Single-Cell RNA Sequencing Identifies Response of Renal Lymphatic Endothelial Cells to Acute Kidney Injury

SIGNIFICANCE STATEMENT

The renal lymphatic vasculature and the lymphatic endothelial cells that make up this network play important immunomodulatory roles during inflammation. How lymphatics respond to AKI may affect AKI outcomes. The authors used single-cell RNA sequencing to characterize mouse renal lymphatic endothelial cells in quiescent and cisplatin-injured kidneys. Lymphatic endothelial cell gene expression changes were confirmed in ischemia-reperfusion injury and in cultured lymphatic endothelial cells, validating renal lymphatic endothelial cells single-cell RNA sequencing data. This study is the first to describe renal lymphatic endothelial cell heterogeneity and uncovers molecular pathways demonstrating lymphatic endothelial cells regulate the local immune response to AKI. These findings provide insights into previously unidentified molecular pathways for lymphatic endothelial cells and roles that may serve as potential therapeutic targets in limiting the progression of AKI.

BACKGROUND

The inflammatory response to AKI likely dictates future kidney health. Lymphatic vessels are responsible for maintaining tissue homeostasis through transport and immunomodulatory roles. Owing to the relative sparsity of lymphatic endothelial cells in the kidney, past sequencing efforts have not characterized these cells and their response to AKI.

METHODS

Here, we characterized murine renal lymphatic endothelial cell subpopulations by single-cell RNA sequencing and investigated their changes in cisplatin AKI 72 hours postinjury. Data were processed using the Seurat package. We validated our findings by quantitative PCR in lymphatic endothelial cells isolated from both cisplatin-injured and ischemia-reperfusion injury, by immunofluorescence, and confirmation in in vitro human lymphatic endothelial cells.

RESULTS

We have identified renal lymphatic endothelial cells and their lymphatic vascular roles that have yet to be characterized in previous studies. We report unique gene changes mapped across control and cisplatin-injured conditions. After AKI, renal lymphatic endothelial cells alter genes involved in endothelial cell apoptosis and vasculogenic processes as well as immunoregulatory signaling and metabolism. Differences between injury models were also identified with renal lymphatic endothelial cells further demonstrating changed gene expression between cisplatin and ischemia-reperfusion injury models, indicating the renal lymphatic endothelial cell response is both specific to where they lie in the lymphatic vasculature and the kidney injury type.

CONCLUSIONS

In this study, we uncover lymphatic vessel structural features of captured populations and injury-induced genetic changes. We further determine that lymphatic endothelial cell gene expression is altered between injury models. How lymphatic endothelial cells respond to AKI may therefore be key in regulating future kidney disease progression.

Sodium, Interstitium, Lymphatics and Hypertension-A Tale of Hydraulics

Blood pressure is regulated by vascular resistance and intravascular volume. However, exchanges of electrolytes and water between intra and extracellular spaces and filtration of fluid and solutes in the capillary beds blur the separation between intravascular, interstitial and intracellular compartments. Contemporary paradigms of microvascular exchange posit filtration of fluids and solutes along the whole capillary bed and a prominent role of lymphatic vessels, rather than its venous end, for their reabsorption. In the last decade, these concepts have stimulated greater interest in and better understanding of the lymphatic system as one of the master regulators of interstitial volume homeostasis. Here, we describe the anatomy and function of the lymphatic system and focus on its plasticity in relation to the accumulation of interstitial sodium in hypertension. The pathophysiological relevance of the lymphatic system is exemplified in the kidneys, which are crucially involved in the control of blood pressure, but also hypertension-mediated cardiac damage. Preclinical modulation of the lymphatic reserve for tissue drainage has demonstrated promise, but has also generated conflicting results. A better understanding of the hydraulic element of hypertension and the role of lymphatics in maintaining fluid balance can open new approaches to prevent and treat hypertension and its consequences, such as heart failure.

Single-cell RNA sequencing identifies response of renal lymphatic endothelial cells to acute kidney injury

The inflammatory response to acute kidney injury (AKI) likely dictates future renal health. Lymphatic vessels are responsible for maintaining tissue homeostasis through transport and immunomodulatory roles. Due to the relative sparsity of lymphatic endothelial cells (LECs) in the kidney, past sequencing efforts have not characterized these cells and their response to AKI. Here we characterized murine renal LEC subpopulations by single-cell RNA sequencing and investigated their changes in cisplatin AKI. We validated our findings by qPCR in LECs isolated from both cisplatin-injured and ischemia reperfusion injury, by immunofluorescence, and confirmation in in vitro human LECs. We have identified renal LECs and their lymphatic vascular roles that have yet to be characterized in previous studies. We report unique gene changes mapped across control and cisplatin injured conditions. Following AKI, renal LECs alter genes involved endothelial cell apoptosis and vasculogenic processes as well as immunoregulatory signaling and metabolism. Differences between injury models are also identified with renal LECs further demonstrating changed gene expression between cisplatin and ischemia reperfusion injury models, indicating the renal LEC response is both specific to where they lie in the lymphatic vasculature and the renal injury type. How LECs respond to AKI may therefore be key in regulating future kidney disease progression.

Indole Propionic Acid Increases T Regulatory Cells and Decreases T Helper 17 Cells and Blood Pressure in Mice with Salt-Sensitive Hypertension

Hypertension affects over a billion adults worldwide and is a major risk factor for cardiovascular disease. Studies have reported that the microbiota and its metabolites regulate hypertension pathophysiology. Recently, tryptophan metabolites have been identified to contribute to and inhibit the progression of metabolic disorders and cardiovascular diseases, including hypertension. Indole propionic acid (IPA) is a tryptophan metabolite with reported protective effects in neurodegenerative and cardiovascular diseases; however, its involvement in renal immunomodulation and sodium handling in hypertension is unknown. In the current study, targeted metabolomic analysis revealed decreased serum and fecal IPA levels in mice with L-arginine methyl ester hydrochloride (L-NAME)/high salt diet-induced hypertension (LSHTN) compared to normotensive control mice. Additionally, kidneys from LSHTN mice had increased T helper 17 (Th17) cells and decreased T regulatory (Treg) cells. Dietary IPA supplementation in LSHTN mice for 3 weeks resulted in decreased systolic blood pressure, along with increased total 24 h and fractional sodium excretion. Kidney immunophenotyping demonstrated decreased Th17 cells and a trend toward increased Treg cells in IPA-supplemented LSHTN mice. In vitro, naïve T cells from control mice were skewed into Th17 or Treg cells. The presence of IPA decreased Th17 cells and increased Treg cells after 3 days. These results identify a direct role for IPA in attenuating renal Th17 cells and increasing Treg cells, leading to improved sodium handling and decreased blood pressure. IPA may be a potential metabolite-based therapeutic option for hypertension.

Genetically inducing renal lymphangiogenesis attenuates hypertension in mice

BACKGROUND

Hypertension (HTN) is associated with renal proinflammatory immune cell infiltration and increased sodium retention. We reported previously that renal lymphatic vessels, which are responsible for trafficking immune cells from the interstitial space to draining lymph nodes, increase in density under hypertensive conditions. We also demonstrated that augmenting renal lymphatic density can prevent HTN in mice. Whether renal lymphangiogenesis can treat HTN in mice is unknown. We hypothesized that genetically inducing renal lymphangiogenesis after the establishment of HTN would attenuate HTN in male and female mice from three different HTN models.

METHODS

Mice with inducible kidney-specific overexpression of VEGF-D (KidVD) experience renal lymphangiogenesis upon doxycycline administration. HTN was induced in KidVD+ and KidVD- mice by subcutaneous release of angiotensin II, administration of the nitric oxide synthase inhibitor L-NAME, or consumption of a 4% salt diet following a L-NAME priming and washout period. After a week of HTN stimuli treatment, doxycycline was introduced. Systolic blood pressure (SBP) readings were taken weekly. Kidney function was determined from urine and serum measures. Kidneys were processed for RT-qPCR, flow cytometry, and imaging.

RESULTS

Mice that underwent renal-specific lymphangiogenesis had significantly decreased SBP and renal proinflammatory immune cells. Additionally, renal lymphangiogenesis was associated with a decrease in sodium transporter expression and increased fractional excretion of sodium, indicating improved sodium handling efficiency.

CONCLUSIONS

These findings demonstrate that augmenting renal lymphangiogenesis can treat HTN in male and female mice by improving renal immune cell trafficking and sodium handling.

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.

Hypertensive Stimuli Indirectly Stimulate Lymphangiogenesis through Immune Cell Secreted Factors

(1) Background: Renal immune cells and lymphatic vessel (LV) density have been reported previously to be increased in multiple mouse models of hypertension (HTN). However, whether interstitial levels of HTN stimuli such as angiotensin II, salt, or asymmetric dimethylarginine have a direct or indirect effect on lymphangiogenesis is unknown. We hypothesized that these 3 HTN stimuli directly increase lymphatic endothelial cell (LEC) proliferation, LEC 3-D matrix invasion and vessel formation, and sprouting of mouse mesometrial LVs. (2) Methods: Human LECs (hLECs) and mouse LECs (mLECs) were treated with HTN stimuli while explanted mouse mesometrial LVs were treated with either the same HTN stimuli or with HTN stimuli-conditioned media. Conditioned media was prepared by treating murine splenocytes with HTN stimuli. (3) Results: HTN stimuli had no direct effect on hLEC or mLEC proliferation. Treatment of hLECs with HTN stimuli increased the number of lumen-forming structures and invasion distance (both p < 0.05) in the 3-D matrix but decreased the average lumen diameter and the number of cells per invading structure (both p < 0.05). Conditioned media from HTN-stimuli-treated splenocytes significantly attenuated the decrease in sprout number (aside from salt) and sprout length of mouse mesometrial LVs that is found in the HTN stimuli alone. (4) Conclusions: These data indicate that HTN stimuli indirectly prevent a decrease in lymphangiogenesis through secreted factors from HTN-stimuli-treated immune cells.

