Sodium sensing in the interstitium and relationship to hypertension

Augmentation of Nitric Oxide Deficient Hypertension by High Salt Diet Is Associated With Reduced TNF-α Receptor Type 1 Expression in the Kidneys

BACKGROUND

High salt (HS) intake induces an augmented hypertensive response to nitric oxide (NO) inhibition, though it causes minimal changes in blood pressure (BP) in NO intact condition. The cause of such augmentation is not known. HS induces tumor necrosis factor-alpha (TNFα) production that causes natriuresis via activation of its receptor type 1 (TNFR1). We hypothesized that NO deficiency reduces renal TNFR1 activity, leading to enhanced sodium retention and hypertension.

METHODS

We examined the changes in renal TNFR1 protein expression (Immunohistochemistry analyses) after HS (4% NaCl) intake in wild-type mice (WT, C57BL6) treated with a NO synthase (NOS) inhibitor, nitro-l-arginine methyl ester (L-NAME; 0.05 mg/min/g; osmotic mini-pump), as well as in endothelial NOS knockout mice (eNOSKO) and compared the responses in WT mice with normal salt (NS; 0.3% NaCl) intake. BP was measured with tail-cuff plethysmography and 24-hour urine collections were made using metabolic cages.

RESULTS

HS alone did not alter mean BP in untreated mice (76 ± 3 to 77 ± 1 mm Hg) but induced an augmented response in L-NAME treated (106 ± 1 vs. 97 ± 2 mm Hg) and in eNOSKO (107 ± 2 vs. 89 ± 3 mm Hg) mice. The percentage area of TNFR1 expression in renal tissue was higher in WT + HS (4.1 + 0.5%) than in WT + NS mice (2.7 ± 0.6%). However, TNFR1 expression was significantly lower in L-NAME treated WT + NS (0.9 ± 0.1%) and in eNOSKO + NS (1.4 ± 0.2%) than in both WT + NS and WT + HS mice.

CONCLUSIONS

These data indicate that TNFR1 activity is downregulated in NO deficient conditions, which facilitates salt retention leading to augmented hypertension during HS intake.

The Congestion "Pandemic" in Acute Heart Failure Patients

Congestion not only represents a cardinal sign of heart failure (HF) but is also now recognized as the primary cause of hospital admissions, rehospitalization, and mortality among patients with acute heart failure (AHF). Congestion can manifest through various HF phenotypes in acute settings: volume overload, volume redistribution, or both. Recognizing the congestion phenotype is paramount, as it implies different therapeutic strategies for decongestion. Among patients with AHF, achieving complete decongestion is challenging, as more than half still experience residual congestion at discharge. Residual congestion is one of the strongest predictors of future cardiovascular events and poor outcomes. Through this review, we try to provide a better understanding of the congestion phenomenon among patients with AHF by highlighting insights into the pathophysiological mechanisms behind congestion and new diagnostic and management tools to achieve and maintain efficient decongestion.

Relationship between serum sodium level and sepsis-induced coagulopathy

Purpose

A discussion about the correlation between the level of serum sodium and sepsis-induced coagulopathy (SIC).

Materials and methods

A retrospective analysis was conducted on sepsis patients who were admitted to the Intensive Care Unit (ICU) of Nanjing Drum Tower Hospital from January 2021 to December 2022. Based on the presence of coagulation disorders, the patients were divided into two groups: sepsis-induced coagulopathy (SIC) and non-sepsis-induced coagulopathy (non-SIC) groups. We recorded demographic characteristics and laboratory indicators at the time of ICU admission, and analyzed relationship between serum sodium level and SIC.

Results

One hundred and twenty-five patients with sepsis were enrolled, among which, the SIC and the non-SIC groups included 62 and 63 patients, respectively. Compared to patients in the non-SIC group, the level of serum sodium of those in the SIC was significantly higher (p < 0.001). Multi-factor logistic regression showed serum sodium level was independently associated with SIC (or = 1.127, p = 0.001). Pearson's correlation analysis indicated that the higher the serum sodium level, the significantly higher the SIC score was (r = 0.373, p < 0.001). Additionally, the mortality rate of patients with sepsis in the ICU were significantly correlated with increased serum sodium levels (p = 0.014).

Conclusion

An increase in serum sodium level was independently associated with an increased occurrence of SIC and also associated with the poor prognosis for patients with sepsis.

The role of glycosaminoglycans in blood pressure regulation

Essential hypertension (HT) is the global health problem and is a major risk factor for the development of cardiovascular and kidney disease. High salt intake has been associated with HT and impaired kidney sodium excretion is considered to be a major mechanism for the development of HT. Although kidney has a very important role in regulation of BP, this traditional view of BP regulation was challenged by recent findings suggesting that nonosmotic tissue sodium deposition is very important for BP regulation. This new paradigm indicates that sodium can be stored and deposited nonosmotically in the interstitium without water retention and without increased BP. One of the major determinants of this deposition is glycosaminoglycans (GAGs). By binding to GAGs found in the endothelial surface layer (ESL) which contains glycocalyx, sodium is osmotically inactivated and not induce concurrent water retention. Thus, GAGs has important function for homeostatic BP and sodium regulation. In the current review, we summarized the role of GAGs in ESL and BP regulation.

Sodium accumulation in the skin is associated with higher density of skin lymphatic vessels in patients with arterial hypertension

PURPOSE

Recent studies, conducted mainly on the rodent model, have demonstrated that regulatory pathway in the skin provided by glycosaminoglycans, nuclear factor of activated T cells 5 (NFAT5), vascular endothelial growth factor C (VEGF-C) and process of lymphangiogenesis may play an important role in extrarenal regulation of sodium (Na+) balance, body water volume, and blood pressure. We aimed to investigate the concentrations and relations among the main factors of this pathway in human skin to confirm that this regulatory axis also exists in humans.

PATIENTS AND METHODS

Skin specimens from patients diagnosed with arterial hypertension and from control group were histologically and molecularly examined.

RESULTS

The primary hypertensive and control groups did not differ in Na+ ​concentrations in the skin. However, the patients with hypertension and higher skin Na+ concentration had significantly greater density of skin lymphatic vessels. Higher skin Na+concentration was associated with higher skin water content. In turn, skin water content correlated with factors associated with lymphangiogenesis, i.e. NFAT5, VEGF-C, and podoplanin (PDPN) mRNA expression in the skin. The strong mutual pairwise correlations of the expressions of NFAT5, VEGF-C, vascular endothelial growth factor D (VEGF-D) and PDPN mRNA were noted in the skin in all of the studied groups.

