Weak power frequency magnetic field acting similarly to EGF stimulation, induces acute activations of the EGFR sensitive actin cytoskeleton motility in human amniotic cells.

In this article, we have examined the motility-related effects of weak power frequency magnetic fields (MFs) on the epidermal growth factor receptor (EGFR)-sensitive motility mechanism, including the F-actin cytoskeleton, growth of invasive protrusions and the levels of signal molecules in human amniotic epithelial (FL) cells. Without extracellular EGF stimulation, the field stimulated a large growth of new protrusions, especially filopodia and lamellipodia, an increased population of vinculin-associated focal adhesions. And, an obvious reduction of stress fiber content in cell centers was found, corresponding to larger cell surface areas and decreased efficiency of actin assembly of FL cells in vitro, which was associated with a decrease in overall F-actin content and special distributions. These effects were also associated with changes in protein content or distribution patterns of the EGFR downstream motility-related signaling molecules. All of these effects are similar to those following epidermal growth factor (EGF) stimulation of the cells and are time dependent. These results suggest that power frequency MF exposure acutely affects the migration/motility-related actin cytoskeleton reorganization that is regulated by the EGFR-cytoskeleton signaling pathway. Therefore, upon the MF exposure, cells are likely altered to be ready to transfer into a state of migration in response to the stimuli.

Optimizing imaging quality and radiation dose by the age-dependent setting of tube voltage in pediatric chest digital radiography.

OBJECTIVE: The quality and radiation dose of different tube voltage sets for chest digital radiography (DR) were compared in a series of pediatric age groups. MATERIALS AND METHODS: Forty-five hundred children aged 0-14 years (yr) were randomly divided into four groups according to the tube voltage protocols for chest DR: lower kilovoltage potential (kVp) (A), intermediate kVp (B), and higher kVp (C) groups, and the fixed high kVp group (controls). The results were analyzed among five different age groups (0-1 yr, 1-3 yr, 3-7 yr, 7-11 yr and 11-14 yr). The dose area product (DAP) and visual grading analysis score (VGAS) were determined and compared by using one-way analysis of variance. RESULTS: The mean DAP of protocol C was significantly lower as compared with protocols A, B and controls (p < 0.05). DAP was higher in protocol A than the controls (p <0.001), but it was not statistically significantly different between B and the controls (p = 0.976). Mean VGAS was lower in the controls than all three protocols (p < 0.001 for all). Mean VGAS did not differ between protocols A and B (p = 0.334), but was lower in protocol C than A (p = 0.008) and B (p = 0.049). CONCLUSION: Protocol C (higher kVp) may help optimize the trade-off between radiation dose and image quality, and it may be acceptable for use in a pediatric age group from these results.

[Effects of 50 Hz magnetic fields on DNA double-strand breaks in human lens epithelial cells].

OBJECTIVE: To investigate the effects of 50 Hz magnetic fields (MF) on DNA double-strand breaks in human lens epithelial cells (hLECs). METHODS: The cultured human lens epithelial cells were exposed to 0.4 mT 50 Hz MF for 2 h, 6 h, 12 h, 24 h and 48 h. Cells exposed to 4-nitroquinoline-1-oxide, a DNA damage agent, at a final concentration of 0.1 micromol/L for 1 h were used as positive controls.After exposure, cells were fixed with 4 % paraformaldehyde and for H2AX (gamma H2AX) immunofluorescence measurement. gamma H2AX foci were detected at least 200 cells for each sample. Cells were classified as positive when more than three foci per cell were observed. Mean values of foci per cell and percentage of foci positive cells were adopted as indexes of DNA double-strand breaks. RESULT: The mean value of foci per cell and the percentage of gamma H2AX foci positive cells in 50 Hz MF exposure group for 24 h were (2.93 +/-0.43) and (27.88 +/-2.59)%, respectively, which were significantly higher than those of sham-exposure group [(1.77 +/-0.37) and (19.38+/-2.70)%, P <0.05], and the mean value of foci per cell and the percentage of gamma H2AX foci positive cells in 50 Hz MF exposure group for 48 h were (3.14 +/-0.35) and (31.00 +/-3.44)%, which were significantly higher than those of sham-exposure group (P <0.01). However there was no significant difference between 50 Hz MF exposure groups for 2 h, 6 h, 12 h and sham-exposure group for above two indexes (P >0.05). CONCLUSION: 0.4 mT 50 Hz MF exposure for longer duration might induce DNA double-strand breaks in human lens epithelial cells in vitro.

