Antioxidant characteristics of some potential anticataract agents. Studies of aspirin, paracetamol, and bendazac provide support for an oxidative component of cataract

The Puzzle of Aspirin and Iron Deficiency: The Vital Missing Link of the Iron-Chelating Metabolites

Acetylsalicylic acid or aspirin is the most commonly used drug in the world and is taken daily by millions of people. There is increasing evidence that chronic administration of low-dose aspirin of about 75-100 mg/day can cause iron deficiency anaemia (IDA) in the absence of major gastric bleeding; this is found in a large number of about 20% otherwise healthy elderly (>65 years) individuals. The mechanisms of the cause of IDA in this category of individuals are still largely unknown. Evidence is presented suggesting that a likely cause of IDA in this category of aspirin users is the chelation activity and increased excretion of iron caused by aspirin chelating metabolites (ACMs). It is estimated that 90% of oral aspirin is metabolized into about 70% of the ACMs salicyluric acid, salicylic acid, 2,5-dihydroxybenzoic acid, and 2,3-dihydroxybenzoic acid. All ACMs have a high affinity for binding iron and ability to mobilize iron from different iron pools, causing an overall net increase in iron excretion and altering iron balance. Interestingly, 2,3-dihydroxybenzoic acid has been previously tested in iron-loaded thalassaemia patients, leading to substantial increases in iron excretion. The daily administration of low-dose aspirin for long-term periods is likely to enhance the overall iron excretion in small increments each time due to the combined iron mobilization effect of the ACM. In particular, IDA is likely to occur mainly in populations such as elderly vegetarian adults with meals low in iron content. Furthermore, IDA may be exacerbated by the combinations of ACM with other dietary components, which can prevent iron absorption and enhance iron excretion. Overall, aspirin is acting as a chelating pro-drug similar to dexrazoxane, and the ACM as combination chelation therapy. Iron balance, pharmacological, and other studies on the interaction of iron and aspirin, as well as ACM, are likely to shed more light on the mechanism of IDA. Similar mechanisms of iron chelation through ACM may also be implicated in patient improvements observed in cancer, neurodegenerative, and other disease categories when treated long-term with daily aspirin. In particular, the role of aspirin and ACM in iron metabolism and free radical pathology includes ferroptosis, and may identify other missing links in the therapeutic effects of aspirin in many more diseases. It is suggested that aspirin is the first non-chelating drug described to cause IDA through its ACM metabolites. The therapeutic, pharmacological, toxicological and other implications of aspirin are incomplete without taking into consideration the iron binding and other effects of the ACM.

Which agent should be used to reduce ischemia-reperfusion injury after testicular torsion: a comparative animal experiment

INTRODUCTION

Testicular torsion is an acute urological emergency that causes severe damage of testis. In order to prevent testicular damage, early diagnosis and surgical intervention is essential. Also pain management in both pre-operative and postoperative periods remains a challenging entity.

OBJECTIVE

In this study, we aimed to determine the possible positive effects of three different analgesics (ibuprofen, metamizole, and paracetamol), which are widely used in clinical practice on testicular tissue, in addition to pain control.

STUDY DESIGN

Forty prepubertal rats (180-210 g) were divided into five experimental groups. Group 1 was sham group in which the left testis was brought out through a scrotal incision and then replaced in the scrotum without torsion. Group 2 was control group (only 0.9% NaCl was applied). Also in group 3, paracetamol, in group 4, ibuprofen, and in group 5, metamizole sodium was applied 1 h after the torsion. Torsion duration was planned as 4 h for all groups.

RESULTS

In the biochemical evaluation, malondialdehyde (MDA), myeloperoxidase (MPO), and total nitrate (NO) levels were measured in the testicular tissue. All groups were compared with group 2 (control group). In group 3, although the MDA level was lower and the MPO level was found to be higher, these were not statistically significant. In group 4, the NO level was low but statistically significant. Histological findings were evaluated due to Cosentino's classification, and the scores of group 4 were better than all groups.

DISCUSSION

In this study, severe damage was observed at the end of torsion period of 4 h. This is in line with previous published data. The beneficial effects of all three drugs have been observed.

CONCLUSIONS

Biochemical results did not clearly highlight any agents. According to pathology results, metamizole was better than paracetamol and the most ideal analgesic preparation was observed as ibuprofen.

Theoretical investigation for the designing of novel antioxidants

In this study, the antioxidant potential of salicylic acid and its derivatives was determined. O–H bond dissociation enthalpy ionization potential and spin densities were computed, which are important characteristics of antioxidants. We have designed new antioxidants on the basis of information obtained from the results of this study and a literature review. O–H bond dissociation enthalpy, ionization potential, and spin densities of designed compounds were also calculated to analyze the effect of the size of the heterocyclic ring, the electronegativity of the heteroatom, the number of hydroxyl groups, and intramolecular hydrogen bonding. The results reveal that compounds with a larger heterocyclic ring, fewer electronegative atoms, and greater number of hydroxyl groups have enhanced antioxidant activity. A comparison of bond dissociation enthalpy of designed compounds IIIA and IV with that of phenolic acid antioxidants shows that these designed compounds are potent antioxidants. From statistical analysis, it is found that for designed compounds, good correlation was found between spin density and bond dissociation enthalpy. The present theoretical investigation will provide help to understand the biological activity of salicylic acid and its derivatives for better utilization in the fields of pharmacy and the food industry. New antioxidants with better antioxidant activity can be synthesized on the basis of the results of this study.

