Physiological Omics Identifies Mechanisms that Attenuate Renal Injury and Blood Pressure in Dahl salt‐sensitive Arhgef11 −/− Rats

Arhgef11 is a Rho guanine nucleotide exchange factor previously implicated in kidney injury in the Dahl salt‐sensitive rat (SS‐WT). Through exchange of GDP for GTP, Arhgef11 regulates cytoskeletal structure, function, and cell‐cell contacts through a variety of stimuli (e.g., G‐protein coupled receptors, growth factors, and shear stress). Genetic studies and reduced Arhgef11 expression in an SS‐ Arhgef11 SHR ‐minimal congenic strain (SHR allele substituted for S allele) significantly decreased proteinuria, fibrosis, and improved renal hemodynamics, without impacting BP compared to the SS‐WT. We hypothesized that actin cytoskeleton regulation through Arhgef11 impacts functional changes in protein reuptake and sodium handling in proximal tubules. Here, we studied the SS‐ Arhgef11 −/− rat model at 4–12 weeks of age under low and high salt (0.3% or 2% NaCl). On low‐salt, starting at week 6 and continuing through week 12, SS‐ Arhgef11 −/− animals (n=17) demonstrated significantly reduced proteinuria (week 6, −43.9.0 ± 13.6 mg/24 hours, p=0.0079 and week 12, −102.8 ± 13.6, p<0.0001) compared to SS‐WT animals (n=16). On high‐salt, beginning at week 6, SS‐ Arhgef11 −/− animals (n=15) demonstrated a significant attenuation of proteinuria from weeks 8 to 12 (week 8, −83.9.0 ± 13.9 mg/24 hours, p<0.0001 and week 12, −118.2 ± 13.9, p<0.0001), along with a substantial reduction in BP (week 12, −42 ± 5 mm Hg, p<0.0001) compared to SS‐WT (n=17). Kidney pathology indices were all significantly improved in SS‐ Arhgef11 −/− compared to SS‐WT animals (all p<0.05), including glomerular injury/hypertrophy, tubulointerstitial injury/fibrosis, and immune cell infiltration (via flow cytometry). To better understand the molecular mechanisms associated with renal protection from loss of Arhgef11 , both RNA sequencing and MS/MS proteomics was performed on kidney from SS‐ Arhgef11 −/− and SS‐WT at week 4 (before onset of renal injury/proteinuria between groups) and at week 12 (low‐salt). At week 4, 416 genes were differentially expressed between groups, whereas 1017 genes and 363 proteins were observed at week 12 (low‐salt). As anticipated, the ‐omics datasets suggest that loss of Arhgef11 (SS‐ Arhgef11 −/− ) initiates early transcriptome/protein changes in the actin cytoskeleton. Of note, reuptake (endocytosis) of filtered albumin by megalin and cubilin and a large number of solute carrier genes [(n=57–63, 2.2 fold‐enrichment (4.22×10 −12 )] were upregulated. Many of the genes and proteins in this pathway are involved in tubular sodium transport (Slc5a= Na+/glucose; Slc6a= Na+/Cl−; Slc8a=Na+/Ca2+; Slc9a3= Na+/H+; and Slc34a= Na+‐Pi). In summary, in vivo phenotyping and multi‐omics techniques provides strong evidence that increased Arhgef11 expression in the Dahl S rat leads to actin cytoskeleton mediated changes in cell morphology and cell function (impaired reuptake filtered protein) that promote kidney injury, hypertension, and decline in kidney function. Support or Funding Information 1R01HL137673 (MRG). The work performed through the UMMC Molecular and Genomics Facility is supported, in part, by funds from the NIGMS, including P20GM103476, P20GM104357, and P20GM121334. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .