Novel heparanase-inhibiting antibody reduces neointima formation

Basic fibroblast growth factor (bFGF), stored bound to heparan sulfate proteoglycans in the extracellular matrix (ECM) of the arterial media, may initiate smooth muscle cell (SMC) proliferation after coronary intervention, thus contributing to restenosis. bFGF mobilization from ECM stores after injury may be induced by platelet degranulation products such as heparanase. Therapies aimed at the inhibition of bFGF release and activation may assist in prevention of restenosis. To test this theory, we first examined the mobilization and activation of bFGF in the arterial media by platelet-derived heparanase. Heparanase, locally delivered to the rat carotid artery, was found to release bFGF and induce substantial SMC proliferation in the absence of actual vascular injury. An antibody that neutralizes heparanase was then developed and evaluated in a rat carotid balloon injury model. Local delivery of anti-heparanase IgG was found to inhibit bFGF release by approximately 60% ( p < 0.001) at 4 d; this correlated with the significant reduction in neointima formation observed at 14 d (intimal area/medial area: control 1.3 +/- 0.3, anti-heparanase 0.35 +/- 0.12, p < 0.0001). Platelet-derived heparanase is therefore likely to be important in initiating events leading to restenosis via bFGF mobilization. Furthermore, heparanase neutralization may assist in the prevention of restenosis following vascular injury.     

Reconstituted HDL containing human apolipoprotein A-1 reduces VCAM-1 expression and neointima formation following periadventitial cuff-induced carotid injury in apoE null mice.

Arterial injury triggers an inflammatory response in part mediated by induction of adhesion molecules such as vascular cell adhesion molecule-1 (VCAM-1) and is implicated in neointimal thickening. Since HDL is known to reduce cytokine-activated VCAM-1 expression, we tested the hypothesis that VCAM-1 expression and neontimal thickening following arterial injury are inhibited by reconstituted human HDL containing plasma-derived apoA-1 (rHDL). We used the carotid cuff injury in apoE (-/-) mice fed high cholesterol. Mice received rHDL (40 mg/kg) intravenously every other day for 3 weeks. Compared to control, rHDL treatment inhibited neointima formation (0. 008 +/- 0.004 mm(2) vs. 0.037 +/- 0.019 mm(2); P < 0.01) 21 days after injury, reduced VCAM-1 expression, and decreased monocyte/macrophage infiltration as assessed by histomorphometric analysis within the first week after injury. These changes occurred without any effect on plasma total and HDL cholesterol levels as well as the arterial tissue cholesterol levels. rHDL treatment also reduced the formation of modified lipoprotein in the arterial wall compared to control within the first week after injury. This finding suggests an antioxidant effect of rHDL associated with reduced VCAM-1 expression and neointimal formation after arterial injury.     

Central proinflammatory cytokines and pain enhancement

Enhanced pain is a component of the 'sickness response' which is an evolutionarily adaptive constellation of responses that enhance the survival of the host. Proinflammatory cytokines mediate these sickness behaviors, and whether proinflammatory cytokines are involved in exaggerated pain has become an intriguing question. Studies suggest that spinal cord glial cells (astrocytes and microglia) are activated in conditions that lead to enhanced pain. Not only is glial activation associated with enhanced pain, but it is also integral to the induction and maintenance of these pain states. Proinflammatory cytokines can be released by activated astrocytes and microglia within the central nervous system. This review will discuss the role of proinflammatory cytokines in experimental models of prolonged pain states. Administration of exogenous proinflammatory cytokines facilitates pain, and agents that antagonize proinflammatory cytokine actions have been shown to block and/or reverse enhanced pain. These findings suggest that blocking the synthesis and/or release of proinflammatory cytokines may be viable strategies for the treatment of pathological pain. Gene therapy to augment the endogenous anti-inflammatory cytokine, interleukin-10, is one of the more promising therapies currently under study.     

The action of proinflammatory cytokines on formation of behavior during early postnatal ontogenesis

The study is devoted to the role of proinflammatory cytokine-interleukin-1beta during early postnatal ontogenesis in formation of behavioral programs. Cytokine was injected in pyrogenic and subpyrogenic doses during 1 week (1, 2 or 3 weeks of life). The behavior was tested in the young (40-45 days) and adult (3 months) rats in the "open field" and "elevated plus maze". The greatest behavior disordes (elevation of act's number and of motor activity, the decrease of investigation activity) are revealed in the young animals treated with IL-Ib during 1 and 3 weeks of life. These behavioral changes were marked in rats injected with pyrogenic and subpyrogenic doses of cytokine. They had a similar tendency in male and female rats. At the age of 3 months, behavior changes revealed in juvenile rats were insignificant.     

