Adverse reactions associated with acetylcysteine

A new opportunity for N-acetylcysteine. An outline of its classic antioxidant effects and its pharmacological potential as an epigenetic modulator in liver diseases treatment

Liver diseases represent a worldwide health problem accountable for two million deaths per year. Oxidative stress is critical for the development of these diseases. N-acetyl cysteine (NAC) is effective in preventing liver damage, both in experimental and clinical studies, and evidence has shown that the pharmacodynamic mechanisms of NAC are related to its antioxidant nature and ability to modulate key signaling pathways. Here, we provide a comprehensive description of the beneficial effects of NAC in the treatment of liver diseases, addressing the first evidence of its role as a scavenger and precursor of reduced glutathione, along with studies showing its immunomodulatory action, as well as the ability of NAC to modulate epigenetic hallmarks. We searched the PubMed database using the following keywords: oxidative stress, liver disease, epigenetics, antioxidants, NAC, and antioxidant therapies. There was no time limit to gather all available information on the subject. NAC has shown efficacy in treating liver damage, exerting mechanisms of action different from those of free radical scavengers. Like different antioxidant therapies, its effectiveness and safety are related to the administered dose; therefore, designing new pharmacological formulations for this drug is imperative to achieve an adequate response. Finally, there is still much to explore regarding its effect on epigenetic marker characteristics of liver damage, turning it into a drug with broad therapeutic potential. According to the literature reviewed, NAC could be an appropriate option in clinical studies related to hepatic injury and, in the future, a repurposing alternative for treating liver diseases.

Hepatoprotective effect of amifostine and WR-1065 on acetaminophen-induced liver toxicity on Wistar rats

PURPOSE

The most important problem with acetaminophen is its hepatotoxicity. N-acetylcysteine (NAC) is used to treat the hepatotoxicity of acetaminophen. Due to the structural similarities of this compound with amifostine, we decided to test the effect of this substance and its metabolite, WR-1065, on the hepatotoxicity of acetaminophen.

METHODS

The single-dose method contained 1. Control; 2. Acetaminophen (1 g/kg, gavage); 3-5. Acetaminophen + amifostine (100, 200, 400 mg/kg, i.p.); 6-8. Acetaminophen + WR-1065 (50, 100, 200 mg/kg, i.p.); and 9. Acetaminophen + NAC (100, 200 mg/kg, i.p.). The multiple-dose method included the same groups: amifostine (50, 100, 200 mg/kg), WR-1065 (25, 50, 100 mg/kg), and NAC (100 mg/kg). Then, animals were sacrificed, and blood samples were collected for measuring ALT, AST, ALP, and T-Bil, liver tissue for histopathological examination, MDA, and GSH amounts.

RESULTS

Acetaminophen increased the levels of MDA, T-Bil, ALT, AST, and ALP, decreased GSH levels, and augmented necrosis, neutrophils, lymphocytes, and macrophages in the port space in single-dose and multiple-dose studies. Amifostine and WR-1065 significantly reduced the levels of MDA, T-Bil, ALT, AST, ALP, increased GSH content, and ameliorated histopathological alterations in a single-dose and multiple-dose method compared to the acetaminophen group. Moreover, NAC caused a significant decrease in the levels of MDA, T-Bil, ALT, AST, and ALP, and reduced GSH amounts in single-dose and multiple-dose studies.

CONCLUSION

Amifostine and WR-1065 as antioxidant and hepatoprotective compounds are effective in reducing acetaminophen-induced hepatotoxicity with a similar effect to NAC and can be administered as an adjunct in the treatment of acetaminophen overdose.

N-acetylcysteine increases dopamine release and prevents the deleterious effects of 6-OHDA on the expression of VMAT2, α-synuclein, and tyrosine hydroxylase

OBJECTIVES

Current treatments for Parkinson's disease using pharmacological approaches alleviate motor symptoms but do not prevent neuronal loss or dysregulation of dopamine neurotransmission. In this article, we have explored the molecular mechanisms underlying the neuroprotective effect of the antioxidant N-acetylcysteine (NAC) on the damaged dopamine system.

METHODS

SH-SY5Y cells were differentiated towards a dopaminergic phenotype and exposed to 6-hydroxydopamine (6-OHDA) to establish an in vitro model of Parkinson's disease. We examined the potential of NAC to restore the pathological effects of 6-OHDA on cell survival, dopamine synthesis as well as on key proteins regulating dopamine metabolism. Specifically, we evaluated gene- and protein expression of tyrosine hydroxylase (TH), vesicle monoamine transporter 2 (VMAT2), and α-synuclein, by using qPCR and Western blot techniques. Moreover, we quantified the effect of NAC on total dopamine levels using a dopamine ELISA assay.

RESULTS

Our results indicate that NAC has a neuroprotective role in SH-SY5Y cells exposed to 6-OHDA by maintaining cell proliferation and decreasing apoptosis. Additionally, we demonstrated that NAC treatment increases dopamine release and protects SH-SY5Y cells against 6-OHDA dysregulations on the proteins TH, VMAT2, and α-synuclein.

CONCLUSIONS

Our findings contribute to the validation of compounds capable to restore dopamine homeostasis and shed light on the metabolic pathways that could be targeted to normalize dopamine turnover. Furthermore, our results highlight the effectiveness of the antioxidant NAC in the prevention of dopaminergic neurodegeneration in the present model.

ABBREVIATIONS

DAT, dopamine transporter; 6-OHDA, 6-hydroxydopamine; NAC, N-acetylcysteine; PARP, poly (ADP-ribose) polymerase; RA; retinoic acid; ROS, reactive oxygen species; TH, tyrosine hydroxylase; TPA, 12-O-tetradecanoyl-phorbol-13-acetate; VMAT2, vesicle monoamine transporter 2.

Paracetamol (acetaminophen) poisoning: The early years

Paracetamol (acetaminophen) was marketed in the 1950s as a nonprescription analgesic/antipyretic without any preclinical toxicity studies. It became used increasingly for self-poisoning, particularly in the UK and was belatedly found to cause acute liver damage, which could be fatal. Management of poisoned patients was difficult as maximum abnormalities of liver function were delayed for 3 days or more after an overdose. There was no treatment and the mechanism of hepatotoxicity was not known. The paracetamol half-life was prolonged with liver damage occurring when it exceeded 4 h and the Rumack-Matthew nomogram was an important advance that allowed stratification of patients into separate zones of risk. It is used to guide prognosis and treatment and its predictive value could be increased by combining it with the paracetamol half-life. The problems of a sheep farmer in Australia in the early 1970s led to the discovery of the mechanism of paracetamol hepatotoxicity, and the first effective treatment of overdosage with intravenous (IV) cysteamine. This had unpleasant side effects and administration was difficult. N-acetylcysteine soon became the treatment of choice for paracetamol overdose and given early it was very effective when administered either IV or orally. N-acetylcysteine could cause anaphylactoid reactions, particularly early during IV administration when the concentrations were highest. Simpler and shorter regimes with slower initial rates of infusion have now been introduced with a reduced incidence of these adverse effects. In addition, there has been a move to use larger doses of N-acetylcysteine given over longer periods for patients who are more severely poisoned and those with risk factors. There has been much interest recently in the search for novel biomarkers such as microRNAs, procalcitonin and cyclophilin that promise to have greater specificity and sensitivity than transaminases. Paracetamol-protein adducts predict hepatotoxicity and are specific biomarkers of toxic paracetamol metabolite exposure. Another approach would be measurement of the plasma levels of cysteine and inorganic sulfate. It is 50 years since the first effective treatment for paracetamol poisoning and, apart from liver transplantation, there is still no effective treatment for patients who present late.

