Salt increases monocyte CCR2 expression and inflammatory responses in humans

Prognostic impact of hypernatremia for septic shock patients in the intensive care unit

BACKGROUND

Hypernatremia represents a significant electrolyte imbalance associated with numerous adverse outcomes, particularly in cases of intensive care unit (ICU)-acquired hypernatremia (IAH). Nevertheless, its relevance in patients with septic shock remains uncertain.

AIM

To identify independent risk factors and their predictive efficacy for IAH to improve outcomes in patients with septic shock.

METHODS

In the present retrospective single-center study, a cohort of 157 septic shock patients with concurrent hypernatremia in the ICU at The First Affiliated Hospital of Soochow University, between August 1, 2018, and May 31, 2023, were analyzed. Patients were categorized based on the timing of hypernatremia occurrence into the IAH group (n = 62), the non-IAH group (n = 41), and the normonatremia group (n = 54).

RESULTS

In the present study, there was a significant association between the high serum sodium concentrations, excessive persistent inflammation, immunosuppression and catabolism syndrome and chronic critical illness, while rapid recovery had an apparent association with normonatremia. Moreover, multivariable analyses revealed the following independent risk factors for IAH: Total urinary output over the preceding three days [odds ratio (OR) = 1.09; 95%CI: 1.02-1.17; P = 0.014], enteral nutrition (EN) sodium content of 500 mg (OR = 2.93; 95%CI: 1.13-7.60; P = 0.027), and EN sodium content of 670 mg (OR = 6.19; 95%CI: 1.75-21.98; P = 0.005) were positively correlated with the development of IAH. Notably, the area under the curve for total urinary output over the preceding three days was 0.800 (95%CI: 0.678-0.922, P = 0.001). Furthermore, maximum serum sodium levels, the duration of hypernatremia, and varying sodium correction rates were significantly associated with 28-day in-hospital mortality in septic shock patients (P < 0.05).

CONCLUSION

The present findings illustrate that elevated serum sodium level was significantly associated with a poor prognosis in septic shock patients in the ICU. It is highly recommended that hypernatremia be considered a potentially important prognostic indicator for the outcome of septic shock.

Transient High Salt Intake Promotes T-Cell-Mediated Hypertensive Vascular Injury

BACKGROUND

Dietary high salt (HS) intake has a strong impact on cardiovascular diseases. Here, we investigated the link between HS-aggravated immune responses and the development of hypertensive vascular disease.

METHODS

ApolipoproteinE-deficient mice were transiently treated with HS (1% NaCl) via drinking water for 2 weeks, followed by a washout period, and subsequent Ang II (angiotensin II) infusion (1000 ng/kg per min for 10 days) to induce abdominal aortic aneurysms/dissections and inflammation.

RESULTS

While transient HS intake alone triggered nonpathologic infiltration of activated T cells into the aorta, subsequent Ang II infusion increased mortality and the incidence of abdominal aortic aneurysms/dissections and atherosclerosis compared with hypertensive control mice. There were no differences in blood pressure between both groups. In transient HS-treated hypertensive mice, the aortic injury was associated with increased inflammation, accumulation of neutrophils, monocytes, CD69+CD4+ T cells, as well as CD4+ and CD8+ memory T cells. Mechanistically, transient HS intake increased expression levels of aortic RORγt as well as splenic CD4+TH17 and CD8+TC1 T cells in Ang II-treated mice. Isolated aortas of untreated mice were incubated with supernatants of TH17, TH1, or TC1 cells polarized in vitro under HS or normal conditions which revealed that secreted factors of HS-differentiated TH17 and TC1 cells, but not TH1 cells accelerated endothelial dysfunction.

CONCLUSIONS

Our data suggest that transient HS intake induces a subclinical T-cell-mediated aortic immune response, which is enhanced by Ang II. We propose a 2-hit model, in which HS acts as a predisposing factor to enhance hypertension-induced TH17 and TC1 polarization and aortic disease.

Causal relationship of salt intake with osteoarthritis: A Mendelian randomization analysis

Recent studies have demonstrated a correlation between salt intake (SI) and various diseases. However, it remains uncertain whether the relationship between SI (including salt added to food and sodium levels in urine) and benign osteoarthritis is causal. To investigate this, we conducted a 2-sample Mendelian randomization (MR) analysis to estimate the causal impact of SI on osteoarthritis (OA). A genome-wide association study of salt added to food and sodium in urine was used as the exposure, while hip osteoarthritis, knee osteoarthritis, and rheumatoid arthritis were defined as the outcomes. Inverse variance weighting (IVW) was used to calculate causal estimates, and sensitivity analyses were performed using methods including weighted mode, weighted median, MR-Egger, and Bayesian weighted MR. All statistical analyses were conducted using R software. Our results, primarily based on the IVW method, support the existence of a causal relationship between salt added to food and knee osteoarthritis (KOA). Specifically, salt added to food was associated with a decreased risk of KOA (OR = 1.248, P = .024, 95% CI: 1.030-1.512). This study is the first MR investigation exploring the causal relationship between salt added to food and KOA, potentially providing new insights and a theoretical basis for the prevention and treatment of KOA in the future.

High dietary salt intake attenuates nitric oxide mediated endothelium-dependent vasodilation and increases oxidative stress in pregnancy

OBJECTIVE

This study aimed to investigate the impact of dietary salt intake during normal pregnancy on maternal microvascular and macrovascular endothelium-dependent reactivity and oxidative stress level.

MATERIALS AND METHODS

In this cross-sectional study, based on their 24-h urinary sodium excretion, pregnant women (37-40 weeks of gestation) were divided into three groups: normal salt (<5.75 g/day, N  = 12), high salt (5.75-10.25 g/day, N  = 36), and very high salt (VHS;>10.25 g/day, N  = 17). Forearm skin microvascular reactivity in response to vascular occlusion, local heating (LTH) and iontophoresis of acetylcholine (AChID), as well as brachial artery flow mediated dilation (FMD) were measured. Serum nitric oxide, endocan, 8-iso-prostaglandin F2α (8-iso-PGF2α), thiobarbituric acid reactive substances (TBARS), and ferric-reducing ability of plasma assay were measured as biomarkers of endothelial function/activation and oxidative stress.

