Abstract P086: Blood Pressure And Salt Differentially Regulate Testicular Immune Cell Populations In Hypertensive Mice

We recently reported that increased proinflammatory (M1) macrophages, inflammation, and inflammation-associated lymphangiogenesis is associated with reproductive dysfunction in mice with salt-sensitive HTN (SSHTN). However, it is unknown whether these effects are primarily due to increased systemic pressure and/or salt. We hypothesized that artificial lowering of blood pressure may not reverse the inflammatory environment within the testes, that is associated with SSHTN. Male C57BL6/J mice were made hypertensive by providing L-NAME (0.5 mg/mL) in the drinking water for 2 weeks, followed by a 2-week washout period, and a subsequent 3-week 4% high salt diet (SSHTN). In another group, mice received L-NAME 2 weeks, followed by a 2-week washout period and a subsequent 3-week 4% high salt diet along with hydralazine (250mg/L) in their drinking water (SSHTN+HDZ). Control (C) mice received L-NAME for 2 weeks and then tap water and normal diet. Systolic blood pressure in SSHTN mice (141±1 mm Hg) was significantly increased when compared to C mice (102±3 mm Hg), but the pressure decreased to 119±1 mm Hg (p<0.05) in SSHTN+HDZ mice. Flow cytometry analysis revealed a significant decrease in M2 macrophages in the testes of SSHTN and SSHTN+HDZ mice when compared to control mice (C: 15.8%±1, SSHTN: 9.8%±2, SSHTN+HDZ: 8.4%±2; p<0.05). There was an increase in Th1 T cells in the testes of SSHTN and SSHTN+HDZ mice when compared to control mice (C:4.8%±1, SSHTN:11.4%±1, SSHTN+HDZ: 10.1%±1; p<0.05), whereas Th17 T cells (C:13.6%±2, SSHTN:19.5%±1, SSHTN+HDZ: 14.8%±1; p<0.05), CD4+TNFa+ (C:8.2%±2, SSHTN:12.5%±1, SSHTN+HDZ: 9%±2; p<0.05) and gamma-delta T cells (C:73%±4, SSHTN:83.5%±1, SSHTN+HDZ: 80%±2; p<0.05) were significantly increased in SSHTN mice but were decreased significantly in SSHTN+HDZ mice. These data demonstrate that high systemic pressure and salt together act on some immune cell populations while others are only altered by salt. Further investigations on the effect of lowering blood pressure on inflammatory markers, lymphatics, and testicular function might help in better understanding the mechanisms behind the differential regulation of immune cells.

Abstract P110: Differential Gene Expression Associated With Ccn1-positive Renal Cells In Murine Hypertensive Models

Hypertension affects roughly half of the U.S. population and is characterized by detrimental pro-inflammatory changes that alter renal function and the cardiovascular system over time. The kidney is a major regulator of blood pressure, however, the specific contributions of renal cell types, including lymphatic endothelial cells (LECs), to hypertension have not been thoroughly explored. Previous work from our lab has shown an increase in renal lymphangiogenesis in response to hypertension and that augmentation of renal lymphangiogenesis can reduce blood pressure. CCN1/Cyr61 is an extracellular matrix protein secreted by multiple cell types, particularly LECs and fibroblasts, which contributes to integrin signaling pathways. CCN1 is also known to be involved in lymphangiogenesis, and has previously been implicated in GWAS studies of hypertension. Given these connections, we performed single cell RNA sequencing using angiotensin II and salt sensitive mouse models of hypertension, which were analyzed separately as well as aggregated into one hypertensive group. Kidneys were turned to a single cell suspension and separated for CD31+/Podoplanin+ cells meant to better represent LECs, which are a small fraction of renal cells. Sequencing was performed and the gene reads were run through the Cell Ranger, Seurat, FGSEA, and Slingshot pipelines, then CCN1+ cells were isolated digitally and analyzed separately. In the AngII model, a total of 60 genes (28 up, 32 down) were differentially expressed (p<0.01) between the renal CCN1+ cells in the hypertensive mice compared to controls, while the salt sensitive model had a total of 331 differentially expressed genes (305 up, 26 down). When the hypertension groups were merged, there were a total of 600 differentially expressed genes (503 up, 97 down) with GSEA showing 48 pathways with enrichment scores >3 or <-3. Additionally, the cellular profile of CCN1+ cells shifted, branching out from a fibroblast-like population to other cell types such as endothelium and tubular epithelium. Overall, the expression of CCN1+ renal cells demonstrates notable changes in response to hypertension in murine models and encourages further study of the mechanisms behind CCN1’s role in the development and maintenance of hypertension.