[Surface markers and functions of human dendritic cells exposed to mobile phone 1800 MHz electromagnetic fields].

OBJECTIVE: To investigate the effects of mobile phone 1800 MHz electromagnetic fields (EMF) on the surface markers and the functions of human dendritic cells (DC). METHODS: Human DCs were exposed to intermittent 5 min on/10 min off EMF with specific absorption rates (SAR) 4 W/kg for 0 h, 1 h, 12 h or 24 h, respectively. FACS analysis was used to detect the positive percentage of DC surface markers including HLA-DR and co-stimulatory molecules such as CD80, CD86, CD40 and CD11c. CCK-8 kit was adopted to examine the function of allo-mixed lymphocyte reaction (allo-MLR) of DC, and enzyme linked immunosorbent assay (ELISA) to identify the levels of IL-12p70 and TNF-alpha secreted by DC. RESULT: Compared with the sham radiation group, after exposure to the electromagnetic fields for 1 h, 12 h, or 24 h, HLA-DR, CD80,CD86 and CD40 were all declined except CD11c. The ability of DC allo-MLR in each exposure group was decreased significantly (P<0.05), especially in the 24 h exposure group. However, the secreted levels of IL-12p70 and TNF-alpha of DC in each exposure group remained no changed. CONCLUSION: The study showed that EMF exposure could down-regulate the surface molecules and stimulation ability of human DC.

[Effects of different cell lysis buffers on protein quantification].

OBJECTIVE: To observe the effects of different cell lysis buffers on protein quantification with Bradford method and bicinchoninic acid (BCA) method. METHODS: Bradford method and BCA method were used to determine the concentration of bovine serum albumin (BSA) in different solutions (distilled water, cell lysis buffer used in two-dimensional differential in-gel electrophoresis and three kinds of cell lysis buffers used in conventional two dimensional gel electrophoresis), as well as the protein concentrations of cell lysates using these different lysis buffers. Bradford method was also applied to determine the protein concentrations of samples with repeated freeze thaw cycle, in different colorimetric cylinders, or using different standard curves from different periods. RESULT: The protein measurements increased for 1.2 to 2 fold when different cell lysis buffers were used in Bradford method, but the measurements increased with the increased concentration of BSA (r=0.989 approximately 0.996, P<0.05). For BCA, measurement reading increased about thousands times higher, even overflowed the limits of machine. Protein measurements didn't change significantly, only showed a declined trend after repeated freeze thaw cycle, while no significant changes were found using different colorimetric cylinders or standard curves from different periods. CONCLUSION: Bradford method may be the choice of the protein quantification in proteomics. However, optimization is required for specific experimental conditions.

[Study of toxicity to rats induced by nanosized SiO2 and standard SiO2].

OBJECTIVE: To study the pulmonary toxicity to rats induced by the nanosized SiO(2) or the standard SiO(2). METHODS: Seventy-two male SD rats were divided into three groups: the nanosized SiO(2) group, the standard SiO(2) group and the control group. 24 rats each group. The nanosized SiO(2) group and the standard SiO(2) group were instilled intratracheally with 0.5 ml suspension of 0.6 mg/ml nanosized SiO(2) or standard SiO(2) respectively while the control group was instilled with 0.5 ml physiological saline. On the 3rd, 7th, 14th, and 28th day after exposure, six rats were sacrificed at each time point and the total white cells counts and total protein in BALF and the histopathological changes were observed. The pulmonary toxicities of the two SiO(2) dusts were compared. RESULTS: Nanosized SiO(2) caused significant increase at 3rd, 7th, 14th day after the exposure [(16.0 +/- 6.0) x 10(6), (11.1 +/- 4.0) x 10(6), (12.2 +/- 4.6) x 10(6)] compared with saline (P < 0.05 or P < 0.01) in the total numbers of white cells and on the 3rd after the exposure compared with standard SiO(2) [(5.7 +/- 3.7) x 10(6), P < 0.01]. Meanwhile, Nanosized SiO(2) significantly increased the total protein on the 14th, 28th day after the exposure (0.41 +/- 0.14, 0.41 +/- 0.19 g/L) compared with saline or standard SiO(2) and nanosized SiO(2) on the 3rd, 7th day after the exposure (P < 0.05 or P < 0.01). Nanosized SiO(2)-treated rats showed marked white cell infiltration in alveolar space or around brondum the blood vessel. Standard SiO(2) caused similar but less severe responses compared with nanosized SiO(2). Van Gieson's-stained sections showed no significant fibrosis in these dust-exposed rats at 28th day after the exposure. CONCLUSION: Nanosized SiO(2) can cause severer and longer pulmonary toxicity in rats than standard SiO(2). The pulmonary particle load threshold of nanosized SiO(2) may be lower than that of standard SiO(2).

