Release of neutrophil extracellular traps by neutrophils stimulated with antiphospholipid antibodies: a newly identified mechanism of thrombosis in the antiphospholipid syndrome

OBJECTIVE

Antiphospholipid antibodies (aPL), especially those targeting β2 -glycoprotein I (β2 GPI), are well known to activate endothelial cells, monocytes, and platelets, with prothrombotic implications. In contrast, the interaction of aPL with neutrophils has not been extensively studied. Neutrophil extracellular traps (NETs) have recently been recognized as an important activator of the coagulation cascade, as well as an integral component of arterial and venous thrombi. This study was undertaken to determine whether aPL activate neutrophils to release NETs, thereby predisposing to the arterial and venous thrombosis inherent in the antiphospholipid syndrome (APS).

METHODS

Neutrophils, sera, and plasma were prepared from patients with primary APS (n = 52) or from healthy volunteers and characterized. No patient had concomitant systemic lupus erythematosus.

RESULTS

Sera and plasma from patients with primary APS had elevated levels of both cell-free DNA and NETs, as compared to healthy volunteers. Freshly isolated neutrophils from patients with APS were predisposed to high levels of spontaneous NET release. Further, APS patient sera, as well as IgG purified from APS patients, stimulated NET release from control neutrophils. Human aPL monoclonal antibodies, especially those targeting β2 GPI, also enhanced NET release. The induction of APS NETs was abrogated with inhibitors of reactive oxygen species formation and Toll-like receptor 4 signaling. Highlighting the potential clinical relevance of these findings, APS NETs promoted thrombin generation.

CONCLUSION

Our findings indicate that NET release warrants further investigation as a novel therapeutic target in APS.

Autoimmune inflammation from the Th17 perspective

Recent studies demonstrated an IL-17-producer CD4+ T cell subpopulation, termed Th17, distinct from Th1 and Th2. It represents a different pro-inflammatory Th-cell lineage. This notion is supported by gene-targeted mice studies. Mice lacking IL-23 (p19-/-) do not develop experimental autoimmune encephalomyelitis (EAE) or collagen-induced arthritis (CIA), while knockout mice for the Th1 cytokine IL-12 (p35-/-) strongly develop both autoimmune diseases. Disease resistance by IL-23 knockout mice correlates well with the absence of IL-17-producing CD4(+) T lymphocytes in target organs despite normal presence of antigen-specific-IFN-gamma-producing Th1 cells. This finding may thus explain previous contradictory reports showing that anti-IFN-gamma-treated mice, IFN-gamma- or IFNR-deficient mice develop CIA or EAE. TGF-beta, IL-6 and IL-1 are the differentiation factors of Th17 cells. IL-23 is dispensable for this function, but necessary for Th17 expansion and survival. The master regulator that directs the differentiation program of Th17 cells is the orphan nuclear receptor RORgammat. IL-27, a member of the IL-12/IL-23 family, potently inhibits Th17 development. Evidence suggesting rheumatoid arthritis and multiple sclerosis as primarily IL-17 autoimmune inflammatory-mediated diseases is rapidly accumulating. The IL-17/23 axis of inflammation and related molecules may rise as therapeutic targets for treating these and perhaps other autoimmune diseases.

Structural organization and regulation of the small proline-rich family of cornified envelope precursors suggest a role in adaptive barrier function

The protective barrier provided by stratified squamous epithelia relies on the cornified cell envelope (CE), a structure synthesized at late stages of keratinocyte differentiation. It is composed of structural proteins, including involucrin, loricrin, and the small proline-rich (SPRR) proteins, all encoded by genes localized at human chromosome 1q21. The genetic characterization of the SPRR locus reveals that the various members of this multigene family can be classified into two distinct groups with separate evolutionary histories. Whereas group 1 genes have diverged in protein structure and are composed of three different classes (SPRR1 (2x), SPRR3, and SPRR4), an active process of gene conversion has counteracted diversification of the protein sequences of group 2 genes (SPRR2 class, seven genes). Contrasting with this homogenization process, all individual members of the SPRR gene family show specific in vivo and in vitro expression patterns and react selectively to UV irradiation. Apparently, creation of regulatory rather than structural diversity has been the driving force behind the evolution of the SPRR gene family. Differential regulation of highly homologous genes underlines the importance of SPRR protein dosage in providing optimal barrier function to different epithelia, while allowing adaptation to diverse external insults.

