Investigation of the resistance to ionizing radiation (gamma rays) exhibited by trypanosomes etiological agents of neglected tropical diseases

• Grant number: 24/21950-1
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: May 01, 2025
• End date: April 30, 2026
• Field of knowledge: Biological Sciences - Genetics - Molecular Genetics and Genetics of Microorganisms
• Principal Investigator: Marcelo Santos da Silva
• Grantee: Fernanda de Jesus Silva
• Host Institution: Instituto de Química (IQ). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Parasitic infections are one of the main causes of morbidity and mortality worldwide. A large proportion of these infections in humans and domestic animals can be attributed to trypanosomatids, including Trypanosoma cruzi (the causative agent of Chagas disease) and Trypanosoma brucei (the causative agent of Sleeping Sickness). Treatment for these diseases relies on drugs that have side effects and allow the selection of persistent parasites capable of performing efficient DNA repair. Studies have shown that trypanosomes present high resistance to ionizing radiation by gamma rays (IR) relative to other eukaryotes. However, the molecular mechanisms that orchestrate this unusual resistance to IR in these parasites remain elusive. Furthermore, most studies aimed at investigating the resistance to IR presented by T. brucei were carried out more than two decades ago, when access to large-scale technologies and diverse molecular tools was scarce. Thus, some questions remain open: 1) Is resistance to IR, in fact, common among trypanosomes (T. cruzi and T. brucei) or prominent in T. cruzi? 2) Are the molecular mechanisms of response to IR similar in T. cruzi and T. brucei? 3) Do these parasites perform more efficient DNA repair or do part of the population have some 'protective mechanism' to avoid DNA damage? The answers to these questions could contribute to a better understanding of the diversification of molecular mechanisms that allow these parasites to survive doses considered lethal to mammalian cells. In this proposal, we intend to comparatively investigate the resistance to IR exhibited by T. cruzi and T. brucei. Initially, we intend to use epimastigote forms of T. cruzi and procyclic trypomastigote forms of T. brucei to perform our analyses. Based on the literature, we assume (hypothesize) that T. cruzi will be more resistant than T. brucei. If this hypothesis supports our assays, we will investigate the main reason for this behavior. The irradiation kinetic assays will be performed at IPEN-USP. We will perform proliferation and viability assays, analysis of DNA content and S-phase progression by flow cytometry, detection and repair of DNA damage by TUNEL and IFA using ¿-¿H2A, and we will verify genes related to specific DNA repair pathways differentially expressed by RT-qPCR. If our hypothesis does not hold up to experimental assays, i.e., T. cruzi and T. brucei show the same level of resistance to IR, we will report this finding at the end of the project. The insights gained from this project will help us to better understand the DNA damage response of trypanosomes and may pave the way for a new approach to combat Neglected Tropical Diseases caused by these parasites.