Frequencies of VKORC1-1639G>A and rs397509427 in Patients on Warfarin and Healthy Syrian Subjects.

Background: Vitamin K epoxide reductase complex subunit 1 (VKORC1) gene encodes a key enzyme with multiple cellular activities, namely, the reduction of vitamin K to its active form. VKORC1-1639G>A (rs9923231) is a common single nucleotide polymorphism with a crucial impact on warfarin dosing and possibly other physiological functions. This study aimed at investigating the frequencies of VKORC1-1639G>A alleles and genotypes in Syrian healthy subjects and patients on warfarin for different indications. Methods: A total of 138 individuals were enrolled in this cross-sectional study. Genomic DNA was extracted from both patients on warfarin and healthy subjects, and polymerase chain reaction (PCR) specific amplicons were genotyped via standard sequencing which also allowed the detection of rs397509427. Comparisons of -1639G>A frequency with other populations were drawn. Results: Of 94 patients on warfarin, 53 (56.38%) were with idiopathic venous thromboembolism (VTE). Despite comparable frequencies of the -1639A allele (47% and 50%), the AA and GA genotypes were at disparate frequencies of 93.2% versus 79.8% in the healthy subjects (n = 44) versus patients on warfarin, respectively. Carriers of the GG genotype were at a four-fold increased risk of VTE in comparison with those of the AA and GA genotypes (odds ratio (OR) = 4, 95% CI = 1.105 - 13.6, P = 0.0469). All study subjects were wild-type for the rs397509427 variant. Conclusions: Our results prove a high -1639A prevalence in Syrian healthy subjects and patients on warfarin at frequencies comparable to other Mediterranean and Middle Eastern populations. The A allele carriers are at a lower VTE risk, whereas a global prevalence gradient of the G allele is suggested to be associated with VTE risk.

Prevalence and Management of Transfusional Iron Overload in Syrian Beta Thalassemia Major Patients Pre and during the Syrian Conflict.

Objectives: The primary aim of this study was to evaluate the prevalence of iron overload and the real-world clinical effectiveness of the iron chelation therapies (ICTs) in Syrian patients with transfusion-dependent beta thalassemia major (BTM) prior to and during the ongoing Syrian conflict. Methods: This single-center, two-stage observational study was conducted at Homs National Thalassemia Center (HNTC) prior to (2009) and during (2019) the armed conflict. The prevalence and the severity of iron overload, as well as the effectiveness of four iron chelation regimens, were assessed using serum ferritin (SF) concentrations as a means of monitoring in two cohorts of BTM patients receiving deferoxamine (DFO), deferiprone (DFP), deferasirox (DFX), or a combination of DFO and DFP therapy in both years. Statistical analyses encompassed one-way ANOVA, Kruskal-Wallis, Mann-Whitney U, and chi-square (χ2) tests for the comparisons of the variables and the frequencies between the two cohorts and subgroups. Results: We included all eligible BTM patients at HNTC in 2009 (n = 205) and 2019 (n = 172). Only 84 patients from the 2009 cohort were accessible in 2019. Our findings revealed that 98% and 89% of the patients had iron overload (SF ≥ 1500 ng/mL) and comparable elevated median SF concentrations (3868 and 3757 ng/mL) in 2009 and 2019, respectively (P = 0.275). Furthermore, patients on DFO demonstrated the poorest control of iron overload and the highest SF concentrations (4319 and 5586 ng/mL), whereas those on DFX achieved superior outcomes and the lowest SF concentrations (3355 and 2152 ng/mL) in both years. Twenty-six patients from the 2019 cohort received no ICT for six years (from 2012 to 2018) and experienced extremely severe iron overload with SF levels ranging between 4481 and 16,000 ng/mL. Conclusions: Our findings prove a high prevalence of iron overload and suboptimal chelation outcomes in Syrian BTM patients, both prior to and during the ongoing armed conflict, despite the provision of free ICTs at HNTC. Poor adherence and older age of patients may explain the unfavorable outcomes of DFO and (DFO+DFP) regimens, whereas younger age and higher socioeconomic status may have contributed to the lowest SF and superior outcomes in patients on DFX. This study also demonstrates the crucial role of the National Thalassemia Centers, namely HNTC, in providing health services to BTM patients in times of peace and conflict.

