Role of hydrazine in the mechanism of isoniazid hepatotoxicity in rabbits

Medicinal chemistry aspects of fat mass and obesity associated protein: structure, function and inhibitors

Adiposity and obesity-related proteins (FTO), the earliest identified mRNA N6-methyladenosine (m6A) demethylases, are known to play crucial roles in several biological processes. Therefore, FTO is a promising target for anticancer treatment. Understanding the biological functions and regulatory mechanisms of FTO targets can serve as guidelines for drug development. Despite significant efforts to develop FTO inhibitors, no specific small-molecule inhibitors have entered clinical trials so far. In this manuscript, we review the relationship between FTO and various cancers, the small-molecule inhibitors developed against FTO targets from the perspective of medicinal chemistry and other fields, and describe their structural optimization process and structure-activity relationship, providing clues for their future development direction.

Old drug, new use: The thalidomide-based fluorescent probe for hydrazine detection

Thalidomide, a widely used ligand for cereblon (CRBN), has been gaining attention for its targeted protein degradation. In this study, we aimed to improve the optical and biocompatible features of hydrazine fluorescent probes by a novel probe called TH-1, based on the thalidomide moiety. Our results demonstrate that TH-1 exhibits remarkable properties including significant colorimetric changes, a fast response time, excellent selectivity, and high sensitivity as a hydrazine fluorescent probe. The mechanism by which TH-1 senses hydrazine has been convincingly verified. Notably, we have successfully applied TH-1 for bioimaging of hydrazine in living A549 cells, highlighting its practical significance. Moreover, the utilization of thalidomide, a clinically approved drug, as a fluorescent skeleton has expanded the repertoire of fluorescent skeleton libraries, paving the way for further on fluorescent probes.

Nutritional intervention is promising in alleviating liver injury during tuberculosis treatment: a review

Liver injury is a main adverse effect of first-line tuberculosis drugs. Current management of tuberculosis-drug-induced liver injury (TBLI) mainly relies on withdrawing tuberculosis drugs when necessary. No effective treatment exists. Various nutrients and functional food ingredients may play a protective role in TBLI. However, a comprehensive review has not been conducted to compare the effects of these nutrients and functional food ingredients. We searched Pubmed and Web of Science databases from the earliest date of the database to March 2023. All available in-vitro, animal and clinical studies that examined the effects of nutritional intervention on TBLI were included. The underlying mechanism was briefly reviewed. Folic acid, quercetin, curcumin, Lactobacillus casei, spirulina and Moringa oleifera possessed moderate evidence to have a beneficial effect on alleviating TBLI mostly based on animal studies. The evidence of other nutritional interventions on TBLI was weak. Alleviating oxidative stress and apoptosis were the leading mechanisms for the beneficial effects of nutritional intervention on TBLI. In conclusion, a few nutritional interventions are promising for alleviating TBLI including folic acid, quercetin, curcumin, L. casei, spirulina and M. oleifera, the effectiveness and safety of which need further confirmation by well-designed randomized controlled trials. The mechanisms for the protective role of these nutritional interventions on TBLI warrant further study, particularly by establishing the animal model of TBLI using the tuberculosis drugs separately.

A DFT study on non-enzymatic degradations of anti-tuberculosis drug isoniazid

CONTEXT

Isoniazid (INH) is one of the medications most used for tuberculosis (TB) treatment. However, long-term continuous therapy can cause hepatotoxicity and peripheral neuritis. The degradation of INH is an important aspect of the research in the field of drug stability as well as drug formulation for controlling release. It is thought that tautomerization, hydrolysis as well as nucleophilic substitutions can cause decrease in INH as non-enzymatic degradation. Therefore, it is crucial to understand the mechanisms and energies of the major reactions in order to provide reference for future drug formulation and application. This study is an effort to understand the kinetic and thermodynamic properties of the non-enzymatic degradation reactions. The chemical reaction phenomena are investigated using the density functional theory (DFT) method. This study shows that major degradation of INH can be done via tautomerization followed by hydrolysis. The general trends in nucleophilic degradation presented here are consistent with experimental pKa of nucleophiles.

METHODS

All DFT calculations were performed using the Gaussian Software Packages (Gaussian 09 revision B.01 and GaussView 5.0.8). MOLEKEL 4.3 software was utilized to visualize the molecular graphics of all relevant species. The optimized molecular geometries were calculated using B3LYP/6-311 + G(d,p) level in the gas phase. The IEF-PCM/B3LYP/6-311 + G(d,p) level was selected for single-point and frequency calculations in aqueous media.

Quantitative Analysis of Isoniazid and Its Four Primary Metabolites in Plasma of Tuberculosis Patients Using LC-MS/MS

Isoniazid and its metabolites are potentially associated with hepatotoxicity and treatment outcomes in patients who receive antituberculosis (TB) therapy. To further understand the pharmacokinetic profiles of these molecules, a method based on LC-MS/MS was developed to determine the concentration of these compounds in human plasma. Isoniazid, acetylisoniazid, and isonicotinic acid were directly analyzed, whereas hydrazine and acetylhydrazine were determined after derivatization using p-tolualdehyde. Chromatographic separation was conducted on reversed-phase C18 columns with gradient elution, and detection was carried out in multiple reaction monitoring mode. The calibration curves were linear with correlation coefficients (r) greater than 0.9947 for all analytes. The intra- and inter-day precision was less than 13.43%, and the accuracy ranged between 91.63 and 114.00%. The recovery and matrix effect of the analytes were also consistent (coefficient of variation was less than 9.36%). The developed method successfully quantified isoniazid and its metabolites in TB patients. The method has broad applications in clinical research, including isoniazid one-point-based therapeutic drug monitoring, genotype-phenotype association studies of isoniazid metabolic profile and isoniazid-induced hepatotoxicity, and the initial dose prediction of isoniazid using population pharmacokinetic modeling.

