Anti-GRP78 autoantibodies induce endothelial cell activation and accelerate the development of atherosclerotic lesions
Elizabeth D. Crane, … , Wadih Arap, Richard C. Austin
Elizabeth D. Crane, … , Wadih Arap, Richard C. Austin
Published December 20, 2018
Citation Information: JCI Insight. 2018;3(24):e99363. https://doi.org/10.1172/jci.insight.99363.
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Research Article

Anti-GRP78 autoantibodies induce endothelial cell activation and accelerate the development of atherosclerotic lesions

Abstract

The 78-kDa glucose-regulated protein (GRP78) is an ER molecular chaperone that aids in protein folding and secretion. However, pathological conditions that cause ER stress can promote the relocalization of GRP78 to the cell surface (csGRP78), where it acts as a signaling receptor to promote cancer progression. csGRP78 also possesses antigenic properties, leading to the production of anti-GRP78 autoantibodies, which contribute to tumor growth. In contrast, the presence and role of anti-GRP78 autoantibodies in atherosclerosis is unknown. Here, we show that atherosclerotic-prone ApoE–/– mice develop circulating anti-GRP78 autoantibodies that bind to csGRP78 on lesion-resident endothelial cells. Moreover, GRP78-immunized ApoE–/– mice exhibit a marked increase in circulating anti-GRP78 autoantibody titers that correlated with accelerated lesion growth. Mechanistically, engagement of anti-GRP78 autoantibodies with csGRP78 on human endothelial cells activated NF-κB, thereby inducing the expression of ICAM-1 and VCAM-1, a process blocked by NF-κB inhibitors. Disrupting the autoantibody/csGRP78 complex with enoxaparin, a low-molecular-weight heparin, reduced the expression of adhesion molecules and attenuated lesion growth. In conclusion, anti-GRP78 autoantibodies play a crucial role in atherosclerosis development, and disruption of the interaction between anti-GRP78 autoantibodies and csGRP78 represents a therapeutic strategy.

Authors

Elizabeth D. Crane, Ali A. Al-Hashimi, Jack Chen, Edward G. Lynn, Kevin Doyoon Won, Šárka Lhoták, Magda Naeim, Khrystyna Platko, Paul Lebeau, Jae Hyun Byun, Bobby Shayegan, Joan C. Krepinsky, Katey J. Rayner, Serena Marchiò, Renata Pasqualini, Wadih Arap, Richard C. Austin

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Figure 1

Anti-GRP78 autoantibodies are elevated in ApoE–/– mice.

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Anti-GRP78 autoantibodies are elevated in ApoE–/– mice. Serum levels of ...
Serum levels of anti-GRP78 autoantibodies were measured by ELISA in female C57BL/6 and ApoE–/– mice on either a chow (A) or HFD (B) (n = 7–9 per group). *P < 0.05 versus age-matched C57BL/6 mice, 2-tailed t test. All data are presented as a ratio of absorbance units (AU) relative to a standard sample. Representative images of aortic root sections from mice in A and B are presented; arrows indicate atherosclerotic lesions. Original magnification, ×10. (C) Location of LP and HP regions on the ascending aorta and proximal arch assessed for atherosclerotic lesions and presence of bound anti-GRP78 autoantibodies. (D) Representative immunofluorescence images of anti-GRP78 autoantibody binding to lesion-resident ECs in the aortic arch of ApoE–/– mice. Mice were injected i.v. with 10 μg b-anti-GRP78 autoantibodies or b-IgG and euthanized 30 minutes after injection. Multiple pieces from LP and HP regions of the arch were dissected for each mouse and stained en face, and 3 images per region were qualitatively assessed for the presence/absence of anti-GRP78 autoantibody or IgG staining in lesion and nonlesion areas. Dashed lines indicate lesion areas. ECs are stained in green (rat anti-mouse CD-31) and anti-GRP78 autoantibodies or IgG are stained in red (streptavidin-conjugated secondary antibody). Nuclei are counterstained with DAPI (blue). One anti-GRP78 autoantibody and one b-IgG mouse were injected in parallel for each experiment. Original magnification, ×40. (E) Anti-GRP78 autoantibody titers in a clinical population with established CVD and age-matched controls, as measured by ELISA (n = 12). *P < 0.05 versus age-matched controls, 2-tailed t test.