Novel isoniazid derivative as promising antituberculosis agent.

Background: A major focus of tuberculosis drug discovery is aimed at the development of novel antibiotics with activity against drug-resistant strains of Mycobacterium tuberculosis. Results: We have synthesized ten isoniazid derivatives and investigated for antibacterial activity toward M. tuberculosis H37Rv and isoniazid-resistant strain SRI 1369. It was revealed that only one compound, isonicotinic acid (1-methyl-1H-pyrrol-2-ylmethylene)-hydrazide (1), is active toward isoniazid-resistant strain with minimum inhibitory concentration value of 0.14 µM. This compound is not cytotoxic toward human liver cells (HepG2; IC50 >100 µM), demonstrates good permeability in Caco-2 cells. Accordingly to the results of plasma protein binding assay, unbound fraction of compound 1, which potentially exhibits pharmacologic effects, is 57.9%. Conclusion: Therefore, isonicotinic acid (1-methyl-1H-pyrrol-2-ylmethylene)-hydrazide is a promising compound for further preclinical studies.

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.

Therapeutic potential of thymoquinone against anti-tuberculosis drugs induced liver damage.

Hepatotoxicity is the most serious adverse effect related to tuberculosis treatment which interrupts the successful completion of tuberculosis treatment. The purpose of this study was to assess therapeutic effect of thymoquinone (TQ) against anti-tuberculosis drugs (ATD) induced liver damage. Rats were treated with ATD for 8 weeks (3 days/week) as given for the treatment of TB. This was followed by therapy of TQ for 8 weeks (3 days/week). Administration of combined ATD induced hepatotoxicity was evident from a significant elevation in the AST, ALT, ALP, bilirubin, albumin, cholesterol, urea, uric acid, creatinine, LPO and decreased activities of enzymes. These altered variables were significantly reversed toward control after treatment with TQ. Histological studies also supported biochemical findings. Results of this study strongly indicated protective effect of TQ and thus, can be expected as promising protective agent in maintenance of normal hepatic function during treatment with ATD.

High throughput screening of a library based on kinase inhibitor scaffolds against Mycobacterium tuberculosis H37Rv.

Kinase targets are being pursued in a variety of diseases beyond cancer, including immune and metabolic as well as viral, parasitic, fungal and bacterial. In particular, there is a relatively recent interest in kinase and ATP-binding targets in Mycobacterium tuberculosis in order to identify inhibitors and potential drugs for essential proteins that are not targeted by current drug regimens. Herein, we report the high throughput screening results for a targeted library of approximately 26,000 compounds that was designed based on current kinase inhibitor scaffolds and known kinase binding sites. The phenotypic data presented herein may form the basis for selecting scaffolds/compounds for further enzymatic screens against specific kinase or other ATP-binding targets in Mycobacterium tuberculosis based on the apparent activity against the whole bacteria in vitro.

Inhibitors of an essential mycobacterial cell wall lipase (Rv3802c) as tuberculosis drug leads.

The first targeted inhibitors of an essential M. tuberculosis cell wall lipase, Rv3802c, are described. Lead compounds exhibited nanomolar inhibition of the enzyme, and encouraging antibacterial activity against M. tuberculosis in vitro, supporting Rv3802c as a novel TB drug target.

Role of oxidative stress and nitric oxide in the protective effects of alpha-lipoic acid and aminoguanidine against isoniazid-rifampicin-induced hepatotoxicity in rats.

