Role of hydrazine in isoniazid-induced hepatotoxicity in a hepatocyte inflammation model

Effect of Fluoride on the Morphology and Electrochemical Property of Co₃O₄ Nanostructures for Hydrazine Detection

In this paper, we systematically investigated the influence of fluoride on the morphology and electrochemical property of Co₃O₄ nanostructures for hydrazine detection. The results showed that with the introduction of NH₄F during the synthesis process of Co₃O₄, both Co(CO₃)_0.5(OH)·0.11H₂O and Co(OH)F precursors would be generated. To understand the influence of F on the morphology and electrochemical property of Co₃O₄, three Co₃O₄ nanostructures that were respectively obtained from bare Co(CO₃)_0.5(OH)·0.11H₂O, Co(OH)F and Co(CO₃)_0.5(OH)·0.11H₂O mixtures and bare Co(OH)F were successfully synthesized. The electrochemical tests revealed the sensing performance of prepared Co₃O₄ nanostructures decreased with the increase in the fluoride contents of precursors. The more that dosages of NH₄F were used, the higher crystallinity and smaller specific surface area of Co₃O₄ was gained. Among these three Co₃O₄ nanostructures, the Co₃O₄ that was obtained from bare Co(CO₃)_0.5(OH)·0.11H₂O-based hydrazine sensor displayed the best performances, which exhibited a great sensitivity (32.42 μA·mM⁻¹), a low detection limit (9.7 μΜ), and a wide linear range (0.010–2.380 mM), together with good selectivity, great reproducibility and longtime stability. To the best of our knowledge, it was revealed for the first time that the sensing performance of prepared Co₃O₄ nanostructures decreased with the increase in fluoride contents of precursors.

Involvement of histone hypoacetylation in INH-induced rat liver injury

This study explores the mechanism of histone acetylation under the effect of oxidative stress in rat liver injury induced by isoniazid (INH). Fifty-six adult SD rats were selected and divided randomly into INH groups (48) and control (8). Rats in INH groups were intragastrically injected with 55 mg kg^-1 day^-1 for 3, 7, 10, 14, 21, and 28 days, and control rats were given an equal volume of distilled water. Pathological changes in liver tissues were observed by HE staining. Western blot analysis was conducted to measure the expression levels of H3k14ac and H4k8ac. The activities of HAT, HDAC and IL-1β, and TNF-α were detected by ELISA in liver tissues. Real-time RT-PCR analysis was performed to determine the protein expression levels of HAT, HDAC, and IL-1β and the mRNA expression of TNF-α. The levels of superoxide dismutase (SOD) and malondialdehyde (MDA) were assayed by biochemical methods in liver tissues. At different time points, the SOD activity decreased, whereas the MDA content significantly increased after 14 days (F_SOD = 11.15, F_MDA = 7.42, P < 0.01). During this period, the expression of histone acetylated H3K14 and H4K8 acetylation decreased compared with the control group (F_H3K14 = 4.18, F_H4K8 = 3.87, P < 0.05); by contrast, HDAC1 and HDAC2 showed a high expression level compared with those in the control group (F_HDAC1 = 29.13, F_HDAC2 = 58.34, P < 0.01). Moreover, the expression of CBP/P300 was lower than that in the control group (F_CBP/P300 = 12.18, P = 0.001), and the protein contents of IL-1β and TNF-α in rat liver tissues were up-regulated (F_IL-1β = 44.88, F_TNF-α = 41.56, P < 0.01). These results suggest that histone acetylation is involved in INH-induced rat liver injury. Furthermore, the hypoacetylation of histones H3K14 and H4K8 is negatively correlated with oxidative stress-mediated rat liver injury.

Evaluation of HepaRG cells for the assessment of indirect drug-induced hepatotoxicity using INH as a model substance

HepaRG cells are widely used as an in vitro model to assess drug-induced hepatotoxicity. However, only few studies exist so far regarding their suitability to detect the effects of drugs requiring a preceding activation via the cytochrome P450 (CYP) system. A prototypic substance is the anti-tuberculosis agent INH, which is metabolized into N-acetylhydrazine, which then triggers hepatotoxicity. Therefore, the aim of the present study was to test if this effect can also be detected in HepaRG cells and if it can be counteracted by the known hepatoprotectant silibinin. For this purpose, differentiated HepaRG cells were treated with increasing concentrations of INH (0.1-100 mM) or 10 mM INH plus escalating concentrations of silibinin (1-100 µM). After 48 h of treatment, cell morphology and parameters indicating cell vitality, oxidative stress, and liver cell function were assessed. High concentrations of INH led to severe histopathological changes, reduced cell vitality and glutathione content, increased LDH and ASAT release into the medium, enhanced lipid peroxidation, and elevated cleaved caspase-3 expression. Additionally, glycogen depletion and reduced biotransformation capacity were seen at high INH concentrations, whereas at low concentrations an induction of biotransformation enzymes was noticed. Silibinin caused clear-cut protective effects, but with few parameters INH toxicity was even aggravated, most probably due to increased metabolization of INH into its toxic metabolite. In conclusion, HepaRG cells are excellently suited to evaluate the effects of substances requiring prior toxification via the CYP system, such as INH. They additionally enable the identification of complex substance interactions.

