Ameliorating effects of Nigella sativa oil on aggravation of inflammation, oxidative stress and cytotoxicity induced by smokeless tobacco extract in an allergic asthma model in Wistar rats.

BACKGROUND: The comparison of smokeless tobacco (ST) exposure versus Ovalbumin (Ova) sensitized rats or asthmatic patients has hardly been studied in the literature. Thus, the present study aims to investigate the aggravation of inflammation, exacerbation of asthma, oxidative stress and cytotoxicity induced by ST. METHODS: ST was given at the dose of 40mg/kg in an allergic asthma model in Wistar rats. Furthermore, the effects of oral administration of Nigella sativa oil (NSO), at a dose of 4mL/kg/day, were investigated. RESULTS: The obtained results showed that ST clearly enhanced lung inflammation through interleukin-4 (IL-4) and Nitric oxide (NO) increased production. Actually, ST was found to intensify the oxidative stress state induced by Ova-challenge in rats, which was proven not only by augmenting lipid peroxidation and protein oxidation, but also by altering the non-enzymatic and enzymatic antioxidant status. Furthermore, the aggravation of inflammation and oxidative stress was obviously demonstrated by the histopathological changes observed in lung. In contrast, NSO administration has shown anti-inflammatory effects by reducing IL-4 and NO production, restoring the antioxidant status, reducing lipid peroxidation and improving the histopathological alterations by both protein oxidation and NSO treatment. CONCLUSIONS: Our data have proven that severe concurrent exposure to allergen and ST increases airway inflammation and oxidative stress in previously sensitized rats. They also suggest that the oral NSO treatment could be a promising treatment for asthma.

Eosinophilic activity and bronchial hyperresponsiveness within an asthmatic paediatric population.

BACKGROUND: Our study aims to assess the importance of serum eosinophil cationic protein (ECP) levels as a non-invasive marker of bronchial hyperresponsiveness (BHR) in children with asthma, and may predict objectively the asthmatic severity and sensitivities. METHODS: This study, which was carried out on 75 asthmatic patients from a paediatric population (average age: nine years old, sex-ratio M/F: 1.64), is based on both interrogation conducted by the clinician and biological explorations, essentially serological testing of ECP and eosinophilia determination, as well as the measurement of serological IgE amounts. RESULTS: The analysis of the questionnaires and the biological results allowed us to evaluate the clinico-biological relations within this population. ECP, more than eosinophilia, proves to be a relevant marker of asthma severity (p<0.05) and sensitivities within this given population (r=0.65). CONCLUSION: We were able to show that the evaluation of the serological levels of ECP seems to be a good biological marker of asthma.

Halogenated chalcones with high-affinity binding to P-glycoprotein: potential modulators of multidrug resistance.

Previous studies have shown that flavonoids are modulators of the transmembrane P-glycoprotein (P-gp) which mediates cell multidrug resistance. Some structural elements have been identified which seem to contribute to these compounds' activity. In the present study, a series of halogenated chalcones was prepared to further explore the structural requirements for the P-gp modulation. Four halogenated chalcones have been synthesized and evaluated as potential modulators of P-gp-mediated multidrug resistance of cancer cells by in vitro assays using a purified recombinant domain of the transporter containing the modulator binding site. Halogenated chalcones exhibited high-affinity binding, the 2',4', 6'-trihydroxy-4-iodochalcone behaving as the most potent compound with a KD value in the nanomolar range.

Botany, traditional uses, phytochemistry and pharmacology of Waltheria indica L. (syn. Waltheria americana): a review.

