Dioclea violacea lectin inhibits tumorigenesis and tumor angiogenesis in vivo.

Dioclea violacea seed mannose-binding lectin (DvL) has attracted considerable attention because of its interesting biological activities, including antitumor, antioxidant, and anti-inflammatory activities. This study evaluated the cytotoxic effect of DvL on tumor and normal cells using the mitochondrial activity reduction (MTT) assay, the carcinogenic and anti-carcinogenic activity by the epithelial tumor test (ETT) in Drosophila melanogaster, and the anti-angiogenic effect by the chick embryo chorioallantoic membrane (CAM) assay. Data demonstrated that DvL promoted strong selective cytotoxicity against tumor cell lines, especially A549 and S180 cells, whereas normal cell lines were weakly affected. Furthermore, DvL did not promote carcinogenesis in D. melanogaster at any concentration tested, but modulated DXR-induced carcinogenesis at the highest concentrations tested. In the CAM and immunohistochemical assays, DvL inhibited sarcoma 180-induced angiogenesis and promoted the reduction of VEGF and TGF-ß levels at all concentrations tested. Therefore, our results demonstrated that DvL is a potent anticancer, anti-angiogenic, and selective cytotoxic agent for tumor cells, suggesting its potential application as a prototype molecule for the development of new drugs with chemoprotective and/or antitumor effects.

Mannose-Binding Lectins as Potent Antivirals against SARS-CoV-2.

The SARS-CoV-2 entry into host cells is mainly mediated by the interactions between the viral spike protein (S) and the ACE-2 cell receptor, which are highly glycosylated. Therefore, carbohydrate binding agents may represent potential candidates to abrogate virus infection. Here, we evaluated the in vitro anti-SARS-CoV-2 activity of two mannose-binding lectins isolated from the Brazilian plants Canavalia brasiliensis and Dioclea violacea (ConBR and DVL). These lectins inhibited SARS-CoV-2 Wuhan-Hu-1 strain and variants Gamma and Omicron infections, with selectivity indexes (SI) of 7, 1.7, and 6.5, respectively for ConBR; and 25, 16.8, and 22.3, for DVL. ConBR and DVL inhibited over 95% of the early stages of the viral infection, with strong virucidal effect, and also protected cells from infection and presented post-entry inhibition. The presence of mannose resulted in the complete lack of anti-SARS-CoV-2 activity by ConBR and DVL, recovering virus titers. ATR-FTIR, molecular docking, and dynamic simulation between SARS-CoV-2 S and either lectins indicated molecular interactions with predicted binding energies of -85.4 and -72.0 Kcal/Mol, respectively. Our findings show that ConBR and DVL lectins possess strong activities against SARS-CoV-2, potentially by interacting with glycans and blocking virus entry into cells, representing potential candidates for the development of novel antiviral drugs.

Structural characterization of a galectin from the marine sponge Aplysina lactuca (ALL) with synergistic effects when associated with antibiotics against bacteria.

Lectins presents the ability to interact with glycans and trigger varied responses, including the inhibition of the development of various pathogens. Structural studies of these proteins are essential to better understand their functions. In marine sponges, so far only a few lectins have their primary structures completely determined. Thus, the objective of this work was to structurally characterize and evaluate antibacterial potential, in association with different antibiotics, of the lectin isolated from the marine sponge Aplysina lactuta (ALL). ALL is a homotetramer of 60 kDa formed by four 15 kDa-subunits. The lectin showed affinity only for the glycoproteins fetuin, asialofetuin, mucin type III, and bovine submaxillary mucin type I. The complete amino acid sequences of two isoforms of ALL, named ALL-a and ALL-b, were determined by a combination of Edman degradation and overlapped peptides sequenced by tandem mass spectrometry. ALL-a and ALL-b have 144 amino acids with molecular masses of 15,736 Da and 15,985 Da, respectively. Both structures contain conserved residues typical of the galectin family. ALL is a protein with antibacterial potential, when in association with ampicillin and oxacillin the lectin potentiates its antibiotic effect, included Methicillin-resistant Staphylococcus strains. Thus, ALL shows to be a molecule with potential for the development of new antibacterial drugs.

Parkia platycephala Lectin (PPL) Inhibits Orofacial Nociception Responses via TRPV1 Modulation.

