Role of glucocorticoids in neutrophil and endothelial adhesion molecule expression and function

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.

The neutrophil migration induced by tumour necrosis factor alpha in mice is unaffected by glucocorticoids

Macrophages harvested from the peritoneal cavities of rats release a neutrophil chemotactic factor (MNCF) in response to stimulation with Gram-negative bacterial lipopolysaccharide (LPS). MNCF has been shown to be active in rats treated with dexamethasone, a glucocorticoid that usually inhibits the neutrophil migration induced in this species by interleukin (IL)-1, tumour necrosis factor alpha (TNFalpha), IL-8, C5a and leukotriene B(4) (LTB(4)). Here we report that macrophages harvested from peritoneal cavities of mice, and stimulated in vitro with LPS, also release a factor that induces neutrophil migration in dexamethasone-treated animals. This chemotactic activity was neutralized by the incubation of the LPS-stimulated macrophage supernatants with a purified polyclonal IgG anti-mouse TNFalpha. In addition, significant amounts of TNF were detected in the supernatants. The neutrophil migration induced by intraperitoneal administration of recombinant murine TNFalpha was also unaffected by pretreatment of the mice with dexamethasone. Moreover, neutrophil migration induced by intraperitoneal injection of LPS was completely blocked by pretreatment of the mice with a monoclonal antibody against murine TNFalpha. In conclusion, our results support the hypothesis that, in contrast to the role of TNF in rats (where it indirectly induces neutrophil migration), in mice, it may be an important mediator in the recruitment of neutrophils to inflammatory sites.

Antirheumatic agents and leukocyte recruitment. New light on the mechanism of action of oxaceprol

Most anti-inflammatory agents used in the treatment of joint diseases exert inhibitory effects on leukocyte infiltration. Methotrexate, a disease-modifying drug, and corticosteroids also inhibit leukocyte accumulation during inflammation. However, the mechanisms of action of these different compounds on leukocytes vary and in the case of non-steroidal anti-inflammatory drugs (NSAIDs) the mechanism(s) may be indirect. No current drug for inflammatory or degenerative joint disease has been proposed to act specifically by an inhibitory action on neutrophilic leukocytes. Oxaceprol is an amino acid derivative that has been used for several years for the treatment of osteoarthritis and rheumatoid arthritis, ameliorating pain and stiffness and showing good gastrointestinal safety, particularly in comparison with NSAIDs. Recent experimental studies have shown that oxaceprol does not inhibit the synthesis of prostaglandins in vitro, but markedly inhibits neutrophil infiltration into the joints of rats with adjuvant arthritis. These results support earlier screening data showing inhibition by oxaceprol of leukocyte infiltration into sites of acute inflammation. In studies on surgical ischemia reperfusion in hamsters in vivo, oxaceprol was an effective inhibitor of leukocyte adhesion and extravasation. It is proposed that oxaceprol represents a therapeutic agent for degenerative and inflammatory joint diseases, which acts predominantly by inhibiting leukocyte adhesion and migration.

Inhibition of VCAM-1 expression in human bronchial epithelial cells by glucocorticoids

We have demonstrated previously that cytokines induce surface expression of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) on BEAS-2B bronchial epithelial cells in vitro. The present studies demonstrate glucocorticoid inhibition of cytokine-induced VCAM-1 expression as detected using flow cytometry and Northern blot analysis. Several commonly used inhaled glucocorticoids were tested for their ability to inhibit VCAM-1 and ICAM-1 expression. All glucocorticoids tested inhibited VCAM-1 expression in a dose-dependent manner. No inhibition of ICAM-1 expression was observed. The most potent of the glucocorticoids tested for inhibition of VCAM-1 expression were mometasone furoate and fluticasone propionate (FP), which had IC50 values (i.e., concentrations at which each glucocorticoid produced 50% inhibition) of under 10 pM. Budesonide, triamcinolone acetonide, and beclomethasone dipropionate (BDP) had intermediate potency, and hydrocortisone and the BDP metabolite beclomethasone-17-monopropionate were the least potent of the steroids tested. Kinetic analysis of the ability of FP to inhibit VCAM-1 expression revealed that preincubation with FP for 3 h completely inhibited VCAM-1 expression induced by tumor necrosis factor-alpha (TNF-alpha). FP inhibited VCAM-1 expression by 50% even when added as late as 6 h after stimulation with TNF-alpha. Using Northern blot analysis, we confirmed inhibition of VCAM-1 and ICAM-1 messenger RNA (mRNA) expression by FP. Pretreatment with FP (10(-11) M to about 10(-7) M, 24 h) inhibited TNF-alpha-induced VCAM-1 mRNA expression in BEAS-2B in a dose-dependent manner, but did not inhibit expression of ICAM-1 mRNA. Studies with actinomycin D indicate that FP treatment accelerated the degradation of TNF-alpha-induced VCAM-1 mRNA. FP (10(-7) M) also inhibited VCAM-1 mRNA expression induced by TNF-alpha in primary human bronchial epithelial cells as assessed by reverse transcription-polymerase chain reaction. These results suggest that suppression of epithelial VCAM-1 expression by glucocorticoids may contribute to their anti-inflammatory effects.

