Urinary excretion of the water channel aquaporin 2 correlated with the pharmacological effect of tolvaptan in cirrhotic patients with ascites

Nakanishi, Hiroyuki; Kurosaki, Masayuki; Hosokawa, Takanori; Takahashi, Yuka; Itakura, Jun; Suzuki, Shinichi; Yasui, Yutaka; Tamaki, Nobuharu; Nakakuki, Natsuko; Takada, Hitomi; Higuchi, Masakazu; Komiyama, Yasuyuki; Yoshida, Teruo; Takaura, Kenta; Hayashi, Tsuguru; Kuwabara, Konomi; Sasaki, Sei; Izumi, Namiki

doi:10.1007/s00535-015-1143-3

Cited by 36 publications

(39 citation statements)

References 36 publications

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“…The response rate of tolvaptan ranged from 25.0 to 62.5% in the previous reports [13][14][15][16][17][18]. Our findings are similar to those of previous reports.…”

Section: Discussionsupporting

confidence: 83%

Positive Response to Tolvaptan Treatment Would Be a Good Prognostic Factor for Cirrhotic Patients with Ascites

Kida¹

2019

Dig Dis

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Aims: Ascites is one of the major complications in advanced cirrhotic patients. Tolvaptan is a non-peptide orally available arginine vasopressin V2 receptor antagonist. We investigated and found that tolvaptan therapy improved the prognosis and predictive factor of cirrhotic patients with ascites. Methods: Overall, 99 patients with newly diagnosed ascites with cirrhosis were enrolled. No patients had intrahepatic malignancy. The patients were divided into 2 groups based on tolvaptan therapy: 86 patients treated with tolvaptan (tolvaptan-group) and 13 patients treated without tolvaptan (non-tolvaptan-group). Tolvaptan-responder was defined as body weight loss of ≥1.5 kg/week after administering tolvaptan. Results: Tolvaptan therapy was effective in 61.6% of cirrhotic patients. There was a significant difference in the overall survival (OS) between the tolvaptan-responder-group and the other groups (p < 0.001). Male (HR 5.05; p = 0.01), tolvaptan responder (HR 0.21; p = 0.02), and dosage of furosemide < 40 mg/day (HR 0.17; p = 0.01) were factors that were independently associated with the OS. The multivariate analysis revealed that C-reactive protein < 0.9 mg/dL (HR 0.07; p = 0.001), and furosemide dosage < 40 mg/day (HR 0.09; p = 0.003) were independently associated with the tolvaptan response. Conclusion: Therapeutic response to tolvaptan was associated with longer survival in cirrhosis patients complicated with ascites. These preliminary findings warrant validation and further exploration.

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“…The response rate of tolvaptan ranged from 25.0 to 62.5% in the previous reports [13][14][15][16][17][18]. Our findings are similar to those of previous reports.…”

Section: Discussionsupporting

confidence: 83%

Positive Response to Tolvaptan Treatment Would Be a Good Prognostic Factor for Cirrhotic Patients with Ascites

Kida¹

2019

Dig Dis

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“…AQP2 is excreted in the urine, and most urinary AQP2 is embedded in membranes of extracellular vesicles (EVs) [4,5,6]. Urine AQP2 may serve as a biomarker for water balance disorders, including congestive heart failure and liver cirrhosis [7,8,9,10]. In a previous study [11], we found that urine samples stored at 4 °C or −80 °C did not show significant AQP2 values, whereas those stored at −25 °C showed stable values in enzyme-linked immunosorbent assay (ELISA) measurement.…”

Section: Introductionmentioning

confidence: 99%

Disruption of Membranes of Extracellular Vesicles Is Necessary for ELISA Determination of Urine AQP2: Proof of Disruption and Epitopes of AQP2 Antibodies

Nameta

Saijo

Ohmoto

et al. 2016

IJMS

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Aquaporin-2 (AQP2) is present in urine extracellular vesicles (EVs) and is a useful biomarker for water balance disorders. We previously found that pre-treatment of urine with alkali/detergent or storage at −25 °C is required for enzyme-linked immunosorbent assay (ELISA) measurement. We speculated that disruptions of EVs membranes are necessary to allow for the direct contact of antibodies with their epitopes. Human urine EVs were prepared using an ultracentrifugation method. Urine EV samples were stored at different temperatures for a week. Electron microscopy showed abundant EVs with diameters of 20–100 nm, consistent with those of exosomes, in normal urine, whereas samples from alkali/detergent pre-treated urine showed fewer EVs with large swollen shapes and frequent membrane disruptions. The abundance and structures of EVs were maintained during storage at −80 °C, but were severely damaged at −25 °C. Binding and competitive inhibition assays showed that epitopes of monoclonal antibody and polyclonal antibody were the hydrophilic Loop D and C-terminus of AQP2, respectively, both of which are present on the inner surface of EVs. Thus, urine storage at −25 °C or pre-treatment with alkali/detergent disrupt EVs membranes and allow AQP2 antibodies to bind to their epitopes located inside EVs.

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“…Thus, in turn, it could serve as a useful biomarker for diagnosis and prognosis of such diseases [3,4]. Kanno et al [5] for the first time identified the presence of AQP2 in human urine.…”

Section: Introductionmentioning

confidence: 99%

AQP2 in human urine is predominantly localized to exosomes with preserved water channel activities

et al. 2018

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Background AQP2 water channel is critical for urinary concentration in the kidney. Interestingly, AQP2 is abundantly excreted in the urine as extracellular vesicles (EVs), which is known to be a useful biomarker for water-balance disorders although the character of AQP2-enriched EVs is poorly understood including water channel function. Methods Human urine EVs were obtained by a differential centrifugation method. AQP2-bearing EVs were isolated by immunoprecipitation with an AQP2-specific antibody, and the proteins in the EVs were analyzed by LC-MS/MS proteomic analysis. Osmotic water permeability (Pf) of the AQP2-rich EVs was measured by a stopped-flow method monitoring scattered light intensity in response to outwardly directed osmotic gradient. Results Sequential centrifugation of human urine showed that AQP2 was present predominantly (80%) in low-density EVs (160,000 g), whereas negligible amount in high-density EVs (17,000 g). Proteomic analysis of the AQP2-bearing EVs identified 137 proteins, mostly in the endosome pathway, including the components of ESCRT (endosomal sorting complex required transporter)-I, II, III. Pf value of the 160,000 g EVs was 4.75 ± 0.38 × 10 −4 cm s −1 (mean ± SE) with the activation energy of 3.51 kcal mol −1 which was inhibited with 0.3 mM HgCl 2 by 63%, suggesting a channel-mediated water transport. Moreover, Pf value showed a significant correlation with the abundance of AQP2 protein in EVs. Conclusion Taken together, AQP2 is localized predominantly to urinary exosomes with preserved water channel activities.

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Urinary excretion of the water channel aquaporin 2 correlated with the pharmacological effect of tolvaptan in cirrhotic patients with ascites

Abstract: These results indicate that the vasopressin-AQP2 system plays a major role in fluid retention in cirrhosis and that the pharmacological effect of tolvaptan to inhibit water reabsorption can be monitored by measurement of the dynamics of urinary AQP2 levels.

Cited by 36 publications

References 36 publications

Positive Response to Tolvaptan Treatment Would Be a Good Prognostic Factor for Cirrhotic Patients with Ascites

Positive Response to Tolvaptan Treatment Would Be a Good Prognostic Factor for Cirrhotic Patients with Ascites

Disruption of Membranes of Extracellular Vesicles Is Necessary for ELISA Determination of Urine AQP2: Proof of Disruption and Epitopes of AQP2 Antibodies

AQP2 in human urine is predominantly localized to exosomes with preserved water channel activities

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