CONCLUSIONS

Our study confirms that skin interstitium and the lymphatic system may be important players in the pathophysiology of arterial hypertension in humans. Based on the results of our study and existing literature in this field, we propose the hypothetical model which might explain the phenomenon of salt-sensitivity.

Sodium in the skin: a summary of the physiology and a scoping review of disease associations

A large and growing body of research suggests that the skin plays an important role in regulating total body sodium, challenging traditional models of sodium homeostasis that focused exclusively on blood pressure and the kidney. In addition, skin sodium may help to prevent water loss and facilitate macrophage-driven antimicrobial host defence, but may also trigger immune dysregulation via upregulation of proinflammatory markers and downregulation of anti-inflammatory processes. We performed a systematic search of PubMed for published literature on skin sodium and disease outcomes and found that skin sodium concentration is increased in patients with cardiometabolic conditions including hypertension, diabetes and end-stage renal disease; autoimmune conditions including multiple sclerosis and systemic sclerosis; and dermatological conditions including atopic dermatitis, psoriasis and lipoedema. Several patient characteristics are associated with increased skin sodium concentration including older age and male sex. Animal evidence suggests that increased salt intake results in higher skin sodium levels; however, there are conflicting results from small trials in humans. Additionally, limited data suggest that pharmaceuticals such as diuretics and sodium-glucose co-transporter-2 inhibitors approved for diabetes, as well as haemodialysis may reduce skin sodium levels. In summary, emerging research supports an important role for skin sodium in physiological processes related to osmoregulation and immunity. With the advent of new noninvasive magnetic resonance imaging measurement techniques and continued research on skin sodium, it may emerge as a marker of immune-mediated disease activity or a potential therapeutic target.

High tissue-sodium associates with systemic inflammation and insulin resistance in obese individuals

BACKGROUND AND AIMS

High sodium intake is associated with obesity and insulin resistance, and high extracellular sodium content may induce systemic inflammation, leading to cardiovascular disease. In this study, we aim to investigate whether high tissue sodium accumulation relates with obesity-related insulin resistance and whether the pro-inflammatory effects of excess tissue sodium accumulation may contribute to such association.

METHODS AND RESULTS

In a cross-sectional study of 30 obese and 53 non-obese subjects, we measured insulin sensitivity determined as glucose disposal rate (GDR) using hyperinsulinemic euglycemic clamp, and tissue sodium content using 23Na magnetic resonance imaging. Median age was 48 years, 68% were female and 41% were African American. Median (interquartile range) BMI was 33 (31.5, 36.3) and 25 (23.5, 27.2) kg/m2 in the obese and non-obese individuals, respectively. In obese individuals, insulin sensitivity negatively correlated with muscle (r = -0.45, p = 0.01) and skin sodium (r = -0.46, p = 0.01). In interaction analysis among obese individuals, tissue sodium had a greater effect on insulin sensitivity at higher levels of high-sensitivity C-reactive protein (p-interaction = 0.03 and 0.01 for muscle and skin Na+, respectively) and interleukin-6 (p-interaction = 0.024 and 0.003 for muscle and skin Na+, respectively). In interaction analysis of the entire cohort, the association between muscle sodium and insulin sensitivity was stronger with increasing levels of serum leptin (p-interaction = 0.01).

CONCLUSIONS

Higher muscle and skin sodium are associated with insulin resistance in obese patients. Whether high tissue sodium accumulation has a mechanistic role in the development of obesity-related insulin resistance through systemic inflammation and leptin dysregulation remains to be examined in future studies.

CLINICALTRIALS

gov registration: NCT02236520.

Glycocalyx-Sodium Interaction in Vascular Endothelium

The glycocalyx generally covers almost all cellular surfaces, where it participates in mediating cell-surface interactions with the extracellular matrix as well as with intracellular signaling molecules. The endothelial glycocalyx that covers the luminal surface mediates the interactions of endothelial cells with materials flowing in the circulating blood, including blood cells. Cardiovascular diseases (CVD) remain a major cause of morbidity and mortality around the world. The cardiovascular risk factors start by causing endothelial cell dysfunction associated with destruction or irregular maintenance of the glycocalyx, which may culminate into a full-blown cardiovascular disease. The endothelial glycocalyx plays a crucial role in shielding the cell from excessive exposure and absorption of excessive salt, which can potentially cause damage to the endothelial cells and underlying tissues of the blood vessels. So, in this mini review/commentary, we delineate and provide a concise summary of the various components of the glycocalyx, their interaction with salt, and subsequent involvement in the cardiovascular disease process. We also highlight the major components of the glycocalyx that could be used as disease biomarkers or as drug targets in the management of cardiovascular diseases.

Association between salt sensitivity of blood pressure and the risk of hypertension in a Chinese Tibetan population

Epidemiological studies have confirmed salt sensitivity as a crucial risk factor for the development of hypertension. However, few studies have investigated the association between salt sensitivity of blood pressure (SSBP) and hypertension in Chinese Tibetan population. Therefore, we conducted a cross-sectional study based on a Tibetan population to evaluate the association between SSBP and the risk of hypertension. Seven hundred and eighty-four participants with hypertension and 645 participants without hypertension were included from five villages in Tibetan Autonomous Region of Gannan during 2013-2014. The assessment of salt sensitivity (SS) and non-salt sensitivity (NSS) was performed according to mean arterial pressure (MAP) changes by the modified Sullivan's acute oral saline load and diuresis shrinkage test (MSAOSL-DST). Logistic regression models and restricted cubic models were used to examine the association between SSBP and hypertension. There were 554 (70.5%) salt-sensitive participants with hypertension and 412 (63.9%) salt-sensitive participants without hypertension in this study. Compared with individuals with NSS, individuals with SS had a significantly increased risk of hypertension, and the multiple-adjusted odds ratios were 2.582 with 95% confidence interval of 1.357-4.912. Furthermore, a significant linear trend was found between MAP changes and hypertension. Subgroup analyses showed significant and stronger associations between SSBP and the risk of hypertension in the older (age ≥ 55 years old), males and participants who took exercise less than 1 time per week. Our results suggest that SS is associated with an increased risk of hypertension in Tibetan population, indicating a need for clinicians dealing with SSBP to decrease the risk of hypertension.