Protective Effect of Bicyclol on Anti-Tuberculosis Drug Induced Liver Injury in Rats

The present study was performed to investigate the effect of bicyclol, a synthetic anti-hepatitis drug with anti-oxidative and anti-inflammatory properties, on anti-tuberculosis (anti-TB) drug-induced liver injury and related mechanisms in rats. Bicyclol was given to rats by gavage 2 h before the oral administration of an anti-TB drug once a day for 30 days. Liver injury was evaluated by biochemical and histopathological examinations. Lipid peroxidation, mitochondrial function, and the activity of antioxidants were measured by spectrophotometric methods. Cytokines expression and CYP2E1 activity were determined by ELISA assay and liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis. The expressions of hepatic CYP2E1 and hepatocyte growth factor (HGF) were assessed by Western blotting. As a result, bicyclol significantly protected against anti-TB drug-induced liver injury by reducing the elevated serum aminotransferases levels and accumulation of hepatic lipids. Meanwhile, the histopathological changes were also attenuated in rats. The protective effect of bicyclol on anti-TB drug-induced hepatotoxicity was mainly due to its ability to attenuate oxidative stress, suppress the inflammatory cytokines and CYP2E1 expression, up-regulate the expression of HGF, and improve mitochondrial function. Furthermore, administration of bicyclol had no significant effect on the plasma pharmacokinetics of the anti-TB drug in rats.

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.

Synthesis, characterization, and efficacy of antituberculosis isoniazid zinc aluminum-layered double hydroxide based nanocomposites

The chemotherapy for tuberculosis (TB) is complicated by its long-term treatment, its frequent drug dosing, and the adverse effects of anti-TB drugs. In this study, we have developed two nanocomposites (A and B) by intercalating the anti-TB drug isoniazid (INH) into Zn/Al-layered double hydroxides. The average size of the nanocomposites was found to bê164 nm. The efficacy of the Zn/Al-layered double hydroxides intercalated INH against Mycobacterium tuberculosis was increased by approximately three times more than free INH. The nanocomposites were also found to be active against Gram-positive and -negative bacteria. Compared to the free INH, the nanodelivery formulation was determined to be three times more biocompatible with human normal lung fibroblast MRC-5 cells and 3T3 fibroblast cells at a very high concentration of 50 µg/mL for up to 72 hours. The in vitro release of INH from the Zn/Al-layered double hydroxides was found to be sustained in human body-simulated buffer solutions of pH 4.8 and 7.4. This research is a step forward in making the TB chemotherapy patient friendly.

Diallyl trisulfide protects the liver against hepatotoxicity induced by isoniazid and rifampin in mice by reducing oxidative stress and activating Kupffer cells

Background & Aim: Diallyl trisulfide (DATS) has been verified to ameliorate hepatotoxicity induced by many drugs, but the protective actions of isoniazid (INH) and rifampicin (RFP) have not been reported. We attempted to elucidate the potential effects and mechanisms of DATS against INH&RFP-caused hepatotoxicity. Methods: Male Kunming mice weighing 18-22 g were divided into 6 groups. For the hepatic-protective study, DATS (10 mg per kg, 20 mg per kg, and 40 mg per kg bw, respectively) was orally administered two hours before the INH&RFP (100 mg per kg, 100 mg per kg bw, respectively) treatments. After 11 days of treatment, 10 mice in each group were taken for the carbon clearance test, while the other 10 mice were sacrificed for the collection of serum and livers for further measurements, including the levels of serum alanine aminotransferase (ALT), aspartate transaminase (AST) and total bilirubin (T.Bili), the liver index, and liver histopathological examination. Malondialdehyde (MDA), glutathione (GSH), and the level of interleukin 1-β (IL-1-β) were measured, the carbon clearance test was performed and the immunohistochemistry of F4/80 marker for activated Kupffer cells (KCs) was analyzed to investigate potential mechanisms. Results: DATS co-administration significantly inhibited the increase of liver index and elevation of serum ALT, AST and T.Bili levels induced by INH&RFP, as well as improved the hepatocellular structure. The further mechanistic studies demonstrated that DATS co-administration counteracted INH&RFP-induced oxidative stress in mice, which was illustrated by the restoration of GSH levels, and the reduction of MDA levels in the liver. Furthermore, DATS co-administration reactivated the KCs inhibited by INH&RFP, which was illustrated by the increase of carbon phagocytosis, and the restoration of the number of activated KCs and IL-1-β levels in the liver. Conclusion: DATS effectively protected the liver against INH&RFP-induced hepatotoxicity, which might be due to its antioxidant effect and enhancement of KCs' activities.

Copper nanoparticles decorated polyaniline–zeolite nanocomposite for the nanomolar simultaneous detection of hydrazine and phenylhydrazine

The high electrocatalytic activity of the CuNPs–PANI–Nano-ZSM-5 nanocomposite can be attributed to the synergistic contribution provided by the highly dispersed copper nanoparticles and conductive PANI film on high surface area Nano-ZSM-5.

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.