Comparison of the protective effect of dipyridamole and acetylsalicylic acid on long-term histologic damage in a rat model of testicular ischemia-reperfusion injury

PURPOSE

Ischemia reperfusion injury arising from testicular torsion results in a loss of spermatogenesis and a significant increase in germ cell apoptosis. We investigated the effects of dipyridamole and acetylsalicylic acid (ASA), 2 well-known platelet inhibitors, on testicular ischemia reperfusion injury.

METHODS

Thirty adult male Sprague-Dawley rats were randomly divided into 5 groups (n = 6 for each group): control, sham-operated, torsion/detorsion (T/D), T/D + dipyridamole, and T/D + ASA. Testicular ischemia was achieved by rotating the left testis 720° clockwise for 2 hours. Thirty minutes before torsion, 10 mg/kg dipyridamole was injected transperitoneally in the T/D + dipyridamole group, and 100 mg/kg ASA was injected transperitoneally in the T/D + ASA group. Sixty days after the initial surgical procedure, ipsilateral orchiectomies were performed for histopathologic examination to determine Johnsen's mean testicular biopsy score (MTBS), mean seminiferous tubular diameter (MSTD), and apoptotic index (AI) in all groups.

RESULTS

Unilateral testicular torsion-detorsion led to a significant decrease in Johnsen's MTBS and MSTD values in the ipsilateral testis and a significant increase in AI values of the T/D group. There were no significant differences between the T/D + dipyridamole and control groups in terms of MSTD and MTBS values. Although an amount of improvement exits in T/D + ASA group, there were significant differences between the T/D + ASA and control group MSTD and MTBS values. There was no significant difference between the T/D + dipyridamole and control groups in terms of AI values (P > .05), but the differences between the T/D + ASA and control groups were significant despite a slight decline in AI values of the T/D + ASA group.

CONCLUSIONS

Our findings show that the use of dipyridamole before testicular reperfusion has a potentially protective effect against long-term injury in testicular ischemia reperfusion injury.

The protective effect of salicylic acid on lysozyme against riboflavin-mediated photooxidation

As a metabolite of aspirin in vivo, salicylic acid was proved to protect lysozyme from riboflavin-mediated photooxidation in this study. The antioxidative properties of salicylic acid were further studied by using time-resolved laser flash photolysis of 355 nm. It can quench the triplet state of riboflavin via electron transfer from salicylic acid to the triplet state of riboflavin with a reaction constant of 2.25×10(9) M(-1) s(-1). Mechanism of antioxidant activities of salicylic acid on lysozyme oxidation was discussed. Salicylic acid can serve as a potential antioxidant to quench the triplet state of riboflavin and reduce oxidative pressure.

Topical metal chelation therapy ameliorates oxidation-induced toxicity in diabetic cataract

Oxidative stress plays a critical role in cataractogenesis, the leading cause of blindness worldwide. Since transition metals generate reactive oxygen species (ROS) formation, metal chelation therapy has been proposed for treatment of cataracts. However, the effectiveness of most chelators is limited by low tissue penetrability. This study is the first to demonstrate that the topically applied divalent metal chelator ethylenediamine tetraacetic acid (EDTA) combined with the carrier and permeability enhancer methyl sulfonyl methane (MSM) ameliorates both oxidation-induced lens opacification and the associated toxic accumulation of protein-4-hydroxynonenal (HNE) adducts. Both in vitro (rat lens culture) and in vivo (diabetic rats), EDTA-MSM (1) significantly reduced lens opacification by about 40-50%, (2) significantly diminished lens epithelial cell proliferation and fiber cell swelling in early stages of cataract formation in vivo, and (3) notably decreased the levels of protein-HNE adducts. These findings have important implications specifically for the treatment of cataract and generally for other diseases in which oxidative stress plays a key pathogenic role.

Antioxidative action of aspirin on endothelial function in hypercholesterolaemic rats

