Interaction of type II alveolar epithelial cells infected by Mycobacterium tuberculosis with populations of infected or non-infected macrophage

Author(s)

Ualter Guilherme Cipriano Rosa

• Document type: Master's Dissertation
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina de Ribeirão Preto (PCARP/BC)
• Defense date: 2022-12-21

Examining board members

Vania Luiza Deperon Bonato

• Advisor: Vania Luiza Deperon Bonato

Abstract

Tuberculosis was the disease that caused the greatest number of deaths in the world from exposure to a single infectious agent, until the emergence of the COVID-19 pademia. Approximately 5-10% of people infected with Mycobacterium tuberculosis, the bacillus that causes this disease, make up more than 10 million people who are symptomatic and ill. The remaining 90-95% of infected individuals have latent/symptomatic infection, and correspond to ¼ of the world\'s population. Innate immunity is believed to be critical in inducing latency. As part of innate immunity, macrophages, dendritic cells, and alveolar epithelial cells are among the first cells that interact with M. tuberculosis. The aim of the present study was to evaluate the interaction of M. tuberculosis-infected alveolar epithelial cells with macrophages, hypothesizing that the microenvironment generated by infected alveolar epithelial cells will affect the macrophage response. We used the lineage (MLE-15) of type II alveolar epithelial cells that were infected with M. tuberculosis (MOI 10) and the supernatant of this cell culture, termed infected cell conditioned medium (ICM), was used to treat bone marrow precursor-derived macrophages (BMDM). Conditioned medium of uninfected MLE-15 cells (NICM), LPS or M. tuberculosis infection alone were used as experimental controls. Macrophages treated with ICM exhibited increased expression of arginase 1 (Arg1), secreted IL-1β, TNF and IL-10. Alveolar macrophages of the AMJ2-C11 lineage exposed to ICM also exhibited increased Arg1 expression. BMDM previously exposed to ICM and then infected with M. tuberculosis showed reduced bacillary load, secreted significant concentrations of IL-1β and IL-6, increased expression of the enzyme induced nitric oxide synthase (iNOS), and death by necrosis when compared to macrophages not stimulated with ICM. To evaluate the function of these macrophages in vivo, we transferred BMDM previously treated with ICM to C57BL/6 wild-type (WT) animals and evaluated the lung condition 10 days after infection. Animals that received macrophages previously exposed to ICM showed reduced bacillary load and inflammation in the lungs, increased IL-1β in total lung cells, and increased iNOS expression in alveolar and interstitial macrophages compared to the group of animals that did not receive transfer. Epithelial cells from the lungs of infected animals exhibited the highest significant death by necrosis, independent of the treatment done on the transferred macrophages. In conclusion, the interface of M. tuberculosis-infected type II epithelial cells with macrophages is important for activating and regulating the innate response, helping to contain the bacillary load. The identification of molecules present in the conditioned medium (ICM) may enable the emergence of new targets for immune therapies against tuberculosis. (AU)

• FAPESP's process: 19/24681-3 - Interaction of type II alveolar epithelial cells infected by Mycobacterium tuberculosis with populations of infected or non-infected macrophage
• Grantee: Ualter Guilherme Cipriano Rosa
• Support Opportunities: Scholarships in Brazil - Master