Ruud Theunissen

Vascular inflammation in cerebral small vessel disease

Cerebral small vessel disease (CSVD) is considered to be caused by an increased permeability of the blood-brain barrier and results in enlargement of Virchow Robin spaces (VRs), white matter lesions, brain microbleeds, and lacunar infarcts. The increased permeability of the blood-brain barrier may relate to endothelial cell activation and activated monocytes/macrophages. Therefore, we hypothesized that plasma markers of endothelial activation (adhesion molecules) and monocyte/macrophage activation (neopterin) relate to CSVD manifestations. In 163 first-ever lacunar stroke patients and 183 essential hypertensive patients, we assessed CSVD manifestations on brain magnetic resonance imaging (MRI) and levels of C-reactive protein (CRP), neopterin, as well as circulating soluble adhesion molecules (sICAM-1, sVCAM-1, sE-selectin, sP-selectin). Neopterin, sICAM-1 and sVCAM-1 levels were higher in patients with extensive CSVD manifestations than in those without (p < 0.01). Neopterin levels independently related to higher numbers of enlarged Virchow Robin spaces (p < 0.001). An inflammatory process with activated monocytes/macrophages may play a role in the increased permeability of the blood brain barrier in patients with CSVD.

Expression of NLRP3 inflammasome and T cell population markers in adipose tissue are associated with insulin resistance and impaired glucose metabolism in humans

Recent studies in rodents indicate that the nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome and a proinflammatory shift in the T cell population in adipose tissue (AT) contribute to AT inflammation and insulin resistance. We investigated: (1) the interplay between the NLRP3 inflammasome and T cell populations in abdominal subcutaneous AT in obese and lean humans in relation to AT inflammatory processes, and (2) involvement of the NLRP3 inflammasome and T cell populations in insulin resistance. Abdominal subcutaneous AT biopsies were collected in 10 obese men with impaired glucose tolerance and 9 lean normal glucose tolerant age-matched controls. AT gene expression of NLRP3 inflammasome-related genes and markers of T cell populations, chemoattraction, macrophage infiltration and other aspects of inflammation were examined. Furthermore, we examined systemic adaptive immune activation and insulin sensitivity (hyperinsulinemic-euglycemic clamp). CASPASE-1 mRNA and the proportion of T(h)1 transcripts (TBX21/CD3ɛ) were significantly higher in AT from obese compared with lean subjects. CASPASE-1 expression and a relative increase in T(h)1 transcripts in AT were strongly associated with insulin resistance and impairments in glucose homeostasis. Gene expression of NLRP3, CASPASE-1, CD3ɛ (pan T cells), TBX21 (T(h)1 cells) and RORC (T(h)17 cells) was positively, whereas GATA3 (T(h)2 cells) was inversely correlated with AT inflammation. Our data suggest that NLRP3 inflammasome activation and a T(h)1 shift in the T cell population in AT of obese subjects is related to insulin resistance and impaired glucose metabolism, which may be explained by AT inflammatory processes.

Haptoglobin Phenotype May Alter Endothelial Progenitor Cell Cluster Formation in Cerebral Small Vessel Disease

Cerebral small vessel disease results in silent ischemic lesions (SIL) among which is leukoaraiosis. In this process, endothelial damage is probably involved. Endothelial progenitor cells (EPC), are involved in endothelial repair. By restoring the damaged endothelium, EPC could mitigate SIL and cerebral small vessel disease. Haptoglobin 1-1, one of three phenotypes of haptoglobin, relates to SIL and may therefore attenuate the endothelial repair by EPC. Our aim was to quantify EPC number and function and to assess haptoglobin phenotype and its effect on EPC function in patients with a high prevalence of SIL: lacunar stroke patients. We assessed EPC In 42 lacunar stroke patients and 18 controls by flow cytometry and culture with fetal calf serum, patient and control serum. We determined haptoglobin phenotype and cultured EPC with the three different haptoglobin phenotypes. We found that EPC cluster counts were lower in patients (96.9 clusters/well +/- 83.4 (mean +/- SD)), especially in those with SIL (85.0 +/- 64.3), than in controls (174.4 +/- 112.2). Cluster formation was inhibited by patient serum, especially by SIL patient serum, but not by control serum. Patients with haptoglobin 1-1 had less clusters in culture, and when haptoglobin 1-1 was added to EPC cultures, cluster numbers were lower than with the other haptoglobin phenotypes. We conclude that lacunar stroke patients, especially those with SIL, have impaired EPC cluster formation, which may point at decreased endothelial repair potential. The haptoglobin 1-1 phenotype is likely a causative factor in this impairment.