RESULTS

Brachial artery FMD, microvascular AChID, and LTH were significantly decreased in VHS compared with NS group, while LTH was also decreased in normal salt compared with high salt group. Nitric oxide was significantly decreased in both high salt and VHS groups compared with normal salt. Endocan, 8-iso-PGF2α, and TBARS were significantly increased in VHS compared with the normal salt group.

CONCLUSION

High dietary salt intake is associated with decreased nitric oxide mediated endothelium-dependent vasodilation in peripheral microcirculation and macrocirculation of healthy pregnant women due to increased oxidative stress.

Sodium as an Important Regulator of Immunometabolism

Salt sensitivity concerns blood pressure alterations after a change in salt intake (sodium chloride). The heart is a pump, and vessels are tubes; sodium can affect both. A high salt intake increases cardiac output, promotes vascular dysfunction and capillary rarefaction, and chronically leads to increased systemic vascular resistance. More recent findings suggest that sodium also acts as an important second messenger regulating energy metabolism and cellular functions. Besides endothelial cells and fibroblasts, sodium also affects innate and adaptive immunometabolism, immune cell function, and influences certain microbes and microbiota-derived metabolites. We propose the idea that the definition of salt sensitivity should be expanded beyond high blood pressure to cellular and molecular salt sensitivity.

Trained immunity induced by high-salt diet impedes stroke recovery

A high-salt diet (HSD) elicits sustained sterile inflammation and worsens tissue injury. However, how this occurs after stroke, a leading cause of morbidity and mortality, remains unknown. Here, we report that HSD impairs long-term brain recovery after intracerebral hemorrhage, a severe form of stroke, despite salt withdrawal prior to the injury. Mechanistically, HSD induces innate immune priming and training in hematopoietic stem and progenitor cells (HSPCs) by downregulation of NR4a family and mitochondrial oxidative phosphorylation. This training compromises alternative activation of monocyte-derived macrophages (MDMs) without altering the initial inflammatory responses of the stroke brain. Healthy mice transplanted with bone marrow from HSD-fed mice retain signatures of reduced MDM reparative functions, further confirming a persistent form of innate immune memory that originates in the bone marrow. Loss of NR4a1 in macrophages recapitulates HSD-induced negative impacts on stroke outcomes while gain of NR4a1 enables stroke recovery in HSD animals. Together, we provide the first evidence that links HSD-induced innate immune memory to the acquisition of persistent dysregulated inflammatory responses and unveils NR4a1 as a potential therapeutic target.

Salt-sensitive trait of normotensive individuals is associated with altered autonomous cardiac regulation: a randomized controlled intervention study

Blood pressure (BP) responses to sodium intake show great variation, discriminating salt-sensitive (SS) from salt-resistant (SR) individuals. The pathophysiology behind salt sensitivity is still not fully elucidated. We aimed to investigate salt-induced effects on body fluid, vascular tone, and autonomic cardiac response with regard to BP change in healthy normotensive individuals. We performed a randomized crossover study in 51 normotensive individuals with normal body mass index and estimated glomerular filtration rate. Subjects followed both a low-Na+ diet (LSD, <50 mmol/day) and a high-Na+ diet (HSD, >200 mmol/day). Cardiac output, systemic vascular resistance (SVR), and cardiac autonomous activity, through heart rate variability and cross-correlation baroreflex sensitivity (xBRS), were assessed with noninvasive continuous finger BP measurements. In a subset, extracellular volume (ECV) was assessed by iohexol measurements. Subjects were characterized as SS if mean arterial pressure (MAP) increased ≥3 mmHg after HSD. After HSD, SS subjects (25%) showed a 6.1-mmHg (SD 1.9) increase in MAP. No differences between SS and SR in body weight, cardiac output, or ECV were found. SVR was positively correlated with Delta BP (r = 0.31, P = 0.03). xBRS and heart rate variability were significantly higher in SS participants compared to SR participants after both HSD and LSD. Sodium loading did not alter heart rate variability within groups. Salt sensitivity in normotensive individuals is associated with an inability to decrease SVR upon high salt intake that is accompanied by alterations in autonomous cardiac regulation, as reflected by decreased xBRS and heart rate variability. No discriminatory changes upon high salt were observed among salt-sensitive individuals in body weight and ECV.NEW & NOTEWORTHY Extracellular fluid expansion in normotensive individuals after salt loading is present in both salt-sensitive and salt-resistant individuals and is not discriminatory to the blood pressure response to sodium loading in a steady-state measurement. In normotensive subjects, the ability to sufficiently vasodilate seems to play a pivotal role in salt sensitivity. In a normotensive cohort, differences in sympathovagal balance are also present in low-salt conditions rather than being affected by salt loading. Whereas treatment and prevention of salt-sensitive blood pressure increase are mostly focused on renal sodium handling and extracellular volume regulation, our study suggests that an inability to adequately vasodilate and altered autonomous cardiac functioning are additional key players in the pathophysiology of salt-sensitive blood pressure increase.

Novel mechanisms of salt-sensitive hypertension

A high dietary sodium-consumption level is considered the most important lifestyle factor that can be modified to help prevent an increase in blood pressure and the development of hypertension. Despite numerous studies over the past decades, the pathophysiology explaining why some people show a salt-sensitive blood pressure response and others do not is incompletely understood. Here, a brief overview of the latest mechanistic insights is provided, focusing on the mononuclear phagocytic system and inflammation, the gut-kidney axis, and epigenetics. The article also discusses the effects of 3 types of novel drugs on salt-sensitive hypertension-sodium-glucose cotransporter 2 inhibitors, nonsteroidal mineralocorticoid receptor antagonists, and aldosterone synthase inhibitors. The conclusion is that besides kidney-centered mechanisms, vasoconstrictor mechanisms are also relevant for both the understanding and treatment of this blood pressure phenotype.

