From identification to functional characterization of cyriotoxin-1a, an antinociceptive toxin from the spider Cyriopagopus schioedtei.

BACKGROUND AND PURPOSE: The NaV 1.7 channel is highly expressed in dorsal root ganglia of the sensory nervous system and plays a central role in the pain signalling process. We investigated a library prepared from original venoms of 117 different animals to identify new selective inhibitors of this target. EXPERIMENTAL APPROACH: We used high throughput screening of a large venom collection using automated patch-clamp experiments on human voltage-gated sodium channel subtypes and then in vitro and in vivo electrophysiological experiments to characterize the active peptides that have been purified, sequenced, and chemically synthesized. Analgesic effects were evaluated in vivo in mice models. KEY RESULTS: We identified cyriotoxin-1a (CyrTx-1a), a novel peptide isolated from Cyriopagopus schioedtei spider venom, as a candidate for further characterization. This 33 amino acids toxin belongs to the inhibitor cystine knot structural family and inhibits hNaV 1.1-1.3 and 1.6-1.7 channels in the low nanomolar range, compared to the micromolar range for hNaV 1.4-1.5 and 1.8 channels. CyrTx-1a was 920 times more efficient at inhibiting tetrodotoxin (TTX)-sensitive than TTX-resistant sodium currents recorded from adult mouse dorsal root ganglia neurons and in vivo electrophysiological experiments showed that CyrTx-1a was approximately 170 times less efficient than huwentoxin-IV at altering mouse skeletal neuromuscular excitability properties. CyrTx-1a exhibited an analgesic effect in mice by increasing reaction time in the hot-plate assay. CONCLUSIONS AND IMPLICATIONS: The pharmacological profile of CyrTx-1a paves the way for further molecular engineering aimed to optimize the potential antinociceptive properties of this peptide.

Nature cures nature: Hypericum perforatum attenuates physical withdrawal signs in opium dependent rats.

CONTEXT: Hypericum perforatum Linn. (Hypericaceae) (St. John's wort) attenuates opium withdrawal signs. AIM: To explore the therapeutic potential of Hypericum perforatum in the management of opium-induced withdrawal syndrome. MATERIALS AND METHODS: The effect of the Hypericum perforatum hydro-ethanol extract was investigated for potential to reverse naloxone (0.25 mg/kg)-induced opium withdrawal physical signs. Rats received opium extract (80-650 mg/kg) twice daily for 8 days along with Hypericum perforatum (20 mg/kg, orally) twice daily in chronic treatment and the same single dose 1 h before induction of withdrawal syndrome in the acute treated group. RESULTS: Hypericum perforatum reduced stereotype jumps and wet dog shake number in the chronic treatment compared to the saline control group (F(2, 24) = 3.968, p < 0. 05) and (F(2, 24) = 3.689, p < 0.05), respectively. The plant extract in the acutely treated group reduced diarrhea (F(2, 24) = 4.850, p < 0. 05 vs. saline). It decreased rectal temperature by chronic treatment at 30 min (F(2, 24) = 4.88, p < 0.05), 60 min (F(2, 240 = 5.364, p < 0.01) and 120 min (F(2, 24) = 4.907, p < 0.05). DISCUSSION AND CONCLUSION: This study reveals that the extract of Hypericum perforatum attenuates some physical signs of opium withdrawal syndrome possibly through direct or indirect interaction with opioid receptors. Further study is needed to clarify its mechanism.

Antagonistic effects of methanolic extract of Polygala telephioides on morphine responses in mice.

The present study was undertaken to investigate the antagonistic effects of the methanolic extract of Polygala telephioides (PT) on morphine responses in mice. Single administration of PT tended to antagonize the morphine-induced analgesia in a hot-plate test. Moreover, PT (300 mg/kg, p.o.) improved the morphine-induced memory impairment in an elevated plus maze test. However, PT alone had no effect on behaviors in the open-field, hot-plate and elevated plus maze tests. We investigated the effects of PT on naloxone-induced jumping (as withdrawal sign) in morphine-dependent mice. To induce dependence, mice were twice daily treated with morphine (10-45 mg/kg, s.c.) for 5 days. Co-administrations of PT (10, 100 and 300 mg/kg, p.o.) during repeated morphine treatments significantly suppressed the naloxone (10 mg/kg, i.p.)-induced jumping. However, the naloxone-induced jumping was not affected by a single large administration of PT on the 5th day. The inhibitory effect of PT on the naloxone-induced jumping was due to the development of dependence rather than expression of withdrawal sign. Moreover, single administration of PT (30 mg/kg, p.o.) decreased the morphine levels in plasma. These results indicate that PT may be useful in facilitating narcotic detoxification.

Extraction and determination by liquid chromatography and spectrophotometry of naloxone in microparticles for drug-addiction treatment.

This paper discusses the development and validation of two analytical methods for the assay of naloxone in microparticles, as used in the therapy of opioid drug addiction (weaning). A UV-Vis spectrophotometric method is proposed to study drug loading and drug release, due to its ease and simplicity of performance, while a high performance liquid chromatographic method is developed as a means of stability-indication. Both analytical procedures were validated according to the International Committee for Harmonization (ICH) guidelines. Although the ranges and wavelengths were different for the two analytical methods, they were both found to be specific, linear, precise, and accurate under the determined conditions.

CJ-15,208, a novel kappa opioid receptor antagonist from a fungus, Ctenomyces serratus ATCC15502.

