Primary mitochondrial disorders and mimics: Insights from a large French cohort

OBJECTIVE

The objective of this study was to evaluate the implementation of NGS within the French mitochondrial network, MitoDiag, from targeted gene panels to whole exome sequencing (WES) or whole genome sequencing (WGS) focusing on mitochondrial nuclear-encoded genes.

METHODS

Over 2000 patients suspected of Primary Mitochondrial Diseases (PMD) were sequenced by either targeted gene panels, WES or WGS within MitoDiag. We described the clinical, biochemical, and molecular data of 397 genetically confirmed patients, comprising 294 children and 103 adults, carrying pathogenic or likely pathogenic variants in nuclear-encoded genes.

RESULTS

The cohort exhibited a large genetic heterogeneity, with the identification of 172 distinct genes and 253 novel variants. Among children, a notable prevalence of pathogenic variants in genes associated with oxidative phosphorylation (OXPHOS) functions and mitochondrial translation was observed. In adults, pathogenic variants were primarily identified in genes linked to mtDNA maintenance. Additionally, a substantial proportion of patients (54% (42/78) and 48% (13/27) in children and adults, respectively), undergoing WES or WGS testing displayed PMD mimics, representing pathologies that clinically resemble mitochondrial diseases.

INTERPRETATION

We reported the largest French cohort of patients suspected of PMD with pathogenic variants in nuclear genes. We have emphasized the clinical complexity of PMD and the challenges associated with recognizing and distinguishing them from other pathologies, particularly neuromuscular disorders. We confirmed that WES/WGS, instead of panel approach, was more valuable to identify the genetic basis in patients with "possible" PMD and we provided a genetic testing flowchart to guide physicians in their diagnostic strategy.

An early onset benign myopathy with glycogen storage caused by a de novo 1.4 Mb-deletion of chromosome 14

Early onset myopathies are a clinically and histologically heterogeneous monogenic diseases linked to approximately 90 genes. Molecular diagnosis is challenging, especially in patients with a mild phenotype. We describe a 26-year-old man with neonatal hypotonia, motor delay and seizures during infancy, and non-progressive, mild muscular weakness in adulthood. Serum Creatine kinase level was normal. Whole-body muscle MRI showed thin muscles, and brain MRI was unremarkable. A deltoid muscle biopsy showed glycogen storage. WGS revealed a de novo 1.4 Mb-deletion of chromosome 14, confirmed by Array-CGH. This microdeletion causes the loss of ten genes including RALGAPA1, encoding for RalA, a regulator of glucose transporter 4 (GLUT4) expression at the membrane of myofibers. GLUT4 was overexpressed in patient's muscle. Here we highlight the importance to search for chromosomal alterations in the diagnostic workup of early onset myopathies.

Very long-term outcomes in 23 patients with cblA type methylmalonic acidemia

OBJECTIVES

To present the very long-term follow up of patients with cobalamin A (cblA) deficiency.

METHODS

A retrospective case series of adult (>16 years) patients with molecular or enzymatic diagnosis of cblA deficiency.

RESULTS

We included 23 patients (mean age: 27 ± 7.6 years; mean follow-up: 24.9 ± 7.6 years). Disease onset was mostly pediatric (78% < 1 year, median = 4 months) with acute neurologic deterioration (65%). Eight patients presented with chronic symptoms, and one had an adult-onset mild cblA deficiency. Most of the patients (61%) were initially classified as vitamin B12-unresponsive methylmalonic aciduria (MMA); in vitro B12 responsiveness was subsequently found in all the tested patients (n = 13). Initial management consisted of protein restriction (57%), B12 (17%), or both (26%). The main long-term problems were intellectual disability (39%) and renal failure (30%). However, 56.5% of the patients were living independently. Intellectual disability was equally distributed among the initial treatment groups, while renal failure (moderate and beginning at the age of 38 years) was present in only one out of seven patients initially treated with B12.

CONCLUSIONS

We provide a detailed picture of the long-term outcome of a series of adult cblA patients, mostly diagnosed before the enzymatic and molecular era. We confirm that about 35% of the patients do not present acutely, underlining the importance of measuring MMA in any case of unexplained chronic renal failure, intellectual disability, or growth delay. In addition, we describe a patient with a milder adult-onset form. Early B12 supplementation seems to protect from severe renal insufficiency.

