Role of N-acetylcysteine in rifampicin-induced hepatic injury of young rats

Cdk5-Mediated Brain Unfolded Protein Response Upregulation Associated with Cognitive Impairments in Type 2 Diabetes and Ameliorative Action of NAC

The role of cyclin-dependent kinase 5 (Cdk5) in the normal functioning of the central nervous system and synaptic plasticity is well established. However, dysregulated kinase activity can have a significant impact on neurodegeneration and cognitive impairment. Cdk5 hyperactivation is linked to diabetes-associated neurodegeneration, but the underlying mechanism is not fully understood. Our study reveals that oxidative stress can lead to Cdk5 hyperactivity, which in turn is linked to neurodegeneration and cognitive impairment. Specifically, our experiments with N2A cells overexpressing Cdk5 and its activators p35 and p25 show ER stress, resulting in activation of the unfolded protein response (UPR) pathway. We identified Cdk5 as the epicenter of this regulatory process, leading to the activation of the CDK5-IRE1-XBP1 arm of UPR. Moreover, our study demonstrated that Cdk5 hyperactivation can lead to ER stress and activation of the UPR pathway, which may contribute to cognitive impairments associated with diabetes. Our findings also suggest that antioxidants such as NAC and GSH can decrease deregulated Cdk5 kinase activity and rescue cells from UPR-mediated ER stress. The accumulation of phosphorylated Tau protein in AD brain protein has been widely described earlier. Notably, we observed that oral treatment with NAC decreased Cdk5 kinase activity in the hippocampus, attenuated high levels of phospho-tau (ser396), and ameliorated memory and learning impairments in a type 2 diabetic (T2D) mouse model. Additionally, the high-fat-induced T2D model exhibits elevated phospho-tau levels, which are rescued by the NAC treatment. Taken together, these results suggest that targeting Cdk5 may be a promising therapeutic strategy for treating diabetes-associated cognitive impairments.

A study to evaluate the hepatoprotective effect of N- acetylcysteine on anti tuberculosis drug induced hepatotoxicity and quality of life

BACKGROUND

Drug induced liver injury (DILI) is a serious adverse effect caused by first-line anti-TB (ATT) drugs, limiting the TB-treatment. The tissue inflammation induced by free radical burst and poor dietary intake in TB induces oxidative stress, which was proposed as one of the mechanisms responsible for ATT induced DILI. N-acetylcysteine (NAC) exerts a hepato-protective effect by enhancing the cellular antioxidant defense mechanism. There are few studies evaluating the effect of NAC on ATT induced DILI in Indian-population.

METHODS

This is a prospective, randomized, double-blind, placebo-controlled, parallel-group study. Thirty-eight newly diagnosed TB patients on first-line ATT with normal liver function test (LFT) were recruited and randomized to receive either NAC 600 mg tablet or placebo twice daily for 4 weeks and followed-up for next 4 weeks. LFT [AST, ALT, ALP and Total bilirubin] was assessed at baseline, 2, 4 and 8 weeks. Oxidative-stress biomarkers [Malondialdehyde (MDA), Nitric Oxide (NO), Glutathione (GSH)] and quality of life (QOL) by SF-36 questionnaire were assessed at baseline, 4 and 8 weeks. Adverse Drug Reactions (ADRs) were monitored at every visit. Compliance was assessed by pill-count method.

RESULTS

Baseline characteristics were homogenous among both the groups. In the NAC group, there was significant reduction in ALT (p < 0.01), ALP (p < 0.01), total bilirubin (p < 0.001) at 4 weeks compared to baseline. AST, MDA and NO showed a reduction of 19%, 21.6% and 5.5% respectively from baseline and GSH at showed an increase of 2.6% from baseline at 4 weeks in the NAC group, however these were not statistically significant. These effects in LFT and oxidative biomarkers persisted even at the end of 8 weeks. Significant improvement from baseline in QOL was observed in both the groups (p < 0.05). Between group analysis showed, significant reduction in ALT (p < 0.05) and AST (p < 0.05) in NAC group at 4 weeks, whereas bilirubin, MDA, NO and GSH showed improvement at 4 weeks compared to placebo in NAC group, however it was not statistically significant. This improvement in the LFT and oxidative biomarkers continued even at the end of 8 weeks. Itching and rashes were the most common ADRs, with similar incidence in both the groups. Compliance to treatment was good in both the groups.