ETHNOPHARMACOLOGICAL RELEVANCE: Waltheria indica L. (syn. Waltheria americana) is commonly used in traditional medicine in Africa, South America and Hawaii, mainly against pain, inflammation, conditions of inflammation, diarrhea, dysentery, conjunctivitis, wounds, abscess, epilepsy, convulsions, anemia, erectile dysfunctions, bladder ailments and asthma. Aim of the review to provide an up-to-date overview of the botany, phytochemistry, traditional uses, pharmacological activities and toxicity data of Waltheria indica. Additionally, studies providing an evidence for local and traditional uses of Waltheria indica are discussed. Further phytochemical and pharmacological potential of this species are suggested for future investigations. MATERIALS AND METHODS: The information was collected from scientific journals, books, theses and reports via academic libraries and electronic search. These sources include Pubmed, Web of Science, Portal de Portales-Latindex, Science Research.com and Google scholar. These studies about the medical botanical, traditional uses, chemical, pharmacological and toxicological data on Waltheria indica were published in English, Portuguese, Spanish, German and French. RESULTS: Crude extracts and isolated compounds from Waltheria indica were investigated and showed analgesic, anti-inflammatory, antibacterial, antifungal, antimalarial, anti-anemic, anti-oxidant, sedative and anticonvulsant activities. The phytochemical investigations showed the presence of cyclopeptid alkaloids, flavonoids (e.g., (-)-epicatechin, quercetin, kaempferol, kaempferol-3-O-ß-d-(6″-E-p-coumaryl)-glucopyranoside), tannins, sterols, terpenes, saponins, anthraquinones. Studies of acute toxicity in animal indicated that Waltheria indica can be toxic. CONCLUSION: Waltheria indica possess therapeutic potential in the treatment of inflammation, malaria, infectious diseases (e.g., lungs infection due to Klebsiella pneumoniae, diarrhea due to Candida albicans or Escherichia coli) and prevention of oxidative stress. Further studies are necessary to explore pure compounds responsible for the pharmacological effects and the mechanisms of action. Further investigations are also needed to provide an evidence base for traditional uses of this species against pain, anemia, convulsions and epilepsy. In addition, there is a pressing need to investigate the other traditional uses such as dysentery, syphilis, erectile dysfunctions and asthma.

Recent advances in the medicinal chemistry of aurones.

The first review regarding the potential of aurones as promising drug candidates was reported in 2003. Since, considerable efforts have been made to explore the pharmacological and therapeutical activities of aurones. In this regard, many biological areas were concerned, including major pathological, such as cancer and neurodegenerative disorders. The aim of the present report is to highlight the progress made during the last ten years on the medicinal chemistry of aurones. A special focus will be made on the structure-activity relationship aspects among aurones and especially in case where aurones were found highly active than the corresponding flavones and chalcones.

Flavonoids as promising lead compounds in type 2 diabetes mellitus: molecules of interest and structure-activity relationship.

There is evidence that hyperglycemia results in the generation of reactive oxygen species, leading to oxidative stress in various tissues, including vascular system. An important link between oxidative stress, inflammatory response and insulin activity is now well established. The ability of antioxidants to protect against the deleterious effects of hyperglycemia and also to improve glucose metabolism and intake must be considered as leads of choice in diabetes treatment. In addition to their antioxidative activity, many flavonoids were demonstrated to act on biological targets involved in type 2 diabetes mellitus such as: α-glycosidase, glucose cotransporter or aldose reductase. In this context, flavonoids behaving as antioxidants were studied as potential drugs by acting as biological targets involved in diabetes development. In this review, we propose to shed light on antioxidants flavonoids investigated as antidiabetics. A special focus was made to address the structure-activity relationship related to the effect of these naturally occurring molecules on different targets involved in diabetes development.

Cytotoxicity of chalcone derivatives towards glioblastoma.