Evaluating the hepatoprotective, ameliorative and antioxidant potentials of the crude aqueous leafy extracts of Mangifera indica plant against acute paracetamol-induced hepatotoxicity in a mouse model

Background: Drug-induced hepatotoxicity is a major public health issue of concern. It significantly affects the development of new pharmaceutical drugs and has led to the withdrawal of many promising pharmaceutical drugs from the pharmaceutical market. Aim: The aim of this study was to evaluate the hepatoprotective, ameliorative and antioxidant effects of the crude aqueous leafy extract of Mangifera indica plant and its different separating medium fractions against acute acetaminophen (paracetamol)-induced hepatotoxicity in a mouse model. Methods & materials: Twelve different groups of six mice (three males and three females) were used for this study. Acetaminophen at a single lethal hepatotoxic dose of 3 g/kg was orally administered on the seventh day to the mice in groups 2 to 12 after their 6-day pretreatment duration for the induction of hepatotoxicity; and were then left for 24 hours before the collection of specimen samples were completed, while group 1 served as control. Results: The crude aqueous leafy extract of M. indica (125-250 mg/kg) produced a dose-dependent reversal of the lethal hepatotoxic effect of oral 3 g/kg dose of paracetamol. At the dose of 250 mg/kg, it significantly (p < 0.0001) reduced the levels of hepatic enzymes markers (alanine transaminase [ALT], aspartate transaminase [AST] and alkaline phosphatase [ALP]) in the serum of treated animals. Also, the effects of the crude aqueous leafy extract were found to be statistically significant (p < 0.0001) more than that of its different separating medium fractional components. Conclusion: The findings from this study demonstrated that the crude aqueous leafy extract of M. indica possesses hepatoprotective effect, possibly mediated through the induction of antioxidant enzymes to prevent the occurrence of oxidative stress damage or most likely through the inhibition of pro-inflammatory mediators which are being induced by the lethal hepatotoxic dose of paracetamol.

Isonicotinylation is a histone mark induced by the anti-tuberculosis first-line drug isoniazid

Isoniazid (INH) is a first-line anti-tuberculosis drug used for nearly 70 years. However, the mechanism underlying the side effects of INH has remained elusive. Here, we report that INH and its metabolites induce a post-translational modification (PTM) of histones, lysine isonicotinylation (K_inic), also called 4-picolinylation, in cells and mice. INH promotes the biosynthesis of isonicotinyl-CoA (Inic-CoA), a co-factor of intracellular isonicotinylation. Mass spectrometry reveals 26 K_inic sites in histones in HepG2 cells. Acetyltransferases CREB-binding protein (CBP) and P300 catalyse histone K_inic, while histone deacetylase HDAC3 functions as a deisonicotinylase. Notably, MNase sensitivity assay and RNA-seq analysis show that histone K_inic relaxes chromatin structure and promotes gene transcription. INH-mediated histone K_inic upregulates PIK3R1 gene expression and activates the PI3K/Akt/mTOR signalling pathway in liver cancer cells, linking INH to tumourigenicity in the liver. We demonstrate that K_inic is a histone acylation mark with a pyridine ring, which may have broad biological effects. Therefore, INH-induced isonicotinylation potentially accounts for the side effects in patients taking INH long-term for anti-tuberculosis therapy, and this modification may increase the risk of cancer in humans.

Isoniazid (INH) is an anti-tuberculosis drug; however the underlying cause of its various side effects are not understood. Here the authors identified lysine isonicotinylation as a histone modification on chromatin that is metabolically regulated by INH and its metabolites.

Cell Type-Specific Roles of CD38 in the Interactions of Isoniazid with NAD+ in the Liver

NAD⁺ is a critical molecule that is involved in multiple cellular functions. CD38 is a multifunctional enzyme with NAD⁺ nucleosidase activity. Our previous work revealed the CD38-dependent interactions of isoniazid (INH), an antituberculosis drug, with NAD⁺ to form INH-NAD adduct. In the current work, our metabolomic analysis discovered a novel NAD⁺ adduct with acetylisoniazid (AcINH), a primary INH metabolite mediated by N-acetyltransferase (NAT), and we named it AcINH-NAD. Using Nat1/2(-/-) and Cd38(-/-) mice, we determined that AcINH-NAD formation is dependent on both NAT and CD38. Because NAT is expressed in hepatocytes (HP), whereas CD38 is expressed in Kupffer cells (KC) and hepatic stellate cells (HSC), we explored cell type-specific roles of CD38 in the formation of AcINH-NAD as well as INH-NAD. We found that both INH-NAD and AcINH-NAD were produced in the incubation of INH or AcINH with KC and HSC but not in HP. These data suggest that hepatic nonparenchymal cells, such as KC and HSC, are the major cell types responsible for the CD38-dependent interactions of INH with NAD⁺ in the liver. SIGNIFICANCE STATEMENT: The current study identified AcINH-NAD as a novel metabolite of INH in the liver. Our work also revealed the essential roles of nonparenchymal cells, including Kupffer cells and hepatic stellate cells, in the CD38-dependent interactions of NAD⁺ with INH, leading to the formation of both INH-NAD and AcINH-NAD in the liver. These data can be used to guide the future studies on the mechanisms of INH and NAD⁺ interactions and their contributions to INH-induced liver injury.

