Tocopherylquinone and tocopherylhydroquinone

Abstract

Tocopherylquinone (TQ) is formed in the antioxidant action of tocopherol (T). TQ was found in human subjects and it was observed that the ratio αTQ/ αT increased in general with increasing oxidative stress. TQ is reduced to tocopheryl hydroquinone (TQH₂) but the ratio TQH₂/TQ in vivo has not been reported. TQH₂ acts as a potent radical-scavenging antioxidant. αTQH₂ is more reactive toward radicals than ubiquinol, a reduced form of coenzyme Q, and αT. The overall efficacy of TQH₂ as an antioxidant is determined by the fate of semiquinone radical formed from TQH₂ as well as the reactivity toward oxygen radicals. Partly substituted γTQ, but not αTQ, exerts cytotoxicity by both redox cycling and reaction with protein thiols and glutathione.     

Comparative study on dynamics of antioxidative action of alpha-tocopheryl hydroquinone, ubiquinol, and alpha-tocopherol against lipid peroxidation.

Alpha-tocopheryl quinone is a metabolite of alpha-tocopherol (TOH) in vivo. The antioxidant action of its reduced form, alpha-tocopheryl hydroquinone (TQH2), has received much attention recently. In the present study, the antioxidative activity of TQH2 was studied in various systems in vitro and compared with that of ubiquinol-10 (UQH2) or TOH to obtain the basic information on the dynamics of the antioxidant action of TQH2. First, their hydrogen-donating abilities were investigated in the reaction with galvinoxyl, a stable phenoxyl radical, and TQH2 was found to possess greater second-order rate constant (1.0 x 10(4) M(-1) s(-1)) than UQH2 (6.0 x 10(3) M(-1) s(-1)) and TOH (2.4 x 10(3) M(-1) s(-1)) at 25 degrees C in ethanol. The stoichiometric numbers were obtained as 1.9, 2.0, and 1.0 for TQH2, UQH2, and TOH, respectively, in reducing galvinoxyl. Second, their relative reactivities toward peroxyl radicals were assessed in competition with N,N'-diphenyl-p-phenylenediamine (DPPD) and found to be 6.0 (TQH2), 1.9 (UQH2), and 1.0 (TOH). Third, their antioxidant efficacies were evaluated in the oxidation of methyl linoleate in organic solvents and in aqueous dispersions. The antioxidant potency decreased in the order TOH > UQH2 > TQH2, as assessed by either the extent of the reduction in the rate of oxidation or the duration of inhibition period. The reverse order of their reactivities toward radicals and their antioxidant efficacies was interpreted by the rapid autoxidation of TQH2 and UQH2, carried out by hydroperoxyl radicals. Although neither TQH2 nor UQH2 acted as a potent antioxidant by itself, they acted as potent antioxidants in combination with TOH. TQH2 and UQH2 reduced alpha-tocopheroxyl radical to spare TOH, whereas TOH suppressed the autoxidation of TQH2 and UQH2. In the micelle oxidation, the antioxidant activities of TQH2, UQH2, and TOH were similar, whereas 2,2,5,7,8-pentamethyl-6-chromanol exerted much more potent efficacy than TQH2, UQH2, or TOH. These results clearly show that the antioxidant potencies against lipid peroxidation are determined not only by their chemical reactivities toward radicals, but also by the fate of an antioxidant-derived radical and the mobility of the antioxidant at the microenvironment.     

Effects of tocopheryl quinone on the heart: model experiments with xanthine oxidase, heart mitochondria, and isolated perfused rat hearts

