Expression Pattern of Renal Transporters in Urinary Exosomes of Patients with Edematous States

Abstract

BackgroundEdema formation in patients with chronic liver, heart or kidney disease is associated with salt and water retention by the kidneys. The molecular pathways in the nephron that lead to this event in humans remain elusive. Furthermore, the pattern of salt retention pathways enhanced can be different depending on the type of edematous state. The use of urinary exosomes (UE) is a powerful non‐invasive tool to study the pathophysiological state of the kidney in many diseases and its potential as a diagnostic tool for assessment of human samples is rising. The objective of our study was to assess the expression of different renal transporters in urinary exosomes of patients with chronic failure of the heart, the liver or the kidney, with and without edema.MethodsWe conducted a prospective and observational study where we obtained clinical and biochemical data, as well as urinary samples from adult patients with liver cirrhosis (Child B–C) (N=9 with, N=10 no‐edema), chronic kidney disease (CKD; KDIGO G3–G4) (N=9 with, N=18 no‐edema), chronic heart failure (NYHA II–III) (N=5 with, N=5 no‐edema), and healthy volunteers (N=4) as the control group. We isolated UE from 8 ml of urine with a two‐step ultracentrifugation process and analyzed with western blot the expression of SGLT2, NHE3, NKCC2, NCC and αENaC. The amount of UE used per patient was adjusted to urinary creatinine.ResultsWe found no significant differences in laboratory findings of cirrhotic patients with or without edema, except for lower serum Na+ in the edema group (133.9±4.9 vs. 140.1±2.1 mEq/l p<0.05). In CKD patients, however, we found differences in the BMI (31±6.9 vs. 25±3 p<0.01), serum K+ (5.2±0.39 vs. 4.6±0.55 mEq/l p<0.01) and Ca2+ (8.6±0.47 vs. 9.3±0.75 mg/dl p<0.05) in the edema vs. no‐edema group, respectively. In heart failure patients we observed differences in serum Na+ (133.8±4.9 vs. 138.6±4.4 mEq/l, p<0.05). Analysis of UE showed a significant increase of SGLT2 and NHE3 expression in cirrhotic patients with edema and in heart failure patients with and without edema, when compared to control group. Patients with heart failure also exhibited increased expression of NKCC2 and αENaC. Interestingly, in both cirrhotic and heart failure patients NCC expression was down‐regulated. In CKD patients, we observed increased expression of SGLT2, NHE3 and αENaC.DiscussionCompared to healthy volunteers, all pathological conditions have upregulation of certain renal transporters. We observed different expression patterns of UE for each pathologic state. Decreased expression of NCC seems to be a compensatory mechanism. These results suggest that the analysis of renal transporters using UE can give insights into the molecular mechanisms of salt retention in patients with edematous states and may contribute to the design of early therapeutic strategies.Support or Funding InformationConacyt‐Fosiss grant No. 261562 to GGThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.