Cross-Reactivity of IgM and IgG Anticardiolipin Antibodies with Oxidized-Low Density Lipoproteins

Abstract: Anticardiolipin antibodies (aCLAs) and antibodies to oxidized‐low density lipoproteins (oxLDL) are associated with two distinct diseases: the antiphospholipid syndrome and atherosclerosis. Because both diseases may be apparent in patients with systemic lupus erythematosus (SLE), it is important to establish the relationship between these two types of antibodies. In the present study, we examined whether sera containing IgM and/or IgG aCLAs also react with LDL that has been oxidized by conjugation with malondialdehyde (MDA‐LDL) or by incubation with copper ions (Cu‐LDL). Results revealed a clear correlation between IgM aCLAs and IgM anti‐MDA‐LDL antibodies, and a weak correlation between IgG aCLAs and IgG anti‐Cu‐LDL antibodies. Cross‐reactivity between both antibodies seemed to be limited. Because aCLAs are heterogeneous, only a minor subset of these antibodies may cross‐react with oxLDL. Therefore, identification of both antibodies may be relevant for determination of the prognosis of accelerated atherosclerosis in SLE patients.

Autoantibodies Against Oxidized Low-Density Lipoprotein in Cerebral Small Vessel Disease

Background and Purpose— Oxidized low-density lipoprotein (oxLDL) induces endothelial dysfunction and antibody formation. Because endothelial dysfunction is involved in cerebral small vessel disease (CSVD) (dilated Virchow Robin spaces, lacunar infarcts, and white matter lesions), oxLDL antibodies could play a role in CSVD pathogenesis. Therefore, we studied oxLDL antibodies in patients with high prevalence of CSVD: lacunar stroke patients and essential hypertensive patients. Methods— A total of 158 lacunar stroke patients, 158 hypertensive patients, and 43 healthy controls were included. We determined levels of IgG and IgM against hypochlorite (HOCl) and malondialdehyde (MDA) oxLDL using ELISA (values in optical density). Results— Patients with CSVD had higher levels of IgG-HOCl-oxLDL (0.77 versus 0.70; P<0.01), as well as lower levels of IgM-MDA-oxLDL (0.55 versus 0.65; P<0.05) than patients without such lesions. Higher IgG-HOCl-oxLDL levels were only independently associated with higher numbers of Virchow Robin spaces at the level of the basal ganglia (&bgr;=0.218; P<0.001). Conclusions— An autoinflammatory process with lower levels of IgM antibodies and higher levels of IgG antibodies against oxLDL may be involved in CSVD.

Monoclonal Antibodies to Human Thyroglobulin as Probes for Thyroglobulin Structure

A panel of monoclonal antibodies (mAbs) against human thyroglobulin (hTg) was obtained by somatic fusion of the nonsecreting myeloma cell line P3X66 Ag8/0 and spleen cells of Balb/c mice immunized with purified hTg. Antibody secreting clones were selected by solid phase enzyme immunoassay and analyzed for cross-reaction with Tg from several animal species. Twelve out of 15 mAbs cross-reacted with both rat and mouse Tg and 11 Mabs cross-reacted with bovine Tg. The cross-reaction with mouse Tg paralleled that of rat Tg, whereas discrete differences between the cross-reactivity patterns with bovine Tg were observed. Two clones secreted mAbs specific for hTg. We further characterized the mAbs and found that three mAbs recognized T4-containing determinants and one mAb reacted with both T4 and T3-containing determinants on the Tg molecule. The binding of the mAbs to hormonogenic determinants depended upon the thyroid hormone content of the molecule and the integrity of the three dimensional structure of Tg. One other mAb reacted with four peptides of CNBr-cleaved hTg, indicating the recognition of a repetitive determinant in the hTg molecule distinct from the hormonogenic regions.

Role of acetylcholine receptor antibody complexes in muscle in experimental autoimmune myasthenia gravis.

In experimental autoimmune myasthenia gravis anti-rat nicotinic acetylcholine receptor (AChR) antibody titers correlated significantly with the AChR-antibody complexes found in muscle. It was shown that at least a large part of the AChR-antibody complexes are formed in vitro, which can be prevented by washing of the muscle homogenate. Using a modified assay, no differences in AChR-antibody complexes could be detected between rats with and without symptoms of experimental autoimmune myasthenia gravis. Also no difference in AChR loss nor in inhibition of alpha-bungarotoxin binding to AChR was found between these groups of rats. However, a significant difference in the reduction of AChR function was found, using an assay measuring agonist-induced 22Na+ flux into the TE671 cell line.

Vitamin D-related gene expression profiles in immune cells of patients with relapsing remitting multiple sclerosis.