Chronic high‑salt intake induces cardiomyocyte autophagic vacuolization during left ventricular maladaptive remodeling in spontaneously hypertensive rats

The role of autophagy in high-salt (HS) intake associated hypertensive left ventricular (LV) remodeling remains unclear. The present study investigated the LV autophagic change and its association with the hypertensive LV remodeling induced by chronic HS intake in spontaneously hypertensive rats (SHR). Wistar Kyoto (WKY) rats and SHR were fed low-salt (LS; 0.5% NaCl) and HS (8.0% NaCl) diets and were subjected to invasive LV hemodynamic analysis after 8, 12 and 16 weeks of dietary intervention. Reverse transcription-quantitative PCR and western blot analysis were performed to investigate the expression of autophagy-associated key components. The LV morphologic staining was performed at the end of the study. The rat H9c2 ventricular myoblast cell-associated experiments were performed to explore the mechanism of HS induced autophagic change. A global autophagy-associated key component, as well as increased cardiomyocyte autophagic vacuolization, was observed after 12 weeks of HS intake. During this period, the heart from HS-diet-fed SHR exhibited a transition from compensated LV hypertrophy to decompensation, as shown by progressive impairment of LV function and interstitial fibrosis. Myocardial extracellular [Na⁺] and the expression of tonicity-responsive enhancer binding protein (TonEBP) was significantly increased in HS-fed rats, indicating myocardial interstitial hypertonicity by chronic HS intake. The global autophagic change and overt deterioration of LV function were not observed in LS-fed SHR and HS-fed WKY rats. The study of rat H9c2 cardiomyocytes demonstrated a cytosolic [Na⁺] elevation-mediated, reactive oxygen species-dependent the autophagic change occurred when exposed to an increased extracellular [Na⁺]. The present findings demonstrated that a myocardial autophagic change participates in the maladaptive LV remodeling induced by chronic HS intake in SHR, which provides a possible target for future intervention studies on HS-induced hypertensive LV remodeling.

Toward quantification of loop diuretic responsiveness for congestive heart failure

Diuretics, such as furosemide, are routinely administered to dogs with congestive heart failure (CHF). Traditionally, dose and determination of efficacy primarily are based on clinical signs rather than quantitative measures of drug action. Treatment of human CHF patients increasingly is guided by quantification of urine sodium concentration (uNa) and urine volume after diuretic administration. Use of these and other measures of diuretic responsiveness is associated with decreased duration of hospitalization, complication rates, future rehospitalization, and mortality. At their core, loop diuretics act through natriuresis, and attention to body sodium (Na) stores and handling offers insight into the pathophysiology of CHF and pharmacology of diuretics beyond what is achievable from clinical signs alone. Human patients with low diuretic responsiveness or diuretic resistance are at risk for difficult or incomplete decongestion that requires diuretic intensification or other remedial strategies. Identification of the specific etiology of resistance in a patient can help tailor personalized interventions. In this review, we advance the concept of loop diuretic responsiveness by highlighting Na and natriuresis. Specifically, we review body water homeostasis and congestion in light of the increasingly recognized role of interstitial Na, propose definitions for diuretic responsiveness and resistance in veterinary subjects, review relevant findings of recent studies, explain how the particular cause of resistance can guide treatment, and identify current knowledge gaps. We believe that a quantitative approach to loop diuretic usage primarily involving natriuresis will advance our understanding and care of dogs with CHF.

Graphene-Based Ion-Selective Field-Effect Transistor for Sodium Sensing

Field-effect transistors have attracted significant attention in chemical sensing and clinical diagnosis, due to their high sensitivity and label-free operation. Through a scalable photolithographic process in this study, we fabricated graphene-based ion-sensitive field-effect transistor (ISFET) arrays that can continuously monitor sodium ions in real-time. As the sodium ion concentration increased, the current–gate voltage characteristic curves shifted towards the negative direction, showing that sodium ions were captured and could be detected over a wide concentration range, from 10⁻⁸ to 10⁻¹ M, with a sensitivity of 152.4 mV/dec. Time-dependent measurements and interfering experiments were conducted to validate the real-time measurements and the highly specific detection capability of our sensor. Our graphene ISFETs (G-ISFET) not only showed a fast response, but also exhibited remarkable selectivity against interference ions, including Ca²⁺, K⁺, Mg²⁺ and NH₄⁺. The scalability, high sensitivity and selectivity synergistically make our G-ISFET a promising platform for sodium sensing in health monitoring.

Epithelial Na+ channel and the glycocalyx: a sweet and salty relationship for arterial shear stress sensing

PURPOSE OF REVIEW

The ability of endothelial cells to sense mechanical force, and shear stress in particular, is crucial for normal vascular function. This relies on an intact endothelial glycocalyx that facilitates the production of nitric oxide (NO). An emerging arterial shear stress sensor is the epithelial Na+ channel (ENaC). This review highlights existing and new evidence for the interdependent activity of the glycocalyx and ENaC and its implications for vascular function.

RECENT FINDINGS

New evidence suggests that the glycocalyx and ENaC are physically connected and that this is important for shear stress sensing. The connection relies on N-glycans attached to glycosylated asparagines of α-ENaC. Removal of specific N-glycans reduced ENaC's shear stress response. Similar effects were observed following degradation of the glycocalyx. Endothelial specific viral transduction of α-ENaC increased blood pressure (∼40 mmHg). This increase was attenuated in animals transduced with an α-ENaC version lacking N-glycans.

SUMMARY

These observations indicate that ENaC is connected to the glycocalyx and their activity is interdependent to facilitate arterial shear stress sensation. Future research focusing on how N-glycans mediate this interaction can provide new insights for the understanding of vascular function in health and disease.

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.

Prediction of subcutaneous drug absorption - do we have reliable data to design a simulated interstitial fluid?

For many years subcutaneous (SC) administration has represented the main route for delivering biopharmaceuticals. However, little information exists about the milieu in the subcutaneous tissue, especially about the properties/composition of the fluid present in this tissue, the interstitial fluid (ISF), which is one of the key elements for the drug release and absorption. Better knowledge on SC ISF composition, properties and dynamics may provide better insight into in vivo drug performance. In addition, a simulated SC ISF, which allows better prediction of in vivo absorption of drugs after subcutaneous administration based on in vitro release experiments, would help to improve formulation design, and reduce the number of animal studies and clinical trials required to obtain marketing authorization. To date, a universal medium for predicting drug solubility/release in the interstitial space does not exist. This review provides an overview of the currently available information on composition and physicochemical properties of SC ISF and critically discusses different isolation techniques in the context of information that could be gained from the isolated fluid. Moreover, it surveys current in vitro release media aiming to mimic SC ISF composition and highlights information gaps that need to be filled for designing a meaningful artificial SC ISF.

