NoxO1 Knockout Promotes Longevity in Mice

Abstract

According to the free radical theory of aging, reactive oxygen species (ROS) have been proposed to be a major cause of aging for a long time. Meanwhile, it became clear that ROS have diverse functions in a healthy organism. They act as second messengers, and as transient inhibitors of phosphatases and others. In fact, their detrimental role is highly dependent on the context of their production. NADPH oxidases (Nox) have been discovered as a controllable source of ROS. NoxO1 enables constitutive ROS formation by Nox1 by acting as a constitutively active cytosolic subunit of the complex. We previously found that both Nox1 and NoxO1 were highly expressed in the colon, and that NoxO1-/- deficiency reduces colon health. We hypothesized that a healthy colon potentially contributes to longevity and NoxO1 deficiency would reduce lifetime, at least in mouse. In contrast, here we provide evidence that the knockout of NoxO1 results in an elongated life expectancy of mice. No better endothelial function, nor an improved expression of genes related to longevity, such as Sirt1, were found, and therefore may not serve as an explanation for a longer life in NoxO1 deficiency. Rather minor systemic differences, such as lower body weight occur. As a potential reason for longer life, we suggest better DNA repair capacity in NoxO1 deficient mice. Although final fatal DNA damage appears similar between wildtype and NoxO1 knockout animals, we identified less intermediate DNA damage in colon cells of NoxO1-/- mice, while the number of cells with intact DNA is elevated in NoxO1-/- colons. We conclude that NoxO1 deficiency prolongs lifetime of mice, which correlates with less intermediate and potentially fixable DNA damage at least in colon cells.

Keywords: NADPH oxidase; NoxO1; longevity; mice.

Figure 1

(A) Kaplan–Meyer curve for survival; (B) body weight development; and (C) femur length at the age of 12 weeks of male wildtype and NoxO1-/- mice. n = 9–10; * p < 0.05.

Figure 2

mRNA expression of (A) sirtuin1 and (B) PGC1α in the organs indicated. n = 5 (5 male mice at the age of 12 weeks with 4 quantitative PCRs for each organ).

Figure 3

Vessel function with (A) contraction in response to phenylephrine and (B) relaxation in response to acetylcholine at the concentrations indicated. (C) L-NA induced contraction as measure of NO formation. n = 10; male mice at the age of 12 weeks.

Figure 4

(A) Comet assay of isolated enterocytes of male mice at the age of 12 weeks with representative pictures and statistics. n = 5 (5 mice with 5 pictures for individual means); (B) QPCR for the genes indicated in colon tissue of 7 mice; * p < 0.05. (C) BioGRID 3.5 based network of potential binding partners of NoxO1 and Venn diagram of secondary interaction partners (VIB/UGent; Bioinformatics and Systems Biology; Gent; BELGIUM).