Seroprevalence and trends of hepatitis B virus, hepatitis C virus and human immunodeficiency virus in Syrian blood donors at Damascus University Blood Center between 2004 and 2021.

Introduction: Seroprevalence of transfusion-transmitted viral infections (TTVIs) is a valuable indicator for assessing blood safety, population health and health system performance in the times of peace and conflicts. Only scarce information is available on the impact of the decade-long violent conflict on the prevalence of TTVIs in Syria. Moreover, hepatitis B vaccine was introduced to the national vaccination program in 1993; however, no data is available on the vaccine effectiveness. Methods: In this retrospective cross-sectional study, we compiled the screening results for major TTVIs, namely hepatitis B virus (HBV), hepatitis C virus (HCV), and human immuno-deficiency virus (HIV), of volunteer donors at Damascus University Blood Center from May 2004 to October 2021. Prevalence was expressed in percentages for the entire study group and subgroups. Chi-square test and linear regression were used to examine the differences and describe trends in prevalence, respectively, based on demographic characteristics (i.e., age and gender) and time. P-value of <0.005 was considered statistically significant. Results: Of the total 307,774 donors (82.27% males, median age 27 years), 5,929 (1.93%) had serological evidence of at least one TTVI, and 26 (0.0085%) had multiple infections. The lowest prevalence (1.09%) was detected in donors aged 18-25 years old, and a higher prevalence (2.05%) was evident in males in comparison with females (1.38%). The seroprevalence of HBV, HCV, and HIV was 1.18, 0.52, and 0.23%, respectively. Trend analyses revealed a significant regression in HBV and HIV prevalence from 2011 to 2021. HBV seropositivity depicted a temporal decline by ~80%, from 0.79% in 2011 to 0.16% in 2021 in those born in 1993 and thereafter. Discussion: The seroprevalence of HBV, HIV, and to a lesser extent HCV dropped over the study 18-year period. Possible explanations may include implementation of the HBV vaccine, robust national health system, conservative sociocultural values, and isolation.

The frequencies of CYP2D6 alleles and their impact on clinical outcomes of adjuvant tamoxifen therapy in Syrian breast cancer patients.

BACKGROUND: Tamoxifen is one of the fundamental pillars of adjuvant endocrine therapy for hormone receptor-positive breast cancer; however, 30-50% of patients receiving tamoxifen experience tumor relapse. CYP2D6, encoded by an extremely polymorphic CYP2D6 gene, is the rate-limiting enzyme of tamoxifen bioactivation. This study aimed at determining the frequencies of the most clinically relevant CYP2D6 alleles and evaluating their impact on the responsiveness to tamoxifen in a cohort of Syrian breast cancer patients. METHODS: This case-control study encompassed positive estrogen and/or progesterone receptor, stage 1-3 breast cancer female patients receiving tamoxifen at Al-Bairouni University Hospital, the major National Oncology Center in Syria. Successfully genotyped eligible patients (n = 97) were classified according to their response into; no recurrence group (n = 39) who had completed a five-year recurrence-free adjuvant tamoxifen therapy, and recurrence group (n = 58) who had experienced recurrence. Several star alleles including CYP2D6*4, CYP2D6*10, CYP2D6*41, and CYP2D6*69 were identified via targeted sequencing of specific polymerase chain reaction (PCR) products and phenotypes were assigned according to activity score (AS). The correlation between genotypes and disease-free survival (DFS) was assessed using Kaplan-Meier method and log-rank test. Hazard ratios were estimated using Cox proportional hazards regression models. RESULTS: The allelic frequencies of CYP2D6*41, CYP2D6*10, CYP2D6*4, and CYP2D6*69 were found to be 9.28%, 7.22%, 7.22%, and 2.58%, respectively. No statistically significant differences were observed in the frequencies of CYP2D6 phenotypes between the two arms (P = 0.24), nor the incidence of tamoxifen-induced hot flashes (P = 0.109). Poor metabolizers (PMs) tended to display shorter DFS than intermediate metabolizers (IMs) and normal metabolizers (NMs) combined (adjusted HR = 2.34, 95% CI = 0.84-6.55, P = 0.104). Notably, patients homozygous for the null CYP2D6*4 allele (1847A/A) had an elevated risk of disease recurrence compared to patients with 1847G/G genotype (adjusted HR = 5.23, 95% CI = 1.22-22.49, P = 0.026). CONCLUSIONS: Our findings show no association between CYP2D6 phenotype and treatment outcomes of tamoxifen in Syrian breast cancer patients. Nevertheless, a worse DFS was revealed in patients with 1847A/A genotype (*4/*4).