CONCLUSION

Significant improvement in liver function parameters is suggestive of hepatoprotective effect of NAC. This observed effect at 4 weeks was found to be persistent at 8 weeks, which signifies prolonged hepato-protective effect of NAC. Long duration studies with large sample size are required for further confirmation of hepato-protective action of NAC.

The Effectiveness of Silymarin in the Prevention of Anti-tuberculosis Drug-induced Hepatotoxicity: A Randomized Controlled Clinical Trial

Background

Several animal studies have shown the protective effect of silymarin (the extract of Silybum marianum seeds) against anti-tuberculosis drug-induced hepatotoxicity (ATDH). However, the knowledge of ATDH of silymarin in humans is scarce. In this study, we aimed to clinically evaluate it.

Methods

During this randomized controlled clinical trial, 36 new cases of tuberculosis (TB) were enrolled to receive either silymarin 150 mg twice daily for two weeks along with a standard anti-TB therapeutic regimen (experimental group; n = 16) or standard anti-TB therapeutic regimen alone (control group; n = 21). Liver function tests (serum AST, ALT, ALP, and total bilirubin) at the end of weeks 1 and 2 as well as the rate of ATDH during the study were determined and compared between the groups.

Results

No significant differences between the experimental and control groups were observed at the end of the first week regarding liver function tests; However, at the end of the second week, the mean serum levels of AST (P = 0.03) and ALP (P = 0.04) were significantly lower in the experimental group. ALT (P = 0.016) and ALP (P = 0.027) levels in the experimental group significantly decreased during the study, while the changes in the control group were not significant. Two patients in the control group (9.5%) developed ATDH, while no one in the experimental group manifested this adverse effect.

Conclusions

Our study suggests that silymarin use has the potential for the reduction of anti-TB drug-induced hepatotoxicity.

Understanding and Exploiting the Effect of Tuberculosis Antimicrobials on Host Mitochondrial Function and Bioenergetics

Almost 140 years after its discovery, tuberculosis remains the leading infectious cause of death globally. For half a century, patients with drug-sensitive and drug-resistant tuberculosis have undergone long, arduous, and complex treatment processes with several antimicrobials that primarily function through direct bactericidal activity. Long-term utilization of these antimicrobials has been well-characterized and associated with numerous toxic side-effects. With the prevalence of drug-resistant strains on the rise and new therapies for tuberculosis urgently required, a more thorough understanding of these antimicrobials is a necessity. In order to progress from the “one size fits all” treatment approach, understanding how these antimicrobials affect mitochondrial function and bioenergetics may provide further insight into how these drugs affect the overall functions of host immune cells during tuberculosis infection. Such insights may help to inform future studies, instigate discussion, and help toward establishing personalized approaches to using such antimicrobials which could help to pave the way for more tailored treatment regimens. While recent research has highlighted the important role mitochondria and bioenergetics play in infected host cells, only a small number of studies have examined how these antimicrobials affect mitochondrial function and immunometabolic processes within these immune cells. This short review highlights how these antimicrobials affect key elements of mitochondrial function, leading to further discussion on how they affect bioenergetic processes, such as glycolysis and oxidative phosphorylation, and how antimicrobial-induced alterations in these processes can be linked to downstream changes in inflammation, autophagy, and altered bactericidal activity.

