Channavajjhala Sarath K, Bramley Roger, Peltz Theresa, Oosthuyzen Wilna, Jia Wenjing, Kinnear Sue, Sampson Barry, Martin Nick, Hall Ian P, Bailey Matthew A, Dear James W, Glover Mark
Division of Therapeutics and Molecular Medicine, University of Nottingham, Nottingham, UK.
NIHR-Nottingham Biomedical Research Centre, Nottinghamshire, UK.
Kidney Int Rep. 2018 Sep 22;4(1):139-147. doi: 10.1016/j.ekir.2018.09.011. eCollection 2019 Jan.
Thiazide diuretics are among the most widely used antihypertensive medications worldwide. Thiazide-induced hyponatremia (TIH) is 1 of their most clinically significant adverse effects. TIH must result from excessive saliuresis and/or water reabsorption. We hypothesized that pathways regulating the thiazide-sensitive sodium-chloride cotransporter NCC and the water channel aquaporin-2 (AQP) may be involved. Our aim was to assess whether patients with TIH would show evidence of altered NCC and AQP expression in urinary extracellular vesicles (UEVs), and also whether abnormalities of renal sodium reabsorption would be evident using endogenous lithium clearance (ELC).
Blood and urine samples were donated by patients admitted to hospital with acute symptomatic TIH, after recovery to normonatremia, and also from normonatremic controls on and off thiazides. Urinary extracellular vesicles were isolated and target proteins evaluated by western blotting and by nanoparticle tracking analysis. Endogenous lithium clearance was assessed by inductively coupled plasma mass spectrometry.
Analysis of UEVs by western blotting showed that patients with acute TIH displayed reduced total NCC and increased phospho-NCC and AQP relative to appropriate control groups; smaller differences in NCC and AQP expression persisted after recovery from TIH. These findings were confirmed by nanoparticle tracking analysis. Renal ELC was lower in acute TIH compared to that in controls and convalescent case patients.
Reduced NCC expression and increased AQP expression would be expected to result in saliuresis and water reabsorption in TIH patients. This study raises the possibility that UEV analysis may be of diagnostic utility in less clear-cut cases of thiazide-associated hyponatremia, and may help to identify patients at risk for TIH before thiazide initiation.
噻嗪类利尿剂是全球使用最广泛的抗高血压药物之一。噻嗪类药物引起的低钠血症（TIH）是其最具临床意义的不良反应之一。TIH必定是由过度利尿和/或水重吸收引起的。我们推测，调节噻嗪类敏感的氯化钠共转运蛋白NCC和水通道水通道蛋白-2（AQP）的途径可能与之有关。我们的目的是评估TIH患者是否会在尿细胞外囊泡（UEV）中表现出NCC和AQP表达改变的证据，以及使用内源性锂清除率（ELC）是否能明显看出肾钠重吸收异常。
急性症状性TIH住院患者恢复至正常血钠水平后捐献血液和尿液样本，同时也采集服用和未服用噻嗪类药物的正常血钠对照组的样本。分离尿细胞外囊泡，通过蛋白质印迹法和纳米颗粒跟踪分析评估靶蛋白。通过电感耦合等离子体质谱法评估内源性锂清除率。
蛋白质印迹法分析UEV显示，与适当的对照组相比，急性TIH患者的总NCC减少，磷酸化NCC和AQP增加；从TIH恢复后，NCC和AQP表达仍存在较小差异。这些发现通过纳米颗粒跟踪分析得到证实。急性TIH患者的肾ELC低于对照组和恢复期患者。
NCC表达降低和AQP表达增加预计会导致TIH患者出现利尿和水重吸收。本研究提出了一种可能性，即UEV分析在不太明确的噻嗪类相关低钠血症病例中可能具有诊断价值，并可能有助于在开始使用噻嗪类药物之前识别有TIH风险的患者。
