Abstract 13172: Critical Role of ROCK2 in Bone Marrow-derived Macrophages in Mediating Atherosclerosis
Background: Rho kinases (ROCKs) are serine-threonine protein kinases that are involved in the regulation of the actin cytoskeleton. Recent studies suggest that ROCKs also play a pivotal role in cardiovascular diseases. There are two isoforms of ROCK, both having distinct downstream targets. While ROCK1 deficiency has been shown to ameliorate atherosclerosis in mice, the role of ROCK2 in atherosclerosis is still unknown.
Methods: To investigate the role of macrophage ROCK2 in atherosclerosis, we transplanted bone marrow (BM) from wild-type, ROCK2+/− and ROCK2−/− mice into irradiated recipient LDLr−/− mice. Atherosclerosis was induced with a 16-week diet containing 15.8% wt/wt fat and 1.25% cholesterol. The degree of atherosclerosis in the en face aorta and subaortic sinus was evaluated using Oil Red O staining. Cholesterol uptake and efflux were evaluated in BM-derived macrophages (BMDMs). Modulation of the PPARg pathway by ROCK2 was determined by RT-PCR and Dual Luciferase assay, respectively. Statistical analysis was performed using Student's t-test or Mann-Whitney U-test. A p value <0.05 was considered significant.
Results: Physiological parameters after BM transplantation (BMT) and following atherogenic diet were not different between the groups. Compared to WT BMT mice, ROCK2+/− and ROCK2−/− BMT mice showed substantially less atherosclerosis in the aorta (15.64% vs. 9.8% and 8.46%, p<0.01) and subaortic sinus (520.2x103 μm2 vs. 330.1x103 μm2 and 158.8x103 μm2, p<0.01). While the overall uptake of AcLDL was unchanged, ROCK2 deficiency was associated with decreased foam cell formation and increased cholesterol efflux. This was mediated through up-regulation of the PPARg-LXR-ABCA1 pathway. This finding was further confirmed by transient transfection of the PPAR response element, which was strongly activated by ROCK inhibition, while co-transfection with constitutive-active mutant of ROCK reversed the effect.
Conclusions: We demonstrate that ROCK2 in BMDMs contributes to atherosclerosis by mediating reverse cholesterol transport in macrophages through regulating the PPARg-LXR-ABCA1 pathway. These findings suggest that inhibition of ROCK2 signaling in BMDMs may have therapeutic benefits in preventing atherosclerosis.
- © 2010 by American Heart Association, Inc.