Endogenous glucocorticoids modulate neutrophil migration and synovial P-selectin but not neutrophil phagocytic or oxidative function in experimental arthritis

Brucella abortus-infected platelets modulate the activation of neutrophils

Brucellosis is a contagious disease caused by bacteria of the genus Brucella. Platelets (PLTs) have been widely involved in the modulation of the immune response. We have previously reported the modulation of Brucella abortus-mediated infection of monocytes. As a result, PLTs cooperate with monocytes and increase their inflammatory capacity, promoting the resolution of the infection. Extending these results, in this study we demonstrate that patients with brucellosis present slightly elevated levels of complexes between PLTs and both monocytes and neutrophils. We then assessed whether PLTs were capable of modulating functional aspects of neutrophils. The presence of PLTs throughout neutrophil infection increased the production of interleukin-8, CD11b surface expression and reactive oxygen species formation, whereas it decreased the expression of CD62L, indicating an activated status of these cells. We next analyzed whether this modulation was mediated by released factors. To discriminate between these options, neutrophils were treated with supernatants collected from B. abortus-infected PLTs. Our results show that CD11b expression was induced by soluble factors of PLTs but direct contact between cell populations was needed to enhance the respiratory burst. Additionally, B. abortus-infected PLTs recruit polymorphonuclear (PMN) cells to the site of infection. Finally, the presence of PLTs did not modify the initial invasion of PMN cells by B. abortus but improved the control of the infection at extended times. Altogether, our results demonstrate that PLTs interact with neutrophils and promote a proinflammatory phenotype which could also contribute to the resolution of the infection.

Modulation of neutrophil extracellular traps release by Klebsiella pneumoniae

One of the main bactericidal mechanisms of polymorphonuclear neutrophils (PMN) is the release of neutrophil extracellular traps (NETs), which capture and destroy pathogens. Klebsiella pneumoniae (Kpn) producer of carbapenemase (KPC) and belonging to the sequence type 258 (ST258), is a hyper epidemic clone that causes a large number of infections worldwide associated with high persistence and mortality. It is necessary to investigate the interaction of Kpn KPC with the immune system to improve prevention and treatment of infections mediated by this bacterium. Based on the hypothesis that Kpn is able to subvert PMN-mediated death, the aim was to assess whether Kpn KPC ST258 could modulate the bactericidal response of PMN, focusing on NETs formation, compared to another opportunistic pathogen, as Escherichia coli (Eco). The results showed that the release of NETs was absent when PMN were challenged with Kpn KPC, while Eco was a strong inducer of NETosis. Moreover, Kpn KPC was able to inhibit NETosis induced by Eco. The inhibition of Kpn KPC-mediated NETs formation still occurred in spite of exogenous addition of hydrogen peroxide (H₂ O₂ ), did not involve bacterial-released soluble factors or cell wall components, and was dependent on bacterial viability. Moreover, when degranulation was investigated, we found that Kpn KPC affected only the mobilization of primary granules, which harbor the proteins with more potent bactericidal properties and those related to NETosis. In conclusion, Kpn KPC ST258 effectively managed to evade the PMN response by inhibiting the release of NETs, and primary granule mobilization.

Klebsiella pneumoniae ST258 Negatively Regulates the Oxidative Burst in Human Neutrophils

The epidemic clone of Klebsiella pneumoniae (Kpn), sequence type 258 (ST258), carbapenamase producer (KPC), commonly infects hospitalized patients that are left with scarce therapeutic option since carbapenems are last resort antibiotics for life-threatening bacterial infections. To improve prevention and treatment, we should better understand the biology of Kpn KPC ST258 infections. Our hypothesis was that Kpn KPC ST258 evade the first line of defense of innate immunity, the polymorphonuclear neutrophil (PMN), by decreasing its functional response. Therefore, our aim was to evaluate how the ST258 Kpn clone affects PMN responses, focusing on the respiratory burst, compared to another opportunistic pathogen, Escherichia coli (Eco). We found that Kpn KPC ST258 was unable to trigger bactericidal responses as reactive oxygen species (ROS) generation and NETosis, compared to the high induction observed with Eco, but both bacterial strains were similarly phagocytized and cause increases in cell size and CD11b expression. The absence of ROS induction was also observed with other Kpn ST258 strains negative for KPC. These results reflect certain selectivity in terms of the functions that are triggered in PMN by Kpn, which seems to evade specifically those responses critical for bacterial survival. In this sense, bactericidal mechanisms evasion was associated with a higher survival of Kpn KPC ST258 compared to Eco. To investigate the mechanisms and molecules involved in ROS inhibition, we used bacterial extracts (BE) and found that BE were able to inhibit ROS generation triggered by the well-known ROS inducer, fMLP. A sequence of experiments led us to elucidate that the polysaccharide part of LPS was responsible for this inhibition, whereas lipid A mediated the other responses that were not affected by bacteria, such as cell size increase and CD11b up-regulation. In conclusion, we unraveled a mechanism of immune evasion of Kpn KPC ST258, which may contribute to design more effective strategies for the treatment of these multi-resistant bacterial infections.