Dietary Salt Accelerates Orthodontic Tooth Movement by Increased Osteoclast Activity

Dietary salt uptake and inflammation promote sodium accumulation in tissues, thereby modulating cells like macrophages and fibroblasts. Previous studies showed salt effects on periodontal ligament fibroblasts and on bone metabolism by expression of nuclear factor of activated T-cells-5 (NFAT-5). Here, we investigated the impact of salt and NFAT-5 on osteoclast activity and orthodontic tooth movement (OTM). After treatment of osteoclasts without (NS) or with additional salt (HS), we analyzed gene expression and the release of tartrate-resistant acid phosphatase and calcium phosphate resorption. We kept wild-type mice and mice lacking NFAT-5 in myeloid cells either on a low, normal or high salt diet and inserted an elastic band between the first and second molar to induce OTM. We analyzed the expression of genes involved in bone metabolism, periodontal bone loss, OTM and bone density. Osteoclast activity was increased upon HS treatment. HS promoted periodontal bone loss and OTM and was associated with reduced bone density. Deletion of NFAT-5 led to increased osteoclast activity with NS, whereas we detected impaired OTM in mice. Dietary salt uptake seems to accelerate OTM and induce periodontal bone loss due to reduced bone density, which may be attributed to enhanced osteoclast activity. NFAT-5 influences this reaction to HS, as we detected impaired OTM and osteoclast activity upon deletion.

Emerging Role of Angiotensin AT2 Receptor in Anti-Inflammation: An Update

The hyperactive RAS and inflammation are closely associated. The angiotensin-II/AT1R axis of the RAS has been explored extensively for its role in inflammation and a plethora of pathological conditions. Understanding the role of AT2R in inflammation is an emerging area of research. The AT2R is expressed on a variety of immune and non-immune cells, which upon activation triggers the release of a host of cytokines and has multiple effects that coalesce to anti-inflammation and prevents maladaptive repair. The anti-inflammatory outcomes of AT2R activation are linked to its well-established signaling pathways involving formation of nitric oxide and activation of phosphatases. Collectively, these effects promote cell survival and tissue function. The consideration of AT2R as a therapeutic target requires further investigations.

Hypotheses about sub-optimal hydration in the weeks before coronavirus disease (COVID-19) as a risk factor for dying from COVID-19

To address urgent need for strategies to limit mortality from coronavirus disease 2019 (COVID-19), this review describes experimental, clinical and epidemiological evidence that suggests that chronic sub-optimal hydration in the weeks before infection might increase risk of COVID-19 mortality in multiple ways. Sub-optimal hydration is associated with key risk factors for COVID-19 mortality, including older age, male sex, race-ethnicity and chronic disease. Chronic hypertonicity, total body water deficit and/or hypovolemia cause multiple intracellular and/or physiologic adaptations that preferentially retain body water and favor positive total body water balance when challenged by infection. Via effects on serum/glucocorticoid-regulated kinase 1 (SGK1) signaling, aldosterone, tumor necrosis factor-alpha (TNF-alpha), vascular endothelial growth factor (VEGF), aquaporin 5 (AQP5) and/or Na⁺/K⁺-ATPase, chronic sub-optimal hydration in the weeks before exposure to COVID-19 may conceivably result in: greater abundance of angiotensin converting enzyme 2 (ACE2) receptors in the lung, which increases likelihood of COVID-19 infection, lung epithelial cells which are pre-set for exaggerated immune response, increased capacity for capillary leakage of fluid into the airway space, and/or reduced capacity for both passive and active transport of fluid out of the airways. The hypothesized hydration effects suggest hypotheses regarding strategies for COVID-19 risk reduction, such as public health recommendations to increase intake of drinking water, hydration screening alongside COVID-19 testing, and treatment tailored to the pre-infection hydration condition. Hydration may link risk factors and pathways in a unified mechanism for COVID-19 mortality. Attention to hydration holds potential to reduce COVID-19 mortality and disparities via at least 5 pathways simultaneously.

Hyperosmolarity and Increased Serum Sodium Concentration Are Risks for Developing Hypertension Regardless of Salt Intake: A Five-Year Cohort Study in Japan

The potential contribution of serum osmolarity in the modulation of blood pressure has not been evaluated. This study was done to examine the relationship between hyperosmolarity and hypertension in a five-year longitudinal design. We enrolled 10,157 normotensive subjects without diabetes who developed hypertension subsequently as determined by annual medical examination in St. Luke's International Hospital, Tokyo, between 2004 and 2009. High salt intake was defined as >12 g/day by a self-answered questionnaire and hyperosmolarity was defined as >293 mOsm/L serum osmolarity, calculated using serum sodium, fasting blood glucose, and blood urea nitrogen. Statistical analyses included adjustments for age, gender, body mass index, smoking, drinking alcohol, dyslipidemia, hyperuricemia, and chronic kidney disease. In the patients with normal osmolarity, the group with high salt intake had a higher cumulative incidence of hypertension than the group with normal salt intake (8.4% versus 6.7%, p = 0.023). In contrast, in the patients with high osmolarity, the cumulative incidence of hypertension was similar in the group with high salt intake and in the group with normal salt intake (13.1% versus 12.9%, p = 0.84). The patients with hyperosmolarity had a higher incidence of hypertension over five years compared to that of the normal osmolarity group (p < 0.001). After multiple adjustments, elevated osmolarity was an independent risk for developing hypertension (OR (odds ratio), 1.025; 95% CI (confidence interval), 1.006-1.044), regardless of the amount of salt intake. When analyzed in relation to each element of calculated osmolarity, serum sodium and fasting blood glucose were independent risks for developing hypertension. Our results suggest that hyperosmolarity is a risk for developing hypertension regardless of salt intake.

A Role of Inflammation and Immunity in Essential Hypertension-Modeled and Analyzed Using Petri Nets

Recent studies have shown that the innate and adaptive immune system, together with low-grade inflammation, may play an important role in essential hypertension. In this work, to verify the importance of selected factors for the development of essential hypertension, we created a Petri net-based model and analyzed it. The analysis was based mainly on t-invariants, knockouts of selected fragments of the net and its simulations. The blockade of the renin-angiotensin (RAA) system revealed that the most significant effect on the emergence of essential hypertension has RAA activation. This blockade affects: (1) the formation of angiotensin II, (2) inflammatory process (by influencing C-reactive protein (CRP)), (3) the initiation of blood coagulation, (4) bradykinin generation via the kallikrein-kinin system, (5) activation of lymphocytes in hypertension, (6) the participation of TNF alpha in the activation of the acute phase response, and (7) activation of NADPH oxidase-a key enzyme of oxidative stress. On the other hand, we found that the blockade of the activation of the RAA system may not eliminate hypertension that can occur due to disturbances associated with the osmotically independent binding of Na in the interstitium. Moreover, we revealed that inflammation alone is not enough to trigger primary hypertension, but it can coexist with it. We believe that our research may contribute to a better understanding of the pathology of hypertension. It can help identify potential subprocesses, which blocking will allow better control of essential hypertension.