BACKGROUND: Among seventeen compounds derived from chalcones investigated as potential anticancer drugs towards LN229 glioblastoma cell line, only two were effective. MATERIALS AND METHODS: Anticancer activity was investigated by evaluating the cell growth, cell cycle, mitotic index and the cell death. RESULTS: Two compounds, namely C2 and C12, inhibited cell proliferation associated with a blockade in the G(2)/M phase of the cell cycle and arrested the growth of tumour spheroid mimicking in vivo tumour. C2 blocked cells in the G(2) phase whereas C12 blocked cells in the M phase of the cell cycle. C12 and C2 killed 40% and 95% of the cells respectively using complex mechanisms. The two compounds increased the fluorescence of rhodamine-123 and N-acetylcysteine inhibited their activity, suggesting a role for reactive oxygen species in cell death mediated by these two compounds. CONCLUSION: C2 and C12 are markedly cytostatic and cytolytic to glioblastoma cells and act through different pathways.

The acridone derivative MBLI-87 sensitizes breast cancer resistance protein-expressing xenografts to irinotecan.

The breast cancer resistance protein ABCG2 confers cellular resistance to irinotecan (CPT-11) and its active metabolite SN-38. We utilised ABCG2-expressing xenografts as a model to evaluate the ability of a non-toxic ABCG2 inhibitor to increase intracellular drug accumulation. We assessed the activity of irinotecan in vivo in SCID mice: irinotecan completely inhibited the development of control pcDNA3.1 xenografts, whilst only delaying the growth of ABCG2-expressing xenografts. Addition of MBLI-87, an acridone derivative inhibitor, significantly increased the irinotecan effect against the growth of ABCG2-expressing xenografts. In vitro, MBLI-87 was as potent as GF120918 against ABCG2-mediated irinotecan efflux, and additionally was specific for ABCG2. A significant sensitisation to irinotecan was achieved despite the fact that doses remained well below the maximum tolerated dose (due to the rather limited solubility of MBLI-87). This suggested that MBLI-87 is an excellent candidate to prevent drug efflux by ABCG2, without altering plasma concentrations of irinotecan and SN-38 after IP (intra-peritoneal) injections. This could constitute a useful strategy to improve drug pharmacology, to facilitate drug penetration into normal tissue compartments protected by ABCG2, and potentially to reverse drug resistance in cancer cells.

Targeting the multidrug ABCG2 transporter with flavonoidic inhibitors: in vitro optimization and in vivo validation.

This review describes the breast cancer resistance protein ABCG2 through its structure, functional roles and involvement in cell multidrug resistance, especially in cancer cells resistance to chemotherapeutics. The different types of known inhibitors are described, some being non-selective, since they also bind to other targets, and others being quite specific such as flavonoids. The different classes of active flavonoids and other polyphenols are described, some as plant natural compounds, but most of them being prepared and derivatized through medicinal chemistry. Quantitative structure-activity relationships of the ability of flavones, chalcones, xanthones, acridones and various benzopyrane/benzofurane derivatives to inhibit ABCG2-mediated drug efflux have led to pharmacophores and molecular models allowing to optimize the available hit compounds and to design new-generation lead compounds. Interestingly, inhibitory flavonoids are quite specific for ABCG2 versus ABCB1 and ABCC1, and appear either non-competitive or partially competitive towards mitoxantrone efflux. Most compounds do not inhibit ATPase activity, and are assumed not to be transported themselves by the transporter. Some acridones, firstly optimized in vitro as potent inhibitors, are indeed efficient in vivo, against human xenografts in SCID mice, more efficiently than gefitinib taken as a control. Future developments should open the way to more efficient/targeted modulators including (i) the potential interest of bimodulation by combining two different inhibitors, (ii) computer-assisted ligand-based drug design for getting more potent and more specific inhibitors, (iii) structure-based drug design from ABCG2 molecular models allowing in silico screening and docking of new inhibitors.

QSAR analysis and molecular modeling of ABCG2-specific inhibitors.