The antiphospholipid/cofactor syndromes: a primary variant with antibodies to beta 2-glycoprotein-I but no antibodies detectable in standard antiphospholipid assays

BACKGROUND

Most systemic lupus erythematosus (SLE) patients with two or more clinical manifestations of the antiphospholipid syndrome (APS) and negative antiphospholipid antibodies (aPL) have antibodies to beta 2-glycoprotein-I (a beta 2 GP-I). Herein we describe a similar set of circumstances, but in patients without evidence of SLE.

PATIENTS AND METHODS

We studied 6 patients with recurrent venous and/or arterial thromboses without aPL as detected by routine assays nor clinical or serological evidence of other autoimmune disease. Immunoglobin (Ig) G and IgM antibodies to bovine and human phospholipid-free beta 2 GP-I were studied by Western blot test and by enzyme-linked immunosorbent assay (ELISA) utilizing radiated and nonirradiated plates. We also tested antibodies to cardiolipin, phosphatidylserine, and phosphatidylethanolamine by ELISA. As controls, 54 normal sera were studied.

RESULTS

All 6 patients had recurrent arterial and/or venous thromboses. Three also had thrombocytopenia, 1 had livedo reticularis, and 2 had valvular heart disease. None of the patients had aPL, but all had serum IgG reactivity against human and bovine beta 2 GP-I (P < 0.001 versus controls for both). Titers of anti-bovine beta 2 GP-I were higher when studied in irradiated plates but were also higher than normal in nonirradiated plates (P < 0.001). These antibodies did not recognize human or bovine beta 2 GP-I bound to cardiolipin in solid phase. We confirmed by Western blot that these autoantibodies recognize human beta 2 GP-I. We found no IgM a beta 2 GP-I.

CONCLUSIONS

We describe a primary condition akin to the antiphospholipid syndrome with negative aPL, but with serum IgG antibodies to human and bovine beta 2 GP-I. These antibodies recognize beta 2 GP-I epitopes that are not accessible when beta 2 GP-I is bound to cardiolipin.

Task Force on Catastrophic Antiphospholipid Syndrome (APS) and Non-criteria APS Manifestations (II): thrombocytopenia and skin manifestations

The objectives of the ‘Task Force on Catastrophic Antiphospholipid Syndrome (APS) and Non-criteria APS Manifestations’ were to assess the clinical utility of the international consensus statement on classification criteria and treatment guidelines for the catastrophic APS, to identify and grade the studies that analyze the relationship between the antiphospholipid antibodies and the non-criteria APS manifestations, and to present the current evidence regarding the accuracy of these non-criteria APS manifestations for the detection of patients with APS. This article summarizes the studies analyzed on thrombocytopenia and skin manifestations, and presents the recommendations elaborated by the Task Force after this analysis.

Des-Acyl Ghrelin Directly Targets the Arcuate Nucleus in a Ghrelin-Receptor Independent Manner and Impairs the Orexigenic Effect of Ghrelin

Ghrelin is a stomach-derived octanoylated peptide hormone that plays a variety of well-established biological roles acting via its specific receptor known as growth hormone secretagogue receptor (GHSR). In plasma, a des-octanoylated form of ghrelin, named des-acyl ghrelin (DAG), also exists. DAG is suggested to be a signalling molecule that has specific targets, including the brain, and regulates some physiological functions. However, no specific receptor for DAG has been reported until now, and, consequently, the potential role of DAG as a hormone has remained a matter of debate. In the present study, we show that DAG specifically binds to and acts on a subset of arcuate nucleus (ARC) cells in a GHSR-independent manner. ARC cells labelled by a DAG fluorescent tracer include the neuropeptide Y (NPY) and non-NPY neurones. Given the well-established role of the ARC in appetite regulation, we tested the effect of centrally administered DAG on food intake. We found that DAG failed to affect dark phase feeding, as well as food intake, after a starvation period; however, it impaired the orexigenic actions of peripherally administered ghrelin. Thus, we conclude that DAG directly targets ARC neurones and antagonises the orexigenic effects of peripherally administered ghrelin.

Stereotypies in Rett syndrome: Analysis of 83 patients with and without detected MECP2 mutations

BACKGROUND

Hand stereotypies are considered a hallmark of Rett syndrome (RTT) and are usually described as symmetric movements at the midline. However, related pathologies may show the same type of involuntary movement. Furthermore, patients with RTT also have stereotypies with other localizations that are less well characterized.

