Abstract 17326: Clues to Attenuating Plaque Inflammation: Heat Shock Protein-27 Augments Macrophage Histone Deacetylase-6 Activity and Cytoskeletal Migratory Capacity
Introduction: We recently demonstrated that elevated serum levels of Heat Shock Protein 27 (HSP27) are associated with reduced 5-year CV events and that extracellular HSP27 attenuates experimental atherogenesis and lesion progression. Indeed, HSP27 therapy reduces plaque macrophage and cholesterol content and enhances histological features associated with resilience to plaque rupture. Cell motility and adhesion involves dynamic microtubule acetylation/deacetylation, a process regulated by the enzyme histone deacetylase 6 (HDAC6), a major cytoplasmic α-tubulin deacetylase. We hypothesize that HSP27 enhances HDAC6 activity to promote favorable plaque remodeling by enhancing macrophage migration.
Methods / Results: 1. The HDAC6 activity of THP-1 macrophages treated with recombinant HSP27 was assessed using a fluorescent plate reader ELISA. In a dose-dependent fashion, rHSP27 treatment resulted in a 100% increase in HDAC-6 activity compared to the control and was independent of HSP27 phosphorylation. Moreover, HDAC-6 activity was enhanced 100% in peritoneal macrophages harvested from rHsp27-treated ApoE-/- vs. control mice. With the addition of cycloheximide HDAC-6 activity was not prolonged, suggesting that HSP27 did not have an effect on the enzymatic half-life.
2. When HSP27 expression was knocked down in THP-1 cells transfected with a lentivirus carrying specific shRNA-HSP27 vector there was a reduction in HDAC6 activity and an increase in tubulin acetylation - and both of these effects were rescued with the addition of rHSP27.
3. Using a Boyden chamber cell migration assay, we found that rHSP27 treatment increased migration of THP-1 cells without and with ox-LDL loading by ~2- and ~1.5-fold; respectively - an effect that was blocked by either Tubacin (a specific inhibitor of HDAC6) or HSP27 knockdown.
Conclusion: Extracellular HSP27 is capable of up-regulating HDAC6 activity in macrophages, an effect associated with enhanced macrophage migratory capacity. These data suggest that HSP27 may be important for potentially improving macrophage egress from plaques thereby resulting in reduced cholesterol content and more stable lesions - factors that may explain the proven predictive biomarker value of elevated serum HSP27 levels.
Author Disclosures: G.A. Koumbadinga: None. D. Alvarez-Omeldo: None. E.R. O’Brien: None.
- © 2015 by American Heart Association, Inc.