Fifty years of paracetamol (acetaminophen) poisoning: the development of risk assessment and treatment 1973-2023 with particular focus on contributions published from Edinburgh and Denver

INTRODUCTION

Fifty years ago, basic scientific studies and the availability of assay methods made the assessment of risk in paracetamol (acetaminophen) poisoning possible. The use of the antidote acetylcysteine linked to new methods of risk assessment transformed the treatment of this poisoning. This review will describe the way in which risk assessment and treatments have developed over the last 50 years and highlight the remaining areas of uncertainty.

METHODS

A search of PubMed and its subsidiary databases revealed 1,166 references published in the period 1963-2023 using the combined terms "paracetamol", "poisoning", and "acetylcysteine". Focused searches then identified 170 papers dealing with risk assessment of paracetamol poisoning, 141 with adverse reactions to acetylcysteine and 114 describing different acetylcysteine regimens. To manage the extensive literature, we focused mainly on contributions made by the authors during their time in Edinburgh and Denver.

DOSE AND CONCENTRATION RESPONSE

The key relationship between paracetamol dose and toxicity risk was established in 1971 and led to the development of the Rumack-Matthew nomogram from data collected in Edinburgh.

MECHANISMS OF TOXICITY

A series of papers on the mechanisms of toxicity were published in 1973, and these showed that paracetamol hepatotoxicity was caused by the formation of a toxic intermediate epoxide metabolite normally detoxified by glutathione but which, in excess, was bound covalently to hepatic enzymes and proteins. An understanding of the relationship between the rate of paracetamol metabolism, paracetamol concentration, and toxic hazard in humans soon followed.

ANTIDOTE DEVELOPMENT AND EFFICACY IN PATIENTS

These discoveries were followed by the testing of a range of sulfhydryl-donors in animals and "at risk" patients. Acetylcysteine was developed as the lead intravenous antidote in the United Kingdom. The license holder in the United States refused to make an intravenous formulation. Thus, oral acetylcysteine became the antidote trialed in the United States National Multicenter Study. Intravenous acetylcysteine regimens used initially in the United Kingdom and subsequently in the United States used loading doses of 150 mg/kg over 15 minutes or one hour, 50 mg/kg over four hours, and 100 mg/kg over 16 hours. These regimens were associated with adverse drug reactions (nausea, vomiting and anaphylactoid reactions) and hence, treatment interruption. Newer dosing regimens now give loading doses more slowly. One, the Scottish and Newcastle Anti-emetic Pretreatment protocol, using an acetylcysteine regimen of 100 mg/kg over two hours followed by 200 mg/kg over 10 hours, has been widely adopted in the United Kingdom. A cohort comparison study suggests this regimen has comparable efficacy to standard regimens and offers opportunities for selective higher acetylcysteine dosing.

RISK ASSESSMENT AT PRESENTATION

No dose-ranging studies with acetylcysteine were done, and no placebo-controlled studies were performed. Thus, there is uncertainty regarding the optimal dose of acetylcysteine, particularly in patients ingesting very large overdoses of paracetamol. The choice of intervention concentration on the Rumack-Matthew nomogram has important consequences for the proportion of patients treated. The United States National Multicenter Study used a "treatment" line starting at 150 mg/L (992 µmol/L) at 4 hours post overdose, extending to 24 hours with a half-life of 4 hours, now standard there, and subsequently adopted in Australia and New Zealand. In the United Kingdom, the treatment line was initially 200 mg/L (1,323 µmol/L) at 4 hours (the Rumack-Matthew "risk" line). In 2012, the United Kingdom Medicines and Healthcare products Regulatory Agency lowered the treatment line to 100 mg/L (662 µmol/L) at 4 hours for all patients, increasing the number of patients admitted and treated at a high cost. Risk assessment is a key issue for ongoing study, particularly following the development of potential new antidotes that may act in those at greatest risk. The development of biomarkers to assess risk is ongoing but has yet to reach clinical trials.

CONCLUSION

Even after 50 years, there are still areas of uncertainty. These include appropriate acetylcysteine doses in patients who ingest different paracetamol doses or multiple (staggered) ingestions, early identification of at-risk patients, and optimal treatment of late presenters.

Evaluation of the Effects of Atorvastatin and N-Acetyl Cysteine on Platelet Counts in Patients with Primary Immune Thrombocytopenia: An Exploratory Clinical Trial

Objective: We aimed to evaluate the efficacy of the combination of atorvastatin and N-acetyl cysteine in increasing platelet counts in patients with immune thrombocytopenia who were resistant to steroid therapy or had a relapse after treatment. Material and Methods: The patients included in this study received oral treatment of atorvastatin at a dose of 40 mg daily and N-acetyl cysteine at a dose of 400 mg every 8 h. The desired treatment duration was 12 months, but we included patients who completed at least 1 month of treatment in the analysis. The platelet counts were measured prior to the administration of the study treatment and in the first, third, sixth, and twelfth months of treatment (if available). A p value < 0.05 was considered statistically significant. Results: We included 15 patients who met our inclusion criteria. For the total treatment duration, the global response was 60% (nine patients); eight patients (53.3%) had a complete response and one patient (6.7%) had a partial response. Six patients (40%) were considered as having undergone treatment failure. Of the responder group, five patients maintained a complete response after treatment (55.5%), three patients maintained a partial response (33.3%), and one patient (11.1%) lost their response to the treatment. All of the patients in the responder group had significant increases in their platelet counts after treatment (p < 0.05). Conclusion: This study provides evidence of a possible treatment option for patients with primary immune thrombocytopenia. However, further studies are needed.

Cyclopeptide mushroom poisoning: A retrospective series of 204 patients

Cyclopeptide mushroom poisoning is responsible for 90%-95% of deaths from macrofungi ingestion. The main objectives of this study are to describe cases of cyclopeptide mushroom poisoning and to determine risk factors that may influence the severity/mortality of poisoned patients. We included all cases of amatoxin toxicity reported to two French Poison Centers from 2013 through 2019. We compared the severity with the Poison Severity Score (PSS) and the outcomes of patients using simple logistic regression and multinomial logistic regression. We included 204 cases of amatoxin toxicity. More than three-quarters developed an increase in AST and/or ALT (78.1%), and over half developed a decrease in prothrombin ratio (<70%: 53%) and/or Factor V (<70%: 54%). One-third developed an acute renal injury (AKI). Twelve patients (5.9%) developed post-poisoning sequelae (persistent kidney injury more than 1 month after ingestion and liver transplant). Five patients (2.5%) received a liver transplant, and nine died (4.4%). The mean time to onset of digestive disorders was shorter in PSS2 and PSS3-4 patients (10.9 ± 3.9/11.3 ± 6.3 h) than in PSS1 patients (14 ± 6.5 h; p < 0.05). Patients who died or developed post-poisoning sequelae had more frequent cardiovascular comorbidities compared with recovered patients (60.0% versus 29.5%; p < 0.01).

Comparison of Two-Bag Versus Three-Bag N-Acetylcysteine Regimens for Pediatric Acetaminophen Toxicity

BACKGROUND

Acetaminophen overdose is a leading cause of liver failure, and a leading cause of pediatric poisoning requiring hospital admission. The antidote, N-acetylcysteine (NAC), is traditionally administered as a three-bag intravenous infusion. Despite its efficacy, NAC is associated with high incidence of nonallergic anaphylactoid reactions (NAARs). Adult evidence demonstrates that alternative dosing regimens decrease NAARs and medication errors (MEs).

OBJECTIVES

To compare NAARs and MEs associated with two- versus three-bag NAC for acetaminophen overdose in a pediatric population.

METHODS

This is a retrospective observational cohort study comparing pediatric patients who received three- versus two-bag NAC for acetaminophen toxicity. The primary outcome was incidence of NAARs. Secondary outcomes were rates of MEs and relevant hospital outcomes (length of stay [LOS], intensive care unit (ICU) admission, liver transplant, death).