Triggering the Resolution of Immune Mediated Inflammatory Diseases: Can Targeting Leukocyte Migration Be the Answer?

Leukocyte recruitment is a pivotal process in the regulation and resolution of an inflammatory episode. It is vital for the protective responses to microbial infection and tissue damage, but is the unwanted reaction contributing to pathology in many immune mediated inflammatory diseases (IMIDs). Indeed, it is now recognized that patients with IMIDs have defects in at least one, if not multiple, check-points regulating the entry and exit of leukocytes from the inflamed site. In this review, we will explore our understanding of the imbalance in recruitment that permits the accumulation and persistence of leukocytes in IMIDs. We will highlight old and novel pharmacological tools targeting these processes in an attempt to trigger resolution of the inflammatory response. In this context, we will focus on cytokines, chemokines, known pro-resolving lipid mediators and potential novel lipids (e.g., sphingosine-1-phosphate), along with the actions of glucocorticoids mediated by 11-beta hydroxysteroid dehydrogenase 1 and 2.

Neuropeptide Kyotorphin Impacts on Lipopolysaccharide-Induced Glucocorticoid-Mediated Inflammatory Response. A Molecular Link to Nociception, Neuroprotection, and Anti-Inflammatory Action

Neuropeptide kyotorphin (KTP) is a potent analgesic if administered directly into the brain. In contrast, KTP-amide (KTP-NH₂) is analgesic, neuroprotective, and anti-inflammatory following systemic administration, albeit its mechanism of action is unknown. The aim of this study was to shed light on the mechanism of action of KTP-NH₂ at the molecular level. KTP-NH₂ does not inhibit the enkephalinases angiotensin-converting-enzyme and dipeptidyl-peptidase 3. Intravital microscopy showed that KTP-NH₂ decreased the number of rolling leukocytes in a mouse model of inflammation induced by lipopolysaccharide (LPS). Pretreatment with metyrapone abrogated the action of KTP-NH₂. Interestingly, stimulating rolling leukocytes using CXCL-1 is also counteracted by the KTP-NH₂, but this effect is not abrogated by metyrapone. We conclude that KTP-NH₂ has dual action: a glucocorticoid-mediated action, which is dominant in the full-fledged LPS-induced inflammation model, and a glucocorticoid-independent mechanism, which is predominant in models in which leukocyte rolling is stimulated but inflammation is not totally developed.

Prokaryotic RNA Associated to Bacterial Viability Induces Polymorphonuclear Neutrophil Activation

Polymorphonuclear neutrophils (PMN) are the first cellular line of antibacterial host defense. They sense pathogens through recognition of pathogen-associated molecular patterns (PAMPs) by innate pattern recognition receptors, such as Toll-like receptors (TLR). The aim of this study was to investigate whether PMN sense bacterial viability and explore which viability factor could be involved in this phenomenon. For this purpose, different functions were evaluated in isolated human PMN using live Escherichia coli (Ec) and heat-killed Ec (HK-Ec). We found that bacterial viability was indispensable to induce PMN activation, as measured by forward-scatter (FSC) increase, CD11b surface expression, chemotaxis, reactive oxygen species (ROS) generation and neutrophil extracellular trap (NET) formation. As uncapped non-polyadenylated prokaryotic mRNA has been recognized as a PAMP associated to bacterial viability by macrophages and dendritic cells, total prokaryotic RNA (pRNA) from live Ec was purified and used as a stimulus for PMN. pRNA triggered similar responses to those observed with live bacteria. No RNA could be isolated from HK-Ec, explaining the lack of effect of dead bacteria. Moreover, the supernatant of dead bacteria was able to induce PMN activation, and this was associated with the presence of pRNA in this supernatant, which is released in the killing process. The induction of bactericidal functions (ROS and NETosis) by pRNA were abolished when the supernatant of dead bacteria or isolated pRNA were treated with RNAse. Moreover, endocytosis was necessary for pRNA-induced ROS generation and NETosis, and priming was required for the induction of pRNA-induced ROS in whole blood. However, responses related to movement and degranulation (FSC increase, CD11b up-regulation, and chemotaxis) were still triggered when pRNA was digested with RNase, and were not dependent on pRNA endocytosis or PMN priming. In conclusion, our results indicate that PMN sense live bacteria through recognition of pRNA, and this sensing triggers potent bactericidal mechanisms.

