Relationship between plasma cholesterol, von Willebrand factor concentrations, extent of atherosclerosis and antibody titres to heat shock proteins-60, -65 and -70 in cholesterol-fed rabbits

Abstract

Epidemiological studies have shown an association between atherosclerosis, Heat shock protein (Hsp) expression, and Hsp antibody titres. We aimed to investigate the time course of appearance of Hsp-60, -65 and -70 antibodies in the cholesterol-fed rabbit and to relate antibody titres to serum concentrations of von Willebrand factor (vWF), a marker of endothelial injury. Rabbits were fed with 0.25-1.0% cholesterol diet for 13 weeks. Plasma levels of anti Hsp-60, -65 and -70 IgG titres, were measured using in-house enzyme-linked immunosorbent assays (ELISAs) together with plasma vWF concentrations. Plasma titres of anti-Hsp-60, -65 and -70 antibodies were all significantly increased by weeks 5, 7 and 9 following commencement of the experimental diet compared with baseline (P < 0.05 for all). In non-cholesterol-fed rabbits, plasma levels of anti-Hsp titres were unchanged over this period. Increased plasma vWF concentrations were also found in the cholesterol-fed rabbits, reaching a maximum at approximately week 8, and falling thereafter. Furthermore, plasma vWF concentrations at 13 weeks correlated strongly with antibody titres to all three Hsps (r = 0.90, P = 0.002; r = 0.80, P = 0.017; r = 0.86, P = 0.006 for Hsp 60, -65 and -70 respectively) and titres were also strongly correlated with final plasma cholesterol concentrations in cholesterol-fed animals (r = 0.95, P = 0.002; r = 0.8, P = 0.001; r = 0.84, P = 0.01 respectively). In cholesterol-fed rabbits, antibody titres to Hsp-60, -65 and -70 appear to rise in association with a marker of endothelial injury, peaking at approximately the same time (8 weeks) after starting a high cholesterol diet.

Figure 1

Time course for changes in plasma anti-Hsp-60, -65 and -70 titres in normal chow and cholesterol-fed rabbits. (a) Antibody titres to Hsp 60 were significant higher for cholesterol compared to normal chow-fed animals during the experimental period (P = 0.0013, by anova), also being significantly higher at weeks 5 (P < 0.05), 7 and 9 (P < 0.01) compared with baseline. (b) Antibody titres to Hsp 65 were significant higher for cholesterol compared to normal chow-fed animals during the experimental period (P = 0.001, by anova), also being significantly higher at weeks 5 (P < 0.05), 7 and 9 (P < 0.01) compared with baseline. (c) Antibody titres to Hsp 70 were significant higher for cholesterol compared with normal chow-fed animals during the experimental period (P = 0.0016, by anova), also being significantly higher at weeks 5 (P < 0.05), 7 and 9 (P < 0.01) compared with baseline.

Figure 2

Time course of changes in plasma von Willebrand Factor (vWF) concentrations in normal chow and cholesterol-fed rabbits. Antibody titres to vWF were significant higher for cholesterol compared to normal chow-fed animals during the experimental period (P < 0.001, by anova) also being significantly higher at week 7 P < 0.01 compared with baseline.

Figure 3

Relationship between plasma levels of anti-Hsp antibody titres and plasma cholesterol level. (a) Relationship between plasma levels of anti-Hsp-60 antibody titres and plasma cholesterol level. (b) Relationship between plasma levels of anti-Hsp-65 antibody titres and plasma cholesterol level. (c) Relationship between plasma levels of anti-Hsp-70 antibody titres and plasma cholesterol level.

Figure 4

Relationship between plasma levels of anti-Hsp antibody titres and plasma vWF level. (a) Relationship between plasma levels of anti-Hsp-60 antibody titres and plasma vWF level. (b) Relationship between plasma levels of anti-Hsp-65 antibody titres and plasma vWF level. (c) Relationship between plasma levels of anti-Hsp-70 antibody titres and plasma vWF.