The Effect Of Benzo(a)pyrene On The Myelotoxicity Induced By Benzene

Benzene(BZ) is a ubiquitous industrial poison and envirnmental pollutant, which can induce hemopoietic toxicity of bone marrow, severely leukemia, by long-time exposure. However, to date, the mechanism of the toxicity is not fully understood, it's supposed by most scientists that the metabolism of benzene by the hepatic CYP2E1 is prerequisite for its bone marrow toxicity. But it was reported that the apoptosis and damage on DNA of bone marrow cells cultured in vitro by benzene exposure not its' metabolisms; and there is no hematotoxicity and myelotoxicity was induced in AHR knockout (AHR^-/-) mice after following inhalation benzene(a potent dose for leukemogenicity) while occurred in AHR wild-type(AHR^+/+) mice. Previously, aromatic hydrocarbon receptor (AHR ) was thought induce CYP1A1 gene expression but not CYP2E1. So the study focused on the role of the receptor mediated and metabolic enzymes on benzene in bone marrow metabolic pathways is important to understand the mechanisms of benzene toxicity.This paper chose benzo(a)pyrene(BP) as the agonist of AHR to activate AHR, elucidated the change and its molecular mechanism of myelotoxicity induced by benzene under the activated AHR. There are three part: â‘ Using orthogonal design table L₁₈(3³), arrange three factors of BZ, BP, time, which has three levels respectively (0, 5, 10mM; 0, 5, 10μM; 2, 4, 6h), exposure to the bone marrow cells(BMSc) which is cultured in vitro and test the rate of apoptosis by flowcytometry (FCM), results demonstrated that percentage of apoptotic BMCs depended on the BZ concentration and time of BZ treatment and there is no interaction between BZ and BP but when BZ is 10mM and BP is 10 μ M combined to treat BMCs, the percentage of apoptosis is the most high and is 12.3%.â‘¡performing verification experiment by Comet Assay(CA) testing DNA damage and FCM detecting the rate of apoptosis to clear activated AHRcan enhance benzene induced myetoxicity or not. The result manifest BP+BZ group had no significant enhance the apoptotic rate, comet tail length and percentage of tail cells contrasting to the BP alone group (P>0.05). ?Simultaneously, using semiquantitative RT-PCR measure relative levels of AHR, CYP1A1,CYP2E1,NQO1 target mRNAs (which were normalized to the internal control) of each groups and find BP+BZ group significant up-regulation of CYP1A1 and NQOl mRNA contrasting to other groups(P<0.05) but AHR,CYP2E1 were undetectable by RT-PCR in all groups.In this study, BP did not increase the benzene-induced myleotoxicity; BP can induce CYPl Al and NQOl gene expression by activating AHR; but activated AHR did not enhance the benzene induce myleotoxicity, which may be attributed to the activated AHR mediate not only the cytochrome oxidase enzymes but also the quinone reductase in the metabolic process of benzene.