RESULTS

Two hundred forty-three patients met inclusion criteria (median age of 15 years): 150 (62%) three-bag NAC and 93 (38%) two-bag NAC. There was no difference in overall NAARs (p = 0.54). Fewer cutaneous NAARs were observed in the two-bag group, three-bag: 15 (10%), two-bag: 2 (2%), p = 0.02. MEs were significantly decreased with the two-bag regimen, three-bag: 59 (39%), two-bag: 21 (23%), p = 0.01. No statistical differences were observed in LOS, ICU admissions, transplant, or death.

CONCLUSION AND RELEVANCE

A significant decrease in cutaneous NAARs and MEs was observed in pediatric patients by combining the first two bags of the traditional three-bag NAC regimen. In pediatric populations, a two-bag NAC regimen for acetaminophen overdose may improve medication tolerance and safety.

Acetaminophen toxicity and overdose: current understanding and future directions for NAC dosing regimens

INTRODUCTION

Although N-acetyl-cysteine (NAC) has long been used for the treatment of acetaminophen poisoning/overdose, the optimal NAC dosing regimen for varying patterns or severity of the poisoning/overdose is still unknown.

AREAS COVERED

Relevant literature was searched for in the MEDLINE (from 1964 until August 31^st, 2022), SCOPUS (from 2004 until August 31^st, 2022) and GOOGLE SCHOLAR (from 2004 until August 31^st, 2022) databases, without restriction in terms of publication date. The inclusion criteria were: original clinical studies reporting results, and studies investigating efficacy and safety of NAC dosing regimens in case(s) of overdose or poisoning with acetaminophen.

EXPERT OPINION

For a more effective treatment of acetaminophen poisoning in the future, it will be crucial to advance the technology of measuring acetaminophen, its metabolites and NAC in the serum, preferably with the point-of-care technique, so that in real time it can be continuously assessed whether it is necessary to administer NAC, and further to increase the dose of NAC and extend the duration of its administration, or not.

E Se tea alleviates acetaminophen-induced liver injury by activating the Nrf2 signaling pathway

E Se tea is a traditional herbal tea used in the prevention of liver diseases. However, the hepatoprotective effect of E Se tea has not been investigated. This study aimed to determine the protective effect of E Se tea on acetaminophen (APAP)-induced acute liver injury and its potential mechanism. Hot water extracts and aqueous-ethanol extracts of E Se tea were obtained, which were analyzed to determine the chemical constituents of the tea. Phlorizin and phloretin were found to be the dominant chemical compounds. Histopathological analysis showed that E Se tea extract inhibited APAP-induced inflammatory infiltration, necrosis, and cellular vacuolization of hepatocytes in the liver tissue. The E Se tea extract could significantly ameliorate liver injury, inhibit an inflammatory response, and reduce oxidative stress. Western blot analysis revealed that E Se tea extract upregulated the expressions of nuclear Nrf2, HO-1 and NQO1 proteins and downregulated the expressions of cytoplasmic Nrf2 and Keap1 proteins in the hepatocyte. qPCR results showed that E Se tea extract also increased the expression of antioxidant genes (SOD2, Gpx1, GCLC and GCLM). These findings exhibited that E Se tea, enriched in dihydrochalcones, can be used to effectively prevent and manage liver dysfunction.

Efficacy of N-acetylcysteine in Preventing Acute Kidney Injury and Major Adverse Cardiac Events After Cardiac Surgery: A Meta-Analysis and Trial Sequential Analysis

Background

The effect of N-acetylcysteine (NAC), an antioxidant, on preventing acute kidney injury (AKI) and major adverse cardiac events (MACE) remains controversial. Therefore, we conducted this meta-analysis and trial sequential analysis to evaluate its efficacy on cardiac surgery-related adverse events.

Methods

PubMed, Embase, and Cochrane Library were searched for relevant studies from inception to June 2021. We selected randomized controlled trials comparing NAC with controls in patients undergoing cardiac surgery.

Results

Twenty-five studies including 2,444 patients met the inclusion criteria. The pooled results showed that there was no significant difference in the incidence of AKI between the NAC and control groups [relative risk (RR) = 0.91, 95% confidence interval (CI) = 0.77, 1.08, P = 0.28], but the trial sequential analysis (TSA) could not confirm this result. No difference was observed in the need for renal replacement therapy (RRT), all-cause mortality, MACE, length of stay in the intensive care unit (ICU), and length of stay in the hospital. Results of subgroup analysis results showed that intravenous infusion instead of oral NAC could significantly reduce the incidence of AKI and arrhythmia (RR = 0.84, 95% CI = 0.71, 0.99, P = 0.03, I² = 3% and RR = 0.74, 95% CI = 0.61, 0.91, P = 0.004, I² = 48%, respectively).

Conclusion

Intravenous administration of NAC can reduce the incidence of AKI and arrhythmia in patients after cardiac surgery, but cannot reduce all-cause mortality, AMI, cardiac insufficiency, and the number of patients using RRT. Oral NAC has no significant effect on the outcomes of patients after cardiac surgery.

Mesenchymal stem cells protect against acetaminophen hepatotoxicity by secreting regenerative cytokine hepatocyte growth factor

BACKGROUND

Acetaminophen (APAP) overdose is a major cause of the morbidity of acute liver failure. The current clinically approved treatment for APAP poisoning, N-acetylcysteine (NAC), has a limited therapeutic window, and prolonged treatment with NAC delays liver regeneration. Mesenchymal stem cells (MSCs) also have therapeutic effects on APAP-induced mouse liver failure, but whether the effects are comparable to those of NAC has not been determined, and the mechanism still needs further exploration.

METHODS

Fasted C57BL/6 mice that received 500 mg/kg APAP were treated intravenously with 300 mg/kg NAC or different amounts of MSCs at 2 h after APAP to investigate survival, hepatocyte necrosis and neutrophil/macrophage recruitment. In vitro co-culture was performed to study the anti-necrotic effects of MSCs on the APAP-injured hepatocyte cell line L-O2.

RESULTS

MSCs dose-dependently rescued the C57BL/6J mice from APAP-induced liver failure, with 87.5% of MSCs (1 × 10⁶) surviving similar to that of NAC (90%). MSC has similar effects on reduced hepatocyte necrosis and granulocytic myeloid-derived suppressor cells (MDSC) infiltration but enhanced the proportion of regenerative monocytic MDSC when compared to NAC. Mechanistically, MSCs attenuate hepatocyte necrosis by secreting hepatocyte growth factor (HGF). When HGF was knocked down, the protective effects of MSCs were reduced on APAP-induced hepatocyte necrosis and mouse liver failure.

CONCLUSIONS

MSCs are comparable to NAC against APAP-induced liver failure by secreting HGF with less regenerative retardation concerns, thus facilitating the application of MSCs in clinical therapy for APAP liver failure.

N-acetylcysteine for non-acetaminophen induced acute liver failure: A review

The use of N-acetylcysteine (NAC) for non-acetaminophen-induced acute liver failure (NAI-ALF) has been increasing despite controversy in its efficacy. National guidelines are in disagreement for NAC use as standard of care; however, many healthcare centers continue to adopt the use of NAC outside of acetaminophen poisoning. While NAC may have multiple mechanisms of action in treatment of ALF, this has not translated to clinical benefit. Murine models have reported antioxidant and anti-inflammatory properties, as well as improvement in liver-specific microcirculation. Multiple case studies and series have reported positive outcomes of NAC treatment for ALF of various etiologies. While prospective studies suggested the benefit of NAC treatment, these studies have methodological and statistical shortcomings that affect the validity of the results. In this review, we aimed to summarize the existing literature on the efficacy of NAC for NAI-ALF including mechanism of action, case studies and series demonstrating outcomes, and prospective studies that have led to its current widespread use, along with the reported rate of adverse events.

