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


CONCLUSIONS
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.
Jamin
Christophe
C
Brest University Medical School, Brest, France.
Dugué
Christophe
C
Alard
Jean-Eric
JE
Jousse
Sandrine
S
Saraux
Alain
A
Guillevin
Loïc
L
Piette
Jean-Charles
JC
Youinou
Pierre
P
D000328:Adult; D000368:Aged; D000595:Amino Acid Sequence; D017209:Apoptosis / Q000276:immunology*; D001323:Autoantibodies / Q000276:immunology; D001327:Autoimmune Diseases / Q000276:immunology* / Q000473:pathology; D018834:Chaperonin 60 / Q000737:chemistry / Q000276:immunology*; D004730:Endothelium, Vascular / Q000276:immunology* / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000737:chemistry / Q000276:immunology; D008875:Middle Aged; D008969:Molecular Sequence Data; D014657:Vasculitis / Q000276:immunology* / Q000473:pathology
D001323:Autoantibodies; D018834:Chaperonin 60; D008565:Membrane Proteins