METHODS

We analyzed stereotypies in 83 patients with RTT, 53 with and 30 without a mutation detected in the MECP2 gene. Patients were observed and videotaped always by the same pediatric neurologist. Stereotypies were classified, and data were submitted to statistical analysis for comparison of mutation-positive and -negative patients and analysis of their evolution with the disease.

RESULTS

All the patients showed hand stereotypies that coincided with or preceded the loss of purposeful hand movements in 62% of the patients with MECP2 mutations. The hair pulling stereotypy was more frequent in the group with detected mutations, whereas hand washing was not. Hand gaze was absent in all RTT patients with MECP2 mutations. Patients with MECP2 mutations also had more varied stereotypies, and the number of stereotypies displayed by each patient decreased significantly with age in this group. In all patients, stereotypies other than manual tended to disappear with the evolution of the disease.

CONCLUSIONS

Although symmetric midline hand stereotypies were not specific to patients with an MECP2 mutation, some of the other stereotypies seemed to be more characteristic of this group. In patients younger than 10 years and meeting the necessary diagnostic criteria of Rett syndrome, the association of hand stereotypies without hand gaze, bruxism, and two or more of the other stereotypies seemed to be highly indicative of the presence of an MECP2 mutation.

Analysis of brain nuclei accessible to ghrelin present in the cerebrospinal fluid

Ghrelin is a stomach-derived peptide hormone that acts in the brain to regulate many important physiological functions. Ghrelin receptor, named the growth hormone secretagogue receptor (GHSR), is present in many brain areas with or without obvious direct access to ghrelin circulating in the bloodstream. Ghrelin is also present in the cerebrospinal fluid (CSF) but the brain targets of CSF ghrelin are unclear. Here, we studied which brain areas are accessible to ghrelin present in the CSF. For this purpose, we centrally injected mice with fluorescein-labeled ghrelin (F-ghrelin) peptide tracer and then systematically mapped the distribution of F-ghrelin signal through the brain. Our results indicated that centrally injected F-ghrelin labels neurons in most of the brain areas where GHSR is present. Also, we detected F-ghrelin uptake in the ependymal cells of both wild-type and GHSR-null mice. We conclude that CSF ghrelin is able to reach most of brain areas expressing GHSR. Also, we propose that the accessibility of CSF ghrelin to the brain parenchyma occurs through the ependymal cells in a GHSR-independent manner.

Effects of norepinephrine on regional blood flow and oxygen extraction capabilities during endotoxic shock

We explored the effects of norepinephrine on blood flow distribution and oxygen extraction capabilities during hyperdynamic endotoxic shock. Twelve anesthetized and mechanically ventilated dogs received 2 mg/kg of Escherichia coli endotoxin followed by a general saline infusion and were then randomly divided into two groups: six received norepinephrine (1 microg/kg/min), and six served as control subjects. The norepinephrine group maintained higher mean arterial pressure, cardiac index, left ventricular stroke work index, and hepatic arterial blood flow without altering blood flow to portal, mesenteric, and renal beds. When cardiac tamponade was induced to study tissue oxygen extraction capabilities, the norepinephrine group had a lower critical oxygen delivery in whole body (11.5 +/- 5.2 versus 14.3 +/- 1.4 ml/kg/min, p < 0.05) and in liver (25.0 +/- 11.3 versus 38.0 +/- 9.0 ml/min, p = NS) and a higher critical oxygen extraction ratio in whole body (53.8 +/- 17.7 versus 32.0 +/- 6.1%, p < 0.05), and in liver (57.0 +/- 11.9 versus 35.2 +/- 4.3%, p < 0.05). We conclude that during endotoxic shock in dogs, norepinephrine hardly influences blood flow distribution and could even increase hepatic artery blood flow, and it can also improve whole body and liver oxygen extraction capabilities.

