The activation of human brain microvascular endothelial cells by Brucella abortus-infected glial cells is mediated by IL-1beta.

MIRAGLIA MC; SILVA COSTA FRANCO MM; RODRÍGUEZ AM; BARRIONUEVO P; DELPINO MV; OLIVEIRA SERGIO C; GIAMBARTOLOMEI GH

Mar del Plata

Congreso; LXII Reunión Científica Anual de la Sociedad Argentina de Inmunología.; 2014

Sociedad Argentina de Inmunologia

B. abortus can interact with human brain microvascular endothelial cells (HBMEC) and gain access to the central nervous system consequently eliciting the inflammatory pathology named neurobrucellosis. We have recently demonstrated that although B. abortus can infect HBMEC, the indirect effect of glial cells infected with the bacterium is more effective in activating the endothelium. Both, TNF-alpha and IL-1beta secreted by glial cells were reported to mediate HBMEC activation. Since we have demonstrated that these cytokines were secreted by B. abortus-infected astrocytes and microglia, we decided to investigate their role in activation of HBMEC (cytokine secretion ad expression of adhesion molecules). Supernatants from B. abortus-infected astrocytes and microglia induced the production of IL-6, IL-8 and MCP-1 and up-regulated the expression of ICAM-1 on HBMEC. When HBMEC were stimulated with culture supernatants of B. abortus-infected astrocytes and microglia from CASP-1 and ASC KO mice (unable to produce IL-1beta), cytokine production and ICAM-1 expression was completely inhibited (p 0.001 vs. WT). Neutralization of TNF-alpha had no effect on glial cells induced HBMEC activation. The involvement of ASC in glial cells-induced HBMEC activation indicated that IL-1beta secretion proceeds via the inflammasome. The activation of this complex requires a first signal which is usually triggered via TLR. Secretion of IL-6, IL-8 and MCP-1 and ICAM-1 expression was completely inhibited (p 0.001) when HBMEC were stimulated with culture supernatants of B. abortus-infected astrocytes and microglia from MAL/ TIRAP and TLR2 KO mice. On the contrary supernatants from TLR4 or TLR6 glial cells induced the same level of activation of HBMEC than supernatants from wild type cells. Our results demonstrate that glial cells-secreted IL-1beta induced by the infection of B. abortus mediates activation of HBMEC. They also show that TLR2 and ASC/CASP mediate IL-1beta production in B. abortus-infected glial cells.