Mitochondrial DNA Variants in Patients with Liver Injury Due to Anti-Tuberculosis Drugs

BACKGROUND

Hepatotoxicity is the most severe adverse effect of anti-tuberculosis therapy. Isoniazid's metabolite hydrazine is a mitochondrial complex II inhibitor. We hypothesized that mitochondrial DNA variants are risk factors for drug-induced liver injury (DILI) due to isoniazid, rifampicin or pyrazinamide.

METHODS

We obtained peripheral blood from tuberculosis (TB) patients before anti-TB therapy. A total of 38 patients developed DILI due to anti-TB drugs. We selected 38 patients with TB but without DILI as controls. Next-generation sequencing detected point mutations in the mitochondrial DNA genome. DILI was defined as ALT ≥5 times the upper limit of normal (ULN), or ALT ≥3 times the ULN with total bilirubin ≥2 times the ULN.

RESULTS

In 38 patients with DILI, the causative drug was isoniazid in eight, rifampicin in 14 and pyrazinamide in 16. Patients with isoniazid-induced liver injury had more variants in complex I's NADH subunit 5 and 1 genes, more nonsynonymous mutations in NADH subunit 5, and a higher ratio of nonsynonymous to total substitutions. Patients with rifampicin- or pyrazinamide-induced liver injury had no association with mitochondrial DNA variants.

CONCLUSIONS

Variants in complex I's subunit 1 and 5 genes might affect respiratory chain function and predispose isoniazid-induced liver injury when exposed to hydrazine, a metabolite of isoniazid and a complex II inhibitor.

Cytoprotective Properties of Carnosine against Isoniazid-Induced Toxicity in Primary Cultured Rat Hepatocytes

Background: Drug-induced liver injury is a critical clinical complication. Hence, finding new and safe protective agents with potential clinical application is of value. Isoniazid (INH) is an antituberculosis agent widely used against Mycobacterium tuberculosis infection in human. On the other hand, hepatotoxicity is a clinical complication associated with isoniazid therapy. Oxidative stress and its associated events are major mechanisms identified for INH-induced liver injury. Carnosine is an endogenously found peptide widely investigated for its hepatoprotective effects. On the other hand, robust antioxidant and cytoprotective effects have been attributed to this peptide. Methods: The current study designed to evaluate the potential cytoprotective properties of carnosine against INH-induced cytotoxicity in drug-exposed primary cultured rat hepatocytes. Primary cultured rat hepatocytes were incubated with INH (1.2 mM). Results: INH treatment caused significant increase in cell death and lactate dehydrogenase (LDH) release. On the other hand, it was found that markers of oxidative stress including reactive oxygen species were significantly increased in INH-treated cells. Cellular glutathione reservoirs were also depleted in INH-treated group. Carnosine treatment (50 and 100 µM) significantly diminished INH-induced oxidative stress and cytotoxicity. Conclusion: These data mention carnosine as a potential protective agent with therapeutic capability against INH hepatotoxicity.

Telfairia occidentalis (Cucurbitaceae) pulp extract mitigates rifampicin-isoniazid-induced hepatotoxicity in an in vivo rat model of oxidative stress

OBJECTIVE

Drug-induced liver injury complicates antituberculosis drug treatment and is a leading cause of death worldwide. The aim of this study is to establish the ethnomedicinal claim of hepatoprotective effects of fruit pulp extract of Telfairia occidentalis against rifampicin (RIF) and isoniazid (INH)-induced oxidative stress in rats.

METHODS

T. occidentalis pulp extract (TOPE) (125-500 mg/kg) and silymarin (50 mg/kg) were evaluated in an induced hepatotoxicity model of oxidative stress in Wistar rats by intoxication with RIF and INH (100 mg/kg each) orally for 60 d. Markers indicating oxidative stress and hepatic damage such as alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) were assessed. Biomarkers of antioxidant status, including catalase, glutathione reductase, glutathione peroxidase and superoxide dismutase, and marker of lipid peroxidation, malondialdehyde (MDA), were assayed using standard procedures. The hematological profile, lipid profile, serum markers for kidney function and histopathological examination were also assessed.

RESULTS

Intoxication with RIF and INH markedly reduced the hematological indices and elevated the biochemical enzyme markers (AST, ALT and ALP, P < 0.001) and lipid profile (P < 0.001), while antioxidant biomarkers were significantly (P < 0.01) depressed and MDA was elevated. However, pretreatment with TOPE significantly (P < 0.001) alleviated this alteration and sustained the antioxidant potentials. The histopathological morphology supports the biochemical evidence of hepatoprotection.

CONCLUSION

Current study is indicative of potential antioxidant activity, hepatoprotective effects and plausible therapeutic alleviation of RIF-INH-induced hepatotoxicity of TOPE in laboratory animals.

Metabolomic Study to Determine the Mechanism Underlying the Effects of Sagittaria sagittifolia Polysaccharide on Isoniazid- and Rifampicin-Induced Hepatotoxicity in Mice

In this study, a non-targeted metabolic profiling method based on ultra-performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS) was used to characterize the plasma metabolic profile associated with the protective effects of the Sagittaria sagittifolia polysaccharide (SSP) on isoniazid (INH)—and rifampicin (RFP)-induced hepatotoxicity in mice. Fourteen potential biomarkers were identified from the plasma of SSP-treated mice. The protective effects of SSP on hepatotoxicity caused by the combination of INH and RFP (INH/RFP) were further elucidated by investigating the related metabolic pathways. INH/RFP was found to disrupt fatty acid metabolism, the tricarboxylic acid cycle, amino acid metabolism, taurine metabolism, and the ornithine cycle. The results of the metabolomics study showed that SSP provided protective effects against INH/RFP-induced liver injury by partially regulating perturbed metabolic pathways.