Hemolytic anemia related to an IgM autoantibody to phosphatidylcholine that binds in vitro to stored and to bromelain-treated human erythrocytes

Both normal and autoimmune mice have IgM natural autoantibodies to bromelain-treated erythrocytes in which phosphatidylcholine (PTC) becomes exposed. At one stage this antibody may participate in the genesis of autoimmune hemolytic anemia in the NZB mouse. We have recently studied a patient with hemolytic anemia who had persistently high serum titers of IgM anticardiolipin antibodies (aCL) that were also demonstrated in a hemolysate of his erythrocytes obtained at the time of the anemia. We affinity-purified the antibody and sought its binding to normal human bromelain-treated erythrocytes (BrE) because of the IgM isotype of the antibody, since cardiolipin is not a constituent of the erythrocyte wall, and because the anionic phospholipids, with which aCL are known to cross-react, are not located at the outer leaflet of the erythrocyte membrane. We found binding of the antibody to HBrE in their hemolysates and by flow cytometry. We also demonstrated that the aCL cross-reacted extensively with PTC, as well as with other anionic or zwitterionic phospholipids. The purified IgM antibody lysed BrE in the presence of complement and also bound to in vitro-aged erythrocytes. Because this patient had no other evidence of systemic lupus erythematosus or any other autoimmune condition, his disease may represent a variant of the recently described primary antiphospholipid syndrome.

Endothelial progenitor dysfunction associates with a type I interferon signature in primary antiphospholipid syndrome

OBJECTIVES

Patients with antiphospholipid syndrome (APS) are at risk for subclinical endothelial injury, as well as accelerated atherosclerosis. In the related disease systemic lupus erythematosus, there is a well-established defect in circulating endothelial progenitors, which leads to an accrual of endothelial damage over time. This defect has been at least partially attributed to exaggerated expression of type I interferons (IFNs). We sought to determine whether these pathways are important in APS.

METHODS

We studied 68 patients with primary APS. Endothelial progenitors were assessed by flow cytometry and functional assay. Type I IFN activity was determined by a well-accepted bioassay, while peripheral blood mononuclear cells were scored for expression of IFN-responsive genes.

RESULTS

Endothelial progenitors from patients with APS demonstrated a marked defect in the ability to differentiate into endothelial cells, a phenotype which could be mimicked by treating control progenitors with APS sera. Elevated type I IFN activity was detected in the circulation of patients with APS (a finding that was then replicated in an independent cohort). While IgG depletion from APS sera did not rescue endothelial progenitor function, the dysfunction was successfully reversed by a type I IFN receptor-neutralising antibody.

CONCLUSIONS

We describe, for the first time to our knowledge, an IFN signature in primary APS and show that this promotes impaired endothelial progenitor function. This work opens the door to novel approaches that may mitigate vascular damage in APS, such as anti-IFN drugs.

Task Force on Catastrophic Antiphospholipid Syndrome (APS) and Non-criteria APS Manifestations (I): catastrophic APS, APS nephropathy and heart valve lesions

The objectives of the 'Task Force on Catastrophic Antiphospholipid Syndrome (APS) and Non-criteria APS Manifestations' were to assess the clinical utility of the international consensus statement on classification criteria and treatment guidelines for the catastrophic APS, to identify and grade the studies that analyse the relationship between the antiphospholipid antibodies and the non-criteria APS manifestations and to present the current evidence regarding the accuracy of these non-criteria APS manifestations for the detection of patients with APS. This article summarizes the studies analysed on the catastrophic APS, APS nephropathy and heart valve lesions, and presents the recommendations elaborated by the Task Force after this analysis.

Human epidermal differentiation complex in a single 2.5 Mbp long continuum of overlapping DNA cloned in bacteria integrating physical and transcript maps

Terminal differentiation of keratinocytes involves the sequential expression of several major proteins which can be identified in distinct cellular layers within the mammalian epidermis and are characteristic for the maturation state of the keratinocyte. Many of the corresponding genes are clustered in one specific human chromosomal region 1q21. It is rare in the genome to find in such close proximity the genes belonging to at least three structurally different families, yet sharing spatial and temporal expression specificity, as well as interdependent functional features. This DNA segment, termed the epidermal differentiation complex, contains 27 genes, 14 of which are specifically expressed during calcium-dependent terminal differentiation of keratinocytes (the majority being structural protein precursors of the cornified envelope) and the other 13 belong to the S100 family of calcium binding proteins with possible signal transduction roles in the differentiation of epidermis and other tissues. In order to provide a bacterial clone resource that will enable further studies of genomic structure, transcriptional regulation, function and evolution of the epidermal differentiation complex, as well as the identification of novel genes, we have constructed a single 2.45 Mbp long continuum of genomic DNA cloned as 45 p1 artificial chromosomes, three bacterial artificial chromosomes, and 34 cosmid clones. The map encompasses all of the 27 genes so far assigned to the epidermal differentiation complex, and integrates the physical localization of these genes at a high resolution on a complete NotI and SalI, and a partial EcoRI restriction map. This map will be the starting resource for the large-scale genomic sequencing of this region by The Sanger Center, Hinxton, U.K.

