Pharmacology of free radicals; recent views on their relation to inflammatory mechanisms

Differential inhibition by oxygen radicals of vasoactive amines-induced contractions in the porcine coronary artery

Reactive oxygen species (ROS) play an important role in normal metabolic and signaling processes. Excess ROS, however, can cause severe cardiovascular damage. Thus, the present study was designed to examine effects of H(2)O(2) and xanthine plus xanthin oxidase (X/XO) on the serotonin (5HT), histamine (His) and acetylcholine (ACh)-induced contractions of porcine coronary arteries. In addition, to explore the site of ROS formation and species of it, the inhibitory effects of edaravone and EDTA were also tested. 5HT- and His-induced contractions were suppressed by H(2)O(2) and X/XO treatment. However, these suppressions of ACh-induced contraction by H(2)O(2) treatment was relatively weak and X/XO treatment caused no suppression on ACh-induced contraction. In the presence of edaravone which is thought to be a scavenger for .OH, significant decrease of inhibition of 5HT- and His-induced contractions was observed when coronary artery strips were treated with X/XO, but not H(2)O(2). On the other hand, inhibitory effects by EDTA treatments were also observed in X/XO treatments. These results suggest that 1) ROSs produced by additions of H(2)O(2) or X/XO are considered to be responsible for several physiological functions of coronary artery contractions, 2) the site of ROS produced by X/XO system, probably .OH, was outside the cell, but the inhibitory action of H(2)O(2), was inside the cell, and 3) a low susceptibility of ACh-induced contraction to H(2)O(2) and X/XO may indicates the signal transduction pathway(s) of ACh-induced contraction is different from those of 5HT and His.

Reduction of oxidative stress in amyotrophic lateral sclerosis following pramipexole treatment

Oxidative abnormalities have been identified both in familial amyotrophic lateral sclerosis (FALS) and the more prevalent sporadic ALS (SALS). Mitochondria dysfunction and toxic free radicals may play a role in this disease process, although the exact pathogenesis of both forms of ALS remains unknown. 2,3-DHBA is a hydroxylated salicylate by product that has been shown to be a reliable marker of increased free radical activity and is reliably assayed by HPLC. Following an oral salicylate load, we found elevated serum levels of 2, 3-dihydroxybenzoic acid (2,3-DHBA) and DHBA/salicylate in SALS subjects. Pramipexole has been shown to reduce oxidative stress and be neuroprotective in cell and animal models of neurodegeneration. We studied 12 SALS patients to determine the levels of 2,3-DHBA both before and after treatment with pramipexole. We found that pramipexole treatment up to 6 mg/day was well tolerated. The mean 2,3-DHBA serum levels were reduced by 45% and DHBA/salicylate ratios declined by 59% following treatment with pramipexole. SALS patients show apparent increases in systemic oxygen radical production that are reduced by pramipexole treatment at conventional doses, suggesting that pramipexole or related compounds may interrupt free radical production in SALS.

Mechanism of acetaminophen inhibition of cyclooxygenase isoforms

Acetaminophen has similar analgesic and antipyretic properties to nonsteroidal antiinflammatory drugs (NSAIDs), which act via inhibition of cyclooxygenase enzymes. However, unlike NSAIDs, acetaminophen is at best weakly antiinflammatory. The mechanism by which acetaminophen exerts its therapeutic action has yet to be fully determined, as under most circumstances, acetaminophen is a very weak cyclooxygenase inhibitor. The potency of acetaminophen against both purified ovine cyclooxygenase-1 (oCOX-1) and human cyclooxygenase-2 (hCOX-2) was increased approximately 30-fold by the presence of glutathione peroxidase and glutathione to give IC50 values of 33 microM and 980 microM, respectively. Acetaminophen was found to be a good reducing agent of both oCOX-1 and hCOX-2. The results are consistent with a mechanism of inhibition of acetaminophen in which it acts to reduce the active oxidized form of COX to the resting form. Inhibition would therefore be more effective under conditions of low peroxide concentration, consistent with the known tissue selectivity of acetaminophen.

Mechanism of action of acetaminophen: is there a cyclooxygenase 3?

