Release of cytokines and proteases from human peripheral blood mononuclear and polymorphonuclear cells following phagocytosis and LPS stimulation

A lack of secretory leukocyte protease inhibitor (SLPI) causes defects in granulocytic differentiation

We identified diminished levels of the natural inhibitor of neutrophil elastase (NE), secretory leukocyte protease inhibitor (SLPI), in myeloid cells and plasma of patients with severe congenital neutropenia (CN). We further found that downregulation of SLPI in CD34(+) bone marrow (BM) hematopoietic progenitors from healthy individuals resulted in markedly reduced in vitro myeloid differentiation accompanied by cell-cycle arrest and elevated apoptosis. Reciprocal regulation of SLPI by NE is well documented, and we previously demonstrated diminished NE levels in CN patients. Here, we found that transduction of myeloid cells with wild-type NE or treatment with exogenous NE increased SLPI messenger RNA and protein levels, whereas transduction of mutant forms of NE or inhibition of NE resulted in downregulation of SLPI. An analysis of the mechanisms underlying the diminished myeloid differentiation caused by reduced SLPI levels revealed that downregulation of SLPI with short hairpin RNA (shRNA) upregulated nuclear factor κB levels and reduced phospho-extracellular signal-regulated kinase (ERK1/2)-mediated phosphorylation and activation of the transcription factor lymphoid enhancer-binding factor-1 (LEF-1). Notably, microarray analyses revealed severe defects in signaling cascades regulating the cell cycle, including c-Myc-downstream signaling, in myeloid cells transduced with SLPI shRNA. Taken together, these results indicate that SLPI controls the proliferation, differentiation, and cell cycle of myeloid cells.

Contribution of different placental cells to the expression and stimulation of antimicrobial proteins (AMPs)

The placenta is a major barrier that prevents potentially infectious agents from causing fetal diseases or related complications during pregnancy. Therefore, we postulated that the placenta might express a broad repertoire of antimicrobial proteins as well as inflammatory chemokines and cytokines to combat invading microorganisms. Here we demonstrate that placental cells indeed express a wide range of AMPs (antimicrobial peptides and proteins) including bactericidal/permeability-increasing protein (BPI), secretory leukocyte protease inhibitor (SLPI), human β-defensin 2 (hBD2), acyloxyacyl hydrolase (AOAH), and cathelicidin (CAP18). In addition, these cells also secrete pro-inflammatory cytokines and chemokines upon stimulation with bacterial ligands. Notably, we show that BPI expression by placental cells could be completely attributed to granulocytes while highly purified placental trophoblasts expressed only a subset of the AMPs like SLPI. Unexpectedly, trophoblast AMPs did not exhibit inducible secretion in response to various TLR ligands and further investigations showed that the unresponsiveness of trophoblasts to lipopolysaccharide (LPS) was due to a lack of TLR4 expression. In summary, we have shown that the expression of different AMPs can be allocated to various cells in the placenta and the repertoire of the AMPs expressed by placental cells is a result of a cooperation of leukocytes as well as cells from embryonic origin.

A genome-wide linkage scan reveals CD53 as an important regulator of innate TNF-alpha levels

Cytokines are major immune system regulators. Previously, innate cytokine profiles determined by lipopolysaccharide stimulation were shown to be highly heritable. To identify regulating genes in innate immunity, we analyzed data from a genome-wide linkage scan using microsatellites in osteoarthritis (OA) patients (The GARP study) and their innate cytokine data on interleukin (IL)-1beta, IL-1Ra, IL-10 and tumor necrosis factor (TNF)alpha. A confirmation cohort consisted of the Leiden 85-Plus study. In this study, a linkage analysis was followed by manual selection of candidate genes in linkage regions showing LOD scores over 2.5. An single-nucleotide polymorphism (SNP) gene tagging method was applied to select SNPs on the basis of the highest level of gene tagging and possible functional effects. QTDT was used to identify the SNPs associated with innate cytokine production. Initial association signals were modeled by a linear mixed model. Through these analyses, we identified 10 putative genes involved in the regulation of TNFalpha. SNP rs6679497 in gene CD53 showed significant association with TNFalpha levels (P=0.001). No association of this SNP was observed with OA. A novel gene involved in the innate immune response of TNFalpha is identified. Genetic variation in this gene may have a role in diseases and disorders in which TNFalpha is closely involved.

