Nicotinamide nucleotide transhydrogenase (NNT) regulates mitochondrial ROS and endothelial dysfunction in response to angiotensin II

Abstract

Endothelial dysfunction is a critical, initiating step in the development of hypertension (HTN) and mitochondrial reactive oxygen species (ROS) are important contributors to endothelial dysfunction. Genome-wide association studies (GWAS) have identified single nucleotide polymorphisms (SNPs) in the nicotinamide nucleotide transhydrogenase ( Nnt ) gene that are associated with endothelial dysfunction and increased risk for HTN. NNT is emerging as an important enzyme that regulates mitochondrial NADPH levels and mitochondrial redox balance by supporting the thiol dependent peroxidase systems in the mitochondria. We have previously shown that the absence of NNT in C57Bl/6J animals promotes a more severe hypertensive phenotype through reductions in • NO and endothelial dependent vessel dilation. However, the impact of NNT on human endothelial cell function remains unclear. We utilized NNT directed shRNA in human aortic endothelial cells to test the hypothesis that NNT critically regulates mitochondrial redox balance and endothelial function in response to angiotensin II (Ang II). We demonstrate that NNT expression and activity are elevated in response to the mitochondrial dysfunction and oxidative stress associated with Ang II treatment. Knockdown of NNT led to a significant elevation of mitochondrial ROS production and impaired glutathione peroxidase and glutathione reductase activities associated with a reduction in the NADPH/NADP + ratio. Loss of NNT also promoted mitochondrial dysfunction, disruption of the mitochondrial membrane potential, and impaired ATP production in response to Ang II. Finally, we observed that, while the loss of NNT augmented eNOS phosphorylation at Ser 1177 , neither eNOS activity nor nitric oxide production were similarly increased. The results from these studies clearly demonstrate that NNT is critical for the maintenance of mitochondrial redox balance and mitochondrial function. Loss of NNT and disruption of redox balance leads to oxidative stress that compromises eNOS activity that could have a profound effect on the endothelium dependent regulation of vascular tone.

Comparative Transcriptome Analysis of the Expression of Antioxidant and Immunity Genes in the Spleen of a Cyanidin 3-O-Glucoside-Treated Alzheimer’s Mouse Model

“…The involvement of most of these upregulated genes in the immune response/immune modulation and the association of two (Slpi and Nnt) of these genes with AD suggests the need to investigate all of these five genes in the future as candidate genes underlying the immunomodulatory mechanism in AD [ 68 , 69 ]. Interestingly, Slpi and Nnt are known to contribute to antioxidant properties, as reported in the literature [ 70 , 71 ]. Similarly, four genes (Cd209e, D630045J12Rik, Gm10260, and Igkv8-28) were found to be downregulated in both comparative analyses.…”

Substrains matter in phenotyping of C57BL/6 mice

“…A study using mitogen-activated protein kinase 9 (Mapk9) knockout mice demonstrated that susceptibility to acetaminophen-induced liver injury was influenced by the presence or absence of the Nnt gene defect carried by C57BL/6 mice [127]. The Nnt gene mutation in the C57BL/6J strain is a prominent phenotype-associated mutation in C57BL/6 substrains that affects protein expression in the mitochondria of many tissues and consequently many different metabolic traits [62,72,78,82,88,106,128]. The Nnt gene deletion status differs among C57BL/6J substrains, and the Nnt gene defect likely originated in C57BL/6J mice at the Jackson Laboratory after 1976 (Fig.…”

Melatonin Attenuates ox‐LDL‐Induced Endothelial Dysfunction by Reducing ER Stress and Inhibiting JNK/Mff Signaling

“…Impaired mitochondrial function resulting from mitochondrial fragmentation and decreased mitochondrial autophagy can act as an upstream regulator of endothelial dysfunction [22,23]. Many physiological processes, such as endothelial cell movement, growth, proliferation, and regeneration, are highly dependent on mitochondrial function [24][25][26]. Mitochondrial damage reduces the available ATP in endothelial cells and therefore contributes to endothelial dysfunction.…”