[Effect of 50 Hz power frequency magnetic field on microfilament cytoskeleton assembly of human amnion FL cells].

OBJECTIVE: Investigations were carried out to understand the effect of 50 Hz power frequency magnetic field on microfilament assembly of human amniotic cells and on expression of actin and epidermal growth factor receptor. METHODS: Human amnion FL cells were exposed to 0.1, 0.2, 0.3, 0.4, 0.5 mT power frequency magnetic field for 30 minutes. Microfilaments were marked using Phalloidin-TRITC, and then were observed under a fluorescence microscope. An optical method was used to detect the relative content of microfilament in cells. A scanning electron microscope was used to detect the cell shape. The content of actin and epidermal growth factor receptor in the preparation of the detergent-insoluble cytoskeleton were measured by western-blotting to analyse the potential mechanism of the change induced by magnetic field. RESULTS: Intracellular stress fibers were found to decrease after exposing cells to a 0.2 mT power frequency magnetic field for 30 minutes. New microfilament and filopodia bundles appeared at the cell periphery after exposure, but the detected total F-actin content per cell was not significantly changed, detected by a F-actin-specific dye. The change in the amount of microfilaments caused by the field could be recovered 2 hours later when the field was withdrawn. The mean height of microfilament cytoskeleton decreased from (12.37 +/- 1.28) microm to (9.97 +/- 0.38) microm (t = 6.96, P > 0.05) after exposure using a confocal microscope. The cell shapes became more flat and lamellipodia appeared after exposure observed by a scanning electron microscope. By using Western blotting method, the intracellular contents of epidermal growth factor receptor and of actin in the preparation of the detergent-insoluble cytoskeleton which are associated with high-affinity epidermal growth factor receptors, increased about (31.2 +/- 4.1)% (t = 17.10, P < 0.05) and (16.8 +/- 2.3)% (t = 16.68, P < 0.05) respectively, compared with that of the control. CONCLUSION: These results suggest that a short time exposure to a 0.2 mT power frequency magnetic field induces re-organization of microfilament in human amnion FL cells. These changes could be recovered by field withdraw and may have something with the clustering of epidermal growth factor receptors induced by magnetic field.

Endogenous histamine inhibits the development of morphine-induced conditioned place preference.

AIM: The conditioned place preference (CPP) paradigm was used to investigate the effects of endogenous histamine on the processes leading to morphine-induced reward-seeking behavior in Sprague-Dawley rats. METHODS: The model of CPP was used to assess the rewarding effect of morphine. The levels of histamine, glutamate, gamma-aminobutyric acid (GABA), dopamine (DA) and 3, 4-dihydroxyphenylacetic acid (DOPAC) in rat brains were measured with high-performance liquid chromatography. Immunohistochemistry technique was used to observe the morphological changes of neurons. RESULTS: Intraperitoneal injection of morphine (2, 5 or 10 mg/kg) induced the development of CPP in a dose-dependent manner. In addition, morphine administrations (10 mg/kg) decreased the histamine content and reduced the number and size of histaminergic neurons in the tubero-mammillary nucleus (TM), as well as markedly increasing the DOPAC/DA ratios in the ventral tegmental area (VTA) and nucleus accumbens (NAc). Intraperitoneal injection of histidine (50, 100 or 200 mg/kg) dose-dependently inhibited the development of morphine-induced CPP. Bilateral lesions of the TM, which decreased the histamine levels in the VTA and NAc, potentiated the development of CPP induced by morphine (1 mg/kg, a dose that produced no appreciable effect when given alone) and increased the DOPAC/DA ratios in the VTA and NAc, but did not change the glutamate or GABA levels in these nuclei. Histidine reversed the effects of the TM lesions. CONCLUSION: These results indicate that endogenous histamine plays a role in inhibiting the development of morphine-induced reward-seeking behavior, and the inhibition may involve the modulation of dopaminergic activity.

