Travoprost Liquid Nanocrystals: An Innovative Armamentarium for Effective Glaucoma Therapy.

To date, the ophthalmic application of liquid crystalline nanostructures (LCNs) has not been thoroughly reconnoitered, yet they have been extensively used. LCNs are primarily made up of glyceryl monooleate (GMO) or phytantriol as a lipid, a stabilizing agent, and a penetration enhancer (PE). For optimization, the D-optimal design was exploited. A characterization using TEM and XRPD was conducted. Optimized LCNs were loaded with the anti-glaucoma drug Travoprost (TRAVO). Ex vivo permeation across the cornea, in vivo pharmacokinetics, and pharmacodynamic studies were performed along with ocular tolerability examinations. Optimized LCNs are constituted of GMO, Tween® 80 as a stabilizer, and either oleic acid or Captex® 8000 as PE at 25 mg each. TRAVO-LNCs, F-1-L and F-3-L, showed particle sizes of 216.20 ± 6.12 and 129.40 ± 11.73 nm, with EE% of 85.30 ± 4.29 and 82.54 ± 7.65%, respectively, revealing the highest drug permeation parameters. The bioavailability of both attained 106.1% and 322.82%, respectively, relative to the market product TRAVATAN®. They exhibited respective intraocular pressure reductions lasting for 48 and 72 h, compared to 36 h for TRAVATAN®. All LCNs exhibited no evidence of ocular injury in comparison to the control eye. The findings revealed the competence of TRAVO-tailored LCNs in glaucoma treatment and suggested the potential application of a novel platform in ocular delivery.

A biodegradable film based on cellulose and thiazolidine bearing UV shielding property.

The current rationale is exploring new eco-friendly UV- shielding films based on cellulose and thiazolidine. Cellulose was oxidized to dialdehyde cellulose (DAC) and tricarboxy cellulose (TCC) by periodate and TEMPO/periodate/hypochlorite, respectively. While E-3-amino-5-(phenyldiazenyl)-2-thioxothiazolidin-4-one (TH) was synthesized by coupling diazonium salt with the 5-methylene of 2-thioxo-4-thiazolidinone. DAC was then coupled with TH via Schiff base reaction and incorporated onto TCC with different ratios to get UV-shielding films. 1HNMR, infrared spectroscopy (FTIR), and thermal gravimetric analysis (TGA) were used to investigate the chemical structure of the synthesized materials. In addition, the films' morphology, thermal, mechanical, and UV-shielding properties were investigated. The UV-shielding studies revealed that the film with 10% DAC-TH has 99.88, 99.99, and 96.19% UV-blocking (UVB), UV-absorbance (UVA), and Ultra-violet protection (UPF), respectively. Moreover, the prepared films demonstrated promising antimicrobial activity against Escherichia coli, S. aureus, P. aeruginosa, and Candida albicans. Finally, the prepared films showed no cytotoxic effects on normal human skin fibroblast's HFB-4 cell line.

Hydrazonoyl chlorides possess promising antitumor properties.

AIMS: the main purpose of this study was to identify new selective antitumor agents. MAIN METHODS: several hydrazonoyl chlorides (HCs) were synthesized and human tumor cell line viability was determined using the MTT assay. Tumor development was assessed using Ehrlich ascites carcinoma (EAC)-bearing mice. KEY FINDINGS: our results showed that 2-oxo-N-phenyl-2-(phenylamino)acetohydrazonoyl chloride (compound 4; CPD 4) and 2-oxo-2-(phenylamino)-N-(p-tolyl)acetohydrazonoyl chloride (CPD 5) were the most cytotoxic HCs to human cervical tumor HeLa (IC50: 20 and 25 µM for CPD 4 and 5 respectively), breast MCF7 (IC50: 29 and 34 µM for CPD 4 and 5 respectively) and colon HCT116 cancer cells (IC50: 26 and 25 µM for CPD 4 and 5 respectively) with the least cytotoxicity to human non-tumor CCD-18Co colon fibroblasts as well as murine splenocytes. The active compounds significantly inhibited colony formation as well as tumor development in EAC-bearing mice. We also observed that PTEN-deficient cells displayed greater sensitivity than cells expressing wild type PTEN. At the molecular level, comet and cell cycle analyses indicated that the active compounds generate DNA damage. In light of the PTEN-dependent sensitivity and genomic instability we examined the influence of HCs on the DNA repair enzyme polynucleotide kinase/phosphatase (PNKP) and the PI3K/AKT/mTOR pathway, which are each known to be synthetic lethal with PTEN. We found that both PNKP and the PI3K/AKT/mTOR pathway to be adversely affected by the HCs, which may partially account for their toxicity. SIGNIFICANCE: hydrazonoyl chlorides can be considered as hit compounds for the development of new antitumor agents.

