The leguminous lectin of Lonchocarpus araripensis promotes antinociception via mechanisms that include neuronal inhibition of Na+ currents

Schinus terebinthifolia leaf lectin has central and peripheral antinociceptive action mediated by its carbohydrate-recognition domain and delta-opioid receptors

ETHNOPHARMACOLOGICAL RELEVANCE

Preparations from the bark and leaves of Schinus terebinthifolia Raddi are commonly used to treat toothaches and sore throats. The use of medications based on leaves of this plant has also been reported for pain of arthritis, toothache, and sore throat. Some evidence indicated that the lectin SteLL is an antinociceptive agent from leaves.

AIM OF THE STUDY

This study evaluated the antinociceptive activity of S. terebinthifolia leaf lectin (SteLL) using mouse models of peripheral and central nociception.

MATERIALS AND METHODS

Animals were treated intraperitoneally with SteLL at 1, 5, and 10 mg/kg. An acetic acid-induced abdominal writhing test was performed to screen for the antinociceptive effect of the lectin. Next, the formalin test was used to assess the effects of SteLL on neurogenic (first phase) and inflammatory (second phase) pain, as well as to investigate the involvement of the carbohydrate-recognition domain (CRD) of SteLL and opioid receptors in the antinociceptive effect. The tail immersion test was performed to assess the central antinociception. Additionally, a rotarod test was performed to evaluate the effects of lectin on motor coordination in mice.

RESULTS

SteLL reduced the number of acetic acid-induced writhes by 83.5-100.0%. In the first phase of the formalin test, SteLL reduced paw licking time by 49.4-50.5%, while in the second phase, SteLL reduced paw licking time by 80.5-82.6%. This antinociceptive effect was reversed by the previous incubation of the lectin with ovalbumin (indicating the possible involvement of the CRD) and by the administration of naloxone, a nonselective opioid receptor antagonist. When testing selective antagonists of opioid receptors (μ, δ, and κ), only naltrindole, a selective δ receptor antagonist, blocked the antinociceptive action of SteLL during the second phase of the formalin test. In the tail immersion test, SteLL (1, 5, and 10 mg/kg) administration reduced sensitivity to thermal stimulus, which was observed even after 2 h. SteLL (10 mg/kg) did not affect animal motor coordination in rotarod test when compared to the control group.

CONCLUSION

SteLL has peripheral and central analgesic action involving opioid receptor modulation without affecting the motor coordination of animals. These results provide new perspectives for developing analgesic agents using lectins.

Antinociceptive effect of Lonchocarpus araripensis lectin: activation of L-arginine/NO/cGMP/K+ATP signaling pathway

OBJECTIVE AND DESIGN

The involvement of nitric oxide pathway in the antinociceptive activity of Lonchocarpus araripensis lectin (LAL) was investigated in the model of carragenan-induced hypernociception.

METHODS

Swiss mice received LAL (0.01-10 mg/kg; i.v.) 30 min before s.c. injection of carragenan in the paws. For the involvement of nociceptive pathways, animals were previously treated with the blockers: NOS (L-NAME, aminoguanidine, 7-nitroindazole); soluble guanylyl cyclase (ODQ); channels of ATP-dependent K⁺ (glibenclamide); L-type Ca²⁺ (nifedipine), or Ca²⁺-dependent Cl^- (niflumic acid). Participation of lectin domain was evaluated by injection of LAL associated with N-acetyl-glucosamine (GlcNAc). nNOS gene relative expression was evaluated in the paw tissues and nNOS immunostaining in dorsal root ganglia.

RESULTS

LAL at all doses inhibited carrageenan-induced hypernociception (4.12 ± 0.58 g), being maximal at 10 mg/kg (3 h: 59%), and reversed by GlcNAc. At this time, LAL effect was reversed by nifedipine (39%), niflumic acid (59%), L-NAME (59%), 7-nitroindazole (44%), ODQ (45%), and glibenclamide (34%), but was unaltered by aminoguanidine. LAL increased (95%) nNOS gene expression in mice paw tissues, but not its immunoexpression in the dorsal root ganglia.

CONCLUSION

The antinociceptive effect of Lonchocarpus araripensis lectin involves activation of the L-arginine/NO/GMPc/K⁺ATP pathway.

Dalbergieae lectins: A review of lectins from species of a primitive Papilionoideae (leguminous) tribe

Lectins are (glyco)proteins capable of reversibly binding to specific carbohydrates, thus having various functions and applications. Plant lectins are the best studied, and the Leguminoseae family is highlighted in a number of published works, especially species of the Papilionoideae subfamily. Dalbergieae is one of the tribes in this subfamily comprising 49 genera and over 1300 species. From this tribe, about 26 lectins were studied, among which we can highlight the Arachis hypogaea lectin, widely used in cancer studies. Dalbergieae lectins demonstrate various carbohydrate specificities and biological activities including anti-inflammatory, vasorelaxant, nociceptive, antibacterial, antiviral among others. Structurally, these lectins are quite similar in their three-dimensional folding but present significant differences in oligomerization patterns and in the conservation of carbohydrate-recognition domain. Despite the existence of structural data from some lectins, only sparse literature has reported on this tribe's diversity, not to mention the range of biological effects, determined through specific assays. Therefore, this work will review the most important studies on Dalbergieae lectins and their potential biomedical applications.

Structural studies and nociceptive activity of a native lectin from Platypodium elegans seeds (nPELa)

A native lectin (nPELa), purified from seeds of the species Platypodium elegans, Dalbergieae tribe, was crystallized and structurally characterized by X-ray diffraction crystallography and bioinformatics tools. The obtained crystals diffracted to 1.6Å resolution, and nPELa structure were solved through molecular substitution. In addition, nPELa has a metal binding site and a conserved carbohydrate recognition domain (CRD) similar to other Dalbergieae tribe lectins, such as PAL (Pterocarpus angolensis) and CTL (Centrolobium tomentosum). Molecular docking analysis indicated high affinity of this lectin for different mannosides, mainly trimannosides, formed by α-1,3 or α-1,6 glycosidic bond, as evidenced by the obtained scores. In addition, molecular dynamics simulations were performed to demonstrate the structural behavior of nPELa in aqueous solution. In solution, nPELa was highly stable, and structural modifications in its carbohydrate recognition site allowed interaction between the lectin and the different ligands. Different modifications were observed during simulations for each one of the glycans, which included different hydrogen bonds and hydrophobic interactions through changes in the relevant residues. In addition, nPELa was evaluated for its nociceptive activity in mice and was reported to be the first lectin of the Dalbergieae tribe to show CRD-dependent hypernociceptive activity.