The heterologous expression of Escherichia coli MutT enzyme is involved in the protection against oxidative stress in Leishmania braziliensis

BACKGROUND

Oxidative stress is responsible for generating DNA lesions and the 8-oxoguanine (8-oxoG) is the most commonly lesion found in DNA damage. When this base is incorporated during DNA replication, it could generate double-strand DNA breaks and cellular death. MutT enzyme hydrolyzes the 8-oxoG from the nucleotide pool, preventing its incorporation during DNA replication.

OBJECTIVES

To investigate the importance of 8-oxoG in Leishmania infantum and L. braziliensis, in this study we analysed the impact of heterologous expression of Escherichia coli MutT (EcMutT) enzyme in drug-resistance phenotype and defense against oxidative stress.

METHODS

Comparative analysis of L. braziliensis and L. infantum H₂O₂ tolerance and cell cycle profile were performed. Lines of L. braziliensis and L. infantum expressing EcMutT were generated and evaluated using susceptibility tests to H₂O₂ and Sb^III, cell cycle analysis, γH2A western blotting, and BrdU native detection assay.

FINDINGS

Comparative analysis of tolerance to oxidative stress generated by H₂O₂ showed that L. infantum is more tolerant to exogenous H₂O₂ than L. braziliensis. In addition, cell cycle analysis showed that L. infantum, after treatment with H₂O₂, remains in G1 phase, returning to its normal growth rate after 72 h. In contrast, after treatment with H₂O₂, L. braziliensis parasites continue to move to the next stages of the cell cycle. Expression of the E. coli MutT gene in L. braziliensis and L. infantum does not interfere in parasite growth or in susceptibility to Sb^III. Interestingly, we observed that L. braziliensis EcMutT-expressing clones were more tolerant to H₂O₂ treatment, presented lower activation of γH2A, a biomarker of genotoxic stress, and lower replication stress than its parental non-transfected parasites. In contrast, the EcMutT is not involved in protection against oxidative stress generated by H₂O₂ in L. infantum.

MAIN CONCLUSIONS

Our results showed that 8-oxoG clearance in L. braziliensis is important to avoid misincorporation during DNA replication after oxidative stress generated by H₂O₂.

Key words:
Leishmania braziliensis; Leishmania infantum; MutT; DNA repair; 8-oxoG; oxidative stress