Inhibition of the C1s Protease and the Classical Complement Pathway by 6-(4-Phenylpiperazin-1-yl)Pyridine-3-Carboximidamide and Chemical Analogs

The classical pathway (CP) is a potent mechanism for initiating complement activity and is a driver of pathology in many complement-mediated diseases. The CP is initiated via activation of complement component C1, which consists of the pattern recognition molecule C1q bound to a tetrameric assembly of proteases C1r and C1s. Enzymatically active C1s provides the catalytic basis for cleavage of the downstream CP components, C4 and C2, and is therefore an attractive target for therapeutic intervention in CP-driven diseases. Although an anti-C1s mAb has been Food and Drug Administration approved, identifying small-molecule C1s inhibitors remains a priority. In this study, we describe 6-(4-phenylpiperazin-1-yl)pyridine-3-carboximidamide (A1) as a selective, competitive inhibitor of C1s. A1 was identified through a virtual screen for small molecules that interact with the C1s substrate recognition site. Subsequent functional studies revealed that A1 dose-dependently inhibits CP activation by heparin-induced immune complexes, CP-driven lysis of Ab-sensitized sheep erythrocytes, CP activation in a pathway-specific ELISA, and cleavage of C2 by C1s. Biochemical experiments demonstrated that A1 binds directly to C1s with a Kd of ∼9.8 μM and competitively inhibits its activity with an inhibition constant (Ki) of ∼5.8 μM. A 1.8-Å-resolution crystal structure revealed the physical basis for C1s inhibition by A1 and provided information on the structure-activity relationship of the A1 scaffold, which was supported by evaluating a panel of A1 analogs. Taken together, our work identifies A1 as a new class of small-molecule C1s inhibitor and lays the foundation for development of increasingly potent and selective A1 analogs for both research and therapeutic purposes.

Deciphering and disrupting PIEZO1-TMEM16F interplay in hereditary xerocytosis

ABSTRACT

Cell-surface exposure of phosphatidylserine (PS) is essential for phagocytic clearance and blood clotting. Although a calcium-activated phospholipid scramblase (CaPLSase) has long been proposed to mediate PS exposure in red blood cells (RBCs), its identity, activation mechanism, and role in RBC biology and disease remain elusive. Here, we demonstrate that TMEM16F, the long-sought-after RBC CaPLSase, is activated by calcium influx through the mechanosensitive channel PIEZO1 in RBCs. PIEZO1-TMEM16F functional coupling is enhanced in RBCs from individuals with hereditary xerocytosis (HX), an RBC disorder caused by PIEZO1 gain-of-function channelopathy. Enhanced PIEZO1-TMEM16F coupling leads to an increased propensity to expose PS, which may serve as a key risk factor for HX clinical manifestations including anemia, splenomegaly, and postsplenectomy thrombosis. Spider toxin GsMTx-4 and antigout medication benzbromarone inhibit PIEZO1, preventing force-induced echinocytosis, hemolysis, and PS exposure in HX RBCs. Our study thus reveals an activation mechanism of TMEM16F CaPLSase and its pathophysiological function in HX, providing insights into potential treatment.

Treatment of thrombocytopenia and thrombosis in HIT in mice using deglycosylated KKO: a novel therapeutic?

Heparin-induced thrombocytopenia (HIT) is characterized by thrombocytopenia associated with a highly prothrombotic state due to the development of pathogenic antibodies that recognize human platelet factor 4 (hPF4) complexed with various polyanions. Although nonheparin anticoagulants are the mainstay of care in HIT, subsequent bleeding may develop, and the risk of developing new thromboembolic events remain. We previously described a mouse immunoglobulin G2bκ (IgG2bκ) antibody KKO that mimics the sentinel features of pathogenic HIT antibodies, including binding to the same neoepitope on hPF4-polyanion complexes. KKO, like HIT IgGs, activates platelets through FcγRIIA and induces complement activation. We then questioned whether Fc-modified KKO could be used as a novel therapeutic to prevent or treat HIT. Using the endoglycosidase EndoS, we created deglycosylated KKO (DGKKO). Although DGKKO retained binding to PF4-polyanion complexes, it inhibited FcγRIIA-dependent activation of PF4-treated platelets triggered by unmodified KKO, 5B9 (another HIT-like monoclonal antibody), and IgGs isolated from patients with HIT. DGKKO also decreased complement activation and deposition of C3c on platelets. Unlike the anticoagulant fondaparinux, injection of DGKKO into HIT mice lacking mouse PF4, but transgenic for hPF4 and FcγRIIA, prevented and reversed thrombocytopenia when injected before or after unmodified KKO, 5B9, or HIT IgG. DGKKO also reversed antibody-induced thrombus growth in HIT mice. In contrast, DGKKO was ineffective in preventing thrombosis induced by IgG from patients with the HIT-related anti-PF4 prothrombotic disorder, vaccine-induced immune thrombotic thrombocytopenia. Thus, DGKKO may represent a new class of therapeutics for targeted treatment of patients with HIT.

