Antiulcer and Antioxidant Activity of a Lectin from Mucuna pruriens Seeds on Ethanol- induced Gastropathy: Involvement of Alpha-2 Adrenoceptors and Prostaglandins.

ETHNOPHARMACOLOGICAL RELEVANCE: Mucuna pruriens (Mp) belongs to Leguminosae family, it is native of tropical regions and used to treat several maladies such as urinary, neurological, and menstruation disorders, constipation, edema, fever, tuberculosis, ulcers, diabetes, arthritis, dysentery, and cardiovascular diseases. Mp seeds are rich in bioactive compounds, for instance, lectins, a heterogeneous group of proteins and glycoproteins with a potential role as therapeutic tools for several conditions, including gastric disorders. This study investigated the acute toxicity, gastroprotective, and antioxidant activities of a lectin from Mucuna pruriens seeds (MpLec) on ethanol-induced gastropathy model in mice. MATERIAL AND METHODS: Mice received MpLec (5 or 10 mg/kg; i.v.) and were observed for acute toxicity signs; in another experimental series, mice were pre-treated with MpLec (0.001; 0.01 or 0.1 mg/kg, i.v.), ranitidine (80 mg/kg, p.o.), or saline (0.3 mL/30g, i.v.) before ethanol 99.9% (0.2 mL/animal, p.o.), and euthanized 30 min after ethanol challenge. Macroscopic and microscopic gastric aspects, biochemical parameters (tissue hemoglobin levels, iron-induced lipid peroxidation, GSH content, SOD activity, and gastric mucosal PGE2) were measured. Additionally, pharmacological tools (yohimbine, indomethacin, naloxone, L-NAME) were opportunely used to clarify MpLec gastroprotective mechanisms of action. RESULTS: No toxicity signs nor death were observed at acute toxicity tests. MpLec reduced ethanol-induced gastric damage, edema, and hemorrhagic patches formation, as well as decreased lipid peroxidation, SOD activity, and increased GSH content. Yohimbine and indomethacin prevented MpLec effects, suggesting the involvement of alpha-2 adrenoceptors and prostaglandins in the MpLec-mediated effects. CONCLUSION: MpLec does not present toxicity signs and shows gastroprotective and antioxidant activities via alpha-2 adrenoceptors and prostaglandins in the ethanol-induced gastropathy model.

The efficacy of a lectin from Abelmoschus Esculentus depends on central opioid receptor activation to reduce temporomandibular joint hypernociception in rats.

Abelmoschus esculentus is largely cultivated in Northeastern Brazil for medicinal purposes, e.g. inflammatory conditions. This study aimed to evaluate the efficacy of Abelmoschus esculentus lectin (AEL) in reducing formalin-induced temporomandibular joint inflammatory hypernociception in rats. The behavioral experiments were performed in male Wistar rats (180-240 g). Rats were pre-treated (i.v.) with AEL (0.001, 0.01 or 0.1 mg/kg) 30 min before formalin injection (i.art.). To analyze the possible effect of opioid pathways on AEL efficacy, animals were pre-treated with naloxone or CTOP (µ opioid receptor antagonist), naltrindole (δ opioid receptor antagonist) or nor-binaltorphimine (κ opioid receptor antagonist) (i.t.) 15 min before AEL administration followed by intra-TMJ injection of 1.5% formalin. Animals were monitored for a 45-min observation period. TMJ tissue, trigeminal ganglion, and subnucleus caudalis were collected for TNF-α dosage (ELISA). In addition, the vascular permeability was evaluated by Evans Blue extravasation. AEL significantly reduced formalin-induced TMJ inflammatory hypernociception and decreased Evans blue extravasation. It decreased TNF-α levels in the TMJ tissue, trigeminal ganglion, and subnucleus caudalis. AEL antinociceptive effects were not observed in the presence of naltrindole or nor-binaltorphimine, suggesting that AEL efficacy depends on TNF-α inhibition and the activation of δ and κ opioid receptors. AEL has provided prominent analgesic and anti-inflammatory effects in this pre-clinical model of TMJ, supporting its possible use as a pharmacological tool for the management of painful conditions.

Role of central opioid on the antinociceptive effect of sulfated polysaccharide from the red seaweed Solieria filiformis in induced temporomandibular joint pain.

This study aimed to investigate the effect of sulfated polysaccharide from red seaweed Solieria filiformis (Fraction F II) in the inflammatory hypernociception in the temporomandibular joint (TMJ) of rats. Male Wistar rats were pretreated (30min) with a subcutaneous injection (s.c.) of vehicle or FII (0.03, 0.3 or 3.0mg/kg) followed by intra-TMJ injection of 1.5% Formalin or 5-hydroxytryptamine (5-HT, 225µg/TMJ). In other set of experiments rats were pretreated (15min) with an intrathecal injection of the non-selective opioid receptors Naloxone, or µ-opioid receptor antagonist CTOP, or δ-opioid receptor Naltridole hydrochloride, or κ-opioid receptor antagonist Nor-Binaltorphimine (Nor-BNI) followed by injection of FII (s.c.). After 30min, the animals were treated with an intra-TMJ injection of 1.5% formalin. After TMJ treatment, behavioral nociception response was evaluated for a 45-min observation period, animals were terminally anesthetized and periarticular tissue, trigeminal ganglion and subnucleus caudalis (SC) were collected plasma extravasation and ELISA analysis. Pretreatment with F II significantly reduced formalin- and serotonin-induced TMJ nociception, inhibit the plasma extravasation and inflammatory cytokines release induced by 1.5% formalin in the TMJ. Pretreatment with intrathecal injection of Naloxone, CTOP, Naltridole or Nor-BNI blocked the antinociceptive effect of F II in the 1.5% formalin-induced TMJ nociception. In addition, F II was able to significantly increase the ß-endorphin release in the subnucleus caudalis. The results suggest that F II has a potential antinociceptive and anti-inflammatory effect in the TMJ mediated by activation of opioid receptors in the subnucleus caudalis and inhibition of the release of inflammatory mediators in the periarticular tissue.