Direct Anti-inflammatory Properties Research Articles

Therapeutic potential of ozone water treatment in alleviating atopic dermatitis symptoms in mouse models: Exploring its bactericidal and direct anti-inflammatory properties

Currently, ozone water is utilized for antibacterial and antiviral purposes without any reported safety concerns. Therefore, ozone water may have clinical applications in treating staphylococcal-specific cutaneous diseases, such as atopic dermatitis (AD) and pyoderma. This study aimed to verify the bactericidal effects of ozone water at different concentrations (3 and 11 mg/L) against staphylococcal species in vitro, as well as evaluate the anti-inflammatory effects of ozone water in a mouse model of AD and pyoderma. Initially, the bactericidal properties of several concentrations of ozone water were confirmed with Staphylococcus aureus and methicillin-resistant S. pseudintermedius. Both 3 and 11 mg/L of ozone water exhibited a significant bactericidal effect against staphylococci at less than 100 times dilution. We next examined the cellular cytotoxicity and cytokine production (Interleukin (IL)-6 and IL-8) induced by S. pseudintermedius pre-treated with ozone water, and our findings indicated that cytotoxicity and cytokine production induced by staphylococci were significantly inhibited after ozone water pre-treatment. In vivo experiments showed that ozone water-pre-treated S. pseudintermedius significantly inhibited the development of pyoderma in mice; however, limited effects were observed in a therapeutic setting. Interestingly, ozone water at concentrations of 3 and 11 mg/L exhibits dual bactericidal and anti-inflammatory effects in mice with AD. This observation was corroborated by the significant inhibition of cytokine production in interferon-γ/tumor necrosis factor-stimulated human epidermal keratinocyte cells exposed to ozone in vitro. These findings indicate that administering ozone can be a novel therapeutic approach for managing allergic skin diseases, such as AD.

The contribution of probiotics for the double-edge effect of cefazolin on postoperative neurocognitive disorders by rebalancing the gut microbiota.

Emerging data suggest that perioperative gut dysbiosis is prevalent and may be associated with postoperative neurocognitive disorders (PND). Antibiotics and probiotics are key factors influencing the microbiota. Many antibiotics have anti-microorganisms and direct anti-inflammatory properties, which may have cognitive repercussions. NLRP3 inflammasome activation has been reported to be involved with cognitive deficits. This study aimed to determine the effect and mechanism of probiotics on neurocognitive problems associated with perioperative gut dysbiosis by the NLRP3 pathway. In a randomized, controlled trial, adult male Kunming mice undergoing surgery were administered cefazolin, FOS + probiotics, CY-09, or a placebo in four distinct experimental cohorts. Fear conditioning (FC) tests evaluate learning and memory. Following FC tests to evaluate inflammatory response (IR) and the permeability of barrier systems, the hippocampus and colon were extracted, and feces were collected for 16 s rRNA. One week after surgery, surgery/anesthesia decreased the frozen behavior. Cefazolin attenuated this declination but aggravated postoperative freezing behavior 3 weeks after surgery. Probiotics ameliorated surgery/anesthesia-induced memory deficits and perioperative cefazolin-induced postoperative memory deficits 3 weeks after surgery. NLRP3, caspase-1, Interleukin-1β (IL-1β), and Interleukin-18 (IL-18) levels were increased 1 week after the hippocampus and colon surgery, which were attenuated by CY-09 and probiotics, respectively. Probiotics could correct dysbacteria and IR caused by surgery/anesthesia stress and cefazolin alone. These findings imply that probiotics are an efficient and effective way of maintaining the balance of gut microbiota, which may reduce NLRP3-related inflammation and alleviate PND.