Heterozygous PNPT1 variants cause spinocerebellar ataxia type 25

OBJECTIVE

Dominant spinocerebellar ataxias (SCA) are characterized by genetic heterogeneity. Some mapped and named loci remain without a causal gene identified. Here we applied next generation sequencing (NGS) to uncover the genetic etiology of the SCA25 locus.

METHODS

Whole-exome and whole-genome sequencing were performed in families linked to SCA25, including the French family in which the SCA25 locus was originally mapped. Whole exome sequence data was interrogated in a cohort of 796 ataxia patients of unknown aetiology.

RESULTS

The SCA25 phenotype spans a slowly evolving sensory and cerebellar ataxia, in most cases attributed to ganglionopathy. A pathogenic variant causing exon skipping was identified in the gene encoding Polyribonucleotide Nucleotidyltransferase PNPase 1 (PNPT1) located in the SCA25 linkage interval. A second splice variant in PNPT1 was detected in a large Australian family with a dominant ataxia also mapping to SCA25. An additional nonsense variant was detected in an unrelated individual with ataxia. Both nonsense and splice heterozygous variants result in premature stop codons, all located in the S1-domain of PNPase. In addition, an elevated type I interferon response was observed in blood from all affected heterozygous carriers tested. PNPase notably prevents the abnormal accumulation of double-stranded mtRNAs in the mitochondria and leakage into the cytoplasm, associated with triggering a type I interferon response.

INTERPRETATION

This study identifies PNPT1 as a new SCA gene, responsible for SCA25, and highlights biological links between alterations of mtRNA trafficking, interferonopathies and ataxia. This article is protected by copyright. All rights reserved.

Expanding the phenotypic spectrum of BCS1L-related mitochondrial disease

Objective

To delineate the full phenotypic spectrum of BCS1L‐related disease, provide better understanding of the genotype–phenotype correlations and identify reliable prognostic disease markers.

Methods

We performed a retrospective multinational cohort study of previously unpublished patients followed in 15 centres from 10 countries. Patients with confirmed biallelic pathogenic BCS1L variants were considered eligible. Clinical, laboratory, neuroimaging and genetic data were analysed. Patients were stratified into different groups based on the age of disease onset, whether homozygous or compound heterozygous for the c.232A>G (p.Ser78Gly) variant, and those with other pathogenic BCS1L variants.

Results

Thirty‐three patients were included. We found that growth failure, lactic acidosis, tubulopathy, hepatopathy and early death were more frequent in those with disease onset within the first month of life. In those with onset after 1 month, neurological features including movement disorders and seizures were more frequent. Novel phenotypes, particularly involving movement disorder, were identified in this group. The presence of the c.232A>G (p.Ser78Gly) variant was associated with significantly worse survival and exclusively found in those with disease onset within the first month of life, whilst other pathogenic BCS1L variants were more frequent in those with later symptom onset.

Interpretation

The phenotypic spectrum of BCS1L‐related disease comprises a continuum of clinical features rather than a set of separate syndromic clinical identities. Age of onset defines BCS1L‐related disease clinically and early presentation is associated with poor prognosis. Genotype correlates with phenotype in the presence of the c.232A>G (p.Ser78Gly) variant.

Cerebral blood flow and acute episodes of Leigh syndrome in neurometabolic disorders

AIM

To investigate cerebral blood flow (CBF) in acute episodes of Leigh syndrome compared with basal state in patients carrying pathogenic mitochondrial disease gene variants responsible for neurometabolic disorders.

METHOD

Arterial spin labelling (ASL) magnetic resonance imaging (MRI) sequences were used to measure CBF in 27 patients with mitochondrial respiratory chain enzyme deficiencies, ascribed to pathogenic variants of reported disease genes who were undergoing either urgent neuroimaging for acute episodes of Leigh syndrome (Group I: 15 MRI, seven females, eight males; mean age 7y; range 7mo-14y) or routine brain MRI (Group II: 15 MRI, eight females, seven males; mean age 5y 2mo; range 2mo-12y).

