Biomedical subjects

Kazuko Kobayashi

Publications and source records attributed to Kazuko Kobayashi.

At least 19 recordsLinked to original sources

PubMed2006

Oxidative modification of low-density lipoprotein and immune regulation of atherosclerosis.

Oxidized low-density lipoprotein (oxLDL) is thought to promote atherosclerosis through complex inflammatory and immunologic mechanisms that lead to lipid dysregulation and foam cell formation. Recent findings suggested that oxLDL forms complexes with beta2-glycoprotein I (beta2GPI) and/or C-reactive protein (CRP) in the intima of atherosclerotic lesions. Autoantibodies against oxLDL/beta2GPI complexes occur in patients with systemic lupus erythematosus (SLE) and/or antiphospholipid syndrome (APS) and significantly correlate with arterial thrombosis. IgG autoantibodies having similar specificity emerged spontaneously in non-immunized NZWxBXSB F1 mice, an animal model of APS, and a monoclonal autoantibody (WB-CAL-1; IgG2a) against complexed beta2GPI (oxLDL/beta2GPI complexes) was derived from the same mice. WB-CAL-1 significantly increased the in vitro uptake of oxLDL/beta(2)GPI complexes by macrophages. This observation strongly suggests that such IgG autoantibodies are pro-atherogenic. In contrast, IgM anti-oxLDL natural antibodies found in the atherosclerosis-prone mice (ApoE(-/-) and LDL-R(-/-) mice) have been proposed to be anti-atherogenic (protective). The presence of IgG anti-oxLDL antibodies in humans has been documented in many publications but their exact clinical significance remains unclear. In this article, we review recent progress in our understanding of the mechanisms involved in oxidation of LDL, formation of oxLDL complexes, and antibody mediated-immune regulation of atherogenesis.

Antibodies↗

PubMed2006

Accelerated atheroma in the antiphospholipid syndrome.

Increased cardiovascular morbidity and mortality due to the pre-mature or accelerated development of atherosclerosis has been reported in patients with systemic autoimmune diseases such as systemic lupus erythematosus. These findings motivated a great deal of research into the role of autoimmunity in atherogenesis. The relationship between atherosclerosis and cholesterol metabolism to atherosclerosis has been well established. However, the participation of newer inflammatory and immunologic mechanisms are emerging as relevant factors for the initiation and progression of atherosclerotic lesions.

Antibodies, Antiphospholipid↗

PubMed2006

Relationship between AUC of 5'-DFUR and toxicity of capecitabine, fluoropyrimidine carbamate analogs, and 5'-DFUR in monkeys, mice, and rats.

Capecitabine is an oral fluoropyrimidine carbamate which is converted to 5-fluorouracil (5-FU) via 3 enzymatic step to 5'-deoxy-5-fluorocytidine (5'-DFCR), 5'-deoxy-5-fluorouridine (5'-DFUR), and finally 5-FU. We performed 4-week toxicity studies of capecitabine (N(4)-pentyloxycarbonyl-5'-deoxy-5-fluorouridine), galocitabine (trimethoxybenzyl-5'-deoxy-5-fluorocytidine), 4 different fluoropyrimidine carbamate analogs (R=butyl, isopentyl, propyl, or phenethyl), and 5'-DFUR in cynomolgus monkeys with toxicokinetic measurements of intact molecules, 5'-DFCR, and 5'-DFUR. Four-week toxicity data for capecitabine in rats and mice were also obtained for comparison. Capecitabine, galocitabine, butyl, and isopentyl analogs showed similar toxicities in hematopoietic and intestinal organs at 1.0 mmol/kg and the AUCs of 5'-DFUR were approximately 40 to 60 microg*hr/ml. These compounds showed slight toxicity at 0.5 mmol/kg and no toxicity at 0.1 mmol/kg, and AUCs of 5'-DFUR were approximately 30 and 5 microg*hr/ml, respectively. Propyl and phenethyl analogs showed slight toxicity at 1.0 mmol/kg and no toxicity at 0.5 mmol/kg, and AUCs of 5'-DFUR were approximately 30 and 10 microg*hr/ml, respectively. On the other hand, severe and slight-to-moderate toxicity was observed at 0.5 and 0.25 mmol/kg in 5'-DFUR-treated monkeys and AUCs of 5'DFUR were 35.6 and 5.2 microg*hr/ml, respectively. In mice and rats, the toxicity of capecitabine was less than in monkeys relative to dose, but 5'-DFUR AUCs were almost the same. In conclusion, 5'-DFUR AUC correlated with toxicity following oral administration of capecitabine and its analogs in monkeys, mice, and rats, although this relationship is not seen in humans. Capecitabine was less toxic in monkeys than oral 5'-DFUR according to dose (mmol/kg) and 5'-DFUR AUC.

