Arhgef11 is a Rho-guanine nucleotide exchange factor that was previously implicated in kidney injury in the Dahl salt-sensitive (SS) rat, a model of hypertension-related chronic kidney disease. Reduced Arhgef11 expression in an SS- Arhgef11 SHR -minimal congenic strain (spontaneously hypertensive rat allele substituted for S allele) significantly decreased proteinuria, fibrosis, and improved renal hemodynamics, without impacting blood pressure compared with the control SS (SS-wild type). Here, SS- Arhgef11 −/− and SS-wild type rats were placed on either low or elevated salt (0.3% or 2% NaCl) from 4 to 12 weeks of age. On low salt, starting at week 6 and through week 12, SS- Arhgef11 −/− animals demonstrated a 3-fold decrease in proteinuria compared with SS-wild type. On high salt, beginning at week 6, SS- Arhgef11 −/− animals demonstrated >2-fold lower proteinuria from weeks 8 to 12 and 30 mm Hg lower BP compared with SS-wild type. To better understand the molecular mechanisms of the renal protection from loss of Arhgef11 , both RNA sequencing and discovery proteomics were performed on kidneys from week 4 (before onset of renal injury/proteinuria between groups) and at week 12 (low salt). The omics data sets revealed loss of Arhgef11 (SS- Arhgef11 −/− ) initiates early transcriptome/protein changes in the cytoskeleton starting as early as week 4 that impact a number of cellular functions, including actin cytoskeletal regulation, mitochondrial metabolism, and solute carrier transporters. In summary, in vivo phenotyping coupled with a multi-omics approach provides strong evidence that increased Arhgef11 expression in the Dahl SS rat leads to actin cytoskeleton-mediated changes in cell morphology and cell function that promote kidney injury, hypertension, and decline in kidney function.

Chronic kidney disease (CKD), which can ultimately progress to kidney failure, is influenced by genetics and the environment. Genes identified in human genome wide association studies (GWAS) explain only a small proportion of the heritable variation and lack functional validation, indicating the need for additional model systems. Outbred heterogeneous stock (HS) rats have been used for genetic fine-mapping of complex traits, but have not previously been used for CKD traits. We performed GWAS for urinary protein excretion (UPE) and CKD related serum biochemistries in 245 male HS rats. Quantitative trait loci (QTL) were identified using a linear mixed effect model that tested for association with imputed genotypes. Candidate genes were identified using bioinformatics tools and targeted RNAseq followed by testing in a novel in vitro model of human tubule, hypoxia-induced damage. We identified two QTL for UPE and five for serum biochemistries. Protein modeling identified a missense variant within Septin 8 (Sept8) as a candidate for UPE. Sept8/SEPTIN8 expression increased in HS rats with elevated UPE and tubulointerstitial injury and in the in vitro hypoxia model. SEPTIN8 is detected within proximal tubule cells in human kidney samples and localizes with acetyl-alpha tubulin in the culture system. After hypoxia, SEPTIN8 staining becomes diffuse and appears to relocalize with actin. These data suggest a role of SEPTIN8 in cellular organization and structure in response to environmental stress. This study demonstrates that integration of a rat genetic model with an environmentally induced tubule damage system identifies Sept8/SEPTIN8 and informs novel aspects of the complex gene by environmental interactions contributing to CKD risk.

