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Ginkgo biloba leaf extract induces DNA damage by inhibiting topoisomerase II activity in human hepatic cells.

Zhang Z, Chen S, Mei H, Xuan J, Guo X, Couch L, Dobrovolsky VN, Guo L, Mei N - Sci Rep (2015)

Bottom Line: In this study, the DNA damaging effects of Ginkgo biloba leaf extract and many of its constituents were evaluated in human hepatic HepG2 cells and the underlying mechanism was determined.In Topo II knockdown cells, DNA damage triggered by Ginkgo biloba leaf extract or quercetin was dramatically decreased, indicating that DNA damage is directly associated with Topo II.Our findings suggest that Ginkgo biloba leaf extract- and quercetin-induced in vitro genotoxicity may be the result of Topo II inhibition.

View Article: PubMed Central - PubMed

Affiliation: Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA.

ABSTRACT
Ginkgo biloba leaf extract has been shown to increase the incidence in liver tumors in mice in a 2-year bioassay conducted by the National Toxicology Program. In this study, the DNA damaging effects of Ginkgo biloba leaf extract and many of its constituents were evaluated in human hepatic HepG2 cells and the underlying mechanism was determined. A molecular docking study revealed that quercetin, a flavonoid constituent of Ginkgo biloba, showed a higher potential to interact with topoisomerase II (Topo II) than did the other Ginkgo biloba constituents; this in silico prediction was confirmed by using a biochemical assay to study Topo II enzyme inhibition. Moreover, as measured by the Comet assay and the induction of γ-H2A.X, quercetin, followed by keampferol and isorhamnetin, appeared to be the most potent DNA damage inducer in HepG2 cells. In Topo II knockdown cells, DNA damage triggered by Ginkgo biloba leaf extract or quercetin was dramatically decreased, indicating that DNA damage is directly associated with Topo II. DNA damage was also observed when cells were treated with commercially available Ginkgo biloba extract product. Our findings suggest that Ginkgo biloba leaf extract- and quercetin-induced in vitro genotoxicity may be the result of Topo II inhibition.

No MeSH data available.


Related in: MedlinePlus

DNA damage induced by some commercial Ginkgo biloba extract products in HepG2 cells.HepG2 cells were exposed to 10 μl of each commercial extract product in 10 ml medium for 4 h. (A) Data points represent the means ± S.D. for three independent experiments, and asterisk indicates p < 0.05 when compared with the concurrent control. (B) Total cellular protein was extracted and level of γ-H2A.X was detected by Western blotting with GAPDH as a loading control. Similar results were obtained from three independent experiments.
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f2: DNA damage induced by some commercial Ginkgo biloba extract products in HepG2 cells.HepG2 cells were exposed to 10 μl of each commercial extract product in 10 ml medium for 4 h. (A) Data points represent the means ± S.D. for three independent experiments, and asterisk indicates p < 0.05 when compared with the concurrent control. (B) Total cellular protein was extracted and level of γ-H2A.X was detected by Western blotting with GAPDH as a loading control. Similar results were obtained from three independent experiments.

Mentions: Since a variety of Ginkgo biloba extract products are commercially available in the United States, we randomly selected a Ginkgo biloba extract products from three different U.S. companies for testing. We determined whether or not these commercial products produce DNA damage in hepatic cells using the Comet assay and γ-H2A.X as the indicator of DNA strand breaks. Ten μl of each Ginkgo biloba extract product was added to separate cultures of HepG2 cells growing in 10 ml medium (final concentration 0.1%, v/v) for 4 h. An increased percentage of DNA in tail and induction of γ-H2A.X was observed in Product #3 (Fig. 2), whereas Products #1 and #2 did not induce a detectable increase in the Comet assay and γ-H2A.X.


Ginkgo biloba leaf extract induces DNA damage by inhibiting topoisomerase II activity in human hepatic cells.

Zhang Z, Chen S, Mei H, Xuan J, Guo X, Couch L, Dobrovolsky VN, Guo L, Mei N - Sci Rep (2015)

DNA damage induced by some commercial Ginkgo biloba extract products in HepG2 cells.HepG2 cells were exposed to 10 μl of each commercial extract product in 10 ml medium for 4 h. (A) Data points represent the means ± S.D. for three independent experiments, and asterisk indicates p < 0.05 when compared with the concurrent control. (B) Total cellular protein was extracted and level of γ-H2A.X was detected by Western blotting with GAPDH as a loading control. Similar results were obtained from three independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588569&req=5

f2: DNA damage induced by some commercial Ginkgo biloba extract products in HepG2 cells.HepG2 cells were exposed to 10 μl of each commercial extract product in 10 ml medium for 4 h. (A) Data points represent the means ± S.D. for three independent experiments, and asterisk indicates p < 0.05 when compared with the concurrent control. (B) Total cellular protein was extracted and level of γ-H2A.X was detected by Western blotting with GAPDH as a loading control. Similar results were obtained from three independent experiments.
Mentions: Since a variety of Ginkgo biloba extract products are commercially available in the United States, we randomly selected a Ginkgo biloba extract products from three different U.S. companies for testing. We determined whether or not these commercial products produce DNA damage in hepatic cells using the Comet assay and γ-H2A.X as the indicator of DNA strand breaks. Ten μl of each Ginkgo biloba extract product was added to separate cultures of HepG2 cells growing in 10 ml medium (final concentration 0.1%, v/v) for 4 h. An increased percentage of DNA in tail and induction of γ-H2A.X was observed in Product #3 (Fig. 2), whereas Products #1 and #2 did not induce a detectable increase in the Comet assay and γ-H2A.X.

Bottom Line: In this study, the DNA damaging effects of Ginkgo biloba leaf extract and many of its constituents were evaluated in human hepatic HepG2 cells and the underlying mechanism was determined.In Topo II knockdown cells, DNA damage triggered by Ginkgo biloba leaf extract or quercetin was dramatically decreased, indicating that DNA damage is directly associated with Topo II.Our findings suggest that Ginkgo biloba leaf extract- and quercetin-induced in vitro genotoxicity may be the result of Topo II inhibition.

View Article: PubMed Central - PubMed

Affiliation: Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA.

ABSTRACT
Ginkgo biloba leaf extract has been shown to increase the incidence in liver tumors in mice in a 2-year bioassay conducted by the National Toxicology Program. In this study, the DNA damaging effects of Ginkgo biloba leaf extract and many of its constituents were evaluated in human hepatic HepG2 cells and the underlying mechanism was determined. A molecular docking study revealed that quercetin, a flavonoid constituent of Ginkgo biloba, showed a higher potential to interact with topoisomerase II (Topo II) than did the other Ginkgo biloba constituents; this in silico prediction was confirmed by using a biochemical assay to study Topo II enzyme inhibition. Moreover, as measured by the Comet assay and the induction of γ-H2A.X, quercetin, followed by keampferol and isorhamnetin, appeared to be the most potent DNA damage inducer in HepG2 cells. In Topo II knockdown cells, DNA damage triggered by Ginkgo biloba leaf extract or quercetin was dramatically decreased, indicating that DNA damage is directly associated with Topo II. DNA damage was also observed when cells were treated with commercially available Ginkgo biloba extract product. Our findings suggest that Ginkgo biloba leaf extract- and quercetin-induced in vitro genotoxicity may be the result of Topo II inhibition.

No MeSH data available.


Related in: MedlinePlus