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Ischaemia-reperfusion injury underlies many of the most important cardiovascular diseases such as myocardial infarction, thrombotic stroke, embolic vascular occlusions and peripheral vascular insufficiency. Neutrophils feature prominently in this inflammatory component of post-ischaemic injury. Experimental therapies, shown to reduce neutrophil-mediated ischaemia-reperfusion injury include neutrophil depletion, direct inhibitors of neutrophil activators, antibodies against neutrophil adhesion molecules and the endothelial adhesion molecules. However, aside from these approaches, it is increasingly recognised that glucocorticoids are potent inhibitors of neutrophil-mediated injury. The anti-inflammatory actions of glucocorticoid include the activation of classical cytoplasmic receptors leading to changes in gene transcription as well as the induction of regulatory proteins, such as annexin 1. Annexin 1 is a potent inhibitor of neutrophil extravasation in vivo. Administration of the annexin 1 or peptides derived from its N-terminal domain, reduce neutrophil extravasation in models of acute inflammation. In addition, as reviewed by this article, annexin 1 protects against ischaemia-reperfusion in the heart and mesenteric microcirculation, as well as in multiple organ failure associated with splanchnic ischaemia-reperfusion. Such findings would suggest annexin 1 is a novel anti-inflammatory agent with a potential for the treatment of cardiovascular pathologies associated with neutrophil activation and recruitment.

Administration of ovalbumin by aerosol to sensitised rats produced a rapid (15 min) protein exudation in different airway tissues, as determined by Evans blue staining. This was associated with marked mast cell degranulation determined by histological examination, with there being no difference between mucosal and connective tissue mast cells. A 5-day administration regimen with compound 48/80 selectively depleted connective tissue mast cell (positive to berberine staining) without modifying ovalbumin-induced plasma protein extravasation. Treatment of rats with dexamethasone (1 mg/kg, −12 h) or nor-dihydroguaiaretic acid (30 mg/kg i.p., −30 min) significantly reduced ovalbumin-induced protein extravasation and preserved mucosal mast cell morphology. Indomethacin (4 mg/kg i.v., −30 min) exerted no effect on either parameter. In conclusion, we propose the mucosal mast cell as a target cell responsible at least partly for the inhibitory actions of known anti-inflammatory drugs. We suggest an involvement of endogenous leukotriene(s), but not prostanoid(s), in mucosal mast cell activation/degranulation.

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.

Contractions elicited by CaClz on isolated rat stomach strip preparations have been reported to be potentiated by interleukin-1β (IL-1β). We have investigated whether this effect can be reduced by the putative IL-1β antagonist, a-melanocyte-stimulating hormone (aMSH). Additionally, the effects of αMSH on the specific binding of IL-1β to B- and T-cells have been investigated to further clarify its inhibitory activities. Both αMSH and its carboxyl terminal tripeptide concentration dependently reduced the potentiation of CaCl 2 -induced contractions caused by IL-1β but not those caused by leukotriene D 4 , the parent molecule being approximately 250 times more active. Additionally, both peptides potently and selectively reduced 125 I-IL-1β binding to the T-cell sub-clone EL4-6.1 but not to the B-cell sub-clone 1H7. The results indicate that IL-1β effects on rat stomach may be mediated through a type-I (80 kDa) IL-1β receptor.

The generation of endogenous hydrogen sulphide may either limit or contribute to the degree of tissue injury caused by ischaemia/reperfusion injury. Here, we have attempted to characterise the endogenous hydrogen sulphide synthesis pathway and the effects of sodium hydrosulphide, a hydrogen sulphide donor, in a mouse model of renal ischaemia/reperfusion injury. Anaesthetised male C57/b mice weighing 20-25 g were divided into two groups; (i) 'Ischaemia/Reperfusion Injury', in which mice were subjected to bilateral renal ischaemia performed by clamping the renal pedicles for 30 min followed by reperfusion for 24 h, (ii) 'Sham', in which mice were subjected to the same surgical procedures as above, except for renal ischaemia/reperfusion. Western blot analysis of the kidney taken at the end of the experiment demonstrated that cystathionine gamma-lyase, the enzyme responsible for generating hydrogen sulphide in the cardiovascular system, is expressed in the normal kidney and is significantly increased after ischaemia/reperfusion injury. Ischaemia/reperfusion injury significantly increased the rate of hydrogen sulphide production in kidney homogenates and increased the plasma concentration of hydrogen sulphide. In addition, we have shown that administration of the hydrogen sulphide donor sodium hydrosulphide (100 micromol/kg) 30 min prior to ischaemia and 6 h into reperfusion significantly attenuated ischaemia/reperfusion injury-induced renal dysfunction indicated by serum creatinine and urea. These findings suggest that hydrogen sulphide protects the kidney against ischaemia/reperfusion injury and that the increase in expression of the enzyme cystathionine gamma-lyase during ischaemia/reperfusion injury may be one of many endogenous mechanisms to limit renal ischaemia/reperfusion injury.

