Inhibitory Effect Of Thymoquinone Research Articles

Inhibitory effect of thymoquinone and capsaicin on Blastocystis grown in vitro

Inhibitory effect of thymoquinone and capsaicin on Blastocystis grown in vitro

Thymoquinone inhibits lung cancer stem cell properties via triggering YAP degradation.

Due to the characteristics of high recurrence and metastasis, it is still difficult to cure lung cancer. Cancer stem cells (CSCs) are a group of tumor cells with self-renewal ability and differentiation potential, which are responsible for lung cancer recurrence. Therefore, targeting CSCs may provide a new strategy for lung cancer treatment. Thymoquinone (TQ), the main active ingredient isolated from black seed oil, has shown significant anti-cancer effects in various cancers. However, the effect of TQ on lung cancer stem cells (LCSCs) has never been clarified. In the present study, we successfully separated and enriched lung cancer tumorsphere cells. Our data showed that TQ significantly inhibited the stem-like properties of LCSCs. In addition, we found TQ promoted Yes-associated protein (YAP) phosphorylation and ubiquitination, and the inhibitory effects of TQ on LCSCs could be enhanced by silencing YAP. Taken together, these results suggest that TQ, functions by targeting YAP, may be a potential therapeutic agent against lung cancer.

Antibacterial Activity of Thymoquinone Against Shigella flexneri and Its Effect on Biofilm Formation.

Thymoquinone (TQ) has been demonstrated to have anti-cancer, anti-inflammatory, antioxidant, and anti-diabetic activities. Shigella flexneri is the main pathogen causing shigellosis in developing countries. In this study, the antibacterial activity of TQ against S. flexneri and its possible antibacterial mechanism were studied. In addition, the inhibitory effect of TQ on the formation of S. flexneri biofilm was also investigated. The results showed that both the minimum inhibitory concentration and the minimum bactericidal concentration of TQ against S. flexneri ATCC 12022 were 0.2 mg/mL. After treatment with TQ at 0.4 mg/mL in Luria-Bertani broth for 3 h, or treatment with 0.2 mg/mL TQ in phosphate-buffered saline for 60 min, the number of S. flexneri (initial number is 6.5 log colony-forming units/mL) dropped below the detection limit. TQ also displayed good antibacterial activity in contaminated lettuce juice. TQ caused an increase in intracellular reactive oxygen species level, a decrease in intracellular adenosine triphosphate (ATP) concentration, a change in the intracellular protein, damage to cell membrane integrity and changes in cell morphology. In addition, TQ showed the ability to inhibit the formation of S. flexneri biofilm; treatment resulted in a decrease in the amount of biofilm and extracellular polysaccharides, and the destruction of biofilm structure. These findings indicated that TQ had strong antimicrobial and antibiofilm activities and a potential to be applied in the fruit and vegetable processing industry or other food industries to control S. flexneri.

Potential herb-drug interaction risk of thymoquinone and phenytoin

Thymoquinone is a main bioactive compound of Nigella sativa L. (N.sativa), which has been used for clinical studies in the treatment of seizures due to its beneficial neuroprotective activity and antiepileptic effects. It has been evidenced that thymoquinone may inhibit the activity of cytochrome P450 2C9 (CYP2C9). However, little is known about the effect of thymoquinone or N.sativa on the pharmacokinetic behavior of phenytoin, a second-line drug widely used in the management of status epilepticus. In this study, we systematically investigated the risk of the potential pharmacokinetic drug interaction between thymoquinone and phenytoin. The inhibitory effect of thymoquinone on phenytoin hydroxylation activity by CYP2C9 was determined using UPLC-MS/MS by measuring the formation rates for p-hydroxyphenytoin (p-HPPH). The potential for drug-interaction between thymoquinone and phenytoin was quantitatively predicted by using in vitro-in vivo extrapolation (IVIVE). Our data demonstrated that thymoquinone displayed effective inhibition against phenytoin hydroxylation activity. Enzyme kinetic studies showed that thymoquinone exerted a competitive inhibition against phenytoin hydroxylation with a Ki value of 4.45 ± 0.51 μM. The quantitative prediction from IVIVE suggested that the co-administration of thymoquinone (>18 mg/day) or thymoquinone-containing herbs (N.sativa > 1 g/day or N.sativa oil >1 g/day) might result in a clinically significant herb-drug interactions. Additional caution should be taken when thymoquinone or thymoquinone-containing herbs are co-administered with phenytoin, which may induce unexpected potential herb-drug interactions via the inhibition of CYP2C9.

