Long-term Biological Effects In The Offspring Of Formaldehyde Induced ESTR Mutation Mice

With raised room decorating, indoor air pollution is increasing. Formaldehyde (FA) is one of major indoor air pollutants released from room decorating. The accumulated evidences have shown that FA is hard to be eliminated and therefore can be existed in indoor air for a long time. Kinds of expanded simple tandem repeats (ESTR) which consist of long arrays of 4- to 6-bp units have recently been discovered in mice genome. The ESTR is unstable in germlines and easy to be mutated as inserted or deleted fragments in genome which may further result in changes of gene (or gene cluster) copy numbers under environmental mutagen exposure.DNA copy number variations (CNVs) play an important role in many human diseases although they exist in healthy people. Comparative genomic hybridization (CGH) is an effective method to detect the gains or losses of genomic DNA copy number. Array-comparative genomic hybridization (aCGH) labels different fluorescein of different samples in one array and can be used to detect the variations of DNA copy number between the sample and the control genomes.Object: To investigate the susceptibility to carbon tetrachloride and benzene in offspring of formaldehyde (FA) induced expanded simple tandem repeats (ESTR) mutation mice, and to evaluate the genome stability of F10 offspring of after formaldehyde exposure.Methods: Both F5 and F10 offspring of formaldehyde exposure (200 mg/m3?2 hours) induced ESTR mutation (group H) and control ICR mice (group C) were used for the models. The F5 and F10 offspring were exposed to carbon tetrachloride (CCl₄) at 10 ml/kg, (0.05%, 0.5% or 5% for 24 hours, respectively) or benzene (500 or 1000 mg/kg for 24 hours, respectively) by intraperitoneal injection. Serum alanine transaminase (ALT), aspartate transaminase (AST), superoxide dismutase (SOD), malondialdehyde (MDA) of liver homogenates were determined as the biomarkers of liver injury or lipid peroxidation, respectively; liver pathological changes were also observed under light microscope; the micronucleus in sternum bone marrow cells were as the biomarker of benzene blood toxicity. In addition, the genome DNA samples extracted from F10 mice in both H and C groups for the aCGH analysis. Furthermore, the realtime qRT-RCR was used to verify gene expression changes in those gained or lost target genome fragments in aCGH analyshis.Results: Our recent studies have shown that exposure to mixed indoor air pollutants in a newly decorated residential apartment could induce significant increase of ESTR mutations in mice and the mutations were mainly inherited from the paternal germline. Our current results showed that, with increasing doses of CCl₄ exposure, serum ALT and AST activities gradually increased, the activity of SOD in liver homogenates was significantly reduced, however, MDA content was obviously increased, and the both showed a dose-dependent manner in F5 and F10 mice. However, the F5 offspring in H group are more sensitive to CCl₄ than control mice; incontrast, the F10 mice in H group are less sensitive to CCl₄ than control mice. In benzene exposure model, both H anc C groups of mice showed a significant dose-depedent increasing in bone marrow micronucleus formation in erythrocytes. Interestingly, F10 offspring of both H and C group mice showed more sensitive to benzene than F5 offspring.The aCGH results showed a gain of 655 genes in both F10 female and male mice, and a loss of 931 genes in total. Further analysis indicated that female mouse gains 329 genes and male mouse gains 431 genes, respectively; and 105 genes were obtained in both female and male mice. Similarly, female mouse losses 638 genes, male mouse losses 847 genes,respectively; and 504 genes were lost in both female and male mice. Futher bioinformatic and Q-RT-PCR verifying data showed that the most obtained or lost genes or clusters in both female and male mice were mainly involved in metabolism signal pathways, especially referred to the UDP glucuronosyltransferase I family genes.In conclusion, in the present study, we investigated the effects of CCl₄ and benzene exposure on the susceptibility of the F5 and F10 offspring mice with genome ESTR mutation after FA exposure. Our results indicated that CCl₄ and benzene exposure produced significant lipid peroxidation, severed injury in hepatocytes and increased micronucleus formation in polychromatic erythrocytes, respectively;these effects showed significant dose-dependent relationships in both ESTR mutation and control mice. Interestingly, the ESTR mutation offspring showed more susceptible to exposure of CCl₄ in F5 than control mice, however less susceptible to CCl₄ in F10 than control mice. The formaldehyde induced ESTR mutation in mice may result in persisitant changed genomic stability, and therefore altered the responses to CCl₄ and benzene exposure. The behind molecular basis may refer to complicated signal networks due to gain or loss the relative genome fragments.