Serum anti-beta2-glycoprotein-I and anticardiolipin antibodies during thrombosis in systemic lupus erythematosus patients

PURPOSE

Antibodies to beta2-glycoprotein-I are more strongly associated with clinical antiphospholipid syndrome than are anticardiolipin antibodies. We previously found a decrease in anticardiolipin antibodies at the time of thrombosis in 6 patients with systemic lupus erythematosus (SLE). We therefore sought to determine the prevalence and levels of antibodies to beta2-glycoprotein-I and to cardiolipin before, during, and after thrombosis in patients with SLE, and to compare them with patients who did not have thrombosis.

METHODS

We studied 24 patients with SLE who had at least one episode of thrombosis and 102 patients with SLE without thrombosis. Serum anticardiolipin antibodies were measured by conventional enzyme-linked immunosorbent assay (ELISA) using newborn calf serum as the blocking agent. Serum anti-beta2-glycoprotein-I antibodies were measured by ELISA on nonirradiated plates, using purified human beta2-glycoprotein-I without phospholipid.

RESULTS

All patients with thrombosis had anti-beta2-glycoprotein-I antibodies, compared with only 17% of controls (P <0.0001). We observed a significant decrease in serum anti-beta2-glycoprotein-I levels at the time of thrombosis, as compared with previous and subsequent samples. The prevalence and levels of IgG and IgM anticardiolipin antibodies were similar in patients with and without thrombosis. A decrease in IgG or IgM anticardiolipin titers occurred during thrombosis in 6 patients. Anticoagulant, corticosteroid, and immunosuppressive treatments did not appear to affect anti-beta2-glycoprotein-I levels at the time of thrombosis.

CONCLUSION

Anti-beta2-glycoprotein-I antibodies are strongly associated with thrombosis in patients with SLE. The decrease of anti-beta2-glycoprotein-I levels at the time of thrombosis may indicate a pathogenic role. This antibody may also be a marker of predisposition for thrombosis in these patients.

Intraoperative sentinel lymph node mapping in patients with colon cancer

BACKGROUND

The sentinel lymph node (SLN) mapping technique has been used in breast cancer and melanoma, and was recently described for colon cancer.

METHODS

Thirty-five patients with colon cancer underwent intraoperative SLN mapping. One milliliter of 1% isosulfan blue was injected subserosally around the tumor. The first nodal area that was highlighted with blue was identified as the SLN. All lymph nodes underwent examination with hematoxylin and eosin (H&E) stain. SLNs underwent additional sectioning and were stained with CAM 5.2.

RESULTS

Lymphatic mapping adequately identified the SLN in 25 patients (71%). In the 15 cases where the SLNs were negative for metastases, all other non-SLNs were also negative (0% false negative rate). The SLN was the only site of metastases in 6 (17%) of 35 patients. CAM 5.2 staining provided the only evidence of micrometastases in 4 (11%) of 35 patients.

CONCLUSIONS

Intraoperative SLN mapping is a feasible technique with a reasonable SLN identification rate (71%). The absence of metastases in the SLNs accurately predicts the status of the non-SLNs. Tumors in 11% of patients were upstaged by the demonstration of micrometastatic involvement, and these patients may benefit from further adjuvant chemotherapy.

Anti-citrullinated peptide antibodies in lupus patients with or without deforming arthropathy