Antimicrobial Activity and Action Mechanism of Thymoquinone against Bacillus cereus and Its Spores.

In this study, thymoquinone (TQ), a natural active substance, was investigated for its antibacterial activity against Bacillus cereus, and its inhibitory effect on B. cereus in reconstituted infant formula (RIF) was evaluated. In addition, the inhibitory effect of TQ on B. cereus spore germination was explored. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of TQ against eight B. cereus strains ranged from 4.0 to 8.0 μg/mL, whereas B. cereus treated with TQ displayed a longer lag phase than the untreated control. TQ exerted a good bactericidal effect on B. cereus in Luria–Bertani broth. In addition, TQ obviously reduced the intracellular ATP concentration of B. cereus, which caused depolarization of the cell membrane, increased the intracellular reactive oxygen species level, impaired the cell morphology, and destroyed proteins or inhibited proteins synthesis. This provides a mechanism for its bacteriostatic effect. TQ also inactivated B. cereus growth in RIF. Moreover, reverse transcription–quantitative polymerase chain reaction illustrated that TQ downregulated the transcription of genes related to hemolysin, non-hemolytic enterotoxin, enterotoxin, and cytotoxin K. Meanwhile, TQ displayed the ability to inhibit the germination of B. cereus spores. These findings indicate that TQ, as an effective natural antimicrobial preservative, has potential applications in controlling food contamination and foodborne diseases caused by B. cereus.

Evaluation of the Antimicrobial Effect of Thymoquinone against Different Dental Pathogens: An In Vitro Study.

This study aimed to evaluate the antimicrobial effect of Thymoquinone (TQ) on four different oral microorganisms. Minimum Bactericidal Concentration (MBC), Minimum Inhibition Concentration (MIC), Broth microdilution, and Well diffusion tests were used to determine the optimum antimicrobial concentrations of TQ against Streptococcus salivarius, Streptococcus oralis, Streptococcus mutans, and Staphylococcus aureus over 1, 3, 6, 12 and 24 h. Chlorhexidine 0.12% was selected as a positive control. The inhibitory effect of TQ on bacterial growth was most noticeable with S. salivarius, while the least affected was S. aureus. TQ’s MBC and MIC for S. oralis and S. aureus were comparable 2 mg/mL and 3 mg/mL, respectively. S. salivarius was most resistant to TQ and displayed a value of 5 mg/mL and 4 mg/mL for MIC and MBC, respectively. The viable count of different strains after exposure to TQ’s MBC values was most noticeable with S. aureus followed by S. oralis and S. mutans, while S. salivarius was least affected. This study emphasized the promising antimicrobial effect of TQ against the four main oral microorganisms. It has a potential preventive effect against dental caries as well as other oral diseases.

Biological Role of AKT and Regulation of AKT Signaling Pathway by Thymoquinone: Perspectives in Cancer Therapeutics.

AKT/PKB is an important enzyme with numerous biological functions, and its overexpression is related to carcinogenesis. AKT stimulates different signaling pathways that are downstream of activated tyrosine kinases and phosphatidylinositol 3-kinase, hence functions as an important target for anti-cancer drugs. In this review article, we have interpreted the role of AKT signaling pathway in cancer and the natural inhibitory effect of Thymoquinone (TQ) in AKT and its possible mechanisms. We have collected the updated information and data on AKT, its role in cancer and the inhibitory effect of TQ in AKT signaling pathway from Google Scholar, PubMed, Web of Science, Elsevier, Scopus, and many more. Many drugs are already developed, which can target AKT, but very few among them have passed clinical trials. TQ is a natural compound, mainly found in black cumin, which has been found to have potential anti-cancer activities. TQ targets numerous signaling pathways, including AKT, in different cancers. In fact, many studies revealed that AKT is one of the major targets of TQ. The preclinical success of TQ suggests its clinical studies on cancer. This review article summarizes the role of AKT in carcinogenesis, its potent inhibitors in clinical trials, and how TQ acts as an inhibitor of AKT and TQ's future as a cancer therapeutic drug.