Update on Immune Mechanisms in Hypertension

The contribution of immune cells in the initiation and maintenance of hypertension is undeniable. Several studies have established the association between hypertension, inflammation, and immune cells from the innate and adaptive immune systems. Here, we provide an update to our 2017 American Journal of Hypertension review on the overview of the cellular immune responses involved in hypertension. Further, we discuss the activation of immune cells and their contribution to the pathogenesis of hypertension in different in vivo models. We also highlight existing gaps in the field of hypertension that need attention. The main goal of this review is to provide a knowledge base for translational research to develop therapeutic strategies that can improve cardiovascular health in humans.

Lymphatics in Cardiovascular Physiology

The lymphatic vessels play an essential role in maintaining immune and fluid homeostasis and in the transport of dietary lipids. The discovery of lymphatic endothelial cell-specific markers facilitated the visualization and mechanistic analysis of lymphatic vessels over the past two decades. As a result, lymphatic vessels have emerged as a crucial player in the pathogenesis of several cardiovascular diseases, as demonstrated by worsened disease progression caused by perturbations to lymphatic function. In this review, we discuss the major findings on the role of lymphatic vessels in cardiovascular diseases such as hypertension, obesity, atherosclerosis, myocardial infarction, and heart failure.

A Kidney-Targeted Nanoparticle to Augment Renal Lymphatic Density Decreases Blood Pressure in Hypertensive Mice

Chronic interstitial inflammation and renal infiltration of activated immune cells play an integral role in hypertension. Lymphatics regulate inflammation through clearance of immune cells and excess interstitial fluid. Previously, we demonstrated increasing renal lymphangiogenesis prevents hypertension in mice. We hypothesized that targeted nanoparticle delivery of vascular endothelial growth factor-C (VEGF-C) to the kidney would induce renal lymphangiogenesis, lowering blood pressure in hypertensive mice. A kidney-targeting nanoparticle was loaded with a VEGF receptor-3-specific form of VEGF-C and injected into mice with angiotensin II-induced hypertension or LNAME-induced hypertension every 3 days. Nanoparticle-treated mice exhibited increased renal lymphatic vessel density and width compared to hypertensive mice injected with VEGF-C alone. Nanoparticle-treated mice exhibited decreased systolic blood pressure, decreased pro-inflammatory renal immune cells, and increased urinary fractional excretion of sodium. Our findings demonstrate that pharmacologically expanding renal lymphatics decreases blood pressure and is associated with favorable alterations in renal immune cells and increased sodium excretion.

Common Metabolites in Two Different Hypertensive Mouse Models: A Serum and Urine Metabolome Study

Recent metabolomics studies have identified a wide array of microbial metabolites and metabolite pathways that are significantly altered in hypertension. However, whether these metabolites play an active role in pathogenesis of hypertension or are altered because of this has yet to be determined. In the current study, we hypothesized that metabolite changes common between hypertension models may unify hypertension's pathophysiology with respect to metabolites. We utilized two common mouse models of experimental hypertension: L-arginine methyl ester hydrochloride (L-NAME)/high-salt-diet-induced hypertension (LSHTN) and angiotensin II induced hypertension (AHTN). To identify common metabolites that were altered across both models, we performed untargeted global metabolomics analysis in serum and urine and the resulting data were analyzed using MetaboAnalyst software and compared to control mice. A total of 41 serum metabolites were identified as being significantly altered in any hypertensive model compared to the controls. Of these compounds, 14 were commonly changed in both hypertensive groups, with 4 significantly increased and 10 significantly decreased. In the urine, six metabolites were significantly altered in any hypertensive group with respect to the control; however, none 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 of the newly identified metabolites from this untargeted metabolomics analysis may lead to a greater understanding of the association between gut dysbiosis and hypertension.

Abstract P203: Time-restricted Feeding Attenuates Hypertension In Mice

Hypertension is associated with inflammation and decreased kidney function. Studies of cardiovascular function have observed that time-restricted feeding (TRF), a form of intermittent fasting, is associated with decreased blood pressure, decreased inflammation, and improved kidney function. We hypothesized that implementation of a time-restricted feeding protocol in hypertensive mice would decrease systolic blood pressure and increase kidney function. C57BL6/J mice were randomly assigned to either an L-arginine methyl ester hydrochloride (LNAME)-induced hypertension (LHTN) model, where they received LNAME in their drinking water, or a salt-sensitive hypertension (SSHTN) model, where they received a 4% high salt diet following LNAME priming and a washout period. Two days following introduction of LNAME or the high salt diet, mice were either provided food ad libitum or placed on a 12-hour TRF protocol, where they were only allowed to eat from 8PM to 8AM. Hypertensive mice receiving TRF treatment displayed a significantly decreased systolic blood pressure (SBP) after 4 weeks when compared to the control hypertensive groups (LHTN SBP: 164±1 vs. 149±2 mmHg, p<0.001; SSHTN SBP: 139±1 vs. 130±1 mmHg, p<0.001). When kidney function was examined in the LHTN group, TRF mice had decreased serum creatinine (Sc) levels along with decreased fractional excretion of sodium (FENa) when compared to their respective control mice (Sc: 0.19±0.01 vs. 0.13±0.01 mg/dL, p=0.007; FENa: 0.59±0.05 vs. 0.32±0.05 %, p=0.009). Glomerular filtration rate was significantly increased in TRF treated LHTN mice. Overall, these data indicate that TRF treatment reduces blood pressure in hypertensive mice, which is associated with an improvement in renal function. These findings could establish TRF as a potential therapeutic option for hypertensive patients.

Abstract MP40: Microbiome-associated Metabolites Are Altered In Mouse Models Of Hypertension

Recent studies suggest that the microbiome plays a key role in hypertension and associated inflammation. Microbiota produce metabolites that may lead to activated pro-inflammatory immune cells and contribute to hypertension; however, the altered metabolites in multiple models of hypertension is currently unknown. We hypothesized that there are significant differences in metabolomic profiles between normotensive and hypertensive mice. We utilized two mouse models of hypertension: L-arginine methyl ester hydrochloride (L-NAME)/high salt diet induced hypertension (LSHTN) and angiotensin II induced hypertension (A2HTN). Serum and fecal samples were collected at the end of the treatment period. Ultra-high performance liquid chromatography and tandem mass spectrometry were performed to identify the biochemical composition of each sample. Random Forest Analysis was performed to classify each sample based on similarities and differences in metabolite composition. These procedures were performed by Metabolon, Inc. A total of 1,066 and 1,028 biochemicals were measured in serum and feces, respectively. There were 263 biochemicals in LSHTN serum and 122 biochemicals in A2HTN serum that were statistically different from controls (p≤0.05). There were 298 biochemicals in LSHTN feces and 64 biochemicals in A2HTN feces that were statistically different from controls (p≤0.05). Five biochemical metabolite groups were shown to have significant differences between hypertensive groups and controls: aromatic amino acids, bile acids and sterols, benzoates, fatty acids, and diacylglycerols. Tryptophan metabolites were significantly reduced in the serum of LSHTN mice but not in the serum of A2HTN mice. Serum tyrosine and benzoate metabolites showed varied differences between the two hypertensive groups. Serum fatty acid beta oxidation metabolites were significantly reduced in both hypertensive models but were significantly increased in the feces of mice with LSHTN. In conclusion, this study provided significant analysis of metabolite changes in two hypertension mouse models. Further investigation of the roles these metabolites play in hypertension may lead to targeted therapeutic interventions.

Abstract MP52: Hypertensive Stimuli Indirectly Stimulate Mouse Mesometrial Lymphangiogenesis Through Immune Cells

We previously reported increased renal lymphatic density in multiple mouse models of hypertension, and further augmenting renal lymphatics lowers blood pressure. However, whether interstitial levels of hypertensive stimuli have a direct effect on lymphatics or an indirect effect through secreted immune cell factors has not been examined. We hypothesized that hypertensive stimuli directly increases lymphatic endothelial cell (LEC) proliferation and increases sprouting of mouse mesometrial lymphatic vessels. Murine LECs were cultured and treated with angiotensin II (angII), salt, and asymmetric dimethylarginine (ADMA) for 24 hours. To mimic the in vivo environment, a lymphatic-specific reporter mouse (Prox1-tdTomato) mesometrium tissue explant was treated with either the same hypertensive stimuli or with hypertensive conditioned media for 8 days. Mesometrial vascular beds were cultured in DMEM supplemented with 20% fetal bovine serum to induce lymphatic sprouting and this was replenished every day. The conditioned media was made by treating murine splenocytes for 24 hours with the same hypertensive stimuli. These stimuli had no effect on murine LEC proliferation. Hypertensive stimuli significantly decreased mesometrial lymphatic vessel sprout length (SL) and sprout number (SN) compared to controls (control SL in pixels by ImageJ analysis: 34.0 ± 2.6, angII: 3.7 ± 2.6, salt: 2.67 ± 2.18, ADMA: 9.06 ± 5.12, all p<0.05; control SN: 7 ± 3, angII: 0 ± 0, salt: 0 ± 0, ADMA: 1 ± 1, all p<0.05). Conditioned media treatment normalized SL and SN by day 8 for all hypertensive stimuli except salt. In conclusion, hypertensive stimuli directly inhibit mesometrial lymphangiogenesis, but this was mitigated by hypertensive stimuli induced immune cell secreted factors.