Animals↗

PubMed2005

Antigenic structures recognized by anti-beta2-glycoprotein I auto-antibodies.

Beta2-glycoprotein I (beta2-GPI) is a major antigen for anti-cardiolipin antibodies and their epitopes are cryptic. Conformation of each domain of beta2-GPI was optimized from its crystal structure by energy minimization and by molecular dynamics simulation. Three electrostatic interactions, i.e. D193-K246, D222-K317 and E228-K308, were observed between domains IV and V in the optimized structure that was constructed based on the consensus sequences obtained by the phage-displayed random peptide library. Antigenic structures determined by the epitope mapping mainly consisted of hydrophobic amino acids located on two discontinuous sequences in domain IV. These amino acid clusters, as an epitope, were covered by domain V and were of a hidden nature. A similar but incomplete counterpart to the epitopic clusters was found in domain I but was not in domains II or III. Binding of anti-beta2-GPI auto-antibodies to solid-phase beta2-GPI was significantly reduced either by L replacement for W235, a common amino acid component for the epitopes, or by V replacement for all of D193, D222 and E228. Structural analysis indicated a hypothesis that these electrostatic interactions between domains IV and V retained exposure to W235 and that epitope spreading occurred in the region surrounding W235. Thus, epitopic structures recognized by anti-beta2-GPI auto-antibodies are cryptic and inter-domain electrostatic interactions are involved in their in exposure.

Amino Acid Substitution↗

PubMed2005

Increase of serum angiopoietin-2 during pregnancy is suppressed in women with preeclampsia.

BACKGROUND: Numerous recent reports demonstrated that changes in serum levels of angiogenesis-related factors were associated with preeclampsia. Here, we determined the serum concentration of angiopoietin-2 (Ang-2), a natural antagonist of angiopoietin-1 (Ang-1) involved in promoting angiogenesis in the presence of angiogenic stimuli such as vascular endothelial growth factor (VEGF), in women with preeclampsia. METHODS: The levels of serum Ang-2 and Tie-2, a receptor for Ang-1 expressed on endothelial cells, were determined by enzyme-linked immunosorbent assay. RESULTS: The concentrations of serum Ang-2 were significantly elevated in healthy pregnant women (18.9 ng/mL) as compared to nonpregnant women or women in postpartum period. Increase in the levels of serum Ang-2 was significantly suppressed in preeclamptic women (4.5 ng/mL). The serum Ang-2 concentrations inversely correlated with gestational age in healthy pregnant women, but not in preeclamptic women. The serum Ang-2 concentrations positively correlated with placental weight or mean blood pressure (BP) in healthy pregnant women, but not in preeclamptic women. The serum Ang-2 concentrations inversely correlated with proteinuria in preeclamptic women. The serum concentrations of Tie-2 were not significantly different between preeclamptic and nonpreeclamptic women. CONCLUSIONS: These results suggest the potential requirement of circulating Ang-2 in proper formation of placental vasculatures during pregnancy. Although we cannot exclude the possibility that suppression in the increase of serum Ang-2 levels during pregnancy in preeclampsia as a consequence rather than a cause, measurement of serum Ang-2 concentration in pregnant women may serve as a useful marker in the diagnosis and potentially in predicting subsequent development of preeclampsia.

Adult↗

PubMed2005

Characterization of a murine anti-laminin-1 monoclonal antibody (AK8) produced by immunization with mouse-derived laminin-1.

