Gal-3 and neuraminidase activity are required to induce phagoptosis of neurons by Brucella abortus-activated microglia

JULIA DE SANTIS ARÉVALO; ARIADNA M. FIORILLO EVEQUOZ; JULIA RODRÍGUEZ; ANA M. RODRÍGUEZ; GUILLERMO H. GIAMBARTOLOMEI

Congreso; LXX Reunión Anual de la Sociedad Argentina de Inmunología (SAI) & 3rd French-Argentine Immunology Congress (FAIC); 2022

Sociedad Argentina de Inmunología (SAI)

We have previously demonstrated that B. abortus-activated microglia kill neurons through primary phagocytosis or phagoptosis. Phagocytosis is a finely regulated process that involves the interaction of different receptors and their ligands. Galectin-3 (Gal-3) is a protein secreted by activated phagocytes and acts as an opsonin through the MERTK receptor. Gal-3 binds to desialylated proteins present on the cell's surface through the action of neuraminidases. The objective of this work was to investigate if Gal-3 is involved in the phagoptosis of neurons mediated by B. abortus-activated microglia. Primary cultures of neurons and microglia from wild type (Balb/c or C57/B6) or Gal-3 deficient mice were infected. Neuron survival was assessed at 48 h by fluorescence microscopy. Co-cultures were treated with Oseltamivir phosphate [neuraminidase (Neu) inhibitor], Tacrolimus (inhibitor of the phosphorylation and subsequent secretion of Gal-3). Neu activity on the cell membrane and TNF-α secretion were measured using commercial kits. B. abortus-infected microglia exhibit Neu activity on their cell membrane, which was significantly inhibited by Oseltamivir (p<0.05). Moreover, neuronal phagoptosis induced by B. abortus-activated microglia was inhibited by Oseltamivir (p<0.05) indicating that the desialylation of neuronal membrane sugars is involved in this phenomenon. Tacrolimus was also able to inhibit neuronal death induced by infected microglia (p<0.05). Microglia from Gal-3-deficient mice infected with B. abortus were unable to induce neuronal death, when compared with microglia from wild-type mice (p<0.05). In all cases microglia activation was not affected, since TNF-α secretion was not significantly different between treatments (p>0.05). These results demonstrate that Gal-3 and neuraminidase activity would be necessary for the neuronal death mediated by B. abortus-activated microglia, describing new molecular mechanisms involved in the pathogenesis of neurobrucellosis.