The role of aspirin on vascular endothelial changes during hypercholesterolaemia prior to development of actual atherosclerotic lesions is not known. Therefore, in the present study, we tested the hypothesis that aspirin by its antioxidant action improves endothelial function in a rat model of hypercholesterolaemia. Hypercholesterolaemia was induced in Wistar rats by feeding a 1% cholesterol-rich diet for 10 weeks. Lipid profile, lipid peroxidation and reduced glutathione were estimated in serum. Endothelial function and beta(2)-adrenoceptor activity was tested by studying the dose-response relationship of acetylcholine and isoproterenol, respectively, on isolated aortic tissues in an organ bath setup. Hypercholesterolaemic rats showed a significant increase in total cholesterol, low-density lipoprotein cholesterol (LDL-C) and very low-density lipoprotein cholesterol (VLDL-C), and a significant fall in high-density lipoprotein cholesterol (HDL-C) compared to the control rats. Isolated aortic tissues from hypercholesterolaemic rats showed endothelial dysfunction and decreased sensitivity to beta(2)-adrenoceptor. Treatment with aspirin was associated with a fall in total cholesterol, LDL-C and VLDL-C, and a significant rise in serum HDL-C. Aspirin treatment also restored endothelial function and beta(2)-adrenoceptor activity. Hypercholesterolaemic rats showed free radical generation, evident by increase in serum lipid peroxidation and reduction in serum reduced glutathione content compared to the control rats. Aspirin treatment was associated with reduction in free radical stress evident by decreased lipid peroxidation and significantly prevented reduction in glutathione content compared to hypercholesterolaemic controls. Aspirin improves endothelial function and beta(2)-adrenoceptor activity during experimentally induced hypercholesterolaemia in rats, possibly due to an antioxidant effect.

Aspirin inhibits the formation of pentosidine, a cross-linking advanced glycation end product, in collagen

Aspirin showed an inhibitory effect on the formation of pentosidine, a cross-linking advanced glycation endproduct, in collagen incubated with glucose in vitro. IC(50) was evaluated at 10mmol/l. Aspirin might act by metallic ion chelating (as did EDTA and DTPA) and by oxygen radical scavenging. Since aspirin was reported to inhibit retinopathy in diabetic dogs, it could act partly by inhibiting advanced glycation endproduct accumulation in long-lived proteins like collagens.

Aspirin restores normal baroreflex function in hypercholesterolemic rats by its antioxidative action

Besides its well-known effects on platelet aggregation, aspirin has been suggested to be an antioxidant and is also known to improve the lipid profile. In the present study we tested the hypothesis that aspirin by its antioxidant effect, improves haemodynamic profile and baroreflex sensitivity in rat model of hypercholesterolemia. Hypercholesterolemia was induced in Wistar rats by feeding 1% cholesterol rich diet for 10 weeks. Lipid profile, lipid peroxidation and reduced glutathione were estimated in serum. Haemodynamic changes and baroreflex were measured in anaesthetized rats. Hypercholesterolemic rats showed significant increase in total cholesterol, low-density lipoprotein-cholesterol (LDL-C), very low-density lipoprotein-cholesterol (VLDL-C) and atherogenic index and significant decrease in high-density lipoprotein-cholesterol (HDL-C). Significant rise in blood pressure, heart rate and attenuation of baroreflex sensitivity were also found in hypercholesterolemic rat. Aspirin in the dose of 100 mg/kg showed significant decrease in total cholesterol, LDL-C, VLDL-C and atherogenic index and significant increase in HDL-C. Aspirin treatment prevented the rise in blood pressure, heart rate and significantly improved baroreflex sensitivity in hypercholesterolemic rats. Hypercholesterolemic rats showed free radical generation, evident by a significant increase in serum lipid peroxidation and significant reduction in serum reduced glutathione content. Aspirin treatment significantly decreased lipid peroxidation and significantly increased reduced glutathione content. We have demonstrated that aspirin improves baroreflex response and prevents the rise in blood pressure and heart rate possibly by reducing sympathetic activity due to its antioxidant effect in experimentally induced hypercholesterolemic rats.

Protective Effect of Aspirin against Dexamethasone-Induced Cataract in Cultured Rat Lens

PURPOSE

To investigate the effect of aspirin on dexamethasone-induced cataract formation in cultured rat lenses.

METHODS

One hundred and forty-eight lenses were divided into 3 groups and cultured in vitro: control (DMEM), cataract (DMEM + 10 microM dexamethasone), aspirin (DMEM + 10 muM dexamethasone + 2 mM aspirin). Following incubation, the transparency of the lenses was evaluated daily using a dissecting microscope. Twelve lenses from each group were homogenized and the activities of enzymes (catalase, superoxide dismutase and lactate dehydrogenase) from supernatants were measured after 1, 3, 5 and 7 days of incubation, respectively. The ultrastructure of lenses from the control and cataract groups was observed on the completion of 7-day incubation.

RESULTS

Opacity was induced by dexamethasone in the nuclear region of the rat lenses. Lenses in the control group exhibited mist-like opacity and lenses in the cataract group showed dense nuclear opacity, whereas lenses in the aspirin-treated group only had a visible demarcation between nuclear and cortical regions at day 7. The activities of catalase, superoxide dismutase and lactate dehydrogenase in the cataract group decreased in a time-dependent manner. There was no significant loss of enzyme activities in either the control or the aspirin group throughout the incubation period. An orderly arrangement of fiber cells was noted, and the cell membrane, cell junction and organelles were normal in the control group. However, in the cataract group the arrangement of fiber cells was untidy and the lenses contained abnormal-appearing cells. The group exhibited swollen mitochondria, a large number of vacuoles and expanded extracellular lacunae.

