Abstract P2066: Age-related Changes In Posttranscriptional Regulation Of Macrophage VEGF As A Mechanism Of Impaired Inflammatory Arteriogenesis

Aging and age-related diseases like peripheral arterial disease are associated with impaired inflammatoryarteriogenesis in response to injury. During ischemia, macrophage recruitment and macrophage pro-angiogenic VEGF-A isoform expression contribute to post developmental arteriogenesis. Preliminary datafrom bone marrow-derived macrophages (BMDMs) demonstrated decreased VEGF-A level by both mRNAand protein in aged (52-week-old) and advanced aged (104-week-old) mice when compared to young (12-week-old). Moreover, VEGF-A165a which is VEGF-A proangiogenic splice variant was also reduced inmacrophages from aged and advanced aged mice. The anti-angiogenic VEGF-A165b variant wassignificantly increased in advanced aged mice. We sought to determine the mechanisms which cancontribute to the reduction of pro-angiogenic VEGF-A and consequently reduced inflammatory-mediatedarteriogenesis response in the context of aging. In a hindlimb ischemia model of angio/arteriogenesis, wefound decreased blood flow recovery in aged mice. Moreover, small arterial angiography by microCTconfirmed decreased arteriogenesis. Loss of functional arteriogenesis was associated with decreased muscletissue VEGF-A and VEGF-A165a levels despite adequate macrophage recruitment to the muscle tissue.Moreover, VEGF-A165b was increased in ischemic tissue from advanced aged mice. The mechanism ofreduced macrophage pro-angiogenic VEGF-A165a expression involved decreased mRNA stability withdecreased association of VEGF-A165a mRNA with the RNA-stabilizing protein HuR. In fact, aged BMDMsdemonstrated a loss of HuR binding to VEGF-A165a mRNA with decreased VEGF-A165a mRNA half-life,and consequently decreased inflammatory angio/arteriogenesis.

Abstract 205: Macrophage Rac1-IL-1β Signaling Axis Promotes Atherosclerotic Calcification

Coronary artery disease caused by atherosclerosis is a major cause of morbidity and mortality worldwide. Calcification of atherosclerotic plaque is a marker of atherosclerotic burden and worsening cardiovascular outcomes. Inflammation plays a role in both atherosclerotic progression and calcification, but the mechanisms of calcification are not entirely well-defined. We sought to understand the role of macrophage Rac1 signaling in the natural progression of atherosclerotic calcification in the context of an experimental model of hyperlipidemia. We developed a tamoxifen-inducible, myeloid specific Rac1 -deletion model ( Csf1r mercremer Rac1 fl/fl ApoE -/- ) to evaluate the impact of macrophage-specific Rac1 on atherosclerotic calcification. After 20 weeks of ad libitum feeding on a cholesterol-supplemented high fat diet, Rac1 -deleted animals demonstrated significantly decreased atherosclerotic calcification compared to wild-type mice, irrespective of modest changes in lipid metabolism as demonstrated by plasma analysis. Mechanistically, Rac1 -deleted bone marrow derived macrophages demonstrated reduced expression of the potent inflammatory cytokine, IL-1β, in response to a cholesterol-based inflammasome activation. Rac1 -deleted macrophages also demonstrated decreased nuclear NF-κB activity and lost binding of NF-κB to its seed site in the IL-1β promoter as evaluated by chromatin immunoprecipitation. We further demonstrated that Rac1 and NF-κB form a complex with each other upon innate inflammatory signaling activation using a proximity ligation assay. We confirmed the important functional role of the Rac1 nuclear localization sequence in the expression of IL-1β, which together with the proximity ligation assay, suggests a role for Rac1 in chaperoning NF-κB to the IL-1β promoter. The interaction between macrophage Rac1 and NF-κB may have implications on numerous inflammatory disease processes, and uncovers a novel signaling contribution of Rac1 as a transcriptional co-factor for IL-1β in the progression of atherosclerosis. Targeted inhibition of Rac1 may have potential as a therapeutic treatment to mitigate progression of vascular calcification.

Abstract 335: Macrophage Interleukin-1 Beta Dependent Angiogenesis During Wound Healing

Angiogenesis during wound healing is thought to require an inflammation suppressed state. However, there is growing evidence that early infiltrating inflammatory macrophages may play an important role in setting the stage for angiogenesis. Here we sought to understand the relationship between the potent inflammatory cytokine, IL-1β, and vascular endothelial growth factor-A (VEFG-A) in the context of two experimental models of angiogenesis-dependent healing: skin punch biopsy and hind limb ischemia. We established a macrophage-specific IL-1 β -deletion model ( mIL-1 β ) to study the relationship between IL-1β and VEGF-A in the context of these models. Using a punch biopsy model, wounds were quantified, showing remarked expansion of the wounds in mIL-1 β -deleted mice on day 2 of the healing process, resulting in slower wound closure. Analysis from mIL-1 β -deleted mice confirmed decreased macrophage expression of IL-1β and VEGF-A early at day two post-wounding by punch biopsy. In our second approach, we used femoral artery ligation to demonstrate hind limb ischemia. We hypothesized that mIL-1 β -deleted mice would exhibit reduced blood flow recovery due to impaired angiogenesis. Analysis from mIL-1 β -deleted mice indicates reduced IL-1β and VEGF-A expression. In establishing a pathway of IL-1β-dependent macrophage VEGF-A upregulation in the acute injury state, we examined transcriptional factors STAT3 and NF-κB. Constitutively active STAT3 and IKK-2 (NF-κB activator) appear to increase VEGF-A expression, while inhibition of STAT3 and NF-κB exhibits a dose-dependent reduction of VEGF-A expression. In summary, two models of angiogenesis-dependent healing from injury indicate that macrophage VEGF-A expression is dependent on IL-1β expression during early inflammation. Strategies to alleviate impaired wound healing where VEGF-A levels may not be sufficient could require upregulation of the downstream effectors of IL-1β to restore macrophage VEGF-A expression levels required for adequate angiogenesis.

