Hypoxia-inducible factor 1 in lower limb ischemia

In the Western world, peripheral vascular disease (PVD) has a high prevalence and is associated with high morbidity and mortality. More patients are presenting with critical limb ischemia (CLI), the end stage of PVD, because of an increased life expectancy owing to improved medical care. In a large percentage of these patients, lower limb amputation is still required, despite current advances in surgery and interventional radiology. Studies of ischemic skeletal muscles disclosed evidence of endogenous angiogenesis and adaptive skeletal muscle metabolic changes in response to hypoxia. Many of the genes responsible for these responses are regulated by hypoxia-inducible factor (HIF)-1. HIF-1, consisting of HIF-1 alpha and HIF-1 beta subunits, is a major transcription factor that functions as a master regulator of oxygen homeostasis that plays essential roles in cellular and systemic pathophysiology. HIF-1 alpha expression and HIF-1 transcriptional activity increase exponentially as cellular oxygen concentration is decreased. More than 60 target genes that are transactivated by HIF-1 have been identified. Many of the target genes, such as vascular endothelial growth factor, have been studied extensively, especially in tumors. However, only recently that interest in HIF-1 is growing in relation to ischemic diseases. Most of the studies concentrated mainly on the angiogenic property of HIF-1. In contrast, there is a lack of information on the role of HIF-1 in skeletal muscle metabolic adaptive changes as the end-organ in PVD. This review aims to summarize our current understanding of HIF-1 roles and the therapeutic potential in PVD.