Clinical and experimental research in antituberculosis drug-induced hepatotoxicity: a review

Drug-induced liver injury is the common adverse effect seen in patients receiving antituberculosis drugs (ATDs). There are several risk factors associated with the development of hepatotoxicity in such patients. Though there have been appreciable efforts taken by carrying out studies investigating the efficacy of several natural and synthetic compounds in minimising this effect, the only choice available for clinicians is withdrawal of drugs. This review would give a precise idea of ATD-induced hepatotoxicity, its underlying mechanisms and alternative therapies for the same.

Hot aqueous leaf extract of Lasianthera africana (Icacinaceae) attenuates rifampicin-isoniazid-induced hepatotoxicity

OBJECTIVES

The aim of this study is to evaluate the hepatoprotective effect of Lasianthera africana (Icacinaceae) against isoniazid (INH) and rifampicin (RIF)-induced liver damage in rats.

METHODS

The hepatoprotective effects of hot aqueous L. africana (HALA) leaf extract (0.1-1 g/kg) and silymarin (50 mg/kg) were assessed in a model of oxidative liver damage induced by RIF and INH (100 mg/kg each) in Wistar rats for 28 days. Biochemical markers of hepatic damage such as alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) were assessed. The antioxidant statuses of plasma glutathione peroxidase (GSPx), glutathione reductase (GSH), catalase (CAT) and superoxide dismutase (SOD) and lipid peroxidation were evaluated.

RESULTS

The pretreatment of INH and RIF decreased hematological indices and the antioxidant levels (P < 0.001) and increased the levels of liver marker enzymes (P < 0.001). However, pretreatment with HALA extract and silymarin provoked significant elevation of hematological indices. The levels of AST, ALT, and ALP were depressed (P < 0.001). Total triglycerides, total cholesterol, total bilirubin and low-density lipoprotein were decreased (P < 0.001). However, high-density lipoprotein, bicarbonate, and electrolytes like chloride and potassium were elevated (P < 0.001), but sodium was depressed (P < 0.05). Additionally, GSH, GSPx, SOD and CAT were elevated (P < 0.01) and malondialdehyde was depressed (P < 0.001) when compared to the RIF-INH-treated rats. Histopathological evaluations support hepatoprotective activity.

CONCLUSION

This study demonstrated that HALA leaf extract attenuated RIF-INH-induced hepatotoxicity. L. africana could be exploited in management of RIF-INH-induced hepatitis.

Effectiveness of hepatoprotective drugs for anti-tuberculosis drug-induced hepatotoxicity: a retrospective analysis

Background

The effectiveness of hepatoprotective drugs for DIH (drug induced hepatotoxicity) during tuberculosis treatment is not clear. We evaluated the effectiveness of hepatoprotective drugs by comparing the period until the normalization of hepatic enzymes between patients who were prescribed with the hepatoprotective drugs after DIH was occurred and patients who were not prescribed with the hepatoprotective drugs.

Methods

During 2006–2010, 389 patients with active tuberculosis were included in this study. DIH was defined as elevation of peak serum aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT) of more than twice the upper limit of normal (ULN). We divided the patients into the severe (peak serum AST and/or ALT elevation of >5 times the ULN), moderate (peak serum AST and/or ALT elevation of >3 to ≤5 times the ULN), and mild DIH groups (peak serum AST and/or ALT elevation of >2 to ≤3 times the ULN). We compared the average period until the normalization of hepatic enzymes between patient subgroups with and without hepatoprotective drugs (ursodeoxycholic acid: UDCA, stronger neo-minophagen C: SNMC, and glycyrrhizin).

Results

In the severe group, there was no significant difference in the average period until the normalization between subgroups with and without hepatoprotective drugs (21.4 ± 10.8 vs 21.5 ± 11.1 days, P = 0.97). In the mild group, the period was longer in the subgroup with hepatoprotective drugs than that without hepatoprotective drugs (15.7 ± 6.2 vs 12.4 ± 7.9 days, P = 0.046).

Conclusion

Regardless of the severity, hepatoprotective drugs did not shorten the period until the normalization of hepatic enzymes.

Isoniazid metabolism and hepatotoxicity

Isoniazid (INH) is highly effective for the management of tuberculosis. However, it can cause liver injury and even liver failure. INH metabolism has been thought to be associated with INH-induced liver injury. This review summarized the metabolic pathways of INH and discussed their associations with INH-induced liver injury.

In vitro studies on the toxicity of isoniazid in different cell lines

The aim of the present study was to investigate in vitrothe mechanism of toxicity of isoniazid (-INH), the drug most widely used for treatment of tuberculosis. The human hepatoma line HepG2, the human lymphoblastoid line AHH-1 and the murine lymphoma cells YAC-1 were used as test systems. Active cell death (-apoptosis) and necrosis were detected by different flow cytometric methods: the binding of annexin V to the cell membrane and staining with propidium iodide (PI), the TUNEL assay for detection of DNA fragmentation and the occurrence of a sub G1 peak in cell cycle histograms. Mitochondrial membrane potential was analysed with the fluorescent probe JC-1. In addition to cytotoxicity, effects of INH on cell cycle were studied in HepG2 cells. The data of the present investigations indicate that INH induces cytotoxicity via apoptosis both in hepatoma and lymphoma cells. Twenty-four hours of application of INH in concentrations -26 mM led to a remarkable number of apoptotic cells positive for Annexin V. The induction of apoptosis was accompanied by a break down of the mitochondrial membrane potential and the occurrence of DNA strand breaks. At incubation times from 36 to 48 hours, a sub-G1 peak of late apoptotic cells was detected in cell cycle analysis. Furthermore, cell cycle studies showed a disruption of the cycle at low concentrations of INH which are only mildly cytotoxic. Thus the present study unequivocally demonstrated that INH induces cytotoxicity via apoptosis and can lead to a significant disturbance of the cell cycle in mammalian cells.