N-Acetylcysteine for Cardiac Protection During Coronary Artery Reperfusion: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Coronary artery reperfusion is essential for the management of symptoms in the patients with myocardial ischemia. However, the benefit of reperfusion often comes at an expense of paradoxical injury, which contributes to the adverse events, and sometimes heart failure. Reperfusion is known to increase the production of reactive oxygen species (ROS). We address whether N-acetylcysteine (NAC) reduces the ROS and alleviates reperfusion injury by improving the clinical outcomes. A literature search for the randomized controlled trials (RCTs) was carried out in the five biomedical databases for testing the effects of NAC in patients undergoing coronary artery reperfusion by percutaneous coronary intervention, thrombolysis, or coronary artery bypass graft. Of 787 publications reviewed, 28 RCTs were identified, with a summary of 2,174 patients. A meta-analysis using the random effects model indicated that NAC administration during or prior to the reperfusion procedures resulted in a trend toward a reduction in the level of serum cardiac troponin (cTn) [95% CI, standardized mean difference (SMD) −0.80 (−1.75; 0.15), p = 0.088, n = 262 for control, 277 for NAC group], and in the incidence of postoperative atrial fibrillation [95% CI, relative risk (RR) 0.57 (0.30; 1.06), p = 0.071, n = 484 for control, 490 for NAC group]. The left ventricular ejection fraction or the measures of length of stay in intensive care unit (ICU) or in hospital displayed a positive trend that was not statistically significant. Among the nine trials that measured ROS, seven showed a correlation between the reduction of lipid peroxidation and improved clinical outcomes. These lines of evidence support the potential benefit of NAC as an adjuvant therapy for cardiac protection against reperfusion injury.

Guideline on management of suspected adverse reactions to ingested histamine: Guideline of the German Society for Allergology and Clinical Immunology (DGAKI), the Society for Pediatric Allergology and Environmental Medicine (GPA), the Medical Association of German Allergologists (AeDA) as well as the Swiss Society for Allergology and Immunology (SGAI) and the Austrian Society for Allergology and Immunology (ÖGAI)

Adverse reactions to food or food ingredients are more often perceived than objectively verifiable. However, reliable laboratory tests are often lacking. As a result, people with perceived adverse reactions to food often follow extensive elimination diets for years and unnecessarily restrict their diet, as in the case of the frequently suspected histamine intolerance. In this condition, laboratory parameters such as the determination of diamine oxidase in serum have been shown to be inconclusive. The lack of symptom reproducibility calls into question the clinical picture of adverse reactions to ingested histamine. In order to approach persons with perceived histamine intolerance and to support them in moving from blanket restrictions, which are often unnecessarily strict, to effective personalized therapeutic strategies, the present guideline of the Working Group on Food Allergy of the German Society of Allergology and Clinical Immunology (DGAKI) in cooperation with the Medical Association of German Allergists (AeDA), the Pediatric Allergology and Environmental Medicine (GPA) as well as the Swiss Society of Allergology and Immunology (SGAI) and the Austrian Society of Allergology and Immunology (ÖGAI) recommends a practicable diagnostic and therapeutic approach.

Use of intravenous N-acetylcysteine in acute severe hepatitis due to severe dengue infection: a case series

Background

Dengue fever is a common mosquito borne viral infection. Severe dengue fever associated severe hepatitis carries high mortality. Based on the beneficial effect of N-acetylcysteine (NAC) in paracetamol poisoning and non-acetaminophen induced liver failure, it is used in dengue fever associated hepatitis in clinical practice. We aim to study the reversal of liver enzymes with NAC in the setting of severe hepatitis due to severe dengue infection.

Methods

A retrospective analysis was conducted on hospitalized 30 adults with severe dengue fever with severe hepatitis. These 30 patients had aspartate transaminase (AST) and alanine transaminases (ALT) more than 500 U/L and/or PT INR (prothrombin time and international normalized ratio) more than 1.5. They were treated with NAC infusion of 100 mg/h for 3 to 5 days.

Results

The mean age of the group was 49.9 ± 11.46 years and 18 (60%) patients were males. Nineteen patients (63%) developed dengue shock. Of them 12 patients (40%) developed hepatic encephalopathy. Median AST on the day of administration of NAC was 1125 U/L interquartile range (IQR) 1653.25 while median ALT was 752 (IQR 459.25). There was a statistically significant reduction of both ALT (p = 0.034) and AST (p = 0.049) from day 1 to 4 after NAC infusion. Rise of platelet count between day 1 and day 4 also showed statistically significant difference (p = 0.011) but the reduction of prothrombin time and international normalized ratio (PT/INR) from 1 to day 4 did not show statistical significance difference. Mean duration of treatment with NAC was 3.61 ± 0.75 days while mean length of hospital stay was 6.2 ± 1.27 days. Only one patient died (3.3%). None of the patients reported adverse drug reaction due to NAC.

Conclusion

Majority of patients demonstrated marked clinical and biochemical improvements and they recovered fully. We observed faster and significant recovery of liver enzymes following administration of NAC. Based on the above findings, this study provides preliminary evidence for the beneficial effect of NAC in severe hepatitis in dengue infection with greater survival benefits.

Retrospective Analysis of the Clinical Efficacy of N-Acetylcysteine in the Treatment of Hepatitis B Virus Related Acute-on-Chronic Liver Failure

Objective: HBV-related acute-on-chronic liver failure (HBV-ACLF) has a high mortality due to severe intrahepatic cholestasis and coagulation dysfunction, thus new treatment measures are urgently needed to improve the therapeutic effect. This study aimed to observe the efficacy of N-acetylcysteine (NAC) in the treatment of HBV-ACLF.

Methods: The data of patients with HBV-ACLF admitted to West China Hospital from October 2019 to August 2020 were collected retrospectively, and they were divided into treatment group and control group according to whether they had received additional NAC treatment. The improvement of biochemistry, coagulation function and disease severity score after 14 days of hospitalization were analyzed between two groups.

Results: A total of 90 HBV-ACLF patients were included, including 42 patients in treatment group and 48 patients in control group. Compared with baseline, serum TBil, DBil, TBA, GGT and ALP in two groups both decreased significantly, while PTA increased significantly. Interesting, the decrease of serum TBil, DBil and TBA and the increase of PTA in treatment group were all significantly than these in control group. Additionally, more patients in treatment group than control group changed from CTP grade C to grade B. Subgroup analysis of CTP grade C patients showed that the decrease of serum TBil, DBil and TBA and the increase of PTA in treatment group were significantly than these in control group.

Conclusion: The NAC treatment may help to improve intrahepatic cholestasis and coagulation dysfunction of HBV-ACLF.

Acetaminophen Poisoning

Acetaminophen is a common medication taken in deliberate self-poisoning and unintentional overdose. It is the commonest cause of severe acute liver injury in Western countries. The optimal management of most acetaminophen poisonings is usually straightforward. Patients who present early should be offered activated charcoal and those at risk of acute liver injury should receive acetylcysteine. This approach ensures survival in most. The acetaminophen nomogram is used to assess the need for treatment in acute immediate-release overdoses with a known time of ingestion. However, scenarios that require different management pathways include modified-release, large/massive, and repeated supratherapeutic ingestions.

Malnourishment-Associated Acetaminophen Toxicity in Pregnancy

BACKGROUND

Although acetaminophen is commonly used in pregnancy, it can deplete glutathione concentrations and cause accumulation of 5-oxoproline, with subsequent metabolic acidosis.

CASE

A malnourished 25-year-old woman, G2P1001, with chronic acetaminophen use presented with abdominal pain and high anion gap metabolic acidosis. After ruling out other potential causes, her urine 5-oxoproline level was found to be elevated. She received N-acetylcysteine, with resolution of the acidosis.

CONCLUSION

Those who care for pregnant patients should remain alert to 5-oxoprolinemia as a cause of metabolic acidosis during pregnancy. Care must be taken when using acetaminophen in states of malnutrition. N-acetylcysteine seems to be an effective antidote.

