Hyperosmolality activates Akt and regulates apoptosis in renal tubular cells

Terada, Yoshio; Inoshita, Seiji; Hanada, Satoko; Shimamura, Haruko; Kuwahara, Michio; Ogawa, Wataru; Kasuga, Masato; Sasaki, Sei; Marumo, Fumiaki

doi:10.1046/j.1523-1755.2001.060002553.x

Cited by 83 publications

(87 citation statements)

References 29 publications

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“…Proteins were separated on 7.5% or 10 -20% polyacrylamide gels and transferred to nitrocellulose membranes. Membranes were blocked for 1 h with 5% (wt/vol) fat-free milk in PBS and probed with the appropriate primary antibodies [anti-LC3 (MBL, RT-PCR analysis of RNA extracted from kidneys was carried out as previously described (39). In brief, total RNA was isolated from renal tissues using TRI-REAGENT (Life Technologies, Gaithersburg, MD).…”

Section: Induction Of Akimentioning

confidence: 99%

“…Caspase-3 assay and TUNEL assay. A Caspase-3 Fluorometric Protease Assay Kit (MBL) was used for the measurement of caspase-3 activity, as previously described (39). In brief, cell lysates were incubated with reaction buffer and 50 mM caspase-3 substrate for 2 h at 37°C, and the enzymatic activity was measured colorimetrically.…”

Section: Induction Of Akimentioning

confidence: 99%

“…In brief, cell lysates were incubated with reaction buffer and 50 mM caspase-3 substrate for 2 h at 37°C, and the enzymatic activity was measured colorimetrically. The Apoptosis TUNEL Kit II (MBL) was used for the staining for TUNEL-positive cells, as previously described (39).…”

Section: Induction Of Akimentioning

confidence: 99%

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Sestrin-2 and BNIP3 regulate autophagy and mitophagy in renal tubular cells in acute kidney injury

Imamura

Urushido

Hamada

et al. 2013

American Journal of Physiology-Renal Physiology

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175

125

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Autophagy is a cellular recycling process induced in response to many types of stress. However, little is known of the signaling pathways that regulate autophagy during acute kidney injury (AKI). Bcl-2/adenovirus E1B 19 kDa-interacting protein (BNIP)3 and sestrin-2 are the target proteins of hypoxia-inducible factor (HIF)-1␣ and p53, respectively. The aim of this study was to investigate the roles of BNIP3 and sestrin-2 in oxidative stressinduced autophagy during AKI. We used rat ischemia-reperfusion injury and cultured renal tubular (NRK-52E) cells as in vivo and in vitro models of AKI, respectively. Renal ischemia-reperfusion injury upregulated the expression of BNIP3 and sestrin-2 in the proximal tubules, as measured by immunohistochemical staining and Western blot analysis. In vitro, NRK-52E cells exposed to hypoxia showed increased expression of BNIP3 mRNA and protein in a HIF-1␣-dependent manner. In contrast, sestrin-2 mRNA and protein expression were upregulated in a p53-dependent manner after exposure to oxidative stress (exogenous H2O2). NRK-52E cells stably transfected with a fusion protein between green fluorescent protein and light chain 3 were used to investigate autophagy. Overexpression of BNIP3 or sestrin-2 in these cells induced light chain 3 expression and formation of autophagosomes. Interestingly, BNIP3-induced autophagosomes were mainly localized to the mitochondria, suggesting that this protein selectively induces mitophagy. These observations demonstrate that autophagy is induced in renal tubules by at least two independent pathways involving p53-sestrin-2 and HIF-1␣-BNIP3, which may be activated by different types of stress to protect the renal tubules during AKI.Bcl-2/adenovirus E1B 19 kDa-interacting protein-3; acute kidney injury; autophagy; mitophagy; sestrin-2 ISCHEMIA is the leading cause of acute kidney injury (AKI) in the adult population. Prominent morphological features of ischemic AKI include effacement and loss of the proximal tubule brush border, patchy loss of tubular cells, focal areas of proximal tubular dilation, and increased apoptosis (9). The mechanisms that dictate the survival or death of renal cells under oxidative stress must be more completely understood before novel therapeutic strategies for the treatment of ischemic AKI can be explored. Proximal renal tubular cells have high rates of ATP consumption and are very sensitive to hypoxia; thus, mitochondrial damage is one of the most important factors in determining the survival of these cells (1,43).Autophagy is one of the cellular processes that protect cells from genotoxic stress, oxidative stress, accumulation of misfolded proteins, and nutrient deprivation. We (20) have previously reported results from a study of autophagy in a mouse model of AKI. Autophagy plays roles in the pathogenesis of many diseases, and, in kidney disease, both beneficial and detrimental effects of autophagy have been reported (19 -22). Our understanding of autophagy has expanded greatly in recent years, largely due to the identification...