Quantification of Hydrazine in Human Urine by HPLC-MS-MS

Currently used on F-16 fighter jets and some space shuttles, hydrazine could be released at toxic levels to humans as a result of an accidental leakage or spill. Lower-level exposures occur in industrial workers or as a result of the use of some pharmaceuticals. A method was developed for the quantitation of hydrazine in human urine and can be extended by dilution with water to cover at least six orders of magnitude, allowing measurement at all clinically significant levels of potential exposure. Urine samples were processed by isotope dilution, filtered, derivatized and then quantified by HPLC-MS-MS. The analytical response ratio was linearly proportional to the urine concentration of hydrazine from 0.0493 to 12.3 ng/mL, with an average correlation coefficientRof 0.9985. Inter-run accuracy for 21 runs, expressed as percent relative error (% RE), was ≤14%, and the corresponding precision, expressed as percent relative standard deviation (% RSD), was ≤15%. Because this method can provide a quantitative measurement of clinical samples over six orders of magnitude, it can be used to monitor trace amounts of hydrazine exposure as well as industrial and environmental exposure levels.

The effect of ageing on isoniazid pharmacokinetics and hepatotoxicity in Fischer 344 rats

Isoniazid is the first-line treatment for tuberculosis; however, its use is limited by hepatotoxicity. Age-related differences in isoniazid pharmacokinetics and hepatotoxicity are uncertain. We aimed to investigate these in young (3 ± 0 months, n = 26) and old (23.0 ± 0.2 months, n = 27) male Fischer 344 rats following a low- or high-dose toxic regimen of isoniazid or vehicle (4 doses/day over 2 days; low: 100, 75, 75, 75 mg/kg; high: 150, 105, 105, 105 mg/kg i.p. every 3 h). Fifteen hours after the last dose, animals were euthanized and sera and livers were prepared for analysis. Isoniazid treatment increased serum hepatotoxicity markers (alanine and aspartate transaminase) in young animals but not in old animals, and only reached significance with the high dose in young animals. Isoniazid treatment caused a trend towards an increase in necrosis in young animals with both doses. In contrast, microvesicular steatosis was increased in old isoniazid-treated animals, reaching significance only with the low dose (steatosis prevalence in old: vehicle 1/9, isoniazid 4/5; P < 0.05). Among isoniazid-treated animals, concentrations of toxic intermediates acetylhydrazine and hydrazine were higher in old than young animals (P < 0.05). With both doses, hepatic cytochrome P450 2E1 activity was higher in young animals compared with old (P < 0.05). There were no other age effects seen on any of the other measured enzymes involved in isoniazid metabolism (N-acetyl transferase, amidase, glutathione-S-transferase). These results show age-related changes in isoniazid pharmacokinetics may contribute towards differential patterns of toxicity and confirm that standard hepatotoxicity markers do not detect isoniazid-induced microvesicular steatosis.

Novel isoniazid–amidoether derivatives: synthesis, characterization and antimycobacterial activity evaluation

A series of isoniazid–amidoether derivatives was synthesized and screened for their antimycobacterial activity in vitro and in vivo.

Development and validation of liquid chromatography tandem mass spectrometry method for simultaneous quantification of first line tuberculosis drugs and metabolites in human plasma and its application in clinical study

Rifampicin (RIF) and isoniazid (INH), first line drugs for the treatment of tuberculosis, are known to cause hepatotoxicity as a serious adverse side effect. To further understand the pharmacokinetic parameters of these two drugs, we have developed and validated a rapid, sensitive and selective LC-MS/MS method for simultaneous quantification of RIF, INH and their metabolites 25-desacetylrifampicin (DRIF), acetylisoniazid (AcINH) and isonicotinic acid (INA). Analytes were extracted from 20 μl of plasma using solid-phase extraction (SPE) followed by chromatographic separation on Zorbax SB-Aq column (50 mm × 4.6mm, particle size 5 μm) using stepwise gradient elution of 5mM ammonium acetate and 90% acetonitrile with 0.1% formic acid. Separation of all analytes was achieved in the total run time of 6 min. The analytes were detected under positive ionization mode by multiple reaction monitoring (MRM) and quantification of analytes was performed by using deuterium-labelled internal standard. Excellent linearity (r(2) ≥ 0.995) was achieved for the analytes at different concentration ranges. The method was accurate (90-115%), precise (CV %<14) and specific. Matrix effect was in the range of 93-111% except for INA (40-42%) while recovery from SPE was reproducible (CV %<7.4) in the range of 60-86%. Post-preparative stability (48 h, 6°C autosampler) and freeze-thaw stability (3 cycles) were assessed with mean recovered concentration of >85%. The method was successfully applied to a clinical study of 33 healthy subjects to evaluate the effect of concomitant of INH on the pharmacokinetic parameters of RIF as well as the segregation of the subjects into slow or fast acetylators of INH.

