The Role of Indoleamine 2,3-Dioxygenase in Renal Tubular Epithelial Cells Senescence under Anoxia or Reoxygenation

Abstract

Ischemia-reperfusion injury is the commonest form of acute kidney injury (AKI). Tubular epithelial cell senescence contributes to incomplete recovery from AKI and predisposes to subsequent chronic kidney disease. In cultures of primary proximal renal tubular epithelial cells (RPTECs) subjected to anoxia or reoxygenation, we evaluated the role of indoleamine 2,3-dioxygenase 1 (IDO) in cellular senescence. Proteins of interest were assessed with Western blotting or enzyme-linked immunosorbent assay or histochemically. Under anoxia or reoxygenation, IDO expression and activity were increased. Moreover, the two IDO-derived pathways, the general control nonderepressible 2 kinase (GCN2K) pathway and the aryl-hydrocarbon receptor (AhR) pathway, were also activated. A DNA damage response (DDR) took place and led to increased levels of the cell-cycle inhibitors p21 and p16, and senescence-associated β-galactosidase (SA-β-Gal) activity. Cell proliferation was inhibited, and more IL-6 was produced. The IDO inhibitor 1-DL-methyl-tryptophan ameliorated the DDR; decreased p21, p16, and SA-β-Gal activity; restored cell proliferation; and decreased IL-6 production. The AhR inhibitor CH223191 did not affect the above parameters. In conclusion, anoxia and the subsequent reoxygenation upregulate IDO. IDO depletes tryptophan and activates GCN2K. The latter enhances the anoxia- or reoxygenation-induced DDR, resulting in increased p21 and p16 expression and eventually leading to RPTEC senescence. Since cellular senescence affects AKI outcome, the role of IDO in cellular senescence and the possible therapeutic role of IDO inhibitors deserve further investigation.

Cellular senescence: the good, the bad and the unknown

“…Elevated gene expression of the senescence markers T p16 , T p19 and T p53 was also observed in mice with obesity-induced kidney injury 208 and p16 expression was strikingly increased in biopsy samples from patients with glomerular disease 209 . Exposure of kidney cells to nephrotoxic factors including radiation 125 , TNF 210 , hypoxia or glucose oxidase 211 , 212 can induce cell-cycle arrest in vitro. Replicative senescence is also involved in the development of chronic allograft nephropathy 213 .…”

Inhibition of Malate Dehydrogenase-2 Protects Renal Tubular Epithelial Cells from Anoxia-Reoxygenation-Induced Death or Senescence

“…The decreased ROS production was accompanied by a reduction of the lipid peroxidation markers MDA and 4-HNE modified proteins. It is known that ROS overproduction causes DNA damage which in turn results in increased p53 levels [ 28 , 29 ]. In our experiments, reoxygenation elevated p53 levels, whereas the decrease in ROS production in RPTCs treated with LW6 prevented the reoxygenation-induced p53 increase.…”

“…LW6 prevented the reoxygenation-induced CC3 upregulation. Likely, the cause of the reoxygenation-induced apoptosis is the upregulation of p53 because of the DNA-damage response after the ROS overproduction [ 28 , 29 , 30 ]. Interestingly, the cell imaging, the LDH release assay, and the CC3 expression results in RPTECs cultured under normoxic conditions and treated with LW6 confirmed that at the used concentration LW6 is not toxic for the cells.…”

Cellular senescence and acute kidney injury

“…Indoleamine 2,3-dioxygenase 1 (IDO) activates the general control nonderepressible-2 kinase (GCN2K) to facilitate DDR in ischemia–reperfusion-induced renal TECs. The IDO inhibitor 1-DL-methyl-tryptophane (1-MT) has been experimentally shown to inhibit senescence [ 85 ]. The B cell lymphoma (Bcl) 2/w/xL inhibitor ABT-263 reduced the number of senescent cells and restored the regenerative phenotype of the kidney after subsequent ischemic perfusion injury.…”