Delineating penetration enhancer-enriched liquid crystalline nanostructures as novel platforms for improved ophthalmic delivery.

Liquid crystalline nanostructures (LCNs), for instance cubosomes, have been widely used as a promising carrier for drug delivery through the last few years. To date, the ophthalmic application of these platforms was not well explored, and the effect of integrating penetration enhancers (PEs) into LCNs has not been investigated yet. Hence, the present work aimed coupling novel PEs into glyceryl monooleate-based cubosomes for ocular administration. Various enhancers viz, free fatty acids (oleic and linoleic acids), natural terpenes (D-limonene and cineole), medium-chain triglycerides (Captex® 1000 and Captex® 8000), mono-/di-glycerides (Capmul® MCM, Capmul® PG-8, and Capmul® PG-12) were tested at different amounts. The morphology of the formed LCNs was investigated using transmission electron microscopy (TEM). The crystallinity and thermal behavior studies were also conducted. The ocular safety of optimized formulae was tested via hen's egg test-chorioallantoic membrane (HET-CAM), rabbit eye Draize test, and histopathological examinations of ocular tissues. Confocal laser scanning microscopy (CLSM) was utilized to assess the enhanced permeation of fluorescently-labeled LCNs across corneal layers. The acceptable formulations exhibited relatively homogenous particle nano-sizes ranging from 139.26 ± 3.68 to 590.56 ± 24.86 nm carrying negative surface charges. TEM images, X-ray patterns and DSC thermograms demonstrated the influential effect of PEs in developing altered crystalline structures. The ocular compatibility of optimized LCNs was confirmed. The corneal distribution using CLSM proved the disseminated fluorescence intensity of LCNs enriched with oleic acid, Captex® 8000 and Capmul® MCM. Selected LCNs showed good physical stability upon storage and lyophilization. The results demonstrated the efficiency of tailored PE-modified LCNs in enhancing the ocular transport with no evidence of any irritation potential, and hence suggested their prospective applicability in ophthalmic drug delivery.

A Rapid Lysostaphin Production Approach and a Convenient Novel Lysostaphin Loaded Nano-emulgel; As a Sustainable Low-Cost Methicillin-Resistant Staphylococcus aureus Combating Platform.

Staphylococcus aureus is a Gram-positive pathogen that is capable of infecting almost every organ in the human body. Alarmingly, the rapid emergence of methicillin-resistant S.aureus strains (MRSA) jeopardizes the available treatment options. Herein, we propose sustainable, low-cost production of recombinant lysostaphin (rLST), which is a native bacteriocin destroying the staphylococcal cell wall through its endopeptidase activity. We combined the use of E. coli BL21(DE3)/pET15b, factorial design, and simple Ni-NTA affinity chromatography to optimize rLST production. The enzyme yield was up to 50 mg/L culture, surpassing reported systems. Our rLST demonstrated superlative biofilm combating ability by inhibiting staphylococcal biofilms formation and detachment of already formed biofilms, compared to vancomycin and linezolid. Furthermore, we aimed at developing a novel rLST topical formula targeting staphylococcal skin infections. The phase inversion composition (PIC) method fulfilled this aim with its simple preparatory steps and affordable components. LST nano-emulgel (LNEG) was able to extend active LST release up to 8 h and cure skin infections in a murine skin model. We are introducing a rapid, convenient rLST production platform with an outcome of pure, active rLST incorporated into an effective LNEG formula with scaling-up potential to satisfy the needs of both research and therapeutic purposes.