Modulation of ultralarge immune complexes in heparin-induced thrombocytopenia

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is a serious thrombotic disorder caused by ultralarge immune complexes (ULICs) containing platelet factor 4 (PF4) and heparin that form the HIT antigen, together with a subset of anti-PF4 antibodies. ULICs initiate prothrombotic responses by engaging Fcγ receptors on platelets, neutrophils, and monocytes. Contemporary anti-thrombotic therapy for HIT is neither entirely safe nor entirely successful and acts downstream of ULIC formation and Fcγ receptor-initiated generation of thrombin.

OBJECTIVES

To determine whether HIT antigen and ULIC formation and stability could be modified favorably by inhibiting PF4-heparin interactions with fondaparinux, together with blocking formation of PF4 tetramers using a humanized monoclonal anti-PF4 antibody (hRTO).

METHODS

Results: The combination of fondaparinux and hRTO inhibited HIT antigen formation, promoted antigen dissociation, inhibited ULIC formation, and promoted ULIC disassembly at concentrations below the effective concentration of either alone and blocked Fcγ receptor-dependent induction of factor Xa activity by monocytic THP1 cells and activation of human platelets in whole blood. Combined with hRTO, fondaparinux inhibited HIT antigen and immune complex formation and activation through Fcγ receptors at concentrations at or below those used clinically to inhibit FXa coagulant activity.

CONCLUSIONS

HIT antigen and immune complexes are dynamic and amenable to modulation. Fondaparinux can be converted from an anticoagulant that acts at a downstream amplification step into a rationale, disease-specific intervention that blocks ULIC formation. Interventions that prevent ULIC formation and stability might increase the efficacy, permit use of lower doses, shorten the duration of antithrombotic therapy, and help prevent this serious thrombotic disorder.

Neutrophil functional heterogeneity is a fixed phenotype and is associated with distinct gene expression profiles

Differences in the ability of neutrophils to perform relevant effector functions has been identified in a variety of disease states. Although neutrophil functional heterogeneity is increasingly recognized during disease, few studies have examined neutrophil functional heterogeneity during periods of health. In this study, we systematically characterize neutrophil functional heterogeneity in a cohort of healthy human subjects using a range of biologically relevant agonists including immune complexes, bacterial ligands, and pathogens. With repeated testing over several years, we show that neutrophil functional capability represents a fixed phenotype for each individual. This neutrophil phenotype is preserved across a range of agonists and extends to a variety of effector functions including degranulation, neutrophil extracellular trap release, reactive oxygen species generation, phagocytosis, and bacterial killing. Using well-phenotyped healthy human subjects, we demonstrate that neutrophil functional heterogeneity is characterized by differences in neutrophil gene expression patterns. Altogether, our findings demonstrate that while neutrophil function is highly heterogeneous among healthy subjects, each individual's functional capability represents a fixed phenotype defined by a distinct neutrophil gene expression profile. These findings may be relevant during disease states where the ability to perform relevant neutrophil effector functions may impact disease course and/or clinical outcome.

Minimal role for the alternative pathway in complement activation by HIT immune complexes

BACKGROUND

Anti-platelet factor 4 (PF4)/heparin immune complexes that cause heparin-induced thrombocytopenia (HIT) activate complement via the classical pathway. Previous studies have shown that the alternative pathway of complement substantially amplifies the classical pathway of complement activation through the C3b feedback cycle.

OBJECTIVES

These studies sought to examine the contributions of the alternative pathway to complement activation by HIT antibodies.

METHODS

Using IgG monoclonal (KKO) and/or patient-derived HIT antibodies, we compared the effects of classical pathway (BBK32 and C1-esterase inhibitor [C1-INH]), alternative pathway (anti-factor B [fB] or factor D [fD] inhibitor) or combined classical and alternative pathway inhibition (soluble complement receptor 1 [sCR1]) in whole blood or plasma.

RESULTS

Classical pathway inhibitors BBK32 and C1-INH and the combined classical/alternative pathway inhibitor sCR1 prevented KKO/HIT immune complex-induced complement activation, including release of C3 and C5 activation products, binding of immune complexes to B cells, and neutrophil activation. The alternative pathway inhibitors fB and fD, however, did not affect complement activation by KKO/HIT immune complexes. Similarly, alternative pathway inhibition had no effect on complement activation by unrelated immune complexes consisting of anti-dinitrophenyl (DNP) antibody and the multivalent DNP--keyhole limpet hemocyanin antigen.

CONCLUSIONS

Collectively, these findings suggest the alternative pathway contributes little in support of complement activation by HIT immune complexes. Additional in vitro and in vivo studies are required to examine if this property is shared by most IgG-containing immune complexes or if predominance of the classic pathway is limited to immune complexes composed of multivalent antigens.

