Lysophosphatidic acid enhances antimycobacterial activity both in vitro and ex vivo.

Lysophosphatidic acid (LPA) is a polar lipid metabolite which is involved in a wide range of biological processes, including cell proliferation and migration, wound healing, and increase of endothelial permeability. The present study reports evidences showing that LPA is able to enhance the antimicrobial activity of human macrophages and of bronchoalveolar lavage cells from tuberculosis patients leading to intracellular growth control of Mycobacterium tuberculosis. Such antimicrobial activity is mediated by the activation of phospholipase D which in turn induces acidification of M. tuberculosis containing phagosomes and is associated with the enhanced expression of Cathepsin D. These results suggest the possible protective role of this lysophospholipid in the activation of innate antimycobacterial response.

Expansion of CCR5+ CD4+ T-lymphocytes in the course of active pulmonary tuberculosis.

Nonsyncytium inducing, macrophage tropic HIV strains predominate in the course of active tuberculosis (TB). The present study assesses the expression of CCR5 in CD4+ T-lymphocytes from blood and bronchoalveolar lavage (BAL) of TB patients, non-TB lung disease controls and healthy controls. Memory (CD45RO+), recently activated (CD69+), proliferating (Ki67+) CCR5+ or CCR3+ CD4+ T-lymphocytes were determined by multiparametric flow cytometry analysis. Results show that BAL CD4+ T-lymphocytes expressing CCR5 or CCR3 were significantly increased when compared to peripheral blood both in patients and in healthy controls. However, the data show that the proportions of peripheral blood CCR5+ CD4+ and CCR3+ CD4+ T-lymphocytes and BAL CCR5+ CD4+ T-lymphocytes, but not BAL CCR3+ CD4+ T-lymphocytes, were significantly increased in TB patients. Furthermore, the observation that BAL CCR5+ CD4+ T-lymphocytes from TB patients expressed early activation markers, were not proliferating and showed down-regulation of CCR5 expression suggests recruitment and trapping at the site of disease. Altogether, these results suggest that the lower respiratory tract mucosa may provide cellular targets accessible for efficient transmission of macrophage tropic HIV-1 variants and that tuberculosis may enhance this phenomenon.

Batimastat reduces Mycobacterium tuberculosis-induced apoptosis in macrophages.

In this study, we report evidences that Mycobacterium tuberculosis (MTB)-induced apoptosis in macrophages is reduced by a broad-spectrum hydroxamic acid-based matrix metalloproteinase (MMP) inhibitor, Batimastat (BB-94). In particular, we show that BB-94 administration to MTB-infected macrophages inhibits apoptosis and the downmodulation of membrane CD14 expression. Moreover, the addition of broad spectrum matrix metalloproteinase inhibitor to cell culture, during MTB infection, decreases the release of soluble TNF-alpha and leads to a simultaneous increase of membrane TNF-alpha. These results show that MTB-induced apoptosis in macrophages is reduced by a MMP inhibitor and most probably is related to TNF-alpha release. This identifies BB-94 as a simultaneous anti-apoptotic and anti-inflammatory molecule during MTB infection.

Proinflammatory cytokines in the course of Mycobacterium tuberculosis-induced apoptosis in monocytes/macrophages.

Mycobacterium tuberculosis (MTB) can induce apoptosis in monocytes/macrophages both in vitro and in vivo, and this phenomenon is associated with mycobacterial survival. The present study addresses the possibility that apoptotic and inflammatory pathways could coexist through a caspase-1-mediated mechanism. In this context, a caspase-1 inhibitor (YVAD), but not caspase-3 (DEVD) or caspase-4 (LEVD) inhibitors, was able to strongly inhibit MTB-induced apoptosis. Moreover, caspase-1 activity was confirmed by the increased maturation of interleukin (IL)-1beta. Of interest, IL-1beta and tumor necrosis factor (TNF)-alpha were produced massively in the course of infection, and both were inhibited by YVAD pretreatment. To determine whether TNF-alpha was produced actively by apoptotic cells, the intracytoplasmatic cytokine content and apoptotic phenotype were analyzed at the single-cell level. Results showed a progressive increase of TNF-alpha production in annexin V-positive cells. These results indicate that MTB-induced apoptosis is associated with proinflammatory cytokine production.

Mycobacterium tuberculosis-induced apoptosis in monocytes/macrophages: early membrane modifications and intracellular mycobacterial viability.

Apoptosis has been observed in monocytes/macrophages in the course of in vivo and in vitro Mycobacterium tuberculosis (MTB) infection. In order to define the early events of MTB-induced apoptosis, membrane CD14 expression and the exposure of Annexin V-binding sites in MTB-infected monocytes/macrophages have been monitored. Moreover, the role of MTB-induced apoptosis was further analyzed in vitro in terms of mycobacterial viability. Results show that monocyte/macrophage apoptosis is a very early event that is strictly dependent on the MTB amount, and this apoptosis is associated with a selective down-regulation of surface CD14 expression. Furthermore, no statistically significant decrease in mycobacterial viability was observed, which indicates that the apoptotic pathway triggered by high doses of MTB is associated with parasite survival rather than with killing of the parasite.