Ps-b08-10: combination of systemic atrap deficiency with angiotensin ii stimulation accelerates the development of diabetic nephropathy in streptozotocin treated mice

Objective: One of the obstacles toward understanding the pathophysiology of diabetic nephropathy (DN) has been the lack of reliable animal models that faithfully replicate features of human DN. Angiotensin II (Ang II) type 1 receptor (AT1R)-associated protein (ATRAP) promotes internalization of AT1R from the cell surface into the cytoplasm, resulting in the suppression of AT1R signaling pathway. We have recently reported that systemic ATRAP deficiency exaggerates streptozotocin (STZ)-induced DN via an activation of renal renin-angiotensin system (RAS) (Haruhara K, et al. Kidney Int 2022). However, STZ-induced diabetic ATRAP knockout mice still exhibited a modest increase in albuminuria with limited pathological changes just in glomerulus. To establish more robust DN models, we examined the effect of Ang II stimulation on the development of DN in STZ-treated ATRAP knockout mice. Design and method: Male eight weeks old C57BL/6 mice (Ctrl) and systemic ATRAP-knockout mice (KO) were divided into three groups: 1) Ctrl-STZ, 2) Ctrl-STZ-Ang II, and 3) KO-STZ-Ang II. Hyperglycemia was induced by intraperitoneal injection of 55 mg/kg STZ for consecutive 5 days. From 4 weeks after STZ administration, Ang II (1000 ng/kg/min) was continuously administered by osmotic mini-pumps for 6 weeks. During the experimental period, body weights and levels of blood glucose were measured every 2 weeks. At 6 and 10 weeks after STZ administration, 24-hour urine samples were collected in metabolic cages, and urinary albumin excretion (UAE) was evaluated by ELISA. At the end of experimental period, mice were euthanized to evaluate renal pathological changes. Results: During the experimental period, body weight gain and levels of blood glucose were not significantly different between the three groups. Nonetheless, although levels of UAE at 6 weeks after STZ administration were still modest and comparable between the three groups, levels of UAE only in the KO-STZ-Ang II group were remarkably increased compared to those in the Ctrl-STZ and Ctrl-STZ-Ang II groups at 10 weeks after STZ administration (679.1 ± 583.7 vs 69.9 ± 10.0 vs 61.3 ± 8.2 μg/day, respectively). Furthermore, in the KO-STZ-Ang II group, exacerbation of mesangial expansion and interstitial fibrosis was observed. Conclusions: In STZ-induced diabetic mice, combination of systemic ATRAP deficiency with Ang II stimulation accelerated the development of DN, suggesting a potential to become a promising mouse model replicating key features of human DN.