Visfatin enhances ICAM-1 and VCAM-1 expression through ROS-dependent NF-kappaB activation in endothelial cells

Visfatin has recently been identified as a novel visceral adipokine which may be involved in obesity-related vascular disorders. However, it is not known whether visfatin directly contributes to endothelial dysfunction. Here, we investigated the effect of visfatin on vascular inflammation, a key step in a variety of vascular diseases. Visfatin induced leukocyte adhesion to endothelial cells and the aortic endothelium by induction of the cell adhesion molecules, ICAM-1 and VCAM-1. Promoter analysis revealed that visfatin-mediated induction of CAMs is mainly regulated by nuclear factor-kappaB (NF-kappaB). Visfatin stimulated IkappaBalpha phosphorylation, nuclear translocation of the p65 subunit of NF-kappaB, and NF-kappaB DNA binding activity in HMECs. Furthermore, visfatin increased ROS generation, and visfatin-induced CAMs expression and NF-kappaB activation were abrogated in the presence of the direct scavenger of ROS. Taken together, our results demonstrate that visfatin is a vascular inflammatory molecule that increases expression of the inflammatory CAMs, ICAM-1 and VCAM-1, through ROS-dependent NF-kappaB activation in endothelial cells.     

Mast cells are potent regulators of endothelial cell adhesion molecule ICAM-1 and VCAM-1 expression

To investigate the possible role of mast cells (MC) in regulating leukocyte adhesion to vascular endothelial cells (EC), microvascular and macrovascular EC were exposed to activated MC or MC conditioned medium (MCCM). Expression of intercellular and vascular adhesion molecules (ICAM-1 and VCAM-1) on EC was monitored. Incubation of human dermal microvascular endothelial cells (HDMEC) and human umbilical vein endothelial cells (HUVEC) with activated MC or MCCM markedly increased ICAM-1 and VCAM-1 surface expression, noted as éarly as 4 hr. Maximal levels were observed at 16 hr followed by a general decline over 48 hr. A dose-dependent response was noted using incremental dilutions of MCCM or by varying the number of MC in coculture with EC. At a ratio as low as 1:1,000 of MC:EC, increased ICAM-1 was observed. The ICAM-1 upregulation by MCCM was >90% neutralized by antibody to tumor necrosis factor alpha (TNF-α), suggesting that MC release of this cytokine contributes significantly to inducing EC adhesiveness. VCAM-1 expression enhanced by MCCM was partly neutralized (70%) by antibody to TNF-α; thus other substances released by MC may contribute to VCAM-1 expression. Northern blot analysis demonstrated MCCM upregulated ICAM-1 and VCAM-1 mRNA in both HDMEC and HUVEC. To evaluate the function of MCCM-enhanced EC adhesion molecules, T cells isolated from normal human donors were used in a cell adhesion assay. T-cell binding to EC was increased significantly after exposure of EC to MCCM, and inhibited by antibodies to ICAM-1 or VCAM-1. Intradermal injection of allergen in human atopic volunteers known to develop late-phase allergic reactions led to marked expression of both ICAM-1 and VCAM-1 at 6 hr, as demonstrated by immunohistochemistry. These studies indicate that MC play a critical role in regulating the expression of EC adhesion molecules, ICAM-1 and VCAM-1, and thus augment inflammatory responses by upregulating leukocyte binding. © 1995 Wiley-Liss Inc.     

RORalpha1 and RORalpha4 suppress TNF-alpha-induced VCAM-1 and ICAM-1 expression in human endothelial cells

Retinoic acid receptor-related orphan receptor-alpha (RORalpha) is a nuclear orphan receptor. Adenovirus-mediated overexpression of RORalpha1 and RORalpha4 suppressed tumor necrosis factor-alpha (TNF-alpha)-induced expression of vascular cell adhesion molecule-1 (VCAM-1) and intracellular adhesion molecule-1 (ICAM-1) in human umbilical vein endothelial cells. Overexpression of RORalpha1 and RORalpha4 also suppressed TNF-alpha-stimulated translocation of p50 and p65 to the nucleus. In contrast, dominant-negative deletion mutants of RORalpha1 and RORalpha4 failed to suppress the induction of VCAM-1 and ICAM-1 and translocations of p50 and p65. These results suggest that RORalpha1 and RORalpha4 regulate the inflammatory responses via inhibition of the nuclear factor-kappaB signaling pathway in endothelial cells.     

