Recurrent acute liver failure due to NBAS deficiency: phenotypic spectrum, disease mechanisms, and therapeutic concepts

BACKGROUND

Acute liver failure (ALF) in infancy and childhood is a life-threatening emergency and in about 50% the etiology remains unknown. Recently biallelic mutations in NBAS were identified as a new molecular cause of ALF with onset in infancy, leading to recurrent acute liver failure (RALF).

METHODS

The phenotype and medical history of 14 individuals with NBAS deficiency was studied in detail and functional studies were performed on patients' fibroblasts.

RESULTS

The phenotypic spectrum of NBAS deficiency ranges from isolated RALF to a multisystemic disease with short stature, skeletal dysplasia, immunological abnormalities, optic atrophy, and normal motor and cognitive development resembling SOPH syndrome. Liver crises are triggered by febrile infections; they become less frequent with age but are not restricted to childhood. Complete recovery is typical, but ALF crises can be fatal. Antipyretic therapy and induction of anabolism including glucose and parenteral lipids effectively ameliorates the course of liver crises. Patients' fibroblasts showed an increased sensitivity to high temperature at protein and functional level and a disturbed tethering of vesicles, pointing at a defect of intracellular transport between the endoplasmic reticulum and Golgi.

CONCLUSIONS

Mutations in NBAS cause a complex disease with a wide clinical spectrum ranging from isolated RALF to a multisystemic phenotype. Thermal susceptibility of the syntaxin 18 complex is the basis of fever dependency of ALF episodes. NBAS deficiency is the first disease related to a primary defect of retrograde transport. Identification of NBAS deficiency allows optimized therapy of liver crises and even prevention of further episodes.

Asthma characteristics and biomarkers from the Airways Disease Endotyping for Personalized Therapeutics (ADEPT) longitudinal profiling study

BACKGROUND

Asthma is a heterogeneous disease and development of novel therapeutics requires an understanding of pathophysiologic phenotypes. The purpose of the ADEPT study was to correlate clinical features and biomarkers with molecular characteristics, by profiling asthma (NCT01274507). This report presents for the first time the study design, and characteristics of the recruited subjects.

METHODS

Patients with a range of asthma severity and healthy non-atopic controls were enrolled. The asthmatic subjects were followed for 12 months. Assessments included history, patient questionnaires, spirometry, airway hyper-responsiveness to methacholine, fractional exhaled nitric oxide (FENO), and biomarkers measured in induced sputum, blood, and bronchoscopy samples. All subjects underwent sputum induction and 30 subjects/cohort had bronchoscopy.

RESULTS

Mild (n = 52), moderate (n = 55), severe (n = 51) asthma cohorts and 30 healthy controls were enrolled from North America and Western Europe. Airflow obstruction, bronchodilator response and airways hyperresponsiveness increased with asthma severity, and severe asthma subjects had reduced forced vital capacity. Asthma control questionnaire-7 (ACQ7) scores worsened with asthma severity. In the asthmatics, mean values for all clinical and biomarker characteristics were stable over 12 months although individual variability was evident. FENO and blood eosinophils did not differ by asthma severity. Induced sputum eosinophils but not neutrophils were lower in mild compared to the moderate and severe asthma cohorts.

CONCLUSIONS

The ADEPT study successfully enrolled asthmatics across a spectrum of severity and non-atopic controls. Clinical characteristics were related to asthma severity and in general asthma characteristics e.g. lung function, were stable over 12 months. Use of the ADEPT data should prove useful in defining biological phenotypes to facilitate personalized therapeutic approaches.

Dietary habits and metabolic control in adolescents and young adults with phenylketonuria: self-imposed protein restriction may be harmful

BACKGROUND

In untreated patients, phenylketonuria (PKU) results in severe encephalopathy with mental retardation. A protein-restricted diet is recommended which can be relaxed in adolescence/adulthood.

METHODS

We contacted all 72 adult/adolescent PKU patients who had been treated in our center during early childhood. Some still regularly attended our outpatient clinics, while others were lost for follow-up, giving 51 patients in our study. We asked all patients to complete a dietary protocol as well as a questionnaire on quality of life. Blood and urine were analyzed and body impedance plethysmography and cerebral MRI were performed.

RESULTS

42 % of the patients followed protein restriction supplemented with amino acid mixtures (AAM), others had a vegan diet with (8 %) or without (14 %) AAM; 36 % said they were eating normally and did not need any AAM. However, based on dietary protocols and blood urea levels, protein intake was restricted in this patient group. None of the patients examined had serious nutritional deficits. Phenylalanine levels were higher in patients not taking AAM. MRI of the brain was not different from those following protein restriction and taking AAM. The lesions score and mood correlated best with the cumulative phenylalanine values during the first 10 years of life.

CONCLUSION

In summary, 50 % of adult/adolescent patients from our center did not take AAM at the start of our survey although they unknowingly followed self-imposed protein restriction. They had no overt nutritional deficits; however, long-term brain function may be compromised. Our study emphasizes the need for specialized metabolic care in PKU during adulthood.

Dexamethasone reduces cell surface levels of CD11b on human eosinophils

Overnight incubation of human eosinophils (Eøs) with the glucocorticoid hormone dexamethasone (DEX; 0.1 μM) resulted in lower expression of the CD11b, but not CD49d, antigen on their plasma membrane, as assessed by flow cytometry. DEX produced a consistent inhibitory effect (ranging from 16% to 20%) when tested at a concentration of 0.1 μM. Eø stimulation with 100 ng/ml eotaxin produced an increase in CD11b (+26%), but not CD11c, levels and concomitantly a reduction (–25%) on CD62L expression. The inhibition exerted by DEX upon CD11b levels was also evident following eotaxin upregulation, with a degree of inhibition similar to that seen on basal levels. These data highlight a novel mechanism of action by which glucocorticoid hormones may be effective in reducing Eø accumulation during allergic inflammation in man.

3-Methylglutaconic aciduria type I redefined: a syndrome with late-onset leukoencephalopathy

OBJECTIVE

3-Methylglutaconic aciduria type I is a rare inborn error of leucine catabolism. It is thought to present in childhood with nonspecific symptoms; it was even speculated to be a nondisease. The natural course of disease is unknown.

METHODS

This is a study on 10 patients with 3-methylglutaconic aciduria type I. We present the clinical, neuroradiologic, biochemical, and genetic details on 2 new adult-onset patients and follow-up data on 2 patients from the literature.

RESULTS

Two unrelated patients with the characteristic biochemical findings of 3- methylglutaconic aciduria type I presented in adulthood with progressive ataxia. One patient additionally had optic atrophy, the other spasticity and dementia. Three novel mutations were found in conserved regions of the AUH gene. In both patients, MRI revealed extensive white matter disease. Follow-up MRI in a 10-year-old boy, who presented earlier with isolated febrile seizures, showed mild abnormalities in deep white matter.

CONCLUSION

We define 3-methylglutaconic aciduria type I as an inborn error of metabolism with slowly progressive leukoencephalopathy clinically presenting in adulthood. In contrast to the nonspecific findings in pediatric cases, the clinical and neuroradiologic pattern in adult patients is highly characteristic. White matter abnormalities may already develop in the first decades of life. The variable features found in affected children may be coincidental. Long-term follow-up in children is essential to learn more about the natural course of this presumably slowly progressive disease. Dietary treatment with leucine restriction may be considered.