The objective was to study the association of antibodies against cyclic citrullinated peptides (anti-CCP) in patients with lupus articular damage. We studied 34 systemic lupus erythematosus patients (30 women) with ( n = 14) or without ( n = 20) deforming arthropathy. Anti-DNA and arthritis were mandatory inclusion criteria for both groups. As controls, 34 patients with rheumatoid arthritis and nine patients with rheumatoid arthritis and systemic lupus erythematosus (rhupus) were included. Anti-CCP and rheumatoid factor were determined by ELISA and nephelometry respectively. All patients had recent x-ray films of the hands that were evaluated according to Sharp’s method. Systemic lupus erythematosus patients had a mean 6.50 ± 0.86 (SD, range 5–8) American College of Rheumatology (ACR) criteria, rheumatoid arthritis patients met 5.38 ± 0.60 (range 4–6) ACR criteria for rheumatoid arthritis and rhupus patients had 5.78 ± 0.44 (range 5–6) criteria for rheumatoid arthritis and 5.11 ± 0.78 (range 4–6) for systemic lupus erythematosus. Systemic lupus erythematosus patients, with or without deforming arthropathy, had normal serum anti-CCP concentrations. In contrast, rheumatoid arthritis and rhupus patients had 30- and 23-fold higher than normal amounts of anti-CCP ( p < 0.001, both comparisons). Rheumatoid arthritis (97%) and rhupus (100%) patients were more frequently positive for anti-CCP than SLE patients with (7%) or without (5%) deforming arthropathy ( p < 0.001, both comparisons). Patients with lupus deforming arthropathy were more frequently positive for rheumatoid factor (65%) than patients with non-deforming arthritis (15%) ( p = 0.005). Patients with lupus deforming arthropathy had similar frequency of erosions and mean Sharp’s score than rhupus patients. Anti-CCP antibodies do not associate with lupus arthropathy, whether deforming, non-deforming or erosive.

Effects of nitric oxide on blood flow distribution and O2 extraction capabilities during endotoxic shock

The effects of the nitric oxide (NO) synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) and the NO donor 3-morpholinosydnonimine (SIN-1) were tested in 18 endotoxic dogs. L-NMMA infusion (10 mg . kg-1 . h-1) increased arterial and pulmonary artery pressures and systemic and pulmonary vascular resistances but decreased cardiac index, left ventricular stroke work index, and blood flow to the hepatic, portal, mesenteric, and renal beds. SIN-1 infusion (2 microg . kg-1 . min-1) increased cardiac index; left ventricular stroke work index; and hepatic, portal, and mesenteric blood flow. It did not significantly influence arterial and pulmonary artery pressures but decreased renal blood flow. The critical O2 delivery was similar in the L-NMMA group and in the control group (13.3 +/- 1.6 vs. 12.8 +/- 3.3 ml . kg-1 . min-1) but lower in the SIN-1 group (9.1 +/- 1.8 ml . kg-1 . min-1, both P < 0.05). The critical O2 extraction ratio was also higher in the SIN-1 group than in the other groups (58.7 +/- 10.6 vs. 42.2 +/- 7.6% in controls, P < 0.05; 43.0 +/- 15.5% in L-NMMA group, P = not significant). We conclude that NO is not implicated in the alterations in O2 extraction capabilities observed early after endotoxin administration.

SPRR4, a novel cornified envelope precursor: UV-dependent epidermal expression and selective incorporation into fragile envelopes

The cornified cell envelope (CE), a structure formed in the outermost layers of stratified squamous epithelia, provides a physical barrier against environmental insults. It is composed of several structural proteins, which are irreversibly crosslinked by calcium-activated transglutaminases. The small proline rich proteins (SPRRs) are one set of CE precursors. SPRR4, a novel member of this gene family, displayed very low or undetectable expression levels in normal human skin or other stratified squamous epithelia, but was clearly induced by UV light both in vivo and in vitro. High epidermal expression of SPRR4 was monitored only after chronic UV exposure and was concomitant with a thickening of the stratum corneum, which is believed to provide protection against subsequent damage. The calcium-dependent translocation of an SPRR4-GFP fusion protein to the cell periphery in living keratinocytes and its integration into both rigid and fragile cornified envelopes proved that SPRR4 is a novel CE precursor. Interestingly, after UV irradiation, SPRR4 was selectively incorporated into fragile CEs. Our results show for the first time that UV-induced cornification is accompanied by qualitative changes in CE precursor assembly. SPRR4 is part of an adaptive tissue response to environmental stress, which is likely to compensate for UV induced impairment of the epidermal barrier function.

Valine/valine genotype at position 247 of the beta2-glycoprotein I gene in Mexican patients with primary antiphospholipid syndrome: association with anti-beta2-glycoprotein I antibodies

OBJECTIVE

To determine the polymorphism at position 247 of the beta(2)-glycoprotein I (beta(2)GPI) gene in Mexican patients with antiphospholipid syndrome (APS) and to compare these data in patients with or without antibodies to beta(2)GPI and with the clinical manifestations of APS.

