The antiinflammatory action of some compounds with antioxidant properties

Anti-inflammatory action of new hybrid N-acyl-[1,2]dithiolo-[3,4-c]quinoline-1-thione

Most of pharmaceutical agents display a number of biological activities. It is obvious that testing even one compound for thousands of biological activities is not practically possible. A computer-aided prediction is therefore the method of choice in this case to select the most promising bioassays for particular compounds. Using the PASS Online software, we determined the probable anti-inflammatory action of the 12 new hybrid dithioloquinolinethiones derivatives. Chemical similarity search in the World-Wide Approved Drugs (WWAD) and DrugBank databases did not reveal close structural analogues with the anti-inflammatory action. Experimental testing of anti-inflammatory activity of the synthesized compounds in the carrageenan-induced inflammation mouse model confirmed the computational predictions. The anti-inflammatory activity of the studied compounds (2a, 3a-3k except for 3j) varied between 52.97% and 68.74%, being higher than the reference drug indomethacin (47%). The most active compounds appeared to be 3h (68.74%), 3k (66.91%) and 3b (63.74%) followed by 3e (61.50%). Thus, based on the in silico predictions a novel class of anti-inflammatory agents was discovered.

Novel Antioxidant, Deethylated Ethoxyquin, Protects against Carbon Tetrachloride Induced Hepatotoxicity in Rats by Inhibiting NLRP3 Inflammasome Activation and Apoptosis

Inflammation and an increase in antioxidant responses mediated by oxidative stress play an important role in the pathogenesis of acute liver injury (ALI). We utilized in silico prediction of biological activity spectra for substances (PASS) analysis to estimate the potential biological activity profile of deethylated ethoxyquin (DEQ) and hypothesized that DEQ exhibits antioxidant and anti-inflammatory effects in a rat model of carbon tetrachloride (CCl₄)-induced ALI. Our results demonstrate that DEQ improved liver function which was indicated by the reduction of histopathological liver changes. Treatment with DEQ reduced CCl₄-induced elevation of gene expression, and the activity of antioxidant enzymes (AEs), as well as the expression of transcription factors Nfe2l2 and Nfkb2. Furthermore, DEQ treatment inhibited apoptosis, downregulated gene expression of pro-inflammatory cytokines (Tnf and Il6), cyclooxygenase 2 (Ptgs2), decreased glutathione (GSH) level and myeloperoxidase (MPO) activity in rats with ALI. Notably, DEQ treatment led to an inhibition of CCl₄-induced NLRP3-inflammasome activation which was indicated by the reduced protein expression of IL-1β, caspase-1, and NLRP3 in the liver. Our data suggest that DEQ has a hepatoprotective effect mediated by redox-homeostasis regulation, NLRP3 inflammasome, and apoptosis inhibition, which makes that compound a promising candidate for future clinical studies.

2 Final Report on the Safety Assessment of Butylated Hydroxyanisole

Butylated hydroxyanisole (BHA) is used in cosmetic formulations as a chemical preservative and as an antioxidant. Both animal and human studies have shown that BHA is absorbed from the gastrointestinal tract and metabolized. Tissue storage may occur with BHA because of its lipid solubility. However, the amount stored is limited by rapid metabolism and excretion. Reported acute oral LD50 values for BHA in rats varied from 2.0 to > 5.0 g/kg. Formulations containing BHA elicited, at most, minimal or moderate skin and eye irritation in rabbits. An extensive number of subchronic and chronic oral studies have been conducted and are reviewed.

BHA given orally or parenterally to mice and rats was shown to inhibit the carcinogenic effects of a broad range of chemical carcinogens. BHA has been shown to inhibit mutagenesis and was not a mutagenic agent in standard in vitro tests. No evidence of carcinogenicity was observed when BHA was administered to mice by subcutaneous injection, by intraperitoneal injection, or by topical application. No carcinogenesis was demonstrated following dietary administration of BHA to either rats or dogs. An increased incidence of forestomach papillomas and squamous cell carcinomas has been observed in rats fed BHA. Studies with pregnant rabbits, mice, rats, and hamsters receiving BHA during gestation by a variety of oral dosage regimens revealed no significant embryotoxic or teratogenic effects.