Obesity in midlife: lifestyle and dietary strategies

As the rate of obesity increases globally, so does the incidence of other non-communicable diseases such as diabetes, cardiovascular disease, cancer, osteoporosis, osteoarthritis, and dementia, which have been referred to as 'adiposity-based chronic disease'. With timely lifestyle modification such as behavioral changes, implementation of a healthy diet, and proper physical activity, many of these diseases can be prevented. Weight gain is one of the major health concerns of midlife. Midlife body changes are the result of aging, menopause, and other influences unique to menopausal women which interfere with adoption of a healthy lifestyle. Reduced metabolism levels lead to low energy levels, which discourage physical activity. In addition, with the onset of bone loss, menopausal women begin to lose muscle mass and gain more fat, resulting in osteopenic sarco-obesity. Adoption of a healthy lifestyle is a first-line option in the treatment for these midlife changes. Lifestyle medicine offers a broad set of network-based interventions, which need to be brought to the forefront in preventing and managing obesity at all stages. This review article focuses on evidence-based lifestyle changes and their benefits for reducing morbidity and mortality related to obesity and its complications prevalent at midlife and beyond.

Polyreactive IgM initiates complement activation by PF4/heparin complexes through the classical pathway

The mechanisms by which exposure to heparin initiates antibody responses in many, if not most, recipients are poorly understood. We recently demonstrated that antigenic platelet factor 4 (PF4)/heparin complexes activate complement in plasma and bind to B cells. Here, we describe how this process is initiated. We observed wide stable variation in complement activation when PF4/heparin was added to plasma of healthy donors, indicating a responder "phenotype" (high, intermediate, or low). Proteomic analysis of plasma from these healthy donors showed a strong correlation between complement activation and plasma immunoglobulin M (IgM) levels (r = 0.898; P < .005), but not other Ig isotypes. Complement activation response to PF4/heparin in plasma displaying the low donor phenotype was enhanced by adding pooled IgM from healthy donors, but not monoclonal IgM. Depletion of IgM from plasma abrogated C3c generation by PF4/heparin. The complement-activating features of IgM are likely mediated by nonimmune, or natural, IgM, as cord blood and a monoclonal polyreactive IgM generate C3c in the presence of PF4/heparin. IgM facilitates complement and antigen deposition on B cells in vitro and in patients receiving heparin. Anti-C1q antibody prevents IgM-mediated complement activation by PF4/heparin complexes, indicating classical pathway involvement. These studies demonstrate that variability in plasma IgM levels correlates with functional complement responses to PF4/heparin. Polyreactive IgM binds PF4/heparin, triggers activation of the classical complement pathway, and promotes antigen and complement deposition on B cells. These studies provide new insights into the evolution of the heparin-induced thrombocytopenia immune response and may provide a biomarker of risk.

Abstract P1-08-07: Withdrawn

This abstract was withdrawn by the authors.

Immune pathogenesis of heparin-induced thrombocytopenia

The immune response to heparin is one of the most common drug-induced allergies, and yet, atypical for a drug hypersensitivity reaction. Whereas most drug-induced allergies are rare, idiosyncratic and life-long, the allergic response to heparin is common, predictable in certain clinical settings and transient. Advances in the last decade with regards to structural characterisation of the PF4/heparin antigenic complex, contributions of innate immunity and development of animal models have provided insights into the distinctive features of the HIT immune response. Recent descriptions of the crystal structure of the PF4/heparin complex, alongside other biophysical studies, have clarified the structural requirements for immunogenicity and heparin-dependency of antibody formation. Studies of interactions of PF4 with bacterial cell walls as well as epidemiologic associations of anti-PF4/heparin antibody formation and infection suggest a role for immune priming and explain the rapid evolution of an isotype-switched immune response in sensitised patients. Murine models have greatly facilitated investigations of cellular basis of the HIT response and identified a major role for T-cells and marginal zone B-cells, but key findings have yet to be validated in human disease. This chapter will summarise recent investigations of the HIT immune response in the context of major pathways of immune activation and identify areas of uncertainty.

Effect of Picroliv on cadmium-induced hepatic and renal damage in the rat

The therapeutic efficacy of Picroliv-a standardized-was investigated in male rats exposed to CdCl2 (0.5 mg/kg, sc), 5 days/week for 18 weeks. Picroliv at two doses (6 and 12 mg/kg, po) was given to the cadmium (Cd)-administered group for the last 4 weeks (ie, weeks 15 -18). The Cd altered oxidative stress indices, such as increased lipid peroxidation and membrane fluidity, reduced levels of non-protein sulphydryls (NPSHs), and Na-K-ATPase activity in the liver and kidney were found close to the control values by Picroliv treatment, suggesting its antioxidant potential. The hepatoprotective action of Picroliv was evident by its ability to lower the Cd-induced liver function parameters-the serum enzymes, such as alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), g-glutamyl transpeptidase (GGT) and lactate dehydrogenase (LDH). Bile flow and biliary Cd also increased as a result of Picroliv's choleretic property. The Cd-induced serum urea and urinary excretion of proteins, calcium (Ca), Cd and enzymes, such as Nacetyl-b-D-glucosaminidase (NAG) and LDH, were less marked on Picroliv treatment, indicating recovery from nephrotoxicity. Organ uptake of Cd and essential metals by Cd exposure was reduced on Picroliv treatment. Cdinduced hepatic metallothionein (MT) was lowered by Picroliv, whereas renal MT was unaltered. Cd-induced hepatic damage was also minimized. However, the renal morphological changes were marginally protected by Picroliv. The 12-mg Picroliv dose was more effective than the 6-mg dose in causing amelioration of the above parameters. This study has provided clear evidence for the hepato-and renal protective efficacy of Picroliv against experimental Cd toxicity.