Design and synthesis of resveratrol-salicylate hybrid derivatives as CYP1A1 inhibitors.

Resveratrol and aspirin are known to exert potential chemopreventive effects through modulation of numerous targets. Considering that the CYP450 system is responsible for the activation of environmental procarcinogens, the aim of this study was to design a new class of hybrid resveratrol-aspirin derivatives possessing the stilbene and the salicylate scaffolds. Using HepG2 cells, we evaluated (a) the inhibition of TCDD-mediated induction of CYP1A1 exerted by resveratrol-aspirin derivatives using the EROD assay, and (b) CYP1A1 mRNA in vitro. We observed significant inhibition (84%) of CYP1A1 activity and a substantial decrease in CYP1A1 mRNA with compound 3, compared to control. Resveratrol did not exert inhibition under the same experimental conditions. This inhibitory profile was supported by docking studies using the crystal structure of human CYP1A1. The potential effect exerted by compound 3 (the most active), provide preliminary evidence supporting the design of hybrid molecules combining the chemical features of resveratrol and aspirin.

Development of cardiac hypertrophy by sunitinib in vivo and in vitro rat cardiomyocytes is influenced by the aryl hydrocarbon receptor signaling pathway.

Sunitinib (SUN) is a new tyrosine kinase inhibitor that possesses both anti-angiogenic and anti-tumor activities. Although SUN has improved survival rate in cancer patients, cardiotoxicity has been reported as a significant side effect. Several studies suggested a role for the aryl hydrocarbon receptor (AhR) and its regulated genes such as cytochrome P4501A1 (CYP1A1) in the pathogenesis of heart failure and cardiac hypertrophy. To test the hypothesis that SUN induces cardiac hypertrophy through the modulation of AhR, Wistar albino rats were treated for 15 and 30 days with increasing doses of SUN (25, 50, and 100 mg/kg), whereas at the in vitro level, rat cardiomyocyte H9c2 cells were incubated with SUN (1, 2.5, and 5 µM). Thereafter, cardiac hypertrophy parameters were determined at the biochemical, histopathology, and gene expression levels. SUN treatment causes increase in cardiac enzymes, changes in histopathology, and induction in several hypertrophic markers. This was associated with proportional increase in the CYP1A1 gene in a concentration- and time-dependent manner. The direct involvement of AhR in the SUN-induced cardiac hypertrophy in H9c2 cells was supported by the ability of resveratrol, an AhR antagonist, to block the SUN-induced hypertrophy and the ability of SB203580, a novel AhR agonist, to potentiate SUN-induced hypertrophic genes. This is the first demonstration that SUN induces hypertrophic genes in vivo and in vitro rat cardiomyocyte through AhR/CYP1A1-mediated mechanism.

Synthetic lethal targeting of PTEN-deficient cancer cells using selective disruption of polynucleotide kinase/phosphatase.

A recent screen of 6,961 siRNAs to discover possible synthetic lethal partners of the DNA repair protein polynucleotide kinase/phosphatase (PNKP) led to the identification of the potent tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN). Here, we have confirmed the PNKP/PTEN synthetic lethal partnership in a variety of different cell lines including the PC3 prostate cancer cell line, which is naturally deficient in PTEN. We provide evidence that codepletion of PTEN and PNKP induces apoptosis. In HCT116 colon cancer cells, the loss of PTEN is accompanied by an increased background level of DNA double-strand breaks, which accumulate in the presence of an inhibitor of PNKP DNA 3'-phosphatase activity. Complementation of PC3 cells with several well-characterized mutated PTEN cDNAs indicated that the critical function of PTEN required to prevent toxicity induced by an inhibitor of PNKP is most likely associated with its cytoplasmic lipid phosphatase activity. Finally, we show that modest inhibition of PNKP in a PTEN knockout background enhances cellular radiosensitivity, suggesting that such a "synthetic sickness" approach involving the combination of PNKP inhibition with radiotherapy may be applicable to PTEN-deficient tumors.

