Analgesics and glutathione

Opioid use and risks in candidates and recipients of liver transplant

Opioid use is extremely prevalent among patients with cirrhosis and those who received liver transplant (LT), despite concerns regarding opioid-related risks in this population. While there are many theoretical risks of opioids in patients with hepatic dysfunction, there is limited evidence on the effect of opioid use on clinical outcomes in cirrhosis and patients before and after LT specifically. As a result, there is significant center-level variability in opioid-related practices and policies. The existing data-largely based on retrospective observational studies-do suggest that opioids are associated with increased health resource utilization pre-LT and post-LT and that they may precipitate HE in patients with cirrhosis and increase the risk of graft loss and death after LT. The strongest predictor of opioid use after LT is opioid use before transplant; thus, a focus on safe opioid use in the pretransplant and peritransplant periods is essential for minimizing opioid-related harms. We describe 3 strategies to guide LT providers including (1) improved characterization of pain, mental health symptoms, and opioid and polysubstance use; (2) minimization of opioid prescriptions for those at highest risk of adverse events; and (3) safe prescribing strategies for those who do use opioids and for the management of opioid use disorder. Ultimately, our goal is to improve the quality of life and transplant outcomes among patients with cirrhosis and those who received LT, particularly those living with concurrent pain, mental health, and substance use disorders.

Propyl gallate induces cell death in human pulmonary fibroblast through increasing reactive oxygen species levels and depleting glutathione

Propyl gallate (PG) exhibits an anti-growth effect on various cell types. The present study investigated the impact of PG on the levels of reactive oxygen species (ROS) and glutathione (GSH) in primary human pulmonary fibroblast (HPF) cells. Moreover, the effects of N-acetyl cysteine (NAC, an antioxidant), L-buthionine sulfoximine (BSO, a GSH synthesis inhibitor), and small interfering RNA (siRNAs) against various antioxidant genes on ROS and GSH levels and cell death were examined in PG-treated HPF cells. PG (100-800 μM) increased the levels of total ROS and O2·- at early time points of 30-180 min and 24 h, whereas PG (800-1600 μM) increased GSH-depleted cell number at 24 h and reduced GSH levels at 30-180 min. PG downregulated the activity of superoxide dismutase (SOD) and upregulated the activity of catalase in HPF cells. Treatment with 800 μM PG increased the number of apoptotic cells and cells that lost mitochondrial membrane potential (MMP; ΔΨm). NAC treatment attenuated HPF cell death and MMP (ΔΨm) loss induced by PG, accompanied by a decrease in GSH depletion, whereas BSO exacerbated the cell death and MMP (ΔΨm) loss without altering ROS and GSH depletion levels. Furthermore, siRNA against SOD1, SOD2, or catalase attenuated cell death in PG-treated HPF cells, whereas siRNA against GSH peroxidase enhanced cell death. In conclusion, PG induced cell death in HPF cells by increasing ROS levels and depleting GSH. NAC was found to decrease HPF cell death induced by PG, while BSO enhanced cell death. The findings shed light on how manipulating the antioxidant system influence the cytotoxic effects of PG in HPF cells.

Ebselen Inhibits the Growth of Lung Cancer Cells via Cell Cycle Arrest and Cell Death Accompanied by Glutathione Depletion

Ebselen is a glutathione (GSH) peroxidase (GPx) mimic originally developed to reduce reactive oxygen species (ROS). However, little is known about its cytotoxicological effects on lung cells. Therefore, this study aimed to investigate the effects of Ebselen on the cell growth and cell death of A549 lung cancer cells, Calu-6 lung cancer cells, and primary normal human pulmonary fibroblast (HPF) cells in relation to redox status. The results showed that Ebselen inhibited the growth of A549, Calu-6, and HPF cells with IC50 values of approximately 12.5 μM, 10 μM, and 20 μM, respectively, at 24 h. After exposure to 15 μM Ebselen, the proportions of annexin V-positive cells were approximately 25%, 65%, and 10% in A549, Calu-6, and HPF cells, respectively. In addition, Ebselen induced arrest at the S phase of the cell cycle in A549 cells and induced G2/M phase arrest in Calu-6 cells. Treatment with Ebselen induced mitochondrial membrane potential (MMP; ΔΨm) loss in A549 and Calu-6 cells. Z-VAD, a pan-caspase inhibitor, did not decrease the number of annexin V-positive cells in Ebselen-treated A549 and Calu-6 cells. Intracellular ROS levels were not significantly changed in the Ebselen-treated cancer cells at 24 h, but GSH depletion was efficiently induced in these cells. Z-VAD did not affect ROS levels or GSH depletion in Ebselen-treated A549 or Ebselen-treated Calu-6 cells. In conclusion, Ebselen inhibited the growth of lung cancer and normal fibroblast cells and induced cell cycle arrest and cell death in lung cancer cells with GSH depletion.

Tempol Inhibits the Growth of Lung Cancer and Normal Cells through Apoptosis Accompanied by Increased O2•- Levels and Glutathione Depletion

Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl) is a stable, cell-permeable redox-cycling nitroxide water-soluble superoxide dismutase (SOD) mimetic agent. However, little is known about its cytotoxic effects on lung-related cells. Thus, the present study investigated the effects of Tempol on cell growth and death as well as changes in reactive oxygen species (ROS) and glutathione (GSH) levels in Calu-6 and A549 lung cancer cells, normal lung WI-38 VA-13 cells, and primary pulmonary fibroblast cells. Results showed that Tempol (0.5~4 mM) dose-dependently inhibited the growth of lung cancer and normal cells with an IC50 of approximately 1~2 mM at 48 h. Tempol induced apoptosis in lung cells with loss of mitochondrial membrane potential (MMP; ∆Ψm) and activation of caspase-3. There was no significant difference in susceptibility to Tempol between lung cancer and normal cells. Z-VAD, a pan-caspase inhibitor, significantly decreased the number of annexin V-positive cells in Tempol-treated Calu-6, A549, and WI-38 VA-13 cells. A 2 mM concentration of Tempol increased ROS levels, including O2•- in A549 and WI-38 VA-13 cells after 48 h, and specifically increased O2•- levels in Calu-6 cells. In addition, Tempol increased the number of GSH-depleted cells in Calu-6, A549, and WI-38 VA-13 cells at 48 h. Z-VAD partially downregulated O2•- levels and GSH depletion in Tempol-treated these cells. In conclusion, treatment with Tempol inhibited the growth of both lung cancer and normal cells via apoptosis and/or necrosis, which was correlated with increased O2•- levels and GSH depletion.