N-Acetyl Cysteine as an Adjunct in the Treatment of Tuberculosis

Oxidative stress is a common feature of tuberculosis (TB), and persons with reduced antioxidants are at more risk of TB. TB patients with relatively severe oxidative stress had also more advanced disease as measured by the Karnofsky performance index. Since adverse effects from anti-TB drugs are also mediated by free radicals, TB patients are prone to side effects, such as hearing loss. In previous articles, researchers appealed for clinical trials aiming at evaluating N-acetyl cysteine (NAC) in attenuating the dreaded hearing loss during multidrug-resistant TB (MDR-TB) treatment. However, before embarking on such trials, considerations of NAC's overall impact on TB treatment are crucial. Unfortunately, such a comprehensive report on NAC is missing in the literature and this manuscript reviews the broader effect of NAC on TB treatment. This paper discusses NAC's effect on mycobacterial clearance, hearing loss, drug-induced liver injury, and its interaction with anti-TB drugs. Based on the evidence accrued to date, NAC appears to have various beneficial effects on TB treatment. However, despite the favorable interaction between NAC and first-line anti-TB drugs, the interaction between the antioxidant and some of the second-line anti-TB drugs needs further investigations.

A comparison of hepatoprotective activity of Bacoside to Silymarin treatment against a combined Isoniazid and Rifampin-induced hepatotoxicity in female Wistar rats

The liver is an important organ that plays a vital role in homeostasis maintenance and regulation. Any liver damage or injury caused by drugs or chemicals is called hepatotoxicity. Isoniazid and rifampin are drugs used separately to treat tuberculosis but have unique side effects and potential hepatotoxicity. The metabolism of isoniazid (INH) and rifampin (RIF) takes place in liver hence hepatotoxicity is the main cause of their continuous use. Bacoside was obtained from the plant Bacopa monnieri, a dammarene type triterpenoid saponin, found distributed throughout India. Bacoside has been used as a nerve tonic, a free radical scavenger, and antioxidant. It is known that the combined INH-RIF induced hepatotoxicity can be antagonized by maintaining hepatocyte membrane integrity in rats. Silymarin, an herbal drug, and its component silybin were reported to work as lipid peroxidation inhibitors and antioxidants which scavenge free radicals. Due to minimal toxicity and no adverse drug interactions, Silymarin is used to treat various medically confirmed hepatic disorders. The aim of this study was to evaluate the beneficial effect of Bacoside against INH- and RIF-induced toxicity in livers of Wistar albino rats. Four experimental groups of rats were used to study four parameters; bodyweight, liver enzyme markers, liver antioxidant, and liver histopathology. INH- and RIF-treated rats showed abnormalities in liver markers which were normalized by Bacoside and that seems similar to the normal control and Silymarin-treated groups. Thus, the current study demonstrated the hepatoprotective effect of Bacoside against INH- and RIF-induced toxicity in Wistar albino rats.

Amelioration of hepatotoxicity by biocleavable aminothiol chimeras of isoniazid: Design, synthesis, kinetics and pharmacological evaluation

AIM

To overcome the hazardous effects on liver caused by long-term use of antitubercular agent isoniazid (INH) by developing a novel hepatoprotective prodrug strategy by conjugating INH with aminothiols as antioxidant promoities for probable synergistic effect.

METHODS

INH was conjugated with N-acetyl cysteine (NAC) and N-(2)-mercaptopropionyl glycine using the Schotten-Baumann reaction and with L-methionine using Boc-anhydride through a biocleavable amide linkage. Synthesized prodrugs were characterized by spectral analysis, and in vitro and in vivo release studies were carried out using HPLC. Their hepatoprotective potential was evaluated in male Wistar rats by performing liver function tests, measuring markers of oxidative stress and carrying out histopathology studies.

