Cutaneous Na+ storage strengthens the antimicrobial barrier function of the skin and boosts macrophage-driven host defense

Macrophage-specific MHCII expression is regulated by a remote Ciita enhancer controlled by NFAT5

NFAT5 regulates macrophage MHCII expression by controlling the transcription of its coactivator Ciita through a remote enhancer. This mechanism differs from those previously found in DCs and B lymphocytes and distinguishes macrophages from these APC lineages.

MHCII in antigen-presenting cells (APCs) is a key regulator of adaptive immune responses. Expression of MHCII genes is controlled by the transcription coactivator CIITA, itself regulated through cell type–specific promoters. Here we show that the transcription factor NFAT5 is needed for expression of Ciita and MHCII in macrophages, but not in dendritic cells and other APCs. NFAT5-deficient macrophages showed defective activation of MHCII-dependent responses in CD4⁺ T lymphocytes and attenuated capacity to elicit graft rejection in vivo. Ultrasequencing analysis of NFAT5-immunoprecipitated chromatin uncovered an NFAT5-regulated region distally upstream of Ciita. This region was required for CIITA and hence MHCII expression, exhibited NFAT5-dependent characteristics of active enhancers such as H3K27 acetylation marks, and required NFAT5 to interact with Ciita myeloid promoter I. Our results uncover an NFAT5-regulated mechanism that maintains CIITA and MHCII expression in macrophages and thus modulates their T lymphocyte priming capacity.

Antiviral innate immune response in non-myeloid cells is augmented by chloride ions via an increase in intracellular hypochlorous acid levels

Phagocytes destroy ingested microbes by producing hypochlorous acid (HOCl) from chloride ions (Cl^-) and hydrogen peroxide within phagolysosomes, using the enzyme myeloperoxidase. HOCl, the active ingredient in bleach, has antibacterial/antiviral properties. As myeloperoxidase is needed for HOCl production, non-myeloid cells are considered incapable of producing HOCl. Here, we show that epithelial, fibroblast and hepatic cells have enhanced antiviral activity in the presence of increasing concentrations of sodium chloride (NaCl). Replication of enveloped/non-enveloped, DNA (herpes simplex virus-1, murine gammaherpesvirus 68) and RNA (respiratory syncytial virus, influenza A virus, human coronavirus 229E, coxsackievirus B3) viruses are inhibited in a dose-dependent manner. Whilst treatment with sodium channel inhibitors did not prevent NaCl-mediated virus inhibition, a chloride channel inhibitor reversed inhibition by NaCl, suggesting intracellular chloride is required for antiviral activity. Inhibition is also reversed in the presence of 4-aminobenzoic hydrazide, a myeloperoxidase inhibitor, suggesting epithelial cells have a peroxidase to convert Cl^- to HOCl. A significant increase in intracellular HOCl production is seen early in infection. These data suggest that non-myeloid cells possess an innate antiviral mechanism dependent on the availability of Cl^- to produce HOCl. Antiviral activity against a broad range of viral infections can be augmented by increasing availability of NaCl.

Renal effects of cytokines in hypertension

PURPOSE OF REVIEW

Inflammatory cytokines contribute to the pathogenesis of hypertension through effects on renal blood flow and sodium handling. This review will update recent advances that explore the renal actions of immune cells and cytokines in the pathogenesis of hypertension.

RECENT FINDINGS

Populations of cells from both the innate and adaptive immune systems contribute to hypertension by modulating functions of the vasculature and epithelial cells in the kidney. Macrophages and T lymphocytes can directly regulate the hypertensive response and consequent target organ damage. Dendritic cells and B lymphocytes can alter blood pressure (BP) indirectly by facilitating T-cell activation. Proinflammatory cytokines, including tumor necrosis factor-α, interleukin 17, interleukin 1, and interferon-γ augment BP and/or renal injury when produced by T helper 1 cells, T helper 17 cells, and macrophages. In contrast, interleukin 10 improves vascular and renal functions in preclinical hypertension studies. The effects of transforming growth factor-β are complex because of its profibrotic and immunosuppressive functions that also depend on the localization and concentration of this pleiotropic cytokine.

SUMMARY

Preclinical studies point to a key role for cytokines in hypertension via their actions in the kidney. Consistent with this notion, anti-inflammatory therapies can attenuate BP elevation in human patients with rheumatologic disease. Conversely, impaired natriuresis may further polarize both T lymphocytes and macrophages toward a proinflammatory state, in a pathogenic, feed-forward loop of immune activation and BP elevation. Understanding the precise renal actions of cytokines in hypertension will be necessary to inhibit cytokine-dependent hypertensive responses while preserving systemic immunity and tumor surveillance.

Control of Propionibacterium acnes by natural antimicrobial substances: Role of the bacteriocin AS-48 and lysozyme

We report the high susceptibility of several clinical isolates of Propionibacterium acnes from different sources (skin, bone, wound exudates, abscess or blood contamination) to the head-to-tail cyclized bacteriocin AS-48. This peptide is a feasible candidate for further pharmacological development against this bacterium, due to its physicochemical and biological characteristics, even when it is growing in a biofilm. Thus, the treatment of pre-formed biofilms with AS-48 resulted in a dose- and time-dependent disruption of the biofilm architecture beside the decrease of bacterial viability. Furthermore, we demonstrated the potential of lysozyme to bolster the inhibitory activity of AS-48 against P. acnes, rendering high reductions in the MIC values, even in matrix-growing cultures, according to the results obtained using a range of microscopy and bioassay techniques. The improvement of the activity of AS-48 through its co-formulation with lysozyme may be considered an alternative in the control of P. acnes, especially after proving the absence of cytotoxicity demonstrated by these natural compounds on relevant human skin cell lines. In summary, this study supports that compositions comprising the bacteriocin AS-48 plus lysozyme must be considered as promising candidates for topical applications with medical and pharmaceutical purposes against dermatological diseases such as acne vulgaris.

Sodium bicarbonate regulates nitric oxide production in mouse macrophage cell lines stimulated with lipopolysaccharide and interferon γ

Macrophages are known to play pivotal roles in host-defense through inflammation via both innate and acquired immune systems, and so on. In an earlier paper, we showed the influence of the type of culture medium, Ham's F-12 or DMEM, on activated macrophage phenotypes induced by LPS and IFNγ. The production of nitric oxide (NO), pro-inflammatory cytokines such as TNFα and IL-1β, as well as the induction of superoxide-generating activity of J774.1/JA-4 cells was different depending on the type of culture medium. In this present study, we showed that sodium bicarbonate concentrations in these culture media, 14 mM in Ham's F-12 and 44 mM in DMEM, were crucial to explaining the differences in the induction of activated macrophage phenotypes, especially in that of iNOS. A concentration-dependent change in pH did not result in any remarkable difference in iNOS expression or NO production. Moreover, high sodium bicarbonate in culture medium increased not only NO production but also TNFα production in the activated macrophages. These results suggest that sodium bicarbonate would be a regulatory factor of NO and TNFα production in macrophages and that its concentration has a crucial role in macrophage activation.

