Novel pathogenic WHRN variant causing hearing loss in a moroccan family

OBJECTIVES

The most prevalent sensory disease in humans is deafness. A variety of genes have been linked to hearing loss, which can either be isolated (non-syndromic) or associated with lesions in other organs (syndromic). It has been discovered that WHRN variants are responsible for non-syndromic hearing loss and Usher syndrome type II.

METHODS AND RESULTS

Exome sequencing in a consanguineous Moroccan patient with severe hearing loss identified a single homozygous mutation c.619G > T; p.Ala207Ser in WHRN, encoding a cytoskeletal scaffold protein that binds membrane protein complexes to the cytoskeleton in ocular photoreceptors and ear hair cell stereocilia. Bioinformatics methods and molecular dynamic modeling were able to predict the pathogenic implications of this variation.

CONCLUSION

We used whole exome sequencing to find a homozygous WHRN gene variant in a Moroccan family. Numerous bioinformatics methods predict that this modification might result in a change in the WHRN protein's structure.

Homozygous Missense Variants in FOXI1 and TMPRSS3 Genes Associated with Non-syndromic Deafness in Moroccan Families

One of the most prevalent sensorineural disorders, autosomal recessive non-syndromic hearing loss (ARNSHL) which can affect all age groups, from the newborn (congenital) to the elderly (presbycusis). Important etiologic, phenotypic, and genotypic factors can cause deafness. So far, the high genetic variability that explains deafness makes molecular diagnosis challenging. In Morocco, the GJB2 gene is the primary cause of non-syndromic hereditary deafness, while the existence of a variant in the LRTOMT gene is the second cause of this condition. After excluding these two frequently occurring GJB2 and LRTOMT variants, whole-exome sequencing was carried out in two Moroccan consanguineous families with hearing loss. As a result, two novel variants in the TMPRSS3 (c.1078G>A, p. Ala 360Thr) and FOXI1 (c.6C>G, p. Ser 2Arg) genes have been discovered in deaf patients and the pathogenic effect has been anticipated by several bioinformatics and molecular modeling systems. For the first time, these variants are identified in the Moroccan population, showing the population heterogeneity and demonstrating the value of the WES in hearing loss diagnosis.

Genetic heterogeneity in GJB2, COL4A3, ATP6V1B1 and EDNRB variants detected among hearing impaired families in Morocco

BACKGROUND

Deafness is the most prevalent human sensorineural defect. It may occur as a result of an external auditory canal involvement, or a deficiency in the sound conduction mechanism, or an impairment of the cochlea, the cochlear nerve or central auditory perception. The genetic causes are the most common, as approximately 70% of hearing disorders are of hereditary origin, divided into two groups, syndromic (associated with other symptoms) and no syndromic (isolated deafness).

METHODS

A whole exome sequencing was performed to identify the genetic cause of hearing loss in six Moroccan families and Sanger sequencing was used to validate mutations in these genes.

THE RESULTS

The results of four out of the six families revealed four genetic variants in the genes GJB2, COL4A3, ATP6V1B1 and EDNRB responsible for non-syndromic and syndromic hearing loss. Multiple Bioinformatics programs and molecular modelling predicted the pathogenic effect of these mutations.

CONCLUSIONS

We identified in Moroccan deaf patients four homozygous mutations. These results show the importance of whole exome sequencing to identify pathogenic mutations in heterogeneous disorders with multiple genes responsible.

Omenn syndrome caused by a novel homozygous mutation in recombination activating gene 1

Omenn syndrome (OS) is a type of severe combined immunodeficiency (SCID) that is distinguished by, lymphadenopathy, hepatosplenomegaly, erythroderma, alopecia with normal to elevated T-cell counts, eosinophilia, and elevated serum IgE levels. Recombination activation gene (RAG) 1 or RAG2 mutations that result in partial V(D)J recombination activity are known to be the main cause of OS. Other genes (DCLRE1C, LIG4, IL7RA, common gamma chain, ADA, RMRP, and CHD7) have also been linked to OS, although with low frequency. Here, we report a two-month-old Moroccan girl from consanguineous marriage with chronic diarrhea, recurrent and opportunistic infections, failure to thrive, desquamative erythroderma, hepatosplenomegaly, and axillary lymphadenitis. The immunological assessment showed normal lymphocyte and NK cell counts but an absence of B cells, agammaglobulinemia contrasting with a high level of IgE. On the other hand, Sanger sequencing of RAG1 and RAG2 exon 2 regions revealed a new homozygous deleterious mutation in the RAG1 gene. This c.1184C > T mutation caused a change from Proline to Leucine at position 395 of the protein, leading to a partial loss of function. Early and rapid diagnosis of the disease may facilitate urgent life-saving treatment.

A Homozygous RAG1 Gene Mutation in a Case of Combined Immunodeficiency: Clinical, Molecular, and Computational Analysis

BACKGROUND

The recombination-activating gene 1 and 2 (RAG1/RAG2) proteins are essential to initiate the V(D)J recombination process, the result is a diverse repertoire of antigen receptor genes and the establishment of the adaptive immunity. RAG1 mutations can lead to multiple forms of combined immunodeficiency.

METHODS

In this report, whole exome sequencing was performed in a Moroccan child suffering from combined immunodeficiency, with T and B lymphopenia, autoimmune hemolytic anemia, and cytomegalovirus (CMV) infection.

RESULTS

After filtering data and Sanger sequencing validation, one homozygous mutation c.2446G>A (p.Gly816Arg) was identified in the RAG1 gene.

CONCLUSION

This finding expands the spectrum of immunological and genetic profiles linked to RAG1 mutation, it also illustrates the necessity to consider RAG1 immunodeficiency in the presence of autoimmune hemolytic anemia and CMV infection, even assuming the immunological phenotype appears more or less normal.