CONCLUSIONS

Dexamethasone induces nuclear cataract in the organ-cultured rat lens by chemically modifying proteins, including enzymes. The enzymes, including those that normally eliminate radial oxygen species, could be especially vulnerable. Aspirin significantly inhibits dexamethasone-induced cataract formation by inhibiting inactivation of those enzymes.

Potential Protective Effects of NSAIDs/ASA in Oxidatively Stressed Human Lens Epithelial Cells and Intact Mouse Lenses in Culture

PURPOSE

To study possible toxic effects of indomethacin, diclofenac, and celecoxib (NSAIDs) and acetylsalicylic acid (ASA) as well as potentially protective effects of these substances in oxidatively stressed human lens epithelial cells (HLEC) and in intact mouse lenses in culture.

METHODS

HLEC and mouse lenses were incubated with NSAIDs or ASA alone or in the presence of H2O2. To study apoptosis the cells were then either stained with Hoechst 33342 or assayed for caspase-3 activity. Mouse lenses were studied with respect to lens transparency.

RESULTS

Low concentrations of NSAIDs/ASA caused a significant protection against H2O2-induced apoptosis in HLEC whereas higher concentrations were toxic.

CONCLUSION

The protective effects of NSAIDs/ASA against oxidative damage are confined to a relatively small therapeutic window.

Heme oxygenase-1 induction may explain the antioxidant profile of aspirin

Aspirin is known to exert antioxidant effects by as yet unidentified mechanisms. In cultured endothelial cells derived from human umbilical vein, aspirin (30-300 microM) increased heme oxygenase-1 (HO-1) protein levels in a concentration-dependent fashion up to fivefold over basal levels. HO-1 induction was accompanied by a marked increase in catalytic activity of the enzyme as reflected by enhanced formation of both carbon monoxide and bilirubin. Pretreatment with aspirin or bilirubin at low micromolar concentrations protected endothelial cells from hydrogen peroxide-mediated toxicity. HO-1 induction and endothelial protection by aspirin were not mimicked by indomethacin, another inhibitor of cyclooxygenase. The nitric oxide (NO) synthase blocker L-NAME prevented aspirin-dependent HO-1 induction. These findings demonstrate that aspirin targets HO-1, presumably via NO-dependent pathways. Induction of HO-1 expression and activity may be a novel mechanism by which aspirin prevents cellular injury under inflammatory conditions and in cardiovascular disease.

Effects of Bacillus thuringiensis toxin on hepatic lipid peroxidation and free-radical scavengers in rats given alpha-tocopherol or acetylsalicylate

The effect of Dipel (D), a Bacillus thuringiensis-based bioinsecticide, on hepatic antioxidant enzyme activities and lipid peroxidation in rat liver was investigated. Administration of D in a dose of 1 mg/100 g body mass for 4 successive days increased the activities of glutathione peroxidase (GPx), glutathione reductase (GR) and the level of malondialdehyde (MDA) in rat hepatocytes. The activity of superoxide dismutase (SOD) and glutathione (GSH) level were decreased. Administration of D in rats pretreated with alpha-tocopherol (alphaT) or acetylsalicylic acid (ASA) decreased the activities of GPx, GR and MDA levels, while the GSH level was increased compared with rats treated with D alone. The SOD activity was increased in rats pretreated with alphaT before D, but decreased on pretreatment with ASA, compared with rats treated with D alone. The results indicated that D induced oxidative stress in rat liver that has been protected by prior administration of alphaT or ASA.

Aspirin protects endothelial cells from oxidant damage via the nitric oxide-cGMP pathway

OBJECTIVE

Aspirin is known to exert cytoprotection by presently unidentified mechanisms. This study investigates the involvement of nitric oxide (NO) in antioxidant cellular protection induced by aspirin.

METHODS AND RESULTS

A 24-hour incubation with hydrogen peroxide markedly reduced viability of cultured endothelial cells. Preincubation with aspirin (3 to 30 micromol/L) protected endothelial cells from hydrogen peroxide-mediated toxicity and increased viability in a concentration-dependent fashion by up to 95% of control. This effect was specific in that other nonsteroidal anti-inflammatory drugs, such as salicylate or indomethacin, did not alter hydrogen peroxide toxicity. Aspirin-induced endothelial protection was abrogated in the presence of the NO scavenger PTIO (30 micromol/L) and the inhibitor of soluble guanylyl cyclase ODQ (1 micromol/L). Moreover, the l-arginine antagonist L-NMMA (25 micromol/L), but not its D-enantiomer, led to complete inhibition of aspirin-dependent cytoprotection. Correspondingly, aspirin enhanced NO synthase activity (citrulline formation) and intracellular cyclic GMP accumulation in endothelial cells. Protein expression of endothelial NO synthase remained unaffected in the presence of aspirin.

CONCLUSIONS

Our data suggest that endothelial NO synthase is a site of action of aspirin and that the NO/cyclic GMP system assumes a crucial function in mediating the cytoprotective action of aspirin.

