Zinc Deficiency‐Induced NFκB Activation Promotes Hypertension by Driving Renal Na + Reabsorption

Abstract

Background : Zinc deficiency (ZnD) is a common comorbidity with chronic disorders including diabetes and kidney disease. Patients with these diseases also have a higher incidence of hypertension. Recently, we reported that a zinc deficient diet is sufficient to induce hypertension in mice. Changes in blood pressure were accompanied by increased Na+ reabsorption via the renal sodium chloride cotransporter (NCC). Although our novel results indicate that zinc plays a critical role in NCC regulation and its downstream effects on blood pressure, the specific mechanisms involved are unknown. Hypothesis : Since nuclear factor-κB (NFκB) is a key transcription factor implicated in ZnD-mediated effects, we tested the hypothesis that ZnD stimulates renal NFκB activation which drives NCC upregulation and thereby promotes hypertension. Experimental Design : Adult, male C57BL/6 mice were fed a zinc adequate (ZnA; 50ppm) or a ZnD (1ppm) diet for 6 weeks. To examine the role of NFκB in ZnD-induced hypertension, mice were switched from a ZnA-diet to a ZnD-diet for 5 weeks. After, ZnD mice were administered caffeic acid phenethyl ester (CAPE), an NFκB inhibitor, for 1 week. In mice, NCC expression (qRT-PCR) and blood pressure (tail-cuff) were measured. To further investigate the role of NFκB in NCC expression (qRT-PCR and Western blot), mouse distal convoluted tubule (mDCT) cells were treated with TPEN (a zinc chelator) or vehicle (DMSO) ± CAPE. Results : Compared to ZnA mice, NCC mRNA abundance was increased in ZnD mice (7.625 ± 1.747 vs 1.0 ± 0.127) and was accompanied by enhanced renal NFκB nuclear localization. In mDCT cells, TPEN-induced ZnD stimulated NCC mRNA expression (3.152 ± 0.966 vs 1.0 ± 0.174) and NFκB upregulation (1.573 ± 0.117 vs 1.0 ± 0). However, NFκB inhibition by CAPE prevented TPEN-induced NCC mRNA (0.636 ± 0.178 vs 3.152 ± 0.966) and protein (1.039 ± 0.018 vs 2.335 ± 0.062) expression in mDCT cells. Finally, CAPE administration lowered blood pressure (154.5 ± 5.42 vs 138.1 ± 1.97 mm Hg) in ZnD mice. Summary : These results demonstrate that 1) renal NFκB is a Zn2+-regulated transcription factor, 2) NFκB is involved in NCC regulation and 3) NFκB mediates ZnD-induced blood pressure increases. Significance : Taken together, these data indicate that ZnD stimulates NFκB activation thereby driving NCC upregulation and hypertension.