METHODS

We studied 39 patients with primary APS and compared them with 106 clinically healthy subjects. Polymorphism was determined by polymerase chain reaction-restriction fragment length polymorphism. The presence of "true" anticardiolipin (aCL) antibodies, beta(2)GPI-dependent aCL antibodies (IgG and IgM), and phospholipid-free anti-beta(2)GPI antibodies (IgG isotype) were detected by enzyme-linked immunosorbent assay (ELISA) utilizing nonirradiated ELISA plates. Clinical manifestations associated with antiphospholipid antibodies were also evaluated.

RESULTS

We found no significant differences in the genotype expression between the control group and the primary APS patients (13% with VV, 52% with VL, and 35% with LL versus 23% with VV, 51% with VL, and 26% with LL, respectively). In contrast, anti-beta(2)GPI-positive patients had significantly higher frequencies of the VV genotype and V allele expression than the control subjects and the anti-beta(2)GPI-negative patients. These genotype and allele frequencies were also significantly higher in patients with arterial thrombosis than in patients without it. Anti-beta(2)GPI-negative patients without arterial thrombosis did not express the VV genotype. We found no differences in the Val/Leu(247) polymorphism of the beta(2)GPI gene in primary APS patients with or without "true" aCL antibodies or in primary APS patients with or without beta(2)GPI-dependent aCL antibodies.

CONCLUSION

Our results suggest that the VV genotype at position 247 of the beta(2)GPI gene may play a role in the generation of anti-beta(2)GPI antibodies and perhaps in the expression of arterial thrombosis in primary APS.

Hidden anti-phospholipid antibodies in normal human sera circulate as immune complexes whose antigen can be removed by heat, acid, hypermolar buffers or phospholipase treatments

Heat treatment of normal human serum reveals otherwise masked anti-cardiolipin antibodies (aCL). We studied the mechanism of masking and the nature of the inhibitor of these aCL IgG. Other forms of treatment, besides heating for 30 min at 56 degrees C, can also unmask hidden aCL IgG. These include acid pH, hypermolar buffers and phospholipase digestion. When unmasked, these aCL recognize other anionic and zwitterionic phospholipids, but do not react with DNA, cell antigens or IgG. Using thin layer chromatography we demonstrate that the heat-labile inhibitor(s) of these aCL are phosphatidylserine, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylcholine. These antibodies are not beta2-glycoprotein-I dependent and actually compete with this protein for phospholipid binding. The hidden antibodies are comprised of two populations of IgG autoantibodies: one reactive with cardiolipin, phosphatidylserine, phosphatidylinositol, phosphatidylglycerol, phosphatidylethanolamine and sphingomyelin, and the other reactive almost exclusively with phosphatidylcholine and phosphorylcholine on enzyme-linked immunosorbent assay plates or when exposed by bromelain on the erythrocyte surface. Our data suggest that hidden aCL are natural oligoreactive IgG anti-phospholipid autoantibodies that circulate masked by their antigen.

Phospholipid specificity and requirement of beta 2-glycoprotein-I for reactivity of antibodies from patients with primary antiphospholipid syndrome

Some disease manifestations are associated with serum antiphospholipid antibodies (aPL) in patients with systemic lupus erythematosus (SLE) in what has been termed antiphospholipid syndrome (aPLS). There are patients with aPLS who do not have SLE or any other illness who have been grouped under the term primary antiphospholipid syndrome (PAPS). However, patients with diverse infections, notably syphilis, may have aPL but do not develop the associated clinical manifestations. This has been attributed, at least in part, to the immunochemical features of their aPL, including the requirement for beta 2-glycoprotein-I (beta 2GP-I) for binding of aPL to phospholipids, but these have not been studied in sera from patients with PAPS. By ELISA we studied 95 sera from 17 patients with PAPS and 100 sera from clinically normal individuals for IgG and IgM antibodies to the main anionic and zwitterionic phospholipids and their related compounds, phosphatidic acid (PA) and synthetic phosphorylcholine (PRC). beta 2GP-I was present, either in newborn calf serum (NBCS) or purified, to block wells and to dilute samples, or was substituted by 0.3% gelatin. Inhibition studies with phospholipid micelles were used to confirm reactivities with the corresponding phospholipids. All 17 patients had IgG and 11 had IgM antibodies to cardiolipin. Antibodies to anionic phospholipids were primarily IgG whereas those to zwitterionic phospholipids were mainly, and often exclusively, IgM. We found a statistically significant difference in the mean levels of antibodies to all anionic phospholipids except aPTS, and to the haptene PA (P < 0.001) between patients and controls. The difference between levels of IgM antibodies to zwitterionic phospholipids was statistically significant with sphingomyelin (P < 0.001) and the haptene (P < 0.001). Levels of most IgG and most IgM aPL correlated significantly among them. The pattern and titers of reactivity are variable between patients, but stable within each patient. Requirement of beta 2GP-I for this reactivity was not an all-or-nothing phenomenon in individual sera. In general, as in lupus sera, antibodies to anionic phospholipids require that this cofactor be present coating the ELISA plates, whereas those to zwitterionic phospholipids do not. It would appear that patients with PAPS have polyclonal mixtures of antibodies that react with various phospholipids and have different requirements for beta 2GP-I for such reactivity.

