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.

Differential Changes in End Organ Immune Cells and Inflammation in Salt-Sensitive Hypertension: Effects of Lowering Blood Pressure.

We reported that salt-sensitive hypertension (SSHTN) is associated with increased pro-inflammatory immune cells, inflammation, and inflammation-associated lymphangiogenesis in the kidneys and gonads of male and female mice.  However, it is unknown whether these adverse end organ effects result from increased blood pressure (BP), elevated levels of salt, or both.  We hypothesized that pharmaceutically lowering BP would not fully alleviate the renal and gonadal immune cell accumulation, inflammation, and lymphangiogenesis associated with SSHTN.  SSHTN was induced in male and female C57BL6/J mice by administering nitro-L-arginine methyl ester hydrochloride (L-NAME; 0.5 mg/mL) in their drinking water for 2 weeks, followed by a 2-week washout period.  Subsequently, the mice received a 3-week 4% high salt diet (SSHTN).  The treatment group underwent the same SSHTN induction protocol but received hydralazine (HYD; 250 mg/L) in their drinking water during the diet phase (SSHTN+HYD). Control mice received tap water and a standard diet for 7 weeks.  In addition to decreasing systolic BP, HYD treatment generally decreased pro-inflammatory immune cells and inflammation in the kidneys and gonads of SSHTN mice.  Furthermore, the decrease in BP partially alleviated elevated renal and gonadal lymphatics and improved renal and gonadal function in mice with SSHTN.  These data demonstrate that high systemic pressure and salt differentially act on end organ immune cells, contributing to the broader understanding of how BP and salt intake collectively shape immune responses and highlight implications for targeted therapeutic interventions.

Differential Changes in End Organ Immune Cells and Inflammation in Salt-Sensitive Hypertension: Effects of Increasing M2 Macrophages.

Salt-sensitive hypertension (SSHTN) is associated with M1 macrophage polarization and inflammatory responses, leading to inflammation-associated lymphangiogenesis and functional impairment across multiple organs, including kidneys and gonads.  However, it remains unclear whether promoting M2 macrophage polarization can alleviate the hypertension, inflammation, and end organ damage in mice with salt sensitive hypertension (SSHTN).  Male and female mice were made hypertensive by administering nitro-L-arginine methyl ester hydrochloride (L-NAME; 0.5 mg/mL) for 2 weeks in the drinking water, followed by a 2-week interval without any treatments, and a subsequent high salt diet for 3 weeks (SSHTN).  AVE0991 (AVE) was intraperitoneally administered concurrently with the high salt diet.  Control mice were provided standard diet and tap water.  AVE treatment significantly attenuated BP and inflammation in mice with SSHTN.  Notably, AVE promoted M2 macrophage polarization, decreased pro-inflammatory immune cell populations, and improved function in renal and gonadal tissues of mice with SSHTN.  Additionally, AVE decreased lymphangiogenesis in the kidneys and testes of male SSHTN mice and the ovaries of female SSHTN mice.  These findings highlight the effectiveness of AVE in mitigating SSHTN-induced elevated BP, inflammation, and end organ damage by promoting M2 macrophage polarization and suppressing pro-inflammatory immune responses.  Targeting macrophage polarization emerges as a promising therapeutic approach for alleviating inflammation and organ damage in SSHTN.  Further studies are warranted to elucidate the precise mechanisms underlying AVE-mediated effects and to assess its clinical potential in managing SSHTN.

Inflammatory Alterations to Renal Lymphatic Endothelial Cell Gene Expression in Mouse Models of Hypertension.

INTRODUCTION: Hypertension (HTN) is a major cardiovascular disease that can cause and be worsened by renal damage and inflammation. We previously reported that renal lymphatic endothelial cells (LECs) increase in response to HTN and that augmenting lymphangiogenesis in the kidneys reduces blood pressure and renal pro-inflammatory immune cells in mice with various forms of HTN. Our aim was to evaluate the specific changes that renal LECs undergo in HTN. METHODS: We performed single-cell RNA sequencing. Using the angiotensin II-induced and salt-sensitive mouse models of HTN, we isolated renal CD31+ and podoplanin+ cells. RESULTS: Sequencing of these cells revealed three distinct cell types with unique expression profiles, including LECs. The number and transcriptional diversity of LECs increased in samples from mice with HTN, as demonstrated by 597 differentially expressed genes (p<0.01), 274 significantly enriched pathways (p<0.01), and 331 regulons with specific enrichment in HTN LECs. These changes demonstrate a profound inflammatory response in renal LECs in HTN, leading to an increase in genes and pathways associated with inflammation-driven growth and immune checkpoint activity in LECs. CONCLUSION: These results reinforce and help to further explain the benefits of renal LECs and lymphangiogenesis in HTN.

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.

Hypertension induces gonadal macrophage imbalance, inflammation, lymphangiogenesis, and dysfunction.