Tissue sodium concentrations in chronic kidney disease and dialysis patients by lower leg sodium-23 magnetic resonance imaging

BACKGROUND

Sodium-23 magnetic resonance imaging (23Na MRI) allows direct measurement of tissue sodium concentrations. Current knowledge of skin, muscle and bone sodium concentrations in chronic kidney disease (CKD) and renal replacement therapy patients is limited. In this study we measured the tissue sodium concentrations in CKD, hemodialysis (HD) and peritoneal dialysis (PD) patients with 23Na MRI of the lower leg and explored their correlations with established clinical biomarkers.

METHODS

Ten healthy controls, 12 CKD Stages 3-5, 13 HD and 10 PD patients underwent proton and 23Na MRI of the leg. The skin, soleus and tibia were segmented manually and tissue sodium concentrations were measured. Plasma and serum samples were collected from each subject and analyzed for routine clinical biomarkers. Tissue sodium concentrations were compared between groups and correlations with blood-based biomarkers were explored.

RESULTS

Tissue sodium concentrations in the skin, soleus and tibia were higher in HD and PD patients compared with controls. Serum albumin showed a strong, negative correlation with soleus sodium concentrations in HD patients (r = -0.81, P < 0.01). Estimated glomerular filtration rate showed a negative correlation with tissue sodium concentrations (soleus: r = -0.58, P < 0.01; tibia: r = -0.53, P = 0.01) in merged control-CKD patients. Hemoglobin was negatively correlated with tissue sodium concentrations in CKD (soleus: r = -0.65, P = 0.02; tibia: r = -0.73, P < 0.01) and HD (skin: r = -0.60, P = 0.04; tibia: r = -0.76, P < 0.01).

CONCLUSION

Tissue sodium concentrations, measured by 23Na MRI, increase in HD and PD patients and may be associated with adverse metabolic effects in CKD and dialysis.

Crosstalk Between Vascular Redox and Calcium Signaling in Hypertension Involves TRPM2 (Transient Receptor Potential Melastatin 2) Cation Channel

Increased generation of reactive oxygen species (ROS) and altered Ca²⁺ handling cause vascular damage in hypertension. Mechanisms linking these systems are unclear, but TRPM2 (transient receptor potential melastatin 2) could be important because TRPM2 is a ROS sensor and a regulator of Ca²⁺ and Na⁺ transport. We hypothesized that TRPM2 is a point of cross-talk between redox and Ca²⁺ signaling in vascular smooth muscle cells (VSMC) and that in hypertension ROS mediated-TRPM2 activation increases [Ca²⁺]_i through processes involving NCX (Na⁺/Ca²⁺ exchanger). VSMCs from hypertensive and normotensive individuals and isolated arteries from wild type and hypertensive mice (LinA3) were studied. Generation of superoxide anion and hydrogen peroxide (H₂O₂) was increased in hypertensive VSMCs, effects associated with activation of redox-sensitive PARP1 (poly [ADP-ribose] polymerase 1), a TRPM2 regulator. Ang II (angiotensin II) increased Ca²⁺ and Na⁺ influx with exaggerated responses in hypertension. These effects were attenuated by catalase-polyethylene glycol -catalase and TRPM2 inhibitors (2-APB, 8-Br-cADPR olaparib). TRPM2 siRNA decreased Ca²⁺ in hypertensive VSMCs. NCX inhibitors (Benzamil, KB-R7943, YM244769) normalized Ca²⁺ hyper-responsiveness and MLC20 phosphorylation in hypertensive VSMCs. In arteries from LinA3 mice, exaggerated agonist (U46619, Ang II, phenylephrine)-induced vasoconstriction was decreased by TRPM2 and NCX inhibitors. In conclusion, activation of ROS-dependent PARP1-regulated TRPM2 contributes to vascular Ca²⁺ and Na⁺ influx in part through NCX. We identify a novel pathway linking ROS to Ca²⁺ signaling through TRPM2/NCX in human VSMCs and suggest that oxidative stress-induced upregulation of this pathway may be a new player in hypertension-associated vascular dysfunction.

Dermal Interstitial Alterations in Patients With Heart Failure and Reduced Ejection Fraction: A Potential Contributor to Fluid Accumulation?

BACKGROUND

Large networks of interstitial glycosaminoglycans help to regulate water and electrolyte homeostasis. The relation between dermal interstitial alterations and occurrence of edema in heart failure patients with reduced ejection fraction (HFrEF) is unknown. We hypothesize that in HFrEF patients (1) interstitial glycosaminoglycan density is increased, (2) changes in the interstitial glycosaminoglycan network are associated with interstitial fluid accumulation, and (3) there is a link between the interstitial glycosaminoglycan network and the renin-angiotensin-aldosterone system.

METHODS AND RESULTS

Two punch biopsies of the skin were obtained in healthy subjects (n=18) and HFrEF patients (n=29). Alcian blue staining and immunostaining for the angiotensin II type 1 receptor was performed. After obtaining tissue water content, total interstitial glycosaminoglycan (uronic acid) and sulfated glycosaminoglycan were quantified. A venous blood sample, clinical examination, and echocardiography were obtained. A significantly higher interstitial glycosaminoglycan content was observed in HFrEF patients compared with healthy subjects (uronic acid: 13.0±4.2 versus 9.6±1.6 μg/mg; P=0.002; sulfated glycosaminoglycan: 14.1 [11.7; 18.1] versus 10.0 [9.1; 10.8] μg/mg; P<0.001). Uronic acid and sulfated glycosaminoglycan density were strongly associated with tissue water content and peripheral edema (uronic acid: ρ=0.66; P<0.0001 and sulfated glycosaminoglycan: τ=0.58; P<0.0001). Expression of the angiotensin II type 1 receptor was found on dermal cells, although use of angiotensin-converting enzyme inhibitors/angiotensin receptor blocker was associated with significantly lower levels of interstitial glycosaminoglycans in HFrEF patients.

CONCLUSIONS

Interstitial glycosaminoglycan concentration is significantly increased in HFrEF patients compared with healthy subjects and correlated with tissue water content and clinical signs of volume overload. A better appreciation of the interstitial compartment might improve management of volume overload in HF.

New insights regarding epithelial Na+ channel regulation and its role in the kidney, immune system and vasculature

PURPOSE OF REVIEW

This review describes recent findings regarding the epithelial Na channel (ENaC) and its roles in physiologic and pathophysiologic states. We discuss new insights regarding ENaC's structure, its regulation by various factors, its potential role in hypertension and nephrotic syndrome, and its roles in the immune system and vasculature.