Hypertonicity-enforced BCL-2 addiction unleashes the cytotoxic potential of death receptors

Attempts to exploit the cytotoxic activity of death receptors (DR) for treating cancer have thus far been disappointing. DR activation in most malignant cells fails to trigger cell death and may even promote tumor growth by activating cell death-independent DR-associated signaling pathways. Overcoming apoptosis resistance is consequently a prerequisite for successful clinical exploitation of DR stimulation. Here we show that hyperosmotic stress in the tumor microenvironment unleashes the deadly potential of DRs by enforcing BCL-2 addiction of cancer cells. Hypertonicity robustly enhanced cytotoxicity of tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) and other DR ligands in various cancer entities. Initial events in TRAIL DR signaling remained unaffected, but hypertonic conditions unlocked activation of the mitochondrial death pathway and thus amplified the apoptotic signal. Mechanistically, we demonstrate that hyperosmotic stress imposed a BCL-2-addiction on cancer cells to safeguard the integrity of the outer mitochondrial membrane (OMM), essentially exhausting the protective capacity of BCL-2-like pro-survival proteins. Deprivation of these mitochondrial safeguards licensed DR-generated truncated BH3-interacting domain death agonist (tBID) to activate BCL-2-associated X protein (BAX) and initiated mitochondrial outer membrane permeabilization (MOMP). Our work highlights that hyperosmotic stress in the tumor environment primes mitochondria for death and lowers the threshold for DR-induced apoptosis. Beyond TRAIL-based therapies, our findings could help to strengthen the efficacy of other apoptosis-inducing cancer treatment regimens.

Sodium chloride triggers Th17 mediated autoimmunity

The detrimental effects of a high-salt diet on human health have received much attention in the past few years. While it has been well established that high dietary salt intake is related to cardiovascular diseases, there is growing evidence that excess salt also affects the immune system and might be considered as a risk factor in autoimmune diseases such as multiple sclerosis (MS). Several studies have implicated T helper 17 cells (Th17) in the pathogenesis of MS. We and others recently demonstrated that excessive salt enhances the differentiation of Th17 cells, inducing a highly pathogenic phenotype that aggravates experimental neuroinflammation. Moreover, a diet rich in sodium affects intestinal microbiota alongside increased intestinal Th17 cells, thus linking the detrimental effects of high salt consumption to the gut-immune axis. First human studies revealed an association of increased MS disease activity with elevated sodium chloride consumption, while more recent epidemiology studies in larger cohorts suggest no correlation between salt intake and MS. However, it is known that ordinary urinary sodium analyses and nutritional questionnaires do not necessarily correspond to the actual sodium load and more sophisticated analyses are needed. Moreover, studies revealed that sodium can temporarily be stored in the body. This review summarizes recent findings on the impact of salt on the immune system and discusses potential challenges investigating dietary salt intake as a risk factor in MS.

Salt, inflammation, IL-17 and hypertension

Traditionally, arterial hypertension and subsequent end-organ damage have been attributed to haemodynamic factors, but increasing evidence indicates that inflammation also contributes to the deleterious consequences of this disease. The immune system has evolved to prevent invasion of foreign microorganisms and to promote tissue healing after injury. However, this beneficial activity comes at a cost of collateral damage when the immune system overreacts to internal injury, such as prehypertension. Over the past few years, important findings have revolutionized hypertension research. Firstly, in 2007, a seminal paper showed that adaptive immunity is involved in the pathogenesis of hypertension. Secondly, salt storage in the skin and its consequences for cardiovascular physiology were discovered. Thirdly, after the discovery that salt promotes the differentiation of CD4⁺ T cells into T_H 17 cells, it was demonstrated that salt directly changes several cells of the innate and adaptive immune system and aggravates autoimmune disease but may improve antimicrobial defence. Herein, we will review pathways of activation of immune cells by salt in hypertension as the framework for understanding the multiple roles of salt and immunity in arterial hypertension and autoimmune disease. 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.

Dendritic Cell Amiloride-Sensitive Channels Mediate Sodium-Induced Inflammation and Hypertension

Sodium accumulates in the interstitium and promotes inflammation through poorly defined mechanisms. We describe a pathway by which sodium enters dendritic cells (DCs) through amiloride-sensitive channels including the alpha and gamma subunits of the epithelial sodium channel and the sodium hydrogen exchanger 1. This leads to calcium influx via the sodium calcium exchanger, activation of protein kinase C (PKC), phosphorylation of p47^phox, and association of p47^phox with gp91^phox. The assembled NADPH oxidase produces superoxide with subsequent formation of immunogenic isolevuglandin (IsoLG)-protein adducts. DCs activated by excess sodium produce increased interleukin-1β (IL-1β) and promote T cell production of cytokines IL-17A and interferon gamma (IFN-γ). When adoptively transferred into naive mice, these DCs prime hypertension in response to a sub-pressor dose of angiotensin II. These findings provide a mechanistic link between salt, inflammation, and hypertension involving increased oxidative stress and IsoLG production in DCs.

High Salt Intake Attenuates Breast Cancer Metastasis to Lung

Diet-related factors are thought to modify the risk of cancers, while the influence of high salt intake remains largely uncharacterized. Breast cancer is the most common cancer in women worldwide. In the present study, we examined the effect of salt intake on breast cancer by using a 4T1 mouse mammary tumor model. Unexpectedly, both the fitness and the survival rate of the tumor-bearing mice were improved by high salt intake. Similarly, high salt intake suppressed the primary tumor growth as well as metastasis to lung in mice. Mechanistically, high salt intake greatly reduced food intake and thus might exert antitumor effect through mimicking calorie restriction. Immunoblotting showed the lower proliferation marker Ki-67 and the higher expression of the tumor suppressor gene p53 in tumors of high salt intake mice. Importantly, high salt intake might induce hyperosmotic stress, which sensitized breast cancer cells to p53-dependent anoikis. Collectively, our findings raise the possibility that endogenous salt deposition might act as the first-line defense system against breast cancer progression as well as metastasis.

The role of salt for immune cell function and disease

The immune system evolved to protect organisms from invading pathogens. A network of pro- and anti-inflammatory cell types equipped with special effector molecules guarantees efficient elimination of intruders like viruses and bacteria. However, imbalances can lead to an excessive response of effector cells incurring autoimmune or allergic diseases. An interplay of genetic and environmental factors contributes to autoimmune diseases and recent studies provided evidence for an impact of dietary habits on the immune status and related disorders. Western societies underwent a change in lifestyle associated with changes in food consumption. Salt (sodium chloride) is one component prevalent in processed food frequently consumed in western countries. Here we summarize recent advances in understanding the mechanisms behind the effects of sodium chloride on immune cells like regulatory T cells (Tregs) and T helper (T_H ) 17 cells and its implication as a risk factor for several diseases.

