FoxO induced inhibition of secreted molecule signalling pathways: role in promoting angiostasis in the ischemic muscle

Abstract

We showed previously that FoxO1 promotes an angiostatic environment within of the vasculature of the ischemic muscle by upregulating of the extracellular matrix (ECM) protein thrombospondin‐1. Here, we aim to identify FoxO targets involved in ECM signalling. BMP and activin membrane‐bound inhibitor (BAMBI) and soluble frizzled‐related protein 1 (sFRP1) are respective inhibitors of the signals of 2 secreted molecules TGF‐β and Wnt. Primary cultures of microvascular endothelial cells (MEC) of mice having the 3 FoxO genes flanked with LoxP sites (FoxOL/L) were transduced with adeno‐Cre recombinase to delete FoxO genes. This increased BAMBI mRNA levels by 7 fold, and decreased sFRP1 expression by 2.8 fold. Conversely, over‐expression of constitutively active FoxO1 in MECs lowered BAMBI mRNA by 70% and increased sFRP1 mRNA levels by 110%. Within murine ischemic muscle (4 days post femoral artery ligation), the levels of sFRP1 were increased (p=0.055) and BAMBI expression was reduced significantly (p=0.03). Ischemia‐induced alterations in sFRP1 and BAMBI expression were abolished in mice with EC‐directed deletion of FoxO (ΔFoxO). Our data indicate that sFRP1 and BAMBI are regulated reciprocally by FoxO1. The FoxO‐dependent regulation of Wnt and TGF‐β signalling pathways may contribute to establish an angiostatic microenvironment within ischemic muscle.