Patients with hypertension or diabetes are at higher risk for developing chronic kidney disease (CKD). Low nephron number has been linked with susceptibility to develop hypertension and CKD, but a clear connection between nephron number and hyperglycemic renal injury has not been established. Thus, we seek to investigate the association between nephron deficiency and the development of diabetic kidney disease using a unique model of nephron deficiency, the HSRA rat. Offspring of HSRA are born with a single kidney 50-75% of the time with the remaining pups born with two kidneys. This provides the advantage of being able to directly compare congenital one-kidney, nephron-deficient rats (HSRA-S, ~20,400 nephrons) with nephrectomized two-kidney rats (HSRA-UNX, ~25,100 nephrons) and two-kidney control rats (HSRA-C, ~50,000 nephrons). Previous work has shown that HSRA-S develops increased renal dysfunction with age compared to HSRA-UNX and HSRA-C, which is greatly exacerbated in the presence of DOCA hypertension. Our hypothesis is that a secondary stressor of hyperglycemia in the context of low nephron number will similarly cause greater decline in renal function in HSRA-S compared to HSRA-UNX and HSRA-C. Streptozotocin (STZ) was administered at 9 weeks of age in all three groups and animals were followed until week 24. Despite overt hyperglycemia (350-450 mg/dl), diabetic groups did not develop increased proteinuria compared to their non-diabetic counterparts. Notably, a significant increase in kidney weight was observed in HSRA-S+STZ compared to HSRA-S (kidney weight to body weight ratio [mg/g] 4.8 ± 0.3089 for HSRA-S vs 7.8 ± 1.204 for HSRA-S+STZ, p=0.02), suggesting that hyperglycemia has a deleterious impact on kidney function via hyperfiltration and hypertrophy. Despite no significant effect on proteinuria after an “early insult,” we are investigating the impact of hyperglycemia after overt injury (“late insult”) is observed in HSRA-S (week >24). We will also revisit an “early insult” of hyperglycemia with the addition of modest hypertension (130 mmHg) via DOCA, which represents patients with both diabetes and hypertension . Through this research, we hope to contribute to the growing knowledge of the relationship between nephron number and disease.

Hypertension is both a cause and effect of chronic kidney disease (CKD) and impacts a significant proportion of patients, with a worldwide prevalence of 10‐15%. Previous genetic studies involving the Dahl salt‐sensitive (SS) rat, a model of hypertensive CKD, identified multiple genetic loci linked to kidney injury, including a region on chromosome (Chr) 8. Subsequently, an S.SHR(8) congenic (i.e. transfer of kidney injury resistant SHR genome onto the SS background) demonstrated significantly reduced proteinuria and improved renal function compared to SS control. To identify the gene/s responsible, genome sequencing and bioinformatics analysis identified cingulin‐like 1 (Cgnl1) as a putative gene linked to kidney injury on Chr. 8. Cgnl1 is known to localize to adherens and tight cell‐cell junctions, mediating junction assembly via regulating the activity of the small GTPases such as RhoA and Rac1. A SS‐Cgnl1−/− knockout (KO) was developed to test the hypothesis that loss of Cgnl1 will result in a significant attenuation of kidney injury compared to SS (WT). Both on low and high‐salt (LS=0.3% or HS=2.0% NaCl), KO animals (n=6) demonstrated reduced proteinuria compared to WT animals (n=6) for the entirety of the experiment (HS; KO= 28.7 ± 2.9 versus WT= 161.4 ± 33.1 mg/24hr at week 15, p<0.0001). To further validate Cgnl1’s effect on blood pressure and kidney injury, a temporal analysis (6‐12 weeks) using telemetry and additional renal measurements were conducted on WT and KO animals. On HS, KO animals (n=6) demonstrated reduced proteinuria compared to WT (n=6) for the entirety of the experiment (52.1 ± 7.2 versus 395.9 ± 29.8 mg/24hr at week 12, p<0.0001). While HS fed WT animals exhibited a significant increase in BP compared to LS WT (MAP=197.0 ± 5.0 versus 142.8 ± 3.5 mmHg, p<0001), KO remained unchanged (MAP= 127.6 ± 2.7 and 133.9 ± 3.7 mmHg respectively, NS). Kidney pathology measures, including glomerular and tubular injury were all significantly improved (all p<0.05) in KO compared to WT. Nephron number was measured with no significant difference between WT and KO in young animals, but HS fed WT demonstrated a significant loss of nephrons compared to KO. Bulk RNAseq of kidneys from WT and KO identified Cgnl1 as top downregulated gene with altered expression of many known genes linked with Cgnl1 compared to WT, along downregulation of genes associated with renal injury, mainly reflective of physiological differences from week12‐15. To better identify genes involved in onset of injury, single nuclei RNAseq was performed at week 4 (before physiological differences) to evaluate impact of Cgnl1 in distinct cell populations initiating injury. Additional work is also currently being done on HEK293‐ Cgnl1 knockout cell lines for more mechanistic study of Cgnl1 and pathways. In total, the molecular work, along with the physiological characterization of the SS‐Cgnl1−/−, is expected to provide insight into the role of Cgnl1 in the onset and progression of hypertensive kidney disease and identify new therapeutic targets.