Safe practice guidance: a review for otorhinolaryngologists during COVID-19 pandemic and after reopen process

COVID-19’s rapid sweep across the world has caused an extraordinary disruption to the otorhinolaryngology (ORL) profession and its subspecialties including the rhinology section. The present pandemic forced our specialty practitioners to make quick clinical and practice management decisions. Staff safety must receive the highest prioritization along with strategies to provide the highest quality care. The purpose of the present manuscript is to provide a narrative review of the current knowledge and committee practices regarding ORL (including rhinology) professionals' safe practice during COVID-19 pandemic and after reopen process. The present review findings will allow the clinical practitioners to understand the factors involved in reducing the risk of transmission of COVID-19 in the ORL and rhinology settings, personal protective equipment (PPE) for different ORL and rhinology practices and criteria of practice in outpatient clinic (OPC), emergency operations and ORL surgeries. The emerging evidence based on COVID-19 is rapidly changing. Further updates may be needed to this review as new details or evidence emerge. ORL including rhinology doctors should consider the specific conditions of each individual place of work and comply with all applicable legislations.

Association of CD209L tandem repeats polymorphism with susceptibility to human immunodeficiency virus-1 infection, disease progression, and treatment outcomes: a Moroccan cohort study

In order to investigate the association between length variation of the CD209L neck region and human immunodeficiency virus (HIV)-1 susceptibility, disease progression, and treatment response outcomes, we genotyped 139 HIV-1-seropositive and 109 seronegative individuals. The heterozygous genotype 6/5 showed a significant increased risk of HIV-1 infection (OR 3.03, 95% CI 0.99-9.33, p 0.046). Moreover, after highly active antiretroviral therapy (HAART), HIV-1-seropositive individuals carrying the 6/5, 7/5 and 7/7 genotypes and alleles 5, 6 and 7 showed good CD4(+) T-cell recovery. In addition, individuals with the 7/5, 6/6 and 7/7 genotypes showed a significant decrease in viral load during the treatment period as compared with baseline (p < 0.05). Interestingly, we found that alleles 4 and 6 were associated with protection against AIDS progression. D209L variation may influence susceptibility to HIV-1, response to treatment, and disease progression.

[Rare primary chest wall sarcoma: the synovialosarcoma]

INTRODUCTION

Malignant primary tumours occurring in the thorax encompass a large group of tumours which may arise from the lung, mediastinal structures, the pleura or the chest wall.

OBSERVATION

We report the case of a 37 year old patient, who presented with left sided chest pain. On clinical examination a right sided chest wall mass was identified. Chest X Ray showed a left sided upper mediastinal opacity, associated with a left sided pleural opacity. Thoracic CT scan revealed a large mass arising from the chest wall and infiltrating the mediastinum associated with a second chest wall mass at the level of the 8(th) and 9(th) right ribs. The biopsy of the chest wall mass revealed it to be a parietal synovialosarcoma. The patient responded to chemotherapy based on ifosfamid and doxorubicin as well as mediastino-pulmonary radiotherapy. There was an improvement in the patient's clinical and radiological state but the patient died by pulmonary embolism after the 3(rd) cause of treatment.

CONCLUSION

Chest wall synovialosarcoma has a poor prognosis, however, its chemosensitivity means that treatment may initially be effective.

[Neuropsychiatric side effects of antituberculosis agents]

Accurency of neurological or psychiatric complications secondary to the administration of antituberculosis may be at the origin of diagnosis and therapeutic problems. This work aims at studying the frequency of these manifestations, their clinical presentations and their therapeutic approach.

PATIENTS AND METHODS

This retrospective study was carried on from January 1990 to June 2008 at Ibn Nafis Pulmonary Department of Abderrahmen Mami Hospital in Ariana. It dealt with 18 in-patients with a neurologic or a psychiatric complication due to antituberculous drugs. Peripheral neuropathy was noted in 6 patients (33%). One of them had a history of chronic alcoolism, another one had a history of diabetes mellitus and 2 other patients were more than 72 years old. We had definitively stopped isoniazide in 2 cases and decreased the dosage in 4 other patients. However, all patients received B6 vitamin. Convulsions occured in 2 women without any history of epileptic status. Anticonvulsivant treatment was prescribed and isoniazid definitively stopped. Hallucinosis was noted in 4 patients, with one having a history of chronic alcoolism. Isoniazide was stopped in all cases. Agressivity, insomnia and memory problems were noted in 6 patients. Isoniazid was interrupted in only one woman who had history of depression. In 5 other patients, anxiolytics were prescribed. Isoniazide was incrimined in all cases and evolution was favorable for the 18 patients. A close monitoring of patients on antituberculous treatment is required to detect the onset of any neuropsychiatric complications incriminating usually isoniazid. Definitive interruption or decrease of the dose of isoniazid depending of the acetylation test were necessary.

[Effect of tobacco smoking on pulmonary tuberculosis]

Tobacco increases the risk of pulmonary infection, especially tuberculosis. We try by this study to analyse this action. It's a comparative study between two groups of patients hospitalized in our department between January 2006 and June 2008. The first group was made of 30 smokers patients hospitalized because of confirmed pulmonary tuberculosis. The second group consists of 30 non smokers patients and also hospitalized because of confirmed pulmonary tuberculosis. Delay of diagnosis was longer in the group of smokers (3, 1 +/- 3 months versus 2 +/- 1 month with p = 0.039). The most frequent symptoms in both groups were cough and loss of weight. The biological investigations showed a high level of white blood cells with predominance of neutrophil cells especially in smokers (p = 0.024). Chest X ray showed essentially nodules in both groups. These nodules were bilateral in smokers (P = 0.045). Evolution after antituberculosis treatment was favourable for all patients. A delay of recovery (time between symptoms and recovery) was longer in smokers than in non smoker patients (p = 0.043). Pulmonary Sequels such as dyspnoea (p = 0.016) and fibrosis (p = 0.041) were most frequent in smokers. No patients had tuberculosis relapse. Tobacco may delay the recovery of pulmonary tuberculosis and may induce pulmonary sequels in spite of correctly antituberculosis treatment.

