Reye syndrome--insights on causation and prognosis

Pharmacokinetics of aspirin: evaluating shortcomings in the literature

INTRODUCTION

Aspirin is known for its therapeutic benefits in preventing strokes and relieving pain. However, it is toxic to some individuals, and the biological mechanisms causing toxicity are unknown. Limited literature is available on the role of glycine conjugation as the principal pathway in aspirin detoxification. Previous studies have quantified this two-step enzyme reaction as a singular enzymatic process. Consequently, the individual contributions of these enzymes to the kinetics remain unclear.

AREAS COVERED

This review summarized the available information on the pharmacokinetics and detoxification of aspirin by the glycine conjugation pathway. Literature searches were conducted using Google Scholar and the academic journal databases accessible through the North-West University Library. Furthermore, the factors affecting interindividual variation in aspirin metabolism and what is known regarding aspirin toxicity were discussed.

EXPERT OPINION

The greatest drawback in understanding the pharmacokinetics of aspirin is the limited information available on the substrate preference of the xenobiotic ligase (ACSM) responsible for activating salicylate to salicyl-CoA. Furthermore, previous pharmacokinetic studies did not consider the contribution of other substrates from the diet or genetic variants, to the detoxification rate of glycine conjugation. Impaired glycine conjugation might contribute to adverse health effects seen in Reye's syndrome and cancer.

Hyperammonaemia: review of the pathophysiology, aetiology and investigation

Acute hyperammonaemia is a medical emergency as it can progress to cerebral oedema, seizures, coma and death. Hepatic encephalopathy secondary to cirrhotic disease or portosystemic shunting are relatively well-known causes, but non-cirrhotic aetiologies of acute hyperammonaemia are less well-known, especially in the emergency department. However, an elevated ammonia is not required to make the diagnosis of hepatic encephalopathy. Although measurement of plasma ammonia is recommended for patients with acute, unexplained, altered mental status, as early identification allows early effective management which may prevent irreversible brain damage, there is currently reduced awareness among physicians of the non-cirrhotic aetiologies of acute hyperammonaemia. Furthermore, measurement of ammonia in patients with cirrhosis has been shown to have low sensitivity and specificity, and not to have altered management in the majority of cases; thus, measurement of ammonia is currently not recommended in guidelines for management of hepatic encephalopathy. We sought to describe the pathophysiology of hyperammonaemia and review the non-cirrhotic causes. This was achieved by review of MEDLINE, PubMed and Web of Science databases to include published English literature within the last 20 years. We also present a framework for investigating the acute non-cirrhotic causes of hyperammonaemia to assist both chemical pathologists and clinicians managing these often challenging cases.

Pharmacogenetic Analysis of an 8-Year Old Girl with Reye Syndrome Associated with Use of Naproxen

BACKGROUND Reye syndrome is a rare, yet potentially life-threatening disease characterized by acute encephalopathy and hepatic failure. This report presents the case of an 8-year-old girl with Reye syndrome and seizures after the use of naproxen. CASE REPORT An 8-year-old girl experienced a 3-day episode of fever and abdominal pain. After receiving naproxen (375 mg twice daily) starting from day -3, she exhibited hypotension, tonic seizure, and loss of consciousness (day 1). Physical examination and laboratory test results revealed acute kidney injury, metabolic acidosis, and elevated levels of lactate dehydrogenase (LDH), liver enzymes, and ferritin. On day 2, the maximum values of aspartate aminotransferase, alanine aminotransferase, LDH, creatinine, and ferritin were 955 U/L, 132 U/L, 8040 U/L, 2 mg/dL, and >40000 ug/L, respectively. She was given supportive care and recovered after 11 days (day 12), with normalization of kidney function and metabolic abnormalities. To identify possible genetic polymorphisms associated with the patient's symptoms, genotypes were tested using a drug metabolizing enzymes and transporters (DMET) gene chip. Among genes involved in the metabolism of naproxen, UGT1A6 (*1/*2) and UGT2B7 (*1/*2) resulted in possibly decreased function. Other results which may have had clinical significance included homozygote results for NAT2*6/*6 (rs1799930). CONCLUSIONS A rare case of Reye syndrome after administration of naproxen was presented in this case. A DMET gene chip was used to screen for possible genetic polymorphisms associated with Reye syndrome, but the result was inconclusive.

Nonsteroidal anti-inflammatory drugs sensitize epithelial cells to Clostridioides difficile toxin-mediated mitochondrial damage

Clostridioides difficile damages the colonic mucosa through the action of two potent exotoxins. Factors shaping C. difficile pathogenesis are incompletely understood but are likely due to the ecological factors in the gastrointestinal ecosystem, mucosal immune responses, and environmental factors. Little is known about the role of pharmaceutical drugs during C. difficile infection (CDI), but recent studies have demonstrated that nonsteroidal anti-inflammatory drugs (NSAIDs) worsen CDI. The mechanism underlying this phenomenon remains unclear. Here, we show that NSAIDs exacerbate CDI by disrupting colonic epithelial cells (CECs) and sensitizing cells to C. difficile toxin-mediated damage independent of their canonical role of inhibiting cyclooxygenase (COX) enzymes. Notably, we find that NSAIDs and C. difficile toxins target the mitochondria of CECs and enhance C. difficile toxin-mediated damage. Our results demonstrate that NSAIDs exacerbate CDI by synergizing with C. difficile toxins to damage host cell mitochondria. Together, this work highlights a role for NSAIDs in exacerbating microbial infection in the colon.