Tomoregulin ectodomain shedding by proinflammatory cytokines

The shedding mechanism for the tomoregulin (TR) ectodomain, which contains two follistatin modules and a single epidermal growth factor (EGF)-like domain, remains unclear. Our study provides the first evidence that proinflammatory cytokines, IL-1beta and TNF-alpha, induce TR-ectodomain shedding in cultured A172 human glioma cells, without affecting TR mRNA expression. In addition, it appears that this shedding process is induced via activation of the NF-kappaB signaling pathway; with consequent increase in the production of metalloproteinases. Furthermore, since due to erbB4 tyrosine phosphorylation TR may have functions similar to EGF/neuregulin (NRG) family growth factors, our results suggest that following inflammation-induced injury, increases in TR shedding may contribute to tissue growth and repair in the central nervous system.     

RX871024 reduces NO production but does not protect against pancreatic beta-cell death induced by proinflammatory cytokines

The imidazoline compound RX871024 reduces IL-1beta-induced NO production thereby protecting against IL-1beta-induced beta-cell apoptosis. The aim of this study was to evaluate whether imidazolines RX871024 and efaroxan protect beta-cells against death in the presence of a combination of the cytokines IL-1beta, IFNgamma, and TNFalpha. To address this issue, experiments involving different methods for detection of cell death, different concentrations of the cytokines, and a variety of conditions of preparation and culturing of ob/ob mouse islets and beta-cells have been carried out. Thoroughly performed experiments have not been able to demonstrate a protective effect of RX871024 and efaroxan on beta-cell death induced by the combination of cytokines. However, the inhibitory effect of RX871024 on NO production in ob/ob mouse islets and beta-cells was still observed in the presence of all three cytokines and correlated with the decrease in p38 MAPK phosphorylation. Conversely, efaroxan did not affect cytokine-induced NO production. Our data indicate that a combination of pro-inflammatory cytokines IL-1beta, IFNgamma, and TNFalpha, conditions modelling those that take place in type 1 diabetes, induces pancreatic beta-cell death that does not directly correlate with NO production and cannot be counteracted with imidazoline compounds.     

Indole-3-carbinol blocks platelet-derived growth factor-stimulated vascular smooth muscle cell function and reduces neointima formation in vivo

The purpose of this study was to determine the effect and associated cell signaling mechanisms of indole-3-carbinol (I3C) on platelet-derived growth factor (PDGF)-BB-induced proliferation and migration of cultured vascular smooth muscle cells (VSMCs) and neointima formation in a carotid injury model. Our data demonstrated that I3C inhibited PDGF-BB-induced proliferation of VSMCs in a dose-dependent manner without causing cell cytotoxicity, as assessed by 5-bromo-2′-deoxyuridine incorporation and WST-1 assays. Further studies revealed that the antiproliferative effect of I3C was caused by the arrest of cells in both the G0/G1 and S phases. Moreover, I3C treatment inhibited migration of VSMCs and partly reversed the expression of smooth-muscle-specific contractile markers. We also demonstrated that I3C-induced growth inhibition was associated with an inhibition of the expression of cyclin D1 and cyclin-dependent kinase 4/6, as well as an increase in p27^Kip1 levels in PDGF-stimulated VSMCs. These beneficial effects of I3C on VSMCs appeared to be at least partly mediated by the inhibition of Akt and the subsequent activation of glycogen synthase kinase (GSK) 3β. Furthermore, using a mouse carotid artery injury model, we found that treatment with 150 mg/kg I3C resulted in a significant reduction of the neointima/media ratio and cells positive for proliferating cell nuclear antigen. These results demonstrate that I3C can suppress the proliferation and migration of VSMCs and neointima hyperplasia after vascular injury via inhibition of the Akt/GSK3β pathway and suggest that this might be feasible as part of a therapeutic strategy for vascular proliferative diseases.     

