Structural studies of human histone deacetylase 8 and its site-specific variants complexed with substrate and inhibitors

Metal-dependent histone deacetylases (HDACs) require Zn(2+) or Fe(2+) to regulate the acetylation of lysine residues in histones and other proteins in eukaryotic cells. Isozyme HDAC8 is perhaps the archetypical member of the class I HDAC family and serves as a paradigm for studying structure-function relationships. Here, we report the structures of HDAC8 complexes with trichostatin A and 3-(1-methyl-4-phenylacetyl-1H-2-pyrrolyl)-N-hydroxy-2-propenamide (APHA) in a new crystal form. The structure of the APHA complex reveals that the hydroxamate CO group accepts a hydrogen bond from Y306 but does not coordinate to Zn(2+) with favorable geometry, perhaps due to the constraints of its extended pi system. Additionally, since APHA binds to only two of the three protein molecules in the asymmetric unit of this complex, the structure of the third monomer represents the first structure of HDAC8 in the unliganded state. Comparison of unliganded and liganded structures illustrates ligand-induced conformational changes in the L2 loop that likely accompany substrate binding and catalysis. Furthermore, these structures, along with those of the D101N, D101E, D101A, and D101L variants, support the proposal that D101 is critical for the function of the L2 loop. However, amino acid substitutions for D101 can also trigger conformational changes of Y111 and W141 that perturb the substrate binding site. Finally, the structure of H143A HDAC8 complexed with an intact acetylated tetrapeptide substrate molecule confirms the importance of D101 for substrate binding and reveals how Y306 and the active site zinc ion together bind and activate the scissile amide linkage of acetyllysine.

Discovery and Characterization of a Ca2+-independent Phosphatidylethanolamine N-Acyltransferase Generating the Anandamide Precursor and Its Congeners

N-Acylphosphatidylethanolamines (NAPEs) are precursors of bioactive N-acylethanolamines, including the endocannabinoid anandamide. In animal tissues, NAPE is formed by transfer of a fatty acyl chain at the sn-1 position of glycerophospholipids to the amino group of phosphatidylethanolamine (PE), and this reaction is believed to be the principal rate-limiting step in N-acylethanolamine synthesis. However, the Ca2+-dependent, membrane-associated N-acyltransferase (NAT) responsible for this reaction has not yet been cloned. In this study, on the basis of the functional similarity of NAT to lecithin-retinol acyltransferase (LRAT), we examined a possible PE N-acylation activity in two rat LRAT homologous proteins. Upon overexpression in COS-7 cells, one protein, named rat LRAT-like protein (RLP)-1, catalyzed transfer of a radioactive acyl group from phosphatidylcholine (PC) to PE, resulting in the formation of radioactive NAPE. However, the RLP-1 activity was detected mainly in the cytosolic rather than membrane fraction and was little stimulated by Ca2+. Moreover, RLP-1 did not show selectivity with respect to the sn-1 and sn-2 positions of PC as an acyl donor and therefore could generate N-arachidonoyl-PE (anandamide precursor) from 2-arachidonoyl-PC and PE. In contrast, under the same assay conditions, partially purified NAT from rat brain was highly Ca2+-dependent, membrane-associated, and specific for the sn-1-acyl group of PC. RLP-1 mRNA was expressed predominantly in testis among various rat tissues, and the testis cytosol exhibited an RLP-1-like activity. These results reveal that RLP-1 can function as a PE N-acyltransferase, catalytically distinguishable from the known Ca2+-dependent NAT.

Biosynthetic Pathways of the Endocannabinoid Anandamide

Anandamide (=N-arachidonoylethanolamine) is the first discovered endocannabinoid, and belongs to the class of bioactive, long-chain N-acylethanolamines (NAEs). In animal tissues, anandamide is principally formed together with other NAEs from glycerophospholipid by two successive enzymatic reactions: 1) N-acylation of phosphatidylethanolamine to generate N-acylphosphatidylethanolamine (NAPE) by Ca2+-dependent N-acyltransferase; 2) release of NAE from NAPE by a phosphodiesterase of the phospholipase D type (NAPE-PLD). Although these anandamide-synthesizing enzymes were poorly understood until recently, our cDNA cloning of NAPE-PLD in 2004 enabled molecular-biological approaches to the enzymes. NAPE-PLD is a member of the metallo-beta-lactamase family, which specifically hydrolyzes NAPE among glycerophospholipids, and appears to be constitutively active. Mutagenesis studies suggested that the enzyme functions through a mechanism similar to those of other members of the family. NAPE-PLD is widely expressed in animal tissues, including various regions in rat brain. Its expression level in the brain is very low at birth, and remarkably increases with development. Analysis of NAPE-PLD-deficient mice and other recent studies revealed the presence of NAPE-PLD-independent pathways for the anandamide formation. Furthermore, calcium-independent N-acyltransferase was discovered and characterized. In this article, we will review recent progress in the studies on these enzymes responsible for the biosynthesis of anandamide and other NAEs.