Development of a biocompatible nanodelivery system for tuberculosis drugs based on isoniazid-Mg/Al layered double hydroxide

The primary challenge in finding a treatment for tuberculosis (TB) is patient non-compliance to treatment due to long treatment duration, high dosing frequency, and adverse effects of anti-TB drugs. This study reports on the development of a nanodelivery system that intercalates the anti-TB drug isoniazid into Mg/Al layered double hydroxides (LDHs). Isoniazid was found to be released in a sustained manner from the novel nanodelivery system in humans in simulated phosphate buffer solutions at pH 4.8 and pH 7.4. The nanodelivery formulation was highly biocompatible compared to free isoniazid against human normal lung and 3T3 mouse fibroblast cells. The formulation was active against Mycobacterium tuberculosis and gram-positive bacteria and gram-negative bacteria. Thus results show significant promise for the further study of these nanocomposites for the treatment of TB.

In vitro antioxidant, antibacterial, and cytotoxic activity and in vivo effect of Syngonium podophyllum and Eichhornia crassipes leaf extracts on isoniazid induced oxidative stress and hepatic markers

The present study reports the in vitro antioxidant, antibacterial, and cytotoxic potential of Syngonium podophyllum (SP) and Eichhornia crassipes (EC) leaf aqueous extracts as well as their in vivo effect on oxidative stress and hepatic biomarkers in isoniazid induced rats. Phytochemical screening of extracts revealed the presence of flavonoids, terpenoids, reducing sugars, alkaloids, and saponins. Phenolic content in SP and EC extracts was 5.36 ± 0.32 and 10.63 ± 0.13 mg PGE/g, respectively, while flavonoid content was 1.26 ± 0.03 and 0.51 ± 0.03 μg QE/mg, respectively. EC extract exhibited comparatively better antioxidant activity as indicated by reducing power (0.197-0.775), DPPH radical scavenging potential (11%-96%), and metal ion chelating ability (42%-93%). Both the extracts provided 13%-65% protection against lipid peroxidation in rat tissue (liver, kidney, and brain) homogenate. SP and EC extracts exhibited 51% and 43% cytotoxicity against lung cancer (NCI-H322) cell line, respectively. Both extracts demonstrated considerable antibacterial activity against Proteus vulgaris, Salmonella typhi, and Bordetella bronchiseptica. Coadministration of E. crassipes extract with isoniazid in rats accounted for 46% decrease in malondialdehyde content and 21% increase in FRAP value of plasma. It also mitigated the isoniazid induced alterations in serum enzymes (SGOT, SGPT, and ALP), total bilirubin, creatinine, and hemoglobin contents. S. podophyllum extract was found to be hepatotoxic.

Evaluation of azathioprine-induced cytotoxicity in an in vitro rat hepatocyte system

Azathioprine (AZA) is widely used in clinical practice for preventing graft rejection in organ transplantations and various autoimmune and dermatological diseases with documented unpredictable hepatotoxicity. The potential molecular cytotoxic mechanisms of AZA towards isolated rat hepatocytes were investigated in this study using “Accelerated Cytotoxicity Mechanism Screening” techniques. The concentration of AZA required to cause 50% cytotoxicity in 2 hrs at 37°C was found to be 400 μM. A significant increase in AZA-induced cytotoxicity and reactive oxygen species (ROS) formation was observed when glutathione- (GSH-) depleted hepatocytes were used. The addition of N-acetylcysteine decreased cytotoxicity and ROS formation. Xanthine oxidase inhibition by allopurinol decreased AZA-induced cytotoxicity, ROS, and hydrogen peroxide (H₂O₂) formation and increased % mitochondrial membrane potential (MMP). Addition of N-acetylcysteine and allopurinol together caused nearly complete cytoprotection against AZA-induced hepatocyte death. TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl), a known ROS scavenger and a superoxide dismutase mimic, and antioxidants, like DPPD (N,N′-diphenyl-p-phenylenediamine), Trolox (a water soluble vitamin E analogue), and mesna (2-mercaptoethanesulfonate), also decreased hepatocyte death and ROS formation. Results from this study suggest that AZA-induced cytotoxicity in isolated rat hepatocytes may be partly due to ROS formation and GSH depletion that resulted in oxidative stress and mitochondrial injury.

Mechanisms of isoniazid-induced idiosyncratic liver injury: emerging role of mitochondrial stress

Idiosyncratic drug-induced liver injury (DILI) is a significant adverse effect of antitubercular therapy with isoniazid (INH). Although the drug has been used for many decades, the underlying mode of action (both patient-specific and drug-specific mechanisms) leading to DILI are poorly understood. Among the patient-specific determinants of susceptibility to INH-associated DILI, the importance of HLA genetic variants has been increasingly recognized, whereas the role of polymorphisms of drug-metabolizing enzymes (NAT2 and CYP2E1) has become less important and remains controversial. However, these polymorphisms are merely correlative, and other molecular determinants of susceptibility have remained largely unknown. Regarding the drug-specific mechanisms underlying INH-induced liver injury, novel concepts have been emerging. Among these are covalent protein adduct formation via novel reactive intermediates, leading to hapten formation and a potential immune response, and interference with endogenous metabolism. Furthermore, INH and/or INH metabolites (e.g. hydrazine) can cause mitochondrial injury, which can lead to mitochondrial oxidant stress and impairment of energy homeostasis. Recent studies have revealed that underlying impairment of complex I function can trigger massive hepatocellular injury induced by otherwise nontoxic concentrations of INH superimposed on these mitochondrial deficiencies. This review discusses these emerging new paradigms of INH-induced DILI and highlights recent insights into the mechanisms, as well as points to the existing large gaps in our understanding of the pathogenesis.