Effect of different metal ions on the oxidative damage and antioxidant capacity of hyaluronic acid

Degradation and the antioxidative effect of Na-, Zn-, Co-, Cu-, and Mn-hyaluronic acid (HA) associates were studied. Our findings revealed the protective effect of certain counterions against ROS-induced HA degradation. We could also separate the antioxidative effect of certain counterions from that of the HA by examining the effect of the counterions in their free ionic forms. The result showed that metal ions with altering oxidative status (Co(2+), Cu(2+), Mn(2+)) proved to be effective in themselves or their effect added to that of HA when HA was also effective. Moreover, the effects of Co-HA against z.rad;O(2)(-) and of Mn-HA against ONOO(-) as well as the synergic effect of Zn-HA associates where Zn(2+) is of fixed oxidative status were attributed to the structure-stabilizing complex formed between certain counterions and HA. Our examination also concerned the influence of HA associates on the indirect antioxidation related to Fe(2+) chelating. The individual effects of Zn(2+), Co(2+), and Cu(2+) were only detectable, which could be explained by the competitive displacement of ferrous from its binding site.

Chelating activity of advanced glycation end-product inhibitors

The advanced glycation end-product (AGE) hypothesis proposes that accelerated chemical modification of proteins by glucose during hyperglycemia contributes to the pathogenesis of diabetic complications. The two most commonly measured AGEs, N(epsilon)-(carboxymethyl)lysine and pentosidine, are glycoxidation products, formed from glucose by sequential glycation and autoxidation reactions. Although several compounds have been developed as AGE inhibitors and are being tested in animal models of diabetes and in clinical trials, the mechanism of action of these inhibitors is poorly understood. In general, they are thought to function as nucleophilic traps for reactive carbonyl intermediates in the formation of AGEs; however alternative mechanisms of actions, such as chelation, have not been rigorously examined. To distinguish between the carbonyl trapping and antioxidant activity of AGE inhibitors, we have measured the chelating activity of the inhibitors by determining the concentration required for 50% inhibition of the rate of copper-catalyzed autoxidation of ascorbic acid in phosphate buffer. All AGE inhibitors studied were chelators of copper, as measured by inhibition of metal-catalyzed autoxidation of ascorbate. Apparent binding constants for copper ranged from approximately 2 mm for aminoguanidine and pyridoxamine, to 10-100 microm for carnosine, phenazinediamine, OPB-9195 and tenilsetam. The AGE-breakers, phenacylthiazolium and phenacyldimethylthiazolium bromide, and their hydrolysis products, were among the most potent inhibitors of ascorbate oxidation. We conclude that, at millimolar concentrations of AGE inhibitors used in many in vitro studies, inhibition of AGE formation results primarily from the chelating or antioxidant activity of the AGE inhibitors, rather than their carbonyl trapping activity. Further, at therapeutic concentrations, the chelating activity of AGE inhibitors and AGE-breakers may contribute to their inhibition of AGE formation and protection against development of diabetic complications.

Protective effects of aspirin and vitamin E (alpha-tocopherol) against copper- and cadmium-induced toxicity

A 24-h exposure to copper (400 microM, 600 microM) or cadmium (5 microM, 10 microM) significantly reduces the viability of COS-7 cells. A 2-h preincubation with vitamin E does not protect COS-7 cells from copper-induced toxicity, but does protect against cadmium-induced toxicity. Preincubation with aspirin protects cells from both copper- and cadmium-induced toxicity. A combination of aspirin and vitamin E (10 microM and 25 microM, respectively) increases cell viability in copper-exposed cells in a clearly additive manner, while in cadmium-exposed cells the effects are slightly additive. These results indicate that aspirin and vitamin E can protect cells from metal-induced toxicity. Differences in the protective effects of aspirin and vitamin E on copper versus cadmium-induced toxicity may be due to alternative mechanisms of metal toxicity or antioxidant activity.

Antidenaturant drugs for cataract and other condensation diseases

'Condensation diseases' are heterogeneous pathological conditions in which the primary pathogenetic step is the loss of solubility of specific substances, resulting in the formation of a condensed phase. Typical examples are cataract, nephrolithiasis, gallstone disease and certain rheumatic conditions in which protein denaturation, aggregation and precipitation may occur. Since the condensing molecules are often proteins, antidenaturant agents should be considered rational drugs for the treatment of these diseases. Surprisingly, however, only a few molecules with these properties are currently available for therapeutic use, including bendazac for cataract.

Preventive aspirin treatment of streptozotocin induced diabetes: blockage of oxidative status and revertion of heme enzymes inhibition

Some late complications of diabetes are associated with alterations in the structure and function of proteins due to glycation and free radicals generation. Aspirin inhibits protein glycation by acetylation of free amino groups. In the diabetic status, it was demonstrated that several enzymes of heme pathway were diminished. The aim of this work has been to investigate the in vivo effect of short and long term treatment with acetylsalicylic acid in streptozotocin induced diabetic mice. In both treatments, the acetylsalicylic acid prevented delta-aminolevulinic dehydratase and porphobilinogen deaminase inactivation in diabetic mice and blocked the accumulation of lipoperoxidative aldehydes. Catalase activity was significantly augmented in diabetic mice and the long term treatment with aspirin partially reverted it. We propose that oxidative stress might play an important role in streptozotocin induced diabetes. Our results suggest that aspirin can prevent some of the late complications of diabetes, lowering glucose concentration and probably inhibiting glycation by acetylation of protein amino groups.

