Heat shock protein 65 promotes atherosclerosis through impairing the properties of high density lipoprotein.

Aim: To explicit whether the functions of high density lipoprotein (HDL) are impaired in murine atherosclerosis by subcutaneous immunization with recombinant mycobacterial heat shock protein 65 (HSP65).

Methods: C57BL/6 mice were fed a normal chow-diet with non immunization as normal group. ApoE knockout (ApoE(-/-)) mice on high-fat diet were randomly divided into three groups (n = 8) and immunized subcutaneously with different concentrations of HSP65 or phosphate-buffered saline (PBS). All animals were treated for 16 weeks. Reverse cholesterol efflux, the anti-oxidant and anti-inflammatory functions of HDL were assayed. Hepatocytes and peritoneal macrophages were isolated to examine the expression of cholesterol transport regulating proteins, including SR-B1, ABCA1, ABCG1, PPAR-γ and LXR-α.

Results: In HSP65-immunized mice, paraoxonase1 (PON1) activity and the expression of IL-10 were reduced, while High-density lipoprotein inflammatory index (HII), myeloperoxidase (MPO) activity, and the expression of IFN-γ were elevated gradually. The MPO/PON1 ratio amount was significantly higher in HSP65-immunized group than in normal or PBS-immunized group. In addition, compared with normal or PBS-immunized group, cholesterol efflux rate and the expression of regulating proteins were markedly decreased in HSP65-immunized group. The mice immunized with HSP65 developed significantly larger aorta atherosclerotic plaques when compared with PBS-treated littermates. The high MPO/PON1 ratio was correlated with HII, cholesterol efflux rate and atherosclerotic plaques.

Conclusions: This study demonstrates that subcutaneous immunization with HSP65 impairs the properties of HDL, which may contribute to its important pathogenic role of HSP65 in atherogenesis. Also, MPO/PON1 ratio may be a predictor of AS.