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Section: Induction Of Akimentioning

confidence: 99%

Section: Induction Of Akimentioning

confidence: 99%

See 1 more Smart Citation

Sestrin-2 and BNIP3 regulate autophagy and mitophagy in renal tubular cells in acute kidney injury

Imamura

Urushido

Hamada

et al. 2013

American Journal of Physiology-Renal Physiology

Self Cite

175

125

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“…Some studies concluded that hypertonicity activates Akt͞PKB, including direct measurements of increased Akt͞PKB activity in NIH 3T3 and CHO cells (25). Also, phosphorylation of Akt͞PKB at S174 increases in MadinDarby canine kidney cells subjected to high NaCl and in inner medullas of rats subjected to dehydration (16). In contrast, other studies concluded that Akt͞PKB actually is inactivated by hypertonicity, including that high sorbitol decreases Akt͞PKB activity in HEK293 and COS cells (26) and that high sucrose decreases it in Swiss 3T3 cells, despite increased PIP3 abundance and increased PI3K activity (19).…”

Section: Relation Between Protein Kinases Involved In High Nacl-depenmentioning

confidence: 99%

“…Taken together, these findings suggest that other wortmannin-inhibitable kinases in addition to ATM contribute to high NaCl-induced activation of TonEBP͞ OREBP. PI3K seemed a likely candidate because high NaCl activates it, as reflected by the increase in phosphorylation (15,16) and activity (15) of its downstream target, AKT͞PKB. Further, high NaCl increases phosphorylation GSK-3␤ in renal medullary interstitial cells (17), which is significant because GSK-3 is a downstream target of PI3K (18) and phosphatidyl inositol 3-phosphate (PIP3) in Swiss 3T3 cells (19).…”

mentioning

confidence: 99%

Phosphatidylinositol 3-kinase mediates activation of ATM by high NaCl and by ionizing radiation: Role in osmoprotective transcriptional regulation

Irarrázabal

Burg

Ward

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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High NaCl causes DNA double-strand breaks and activates the transcription factor, TonEBP͞OREBP, resulting in increased transcription of several protective genes, including those involved in accumulation of compatible organic osmolytes. Several kinases are known to contribute to signaling activation of TonEBP͞OREBP, including ATM, which is a member of the phosphatidylinositol 3-kinase (PI3K)-like kinase family and is activated by DNA doublestrand breaks. The purpose of the present studies was to investigate a possible role of PI3K Class IA (PI3K-IA). We found that high NaCl increases PI3K-IA lipid kinase activity. Inhibiting PI3K-IA either by expressing a dominant negative of its regulatory subunit, p85, or by small interfering RNA-mediated knockdown of its catalytic subunit, p110␣, reduces high NaCl-induced increases in TonEBP͞ OREBP transcriptional activity and transactivation, but not nuclear translocation of TonEBP͞OREBP, or increases in its abundance. Further, suppression of PI3K-IA inhibits the activation of ATM that is caused by either ionizing radiation or high NaCl. High NaClinduced increase in TonEBP͞OREBP activity is reduced equally by inhibition of ATM or PI3K-IA, and the effects are not additive. The conclusions are as follows: (i) PI3K-IA activity is necessary for both high NaCl-and ionizing radiation-induced activation of ATM and (ii) high NaCl activates PI3K-IA, which, in turn, contributes to full activation of TonEBP͞OREBP via ATM.DNA damage ͉ osmotic stress ͉ TonEBP͞OREBP

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Hyperosmolality in CHO culture: Effects on cellular behavior and morphology

Romanova

Niemann

Greiner

et al. 2021

Biotech & Bioengineering

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Exposure of Chinese hamster ovary cells (CHO) to highly concentrated feed solution during fed-batch cultivation is known to result in an unphysiological osmolality increase (>300 mOsm/kg), affecting cell physiology and morphology. Extending previous observation on osmotic adaptation, the present study investigates for the first time potential effects of hyperosmolality on CHO cells on both population and single-cell level.We intentionally exposed CHO cells to hyperosmolality of up to 545 mOsm/kg during fed-batch cultivation. In concordance with existing research data, hyperosmolalityexposed CHO cells showed a nearly triplicated volume accompanied by ablation of proliferation. On the molecular level, we observed a strong hyperosmolality-dependent increase in mitochondrial activity in CHO cells compared to control. In contrast to mitochondrial activity, hyperosmolality-dependent proliferation arrest of CHO cells was not accompanied by DNA accumulation or caspase-3/7-mediated apoptosis. Notably, we demonstrate for the first time a formation of up to eight multiple, small nuclei in single hyperosmolality-stressed CHO cells. The here presented observations reveal previously unknown hyperosmolality-dependent morphological changes in CHO cells and support existing data on the osmotic response in mammalian cells.

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Hyperosmolality activates Akt and regulates apoptosis in renal tubular cells

Abstract: The Akt pathway is activated by hyperosmolality in vitro and in vivo, and activation of Akt prevents the mild hyperosmolality-induced apoptotic changes in MDCK cells. PI3-K/Akt pathways are involved in a hypertonic condition that confers the balance between cell survival and apoptosis.

Cited by 83 publications

References 29 publications

Sestrin-2 and BNIP3 regulate autophagy and mitophagy in renal tubular cells in acute kidney injury

Sestrin-2 and BNIP3 regulate autophagy and mitophagy in renal tubular cells in acute kidney injury

Phosphatidylinositol 3-kinase mediates activation of ATM by high NaCl and by ionizing radiation: Role in osmoprotective transcriptional regulation

Hyperosmolality in CHO culture: Effects on cellular behavior and morphology

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