An in vivo study of the toxic effects of triclosan on Xenopus laevis (Daudin, 1802) frog: Assessment of viability, tissue damage and mitochondrial dysfunction

The present study describes the in vivo effect of triclosan on the frog Xenopus laevis (Daudin, 1802). We have found a dose-dependence of the effect of triclosan on the survival of frogs. At a dose of 2 mg/L, the death of frogs was observed already on the 4th day of the experiment, while at a concentration of 0.5 mg/L, the frogs remained viable for 11 days. Triclosan caused damage to the liver tissue, which was expressed in an increase in the area of hemorrhage and the number of melanomacrophage centers. 0.5 mg/L of this agent did not affect the number of frog red blood cells, but reduced their osmotic resistance. Keeping animals in water containing triclosan (0.5 mg/L for 96 h) led to the suppression of the state 3 respiration rate of frog liver mitochondria. This effect was accompanied by suppression of the combined activity of complexes II and III of the mitochondrial respiratory chain. In parallel with this, we observed a reduction in the Ca²⁺ retention capacity of frog liver mitochondria, indicating a decrease in the resistance of organelles to mitochondrial permeability transition pore opening. The paper discusses the effects of triclosan on aquatic organisms.

Pediatric Acute Liver Failure: A Clinicopathological Perspective

Pediatric acute liver failure (PALF) is a life-threatening disorder characterized by acute hepatocellular injury occurring in children without recognized underlying liver disease. The clinicopathologic evaluation of PALF requires a different approach from that in adults. The diagnostic considerations differ depending on the age, personal and family history, geographical region, and clinical presentation. Distinct entities such as gestational alloimmune liver disease, herpes simplex virus infection, and metabolic disorders should be considered in neonates with acute liver failure, while acetaminophen toxicity and autoimmune hepatitis are more frequently seen in older children and adolescents. An identified cause for PALF despite a negative complete evaluation (indeterminate) is lacking in 30 to 50% of cases. Although not routinely performed in the setting of PALF, liver biopsy may be helpful in assessing the etiology, potential mechanisms of injury, determining the appropriateness of liver transplantation, and prognostication of the patients. In this article, we review the clinicopathologic characteristics of PALF with an emphasis on general approach of pathologic evaluation and histopathologic characteristic of selected entities.

Analysis of a family with mitochondrial trifunctional protein deficiency caused by HADHA gene mutations

Mitochondrial trifunctional protein (MTP) deficiency (MTPD; MIM 609015) is a metabolic disease of fatty acid oxidation. MTPD is an autosomal recessive disorder caused by mutations in the HADHA gene, encoding the α-subunit of a trifunctional protease, or in the HADHB gene, encoding the β-subunit of a trifunctional protease. To the best of our knowledge, only two cases of families with MTPD due to HADHB gene mutations have been reported in China, and the HADHA gene mutation has not been reported in a Chinese family with MTPD. The present study reported the clinical characteristics and compound heterozygous HADHA gene mutations of two patients with MTPD in the Chinese population. The medical history, routine examination data, blood acyl-carnitine analysis results, results of pathological examination after autopsy and family pedigree map were collected for patients with MTPD. The HADHA gene was analyzed by Sanger sequencing or high-throughput sequencing, the pathogenicity of the newly discovered variant was interpreted by bioinformatics analysis, and the function of the mutated protein was modeled and analyzed according to 3D structure. The two patients with MTPD experienced metabolic crises and died following an infectious disease. Lactate dehydrogenase, creatine kinase (CK), CK-MB and liver enzyme abnormalities were observed in routine examinations. Tandem mass spectrometry revealed that long-chain acyl-carnitine was markedly elevated in blood samples from the patients with MTPD. The autopsy results for one child revealed fat accumulation in the liver and heart. Next-generation sequencing detected compound heterozygous c.703C>T (p.R235W) and c.2107G>A (p.G703R) mutations in the HADHA gene. The mother did not have acute fatty liver during pregnancy with the two patients. Using amniotic fluid prenatal diagnostic testing, the unborn child was confirmed to carry only c.2107G>A (p.G703R). Molecular mechanistic analysis indicated that the two variants affected the conformation of the α-subunit of the MTP enzyme complex, and consequently affected the stability and function of the enzyme complex. The present study comprehensively analyzed the cases, including exome sequencing and protein structure analysis and, to the best of our knowledge, describes the first observation of compound heterozygous mutations in the HADHA gene underlying this disorder in China. The clinical phenotypes of the two heterozygous variants of the HADHA gene are non-lethal. The present study may improve understanding of the HADHA gene mutation spectrum and clinical phenotype in the Chinese population.

Ornithine Transcarbamylase - From Structure to Metabolism: An Update

Ornithine transcarbamylase (OTC; EC 2.1.3.3) is a ubiquitous enzyme found in almost all organisms, including vertebrates, microorganisms, and plants. Anabolic, mostly trimeric OTCs catalyze the production of L-citrulline from L-ornithine which is a part of the urea cycle. In eukaryotes, such OTC localizes to the mitochondrial matrix, partially bound to the mitochondrial inner membrane and part of channeling multi-enzyme assemblies. In mammals, mainly two organs express OTC: the liver, where it is an integral part of the urea cycle, and the intestine, where it synthesizes citrulline for export and plays a major role in amino acid homeostasis, particularly of L-glutamine and L-arginine. Here, we give an overview on OTC genes and proteins, their tissue distribution, regulation, and physiological function, emphasizing the importance of OTC and urea cycle enzymes for metabolic regulation in human health and disease. Finally, we summarize the current knowledge of OTC deficiency, a rare X-linked human genetic disorder, and its emerging role in various chronic pathologies.