Acetaminophen, also known as paracetamol, is a nonsteroidal anti-inflammatory drug with potent antipyretic and analgesic actions but with very weak anti-inflammatory activity. When administered to humans, it reduces levels of prostaglandin metabolites in urine but does not reduce synthesis of prostaglandins by blood platelets or by the stomach mucosa. Because acetaminophen is a weak inhibitor in vitro of both cyclooxygenase (COX)-1 and COX-2, the possibility exists that it inhibits a so far unidentified form of COX, perhaps COX-3. In animal studies, COX enzymes in homogenates of different tissues vary in sensitivity to the inhibitory action of acetaminophen. This may be evidence that there are >2 isoforms of the enzyme. Recently, a variant of COX-2 induced with high concentrations of nonsteroidal anti-inflammatory drugs was shown to be highly sensitive to inhibition by acetaminophen. Therefore COX-3 may be a product of the same gene that encodes COX-2, but have different molecular characteristics.

Regulation of astrocyte gap junctions by hypoxia-reoxygenation

Confluent cultures of rat cortical astrocytes were subjected to 12-h hypoxia (<1% O(2)) followed by reoxygenation. Just after hypoxia, the cellular distribution, phosphorylation state and levels of connexin43 (Cx43), as well as the extent of dye coupling were as in control conditions. Nonetheless, 15-30 min after reoxygenation, dye coupling was transiently reduced by approximately 70%. The reduction in dye coupling occurred without changes in the state of phosphorylation or levels of Cx43. Nevertheless, it was correlated with a decrease in Cx43 reactivity found at membrane appositions and the appearance of intracellular Cx43-positive vesicle-like structures of variable size, suggesting internalization of gap junction channels. Reoxygenation-induced cellular uncoupling and redistribution of Cx43 were prevented by melatonin (500 microM), a potent-free radical scavenger, or indomethacin (50 microM), an inhibitor of the cyclooxygenase-dependent arachidonic acid metabolism. In astrocytes cultured under normoxia, the state of phosphorylation of Cx43 was not affected by antimycin A, a blocker of the mitochondrial oxidative metabolism, but phosphorylation was drastically reduced by iodoacetate, a blocker of anaerobic glycolysis. Thus, these results strongly suggest that reoxygenation-induced uncoupling is mediated by arachidonic acid byproducts that induce, at least, disorganization of Cx43 gap junction channels.

L-glutamine enemas attenuate mucosal injury in experimental colitis

PURPOSE

The aim of this study was to investigate the role of 1-glutamine, short chain fatty acid, prednisolone, and mesalazine (5-aminosalicylic acid) enemas on mucosal damage and inflammation in experimental colitis.

METHODS

Colitis was induced in rats with trinitrobenzene sulfonic acid in ethanol. Saline (n = 14), prednisolone (n = 13), 5-aminosalicylic acid (n = 14), 1-glutamine (n = 14), and short chain fatty acid (n = 13) enemas were applied twice daily to the rats for seven days after the induction of colitis. The sham group (n = 9) received only saline enemas. Rats were killed at the seventh day and their colonic macroscopic inflammatory scores were determined. Colonic mucosal gamma glutamyl transpeptidase activity and colonic mucosal malondialdehyde levels were measured. The same measurements but no enemas were done in the control group (n = 7).

RESULTS

There were significant differences in macroscopic inflammatory scores between sham and colitis groups (P < 0.001). The macroscopic inflammatory scores of the colitis group were higher than the short chain fatty acid and glutamine groups (P < 0.05). Whereas the mucosal gamma glutamyl transpeptidase activity was diminished in prednisolone, 5-aminosalicylic acid, and short chain fatty acid groups when compared with the control group; in the colitis, sham, and glutamine groups the activity of this enzyme did not change. The mucosal malondialdehyde levels were significantly lower in the prednisolone and glutamine groups than in the colitis group.

CONCLUSION

Only one of four agents tested, namely, 1-glutamine enemas, could decrease the severity of colitis both morphologically and biochemically. Moreover, L-glutamine prevented the colitis-induced oxidant injury in the colonic mucosa. On the other hand, prednisolone and short chain fatty acids seemed to improve only the physiologic changes of colitis.