It is generally accepted that the protection effect of biological tissues by vitamin E is due to its radical scavenging potency in membranes, thereby being transformed to a vitamin E radical. A deficiency of appropriate reductants, which recycle vitamin E radicals back to its antioxidative active form, causes an irreversible degradation of vitamin E leading to tocopheryl quinone (TQ). TQ-like compounds were shown to result from both vitamin E and corresponding hydrophilic analogues of this antioxidant in vitro. In vivo elevated concentrations of tocopheryl quinones were detected after oxidative stress and TQ supplementation as well. Quinones in general are known to be efficient one-electron donors and acceptors. Therefore the question arises whether TQ-like compounds can undergo redox-cycling in conjunction with redox-active enzymes in the heart, thereby producing harmful oxygen radicals, or whether these compounds exhibit antioxidant properties. In order to elucidate this question we focused our interest on the interaction of TQ and a corresponding short-chain homologue (TQ(0)) with xanthine oxidase and heart mitochondria. Furthermore, we tested the influence of TQ on the recovery of isolated perfused rat hearts after ischemia/reperfusion. Our experiments revealed that hydrophilic TQ(0) was univalently reduced by xanthine oxidase (XOD) yielding semiquinone radicals in the absence of oxygen. However, under aerobic conditions TQ(0) enhanced the O(2)(*)(-) radical output of XOD. In the mitochondrial respiratory chain TQ was shown to interact with high potential cytochrome b in the bc(1) complex specifically. In contrast to the system XOD/TQ(0), lipophilic TQ in submitochondrial particles decreased the O(2)(*)(-) radical release during regular respiration possibly due to its interaction with b-cytochromes in the mitochondrial respiratory chain. In isolated rat hearts perfused with liposomes containing lipophilic TQ, it was efficiently accumulated in the heart tissue. When hearts were subjected to conditions of ischemia/reperfusion, infusion of TQ prior to ischemia significantly improved the recovery of hemodynamic parameters. Our results demonstrate that TQ derivatives may induce pro-oxidative and antioxidative effects depending on the distribution of TQ derivatives in the heart tissue and the interacting redox system.     

Nonenzymatic reduction of thymoquinone in physiological conditions

Thymoquinone (TQ) is the bioactive constituent of the volatile oil of Nigella sativa L. and has been shown to exert antioxidant antineoplastic and anti-inflammatory effects. During the study of its possible mechanism of action, we found that TQ reacts chemically (i.e. nonenzymatically) with glutathione (GSH), NADH and NADPH. A combination of liquid chromatography/UV-Vis spectrophotometry/Mass spectrometry analyses was used to identify the products of these reactions. The reaction that occur in physiological conditions indicates the formation of only two products, glutathionyl-dihydrothymoquinone after rapid reaction with GSH, and dihydrothymoquinone (DHTQ) after slow reaction time with NADH and NADPH. Measurement of the antioxidant activity of reduced compounds against organic radicals such as 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) also revealed a potential scavenging activity for glutathionyl-dihydrothymoquinone similar to that of DHTQ. Under our experimental conditions, TQ shows lower scavenging activities than glutathionyl-dihydrothymoquinone and DHTQ; it is very interesting to observe that the reduced compounds apparently show an antioxidant capacity equivalent to Trolox. The results indicate a possible intracellular nonenzymatic metabolic activation of TQ dependent on GSH, NADH or NADPH that may represent a “cellular switch” able to modulate cellular antioxidant defences.     

Reduction of hypervalent states of myoglobin and hemoglobin to their ferrous forms by thymoquinone: the role of GSH, NADH and NADPH

The reactivity of thymoquinone towards different redox states of hemoglobin and myoglobin in the presence of GSH, NADH, and NADPH was evaluated by optical spectral analysis. Thymoquinone reduces the ferryl forms (HbIV/MbIV) of both met-hemoglobin (HbIII) and met-myoglobin (MbIII) to oxy-hemoglobin (HbIIO2) and oxy-myoglobin (MbIIO2) under physiological conditions. The reaction is mediated by the intermediate quinone forms of TQ, that is, glutathionyl-dihydrothymoquinone (DHTQ-GS) and dihydrothymoquinone (DHTQ), formed from direct interaction of TQ with GSH or NADH (NADPH). In vitro incubation of oxidized human erythrocytes with TQ, DHTQ, and the GSH/TQ mixture reduces the intracellular met-Hb at different rates. In the present study, we report that TQ and its reduced derivatives can also prevent lipid peroxidation induced by the MbFeIII/H2O2 system. In this system, lipid peroxidation is induced by MbIV or a putative MbIV/.MbVI composite; it is plausible that the antioxidant function of TQ derivatives is related to their ability to reduce these oxidizing species. This is of particular biological significance, as natural quinones may participate in reducing processes that lead to recovery of hemoglobin and myoglobin during oxidative stress.     