Molecular Docking and Dynamics Simulation Analysis of Thymoquinone and Thymol Compounds from Nigella sativa L. that Inhibit Cag A and Vac A Oncoprotein of Helicobacter pylori: Probable Treatment of H. pylori Infections.

Helicobacter pylori infection is accountable for most of the peptic ulcer and intestinal cancers. Due to the uprising resistance towards H. pylori infection through the present and common proton pump inhibitors regimens, the investigation of novel candidates is the inevitable issue. Medicinal plants have always been a source of lead compounds for drug discovery. The research of the related effective enzymes linked with this gram-negative bacterium is critical for the discovery of novel drug targets. The aim of the study is to identify the best candidate to evaluate the inhibitory effect of thymoquinone and thymol against H. pylori oncoproteins, Cag A and Vac A in comparison to the standard drug, metronidazole by using a computational approach. The targeted oncoproteins, Cag A and Vac A were retrieved from RCSB PDB. Lipinski's rule and ADMET toxicity profiling were carried out on the phytoconstituents of the N. sativa. The two compounds of N. sativa were further analyzed by molecular docking and MD simulation studies. The reported phytoconstituents, thymoquinone and thymol present in N. sativa were docked with H. pylori Cag A and Vac A oncoproteins. Structures of ligands were prepared using ChemDraw Ultra 10 software and then changed into their 3D PDB structures using Molinspiration followed by energy minimization by using software Discovery Studio client 2.5. The docking results revealed the promising inhibitory potential of thymoquinone against Cag A and Vac A with docking energy of -5.81 kcal/mole and -3.61kcal/mole, respectively. On the contrary, the inhibitory potential of thymol against Cag A and Vac A in terms of docking energy was -5.37 kcal/mole and -3.94kcal/mole as compared to the standard drug, metronidazole having docking energy of -4.87 kcal/mole and -3.20 kcal/mole, respectively. Further, molecular dynamic simulations were conducted for 5ns for optimization, flexibility prediction, and determination of folded Cag A and Vac A oncoproteins stability. The Cag A and Vac A oncoproteins-TQ complexes were found to be quite stable with the root mean square deviation value of 0.2nm. The computational approaches suggested that thymoquinone and thymol may play an effective pharmacological role to treat H. pylori infection. Hence, it could be summarized that the ligands thymoquinone and thymol bound and interacted well with the proteins Cag A and Vac A as compared to the ligand MTZ. Our study showed that all lead compounds had good interaction with Cag A and Vac A proteins and suggested them to be a useful target to inhibit H. pylori infection.

Uranium exposure increases spermatocytes metaphase apoptosis in rats: inhibitory effect of thymoquinone and N-acetylcysteine.

Uranyl acetate (UA), a commercial stock from depleted uranium (DU), has a combined effect of chemical toxicity and mild radioactivity. Here, we investigated the potential antioxidant, antiapoptotic and cytoprotective effects of thymoquinone (TQ) and N-acetylcysteine (NAC) against UA-induced testicular damage in rats. UA reduced testicular superoxide dismutase (SOD) activity and nitric oxide (NO) and glutathione (GSH) levels relative to the control group. Interestingly, the testicular SOD activity and NO and GSH levels of UA/TQ- and UA/NAC-treated groups were also significantly lower relative to the control. A marked increase in spermatocytes metaphase apoptosis was found (stage XIII) in UA-treated rats, which is probably due to difficulties in segregation of homologous-chromosomes. This may clarify why UA exposure decreased round spermatids numbers and fertility in previous studies. To check the reason of partial metaphase arrest, the presence of DNA-damage-related γ-H2AX foci in late spermatocytes of all groups was checked, but only insignificant increase was found in UA-treated group. TQ or NAC supplementation reduced the apoptosis and improved the testicular histological alterations. Thus, TQ and NAC attenuate UA adverse effects on the testicular microenvironement through anti-apoptotic and cytoprotective but not antioxidant effects.

The Effect of Thymoquinone on Apoptosis of SK-OV-3 Ovarian Cancer Cell by Regulation of Bcl-2 and Bax.