Laminin-1 is a structural glycoprotein that forms an integral part of the scaffolding of basement membranes, and plays an important role during embryonic development. We have recently demonstrated a significant association between anti-laminin1 antibodies (Abs) and reproductive failure, such as recurrent spontaneous abortions and infertility-associated endometriosis in both human and mouse studies. In the present study, we established an IgM (micro, kappa) monoclonal anti-laminin-1 Ab (AK8) by immunizing mice with mouse Engelbreth-Holm-Swarm sarcoma (EHS)-derived laminin-1. The AK8 monoclonal antibody (mAb) reacted with particular peptide sequences from the globular G domain of mouse laminin-alpha1 chain of using ELISA and Western blot techniques. The peptide tertiary structure of the epitope recognized by AK8 mAb was predicted using eight synthesized domain peptide sequences and three consensus sequences obtained by phage displayed random peptide library. Basement membranes of endometrium of pregnant mice and humans were immunostained with AK8 mAb. Thus, AK8 mAb recognized a common structure present in the G domain of the laminin-alpha1 chain in both mice and humans. The passive immunization of mice with AK8 mAb may represent a suitable animal model for anti-laminin-1 Ab-mediated reproductive failure.

Amino Acid Sequence↗

PubMed2005

The role of innate and adaptive immunity to oxidized low-density lipoprotein in the development of atherosclerosis.

Atherosclerosis is a chronic inflammatory process of the arterial wall associated with systemic and local immune responses to various antigens, oxidized low-density lipoprotein (oxLDL) being the most significant. Both IgM and IgG antibodies to oxLDL are produced during atherosclerosis. Some studies have shown that elevated levels of antibody to oxLDL correlate with the degree of atherosclerosis. Other studies reported that immunization of experimental animals with oxLDL induces high levels of antibodies to oxLDL, with decreased atherosclerosis, suggesting that the immune response to oxLDL may be antiatherogenic. The accelerated development of atherosclerosis has been observed in patients with systemic autoimmune diseases. In patients with antiphospholipid syndrome (APS), beta2-glycoprotein I (beta2GPI) is a major antigenic target for anticardiolipin antibodies (aCLs). We recently reported that oxLDL interacts with beta2GPI via oxLDL-derived specific ligands, such as 7-ketocholesteryl-9-carboxynonanoate (oxLig-1) to form complexes. In vitro, anti-beta2GPI autoantibodies bind to oxLDL/beta2GPI complexes that are actively taken up by macrophages via Fcgamma receptors. Circulating oxLDL/beta2GPI complexes were detected in patients with systemic lupus erythematosus (SLE) and APS, at higher levels than in healthy individuals. Autoantibodies against these complexes were also present; however, IgG anti-oxLig-1/beta2GPI antibody levels in SLE patients with APS were significantly higher than those in SLE patients without APS and those in healthy individuals.

Animals↗

PubMed2005

Stomach- and site-selective delivery of 5-fluorouracil following its application on the gastric serosal surface in rats.

The present study was undertaken to elucidate the stomach- and site-selective delivery of 5-fluorouracil (5-FU) following its application on the gastric serosal surface in rats. An experimental system utilizing a cylindrical diffusion cell attached to the gastric serosal surface was established. To evaluate the gastric distribution of 5-FU, the stomach was separated into the site under the diffusion cell (site 1) and the site not under the diffusion cell (site 2). Furthermore, the mucosal side at site 1 was separated from the serosal side. After intravenous and oral administration of 5-FU, the 5-FU concentrations at sites 1 and 2 until 240 min were similar. After gastric serosal surface application of 5-FU, however, the concentration of 5-FU at site 1 until 240 min was approximately 10-fold higher than that at site 2, and was sustained. Furthermore, the 5-FU concentration on the mucosal side at site 1 and the serosal side at site 1 were comparable after gastric serosal surface application. The blood concentration of 5-FU was low (<4.4 microg/ml) until 240 min after gastric serosal surface application. The maximum blood concentration of 5-FU after gastric serosal surface application was significantly lower than after intravenous administration. Thus, the stomach- and site-selective delivery system following application on the gastric serosal surface could be applied with anticancer drugs for the treatment of gastric cancer.