Rapid quantification of conjugated and unconjugated bile acids and C27 precursors in dried blood spots and small volumes of serum

The aim of the study was to develop a method for fast and reliable diagnosis of peroxisomal diseases and to facilitate differential diagnosis of cholestatic hepatopathy. For the quantification of bile acids and their conjugates as well as C(27) precursors di- and trihydroxycholestanoic acid (DHCA, THCA), in small pediatric blood samples we combined HPLC separation on a reverse-phase C18 column with ESI-MS/MS analysis in the negative ion mode. Analysis was done with good precision (CV 3,7%-11.1%) and sufficient sensitivity (LOQ: 11-91 nmol/L) without derivatization. Complete analysis of 17 free and conjugated bile acids from dried blood spots and 10 microL serum samples, respectively, was performed within 12 min. Measurement of conjugated primary bile acids plus DHCA and THCA as well as ursodeoxycholic acid was done in 4.5 min. In blood spots of healthy newborns, conjugated primary bile acids were found in the range of 0.01 to 2.01 micromol/L. Concentrations of C(27) precursors were below the detection limit in normal controls. DHCA and THCA were specifically elevated in cases of peroxysomal defects and one Zellweger patient.

Biochemical basis of Fabry disease with emphasis on mitochondrial function and protein trafficking

Fabry disease, also known as Anderson-Fabry disease, is an X-linked lysosomal storage disorder. The clinical picture is highly variable and usually milder in females. It is a multisystemic disease involving many organs. Fabry disease is due to a deficiency of alpha-galactosidase A caused by different usually "private" mutations. Enzyme replacement therapy (ERT) has been established, other therapeutic options are at an experimental stage. Classically, mechanical deposition of storage material in blood vessels was believed to lead to decreased blood supply with consecutive organ dysfunction. Recently, however, many secondary biochemical processes have been discussed to be involved in the pathogenesis of Fabry disease. For example, compromised energy metabolism has been found both in vitro and in vivo, altered lipid composition of membranes can lead to abnormalities in trafficking and sorting of rafts-associated proteins. We discuss the role of these secondary phenomena in the pathogenesis of Fabry disease.

Scheie syndrome: enzyme replacement therapy does not prevent progression of cervical myelopathy due to spinal cord compression

Hurler-Scheie syndrome is caused by alpha-l-iduronidase deficiency. Enzyme replacement therapy (ERT) can improve physical capacity and reduces organomegaly. However, the effect on bradytrophic connective tissue is limited. As intravenously administered enzyme cannot cross the blood-brain barrier, the therapy of choice for the more severe Hurler syndrome is haematopoietic stem cell transplantation (HCT). In the more attenuated Scheie syndrome, neurological impairment is less severe; therefore, ERT may be appropriate to treat these patients. Information on long-term outcome in Scheie patients undergoing ERT is scarce. We report a 38-year-old female Scheie patient who has been on ERT for 8 years. While non-neurological symptoms improved, she developed paresthesias in her hands and feet and progressive pain in her legs. Somatosensory evoked potentials were abnormal, suggesting dysfunction of the dorsal funiculus and lemniscus medialis. After 6 years of ERT, a spinal MRI showed dural thickening at the upper cervical spine. These soft-tissue deposits are presumably due to the accumulation of mucopolysaccharides. Intramedullary hyperintensities at the level of C1/2 revealed cervical myelopathy. An MRI before the start of ERT had shown milder spinal lesions. Cystic lesions in the white matter of the centrum semiovale due to dilated Virchow-Robin spaces were essentially unchanged compared with the MRI scan before ERT. Decompression of the spinal cord resulted in clinical improvement. In an adult patient with Scheie syndrome, ERT failed to prevent progression of cervical myelopathy. Clinical significance of cerebral changes is unclear. Whether early HCT or intrathecal ERT could have prevented these lesions remains speculative.

Prediction of outcome in isolated methylmalonic acidurias: combined use of clinical and biochemical parameters

Objectives Isolated methylmalonic acidurias (MMAurias) are caused by deficiency of methylmalonyl-CoA mutase or by defects in the synthesis of its cofactor 5'-deoxyadenosylcobalamin. The aim of this study was to evaluate which parameters best predicted the long-term outcome. Methods Standardized questionnaires were sent to 20 European metabolic centres asking for age at diagnosis, birth decade, diagnostic work-up, cobalamin responsiveness, enzymatic subgroup (mut(0), mut(-), cblA, cblB) and different aspects of long-term outcome. Results 273 patients were included. Neonatal onset of the disease was associated with increased mortality rate, high frequency of developmental delay, and severe handicap. Cobalamin non-responsive patients with neonatal onset born in the 1970s and 1980s had a particularly poor outcome. A more favourable outcome was found in patients with late onset of symptoms, especially when cobalamin responsive or classified as mut(-). Prevention of neonatal crises in pre-symptomatically diagnosed newborns was identified as a protective factor concerning handicap. Chronic renal failure manifested earlier in mut(0) patients than in other enzymatic subgroups. Conclusion Outcome in MMAurias is best predicted by the enzymatic subgroup, cobalamin responsiveness, age at onset and birth decade. The prognosis is still unfavourable in patients with neonatal metabolic crises and non-responsiveness to cobalamin, in particular mut(0) patients.

Prenatal benzoate treatment in urea cycle defects

OBJECTIVE

In patients with severe urea cycle defects (UCD) metabolic decompensation with hyperammonaemia typically occurs during the first days of life resulting in severe neurological damage or death. Benzoate can eliminate nitrogen independent of the urea cycle. Usually, benzoate is started soon after birth, but prenatal administration might improve metabolic stability.

DESIGN

Two fetuses with a prenatal diagnosis of UCD (female: citrullinaemia; male: ornithine transcarbamylase deficiency) were loaded with benzoate prenatally via the placenta by infusing their mothers with benzoate. Benzoate concentrations were measured in umbilical cord blood and the blood of the mothers and their newborns.

RESULTS

Therapeutic concentrations of benzoate were found in umbilical cord blood and in the children's blood. Thus, benzoate transfer across the placenta was demonstrated. Plasma ammonia and glutamine levels in the postnatal period were within the normal range.

CONCLUSIONS

Benzoate infusion of the mother shortly before birth is safe and results in therapeutic levels of benzoate in umbilical cord blood.

