Background
Central nervous system (CNS) invasion by bacteria of the genus Brucella
Conclusions
Our results indicate that the inflammatory response elicited by B. abortus in astrocytes would lead to the production of MMP-9 and that MAPK may play a role in this phenomenon. MAPK inhibition may thus be considered as a strategy to control inflammation and CNS damage in neurobrucellosis.
Methods
In this study, the molecular mechanisms that regulate MMP secretion from Brucella-infected astrocytes in vitro were investigated. MMP-9 was evaluated in culture supernatants by ELISA, zymography and gelatinolytic activity. Involvement of mitogen-activated protein kinases (MAPK) signaling pathways was evaluated by Western blot and using specific inhibitors. The role of TNF-α was evaluated by ELISA and by assays with neutralizing antibodies.
Results
B. abortus infection induced the secretion of MMP-9 from murine astrocytes in a dose-dependent fashion. The phenomenon was independent of bacterial viability and was recapitulated by L-Omp19, a B. abortus lipoprotein model, but not its LPS. B. abortus and L-Omp19 readily activated p38 and Erk1/2 MAPK, thus enlisting these pathways among the kinase pathways that the bacteria may address as they invade astrocytes. Inhibition of p38 or Erk1/2 significantly diminished MMP-9 secretion, and totally abrogated production of this MMP when both MAPK pathways were inhibited simultaneously. A concomitant abrogation of B. abortus- and L-Omp19-induced TNF-α production was observed when p38 and Erk1/2 pathways were inhibited, indicating that TNF-α could be implicated in MMP-9 secretion. MMP-9 secretion induced by B. abortus or L-Omp19 was completely abrogated when experiments were conducted in the presence of a TNF-α neutralizing antibody. MMP-9 activity was detected in cerebrospinal fluid (CSF) samples from patients suffering from neurobrucellosis. Conclusions: Our results indicate that the inflammatory response elicited by B. abortus in astrocytes would lead to the production of MMP-9 and that MAPK may play a role in this phenomenon. MAPK inhibition may thus be considered as a strategy to control inflammation and CNS damage in neurobrucellosis.