Abstract 065: Decreasing Blood Pressure In Mice With Salt-Sensitive Hypertension Changes Renal Immune Cell Populations

Salt-induced hypertension is associated with chronic interstitial inflammation and increases in activated inflammatory immune cells in the kidney. It is currently unknown if these renal immune cell changes result from high blood pressure or directly from high salt concentrations. Using a salt-sensitive hypertension (SSH) mouse model and hydralazine (HDZ), we hypothesized that some renal immune cells are affected by high blood pressure, and some will be affected by the high salt content without increased systemic pressure. Three groups of mice (n=5 in each) were generated and given L-NAME via drinking water for 2 weeks, with two groups receiving a high salt (4%) diet for 3 weeks after a 2-week washout, and one of these receiving HDZ (250 mg/L) via drinking water simultaneously during the high salt diet. Systolic blood pressure was significantly decreased in the SSH group treated with HDZ, dropping to 119±1 mmHg from 141±1 mmHg (p<0.001) in the untreated SSH group. Kidneys were immunophenotyped via flow cytometry, and had decreased M2 macrophages (SSH: -55%, p=0.012; SSH+HDZ: -58%, p=0.0096), increased Th17 cells (SSH: 60%, p=0.0015; SSH+HDZ: 47%, p=0.0086), and increased natural killer cells (SSH: 223%, p=0.013; SSH+HDZ: 276%, p=0.0031). In the SSH group only, Th1 cells increased 50% (p=0.047), Th2 cells increased 67% (p=0.035), dendritic cells increased 31% (p=0.025), and CD3+ T cells decreased -46% (p=0.0092). qPCR of collected kidney tissue revealed a three-fold increase in the macrophage/lymphatic marker Lyve1 (p=0.014) only in the SSH group. These results imply that SSH plays a significant role in shaping renal immune cell populations and renal inflammation. Specific renal immune cell subsets undergo changes due to both the high salt and high systemic pressure while others undergo changes only due to the high salt. Future studies will evaluate the therapeutic potential for targeting these immune cell populations and the effect it has on salt-induced hypertension.

Abstract MP42: Metabolomic Study To Identify Common Metabolites In Two Different Mouse Models Of Hypertension

Metabolomic Study to Identify Common Metabolites in Two Different Mouse Models of Hypertension

Recent studies have reflected the importance of the body’s microbiome and associated metabolites and their changes in hypertension. In the current study, we hypothesized that metabolite changes common between hypertension models may unify hypertension’s pathophysiology with respect to metabolites. Two different mice models of experimental hypertension were used in the study: (1) L-arginine methyl ester hydrochloride (L-NAME)/High salt diet induced hypertension (LSHTN) and (2) angiotensin II induced hypertension (AHTN). Untargeted global metabolomics analysis in serum and urine samples were performed to identify common metabolites altered across both hypertensive models, and the resulting data were analyzed using MetaboAnalyst software and compared to control mice. A list of metabolites that were altered significantly in both models of hypertension were identified. A total of 41 serum metabolites were identified as being altered significantly in any hypertensive model compared to controls. Of these, however, only 4 were increased significantly, and 10 were decreased significantly in common across both hypertensive groups. In the urine, 6 metabolites were altered significantly in any hypertensive group with respect to control, however, 0 of them were common between the hypertensive groups. These findings demonstrate that a modest, but potentially important, number of serum metabolites are commonly altered between experimental hypertension models. Further studies to understand the role of these identified metabolites may lead to a greater understanding of the association between gut dysbiosis and hypertension. Submitted to American Heart Association Council on Hypertension Scientific Sessions (September 27-29, 2021, Virtual)Abstract#: 21-HBPR-A-578-AHA