| Benzene (BZ) is an occupational toxicant which widely used in paint, pesticide, synthetic rubber, dye and leather industry. BZ is also an indoor environmental toxicant which comes from furniture painting, wall painting and decoration materials. There were some reports that BZ indoor pollution led to nerve system and blood cells reproductive system damage in inhabitants. Recent studies showed that BZ indoor pollution led to cancer and reproductive toxicity which included leucocythemia,procreation disable,miscarry,malformation and nerve system reproductive disorder. An investigate results showed that over 80% children leucocythemia resulted from BZ indoor pollution by newly indoor decoration. The study on BZ genotoxcity is obviously significant especially for cellular,molecular levels and new technique studies which will promote understanding in BZ genotoxcity and mechanism.Objective The purpose of this study is to identify the situation of BZ indoor pollution by new indoor decoration and the effect of BZ and its metabolite, hydroquinone (HQ) on genotoxicity in inhabitants. These experimental results provided data for for BZ and HQ safety evaluation. Methods In the present study, benzene level in decorated 124 houses in Nanning city were detected by national standing methods and health survey was carried out for high benzene level houses and control houses in recent five years. Moreover, human lymphocytes were isolated and cultivated by general method, then, the cells were divided into five groups including negative control, solution control, and test substance (benzene or hydroquinone) low, middle, high groups by completely randomized method in vitro. After the treatment, Apoptosis was measured by annexin V/propidium iodide staining and flow cytometry. Lymphocyte DNA damage was detected by single cell gel electrophoresis technology (comet assay) and micronucleus assay. IR spectra of human lymphocytes were examined in spectral regions (900～1900 cm-1) corresponding to proteins, DNA, RNA, glycoproteins, carbohydrates, lipids, and levels of protein phosphorylation by ATR microspectroscope.Results1. Experimental research shows that approximately 2.4%, 10.5%, and 8.1 % of indoor environmental contamination samples exceeded the international indoor air quality standard for toluene, benzene and dimethylbenzene, respectively. Indoor benzene pollution demonstrated a trend of nerve system disease increase and resistance for pathogen decrease in habitants.2.In vitro experimental, compared with blank control group, the flow cytometer showed that the total percentage of the apoptotic cells to all cells was 60.73% in the low benzene group, 74.22% in the model benzene group, and 92.85% in the high benzene group; 2 h of treatment with hydroquinone(Low, Middle, High group) percentage of apoptotic cells was 54.36%,95.09%,97.65% respectively compared with blank control group (P<0.05 or P<0.01).3.In treatment groups of benzene and hydroquinone, apoptosis rate were raised with the concentration increase in four concentrations, the differences were significant (P<0.05 or P<0.01) compared with the control group. Compared with the solution control group, benzene groups'comet rate, comet tail length and micronucleus rate respectively increased 11.7～31.5 %, 78.3～118.2 % and 90.9～2527.3 %(all P < 0.05). Compared with the low hydroquinone group, middle and high hydroquinone groups'comet rate and comet tail lengt respectively increased 13.0～58.9% and 213.5～215.1% (all P < 0.01 ) . Compare with negtive control group, hydroquinone groups micronucleus rate increased 400～3076%(all P < 0.01).4. Benzene and hydroquinone groups'ATR liners were different with control'line in ATR microspectroscope figure,primarily in the DNA/RNA spectral region(≈1000～1490cm-1). Their line score plots showed different distribution in 3-D figure which deriverd from principal component analysis.Conclusions1. Both of benzene and hydroquinone could induce cell apoptosis of human lymphocytes. The chaos of the regulation of apoptosis contributed to cell proliferation and the development of tumors, which was one of important mechanisms in the forming of tumor.2. Human lymphocyte DNA fragmentation caused by High levels of Benzene and hydroquinone indicating that benzene is genotoxic. DNA breakage is the main marker of apoptosis,so as to further explain cell apoptosis could induce by Benzene and hydroquinone.3. Marked variations in the DNA/RNA spectral region (≈1000～1490cm-1) that correlate with alterations in cell-cycle distributions are apparent. ATR microspectroscope can be used to detect cellular early damage. Changes of characterization of molecular species in biological systems could induce by benzene and hydroquinone.4.The genotoxic effects of benzene on the lymphocytes can be primaly summarized as cellular damage due to benzene metabolites and oxidative stress, dysfunction of the machinery of cell cycle arrest for repairing damaged DNA, resulting in benzene toxicity. |
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