Atypical Reye syndrome: three cases of a problem that pediatricians should consider and remember

INTRODUCTION

Reye syndrome is a rare acquired metabolic disorder appearing almost always during childhood. Its aetiopathogenesis, although controversial, is partially understood. The classical disease is typically anticipated by a viral infection with 3-5 days of well-being before the onset of symptoms, while the biochemical explanation of the clinical picture is a mitochondrial metabolism disorder, which leads to a metabolic failure of different tissues, especially the liver. Hypothetically, an atypical response to the preceding viral infection may cause the syndrome and host genetic factors and different exogenous agents, such as toxic substances and drugs, may play a critical role in this process. Reye syndrome occurs with vomiting, liver dysfunction and acute encephalopathy, characterized by lack of inflammatory signs, but associated with increase of intracranial pressure and brain swelling. Moreover, renal and cardiac dysfunction can occur. Metabolic acidosis is always  detected, but diagnostic criteria are not specific. Therapeutic strategies are predominantly symptomatic, in order to manage the clinical and metabolic dysfunctions.

CASE REPORTS

We describe three cases of children affected by Reye syndrome with some atypical features, characterized by no intake of potentially trigger substances, transient hematological changes and dissociation between hepatic metabolic impairment, severe electroencephalographic slowdown and slightly altered neurological examination.

CONCLUSIONS

The syndrome prognosis is related to the stage of the syndrome and the rapidity and the adequateness of intensive care treatments. The analysis of the patients leads to a greater awareness of the difficult diagnosis of this not well completely known syndrome.

Management of acute mitochondriopathy and encephalopathy syndrome in pediatric intensive care unite: a new clinical entity

Acute mitochondriopathy and encephalopathy syndrome (AMES) is described differently by different authors in the literature. As a new clinical entity, we aimed to present the clinical signs and symptoms, diagnosis and treatment algorithm of our patients with AMES. 56 patients aged between 2 months and 18 years who were followed up in pediatric intensive care units of Konya Training and Research Hospital and Selcuk University Medical Faculty Hospital, between January 2010 and June 2017 were included. Patients' data were obtained retrospectively from the intensive care unit patient files. 34 (60.7%) of the patients were male and 22 (39.3%) were female. The median age of our patients was 10.0 months. At the time of admission, 42 (75%) of the patients had fever, 35 (62.5%) vomiting, 27 (48.2%) abnormal behaviour and agitation and 28 (50%) convulsion. The etiological classification of patients with AMES was divided into four groups as infection, metabolic disorder, toxic, and hypoxic-ischemic. 39 (69.6%) patients were found to have infection, 10 (17.9%) patients hypoxia, 7 (12.5%) patients metabolic disorders. AMES occurs rarely, but should be kept in mind in the differential diagnosis of patients with any encephalopathy of unknown origin especially in those with a history of ingestion of drugs, previous viral infection and vomiting. Early recognition and treatment is imperative to reduce morbidity and mortality in children with AMES.

Alcohol and Liver Clock Disruption Increase Small Droplet Macrosteatosis, Alter Lipid Metabolism and Clock Gene mRNA Rhythms, and Remodel the Triglyceride Lipidome in Mouse Liver

Heavy alcohol drinking dysregulates lipid metabolism, promoting hepatic steatosis – the first stage of alcohol-related liver disease (ALD). The molecular circadian clock plays a major role in synchronizing daily rhythms in behavior and metabolism and clock disruption can cause pathology, including liver disease. Previous studies indicate that alcohol consumption alters liver clock function, but the impact alcohol or clock disruption, or both have on the temporal control of hepatic lipid metabolism and injury remains unclear. Here, we undertook studies to determine whether genetic disruption of the liver clock exacerbates alterations in lipid metabolism and worsens steatosis in alcohol-fed mice. To address this question, male liver-specific Bmal1 knockout (LKO) and flox/flox (Fl/Fl) control mice were fed a control or alcohol-containing diet for 5 weeks. Alcohol significantly dampened diurnal rhythms of mRNA levels in clock genes Bmal1 and Dbp, phase advanced Nr1d1/REV-ERBα, and induced arrhythmicity in Clock, Noct, and Nfil3/E4BP4, with further disruption in livers of LKO mice. Alcohol-fed LKO mice exhibited higher plasma triglyceride (TG) and different time-of-day patterns of hepatic TG and macrosteatosis, with elevated levels of small droplet macrosteatosis compared to alcohol-fed Fl/Fl mice. Diurnal rhythms in mRNA levels of lipid metabolism transcription factors (Srebf1, Nr1h2, and Ppara) were significantly altered by alcohol and clock disruption. Alcohol and/or clock disruption significantly altered diurnal rhythms in mRNA levels of fatty acid (FA) synthesis and oxidation (Acaca/b, Mlycd, Cpt1a, Fasn, Elovl5/6, and Fads1/2), TG turnover (Gpat1, Agpat1/2, Lpin1/2, Dgat2, and Pnpla2/3), and lipid droplet (Plin2/5, Lipe, Mgll, and Abdh5) genes, along with protein abundances of p-ACC, MCD, and FASN. Lipidomics analyses showed that alcohol, clock disruption, or both significantly altered FA saturation and remodeled the FA composition of the hepatic TG pool, with higher percentages of several long and very long chain FA in livers of alcohol-fed LKO mice. In conclusion, these results show that the liver clock is important for maintaining temporal control of hepatic lipid metabolism and that disrupting the liver clock exacerbates alcohol-related hepatic steatosis.