Why paracetamol (acetaminophen) is a suitable first choice for treating mild to moderate acute pain in adults with liver, kidney or cardiovascular disease, gastrointestinal disorders, asthma, or who are older

Acute pain is among the most common reasons that people consult primary care physicians, who must weigh benefits versus risks of analgesics use for each patient. Paracetamol (acetaminophen) is a first-choice analgesic for many adults with mild to moderate acute pain, is generally well tolerated at recommended doses (≤4 g/day) in healthy adults and may be preferable to non-steroidal anti-inflammatory drugs that are associated with undesirable gastrointestinal, renal, and cardiovascular effects. Although paracetamol is widely used, many patients and physicians still have questions about its suitability and dosing, especially for older people or adults with underlying comorbidities, for whom there are limited clinical data or evidence-based guidelines. Inappropriate use may increase the risks of both overdosing and inadequate analgesia. To address knowledge deficits and augment existing guidance in salient areas of uncertainty, we have researched, reviewed, and collated published evidence and expert opinion relevant to the acute use of paracetamol by adults with liver, kidney, or cardiovascular diseases, gastrointestinal disorders, asthma, or/and who are older. A concern is hepatotoxicity, but this is rare among adults who use paracetamol as directed, including people with cirrhotic liver disease. Putative epidemiologic associations of paracetamol use with kidney or cardiovascular disease, hypertension, gastrointestinal disorders, and asthma largely reflect confounding biases and are of doubtful relevance to short-term use (<14 days). Paracetamol is a suitable first-line analgesic for mild to moderate acute pain in many adults with liver, kidney or cardiovascular disease, gastrointestinal disorders, asthma, and/or who are older. No evidence supports routine dose reduction for older people. Rather, dosing for adults who are older and/or have decompensated cirrhosis, advanced kidney failure, or analgesic-induced asthma that is known to be cross-sensitive to paracetamol, should be individualized in consultation with their physician, who may recommend a lower effective dose appropriate to the circumstances.

Potential deleterious effects of paracetamol dose regime used in Nigeria versus that of the United States of America

Paracetamol, also known as acetaminophen (N-acetyl-para-aminophenol, APAP) is the world's most used over-the-counter analgesic-antipyretic drug. Despite its good safety profile, acetaminophen can cause severe hepatotoxicity in overdose, and poisoning from paracetamol has become a major public health concern. Paracetamol is now the major cause of acute liver failure in the United States and Europe. This systematic review aims at examining the likelihood of paracetamol use in Nigeria causing more liver toxicity vis-à-vis the reduced maximum recommended daily adult dose of 3 g for the 500 mg tablet. Online searches were conducted in the databases of PubMed, Google Scholar and MEDLINE for publications using terms like "paracetamol toxicity," "acetaminophen and liver toxicity," "paracetamol and liver diseases in Nigeria," and other variants. Further search of related references in PubMed was carried out, and synthesis of all studies included in this review finalized. There were 94 studies that met the inclusion criteria. Evaluation of hepatic disorder was predicated mostly on a constellation of clinical features and limited clinical laboratory investigations. Determination of blood paracetamol concentration was rarely reported, thus excluding paracetamol poisoning as one of the likely causes of liver disorders in Nigeria. In Nigeria and elsewhere, several factors are known to increase paracetamol's predisposition to liver injury. They include: the over-the-counter status of paracetamol, use of fixed-dose combinations of paracetamol with other drugs, malnutrition, dose miscalculations, and chronic alcohol consumption. The tendency to exceed the new paracetamol maximum daily dose of 3 g in Nigeria may increase its risk for hepatotoxicity than observed in the United States of America known for emphasizing lower dose of the drug. In addition to recommending the new maximal daily paracetamol dose allowance, the historical maximum daily adult dose of 4 g should be de-emphasized in Nigeria.

Hepatoprotective Effects of Bioflavonoid Luteolin Using Self-Nanoemulsifying Drug Delivery System

Luteolin (LUT) is a natural pharmaceutical compound that is weakly water soluble and has low bioavailability when taken orally. As a result, the goal of this research was to create self-nanoemulsifying drug delivery systems (SNEDDS) for LUT in an attempt to improve its in vitro dissolution and hepatoprotective effects, resulting in increased oral bioavailability. Using the aqueous phase titration approach and the creation of pseudo-ternary phase diagrams with Capryol-PGMC (oil phase), Tween-80 (surfactant), and Transcutol-HP (co-emulsifier), various SNEDDS of LUT were generated. SNEDDS were assessed for droplet size, polydispersity index (PDI), zeta potential (ZP), refractive index (RI), and percent of transmittance (percent T) after undergoing several thermodynamic stability and self-nanoemulsification experiments. When compared to LUT suspension, the developed SNEDDS revealed considerable LUT release from all SNEDDS. Droplet size was 40 nm, PDI was <0.3, ZP was -30.58 mV, RI was 1.40, percent T was >98 percent, and drug release profile was >96 percent in optimized SNEDDS of LUT. For in vivo hepatoprotective testing in rats, optimized SNEDDS was chosen. When compared to LUT suspension, hepatoprotective tests showed that optimized LUT SNEDDS had a substantial hepatoprotective impact. The findings of this investigation suggested that SNEDDS could improve bioflavonoid LUT dissolution rate and therapeutic efficacy.

Imbalanced GSH/ROS and sequential cell death

Reactive oxygen species (ROS) are produced in cells during metabolic processes. Excessive intracellular ROS may react with large biomolecules, such as DNA, RNA, proteins, and small biomolecules, that is, glutathione (GSH) and unsaturated fatty acids. GSH has physiological functions, including free radical scavenging, anti-oxidation, and electrophile elimination. The disruption of ROS/GSH balance results in the deleterious oxidation and chemical modification of biomacromolecules, which eventually leads to cell-cycle arrest and proliferation inhibition, and even induces cell death. Imbalanced ROS/GSH may result from a direct increase of ROS, consumption of GSH, intracellular oxidoreductase interference, or thioredoxin activity reduction. Some chemicals including arsenic trioxide (ATO), pyrogallol (PG), and carbobenzoxy-Leu-Leu-leucinal (MG132) could also disrupt the balance of GSH and ROS. This article reviews the occurrence and consequences of the imbalance between GSH and ROS and introduces factors responsible for the disruption of cellular ROS and GSH balance, resulting in cell death. "GSH" and "ROS" were used as keywords to search the relevant literaturess.

Tempol differently affects cellular redox changes and antioxidant enzymes in various lung-related cells

Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl) is a potential redox agent in cells. The present study investigated changes in cellular reactive oxygen species (ROS) and glutathione (GSH) levels and in antioxidant enzymes, in Tempol-treated Calu-6 and A549 lung cancer cells, normal lung WI-38 VA-13 cells, and primary pulmonary fibroblasts. Results demonstrated that Tempol (0.5–4 mM) either increased or decreased general ROS levels in lung cancer and normal cells at 48 h and specifically increased O₂^•− levels in these cells. In addition, Tempol differentially altered the expression and activity of antioxidant enzymes such as superoxide dismutase, catalase, and thioredoxin reductase1 (TrxR1) in A549, Calu-6, and WI-38 VA-13 cells. In particular, Tempol treatment increased TrxR1 protein levels in these cells. Tempol at 1 mM inhibited the growth of lung cancer and normal cells by about 50% at 48 h but also significantly induced cell death, as evidenced by annexin V-positive cells. Furthermore, down-regulation of TrxR1 by siRNA had some effect on ROS levels as well as cell growth inhibition and death in Tempol-treated or -untreated lung cells. In addition, some doses of Tempol significantly increased the numbers of GSH-depleted cells in both cancer cells and normal cells at 48 h. In conclusion, Tempol differentially increased or decreased levels of ROS and various antioxidant enzymes in lung cancer and normal cells, and induced growth inhibition and death in all lung cells along with an increase in O₂^•− levels and GSH depletion.