Clinical data for BHA in cosmetic formulations indicated that they were generally nonsensitizing, nonphotosensitizing, and only minimally or mildly irritating. It is concluded that BHA is safe as a cosmetic ingredient in the present practices of use.

Properties of hydrogen peroxide-induced histamine release from rat mast cells

Incubation of rat peritoneal mast cells with hydrogen peroxide results in a marked release of histamine. Maximal release is observed with 0.05-0.1 mM H(2)O(2), but higher concentrations of H(2)O(2) instead suppresses the release. Histamine release starts after about 2 min of lag time and reaches a plateau in about 10 min. Hydrogen peroxide-induced release does not exceed 50-60 per cent of total histamine if the incubations are prolonged or additional H(2)O(2) is given at 10 min. This would be explained by the fact that H(2)O(2) causes impairment of the histamine releasing system of mast cells simultaneously with the release of histamine. Hydrogen peroxide-induced release is not due to nonspecific lysis of the cells because lactate dehydrogenase, a cytoplasmic enzyme, is not liberated during the reaction. The reaction requires the presence of Ca(2+), is enhanced by D(2)O and suppressed by colchicine. It is not, however, affected by dibutyryl cAMP or dibutyryl cGMP. No significant alteration of intracellular levels of cyclic AMP and cyclic GMP is observed during the incubation of mast cells with 0.1 mM H(2)O(2). These results indicate that microtubular functions would be involved in the releasing reaction although they are not under the control of cyclic nucleotides. Microscopic observation shows that H(2)O(2)-induced release is accompanied by degranulation.

Protective effect of the antioxidant 6-ethoxy-2,2-pentamethylen-1,2-dihydroquinoline (S 33113) in models of cerebral neurodegeneration

In a previous study Dorey et al. [Bio. Org. Chem. Lett., 10 (2000) 935] a series of novel dihydroquinoline compounds were developed, based on the potent antioxidant 6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline (ethoxyquin), and permitted the selection of the analogue 6-ethoxy-2,2-pentamethylen-1,2-dihydroquinoline (S 33113) lacking the hypothermic effects associated with ethoxyquin at equivalent doses. Herein, an extensive investigation of the neuroprotective capacity of S 33113 in different in vitro and in vivo paradigms of oxidative stress-mediated cellular degeneration was undertaken. In vitro S 33113 was a potent inhibitor (IC(50) = 0.29 microM) of Fenton-reaction-induced lipid peroxidation in mouse cortical membranes. Administration of S 33113 either intraperitoneally (< or =150 mg/kg i.p.) or orally (< or =600 mg/kg p.o.) did not significantly modify body temperature in NMRI mice. Furthermore, S 33113 (150 mg/kg i.p. or 600 mg/kg p.o.) markedly reduced the lethality induced by an intracerebroventricular injection of t-butylhydroperoxide in NMRI (naval medical research institute) mice for up to 5 h. Oral administration of S 33113, significantly attenuated alloxan-mediated hyperglycaemia in NMRI mice at 400 and 600 mg/kg (60%; P < 0.001). Administration of S 33113 (150 mg/kg i.p.) 30 min before transient global ischaemia significantly prevented delayed neuronal cell death in the CA1 region of the rat hippocampal formation, 7 days post-ischaemia (33% cell loss vs. 88% in ischaemia controls; P < 0.001). Similarly, a single pre-administration of S 33113 (150 mg/kg i.p.) prevented kainic acid-induced cell death in the CA3 hippocampal region at 7 days post-exposure (17% cell loss vs. 52% in kainate-treated controls; P < 0.01). Furthermore, D-methamphetamine-mediated dopamine depletion in the striatum of C57BL/6 mice (39-46%) was significantly prevented with S 33113 administered at either (2 x 150mg/kg i.p.) (11%; P < 0.01) or (2x150 mg/kg p.o.) (17%; P < 0.001). In conclusion, S 33113 represents a novel dihydroquinoline compound with potential for the treatment of cerebral pathologies implicating chronic neurodegeneration.