Aided air conduction threshold as a predictor of cochlear reserve in otosclerosis patients

Otosclerosis classically presents with conductive deafness. However, mainly in older patients or those with a progressive (active) form of this disease, it presents with elevated bone conduction (BC) thresholds. In many cases, an elevation in the BC threshold during otosclerosis is not a true indicator of 'cochlear reserve' and this apparent loss can be corrected by surgery. It is generally accepted that in those patients, elevated BC thresholds are not due to pure sensorineural hearing loss but to the Carhart effect. Speech discrimination tests are routinely done, and the results of these tests determine if a patient is a good candidate for surgery. In most institutions, those with poor speech discrimination scores are considered to be poor candidates due to inadequate cochlear reserve. Using hearing-aid-assisted pure-tone audiometry, we developed an accurate method to identify suitable candidates for surgery among the patients with elevated BC thresholds. This method is meant to complement speech discrimination tests in predicting the success of surgery in those patients. Different variables render speech discrimination tests unreliable in many patients. The rationale behind the current study was the lack of an easy and accurate clinical method to determine if a patient has a good cochlear reserve, and to predict the postoperative hearing threshold outcome.

Multiple myeloma presenting with multiple thoracic manifestations

Multiple myeloma is a malignant proliferation of plasma cells that affects mainly bone marrow but may also involve other organs as well. We report thoracic involvement in the form of left-sided pleural effusion, osseous lesions, bronchial infiltration, and mediastinal lymphadenopathy in a 61-year-old woman, non-smoker presented with chest pain, dyspnoea, cough and deterioration in general health over the preceding seven months. Immunoelectrophoresis and immunofixation showed raised kappa-light chain immunoglobulin G (IgG) in serum and pleural fluid. Bronchial and pleural biopsies documented myelomatous infiltration and bone marrow aspirate revealed extensive plasma cell infiltration. At eight months, following the fourth cycle of melphalan, endoxan and prednisone based chemotherapy, the patient died.

The macrolide roxithromycin impairs NADPH oxidase activation and alters translocation of its cytosolic components to the neutrophil membrane in vitro

We have studied the interference of roxithromycin with NADPH oxidase, the key enzymatic system for oxidant production by human neutrophils. Roxithromycin alters the reconstitution of an active enzyme and impairs the translocation to the outer membrane of the cytosolic components p47-phox and p67-phox. Interestingly, in resting cells roxithromycin directly triggers the translocation of these factors without stimulating the oxidative burst.

Interaction of the new ketolide ABT-773 (cethromycin) with human polymorphonuclear neutrophils and the phagocytic cell line PLB-985 in vitro

A classical velocity centrifugation technique was used to study the in vitro uptake of the new ketolide ABT-773 by human polymorphonuclear neutrophils (PMNs) and a myelomonoblastic cell line, PLB-985, which can be differentiated into PMNs under certain culture conditions, compared to that of HMR 3004. ABT-773 was rapidly taken up by PMNs (cellular concentration to extracellular concentration ratio [C/E], about 34 at 30 s and up to 207 at 5 min), and uptake plateaued from 30 to 180 min (C/E, about 300). ABT-773 was accumulated significantly better than HMR 3004 from 5 to 180 min. Nondifferentiated PLB-985 cells (ND-PLB) accumulated significantly less ABT-773 and HMR 3004 than PMNs and PLB-985 cells differentiated into PMNs (D-PLB). Whatever the cell type and in contrast to the results obtained with HMR 3004, ABT-773 was mainly located in the cytosol (about 75%) and was rapidly released from loaded cells (about 40% at 5 min), followed by a plateau, likely owing to avid reuptake. Verapamil and H89, an inhibitor of protein kinase A, increased drug efflux. Uptake was sensitive to external pH, and the activation energy was moderate (about 50 kJ/mol). The existence of an active transport system on the PMN membrane was suggested by the following findings: concentration-dependent and saturable uptake (V(max), about 10,000 ng/2.5 x 10(6) PMNs/5 min; K(m), about 60 microg/ml) the inhibitory effects of PMN activators or inhibitors (phorbol myristate acetate, verapamil, Ni(2+)) and the significantly decreased levels of accumulation by killed cells and cells treated at low temperatures. In addition, various macrolides impaired ABT-773 uptake, contrary to the findings for the quinolone levofloxacin. ND- and D-PLB also presented saturation kinetics that defined an active transport system (V(max) and K(m) values were similar to those obtained with PMNs), but the activation pathway of the carrier system did not seem to be fully functional in ND-PLB. As has been observed with other erythromycin A derivatives, ABT-773 impaired oxidant production by phagocytes in a time- and concentration-dependent manner. These data extend our previous results on the existence of an active transport system common to all macrolides and ketolides, at least in PMNs.