Assessment of the biochemical pathways for acetaminophen toxicity: Implications for its carcinogenic hazard potential

In 2019 California's Office of Environmental Health Hazard Assessment (OEHHA) initiated a review of the carcinogenic hazard potential of acetaminophen. In parallel with this review, herein we evaluated the mechanistic data related to the steps and timing of cellular events following therapeutic recommended (≤4 g/day) and higher doses of acetaminophen that may cause hepatotoxicity to evaluate whether these changes indicate that acetaminophen is a carcinogenic hazard. At therapeutic recommended doses, acetaminophen forms limited amounts of N-acetyl-p-benzoquinone-imine (NAPQI) without adverse cellular effects. Following overdoses of acetaminophen, there is potential for more extensive formation of NAPQI and depletion of glutathione, which may result in mitochondrial dysfunction and DNA damage, but only at doses that result in cell death - thus making it implausible for acetaminophen to induce the kind of stable, genetic damage in the nucleus indicative of a genotoxic or carcinogenic hazard in humans. The collective data demonstrate a lack of a plausible mechanism related to carcinogenicity and are consistent with rodent cancer bioassays, epidemiological results reviewed in companion manuscripts in this issue, as well as conclusions of multiple international health authorities.

Are some people at increased risk of paracetamol-induced liver injury? A critical review of the literature

Purpose

Paracetamol is one of the world’s most commonly used drugs. In overdose, it is well established to be hepatotoxic. The aim of this review was to identify factors that have been, or actually are, associated with the development of liver injury after paracetamol exposure in humans.

Method

Google Scholar and PubMed were searched on various dates between December 2016 and March 2017. Papers identified had their references analysed for further studies that might be relevant.

Results

At the time of writing, there was little good quality clinical evidence—from studies of paracetamol overdose or therapeutic use—to suggest that any groups of people are relatively protected from, or are at greater risk of, liver injury. The factors that were historically used to indicate higher risk in the UK have no good quality clinical evidence to support their re-introduction into clinical practice. The safe (and still effective) oral dose of paracetamol in patients weighing less than 50 kg has not been established.

Conclusion

There is no patient group that is unequivocally at elevated risk of paracetamol-induced liver toxicity. We propose two clinical scenarios that warrant further research. Firstly, there is a need to establish whether the dose of paracetamol should be reduced in patients with low body weight. Secondly, if or when genomic information regarding individual patients becomes readily available to inform prescribing, we propose the contribution of the genome to paracetamol toxicity should be re-investigated with robustly designed studies. Such studies could enhance the safe use of one of the most frequently taken drugs.

Electronic supplementary material

The online version of this article (10.1007/s00228-017-2356-6) contains supplementary material, which is available to authorized users.

Oral bioavailability enhancement and hepatoprotective effects of thymoquinone by self-nanoemulsifying drug delivery system

Thymoquinone (TQ) is a poorly water soluble bioactive compound which shows poor oral bioavailability upon oral administration. Due to poor aqueous solubility and bioavailability of TQ, various self-nanoemulsifying drug delivery systems (SNEDDS) of TQ were developed and evaluated for enhancement of its hepatoprotective effects and oral bioavailability. Hepatoprotective and pharmacokinetic studies of TQ suspension and TQ-SNEDDS were carried out in rat models. Different SNEDDS formulations of TQ were developed and thermodynamically stable TQ-SNEDDS were characterized for physicochemical parameters and evaluated for drug release studies via dialysis membrane. Optimized SNEDDS formulation of TQ was selected for further evaluation of in vivo evaluation. In vivo hepatoprotective investigations showed significant hepatoprotective effects for optimized TQ-SNEDDS in comparison with TQ suspension. The oral administration of optimized SNEDDS showed significant improvement in in vivo absorption of TQ in comparison with TQ suspension. The relatively bioavailability of TQ was enhanced 3.87-fold by optimized SNEDDS in comparison with TQ suspension. The results of this research work indicated the potential of SNEDDS in enhancing relative bioavailability and therapeutic effects of natural bioactive compounds such as TQ.

Gene Expression Analysis Offers Unique Advantages to Histopathology in Liver Biopsy Evaluations

Liver diseases that induce nonuniform lesions often give rise to greatly varying histopathology results in needle biopsy samples from the same patient. This study examines whether gene expression analysis of such biopsies could provide a more representative picture of the overall condition of the liver. We utilized acetaminophen (APAP) as a model hepatotoxicant that gives a multifocal pattern of necrosis following toxic doses. Rats were treated with a single toxic or subtoxic dose of APAP and sacrificed 6, 24, or 48 hours after exposure. Left liver lobes were harvested, and both gene expression and histopathological analysis were performed on biopsy-sized samples. While histopathological evaluation of such small samples revealed significant sample to sample differences after toxic doses of APAP, gene expression analysis provided a very homogeneous picture and allowed clear distinction between subtoxic and toxic doses. The main biological function differentiating animals that received sub-toxic from those that had received toxic doses was an acute stress response at 6 hours and signs of energy depletion at later time points. Our results suggest that the use of genomic analysis of biopsy samples together with histopathological analysis could provide a more precise representation of the overall condition of a patient’s liver than histopathological evaluation alone.

Down-Regulation of Thioredoxin1 Is Involved in Death of Calu-6 Lung Cancer Cells Treated With Suberoyl Bishydroxamic Acid

Suberoyl bishydroxamic acid (SBHA), a histone deacetylase (HDAC) inhibitor, can show an anticancer effect. In this study, we investigated the effects of SBHA on the growth inhibition and death of Calu-6 and NCI-H1299 cells in relation to reactive oxygen species (ROS) and antioxidant levels. SBHA inhibited the growth of Calu-6 and NCI-H1299 lung cancer cells with an IC50 of 50 µM at 72 h. This agent induced apoptosis in Calu-6 cells and triggered to a G2/M phase arrest in NCI-H1299 cells. Although it also reduced the growth of normal human pulmonary fibroblast (HPF) cells, the susceptibility of Calu-6 cells to SBHA was higher than that of HPF cells. In addition, SBHA did not affect the growth of human small airway epithelial cells (HSAEC). Regarding ROS and antioxidant levels, SBHA increased ROS level and glutathione (GSH) depletion in Calu-6 and NCI-H1299 cells whereas it decreased ROS levels in HPF and HSAEC. SBHA also decreased thioredoxin1 (Trx1) level in Calu-6 cells. Although the down-regulation of Trx1 intensified apoptosis and ROS level in SBHA-treated Calu-6 cells, the overexpression of Trx1 attenuated apoptosis and ROS level in these cells. This down-regulation of Trx1 did not affect apoptosis-signaling regulating kinase1 (ASK1) activation. In conclusion, the down-regulation of Trx1 by SBHA was closely involved in cell death in Calu-6 cells.

