[Effects of hexabromocyclododecanes on retinoid X receptor α, pregnane X receptor and peroxisome proliferator-activated receptor γ].

Objective: To investigate the effect of hexabromocyclododecanes( HBCDs) on cell proliferation and the expression of the three important cell nuclear receptor of retinoic X receptor α( RXRα), peroxisome proliferator-activated receptor-γ( PPARγ), pregnane X receptor( PXR) and their interaction in Neuro-2a(N2a).

Methods: Neuro-2a cells were treated with different concentrations of diastereoisomers, of HBCDs which were α-HBCD, β-HBCD, γ-HBCD, respectively, and cell toxicity was analyzed using the cell counting kit-8( CCK-8) assay. The impact of HBCDs on cell cycles of Neuro-2a were analyzed by flow cytometry analysis, and the expression levels in mRNA and protein for the three nuclearreceptors( RXRα, PPARγ, PXR andits target genes CYP3A11) were determined by RT-PCR and Western blot, respectively. The interaction between the receptors of RXRα, PXR, PPARγ was explored by immunoprecipitation.

Results: Cytotoxicity of β-HBCD was the greatest among the three diastereoisomers, it was significantly greater than α-HBCD, however cytotoxicity of γ-HBCD for the Neuro-2a cells couldn 't be determined. Moreover α-HBCD, β-HBCD induced significant cytotoxicity in a time-dose-response relationship to Neuro-2a cells( P < 0. 05), IC_(50) of α-HBCD, β-HBCD to Neuro-2a cells were 60. 07 and 10. 52 μmol/L, respectively. α-, β-HBCD blocked the cell cycle at G2/M phase. The expression levels in mRNA and protein of RXRα, PPARγ, PXR, CYP3A11 were significantly increased after cells exposure to α-HBCD and β-HBCD 24 h. An interaction between RXRα, PPARγ and PXR in Neuro-2a cells existed no matter before and after exposure to HBCD.

Conclusion: α-HBCD, β-HBCD inhibit proliferation of Neuro-2a cells, cell cycle mainly was arrested at G2/M phase. α-HBCD, β-HBCD could up-regulated the expression levels of RXRα, PPARγ, PXR. Meanwhile, the expression of CYP3A11 which is downstream gene of PXR also significantly increased( P < 0. 05). Interaction between RXRα, PPARγ and PXR exist whether or not exposure to α-, β-HBCD. The molecular mechanisms of interaction between the receptors need further study.