RESULTS

Patients displayed markedly increased CBF in the striatum (2.8-fold greater, p<0.001 [1.05-2.53]) during acute episodes of Leigh syndrome compared to basal conditions. Detection of elevated CBF preceded identification of structural MRI lesions in four out of 15 cases.

INTERPRETATION

Our results suggest that increased CBF is an overt hallmark of Leigh syndrome episodes and ASL MRI sequences should facilitate early diagnosis of acute episodes of Leigh syndrome, especially during the first attack in young children, when structural MRI is insufficiently informative.

Biallelic <i>IARS2</i> mutations presenting as sideroblastic anemia

Not available.

Novel NDUFA12 variants are associated with isolated complex I defect and variable clinical manifestation

Isolated biochemical deficiency of mitochondrial complex I is the most frequent signature among mitochondrial diseases and is associated with a wide variety of clinical symptoms. Leigh syndrome represents the most frequent neuroradiological finding in patients with complex I defect and more than 80 monogenic causes have been involved in the disease. In this report, we describe seven patients from four unrelated families harboring novel NDUFA12 variants, with six of them presenting with Leigh syndrome. Molecular genetic characterization was performed using next-generation sequencing combined with the Sanger method. Biochemical and protein studies were achieved by enzymatic activities, blue native gel electrophoresis, and western blot analysis. All patients displayed novel homozygous mutations in the NDUFA12 gene, leading to the virtual absence of the corresponding protein. Surprisingly, despite the fact that in none of the analyzed patients, NDUFA12 protein was detected, they present a different onset and clinical course of the disease. Our report expands the array of genetic alterations in NDUFA12 and underlines phenotype variability associated with NDUFA12 defect.

Heterogeneity of PNPT1 neuroimaging: mitochondriopathy, interferonopathy or both?

BACKGROUND

Biallelic variants in PNPT1 cause a mitochondrial disease of variable severity. PNPT1 (polynucleotide phosphorylase) is a mitochondrial protein involved in RNA processing where it has a dual role in the import of small RNAs into mitochondria and in preventing the formation and release of mitochondrial double-stranded RNA into the cytoplasm. This, in turn, prevents the activation of type I interferon response. Detailed neuroimaging findings in PNPT1-related disease are lacking with only a few patients reported with basal ganglia lesions (Leigh syndrome) or non-specific signs.

OBJECTIVE AND METHODS

To document neuroimaging data in six patients with PNPT1 highlighting novel findings.

RESULTS

Two patients exhibited striatal lesions compatible with Leigh syndrome; one patient exhibited leukoencephalopathy and one patient had a normal brain MRI. Interestingly, two unrelated patients exhibited cystic leukoencephalopathy resembling RNASET2-deficient patients, patients with Aicardi-Goutières syndrome (AGS) or congenital CMV infection.

CONCLUSION

We suggest that similar to RNASET2, PNPT1 be searched for in the setting of cystic leukoencephalopathy. These findings are in line with activation of type I interferon response observed in AGS, PNPT1 and RNASET2 deficiencies, suggesting a common pathophysiological pathway and linking mitochondrial diseases, interferonopathies and immune dysregulations.

Improving post-natal detection of mitochondrial DNA mutations

INTRODUCTION

Currently, genetic testing of mitochondrial DNA mutations includes screening for single-nucleotide variants, several base pair insertions or deletions, large-scale deletions, or relative depletion of total mitochondrial DNA content. Within the last decade, next-generation sequencing (NGS) has resulted in remarkable advances in the field of mitochondrial diseases (MD) and has become a routine step of the diagnostic workup.

AREAS COVERED

We aimed to present an overview of current technologies employed in molecular diagnosis of mitochondrial DNA diseases. We report on the recent contributions of NGS testing to the diagnosis and understanding of MD.

EXPERT OPINION

The progress of NGS technologies allows the simultaneous detection of mutations and quantification of the heteroplasmy level, ensuring sensitivity and specificity requested for the detection of mitochondrial DNA point mutations. NGS protocols enabling the simultaneous analysis of mitochondrial and nuclear DNA are now efficient and cost-saving approaches, and have become the gold-standard technique in diagnostic laboratories.