Hyper-responsiveness to warfarin in a young patient with the VKORC1 -1639GA/CYP2C9*1*46 genotype: a case report.

BACKGROUND: Warfarin is the most widely used oral anticoagulant; nevertheless, dosing of warfarin is problematic for clinicians worldwide. Inter-individual variability in response to warfarin is attributed to genetic as well as non-genetic factors. Pharmacogenomics studies have identified variants in CYP2C9 and VKORC1 genes as significant predictors of warfarin dose, however, phenotypes of rare variants are not well characterized. CASE PRESENTATION: We report a case of hyper-responsiveness to warfarin in a 22-year-old outpatient with Crohn's disease who presented with a swollen, red, and painful left calf. Deep venous thrombosis (DVT) in the left lower extremity was confirmed via ultrasonography, and hence, anticoagulation therapy of heparin and concomitant warfarin was initiated. Warfarin dose of 7.5 mg/day was estimated by the physician based on clinical factors. Higher than the expected international normalized ratio (INR) value of 4.5 necessitated the reduction of the warfarin dose to 5 and eventually to 2.5 mg/day to reach a therapeutic INR value of 2.6. Pharmacogenetic profiling of the VKORC1 -1639G > A and CYP2C9 *2, *3, *4, *5, *8, *14, *20, *24, *26, *33, *40, *41, *42, *43, *45, *46, *55, *62, *63, *66, *68, *72, *73 and *78 revealed a VKORC1-1639GA/CYP2C9*1*46 genotype. The lower catalytic activity of the CYP2C9*46 (A149T) variant was previously reported in in vitro settings. CONCLUSIONS: This is the first report on a case of warfarin hyper-responsive phenotype of a patient with the heterozygous CYP2C9*1*46 polymorphism.

Frequencies of CYP2D6 genetic polymorphisms in Arab populations.

CYP2D6 is a key drug-metabolizing enzyme implicated in the biotransformation of approximately 25% of currently prescribed drugs. Interindividual and interethnic differences in CYP2D6 enzymatic activity, and hence variability in substrate drug efficacy and safety, are attributed to a highly polymorphic corresponding gene. This study aims at reviewing the frequencies of the most clinically relevant CYP2D6 alleles in the Arabs countries. Articles published before May 2021 that reported CYP2D6 genotype and allelic frequencies in the Arab populations of the Middle East and North Africa (MENA) region were retrieved from PubMed and Google Scholar databases. This review included 15 original articles encompassing 2737 individuals from 11 countries of the 22 members of the League of Arab States. Active CYP2D6 gene duplications reached the highest frequencies of 28.3% and 10.4% in Algeria and Saudi Arabia, respectively, and lowest in Egypt (2.41%) and Palestine (4.9%). Frequencies of the loss-of-function allele CYP2D6*4 ranged from 3.5% in Saudi Arabia to 18.8% in Egypt. The disparity in frequencies of the reduced-function CYP2D6*10 allele was perceptible, with the highest frequency reported in Jordan (14.8%) and the lowest in neighboring Palestine (2%), and in Algeria (0%). The reduced-function allele CYP2D6*41 was more prevalent in the Arabian Peninsula countries; Saudi Arabia (18.4%) and the United Arab Emirates (15.2%), in comparison with the Northern Arab-Levantine Syria (9.7%) and Algeria (8.3%). Our study demonstrates heterogeneity of CYP2D6 alleles among Arab populations. The incongruities of the frequencies of alleles in neighboring countries with similar demographic composition emphasize the necessity for harmonizing criteria of genotype assignment and conducting comprehensive studies on larger MENA Arab populations to determine their CYP2D6 allelic makeup and improve therapeutic outcomes of CYP2D6- metabolized drugs.