A novel kappa opioid receptor binding inhibitor CJ-15,208 (I) was isolated from the fermentation broth of a fungus, Ctenomyces serratus ATCC15502. The structure of I was determined to be a cyclic tetrapeptide consisting of one tryptophan, one D-proline, and two L-phenylalanine. Compound I was a selective binding inhibitor for the kappa opioid receptor: 47 nM (IC50) for kappa, 260 nM for mu, and 2,600 nM for delta. In the electrically-stimulated twitch response assay of rabbit vas deferens I recovered the suppression by a kappa agonist asimadoline with an ED50 of 1.3 microM, indicating that it is a kappa antagonist.

Determination of naltrexone and 6-beta-naltrexol in plasma by solid-phase extraction and gas chromatography-negative ion chemical ionization-mass spectrometry.

Solid-phase extraction (SPE) and a one-step derivatization are combined with gas chromatography-negative ion chemical ionization-mass spectrometry to simplify a previously reported method for the determination of naltrexone and its metabolite, 6-beta-naltrexol, in human plasma. Deuterated isotopomers of naltrexone and 6-beta-naltrexol are used as internal standards. After SPE, the extracts are derivatized with pentafluoropropionic anhydride at room temperature to form predominantly the bispentafluoropropionyl derivative of naltrexone and the trispentafluoropropionyl derivative of 6-beta-naltrexol. The derivatized extracts are analyzed by monitoring ion currents at m/z 633 (naltrexone), m/z 636 (naltrexone-2H3), m/z 633 6-beta-naltrexol), and m/z 640 (6-beta-naltrexol-2H7). Control plasma samples containing 0.3, 3, or 30 ng/nl of each analyte were analyzed for precision and accuracy with the following results: intra-assay, the percentage of target concentrations were 107-113% for naltrexone and 107-120% for 6-beta-naltrexol, and the coefficients of variation (CVs) were 3.1-6.3% for naltrexone and 3.1-5.7% for 6-beta-naltrexol; interassay, the percentage of target concentrations were 103-110% for naltrexone and 110-113% for 6-beta-naltrexol, and the CVs were 6.1-9.1% for naltrexone and 5.9-9.1% for 6-beta-naltrexol. At the limit of quantitation (LOQ) of 0.1 ng/ml, both analytes quantified within 20% of the target concentration with CVs less than 17%. The extraction recoveries determined at 0.3 and 30 ng/ml were 79 and 80% for naltrexone and 76 and 75% for 6-beta-naltrexol. Bench-top stability tested with concentrations of 0.3 and 3.0 ng/ml did not decrease more than 10% from the zero-hour controls at 3, 6 and 24 h. Selectively was determined using plasma from six donors and none showed interfering peaks greater than 22% of the LOQ for naltrexone and 53% of the LOQ for 6-beta-naltrexol. Using this method, naltrexone and 6-beta-naltrexol were readily detected in plasma specimens collected 5.5 h after oral doses of 25 or 100 mg naltrexone. Following discontinuation of treatment, naltrexone was detected 30 h after the 100-mg dose, whereas 6-beta-naltrexol was detected 125 h after both the 25- and 100-mg doses.

High-performance liquid chromatographic resolution of synthetic opiate and "anti-opiate" peptides from human plasma.

An assay system using reversed-phase high-performance liquid chromatographic (HPLC) resolution of synthetic anti-opioid peptides (AOPs) and opioid peptides (OPs) was developed. Samples were diluted with trifluoroacetic acid, loaded onto Sep-Pak C18 cartridges, eluted, dried, and redissolved in ethanol-acetic acid-water. Retention-time consistency was established, and high levels of synthetic AOP and OP recovery, generally higher than 80%, were achieved. In a single HPLC run synthetic enkephalins, dynorphins, and beta-endorphins were separated even when extracted from human plasma using a volatile mobile phase which yielded fractions totally compatible with quantitation by radioimmunoassay. Combining the resolution of HPLC with the sensitivity of radioimmunoassay (RIA) may facilitate simultaneous measurement of numerous neuropeptides in body fluids such as plasma and cerebrospinal fluid.

Isolation and characterization of opioid antagonist peptides derived from human lactoferrin.

Peptides with affinity for opioid receptors were found in an artificially methyl-esterified peptic digest of human lactoferrin. Three active peptides were purified by two steps of reverse-phase high-performance liquid chromatography. Their structures were Tyr-Leu-Gly-Ser-Gly-Tyr-OCH3, Arg-Tyr-Tyr-Gly-Tyr-OCH2, and Lys-Tyr-Leu-Gly-Pro-Gln-Tyr-OCH3, which respectively correspond to the methyl esters of residues 318-323, 536-540, and 673-679 of human lactoferrin. The IC50 values of these peptides were 15, 10 and 23 microM, respectively, in a radioreceptor assay in the presence of 1 nM [3H]naloxone. In the myenteric plexus preparation of the longitudinal muscle of guinea pig ileum, the individual peptides had no opioid agonist activities, but they antagonized [Met5]enkephalin and morphiceptin when they were at a concentration of 10(-6)-10(-5) M, suggesting that these were the opioid antagonist peptides. These three opioid antagonist peptides were named lactoferroxin A, B and C, after casoxin, the opioid antagonist peptide derived from bovine kappa-casein. Concerning the antagonist activities of lactoferroxins for opioid receptor sub-types, lactoferroxin A showed preference for mu-receptors, while lactoferroxin B and C had somewhat higher degrees of preference for kappa-receptors than for mu-receptors. A study of the structure-activity relationship of the three lactoferroxins and their synthetic analogues showed that these opioid antagonist peptides derived from food protein could be expressed by the general formula XA-Tyr-XB-Tyr-OCH3. An amino acid in position XA may affect the specificity of the antagonist peptide for opioid receptor sub-types.