Proteomic profile of acute kidney disease induced by ischemia and reperfusion

The main bottleneck in studies aiming to identify novel biomarkers in kidney disease has been the identification of markers that are organ and process specific and characterize the kidney disease regarding other other pre-existing diseases. The aim of this study was to identify new candidates, predominantly renal, that could be used as systemic biomarkes for acute kidney disease (AKI) in a unilateral percutaneous controlled porcine renal ischemia/reperfusion (I/R) model. The nitroproteome and proteome of urine and serum samples were analyzed in Q-ExactiveTM on the period pre-ischemia, ischemia (60 min) and 4, 11 and 16 h post-reperfusion. The renal cortex samples were analyzed only after 24 h of reperfusion. The results were analyzed in the MaxQuant followed by systems biology analysis. The selection of candidate proteins for renal injury was based on the predominance of expression of these proteins in the kidney through TiGER and Atlas Human Protein. In renal cortex proteome, it was identified 1365 proteins which 535 were present at least 3 animals and more expressed in ischemic kidney, with exception of Xaa-pro aminopeptidase 2. These proteins participate of transcription, translational, cellular adhesion, proliferation and repair, important for the recovery of renal injury after 24h. Intersecting the set of proteins up- or down-regulated in the ischemic tissue with both serum and urine proteomes, 6 serum proteins from 170 identified proteins (VIM, HPSA8, HSPD1, COL1A1, LCP1 and TPI1) were identified that may provide a set of targets for AKI or degenerative process. Additionally, 49 from 501 urinary proteins were identified in the intersection, being 4 predominantly renal (BHMT2, GBA3, DDC and DPPIV). As a proof of concept, the activity of DPPIV in the urine increased after 4h of reperfusion returning to baseline levels after this period and with subsequent translational validation in a cohort of patients with diabetic nephropathy who presented a moderate correlation with the parameters related to renal dysfunction: MDRD, proteinuria, glycated hemoglobin, PTH and renin Althought there was no diference between nitrated proteins levels in contralateral and ischemic kidneys, there was difference in the protein profile found. In niroproteome from cortex were identified 843 proteins, of which 53 were up-regulated in the ischemic kidney and 2 in the contralateral kidney. Of the 55 proteins, 38% were mitochondrial and related to the energy pathways. It was possible to validate the nitration of two of these proteins, DPPIV and BHMT2. In the urine nitroproteome, 126 proteins were identified, 27 of which were grouped differently for each period of the experiment based on the behavior of protein expression. The nitrated protein excretion was also observed at baseline, assuming a physiological role of nitration. In adition, the profile of urine proteins along I/R was independent of changes in the total protein profile. Finally, two proteins stood out as candidates for biomarker, UMOD and ALDOB. The serum nitroproteome resulted in 55 identified proteins, 33 were more representative from animals and they able to distinguish the periods before and after renal reperfusion. Two predominantly renal proteins, SEMG2 and DMGDH, were described as candidates to renal injury biomarkers and the last protein was validated. From these results, proteins changes were observed along the renal I/R, new nitrated proteins and new candidates for biomarkers of kidney injury were identified. New studies with a more focused and in-depth approach should be developed both to confirm the candidates for biomarkers and their potential clinical use and to analyze the pathophysiological and biochemical behavior of the proteins with and without nitration in AKI by I/R renal in kidneys morphologically and physiologically similar to those found in humans (AU)