Speculations on salt and the genesis of arterial hypertension

Blood pressure salt sensitivity and salt resistance are mechanistically imperfectly explained. A prescient systems medicine approach by Guyton and colleagues-more than 50 years ago-suggested how salt intake might influence blood pressure. They proposed that a high-salt diet engenders sodium accumulation, volume expansion, cardiac output adjustments, and then autoregulation for flow maintenance. The autoregulation in all vascular beds increases systemic vascular resistance, causing the kidneys to excrete more salt and water, thus reducing systems to normal and minimizing any changes in blood pressure. This schema, which is remarkably all encompassing, included all regulatory mechanisms Guyton could identify at the time. Guyton introduced the idea that the kidney is central, particularly concerning the regulation of renal pressure natriuresis. Numerous criticisms have been subsequently raised, particularly recently. Kurtz and colleagues argue that the ability of individuals to respond with an appropriate vasodilatory response to increased salt intake is pivotal. Data exist to address that issue. Salt-resistant hypertensive models provide additional information. We identified a mendelian form of hypertension not related to sodium reabsorption in the distal nephron. The hypertension develops because of increased systemic vascular resistance. In addition, we rediscovered a third salt-storage glycose-aminoglycan-related compartment, largely in the skin. This compartment operates independently of renal function, and when perturbed, is associated with salt sensitivity. More recently, we found novel molecular mechanisms demonstrating how large salt quantities are excreted by the kidneys with minimal water losses. We introduce novel interpretations as to how the kidneys excrete salt when the intake is high. The findings could have relevance as to how blood pressure may be regulated at varying salt intakes. Our purposes are to provide the readership with a banquet of thoughts to digest, to pursue Guyton's ideas, and to adjust them accordingly.

Recommendations for active correction of hypernatremia in volume-resuscitated shock or sepsis patients should be taken with a grain of salt: A systematic review

Background:

Healthcare-acquired hypernatremia (serum sodium >145 mEq/dL) is common among critically ill and other hospitalized patients and is usually treated with hypotonic fluid and/or diuretics to correct a “free water deficit.” However, many hypernatremic patients are eu- or hypervolemic, and an evolving body of literature emphasizes the importance of rapidly returning critically ill patients to a neutral fluid balance after resuscitation.

Objective:

We searched for any randomized- or observational-controlled studies evaluating the impact of active interventions intended to correct hypernatremia to eunatremia on any outcome in volume-resuscitated patients with shock and/or sepsis.

Data sources:

We performed a systematic literature search with studies identified by searching MEDLINE, Embase, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, ClinicalTrials.gov, Index-Catalogue of the Library of the Surgeon General’s Office, DARE (Database of Reviews of Effects), and CINAHL and scanning reference lists of relevant articles with abstracts published in English.

Data synthesis:

We found no randomized- or observational-controlled trials measuring the impact of active correction of hypernatremia on any outcome in resuscitated patients.

Conclusion:

Recommendations for active correction of hypernatremia in resuscitated patients with sepsis or shock are unsupported by clinical research acceptable by modern evidence standards.

The interstitium conducts extrarenal storage of sodium and represents a third compartment essential for extracellular volume and blood pressure homeostasis

The role of salt in the pathogenesis of arterial hypertension is not well understood. According to the current understanding, the central mechanism for blood pressure (BP) regulation relies on classical studies linking BP and Na⁺ balance, placing the kidney at the very centre of long-term BP regulation. To maintain BP homeostasis, the effective circulating fluid volume and thereby body Na⁺ content has to be maintained within very narrow limits. From recent work in humans and rats, the notion has emerged that Na⁺ could be stored somewhere in the body without commensurate water retention to buffer free extracellular Na⁺ and that previously unidentified extrarenal, tissue-specific regulatory mechanisms are operative regulating the release and storage of Na⁺ from a kidney-independent reservoir. Moreover, immune cells from the mononuclear phagocyte system not only function as local on-site sensors of interstitial electrolyte concentration, but also, together with lymphatics, act as systemic regulators of body fluid volume and BP. These studies have established new and unexpected targets in studies of BP control and thus the pathophysiology of hypertension: the interstitium/extracellular matrix of the skin, its inherent interstitial fluid and the lymphatic vasculature forming a vessel network in the interstitium. Aspects of the interstitium in relation to Na⁺ balance and hypertension are the focus of this review. Taken together, observations of salt storage in the skin to buffer free extracellular Na⁺ and macrophage modulation of the extracellular matrix and lymphatics suggest that electrolyte homeostasis in the body cannot be achieved by renal excretion alone, but also relies on extrarenal regulatory mechanisms.

High dietary salt intake correlates with modulated Th17-Treg cell balance resulting in enhanced bone loss and impaired bone-microarchitecture in male mice

Osteoporosis is associated with reduced density and quality of bone leading to weakened skeleton thereby increasing the risk of fractures responsible for increased morbidity and mortality. Due to preference for western food style the consumption of salt intake in our diets has increased many folds. High dietary salt intake has recently been linked with induction of Th17 cells along with impairment of Treg cells. Also, Th17 cells have been one of major players in the pathophysiology of various bone pathologies including osteoporosis. We thus hypothesized that high salt diet (HSD) intake would lead to enhanced bone loss by modulating Th17-Treg cell balance. In the present study, we report for the first time that HSD intake in male mice impairs both trabecular and cortical bone microarchitecture along with decreasing the mineral density and heterogeneity of bones. The HSD modulates host immune system and skews Treg-Th17 balance by promoting osteoclastogenic Th17 cells and inhibiting development of anti-osteoclastogenic Treg cells in mice. HSD also enhanced expression of proinflammatory cytokines (IL-6, TNF-α, RANKL and IL-17) and decreased the expression of anti-inflammatory cytokines (IL-10, IFN-γ). Taken together the present study for the first time establishes a strong correlation between high dietary salt intake and bone health via interplay between Th17-Treg cells.

Tissue Sodium Content is Elevated in the Skin and Subcutaneous Adipose Tissue in Women with Lipedema

OBJECTIVE

To test the hypothesis that tissue sodium and adipose content are elevated in patients with lipedema; if confirmed, this could establish precedence for tissue sodium and adipose content representing a discriminatory biomarker for lipedema.

METHODS

Participants with lipedema (n = 10) and control (n = 11) volunteers matched for biological sex, age, BMI, and calf circumference were scanned with 3.0-T sodium and conventional proton magnetic resonance imaging (MRI). Standardized tissue sodium content was quantified in the calf skin, subcutaneous adipose tissue (SAT), and muscle. Dixon MRI was employed to quantify tissue fat and water volumes of the calf. Nonparametric statistical tests were applied to compare regional sodium content and fat-to-water volume between groups (significance: two-sided P ≤ 0.05).

RESULTS

Skin (P = 0.01) and SAT (P = 0.04) sodium content were elevated in lipedema (skin: 14.9 ± 2.9 mmol/L; SAT: 11.9 ± 3.1 mmol/L) relative to control participants (skin: 11.9 ± 2.0 mmol/L; SAT: 9.4 ± 1.6 mmol/L). Relative fat-to-water volume in the calf was elevated in lipedema (1.2 ± 0.48 ratio) relative to control participants (0.63 ± 0.26 ratio; P < 0.001). Skin sodium content was directly correlated with fat-to-water volume (Spearman's rho = 0.54; P = 0.01).

CONCLUSIONS

Internal metrics of tissue sodium and adipose content are elevated in patients with lipedema, potentially providing objective imaging-based biomarkers for differentially diagnosing the under-recognized condition of lipedema from obesity.

Western lifestyle and immunopathology of multiple sclerosis

There is increasing evidence for a sudden and unprecedented rise in the incidence of multiple sclerosis (MS) in Westernized countries over the past decades, emphasizing the role of environmental factors. Among many candidates, rapid changes in dietary habits seem to play a role in the pathogenesis of MS. Here, we summarize and discuss the available evidence for the role of dietary nutrients, such as table salt, fatty acids, and flavonoids, in the development and pathogenesis of MS. We also discuss new and emerging risk factors accompanying Western lifestyle, such as shift work, sleep, and circadian disruption.

