Calorie restriction enhances cell adaptation to hypoxia through Sirt1-dependent mitochondrial autophagy in mouse aged kidney
Shinji Kume, Takashi Uzu, Kihachiro Horiike, Masami Chin-Kanasaki, Keiji Isshiki, Shin-ichi Araki, Toshiro Sugimoto, Masakazu Haneda, Atsunori Kashiwagi, Daisuke Koya
Shinji Kume, Takashi Uzu, Kihachiro Horiike, Masami Chin-Kanasaki, Keiji Isshiki, Shin-ichi Araki, Toshiro Sugimoto, Masakazu Haneda, Atsunori Kashiwagi, Daisuke Koya
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Research Article

Calorie restriction enhances cell adaptation to hypoxia through Sirt1-dependent mitochondrial autophagy in mouse aged kidney

Abstract

Mitochondrial oxidative damage is a basic mechanism of aging, and multiple studies demonstrate that this process is attenuated by calorie restriction (CR). However, the molecular mechanism that underlies the beneficial effect of CR on mitochondrial dysfunction is unclear. Here, we investigated in mice the mechanisms underlying CR-mediated protection against hypoxia in aged kidney, with a special focus on the role of the NAD-dependent deacetylase sirtuin 1 (Sirt1), which is linked to CR-related longevity in model organisms, on mitochondrial autophagy. Adult-onset and long-term CR in mice promoted increased Sirt1 expression in aged kidney and attenuated hypoxia-associated mitochondrial and renal damage by enhancing BCL2/adenovirus E1B 19-kDa interacting protein 3–dependent (Bnip3-dependent) autophagy. Culture of primary renal proximal tubular cells (PTCs) in serum from CR mice promoted Sirt1-mediated forkhead box O3 (Foxo3) deacetylation. This activity was essential for expression of Bnip3 and p27Kip1 and for subsequent autophagy and cell survival of PTCs under hypoxia. Furthermore, the kidneys of aged Sirt1+/– mice were resistant to CR-mediated improvement in the accumulation of damaged mitochondria under hypoxia. These data highlight the role of the Sirt1-Foxo3 axis in cellular adaptation to hypoxia, delineate a molecular mechanism of the CR-mediated antiaging effect, and could potentially direct the design of new therapies for age- and hypoxia-related tissue damage.

Authors

Shinji Kume, Takashi Uzu, Kihachiro Horiike, Masami Chin-Kanasaki, Keiji Isshiki, Shin-ichi Araki, Toshiro Sugimoto, Masakazu Haneda, Atsunori Kashiwagi, Daisuke Koya

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Figure 8

Role of Sirt1 in cell adaptation to hypoxia.

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Role of Sirt1 in cell adaptation to hypoxia. (A) Expression levels of Bn...
(A) Expression levels of Bnip3, p27Kip1, cleaved caspase 3, and Sirt1 and formation of LC3II in retrovirally mediated Sirt1-knockdown cells under hypoxia (1% O2, 24 hours) in CR serum condition. To detect LC3I and LC3II bands, cells were preincubated with lysosomal inhibitor (E64d and pepstatin A). (B) Quantitative analysis of the ratio of LC3II to LC3I (n = 4). (C) Acetylation of Foxo3 in Sirt1-knockdown cells under hypoxia in CR serum. (D) ChIP analysis to determine Foxo3 binding to promoters of Bnip3, p27Kip1, and Bim in Sirt1-knockdown cells under hypoxia in CR serum. (E) Expression levels of Bnip3, p27Kip1, cleaved caspase 3, and Sirt1 and formation of LC3II in retrovirally mediated Sirt1-overexpressing cells transfected with siRNA control or siRNA for Foxo3 under hypoxia in AL serum. To detect LC3I and LC3II bands, cells were preincubated as in A. (F) Quantitative analysis of the ratio of LC3II to LC3I (n = 4). (G) ChIP analysis to determine Foxo3 binding to promoters of Bnip3, p27Kip1, and Bim in Sirt1-overexpressing cells transfected with siRNA control or siRNA for Foxo3 under hypoxia in AL serum. LY294002 was used as a PI3K inhibitor at 20 μM. Data are mean ± SEM. *P < 0.05.