Complement activation products in the circulation and urine of primary membranous nephropathy.

BACKGROUND: Complement activation plays a substantial role in the pathogenesis of primary membranous nephropathy (pMN). C5b-9, C3c, MBL, and factor B have been documented in the subepithelial immune deposits. However, the changing of complement activation products in circulation and urine is not clear. METHODS: We measured the circulating and urinary levels of C1q, MBL, C4d, Bb, properdin, C3a, C5a, and sC5b-9, in 134 patients with biopsy-proven pMN, by enzyme-linked immunosorbent assay. All the plasma values were corrected by eGFR and all the urinary values were corrected by urinary creatinine and urinary protein excretion. Anti-PLA2R antibodies were measured in all patients. RESULTS: The plasma complement activation products were elevated both in the patients with and without anti-PLA2R antibodies. C3a levels were remarkably increased in the circulation and urine, much higher than the elevated levels of C5a. C5b-9 was in normal range in plasma, but significantly higher in urine. The urinary C5a had a positive correlation with anti-PLA2R antibody levels and urinary protein. The plasma level of C4d was elevated, but C1q and MBL were comparable to healthy controls. Positive correlations were observed between plasma C4d/MBL and urinary protein, only in the patients with positive anti-PLA2R antibodies but not in those without. The plasma level of Bb was elevated and had positive correlation with urinary protein only in the patients without anti-PLA2R antibodies. CONCLUSION: Complement activation products were remarkable increased in pMN and may serve as sensitive biomarkers of disease activity. The complement may be activated through lectin pathway with the existence of anti-PLA2R antibodies, while through alternative pathway in the absence of antibody.

C3a and suPAR drive versican V1 expression in tubular cells of focal segmental glomerulosclerosis.

Chronic tubulointerstitial injury impacts the prognosis of focal segmental glomerulosclerosis (FSGS). We found that the level of versican V1 was increased in tubular cells of FSGS patients. Tubular cell-derived versican V1 induced proliferation and collagen synthesis by activating the CD44/Smad3 pathway in fibroblasts. Both urine C3a and suPAR were increased and bound to the tubular cells in FSGS patients. C3a promoted the transcription of versican by activating the AKT/ß-catenin pathway. C3aR knockout decreased the expression of versican in Adriamycin-treated (ADR-treated) mice. On the other hand, suPAR bound to integrin ß6 and activated Rac1, which bound to SRp40 at the 5' end of exon 7 in versican pre-mRNA. This binding inhibited the 3'-end splicing of intron 6 and the base-pair interactions between intron 6 and intron 8, leading to the formation of versican V1. Cotreatment with ADR and suPAR specifically increased the level of versican V1 in tubulointerstitial tissues and caused more obvious interstitial fibrosis in mice than treatment with only ADR. Altogether, our results show that C3a and suPAR drive versican V1 expression in tubular cells by promoting transcription and splicing, respectively, and the increases in tubular cell-derived versican V1 induce interstitial fibrosis by activating fibroblasts in FSGS.

Pathological significance of urinary complement activation in diabetic nephropathy: A full view from the development of the disease.

AIMS/INTRODUCTION: The aim of the present study was to obtain a full view of the changes of urinary complement activation products in the development of diabetic nephropathy and explore their possible significance in the disease process. MATERIALS AND METHODS: A total of 62 patients at different stages of diabetic nephropathy, 20 diabetes patients without nephropathy and 20 healthy persons were enrolled. Urinary complement activation products, including C3a, C5a and C5b-9, were measured, and their associations with the progression of the disease were analyzed. RESULTS: The urinary complement activation products increased markedly since the proteinuria stage, and were parallel with the progression of diabetic nephropathy. More severe renal tubular damage was observed in patients with higher levels of urinary complement activation products. The urinary complement activation products levels correlated closely with renal tubulointerstitial injury score and relative tubular interstitial volume. Multivariate regression analysis showed that elevated urinary complement activation products were independent risk factors for tubular injury in diabetic nephropathy patients. CONCLUSIONS: Urinary complement activation might have a role in renal tubular interstitial injury in patients with diabetic nephropathy, especially in patients at a later stage of the disease.

Plasma Exchange as an Adjunctive Therapy for Crescentic IgA Nephropathy.

BACKGROUND: Crescentic IgA nephropathy (CreIgAN) has a poor prognosis despite aggressive immunosuppressive therapy. The efficacy of plasma exchange (PE) in CreIgAN is not well defined. METHODS: Twelve patients with severe CreIgAN who received PE as addition to routine immunosuppressive therapy, followed for more than 6 months, were involved. Twelve matched historical controls who received immunosuppressive therapy alone were selected by propensity score matching. Renal survival, plasma IgA-IgG complex and active complement products were assessed. RESULTS: Nine men and 3 women received a median of 7 PE courses (range 5-10). Their baseline urine protein excretion rate was 5.8 (4.5-8.7) g/day, and their serum creatinine level was 705.3 ± 296.4 µmol/l. During a mean follow-up of 15.6 months (6-51 months), 6 of the 12 PE group patients were free of dialysis, while all the control patients were dialysis dependent (6 of 12 vs. 0 of 12, p = 0.014). In the PE group, dialysis had to be restarted for 1 patient owing to the development of severe pneumonia and pulmonary failure. PE was associated with a higher kidney survival rate (log rank test, p = 0.026) during follow-up. It also significantly decreased plasma IgA-IgG complex levels (pre-PE: 85.3 ± 25.9% vs. post-PE: 38.4 ± 12.4%, p < 0.001) and plasma and urinary active complement product levels, including C3a, C5a and soluble C5b-9. The latter levels remained low until the last follow-up. CONCLUSION: This study indicated that PE could increase renal recovery rates in severe CreIgAN.

