The alpha subunit of the GTP binding protein Gk opens atrial potassium channels

Guanine nucleotide binding (G) proteins (subunit composition alpha beta gamma) dissociate on activation with guanosine triphosphate (GTP) analogs and magnesium to give alpha-guanine nucleotide complexes and free beta gamma subunits. Whether the opening of potassium channels by the recently described Gk in isolated membrane patches from mammalian atrial myocytes was mediated by the alpha k subunit or beta gamma dimer was tested. The alpha k subunit was found to be active, while the beta gamma dimer was inactive in stimulating potassium channel activity. Thus, Gk resembles Gs, the stimulatory regulatory component of adenylyl cyclase, and transducin, the regulatory component of the visual system, in that it regulates its effector function--the activity of the ligand-gated potassium channel--through its guanine nucleotide binding subunit.

Phagocytosis and intracellular fate of Aspergillus fumigatus conidia in alveolar macrophages

Aspergillus fumigatus is the most prevalent airborne fungal pathogen responsible for fatal invasive aspergillosis in immunocompromised patients. Upon arrival in the lung alveolus, conidia of A. fumigatus are phagocytosed by alveolar macrophages, the major phagocytic cells of the lung. Engulfment and intracellular trafficking of A. fumigatus conidia in alveolar macrophages of two different origins, the murine cell line MH-S and human pulmonary alveolar macrophages, were analyzed by electron microscopy and immunofluorescence. Phagocytosis of A. fumigatus conidia required actin polymerization and phosphatidylinositol 3-kinase activity. Fusion of A. fumigatus phagosomes with early and late endosomes was shown by immunolabeling with specific markers for the transferrin receptor, early endosome antigen, and Rab7. Maturation of A. fumigatus phagolysosomes was monitored by using a fixable acidotropic probe, LysoTracker Red DND-99, and an anti-cathepsin D antibody. Bafilomycin A-induced inhibition of lysosomal acidification abolished the conidial killing by the macrophages. These data suggest that the maturation of A. fumigatus phagosomes results from fusion with the compartments of the endocytic pathway and that the killing of conidia depends on phagolysosome acidification. A model for the phagocytosis of A. fumigatus conidia by alveolar macrophages is proposed on the basis of these results.

Antibody-Mediated Rejection in Lung Transplantation: Clinical Outcomes and Donor-Specific Antibody Characteristics

In the context of lung transplant (LT), because of diagnostic difficulties, antibody-mediated rejection (AMR) remains a matter of debate. We retrospectively analyzed an LT cohort at Foch Hospital to demonstrate the impact of AMR on LT prognosis. AMR diagnosis requires association of clinical symptoms, donor-specific antibodies (DSAs), and C4d(+) staining and/or histological patterns consistent with AMR. Prospective categorization split patients into four groups: (i) DSA positive, AMR positive (DSA(pos) AMR(pos) ); (ii) DSA positive, AMR negative (DSA(pos) AMR(neg) ); (iii) DSA limited, AMR negative (DSA(Lim) ; equal to one specificity, with mean fluorescence intensity of 500-1000 once); and (iv) DSA negative, AMR negative (DSA(neg) ). AMR treatment consisted of a combination of plasmapheresis, intravenous immunoglobulin and rituximab. Among 206 transplanted patients, 10.7% were DSA(pos) AMR(pos) (n = 22), 40.3% were DSA(pos) AMR(neg) (n = 84), 6% were DSA(Lim) (n = 13) and 43% were DSA(neg) (n = 88). Analysis of acute cellular rejection at month 12 showed higher cumulative numbers (mean plus or minus standard deviation) in the DSA(pos) AMR(pos) group (2.1 ± 1.7) compared with DSA(pos) AMR(neg) (1 ± 1.2), DSA(Lim) (0.75 ± 1), and DSA(neg) (0.7 ± 1.23) groups. Multivariate analysis demonstrated AMR as a risk factor for chronic lung allograft dysfunction (hazard ratio [HR] 8.7) and graft loss (HR 7.56) for DSA(pos) AMR(pos) patients. Our results show a negative impact of AMR on LT clinical course and advocate for an early active diagnostic approach and evaluation of therapeutic strategies to improve prognosis.

