46 research outputs found
A Novel G Protein-Coupled Receptor of Schistosoma mansoni (SmGPR-3) Is Activated by Dopamine and Is Widely Expressed in the Nervous System
Schistosomes have a well developed nervous system that coordinates virtually every activity of the parasite and therefore is considered to be a promising target for chemotherapeutic intervention. Neurotransmitter receptors, in particular those involved in neuromuscular control, are proven drug targets in other helminths but very few of these receptors have been identified in schistosomes and little is known about their roles in the biology of the worm. Here we describe a novel Schistosoma mansoni G protein-coupled receptor (named SmGPR-3) that was cloned, expressed heterologously and shown to be activated by dopamine, a well established neurotransmitter of the schistosome nervous system. SmGPR-3 belongs to a new clade of âorphanâ amine-like receptors that exist in schistosomes but not the mammalian host. Further analysis of the recombinant protein showed that SmGPR-3 can also be activated by other catecholamines, including the dopamine metabolite, epinine, and it has an unusual antagonist profile when compared to mammalian receptors. Confocal immunofluorescence experiments using a specific peptide antibody showed that SmGPR-3 is abundantly expressed in the nervous system of schistosomes, particularly in the main nerve cords and the peripheral innervation of the body wall muscles. In addition, we show that dopamine, epinine and other dopaminergic agents have strong effects on the motility of larval schistosomes in culture. Together, the results suggest that SmGPR-3 is an important neuronal receptor and is probably involved in the control of motor activity in schistosomes. We have conducted a first analysis of the structure of SmGPR-3 by means of homology modeling and virtual ligand-docking simulations. This investigation has identified potentially important differences between SmGPR-3 and host dopamine receptors that could be exploited to develop new, parasite-selective anti-schistosomal drugs
A new class of glycomimetic drugs to prevent free fatty acid-induced endothelial dysfunction
Background: Carbohydrates play a major role in cell signaling in many biological processes. We have developed a set of glycomimetic drugs that mimic the structure of carbohydrates and represent a novel source of therapeutics for endothelial dysfunction, a key initiating factor in cardiovascular complications. Purpose: Our objective was to determine the protective effects of small molecule glycomimetics against free fatty acidÂinduced endothelial dysfunction, focusing on nitric oxide (NO) and oxidative stress pathways. Methods: Four glycomimetics were synthesized by the stepwise transformation of 2,5Âdihydroxybenzoic acid to a range of 2,5Âsubstituted benzoic acid derivatives, incorporating the key sulfate groups to mimic the interactions of heparan sulfate. Endothelial function was assessed using acetylcholineÂinduced, endotheliumdependent relaxation in mouse thoracic aortic rings using wire myography. Human umbilical vein endothelial cell (HUVEC) behavior was evaluated in the presence or absence of the free fatty acid, palmitate, with or without glycomimetics (1ÂľM). DAFÂ2 and H2DCFÂDA assays were used to determine nitric oxide (NO) and reactive oxygen species (ROS) production, respectively. Lipid peroxidation colorimetric and antioxidant enzyme activity assays were also carried out. RTÂPCR and western blotting were utilized to measure Akt, eNOS, NrfÂ2, NQOÂ1 and HOÂ1 expression. Results: Ex vivo endotheliumÂdependent relaxation was significantly improved by the glycomimetics under palmitateÂinduced oxidative stress. In vitro studies showed that the glycomimetics protected HUVECs against the palmitateÂinduced oxidative stress and enhanced NO production. We demonstrate that the protective effects of preÂincubation with glycomimetics occurred via upregulation of Akt/eNOS signaling, activation of the Nrf2/ARE pathway, and suppression of ROSÂinduced lipid peroxidation. Conclusion: We have developed a novel set of small molecule glycomimetics that protect against free fatty acidinduced endothelial dysfunction and thus, represent a new category of therapeutic drugs to target endothelial damage, the first line of defense against cardiovascular disease