Enteric microflora contribute to constitutive ICAM-1 expression on vascular endothelial cells

Quantitative estimates of endothelial cell adhesion molecule expression have revealed that some adhesion molecules [e.g., intercellular adhesion molecule-1 (ICAM-1)] are abundantly expressed in different vascular beds under normal conditions. The objective of this study was to determine whether the enteric microflora contribute to the constitutive expression of ICAM-1 and other endothelial cell adhesion molecules in the gastrointestinal tract and other regional vascular beds. The dual radiolabeled monoclonal antibody technique was used to measure endothelial expression of ICAM-1, ICAM-2, vascular cell adhesion molecule-1 (VCAM-1), and E-selectin in conventional, germ-free mice and germ-free mice receiving the cecal contents of conventional mice to reestablish the enteric microflora (total association). Constitutive ICAM-1 expression was significantly lower in the splanchnic organs (pancreas, stomach, small and large intestine, mesentery, and liver), kidneys, skeletal muscle, and skin of germ-free mice compared with their conventional counterparts. These differences were abolished after total association of germ-free mice with the indigenous gastrointestinal flora. The expression of ICAM-2, VCAM-1, and E-selectin in the various tissues studied did not differ between conventional and germ-free mice. These findings indicate that the indigenous gastrointestinal microflora are responsible for a significant proportion of the basal ICAM-1 expression detected in both intestinal and extraintestinal tissues.     

Butyrate inhibits cytokine-induced VCAM-1 and ICAM-1 expression in cultured endothelial cells: the role of NF-kappaB and PPARalpha

Adhesion and migration of leukocytes into the surrounding tissues is a crucial step in inflammation, immunity, and atherogenesis. Expression of cell adhesion molecules by endothelial cells plays a leading role in this process. Butyrate, a natural short-chain fatty acid produced by bacterial fermentation of dietary fiber, has been attributed with anti-inflammatory activity in inflammatory bowel disease. Butyrate in vitro is active in colonocytes and several other cell types. We have studied the effect of butyrate on expression of endothelial leukocyte adhesion molecules by cytokine-stimulated human umbilical vein endothelial cells (HUVEC). Pretreatment of HUVEC with butyrate-inhibited tumor necrosis factor-alpha (TNFalpha)-induced expression of vascular cell adhesion molecule-1 (VCAM-1) and intracellular cell adhesion molecule-1 (ICAM-1) in a time and concentration-dependent manner. Butyrate at 10 mM/L inhibited interleukin-1 (IL-1)-stimulated VCAM-1 and ICAM-1 expression. The effect of butyrate on cytokine-stimulated VCAM-1 expression was more pronounced than in the case of ICAM-1. Butyrate decreased TNFalpha-induced expression of mRNA for VCAM-1 and ICAM-1. Suppressed expression of VCAM-1 and ICAM-1 was associated with reduced adherence of monocytes and lymphocytes to cytokine-stimulated HUVEC. Butyrate inhibited TNFalpha-induced activation of nuclear factor-kappaB (NF-kappaB) in HUVEC. Finally, butyrate enhanced peroxisome proliferator-activated receptor-alpha (PPARalpha) expression in HUVEC. These results demonstrate that butyrate may have anti-inflammatory properties not only in colonocytes but also in endothelial cells. The anti-inflammatory and (perhaps) antiatherogenic properties of butyrate may partly be attributed to an effect on activation of NF-kappaB and PPARalpha and to the associated expression of VCAM-1 and ICAM-1. The present findings support further investigations on the therapeutic benefits of butyrate in several pathological events involving leukocyte recruitment.     