Aspirin Causes Lipid Accumulation and Damage to Cell Membrane by Regulating DCI1/OLE1 in Saccharomyces cerevisiae

Aspirin is one of the most commonly used nonsteroidal anti-inflammatory drugs. Various potential pharmacological effects of aspirin, such as anticancer, antibacterial activity, and prolonging life expectancy have been discovered. However, the mechanism of aspirin is not fully elucidated. Herein, the effects of aspirin on fatty acid metabolism in yeast cell model Saccharomyces cerevisiae were studied. The results showed that aspirin can induce lipid accumulation and reduce the unsaturated fat index in cells. The assessment of cell membrane integrity demonstrated that aspirin caused damage to the cell membrane. These effects of aspirin were attributed to the alterations of the expression of DCI1 and OLE1. Similarly, aspirin was able to cause lipid accumulation and damage to the cell membrane by interfering with the expression of OLE1 in Candida albicans. These findings are expected to improve current understanding of the mode of action of aspirin and provide a novel strategy for antifungal drug design. Graphical abstract [Figure: see text].

A rare case of Reye's syndrome induced by influenza A virus with use of ibuprofen in an adult

Background

Reye's syndrome (RS) is a rare but severe acute life‐threating disease characterized by encephalopathy and fatty liver damage. Reye's syndrome is most common in children and rarely occurs in adults.

Case presentation

A 56‐year‐old woman was admitted to the emergency department with disturbance of consciousness and respiratory failure. She had taken ibuprofen for headache. Her Glasgow Coma Scale score was E3V3M5 on admission. The laboratory findings revealed acute liver failure with prothrombin time – international normalized ratio of 3.16, aspartate aminotransferase 12,548 IU/L, alanine aminotransferase 5,725 IU/L, and blood ammonia 102 μg/dL. Head magnetic resonance imaging showed hyperintense signals on diffusion‐weighed images of globus pallidus.

We diagnosed the patient with RS induced by influenza A and use of ibuprofen. The patient received supportive care in the intensive care unit and her clinical outcome was favorable.

Conclusion

Ibuprofen might be a risk factor for RS.

Acute hepatitis and acute liver failure: Pathologic diagnosis and differential diagnosis

Acute hepatitis and acute liver failure are severe medical conditions that require early clinical intervention. Histopathologic findings on a liver biopsy or a liver explant may help identify the underlying etiology or provide an important direction for further clinical, laboratory and radiographical investigation. This review is divided into two main portions. The first portion concentrates on various etiologies and discusses unique histologic features that can be associated with specific etiologies. The second portion describes the general morphologic features based on which the diagnosis of acute hepatitis and acute liver failure are made. Histopathologic distinction between collapse and cirrhosis and limitations of histopathologic assessment for underlying etiologies are addressed in this portion. Another focus of this review is non-necrotic acute liver failure, which typically features diffuse microvesicular steatosis secondary to various etiologies causing mitochondrial dysfunction. Molecular testing serves an increasingly important role in the diagnosis and management of this group of disorders.

Acute pediatric hyperammonemia: current diagnosis and management strategies

Acute hyperammonemia may induce a neurologic impairment leading to an acute life-threatening condition. Coma duration, ammonia peak level, and hyperammonemia duration are the main risk factors of hyperammonemia-related neurologic deficits and death. In children, hyperammonemia is mainly caused by severe liver failure and inborn errors of metabolism. In an acute setting, obtaining reliable plasma ammonia levels can be challenging because of the preanalytical difficulties that need to be addressed carefully. The management of hyperammonemia includes 1) identification of precipitating factors and cerebral edema presence, 2) a decrease in ammonia production by reducing protein intake and reversing catabolism, and 3) ammonia removal with pharmacologic treatment and, in the most severe cases, with extracorporeal therapies. In case of severe coma, transcranial Doppler ultrasound could be the method of choice to noninvasively monitor cerebral blood flow and titrate therapies.

Co-ingestion of aspirin and acetaminophen promoting fulminant liver failure: A critical review of Reye syndrome in the current perspective at the dawn of the 21st century

In the paediatric population, there is some evidence of possible interaction, synergism, and co-toxicity of aspirin and acetaminophen. The toxicity of salicylates such as aspirin in this population is well known and documented, specifically in the form of Reye syndrome. The possible toxic synergism with aspirin and acetaminophen, however, is not previously described; though case reports suggest such co-toxicities with low levels of aspirin and other compounds can exist. In vitro studies into mechanistic processes of salicylate toxicity propose that there is a bi-directional link and potentiation with glutathione (GSH) depletion and salicylate toxicity. Data may suggest a plausible explanation for salicylate and acetaminophen toxic synergism. Further studies investigating this potential toxic synergism are warranted. Given the lack of awareness in the clinical community about potential toxic synergism between these relatively common medications, caution is advised in the co-administration of these drugs, particularly in communities using natural or alternative therapy.

Genotype-Phenotype Correlations in Ornithine Transcarbamylase Deficiency: A Mutation Update

Ornithine transcarbamylase (OTC) deficiency is an X-linked trait that accounts for nearly half of all inherited disorders of the urea cycle. OTC is one of the enzymes common to both the urea cycle and the bacterial arginine biosynthesis pathway; however, the role of OTC has changed over evolution. For animals with a urea cycle, defects in OTC can trigger hyperammonemic episodes that can lead to brain damage and death. This is the fifth mutation update for human OTC with previous updates reported in 1993, 1995, 2002, and 2006. In the 2006 update, 341 mutations were reported. This current update contains 417 disease-causing mutations, and also is the first report of this series to incorporate information about natural variation of the OTC gene in the general population through examination of publicly available genomic data and examination of phenotype/genotype correlations from patients participating in the Urea Cycle Disorders Consortium Longitudinal Study and the first to evaluate the suitability of systematic computational approaches to predict severity of disease associated with different types of OTC mutations.

