Induction of endothelial cell apoptosis by the binding of anti–endothelial cell antibodies to Hsp60 in vasculitis‐associated systemic autoimmune diseases

Abstract

Objective. Anti-endothelial cell antibodies (AECAs), which recognize a number of endothelial antigens, are seen in patients with systemic autoimmune diseases, more often in the presence of vasculitis than in its absence. Some AECAs induce apoptosis of endothelial cells (ECs), but their target antigens remain unknown. The aim of this study was to determine whether Hsp60 is a target antigen and whether AECAs induce apoptosis in ECs.Methods. Two-dimensional electrophoresis and conventional Western blotting techniques were used to characterize AECA targets. Hsp60 reactivity was determined by enzyme-linked immunosorbent assay.Results. Hsp60 was shown to be targeted by a proportion of AECAs. The level of reactivity was higher in patients with systemic autoimmune disease and vasculitis than in those without vasculitis and in patients with systemic lupus erythematosus than in patients with other systemic autoimmune diseases. Hsp60 was expressed on the plasma membrane of heat-stressed ECs, and this followed Hsp60 messenger RNA transcription, confinement of the protein to the cytoplasm, and translocation of the protein to the surface. Shedding of Hsp60 from ECs was induced by stress and resulted in the binding of soluble Hsp60 to the surface of ECs, particularly stressed ECs. Apoptosis of ECs was triggered by anti-Hsp60-containing AECA-positive sera and was inhibited by preincubation of the ECs with recombinant Hsp60.Conclusion. Our data support the notion that Hsp60 is an important target for AECAs and that such an interaction contributes to pathogenic effects, especially in vasculitis-associated systemic autoimmune disease.

Association of autoantibodies to heat‐shock protein 60 with arterial vascular events in patients with antiphospholipid antibodies

“…Differential endothelial cell expression of Hsp60 may at least partially explain the greater susceptibility of the arterial bed to antiHsp60. We and others have provided both in vitro and in vivo evidence that the presence of anti-Hsp60 is itself sufficient to cause endothelial cell dysfunction (apoptosis, activation, and/or injury) (2,(16)(17)(18). Such antiHsp60-induced endothelial damage would constitute the "first hit" and would favor the recruitment of aPL by exposing phosphatidylserine, a negatively charged phospholipid that interacts with phospholipid-binding proteins.…”

“…Anti-Hsp65 antibodies, induced in response to these pathogens, can cross-react with self Hsp60 expressed on endothelial cells (4)(5)(6)(7). Elevated levels of anti-Hsp60 have been associated with progression and severity of atherosclerosis (8)(9)(10)(11)(12)(13)(14)(15), with vasculitis in systemic autoimmune diseases (16), and with thrombotic events in the context of systemic lupus erythematosus (SLE) and lupus anticoagulant (LAC) positivity (17). Moreover, anti-Hsp60 from SLE patients were shown to bind to the surface of endothelial cells and induce apoptosis in these cells (17).…”

On the brotherhood of the mitochondrial chaperones mortalin and heat shock protein 60

“…And third, (on the plasma membrane) of endothelial cells, Hsp60 displays cross-reactivity to antiendothelial cell antibodies (AECAs) from patients with systemic autoimmune diseases, ie, vasculitis and lupus erythematosus. By an ambiguous mechanism, apoptosis was triggered by anti-Hsp60-containing AECA-positive sera and was inhibited by neutralization with free recombinant Hsp60 (Jamin et al 2005).…”

Evidence for a novel human-specific xeno-auto-antibody response against vascular endothelium

“…Among primary autoimmune vasculitides such as Wegener granulamatosis, Kawasaki disease, and Henoch-Schonlein purpura, there is an association between antiendothelial cell antibodies (AECA) and disease status. [22][23][24][25][26][27] Systemic lupus erythematosus also shows a relationship between AECA prevalence and disease status. 28,29 Indeed, transfer of AECA into rabbits results in systemic lupus erythematosus-like nephritis.…”

“…[33][34][35][36] The AECA epitopes thus far identified are proteins either constitutively expressed by endothelial cells or up-regulated by endothelial activation or inflammation. 22,26,27,37,38 Here we hypothesize that metabolic incorporation of dietary Neu5Gc into human endothelial cell surface glycoproteins leads to an immunogenic endothelium that reacts with circulating human anti-Neu5Gc antibodies, causing complement deposition, endothelial activation, and increased leukocyte binding. In contrast to previous examples, the Neu5Gc-containing antigens are dependent on the endothelial cell's ability to metabolically incorporate Neu5Gc, which originates from food.…”