A new simple whole blood flow cytometry-based method for simultaneous identification of activated cells and quantitative evaluation of cytokines released during activation

The multiple cellular and soluble elements of the immune system respond in a coordinated way, orchestrated by cytokines, to preserve the integrity of the organism. In this study, we describe a new and unique whole blood method that, with minimal sample manipulation, allows an overall evaluation of immune responses by simultaneously measuring cell activation and cytokine secretion. The identification of cells actively secreting cytokines is based on the stabilization of tumor necrosis factor alpha (TNFalpha) at the cell surface through the use of a specific inhibitor of the TNFalpha-converting enzyme. This inhibitor does not affect the release of cytokines other than TNFalpha and makes it possible to assess, in the same measurement, the phenotype of TNFalpha(+)-secreting cells and quantify multiple secreted cytokines by using a specific and highly sensitive flow cytometry-based bead immunoassay. Upon stimulation of normal peripheral blood samples with either phorbol 12-myristate 13 acetate (PMA) plus ionomycin or lipopolysaccharide (LPS), both the number of TNFalpha+ cells and the amount of secreted cytokines progressively increased, the former becoming detectable first. After stimulation for 3 h with PMA plus ionomycin, cellular responses were associated with surface TNFalpha expression on the majority of CD3+ T cells and secretion of Th1-associated cytokines: interferon gamma, interleukin (IL)-2, and to a lesser extent IL4. In turn, stimulation with LPS induced a response mainly by inflammatory cells. After 4 h of LPS-stimulation, the majority of CD14+ monocytes showed surface TNFalpha expression; in parallel, high amounts of soluble IL1beta, IL6, and IL8 became detectable. Likewise, stimulation of blood samples with cytomegalovirus (CMV) lysates induced viral-specific immune responses detectable in seropositive but not seronegative volunteers; such responses were associated with the detection of increased numbers of TNFalpha+ monocytes, TNFalpha+/CD8+ T cells and TNFalpha+/CD8- T lymphocytes in association with an increased secretion of IFNgamma, IL6 and TNFalpha.

Increased circulating levels of proteinase 3 in patients with anti-neutrophilic cytoplasmic autoantibodies-associated systemic vasculitis in remission

In systemic small vessel vasculitides, patients form autoantibodies against neutrophil granular proteins, anti-neutrophilic cytoplasmic autoantibodies (ANCA). Some correlation is seen between ANCA titre and disease activity, but whether this is cause or effect is still unknown. It has been reported that levels of proteinase 3 (PR3), one of the main ANCA antigens, are increased in patients with active disease. An increased level of circulating antigen could mean a predisposition to autoimmunity. In order to explore this we measured PR3 levels in patients with stable disease. In addition we measured neutrophil gelatinase-associated lipocalin (NGAL) as a specific marker of neutrophil degranulation, cystatin C as a marker of renal function as well as C-reactive protein (CRP), IL-6 and sTNFr1 as markers of inflammation. PR3, NGAL, IL-6 and sTNFr1 were measured in plasma by the ELISA technique. In the PR3 ELISA, we used anti-PR3 monoclonal antibodies as capture-antibodies and affinity-purified rabbit-anti-PR3 antibodies for detection. PR3-ANCA, myeloperoxidase (MPO)-ANCA, CRP and cystatin C were measured by routine methods. PR3 was significantly raised (P < 0.0001) in vasculitis patients (median 560 micro g/l, range 110-3,940, n = 59) compared with healthy blood donors (350 micro g/l, 110-580, n = 30) as well as disease controls (360, 110-580, n = 46). No correlation was seen with disease activity, inflammation or renal function. The raised NGAL levels correlated strongly with decreased renal function (r = 0.8, P < 0.001). After correcting for this, slightly increased levels (110, 42-340, n = 59) were observed compared with healthy blood donors (81, 38-130, n = 25), but not compared with the disease controls (120, 57-260, n = 48). In the disease controls, there was a significant correlation between NGAL and proteinase 3 (r = 0.3, p < 0.05), but this was not the case in the vasculitis patients. Whether patients had PR3-ANCA or MPO-ANCA was of no significance. In our measurements, we found significantly raised levels of PR3 in plasma from patients with small vessel vasculitis, regardless of ANCA specificity. This was not due to decreased renal function, ongoing inflammation or neutrophil activation. Plausible mechanisms for this include defects in the reticuloendothelial system, genetic factors and selective neutrophil degranulation or leakage.

