Brucella abortus Induces Collagen Deposition and MMP-9 Down-Modulation in Hepatic Stellate Cells via TGF-β1 Production

Abstract

In patients with active brucellosis, the liver is frequently affected by histopathologic lesions, such as granulomas, inflammatory infiltrations, and parenchymal necrosis. Herein, we examine some potential mechanisms of liver damage in brucellosis. We demonstrate that Brucella abortus infection inhibits matrix metalloproteinase-9 (MMP-9) secretion and induces collagen deposition and tissue inhibitor of matrix metalloproteinase-1 secretion induced by hepatic stellate cells (LX-2). These phenomena depend on transforming growth factor-β1 induction. In contrast, supernatants from B. abortus-infected hepatocytes and monocytes induce MMP-9 secretion and inhibit collagen deposition in hepatic stellate cells. Yet, if LX-2 cells are infected with B. abortus, the capacity of supernatants from B. abortus-infected hepatocytes and monocytes to induce MMP-9 secretion and inhibit collagen deposition is abrogated. These results indicate that depending on the balance between interacting cells and cytokines of the surrounding milieu, the response of LX-2 cells could be turned into an inflammatory or fibrogenic phenotype. Livers from mice infected with B. abortus displayed a fibrogenic phenotype with patches of collagen deposition and transforming growth factor-β1 induction. This study provides potential mechanisms of liver immune response induced by B. abortus-infected hepatic stellate cells. In addition, these results demonstrate that the cross talk of these cells with hepatocytes and macrophages implements a series of interactions that may contribute to explaining some of mechanisms of liver damage observed in human brucellosis.

The Effector Protein BPE005 from Brucella abortus Induces Collagen Deposition and Matrix Metalloproteinase 9 Downmodulation via Transforming Growth Factor β1 in Hepatic Stellate Cells

“…B. abortus infection inhibits basal levels of MMP-9 secretions and induces collagen deposition and TIMP-1 secretion by hepatic stellate cells. These phenomena were dependent on TGF-␤1 induction (16). As occurs in other bacterial infections (41,42), a fibrotic phenotype may contribute to the persistence of infection, leading to poor penetration of antibiotics and immune mediators into the lesion.…”

“…In this context, hepatic stellate cells have a fundamental role in tissue homeostasis and injury repair through the production of extracellular matrix proteins (33). We have demonstrated that infection of LX-2 cells with Brucella inhibits the spontaneous secretion of MMP-9 (as determined by ELISA and by measurement of its activity by zymography) and induces collagen deposition (16). To determine whether intracellular replication is critical for inhibition of MMP-9 secretion and for induction of collagen deposition, experiments were performed using the B. abortus virB10 mutant and the RB51 rough mutant.…”

“…Collagen deposition was quantified using Sirius red (Sigma-Aldrich, Argentina), a strong anionic dye that binds strongly to collagen molecules (28). Sirius red staining was performed as previously described (16).…”

“…These phenomena were dependent on TGF-␤1 induction (16). However, the molecular mechanisms exerted by Brucella to activate this fibrogenic phenotype of HSCs have not yet been identified.…”

Fever-range hyperthermia improves the anti-apoptotic effect induced by low pH on human neutrophils promoting a proangiogenic profile

“…60 Briefly, 50  μ l of neutrophil supernatants (1 × 10 6 cells/ml) were mixed with 10  μ l of 5 × loading buffer (0.25 M Tris pH 6.8, 50% glycerol, 5% SDS, and bromophenol blue crystals) and loaded onto 10% SDS-PAGE gels containing 1 mg/ml gelatin (Sigma-Aldrich). Following electrophoresis, gels were washed using a solution with 50 mM Tris-HCl, pH 7.5, and 2.5% Triton X-100 (buffer A) for 30 min.…”