Abstract P217: Imbalance Of M1/M2 Macrophages In Ovaries Of Hypertensive Mice Is Associated With Reproductive Dysfunction And Lymphangiogenesis

Macrophages are the principal immune cells in ovaries. Besides protecting against invading pathogens and antigens, macrophages also play an essential role in folliculogenesis, ovulation, luteinization, lymphangiogenesis, and other functions. An imbalance in M1/M2 macrophages is observed in systemic circulation in patients and animals with hypertension (HTN). Although studies have demonstrated an association between HTN and reproductive dysfunction in females, the effect of HTN on ovarian M1/M2 ratio and lymphatics is largely unknown. We hypothesized that L-NAME-induced HTN (LHTN) and salt-sensitive hypertension (SSHTN) may increase the M1/M2 balance in ovaries which is associated with lymphangiogenesis and reproductive dysfunction in mice. Female mice were either provided L-NAME (0.5 mg/mL) in their drinking water for 3 weeks or L-NAME for 2 weeks, followed by a 2-week washout period and subsequent 3-week 4% high salt diet (SSHTN). Control mice (C) received tap water and normal diet. Flow cytometry analysis revealed a significant decrease in M1 (C: 46%±1, LHTN: 33%±2; p<0.05) and an increase in M2 (C: 7%±1, LHTN: 12%±1; p<0.05) macrophages in ovaries from LHTN mice. In SSHTN mice, ovaries had significantly increased M1 (C: 24%±1, SSHTN: 44%±2; p<0.05) and decreased M2 (C: 12%±1, SSHTN: 4%±1; p<0.05) macrophages. There was a significant increase in gene expression of the hormone receptors AR, FSHR, ERa, ERb, and LHR, and the steroidogenic enzymes StAR, 3bHSD, CYP11a1, and CYP17a1. Ovaries of hypertensive mice had a significant increase in gene expression of the lymphatic vessel markers Lyve-1, Podoplanin, and Prox-1, the lymphangiogenic growth factor VEGF-C and receptors VEGFR-2 and VEGFR-3. Taken together these data demonstrate that HTN disturbs M1/M2 macrophages in ovaries and is associated with reproductive dysfunction and lymphangiogenesis. Manipulation of M1/M2 ratio may be a therapeutic opportunity to improve reproductive health in hypertensive women.

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

Abstract 16: Altered Testicular Macrophage Polarization Is Associated With Reproductive Dysfunction In Hypertensive Mice

Elevated circulating proinflammatory (M1) and decreased anti-inflammatory (M2) macrophages contribute to hypertension (HTN) and end-organ damage. HTN is associated with reproductive dysfunction in men. However, the impact of HTN on testicular macrophages and inflammation is unknown. We hypothesized that HTN increases M1 and decreases M2 testicular macrophages, which is associated with inflammation and reproductive dysfunction. Male mice were made hypertensive by either providing L-arginine methyl ester hydrochloride (L-NAME) (0.5 mg/mL) in the drinking water for 3 weeks [L-NAME-induced HTN (LHTN)] or L-NAME water for 2 weeks, followed by a 2-week washout period and a subsequent 3-week 4% high salt diet [salt-sensitive hypertension (SSHTN)]. Control (C) mice received tap water and normal diet. Flow cytometry analysis revealed a significant increase in both M1 (C: 15%±1, LHTN: 22%±2; p<0.05) and M2 (C: 10%±1, LHTN: 21%±2; p<0.05) macrophages in testes from LHTN mice. Similarly, testes from SSHTN mice had a significant increase in M1 (C: 17%±1, SSHTN: 28%±2; p<0.05) but had a significant decrease in M2 (C: 14%±1, SSHTN: 7%±1; p<0.05) macrophages. Testes from both hypertension models had a significant increase in gene expression of the proinflammatory cytokines TNFa, IFNg, IL-1b, IL-6, and IL-17. Sperm concentration (C: 8.5±0.7, LHTN: 6.5±0.2, SSHTN: 4.7±0.5; both p<0.05) and the percentage of sperm mitochondrial activity (C: 88%±3, LHTN: 71±5, SSHTN: 64%±3; both p<0.05) were decreased significantly in both hypertension groups. Hypertensive mice presented a significantly increased percentage of sperm with abnormal morphology (C: 5%±1, LHTN: 8%±1, SSHTN: 13%±2; both p<0.05) and damaged acrosome (C: 1.4%±0.2, LHTN: 2.8%±0.2, SSHTN: 4%±0.5; both p<0.05). There was a significant decrease in gene expression of the hormone receptors AR, ERa, and LHR, and the steroidogenic enzymes StAR, 3bHSD, 17bHSD, and CYP17a1 in the testes of LHTN and SSHTN mice. These data demonstrate that HTN alters testicular macrophage polarization which is associated with inflammation and impaired reproductive health. Therapeutic strategies may be developed to improve reproductive health in male hypertensive patients by targeting testicular macrophage imbalance.

Abstract P146: Testicular Inflammation Is Associated With Immune Cell Infiltration And Lymphangiogenesis In L-NAME-induced Hypertension

Hypertension (HTN) is associated with reduced fertility in men. Although numerous studies report that HTN disrupts hormonal balance in men, less is known about the direct effect of HTN on testes and how HTN influences testicular inflammation and lymphatics. We hypothesized that HTN increases testicular lymphatic vessel density and this is associated with immune cell infiltration and inflammation. Male mice (8 weeks old) were made hypertensive by providing them with L-arginine methyl ester hydrochloride (L-NAME) (0.5 mg/mL) in the drinking water for 3 weeks and control mice received tap water. Testes of hypertensive mice had a significant increase in gene expression of the lymphatic vessel markers Lyve-1 (17.7 ± 2.1 fold; p<0.05), Podoplanin (6.7 ± 1.2 fold; p<0.05), and Prox-1 (68.1 ± 10.6 fold; p<0.05), the lymphangiogenic growth factors VEGF-C (5.7 ± 1.1 fold; p<0.05), VEGF-D (2.2 ± 0.7 fold; p<0.05), and VEGF-A (5.8 ± 1.1 fold; p<0.05) and their receptors VEGFR-2 (8.0 ± 2.0 fold; p<0.05) and VEGFR-3 (25.4 ± 3.5 fold; p<0.05). There was also a significant increase in the expression of the pro-inflammatory cytokines TNF-a (24.0 ± 6.8 fold; p<0.05), IFN-g (17.5 ± 3.0 fold; p<0.05), IL-1b (4.2 ± 1.2 fold; p<0.05), IL-6 (24.8 ± 13.0 fold; p<0.05), and IL-17 (4.4 ± 0.4 fold; p<0.05). There were also increases in the lymphatic endothelial cell-derived immune cell trafficking chemokines CCL21 (7.8 ± 1.7 fold; p<0.05) and CCL19 (9.0 ± 4.1 fold; p<0.05) and their receptor CCR7 (9.6 ± 3.2 fold; p<0.05), as well as the cell adhesion molecule ICAM (6.2 ± 1.0 fold; p<0.05) in testes of hypertensive mice. Flow cytometry analysis revealed an increased accumulation of F4/80+ macrophages in the testes from hypertensive mice. Together, these data demonstrate that HTN induces inflammation-associated lymphangiogenesis in testes, in association with immune cell infiltration. It is possible that increasing testicular lymphatics may reduce inflammation and improve reproductive function in hypertensive men.

Abstract P132: A Kidney-Targeted Nanoparticle To Augment Renal Lymphatic Density Decreases Blood Pressure In Mice With L-NAME- And Angiotensin II-Induced Hypertension

Chronic interstitial inflammation and renal infiltration of activated immune cells play an integral role in hypertension. Lymphatic vessels attenuate inflammation by trafficking activated immune cells and excess fluid from the interstitial space to lymph nodes. Previously, our laboratory demonstrated that genetically inducing renal lymphangiogenesis could treat hypertension in three different mouse models. In an effort to translate these findings into a clinical treatment, we hypothesized that a targeted nanoparticle could deliver the pro-lymphangiogenic factor VEGF-C156S to the kidney, induce lymphangiogenesis, and lower blood pressure in hypertensive mice. A micellar nanoparticle was developed with the capacity to deliver protein to the kidney, as demonstrated through delivery trials. This nanoparticle was loaded with VEGF-C156S and injected into mice with LNAME-induced hypertension (LHTN) or angiotensin II-induced hypertension (AIIHTN) via tail vein every 3 days. Compared to hypertensive mice injected with VEGF-C156S only (no nanoparticle) every 3 days, nanoparticle-treated mice exhibited a significantly lower systolic blood pressure (SBP) after 4 injections (LHTN SBP: 160±5 vs. 120±3 mmHg, p<0.001; AIIHTN SBP: 150±8 vs. 126±6 mmHg, p=0.03). Immunolabeled kidney sections from nanoparticle-treated LHTN mice showed a significant increase in podoplanin+ pixels, corresponding to an increase in lymphatic vessel density (p<0.01). A 5-fold increase in renal gene expression of podoplanin in nanoparticle-treated LHTN mice further supported this finding (p=0.01). Flow cytometric analysis of the nanoparticle-treated LHTN mice showed decreased renal CD45+F4/80+CD11c- cells, while AIIHTN mice revealed decreased levels of renal CD45+CD3e+, CD45+CD4+CD8-, and CD45+F4/80+CD11c+ cells (p<0.01, p=0.03, and p<0.001, respectively) when compared to their respective hypertensive groups. These data support our previous findings that expanding the renal lymphatic vasculature can treat existing hypertension by reducing renal immune cells. The results of this study may provide clinicians with a renal lymphatic-targeted therapeutic for treating hypertensive patients.