Vegetarian and vegan diets: benefits and drawbacks

Plant-based diets have become increasingly popular thanks to their purported health benefits and more recently for their positive environmental impact. Prospective studies suggest that consuming vegetarian diets is associated with a reduced risk of developing cardiovascular disease (CVD), diabetes, hypertension, dementia, and cancer. Data from randomized clinical trials have confirmed a protective effect of vegetarian diets for the prevention of diabetes and reductions in weight, blood pressure, glycosylated haemoglobin and low-density lipoprotein cholesterol, but to date, no data are available for cardiovascular event rates and cognitive impairment, and there are very limited data for cancer. Moreover, not all plant-based foods are equally healthy. Unhealthy vegetarian diets poor in specific nutrients (vitamin B12, iron, zinc, and calcium) and/or rich in highly processed and refined foods increase morbidity and mortality. Further mechanistic studies are desirable to understand whether the advantages of healthy, minimally processed vegetarian diets represent an all-or-nothing phenomenon and whether consuming primarily plant-based diets containing small quantities of animal products (e.g. pesco-vegetarian or Mediterranean diets) has beneficial, detrimental, or neutral effects on cardiometabolic health outcomes. Further, mechanistic studies are warranted to enhance our understanding about healthy plant-based food patterns and the biological mechanisms linking dietary factors, CVD, and other metabolic diseases.

A new immune disease: systemic hypertension

Systemic hypertension is the most common medical comorbidity affecting the adult population globally, with multiple associated outcomes including cerebrovascular diseases, cardiovascular diseases, vascular calcification, chronic kidney disease, metabolic syndrome and mortality. Despite advancements in the therapeutic field approximately one in every five adult patients with hypertension is classified as having treatment-resistant hypertension, indicating the need for studies to provide better understanding of the underlying pathophysiology and the need for more therapeutic targets. Recent pre-clinical studies have demonstrated the role of the innate and adaptive immune system including various cell types and cytokines in the pathophysiology of hypertension. Moreover, pre-clinical studies have indicated the potential beneficial effects of immunosuppressant medications in the control of hypertension. Nevertheless, it is unclear whether such pathophysiological mechanisms and therapeutic alternatives are applicable to human subjects, while this area of research is undoubtedly a rapidly growing field.

Assessment of interleukin-10 promoter variant (-1082A/G) and cytokine production in patients with hemolytic uremic syndrome

Introduction

Hemolytic uremic syndrome (HUS) is a condition that results in acute kidney failure mainly in children, which is caused by Shiga toxin-producing Escherichia coli and inflammatory response. Although anti-inflammatory mechanisms are triggered, studies on the implication in HUS are scarce. Interleukin-10 (IL-10) regulates inflammation in vivo, and the interindividual differences in its expression are related to genetic variants. Notably, the single nucleotide polymorphism (SNP) rs1800896 -1082 (A/G), located in the IL-10 promoter, regulates cytokine expression.

Methods

Plasma and peripheral blood mononuclear cells (PBMC) were collected from healthy children and HUS patients exhibiting hemolytic anemia, thrombocytopenia, and kidney damage. Monocytes identified as CD14⁺ cells were analyzed within PBMC by flow cytometry. IL-10 levels were quantified by ELISA, and SNP -1082 (A/G) was analyzed by allele-specific PCR.

Results

Circulating IL-10 levels were increased in HUS patients, but PBMC from these patients exhibited a lower capacity to secrete this cytokine compared with those from healthy children. Interestingly, there was a negative association between the circulating levels of IL-10 and inflammatory cytokine IL-8. We observed that circulating IL-10 levels were threefold higher in HUS patients with -1082G allele in comparison to AA genotype. Moreover, there was relative enrichment of GG/AG genotypes in HUS patients with severe kidney failure.

Discussion

Our results suggest a possible contribution of SNP -1082 (A/G) to the severity of kidney failure in HUS patients that should be further evaluated in a larger cohort.

Associations between dietary patterns and an array of inflammation biomarkers and plasma lipid profile in postmenopausal women

OBJECTIVE AND DESIGN

In this cross-sectional study, evaluation of the association between four dietary patterns, nutrients and food intakes and an array of systemic inflammation biomarkers and lipid profile among 80 New Zealand postmenopausal women were conducted.

MATERIALS

Eighty postmenopausal women participated in the study. A validated food frequency questionnaire was used to collect nutrients and food intake. Four dietary patterns were identified by principal component analysis (PCA) and plasma samples collected for inflammatory biomarkers and lipid profile measures.

RESULTS

There were negative correlations between intake of dietary fibre, soluble and insoluble non-starch polysaccharides (NSP), vitamin C and niacin and with almost all the inflammatory markers for the whole group. Vegetables, tea/coffee and especially fruit intake were negatively correlated with the inflammatory biomarkers in the whole group. A high intake of Pattern 1 (potato, bread, and fruit pattern) was associated with a low risk of high interferon (IFN)-α2, IFN-λ, interleukin (IL)-6 and IL-8 levels while a high intake of Pattern 3 (fast-food pattern) was associated high risk of IFN-α2 levels. Multiple linear regression showed a negative correlation between Pattern 2 (soups and vegetables pattern) and levels of C-reactive protein (CRP) as well as ferritin. A positive association was observed between Pattern 3 (fast-food pattern) and CRP levels. Positive correlation was also observed between Pattern 2 and high-density lipoprotein (HDL) and total cholesterol (TC) levels, Pattern 4 (meat and vegetables pattern) was however negatively correlated with TC, low-density lipoprotein (LDL) and TC/HDL ratio.

CONCLUSIONS

The result of this study reinforces the contribution and role of diet in modifying inflammation in postmenopausal women.

