Contribution of the carbohydrate-binding ability of Vatairea guianensis lectin to induce edematogenic activity

Antimicrobial Prenylated Isoflavones from the Leaves of the Amazonian Medicinal Plant Vatairea guianensis Aubl

Vatairea guianenis Aubl. (Fabaceae) is an Amazonian medicinal plant species traditionally used for treating skin diseases. In an initial screening, a V. guianensis leaf extract and its subextracts showed antibacterial and antifungal activities. The EtOAc subextract was selected for chemical workup and afforded five known (1-4 and 8) and six undescribed isoflavones, vatairenones C-H (5-7 and 9-11). All isoflavones are prenylated in position C-8, displaying either chain-prenylated (1-7) or ring-closed forms (8-11). The most bioactive compound (3) exhibited in vitro activity against clinically relevant bacteria and fungi with IC₅₀ values ranging from 6.8 to 26.9 μM. Due to its broad antimicrobial activity and low general toxicity, compound 3 is a potential lead compound for structural modifications. The results of the present study support the ethnomedicinal use of V. guianensis in the treatment of dermatological disorders. ¹H NMR spectra of some of the isolated compounds showed intricate signal patterns, which might explain repeated errors in assigning the correct structure of the isoflavonoid B-ring in the literature and which we resolved by higher order spectra simulations.

Vatairea guianensis lectin stimulates changes in gene expression and release of TNF-α from rat peritoneal macrophages via glycoconjugate binding

Using a rat model of peritonitis, we herein report the inflammatory effect induced by the lectin isolated from Vatairea guianensis (VGL) seeds in the context of interactions between VGL and both toll-like receptor 4 (TLR4) and tumor necrosis factor receptor 1 (TNFR1). Peritoneal macrophages were stimulated with VGL for dose-dependent gene expression and release of TNF-α. In vivo results showed that VGL (1 mg/kg; intraperitoneal) induced peritonitis in female Wistar rats. Leukocyte migration, macrophage activation, and protein leakage were measured 3 and 6 hours after induction. In vitro, peritoneal macrophages were stimulated with VGL for gene expression and TNF-α dosage (mean ± SEM (n = 6), analysis of variance, and Bonferroni's test (P < .05)). In silico, VGL structure was applied in molecular docking with representative glycans. It was found that (a) VGL increases vascular permeability and stimulates leukocyte migration, both rolling and adhesion; (b) lectin-induced neutrophil migration occurs via macrophage stimulation, both in vitro and in vivo; (c) lectin interacts with TLR4 and TNFR1; and (d) stimulates TNF-α gene expression (RT-PCR) and release from peritoneal macrophages. Thus, upon lectin-glycan binding on the cell surface, our results suggest that VGL induces an acute inflammatory response, in turn activating the release of peritoneal macrophages via TNF-α and TLR and/or TNFR receptor pathways.

Differential vasodilator effect of Dioclea rostrata lectin in conductance and resistance arteries: Mechanisms and glycoconjugate binding relationships

Lectins are proteins that recognize specific carbohydrates, and the vasorelaxant effect of legume lectins has been previously reported, for example the Dioclea rostrata lectin (DRL). This study evaluated major pathways of DRL-induced relaxation in different artery segments and the possible molecular interactions involved. Rat thoracic aorta, coronary and mesenteric resistance arteries were tested "in vitro" with concentration-response curves to DRL (0.01-100 µg/mL). L-NAME, indomethacin and high KCl were used to evaluate nitric oxide, cyclooxygenase and hyperpolarization-dependent effects. DRL promoted relaxation of all vessels throughout different mechanisms. L-NAME blunted DRL-induced effects only in the aorta and mesenteric resistance artery. By the use of depolarizing KCl solution, vasodilation was reduced in all arteries, while incubation with indomethacin indicated a role of cyclooxygenase-derived factors for DRL effects in mesenteric and coronary arteries, but not in the aorta. Molecular docking results suggested interactions between DRL and heparan sulphate, CD31 and other glycans present on the membrane surface. These data indicate that the mechanisms involved in DRL-mediated vasodilation vary between conductance and resistance arteries of different origins, and these effects may be related to the capacity of DRL to bind a diversity of glycans, especially heparan sulphate, a proposed mechanoreceptor for nitric oxide synthase and cyclooxygenase activation.

