Using proteomics to identify preprocedural risk factors for contrast induced nephropathy

Abstract

Contrast induced nephropathy (CIN) is the third leading cause of hospital acquired acute kidney injury (AKI). We conducted a cross-sectional study in children undergoing elective cardiac catheterization to determine if there is a distinct preprocedural urinary proteomic profile in subjects who subsequently develop CIN. Of 90 patients enrolled, AKI due to CIN (defined as a 50% or greater increase in serum creatinine) occurred in 10 participants by the 24 h postcontrast time point. Seven patients who did not develop AKI served as age and gender matched controls. SELDI-TOF-MS was performed using Protein Chips with different chromatographic surfaces. A 4480 Da biomarker displayed significantly greater peat intensities on three chromatographic surfaces (p = 0.02-0.001) in control patients at time = 0 with an area under the curve (AUC) of 0.89-0.99. This biomarker was identified as the 41 amino acid (a.a.) variant of human beta-defensin-1. Another biomarker of 4631 Da was found to have a significantly greater peak intensity (p = 0.03) in AKI patients at time = 0, with an AUC of 0.84. Thus, the presence of a 4631 Da peptide, as well as the absence of the 41 a.a. variant of human beta-defensin-1 in the pre-procedural urine, may prove to be useful biomarkers for the early prediction of CIN.

Figure 1

Representative SELDI-TOF-MS spectra of urine from patients undergoing cardiac catheterization who either did not develop AKI (control) or subsequently developed AKI. (A) Spectra obtained on a CM10 cation exchange ProteinChip. Note the prominent 4750 Da peak present in ail spectra and the 4480 Da peak that is only prominent in the control patients at time = 0, but is depleted postcontrast administration in the controls and is very weak in the patients who develop AKI at both time points. The intensity of the 3730 Da peak was highly variable and did not differ significantiy between groups. (B) Spectra obtained on an H50 RP ProteinChip, Note the prominent 4750 Da peak present in all spectra as on the CM10 spectra. The 4631 Da peak is present only in the AKI patients at time = 0 and absent in the controls at both time points.

Figure 2

Scatter plots of the 4480 and 4631 Da biomarkers. Comparisons were made between control and AKI patients at time = 0 and reported p-values calculated using the Mann-Whitney rank sum analysis. The top three panels represent the relative intensity of the 4480 Da biomarker on the H50, IMAC30, and CM10 ProteinChip. The bottom panel represents the relative intensity of the 4631 Da biomarker on the H50 ProteinChip.

Figure 3

ProteinChip immunoassay for human beta-defensin 1 (HBD-1). The top spectrum represents neat urine spotted onto an NP20 chip for comparison of peak sizes. The second and third panels result from incubating control (2nd) and AKI patient (3rd) urine with beads bound to HBD-1 antibody and spotting the eluate onto an NP20 ProteinChip. Note the 4480 Da peak representing the 41 a.a. variant of HBD-1 appearing exclusively in the control patient sample and the 4750 Da peak representing the predominant 44 a.a. variant of HBD-1 present in both groups. The bottom panel represents control urine incubated with beads bound to rabbit IgG, followed by spotting the eluate onto an NP20 ProteinChip.