Harmine and harmaline downregulate TCDD-induced Cyp1a1 in the livers and lungs of C57BL/6 mice.

We previously demonstrated that Peganum harmala L. extract and its main active constituents, harmine and harmaline inhibit the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-mediated induction of the carcinogen-activating enzyme, Cyp1a1, in vitro. However, the effect of both alkaloids on Cyp1a1 in vivo has not been investigated. Therefore, the aim of this study is to examine the effect of harmine and harmaline on TCDD-mediated induction of Cyp1a1 in mice livers and lungs. C57BL/6 male mice were distributed into four groups (n = 6). First group received vehicle, while the second group received TCDD (i.p.). The third and fourth groups received either harmine or harmaline (i.p.) × 3 times along with TCDD one time with the mid dose of harmine and harmaline. All mice were sacrificed after 14 h from TCDD injection, and livers and lungs were isolated. The effect of harmine and harmaline on TCDD-mediated induction of Cyp1a1 mRNA, protein, and activity levels was determined using real-time PCR, Western blot analysis, and 7-ethoxyresurofin as a substrate, respectively. Our results showed that harmine and harmaline significantly decreased the TCDD-mediated induction of Cyp1a1 in both the livers and lungs. We concluded that harmine and harmaline are promising candidate to inhibit TCDD-mediated induction of Cyp1a1 in mice hepatic and extrahepatic tissues.

Sunitinib, a tyrosine kinase inhibitor, induces cytochrome P450 1A1 gene in human breast cancer MCF7 cells through ligand-independent aryl hydrocarbon receptor activation.

Sunitinib (SUN) is a new multi-targeted oral tyrosine kinase inhibitor that has both anti-angiogenic and anti-tumor activities. However, information reported in the literature on the effects of SUN on the constitutive expression of cytochrome P450 1A1 (CYP1A1) gene in cells from mammalian species remains unclear. Therefore, the main objectives of the current work were to investigate the potentiality of SUN to induce CYP1A1 gene expression in human breast cancer MCF7 cells and to explore the molecular mechanisms involved. Our results showed that SUN induced the CYP1A1 mRNA, protein, and activity levels in a concentration-dependent manner in MCF7 cells. The increase in CYP1A1 mRNA by SUN was completely blocked by the transcriptional inhibitor, actinomycin D; implying that SUN increased de novo RNA synthesis. Furthermore, the ability of SUN to increase luciferase reporter gene expression suggests an aryl hydrocarbon receptor (AhR)-dependent transcriptional control and excludes the possibility of any posttranscriptional mechanisms. In addition, blocking of AhR activation by resveratrol, a well-known AhR antagonist, prevented the SUN-induced CYP1A1 gene expression, further confirms the involvement of AhR. Interestingly, this was associated with the inability of SUN to directly bind to and induce transformation of cytosolic AhR to its DNA-binding form in vitro, suggesting that the effect of SUN does not involve direct binding to AhR. The current manuscript provides the first evidence for the ability of SUN to induce CYP1A1 gene expression in MCF7 cells through AhR ligand-independent mechanisms.

Induction of quinone oxidoreductase 1 enzyme by Rhazya stricta through Nrf2-dependent mechanism.

