BackgroundHydrogen peroxide (H2O2) is a common reactive oxygen intermediate generated by various forms of oxidative stress.AimThe aim of this study was to investigate the DNA damage capacity of H2O2 in HepG2 cells.MethodsCells were treated with H2O2 at concentrations of 25 µM or 50 µM for 5 min, 30 min, 40 min, 1 h, or 24 h in parallel. The extent of DNA damage was assessed by the comet assay.ResultsCompared to the control, DNA damage by 25 and 50 µM H2O2 increased significantly with increasing incubation time up to 1 h, but it was not increased at 24 h.ConclusionsOur findings confirm that H2O2 is a typical DNA damage-inducing agent and thus is a good model system to study the effects of oxidative stress. DNA damage in HepG2 cells increased significantly with H2O2 concentration and time of incubation but later decreased likely due to DNA repair mechanisms and antioxidant enzymes.

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Sildenafil is an active cGMP-specific phosphodiesterase type 5 inhibitor that is effective in the treatment of male erectile dysfunction. None of the previous studies havemeasured sildenafil or its possibly related neurochemical changes, but mainly they related their finding to sildenafil associated behavior changes. In this work, behavioral and brain neurochemical changes (excitatory and inhibitory neurotransmitters) associated with acute administration of sildenafil using male albino rats were investigated. Rats were divided into three groups (n=6); group1 received saline (1ml/kg), group2 received single doses of sildenafil (1.5mg/kg), while group 3 received single doses of sildenafil (100mg/kg). Administration was via the intraperitoneal route. Behavior scores using EPM and brain homogenate for neurotransmitters evaluation by HPLC were carried out 60min after administration. Sildenafil did not produce any changes in behavior using the EPM test; also it did not alter the brain levels of excitatory, inhibitory and dopamine. Sildenafil produced dose dependent decreases in plasma dopamine level by mechanism(s) needs more neurochemical investigation. The chronic effect of sildenafil should be taken into consideration.