Complement activation and kidney injury molecule-1-associated proximal tubule injury in severe preeclampsia.

Kidney injury with proteinuria is a characteristic feature of preeclampsia, yet the nature of injury in specific regions of the nephron is incompletely understood. Our study aimed to use existing urinary biomarkers to describe the pattern of kidney injury and proteinuria in pregnancies affected by severe preeclampsia. We performed a case-control study of pregnant women from Brigham and Women's Hospital from 2012 to 2013. We matched cases of severe preeclampsia (n=25) 1:1 by parity and gestational age to 2 control groups with and without chronic hypertension. Urinary levels of kidney injury molecule-1 and complement components (C3a, C5a, and C5b-9) were measured by enzyme-linked immunosorbent assay, and other markers (albumin, ß2 microglobulin, cystatin C, epithelial growth factor, neutrophil gelatinase-associated lipocalin, osteopontin, and uromodulin) were measured simultaneously with a multiplex electrochemiluminescence assay. Median values between groups were compared with the Wilcoxon signed-rank test and correlations with Spearman correlation coefficient. Analysis of urinary markers revealed higher excretion of albumin and kidney injury molecule-1 and lower excretion of neutrophil gelatinase-associated lipocalin and epithelial growth factor in severe preeclampsia compared with chronic hypertension and healthy controls. Among subjects with severe preeclampsia, urinary excretion of complement activation products correlated most closely with kidney injury molecule-1, a specific marker of proximal tubule injury (C5a: r=0.60; P=0.001; and C5b-9: r=0.75; P<0.0001). Taken together, we describe a pattern of kidney injury in severe preeclampsia that is characterized by glomerular impairment and complement-mediated inflammation and injury, possibly localized to the proximal tubule in association with kidney injury molecule-1.

Non-invasive serum amyloid A (SAA) measurement and plasma platelets for accurate prediction of surgical intervention in severe necrotizing enterocolitis (NEC).

OBJECTIVE: To evaluate the value of biomarkers to detect severe NEC. SUMMARY BACKGROUND DATA: The time point of surgery in necrotizing enterocolitis (NEC) is critical. Therefore, there is a need for markers that detect severe NEC, because clinical signs of severe NEC often develop late. This study evaluated the value of biomarkers reflecting intestinal cell damage and inflammation to detect severe NEC. METHODS: 29 neonates with NEC were included. Two definitions of moderate versus severe NEC were analyzed: medical NEC (n = 12) versus surgical or fatal NEC (n = 17); and Bell stage II NEC (n = 13) versus stage III NEC (n = 16). Urinary intestinal fatty acid binding protein (I-FABP), serum amyloid A (SAA), C3a and C5a, and fecal calprotectin were measured. C-reactive protein (CRP), white blood cell count (WBC) and platelet count data were measured in blood. RESULTS: In both definitions of moderate versus severe NEC, urinary SAA levels were significantly higher in severe NEC. A cut-off value of 34.4 ng/ml was found in surgical NEC versus medical NEC (sensitivity, 83%; specificity, 83%; LR+, 4.88 (95% CI, 1.37-17.0); LR-, 0.20 (95% CI, 0.07-0.60)) at diagnosis of NEC and at one day prior to surgery in neonates who were operated later on. Combination of urinary SAA and platelet count increased the accuracy, with a sensitivity, 94%; specificity, 83%; LR+, 5.53 (95% CI, 1.57-20.0); and LR-, 0.07 (95% CI, 0.01-0.48). CONCLUSION: Urinary SAA is an accurate marker in differentiating severe NEC from moderate NEC; particularly if combined with serum platelet count.

Identification of urinary biomarkers for age-related macular degeneration.

PURPOSE: Age-related macular degeneration (AMD) can be considered as a chronic low-grade systemic inflammatory disease. This study was undertaken to test the associations of AMD with the urinary proinflammatory cytokines transforming growth factor (TGF)-ß1, macrophage chemoattractant protein (MCP)-1 and C3a-desArg, as potential noninvasive biomarkers for monitoring AMD. METHODS: A cross-sectional study of 103 AMD cases, comprising early AMD (n = 51), geographic atrophy (GA; n = 19), or choroidal neovascularization (CNV; 33), and 54 unrelated controls, aged 73 ± 9 years, who attended the Royal Victorian Eye and Ear Hospital and private practice in Victoria, Australia. AMD status was determined from the bilateral retinal digital photographs and through angiography and optical coherence tomography images when confirmation of CNV was needed. Serum and urine cytokine levels were measured by immunoassay and the rs1061170 (Y402H) single-nucleotide polymorphism of the complement factor H (CFH) gene was determined. RESULTS: Multivariate logistic regression analyses demonstrated significant associations of urinary TGF-ß1 levels (odds ratio [95% confidence interval]: OR = 1.24 [1.02-1.50]; P < 0.031) and MCP-1 levels (OR = 1.07 [1.02-1.12]; P < 0.008), in early AMD, and also MCP-1 levels with GA (OR = 1.10 [1.03-1.17]; P < 0.003). There was no correlation between urinary and serum cytokine levels. Individuals with one or more copies of the C allele (Y402H) were 2.5 times more likely to have urinary MCP-1 above median levels (P < 0.040). CONCLUSIONS: This study demonstrates a novel finding of an association between elevated urinary cytokines TGF-ß1 and MCP-1 and AMD. Further development of a urinary biomarker profile could provide a practical tool for detection of early AMD, progression monitoring, and assessment of treatment efficacy.