We aim to determine how cisplatin, thymoquinone (TQ), and combination regimen can affect apoptosis of cultured SK-OV-3 cells. We also want to explore the mechanism of these influences on the cells' apoptosis by Bcl-2 and Bax gene. Cell Counting Kit-8 assay was used to measure the viability of cultured ovarian cancer cells. Propidium iodide with flow cytometry was used in cell cycle analysis. Thereafter, we used fluorescein isothiocyanate-stained annexin V and propidium iodide to detect the effect of cisplatin, TQ, and combination regimen on apoptosis. Real-time PCR was used to measure the Bcl-2 and Bax levels. Western blotting was used to measure on protein expression levels of Bcl-2 and Bax. In Cell Counting Kit-8 assay, we found that inhibitory effect of TQ was even better than cisplatin, and combination regimen had best inhibitory effect on cell proliferation. In cell cycle analysis, we found all regimens had obvious effect to stop cell cycle in S phase. In apoptosis assay, we found that combination regimen was better to activate cell apoptosis than cisplatin alone. Combination regimen could decrease expression of Bcl-2 and increase expression of Bax more than cisplatin or TQ alone. Thymoquinone and cisplatin had comparable antitumoric effects on SK-OV-3 cells, and combination regimen was even better. Thymoquinone could also activate apoptosis by regulating Bcl-2 and Bax genes. These indicated potential advantage of TQ for ovarian cancer in clinical practice and suggested future clinical trials to confirm its effectiveness.

Inhibitory Effect of Thymoquinone on Testosterone-Induced Benign Prostatic Hyperplasia in Wistar Rats.

This study addresses the possible protective effects of thymoquinone (TQ) against the development of experimentally-induced benign prostatic hyperplasia (BPH) in Wistar rats. Eighteen adult male rats were divided into three groups; the negative control group (n=6) received vehicle, and two groups received subcutaneous testosterone injection (3mg/kg). Animals receiving testosterone were randomized to untreated BPH group (n=6) and BPH+TQ treated group (n=6, 50mg/kg orally for 14days). Histological changes and the mRNA levels of transforming growth factor-β1 (TGF-β1 ) and vascular endothelial growth factor-A (VEGF-A) were analyzed. Additionally, dihydrotestosterone and interleukin-6 (IL-6) serum levels were determined. The presented research shows significant increases in prostate weight/body weight ratio, prostate epithelial thickness, serum IL-6 and dihydrotestosterone levels, and the prostatic expressions of TGF-β1 and VEGF-A in the untreated BPH rats. Histological examination of the prostate tissues in the BPH rats showed an elevated level of proliferation in the stromal area and glandular epithelia with abundant intraluminal papillary folds. However, a reduction in prostate weight/body weight ratio, epithelial hyperplasia, serum IL-6 levels, and the expressions of TGF-β1 and VEGF-A were observed in the BPH+TQ treated rats compared with the untreated BPH rats. The findings support TQ as a useful natural treatment for animal BPH model. Copyright © 2017 John Wiley & Sons, Ltd.

Thymoquinone inhibits murine leukemia WEHI-3 cells in vivo and in vitro.

BackgroundThymoquinone is an active ingredient isolated from Nigella sativa (Black Seed). This study aimed to evaluate the in vitro and in vivo anti-leukemic effects of thymoquinone on WEHI-3 cells.Methodology/Principal FindingsThe cytotoxic effect of thymoquinone was assessed using an MTT assay, while the inhibitory effect of thymoquinone on murine WEHI-3 cell growth was due to the induction of apoptosis, as evidenced by chromatin condensation dye, Hoechst 33342 and acridine orange/propidium iodide fluorescent staining. In addition, Annexin V staining for early apoptosis was performed using flowcytometric analysis. Apoptosis was found to be associated with the cell cycle arrest at the S phase. Expression of Bax, Bcl2 and HSP 70 proteins were observed by western blotting. The effects of thymoquinone on BALB/c mice injected with WEHI-3 cells were indicated by the decrease in the body, spleen and liver weights of the animal, as compared to the control.ConclusionThymoquinone promoted natural killer cell activities. This compound showed high toxicity against WEHI-3 cell line which was confirmed by an increase of the early apoptosis, followed by up-regulation of the anti-apoptotic protein, Bcl2, and down-regulation of the apoptotic protein, Bax. On the other hand, high reduction of the spleen and liver weight, and significant histopathology study of spleen and liver confirmed that thymoquinone inhibited WEHI-3 growth in the BALB/c mice. Results from this study highlight the potential of thymoquinone to be developed as an anti-leukemic agent.