ConBr lectin modulates MAPKs and Akt pathways and triggers autophagic glioma cell death by a mechanism dependent upon caspase-8 activation

Glioblastoma multiforme is the most aggressive type of glioma, with limited treatment and poor prognosis. Despite some advances over the last decade, validation of novel and selective antiglioma agents remains a challenge in clinical pharmacology. Prior studies have shown that leguminous lectins may exert various biological effects, including antitumor properties. Accordingly, this study aimed to evaluate the mechanisms underlying the antiglioma activity of ConBr, a lectin extracted from the Canavalia brasiliensis seeds. ConBr at lower concentrations inhibited C6 glioma cell migration while higher levels promoted cell death dependent upon carbohydrate recognition domain (CRD) structure. ConBr increased p38^MAPK and JNK and decreased ERK1/2 and Akt phosphorylation. Moreover, ConBr inhibited mTORC1 phosphorylation associated with accumulation of autophagic markers, such as acidic vacuoles and LC3 cleavage. Inhibition of early steps of autophagy with 3-methyl-adenine (3-MA) partially protected whereas the later autophagy inhibitor Chloroquine (CQ) had no protective effect upon ConBr cytotoxicity. ConBr also augmented caspase-3 activation without affecting mitochondrial function. Noteworthy, the caspase-8 inhibitor IETF-fmk attenuated ConBr induced autophagy and C6 glioma cell death. Finally, ConBr did not show cytotoxicity against primary astrocytes, suggesting a selective antiglioma activity. In summary, our results indicate that ConBr requires functional CRD lectin domain to exert antiglioma activity, and its cytotoxicity is associated with MAPKs and Akt pathways modulation and autophagy- and caspase-8- dependent cell death.

Reviewing Mimosoideae lectins: A group of under explored legume lectins

Lectins are proteins capable of specific and reversible binding to mono- and/or oligosaccharides, and within this group, Legume lectins are the most studied. However, most of these studies focus on the Papilionoideae subfamily, with Caesalpinioideae and Mimosoideae lectins being significantly less explored in the literature. The Mimosoideae subfamily consists of at least 79 genera and 3275 species, but, to date, only about 14 lectins have been purified, a fact which shows the lack of studies for this group. Based on their purification protocols, as well as physicochemical and structural properties, Mimosoideae lectins are very heterogeneous. Despite the few studies, a wide variety of biological activities have been tested, including, for example, inflammatory, anticancer, antibacterial, and antifungal. In this context, the present review aims to summarize the available data regarding the purification, physicochemical and structural properties, as well as biological activities, of lectins extracted from plants of the Mimosoideae subfamily in order to bring more insight to researchers interested in further exploring the potential of these molecules.

Molecular dynamics and binding energy analysis of Vatairea guianensis lectin: a new tool for cancer studies

The Tn antigen is an epitope containing N-acetyl-D-galactosamine present in the extracellular matrix of some carcinoma cells in humans, and it is often used as a biomarker. Lectins are proteins capable of binding to carbohydrates and can be used as a molecular tool to recognize antigens and to differentiate cancer cells from normal cells. In this context, the present work aimed to characterize the interaction of Vatairea guianensis seed lectin with N-acetyl-D-galactosamine and the Tn antigen by molecular dynamics and molecular mechanics/Poisson-Boltzmann solvent-accessible surface area analysis. This study revealed new interacting residues not previously identified in static analysis of the three-dimensional structures of Vatairea lectins, as well as the configuration taken by the carbohydrate recognition domain, as it interacts with each ligand. During the molecular dynamics simulations, Vatairea guianensis lectin was able to bind stably to Tn antigen, which, as seen previously for other lectins, enables its use in cancer research, diagnosis, and therapy. This work further demonstrates the efficiency of bioinformatics in lectinology.

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.

ConA-Like Lectins: High Similarity Proteins as Models to Study Structure/Biological Activities Relationships

Lectins are a widely studied group of proteins capable of specific and reversible binding to carbohydrates. Undoubtedly, the best characterized are those extracted from plants of the Leguminosae family. Inside this group of proteins, those from the Diocleinae subtribe have attracted attention, in particular Concanavalin A (ConA), the best-studied lectin of the group. Diocleinae lectins, also called ConA-like lectins, present a high similarity of sequence and three-dimensional structure and are known to present inflammatory, vasoactive, antibiotic, immunomodulatory and antitumor activities, among others. This high similarity of lectins inside the ConA-like group makes it possible to use them to study structure/biological activity relationships by the variability of both carbohydrate specificity and biological activities results. It is in this context the following review aims to summarize the most recent data on the biochemical and structural properties, as well as biological activities, of ConA-like lectins and the use of these lectins as models to study structure/biological activity relationships.

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.

Canavalia bonariensis lectin: Molecular bases of glycoconjugates interaction and antiglioma potential

CaBo is a mannose/glucose-specific lectin purified from seeds of Canavalia bonariensis. In the present work, we report the CaBo crystal structure determined to atomic resolution in the presence of X-man, a specific ligand. Similar to the structural characteristics of other legume lectins, CaBo presented the jellyroll motif, a metal binding site occupied by calcium and manganese ions close to the carbohydrate-recognition domain (CRD). In vitro test of CaBo cytotoxicity against glioma cells demonstrated its ability to decrease the cellular viability and migration by induction of autophagy and cell death. Molecular docking simulations corroborate previous data indicating that the lectin's biological activities occur mostly through interactions with glycoproteins since the lectin interacted favorably with several N-glycans, especially those of the high-mannose type. Together, these results suggest that CaBo interacts with glycosylated cell targets and elicits a remarkable antiglioma activity.