Effects of phenolic antioxidants and flavonoids on DNA synthesis in rat liver, spleen, and testis in vitro

Paracetamol (acetaminophen) and hydroxyurea were found to inhibit DNA synthesis in a dose-dependent manner in tissue slices in vitro, with little effect on protein synthesis. Considerable variation in the sensitivity of the different tissues was also observed with an order of least sensitive to most sensitive tissue of liver < testis < spleen. The phenolic antioxidant properties of paracetamol are thought to be the mechanism by which paracetamol inhibits DNA synthesis, which led us to study other phenolic antioxidant molecules and flavonoids for specific inhibition of DNA synthesis. (+)-catechin, m-aminophenol, p-aminophenol and p-cresol all displayed a highly specific inhibition of DNA synthesis. Quercetin displayed a preferential inhibition of DNA synthesis but a significant level of inhibition of protein synthesis was also seen. Nordihydroguaiaretic acid (NDGA) and n-propyl gallate showed preferential inhibition of DNA synthesis at the lower doses tested, but at higher doses showed significant inhibition of protein synthesis, presumably because of cytotoxicity. Caffeic acid and naringenin did not display any specific inhibition of DNA synthesis as protein synthesis was equally inhibited at all doses tested. This study demonstrates that certain phenolic antioxidants can inhibit DNA synthesis specifically but this is not a property shared by all phenolic antioxidants; and that these inhibitors show considerable variation in effectiveness between different tissues.

Inhibition of bacterial adherence to a high-water-content polymer by a water-soluble, nonsteroidal, anti-inflammatory drug

Deposition and aggregation of lachrymal proteins on the contact lens surface can promote bacterial adherence. Lysozyme is the major tear protein and is also mainly responsible for the formation of protein deposits on contact lenses. Nonsteroidal anti-inflammatory drugs (NSAID) prevent protein aggregation. The effect of a water-soluble NSAID drug on bacterial adherence to high-water-content/ionic disposable contact lenses was examined in a radiolabeling study. Dose-related inhibition of adherence of Staphylococcus aureus, S. epidermidis, and Pseudomonas aeruginosa on both pretreated lenses and after adding the drug to the medium was investigated. When the drug was added to the media, maximal inhibition of S. aureus adherence was observed in trypticase soy broth (59-98% at the lower and higher drug concentrations, respectively); inhibition progressively decreased in calf aqueous humor (48-75%), lysozyme (34-63%), and saline (12-20%) solutions. Inhibition of adherence varied with the three bacterial species; it was maximal with S. aureus, intermediate with S. epidermidis, and minimal with P. aeruginosa. When lenses were pretreated with the drug, consistent, and even higher, inhibitory effects were observed. The results suggest that water-soluble NSAIDs could be used in preventive treatments for conjunctivae and corneal infections in contact lens wearers, and may provide a clue as to which compounds might inhibit protein interaction and bacterial adhesion.

Aspirin increases ferritin synthesis in endothelial cells: a novel antioxidant pathway

Aspirin has recently been shown to increase endothelial resistance to oxidative damage. However, the mechanism underlying aspirin-induced cytoprotection is still unknown. Using cultured cells, the present study investigates the effect of aspirin on the expression of ferritin, a cytoprotective protein that sequesters free cytosolic iron, the main catalyst of oxygen radical formation. In bovine pulmonary artery endothelial cells, aspirin at low antithrombotic concentrations (0.03 to 0.3 mmol/L) induced the synthesis of ferritin protein in a time- and concentration-dependent fashion up to 5-fold over basal levels, whereas ferritin H (heavy chain) mRNA remained unaltered. Aspirin-induced cytoprotection from hydrogen peroxide toxicity was mimicked by exogenous iron-free apoferritin but not iron-loaded ferritin, demonstrating the antioxidant function of newly synthesized ferritin under these conditions. Ferritin induction by aspirin was specific in that other nonsteroidal anti-inflammatory drugs such as salicylic acid, indomethacin, or diclofenac failed to alter ferritin protein levels. Aspirin-induced ferritin synthesis was abrogated in the presence of the iron chelator desferrioxamine, pointing to an interaction of aspirin with iron-responsive activation of ferritin translation. Together, our results suggest induction of ferritin as a novel mechanism by which aspirin may prevent endothelial injury in cardiovascular disease, eg, during atherogenesis.

Association between body iron stores and the risk of acute myocardial infarction in men

BACKGROUND

Epidemiological evidence concerning the role of iron, a lipid peroxidation catalyst, in coronary heart disease (CHD) is inconsistent. We investigated the association of the concentration ratio of serum transferrin receptor to serum ferritin (TfR/ferritin), a state-of-the-art measurement of body iron stores, with the risk of acute myocardial infarction (AMI) in a prospective nested case-control study in men from eastern Finland.

