Inhibition of lectin-like oxidized low-density lipoprotein receptor-1 reduces leukocyte adhesion within the intestinal microcirculation in experimental endotoxemia in rats

Martin Landsberger,Sebastian Wilk,Orlando Hung,Corinna Thaumuller,Marion Otto,Stephan B Felix,Sara Whynot,Michael F Murphy,Juan Zhou,Vladimir Cerny,Christian Lehmann,Dragan Pavlovivc

doi:10.1186/cc9367

Abstract

IntroductionLectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), the major endothelial receptor for oxidized low-density lipoprotein, is also involved in leukocyte recruitment. Systemic leukocyte activation in sepsis represents a crucial factor in the impairment of the microcirculation of different tissues, causing multiple organ failure and subsequently death. The aim of our experimental study was to evaluate the effects of LOX-1 inhibition on the endotoxin-induced leukocyte adherence and capillary perfusion within the intestinal microcirculation by using intravital microscopy (IVM).MethodsWe used 40 male Lewis rats for the experiments. Ten placebo-treated animals served as a control. Thirty animals received 5 mg/kg lipopolysaccharide (LPS) intravenously. Ten endotoxemic rats remained untreated. In 10 LPS animals, we administered additionally 10 mg/kg LOX-1 antibodies. Ten further LPS animals received a nonspecific immunoglobulin (rat IgG) intravenously. After 2 hours of observation, intestinal microcirculation was evaluated by using IVM; the plasma levels of monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-alpha (TNF-α) were determined; and LOX-1 expression was quantified in intestinal tissue with Western blot and reverse-transcription polymerase chain reaction (PCR).ResultsLOX-1 inhibition significantly reduced LPS-induced leukocyte adhesion in intestinal submucosal venules (P < 0.05). At the protein and mRNA levels, LOX-1 expression was significantly increased in untreated LPS animals (P < 0.05), whereas in animals treated with LOX-1 antibody, expression of LOX-1 was reduced (P < 0.05). MCP-1 plasma level was reduced after LOX-1 antibody administration.ConclusionsInhibition of LOX-1 reduced leukocyte activation in experimental endotoxemia. LOX-1 represents a novel target for the modulation of the inflammatory response within the microcirculation in sepsis.

Highlights

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), the major endothelial receptor for oxidized low-density lipoprotein, is involved in leukocyte recruitment
Microcirculation We observed a significant increase of the number of adherent leukocytes in V1 and V3 venules of untreated LPS animals compared with control animals (Figure 1a and 1b; P < 0.05)
Our findings suggest that LOX-1 antibodies are able to reduce the endotoxin-induced expression of LOX-1

Summary

Introduction

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), the major endothelial receptor for oxidized low-density lipoprotein, is involved in leukocyte recruitment. Several factors contribute to the impairment of the microcirculation in sepsis, LOX-1 is a 50-kDa type II membrane protein that structurally belongs to the C-type lectin family, with a short intracellular N-terminal hydrophilic and a long extracellular C-terminal hydrophilic domain separated by a hydrophobic domain of 26 amino acids [3]. LOX-1 might be involved in the binding of OxLDL and cellular ligands to activate endothelial cells, the transformation of smooth muscle cells (SMCs), and the accumulation of lipids in macrophages, especially important in the development of atherosclerosis [7,8,9]. LOX-1 is a potent mediator of ‘’endothelial dysfunction’’: binding of endothelial LOX-1 by ligands induces superoxide generation, inhibits nitric oxide production, enhances endothelial adhesiveness for leukocytes, and induces expression of chemokines [11,12,13]

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