Short-term high-salt consumption does not influence resting or exercising heart rate variability but increases MCP-1 concentration in healthy young adults

High salt consumption increases blood pressure (BP) and cardiovascular disease risk by altering autonomic function and increasing inflammation. However, it is unclear whether salt manipulation alters resting and exercising heart rate variability (HRV), a noninvasive measure of autonomic function, in healthy young adults. The purpose of this investigation was to determine whether short-term high-salt intake 1) alters HRV at rest, during exercise, or exercise recovery and 2) increases the circulating concentration of the inflammatory biomarker monocyte chemoattractant protein 1 (MCP-1). With the use of a randomized, placebo-controlled, crossover study, 20 participants (8 females; 24 ± 4 yr old, 110 ± 10/64 ± 8 mmHg) consumed salt (3,900 mg sodium) or placebo capsules for 10 days each separated by ≥2 wk. We assessed HRV during 10 min of baseline rest, 50 min of cycling (60% V̇o2peak), and recovery. We quantified HRV using the standard deviation of normal-to-normal RR intervals, the root mean square of successive differences (RMSSD), and additional time and frequency domain metrics of HRV. Plasma samples were collected to assess MCP-1 concentration. No main effect of high salt or condition × time interaction was observed for HRV metrics. However, acute exercise reduced HRV (e.g., RMSSD time: P < 0.001, condition: P = 0.877, interaction: P = 0.422). High salt elevated plasma MCP-1 (72.4 ± 12.5 vs. 78.14 ± 14.7 pg/mL; P = 0.010). Irrespective of condition, MCP-1 was moderately associated (P values < 0.05) with systolic (r = 0.32) and mean BP (r = 0.33). Short-term high-salt consumption does not affect HRV; however, it increases circulating MCP-1, which may influence BP in young adults.

A High-Salt Diet Exacerbates Liver Fibrosis through Enterococcus-Dependent Macrophage Activation

People consume more salt than the recommended levels due to poor dietary practices. The effects of long-term consumption of high-salt diets (HSD) on liver fibrosis are unclear. This study aimed to explore the impact of HSD on liver fibrosis. In this study, a carbon tetrachloride (CCL4)-induced liver fibrosis mouse model was used to evaluate fibrotic changes in the livers of mice fed a normal diet (ND) and an HSD. The HSD exacerbated liver injury and fibrosis. Moreover, the protein expression levels of transforming growth factor β (TGF-β), tumor necrosis factor alpha (TNF-α), and monocyte chemoattractant protein 1 (MCP-1) were significantly higher in the HSD group than in the normal group. The proportion of macrophages and activation significantly increased in the livers of HSD-fed mice. Meanwhile, the number of macrophages significantly increased in the small intestinal lamina propria of HSD-fed mice. The levels of profibrotic factors also increased in the small intestine of HSD-fed mice. Additionally, HSD increased the profibrotic chemokines and monocyte chemoattractant levels in the portal vein blood. Further characterization suggested that the HSD decreased the expression of tight junction proteins (ZO-1 and CLDN1), enhancing the translocation of bacteria. Enterococcus promoted liver injury and inflammation. In vitro experiments demonstrated that Enterococcus induced macrophage activation through the NF-κB pathway, thus promoting the expression of fibrosis-related genes, leading to liver fibrogenesis. Similarly, Enterococcus disrupted the gut microbiome in vivo and significantly increased the fibrotic markers, TGF-β, and alpha smooth muscle actin (α-SMA) expression in the liver. IMPORTANCE This study further confirms that Enterococcus induce liver fibrosis in mice. These results indicate that an HSD can exacerbate liver fibrosis by altering the gut microbiota composition, thus impairing intestinal barrier function. Therefore, this may serve as a new target for liver fibrosis therapy and gut microbiota management.

Phenotypic and functional alterations of monocyte subsets with aging

BACKGROUND

It has been widely accepted that monocytes are one of the central mediators contributing to inflammaging. However, it remains unclear whether aged monocytes, similar to aged T cells, have characteristics of hyperactivation and increased expression of co-inhibitory molecules.

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from young (21-40 years old), middle-aged (41-60 years old), and older human subjects (> 60 years old). Flow cytometry was used to monitor changes in the expression of surface molecules of monocyte subsets and cytokine-producing capacity.

RESULTS

We observed increased tumor necrosis factor-α: TNF-α and decreased interleukin-6 (IL-6) production in monocytes from older adults compared with young and middle-aged adults. Older adults had a greater percentage of intermediate and non-classical monocyte subsets, along with increased levels of the immune activation markers human leukocyte antigen-DR (HLA-DR), and adhesion molecules cluster of differentiation molecule 11b (CD11b) and L-selectin (CD62L). Furthermore, we observed increased C-C motif chemokine receptor 2 (CCR2) expression on classical monocytes and decreased C-X3-C motif chemokine receptor 1 (CX3CR1) expression on non-classical monocytes in older adult subjects. The expression of co-inhibitory receptors was reduced on monocyte subsets in older adults.

CONCLUSIONS

Circulating monocytes in older adults exhibit increased expression of activation, adhesion, and migration markers, but decreased expression of co-inhibitory molecules.

Association of early dysnatremia with mortality in the neonatal intensive care unit: results from the AWAKEN study

OBJECTIVE

To determine the association of dysnatremia in the first postnatal week and risk of acute kidney injury (AKI) and mortality.

STUDY DESIGN

A secondary analysis of 1979 neonates in the AWAKEN cohort evaluated the association of dysnatremia with (1) AKI in the first postnatal week and (2) mortality, utilizing time-varying Cox proportional hazard models.

RESULT

Dysnatremia developed in 50.2% of the cohort and was not associated with AKI. Mortality was associated with hyponatremia (HR 2.15, 95% CI 1.07-4.31), hypernatremia (HR 4.23, 95% CI 2.07-8.65), and combined hypo/hypernatremia (HR 6.39, 95% CI 2.01-14.01). In stratified models by AKI-status, hypernatremia and hypo/hypernatremia increased risk of mortality in neonates without AKI.

CONCLUSION

Dysnatremia within the first postnatal week was associated with increased risk of mortality. Hypernatremia and combined hypo/hypernatremia remained significantly associated with mortality in neonates without AKI. This may reflect fluid strategies kidney injury independent of creatinine and urine-output defined AKI, and/or systemic inflammation.