A systems biology approach utilizing a mouse diversity panel identifies genetic differences influencing isoniazid-induced microvesicular steatosis

Isoniazid (INH), the mainstay therapeutic for tuberculosis infection, has been associated with rare but serious hepatotoxicity in the clinic. However, the mechanisms underlying inter-individual variability in the response to this drug have remained elusive. A genetically diverse mouse population model in combination with a systems biology approach was utilized to identify transcriptional changes, INH-responsive metabolites, and gene variants that contribute to the liver response in genetically sensitive individuals. Sensitive mouse strains developed severe microvesicular steatosis compared with corresponding vehicle control mice following 3 days of oral treatment with INH. Genes involved in mitochondrial dysfunction were enriched among liver transcripts altered with INH treatment. Those associated with INH treatment and susceptibility to INH-induced steatosis in the liver included apolipoprotein A-IV, lysosomal-associated membrane protein 1, and choline phosphotransferase 1. These alterations were accompanied by metabolomic changes including reduced levels of glutathione and the choline metabolites betaine and phosphocholine, suggesting that oxidative stress and reduced lipid export may additionally contribute to INH-induced steatosis. Finally, genome-wide association mapping revealed that polymorphisms in perilipin 2 were linked to increased triglyceride levels following INH treatment, implicating a role for inter-individual differences in lipid packaging in the susceptibility to INH-induced steatosis. Taken together, our data suggest that INH-induced steatosis is caused by not one, but multiple events involving lipid retention in the livers of genetically sensitive individuals. This work also highlights the value of using a mouse diversity panel to investigate drug-induced responses across a diverse population.

Hepatoprotective activity of Ficus religiosa leaves against isoniazid+rifampicin and paracetamol induced hepatotoxicity

Background:

The present study was designed to investigate the hepato protective effect of methanolic extract of Ficus religisoa L., Moraceae, on isoniazid-rifampicin and paracetamol induced hepatotoxicity in rats.

Materials and Methods:

Male Wistar albino rats were divided into six groups; group 1 served as a control received vehicle (Distilled water), group 2 served as a toxic control, received isoniazid-rifampicin (100 mg/ kg, i.p.) or paracetamol 200mg/kg, p.o in sterile water, groups 3, 4 and 5 received 100, 200 and 300mg/kg bw, p.o. methanolic extract of F. religisoa along with INH+RIF or paracetamol and group 6 received Liv 52 as reference standard. All the treatment protocols followed 21 days for INH+RIF model and seven days for paracetamol model, after treatment rats were sacrificed and blood was used for biochemical and liver was used for histological studies.

Results:

Administration of INH+RIF and paracetamol caused a significant elevation in the levels of liver marker enzymes (P < 0.05 and P < 0.01) and thiobarbituric acid reactive substances (P < 0.001) in experimental rats. Administration of methanolic extracts of F. religisoa significantly prevented isoniazid-rifampicin and paracetamol induced elevation in the levels of serum diagnostic liver marker enzymes and TBARS level in experimental groups of rats. Moreover, total protein and reduced glutathione levels were significantly (P < 0.001) increased in treatment group. The effect of extract was compared with a standard drug, Liv 52. The changes in biochemical parameters were supported by histological profile.

Conclusion:

The methanolic extract of F. religisoa protects against isoniazid- rifampicin and paracetamol induced oxidative liver injury in rats.

Role of CYP3A in isoniazid metabolism in vivo

Isoniazid (INH), a first-line drug for tuberculosis control, frequently causes liver injury. Multiple previous reports suggest that CYP3A is involved in INH metabolism, bioactivation and hepatotoxicity, although direct evidence is unavailable. In the current study, wild-type and Cyp3a-null mice were used to determine the potential role of Cyp3a in INH metabolism in vivo. Compared to wild-type mice, there were no significant differences in the pharmacokinetic profiles of INH or acetyl-isoniazid in Cyp3a-null mice after an oral administration of 50 mg/kg INH. With the same treatment, distribution of INH and its major metabolites was similar in the liver of wild-type and Cyp3a-null mice. A reactive metabolite of INH was trapped by N-α-acetyl-L-lysine in mouse liver microsomes, but Cyp3a does not contribute to this bioactivation pathway. In addition, no liver injury was observed in wild-type or Cyp3a-null mice treated with 60 or 120 mg/kg INH. In summary, Cyp3a has no effect on systemic pharmacokinetics of INH in mice. Further studies are needed to determine whether and how exactly CYP3A is involved in INH bioactivation and hepatotoxicity.

Lack of liver injury in Wistar rats treated with the combination of isoniazid and rifampicin

Isoniazid (INH) can cause serious idiosyncratic liver injury. An animal model would greatly facilitate mechanistic studies, but it is essential that the mechanism in the model be similar to the liver injury that can occur in humans. We attempted to replicate a previous study in which Wistar rats treated with INH and rifampicin (RMP) developed liver injury, which was promising because of its delayed onset similar to the liver injury that can occur in humans. Wistar rats were treated with either a high dose of INH (150 mg/kg/day) or a combination of INH and RMP (75 mg/kg/day and 50 mg/kg/day, respectively) for up to 4 weeks. However, we did not observe any liver injury or evidence of an inflammatory infiltrate as had been reported; rather, we observed an increase in CTLA4-positive cells in the cervical lymph nodes as well as a decrease in serum CXCL1 and MCP-1. In short, we were unable to reproduce a previously reported model of delayed onset INH-induced liver injury in Wistar rats.

Human PXR modulates hepatotoxicity associated with rifampicin and isoniazid co-therapy

Rifampicin and isoniazid co–therapy frequently causes liver injury in humans. A pregnane X receptor–humanized mouse model revealed that rifampicin and isoniazid co–treatment causes accumulation of protoporphyrin IX, an endogenous hepatotoxin, in the liver via a pregnane X receptor–mediated alteration of heme biosynthesis pathway. These results provide novel insight into the mechanism of rifampicin and isoniazid–induced liver injury that may be applied to clinical management of the hepatotoxicity associated with tuberculosis chemotherapy.