A Prospective, Randomized, Placebo-Controlled Study of a Combination of Simvastatin and Chemotherapy in Metastatic Breast Cancer.

Preclinical studies support the anticancer activity of statins; however, the existing clinical evidence is inconsistent and not definitive. Our study aimed at evaluating a postulated cancer chemo-sensitizing effect of statin (simvastatin) in a cohort of metastatic breast cancer (MBC) patients. We designed a prospective, single-centered, randomized, double blinded, placebo-controlled trial that encompassed MBC patients with an ECOG Performance Status Scale ≤2 and scheduled to be treated with a chemotherapy regimen consisting of carboplatin and vinorelbine every 3 weeks at Al-Baironi Hospital, Damascus, Syria. Patients were enrolled between August 2011 and July 2012 and randomly allocated to receive a 15-day course of either simvastatin (40 mg) or placebo seven days prior to the first day of each chemotherapy cycle and then continued for eight days in each individual cycle. Primary endpoints were objective response rate (ORR) and toxicity, and the secondary endpoint was overall survival (OS). Eighty-two patients met the inclusion criteria and consented. ORR (35% vs. 32.5%) and predominant toxicity and grade ≥3 neutropenia (occurred in 30% vs. 40% of the patients) were not significantly different between simvastatin and placebo groups, respectively. Over a median follow-up of 44 months (range, 10-60), median OS was 15 months in the simvastatin group and 17 the in placebo group (hazard ratio (HR) = 1.16, 95% CI (0.70-1.91), P=0.57). Elevated baseline values of high-sensitivity C-reactive protein (hsCRP >10 mg/l), lactate dehydrogenase (LDH >480 U/L), and chemotherapy being ≥2nd line were significantly associated with shorter OS for the total cohort in both Univariate and multivariate analyses. Our data prove a safe profile of simvastatin at 40 mg per day combined with carboplatin and vinorelbine in MBC patients but without any beneficial increase of tumor sensitivity to chemotherapy. Moreover, we demonstrated a strong clinical advantage of baseline values of hsCRP and LDH as useful prognostic tools in MBC patients. This trial is registered with ISRCTN12964275.

Prevalence, diagnosis, and management of iron deficiency and iron deficiency anemia among Syrian children in a major outpatient center in Damascus, Syria.

BACKGROUND: Given the public health significance of anemia, the long-term sequelae of iron deficiency anemia (IDA) on children, the expected effect of war on the trends of anemia in Syrian society, and the lack of assessment on the national burden of anemia and/or iron deficiency (ID) data, there is a vital need to investigate all-cause anemia, ID, and IDA in Syria during the crisis. OBJECTIVE: To investigate the prevalence of ID and IDA in Syrian children, the effectiveness of oral iron supplements in the management of ID, and the diagnostic effectiveness of conventional iron markers. METHODS: We conducted a retrospective study on hemoglobin (Hb) levels in 4-month-old to 14-year-old children and a prospective study on hematological (complete blood count, reticulocytes, and reticulocyte Hb content) and biochemical iron indices (serum ferritin, iron, and total iron-binding capacity) of infants visiting the primary care clinic at Children's Hospital in Damascus, Syria. RESULTS: Of the 1128 children in the retrospective study, 648 children (57%) were found to be anemic, with 417 (37%) moderately-severely anemic. The prevalence of ID and IDA in the 135 children of the prospective study was 71.85% and 55.55%, respectively. Infants with ID who underwent a 4-8-week course of oral iron supplementation demonstrated good responsiveness. Except mean corpuscular hemoglobin (MCH), conventional iron markers (i.e., ferritin) routinely used to assess iron status proved unreliable. CONCLUSION: This study reveals a high prevalence of anemia, ID, and IDA among a group of apparently healthy Syrian children. Our findings necessitate a framework of urgent public health interventions that can address two major limitations; the poor follow-up by the parents and unreliability of the conventional iron diagnostic markers. MCH may represent a simple and cheap ID screening index in children.

Small Molecule Catalysts with Therapeutic Potential.