Insulin potentiates cytokine-induced VCAM-1 expression in human endothelial cells

Hyperinsulinemia is an independent risk factor for cardiovascular events and may contribute to cardiovascular disease. Low-grade chronic inflammation has been implicated in the pathogenesis of atherosclerosis. We aimed at determining the impact of pathophysiologically high insulin concentrations on cytokine-induced endothelial activation in human umbilical vein endothelial cells (HUVEC). HUVEC were incubated with insulin (0-24 h)+/-tumor necrosis factor (TNF)-alpha or lipopolysaccharide (LPS). At pathophysiological/pharmacological concentrations (10(-9)-10(-7) mol/L), insulin selectively induced VCAM-1 expression and potentiated the effects of TNF-alpha andLPS, effects reverted by the proteasome inhibitor lactacystin. Compared with TNF-alpha alone, insulin+TNF-alpha doubled U937 cell adhesion. Insulin markedly increased TNF-alpha-induced NF-kappaB activation and induced phosphorylated IkappaB-alpha accumulation. Therefore, hyperinsulinemia enhances cytokine-induced VCAM-1 expression in endothelial cells, thus potentially contributing to detrimental effects of other inflammatory stimuli on atherogenesis.     

Vascular endothelial growth factor expression of intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and E-selectin through nuclear factor-kappa B activation in endothelial cells

Vascular endothelial growth factor (VEGF) induces adhesion molecules on endothelial cells during inflammation. Here we examined the mechanisms underlying VEGF-stimulated expression of intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and E-selectin in human umbilical vein endothelial cells. VEGF (20 ng/ml) increased expression of ICAM-1, VCAM-1, and E-selectin mRNAs in a time-dependent manner. These effects were significantly suppressed by Flk-1/kinase-insert domain containing receptor (KDR) antagonist and by inhibitors of phospholipase C, nuclear factor (NF)-kappaB, sphingosine kinase, and protein kinase C, but they were not affected by inhibitors of mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) 1/2 or nitric-oxide synthase. Unexpectedly, the phosphatidylinositol (PI) 3'-kinase inhibitor wortmannin enhanced both basal and VEGF-stimulated adhesion molecule expression, whereas insulin, a PI 3'-kinase activator, suppressed both basal and VEGF-stimulated expression. Gel shift analysis revealed that VEGF stimulated NF-kappaB activity. This effect was inhibited by phospholipase C, NF-kappaB, or protein kinase C inhibitor. VEGF increased VCAM-1 and ICAM-1 protein levels and increased leukocyte adhesiveness in a NF-kappaB-dependent manner. These results suggest that VEGF-stimulated expression of ICAM-1, VCAM-1, and E-selectin mRNAs was mainly through NF-kappaB activation with PI 3'-kinase-mediated suppression, but was independent of nitric oxide and MEK. Thus, VEGF simultaneously activates two signal transduction pathways that have opposite functions in the induction of adhesion molecule expression. The existence of parallel inverse signaling implies that the induction of adhesion molecule expression by VEGF is very finely regulated.     

Anthrax lethal toxin enhances cytokine-induced VCAM-1 expression on human endothelial cells

Vascular endothelial dysfunction is thought to play a prominent role in systemic anthrax pathogenesis. We examined the effect of anthrax lethal toxin (LTx), a key virulence factor of Bacillus anthracis, on the expression of vascular cell adhesion molecule-1 (VCAM-1) on normal and cytokine-stimulated human lung microvascular endothelial cells. Confluent endothelial monolayers were treated with lethal factor (LF), protective antigen (PA), or both (LTx) in the presence or absence of tumor necrosis factor-alpha (TNFalpha). LTx enhanced cytokine-induced VCAM-1 expression and monocyte adhesion. LTx alone had no effect on VCAM-1 expression. LF, PA or the combination of a catalytically inactive mutant LF and PA failed to enhance cytokine-induced VCAM-1 expression. Treatment with inhibitors of mitogen-activated protein kinase kinases (MEKs) and mitogen-activated protein kinases did not reproduce the VCAM-1 enhancement effect of LTx, a known MEK metalloprotease, suggesting LTx-mediated MEK cleavage may not be a contributing factor.     