Generation of biologically active angiostatin kringle 1-3 by activated human neutrophils

The contribution of polymorphonuclear neutrophils (PMN) to host defense and natural immunity extends well beyond their traditional role as professional phagocytes. In this study, we demonstrate that upon stimulation with proinflammatory stimuli, human PMN release enzymatic activities that, in vitro, generate bioactive angiostatin fragments from purified plasminogen. We also provide evidence that these angiostatin-like fragments, comprising kringle domain 1 to kringle domain 3 (kringle 1-3) of plasminogen, are generated as a byproduct of the selective proteolytic activity of neutrophil-secreted elastase. Remarkably, affinity-purified angiostatin kringle 1-3 fragments generated by neutrophils inhibited basic fibroblast growth factor plus vascular endothelial growth factor-induced endothelial cell proliferation in vitro, and both vascular endothelial growth factor-induced angiogenesis in the matrigel plug assay and fibroblast growth factor-induced angiogenesis in the chick embryo chorioallantoic membrane assay, in vivo. These results represent the first demonstration that biologically active angiostatin-like fragments can be generated by inflammatory human neutrophils. Because angiostatin is a potent inhibitor of angiogenesis, tumor growth, and metastasis, the data suggest that activated PMN not only act as potent effectors of inflammation, but might also play a critical role in the inhibition of angiogenesis in inflammatory diseases and tumors, by generation of a potent anti-angiogenic molecule.

Enzyme leakage, trypsinogen activation, and inflammatory response in endoscopic retrograde cholangiopancreatography-induced pancreatitis

INTRODUCTION

Endoscopic retrograde cholangiopancreatography (ERCP)-induced pancreatitis (EIP) provides an opportunity to study different pathophysiologic events early in the course of acute pancreatitis.

AIMS

To investigate whether the leakage of pancreatic proenzymes (anionic trypsinogen), pancreatic protease activation (carboxypeptidase B activation peptide), cytokine response (interleukin [IL]-1 receptor antagonist, IL-6, and soluble tumor necrosis factor receptor-I) and neutrophil activation (neutrophil gelatinase-associated lipocalin and polymorphonuclear elastase) differ between patients with and without EIP. A second aim was to clarify the temporal relation between these different events.

METHODOLOGY

Ninety-nine nonconsecutive patients undergoing ERCP were investigated in the study.

RESULTS

Fourteen of 99 patients undergoing ERCP developed mild EIP. Six hours after the investigation the concentration of anionic trypsinogen was significantly higher in patients with EIP than in patients without EIP. The day after ERCP, higher concentrations of anionic trypsinogen, carboxypeptidase B activation peptide, IL-6, and polymorphonuclear elastase were recorded in the EIP group. No significant differences in IL-1 receptor antagonist, soluble tumor necrosis factor receptor-I or neutrophil gelatinase-associated lipocalin were found between the groups in this study.

CONCLUSION

Mild EIP was accompanied by early leakage of proenzymes and later activation of trypsinogen/proteases. A significant cytokine response and neutrophil activation were recorded the day after ERCP, but further studies are needed to determine the temporal relation between these different pathophysiologic events.

