M. Di Rosa

Glucocorticoids inhibit the induction of nitric oxide synthase in macrophages

The effect of glucocorticoids on the production of NO2- and NO by the macrophage cell line J774 was investigated. Stimulation of the cells with lipopolysaccharide (LPS) resulted in a time-dependent accumulation of NO2- in the medium, reaching a plateau after 48h. Concomitant incubation of the cells for 24h with dexamethasone (0.001-1.0 microM) or hydrocortisone (0.01-10.0 microM) caused a concentration-dependent inhibition of NO2- formation. The cytosol of J774 cells stimulated with LPS and IFN-gamma produced a time-dependent increase in the release of NO. This was blocked in a concentration-dependent manner by dexamethasone and hydrocortisone, but not progesterone, administered concomitantly with the immunological stimulus. None of these compounds had any effect on the release of NO once the enzyme had been induced. The inhibitory effect of hydrocortisone on NO formation was blocked by cortexolone. These data suggest that part of the anti-inflammatory and immunosuppressive actions of glucocorticoids is due to their inhibition of the induction of the NO synthase.

Glucocorticoids induce the formation and release of anti-inflammatory and anti-phospholipase proteins into the peritoneal cavity of the rat.

1 Dexamethasone and hydrocortisone induce the release of anti‐phospholipase proteins into the peritoneal cavities of rats. 2 Adrenocorticotropic hormone (ACTH) also releases these proteins in normal but not in adrenalectomized rats. 3 Peritoneal lavage proteins were separated by ion‐exchange and size exclusion chromatography. The anti‐phospholipase activity occurred in four separate fractions with the major component having an apparent mol. wt. of 40 k. 4 Column fractions containing these anti‐phospholipase proteins had anti‐inflammatory effects in the rat carrageenin pleurisy model whereas other fractions were inactive. 5 The proteins appear to be identical to macrocortin and lipomodulin, the ‘second messengers’ of glucocorticoid hormone action on the arachidonate system.

MECHANISM OF INHIBITION OF PROSTAGLANDIN BIOSYNTHESIS BY HYDROCORTISONE IN RAT LEUCOCYTES

Hydrocortisone (10 μg/ml) greatly inhibits the prostaglandin release by rat peritoneal leucocytes phagocytosing killed bacteria. The inhibition, which occurs after an initial latency of 30 min, is completely reversed by either actinomycin D (0.5 μg/ml) or cycloheximide (1 μg/ml). Since these antibiotics are known inhibitors of DNA‐dependent RNA synthesis and protein synthesis respectively, it appears that the mechanism of inhibition of prostaglandin biosynthesis by hydrocortisone in rat leucocytes involves stimulation of transcription and induction of protein synthesis.

The mechanism of the inflammatory effect of carrageenin

Abstract Inhibition by trasylol of carrageenin-induced swelling in the rats paw was studied as well as the ability of carrageenin to release kinin-like substances from plasma substrates. The findings support the hypothesis that carrageenin acts through a proteolytic process with formation of kinin-like mediator(s).

HYDROCORTISONE‐INDUCED INHIBITOR OF PROSTAGLANDIN BIOSYNTHESIS IN RAT LEUCOCYTES

Rat peritoneal leucocytes incubated with hydrocortisone (10 μg/ml) release a factor which inhibits prostaglandin generation. The steroid‐induced inhibitor, which mediates the anti‐phospholipase effect of anti‐inflammatory steroids, may be a protein or a polypeptide since its formation is blocked by cycloheximide, a known inhibitor of protein synthesis.

Some pharmacodynamic properties of carrageenin in the rat

1 Carrageenin oedema is suppressed by pre‐treating the rats with cellulose sulphate, a kininogen depleting agent. This inhibition is closely related to the dose of cellulose sulphate and to the time course of kininogen depletion. 2 Oedema induced by egg white or by dextran, in which the mediators are histamine and 5‐hydroxytryptamine, is quite unaffected by cellulose sulphate treatment. 3 Carrageenin injected intravenously lowers the arterial blood pressure of rats. This hypotensive effect is unaffected by histamine antagonists and is abolished by protease inhibitors and thus seems to be due to kinin release from plasma substrates. 4 Like cellulose sulphate, carrageenin enhances the esterolytic activity of the blood from treated rats when incubated with benzoyl‐arginine ethyl ester. 5 The ability of carrageenin to activate the kinin‐forming system could account for both its inflammatory and hypotensive effects.

THE INHIBITION BY HYDROCORTISONE OF PROSTAGLANDIN BIOSYNTHESIS IN RAT PERITONEAL LEUCOCYTES IS CORRELATED WITH INTRACELLULAR MACROCORTIN LEVELS

Hydrocortisone inhibits prostaglandin generation by rat peritoneal leucocytes by releasing the polypeptide phospholipase inhibitor, macrocortin. The susceptibility of these cells to hydrocortisone is directly correlated with their intracellular macrocortin content. Cells depleted of the peptide by prior incubation with steroid cannot respond to the steroid, until a fresh intracellular store has been synthesized. In vitro, this process requires 4–5 h. Cells remain sensitive to the inhibitory action of the peptide at all times.

Endogenous nitric oxide modulates morphine-induced constipation.

Administration of morphine in mice causes inhibition of the gastrointestinal transit of a charcoal meal. Morphine-induced constipation in mice seems to depend predominantly on action(s) on the central nervous system since N-methyl morphine, a quaternary derivative, inhibits intestinal transit only when administered intracerebroventricularly (i.c.v.). L- but not D-arginine, given intraperitoneally, reversed the constipation induced by both morphine and its quaternary analogue. L-arginine was ineffective when given i.c.v. and did not reverse atropine-induced constipation. These results suggest that L-arginine preferentially modulates opioid-induced constipation through a stereospecific and peripheral action(s). It is possible that the effect of L-arginine is achieved by increasing the amount of nitric oxide released by non-adrenergic, non-cholinergic nerves in the gut. Thus, L-arginine may represent a useful agent for the treatment of undesirable constipation associated with the use of narcotic analgesics.

Leucocyte migration and lysosomal enzymes release in rat carrageenin pleurisy.

The time course of rat carrageenin pleurisy has been studied. The inflammatory reaction is characterized by exudate formation and massive leucocyte emigration into the pleural space both reaching peak values at 24 hours. Moreover beta-glucuronidase, acid phosphatase and lactic dehydrogenase have been assayed in the exudate. The activity of lysosomal enzymes parallels the severity of the inflammatory response, while that of cytoplasmic enzyme lactic dehydrogenase resulted unmodified. Treatment of animals with indomethacin, phenylbutazone, aspirin and flufenamic acid inhibited both exudate formation and leucocyte emigration. In contrast none of these drugs was able to reduce lysosomal enzyme release.

Indomethacin and prostaglandins

Abstract The effects of indomethacin on inflammation mediators histamine, 5-hydroxytryptamine, bradykinin and prostaglandin E 2 have been studied. Indomethacin, 10–160 ωg/ml, exhibits an inhibitory effect on the contractions induced by each one of the studied mediators on isolated rat uterus and guinea pig ileum. Indomethacin was about 4 times more effective in inhibiting prostaglandin E 2 than in counteracting histamine, 5-hydroxytryptamine and bradykinin.