Stefan Dunzendorfer

Association of endotoxemia with carotid atherosclerosis and cardiovascular disease: prospective results from the Bruneck Study.

OBJECTIVES Focus of the current study was on the significance of bacterial endotoxin, which shows a variety of pro-atherogenic properties and may occur at high concentration in the circulation of infected subjects. BACKGROUND The possibility of an infectious risk factor in atherogenesis and cardiovascular disease has stimulated research interest, but the nature of such process remains obscure. METHODS We measured plasma endotoxin levels (LAL assay) in a random population of 516 men and women 50 to 79 years old at the 1990 baseline evaluation (Bruneck Study). End points of this prospective survey were incident (early) atherosclerosis in the carotid arteries as assessed with high-resolution Duplex ultrasound (five-year follow-up rate, 98%) and incident cardiovascular disease (follow-up rate, 100%). RESULTS Median endotoxin concentration amounted to 14.3 pg/ml (range, 6.0 to 209.2 pg/ml). Subjects with levels beyond 50 pg/ml (90th percentile) faced a threefold risk of incident atherosclerosis (odds ratio [95% confidence interval] 2.9 [1.4-6.3]; p < 0.01). The risk associated with high endotoxin was most pronounced in subjects with chronic infections and in current and ex-smokers. Notably, smokers with low endotoxin levels and nonsmokers did not differ in their atherosclerosis risk, whereas smokers with high levels almost invariably developed new lesions. All findings emerged as independent of vascular risk factors. Similar results were obtained for incident cardiovascular disease. CONCLUSIONS The current study yields first epidemiologic evidence that endotoxemia constitutes a strong risk factor of early atherogenesis in subjects with chronic or recurrent bacterial infections and a link in the association between cigarette smoking and atherosclerotic disease.

Increased Expression of CCL20 in Human Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) constituting Crohns disease (CD) and ulcerative colitis (UC) is related to a dysregulated T cell response. CCL20 attracts memory T lymphocytes and dendritic cells. We asked whether CCL20 expression is altered in IBD. Colonic biopsies were obtained from 114 subjects with IBD, non-IBD colitis, irritable bowel syndrome, and healthy controls. CCL20 and CCR6 mRNA expression was measured by Taqman-PCR, and protein secretion from colonic explant cultures (CEC) and its regulation by TNF-α by ELISA. CCL20, CCR6, and Langerin were identified by immunohistochemistry and immunofluorescence. CCL20 mRNA and protein were severalfold increased in involved CD and UC but not in non-IBD colitis. TNF-α increased and anti-TNF-α decreased CCL20 release in healthy control CEC but not in involved IBD colonic specimens. CCL20 localized to follicle-associated epithelium, and CCR6 to the adjacent mantle zone of lymphoid follicles. Furthermore, abundant numbers of Langerin+ immature dendritic cells were identified in the subepithelial space of IBD specimens. CCL20 might regulate the attraction of T lymphocytes and dendritic cells in IBD.

Mevalonate-Dependent Inhibition of Transendothelial Migration and Chemotaxis of Human Peripheral Blood Neutrophils by Pravastatin

Pravastatin, a hydrophilic inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, has been reported to beneficially affect atherogenesis, plaque stability, and transient myocardial ischemia in significant coronary artery disease by influencing lipid metabolism and by intracellular signaling via mevalonate pathway products other than cholesterol. Leukocytes are implicated to play a pathophysiological role in these events. We were interested in finding out whether pravastatin could affect transendothelial migration (TEM), chemotaxis, and respiratory burst activity of the neutrophil ex vivo. In addition, effects on monocyte and T-lymphocyte chemotaxis were tested. For TEM assays, monolayers of human umbilical vein endothelial cells (HUVECs) were grown to confluence on polycarbonate filters bearing 5-microns pores in Transwell (Costar) culture plate inserts. Chemotaxis experiments were performed using modified Boyden chambers with cellulose nitrate micropore filters. Respiratory burst activity was measured fluorometrically. Treatment of neutrophils and monocytes with pravastatin at 2 to 200 mumol/L and 10 to 1000 mumol/L, respectively, significantly decreased chemotaxis triggered by fMet-Leu-Phe. This effect was abolished in the presence of mevalonic acid (500 mumol/L); no effect of pravastatin was seen on T-lymphocyte chemotaxis triggered by interleukin-8. Preincubation of neutrophils with pravastatin (200 mumol/L) also resulted in a significant reduction in the number of neutrophils that transmigrated a tumor necrosis factor-stimulated or lipopolysaccharide-stimulated HUVEC monolayer. At none of the concentrations tested (2 pmol/L to 200 mumol/L) did pravastatin affect neutrophil respiratory burst activity. We conclude that pravastatin may alter monocyte chemotaxis and neutrophil-endothelial interactions in migratory responses at concentrations obtained in vivo with cholesterol-lowering doses.