Interaction of macrolides and ketolides with the phagocytic cell line PLB-985

Interactions between antibacterial agents and polymorphonuclear neutrophils (PMNs) are a major focus of investigation. Owing to the variable drug susceptibility of PMNs from different individuals, in vitro studies require samples from large panels of healthy volunteers to reach statistical significance. Here, we used a phagocytic cell line, PLB-985, which can differentiate into mature PMNs in vitro, for the study of cellular interactions (drug uptake and antioxidant effects) of two macrolides (azithromycin and roxithromycin) and four ketolides [HMR 3004, HMR 3647 (telithromycin), HMR 3562 and HMR 3787]. The oxidative burst of differentiated (D) cells was inhibited by macrolides and ketolides. IC50% values (concentrations impairing the oxidative burst by 50%), determined after 30 min of incubation, were as follows for azithromycin, roxithromycin, HMR 3004, telithromycin, HMR 3562 and HMR 3787, respectively: 40, 39, 15, 23, 26, and 33 mg/l (fMLP stimulation) and 37, 86, 39, 43, 14, and 31 mg/l (PMA stimulation). These values were similar to those obtained with PMNs. Uptake of the two macrolides was significantly lower in non-differentiated (ND) cells than in D cells and PMNs. The cellular/extracellular (C/E) concentration ratios at 60 min for PMNs, D and ND PLB were respectively 67, 25 and 11 (roxithromycin) and 159, 137 and 48 (azithromycin). Ketolide uptake by ND-PLB was also significantly lower than that obtained with PMNs (C/E ratios at 60 min were about 75 versus 265 (HMR 3004), 36 vs 230 (telithromycin), 75 vs 235 (HMR 3562) and 20 vs 130 (HMR 3787). Although the active carrier system seemed to be present in ND cells, its activation pathway was not functional. Thus, the PLB-985 cell line is a good in vitro model for studying drug-PMN interactions. The use of ND and D cells may shed light on the nature and activation pathways of macrolide transport systems present on the PMN membrane.

Effect of telithromycin (HMR 3647) on polymorphonuclear neutrophil killing of Staphylococcus aureus in comparison with roxithromycin

HMR 3647 (telithromycin), a new ketolide, is active on intracellular pathogens. It was previously demonstrated that it inhibits superoxide anion production in a time- and concentration-dependent manner, at concentrations which inhibit 50% of the control response of about 55 microg/ml (5 min) to 30 microg/ml (30 min); these values are similar to those obtained with roxithromycin, a classical erythromycin A derivative. Here we investigated whether these drugs modified the bactericidal activity of human polymorphonuclear neutrophils (PMN) on four strains of Staphylococcus aureus with different profiles of susceptibility to macrolides and ketolides. We found that the main factor involved in killing was the antibacterial potency of the drugs, although combinations of antibiotics with PMN were slightly more active than each component used alone against two of the four strains. In addition, high concentrations of the drugs, which impaired the PMN oxidative burst, did not impair PMN bactericidal activity. Likewise, some cytokines which enhance PMN oxidative metabolism did not modify PMN bactericidal activity in the presence or absence of macrolides or ketolides. These data suggest that oxygen-independent mechanisms contribute to the bactericidal activity of PMN on these strains of S. aureus. Both live and/or heat-killed bacteria impaired the uptake of telithromycin and roxithromycin (but not that of levofloxacin, a quinolone) in a concentration-dependent manner, owing to a modulation of PMN transductional systems involved in the activation of the macrolide carrier.

Structure-activity relationships among 9-N-alkyl derivatives of erythromycylamine and their effect on the oxidative burst of human neutrophils in vitro

Macrolide antibiotics have recently triggered much interest owing to the immunomodulatory potential of some derivatives, particularly in the field of inflammatory diseases. Among the possible mechanisms underlying these anti-inflammatory effects, macrolide-induced inhibition of oxidant production by phagocytes has attracted much attention. We and others have previously reported that erythromycin A-derived macrolides impair the phagocyte oxidative burst, a property linked to the presence of L-cladinose. However, we have also demonstrated that other substituents can be involved in the modulation of phagocyte function. Here we have extended the analysis of structure-activity relationships by studying the effects of five 9-N-alkyl derivatives of erythromycylamine on oxidant production by human neutrophils in vitro. LY211397 (2-methoxyethyl derivative) neither altered cell viability nor superoxide anion production. LY281389 (n-propyl derivative) did not alter cell viability and was slightly more inhibitory than erythromycylamine for the production of superoxide anion; its IC50 (concentration that inhibits 50% of the neutrophil response) was about 18 and 24 microM (versus 72 and 74 pM for erythromycylamine) after 60 min of incubation following fMLP and PMA stimulation, respectively. LY80576 (N-phenyl-3-indolylmethyl derivative), LY281981 (3-phenyl-n-propyl derivative) and LY57843 (benzyl derivative) all displayed cellular toxicity at high pharmacological concentrations after 30 to 60 min of incubation. Interestingly, these latter three drugs exhibited a rapid (5 min incubation) and strong inhibitory effect on the neutrophil oxidative burst from either stimulus, with IC50 values of 3 to 10 pM. Further in-vitro and in-vivo investigations are required to analyze the anti-inflammatory potential of these three derivatives.

Cellular uptake of two fluoroketolides, HMR 3562 and HMR 3787, by human polymorphonuclear neutrophils in vitro

We analyzed the cellular accumulation of two new fluoroketolides, HMR 3562 and HMR 3787, by human polymorphonuclear neutrophils (PMN) in vitro. Both compounds were rapidly taken up by PMN, with a cellular-to-extracellular concentration ratio (C/E) of about 141 (HMR 3562) and 117 (HMR 3787) at 5 min, and this was followed by a plateau at 60 to 180 min, with a C/E of >300 at 180 min. Both ketolides were mainly located in PMN granules (about 75%) and egressed slowly from loaded cells (about 40% at 60 min), owing to avid reuptake. Uptake was moderately sensitive to external pH, and activation energy was also moderate (about 70 kJ/mol). As with other macrolides and ketolides, the existence of an active transport system was suggested by (i) the strong interindividual variability in uptake kinetics, suggesting variability in the number or activity of a transport protein; (ii) the saturation kinetics characteristic of a carrier-mediated transport system (V(max), about 2,300 ng/2.5 x 10(6) PMN/5 min; K(m), about 50 microg/ml); (iii) the inhibitory effects of Ni(2+) (a blocker of the Na+-Ca(2+) exchanger), phorbol myristate acetate (a protein kinase C activator), and H89 (a protein kinase A inhibitor). Although these two ketolides are more related to HMR 3647 (telithromycin), it is interesting that the presence of a fluoride gave these molecules a cellular pharmacokinetics more like those of HMR 3004 than those of HMR 3647. The macrolide transport system has not been yet elucidated, but our data confirm that, despite variations in chemical structure, all erythromycin A derivatives share a transmembrane transport system.

