The Study On Apoptosis And Genes Different Expression Of Rat's Cultured Bone Marrow Cells Induced By Benzene In Vitro

Benzene, a heavily used industrial chemical, is ubiquitous in the environment. Exposure to benzene may result in progressive degeneration of the bone marrow, aplastic anaemia, and leukemia.The mechanism of benzene-haematotoxicity is not known completely. However, it is commonly accepted as follows: (1) Although benzene is metabolized in the liver primarily, benzene metabolites subsequently undergo secondary activation by myeloperoxidase (MPO) that is present at high levels in the bone marrow tissue, which interfere with hemaopoiesis and exacerbate benzene toxicity. The liver S9 microsomal activation system is concerned as one of the key enzyme of benzene metabolism. (2) Benzene toxicity is due to multi-factor and multi-level synthetic effects. In this paper, the direct effect of bone marrow cells (BMCs) induced by benzene was detected on the purpose of getting more information about the mechanism of benzene cytotoxicity.The study is follows:The effect on apoptosis of BMCs induced by benzene in vitro: in the presence of 10% S9mix(group 3), different-dose of benzene((K 3.75, 7.5. 11.25. 15. 18.75mM) induced apoptosis rate of BMCs was 5.19%. 16.58%. 19.82%. 19.98%. 20.96%. 24.78%, respectively. While in the absence of S9 mix (group 2) and with same dose of benzene ,the apoptosis rate of that was 5.19%.9.17%. 14.61 %. 15.38%. 16.52%.22.88%, respectively, the apoptosis inductions of two groups were dose-dependent up to 18.75mM(groupII: rs =0.939, P<0.01; group 3 rs=0.876, P<0.01).SimultaneousIy, The comparisons showed significant difference between group II and 3 except 0 and 18.75mM benzene.During time-response studies, the inductions weren't time-dependent up to 5hr (rs =0.214, P>0.05) in control group (group 1), while time-dependent correlations were present in both group II and group III (group II: rs =0.969, P< 0.01; group ffl: r,=0.851, />0.01). The comparisons showed significant difference between group II,ffl andgroup I , which suggest that benzene can induce apoptosis of BMCs without S9 directly, and benzene-induced bone marrow depression maybe cause cells transformation.The screening to specific genes correlated to benzene toxicity: In vitro, BMCs were cultured for 3h with benzene(11.25mM), and the differently expressed genes were detected by GeneChip array. The results reveal that a number of genes expression show increase or decrease after exposure to benzene, to which sress-responsed and detoxicative proteins DNA synthesis and plerosis genes some important genes connected with cell cycle and signal transduction-kinase-phosphatase are concerned. In these differently expressed genes, some genes such as glutathione S-transferase (GST) and NAD(P)H: Quinone Oxidoreductase-l(NQOl) mediating benzene metabolism . tissue inhibitor of metalloproteinase-l(TIMP-l) ras inhibitor heat shock protein 60 and so on emerged decrease expression, while other genes such as cyclin BK protein tyrosine phosphatase (receptor type) met proto-oncogene MX protein showed increase expression.In conclusion, our experiment suggest: l)benzene could induce BMCs apoptosis in vitro; and inductions are dose-response and time-response;S9 microsomal enzymes maybe enhance benzene toxicity. 2)benzene could alter multigene expression. Thereby the results could provide an important point to study mechanism of benzene toxicity.