Cutting Edge: Peripheral Neuropeptides Attract Immature and Arrest Mature Blood-Derived Dendritic Cells

Dendritic cells (DC) are highly motile and play a key role in mediating immune responses in various tissues and lymphatic organs. We investigated locomotion of mononuclear cell-derived DC at different maturation stages toward gradients of sensory neuropeptides in vitro. Calcitonin gene-related peptide, vasoactive intestinal polypeptide, secretin, and secretoneurin induced immature DC chemotaxis comparable to the potency of RANTES, whereas substance P and macrophage-inflammatory protein-3β stimulated immature cell migration only slightly. Checkerboard analyses revealed a true chemotactic response induced by neuropeptides. Upon maturation of DC, neuropeptides inhibited spontaneous, macrophage-inflammatory protein-3β- and 6Ckine-induced cell migration. Maturation-dependent changes in migratory behavior coincided with distinct neuropeptide-induced signal transduction in DC. Peripheral neuropeptides might guide immature DC to peripheral nerve fibers where high concentrations of these peptides can arrest the meanwhile matured cells. It seems that one function of sensory nerves is to fasten DC at sites of inflammation.

Signaling in neuropeptide-induced migration of human eosinophils.

At inflammatory sites, leukocytes may confront multiple, competing chemoattractive signals. We compared the chemotactic potencies of several sensory neuropeptides with regard to signal transduction pathways in eosinophils. Eosinophils were enriched using magnetic cell sorting and migration was assayed in a Boyden microchemotaxis chamber. We found stimulatory effects of substance P, calcitonin gene‐related peptide (CGRP), secretoneurin, vasoactive intestinal peptide (VIP), and secretin on eosinophil migration. Actions of VIP are predominantly mediated via VIP receptor type I. Migration toward secretoneurin, VIP, and secretin was blocked by a phosphodiesterase inhibitor, which, in contrast failed to affect substance P‐ and CGRP‐induced eosinophil chemotaxis. Wortmannin blunted the migratory responses induced by all neuropeptides tested and substance P‐induced effects on eosinophils were tyrphostin‐23‐sensitive. We conclude that substance P, CGRP, secretoneurin, and VIP/secretin stimulate eosinophil migration involving wortmannin‐sensitive enzymes. Moreover, secretoneurin and VIP/secretin require additional activation of phosphodiesterases to stimulate eosinophil migration. J. Leukoc. Biol. 64:828–834; 1998.

Hyperoncotic colloids and acute kidney injury: a meta-analysis of randomized trials

IntroductionIt has been hypothesized that hyperoncotic colloids might contribute to acute kidney injury (AKI). However, the validity of this hypothesis remains unclear.MethodsA meta-analysis was conducted of randomized controlled trials evaluating AKI after infusion of hyperoncotic albumin and hydroxyethyl starch (HES) solutions. Mortality was a secondary endpoint. Eligible trials were sought by multiple methods, and the pooled odds ratios (OR) for AKI and death and 95% confidence intervals (CI) were computed under a random effects model.ResultsEleven randomized trials with a total of 1220 patients were included: 7 evaluating hyperoncotic albumin and 4 hyperoncotic HES. Clinical indications were ascites, surgery, sepsis and spontaneous bacterial peritonitis. Hyperoncotic albumin decreased the odds of AKI by 76% (OR, 0.24; CI, 0.12-0.48; P < 0.0001), while hyperoncotic HES increased those odds by 92% (OR, 1.92; CI, 1.31-2.81; P = 0.0008). Parallel effects on mortality were observed, with hyperoncotic albumin reducing the odds of death by 48% (OR, 0.52; CI, 0.28-0.95; P = 0.035) and hyperoncotic HES raising those odds by 41% (OR, 1.41; CI, 1.01-1.96; P = 0.043).ConclusionsThis meta-analysis does not support the hypothesis that hyperoncotic colloid solutions per se injure the kidney. Renal effects appear instead to be colloid-specific, with albumin displaying renoprotection and HES showing nephrotoxicity.

B Lymphocyte-Derived IL-16 Attracts Dendritic Cells and Th Cells

Interaction of B lymphocytes with Th cells is a fundamental step in the establishment of humoral immunity, and recent evidence suggests that direct interaction between B lymphocytes and dendritic cells (DCs) is also an important prerequisite. Factors involved in the selective recruitment of Th cells and DCs by B lymphocytes are insufficiently defined. We set out to delineate the role of IL-16, the soluble ligand of CD4, which is expressed on Th cells and DCs. B lymphocytes express IL-16 mRNA and synthesize bioactive IL-16 protein, and IL-16 is expressed in lymph node follicles in situ. B lymphocyte supernatant efficiently induces migration of CD4+ Th cells, monocyte-derived DCs, and circulating blood DCs in nitrocellulose filter-based assays. Neutralization of IL-16 bioactivity strongly inhibits this migratory response, suggesting that IL-16 might be a major chemotactic factor derived from B cells. The present data further support the idea that IL-16 might have a role in the initiation of cellular as well as humoral immunity by mediating the cellular cross-talk among T lymphocytes, B cells, and DCs, leading to recruitment of these cell types at common anatomical sites.

Induction of apoptosis and inhibition of migration of inflammatory and vascular wall cells by cerivastatin.