Animals↗

PubMed2005

Intravenous immunoglobulin and atherosclerosis.

Several inflammatory and immunological factors have been established as important contributors to atherogenesis. Among these, oxidized low-density lipoprotein (oxLDL) play a central role in the initiation and progression of atherosclerotic lesions. In atherosclerotic lesions, oxLDL was also found to co-localize with beta2-glycoprotein I (beta2-GPI). Immunoglobulin (Ig)G autoantibodies against beta2-GPI complexed with oxLDL are pro-atherogenic because they increase uptake of the complexes by macrophages. In contrast, IgM natural anti-oxLDL antibodies derived from atherosclerosis-prone apolipoprotein E (ApoE) deficient mice reduced incidence of atherosclerosis. Such anti-oxLDL antibodies have been found in humans, and the accumulating evidences seem to support the idea that anti-oxLDL antibodies have a protective role for atherogenesis. Intravenous immunoglobulins (IVIgs) contain natural anti-oxLDL antibodies and infusion of IVIg into ApoE-deficient mice has been reported to decrease atherosclerosis. The anti-atherogenic property of IVIg may be derived from non-antigen-specific antibody binding to FCgamma receptors, which blocks foam cell formation of macrophages. Several other possible mechanisms are also discussed.

Animals↗

PubMed2004

Binding of beta 2-glycoprotein I to anionic phospholipids facilitates processing and presentation of a cryptic epitope that activates pathogenic autoreactive T cells.

Antiphospholipid syndrome (APS) is an autoimmune prothrombotic disorder in association with autoantibodies to phospholipid (PL)-binding plasma proteins, such as beta(2)-glycoprotein I (beta(2)GPI). We have recently found that CD4(+) T cells autoreactive to beta(2)GPI in patients with APS preferentially recognize a cryptic peptide encompassing amino acid residues 276-290 (p276-290), which contains the major PL-binding site, in the context of DR53. However, it is not clear how previously cryptic p276-290 becomes visible to the immune system and elicits a pathogenics autoimmune response to beta(2)GPI. Here we show that presentation of a disease-relevant cryptic T-cell determinant in beta(2)GPI is induced as a direct consequence of antigen processing from beta(2)GPI bound to anionic PL. Dendritic cells or macrophages pulsed with PL-bound beta(2)GPI induced a response of p276-290-specific CD4(+) T-cell lines generated from the patients in an HLA-DR-restricted and antigen-processing-dependent manner but those with beta(2)GPI or PL alone did not. In addition, the p276-290-reactive T-cell response was primed by stimulating peripheral blood T cells from DR53-carrying healthy individuals with dendritic cells bearing PL-bound beta(2)GPI in vitro. Our finding is the first demonstration of an in vitro mechanism eliciting pathogenic autoreactive T-cell responses to beta(2)GPI and should be useful in clarifying the pathogenesis of APS.

Animals↗

PubMed2004

Nicked beta2-glycoprotein I: a marker of cerebral infarct and a novel role in the negative feedback pathway of extrinsic fibrinolysis.

BEta(2)-glycoprotein I (beta(2)-GPI) is proteolytically cleaved by plasmin in domain V (nicked beta(2)-GPI), being unable to bind to phospholipids. This cleavage may occur in vivo and elevated plasma levels of nicked beta(2)-GPI were detected in patients with massive plasmin generation and fibrinolysis turnover. In this study, we report higher prevalence of elevated ratio of nicked beta(2)-GPI against total beta(2)-GPI in patients with ischemic stroke (63%) and healthy subjects with lacunar infarct (27%) when compared to healthy subjects with normal findings on magnetic resonance imaging (8%), suggesting that nicked beta(2)-GPI might have a physiologic role beyond that of its parent molecule in patients with thrombosis. Several inhibitors of extrinsic fibrinolysis are known, but a negative feedback regulator has not been yet documented. We demonstrate that nicked beta(2)-GPI binds to Glu-plasminogen with K(D) of 0.37 x 10(-6) M, presumably mediated by the interaction between the fifth domain of nicked beta(2)-GPI and the fifth kringle domain of Glu-plasminogen. Nicked beta(2)-GPI also suppressed plasmin generation up to 70% in the presence of tissue plasminogen activator, plasminogen, and fibrin. Intact beta(2)-GPI lacks these properties. These data suggest that beta(2)-GPI/plasmin-nicked beta(2)-GPI controls extrinsic fibrinolysis via a negative feedback pathway loop.