In addition to its critical role is controlling drug availability and protecting sensitive organs and stem cells through cellular detoxification, breast cancer resistance protein (BCRP/ABCG2) plays an important role in cancer cell resistance to chemotherapy, together with P-glycoprotein/ABCB1. A main approach to abolish multidrug resistance is to find out specific inhibitors of the drug-efflux activity, able to chemosensitize cancer cell proliferation. Many efforts have been primarily focused on ABCB1, discovered thirty years ago, whereas very few studies have concerned ABCG2, identified much more recently. This review describes the main types of inhibitors presently known for ABCG2, and how quantitative structure-activity relationship analysis among series of compounds may lead to build up molecular models and pharmacophores allowing to design lead inhibitors as future candidates for clinical trials. A special attention is drawn on flavonoids which constitute a structurally-diverse class of compounds, well suited to identify potent ABCG2-specific inhibitors.

Involvement of Tetrahymena pyriformis and selected fungi in the elimination of anthracene, and toxicity assessment of the biotransformation products.

Anthracene (AC) is a non-mutagenic and non-carcinogenic, low-molecular-weight polycyclic aromatic hydrocarbon present in the environment. Its toxicity can be dramatically increased after solar-light exposure. Biotransformation capacities of AC by Tetrahymena pyriformis and a selection of eight micromycetes were studied, and the ability of these microorganisms to detoxify the polluted ecosystems was assessed. We showed that T. pyriformis was able to accumulate high amounts of AC without any transformation. In contrast, the fungi Cunninghamella elegans, Absidia fusca, Absidia cylindrospora, Rhodotorula glutinis, and Aspergillus terreus were able to transform AC with a high efficiency. Cytotoxicity assays conducted on HeLa cells and T. pyriformis showed that crude extract from A. fusca culture medium obtained after AC biotransformation was not toxic. For A. fusca and A. cylindrospora, 1-4 dihydroxyanthraquinone was shown to be the major product during the biotransformation process. This compound seemed to be a dead-end metabolite at least for the Absidia strains. The cytotoxicity of 1-4 dihydroxyanthraquinone was higher than that of AC to T. pyriformis but lower to HeLa cells. On the whole our results showed that the microorganisms studied were all able to decontaminate an AC-polluted ecosystem, either by accumulating or transforming the compound. A possible detoxification process resulting from AC biotransformation can be considered only using the human cell model.

Synthesis of sphingosine-1-phosphate and dihydrosphingosine-1-phosphate.

The syntheses of D-erythro-sphingosine-1-phosphate and DL-erythro-sphinganine-1-phosphate are described starting from the commercially available D-erythro-sphingosine and DL-erythro-sphinganine. The phosphate group is introduced via phosphoramidite chemistry using bis(2-cyanoethyl)-N,N-diisopropylamino-phosphoramidite as the monophosphorylating reagent. The procedure generates the phosphorylated sphingoid bases in three steps and 32-39% overall yields.

Alkylation of 2-phenyl-4-quinolones: synthetic and structural studies.

The alkylation of 2-phenyl-4-quinolones was investigated and showed that the N-alkylation versus O-alkylation is highly dependent on whether C-5 is hydroxylated or not. N-Alkylation is favoured by the presence of a 5-hydroxyl group. The synthetic and the NMR structural studies are reported.

B-ring substituted 5,7-dihydroxyflavonols with high-affinity binding to P-glycoprotein responsible for cell multidrug resistance.

Starting from the interaction of galangin (3,5,7-trihydroxyflavone) with a cytosolic nucleotide-binding domain of P-glycoprotein, a series of flavonol derivatives was synthesized and tested for their binding affinity towards the same target. The 5,7-dihydroxy-4'-iodoflavonol and 5,7-dihydroxy-4'-n-octylflavonol derivatives displayed much higher binding affinities, with respective increases of 6- and 93-fold as compared to galangin.

Synthesis and biological activity of 4-alkoxy chalcones: potential hydrophobic modulators of P-glycoprotein-mediated multidrug resistance.

A series of 4-alkoxy-2',4',6'-trihydroxychalcones have been synthesized and evaluated for their ability to inhibit P-glycoprotein-mediated multidrug resistance (MDR) by direct binding to a purified protein domain containing an ATP-binding site and a modulator-interacting region. The introduction of hydrophobic alkoxy groups at position 4 led to much more active compounds as compared to the parent chalcone. The binding affinity increased as a function of the chain length, up to the octyloxy derivative for which a K(D) of 20 nM was obtained.