Fluid Overload and Inflammation Axis

Extracellular fluid overload (FO), which is assessed using bioimpedance technologies, is an important predictor of outcome in dialysis patients and in patients with early stages of chronic kidney disease. While traditional cardiovascular abnormalities are assumed to mediate this risk, recently also, the importance of noncardiovascular factors, such as systemic inflammation and malnutrition has been shown. While both FO and inflammation are independent risk factors for mortality, recent studies have shown that their combined presence can lead to a cumulative risk profile. From a pathophysiologic viewpoint, FO and inflammation can also be mutually reinforcing. Inflammation could contribute to FO by hypoalbuminemia, capillary leakage, and a (unnoticed) decline in lean and/or fat tissue mass resulting in incorrect estimation of dry weight. Reciprocally, FO could lead to inflammation by the translocation of endotoxins through a congested bowel wall or by a proinflammatory effect of tissue sodium. The relative importance of these putative factors is, however, not clear yet and epidemiological studies have shown no clear temporal direction regarding the relationship between FO and inflammation. FO and inflammation appear to be part of (dynamic) clusters of risk factors, including malnutrition and hyponatremia. Technology-guided fluid management of the often vulnerable dialysis patient with FO and inflammation cannot yet be based on evidence from randomized controlled trials, in which these specific patients were in general not included. In the absence of those trials, treatment should be based on identifying actionable causes of inflammation and on the judicious removal of excess volume based on frequent clinical reassessment.

Urinary potassium is a potential biomarker of disease activity in Ulcerative colitis and displays in vitro immunotolerant role

We evaluated the in-vitro effect of potassium on CD4⁺ T cells and the role of urinary potassium as a potential biomarker of disease activity in patients with ulcerative colitis (UC). This prospective observational cohort study included healthy controls (n = 18) and UC patients [n = 30, median age: 40 (IQR: 28–46) years, 17 males)] with active disease(assessed by Mayo score) from September 2015–May 2016. Twenty-four hours urinary potassium along with fecal calprotectin (FCP) were estimated in UC patients (at baseline and follow-up after 3–6 months) and controls. In healthy volunteers, we also assessed the effect of potassium on CD4⁺ T cells differentiated in the presence of Th17 polarizing condition. UC patients had significantly higher FCP (368.2 ± 443.04 vs 12.44 ± 27.51, p < 0.001) and significantly lower urinary potassium (26.6 ± 16.9 vs 46.89 ± 35.91, p = 0.01) levels than controls. At follow-up, a significant increase in urinary potassium among patients who had clinical response [n = 22, 21.4 (14.4–39.7) to 36.5 (20.5–61.6), p = 0.04] and remission [n = 12, 18.7 (9.1–34.3) to 36.5 (23.4–70.5), p = 0.05] was accompanied with a parallel decline in FCP. On in-vitro analysis, potassium under Th17 polarizing conditions significantly inhibited IL-17 and interferon-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma $$\end{document}γ expression while favoring the induction of FoxP3⁺ T cells. Therefore, urinary potassium levels are inversely associated with disease activity in UC with in-vitro data supporting an immune-tolerant role of potassium.

A sodium binding system alleviates acute salt stress during seawater acclimation in eels

BACKGROUND

Teleosts transiting from freshwater (FW) to seawater (SW) environments face an immediate osmotic stress from ion influxes and water loss, but some euryhaline species such as eels can maintain a stable plasma osmolality during early SW exposure. The time course changes in the gene expression, protein abundance, and localization of key ion transporters suggested that the reversal of the ion transport systems was gradual, and we investigate how eels utilize a Na-binding strategy to slow down the ion invasion and complement the transporter-mediated osmoregulation.

RESULTS

Using an electron probe micro-analyzer, we localized bound Na in various eel tissues in response to SW transfer, suggesting that the Na-binding molecules were produced to sequester excess ionic Na⁺ to negate its osmotic potential, thus preventing acute cellular dehydration. Mucus cells were acutely activated in digestive tract, gill, and skin after SW transfer, producing Na-binding molecule-containing mucus layers that fence off high osmolality of SW. Using gel filtration HPLC, some molecules at 18 kDa were found to bind Na in the luminal secretion of esophagus and intestine, and higher binding was associated with SW transfer. Transcriptome and protein interaction results indicated that downregulation of Notch and β-catenin pathways, and dynamic changes in TGFβ pathways in intestine were involved during early SW transition, supporting the observed histological changes on epithelial desquamation and increased mucus production.

CONCLUSIONS

The timing for the activation of the Na-binding mechanism to alleviate the adverse osmotic gradient was temporally complementary to the subsequent remodeling of branchial ionocytes and transporting epithelia of the digestive tract. The strategy to manipulate the osmotic potential of Na⁺ by specific binding molecules is similar to the osmotically inactive Na described in human skin and muscle. The Na-binding molecules provide a buffer to tolerate the salinity changes, which is advantageous to the estuary and migrating fishes. Our data pave the way to identify this unknown class of molecules and open a new area of vertebrate osmoregulation research.

Elevated sodium chloride drives type I interferon signaling in macrophages and increases antiviral resistance

Type I IFN production and signaling in macrophages play critical roles in innate immune responses. High salt (i.e. high concentrations of NaCl) has been proposed to be an important environmental factor that influences immune responses in multiple ways. However, it remains unknown whether high salt regulates type I IFN production and signaling in macrophages. Here, we demonstrated that high salt promoted IFNβ production and its signaling in both human and mouse macrophages, and consequentially primed macrophages for strengthened immune sensing and signaling when challenged with viruses or viral nucleic acid analogues. Using both pharmacological inhibitors and RNA interference we showed that these effects of high salt on IFNβ signaling were mediated by the p38 MAPK/ATF2/AP1 signaling pathway. Consistently, high salt increased resistance to vesicle stomatitis virus (VSV) infection in vitro. In vivo data indicated that a high-salt diet protected mice from lethal VSV infection. Taken together, these results identify high salt as a crucial regulator of type I IFN production and signaling, shedding important new light on the regulation of innate immune responses.

Salt-responsive gut commensal modulates TH17 axis and disease

A Western lifestyle with high salt consumption can lead to hypertension and cardiovascular disease. High salt may additionally drive autoimmunity by inducing T helper 17 (TH17) cells, which can also contribute to hypertension. Induction of TH17 cells depends on gut microbiota; however, the effect of salt on the gut microbiome is unknown. Here we show that high salt intake affects the gut microbiome in mice, particularly by depleting Lactobacillus murinus. Consequently, treatment of mice with L. murinus prevented salt-induced aggravation of actively induced experimental autoimmune encephalomyelitis and salt-sensitive hypertension by modulating TH17 cells. In line with these findings, a moderate high-salt challenge in a pilot study in humans reduced intestinal survival of Lactobacillus spp., increased TH17 cells and increased blood pressure. Our results connect high salt intake to the gut-immune axis and highlight the gut microbiome as a potential therapeutic target to counteract salt-sensitive conditions.

A novel role for renal epithelial cells and the medullary sodium gradient in the local immune response

The extreme hypertonicity of the renal medulla plays a central role in regulating volume status. A recent publication in Cell has identified a novel role for the high sodium environment and the local epithelial cells in the recruitment of mononuclear phagocytes, potentially contributing to the defense against ascending urinary tract infection.

