Brucella abortus promotes a fibrotic phenotype in hepatic stellate cells with concomitant autophagy pathway activation.
Arriola Benitez, P. C., Pesce Viglietti, A. I., Herrmann, C. K., Dennis, V. A., Comerci, D. J., Giambartolomei, G. H. and Delpino, M. V.
Instituto de Inmunologia, Genetica y Metabolismo (INIGEM). CONICET. Universidad de Buenos Aires. Buenos Aires, Argentina.
Instituto de Investigaciones Biotecnologicas Dr. Rodolfo A. Ugalde (IIB-INTECH) CONICET, Universidad Nacional de San Martin, Buenos Aires, Argentina .
Center for NanoBiotechnology Research, Alabama State University, Montgomery, AL 36104.
The liver is frequently affected in patients with active brucellosis. The present study demonstrates that B. abortus infection induces the activation of the autophagic pathway in hepatic stellate cells to create a microenvironment that promote a profibrogenic phenotype through the induction of transforming growth factor-beta1 (TGF-beta1), collagen deposition and inhibition of matrix metalloproteinase-9 (MMP-9) secretion. Autophagy was revealed by up-regulation of the LC3II/LC3I ratio and beclin-1 expression as well as inhibition of p62 expression in infected cells. The above findings were dependent on the type IV secretion system (VirB) and the secreted BPE005 protein; which were partially corroborated using the pharmacological inhibitors wortmannin - a PI3-kinase inhibitor - and leupeptin plus E64 (inhibitors of lysosomal proteases). Activation of the autophagic pathway in hepatic stellate cells during Brucella infection could have an important contribution in attenuating inflammatory hepatic injury by inducing fibrosis. However, with time, B. abortus infection induced beclin-1 cleavage with concomitant cleavage of caspase-3 indicating the onset of apoptosis of LX-2 cells, as was confirmed by the TUNEL assay and Hoechst staining. These results demonstrate that the crosstalk of LX-2 cells and B. abortus induces autophagy and fibrosis with concomitant apoptosis of LX-2 cells, which may explain some potential mechanisms of liver damage observed in human brucellosis.
Infection and Immunity : en prensa (2017)