Developmental changes of oxalate excretion in enterally fed preterm infants

To further substantiate gestational age-related changes in oxalate excretion, we studied urinary oxalate excretion in 66 preterm infants born at 23.4-34.7 weeks of gestation. Spot urine of 66 preterm infants was analysed by ion chromatography as soon as they were completely orally fed with enriched breast milk and/or special preterm milk formula (days 7 to 57 of postnatal life). Infants with evidence of renal, gastrointestinal, muscular or metabolic disease were not included. Newborns on parenteral nutrition were excluded. Oxalate/creatinine ratios (Ox/Cr) decreased with gestational age (three age groups: group 1, 23 0/7-28 0/7; group 2, 28 1/7-32 0/7; and group 3, 32 1/7-35 0/7 weeks of gestation). The mean Ox/Cr was highest in group 1 (398.2 mmol/mol +/- 116.8; n = 21). Differences between groups 1 + 3 were statistically significant; p = 0.001; those between groups 1 + 2 and between groups 2 + 3 were not. Ox/Cr correlated inversely with gestational and maturational age (r = -0.41, p = 0.001; r = -0.33, p = 0.007) and positively with postnatal age (r = 0.32, p = 0.008). It correlated inversely with birth weight as well as actual weight at sample collection (r = -0.46 and -0.44, p < 0.001). Ox/Cr was significantly linked to energy and carbohydrate intake (r = 0.3 and 0.4, p = 0.03 and 0.001). These results were independent of sex. In the present study we show that urinary oxalate excretion in preterm infants depends on gestational age.

Fibrosis, chronic inflammation and new pathways for drug discovery

Recent studies have challenged the conventional hypothesis that inflammation is the major player in the fibrosis cascade. Emerging evidence points to a critical role for interactions between tissue-resident and infiltrating, non-resident cells, in mediating fibrotic responses. Improved understanding of the biology of extracellular matrix (ECM) remodeling and the pathways that regulate assembly of the ECM and its interactions with growth factors/cytokines have led to the identification of new and attractive therapeutic targets. These include molecules that regulate fibrocytic cell infiltration, epithelial and myofibroblast differentiation, ECM synthesis and degradation. However, it is imperative that these new therapies be timed and compartmentalized to target the tissue of interest, as the dynamics of cellular differentiation and ECM remodeling may be different between organ systems. This review will summarize the current understanding of the mechanisms involved in the development of fibrosis, based on recent in vitro and in vivo studies, and comment on novel molecular pathways for drug discovery.

Amyloid precursor protein and amyloid beta-peptide bind to ATP synthase and regulate its activity at the surface of neural cells

Amyloid precursor protein (APP) and amyloid beta-peptide (Abeta) have been implicated in a variety of physiological and pathological processes underlying nervous system functions. APP shares many features with adhesion molecules in that it is involved in neurite outgrowth, neuronal survival and synaptic plasticity. It is, thus, of interest to identify binding partners of APP that influence its functions. Using biochemical cross-linking techniques we have identified ATP synthase subunit alpha as a binding partner of the extracellular domain of APP and Abeta. APP and ATP synthase colocalize at the cell surface of cultured hippocampal neurons and astrocytes. ATP synthase subunit alpha reaches the cell surface via the secretory pathway and is N-glycosylated during this process. Transfection of APP-deficient neuroblastoma cells with APP results in increased surface localization of ATP synthase subunit alpha. The extracellular domain of APP and Abeta partially inhibit the extracellular generation of ATP by the ATP synthase complex. Interestingly, the binding sequence of APP and Abeta is similar in structure to the ATP synthase-binding sequence of the inhibitor of F1 (IF(1)), a naturally occurring inhibitor of the ATP synthase complex in mitochondria. In hippocampal slices, Abeta and IF(1) similarly impair both short- and long-term potentiation via a mechanism that could be suppressed by blockade of GABAergic transmission. These observations indicate that APP and Abeta regulate extracellular ATP levels in the brain, thus suggesting a novel mechanism in Abeta-mediated Alzheimer's disease pathology.

Diagnostic work-up and management of patients with isolated methylmalonic acidurias in European metabolic centres

The long-term outcome of patients with methylmalonic aciduria (MMA) is still uncertain due to a high frequency of complications such as chronic renal failure and metabolic stroke. The understanding of this disease is hampered by a huge variation in the management of these patients. The major aim of this study was to evaluate the current practice in different European metabolic centres. A standardized questionnaire was sent to 20 metabolic centres asking for standard procedures for confirmation of diagnosis, testing cobalamin responsiveness, dietary treatment, pharmacotherapy, and biochemical and clinical monitoring. Sixteen of 20 metabolic centres (80%) returned questionnaires on 183 patients: 89 of the patients were classified as mut(0), 36 as mut(-), 13 as cblA, 7 as cblB, and 38 as cblA/B. (1) Confirmation of diagnosis: All centres investigate enzyme activity by propionate fixation in fibroblasts; six centres also perform mutation analysis. (2) Cobalamin response: Ten centres follow standardized protocols showing large variations. A reliable exclusion of nonspecific effects has not yet been achieved by these protocols. (3) Long-term treatment: In cobalamin-responsive patients, most centres use hydroxocobalamin (1-14 mg/week i.m. or 5-20 mg/week orally), while two centres use cyanocobalamin. All cobalamin-nonresponsive patients and most cobalamin-responsive patients are supplemented with L: -carnitine (50-100 mg/kg per day). Fourteen centres use intestinal decontamination by antibiotic therapy. Most centres follow D-A-CH (n = 6) or Dewey (n = 4) recommendations for protein requirements. Fourteen centres regularly use precursor-free amino acid supplements. Standardized monitoring protocols are available in seven centres, again showing high variability.

Applicability and reproducibility of biomarkers for the evaluation of anti-inflammatory therapy in allergic rhinitis

BACKGROUND

We aimed to study the reproducibility of several biomarkers of allergic rhinitis to investigate their potential as outcome measures in clinical intervention trials. Furthermore, we investigated the kinetics of the biomarkers studied in nasal lavage and brush material following a placebo-controlled nasal allergen challenge.

METHODS

We performed a skin prick test and measured serum specific immunoglobulin (Ig) E levels and inflammatory biomarkers in nasal lavage and brush material in 20 patients with allergic rhinitis on 2 separate days (washout, 14-21 days). The patients were then randomly assigned to undergo an intranasal challenge with a relevant allergen (n=10) or diluent (n=10) in order to assess the kinetics of several biomarkers of allergic airway inflammation in nasal lavage and brush samples.

RESULTS

Baseline serum IgE levels and skin wheal sizes were highly reproducible measurements, with a coefficient of variation (CV) of 13.4% and 18.2%, respectively. This was not the case with the majority of inflammatory biomarkers, whose CV varied considerably (range, 6.1%-224.1%). The nasal allergen challenge induced an increase in composite symptom scores in all patients. Compared to placebo, tryptase (P=.004), eosinophilic cationic protein (ECP) (P=.03) and alpha2-macroglobulin (P=.002) were increased in nasal lavage at 20 minutes post allergen. Nasal lavage ECP levels and nasal brush eosinophils were still significantly increased at 7 hours (P=.03 and P=.04), but all statistical significance had been lost at 24 hours post challenge.

CONCLUSION

Serum specific IgE assays and skin prick tests exhibited good reproducibility in patients with clinically stable allergic rhinitis. We were also able to investigate the kinetics of allergen-induced upper airway inflammatory markers in nasal lavage and brush material. Hence, nasal allergen challenge, when used in combination with nasal lavage and brush sampling, is a suitable research tool for early drug development.

[Maternal vitamin B12 deficiency: cause for neurological symptoms in infancy]

BACKGROUND

Symptoms of Vitamin B (12) deficiency in infancy include growth retardation, regression of psychomotor development, muscular hypotonia and brain atrophy. Besides an inappropriate vegetarian diet of the infants, a vegan diet or a pernicious anaemia of the mother may lead to an insufficient vitamin B (12) supply of the child.