Redox cycles of vitamin E: hydrolysis and ascorbic acid dependent reduction of 8a-(alkyldioxy)tocopherones

Oxidation of the biological antioxidant alpha-tocopherol (vitamin E; TH) by peroxyl radicals yields 8a-(alkyldioxy)tocopherones, which either may hydrolyze to alpha-tocopheryl quinone (TQ) or may be reduced by ascorbic acid to regenerate TH. To define the chemistry of this putative two-electron TH redox cycle, we studied the hydrolysis and reduction of 8a-[(2,4-dimethyl-1-nitrilopent-2-yl)dioxy]tocopherone (1) in acetonitrile/buffer mixtures and in phospholipid liposomes. TQ formation in acetonitrile/buffer mixtures, which was monitored spectrophotometrically, declined with increasing pH and could not be detected above pH 4. The rate of TQ formation from 1 first increased with time and then decreased in a first-order terminal phase. Rearrangement of 8a-hydroxy-alpha-tocopherone (2) to TQ displayed first-order kinetics identical with the terminal phase for TQ formation from 1. Both rate constants increased with decreasing pH. Hydrolysis of 1 in acetonitrile/H2(18)O yielded [18O]TQ. These observations suggest that 1 loses the 8a-(alkyldioxy) moiety to produce the tocopherone cation (T+), which hydrolyzes to 2, the TQ-forming intermediate. Incubation of either 1 or 2 with ascorbic acid in acetonitrile/buffer yielded TH. Reduction of both 1 and 2 decreased with increasing pH. In phosphatidylcholine liposomes at pH 7, approximately 10% of the T+ generated from 1 was reduced to TH by 5 mM ascorbic acid. The results collectively demonstrate that T+ is the ascorbic acid reducible intermediate in a two-electron TH redox cycle, a process that probably would require biocatalysis to proceed in biological membranes.     

Effects of thymoquinone on antioxidant enzyme activities, lipid peroxidation and DT-diaphorase in different tissues of mice: a possible mechanism of action

The present investigation focused, firstly, on the effects of oral administration of thymoquinone (TQ) on antioxidant enzyme activities, lipid peroxidation and DT-diaphorase activity in hepatic, cardiac and kidney tissues of normal mice. Superoxide dismutase (SOD; E.C:1.15.1.1), catalase (CAT; E.C:1.11.1.6), glutathione peroxidase (GSH-Px; E.C:1.11.1.9), glutathione-S-transferase (GST; E.C:2.5.1.18), and DT-diaphorase (E.C:1.6.99.2) enzyme activities in each tissue type were determined. Treatment of mice with the different doses of TQ (25, 50 and 100 mg kg(-1) day(-1) orally) for 5 successive days, produced significant reductions in hepatic SOD, CAT and GSH-Px activities. In addition cardiac SOD activity was markedly inhibited with the higher doses of TQ, (namely 50 and 100 mg kg(-1)). Moreover, TQ (100 mg kg(-1)) significantly reduced hepatic and cardiac lipid peroxidation as compared with the respective control group. Conversely, TQ (50,100 mg kg(-1)) and TQ (100 mg kg(-1)) enhanced cardiac and renal DT-diaphorase activity respectively. However, the selected doses of TQ neither produced any change in GST activity nor influenced reduced glutathione content in all tissues studied. TQ was tested, secondly, as a substrate for hepatic, cardiac and renal DT-diaphorase of normal mice in the presence of NADPH. Kinetic parameters for the reduction of TQ to dihydrothymoquinone (DHTQ) indicated that DT-diaphorase of different tissues can efficiently reduce TQ to DHTQ. K(m) and V(max) values revealed that hepatic DT-diaphorase exhibited the higher values, while the lower values were associated with renal DT-diaphorase. TQ and DHTQ were tested, thirdly, as specific scavengers for superoxide anion (generated biochemically) or as general scavengers for free radicals (generated photochemically). The results revealed that TQ and DHTQ acted not only as superoxide anion scavengers but also as general free radical scavengers. The IC(50) for TQ and DHTQ in biochemical and photochemical assays were in the nanomolar and micromolar range respectively. Our data may explain at least partly the reported beneficial in vivo protective effects of TQ through the combined antioxidant properties of TQ and its metabolite DHTQ.     