Catalysts are employed in many areas of research and development where they combine high efficiency with often astonishing selectivity for their respective substrates. In biology, biocatalysts are omnipresent. Enzymes facilitate highly controlled, sophisticated cellular processes, such as metabolic conversions, sensing and signalling, and are prominent targets in drug development. In contrast, the therapeutic use of catalysts per se is still rather limited. Recent research has shown that small molecule catalytic agents able to modulate the redox state of the target cell bear considerable promise, particularly in the context of inflammatory and infectious diseases, stroke, ageing and even cancer. Rather than being "active" on their own in a more traditional sense, such agents develop their activity by initiating, promoting, enhancing or redirecting reactions between biomolecules already present in the cell, and their activity therefore depends critically on the predisposition of the target cell itself. Redox catalysts, for instance, preferably target cells with a distinct sensitivity towards changes in an already disturbed redox balance and/or increased levels of reactive oxygen species. Indeed, certain transition metal, chalcogen and quinone agents may activate an antioxidant response in normal cells whilst at the same time triggering apoptosis in cancer cells with a different pre-existing "biochemical redox signature" and closer to the internal redox threshold. In pharmacy, catalysts therefore stand out as promising lead structures, as sensor/effector agents which are highly effective, fairly selective, active in catalytic, i.e., often nanomolar concentrations and also very flexible in their structural design.

The impact of baseline body mass index on clinical outcomes in metastatic breast cancer: a prospective study.

OBJECTIVE: The prognostic value of body mass index (BMI) in metastatic breast cancer (MBC) has not been fully elucidated. In a prospective study to investigate the chemo-sensitizing effect of statins on clinical outcomes in MBC patients who were scheduled to receive palliative chemotherapy (Carboplatin and Vinorelbine), we sought to investigate the relationship between baseline BMI and clinical outcomes; response, overall survival (OS) and progression free survival (PFS), over a median follow-up of 40-months. RESULTS: Eighty-Two MBC patients were enrolled and categorized using baseline BMI as underweight (BMI, < 18.5 kg/m2, n = 1), normal-weight (BMI, 18.5-24.9 kg/m2, n = 20), overweight (BMI, 25-29.9 kg/m2, n = 34), and obese (BMI, ≥ 30 kg/m2, n = 27). Median OS was 10 months in normal/underweight, 19 months in overweight, and 16 months in obese (P = 0.083). Univariate Cox model revealed that overweight patients were significantly less likely to die of MBC as normal BMI patients (hazard ratio [HR] = 0.54, 95% confidence interval [CI], (0.29-0.98), P = 0.044). Similarly, multivariate Cox model, after adjusting for age, number of metastatic sites, chemotherapy line's grade, HER2 and hormone receptors status, confirmed longer survivorship of overweight in comparison with normal BMI patients (HR = 0.51, 95% CI (0.26-0.99), P = 0.047). Our data suggest that being overweight could improve OS in MBC patients.

Allergen Valency, Dose, and FcεRI Occupancy Set Thresholds for Secretory Responses to Pen a 1 and Motivate Design of Hypoallergens.

Ag-mediated crosslinking of IgE-FcεRI complexes activates mast cells and basophils, initiating the allergic response. Of 34 donors recruited having self-reported shrimp allergy, only 35% had significant levels of shrimp-specific IgE in serum and measurable basophil secretory responses to rPen a 1 (shrimp tropomyosin). We report that degranulation is linked to the number of FcεRI occupied with allergen-specific IgE, as well as the dose and valency of Pen a 1. Using clustered regularly interspaced palindromic repeat-based gene editing, human RBLrαKO cells were created that exclusively express the human FcεRIα subunit. Pen a 1-specific IgE was affinity purified from shrimp-positive plasma. Cells primed with a range of Pen a 1-specific IgE and challenged with Pen a 1 showed a bell-shaped dose response for secretion, with optimal Pen a 1 doses of 0.1-10 ng/ml. Mathematical modeling provided estimates of receptor aggregation kinetics based on FcεRI occupancy with IgE and allergen dose. Maximal degranulation was elicited when ∼2700 IgE-FcεRI complexes were occupied with specific IgE and challenged with Pen a 1 (IgE epitope valency of ≥8), although measurable responses were achieved when only a few hundred FcεRI were occupied. Prolonged periods of pepsin-mediated Pen a 1 proteolysis, which simulates gastric digestion, were required to diminish secretory responses. Recombinant fragments (60-79 aa), which together span the entire length of tropomyosin, were weak secretagogues. These fragments have reduced dimerization capacity, compete with intact Pen a 1 for binding to IgE-FcεRI complexes, and represent a starting point for the design of promising hypoallergens for immunotherapy.