Metalloporphyrins are potent inhibitors of lipid peroxidation

The objectives of these studies were to determine whether metalloporphyrins could inhibit lipid peroxidation, characterize factors that influence their potency and compare their potency to prototypical antioxidants. Lipid peroxidation was initiated with iron and ascorbate in rat brain homogenates and the formation of thiobarbituric acid reactive species was used as an index of lipid peroxidation. Metalloporphyrins were found to be a novel and potent class of lipid peroxidation inhibitors. Inhibition of lipid peroxidation by metalloporphyrins was dependent on the transition metal ligated to the porphyrin, indicating that metal centered redox chemistry was important to the mechanism of their antioxidant activities. Manganese porphyrins with the highest superoxide dismutase (SOD) activities, MnOBTM-4-PyP and MnTM-2-PyP (charges are omitted throughout text for clarity), were the most potent inhibitors of lipid peroxidation with calculated IC50s of 1.3 and 1.0 microM, respectively. These manganese porphyrins were 2 orders of magnitude more potent than either trolox (IC50 = 204 microM) or rutin (IC50 = 112 microM). The potencies of the manganese porphyrins were related not only to their redox potentials and SOD activities, but also to other factors that may contribute to their ability to act as electron acceptors. The broad array of antioxidant activities possessed by metalloporphyrins make them attractive therapeutic agents in disease states that involve the overproduction of reactive oxygen species.

Arachidonic acid-induced dye uncoupling in rat cortical astrocytes is mediated by arachidonic acid byproducts

Arachidonic acid (AA) induced a concentration- and time-dependent reduction in gap junction-mediated dye coupling between cultured astrocytes. The effect was greatly diminished by inhibition of cyclooxygenases and lipoxygenases. The action of a low concentration of AA (5 microM) was also prevented by Ca2+-free extracellular solution or a high concentration of melatonin, a potent free radical scavenger, but not by Nomega-nitro-l-arginine, a nitric oxide (NO) synthase inhibitor. Thus, this effect may depend on Ca2+ influx and oxygen free radicals but not on NO generation. Cellular uncoupling induced by a high (100 microM), but not a low, AA concentration was rapidly reversed by washing with albumin containing solution. After reversal from 5 min but not 2.5 min inhibition with a high AA concentration dye coupling between astrocytes became refractory to a low concentration of AA, suggesting desensitization of the response elicited by a low concentration of the fatty acid. Dye uncoupling occurred without changes in levels and state of phosphorylation (immunoblotting and 32P-incorporation) of connexin43, the main astrocyte gap junctional protein. However, maximal cell uncoupling induced by a low (Slow action) but not by a high (Fast action) AA concentration was paralleled by a reduction in connexin43 (immunofluorescence) at cell-to-cell contacts. It is proposed that the AA-induced dye uncoupling is mediated by byproducts that induce rapid channel closure or slow removal of connexin43 gap junctions.

Inflammatory molecule release by beta-amyloid-treated T98G astrocytoma cells: role of prostaglandins and modulation by paracetamol

Deposition of beta-amyloid in the brain triggers an inflammatory response which accompanies the neuropathologic events of Alzheimer's disease and contributes to the destruction of brain tissue. The present study shows that beta-amyloid can stimulate human astrocytoma cells (T98G) to secrete the proinflammatory factors interleukin-6 and prostaglandins. Furthermore, prostaglandins can stimulate T98G to secrete interleukin-6, which in turn triggers the formation of additional prostaglandins. Prostaglandins are, therefore, a key element in the induction and maintenance of a state of chronic inflammation in the brain which may exacerbate the fundamental pathology in Alzheimer patients. Paracetamol (0.01-1000 microM), an unusual analgesic/antipyretic drug which acts preferentially by reducing prostaglandin production within the central nervous system, and indomethacin (0.001-10 microM) caused a clear dose-dependent reduction of prostaglandin E2 production by stimulated T98G cells whereas interleukin-6 release was not affected. These data provide further evidence of the involvement of non-steroidal anti-inflammatory drugs in the inflammatory processes that can be generated by glial cells in intact brain.

Oxidative stress and degenerative temporomandibular joint disease: a proposed hypothesis

The molecular events that underlie degenerative temporomandibular joint diseases are poorly understood. Recent studies have provided evidence that a variety of molecular species, including cytokines, matrix degrading enzymes, neuropeptides, and arachidonic acid catabolites may be involved. This paper advances the theory that mechanical stresses lead to the accumulation of damaging free radicals in affected articular tissues of susceptible individuals. This condition is called oxidative stress. The authors postulate mechanisms that may be involved in the production of free radicals in the temporomandibular joint and in the subsequent induction of molecular events that may amplify damage of articular tissues initiated by free radicals. If the proposed model is correct, then future therapeutic strategies directed at the control of oxidative stress could be effective in the management of degenerative temporomandibular joint diseases.