RESULTS

Prodrugs were found to be stable in acidic (pH 1.2) and basic (pH 7.4) buffers and in rat stomach homogenates, whereas they were hydrolysed significantly (59.43%-94.93%) in intestinal homogenates over a period of 6 h. Upon oral administration of prodrug NI to rats, 52.4%-61.3% INH and 47.4%-56.8% of NAC were recovered in blood in 8-10 h. Urine and faeces samples pooled over a period of 24 h exhibited 1.3%-2.5% and 0.94%-0.9% of NAC, respectively, without any presence of intact NI or INH. Prodrugs were biologically evaluated for hepatoprotective activity. All the prodrugs were effective in abating oxidative stress and re-establishing the normal hepatic physiology. The effect of prodrug of INH with NAC in restoring the levels of the enzymes superoxide dismutase and glutathione peroxidase and abrogating liver damage was noteworthy especially.

CONCLUSION

The findings of this investigation demonstrated that the reported prodrugs can add safety and efficacy to future clinical protocols of tuberculosis treatment.

First-line antituberculosis drugs disrupt endocrine balance and induce ovarian and uterine oxidative stress in rats

BACKGROUND

The first-line antituberculosis (anti-TB) drugs, isoniazid (INH), rifampicin (RIF), ethambutol (EMB), and pyrazinamide (PZA), are effective in the treatment of pulmonary tuberculosis. However, the toxicity of these drugs in the clinical setting limits their use. Here, we evaluated the effects of anti-TB drugs on the reproductive system in female rats.

METHODS

Thirty-five female Wistar rats were assigned into five groups of seven animals each. The control group received normal saline, whereas others received INH (5 mg/kg), RIF (10 mg/kg), EMB (15 mg/kg), and PZA (15 mg/kg) through gavage thrice a week for 8 consecutive weeks.

RESULTS

Administration of anti-TB drugs significantly (p<0.05) reduced uterine and ovarian weight, as well as the relative weight of the uterus when compared with controls. In addition, anti-TB drugs increased the activities of alanine aminotransferase as well as the level of total bilirubin. Treatment with INH, RIF, and PZA significantly (p<0.05) reduced the levels of follicle-stimulating and luteinizing hormones, estrogen, and prolactin. The INH, RIF, EMB, and PZA caused significant (p<0.05) increases in uterine malondialdehyde (MDA) levels by 281%, 214%, 273% and 190%, respectively, whereas INH and EMB increased the ovarian malondialdehyde by 111% and 129%, respectively. These drugs significantly (p<0.05) decreased the activities of ovarian glutathione-S-transferase and uterine glutathione peroxidase, superoxide dismutase, and catalase. Histology revealed the erosion of uterine mucosa, debris in the lumen of the uterus, congestion, and underdeveloped follicles in ovaries.

CONCLUSIONS

The first-line anti-TB drugs elicited reproductive toxicity in the uterus and ovaries of rats through mechanisms that involved oxidative stress.

Drug-Induced Liver Toxicity and Prevention by Herbal Antioxidants: An Overview

The liver is the center for drug and xenobiotic metabolism, which is influenced most with medication/xenobiotic-mediated toxic activity. Drug-induced hepatotoxicity is common and its actual frequency is hard to determine due to underreporting, difficulties in detection or diagnosis, and incomplete observation of exposure. The death rate is high, up to about 10% for drug-induced liver damage. Endorsed medications represented >50% of instances of intense liver failure in a study from the Acute Liver Failure Study Group of the patients admitted in 17 US healing facilities. Albeit different studies are accessible uncovering the mechanistic aspects of medication prompted hepatotoxicity, we are in the dilemma about the virtual story. The expanding prevalence and effectiveness of Ayurveda and natural products in the treatment of various disorders led the investigators to look into their potential in countering drug-induced liver toxicity. Several natural products have been reported to date to mitigate the drug-induced toxicity. The dietary nature and less adverse reactions of the natural products provide them an extra edge over other candidates of supplementary medication. In this paper, we have discussed the mechanism involved in drug-induced liver toxicity and the potential of herbal antioxidants as supplementary medication.