ETHNOPHARMACOLOGICAL RELEVANCE: Rhazya stricta Decne. (Apocynaceae) is a common medicinal plant in the Arabian Peninsula, Pakistan and India. Rhazya stricta has been used traditionally to treat several diseases including tumors; however, the underlying mechanism is still not fully elucidated. AIM OF THE STUDY: The aim of this study is to examine the ability of Rhazya stricta to induce a key enzyme involved in cancer chemoprevention, NAD(P)H:quinone oxidoreductase 1 (Nqo1) in murine and human hepatoma cells. Nqo1 is regulated by the nuclear factor erythroid 2-related factor 2 (Nrf2) and the aryl hydrocarbon receptor (AhR) transcription factors. MATERIALS AND METHODS: Rhazya stricta leaves were extracted using ethanol, the strong basic alkaloid fraction (AF) was isolated according to a bioassay-guided fractionation and its mass spectrum was used as a fingerprint for its identity. The effect of increasing concentrations of AF on Nqo1 was tested in murine hepatoma Hepa 1c1c7 and human HepG2 cells. The role of Nrf2-dependent mechanism was tested by using Nrf2-dependent luciferase assay and by determining the Nrf2 nuclear accumulation in Hepa 1c1c7 cells. The role of AhR-dependent mechanism was assessed by using an AhR-deficient version of murine hepatoma c12 cells. RESULTS: AF significantly induced the Nqo1 at mRNA, protein and catalytic activity levels in murine hepatoma Hepa 1c1c7 cells. Moreover, the induction of Nqo1 by AF was completely abolished by using the transcriptional inhibitor, actinomycin D, implying a role of transcriptional regulation. In addition, the role of Nrf2 signaling pathway was confirmed by the induction of Nrf2-dependent luciferase activity and the induced Nrf2 nuclear accumulation in Hepa 1c1c7 cells. Interestingly, AF induced Nqo1 at mRNA and catalytic activity in c12 and HepG2 cells. Finally, the AF induced the Nrf2-dependent luciferase activity in HepG2 cells, confirming the role of Nrf2 in its regulation. CONCLUSIONS: The present study presents the first evidence that Rhazya stricta and its active strongly basic alkaloid fraction induce the chemopreventative enzyme, Nqo1 through Nrf2-dependent mechanism.

Camel milk modulates the expression of aryl hydrocarbon receptor-regulated genes, Cyp1a1, Nqo1, and Gsta1, in murine hepatoma Hepa 1c1c7 cells.

There is a traditional belief in the Middle East that camel milk may aid in prevention and treatment of numerous cases of cancer yet, the exact mechanism was not investigated. Therefore, we examined the ability of camel milk to modulate the expression of a well-known cancer-activating gene, Cytochrome P450 1a1 (Cyp1a1), and cancer-protective genes, NAD(P)H:quinone oxidoreductase 1 (Nqo1) and glutathione S-transferase a1 (Gsta1), in murine hepatoma Hepa 1c1c7 cell line. Our results showed that camel milk significantly inhibited the induction of Cyp1a1 gene expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most potent Cyp1a1 inducer and known carcinogenic chemical, at mRNA, protein, and activity levels in a concentration-dependent manner. In addition, camel milk significantly decreased the xenobiotic responsive element (XRE)-dependent luciferase activity, suggesting a transcriptional mechanism is involved. Furthermore, this inhibitory effect of camel milk was associated with a proportional increase in heme oxygenase 1. On the other hand, camel milk significantly induced Nqo1 and Gsta1 mRNA expression level in a concentration-dependent fashion. The RNA synthesis inhibitor, actinomycin D, completely blocked the induction of Nqo1 mRNA by camel milk suggesting the requirement of de novo RNA synthesis through a transcriptional mechanism. In conclusion, camel milk modulates the expression of Cyp1a1, Nqo1, and Gsta1 at the transcriptional and posttranscriptional levels.

Transcriptional and posttranslational inhibition of dioxin-mediated induction of CYP1A1 by harmine and harmol.

Dioxins are widespread environmental contaminants that induce the carcinogen-activating enzyme, cytochrome P450 1A1 (CYP1A1) through an aryl hydrocarbon receptor (AhR)-dependent mechanism. We previously demonstrated that harmine inhibits the dioxin-mediated induction of Cyp1a1 activity in murine hepatoma cells. Therefore, the aim of this study is to determine the effect of harmine and its main metabolite, harmol, on the dioxin-mediated induction of CYP1A1 in human HepG2 and murine Hepa 1c1c7 hepatoma cells. Our results showed that harmine and harmol significantly inhibited the dioxin-mediated induction of CYP1A1 at mRNA, protein, and activity levels in a concentration-dependent manner in human and murine hepatoma cells. Moreover, harmine and harmol inhibited the AhR-dependent luciferase activity and the activation and transformation of AhR using the electrophoretic mobility shift assay. In addition, harmine and harmol displaced [(3)H]TCDD in the competitive ligand binding assay. At posttranslational level, both harmine and harmol decreased the protein stability of CYP1A1, suggesting that posttranslational mechanism is involved. Furthermore, we demonstrated that the underlying mechanisms of the posttranslational modifications of both compounds involve ubiquitin-proteasomal pathway and direct inhibitory effects of CYP1A1 enzyme. We concluded that harmine and its metabolite, harmol, are new inhibitors of dioxin-mediated effects.

