The effects of Pycnogenol on DNA damage in vitro and expression of superoxide dismutase and HP1 in Escherichia coli SOD and catalase deficient mutant cells

Abstract

The procyanidin-rich French maritime pine bark extract Pycnogenol (PYC) is believed to be an antioxidant. To access whether PYC protects DNA against Fenton reaction radicals, pUC 19 plasmid DNA was damaged by OH- radicals generated from Fe(II) plus H2O2 in the presence and absence of PYC. DNA damage was quantified by measuring decreases in supercoiled DNA (SC-DNA) using agarose gel electrophoresis. The results showed that PYC (50 microg/mL) did not inhibit DNA damage from Fenton reaction-generated oxyradicals, when the Fenton reaction was allowed to proceed. However, PYC did protect against DNA damage when added prior to the initiation of the Fenton reaction, suggesting that protection resulted from chelation of Fe rather than from the scavenging of radicals. Moreover, we unexpectedly observed PYC-associated DNA breakage, which was dose- and time- dependent. Other antioxidants such as desferrioxamine (DFO) including butylated hydroxyltoluene (BHT), curcumin and alpha-tocopherol exhibited protective effects against DNA damage caused by the Fenton reaction. Subsequently, we assessed the possible pro-oxidant function of PYC on DNA damage in E. coli SOD deficient mutants under oxidative stress, after observing that PYC can induce SOD under oxidative stress. Although, PYC did not enhance DNA damage, it likewise did not protect against oxidative stress-mediated DNA damage. All together, our data indicate that PYC under some circumstances can enhance oxidative stress-mediated DNA damage in vitro and in vivo.