Sodium Chloride Cotransporter Upregulation in Settings of Zinc Deficiency Offers New Insight into Blood Pressure Dysregulation in Chronic Diseases

Abstract

BackgroundZn2+ deficiency is a common comorbidity with numerous chronic diseases including type II diabetes and chronic kidney disease. Experimental data show that Zn2+ deficiency exacerbates hypertension in these settings. Moreover, Zn2+ deficiency alone is sufficient to alter blood pressure. However, the mechanisms involved are unknown.ObjectiveThe renal distal convoluted tubule sodium chloride cotransporter (NCC) plays a critical role in blood pressure regulation and hypertension. The objective of this study was to determine if NCC plays a role in Zn2+ deficiency‐induced hypertension.Experimental DesignTo this end, WT mice were pair‐fed a diet with 50 ppm Zn2+ (Zn2+ adequate [ZnA]) or a diet with 1 ppm Zn2+ (Zn2+ deficient [ZnD]) for 6 weeks. A subset of mice was administered 50 mg/kg hydrochlorothiazide, a NCC inhibitor. To reduce intracellular Zn2+ levels in vitro, WT mouse distal convoluted tubular (mDCT‐15) cells were cultured in 1 nM N,N,N′,N′‐tetrakis(2‐pyridylmethyl)ethylenediamine (TPEN)‐ or vehicle (DMSO)‐containing medium for 24 hours. To replete intracellular Zn2+, TPEN‐exposed cells were then cultured in 1 nM Zn2+‐supplemented medium for 24 hours. Select cell monolayers were treated with 100 nM diphenyliodonium (DPI), a general NADPH oxidase inhibitor, prior to TPEN treatment. In mice, systolic blood pressure was monitored by tail cuff plethysmography. NCC protein expression was examined in vivo and in vitro via western blot and immunohistochemistry. NCC activation was assessed by cellular localization (via biotinylation and immunofluorescence) and Na+ uptake activity (via thiazide‐sensitive assays).ResultsIn ZnD mice, increased blood pressure is accompanied with enhanced NCC protein expression compared to mice receiving a ZnA‐diet. However, NCC inhibition by hydrochlorothiazide treatment reverses blood pressure increases. In the in vitro model of Zn2+ deficiency, Zn2+ chelation with TPEN stimulates NCC protein expression compared to vehicle‐treated cells. Furthermore, TPEN promotes NCC surface localization and Na+ uptake activity. Notably, restoration of intracellular Zn2+ levels by supplementation reverses TPEN effects on NCC. Additionally, NADPH oxidase inhibition with DPI treatment prevents TPEN‐induced NCC upregulation.ConclusionsOur findings indicate that NCC is a Zn2+‐sensitive transporter and is upregulated in settings of Zn2+ deficiency via a NADPH oxidase‐mediated mechanism.SignificanceNCC represents a novel mechanism by which Zn2+ deficiency alters blood pressure and contributes to hypertension in chronic disease settings.Support or Funding InformationCR. Williams (AHA‐SDG), JL. Gooch (VA‐MERIT), RS. Hoover (VA‐MERIT and NIH‐R01)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.