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

Near-infrared Absorption and Emission Probes with Optimal Connection Bridges for Live Monitoring of NAD(P)H Dynamics in Living Systems

Two NAD(P)H-biosensing probes consisting of 1,3,3-trimethyl-3H-indolium and 3-quinolinium acceptors, linked by thiophene, A, and 3,4-ethylenedioxythiophene, B, bridges are detailed. We synthesized probes C and D, replacing the thiophene connection in probe A with phenyl and 2,1,3-benzothiadiazole units, respectively. Probe E was prepared by substituting probe A's 3-quinolinium unit with a 1-methylquinoxalin-1-ium unit. Solutions are non-fluorescent but in the presence of NADH, exhibit near-infrared fluorescence at 742.1 nm and 727.2 nm for probes A and B, respectively, and generate absorbance signals at 690.6 nm and 685.9 nm. In contrast, probes C and D displayed pronounced interference from NADH fluorescence at 450 nm, whereas probe E exhibited minimal fluorescence alterations in response to NAD(P)H. Pre-treatment of A549 cells with glucose in the presence of probe A led to a significant increase in fluorescence intensity. Additionally, subjecting probe A to lactate and pyruvate molecules resulted in opposite changes in NAD(P)H levels, with lactate causing a substantial increase in fluorescence intensity, conversely, pyruvate resulted in a sharp decrease. Treatment of A549 cells with varying concentrations of the drugs cisplatin, gemcitabine, and camptothecin (5, 10, and 20 μM) led to a concentration-dependent increase in intracellular fluorescence intensity, signifying a rise in NAD(P)H levels. Finally, fruit fly larvae were treated with different concentrations of NADH and cisplatin illustrating applicability to live organisms. The results demonstrated a direct correlation between fluorescence intensity and the concentration of NADH and cisplatin, respectively, further confirming the efficacy of probe A in sensing changes in NAD(P)H levels within a whole organism.

Potential Pharmacological Applications of Nigella Seeds with a Focus on Nigella sativa and Its Constituents against Chronic Inflammatory Diseases: Progress and Future Opportunities

The leading cause of death worldwide has been identified as chronic illnesses, according to the World Health Organization (WHO). Chronic inflammatory conditions such as asthma, cancer, diabetes, heart disease, and obesity account for three out of every five deaths. Although many people benefit from using nonsteroidal anti-inflammatory medicines (NSAIDs) for pain and inflammation relief, there are significant adverse effects to using these medications. Medicinal plants possess anti-inflammatory properties with minimal or no side effects. Nigella sativa (NS), also known as black cumin, is one of the plants used in traditional medicine the most. Many studies on the NS have shown that their therapeutic properties are attributed to the seed, oil, and secondary metabolites. This plant has been studied extensively and has many medical uses, such as anti-inflammatory. NS or its phytochemical compounds, such as thymoquinone, can cause cell apoptosis via oxidative stress, block efflux pumps, enhance membrane permeability, and exert potent biocidal effects. Notwithstanding the extensively documented anti-inflammatory effectiveness observed in the experimental model, the precise mechanisms underlying its anti-inflammatory effects in diverse chronic inflammatory diseases and its multi-targeting characteristics remain largely unexplored. This review examines NS or its secondary metabolites, a valuable source for the therapeutic development of chronic inflammatory diseases. Most clinical studies were done for diabetes and cardiovascular disease; therefore, more studies are required to examine the NS extracts and phytoconstituents to treat cancer, obesity, diabetes, asthma, neurological disorders, and COVID-19. This study will be a significant resource for clinicians and biologists seeking a pharmaceutical solution for inflammatory diseases.

Mechanism of the antidiabetic action of Nigella sativa and Thymoquinone: a review

Introduction

Long used in traditional medicine, Nigella sativa (NS; Ranunculaceae) has shown significant efficacy as an adjuvant therapy for diabetes mellitus (DM) management by improving glucose tolerance, decreasing hepatic gluconeogenesis, normalizing blood sugar and lipid imbalance, and stimulating insulin secretion from pancreatic cells. In this review, the pharmacological and pharmacokinetic properties of NS as a herbal diabetes medication are examined in depth, demonstrating how it counteracts oxidative stress and the onset and progression of DM.