Adenosine diphosphate ribosylation of G proteins by pertussis and cholera toxin in isolated membranes. Different requirements for and effects of guanine nucleotides and Mg2+

ADP ribosylation of membranes by pertussis toxin (PT) and cholera toxin (CT) was studied as a function of addition of ATP, various guanine nucleotides, Mg2+, and inorganic phosphate (Pi). ADP ribosylation of a 40 kilodalton (kDa) band by PT is markedly enhanced by ATP and GTP and is strongly inhibited by Pi or Mg2+. GTP analogs (GTP gamma S and GMP-adenyl-5'-yl imidodiphosphate) were less effective. In contrast, ADP ribosylation of two substrates for CT (of 42 and 50 kDa) is stimulated by Pi, Mg2+, and GTP or GTP analogs such as GTP gamma S, but is unaffected by ATP. These stimulatory conditions correlate well with GTP-mediated activation of stimulated nucleotide-binding regulatory component of adenyl cyclase. Optimal conditions for ADP ribosylation by PT do not correlate simply with conditions thought to lead to stabilization of an inactive form of inhibitory nucleotide-binding regulatory component of adenyl cyclase (Gi) or Gi-like protein; rather, the data suggest the involvement of both a stimulatory nucleotide site on PT (positively affected by either ATP or GTP) and a stabilizing site on the PT substrate (affected by GDP, GDP beta S, or GTP). Treatment of membranes with Lubrol PX increased ADP ribosylation by PT by as much as 25- to 30-fold, but inhibited the action of CT. Using defined conditions for ADP ribosylation by PT and CT, distinct labeling patterns were observed in thyroid, brain, corpus luteum, liver, heart, and erythrocytes membranes. All membranes were more intensely labeled by PT rather than CT.

Hormonal regulation of pituitary GH3 cell K+ channels by Gk is mediated by its alpha-subunit

The resolved alpha-GTP gamma S (alpha*) and beta gamma-subunits of human erythrocyte Gk, the stimulatory regulatory component of hormone-responsive K+ channels, were tested for their potential stimulatory activities on the K+ channel of the endocrine GH3 cell. Concentrations as low as 0.5 pM alpha k* consistently activated K+ channels in isolated membrane patches, and saturating effects were obtained with 50 pM alpha k*. In contrast 2000-4000 pM beta gamma was without effect. We conclude that Gk acts on K+ channels through its alpha-subunit in a manner akin to that of Gs acting on adenylyl cyclase and transducin acting on cGMP-specific phosphodiesterase of photo-receptor cells.

Failure of ganciclovir treatment associated with selection of a ganciclovir-resistant cytomegalovirus strain in a lung transplant recipient

We report the case of a lung transplant recipient with progressive cytomegalovirus (CMV) disease due to a resistant CMV strain emerging under ganciclovir (GCV) therapy. A discriminative polymerase chain reaction (PCR) assay, designed to detect the resistance-related V460 mutation within the viral enzyme UL97, revealed the presence of a mutated strain in a heterogeneous isolate 51 days after transplantation. The conventional antiviral susceptibility assay had failed to demonstrate resistance to GCV. Under prolonged GCV therapy, the mutated strain dominated the wild-type strain, as shown by the PCR assay. This domination led to laboratory resistance, associated with recurrent fever and progressively severe retinitis. As this discriminative PCR assay was shown to be effective in detecting mutated strains that constitute a minority in the virus load, it should allow better management of patients with CMV disease.

