A high content screening assay for identifying inhibitors against active and dormant state intracellular Mycobacterium tuberculosis.

The antitubercular drug development pipeline could start with an in vitro investigation of several compounds to examine their effect on active and dormant state Mycobacterium tuberculosis (Mtb). However, in vitro screening of dormant state bacilli cannot provide enough information on the simultaneous effect of a compound on the host. Therefore, we developed a live cell fluorescence based screening protocol by utilizing the high content system for determining the effect of inhibitors against active and dormant state intracellular mycobacteria. THP-1 macrophages infected with an actively growing and hypoxia derived dormant Mtb culture were standardized to develop the screening protocol. The signal to noise ratio and the Z' factor of this assay were found to be 7.5-29 and 0.6-0.8, respectively, which confirm the robustness of the protocol. The protocol was then validated with standard inhibitors. This newly developed drug screening assay offers an easy, safe, image based high content screening tool to search for novel antitubercular inhibitors against both active and dormant state intracellular mycobacteria. Therefore, this assay could fill in the gap between in vitro and in vivo latent tuberculosis drug screening programs.

Therapeutic Efficacy of Nigella Sativa Linn. against Antituberculosis Drug-Induced Hepatic Injury in Wistar Rats.

Antituberculosis drug (ATD)-induced hepatotoxicity is a major impediment for the effective treatment of tuberculosis (TB). All first-line anti-TB medications have adverse effects that interrupt the successful completion of TB treatment. This investigation focuses on the evaluation of the protective role of Nigella sativa (NS) against liver injury caused by ATDs. Female rats were treated with ATDs for 8 weeks (3 d/wk) followed by NS for 8 weeks (3 d/wk). The antioxidant activity of NS was estimated with a 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay and by analyzing total phenolic contents. Qualitative characterization of active compounds of the plant was done by high-performance liquid chromotography (HPLC). ATD-induced adverse effects were associated with sharp elevation in levels of serum transaminases, albumin, cholesterol, urea, uric acid, creatinine, and blood urea nitrogen (BUN). ATDs significantly increased lipid peroxidation (LPO) and decreased enzyme activities (superoxide dismutase [SOD], catalase [CAT], adenosine triphosphatase [ATPase], and glucose-6-phosphatase [G6Pase]) in liver, indicating oxidative stress. Conjoint treatment with NS could reverse the serological biochemistry and inhibit oxidative stress by suppressing LPO and augmenting antioxidant enzyme activity toward that of the control. Histological studies support the above biochemical findings. Results indicate that NS exerts excellent hepatoprotective abilities and can be used as a supplement to improve patient adherence and reduce interruptions in treatment due to ATD-related liver injury.

Pantothenate and pantetheine antagonize the antitubercular activity of pyrazinamide.

Pyrazinamide (PZA) is a first-line tuberculosis drug that inhibits the growth of Mycobacterium tuberculosis via an as yet undefined mechanism. An M. tuberculosis laboratory strain that was auxotrophic for pantothenate was found to be insensitive to PZA and to the active form, pyrazinoic acid (POA). To determine whether this phenotype was strain or condition specific, the effect of pantothenate supplementation on PZA activity was assessed using prototrophic strains of M. tuberculosis. It was found that pantothenate and other ß-alanine-containing metabolites abolished PZA and POA susceptibility, suggesting that POA might selectively target pantothenate synthesis. However, when the pantothenate-auxotrophic strain was cultivated using a subantagonistic concentration of pantetheine in lieu of pantothenate, susceptibility to PZA and POA was restored. In addition, we found that ß-alanine could not antagonize PZA and POA activity against the pantothenate-auxotrophic strain, indicating that the antagonism is specific to pantothenate. Moreover, pantothenate-mediated antagonism was observed for structurally related compounds, including n-propyl pyrazinoate, 5-chloropyrazinamide, and nicotinamide, but not for nicotinic acid or isoniazid. Taken together, these data demonstrate that while pantothenate can interfere with the action of PZA, pantothenate synthesis is not directly targeted by PZA. Our findings suggest that targeting of pantothenate synthesis has the potential to enhance PZA efficacy and possibly to restore PZA susceptibility in isolates with panD-linked resistance.

Isoniazid-induced hepatotoxicity in rat hepatocytes of gel entrapment culture.

Gel entrapment culture of rat hepatocytes in hollow fibers were evaluated as a potential in vitro model for studies on isoniazid-induced hepatotoxicity. After exposure to isoniazid (0.11 mM and 1.1 mM) for 24-96 h, gel entrapped hepatocytes were more severely damaged than hepatocyte monolayers according to the assays on methyl thiazolyl tetrazolium (MTT) reduction, intracellular glutathione (GSH) content, reactive oxygen species (ROS) levels, and albumin secretion. Furthermore, CYP 2E1 activity detected by 4-nitrocatechol (4-NC) formation maintained at least 7 days in gel entrapped hepatocytes but decreased to an undetectable level within 2 days in hepatocyte monolayer. And the addition of CYP 2E1 inhibitor, diethyl-dithiocarbamate (DDC), significantly reduced isoniazid-induced GSH depletion in gel entrapped hepatocytes. In addition, the protective effects of N-acetylcysteine (NAC), GSH, liquorice extract and glycyrrhizic acid (GA), a purified compound from liquorice extract, against isoniazid hepatotoxicity were clearly observed in gel entrapped hepatocytes at 72 h incubation. Overall, gel entrapped hepatocytes were more susceptible to isoniazid-induced hepatotoxicity than hepatocyte monolayers by a possible mechanism that higher CYP 2E1 activity in gel entrapped hepatocytes could enhance isoniazid toxicity. This indicates that gel entrapped hepatocytes in hollow fibers could be a more effective model than hepatocyte monolayer for hepatotoxicity research in vitro.

[The current situation of mycobacterial chemoresistance and its implications for antitubercular treatment]. / Situatia actuala a chimiorezistentei micobacteriene si implicatiile acesteia asupra tratamentului antituberculos.

The data in the present paper consider, for a longer period, the secondary and the initial drug resistance in pulmonary and extrapulmonary tuberculosis. The paper studies mainly the period of the last 9 years (1979-1987) in comparison with a previous period of 6 years (1973-1978). The 2,194 antibiograms performed for 7 common tuberculostatics show an increase, in the last years, of the general resistance of the germs from 24.3% to 36%. The increase of the resistance is noticed to all the tuberculostatics, but mainly to Rifampicin, from 14.8% to 49.3% and to streptomycin, from 22.7% to 44.8%. An important increase is found, at present, mainly in the drug resistance of germs in the extrapulmonary specimens (lymph nodes 28.5% and CSF 40%) to streptomycin and INH.