Bone health and vitamin D status in young epilepsy patients on valproate monotherapy.

OBJECTIVE: To evaluate bone health and vitamin D adequacy in a cohort of epilepsy patients on chronic valproate (VPA) monotherapy. METHODS: Bone mineral density (BMD) using dual X-ray absorptiometry and serum concentrations of 25-hydroxyvitamin D, parathyroid hormone, calcium, phosphorus, and alkaline phosphatase were measured in 50 young adult epilepsy patients on VPA monotherapy and 50 age, sex and socioeconomically matched healthy subjects. RESULTS: Mean age of epilepsy patients was 26±7.2 (±SD) years, and females constituted 66%. Significantly lower mean lumbar spine and femoral neck BMDs (g/cm(2)) and lower femoral neck Z-score were observed in epilepsy patients in comparison with controls. Prevalence of low BMD (Z-score ≤-2.0) was 26% and 10% at lumbar spine, and 10% and 4% at femoral neck in epileptic and control groups respectively. No correlation was found between duration or dosage of VPA and BMDs. Vitamin D deficiency (≤20ng/ml) was highly prevalent (>90%) in epilepsy patients and controls. CONCLUSION: Chronic VPA therapy is associated with lower BMD measurements in young epilepsy patients. Hypovitaminosis D is highly prevalent in general population. PRACTICE IMPLICATIONS: Prophylactic and therapeutic strategies against osteoporosis should be implemented in VPA-treated patients. Routine evaluation for bone disease by measuring BMD and supplementation of calcium and vitamin D can allow effective treatment of epilepsy without bone adverse effects.

Roles for the High Affinity IgE Receptor, FcεRI, of Human Basophils in the Pathogenesis and Therapy of Allergic Asthma: Disease Promotion, Protection or Both?

The role of basophils, the rarest of blood granulocytes, in the pathophysiology of allergic asthma is still incompletely understood. Indirect evidence generated over many decades is consistent with a role for basophils in disease promotion. Recent improvements in procedures to purify and analyze very small numbers of human cells have generally supported this view, but have also revealed new complexities. This chapter focuses on our analyses of Fcε R1 function in basophils in the context of understanding and treating human allergic asthma. In long-term studies, we demonstrated that asthmatic subjects have higher circulating numbers of basophils than non-atopic non-asthmatic subjects and that their basophils show higher rates of both basal and anti-IgE or antigen-stimulated histamine release. These results hint at a direct role for basophils in promoting asthma. Supporting this interpretation, the non-releaser phenotype that we linked to the excessive proteolysis of Syk via the ubiquitin/proteasomal pathway is less common in basophils from asthmatic than non-asthmatic donors. The discovery of a basophil-specific pathway regulating Syk levels presents a clear opportunity for therapy. Another route to therapy was revealed by evidence that basophil FcεRI signaling can be downregulated by co-crosslinking the ITAM-containing IgE receptor, FcγRI, to the ITIM-containing IgG receptor, FcγRIIB. Based on this discovery, hybrid co-crosslinking fusion proteins are being engineered as potential therapies targeting basophils. A third distinguishing property of human basophils is their high dependence on IgE binding to stabilize membrane FcεRI. The circulating IgE scavenging mAb, Omalizumab, reduces FcεRI expression in basophils from asthmatics by over 95% and produces a substantial impairment of IL-4, IL-8 and IL-13 production in response to the crosslinking of residual cell surface IgE-FcεRI. A search for small molecule inhibitors that similarly impair high affinity IgE binding to basophils may yield reagents that mimic Omalizumab's therapeutic benefits without the potential for immune side effects. Although studies on allergen and FcεRI-mediated basophil activation all point to a role in promoting disease, a case can also be made for an alternative or additional role of basophil FcεRI in protection against allergic asthma. Human basophils have high affinities for IgE, they upregulate receptor levels over a >100-fold range as circulating IgE levels increase and they have short half-lives in the circulation. Thus, when allergen is absent, basophil FcεRI could serve as scavengers of serum IgE and therefore protectors against mast cell IgE-mediated inflammatory responses. Further studies are clearly needed to determine if FcεR-expressing basophils play pathogenic or protective roles - or both - in human allergic asthma and other IgE-mediated inflammatory disorders.

