Local anti-inflammatory activities of tixocortol 21-pivalate, inhibition of prostaglandins and leukotrienes synthesis, in carrageenin-induced pleurisy. Reversion of effects by RU 486.

Since a direct effect of tixocortol pivalate (TP) has been described on cyclooxygenase pathway, local anti-inflammatory activities of some 21 thiol derivatives of steroids were investigated on the carrageenin-induced pleurisy model in comparison with dexamethasone (Dex) or other anti-inflammatory drugs. LTC4/D4 contents in pleural fluid were assayed by RIA as well as PGE2 levels to characterize the effects on arachidonate pathways. After oral administration, TP was inactive up to 1 g/kg on exudate volume and leukocyte migration as expected for this strict local anti-inflammatory steroid contrary to Dex (ID50 = 0.05-0.41 mg/kg). When administered locally, TP and tixocortol (T) exerted a dose dependent inhibitory activity on exudate volume (ID30 = 12.4 micrograms or 13.1 micrograms/pleural cavity) and leukocyte count (ID30 = 83 or 230 micrograms); in the same conditions. Dex was more active (ID30 = 0.7 and 2.6 micrograms). All these steroids decreased PGE2 and LTC4/D4 contents in exudate fluids, respectively TP (50 micrograms/pleural cavity) by 28 and 63%; T (100 micrograms) by 33 and 31%; Dex (5 micrograms) by 43 and 40%. Local co-administration of RU 486 (50 micrograms) with either TP, T or Dex reversed the anti-inflammatory effects of all steroids, indicating in these conditions a local activity through glucosteroid receptor occupancy.

Direct inhibition of cyclooxygenase pathway in platelets by tixocortol 21-pivalate: comparison with related structures, steroidal and non steroidal anti-inflammatory drugs.

Direct activity of the local anti-inflammatory steroid, tixocortol 21-pivalate (21 thioester derivative of cortisol) on metabolism of exogenous arachidonate by rabbit platelets was investigated in vitro. Tixocortol 21-pivalate inhibited generation of prostanoids from cyclooxygenase with an IC50 value of 19.6 microM without affecting the 12-lipoxygenase pathway. In this model, reference anti-inflammatory glucosteroids were ineffective, whereas indomethacin and aspirin inhibited the cyclooxygenase activity. Among tixocortol 21-pivalate related structures, tixocortol and its disulfide dimere or several other tixocortol esters exhibited a quite similar efficacy while S-methylation and subsequent S-oxydations of tixocortol abolished inhibitory activity. These results indicate that tixocortol 21-pivalate in contrast to other glucosteroids is able to act directly on cyclooxygenase pathway and that some specific chemical environment of the 21 thiol side chain are required for this inhibition.

The presence of lipocortin in human embryonic skin fibroblasts and its regulation by anti-inflammatory steroids.

Human embryonic skin fibroblasts in culture produce pro-inflammatory lipid mediators and all types of prostanoids. When these cells were treated with the anti-inflammatory steroid, dexamethasone, prostaglandin production was inhibited. This phenomenon required glucocorticoid receptor occupancy and mRNA and protein synthesis. The inhibitory effect was prevented by treating the cells with a monoclonal antibody, BF 26, raised against renocortin, a lipocortin-like protein formed in rat kidney medulla interstitial cells in culture. When the proteins present in the supernatants and the cell pellets derived from control and dexamethasone-treated cells were analyzed for their ability to inhibit phospholipase A2, four inhibitory peaks, at 45, 30, 15 kDa and one peak under 12 kDa, were found in the supernatants of control and dexamethasone-treated cells, whereas one single inhibitory peak at 15 kDa was found in the cell pellets. The antiphospholipase activity was much greater in dexamethasone-treated cells than in control cells. These results suggest that preformed lipocortin exists in human cells and that lipocortin is synthesized and released under glucocorticoid treatment.

Inflammatory response linked to oxazolone-indued cutaneous basophil hypersensitivity: effect of different immunomodulator and anti-inflammatory drugs.

The potency of cytostatic and anti-inflammatory drugs was tested on the oxazolone-induced cutaneous basophil hypersensitivity (CBH) in mice. The challenge reaction was performed early after sensitization in order to minimize B-cell expression; exudative and cellular infiltration was estimated 6 h, 24 h and 48 h after challenge. The potency of drugs was tested at three different periods of immunization: 2 days before or after sensitization or before challenge. Cytostatics act mainly when cells are being committed, a corticoid acts on inflammation linked to committed cells, NSAIDs show inconstant anti-inflammatory effects on this test. D-Penicillamine and levamisole act in the same depressive profile in normal animals. Thus the CBH model appears to be relevant in studying drug activities on inflammation linked to T-cell expression.

The effect of high glucose concentration on the proliferation and the synthesis of lipids in endothelial cells in culture.

Influence of glucose concentration on growth and lipid synthesis was investigated in human endothelial cells in culture. The biosynthesis of lipids from acetate and glucose was present in endothelial cells, but a high glucose level in the culture medium failed to modify lipid synthesis. Neosynthesis in the lipidic fraction in the medium is higher when precursor is acetate compared to glucose.