[Effects of GSM 1800 MHz radiofrequency electromagnetic fields on DNA damage in Chinese hamster lung cells].

OBJECTIVE: To study the effects of GSM 1800 MHz radiofrequency electromagnetic fields (RF EMF) on DNA damage in Chinese hamster lung (CHL) cells. METHODS: The cells were intermittently exposed or sham-exposed to GSM 1800 MHz RF EMF (5 minutes on/10 minutes off) at a special absorption rate (SAR) of 3.0 W/kg for 1 hour or 24 hours. Meanwhile, cells exposed to 2-acetylaminofluorene, a DNA damage agent, at a final concentration of 20 mg/L for 2 hours were used as positive control. After exposure, cells were fixed by using 4% paraformaldehyde and processed for phosphorylated form of H2AX (gammaH2AX) immunofluorescence measurement. The primary antibody used for immunofluorescence was mouse monoclonal antibody against gammaH2AX and the secondary antibody was fluorescein isothiocyanate (FITC)-conjugated goat anti-mouse IgG. Nuclei were counterstained with 4, 6-diamidino-2-phenylindole (DAPI). The gammaH2AX foci and nuclei were visualized with an Olympus AX70 fluorescent microscope. Image Pro-Plus software was used to count the gammaH2AX foci in each cell. For each exposure condition, at least 50 cells were selected to detect gammaH2AX foci. Cells were classified as positive when more than five foci were detected. The percentage of gammaH2AX foci positive cells was adopted as the index of DNA damage. RESULTS: The percentage of gammaH2AX foci positive cell of 1800 MHz RF EMF exposure for 24 hours (37.9 +/- 8.6)% or 2-acetylaminofluorene exposure (50.9 +/- 9.4)% was significantly higher compared with the sham-exposure (28.0 +/- 8.4)%. However, there was no significant difference between the sham-exposure and RF EMF exposure for 1 hour (31.8 +/- 8.7)%. CONCLUSION: 1800 MHz RF EMF (SAR, 3.0 W/kg) for 24 hours might induce DNA damage in CHL cells.

[Effects of GSM 1800 MHz radiofrequency electromagnetic fields on protein expression profile of human breast cancer cell MCF-7].

OBJECTIVE: To study the effects of GSM 1800 MHz radiofrequency electromagnetic fields (RF EMF) exposure on protein expression profile of human breast cancer cell line (MCF-7), as to exploring the possible effects on normal cell physiological function. METHODS: MCF-7 cells were continuously or intermittently (5 minutes field on followed by 10 minutes off) exposed to RF EMF for different duration (1 hour, 3 hours, 6 hours, 12 hours, or 24 hours) at an average specific absorption rate (SAR) of 3.5 W/kg. The extracted proteins were separated by 2-dimensional electrophoresis and the protein-spot distribution of the silver-stained gels was analyzed by using PDQuest software 7.1. Each experiment was repeated three times. RESULTS: On the average, around 1100 proteins were detected using pH 4 - 7 IPG strip. There were no differential proteins found under continuous exposure at SAR of 3.5 W/kg for 6 hours. Under other exposure conditions, we found various differentially expressed proteins in exposure groups as compared with the sham-exposed controls. Especially in 3 hours intermittent exposure and 12 hours continuous exposure, eighteen and seven differential proteins were detected, respectively. The categories and functions of these differentially expressed proteins were analyzed by searching of SWISS-PROT protein database, which suggested that these proteins should be related to the functions of biosynthesization, signal transduction, and DNA damage and repair. CONCLUSIONS: Data indicated that the protein expression changes induced by RF radiation might depend on exposure duration and mode. Many biological processes might be affected by RF exposure.

50-Hertz electromagnetic fields induce gammaH2AX foci formation in mouse preimplantation embryos in vitro.