Scavenging effect of benzophenones on the oxidative stress of skeletal muscle cells

Benzophenone is an ultraviolet (UV)-absorbing agent that has been used in industry and medicine for more than 30 years. Consumers of cosmetics and sunscreens containing UV-absorbers are exposed to benzophenones on a daily basis, owing to the widespread use of these compounds. However, the efficacy of these compounds as scavengers of oxidative stress is still not well established. In the present study, we investigate the antioxidative capacity of six sunscreen benzophenone compounds. A primary myoblast culture was mixed in vitro with 100 microM menadione. The cytotoxic effect by menadione-induced oxidative stress was monitored by the lucigenin- or luminol-amplified chemiluminescence, methylthiotetrazole (MTT) assay, and the antioxidative effects of various benzophenone compounds were evaluated. The results showed that the addition of menadione can induce oxidative stress on myoblasts by superoxide and hydrogen peroxide production, which can be eradicated by superoxide dismutase (SOD) and catalase, respectively, in a dose-dependent mode. The catalase has a protective effect on the cytotoxicity induced by menadione as measured by the MTT assay, while the SOD does not. The selected benzophenones also have a significant scavenging effect on the menadione-induced cell death on the myoblasts. The ortho-dihydroxyl structure and other hydroxy groups in the same ring have a stronger scavenging effect on the superoxide anion on myoblasts; thus, a stable penoxy radical may be formed. The mechanism of this effect remains to be clarified.

Effects of indole-3-acetic acid on croton oil- and arachidonic acid-induced mouse ear edema

The indole-3-acetic acid (IAA) is a plant growth hormone (auxin) being considered as a tryptophan metabolite in animals. The main purpose of this work was to verify IAA's topical anti-inflammatory action using croton oil- or arachidonic acid-induced mouse ear edema, in comparison to known anti-inflammatory agents. IAA antioxidant activity was also verified by measuring the inhibition of brain homogenate lipid peroxidation with the thiobarbituric acid reactive substances (TBARS) test. IAA inhibited the action of both croton oil-and arachidonic acid-induced edema in a dose-dependent manner (4.0 mumoles IAA inhibited 75.8% in croton oil and 82.5% in arachidonic acid induced ear edema). Both IAA (5.3 mM) and indomethacin (8.0 mM) inhibited TBARS formation. Data suggest that IAA exhibits antiinflammatory effect possibly by its anti-oxidant activity.

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

Production of free radicals from molecular oxygen during the inflammatory process can exhibit beneficial effects against the phlogistic stimulus and may act as a defence mechanism. Nevertheless, in many cases this production is associated with toxic reactions related to inflammatory response. Many compounds including bovine superoxide dismutase, non steroidal anti-inflammatory drugs, radical scavengers (e.g. acetaminophen), corticoids etc., have been shown to counteract this phenomenon. Their beneficial effects and mechanism of action are reviewed.

2,6-Di-tert-butyl-4-(2'-thenoyl)phenol(R-830): a novel nonsteroidal anti-inflammatory agent with antioxidant properties

R-830, a di-tert-butylphenol, has been shown to be anti-inflammatory in a number of animal models. These include conventional systems such as carrageenan-induced edema and adjuvant arthritis of the rat and ultraviolet-induced erythema in the guinea pig in which the acidic nonsteroidal anti-inflammatory drugs (e.g., indomethacin) are effective. The anti-inflammatory activity of R-830 has also been demonstrated in other models (e.g., graft vs. host reaction and reversed passive cutaneous Arthus reaction in the rat, contact sensitivity in the mouse) in which the acidic nonsteroidal drugs are not effective. In vitro, R-830 inhibits guinea pig lung lipoxygenase and bovine seminal vesicle cyclo-oxygenase. The antioxidant properties of R-830 were demonstrated in two in vitro systems. We speculate that the antioxidant activity of this molecule might be related to its unusual profile of pharmacological activity.

