CHARACTERIZATION OF BRAIN DAMAGE AFTER ACUTE KIDNEY INJURY

Background and Aims Acute kidney injury (AKI) is a very common condition in inpatients. Severe AKI is frequently associated with by neurological disorders such as confusion, the mechanisms of which are poorly understood. We have shown in several animal models that chronic kidney disease is associated with impaired cognitive performance such as memory and increased permeability of the blood-brain barrier (BBB), related to the accumulation of uremic toxin indoxyl sulfate. The goal of these experiments was to highlight the influence of AKI on cerebral impairment in mice, particularly the BBB permeability, and to describe the mechanisms involved. Method We performed an AKI in C57/Bl6 WT mice, by unilateral nephrectomy and transient ischemia-reperfusion of the remaining kidney for 20 minutes (RIRI20 group) and compared them to two other groups: control mice and mice with unilateral ischemia-reperfusion without nephrectomy (IR20). Modified neurological severity score (mNSS) was performed daily. BBB permeability was assessed by quantification of the Evans Blue leakage in the brain and by cerebral 68Ga-DTPA TEP/CT imaging. Cerebral immuno-histochemistry was performed to evaluate the neuro-inflammatory processes. Results Glomerular filtration rate at Day 1 was lower in AKI group compared to the control group 0.21 ± 0.26 vs. 0.94 ± 0.13 mL/min/100g b.w (p<0.0001) and IR group: 0.75 ± 0.17 mL/min/100g b.w (p = 0.0007). Mice with AKI displayed a neurological impairment at day 1 and day 2 post-AKI, compared to control mice and IR20 mice, with mainly an impairment of the balance. Mean mNSS score at Day 1 was 2.6 ± 4.5 in AKI group, and 0.0 ±-0.0 in both the control and IR groups (p = 0.002). BBB permeability at Day 2 was higher in the AKI group than in the control group (p = 0.10) and the IR group (p = 0.0006) by Evans blue staining. Cerebral TEP imaging found similar results with increased BBB permeability in AKI mice to compared to control mice at D1 and D2 (p = 0.004 and p = 0.009, respectively). On immunohistochemistry, brains of mice after AKI displayed more astrocytosis and microglial activation compared to brains of control mice. Conclusion AKI in mice is specifically associated with early neurological damage, unlike renal ischemia-reperfusion alone, related to a BBB disruption in the first two days after AKI. AKI appears to induce astrocytosis and altered microglial phenotype, potentially due to increased neuroinflammatory processes following BBB disruption.