Oxidative Stress and Inflammation in Hepatic Diseases: Therapeutic Possibilities of N-Acetylcysteine

Liver disease is highly prevalent in the world. Oxidative stress (OS) and inflammation are the most important pathogenetic events in liver diseases, regardless the different etiology and natural course. N-acetyl-l-cysteine (the active form) (NAC) is being studied in diseases characterized by increased OS or decreased glutathione (GSH) level. NAC acts mainly on the supply of cysteine for GSH synthesis. The objective of this review is to examine experimental and clinical studies that evaluate the antioxidant and anti-inflammatory roles of NAC in attenuating markers of inflammation and OS in hepatic damage. The results related to the supplementation of NAC in any form of administration and type of study are satisfactory in 85.5% (n = 59) of the cases evaluated (n = 69, 100%). Within this percentage, the dosage of NAC utilized in studies in vivo varied from 0.204 up to 2 g/kg/day. A standard experimental design of protection and treatment as well as the choice of the route of administration, with a broader evaluation of OS and inflammation markers in the serum or other biological matrixes, in animal models, are necessary. Clinical studies are urgently required, to have a clear view, so that, the professionals can be sure about the effectiveness and safety of NAC prescription.

A double-blinded randomized controlled trial of silymarin for the prevention of antituberculosis drug-induced liver injury

Background

Hepatitis is a common adverse effect of antituberculosis drugs. Silymarin prevented drug-induced hepatoxicity in animals with anti-oxidative mechanisms but its effect in human has been unknown. We aimed to evaluate the efficacy of silymarin for preventing antituberculosis-drug induced liver injury (antiTB-DILI) in patients with tuberculosis.

Methods

A double-blind randomized placebo-controlled trial was performed. Tuberculosis patients were randomly allocated to receive placebo or silymarin. The outcomes of interests were antiTB-DILI and the maximum liver enzymes at week 4. Antioxidative enzymes (i.e., superoxide dismutase (SOD), glutathione and malondialdehyde assays) were assessed. The risks of antiTB-DILI between the two groups were compared. A number need to treat was estimated.

Results

A total of 55 out of 70 expected numbers of patients were enrolled. There were 1/27 (3.7 %) and 9/28 (32.1 %) patients who developed antiTB-DILI in the silymarin and the placebo groups. Risk reduction was 0.28 (0.10, 0.47), i.e., receiving silymarin was 28 % at lower risk for antiTB-DILI than placebo. This led to prevention of 28 patients from being antiTB-DILI among 100 treated patients. Median (IQR) of ALT levels at week 4 in the placebo and the silymarin group were 35.0 (15, 415) IU/L and 31.5 (20, 184) IU/L (p = 0.455). The decline of SOD level at week 4 in the silymarin group was less than the placebo group (p < 0.027).

Conclusions

Silymarin reduced the incidence of antiTB-DILI. The benefit of silymarin may be explained from superoxide dismutase restoration. Larger clinical trials are required to confirm the result of our small study [Clinicaltrials.Gov Identifier Nct01800487].

Hepatoprotective Effect of Cissus quadrangularis Stem Extract Against Rifampicin-induced Hepatotoxicity in Rats

The study was designed to investigate the hepatoprotective activity of methanol extract of Cissus quadrangularis against rifampicin-induced hepatotoxicity in rats.The coarse powder of the shade dried stem of Cissus quadrangularis was subjected to successive extraction in a Soxhlet apparatus using solvents petroleum ether (60-80°) and methanol. Liver damage was induced in Wistar rats by administering rifampicin (54 mg/kg, p.o.) once daily for 30 days. Methanol extract of Cissus quadrangularis (500 mg/kg, p.o) was administered 1 h prior to the administration of rifampicin (54 mg/kg, p.o.) once daily for 30 days. Silymarin (50 mg/kg p.o) used as reference drug. Elevated levels of aspartate transaminase, alanine transaminase, alkaline posphatase and bilirubin following rifampicin induction were significantly lowered due to pretreatment with methanol extract of Cissus quadrangularis. Rifampicin administration significantly increased lipid peroxidation and decreased antioxidant activities like reduced glutathione, superoxide dismutas and catalase. Pretreatment of rats with methanol extract of Cissus quadrangularis significantly decreased lipid peroxidation and increased the antioxidant activities. Histology of the liver section of the animals treated with the methanol extract of Cissus quadrangularis further confirms the hepatoprotective activity. The results of the present study indicated the hepatoprotective effect of methanol extract of Cissus quadrangularis which might be ascribable to its antioxidant property due to the presence of β-carotene.