Methylprednisolone-induced neutrophil leukocytosis--down-modulation of neutrophil L-selectin and Mac-1 expression and induction of granulocyte-colony stimulating factor

The mechanisms underlying corticosteroid-induced neutrophil leukocytosis are not fully understood; however, leukocyte/endothelial cell adhesion molecule interactions are known to be key to the movement of neutrophils within and out of the vasculature. This study was designed to investigate the effects of corticosteroids on neutrophil adhesion molecules in relation to neutrophil leukocytosis. Circulating neutrophil counts, neutrophil L-selectin and Mac-1 expression (measured by flow cytometry), soluble L-selectin, and granulocyte-colony stimulating factor concentrations were determined in 15 multiple sclerosis patients receiving intravenous methylprednisolone prior to and at 6 and 24 h following the initial 500-mg dose. A follow-up sample was obtained 48 h after the 5-day therapeutic course. Neutrophil counts were elevated at 6 h (threefold) and 24 h (twofold). This was associated with a 40% reduction in L-selectin expression at 6 and 24 h and a 35% reduction in Mac-1 expression at 6 h. Serum granulocyte-colony stimulating factor levels were increased (6 h: threefold; 24 h: twofold), whereas soluble L-selectin concentrations were unaltered. All of the above parameters had returned to basal levels in the follow-up sample. Short-term in vitro cultures (6 and 24 h) of blood samples from untreated multiple sclerosis patients and controls with 0.01 mg/ml methylprednisolone resulted in minimal reductions in neutrophil L-selectin and Mac-1 and no change in soluble L-selectin. Granulocyte-colony stimulating factor induced Mac-1 expression in a dose-dependent manner, whereas L-selectin expression was unaffected or reduced at high concentrations. Reduction in neutrophil L-selectin and Mac-1 expression following methylprednisolone infusion may cause decreased adhesion of marginated neutrophils and/or reduced capacity of neutrophils to migrate from the vasculature. Additionally, the induction of granulocyte-colony stimulating factor may contribute to neutrophil production and release into the circulation.

Pharmacological modulation of cell adhesion molecules

Cell adhesion molecules mediate the contact between two cells or between cells and the extracellular matrix. They are essential for morphogenesis, organization of tissues and organs, regulation of immune cell responses and migration of inflammatory cells from the blood vessels into inflamed tissues. Many diseases have been shown to be associated with dysfunction or with overexpression of certain adhesion molecules. Increased cell adhesion molecule function and number are found in clinical disorders in which inflammation and immune cells are involved. Several possible therapeutic agents are described here which have been shown to reduce the expression and/or function of cell adhesion molecules. Anti-adhesion treatment can lead to diminished infiltration and activation of inflammatory immune cells resulting in decreased tissue injury and malfunction.

Dexamethasone inhibits cytokine-induced intercellular adhesion molecule-1 up-regulation on endothelial cell lines

Intercellular adhesion molecule-1 (ICAM-1) expression on three endothelial cell lines was differently modulated by pro-inflammatory cytokines, such as interleukin-1beta and tumour necrosis factor-alpha (TNF-alpha) and the glucocorticoid hormone dexamethasone. Incubation of EA.hy926 cells with 1 microM dexamethasone prior to addition of TNF-alpha consistently reduced ICAM-1 induction by approximately 40%. EA.hy926 cell responsiveness to the steroid was validated by detecting specific dexamethasone binding, with a calculated affinity constant of 1.3 nM and a maximal number of sites of 35 x 10(3) per cell. To establish the generality of dexamethasone inhibition upon ICAM-1 up-regulation, two other endothelial cell lines were assessed. Incubation of LT4 and ECV304 cells with interleukin-1beta or TNF-alpha produced a significant increase in ICAM-1 expression on their cell surface (ranging from a 2-fold increase for interleukin-1beta to a 5-fold increase for TNF-alpha). Addition of dexamethasone was again able to significantly reduced this induction. Finally, the effect of the steroid on cytokine-induced ICAM-1 up-regulation was functionally related to its ability to suppress in vitro neutrophil trans-endothelial passage. Overall these data indicate that ICAM-1 is a likely molecular target for the anti-inflammatory action exerted by dexamethasone. Inhibition of ICAM-1 up-regulation may, at least in part, mediate the potent anti-migratory action displayed by this class of anti-inflammatory drugs.