Prevention of acute cadmium toxicity by Picroliv

The potential of Picroliv, a herbal extract against acute cadmium (Cd) intoxication, was evaluated in male rats. Biochemical and histopathological profile in rats pretreated with Picroliv (12 mg/kg, oral) followed by a single dose of Cd as cadmium chloride (CdCl2) (3 mg/kg, ip) revealed marked suppression of oxidative stress in liver and testes. The Cd-induced enhanced levels of lipid peroxidation, membrane fluidity and reduced levels of nonprotein sulphydryls and Na+K+ATPase were significantly restored to near normal by Picroliv pretreatment. In addition, the Cd-induced serum levels of glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, gamma glutamyl transpeptidase and lactate dehydrogenase were restored to near basal levels. Hepatic and testicular histopathological damage was also minimized. The results strongly suggest definite hepatoand testicular protection by Picroliv. The antioxidant potential of the herbal extract in the major part, and not its chelating property, seems to be responsible for its ameliorative action.

Changing Pattern of Clinical Profile of First Contact Patients Attending Outpatient Services At the General Hospital Psychiatric Units In India Over the Last 50 Years

Introduction

Over the last eight decades, general hospital psychiatric units (GHPUs) have become important mental health service set-ups in India. This period has seen a large number of radical changes in the Indian society. In this background, it is important to know if it had any effects on the patients attending the GHPUs.

Methodology

A total of five hundred subjects, attending a GHPU were recruited prospectively for the study. The subjects were assessed using a semi-structured proforma. A comparison was made with similar studies conducted in GHPU settings over the last 5 decades.

Results

Neurotic, stress related and somatoform disorders was the commonest diagnostic group (33%) followed by psychotic disorders (17%) and mood disorders (15%). The finding is broadly similar to the studies done at different times in the last 5 decades. However, there were lesser number of patients with mental retardation, organic brain syndrome and seizure disorder.

Conclusion

The study highlights the strengths of GHPU set-ups like inter-speciality referrals, fewer stigmas, patients travelling from far off places to seek treatment and involvement of family in the care of mentally ill.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Heparin enhances uptake of platelet factor 4/heparin complexes by monocytes and macrophages

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is an iatrogenic complication of heparin therapy caused by antibodies to a self-antigen, platelet factor (4) and heparin. The reasons why antibodies form to PF4/heparin, but not to PF4 bound to other cellular glycosaminoglycans are poorly understood.

OBJECTIVE

To investigate differences in cellular responses to cell-bound PF4 and PF4/heparin complexes, we studied the internalization of each by peripheral blood-derived monocytes, dendritic cells and neutrophils.

METHODS AND RESULTS

Using unlabeled and fluorescently-labeled antigen and/or labeled monoclonal antibody to PF4/heparin complexes (KKO), we show that PF4/heparin complexes are taken up by monocytes in a heparin-dependent manner and are internalized by human monocytes and dendritic cells, but not by neutrophils. Complexes of PF4/low-molecular-weight heparin and complexes composed of heparin and murine PF4, protamine or lysozyme are internalized similarly, suggesting a common endocytic pathway. Uptake of complexes is mediated by macropinocytosis, as shown by inhibition using cytochalasin D and amiloride. Internalized complexes are transported intact to late endosomes, as indicated by co-staining of vesicles with KKO and lysosomal associated membrane protein-2 (LAMP-2). Lastly, we show that cellular uptake is accompanied by expression of MHCII and CD83 co-stimulatory molecules.

CONCLUSIONS

Taken together, these studies establish a distinct role for heparin in enhancing antigen uptake and activation of the initial steps in the cellular immune response to PF4-containing complexes.

Pigmented villonodular synovitis great toe

A young boy of 14 years. presented with swelling over dorsal aspect of right great toe, which was slightly tender, non fluctuant. It was excised under subarachnoid block. The mass was golden brown in colour encircling the extensor tendon (Extensor Hallucis Longus Tendon). Histopathology reported to be Pigmented Villonodular Synovitis.