Aged↗

PubMed2004

Clinical significance of serum oxidized low-density lipoprotein/beta2-glycoprotein I complexes in patients with chronic renal diseases.

BACKGROUND: Peroxidation of low-density lipoprotein (LDL) plays an important role in the development of dyslipidemias associated with the progression of chronic renal disorders. We recently reported [J Lipid Res 2001;42:697, 2002;43:1486, 2003;44:716] that oxidized LDL (oxLDL) interacts with an endogenous plasma protein, beta2-glycoprotein I (beta2GPI), via specific ligands. In the present study, the prevalence and clinical significance of oxLDL/beta2GPI complexes were evaluated in patients with chronic renal disorders. METHODS: Serum levels of oxLDL/beta(2)GPI complexes were measured by ELISA in patients with chronic renal disease and their association with clinical manifestations was assessed. RESULTS: The serum levels of oxLDL/beta2GPI complexes were significantly higher in patients with chronic renal failure (CRF), chronic nephritis (CN) and diabetes mellitus than those in healthy individuals. The presence of complexes in patients with CN was significantly associated with high dietary protein and sodium chloride intake, but not with lipid metabolic parameters. Malondialdehyde-modified LDL was significantly associated with total cholesterol and LDL cholesterol in all patient groups, but did not correlate with renal function parameters. CONCLUSIONS: Serum oxLDL/beta2GPI complexes, generated by oxidative stress and associated with high dietary protein and salt intake, might be a novel risk factor and a diagnostic marker for the development of chronic renal diseases, especially IgA nephropathy.

Biomarkers↗

PubMed2004

Oxidized low-density lipoprotein/beta2-glycoprotein I complexes and autoantibodies to oxLig-1/beta2-glycoprotein I in patients with systemic lupus erythematosus and antiphospholipid syndrome.

Oxidized low-density lipoprotein (oxLDL) interacts with beta2-glycoprotein I (beta2-GPI) via oxLDL-derived specific ligands (oxLig-1) forming complexes. The prevalence and significance of oxLDL/alpha2-GPI complexes and antibodies to oxLig-1/alpha2-GPI were evaluated in patients with systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS). The oxLDL/beta2-GPI complex was 69% positive (above mean + 3 SD of control subjects) in 97 consecutive patients with SLE, 62% in 40 patients with SLE with secondary APS, and 60% in 50 control patients with SLE without APS. IgG anti-oxLig-1/beta2-GPI antibody was positive in 31 (32%) of 97 consecutive patients with SLE, in 26 (65%) of 40 patients with SLE with secondary APS, and in 6 (19%) of 32 control patients with SLE. Anti-oxLig-1/beta2-GPI antibodies were 93.7% specific with a positive predictive value of 90.0% for APS, better than anticardiolipin antibodies (80.0% specific, 71.4% predictive value). These results confirm that oxLDL/beta2-GPI complexes are common in SLE and suggest a possible immunogenic role in APS. In contrast, IgG anti-oxLig-1/beta2-GPI antibodies not only are associated with but also are clinically useful risk factors for APS.

Adolescent↗

PubMed2003

Circulating oxidized LDL forms complexes with beta2-glycoprotein I: implication as an atherogenic autoantigen.