RECENT FINDINGS

A recently resolved structure of ENaC provides clues regarding mechanisms of ENaC activation by proteases. The use of amiloride in nephrotic syndrome, and associated complications are discussed. ENaC is expressed in dendritic cells and contributes to immune system activation and increases in blood pressure in response to NaCl. ENaC is expressed in endothelial ENaC and has a role in regulating vascular tone.

SUMMARY

New findings have emerged regarding ENaC and its role in the kidney, immune system, and vasculature.

Search for Upstream Cell Volume Sensors: The Role of Plasma Membrane and Cytoplasmic Hydrogel

The plasma membrane plays a prominent role in the regulation of cell volume by mediating selective transport of extra- and intracellular osmolytes. Recent studies show that upstream sensors of cell volume changes are mainly located within the cytoplasm that displays properties of a hydrogel and not in the plasma membrane. Cell volume changes occurring in anisosmotic medium as well as in isosmotic environment affect properties of cytoplasmic hydrogel that, in turn, trigger rapid regulatory volume increase and decrease (RVI and RVD). The downstream signaling pathways include reorganization of 2D cytoskeleton and altered composition of polyphosphoinositides located on the inner surface of the plasma membrane. In addition to its action on physico-chemical properties of cytoplasmic hydrogel, cell volume changes in anisosmotic conditions affect the ionic strength of the cytoplasm and the [Na⁺]_i/[K⁺]_i ratio. Elevated intracellular ionic strength evoked by long term exposure of cells to hypertonic environment resulted in the activation of TonEBP and augmented expression of genes controlling intracellular organic osmolyte levels. The role of Na⁺_i/K⁺_i -sensitive, Ca²⁺_i -mediated and Ca²⁺_i-independent mechanisms of excitation-transcription coupling in cell volume-adjustment remains unknown.

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.

The American Heart Association Scientific Statement on salt sensitivity of blood pressure: Prompting consideration of alternative conceptual frameworks for the pathogenesis of salt sensitivity?

: Recently, the American Heart Association (AHA) published a scientific statement on salt sensitivity of blood pressure which emphasized a decades old conceptual framework for the pathogenesis of this common disorder. Here we examine the extent to which the conceptual framework for salt sensitivity emphasized in the AHA Statement accommodates contemporary findings and views of the broader scientific community on the pathogenesis of salt sensitivity. In addition, we highlight alternative conceptual frameworks and important contemporary theories of salt sensitivity that are little discussed in the AHA Statement. We suggest that greater consideration of conceptual frameworks and theories for salt sensitivity beyond those emphasized in the AHA Statement may help to advance understanding of the pathogenesis of salt-induced increases in blood pressure and, in consequence, may lead to improved approaches to preventing and treating this common disorder.

Salt sensitivity of blood pressure at age 8 years in children born preterm

Preterm birth and low birth weight have been associated with an increased risk of hypertension; postnatal growth and dietary salt intake may contribute to these associations. In adults, the change of blood pressure (BP) in response to modifications in salt intake, i.e., salt sensitivity of BP, has been independently associated with cardiovascular disease. Little is known about salt sensitivity in children. We hypothesize that it may partly explain the association between preterm birth and higher BP in later life. We assessed salt sensitivity of BP at age 8 years in 63 preterm-born children, and explored its association with postnatal growth, sodium intake, and body composition from infancy onwards. BP was measured at baseline and after a 7-day high-salt diet. The difference in mean arterial pressure (MAP) was calculated; salt sensitivity was defined as an increase in MAP of ≥5%. Ten children (16%) showed salt sensitivity of BP, which was associated with neonatal growth restriction as well as with lower fat mass and BMI from infancy onwards. At age 8 years, children classified as salt sensitive had a lower weight-for-age SD-score (-1.5 ± 1.3 vs. -0.6 ± 1.1) and BMI (13.8 ± 1.7 vs. 15.5 ± 1.8 kg/m²) compared to their salt resistant counterparts. Sodium intake was not associated with (salt sensitivity of) BP. Salt sensitivity of BP was demonstrated in preterm-born children at age 8 years and may contribute to the development of cardiovascular disease at later age. Long-term follow-up studies are necessary to assess reproducibility of our findings and to explore clustering with other cardiovascular risk factors.

Understanding the Two Faces of Low-Salt Intake

Fierce debate has developed whether low-sodium intake, like high-sodium intake, could be associated with adverse outcome. The debate originates in earlier epidemiological studies associating high-sodium intake with high blood pressure and more recent studies demonstrating a higher cardiovascular event rate with both low- and high-sodium intake. This brings into question whether we entirely understand the consequences of high- and (very) low-sodium intake for the systemic hemodynamics, the kidney function, the vascular wall, the immune system, and the brain. Evolutionarily, sodium retention mechanisms in the context of low dietary sodium provided a survival advantage and are highly conserved, exemplified by the renin-angiotensin system. What is the potential for this sodium-retaining mechanism to cause harm? In this paper, we will consider current views on how a sodium load is handled, visiting aspects including the effect of sodium on the vessel wall, the sympathetic nervous system, the brain renin-angiotensin system, the skin as "third compartment" coupling to vascular endothelial growth factor C, and the kidneys. From these perspectives, several mechanisms can be envisioned whereby a low-sodium diet could potentially cause harm, including the renin-angiotensin system and the sympathetic nervous system. Altogether, the uncertainties preclude a unifying model or practical clinical guidance regarding the effects of a low-sodium diet for an individual. There is a very strong need for fundamental and translational studies to enhance the understanding of the potential adverse consequences of low-salt intake as an initial step to facilitate better clinical guidance.

Endothelial Glycocalyx as Biomarker for Cardiovascular Diseases: Mechanistic and Clinical Implications

INTRODUCTION

The endothelial surface layer is covered with abundant proteoglycans, of which syndecans and glycosaminoglycans are major constituents.

RECENT FINDINGS

Among the endothelial glycocalyx (eGC) constituents, syndecan-1 (sdc1) is a main component, and an elevated serum level of sdc1 may indicate the degradation of eGC. In patients with ischemic heart disease or heart failure, elevation of serum sdc1 has been associated with worsening cardiac and renal function; however, the causal relationship between degradation of eGC and clinical outcomes is unclear. Herein, we review the previous literature on eGC in cardiovascular and noncardiovascular diseases and their clinical implications.