Harmaline and harmalol inhibit the carcinogen-activating enzyme CYP1A1 via transcriptional and posttranslational mechanisms.

Dioxins are known to cause several human cancers through activation of the aryl hydrocarbon receptor (AhR). Harmaline and harmalol are dihydro-ß-carboline compounds present in several medicinal plants such as Peganum harmala. We have previously demonstrated the ability of P. harmala extract to inhibit TCDD-mediated induction of Cyp1a1 in murine hepatoma Hepa 1c1c7 cells. Therefore, the aim of this study is to examine the effect of harmaline and its main metabolite, harmalol, on dioxin-mediated induction of CYP1A1 in human hepatoma HepG2 cells. Our results showed that harmaline and harmalol at concentrations of (0.5-12.5µM) significantly inhibited the dioxin-induced CYP1A1 at mRNA, protein and activity levels in a concentration-dependent manner. The role of AhR was determined by the inhibition of the TCDD-mediated induction of AhR-dependent luciferase activity and the AhR/ARNT/XRE formation by both harmaline and harmalol. In addition, harmaline significantly displaced [(3)H]TCDD in the competitive ligand binding assay. At posttranslational level, both harmaline and harmalol decreased the protein stability of CYP1A1, suggesting that posttranslational modifications are involved. Moreover, the posttranslational modifications of harmaline and harmalol involve ubiquitin-proteasomal pathway and direct inhibitory effects of both compounds on CYP1A1 enzyme. These data suggest that harmaline and harmalol are promising agents for preventing dioxin-mediated effects.

Nitric oxide release is not required to decrease the ulcerogenic profile of nonsteroidal anti-inflammatory drugs.

The objective of this work was to evaluate the biological properties of a new series of nitric oxide-releasing nonsteroidal anti-inflammatory drugs (NO-NSAIDs) possessing a tyrosol linker between the NSAID and the NO-releasing moiety (PROLI/NO); however, initial screening of ester intermediates without the PROLI/NO group showed the required (desirable) efficacy/safety ratio, which questioned the need for NO in the design. In this regard, NSAID ester intermediates were potent and selective COX-2 inhibitors in vitro, showed equipotent anti-inflammatory activity compared to the corresponding parent NSAID, but showed a markedly reduced gastric toxicity when administered orally. These results provide complementary evidence to challenge the currently accepted notion that hybrid NO-NSAIDs exert their cytoprotective effects by releasing NO. Results obtained in this work constitute a good body of evidence to initiate a debate about the future replacement of NSAID prodrugs for unprotected NSAIDs (possessing a free carboxylic acid group) currently in clinical use.

Contribution to in vitro screening of Egyptian plants for schistosomicidal activity.