Beta2-glycoprotein I (beta2-GPI) is a major antigen for antiphospholipid antibodies (Abs, aPL) present in patients with antiphospholipid syndrome (APS). We recently reported (J. Lipid Res., 42: 697, 2001; J. Lipid Res., 43: 1486, 2002) that beta2-GPI specifically binds to Cu2+-oxidized LDL (oxLDL) and that the beta2-GPI ligands are omega-carboxylated 7-ketocholesteryl esters. In the present study, we demonstrate that oxLDL forms stable and nondissociable complexes with beta2-GPI in serum, and that high serum levels of the complexes are associated with arterial thrombosis in APS. A conjugated ketone function at the 7-position of cholesterol as well as the omega-carboxyl function of the beta2-GPI ligands was necessary for beta2-GPI binding. The ligand-mediated noncovalent interaction of beta2-GPI and oxLDL undergoes a temperature- and time-dependent conversion to much more stable but readily dissociable complexes in vitro at neutral pH. In contrast, stable and nondissociable beta2-GPI-oxLDL complexes were frequently detected in sera from patients with APS and/or systemic lupus erythematodes. Both the presence of beta2-GPI-oxLDL complexes and IgG Abs recognizing these complexes were strongly associated with arterial thrombosis. Further, these same Abs correlated with IgG immune complexes containing beta2-GPI or LDL. Thus, the beta2-GPI-oxLDL complexes acting as an autoantigen are closely associated with autoimmune-mediated atherogenesis.

Adolescent↗

PubMed2003

An association of IgG anti-laminin-1 autoantibodies with endometriosis in infertile patients.

BACKGROUND: Laminin-1, a multifunctional glycoprotein of the basement membrane, is thought to be important in embryogenesis, embryonic implantation, and placentation. We recently showed that serum IgG anti-laminin-1 autoantibodies (auto-Abs) are associated with recurrent first-trimester miscarriages. The present study assessed the clinical significance of anti-laminin-1 Abs with infertility, accompanied with or without endometriosis. METHODS: Sixty-eight infertile patients who underwent laparoscopy or laparotomy and 39 healthy non-pregnant women were tested for IgG anti-laminin-1 Abs. The association between the Abs and endometriosis was analysed. The presence of laminin-1 mRNA was detected in endometriotic lesions. RESULTS: Twenty infertile patients were positive for anti-laminin-1 Abs. The Ab levels in those patients were significantly higher than those in healthy non-pregnant women (P = 0.0005). The presence of the Abs was significantly associated with endometriosis in those patients (P = 0.0096). The Abs recognized a particular domain, i.e., the laminin-alpha1 chain G domain. mRNA encoding laminin-alpha1, -beta1, and -gamma1 chains was expressed in 90% of endometriotic lesions. CONCLUSIONS: IgG anti-laminin-1 Abs were significantly associated with endometriosis in infertile patients. The Abs might be clinically important in the development of autoimmune-mediated reproductive failures and the assessment of the Abs may provide a novel non-invasive diagnosis of endometriosis.

Adult↗

PubMed2003

Mechanisms of benzene-induced hematotoxicity and leukemogenicity: cDNA microarray analyses using mouse bone marrow tissue.

Although the mechanisms underlying benzene-induced toxicity and leukemogenicity are not yet fully understood, they are likely to be complicated by various pathways, including those of metabolism, growth factor regulation, oxidative stress, DNA damage, cell cycle regulation, and programmed cell death. With this as a background, we performed cDNA microarray analyses on mouse bone marrow tissue during and after a 2-week benzene exposure by inhalation. Our goal was to clarify the mechanisms underlying the hematotoxicity and leukemogenicity induced by benzene at the level of altered multigene expression. Because a few researchers have postulated that the cell cycle regulation mediated by p53 is a critical event for benzene-induced hematotoxicity, the present study was carried out using p53-knockout (KO) mice and C57BL/6 mice. On the basis of the results of large-scale gene expression studies, we conclude the following: (a) Benzene induces DNA damage in cells at any phase of the cell cycle through myeloperoxidase and in the redox cycle, resulting in p53 expression through Raf-1 and cyclin D-interacting myb-like protein 1. (b) For G1/S cell cycle arrest, the p53-mediated pathway through p21 is involved, as well as the pRb gene-mediated pathway. (c) Alteration of cyclin G1 and Wee-1 kinase genes may be related to the G2/M arrest induced by benzene exposure. (d) DNA repair genes such as Rad50 and Rad51 are markedly downregulated in p53-KO mice. (e) p53-mediated caspase 11 activation, aside from p53-mediated Bax gene induction, may be an important pathway for cellular apoptosis after benzene exposure. Our results strongly suggest that the dysfunction of the p53 gene, possibly caused by strong and repeated genetic and epigenetic effects of benzene on candidate leukemia cells, may induce fatal problems such as those of cell cycle checkpoint, apoptosis, and the DNA repair system, finally resulting in hemopoietic malignancies. Our cDNA microarray data provide valuable information for future investigations of the mechanisms underlying the toxicity and leukemogenicity of benzene.