Pharmacological inhibition of fatty acid oxidation reduces atherosclerosis progression by suppression of macrophage NLRP3 inflammasome activation

BackgroundInflammation is a key process during atherosclerotic lesion development and propagation. Recent evidence showed clearly that especially the inhibition of interleukin (IL)-1β reduced atherosclerotic adverse events in human patients. Fatty acid oxidation (FAO) was previously demonstrated to interact with the NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) pathway which is required for mature IL-1β secretion. To understand possible anti-inflammatory properties of FAO inhibition, we tested the effect of pharmacological FAO inhibition using the inhibitor for long-chain 3-ketoacyl coenzyme A thiolase trimetazidine on atherosclerotic plaque development and inflammation. Experimental ApproachThe effect of FAO inhibition was determined in LDL-R−/− male mice on a C57/BL6 background. In vitro effects of trimetazidine treatment were analyzed in human umbilical vein endothelial cells and human monocyte derived macrophages. Key ResultsWe were able to demonstrate that inhibition of FAO reduced atherosclerotic plaque growth. We did not find direct anti-inflammatory properties of trimetazidine in endothelial cells or macrophages in vitro. However, we found that the activation of the NLRP3 system and the secretion of IL-1β were significantly reduced in macrophages after FAO inhibition. These results were confirmed in atherosclerotic lesions of mice treated with trimetazidine as they showed a significant reduction of IL-1β and cleaved caspase-1 in the atherosclerotic lesion as well as of IL-1β and IL-18 in the circulation. ConclusionOverall, we therefore suggest that the main mechanism of reducing inflammation of trimetazidine and FAO inhibition is the reduction of the NLRP-3 activation leading to reduced levels of the proinflammatory cytokine IL-1β.

Dilodendron bipinnatum Radlk. ameliorates airway inflammation through multiple targets in a murine model of ovalbumin-induced allergic airway disease

Ethnopharmacological relevanceDilodendron bipinnatum Radlk., Sapindaceae, a tree of the Mato Grosso Pantanal, is popularly known as “mulher-pobre”. The decoction or infusion of its inner stem bark is used for treating inflammatory conditions. Aim of the studyTo determine if a 70% hydroethanolic extract of Dilodendron bipinnatum stem bark (HEDb) is able to reduce allergic airway inflammation in a murine model of ovalbumin (OVA)-induced allergic asthma. Material and methodsThe inner stem bark powder was macerated in a 70% hydroethanolic solution (1:3 w/v) to obtain HEDb. The induction of experimental asthma was accomplished as follows: on days 1 and 10, Swiss mice were sensitized by an intraperitoneal injection of OVA (100 µg/mL) and aluminum hydroxide (10 µg/mL). From day 19 to 24, animals (n = 6/per group) were treated (p.o.) twice a day with either vehicle (distilled water), HEDb (20, 100 and 500 mg/kg) or dexamethasone (0.5 mg/kg). Sham group animals were intraperitoneally injected and challenged with saline solution (0.9%) instead of OVA and received distilled water orally instead of HEDb, whereas the other groups were challenged with OVA (3% in saline) by aerosolization. On day 25, bronchoalveolar lavage fluid (BALF) was collected for the quantification of total leukocytes, neutrophils, eosinophils, mononuclear cells and Th2 cytokines (IL-4, IL-5, and IL-13). The lungs were collected for histopathological analysis and blood was assayed to determine serum IgE levels. The anti-inflammatory activity of HEDb was additionally confirmed by a lipoxygenase (LO) inhibitory assay in vitro. ResultsCompared to the sham group, the OVA group showed significantly greater numbers of total leukocytes, neutrophils, eosinophils, and mononuclear cells, as well as inflammatory cytokines in BALF, and also IgE in the serum. HEDb treated mice showed a significant decrease in inflammatory cell accumulation in BALF, with the maximum response observed at 500 mg/kg. Furthermore, the levels of IL-4, IL-5 and IL-13 in BALF, and of IgE in serum, were also considerably reduced as compared to the OVA group. The histopathological examination of the lungs of mice in the vehicle group showed a significant increase in hemorrhagic damage, mucus, perivascular and peribronchial inflammatory cell infiltrates, as well as mast cell degranulation compared to sham. HEDb (100 and 500 mg/kg) remarkably decreased all these parameters, presenting at the highest dose an anti-inflammatory effect comparable to that of dexamethasone (0.5 mg/kg). HEDb also had notable direct anti-inflammatory properties demonstrated by the inhibition of 15-LO activity in vitro (IC50 = 1.0–5.0 µg/mL). ConclusionsThese results somewhat agree on the popular use of the inner stem bark of D. bipinnatum as a treatment for allergic asthma. The HEDb exhibits significant anti-inflammatory activity in the OVA-induced mouse model of allergic asthma, possibly due to the down-regulation of the Th2 responses and LO inhibition, resulting in improvements in all analyzed inflammatory parameters.

