C5a modulation of Mtb-induced ROS production in human monocytes

CARMEN SABIO Y GARCÍA; NOEMÍ YOKOBORI; JUAN BASILE; BEATRIZ LÓPEZ; SILVIA DE LA BARRERA; MARÍA DEL CARMEN SASIAIN

Keystone

Simposio; Novel Therapeutic Approaches to Tuberculosis; 2014

Keystone Symposia

Tuberculosis (TB) remains a serious global health problem, aggravated by the appearance of multidrug resistant strains (MDR). In Argentina, the TB cases reported in 2011 were of 23.61/100.000 inhabitants; and between 2003 and 2011, an average of 118 of all cases were due to MDR strains. Mycobacterium tuberculosis (Mtb) is engulfed by phagocytic cells, where this pathogen can survive and replicate by altering the bactericidal mechanisms of these defense cells. Phagocytosis can be facilitated by Mtb complement system (C) activation. Indeed, C activation products are elevated in pleural effusions from tuberculosis patients. C5a C anaphylatoxin activates oxidative burst in neutrophils and macrophages. In this sense, macrophages from C5-deficient mice have a reduced bactericidal response against Mtb owing to a defective reactive oxygen species (ROS) production. In this work, we studied the C5a modulation of ROS production induced by gamma-irradiated H37Rv in human monocytes (Mo), and compared the results with the data obtained with two Argentinean outbreak clinical isolates: Ra and M. In addition, we evaluated the participation of TLR2 and TLR4 in H37Rv induction of ROS and a possible crosstalk with C5a receptors. We found that H37Rv, M and Ra induced ROS production (p<0.05) dose-dependently, being H37Rv the greater inducer. In addition, the three induced local production of C5a by Mo also in a dose-dependent way (p<0.05). Exogenously added recombinant C5a (rC5a) increased H37Rv-induced ROS production (p<0.05), and the same tendency was observed with M and Ra. Preliminary results demonstrated that TLR2 blockage reduced the H37Rv-induced ROS production (p<0.05) and the addition of rC5a could not revert this reduction (p~0.5). TLR4 blockage also tended to diminish H37Rv-induced ROS production. However, the addition of rC5a in this case seemed to partially revert this reduction. We conclude that the Mtb-induced ROS production in Mo is strain dependent and that rC5a addition increases ROS production. Furthermore, signaling through C5a receptors seems to be connected with TLR2 pathway, as TLR2 blockage also blocked rC5a-induced ROS increment.