Exploring Ubiquinone Biosynthesis Inhibition as a Strategy for Improving Atovaquone Efficacy in Malaria

Author(s)

Verdaguer, I. B. ^[1] ; Crispim, M. ^[1] ; Zafra, C. A. ^[1] ; Sussmann, R. A. C. ^[2] ; Buritica, N. L. ^[1] ; Melo, H. R. ^[3] ; Azevedo, M. F. ^[3] ; Almeida, F. G. ^[1] ; Kimura, E. A. ^[1] ; Katzin, A. M. ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Biomed Sci, Dept Parasitol, Sao Paulo, SP - Brazil

^[2] Fed Univ Southern Bahia, Ctr Environm Sci, Inst Humanities, Itabuna - Brazil

^[3] Univ Fed Sao Paulo, Dept Biosci, Sao Paulo, SP - Brazil

• Document type: Journal article
• Source: Antimicrobial Agents and Chemotherapy; v. 65, n. 4 APR 2021.
• Web of Science Citations: 0

Abstract

Atovaquone (AV) acts on the malaria parasite by competing with ubiquinol (UQH(2)) for its union to the mitochondrial bc(1) complex, preventing the ubiquinone-8 and ubiquinone-9 (UQ-8 and UQ-9) redox recycling, which is a necessary step in pyrimidine biosynthesis. This study focused on UQ biosynthesis in Plasmodium falciparum and adopted proof-of-concept research to better elucidate the mechanism of action of AV and improve its efficacy. Initially, UQ biosynthesis was evaluated using several radioactive precursors and chromatographic techniques. This methodology was suitable for studying the biosynthesis of both UQ homologs and its redox state. Additionally, the composition of UQ was investigated in parasites cultivated at different oxygen saturations or in the presence of AV. AV affected the redox states of both UQ-8 and UQ-9 homologs by increasing the levels of the respective reduced forms. Conversely, low-oxygen environments specifically inhibited UQ-9 biosynthesis and increased the antimalarial efficacy of AV. These findings encouraged us to investigate the biological importance and the potential of UQ biosynthesis as a drug target based on its inhibition by 4-nitrobenzoate (4-NB), a 4-hydroxybenzoate (4-HB) analog. 4-NB effectively inhibits UQ biosynthesis and enhances the effects of AV on parasitic growth and respiration rate. Although 4-NB itself exhibits poor antimalarial activity, its 50% inhibitory concentration (IC50) value increased significantly in the presence of a soluble UQ analog, p-aminobenzoic acid (pABA), or 4-HB. These results indicate the potential of AV combined with 4-NB as a novel therapy for malaria and other diseases caused by AV-sensitive pathogens. (AU)

• FAPESP's process: 18/12589-2 - Multi-user equipment approved in grant 15/19316-3: flow cytometer
• Grantee: Mauro Ferreira de Azevedo
• Support Opportunities: Multi-user Equipment Program
• FAPESP's process: 17/22452-1 - Biosynthesis of isoprenoids in Plasmodium falciparum: evaluation of possible targets to obtain new anti-malarial drugs
• Grantee: Alejandro Miguel Katzin
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 15/19316-3 - Regulation of P. falciparum egress from the host cell: identification of new targets
• Grantee: Mauro Ferreira de Azevedo
• Support Opportunities: Research Grants - Young Investigators Grants