SB 203580, a mitogen-activated protein kinase inhibitor, abolishes resistance to myocardial infarction induced by heat stress.

Heat stress (HS) is known to confer protection against ischemia-reperfusion injury, including mechanical dysfunction and myocardial necrosis. However, the mechanisms involved in this cardioprotection are yet to be elucidated. Mitogen-activated protein (MAP) kinase cascades have been demonstrated to be involved in cellular response to different stresses. In particular, p38 MAP kinase is known to be activated by HS. Therefore, we investigated the implication of this kinase in HS-induced resistance to myocardial infarction, in the isolated rat heart model, using SB 203580 (SB) to selectively inhibit p38 MAP kinase. Rats were treated with SB (2.83 mg/kg, i.p.) or vehicle (1% DMSO in saline, i.p.) before they were either heat stressed (42 degrees C for 15 minutes) or sham anesthetized. Their hearts were isolated 24 hours later, retrogradely perfused, and subjected to a 35-minute occlusion of the left coronary artery followed by 120 minutes of reperfusion. The infarct-to-risk ratio was significantly reduced in HS (16.9 +/- 2.0%) compared with sham (41.6 +/- 2.5%) hearts. This reduction in infarct size was abolished in the SB 203580-treated group (37.8 +/- 1.9% in HS + SB vs. 42.0 +/- 1.9% in sham + SB). Risk zones were similar between experimental groups. Western blot analysis of the myocardial HSP72 showed an HS-induced increase of this protein, which was not modified by the p38 MAP kinase inhibitor, SB 203580. We conclude that activation of p38 MAP kinase appears to play a role in the functional cardioprotection associated with the heat stress response, which seems to be unrelated to the HSP72 level. Further investigations are required to elucidate the precise role of the p38 MAP kinase and heat stress proteins in this adaptative response.

Modulation by flavonoids of cell multidrug resistance mediated by P-glycoprotein and related ABC transporters.

Cancer cell resistance to chemotherapy is often mediated by overexpression of P-glycoprotein, a plasma membrane ABC (ATP-binding cassette) transporter which extrudes cytotoxic drugs at the expense of ATP hydrolysis. P-glycoprotein (ABCB1, according to the human gene nomenclature committee) consists of two homologous halves each containing a transmembrane domain (TMD) involved in drug binding and efflux, and a cytosolic nucleotide-binding domain (NBD) involved in ATP binding and hydrolysis, with an overall (TMD-NBD)2 domain topology. Homologous ABC multidrug transporters, from the same ABCB family, are found in many species such as Plasmodiumfalciparum and Leishmania spp. protozoa, where they induce resistance to antiparasitic drugs. In yeasts, some ABC transporters involved in resistance to fungicides, such as Saccharomyces cerevisiae Pdr5p and Snq2p, display a different (NBD-TMD)2 domain topology and are classified in another family, ABCG. Much effort has been spent to modulate multidrug resistance in the different species by using specific inhibitors, but generally with little success due to additional cellular targets and/or extrusion of the potential inhibitors. This review shows that due to similarities in function and maybe in three-dimensional organization of the different transporters, common potential modulators have been found. An in vitro 'rational screening' was performed among the large flavonoid family using a four-step procedure: (i) direct binding to purified recombinant cytosolic NBD and/or full-length transporter, (ii) inhibition of ATP hydrolysis and energy-dependent drug interaction with transporter-enriched membranes, (iii) inhibition of cell transporter activity monitored by flow cytometry and (iv) chemosensitization of cell growth. The results indicate that prenylated flavonoids bind with high affinity, and strongly inhibit drug interaction and nucleotide hydrolysis. As such, they constitute promising potential modulators of multidrug resistance.