Keisuke Sano

Combined Effects of ATP on the Therapeutic Efficacy of Antimicrobial Drug Regimens against Mycobacterium avium Complex Infection in Mice and Roles of Cytosolic Phospholipase A2-Dependent Mechanisms in the ATP-Mediated Potentiation of Antimycobacterial Host Resistance

ATP, which serves as a mediator of intramacrophage signaling pathways through purinoceptors, is known to potentiate macrophage antimycobacterial activity. In this study we examined the effects of ATP in potentiating host resistance to Mycobacterium avium complex (MAC) infection in mice undergoing treatment with a drug regimen using clarithromycin and rifamycin and obtained the following findings. First, the administration of ATP in combination with the clarithromycin and rifamycin regimen accelerated bacterial elimination in MAC-infected mice without causing changes in the histopathological features or the mRNA expression of pro- or anti-inflammatory cytokines from those in the mice not given ATP. Second, ATP potentiated the anti-MAC bactericidal activity of macrophages cultivated in the presence of clarithromycin and rifamycin. This effect of ATP was closely related to intracellular Ca2+ mobilization and was specifically blocked by a cytosolic phospholipase A2 (cPLA2) inhibitor, arachidonyl trifluoromethylketone. Third, intramacrophage translocation of membranous arachidonic acid molecules to MAC-containing phagosomes was also specifically blocked by arachidonyl trifluoromethylketone. In the confocal microscopic observation of MAC-infected macrophages, ATP enhanced the intracellular translocation of cPLA2 into MAC-containing phagosomes. These findings suggest that ATP increases the host anti-MAC resistance by potentiating the antimycobacterial activity of host macrophages and that the cPLA2-dependent generation of arachidonic acid from the phagosomal membrane is essential for such a phenomenon.

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 (MΦ) 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 H2O2-halogen (H2O2-Fe2+-NaI)-mediated bactericidal system, reactive nitrogen intermediates (RNIs), and free fatty acids (FFAs), which are known as central antimicrobial effectors of host MΦs 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 H2O2-Fe2+-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 H2O2-Fe2+-NaI system. This phenomenon is specific to the H2O2-Fe2+-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 MΦs against intracellular MAC organisms.

Intramacrophage Passage of Mycobacterium tuberculosis and M. avium Complex Alters the Drug Susceptibilities of the Organisms as Determined by Intracellular Susceptibility Testing Using Macrophages and Type II Alveolar Epithelial Cells

ABSTRACT Mycobacterium tuberculosis and M. avium complex strains given intramacrophage passage (I-type) were compared with those cultured in a liquid medium (E-type) for their drug susceptibilities when they were replicating in Mono-Mac-6 macrophages or A-549 cells. Their intracellular susceptibilities to rifalazil, clarithromycin, and levofloxacin were decreased more in I-type organisms than in E-type organisms, except that their rifalazil susceptibility inside A-549 cells was markedly increased in I-type organisms.

Intracranial Invasion of an Extramedullary Plasmacytoma in the Paranasal Sinus: A Case Report with a Reference to Magnetic Resonance Imaging

A case of extramedullary plasmacytoma arising from the paranasal sinus with intracranial invasion at recurrence is reported. In this case, magnetic resonance imaging was first employed not only to delineate tumor extension into the cranial space, but also to evaluate the therapeutic response. Histological confirmation was made after a biopsy was performed. Despite widespread tumor involvement of orbit in the cavernous sinus and anterior skull base, radiotherapy and subsequent maintenance chemotherapy with cisplatin and etoposide induced a long-term, 42-month partial remission. The pertinent clinical characteristics are reviewed in the literature and the therapeutic problems and prognostic factors are discussed with an introduction of advantage of magnetic resonance imaging.