An effective antioxidant drug on prevention of the necrosis of zone of stasis: N-acetylcysteine

The zone of stasis, the encircling area of the zone of coagulation, is a critical area which determines the depth and width of the necrosis in burns. Many agents were proposed to salvage the zone of stasis. Due to the known preventive and therapeutic effects of N-acetylcysteine on hepatotoxicity, nephrotoxicity, pulmonary injury, and multiple organ failure in humans, the effect of N-acetylcysteine on saving the zone of stasis was investigated in this experimental study. The effects of N-acetylcysteine administration via oral or intraperitoneal route was compared in a rat comb-burn model. The extent of burn wounds was evaluated by photography and planimetry in the groups. Additionally, skin samples were obtained to analyze malondialdehyde levels to see the antioxidant effect of N-acetylcysteine. In control group (no treatment), the burn areas went to near total necrosis. In intraperitoneal and oral treatment groups, skin survival occurred in the interspace area of the comb. There was no difference between the groups in terms of MDA concentrations. In conclusion, this study showed us the possible saving effect of N-acetylcysteine on the zone of stasis. N-acetylcysteine may be used in the cases of severe burns, not only for its effects on wound healing but also the systemic effects of the drug.

Protective effect of curcumin, silymarin and N-acetylcysteine on antitubercular drug-induced hepatotoxicity assessed in an in vitro model

Tuberculosis (TB) is highly endemic in India. The first-line anti-TB therapy (ATT) involving isoniazid (INH), rifampicin and pyrazinamide causes hepatotoxicity in approximately 11.5% of Indian patients. Studies have shown that ATT-induced hepatotoxicity is primarily due to oxidative stress caused by the drugs and metabolites. Herbal drugs with antioxidative properties have been tested in animal studies and clinical trials for the management of hepatotoxicity. The objective of this study was to investigate the role of curcumin (CUR), silymarin (SILY) and N-acetylcysteine (N-ACET) on hepatotoxicity by ATT drugs using an in vitro model of human hepatocellular carcinoma cell line (HepG2). HepG2 cells were treated with ATT drugs alone or along with CUR, SILY or N-ACET for a 48-h duration. The cells were monitored for viability, morphology, respiring mitochondria and cell cycle. Our results suggest that the presence of hepatoprotective drugs during treatment of HepG2 cells with ATT drugs lowers the hepatotoxic effect of the latter. This is observed in terms of (a) increased cell viability, (b) healthy-looking cell morphology as revealed by phase contrast microscopy, (c) active respiring cells as observed with confocal microscopy upon staining with a mitochondrial membrane-specific dye, MitoTracker(®) Red, and reduction in the sub-G(1) peak in cell cycle analysis by flow cytometry. Our results suggest that these hepatoprotective drugs need to be further explored as potential adjuvant therapy along with ATT drugs.

