IMPACT OF EXTRACELLULAR VESICLES SECRETED BY (NIH3T3-L1) ADIPOCYTES ON MACROPHAGE ACTIVATION DURING Mycobacterium bovis BCG INFECTION in vitro

Introduction: Obesity is characterized by a chronic low-grade inflammatory state known as metainflammation. Factors secreted by adipocytes, including Extracellular Vesicles (EVs), have been proposed as modulators of macrophage function and profile, thereby intensifying the processes of metabolic inflammation. Among these EVs, transcription factors such as PPARγ play a significant role in regulating macrophage function and are involved in the biogenesis of lipid bodies (LBs) during BCG infection. LBs are dynamic organelles with functions in lipid storage, synthesis of inflammatory mediators, cellular signaling, and providing a survival niche for pathogens. However, the specific signaling pathways and metabolic processes regulated by adipocyte-derived-EVs, as well as their impact on the progression of infection by intracellular pathogens, remain poorly understood. Objectives: To analyze the interactions between EVs secreted by adipocytes in the macrophage activation during Mycobacterium bovis BCG infection, in vitro. Methods: LBs were quantified using fluorescence microscopy, cytokine levels were measured using ELISA. EVs were isolated using a series of centrifugation steps and characterized and quantified using flow cytometry, Zeta Size analysis, and Micro BCA. Results: Specific subpopulations of EVs, namely microvesicles and exosomes, positively influenced LBs formation and macrophage activation during BCG infection. They induced the synthesis of TNF-α and microvesicles also induced KC synthesis, which was negatively modulated in the infected groups, whereas this effect was not observed for macrophages stimulated with exosomes. Conclusion: Our findings suggest that EVs secreted by adipocytes play a crucial role in BCG-infected macrophages by promoting LBs formation and the cytokines synthesis. However, further studies are required to fully understand the intricate interactions between adipocytes and macrophages during infections caused by intracellular pathogens such as BCG.