Induction of Apoptosis and Reduction of Endogenous Glutathione Level by the Ethyl-Acetate Soluble Fraction of the Methanol Extract of the Roots of Potentilla fulgens in Cancer Cells

Potentilla fulgens root traditionally used as a folk remedy in Meghalaya, India. However, systematic evaluation of its anticancer efficacy was limited. We investigated the anticancer potentials of the various extracts prepared by partitioning of the methanol extract of the root with the aim to discover major contributing factors from the most effective fractions. Methanol extract of P. fulgens roots (PRE) was prepared by maceration which was subsequently fractionated into hexane, ethyl-acetate (EA) and n-butanol soluble fractions. Various assays (clonogenic assay, Flow cytometry analysis, western blot, semiquantitative RT-PCR and the level of endogenous glutathione) were used to evaluate different parameters, such as Cell survivability, PARP-1 proteolysis, expression pattern of anti-apoptotic and γ-glutamyl-cysteine synthetase heavy subunit (GCSC) genes in both MCF-7 and U87 cancer cell lines. Since the EA-fraction showed most efficient growth inhibitory effect, it was further purified and a total of nine compounds and some monomeric and dimeric flavan-3-ols were identified and characterized. Three compounds viz., epicatechin (EC), gallic acid (GA) and ursolic acid (UA) were taken on the basis of their higher yield and 10 μg/ml of each was mixed together. The concentration used in this study for PRE, EA- and Hex-fraction was 100 μg/ml, which was higher than the IC₅₀ value. Apoptotic cell death in the PRE, EA-fraction and EC+GA+UA treated cancer cell cultures was significantly greater than in normal cells due to suppression of anti-apoptotic protein Bcl2 following treatment. Depletion of glutathione by downregulating GCSC was also observed. Induction of apoptosis and lowering the level of glutathione are considered to be positive activity for an anticancer agent. Therefore, modulation of GSH concentration in tumor cells by PRE and its EA-fraction opened up the possibility of a new therapeutic approach because these plant products are not harmful to normal cells and may regulate the tumor cellular response to different anticancer treatments. Thus, it would be interesting to examine efficacy of these plant products or EA-fraction in human cancer treatment.

Late-onset acetaminophen-induced allergic hepatitis with progression to chronicity

Acetaminophen (paracetamol), a widely used antipyretic/analgesic, is a well-known agent causing acute hepatic injury. Whereas most cases are caused by its intrinsic hepatotoxicity, idiosyncratic hepatitis by the allergic mechanism is extremely rare. We herein report a case of late-onset acetaminophen-induced allergic hepatitis with progression to chronicity. This unique case extends the spectrum of acetaminophen-induced liver injury. Clinicians should be aware of this unusual clinical manifestation. The mechanism underlying the immunological reaction to acetaminophen remains to be elucidated.

The association between acetaminophen and asthma: is there anything to learn from the upper airways?

PURPOSE OF REVIEW

To examine the literature evidence for the association between acetaminophen (paracetamol) use and development of rhinitis.

RECENT FINDINGS

Increased use of acetaminophen (paracetamol) as the favored antipyretic during pregnancy and infancy has been hypothesized to be a risk factor for the development of asthma. There is a paucity of well designed birth cohort studies to examine paracetamol as a risk factor in the development of rhinitis. Confounding by antibiotic use, viral infections, and recall bias are problematic for many of the studies that are published.

SUMMARY

Prospective birth cohorts need to dedicate sufficient time and research personnel to adequately assess paracetamol exposure as a primary variable of interest rather than as an incidental exposure variable collected during routine questionnaire administration.

Thymol from Thymus quinquecostatus Celak. protects against tert-butyl hydroperoxide-induced oxidative stress in Chang cells

The present work describes the protective effects of thymol isolated from Thymus quinquecostatus Celak. against tert-butyl hydroperoxide (t-BHP)-induced oxidative damage through various experiments with Chang liver cells. Thymol significantly protected hepatocytes against t-BHP-induced cell cytotoxicity as demonstrated by increased viability. Furthermore, observation of Hoechst staining, annexin V/PI staining, and expression of Bcl-2 and Bax indicated that thymol inhibited t-BHP-induced Chang cell damage. Further, thymol inhibited the loss of mitochondrial membrane potential in t-BHP-treated Chang cells and prevented oxidative stress-triggered reactive oxygen species (ROS) and lipid peroxidation (malondialdehyde, MDA). Thymol restored the antioxidant capability of hepatocytes including glutathione (GSH) levels which were reduced by t-BHP. These results indicated that thymol prevents oxidative stress-induced damage to liver cells through suppression of ROS and MDA levels and increase of GSH level.

The modern pharmacology of paracetamol: therapeutic actions, mechanism of action, metabolism, toxicity and recent pharmacological findings

Paracetamol is used worldwide for its analgesic and antipyretic actions. It has a spectrum of action similar to that of NSAIDs and resembles particularly the COX-2 selective inhibitors. Paracetamol is, on average, a weaker analgesic than NSAIDs or COX-2 selective inhibitors but is often preferred because of its better tolerance. Despite the similarities to NSAIDs, the mode of action of paracetamol has been uncertain, but it is now generally accepted that it inhibits COX-1 and COX-2 through metabolism by the peroxidase function of these isoenzymes. This results in inhibition of phenoxyl radical formation from a critical tyrosine residue essential for the cyclooxygenase activity of COX-1 and COX-2 and prostaglandin (PG) synthesis. Paracetamol shows selectivity for inhibition of the synthesis of PGs and related factors when low levels of arachidonic acid and peroxides are available but conversely, it has little activity at substantial levels of arachidonic acid and peroxides. The result is that paracetamol does not suppress the severe inflammation of rheumatoid arthritis and acute gout but does inhibit the lesser inflammation resulting from extraction of teeth and is also active in a variety of inflammatory tests in experimental animals. Paracetamol often appears to have COX-2 selectivity. The apparent COX-2 selectivity of action of paracetamol is shown by its poor anti-platelet activity and good gastrointestinal tolerance. Unlike both non-selective NSAIDs and selective COX-2 inhibitors, paracetamol inhibits other peroxidase enzymes including myeloperoxidase. Inhibition of myeloperoxidase involves paracetamol oxidation and concomitant decreased formation of halogenating oxidants (e.g. hypochlorous acid, hypobromous acid) that may be associated with multiple inflammatory pathologies including atherosclerosis and rheumatic diseases. Paracetamol may, therefore, slow the development of these diseases. Paracetamol, NSAIDs and selective COX-2 inhibitors all have central and peripheral effects. As is the case with the NSAIDs, including the selective COX-2 inhibitors, the analgesic effects of paracetamol are reduced by inhibitors of many endogenous neurotransmitter systems including serotonergic, opioid and cannabinoid systems. There is considerable debate about the hepatotoxicity of therapeutic doses of paracetamol. Much of the toxicity may result from overuse of combinations of paracetamol with opioids which are widely used, particularly in USA.