Association of Hypernatremia with Immune Profiles and Clinical Outcomes in Adult Intensive Care Unit Patients with Sepsis

Both hypernatremia and an abnormal immune response may increase hospital mortality in patients with sepsis. This study examined the association of hypernatremia with abnormal immune response and mortality in 520 adult patients with sepsis in an intensive care unit (ICU). We compared the mortality and ex vivo lipopolysaccharide (LPS)-induced inflammatory response differences among patients with hyponatremia, eunatremia, and hypernatremia, as well as between patients with acquired hypernatremia on ICU day 3 and those with sustained eunatremia over first three ICU days. Compared with eunatremia or hyponatremia, hypernatremia led to higher 7 day, 14 day, 28 day, and hospital mortality rates (p = 0.030, 0.009, 0.010, and 0.033, respectively). Compared with sustained eunatremia, acquired hypernatremia led to higher 7, 14, and 28 day mortality rates (p = 0.019, 0.042, and 0.028, respectively). The acquired hypernatremia group nonsignificantly trended toward increased hospital mortality (p = 0.056). Day 1 granulocyte colony-stimulating factor (G-CSF) and tumor necrosis factor (TNF) α levels were relatively low in patients with hypernatremia (p = 0.020 and 0.010, respectively) but relatively high in patients with acquired hypernatremia (p = 0.049 and 0.009, respectively). Thus, in ICU-admitted septic patients, hypernatremia on admission and in ICU-acquired hypernatremia were both associated with higher mortality. The higher mortality in patients with hypernatremia on admission was possibly related to the downregulation of G-CSF and TNF-α secretion after endotoxin stimulation. Compared to sustained eunatremia, acquired hypernatremia showed immunoparalysis at first and then hyperinflammation on day 3.

The modulatory effect of high salt on immune cells and related diseases

BACKGROUND

The adverse effect of excessive salt intake has been recognized in decades. Researchers have mainly focused on the association between salt intake and hypertension. However, studies in recent years have proposed the existence of extra-renal sodium storage and provided insight into the immunomodulatory function of sodium.

OBJECTIVES

In this review, we discuss the modulatory effects of high salt on various innate and adaptive immune cells and immune-regulated diseases.

METHODS

We identified papers through electronic searches of PubMed database from inception to March 2022.

RESULTS

An increasing body of evidence has demonstrated that high salt can modulate the differentiation, activation and function of multiple immune cells. Furthermore, a high-salt diet can increase tissue sodium concentrations and influence the immune responses in microenvironments, thereby affecting the development of immune-regulated diseases, including hypertension, multiple sclerosis, cancer and infections. These findings provide a novel mechanism for the pathology of certain diseases and indicate that salt might serve as a target or potential therapeutic agent in different disease contexts.

CONCLUSION

High salt has a profound impact on the differentiation, activation and function of multiple immune cells. Additionally, an HSD can modulate the development of various immune-regulated diseases.

Relationship of Sodium Intake With Granulocytes, Renal and Cardiovascular Outcomes in the Prospective EPIC-Norfolk Cohort

Background Experimental studies show that high-sodium intake affects the innate immune system, among others with increased circulating granulocytes. Whether this relationship exists on a population level and whether this relates to disease outcomes is unclear. We aimed to test the hypotheses that (1) sodium intake is associated with granulocytes on a population level; (2) granulocytes are associated with the presence of hypertension and both cardiovascular and renal outcomes; and (3) the relation between high-sodium intake and these outcomes is mediated by granulocytes. Methods and Results We performed an analysis in 13 804 participants from the prospective EPIC (European Prospective Investigation into Cancer)-Norfolk cohort, with a mean age of 58 years and median follow-up of 19.3 years. Analyses were carried out using calculated estimated sodium intake and sodium-to-potassium ratios from spot urines at baseline. The main outcomes were hypertension at baseline, and composite cardiovascular (mortality or cardiovascular events) and renal (mortality or renal events) outcomes during follow-up. Sodium intake and urine sodium-to-potassium ratio were positively associated with circulating granulocyte concentrations after adjustment for confounders (β=0.03; P=0.028 and β=0.06; P<0.001, respectively). Granulocytes significantly mediated the associations of, respectively, sodium intake and urine sodium-to-potassium ratio with hypertension at baseline, and cardiovascular and renal outcomes. Conclusions Sodium intake is positively associated with circulating granulocyte concentrations, and higher granulocyte concentrations associate with worse long-term cardiovascular and renal outcomes. Given the recently established immune-modulating effects of sodium and the role of immune cells in both cardiovascular and renal disease, causality for this pathway may need consideration in further studies.

A Systematic Review and Meta-analysis of Dietary Interventions Modulating Gut Microbiota and Cardiometabolic Diseases-Striving for New Standards in Microbiome Studies

BACKGROUND & AIMS

Cardiometabolic diseases (CMDs) have shared properties and causes. Insulin resistance is a risk factor and characteristic of CMDs and has been suggested to be modulated by plasma metabolites derived from gut microbiota (GM). Because diet is among the most important modulators of GM, we performed a systematic review of the literature to assess whether CMDs can be modulated via dietary interventions targeting the GM.

METHODS

A systematic review of the literature for clinical studies was performed on Ovid MEDLINE and Ovid Embase. Studies were assessed for risk of bias and patterns of intervention effects. A meta-analysis with random effects models was used to evaluate the effect of dietary interventions on clinical outcomes.

RESULTS

Our search yielded 4444 unique articles, from which 15 randomized controlled trials and 6 nonrandomized clinical trials were included. The overall risk of bias was high in all studies. In general, most dietary interventions changed the GM composition, but no consistent effect could be found. Results of the meta-analyses showed that only diastolic blood pressure is decreased across interventions compared with controls (mean difference: -3.63 mm Hg; 95% confidence interval, -7.09 to -0.17; I² = 0%, P = .04) and that a high-fiber diet was associated with reduced triglyceride levels (mean difference: -0.69 mmol/L; 95% confidence interval, -1.36 to -0.02; I² = 59%, P = .04). Other CMD parameters were not affected.

CONCLUSIONS

Dietary interventions modulate GM composition, blood pressure, and circulating triglycerides. However, current studies have a high methodological heterogeneity and risk of bias. Well-designed and controlled studies are thus necessary to better understand the complex interaction between diet, microbiome, and CMDs.