Exclusive enteral nutrition for inducing remission in inflammatory bowel disease in paediatric patients.

Enteral nutrition as a treatment for inflammatory bowel diseases is an ongoing area of interest. Even in the era of biologic agents, exclusive enteral nutrition (EEN) offers a unique, drug-free measure for induction of remission in luminal Crohn's disease. The purpose of this review is to discuss the role of EEN in the evolving therapeutic scheme for Crohn's disease, to report on new evidence for short and long-term efficacy and highlight findings on the mechanisms of the anti-inflammatory effects of EEN in light of current understanding of disease pathogenesis. Recent clinical studies have suggested that EEN has an established advantage over corticosteroids for inducing remission in children with luminal Crohn's disease with comparable clinical efficacy but superior mucosal healing effect as well as better safety profile. Preoperative EEN therapy can also improve postoperative outcome of intestinal resection. Basic research has demonstrated that EEN has direct anti-inflammatory properties, can correct localization of tight junction proteins, alter micro RNAs expression, and profoundly affect the intestinal microbiota. EEN is an effective treatment for induction of remission in pediatric luminal Crohn's disease and should be offered as a first-line treatment. Accumulating evidence suggest that EEN has direct anti-inflammatory properties with an effect on the intestinal microbiota. However, the relationships between these effects and the specific triggers for these changes have yet to be elucidated.

A Tangled Threesome: Adiponectin, Insulin Sensitivity, and Adiposity

The discovery nearly two decades ago that the adipocyte is more than a passive storehouse for lipids, that it is also an active secretory unit for peptides capable of system-wide regulation of energy metabolism, ushered in an exciting era of investigation into these newfound adipose-derived hormones (1). One intriguing object of these efforts has been the 244–amino acid protein adiponectin (2). Alone among major adipokines, adiponectin exhibits decreased rather than increased production with fat-mass expansion. Adiponectin is also the most abundantly secreted of all adipose-tissue peptides, and circulating levels correlate negatively with insulin resistance (IR), dyslipidemia, and inflammation (3). Such features have heightened interest in this molecule as a potential therapeutic target against the modern scourges of obesity and obesity-related disorders (2,3). That adiponectin has insulin-sensitizing effects in mice is now well established (2). Available experimental data are most compelling for adiponectin’s actions on the liver, where it promotes fatty acid oxidation and suppresses gluconeogenesis, and on adipocytes, where it inhibits lipolysis (3). In addition, adiponectin has direct anti-inflammatory properties (1), further enabling salutary fat-mass expansion, which is deemed pivotal to its insulin-sensitizing effects (3). Consistent with data in mice, prospective epidemiological studies have shown higher circulating adiponectin to be associated with lower risk of diabetes (4,5). Yet such observational data, susceptible as it is to confounding and reverse causation, cannot determine causality (6). In fact, observations from naturally occurring disorders of insulin action or from exogenous administration of insulin in humans have been cited to support the proposition that the direction of the association may be the reverse of that supposed (7). According to this hypothesis, the inverse association between adiponectin and IR may in fact reflect suppression of adiponectin production by hyperinsulinemia acting through spared, as yet undefined, signaling pathways (7). Hence, …

Regulation of Complement Activation by Thrombomodulin.