Nigella sativa thymoquinone-rich fraction greatly improves plasma antioxidant capacity and expression of antioxidant genes in hypercholesterolemic rats

The antioxidant activities of the thymoquinone-rich fraction (TQRF) extracted from Nigella sativa and its bioactive compound, thymoquinone (TQ), in rats with induced hypercholesterolemia were investigated. Rats were fed a semipurified diet supplemented with 1% (w/w) cholesterol and were treated with TQRF and TQ at dosages ranging from 0.5 to 1.5 g/kg and 20 to 100 mg/kg body wt, respectively, for 8 weeks. The hydroxyl radical (OH^·)-scavenging activity of plasma samples collected from experimental rats was measured by electron spin resonance. The GenomeLab Genetic Analysis System was used to study the molecular mechanism that mediates the antioxidative properties of TQRF and TQ. Plasma total cholesterol and low-density-lipoprotein cholesterol levels were significantly decreased in the TQRF- and TQ-treated rats compared to untreated rats. Feeding rats a 1% cholesterol diet for 8 weeks resulted in a significant decrease in plasma antioxidant capacity, as measured by the capacity to scavenge hydroxyl radicals. However, rats treated with TQRF and TQ at various doses showed significant inhibitory activity toward the formation of OH^· compared to untreated rats. Upon examination of liver RNA expression levels, treatment with TQRF and TQ caused the up-regulation of the superoxide dismutase 1 (SOD1), catalase, and glutathione peroxidase 2 (GPX) genes compared to untreated rats (P < 0.05). In support of this, liver antioxidant enzyme levels, including SOD1 and GPX, were also apparently increased in the TQRF- and TQ-treated rats compared to untreated rats (P < 0.05). In conclusion, TQRF and TQ effectively improved the plasma and liver antioxidant capacity and enhanced the expression of liver antioxidant genes of hypercholesterolemic rats.     

Characterization of cellular uptake and distribution of coenzyme Q10 and vitamin E in PC12 cells

Coenzyme Q (CoQ) is a well-known electron transporter in the mitochondrial respiratory chain. Furthermore, ubiquinol (UQH(2))--a reduced form of ubiquinone (UQ)--has been shown to act as a radical-scavenging antioxidant. Some studies have reported the beneficial effect of CoQ addition to cultured cells; however, the cellular uptake and distribution of CoQ have not been elucidated. In the present study, we used rat pheochromocytoma PC12 cells to investigate and compare the cellular uptake and distribution of CoQ(10) and alpha-tocopherol (alphaT). UQ(10) or UQ(10)H(2) treatment resulted in an increase in the cellular content of both CoQ(10) in a time- and concentration-dependent manner. A subcellular fractionation study revealed that the added UQ(10) as well as UQ(10)H(2) mainly localized in the mitochondrial fraction, which is similar to the localization of endogenous CoQ but different from that of alphaT. The cellular distribution of alphaT directly corresponded to the lipid distribution, while the CoQ distribution did not show any relationship with the lipid distribution, particularly in the mitochondrial and microsomal fractions. These results indicate that the cellular distribution of CoQ is completely different from that of alphaT; moreover, a certain system which accumulates CoQ preferentially in mitochondria may be suggested.     