The simultaneous detection and quantification of p-aminobenzoic acid and its phase 2 biotransformation metabolites in human urine using LC–MS/MS

Background: p-Aminobenzoic acid (PABA) can be used as a probe substance to investigate glycine conjugation, a reaction of phase 2 biotransformation. Methodology/Results: An LC–MS/MS method for simultaneous quantification of PABA and its metabolites from human urine was developed and validated. The metabolites can be quantified with acceptable precision and accuracy directly from human urine samples after ingestion of 550 mg PABA. Conclusion: The developed LC–MS/MS assay is to our knowledge the first method available for the simultaneous quantification of PABA and its glycine conjugation metabolites in human urine and provides important quantitative data for studies of this phase 2 biotransformation pathway.

Neuroepidemiology and the epidemiology of viral infections of the nervous system

The field of neurovirology will undoubtedly experience evolution and change in the years to come. The epidemiology of viral CNS diseases continues to change, and as our understanding of the pathogenesis and pathophysiology associated with viral agents grows, so does our understanding of the behavior of these pathogens among populations. The appearance of viral pathogens in newsettings, new or unrecognized modes of transmission,and the emergence of previously unrecognized pathogens will continue to challenge our laboratory diagnostic and epidemiologic capabilities. However, each lesson that is learned from this evolving epidemiology will hopefully result in improved surveillance, diagnostic,and treatment and prevention capabilities.

Resveratrol protects against experimental induced Reye's syndrome by prohibition of oxidative stress and restoration of complex I activity

This study was designed to investigate whether resveratrol could provide protection against Reye's syndrome induced by 4-pentenoic acid in Wistar albino rats. Compared with rats with untreated Reye's syndrome, 1 h pretreatment by low dose resveratrol (10 mg/kg by oral gavage) resulted in marked amelioration in liver functions in the form of significant decrease in serum transaminases (AST, ALT) and plasma ammonia levels, shortening of prothrombin time, and increase in serum albumin levels. In addition, resveratrol prohibited oxidative stress markers, as indicated by a significant increase in GSH and decrease in MDA, with restoration of complex I activity in liver tissues. The classical histopathological presentation in Reye's syndrome of microvesicular steatosis by light microscope and mitochondria distortion by electron microscope has been improved by resveratrol pretreatment. The efficient protection by resveratrol was determined by normalization in serum levels of AST and albumin, as well as complex I activity, GSH, and MDA. In conclusion, pretreatment by resveratrol in low doses could protect against Reye's syndrome partially via prohibition of oxidative stress and restoration of complex I activity. This may provide the opportunity to reconsider aspirin therapy for infants and young children. However, the verification of such results in clinical practice remains a challenge.

The Study of Pyridazine Compounds on Prostanoids: Inhibitors of COX, cAMP Phosphodiesterase, and TXA2Synthase

The pyridazine moiety is an important structural feature of various pharmacological active compounds. Synthetic pyridazine compounds have been reported as effective antiprostaglandins (PGs), 5-lipoxygenase (5-LOX), and antiplatelet agents, that is, inhibitors of prostaglandin or cyclooxygenase (COX-I & COX-II) enzyme, platelet cAMP phosphodiesterase, and thromboxane A2 (TXA2) synthase. These compounds are selective and nonselective COX inhibitors and showed analgesic, anti-inflammatory, and antipyretic activity. Pyridazine compounds with antiplatelet agents inhibited TXA2enzyme. Pyridazines also exhibited antirheumatoid activity. These pyridazine compounds hold considerable interest relative to the preparation of organic intermediates and other anticipated biologically active compounds.

Glycine conjugation: importance in metabolism, the role of glycine N-acyltransferase, and factors that influence interindividual variation

INTRODUCTION

Glycine conjugation of mitochondrial acyl-CoAs, catalyzed by glycine N-acyltransferase (GLYAT, E.C. 2.3.1.13), is an important metabolic pathway responsible for maintaining adequate levels of free coenzyme A (CoASH). However, because of the small number of pharmaceutical drugs that are conjugated to glycine, the pathway has not yet been characterized in detail. Here, we review the causes and possible consequences of interindividual variation in the glycine conjugation pathway.

AREAS COVERED

The authors review the importance of CoASH in metabolism, formation and toxicity of xenobiotic acyl-CoAs, and mechanisms for restoring levels of CoASH. They focus on GLYAT, glycine conjugation, how genetic variation in the GLYAT gene could influence glycine conjugation, and the emerging roles of glycine metabolism in cancer and musculoskeletal development.

EXPERT OPINION

The substrate selectivity of GLYAT and its variants needs to be further characterized, as organic acids can be toxic if the corresponding acyl-CoA is not a substrate for glycine conjugation. GLYAT activity affects mitochondrial ATP production, glycine availability, CoASH availability, and the toxicity of various organic acids. Therefore, variation in the glycine conjugation pathway could influence liver cancer, musculoskeletal development, and mitochondrial energy metabolism.