Lectins are a heterogeneous group of proteins that reversibly bind to simple sugars or complex carbohydrates. The plant lectin purified from the seed of Parkia platycephala (PPL) was studied. This study aimed to investigate the possible orofacial antinociceptive of PPL lectin in adult zebrafish and rodents. Acute nociception was induced by cinnamaldehyde (0.66 µg/mL), 0.1% acidified saline, glutamate (12.5 µM) or hypertonic saline (5 M NaCl) applied into the upper lip (5.0 µL) of adult wild zebrafish. Zebrafish were pretreated by intraperitoneal injection (20 µL) with vehicle (Control) or PPL (0.025; 0.05 or 0.1 mg/mL) 30 min before induction. The effect of PPL on zebrafish locomotor behaviour was evaluated in the open field test. Naive groups were included in all tests. In one experiment, animals were pre-treated with capsazepine to investigate the mechanism of antinociception. The involvement of central afferent C-fibres was also investigated. In another experiment, rats pre-treated with PPL or saline were submitted to the temporomandibular joint formalin test. Other groups of rats were submitted to infraorbital nerve transection to induce chronic pain, followed by induction of mechanical sensitivity using von Frey. PPL reduced nociceptive behaviour in adult zebrafish, and this is related to the activation of the TRPV1 channels since antinociception was effectively inhibited by capsazepine and by capsaicin-induced desensitization. PPL reduced nociceptive behaviour associated with temporomandibular joint and neuropathic pain. The results confirm the potential pharmacological relevance of PPL as an inhibitor of orofacial nociception in acute and chronic pain.

Canavalia ensiformis lectin induced oxidative stress mediate both toxicity and genotoxicity in Drosophila melanogaster.

Mannose/glucose-binding lectin from Canavalia ensiformis seeds (Concanavalin A - ConA) has several biological applications, such as mitogenic and antitumor activity. However, most of the mechanisms involved in the in vivo toxicity of ConA are not well known. In this study, the Drosophila melanogaster model was used to assess the toxicity and genotoxicity of different concentrations of native ConA (4.4, 17.5 and 70 µg/mL) in inhibited and denatured forms of ConA. The data show that native ConA affected: the survival, in the order of 30.6 %, and the locomotor performance of the flies; reduced cell viability to levels below 50 % (4.4 and 17.5 µg/mL); reduced nitric oxide levels; caused lipid peroxidation and increased protein and non-protein thiol content. In the Comet assay, native ConA (17.5 e 70 µg/mL) caused DNA damage higher than 50 %. In contrast, treatments with inhibited and denatured ConA did not affect oxidative stress markers and did not cause DNA damage. We believe that protein-carbohydrate interactions between ConA and carbohydrates of the plasma membrane are probably the major events involved in these activities, suggesting that native ConA activates mechanisms that induce oxidative stress and consequently DNA damage.

Lectins ConA and ConM extracted from Canavalia ensiformis (L.) DC and Canavalia rosea (Sw.) DC inhibit planktonic Candida albicans and Candida tropicalis.

Lectins participate in the defense against microorganisms and in signaling the damage caused by pathogens to the cell surface and/or intracellular in plants. This study aims to analyze the antifungal potential of lectins extracted from seeds of Canavalia ensiformis (L.) DC and Canavalia rosea (Sw.) DC, against Candida albicans and Candida tropicalis. The antimicrobial tests were performed by microdilution against Candida spp. The test to verify the combined lectin/fluconazole effect was performed using subinhibitory concentrations of lectins and with antifungal ranging from 0.5 to 512 µg/mL. The ability to inhibit the morphological transition of Candida spp. was evaluated by microcultivation in a moist chamber. The results of the minimum inhibitory concentration revealed no antifungal activity against the tested strains. However, lectins modified the action of fluconazole, reducing the IC50 of the drug against C. albicans. Lectins were also able to discretely modulate the morphological transition of the tested strains.

Lactose-binding lectin from Vatairea macrocarpa seeds induces in vivo angiogenesis via VEGF and TNF-ɑ expression and modulates in vitro doxorubicin-induced genotoxicity.

