Role of Akt1 in renal fibrosis and tubular dedifferentiation during the progression of acute kidney injury to chronic kidney disease.

BACKGROUND/AIMS: Acute kidney injury (AKI) is an underestimated yet important risk factor for the development of chronic kidney disease (CKD), characterized by tubulointerstitial fibrosis and tubular dedifferentiation. Tubular dedifferentiation, which is associated with the loss of epithelial markers and the gain of mesenchymal features, is thought to be involved in tubulointerstitial fibrosis. As protein kinase B/Akt is involved in the development of CKD, we investigated the role of Akt1, one of the three Akt isoforms, in a murine model of AKI-to-CKD progression. METHODS: We subjected C57BL/6 male mice to unilateral ischemia-reperfusion injury (UIRI) and harvested their kidneys after 6 weeks. Mice were divided into four groups, namely, wild-type (WT) UIRI, Akt1-/- UIRI, WT sham, and Akt1-/- sham. RESULTS: Akt1 (but not Akt2 or Akt3) was markedly activated in WT UIRI mice than in WT sham mice. Tubulointerstitial fibrosis and tubular dedifferentiation significantly increased in WT UIRI mice, but were attenuated in Akt1-/- UIRI mice. Both WT UIRI and Akt1-/- UIRI mice showed markedly upregulated transforming growth factor-ß1 (TGF-ß1)/Smad signaling compared with WT sham mice. However, TGF-ß1/Smad expression did not differ between the two groups. The levels of phosphorylated GSK-3ß, ß-catenin, and Snail were attenuated in Akt1-/- UIRI mice compared with those in WT UIRI mice. CONCLUSION: Deletion of Akt1 results in the attenuation of renal fibrosis and tubular dedifferentiation, independent of TGF-ß1/Smad signaling, during AKI-to-CKD progression in a UIRI without contralateral nephrectomy model. Thus, Akt1 may serve as a therapeutic target in AKI-to-CKD progression.

Akt1 is involved in tubular apoptosis and inflammatory response during renal ischemia-reperfusion injury.

Renal ischemia-reperfusion injury (IRI) is one of the major causes of acute kidney injury (AKI). Although Akt is involved in renal IRI, it is unclear as to which Akt isoform plays an important role in renal IRI. In this study, we investigated the role of Akt1 in renal IRI. We subjected the C57BL/6 male mice to unilateral IRI with contralateral nephrectomy. Two days after IRI, IRI-kidneys were harvested. The mice were divided into four groups: wild type (WT) IRI, Akt1-/- IRI, WT sham, and Akt1-/- sham. We found that Akt1, not Akt2 or Akt3, was markedly activated in WT IRI than in WT sham mice. The histologic damage score and serum creatinine level significantly increased in WT IRI mice, the increase being the highest in Akt1-/- IRI mice. The number of TdT-mediated dUTP nick-end labeling (TUNEL)-positive tubular cells and expression of cleaved caspase-3/Bax were higher in Akt1-/- IRI mice than in WT IRI mice. The expression of Bcl-2 was lower in Akt1-/- IRI mice than in WT IRI mice. The expression of tumor necrosis factor-α/interleukin-6/interleukin-1ß and number of F4/80-positive macrophages were markedly higher in Akt1-/- IRI than in WT IRI mice. The expression of phosphorylated nuclear factor-κB p65 was also higher in Akt1-/- IRI mice than in WT IRI mice. Our results show that Akt1 deletion exacerbates kidney damage as it increases tubular apoptosis and inflammatory response during renal IRI. Akt1 could be a potential therapeutic target for developing treatments against IRI-induced AKI.

Design, synthesis, and mode of action studies of a mitomycin tetramer inducing double activations with a single probe.

We report design, synthesis, and mechanistic studies of a new mitomycin tetramer 9 along with a new mitomycin dimer 10. Mitomycin 9 is a tetramer connected by the disulfide linker 11, and easily undergoes disulfide cleavage to provide two dimeric structures 9r that each contains a single thiol probe for activations. So, tetramer 9 as a precursor of 9r was specifically targeted to undergo double activations with a single probe. A tetramer 9 was synthesized using 1 and key intermediate 11, and a dimer 10 was synthesized from 1 and diamine 12. Activation studies revealed that 9 underwent effective double activations with a single probe by nucleophiles while the reference 10 did not. Evaluations of DNA ISC formations showed that 9 generated substantial levels of DNA ISC by nucleophilic activation while the references 10 and 2 did not. The effectiveness of 9 in activation and formation of DNA ISC per probe was verified by comparing with dimers 5-8 of double activations with two probes. These findings highlighted the role of a single thiol in 9r and demonstrated the intended double activations with a single probe, which marks the first case in mitomycin studies.