Effects os cholesterol manipulation in the inflammatory response of Dendritic Cells infected by M. bovis BCG

Tuberculosis (TB) remains a major global health challenge, causing more than 1 million deaths annually worldwide. Dendritic cells (DCs) play a central role in the adaptive Immune response and constitute an important reservoir for Mycobacterium tuberculosis (Mtb) within the pulmonary alveoli. Mtb can persist intracellularly by exploiting host cholesterol into lipid droplets (LDs) as a carbon source. This study aimed to investigate the role of LDs and cholesterol metabolism in DC activation, inflammatory responses, andbacterial burden during M. bovis BCG infection.

Bone marrow cells obtained from C57BL/6 mice were differentiated into bone Marrow-derived dendritic cells (BMDCs) using 10 ng/mL GM-CSF. BMDCs were infected with M. bovis BCG at a multiplicity of infection (MOI) of 5. BCG infection promoted increased LD area and cholesterol ester (CE) accumulation. To investigate the role of cholesterol esterification, BCG-infected DCs were treated with the acyl-CoA:cholesterolacyltransferase (ACAT) inhibitor Ci976. Furthermore, the effects of cholesterol availability were assessed via cholesterol supplementation in BMDC cultures.

ACAT inhibition did not alter LD area by fluorescence but significantly increased BCG burden in DCs. In addition, ACAT inhibition reduced the secretion of the cytokines IL-1β, IL-10, IL-6, and TNF-α, as well as the eicosanoid PGE2. However, Ci976 treatment did not modulate the expression of activation markers in infected DCs. These data point to a role for cholesterol esters in the inflammatory response and bacterial burden of BCG-infected DCs. We are currently further investigating the role of cholesterol metabolism in BCG-infected DCs through cholesterol supplementation in BMDC.