Triggering the immune response by proinflammatory cytokines

What determines whether or not an immune response takes place? The older view that it is only the presence or absence of T cells bearing appropriate receptors that matters has been replaced by one which lays at least equal emphasis on inflammation: whether or not antigenpresenting cells become activated and secrete proinflammatory cytokines. The evidence for this view comes partly from older work on animal models of autoimmunity and tolerance, partly signs of “immunological neglect” in transgenic mice akin to “immunological privilege”, and partly from some remarkably supportive genetics. The genetics includes genome scanning for quantitative trait loci determining disease susceptibility and case/control disease associations. Migration inhibitory factor is an interesting proinflammatory cytokine which does not yet fit into this scheme. We ask but do not answer the question whether protective T cell populations are subject to the same rules of activation.     

Synthetic melanin suppresses production of proinflammatory cytokines

An overproduction of proinflammatory cytokines mediates the damaging sequelae of inflammation in pathologic conditions such as rheumatoid arthritis, graft-vs-host reaction, cachexia, and sepsis syndrome. We examined the cytokine regulatory activity of synthetic melanin, exemplified by biosynthetic l-glycine-l-tyrosine-based polymer (ME-1) and chemosynthetic dihydroxyphenylalanine-based polymer (MC-1). At nontoxic concentrations, both compounds effectively (>/=60%) and reversibly suppressed the production of tumor necrosis factor (TNF), even when applied after stimulation of human peripheral blood monocytes with lipopolysaccharide (LPS). The inhibitory activity of melanin was selective with regard to cytokine response but not inducer- or cell-type-specific. In addition to TNF, melanin inhibited production of interleukin (IL)-1beta, IL-6, and IL-10 but not granulocyte-macrophage colony-stimulating factor by the LPS-stimulated monocytes. Melanin was equally effective in inhibiting production of TNF by monocytes stimulated with the purified protein derivative of Mycobacterium tuberculosis and production of IL-6 by IL-1alpha-stimulated human fibroblasts and endothelial cells. Northern blot analysis, mRNA stability determination, immunoprecipitation studies on metabolically labeled intracellular TNF, and pulse chase experiments revealed that melanin reduced efficiency of mRNA translation. The finding that melanin arrests ongoing cytokine synthesis suggests that this compound may be useful as an adjunct therapy for conditions showing involvement of proinflammatory cytokines.     

Role of inflammation and proinflammatory cytokines in cholangiocyte pathophysiology

Cholangiocytes, the epithelial cells lining the bile ducts, are an important subset of liver cells. They are involved in the modification of bile volume and composition, and respond to endogenous and exogenous stimuli. Along the biliary tree, two different kinds of cholangiocytes exist: small and large cholangiocytes. Each type has different features and biological role in physiologic and pathologic conditions, and their immunobiology is important for understanding biliary diseases. Cholangiocytes provide the first line of defence against luminal microbes in the hepatobiliary system. Indeed, they express a variety of pattern recognition receptors and may start an antimicrobial defence activating a set of intracellular signalling cascades. In response to injury, cholangiocytes that are normally quiescent become reactive and acquire a neuroendocrine-like phenotype with the release of proinflammatory mediators and antimicrobial peptides, which support biliary epithelial integrity. These molecules act in an autocrine/paracrine manner to modulate cholangiocyte biology and determine the evolution of biliary damage. Failure or dysregulation of such mechanisms may influence the progression of cholangiopathies, a group of diseases that selectively target biliary cells. In this review, we focus on the response of cholangiocytes in inflammatory conditions, with a particular focus on the mechanism driving cholangiocytes adaptation to damage. This article is part of a Special Issue entitled: Cholangiocytes in Health and Diseaseedited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.     

Maturation-dependent neointima formation in fowl aorta.