Effect of steroid on hyperoxia-induced ICAM-1 expression in pulmonary endothelial cells

Intercellular adhesion molecule-1 (ICAM-1) of the vascular endothelium plays a key role in the development of pulmonary oxygen toxicity. We studied the effect of steroid on hyperoxia-induced ICAM-1 expression using cultured endothelial cells in vitro. Human pulmonary artery endothelial cells (HPAECs) were cultured to confluence, and then the monolayers were exposed to either control (21% O(2)-5% CO(2)) or hyperoxic (90% O(2)-5% CO(2)) conditions with and without a synthetic glucocorticoid, methylprednisolone (MP). MP reduced hyperoxia-induced ICAM-1 and ICAM-1 mRNA expression in a dose-dependent manner. Neutrophil adhesion to hyperoxia-exposed endothelial cells was also inhibited by MP treatment. In addition, MP attenuated hyperoxia-induced H(2)O(2) production in HPAECs as assessed by flow cytometry. An electrophoretic mobility shift assay demonstrated that hyperoxia activated nuclear factor-kappaB (NF-kappaB) but not activator protein-1 (AP-1) and that MP attenuated hyperoxia-induced NF-kappaB activation dose dependently. With Western immunoblot analysis, IkappaB-alpha expression was decreased by hyperoxia and increased by MP treatment. These results suggest that MP downregulates hyperoxia-induced ICAM-1 expression by inhibiting NF-kappaB activation via increased IkappaB-alpha expression.     

Eosinophil adhesion to cholinergic nerves via ICAM-1 and VCAM-1 and associated eosinophil degranulation

In vivo, eosinophils localize to airway cholinergic nerves in antigen-challenged animals, and inhibition of this localization prevents antigen-induced hyperreactivity. In this study, the mechanism of eosinophil localization to nerves was investigated by examining adhesion molecule expression by cholinergic nerves. Immunohistochemical and functional studies demonstrated that primary cultures of parasympathetic nerves express vascular cell adhesion molecule-1 (VCAM-1) and after cytokine pretreatment with tumor necrosis factor-alpha and interferon-gamma intercellular adhesion molecule-1 (ICAM-1). Eosinophils adhere to these parasympathetic neurones after cytokine pretreatment via a CD11/18-dependent pathway. Immunohistochemistry and Western blotting showed that a human cholinergic nerve cell line (IMR-32) expressed VCAM-1 and ICAM-1. Inhibitory experiments using monoclonal blocking antibodies to ICAM-1, VCAM-1, or CD11/18 and with the very late antigen-4 peptide inhibitor ZD-7349 showed that eosinophils adhered to IMR-32 cells via these adhesion molecules. The protein kinase C signaling pathway is involved in this process as a specific inhibitor-attenuated adhesion. Eosinophil adhesion to IMR-32 cells was associated with the release of eosinophil peroxidase and leukotriene C(4). Thus eosinophils adhere to cholinergic nerves via specific adhesion molecules, and this leads to eosinophil activation and degranulation; this may be part of the mechanism of eosinophil-induced vagal hyperreactivity.     

NF-kappaB activation for constitutive expression of VCAM-1 and ICAM-1 on B lymphocytes and plasma cells.

Cytokine stimulation can activate NF-kappaB that triggers inducible expression of E-selectin, VCAM-1 (Vascular Cell Adhesion Molecule-1) and ICAM-1 (Intercellular Cell Adhesion Molecule-1) in endothelial cells. In the previous study, we have shown that B lymphocytes and plasma cells can express E-selectin by constitutive activation of NF-kappaB. Here we show that human B lymphocytes and ARH-77 plasma cells expressed VCAM-1 and ICAM-1 in a cytokine dispensable mechanism. NF-kappaB antagonists could inhibit their expressions in ARH-77 cells. The activities of NF-kappaB for VCAM-1 and ICAM-1 promoters prior to cytokine stimulation were detected in ARH-77 cells using electrophoretic mobility shift assays. Again, NF-kappaB antagonists could abrogate these promoter activities. Taken together, our results demonstrate that NF-kappaB activation is the underlying molecular mechanism for constitutive expression of E-selectin, VCAM-1, and ICAM-1 on human B lymphocytes and plasma cells.     

Influence of polyelectrolyte multilayer films on the ICAM-1 expression of endothelial cells

Recently, the use of polyelectrolyte films has been suggested as a new versatile technique of surface modification aimed at tissue engineering. In the present study, we evaluated the expression of intercellular adhesion molecule (ICAM)-1 of endothelial cells (ECs) seeded on two types of polyelectrolyte multilayer films either terminated by poly(D-lysine) (PDL) or poly(allylamine hydrochloride) (PAH). This work showed that chemical stimulations with tumor necrosis factor (TNF)-alpha induced the ICAM-1 expression of ECs differently depending largely on the film architecture employed. Compared with PAH-ending films, the PDL-ending ones upregulated the ICAM-1 expression of the ECs after a prolonged exposition to TNF-alpha, rendering this film type less favorable in tissue engineering. Cytochalasin D (an F-actin disrupting agent) showed the involvement of the cytoskeleton in the upregulation of ICAM-1 for cells deposited on films terminated by PDL. The PAH-ending films did not perturb the ICAM-1 expression of ECs and might thus enhance the seeding of ECs in vascular engineering.     