Treatment of systemic vasculitis with cyclophosphamide and steroids: daily oral low-dose cyclophosphamide administration after failure of a pulse intravenous high-dose regimen in four patients

The efficacy of cyclophosphamide (CY) in the treatment of severe systemic vasculitis has been demonstrated, but its optimal administration regimen remains to be defined. The four patients described participated in prospective therapeutic trials of polyarteritis nodosa (PAN) without hepatitis B infection markers, Churg-Strauss syndrome (CSS) and Wegener's granulomatosis (WG) and received daily oral low-dose CY after failure of a monthly pulse regimen. These patients were included in this study because of failure to induce clinical remission (two patients) and relapse during the course of treatment (two patients). The results were good with initial clinical remission in three patients and stabilization in one. One patient with WG relapsed 10 months after changing therapeutics. The advantages of the different administration protocols are discussed.

Urea gradient/SDS-PAGE; a useful tool in the investigation of signal transducing G proteins

We describe an updated and improved protocol to perform urea gradient/SDS-PAGE in which proteins are electrophoresed through 9% polyacrylamide gel slabs in the presence of a linear 4 M to 8 M gradient of urea using Laemmli's separation buffers. We provide examples of this technique to separate PTX labeled G protein alpha subunits, as well as unlabeled alpha and beta subunits of G proteins. Applications of the technique are exemplified in which (1) the chromatographic separations of G proteins in DEAE-Toyopearl and MonoQ columns are compared, (2) the complexity of PTX substrates expressed in human erythrocytes, bovine brain, dog ventricle, FRTL-5 cells, HIT cells, GH4C1 cells and RIN cells are compared, and (3) the polypeptide composition of G protein beta gamma subunits, as expressed in several tissues and found in three distinct G proteins from a single cell population, are analyzed.

Insulinlike growth factor-1 in lung transplants with obliterative bronchiolitis

Bronchiolitis obliterans syndrome (BOS) is the major complication limiting survival of lung transplant recipients (Tx patients). The mechanisms underlying this fibrotic process are not known. We assessed IGF-1 and IGFBP-3 expression, critical mediators in different models of pulmonary fibrosis, in nine Tx patients. Three of them developed a BOS at 8, 14, and 17 mo postgraft, respectively. Two of the remaining six displayed a recurrent cytomegalovirus (CMV) infection, and four are in stable condition. IGF-1 mRNA expression was quantitated by RT-PCR in cells from four to six BAL per patient performed during the first 6 mo postgraft. Contrasting with a constantly low expression of IGF-1 mRNA in BAL cells from the six patients without BOS, the three patients with BOS presented marked peaks of IGF-1 on two to five occasions during the study period. These peaks, 3- to 13-fold increased compared with values from the former patients, preceded the diagnosis of BOS by 7, 13, and 17 mo, respectively. On the other hand, IGFBP-3 was highly and exclusively expressed in the three patients with BOS, the mRNA as well as the gene product as demonstrated by Western blotting. Our data strongly argue for a role of IGF-1 and IGFBP-3 in the fibrotic process underlying BOS, and for their possible value as an early marker of this complication.

Non-classic cystic fibrosis associated with D1152H CFTR mutation

BACKGROUND

Limited knowledge exists on phenotypes associated with the D1152H cystic fibrosis transmembrane conductance regulator (CFTR) mutation.

METHODS

Subjects with a D1152H allele in trans with another CFTR mutation were identified using the French Cystic Fibrosis Registry. Phenotypic characteristics were compared with those of pancreatic insufficient (PI) and pancreatic sufficient (PS) cystic fibrosis (CF) subjects in the Registry (CF cohort).

RESULTS

Forty-two subjects with D1152H alleles were identified. Features leading to diagnosis included chronic sinopulmonary disease (n = 25), congenital absence of the vas deferens (n = 11), systematic neonatal screening (n = 4), and genetic counseling (n = 2). Median age at diagnosis was 33 [interquartile range (IQR, 24-41)] years in D1152H subjects. Median sweat chloride concentrations were 43.5 (39-63) mmol/l in D1152H subjects and were markedly lower than in PI and PS CF subjects (p < 0.05). Bronchiectasis was present in 67% of D1152H subjects, but Pseudomonas aeruginosa colonization and pancreatic insufficiency were present in <30% of subjects. Estimated rates of decline in forced expiratory volume in 1 s (FEV(1)) were lower in D1152H subjects vs PI CF subjects (p < 0.05). None of the D1152H subjects identified since 1999 had died or required lung transplantation.