Nocturnal enteral nutrition is therapeutic for growth failure in Fanconi-Bickel syndrome

Fanconi-Bickel syndrome (FBS) is a rare autosomal recessive disorder characterised by impaired glucose liver homeostasis and proximal renal tubular dysfunction. It is caused by pathogenic variants in SLC2A2 coding for the glucose transporter GLUT2. Main clinical features include hepatomegaly, fasting hypoglycaemia, postprandial hyperglycaemia, Fanconi-type tubulopathy occasionally with rickets, and a severe growth disorder. While treatment for renal tubular dysfunction is well established, data regarding optimal nutritional therapy are scarce. Similarly, detailed clinical evaluation of treated FBS patients is lacking. These unmet needs were an incentive to conduct the present pilot study. We present clinical findings, laboratory parameters and molecular genetic data on 11 FBS patients with emphasis on clinical outcome under various nutritional interventions. At diagnosis, the patients' phenotypic severity could be classified into two categories: a first group with severe growth failure and rickets, and a second group with milder signs and symptoms. Three patients were diagnosed early and treated because of family history. All patients exhibited massive glucosuria at diagnosis and some in both groups had fasting hypoglycaemic episodes. Growth retardation improved drastically in all five patients treated by intensive nutritional intervention (nocturnal enteral nutrition) and uncooked cornstarch with final growth parameters in the normal range. The four severely affected patients who were treated with uncooked cornstarch alone did not catch up growth. All patients received electrolytes and l-carnitine supplementation to compensate for the tubulopathy. This is one of the largest series of FBS on therapeutic management with evidence that nocturnal enteral nutrition rescues growth failure.

Expanding the clinical spectrum of MTTF mutations

We report on a de novo m.586G > A MTTF mutation in a 14 yrs old boy with non-progressive muscle weakness, myalgia, normal brain MRI, normal schooling and absent central nervous system involvement. The same m.586G > A MTTF mutation has been previously reported in a 57 yrs-old woman with a progressive neurodegenerative disorder, akinesia-rigidity, abnormal movements, dementia, and psychiatric disorder. Those two strikingly different clinical presentations emphasize the impact of either mitochondrial factors (heteroplasmy, mitotic segregation) or hitherto unknown nuclear factors on the clinical expression of genetically homogeneous mtDNA mutations.

Abstract P6-10-06: Inducing immune responses to tumor associated carbohydrate antigens by a carbohydrate mimetic peptide vaccine: Clinical experience in phase I and phase II trials

Active immunization of cancer patients to induce de novo functional anti-tumor immune responses is an alternative/complementary approach to chemotherapy. Tumor vaccines hold the potential to deliver durable, specific and systemic anti-tumor responses in patients. We have been developing active vaccination strategies targeting tumor associated carbohydrate antigens (TACAs) using carbohydrate mimetic peptides. TACAs play roles in initiation and metastasis of cancer and considered as common targets shared by many tumor types. TACA support cell survival that can be interrupted by anti-carbohydrate antibodies. An early-phase 3+3 clinical trial was conducted to evaluate the feasibility, safety and immune functionality of a carbohydrate mimetic-peptide (CMP) vaccine referred to as P10s, which can induce TACA reactive, proapoptotic antibodies. In this trial a dose-escalation trial of vaccine plus adjuvant was conducted in two cohorts of 3 subjects each. Patients were restricted to females of all races with histologically or cytologically confirmed stage IV breast cancer who had stable disease and a positive recall-antigen response. P10s was synthesized with the Pan-T-cell epitope PADRE and formulated at 300 and 500 µg/injection with MONTANIDE™ ISA 51 VG for the 1st and 2nd cohorts, respectively. Doses of the appropriate formulation of the vaccine were administered to research participants subcutaneously on weeks 1, 2, 3, 7 and 19. Blood samples were collected at various time points and tested for presence and functionality of antibodies. Antibody response to P10s and in particular against the ganglioside GD2 was measured by ELISA. Binding of pre-immune and post-immune sera was assessed against breast cancer cell lines. Vaccination generates IgG response with serum antibodies capable of inhibiting tumor growth in spheroid culture of breast cancer cell lines. The vaccine induced antibodies in all 6 subjects, displaying significant cytotoxic activity against several representative human breast-cancer cell lines. Caspase 3 was involved in the postimmune serum-mediated apoptosis. No cytotoxicity toward a normal breast epithelial cell line was detected. Apoptosis and caspase 3 activation seems to be involved in anti-tumor cell activity. Immunization with the P10s vaccine was found to be safe and tolerable, and induces functional antibodies that potentially have a cell-death-mediated therapeutic benefit. Incubation of spheroids with post-immune serum further sensitized cells to drugs, improving the efficacy of drug treatment at lower doses. The data suggest that the vaccine-induced anti-tumor immune response in combination with standard of care chemotherapy may further improve clinical outcome. Consequently, we are testing the vaccine in a Phase II study in the neoadjuvant setting. 5 Cohorts of 5 patients each administered with the vaccine at different schedules of chemotherapy are being assessed for immune response to the vaccine as in the Phase I study and if the combination approach contributes to a difference in pathological complete response (PCR) from chemotherapy alone.