Evaluation of accuracy and uncertainty of ELISA assays for the determination of interleukin-4, interleukin-5, interferon-gamma and tumor necrosis factor-alpha

The comparison of analytical results calls for validation of the assays used, i.e. for the documentation of accuracy (trueness and precision), linearity and specificity. In addition, there is a growing demand for evaluation and documentation of traceability and uncertainty of analytical results. However, models for establishing the traceability and uncertainty of immunoassay results are lacking. Sandwich enzyme-linked immunosorbent assays (ELISAs) were developed for determination of the human cytokines interleukin-4 (IL-4), interleukin-5 (IL-5), interferon-y (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha). The accuracy of each of the assays was evaluated in the ranges of 1-15 microg/l (IL-4), 0.001-1 microg/l (IL-5), 0.5-2.5 microg/l (IFN-T) and 0.14-2.2 microg/l (TNF-alpha). Other evaluated performance characteristics were the limit of detection (LOD), immunological specificity, and robustness. Traceability was ensured by the use of World Health Organization International Standards (WHO IS). An uncertainty budget, which combined the contribution from all known uncertainty components, was established for each cytokine ELISA. The between-run relative analytical standard deviation (RSDA) of the assessed ELISAs was found to be in the range of 11-18%, except for IL-5 where RSDA increased at decreasing concentrations. The LOD was 0.12 microg/l, 0.0077 microg/l, 0.0069 microg/l and 0.0063 microg/l for IL-4, IL-5, IFN-gamma and TNF-alpha, respectively. Traceability to the WHO IS was established for each of the cytokines. The combined relative standard uncertainty (U(result)/C(result)) was 28%, 22-62%, 28% and 24% for the IL-4, IL-5, IFN-gamma and TNF-alpha results, respectively. The major contributions to uncertainty came from the relative analytical standard deviation and from the uncertainty of the mass concentration of the WHO IS. The uncertainty of the WHO IS was not stated in the accompanying certificate and was evaluated by other means. The largest sources of uncertainty were located outside our laboratory. This means that the possibilities to improve the reliability of the results produced by the ELISAs are very limited. The task of evaluating measurement uncertainty would be much easier if producers of international reference standards reported the uncertainty of the value of standards. The model for evaluating uncertainty presented in this paper is applicable to other types of assays and to most analytical methods.

Rheumatoid arthritis, gold therapy, contact allergy and blood cytokines

OBJECTIVE

To study the clinical and biochemical effects of a low starting dose for gold therapy in rheumatoid arthritis patients with a contact allergy to gold.

METHODS

Serum cytokines were assayed before and 24 h after the first injection of gold sodium thiomalate (GSTM).

RESULTS

Contact allergy to gold was found in 4 of 19 patients. Compared to gold-negative patients (starting dose: 10 mg GSTM), there was a larger increase in serum TNFalpha (p < 0.05), sTNF-R1 (NS), and IL-1 ra (p < 0.05) in gold-allergic patients.

CONCLUSIONS

Cytokines are released in blood by GSTM in RA patients with gold allergy. To minimize the risk of acute adverse reactions the starting dose of GSTM should be lowered to 5 mg. Alternatively, patients should be patch-tested before gold therapy; in test-positive cases, 5 mg is recommended as the first dose.

IL-8 and TNF-alpha from peripheral neutrophils and acute-phase proteins in periodontitis

OBJECTIVE

In other studies, we have found deviant functions in peripheral neutrophils in periodontitis. The aim here was to study (1) the release of cytokines, IL-8 and TNFalpha, from neutrophils in 15 treated periodontitis patients and pair-matched controls as well as (2) the effects of cigarette smoking.

MATERIAL AND METHODS

Cytokines released in the incubation medium from un-stimulated and Fcgamma-R-stimulated neutrophils and some acute-phase reactants were measured with ELISA.