PROSPERO

CRD42020188405.

High dietary salt intake increases urinary NGAL excretion and creatinine clearance in healthy young adults

In rodents and older patients with elevated blood pressure (BP), high dietary sodium increases excretion of biomarkers of kidney injury, but it is unclear whether this effect occurs in healthy young adults. The purpose of this study was to determine whether short-term high dietary salt increases urinary excretion of the kidney injury biomarkers neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) in healthy young adults. Twenty participants participated in a double-blind, placebo-controlled, randomized crossover study. For 10 days each, participants were asked to consume salt (3,900 mg sodium) or placebo capsules. We measured BP during each visit, obtained 24-h urine samples for measurements of electrolytes, NGAL, and KIM-1, and assessed creatinine clearance. Compared with placebo, salt loading increased daily urinary sodium excretion (placebo: 130.3 ± 62.4 mmol/24 h vs. salt: 287.2 ± 72.0 mmol/24 h, P < 0.01). There was no difference in mean arterial BP (placebo: 77 ± 7 mmHg vs. salt: 77 ± 6 mmHg, P = 0.83) between conditions. However, salt loading increased the urinary NGAL excretion rate (placebo: 59.8 ± 44.4 ng/min vs. salt: 80.8 ± 49.5 ng/min, P < 0.01) and increased creatinine clearance (placebo: 110.5 ± 32.9 mL/min vs. salt: 145.0 ± 24.9 mL/min, P < 0.01). Urinary KIM-1 excretion was not different between conditions. In conclusion, in healthy young adults 10 days of dietary salt loading increased creatinine clearance and increased urinary excretion of the kidney injury biomarker marker NGAL but not KIM-1.NEW & NOTEWORTHY In healthy young adults, 10 days of dietary salt loading increased creatinine clearance and increased urinary excretion of the kidney injury biomarker marker neutrophil gelatinase-associated lipocalin despite no change in resting blood pressure.

High Estimated 24-Hour Urinary Sodium Excretion Is Related to Symptomatic Knee Osteoarthritis: A Nationwide Cross-Sectional Population-Based Study

OBJECTIVES

High salt intake results in various harmful effects on human health including hypertension, cardiovascular disease, and reduced bone density. Despite this, there are very few studies in the literature that have investigated the association between sodium intake and osteoarthritis (OA). Therefore, we aimed to explore these associations in a Korean population.

METHODS

This study used cross-sectional data from adult subjects aged 50-75 years from two consecutive periods of the Korean National Health and Nutrition Examination Survey V-VII (2010-2011 and 2014-2016). The estimated 24-hour urinary sodium excretion (24HUNa) was used as a surrogate marker of salt intake. In the 2010-2011 dataset, knee OA (KOA) was defined as the presence of the radiographic features of OA and knee pain. The association between KOA and salt intake was analysed using univariable and multivariable logistic regression methods. For the sensitivity analysis, the same procedures were conducted on subjects with self-reported OA (SR-OA) with knee pain in the 2010-2011 dataset and any site SR-OA in the 2014-2016 dataset.

RESULTS

Subjects with KOA had significantly lower energy intake, but higher 24HUNa than those without KOA. The restricted cubic spline plots demonstrated a J-shaped distribution between 24HUNa and prevalent KOA. When 24HUNa was stratified into five groups (<2, 2-3, 3-4, 4-5 and ≥5 g/day), subjects with high sodium intake (≥5 g/day) had a higher risk of KOA (odds ratio [OR] = 1.64, 95% confidence interval [CI] 1.03-2.62) compared to the reference group (3-4 g/day) after adjusting for covariates. The sensitivity analysis based on SR-OA with knee pain showed that high sodium intake was also significantly associated with increased prevalence of OA (OR = 1.84, 95% CI 1.10-3.10) compared with the reference group. Regarding SR-OA at any site in the 2014-2016 dataset, estimated 24HUNa showed a significantly positive association with the presence of SR-OA after adjusting for potential confounders.

CONCLUSIONS

This nationwide Korean representative study showed a significant association between symptomatic KOA and high sodium intake (≥5 g/day). Avoidance of a diet high in salt might be beneficial as a non-pharmacologic therapy for OA.

Salt Sensitivity of Blood Pressure in Blacks and Women: A Role of Inflammation, Oxidative Stress, and Epithelial Na+ Channel

Significance: Salt sensitivity of blood pressure (SSBP) is an independent risk factor for mortality and morbidity due to cardiovascular disease, and disproportionately affects blacks and women. Several mechanisms have been proposed, including exaggerated activation of sodium transporters in the kidney leading to salt retention and water. Recent Advances: Recent studies have found that in addition to the renal epithelium, myeloid immune cells can sense sodium via the epithelial Na+ channel (ENaC), which leads to activation of the nicotinamide adenine dinucleotide phosphate oxidase enzyme complex, increased fatty acid oxidation, and production of isolevuglandins (IsoLGs). IsoLGs are immunogenic and contribute to salt-induced hypertension. In addition, aldosterone-mediated activation of ENaC has been attributed to the increased SSBP in women. The goal of this review is to highlight mechanisms contributing to SSBP in blacks and women, including, but not limited to increased activation of ENaC, fatty acid oxidation, and inflammation. Critical Issues: A critical barrier to progress in management of SSBP is that its diagnosis is not feasible in the clinic and is limited to expensive and laborious research protocols, which makes it difficult to investigate. Yet without understanding the underlying mechanisms, this important risk factor remains without treatment. Future Directions: Further studies are needed to understand the mechanisms that contribute to differential blood pressure responses to dietary salt and find feasible diagnostic tools. This is extremely important and may go a long way in mitigating the racial and sex disparities in cardiovascular outcomes. Antioxid. Redox Signal. 35, 1477-1493.

Targeting the CCL2/CCR2 Axis in Cancer Immunotherapy: One Stone, Three Birds?

