Abstract 14072: Novel Atheroprotection Therapy: Reduction in Serum Lipid Levels by HSP27 Via Down-regulation of HNF1a and PCSK9 Expression
Background: Heat Shock Protein 27 (HSP27) levels are reduced in patients with CAD and are predictive of future cardiovascular risk. Experimental atherogenesis is attenuated when HSP27 levels are augmented - likely due to observed reductions in serum and plaque cholesterol levels. Recently we noted that HSP27 lowers the expression of PCSK9 and increases LDL-R levels. Moreover, we noted the presence of serum auto-antibodies (AAbs) to HSP27 that obfuscate the ELISA measurement of HSP27 levels and therefore developed a new mass spectrometry based assay to more accurately assess HSP27 levels (reported separately, HSP27 levels are 100-fold higher with MS). In recent in vitro studies we uncovered the mechanism by which these AAbs potentiate HSP27 signaling.
Purpose #1: Determine how HSP27 attenuates PCSK9 levels, including its potential impact on HNF1a, an important transcriptional regulator of PCSK9.
Purpose #2: Test the hypothesis that immunization to augment AAbs might reduce atherogenesis and ameliorate lipid parameters.
Methods/Results: a) Mechanism of HSP27 reducing PCSK9 expression: HepG2 (liver) cells treated with recombinant HSP27 (rHSP27) expressed lower levels of PCSK9 mRNA and protein, as well as ~40% reduction of HNF1a mRNA and protein. b) As statins activate SREBP-2 to increase the expression of PCSK9, HepG2 cells were treated with atorvastatin resulting in an increase in PCSK9 secretion that was markedly attenuated by rHSP27 treatment. Conversely, when HSP27 expression was silenced PCSK9 secretion increased in atorvastatin treated HEPG2 cells. c) To determine the role of AAbs in experimental atherogenesis, apoE-/- mice were treated for 4 weeks as follows: Group I: rHSP27 protein s.c. twice daily, Group II: immunization with rHSP27 protein and an alum adjuvant once weekly to boost AAbs, Group III: immunization with rC1 (a truncated C-terminus fragment of HSP27 without biological activity) and alum once weekly. Total serum cholesterol fell by 63% in Group II vs. III, and was associated with a 32% reduction in aortic plaque volume.
Conclusions: By reducing the expression of HNF1-alpha and PCSK9, HSP27 lowers serum cholesterol levels. Immunization to augment HSP27 athero-protection represents a novel therapeutic strategy for hyperlipidemia.
Author Disclosures: C. Shi: None. Y. Chen: None. C. Diao: None. Z. Batulan: None. E.R. OBrien: None.
- © 2016 by American Heart Association, Inc.