Analgesics in patients with hepatic impairment: pharmacology and clinical implications

The physiological changes that accompany hepatic impairment alter drug disposition. Porto-systemic shunting might decrease the first-pass metabolism of a drug and lead to increased oral bioavailability of highly extracted drugs. Distribution can also be altered as a result of impaired production of drug-binding proteins or changes in body composition. Furthermore, the activity and capacity of hepatic drug metabolizing enzymes might be affected to various degrees in patients with chronic liver disease. These changes would result in increased concentrations and reduced plasma clearance of drugs, which is often difficult to predict. The pharmacology of analgesics is also altered in liver disease. Pain management in hepatically impaired patients is challenging owing to a lack of evidence-based guidelines for the use of analgesics in this population. Complications such as bleeding due to antiplatelet activity, gastrointestinal irritation, and renal failure are more likely to occur with nonsteroidal anti-inflammatory drugs in patients with severe hepatic impairment. Thus, this analgesic class should be avoided in this population. The pharmacokinetic parameters of paracetamol (acetaminophen) are altered in patients with severe liver disease, but the short-term use of this drug at reduced doses (2 grams daily) appears to be safe in patients with non-alcoholic liver disease. The disposition of a large number of opioid drugs is affected in the presence of hepatic impairment. Certain opioids such as codeine or tramadol, for instance, rely on hepatic biotransformation to active metabolites. A possible reduction of their analgesic effect would be the expected pharmacodynamic consequence of hepatic impairment. Some opioids, such as pethidine (meperidine), have toxic metabolites. The slower elimination of these metabolites can result in an increased risk of toxicity in patients with liver disease, and these drugs should be avoided in this population. The drug clearance of a number of opioids, such as morphine, oxycodone, tramadol and alfentanil, might be decreased in moderate or severe hepatic impairment. For the highly excreted morphine, hydromorphone and oxycodone, an important increase in bioavailability occurs after oral administration in patients with hepatic impairment. Lower doses and/or longer administration intervals should be used when these opioids are administered to patients with liver disease to avoid the risk of accumulation and the potential increase of adverse effects. Finally, the pharmacokinetics of phenylpiperidine opioids such as fentanyl, sufentanil and remifentanil appear to be unaffected in hepatic disease. All opioid drugs can precipitate or aggravate hepatic encephalopathy in patients with severe liver disease, thus requiring cautious use and careful monitoring.

Protective effect of Amorphophallus campanulatus (Roxb.) Blume. tuber against thioacetamide induced oxidative stress in rats

OBJECTIVE

To identify the phytochemical constituents of Amorphophallus campanulatus (A. campanulatus) tuber and to evaluate its antioxidant potential through in vitro and in vivo models.

METHODS

Phytochemical screening and in vitro antioxidant activities of A. campanulatus tuber n-hexane extract (ACHE) and methanolic extract (ACME) were evaluated using DPPH, hydroxyl radical, reducing power and total antioxidant capacity assays. The total phenolic and flavonoid contents were also investigated. The protective potential of two different doses of ACME (125 and 250 mg/kg) was also evaluated against thioacetamide (TAA) induced oxidative stress in rats. Silymarin used as a standard drug control. Hepatotoxicity was assessed by quantifying the serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH). The antioxidant potential of ACME were also evaluated by the estimation of catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione-S-transferase (GST), reduced glutathione (GSH) and lipid peroxidation (Thiobarbituric acid reactive substances) in hepatic and renal tissues. Histopathologic changes of liver were also evaluated.

RESULTS

In vitro studies revealed that ACME has higher antioxidant and radical scavenging activity than ACHE, which may be attributed to its higher phenolic and flavonoid content. ACME significantly prevented the elevation of serum AST, ALT, ALP, LDH, and tissue malondialdehyde levels(P < 0.05). Hepatic and renal GSH, GST, GR, GPx, and catalase levels were remarkably increased by the treatment with the extract. Quantification of histopathological changes also supported the dose dependent protective effects of ACME.

CONCLUSIONS

The results do suggest that A. campanulatus tuber could be considered as a potential source of natural antioxidant.

Dietary saturated and monounsaturated fats protect against acute acetaminophen hepatotoxicity by altering fatty acid composition of liver microsomal membrane in rats

Background

Dietary polyunsaturated fats increase liver injury in response to ethanol feeding. We evaluated the effect of dietary corn oil (CO), olive oil (OO), and beef tallow (BT) on fatty acid composition of liver microsomal membrane and acute acetaminophen hepatotoxicity.

Methods

Male Sprague-Dawley rats were fed 15% (wt/wt) CO, OO or BT for 6 weeks. After treatment with acetaminophen (600 mg/kg), samples of plasma and liver were taken for analyses of the fatty acid composition and toxicity.

Results

Treatment with acetaminophen significantly elevated levels of plasma GOT and GPT as well as hepatic TBARS but reduced hepatic GSH levels in CO compared to OO and BT groups. Acetaminophen significantly induced protein expression of cytochrome P450 2E1 in the CO group. In comparison with the CO diet, lower levels of linoleic acid, higher levels of oleic acids and therefore much lower ratios of linoleic to oleic acid were detected in rats fed OO and BT diets.

Conclusions

Dietary OO and BT produces similar liver microsomal fatty acid composition and may account for less severe liver injury after acetaminophen treatment compared to animals fed diets with CO rich in linoleic acid. These findings imply that types of dietary fat may be important in the nutritional management of drug-induced hepatotoxicity.

Inhibition of mitochondrial respiratory chain in the brain of rats after hepatic failure induced by acetaminophen

Hepatic encephalopathy is an important cause of morbidity and mortality in patients with severe hepatic failure. This disease is clinically characterized by a large variety of symptoms including motor symptoms, cognitive deficits, as well as changes in the level of alertness up to hepatic coma. Acetaminophen is frequently used in animals to produce an experimental model to study the mechanisms involved in the progression of hepatic disease. The brain is highly dependent on ATP and most cell energy is obtained through oxidative phosphorylation, a process requiring the action of various respiratory enzyme complexes located in a special structure of the inner mitochondrial membrane. In this context, the authors evaluated the activities of mitochondrial respiratory chain complexes in the brain of rats submitted to acute administration of acetaminophen and treated with the combination of N-acetylcysteine (NAC) plus deferoxamine (DFX) or taurine. These results showed that acetaminophen administration inhibited the activities of complexes I and IV in cerebral cortex and that the treatment with NAC plus DFX or taurine was not able to reverse this inhibition. The authors did not observe any effect of acetaminophen administration on complexes II and III activities in any of the structures studied. The participation of oxidative stress has been postulated in the hepatic encephalopathy and it is well known that the electron transport chain itself is vulnerable to damage by reactive oxygen species. Since there was no effect of NAC + DFX, the effect of acetaminophen was likely to be due to something else than oxidative stress.

MG132, a proteasome inhibitor decreased the growth of Calu-6 lung cancer cells via apoptosis and GSH depletion

The inhibition of proteasome function has emerged as a useful strategy to maneuver apoptosis. In the present study, we evaluated the effects of MG132 as a proteasome inhibitor on the growth of Calu-6 lung cancer cells in relation to the cell cycle, cell death, reactive oxygen species (ROS) and glutathione (GSH) levels. MG132 dose-dependently inhibited the growth of Calu-6 cells at 24h. DNA flow cytometric analysis indicated that 1-30 microM MG132 induced an S phase arrest in Calu-6 cells. MG132 also induced apoptosis, which was accompanied by the loss of mitochondrial membrane potential (MMP; Deltapsi(m)). The pan-caspase inhibitor (Z-VAD) significantly rescued Calu-6 cells from MG132-induced cell death. The intracellular ROS levels including O(2)(-) were increased in MG132-treated Calu-6 cells. MG132 also increased GSH-depleted cell numbers in Calu-6 cells. Z-VAD significantly decreased O(2)(-) levels and GSH-depleted cell numbers in MG132-treated Calu-6 cells. In conclusion, MG132 inhibited the growth of Calu-6 cells via apoptosis and GSH depletion.