Lactose-binding lectin from Vatairea macrocarpa seeds (VML) has attracted great attention due to its interesting biological activities, such as pro-inflammatory effects and macrophage activation. This study evaluated the cytotoxicity and genotoxicity/antigenotoxicity of VML in human lymphocytes using the CometChip assay, and angiogenic activity by the chick embryo chorioallantoic membrane (CAM) assay. In genotoxicity, lymphocytes were treated with different concentrations of VML (0.5, 2 and 8 µM). In antigenotoxicity, lymphocytes were treated with the same concentrations of VML concomitant doxorubicin (90 µM DXR). To evaluate angiogenesis, all CAM were treated with different concentrations of VML (0.5, 2 and 8 µM) alone or co-treated with lactose (0.1 M). Furthermore, the levels of vascular endothelial growth factor (VEGF) and tumor necrosis factor-alpha (TNF-α) in CAM were assessed by immunohistochemistry. The results showed that VML was cytotoxic to lymphocytes, genotoxic at the highest concentration (8 µM) and antigenotoxic at low concentrations (0.5, and 2 µM). Regarding the CAM assay and immunohistochemistry, VML was angiogenic and significantly increased VEGF and TNF-α levels. In contrast, co-treatment with lactose significantly reduced the angiogenic effect and VEGF levels. We propose that protein-carbohydrate interactions between VML and glycans in the cell membrane are probably the major events involved in these activities. It seems likely that VML elicits a pro-inflammatory response through VEGF and TNF-α expression, resulting in increased vascularization at the site of inflammation. Therefore, our results show novel information on the effects of VML on DNA, as well as provide data regarded the neovascularization process involving this lectin.

A review on the antimicrobial properties of lectins.

Lectins are biologically versatile biomolecules with remarkable antimicrobial effects, notably against bacteria, fungi and protozoa, in addition to modulating host immunity. For this, the lectins bind to carbohydrates on the surface of the pathogen, which can cause damage to the cell wall and prevent the attachment of microorganisms to host cells. Thus, this study intends to review the biological activities of lectins, with an emphasis on antimicrobial activity. Lectins of plant stood out for its antimicrobial effects, demonstrating that they act against a variety of strains, where in vitro were able to inhibit their development and affect their morphology. In vivo, they modulated host immunity, signaling and activating defense cells. Some of these lectins were capable to modulate the action of antibiotics, indicating their potential to minimize the antibiotic resistance. The results suggest that lectins have antimicrobial activity with potential to be used in drug development.

Structural characterization of a galectin isolated from the marine sponge Chondrilla caribensis with leishmanicidal potential.

BACKGROUND: Solving primary structure of lectins leads to an understanding of the physiological roles within an organism and its biotechnological potential. Only eight sponge lectins have had their primary structure fully determined. METHODS: The primary structure of CCL, Chondrilla caribensis lectin, was determined by tandem mass spectrometry. The three-dimensional structure was predicted and the protein-carbohydrate interaction analysed by molecular docking. Furthermore, the anti-leishmanial activity was observed by assays with Leishmania infantum. RESULTS: The amino acid sequence consists of 142 amino acids with a calculated molecular mass of 15,443 Da. The lectin has a galectin-like domain architecture. As observed in other sponge galectins, the signature sequence of a highly conserved domain was also identified in CCL with some modifications. CCL exhibits a typical galectin structure consisting of a ß-sandwich. Molecular docking showed that the amino acids interacting with CCL ligands at the monosaccharide binding site are mostly the same as those conserved in this family of lectins. Through its interaction with L. infantum glycans, CCL was able to inhibit the development of this parasite. CCL also induced apoptosis after eliciting ROS production and altering the membrane integrity of Leishmania infantum promastigote. CONCLUSIONS: CCL joins the restricted group of sponge lectins with determined primary structure and very high biotechnological potential owing to its promising results against pathogens that cause Leishmaniasis. GENERAL SIGNIFICANCE: As the determination of primary structure is important for biological studies, now CCL can become a sponge galectin with an exciting future in the field of human health.

Epidemiology and Etiopathogeny of COVID-19.

Despite the recent announcement of the new pathogenic coronavirus to man, SARS-CoV2, a large number of publications are presented to the scientific community. An organized and systematic review of the epidemiological, etiological, and pathogenic factors of COVID-19 is presented. This is a systematic review using the databases MEDLINE, EMBASE, Web of Science, SCIELO; the descriptors coronavirus, SARS-CoV-2, etiology, epidemiology, pathophysiology, pathogenesis, COVID-19, with publications from December 2019 to January 2021, resulting in more than 800 publications and 210 selected. The data suggest that COVID-19 is associated with SAR-CoV-2 infection, with the transmission of contagion by fomites, salivary droplets, and other forms, such as vertical and fecal-oral. The bat and other vertebrates appear to be reservoirs and part of the transmission chain. The virus uses cell receptors to infect human cells, especially ACE2, like other coronaviruses. Heat shock proteins have different roles in the infection, sometimes facilitating it, sometimes participating in more severe conditions, when not serving as a therapeutic target. The available data allow us to conclude that COVID-19 is a pandemic viral disease, behaving as a challenge for public health worldwide, determining aggressive conditions with a high mortality rate in patients with risk factors, without treatment, but with the recent availability of the first vaccines.

