Urine excretion of protein HC in proteinuric glomerular diseases correlates to urine IgG but not to albuminuria

Immunoglobulin G deposition on proximal tubules and the tubular basement membrane in acute tubular injury complicated with focal segmental glomerulosclerosis (FSGS): A possible prediction tool for subclinical FSGS

Immunofluorescent deposition of immunoglobulin G (IgG) in the tubular basement membrane (TBM) has been evaluated in the diagnosis of various diseases; however, few studies have investigated the immunofluorescence of acute tubular injury (ATI). Herein, we attempted to clarify IgG expression in the proximal tubular epithelium and TBM in ATI due to various causes. Patients with ATI with nephrotic-range proteinuria, including focal segmental glomerulosclerosis (FSGS, n = 18) and minimal change nephrotic syndrome (MCNS, n = 8), ATI with ischemia (n = 6), and drug-induced ATI (n = 7), were enrolled. ATI was evaluated by light microscopy. CD15 and IgG double staining and IgG subclass staining were performed to evaluate immunoglobulin deposition in the proximal tubular epithelium and TBM. IgG deposition was identified in the proximal tubules only in the FSGS group. Furthermore, IgG deposition in the TBM was observed in the FSGS group showing severe ATI. IgG3 was predominantly deposited by the IgG subclass study. Our results indicate that IgG deposition in the proximal tubular epithelium and TBM suggests the leaking of IgG from the glomerular filtration barrier and its reabsorption by proximal tubules, which may predict disruption of the glomerular size barrier, including subclinical FSGS. FSGS with ATI should be included as a differential diagnosis when IgG deposition in TBM is observed.

Clinical and prognostic values of urinary alpha1-microglobulin as a tubular marker in acute heart failure

BACKGROUND

Although urinary alpha-1-microglobulin has been used as a marker of tubular dysfunction, its clinical and prognostic values in patients with acute heart failure have not been validated.

METHODS

We analyzed 623 patients (74 ± 13 years old, 60.0% male) with acute heart failure in whom urinary alpha-1-microglobulin (A1MG) levels were measured as tubular markers at the time of admission. The primary endpoint was all-cause mortality.

RESULTS

The median levels of urinary alpha-1-microglobulin with and without correction for urinary creatinine concentration were 8.80 (interquartile range: 4.20-17.7) mg/dL and 12.9 (5.92-30.7) mg/gCr, respectively. Urinary A1MG levels were significantly correlated with all of beta-2-microglobulin (r = 0.77), N-acetyl-β-D-glucosaminidase (r = 0.51), and estimated glomerular filtration rate (r = -0.42); however, alpha-1-microglobulin was most often predicted using beta-2-microglobulin or N-acetyl-β-D-glucosaminidase. During the 488-day (interquartile range: 185-938 days) follow-up, 141 deaths occurred. Higher A1MG levels were associated with higher mortality even after adjustment for other covariates. Only A1MG, but not beta-2-microglobulin or N-acetyl-β-D-glucosaminidase, yielded incremental prognostic information in addition to the preexisting prognostic factors (net-reclassification improvement: 0.254, P = 0.023; integrated discrimination improvement: 0.015, P = 0.028).

CONCLUSIONS

In patients hospitalized due to acute heart failure, urinary alpha-1-microglobulin was a marker of tubular dysfunction. High alpha-1-microglobulin was associated with all-cause mortality independent of glomerular function and was a better predictor of mortality than urinary beta-2-microglobulin.

The ratio and difference of urine protein-to-creatinine ratio and albumin-to-creatinine ratio facilitate risk prediction of all-cause mortality

The role of the difference and ratio of albuminuria (urine albumin-to-creatinine ratio, uACR) and proteinuria (urine protein-to-creatinine ratio, uPCR) has not been systematically evaluated with all-cause mortality. We retrospectively analyzed 2904 patients with concurrently measured uACR and uPCR from the same urine specimen in a tertiary hospital in Taiwan. The urinary albumin-to-protein ratio (uAPR) was derived by dividing uACR by uPCR, whereas urinary non-albumin protein (uNAP) was calculated by subtracting uACR from uPCR. Conventional severity categories of uACR and uPCR were also used to establish a concordance matrix and develop a corresponding risk matrix. The median age at enrollment was 58.6 years (interquartile range 45.4-70.8). During the 12,391 person-years of follow-up, 657 deaths occurred. For each doubling increase in uPCR, uACR, and uNAP, the adjusted hazard ratios (aHRs) of all-cause mortality were 1.29 (95% confidence interval [CI] 1.24-1.35), 1.12 (1.09-1.16), and 1.41 (1.34-1.49), respectively. For each 10% increase in uAPR, it was 1.02 (95% CI 0.98-1.06). The linear dose-response association with all-cause mortality was only observed with uPCR and uNAP. The 3 × 3 risk matrices revealed that patients with severe proteinuria and normal albuminuria had the highest risk of all-cause mortality (aHR 5.25, 95% CI 1.88, 14.63). uNAP significantly improved the discriminative performance compared to that of uPCR (c statistics: 0.834 vs. 0.828, p-value = 0.032). Our study findings advocate for simultaneous measurements of uPCR and uACR in daily practice to derive uAPR and uNAP, which can provide a better mortality prognostic assessment.