Pharmaceuticals targeting signaling pathways of endometriosis as potential new medical treatment: A review

Endometriosis (EM) is defined as endometrial tissues found outside the uterus. Growth and development of endometriotic cells in ectopic sites can be promoted via multiple pathways, including MAPK/MEK/ERK, PI3K/Akt/mTOR, NF-κB, Rho/ROCK, reactive oxidative stress, tumor necrosis factor, transforming growth factor-β, Wnt/β-catenin, vascular endothelial growth factor, estrogen, and cytokines. The underlying pathophysiological mechanisms include proliferation, apoptosis, autophagy, migration, invasion, fibrosis, angiogenesis, oxidative stress, inflammation, and immune escape. Current medical treatments for EM are mainly hormonal and symptomatic, and thus the development of new, effective, and safe pharmaceuticals targeting specific molecular and signaling pathways is needed. Here, we systematically reviewed the literature focused on pharmaceuticals that specifically target the molecular and signaling pathways involved in the pathophysiology of EM. Potential drug targets, their upstream and downstream molecules with key aberrant signaling, and the regulatory mechanisms promoting the growth and development of endometriotic cells and tissues were discussed. Hormonal pharmaceuticals, including melatonin, exerts proapoptotic via regulating matrix metallopeptidase activity while nonhormonal pharmaceutical sorafenib exerts antiproliferative effect via MAPK/ERK pathway and antiangiogenesis activity via VEGF/VEGFR pathway. N-acetyl cysteine, curcumin, and ginsenoside exert antioxidant and anti-inflammatory effects via radical scavenging activity. Natural products have high efficacy with minimal side effects; for example, resveratrol and epigallocatechin gallate have multiple targets and provide synergistic efficacy to resolve the complexity of the pathophysiology of EM, showing promising efficacy in treating EM. Although new medical treatments are currently being developed, more detailed pharmacological studies and large sample size clinical trials are needed to confirm the efficacy and safety of these treatments in the near future.

Role of liver sinusoidal endothelial cells in liver diseases

Liver sinusoidal endothelial cells (LSECs) form the wall of the hepatic sinusoids. Unlike other capillaries, they lack an organized basement membrane and have cytoplasm that is penetrated by open fenestrae, making the hepatic microvascular endothelium discontinuous. LSECs have essential roles in the maintenance of hepatic homeostasis, including regulation of the vascular tone, inflammation and thrombosis, and they are essential for control of the hepatic immune response. On a background of acute or chronic liver injury, LSECs modify their phenotype and negatively affect neighbouring cells and liver disease pathophysiology. This Review describes the main functions and phenotypic dysregulations of LSECs in liver diseases, specifically in the context of acute injury (ischaemia-reperfusion injury, drug-induced liver injury and bacterial and viral infection), chronic liver disease (metabolism-associated liver disease, alcoholic steatohepatitis and chronic hepatotoxic injury) and hepatocellular carcinoma, and provides a comprehensive update of the role of LSECs as therapeutic targets for liver disease. Finally, we discuss the open questions in the field of LSEC pathobiology and future avenues of research.

Bottom-up analysis of emergent properties of N-acetylcysteine as an adjuvant therapy for COVID-19

N-acetylcysteine (NAC) is an abundantly available antioxidant with a wide range of antidotal properties currently best studied for its use in treating acetaminophen overdose. It has a robustly established safety profile with easily tolerated side effects and presents the Food and Drug Administration's approval for use in treating acetaminophen overdose patients. It has been proven efficacious in off-label uses, such as in respiratory diseases, heart disease, cancer, human immunodeficiency virus infection, and seasonal influenza. Clinical trials have recently shown that NAC's capacity to replenish glutathione stores may significantly improve coronavirus disease 2019 (COVID-19) outcomes, especially in high risk individuals. Interestingly, individuals with glucose 6-phosphate dehydrogenase deficiency have been shown to experience even greater benefit. The same study has concluded that NAC's ability to mitigate the impact of the cytokine storm and prevent elevation of liver enzymes, C-reactive protein, and ferritin is associated with higher success rates weaning from the ventilator and return to normal function in COVID-19 patients. Considering the background knowledge of biochemistry, current uses of NAC in clinical practice, and newly acquired evidence on its potential efficacy against COVID-19, it is worthwhile to investigate further whether this agent can be used as a treatment or adjuvant for COVID-19.

Dietary γ-Glutamylcysteine: Its Impact on Glutathione Status and Potential Health Outcomes

Glutathione (GSH) is a tripeptide that is readily synthesized intracellularly in humans and other mammals. More than a century of research suggests that GSH has numerous biological functions, including protection from the potential adverse events associated with reactive oxygen species (ROS) and related redox reactions that may induce oxidative stress, and that may be linked to innate detoxification processes. Normal tissue and plasma levels of GSH decline through the aging process and decrease during various disease states. While the health value of dietary GSH remains controversial, there is evidence that some metabolic intermediates, such as γ-glutamylcysteine (GGC) may function to preserve adequate GSH levels when the synthetic pathways decline in activity, and the innate antioxidant system is challenged. It is also important to recognize that among the thousands of protein-coding human genes and their respective polymorphisms, at least two genes (Gclc and Gclm) are directly involved with GSH synthesis via glutamate-cysteine ligase. This commentary examines the classic biochemistry, toxicology, safety, and clinical value of GSH and its intermediates that may be modulated by dietary supplementation.

Possible role for acetylcysteine as a treatment for acute liver failure secondary to antitubercular medication use

PURPOSE

Drug-induced liver injury (DILI) that progresses to acute liver failure (ALF) has a high mortality rate, and therapeutic options are limited. Acetylcysteine has a labeled indication for use as an antidote for acetaminophen toxicity and has also been used with limited success in treatment of non-acetaminophen-induced liver injury, with small clinical trials indicating an increase in transplant-free survival. Recommendations for management of non-acetaminophen-induced DILI include withdrawal of the offending agent and supportive care. Treatment guidelines generally discourage a rechallenge with an offending medication, except in cases where there are no other therapeutic options for management of a serious disease, such as active tuberculosis (TB).

SUMMARY

This case report describes the reversal of ALF due to DILI in a patient receiving antitubercular agents for active TB. After withdrawal of initially prescribed antitubercular agents, the patient was switched to a less hepatotoxic anti-TB regimen and intravenous acetylcysteine pending results of antimicrobial susceptibility testing. After stabilization of the patient's liver enzyme levels, intravenous acetylcysteine was discontinued and oral acetylcysteine was continued for 5 days without an increase in hepatic enzyme levels or clinical deterioration. After 5 days, oral acetylcysteine was discontinued due to patient-reported nausea and vomiting.

CONCLUSION

Given the limited number of therapeutic interventions shown to be beneficial in ALF and data suggesting a protective effect against DILI with initiation of acetylcysteine at the start of treatment with anti-TB medications, acetylcysteine can be considered for patients with anti-TB - associated DILI.

A Case Report of a Severe, Unusually Delayed Anaphylactoid Reaction to Intravenous N-Acetylcysteine During Treatment of Acute Acetaminophen Toxicity in an Adolescent

INTRODUCTION

Anaphylactoid reactions are well-documented adverse events associated with the intravenous administration of N-acetylcysteine (NAC) in patients with acetaminophen overdose. Most reactions are mild, occurring within the first 1-5 hours of initiation. This report presents the case of an adolescent with a delayed, life-threatening anaphylactoid reaction 24.5 hours after starting NAC, where discontinuing NAC could have resulted in fulminant hepatic failure (FHF) and death.

CASE REPORT

A 17-year-old previously healthy female presented with nausea, vomiting, and abdominal pain 10 hours after an acute acetaminophen ingestion. Her 11-hour serum acetaminophen concentration was above the treatment line (149 μg/mL), and she had elevated transaminases (AST = 202 U/L, ALT = 284 U/L). She was treated with intravenous NAC, which was suspended for 3 hours after she developed an apparent life-threatening anaphylactoid reaction with angioedema and respiratory distress 24.5 hours after treatment initiation. Given her high risk of progression to FHF, NAC was resumed at double the previous rate along with scheduled corticosteroids and antihistamines after resolution of her symptoms. Her AST increased to 10,927 U/L, and INR peaked at 3.6, but she had no further anaphylactoid symptoms. She was discharged in her normal state of health after 6 days.

