Heat shock protein 65 increases arterial contractility

Abstract

Background An association has been shown between raised serum antibody levels to 65-kDa heat shock protein (HSP 65) and vascular disease suggesting that HSP 65 might play a role in its pathogenesis. The aim of this study was to investigate the direct effects of HSP 65 on the vasculature.

Methods Male Dark Agouti rats were immunized with 200 mu g HSP 65 in Freund's incomplete adjuvant (HSP group). Five rats were used as control group. The animals were killed at 6 and 10 weeks following immunization. Rings of thoracic aorta were assessed for contraction and relaxation in response to phenylephrine and acetylcholine using an organ bath technique. The distal thoracic aorta was fixed and stained to determine intima/media thickness and to detect proliferating cellular nuclear antigen (PCNA). T-helper (Th) cell type 1 and 2 status was also assessed using flow cytometry.

Results The HSP group showed increased contractility in response to phenylephrine compared with controls (mean(s.e.) maximum contraction 0.701(0.030) mu g (n = 9) versus 0.533(0.020) mu g (n = 5); P = 0.004, analysis of variance, Bonferoni/Dunn). The dose-response curve for acetylcholine was not significantly different. Controls reached 93 per cent maximal relaxation and rats in the HSP group 92 per cent suggesting intact endothelial nitric oxide synthesis. No significant difference could be found in intima/media thickness between the two groups (control group: intimal, 3.8 mu m; media, 80.5 mu m versus HSP group: intima, 3.8 mu m; media, 78.0 mu m). Staining for PCNA showed no difference between the groups. Cytokine expression was shifted from Th1 towards a Th2 status.

Conclusion This study has shown a change in vasoactivity produced by immunization with HSP 65. This novel finding may have implications for understanding the aetiology of vasospastic disorders and may give new ideas for possible therapeutic strategies such es the use of Th1 adjuvants in patients with vascular disease.