Editorial: The CXCR4 Ligand/Receptor Family and the DPP4 Protease in High-Risk Cardiovascular Patients

Cardiovascular disease (CVD) is the most common cause of morbidity and mortality worldwide and was responsible for 17.5 million deaths in 2012. This equals 31% of all deaths globally and is almost double the amount of cancer-related deaths (1). Although CVD encompasses a broad range of pathologic conditions, 80% of all CVD-related deaths are due to heart attacks and stroke (1). An important underlying pathology is atherosclerosis, a chronic inflammatory state of the arterial wall that is characterized by lipid deposition, dysfunction of the endothelium, and infiltration of inflammatory cells into the vessel wall, resulting in the development of atherosclerotic lesions (2). Type 2 diabetes mellitus (T2DM) and chronic kidney disease (CKD) have been identified as important risk factors for CVD. Fifty percent of patients with CKD stages 4–5 suffer from CVD (3), and cardiovascular mortality accounts for ~40–50% of all deaths in these patients, compared with 26% in controls with normal kidney function (4, 5). Also in patients with diabetes, CVD accounts for at least 50% of deaths (6). With currently around 10–13% of people presenting with CKD and more than 8% of adults suffering from diabetes (6–8), the social and economic burden of diabetes, CKD, and CVD is extremely high. Thus, a better understanding of the mechanisms contributing to and mediating the interplay between T2DM, CKD, and CVD is required to improve the prevention and treatment of these diseases. In this Research Topic, we focus on the classical CXC chemokine receptor CXCR4 (9), its cognate ligand CXCL12 (10), and the chemokine-like cytokine macrophage migration inhibitory factor (MIF), which functions as a non-cognate ligand of CXCR4 (11), in the context of CVD. An emphasis is made on links with T2DM and CKD. Also, we discuss dipeptidyl peptidase-4 (DPP4) as an important protease known to destabilize CXCL12 and thus to influence signaling through the CXCL12/CXCR4 axis. Chemokines and their receptors are important mediators of cell mobilization, recruitment and arrest, and additionally more broadly induce cell activation by triggering various intracellular signaling tracks. Chemokines control basic homeostatic conditions but are also critically involved in inflammatory processes, e.g., in atherosclerosis (12, 13). Genome-wide association studies revealed single nucleotide polymorphisms connecting CXCL12 as well as MIF with CVD (2, 14–19), and a role for both of these mediators in T2DM and CKD has been reported. In this Research Topic, we introduce the reader to the comorbidities T2DM