Annexin A1 modulation mechanism on the expression of the Translocator Protein (TSPO) in BV2 cells.

Inflammation in the Central Nervous System (CNS) is involved in the genesis of a number of neurodegenerative diseases, so understanding the inflammatory process in these circumstances is essential to proposal new therapeutic approaches. We know that Annexin A1 (ANXA1) and the TSPO receptor are two important modulators of neuroinflammation. While it is known that ANXA1 has anti-inflammatory properties, the role of TSPO has not yet been clarified. Thus, this project evaluated the interference of ANXA1 on the expression of TSPO in microglia cell line (BV2), and its connection with the Toll-like receptor-4 receptor (TLR4) in BV2 activated by E. coli lipopolysaccharide LPS). The results show that the treatment of BV2 with LPS induces the expression of TSPO, dependent on activation of TLR4, through the pathways of the adapter molecule of myeloid differentiation factor 88 (MyD88) and nuclear factor κB (NFκB). Treatment with recombinant ANXA1 induces an anti-inflammatory profile in LPS-stimulated BV2 cells, by reducing the secretion of proinflammatory cytokines and, at the same time, increasing secretion of anti-inflammatory cytokines. Exposure with ANXA1 still prevents the increase of LPS-induced TSPO expression. We also show that this action of ANXA1 is dependent on the interaction with the formylated peptide receptor (FPR2). In addition, TSPO silencing in BV2 cells predisposes these cells to an activated profile exacerbating secretion of tumor necrosis factor (TNFα) in response to LPS, which can not be reversed by treatment with recombinant ANXA1. Together, the results show the relationship between ANXA1 and TSPO in LPS activated microglia, showing that ANXA1 negatively modulates TSPO 11 expression. In addition, TSPO silencing inhibited the phagocytosis of apoptotic neurons, which still suggests the participation of TSPO in eferocytosis. (AU)