Role of the glucocorticoid-induced leucine zipper gene in dexamethasone-induced inhibition of mouse neutrophil migration via control of annexin A1 expression

The glucocorticoid-induced leucine zipper (GILZ) gene is a pivotal mediator of the anti-inflammatory effects of glucocorticoids (GCs) that are known to regulate the function of both adaptive and innate immunity cells. Our aim was to investigate the role of GILZ in GC-induced inhibition of neutrophil migration, as this role has not been investigated before. We found that GILZ expression was induced by dexamethasone (DEX), a synthetic GC, in neutrophils, and that it regulated migration of these cells into inflamed tissues under DEX treatment. Of note, inhibition of neutrophil migration was not observed in GILZ-knockout mice with peritonitis that were treated by DEX. This was because DEX was unable to up-regulate annexin A1 (Anxa1) expression in the absence of GILZ. Furthermore, we showed that GILZ mediates Anxa1 induction by GCs by transactivating Anxa1 expression at the promoter level via binding with the transcription factor, PU.1. The present findings shed light on the role of GILZ in the mechanism of induction of Anxa1 by GCs. As Anxa1 is an important protein for the resolution of inflammatory response, GILZ may represent a new pharmacologic target for treatment of inflammatory diseases.-Ricci, E., Ronchetti, S., Pericolini, E., Gabrielli, E., Cari, L., Gentili, M., Roselletti, E., Migliorati, G., Vecchiarelli, A., Riccardi, C. Role of the glucocorticoid-induced leucine zipper gene in dexamethasone-induced inhibition of mouse neutrophil migration via control of annexin A1 expression.

Macrophage migration inhibitory factor inhibits the antiinflammatory effects of glucocorticoids via glucocorticoid-induced leucine zipper

OBJECTIVE

Glucocorticoids remain a mainstay in the treatment of rheumatoid arthritis (RA). Dose-dependent adverse effects highlight the need for therapies that regulate glucocorticoid sensitivity to enable dosage reduction. Macrophage migration inhibitory factor (MIF) is a proinflammatory protein that has been implicated in the pathogenesis of RA; it impairs glucocorticoid sensitivity via MAPK phosphatase 1 (MKP-1) inhibition. The intracellular protein glucocorticoid-induced leucine zipper (GILZ) mimics the effects of glucocorticoids in models of RA, but whether it represents a target for the modulation of glucocorticoid sensitivity remains unknown. We undertook this study to investigate whether GILZ is involved in the regulation of glucocorticoid sensitivity by MIF.

METHODS

GILZ expression was studied in the presence and absence of MIF, and the role of GILZ in the MIF-dependent regulation of the glucocorticoid sensitivity mediator MKP-1 was studied at the level of expression and function.

RESULTS

GILZ expression was significantly inhibited by endogenous MIF, both basally and during responses to glucocorticoid treatment. The effects of MIF on GILZ were dependent on the expression and Akt-induced nuclear translocation of the transcription factor FoxO3A. GILZ was shown to regulate the expression of MKP-1 and consequent MAPK phosphorylation and cytokine release.

CONCLUSION

MIF exerts its effects on MKP-1 expression and MAPK activity through inhibitory effects on GILZ. These findings suggest a previously unsuspected interaction between MIF and GILZ and identify GILZ as a potential target for the therapeutic regulation of glucocorticoid sensitivity.