Abstract 5127Thrombomodulin (TM) is an integral membrane glycoprotein, ubiquitously expressed by vascular endothelial cells. Its epidermal growth factor (EGF)-like repeats amplify thrombin-mediated generation of activated protein C and activated thrombin activatable fibrinolysis inhibitor, thereby suppressing coagulation, inflammation and fibrinolysis, and inactivating the anaphylatoxins, C3a and C5a. TM also has direct anti-inflammatory properties, interfering with leukocyte adhesion, and preventing complement activation via its lectin-like domain. We recently established that TM is a physiologically important negative regulator of the alternative pathway (AP) of complement activation, defects of which increase the risk of the thrombotic microangiopathy, atypical hemolytic uremic syndrome. In this report, we assessed the role of TM in the other complement activation pathways. In serum, TM interferes with classical pathway (CP) mediated erythrocyte cell lysis, and protects against CP-induced cell death. TM co-precipitates with C4b, and enhances its inactivation and cleavage to C4c and C4d by complement factor I in the presence of the cofactor C4b binding protein. TM also interferes with the coagulation complement pathway by interfering with thrombin cleavage and activation of C5 to C5a. Overall, TM negatively regulates complement via the major recognized pathways. The findings implicate defects in TM in a wide range of diseases in which complement plays a role, and underlines the potential of TM as a therapeutic target. DisclosuresNo relevant conflicts of interest to declare.

Suppression of interleukin-6-induced C-reactive protein expression by FXR agonists

C-reactive protein (CRP), a human acute-phase protein, is a risk factor for future cardiovascular events and exerts direct pro-inflammatory and pro-atherogenic properties. The farnesoid X receptor (FXR), a member of the nuclear hormone receptor superfamily, plays an essential role in the regulation of enterohepatic circulation and lipid homeostasis. In this study, we report that two synthetic FXR agonists, WAY-362450 and GW4064, suppressed interleukin-6-induced CRP expression in human Hep3B hepatoma cells. Knockdown of FXR by short interfering RNA attenuated the inhibitory effect of the FXR agonists and also increased the ability of interleukin-6 to induce CRP production. Furthermore, treatment of wild type C57BL/6 mice with the FXR agonist, WAY-362450, attenuated lipopolysaccharide-induced serum amyloid P component and serum amyloid A3 mRNA levels in the liver, whereas no effect was observed in FXR knockout mice. These data provide new evidence for direct anti-inflammatory properties of FXR.

Insulin Increases the Release of Proinflammatory Mediators

Strict glucose control with insulin is associated with decreased mortality in a mixed patient population in the intensive care unit. Controversy exists regarding the relative benefits of glucose control versus a direct advantageous effect of exogenous insulin. As a combined medical/surgical population differs significantly from the critically injured patient primed for secondary insult, our purpose was to determine the influence of insulin on activated macrophages. Our hypothesis was that insulin would directly abrogate the inflammatory cascade. Differentiated human monocytic THP-1 cells were stimulated with endotoxin (lipopolysaccharide [LPS], 100 ng/mL) for 6 hours. Cells were treated +/-10(-7) M insulin for 1 hour and 24 hours. Total RNA was isolated and gene expression for TNF-alpha and IL-6 performed using Q-RT-PCR. Supernatants were assayed for TNF-alpha and IL-6 protein by ELISA. At 1 hour, compared with macrophages treated with LPS alone, macrophages treated with insulin produced significantly more TNF-alpha protein (11.4 +/- 5.9 pg/mL vs. 32.5 +/- 3.1 pg/mL; p < 0.03). At 24 hours compared with macrophages treated with LPS alone, macrophages treated with insulin produced significantly more TNF-alpha protein (83 +/- 2.02 pg/mL vs. 114 +/- 6.54 pg/mL; p < 0.01). However, gene expression of TNF-alpha and IL-6 was not different in LPS stimulated macrophages with and without insulin treatment at both 1 hour and 24 hours. Contrary to our hypothesis, insulin does not have direct anti-inflammatory properties in this experimental model. In fact, insulin increases proinflammatory cytokine protein levels from activated macrophages.