Pharmacokinetics, tissue distribution and relative bioavailability of isoniazid-solid lipid nanoparticles

Low levels of isoniazid gain access into plasma following oral administration due to its high aqueous solubility, poor permeability and rapid and extensive hepatic metabolism. Further, a small t(1/2) of 1-4 h indicates its short stay in plasma and the need for repetitive or high doses which may subsequently result in hepatotoxicity and neurotoxicity associated with its use. Isoniazid-solid lipid nanoparticles (SLNs) were prepared to achieve improved bioavailability and prolonged effect, thus minimizing pulsatile plasma concentrations (and associated side effects at peak plasma concentrations). Developed SLNs showed high entrapment efficiency (69%) and small size (d(90) 48.4 nm) such that they are expected to bypass reticulo-endothelial system (RES) pickup resulting in prolonged circulation times and since liver is the major site of metabolism of isoniazid, RES avoidance will reduce its elimination from the body. Single dose (25 mg/kg BW) oral pharmacokinetic studies were performed in plasma and various tissues of rats. A significant improvement (p<0.001) in relative bioavailability in plasma (6 times) and brain (4 times) was observed after administration of isoniazid-SLNs with respect to the free drug solution at the same dose. Insignificant changes in liver concentration coupled with bypass of first pass metabolism and slow release of isoniazid (60%, in 24 h) indicate low incidence of hepatotoxicity. Isoniazid-SLNs showed a 3 times higher LD50.

Direct oxidation and covalent binding of isoniazid to rodent liver and human hepatic microsomes: humans are more like mice than rats

Isoniazid (INH) is associated with serious liver injury and autoimmunity. Classic studies in rats indicated that a reactive metabolite of acetylhydrazine is responsible for the covalent binding and toxicity of INH. Studies in rabbits suggested that hydrazine might be the toxic species. However, these models involved acute toxicity with high doses of INH, and INH-induced liver injury in humans has very different features than such animal models. In this study, we demonstrated that a reactive metabolite of INH itself can covalently bind in the liver of mice and also to human liver microsomes. Covalent binding also occurred in rats, but it was much less than that in mice. We were able to trap the reactive metabolite of INH with N-α-acetyl-l-lysine in incubations with human liver microsomes. This suggests that the reactive intermediate of INH that leads to covalent binding is a diazohydroxide rather than a radical or carbocation because those reactive metabolites would be too reactive to trap in this way. Treatment of mice or rats with INH for up to 5 weeks did not produce severe liver injury. The alanine transaminase assay (ALT) is inhibited by INH, and other assays such as glutamate and sorbitol dehydrogenase (SDH) were better biomarkers of INH-induced liver injury. High doses of INH (200 and 400 mg/kg/day) for one week produced steatosis in rats and an increase in SDH, which suggests that it can cause mitochondrial injury. However, steatosis was not observed when INH was given at lower doses for longer periods of time to either mice or rats. We propose that covalent binding of the parent drug can contribute to INH-induced hepatotoxicity and autoimmunity. We also propose that these are immune-mediated reactions, and there are clinical data to support these hypotheses.

NAT2, CYP2C9, CYP2C19, and CYP2E1 genetic polymorphisms in anti-TB drug-induced maculopapular eruption

PURPOSE

It has been suggested that drug-metabolizing enzymes might play important roles in the development of anti-tuberculosis drug (ATD)-induced maculopapular eruption (MPE), as in ATD-induced hepatitis. We investigated the associations between the genetic polymorphisms of drug-metabolizing enzymes and ATD-induced MPE.

METHODS

We enrolled 62 patients with ATD-induced MPE (mean age 47.2 ± 19.0, male 59.7%) and 159 patients without any adverse reactions to ATD (mean age 42.8 ± 17.6, male 65.4%), among patients with pulmonary tuberculosis (TB) and/or TB pleuritis and treated with first-line anti-TB medications, including isoniazid, rifampin, ethambutol, and pyrazinamide. We compared the genotype distributions of single nucleotide polymorphisms and haplotypes in four drug-metabolizing enzymes (N-acetyltransferase 2 (NAT2), cytochrome P450 (CYP) 2 C9, CYP2C19, and CYP2E1) among patients with ATD-induced MPE and patients tolerant to ATD using a multivariate logistic regression analysis. These analyses were made without identification of the responsible ATD.

RESULTS

-1565 C > T of CYP2C9 showed a significant association with ATD-induced MPE (P = 0.022, OR = 0.23, 95% CI 0.07-0.78), with a lower frequency of genotypes carrying minor alleles (CT or TT) in the case group than in the controls. Additionally, W212X of CYP2C19 was significantly associated with the risk of ATD-induced MPE (P = 0.042, OR = 0.27, 95% CI 0.09-0.82). In an analysis of the CYP2C19-CYP2C9 haplotypes (-1418 C > T_W212X_-1565 C > T_-1188 C > T), ht3[T-A-T-C] showed a significant association with the development of ATD-induced MPE (P = 0.012, OR = 0.13, 95% CI 0.03-0.57). No significant associations between the other genetic polymorphisms and ATD-induced MPE were observed.

CONCLUSIONS

CYP2C19 and CYP2C9 genetic polymorphisms are significantly associated with the risk of developing ATD-induced MPE, and the genetic variants in NAT2 and CYP2E1 are not closely related to the development of this adverse reaction.

