Abstract 5275: STAT3-dependent Acute RANTES Production in Vascular Smooth Muscle Cells Modulates Inflammation Following Arterial Injury
Inflammation is a key component of arterial injury, with vascular smooth muscle cell (VSMC) proliferation and neointimal formation the final outcome of this process. However, the acute events that establish the blueprint for this vascular inflammatory response are incompletely understood. To address this deficiency we examined events immediately after femoral artery wire injury in mice and identified a marked acute recruitment of macrophages and T cells, with vessel-associated CD3+ T cells increasing ~20-fold within 1 day of injury. Correspondingly RANTES, a T cell and macrophage chemo-attractant, was upregulated in vessels > 20-fold within 6 h of injury. RANTES production was modulated by p21Cip1; at 6 h local RANTES was 45-fold higher in p21−/− than wild type (WT) mice, and acute T cell infiltration was > 2-fold greater in p21−/− than WT mice at 1 day post injury. Immune-staining and reciprocal bone marrow (BM) transplantation between WT and RANTES−/− mice identified medial VSMCs as the principal source of acute RANTES production. Unique to VSMCs, RANTES production was initiated by TNFα, but not IL-6 or gp130 (an IL-6 signal transducer). RANTES transcription was dependent on downstream binding of a complex formed between NF-κB (p65 subunit) and STAT3 to NF-κB binding sites in the RANTES promoter, with shRNA knockdown of either STAT3 or p65 in VSMCs markedly abrogating RANTES production. p21Cip1 potentially modulated RANTES levels by both restraining STAT3 transcription and co-association with p65. In vivo, acute activation of NF-κB and STAT3 in medial VSMCs was identified, with RANTES levels 6 h after injury in TNFα−/− mice significantly reduced compared to WT controls. One day after injury, RANTES−/− mice reconstituted with WT BM displayed a marked reduction in T cell and macrophage infiltration compared to identically reconstituted WT mice. Finally, we generated mice with smooth muscle cell-specific conditional STAT3-knockout (STAT3fl/fl;SM22α-Cre) and confirmed the STAT3-dependence of acute RANTES production by VSMCs. We conclude that early inflammatory cell recruitment following arterial injury is regulated by acute local RANTES production by medial VSMCs, which is in turn stimulated by TNFα and modulated by downstream NF-κB-STAT3 signaling.