CONCLUSIONS

When present in trans with a CF-causing mutation, D1152H causes significant pulmonary disease, but all subjects had prolonged survival.

Predictive value of cytomegalovirus DNA detection by polymerase chain reaction in blood and bronchoalveolar lavage in lung transplant patients

BACKGROUND

Despite promising results, the efficacy of polymerase chain reaction (PCR) for clinical management of cytomegalovirus (CMV) infection in transplanted patients is still controversial.

METHODS

A prospective study of CMV detection, with concurrent shell vial cultures and PCR in blood and bronchoalveolar lavage (BAL), was conducted in 13 lung transplant recipients, monitored for 15 months (range: 1-42 months). CMV DNA was detected by PCR amplification of a 406-bp fragment in the Us region and a 290-bp fragment in the immediate early region of the viral genome.

RESULTS

When comparing PCR to viral culture, the sensitivity and specificity of CMV DNA detection were 100% and 65.7% in blood (n=122) and 100% and 75% in BAL (n=104). The positive and negative predictive values of PCR for a forthcoming diagnosis of CMV infection were 50% and 97% in blood, and 67% and 85% in BAL. Seventeen CMV infections were evaluated at the end of treatment: when PCR was still positive either in blood or BAL, CMV infection relapsed within 35+/-5 days; when PCR was negative, CMV infection relapsed after 142+/-57 days (P=0.01).

CONCLUSIONS

Negative CMV detection by PCR strongly advocates against a forthcoming CMV infection. PCR assay seems to be a good predictor for early recurrence of CMV infection, and would be useful for monitoring the response to antiviral therapy.

Blood CD9+ B cell, a biomarker of bronchiolitis obliterans syndrome after lung transplantation

Bronchiolitis obliterans syndrome is the main limitation for long-term survival after lung transplantation. Some specific B cell populations are associated with long-term graft acceptance. We aimed to monitor the B cell profile during early development of bronchiolitis obliterans syndrome after lung transplantation. The B cell longitudinal profile was analyzed in peripheral blood mononuclear cells from patients with bronchiolitis obliterans syndrome and patients who remained stable over 3 years of follow-up. CD24^hi CD38^hi transitional B cells were increased in stable patients only, and reached a peak 24 months after transplantation, whereas they remained unchanged in patients who developed a bronchiolitis obliterans syndrome. These CD24^hi CD38^hi transitional B cells specifically secrete IL-10 and express CD9. Thus, patients with a total CD9⁺ B cell frequency below 6.6% displayed significantly higher incidence of bronchiolitis obliterans syndrome (AUC = 0.836, PPV = 0.75, NPV = 1). These data are the first to associate IL-10-secreting CD24^hi CD38^hi transitional B cells expressing CD9 with better allograft outcome in lung transplant recipients. CD9-expressing B cells appear as a contributor to a favorable environment essential for the maintenance of long-term stable graft function and as a new predictive biomarker of bronchiolitis obliterans syndrome-free survival.

