Culture of Mycobacterium smegmatis in Different Carbon Sources to Induce In Vitro Cholesterol Consumption Leads to Alterations in the Host Cells after Infection: A Macrophage Proteomics Analysis

Abstract

During tuberculosis, Mycobacterium uses host macrophage cholesterol as a carbon and energy source. To mimic these conditions, Mycobacterium smegmatis can be cultured in minimal medium (MM) to induce cholesterol consumption in vitro. During cultivation, M. smegmatis consumes MM cholesterol and changes the accumulation of cell wall compounds, such as PIMs, LM, and LAM, which plays an important role in its pathogenicity. These changes lead to cell surface hydrophobicity modifications and H2O2 susceptibility. Furthermore, when M. smegmatis infects J774A.1 macrophages, it induces granuloma-like structure formation. The present study aims to assess macrophage molecular disturbances caused by M. smegmatis after cholesterol consumption, using proteomics analyses. Proteins that showed changes in expression levels were analyzed in silico using OmicsBox and String analysis to investigate the canonical pathways and functional networks involved in infection. Our results demonstrate that, after cholesterol consumption, M. smegmatis can induce deregulation of protein expression in macrophages. Many of these proteins are related to cytoskeleton remodeling, immune response, the ubiquitination pathway, mRNA processing, and immunometabolism. The identification of these proteins sheds light on the biochemical pathways involved in the mechanisms of action of mycobacteria infection, and may suggest novel protein targets for the development of new and improved treatments.

The Lack of the TetR-Like Repressor Gene BCG_2177c (Rv2160A) May Help Mycobacteria Overcome Intracellular Redox Stress and Survive Longer Inside Macrophages When Surrounded by a Lipid Environment

“…Taken together, our results would indicate that our mutant strain, while in the presence of high ROS levels, may modulate the intracellular redox balance and survive longer inside macrophages. This agrees with a recent report carried out by de Lima et al. (2021) where it was found that M. smegmatis grown in cholesterol persists intracellularly for a longer time causing less damage than when it grows in dextrose or glycerol.…”

“…de Lima et al (2021) where it was found that M. smegmatis grown in cholesterol persists intracellularly for a longer time causing less damage than when it grows in dextrose or glycerol. Our data also reveal that, after growing in a lipid mixture, the infection of THP-1 macrophages by M. bovis BCG strains (wildtype and mutant) somehow results in a modulation of the immune response to facilitate their survival inside the host.…”

Deep Proteomic Investigation of Metabolic Adaptation in Mycobacteria under Different Growth Conditions

“…Another important host-associated carbon source is cholesterol. In recent years, several groups have investigated metabolic and transcriptional changes induced by cholesterol, since fatty acids and cholesterol are proposed to act as major carbon and energy sources for Mtb in vivo, especially at later stages of infection [21][22][23]. Glycerol and Tween 80 were each applied as both molecules are traditionally used in mycobacterial culture and drug screening assays to promote growth.…”