NFAT5-Regulated Macrophage Polarization Supports the Proinflammatory Function of Macrophages and T Lymphocytes

Macrophages are exquisite sensors of tissue homeostasis that can rapidly switch between pro- and anti-inflammatory or regulatory modes to respond to perturbations in their microenvironment. This functional plasticity involves a precise orchestration of gene expression patterns whose transcriptional regulators have not been fully characterized. We had previously identified the transcription factor NFAT5 as an activator of TLR-induced responses, and in this study we explore its contribution to macrophage functions in different polarization settings. We found that both in classically and alternatively polarized macrophages, NFAT5 enhanced functions associated with a proinflammatory profile such as bactericidal capacity and the ability to promote Th1 polarization over Th2 responses. In this regard, NFAT5 upregulated the Th1-stimulatory cytokine IL-12 in classically activated macrophages, whereas in alternatively polarized ones it enhanced the expression of the pro-Th1 mediators Fizz-1 and arginase 1, indicating that it could promote proinflammatory readiness by regulating independent genes in differently polarized macrophages. Finally, adoptive transfer assays in vivo revealed a reduced antitumor capacity in NFAT5-deficient macrophages against syngeneic Lewis lung carcinoma and ID8 ovarian carcinoma cells, a defect that in the ID8 model was associated with a reduced accumulation of effector CD8 T cells at the tumor site. Altogether, detailed analysis of the effect of NFAT5 in pro- and anti-inflammatory macrophages uncovered its ability to regulate distinct genes under both polarization modes and revealed its predominant role in promoting proinflammatory macrophage functions.

Salt, Hypertension, and Immunity

The link between inappropriate salt retention in the kidney and hypertension is well recognized. However, growing evidence suggests that the immune system can play surprising roles in sodium homeostasis, such that the study of inflammatory cells and their secreted effectors has provided important insights into salt sensitivity. As part of the innate immune system, myeloid cells have diverse roles in blood pressure regulation, ranging from prohypertensive actions in the kidney, vasculature, and brain, to effects in the skin that attenuate blood pressure elevation. In parallel, T lymphocyte subsets, as key constituents of the adaptive immune compartment, have variable effects on renal sodium handling and the hypertensive response, accruing from the functions of the cytokines that they produce. Conversely, salt can directly modulate the phenotypes of myeloid and T cells, illustrating bidirectional regulatory mechanisms through which sodium and the immune system coordinately impact blood pressure. This review details the complex interplay between myeloid cells, T cells, and salt in the pathogenesis of essential hypertension.

Effects of Food Additives on Immune Cells As Contributors to Body Weight Gain and Immune-Mediated Metabolic Dysregulation

Food additives are compounds used in order to improve food palatability, texture, and shelf life. Despite a significant effort to assure safety of use, toxicological analysis of these substances, generally, rely on their direct toxicity to target organs (liver and kidney) or their genotoxic effects. Much less attention is paid to the effects of these compounds on cells of the immune system. This is of relevance given that metabolic dysregulation and obesity have a strong immune-mediated component. Obese individuals present a state of chronic low-grade inflammation that contributes to the establishment of insulin resistance and other metabolic abnormalities known as the metabolic syndrome. Obesity and metabolic syndrome are currently recognized as worldwide epidemics that pose a profound socioeconomic impact and represent a concern to public health. Cells of the immune system contribute to both the maintenance of "lean homeostasis" and the metabolic dysregulation observed in obese individuals. Although much attention has been drawn in the past decades to obesity and metabolic syndrome as a result of ingesting highly processed food containing large amounts of fat and simple sugars, mounting evidence suggest that food additives may also be important contributors to metabolic derangement. Herein, we review pieces of evidence from the literature showing that food additives have relevant effects on cells of the immune system that could contribute to immune-mediated metabolic dysregulation. Considering their potential to predispose individuals to develop obesity and metabolic syndrome, their use should be taken with caution or maybe revisited.

A new paradigm of sodium regulation in inflammation and hypertension

Dysregulation of sodium (Na⁺) balance is a major cause of hypertensive cardiovascular disease. The current dogma is that interstitial Na⁺ readily equilibrates with plasma and that renal excretion and reabsorption is sufficient to regulate extracellular fluid volume and control blood pressure. These ideas have been recently challenged by the discovery that Na⁺ accumulates in tissues without commensurate volume retention and activates immune cells, leading to hypertension and autoimmune disease. However, objections have been raised to this new paradigm, with some investigators concerned about where and how salt is stored in tissues. Further concerns also include how Na⁺ is mobilized from tissue stores and how it interacts with various organ systems to cause hypertension and end-organ damage. This review assesses these two paradigms of Na⁺ regulation in the context of inflammation-mediated hypertension and cardiovascular disease pathogenesis. Also highlighted are future perspectives and important gaps in our understanding of how Na⁺ is linked to inflammation and hypertension. Understanding mechanisms of salt and body fluid regulation is the sine qua non of research efforts to identify therapeutic targets for hypertension and cardiovascular disease.

Myxinidin2 and myxinidin3 suppress inflammatory responses through STAT3 and MAPKs to promote wound healing

Skin wounds are continuously exposed to bacteria and can easily become infected. Infected wounds require antibiotic treatment, and infections caused by drug-resistant bacteria are an important public health problem. Antimicrobial peptides have broad-spectrum antibacterial activity, induce little or no drug resistance and may be suitable for treating skin infections caused by drug-resistant bacteria. We previously reported the design and function of myxinidin and myxinidin analogues. Here we showed that myxinidin2 and myxinidin3 exhibit antimicrobial and anti-biofilm activities against antibiotic-resistant Staphylococcus aureus, Acinetobacter baumannii, and Pseudomonas aeruginosa in high salt environments and in gelatin. Moreover, these peptides facilitated infected wound healing by decreasing inflammation through suppression of IL-6, IL-8, and TNF-α and regulation of downstream mediators such as STAT3, p38, JNK, and EGFR. In a mouse skin wound model infected with antibiotic-resistant bacteria, myxinidin2 and myxinidin3 eliminated the infection and enhanced wound healing. We therefore propose the use of these peptides for treating infected wounds and burns.

3 Tesla 23Na Magnetic Resonance Imaging During Acute Kidney Injury

RATIONALE AND OBJECTIVES

Sodium and proton magnetic resonance imaging (²³Na/¹H-MRI) have shown that muscle and skin can store Na⁺ without water. In chronic renal failure and in heart failure, Na⁺ mobilization occurs, but is variable depending on age, dialysis vintage, and other features. Na⁺ storage depots have not been studied in patients with acute kidney injury (AKI).

MATERIALS AND METHODS

We studied 7 patients with AKI (mean age: 51.7 years; range: 25-84) and 14 age-matched and gender-matched healthy controls. All underwent ²³Na/¹H-MRI at the calf. Patients were studied before and after acute hemodialysis therapy within 5-6 days. The ²³Na-MRI produced grayscale images containing Na⁺ phantoms, which served to quantify Na⁺ contents. A fat-suppressed inversion recovery sequence was used to quantify H₂O content.

