Abstract 16310: Differential Activation of HIF1-α is Associated with Reduced Arteriogenesis After Hind Limb Ischemia in PCAF-/- Mice
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. 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). PCAF-/- mice showed a 30% decrease in blood flow recovery compared to wildtype mice 7 days after ligation. Less and smaller α-SMA positive collateral arteries were observed in the adductor muscle of PCAF-/- mice. PCAF-/- mice had an 11% reduction in the pre-existing collateral density measured in the pial circulation, whereas pharmacological inhibition of PCAF with Garcinol in wildtype animals still resulted in a 30% reduction in blood flow recovery 7 days after ligation, indicating that impaired collateral remodelling was the predominant mechanism in PACF-/- mice. To study which genes were regulated by PCAF during arteriogenesis, wildtype and PCAF-/- C57BL/6 mice were sacrificed 24 hours after single femoral artery ligation. Gene expression profiles in the adductor muscles of the mice were obtained by microArray and compared to expression patterns before 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 jointly upregulated HIF-1α induced genes, each strain also showed upregulation of a different, separate set of HIF1α induced genes. The most striking gene that was upregulated in PCAF-/- mice only was Sirtuin 1 (SIRT1). SIRT1 counteracts PCAF by deacetylating Lys674 of HIF-1α, thereby blocking p300 recruitment to HIF-1α. Upregulation of SIRT1 in PCAF-/- mice further contributes to differential HIF-1α activation under ischemia. Although HIF-1α is activated and still induces upregulation of a specific subset of target genes in PCAF-/- mice, this no longer leads to efficient recovery of blood flow after hind limb ischemia.
- © 2012 by American Heart Association, Inc.