MG132 as a proteasome inhibitor induces cell growth inhibition and cell death in A549 lung cancer cells via influencing reactive oxygen species and GSH level

Carbobenzoxy-Leu-Leu-leucinal (MG132) as a proteasome inhibitor has been shown to induce apoptotic cell death through formation of reactive oxygen species (ROS). In the present study, we evaluated the effects of MG132 on the growth of A549 lung cancer cells in relation to cell growth, ROS and glutathione (GSH) levels. Treatment with MG132 inhibited the growth of A549 cells with an IC50 of approximately 20 μM at 24 hours. DNA flow cytometric analysis indicated that 0.5 ∼ 30 μM MG132 induced a G1 phase arrest of the cell cycle in A549 cells. Treatment with 10 or 30 μM MG132 also induced apoptosis, as evidenced by sub-G1 cells and annexin V staining cells. This was accompanied by the loss of mitochondrial membrane potential (MMP; Δψm). The intracellular ROS levels including O2•- were strongly increased in 10 or 30 μM MG132-treated A549 cells but were down-regulated in 0.1, 0.5 or 1 μM MG132-treated cells. Furthermore, 10 or 30 μM MG132 increased mitochondrial O2•- level but 0.1, 0.5 or 1 μM MG132 decreased that. In addition, 10 or 30 μM MG132 induced GSH depletion in A549 cells. In conclusion, MG132 inhibited the growth of human A549 cells via inducing the cell cycle arrest as well as triggering apoptosis, which was in part correlated with the changes of ROS and GSH levels. Our present data provide important information on the anti-growth mechanisms of MG132 in A549 lung cancer cells in relation to ROS and GSH.

Biochemical mechanisms in drug-induced liver injury: Certainties and doubts

Drug-induced liver injury is a significant and still unresolved clinical problem. Limitations to knowledge about the mechanisms of toxicity render incomplete the detection of hepatotoxic potential during preclinical development. Several xenobiotics are lipophilic substances and their transformation into hydrophilic compounds by the cytochrome P-450 system results in production of toxic metabolites. Aging, preexisting liver disease, enzyme induction or inhibition, genetic variances, local O₂ supply and, above all, the intrinsic molecular properties of the drug may affect this process. Necrotic death follows antioxidant consumption and oxidation of intracellular proteins, which determine increased permeability of mitochondrial membranes, loss of potential, decreased ATP synthesis, inhibition of Ca²⁺-dependent ATPase, reduced capability to sequester Ca²⁺ within mitochondria, and membrane bleb formation. Conversely, activation of nucleases and energetic participation of mitochondria are the main intracellular mechanisms that lead to apoptosis. Non-parenchymal hepatic cells are inducers of hepatocellular injury and targets for damage. Activation of the immune system promotes idiosyncratic reactions that result in hepatic necrosis or cholestasis, in which different HLA genotypes might play a major role. This review focuses on current knowledge of the mechanisms of drug-induced liver injury and recent advances on newly discovered mechanisms of liver damage. Future perspectives including new frontiers for research are discussed.

Brain creatine kinase activity is inhibited after hepatic failure induced by carbon tetrachloride or acetaminophen

Encephalopathy is an important cause of morbidity and mortality in patients with severe hepatic failure and the mechanisms underlying hepatic encephalopathy are still not fully known. Considering that creatine kinase (CK) play a crucial role in brain energy homeostasis and is inhibited by free radicals, and that oxidative stress is probably involved in the pathogenesis of hepatic encephalopathy, we evaluated CK activity in hippocampus, striatum, cerebellum, cerebral cortex and prefrontal cortex of rats submitted to acute administration of carbon tetrachloride or acetaminophen. The effects of the administration of antioxidants, N-acetylcysteine (NAC) plus deferoxamine (DFX) in association, and taurine, were also evaluated. Our findings demonstrated that carbon tetrachloride inhibited CK activity in cerebellum; acetaminophen inhibited the enzyme in cerebellum and hippocampus. CK activity was not affected in other brain areas. The administration of NAC plus DFX reversed the inhibition of CK activity caused by carbon tetrachloride in cerebellum and by acetaminophen in cerebellum and hippocampus. On the other hand, taurine was not able to reverse the inhibition in CK activity. Although it is difficult to extrapolate our findings to the human condition, the inhibition of brain CK activity after hepatic failure may be involved in the pathogenesis of hepatic encephalopathy.

Prevention of hepatocarcinogenesis and increased susceptibility to acetaminophen-induced liver failure in transaldolase-deficient mice by N-acetylcysteine

Although oxidative stress has been implicated in acute acetaminophen-induced liver failure and in chronic liver cirrhosis and hepatocellular carcinoma (HCC), no common underlying metabolic pathway has been identified. Recent case reports suggest a link between the pentose phosphate pathway (PPP) enzyme transaldolase (TAL; encoded by TALDO1) and liver failure in children. Here, we show that Taldo1-/- and Taldo1+/- mice spontaneously developed HCC, and Taldo1-/- mice had increased susceptibility to acetaminophen-induced liver failure. Oxidative stress in Taldo1-/- livers was characterized by the accumulation of sedoheptulose 7-phosphate, failure to recycle ribose 5-phosphate for the oxidative PPP, depleted NADPH and glutathione levels, and increased production of lipid hydroperoxides. Furthermore, we found evidence of hepatic mitochondrial dysfunction, as indicated by loss of transmembrane potential, diminished mitochondrial mass, and reduced ATP/ADP ratio. Reduced beta-catenin phosphorylation and enhanced c-Jun expression in Taldo1-/- livers reflected adaptation to oxidative stress. Taldo1-/- hepatocytes were resistant to CD95/Fas-mediated apoptosis in vitro and in vivo. Remarkably, lifelong administration of the potent antioxidant N-acetylcysteine (NAC) prevented acetaminophen-induced liver failure, restored Fas-dependent hepatocyte apoptosis, and blocked hepatocarcinogenesis in Taldo1-/- mice. These data reveal a protective role for the TAL-mediated branch of the PPP against hepatocarcinogenesis and identify NAC as a promising treatment for liver disease in TAL deficiency.