MIF, CD74 and other partners in kidney disease: tales of a promiscuous couple

Macrophage migration inhibitory factor (MIF) is increased in kidney and urine during kidney disease. MIF binds to and activates CD74 and chemokine receptors CXCR2 and CXCR4. CD74 is a protein trafficking regulator and a cell membrane receptor for MIF, D-dopachrome tautomerase (D-DT/MIF-2) and bacterial proteins. MIF signaling through CD74 requires CD44. CD74, CD44 and CXCR4 are upregulated in renal cells in diseased kidneys and MIF activation of CD74 in kidney cells promotes an inflammatory response. MIF or CXCR2 targeting protects from experimental kidney injury, CD44 deficiency modulates kidney injury and CXCR4 activation promotes glomerular injury. However, the contribution of MIF or MIF-2 to these actions of MIF receptors has not been explored. The safety and efficacy of strategies targeting MIF, CD74, CD44 and CXCR4 are under study in humans.

Maraviroc, a chemokine receptor-5 antagonist, fails to demonstrate efficacy in the treatment of patients with rheumatoid arthritis in a randomized, double-blind placebo-controlled trial

INTRODUCTION

The purpose of this study was to determine whether maraviroc, a human CC chemokine receptor 5 (CCR5) antagonist, is safe and effective in the treatment of active rheumatoid arthritis (RA) in patients on background methotrexate (MTX).

METHODS

This phase IIa study comprised two distinct components: an open-label safety study of the pharmacokinetics (PK) of MTX in the presence of maraviroc, and a randomized, double-blind, placebo-controlled, proof-of-concept (POC) component. In the PK component, patients were randomized 1:1 to receive maraviroc 150 or 300 mg twice daily (BID) for four weeks. In the POC component, patients were randomized 2:1 to receive maraviroc 300 mg BID or placebo for 12 weeks. Patients were not eligible for inclusion in both components.

RESULTS

Sixteen patients were treated in the safety/PK component. Maraviroc was well tolerated and there was no evidence of drug-drug interaction with MTX. One hundred ten patients were treated in the POC component. The study was terminated after the planned interim futility analysis due to lack of efficacy, at which time 59 patients (38 maraviroc; 21 placebo) had completed their week 12 visit. There was no significant difference in the number of ACR20 responders between the maraviroc (23.7%) and placebo (23.8%) groups (treatment difference -0.13%; 90% CI -20.45, 17.70; P = 0.504). The most common all-causality treatment-emergent adverse events in the maraviroc group were constipation (7.8%), nausea (5.2%), and fatigue (3.9%).

CONCLUSIONS

Maraviroc was generally well tolerated over 12 weeks; however, selective antagonism of CCR5 with maraviroc 300 mg BID failed to improve signs and symptoms in patients with active RA on background MTX.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00427934.

Diazepam decreases leukocyte-endothelium interactions in situ

High doses of diazepam reduce the inflammatory paw edema in rats. This effect was attributed to an action of diazepam on the Translocator Protein (TSPO). We evaluated the effects of diazepam (10 mg/kg, intraperitoneally) on leukocyte rolling and migration. In carrageenan-induced acute inflammation, diazepam decreased the interaction of leukocytes with endothelial cells (rolling) and the number of leukocytes in the mesentery (migration). RU486 (antagonist of glucocorticoid receptors) reduced the effects of diazepam on leukocyte rolling and migration, suggesting a participation of endogenous corticosteroids. We also showed that the effects of diazepam on leukocyte-endothelium interactions are mediated by nitric oxide (NO), since prior treatment with l-arginine (precursor of NO) partially precludes the inhibitory effects of diazepam; conversely, pretreatment with L-NAME (false substrate of the NO synthase) somewhat potentiates the effects of diazepam. The pathways that underlie the effects of diazepam remain to be further elucidated, but we believe that both local and systemic mechanisms may overlap to explain the influence of diazepam on leukocyte-endothelium interactions.

Independent roles of macrophage migration inhibitory factor and endogenous, but not exogenous glucocorticoids in regulating leukocyte trafficking

OBJECTIVES

Macrophage migration inhibitory factor (MIF) promotes leukocyte recruitment and antagonizes the anti-inflammatory effects of glucocorticoids (GC). The aim of this study was to examine whether interaction between MIF and GC underlies the ability of MIF to promote leukocyte-endothelial cell (EC) interactions.

METHODS

Intravital microscopy was used to assess leukocyte-EC interactions in wild-type and MIF(-/-) mice following treatment with lipopolysaccharide (LPS), the GC dexamethasone, and inhibition of endogenous GC, using the GC-receptor antagonist, RU486.