Enhancement of anti-inflammatory effects of calcium channel blockers by allopurinol and dimethylsulphoxide

The effects of the calcium channel blockers, nifedipine, verapamil and flunarizine, and the antioxidants, allopurinol and dimethylsulphoxide, were investigated on carrageenan-induced rat paw oedema and changes in vascular permeability. Paw volume was measured by using a plethysmometer and vascular permeability was quantified by measuring the extravasated Evans blue dye 3 h after injecting the phlogistic agent. Intraperitoneal administration of nifedipine (1,2 and 4 mg/kg), verapamil (5, 10 and 20 mg/kg), flunarizine (2.5, 5 and 10 mg/kg), allopurinol (6.25, 12.5 and 25 mg/kg) and dimethylsulphoxide (20, 40 and 80 mg/kg) 30 min before carrageenan, dose dependently inhibited oedema formation and increased vascular permeability. Co-administration of the lowest doses of calcium channel blockers with the lowest doses of antioxidants produced synergistic inhibitory effects. These results indicate that both calcium influx and oxygen-derived free radicals are involved in carrageenan-induced inflammatory responses. Thus, the synergistic effects of their combination may be due to the blockade of calcium entry and reduction in the generation of oxygen-derived free radicals.

Effect of aminoethylpyrroles on carrageenan-induced inflammation and on lipid peroxidation in rats: some structural aspects

Nine 3-(2-aminoethyl)pyrrole derivatives were investigated as anti-inflammatory agents in the carrageenan-induced rat paw oedema model and as antioxidants in the non-enzymatic lipid peroxidation assay. It was found that the derivatives which were substituted with a p-toluenesulphonyl group exhibited considerable anti-inflammatory activity and some also showed antioxidant properties. However, the presence of a p-toluenesulphonyl group did not invariably lead to activity. A structural feature which was essential for both activities was the aminoethyl side chain. Although a relationship between the antiinflammatory and the antioxidant activities was not apparent, the combination of these properties could be useful.

The cyclooxygenase and lipoxygenase inhibitor BW755C protects rats against kainic acid-induced seizures and neurotoxicity

In this study the effect of the anti-inflammatory drugs indomethacin, ibuprofen, ebselen (PZ 51, 2-phenyl-1,2-benzoisoselenazol-3(2H)-one), and BW755C (3-amino-1-(m-(trifluoromethyl-phenyl)-2-pyrazoline) on kainic acid (KA)-induced behavioral and neurochemical changes in rats was investigated. Rats injected with KA (10 mg/kg s.c.) developed seizure activity with a 20% mortality within the first 4 h and neuronal degeneration in the limbic system after 3 days. Pretreatment with the cyclooxygenase inhibitor indomethacin (10 mg/kg i.p.) augmented KA-induced epileptic activity and increased the mortality in status epilepticus to 80%. Another cyclooxygenase inhibitor, ibuprofen (20 mg/kg i.p.), and the lipoxygenase inhibitor ebselen (20 mg/kg i.p.) showed no effect on KA-induced symptoms and neurochemical changes. Application of the cyclooxygenase/lipoxygenase inhibitor BW755C (40 mg/kg i.p.) reduced the severity of seizures and protected significantly from irreversible brain lesions induced by KA. The marked reduction of glutamate decarboxylase (GAD; 53.3 +/- 12.2% of control) and choline acetyltransferase (ChAT; 60.9 +/- 9.1% of control) activities in amygdala/pyriform cortex and GAD activity in hippocampus (69.4 +/- 5.6% of control) observed 3 days after KA injection was abolished by BW755C treatment. Histopathological analyses of brain tissue showed that treatment with BW755C prevented the KA-induced nerve cell degeneration, edema, hemorrhages, and tissue necrosis in amygdala/pyriform cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipid peroxidation--a common pathogenetic mechanism?

Lipid peroxidation is considered at present as one of the basic mechanisms involved in reversible and irreversible cell and tissue damage. The current knowledge about the role of peroxidative breakdown of polyunsaturated fatty acids in the pathogenesis of various diseases has been reviewed. Lipid peroxidation leads to degradation of the lipid membrane, interaction of degradation products with intra- and extracellular targets and to the production of new reactive oxygen species during the course of the chain reaction thus leading to damage of cells and tissues. According to our current view lipid peroxidation is implicated in the pathogenesis of cancer, inflammatory processes, atherosclerosis, toxic injury by xenobiotics and ischemic-reperfusion damage.