DISCUSSION

Discontinuing NAC in this case of severe, delayed anaphylactoid reaction could have resulted in FHF requiring liver transplant. The reason for her reaction is unclear but could be related to patient risk factors or medication error. Guidelines for reinitiation of NAC after development of delayed anaphylactoid reactions are not well-established.  Close observation beyond the first 1-5 hours of NAC administration is warranted.

N-acetylcysteine as a treatment for amatoxin poisoning: a systematic review

Introduction: Amatoxin leads to the majority of deaths by mushroom poisoning around the world. Amatoxin causes gastrointestinal disturbances and multiple organ dysfunction, including liver and renal failure. As a potential treatment for amatoxin poisoning, N-acetylcysteine (NAC) has been used for decades but its benefit is still unproven.Objectives: We undertook a systematic review to evaluate the performance and safety of N-acetylcysteine on patients suffering amatoxin intoxication.Methods: We searched Pubmed, EMBASE, CENTRAL and SinoMed databases, from inception to August 31, 2019. Articles were eligible if there were five or more patients with amatoxin poisoning and N-acetylcysteine was included in the therapeutic regimen. Mortality rate including liver transplant cases (MRLTi) was the primary outcome. Mortality rate not including liver transplant cases, liver and renal function, clinical complications, as well as any adverse reactions to intravenous NAC were secondary outcomes.Results: Thirteen studies with a total of 506 patients were included. The MRLTi of amatoxin-poisoning patients with NAC treatment was 11% (57/506), and a MRLTe of 7.9% (40/506) and a liver transplantation rate of 4.3% (22/506). Transaminase concentrations generally peaked around 3 days after ingestion, prothrombin time/International Normalized Ratio (PT/INR) generally worsened during the first 3-4 days after ingestion before returning to normal four to 7 days after ingestion, and Factor V levels normalized in about 4-5 days after ingestion in patients treated with NAC. Renal failure was reported in 3% (3/101) and acute kidney injury was reported in 19% (5/27). Gastrointestinal bleeding occurred in 21% (15/71). Anaphylactoid reactions were the principle adverse reaction to NAC treatment in amatoxin-poisoning patients with an incidence of 5% (4/73).Conclusions: NAC treatment combined with other therapies appears to be beneficial and safe in patients with amatoxin poisoning. Until further data emerge, it is reasonable to use NAC in addition to other treatments for amatoxin poisoning.

Cysteine/cystine-rich undenatured whey protein supplement in patients' pressure ulcers outcomes: an open label study

OBJECTIVE

The prevalence and costs associated with treating pressure ulcers (PU) are at high levels. Frequently, PUs heal slowly or not at all, which may be due to the patient's catabolic state which may include protein energy malnutrition. The objective of this open label clinical trial was to improve healing rates by providing patients with a patented, high-quality protein containing all essential amino acids to ensure positive nitrogen balance. An additional benefit of this protein is the delivery of bioavailable cysteine (cystine) to promote glutathione (GSH) synthesis which supports immune function and heightens antioxidant defences.

METHODS

Patients with category II, III and IV PUs were fed 20g BID whey protein dietary supplement for 16-120 days, without change in ongoing 'best practice' PU management and their progress recorded.

RESULTS

A total of 10 patients were recruited, with an average age of 77 years. Most had shown no improvement in healing for ≥2 months before treatment and usually had other complications including chronic obstructive pulmonary disease (COPD), diabetes and various cardiovascular diseases. There were a total of 23 PUs, with some patients having more than one. Of these, 44% (n=10) showed complete resolution 83% (n=19) had better than 75% resolution over the observation period. Healing rates ranged from 16.9-0.2cm²/month (healed PUs) and 60.0-1.6cm²/month for resolving PUs.

CONCLUSION

By providing the necessary amino acids to rebuild tissues and bioactive cysteine (cystine) to promote synthesis of intracellular GSH and positive nitrogen balance, improvement in PUs healing was achieved.

Upregulation of Nrf2-related cytoprotective genes expression by acetaminophen-induced acute hepatotoxicity in mice and the protective role of betaine

Overdose of acetaminophen (APAP) is the main reason for acute liver failure. Oxidative stress is associated with hepatotoxicity caused by APAP. Betaine is a methyl donor and S-adenosylmethionine precursor. The present study investigated the effect of betaine and the role of nuclear factor-erythroid-2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) genes in hepatotoxicity induced by APAP in mice. In this study, male Naval Medical Research Institute (NMRI) mice were treated with 500 mg/kg of betaine for 5 days followed with a single dose of APAP 300 mg/kg on the fifth day. Biochemical, histological, immunohistochemical, Western blot, and real-time polymerase chain reaction (PCR) analyses were then conducted. The results of the present study showed that betaine pretreatment improved hepatotoxicity through the reduction of serum ALT and AST levels and ameliorating histopathological finding. Betaine pretreatment also increased glutathione level and decreased malondialdehyde level. Importantly, the results of immunohistochemical, Western blot and real-time PCR showed that the APAP increased the expression of the genes and proteins of Nrf2 and HO-1. While betaine decreased Nrf2 and HO-1 expression in comparison with the APAP group. The findings of this study demonstrated that the increased expression of Nrf2 and HO-1 genes and proteins by APAP is a compensatory mechanism to combat acute liver toxicity. While the protective effect of betaine against acute liver injury induced by APAP is independent on the Nrf2 and HO-1 genes but occurs via modifying cysteine supply as a precursor of glutathione in the transsulfuration pathway in the liver.

Silkworm pupa oil attenuates acetaminophen-induced acute liver injury by inhibiting oxidative stress-mediated NF-κB signaling

Acetaminophen (APAP) overdose causes severe hepatotoxicity and acute liver failure. The current study aims to investigate the protection effects of silkworm pupa oil (SPO) against acute hepatic injury in APAP-exposed Kunming mice. Our results showed that the liver index and the levels of serum alanine transaminase (ALT) and aspartate transaminase (AST) in mice subjected to APAP treatment were decreased by SPO. Supplement of SPO also restored hepatic histopathological alterations induced by APAP. The APAP-induced increase in proinflammatory cytokines, including TNF-α, IL-6, and IL-12, was reversed by SPO, which was mediated by the reduction of nuclear factor (NF)-κB p65 expression and the increase in the expression of IκB-α in liver tissue. Moreover, SPO inhibited APAP-triggered oxidative stress by decreasing MDA level and increasing the activities of SOD and GSH-Px. Collectively, SPO attenuated hepatic injury induced by APAP, which attributed to the suppression of oxidative stress-mediated NF-κB signaling. Our findings suggest that SPO supplementation may be potential strategy against acute hepatic injury.

Susceptibility to adverse drug reactions

The pharmacological effects of a drug depend on its concentration at the site of action, and therefore on the concentration in blood and on the dose. The relationship between the concentration or dose and the corresponding effect can usually be represented mathematically as a rectangular hyperbola; when effect is plotted against log concentration or log dose, the curve is sigmoidal. Inevitably, the effect size and the doses causing benefit and harm will differ among individuals, since they are biological phenomena: some individuals are more likely than others to suffer harm at any given dose. Some harmful effects can occur at much lower doses than those used in therapeutics; that is, the log dose-response curve for harm lies far to the left of the log dose-response curve for benefit. Those who suffer such reactions are hypersusceptible. When the dose-response curves for harm and therapeutic effect are in the same range, dose cannot separate the harmful effects from the therapeutic effects, and adverse reactions are collateral. Toxic effects occur when harmful doses are above the doses needed for benefit. In this review we consider factors that influence a subject's susceptibility to adverse drug reactions. Determinants of susceptibility include Immunological, Genetic, demographic (Age and Sex), Physiological and Exogenous factors (drug-drug interactions, for example), and Diseases and disorders such as renal failure, giving the mnemonic I GASPED. Some susceptibility factors are discrete (for example, all-or-none) and some are continuous; susceptibility can therefore be discrete or continuous; and the factors can interact to determine a person's overall susceptibility to harm.