Fear state induced by ethanol withdrawal may be due to the sensitization of the neural substrates of aversion in the dPAG

The neural substrate underlying the aversive effects induced by ethanol abstinence is still unclear. One candidate for such effects is the dorsal periaqueductal gray (dPAG), a core structure of the brain aversion system. The main aim of this study is to examine the role of the dPAG as a possible locus of the aversive effects following abrupt alcohol withdrawal. To this end, rats were subjected to an oral ethanol self-administration procedure, in which animals were offered 6-8% (v/v) ethanol solution for a period of 21 days followed by an abrupt discontinuation of the treatment on the two subsequent days. Control animals received control dietary fluid for similar periods of time. The effects of ethanol withdrawal were examined in the elevated plus-maze (EPM) (Exp. I), on the prepulse inhibition of startle to loud sounds (Exp. II) and on the freezing and escape responses induced by electrical stimulation of the dPAG (Exp. III). In Experiment III, rats were implanted with an electrode aimed at the dPAG and the number and duration of ultrasonic vocalizations (USVs) were also recorded in the rats that received dPAG stimulation at freezing and escape thresholds. Data obtained showed that ethanol withdrawal elicited significant "anxiety-like" behaviors, as revealed by the decrease in the number of entries into and time spent onto the open arms of the EPM. Startle reflex and prepulse inhibition remained unchanged in withdrawn animals. In addition, discontinuation from the chronic ethanol regimen caused a reduction in the stimulation thresholds for freezing and escape and in the number and duration of USVs. Together, these effects have been interpreted in the frame of a high fear state elicited by activation of the dPAG. These findings are indicative that ethanol withdrawal sensitizes the substrates of fear at the level of this midbrain structure.

Characterization of anti-phosphatidylcholine polyreactive natural autoantibodies from normal human subjects

In 1990 our group reported a patient with autoimmune hemolytic anemia and high titers of IgM anticardiolipin antibodies that cross-reacted with phosphatidylcholine (PTC). These autoantibodies also recognized bromelain-treated erythrocytes (BrE) and in vitro aged erythrocytes. The epitope exposed with this treatment is PTC. To detect and characterize antiphosphatidylcholine antibodies (anti-PTC) in a normal human population, we studied by ELISA the presence of serum anti-PTC (IgG and IgM) in clinically healthy human subjects. The most representative samples were also studied for IgG or IgM activity against BrE by flow cytometry, rheumatoid factor activity, anti-dsDNA, anti-ssDNA by ELISA and by indirect immunofluorecence (IIF) using HEp-2 line and a healthy human fibroblast strain as substratum. Eighty five percent of sera had IgM anti-PTC and none had IgG. IgM antibodies against BrE were inhibited by PTC micelles (mPTC). Anti-PTC were also inhibited by phosphorylcholine and phosphatidic acid. Aggregated gammaglobulin (AGG) reactivity was inhibited by dsDNA and mPTC. The IgM anti-dsDNA activity was inhibited by soluble dsDNA, AGG and mPTC. All sera gave intermediate filaments pattern by IIF and reacted against purified vimentin by dot blot and Western blot.Our study shows hemolytic IgM anti-PTC present in normal human serum. The main epitope recognized by these autoantibodies is phosphorylcholine. The physicochemical characteristics, crossreactivity with self-antigens and functional properties are typical features of natural autoantibodies.