Molecular mechanism of 17α-ethinylestradiol cytotoxicity in isolated rat hepatocytes

17α-Ethinylestradiol (17-EE) is used in formulations of contraceptives and hormone replacement therapy because it is an estradiol derivative. However, it has been associated with an increase in the risk of liver cancers and injury. The carcinogenic properties of 17-EE are similar to that of other estrogens, but the molecular mechanism of liver injury is still unclear. It is important to identify any secondary toxic mechanisms that can be used to prevent or treat the toxicity. The LC50 of 17-EE toward isolated rat hepatocytes was determined to be 150 ± 8 μmol/L. Accelerated cytotoxicity mechanism screening (ACMS) techniques using isolated rat hepatocytes showed that CYP1A inhibitors decreased cytotoxicity, whereas tyrosinase increased toxicity; this suggests that the toxic mechanism involved is the oxidation of 17-EE. A hepatocyte inflammation model also increased 17-EE-induced mitochondrial toxicity, as well as the formation of ROS and H2O2. Cytotoxicity was increased when inhibitors of quinone reduction, catechol-O-methylation, glucuronidation, glutathione conjugation, and sulfation were co-incubated with 17-EE. The hepatocytes could be rescued with antioxidants and quinone trapping agents, thereby suggesting a role for quinoid moiety induced oxidative stress in 17-EE induced cytotoxicity. These mechanisms for 17-EE hepatotoxicity could provide a new perspective for the treating 17-EE-induced liver injury.

Isoniazid-induced cell death is precipitated by underlying mitochondrial complex I dysfunction in mouse hepatocytes

Isoniazid (INH) is an antituberculosis drug that has been associated with idiosyncratic liver injury in susceptible patients. The underlying mechanisms are still unclear, but there is growing evidence that INH and/or its major metabolite, hydrazine, may interfere with mitochondrial function. However, hepatic mitochondria have a large reserve capacity, and minor disruption of energy homeostasis does not necessarily induce cell death. We explored whether pharmacologic or genetic impairment of mitochondrial complex I may amplify mitochondrial dysfunction and precipitate INH-induced hepatocellular injury. We found that INH (≤ 3000 μM) did not induce cell injury in cultured mouse hepatocytes, although it decreased hepatocellular respiration and ATP levels in a concentration-dependent fashion. However, coexposure of hepatocytes to INH and nontoxic concentrations of the complex I inhibitors rotenone (3 μM) or piericidin A (30 nM) resulted in massive ATP depletion and cell death. Although both rotenone and piericidin A increased MitoSox-reactive fluorescence, Mito-TEMPO or N-acetylcysteine did not attenuate the extent of cytotoxicity. However, preincubation of cells with the acylamidase inhibitor bis-p-nitrophenol phosphate provided protection from hepatocyte injury induced by rotenone/INH (but not rotenone/hydrazine), suggesting that hydrazine was the cell-damaging species. Indeed, we found that hydrazine directly inhibited the activity of solubilized complex II. Hepatocytes isolated from mutant Ndufs4(+/-) mice, although featuring moderately lower protein expression levels of this complex I subunit in liver mitochondria, exhibited unchanged hepatic complex I activity and were therefore not sensitized to INH. These data indicate that underlying inhibition of complex I, which alone is not acutely toxic, can trigger INH-induced hepatocellular injury.

An update on amine oxidase inhibitors: multifaceted drugs

Although not used as extensively as other antidepressants for the treatment of depression, the monoamine oxidase (MAO) inhibitors continue to hold a niche in psychiatry and to have a relatively broad spectrum with regard to treatment of psychiatric and neurological disorders. Experimental and clinical research on MAO inhibitors has been expanding in the past few years, primarily because of exciting findings indicating that these drugs have neuroprotective properties (often independently of their ability to inhibit MAO). The non-selective and irreversible MAO inhibitors tranylcypromine (TCP) and phenelzine (PLZ) have demonstrated neuroprotective properties in numerous studies targeting elements of apoptotic cascades and neurogenesis. l-Deprenyl and rasagiline, both selective MAO-B inhibitors, are used in the management of Parkinson's disease, but these drugs may be useful in the treatment of other neurodegenerative disorders given that they demonstrate neuroprotective/neurorescue properties in a wide variety of models in vitro and in vivo. Although the focus of studies on the involvement of MAO inhibitors in neuroprotection has been on MAO-B inhibitors, there is a growing body of evidence demonstrating that MAO-A inhibitors may also have neuroprotective properties. In addition to MAO inhibition, PLZ also inhibits primary amine oxidase (PrAO), an enzyme implicated in the etiology of Alzheimer's disease, diabetes and cardiovascular disease. These multifaceted aspects of amine oxidase inhibitors and some of their metabolites are reviewed herein.

