The hyperinsulinemia produced by concanavalin A in rats is opioid-dependent and hormonally regulated

Systematic review of sex-based differences in opioid-based effects

There are several biological factors that might play a role in physiological response to opioids and/or the onset of problematic opioid use; however, sex-based differences in non-analgesic opioid-based effects are poorly understood. The goal of this review is to provide a current analysis of the pre-clinical literature on sex-based differences in response to endogenous and exogenous opioids, including the interplay between sex hormones and opioid receptor-mediated neuronal activity and associated behaviours. A systematic search was performed on the following terms within PubMed between March and April 2018: 'opioid oestrogen', 'opioid progesterone', 'opioid oestradiol', and 'opioid testosterone'. Pre-clinical research on the non-analgesic, sex-based effects of opioids is disparate, both in terms of methodology and outcomes, which prohibits a cohesive summary of the results. Themes from the pre-clinical literature suggest that opioid receptor binding, coupling, and density vary as a function of hormone exposure. Findings also suggest that interactions between endogenous opioid and stress systems may differ between males and females as a function of ovarian hormones. Given the current opioid-related public health crisis, there is a pressing need to increase systematic pre-clinical and clinical research on sex-based differences in opioid-effects and opioid use disorder.

Opioid-like antinociceptive effects of oral administration of a lectin purified from the seeds of Canavalia brasiliensis

The objective of this study was to evaluate the antinociceptive effects of a lectin from Canavalia brasiliensis (ConBr) when administered orally to murine models of chemical and thermal nociception. ConBr up to 100 mg/kg produced significant and dose-dependent antinociceptive effects: 81% reduction in abdominal writhing induced by 0.6% acetic acid; 26 and 52% reduction in early- and late-stage paw licking, respectively, induced by 2.5% formalin; and 155% increase in reaction latency (heightened thermal pain threshold). In all models, the antinociceptive effect was reversed by the lectin-binding carbohydrate α-d-methyl-mannoside and by the nonselective opioid antagonist naloxone. The antinociceptive effect observed in the formalin test was inhibited by the δ-selective antagonist naltrindole and the κ-selective antagonist nor-binaltorphimine but not by the μ-selective antagonist cyprodime. In conclusion, when administered orally to Swiss mice, the ConBr lectin displayed antinociceptive activity, both peripheral and central, mediated by the opioid system and involving δ-and κ-receptors and the lectin domain.

Taenia saginata metacestode antigenic fractions without affinity to concanavalin A are an important source of specific antigens for the diagnosis of human neurocysticercosis

Taenia saginata metacestode antigens have been constituted a useful alternative antigen for neurocysticercosis (NC) serodiagnosis, particularly due to an increasing difficulty to obtain Taenia solium homologous antigen. Cross-reactivity with Echinococcus granulosus infection occurs in homologous and heterologous antigens and could be avoided by using different purified methods. The present study evaluated antigen fractions obtained from saline extracts of T. saginata metacestodes purified by affinity chromatography with jacalin or concanavalin A (ConA) lectins to detect IgG antibodies by enzyme-linked immunosorbent assay (ELISA) and immunoblot analysis to diagnose human NC. Serum samples were collected from 142 individuals: 40 of them were diagnosed with NC, 62 presented Taenia sp. and other parasites, and 40 were apparently healthy individuals. The jacalin- and ConA-unbound fractions demonstrated sensitivity and specificity higher than those of bound fractions. Among unbound fractions, ConA demonstrated statistically higher sensitivity and specificity by ELISA (90% and 93.1%, respectively). By immunoblot assay, the 64- to 68-kDa component from the ConA-unbound fraction showed 100% sensitivity and specificity, making this component suitable for use as a specific antigen for diagnosis of NC. To our knowledge, this is the first report showing the relevance of using the unbound ConA fraction of T. saginata metacestodes to diagnose NC. In conclusion, the results obtained herein clearly demonstrate that antigenic fractions without affinity to ConA, obtained from T. saginata metacestodes, are an important source of specific peptides and are efficient in the diagnosis of NC when tested by immunoblot assay.

Systemic effect of peanut agglutinin following intravenous infusion into rats

BACKGROUND

Ingested peanut agglutinin stimulates colonic proliferation in humans. In rats, ingested peanut agglutinin stimulates hormone release and proliferation in the small and large intestines. Peanut agglutinin is absorbed into the circulation but little is known about the systemic effect of this lectin. Therefore, we studied the effect of intravenous peanut agglutinin on hormone release and intestinal growth.

METHOD

Six rats per group received peanut agglutinin infusion at 0, 2, 20 or 200 microg/rat/day for 6 days via the right jugular vein. Organ weights were measured, pancreatic enzymes, DNA, RNA and protein levels were analysed. Plasma hormones were measured by radioimmunoassay. All tissues were examined histologically. Small intestinal and colonic proliferation rates were estimated by metaphase arrest.

RESULTS

High-dose peanut agglutinin significantly reduced the wet weight of the stomach by 7% (P < 0.05) and large intestine by 10% (P < 0.05). Peanut agglutinin dose-dependently released enteroglucagon; low-, medium- and high-dose by 64%, 126% (P < 0.01) and 180% (P < 0.01), respectively, and glucagon-like peptide-1 by 127% (P < 0.01), 169% (P < 0.01) and 315% (P < 0.001), respectively. Peanut agglutinin had no effect on cholesystokinin, gastrin or insulin levels. Peanut agglutinin, low-, medium- and high-dose stimulated proliferation in the mid colon by 42% (P < 0.01), 30% and 38%, respectively. Only high-dose peanut agglutinin stimulated proliferation in the distal colon by 54% (P < 0.01). No histological changes were evident in any tissue.

CONCLUSION

Intravenous peanut agglutinin released hormones and stimulated colonic proliferation. Proliferation of the small intestine seen after ingestion of peanut agglutinin in previous studies appears to require luminal contact between enterocytes and the lectin. Possible clinical applications include reversal of atrophy during total parenteral nutrition, anastomotic healing after surgery and restoration of mucosa integrity in colitis.