Increased superoxide dismutase activity in aged human cerebrospinal fluid and rat brain determined by electron spin resonance spectrometry using the spin trap method

Superoxide dismutase (SOD) activity in CSF of patients was determined by electron spin resonance spectrometry using the spin trap method. Variation in SOD activity was found among patients. SOD activity in CSF of subjects increased with age and this was identified as Cu,Zn-SOD activity by electrophoresis. In addition, animal experiments showed that SOD activities were higher in mitochondrial and cytosol fractions of aged rats than in those of adult rats. This finding on aged rat brain validates the increase of SOD activity in aged human CSF.

Oxidative status and oral contraceptive. Its relevance to platelet abnormalities and cardiovascular risk

Oral contraceptive (OC) use is a risk for thrombogenic events. This paper reviews effects of OC on oxidative status, coagulation, and platelet activity. Complicating effects of cardiovascular risk factors such as smoking, diabetes, hyperpidemia, and hypertension, are discussed. From these data we conclude that: 1. OC use modifies slightly but significantly the oxidative status in women and in animals by decreasing in plasma and blood cells the antioxidant defenses (vitamins and enzymes). 2. The changes in the oxidative status are related to an increase in plasma lipid peroxides apparently responsible for the hyperaggregability and possibly the imbalance in clotting factors associated with the OC-induced prethrombotic state. 3. These effects of OC appear to be increased by a high intake of polyunsaturated fat and counteracted by supplements of vitamin E. 4. The risk factors acting synergistically with OC, have all been shown to increase platelet reactivity. In addition, smoking, diabetes, and, to some extent, dyslipidemia are associated with an increased level of lipid peroxides and concomitant changes in the antioxidant defenses that can be additive to those induced by OC. Thus, free radicals and lipid peroxidation could be the underlying mechanism in the predisposition to thrombosis induced by most risk factors in OC users. 5. Results of epidemiologic and experimental studies in this field will be concordant only when diet and natural antioxidants will be systematically taken into consideration.

The antinociceptive activity of paracetamol in zymosan-induced peritonitis in mice: the role of prostacyclin and reactive oxygen species

1. Oral administration of high doses of paracetamol (600 mg kg-1 or more) resulted in inhibition of the writhing and reduced the levels of prostacyclin (PGI2, measured as 6-keto-PGF1 alpha) induced by intraperitoneal administration of zymosan in mice. The high oral doses of paracetamol required were accompanied by behavioural toxicity which may have contributed to the inhibition of writhing. 2. The number of writhes per mouse and the proportion of mice writhing at least once correlated significantly with the levels of 6-keto-PGF1 alpha. However, inhibition of writhing by paracetamol occurred at higher levels of 6-keto-PGF1 alpha than was previously observed with acidic non-steroidal anti-inflammatory agents. 3. When injected i.p., PGI2, carbacyclin and iloprost (agonists at the PGI2 receptor) induced writhing. Intraperitoneal injection of PGI2 reversed the inhibition of writhing induced by indomethacin (1 mg kg-1, p.o.) but not that induced by oral administration of paracetamol. 4. Paracetamol at 800 mg kg-1, p.o., inhibited carbacyclin-induced writhing but indomethacin at 1 mg kg-1 p.o. did not. Paracetamol administered i.p. at 100 mg kg-1 reduced the peritoneal levels of 6-keto-PGF1 alpha and inhibited zymosan-induced but not carbacyclin-induced writhing and did not produce behavioural toxicity. 5. The in vitro potency of paracetamol as a prostaglandin synthesis inhibitor is known to be reduced by the presence of lipid peroxides. However, no lipid peroxides, measured as thiobarbituric acid reactive material, were detected in the peritoneal lavage fluid of zymosan-injected mice. 6. Intraperitoneal administration of a mixture of superoxide dismutase and catalase reduced detectable superoxide anion by 98% without inhibiting the writhing response to zymosan or the antinociceptive potency of paracetamol. 7. The data are consistent with the suggestion that inhibition of PGI2 synthesis in the peritoneal cavity by paracetamol is responsible for only a part of its antinociceptive activity in this test. However, extremely high oral doses of paracetamol were required which produced behavioural toxicity which clearly contributed to the inhibition of writhing. The low potency of paracetamol in this model cannot be attributed to the generation of lipid peroxides via the oxidative burst.