Immunomodulation by macrolide antibiotics

Macrolide antibiotics are strongly concentrated within host cells, a property that sustains their activity against intracellular pathogens and is likely responsible for the modulation of cell metabolism and function. There is extensive literature on the subject of macrolide-induced modulation of immune responses. Erythromycin A derivatives seem to display anti-inflammatory activity in vitro, in some animal models and in various clinical settings such as diffuse panbronchiolitis (DPB). The underlying mechanisms are not yet fully understood: inflammatory cytokine and oxidant production by phagocytes is down-regulated by these drugs, but other possible targets include bacterial virulence factors, bronchial and epithelial cells, etc. Also, a link has been suggested between the macrolide transmembrane carrier system and the P-glycoprotein family, which comprises MDR (multiple drug resistance) and CFTR (cystic fibrosis transmembrane conductance regulator), which are respectively involved in the chemotherapeutic resistance of cancer cells and in the genesis of cystic fibrosis.

Erythromycin A-derived macrolides modify the functional activities of human neutrophils by altering the phospholipase D-phosphatidate phosphohydrolase transduction pathway: L-cladinose is involved both in alterations of neutrophil functions and modulation of this transductional pathway

All erythromycin A derivatives, irrespective of the size of the lactone ring and the nature of the substituent, inhibit oxidant production by neutrophils and promote their degranulation. We demonstrate in this study that the L-cladinose at position 3 of the lactone ring is a key structure in the modulation of these two neutrophil functions, suggesting that this sugar (alone or combined with a lactone structure) interferes with cell target(s) involved in both oxidant production and exocytosis. Taking roxithromycin as an example of erythromycin A derivatives, we also found that these molecules interfered with the phospholipase D (PLD)-phosphatidate phosphohydrolase pathway in two ways. In nonstimulated neutrophils, roxithromycin and all L-cladinose-bearing molecules activated PLD, as reflected by 1-O-[3H]alkyl-2-acyl-phosphatidyl-ethanol production. In addition, these drugs induced an accumulation of 1-O-[3H]alkyl-2-acyl-phosphatidic acid (PA), but not 1-O-[3H]alkyl-2-acylglycerol. PA accumulation seems to be involved in the induction of exocytosis by macrolides, as the roxithromycin-induced release of granular enzymes was impaired strongly in the presence of ethanol. By contrast, in stimulated neutrophils, roxithromycin inhibited PLD activity and totally impaired 1-O-[3H]alkyl-2-acylglycerol production. The inhibition of diglyceride production by roxithromycin (not its descladinosyl derivative) could explain its inhibitory effect on oxidant production. The relevance of our data to the clinical situation, particularly the anti-inflammatory activity of these drugs, requires further investigation.

Erythromycin A-derived macrolides modify the functional activities of human neutrophils by altering the phospholipase D-phosphatidate phosphohydrolase transduction pathway: L-cladinose is involved both in alterations of neutrophil functions and modulation of this transductional pathway

All erythromycin A derivatives, irrespective of the size of the lactone ring and the nature of the substituent, inhibit oxidant production by neutrophils and promote their degranulation. We demonstrate in this study that the L-cladinose at position 3 of the lactone ring is a key structure in the modulation of these two neutrophil functions, suggesting that this sugar (alone or combined with a lactone structure) interferes with cell target(s) involved in both oxidant production and exocytosis. Taking roxithromycin as an example of erythromycin A derivatives, we also found that these molecules interfered with the phospholipase D (PLD)-phosphatidate phosphohydrolase pathway in two ways. In nonstimulated neutrophils, roxithromycin and all L-cladinose-bearing molecules activated PLD, as reflected by 1-O-[3H]alkyl-2-acyl-phosphatidyl-ethanol production. In addition, these drugs induced an accumulation of 1-O-[3H]alkyl-2-acyl-phosphatidic acid (PA), but not 1-O-[3H]alkyl-2-acylglycerol. PA accumulation seems to be involved in the induction of exocytosis by macrolides, as the roxithromycin-induced release of granular enzymes was impaired strongly in the presence of ethanol. By contrast, in stimulated neutrophils, roxithromycin inhibited PLD activity and totally impaired 1-O-[3H]alkyl-2-acylglycerol production. The inhibition of diglyceride production by roxithromycin (not its descladinosyl derivative) could explain its inhibitory effect on oxidant production. The relevance of our data to the clinical situation, particularly the anti-inflammatory activity of these drugs, requires further investigation.