Influence on retrolental fibroplasia of intramuscular vitamin E administration during respiratory distress syndrome

The effect of vitamin E administered during the acute phase of therapy for respiratory distress syndrome (RDS) on the development of retinopathy of prematurity (ROP) was evaluated in a randomized double-masked study. One hundred neonates received either vitamin E or placebo intramuscularly within the first 24 hours of birth and at 24, 48, and 168 hours respectively. Additional doses were given twice weekly while the infant remained in an oxygen-enriched environment and could not tolerate feedings and vitamin supplements. Parenteral vitamin E-treated infants had significantly increased serum vitamin E levels compared to placebo-treated infants. Most placebo-treated patients attained normal serum vitamin E levels during the second week of life because of nutritional sources of vitamin E. Infants in both groups had RDS of similar severity. Seventy-four infants, 37 vitamin E-treated and 37 placebo-treated, survived longer than 10 days and had ophthalmologic examinations. Active changes of Stage I and Stage II ROP were noted in 17 of those patients; 9 (24.3%) vitamin E-treated and 8 (21.6%) placebo-treated patients (P = 0.572). No infants developed severe cicatricial changes, and their retinal findings regressed. The incidence of risk factors associated with ROP development occurred equally in the vitamin E-treated and placebo-treated infants that developed ROP. Thus, vitamin E-administration as described in this study did not result in any further reduction in the incidence of the active stages of ROP over that seen with standard neonatal care, which included daily oral Vitamin E supplements.

Agents which block membrane lipid peroxidation enhance mouse spleen cell immune activities in vitro: relationship to the enhancing activity of 2-mercaptoethanol

A broad spectrum of agents known to block various steps in the lipid peroxidation process were tested for their ability to protect mouse spleen cells and thereby enhance their activities, in vitro, in either the primary antibody response or the lipopolysaccharide-stimulated proliferation response. Each agent (superoxide dismutase, butylated hydroxyanisole/butylated hydroxytoluene/n-propyl gallate, lucigenin, and alpha-tocopherol) was able to enhance the cellular response in both assay systems. The degree of enhancement of these immune functions was in proportion to the efficacy of each agent in blocking the overall process in lipid peroxidation. Previous work in this laboratory has shown that the enhancement of the primary antibody response by 2-mercaptoethanol (2-ME) is mediated by the enhanced availability of reduced glutathione in the culture medium. Suboptimal doses of each lipid antioxidant agent were able to enhance the antibody response in the additive manner with a suboptimal dose of 2-ME up to a maximum response equal to that achieved with an optimal dose of 2-ME alone. These data support the hypothesis that the enhancement of cellular responses in the presence of 2-ME is mediated by the lipid antioxidant activity of reduced glutathione.

Structure-activity relationships for inhibition of prostaglandin cyclooxygenase by phenolic compounds

Sixty-three phenolic compounds were examined for their ability to inhibit sheep vesicular gland prostaglandin cyclooxygenase. Examination of structure-activity relationships for these compounds indicated that inhibition was increased by ring substituents which were electron donating and by substituents which were hydrophobic. Inhibition was decreased by steric masking of the phenolic hydroxyl. The most potent inhibitors possessed a two aromatic ring structure connected by a short bridge. In these inhibitors, one ring was apolar, the other ring contained a phenolic hydroxyl ortho to the bridge, and the bridge contained a Lewis base such that the compounds could form bidentate metal chelates. Compounds with [I]50 values of less than 10 mM included 2,4,6-trimethylphenol, 7.2 microM; 2-(2-hydroxyphenyl)benzothiazole, 7.0 microM; 2-benzyloxyphenol, 5.2 microM; and 2-hydroxybenzophenone, 3.8 microM. Inhibition of arachidonate induced platelet aggregation was examined for three of the more potent inhibitors. 2-Benzyloxyphenol and 2,4,6-trimethylphenol were more potent than indomethacin when assayed using a 2 min preincubation of inhibitor with platelets.

Observations of vitamin E in experimental oxygen-induced retinopathy

Retrolental fibroplasia (RLF) is a proliferative retinopathy observed in premature infants. Its relationship to oxygen has led to both clinical and laboratory research into the potential benefits of the antioxidant tocopherol in this disorder. Although the clinical trials to date have only suggested a beneficial result, studies in the kitten model demonstrate two significant actions of tocopherol in protecting against this retinopathy, only one of which is predicted by theory. These data support the need for prospective controlled trials in human premature infants.