Vasodilatação mediada pela lectina de Dioclea rostrata em artérias de condutância e resistência: mecanismos e predições de ligação com glicoconjugados

Abstract

Lectins are proteins found in many organisms, from microorganisms such as viruses and bacteria to animals and plants, and have the ability to specifically and reversibly bind carbohydrates through the carbohydrate recognition domain (CDR). Lectins found in legume seeds have several effects that include anti-inflammatory, nociceptive, antiproliferative, antimicrobial and antitumor actions. A previous study has demonstrated that the lectin isolated from the legume Dioclea rostrata (DRL) has a vasodilator effect in rat aorta. The aim of this study was to test whether DRL-induced vasorelaxation pathways may vary among diferent types of arteries, and to identify possible molecular interactions involved. Rat thoracic aorta, resistance mesenteric and coronary arteries were tested "in vitro" with cumulative DRL curves (0.01-100 µg/mL). Also, the possible interactions of DRL with glycans or glycoproteins present in the cell membrane were tested by “in silico” molecular docking study. In vascular reactivity studies, L-NAME, indomethacin and high KCl were used to assess the nitric oxide (NO), cyclooxygenase (COX) and hyperpolarization dependent effects. Our results indicated that DRL promotes relaxation of all vessels through different mechanisms. The inhibition of NO release with L-NAME attenuated the DRL effects only in the aorta and resistance mesenteric artery, but not in the coronary artery. When using the depolarizing solution (KCl), DRL-mediated vasodilation was inhibited in all arteries, but with smaller effect in the coronary arteries. Although incubation with indomethacin significantly reduced the relaxation of DRL in mesenteric and coronary arteries, indicating a role for COX-derived factors, no effect was found in the aortic segments. Interestingly, the DRL-mediated effect on the resistance mesenteric artery was biphasic (relaxation followed by contraction), with the final effect probably mediated by the release of COX-derived constrictor prostanoids. The molecular docking assays suggested interactions between DRL and heparan sulfate, CD31 (PECAM-1) and several other biologically relevant glycans present on the membrane surface and endothelial glycocalyx. These data indicate that the mechanisms involved in DRLmediated vasodilation vary between conductance and resistance arteries from different origins, and these effects may be related to the ability of DRL to bind a diversity of glycans, especially heparan sulfate and PECAM-1, two proposed mechanoreceptors involved in the activation of NO synthase and COX in the vascular endothelium.