Cellular accumulation of the new ketolide RU 64004 by human neutrophils: comparison with that of azithromycin and roxithromycin

We analyzed the uptake of RU 64004 by human neutrophils (polymorphonuclear leukocytes [PMNs]) relative to those of azithromycin and roxithromycin. RU 64004 was strongly and rapidly accumulated by PMNs, with a cellular concentration/extracellular concentration ratio (C/E) of greater than 200 in the first 5 min, and this was followed by a plateau at 120 to 180 min, with a C/E of 461 +/- 14.8 (10 experiments) at 180 min. RU 64004 uptake was moderately sensitive to external pH, and activation energy was also moderate (63 +/- 3.8 kJ/mol). RU 64004 was mainly located in PMN granules (about 70%) and egressed slowly from loaded cells, owing to avid reuptake. The possibility that PMN uptake of RU 64004 and other macrolides occurs through a carrier-mediated system was suggested by three key results. First, there existed a strong interindividual variability in uptake kinetics, suggesting variability in the numbers or activity of a transport protein. Second, macrolide uptake displayed saturation kinetics characteristic of that of a carrier-mediated transport system: RU 64004 had the highest Vmax value (3,846 ng/2.5 x 10(6) PMNs/5 min) and the lowest Km value (about 28 microM), indicating a high affinity for the transporter. Third, as observed previously with other erythromycin A derivatives, Ni2+ (a blocker of the Na+/Ca2+ exchanger which mediates Ca2+ influx in resting neutrophils) impaired RU 64004 uptake by PMNs, with a 50% inhibitory concentration of about 3.5 mM. In addition, we found that an active process is also involved in macrolide efflux, because verapamil significantly potentiated the release of all three macrolides tested. This effect of verapamil does not seem to be related to an inhibition of Ca2+ influx, because neither EGTA [ethylene glycol-bis (beta-aminoethyl ether)-N,N',N'-tetraacetic acid] nor Ni2+ modified macrolide efflux. The nature and characteristics of the entry- and efflux-mediating carrier systems are under investigation.

Comparison of various macrolides on stimulation of human neutrophil degranulation in vitro

Macrolide antibiotics are taken up and concentrated by host cells, particularly phagocytes, and are likely candidates to modify cell functions. In this study, we extended our previous work concerning the effect of three 14-membered-ring macrolides (dirithromycin, erythromycin and erythromycylamine) on human neutrophil exocytosis, and found that three other erythromycin A derivatives (roxithromycin, clarithromycin and the azalide, azithromycin) also triggered neutrophil degranulation in a time- and concentration-dependent manner. After 30 min of incubation, the correlation coefficients for concentration-dependence for roxithromycin were 0.885, 0.739 and 0.750 (P < 0.005) and for clarithromycin were 0.795, 0.599, 0.733 (P < 0.02), respectively, for lysozyme, beta-glucuronidase and lactoferrin release. Although the underlying mechanism was not elucidated, these and previous data suggest that intracellular accumulation is a prerequisite. Furthermore, comparison of the characteristics of macrolide-induced exocytosis with those of exocytosis triggered by the synthetic chemotactic stimulus FMLP suggested that different mechanisms are involved. In keeping with this possibility, we showed that combined treatment (macrolides plus FMLP) resulted in totally additive exocytosis of azurophilic but not specific granules. The clinical relevance of our data remains to be ascertained.

Role of extracellular calcium in in vitro uptake and intraphagocytic location of macrolides

We compared the uptakes and intracellular locations of four 14-membered-ring macrolides (roxithromycin, dirithromycin, erythromycin, and erythromycylamine) in human polymorphonuclear neutrophils (PMNs) in vitro. Intracellular location was assessed by cell fractionation and uptake kinetics in cytoplasts (granule-poor PMNs). Trapping of dirithromycin within PMN granules (up to 80% at 30 min) was significantly more marked than the intracellular trapping of the other drugs (erythromycylamine, 45% +/- 5.1%; erythromycin, 42% +/- 3.7%; roxithromycin, 35% +/- 3.0%). A new finding was that, in the absence of extracellular calcium, the uptakes of all of the macrolides by PMNs and cytoplasts were significantly impaired, by about 50% (PMN) and 90% (cytoplasts). Furthermore, inorganic Ca2+ channel blockers inhibited macrolide uptake in a concentration-dependent manner, with 50% inhibitory concentrations of 1.6 to 2.0 mM and 29 to 35 microM, respectively, for Ni2+ and La3+. The intracellular distributions of the drugs were unchanged in the presence of Ni2+ and La3+ and in Ca(2+)-free medium supplemented with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. The organic Ca2+ channel blocker nifedipine had no effect on macrolide uptake, whereas verapamil inhibited it in a time- and concentration-dependent manner. These data show the importance of extracellular Ca2+ in macrolide uptake by phagocytes and suggest a link with Ca2+ channels or a Ca2+ channel-operated mechanism.

Effects of dirithromycin and erythromycylamine on human neutrophil degranulation

Dirithromycin and, to a lesser extent, erythromycylamine and erythromycin directly induced the release of three intragranular enzymes (lysozyme, lactoferrin, and beta-glucuronidase) from unstimulated human neutrophils. Macrolide-induced enzyme release was dependent upon the incubation time (30 to 180 min) and drug concentration. Dirithromycin was the most effective. At 120 min, release of lysozyme, beta-glucuronidase, and lactoferrin by macrolide (100 micrograms/ml)-treated cells, expressed as a percentage of total enzyme content, was, respectively, 58% +/- 8.3%, 52% +/- 10.7%, and 35% +/- 5.1% (dirithromycin); 42% +/- 3.9%, 28% +/- 5.8%, and 10% +/- 2.2% (erythromycylamine); and 35% +/- 4.0%, 19% +/- 4.3%, and 10% +/- 5.2% (erythromycin) (mean +/- standard error of the mean of three to eight experiments). The lowest macrolide concentrations which induced significant enzyme release were 10, 100, and 25 micrograms/ml, respectively, for dirithromycin, erythromycylamine, and erythromycin. Furthermore, we obtained evidence of a link between the prodegranulation effects of dirithromycin and erythromycylamine and the intragranular location of these drugs. Indeed, cell-associated drug levels increased for up to 60 min and then plateaued and declined substantially. Increasing the pH from 7 to 9 resulted in a parallel increase in drug uptake and the prodegranulation effect. Finally, when macrolide-treated neutrophils were disrupted by sonication and centrifuged, a correlation was found between lysozyme and beta-glucuronidase activities (both granule markers) and pellet-associated macrolide levels. Taken together, our results suggest that dirithromycin and erythromycylamine concentrate within neutrophil granules and then induce degranulation.