Effects of electromagnetic fields (EMFs) on DNA damage in mammals are still controversial. In the present study, the effects of EMFs on DNA damage in preimplantation mouse embryos in vitro were investigated by using gammaH2AX foci formation, a new sensitive indicator for detecting DNA double-strand breaks (DSBs). The data obtained demonstrated that EMFs decreased the cleavage rate of preimplantation mouse embryos. This decreasing effect of EMFs was related to the DNA-damaging effect indicated by the induction of gammaH2AX foci formation in preimplantation mouse embryos. The inducing effects of EMFs on gammaH2AX foci formation could be inhibited by the treatment of noise MFs or wortmannin, a phosphatidylinositol 3-kinase (PI3K) family inhibitor. Furthermore, the data obtained also showed that EMFs could activate the DNA damage-repair mechanism by recruiting repair factor Rad50 to the damaged DNA sites to repair the corresponding DNA damage. These findings suggest that EMFs could cause DNA damage in preimplantation embryos in vitro and that the adverse effects of EMFs on development might at least partly act through DNA damage. The DNA damage induced by EMFs could be at least partly repaired by the natural activation of DNA damage-repair mechanism or prevented by the simultaneous treatment of noise magnetic fields.

[Effects of phytoestrogens on gap junctional intercellular communication].

OBJECTIVE: To observe effects of phytoestrogens quercetin (QC), Genistein (GEN), coumestrol (COM), and enterolactone (ENL) on gap junctional intercellular communication (GJIC) in HaCaT cells. METHODS: HaCaT cells were exposed to QC, GEN, COM, and ENL at 0.1, 1.0, 10.0 and 100.0 micromol/L for 24 hours. The effects of phytoestrogens on GJIC were determined by fluorescence redistribution after photobleaching (FRAP) technique of using a laser scanning confocal microscope (LSCM). RESULTS: QC did not affect the GJIC at 0.1-10.0 micromol/L, whereas, GEN, COM, and ENL exhibited inhibition on the GJIC in some extent at 0.1-10.0 micromol/L without showing significant cytotoxicity. The ratio of fluorescence recovery were between 31.77% to 37.06%, which were significantly decreased compared the vehicle control (44.74%). CONCLUSION: The phytoestrogens GEN, COM, and ENL, but not QC, could inhibit the GJIC function in HaCaT cells at concentrations could be reached in human serum in some instance, indicating they could, under certain conditions, be cancer promoters. Therefore, it should be prudent to use these chemicals as pharmaceuticals or dietary supplements.

[Effects of millimeter wave on gap junctional intercellular communication in human keratinocytes].

OBJECTIVE: To explore the effect of millimeter wave (MW) at low power density on gap junctional intercellular communication (GJIC) in human keratinocytes (HaCaTs). METHODS: Fluorescence recovery after photobleaching (FRAP) technique was employed to determine effect of 30.16 GHz MW exposure at 1.0 and 3.5 mW/cm(2) on GJIC with laser confocal scanning microscope. RESULTS: FRAP analysis revealed that 12-O-tetradecanoylphorbol-13-acetate (TPA) at a dose of 5 microg/L could inhibit GJIC in HaCaTs. Fluorescence recovery rate fell from (55 +/- 17)% in the controls to (34 +/- 13)% after photobleaching, with a very significant difference (P < 0.001). Exposure to MW alone for one hour at either 1.0 mW/cm(2) or 3.5 mW/cm(2) did not affect GJIC, with fluorescence recovery rates of (52 +/- 16)% and (50 +/- 17)%, respectively. GJIC suppression induced by TPA was weakened by MW combined with 5 microg/L TPA treatment for one hour, which could be partially recovered by exposure to 1.0 mW/cm(2) MW with fluorescence recovery rate of (47 +/- 16)%, P < 0.01, and fully recovered by exposure to 3.5 mW/cm(2) MW with fluorescence recovery rate of (50 +/- 16)%, P < 0.001, with a very significant difference. CONCLUSIONS: GJIC suppression induced by TPA could be eliminated or diminished by exposure to millimeter wave in HaCaTs.

[Noise magnetic fields block co-suppression effect induced by power frequency magnetic field and phorbol ester].