RESULTS

Dexamethasone reduced LPS-induced leukocyte interactions in wild-type mice to levels similar to those observed in MIF(-/-) mice not treated with dexamethasone, whereas in MIF(-/-) mice, leukocyte interactions were not further inhibited by dexamethasone. RU486 increased LPS-induced leukocyte adhesion and emigration to a similar extent in both wild-type and MIF(-/-) mice, indicating that endogenous GC exert a similar inhibitory effect on leukocyte trafficking in wild-type and MIF(-/-) mice. Both MIF deficiency and RU486 treatment reduced VCAM-1 expression, while neither treatment modulated expression of ICAM-1 or chemokines CCL2, KC, and MIP-2.

CONCLUSIONS

These results suggest that endogenous MIF and GC regulate leukocyte-EC interactions in vivo reciprocally but through predominantly independent mechanisms, and that the anti-inflammatory effect of MIF deficiency is comparable to that of exogenous GC.

Contribution of TNFα, IL-1β and CINC-1 for articular incapacitation, edema and cell migration in a model of LPS-induced reactive arthritis

The protective effect of anti-CINC-1, -TNFalpha and -IL-1beta antisera on articular inflammatory incapacitation, articular diameter and synovial fluid cell content, which are correlated to nociception, edema and cell migration, respectively, were evaluated in a rat model of LPS-induced reactive arthritis. In this model, Escherichia coli lipopolysaccharide (LPS; 30 ng) was injected in a knee-joint previously primed with carrageenan (300 microg). Articular incapacitation was evaluated hourly by the automated registering of the knee-joint function during animal walking, and the knee-joint edema was evaluated by measuring the articular diameter increase. After 6 h, the animals were euthanized for collecting synovial fluid for the evaluation of cell migration. LPS produced dose-dependent incapacitation and edema. Anti-TNFalpha, -IL-1beta, and -CINC-1 antisera (20 and 40 microl) were used as pretreatment into knee-joint before LPS injection. At higher dose, Anti-TNFalpha and anti-CINC-1 were able to inhibit incapacitation, articular edema and mononuclear (MON) migration. Anti-IL1beta did not affect incapacitation at any dose, although inhibited edema and cell migration. Surprisingly, the higher dose of anti-IL1beta antisera did not inhibit cell migration, although inhibited articular edema. These findings corroborate the role TNFalpha has in different forms of arthritis, but points out the idea that CINC-1 (the homologue for human IL-8) may constitute a promising target for reactive arthritis management. Indeed, the potent antiedematogenic effect, and principally the anti-migration effect of anti-CINC-1, raises the possibility of a better control of disease progression than with anti-IL-1beta therapies.

Endogenous glucocorticoids modulate neutrophil function in a murine model of haemolytic uraemic syndrome

Haemolytic uraemic syndrome (HUS) is caused by Shiga-toxin-producing Escherichia coli (STEC). Although, Shiga toxin type 2 (Stx2) is responsible for the renal pathogenesis observed in patients, the inflammatory response, including cytokines and polymorphonuclear neutrophils (PMN), plays a key role in the development of HUS. Previously, we demonstrated that Stx2 injection generates an anti-inflammatory reaction characterized by endogenous glucocorticoid (GC) secretion, which attenuates HUS severity in mice. Here, we analysed the effects of Stx2 on the pathogenic function of PMN and the potential role of endogenous GC to limit PMN activation during HUS development in a murine model. For this purpose we assessed the functional activity of isolated PMN after in vivo treatment with Stx2 alone or in simultaneous treatment with Ru486 (GC receptor antagonist). We found that Stx2 increased the generation of reactive oxygen intermediates (ROI) under phobol-myristate-acetate (PMA) stimulation and that the simultaneous treatment with Ru486 strengthened this effect. Conversely, both treatments significantly inhibited in vitro phagocytosis. Furthermore, Stx2 augmented in vitro PMN adhesion to fibrinogen (FGN) and bovine serum albumin (BSA) but not to collagen type I (CTI). Stx2 + Ru486 caused enhanced adhesion to BSA and CTI compared to Stx2. Whereas Stx2 significantly increased migration towards N-formyl-methionyl-leucyl-phenylalanine (fMLP), Stx2 + Ru486 treatment enhanced and accelerated this process. The percentage of apoptotic PMN from Stx2-treated mice was higher compared with controls, but equal to Stx2 + Ru486 treated mice. We conclude that Stx2 activates PMN and that the absence of endogenous GC enhances this activation suggesting that endogenous GC can, at least partially, counteract PMN inflammatory functions.

