The Effect of High-Salt Diet on Oxidative Stress Production and Vascular Function in Tff3^−/−/C57BL/6N Knockout and Wild Type (C57BL/6N) Mice

Abstract

<b><i>Introduction:</i></b> It is well documented that high-salt (HS) diet increases systemic and vascular oxidative stress in various animal models and in humans, leading to impairment of vascular reactivity. The present study examined the interaction of genotype and HS diet intake and the potential effects of oxidative stress – antioxidative system balance on the flow-induced dilation (FID) in pressurized carotid arteries of normotensive Tff3^−/−/C57BL/6N knockout mice and their wild-type (WT) controls. <b><i>Methods:</i></b> Male, ten-week-old transgenic <i>Tff3</i>^{<i>−/−</i>}<i>/</i>C57BL/6N (<i>Tff3</i>^{<i>−/−</i>}) knockout mice and WT/C57BL/6N (WT) (parental strain) healthy mice were divided in LS (0.4% NaCl in rodent chow) and HS (4% NaCl in rodent chow fed for 1 week) groups. Additionally, LS and HS groups were treated with 1 mmol/L 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL) dissolved in the drinking water. After anesthesia with ketamine chloride (100 mg/kg) and midazolam (5 mg/kg), blood pressure was measured, carotid arteries and aortas were isolated, and blood samples were collected. <b><i>Results:</i></b> FID was decreased in WT_HS mice and restored by superoxide scavenger TEMPOL in vivo. On the other hand, attenuated FID of Tff3^−/− mice was not further affected by HS diet or TEMPOL in vivo treatment. Vascular superoxide/reactive oxygen species levels were increased with HS diet in both strains and restored by TEMPOL. HS upregulated glutathione peroxidase 1 (GPx1) gene expression in WT_HS and Tff3^−/−_HS mice, while GPx activity was significantly decreased only in WT_HS group. Systemic (serum) markers of oxidative stress (oxLDL and AOPP) and arterial blood pressure were similar among groups. <b><i>Conclusion:</i></b> HS diet increases vascular oxidative stress and impairs vasodilation in WT mice. <i>Tff3</i> gene deficiency attenuates vasodilation per se, without further effects of HS intake. This can be attributed to vascular upregulation of antioxidative enzyme GPx1 in Tff3^−/−/C57BL/6N mice conferring protection from oxidative stress.