Effect of the DASH diet on the sodium-chloride cotransporter and aquaporin-2 in urinary extracellular vesicles

The dietary approach to stop hypertension (DASH) diet combines the antihypertensive effect of a low sodium and high potassium diet. In particular, the potassium component of the diet acts as a switch in the distal convoluted tubule to reduce sodium reabsorption, similar to a diuretic but without the side effects. Previous trials to understand the mechanism of the DASH diet were based on animal models and did not characterize changes in human ion channel protein abundance. More recently, protein cargo of urinary extracellular vesicles (uEVs) has been shown to mirror tissue content and physiological changes within the kidney. We designed an inpatient open label nutritional study transitioning hypertensive volunteers from an American style diet to DASH diet to examine physiological changes in adults with stage 1 hypertension otherwise untreated (Sacks FM, Svetkey LP, Vollmer WM, Appel LJ, Bray GA, Harsha D, Obarzanek E, Conlin PR, Miller ER 3rd, Simons-Morton DG, Karanja N, Lin PH; DASH-Sodium Collaborative Research Group. N Engl J Med 344: 3-10, 2001). Urine samples from this study were used for proteomic characterization of a large range of pure uEVs (small to large) to reveal kidney epithelium changes in response to the DASH diet. These samples were collected from nine volunteers at three time points, and mass spectrometry identified 1,800 proteins from all 27 samples. We demonstrated an increase in total SLC12A3 [sodium-chloride cotransporter (NCC)] abundance and a decrease in aquaporin-2 (AQP2) in uEVs with this mass spectrometry analysis, immunoblotting revealed a significant increase in the proportion of activated (phosphorylated) NCC to total NCC and a decrease in AQP2 from day 5 to day 11. This data demonstrates that the human kidney's response to nutritional interventions may be captured noninvasively by uEV protein abundance changes. Future studies need to confirm these findings in a larger cohort and focus on which factor drove the changes in NCC and AQP2, to which degree NCC and AQP2 contributed to the antihypertensive effect and address if some uEVs function also as a waste pathway for functionally inactive proteins rather than mirroring protein changes.NEW & NOTEWORTHY Numerous studies link DASH diet to lower blood pressure, but its mechanism is unclear. Urinary extracellular vesicles (uEVs) offer noninvasive insights, potentially replacing tissue sampling. Transitioning to DASH diet alters kidney transporters in our stage 1 hypertension cohort: AQP2 decreases, NCC increases in uEVs. This aligns with increased urine volume, reduced sodium reabsorption, and blood pressure decline. Our data highlight uEV protein changes as diet markers, suggesting some uEVs may function as waste pathways. We analyzed larger EVs alongside small EVs, and NCC in immunoblots across its molecular weight range.

Extracellular Vesicles in Acute Kidney Injury

Extracellular vesicles (EVs) are promising novel cellular communicators and biomarkers in acute kidney injury (AKI). These submicron vesicles derive from all cell types along the urinary tract and reflect molecular processes of their parent cells and physiological and pathological conditions in AKI. Several EV protein and RNA biomarker candidates have been identified. They have shown to differentiate AKI etiology and pinpoint to disease mechanisms. In fact, EV research has opened up a new frontier of biomarker discovery since some less abundant biomarkers are concentrated in EVs, which makes them more easily detectable. EVs are also functional and are involved in intra-nephron communication. Tubular-interstitial communication is current focus in EV research in AKI as it can help to understand maladaptive processes in AKI. EVs are also promising therapeutic tools and have been shown to be regenerative in many different models of AKI. Rigorous studies are needed to validate these findings, and more sensitive EV detection and characterization tools need to be developed to dissect EV biology in renal disease and AKI.

Pulmonary malakoplakia secondary to Rhodococcus equi infection mimicking a lung neoplasm in a lung transplant recipient

Pulmonary masses occasionally occur after lung transplantation and vary in etiology, which includes malignant and benign conditions, such as infection. Here, we report a case of a patient presenting with a lung mass 3 years after lung transplant. To our knowledge, this is the first described case of pulmonary malakoplakia due to Rhodococcus equi infection in an allograft post-lung transplantation. This case outlines the challenges of differentiating benign from malignant masses after transplantation.

Role of bronchodilators in chronic obstructive pulmonary disease

The prevalence of chronic obstructive pulmonary disease (COPD) continues to be on the rise. Bronchodilators are first line agents for the symptomatic management of this disease and have proven to be effective in both stable disease status and exacerbations. The stepwise escalation of therapy for COPD according to severity has been outlined in international guidelines. Different classes of bronchodilators exist. The most experience is available for short-acting beta-agonists and anticholinergics. These agents are mainly recommended for the treatment of mild COPD and for symptomatic patients on an as needed basis. Long-acting beta-agonists and anticholinergics have been developed more recently. They are more convenient to use for patients with advanced disease who require maintenance therapy with bronchodilators, and have been shown in this group of patients to provide superior efficacy compared with short-acting agents. Tiotropium, a long-acting anticholinergic, appears to be particularly powerful and may eventually replace ipratropium as the primary agent for COPD treatment. In contrast, the usage of theophylline, which used to be part of the mainstay of treatment for COPD, has declined, mainly secondary to a narrow therapeutic margin and side effects, but it is inexpensive and still has its role. New agents like phosphodiesterase-4-inhibitors are interesting substances that may become important adjuncts in COPD management, but there is limited experience so far. None of the bronchodilators have been shown to change outcome in COPD, but this issue is under active investigation.