RESULTS

Plasma Na⁺ levels did not change. Mean Na⁺ contents in muscle and skin did not significantly change following four to five cycles of hemodialysis treatment (before therapy: 32.7 ± 6.9 and 44.2 ± 13.5 mmol/L, respectively; after dialysis: 31.7 ± 10.2 and 42.8 ± 11.8 mmol/L, respectively; P > .05). Water content measurements did not differ significantly before and after hemodialysis in muscle and skin (P > .05). Na⁺ contents in calf muscle and skin of patients before hemodialysis were significantly higher than in healthy subjects (16.6 ± 2.1 and 17.9 ± 3.2) and remained significantly elevated after hemodialysis.

CONCLUSIONS

Na⁺ in muscle and skin accumulates in patients with AKI and, in contrast to patients receiving chronic hemodialysis and those with acute heart failure, is not mobilized with hemodialysis within 5-6 days.

Classification and possible bacterial infection in outpatients with eczema and dermatitis in China: A cross-sectional and multicenter study

Little is known about the classification and bacterial infection in outpatients with eczema and dermatitis in China.To investigate the prevalence of eczema and dermatitis in outpatients of dermatology clinics in China, examine classification and proportion of common types of dermatitis and the possible bacterial infection, and analyze the possible related factors.Outpatients with eczema or dermatitis from 39 tertiary hospitals of 15 provinces in mainland China from July 1 to September 30, 2014, were enrolled in this cross-sectional and multicenter study. Among 9393 enrolled outpatients, 636 patients (6.7%) were excluded because of incomplete information.The leading subtypes of dermatitis were unclassified eczema (35.5%), atopic dermatitis (13.4%), irritant dermatitis (9.2%), and widespread eczema (8.7%). Total bacterial infection rate was 52.3%, with widespread eczema, stasis dermatitis, and atopic dermatitis being the leading three (65.7%, 61.8%, and 61.4%, respectively). Clinically very likely bacterial infection has a significant positive correlation with disease duration, history of allergic disease, history of flexion dermatitis, and severe itching.Atopic dermatitis has become a common subtype of dermatitis in China. Secondary bacterial infection is common in all patients with dermatitis, and more attentions should be paid on this issue in other type of dermatitis apart from atopic dermatitis.

Modulation of CD4+ T Helper Cell Memory Responses in the Human Skin

Immunological memory is defined as the capacity to mount faster and more effective immune responses against antigenic challenges that have been previously encountered by the host. CD4+ T helper (Th) cells play central roles in the establishment of immunological memory as they assist the functions of other leukocytes. Th cells express polarized cytokine profiles and distinct migratory and seeding capacities, but also retain a certain functional plasticity that allows them to modulate their proliferation, activity, and homing behaviour upon need. Thus, in healthy individuals, T cell immunomodulation fulfils the task of eliciting protective immune responses where they are needed. At times, however, Th plasticity can lead to collateral tissue damage and progression to autoimmune diseases or, conversely, incapacity to reject malignant tissues and clear chronic infections. Furthermore, common immune players and molecular pathways of diseases can lead to different outcomes in different individuals. A mechanistic understanding of those pathways is therefore crucial for developing precise and curative medical interventions. Here, I focus on the skin microenvironment and comprehensively describe some of the cellular and molecular determinants of CD4+ T cell memory responses in homeostatic and pathological conditions. In discussing the cellular network orchestrating cutaneous immunity, I comprehensively describe the bidirectional interaction of skin antigen-presenting cells and mononuclear phagocytes with Th17 lymphocytes, and examine how the outcome of this interaction is influenced by endogenous skin molecules, including sodium salts and neuropeptides.

Use of Biomarkers in the Evaluation and Treatment of Hypertensive Patients

The current definition of hypertension is based on blood pressure values, and blood pressure also drives treatment decisions, is the most important treatment monitoring tool and helps estimating risk of hypertension-related organ damage. In an era of precision medicine, additional biomarkers are needed in the diagnosis and management of patients with hypertension. In this review, we outline the areas in which functional, imaging and circulating biomarkers could help in a more individualised definition of hypertension and associated risk. We will cover biomarkers for diagnosis; of pathophysiology and prediction of hypertension; response to treatment, organ damage; and to monitor treatment. A clear focus is on the vasculature, the heart and the kidneys, whereas we see a need to further develop biomarkers of cerebral function in order to diagnose cognition deficits and monitor changes in cognition in the future to support addressing the growing burden of hypertension-associated vascular dementia.

Titanium dioxide nanoparticles prime a specific activation state of macrophages

Titanium dioxide nanoparticles (TiO₂ NPs) are widely used in foods, cosmetics, and medicine. Although the inhalation toxicity of TiO₂ NPs has been studied, the potential adverse effects of oral exposure of low-dose TiO₂ NPs are largely unclear. Herein, with macrophage cell lines, primary cells, and mouse models, we show that TiO₂ NPs prime macrophages into a specific activation state characterized by excessive inflammation and suppressed innate immune function. After a month of dietary exposure in mice or exposure in vitro to TiO₂ NPs (10 and 50 nm), the expressions of pro-inflammatory genes in macrophages were increased, and the expressions of anti-inflammatory genes were decreased. In addition, for macrophages exposed to TiO₂ NPs in vitro and in vivo, their chemotactic, phagocytic, and bactericidal activities were lower. This imbalance in the immune system could enhance the susceptibility to infections. In mice, after a month of dietary exposure to low doses of TiO₂ NPs, an aggravated septic shock occurred in response to lipopolysaccharide challenge, leading to elevated levels of inflammatory cytokines in serum and reduced overall survival. Moreover, TLR4-deficient mice and primary macrophages, or TLR4-independent stimuli, showed less response to TiO₂ NPs. These results demonstrate that TiO₂ NPs induce an abnormal state of macrophages characterized by excessive inflammation and suppressed innate immune function in a TLR4-dependent manner, which may suggest a potential health risk, particularly for those with additional complications, such as bacterial infections.

Inflammation and premature aging in advanced chronic kidney disease

Systemic inflammation in end-stage renal disease is an established risk factor for mortality and a catalyst for other complications, which are related to a premature aging phenotype, including muscle wasting, vascular calcification, and other forms of premature vascular disease, depression, osteoporosis, and frailty. Uremic inflammation is also mechanistically related to mechanisms involved in the aging process, such as telomere shortening, mitochondrial dysfunction, and altered nutrient sensing, which can have a direct effect on cellular and tissue function. In addition to uremia-specific causes, such as abnormalities in the phosphate-Klotho axis, there are remarkable similarities between the pathophysiology of uremic inflammation and so-called "inflammaging" in the general population. Potentially relevant, but still somewhat unexplored in this respect, are abnormal or misplaced protein structures, as well as abnormalities in tissue homeostasis, which evoke danger signals through damage-associated molecular patterns, as well as the senescence-associated secretory phenotype. Systemic inflammation, in combination with the loss of kidney function, can impair the resilience of the body to external and internal stressors by reduced functional and structural tissue reserves, and by impairing normal organ crosstalk, thus providing an explanation for the greatly increased risk of homeostatic breakdown in this population. In this review, the relationship between uremic inflammation and a premature aging phenotype, as well as potential causes and consequences, are discussed.