PATIENTS AND METHODS

We report here the neurological symptoms of 4 fully breast-fed infants from mothers on vegan diet or with pernicious anaemia.

DISCUSSION AND CONCLUSION

Vitamin B (12) deficiency can easily be diagnosed by detection of methylmalonic acid when measuring the organic acids in urine. Vitamin B (12) deficiency should be avoided or diagnosed as early as possible since a supplementation of mother and child can prevent neurological symptoms of the baby. Furthermore, the neurological symptoms of the infant with manifest vitamin B (12) deficiency are (partially) reversible.

Novel mutations in exon 6 of the GFAP gene affect a highly conserved if motif in the rod domain 2B and are associated with early onset infantile Alexander disease

Alexander disease is a rare disorder of cerebral white matter due to a dysfunction of astrocytes. The most common infantile form presents as a megalencephalic leukodystrophy. Mutations of the GFAP gene, encoding Glial Fibrillary Acidic Protein, have been recognized as the cause of Alexander disease. Glial Fibrillary Acidic Protein is the major intermediate filament protein in astrocytes, its functional rod domain is conserved in sequence and structure among other intermediate filament proteins. We report here two cases of infantile Alexander disease with early onset and severe course, caused by DE NOVO mutations A364 V and Y366C. Both affected GFAP residues are part of a highly conserved coiled-coil trigger motif in the C-terminal end of segment 2B, probably required for the stability of intermediate filament molecules. Comparable effects are seen with mutations of the corresponding residues of the gene coding for keratin 14, another intermediate filament, this further supports the hypothesis that these positions of the trigger motif are generally critical for a normal function of intermediate filaments.

Biopharmaceutical therapeutics for asthma remodeling

Current asthma therapy is aimed at controlling disease symptoms. A subset of asthma patients remains symptomatic despite optimal therapy indicating that an unmet medical need exists for these patients. Innovative therapeutics are needed to treat the unmet need in asthma and biopharmaceutical approaches may provide an opportunity for identifying these agents. It is proposed that airway remodeling contributes to asthma symptoms and this feature of disease pathology may be a target for future therapies. The current review focuses on the contribution of one feature of airway remodeling, subepithelial fibrosis, towards disease and highlights some of the mechanisms that may contribute to this feature of airway remodeling. Further, some potential molecular targets are identified for consideration for therapeutic intervention.

Vaso-occlusion in Schimke-immuno-osseous dysplasia: is the NO pathway involved?

Schimke-immuno-osseous dysplasia (SIOD) is an autosomal recessive disorder with the main clinical findings of spondyloepiphyseal dysplasia, nephrotic syndrome, and defective cellular immunity. Vaso-occlusive processes, especially generalized atherosclerosis, are a life-limiting complication in patients with severe SIOD. The nitric oxide synthase (NOS) oxidizes L-arginine to nitric oxide (NO). NO is a potent vasodilator with inhibitory effects on platelet aggregation and the development of atherosclerosis. We hypothesized that reduced NO production due to antagonism of NOS by asymmetric dimethylarginine (ADMA) would be a possible pathophysiological mechanism for vaso-occlusion in SIOD. We tested this hypothesis in 10 patients with SIOD and 10 age-matched healthy controls. Plasma and urine levels of nitrite and nitrate, the indicators of NO synthesis, and of ADMA, an endogenous NOS inhibitor, in children suffering from SIOD were not significantly different from those in the age-matched healthy controls. Our results suggest that the L-arginine/NO pathway is not altered in SIOD. Antagonism of NOS by ADMA does not seem to be the cause of premature general atherosclerosis in SIOD. The underlying pathology of vaso-occlusion in SIOD still remains unclear.

Role of chemokines in severe asthma

The severe asthma phenotype is exhibited by a subset of asthma patients whose asthma symptom is poorly controlled by current therapies. Severe asthma represents a high unmet medical need and warrants research into the mechanisms driving the underlying pathophysiology. It is hypothesized that the underlying pathology associated with severe asthma is driving the symptoms experienced by these patients, which may share common features with mild to moderate asthma or may represent a unique pathological phenotype. For the purpose of this review, the pathophysiology associated with asthma in general are described and extended to incorporate severe asthma. Chemokines may contribute towards multiple features of asthma pathophysiology and this current review focuses on the biology of chemokines pertaining to asthma pathophysiology. Chemokines are important recruiters and activators of inflammatory cells and these infiltrating cells interact with resident cells, such as fibroblasts and it is through these pathways that chemokines appear to exert multiple biological actions. Clinical trials are underway with therapeutics targeting chemokine pathways for other inflammatory diseases. It is hoped that the information generated from these studies will contribute towards furthering our understanding of chemokine biology and be applied towards targeting severe asthma.

Branched chain amino acids as a parameter for catabolism in treated phenylketonuria

This study was performed to study an association between nutritional status on one hand and BCAA- and Phe-concentrations on the other hand in PKU patients free of infection. AA profiles from 70 PKU patients were measured. 9 patients (subgroup I) with elevated Phe- and BCAA-concentrations as well as 23 patients (subgroup II) with only elevated Phe-levels were included. Dietary records were obtained from both groups; low caloric intake in subgroup I was increased with Duocal or p-am ANAMIX without modifying total protein- and Phe-intake. AA profiles were controlled after 2 weeks. Additionally, we investigated AA profiles from 26 liver transplanted patients with increased carbohydrate and caloric intake as an example for anabolism. In subgroup I Phe- and Isoleu-concentrations decreased sign. After dietary intervention. Leu, Val and Tyr levels decreased not sign. Initial Phe-levels correlated negatively with protein and caloric intake. BCAA concentrations of liver transplanted patients receiving high amounts of carbohydrates were in the lower range of normal. Increased caloric intake lowered most of the elevated Phe- and BCAA- concentrations.

Agenesis of the corpus callosum, abnormal genitalia and intractable epilepsy due to a novel familial mutation in the Aristaless-related homeobox gene

Mutations in the Aristaless-related homeobox (ARX) gene are associated with a broad spectrum of disorders including X-linked lissencephaly with abnormal genitalia (XLAG) and absent corpus callosum. Here, we describe a family with two male infants suffering from agenesis of the corpus callosum (ACC), intractable epilepsy, and abnormal genitalia. The phenotype of both affected patients differed in severity of the cerebral malformation with one showing no obvious evidence for lissencephaly. Both infants lacked any psychomotor development and died at the age of 17 weeks and 18 months, respectively. Genetic analysis of the ARX gene revealed a novel frameshift mutation in exon 4 (nt1419_1420insAC) leading to a shortened protein lacking the aristaless domain. In summary, analysis of the ARX gene should not only be considered in male patients with typical features of XLAG but also in those presenting with early onset epilepsy, ACC, and abnormal genitalia without obvious neuroradiological features of lissencephaly.

