ConBr, A Lectin Purified from the Seeds of Canavalia brasiliensis, Protects Against Ischemia in Organotypic Culture of Rat Hippocampus: Potential Implication of Voltage-Gated Calcium Channels.

Lectins are proteins that bind cellular glycans and can modulate various neuronal functions. We have evaluated the neuroprotective effect of ConBr, a lectin purified from the seeds of Canavalia brasiliensis in a model of rat organotypic hippocampal cultures (OHCs) exposed to oxygen and glucose deprivation (OGD). OGD for 15 min followed by 24 h re-oxygenation significantly increased cell death, caused mitochondrial depolarization and increased reactive oxygen species (ROS) in CA1 region of OHCs. ConBr (0.1 µg/mL) added during the re-oxygenation period counteracted cell death, mitochondrial depolarization and overproduction of ROS induced by OGD. Moreover, ConBr restored the levels of Akt and ERK1 phosphorylation that were reduced by OGD. Modulation of intracellular Ca2+ by ConBr was evaluated in isolated hippocampal neurons loaded with the fluorescent calcium dye Fluo-4/AM. ConBr (0.1 and 1 µg/mL) reduced by 25-30 % the Ca2+ increment induced by 70 mM K+. A sub effective concentration of ConBr (0.01 µg/mL) together with a sub effective concentration of the L-type calcium channel antagonist nifedipine (0.3 µM) conferred a synergic neuroprotective effect in OHCs subjected to OGD. In conclusion, ConBr provides OHCs neuroprotection against OGD. The mechanism was not fully addressed but it may involve modulation of L-type voltage-gated Ca2+ channels by ConBr.

Estabelecimento in vitro e micropropagação de maracujá silvestre (Passiflora foetida L. ) / In vitro establishment and micropropagation of Passiflora foetida L

Entre as espécies do gênero Passiflora, a P. foetida L. apresenta a maior variabilidade genética e tem grande importância medicinal, pois é usada no tratamento de doenças como asma, icterícia, e na forma de emplastros, para as erisipelas e doenças de pele com inflamação. Portanto, são necessários estudos que visem a micropropagação e conservação. As sementes de P. foetida L. apresentam dormência e muitas vezes, levam alguns meses para germinar, produzindo mudas desuniformes e de baixo vigor. Neste sentido, a cultura de tecidos apresenta-se como uma forma alternativa a propagação. Assim, o objetivo do trabalho foi estabelecer e micropropagar P. foetida L., para formação de um banco de germoplasma. Para tanto, sementes foram escarificadas, desinfestadas e inoculadas em meio MS(½) sem reguladores de crescimento e cultivados por 66 dias. Explantes de hipocótilos obtidos de plantas germinadas in vitro, foram cultivados no mesmo meio suplementado com 1,0 mg L-1 de BAP. Na fase de estabelecimento, 45% dos explantes brotaram e formaram gemas axilares. 88,9% dos explantes de hipocótilo induziram brotação e 11,1% produziram calos. Plântulas regeneradas com 1,82 cm de altura, com raízes foram aclimatadas.

Among the species of the genus Passiflora, P. foetida L. presents highest genetic variability and also great medicinal importance. This species is used in the treatment of diseases such as asthma, jaundice, and in the form of poultices for erysipelas and skin diseases with inflammation. Therefore, studies are needed to preserve them. Its seeds present dormancy and often take several months to germinate. The tissue culture is a alternative form to propagate species. The objective was to establish and micropropagation P. foetida L., and create a germplasm bank. Seeds were scarified, disinfected, and inoculated on MS medium (½) without regulators for 66 days. Hypocotyls explants obtained of seedlings in vitro germinated were transferred and placed in the same medium supplemented with BAP (1,0 mg L-1). In the establishment phase of 45% of the explants sprouted and formed axillary buds. 88,9% of hypocotyl explants induced shoots and 11,1% produced callus. Seedling measuring 1,82 cm length and rooted were acclimatized.

Crystal structure of Dioclea rostrata lectin: insights into understanding the pH-dependent dimer-tetramer equilibrium and the structural basis for carbohydrate recognition in Diocleinae lectins.