Augmenting Renal Lymphatic Density Prevents Angiotensin II-Induced Hypertension in Male and Female Mice

BACKGROUND

Renal inflammation and immune cell infiltration are characteristic of several forms of hypertension. Our laboratory has previously demonstrated that renal-inflammation-associated lymphangiogenesis occurs in salt-sensitive and nitric-oxide-inhibition-induced hypertension. Moreover, enhancing renal lymphatic density prevented the development of these two forms of hypertension. Here, we investigated the effects of angiotensin II-induced hypertension on renal lymphatic vessel density in male and female mice.

METHODS

Wild-type and genetically engineered male and female mice were infused with angiotensin II for 2 or 3 weeks. Isolated splenocytes and peritoneal macrophages from mice, and commercially available mouse lymphatic endothelial cells were used for in vitro studies.

RESULTS

Compared to vehicle controls, angiotensin II-infused male and female mice had significantly increased renal lymphatic vessel density in association with pro-inflammatory immune cells in the kidneys of these mice. Direct treatment of lymphatic endothelial cells with angiotensin II had no effect as they lack angiotensin II receptors; however, angiotensin II treatment of splenocytes and peritoneal macrophages induced secretion of the lymphangiogenic growth factor VEGF-C in vitro. Utilizing our genetic mouse model of inducible renal lymphangiogenesis, we demonstrated that greatly augmenting renal lymphatic density prior to angiotensin II infusion prevented the development of hypertension in male and female mice and this was associated with a reduction in renal CD11c+F4/80- monocytes.

CONCLUSION

Renal lymphatics play a significant role in renal immune cell trafficking and blood pressure regulation, and represent a novel avenue of therapy for hypertension.

Abstract 143: Enhancing Renal Lymphatic Vessel Density Blunts Both Salt-Sensitive and Angiotensin II-Dependent Hypertension in Mice

Sodium retention is a hallmark of most forms of experimental hypertension. Renal lymphatics maintain fluid homeostasis by draining cortical interstitial fluid to the draining lymph node. Our lab has previously demonstrated that augmenting renal lymphatics prevents hypertension, but whether this can treat hypertension and whether expanding renal lymphatics alters renal sodium handling remain unknown. Our hypotheses were that augmenting renal lymphatic vessel density after hypertension is established will treat salt sensitive hypertension (SSHTN) and angiotensin II-induced hypertension (AIIHTN) and that this will be accompanied by an increase in urinary sodium excretion. To test our hypotheses, we utilized transgenic mice that overexpress the lymphangiogenic growth factor VEGF-D specifically in the kidney when administered doxycycline (KidVD+ mice). KidVD+ mice and KidVD- littermates were made salt-sensitive by treatment with L-NAME (0.5 mg/mL) for two weeks, followed by a washout period of two weeks, and then given a 4% high salt diet for four weeks. To induce AIIHTN, mice were infused with angiotensin II (490 ng/kg/min) for four weeks. Doxycycline was administered to all mice a week after beginning the high salt diet or a week after angiotensin II infusion. Prior to doxycycline initiation, KidVD- and KidVD+ mice were hypertensive (SSHTN SBP: 130±2 and 134±2 mmHg, respectively; AIIHTN SBP: 125±2 and 128±2 mmHg, respectively). Compared to KidVD- mice, doxycycline administration for three weeks augmented renal lymphatics in KidVD+ mice and significantly decreased blood pressure after four weeks of high salt diet or angiotensin II (SSHTN SBP: 134±4 vs. 125±2 mmHg; p<0.05; AIIHTN: 145±3 vs. 125±5 mmHg; p<0.05). The reduction in blood pressure was accompanied by an increase in urinary fractional excretion of sodium in SSHTN and AIIHTN KidVD+ mice. AIIHTN induced an elevated glomerular filtration rate (GFR) in KidVD- mice while this was reduced in KidVD+ mice; however, GFR was unaltered in SSHTN KidVD+ mice. Thus, augmenting renal lymphatics increased fractional excretion of sodium and lowered blood pressure in both mouse models of hypertension. Augmenting renal lymphatics may be a promising anti-hypertensive and natriuretic therapeutic strategy.

Abstract P3020: Therapeutic Induction of Renal Lymphatic Expansion Attenuates Blood Pressure in Mice With L-NAME Hypertension

Renal immune cell infiltration and accompanying inflammation activates renal sodium transporters leading to sodium retention and hypertension. Lymphatic vessels traffic interstitial immune cells to the draining lymph nodes and help resolve inflammation. We have previously demonstrated that genetically inducing renal lymphangiogenesis prevents hypertension associated with a reduction in renal immune cell accumulation; however, it is unknown whether augmenting renal lymphatics can treat hypertension. Our hypothesis was that augmenting renal lymphatics after hypertension is established will lower blood pressure during L-NAME-induced hypertension (LHTN). Transgenic mice that overexpress the lymphangiogenic signal VEGF-D only in the kidney upon doxycycline administration (KidVD+ mice) and KidVD- littermates were administered L-NAME (0.5 mg/mL) in their drinking water for four weeks with doxycycline initiated at the second week of L-NAME. Treatment with L-NAME for one week induced LHTN in both KidVD- and KidVD+ mice (SBP: 134±4 and 142±5 mmHg, respectively). However, doxycycline-induced renal lymphangiogenesis significantly decreased blood pressure in KidVD+ mice compared to KidVD- mice after four weeks of L-NAME (SBP: 127±5 vs. 151±6 mmHg; p<0.05). This was associated with a significant decrease in renal CD11c + F4/80 - monocytes and a significant increase in 24-hour urinary sodium excretion and fractional excretion of sodium in KidVD+ mice. Urinary volume over 24 hours was also increased in KidVD+ mice (1.7±0.8 vs. 3±0.9 mL/24 hours; p<0.05); however, this was not associated with a change in glomerular filtration rate. Thus, augmenting renal lymphatics lowers blood pressure in mice with LHTN and this is associated with a decrease in renal monocyte accumulation and an increase in urinary sodium excretion. Augmenting renal lymphatics may be a promising anti-hypertensive and natriuretic therapeutic strategy.

Abstract P166: Identification of Cyr61 and Tfgbi as Hypertensive Renal LEC Genes

Increased renal lymphatic density is observed in various experimental models of hypertension. To identify differentially expressed genes in lymphatic endothelial cells (LECs) from hypertensive kidneys, we utilized Gene Expression Omnibus (GEO) which was developed by the NIH NCBI. GEO is an international public repository that archives and distributes high-throughput functional genomic data sets such as microarray and next-generation sequencing data. GEO2R is an interactive web tool that allows users to compare samples across experimental conditions in a GEO Series in order to identify genes that are differentially expressed. Results are presented as a table of genes ordered by significance. Using GEO2R, the search terms “lymphatic” and “hypertensive kidney” were used to identify studies of LEC-associated genes and renal hypertension-associated genes. Among the search results for LEC genes, 4 studies were chosen that were done in mice comparing: a) murine primary LECs vs. murine endothelial SVEC4-10 cell line, b) collecting lymphatic endothelium of mice with 293EBNA xenografts with and without overexpression of VEGFD, c) LECs from afferent and efferent lymphatic vessels, and d) LECs and blood vascular endothelial cells from mouse intestine. For renal hypertensive genes, we chose a study that reported differentially expressed genes in kidneys of mice treated with angiotensin II for 1, 3 or 7 days compared to controls. From all of these lists, the top 250 differentially expressed genes were chosen. The list of renal genes was crossed with a combined list of LEC genes to obtain potential “LEC genes differentially expressed in hypertensive kidneys”. This yielded a list of 40 genes for which mRNA expression was tested in the kidneys of mice from 3 different models of hypertension: nitric oxide inhibition-induced, salt-sensitive, and angiotensin II-induced. Among the differentially expressed genes, Cyr61 and Tgfbi were elevated significantly in all 3 hypertensive models. Cyr61 is a well-known inducer of angiogenesis. Tfgbi is involved in LEC adhesion to extracellular matrix under hypoxic conditions. The upregulation of these two genes likely play a major role in renal LEC function during hypertension.

Abstract 024: Genetically Inducing Renal Lymphangiogenesis Prevents Angiotensin II-Induced Hypertension in Mice

Angiotensin II (AII)-dependent hypertension (AIIHTN) is associated with renal immune cell infiltration and inflammation. Lymphatic vessels drain interstitial fluid and traffic immune cells to draining lymph nodes; however, the role of renal lymphatics in AIIHTN is unknown. Our hypotheses were that: 1) renal lymphatic vessel density is increased in mice with AIIHTN, and 2) that further augmenting renal lymphatic vessels will prevent AIIHTN. Male and female mice were infused with AII (490 ng/kg/min) or saline for 2 or 3 weeks by subdermal osmotic mini pumps. Male and female mice with AIIHTN had markedly increased renal lymphatic vessel density compared to controls. AIIHTN males had significantly increased renal gene expression of the lymphatic vessel markers Lyve1, Pdpn, and Vegfr3, while Pdpn and the lymphangiogenic signal Vegfc were increased significantly in AIIHTN females. Kidneys of AIIHTN males had significantly increased F4/80+ macrophages at 2 weeks and F4/80+ macrophages and CD3e+ T cells at 3 weeks as determined by flow cytometry. Unlike in males, renal CD11c+ dendritic cells were increased significantly in females. Renal mRNA levels of the pro-inflammatory cyto/chemokines Tnfa , Il1b , Mcp1 , and Cxcl13 were elevated significantly in males at 2 and 3 weeks and in females at 3 weeks. To determine whether augmenting renal lymphatic vessels prior to AII infusion could prevent AIIHTN, we used transgenic mice that overexpress the lymphangiogenic signal VEGF-D only in the kidney under the control of doxycycline (KidVD+ mice) and thus exhibit renal-specific lymphangiogenesis. Doxycycline initiated 1 week prior to 3-week AII infusion prevented AIIHTN in KidVD+ mice while KidVD- mice still developed AIIHTN (Males SBP: 122±2 vs. 161±3 mmHg; p<0.05; Females SBP: 114±1 vs. 131±4 mmHg; p<0.05). KidVD+ AIIHTN mice had significantly decreased renal levels of CD11c+ dendritic cells and CD8+ T cells. Renal gene expression of Tnfa and Il1b were normalized in all KidVD+ mice. These data demonstrate that renal lymphatic vessel density is increased in AIIHTN and that genetically inducing renal lymphangiogenesis prior to AII infusion can prevent AIIHTN by reducing renal immune cells and inflammation.