Investigation of dirithromycin and erythromycylamine uptake by human neutrophils in vitro

Dirithromycin, a new semisynthetic 14-membered-ring macrolide was avidly concentrated by human neutrophils in a time- but not concentration-dependent manner with mean cellular/extracellular, concentration ratios (C/E) of 9 within the first 5 min and up to 47 at 120 min. Erythromycylamine, the hydrolysis product of dirithromycin, was concentrated significantly less by neutrophils, reaching C/E values of 4 and 19 (at 5 and 120 min). A point of interest was the interindividual variability in the antibiotic uptake kinetics; in particular, 7 out of 47 neutrophil samples from different healthy volunteers displayed very slow uptake of both drugs (C/E values at 30 min: dirithromycin, 5.8; erythromycylamine, 4.6). The reason(s) for this is unknown. The uptake of both drugs was decreased at acidic pH and increased at basic pH. Chloroquine, an antimalarial drug which is concentrated in and alkalinizes azurophilic granules, reduced uptake by half. Metabolic inhibitors (2-4 dinitrophenol, sodium fluoride, potassium cyanide and sodium azide) did not impair the uptake of either drug but, interestingly, ouabain, an inhibitor of membrane Na+/K+ ATPase activity, impaired uptake by about 30%. Competitive inhibitors of some transport systems identified on neutrophil membrane (nucleosides, D-glucose and various aminoacids) did not alter the uptake of either drug. Dirithromycin and to a lesser extent, erythromycylamine, reached intracellular concentrations much higher than those required to inhibit the growth of sensitive microorganisms. Although the mechanism of uptake is not clear, one interesting hypothesis involves trapping by protonation into acidic compartments of neutrophils.

Cefdinir (CI-983), a new oral amino-2-thiazolyl cephalosporin, inhibits human neutrophil myeloperoxidase in the extracellular medium but not the phagolysosome

Cefdinir, a new oral 2-amino-5-thiazolyl cephalosporin, inhibited the luminol-amplified chemiluminescence (LACL) response of human neutrophils stimulated by PMA but not opsonized zymosan, in a concentration-dependent but not time-dependent manner. The LACL response to opsonized zymosan in cytochalasin B-treated neutrophils was, however, inhibited by cefdinir. Various cephalosporins, regardless of the presence of a 2-amino-5-thiazolyl moiety, did not significantly alter the neutrophil LACL response triggered by PMA and zymosan. The LACL response induced by the calcium ionophore A23187 and FMLP was also impaired by cefdinir, and this impairment was increased in cytochalasin B-treated neutrophils. Superoxide anion generation by neutrophils, measured in terms of lucigenin-amplified chemiluminescence and cytochrome c reduction, was not altered. Spontaneous and FMLP-induced neutrophil degranulation, assessed by lysozyme and beta-glucuronidase release, were not modified by cefdinir. Furthermore, cefdinir inhibited LACL generation in cell-free systems consisting of H2O2, NaI, and either horseradish peroxidase or a myeloperoxidase-containing neutrophil extract. Orthodianisidine oxidation in these two acellular systems was inhibited by cefdinir. Cefdinir did not alter neutrophil bacterial killing at concentrations that inhibited myeloperoxidase-containing neutrophil extract-dependent reactions induced by soluble stimuli. Taken together, these data strongly suggest that cefdinir directly inhibits the activity of myeloperoxidase-containing neutrophil extract released into the extracellular medium during neutrophil stimulation by soluble mediators, but has no effect on that released into the phagolysosome during phagocytosis. This unusual property of a member of the beta-lactam family could be of interest in modulating the exaggerated inflammatory process often associated with infectious diseases.

Cefdinir (CI-983), a new oral amino-2-thiazolyl cephalosporin, inhibits human neutrophil myeloperoxidase in the extracellular medium but not the phagolysosome

Cefdinir, a new oral 2-amino-5-thiazolyl cephalosporin, inhibited the luminol-amplified chemiluminescence (LACL) response of human neutrophils stimulated by PMA but not opsonized zymosan, in a concentration-dependent but not time-dependent manner. The LACL response to opsonized zymosan in cytochalasin B-treated neutrophils was, however, inhibited by cefdinir. Various cephalosporins, regardless of the presence of a 2-amino-5-thiazolyl moiety, did not significantly alter the neutrophil LACL response triggered by PMA and zymosan. The LACL response induced by the calcium ionophore A23187 and FMLP was also impaired by cefdinir, and this impairment was increased in cytochalasin B-treated neutrophils. Superoxide anion generation by neutrophils, measured in terms of lucigenin-amplified chemiluminescence and cytochrome c reduction, was not altered. Spontaneous and FMLP-induced neutrophil degranulation, assessed by lysozyme and beta-glucuronidase release, were not modified by cefdinir. Furthermore, cefdinir inhibited LACL generation in cell-free systems consisting of H2O2, NaI, and either horseradish peroxidase or a myeloperoxidase-containing neutrophil extract. Orthodianisidine oxidation in these two acellular systems was inhibited by cefdinir. Cefdinir did not alter neutrophil bacterial killing at concentrations that inhibited myeloperoxidase-containing neutrophil extract-dependent reactions induced by soluble stimuli. Taken together, these data strongly suggest that cefdinir directly inhibits the activity of myeloperoxidase-containing neutrophil extract released into the extracellular medium during neutrophil stimulation by soluble mediators, but has no effect on that released into the phagolysosome during phagocytosis. This unusual property of a member of the beta-lactam family could be of interest in modulating the exaggerated inflammatory process often associated with infectious diseases.

