Endothelin-1 (ET-1), the most abundant protein of the endothelin family (ET-1, ET-2 and ET-3), is a 21-amino-acid long potent vasoconstrictor peptide that plays a pathophysiological role in various cardiovascular diseases including pulmonary arterial hypertension and atherosclerosis, as well as non-cardiovascular inflammatory diseases such as inflammatory bowel disease [39,40], rheumatoid arthritis [41,42,43] and SLE [44]. The gene discussed is EDN1; the disease is rheumatoid arthritis.