Thymoquinone inhibits phorbol ester-induced activation of NF-κB and expression of COX-2, and induces expression of cytoprotective enzymes in mouse skin in vivo

Thymoquinone (TQ), the active ingredient of Nigella sativa, has been reported to possess anti-inflammatory and chemopreventive properties. The present study was aimed at elucidating the molecular mechanisms of anti-inflammatory and antioxidative activities of thymoquinone in mouse skin. Pretreatment of female HR-1 hairless mouse skin with TQ attenuated 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced expression of cyclooxygenase-2 (COX-2). TQ diminished nuclear translocation and the DNA binding of nuclear factor-kappaB (NF-κB) via the blockade of phosphorylation and subsequent degradation of IκBα in TPA-treated mouse skin. Pretreatment with TQ attenuated the phosphorylation of Akt, c-Jun-N-terminal kinase and p38 mitogen-activated protein kinase, but not that of extracellular signal-regulated kinase-1/2. Moreover, topical application of TQ induced the expression of heme oxygenase-1, NAD(P)H-quinoneoxidoreductase-1, glutathione-S-transferase and glutamate cysteine ligase in mouse skin. Taken together, the inhibitory effects of TQ on TPA-induced COX-2 expression and NF-κB activation, and its ability to induce the expression of cytoprotective proteins provide a mechanistic basis of anti-inflammatory and antioxidative effects of TQ in hairless mouse skin.

Inhibition of brain oxidative stress and inducible nitric oxide synthase expression by thymoquinone attenuates the development of morphine tolerance and dependence in mice

In this study, the effect of thymoquinone on morphine-induced tolerance and dependence in mice was investigated. Repeated administration of thymoquinone along with morphine attenuated the development of morphine tolerance, as measured by the hot plate test, and dependence, as assessed by naloxone-precipitated withdrawal manifestations. Concurrently, morphine-induced progressive increase in brain malondialdehyde (MDA) level and nitric oxide (NO) production as well as progressive decrease in brain intracellular reduced glutathione (GSH) level and glutathione peroxidase (GSH-Px) activity were inhibited by co-administration of thymoquinone. Morphine-induced progressive increase in brain glutamate level was not inhibited by concomitant administration of thymoquinone. Similarly, co-administration of thymoquinone inhibited naloxone-induced increase in brain MDA level, NO overproduction and decrease in brain intracellular GSH level and GSH-Px activities but it did not inhibit naloxone-induced elevation of brain glutamate level in morphine-dependent mice. The inhibitory effect of thymoquinone on morphine-induced tolerance and dependence on naloxone-induced biochemical alterations in morphine-dependent mice was enhanced by concurrent i.p. administration of the NMDA receptor antagonist, dizocilpine, the antioxidant, N-acetylcysteine or the NO synthase inhibitor, L-N (G)-nitroarginine methyl ester. On the other hand, this inhibitory effect of thymoquinone was antagonized by concurrent i.p. administration of NO precursor, l-arginine. In addition, concomitant administration of thymoquinone inhibited morphine tolerance and dependence-induced increase in inducible but not in neuronal NO synthase mRNA expression in mice brain. These results demonstrate that inhibition of morphine-induced oxidative stress, increase in the expression of brain inducible NO synthase and NO overproduction by thymoquinone can attenuate the development of morphine tolerance and dependence.

Inhibitory effects of thymoquinone on human pancreatic carcinoma orthotopically implanted in nude mice

