Abstract 489: Disruption of HuR-mediated VEGF-A mRNA Stabilization as a Mechanism of Age-related Defects in Arteriogenesis

Abstract

Aging and age-related diseases like peripheral arterial disease are associated with impaired inflammatory arteriogenesis in response to injury. Macrophage expression of pro-inflammatory and pro-angiogenenic factors can be altered during aging. We seek to define the molecular mechanism that determine the impact of aging on macrophage-dependent arteriogenesis. Recently, we defined a critical signaling pathway that involves CCL2 stimulation coupled to ICAM-1 adhesion, resulting in rapid nuclear-to-cytosolic translocation of the RNA-binding protein, HuR, with its consequent stabilization of VEGF-A mRNA. Preliminary data from bone marrow-derived macrophages (BMDMs) demonstrated decreased VEGF-A level by both mRNA and protein in aged mice (52-week old) when compared to young (10-week old). BMDMs from aged mice also revealed increased markers of senescence. The hypothesis is that age-related changes in arteriogenesis are a conseqeuence of altered HuR-mediated VEGF-A stabilization. In a hindlimb ischemia model of arteriogenesis, we found reduced flow recovery in aged mice. Moreover, small arterial angiography by microCT confirmed decreased arteriogenesis. Loss of functional arteriogenesis was associated with decreased muscle tissue VEGF-A levels despite adequate macrophage recruitment to the muscle tissue. BMDM HuR expression was unaffected in aged mice, and CCL2-coupled ICAM-1 adhesion demonstrated comparable nuclear-to-cytosolic translocation in aged BMDMs, indicating the signaling of HuR activation remained intact. However, BMDMs demonstrated a loss of HuR binding to VEGF-A mRNA with consequent decreased VEGF-A mRNA half-life. In summary, HuR-mediated VEGF-A mRNA stabilization and consequent inflammatory-mediated arteriogenesis is disrupted in aged animals.