There is a growing interest in the detection of subtle changes in cardiovascular physiology in response to viral infection to develop better disease surveillance strategies. This is not only important for earlier diagnosis and better prognosis of symptomatic carriers, but also useful to diagnose asymptomatic carriers of the virus. Previous studies provide strong evidence of an association between inflammatory biomarker levels and both blood pressure (BP) and heart rate (HR) during infection. The identification of novel biomarkers during an inflammatory event could significantly improve predictions for cardiovascular events. Thus, we evaluated changes in cardiovascular physiology induced in A/Puerto Rico/8/34 (PR8) influenza infections in female and male C57BL/6J mice and compared them to the traditional method of influenza disease detection using body weight (BW). Using radiotelemetry, changes in BP, HR, and activity were studied. Change in BW of infected females was significantly decreased 5 to 13 days post infection (dpi), yet alterations in normal physiology including loss of diurnal rhythm and reduced activity starting at about 3 dpi for HR and 4 dpi for activity and BP; continuing until about 13 dpi. In contrast, males had significantly decreased BW 8 to 12 dpi and demonstrated altered physiological measurements for a shorter period compared to females with a reduction starting at 5 dpi for activity, 6 dpi for BP, and 7 dpi for HR until about 12 dpi, 10 dpi, and 9 dpi, respectively. Lastly, females and males exhibited different patterns of inflammatory maker expression in lungs at peak disease by analyzing bulk RNA sequencing data for lungs and Bio-plex cytokine assay for blood collected from influenza infected and naïve C57BL/6J female and male mice at 7 dpi. In total, this study provides insight into cardiovascular changes and molecular markers to distinguish sex differences in peak disease caused by influenza virus infection.

For better infectious disease surveillance, there is a growing interest in the detection of subtle changes in cardiovascular physiology in response to viral infection. This is not only important for earlier diagnosis and better prognosis of symptomatic carriers, but also useful to diagnose asymptomatic carriers of the virus. Previous studies and literature provide strong evidence of an association between inflammatory biomarker levels and changes in both blood pressure (BP) and heart rate (HR). Thus, the identification of novel biomarkers during an inflammatory event could significantly improve predictions for cardiovascular events. We saw changes in cardiovascular physiology can be induced and detected in A/Puerto Rico/8/34 (PR8) influenza infections in female and male C57B6/j mice. Using PA-C10 implanted radio telemeter devices, we were able to track changes in BP, heart rate HR, and activity. Infected females showed reduction in normal physiology for approximately 10 days during infection including loss of diurnal rhythm and reduced activity starting at about 3 dpi for HR and 4 dpi for activity and BP; this continued until about 13 dpi. Males on the other hand had less reduction in physiological measurements for a shorter period compared to females with a reduction starting at 5 dpi for activity, 6 dpi for BP, and 7 dpi for HR until about 12 dpi, 10 dpi, and 9 dpi, respectively. Lastly, we found females and males had different patterns of inflammatory maker expression in lungs at peak infection by analyzing bulk RNA sequencing (RNA-seq) data for lungs and Bio-plex cytokine assay for blood collected from influenza infected (n=6) and naïve (n=6) C57B6/j female and male mice at 7 dpi.

