Homocysteinylated Albumin Promotes Increased Monocyte-Endothelial Cell Adhesion and Up-Regulation of MCP1, Hsp60 and ADAM17

Rosanna Capasso,Ersilia Satta,Donald L Puppione,Amelia Cimmino,Alessandra F Perna,Sofia Salemme,Cinzia Lombardi,Irene Sambri,Diego Ingrosso,Filomena Acanfora

doi:10.1371/journal.pone.0031388

Abstract

RationaleThe cardiovascular risk factor homocysteine is mainly bound to proteins in human plasma, and it has been hypothesized that homocysteinylated proteins are important mediators of the toxic effects of hyperhomocysteinemia. It has been recently demonstrated that homocysteinylated proteins are elevated in hemodialysis patients, a high cardiovascular risk population, and that homocysteinylated albumin shows altered properties.ObjectiveAim of this work was to investigate the effects of homocysteinylated albumin - the circulating form of this amino acid, utilized at the concentration present in uremia - on monocyte adhesion to a human endothelial cell culture monolayer and the relevant molecular changes induced at both cell levels.Methods and ResultsTreated endothelial cells showed a significant increase in monocyte adhesion. Endothelial cells showed after treatment a significant, specific and time-dependent increase in ICAM1 and VCAM1. Expression profiling and real time PCR, as well as protein analysis, showed an increase in the expression of genes encoding for chemokines/cytokines regulating the adhesion process and mediators of vascular remodeling (ADAM17, MCP1, and Hsp60). The mature form of ADAM17 was also increased as well as Tnf-α released in the cell medium. At monocyte level, treatment induced up-regulation of ICAM1, MCP1 and its receptor CCR2.ConclusionsTreatment with homocysteinylated albumin specifically increases monocyte adhesion to endothelial cells through up-regulation of effectors involved in vascular remodeling.

Highlights

Hyperhomocysteinemia is a cardiovascular risk factor both in the general population and in selected patient groups [1]
Treatment with homocysteinylated albumin increases monocyte adhesion to endothelial cells through up-regulation of effectors involved in vascular remodeling
Previous evidence showed that high homocysteine increases cell adhesion and induces a proinflammatory state in the vessel wall by promoting adhesion molecule expression and monocyte recruitment

Summary

Introduction

Hyperhomocysteinemia is a cardiovascular risk factor both in the general population and in selected patient groups [1]. Previous evidence showed that high homocysteine increases cell adhesion and induces a proinflammatory state in the vessel wall by promoting adhesion molecule expression and monocyte recruitment. Nuclear factor (NF)-kB activation and intercellular adhesion molecule-1 (ICAM-1) stimulation have been shown [2]. High homocysteine up-regulates monocyte chemoattractant protein-1 (MCP1), interleukin-8 (IL-8) expression and secretion in cultured human endothelial cells, smooth muscles cells, and monocytes [3,4,5,6]. In many of previous studies, homocysteine was added to cell culture medium in its rather unphysiological free reduced form, rising concerns about the possibility of artifactual effects mediated through intervening formation of adducts with unpredictable protein targets

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Conclusion