Lipid peroxidation and lung ultrastructural changes in an experimental model of leukocyte-mediated pulmonary injury

The aim of this study was to study ultrastructural changes and lipid peroxidation in rabbits lung after massive complement activation and leukocyte aggregation. A prolonged and massive leukocyte activation was induced by intraperitoneal inoculation of zymosan suspected in paraffin. Fifteen animals (group 3) were given 0.6 g/kg of zymosan, 22 animals (group 2) received 1 g/kg, and 11 rabbits (group 1) were treated with paraffin alone and served as controls. An acute mortality rate of 40% was observed in group 3 and of 68% in group 2. Surviving animals were studied for 10 days. In these animals a marked decrease in circulating granulocytes and a progressive decline in arterial PO2 were recorded (PO2 on day 10 in group 2 animals was 51.94 +/- 4.26, p less than 0.01). Microscopic and ultrastructural evaluation revealed sequestration of granulocytes in the pulmonary microvasculature. Studies of lung homogenates demonstrated increased levels of lipid peroxide derivative malondialdehyde (group 2 rabbits, 1624 +/- 638; group 1, 795 +/- 57 pm/mg pt, p less than .001) and decreased levels of the tissue antioxidant alpha-tocopherol. The results of this study are compatible with the hypothesis of leukocyte-mediated injury through production of oxygen radicals.

Ceramide lactoside in amniotic fluid: high concentration in chorioamnionitis and in preterm labor

The mechanisms responsible for the onset and progression of preterm labor are poorly understood. In the present study a total of 115 amniotic fluid specimens were analyzed for a lipid that has not previously been detected in amniotic fluid. This glycolipid was identified as ceramide lactoside. It was found in two-dimensional thin-layer chromatograms for evaluation of lung maturity and quantified by gas chromatography. Ceramide lactoside concentrations in amniotic fluid were low in spontaneous labor at term (1.7 +/- 0.7 nmol/ml) and in pregnancies that were not associated with spontaneous preterm labor (1.4 +/- 0.6 nmol/ml). The concentrations were high in chorioamnionitis with signs of infection (11.8 +/- 5.8 nmol/ml) and in preterm labor without clinical signs of chorioamnionitis (5.4 +/- 4.0 nmol/ml). A high ceramide lactoside (greater than or equal to 5 nmol/ml) predicted chorioamnionitis with signs of infection at a sensitivity and a specificity of 94% and 95%, respectively. A moderately high ceramide lactoside concentration (greater than or equal to 2.5 nmol/ml) predicted spontaneous preterm labor: sensitivity, 82%; specificity, 95%. Little, if any, ceramide lactoside was present in urine, vernix, normal fetal membranes, or lung effluent, whereas this glycolipid was present in large amounts in granulocytes and in inflamed fetal membranes. We propose that phagocytosing granulocytes release ceramide lactoside into amniotic fluid.

Determination of carbonyl groups in oxidatively modified proteins by reduction with tritiated sodium borohydride

Oxidatively modified proteins have been implicated in a variety of physiologic and pathologic processes. Oxidative modification typically causes inactivation of enzymes and also the introduction of carbonyl groups into amino acid side chains of the protein. We describe a method to quantify oxidatively modified proteins through reduction of these carbonyl groups with tritiated borohydride. The technique was applied to purified, oxidatively modified glutamine synthetase and to bronchoalveolar lavage fluid from dogs and from humans. Since the protein content of lung lavage fluid is low, a very sensitive method was required to measure the oxidized residues. Reduction of the carbonyl group generated during oxidation of proteins with tritiated borohydride provided excellent sensitivity. Incorporation of tritium was directly proportional to the amount of protein with a range from 10 to 1000 micrograms. Should moieties other than amino acids be labeled, they are easily removed by rapid benchtop hydrolysis of the protein followed by chromatography on Dowex 50.