Eliciting a policy response for the rising epidemic of overweight-obesity in India

India is experiencing multiple transitions with respect to nutrition patterns, epidemiology and demography. Along with staggering childhood undernutrition, a rapid rise in chronic diseases and their risk factors including overweight-obesity (O-O), among all sections of society, is compounding India's health challenges. We present an overview of the O-O scenario (prevalence, determinants) and profile existing initiatives to address this modifiable risk factor in India. Urgent attention from all sectors, committed resources, policy support and targeted actions are warranted to combat the dual burden of malnutrition. The health systems should be reoriented and strengthened, in addition to enabling actions in other sectors, to address prevention and control of non-communicable diseases and associated risk factors like O-O.

Disruption of multivesicular body vesicles does not affect major histocompatibility complex (MHC) class II-peptide complex formation and antigen presentation by dendritic cells

The antigen processing compartments in antigen-presenting cells (APCs) have well known characteristics of multivesicular bodies (MVBs). However, the importance of MVB integrity to APC function remains unknown. In this study, we have altered the ultrastructure of the MVB by perturbing cholesterol content genetically through the use of a deletion of the lipid transporter Niemann-Pick type C1 (NPC1). Immunofluorescence and electron microscopic analyses reveal that the antigen processing compartments in NPC1(-/-) dendritic cells (DCs) have an abnormal ultrastructure in that the organelles are enlarged and the intraluminal vesicles are almost completely absent and those remaining are completely disorganized. MHC-II is restricted to the limiting membrane of these enlarged MVBs where it colocalizes with the peptide editor H2-DM. Curiously, proteolytic removal of the chaperone protein Invariant chain from MHC-II, degradation of internalized foreign antigens, and antigenic-peptide binding to nascent MHC-II are normal in NPC1(-/-) DCs. Antigen-pulsed NPC1(-/-) DCs are able to effectively activate antigen-specific CD4 T cells in vitro, and immunization of NPC1(-/-) mice reveals surprisingly normal CD4 T cell activation in vivo. Our data thus reveal that the localization of MHC-II on the intraluminal vesicles of multivesicular antigen processing compartments is not required for efficient antigen presentation by DCs.

A Double in vivo Biotinylation Technique for Objective Assessment of Aging and Clearance of Mouse Erythrocytes in Blood Circulation

SUMMARY

We have recently developed a new technique to objectively identify erythrocyte cohorts of defined age in mouse blood. The technique (termed double in vivo biotinylation, DIB) involves an initial biotinylation of all erythrocytes in circulation, followed after a few days by a second biotinylation, at a lower density, that labels the biotin-negative erythrocytes that have entered since the first biotinylation. The proportions of biotin(high), biotin(low), and biotin(negative) erythrocytes are enumerated by flow cytometry. The DIB technique allows us to track age-related changes on erythrocyte cohorts (Protocol A), and to simultaneously identify very young and older erythrocyte populations in the blood (Protocol B). Using this technique, we have reexamined: i) the relationship between age and buoyant density of erythrocytes, ii) erythrocyte destruction through a random removal mechanism, and iii) the expression of phosphatidylserine on aging erythrocytes. We have also used the DIB technique to study age-related changes in the expression of various markers like CD47 and CD147 and green autofluorescence in aging erythrocyte populations.

Transmembrane domain sequences regulate the association of MHC- class II with lipid raft microdomains (106.19)

MHC II is known to be present in cholesterol-dependent lipid raft plasma membrane microdomains, and this association is important for MHC II- dependent activation of CD4 T cells by Dendritic cells (DCs). Until now it is not clear what regulates MHC II lipid raft association. In the present study we attempt to define the signals present in the MHC II transmembrane (TM) domain that regulate MHC II association with lipid rafts. Palmitoylation of cysteine residues is a well-known modification that often results in lipid raft association of TM protein and each MHC II I-Ab subunit contains a TM cysteine. We therefore expressed MHC II-α and β-chains containing TM domain cysteine → serine mutants in DCs obtained from MHC II null mice and analyzed MHC II lipid raft association. These experiments showed that the mutation of the TM cysteine residues actually enhanced MHC II raft localization about 3 fold. We also examined the role of the entire MHC II TM domain in lipid raft association. Replacement of the MHC II-α and β-chain TM domains with that of the non-raft protein ICAM 1 reduces MHC II lipid raft association 5 fold. We are currently examining the role of TM domain sequences present in each MHC II subunit in an attempt to identify dominant raft localization sequences in MHC II.

Oral mucoceles - review of the literature

Oral mucoceles are mucin filled cavities and lined by ductal epithelium or covered by granulation tissue in retention or extravasation type respectively. The extra-vasation type is very common in the minor salivary glands (particularly in the labial glands), but very infrequent in the major salivary glands, whilst most of the retention cyst affect the major salivary glands. Partial obstruction of duct and spillage of mucin following trauma are the chief etiological factors. Though the two lesions are clinically indistinguishable, the patients are typically older than in the case of extra-vasation type. The case history along with heedful clinical examination of the lesion is crucial for diagnosing mucoceles correctly, but to avoid recurrences histopathological examination is mandatory. The surgical approach to mucoceles is the most common mode of treatment amongst various other techniques including cryosurgery, laser and so on.