RESULTS

Non-smoking patients had trends for lower TNFalpha release compared to non-smoking controls, while corresponding trends were rather similar for Il-8. Smoking had a moderate but inconsistent effect on the release of both cytokines. However, in patients, the ratio between stimulated/un-stimulated release of Il-8 was significantly lowered by smoking (p<0.03). The parameters of inflammation in plasma differed only slightly between patients and controls, indicating that periodontal disease in a quiet phase has a negligible systemic effect with the possible exception for a higher IL-8 level. In contrast, smoking had significant systemic effect on the neutrophil count and IgG levels.

CONCLUSIONS

Release of IL-8 and TNF-alpha from peripheral neutrophils and various parameters of inflammation in plasma seem to be affected more by cigarette smoking than periodontal disease.

Dendritic cells as a major source of macrophage-derived chemokine/CCL22 in vitro and in vivo

Macrophage-derived chemokine (MDC)/CCL22 is a CC chemokine active on dendritic cells (DC), NK cells and Th2 lymphocytes. The present study was aimed at comprehensively investigating MDC production in vitro and in vivo. DC were the most potent producers of MDC among leukocytes tested. Endothelial cells did not produce MDC under a variety of conditions. Signals that induce maturation (lipopolysaccharide, IL-1, TNF, CD40 ligand, recognition of bacteria and yeast) dramatically augmented MDC production, and dexamethasone and vitamin D3 blocked it. Prostaglandin E(2), which blocked the acquisition of IL-12 production and the capacity to promote Th1 generation, did not affect MDC production. Using mass spectrometry-based techniques, DC supernatants were found to contain N-terminally truncated forms of MDC [MDC(3-69), MDC(5-69) and MD(C7-69)] as well as the full-length molecule. In vivo, CD1a(+), CD83(+), MDC(+) DC were found in reactive lymph nodes, and in Langerhans' cell histiocytosis. Skin lesions of atopic dermatitis patients showed that CD1a(+) or CD1b(+) DC, and DC with a CD83(+) phenotype were responsible for MDC production in this Th2-oriented disorder. Thus, DC are the predominant source of MDC in vitro and in vivo under a variety of experimental and clinical conditions. Processing of MDC to MDC(3-69) and shorter forms which do not recognize CCR4 is likely to represent a feedback mechanism of negative regulation.

The protease-activated receptor-2 upregulates keratinocyte phagocytosis

The protease-activated receptor-2 (PAR-2) belongs to the family of seven transmembrane domain receptors, which are activated by the specific enzymatic cleavage of their extracellular amino termini. Synthetic peptides corresponding to the tethered ligand domain (SLIGRL in mouse, SLIGKV in human) can activate PAR-2 without the need for receptor cleavage. PAR-2 activation is involved in cell growth, differentiation and inflammatory processes, and was shown to affect melanin and melanosome ingestion by human keratinocytes. Data presented here suggest that PAR-2 activation may regulate human keratinocyte phagocytosis. PAR-2 activation by trypsin, SLIGRL or SLIGKV increased the ability of keratinocytes to ingest fluorescently labeled microspheres or E. coli K-12 bioparticles. This PAR-2 mediated increase in keratinocyte phagocytic capability correlated with an increase in actin polymerization and *-actinin reorganization, cell surface morphological changes and increased soluble protease activity. Moreover, addition of serine protease inhibitors downmodulated both the constitutive and the PAR-2 mediated increases in phagocytosis, suggesting that serine proteases mediate this functional activity in keratinocytes. PAR-2 involvement in keratinocyte phagocytosis is a novel function for this receptor.

Elevated levels of interleukin-8 and transforming growth factor-beta in bronchoalveolar lavage fluid from patients with bronchiolitis obliterans syndrome: proinflammatory role of bronchial epithelial cells. Munich Lung Transplant Group

BACKGROUND

Obliterative bronchiolitis (OB), the most important long-term complication after lung transplantation, is thought to be a manifestation of chronic rejection within the airways, with the hallmarks inflammation and fibroproliferation.