Free radicals in medicine. II. Involvement in human disease

This review explores evidence that free radicals might be involved in various human disease processes. Such involvement is difficult to prove because direct evidence is often lacking and is based on animal models of the disease process. Evidence for free radical involvement includes demonstrating abnormal free radical production in the disease, finding that deliberately applying free radical-producing systems into the cellular locus responsible for the disease reproduces its manifestations, and showing that free radical scavengers control facets of the disease process. Confirmation of free radical involvement in a particular disease may have clinical relevance, inasmuch as clinically applicable techniques are currently being developed to remove free radicals from cellular sites where they are injurious and, in other situations such as chemotherapy, techniques or drugs that produce free radicals are available to destroy harmful cells.

Prooxidative activities of 10 phenazine derivatives relative to that of clofazimine

The objective of this study was to investigate the relationship between the antimycobacterial properties of the antileprosy drug clofazimine and its stimulatory effect on the release of reactive oxidants by polymorphonuclear leukocytes by using a variety of phenazine derivatives. The effects of these compounds on myeloperoxidase-mediated iodination, luminol-enhanced chemiluminescence, and the release of superoxide anion by polymorphonuclear leukocytes were investigated. Dissociation of the antimycobacterial and prooxidative effects of clofazimine was possible by manipulation of the chemical group in position 2 of the phenazine molecule. When nitrogen-containing substituents in this position were replaced by oxygen, the mode of the prooxidative action of the compounds was altered.

Free Radicals: Relation to Tissue Damaae - A Review

Free radicals are any molecules having an odd number of electrons. These molecules are highly reactive and can be generated as byproducts of normal metabolism as well as by exposure to a number of environmental factors including drugs, radiation and air pollutants. Due to the ubiquity of molecular oxygen, the oxygen metabolites superoxide anion, hydrogen peroxide, and the hydroxyl radical are frequently involved in both beneficial and detrimental free radical reactions. Intracellular enzymes and radical scavengers help to protect against tissue damage by these reactive metabolites. The extent of free radical damage to tissue depends on the nature of the radical produced and its site of generation.

Salicylates and 12-lipoxygenase activity in human washed platelets

In vitro salicylates /aspirin, salicylic acid, salicylamide and gentisic acid/ inhibited formation of 12-lipoxygenase products in intact human washed platelets which were stimulated with thrombin or arachidonic acid. Salicylates did not affect 12-lipoxygenase activity in platelet lysates. Ex vivo aspirin or salicylamide at a dose of 1 g given orally to healthy volunteers potentiated formation of 12-lipoxygenase products in washed platelets. It is concluded that the effect of salicylates on 12-lipoxygenase pathway is independent from their influence on cyclooxygenase activity in platelets and aspirin cannot be considered as a selective inhibitor of platelet cyclooxygenase.

Ocular phototoxicity: guidelines for selecting sunglasses

Within the last two decades appreciable laboratory and epidemiologic evidence has accumulated to support the notion that near ultraviolet radiation and lower wavelength visible light may be hazardous to the human lens and retina. However, a substantial number of commercially available sunglasses are being manufactured without apparent regard for these potential hazards. This review surveys the mechanism(s) for phototoxic damage to the eye, outlines persons at potentially greatest risk of injury, and summarizes recommendations for the selection of optimally efficient sunglasses.

Lowered glutathione-peroxidase activity in asthmatic patients with food and aspirin intolerance

In analogy with findings from animal experiments, people with low glutathione-peroxidase (GSH-Px) activity could be expected to have altered sensitivities to effects of drugs, chemicals and possibly food. We have investigated GSH-Px activity in 12 patients with intrinsic asthma and food and aspirin intolerance. Ten of the 12 patients had very low or low GSH-Px activity and the frequency of low GSH-Px activity in this group was statistically significant (P less than 0.001) compared with the control material of age- and sex-matched healthy individuals. Our finding of lowered GSH-Px activity in patients with aspirin intolerance may indicate the involvement of hitherto unknown mechanisms in the pathogenesis of asthmatic disorders.

Reaction of some antiinflammatory 17 beta-(2-aminooxazol-4-yl) steroids with hydrogen peroxide. Synthesis of steroid-17-spiro-5'-oxazolidine-2',4'-diones

The heterocyclic moiety of 17 beta-(2-aminooxazol-4-yl) steroids is sensitive to the oxidizing action of hydrogen peroxide and yields products mainly from the opening of the amino-oxazole ring. Unlike simple 2-aminooxazoles, it does not rearrange to 2-imidazolone and the expected steroidal hydroperoxyimidazolidinones were not detected. Among the substances we isolated, N-(aminocarbonyl)-17 alpha-hydroxy-17-carboxamides (2a) and (3a) undergo spontaneous cyclization, in the reaction conditions, giving steroid-17-spirooxazolidinediones (2d) and (3d). Spirane (2d) was synthesized in high yields from (2a) in strongly alkaline medium.