Glutaric aciduria I: creatine supplementation restores creatinephosphate levels in mixed cortex cells from rat incubated with 3-hydroxyglutarate

The pathogenesis of neurological sequelae in glutaric aciduria I (GA I) is still unclear. Some evidence exists for compromised energy generation in the brain of patients with GA I resulting in 'slow-onset' excitotoxicity. Previously, we have shown a reduced activity of the mitochondrial ATPsynthase in cultured mixed cortex cells from neonatal rats incubated with 2-4mM 3-hydroxyglutarate (3-OH glut) for 24h. In the present study we measured cellular contents of high energy phosphate compounds (creatinephosphate CP, ATP, and ADP) in this model after a 24h incubation period with 2-4mM glutarate (glut) or 3-OH glut. 3-OH glut specifically led to a reduction of CP content in a dose-dependent manner, whereas concentrations of ATP, ADP, and AMP remained unchanged. The drop in CP-concentration could be prevented by preincubation with the non-competitive NMDA-receptor antagonist MK 801 or coincubation with 1mM creatine. NMDA-receptor associated ion channels may be opened due to a lack of energy inside the neurons caused by a reduction of CP. This is followed by membrane depolarization which could impair electrogenic creatine transport into the cell.

Seventeen novel mutations that cause profound biotinidase deficiency

We report 17 novel mutations that cause profound biotinidase deficiency. Six of the mutations are due to deletions, whereas the remaining 11 mutations are missense mutations located throughout the gene and encode amino acids that are conserved in mammals. Our results increase the total number of different mutations that cause biotinidase deficiency to 79. These additional mutations will undoubtedly be helpful in identifying structure/function relationships once the three-dimensional structure of biotinidase is determined.

Mitochondrial dysfunction in the neuronal ceroid-lipofuscinoses (Batten disease)

There are at least eight genetic entities known as the ceroid-lipofuscinoses in humans which share clinical and pathological features that have caused them to be grouped together under the eponym of Batten disease. They present pathologically as lysosomal storage diseases but are also characterised by severe neurodegeneration. Although the biochemical defects appear primarily centred on lysosomes and defects in proteolysis, the link between this and pathogenesis of neuronal death is poorly understood. The pathogenesis of neurodegeneration has been studied particularly in two animal models these being the English setter dog and the New Zealand Southhampshire sheep (OCL6). In these, and some of the human entities, there is evidence of mitochondrial dysfunction. This includes the accumulation of subunit c of ATP synthase as a component of storage material in at least six of eight genetic forms of the disease; structural abnormalities of mitochondria and selective loss of neurons in areas of the brain that are particularly metabolically active. Direct evidence of dysfunction comes from mitochondrial function tests in fibroblasts and, in animal models, isolated liver mitochondria. Supporting evidence of mitochondrial dysfunction was shown by disturbances in proportions of energy-rich phosphates in fibroblasts in some of these diseases. If these various defects were reflected in neurons, then it would support the hypothesis that neuron death was associated with energy-linked excitotoxicity.

Morphological alteration of peritoneal mast cells and macrophages in the mouse peritoneal cavity during the early phases of an allergic inflammatory reaction

We investigated the presence of mast cell granules in macrophages following an in vivo model of an allergic reaction. Injection of ovalbumin (100 microg) into the peritoneal cavity of sensitised mice produced a rapid (within 2 h) influx of neutrophils followed by a slower (after >4 h) eosinophil migration. Ovalbumin treatment induced a high incidence (approximately 50%) of mast cell degranulation compared to control phosphated-buffered saline-treated mice. The majority (approximately 90%) of peritoneal macrophages contained mast cell granules as early as 2 h post-ovalbumin, with lower values at later time-points, as determined by staining with Toluidine blue and Berberine sulphate. This was confirmed by electron microscopy which enabled us to identify the complex mast cell granule sub-structural components in macrophage phagosomes. In conclusion, we used histochemical and ultrastructural analyses to show that mast cell granules become internalised with macrophages during the early stages of an experimental allergic reaction.

Altered levels of high-energy phosphate compounds in fibroblasts from different forms of neuronal ceroid lipofuscinoses: further evidence for mitochondrial involvement

The pathogenesis of neurodegeneration in neuronal ceroid lipofuscinosis (NCL) is still not clear despite progress in mutation analysis of these diseases. We have recently observed anomalies at the level of the mitochondrial ATPsynthase (complex V of the respiratory chain) in fibroblasts from children with CLN1, CLN2, CLN3 and in an ovine model (OCL6). The measurements were carried out in vitro. If these alterations were of relevance in vivo as well, contents of high-energy phosphate compounds should be reduced. In the present study, we measured levels of creatine phosphate (CP), ATP, ADP and AMP in fibroblasts from children with CLN1, CLN2, CLN3 and in OCL6. ATP was reduced to about 50% of normal in CLN1, CLN2 and CLN3, ADP was about 30% of normal in these cells, and CP was 50% of normal in CLN1 and CLN2 but remained normal in CLN3. In fibroblasts of NCL-sheep, however, CP and ADP were increased to 690% and 220% of normal, respectively, while ATP remained normal. If the anomalies found in cellular energy metabolism in fibroblasts were expressed in neurons from NCL patients and NCL sheep 'slow-onset excitotoxicity' could occur leading to cellular dysfunction and eventually to cell death.

Glucocorticoid receptor activation reduces CD11b and CD49d levels on murine eosinophils: characterization and functional relevance

In vitro incubation of mouse blood eosinophils with dexamethasone (DEX) resulted in concentration- and time-dependent reduction in CD11b and CD49d cell-surface expression as detected by flow cytometry. This inhibitory effect ranged between 20 and 40% for both integrins, and it was not related to alteration of cell survival. DEX was maximally effective at 1 microM, and it was prevented by coaddition of the glucocorticoid receptor antagonist RU486 (mifepristone; 10 microM). Budesonide, hydrocortisone, and prednisolone, but not the sex steroids testosterone and progesterone, reduced CD11b and CD49d cell-surface expression to a similar extent. Subchronic treatment of mice with 1 mg/kg DEX again reduced both CD11b and CD49d expression on circulating eosinophils, without alterations in CD11b messenger RNA expression as assessed by polymerase chain reaction analysis. In contrast, membrane but not intracellular protein expression of either CD11b or CD49d was inhibited by eosinophil incubation with DEX in vitro; thus, an interference with exportation of these adhesion molecules to the cell surface is proposed as the mechanism of action of the glucocorticoid. Finally, steroid effects on integrin expression were linked to a reduced eosinophil function as indicated by a lower degree of cell chemotaxis after incubation with DEX, an effect which was again prevented by 10 microM RU486. These observations may explain part of the therapeutic efficacy displayed by glucocorticoid hormones in the clinical control of tissue eosinophilia in allergic disease conditions.

Secondary respiratory chain defect in a boy with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency: possible diagnostic pitfalls

We report on a boy who suffered from microcephaly, growth retardation, cardiomyopathy and hepatic dysfunction. When he had his first febrile infection at the age of 3 months he showed metabolic decompensation. Laboratory parameters and clinical features were compatible with a beta-oxidation defect or a respiratory chain disorder. Measurement of beta-oxidation enzymes showed long-chain 3-hydroxyacyl CoA dehydrogenase (LCHAD) deficiency; determination of respiratory chain complex activities revealed complete absence of complex I, II, III and IV activities in skeletal muscle and reduced activities of complexes II and IV in cultured fibroblasts, with secondary dysregulation of ATP synthase. The patient was found to be homozygous for the MTP:G1528 C mutation (LCHAD-deficiency).