Integrin αvβ3acts downstream of insulin in normalization of interstitial fluid pressure in sepsis and in cell-mediated collagen gel contraction

The administration of insulin is recommended to patients with severe sepsis and hyperglycemia. Previously, we demonstrated that insulin may have direct anti-inflammatory properties and counteracted fluid losses from the circulation by normalizing the interstitial fluid pressure (P(IF)). P(IF) is one of the Starling forces determining fluid flux over the capillary wall, and a lowered P(IF) is one of the driving forces in early edema formation in inflammatory reactions. Here we demonstrate that insulin restores a lipopolysaccharide (LPS)-lowered P(IF) via a mechanism involving integrin alpha(v)beta(3). In C57 black mice (n = 6), LPS lowered P(IF) from -0.2 +/- 0.2 to -1.6 +/- 0.3 (P < 0.05) and after insulin averaged -0.8 +/- 0.2 mmHg (P = 0.098 compared with after LPS). Corresponding values in wild-type BALB/c mice (n = 5) were -0.8 +/- 0.1, -2.1 +/- 0.3 (P < 0.05), and -0.8 +/- 0.3 mmHg (P < 0.05 compared with LPS) after insulin administration. In BALB/c integrin beta(3)-deficient (beta(3)(-/-)) mice (n = 6), LPS lowered P(IF) from -0.1 +/- 0.2 to -1.5 +/- 0.3 mmHg (P < 0.05). Insulin did not, however, restore P(IF) in these mice (averaged -1.7 +/- 0.3 mmHg after insulin administration). Cell-mediated collagen gel contraction can serve as an in vitro model for in vivo measurements of P(IF). Insulin induced alpha(v)beta(3)-integrin-dependent collagen gel contraction mediated by C2C12 cells. Our findings suggest a beneficiary effect of insulin for patients with sepsis with regard to the fluid balance, and this effect may in part be due to a normalization of P(IF) by a mechanism involving the integrin alpha(v)beta(3).

Simvastatin attenuates cardiac isograft ischemia-reperfusion injury by down-regulating CC chemokine receptor-2 expression

Accumulating evidence reveals that statins possess direct anti-inflammatory properties through inhibition of proinflammatory cytokine and chemokine secretion in addition to their antioxidant effects, which may contribute to amelioration of ischemia-reperfusion injury. This study tested the hypothesis that perioperative treatment of simvastatin suppresses the cardiac isograft ischemia-reperfusion injury by down-regulation of CC chemokine receptor-2 expression in an inbred rat model of cardiac transplantation. Donor hearts from Lewis rats were heterotopically transplanted to Lewis rat recipients. Recipients were orally treated with simvastatin (1 mg/kg) or vehicle every morning 3 days before the surgery until the harvest day. Rats were killed at 6 hours and at 1, 3, and 7 days after transplantation. Injury was assessed by infarct size measurement, histologic and immunohistochemical examination, and intragraft myeloperoxidase activity assay. Monocyte chemoattractant protein-1 levels in serum and graft were analyzed by enzyme-linked immunosorbent assay, and intragraft CC chemokine receptor-2 expression was measured by quantitative real-time polymerase chain reaction. The infarct size and macrophage infiltration were all significantly reduced in the simvastatin-treated group compared with those of the control group at 1 day after transplantation. Neutrophil accumulation was significantly suppressed until 3 days after transplantation, whereas myeloperoxidase activity had been significantly diminished at 1 day after transplantation. Both monocyte chemoattractant protein-1 concentrations in serum and graft were remarkably decreased at 6 hours after transplantation. Intragraft CC chemokine receptor-2 expression was also down-regulated at 1 day and 3 days after transplantation. Perioperative treatment of simvastatin could suppress the isograft ischemia-reperfusion injury through retarding intragraft monocyte chemoattractant protein-1 accumulation and CC chemokine receptor-2 expression.

