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.

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.

Donor Urinary C5a Levels Independently Correlate With Posttransplant Delayed Graft Function.

BACKGROUND: Accumulating evidence implicates the complement cascade as pathogenically contributing to ischemia-reperfusion injury and delayed graft function (DGF) in human kidney transplant recipients. Building on observations that kidney injury can initiate in the donor before nephrectomy, we tested the hypothesis that anaphylatoxins C3a and C5a in donor urine before transplantation associate with risk of posttransplant injury. METHODS: We evaluated the effects of C3a and C5a in donor urine on outcomes of 469 deceased donors and their corresponding 902 kidney recipients in a subset of a prospective cohort study. RESULTS: We found a threefold increase of urinary C5a concentrations in donors with stage 2 and 3 acute kidney injury (AKI) compared donors without AKI (P < 0.001). Donor C5a was higher for the recipients with DGF (defined as dialysis in the first week posttransplant) compared with non-DGF (P = 0.002). In adjusted analyses, C5a remained independently associated with recipient DGF for donors without AKI (relative risk, 1.31; 95% confidence interval, 1.13-1.54). For donors with AKI, however, urinary C5a was not associated with DGF. We observed a trend toward better 12-month allograft function for kidneys from donors with C5a concentrations in the lowest tertile (P = 0.09). Urinary C3a was not associated with donor AKI, recipient DGF, or 12-month allograft function. CONCLUSIONS: Urinary C5a correlates with the degree of donor AKI. In the absence of clinical donor AKI, donor urinary C5a concentrations associate with recipient DGF, providing a foundation for testing interventions aimed at preventing DGF within this high-risk patient subgroup.

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.

Detection of renal allograft rejection by complement components C5A and TCC in plasma and urine.

Allograft rejection is associated with complement activation. Yet inconsistent results were obtained in evaluating plasma levels of complement factors or activation products as rejection markers. Therefore the human anaphylatoxin C5a and the soluble terminal complement complex (TCC) were measured by daily enzyme immunoassays on plasma (P) and urine (U) samples from 28 patients undergoing renal transplantation over a mean postoperative period of 25.8 days. The complement levels were evaluated longitudinally (cutoff of 100% increase on the previous day's level) during periods of rejection, stable graft function, acute tubular necrosis, and cytomegalovirus disease. Regarding the detection of 13 acute rejection episodes, U-C5a showed a diagnostic accuracy of 81% (sensitivity of 85%, specificity of 77%), P-C5a one of 62%, and P-TCC one of only 30%. The U-C5a increment (mean rise of 379%) preceded the clinical diagnosis of rejection by an average of 1.6 days. Cytomegalovirus diseases (n = 4) were associated with high P-C5a levels (mean increase of 251% by the time of the first detection of viral DNA). In contrast, resumption of kidney function after acute tubular necrosis (n = 10 periods) was heralded by marked peaks of U-C5a (x = 43.7 microg/l). U-TCC was not detected in any clinical setting. In conclusion, as opposed to P-TCC, U-TCC, and P-C5a, the anaphylatoxin C5a, measured daily in urine, might have potential as an early and reliable marker for acute renal allograft rejection.