To explore the anti-neoplastic and anti-metastatic effects of thymoquinone on the model of human pancreatic carcinoma established by surgical orthotopic implantation (SOI) in nude mice. After a 3-week implantation, 40 mice were randomized into 4 groups: control group, feed with 1% ethanol; low-dose thymoquinone group (L-TQ 5 mg/kg BW daily by i.g.), high-dose thymoquinone group (H-TQ 20 mg/kg BW daily by i.g.) and gemcitabine group (GEM 100 mg/kg BW twice a week by i.p.) (n = 10 each). All treatment sessions lasted for 2 weeks. At Week 8 post-implantation, tumor weight, inhibition rate and the presence of metastasis were evaluated respectively after sacrificing. Immunohistochemistry was used to detect the positive expressions of Ki-67, XIAP (X-linked inhibitor of apoptosis protein) and MMP-9 (matrix metalloproteinase 9) in tumors. The tumor growth-inhibiting rates of L-TQ group, H-TQ group and GEM group were 42.57%, 64.11% and 54.77% respectively. The rates of metastasis in L-TQ group and H-TQ group were 60% and 50% versus GEM group (100%). And the differences had statistical significance (P < 0.05). The positive rates of Ki-67 in group L-TQ and group H-TQ were 37% ± 3% and 32% ± 2% versus group GEM (55% ± 4%). And the differences had statistical significance (P < 0.05). The positive rates of XIAP in group L-TQ and group H-TQ were 30% ± 3% and 28% ± 5% versus group GEM (56% ± 4%). And the differences had statistical significance (P < 0.05). The positive rates of MMP-9 in group L-TQ and group H-TQ were 57% ± 7% and 53% ± 2% versus group GEM (73% ± 4%). And the differences had statistical significance (P < 0.05). Thymoquinone has the anti-neoplastic and anti-metastatic effects on the human pancreatic carcinoma in nude mice. And the above effects may be correlated with the down-regulated expressions of XIAP and MMP-9.

Effects of thymoquinone on growth and apoptosis of osteosarcoma SaOS-2 cell line in vitro

Objective To investigate the inhibitory effect of thymoquinone on the growth of human osteosarcoma cell line SaOS-2 in vitro.Methods After human osteosarcoma SaOS-2 cells were treated with different concentrations of thymoquinone, the proliferation was measured by Cell Counting Kit-8 (CCK-8) assay. The flowcytometry (FCM) was used to determine apoptosis of SaOS-2 cells. The morphological changes of SaOS-2 cells were observed under the fluorescence microscopy after DAPI staining. Western blotting was used to detect the protein expression of Caspase-3, X-linked inhibitor of apoptosis protein (XIAP) and Smac.Results Thymoquinone obviously suppressed proliferation of SaOS-2 cells in a dose-dependent manner, and the apoptosis rate was (8.1±0.7)%, (13.2±1.1)% and (20.2±1.7)% respectively when the concentrations of thymoquinone exposed were 20, 40 and 80 μmol/L. After treatment with thymoquinone, the expression of Caspase-3 and Smac was up-regulated in SaOS-2 cells, and thymoquinone treatment significantly decreased the XIAP levels in SaOS-2 cells.Conclusion Thymoquinone has the anti-tumor effect on the human osteosarcoma SaOS-2 cells in vitroprobably by up-regulating the expression of Caspase-3 and Smac and down-regulating the expression of XIAP. Key words: Thymoquinone; Osteosarcoma; Apoptosis

Inhibitory Effects of Topical Thymoquinone on Corneal Neovascularization

Thymoquinone, one of the biologically active components of black seed oil, has anti-inflammatory and antioxidant properties. We aimed to study the effect of thymoquinone on corneal neovascularization in rats and to compare its efficacy with that of triamcinolone acetonide. Chemical cauterization of the cornea was performed with silver nitrate/potassium nitrate sticks in 40 eyes in 40 rats. An examiner blinded to the experiments scored the intensity of the cauterization. Topical instillation of thymoquinone 0.1%, thymoquinone 0.4%, and triamcinolone acetonide was continued for 7 days. The inhibitory effects of the drugs on corneal neovascularization were tested and compared with each other and with controls with a computer program that evaluates percent areas of cornea covered by neovascularization. The means of percent area of corneal neovascularization in the thymoquinone 0.1%, thymoquinone 0.4%, triamcinolone acetonide, and control groups were 60.1%, 45%, 46%, and 72%, respectively. The inhibitory effect of thymoquinone 0.4% was found to be equal to that of triamcinolone acetonide (P = 0.87). The thymoquinone 0.4% and triamcinolone groups were different from the thymoquinone 0.1% and control groups (P < 0.05). There was also a significant difference between the percent area of corneal neovascularization in the thymoquinone 0.1% group and that of the controls (P < 0.05). The mean burn stimulus intensities were not different among the groups (P = 0.54). Thymoquinone was shown to have an inhibitory effect, comparable with that of triamcinolone, on corneal neovascularization in this rat model. However, thymoquinone decreased corneal neovascularization in a dose-dependent manner.