Immune cell trafficking, lymphatics and hypertension

Activated immune cell infiltration into organs contributes to the development and maintenance of hypertension. Studies targeting specific immune cell populations or reducing their inflammatory signalling have demonstrated a reduction in BP. Lymphatic vessels play a key role in immune cell trafficking and in resolving inflammation, but little is known about their role in hypertension. Studies from our laboratory and others suggest that inflammation-associated or induction of lymphangiogenesis is organ protective and anti-hypertensive. This review provides the basis for hypertension as a disease of chronic inflammation in various tissues and highlights how renal lymphangiogenesis is a novel regulator of kidney health and BP. LINKED ARTICLES: This article is part of a themed section on Immune Targets in Hypertension. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.12/issuetoc.

Both maternal and placental toll-like receptor activation are necessary for the full development of proteinuric hypertension in mice

OBJECTIVE

Innate immune system activation and excessive inflammation contributes to hypertension during pregnancy (HTN-preg). Activation of Toll-like receptors (TLRs), the primary innate immune system sensor, is evident in women with HTN-preg and is sufficient to induce pregnancy-dependent, proteinuric hypertension in animals. However, whether HTN-preg is a maternal disease, a placental disease, or both is unclear. We hypothesized that activation of TLR3, the double-stranded RNA sensor, in both maternal systemic and placental cells would be necessary for the full development of HTN-preg in mice.

STUDY DESIGN

Various mating schemes generated pregnant mice that lacked TLR3 in maternal cells, paternally-derived placental cells, and both. Mice were then injected with a TLR3 agonist on days 13, 15, and 17 of pregnancy.

MAIN OUTCOME MEASURES

Blood pressure, urinary protein excretion, fetal development, maternal vascular endothelial function, and immune system activation were all assessed and compared between groups.

RESULTS

Pregnant mice lacking TLR3 in maternal cells as well as pregnant mice lacking TLR3 in placental cells had significantly attenuated increases in systolic blood pressure, urinary protein excretion, fetal demise, and endothelial dysfunction compared to wild-type pregnant mice following TLR3 activation. Pregnant mice lacking TLR3 in both maternal systemic and placental cells were completely resistant to the hypertension, proteinuria, fetal demise, endothelial dysfunction, splenomegaly, and increases in pro-inflammatory immune cells induced by TLR3 activation.

CONCLUSIONS

These data suggest that both maternal and placental TLR3 activation are crucial for the full development of HTN-preg and that TLR3 antagonists may be beneficial in some women with HTN-preg.

Enhancing Renal Lymphatic Expansion Prevents Hypertension in Mice

RATIONALE

Hypertension is associated with renal infiltration of activated immune cells; however, the role of renal lymphatics and immune cell exfiltration is unknown.

OBJECTIVE

We tested the hypotheses that increased renal lymphatic density is associated with 2 different forms of hypertension in mice and that further augmenting renal lymphatic vessel expansion prevents hypertension by reducing renal immune cell accumulation.

METHODS AND RESULTS

Mice with salt-sensitive hypertension or nitric oxide synthase inhibition-induced hypertension exhibited significant increases in renal lymphatic vessel density and immune cell infiltration associated with inflammation. Genetic induction of enhanced lymphangiogenesis only in the kidney, however, reduced renal immune cell accumulation and prevented hypertension.

CONCLUSIONS

These data demonstrate that renal lymphatics play a key role in immune cell trafficking in the kidney and blood pressure regulation in hypertension.

Myeloid-Derived Suppressor Cells Ameliorate Cyclosporine A-Induced Hypertension in Mice

The calcineurin inhibitor cyclosporine A (CsA) suppresses the immune system but promotes hypertension, vascular dysfunction, and renal damage. CsA decreases regulatory T cells and this contributes to the development of hypertension. However, CsA's effects on another important regulatory immune cell subset, myeloid-derived suppressor cells (MDSCs), is unknown. We hypothesized that augmenting MDSCs would ameliorate the CsA-induced hypertension and vascular and renal injury and dysfunction and that CsA reduces MDSCs in mice. Daily interleukin-33 treatment, which increased MDSC levels, completely prevented CsA-induced hypertension and vascular and renal toxicity. Adoptive transfer of MDSCs from control mice into CsA-treated mice after hypertension was established dose-dependently reduced blood pressure and vascular and glomerular injury. CsA treatment of aortas and kidneys isolated from control mice for 24 hours decreased relaxation responses and increased inflammation, respectively, and these effects were prevented by the presence of MDSCs. MDSCs also prevented the CsA-induced increase in fibronectin in microvascular and glomerular endothelial cells. Last, CsA dose-dependently reduced the number of MDSCs by inhibiting calcineurin and preventing cell proliferation, as other direct calcineurin signaling pathway inhibitors had the same dose-dependent effect. These data suggest that augmenting MDSCs can reduce the cardiovascular and renal toxicity and hypertension caused by CsA.

Abstract 098: Augmenting Renal Lymphatic Vessel Density Prevents Salt-sensitive Hypertension in Mice

Salt-sensitive hypertension (SSHTN) is associated with renal immune cell infiltration and interstitial inflammation. Lymphatic vessels drain the interstitial compartment and traffic immune cells to draining lymph nodes; however little is known about the role of lymphatics and immune cell trafficking in the kidney during SSHTN. Our hypotheses were that renal lymphatic vessel density is increased in mice with SSHTN and that further augmenting renal lymphatic vessels will prevent SSHTN. SSHTN mice were made by administering L-NAME for two weeks, followed by a two week washout, and then were fed a 4% high salt diet for three weeks. Compared to control mice, mice with SSHTN (SBP: 103±3 vs. 136±2 mmHg; p<0.05) had markedly increased renal lymphatic vessel density. Kidneys of SSHTN mice had significantly increased gene expression of the lymphatic vessel marker Lyve1 , the macrophage marker Adgre1 (F4/80), the Th1 cell marker Tbx21 , and the pro-inflammatory cytokine Il6 while expression of the immune cell-lymphatic chemokine receptor Ccr7 was decreased significantly. Mice solely fed a 4% salt diet for three weeks did not exhibit hypertension or increased renal lymphatic vessel density. To determine whether augmenting renal lymphatic vessels prior to the high salt diet could prevent SSHTN, we used transgenic mice that overexpress the lymphangiogenic signal VEGF-D only in the kidney under the control of doxycycline (KidVD+ mice) and thus exhibit renal lymphangiogenesis. Doxycycline initiated one week prior to the high salt diet prevented SSHTN in KidVD+ mice while having no effect on blood pressure in KidVD- mice (SBP: 117±4 vs. 139±5 mmHg; p<0.05). Renal gene expression of Tbx21 was decreased in KidVD+ mice while Ccr7 gene expression was increased significantly. These data demonstrate that renal lymphatic vessel density is increased in SSHTN and that augmenting renal lymphatic vessel density prior to a high salt diet can prevent SSHTN by improving renal immune cell exfiltration.

Abstract P339: Genetically Induced Renal Lymphangiogenesis Prevents the Development of L-NAME Hypertension in Mice

In humans and experimental animals, persistent immune system activation, accumulation of immune cells in the kidney, and subsequent inflammation plays an essential role in the development of hypertension (HTN). To reduce inflammation, lymphatic vessels drain extracellular fluid from the interstitium and traffic immune cells to draining lymph nodes. However, little is known about the connection between hypertension and renal lymphatic vessels. We hypothesized that renal lymphatic vessel density would increase in mice with L-NAME HTN and that genetically induced renal lymphangiogenesis would prevent this increase in blood pressure. L-NAME (0.5 mg/mL) was administered in the drinking water for two weeks and caused HTN (SBP: 153±3 vs. 103±3 mmHg; p<0.05) and renal lymphatic vessel dilation compared to control mice. Kidneys from mice with L-NAME HTN had significantly increased gene expression of the lymphangiogenic marker Vegfc , macrophage marker Adgre1 (F4/80), dendritic cell marker Cd11c , Th1 cell marker Tbx21 , and the pro-inflammatory cytokine Il6 . Blood pressure decreased after a two-week washout period following L-NAME (SBP: 113±2 mmHg) which was associated with a decrease in renal gene expression of Adgre1 (F4/80) and Cd11c , however renal lymphatic vessels remained dilated. To determine if augmenting renal lymphatic vessel density prior to L-NAME treatment would prevent HTN, we used transgenic mice that in response to doxycycline undergo kidney-specific VEGF-D overexpression (KidVD+ mice) and renal lymphangiogenesis. Doxycycline (200 mg/L) was administered in the drinking water of KidVD+ and KidVD- mice for four weeks with L-NAME being added during the final three weeks. Starting doxycycline one week prior to L-NAME prevented HTN in KidVD+ mice while slightly decreasing SBP in KidVD- mice (SBP: 112±4 vs. 134±2 mmHg; p<0.05). Renal gene expression of the Th17 cell marker Rorc was decreased and the lymphatic chemokine markers Ccl21 and Ccl19 were increased significantly in KidVD+ mice. These data together demonstrate that L-NAME HTN can alter the size of renal lymphatic vessels and genetically augmenting renal lymphatic vessel density prior to L-NAME can prevent the development of HTN.