For better infectious disease surveillance, there is growing interest in the detection of subtle changes in cardiovascular physiology in response to viral infection. This is not only important for earlier diagnosis and better prognosis of symptomatic carriers, but also useful to diagnose asymptomatic carriers of the virus. In our previous study, we found changes in cardiovascular physiology induced in A/Puerto Rico/8/34 (PR8) influenza infections in female and male C57BL/6J mice. Reduction in activity, blood pressure (BP) and heart rate (HR) for females was observed approximately 3-13 days post infection (dpi) and males approximately 5-12 dpi. Additionally, we found sex differences in inflammatory maker expression in lungs at 7dpi with bulk RNA sequencing (RNA-seq) data of lungs and Bio-plex cytokine assay for blood. In this study, we aim to associate changes in cardiovascular measurements with biomarkers throughout infection. Blood, brain, heart, lung, kidney, and nasal septum were collected at 1, 3, 5, and 9 dpi from influenza infected and naïve C57BL/6J female and male mice (n=6 for each time point and experimental group). Using body weight loss as a marker for disease in mice, we found both females and males had significant decrease in body weight at 9 dpi, yet infected females had a significant increase in brain, lung, and kidney weight at 9 dpi compared to naïve females. We are currently in process of analyzing pathological impacts of each tissue with histology and differing patterns of inflammatory maker expression in lungs throughout infection by analyzing bulk RNA sequencing (RNA-seq) data of lungs and Bio-plex cytokine assay for blood. Both cardiovascular measurements and molecular markers throughout influenza infection help to distinguish sex differences caused by influenza virus infection for better, earlier disease diagnosis. Hypertension and Cardiorenal Diseases Research Training Program T32HL105324 (NIH) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Low nephron (the functional unit in the kidney) numbers are linked to the development of hypertension and chronic kidney disease (CKD), which are both significant health problems. Our lab has established a novel inbred genetic animal model (HSRA rat) to study the genetic and physiological impact of low nephron number. In the HSRA model, ~75% of offspring are born with a single kidney (HSRA-S) compared to normal two-kidney littermates (HSRA-C). HSRA-S rats also exhibit altered development in the solitary kidney leading to ~20% less nephrons vs. individual kidney from the HSRA-C. Although the underlying genetic causes in the HSRA remains unknown, we hypothesize that there are genetic variants in the HSRA-S that promote altered expression of specific genes during kidney development leading to failure of one kidney to develop and reduced nephrons (compared to HSRA-C). To better understand the genes/pathways that may be involved in the altered kidney development, single nuclei (sn)RNA-seq was performed on kidneys of 4-week-old male HSRA rats (n=4 -S and -C kidneys). Nuclei were isolated from frozen kidney samples using 10X Chromium Nuclei Isolation Kit and processed through the 10X Genomics Chromium Single Cell 3’ protocol v3.1 per manufactures’ instruction. Libraries were sequenced on the Illumina NextSeq 2000 per 10X generating on average 40,000 reads per cell, >30,000 cells. FASTQ were processed using Cellranger mkfastq(v6.1.1)(10x Genomics) and for differential expression between the samples, the output files from each count were combined using Cellranger aggr(v6.1.1) to generate a combined cloupe file and visualized in Loupe browser 6. The cell specific clusters were grouped based on canonical cell-specific markers. The preliminary analysis of snRNA-seq of HSRA-S vs. HSRA-C kidneys identified distinct clusters of kidney-specific cell types, including podocytes, proximal tubule (PTCs1-3), Loop of Henle, and endothelial cells, among others. Differentially expressed genes (DEGs) were identified between -S and -C for most cell types, with proximal tubule cells accounting for largest number (n=41). Interestingly, a top downregulated DEG in the –S was leukemia inhibitory factor receptor (LIFR), which has recently been associated with renal malformations. In addition, studies are underway involving timed breeding of HSRA rats and subsequent isolation of fetal kidney at different days of gestation (GD14.5-17.5) for multi-omics analysis, including snRNA-seq, smallRNA-seq, and reduced-representation bisulfite sequencing. To date, we’ve collected n=23 fetal kidneys from E17.5 [2K= 8 (5m/3f); SK=15 (8m/7f)] and n=19 at E16.5 [2K= 10 (8m/2f); SK=9 (4m/5f)]. The analysis of snRNA-seq data in young HSRA and at early developmental points will provide insight into genes/pathways involved in kidney development that can increase predisposition to hypertension and CKD later in life. Graduate School of Health Sciences at UMMC; NIH R01HL137673; P20GM103476; P20GM104357 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.