Targeting P-glycoprotein: Investigation of piperine analogs for overcoming drug resistance in cancer

P-glycoprotein (P-gp) is a drug transporter that effluxes chemotherapeutic drugs and is implicated in the development of resistance of cancer cells to chemotherapeutic drugs. To date, no drug has been approved to inhibit P-gp and restore chemotherapy efficacy. Moreover, majority of the reported inhibitors have high molecular weight and complex structures, making it difficult to understand the basic structural requirement for P-gp inhibition. In this study, two structurally simple, low molecular weight piperine analogs Pip1 and Pip2 were designed and found to better interact with P-gp than piperine in silico. A one step, acid-amine coupling reaction between piperic acid and 6,7-dimethoxytetrahydroisoquinoline or 2-(3,4-dimethoxyphenyl)ethylamine afforded Pip1 and Pip2, respectively. In vitro testing in drug resistant P-gp overexpressing KB (cervical) and SW480 (colon) cancer cells showed that both analogs, when co-administered with vincristine, colchicine or paclitaxel were able to reverse the resistance. Moreover, accumulation of P-gp substrate (rhodamine 123) in the resistant cells, a result of alteration of the P-gp efflux, was also observed. These investigations suggest that the natural product analog - Pip1 ((2E,4E)-5-(benzo[d][1,3]dioxol-5-yl)-1-(6,7-dimethoxy-3,4-dihydroisoquinolin-2(1 H)-yl)penta-2,4-dien-1-one) - is superior to piperine and could inhibit P-gp function. Further studies are required to explore the full potential of Pip1 in treating drug resistant cancer.

Cannabimimetic plants: are they new cannabinoidergic modulators?

Phytochemicals and secondary metabolites able to interact with the endocannabinoid system (Cannabimimetics) have been recently described in a broad range of plants and fruits. These findings can open new alternative avenues to explore for the development of novel therapeutic compounds. The cannabinoids regulate many physiological and pathological functions in both animals and plants. Cannabis sativa is the main plant that produces phytocannabinoids inside resins capable to defend the plant from the aggression of parasites and herbivores. Animals produce anandamide and 2-arachidonoyl glycerol, which thanks to binding with main receptors such as type-1 cannabinoid receptor (CB1R) and the type-2 cannabinoid receptor (CB2R) are involved in inflammation processes and several brain functions. Endogenous cannabinoids, enzymes for synthesis and degradation of cannabinoids, and CB1R and CB2R constitute the endocannabinoid system (ECS). Other plants can produce cannabinoid-like molecules such as perrottetinene extracted from Radula perrottetii, or anandamide and 2-arachidonoyl glycerol extracted from some bryophytes. Moreover, several other secondary metabolites can also interact with the ECS of animals and take the name of cannabimimetics. These phytoextracts not derived from Cannabis sativa can act as receptor agonists or antagonist, or enzyme inhibitors of ECS and can be involved in the inflammation, oxidative stress, cancer, and neuroprotection. Finally, given the evolutionary heterogeneity of the cannabimimetic plants, some authors speculated on the fascinating thesis of the evolutionary convergence between plants and animals regarding biological functions of ECS. The review aims to provide a critical and complete assessment of the botanical, chemical and therapeutic aspects of cannabimimetic plants to evaluate their spread in the world and medicinal potentiality.

Quantitative method for the profiling of the endocannabinoid metabolome by LC-atmospheric pressure chemical ionization-MS

The endocannabinoid system's biological significance continues to grow as novel endocannabinoid metabolites are discovered. Accordingly, a myopic view of the system that focuses solely on one or two endocannabinoids, such as anandamide or 2-arachidonoyl glycerol, is insufficient to describe the biological responses to perturbations of the system. Rather, the endocannabinoid metabolome as a whole must be analyzed. The work described here is based on liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry. This method has been validated to quantify, in a single chromatographic run, the levels of 15 known or suspected metabolites of the endocannabinoid system in the rat brain and is applicable to other biological matrixes. We have obtained an endocannabinoid profile specifically for the frontal cortex of the rat brain and have determined anandamide level differences following the administration of the fatty acid amide hydrolase inhibitor AM374.

All-trans-configuration in Zanthoxylum alkylamides swaps the tingling with a numbing sensation and diminishes salivation

The methanol soluble prepared from a supercritical fluid extract of Szechuan pepper (Zanthoxylum piperitum) was screened for its key tingling and numbing chemosensates by application of taste dilution analysis. Further separation of fractions perceived with the highest sensory impact, followed by LC-TOF-MS, LC-MS, and 1D/2D NMR experiments, led to the structure determination of the known alkylamides hydroxy-γ-sanshool (1), hydroxy-α-sanshool (2), hydroxy-β-sanshool (3), bungeanool (4), isobungeanool (5), and hydroxy-γ-isosanshool (6), as well as hydroxy-ε-sanshool (7), the structure of which has not yet been confirmed by NMR, and hydroxy-ζ-sanshool (8), which has not been previously reported in the literature. Psychophysical half-tongue experiments using filter paper rectangles (1 × 2 cm) as the vehicle revealed amides 1, 2, 4, 5, 7, and 8, showing at least one cis-configured double bond, elicited the well-known tingling and paresthetic orosensation above threshold levels of 3.5-8.3 nmol/cm(2). In contrast, the all-trans-configured amides 3 and 6 induced a numbing and anesthetic sensation above thresholds of 3.9 and 7.1 nmol/cm(2), respectively. Interestingly, the mono-cis-configured major amide 2 was found to induce massive salivation, whereas the all-trans-configuration of 3 did not.

Conjugation of Docetaxel with Multiwalled Carbon Nanotubes and Codelivery with Piperine: Implications on Pharmacokinetic Profile and Anticancer Activity

Nanotechnology-based drug products are emerging as promising agents to enhance the safety and efficacy of established chemotherapeutic molecules. Carbon nanotubes (CNTs), especially multiwalled CNTs (MWCNTs), have been explored for this potential owing to their safety and other desired attributes. Docetaxel (DTX) is an indispensable anticancer agent, which has wide applicability in variety of cancers. However, the potential of DTX is still not completely harvested due to problems like poor aqueous solubility, low tissue permeability, poor bioavailability, high first pass metabolism, and dose-related toxicity. Hence, it was proposed to attach DTX to MWCNTs and coadminister it along with piperine with an aim to enhance the tissue permeation, anticancer activity, and bioavailability. The Fourier transform infrared, UV, and NMR spectroscopic data confirmed successful conjugation of DTX to MWCNTs and adsorption of piperine onto MWCNTs. The codelivery MWCNT-based system offered drug release moderation and better cancer cell toxicity than that of plain DTX as well as DTX-CNT conjugate. The pharmacokinetic profile of DTX was exceptionally improved by the conjugation, in general, and coadministration with piperine, in specific vis-à-vis plain drug. Hence, the dual approach of MWCNTs conjugation and piperine coadministration can serve as a beneficial option for enhancement of the performance of DTX in cancer chemotherapy.

The role of alkamides as an active principle of echinacea

Alkamides are the major lipophilic constituents of ECHINACEA preparations, which are widely used in some European countries and in North America for common colds. In earlier investigations they have been shown to possess stimulatory effects on phagocytosis. Recent experiments have demonstrated that alkamides are detectable in human blood in relevant concentrations after oral administration of Echinacea preparations. Alkamides show structural similarity with anandamide, an endogenous ligand of cannabinoid receptors. Consequently, it was found that alkamides bind significantly to CB (2) receptors, which is now considered as a possible molecular mode of action of Echinacea alkamides as immunomodulatory agents. It was also demonstrated recently in several studies that alkamide-containing Echinacea preparations trigger effects on the pro-inflammatory cytokines. They were therefore suggested as a new class of cannabinomimetics. However, the therapeutic relevance of these findings is still not clear as clinical studies on the common cold show contradictory results. Among the many pharmacological properties reported, investigations concerning herb-drug interactions have been neglected for a long time. Latest research concludes that prolonged use of Echinacea poses a minimal risk for co-medications metabolized by the P450 enzymes.

A novel β-catenin signaling pathway activated by IL-1β leads to the onset of epithelial-mesenchymal transition in breast cancer cells

Interleukin 1β has been associated with tumor development, invasiveness and metastasis in various types of cancer. However, the molecular mechanisms underlying this association have not been clearly elucidated. The present study is the first to show, in breast cancer cells, that an IL-1β/IL-1RI/β-catenin signaling pathway induces β-catenin accumulation due to GSK3β inactivation by Akt phosphorylation. Translocation to the nucleus of accumulated β-catenin and formation of the TCF/Lef/β-catenin complex induce sequential expression of c-MYC, CCDN1, SNAIL1 and MMP2, leading to up-regulation of proliferation, migration and invasion; all of the processes shown to be required, in cancerous cells, to initiate transition from a non-invading to an invasive phenotype.

Bioactive maca (Lepidium meyenii) alkamides are a result of traditional Andean postharvest drying practices

Maca, Lepidium meyenii Walpers (Brassicaceae), is an annual herbaceous plant native to the high plateaus of the Peruvian central Andes. Its underground storage hypocotyls have been a traditional medicinal agent and dietary staple since pre-Columbian times. Reported properties include energizing and fertility-enhancing effects. Published reports have focused on the benzylalkamides (macamides) present in dry hypocotyls as one of the main bioactive components. Macamides are secondary amides formed by benzylamine and a fatty acid moiety, with varying hydrocarbon chain lengths and degree of unsaturation. Although it has been assumed that they are usually present in fresh undamaged tissues, analyses show them to be essentially absent from them. However, hypocotyls dried by traditional Andean postharvest practices or industrial oven drying contain up to 800μgg(-1) dry wt (2.3μmolg(-1) dry wt) of macamides. In this study, the generation of macamides and their putative precursors were studied during nine-week traditional drying trials at 4200m altitude and in ovens under laboratory conditions. Freeze-thaw cycles in the open field during drying result in tissue maceration and release of free fatty acids from storage and membrane lipids up to levels of 1200μgg(-1) dry wt (4.3μmolg(-1) dry wt). Endogenous metabolism of the isothiocyanates generated from glucosinolate hydrolysis during drying results in maximal benzylamine values of 4300μgg(-1) dry wt (40.2μmolg(-1) dry wt). Pearson correlation coefficients of the accumulation profiles of benzylamine and free fatty acid to that of macamides showed good values of 0.898 and 0.934, respectively, suggesting that both provide sufficient substrate for amide synthesis during the drying process.

Safety evaluation of Trikatu, a generic Ayurvedic medicine in Charles Foster rats

Chemical characterization and acute and sub-acute toxicity study of Trikatu, a generic herbal formulation of Indian system of medicine, was carried out in Charles Foster (CF) rats for safety profiling. In acute toxicity experiment, Trikatu at 2,000 mg/kg body weight once orally was well tolerated by the experimental animals (both male and female) and no changes were observed in mortality, morbidity, gross pathology, gain in weight, vital organ weight, hematological (total white blood cells (WBC) and red blood cells (RBC) count), biochemical parameters such as serum creatinine, serum glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT), serum lipid profile and tissue biochemical parameters such as reduced glutathione and malonaldehyde content as oxidative stress markers. In sub-acute experiment, Trikatu was administered at 5, 50 and 300 mg/kg body weight once daily for 28 days in female CF rats, and non-significant changes were found in most of the parameters studied such as acute experiment except significant increase in low density lipoprotein (LDL) cholesterol level at 50 and 300 mg/kg body weight, decrease in high density lipoprotein (HDL) cholesterol level at 300 mg/kg body weight, increase in SGPT activity at 50 mg/kg body weight and decrease in WBC count at 300 mg/kg body weight on 28(th) day post treatment.

Targeting hepatocellular carcinoma with piperine by radical-mediated mitochondrial pathway of apoptosis: An in vitro and in vivo study

Redox mediated cancer therapeutics are of immense interest in the recent decade due to their anticancer activity. Piperine is the principal alkaloid of black and long pepper. Although its anticancer activity has been reported in number of cancers , the precise molecular mechanism of action remains to be unravelled. Hence, in this study, for the first time, we delineated the mechanistic insight into the effect of piperine against hepatocellular carcinoma (HCC).MTT analysis determined the dose and time dependent cytotoxicity of piperine against Hep G2 cells. Further molecular studies evidenced the prooxidant property of piperine by inducing H₂O₂ driven mitochondria-mediated apoptosis in Hep G2 cells by inhibiting the peroxide detoxifying enzyme Catalase. Molecular docking and western blotting analysis uncovered the piperine mediated receptor tyrosine kinase inhibition and mitigation of HCC progression. In addition, histological investigations of piperine - treated, DEN-induced HCC rats showed significant prognosis with apoptotic cell death. Whereas,co-treatment of an antioxidant EUK-134 significantly abrogated its chemotherapeutic activity substantiating its radical-mediated anticancer property. Altogether, this study shows that the piperine may be a promising prooxidant drug for the amelioration of hepatocellular carcinoma.

Transdermal behaviour of the N-alkylamide spilanthol (affinin) from Spilanthes acmella (Compositae) extracts

AIM OF THE STUDY

N-Alkylamides are a large group of bioactive molecules found in several plants from the genera Echinacea, Xanthoxylum and Spilanthes. Extracts and formulations derived from these plants are not only orally used, but also applied on the skin as well. However, there is currently no specific information available about the intrinsic local pharmacokinetics of N-alkylamides after topical application on human skin, questioning the role of this mode of administration. The present study investigates the transdermal behaviour of spilanthol, a prominent N-alkylamide.

MATERIALS AND METHODS

Two pharmaceutically accepted dose solutions (ethanol and propylene glycol based aqueous donor vehicles), combined with three different receptor fluids (PBS, PBS+0.5% HPbetaCD, EtOH/H(2)O (30:70, v/v)), were applied on split-thickness human skin in a Franz diffusion cell (FDC) system. Fundamental permeation characteristics of spilanthol in a solvent-independent way (100% aqueous dose solution) were also obtained using an extrapolation approach with different organic solvent/H(2)O ratios.

RESULTS AND CONCLUSIONS

We demonstrated for the first time that spilanthol permeates the skin. The following aqueous-extrapolated primary transdermal parameters were obtained (mean+/-SEM): K(p,aq)=3.31 (+/-0.29)x10(-3)cm/h, D(m,aq)=1.86 (+/-0.09)x10(-4)cm(2)/h and K(m,aq)=7.28 (+/-1.59)x10(-1). Partitioning (K(m)) was strongly dependent on the donor solution composition, while diffusion (D(m)) was mainly influenced by the receptor fluid composition.

Endocannabinoids anandamide and 2-arachidonoylglycerol are substrates for human CYP2J2 epoxygenase

The endocannabinoids, anandamide (AEA) and 2-arachidonoylglycerol (2-AG), are arachidonic acid (AA) derivatives that are known to regulate human cardiovascular functions. CYP2J2 is the primary cytochrome P450 in the human heart and is most well known for the metabolism of AA to the biologically active epoxyeicosatrienoic acids. In this study, we demonstrate that both 2-AG and AEA are substrates for metabolism by CYP2J2 epoxygenase in the model membrane bilayers of nanodiscs. Reactions of CYP2J2 with AEA formed four AEA-epoxyeicosatrienoic acids, whereas incubations with 2-AG yielded detectable levels of only two 2-AG epoxides. Notably, 2-AG was shown to undergo enzymatic oxidative cleavage to form AA through a NADPH-dependent reaction with CYP2J2 and cytochrome P450 reductase. The formation of the predominant AEA and 2-AG epoxides was confirmed using microsomes prepared from the left myocardium of porcine and bovine heart tissues. The nuances of the ligand-protein interactions were further characterized using spectral titrations, stopped-flow small-molecule ligand egress, and molecular modeling. The experimental and theoretical data were in agreement, which showed that substitution of the AA carboxylic acid with the 2-AG ester-glycerol changes the binding interaction of these lipids within the CYP2J2 active site, leading to different product distributions. In summary, we present data for the functional metabolomics of AEA and 2-AG by a membrane-bound cardiovascular epoxygenase.

Identification of endocannabinoid system-modulating N-alkylamides from Heliopsis helianthoides var. scabra and Lepidium meyenii

The discovery of the interaction of plant-derived N-alkylamides (NAAs) and the mammalian endocannabinoid system (ECS) and the existence of a plant endogenous N-acylethanolamine signaling system have led to the re-evaluation of this group of compounds. Herein, the isolation of seven NAAs and the assessment of their effects on major protein targets in the ECS network are reported. Four NAAs, octadeca-2E,4E,8E,10Z,14Z-pentaene-12-ynoic acid isobutylamide (1), octadeca-2E,4E,8E,10Z,14Z-pentaene-12-ynoic acid 2'-methylbutylamide (2), hexadeca-2E,4E,9Z-triene-12,14-diynoic acid isobutylamide (3), and hexadeca-2E,4E,9,12-tetraenoic acid 2'-methylbutylamide (4), were identified from Heliopsis helianthoides var. scabra. Compounds 2-4 are new natural products, while 1 was isolated for the first time from this species. The previously described macamides, N-(3-methoxybenzyl)-(9Z,12Z,15Z)-octadecatrienamide (5), N-benzyl-(9Z,12Z,15Z)-octadecatrienamide (6), and N-benzyl-(9Z,12Z)-octadecadienamide (7), were isolated from Lepidium meyenii (Maca). N-Methylbutylamide 4 and N-benzylamide 7 showed submicromolar and selective binding affinities for the cannabinoid CB1 receptor (Ki values of 0.31 and 0.48 μM, respectively). Notably, compound 7 also exhibited weak fatty acid amide hydrolase (FAAH) inhibition (IC50 = 4 μM) and a potent inhibition of anandamide cellular uptake (IC50 = 0.67 μM) that was stronger than the inhibition obtained with the controls OMDM-2 and UCM707. The pronounced ECS polypharmacology of compound 7 highlights the potential involvement of the arachidonoyl-mimicking 9Z,12Z double-bond system in the linoleoyl group for the overall cannabimimetic action of NAAs. This study provides additional strong evidence of the endocannabinoid substrate mimicking of plant-derived NAAs and uncovers a direct and indirect cannabimimetic action of the Peruvian Maca root.

Chemical determinants involved in anandamide-induced inhibition of T-type calcium channels

Anandamide, originally described as an endocannabinoid, is the main representative molecule of a new class of signaling lipids including endocannabinoids and N-acyl-related molecules, eicosanoids, and fatty acids. Bioactive lipids regulate neuronal excitability by acting on G-protein-coupled receptors (such as CB1) but also directly modulate various ionic conductances including voltage-activated T-type calcium channels (T-channels). However, little is known about the properties and the specificity of this new class of molecules on their various targets. In this study, we have investigated the chemical determinants involved in anandamide-induced inhibition of the three cloned T-channels: Ca(V)3.1, Ca(V)3.2, and Ca(V)3.3. We show that both the hydroxyl group and the alkyl chain of anandamide are key determinants of its effects on T-currents. As follows, T-currents are also inhibited by fatty acids. Inhibition of the three Ca(V)3 currents by anandamide and arachidonic acid does not involve enzymatic metabolism and occurs in cell-free inside-out patches. Inhibition of T-currents by fatty acids and N-acyl ethanolamides depends on the degree of unsaturation but not on the alkyl chain length and consequently is not restricted to eicosanoids. Inhibition increases for polyunsaturated fatty acids comprising 18-22 carbons when cis-double bonds are close to the carboxyl group. Therefore the major natural (food-supplied) and mammalian endogenous fatty acids including gamma-linolenic acid, mead acid, and arachidonic acid as well as the fully polyunsaturated omega3-fatty acids that are enriched in fish oil eicosapentaenoic and docosahexaenoic acids are potent inhibitors of T-currents, which possibly contribute to their physiological functions.

HPLC-based activity profiling: discovery of piperine as a positive GABA(A) receptor modulator targeting a benzodiazepine-independent binding site

A plant extract library was screened for GABA(A) receptor activity making use of a two-microelectrode voltage clamp assay on Xenopus laevis oocytes. An ethyl acetate extract of black pepper fruits [Piper nigrum L. (Piperaceae) 100 microg/mL] potentiated GABA-induced chloride currents through GABA(A) receptors (composed of alpha(1), beta(2), and gamma(2S) subunits) by 169.1 +/- 2.4%. With the aid of an HPLC-based activity profiling approach, piperine (5) was identified as the main active compound, together with 12 structurally related less active or inactive piperamides (1-4, 6-13). Identification was achieved by on-line high-resolution mass spectrometry and off-line microprobe 1D and 2D NMR spectroscopy, using only milligram amounts of extract. Compound 5 induced a maximum potentiation of the chloride currents by 301.9 +/- 26.5% with an EC(50) of 52.4 +/- 9.4 microM. A comparison of the modulatory activity of 5 and other naturally occurring piperamides enabled insights into structural features critical for GABA(A) receptor modulation. The stimulation of chloride currents through GABA(A) receptors by compound 5 was not antagonized by flumazenil (10 microM). These data show that piperine (5) represents a new scaffold of positive allosteric GABA(A) receptor modulators targeting a benzodiazepine-independent binding site.

Daryamides A-C, weakly cytotoxic polyketides from a marine-derived actinomycete of the genus Streptomyces strain CNQ-085

In the course of our continuing search for new antitumor-antibiotics from marine-derived actinomycete bacteria, four new cytotoxic compounds, designated as daryamides A (1), B (2), and C (3) and (2E,4E)-7-methylocta-2,4-dienoic acid amide (4), were isolated from the culture broth of a marine-derived Streptomyces strain CNQ-085. The structures of these new compounds were assigned by detailed interpretation of spectroscopic data. The relative configuration of 1 was determined by comprehensive NMR analysis, while the absolute configuration of 1 was determined as 4S,5R using the modified Mosher method. The daryamides show weak to moderate cytotoxic activity against the human colon carcinoma cell line HCT-116 and very weak antifungal activities against Candida albicans.

Bioactive Self-Nanoemulsifying Drug Delivery Systems (Bio-SNEDDS) for Combined Oral Delivery of Curcumin and Piperine

Background: Bioactive oils of natural origin have gained huge interests from health care professionals and patients. Objective: To design a bioactive self-nanoemulsifying drug delivery system (Bio-SNEDDS) comprising curcumin (CUR) and piperine (PP) by incorporating bioactive natural oils in the formulation. Methods: The self-emulsifying properties of apricot, avocado, black seed and Zanthoxylum rhetsa seed oils were screened within various SNEDDS formulations. Each liquid SNEDDS formulation was loaded with both CUR and PP. The optimal liquid SNEDDS were solidified using Aeroperl® and Neusilin® at 1:1 w/w ratio. Liquid and solid SNEDDS were characterized by droplet size analysis, equilibrium solubility, scanning electron microscopy, X-ray powder diffraction, differential scanning calorimetry, and Fourier transform infrared spectroscopy. In-vitro dissolution studies were performed to evaluate the efficiency of CUR and PP release from solid Bio-SNEDDS. Results: The liquid SNEDDS comprised of black seed oil exhibited excellent self-emulsification performance, low droplet size along with transparent appearance. The inclusion of the cosolvent Transcutol P improved the solubilization capacity of both CUR and PP. The liquid SNEDDS were efficiently solidified using the two adsorbents and presented the drugs within amorphous state. In particular, SNEDDS comprised of black seed oil/Imwitor988/Transcutol P/Cremophor RH40 (20/20/10/50) and when solidified with Neusilin showed enhanced CUR and PP release (up to 60% and 77%, respectively). In addition, this formulation efficiently delivers the highly bioactive black seed oil to the patient. Conclusions: The optimized Bio-SNEDDS comprising black seed oil showed outstanding self-emulsification characteristics along with enhanced CUR/PP dissolution upon solidification.

Crystallographic study of FABP5 as an intracellular endocannabinoid transporter

In addition to binding intracellular fatty acids, fatty-acid-binding proteins (FABPs) have recently been reported to also transport the endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG), arachidonic acid derivatives that function as neurotransmitters and mediate a diverse set of physiological and psychological processes. To understand how the endocannabinoids bind to FABPs, the crystal structures of FABP5 in complex with AEA, 2-AG and the inhibitor BMS-309403 were determined. These ligands are shown to interact primarily with the substrate-binding pocket via hydrophobic interactions as well as a common hydrogen bond to the Tyr131 residue. This work advances our understanding of FABP5-endocannabinoid interactions and may be useful for future efforts in the development of small-molecule inhibitors to raise endocannabinoid levels.

Pellitorine, a potential anti-cancer lead compound against HL6 and MCT-7 cell lines and microbial transformation of piperine from Piper Nigrum

Pellitorine (1), which was isolated from the roots of Piper nigrum, showed strong cytotoxic activities against HL60 and MCT-7 cell lines. Microbial transformation of piperine (2) gave a new compound 5-[3,4-(methylenedioxy)phenyl]-pent-2-ene piperidine (3). Two other alkaloids were also found from Piper nigrum. They are (E)-1-[3’,4’-(methylenedioxy)cinnamoyl]piperidine (4) and 2,4-tetradecadienoic acid isobutyl amide (5). These compounds were isolated using chromatographic methods and their structures were elucidated using MS, IR and NMR techniques.

Development and evaluation of a novel drug delivery: Soluplus®/TPGS mixed micelles loaded with piperine in vitro and in vivo

BACKGROUND

Although piperine can inhibit cells of tumors, the poor water solubility restricted its clinical application. This paper aimed to develop mixed micelles based on Soluplus® and D-α-tocopherol polyethylene glycol succinate (TPGS) to improve the aqueous solubility and anti-cancer effect.

METHODS

Piperine-loaded mixed micelles were prepared using a thin-film hydration method, and their physicochemical properties were characterized. The cellular uptake of the micelles was confirmed by confocal laser scanning microscopy in A549 lung cancer cells and HepG2 liver cancer cells. In addition, cytotoxicity of the piperine mixed micelles was studied in A549 lung cancer cells and HepG2 liver cancer cells. Free piperine or piperine-loaded Soluplus®/TPGS mixed micelles were administered at an equivalent dose of piperine at 3.2 mg/kg via a single intravenous injection in the tail vain for the pharmacokinetic study in vivo.

RESULTS

The diameter of piperine-loaded Soluplus®/TPGS (4:1) mixed micelles was about 61.9 nm and the zeta potential -1.16 ± 1.06 mV with 90.9% of drug encapsulation efficiency and 4.67% of drug-loading efficiency. Differential scanning calorimetry (DSC) studies confirmed that piperine is encapsulated by the Soluplus®/TPGS. The release results in vitro showed that the piperine-loaded Soluplus®/TPGS mixed micelles presented sustained release behavior compared to the free piperine. The mixed micelles exhibited better antitumor efficacy compared to free piperine and physical mixture against in A549 and HepG2 cells by MTT assay. The pharmacokinetic study revealed that the AUC of piperine-loaded mixed micelles was 2.56 times higher than that of piperine and the MRT for piperine-loaded mixed micelles was 1.2-fold higher than piperine (p < .05).

CONCLUSION

The results of the study suggested that the piperine-loaded mixed micelles developed might be a potential nano-drug delivery system for cancer chemotherapy. These results demonstrated that piperine-loaded Soluplus®/TPGS mixed micelles are an effective strategy to deliver piperine for cancer therapy.

Anandamide oxidation by wild-type and polymorphically expressed CYP2B6 and CYP2D6

Anandamide is an arachidonic acid-derived endogenous cannabinoid that regulates normal physiological functions and pathophysiological responses within the central nervous system and in the periphery. Several cytochrome P450 (P450) isoforms metabolize anandamide to form hydroxylated and epoxygenated products. Human CYP2B6 and CYP2D6, which are expressed heterogeneously throughout the brain, exhibit clinically significant polymorphisms and are regulated by external factors, such as alcohol and smoking. Oxidative metabolism of anandamide by these two P450s may have important functional consequences for endocannabinoid system signaling. In this study, we investigated the metabolism of anandamide by wild-type CYP2B6 (2B6.1) and CYP2D6 (2D6.1) and by their common polymorphic mutants 2B6.4, 2B6.6, 2B6.9, and 2D6.34. Major differences in anandamide metabolism by the two isoforms and their mutants were found in vitro with respect to the formation of 20-hydroxyeicosatetraenoic acid ethanolamide (20-HETE-EA) and 14,15-epoxyeicosatetraenoic acid ethanolamide (14,15-EET-EA). Pharmacological studies showed that both 20-HETE-EA and 14,15-EET-EA bind to the rat brain cannabinoid CB1 receptor with lower affinities relative to that of anandamide. In addition, both products are degraded more rapidly than anandamide in rat brain homogenates. Their degradation occurs via different mechanisms involving either fatty acid amide hydrolase (FAAH), the major anandamide-degrading enzyme, or epoxide hydrolase (EH). Thus, the current findings provide potential new insights into the actions of inhibitors FAAH and EH, which are being developed as novel therapeutic agents, as well as a better understanding of the interactions between the cytochrome P450 monooxygenases and the endocannabinoid system.