Mifepristone (Ru486) antagonizes monocyte chemotactic protein-3 down-regulation at early mouse pregnancy revealing immunomodulatory events in Ru486 induced abortion

PROBLEM

The survival of an embryo bearing the paternal antigens within the immunocompetent environment of the maternal uterus renders 'pregnancy' to be a state of immunological paradox. The ratio of Th1/Th2 responses is crucial for pregnancy maintenance. Monocyte Chemotactic Protein-3 (MCP3) is a pro-inflammatory, CC chemokine and a Th1 effector which is capable of eliciting significant anti-tumoral immune responses.

METHOD OF STUDY

MCP3 expression was investigated in the murine uterine tissue at different days of initial pregnancy and the effect of RU 486 in immature and delayed implantation model studied using Western blotting and Immunocytochemical techniques.

RESULTS AND CONCLUSION

Our results show very high uterine MCP3 expression during pre-implantation followed by a significant MCP3 down-regulation at peri-implantation and low levels of MCP3 during post-implantation period. At the peri-implantation stage, embryos exhibited lowered MCP3 expression when compared with the pre-implantation stage. Ru486, a progesterone antagonist when given in a competitive mode with progesterone resulted in a massive surge in MCP3 expression in both immature mice and delayed implantation models. We hypothesize that it is imperative for MCP3 expression to be down-regulated for the success of pregnancy. The cross-talk between Ru486 and amplified MCP3 expression may be one of the mechanisms by way of which RU486 performs its abortificient and anti tumor role.

Endogenous glucocorticoids attenuate Shiga toxin-2-induced toxicity in a mouse model of haemolytic uraemic syndrome

The concept that during an immune challenge the release of glucocorticoids (GC) provides feedback inhibition on evolving immune responses has been drawn primarily from studies of autoimmune and/or inflammatory processes in animal models. The epidemic form of haemolytic uraemic syndrome (HUS) occurs secondary to infection with Gram-negative bacteria that produce Shiga toxin (Stx). Although Stx binding to the specific receptors present on renal tissue is the primary pathogenic mechanism, inflammatory or immune interactions are necessary for the development of the complete form of HUS. The aim of this study was to investigate the influence of endogenous GC on Stx-toxicity in a mouse model. Stx2 was injected into GC-deprived mice and survival rate, renal damage and serum urea levels were evaluated. Plasma corticosterone and cytosolic GC receptor (GR) concentration were also determined at multiple intervals post-Stx2 treatment. Higher sensitivity to Stx2 was observed in mice lacking endogenous GC, evidenced by an increase in mortality rates, circulating urea levels and renal histological damage. Moreover, Stx2 injection was associated with a transient but significant rise in corticosterone secretion. Interestingly, 24 h after Stx inoculation significant increases in total GR were detected in circulating neutrophils. These results indicate that interactions between the neuroendocrine and immune systems can modulate the level of damage significantly during a bacterial infection.

Hypothalamic-pituitary-adrenal axis regulation of inflammation in rheumatoid arthritis

The profound anti-inflammatory effects of glucocorticoids in drug therapy are reflected in the effects in vivo of endogenous glucocorticoids produced by the adrenals. The production of adrenal glucocorticoids is driven by the hypothalamus and pituitary, which in turn are responsive to circulating products of the inflammatory response, especially cytokines. That inflammation can drive the production of anti-inflammatory glucocorticoids denotes the hypothalamic-pituitary-adrenal (HPA)-immune axis as a classic negative feedback control loop. Defects in HPA axis function are implicated in susceptibility to, and severity of, animal models of rheumatoid arthritis (RA), and are hypothesized to contribute to the human disease. In this paper, data supporting the concept of the HPA axis as a regulator of the inflammatory response in animal models of arthritis are reviewed, along with data from studies in humans. Taken together, these data support the hypothesis that the HPA axis provides one of the key mechanisms for inhibitory regulation of the inflammatory response. Manipulation of HPA axis-driven endogenous anti-inflammatory responses may provide new methods for the therapeutic control of inflammatory diseases.

Role of crotoxin, a phospholipase A2 isolated from Crotalus durissus terrificus snake venom, on inflammatory and immune reactions

BACKGROUND

Crotoxin (CTX) is a potent neurotoxin from Crotalus durissus terrificus snake venom (CdtV) composed of two subunits: one without catalytic activity (crotapotin), and a basic phospolipase A2. Recent data have demonstrated that CdtV or CTX inhibit some immune and inflammatory reactions.