Methods

This literature review drew on databases such as Google Scholar and PubMed and various gray literature sources using search terms like the etiology of diabetes, conventional versus herbal therapy, subclinical pharmacology, pharmacokinetics, physiology, behavior, and clinical outcomes.

Results

The efficiency and safety of NS in diabetes, notably its thymoquinone (TQ) rich volatile oil, have drawn great attention from researchers in recent years; the specific therapeutic dose has eluded determination so far. TQ has anti-diabetic, anti-inflammatory, antioxidant, and immunomodulatory properties but has not proved druggable. DM's intimate link with oxidative stress, makes NS therapy relevant since it is a potent antioxidant that energizes the cell's endogenous arsenal of antioxidant enzymes. NS attenuates insulin resistance, enhances insulin signaling, suppresses cyclooxygenase-2, upregulates insulin-like growth factor-1, and prevents endothelial dysfunction in DM.

Conclusion

The interaction of NS with mainstream drugs, gut microbiota, and probiotics opens new possibilities for innovative therapies. Despite its strong potential to treat DM, NS and TQ must be examined in more inclusive clinical studies targeting underrepresented patient populations.

Thymoquinone Ameliorates Carfilzomib-Induced Renal Impairment by Modulating Oxidative Stress Markers, Inflammatory/Apoptotic Mediators, and Augmenting Nrf2 in Rats

Chemotherapy-induced kidney damage is an emerging problem that restricts cancer treatment effectiveness. The proteasome inhibitor carfilzomib (CFZ) is primarily used to treat multiple myeloma and has been associated with severe renal injury in humans. CFZ-induced nephrotoxicity remains an unmet medical need, and there is an urgent need to find and develop a nephroprotective and antioxidant therapy for this condition. Thymoquinone (TQ) is a bioactive compound that has been isolated from Nigella sativa seeds. It has a wide range of pharmacological properties. Therefore, this experimental design aimed to study the effectiveness of TQ against CFZ-induced renal toxicity in rats. The first group of rats was a normal control (CNT); the second group received CFZ (4 mg/kg b.w.); the third and fourth groups received TQ (10 and 20 mg/kg b.w.) 2 h before receiving CFZ; the fifth group received only TQ (20 mg/kg b.w.). This experiment was conducted for 16 days, and at the end of the experiment, blood samples and kidney tissue were collected for biochemical assays. The results indicated that administration of CFZ significantly enhanced serum marker levels such as BUN, creatinine, and uric acid in the CFZ group. Similarly, it was also noticed that CFZ administration induced oxidative stress by reducing antioxidants (GSH) and antioxidant enzymes (CAT and SOD) and increasing lipid peroxidation. CFZ treatment also enhanced the expression of IL-1β, IL-6, and TNF-α production. Moreover, CFZ increased caspase-3 concentrations and reduced Nrf2 expression in the CFZ-administered group. However, treatment with 10 and 20 mg/kg TQ significantly decreased serum markers and increased antioxidant enzymes. TQ treatment considerably reduced IL-1β, IL-6, TNF-α, and caspase-3 concentrations. Overall, this biochemical estimation was also supported by histopathological outcomes. This study revealed that TQ administration significantly mitigated the negative effects of CFZ treatment on Nrf2 expression. Thus, it indicates that TQ may have utility as a potential drug to prevent CFZ-induced nephrotoxicity in the future.

Thymoquinone Induces Nrf2 Mediated Adaptive Homeostasis: Implication for Mercuric Chloride-Induced Nephrotoxicity

BACKGROUND

the primary function of the kidney is to eliminate metabolic waste products and xenobiotics from the circulation. During this process, the kidney may become vulnerable to toxicity.

OBJECTIVE

it was aimed to investigate the impact of thymoquinone (TQ) in mercuric chloride (HgCl₂)-induced nephrotoxicity through estimation of various proteins involved in natural defense mechanisms.