Chronic kidney disease: a review of proteomic and metabolomic approaches to membranous glomerulonephritis, focal segmental glomerulosclerosis, and IgA nephropathy biomarkers

Chronic Kidney Disease (CKD) is a global health problem annually affecting millions of people around the world. It is a comprehensive syndrome, and various factors may contribute to its occurrence. In this study, it was attempted to provide an accurate definition of chronic kidney disease; followed by focusing and discussing on molecular pathogenesis, novel diagnosis approaches based on biomarkers, recent effective antigens and new therapeutic procedures related to high-risk chronic kidney disease such as membranous glomerulonephritis, focal segmental glomerulosclerosis, and IgA nephropathy, which may lead to end-stage renal diseases. Additionally, a considerable number of metabolites and proteins that have previously been discovered and recommended as potential biomarkers of various CKD_s using ‘-omics-’ technologies, proteomics, and metabolomics were reviewed.

Proteinuria selectivity index as a prognostic biomarker in lupus nephritis

Objectives The selectivity index has been proposed in predicting the response to immunosuppressive therapy in nephrotic syndrome and other primary kidney disorders. The aim of this study was to elucidate the predictive value of the selectivity index for the treatment response and renal outcome in patients with lupus nephritis. Methods Forty-four patients with lupus nephritis with selectivity index available at the time of renal biopsy were divided into two groups according to the cut-off value of the selectivity index determined by a receiver operating characteristics curve to differentiate treatment responders from non-responders. The baseline characteristics, overall response rate and renal functional outcome were studied retrospectively, and compared between the two groups. Prognostic factors for achieving remission were identified. Results The cut-off value of the selectivity index was 0.167. The low selectivity index (<0.167) and the high selectivity index (≥0.167) group included 24 and 20 patients, respectively. The overall response rate was significantly higher (88% vs. 50%, P = 0.007) and the rate of progression to end-stage renal disease was lower in the low selectivity index group (0% vs. 15%, P = 0.049). More patients in the high selectivity index group had chronic lesions on renal biopsy ( P = 0.002). The selectivity index was the prognostic factor for achieving overall response based on a multivariate analysis ( P = 0.020). Conclusions A selectivity index ≥0.167 was a strong predictor for a poor treatment response and the presence of chronic lesions on renal biopsy. Further exploration with a larger cohort and longer follow-up period is warranted.

Urinary Markers of Tubular Injury in HIV-Infected Patients

Renal disease is a common complication of HIV-infected patients, associated with increased risk of cardiovascular events, progression to AIDS, AIDS-defining illness, and mortality. Early and accurate identification of renal disease is therefore crucial to improve patient outcomes. The use of serum creatinine, along with proteinuria, to detect renal involvement is essentially to screen for markers of glomerular disease and may not be effective in detecting earlier stages of renal injury. Therefore, more sensitive and specific markers are needed in order to early identify HIV-infected patients at risk of renal disease. This review article summarizes some new and important urinary markers of tubular injury in HIV-infected patients and their clinical usefulness in the renal safety follow-up of TDF-treated patients.

Urinary Markers of Tubular Injury in Early Diabetic Nephropathy

Diabetic nephropathy (DN) is a common and serious complication of diabetes associated with adverse outcomes of renal failure, cardiovascular disease, and premature mortality. Early and accurate identification of DN is therefore of critical importance to improve patient outcomes. Albuminuria, a marker of glomerular involvement in early renal damage, cannot always detect early DN. Thus, more sensitive and specific markers in addition to albuminuria are needed to predict the early onset and progression of DN. Tubular injury, as shown by the detection of tubular injury markers in the urine, is a critical component of the early course of DN. These urinary tubular markers may increase in diabetic patients, even before diagnosis of microalbuminuria representing early markers of normoalbuminuric DN. In this review we summarized some new and important urinary markers of tubular injury, such as neutrophil gelatinase associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), liver-type fatty acid binding protein (L-FABP), N-acetyl-beta-glucosaminidase (NAG), alpha-1 microglobulin (A1M), beta 2-microglobulin (B2-M), and retinol binding protein (RBP) associated with early DN.