Hepatoprotection by carotenoids in isoniazid–rifampicin induced hepatic injury in rats

This study evaluates the hepatoprotective effect of carotenoids against isoniazid (INH) and rifampicin (RIF). Thirty-six adult rats were divided into the following 4 groups: (1) control group treated with normal saline; (2) INH + RIF group treated with 50 mg·(kg body mass)–1·day–1 of INH and RIF each; (3) INH + RIF+ carotenoids group treated with 50 mg·(kg body mass)–1·day–1 of INH and RIF each and 10 mg·(kg body mass)–1·day–1 of carotenoids; and (4) carotenoids group treated with 10 mg·(kg body mass)–1·day–1 of carotenoids for 28 days intragastrically. Oxidative stress and antioxidant levels in liver and blood, liver histology and change in transaminases were measured in all the above-mentioned groups. There was an increase in lipid peroxidation with a reduction in thiols, catalase, and superoxide dismutase (SOD) in the liver and blood of rats accompanied by an increase in transaminases, bilirubin, and alkaline phosphatase. Treatment with carotenoids along with INH + RIF partially reversed lipid peroxidation, thiols, catalase, and SOD in the liver and blood of rats. Elevated levels of the enzymes in serum were also reversed partially by this treatment. The degree of necrosis, portal triaditis, and inflammation were also lowered in the carotenoids group. In conclusion, carotenoids supplementation in INH + RIF treated rats showed partial protection.

Protective effect of N-acetylcysteine on antituberculosis drug-induced hepatotoxicity

INTRODUCTION

Isoniazid, rifampicin, and pyrazinamide, the first-line antituberculosis (anti-TB) drugs, are associated with hepatotoxicity.

AIMS AND OBJECTIVES

To study the hepatoprotective effect of N-acetylcysteine (NAC) on liver injury induced by anti-TB drugs.

METHODS

A randomized clinical trial was conducted on 60 new TB patients who were aged 60 years or more. Patients were randomized into two groups. In group I (n=32), drug regimen included daily doses of isoniazid, rifampicin, pyrazinamide, and ethambutol. Patients in group II (n=28) were treated with the same regimen and NAC. The patients were followed up for 2 weeks. Liver enzymes and bilirubins were measured at baseline, after 1 and 2 weeks of treatment, and whenever the patients presented with clinical symptoms of hepatotoxicity.

RESULTS

The mean+/-SD values of aspartate aminotransferase and alanine aminotransferase were significantly higher in group I than in group II after 1 and 2 weeks of treatment. Hepatotoxicity occurred in 12 patients with (37.5%) group I and none in group II. The mean duration of treatment before the onset of hepatotoxicity was 4.67+/-4.58 days.

CONCLUSION

NAC protects against anti-TB drug-induced hepatotoxicity.

Silymarin protects liver against toxic effects of anti-tuberculosis drugs in experimental animals

BACKGROUND

The first line anti-tuberculosis drugs isoniazid (INH), rifampicin (RIF) and pyrazinamide (PZA) continues to be the effective drugs in the treatment of tuberculosis, however, the use of these drugs is associated with toxic reactions in tissues, particularly in the liver, leading to hepatitis. Silymarin, a standard plant extract with strong antioxidant activity obtained from S. marianum, is known to be an effective agent for liver protection and liver regeneration. The aim of this study was to investigate the protective actions of silymarin against hepatotoxicity caused by different combinations of anti-tuberculosis drugs.

METHODS

Male Wistar albino rats weighing 250-300 g were used to form 6 study groups, each group consisting of 10 rats. Animals were treated with intra-peritoneal injection of isoniazid (50 mg/kg) and rifampicin (100 mg/kg); and intra-gastric administration of pyrazinamid (350 mg/kg) and silymarin (200 mg/kg). Hepatotoxicity was induced by a combination of drugs with INH+RIF and INH+RIF+PZA. Hepatoprotective effect of silymarin was investigated by co-administration of silymarin together with the drugs. Serum biochemical tests for liver functions and histopathological examination of livers were carried out to demonstrate the protection of liver against anti-tuberculosis drugs by silymarin.