MATERIAL AND METHODS

HgCl₂ (0.4 mg/kg) was administered to all groups (n = 5) except for the normal control. Three treatment groups received TQ (5, 10, and 15 mg/kg) 60 min before HgCl₂ administration. The protective effect of TQ was evaluated from renal and liver function biomarkers, urine examination, glomerulus filtration rate (GFR), histopathological features, oxidative stress biomarkers, Hsp-70, apoptosis biomarkers, and gene expression.

RESULTS

TQ significantly attenuated hazardous effects of HgCl₂ on renal and hepatic tissues. Urine albumin and glucose were considerably low in the treated groups in comparison with the HgCl₂ group. TQ treatment also enhanced % GFR in rats. TQ-enhanced superoxide dismutase, catalase, and glutathione levels by enhancing the expression level of nuclear factor erythroid 2-related factor 2 (Nrf2). TQ increased Hsp-70 and Bcl-2 levels and reduced caspase-3 activity. TQ also protected cells against HgCl₂-induced cell death and decreased % DNA fragmentation. TQ increased the expression of protective proteins metallothionein I and II and reduced the expression of kidney injury molecule-1 (Kim-1).

CONCLUSION

TQ showed protective effects against HgCl₂-induced nephrotoxicity through modifications of various constitutive and inducible protein and enzyme levels in renal tissues.

Thymoquinone: A Review of Pharmacological Importance, Oxidative Stress, COVID-19, and Radiotherapy

Widely consumed worldwide, Nigella sativa (NS) is a medicinal herb commonly used in various alternative medicine systems such as Unani and Tibb, Ayurveda, and Siddha. Recommended for regular use in Tibb-e-Nabwi (Prophetic Medicine), NS is considered one of the most notable forms of healing medicine in Islamic literature. Thymoquinone (TQ), the main component of the essential oil of NS, has been reported to have many properties such as antioxidant, anti-inflammatory, antiviral, and antineoplastic. Its chemical structure indicates antiviral potential against many viruses, including the hepatitis C virus, human immunodeficiency virus, and other coronavirus diseases. Interestingly, molecular docking studies have demonstrated that TQ can potentially inhibit the development of the coronavirus disease 2019 (COVID-19) by binding to the receptor site on the transmembrane serine proteinase 2 (the activator enzyme that attaches the virus to the cell). In addition, TQ has been shown to be effective against cancer cells due to its inhibitory effect by binding to the different regions of MDM2, according to the proposed molecular docking study. Detailed in this review is the origin of TQ, its significance in alternative medicine, pharmacological value, potential as a cancer anti-proliferative agent, use against the coronavirus disease 2019 (COVID-19), and treatment of other diseases.

Influence of Supercritical Carbon Dioxide Extraction Conditions on Extraction Yield and Composition of Nigella sativa L. Seed Oil-Modelling, Optimization and Extraction Kinetics regarding Fatty Acid and Thymoquinone Content

Nigella sativa L. is cultivated in many regions and its seeds have found use in variety of foods, but also in traditional medicine due to high content of biologically active essential oils. In this work optimization of supercritical carbon dioxide extraction from N. sativa seeds was performed using response surface methodology to describe the influence of extraction conditions on oil yield. Kinetics of oil and thymoquinone extraction were analyzed as well. It was demonstrated that in order to collect thymoquinone-rich N. sativa oil fraction, appropriate for health-related applications, the extraction should be carried out at 40 °C and 10-15 MPa. Following application of higher pressure of 35 MPa enables effective extraction of remaining oil rich in polyunsaturated fatty acids suitable for use in food industry. Thymoquinone-dependent antibacterial activity of the N. sativa seed oil was observed against bacterial pathogens: Haemophilus influenzae, Staphylococcus haemolyticus, Staphylococcus epidermidis, Enterococcus faecalis and Escherichia coli.

