salicylates and 1-3-dimethylthiourea

A mouse model of hypersensitivity pneumonitis was generated by challenge with a thermophilic actinomycete. Oxygen radical scavengers were administered to challenged mice: vitamin E at 1000 units daily, polyethylene glycol-superoxide dismutase (SOD) at 500 units daily, polyethylene glycol-catalase at 10,000 units daily, 1,3,dimethyl-2-thiourea (DMTU) at 2 mg daily, and the biomimetic SOD, copper(II) [diisopropyl salicylate]2 (CuDIPS) at 1 mg daily. At three weeks after actinomycete challenge, a 10-fold increase in bronchoalveolar (BAL) cell number was observed. Treatments with catalase or DMTU were without effect on the BAL cell number in challenged mice. However, infusion of vitamin E was associated with an increased BAL cell influx (15-fold increase at two and three weeks). Similarly, treatment with PEG-SOD and CuDIPS resulted in an increase in cell number at two and three weeks. PEG-SOD or CuDIPS treatment resulted in a strong neutrophilia, whereas control challenged mice had a cellular influx mostly of macrophages and lymphocytes. Vitamin E treatment of challenged mice led to an increased T lymphocyte recruitment at two and three weeks. In vitro studies showed that actinomycete challenge was associated with an enhancement of alveolar macrophage O2- release, which was blocked by PEG-SOD, vitamin E, or DSC treatment but was unaffected by catalase or DMTU treatment. In control challenged mice, there was a 25-fold increase in the BAL albumin concentration at two weeks. PEG-SOD, vitamin E, or CuDIPS treatment all decreased the albumin concentration; the three modulators also diminished lung fibrosis at two or three weeks, as seen by a decrease in lung hydroxyproline and collagen synthesis by lung fibroblasts. Examination of sections from lungs of challenged animals showed evidence of cellular infiltrates around the bronchi and the blood vessels. Challenged mice given continuous infusions of vitamin E, SOD, or CuDIPS had lung histological scores that were significantly lower than control challenged mice or challenged mice treated with catalase or DMTU. Thus, therapies based on O2- scavenging or treatment with a general antioxidant such as vitamin E may hold some promise in the treatment of hypersensitivity pneumonitis.

Topics: Animals; Antigens, Fungal; Antioxidants; Bronchoalveolar Lavage Fluid; Collagen; Farmer's Lung; Fibroblasts; Free Radical Scavengers; Hydroxyproline; Macrophages, Alveolar; Mice; Mice, Inbred C57BL; Micromonosporaceae; Neutrophils; Pulmonary Fibrosis; Reactive Oxygen Species; Salicylates; Specific Pathogen-Free Organisms; Superoxide Dismutase; T-Lymphocytes; Thiourea; Vitamin E

Recent in vivo studies suggest that heme Fe causes proximal tubular lipid peroxidation and cytotoxicity, thereby contributing to the pathogenesis of myoglobinuric (Mgb) acute renal failure. Because hydroxyl radical (.OH) scavengers [dimethylthiourea (DMTU), benzoate, mannitol] can mitigate this injury, it is postulated that .OH is a mediator of Mgb-induced renal damage. The present study has tested these hypotheses using an isolated rat proximal tubular segment (PTS) system. An equal mixture of Fe2+/Fe3+ (4 mM total), when added to PTS, caused marked cytotoxicity [as defined by lactate dehydrogenase (LDH) release] and lipid peroxidation [assessed by malondialdehyde (MDA) increments]. Fe2+ or Fe3+ alone each induced massive MDA elevations, but only Fe2+ caused cytotoxicity. Although both DMTU and benzoate decreased LDH release during the Fe2+/Fe3+ challenge, mannitol and GSH did not, despite equivalent reductions in .OH (gauged by the salicylate trap method). GSH and catalase (but not DMTU, benzoate, or mannitol) decreased MDA concentrations, suggesting the Fe-driven lipid peroxidation was more H2O2 than .OH dependent. Deferoxamine totally blocked Fe-induced LDH release, even under conditions in which it caused an apparent increase in .OH generation. Mgb paradoxically protected against Fe-mediated PTS injury, an effect largely reproduced by albumin. In conclusion, these data suggest that: (a) Fe can cause PTS lipid peroxidation and cytotoxicity by a non-.OH-dependent mechanism; (b) Fe-mediated cytotoxicity and lipid peroxidation are not necessarily linked; and (c) Mgb paradoxically protects PTS against Fe-mediated injury, suggesting that: (i) Mgb Fe may require liberation from its porphyrin ring before exerting toxicity; and (ii) the protein residue may blunt the resulting injury.