Costus spiralis (Jacq.) Roscoe leaves fractions have potential to reduce effects of inflammatory diseases.

ETHNOPHARMACOLOGICAL RELEVANCE: Since drugs currently used to manage pain and inflammatory conditions present several side effects, the investigation of new anti-inflammatory and antinociceptive agents from folk-medicine plants is an important approach. Costus spiralis (Costaceae) has been used in Brazilian medicinal teas to treat urinary infection, cough, inflammation, arthritis, among others. AIM OF THE STUDY: The current study focused on investigating anti-inflammatory and antinociceptive effects of fractions from C. spiralis leaves using animal models. MATERIALS AND METHODS: Adults Swiss mice were used in the following experimental models: acetic acid-induced abdominal writhing, formalin-induced nociception, hot plate, zymosan-induced peritonitis, and arthritis induced by complete Freund's adjuvant. RESULTS: The presence of steroids was confirmed in all fractions. Flavonoids, condensed tannins and saponins were observed in EFL. In methanolic fraction leaves (MFL), the presence of flavonoids and pentacyclic triterpenoids was confirmed. Orally administered leaf fractions significantly reduced abdominal writhing. Fractions were ineffective in the neurogenic stage of the formalin test, but in the inflammatory stage, ethyl acetate fraction levaes (AcFL), ethanolic fraction leaves (EFL), and MFL significantly reduced paw licking time by 69.6 ± 11.9%, 58.2 ± 9.4%, and 79.6 ± 8.3%, respectively. In the hot plate test, the reaction latency was similar for treated animals and controls. However, in the peritonitis test, cell migration was significantly reduced in animals treated with chloroform fractions leaves ClFL (61.8 ± 11.4%), AcFL (58.7 ± 8.3%), EFL (39.2 ± 5.0%), and MFL (64.8 ± 4.4%). This was similar to the result observed in the chronic inflammation model, this time only the chloroform fraction was able to reduce paw edema. CONCLUSION: Our results show that leaf fractions of Costus spiralis are capable of modulating peripheral nociceptive and inflammatory responses without effects on central nervous system being potential substrates for phytochemical purification, structural and mechanistic studies.

Is the orofacial antinociceptive effect of lectins intrinsically related to their specificity to monosaccharides?

Lectins are proteins of non-immunological origin that may play several biological applications, of which we can highlight the anti-inflammatory and antinociceptive activities. In this work, we evaluated the possible effect of orofacial antinociceptive activity of three plant lectins, Dioclea violacea (DVL - Man/Glc-binding), Vatairea macrocarpa (VML - Gal-binding) and PPL (Parkia platycephala - Man/Glc-binding) in adult zebrafish. Acute nociception was induced by menthol (1.2 µM), or capsaicin (4.93 µM) applied into in the upper lip (5.0 µL) of adult wild zebrafish. Zebrafish were pretreated by intraperitoneal injection (20 µL) with vehicle (Control) or lectins (0.025; 0.05 or 0.1 mg/mL) 30 min before induction. The effect of lectins on zebrafish locomotor behavior was evaluated with the open field test. Naive groups (n = 8) were included in all tests. Our results indicate that only PPL presented antinociceptive induced by capsaicin, suggesting the potential clinical application of PPL as inhibitor of orofacial nociception and that this effect may be due to the modulation of TRPV1 channel. In conclusion, lectins that exhibit affinity to the same or different carbohydrates do not necessarily have an antinociceptive effect on the orofacial nociception model, indicating that the glycan carbohydrate binding pattern may be related to the effect on nociception inhibition.

Lectins from Parkia biglobosa and Parkia platycephala: A comparative study of structure and biological effects.