CONCLUSION

This patient had LCHAD deficiency as his primary metabolic disorder, leading to secondary inhibition of respiratory chain enzymes by 'toxic' metabolites.

Contrasting roles for RANTES and macrophage inflammatory protein-1 alpha (MIP-1 alpha) in a murine model of allergic peritonitis

Cell accumulation and CC chemokine production were assessed in the peritoneal cavity of ovalbumin (OVA)-sensitized mice following antigen challenge. Intraperitoneal challenge with OVA induced a significant eosinophil influx from 6 h post-challenge with increased numbers persisting at 24 h. At 6 h there was also a marked presence of neutrophils. Messenger RNA expression and protein levels for the chemokines RANTES and MIP-1 alpha were measured in the cell pellets and supernatants, respectively, from peritoneal washes following OVA challenge. RANTES mRNA was detected from 2 h to 4 h following OVA injection, whereas mRNA for MIP-1 alpha was only detectable at 4 h. RANTES protein was first detected from 4 h after OVA injection and by 24 h the protein levels had increased further. Basal levels of MIP-1 alpha were detected in peritoneal washes. These levels peaked at 2 h after OVA challenge and rapidly declined to basal levels by 6 h. A functional role for the chemokines was assessed using neutralizing polyclonal antibodies. Co-injection of OVA with anti-RANTES antibodies resulted in a significant inhibition of eosinophil infiltration into the cavity at 6 h and 24 h (63% and 52% inhibition, respectively) without significantly influencing the number of neutrophils present. In contrast, injection of anti-MIP-1 alpha antibodies only inhibited neutrophil migration at the 6 h time point by 44% without significantly affecting the accumulation of eosinophils. These results demonstrate an important role for RANTES in mediating eosinophil influx in allergic inflammation and a contrasting role for MIP-1 alpha in mediating neutrophil recruitment.

Anomalies of mitochondrial ATP synthase regulation in four different types of neuronal ceroid lipofuscinosis

Several neuronal ceroid lipofuscinoses (NCL) show storage of subunit c of mitochondrial ATP synthase. The neurodegenerative process, however, remains obscure. We previously reported a decreased basal ATP synthase activity in fibroblasts from late-infantile NCL (CLN2) and juvenile NCL (CLN3) patients. We have now extended the study of the ATP synthase system to an ovine NCL (a model for the late-infantile NCL variant, CLN6) and the infantile NCL (CLN1). In fibroblasts from healthy sheep, active regulation of ATP synthase in response to cellular energy demand was present similar to human cells: ATP synthase was down-regulated under conditions of anoxia or functional uncoupling and was up-regulated in response to calcium. In fibroblasts from NCL sheep, basal ATP synthase activity was slightly elevated and down-regulation in response to anoxia or uncoupling of mitochondria also occurred. Calcium produced an unexpected down-regulation to 55% of basal activity. Activities of respiratory chain enzymes did not differ between healthy and NCL sheep. In fibroblasts from CLN1 patients, basal ATP synthase activity was reduced and regulation of the enzyme was absent. Activities of respiratory chain complexes II and IV were reduced. The defect of ATP synthase regulation found in fibroblasts from NCL sheep and infantile NCL patients is different from the ATP synthase deficiencies demonstrated in late-infantile and juvenile NCL, but problems of mitochondrial energy production, if also expressed in brain, would be a common feature of several NCL forms. Deficient ATP supply could result in degeneration of neurons, especially in those with high energy requirements.

Regulation of macrophage inflammatory protein-1 alpha expression and function by endogenous interleukin-10 in a model of acute inflammation

In this study we have determined the role of endogenous interleukin (IL)-10 on leucocyte recruitment and production of the CC chemokine macrophage inflammatory protein-1alpha (MIP-1alpha) in a murine model of acute inflammation. Intraperitoneal injection of zymosan produced a dose-dependent cellular infiltration which was concomitant with MIP-1alpha release in the lavage fluids. Release of this chemokine had a functional role since treatment of mice with a specific anti-MIP-1alpha antibody reduced both neutrophil and monocyte accumulation into the peritoneal cavity. An unexpected increase in cell influx and MIP-1alpha production was measured following depletion of resident peritoneal macrophages, as achieved by a 3-day liposome treatment. A similar result was obtained when the zymosan peritonitis response was elicited in IL-10 knock-out mice. In summary we propose a functional cross talk between endogenous IL-10 and this CC chemokine during the host inflammatory response.

Role of resident peritoneal macrophages and mast cells in chemokine production and neutrophil migration in acute inflammation: evidence for an inhibitory loop involving endogenous IL-10

The roles played by resident macrophages (Mphi) and mast cells (MCs) in polymorphonuclear leukocyte (PMN) accumulation and chemokine production within the mouse peritoneal cavity in response to administration of zymosan (0.2 and 1 mg), LPS (1 mg/kg), and thioglycolate (0.5 ml of a 3% suspension) were investigated. A marked reduction (>95%) in intact MC numbers was obtained by pretreatment with the MC activator compound 48/80, whereas resident Mphi were greatly diminished (>85%) by a 3-day treatment with liposomes encapsulating the cytotoxic drug dichloromethylene-bisphosphonate. No modulation of thioglycolate-induced inflammation was seen with either pretreatment. Removal of either MCs or Mphi attenuated LPS-induced PMN extravasation without affecting the levels of the chemokines murine monocyte chemoattractant protein-1 and KC measured in the lavage fluids. In contrast, MC depletion inhibited PMN accumulation and murine monocyte chemoattractant protein-1 and KC production in the zymosan peritonitis model. Removal of Mphi augmented the accumulation of PMN elicited by the latter stimulus. This was due to an inhibitory action of Mphi-derived IL-10 because there was 1) a time-dependent release of IL-10 in the zymosan exudates; 2) a reduction in IL-10 levels following Mphi, but not MC, depletion; and 3) an increased PMN influx and chemokine production in IL-10 knockout mice. In conclusion, we propose a stimulus-dependent role of resident MCs in chemokine production and the existence of a regulatory loop between endogenous IL-10 and the chemokine-mediated cellular component of acute inflammation.

Investigation of the functional role played by the chemokine monocyte chemoattractant protein-1 in interleukin-1-induced murine peritonitis

1. Intraperitoneal (i.p.) injection of murine recombinant IL-1beta (mrIL-1beta) produced a dose-dependent (0.5-50 ng) and time-related (0.5-2 h) secretion of murine monocyte chemoattractant protein-1 (mMCP-1; 3-4 ng per cavity) in the lavage fluids. MCP-1 mRNA could also be detected in the cell pellets by reverse transcriptase-polymerase chain reaction (RT-PCR). 2. MCP-1 levels were reduced by more than 90% by co-administration of IL-1 receptor antagonist (10 microg) (n=6, P<0.05). In contrast, an IL-1 mutant with low affinity for IL-1 receptor type I, termed yIL-1betadelta4 (50 ng), produced only a modest release of the chemokine. Treatment of mice with dexamethasone (DEX) (approximately 1 mg kg(-1) s.c.) reduced mrIL-1beta-induced mMCP-1 gene expression (apparent total inhibition) and protein release in the lavage fluids (approximately 40% reduction; n=10; P<0.05). Drastic reductions in the numbers of residential macrophages or mast cells did not modify the levels of mMCP-1 recovered in the lavage fluids. 3. Injection of mrIL-1beta produced neutrophil accumulation into the peritoneal cavities (maximal at 4 h with 1.42+/-0.15 x 10(6) cells per mouse). Co-injection of a specific polyclonal antibody against mMCP-1 reduced this process by more than 50% (n=6; P<0.05). In conclusion, we studied the mechanisms leading to the specific release of the CC chemokine mMCP-1 after in vivo administration of mrIL-1beta.

