Hepatic and renal expression of Oatp1 in obstructive uropathy. First detection of Oatp1 in urine, a potential biomarker

Abstract

Obstructive nephropathy is a relatively common urological problem, which can occur as a consequence of a variety of conditions, such as abnormal ureteral structures, polyps, vesicoureteral reflux or nephrolithiasis. The obstruction of both ureters is a situation especially severe because of its physiological consequences; excessive salt and water loss, urine concentrating defects and alterations in the tubular handling of metabolites of endogenous and exogenous origin. [1][2][3] The renal excretion pathway of many drugs may be compromised during obstructive nephropathy. Although the liver may complement the depurating function of the kidneys, becoming an alternative pathway for the elimination of specific compounds, the relationship between renal and hepatic excretion routes depend on the structural and functional integrity of both organs. It has been observed that the hepatic extraction of some clinical important drugs is significantly decreased in rats with obstructive nephropathy. [4][5][6] Despite this, the effects of obstruction of the ureters on liver function remain a limited area of knowledge.

Novel Finding of Urinary Erythropoietin as an Early Biomarker of Cisplatin-Induced Nephrotoxicity

“…Studies performed in our laboratory using animal experimental models of renal pathologies have proposed different proteins as urinary AKI biomarkers. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] In cisplatininduced AKI (the experimental model employed in the present work), urinary Oat5 was proposed as a diagnostic, as an early biomarker, and as a biomarker for treatment monitorization, and urinary Cav2 was claimed to be useful as a biomarker of renal recovery. [18][19][20]28 In this connection, urinary Epo has similar behaviour to Oat5 as a diagnostic and as an early biomarker of cisplatin nephrotoxicity, while its application as a biomarker for treatment monitorization remains to be studied.…”

“…Ponceau Red was employed to verify equal protein loading and transfer between lanes as was broadly described. [18][19][20][21][22][23][24][25][26][27][28][29]32 The membranes were later incubated for 1 h with 5% non-fat dry milk (5% in phosphate-buffered saline containing 1% Tween 20) and after that, incubated overnight at 4°C with a commercial mouse monoclonal antibody against rat and human Epo (1/800) or with a commercial mouse monoclonal antibody against rat NGAL (1/4000), as appropriate. Subsequently, the membranes were incubated with a peroxidase coupled sheet antimouse IgG (Amersham, Buckinghamshire, UK) for 1 h. To detect the signal, the blots were processed with a commercial kit (ECL enhanced chemiluminescence system, Amersham, Buckinghamshire, UK).…”

“…To correct for variations in urine production, Epo and NGAL abundances in urine were expressed as optical density (O.D., arbitrary units) related to urinary creatinine concentration (Cr u ) using the equation [O.D./Vu/Cr u ] (Vu: volume of urine sample used in the electrophoresis, 10 uL in this work), as previously reported for different urinary proteins. [18][19][20][21][22][23][24][25][26][27][28][29] The value obtained was finally expressed as a percentage of the mean value from the control group. As molecular mass indicators, Kaleidoscope Prestained Standards were employed (Bio-Rad Laboratories, Hercules, CA, USA).…”

“…Among them, we can name the Organic Anion Transporter 5 (Oat5), Aquaporin-2 (AQP2), Na-K-2Cl-cotransporter (NKCC2), Caveolin-2 (Cav2), Sodium-dependent Dicarboxylate Cotransporter 1 (NaDC1), and Organic Anion Transporting Polypeptide 1 (Oatp1). [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] Therefore, based on our previous experience in urinary biomarkers of kidney damage, and taking into account the little information available about the role of endogenous Epo in urine, the aim of this study was to evaluate the presence of endogenous Epo in rat urine and to analyse possible changes in urinary Epo levels in response to nephrotoxic injury induced by cisplatin.…”

Extracellular Vesicles as Surrogates for Drug Metabolism and Clearance: Promise vs. Reality

“…Additionally, the presence of Oatp1A1 (Slco1A1) was demonstrated in urine from rats with bilateral ureteral obstruction (i.e., model of obstructive nephropathy). The protocol used by the authors was based on the western blot analysis of urine samples after clearing the urine by centrifugation at 3000 g [ 65 ]. In this regard, although membrane proteins carried by urinary EVs have been already detected by antibody-based methods in urinary samples subject to a similar preparation (i.e., without prior EV enrichment) [ 66 ], the specific confirmation of the localization of OATP1A1 in EVs is still missing (e.g., by colocalization with EV markers) [ 65 ].…”