Abstract 296: Role Of Endothelial Cell-specific Knockout Of The Aryl Hydrocarbon Receptor In Ischemic Limb Myopathy In Mice Subjected To Hind Limb Ischemia

Abstract

Introduction: Chronic kidney disease (CKD) is a risk factor for peripheral arterial disease (PAD) that accelerates disease evolution and worsens limb outcomes, however the molecular mechanisms linking the pathobiologies are ill-defined. The aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor, has been previously shown to regulate angiogenesis. Notably, CKD results in the accumulation of tryptophan-derived metabolites that are endogenous ligands for the AHR. On this basis, we tested the hypothesis that endothelial cell-specific knockout of the AHR would enhance limb perfusion recovery and capillarity in mice with CKD subjected to hindlimb ischemia. Methods: Twelve-week-old conditional AHR knockout mice (AHR fl/fl , Cre-negative) and endothelium-specific AHR knockout mice (AHR ecKO ) were fed 0.2% adenine to induce CKD or casein control diet (n=10/group/sex). Femoral artery ligation (FAL) was performed on the left limb using the right limb as a non-ischemic control. Limb perfusion was measured using laser Doppler flowmetry. Skeletal muscle function was measured using nerve stimulus. Gastrocnemius mitochondrial respiratory function and H 2 O 2 production were assessed. Results: Regardless of genotype, mice with CKD had significantly lower renal function. Interestingly, male AHR ecKO mice with CKD displayed a significant increase in percentage of perfused capillaries within the ischemic tibialis anterior muscle (AHR ecKO 73.41% ± 4.80% vs AHR fl/fl 64.75% ± 8.325%; p= 0.0074 ) and improved laser Doppler perfusion recovery in the paw and gastrocnemius muscle compared to male AHR fl/fl mice with CKD. AHR ecKO mice had a larger mean myofiber size ( p=0.0258 ), although muscle weight and contractile function were not different. Mitochondrial respiratory capacity was significantly higher (p=0.0085) in AHR ecKO than AHR fl/fl mice. Conclusion: In mice with CKD, endothelium-specific deletion of the AHR improved blood perfusion and increased myofiber size in the ischemic limb muscle. These changes conferred improvement in muscle mitochondrial function, but not muscle strength. Interestingly, these changes were observed in male, but not female, mice.