Abstract
The electronegative low-density lipoprotein, LDL (−), is an endogenously modified LDL subfraction with cytotoxic and proinflammatory actions on endothelial cells, monocytes, and macrophages contributing to the progression of atherosclerosis. In this study, epitopes of LDL (−) were mapped using a phage display library of peptides and monoclonal antibodies reactive to this modified lipoprotein. Two different peptide libraries (X6 and CX8C for 6- and 8-amino acid-long peptides, respectively) were used in the mapping. Among all tested peptides, two circular peptides, P1A3 and P2C7, were selected based on their high affinities for the monoclonal antibodies. Small-angle X-ray scattering analysis confirmed their structures as circular rings. P1A3 or P2C7 were quickly internalized by bone marrow-derived murine macrophages as shown by confocal microscopy. P2C7 increased the expression of TNFα, IL-1 β and iNOS as well as the secretion of TNFα, CCL2, and nitric oxide by murine macrophages, similar to the responses induced by LDL (−), although less intense. In contrast, P1A3 did not show pro-inflammatory effects. We identified a mimetic epitope associated with LDL (−), the P2C7 circular peptide, that activates macrophages. Our data suggest that this conformational epitope represents an important danger-associated molecular pattern of LDL (−) that triggers proinflammatory responses.
Highlights
The pathogenesis of atherosclerosis involves innate and adaptive immune responses
We showed that low-density lipoproteins (LDLs) (−) and its autoantibodies were increased in individuals with high atherosclerosis risk, such as chronic coronary syndromes [19]
To prevent the selection of peptides binding to conserved domains of immunoglobulins, the anti-LDL (−) monoclonal antibodies (mAbs) 1A3 and 2C7 were immobilized on microtiter plates and incubated in the presence of excess soluble, unrelated mouse immunoglobulin
Summary
A high blood level of low-density lipoproteins (LDLs) is considered a major risk factor for atherosclerosis due to increased subendothelial retention of LDL particles, their modification, and the production of new autoantigens that trigger maladaptive immune responses in the arterial wall [1,2]. In this context, a subfraction of modified LDLs found in blood and characterized by high electronegativity [3,4,5] is called electronegative LDL [LDL (−)], and has been shown to trigger proinflammatory responses in Biomolecules 2019, 9, 386; doi:10.3390/biom9080386 www.mdpi.com/journal/biomolecules. Different lipids derived from LDL have been identified as triggers of inflammatory responses, some studies have indicated that the LDL protein moiety can be bioactive
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