Introduction: severe sepsis and drotrecogin alfa (activated)

Introduction: severe sepsis and drotrecogin alfa (activated)

The lectin-like domain of thrombomodulin interferes with complement activation and protects against arthritis.

Thrombomodulin (TM) is predominantly a vascular endothelial cell plasma membrane glycoprotein that, via distinct structural domains, interacts with multiple ligands, thereby modulating coagulation, fibrinolysis, complement activation, inflammation and cell proliferation. We previously reported that by mediating signals that interfere with mitogen-activated protein kinase and nuclear factor kappaB pathways, the amino-terminal C-type lectin-like domain of TM has direct anti-inflammatory properties. In the current study, we use murine models of acute inflammatory arthritis and biochemical approaches to assess the mechanism by which the lectin-like domain of TM modifies disease progression. Mice lacking the lectin-like domain of TM (TM(LeD/LeD)mice) develop inflammatory arthritis that is more rapid in onset and more severe than that developed in their wildtype counterparts. In two models of arthritis, treatment of mice with recombinant soluble lectin-like domain of TM significantly suppresses clinical evidence of disease and diminishes monocyte/macrophage infiltration into the synovium, with weaker expression of the pro-inflammatory high mobility group box chromosomal protein 1. While thrombin-TM mediated activation of thrombin activatable fibrinolysis inhibitor inactivates complement factors C3a and C5a, we show that TM has a second independent mechanism to regulate complement: the lectin-like domain of TM directly interferes with complement activation via the classical and lectin pathways. These data extend previous insights into the mechanisms by which TM modulates innate immunity, and highlight its potential as a therapeutic target for inflammatory diseases.

Statins Reduce Interleukin-6–Induced C-Reactive Protein in Human Hepatocytes

Besides its predictive role in determining cardiovascular risk, C-reactive protein (CRP) may exert direct proatherogenic effects through proinflammatory properties. CRP is mainly produced by hepatocytes in response to interleukin-6 (IL-6) and is then released into the systemic circulation. 3-hydroxy-3-methylglutaryl (HMG)-coenzyme A (CoA) reductase inhibitors, or statins, significantly reduce cardiovascular events and mortality in patients with or without coronary artery disease and reduce plasma CRP levels in humans. However, the mechanism by which statins reduce plasma CRP levels remains unknown. In this study, we report that statins limit both protein and RNA levels of IL-6-induced CRP in human hepatocytes. These effects are reversed by l-mevalonate and mimicked by an inhibitor of the geranylgeranyltransferase. IL-6-induced CRP production requires the binding of IL-6 to its cognate receptors, which results in activation and phosphorylation of the transcription factor STAT3. We provide evidence that statins reduce this IL-6-induced phosphorylation of STAT3 in hepatocytes. These results demonstrate that statins reduce IL-6-induced CRP production directly in hepatocytes via inhibition of protein geranylgeranylation. We further show that statins act via inhibition of STAT3 phosphorylation. These findings furnish new evidence for direct antiinflammatory properties of statins and provide new mechanistic insight into their clinical benefits.

Anti-inflammatory Properties of Statins

Increasing clinical and experimental evidence indicates that some beneficial effects of statins, known as efficient therapeutic agents in cardiovascular disease treatment, may result from their ability to modulate vascular and endothelial cell gene expression by mechanisms independent of cholesterol reduction. It has been shown that statins exhibit direct anti-inflammatory properties via inhibition of proinflammatory cytokine and chemokine secretion, as well as through adhesion molecule expression on leukocytes. Another important mechanism by which statins may modulate the immune response is inhibition of interferon gamma-induced expression of class II major histocompatibility complexes. Class II major histocompatibility complex expression is central to immune regulation in T cell-mediated autoimmune diseases, indicating a potential beneficial role of statins in these pathologies. Indeed, promising new preclinical data indicate that statins might be useful in the treatment of multiple sclerosis and rheumatoid arthritis.