Resident mast cells are important for eotaxin-induced eosinophil accumulation in vivo

Eotaxin administration intraperitoneally, but not into dorsal air-pouches, of ovalbumin-sensitized mice exhibiting blood eosinophilia induced a threefold increase in eosinophil (E phi s) infiltration. Transfer of 1 x 10(6) mixed peritoneal cavity cells (PCC), containing 3.5 to 4.5 x 10(4) mast cells (MC), from donor mice to air-pouches of sensitized (but not unsensitized) recipient mice, established an E phi infiltration to eotaxin (vehicle, 0.86 +/- 0.27 x 10(6); eotaxin, 1.63 +/- 0.16 x 10(6) E phi s/air-pouch). Neutrophil numbers were also increased. When MC-depleted (-93%) PCC were injected into air-pouches of recipient animals, E phi infiltration was not supported (-52%). Injection of macrophage-depleted (-99%) PCC into air-pouches elicited a full E phi response to eotaxin but not neutrophil infiltration (-81%). Systemic dexamethasone treatment of recipient mice reduced E phi accumulation; treatment of donor mice only reduced neutrophil accumulation. Our study points to a crucial role for MC in E phi recruitment by eotaxin.

Regulation of mitochondrial ATP synthase activity in human myocardium

1. In previous studies regulation of the F1F0-ATPase of mitochondrial complex V (ATP synthase) has been demonstrated in rat cardiomyocytes, canine mycocardium and skeletal muscle from children. The aim of the present study was to examine regulation of ATP synthase in human myocardium in response to different metabolic states. 2. Biopsy material was obtained from 10 children undergoing cardiac surgery. Mitochondria in the post-nuclear supernatant were incubated under different metabolic conditions for 15 min and then broken by sonication. ATP synthase was measured spectrophotometrically using a coupled enzyme assay. 3. ATP synthase can be rapidly measured in sonicated preparations of heart mitochondria from children. We show that direct regulation at the level of ATP synthase occurs in these mitochondria. ATP synthase capacity is decreased in response to blocking of the respiratory chain by cyanide (mimicking anoxia) or uncoupling of mitochondria, falling to 76% and 66% of control values respectively. Upregulation of ATP synthase can be demonstrated in heart mitochondria when the calcium concentration in the incubation medium is increased to 5 microM (130% of control). 4. ATP synthase is actively regulated in heart mitochondria from children. The enzyme is upregulated in response to increased calcium. This transition may reflect the increased energy demand when cardiac workload is increased.

The role of lipocortin-1 in the inhibitory action of dexamethasone on eosinophil trafficking in cutaneous inflammatory reactions in the mouse

1. The ability of glucocorticosteroids to inhibit tissue eosinophilia may be an important feature of their anti-inflammatory action in allergic diseases. Our previous work showed that an effect of dexamethasone on the release of eosinophils from the bone marrow could explain its inhibitory action on eosinophil accumulation in a mouse air-pouch model. Thus, it was unclear from that study whether dexamethasone could interfere with the process of eosinophil trafficking. In the present study, therefore, we used a newly developed mouse model to evaluate the effects of systemic treatment with dexamethasone on the recruitment of (111)In-labelled blood eosinophils to sites of cutaneous inflammation in the mouse and whether lipocortin-1 (LC-1) was involved. 2. The i.d. injection of ovalbumin (OVA) in sensitized mice induced a dose-dependent recruitment of (111)In-labelled blood eosinophils which peaked at 4 to 8 h after antigen challenge. Systemic treatment with dexamethasone (50 microg per mouse, 3 h after antigen) effectively inhibited (111)In-eosinophil recruitment in this reaction by 70 to 85%. Similarly, a 1 h pretreatment with dexamethasone significantly suppressed (111)In-eosinophil induced by platelet-activating factor (PAF), leukotriene B4(LTB4) and the chemokine macrophage inflammatory protein-1alpha (MIP-1alpha) by 40 to 70%. 3. Two experimental approaches were used to evaluate the role of LC-1: treatment with LC-1 fragment Ac2-26 and use of an anti-LC-1 antiserum. LC-1 fragment Ac2-26 (100 microg per mouse) failed to affect (111)In-eosinophil recruitment. Moreover, pretreatment of animals with an anti-LC-1 antiserum failed to reverse the inhibitory effects of dexamethasone on (111)In-eosinophil recruitment induced by MIP-1alpha and by antigen in sensitized mice. 4. In contrast, the LC-1 fragment significantly inhibited glycogen-induced neutrophil recruitment into the peritoneal cavity of mice. Furthermore, the anti-LC-1 antiserum reversed the inhibitory effects of dexamethasone on the glycogen-induced neutrophil recruitment. 5. Thus, our results suggest that dexamethasone can inhibit the recruitment of eosinophils in mouse skin independent of an action on the bone marrow. However, by use of two different approaches, we showed that LC-1 does not play a role in mediating the inhibitory action of dexamethasone on eosinophil migration into cutaneous inflammatory reactions in the mouse. These data add further support to a LC-1-independent action of dexamethasone on eosinophils in vivo.

Eotaxin-induced eosinophil migration in the peritoneal cavity of ovalbumin-sensitized mice: mechanism of action

Cell accumulation in response to i.p. administration of the C-C chemokine, eotaxin, was studied in vivo. OVA-sensitized mice, exhibiting blood eosinophilia, had greater eosinophil (Eø) accumulation in response to 500 ng of eotaxin at 6 h (vehicle-injected, 3.0 +/- 0.5 x 10(5); eotaxin-injected, 8.6 +/- 1.0 x 10(5)) than nonsensitized, eotaxin-injected mice (2.5 +/- 0.4 x 10(5)). A nonspecific neutrophil migration was observed in both vehicle- and eotaxin-injected cavities. The number of intact mast cells in the peritoneal lavages after eotaxin injection was significantly lower than that in vehicle-injected animals (0.8 +/- 0.3 x 10(4) vs 2.8 +/-0.6 x 10(4), respectively). When endogenous peritoneal mast cells were depleted with compound 48/80 before eotaxin administration, there was a 51% reduction in Eø accumulation. This suggests an important role for endogenous mast cells in mediating the actions of eotaxin. The potential role of mast cell mediators in the actions of eotaxin was also investigated. Pretreatment with histamine-H1 or serotonin antagonists reduced Eø migration in response to eotaxin by 50 to 65%. Further, following pretreatment with a specific mAb against TNF-alpha, only nonspecific neutrophil influx was attenuated. Using neutralizing mAbs, Eø migration was found to be dependent on the adhesion molecules P- and E-selectin and CD11b. Eø accumulation was also sensitive to dexamethasone, with doses as low as 0.2 mg/kg inducing 100% inhibition. This study provides useful insight into the mechanisms of action of eotaxin.