METHODS AND RESULTS

Transferrin receptor assays were carried out for 99 men who had an AMI during an average 6.4 years of follow-up and 98 control men. Both the cases and the controls were nested from the Kuopio Ischemic Heart Disease Risk Factor Study (KIHD) cohort of 1931 men who had no clinical CHD at the baseline study. The controls were matched for age, examination year, and residence. AMIs were registered prospectively. Soluble transferrin receptors were measured by immunoenzymometric assay and ferritin concentration by radioimmunoassay from frozen baseline serum samples. The mean TfR/ferritin ratio was 15.1 (SE, 2.0) among cases and 21.3 (SE, 2.2) among controls (P=.035 for difference). In logistic regression models adjusting for other strongest risk factors for AMI and indicators of inflammation and alcohol intake, men in the lowest and second lowest thirds of the TfR/ferritin ratio had a 2.9-fold (95% CI, 1.3 to 6.6, P=.011) and 2.0-fold (0.9 to 4.2, P=.081) risk of AMI compared with men in the highest third (P=.010 for trend).

CONCLUSIONS

These data show an association between increased body iron stores and excess risk of AMI, confirming previous epidemiological findings.

Acetaminophen protection against estramustine-induced cytotoxicity on cultured fibroblasts

Two commonly used analgesics, ibuprofen and acetaminophen (paracetamol) were investigated for possible influence on Chinese hamster fibroblast (V-79) cytotoxicity (measured by cells cloning ability and 86Rb accumulation) of the anti-neoplastic drugs estramustine and bleomycin in vitro. Fibroblast exposure to estramustine (80 mg/l) or bleomycin (50 mg/l), for 1 or 24 hr, reduced the number of surviving clones to approximately 35% and 50% respectively. Acetaminophen (10 or 100 mg/l), but not ibuprofen, significantly increased the number of surviving clones with estramustine. The analgesics had no effect on bleomycin cytotoxicity. The uptake of 86Rb+ (K+ analogue) by V-79 cells was reduced after incubation with 80 mg/l estramustine phosphate. Acetaminophen (30 mg/l) but not 10 mg/l acetaminophen or ibuprofen (30 or 100 mg/l), significantly protected against estramustine reduction of 86Rb accumulation. Acetaminophen inhibition of estramustine cytotoxicity is suggested to be due to reversal of estramustine-induced inhibition of cellular potassium channel ion transport.

Aspirin protects endothelial cells from oxidative stress--possible synergism with vitamin E

A 24-h incubation with hydrogen peroxide (0.65 mM) markedly reduced viability of cultured endothelial cells. Preincubation with aspirin (3-30 microM) protected endothelial cells from hydrogen peroxide-induced toxicity and increased viability in a concentration-dependent fashion by up to 64% of control. A similar protection was observed with D-alpha-tocopherol acetate (vitamin E, 3-30 microM). The cytoprotective effects of aspirin and vitamin E against hydrogen peroxide were overadditive suggesting different mechanisms of antioxidant action. In agreement with this, cytotoxicity induced by iron, the main catalyst of oxygen radical formation, was substantially reduced by aspirin but not vitamin E. These results show that aspirin protects endothelial cells from oxidative stress possibly via binding or chelation of free cytosolic iron. Moreover, a combination of aspirin and vitamin E might be useful for the prevention of endothelial injury in cardiovascular disease, e.g. during atherogenesis.

Radical scavenger activity of bendazac, an anticataract non-steroidal anti-inflammatory agent

Oxidative damage to lens components is associated with cataract formation and reactive oxygen species (ROS) overproduction at inflammation sites is thought to lead to the development of inflammatory disorders. Bendazac is a non-steroidal anti-inflammatory drug able to delay the cataractogenic process. Aim of the present study is to characterize, both chemically and biologically, the activity of this anticataract agent as a radical scavenger. Bendazac has been shown to be a strong reacting substrate in a chemical oxidizing system, which mimics a physiological pathway of hydroxy radical generation. In the Fenton-Cier reaction the drug rapidly forms a mixture of hydroxylated derivatives, among which 5-hydroxybendazac, bendazac's main metabolite, being a hydroxy radical scavenger itself. Moreover, by means of a rapid and sensitive flow cytometric method able to determine reactive oxygen intermediate production, bendazac and its 5-hydroxy derivative were shown to inhibit oxidative burst activation in polymorphonuclear neutrophil leukocytes (PMNLs).

H2-receptor antagonists are scavengers of oxygen radicals

Potential oxygen radical scavenging properties of the H2-receptor antagonists cimetidine, ranitidine and famotidine were investigated. These drugs, although ineffective against superoxide anion and hydrogen peroxide, can scavenge hydroxyl radical (OH.) with a very high rate constant, which is about tenfold higher than that of the specific scavenger mannitol for famotidine (1.7 x 10(10) mol-1 s-1) and cimetidine (1.6 x 10(10) mol-1 s-1), ranitidine displaying a rate constant of 7.5 x 10(9) mol-1 s-1. These OH. savenging effects are significant beginning from 10, 28 and 100 mumol l-1 concentration for famotidine, cimetidine and ranitidine, respectively, thus suggesting that the drugs may effectively act as OH. scavengers in vivo especially in the gastric lumen. Only cimetidine can apparently bind and inactivate iron, which further emphasizes its antioxidant capacity. Moreover, all drugs, even at 10 mumol l-1 concentration, show powerful scavenging effects on hypochlorous acid and monochloramine, which are cytotoxic oxidants arising from inflammatory cells, such as neutrophils. These data suggest that some therapeutical effects of H2-receptor antagonists in peptic ulcer may also be related to their antiradical-antioxidant capacity, and that these drugs could potentially be used in other disease entities characterized by free radical-mediated oxidative stress in vivo.

