The role of DNA damage and of the XPC protein in the activation and function of macrophages

• Grant number: 24/10650-7
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2024
• Status: Discontinued
• Field of knowledge: Biological Sciences - Immunology - Cellular Immunology
• Principal Investigator: Niels Olsen Saraiva Câmara
• Grantee: Sofia Xavier Bustia
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 23/07482-2 - Sensing extra and intracellular stressors by renal and immune cells: new insights into signal reception and transduction, and their relevance for understanding renal diseases, AP.TEM

Abstract

Endogenous and exogenous factors (such as UV radiation and mutagenic compounds) can damage DNA integrity, leading to genomic instability that may result in immunodeficiencies, neoplasms, and cellular aging. The genetic material is subjected to approximately 70,000 damages per day, yet there are pathways that repair them, one of which is the nucleotide excision repair (NER) pathway, primarily repairing UV radiation-induced damage. There are two pathways: TC-NER and GG-NER. GG-NER corrects damage throughout the genome, not only in actively transcribed regions like TC-NER. The XPC protein is part of GG-NER, recognizing damage and recruiting subsequent proteins involved in this pathway. However, there is evidence that XPC protein is also involved in the base excision repair (BER) pathway, which repairs oxidative DNA damage. Consequently, cells deficient in XPC have compromised DNA repair, making them more susceptible to oxidative stress. In this context, macrophages, as phagocytic cells of the immune system, produce reactive oxygen and nitrogen species (ROS and RNS) to combat engulfed pathogens, and excessive production of these compounds can damage the genome. Nucleic acids with excessive damage can enter the cytosol and activate cytosolic DNA sensors such as inflammasomes, TLRs, and cGAS, leading to macrophage activation and inflammatory cascade activation. Therefore, macrophages lacking XPC would exhibit more oxidative DNA damage and consequently higher activation and secretion of pro-inflammatory compounds compared to macrophages with XPC. To test this hypothesis, we plan to compare macrophage activation in mice with and without XPC through: analysis of activation marker expression using flow cytometry and ELISA; assessment of increased DNA damage in XPC-deficient cells using comet assays; and investigation of whether XPC deficiency is associated with mitochondrial ROS accumulation using MitoSOX and changes in cellular glycolytic metabolism.