CCR2 is predominantly expressed by monocytes/macrophages with strong proinflammatory functions, prompting the development of CCR2 antagonists to dampen unwanted immune responses in inflammatory and autoimmune diseases. Paradoxically, CCR2-expressing monocytes/macrophages, particularly in tumor microenvironments, can be strongly immunosuppressive. Thus, targeting the recruitment of immunosuppressive monocytes/macrophages to tumors by CCR2 antagonism has recently been investigated as a strategy to modify the tumor microenvironment and enhance anti-tumor immunity. We present here that beneficial effects of CCR2 antagonism in the tumor setting extend beyond blocking chemotaxis of suppressive myeloid cells. Signaling within the CCL2/CCR2 axis shows underappreciated effects on myeloid cell survival and function polarization. Apart from myeloid cells, T cells are also known to express CCR2. Nevertheless, tissue homing of Treg cells among T cell populations is preferentially affected by CCR2 deficiency. Further, CCR2 signaling also directly enhances Treg functional potency. Thus, although Tregs are not the sole type of T cells expressing CCR2, the net outcome of CCR2 antagonism in T cells favors the anti-tumor arm of immune responses. Finally, the CCL2/CCR2 axis directly contributes to survival/growth and invasion/metastasis of many types of tumors bearing CCR2. Together, CCR2 links to two main types of suppressive immune cells by multiple mechanisms. Such a CCR2-assoicated immunosuppressive network is further entangled with paracrine and autocrine CCR2 signaling of tumor cells. Strategies to target CCL2/CCR2 axis as cancer therapy in the view of three types of CCR2-expessing cells in tumor microenvironment are discussed.

High-fat and high-sodium diet induces metabolic dysfunction in the absence of obesity

OBJECTIVE

Excess dietary fat and sodium (NaCl) are both associated with obesity and metabolic dysfunction. In mice, high NaCl has been shown to block high-fat (HF) diet-induced weight gain. Here, the impact of an HF/NaCl diet on metabolic function in the absence of obesity was investigated.

METHODS

Wild-type mice were administered chow, NaCl (4%), HF, and HF/NaCl diets. Metabolic analysis was performed by measuring fasted blood glucose and insulin levels and by glucose tolerance test and insulin tolerance test.

RESULTS

After 10 weeks on diets, male and female mice on the HF diet gained weight, and HF/NaCl mice had significantly reduced weight gain similar to chow-fed mice. In the absence of obesity, HF/NaCl mice had significantly elevated fasting blood glucose and impaired glucose control during glucose tolerance tests. Both NaCl and HF/NaCl mice had decreased pancreas and β-cell mass. Administration of NaCl in drinking water did not protect mice from HF-diet-induced weight gain and obesity. Further analysis revealed that longer administration of HF/NaCl diets for 20 weeks resulted in significant weight gain and insulin resistance.

CONCLUSIONS

The data demonstrate that despite early inhibitory effects on fat deposition and weight gain, an HF/NaCl diet does not prevent the metabolic consequences of HF diet consumption.

Assessing the (anti)-inflammatory potential of diets

PURPOSE OF REVIEW

It is accepted that several chronic diseases are associated with inflammation. Dietary habits and the consumption of certain nutrients have been shown to influence inflammation, reflected by inflammatory cytokines. In this narrative review, we discuss currently developed tools to assess the inflammatory potential of diets and compare them with established tools.

RECENT FINDINGS

Four new indices were recently developed. The Inflammatory Score of the Diet is a modified version of the established Dietary Inflammatory Index. The novel Empirical Dietary Inflammatory Index works without previous dietary intake assessment and the Anti-Inflammatory Diet Index was specifically developed in a northern European population. The Dietary and Lifestyle Inflammation Scores addresses additional confounders. The informative value of dietary indices relies on the accuracy and completeness of dietary intake assessment.

SUMMARY

Dietary inflammatory indices are important tools to assess, compare and validate the inflammatory potential of diets across populations without the need for biomarker assessments. They allow to investigate associations between an (anti)-inflammatory diet with disease risk and course. Although the Dietary Inflammatory Index remains the most used index worldwide, currently developed indices allow more flexibility, have a different focus or simplify assessment. Additional foods, that were recently shown to modulate inflammation, but are not (fully) considered yet, may deserve more attention in the future.

Does Sodium Intake Induce Systemic Inflammatory Response? A Systematic Review and Meta-Analysis of Randomized Studies in Humans

Experimental studies suggest that sodium induced inflammation might be another missing link leading to atherosclerosis. To test the hypothesis that high daily sodium intake induces systemic inflammatory response in humans, we performed a systematic review according to PRISMA guidelines of randomized controlled trials (RCTs) that examined the effect of high versus low sodium dose (HSD vs. LSD), as defined per study, on plasma circulating inflammatory biomarkers. Eight RCTs that examined CRP, TNF-a and IL-6 were found. Meta-analysis testing the change of each biomarker in HSD versus LSD was possible for CRP (n = 5 studies), TNF-a (n = 4 studies) and IL-6 (n = 4 studies). The pooled difference (95% confidence intervals) per biomarker was for: CRP values of 0.1(-0.3, 0.4) mg/L; TNF-a -0.7(-5.0, 3.6) pg/mL; IL-6 -1.1(-3.3 to 1.1) pg/mL. Importantly, there was inconsistency between RCTs regarding major population characteristics and the applied methodology, including a very wide range of LSD (460 to 6740 mg/day) and HSD (2800 to 7452 mg/day). Although our results suggest that the different levels of daily sodium intake are not associated with significant changes in the level of systemic inflammation in humans, this outcome may result from methodological issues. Based on these identified methodological issues we propose that future RCTs should focus on young healthy participants to avoid confounding effects of comorbidities, should have three instead of two arms (very low, "normal" and high) of daily sodium intake with more than 100 participants per arm, whereas an intervention duration of 14 days is adequate.

