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Objective: This study investigated the role of 5-lipoxygenase in the pathogenesis of multiple organ failure (MOF) induced by zymosan. Design: Male mice with a targeted disruption of the 5-lipoxygenase gene (5-LOKO) and littermate wild-type (WT) controls (5-LOWT) were used to evaluate the role of 5-lipoxygenase (5-LO) in the pathogenesis of MOF. Setting: University research laboratory. Interventions and measurements: MOF was induced by peritoneal injection of zymosan (500 mg/kg i.p. as a suspension in saline) in 5-LOWT and in 5-LOKO mice. MOF was assessed 18 h after administration of zymosan and monitored for 12 days (for loss of body weight and mortality). Results: A severe inflammatory process induced by zymosan administration in WT mice coincided with the damage of lung and small intestine, as assessed by histological examination. Myeloperoxidase activity indicative of neutrophil infiltration and lipid peroxidation were significantly increased in zymosan-treated WT mice. Zymosan in the WT mice also induced a significant increase in the plasma level of nitrite/nitrate. Immunohistochemical examination demonstrated a marked increase in the immunoreactivity to ICAM-1 and P-selectin in the lung and intestine of zymosan-treated WT mice. In contrast, the degree of (a) peritoneal inflammation and tissue injury, (b) upregulation/expression of P-selectin and ICAM-1, and (c) neutrophil infiltration were markedly reduced in intestine and lung tissue obtained from zymosan-treated 5-LO deficient mice. Zymosan-treated 5-LOKO showed also a significantly decreased mortality. Conclusions: These findings clearly demonstrate that 5-LO exerts a role in zymosan-induced nonseptic shock.

Here we compare the degree of pancreatitis caused by cerulein in mice lacking 5-lipoxygenase (5-LO) and in the corresponding wild-type mice. Intraperitoneal injection of cerulein in mice resulted in severe, acute pancreatitis characterized by oedema, neutrophil infiltration and necrosis and elevated serum levels of amylase and lipase. Infiltration of pancreatic and lung tissue with neutrophils (measured as increase in myeloperoxidase activity) was associated with enhanced lipid peroxidation (increased tissue levels of malondialdehyde). Immunohistochemical examination demonstrated a marked increase in immunoreactivity for intracellular adhesion molecule-1 (ICAM-1), P-selectin and E-selectin in the pancreas and lung of cerulein-treated mice. In contrast, the degree of (1) pancreatic inflammation and tissue injury (histological score), (2) up-regulation/expression of P-selectin, E-selectin and ICAM-1, and (3) neutrophil infiltration was markedly reduced in pancreatic and lung tissue obtained from cerulein-treated 5-LO-deficient mice. These findings support the view that 5-LO plays an important, pro-inflammatory role in the acute pancreatitis caused by cerulein in mice.

Anthocyanins are a group of naturally occuring phenolic compounds related to the coloring of plants, flowers and fruits. These pigments are important as quality indicators, as chemotaxonomic markers and for their antioxidant activities. Here, we have investigated the therapeutic efficacy of anthocyanins contained in blackberry extract (cyanidin-3-O-glucoside represents about 80% of the total anthocyanin contents) in an experimental model of lung inflammation induced by carrageenan in rats. Injection of carrageenan into the pleural cavity elicited an acute inflammatory response characterized by fluid accumulation which contained a large number of neutrophils as well as an infiltration of polymorphonuclear leukocytes in lung tissues and subsequent lipid peroxidation, and increased production of nitrite/nitrate (NOx) and prostaglandin E2 (PGE2). All parameters of inflammation were attenuated in a dose-dependent manner by anthocyanins (10, 30 mg kg(-1) 30 min before carrageenan). Furthermore, carrageenan induced an upregulation of the adhesion molecule ICAM-1, nitrotyrosine and poly (ADP-ribose) synthetase (PARS) as determined by immunohistochemical analysis of lung tissues. The degree of staining was lowered by anthocyanins treatment. Thus, the anthocyanins contained in the blackberry extract exert multiple protective effects in carrageenan-induced pleurisy.

