Urinary endothelin-1 in chronic kidney disease and as a marker of disease activity in lupus nephritis

1 Clinical Pharmacology Unit and 2 Centre for Inflammation Research, University of Edinburgh, The Queen's Medical Research Institute, Edinburgh; and 3 Department of Renal Medicine, Royal Infirmary of Edinburgh, Edinburgh, United Kingdom Submitted 27 November 2008 ; accepted in final form 9 March 2009 Chronic inflammation contributes to the development and progression of chronic kidney disease (CKD). Identifying renal inflammation early is important. There are currently no specific markers of renal inflammation. Endothelin-1 (ET-1) is implicated in the pathogenesis of CKD. Thus, we investigated the impact of progressive renal dysfunction and renal inflammation on plasma and urinary ET-1 concentrations. In a prospective study, plasma and urinary ET-1 were measured in 132 subjects with CKD stages 1 to 5, and fractional excretion of ET-1 (FeET-1) was calculated. FeET-1, serum C-reactive protein (CRP), urinary ET-1:creatinine ratio, and urinary albumin:creatinine ratio were also measured in 29 healthy volunteers, 85 subjects with different degrees of inflammatory renal disease but normal renal function, and in 10 subjects with rheumatoid arthritis without renal involvement (RA). In subjects with nephritis associated with systemic lupus erythematosus (SLE), measurements were done before and after 6 mo of treatment. In subjects with CKD, plasma ET-1 increased linearly as renal function declined, whereas FeET-1 rose exponentially. In subjects with normal renal function, FeET-1 and urinary ET-1:creatinine ratio were higher in SLE subjects than in other groups (7.7 ± 2.7%, 10.0 ± 3.0 pg/µmol, both P < 0.001), and correlated with CRP, and significantly higher than in RA subjects (both P < 0.01) with similar CRP concentrations. In SLE patients, following treatment, FeET-1 fell to 3.6 ± 1.4% ( P < 0.01). Renal ET-1 production increases as renal function declines. In subjects with SLE, urinary ET-1 may be a useful measure of renal inflammatory disease activity while measured renal function is still normal. systemic lupus erythematosus; renal inflammation; biomarker Address for reprint requests and other correspondence: N. Dhaun, The Queen's Medical Research Institute, 3rd Floor East, Rm. E3.23, 47 Little France Crescent, Edinburgh, EH16 4TJ, United Kingdom (e-mail: bean.dhaun{at}ed.ac.uk )