MRSA screening in the vascular day-case population

INTRODUCTION

The UK Government has prioritised methicillin-resistant Staphylococcus aureus (MRSA) screening and new operational guidance has instructed that all day-case surgical patients should be screened from April 2009. We sought to identify the number of MRSA-positive patients in the vascular day-case population over a 1-year period and to profile this cohort in terms of risk-factors for MRSA. We also sought to identify whether the new guidance from the Department of Health (DH) had resulted in increased screening rates.

PATIENTS AND METHODS

Electronic records and laboratory culture results were prospectively consulted to identify whether patients had been screened and if MRSA had been isolated. Consideration was given to whether any patients had a delayed discharge or subsequent admission with an MRSA-related complication.

RESULTS

Six patients (2.1%) screened MRSA-positive (DH estimate 7%); five were previously known to be MRSA-positive, therefore only 0.36% patients were newly-identified as MRSA-positive. The proportion of patients screened increased from 35% to 72.5% after April 2009, in accordance with DH guidance. Successful decolonisation was proved in two patients (33.3%).

CONCLUSIONS

There is dispute with several of the key assumptions behind the DH's impact assessment justifying an expanded MRSA-screening policy. It is not cost-effective to screen all vascular day-case admissions. We recommend selective screening for patients previously identified as MRSA-positive, or considered high risk.

Distinct MHC class II molecules are associated on the dendritic cell surface in cholesterol-dependent membrane microdomains

Very small amounts of MHC class II-peptide complexes expressed on the surface of antigen-presenting cells (APCs) are capable of stimulating antigen-specific CD4 T cells. There is intense interest to elucidate the molecular mechanisms by which these small amounts of MHC-II can cluster, cross-link T cell receptors, and promote T cell proliferation. We now demonstrate that a significant fraction of the total pool of MHC-II molecules on the surface of dendritic cells is physically associated in macromolecular aggregates. These MHC-II/MHC-II interactions have been probed by co-immunoprecipitation analysis of the MHC-II I-A molecule with the related I-E molecule. These molecular associations are maintained in gentle detergents but are disrupted in harsh detergents such as Triton X-100. MHC-II I-A/I-E interactions are disrupted when plasma membrane cholesterol is extracted using methyl β-cyclodextrin, suggesting that lipid raft microdomains are important mediators of these MHC-II interactions. Although it has been proposed that tetraspanin proteins regulate molecular clustering, aggregation, and co-immunoprecipitation in APCs, genetic deletion of the tetraspanin family members CD9 or CD81 had no effect on MHC-II I-A/I-E binding. These data demonstrate that the presence of distinct forms of MHC-II with plasma membrane lipid rafts is required for MHC-II aggregation in APCs and provides a molecular mechanism allowing dendritic cells expressing small amounts of MHC-II-peptide complexes to cross-link and stimulate CD4 T cells.

Case report: successful use of hyperbaric oxygen therapy for a complete scalp degloving injury

We report a case of a complete scalp degloving injury in a 43-year-old previously healthy, tobacco-using female whose hair was caught in a tractor power take-off causing an instantaneous total scalping injury. Microsurgical replantation was started 4 hours after injury with the surgical procedure lasting 4 hours. Only the superficial temporal arteries were reanastomosed with no venous anastomosis possible. Hyperbaric oxygen (HBO2) treatment at 2.5 atmospheres absolute (ATA) for 90 minutes was administered immediately after surgery due to duskiness of the flap. Further HBO2 treatments were administered twice daily for seven days and then once daily for 30 days. Additionally, leech therapy was used for the first ten postoperative days. The patient's right auricle and most of the left auricle were completely lost. Despite the tenuous vascular inflow and initially absent venous drainage, at 3 month follow-up there was reepithelialization of her scalp except for an area of granulation tissue in the occipitoparietal area. At one year follow-up the area of granulation tissue was reduced, but there was no detectable hair growth or nerve function. We propose that HBO2 may facilitate tissue survival in scalp degloving injuries in the face of incomplete surgical revascularization.

A role of phosphatidylserine externalization in clearance of erythrocytes exposed to stress but not in eliminating aging populations of erythrocyte in mice

Age dependent changes in phosphatidylserine (PS) externalization were studied in mouse erythrocytes of different age groups (range 1-55 days) by using a newly developed double in vivo biotinylation (DIB) technique. Around 3-4% of the erythrocytes freshly released in the circulation were PS(+) but this proportion fell rapidly to 1% or less and did not increase at later time points. Blocking erythrocyte clearance from the circulation by in vivo depletion of macrophages (by treatment with clodronate loaded liposomes) for up to 7 days did not result in accumulation of PS(+) erythrocytes in the circulation indicating that the low percentage of PS(+) cells within old erythrocytes (age >40 days) was not related to the clearance of PS(+) erythrocytes by macrophages. In vitro treatment with stress inducing agents like deoxyglucose or Ca(++)/calcium ionophore resulted in a marked induction of PS externalization in mouse erythrocytes and this effect was most prominent in the youngest erythrocyte population (age <10 days). Kinetics of clearance of different age groups of stress exposed erythrocytes after intravenous infusion into recipient mice indicated that the young erythrocytes were cleared at fastest rate from the circulation as compared to erythrocytes of older age groups. Within young erythrocytes exposed to stress, PS(+) erythrocytes were preferentially cleared. Taken together our results suggest that PS externalization is unlikely to have a role in the removal of old erythrocytes from blood circulation but may have a role in the clearance of stressed and damaged young erythrocytes in blood circulation.

