Abstract 14939: Small Molecule Agonists of Integrin Mac-1 Disrupt the Pro-Inflammatory Effect of Il-18 in Injured Blood Vessels and Accelerate Vascular Healing
Background: We recently described a new class of compounds called leukadherins (LA) that reduce inflammation and neointimal formation after vascular injury. These compounds allosterically activate Mac-1 thereby increasing cell adhesion and preventing leukocyte extravasation into the site of injury. This study reveals novel mechanistic insights into surprising, additional beneficial effects of leukadherins in vascular healing.
Methods and Results: We measured the relative levels of 22 cytokines in balloon-injured arteries of LA1- and vehicle- treated rats and were surprised to find that LA1 blunted the secretion of inflammatory by leukocytes after injury. Interestingly, LA1 reduced the post-injury levels of IL-18, a monocyte derived cytokine that stimulates smooth muscle cells accumulation after injury. We then used TNF-α stimulated THP-1 monocytes to test if Mac-1 activation by LA1 was sufficient to block cytokines secretion in vitro. TNFα in the absence of LA1 induced a robust gene expression of IL-18, IL-1β, MCP1, and RANTES while downregulating the anti-inflammatory factor, IL-10. Mac-1 activation with LA1 reversed the TNF-α inflammatory effect in these cells and, more importantly, inhibited the expression of MyD88 and TRIF, two important adaptor proteins in the amplification of pro-inflammatory loops in monocytes. Mac-1 activation with LA1 also reduced the expression of IL-18 in rat monocytes after stimulation with the platelet-related inflammatory factor MCP-1. Finally, we determined if the anti-inflammatory effects of LA1 could accelerate vascular re-endothelialization (healing) in LA-treated versus control (vehicle) rats using the Evans blue vital staining. Seven days after balloon injury, only minimal blue staining was observed in injured arteries of LA1-treated rats while control animals showed minimal re-endothelialization. Immunohistochemistry using cell-specific antibodies further confirmed the presence of re-endothelialized vasculature.
Conclusions: These data demonstrate that Mac-1 activation with LA1 significantly reduces the secretion of pro-inflammatory cytokines from treated leukocytes, by reducing MyD88/TRIF-dependent signaling pathways, and results in faster recovery of the injured vasculature.
- © 2013 by American Heart Association, Inc.