Despite the great efficacy of isoniazid (INH) and rifampicin (RIF) combination, in the treatment of tuberculosis, hepatotoxicity is the most common serious complication. The potential protective effect of alpha-lipoic acid and aminoguanidine; against combination-induced hepatotoxicity was investigated in the present study. Administration of INH-RIF combination (50 mg/kg each for 14 days) resulted in an elevation of serum hepatic marker enzymes and a significant increase in lipid profile parameters. Combinations treatment increased lipid peroxidation products, decreased glutathione content, superoxide dismutase, catalase and myeloperoxidase activities. Furthermore, liver total nitrite level was significantly increased in INH-RIF treated rats. Co-administration of either alpha-lipoic acid or aminoguanidine significantly ameliorate combination-induced alterations in hepatic marker enzymes. These effects were directly linked to a greater decrease in the combination-induced elevation in lipid peroxidation products and total nitrite levels. Furthermore, co-administration of alpha-lipoic acid and aminoguanidine restore superoxide dismutase, catalase and myeloperoxidase activities and maintained the imbalance in the glutathione level. Additionally, such beneficial effect of alpha-lipoic acid was linked to a marked lipid-lowering effect. Histopathological examination revealed preservation of liver integrity of the protected groups compared to combination-treated rats alone.

Investigation of rifampicin-induced hepatotoxicity in rat hepatocytes maintained in gel entrapment culture.

Rifampicin-induced hepatotoxicity has been well recognized in animals and patients. However, it is undetectable in cultured hepatocyte monolayers in vitro at the equivalent toxic concentration in vivo. This study investigated the rifampicin-induced toxicity on rat hepatocytes in gel entrapment vs. in monolayer culture. Thiazolyl tetrazolium reduction and albumin secretion were routinely detected to identify the toxic responses of rat hepatocytes to rifampicin, while reactive oxygen species (ROS) accumulation and intracellular glutathione (GSH) content were assayed as biomarkers of oxidative stress. In addition, Nile red staining and malondialdehyde (MDA) generation were, respectively, used as endpoints for lipid accumulation and peroxidation. After treatment of hepatocytes for 96 h at a serum rifampicin concentration (12 microM), gel-entrapped rat hepatocytes showed significant cellular damage indicated by alternations of all parameters indicated above, while hepatocyte monolayers did not show severe responses. In contrast to a lack of protections by cytochrome P 450 inhibitors, the ROS scavenger (glycyrrhizic acid) and thiol compounds (N-acetylcysteine and GSH) significantly reduced rifampicin toxicity in gel-entrapped hepatocytes. It appears that gel-entrapped rat hepatocytes reflected significant hepatotoxicity of rifampicin in vivo, and this toxicity was most possibly associated with oxidative stress and lipid accumulation.

Effect of antitubercular medications on blood pressure control in chronic kidney disease patients with tuberculosis: a prospective cohort study.

BACKGROUND: Previous anecdotal reports suggested a decrease in antihypertensive medication potency after starting antitubercular medications. This interaction could be unpredictable in presence of renal failure due to increased half-lives of most commonly used antihypertensive medications. METHODS: In a cohort study involving 135 patients with chronic kidney disease (CKD), 62 patients with tuberculosis star-ted on antitubercular medications (TB group) were prospectively compared with 73 CKD controls (with no TB and not on antitubercular medications) for a change in antihypertensive medications. Antihypertensive dose was converted to unit score. RESULTS: The TB group had a greater increase in antihypertensive medication dose as compared with controls (89% vs. 54%, p<0.0001). In absolute terms an overall increase in antihypertensive medications was observed in 60% of pa-tients in the TB group, with a 2-fold dose increase from the baseline (p<0.0001). Four patients from the TB group de-veloped a hypertensive emergency. In multivariate linear regression, the association between TB group and increase in antihypertensives remained significant ( beta =0.38; p<0.0001). CONCLUSIONS: In CKD patients, antihypertensive medication potency is reduced in TB patients on antitubercular the-rapy in a significant number of patients, to a clinically significant degree with a potential risk for hypertensive emergency.

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.

Terminalia chebula (fruit) prevents liver toxicity caused by sub-chronic administration of rifampicin, isoniazid and pyrazinamide in combination.

Terminalia chebula Gertn. (Combetraceae) is an important herbal drug in Ayurvedic pharmacopea. In the present study, a 95% ethanolic extract of T. chebula (fruit) (TC extract), which was chemically characterized on the basis of chebuloside II as a marker, was investigated for hepatoprotective activity against anti-tuberculosis (anti-TB) drug-induced toxicity. TC extract was found to prevent the hepatotoxicity caused by the administration of rifampicin (RIF), isoniazid (INH) and pyrazinamide (PZA) (in combination) in a sub-chronic mode (12 weeks). The hepatoprotective effect of TC extract could be attributed to its prominent anti-oxidative and membrane stabilizing activities. The changes in biochemical observations were supported by histological profile.