Recent Advances in Immunity and Hypertension

Persistent immune system activation plays an important role in the development of various forms of hypertension. Activation of the innate immune system, inflammation, and subsequent adaptive immune system response causing end-organ injury and dysfunction ultimately leads to hypertension and its associated sequelae including coronary artery disease, heart failure, stroke, and chronic kidney disease. In this review, we will provide updates on the innate and adaptive immune cells involved in hypertension, the current understanding of how the immune system gets activated, and examine the recently discovered mechanisms involved in several forms of experimental hypertension.

Regulatory T-Cell Augmentation or Interleukin-17 Inhibition Prevents Calcineurin Inhibitor-Induced Hypertension in Mice

The immunosuppressive calcineurin inhibitors cyclosporine A and tacrolimus alter T-cell subsets and can cause hypertension, vascular dysfunction, and renal toxicity. We and others have reported that cyclosporine A and tacrolimus decrease anti-inflammatory regulatory T cells and increase proinflammatory interleukin-17-producing T cells; therefore, we hypothesized that inhibition of these effects using noncellular therapies would prevent the hypertension, endothelial dysfunction, and renal glomerular injury induced by calcineurin inhibitor therapy. Daily treatment of mice with cyclosporine A or tacrolimus for 1 week significantly decreased CD4⁺/FoxP3⁺ regulatory T cells in the spleen and lymph nodes, as well as induced hypertension, vascular injury and dysfunction, and glomerular mesangial expansion in mice. Daily cotreatment with all-trans retinoic acid reported to increase regulatory T cells and decrease interleukin-17-producing T cells, prevented all of the detrimental effects of cyclosporine A and tacrolimus. All-trans retinoic acid also increased regulatory T cells and prevented the hypertension, endothelial dysfunction, and glomerular injury in genetically modified mice that phenocopy calcineurin inhibitor-treated mice (FKBP12-Tie2 knockout). Treatment with an interleukin-17-neutralizing antibody also increased regulatory T-cell levels and prevented the hypertension, endothelial dysfunction, and glomerular injury in cyclosporine A-treated and tacrolimus-treated mice and FKBP12-Tie2 knockout mice, whereas an isotype control had no effect. Augmenting regulatory T cells and inhibiting interleukin-17 signaling using noncellular therapies prevents the cardiovascular and renal toxicity of calcineurin inhibitors in mice.

Renal inflammation and injury are associated with lymphangiogenesis in hypertension

Lymphatic vessels are vital for the trafficking of immune cells from the interstitium to draining lymph nodes during inflammation. Hypertension is associated with renal infiltration of activated immune cells and inflammation; however, it is unknown how renal lymphatic vessels change in hypertension. We hypothesized that renal macrophage infiltration and inflammation would cause increased lymphatic vessel density in hypertensive rats. Spontaneously hypertensive rats (SHR) that exhibit hypertension and renal injury (SHR-A3 strain) had significantly increased renal lymphatic vessel density and macrophages at 40 wk of age compared with Wistar-Kyoto (WKY) controls. SHR rats that exhibit hypertension but minimal renal injury (SHR-B2 strain) had significantly less renal lymphatic vessel density compared with WKY rats. The signals for lymphangiogenesis, VEGF-C and its receptor VEGF-R3, and proinflammatory cytokine genes increased significantly in the kidneys of SHR-A3 rats but not in SHR-B2 rats. Fischer 344 rats exhibit normal blood pressure but develop renal injury as they age. Kidneys from 24-mo- and/or 20-mo-old Fischer rats had significantly increased lymphatic vessel density, macrophage infiltration, VEGF-C and VEGF-R3 expression, and proinflammatory cytokine gene expression compared with 4-mo-old controls. These data together demonstrate that renal immune cell infiltration and inflammation cause lymphangiogenesis in hypertension- and aging-associated renal injury.

Abstract P145: Renal Inflammation and Injury is Associated with Increased Lymphangiogenesis in Hypertension

Hypertension is associated with immune system activation and inflammation. Renal infiltration of both innate and adaptive immune cells contributes to injury, dysfunction, and increased blood pressure. Activated immune cells that exit blood vessels into the interstitium then travel through lymphatic vessels to draining lymph nodes where they signal to other immune cells to increase the immune response. It is unknown how renal lymphatic vessels change in the context of hypertension, immune system activation, inflammation, and injury. We hypothesized that renal macrophage infiltration, inflammation, and injury would significantly increase lymphangiogenesis in various strains of rats. SHR rats that exhibit hypertension and renal injury (SHR-A3 strain) had significantly increased numbers of renal lymphatic vessels at 40 weeks of age compared to WKY controls (total of 3 fields of view: 52 ± 1 vs. 28 ± 1; p<0.05). This was associated with increased renal macrophage infiltration. SHR rats that exhibit hypertension but minimal renal injury (SHR-B2 strain) had significantly less renal lymphatic vessel numbers compared to WKY controls (25 ± 2 vs. 28 ± 1; p<0.05) and normal levels of macrophages. The signals for lymphangiogenesis, VEGF-C and its receptor VEGF-R3, were both increased significantly at the protein level in the kidneys of SHR-A3 rats at 18 weeks but not different in the kidneys of SHR-B2 rats compared to WKY controls. To test whether the increased lymphangiogensis is due to hypertension and/or renal inflammation and injury, we obtained kidneys from Fischer 344 rats that exhibit normal blood pressure but develop renal inflammation and injury as they age. Compared to kidneys from control 4-month old Fischer rats, kidneys from 20-month and 24-month old Fischer rats had significantly increased numbers of lymphatic vessels (32 ± 3 vs. 74 ± 1 vs. 110 ± 6, respectively; p<0.05) and this was also associated with increased macrophage infiltration. Protein levels of VEGF-C and VEGF-R3 were increased significantly in 20-month old Fischer rats compared to 4-month old controls. These data together demonstrate that renal immune cell infiltration, inflammation, and injury increases lymphangiogenesis.

Abstract P183: Myeloid-Derived Suppressor Cells Prevent Cyclosporine A-Induced Hypertension, Endothelial Dysfunction, and Renal Injury in Mice

Cyclosporine A (CsA) is an immunosuppressive drug used to treat focal segmental glomerulosclerosis, reduce autoimmune diseases, and prevent allograft rejection; however a limitation of CsA is that it can induce vascular and renal injury as well as hypertension. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature granulocytes, macrophages, and dendritic cells that suppress pro-inflammatory immune responses by secreting anti-inflammatory cytokines, inhibiting innate and adaptive immune cells, and inducing regulatory T cells (Tregs). We hypothesized that adoptive transfer of MDSCs would prevent CsA-induced vascular and renal injury and hypertension. Daily treatment of male C57BL6/J mice for 1 week with CsA (50 mg/kg/day, i.p. injection) significantly increased systolic blood pressure (Day 7 SBP in mmHg: Con=97±2 vs. CsA=145±3, p<0.05 vs. Con), decreased aortic endothelium-dependent relaxation responses, increased aortic fibronectin levels, increased renal glomerular mesangial expansion, increased renal fibronectin levels, and decreased splenic Treg levels. Adoptive transfer of 1 million MDSCs by i.p. injection on days 1, 4, and 7 partially prevented the CsA-induced rise in systolic blood pressure (CsA+1M MDSCs=120±3 mmHg) and the detrimental vascular and renal effects. However, adoptive transfer of 2 million MDSCs fully prevented the CsA-induced hypertension (CsA+2M MDSCs=105±1 mmHg) and vascular and renal effects. The anti-hypertensive and vascular and renal protective effects of 2 million MDSCs were independent of Treg induction as splenic Treg levels remained significantly decreased. These data suggest that MDSCs can prevent the hypertension and toxicity caused by CsA independent of Tregs and may be a therapeutic target for CsA-treated patients.

Abstract P178: Depletion of Gamma-Delta T Cells Protects Against Toll-Like Receptor-Induced Preeclampsia in Mice

Preeclampsia (PE), a hypertensive disorder of pregnancy, is associated with vascular endothelial dysfunction and excessive immunity and inflammation. However, it is unclear which innate immune cells propagate the pro-inflammatory state. Gamma-delta T (gdT) cells can secrete tolerogenic anti-inflammatory cytokines or cytotoxic pro-inflammatory cytokines depending on their activation status. gdT cells from women with PE produce significantly more IFNg and perforin and are less susceptible to apoptosis than gdT cells from normal pregnant women. We hypothesized that Toll-like receptor (TLR) activation in gdT cells induces inflammation and causes PE-like features in mice and that gdT cell KO mice would be resistant to developing TLR-induced PE-like features. Activation of splenocytes isolated from day 14 normal pregnant mice with the TLR3 agonist poly I:C or the TLR7 agonist R837 for 24 hours significantly increased gdT cells as well as IFNg and TNFa production. We have reported that poly I:C or R837 treatment of normal pregnant mice elicits a pregnancy-dependent PE-like syndrome by inducing a pro-inflammatory immune response. Pregnant poly I:C-treated and R837-treated mice had significantly increased splenic levels of gdT cells and plasma levels of IFNg and TNFa compared to pregnant vehicle-treated mice. Pregnant gdT cell KO mice treated with poly I:C or R837 did not develop hypertension or endothelial dysfunction. These data demonstrate that gdT cells mediate the TLR-induced PE-like features in mice and depletion of gdT cells may reduce the severity of PE in women.