CONTEXT: This study is a continuation of our previous work in which a bioassay screening of 346 methanol extracts from 281 Egyptian plant species was carried out for in vitro schistosomicidal activity. OBJECTIVE: Another 309 methanol extracts from 278 plant species were subjected to the bioassay screening using the same technique on viable Schistosoma mansoni Sambon (Schistosomatidae) mature worms in specialized culture medium (Roswell Park Memorial Institute medium 1640) in a trial to discover a source for a schistosomiasis drug from Egyptian flora. MATERIAL AND METHODS: The methanol plant extracts were tested in vitro against viable S. mansoni mature worms in culture medium. Viability of worms was examined after exposure to 100 µg/ml of the extract in the medium for 24 h. Negative (dimethyl sulfoxide) and positive (praziquantel) controls were simultaneously used. Extracts showing schistosomicidal activity were further subjected to determination of their (Lethal concentration) LC50 and LC90 values. RESULTS: Confirmed in vitro antischistosomal activity was found in 42 extracts. Of these, 14 plant species possessed considerably high antischistosomal activity (LC50 ≤ 15 µg/ml), viz. Callistemon viminalis (Soland. Ex Gaertn) Cheel, C. rigidus R.Br., C. speciosus (Sims.) DC, C. citrinus Stapf, Eucalyptus citriodora Hook, E. rostrata Dehnh., Eugenia edulis Vell, E. javanica Lam syn. Syzygium samarangense (Blume) Merril, Melaleuca leucadendron (L.) L., M. stypheloides Sm. (all belong to Myrtaceae), Cryptostegia grandiflora R.Br. (Asclepiadaceae), Zilla spinosa (L.) Prantl (Cruciferae), Ficus trijuja L. (Moraceae) and Fagonia mollis Delile (Zygophylacae). DISCUSSION AND CONCLUSION: These species may represent additional natural sources of bioactive material that deserve further investigation for drug discovery against schistosomiasis.

The effect of Nrf2 knockout on the constitutive expression of drug metabolizing enzymes and transporters in C57Bl/6 mice livers.

Previous reports have proposed a cross-talk between the nuclear factor erythroid-2 p45-related factor-2 (Nrf2)/antioxidant response element (ARE) and the aryl hydrocarbon receptor (AhR)/xenobiotic response element (XRE) signaling pathways. Therefore, the aim of the current study was to examine the level of phase I, phase II drug metabolizing enzymes (DMEs), and phase III transporters and their related transcription factors in the Nrf2 knockout model. Our results showed that phase II DMEs that are under the control of Nrf2 typified by NAD(P)H: quinone oxidoreductase 1 (Nqo1), and glutathione S-transferase (Gst) were significantly lower at the mRNA, protein, and catalytic activity levels in the livers of Nrf2 knockout mice compared to wild type. Furthermore, phase I cytochrome P450s (CYPs), Cyp1, and Cyp2b10 at mRNA, protein, and catalytic activity levels were significantly lower in the livers of Nrf2 knockout mice. Interestingly, our results showed that the transcription factors AhR, constitutive androstane receptor (CAR), and pregnane X receptor (PXR) at mRNA, and protein expression levels were significantly lower in the livers of Nrf2 knockout mice compared to wild type. Importantly, phase III drug transporters mRNA levels of the multiple drug resistance associated proteins (Mrp2 and Mrp3), and solute carrier organic anion transporters (Slco1a6 and Slco2b1) were significantly lower in the liver of Nrf2 knockout mice. Co-activators, Ncoa1, Ncoa2, and Ncoa3 mRNA levels were not altered while co-repressors, Ncor1 and Ncor2 were significantly lower in the livers of Nrf2 knockout mice. In conclusion, knockout of Nrf2 causes disruption to the coordination of phase I, phase II drug DMEs, and phase III drug transporters through altering the transcription factors controlling them.

Camel urine inhibits the cytochrome P450 1a1 gene expression through an AhR-dependent mechanism in Hepa 1c1c7 cell line.

