2AX (indicating double-strand DNA breaks); the metabolites formed by CYP1B1 from AFB1 after incubation of AFB1 with human CYP1B1 isoenzyme microsomes were determined by LC-MS. The results showed significantly more potent induction of micronucleus by AFB1 in L-02-hCYP1B1 and TK6-hCYP1B1 than in the parental (L-02 and TK6) cells, and the effects were reduced by (E)- 2,3',4,5'-tetramethoxystilbene, a specific CYP1B1 inhibitor. In the AFB1- CYP1B1 microsomes incubations AFM1, a known stable metabolite of AFB1, was detected. Moreover, in L-02 and TK6 cells, AFB1 apparently increased the protein levels of AhR, ANRT and CYP1B1, and caused the nuclear translocation of AhR and ARNT, the latter effect being blocked by BAY-218 (an inhibitor of AhR). In conclusion, this study indicates that human CYP1B1 is capable of metabolically activating AFB1 through the AhR signaling pathway.

 

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The provided information outlines a study investigating the effects of aflatoxin B1 (AFB1) in human cells, specifically focusing on the role of human cytochrome P450 (CYP) 1B1, the aryl hydrocarbon receptor (AhR) signaling pathway, and the metabolism of AFB1 by CYP1B1. Here's a breakdown of the key findings:

1. **Previous Study Background:**
   - AFB1 is a human procarcinogen known to be activated by cytochrome P450 (CYP) 1A2 and 3A4.
   - AFB1 caused chromosomal rearrangement in a yeast strain genetically engineered to express human CYP1B1.

2. **Objective of the Study:**
   - Further verification of the effect of AFB1 in human cells.
   - Investigation of the potential role of the aryl hydrocarbon receptor (AhR) in AFB1 effects.
   - Exploration of CYP1B1-catalyzed AFB1 metabolism.

3. **Experimental Setup:**
   - Human hepatocyte (L-02) and human lymphoblastoid (TK6) cell lines were genetically engineered to express human CYP1B1, creating L-02-hCYP1B1 and TK6-hCYP1B1.
   - Cells were exposed to AFB1.
   - Analysis included the formation of micronuclei and elevation of γ-H2AX (indicating double-strand DNA breaks).

4. **Results:**
   - L-02-hCYP1B1 and TK6-hCYP1B1 cells showed significantly more potent induction of micronuclei by AFB1 compared to parental cells.
   - Effects were reduced by (E)-2,3',4,5'-tetramethoxystilbene, a specific CYP1B1 inhibitor.

5. **Metabolism of AFB1 by CYP1B1:**
   - In AFB1-CYP1B1 microsome incubations, AFM1 (a known stable metabolite of AFB1) was detected.

6. **AhR Signaling Pathway:**
   - AFB1 increased the protein levels of AhR, ARNT, and CYP1B1 in L-02 and TK6 cells.
   - AFB1 caused the nuclear translocation of AhR and ARNT.
   - The nuclear translocation of ARNT was blocked by BAY-218, an inhibitor of AhR.

7. **Conclusion:**
   - The study suggests that human CYP1B1 is capable of metabolically activating AFB1 through the AhR signaling pathway.

In summary, the research provides insights into the molecular mechanisms underlying the genotoxic effects of AFB1 in human cells, highlighting the involvement of CYP1B1 and the AhR signaling pathway in the process. The findings contribute to our understanding of AFB1 metabolism and its potential implications in carcinogenesis.

Related Products

Cat.No. Product Name Information
S8842 BAY-218 BAY-218 is a potent and selective small-molecule AhR inhibitor, inhibiting AhR nuclear translocation, dioxin response element (DRE)-luciferase reporter expression and AhR-regulated target gene expression induced by both exogenous and endogenous AhR ligands.

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