Reduced expression of CD47 during murine red blood cell (RBC) senescence and its role in RBC clearance from the circulation

BACKGROUND

Almost 2 percent of murine blood red blood cells (RBCs) are destroyed each day and are replaced by fresh RBCs generated through the process of erythropoiesis. RBCs to be destroyed are phagocytosed by macrophages in the reticuloendothelial system, especially in the spleen. CD47 molecules on RBCs may regulate the susceptibility of RBC to destruction by phagocytosis because its recognition by inhibitory receptor (signal regulatory protein alpha) on macrophages sends a negative signal, which if sufficiently strong, may abort the phagocytic response altogether. The aim of this study was to investigate whether age-dependent changes in CD47 expression on circulating RBCs have a role in destruction of senescent RBCs by macrophages.

STUDY DESIGN AND METHODS

A two-step in vivo biotinylation method for labeling mouse RBCs in vivo was used to track the CD47 expression levels as well as the turnover of circulating RBCs of defined age groups.

RESULTS

Our results indicate that CD47 expression levels decrease on circulating RBCs throughout their life span in circulation. The oldest RBCs in circulation have 30 percent lower mean expression of CD47 than the youngest RBCs. Depletion of macrophages by administration of clodronate-loaded liposomes resulted in a significant decrease in the mean expression of CD47 on RBCs of all age groups and a significant accumulation of senescent RBCs in blood and spleen. A decrease in mean expression of CD47 and accumulation of senescent RBCs in macrophage-depleted mice were significantly higher for spleen RBCs compared to blood RBCs.

CONCLUSIONS

Our results provide supportive evidence for a role of decreasing CD47 expression on aging circulating RBCs in their destruction by macrophages.

Age dependent decline in CD47 expression on circulating mouse erythrocytes and susceptibility to destruction by macrophages (85.11)

We have recently described a novel technique to tag a cohort of mouse erythrocytes released into blood circulation over a defined time window, and follow age related changes in this population in circulation (Khandelwal S and Saxena RK, Expt. Gerontol. 41, 855, 2006). In the current study, we report the kinetics of age dependent decline in CD47 expression on circulating erythrocytes and its role on destruction of senescent erythrocytes by macrophages. CD47 expression was highest on erythrocytes freshly released into circulation and fell steadily thereafter. Oldest erythrocytes in circulation had 30% lower expression of CD47 than the youngest erythrocytes. Depletion of macrophages by administration of clodronate loaded liposomes resulted in a significant fall in the average expression of CD47 on erythrocytes of young (&lt;15 d), intermediate (15–40 d)and old (&gt;40 d) age groups, but a significant increase was observed only in the numbers of old erythrocytes in blood. A time dependent accumulation of CD47low erythrocytes was noted in blood and spleen though the accumulation was markedly higher in spleen. Taken together our results support the proposition that an age dependent fall in CD47 expression on blood erythrocytes may have a role in regulating the destruction of senescent blood erythrocytes by the macrophages.

This work was supported by a research grant from the Department of Science and Technology, Government of India.

Assessment of survival of aging erythrocyte in circulation and attendant changes in size and CD147 expression by a novel two step biotinylation method

Three intravenous injections (1mg each) of biotin-X-NHS (BXN) given at 24h intervals labeled all circulating erythrocytes with biotin in C57Bl/6 mice. After 5 days, administration of another i.v. injection of BXN (0.6mg) resulted in the labeling of erythrocytes released in blood circulation after the first biotinylation step, with a lower intensity of biotin. The older erythrocyte population with high intensity of biotin (biotin(high) population) and the later population of newly formed erythrocytes with lower intensity of biotin (biotin(low) population) could be stained with streptavidin-APC (SAv) and identified by flow cytometry. Using the double biotinylation technique, we could examine the survival and age related changes in biotin(low) population of erythrocytes that was released in circulation during a defined time period (5 days). Our results indicate that the percentage of Biotin(low) erythrocytes in circulation remained static for 10 days after the second biotinylation step and than started to decline steadily with time. Mean fluorescence intensity of biotin label on surviving biotin(low) population of erythrocytes however remained stable. These results suggest that after 15 days of release in blood, erythrocytes may undergo random destruction. Furthermore, forward scatter as well as CD147 expression of Biotin(low) population also declined with age. Double biotinylation technique described in this communication offers an easy method for tracking age related changes in populations of erythrocytes released in circulation during a defined period of time.