Eotaxin-induced eosinophil migration in the peritoneal cavity of ovalbumin-sensitized mice: mechanism of action

Cell accumulation in response to i.p. administration of the C-C chemokine, eotaxin, was studied in vivo. OVA-sensitized mice, exhibiting blood eosinophilia, had greater eosinophil (Eø) accumulation in response to 500 ng of eotaxin at 6 h (vehicle-injected, 3.0 +/- 0.5 x 10(5); eotaxin-injected, 8.6 +/- 1.0 x 10(5)) than nonsensitized, eotaxin-injected mice (2.5 +/- 0.4 x 10(5)). A nonspecific neutrophil migration was observed in both vehicle- and eotaxin-injected cavities. The number of intact mast cells in the peritoneal lavages after eotaxin injection was significantly lower than that in vehicle-injected animals (0.8 +/- 0.3 x 10(4) vs 2.8 +/-0.6 x 10(4), respectively). When endogenous peritoneal mast cells were depleted with compound 48/80 before eotaxin administration, there was a 51% reduction in Eø accumulation. This suggests an important role for endogenous mast cells in mediating the actions of eotaxin. The potential role of mast cell mediators in the actions of eotaxin was also investigated. Pretreatment with histamine-H1 or serotonin antagonists reduced Eø migration in response to eotaxin by 50 to 65%. Further, following pretreatment with a specific mAb against TNF-alpha, only nonspecific neutrophil influx was attenuated. Using neutralizing mAbs, Eø migration was found to be dependent on the adhesion molecules P- and E-selectin and CD11b. Eø accumulation was also sensitive to dexamethasone, with doses as low as 0.2 mg/kg inducing 100% inhibition. This study provides useful insight into the mechanisms of action of eotaxin.

A novel murine model of allergic inflammation to study the effect of dexamethasone on eosinophil recruitment

1. We have developed a novel model of allergen-induced eosinophil into mouse air-pouches following sensitization and challenge with ovalbumin (Ova). This model was used to investigate the mechanism(s) underlying the anti-inflammatory action of the glucocorticoid hormone dexamethasone (Dex). 2. Injection of 10 micrograms Ova into 6-day-old dorsal air-pouches of mice sensitized to the same antigen provoked an intense cell accumulation as early as 6 h post-challenge (0.08 +/- 0.03 and 4.0 +/- 1.0 x 10(5) leucocytes in saline and Ova-treated air-pouches, respectively), maximal at 24 h (0.02 +/- 0.01 and 6.0 +/- 0.8 x 10(5) leucocytes in saline and Ova-treated air-pouches, respectively) and persisted up to 48 h. At the 24 h time-point, the cellular infiltrate consisted of 37% eosinophils, 18% neutrophils and 45% mononuclear cells, as assessed by histological examination. The same ratio of eosinophil/neutrophil was obtained by fluorescence-activated cell sorting (FACS) analysis, since 72% of the polymorphonuclear (PMN) population was positive for very-late antigen-4 (VLA-4) expression. 3. Subcutaneous (s.c.) administration of Dex (50 or 100 micrograms per mouse, -1 h) inhibited eosinophil accumulation into Ova challenged air-pouches by about 70% (P < 0.05) and 75% (P < 0.05), respectively, when compared to controls. Cell accumulation measured at 48 h after Ova injection was also significantly reduced (-75%) by Dex administration at the 24 h time-point (n = 12, P < 0.05). 4. Eosinophil numbers in the bone marrow and blood were quantitated. We found that the sensitization protocol induced a 3 fold increase in eosinophil numbers in the bone marrow (naive mice: 2.7 +/- 0.3 x 10(5); sensitized mice: 8.7 +/- 1.7 x 10(5), P < 0.05) and blood (naive mice: 0.5 +/- 0.2 x 10(5); sensitized mice: 1.5 +/- 0.3 x 10(5), P < 0.01). However, 24 h following Ova challenge, the eosinophil numbers in the bone marrow had dropped (3.7 +/- 0.8 x 10(5) with no change in the circulating pool, suggesting an equilibrium within the eosinophil pools had been reached. 5. Dex administration provoked a profound eosinopaenia in the blood of naive (5.2 +/- 1.5 to 0.9 +/- 0.6 x 10(4)) and sensitized mice (1.5 +/- 0.3 to 0.08 +/- 0.02 x 10(5)) at 4 h. This effect was reversed within 24 h. Dex also inhibited the release of eosinophils from the bone marrow in response to Ova challenge. 6. We show for the first time that express the steroid-inducible protein lipocortin 1 (LC1). FACS analysis of eosinophils emigrated into the Ova challenged air-pouches revealed detectable LC1-like immunoreactivity (373 x 10(3)). These data were also substantiated by LC1 detection in circulating eosinophils of interleukin-5 transgenic mice (strain: CBA/Ca). However, s.c. injection of Dex (50 micrograms) did not alter LC1 levels in blood eosinophils, such that 235 +/- 21 x 10(3) LC1-like molecules per cell were measured after vehicle treatment (n = 5), and 224 +/- 8 x 10(3) LC1-like molecules per cell were associated with this cell type 1 h after steroid treatment (n = 5, not significant). Finally, resident eosinophils (in the pleural cavity) were found to have much higher LC1 levels than that found in the blood circulation (2 fold increase, P < 0.05). 7. Passive immunization of mice against LC1 with a validated antiserum (termed LCS3) and protocol failed to modify the anti-migratory activity exerted by Dex towards eosinophil extravasation into Ova-challenged air-pouches. The steroid (50 micrograms s.c., -1 h) produced a similar degree of inhibition of eosinophil accumulation both in control animals (treated with a non-immune sheep serum) the LCS3-treated mice (-56% and 59%, respectively, n = 15-21, not significant). 8. In conclusion, the air-pouch provides a novel and convenient cavity to study allergen-induced cell recruitment which is sensitive to glucocorticoid hormone treatment. The effect of Dex on eosinophil distribution in these experimental conditions has been studied in detail and

Subacute treatment of rats with dexamethasone reduces ICAM-1 levels on circulating monocytes

We report for the first time that in vivo treatment with dexamethasone (DEX) reduces levels of intercellular adhesion molecule-1 (ICAM-1) expression on rat circulating unstimulated monocytes (-55%) and peritoneal macrophages (-26%). This effect was present following sub-acute (5 days) treatment with a low dose (0.1 mg/kg per day), but not after single administration of a high dose (1 mg/kg, -2 h), of the steroid. Both acute and sub-acute treatment with DEX failed to modify either basal or up-regulated CD11b expression on peripheral blood monocytes and neutrophils, elastase release from neutrophils, and beta-glucuronidase release from cultured macrophages. The lack of alteration of CD11b expression on circulating leukocytes suggests that the effect of DEX on ICAM-1 expression is secondary to gene repression rather than a non-specific blockade of cell differentiation. These data promote the concept that different dose-regimens with glucocorticoids affect distinct molecular targets and indicate that clinically-related protocols of DEX may reveal new mechanism(s) of action.