Hypertension (HTN) is associated with gonadal dysfunction and impaired reproductive health in both men and women. An imbalance in the systemic and renal proinflammatory (M1)/anti-inflammatory (M2) macrophage ratio, increased inflammation, and inflammation-associated lymphangiogenesis have been observed in animals with HTN. However, the impact of HTN on gonadal macrophages, inflammation, and lymphatics remains obscure. We hypothesized that salt-sensitive HTN (SSHTN) and HTN alters gonadal macrophage polarization, which is associated with inflammation, inflammation-associated lymphangiogenesis, and reproductive dysfunction. Flow cytometry analyses revealed a significant increase in M1 macrophages in the testes of SSHTN and nitro-L-arginine methyl ester hydrochloride (L-NAME)-induced HTN (LHTN) mice, with a concurrent decrease in M2 macrophages in SSHTN mice yet an increase in M2 macrophages in LHTN mice. Ovaries from SSHTN mice exhibited an increase in M1 and a decrease in M2 macrophages, while ovaries from LHTN mice had a significant increase in M2 and a decrease in M1 macrophages. Gene expression patterns of proinflammatory cytokines revealed gonadal inflammation in all hypertensive mice. Increased lymphatic vessel density in the gonads of both male and female hypertensive mice was confirmed by immunofluorescence staining for lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1). HTN adversely affected the expression pattern of steroidogenic enzymes, hormone receptors, and secretory proteins in both the testes and ovaries. In line with these results, male hypertensive mice also presented with decreased sperm concentration, and increased percentage of sperm with abnormal morphology, damaged acrosome, and nonfunctional mitochondrial activity. These data demonstrate that HTN alters gonadal macrophage polarization, which is associated with gonadal inflammation, inflammation-associated lymphangiogenesis, and dysfunction.

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.

Hypertension and reproductive dysfunction: a possible role of inflammation and inflammation-associated lymphangiogenesis in gonads.

Hypertension is one of the most prevalent diseases that leads to end organ damage especially affecting the heart, kidney, brain, and eyes. Numerous studies have evaluated the association between hypertension and impaired sexual health, in both men and women. The detrimental effects of hypertension in men includes erectile dysfunction, decrease in semen volume, sperm count and motility, and abnormal sperm morphology. Similarly, hypertensive females exhibit decreased vaginal lubrication, reduced orgasm, and several complications in pregnancy leading to fetal and maternal morbidity and mortality. The adverse effect of hypertension on male and female fertility is attributed to hormonal imbalance and changes in the gonadal vasculature. However, mechanistic studies investigating the impact of hypertension on gonads in more detail on a molecular basis remain scarce. Hence, the aim of the current review is to address and summarize the effects of hypertension on reproductive health, and highlight the importance of research on the effects of hypertension on gonadal inflammation and lymphatics.

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.

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.

Depletion of MHC class II invariant chain peptide or γ-δ T-cells ameliorates experimental preeclampsia.

Excessive innate immune system activation and inflammation during pregnancy can lead to organ injury and dysfunction and preeclampsia (PE); however, the molecular mechanisms involved are unknown. We tested the hypothesis that Toll-like receptor (TLR) activation induces major histocompatibility complex (MHC) class II invariant chain peptide (CLIP) expression on immune cells, makes them pro-inflammatory, and are necessary to cause PE-like features in mice. Treatment with VG1177, a competitive antagonist peptide for CLIP in the groove of MHC class II, was able to both prevent and treat PE-like features in mice. We then determined that γ-δ T cells are critical for the development of PE-like features in mice since γ-δ T-cell knockout mice, like CLIP deficient mice, are resistant to developing PE-like features. Placentas from women with PE exhibit significantly increased levels of γ-δ T cells. These preclinical data demonstrate that CLIP expression and activated γ-δ T cells are responsible for the development of immunologic PE-like features and that temporarily antagonizing CLIP and/or γ-δ T cells may be a therapeutic strategy for PE.

Toll-like receptor activation, vascular endothelial function, and hypertensive disorders of pregnancy.

Aberrant innate immune system activation in the mother contributes greatly to the development of hypertension during pregnancy. Numerous groups have elicited vascular inflammation, endothelial dysfunction, and hypertension in animals during gestation by directly activating Toll-like receptors. Additionally, several experimental therapies that reduce pro-inflammatory immune cells and cytokines restore vascular endothelial function and normalize blood pressure. This review will summarize the research demonstrating that an excessive maternal innate immune response is sufficient to cause vascular inflammation and endothelial dysfunction, which contributes to the development of hypertension during pregnancy. Dampening the vascular inflammation caused by immune responses may reduce the incidence and severity of hypertensive disorders of pregnancy.

Human placenta-derived stromal cells decrease inflammation, placental injury and blood pressure in hypertensive pregnant mice.