Fowl show spontaneous elevation of blood pressure (BP) and neointimal plaque formation in the abdominal aorta at young ages. Maturation/age-dependent modulation of vascular lesions and a causal relationship between elevated BP and neointima formation, however, have not been clarified. We therefore intended to characterize, first, maturation/age-dependent neointimal plaque formation and vascular lesions and, second, their relationship to BP elevation. The BP measured in conscious domestic fowl, Gallus gallus, White Leghorn breed, DeKalb strain, via an indwelling catheter inserted into the ischiadic artery, increased with maturation in males; and at plateau level, BP (mmHg) was significantly (P<0.01) higher in males (194.0+/-4.6, n=11) than in females (169.3+/-3.1, n=10). Neointimal plaques consisting of neointimal cells and abundant extracellular matrix appeared initially in the distal segment of the abdominal aorta (lesion-prone area) of chicks as early as 6 weeks old. The area (size) of neointimal plaques right above the ischiadic bifurcation increased with maturation, whereas the plaque area became smaller with some degenerative changes in adult birds. In some birds, diffuse subendothelial hyperplasia and more extensive plaque formation at the branching points of the aorta were observed. The plaque area appears to be larger in birds, particularly in males that have higher BP (r=0.68). The width of aortic smooth muscle (SM) layers, measured in regions with no plaque, increased with age, whereas the number of cells per unit of area decreased, suggesting that hypertrophy of vascular SM occurs in response to exposure of the vascular wall to high BP. The number of cells was significantly (P<0.01) higher in the plaque than in underlying aortic SM layers or in layers with no plaque formation. Both neointimal plaques and underlying SM layers are immunohistochemically positive for alpha SM actin, suggesting that neointimal cells are modulated SM cells, whereas the staining with SM myosin heavy chain antibody is low in neointimal plaques. Furthermore, plasma arginine levels dropped in accordance with the time of neointimal plaque formation, whereas plasma cholesterol levels showed an age-dependent increase. The results suggest that spontaneous development of neointimal plaques may be a consequence of exposure to high BP and associated local hemodynamic changes.     

IL-4 adenoviral gene therapy reduces inflammation, proinflammatory cytokines, vascularization, and bony destruction in rat adjuvant-induced arthritis

IL-4 is a cytokine with anti-inflammatory properties on activated macrophages. Rheumatoid arthritis, an autoimmune inflammatory disease, is characterized by a paucity of IL-4 and an abundance of synovial macrophage-derived mediators. Herein, the effect of a single injection of adenovirus-producing rat IL-4 (AxCAIL-4) or a control virus with no inserted gene was compared with the effect of PBS injection into rat ankles. Ankles were injected before arthritis onset or at maximal inflammation. Preventatively, AxCAIL-4 reduced adjuvant-induced arthritis (AIA)- and/or AIA/adenoviral-induced ankle inflammation, decreasing articular index scores, ankle circumferences, paw volumes, radiographic scores, mean levels of monocyte chemoattractant protein-1, the number of inflammatory cells, and the number of synovial blood vessels. Therapeutically, AxCAIL-4 also decreased ankle circumferences and paw volumes in comparison with a control virus with no inserted gene and PBS groups. After arthritis onset, mean levels of TNF-alpha, IL-1beta, macrophage inflammatory protein-2, and RANTES were decreased in AxCAIL-4 rat ankle homogenates compared with PBS-treated homogenates. Thus, increased expression of IL-4 via gene therapy administered in a preventative and/or therapeutic manner reduced joint inflammation, synovial cellularity, levels of proinflammatory cytokines, vascularization, and bony destruction in rat AIA, suggesting that a similar treatment in humans may be beneficial.     

Mast cells promote atherosclerosis by releasing proinflammatory cytokines

Mast cells contribute importantly to allergic and innate immune responses by releasing various preformed and newly synthesized mediators. Previous studies have shown mast cell accumulation in human atherosclerotic lesions. This report establishes the direct participation of mast cells in atherogenesis in low-density lipoprotein receptor-deficient (Ldlr(-/-)) mice. Atheromata from compound mutant Ldlr(-/-) Kit(W-sh)(/W-sh) mice showed decreased lesion size, lipid deposition, T-cell and macrophage numbers, cell proliferation and apoptosis, but increased collagen content and fibrous cap development. In vivo, adoptive transfer of syngeneic wild-type or tumor necrosis factor (TNF)-alpha-deficient mast cells restored atherogenesis to Ldlr(-/-)Kit(W-sh/W-sh) mice. Notably, neither interleukin (IL)-6- nor interferon (IFN)-gamma-deficient mast cells did so, indicating that the inhibition of atherogenesis in Ldlr(-/-)Kit(W-sh/W-sh) mice resulted from the absence of mast cells and mast cell-derived IL-6 and IFN-gamma. Compared with wild-type or TNF-alpha-deficient mast cells, those lacking IL-6 or IFN-gamma did not induce expression of proatherogenic cysteine proteinase cathepsins from vascular cells in vitro or affect cathepsin and matrix metalloproteinase activities in atherosclerotic lesions, implying that mast cell-derived IL-6 and IFN-gamma promote atherogenesis by augmenting the expression of matrix-degrading proteases. These observations establish direct participation of mast cells and mast cell-derived IL-6 and IFN-gamma in mouse atherogenesis and provide new mechanistic insight into the pathogenesis of this common disease.     