Activated protein C inhibits the release of macrophage inflammatory protein-1-alpha from THP-1 cells and from human monocytes

Several lines of evidence have implicated activated protein C (APC) to be an endogenous inhibitor of the inflammatory septic cascade. APC may exhibit direct anti-inflammatory properties, independent of its antithrombotic effects. Chemokines influence the interaction of monocytes at the endothelium during infection and sepsis and are involved in the molecular events leading to an adverse and lethal outcome of sepsis. Defining regulatory mechanisms on the monocytic release profile of the proinflammatory C-C chemokines macrophage inflammatory protein-1-alpha (MIP-1-α) and monocyte chemoattractant protein-1 (MCP-1) might have therapeutic implications for the treatment of sepsis. We established a monocytic cell model of inflammation by the addition of lipopolysaccharide (LPS) and examined the effect of human APC on LPS-stimulated chemokine release from the monocytic cell line THP-1. We found that human APC in supra-physiological concentrations of 2.5–10 μg/ml inhibited the LPS-induced release of the chemokines MIP-1-α and MCP-1, as measured by enzyme-linked immunosorbent assays (ELISA) at 6 up to 24 h. In addition to experiments on THP-1 cells, recombinant human APC in concentrations of 50 ng/ml was found to have an inhibiting effect on the release of MIP-1-α from freshly isolated mononuclear cells of septic patients. The ability of APC to decrease the release of the C-C chemokine MIP-1-α from the monocytic cell line THP-1 and from human monocytes may identify a novel immunomodulatory pathway by which APC exerts its anti-inflammatory action and may contribute to control the inflammatory response in sepsis.

Regulation of epidermal Langerhans cell migration by lactoferrin.

Lactoferrin (LF) is a member of the transferrin family of iron-binding glycoproteins to which several anti-inflammatory functions have been ascribed. LF has been shown to down-regulate expression of the pro-inflammatory cytokine tumour necrosis factor-alpha (TNF-alpha), although the possibility has been raised that the activity of LF in this regard was indirect and secondary to its ability to bind to and inactivate the bacterial lipopolysaccharide (LPS) used to induce cytokine production. However, the identification of putative membrane receptors for LF raises the possibility that the interaction of LF with its receptor may be one important route through which this protein exerts anti-inflammatory activity. In the present investigations the biological properties of LF have been examined in a model of cutaneous immune function where the allergen-induced migration of epidermal Langerhans cells (LC) from the skin and their subsequent accumulation as dendritic cells (DC) in skin-draining lymph nodes are known to be dependent upon the de novo synthesis of TNF-alpha, but independent of exogenous LPS. Consistent with the protein having direct anti-inflammatory properties, it was found that the intradermal injection of recombinant murine LF (either iron-saturated or iron-depleted LF) inhibited significantly allergen (oxazolone) -induced LC migration and DC accumulation. That these inhibitory effects were secondary to the inhibition of local TNF-alpha synthesis was suggested by the findings that first, LF was unable to inhibit LC migration induced by intradermal injection of TNF-alpha itself, and second, that migration stimulated by local administration of another epidermal cytokine, interleukin 1beta, which is also dependent upon TNF-alpha production, was impaired significantly by prior treatment with LF. Finally, immunohistochemical analyses demonstrated the presence of LF in skin, associated primarily with keratinocytes. Collectively these data support the possession by LF of direct immunomodulatory and/or anti-inflammatory activity, probably associated in this case with inhibition of cytokine production. Furthermore, the results suggest that as a constituent of normal skin, LF may play a role in homeostatic regulation of cutaneous immune function.