Citation Format: Kieber-Emmons T, Hutchins LF, Emanuel PD, Pennisi A, Siegel E, Jousheghany F, Karbassi BM, Makhoul I. Inducing immune responses to tumor associated carbohydrate antigens by a carbohydrate mimetic peptide vaccine: Clinical experience in phase I and phase II trials [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-10-06.

Abstract P5-11-19: Sexual functioning among breast cancer survivors and their partners: A pilot study

Introduction: Although a number of studies have examined sexual difficulties among breast cancer survivors, few have focused on multiple dimensions of sexual functioning or partners' attitudes and difficulties. This pilot study sought a more comprehensive examination of sexual functioning among couples after breast cancer.

Methods: Patients who were at least 6 months post-treatment and were involved in committed relationships were recruited during routine clinic visits. Those who accepted to participate in the study were handed by the investigator a stamped self-addressed envelope (to the research office of the Cancer Institute) containing two questionnaires, for the patient and for her partner, and a cancer information sheet. No identifiable information was collected. Thus, the IRB did not require a written consent form.

Results: 200 patients were invited to participate in the study. 120 were in a stable relationship but only 100 accepted to take the envelope. The rest of the patients were single (76) or separated after their diagnosis (4; 2%). 38 couples participated by returning their completed questionnaires; they had been partnered for an average of 34.9 (14.3) years. Mean time since diagnosis was 40.4 (22.4) months, and mean age was 58.1 (11.5). 71.05% were currently receiving hormonal therapy.

Among the patients, 63.2% reported that they were sexually active and, retrospectively, reported that their sexual relationship had been satisfying prior to diagnosis. Currently, however, a large subgroup of patients (30.4%) reported markedly limited sexual satisfaction (“a little bit” or “not at all”). Additionally, 30.4%-to-43.5% reported low sexual interest; 69.6% reported significant problems with lubrication; 52.2% reported limited orgasm; and 30.4%-to- 60.9% had difficulties with vaginal discomfort.

Among partners, 67.6% reported that they were sexually active. Their sexual relationships prior to diagnosis were recalled as having been highly satisfying. Currently, none of the sexually active partners reported low satisfaction, though a few (8.3%) had not been active in the past month. Few partners reported low sexual interest (0% - 4.2%). Marked erectile difficulties were reported by 16.7% to 20.8%, and 25.0% reported difficulties with orgasm.

The top 3 factors that patients endorsed as interfering with their current sexual functioning (“quite a bit” or “very much”) were (1) pain (41.7%), (2) fatigue (37.5%), and (3) feeling unattractive (20.8%). Fewer participants endorsed concerns about breast tenderness (16.7%), hot flashes (12.5%), surgical scars (12.5%), their partners' reactions (16.7%), and their partners' own sexual difficulties (12.5%). For partners, the factors most commonly viewed as disrupting the sexual relationship were the patient's vaginal dryness (32.0%), the patient's fatigue (28.0%), and the partner's own sexual problems (20.0%).

Conclusion: Our results suggest that a large proportion of breast cancer survivors experience difficulties in multiple dimensions of sexual functioning. Contrary to a popular belief, separation rate after the diagnosis of breast cancer was low (2%) and most patients and their partners identified vaginal dryness and fatigue (not the breast surgery) as the major factors interfering with their sexual functioning.

Citation Format: Makhoul I, Pennisi A, Ochoa D, Klimberg S, Henry-Tillman R, Mack K, Hutchins L, Sherman AAC. Sexual functioning among breast cancer survivors and their partners: A pilot study [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-11-19.