RESULTS

Treatment of rats with INH+RIF or INH+RIF+PZA induced hepatotoxicity as evidenced by biochemical measurements: serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) activities and the levels of total bilirubin were elevated, and the levels of albumin and total protein were decreased in drugs-treated animals. Histopathological changes were also observed in livers of animals that received drugs. Simultaneous administration of silymarin significantly decreased the biochemical and histological changes induced by the drugs.

CONCLUSION

The active components of silymarin had protective effects against hepatotoxic actions of drugs used in the chemotherapy of tuberculosis in animal models. Since no significant toxicity of silymarin is reported in human studies, this plant extract can be used as a dietary supplement by patients taking anti-tuberculosis medications.

Isoniazid-rifampicin induced lipid changes in rats

INTRODUCTION

Isoniazid (INH) and rifampicine (RIF) continues to be highly effective drugs in the chemoprophylaxis and treatment of tuberculosis. It is associated with hepatotoxicity in some individuals. Change in liver and serum lipids may be one of the reasons of hepatotoxicity. We examined isoniazid-rifampicine induced lipid changes in liver and serum of rats.

METHODS

In a rat model of INH-RIF induced hepatotoxicity we evaluated the effect of oral administration of INH-RIF (50 mg/kg body weight /day each) on hepatic marker enzymes, total lipids, cholesterol, triglycerides and phospholipids in serum and liver of experimental rats after 28 days. Enzymes, total lipids and lipid fractions were measured according to standard methods.

RESULTS

Treatment with INH-RIF increased the hepatic marker enzymes after 28 days and altered the lipid levels in serum and liver. Administration of INH-RIF resulted in significantly increased liver and serum cholesterol and total Lipids as compared to control group, while triglycerides were significantly elevated in liver only. In contrast, phospholipids were significantly decreased in liver and no effect in serum was observed.

CONCLUSION

Changes in lipids (both in serum and liver) are likely involved in the pathogenesis of INH-RIF induced hepatoxicity in rats.

Effect of silymarin on pyrogallol- and rifampicin-induced hepatotoxicity in mouse

Rifampicin and pyrogallol, besides beneficial effects, elicit hepatotoxicity in experimental animals and humans. The present investigation was undertaken to elucidate the role of drug/toxicant-metabolizing enzymes in rifampicin- and pyrogallol-induced hepatotoxicity and the effect of silymarin, a herbal antioxidant, on rifampicin- and pyrogallol-induced alterations in mouse liver. Male Swiss albino mice were treated intraperitoneally with and without rifampicin (20 mg/kg) and/or pyrogallol (40 mg/kg) for 1, 2, 3 and 4 weeks. In some experiments, animals were treated with silymarin (40 mg/kg), 2 h prior to rifampicin and/or pyrogallol. The differential expression and catalytic activity of cytochrome P-450 (CYP) 1A1, CYP1A2 and CYP2E1, the activity of glutathione-S-transferase, glutathione peroxidase and glutathione reductase, and lipid peroxidation were measured in the liver of control and treated groups. CYP1A1 expression and catalytic activity were not altered following individual or combinational treatment. A significant augmentation in the expression and activity of CYP1A2 and CYP2E1 was observed following pyrogallol and rifampicin+pyrogallol treatment; however, rifampicin exhibited a significant induction of CYP2E1 only. Attenuation of glutathione-S-transferase, glutathione reductase and glutathione peroxidase activities and augmentation of lipid peroxidation were observed following rifampicin and/or pyrogallol treatment and a cumulative effect was seen when the two drugs were administered in combination. Silymarin restored the rifampicin- and/or pyrogallol-induced alterations in the expression and activity of CYP1A2 and CYP2E1, the activity of glutathione-S-transferase, glutathione reductase, and glutathione peroxidase, and lipid peroxidation. The results demonstrate the role of CYP1A2, CYP2E1, glutathione-S-transferase, glutathione reductase and glutathione peroxidase in rifampicin- and pyrogallol-induced hepatotoxicity and provide evidence for the involvement of silymarin in attenuation of drug-induced hepatotoxicity.