AIM

The aim of this paper was to investigate the mechanisms involved in these impaired responses.

MATERIALS AND METHODS

Male Swiss mice were bled before and at different intervals of time after subcutaneous injection of CTX or bovine serum albumin (BSA) (control animals). The effect of treatments on circulating leukocyte mobilisation and on serum levels of interleukin (IL)-6, IL-10, interferon (IFN)-gamma and corticosterone were investigated. Spleen cells from treated animals were also stimulated in vitro with concanavalin A to evaluate the profile of IL-4, IL-6, IL-10 or IFN-gamma secretion. Cytokine levels were determined by immunoenzymatic assay and corticosterone levels by radioimmunoassay. To investigate the participation of endogenous corticosteroid on the effects evoked by CTX, animals were treated with metyrapone, an inhibitor of glucocorticoid synthesis, previous to CTX treatment.

RESULTS

Marked alterations on peripheral leukocyte distribution, characterised by a drop in the number of lymphocytes and monocytes and an increase in the number of neutrophils, were observed after CTX injection. No such alteration was observed in BSA-treated animals. Increased levels of IL-6, IL-10 and corticosterone were also detected in CTX-injected animals. IFN-gamma levels were not modified after treatments. In contrast, spleen cells obtained from CTX-treated animals and stimulated with concanavalin A secreted less IL-10 and IL-4 in comparison with cells obtained from control animals. Metyrapone pretreatment was effective only to reverse the neutrophilia observed after CTX administration.

CONCLUSIONS

Our results suggest that CTX may contribute to the deficient inflammatory and immune responses induced by crude CdtV. CTX induces endogenous mechanisms that are responsible, at least in part, for these impaired responses.

Glucocorticoid receptor-mediated suppression of activator protein-1 activation and matrix metalloproteinase expression after spinal cord injury

Post-traumatic inflammatory reaction may contribute to progressive tissue damage after spinal cord injury (SCI). Two key transcription factors, nuclear factor kappaB (NF-kappaB) and activator protein-1 (AP-1), are activated in inflammation. An increase in NF-kappaB binding activity has been shown in the injured spinal cord. We report activation of AP-1 after SCI. Electrophoretic mobility shift assay showed that AP-1 binding activity increased after SCI, starting at 1 hr, peaking at 8 hr, and declining to basal levels by 7 d. Methylprednisolone (MP) is the only therapeutic agent approved by the Food and Drug Administration for treating patients with acute traumatic SCI. MP reduced post-traumatic AP-1 activation. RU486, a glucocorticoid receptor (GR) antagonist, reversed MP inhibition of AP-1 activation. Immunostaining showed an increase in the expression of the Fos-B and c-Jun components of AP-1 in the injured cord. A c-fos antisense oligodeoxynucleotide (ODN) inhibited AP-1, but not NF-kappaB, activation after SCI. AP-1 and NF-kappaB can transactivate genes encoding matrix metalloproteinase-1 (MMP-1) and MMP-9. Western blotting and immunostaining show increased expression of MMP-1 and MMP-9 in the injured cord. MP inhibited MMP-1 and MMP-9 expression after SCI. RU486 reversed this MP effect. The c-fos antisense ODN, however, failed to suppress MMP-1 or MMP-9 expression. These findings demonstrate that MP may suppress post-traumatic inflammatory reaction by inhibiting both the AP-1 and NF-kappaB transcription cascades via a GR mechanism. Expression of inflammatory genes such as MMP-1 and MMP-9 that are transactivated jointly by AP-1 and NF-kappaB may not be suppressed by inhibiting only AP-1 activity.

Glucocorticoid receptor-mediated suppression of activator protein-1 activation and matrix metalloproteinase expression after spinal cord injury