Vaccines and recommendations for their use in inflammatory bowel disease

The patient with inflammatory bowel disease will be predisposed to numerous infections due their immune status. It is therefore important to understand the immune and serologic status at diagnosis and to put the patient into an adapted vaccination program. This program would be applied differently according to two patient groups: the immunocompromised and the non-immunocompromised. In general, the first group would avoid the use of live-virus vaccines, and in all cases, inflammatory bowel disease treatment would take precedence over vaccine risk. It is important to individualize vaccination schedules according to the type of patient, the treatment used and the disease pattern.In addition, patient with inflammatory bowel disease should be considered for the following vaccines: varicella vaccine, human papilloma virus, influenza, pneumococcal polysaccharide vaccine and hepatitis B vaccine.

Electron attachment to antipyretics: possible implications of their metabolic pathways

The empty-level structures and formation of negative ion states via resonance attachment of low-energy (0-15 eV) electrons into vacant molecular orbitals in a series of non-steroidal anti-inflammatory drugs (NSAIDs), namely aspirin, paracetamol, phenacetin, and ibuprofen, were investigated in vacuo by electron transmission and dissociative electron attachment (DEA) spectroscopies, with the aim to model the behavior of these antipyretic agents under reductive conditions in vivo. The experimental findings are interpreted with the support of density functional theory calculations. The negative and neutral fragments formed by DEA in the gas phase display similarities with the main metabolites of these commonly used NSAIDs generated in vivo by the action of cytochrome P450 enzymes, as well as with several known active agents. It is concluded that xenobiotic molecules which possess pronounced electron-accepting properties could in principle follow metabolic pathways which parallel the gas-phase dissociative decay channels observed in the DEA spectra at incident electron energies below 1 eV. Unwanted side effects as, e.g., hepatoxicity or carcinogenicity produced by the NSAIDs under study in human organism are discussed within the "free radical model" framework, reported earlier to describe the toxic action of the well-known model toxicant carbon tetrachloride.

Adult Reye-like syndrome associated with serologic evidence of acute parvovirus B19 infection

Reye's syndrome is an infrequently diagnosed medical condition affecting mainly children. The etiology, epidemiology and natural history of Reye's syndrome have been cloudily written in footnotes of medical books and exotic papers since the initial description in early 1950s. We report here a case of adult Reye's syndrome associated with serologic evidence of parvovirus B19 infection.

Pandemism of swine flu and its prospective drug therapy

Swine flu is a respiratory disease caused by influenza A H1N1 virus. The current pandemic of swine flu is most probably due to a mutation-more specifically, a re-assortment of four known strains of influenza A virus subtype H1N1. Antigenic variation of influenza viruses while circulating in the population is an important factor leading to difficulties in controlling influenza by vaccination. Due to the global effect of swine flu and its effect on humans, extensive investigations are being undertaken. In this context, Tamiflu is the only available drug used in the prophylaxis of this disease and is made from the compound shikimic acid. Due to the sudden increase in the demand of shikimic acid, its price has increased greatly. Thus, it is necessary to find an alternative approach for the treatment of swine flu. This review presents the overall information of swine flu, beginning from its emergence to the prevention and treatment of the disease, with a major emphasis on the alternative approach (bacterial fermentation process) for the treatment of swine flu. The alternative approach for the treatment of swine flu includes the production of shikimic acid from a fermentation process and it can be produced in large quantities without any time limitations.

Liver pathology in Malawian children with fatal encephalopathy

A common clinical presentation of Plasmodium falciparum is parasitemia, complicated by an encephalopathy for which other explanations cannot be found, termed cerebral malaria-an important cause of death in young children in endemic areas. Our objective was to study hepatic histopathology in Malawian children with fatal encephalopathy, with and without P falciparum parasitemia, to assess the contributions of severe malaria. We report autopsy results from a series of 87 Malawian children who died between 1996 and 2008. Among 75 cases with P falciparum parasitemia, 51 had intracerebral sequestered parasites, whereas 24 without sequestered parasites had other causes of death revealed by autopsy including 4 patients with clinicopathologic findings which may represent Reye syndrome. Hepatic histology in parasitemic cases revealed very limited sequestration of parasites in hepatic sinusoids, even in cases with extensive sequestration elsewhere, but increased numbers of hemozoin-laden Kupffer cells were invariably present with a strong association with histologic evidence of cerebral malaria by quantitative analysis. Of 12 patients who were consistently aparasitemic during their fatal illness, 5 had clinicopathologic findings which may represent Reye syndrome. Hepatic sequestration of parasitized erythrocytes is not a feature of fatal malaria in Malawian children, and there is no structural damage in the liver. Reye syndrome may be an important cause of fatal encephalopathy in children in Malawi with and without peripheral parasitemia and warrants close scrutiny of aspirin use in malaria-endemic areas.

Competitive inhibition of organic anion transporting polypeptide 1c1-mediated thyroxine transport by the fenamate class of nonsteroidal antiinflammatory drugs

Organic anion transporting polypeptide (Oatp) 1c1 is a high-affinity T(4) transporter with narrow substrate specificity expressed at the blood-brain barrier. A transport model using cells overexpressing Oatp1c1 was created to identify novel Oatp1c1 substrates and inhibitors. Rat Oatp1c1 was cloned and stably expressed in human embryonic kidney 293 cells. Oatp1c1-transfected human embryonic kidney 293 cells transported (125)I-labeled T(4) in a time-dependent manner that was completely abolished in the presence of excess unlabeled T(4). Next, various compounds, including inhibitors of thyroid hormone uptake, were screened for inhibitory effects on Oatp1c1-mediated T(4) uptake. Phenytoin (64%), indocyanine green (17%), fenamic acid (68%), diclofenac (51%), and meclofenamic acid (33%) all reduced T(4) uptake by Oatp1c1 when assayed at concentrations of 10 microM. Dose-response assays for the fenamic acids, iopanoic acid, indocyanine green, and phenytoin revealed IC(50) values for Oatp1c1 T(4) uptake below or near the blood plasma levels after therapeutic doses. Further kinetic assays and reciprocal plot analyses demonstrated that the fenamic acid diclofenac inhibited in a competitive manner. Finally, microvessels were isolated from adult rat brain and assessed for T(4) uptake. Ten micromolar of fenamate concentrations inhibited T(4) microvessel uptake with a similar hierarchical inhibition profile [fenamic acid (43%), diclofenac (78%), and meclofenamic acid (85%)], as observed for Oatp1c1 transfected cells. Oatp1c1 is expressed luminally and abluminally in the blood-brain barrier endothelial cell, and exhibits bidirectional transport capabilities. Together, these data suggest that Oatp1c1 transports fenamates into, and perhaps across, brain barrier cells.