Reactivity toward oxygen radicals and antioxidant action of thiol compounds

Thiol compounds exert diverse functions in the defense network against oxidative stress in vivo. Above all, the role of glutathione in the enzymatic removal of hydrogen peroxide and lipid hydroperoxides has been well established. The scavenging of reactive free radicals is one of the many functions. In this study, the reactivities of several thiol compounds toward oxygen- and nitrogen-centered radicals were measured from their reaction with galvinoxyl and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and also from their sparing effects on the decay of fluorescein, pyrogallol red, and BODIPY induced by peroxyl radicals. Furthermore, the antioxidant capacity against lipid peroxidation was assessed in the oxidation of methyl linoleate induced by free radicals in micelle systems. Cysteine, homocysteine, and glutathione exhibited considerable reactivity toward galvinoxyl, DPPH, and peroxyl radicals in this order but methionine did not. Bovine serum albumin (BSA) was less reactive toward these radicals than cysteine on molar base. Cysteine, homocysteine, and glutathione suppressed the oxidation of methyl linoleate in micelle systems, but methionine did not. The reactivity toward free radicals and antioxidant capacity of these thiol compounds were less than that of ascorbic acid, but higher than that of uric acid.     

Cadmium-induced hepatotoxicity and its abrogation by thymoquinone

Cadmium (Cd(2+) ) causes alteration of the cellular homeostasis and oxidative damage. The aim of the present study was to investigate the possible protective role of thymoquinone (TQ), a predominant bioactive component present in black seed oil (Nigella sativa) on the hepatotoxicity of Cd(2+) with special reference to its protection against perturbation of nonenzymatic and enzymatic antioxidants. The effect of TQ pretreatment was examined in postnuclear supernatant prepared from liver of Swiss albino mice under in vitro conditions. CdCl(2) treatment (5 mM) resulted in a significant increase in antioxidant enzymatic activities. It also caused a significant (p < 0.001) increase in protein carbonyl and reduced glutathione content. Pretreatment with TQ (10 μM) showed a significant protection as manifested by noticed attenuation of protein oxidation and rejuvenation of the depleted antioxidants of cellular fraction. These results strengthen the hypothesis that TQ exerts modulatory influence on the antioxidant defense system on being subjected to toxic insult.     

Protective effects of thymoquinone against cholestatic oxidative stress and hepatic damage after biliary obstruction in rats

The aim of this study was to examine the preventive and therapeutic effects of thymoquinone (TQ) against cholestatic oxidative stress and liver damage in common bile duct ligated rats. A total of 24 male Sprague–Dawley rats were divided into three groups: control, bile duct ligation (BDL) and BDL + received TQ; each group contain 8 animals. The rats in TQ treated groups were given TQ (50 mg/kg body weight) once a day orally for 2 weeks starting 3 days prior to BDL operation. To date, no more biochemical and histopathological changes on common bile duct ligated rats by TQ treatment have been reported. The application of BDL clearly increased the tissue hydroxyproline (HP) content, malondialdehyde (MDA) levels and decreased the antioxidant enzyme [superoxide dismutase (SOD), glutathione peroxidase (GPx)] activities. TQ treatment significantly decreased the elevated tissue HP content, and MDA levels and raised the reduced of SOD, and GPx enzymes in the tissues. The changes demonstrating the bile duct proliferation and fibrosis in expanded portal tracts include the extension of proliferated bile ducts into lobules, mononuclear cells, and neutrophil infiltration into the widened portal areas were observed in BDL group. Treatment of BDL with TQ attenuated alterations in liver histology. The immunopositivity of alpha smooth muscle actin and proliferating cell nuclear antigen in BDL were observed to be reduced with the TQ treatment. The present study demonstrates that oral administration of TQ in bile duct ligated rats maintained antioxidant defenses and reduces liver oxidative damage and ductular proliferation. This effect of TQ may be useful in the preservation of liver function in cholestasis.     