Regulation of airway tight junctions by proinflammatory cytokines

Epithelial tight junctions (TJs) provide an important route for passive electrolyte transport across airway epithelium and provide a barrier to the migration of toxic materials from the lumen to the interstitium. The possibility that TJ function may be perturbed by airway inflammation originated from studies reporting (1) increased levels of the proinflammatory cytokines interleukin-8 (IL-8), tumor necrosis factor alpha (TNF-alpha), interferon gamma (IFN-gamma), and IL-1beta in airway epithelia and secretions from cystic fibrosis (CF) patients and (2) abnormal TJ strands of CF airways as revealed by freeze-fracture electron microscopy. We measured the effects of cytokine exposure of CF and non-CF well-differentiated primary human airway epithelial cells on TJ properties, including transepithelial resistance, paracellular permeability to hydrophilic solutes, and the TJ proteins occludin, claudin-1, claudin-4, junctional adhesion molecule, and ZO-1. We found that whereas IL-1beta treatment led to alterations in TJ ion selectivity, combined treatment of TNF-alpha and IFN-gamma induced profound effects on TJ barrier function, which could be blocked by inhibitors of protein kinase C. CF bronchi in vivo exhibited the same pattern of expression of TJ-associated proteins as cultures exposed in vitro to prolonged exposure to TNF-alpha and IFN-gamma. These data indicate that the TJ of airway epithelia exposed to chronic inflammation may exhibit parallel changes in the barrier function to both solutes and ions.     

Leptin downregulates ethanol-induced secretion of proinflammatory cytokines and growth factor

Inflammatory mediators, including cytokines and growth factors are associated with the pathology of chronic liver diseases. The aim of our present work was to study the effect of exogenous leptin and/or ethanol on the secretion of TNF-alpha, IL-6 and TGF-beta1 both in vivo and in vitro. Forty eight hours after the exposure to ethanol (500 mM) significantly elevated the secretion of TNF-alpha, IL-6 and TGF-beta1 in the cell-free culture supernatant (HepG2 and mouse HCC cell lines), which were decreased on leptin (31.2 nM) treatment. Similarly, leptin administration to ethanol (6.32 g kg(-1) body weight) fed mice for 45 days significantly lowered the concentration of these cytokines in the circulation; however, leptin alone (230 microg kg(-1) body weight i.p. administered every alternate day for the last 15 days) had no such significant effect on cytokine secretion both in vivo and in vitro conditions. We conclude that leptin is involved in the protective mechanisms that allow an organism to cope with the potentially autoaggressive effects of its immune system in alcoholic liver disease.     

Myeloid-derived suppressor cells and proinflammatory cytokines as targets for cancer therapy

Myeloid-derived suppressor cells represent a heterogeneous population of immature myeloid cells. Under normal conditions, these cells differentiate into macrophages, dendritic cells, and granulocytes. However, in pathological states such as inflammation, infection, or tumor growth, there is an arrest of their differentiation that results in the accumulation of immature myeloid cells in the organism. In addition, these cells acquire a suppressor phenotype, expressing anti-inflammatory cytokines and reactive oxygen and nitrogen species, and suppress T-cell immune response. Myeloid-derived suppressor cells (MDSC) contribute to cancerogenesis by forming a favorable microenvironment for tumor growth. Proinflammatory cytokines, secreted by tumor cells and the tumor microenvironment, induce angiogenesis and metastasis and promote tumor growth. They also provide signals necessary for survival, accumulation, and function of MDSC. Understanding the mechanisms of myeloid suppressor cell development and the use of proinflammatory cytokine inhibitors may prove beneficial for tumor therapy.     