FK506 suppresses E-selectin, ICAM-1 and VCAM-1 expression on vascular endothelial cells by inhibiting tumor necrosis factor alpha secretion from peripheral blood mononuclear cells

FK506 suppresses activation of T cells; however, it down-regulates E-selectin, ICAM-1 and VCAM-1 expression in inflamed tissues. In this study, we investigated the effect of FK506 on expression of those adhesion molecules on human vascular endothelial cells (HMVEC). Culture supernatant from peripheral blood mononuclear cells (PBMC) stimulated with anti-CD3 plus anti-CD2 antibodies effectively induced the expression of E-selectin, ICAM-1 and VCAM-1 on HMVEC, and treatment with FK506 down-regulated their expression. Culture supernatant contained tumor necrosis factor (TNF) alpha and interleukin (IL)-1beta, which effectively induced adhesion molecules, and FK506 suppressed both cytokine secretions. TNFalpha content in culture supernatant was parallel to the induction of adhesion molecules by the culture supernatant. IL-1beta content was not enough to induce those adhesion molecules. Anti-TNFalpha antibody completely inhibited those expressions. FK506 did not inhibit either TNFalpha- or IL-1beta-induced expression of adhesion molecules, or viability of HMVEC. These results indicate that FK506 suppresses migration of inflammatory cells through the inhibition of TNFalpha secretion from leukocytes.     

Ca2+ influx induced by protease-activated receptor-1 activates a feed-forward mechanism of TRPC1 expression via nuclear factor-kappaB activation in endothelial cells

Thrombin activation of protease-activated receptor-1 induces Ca(2+) influx through store-operated cation channel TRPC1 in endothelial cells. We examined the role of Ca(2+) influx induced by the depletion of Ca(2+) stores in signaling TRPC1 expression in endothelial cells. Both thrombin and a protease-activated receptor-1-specific agonist peptide induced TRPC1 expression in human umbilical vein endothelial cells, which was coupled to an augmented store-operated Ca(2+) influx and increase in endothelial permeability. To delineate the mechanisms of thrombin-induced TRPC1 expression, we transfected in endothelial cells TRPC1-promoter-luciferase (TRPC1-Pro-Luc) construct containing multiple nuclear factor-kappaB (NF-kappaB) binding sites. Co-expression of dominant negative IkappaBalpha mutant prevented the thrombin-induced increase in TRPC1 expression, indicating the key role of NF-kappaB activation in mediating the response. Using TRPC1 promoter-deletion mutant constructs, we showed that NF-kappaB binding sites located between -1623 and -871 in the TRPC1 5'-regulatory region were required for thrombin-induced TRPC1 expression. Electrophoretic mobility shift assay utilizing TRPC1 promoter-specific oligonucleotides identified that the DNA binding activities of NF-kappaB to NF-kappaB consensus sites were located in this domain. Supershift assays using NF-kappaB protein-specific antibodies demonstrated the binding of p65 homodimer to the TRPC1 promoter. Inhibition of store Ca(2+) depletion, buffering of intracellular Ca(2+), or down-regulation of protein kinase Calpha downstream of Ca(2+) influx all blocked thrombin-induced NF-kappaB activation and the resultant TRPC1 expression in endothelial cells. Thus, Ca(2+) influx via TRPC1 is a critical feed-forward pathway responsible for TRPC1 expression. The NF-kappaB-regulated TRPC1 expression may be an essential mechanism of vascular inflammation and, hence, a novel therapeutic target.     