Statins are thought to play a role in directly affecting immune and mesenchymal cells. Since cerivastatins pleiotropic effects are poorly investigated, we were interested to find out whether this drug can modulate leukocyte and vessel wall cell functions. Leukocyte migration was tested in modified Boyden microchemotaxis chambers and oxygen radical production was measured fluorometrically. Transendothelial migration experiments were performed with human umbilical vein endothelial cells and neutrophils. Neutrophil, monocyte, and vascular smooth muscle cell caspase-3 activity and annexin-V binding were quantified by FIENA and FACS, respectively. Cerivastatin [10 pM to 100 microM] decreased leukocyte chemotaxis towards interleukin-8 or RANTES. Migration of cells was completely restored by addition of mevalonic acid. In neutrophils, cerivastatin [100 microM] reduced transendothelial migration, whereas treatment of endothelial cells failed to affect transmigration. Neutrophil respiratory burst activity was unaffected by cerivastatin. At concentrations of 10 nM or higher, cerivastatin increased the rate of apoptosis in phagocytes and smooth muscle cells. Results show that cerivastatin is able to inhibit leukocyte chemotaxis, and that cerivastatin induces neutrophil, monocyte, and smooth muscle cell apoptosis. The drugs impact on transendothelial migration is due to its effects on neutrophils. In addition to its lipid-lowering effects, pharmacological properties of cerivastatin may include modulatory actions in leukocytes and mesenchymal cells.

Theoretical Basis for the Activity of Thalidomide

The revival of thalidomide began shortly after the drug was withdrawn from the market because of its teratogenic properties. Therapeutic effects of thalidomide were found accidentally in leprosy patients with erythema nodosum leprosum (ENL). Subsequent research widened the understanding of the activity of thalidomide, and with improved methodology and the augmented background knowledge of immunology it was possible to interpret the properties of thalidomide more coherently.Effects on tumour necrosis factor-α (TNFα) release play an important role in the ability of thalidomide to affect the immune system. Alteration of synthesis and release of cytokines such as interleukin (IL)-1, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12 and interferon-γ is involved in the complex mechanisms of thalidomide. Thalidomide targets leucocytes, endothelial cells and keratinocytes, affecting them in a different manner and at different cellular levels. Changes in the density of adhesion molecules alter leucocyte extravasation and the inflammatory response in the tissue involved. Several mechanisms for the teratogenic action of thalidomide are currently under review, but this mode of action of the drug still remains unclear and we review evidence-based hypotheses for the teratogenicity of thalidomide.Thalidomide shows significant clinical impact in several diseases such as ENL in lepromatous leprosy, chronic graft-versus-host disease, systemic lupus erythematosus, sarcoidosis, aphthous lesions in HIV infection, wasting syndrome in chronic illness, inflammatory bowel disease, multiple myeloma and some solid tumours. In 1998 the US Food and Drug Administration approved thalidomide exclusively for the treatment of ENL, and strict conditions were stipulated for its use in order to prevent teratogenic adverse effects. However, despite the promising findings of thalidomide at the molecular level, namely its anti-TNFα properties and its intercalation with DNA, and activity in clinical trials, there is still a great need for more intensive research.

Levosimendan inhibits release of reactive oxygen species in polymorphonuclear leukocytes in vitro and in patients with acute heart failure and septic shock: a prospective observational study

IntroductionLevosimendan is an extensively investigated inodilator showing also cardioprotective and antiinflammatory effects. The aim of our study was to explore the influence of levosimendan on polymorphonuclear leucocytes (PMN), a main source of reactive oxygen species, in vitro and in patients with acute heart failure or septic myocardial depression.MethodsPMN isolated from healthy volunteers were incubated with levosimendan in vitro. After stimulation with N-formyl-Met-Leu-Phe (fMLP) or phorbol 12-myristate 13-acetate (PMA) respiratory burst was quantified using a fluorescent dye. Apoptosis and expression of cell adhesion molecules of PMN were measured by flow cytometry. For determination of in vivo effects patients with acute heart failure (n = 16) or septic cardiac failure (n = 9) receiving levosimendan treatment were enrolled consecutively. PMN were isolated to measure respiratory burst activity before treatment as well as one and two hours after initiation of levosimendan administration. Furthermore inflammatory, hemodynamic and renal function parameters were obtained.ResultsIn vitro, levosimendan suppressed respiratory burst activity in fMLP or PMA stimulated PMN in a dose dependent manner by 30 ± 11% (P < 0.001) at 100 ng/mL and by 27 ± 17% (P < 0.001) at 1000 ng/mL respectively. Markers of apoptosis and PMN cell adhesion molecule expression remained unaffected by levosimendan treatment.In vivo, levosimendan treatment for two hours resulted in a significant reduction of PMA stimulated oxidative burst by 45% (P < 0.01) and fMLP stimulated oxidative burst by 49% (P < 0.05) in patients with acute heart failure. In patients suffering from septic shock levosimendan treatment decreased oxidative burst activity in unstimulated, fMLP and PMA stimulated PMN by 48% (P < 0.05), 46% (P < 0.01) and 43% (P < 0.01) respectively.ConclusionsLevosimendan appears to exert distinct immunomodulatory effects by decreasing oxidative burst activity of PMN. This property might contribute to the previously described cardioprotective effects of the drug.