Thymoquinone decreases AGE‐induced NF‐κB activation in proximal tubular epithelial cells

The inhibitory effects of thymoquinone (TQ) on activation of the redox-sensitive transcription factor nuclear factor kappa B (NF-kappaB) and interleukin-6 (IL-6) were studied in vitro. Human proximal tubular epithelial cells (pTECs) were cultivated and stimulated with advanced glycation end products (AGEs) and the effects of TQ were studied. A significant reduction of AGE-induced NF-kappaB-activation and Il-6 expression was observed. This points to potential antioxidative qualities of TQ.

Thymoquinone, a component of the herb Nigella sativa, suppresses proliferation and viability of prostate cancer cells by down-regulating androgen receptor and E2F-1

20038 Background: Prostate cancer (CaP) that relapses following androgen-ablation therapy is hormone refractory, yet its growth continues to depend on androgen receptor (AR). Therefore, a curative strategy must include structural elimination of AR. Thymoquinone (TQ) is a component of Nigella sativa, an herb that has been used for thousands of years for a variety of diseases including cancer. We examined TQ effect on AR and cell cycle regulatory proteins required for proliferation and viability of CaP cells. Methods: Inhibitory effect of TQ on DNA synthesis and proliferation of exponentially growing LNCaP cells was assessed by 3H-thymidine incorporation into DNA and MTS assay respectively. We examined TQ effect on AR and cell cycle regulatory proteins by Western blot analysis. The effect of TQ on cell cycle progression was determined using synchronized LNCaP cells. Western blots were then used to analyze equal amounts of protein isolated from cells at regular intervals during their progression through the cell cycle in the presence or absence of TQ. Results: We observed a dose-dependent increase in the inhibitory effect of TQ on DNA synthesis and proliferation of LNCaP cells. We also observed a significant decrease in AR and E2F-1, and a dramatic increase in p21, p27, and pRB, and Bax. Synchronized LNCaP cells treated with TQ failed to enter S phase. Western blot analysis revealed that TQ treatment of synchronized cells resulted in: (i) a significant decrease in AR, that normally increases in early- to late-G1phase, and E2F-1, that normally increases in late-G1phase (ii) down-regulation of cyclins A and E, Cdks-2 and 4, and Cdc-6 (iii) induction of p53 and p27. Conclusion: These observations demonstrate that TQ inhibits proliferation and viability of prostate cancer cells by decreasing AR and E2F-1 levels and inducing the proteins that cause cell cycle arrest and promote apoptotic events. Thus TQ may prove to be an effective treatment of hormone refractory CaP and a promising chemo- and/or radiation- sensitizing agent in adjuvant therapy as well. This could represent a novel approach for treatment of prostate cancer by an herbal agent that was shown to spare normal cells in previous studies. No significant financial relationships to disclose.

Thymoquinone suppresses expression of inducible nitric oxide synthase in rat macrophages

The objective of the present study was to determine the immunomodulatory role of thymoquinone (TQ) regarding its effect on the production of nitric oxide (NO) by rat peritoneal macrophages. Under certain conditions, macrophages and certain other cells can produce high concentrations of NO from its precursor l-arginine via inducible nitric oxide synthase (iNOS) pathway. TQ has been established as the major component of the oil extracted from Nigella sativa plant seeds, which is being used frequently in herbal medicine. TQ (IC 50 1.4–2.76 μM) dose- and time-dependently reduced nitrite production, a parameter for NO synthesis, in supernatants of lipopolysaccharide (LPS)-stimulated (5 μg/ml) macrophages without affecting the cell viability. The protein level of iNOS in peritoneal macrophages was also decreased by TQ in a concentration-dependent manner. In addition, TQ inhibited the increase in iNOS mRNA expression induced by LPS indicated by reverse transcription-polymerase chain reaction (RT-PCR). These inhibitory effects of TQ were confirmed by immunofluorescence staining of iNOS in macrophages which showed decreased immunoreactivity for iNOS after treatment with TQ if compared with the control LPS-stimulated cells. These results suggest that TQ suppresses the production of NO by macrophages; an effect which may be useful in ameliorating the inflammatory and autoimmune conditions.