Post-traumatic inflammatory reaction may contribute to progressive tissue damage after spinal cord injury (SCI). Two key transcription factors, nuclear factor kappaB (NF-kappaB) and activator protein-1 (AP-1), are activated in inflammation. An increase in NF-kappaB binding activity has been shown in the injured spinal cord. We report activation of AP-1 after SCI. Electrophoretic mobility shift assay showed that AP-1 binding activity increased after SCI, starting at 1 hr, peaking at 8 hr, and declining to basal levels by 7 d. Methylprednisolone (MP) is the only therapeutic agent approved by the Food and Drug Administration for treating patients with acute traumatic SCI. MP reduced post-traumatic AP-1 activation. RU486, a glucocorticoid receptor (GR) antagonist, reversed MP inhibition of AP-1 activation. Immunostaining showed an increase in the expression of the Fos-B and c-Jun components of AP-1 in the injured cord. A c-fos antisense oligodeoxynucleotide (ODN) inhibited AP-1, but not NF-kappaB, activation after SCI. AP-1 and NF-kappaB can transactivate genes encoding matrix metalloproteinase-1 (MMP-1) and MMP-9. Western blotting and immunostaining show increased expression of MMP-1 and MMP-9 in the injured cord. MP inhibited MMP-1 and MMP-9 expression after SCI. RU486 reversed this MP effect. The c-fos antisense ODN, however, failed to suppress MMP-1 or MMP-9 expression. These findings demonstrate that MP may suppress post-traumatic inflammatory reaction by inhibiting both the AP-1 and NF-kappaB transcription cascades via a GR mechanism. Expression of inflammatory genes such as MMP-1 and MMP-9 that are transactivated jointly by AP-1 and NF-kappaB may not be suppressed by inhibiting only AP-1 activity.

Inhibitory effect of annexin I on synovial inflammation in rat adjuvant arthritis

OBJECTIVE

Annexin I is an endogenous antiinflammatory mediator, expressed in rheumatoid arthritis (RA) synovium, the contribution of which to autoregulation of the synovial inflammatory response has not been examined in models of RA. We investigated the antiinflammatory role of annexin I in rat adjuvant arthritis.

METHODS

Rats with adjuvant-induced arthritis (AIA) were treated with a specific anti-annexin I monoclonal antibody (mAb), isotype control IgG, and/or dexamethasone. Clinical outcomes and synovial synthesis of tumor necrosis factor alpha (TNFalpha), prostaglandin E2 (PGE2), and nitric oxide were examined, and annexin I expression was assessed by flow cytometry and reverse transcription-polymerase chain reaction.

RESULTS

Anti-annexin I mAb reversed the effects of dexamethasone on the clinical features of AIA and exacerbated AIA in the absence of exogenous glucocorticoid. Clinical exacerbation of AIA by anti-annexin I mAb was accompanied by significantly increased synovial TNFalpha and PGE2, suggesting that annexin I tonically inhibits the production of these mediators. Anti-annexin I mAb treatment was associated with significantly reduced leukocyte intracellular annexin I, despite increased annexin I messenger RNA expression, consistent with a depletion effect of extracellular mAb via the cell surface.

CONCLUSION

Annexin I is a key endogenous inhibitory mediator of arthritis via mechanisms that include inhibition of cytokine and effector molecule production. Moreover, a synthesis-independent depletion of intracellular annexin I by extracellular antibody supports the hypothesis that externalization of annexin I is involved in its mode of action.

Dexamethasone inhibits IFNgamma-induced MHC class II expression of intestinal epithelial cells independently of the TGF-beta1 regulatory pathway

BACKGROUND

In the presence of inflammation, an increased expression of enterocyte MHC class II is observed, leading to altered mucosal antigen handling. Corticosteroids are potent anti-inflammatory drugs, widely used in treating inflammatory bowel disorders. However, their diverse mechanisms of action are only partially understood.

AIM

To evaluate effect and mechanisms of corticosteroids on intestinal crypt epithelial cell MHC class II.

METHODS

The effect of dexamethasone treatment on cytokine-induced MHC class II expression was measured in IEC-6 cells by immunofluorescence and flow cytometry. To determine the role of the TGF-beta1 regulatory pathway in mediating the effects of dexamethasone, neutralizing anti-TGF-beta antibodies were used. Additionally, endogenous and dexamethasone-stimulated IEC-6 cell TGF-beta1 production was measured by ELISA.

RESULTS

Dexamethasone potently down-regulated IFNgamma-induced class II expression on IEC-6 cells, in a dose-dependent manner. TGF-beta1 had a similar inhibitory effect on class II expression. However, neutralizing anti-TGF-beta antibodies did not alter the effect of dexamethasone. Furthermore, dexamethasone reduced endogenous TGF-beta1 synthesis.

CONCLUSIONS

Corticosteroids inhibit cytokine-induced MHC class II expression on IEC-6 cells in a TGF-beta1 independent way. This effect may markedly alter enterocytic antigen presentation, reducing the aberrant state of activation of mucosal immune cells.