The legume lectins from the subtribe Diocleinae, often referred to as concanavalin A-like lectins, are a typical example of highly similar proteins that show distinct biological activities. The pH-dependent oligomerization that some of these lectins undergo and the relative position of amino acids within the carbohydrate-binding site are factors that have been reported to contribute to these differences in the activities of Diocleinae lectins. In the present work, we determined the amino acid sequence and the crystal structure of the lectin of Dioclea rostrata seeds (DRL), with the aim of investigating the structural bases of the different behavior displayed by this lectin in comparison to other Diocleinae lectins and determining the reason for the distinct pH-dependent dimer-tetramer equilibrium. In addition, we discovered a novel multimeric arrangement for this lectin.

In vitro inhibition of oral streptococci binding to the acquired pellicle by algal lectins.

AIMS: The initial colonization of the tooth by streptococci involves their attachment to adsorbed components of the acquired pellicle. Avoiding this adhesion may be successful in preventing caries at early stages. Salivary mucins are glycoproteins that when absorbed onto hydroxyapatite may provide binding sites for certain bacteria. Algal lectins may be especially interesting for oral antiadhesion trials because of their great stability and high specificity for mucins. This work aimed to evaluate the potential of two algal lectins to inhibit the adherence of five streptococci species to the acquired pellicle in vitro. METHODS AND RESULTS: The lectins used were extracted from Bryothamnion triquetrum (BTL) and Bryothamnion seaforthii (BSL). Fluorescence microscopy was applied to visualize the ability of fluorescein isothiocyanate-labelled lectins to attach to the pellicle and revealed a similar capability for both lectins. Streptococcal adherence assays were performed using saliva-coated microtitre plates. BSL inhibited more than 75% of Streptococcus sanguis, Streptococcus mitis, Streptococcus sobrinus and Streptococcus mutans adherence, achieving 92% to the latter. BTL only obtained statistically significant results on S. mitis and S. sobrinus, whose adherence was decreased by 32.5% and 54.4%, respectively. CONCLUSION: Algal lectins are able to inhibit streptococcal adherence. SIGNIFICANCE AND IMPACT OF THE STUDY: Our results support the proposed application of lectins in antiadhesion therapeutics.

Isolation and characterization of a new agglutinin from the red marine alga Hypnea cervicornis J. Agardh.

The biochemical characterization of a new lectin (Hypnea cervicornis agglutinin or HCA) isolated from the Brazilian red alga H. cervicornis is reported. The haemagglutinating activity of the lectin was only inhibited by the glycoprotein porcine stomach mucin at a minimum inhibitory concentration of 19 microg x mL(-1). No haemagglutination inhibition was detected after the addition of simple sugars. The MALDI-TOF molecular masses of native and reduced and carbamidomethylated HCA were, respectively, 9196.6 Da and 9988.2 Da, indicating that the primary structure of the protein is crosslinked by 7 disulfide bonds. This unusual structural feature among lectins, along with its N-terminal sequence and amino-acid composition, clearly shows that HCA belongs to a protein family distinct from the isolectins Hypnin A1 and A2 isolated from the related Japanese alga Hypnea japonica. On the other hand, HCA displayed a high degree of similarity to the agglutinin from the Brazilian species Hypnea musciformis. Our data indicate the occurrence of structural diversity among lectins of closely related species living in distant ecosystems, i.e., the Pacific coast of Japan and the Atlantic coast of Brazil, and support the hypothesis that the lectin content (lectinome) might serve as a biomarker for taxonomical purposes.

Purification and characterization of a new lectin from the red marine alga Hypnea musciformis.

A lectin from the red marine alga Hypnea musciformis (HML) was purified by extraction with 20 mM PBS, precipitation with 70% saturated ammonium sulphate, ion-exchange DEAE-Cellulose chromatography and RP-HPLC. The 9.3 kDa polypeptide agglutinates erythrocytes from various sources and shows oligomerization tendencies under certain MALDI-TOF/MS conditions. Preliminary N-terminal sequencing and biological assays strongly suggest that the HML may belong to a new class of algae lectins.