METHODS

To characterize the inflammatory process in the context of OB we quantified tumor necrosis factor-alpha, interleukin (IL)-8, IL-10, and transforming growth factor (TGF)-beta on the protein and mRNA level in bronchoalveolar lavage fluid samples obtained from patients with bronchiolitis obliterans syndrome (BOS) and without BOS. In addition, bronchial cells sampled by bronchial brushing were analyzed for mRNA expression.

RESULTS

In respiratory epithelial lining fluid (ELF) from BOS patients the protein levels of IL-8 (52.4+/-22.2 vs. 4.4+/-0.9 pg/ml ELF, P<0.005) and TGF-beta (5.6+/-1.9 vs. 0.9+/-0.2 ng/ml ELF, P<0.005) were significantly elevated. In addition, bronchoalveolar lavage fluid cells of BOS patients showed increased expression of TGF-beta (1.13+/-0.44 vs. 0.45+/-0.16, optical density [O.D.]/O.D. glyceraldehyde-3-phosphate dehydrogenase [GAPDH], P=0.11) and IL-8 (0.25+/-0.13 vs. 0.09+/-0.03 O.D/O.D. GAPDH, P=0.53) without the differences reaching statistical significance. In contrast, IL-8 mRNA expression of bronchial cells was significantly higher in the BOS group (0.85+/-0.40 vs. 0.22+/-0.10 O.D./O.D. GAPDH, P<0.05).

CONCLUSIONS

We assume that IL-8 and TGF-beta may act as key mediators for airway inflammation and fibroproliferation in the pathogenesis of OB, with bronchial epithelial cells serving as a relevant source of IL-8.

The flare-up reactions after systemic provocation in contact allergy to nickel and gold

In a controlled double-blind experimental study, patients with contact allergy to nickel or gold were exposed systemically to their contact allergen. Nickel sulfate was given orally, gold sodium thiomalate intramuscularly, and placebo by both routes. Clinical reactions including body temperature were followed and 7 plasma cytokines and acute phase reactants were assayed before and 24 h after provocation. Clinical flare-up, with reactivation of healing patch tests and/or toxicoderma-like reactions, was observed in patients receiving their specific allergen. A transient fever was noted in patients allergic to gold when exposed to gold, not in others. There was a significant increase in plasma tumour necrosis factor-alpha, soluble tumour necrosis factor receptor 1, interleukin-1 receptor antagonist, and neutrophil gelatinase associated lipocalin in patients allergic to gold when exposed to gold allergen. Furthermore, in patients allergic to nickel exposed to nickel allergen there was a highly significant increase in plasma soluble tumour necrosis factor receptor 1. Interferon-gamma, interleukin-4, and C-reactive protein did not increase in any of the patient groups. Clinical reactions during flare-up in contact allergy are accompanied by release in the blood of several cytokines. This release is not a consequence of a toxic effect or bound to a particular allergen. Instead, the cytokine release should be considered a general phenomenon characteristic of the flare-up in contact allergy.

Alteration of cytoskeletal structure, integrin distribution, and migratory activity by phagocytic challenge in cells from an ocular tissue--the trabecular meshwork

The trabecular meshwork is a specialized tissue in the anterior chamber of the eye that regulates the aqueous humor outflow and controls the intraocular pressure. Cells in the trabecular meshwork are believed to be essential for maintenance of the outflow system, and their malfunctioning may lead to elevation of intraocular pressure and development of glaucoma. These cells are avid phagocytes. Using an in vitro tissue culture system, we have previously shown that bovine trabecular meshwork cells exhibited a short-term loss of cell-matrix adhesiveness after exposure to latex microspheres. The current study showed that 4 h after phagocytosis, the cytoskeletal structure in trabecular meshwork cells was disrupted, the formation of focal contact formation was limited, and the cellular migratory activity was increased. These in vitro responses paralleled those that occur in vivo. By 24 h, all the changes demonstrated returned to normal. Our data suggest that the short-term loss in cell-matrix cohesiveness observed after phagocytic challenge may be related to the reorganization of cytoskeletal structures and the decline of focal contact formation. The altered cell migration may also be interlinked.

