Abstract 17586: HSP27 Mediated Atheroprotection Requires GM-CSF Induction: Potential Role in Reverse Cholesterol Transport? (Best of Basic Science Abstract)
Introduction: Previously, we demonstrated that Heat Shock Protein 27 (HSP27) reduces experimental atherogenesis and patients with elevated serum HSP27 levels are relatively protected against future CV events. We previously reported that extracellular HSP27 activates the NF-kB pathway and increases the expression of GM-CSF. While the potential atheroprotective role of GM-CSF remains controversial, clinical reports highlight its effect on reducing serum cholesterol levels. We now hypothesize that GM-CSF plays an important role in HSP27-mediated atheroprotection, potentially by up-regulating reverse cholesterol transport (RCT).
Methods / Results: 1. NF-KB signaling in vitro: Treatment of macrophages with recombinant HSP27 (rHSP27) activated NF-kB 15-fold via TLR-4 (NF-kB reporter gene assay; controls: truncated rHSP27 peptide and TLR-4 deficient cells; p<0.05). While rHSP27 substantially induced GM-CSF expression and secretion (300- and 400-fold respectively; p<0.05) both processes were blocked by NF-kB inhibitors.
2. In vivo role of GM-CSF induction in HSP27-mediated atheroprotection: Aortic atherogenesis in apoE null treated with rHSP27 was reduced by an expected 40%, while ApoE null / GM-CSF null did not respond to rHSP27 treatment. Moreover, apoE null / GM-CSF null macrophages expressed ~33% lower levels of the reverse cholesterol transporters, ABC-A1 and ABC-G1.
3. rHSP27 & Reverse Cholesterol Transport: THP-1 macrophages pre-treated with oxLDL and incubated with rHSP27 for 24h showed enhanced mRNA and protein expression of ABCA1 and ABCG1 (p<0.01). In a RCT assay, THP-1 macrophages labeled with NBD-cholesterol and treated with rHSP27 for 24h before being incubated with apoA1 or HDL showed increased cholesterol efflux compared to controls (p<0.0001 for both).
Conclusion: HSP27 up regulates expression of GM-CSF that appears to play an important role in RCT-mediated atheroprotection.
Author Disclosures: V. Pulakazhi Venu: None. A. Adijiang: None. C. Shi: None. Y. Chen: None. E.R. O’Brien: None.
- © 2015 by American Heart Association, Inc.