Four Pathways Involving Innate Immunity in the Pathogenesis of Preeclampsia

The maternal innate immune system plays an important role both in normal pregnancy as well as hypertensive disorders of pregnancy including preeclampsia (PE). We propose four pathways that involve excessive innate immunity that lead to most forms of PE. Pre-existing endothelial dysfunction plus pregnancy leads to an excessive innate immune response resulting in widespread inflammation, placental and renal dysfunction, vasoconstriction, and PE. Placental dysfunction due to shallow trophoblast invasion, inadequate spiral artery remodeling, and/or low placental perfusion initiates an innate immune response leading to excessive inflammation, endothelial and renal dysfunction, and PE. A heightened innate immune system due to pre-existing or acquired infections plus the presence of a paternally derived placenta and semi-allogeneic fetus cause an excessive innate immune response which manifests as PE. Lastly, an abnormal and excessive maternal immune response to pregnancy leads to widespread inflammation, organ dysfunction, and PE. We discuss the potential role of innate immunity in each of these scenarios, as well as the overlap, and how targeting the innate immune system might lead to therapies for the treatment of PE.

Phosphorylation of cardiac Myosin-binding protein-C is a critical mediator of diastolic function

BACKGROUND

Heart failure (HF) with preserved ejection fraction (HFpEF) accounts for ≈50% of all cases of HF and currently has no effective treatment. Diastolic dysfunction underlies HFpEF; therefore, elucidation of the mechanisms that mediate relaxation can provide new potential targets for treatment. Cardiac myosin-binding protein-C (cMyBP-C) is a thick filament protein that modulates cross-bridge cycling rates via alterations in its phosphorylation status. Thus, we hypothesize that phosphorylated cMyBP-C accelerates the rate of cross-bridge detachment, thereby enhancing relaxation to mediate diastolic function.

METHODS AND RESULTS

We compared mouse models expressing phosphorylation-deficient cMyBP-C(S273A/S282A/S302A)-cMyBP-C(t3SA), phosphomimetic cMyBP-C(S273D/S282D/S302D)-cMyBP-C(t3SD), and wild-type-control cMyBP-C(tWT) to elucidate the functional effects of cMyBP-C phosphorylation. Decreased voluntary running distances, increased lung/body weight ratios, and increased brain natriuretic peptide levels in cMyBP-C(t3SA) mice demonstrate that phosphorylation deficiency is associated with signs of HF. Echocardiography (ejection fraction and myocardial relaxation velocity) and pressure/volume measurements (-dP/dtmin, pressure decay time constant τ-Glantz, and passive filling stiffness) show that cMyBP-C phosphorylation enhances myocardial relaxation in cMyBP-C(t3SD) mice, whereas deficient cMyBP-C phosphorylation causes diastolic dysfunction with HFpEF in cMyBP-C(t3SA) mice. Simultaneous force and [Ca(2+)]i measurements on intact papillary muscles show that enhancement of relaxation in cMyBP-C(t3SD) mice and impairment of relaxation in cMyBP-C(t3SA) mice are not because of altered [Ca(2+)]i handling, implicating that altered cross-bridge detachment rates mediate these changes in relaxation rates.

CONCLUSIONS

cMyBP-C phosphorylation enhances relaxation, whereas deficient phosphorylation causes diastolic dysfunction and phenotypes resembling HFpEF. Thus, cMyBP-C is a potential target for treatment of HFpEF.

Cotreatment with interleukin 4 and interleukin 10 modulates immune cells and prevents hypertension in pregnant mice

BACKGROUND

Excessive maternal immune system activation plays a central role in the development of the hypertensive disorder of pregnancy preeclampsia (PE). The immunomodulatory cytokines interleukin 4 (IL-4) and interleukin 10 (IL-10) are dysregulated during PE; therefore we hypothesized that treatment with both recombinant IL-4 and IL-10 during pregnancy could prevent the development of PE in mice.

METHODS

Using our mouse model of PE in which immune system activation is induced by the double-stranded RNA receptor agonist poly I:C, we gave daily injections of IL-4, IL-10, or both on days 13-17 of pregnancy. Mice were then killed on day 18.

RESULTS

Poly I:C caused a significant increase in systolic blood pressure in pregnant (P-PIC) mice compared with vehicle-treated pregnant (P) mice. All 3 treatments significantly decreased blood pressure in P-PIC mice to P levels, ameliorated the endothelial dysfunction, and decreased placental TLR3 levels in P-PIC mice. However, only IL-4/IL-10 cotreatment prevented the proteinuria and increased incidence of fetal demise in P-PIC mice; IL-4 or IL-10 alone had no effect. Additionally, only IL-4/IL-10 cotreatment prevented the significant increase in CD3(+)/γδ(+) T cells and CD11c(+) dendritic cells and significant decrease in CD11b(+)/CD14(-) suppressor monocytes, as well as completely prevented placental necrosis, in P-PIC mice. Importantly, IL-4/IL-10 cotreatment in P mice had no detrimental effects.

CONCLUSIONS

Taken together, these data demonstrate that exogenous IL-4 and IL-10 administration concurrently during pregnancy can normalize immune cell subsets and prevent PE induced by maternal immune system activation.

Abstract 668: Deficiency of miR-155 Attenuates TLR3-Induced Preeclampsia-Like Symptoms in Mice

Preeclampsia (PE) is one of the leading causes of maternal morbidity and mortality worldwide. PE is diagnosed by new onset hypertension and proteinuria or end-organ damage at or after mid-gestation. Although it is known that excessive maternal inflammation contributes to PE, the underlying mechanisms that cause hypertension during pregnancy are still unclear. Excessive maternal inflammation may be in part mediated by ligation of Toll-like receptors (TLRs) by pathogen- or danger-associated molecular patterns. MicroRNAs are small endogenous regulators of gene expression and recently numerous inflammation-related microRNAs have been identified. Several clinical studies reported that miR-155 expression, which is known to regulate inflammation in various disease conditions, is also up-regulated in the placentas of women with PE. We confirmed by qRT-PCR that miR-155 expression was significantly increased in formalin-fixed paraffin-embedded placentas from patients with PE compared to normal pregnant women. Poly I:C (a TLR3 agonist) treatment of human placental cytotrophoblasts (CTBs) for 24 hours significantly increased miR-155 expression compared to vehicle-treated CTBs. Based on these data we hypothesized that TLR3 activation induces placental miR-155 expression which in turn contributes to excessive maternal inflammation leading to PE whereas miR-155 deficiency will attenuate PE-like symptoms in a TLR3-induced PE mouse model. Pregnant WT and miR-155 KO mice were treated with poly I:C or saline on gestational days (gd) 13, 15, and 17 prior to sacrifice on gd 18. Poly I:C treatment induced hypertension in pregnant WT mice (P-PIC WT) (gd 17 SBP: 139±4 mmHg) compared to P WT mice (99±4 mmHg), however this was attenuated in P-PIC miR-155 KO mice (100±1 mmHg ). P-PIC WT mice exhibited endothelial dysfunction and splenomegaly compared to P WT mice and these were also attenuated in PPIC miR-155 KO mice. Our data taken together suggest that miR-155 plays a role in the pathogenesis of PE likely by increasing the maternal inflammatory response.

Abstract 460: IL-33 Treatment Prevents Cyclosporine A-Induced Hypertension, Endothelial Dysfunction, and Vascular Remodeling in Mice

The immunosuppressive drug cyclosporine A (CsA) causes systemic and renal vascular remodeling, endothelial dysfunction, and hypertension and this is associated with decreased anti-inflammatory regulatory T cells (Tregs). Myeloid-derived suppressor cells (MDSCs), a heterogeneous population of immature granulocytes, macrophages, and dendritic cells, play a central regulatory role in immune responses by inhibiting various pro-inflammatory innate and adaptive immune cells as well as stimulating Treg expansion. We hypothesized that CsA causes vascular remodeling, endothelial dysfunction, and hypertension in part by decreasing MDSCs and that augmentation of MDSCs in vivo with IL-33 treatment can prevent these effects. Daily treatment of male C57BL6/J mice for 1 week with CsA (50 mg/kg/day, ip) and IL-33 (0.5 ug/day, ip) prevented the CsA-induced decrease in splenic MDSC levels (Day 7 % of lymphocytes: Con=3.7±0.9, CsA=2.1±0.5*, CsA+IL-33=3.2±0.3; *p<0.05 vs. Con), increase in SBP (Day 7 SBP in mmHg: Con=94±3, CsA=148±4*, CsA+IL-33=100±3; *p<0.05 vs. Con), and decrease in maximal aortic endothelium-dependent relaxation responses (Con=78±2%, CsA=29±6%*, CsA+IL-33=74±2%; *p<0.05 vs. Con). Additionally, CsA treatment increased fibronectin protein levels in aortas and kidneys and caused renal intraglomerular mesangial expansion and congestion, all of which were ameliorated by co-treatment with IL-33. Together, these data suggest that the hypertension, endothelial dysfunction, and vascular remodeling caused by CsA is mediated in part by decreased MDSCs and that IL-33 treatment may have beneficial cardiovascular effects in CsA-treated patients.

