Affinity labeling of catechol O-methyltransferase by N-haloacetyl derivatives of 3,5-dimethoxy-4-hydroxyphenylethylamine and 3,4-dimethoxy-5-hydroxyphenylethylamine. Kinetics of inactivation.

In an attempt to elucidate the relationship between the chemical structure and the catalytic function of catechol O-methyltransferase (COMT), several classes of affinity labeling reagents have been synthesized and their interaction with COMT has been studied. Earlier studies have shown that various N-haloacetyl derivatives of 3,5-dimethoxy-4-hydroxyphenylethylamine were effective affinity labeling reagents for this enzyme. In this report we have shown that N-haloacetyl derivatives of the isomeric 3,4-dimethoxy-5-hydroxyphenylethylamine also rapidly and irreversibly inactivate COMT ant they satisfy many of the criteria established for affinity labeling reagents. This latter group of agents appear to modify a nucleophilic residue at the active site of COMT different from that modified by the 3,5-dimethoxy-4-hydroxyphenylethylamine series. Evidence to support this conclusion has been obtained by comparing the kinetics of COMT inactivation and the substrate protection profiles for these two classes of affinity labeling reagents.     

Mycobacterial growth and ultrastructure in mouse L-929 fibroblasts and bone marrow-derived macrophages: Evidence that infected fibroblasts secrete mediators capable of modulating bacterial growth in macrophages

The intracellular growth kinetics ofMycobacterium avium and H37Rv (virulent) and H37Ra (avirulent) strains ofMycobacterium tuberculosis were compared by use of both the professional (mouse bone marrow-derived macrophages, BMMØ) and nonprofessional (mouse L-929 fibroblast cell line) phagocytes. The results obtained showed that all the mycobacterial strains grew more actively in fibroblasts than in BMMØ. This difference was paralleled by lesser acid phosphatase (AcP) labeling of noninfected fibroblasts and the observation that upon infection both the proportion of AcP-positive cells and AcP content were higher in BMMØ than in L-cells during the 7 days of infection. In parallel experiments, intracellular growth ofM. tuberculosis H37Rv andM. avium was compared inside BMMØ from both theBcg ^s (C57BL/6) andBcg ^r (DBA-2) mice, which were matured and differentiated with either an L-cell-conditioned medium (LCM) obtained from control, noninfected L-929 cells, or a LCM obtained withM. tuberculosis-orM. avium-infected L-cells. Upon mycobacterial infection, fibroblasts were able to secrete mediators that stimulated the BMMØ to better control the infection by pathogenic mycobacteria. These results are discussed in terms of the mycobacteria-fibroblast interactions and their eventual role in the immune modulation of the host's response to invading mycobacteria.     

In Vitro Activities of Fourteen Antimicrobial Agents Against Drug Susceptible and Resistant Clinical Isolates of Mycobacterium tuberculosis and Comparative Intracellular Activities Against the Virulent H37Rv Strain in Human Macrophages

Minimal inhibitory concentrations (MICs) of 14 first and second-line antituberculous drugs against drug-susceptible and drug-resistant clinical isolates of Mycobacterium tuberculosis (including the multiple drug-resistant or MDR-TB isolates), as well as the type strain H37Rv, were determined radiometrically by the Bactec 460-TB methodols. MICs (μg/ml) of all the fourteen drugs were within an extremely narrow range in case of susceptible strains; isoniazid (0.02–0.04), rifampin (0.2–0.4), ethambutol and streptomycin (0.5–2.0), ethionamide (0.25–0.5), D-cycloserine (25–75), capreomycin (1–2), kanamycin (2–4), amikacin (0.5–1.0), clofazimine (0.1–0.4), ofloxacin (0.5–1.0), ciprofloxacin (0.25–1.0), and sparfloxacin (0.1–0.4). The activity of second-line drugs remained unaltered against MDR-TB isolates resistant to routine first-line drugs. With peak serum level concentrations (Cmax), the intracellular killing of the virulent H37Rv strain was studied in detail in cultured human macrophages. Based on an decreasing order of bactericidal activity, our results showed the following spectrum of intracellular drug action: among the first-line drugs, rifampin > ethionamide = isoniazid > ethambutol > streptomycin > D-cycloserine; among second-line drugs, clofazimine = amikacin > kanamycin = capreomycin; among fluoroquinolones, sparfloxacin > ofloxacin > ciprofloxacin. On the other hand, contrary to atypical mycobacteria, the macrolide drug clarithromycin was inactive against both extracellular and intracellular M. tuberculosis. Received: 23 January 1996 / Accepted: 5 April 1996