Isoniazid-induced apoptosis in HepG2 cells: generation of oxidative stress and Bcl-2 down-regulation

Isoniazid (INH) is a first-line antibiotic used in the treatment of infections caused by Mycobacterium tuberculosis. However it has a serious limitation of being hepatotoxic. Delineating the mechanism underlying INH-induced hepatotoxicity may be beneficial in devising ways to counteract its toxic manifestations. Studies in human hepatoma HepG2 cells have indicated that INH exposure causes induction of apoptosis. This study was aimed at identifying the key components/pathways of the INH-induced apoptotic pathway using HepG2 cells. HepG2 cells were exposed to increasing concentrations of INH (6.5, 13, 26, and 52 mM). Hydrogen peroxide (0.3 mM) served as positive control. After incubating for specific time intervals cells were harvested and evidences of cytotoxicity, oxidative stress, and apoptosis were sought. The findings indicated that INH exposure causes increased ROS generation along with alteration in levels of enzymatic antioxidants such as Superoxide dismutase, Catalase, and Glucose-6-Phosphate dehydrogenase. Altered Bcl-2/Bax content, cytochrome-c translocation, caspase activation, and DNA fragmentation emphasized involvement of apoptosis.

Metabolomics of urine for the assessment of microvesicular lipid accumulation in the liver following isoniazid exposure

This study was conducted to develop a noninvasive marker of hepatic microvesicular lipid accumulation (MVLA), a histopathological effect currently diagnosed in humans following liver biopsy. MVLA is detected in animal studies of chemicals and drugs and occurs in some humans exposed to chemicals or pharmaceuticals. Because MVLA is a reversible histopathology, early detection of MVLA using a noninvasive method, could aid clinicians in the treatment of patients taking drugs that are known to induce this injury. Isoniazid (INH) was selected as a model compound for this investigation, because MVLA occurs in tuberculosis (TB) patients treated with a combination therapy, which includes INH. This study used male rats dosed daily with INH at 0, 10, or 300 mg/kg/day for up to 8 days. Urine, blood, and liver were obtained following 1 and 8 days. NMR metabolomics of urine revealed markers that correlated (100%) with the findings of MVLA in the right, left, and median liver lobes in 4/9 rats administered the high dose of INH for 8 days. Metabolomics of liver extracts also revealed markers that correlated with the MVLA injury. Serum enzymes that are clinically used to assess liver injury were not consistently correlated to the findings of MVLA. Metabolite changes consistent with the presence of MVLA correlated with interruptions in inositol, carbohydrate, glycerolipid, and glyoxylate metabolism. This study reveals markers that could find pre-clinical use, provides insights into mechanisms involved in MVLA, and demonstrates the need for the validation of noninvasive MVLA markers in human patients.

Effect of vitamin C on oxidative liver injury due to isoniazid in rats

BACKGROUND

The aim of the present study was to investigate the effect of different doses of vitamin C on oxidative liver injury due to isoniazid (INH) in rats.

METHODS

Rats were divided into four subgroups, each containing 10 rats. Group 1 was the control group; group 2, INH 50 mg/kg per day; group 3, INH 50 mg/kg per day + low-dose vitamin C (100 mg/kg per day); group 4, INH 50 mg/kg per day + high-dose vitamin C (1000 mg/kg per day). INH and vitamin C were administered into their stomachs through an oral tube. After 21 days, measurements were made in both serum and homogenized liver tissues. The levels of glutathione (GSH), superoxide dismutase (SOD) and other biochemical variables were measured. Malondialdehyde (MDA), glutathione peroxidase (GSH-px) and vitamin C were measured using commercial kits.

RESULTS

Aspartate amino transferase and alanine aminotransferase in group 2 were higher than those in groups 1, 3 and 4 (P < 0.008 for both). Serum and tissue levels of MDA in group 2 were higher than that in groups 1 and 3 (P < 0.008 for both). There was no difference in the SOD levels between the four groups (P= 0.095). Erythrocyte and tissue GSH in group 2 were higher than that in groups 1 and 3 (P < 0.008 for both). Interestingly, erythrocyte and tissue GSH in group 4 were lower than those in group 1 (P < 0.008 for both). Erythrocyte level of GSH-px in group 2 was higher than that in groups 1 and 3 (P < 0.008 for both).

CONCLUSIONS

INH-induced liver injury is associated with oxidative stress, and co-administration of low-dose vitamin C may reduce this damage effectively in a rat model. The antioxidant effect of high-dose vitamin C does not seem more potent compared to the low dose.

Role of reactive metabolites in drug-induced hepatotoxicity

Drugs are generally converted to biologically inactive forms and eliminated from the body, principally by hepatic metabolism. However, certain drugs undergo biotransformation to metabolites that can interfere with cellular functions through their intrinsic chemical reactivity towards glutathione, leading to thiol depletion, and functionally critical macromolecules, resulting in reversible modification, irreversible adduct formation, and irreversible loss of activity. There is now a great deal of evidence which shows that reactive metabolites are formed from drugs known to cause hepatotoxicity, such as acetaminophen, tamoxifen, isoniazid, and amodiaquine. The main theme of this article is to review the evidence for chemically reactive metabolites being initiating factors for the multiple downstream biological events culminating in toxicity. The major objectives are to understand those idiosyncratic hepatotoxicities thought to be caused by chemically reactive metabolites and to define the role of toxic metabolites.

Preparation and antitubercular activities in vitro and in vivo of novel Schiff bases of isoniazid

Structural modification of the frontline antitubercular isonicotinic acid hydrazide (INH) provides lipophilic adaptations (3-46) of the drug in which the hydrazine moiety of the parent compound has been chemically blocked from the deactivating process of N(2)-acetylation by N-arylaminoacetyl transferases. As a class, these compounds show high levels of activity against Mycobacterium tuberculosis in vitro and in tuberculosis-infected macrophages. They provide strong protection in tuberculosis-infected mice and have low toxicity. With some representatives of this class achieving early peak plasma concentrations approximately three orders of magnitude above minimum inhibitory concentration, they may serve as tools for improving our understanding of INH-based treatment modalities, particularly for those patients chronically underdosed in conventional INH therapy.