Factors associated with humoral immune response to pandemic A/H1N1(v) 2009 influenza vaccine in cystic fibrosis

Influenza vaccination is recommended in cystic fibrosis patients. The objective of this study was to assess the immunogenicity of vaccination against 2009 pandemic A/H1N1 influenza and to study the factors associated with the immune response in patients with cystic fibrosis. 122 patients with cystic fibrosis were enrolled in a prospective study and received 1 dose of 2009/H1N1v adjuvanted vaccine, or for children <2 years and lung-transplanted patients, two doses of non-adjuvanted 2009/H1N1v vaccine administered 21 days apart. Hemagglutination inhibition antibodies were assessed before and 21 days after vaccination and at least 6 months after vaccination. After vaccination, 85% of the patients had an influenza antibody titer ≥1:40 and 69% seroconverted. 13% of the transplanted patients seroconverted compared with 72% of the non-transplanted patients. In this latter group, non-adjuvanted vaccine and low body mass index were independently associated with lower response to vaccination. 86% of the non-transplanted patients with normal BMI and receiving adjuvanted vaccine seroconverted. Persistence of seroprotection 10 months after vaccination was found in 50% of the patients. In patients with cystic fibrosis, malnutrition and receipt of non-adjuvanted vaccine were associated with lower immune response to pandemic influenza vaccination. Our data also suggest a potential defect in the immune response to influenza vaccination of patients with cystic fibrosis and raise the question of whether a different immunization strategy is needed.

Increased endothelin-1 associated with bacterial infection in lung transplant recipients

BACKGROUND

Endothelin-1 (ET-1) has fibrogenic and inflammatory properties. Its pathogenic role in pulmonary fibrosis and certain inflammatory airway diseases is now well known. Its production is, in part, triggered by infectious processes. Episodes of infection are suspected to be involved in the development of bronchiolitis obliterans syndrome (BOS), which is the main feature of chronic lung rejection and the major factor limiting the long-term survival of transplanted patients. We postulated that ET-1 is upregulated during infectious complications arising from the graft and that this could partly explain the remodeling of airway structures observed in BOS. We, therefore, set up this study to assess ET-1 expression in relation to complications of the graft in human lung transplant recipients.

METHODS

ET-1 mRNA was quantified by reverse transcription-competitive polymerase chain reaction in cells from 119 samples of bronchoalveolar lavage (BAL) fluid from 17 lung transplant recipients. ET-1 and big ET-1 proteins were assessed in BAL cell culture supernatants by enzyme immunoassay. Transbronchial biopsies (n=21) were stained immunohistochemically for ET-1 receptors.

RESULTS

Episodes of bacterial infection strongly correlated with increased ET-1 mRNA and protein expression. ET-1 receptors were also upregulated during these episodes, especially on endothelial and smooth muscle cells. Five of the seven patients with the highest ET-1 levels subsequently developed BOS.

CONCLUSIONS

These results raise the possibility that ET-1, part of whose production is triggered by infectious postgraft complications, might play a role in the development of BOS through its potential effects on airway remodeling.

Amikacin Liposomal Inhalation Suspension (ALIS) in the treatment of Mycobacterium abscessus lung infection: a French observational experience

Background

Mycobacterium abscessus infections remain difficult to manage in both cystic fibrosis (CF) and non-CF patients and reported clinical outcomes are largely unsatisfactory. Clinical trial data are limited and no approved therapies are currently available for the management of M abscessus lung diseases. As an alternative, cohort studies may provide insightful information into the management of M abscessus pulmonary disease.

Methods

Based on a retrospective observational cohort study, we investigated the safety and efficacy of amikacin liposome inhaled suspension (ALIS) as an adjunct to a standard antibiotic regimen for M abscessus lung infection in both CF and non-CF patients. We also assessed the association of patient drug compliance with culture conversion and clinical outcomes.

Results

Twenty-six patients had long-term follow-up data available. Culture conversion was achieved in 54% (14/26) of the patients with no difference between CF and non-CF patients after an average treatment duration of 10 months. Patient treatment compliance was significantly better in the converter group compared to nonconverters with an odds ratio of 44.78 associated with good compared to poor patient compliance. Overall, 9 patients (35%) experienced an adverse event that led to treatment discontinuation.

Conclusions

ALIS appears beneficial in both CF and non-CF populations with M abscessus lung disease.