Caveolin-1 deficiency stimulates neointima formation during vascular injury

Neointima formation is a process characterized by smooth muscle cell (SMC) proliferation and extracellular matrix deposition in the vascular intimal layer. Here, we critically evaluate the role of caveolin-1 (Cav-1) in the pathogenesis of neointima formation. Cav-1 and caveolae organelles are particularly abundant in SMCs, where they are thought to function in membrane trafficking and signal transduction events. To directly evaluate the role of Cav-1 in the pathogenesis of neointimal lesions, we used Cav-1-deficient (Cav-1 -/-) mice as a model system. The right common carotid artery of wild-type and Cav-1 -/- mice was ligated just proximal to its bifurcation. Specimens were then harvested 4-weeks postligation and processed for morphometric and immunohistochemical analyses. The carotids of Cav-1 -/- mice showed significantly more intimal hyperplasia with subtotal luminal obstruction, as compared to wild-type mice. These neointimal lesions consisted mainly of SMCs. Mechanistically, neointimal lesions derived from Cav-1 -/- mice exhibited higher levels of phospho-p42/44 MAP kinase and cyclin D1 immunostaining, consistent with the idea that Cav-1 functions as a negative regulator of signal transduction. A significant increase in phospho-Rb (Ser780) immunostaining was also observed, in line with the upregulation of cyclin D1. In conclusion, using a carotid artery blood-flow cessation model, we show that genetic ablation of Cav-1 in mice stimulates SMC proliferation (neointimal hyperplasia), with concomitant activation of the p42/44 MAP kinase cascade and upregulation of cyclin D1. Importantly, our current study is the first to investigate the role of Cav-1 in SMC proliferation in the vascular system using Cav-1 -/- mice.     

Cannabinoid receptor CB2 protects against balloon-induced neointima formation

Cannabinoid receptor CB(2) activation inhibits inflammatory proliferation and migration of vascular smooth muscle cells in vitro. The potential in vivo relevance of these findings is unclear. We performed carotid balloon distension injury in hypercholesterolemic apolipoprotein E knockout (ApoE(-/-)) mice receiving daily intraperitoneal injection of the CB(2) agonist JWH133 (5 mg/kg) or vehicle, with the first injection given 30 min before injury. Alternatively, we subjected CB(2)(-/-) and wild-type (WT) mice to balloon injury. We determined CB(2) mRNA and protein expression in dilated arteries of ApoE(-/-) mice. Neointima formation was assessed histologically. We used bone marrow-derived murine CB(2)(-/-) and WT macrophages to study adhesion to plastic, fibronectin, or collagen, and migration was assayed by modified Boyden chamber. Aortic smooth muscle cells were isolated to determine in vitro proliferation rates. We found increased vascular CB(2) expression in ApoE(-/-) mice in response to balloon injury. Seven to twenty-one days after dilatation, injured vessels of JWH133-treated mice had less intimal nuclei numbers as well as intimal and medial areas, associated with less staining for proliferating cells, smooth muscle cells, and macrophages. Complete endothelial repair was observed after 14 days in both JWH133- and vehicle-treated mice. CB(2) deficiency resulted in increased intima formation compared with WT, whereas JWH133 did not affect intimal formation in CB(2)(-/-) mice. Apoptosis rates assessed by in situ terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling staining 1 h postballooning were significantly higher in the CB(2) knockouts. In vitro, bone marrow-derived CB(2)(-/-) macrophages showed enhanced adherence and migration compared with WT cells and elevated mRNA levels of adhesion molecules, chemokine receptors CCR1 and 5, and chemokine CCL2. Proliferation rates were significantly increased in CB(2)(-/-) smooth muscle cells compared with WT. In conclusion, pharmacological activation or genetic deletion of CB(2) receptors modulate neointima formation via protective effects in macrophages and smooth muscle cells.     

Resistin messenger-RNA expression is increased by proinflammatory cytokines in vitro

Resistin is a recently discovered polypeptide that induces insulin resistance in rodents. While in rodents resistin is predominantly expressed in adipocytes, in humans peripheral blood mononuclear cells (PBMC) seem to a be a major source of resistin. In the present study, we show that in human PBMC resistin mRNA expression-determined by fluorescence-based real-time polymerase chain reaction-is strongly increased by the proinflammatory cytokines interleukin (IL)-1, IL-6, tumor necrosis factor alpha (TNF-alpha), and also by lipopolysaccharides (LPS), respectively, while no effect was found by interferon-gamma (IFN-gamma) or leptin. Our results suggest that in humans resistin may be a link in the well-known association between inflammation and insulin resistance.