Aims Prior studies have focused on the role of the kidney and vasculature in salt-induced modulation of blood pressure, however recent data indicate that sodium accumulates in tissues and can activate immune cells. We sought to examine mechanisms by which salt causes activation of human monocytes both in vivo and in vitro. Methods and Results To study the effect of salt in human monocytes, monocytes were isolated from volunteers to perform several in vitro experiments. Exposure of human monocytes to elevated Na+ ex vivo caused a coordinated response involving isolevuglandin (IsoLG)-adduct formation, acquisition of a dendritic cell-like morphology, expression of activation markers CD83 and CD16, and increased production of pro-inflammatory cytokines TNF-α, IL-6 and IL-1β. High salt also caused a marked change in monocyte gene expression as detected by RNA sequencing and enhanced monocyte migration to the chemokine CC motif chemokine ligand 5. NADPH-oxidase inhibition attenuated monocyte activation and IsoLG-adduct formation. The increase in IsoLG-adducts correlated with risk factors including body mass index, pulse pressure, total cholesterol and glucose. Monocytes exposed to high salt stimulated IL-17A production from autologous CD4+ and CD8+ T cells. In addition, to evaluate the effect of salt in vivo, monocytes and T cells isolated from humans were adoptively transferred to immunodeficient NSG mice. Salt feeding of humanized mice caused monocyte-dependent activation of human T cells reflected by proliferation and accumulation of T cells in the bone marrow. Moreover, we performed a cross-sectional study in 70 prehypertensive subjects. Blood was collected for flow cytometric analysis and 23Na MRI was performed for tissue sodium measurements. Monocytes from humans with high skin Na+ exhibited increased IsoLG-adduct accumulation and CD83 expression. Conclusions Human monocytes exhibit coordinated increases in parameters of activation, conversion to a DC-like phenotype and ability to activate T cells upon both in vitro and in vivo sodium exposure. The ability of monocytes to be activated by sodium is related to in vivo cardiovascular disease risk factors. We therefore propose that in addition to the kidney and vasculature, immune cells like monocytes convey salt-induced cardiovascular risk in humans. Translational perspective Immune cells like monocytes convey salt-sensitivity to humans and this is associated with cardiovascular risk factors. Our research provides a new mechanism by which a high salt diet may induce inflammation and hypertension and support the current recommendations of a low sodium consumption, especially in subjects with elevated cardiovascular risk. Our data indicates that scavenging IsoLGs or targeting monocytes may be therapeutically beneficial in salt-sensitive hypertension.

Background Tissue sodium content in patients on maintenance hemodialysis (MHD) and peritoneal dialysis (PD) were previously explored using 23Sodium magnetic resonance imaging (23NaMRI). Larger studies would provide a better understanding of sodium stores in patients on dialysis as well as the factors influencing this sodium accumulation. Methods In this cross-sectional study, we quantified the calf muscle and skin sodium content in 162 subjects (10 PD, 33 MHD patients, and 119 controls) using 23NaMRI. Plasma levels of interleukin-6 (IL-6) and high-sensitivity C-reactive protein (hsCRP) were measured to assess systemic inflammation. Sixty-four subjects had repeat 23NaMRI scans that were analyzed to assess the repeatability of the 23NaMRI measurements. Results Patients on MHD and PD exhibited significantly higher muscle and skin sodium accumulation compared to controls. African American patients on dialysis exhibited greater muscle and skin sodium content compared to non-African Americans. Multivariable analysis showed that older age was associated with both higher muscle and skin sodium. Male sex was also associated with increased skin sodium deposition. Greater ultrafiltration was associated with lower skin sodium in patients on PD (Spearman’s rho=-0.68, P = 0.035). Higher plasma IL-6 and hsCRP levels correlated with increased muscle and skin sodium content in the overall study population. Patients with higher baseline tissue sodium content exhibited greater variability in tissue sodium stores on repeat measurements. Conclusions Our findings highlight greater muscle and skin sodium content in dialysis patients compared to controls without kidney disease. Tissue sodium deposition and systemic inflammation seen in dialysis patients might influence one another bidirectionally.

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Introduction: Patients are often instructed to engage in multiple weekly sessions of exercise to increase physical activity. We aimed to determine whether assignment to a supervised exercise regimen increases overall weekly activity in individuals with chronic kidney disease (CKD). Methods: We performed a secondary analysis of a pilot randomized 2 Â 2 factorial design trial examining the effects of diet and exercise (10%À15% reduction in caloric intake, 3 supervised exercise sessions/wk, combined diet restriction/exercise, and control). Activity was measured as counts detected by accelerometer. Counts data were collected on all days for which an accelerometer was worn at baseline, month 2, and month 4 follow-up. The primary outcome was a relative change from baseline in log-transformed counts/min. Generalized estimating equations were used to compare the primary outcome in individuals in the exercise group and the nonexercise group. Results: We examined 111 individuals randomized to aerobic exercise or usual activity (n ¼ 48 in the exercise group and n ¼ 44 controls). The mean age was 57 years, 42% were female, and 28% were black. Median overall adherence over all time was 73%. Median (25th, 75th percentile) counts/min over nonsupervised exercise days at months 2 and 4 were 237.5 (6.5, 444.4) for controls and 250.9 (7.7, 529.8) for the exercise group (P ¼ 0.74). No difference was observed in the change in counts/min between the exercise and control groups over 3 time points (b [fold change], 0.96, 95% confidence interval [CI], 0.91, 1.02). Conclusion: Engaging in a supervised exercise program does not increase overall weekly physical activity in individuals with stage 3 to 4 CKD.