An impaired vitamin D (vit-D) processing by immune cells of relapsing remitting multiple sclerosis (RRMS) patients may increase their vulnerability for a poor vit-D status. We assessed with qPCR the expression of vit-D related genes in PBMC and CD4+ T-cells. Gene expression profiles of vit-D receptor (VDR), CYP27B1 and CYP24A1 did not differ between RRMS patients and healthy controls. Interestingly, more VDR expression in PBMC correlated with less circulating IFN-γ+ CD4+ T-cells. Our results suggest that vit-D processing by immune cells is not impaired in RRMS, and is potentially relevant for the composition of the peripheral CD4+ T-cell compartment.

Evaluation of antibodies against human HSP60 in patients with MPO-ANCA associated glomerulonephritis: a cohort study

BackgroundHuman Heat Shock Protein 60 (hHSP60) has been implicated in autoimmunity through molecular mimicry, based on the high degree of homology with HSP65 of micro-organisms leading to autoimmune recognition of the human protein. Additionally, sequence homology between hHSP60 and myeloperoxidase (MPO) has been described. MPO is a major autoantigen in vasculitis associated with antineutrophil cytoplasmic antibodies (ANCA). We hypothesized that infections may trigger the ANCA response against MPO through hHSP60.MethodsIn 86 consecutive patients with ANCA-associated vasculitis (AAV), anti-hHSP60 and anti-mycobacterial HSP65 were measured by ELISA. Patients were compared with 69 healthy controls (HC). Continuous data between groups were compared using Wilcoxon signed rank test and Kruskal-Wallis test with Dunns post-test when appropriate. Correlations between data were derived using Spearman correlation. Odds ratios and 95% confidence intervals were obtained using Fishers exact test.ResultsAt diagnosis, median anti-mHSP65 level was higher in AAV (median [range]: 42.5 [0–500]), and subsequently in MPO-ANCA (44 [7–500]), compared to HC (22 [0–430]). Anti-hHSP60 levels in AAV were not higher compared to HC (18 [0–319] and 18.5 [0–98], respectively). However, in MPO-ANCA anti-hHSP60 levels were increased (32.5 [0–319]) compared to PR3-ANCA (13 [0–79]) and HC. We could not detect cross-reactivity between hHSP60 and MPO-ANCA. There was a correlation between anti-mHSP65 and anti-hHSP60 levels (r = 0.32, P = 0.003) but not between anti-hHSP60 and MPO-ANCA (r = -0.064, P = 0.69).ConclusionAntibodies against mHSP65 are higher in AAV compared to HC, and anti-hHSP60 antibodies are higher in patients with MPO-ANCA than in patients with PR3-ANCA and HC. Although this finding may be indicative for cross-reactivity between MPO-ANCA and hHSP60, additional assays did not support this hypothesis.

Anti‐oxidized low‐density lipoprotein antibodies in myeloperoxidase–positive vasculitis patients preferentially recognize hypochlorite‐modified low density lipoproteins

Many patients surviving vasculitis are prone to accelerated atherosclerosis and often have enhanced levels of antibodies to oxidized low‐density lipoprotein (oxLDL). To measure anti‐oxLDL antibodies, oxidation of LDL is achieved with copper (Cu) or malondialdehyde (MDA). Because, in vivo, LDL may be oxidized with myeloperoxidase (MPO) or its product hypochlorite, we measured anti‐hypochlorite LDL antibodies in patients with vasculitis, haemodialysis patients and healthy controls. A newly developed enzyme‐linked immunosorbent assay (ELISA) was used to detect antibodies to oxLDL as modified by hypochlorite. Results are compared with data obtained by standard LDL oxidation using MDA–LDL or Cu–LDL as substrate. Results were compared between anti‐neutrophil cytoplasmic antibodies (ANCA)‐associated vasculitis (AAV) patients (nu2003=u200393), haemodialysis (HD) patients (nu2003=u200359) and healthy controls (HC; nu2003=u200343). Furthermore, patients with MPO–ANCA‐associated vasculitis (nu2003=u200347) were compared with patients with proteinase 3 (PR3)–ANCA associated vasculitis (nu2003=u200346). Optimal cut‐off points were determined by receiver operator characteristic (ROC) curve analysis. Anti‐oxLDL antibodies are enhanced in AAV patients (MDA–LDL and hypochlorite–LDL) and in HD patients (hypochlorite–LDL), when compared to HC. Furthermore, patients with MPO–ANCA‐associated vasculitis had higher levels of antibodies to hypochlorite–LDL than patients with PR3–ANCA‐associated vasculitis. Our newly developed assay, in which hypochlorite–LDL is used as substrate, seems a more sensitive assay than traditional assays to measure oxLDL antibodies. Furthermore, our results suggest that enhanced MPO‐mediated LDL oxidation occurs in patients with MPO–ANCA.