Abstract 19463: Impaired Post-Ischemic Neovascularization Resulting From Macrophage-Specific Overexpression of Catalase
Introduction: The formation of collateral circulation is an important determinant of outcome in vascular occlusive diseases such as CAD. Macrophages, as well as reactive oxygen species (ROS), play a key role in post-ischemic neovascularization. However, the role of macrophage-derived H2O2 in vivo is not well defined.
Hypothesis: Decreased production of H2O2 by macrophages leads to impaired collateral vessel formation after acute ischemia.
Methods: Transgenic mice with macrophage-specific overexpression of catalase (TgCat-Mac mice) were created on a C57/Bl6 background. After femoral artery ligation, Laser Doppler perfusion imaging (LDPI) or micro computerized tomography (μCT) was performed to quantitatively evaluate collateral vessel development. Functional recovery of the ischemic limb was monitored by treadmill activity. QPCR and western blot analyses of ischemic leg muscle was performed to determine levels of inflammatory markers. H2O2 production was determined using Amplex Red. Inflammatory cell infiltration was assessed histologically by H&E staining.
Results: Peritoneal macrophages from TgCat-Mac mice had a 3.5 fold increase in catalase activity, and ischemic muscle showed a 34% reduction in H2O2 production compared to wild type (WT) mice. Perfusion ratios measured by LDPI at post-operative day 14 were lower in TgCat-Mac mice (0.41±0.025 vs. 0.32±0.02, p<0.01). The difference was maintained through post-operative day 28. μCT angiograms of ischemic legs showed a 23% reduction in the vascular volume to tissue volume ratio (p<0.05) and a 16% reduction in vascular density (p<0.05) in TgCat-Mac mice. Treadmill monitoring showed that TgCat-Mac mice ran less than WT mice (24.9±6.5 Km vs. 41.8±3.3 Km, respectively, p=0.052). Infiltration of ischemic tissues by macrophages was decreased in TgCat-Mac mice as assessed histologically and by qPRC for CD68. Levels of inflammatory markers such as TNFα, ICAM, and OPN were significantly lower in TgCat-Mac mice both at the mRNA and protein level.
Conclusions: Macrophage-derived H2O2 promotes neovascularization after hind limb ischemia, which is associated with an increased inflammatory response. Reducing H2O2 levels in macrophages impairs their ability to infiltrate ischemic tissues.
- © 2010 by American Heart Association, Inc.