Ps-b01-11: generation of transgenic mice with proximal tubule-specific overexpression of atrap and analysis of proximal tubule atrap in blood pressure regulation

Objective: Proximal tubule angiotensin II type 1 receptor (AT1R) is involved in blood pressure (BP) regulation (Li XC, et al. Hypertension, 77:1285-1298, 2021). AT1 receptor-associated protein (ATRAP) interacts with AT1R and promotes constitutive internalization of AT1R, to inhibit pathological activation of its downstream signaling (Tamura K, et al. Hypertens Res, 45:32–39, 2022). Endogenous ATRAP is abundantly expressed along kidney tubules in the kidney, and our previous investigations using systemic ATRAP knockout and distal tubule-dominant ATRAP transgenic mice revealed that ATRAP suppressed Ang II-induced hypertension mainly through a distal tubule-mediated mechanism (Wakui H, et al. Hypertension, 61:1203–10, 2013; Ohsawa M, et al. Kidney Int, 86:570–81, 2014). On the other hand, proximal tubule-specific ATRAP knockout mice exhibited similar baseline BP and pressor response to Ang II compared with wild-type mice (Kinguchi S, et al. J Am Heart Assoc, 8(8):e012395, 2019). The present study was performed to investigate the effects of enhancement of proximal tubule ATRAP on Ang II-mediated hypertension, using proximal tubule-specific ATRAP transgenic mice. Design and method: [Experiment 1] Using mouse ATRAP cDNA linked to the type II sodium-dependent phosphate cotransporters (NPT2) promoter, we generated transgenic mice (NPT2-Tg mice) with proximal tubule-specific overexpression of ATRAP. ATRAP mRNA expression in the proximal tubule was quantified by a laser capture microdissection and quantitative reverse transcription-polymerase chain reaction analysis. [Experiment 2] Male NPT2-Tg and wild-type littermate control (LC) mice were divided into Ang II (1000 ng/kg/min) and vehicle groups. BP was measured using a tail-cuff method before and 14 days after treatment, and then mice were sacrificed and their organs were collected. Results: [Experiment 1] 5 of 12 lines of ATRAP Tg mice exhibited kidney overexpression of the ATRAP-transgene in comparison with LC mice. Kidney ATRAP expression at the protein level revealed the highest expression level of ATRAP in lines 23, approximately 10-fold higher compared to LC mice. Therefore, we chose line 23 (NPT2-Tg23) for further analysis. ATRAP mRNA expression was increased approximately 9-fold in the proximal tubules of NPT2-Tg23 mice compared with LC mice. On the other hand, ATRAP mRNA expression in the distal tubules was comparable between NPT2-Tg23 and LC mice. [Experiment 2] We are currently conducting the experiments and will present our findings at this conference. Conclusions: We succeeded in generating transgenic mice with proximal tubule-specific overexpression of ATRAP. We plan to present the results of the impact of enhancement of proximal tubular ATRAP on Ang II-dependent hypertension at this conference.