NADPH oxidase-2 mediates zinc deficiency-induced oxidative stress and kidney damage

Abstract

Zn deficiency (ZnD) is comorbid with chronic kidney disease and worsens kidney complications. Oxidative stress is implicated in the detrimental effects of ZnD. However, the sources of oxidative stress continue to be identified. Since NADPH oxidases (Nox) are the primary enzymes that contribute to renal reactive oxygen species generation, this study's objective was to determine the role of these enzymes in ZnD-induced oxidative stress. We hypothesized that ZnD promotes NADPH oxidase upregulation, resulting in oxidative stress and kidney damage. To test this hypothesis, wild-type mice were pair-fed a ZnD or Zn-adequate diet. To further investigate the effects of Zn bioavailability on NADPH oxidase regulation, mouse tubular epithelial cells were exposed to the Zn chelator N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) or vehicle followed by Zn supplementation. We found that ZnD diet-fed mice develop microalbuminuria, electrolyte imbalance, and whole kidney hypertrophy. These markers of kidney damage are accompanied by elevated Nox2 expression and HO levels. In mouse tubular epithelial cells, TPEN-induced ZnD stimulates HO generation. In this in vitro model of ZnD, enhanced HO generation is prevented by NADPH oxidase inhibition with diphenyleneiodonium. Specifically, TPEN promotes Nox2 expression and activation, which are reversed when intracellular Zn levels are restored following Zn supplementation. Finally, Nox2 knockdown by siRNA prevents TPEN-induced HO generation and cellular hypertrophy in vitro. Together, these findings reveal that Nox2 is a Zn-regulated enzyme that mediates ZnD-induced oxidative stress and kidney hypertrophy. Understanding the specific mechanisms by which ZnD contributes to kidney damage may have an important impact on the treatment of chronic kidney disease.

Zinc deficiency induces hypertension by promoting renal Na+ reabsorption

“…In vivo. An established protocol (12) was used to induce ZnD in male mice on a C57BL/6 background (8 wk old). Mice (n ϭ 20) were acclimated to a Zn 2ϩ -adequate (50 ppm Zn 2ϩ , ZnA) diet (diet TD.85420, Harlan Teklad) for 2 wk.…”

“…Mouse DCT (mDCT-15) cells (6,19) were grown in DMEM growth medium. The mDCT-15 cells were cultured in 1 nM N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN)-or vehicle (DMSO)-containing medium for 24 h to reduce intracellular Zn 2ϩ levels (12). TPEN-exposed mDCT-15 cells were cultured in 1 nM Zn 2ϩ -supplemented medium for 24 h to replete intracellular Zn 2ϩ (12).…”

Oxidative stress in chronic kidney disease

“…ATII-R blockers are considered renoprotective against OS not only by decreasing NOX expression but also by improving eNOS and SOD expression and/or activity [64,103]. Another cause of NOXmediated ROS generation in the kidney appears to be zinc deficiency, as shown by several groups [63] and discussed in more detail below.…”

Zinc against advanced glycation end products

“…Nicotinamide adenine dinucleotide phosphate oxidase (NADPH‐oxidase) is a member of enzymes that are involved in production of ROS. It has been reported that zinc deficiency stimulates up regulation of NADPH‐oxidase . Besides, it has been suggested that zinc inhibits ROS production through prevention of the NADPH‐oxidase activity …”