Chronic high-sodium diet intake after weaning lead to neurogenic hypertension in adult Wistar rats

In this study, we investigated some mechanisms involved in sodium-dependent hypertension of rats exposed to chronic salt (NaCl) intake from weaning until adult age. Weaned male Wistar rats were placed under high (0.90% w/w, HS) or regular (0.27% w/w, Cont) sodium diets for 12 weeks. Water consumption, urine output and sodium excretion were higher in HS rats compared to control. Blood pressure (BP) was directly measured by the arterial catheter and found 13.8% higher in HS vs Cont rats. Ganglionic blockade with hexamethonium caused greater fall in the BP of HS rats (33%), and central antagonism of AT₁ receptors (losartan) microinjected into the lateral ventricle reduced BP level of HS, but not of Cont group. Heart rate variability analysis revealed sympathetic prevalence on modulation of the systolic interval. HS diet did not affect creatinine clearance. Kidney histological analysis revealed no significant change in renal corpuscle structure. Sodium and potassium concentrations in CSF were found higher in HS rats despite no change in plasma concentration of these ions. Taken together, data suggest that animals exposed to chronic salt intake to a level close to that reported for human' diet since weaning lead to hypertension, which appears to rely on sodium-driven neurogenic mechanisms.

VEGF-C-mediated cardiac lymphangiogenesis in high salt intake accelerated progression of left ventricular remodeling in spontaneously hypertensive rats

High salt (HS) diet can accelerate the progress of hypertensive left ventricular (LV) remodeling. But the detailed mechanism remains poorly understood. We hypothesized HS intake could impact cardiac lymphangiogenesis through tonicity-responsive enhancer binding protein (TonEBP)/vascular endothelial growth factor-C (VEGF-C) signaling pathway which might play an important role in HS intake accelerated LV remodeling. Eight-week-old male spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were randomized to 0.5% NaCl (Low salt, LS) and 8% NaCl (high salt, HS) diets for 12 weeks. LV remodeling was determined by echocardiography. LV invasive hemodynamic analysis and morphologic staining (cardiomyocyte hypertrophy, collagen deposition, TonEBP expression, macrophage infiltration and lymphatic density) were performed at the time of sacrifice. The blood pressure of SHR-HS group was significantly increased compared to SHR-LS and WKY groups. Meanwhile, The LV chamber size was markedly enlargement, LV function apparently compromised accompanied with a severe macrophage infiltration, and fibrosis in the perivascular and interstitium of LV compared with SHR-LS group. Furthermore, the expression levels of VEGF-C, TonEBP, and lymphatic markers in SHR-HS group were significantly increased parallel with apparent lymphangiogenesis compared with SHR-LS group. Our work indicates that TonEBP/VEGF-C signaling pathway was up-regulated in HS intake accelerated hypertensive LV remodeling process that may be valuable for further investigation.

Advances in understanding the renin-angiotensin-aldosterone system (RAAS) in blood pressure control and recent pivotal trials of RAAS blockade in heart failure and diabetic nephropathy

The renin-angiotensin-aldosterone system (RAAS) plays a fundamental role in the physiology of blood pressure control and the pathophysiology of hypertension (HTN) with effects on vascular tone, sodium retention, oxidative stress, fibrosis, sympathetic tone, and inflammation. Fortunately, RAAS blocking agents have been available to treat HTN since the 1970s and newer medications are being developed. In this review, we will (1) examine new anti-hypertensive medications affecting the RAAS, (2) evaluate recent studies that help provide a better understanding of which patients may be more likely to benefit from RAAS blockade, and (3) review three recent pivotal randomized trials that involve newer RAAS blocking agents and inform clinical practice.

[The effect of the level of total sodium deposited in the myocardium on its stiffness]

AIM

To determine a relationship between the level of total sodium in the myocardium to its stiffness.

SUBJECTS AND METHODS

The investigation enrolled 18 hypertensive patients who had suddenly died; their mean age was 40±10 years; mean waist circumference, 102±12.5 cm; height, 170±7.7 cm; myocardial mass, 319±53 g.

RESULTS

The variation in the myocardial level of total sodium averaged 211.7±37.5 (min, 71.5; max, 226.17) mmol/l. The sodium level was ascertained to be affected to the greatest extent by myocardial mass (SS=3615.56; p=0.00029) and age at death (SS=1965.568; p=0.0029), whereas gender and smoking had a considerably lower impact (SS=778.584; p=0.03). A univariate regression analysis showed that there was a relationship between myocardial sodium levels and the thickness of the anterior wall of the left ventricle (β=0.94; p=0.000001; r2=0.88), that of the anterior wall of the right ventricle (β=0.82; p=0.000021; r2=0.66), and that of the interventricular septum (β=0.94; p=0.000001; r2=0.89). The wall thickness of the myocardium was established to depend on its sodium level (SS=21813.89; p=0.000001; r2=0.88): the higher sodium amount in the myocardium, the thicker its walls. The average velocity of acoustic wave propagation was 6.24±0.51 m/sec. A significant correlation was observed between sodium concentrations in the myocardium and its stiffness (β=0.72; p=0.00062; r2=0.49).

CONCLUSION

The level of sodium deposited in the myocardium, which is directly related to dietary sodium intake, is significantly correlated with myocardial stiffness. It can be assumed that the elevated level of sodium deposited in the myocardium is an independent factor that changes the stiffness of the myocardium and appears to influence the development of its diastolic dysfunction.

Lymphedema evaluation using noninvasive 3T MR lymphangiography

PURPOSE

To exploit the long 3.0T relaxation times and low flow velocity of lymphatic fluid to develop a noninvasive 3.0T lymphangiography sequence and evaluate its relevance in patients with lymphedema.

MATERIALS AND METHODS

A 3.0T turbo-spin-echo (TSE) pulse train with long echo time (TE_effective  = 600 msec; shot-duration = 13.2 msec) and TSE-factor (TSE-factor = 90) was developed and signal evolution simulated. The method was evaluated in healthy adults (n = 11) and patients with unilateral breast cancer treatment-related lymphedema (BCRL; n = 25), with a subgroup (n = 5) of BCRL participants scanned before and after manual lymphatic drainage (MLD) therapy. Maximal lymphatic vessel cross-sectional area, signal-to-noise-ratio (SNR), and results from a five-point categorical scoring system were recorded. Nonparametric tests were applied to evaluate study parameter differences between controls and patients, as well as between affected and contralateral sides in patients (significance criteria: two-sided P < 0.05).