Pre-eclampsia, the development of hypertension and proteinuria or end-organ damage during pregnancy, is a leading cause of both maternal and fetal morbidity and mortality, and there are no effective clinical treatments for pre-eclampsia aside from delivery. The development of pre-eclampsia is characterized by maladaptation of the maternal immune system, excessive inflammation and endothelial dysfunction. We have reported that detection of extracellular RNA by the Toll-like receptors (TLRs) 3 and 7 is a key initiating signal that contributes to the development of pre-eclampsia. PLacental eXpanded (PLX-PAD) cells are human placenta-derived, mesenchymal-like, adherent stromal cells that have anti-inflammatory, proangiogenic, cytoprotective and regenerative properties, secondary to paracrine secretion of various molecules in response to environmental stimulation. We hypothesized that PLX-PAD cells would reduce the associated inflammation and tissue damage and lower blood pressure in mice with pre-eclampsia induced by TLR3 or TLR7 activation. Injection of PLX-PAD cells on gestational day 14 significantly decreased systolic blood pressure by day 17 in TLR3-induced and TLR7-induced hypertensive mice (TLR3 144-111 mmHg; TLR7 145-106 mmHg; both P<0.05), and also normalized their elevated urinary protein:creatinine ratios (TLR3 5.68-3.72; TLR7 5.57-3.84; both P<0.05). On gestational day 17, aortic endothelium-dependent relaxation responses improved significantly in TLR3-induced and TLR7-induced hypertensive mice that received PLX-PAD cells on gestational day 14 (TLR3 35-65%; TLR7 37-63%; both P<0.05). In addition, markers of systemic inflammation and placental injury, increased markedly in both groups of TLR-induced hypertensive mice, were reduced by PLX-PAD cells. Importantly, PLX-PAD cell therapy had no effects on these measures in pregnant control mice or on the fetuses. These data demonstrate that PLX-PAD cell therapy can safely reverse pre-eclampsia-like features during pregnancy and have a potential therapeutic role in pre-eclampsia treatment.

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.

Endothelial cell transforming growth factor-ß receptor activation causes tacrolimus-induced renal arteriolar hyalinosis.

Arteriolar hyalinosis is a common histological finding in renal transplant recipients treated with the calcineurin inhibitor tacrolimus; however, the pathophysiologic mechanisms remain unknown. In addition to increasing transforming growth factor (TGF)-ß levels, tacrolimus inhibits calcineurin by binding to FK506-binding protein 12 (FKBP12). FKBP12 alone also inhibits TGF-ß receptor activation. Here we tested whether tacrolimus binding to FKBP12 removes an inhibition of the TGF-ß receptor, allowing ligand binding, ultimately leading to receptor activation and arteriolar hyalinosis. We found that specific deletion of FKBP12 from endothelial cells was sufficient to activate endothelial TGF-ß receptors and induce renal arteriolar hyalinosis in these knockout mice, similar to that induced by tacrolimus. Tacrolimus-treated and knockout mice exhibited significantly increased levels of aortic TGF-ß receptor activation as evidenced by SMAD2/3 phosphorylation, along with increased collagen and fibronectin expression compared to controls. Treatment of isolated mouse aortas with tacrolimus increased TGF-ß receptor activation and collagen and fibronectin expression. These effects were independent of calcineurin, absent in endothelial denuded aortic rings, and could be prevented by the small molecule TGF-ß receptor inhibitor SB-505124. Thus, endothelial cell TGF-ß receptor activation is sufficient to cause vascular remodeling and renal arteriolar hyalinosis.

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.

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.

Time restricted feeding decreases renal innate immune cells and blood pressure in hypertensive mice.

BACKGROUND: Renal innate immune cell accumulation and inflammation are associated with hypertension. Time restricted feeding (TRF) has been reported to decrease inflammation and blood pressure. Whether TRF can decrease blood pressure by decreasing renal innate immune cells in hypertension is unknown. METHODS AND RESULTS: We determined whether TRF can decrease blood pressure in two separate mouse models of hypertension, N(G)-nitro-L-arginine methyl ester hydrochloride-induced hypertension (LHTN) and salt-sensitive hypertension (SSHTN). Once hypertension was established after 2 days, TRF (12-h food/12-h no food) for 4 weeks significantly decreased systolic blood pressure in both LHTN and SSHTN mice despite no differences in the amount of food eaten or body weight between groups. Activated macrophages and dendritic cells in the kidneys of both LHTN and SSHTN mice were decreased significantly in mice that underwent TRF. This was associated with an improvement in kidney function (decreased serum creatinine, decreased fractional excretion of sodium, and increased creatinine clearance) which achieved significance in LHTN mice and trended towards improvement in SSHTN mice. CONCLUSIONS: Our findings demonstrate that TRF can significantly decrease renal innate immune cells and blood pressure in two mouse models of 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.