[The management of lung transplantation candidates. A case series]

INTRODUCTION

Lung transplantation (LT) is associated with an increased risk of infection, cancer, chronic renal failure, cardiovascular disease and osteoporosis. Some risk factors precede transplantation and could benefit for early diagnosis and optimised care.

METHODS

The incidence of comorbidities and their treatment before referral were assessed in 157 consecutive lung transplant candidates between 2008 and 2011.

RESULTS

The median age was 37years [25; 51]. Fifty-six percent had a body mass index below 19kg/m(2). In the COPD group, only 50 % had undergone a pulmonary rehabilitation program in the preceding 2 years. Osteoporosis was present in 42 %, of whom 36 % were on bisphophonate therapy. Vitamin D deficiency was present in 65 %. Previously undiagnosed cardiovascular risk factors were discovered during LT assessment: hypertension in one patient, hypercholesterolemia in 6 % and diabetes in 4 %. Poor dental condition necessitating extractions were found in 41 % of patients. Protective anti-HBs antibodies levels were present in 50 % of the patients at the time of referral.

CONCLUSION

The assessment and early treatment of nutritional disorders, osteoporosis and risk factors for infection as well as addressing associated cardiovascular risk factors should be optimised in the care of patients with chronic respiratory insufficiency. The potential for becoming a lung transplant candidate in the future should be kept in mind early in the global management of those patients.

[Specific aspects and care of lung involvement in adults with cystic fibrosis]

Respiratory impairment is present in almost all adult cystic fibrosis patients and makes the prognosis. Viscous, infected and abundant secretions, inflammation and bronchial oedema, bronchoconstriction and respiratory muscle fatigue lead to airway obstruction, bronchiectasis and respiratory failure. The disease is preferentially located in the upper lobes. Exacerbations of the disease are due to bronchial infections and are often responsible for drops of the respiratory function. Regular spirometric surveillance is fundamental for the prognosis and the assessment of the effects of the treatment. Among adult patients chronic colonisation with mucoid and often multiresistant strains of Pseudomonas Aeruginosa are common. It is treated with i.v. high doses antibiotic courses and nebulized antibiotics between i.v. courses. Respiratory failure may require long term oxygen and non invasive mechanical ventilation. Systemic hypervascularization around the bronchiectasis may lead to moderate to severe hemoptysis, which may require embolization. Pneumothorax are associated with poor prognosis and are treated by pleural drainage and if failure by thoracoscopy.

[Antiphospholipid syndrome. 20 cases]

OBJECTIVES

We analyzed the clinical and biological characteristics as well as the clinical course and outcome observed in 20 patients with antiphospholipid antibodies and clinical signs including thrombosis or repeated spontaneous abortion to better identify the recently described antiphospholipid syndrome.

METHODS

We retrospectively studied all patients observed in our unit from 1981 to 1992 who fulfilled the following inclusion criteria: a) at least one episode of arterial or venous thrombosis and/or repeated spontaneous abortions, b) positive for antiphospholipid antibodies.

RESULTS

Twenty patients were included, 3 with systemic lupus erythematosus (according to the American Rheumatism Association criteria). Arterial or venous thrombosis occurred in 9 and 16 respectively, including exceptional cases of cerebral phlebitis and thrombosis of dermal capillaries. High blood pressure was recorded in 8. Only 1 or 2 types of antiphospholipid antibodies were found in most patients. Anticardiolipin, a circulating anticoagulant and a false-positive Bordet-Wassermann reaction were found together in only 3 out of 16. In addition, the antibody level varied independently from the thrombotic events. There was no case with a clinical course from primary antiphospholipid syndrome to systemic erythromatosus lupus. The effect to treatment on occurrence of new thrombotic events was studied. Three patients suffered one or more haemorrhagic events during antivitamin K treatment.

CONCLUSION

It is difficult to establish a differentiation between primary antiphospholipid syndrome, systemic lupus erythematosus and lupus-like syndromes, and precise methods of identifying antiphospholipid antibodies should be further developed.