Tingskov Stine Julie, Choi Hyo-Jung, Holst Mikkel R, Hu Shan, Li Chunling, Wang Weidong, Frøkiær Jørgen, Nejsum Lene N, Kwon Tae-Hwan, Nørregaard Rikke
Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.
Department of Biochemistry and Cell Biology, School of Medicine, Kyungpook National University, Daegu, South Korea.
Front Physiol. 2019 Aug 9;10:948. doi: 10.3389/fphys.2019.00948. eCollection 2019.
Arginine vasopressin (AVP) mediates water reabsorption in the kidney collecting ducts through regulation of aquaporin-2 (AQP2). Also, estrogen has been known to regulate AQP2. Consistently, we previously demonstrated that tamoxifen (TAM), a selective estrogen receptor modulator, attenuates the downregulation of AQP2 in lithium-induced nephrogenic diabetes insipidus (NDI). In this study, we investigated the AVP-independent regulation of AQP2 by TAM and the therapeutic effect of TAM on the dysregulation of AQP2 and impaired urinary concentration in a unilateral ureteral obstruction (UUO) model. Primary cultured inner medullary collecting duct (IMCD) cells from kidneys of male Sprague-Dawley rats were treated with TAM. Rats subjected to 7 days of UUO were treated with TAM by oral gavage. Changes of intracellular trafficking and expression of AQP2 were evaluated by quantitative PCR, Western blotting, and immunohistochemistry. TAM induced AQP2 protein expression and intracellular trafficking in primary cultured IMCD cells, which were independent of the vasopressin V2 receptor (V2R) and cAMP activation, the critical pathways involved in AVP-stimulated regulation of AQP2. TAM attenuated the downregulation of AQP2 in TGF-β treated IMCD cells and IMCD suspensions prepared from UUO rats. TAM administration attenuated the downregulation of AQP2, associated with an improvement of urinary concentration in UUO rats. In addition, TAM increased CaMKII expression, suggesting that calmodulin signaling pathway is likely to be involved in the TAM-mediated AQP2 regulation. In conclusion, TAM is involved in AQP2 regulation in a vasopressin-independent manner and improves urinary concentration by attenuating the downregulation of AQP2 and maintaining intracellular trafficking in UUO.
精氨酸加压素（AVP）通过调节水通道蛋白2（AQP2）介导肾脏集合管对水的重吸收。此外，已知雌激素可调节AQP2。与此一致的是，我们之前证明，他莫昔芬（TAM），一种选择性雌激素受体调节剂，可减轻锂诱导的肾性尿崩症（NDI）中AQP2的下调。在本研究中，我们调查了TAM对AQP2的非AVP依赖性调节以及TAM对单侧输尿管梗阻（UUO）模型中AQP2失调和尿浓缩受损的治疗作用。用TAM处理来自雄性Sprague-Dawley大鼠肾脏的原代培养的髓质内集合管（IMCD）细胞。对接受7天UUO的大鼠通过灌胃给予TAM。通过定量PCR、蛋白质印迹和免疫组织化学评估AQP2的细胞内转运和表达变化。TAM诱导原代培养的IMCD细胞中AQP2蛋白表达和细胞内转运，这独立于加压素V2受体（V2R）和cAMP激活，这是AVP刺激调节AQP2所涉及的关键途径。TAM减轻了TGF-β处理的IMCD细胞和从UUO大鼠制备的IMCD悬浮液中AQP2的下调。给予TAM可减轻AQP2的下调，这与UUO大鼠尿浓缩的改善相关。此外，TAM增加了CaMKII的表达，表明钙调蛋白信号通路可能参与TAM介导的AQP2调节。总之，TAM以非加压素依赖性方式参与AQP2调节，并通过减轻AQP2的下调和维持UUO中的细胞内转运来改善尿浓缩。