Platelet-activating factor (PAF; 100 ng i.v.) transiently modified the number of circulating neutrophils in the mouse, inducing a fast neutropenia (2 min) followed by a late onset neutrophilia (2 h). The potential involvement in PAF-induced neutrophilia of granulocytotic agents such as interleukin-1 and tumor necrosis factor-alpha could be excluded on the basis of the ineffectiveness of interleukin-1 receptor antagonist and of a specific monoclonal antibody anti-murine tumor necrosis factor-alpha. PAF granulocytosis was preceded by a significant rise in plasma corticosterone at 20 min. The involvement of endogenous corticosteroids was confirmed by the experiments with adrenalectomized mice and in animals pretreated with the steroid antagonist RU486 (11 beta-(4-dimethyl amino-phenyl) 17 beta-hydroxy, 17 alpha(prop-1-ynyl) estra 4,9-dien-3-one), where PAF-induced neutrophilia was greatly reduced (approximately 50%). Moreover, sustained increase in plasma corticosterone by administration of adrenocorticotropic hormone was paralleled by an intense neutrophilia. We show evidence that endogenous corticosterone acts through the glucocorticoid-inducible protein lipocortin 1.

The intracerebroventricular administration of interleukin-1 beta (12.5 ng/kg) in rabbits caused a prompt rise of prostaglandin E2 concentration (+ 632.6 +/- 243.9%) in the cerebrospinal fluid followed by hyperthermia (+ 1.61 +/- 0.14 delta degrees C). The intracerebroventricular administration of an anti-inflammatory nonapeptide (amino acids 204-212, SHLRKVFDK) derived from lipocortin 5, thereafter referred to as lipocortin 5-(204-212)-peptide, inhibited in a significant manner both the increase in cerebrospinal fluid [prostaglandin E2] and the febrile response induced by the cytokine. This inhibitory effect is probably due to interference by the peptide with phospholipase A2 activity. A control peptide (FKRVHDLKS) formed by the same amino acids in a randomly shuffled sequence had no effect. These results show that, in addition to the anti-inflammatory effect previously reported, the peptide 204-212 of lipocortin 5 possesses, like glucocorticoids, anti-pyretic activity. The research on lipocortin-derived peptides may lead to the development of novel anti-inflammatory and anti-pyretic compounds.

Treatment of mice with rolipram, a phosphodiesterase type 4 inhibitor, selectively modified the acute inflammatory reaction elicited by zymosan administration in 6-day-old mouse air-pouches. Rolipram (1-10 mg kg-1, i.p.) prevented the rise of endogenous tumor necrosis factor-alpha (TNF-alpha) in the lavage fluids (approximately 60% inhibition) induced by zymosan, with no effect upon interleukin-1 alpha levels. This action was not accompanied by changes in neutrophil accumulation, but the amount of elastase released in the lavage fluids was significantly reduced (approximately 50%). Dexamethasone (1.5 mg kg-1, i.v.), used for comparative purposes, significantly reduced the release of TNF-alpha (> 50%), interleukin-1 alpha (> 70%) and cellular infiltration (approximately 50%), but had only a marginal effect on the release of elastase activity. In conclusion, in this murine model of acute inflammation induced by zymosan, rolipram inhibited the endogenous TNF-alpha production at a local site of inflammation, such as the subcutaneous air-pouch, and prevented the full activation of migrated cells.

Sialidase, fucoidin and a peptide corresponding to most of lipocortin 1 N-terminus, termed LC1-(Ac2-26)-peptide, induced an intense 2 h neutrophilia whereas a monoclonal antibody to murine CD11b induced an effect by 1 h. The neutropenic response stimulated by platelet-activating factor (PAF) was significantly reduced in the presence of sialidase, fucoidin, LC1-(Ac2-26)-peptide and monoclonal antibody anti-CD11b. Neutrophil migration into a 6-day-old mouse air-pouch induced by interleukin-1 was inhibited by all the pharmacological agents. In vitro, PAF up-regulated CD11b expression on the neutrophil surface but neither human or mouse LC1-(Ac2-26)-peptide inhibited this response. CD11b up-regulation on neutrophils occurred after PAF administration in vivo and was maximal at 2 min. LC1-(Ac2-26)-peptide mimics the action of agents interfering with leucocyte rolling and adhesion in vivo, however, does not inhibit CD11b up-regulation in vitro suggesting other phenomena are important in the activity of this peptide.

Interleukin-1 beta (1 and 5 ng) produced an intense migration of neutrophils into a 6-day-old murine air-pouch at 4 h time-point. Endogenous calcitonin gene-related peptide (CGRP) was found to be involved as a mediator of interleukin-1 beta (5 ng)-induced migration, since the CGRP receptor antagonist, CGRP-(8-37), attenuated the cellular response. The polymorphonuclear leukocyte accumulation induced by both doses of interleukin-1 beta was also potentiated by exogenously added CGRP, a response blocked by CGRP-(8-37). Interleukin-1 beta also caused plasma protein extravasation into the pouch as assessed by measuring leakage of 125I-albumin. Whereas plasma protein extravasation was potentiated by CGRP, again an effect abolished by co-administration of CGRP-(8-37), the antagonist had no effect upon the plasma extravasation induced by the cytokine alone. These results suggest that endogenous CGRP is involved in mediating the cellular response but not plasma protein extravasation evoked by interleukin-1 beta and point to CGRP receptor heterogeneity.