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itself or react with other compounds to yield radicals that are more reactive. Also, it is
reported that taurine prevents the diversion of electrons into superoxide generation by
improving the function of the electron transport chain in vivo (Turrens
2007
) . In our
present study, the superoxide radical scavenging activity of taurine at the concentra-
tions from 0.25 to 1 mg/mL was elevated with a decrease of ESR signals in a dose-
dependent manner, although the superoxide radical scavenging activity by taurine was
weaker than for DPPH, hydroxyl, and alkyl radical scavenging activities. Oliveira
et al. (
2010
) reported that taurine concentrations above 15 mM may prevent the super-
oxide radical generation. Another previous study indicates that taurine can serve as a
general scavenger of ROS, such as superoxide and peroxide (Babior et al.
1983
) . Also,
it was reported that the superoxide scavenging by taurine was larger than for hydroxyl
radical scavenging by ESR spin trapping (Kilic et al.
1999
). In our previous study,
however, the IC
50
values of taurine against DPPH radical, alkyl radical, and hydroxyl
radical scavenging activity were above 4 mg/mL, although taurine has very weak radi-
cal scavenging activities (Du et al.
2010
) .
In the present study, we examined the free radical scavenging effect on plasmid
DNA damage of taurine additionally. In general, DNA damage may cause perturba-
tions in inner mitochondrial membrane permeability, the so-called mitochondrial per-
meability transition (MPT). A sudden increase in MPT is a central coordination event
in the apoptotic process (Gottlieb
2000
; Tada-Oikawa et al.
2000
). In the present inves-
tigation involving plasmid nicking assay, it was seen that the taurine provided protec-
tion against the damage caused by hydroxyl radical. In a previous study, it was reported
that taurine at concentrations normally found in cells can inhibit oxidative damage to
DNA (Messina and Dawson
2000
). Recently, Das et al. (
2011
) reported that taurine
suppressed doxorubicin-triggered oxidative stress and cardiac apoptosis in rat. Similarly,
it was reported that administration of taurine alleviated pathological changes and DNA
damage caused by arsenic through the RNS signal pathway in vivo (Ma et al.
2010
) . In
another previous study, it was reported that taurine (100 mg/kg) prevents tamoxifen-
induced mitochondrial oxidative damage in mice (Parvez et al.
2008
) .
Although the antioxidant acts of taurine remains a controversial topic, our pres-
ent in vitro data suggests that taurine may protect DNA damage and oxidative stress
by acting as an efficient scavenger against several free radicals including DPPH,
hydroxyl, superoxide, and alkyl radicals in vitro system. It is worthy to further
investigate the potential effectiveness of taurine in preventing the diseases caused
by overproduction of radicals.
17.5
Conclusion
In summary, our present study shows that taurine has protective effect on the DNA
damage and oxidative stress by acting as an efficient scavenger against several free
radicals. These protective effects of taurine may contribute to prevent several dis-
eases caused by overproduction of radicals.
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