Abstract 459: Myeloid-Derived Suppressor Cells (MDSCs) Prevent Cyclosporine A-Induced Vascular and Renal Endothelial Cell Injury

Cyclosporine A (CsA) is an immunosuppressive drug that can cause vascular and renal endothelial dysfunction and hypertension. Myeloid-derived suppressor cells (MDSCs) exert anti-inflammatory activity by inhibiting various innate and adaptive immune cells; however, the direct effects of CsA on MDSCs and whether MDSCs can prevent the detrimental CsA effects on endothelial cells are unknown. We hypothesized that CsA directly decreases MDSCs and that MDSCs prevent CsA-induced endothelial injury. CsA (50 uM) treatment of CD11b+/Gr-1+ MDSCs isolated from male C57BL6/J mice for 24 hours caused a dose-dependent decrease in MDSCs (Total CD11b+/Gr-1+ cell number: Veh=6,358,000, CsA 10 uM=3,505,000, CsA 25 uM=2,685,000, CsA 50 uM=1,425,000). Mouse cardiac vascular and glomerular endothelial cells were treated with CsA (50 uM) in the absence and presence of 75,000 isolated MDSCs for 24 hours. CsA significantly increased fibronectin and ICAM protein levels 1.5-2-fold in both vascular and glomerular endothelial cells compared to vehicle-treated endothelial cells. The presence of MDSCs prevented the CsA-induced increase in fibronectin and ICAM while having no effects in vehicle-treated endothelial cells. Additionally, CsA (50 uM) treatment of aortas isolated from male C57BL6/J mice for 24 hours markedly decreased maximal acetylcholine-induced relaxation responses and this was partially restored by co-incubation with MDSCs, and isolated kidneys treated with CsA had increased levels of fibronectin and this was ameliorated by co-incubation with MDSCs. In conclusion, CsA-induced decreases in MDSCs may play a role in endothelial cell injury and the augmentation of MDSCs may prevent the vascular and renal dysfunction and hypertension caused by CsA.

Regulation of the Anti-Inflammatory Cytokines Interleukin-4 and Interleukin-10 during Pregnancy

Inflammation mediated by both innate and adaptive immune cells is necessary for several important processes during pregnancy. Pro-inflammatory immune cell activation plays a critical role in embryo implantation, placentation, and parturition; however dysregulation of these cells can lead to detrimental pregnancy outcomes including spontaneous abortion, fetal growth restriction, maternal pathology including hypertensive disorders, or fetal and maternal death. The resolution of inflammation plays an important role throughout pregnancy and is largely mediated by immune cells that produce interleukin (IL)-4 and IL-10. The temporal and spatial aspects of reducing inflammation during pregnancy represent a complex process that if not functioning optimally can lead to persistent inflammation and pregnancy complications. In this review, we examine how immune cells that produce IL-4 and IL-10 are regulated throughout pregnancy as well as the effects that reduced IL-4 and IL-10 signaling has on fetal and maternal physiology.

Abstract 7: Both Maternal Systemic and Paternal-Derived Placental Trophoblast TLR3 Activation Are Necessary for the Development of Preeclampsia in Mice

Preeclampsia (PE) is a pregnancy-specific hypertensive disorder which affects ~8% of all pregnancies worldwide. The placenta is considered to be the main culprit in the etiology of PE as the symptoms of PE typically abate following removal of the placenta. PE is also known to be mediated in part by excessive maternal immune system activation and inflammation. We developed a mouse model of PE by excessively activating TLR3, which recognizes dsRNA from necrotic tissue and viruses; however, it is unknown whether TLR3 activation in maternal systemic cells, in paternally-derived placental trophoblasts, or both play a role in the development of hypertension during pregnancy. We hypothesized that both contribute and to test this we used the following mating schemes: 1) female WT mice mated with male WT mice (control), 2) female TLR3 KO mated with WT male (Ma TLR3 KO, TLR3 deficiency in all maternal cells), 3) male TLR3 KO mated with female WT (Pa TLR3 KO, TLR3 deficiency in paternally-derived trophoblasts, the major cell type in the placenta), and 4) female TLR3 KO mated with male TLR3 KO (MaPa TLR3 KO, TLR3 deficiency in all maternal cells and trophoblasts). Pregnant WT and TLR3 KO (Ma, Pa, and MaPa) mice were subjected to poly I:C or saline treatment on gestational days 13, 15, and 17. Poly I:C treatment induced pregnancy-dependent hypertension in pregnant WT mice (PPIC WT) (day 17 SBP in mmHg: PPIC WT: 147±5 vs. P WT: 100±4; p<0.05), however this was attenuated in PPIC Ma TLR3 KO mice (109±2 mmHg; p<0.05 vs. P WT) and PPIC Pa TLR3 KO mice (109±1 mmHg; p<0.05 vs. P WT), and completely normalized in PPIC MaPa TLR3 KO mice (102±3 mmHg; P>0.05 vs. P WT). PPIC WT mice exhibited endothelial dysfunction, proteinuria, and increased fetal demise compared to P WT mice which were attenuated in PPIC Ma TLR3 KO and PPIC Pa TLR3 KO mice, but completely normalized in PPIC MaPa TLR3 KO mice. PPIC WT mice exhibited splenomegaly which was only completely reduced in PPIC MaPa TLR3 KO mice. In conclusion, our data suggest that both maternal systemic and paternal-derived placental trophoblast TLR3 activation contribute to the full development of PE-like symptoms in mice.

Abstract 545: PLacental eXpanded (PLX) Cell Treatment Ameliorates Preeclampsia Induced by TLR3 or TLR7 Activation in Mice

PLacental eXpanded (PLX) cells (Pluristem Therapeutics Inc.) are human placenta-derived, mesenchymal-like adherent stromal cells that release proteins in response to the environment of the host. PLX cells are non-immunogenic and have been shown to decrease inflammation and increase angiogenesis in inflammatory and ischemic conditions. Therefore, we tested whether PLX cell treatment could attenuate symptoms of preeclampsia (PE) in mice. We hypothesized that one-time PLX cell treatment would decrease the pregnancy-dependent hypertension, proteinuria, endothelial dysfunction, splenomegaly, inflammation, and placental injury induced by Toll-like receptor (TLR) activation during pregnancy. Pregnant C57BL/6 mice were given ip injections of saline vehicle (P), the TLR3 agonist poly I:C (PPIC), or the TLR7 agonist R837 (PR) on days 13, 15, and 17 of gestation. P, PPIC, and PR mice were also given either plasmalyte A (PLA, vehicle) or PLX cells (1 million) by im injection in the right leg on gestational day 14 (n=8 in each group). PLX cell treatment progressively decreased SBP over 3 days in PPIC and PR mice and had no effect in P control mice (day 17 SBP in mmHg: P+PLA = 100±4, P+PLX = 96±4, PPIC+PLA = 144±3, PPIC+PLX = 111±1, PR+PLA = 145±2, PR+PLX = 106±3; PPIC+PLA and PR+PLA p<0.05 vs. P+PLA). PLX cell treatment also normalized the urinary protein/creatinine ratio and aortic endothelium-dependent relaxation responses in PPIC and PR mice to that of P mice while having no significant effects on the number of fetuses or incidence of fetal demise per litter. Inflammation plays a central role in the development of TLR-induced PE and PLX cell treatment reduced spleen weight/body weight ratios, normalized splenic levels of gamma-delta T cells, decreased plasma IL-6 levels, and restored plasma IL-4 levels in PPIC and PR mice. Additionally, PLX cell treatment reduced fibrin deposition in the placental vasculature and significantly reduced placental HIF-1alpha protein levels. These data demonstrate that one-time PLX cell treatment after PE is induced was able to decrease inflammation, proteinuric hypertension, endothelial dysfunction, and placental injury in mice and may be beneficial in women with PE.

Interleukin-17 causes Rho-kinase-mediated endothelial dysfunction and hypertension

AIMS

Elevated levels of pro-inflammatory cytokine interleukin-17A (IL-17) are associated with hypertensive autoimmune diseases; however, the connection between IL-17 and hypertension is unknown. We hypothesized that IL-17 increases blood pressure by decreasing endothelial nitric oxide production.

METHODS AND RESULTS

Acute treatment of endothelial cells with IL-17 caused a significant increase in phosphorylation of the inhibitory endothelial nitric oxide (NO) synthase residue threonine 495 (eNOS Thr495). Of the kinases known to phosphorylate eNOS Thr495, only inhibition of Rho-kinase prevented the IL-17-induced increase. IL-17 caused a threefold increase in the Rho-kinase activator RhoA, and this was prevented by an IL-17 neutralizing antibody. In isolated mouse aortas, IL-17 significantly increased eNOS Thr495 phosphorylation, induced RhoA expression, and decreased NO-dependent relaxation responses, all of which were prevented by either an IL-17 neutralizing antibody or inhibition of Rho-kinase. In mice, IL-17 treatment for 1 week significantly increased systolic blood pressure and this was associated with decreased aortic NO-dependent relaxation responses, increased eNOS Thr495 phosphorylation, and increased RhoA expression. Inhibition of Rho-kinase prevented the hypertension caused by IL-17.

CONCLUSION

These data demonstrate that IL-17 activates RhoA/Rho-kinase leading to endothelial dysfunction and hypertension. Inhibitors of IL-17 or Rho-kinase may prove useful as anti-hypertensive drugs in IL-17-associated autoimmune diseases.