722.3 - Kidney-Specific BMAL1 Knockout is Protective in High Salt Diet-Induced Renal Inflammation

Gene Crislip (University of Florida, University of Florida), Hannah Costello (University of Florida, University of Florida), Alexandria Juffre (University of Florida, University of Florida), Kit-Yan Cheng (University of Florida), Charles Wingo (University of Florida, University of Florida, University of Florida), Yogesh Scindia (University of Florida), Michelle Gumz (University of Florida, University of Florida, University of Florida)

The circadian clock factor BMAL1, particularly within the kidney, has been shown to influence systemic blood pressure (BP) control. A diet high in salt is linked to immune cell infiltration in the kidney and development of hypertension. Previously, we generated renal distal segment BMAL1 knockout mice (KS-BMAL1 KO) using Ksp-cadherin Cre. Male KS-BMAL1 KO exhibit lower BP than control floxed BMAL1 Cre negative mice (CNTL). In this study, we tested the effect of a low potassium, high salt (0KHS; 4% NaCl) diet in order to determine if KS-BMAL1 KO are protected from salt-sensitive hypertension. The goal of this study was to test the hypothesis that male KS-BMAL1 KO display reduced BP and a lower renal inflammatory phenotype than CNTL in response to a 0KHS diet. BP was measured via telemeter implants (N=7-8). Panels of inflammatory and injury markers were measured using Millipore multiplex immunoassay kits in renal cortical and medullary tissue from KS-BMAL1 KO and CNTL on a normal diet and following 10 days of 0KHS diet (N=6-7). Additionally, whole kidney tissue from mice treated with 0KHS for 10 days was digested and flow cytometric analysis was performed (N=5-6). KS-BMAL KO did not exhibit the increase in BP as seen in control mice following 0KHS (CNTL: 125±2 to 132±1; KO: 123±2 to 122±2 mmHg; Interaction Plt;0.05). CNTL had a greater increase in cortical Kidney Injury Molecule-1 levels following 0KHS than KS-BMAL1 KO (CNTL: 31±5 to 975±103; KO: 20±6 to 651±61 pg/mg; Interaction P=0.02). Additionally, CNTL displayed a greater increase in cortical interleukin (IL) 6 following 0KHS than CNTL (CNTL: 0.5±0.04 to 9±1; KO: 0.4±0.07 to 5±0.9 pg/mg; Interaction P=0.04). Medullary IL6 levels were more than 15 times greater following 0KHS but no genotype effect was seen. Although cortical interferon gamma (IFNγ) levels increased more than 8-fold following 0KHS, there were no differences between genotypes. However, CNTL had a greater increase in cortical IL17 following 0KHS than CNTL (CNTL: 0.8±0.03 to 2.5±0.2; KO: 0.8±0.04 to 1.9±0.1 pg/mg; Interaction P=0.01). CNTL also had greater medullary IL17. Furthermore, CNTL had nearly 2 times greater CD45+ total leukocytes and neutrophils than KS-BMAL1 KO following 0KHS. BMAL1 in renal distal segments contributes to BP regulation. Additionally, KS-BMAL1 KO exhibit a reduced proinflammatory phenotype following 0KHS compared to CNTL. These data suggest that BMAL1 may play a role in the renal inflammatory response to 0KHS. Whether BMAL1 protects against inflammation because of or in addition to the lower BP phenotype remains to be determined.

NIH/NIDDK 1R01DK109570-01A1, NIH/NIDDK 1F32DK121424-01A1, 19POST34450134 AHA Postdoc Fellowship, 5T32HL083810-10, Gatorade Trust through the UF Department of Medicine, North Florida/South Georgia Veterans Health Systems