Administration, Inhalation↗

PubMed2002

Autoantibody-mediated atherosclerosis.

Beta2-glycoprotein I (beta2-GPI) is a major antigen for antiphospholipid antibodies (aPL) present in patients with antiphospholipid syndrome (APS). Oxidized low-density lipoprotein (oxLDL) is subsequently targeted by beta2-GPI and anti-beta2-GPI autoantibodies. Ligands specific for beta2-GPI derived from oxLDL have been characterized as oxidized forms of cholesteryl linoleate, such as 7-ketocholesterol-9-carboxynonanoate, i.e. 9-oxo-9-(7-ketocholest-5-en-3beta-yloxy) nonanoic acid, (namely oxLig-1). The in vitro phenomenon that it is significantly increased in binding of oxLig-1 containing liposomes to macrophages via an interaction with beta2-GPI and an anti-beta2-GPI autoantibody (via the Fcgamma receptor) may propose a novel mechanism on 'autoantibody-mediated atherosclerosis'. Furthermore, autoantibodies against a complex of beta2-GPI and oxLig-1 are detected in sera of APS patients and appearance of the antibodies is associated with episodes of thrombosis, especially, arterial thrombosis. Thus, autoimmune atherogenesis linked to beta2-GPI interaction with oxLDL and autoantibodies may be present in APS.

Antibodies, Antiphospholipid↗

PubMed2002

Omega-carboxyl variants of 7-ketocholesteryl esters are ligands for beta(2)-glycoprotein I and mediate antibody-dependent uptake of oxidized LDL by macrophages.

beta(2)-Glycoprotein I (beta(2)-GPI) is a major antigen for anticardiolipin antibodies (aCL, Abs) present in patients with antiphospholipid syndrome. We recently reported that beta(2)-GPI specifically binds to oxidized LDL (oxLDL) and that the beta(2)-GPI's major ligand, oxLig-1 is 7-ketocholesteryl-9-carboxynonanoate (Kobayashi, K., E. Matsuura, Q. P. Liu, J. Furukawa, K. Kaihara, J. Inagaki, T. Atsumi, N. Sakairi, T. Yasuda, D. R. Voelker, and T. Koike. 2001. A specific ligand for beta(2)-glycoprotein I mediates autoantibody-dependent uptake of oxidized low density lipoprotein by macrophages. J. Lipid Res. 42: 697-709). In the present study, we demonstrate that omega-carboxylated 7-ketocholesteryl esters are critical for beta(2)-GPI binding. A positive ion mass spectrum of a novel ligand, designated oxLig-2, showed fragmented ions at m/z 383 and 441 in the presence of acetone, which share features of oxLig-1 and 7-ketocholesterol. In the negative ion mode, ions at m/z 627, 625, and 243 were observed. oxLig-2 was most likely 7-ketocholesteryl-12-carboxy (keto) dodecanoate. These ligands were recognized by beta(2)-GPI. Liposome binding to macrophages was significantly increased depending on the ligand's concentration, in the presence of beta(2)-GPI and an anti-beta(2)-GPI Ab. Synthesized variant, 7-ketocholesteryl-13-carboxytridecanoate (13-COOH-7KC), also showed a significant interaction with beta(2)-GPI and a similar binding profile with macrophages. Methylation of the carboxyl function diminished all of the specific ligand interactions with beta(2)-GPI. Thus, omega-carboxyl variants of 7-ketocholesteryl esters can mediate anti-beta(2)-GPI Ab-dependent uptake of oxLDL by macrophages, and autoimmune atherogenesis linked to beta(2)-GPI interaction with oxLDL.

Antibodies↗