Modulation of human polymorphonuclear neutrophil function by macrolides: preliminary data concerning dirithromycin

Polymorphonuclear neutrophils (PMN) play a prominent role in the host response to infectious diseases. One major bactericidal mechanism used by these cells is the production of reactive oxygen species during what is referred to as the oxidative burst. However, excessive oxidant generation can also be involved in cell and tissue damage associated with severe inflammatory reactions. Macrolide antibiotics are able to penetrate and concentrate within phagocytes and have been successfully used to treat infections due to facultative intracellular pathogens. However, intracellular accumulation of macrolides with possible alkalinization of cellular compartments may interfere with normal cell function. In-vitro and ex-vivo data suggest that macrolides affect various phagocytic functions. This paper presents an overview of the published data concerning the modulation of neutrophil function by macrolides. Preliminary data concerning the in-vitro modulation of the neutrophil oxidative burst by dirithromycin and its metabolite, erythromycylamine, are also discussed.

Early immunological prediction of renal allograft rejection

Reliable predictors of impending renal allograft rejection would be valuable for better patient management. To date, no available test has been shown to be consistently predictive and results have often been conflicting. We evaluated an effector of cell-mediated immunity, antibody-dependent cell-mediated cytotoxicity (ADCC) as well as the response of these cells to different biological response modifiers (BRM) in patients following renal allograft transplantation. The in vitro test used assayed monocytes as ADCC effector cells against antibody-sensitized chicken red blood cells. The effects of BRM were studied by preincubating the monocytes with lymphoblastoid IFN, recombinant alpha 2-interferon or gamma-interferon. A follow-up study was performed on 47 patients with end-stage renal disease treated with renal allograft transplantation. ADCC activity and its response to BRM were assayed prior to transplantation, 2, 4, and 9 weeks post transplantation. In the case of rejection, ADCC was then studied prior to initiation of antirejection therapy and for 2 months following treatment of rejection episode. We noted that in patients with stable grafts, the ADCC activity as well as its response to BRM declined gradually during the first 2 weeks post grafting and remained decreased up to 3 months after transplantation. In contrast, in recipients who experienced rejection episodes there was a sustained and significant increase in ADCC response to BRM during the first 3 weeks post grafting. By the time the diagnosis of rejection had been established the baseline ADCC activity had also increased. Following treatment and stabilization of the graft, ADCC activity and its response to BRM was decreased, similar to that in patients with stable grafts.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunological monitoring and early prediction of rejection in renal allograft recipients

Graft rejection remains the major problem complicating renal allograft transplantation. A reliable posttransplant predictor of impending rejection will be valuable to help maintain better graft function. We monitored 47 patients with end-stage renal disease treated by renal allograft starting 1 day pretransplantation and continuing for up to 90 days postgrafting. Peripheral blood mononuclear cells (PBMC) from both patients and 71 healthy subjects were compared for: (1) DNA synthesis in T and B lymphocytes in response to mitogens; (2) interleukin-2 (IL-2) production; (3) natural killer (NK) and antibody-dependent cell-mediated cytotoxic (ADCC) activities; (4) induced augmentation of NK and ADCC activities by the biological response modifiers (BRM), lymphoblastoid interferon, recombinant alpha-2-interferon, gamma-interferon and recombinant IL-2. During the 2 weeks preceding rejection we found lower than normal levels of IL-2 production (p less than 0.0005) and DNA synthesis (p less than 0.01) in concanavalin A-stimulated PBMC. IL-2 yield reached its lowest level on the day of rejection and increased sharply the following week after antirejection therapy was started. Mitogen-stimulated DNA synthesis rose in parallel with increasing levels of IL-2 production. Both NK and ADCC activities increased during rejection (p less than 0.05). The ADCC response to BRM activation measured during the first 2 weeks postgrafting was found to correlate with the stability of the graft. Recipients whose graft function remained stable had a minimal ADCC response to BRM.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell-mediated immunity and biological response modifiers in insulin-dependent diabetes mellitus complicated by end-stage renal disease

Previous studies have shown several immunoregulatory abnormalities in insulin-dependent diabetes mellitus (IDDM). In this report we compared peripheral blood mononuclear cells (PBMC) from patients with IDDM complicated by end-stage renal disease (ESRD) to those from normal subjects and from patients with ESRD of different etiologies for their: natural killer (NK) and antibody-dependent cell-mediated cytotoxic (ADCC) activities; modulation of NK and ADCC activities by biological response modifiers (BRM) including purified human lymphoblastoid interferon, human recombinant alpha-2 interferon, human gamma interferon and human recombinant interleukin 2; proliferative response of T and B lymphocytes to concanavalin A (Con A), phytohemagglutinin and pokeweed mitogen, and ability to produce T-cell growth factor (interleukin 2; IL-2). PBMC of diabetic patients demonstrated significantly lower NK activity than normal and ESRD subjects. Upon treatment with BRM, NK activity was augmented and achieved normal levels. ADCC activity was not different from that of normal controls and exhibited similar increases when stimulated by BRM. The proliferative responses to Con A, phytohemagglutinin and pokeweed mitogen as well as IL-2 production in response to Con A stimulation were significantly lower in the IDDM group. Our results indicated that NK cells from patients with IDDM can respond to IL-2 with enhanced cytotoxicity, and, because activation of resting T cells by mitogenic stimuli depends on the production of IL-2 as well as the appearance of a receptor for IL-2, our finding of low levels of in vitro IL-2 production by PBMC from patients with IDDM may explain the depressed NK activity and the observed poor response to T-cell mitogens.