Brucella abortus induces collagen deposition and MMP-9 down-modulation in hepatic stellate cells via TGF-β1 production through a mechanism that is dependent on a functional type IV secretion system and its effector protein BPE005

ARRIOLA BENITEZ, PAULA CONSTANZA; HERRMANN, CLAUDIA; FOSSATI,C ALBERTO; COMERCI, DIEGO; GIAMBARTOLOMEI, GUILLERMO H; DELPINO, M. VICTORIA

Los Cocos, Córdoba.

Congreso; LXI Reunión Anual de la Sociedad Argentina de Inmunología; 2013

Sociedad Argentina de Inmunología

The liver is frequently affected in patients with active brucellosis. Previously, we demonstrated that B. abortus (Ba) inhibits the basal levels of MMP-9 secretion and induces collagen deposition and TIMP-1 secretion by hepatic stellate cells (LX-2). These phenomena were dependent on TGF-β1 induction. Since the type IV secretion system (virB) from Ba has been involved in the modulation of immune responses during infection, we decided to investigate whether the effect of Ba infection on LX-2 is dependent on a functional virB system and/or its putative secreted proteins (BPE123, BPE275 and BPE005). To this end, LX-2 were infected with Ba or its isogenic mutants. MMPs production was determined by gelatin zymography, collagen deposition by Sirius red staining and TGF-β1 secretion by ELISA. Our results indicated that virB or the BPE005 mutant were unable to inhibit MMP-9 secretion, concomitant collagen deposition and TGF-β1 induction, indicating that the mechanisms described involved the presence of a functional virB secretion system and the secretion of the BPE005 protein. Since BPE005 has homology with cyclic AMP binding proteins we attempt to revert its role by using butiril-cAMP. All phenomena were dependent on cAMP since they were reverted when we performed the infection with Ba in the presence of butiril-cAMP. We also determine the rol of PKA in the signaling pathway by using the inhibitor KT5720. Our results indicated that the PKA signaling pathway is also involved in the described phenomena on LX-2. The importance of this finding it that BPE005 could be the first reported effector with a proposed function for B. abortus. All together, these results indicate that Ba inhibit MMP-9 secretion inducing concomitant collagen deposition and TGF-β1 secretion in a way that involved a functional virB secretion system and the secreted protein BPE005 through a mechanisms that involved cAMP and PKA signaling pathway.