Effects of a new nutraceutical ingredient on allergen-induced sulphidoleukotrienes production and CD63 expression in allergic subjects

Allergic diseases represent conditions affecting millions of individuals across the world. The objective of this study was to investigate the potential anti-allergic effects of a new nutraceutical ingredient, Pantescal (Bionap, Italy), contained in different food supplements. Pantescal is a mixture of plant extracts, such as Capparis spinosa, Olea europaea, Panax Ginseng and Ribes nigrum. The study was a randomized, double-blind, placebo controlled design. 60 patients allergic to common aeroallergens were chosen. Allergic patients were divided into two groups: one group was supplemented by Pantescal and the other, using a placebo formulation. Two in vitro tests were performed on blood samples taken from patients before and at 2 h, 2, 3 and 10 days after supplementation: cellular antigen stimulation test (CAST) was used to analyze the amount of sulphidoleukotrienes (SLT) production and flow-cytometric antigen stimulation test (FAST) to measure expression of basophil degranulation marker (CD63) was also performed. CAST showed that after 2 and 3 days, a slight decrease of SLT production was evident but only after 10 days did it become significant with a percentage of inhibition (P.I)=43.3%. FAST revealed that there were no statistical differences for the first 2 days after supplementation although there was an inhibitory trend in the supplemented patients. CD63 expression was significantly reduced after 10 days (P.I.=64.8%). This study suggests that Pantescal is effective in reducing allergic biomarkers such as CD63 protein and SLT in atopic subjects. The higher inhibitory effect on CD63 expression compared to SLT production allows us to hypothesize cell membrane stabilization as the main potential mechanism to explain the observed Pantescal protective effects.

[Management of multiple myeloma]

Multiple myeloma (MM) remains an incurable malignancy, the median overal survival of patients receiving conventional chemotherapy being only 36-60 months. MGUS can evolve to MM in a percentage of 0.6-3% per year. The therapeutic management of multiple myeloma (MM) for the last several decades has mainly involved regimens based on use of glucocorticoids and cytotoxic chemotherapeutics. Melphaln and Prednisone (MP) are recognized as the classic treatment of MM. In patients candidate to bone marrow transplantation, VAD (Vincrisrine, Adriamicin, Dexamethasone) regimen is more indicated because it does not cause stem cell injury. High dose chemotherapy and and Autologous stem cells transplantation represent the best treatment for patients with MM who are younger than 65 years and free of severe comorbidities. Thalidomide alone or in combination with steroids has significant activity in multiple myeloma (MM). After the role of thalidomide in the management of patients with advanced or refractory MM had been established, many studies are evaluating the efficacy and toxicity of thalidomide as first-line therapy for patients with newly diagnosed disease. Recent studies have enhanced our understanding of disease pathogenesis and also provided the framework for a new treatment paradigm targeting the MM cell in its bone marrow microenvironment to overcome drug resistance and improve patient outcome. Clinical trials are confirming the remarkable activity and improved tolerability of some of the new agents identified through this paradigm.

[Neonatal conjunctivitis in a hospital at Gran Buenos Aires. Last 5 years up-date]

Neonatal conjunctivitis is one of the most important consultation reasons in the first days of life. Causes may be chemical or infectious. Neonatal conjunctivitis study for common microorganisms and Chlamydia trachomatis is being performed at Posadas Hospital since 1995, in a progressive form. The objective of this study was to know the epidemiological situation in the last five years (1999-2003), and to describe the variations detected between two periods, 1995-1998, and 1999-2003. It was observed no change about C. trachomatis prevalence (8%), during all the time in the population studied. With regard to common microorganisms it was showed a decrease in the second period (36.6%) with respect to the first (52.4%). Likely, the causes may be due to changes about sample collection conditions, or to epidemiological variations. The most frequent microorganisms found were: Staphylococcus aureus 69 (27.6%), Streptococcus pneumoniae 68 (27.2%), and Haemophilus influenzae 64 (25.6%). We consider important to evaluate the kind of ocular secretions at the first consultation, which can lead to a symptomatic treatment that will be corroborated or not, according to microbiological results.

