Study Of The Protective Effect Of Taurine On B(a)P-induced DNA Damage Of L-02 Cells And It's Mechanism

Objectieve Benzo(a)pyrene(B(a)P) as the representative of polycyclic aromatic hydrocarbons(PAHs),is the first discoverable environmental cancinogen,has strong carcinogenicity,can cause multiplicate human cancer,is contamination existing ubiquitously in food and environment. Taurine is a kind of freedom amino acid of abundant content in vivo possessing broad biological function,and the effect of antioxidant is played close attention increasingly.However,there is seldom report on the study of taurine to antagonize DNA damages of hepatocytes induced by B(a)P.Therefore in our study we aims to make a tentative study of the DNA damages induced by B(a)P in hepatocytes and the protective effect of taurine and to explored it's mechanism.Methods Human embryo hepatocytes (L-02 cells) were selected to make an expriment in completely randomized design in vitro. L-02 cells were cultivated routinely and test were subjected when cells were in the period of logarithmical growth and in good condition. Explored to taurine at the three different concentrations of 1.0,2.0,4.0mmol/L and B(a)P at three different concentrations of 12.5,25,50μmol/L.L-02 cells were randomized into five groups:(Ⅰ) Blank control group;(Ⅱ)Solvent control group;(Ⅲ) B(a)P group;(IV) Taurine group;(V) Taurine intervention group:explored to taurine at three different concentration in culture medium for 24 hours and treated further for 24 hours by adding 25μmol/L B(a)P into the culture media;when detected the phaseⅠenzyme activity,we increased a Positive control groud 3-MC.Every groups designed three parallel samples. EROD,PROD activity and micronuclei (MN) formation were analyzed through fluorescence spectrophotometry,colorimetric method and a cytokinesis-block micronucleus(CBMN) assay respectively. The frequencies of MN (‰) and nuclei division index (NDI) were calculated.Results⑴Toxicity of B(a)P in human embyro hepatocytes:B(a)P at concentrations of 12.5,25 and 50μmol/L all obviously induced DNA damages in vitro, Comparing to solvent control, the difference has the statistical significantly(P<0.01);The DNA damage was more serious with the concentration increasing;The EROD and PROD levers of B(a)P groups are increased dose-dependently with B(a)P concentration.⑵The protective effect of taurine on damage of L-02 cells induced by B(a)P: the MN and IND leves of three different concentration taurine intervention group,Comparing to solvent control,the difference hasn't the statistical significantly;Comparing to B(a)P treatment alone,the MN leves of all taurine intervention groups are lower,the differnence has the statistical significantly(P<0.01);the 4.0mmol/L taurine intervention group is the lowest.The IND leves of taurine intervention groups are more high than B(a)P treatment alone,are increased dose-dependently with taurine concentration.Comparing to B(a)P treatment alone,The EROD and PROD levels of taurine intervention groups are all lower, the differnence has the statistical significantly(P<0.01);The results suggest that taurine can significantly inhibited the activity of CYP1A1 and CYP2B.The analysis of Spearman correlation showed that there was a positive association betweed DNA damage and EROD,PROD level(linear correlation coefficient r and P respectively is r=0.926,P<0.01; r=0.814,P<0.01);and a nagative association betweed DNA damage and EROD,PROD level(linear correlation coefficient r and P respectively is r=-0.416,P<0.05; r=-0.398,P<0.05).Conclusion B(a)P could induced DNA damage of L-02 cells and the effect was obvious even at a low concentration of 12.5μmol/L; B(a)P induced the enzyme activities of CYP1A1 and CYP2B increased dose-dependently with concentration.Taurine intervention group of 1.0~4.0 mmol/L could antagonize the toxicity of L-02 cells induced by B(a)P,they also could significantly inhibited the enzyme activity of CYP1A1 and CYP2B induced by B(a)P.There was a positive association betweed MN level and EROD,PROD levels and a negative association betweed IND level and EROD,PROD levels,these result suggested that phase I enzyme CYP1A1 and CYP2B play the key role at BaP be metabolized into ultimate carcinogenic. So we could conjecture that the proctective effect of taurine on damage of hepatocytes induced by B(a)P,was possible through inhibited the enzyme activity of CYP1A1 and CYP2B,but it's mechanism could be further explored.