1. Intracranial administration of leptin reduces both food intake and body weight gain in the mouse. Inhibitors of nitric oxide (NO) synthase produce similar effects. 2. To investigate the role of the brain L-arginine/NO pathway in mediating this effect of leptin, we have evaluated food intake and body weight gain after daily (5 days) intracerebroventricular (i.c.v.) administration of leptin (0.5-2 microg) alone or in association with L-arginine (10 microg). Moreover, we measured diencephalic nitric oxide synthase (NOS) activity after a single i.c.v. leptin (0.25-2 microg) injection and after consecutive doses of leptin (0.25-2 microg) over 5 days. The time course of the effect of leptin on NOS activity was also evaluated. 3. I.c.v. injected leptin (1 and 2 microg) significantly and dose-dependently reduced food intake and body weight gain with respect to vehicle (food intake: 5.97+/-0.16 g 24 h(-1) and 4.27+/-0.18 g 24 h(-1), respectively, vs 8.05+/-0.34 g 24 h(-1), P0.001, n=6 for each group; body weight gain: -10.7+/-0.46% and -15.7+/-0.65%, respectively, vs 5.14+/-0.38%, P0.001, n=6 for each group). This effect was antagonized by L-arginine (food intake: 7.90+/-0.37 g 24 h; body weight gain: 5.11+/-0.31%, n=6). Diencephalic NOS activity was significantly reduced by the highest doses of leptin with respect to vehicle (vehicle: 0.90+/-0.04 nmol citrulline min(-1) g(-1) tissue; leptin 1 microg: 0.62+/-0.03 nmol citrulline min(-1) g(-1) tissue, P0.001; leptin 2 microg: 0.44+/-0.03 nmol citrulline min(-1) g(-1) tissue, P0.001, n=6 for each group). Similar results were obtained in animals treated with daily consecutive doses of leptin. The inhibitory effect appeared rapidly (within 30 min) and was long lasting (up to 12 h). 4. Our results suggest that the brain L-arginine/NO pathway may be involved in the central effect of leptin on feeding behaviour and body weight gain in mice.

The effect of four macrolide antibiotics (roxithromycin, clarithromycin, erythromycin, and azithromycin) on the generation of some mediators and cytokines involved in the inflammatory process has been studied both in vivo and in vitro. Rat carrageenin pleurisy was used as a model of acute inflammation, and the macrolides were administered (10, 20, and 40 mg/kg p.o.) 1 h before the carrageenin challenge. Exudate volume and leukocyte accumulation were both dose-dependently reduced by roxithromycin, clarithromycin and erythromycin in either normal or adrenalectomized animals. Furthermore, in normal rats, prostaglandin (PG)E(2), nitrate plus nitrite, and tumor necrosis factor-alpha levels in pleural exudate were significantly reduced by these macrolides. Roxithromycin appeared more effective than erythromycin and clarithromycin, whereas azithromycin only slightly affected the inflammatory reaction. None of the macrolides were able to modify leukotriene B(4) exudate levels. In vitro experiments have shown that the four macrolides (5-80 microM) reduced in a concentration-dependent manner the production of 6-keto-PGF(1alpha), NO(2)(-), tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6 by lipopolysaccharide-stimulated J774 macrophages. In J774 cells, the inhibition of 6-keto-PGF(1alpha) and NO(2)(-) production by roxithromycin and erythromycin was not dependent on direct inhibition of cyclooxygenase-2 and inducible nitric oxide synthase activity because it appears to be related to the inhibition of cyclooxygenase-2 and inducible nitric oxide synthase protein expression. In conclusion, the present study shows that macrolide antibiotics have anti-inflammatory activity, which likely depends on their ability to prevent the production of proinflammatory mediators and cytokines, and suggest that these agents, particularly roxithromycin, can exert therapeutic effects independently of their antibacterial activity.