Macula Densa NOS1 Protects Against Acute Kidney Injury (AKI) Mediated by Primary Cilia

Abstract

We hypothesize ischemia‐reperfusion induced AKI damages primary cilia on the MD and reduces NOS1 activity. After 18 min of bilateral ischemia‐reperfusion injury (IRI) in C57BL/6 mice (WT), the number and length of primary cilia were decreased. When increasing tubular flow in isolated JGA, NO (unit/min) in the MD was elevated from 120.2±21.5 to 164.0±13.8 in control, and from 72.3±15.6 to 86.4±14.7 after AKI. In cultured MD cells, elevating flow increased NO from 174.8 ± 21.5 to 276.1 ± 24.3, while no effect when cilia were removed by siRNA(48.6 ± 17.5 vs. 62.7 ± 15.2). Two strains of NKCC2‐tissue‐specific KO mice we developed (Cilia KO in which the primary cilia on the MD and thick ascending limb were deleted and the NOS1 KO in which all splice variants of NOS1 in the MD were deleted) received IRI. After 24 hrs, plasma creatinine (mg/dl) was 0.075±0.03 in sham, 0.56±0.02 in WT, 1.25±0.05 in Cilia KO and 0.89±0.03 in NOS1 KO. Urine KIM‐1(pg/24h) was 10.7±2.9 in sham, 31.2±5.5 in WT, 274.7±9.3 in Cilia KO and 1340.3±362.2 in NOS1 KO. Morphologically, we observed mild injury in WT and more severe cortical injury in both the Cilia KO and NOS1 KO while no injury in sham. Tubuloglomerular feedback (TGF) was enhanced (4.5±0.3 vs 8.4±0.7 mmHg) and NO in the MD was absent in intact NOS1 KO compared with WT. We conclude renal IRI damages cilia and reduces NO; KO of cilia/NOS1 exacerbates AKI probably via enhanced TGF. (R01‐HL086767 AHA11POST7750023)