Adult respiratory distress syndrome after allogeneic bone-marrow transplantation: evidence for a neutrophil-independent mechanism

5 patients in whom the adult respiratory distress syndrome (ARDS) developed after bone-marrow transplantation (BMT) for chronic myeloid leukaemia are described. Donors in all cases were siblings who were matched for all major-histocompatibility-complex determinants. All patients were neutropenic to varying degrees at the onset of respiratory symptoms. Histological evaluation in all patients at necropsy showed diffuse alveolar damage with no evidence of intrapulmonary neutrophil sequestration. No patient had detectable levels of plasma peroxidation products, which were measured as an index of neutrophil oxidant function. Significantly increased clearance of inhaled 99mTc-diethylene-triamine-pentacetate was a uniform finding, suggesting impaired alveolar-capillary barrier function in keeping with ARDS. An increase in an index of lung epithelial permeability leading to ARDS may develop in neutropenic patients who have evidence of neither intrapulmonary neutrophil sequestration not tissue oxidant injury. ARDS after BMT is probably multifactorial in aetiology, but neutrophil-derived oxidant products play no part in its genesis.

Lipid peroxidation modifies the effect of phenolic anti-inflammatory drugs on prostaglandin biosynthesis

The effects of phenolic anti-inflammatory drug, MK-447, on prostaglandin (PG) I2 and thromboxane (TX) A2 biosynthesis by rat dental pulp tissue were evaluated in the presence of 10 mM mannitol (MA) or 1 mM ascorbic acid with 0.3 mM Fe2+ (A + F). Although MK-447 alone at 1 and 10 microM had no significant effects, MK-447 at 100 microM stimulated both PGI2 and TXA2 biosynthesis, and suppressed the lipid peroxidation in the pulp tissue as estimated by thiobarbituric acid method. MA also reduced the lipid peroxidation, but had no effect on PG and TX production. However, in the presence of MA, the stimulatory effect of MK-447 was potentiated, and the significant effects were observed at concentrations higher than 1 microM. In contrast, A + F remarkably stimulated the lipid peroxidation, and inhibited both PG and TX biosynthesis. In the presence of A + F, MK-447 showed no stimulatory effect, and contrary, at 100 microM inhibited PG and TX production. These results suggest that the cellular levels of lipid peroxidation exert a significant influence on the effects of phenolic anti-inflammatory drugs like MK-447 on PG biosynthesis. The possible mechanism of action for such drugs has been discussed in view of the significance of lipid peroxidation in inflammatory condition.

Peroxidation of linolenic acid promoted by human polymorphonuclear leucocytes

Human polymorphonuclear leucocytes were found to promote peroxidation linolenic acid micelles. The peroxidation was markedly enhanced by addition of ferric iron, either in the form of chloride, ADP-complex or EDTA to the phosphate-buffered reaction mixture. The leucocyte oxygen burst was induced by the addition of the lipid micelles, and no other stimulatory agent was therefore required. Pretreatment of the leucocytes with cytochalasin B did not inhibit t.e lipid peroxidation which indicates that phagocytosis was not part of the peroxidative mechanism. Lipid peroxidation was inhibited by alpha-tocopherol acetate, butylated hydroxytoluene, manganese ions and desferrioxamine but not by superoxide dismutase, catalase or the hydroxyl radical scavenger dimethylsulfoxide. Lipid peroxidation promoted by xanthine oxidase, was studied for comparison. This was inhibited by superoxide dismutase, indicating that xanthine oxidase, in contrast to leucocytes, promotes lipid peroxidation via a superoxide-dependent mechanism. Manganese ions and butylated hydroxytoluene, and to a lesser extent alpha-tocopherol, were also inhibitors. The leucocyte promoted lipid peroxidation is similar to the well-known peroxidation promoted by microsomal NADPH-cytochrome P450 reductase, which also is not induced by superoxide radicals. Peroxidation of lipids may be a mechanism whereby granulocytes express tissue damage in for example inflammation and ischaemia.