RESULTS

Patient volunteers demonstrated larger lymphatic cross-sectional areas in the affected (arm = 12.9 ± 6.3 mm² ; torso = 17.2 ± 15.6 mm² ) vs. contralateral (arm = 9.4 ± 3.9 mm² ; torso = 9.1 ± 4.6 mm² ) side; this difference was significant both for the arm (P = 0.014) and torso (P = 0.025). Affected (arm: P = 0.010; torso: P = 0.016) but not contralateral (arm: P = 0.42; torso: P = 0.71) vessel areas were significantly elevated compared with control values. Lymphatic cross-sectional areas reduced following MLD on the affected side (pre-MLD: arm = 8.8 ± 1.8 mm² ; torso = 31.4 ± 26.0 mm² ; post-MLD: arm = 6.6 ± 1.8 mm² ; torso = 23.1 ± 24.3 mm² ). This change was significant in the torso (P = 0.036). The categorical scoring was found to be less specific for detecting lateralizing disease compared to lymphatic-vessel areas.

CONCLUSION

A 3.0T lymphangiography sequence is proposed, which allows for upper extremity lymph stasis to be detected in ∼10 minutes without exogenous contrast agents.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2017;46:1349-1360.

The role of macrophages in skin homeostasis

The skin and its appendages comprise the largest and fastest growing organ in the body. It performs multiple tasks and maintains homeostatic control, including the regulation of body temperature and protection from desiccation and from pathogen invasion. The skin can perform its functions with the assistance of different immune cell populations. Monocyte-derived cells are imperative for the completion of these tasks. The comprehensive role of macrophages and Langerhans cells in establishing and maintaining skin homeostasis remains incompletely defined. However, over the past decade, innovations in mouse genetics have allowed for advancements in the field. In this review, we explore different homeostatic roles of macrophages and Langerhans cells, including wound repair, follicle regeneration, salt balance, and cancer regression and progression in the skin. The understanding of the precise functions of myeloid-derived cells in the skin under basal conditions can help develop specific therapies that aid in skin and hair follicle regeneration and cutaneous cancer prevention.

Salt, aldosterone and extrarenal Na+ - sensitive responses in pregnancy

Outside of pregnancy excessive salt consumption is known to be harmful being linked to increased blood pressure and cardiovascular disease. However, pregnancy represents a major change to a woman's physiology resulting in an intimate adaptation to environmental conditions. It is now becoming apparent that salt is essential for a number of these changes during pregnancy including haematological, cardiac adaptations as well as directly influencing placental development and the uteroplacental immune environment. The present review discusses the important role that salt has during normal pregnancy and evidence will also be presented to show how the placenta may act as a salt sensing organ temporarily, yet substantially regulating maternal blood pressure.

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The placenta may function as an extrarenal regulator of maternal blood pressure.

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Na⁺handling in pregnancy is completely different to the non-pregnant situation.

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Na⁺may actually lower blood pressure in pregnancy affected with pre-eclampsia.

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Aldosterone is an important regulator of placental and fetal development.

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Na⁺ may compensate for aldosterone deficiency in pregnancy.

Involvement of systemic venous congestion in heart failure

Systemic venous congestion has gained significant importance in the interpretation of the pathophysiology of acute heart failure, especially in the development of renal function impairment during exacerbations. In this study, we review the concept, clinical characterisation and identification of venous congestion. We update current knowledge on its importance in the pathophysiology of acute heart failure and its involvement in the prognosis. We pay special attention to the relationship between abdominal congestion, the pulmonary interstitium as filtering membrane, inflammatory phenomena and renal function impairment in acute heart failure. Lastly, we review decongestion as a new therapeutic objective and the measures available for its assessment.

Metabolic and Kidney Diseases in the Setting of Climate Change, Water Shortage, and Survival Factors

Climate change (global warming) is leading to an increase in heat extremes and coupled with increasing water shortage, provides a perfect storm for a new era of environmental crises and potentially, new diseases. We use a comparative physiologic approach to show that one of the primary mechanisms by which animals protect themselves against water shortage is to increase fat mass as a means for providing metabolic water. Strong evidence suggests that certain hormones (vasopressin), foods (fructose), and metabolic products (uric acid) function as survival signals to help reduce water loss and store fat (which also provides a source of metabolic water). These mechanisms are intricately linked with each other and stimulated by dehydration and hyperosmolarity. Although these mechanisms were protective in the setting of low sugar and low salt intake in our past, today, the combination of diets high in fructose and salty foods, increasing temperatures, and decreasing available water places these survival signals in overdrive and may be accelerating the obesity and diabetes epidemics. The recent discovery of multiple epidemics of CKD occurring in agricultural workers in hot and humid environments may represent harbingers of the detrimental consequences of the combination of climate change and overactivation of survival pathways.

Immune Mechanisms in Arterial Hypertension

Traditionally, arterial hypertension and subsequent end-organ damage have been attributed to hemodynamic 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 organisms 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. Renal inflammation results in injury and impaired urinary sodium excretion, and vascular inflammation leads to endothelial dysfunction, increased vascular resistance, and arterial remodeling and stiffening. Notably, modulation of the immune response can reduce the severity of BP elevation and hypertensive end-organ damage in several animal models. Indeed, recent studies have improved our understanding of how the immune response affects the pathogenesis of arterial hypertension, but the remarkable advances in basic immunology made during the last few years still await translation to the field of hypertension. This review briefly summarizes recent advances in immunity and hypertension as well as hypertensive end-organ damage.

[Hemodynamic effects of succinate-containing dialyzing solution]

AIM

To assess the results of using an acetate-free succinate-containing dialyzing solution (SDS) against natremia and blood pressure (BP) in patients on chronic hemodialysis (HD).

SUBJECTS AND METHODS

Ninety-two patients were transferred from 3 Saint Petersburg HD centers to 3-month HD treatment using SDS. The investigators measured blood biochemical indicators immediately before and 1 and 3 months after the investigation, BP before and after a successive HD session, and the patients' weight and its gain in the period between HD sessions. Hypotensive and hypertensive episodes were recorded during HD sessions throughout the investigation.

RESULTS

Following 3-month treatment using SDS, there were statistically significant decreases in blood sodium levels and systolic BP (SBP) prior to a HD session. At the same time, patients with a baseline pre-HD SBP of less than 100 mm Hg were observed to have a statistically significant increase in this indicator by the end of the investigation. Pre-dialysis diastolic BP (DBP) and post- dialysis SBP and DBP substantially unchanged. After 3 months of SDS use, there was a statistically significant reduction in weight gain in the period between HD sessions. When SDS was administered, the frequency of hypertensive episodes tended to decline after a HD session.

CONCLUSION

The use of SDS causes a drop in pre-dialysis blood sodium levels, ensuring adequate dehydration in patients and improving hypertension control. In doing so, SDS prevents hypotension during a HD session.