A study of the effect of Nigella sativa (Black seeds) in isoniazid (INH)-induced hepatotoxicity in rabbits

Objective:

To investigate the possibility of hepatoprotective effect of Nigella sativa (NS) in INH-induced hepatotoxicity.

Materials and Methods:

The experiments were carried out on 24 male rabbits. They were divided into 4 groups (6 each); rabbits in group 1 were treated with INH following a standard protocol to induce hepatotoxicity. Rabbits in group 2 received starch. Group 3 received NS 1 g/kg/day before INH treatment. Group 4 rabbits were treated with NS only. Phenobarbital sodium (IP) was given to induce metabolism of INH. INH and NS were given orally. The experiment continued for 12 days; at day 13, animals were sacrificed. Liver function tests, malondialdehyde (MDA) were estimated in serum and in liver homogenates. Liver histopathological examinations were performed.

Results:

Histopathological changes of hepatotoxicity were found in all INH-treated rabbits. The histopathological findings were normal in three rabbits treated with NS before INH, very mild in two, and with moderate changes in one rabbit. Serum alanine aminotransferase (S.ALT) was elevated after INH treatment and returned back to the control value when NS was given before INH. Similar pattern of effect was noticed with serum aspartate aminotransferase (S.AST), S. total bilirubin, S. MDA, and Serum alkaline phosphatase.In liver homogenate, AST, ALT, and MDA were increased with INH treatment compared to the control, then decreased with NS treatment given before INH

Conclusions:

NS has hepatoprotective effects against INH-induced hepatotoxicity in rabbits. NS 1 g/kg proved safe, no adverse effects; no histopathological or biological abnormalities were seen.

Protective effects of kaempferol on isoniazid- and rifampicin-induced hepatotoxicity

Isoniazid (INH) and rifampicin (RIF) are the first-line drugs for antituberculosis (anti-TB) chemotherapy. The levels of serum transaminases [aspartate aminotransferase (AST) and alanine aminotransferase (ALT)] are abnormal in 27% of patients undergoing INH and RIF treatments and in 19% of patients undergoing treatment with INH alone. Cytochrome P450 2E1 (CYP2E1) metabolizes many toxic substrates, including ethanol, carbon tetrachloride, and INH, which ultimately results in liver injury. The objective of this study was to screen for CYP2E1 inhibitors in vitro and investigate whether the selected compound could prevent INH/RIF-induced hepatotoxicity in vivo. We screened 83 known compounds from food and herbal medicines as inhibitors of CYP2E1. The hepatotoxic dose of INH/RIF was 50/100 mg kg(-1) day(-1). Hepatotoxicity was assessed using galactose single-point (GSP) method (a quantitative measurement of liver function), histopathological examination of the liver, malondialdehyde (MDA) assay, and measurement of AST and ALT activities. Kaempferol inhibited CYP2E1 activity in mice by 0.31- to 0.48-fold (p < 0.005). Mice with INH/RIF-induced hepatotoxicity showed significantly abnormal serum levels of AST and ALT, and GSP value, and these values could be decreased by the administration of kaempferol (p < 0.005). Kaempferol significantly reduced the depletion of hepatic glutathione and prevented the increase in MDA formation in mice. Furthermore, kaempferol did not affect the anti-TB effects of INH/RIF. To our knowledge, this is the first report of kaempferol's utility as an adjuvant for preventing CYP2E1-mediated hepatotoxicity induced by drugs such as INH and RIF.

Discovery of novel inhibitors of LEDGF/p75-IN protein-protein interactions

Human lens epithelium-derived growth factor (LEDGF)/p75 plays an important role in the HIV life cycle by stimulating integrase (IN)-led viral DNA integration into cellular chromosomes. Mechanistic studies show the majority of IN inhibitors chelate magnesium ions in the catalytic active site, a region topologically distant from the LEDGF/p75 binding site. Compounds disrupting the formation of LEDGF/p75 and IN complexes serve as a novel mechanistic approach different from current antiretroviral therapies. We previously built pharmacophore models mimicking LEDGF/p75 residues and identified four classes of LEDGF/p75-IN inhibitors. Substructure and similarity searches yielded additional LEDGF/p75-IN inhibitors containing an acylhydrazone moiety. The most potent of the acylhydrazones inhibited LEDGF/p75-IN interaction with an IC(50) value of 400nM. We explored structure-activity relationships (SAR) and identified new acylhydrazones, hydrazines, and diazenes as lead molecules for further optimization. Two lead LEDGF/p75-IN inhibitors showed antiviral activity.

Evaluation of the physicians' approach to the diagnosis and treatment of patients with antituberculosis drug-induced hepatotoxicity

OBJECTIVES

To describe the practices of physicians on the diagnosis and treatment of antituberculosis drug-induced hepatotoxicity (ATH), and to evaluate the concordance between these practices and the American Thoracic Society (ATS) 2006 guidelines.