Prognostic factors in influenza-associated encephalopathy

BACKGROUND

Recently, reports of influenza-associated encephalopathy have increased worldwide. Given the high mortality and morbidity rates attributable to this severe neurologic complication of influenza, we conducted a nationwide study in Japan to identify the prognostic factors.

METHODS

We retrospectively evaluated 442 cases of influenza-associated encephalopathy that were reported to the Collaborative Study Group on Influenza-Associated Encephalopathy, which was organized by the Japanese Ministry of Health, Labor, and Welfare in collaboration with hospitals, clinics, and local pediatric practices in Japan between 1998 and 2002. The outcome for each patient was classified as either survival or death. Predictors of death were identified using logistic regression analysis.

RESULTS

Four major prognostic factors for death were found to be significant by multivariate analysis (P < 0.05) in the 184 patients for whom we had complete data: elevation of aspartate aminotransferase, hyperglycemia, the presence of hematuria or proteinuria, and use of diclofenac sodium.

CONCLUSIONS

We identified patients who had factors associated with a poor prognosis, and these findings might be clinically useful for the management of this illness.

The neurotropic herpes viruses: herpes simplex and varicella-zoster

Herpes simplex viruses types 1 and 2 (HSV1 and HSV2) and varicella-zoster virus (VZV) establish latent infection in dorsal root ganglia for the entire life of the host. From this reservoir they can reactivate to cause human morbidity and mortality. Although the viruses vary in the clinical disorders they cause and in their molecular structure, they share several features that affect the course of infection of the human nervous system. HSV1 is the causative agent of encephalitis, corneal blindness, and several disorders of the peripheral nervous system; HSV2 is responsible for meningoencephalitis in neonates and meningitis in adults. Reactivation of VZV, the pathogen of varicella (chickenpox), is associated with herpes zoster (shingles) and central nervous system complications such as myelitis and focal vasculopathies. We review the biological, medical, and neurological aspects of acute, latent, and reactivated infections with the neurotropic herpes viruses.

Effect of acetaminophen, a cyclooxygenase inhibitor, on Morris water maze task performance in mice

Although the mechanism of action of acetaminophen (AAP) is not fully understood, some studies suggest that AAP and phenacetin (PHE) are selective cyclooxygenase (COX)-3 inhibitors. To examine the participation of COX-3 in memory formation, water maze performance was studied in mice treated with AAP, PHE or other COX inhibitors. Mice received intraperitoneal injections of drugs immediately after each training session. Administration of high-dose AAP [302.3 mg/kg (IC50 for COX-2)] or PHE [179.2 mg/kg (IC50 for COX-2)] and of non-specific (indomethacin: 20 mg/kg) or specific COX-2 (NS-398: 10 mg/kg) inhibitor impaired the performance in hidden platform (HP) not visible platform (VP) tasks, whereas low-dose (15.1 mg/kg) AAP facilitated performance in HP and VP tasks. The facilitation of performance by low-dose AAP was reversed by co-administration with a 5-HT(1/2) receptor antagonist (methysergide: 0.47 mg/kg). The middle-dose [69.5 mg/kg (IC50 for COX-3)] of AAP, the PHE [17.9 mg/kg (IC50 for COX-3)] and a specific COX-1 inhibitor (piroxicam: 10-20 mg/kg) did not influence performance in either task. These results suggest that the memory impairment by high-dose AAP and PHE and facilitation of performance by low-dose AAP could involve endogenous COX-2 and serotonergic neuronal activity, but not COX-3, respectively.

Amino acid conjugation: contribution to the metabolism and toxicity of xenobiotic carboxylic acids

Despite being the first conjugation reaction demonstrated in humans, amino acid conjugation as a route of metabolism of xenobiotic carboxylic acids is not well characterised. This is principally due to the small number and limited structural diversity of xenobiotic substrates for amino acid conjugation. Unlike CYP and uridine 5'-diphosphate glucuronosyltransferase, which are localised in the endoplasmic reticulum, the enzymes of amino acid conjugation reside in mitochondria. Unique among drug metabolism pathways, amino acid conjugation involves initial formation of a xenobiotic acyl-CoA thioester that is then conjugated principally with glycine in humans. However, formation of the xenobiotic acyl-CoA thioester does not always infer subsequent amino acid conjugation. Evidence is presented that in the absence of glycine conjugation substrates that form acyl-CoA thioesters perturb mitochondrial function. This review discusses literature on the enzymes involved and the concept that xenobiotic substrate selectivity provides a barrier to protect the metabolic integrity of the mitochondria.