Regulation of ICAM-1 by dexamethasone in a human vascular endothelial cell line EAhy926

Regulation by dexamethasone of intercellular adhesion molecule-1 (ICAM-1) in cultured monolayers of the human umbilical vein endothelial cell line EAhy926 was investigated. Tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) in combination or lipopolysaccharide (LPS) alone gave time- and dose-dependent increases in ICAM-1. Sustained expression of ICAM-1 was observed after short exposure (30 min) to TNF-alpha + IFN-gamma, but not to LPS. LPS-induced ICAM-1 expression was not inhibited by interleukin-1 (IL-1) receptor antagonist (0.01-100 micrograms/ml). Dexamethasone (1,000 nM) did not inhibit TNF-alpha + IFN-gamma-induced ICAM-1 expression or mRNA induction. In contrast, dexamethasone dose dependently (0.1-1,000 nM) inhibited LPS-induced ICAM-1 expression; however, its effect on mRNA was not established, because ICAM-1 mRNA induced by LPS was not detected at the time points investigated in this study (3 and 20 h). Adhesion of unstimulated human neutrophils to EAhy926 monolayers activated with TNF-alpha + IFN-gamma or LPS was increased in the presence of dexamethasone at low doses, whereas neutrophil adhesion to LPS- but not cytokine-stimulated endothelial cells was significantly reduced (P < 0.05) in the presence of a high dose of dexamethasone (1,000 nM). In conclusion, dexamethasone was demonstrated to regulate the expression and function of ICAM-1 in a stimulus-dependent manner.

Effect of dexamethasone on neutrophil accumulation and oedema formation in rabbit skin: an investigation of site of action

1. The anti-inflammatory actions of dexamethasone on vascular and leukocyte responses in rabbit skin were investigated. 2. Neutrophil accumulation and oedema formation were simultaneously measured as the local accumulation of i.v. administered 111In-labelled neutrophils and 125I-labelled albumin. Systemically administered dexamethasone (3 mg kg-1) inhibited neutrophil accumulation induced by i.d. zymosan activated plasma (ZAP), N-formyl-methionyl-leucyl-phenylalanine (FMLP) and leukotriene B4 (LTB4) when co-injected with prostaglandin E2 (PGE2). Dexamethasone also inhibited oedema formation elicited by these stimuli and the responses induced by i.d. platelet activating factor (PAF)+PGE2 and bradykinin (BK)+PGE2. 3. Intradermal dexamethasone (2 x 10(-10) mol per site) but not indomethacin (10(-8) mol per site) inhibited oedema formation induced by i.d. ZAP+PGE2 and BK+PGE2. This inhibitory effect of dexamethasone was significant only with pretreatment periods of 4 h, shorter pretreatment periods resulting in greatly reduced effects. Intradermal dexamethasone had no effect on neutrophil accumulation induced by ZAP+PGE2. 4. Intradermal dexamethasone (2 x 10(-10) mol per site) had no effect on increase in blood flow induced by PGE2 as measured by 133Xenon clearance. 5. The accumulation of neutrophils isolated from donor rabbits pretreated with i.v. saline or dexamethasone (3 mg kg-1) was investigated in untreated recipient rabbits. The accumulation of neutrophils, induced by ZAP+PGE2, FMLP+PGE2 and LTB4+PGE2, from dexamethasone-pretreated donors was significantly smaller than the accumulation of neutrophils from saline-pretreated donors. 6. The results of this study suggest that dexamethasone can have a direct effect on vascular endothelial cells resulting in an inhibition of oedema formation. 7. Neutrophil accumulation can be inhibited by an effect of dexamethasone on the neutrophil itself or on the vascular endothelium. These results indicate that at least part of the inhibitory effect is on the circulating neutrophil induced by dexamethasone or a dexamethasone-induced product.