Thymoquinone reduces mitochondrial damage and death of cardiomyocytes induced by clozapine

The generation of a reactive nitrenium ion by microsomal/mitochondrial cytochrome P450 (CYPs) from clozapine (CLZ) has been suggested as the main cause of cardiotoxicity by this drug. Previous studies indicated that thymoquinone (TQ) as an active constituent of Nigella sativa has pharmacological effects such as antioxidant, reactive oxygen species (ROS) scavenger, and inhibitory effect on CYPs enzymes. Therefore, we hypothesized that TQ with these pharmacological effects can reduce CLZ-induced toxicity in isolated cardiomyocytes and mitochondria. Rat left ventricular cardiomyocytes and mitochondria were isolated by collagenase perfusion and differential centrifugation respectively. Then, isolated cardiomyocytes and mitochondria were pretreated with different concentrations of TQ (1, 5, and 10 μmol/l) for 30 min and then followed by exposure to CLZ (50 μmol/l) for 6 h. After 6 h of incubation, using biochemical evaluations and flow cytometric analysis, the parameters of cellular toxicity including cytotoxicity, the level of oxidized/reduced glutathione (GSH/GSSG), malondialdehyde (MDA), reactive oxygen species (ROS) formation, lysosomal membrane integrity, mitochondria membrane potential (ΔΨm) collapse, and mitochondrial toxicity including succinate dehydrogenase (SDH) activity and mitochondrial swelling were analyzed. We observed a significant toxicity in isolated cardiomyocytes and mitochondria after exposure with CLZ which was related to ROS formation, oxidative stress, GSH depletion, lysosomal and mitochondrial damages, and mitochondrial dysfunction and swelling, while TQ pretreatment reverted the above toxic effect of CLZ on isolated cardiomyocytes and mitochondria. Our results indicate that TQ prevents and reverses CLZ-induced cytotoxicity and mitochondrial damages in isolated cardiomyocytes and mitochondria, providing an experimental basis for clinical treatment on CLZ-induced cardiotoxicity.

A peroxidase mimetic protects skeletal muscle cells from peroxide challenge and stimulates insulin signaling

Reactive oxygen species such as hydrogen peroxide have been implicated in causing metabolic dysfunction such as insulin resistance. Heme groups, either by themselves or when incorporated into proteins, have been shown to scavenge peroxide and demonstrate protective effects in various cell types. Thus, we hypothesized that a metalloporphyrin similar in structure to heme, Fe(III)tetrakis(4-benzoic acid)porphyrin (FeTBAP), would be a peroxidase mimetic that could defend cells against oxidative stress. After demonstrating that FeTBAP has peroxidase activity with reduced nicotinamide adenine dinucleotide phosphate (NADPH) and NADH as reducing substrates, we determined that FeTBAP partially rescued C2C12 myotubes from peroxide-induced insulin resistance as measured by phosphorylation of AKT (S473) and insulin receptor substrate 1 (IRS-1, Y612). Furthermore, we found that FeTBAP stimulates insulin signaling in myotubes and mouse soleus skeletal muscle to about the same level as insulin for phosphorylation of AKT, IRS-1, and glycogen synthase kinase 3β (S9). We found that FeTBAP lowers intracellular peroxide levels and protects against carbonyl formation in myotubes exposed to peroxide. Additionally, we found that FeTBAP stimulates glucose transport in myotubes and skeletal muscle to about the same level as insulin. We conclude that a peroxidase mimetic can blunt peroxide-induced insulin resistance and also stimulate insulin signaling and glucose transport, suggesting a possible role of peroxidase activity in regulation of insulin signaling.

Nigella sativa seed extract applicability in preparations against methicillin-resistant Staphylococcus aureus and effects on human dermal fibroblasts viability

ETHNOPHARMACOLOGICAL RELEVANCE

Nigella sativa L. seed extracts and oils have been embraced by traditional medicine of cultures inhabiting Middle East and North Africa for centuries. Among other uses, it has been applied against dermatitis and eczema often worsened by staphylococcal colonization of the skin.

AIM OF THE STUDY

The study was conducted to evaluate applicability of N. sativa seed extract in antibacterial skin formulations by examination of its activity against methicillin-resistant Staphylococcus aureus as well as cytotoxicity against human dermal fibroblasts.