Hyperketonemia increases monocyte adhesion to endothelial cells and is mediated by LFA-1 expression in monocytes and ICAM-1 expression in endothelial cells

Frequent episodes of hyperketonemia are associated with a higher incidence of vascular disease. The objective of this study was to examine the hypothesis that hyperketonemia increases monocyte-endothelial cell (EC) adhesion and the development of vascular disease in diabetes. Human U937 and THP-1 monocyte cell lines and human umbilical vein endothelial cells (HUVECs) were cultured with acetoacetate (AA) (0-10 mM) or β-hydroxybutyrate (BHB) (0-10 mM) for 24 h prior to evaluating adhesion and adhesion molecule expression. The results demonstrate a significant (P < 0.01) increase in both U937 and THP-1 adhesion to HUVEC monolayers treated with 4 mM AA compared with control. Equal concentrations of BHB resulted in similar increases in monocyte-EC adhesion. Similarly, treatments of AA or BHB to isolated monocytes from human blood also show increases in adhesion to endothelial cells. intercellular adhesion molecule-1 (ICAM-1) was significantly increased on the surface of HUVECs and an increase in total protein expression with AA treatment compared with control. The expression level of lymphocyte function-associated antigen-1 (LFA-1) was increased in monocytes treated with AA, and LFA-1 affinity was altered from low to high affinity following treatment with both AA and BHB. Monocyte adhesion could be blocked when cells were preincubated with an antibody to ICAM-1 or LFA-1. Results also show a significant increase in IL-8 and MCP-1 secretion in monocytes and HUVECs treated with 0-10 mM AA. These results suggest that hyperketonemia can induce monocyte adhesion to endothelial cells and that it is mediated via increased ICAM-1 expression in endothelial cells and increased expression and affinity of LFA-1 in monocytes.     

TNF-alpha and IL-1 sequentially induce endothelial ICAM-1 and VCAM-1 expression in MRL/lpr lupus-prone mice.

Dysfunctional leukocyte-endothelial interactions are thought to play a key role in systemic lupus erythematosus pathogenesis. We questioned the importance of TNF-alpha and IL-1 for endothelial activation in MRL/lpr lupus-prone mice. Endothelial ICAM-1 and VCAM-1 expression increased significantly with disease evolution in kidney, heart, and brain, as shown by i.v. injected radiolabeled Ab uptake. Lung endothelial VCAM-1 also increased, while lung endothelial ICAM-1 did not rise above a high basal level. Immunoassays showed a significantly raised circulating level of TNF-alpha by 14 wk, with levels of circulating IL-1alpha and IL-1beta being additionally raised by 20 wk. With 14-wk-old MRL/lpr, anti-TNF-alpha antiserum inhibited expression of ICAM-1 and VCAM-1 by endothelial cells cultured with sera in vitro, and uptake of anti-ICAM-1 and anti-VCAM-1 mAb in lung, kidney, brain, and heart in vivo. In contrast, both anti-TNF-alpha and anti-IL-1 antisera were required for maximal inhibition in vitro and in vivo at 20 wk. These data indicate that TNF-alpha is largely responsible for the early up-regulation of endothelial ICAM-1 and VCAM-1, but that IL-1 enhances expression in late disease. Our observations provide novel insights of possible relevance to understanding endothelial activation in systemic lupus erythematosus, and highlight an approach that can be extended to dissecting other chronic inflammatory diseases.     

Crosslinking of CD44 on human osteoblastic cells upregulates ICAM-1 and VCAM-1

Cancer-induced cachexia affects most advanced cancer patients. It is characterized by anorexia, profound metabolic dysfunctions, and severe neurological disorders. Here we show that voltage-gated potassium channel (Kv) expression is impaired in the brain of tumor-bearing animals. Expression of both delayed rectifier (Kv1.1, Kv1.2, Kv1.3, Kv1.5, Kv1.6, Kv2.1, Kv3.1, Kv4.2) and A-type potassium channels (Kv1.4, Kv3.3, Kv3.4) was greatly down-regulated in brain from animals bearing a Yoshida AH-130 ascites hepatoma. The possible compensatory mechanisms (Kv1.4/Kv4.2), expression of redundant genes (Kv3.1/Kv3.3) and heteromultimeric channel formation (Kv2.1/Kv9.3) were also affected. The high circulating levels of TNFalpha and the reduced expression of the anti-apoptotic protein Bcl-XL found in the brain of tumor-bearing animals indicate that this response could be mediated by an increase in brain cell death due to apoptosis. The results suggest that brain function is impaired during cancer cachexia, and may account for the cancer-induced anorectic response and other neurological alterations.