Salicylate reduces susceptibility of Mycobacterium tuberculosis to multiple antituberculosis drugs.

Salicylate induces multiple antibiotic resistance in various bacterial species. Here we investigated the effect of salicylate on the susceptibility of Mycobacterium tuberculosis to a range of antituberculosis (anti-TB) drugs. In the presence of salicylate, the killing effects of isoniazid (INH), rifampin (RMP), ethambutol (EMB), streptomycin (STR), and p-aminosalicylate (PAS) were reduced, as shown with a tetrazolium redox dye viability assay and a bacterial survival assay. Salicylate-induced resistance was more pronounced for PAS, STR, and EMB but was not apparent for INH and RMP when salicylate and the anti-TB agents were incorporated into 7H11 plates. The significance of these findings for TB treatment needs to be further evaluated in vivo.

[The monitoring of the drug resistance of the causative agent of tuberculosis in Russia in 1979-1998]. / Monitoring lekarstvennoi ustoichivosti vozbuditelia tuberkuleza v Rossii za 1979--1998 gg.

The Russian 1979-1998 annual reports of the centralized microbiology laboratories of the tuberculosis controlling service were used to examine the pattern and trends of formation of drug-resistance in the tuberculosis pathogen. The data on over 1.2 million cases of drug resistance to 7 antituberculous drugs were pooled. The analysis indicated that drug resistance had increased in two steps in the past 2 decades. The maximum levels of the drug resistance of Mycobacterium tuberculosis to some drugs were limited (7.8 and 37.2%), which are not greater those as indicated by the international statistics.

[Drug resistance in Mycobacterium tuberculosis. A multicenter study of the Barcelona area. Grupo de Trabajo sobre Resistencias en Tuberculosis]. / Farmacorresistencia de Mycobacterium tuberculosis. Estudio multicéntrico en el area de Barcelona. Grupo de Trabajo sobre Resistencias en Tuberculosis.

BACKGROUND: The aims of this multicenter study was to establish the level of primary and acquired drug resistance of M. Tuberculosis strains isolated in Barcelona and to identify possible risk groups using clinical data. PATIENTS AND METHODS: All tuberculosis patients with isolation and identification of M. tuberculosis strains from October 1995 to September 1997 were included. Susceptibility tests isoniazid, rifampin, ethambutol, streptomycin and pyrazinamide were performed using the Bactec 460 system and the proportions method on solid medium. Logistic progression was used for statistical analysis. RESULTS: The total number of patients included was 1,749 (1,535 non-treated and 214 previously treated). Primary drug resistance was 5.7% (isoniazid 3.8%; rifampin 1.0%, streptomycin 2.1%, ethambutol 0.3% and pyrazinamide 1.0%). Acquired drug resistance was 20.5% (isoniazid 17.3%, rifampin 9.8%, ethambutol 1.9%, streptomycin 4.7% and pyrazinamide 6.5%). Primary drug resistance was associated with people over 60 years old and women. CONCLUSIONS: The low level of drug resistance enables antituberculosis treatment of non-treated patients to start with the standardised three-drug regimes except in the case of foreign people from countries with a high level of drug resistance. Susceptibility tests are recommended on all M. tuberculosis strains isolated, together with controlled studies of drug resistance surveillance.

[The resistance of atypical mycobacteria to antitubercular preparations]. / Stiikist' atypovykh mikobakterii do protytuberkul'oznykh preparativ.

The atypical mycobacteria isolated from patients of the Lviv regional phthisio-pulmonary center who recovered from 1986 till 1995 have been analysed. The increase of the number of primary isolated atypical mycobacterial species, the increase of the number of strains resistant to antituberculosis drugs among them and growth of their multiple resistance to main antituberculosis drugs were established.