Cellular zinc homeostasis modulates polarization of THP-1-derived macrophages

PURPOSE

Polarization of macrophages by environmental stimuli leads to the characteristic of different phenotypes that exhibit distinct functions, ranging in a continuous spectrum from pro-inflammatory M1 up to immunoregulatory and wound-healing M2 macrophages. Diseases like cancer, allergic asthma or diabetes are associated with an M1/M2 imbalance. Owing to the importance of the essential trace element zinc for the immune system and its involvement in signal transduction as a second messenger, we investigated the impact of zinc on M1 and M2 polarization of macrophages in vitro.

METHODS

A polarization model with human THP-1 cells was established and validated with previously described markers using quantitative real-time PCR, Western blot and flow cytometry. Intracellular free Zn²⁺ was determined with FluoZin-3-AM.

RESULTS

Whereas pSTAT1 and HLA-DR or pSTAT6 and Dectin-1 distinguish between M1 and M2 macrophages, respectively, CD86 and CD206 failed. Depending on the used markers, both zinc supplementation in physiological dose (50 µM) and zinc deficiency promote M1 polarization of THP-1-derived macrophages. Furthermore, zinc supplementation strongly inhibits M2 polarization.

CONCLUSION

For the first time, we show a modulating effect of zinc for the polarization of human macrophages. The strong inhibitory effect of zinc supplementation on M2 polarization indicates a relevance regarding M2-dominated diseases like allergic asthma or cancer. All in all, zinc achieves a great potential for modulating macrophage polarization.

A salt-sensing kinase in T lymphocytes, SGK1, drives hypertension and hypertensive end-organ damage

We previously showed that angiotensin II (Ang II) increases T cell production of IL-17A, and that mice deficient in IL-17A have blunted hypertension and attenuated renal and vascular dysfunction. It was recently shown that salt enhances IL-17A production from CD4+ T cells via a serum- and glucocorticoid-regulated kinase 1-dependent (SGK1-dependent) pathway. Thus, we tested the hypothesis that SGK1 signaling in T cells promotes hypertension and contributes to end-organ damage. We show that loss of T cell SGK1 results in a blunted hypertensive response to Ang II infusion by 25 mmHg. Importantly, renal and vascular inflammation is abrogated in these mice compared with control mice. Furthermore, mice lacking T cell SGK1 are protected from Ang II-induced endothelial dysfunction and renal injury. Loss of T cell SGK1 also blunts blood pressure and vascular inflammation in response to deoxycorticosterone acetate-salt (DOCA-salt) hypertension. Finally, we demonstrate that the Na+-K+-2Cl- cotransporter 1 (NKCC1) is upregulated in Th17 cells and is necessary for the salt-induced increase in SGK1 and the IL-23 receptor. These studies demonstrate that T cell SGK1 and NKCC1 may be novel therapeutic targets for the treatment of hypertension and identify a potentially new mechanism by which salt contributes to hypertension.

Na+ deposition in the fibrotic skin of systemic sclerosis patients detected by 23Na-magnetic resonance imaging

Objective

Skin fibrosis is the predominant feature of SSc and arises from excessive extracellular matrix deposition. Glycosaminoglycans are macromolecules of the extracellular matrix, which facilitate Na + accumulation in the skin. We used 23 Na-MRI to quantify Na + in skin. We hypothesized that skin Na + might accumulate in SSc and might be a biomarker for skin fibrosis.

Methods

In this observational case-control study, skin Na + was determined by 23 Na-MRI using a Na + volume coil in 12 patients with diffuse cutaneous SSc and in 21 control subjects. We assessed skin fibrosis by the modified Rodnan skin score prior to 23 Na-MRI and on follow-up 12 months later.

Results

23 Na-MRI demonstrated increased Na + in the fibrotic skin of SSc patients compared with skin from controls [mean ( s . d .): 27.2 (5.6) vs 21.4 (5.3) mmol/l, P < 0.01]. Na + content was higher in fibrotic than in non-fibrotic SSc skin [26.2 (4.8) vs 19.2 (3.4) mmol/l, P < 0.01]. Furthermore, skin Na + amount was correlated with changes in follow-up modified Rodnan skin score (R 2 = 0.68).

Conclusions

23 Na-MRI detected increased Na + in the fibrotic SSc skin; high Na + content was associated with progressive skin disease. Our findings provide the first evidence that 23 Na-MRI might be a promising tool to assess skin Na + and thereby predict progression of skin fibrosis in SSc.

Dietary Salt Exacerbates Experimental Colitis

The Western diet is characterized by high protein, sugar, fat, and low fiber intake, and is widely believed to contribute to the incidence and pathogenesis of inflammatory bowel disease (IBD). However, high sodium chloride salt content, a defining feature of processed foods, has not been considered as a possible environmental factor that might drive IBD. We set out to bridge this gap. We examined murine models of colitis on either a high salt diet (HSD) or a low salt diet. We demonstrate that an HSD exacerbates inflammatory pathology in the IL-10-deficient murine model of colitis relative to mice fed a low salt diet. This was correlated with enhanced expression of numerous proinflammatory cytokines. Surprisingly, sodium accumulated in the colons of mice on an HSD, suggesting a direct effect of salt within the colon. Similar to the IL-10-deficient model, an HSD also enhanced cytokine expression during infection by Salmonella typhimurium This occurred in the first 3 d of infection, suggesting that an HSD potentiates an innate immune response. Indeed, in cultured dendritic cells we found that high salt media potentiates cytokine expression downstream of TLR4 activation via p38 MAPK and SGK1. A third common colitis model, administration of dextran sodium sulfate, was hopelessly confounded by the high sodium content of the dextran sodium sulfate. Our results raise the possibility that high dietary salt is an environmental factor that drives increased inflammation in IBD.

Tissue sodium accumulation and peripheral insulin sensitivity in maintenance hemodialysis patients

BACKGROUND

Recent data suggest that sodium (Na⁺ ) is stored in the muscle and skin without commensurate water retention in maintenance hemodialysis (MHD) patients. In this study, we hypothesized that excessive Na⁺ accumulation would be associated with abnormalities in peripheral insulin action.

METHODS

Eleven MHD patients and eight controls underwent hyperinsulinemic-euglycemic-euaminoacidemic clamp studies to measure glucose (GDR) and leucine disposal rates (LDR), as well as lower left leg ²³ Na magnetic resonance imaging to measure Na⁺ concentration in the muscle and skin tissue.

RESULTS

The median GDR and LDR levels were lower, and the median muscle Na⁺ concentration was higher in MHD patients compared with controls. No significant difference was found regarding skin Na⁺ concentration between group comparisons. Linear regression revealed inverse relationships between muscle Na⁺ concentration and GDR and LDR in MHD patients, whereas no relationship was observed in controls. There was no association between skin Na⁺ content and GDR or LDR in either MHD patients or controls.

CONCLUSIONS

These data suggest that excessive muscle Na⁺ content might be a determinant of IR in MHD patients, although the causality and mechanisms remain to be proven.

Impact of environmental factors on alloimmunity and transplant fate

Although gene-environment interactions have been investigated for many years to understand people's susceptibility to autoimmune diseases or cancer, a role for environmental factors in modulating alloimmune responses and transplant outcomes is only now beginning to emerge. New data suggest that diet, hyperlipidemia, pollutants, commensal microbes, and pathogenic infections can all affect T cell activation, differentiation, and the kinetics of graft rejection. These observations reveal opportunities for novel therapeutic interventions to improve graft outcomes as well as for noninvasive biomarker discovery to predict or diagnose graft deterioration before it becomes irreversible. In this Review, we will focus on the impact of these environmental factors on immune function and, when known, on alloimmune function, as well as on transplant fate.