Reactive oxygen species mediate thymoquinone-induced apoptosis and activate ERK and JNK signaling

Thymoquinone (TQ), a component of black seed essential oil, is known to induce apoptotic cell death and oxidative stress, however, the direct involvement of oxidants in TQ-induced cell death has not been established yet. Here, we show that TQ inhibited the proliferation of a panel of human colon cancer cells (Caco-2, HCT-116, LoVo, DLD-1 and HT-29), without exhibiting cytotoxicity to normal human intestinal FHs74Int cells. Further investigation in DLD-1 revealed that apoptotic cell death is the mechanism for TQ-induced growth inhibition as confirmed by flow cytometry, M30 cytodeath and caspase-3/7 activation. Apoptosis was induced via the generation of reactive oxygen species (ROS) as evidenced by the abrogation of TQ apoptotic effect in cells preincubated with the strong antioxidant N-acetyl cysteine (NAC). TQ increased the phosphorylation states of the mitogen-activated protein kinases (MAPK) JNK and ERK, but not of p38. Their activation was completely abolished in the presence of NAC. Using PD98059 and SP600125, specific ERK and JNK inhibitors, the two kinases were found to possess pro-survival activities in TQ-induced cell death. These data present evidence linking the pro-oxidant effects of TQ with its apoptotic effects in colon cancer and prove a protective role of MAPK.     

Dynamics of action of bisphenol as radical-scavenging antioxidant against lipid peroxidation in solution and liposomal membranes

Probucol is used commercially as an antiatherogenic drug. Bisphenol is formed in vivo as a metabolite of probucol. The structure of bisphenol suggests the antioxidant function but its capacity has not been studied in detail. In the present study, dynamics of the antioxidant action of bisphenol were studied in several model systems and compared with those of probucol and alpha-tocopherol. The reactivity toward radicals and antioxidant activity of bisphenol per se were found to be much smaller than those of alpha-tocopherol or N,N'-diphenyl-p-phenylenediamine (DPPD) but stronger than probucol. However, bisphenol spared alpha-tocopherol in the oxidation of phosphatidylcholine liposomal membranes and it spared DPPD and acted as a synergist against the oxidant of methyl linoleate in solution. These results imply that bisphenol may act as a potent antioxidant in combination with other antioxidants.     

The fate of antioxidant radicals during lipid autooxidation. I. The tocopheroxyl radicals

Peroxidizing lipids were used to induce the formation of antioxidant radicals. It has been shown by electron spin resonance (ESR) spectroscopy and simulation of the first derivative ESR spectra that the radicals formed by this method are the already known tocopheroxyl radicals. dl-alpha-Tocopheroxyl radicals were formed in relatively high concentration but were rather rapidly destroyed as compared to the dl-delta-tocopheroxyl radicals, which were formed in rather low concentration and were destroyed rather slowly, dl-beta- and dl-gamma-tocopheroxyl radicals reacted in an intermediate way. Autooxidation induction times of the same lipids stabilized with the tocopherols show the well accepted series of antioxidant activities alpha less than beta congruent to gamma less than delta. Their relative antioxidant activity is nicely explained by the ESR experiment: the fast reacting dl-alpha-tocopherol is reacting more rapidly and traps the radicals more thoroughly and is therefore only available as an antioxidant for a short period of time as compared with the slowly reacting dl-delta-tocopherol. dl-beta- and dl-gamma-Tocopherols behave in an intermediate way.     

Free radical scavenging and antioxidant effects of lactate ion: an in vitro study.

Divergent literature data are found concerning the effect of lactate on free radical production during exercise. To clarify this point, we tested the pro- or antioxidant effect of lactate ion in vitro at different concentrations using three methods: 1) electron paramagnetic resonance (EPR) was used to study the scavenging ability of lactate toward the superoxide aion (O(2)(-).) and hydroxyl radical (.OH); 2) linoleic acid micelles were employed to investigate the lipid radical scavenging capacity of lactate; and 3) primary rat hepatocyte culture was used to study the inhibition of membrane lipid peroxidation by lactate. EPR experiments exhibited scavenging activities of lactate toward both O(2)(-). and.OH; lactate was also able to inhibit lipid peroxidation of hepatocyte culture. Both effects of lactate were concentration dependent. However, no inhibition of lipid peroxidation by lactate was observed in the micelle model. These results suggested that lactate ion may prevent lipid peroxidation by scavenging free radicals such as O(2)(-). and.OH but not lipid radicals. Thus lactate ion might be considered as a potential antioxidant agent.     