Inhaled platelet-activating factor increases airway sensitivity but not maximal airway narrowing to methacholine in normal subjects

To examine the effect of inhaled platelet-activating factor (PAF) on airway sensitivity and on maximal airway narrowing, we measured airway response to doubling concentrations of methacholine (MCh) 48 h before and 48 h after inhalation of 10, 50 and 100 micrograms of PAF in six nonatopic, nonasthmatic subjects. The forced expiratory volume in one second (FEV1) and airflow at 30 percent of vital capacity (V30) from partial forced expiration were used to assess changes in airway calibre. Inhalation of PAF caused only minor changes in FEV1. In contrast, inhalation of 100 micrograms of PAF caused a significant fall in V30 from 2.64 +/- 0.35 to 1.35 +/- 0.43 l.min-1 (p < 0.05). Two days after PAF inhalation a leftward shift of the concentration-response curve to MCh was observed. The MCh concentration causing a 20% fall in FEV1 (PC20FEV1) was 11.25 +/- 1.78 and 2.38 +/- 1.29 mg.ml-1 (geometric mean +/- GSEM; p < 0.05) before and after PAF inhalation, respectively. PAF did not affect the maximal airway response to MCh. The maximum percentage fall in FEV1 was 36.2 +/- 1.9% at baseline and 37.6 +/- 1.8% after PAF inhalation. Likewise, maximum percentage change in V30 was 72.8 +/- 3.7% at baseline and 73.6 +/- 3.4% after PAF inhalation. The results of this study show that PAF inhalation increases airway sensitivity without altering the maximal bronchoconstrictive response to MCh in normal subjects.

Neutral endopeptidase inhibitor thiorphan increases airway narrowing to inhaled sodium metabisulfite in normal subjects

Possible mechanisms involved in inhaled sodium metabisulfite (MBS)-induced bronchoconstriction include cholinergic reflex and release of tachykinins from sensory nerve endings. Tachykinins are potent bronchoconstrictors cleaved and inactivated by neutral endopeptidase (NEP) in the airways. To investigate the role of tachykinins in airway response to MBS, we assessed the effect of NEP-inhibitor thiorphan on airway response to MBS in nine nonatopic, nonasthmatic subjects. Two inhalational challenges with doubling doses of MBS (0.03 to 16 mumol) were performed 3 d apart. Ten minutes before MBS challenge, subjects randomly inhaled either thiorphan (1.25 mg) or placebo according to a double-blind cross-over design. Airflow at 30% of vital capacity (V30p) from partial expiratory flow-volume curves was measured at baseline, 10 min after thiorphan or placebo, and 2 min after each MBS dose. The dose of MBS causing 40% fall in V30p (PD40V30p) was calculated. Neither thiorphan nor placebo affected baseline airway caliber. Thiorphan caused a leftward shift of the dose-response curve to MBS. After placebo a measurable PD40V30p was obtained in four of nine subjects. In these subjects PD40V30p fell significantly after thiorphan inhalation. Four of five subjects who did not exhibit PD40V30p after placebo showed measurable PD40V30p after thiorphan. Percent fall in V30p caused by highest dose of MBS was significantly greater after thiorphan compared with placebo (55.9 +/- 4.6% versus 30.8 +/- 5.6%; mean +/- SE; p < 0.001). Results of this study demonstrate that the NEP-inhibitor thiorphan increases MBS-induced bronchoconstriction in normal subjects, suggesting that tachykinins are involved in airway responses to inhaled MBS.

Growth and glucocorticoids in children with kidney disease

Glucorticoid therapy inhibits statural growth. Alternate-day therapy causes less growth suppression than does daily therapy, and, in experimental animals and children with asthma, it has been associated with normal growth. Although catch-up growth may occur after cessation of steroid therapy, this is not always the case, especially when therapy has been prolonged. In children treated with steroids for glomerulonephritis or nephrotic syndrome and especially in children after renal transplantation, factors other than steroid therapy may contribute to growth retardation. Steroids may suppress growth by direct action on cell metabolism, by inhibition of growth hormone or somatomedin and/or by effects on calcium and phosphorus metabolism. Present knowledge of mechanisms of action and dose-response relationships is complete, and it is difficult to prescribe therapy which will achieve a predictable therapeutic effect without inhibiting growth.