Interaction of antimycobacterial drugs with the anti-Mycobacterium avium complex effects of antimicrobial effectors, reactive oxygen intermediates, reactive nitrogen intermediates, and free fatty acids produced by macrophages

Abstract

The profiles of the interaction of antimycobacterial drugs with macrophage (MPhi) antimicrobial mechanisms have yet to be elucidated in detail. We examined the effects of various antimycobacterial drugs on the anti-Mycobacterium avium complex (MAC) antimicrobial activity of reactive oxygen intermediates (ROIs), especially of an H(2)O(2)-halogen (H(2)O(2)-Fe(2+)-NaI)-mediated bactericidal system, reactive nitrogen intermediates (RNIs), and free fatty acids (FFAs), which are known as central antimicrobial effectors of host MPhis against mycobacterial pathogens. We have found that certain drugs, such as rifampin (RIF), rifabutin (RFB), isoniazid (INH), clofazimine (CLO), and some fluoroquinolones, strongly or moderately reduced the anti-MAC activity of the H(2)O(2)-Fe(2+)-NaI system, primarily by inhibiting the generation of hypohalite ions and in part by interfering with the halogenation reaction of bacterial cell components due to the H(2)O(2)-Fe(2+)-NaI system. This phenomenon is specific to the H(2)O(2)-Fe(2+)-NaI system, since these drugs did not reduce the anti-MAC activity of RNIs and FFAs. From the perspective of the chemotherapy of MAC infections, the present findings indicate an important possibility that certain antimycobacterial drugs, such as rifamycins (RIF and RFB), INH, CLO, and also some types of fluoroquinolones, may interfere with the ROI-mediated antimicrobial mechanisms of host MPhis against intracellular MAC organisms.

FIG. 1.

Effects of various antimicrobial drugs on the generation of hypohalite ions in the H₂O₂-Fe²⁺-NaI system, measured in terms of H₂O₂-HOI-mediated CL. Each test drug was added to the incubation mixture at a concentration of 10 μM. Each bar indicates the mean ± standard error of the mean (n = 3) of the relative CL intensity, when the value of the control incubation (without drug; 17,778 ± 371 cpm) was fixed to be 100%. *, value significantly smaller than the value of the control incubation (P < 0.01).

FIG. 2.

Effects of various antimicrobial drugs on the halogenation reaction caused by the H₂O₂-Fe²⁺-NaCl system. Chlorination of the substrate MCD added as a halogen acceptor was monitored by measuring the decrease in the absorbance at 278 nm (−ΔOD₂₇₈). Each test drug was added to the reaction mixture at a concentration of 10 μM. Each bar indicates the mean ± standard error of the mean (n = 3) of the relative value of −ΔOD₂₇₈, when the value of the control incubation (without drug; ca. −0.038/10 min.) was fixed to be 100%. The other details are the same as described in the legend of Fig. 1.

FIG. 3.

Effects of various antimicrobial drugs on the ROI-producing ability of MΦs, measured in terms of PMA-triggered luminol-dependent CL. Each test drug was added to the incubation mixture at a concentration of 10 μM. Each bar indicates the mean ± standard error of the mean (n = 3) of the relative MΦ CL, when the value of the control incubation (without drug; 22,264.7 ± 680.6 cpm) was fixed to be 100%. The other details are the same as described in the legend of Fig. 1.