Evaluation of the Protective Effects of Doxycycline on Acetaminophen-Induced Hepatotoxicity in Mice

Acetaminophen (APAP) toxicity threatens human health due to increased mortality associated with its overdose. Doxycycline (DC) because of its properties such as antioxidant and anti-inflammatory can be a good therapeutic strategy to treat the acute toxicity induced by APAP. Male mice were divided into six groups in two periods of 3 h and 24 h as normal saline, APAP 400 mg/kg, DC 100 mg/kg and groups treated by 25, 50 and 100 mg/kg DC just before APAP, respectively. At the end of the 3 h and 24 h periods, the hepatic index, biochemical parameters including serum aspartate transaminase (AST) and alanine transaminase (ALT) activity and hepatic catalase activity, glutathione (GSH) and malondialdehyde (MDA) levels in liver and histopathological changes were evaluated. The results indicated that DC had no apparent effect on the hepatic index but significantly normalized the level of biochemical parameters and reduced APAP induced liver damage. Overall, it could be concluded that DC can inhibit or resolve harmful effects of APAP through antioxidant and anti-inflammatory properties. However, more studies are needed to understand exact mechanism of DC and its application for clinical use.

The effect of a mesenchymal stem cell conditioned medium fraction on morphological characteristics of hepatocytes in acetaminophen-induced acute liver failure: a preliminary study

Background: In our studies, it was shown that the effectiveness of the conditioned medium obtained by cultivating mesenchymal stem cells depends on the microenvironment conditions used to cultivate the cells. It was demonstrated that the conditioned medium obtained by culturing cells with low oxygen content (10%) has a much more pronounced protective effect.

Methods: Protein compositions obtained from MSCs cultured under hypoxic (10% O₂ hc-MSC) and normal (21% O₂ nc-MSC) conditions were used to treat acute liver failure (ALF) induced in mice by acetaminophen injection. Thus, we obtained fractions normalized by volume, which predominantly contained proteins with masses > 50, 50-30, 30-10, and 10-3 kDa.

Results: The data from biochemical studies have shown that only fractions from 10 to 30 kDa (hcMSC and ncMSC) significantly reduced the level of liver enzymes in the beginning of the acute period after acetaminophen administration. Mass spectrometry analysis of the proteins contained in the isolated fractions showed a sharp increase in the protein levels in the 10-30 kDa hcMSC fraction as compared with that in 10-30 kDa ncMSCs. The composition obtained from MSCs cultured at lower O₂ level (fraction 10-30 kDa hcMSC) was shown to be more potent than the composition prepared from normoxic cells.

Conclusion: The results have shown that a composition obtained by culturing the cells under a reduced content of O₂ (10%), significantly improves the biochemical parameters, and histological arrester reduces the degree of inflammation and stimulates regenerative processes in liver, compared to both the control group and group treated with the composition that was obtained by culturing the cells under normal oxygen content.

Natural-Product-Inspired Compounds as Countermeasures against the Liver Carcinogen Aflatoxin B1

Aflatoxin B₁ (AfB₁) ranks among the most potent liver carcinogens known, and the accidental or intentional exposure of humans and livestock to this toxin remains a serious global threat. One protective measure that had been proposed is employing small-molecule therapeutics capable of mitigating the toxicity of AfB₁; however, to date, these efforts have had little clinical success. To identify molecular scaffolds that reduce the toxicity of AfB₁, we developed a cell-based high-throughput high-content imaging assay that enabled our team to test natural products (pure compounds, fractions, and extracts) for protection of monolayers and spheroids composed of HepG2 liver cells against AfB₁. The spheroid assay showed notable potential for further development, as it afforded greater sensitivity of HepG2 cells to AfB1, which is believed to better mimic the in vivo response of hepatocytes to the toxin. One of the most bioactive compounds to arise from this investigation was alternariol-9-methyl ether (1, purified from an Alternaria sp. isolate), which inspired the synthesis and testing of several structurally related molecules. Based on these findings, it is proposed that several types of natural and synthetic polyarene molecules that have undergone oxidative functionalization (e.g., compounds containing 3-methoxyphenol moieties) are promising starting points for the development of new agents that protect against AfB₁ toxicity.

Pyroglutamic acidosis as a cause for high anion gap metabolic acidosis: a prospective study

5-oxoprolinemia (pyroglutamic acid, PGA) in the absence of acetaminophen use has been rarely reported as a cause for high anion gap metabolic acidosis. We investigated the prevalence and risk factors for elevated PGA concentrations among hospitalized patients with high anion gap metabolic acidosis: We prospectively enrolled patients with high anion gap metabolic acidosis hospitalized in the department of medicine. For each patient we collected the main diagnosis, concurrent medications and laboratory parameters. Spot urine samples were tested for PGA concentration. Levels ≥63 µmol/mmol creatinine were considered elevated. Overall, forty patients were prospectively followed. Mean age was 66.9 (17.9) years. Four (6.3%) patients had a high urine PGA level and demonstrated also lower blood pH (7.2 vs 7.3, p = 0.05) and lower serum lactate concentration (17.5 mg/dl vs 23.0 mg/dl, p = 0.04). Additionally, the high PGA level group consisted of more patients with septic shock [2/4 (50%) vs 3/36 (8.3%)] with a trend towards significance (p = 0.07). In conclusion, PGA might have a role in patients with septic shock and acidosis. Being a treatable condition, PGA should be taken into consideration particularly when no other cause for high anion gap is identified.

Shikonin attenuates acetaminophen-induced acute liver injury via inhibition of oxidative stress and inflammation

Acetaminophen (APAP) overdose causes acute liver injury and leads to fatal liver damage. However, the therapies are quite limited. Shikonin is a natural product with antioxidant and anti-inflammatory activities. In the present study, the hepatoprotective effects and the underlying mechanisms of shikonin in APAP-induced hepatotoxicity in vivo and in vitro were investigated. APAP-induced acute liver injury and shikonin pretreatment models were established in vivo and in vitro, as evidenced by serum hepatic enzymes, histological changes, oxidative stress indicators and proinflammatory cytokines. The results revealed that shikonin pretreatment prevented the elevation of serum alanine transaminase (ALT), aspartate transaminase (AST) and lactate dehydrogenase (LDH) levels and markedly reduced APAP-induced histological alterations in liver tissues. Additionally, shikonin restored superoxide dismutase (SOD) expression and glutathione (GSH) content in line with the blockade of oxidative stress. The changes in gene expression involved in oxidative stress including methionine sulfoxide reductase (such as MsrA and MsrB1), heme oxygenase-1 (HO-1), SOD2 and cytochrome P450 2E1 (CYP2E1), were markedly reversed after shikonin therapy. Furthermore, shikonin markedly attenuated the APAP-induced production of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) and suppressed the expression of genes related to inflammation. In AML-12 cells, shikonin pretreatment decreased APAP-induced cytotoxicity as measured by CCK-8 assay and LDH release. The changes in gene expression involved in oxidative stress and the inflammatory response were consistent with those in mouse livers. This study indicated that shikonin attenuated APAP-induced acute liver injury via inhibiting oxidative stress and inflammatory responses in vivo and in vitro. These findings offer new insights into the potential therapy for APAP hepatotoxicity.

