Bilirubin, a potent and persistent inhibitor of genetic damage induced by gamma rays in D. melanogaster

The antimutagenic and radioprotective action as well as the persistence of the effects of chlorophyllin, a tetrapyrrole with copper-chelate ring, was demonstrated in our laboratory, using the in vivo system Drosophila melanogaster. The aim of this investigation was to evaluate the inhibitory capacity of bilirubin (BRB) on gamma radiation-induced oxidative genetic damage. For this purpose, the SMART assay on the wing of D. melanogaster was used. Second instar larvae were pretreated with BRB for 24 hours and then groups of them were exposed to gamma ray at 0, 24, 48 or 72 hours after pretreatment. For the antioxidant action, Canton-S strain larvae were pretreated during 2 h with BRB, and after that, they were exposed to gamma rays to measure the activity of the SOD, CAT and GSH-Px enzymes and overexpression of genes Sod and Cat. The results indicated that the group treated with BRB+Gamma rays sharply reduced (56 %) the genetic damage compared to the groups exposed only to gamma rays. Furthermore, this effect was persistent up to 72 h after pretreatment. Bilirubin did not modify CAT nor GSH-Px enzymes activity, neither the transcription of Sod1 gene at any time tested, however, the Cat gene only overexpressed 24 h after BRB and BRB+10 Gy treatment. These findings suggest that these porphyrins act as antioxidants probably by itself, which positions BRB as a possible radioprotector.