Interference by toxic metal ions with zinc-dependent proteins involved in maintaining genomic stability

Metal ions are essential components of biological systems; nevertheless, even essential elements may have toxic or carcinogenic properties. Thus, besides As(III) and Cd(II), also Ni(II) and Co(II) have been shown previously to disturb different types of DNA repair systems at low, non-cytotoxic concentrations. Since some metals exert high affinities for SH groups, we investigated whether zinc finger structures in DNA-binding motifs of DNA repair proteins are potential targets for toxic metal ions. The bacterial formamidopyrimidine-DNA glycosylase (Fpg protein) involved in base excision repair was inhibited by Cd(II), Cu(II) and Hg(II) with increasing efficiencies, whereas Co(II), As(III), Pb(II) and Ni(II) had no effect. Furthermore, Cd(II) still disturbed enzyme function when bound to metallothionein. Strong inhibition was also observed in the presence of phenylselenyl chloride, followed by selenocystine, while selenomethionine was not inhibitory. Regarding the mammalian XPA protein involved in the recognition of DNA lesions during nucleotide excision repair, its DNA-binding capacity was diminished by Cd(II), Cu(II), Ni(II) and Co(II), while Hg(II), Pb(II) and As(III) were ineffective. Finally, the H(2)O(2)-induced activation of the poly(ADP-ribose)polymerase (PARP) involved in DNA strand break detection and apoptosis was greatly reduced by Cd(II), Co(II), Ni(II) and As(III). Similarly, the disruption of correct p53 folding and DNA binding by Cd(II), Ni(II) and Co(II) has been shown by other authors. Therefore, zinc-dependent proteins involved in DNA repair and cell-cycle control may represent sensitive targets for some toxic metals such as Cd(II), Ni(II), Co(II) and Cu(II), as well as for some selenium compounds. Relevant mechanisms of inhibition appear to be the displacement of zinc by other transition metals as well as redox reactions leading to thiol/disulfide interchange.

Modulation of acute cadmium toxicity by Emblica officinalis fruit in rat

The efficacy of Emblica officinalis in modifying the acute cytotoxicity of cadmium in male rats was evaluated. Oral administration of Emblica fruit juice (500 mg/kg, b.w.) for 8 days followed by a single toxic dose of Cd as CdCl2 (3 mg/kg,b.w. ip), considerably reduced the mortality in rats as well as prevented to some extent the cadmium induced histopathological damage in testis, liver and kidneys. Biochemical investigation also revealed reduced levels of Cd induced serum glutamate oxaloacetate transaminase, glutamate pyruvate transaminase and gamma glutamyltranspeptidase. The enhanced levels of Cd and lipid peroxidation in liver, kidney, and testes and metallothionein and total sulphydryl in liver and kidney by Cd were significantly reduced by Emblica pretreatment. These results suggest cytoprotective potential of Emblica fruit in acute cadmium toxicity which could be due to its multiple role in biological system.

Accuracy of teen and parental reports of obesity and body mass index

OBJECTIVES

Adolescent obesity is becoming an increasing public health problem. This study determines: 1) differences in teen and parental report of obesity, 2) amount of misclassification using body mass index (BMI) from self-reported versus measured height and weight as an indicator of obesity, and 3) whether misclassification varies by gender and socioeconomic status.

DESIGN

Weighted data from 15 483 baseline (T1) youth and parental interviews from the National Longitudinal Study of Adolescent Health were used. Seventy-four percent of teens were reinterviewed 1 year later (T2). Parents reported socioeconomic status indicators and whether their teen was obese. Teens reported height, weight, and weight perception. BMI was calculated from both self-reported height and weight at T1 and T2 and from measured height and weight at T2. Those with a BMI > or =95% corrected for age and gender were considered obese.

RESULTS

At T1, nearly one half of teens (47%) reporting they were very overweight were not obese by BMI. For teens obese by BMI, 19.6% were reported to be obese by both parent and teen, 6.4% by teen only, 29. 9% by parent only, and 44.2% by neither teen nor parent. For those with persistent obesity, teen and/or parental report failed to identify more than one third (34%) as obese; 23.4% were identified by both teen and parent report, 5.4% by teen report only, and 37.2% by parent only. At T2, the correlation between BMI calculated from self-reported versus measured height and weight for the overall population was very strong (r = .92). Specificity of obesity status based on self-reported BMI, compared with obesity status based on measured BMI was .996; sensitivity, .722; positive predictive value, .860; and negative predictive value, .978. Overall, 3.8% of teens were misclassified using self-report measures. Girls were no more likely than boys to be misclassified as obese using BMI from self-reported height and weight.

CONCLUSIONS

Parental report is a better indicator of obesity than teen report of weight status, but parental and teen reports are both poor predictors of adolescent obesity. Using BMI based on self-reported height and weight correctly classified 96% as to obesity status. Thus, studies can use self-reported height and weight to understand teen obesity and its correlates/sequelae.