POS-064 DcR2 mediates the maladaptive repair of acute kidney injury by regulating the synthesis the β-hydroxybutyrate

Abstract

Acute kidney injury (AKI) is a common clinical emergency and critical illness, and has a high mortality rate among hospitalized patients. The repair and regeneration of renal tubular cells determine the prognosis of AKI. Our previous study found that decoy receptor 2 (DcR2), a trans-membrane receptor of tumor necrosis factor-related apoptosis inducing ligand (TRAIL), was specifically expressed renal tubules and did not have the ability of proliferation in AKI, suggesting DcR2 may be associated with regeneration and repair of tubular cells. This study aims to investigate the role and mechanism of DcR2-positive tubular cells in the repair of AKI. The DcR2-GFP lineage trace mice,KSP-creDcR2f/fmice (Distal tubular DcR2 Conditional Knockout CKO) mice and GGT1-creDcR2f/f(proximal tubular DcR2 Conditional Knockout CKO) mice and Ischemia-Reperfusion (I/R) Injury models were constructed. The models were divided into moderated (ischemia 25min) and severe (ischemia 35min) injury. Light microscopic examination of paraffin-embedded sections stained with haematoxylin and eosin, periodic acid–Schiff stain and Masson stain. Confocal analysis the co-expression of DcR-GFP and proximal tubular markers(AQP1, Villin), distal markers (AQP2), failed repair markers (Vcam1, Dcdc2), proliferative markers (Ki-67, Edu, PCNA), Kim1, differentiated markers (pax2, sox9, six2), senescent markers (P16, P21, SA-β-gal), senescent phenotype (IL-6, TGF-β1) and fibrotic markers (a-SMA, collagen I, Fibronectin). And wild type (WT) mice and DcR2 CKO mice were used to compare the degree of kidney injury, renal function and tubular repair after I/R injury. Furthermore, quantitative proteomics and bioinformatics analyzed the downstream molecules of DcR2 in renal tissues from WT-AKI and CKO-AKI, and validated studied were done. The DcR2-GFP were mainly expressed proximal tubular cells in AKI. DcR2-GFP positive cells were co-expressed failed repair markers, senescent markers and co-localization with fibrotic markers. And DcR2-GFP positive cells were not expressed Kim1, proliferative markers and differentiated markers, suggesting that DcR2-positve tubules were maladaptive repair cells. The levels of Scr, BUN and urinary DcR2 and renal acute and chronic injury scores were significantly lower inGGT1-creDcR2f/f-AKI than that of WT-AKI. Meanwhile, the area of renal fibrosis and fibrotic markers expression was decreased inGGT1-creDcR2f/fmice compared with WT. However, the above phenomenon of KSP-creDcR2f/f–AKI were not obviously improved. These results suggested that proximal tubular DcR2 gene knockout alleviated kidney injury and promote tubular repair. Additionally, quantitative proteomics and validated studies showed HMGCS2, a key enzyme for ketone synthesis, was increased in GGT1-creDcR2f/fmice compared with WT. And the levels of urinary and serum β-hydroxybutyrate were higher inGGT1-creDcR2f/fmice, suggesting DcR2 affects the synthesis of β-hydroxybutyrate through regulating the expression of HMGCS2. DcR2-positive cells were failed-repair tubules in AKI. And DcR2 promotes maladaptive repair of tubular cells through regulating the expression of HMGCS2 and affects the synthesis of β-hydroxybutyrate, suggesting that DcR2 may be a potential intervention target during the progression of AKI, and β-hydroxybutyrate play a critical role in the repair of AKI.