Salt suppresses IFNγ inducible chemokines through the IFNγ-JAK1-STAT1 signaling pathway in proximal tubular cells

The mechanisms of immunoactivation by salt are now becoming clearer. However, those of immunosuppression remain unknown. Since clinical evidence indicates that salt protects proximal tubules from injury, we investigated mechanisms responsible for salt causing immunosuppression in proximal tubules. We focused on cytokine-related gene expression profiles in kidneys of mice fed a high salt diet using microarray analysis and found that both an interferon gamma (IFNγ) inducible chemokine, chemokine (C-X-C motif) ligand 9 (CXCL9), and receptor, CXCR3, were suppressed. We further revealed that a high salt concentration suppressed IFNγ inducible chemokines in HK2 proximal tubular cells. Finally, we demonstrated that a high salt concentration decreased IFNGR1 expression in the basolateral membrane of HK2 cells, leading to decreased phosphorylation of activation sites of Janus kinase 1 (JAK1) and Signal Transducers and Activator of Transcription 1 (STAT1), activators of chemokines. JAK inhibitor canceled the effect of a high salt concentration on STAT1 and chemokines, indicating that the JAK1-STAT1 signaling pathway is essential for this mechanism. In conclusion, a high salt concentration suppresses IFNγ-JAK1-STAT1 signaling pathways and chemokine expressions in proximal tubules. This finding may explain how salt ameliorates proximal tubular injury and offer a new insight into the linkage between salt and immunity.

Increased salt consumption induces body water conservation and decreases fluid intake

BACKGROUND

The idea that increasing salt intake increases drinking and urine volume is widely accepted. We tested the hypothesis that an increase in salt intake of 6 g/d would change fluid balance in men living under ultra-long-term controlled conditions.

METHODS

Over the course of 2 separate space flight simulation studies of 105 and 205 days' duration, we exposed 10 healthy men to 3 salt intake levels (12, 9, or 6 g/d). All other nutrients were maintained constant. We studied the effect of salt-driven changes in mineralocorticoid and glucocorticoid urinary excretion on day-to-day osmolyte and water balance.

RESULTS

A 6-g/d increase in salt intake increased urine osmolyte excretion, but reduced free-water clearance, indicating endogenous free water accrual by urine concentration. The resulting endogenous water surplus reduced fluid intake at the 12-g/d salt intake level. Across all 3 levels of salt intake, half-weekly and weekly rhythmical mineralocorticoid release promoted free water reabsorption via the renal concentration mechanism. Mineralocorticoid-coupled increases in free water reabsorption were counterbalanced by rhythmical glucocorticoid release, with excretion of endogenous osmolyte and water surplus by relative urine dilution. A 6-g/d increase in salt intake decreased the level of rhythmical mineralocorticoid release and elevated rhythmical glucocorticoid release. The projected effect of salt-driven hormone rhythm modulation corresponded well with the measured decrease in water intake and an increase in urine volume with surplus osmolyte excretion.

CONCLUSION

Humans regulate osmolyte and water balance by rhythmical mineralocorticoid and glucocorticoid release, endogenous accrual of surplus body water, and precise surplus excretion.

FUNDING

Federal Ministry for Economics and Technology/DLR; the Interdisciplinary Centre for Clinical Research; the NIH; the American Heart Association (AHA); the Renal Research Institute; and the TOYOBO Biotechnology Foundation. Food products were donated by APETITO, Coppenrath und Wiese, ENERVIT, HIPP, Katadyn, Kellogg, Molda, and Unilever.

Inflammatory role of high salt level in tumor microenvironment (Review)

Chronic inflammation is known to play a critical role in cancer development and progression. High salt is known to mediate several chronic inflammatory diseases including hypertension, myocardial infarction, neurological ischemic attack, autoimmune diseases and cancers. High salt level is shown to induce angiogenesis and immune-dysfunction, both of which play a direct role in cancer proliferation. Furthermore, salt has been suggested to enhance Warburg-like metabolic phenotype in cancer cells and at the same time also induce pro-tumor MΦ2-macrophage phenotype. Recent studies have identified several molecular targets such as tonicity specific transcript factor NFAT5/TonEBP, sodium ion channel γENaC, and vascular endothelial growth factor, VEGF, which are upregulated under high salt external environment. These molecular targets offer futuristic therapeutic application in precision medicine. In this review, we discuss the current understanding of the salt mediated metabolic and immune dysfunctions playing a potential role in cancerous changes.

Enterocin AS-48 as Evidence for the Use of Bacteriocins as New Leishmanicidal Agents

We report the feasibility of enterocin AS-48, a circular cationic peptide produced by Enterococcus faecalis, as a new leishmanicidal agent. AS-48 is lethal to Leishmania promastigotes as well as to axenic and intracellular amastigotes at low micromolar concentrations, with scarce cytotoxicity to macrophages. AS-48 induced a fast bioenergetic collapse of L. donovani promastigotes but only a partial permeation of their plasma membrane with limited entrance of vital dyes, even at concentrations beyond its full lethality. Fluoresceinated AS-48 was visualized inside parasites by confocal microscopy and seen to cause mitochondrial depolarization and reactive oxygen species production. Altogether, AS-48 appeared to have a mixed leishmanicidal mechanism that includes both plasma membrane permeabilization and additional intracellular targets, with mitochondrial dysfunctionality being of special relevance. This complex leishmanicidal mechanism of AS-48 persisted even for the killing of intracellular amastigotes, as evidenced by transmission electron microscopy. We demonstrated the potentiality of AS-48 as a new and safe leishmanicidal agent, expanding the growing repertoire of eukaryotic targets for bacteriocins, and our results provide a proof of mechanism for the search of new leishmanicidal bacteriocins, whose diversity constitutes an almost endless source for new structures at moderate production cost and whose safe use on food preservation is well established.

Hyperosmolarity impedes the cross-priming competence of dendritic cells in a TRIF-dependent manner

Tissue osmolarity varies among different organs and can be considerably increased under pathologic conditions. Hyperosmolarity has been associated with altered stimulatory properties of immune cells, especially macrophages and dendritic cells. We have recently reported that dendritic cells upon exposure to hypertonic stimuli shift their profile towards a macrophage-M2-like phenotype, resulting in attenuated local alloreactivity during acute kidney graft rejection. Here, we examined how hyperosmotic microenvironment affects the cross-priming capacity of dendritic cells. Using ovalbumin as model antigen, we showed that exposure of dendritic cells to hyperosmolarity strongly inhibits activation of antigen-specific T cells despite enhancement of antigen uptake, processing and presentation. We identified TRIF as key mediator of this phenomenon. Moreover, we detected a hyperosmolarity-triggered, TRIF-dependent clustering of MHCI loaded with the ovalbumin-derived epitope, but not of overall MHCI molecules, providing a possible explanation for a reduced T cell activation. Our findings identify dendritic cells as important players in hyperosmolarity-mediated immune imbalance and provide evidence for a novel pathway of inhibition of antigen specific CD8⁺ T cell response in a hypertonic micromilieu.