METHODS

Information was reviewed on 670 new cases of tuberculosis patients aged not less than 15 years and registered at the outpatient clinics of a large hospital in southern Thailand during October 2006 to September 2009. The patient was identified as having ATH if: (1) he/she was diagnosed as transaminitis, hepatitis or hepatotoxicity from antituberculosis (anti-TB) drugs; (2) their treatment regimen was subsequently modified by their attending physicians; and (3) their liver enzyme decreased after withdrawal of the suspected anti-TB drugs. Compliance with the ATS guidelines was considered on diagnosis, initial management, selection of alternative regimens, and a reintroduction strategy.

RESULTS

The prevalence of ATH was 6.7%. The proportion of patients diagnosed as ATH in accordance with the ATS 2006 guidelines was 73.8%. For the initial management, isoniazid, rifampicin and pyrazinamide were concurrently stopped in 55.0% of patients. While waiting for normalization of liver enzymes, 28 patients (70.0%) were treated with alternative regimens and 12 patients (30.0%) took no drug. Only 47.5% of the ATH patients received a regimen in accordance with ATS guidelines, including three less hepatotoxic drugs (ethambutol, ofloxacin and streptomycin). Of 34 patients who discontinued the treatment, anti-TB drugs were reintroduced sequentially in 30 patients (88.2%). Of these, only 23.4% were firstly rechallenged with rifampicin as suggested by the ATS guidelines.

CONCLUSIONS

The practice of physicians on the diagnosis and management of ATH varied. The practices of physicians on the diagnosis and rechallenged method were in high compliance with the ATS guidelines. For the initial management and selection of alternative regimens, the physicians' compliance was not good.

Protective effects of Asparagusracemosus on oxidative damage in isoniazid-induced hepatotoxic rats

To investigate the hepatoprotective activity of Asparagus racemosus against isoniazid-induced hepatotoxicity in male albino rats. Rats ( n = 6 per group)were divided into four groups: saline-treated control, saline-treated control with A. racemosus extract (50 mg/kg), isoniazid treatment alone (100 mg/kg, intraperitoneal [i.p.]), and isoniazid– A. racemosus extract (50 mg/kg)administered orally as cotreatment. Animals were treated for 21 days and euthanized 1 h after the last drug administration. Evaluated body weight, serum levels of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, g-glutamyl transferase, total protein, albumin, hepatic malondialdehyde content, superoxide dismutase, catalase, cytochrome P450 2E1 (CYP2E1)activity and glutathione (GSH). A. racemosus extract prevented isoniazid-induced hepatotoxicity, indicated by both diagnostic indicators of liver damage, liver functional profile, significantly ( p < 0.05)inhibited CYP2E1 activity, markedly attenuated oxidative stress by improved enzymatic, non-enzymatic antioxidants levels and mitigate malondialdehyde, lipid hydroperoxide significantly ( p < 0.05). These results suggest that A. racemosus extract exerts its hepatoprotective activity by inhibiting the production of free radicals and acts as a scavenger, reducing the free radical generation via inhibition of hepatic CYP2E1 activity, increasing the removal of free radicals through the induction of antioxidant enzymes and improving non-enzymatic thiol antioxidant GSH.

Utility of the carboxylesterase inhibitor bis-para-nitrophenylphosphate (BNPP) in the plasma unbound fraction determination for a hydrolytically unstable amide derivative and agonist of the TGR5 receptor

The potent, functional agonist of the bile acid Takeda G-protein-coupled receptor 5 (TGR5), (S)-1-(6-fluoro-2-methyl-3,4-dihydroquinolin-1(2H)-yl)-2-(isoquinolin-5-yloxy)ethanone (3), represents a useful tool to probe in vivo TGR5 pharmacology. Rapid degradation of 3 in both rat and mouse plasma, however, hindered the conduct of in vivo pharmacokinetic/pharmacodynamic investigations (including plasma-free fraction (f(u plasma)) determination) in rodent models of pharmacology. Studies were therefore initiated to understand the biochemical basis for plasma instability so that appropriate methodology could be implemented in in vivo pharmacology studies to prevent the breakdown of 3. Compound 3 underwent amide bond cleavage in both rat and mouse plasma with half-lives (T(1/2)) of 39 + or - 7 and 9.9 + or - 0.1 min. bis(p-nitrophenyl) phosphate (BNPP), a specific inhibitor of carboxylesterases, was found to inhibit hydrolytic cleavage in a time- and concentration-dependent manner, which suggested the involvement of carboxylesterases in the metabolism of 3. In contrast with the findings in rodents, 3 was resistant to hydrolytic cleavage in both dog and human plasma. The instability of 3 was also observed in rat and mouse liver microsomes. beta-Nicotinamide adenine dinucleotide phosphate, reduced form (NADPH)-dependent metabolism of 3 occurred more rapidly (T(1/2) approximately 2.22-6.4 min) compared with the metabolic component observed in the absence of the co-factor (T(1/2) approximately 89-130 min). Oxidative metabolism dominated the NADPH-dependent decline of 3, whereas NADPH-independent metabolism of 3 proceeded via simple amide bond hydrolysis. Compound 3 was highly bound (approximately 95%) to both dog and human plasmas. Rat and mouse plasma, pre-treated with BNPP to inhibit carboxylesterases activity, were used to determine the f(u plasma) of 3. A BNPP concentration of 500 microM was determined to be optimal for these studies. Higher BNPP concentrations (1000 microM) appeared to displace 3 from its plasma protein-binding sites in preclinical species and human. Under the conditions of carboxylesterases-inhibited rat and mouse plasma, the level of protein binding displayed by 3 was similar to those observed in dog and human. In conclusion, a novel system has been devised to measure f(u plasma) for a plasma-labile compound. The BNPP methodology can be potentially applied to stabilize hydrolytic cleavage of structurally diverse carboxylesterase substrates in the plasma (and other tissue), thereby allowing the characterization of pharmacology studies on plasma-labile compounds if and when they emerge as hits in exploratory drug-discovery programmes.

