HIF3A and pulmonary arterial hypertension: Foxf1 has been reported to be down-regulated in mice with endothelial cell-specific deletion of Foxm1[35], indicating a reciprocal feedback loop between Foxf1 and Foxm1. Finally, up-regulation of Hif3α and Nos3 is also observed, suggesting a compensatory mechanism to counteract the effects of hypoxia-induced pulmonary hypertension.