MATERIALS AND METHODS

Two variants of N. sativa seed extract containing 9.91 and 2.10 % of thymoquinone were prepared by supercritical carbon dioxide extraction. The extracts and standards of their major volatile ingredients; thymoquinone, thymol, p-cymene alongside with the reference antiseptics; chlorquinaldol and a combination of amylmetacresol with 2,4-dichlorobenzyl alcohol were subjected to evaluation of antibacterial efficacy against a collection of Staphylococcus aureus strains. The preparation based on Vaseline containing 1% of N. sativa extract was applied on Mueller-Hinton agar plates and its ability to inhibit S. aureus growth was examined. The MTT assay was employed to study cytotoxic effects of the thymoquinone-rich N. sativa seed extract against HDFa fibroblasts.

RESULTS

N. sativa seed extract and thymoquinone have shown potent bacteriostatic and bactericidal effect against Staphylococcus aureus, including methicillin-resistant strains (MRSA) isolated in Poland. Results suggest that N. sativa seed extract activity against S. aureus should mainly be attributed to thymoquinone, which was effective in concentrations of 4-16 μg/ml. Regarding the activity against S. aureus, thymoquinone was more efficient than a combination of amylmetacresol with 2,4-dichlorobenzyl alcohol and comparable to chlorquinaldol. The Vaseline-based preparation containing N. sativa extract caused growth inhibition comparable to an equally concentrated DMSO solution of the extract. The IC50 of N. sativa extract against HDFa fibroblast was determined at 0.2 mg/ml, which was 2-fold higher than the average MIC and MBC of the extract against S. aureus.

CONCLUSIONS

The observed effectiveness of N. sativa seed extracts against bacteria was found to be dominantly dependent on concentration of thymoquinone. Its efficiency against S. aureus isolates as well as results of cytotoxicity examination against human dermal fibroblasts indicate on its applicability as an antibacterial agent for topical use and motivates further research in this area.

Thymoquinone activates MAPK pathway in hippocampus of streptozotocin-treated rat model

Streptozotocin (STZ), a glucosamine-nitrosourea compound, produces deficiencies in learning, memory, and cognitive functions when it was administered intracerebroventricularly (i.c.v). In molecular level, increase in neuroinflammation and oxidative stress in brain, and decrease in the number of surviving neurons are the outcomes of STZ administration. Herein, we aimed to investigate the effect of thymoquinone (TQ), an anti-inflammatory, immunomodulatory and neuroprotective agent, on STZ-induced neurodegeneration in rats. For this purpose, bilateral i.c.v. injection of STZ (3 mg/kg) was given to adult female rats on days 1 and 3. TQ (20 mg/kg/day in cornoil) was administered intragastrically to rats for 15 days starting from the 15th day of STZ injection. The Morris water maze test and passive avoidance test were applied to measure the learning and memory performance of animals. Following the behavioral tests, all of the rats were sacrificed for evaluation of molecular alterations. Rats in the STZ-TQ group showed higher performance in passive avoidance test than rats in the STZ group whose memory performance declined compared to control group. The worse memory performance in STZ group was correlated with low number of surviving neurons and high number of degenerating neurons. In addition, an increase in APOE expression and a decrease in NGF expression were observed with STZ injection. Administration of TQ reversed these STZ-triggered cognitive and molecular alterations. In the present study, we observed the neuroregenerative effects of TQ by activation of JNK protein, upregulation of mir-124, and downregulation of ERK1/2 and NOS enzymes. The same ameliorative effect of TQ was also observed in the pTau protein expression. To sum up, we can say that the healing effect of TQ on STZ induced neurodegeneration opens a new door for the development of Alzheimer's disease treatment using natural products as an adjuvant when their action mechanism was explained in detail.

Thymoquinone treatment for inner-ear acoustic trauma in rats

OBJECTIVE

To investigate whether thymoquinone has any eliminative effects against inner-ear damage caused by acoustic trauma.

METHODS

Thirty-two male rats were divided into four groups. Group 1 was only exposed to acoustic trauma. Group 2 was given thymoquinone 24 hours before acoustic trauma and continued to receive it for 10 days after the trauma. Group 3 was only treated with thymoquinone, for 10 days. Group 4, the control group, suffered no trauma and received saline instead of thymoquinone. Groups 1 and 2 were exposed to acoustic trauma using 105 dB SPL white noise for 4 hours.