The relation structure-activity of the Mimosoideae lectins of Parkia platycephala (PPL) and Parkia biglobosa (PBL) was analyzed in this study. PBL was solved by X-ray crystallography at a resolution of 2.1Å, and the crystal structure belonged to the C2221 space group. Structural organization and binding sites were also characterized. Specifically, PBL monomer consists of three ß-prism domains tandemly arranged with each one presenting a different carbohydrate recognition domain (CRD). PPL showed antinociceptive activity in the mouse model of acetic acid-induced writhes with maximal inhibitory effect by 74% at 1mg/mL. PPL also demonstrated anti-inflammatory effect causing inhibition of leukocyte migration induced by both direct and indirect chemoattractants. These PPL activities were compared to that of PBL described previously. Molecular docking of both PBL and PPL demonstrated some differences in carbohydrate-lectin interaction energy. Comparing structure and biological effects of the two lectins provided new data about their structure and the relation with its biological activities.

Structural analysis of Centrolobium tomentosum seed lectin with inflammatory activity.

A glycosylated lectin (CTL) with specificity for mannose and glucose has been detected and purified from seeds of Centrolobium tomentosum, a legume plant from Dalbergieae tribe. It was isolated by mannose-sepharose affinity chromatography. The primary structure was determined by tandem mass spectrometry and consists of 245 amino acids, similar to other Dalbergieae lectins. CTL structures were solved from two crystal forms, a monoclinic and a tetragonal, diffracted at 2.25 and 1.9 Å, respectively. The carbohydrate recognition domain (CRD), metal-binding site and glycosylation site were characterized, and the structural basis for mannose/glucose-binding was elucidated. The lectin adopts the canonical dimeric organization of legume lectins. CTL showed acute inflammatory effect in paw edema model. The protein was subjected to ligand screening (dimannosides and trimannoside) by molecular docking, and interactions were compared with similar lectins possessing the same ligand specificity. This is the first crystal structure of mannose/glucose native seed lectin with proinflammatory activity isolated from the Centrolobium genus.

L-Rhamnose-binding lectin from eggs of the Echinometra lucunter: Amino acid sequence and molecular modeling.

An L-rhamnose-binding lectin named ELEL was isolated from eggs of the rock boring sea urchin Echinometra lucunter by affinity chromatography on lactosyl-agarose. ELEL is a homodimer linked by a disulfide bond with subunits of 11 kDa each. The new lectin was inhibited by saccharides possessing the same configuration of hydroxyl groups at C-2 and C-4, such as L-rhamnose, melibiose, galactose and lactose. The amino acid sequence of ELEL was determined by tandem mass spectrometry. The ELEL subunit has 103 amino acids, including nine cysteine residues involved in four conserved intrachain disulfide bonds and one interchain disulfide bond. The full sequence of ELEL presents conserved motifs commonly found in rhamnose-binding lectins, including YGR, DPC and KYL. A three-dimensional model of ELEL was created, and molecular docking revealed favorable binding energies for interactions between ELEL and rhamnose, melibiose and Gb3 (Galα1-4Galß1-4Glcß1-Cer). Furthermore, ELEL was able to agglutinate Gram-positive bacterial cells, suggesting its ability to recognize pathogens.

Molecular modeling of lectin-like protein from Acacia farnesiana reveals a possible anti-inflammatory mechanism in Carrageenan-induced inflammation.

Acacia farnesiana lectin-like protein (AFAL) is a chitin-binding protein and has been classified as phytohaemagglutinin from Phaseolus vulgaris (PHA). Legume lectins are examples for structural studies, and this family of proteins shows a remarkable conservation in primary, secondary, and tertiary structures. Lectins have ability to reduce the effects of inflammation caused by phlogistic agents, such as carrageenan (CGN). This paper explains the anti-inflammatory activity of AFAL through structural comparison with anti-inflammatory legume lectins. The AFAL model was obtained by molecular modeling and molecular docking with glycan and carrageenan were performed to explain the AFAL structural behavior and biological activity. Pisum sativum lectin was the best template for molecular modeling. The AFAL structure model is folded as a ß sandwich. The model differs from template in loop regions, number of ß strands and carbohydrate-binding site. Carrageenan and glycan bind to different sites on AFAL. The ability of AFAL binding to carrageenan can be explained by absence of the sixth ß -strand (posterior ß sheets) and two ß strands in frontal region. AFAL can inhibit pathway inflammatory process by carrageenan injection by connecting to it and preventing its entry into the cell and triggers the reaction.