Macrophage Control of Mycobacterial Growth Induced by Picolinic Acid Is Dependent on Host Cell Apoptosis

Abstract

The effects of picolinic acid (PA) on the intramacrophagic growth of Mycobacterium avium were studied. PA reduced M. avium growth inside mouse macrophages and led to a complete control of mycobacterial growth when added together with IFN-γ. The mechanism involved did not require TNF-α, NO, or the respiratory burst, and was not dependent on either iron or zinc withholding. The mycobacteriostatic activity of the macrophages was associated with the induction of morphological changes that culminated in apoptosis at day 4 of treatment. PA alone induced apoptosis in macrophages, and this effect was increased by IFN-γ treatment. Apoptosis at day 4 of infection was reduced by inhibiting macrophage activation with the prostaglandin 15 deoxy-prostaglandin J2 or by treating the cells with the antioxidant N-acetylcysteine. Mycobacterial growth was partially restored in macrophages treated with PA and IFN-γ when 15 deoxy-prostaglandin J2 was added, concomitant with a delay in apoptosis. N-Acetylcysteine or glutathione could also completely revert the mycobacteriostatic effects of PA or PA plus IFN-γ.

Induction of Mycobacterium avium growth restriction and inhibition of phagosome–endosome interactions during macrophage activation and apoptosis induction by picolinic acid plus IFNγ

“…In addition, there is an increase in the catabolism of tryptophan in humans infected with HIV, Mycobacterium tuberculosis and Salmonella (Fuchs et al, 1990;Wannemacher, 1977) and high levels of PA have been detected in the cerebrospinal fluids of children with cerebral malaria (Medana et al, 2003). We have previously described that the treatment of mouse macrophages with PA in the presence of IFNc makes these phagocytes able to completely inhibit the replication of virulent M. avium (Pais & Appelberg, 2000). The induction of anti-M. avium activity was closely associated with the induction of apoptosis which occurred over a protracted period of a few days.…”

“…However, confocal microscopy requires that cells remain associated with the slide. We next studied the effect of N-acetylcysteine, an inhibitor of the bacteriostasis induced by PA plus IFNc (Pais & Appelberg, 2000) on the interactions between phagosomes and endosomes. N-Acetylcysteine restored the fusion pattern between M. avium vacuoles and TMR-dextrancontaining vesicles in treated macrophages (Fig.…”

“…Phosphatidylserine (PS) exposure. PS externalization was quantified by annexin V staining as described previously (Pais & Appelberg, 2000). Briefly, at day 4 of infection, non-adherent and adherent macrophages were pooled and 2610 5 -5610 5 cells were incubated in 100 ml binding buffer (10 mM HEPES buffer containing 0?14 mM NaCl and 2?5 mM CaCl 2 , pH 7?4) containing 2?5 ml annexin V-FITC (BD Biosciences) for 20 min in ice.…”

“…M. avium. Cells were left untreated, treated with PA plus IFNc or incubated with 50 mM N-acetylcystein as described previously (Pais & Appelberg, 2000). Macrophages were loaded with 1?5 mg TMR-dextran ml 21 for 6 h (Heinzen et al, 1996) at different time points of infection.…”

Picolinic acid- or desferrioxamine-inducible autocrine activation of macrophages engineered to produce IFNγ: an approach for gene therapy

“…Furthermore, the induction of apoptosis may contribute to the destruction of mycobacteria, as shown in PAtreated Mf. 28 PA can be used pharmacologically and it has been tested on human patients as a chelating agent. 29 Furthermore, PA is a molecule that can be produced in pathological tissues.…”