OBJECTIVES: To explore intervention with electromagnetic noise for co-suppression effect on gap-junctional intercellular communication (GJIC) induced or strengthened by low intensity magnetic field with carcinogen 12-O-tetradecanoylphorbol-13-acetate (TPA). METHODS: Fibroblast cells from NIH 3T3 mice were exposed to extremely low intensity magnetic field (MF) 0.2 mT, 0.2 mT + TPA or/and electromagnetic noise with the same intensity of MF for 24 h, and GJIC was determined using fluorescence recovery analysis after photobleaching (FRAP) with a laser-scanning confocal microscope (Leica, Germany). RESULTS: GJIC function could be co-suppressed by MF of 0.2 mT with TPA, with fluorescence recovery of (23 +/- 11)%, lower than that in the control group [(46 +/- 19)%] and in the group with TPA only [(34 +/- 17) %] (P < 0.01), indicating 0.2 mT MF plus TPA could co-inhibit GJIC (P < 0.01). Superposition of 0.2 mT noise MF could get a fluorescence recovery of (35 +/- 19)% and significantly antagonize its co-suppression by TPA. CONCLUSION: Electromagnetic noise of 0.2 mT could block the intensifying effect of power frequency magnetic field on TPA-induced GJIC inhibition.

[Influence of combined cyclosporine A and tacrolimus with 5-fluorouracil on hepatocellular carcinoma rats].

OBJECTIVE: To investigate the effect of combined CsA and FK506 with 5-FU on hepatocellular carcinoma rats. METHODS: A syngeneic rat model of hepatocellular carcinoma was used. Control group (A) underwent 4 ml 5% GS. Treatment group was divided into 3 groups namely, group B: only 5-FU and 5% GS; group C: 5-FU, CsA and 5% GS; group D: 5-FU, FK506 and 5%GS. Cell cycle, apoptosis, necrosis and mitochondrial transmembrane potential were measured by flow cytometry, laser scanning confocal microscopy, and electron transmission microscopy. Statistical analysis was performed by SPSS 10.0 for Windows software. Statistical comparisons were made with ANOVA followed by Dunnett's T3 or LSD test. RESULTS: Compared to the control group, the percentage of apoptotic cells including trifle necrotic cells was significantly higher, and among the treatment group, group D was the highest, and group C was higher than group B. In the treatment group, cell cycle of hepatoma cells was mainly arrested at S phase, but in group D, G0/G1 phase cells were significantly decreased and S phase cells significantly increased. Compared to the control group, mitochondrial transmembrane potential was significantly decreased in the treatment group, among with, group B was the lowest, group C was higher than group D. Morphological changes demonstrated by electron microscopy included dispersed nuclear chromatin, loss of nucleoli, membrane bleeding, cell shrinkage, typical apoptotic bodies and marked swelling of mitochondria in the treatment group. In the control group, however, they were characterized by normal cell ultrastructure. CONCLUSIONS: The present study reveals that 5-FU combined with CsA or FK506 demonstrated a synergistic effect on hepatocellular carcinoma rats. For FK506, the powerful mutual effect is related to the increase of tumor cell's quantity in S phase. Both CsA and FK506 can provide protection on mitochondrial transmembrane potential reduction against hepatoma cells damage from 5-FU.

[Effects of acrylamide on DNA damage in human keratinocytes].

OBJECTIVE: To investigate the toxic and DNA damaging effect of acrylamide (AA) on human keratinocytes and its mechanism. METHODS: (1) After the keratinocyte cell line HaCaT cells were exposed to AA with different concentrations for 44 hours, cell survival rate was detected by MTT method. (2) The effects of DNA damage of exposed cells were detected by comet assay. (3) After treating the cells with 2.00 mmol/L of AA plus 0.50 mmol/L of 1-aminobenzotriazole (1-ABT), an inhibitor of cytochrome P-450 enzymes (CYP-450), for 4 hours, the relationship between DNA damage and CYP-450 was studied. RESULTS: (1) Cytotoxicity measurement of AA showed that cell survival rate decreased significantly after 44-hour treatment. (2) Cytotoxicity was not detected after 4-hour AA treatment, but significant DNA damage was observed in all treatment groups, and the degree of damage increased with the concentration of AA. Moreover, the tail lengths of comet cells were in dose-effect relationship. As for cells treated by 1-ABT with 2 mmol/L AA, comet rate and tail length were 15.4% and (8.2 +/- 2.0) micro m respectively, which were decreased significantly (P < 0.01) when compared with 2 mmol/L AA treatment group [80.6% and (44.3 +/- 4.0) micro m]. CONCLUSIONS: Acrylamide has significant cytotoxicity and genotoxicity on HaCaT cells. AA-induced DNA damage may be related to the oxidative metabolite(s) of AA through CYP-450.