Purpurogallin as an antioxidant protector of human erythrocytes against lysis by peroxyl radicals

Purpurogallin, a flavinol obtainable from oak nutgalls, prevented lysis of human erythrocytes exposed to an azo-initiator of peroxyl radicals [2,2'-azo-bis (2-amidinopropane) dihydrochloride] at 37 degrees C. The percentage of this inhibition of erythrocyte lysis varied with the concentration of purpurogallin. In this system, the effect of purpurogallin surpassed those of lactosylphenyl-trolox, trolox and ascorbate, while mannitol, superoxide dismutase and/or catalase were without effect. While other concurrent mechanisms may be involved in purpurogallin action, it would appear that the amphipathic (both hydrophilic and lipophilic) nature of this flavinol and of trolox and lactosylphenyl-trolox, is an important factor. In fact, these three antioxidants, with purpurogallin as the best red cell protector here, excelled the protective effects of the other more hydrophilic antioxidants.

Heparin: does it act as an antioxidant in vivo?

Previous studies have shown that heparin antagonizes oxygen radical-mediated injury to endothelial cells, suggesting an antioxidant role of the drug. In the present investigation, the hypothesis that heparin exerts direct antioxidant effects was tested in several experimental models. We have found that 1, 3, 5, 10, 20, 40 and 80 U/mL of heparin do not scavenge superoxide anion, hydrogen peroxide, hydroxyl radical or the stable free radical 1,1-diphenyl-2-pycrylhydrazyl. Moreover, the drug is ineffective towards iron-driven linolenic acid peroxidation, autooxidation of brain homogenate and linolenic acid peroxidation mediated by human internal mammary artery homogenate. Specific studies on the potential iron-binding-inactivating capacity of heparin prove the drug to be totally ineffective. Finally, the loss of protein sulphydryls from human plasma induced by hypoxanthine-xanthine oxidase-generated oxygen radicals is not prevented by heparin. In conclusion, heparin, even at concentrations far higher than those usually used therapeutically, has no direct antioxidant properties. Thus, other mechanisms not strictly antioxidant-type must be involved in heparin-mediated cell protection against toxic oxygen metabolites.

Pharmacological treatment strategies in age-related cataracts

Cataract is the major cause of blindness worldwide and at present the only approved treatment in many countries including the UK and USA is surgical removal of the lens. In other countries various anti-cataract drugs are available without proof of their efficacy. Research is continuing into the possible benefits of several groups of drugs and some vitamins. The first to be studied were sorbitol-lowering agents (aldose reductase inhibitors) based on the sorbitol hypothesis for diabetic cataract. Sorbitol-lowering agents have distinct effects in vitro and many of them delay the development of cataract in galactose-fed rats. A few delay cataract in diabetic rats but none have been proved effective in clinical trials, although these continue. Aspirin, paracetamol (acetaminophen) and ibuprofen delay diabetic cataract in rats, and have been shown to delay other experimental cataracts. Case-control studies from 3 continents indicate that these drugs, or at least aspirin, protect against cataract. Results of studies on all 3 drugs indicate a benefit even at low doses. Population-based studies did not identify any protection against early lens opacities but tiny opacities that do not impair vision are not a problem. Bendazac protects lens proteins in vitro and delays cataractogenesis in x-irradiated rats. In humans, it reached the clinical trial stage but most trials have been small and with subjective criteria of opacification. One objectively monitored trial suffered from a high drop-out rate. Other preparations studied less extensively include vitamins, aminoguanidine to prevent protein cross-linking in diabetes and agents designed to boost glutathione levels. It is probable that some agents which may delay or prevent cataract will be proved effective soon, and in the end there may be different drugs to delay cataract in different high risk groups. This is what might be expected of a multifactorial disease, although compounds that intervene in the final common pathways to cataract could have a broad efficacy.

Spirohydantoin inhibitors of aldose reductase inhibit iron- and copper-catalysed ascorbate oxidation in vitro

Transition metal-catalysed oxidations have been implicated in the complications of diabetes. We report here that some experimental inhibitors of the enzyme aldose reductase (implicated in diabetes mellitus via its ability to catalyse glucose reduction to sorbitol) are also potent inhibitors of transition metal-catalysed ascorbate oxidation. The inhibition appears to be dependent upon the presence of a spirohydantoin group. It is conceivable that the copper- and iron-binding capacity of these compounds may contribute to some of their observed biological effects and may provide a starting point for a new generation of experimental drugs for the treatment of diabetes mellitus.