The NACSTOP Trial: A Multicenter, Cluster-Controlled Trial of Early Cessation of Acetylcysteine in Acetaminophen Overdose

Historically, intravenous acetylcysteine has been delivered at a fixed dose and duration of 300 mg/kg over 20 to 21 hours to nearly every patient deemed to be at any risk for hepatotoxicity following acetaminophen overdose. We investigated a 12-hour treatment regimen for selected low-risk patients. This was a multicenter, open-label, cluster-controlled trial at six metropolitan emergency departments. We enrolled subjects following single or staggered acetaminophen overdose with normal serum alanine transaminase (ALT) and creatinine on presentation and at 12 hours, and less than 20 mg/L acetaminophen at 12 hours. Patients were allocated to intervention (250 mg/kg over 12-hour) or control (300 mg/kg over 20-hour) regimens by site. The primary outcome was incidence of "hepatic injury" 20 hours following initiation of acetylcysteine treatment, defined as ALT doubling and peak ALT greater than 100 IU/L, indicating the need for further antidotal treatment. Secondary outcomes included incidence of hepatotoxicity (ALT > 1,000 IU/L), peak international normalized ratio (INR), and adverse drug reactions. Of the 449 acetaminophen overdoses receiving acetylcysteine, 100 were recruited to the study. Time to acetylcysteine (median 7 hours [interquartile ratio 6,12] versus 7 hours [6,10]) and initial acetaminophen (124 mg/L [58,171] versus 146 mg/L [66,204]) were similar between intervention and control groups. There was no difference in ALT (18 IU/L [13,22] versus 16 IU/L [13,21]) or INR (1.2 versus 1.2) 20 hours after starting acetylcysteine between groups. No patients developed hepatic injury or hepatotoxicity in either group (odds ratio 1.0 [95% confidence interval 0.02, 50]). No patients represented with liver injury, none died, and 96 of 96 were well at 14-day telephone follow-up. Conclusion: Discontinuing acetylcysteine based on laboratory testing after 12 hours of treatment is feasible and likely safe in selected patients at very low risk of liver injury from acetaminophen overdose.

Hepatoprotective Effect of Baicalein Against Acetaminophen-Induced Acute Liver Injury in Mice

Baicalein (BAI), one of the main components of Scutellaria baicalensis Georgi, possesses numerous pharmacological properties, including anti-cancer, anti-oxidative, anti-virus and anti-bacterial activities. The purpose of this study was to evaluate the hepatoprotective effect of baicalein against acetaminophen (APAP)-exposed liver injury in mice, and elucidate the underlying hepatoprotective mechanism. Baicalein pretreatment significantly alleviated the elevation of IL-6, IL-1β and TNF-α in serum and hepatic in a dose-dependent manner. It also dose-dependently reduced the hepatic malondialdehyde (MDA) concentration, as well as the depletion of hepatic superoxide dismutase (SOD), hepatic glutathione (GSH) and hepatic catalase (CAT). Moreover, pretreatment with baicalein significantly ameliorated APAP-exposed liver damage and histological hepatocyte changes. Baicalein also relieved APAP-induced autophagy by regulating AKT/mTOR pathway, LC3B and P62 expression. Furthermore, the hepatoprotective effect of baicalein to APAP-induced liver injury involved in Jak2/Stat3 and MAPK signaling pathway. Taken together, our findings suggested that baicalein exhibits the ability to prevent liver from APAP-induced liver injury and provided an underlying molecular basis for potential applications of baicalein to cure liver injuries.

Monitoring the in Vitro Thiazolidine Ring Formation of Antioxidant Drug N-Acetyl-l-cysteine at Basic pH and Detection of Reaction Intermediates: A Raman Spectroscopic and Ab Initio Study

The important cyclization reaction of antioxidant drug N-acetyl-l-cysteine (NAC) has been monitored in vitro at basic pH with the help of time series Raman spectroscopy. The thiazoline ring formation of NAC at acidic pH is a well-known reaction and has been studied extensively. However, the formation of a thiazolidine ring from NAC at basic pH has not been investigated precisely till date. The effect of basicity of the medium on the rate of cyclization has been investigated by studying the reaction at five different basic pH values. Raman signatures of cyclization have been observed with the passage of time and are found to appear faster as the basicity of the medium increases. Ab initio calculations have been done to understand the plausible mechanism of the reaction at basic pH. It is observed that formation of a thiazolidine ring from NAC occurs primarily in four steps, which involve proton abstraction from the thiol (SH) group of NAC and subsequent formation of an S-C bond by a nucleophilic attack of the C-S group on the protonated C-O-H group in NAC. Correlation of the theoretically calculated results with experimental Raman spectral analysis has led to a detailed and proper understanding of this important biochemical reaction.

Retrospective study of paracetamol poisoning in children aged zero to six years found no cases of liver injury

AIM

This study focused on children aged zero to six years with suspected single-dose paracetamol poisoning, which has not been investigated in Denmark. We evaluated the incidence of liver injuries and the use of activated charcoal and N-acetylcysteine treatment.

METHODS

Our retrospective study was performed in three paediatric hospital centres from 2001 to 2012. Data on symptoms, time of ingestion, blood biochemistry, treatment and adverse reactions were collected. The results were evaluated against the Rumack-Matthew nomogram.

RESULTS

We identified 221 children (58% male), with a mean age of 2.67 ± 1.05 years. Activated charcoal treatment was given in 87% of cases, but only 15% of the children received treatment within one hour of the suspected paracetamol poisoning. Although 80% of the children received N-acetylcysteine treatment, only one case (0.5%) had a toxic plasma paracetamol level according to the treatment nomogram. Abdominal pain or vomiting was associated with higher paracetamol levels in plasma. None of the children developed liver injuries.

CONCLUSION

We found a low incidence of significant poisoning and liberal use of N-acetylcysteine and activated charcoal treatment in Danish children aged zero to six years with suspected paracetamol poisoning. Vomiting or abdominal pain was associated with elevated plasma paracetamol levels. No liver injuries were reported.

Transaminase and Creatine Kinase Ratios for Differentiating Delayed Acetaminophen Overdose from Rhabdomyolysis

Introduction

Rhabdomyolysis and delayed acetaminophen hepatotoxicity may be associated with elevated serum transaminase values. Establishing the cause of elevated transaminases may be especially difficult because of limited or inaccurate histories of acetaminophen ingestion. We hypothesized that the comparative ratios of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and creatine kinase (CK) can differentiate acetaminophen hepatotoxicity from rhabdomyolysis.

Methods

A retrospective chart review of patients in four hospitals from 2006 to 2011 with a discharge diagnosis of acetaminophen toxicity or rhabdomyolysis was performed. Subjects were classified into three groups: rhabdomyolysis, acetaminophen overdose (all), and acetaminophen overdose with undetectable serum acetaminophen concentrations [acetaminophen(delayed)]. Ratios of AST, ALT, and CK were compared using non-parametric statistical methods.

Results

1,353 subjects were identified and after applying our exclusion criteria there were 160 in the rhabdomyolysis group, 68 in the acetaminophen overdose (all) group, and 29 in the acetaminophen (delayed) group. The AST/ALT ratio for the rhabdomyolysis group was 1.66 (Interquartile range: 1.18–2.22), for the acetaminophen overdose (all) group was 1.38 (1.08–1.69, statistically lower than the rhabdomyolysis group, p = 0.018), and for the acetaminophen (delayed)group was 1.30 (1.06–1.63, p = 0.037). CK/AST ratios were 21.3 (12.8–42.2), 5.49 (2.52–15.1, p < 0.001), and 3.80 (1.43–13.8, p < 0.001) respectively. CK/ALT ratios were 37.1 (16.1–80.0), 5.77 (2.79–25.2, p < 0.001), and 5.03 (2.20–17.4, p < 0.001) respectively. Increasing CK to transaminase ratio cutoffs resulted in increasing test sensitivity but lower specificity.

Conclusion

AST/ALT, CK/AST and CK/ALT ratios are significantly larger in rhabdomyolysis when compared to patients with acetaminophen toxicity. This result suggests that the ratios could be used to identify patients with rhabdomyolysis who otherwise might have been diagnosed as delayed acetaminophen toxicity. Such patients may not require treatment with N-acetylcysteine, resulting in cost savings and improved resource utilization.