RESULTS

There was a significant decrease in distortion product otoacoustic emission values and an increase in auditory brainstem response thresholds in group 1 on days 1, 5 and 10, compared with baseline measurements. In group 2, a decrease in distortion product otoacoustic emission values and an increase in auditory brainstem response threshold were observed on day 1 after acoustic trauma, but measurements were comparable to baseline values on days 5 and 10. In group 3, thymoquinone had no detrimental effects on hearing. Similarly, the control group showed stable results.

CONCLUSION

Thymoquinone was demonstrated to be a reparative rather than preventive treatment that could be used to relieve acoustic trauma.

Reducing effects of polyphenols on metmyoglobin and the in vitro regeneration of bright meat color by polyphenols in the presence of cysteine

The effect of polyphenols and related phenolic compounds on the reduction of metmyoglobin (MetMb) to oxymyoglobin (MbO2), in the presence of cysteine, was investigated. Caffeic acid, dihydrocaffeic acid, and hydroxtyrosol (600 μmol/L) did not show any reducing activity individually. However, their highly potent activity in the reduction of MetMb to MbO2 was observed in the presence of equimolar amounts of cysteine. On the basis of the analytical results for the redox reaction products generated during the MetMb-reducing reaction of caffeic acid, we proposed a mechanism for the polyphenol-mediated reduction of MetMb. As per the proposed mechanism, the antioxidant polyphenols having a catechol substructure can effectively reduce MetMb to MbO2 with chemical assistance from nucleophilic reactive thiol compounds such as cysteine. Moreover, cysteine-coupled polyphenols such as cysteinylcaffeic acids (which are coupling products of caffeic acid and cysteine) can be used as preserving agents for retaining the fresh meat color, because of their powerful reducing effect on MetMb. The reduction of MetMb to MbO2 changes the color of meat from brown to the more desirable bright red.

Metmyoglobin reduction by polyphenols and mechanism of the conversion of metmyoglobin to oxymyoglobin by quercetin

The effect of antioxidant polyphenols and related phenolic compounds from plants on the reduction of metmyoglobin (MetMb) was investigated. Potent activity in the reduction of MetMb to oxymyoglobin (MbO2), a bright red protein in meat, was observed for three flavonols, kaempferol, myricetin, and quercetin, at 300 μmol/L against 60 μmol/L MetMb. Sinapic acid, catechin, nordihydroguaiaretic acid, taxifolin, morin, and ferulic acid promoted reduction at 600 μmol/L. A mechanism for the reduction by one of the active flavonols, quercetin, was proposed on the basis of analytical results for redox reaction products derived from quercetin. This suggested the importance of a high propensity toward reduction of the flavonol structure and rapid convertibility of the quinone form to the phenol form for the MbO2 reduction and the maintenance of the level of MbO2 produced.

Redox reactions of myoglobin

SIGNIFICANCE

Failure to maintain myoglobin (Mb) in the reduced state causes the formation of metMb, ferryl Mb species, and cross-linked Mb. Dissociation of ferriprotoporphyrin IX from the globin and release of iron atoms can also occur as oxidized Mb accumulates. These modifications may contribute to various oxidative pathologies in muscle and muscle foods.

RECENT ADVANCES

The mechanism of ferryl Mb-mediated oxidative damage to nearby structures has been partially elucidated. Dissociation of ferriprotoporphyrin IX from metMb occurs more readily at acidic pH values. The dissociated ferriprotoporphyrin IX (also called hemin) readily decomposes preformed lipid hydroperoxides to reactive oxygen species. Heme oxygenase as well as lipophilic free radicals can degrade the protoporphyrin IX moiety, which results in the formation of free iron.

CRITICAL ISSUES

The multiple pathways by which Mb can incur toxicity create difficulties in determining the major cause of oxidative damage in a particular system. Peroxides and low pH activate each of the oxidative Mb forms, ferriprotoporphyrin IX, and released iron. Determining the relative concentration of these species is technically difficult, but essential to a complete understanding of oxidative pathology in muscle tissue.