Hepatocyte or serum albumin protein carbonylation by oxidized fructose metabolites: Glyceraldehyde or glycolaldehyde as endogenous toxins?

Excessive sugar intake in animal models may cause tissue damage associated with oxidative and carbonyl stress cytotoxicity as well as inflammation. Fructose became a 100-fold more cytotoxic if hepatocytes were exposed to a non-toxic infusion of H(2)O(2) so as to simulate H(2)O(2) released by Kupffer cells or infiltrating immune cells. In order to determine the molecular mechanisms involved, protein carbonylation of fructose and its metabolites were determined using the 2,4-dinitrophenylhydrazine method. In a cell-free system, fructose was found to carbonylate bovine serum albumin (BSA) only if low concentrations of FeII/H(2)O(2) were added. Protein carbonylation by the fructose metabolites glyceraldehyde or glycolaldehyde was also markedly increased by FeII/H(2)O(2). The protein carbonylation may be attributed to glyoxal formation by hydroxyl radicals as the glyoxal trapping agent aminoguanidine or hydroxyl radical scavengers prevented protein carbonylation. Glyoxal was also much more effective than other carbonyls at causing protein carbonylation. When BSA was replaced by isolated rat hepatocytes, fructose metabolite glyceraldehyde in the presence of non-toxic 2 microM FeII:8-hydroxyquinoline (HQ) and a H(2)O(2) generating system (glucose/glucose oxidase) markedly increased cytotoxicity, protein carbonylation and reactive oxygen species (ROS)/H(2)O(2) formation. Furthermore this was prevented by hydroxyl radical scavengers or aminoguanidine, a glyoxal scavenger. CuII: 8-hydroxyquinoline increased H(2)O(2) induced hepatocyte protein carbonylation less but was prevented by aminoguanidine. However, cytotoxicity and protein carbonylation induced by glyceraldehyde/CuII:HQ/H(2)O(2) were not affected by hydroxyl radical scavengers. Although fatty liver induced by an excessive sugar diet in animal models has been proposed as the first hit for non-alcoholic steatohepatitis (NASH) we propose that oxidative stress induced by the oxidation of fructose or fructose metabolites catalysed by Fenton FeII/H(2)O(2) could be a 'second hit'. A perpetual cycle of oxidative stress in hepatocytes could lead to cytotoxicity and contribute to NASH development.

EIDOS: a mechanistic classification of adverse drug effects

The mechanisms of adverse drug effects have not been adequately classified. Here, we propose a comprehensive mechanistic classification of adverse drug effects that considers five elements: the Extrinsic chemical species (E) that initiates the effect; the Intrinsic chemical species (I) that it affects; the Distribution (D) of these species in the body; the (physiological or pathological) Outcome (O); and the Sequela (S), which is the adverse effect. This classification, which we have called EIDOS, describes the mechanism by which an adverse effect occurs; it complements the DoTS classification of adverse effects (based on clinical pharmacology), which takes into account Dose responsiveness, Time course, and Susceptibility factors. Together, these two classification systems, mechanistic and clinical, comprehensively delineate all the important aspects of adverse drug reactions; they should contribute to areas such as drug development and regulation, pharmacovigilance, monitoring therapy, and the prevention, diagnosis, and treatment of adverse drug effects.

Genetic polymorphisms of drug-metabolizing enzymes and anti-TB drug-induced hepatitis

AIMS

Although some genetic risk factors have been reported for the development of hepatitis due to anti-TB drugs, an extensive candidate gene approach evaluating drug-metabolizing enzymes has not been attempted. This study aimed to investigate the association of genetic polymorphisms in drug-metabolizing enzymes with anti-TB drug-induced hepatitis.

MATERIALS & METHODS

We compared genotype distributions of tagging SNPs in promoter, exons and haplotypes in seven drug-metabolizing enzyme genes (CYP2C9, CYP2C19, CYP2D6, CYP2E1, NAT2, UGT1A1 and UGT1A3) between 67 cases and 159 controls.

RESULTS

Among four tagging SNPs of N-acetyltransferase 2 (NAT2), -9796T>A in promoter and R197Q were significantly associated (p = 0.0016 and p = 0.0007, respectively). NAT2 haplotype 2 [A-A-A-G] carrying A allele of -9796T>A and A allele of R197Q showed significant association (p = 0.0004). However, there was no significant association between genotypes of other enzyme-metabolizing genes and anti-TB drug-induced hepatitis. The constructs containing -9796A of NAT2 showed significantly lower luciferase activity (p < 0.01), suggesting decreased expression of NAT2. The variant alleles and haplotype 2 showed significantly higher peak serum levels of isoniazid, lower acetyl isoniazid:isoniazid ratio and lower isoniazid clearance compared with wild-types.