Apoptosis in arsenic trioxide-treated Calu-6 lung cells is correlated with the depletion of GSH levels rather than the changes of ROS levels

Arsenic trioxide (ATO) can regulate many biological functions such as apoptosis and differentiation in various cells. We investigated an involvement of ROS such as H(2)O(2) and O(2)(*-), and GSH in ATO-treated Calu-6 cell death. The levels of intracellular H(2)O(2) were decreased in ATO-treated Calu-6 cells at 72 h. However, the levels of O(2)(*-) were significantly increased. ATO reduced the intracellular GSH content. Many of the cells having depleted GSH contents were dead, as evidenced by the propidium iodine staining. The activity of CuZn-SOD was strongly down-regulated by ATO at 72 h while the activity of Mn-SOD was weakly up-regulated. The activity of catalase was decreased by ATO. ROS scavengers, Tiron and Trimetazidine did not reduce levels of apoptosis and intracellular O(2)(*-) in ATO-treated Calu-6 cells. Tempol showing a decrease in intracellular O(2)(*-) levels reduced the loss of mitochondrial transmembrane potential (DeltaPsi(m)). Treatment with NAC showing the recovery of GSH depletion and the decreased effect on O(2)(*-) levels in ATO-treated cells significantly inhibited apoptosis. In addition, BSO significantly increased the depletion of GSH content and apoptosis in ATO-treated cells. Treatment with SOD and catalase significantly reduced the levels of O(2)(*-) levels in ATO-treated cells, but did not inhibit apoptosis along with non-effect on the recovery of GSH depletion. Taken together, our results suggest that ATO induces apoptosis in Calu-6 cells via the depletion of the intracellular GSH contents rather than the changes of ROS levels.

Carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP) as an O2(*-) generator induces apoptosis via the depletion of intracellular GSH contents in Calu-6 cells

Carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP) is an uncoupler of mitochondrial oxidative phosphorylation in eukaryotic cells. Here, we investigated an involvement of O(2)(*-) and GSH in FCCP-induced Calu-6 cell death and examined whether ROS scavengers rescue cells from FCCP-induced cell death. Levels of intracellular O(2)(*-) were markedly increased depending on the concentrations (5-100 microM) of FCCP. A depletion of intracellular GSH content was also observed after exposing cells to FCCP. Stable SOD mimetics, Tempol and Tiron did not change the levels of intracellular O(2)(*-), apoptosis and the loss of mitochondrial membrane potential (DeltaPsi(m)). Treatment with thiol antioxidants, NAC and DTT, showed the recovery of GSH depletion and the reduction of O(2)(*-) levels in FCCP-treated cells, which were accompanied by the inhibition of apoptosis. In contrast, BSO, a well-known inhibitor of GSH synthesis, aggravated GSH depletion, oxidative stress of O(2)(*-) and cell death in FCCP-treated cells. Taken together, our data suggested that FCCP as an O(2)(*-) generator, induces apoptosis via the depletion of intracellular GSH contents in Calu-6 cells.

Potential hepatoprotective effects of fullerenol C60(OH)24 in doxorubicin-induced hepatotoxicity in rats with mammary carcinomas

The aim of this study was to investigate the potential protective role of fullerenol C60(OH)24 on doxorubicin-induced liver toxicity using in vivo (female Sprague-Dawley rats) and in vitro (human hepatocellular carcinoma - HepG2; colorectal adenocarcinoma cell lines - Caco-2) approaches. The first (healthy control) and second (control with chemically induced mammary carcinomas) group received saline only. The third, fourth and fifth group (all with breast cancer) were injected (i.p.) with a single dose of doxorubicin (8mg/kg), doxorubicin/fullerenol (100mg/kg of fullerenol 30min before administration of 8mg/kg doxorubicin) and fullerenol (100mg/kg), respectively. Two days after treatment, the rats were sacrificed. Results showed that treatment with doxorubicin alone caused significant changes in the serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and alpha-hydroxybutyrate dehydrogenase (alpha-HBDH), as well as in the levels of malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GSH-Px), total antioxidant status (TAS), glutathione reductase (GR), catalase (CAT) and superoxide dismutase (SOD) in the liver tissue. These effects were significantly reduced for all investigated parameters by pre-treatment with fullerenol but not for the MDA and GSH level. The HepG2 and Caco-2 cell lines were continuously treated with fullerenol for 12h, 24h, 48h and 96h at concentrations of 10microg/mL and 44microg/mL. With the aim of evaluating the modulating activity of fullerenol on doxorubicin-induced hepatotoxicity, the cell lines were simultaneously treated with doxorubicin (1microm; 5microm) and fullerenol (10microg/mL; 44microg/mL) in different combinations. When the cells are treated with 5microm doxorubicin along with the fullerenol, we can see a significant improvement of the cell capability during the entire time-line. We can conclude that fullerenol has cytotoxic effects on HepG2 by itself, but when the oxidative stress is too high the cytotoxic effects of fullerenol are overcome by its protective role as a strong antioxidant compound.

Metabonomics evaluation of urine from rats given acute and chronic doses of acetaminophen using NMR and UPLC/MS

Urinary metabolic perturbations associated with acute and chronic acetaminophen-induced hepatotoxicity were investigated using nuclear magnetic resonance (NMR) spectroscopy and ultra performance liquid chromatography/mass spectrometry (UPLC/MS) metabonomics approaches to determine biomarkers of hepatotoxicity. Acute and chronic doses of acetaminophen (APAP) were administered to male Sprague-Dawley rats. NMR and UPLC/MS were able to detect both drug metabolites and endogenous metabolites simultaneously. The principal component analysis (PCA) of NMR or UPLC/MS spectra showed that metabolic changes observed in both acute and chronic dosing of acetaminophen were similar. Histopathology and clinical chemistry studies were performed and correlated well with the PCA analysis and magnitude of metabolite changes. Depletion of antioxidants (e.g. ferulic acid), trigonelline, S-adenosyl-L-methionine, and energy-related metabolites indicated that oxidative stress was caused by acute and chronic acetaminophen administration. Similar patterns of metabolic changes in response to acute or chronic dosing suggest similar detoxification and recovery mechanisms following APAP administration.

Hepatoprotective effect of L-carnitine against acute acetaminophen toxicity in mice

L-carnitine is a cofactor in the transfer of long-chain fatty acid allowing the beta-oxidation of fatty acid in the mitochondria. It is also a known antioxidant with protective effects against lipid peroxidation. In this study, hepatoprotective effect of L-carnitine was investigated against acetaminophen (AA)-induced liver toxicity where mitochondrial dysfunction and oxidative stress are thought to be involved in AA hepatotoxicity. Sixty-four Balb/C mice were divided into eight groups. Mice were dosed with single-AA injection (500 mg/kg via the intra peritoneal route) with or without L-carnitine (500 mg/kg for 5 days starting 5 days before AA injection via intra peritoneal route) and sampled at 4, 8 and 24 h following AA injection. AA increased serum AST, ALT, total sialic acid (TSA) and MDA as well as tissue TSA and MDA levels significantly with the highest increase observed at 4 h, but there was a decrease in blood and tissue GSH level. Administration of L-carnitine significantly reduced AA-induced elevations in AST, ALT, TSA and MDA concentrations and increased GSH levels at all sampling points. AA also induced necrosis, hyperemia, sinusoidal congestion and hemorrhage with time-dependent increase in severity, but the degree of necrosis and histopathologic alterations were most severe at 24 h following AA administration. However, the degree of pathologic alterations was less severe with simultaneous L-carnitine application. These results suggest that AA results in oxidative damage in the liver with an acute effect. L-carnitine also has a prominent protective effect against AA toxicity and may be of therapeutic value in the treatment of AA-induced hepatotoxicity.