FUTURE DIRECTIONS

Improved methods to assess the different pathways of Mb toxicity are needed. Although significant advances have been made in the understanding of Mb interactions with other biomolecules, further investigation is needed to understand the physical and chemical nature of these interactions.

Thymoquinone attenuates tumor growth in ApcMin mice by interference with Wnt-signaling

Background

Patients with familial adenomatous polyposis (FAP) are at increased risk for the development of colorectal cancer. Surgery and chemoprevention are the most effective means to prevent cancer development. Thymoquinone (TQ) is considered the main compound of the volatile Nigella sativa seed oil and has been reported to possess anticarcinogenic properties. In this study we evaluated the chemopreventive properties of TQ in a mouse model of FAP.

Methods

APC^Min mice were fed with chow containing 37.5 mg/kg or 375 mg/kg TQ for 12 weeks. H&E stained intestine tissue sections were assessed for tumor number, localization, size, and grade. Immunohistochemistry for β-catenin, c-myc, Ki-67 and TUNEL-staining was performed to investigate TQ’s effect on major colorectal cancer pathways. TQ’s impact on GSK-3β and β-catenin were studied in RKO cells.

Results

375 mg/kg but not 37.5 mg/kg TQ decreased the number of large polyps in the small intestine of APC^Min mice. TQ induced apoptosis in the neoplastic tissue but not in the normal mucosa. Furthermore, upon TQ treatment, β-catenin was retained at the membrane and c-myc decreased in the nucleus, which was associated with a reduced cell proliferation in the villi. In vitro, TQ activated GSK-3β, which induced membranous localization of β-catenin and reduced nuclear c-myc expression.

Conclusions

In summary, TQ interferes with polyp progression in Apc^Min mice through induction of tumor-cell specific apoptosis and by modulating Wnt signaling through activation of GSK-3β. Nigella sativa oil (or TQ) might be useful as nutritional supplement to complement surgery and chemoprevention in FAP.

Mitigation of obesity-promoted diseases by Nigella sativa and thymoquinone

Obesity is closely associated with increased incidence of cardiovascular diseases, cancer, insulin resistance, and immune dysfunction, and thus obesity-mitigation strategies should take into account these secondary pathologies in addition to promoting weight loss. Recent studies indicate that black cumin (Nigella sativa) has cardio-protective, anti-cancer, anti-diabetic, antioxidant, and immune-modulatory properties. While black cumin and/or its major bioactive constituent, thymoquinone have demonstrated bioactivity in a variety of disease models, the mechanisms of action are largely unknown. Given the growing interest in and the use of functional foods and nutraceuticals, as well as the increase in obesity and chronic diseases worldwide, further research into the therapeutic/preventive effects of black cumin may be beneficial.

Polyphenols activate Nrf2 in astrocytes via H2O2, semiquinones, and quinones

Polyphenols, which occur both in edible plants and in foodstuff, have been reported to exert a wide range of health effects; however, the mechanism of action of these molecules is not fully understood. One important cellular pathway affected by polyphenols is the activation of the transcription factor Nrf2 via the electrophile response element, which mediates generation of phase 2 detoxifying enzymes. Our study found that Nrf2 nuclear translocation and the activity of NAD(P)H quinone oxidoreductase (NQO1) were increased significantly after treatment of astrocytes with tert-butylhydroquinone (tBHQ), resveratrol, or curcumin, at 20-50μM. Incubation of tBHQ, resveratrol, and curcumin in the growth medium in the absence of astrocytes caused the accumulation of H(2)O(2). Treatment of cells with either glutathione or metmyoglobin was found to decrease Nrf2 translocation and NQO1 activity induced by polyphenols by up to 40 and 60%, respectively. Addition of both glutathione and metmyoglobin to growth medium decreased Nrf2 translocation and NQO1 activity by up to 100 and 80%, respectively. In conclusion, because metmyoglobin, in the presence of polyphenols and glutathione, is known to interact with H(2)O(2), semiquinones, and quinones, the up-regulation of the antioxidant defense of the cells through activation of the Nrf2 transcription factor, paradoxically, occurs via the generation of H(2)O(2) and polyphenol-oxidized species generated from the exogenous microenvironment of the cells.

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.