Urine protein profile of IgA nephropathy patients may predict the response to ACE‐inhibitor therapy

Abstract

This study was aimed at the search of urinary biomarkers which might help to predict the clinical response of IgA nephropathy (IgAN) patients to angiotensin converting enzyme inhibitors (ACEi). First, we studied the urinary proteome of 18 IgAN patients (toward 20 healthy controls) who had been chronically treated with ACEi by using 2-D PAGE coupled to nano-HPLC-ESI-MS/MS analysis. We identified 3 proteins, kininogen (p = 0.02), inter-alpha-trypsin-inhibitor heavy chain 4 (35 kDa fragment) (p = 0.02) and transthyretin (p<0.0001), whose urinary excretion was different in IgAN patients' responders when compared to those who had not responded to ACEi. A reduction of daily proteinuria >50% and a stable renal function over time were used to classify patients as responders. Then, we adopted immunoblotting to confirm the predictive power of one of the above proteins, kininogen, in 20 patients with biopsy-proven IgAN, before starting any therapy. Thus, we confirmed that very low levels of kininogen urine excretion were indeed predictive of an inadequate or absent clinical response to ACEi therapy of IgAN patients, after 6-month follow-up. Concluding, the analysis of urine proteome of IgAN patients generated a set of proteins which distinguished subjects responsive to ACEi from those unresponsive to the inhibition of renin-angiotensin system (RAS).

Association of Urinary Laminin G-Like 3 and Free K Light Chains with Disease Activity and Histological Injury in IgA Nephropathy

“…At variance, Perlecan expression was increased in renal biopsies from IgAN patients, confirming the recent report by Ebefors et al (46) (Supplemental Figure 3). Of note, we already found lower levels of LG3 in the urine of a different population of IgAN patients in previous studies (24).…”

“…Parts of this study were presented in abstract form at the 49th Meeting of the European Renal Association -European Dialysis and Transplant Association, Paris, France, May [24][25][26] 2012, and the 52nd Italian Society of Nephrology, Milan, Italy, October 3-6, 2012.…”

“…Urine samples were run on an Image 800TM analyzer (Beckman Coulter, Brea, CA) using a goat anti-human Ig-k/l LC antiserum for Ig k LC and an Image 880 analyzer (Beckman Coulter) using the Free Light Chains Kit (New Scientific Company, Como, Italy) for free k LC (k FLC). Western blotting analysis was performed as previously described (24). Polyclonal rabbit anti-LG3 (Perlecan-H300; Santa Cruz Biotechnology, Santa Cruz, CA) was used as primary antibody.…”

Searching for New Biomarkers of Renal Diseases through Proteomics

“…Finally, in an ambitious study investigators examined urine markers of responsiveness to angiotensinconverting enzyme inhibitor (ACEI) in IgAN (73 ). Urine of IgAN patients on ACEIs was subjected to 2-dimensional PAGE coupled to nano-HPLC-ESI-MS/ MS. Three proteins (kininogen, transthyretin, and inter-␣-trypsin-inhibitor heavy chain-4) differentiated responders from nonresponders to ACEI.…”

Urinary proteomics as a novel tool for biomarker discovery in kidney diseases

“…In addition, compared with the patterns established earlier in minimal change disease (n=16), focal segmental glomerulosclerosis (FSGS) (n=10), and diabetic nephropathy (n=23), the pattern of IgAN had both sensitivity and specificity of 100%. Rocchetti et al (2008) employed 2DE to obtain urine protein spots from controls (n=20), IgA patients responsive to angiotension converting enzyme inhibitors (ACEI) therapy (IgAN R) (n=9), and IgA patients unresponsive to ACEI therapy (IgAN NR) (n=9). By using nano-high performance liquid chromatography coupled with electrospray ionizationtandem MS (nano-HPLC-ESI-MS/MS), three of the spots were identified as kininogen, inter-α-trypsin inhibitor heavy chain H4 precursor (ITIH4), and transthyretin.…”