Acetaminophen hepatotoxicity

Acetaminophen is a commonly used antipyretic and analgesic agent. It is safe when taken at therapeutic doses; however, overdose can lead to serious and even fatal hepatotoxicity. The initial metabolic and biochemical events leading to toxicity have been well described, but the precise mechanism of cell injury and death is unknown. Prompt recognition of overdose, aggressive management, and administration of N-acetylcysteine can minimize hepatotoxicity and prevent liver failure and death. Liver transplantation can be lifesaving for those who develop acute liver failure.

Protective effects of Gingko biloba on thioacetamide-induced fulminant hepatic failure in rats

Gingko biloba (GB) has antioxidant and platelet-activating factor (PAF) antagonistic effects. We investigated the protective effects of GB on thioacetamide (TAA)-induced fulminant hepatic failure in rats. Fulminant hepatic failure was induced in treatment groups by three intraperitoneal (ip) injections of TAA (350 mg/kg) at 24-hour intervals. Treatments with GB (100 mg/kg per day, orally) and N-acetylcysteine (20 mg/kg twice daily, sc) were initiated 48 hours prior to TAA administration. The liver was removed for histopathological examinations. Serum and liver thiobarbituric acid-reactive substance (TBARS) levels were measured for assessment of oxidative stress. Liver necrosis and inflammation scores and serum and liver TBARS levels were significantly higher in the TAA group compared to the control group (P < 0.001, < 0.001, 0.001, < 0.001, respectively). Liver necrosis and inflammation scores and liver TBARS levels were significantly lower in the GB group compared to the TAA group (P < 0.001, < 0.001 and 0.01, respectively). GB ameliorated hepatic damage in TAA-induced fulminant hepatic failure. This may be due to the free radical-scavenging effects of GB.

Attenuation of mitochondrial injury by L-arginine preconditioning of the liver

The present study was aimed to evaluate the efficacy of L-arginine on mitochondrial function in ischemic and reperfusion (I/R) induced hepatic injury. Adult Wistar rat were subjected to 1 h of partial liver ischemia followed by 3 hour reperfusion. Eighteen wistar rats were divided into three groups viz. sham-operated control group (I) (n=6), ischemia and reperfusion (I/R) group (II) (n=6), L-arginine treated group (100 mg/kg body weight/daily by oral route for 7 days before induced ischemia reperfusion maneuver) (III) (n=6). Mitochondrial injury was assessed in terms of decreased (P<0.05) activities of mitochondrial antioxidant enzymes (GSH, SOD, CAT), respiratory marker enzymes (NADH dehydrogenase, cytochrome c oxidases) and hepatocytes nitric oxide production. Pre-treatment with L-arginine (10 mg/kg/p.o. for 7 days) significantly counteracted the alternations of hepatic enzymes and mitochondrial respiratory and antioxidant enzymes. In addition, electron microscopy and histopathology study showed the restoration of cellular normalcy and accredits the cytoprotective role of L-arginine against I/R induced hepatocellular injury. On the basis of these findings it may be concluded that L-arginine protects mitochondrial function in hepatic ischemic and reperfused liver.

Practical considerations for the treatment of elderly patients with migraine

Treatment of migraine presents special problems in the elderly. Co-morbid diseases may prohibit the use of some medications. Moreover, even when these contraindications do not exist, older patients are more likely than younger ones to develop adverse events. Managing older migraine patients, therefore, necessitates particular caution, including taking into account possible pharmacological interactions associated with the greater use of drugs for concomitant diseases in the elderly. Paracetamol (acetaminophen) is the safest drug for symptomatic treatment of migraine in the elderly. Use of selective serotonin 5-HT(1B/1D) receptor agonists ('triptans') is not recommended, even in the absence of cardiovascular or cerebrovascular risk, and NSAID use should be limited because of potential gastrointestinal adverse effects. Prophylactic treatments include antidepressants, beta-adrenoceptor antagonists, calcium channel antagonists and antiepileptics. Selection of a drug from one of these classes should be dictated by the patient's co-morbidities. Beta-adrenoceptor antagonists are appropriate in patients with hypertension but are contraindicated in those with chronic obstructive pulmonary disease, diabetes mellitus, heart failure and peripheral vascular disease. Use of antidepressants in low doses is, in general, well tolerated by elderly people and as effective, overall, as in young adults. This approach is preferred in patients with concomitant mood disorders. However, prostatism, glaucoma and heart disease make the use of tricyclic antidepressants more difficult. Fewer efficacy data in the elderly are available for selective serotonin reuptake inhibitors, which can be tried in particular cases because of their good tolerability profile. Calcium channel antagonists are contraindicated in patients with hypotension, heart failure, atrioventricular block, Parkinson's disease or depression (flunarizine), and in those taking beta-adrenoceptor antagonists and monoamine oxidase inhibitors (verapamil). Antiepileptic drug use should be limited to migraine with high frequency of attacks and refractoriness to other treatments. Promising additional strategies include ACE inhibitors and angiotensin II type 1 receptor antagonists because of their effectiveness and good tolerability in patients with migraine, particularly in those with hypertension. Because of its favourable compliance and safety profile, botulinum toxin type A can be considered an alternative treatment in elderly migraine patients who have not responded to other currently available migraine prophylactic agents. Pharmacological treatment of migraine poses special problems in regard to both symptomatic and prophylactic treatment. Contraindications to triptan use, adverse effects of NSAIDs, and unwanted reactions to some antiemetics reduce the list of drugs available for the treatment of migraine attacks in elderly patients. The choice of prophylactic treatment (beta-adrenoceptor antagonists, calcium channel antagonists, antiepileptics, and more recently, some antihypertensive drugs) is influenced by co-morbidities and should be directed at those drugs that are believed to have fewer adverse effects and a better safety profile. Unfortunately, for most of these drugs, efficacy studies are lacking in the elderly.

The Therapeutic Use of Acetaminophen in Patients with Liver Disease

Acetaminophen has been used safely and effectively for many years to manage pain and/or fever in patients of all ages. It is commonly recommended as first-line therapy for a variety of patients and conditions, including the elderly, children with viral illnesses, and patients with osteoarthritis, gastrointestinal conditions, bleeding disorders, cardiovascular disease, or renal disease. However, its use is often avoided in patients with chronic liver disease. The perception that acetaminophen should be avoided in such patients arose from awareness of the association between massive acetaminophen overdose and hepatotoxicity, combined with a lack of understanding of the metabolism of acetaminophen in patients with liver disease. There are various theoretical mechanisms of acetaminophen hepatotoxicity in chronic liver disease including: altered metabolism and depleted glutathione stores that would be expected to increase accumulation of the hepatotoxic intermediate, N-acetyl-p-benzoquinone imine (NAPQI). Available studies in patients with chronic liver disease, however, have shown that although the half-life of acetaminophen may be prolonged, cytochrome P-450 activity is not increased and glutathione stores are not depleted to critical levels in those taking recommended doses. Furthermore, acetaminophen has been studied in a variety of liver diseases without evidence of increased risk of hepatotoxicity at currently recommended doses. Therefore, acetaminophen can be used safely in patients with liver disease and is a preferred analgesic/antipyretic because of the absence of the platelet impairment, gastrointestinal toxicity, and nephrotoxicity associated with nonsteroidal antiinflammatory drugs.