Maresin 1 activates LGR6 signaling to inhibit smooth muscle cell activation and attenuate murine abdominal aortic aneurysm formation

The specialized pro-resolving lipid mediator maresin 1 (MaR1) is involved in the resolution phase of tissue inflammation. It was hypothesized that exogenous administration of MaR1 would attenuate abdominal aortic aneurysm (AAA) growth in a cytokine-dependent manner via LGR6 receptor signaling and macrophage-dependent efferocytosis of smooth muscle cells (SMCs). AAAs were induced in C57BL/6 wild-type (WT) mice and smooth muscle cell specific TGF-beta 2 receptor knockout (SMC-TGF beta r2(-/-)) mice using a topical elastase AAA model. MaR1 treatment significantly attenuated AAA growth as well as increased aortic SMC alpha-actin and TGF-beta 2 expressions in WT mice, but not SMC-TGF beta r2(-/-) mice, compared to vehicle-treated mice. In vivo inhibition of LGR6 receptors obliterated MaR1-dependent protection in AAA formation and SMC alpha-actin expression. Furthermore, MaR1 upregulated macrophage-dependent efferocytosis of apoptotic SMCs in murine aortic tissue during AAA formation. In vitro studies demonstrate that MaR1-LGR6 interaction upregulates TGF-beta 2 expression and decreases MMP2 activity during crosstalk of macrophage-apoptotic SMCs. In summary, these results demonstrate that MaR1 activates LGR6 receptors to upregulate macrophage-dependent efferocytosis, increases TGF-beta expression, preserves aortic wall remodeling and attenuate AAA formation. Therefore, this study demonstrates the potential of MaR1-LGR6-mediated mitigation of vascular remodeling through increased efferocytosis of apoptotic SMCs via TGF-beta 2 to attenuate AAA formation.