Topics: Acute Kidney Injury; Animals; Benzoates; Benzoic Acid; Deferoxamine; Hydroxides; Hydroxyl Radical; In Vitro Techniques; Iron; Kidney Tubules, Proximal; L-Lactate Dehydrogenase; Lipid Peroxidation; Male; Myoglobin; Perfusion; Rats; Rats, Inbred Strains; Salicylates; Superoxide Dismutase; Thiourea

Although the presence of free radicals has been indicated in ischemic-reperfused heart, the exact nature and source of these free radicals are not known. The present study utilized a chemical trap, salicylic acid, to trap hydroxyl radical which could be detected as hydroxylated benzoic acid using high pressure liquid chromatography. Since the hydroxylated product is extremely stable, heart was subjected to subcellular fractionation after ischemia and reperfusion, and each fraction was separately examined for the presence of hydroxyl radical. The results indicated for the first time the presence of hydroxyl radical in the mitochondrial fraction during early reperfusion, which decreased in intensity as the reperfusion progressed.

Topics: Animals; Catalase; Chromatography, High Pressure Liquid; Coronary Disease; Dimethyl Sulfoxide; Free Radicals; Hydroxides; Hydroxyl Radical; Male; Mitochondria, Heart; Myocardial Reperfusion; Rats; Rats, Inbred Strains; Salicylates; Salicylic Acid; Superoxide Dismutase; Thiourea

Although salicylates have been used for centuries as treatment of inflammatory diseases, the mechanism of action of these drugs is still not clear. Aspirin (acetylsalicylic acid) and other nonsteroidal anti-inflammatory drugs (NSAID) inhibit prostaglandin biosynthesis, a property that appears to explain part of their anti-inflammatory activity. However, this mechanism does not appear to explain the anti-inflammatory properties of salicylic acid, which is a major metabolite of ASA in vivo. Results of prior studies in our laboratory have established that benzoic acid, the parent compound of the salicylate group of drugs, is decarboxylated and hydroxylated by the hydroxyl free radical (OH.) produced by stimulated granulocytes. These observations suggested that salicylates might be similarly metabolized by granulocytes. If so, the capacity of salicylates to rapidly react with OH. might relate directly to their known anti-inflammatory properties. Preliminary experiments established that salicylic acid and aspirin were decarboxylated by the hydroxyl free radical generated by the enzyme system xanthine-xanthine oxidase. We then studied the metabolism of salicylates by human granulocytes. Unstimulated granulocyte suspensions did not oxidize ASA or salicylic acid. However, suspensions stimulated by opsonized zymosan particles rapidly oxidized both substrates in pharmacological concentrations. The rate of oxidation of salicylic acid was 16-fold higher than benzoic acid, whereas the rate of oxidation of ASA was four-fold higher. The reaction was oxygen dependent and could be inhibited by known hydroxyl scavengers, particularly dimethylthiourea. The reaction could also be inhibited by superoxide dismutase and azide, indicating that O-2 and heme or an iron-dependent enzyme were required for the reaction. The reaction was not impaired by compounds known to react with the HOCL and the chloramines generated by stimulated PMN. Furthermore, salicylic acid in high concentrations did not impair the HMPS pathway, the production of O-2 or the production of H2O2 by granulocytes. These data provide evidence that salicylates are rapidly oxidized by the hydroxyl free radical produced by granulocytes and not O-2, H2O2, or HOCL. This capacity of salicylates to react rapidly and selectively react with OH. may directly relate to their anti-inflammatory properties. In addition, results of our experiments indicate that stimulated granulocytes acquire the capacity to metabolize these dru

Topics: Aspirin; Benzoates; Benzoic Acid; Chloramines; Free Radicals; Granulocytes; Hydrogen Peroxide; Hydroxides; Hypochlorous Acid; Oxidation-Reduction; Salicylates; Salicylic Acid; Superoxides; Thiourea; Xanthine Oxidase; Xanthines