Aspirin and Reye syndrome: a review of the evidence

Reye syndrome is an extremely rare but severe and often fatal disease. Death occurs in about 30-40% of cases from brainstem dysfunction. The disease typically is preceded by a viral infection with an intermediate disease-free interval of 3-5 days. The biochemical explanation for Reye-like symptoms is a generalized disturbance in mitochondrial metabolism, eventually resulting in metabolic failure in the liver and other tissues. The etiology of 'classical' Reye syndrome is unknown. Hypothetically, the syndrome may result from an unusual response to the preceding viral infection, which is determined by host genetic factors but can be modified by a variety of exogenous agents. Thus, several infections and diseases might present clinically with Reye-like symptoms. Exogenous agents involve a number of toxins, drugs (including aspirin [acetylsalicylic acid]), and other chemicals. The 'rise and fall' in the incidence of Reye syndrome is still poorly understood and unexplained. With a few exceptions, there were probably no new Reye-like diseases reported during the last 10 years that could not be explained by an inherited disorder of metabolism or a misdiagnosis. This may reflect scientific progress in the better understanding of cellular and molecular dysfunctions as disease-determining factors. Alternatively, the immune response to and the virulence of a virus might have changed by alteration of its genetic code. The suggestion of a defined cause-effect relationship between aspirin intake and Reye syndrome in children is not supported by sufficient facts. Clearly, no drug treatment is without side effects. Thus, a balanced view of whether treatment with a certain drug is justified in terms of the benefit/risk ratio is always necessary. Aspirin is no exception.

Reye's syndrome: the case for a causal link with aspirin

Reye's syndrome is a serious, acute encephalopathy that has been linked with aspirin (acetylsalicylic acid) use in children and teenagers <18 years of age. Although others may disagree, it is my belief that any objective analysis of published material in the last 20 years must conclude that there is a close link between the devastating encephalopathy Reye's syndrome and ingestion of aspirin during the febrile prodrome. The drug appears to act as a co-factor in susceptible individuals. Although some of the epidemiological data indicate an association between the two, the burden of evidence suggests actual causality and is both consistent and specific as well as strong and time related. Some of the evidence points to illness severity being dose related although it seems that in the presence of a viral infection, no dose of aspirin can be considered safe. No published work, using methodology that can be critically evaluated, has shown evidence to contradict these conclusions and they have been widely accepted. Since government health warnings were appended to aspirin-containing formulations, the decline in case numbers on both sides of the Atlantic has been nothing short of remarkable. Recent in vitro findings have pinpointed the site of action of the drug on the long chain hydroxyacyl-CoA dehydrogenase enzyme (a component of the mitochondrial trifunctional enzyme) and, even at therapeutic concentrations, oxidation is impaired in cultured fibroblasts from patients who have recovered from the disorder. This is quite unlike that seen in cells from normal controls. Even when major influenza outbreaks occur in the future, Reye's syndrome is preventable provided government health warnings are heeded and the cogent evidence set forth here is acted upon by the parents of feverish children and self-medicating teenagers.

Pathogenesis of fulminant type 1 diabetes

Fulminant type 1 diabetes is a new subtype of type 1 diabetes. The term was established in 2000. It is a syndrome characterized by a markedly rapid and almost complete destruction of pancreatic beta-cells. Several lines of evidence suggest that both genetic factors, such as human leukocyte antigen (HLA), and environmental factors, such as viral infection, contribute to the development of this disease. It is also suggested that autoimmune processes contribute less critically to fulminant type 1 diabetes than to classic type 1A diabetes. Based on the findings made to date, both viral infection and the subsequent immune reaction in genetically susceptible individuals cause beta-cell destruction and lead to fulminant type 1 diabetes.

Vitamin D3upregulated protein 1 (VDUP1) is a regulator for redox signaling and stress-mediated diseases

Vitamin D(3) upregulated protein 1 (VDUP1) is a 46-kDa multifunctional protein, initially isolated in HL-60 cells as a protein of which expression is upregulated by vitamin D(3) administration. Subsequently, it was identified independently by investigators from diverse scientific backgrounds as a thioredoxin binding protein that negatively regulates the expression and the activity of thioredoxin, and is thus involved in redox regulation. Further studies have revealed that VDUP1 plays multiple roles in a wide range of cellular processes such as proliferation or apoptosis. Recently, it has been reported that VDUP1 is also involved in the immune system via positive regulation of natural killer development. In addition, VDUP1 has been revealed to be associated with the fatty acid utilization. In the present review, we discuss the novel aspects of VDUP1 function as well as the historical background of VDUP1. Future studies will explore the diagnostic and therapeutic potential of modulating the function of VDUP1 in vivo.

Acute infantile encephalopathy predominantly affecting the frontal lobes (AIEF): A novel clinical category and its tentative diagnostic criteria

Acute infantile encephalopathy predominantly affecting the frontal lobes (AIEF) is proposed as a novel form of acute encephalopathy in infancy. To establish the diagnostic criteria for AIEF, we reviewed the clinical data of 10 patients who were seen by us and diagnosed as having AIEF, and those of 7 patients in the literature compatible with the diagnosis of AIEF. The mean age of onset was 1 year and 7 months. Boys and girls were equally affected. There is always an association with hyperpyrexia due to viral illness. Manifestations at the onset were convulsive status epilepticus and prolonged coma followed by signs of frontal lobe dysfunction such as a lack of spontaneity and regression of verbal functions. Imaging studies demonstrated edematous changes of the bilateral frontal lobes, which showed increased cerebral perfusion initially but attenuated perfusion several weeks later. The recovery of intellectual deficit was generally slower than that of motor disability. Based on these findings, we propose tentative diagnostic criteria of AIEF.