AIM OF THE STUDY: Drinking camel urine has been used traditionally to treat numerous cases of cancer yet, the exact mechanism was not investigated. Therefore, we examined the ability of three different camel urines (virgin, lactating, and pregnant source) to modulate a well-known cancer-activating enzyme, the cytochrome P450 1a1 (Cyp1a1) in murine hepatoma Hepa 1c1c7 cell line. MATERIALS AND METHODS: The effect of different camel urines, compared to bovine urines, on Cyp1a1 mRNA was determined using real-time polymerase chain reaction. Cyp1a1 protein and catalytic activity levels were determined using Western blot analysis and 7-ethoxyresorufin as a substrate, respectively. The role of aryl hydrocarbon receptor (AhR)-dependent mechanism was determined using electrophoretic mobility shift assay (EMSA) and the AhR-dependent luciferase reporter gene. RESULTS: All types of camel, but not bovine, urines differentially inhibited the induction of Cyp1a1 gene expression by TCDD, the most potent Cyp1a1 inducer and known carcinogenic chemical. Importantly, virgin camel urine showed the highest degree of inhibition at the activity level, followed by lactating and pregnant camel urines. Furthermore, we have shown that virgin camel urine significantly inhibited the TCDD-mediated induction of Cyp1a1 at the mRNA and protein expression levels. Mechanistically, the ability of virgin camel urine to inhibit Cyp1a1 was strongly correlated with its ability to inhibit AhR-dependent luciferase activity and DNA binding as determined by EMSA, suggesting that AhR-dependent mechanism is involved. CONCLUSIONS: The present work provides the first evidence that camel urine but not that of bovine inhibits the TCDD-mediated toxic effect by inhibiting the expression of Cyp1a1, at both transcriptional and post-transcriptional levels through an AhR-dependent mechanism.

Harman induces CYP1A1 enzyme through an aryl hydrocarbon receptor mechanism.

Harman is a common compound in several foods, plants and beverages. Numerous studies have demonstrated its mutagenic, co-mutagenic and carcinogenic effects; however, the exact mechanism has not been fully identified. Aryl hydrocarbon receptor (AhR) is a transcription factor regulating the expression of the carcinogen-activating enzyme; cytochrome P450 1A1 (CYP1A1). In the present study, we examined the ability of harman to induce AhR-mediated signal transduction in human and rat hepatoma cells; HepG2 and H4IIE cells. Our results showed that harman significantly induced CYP1A1 mRNA in a time- and concentration-dependent manner. Similarly, harman significantly induced CYP1A1 at protein and activity levels in a concentration-dependent manner. Moreover, the AhR antagonist, resveratrol, inhibited the increase in CYP1A1 activity by harman. The RNA polymerase inhibitor, actinomycin D, completely abolished the CYP1A1 mRNA induction by harman, indicating a transcriptional activation. The role of AhR in CYP1A1 induction by harman was confirmed by using siRNA specific for human AhR. The ability of harman to induce CYP1A1 was strongly correlated with its ability to stimulate AhR-dependent luciferase activity and electrophoretic mobility shift assay. At post-transcriptional and post-translational levels, harman did not affect the stability of CYP1A1 at the mRNA and the protein levels, excluding other mechanisms participating in the obtained effects. We concluded that harman can directly induce CYP1A1 gene expression in an AhR-dependent manner and may represent a novel mechanism by which harman promotes mutagenicity, co-mutagenicity and carcinogenicity.

Peganum harmala L. is a candidate herbal plant for preventing dioxin mediated effects.

Dioxins are widespread environmental contaminants that have been linked with a variety of deleterious effects on human health including increased cancer rates. The detrimental effects of 2,3,7,8-tetrachlorodibenzo- P-dioxin (TCDD, one of the most common environmental dioxins) are mediated via the aryl hydrocarbon receptor (AhR). AhR is a transcription factor that regulates the expression of the carcinogen-activating enzyme, cytochrome P450 1a1 (Cyp1a1). In the present study, we examined the ability of the methanolic extract of Peganum harmala L. (Zygophyllaceae) fruiting tops to affect TCDD-activated AhR-mediated signal transduction in mouse hepatoma Hepa 1c1c7 cells. Our results showed that Peganum harmala extract significantly inhibited the TCDD-mediated induction of Cyp1a1 at mRNA, protein, and activity levels. A similar pattern of inhibition at the catalytic activity level was observed with the other AhR ligands tested. The ability of the extract to inhibit Cyp1a1 was strongly correlated with its ability to inhibit AhR-dependent luciferase activity and electrophoretic mobility shift assays. Harmine and harmaline were found to be the dominant components of the plant extract with a relative abundance of 7 and 4.85 % (w/w), respectively. In addition, both of the active alkaloids showed an inhibitory effect on TCDD-induced Cyp1a1 activity level. We concluded that Peganum harmala L. can interfere with AhR ligands-mediated effects.