ABSTRACT
High-density lipoproteins (HDLs) represent a family of particles characterized by the presence of apolipoprotein A-I (apoA-I) and by their ability to transport cholesterol from peripheral tissues back to the liver. In addition to this function, HDLs display pleiotropic effects including antioxidant, anti-apoptotic, anti-inflammatory, anti-thrombotic or anti-proteolytic properties that account for their protective action on endothelial cells. Vasodilatation via production of nitric oxide is also a hallmark of HDL action on endothelial cells. Endothelial cells express receptors for apoA-I and HDLs that mediate intracellular signalling and potentially participate in the internalization of these particles. In this review, we will detail the different effects of HDLs on the endothelium in normal and pathological conditions with a particular focus on the potential use of HDL therapy to restore endothelial function and integrity.
Subject(s)
Endothelium, Vascular/metabolism , Lipoproteins, HDL/metabolism , Models, Biological , Receptors, Lipoprotein/metabolism , Vasculitis/metabolism , Animals , Apoptosis , Biological Transport , Blood-Brain Barrier/metabolism , Diabetic Angiopathies/immunology , Diabetic Angiopathies/metabolism , Diabetic Angiopathies/physiopathology , Diabetic Angiopathies/therapy , Drug Delivery Systems , Endothelium, Vascular/immunology , Endothelium, Vascular/physiopathology , Humans , Lipoproteins, HDL/blood , Lipoproteins, HDL/therapeutic use , Lysophospholipids , Sphingosine/analogs & derivatives , Vasculitis/immunology , Vasculitis/physiopathology , Vasculitis/therapyABSTRACT
In annelids, it has been established that arginine-vasopressin (AVP)/oxytocin (OT) superfamily peptides are involved in the maintenance of water and electrolyte homeostasis as well as reproduction. At present, there is little information on their receptors. In this study, we report the characterization of a 1.7 kb cDNA for an AVP-related receptor from the leech Theromyzon tessulatum. The open reading frame encodes a 435-aminoacid transmembrane protein that displays seven segments of hydrophobic amino acids, typical of G-protein-coupled receptors. The overall predicted protein exhibits about 30% amino-acid identities to other invertebrate, as well as vertebrate, AVP/OT receptor family members, and displays conserved characteristic features belonging to the AVP/OT receptor superfamily. RT-PCR expression experiments showed that mRNA is expressed in the genital tract, the ovary and the brain. The receptor expression is stage specific, showing a weak expression after the two first blood meals, increasing dramatically after the last blood meal during the period of sexual maturation and disappearing after egg laying. Thus, the leech AVP-related receptor may mediate reproductive functions. When expressed in COS-7 cells, the receptor binds ligands with the following rank order of potency: AVP= Arg-vasotocin >Arg-conopressin >mesotocin = OT = Lys-conopressin=isotocin>annetocin. This shows an AVP-like pharmacological profile. The transfected receptor mediates AVP-induced accumulation of inositol phosphates, indicating that the leech AVP-related receptor is functional. This study describes the characterization of a novel AVP/OT superfamily receptor in annelids, which are considered the most distant group of coelomate metazoans possessing a functional AVP/OT-related endocrine system.