CONCLUSION

These findings suggest that genetic variants in the promoter and exons of NAT2 increase the risk of anti-TB drug-induced hepatitis by modifying acetylation phenotypes and/or gene expression of NAT2, and there is no essential role for genetic mutation of the other metabolizing enzymes in the development of this adverse reaction.

Hepatocyte inflammation model for cytotoxicity research: fructose or glycolaldehyde as a source of endogenous toxins

Insulin resistance and hepatotoxicity induced in high fructose fed rats may involve fructose derived endogenous toxins formed by inflammation. Thus fructose was seventy-fold more toxic if hepatocytes were exposed to non-toxic levels of hydrogen peroxide (H(2)O(2)) released by inflammatory cells. This was prevented by iron (Fe) chelators, hydroxyl radical scavengers, and increased by Fe, copper (Cu) or catalase inhibition. Fructose or glyceraldehyde/dihydroxyacetone metabolites were oxidized by Fenton radicals to glyoxal. Glyoxal (15 microM) cytotoxicity was increased about 200-fold by H(2)O(2). Glycolaldehyde was enzymically formed from glyceraldehyde, the fructokinase/aldolase B product of fructose. Glycolaldehyde cytotoxicity was increased 20-fold by H(2)O(2). The oxidative stress cytotoxicity induced was attributed to the Fenton oxidation of glycolaldehyde forming glycolaldehyde radicals and glyoxal, since cytotoxicity was prevented by aminoguanidine (glyoxal trap) or Fenton inhibitors. Glyoxal was also the Fenton product responsible for glycolaldehyde protein carbonylation as carbonylation was prevented by aminoguanidine or Fenton inhibitors.

Fructose and carbonyl metabolites as endogenous toxins

Dietary fructose consumption is one of the environmental factors contributing to the development of obesity and a fatty liver (hepatic steatosis). A two-hit hypothesis has been proposed for progression of hepatic steatosis to the more serious non-alcoholic steatosis (NASH), with the first hit being hepatic steatosis, and the second hit being inflammation and associated oxidative stress caused by reactive oxygen species (ROS) formation. As well, fructose-fed rats develop insulin resistance and serum levels of methylglyoxal, a glycolytic metabolite, are increased. Previously we reported that glyoxal-induced hepatocyte cytotoxicity could be attributed to mitochondrial toxicity as mitochondrial membrane potential was decreased and cytotoxicity was increased several orders of magnitude by low non-cytotoxic doses of H(2)O(2) (hepatocyte inflammation model). In this study, we have assessed the toxicity of fructose towards hepatocytes and investigated the molecular cytotoxic mechanisms involved. Fructose itself was only toxic at 1.5M, whereas 12 mM caused 50% cell death in 2h if the hepatocytes were exposed to a non-cytotoxic dose of H(2)O(2) continuously generated by glucose and glucose oxidase. The cytotoxic mechanism involved oxidative stress as ROS and H(2)O(2) formation preceded cytotoxicity, and cytotoxicity was prevented by radical scavengers, lipid antioxidants and ROS scavengers. It is proposed that the highly potent Fenton derived ROS catalyse the oxidation of fructose and particularly its carbonyl metabolites glycolaldehyde, dihydroxyacetone, glyceraldehyde. The carbon radicals and glyoxal formed compromise the cell's resistance to H(2)O(2).

FAF-Drugs2: free ADME/tox filtering tool to assist drug discovery and chemical biology projects

BACKGROUND

Drug discovery and chemical biology are exceedingly complex and demanding enterprises. In recent years there are been increasing awareness about the importance of predicting/optimizing the absorption, distribution, metabolism, excretion and toxicity (ADMET) properties of small chemical compounds along the search process rather than at the final stages. Fast methods for evaluating ADMET properties of small molecules often involve applying a set of simple empirical rules (educated guesses) and as such, compound collections' property profiling can be performed in silico. Clearly, these rules cannot assess the full complexity of the human body but can provide valuable information and assist decision-making.

RESULTS

This paper presents FAF-Drugs2, a free adaptable tool for ADMET filtering of electronic compound collections. FAF-Drugs2 is a command line utility program (e.g., written in Python) based on the open source chemistry toolkit OpenBabel, which performs various physicochemical calculations, identifies key functional groups, some toxic and unstable molecules/functional groups. In addition to filtered collections, FAF-Drugs2 can provide, via Gnuplot, several distribution diagrams of major physicochemical properties of the screened compound libraries.

CONCLUSION

We have developed FAF-Drugs2 to facilitate compound collection preparation, prior to (or after) experimental screening or virtual screening computations. Users can select to apply various filtering thresholds and add rules as needed for a given project. As it stands, FAF-Drugs2 implements numerous filtering rules (23 physicochemical rules and 204 substructure searching rules) that can be easily tuned.