Aortic Valve Calcification Is Associated with Future Cognitive Impairment

BACKGROUND

While an association between atherosclerosis and dementia has been identified, few studies have assessed the longitudinal relationship between aortic valve calcification (AVC) and cognitive impairment (CI).

OBJECTIVE

We sought to determine whether AVC derived from lung cancer screening CT (LCSCT) was associated with CI in a moderate-to-high atherosclerotic risk cohort.

METHODS

This was a single site, retrospective analysis of 1401 U.S. veterans (65 years [IQI: 61, 68] years; 97%male) who underwent quantification of AVC from LCSCT indicated for smoking history. The primary outcome was new diagnosis of CI identified by objective testing (Mini-Mental Status Exam or Montreal Cognitive Assessment) or by ICD coding. Time-to-event analysis was carried out using AVC as a continuous variable.

RESULTS

Over 5 years, 110 patients (8%) were diagnosed with CI. AVC was associated with new diagnosis of CI using 3 Models for adjustment: 1) age (HR: 1.104; CI: 1.023-1.191; p = 0.011); 2) Model 1 plus hypertension, hyperlipidemia, diabetes, CKD stage 3 or higher (glomerular filtration rate < 60 mL/min) and CAD (HR: 1.097; CI: 1.014-1.186; p = 0.020); and 3) Model 2 plus CVA (HR: 1.094; CI: 1.011-1.182; p = 0.024). Sensitivity analysis demonstrated that the association between AVC and new diagnosis of CI remained significant upon exclusion of severe AVC (HR: 1.100 [1.013-1.194]; p = 0.023). Subgroup analysis demonstrated that this association remained significant when including education in the multivariate analysis (HR: 1.127 [1.030-1.233]; p = 0.009).

CONCLUSION

This is the first study demonstrating that among mostly male individuals who underwent LCSCT, quantified aortic valve calcification is associated with new diagnosis of CI.

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

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.

Characterization of nerve and microvessel damage and recovery in type 1 diabetic mice after permanent femoral artery ligation

Neuropathy is the most common complication of the peripheral nervous system during the progression of diabetes. The pathophysiology is unclear but may involve microangiopathy, reduced endoneurial blood flow, and tissue ischemia. We used a mouse model of type 1 diabetes to study parallel alterations of nerves and microvessels following tissue ischemia. We designed an easily reproducible model of ischemic neuropathy induced by irreversible ligation of the femoral artery. We studied the evolution of behavioral function, epineurial and endoneurial vessel impairment, and large nerve myelinated fiber as well as small cutaneous unmyelinated fiber impairment for 1 month following the onset of ischemia. We observed a more severe hindlimb dysfunction and delayed recovery in diabetic animals. This was associated with reduced density of large arteries in the hindlimb and reduced sciatic nerve epineurial blood flow. A reduction in sciatic nerve endoneurial capillary density was also observed, associated with a reduction in small unmyelinated epidermal fiber number and large myelinated sciatic nerve fiber dysfunction. Moreover, vascular recovery was delayed, and nerve dysfunction was still present in diabetic animals at day 28. This easily reproducible model provides clear insight into the evolution over time of the impact of ischemia on nerve and microvessel homeostasis in the setting of diabetes. © 2015 Wiley Periodicals, Inc.

Ephrin-B2-activated peripheral blood mononuclear cells from diabetic patients restore diabetes-induced impairment of postischemic neovascularization

We hypothesized that in vitro treatment of peripheral blood mononuclear cells (PB-MNCs) from diabetic patients with ephrin-B2/Fc (EFNB2) improves their proangiogenic therapeutic potential in diabetic ischemic experimental models. Diabetes was induced in nude athymic mice by streptozotocin injections. At 9 weeks after hyperglycemia, 10(5) PB-MNCs from diabetic patients, pretreated by EFNB2, were intravenously injected in diabetic mice with hindlimb ischemia. Two weeks later, the postischemic neovascularization was evaluated. The mechanisms involved were investigated by flow cytometry analysis and in vitro cell biological assays. Paw skin blood flow, angiographic score, and capillary density were significantly increased in ischemic leg of diabetic mice receiving EFNB2-activated diabetic PB-MNCs versus those receiving nontreated diabetic PB-MNCs. EFNB2 bound to PB-MNCs and increased the adhesion and transmigration of PB-MNCs. Finally, EFNB2-activated PB-MNCs raised the number of circulating vascular progenitor cells in diabetic nude mice and increased the ability of endogenous bone marrow MNCs to differentiate into cells with endothelial phenotype and enhanced their proangiogenic potential. Therefore, EFNB2 treatment of PB-MNCs abrogates the diabetes-induced stem/progenitor cell dysfunction and opens a new avenue for the clinical development of an innovative and accessible strategy in diabetic patients with critical ischemic diseases.