Thymoquinone ameliorates chemical induced oxidative stress and β-cell damage in experimental hyperglycemic rats

The present study was aimed to investigate the effect of thymoquinone (TQ) on pancreatic insulin levels, tissue antioxidant and lipid peroxidation (LPO) status in streptozotocin (STZ) nicotinamide (NA) induced diabetic rats. Diabetes was induced in experimental rats by a single intraperitoneal (i.p) injection of STZ (45 mg/kg b.w) dissolved in 0.1 mol/L citrate buffer (pH 4.5), 15 min after the i.p administration of NA (110 mg/kg b.w). Diabetic rats exhibited increased blood glucose with significant decrease in plasma insulin levels. The activities of antioxidant enzymes catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and the levels of low-molecular weight antioxidants Vitamin C, Vitamin E and reduced glutathione (GSH) were decreased while increases in the levels of lipid peroxidation markers were observed in liver and kidney tissues of diabetic control rats as compared to control rats. In addition, diabetic rats showed an obvious decrease in pancreatic insulin levels. Administration of TQ (80 mg/kg b.w) to diabetic rats for 45 days significantly reversed the damage associated with diabetes. Biochemical findings were supported by histological studies. These results indicated that TQ exerts a protective action on pancreatic beta cell function and overcomes oxidative stress through its antioxidant properties.     

Thymoquinone protects against 5-Fluorouracil-induced mucositis by NF-κβ and HIF-1 mechanisms in mice

Mucositis is among the most common side effects of 5-Fluorouracil (5-FU) and other cancer therapeutic drugs. Thymoquinone (TQ), a bioactive constituent extracted from Nigella sativa, has antioxidant and anti-inflammatory properties and can modify acute gastrointestinal injury. To investigate the effects of TQ on mucositis induced by 5-FU, studied animals were divided into four groups: control, 5-FU unit dose (300 mg/kg) to cause oral and intestinal mucositis (OM and IM), TQ (2.5 mg/kg) and TQ (2.5 mg/kg) plus 5-FU. Due to The molecular mechanisms, it was confirmed that the expression of NF-κβ and HIF-1 increases in OM. The serum levels of malondialdehyde (MDA), catalase (CAT), and superoxide dismutase (SOD), as well as pathological parameters, were assessed. Based on our results, the nuclear factor-kappa β gene expression in the tongue was downregulated significantly in the 5-FU + TQ compared to the 5-FU. TQ treatment can diminish MDA, and a reduction in oxidative stress was shown. TQ could also reduce the severity of tissue destruction and damaging effects induced by 5-FU on the tongue and intestine. We also observed lower villus length and width in the intestine of the 5-FU group compared to the control group. According to our research's pathological, biochemical, and molecular results, treatment with TQ as an anti-inflammatory and antioxidant compound may be the potential to improve and treat 5-FU-induced OM and IM, and TQ could be used against cancer treatment drugs and exhibit fewer adverse effects.     

Modulation of the oxidative stress and inflammatory cytokine response by thymoquinone in the collagen induced arthritis in Wistar rats

Thymoquinone (TQ) is the major active compound derived from Nigella sativa. Our aim of this work was to evaluate the antioxidant and antiarthritic activity of TQ in Wistar rat by collagen induced arthritis (CIA). TQ was administered at a dose of 5mgkg(-1) body weight once daily for 21days. The effects of treatment in the rats were assessed by biochemical (articular elastase, MPO, LPO, GSH, catalase, SOD and NO), inflammatory mediators (IL-1β, IL-6, TNF-α, IL-10, IFN-γ and PGE(2)) and histological studies in joints. TQ was effective in bringing significant changes on all the parameters (articular elastase, MPO, LPO, GSH, catalase, SOD and NO) studied. Oral administration of TQ resulted in significantly reduced the levels of pro-inflammatory mediators (IL-1β, IL-6, TNF-α, IFN-γ and PGE(2)) and increased level of IL-10. The protective effects of TQ against RA were also evident from the decrease in arthritis scoring and bone histology. In conclusion, the fact that TQ abolished a number of factors known to be involved in RA pathogenesis indicates that the administration of thymoquinone may have potential value in the treatment of inflammatory disease.