β2 integrin activation and signal transduction in leukocyte recruitment

Leukocyte recruitment is a critical step in the pathogenesis of inflammatory and immunological responses. Cell adhesion molecules (CAMs) are involved in controlling cell movements and the recruitment process, and the integrin family of CAMs plays a key role. During cell movement, integrin function is dynamically and precisely regulated. However, this balance might be broken under pathological conditions. Thus, the functional regulation and molecular mechanisms of integrins related to diseases are often a focus of research. Integrin β2 is one of the most commonly expressed integrins in leukocytes that mediate leukocyte adhesion and migration, and it plays an important role in immune responses and inflammation. In this review, we focus on specific functions of integrin β2 in leukocyte recruitment, the conformational changes and signal transduction of integrin β2 activation, the similarities between murine and human factors, and how new insights into these processes can inform future therapies for inflammation and immune diseases.

Sodium and its manifold impact on our immune system

The Western diet is rich in salt, and a high salt diet (HSD) is suspected to be a risk factor for cardiovascular diseases. It is now widely accepted that an experimental HSD can stimulate components of the immune system, potentially exacerbating certain autoimmune diseases, or alternatively, improving defenses against certain infections, such as cutaneous leishmaniasis. However, recent findings show that an experimental HSD may also aggravate other infections (e.g., pyelonephritis or systemic listeriosis). Here, we discuss the modulatory effects of a HSD on the microbiota, metabolic signaling, hormonal responses, local sodium concentrations, and their effects on various immune cell types in different tissues. We describe how these factors are integrated, resulting either in immune stimulation or suppression in various tissues and disease settings.

The effect of macrophage-targeted interventions on blood pressure - a systematic review and meta-analysis of preclinical studies

An increasing body of evidence shows a role for macrophages and monocytes (as their precursors) in hypertension, but with conflicting results with regard to whether they are protective or harmful. Therefore, we systematically reviewed the effect of macrophage interventions on blood pressure in animal models, to explore which factors determine the blood pressure increasing vs. decreasing effect. A search in PubMED and EMBASE yielded 9620 records, 26 of which were included. Eighteen studies (involving 22 different experiments (k = 22)) performed macrophage depletion, whereas 12 studies specifically deleted certain macrophage proteins. The blood pressure effects of macrophage depletion were highly various and directed toward both directions, as expected, which could not be reduced to differences in animal species or methods of hypertension induction. Prespecified subgroup analysis did reveal a potential role for the route in which the macrophage-depleting agent is being administrated (intraperitoneal vs intravenous subgroup difference of P = 0.07 (k = 22), or P < 0.001 in studies achieving considerable (ie, >50%) depletion (k = 18)). Along with findings from specific macrophage protein deletion studies-showing that deletion of one single macrophage protein (like TonEBP, endothelin-B, EP₄, NOX-2 and the angiotensin II type 1 receptor) can alter blood pressure responses to hypertensive stimuli-the indication that each route has its specific depletion pattern regarding targeted tissues and macrophage phenotypes suggests a determinative role for these features. These hypothesis-generating results encourage more detailed depletion characterization of each technique by direct experimental comparisons, providing a chance to obtain more knowledge on which macrophages are beneficial versus detrimental in hypertension development.

Innate Immune Mechanisms of Arterial Hypertension and Autoimmune Disease

The immune system is indispensable in the development of vascular dysfunction and hypertension. The interplay between immune cells and the vasculature, kidneys, heart, and blood pressure regulating nuclei in the central nervous system results in a complex and closely interwoven relationship of the immune system with arterial hypertension. A better understanding of this interplay is necessary for optimized and individualized antihypertensive therapy. Our review article focuses on innate cells in hypertension and to what extent they impact on development and preservation of elevated blood pressure. Moreover, we address the association of hypertension with chronic autoimmune diseases. The latter are ideally suited to learn about immune-mediated mechanisms in cardiovascular disease leading to high blood pressure.

Innate Immune Cells and Hypertension: Neutrophils and Neutrophil Extracellular Traps (NETs)

Uncontrolled immune system activation amplifies end-organ injury in hypertension. Nonetheless, the exact mechanisms initiating this exacerbated inflammatory response, thereby contributing to further increases in blood pressure (BP), are still being revealed. While participation of lymphoid-derived immune cells has been well described in the hypertension literature, the mechanisms by which myeloid-derived innate immune cells contribute to T cell activation, and subsequent BP elevation, remains an active area of investigation. In this article, we critically analyze the literature to understand how monocytes, macrophages, dendritic cells, and polymorphonuclear leukocytes, including mast cells, eosinophils, basophils, and neutrophils, contribute to hypertension and hypertension-associated end-organ injury. The most abundant leukocytes, neutrophils, are indisputably increased in hypertension. However, it is unknown how (and why) they switch from critical first responders of the innate immune system, and homeostatic regulators of BP, to tissue-damaging, pro-hypertensive mediators. We propose that myeloperoxidase-derived pro-oxidants, neutrophil elastase, neutrophil extracellular traps (NETs), and interactions with other innate and adaptive immune cells are novel mechanisms that could contribute to the inflammatory cascade in hypertension. We further posit that the gut microbiota serves as a set point for neutropoiesis and their function. Finally, given that hypertension appears to be a key risk factor for morbidity and mortality in COVID-19 patients, we put forth evidence that neutrophils and NETs cause cardiovascular injury post-coronavirus infection, and thus may be proposed as an intriguing therapeutic target for high-risk individuals. © 2021 American Physiological Society. Compr Physiol 11:1575-1589, 2021.

The effect of high-salt diet on t-lymphocyte subpopulations in healthy males-A pilot study

Animal studies show that high‐salt diet affects T‐cell subpopulations, but evidence in humans is scarce and contradictory. This pilot study investigated the effect of a 2‐week high‐salt diet on T‐cell subpopulations (ie, γδ T cells, Th17 cells, and regulatory T cells) in five healthy males. The mean (SD) age of the participants was 33 (2) years, with normal body mass index, kidney function, and baseline blood pressure. In terms of phenotype, there was an isolated increase of CD69 expression in Vδ1 T cells (P = .04), which is an early activation marker. There were no statistically significant changes or trends in any of the other tested markers or in the Th17 or regulatory T‐cell subsets. The increase in CD69 was strongly correlated to increases in 24‐hour urinary sodium excretion (r = .93, P = .02). These results of this pilot may motivate the use of longer dietary salt interventions in future studies on salt and adaptive immune cells.