Histamine release from the basophils of control and asthmatic subjects and a comparison of gene expression between "releaser" and "nonreleaser" basophils.

Most human blood basophils respond to FcepsilonRI cross-linking by releasing histamine and other inflammatory mediators. Basophils that do not degranulate after anti-IgE challenge, known as "nonreleaser" basophils, characteristically have no or barely detectable levels of the Syk tyrosine kinase. The true incidence of the nonreleaser phenotype, its relationship (if any) to allergic asthma, and its molecular mechanism are not well understood. In this study, we report statistical analyses of degranulation assays performed in 68 control and 61 asthmatic subjects that establish higher basal and anti-IgE-stimulated basophil degranulation among the asthmatics. Remarkably, 28% of the control group and 13% of the asthmatic group were nonreleasers for all or part of our 4-year long study and cycling between the releaser and nonreleaser phenotypes occurred at least once in blood basophils from 8 (of 8) asthmatic and 16 (of 23) control donors. Microarray analysis showed that basal gene expression was generally lower in nonreleaser than releaser basophils. In releaser cells, FcepsilonRI cross-linking up-regulated >200 genes, including genes encoding receptors (the FcepsilonRI alpha and beta subunits, the histamine 4 receptor, the chemokine (C-C motif) receptor 1), signaling proteins (Lyn), chemokines (IL-8, RANTES, MIP-1alpha, and MIP-1beta) and transcription factors (early growth response-1, early growth response-3, and AP-1). FcepsilonRI cross-linking induced fewer, and quite distinct, transcriptional responses in nonreleaser cells. We conclude that "nonreleaser" and "cycler" basophils represent a distinct and reversible natural phenotype. Although histamine is more readily released from basophils isolated from asthmatics than controls, the presence of nonreleaser basophils does not rule out the diagnosis of asthma.

Proteasome-dependent regulation of Syk tyrosine kinase levels in human basophils.

BACKGROUND: In human basophils, FcepsilonRI signal initiation, leading to histamine release, relies on activation of Syk protein tyrosine kinase. Basophils from approximately 10% of unselected donors do not degranulate in response to FcepsilonRI cross-linking. Their unresponsiveness has been linked to the absence of Syk protein despite apparently normal levels of Syk mRNA. OBJECTIVE: The aim of this study was to explore pathways of Syk protein degradation as a possible posttranslational mechanism for downregulating Syk protein levels in human basophils and other leukocytes. METHODS: Highly purified basophils, lymphocytes, and monocytes were incubated in the presence or absence of a panel of cell-permeable inhibitors of proteolytic degradation pathway(s). Subsequently, the protein level of Syk tyrosine kinase was determined by means of Western blotting. In vitro assays were conducted through use of immunoprecipitated basophil Syk and a rabbit reticulocyte lysate system. RESULTS: Three inhibitors of proteasome-mediated degradation-PSI, lactacystin, and ALLN-substantially increased Syk levels in releaser basophils and restored Syk expression in nonreleaser basophils. Caspase inhibitors were less effective, and inhibitors of calpain-mediated proteolysis had no effect. Among other leukocytes tested, only naive CD4(+) T cells had more Syk after proteasome inhibitor treatment. In vitro ubiquitination assays demonstrated that Syk is readily ubiquitinated in vitro and also that Syk ubiquitination is associated with a substantial decrease in total levels of Syk protein. CONCLUSION: These data provide evidence for a ubiquitin/proteasome-dependent mechanism that contributes to Syk regulation in human basophils and might also be relevant to naive T cells. Understanding this regulatory pathway might lead to strategies for suppressing allergic inflammation while preserving essential Syk-mediated functions in other hematopoietic cells.