Abstract 15: Differential Activation of HIF1-α Is Associated with Reduced Arteriogenesis After Hindlimb Ischemia in PCAF -/- Mice

Abstract

Although arteriogenesis is generally considered to be a shear stress-driven process, hypoxia-inducible factor-1α (HIF-1α) has a strong stimulatory effect on arteriogenesis. Recently, it was shown that the P300/CBP-associated factor (PCAF) acetylates (and activates) HIF-1α at Lys674 and can act as a co-factor in transcriptional activation of HIF-1α target genes (1). We investigated whether PCAF plays a role in arteriogenesis. Wildtype C57Bl/6 mice or C57Bl/6 PCAF -/- mice were subjected to double ligation of the femoral artery. Blood flow recovery was followed over time using Laser Doppler Perfusion Imaging (LDPI) and after 28 days, animals were sacrificed and adductor muscles harvested for immunohistochemistry. PCAF -/- mice showed marked decrease in blood flow recovery compared to wildtype mice. Also, when staining for α-SMA, less and smaller collateral arteries were observed in the adductor muscle of PCAF -/- mice compared to wildtype mice. To study which genes were regulated by PCAF during arteriogenesis, wildtype and PCAF -/- C57Bl/6 mice were sacrificed 24 hours after double femoral artery ligation. Gene expression profiles in the adductor muscles of the mice were obtained by microArray and compared to expression patterns in the adductor muscle before femoral artery ligation. Transcription factor binding site analyses showed strong up-regulation of a large number of HIF-1α induced genes in both mouse strains. However, besides a group of 93 jointly up-regulated HIF-1α induced genes, each strain also showed up-regulation of a different set of HIF1α induced genes. The most striking gene that was up-regulated in PCAF -/- mice only, was Sirtuin 1 (SIRT1). Recently, it was shown that SIRT1 counteracts PCAF by deacetylating Lys674 of HIF-1α, thereby blocking p300 recruitment to HIF-1α (2). Up-regulation of SIRT1 in PCAF -/- mice further contributes to differential activation of HIF-1α under ischemia. Although HIF-1α is activated and can still induce up-regulation of a specific subset of its target genes in PCAF -/- mice, this no longer leads to efficient recovery of blood flow after hind limb ischemia. (1) Xenaki G et al. Oncogene 2008; 27(44) (2) Lim JH et al. Mol Cell 2010; 38(6)