Ricerc@Sapienza

PLP or vitamin B6 is produced by Pyridoxal kinase (PDXK) enzyme. We recently demonstrated in Drosophila that PLP deficiency caused by dPdxk1 mutation or PLP inhibitors results in chromosome aberrations (CABs), a well-known tumorigenic factor, and impairs glucose homeostasis. Interestingly we found that glucose causes an increase of CABs in dPdxk1 mutants and in human cells depleted of PDXK enzyme, suggesting that the clastogenic effect of glucose in PLP-depleted cells is evolutionarily conserved. These results prompted us to speculate that low levels of PLP could increase cancer risk in diabetic patients.
This proposal is aimed at clarifying the mechanisms through which PLP protects from DNA and chromosome damage in high glucose conditions. We first planned to test whether the silencing of Drosophila insulin pathway genes (namely InR, chico/IRS1, Akt1, Dp110/PI3K, and GlyS) causes DNA damage enhanced by PLP depletion. Preliminary results indicated that the depletion of Insulin-like receptor (InR) and Insulin substrate (Chico/IRS1) results in CABs and gamma-H2AV foci accumulation, whose frequencies are increased by PLP inhibitors. We also observed that Drosophila brain cells depleted of InR and Chico/IRS1 accumulated Advanced Glycation End products (AGEs). Thus we will evaluate if the silencing of the other insulin pathway genes causes the same phenotype. To investigate the mechanism underlying the protective role of PLP in high sugar conditions we will determinate whether the antioxidant alpha-lipoic acid (ALA) compound decreases AGEs and CABs frequencies when insulin pathway is impaired. We planned to extend our experiments also to human cells studying the genes that will give the best results in Drosophila. Finally, we will test whether drugs used for diabetes treatment reduce the clastogenic effects of mutations in the dPdxk gene both in the presence and absence of high sugar.