Inhibitors of elastase in airway lavage samples from ventilated preterm human neonates

Surplus elastase released from neutrophils during lung injury is balanced mainly by alpha1-protease inhibitor (alpha1-PI) and by two acid-resistant inhibitors. The latter include mucus protease inhibitor (MPI, also named SLPI, BSI, ALP) and elastase-specific inhibitor (ESI or Elafin), but their functional role during the neonatal period has not yet been characterized precisely. The saline airway lavage samples from neonates intubated for respiratory distress were separated by centrifugation into a cellular and a soluble, supernatant fraction and then analyzed. During the first 36 h of life (42 neonates, gestational age 24-40 wk), elastase activity was confined to the cellular fraction. Thirty percent of the acid-resistant inhibitors but almost no alpha1-PI, was cell-associated. In the soluble fraction, about 20-30% of the acid-resistant inhibitors was functionally active, but only about 10% of alpha1-PI was. In seven infants with a nosocomial infection and deterioration during mechanical ventilation, only a very modest increase in elastase activity was observed. However, the functional activity of the acid-resistant inhibitors was reduced in the soluble fraction, whereas total mass remained unchanged. A full assessment of protease and protease inhibitors should include the cellular and the soluble lavage compartments.

Distribution of the secretory leucocyte proteinase inhibitor in human articular cartilage

The secretory leucocyte protease inhibitor, SLPI, is a low molecular weight inhibitor of proteases such as elastase and cathepsin G, which are released from leucocytes during phagocytosis. The purpose of this study was to show whether or not SLPI is produced in articular chondrocytes. In articular disorders, the protease-antiprotease balance is disturbed. For this reason it would be interesting to establish the source of SLPI. The presence of SLPI was demonstrated using immunohistochemistry and in situ hybridization, hence we conclude that SLPI is produced in the chondrocytes of human articular cartilage.

Leukocyte activation in atherosclerosis: correlation with risk factors

Leukocytes have been implicated in the development of atherosclerotic vascular diseases, and numerous abnormalities of leukocytes in conjunction with atherosclerosis have been reported. The aim of this study of middle-aged asymptomatic subjects with early atherosclerosis was to determine whether a relationship exists between the levels of plasma markers of leukocyte activation, i.e. cytokines and proteases and risk factors for atherosclerosis or the degree of atherosclerotic disease. Using ELISAs we measured the plasma levels of neutrophil gelatinase-associated lipocalin (NGAL), neutrophil protease 4 (NP4) as markers for neutrophil activation, tumor necrosis factor alpha (TNF) and soluble TNF receptor-1 (sTNFR-1) as markers of monocyte/macrophage activation in 156 subjects with asymptomatic carotid artery plaque detected at ultrasound examination. Plasma TNF and sTNFR-1 levels were found to correlate with systolic blood pressure (r = 0.32, P < 0.04 and r = 0.22, P < 0.05, respectively). plasma NGAL level to correlate with diastolic blood pressure (r = 0.22; P < 0.005), the plasma levels of sTNFR-1 and NGAL to correlate with age (r = 0.28, P < 0.001 and r = 0.20, P < 0.05, respectively). As compared with non-smokers (n = 112), smokers (n = 43) had higher plasma levels of TNF (2.9 vs. 1.4 microg/l; P < 0.02) and of NP4 (27.5 vs. 23.4 microg/l; P < 0.05). The plasma NGAL level was higher in hypertensive women (n = 7) than in normotensive women (n = 85) (109 vs. 87 microg/l; P < 0.05). We thus demonstrated that, in subjects with asymptomatic early atherosclerosis, the plasma levels of markers of systemic leukocyte activation were correlated with age and blood pressure, and were higher in smokers and hypertensives. These results support the hypothesized relationship between the level of systemic leukocyte activation and risk factors for atherosclerotic vascular disease.