Twenty-Four-Hour Urine α1 -Microglobulin as a Marker of Hypertension-Induced Renal Impairment and Its Response on Different Blood Pressure-Lowering Drugs

The purpose of this study was to assess the role of urine α₁ -microglobulin as a marker of hypertension-induced renal damage compared with estimated glomerular filtration rate, (eGFR), urine albumin, and urine albumin-to-creatinine ratio (ACR). Its response on different blood pressure (BP)-lowering drugs was also studied. Sixty never-treated hypertensive patients (65.0% men, 46.9 years, BP 141.4/94.0 mm Hg) were randomized to an irbesartan (an angiotensin receptor blocker [ARB]) or a diltiazem (a nondihydropyridine calcium channel blocker [CCB])-based regimen. Patients with diabetes or established cardiovascular, renal, or liver disease were excluded. Blood samples and 24-hour urine were analyzed at baseline and 6 months after pharmaceutical BP normalization. Serum creatinine was measured and eGFR was calculated. Urine albumin, creatinine, and α₁ -microglobulin were measured and ACR was calculated. Minor changes (P=not significant [NS]) in eGFR were noted during follow-up in both groups (from 111.0 mL/min/1.73 m² to 108.4 mL/min/1.73 m² in the ARB group and from 111.3 mL/min/1.73 m² to 114.0 mL/min/1.73 m² in the CCB group). Twenty-four-hour urine indices were all significantly improved (P<.01) in the ARB group (albumin from 19.4 mg/L to 8.2 mg/L, ACR from 21.5 mg/g to 10.0 mg/g, α₁ -microglobulin from 5.06 mg/L to 3.64 mg/L) but not (P=NS) in the CCB group (albumin from 15.6 mg/L to 13.9 mg/L, ACR from 17.6 mg/g to 17.1 mg/g, α₁ -microglobulin from 4.94 mg/L to 4.79 mg/L). These differences between groups remained significant (P<.05) after adjusting for office heart rate and BP. α₁ -Microglobulin was significantly correlated (P<.05) with albumin and ACR both at baseline (r=0.283 and 0.299, respectively) and at the end of follow-up (r=0.432 and 0.465, respectively) but not (P=NS) with eGFR. It was also significantly related (P<.05) to cardiovascular risk scores (Framingham and HeartScore) both at baseline (r=0.264 and 0.436, respectively) and at the end of follow-up (r=0.308 and 0.472, respectively). Urine α₁ -microglobulin emerges as a potentially usable marker of hypertension-induced renal impairment. Its excretion rate and its response to treatment appears similar to that of albumin. Irbesartan but not diltiazem seems to be associated with reduced excretion of α₁ -microglobulin in urine.

Melatonin attenuates hypertension-induced renal injury partially through inhibiting oxidative stress in rats

The aim of the present study was to investigate the protective effects of melatonin (MLT) on hypertension-induced renal injury and identify its mechanism of action. Twenty-four healthy male Wistar rats were divided into a sham control group (n=8), which was subjected to sham operation and received vehicle treatment (physiological saline intraperitoneally at 0.1 ml/100 g), a vehicle group (n=8), which was subjected to occlusion of the left renal artery and vehicle treatment, and the MLT group (n=8), which was subjected to occlusion of the left renal artery and treated with MLT (10 mg/kg/day). Pathological features of the renal tissues were determined using hematoxylin and eosin staining and Masson staining. Urine protein, serum creatinine (Scr), superoxide dismutase (SOD) and malondialdehyde (MDA) were determined. Immunohistochemical analysis was performed to determine the expression of heme oxygenase-1 (HO-1), intercellular adhesion molecule-1 (ICAM-1), inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS). Furthermore, reverse transcription polymerase chain reaction was conducted to determine the mRNA expression of HO-1, ICAM-1, eNOS and iNOS. A marked decrease in blood pressure was noticed in the MLT group at week 4 compared with that of the vehicle group (P<0.01). Furthermore, MLT treatment attenuated the infiltration of inflammatory cells and oedema/atrophy of renal tubules. MLT attenuated hypertension-induced increases in urine protein excretion, serum creatinine and MDA as well as decreases in SOD activity in renal tissues. Furthermore, MLT attenuated hypertension-induced increases in iNOS and ICAM-1 as well as decreases in eNOS and HO-1 expression at the mRNA and protein level. In conclusion, the results of the present study indicated that MLT had protective roles in hypertension-induced renal injury. Its mechanism of action is, at least in part, associated with the inhibition of oxidative stress.

β2-microglobulin induces epithelial-mesenchymal transition in human renal proximal tubule epithelial cells in vitro

Background

The objective of this study was to investigate the influence of β2-microglobulin (β2-M) on the epithelial-mesenchymal transition (EMT) in renal tubular epithelial cells.

Methods

A human kidney proximal tubular cell line (HK-2) was used as the proximal tubular cell model. HK-2 cells were exposed to different concentrations of β2-M (5, 10, 25, and 50 μM) for up to 24, 48 and 72 h. The effects of β2-M on cell morphology were observed by phase contrast microscopy, and the possible associated mechanisms were assessed by immunofluorescence staining, western blot, RNA interference, immunoprecipitation, and induced coupled plasma mass spectroscopy.

Results

β2-M induced marked morphological alterations in the HK-2 cells, accompanied by the increased expression of extracellular matrix components and α-smooth muscle actin (α-SMA), vimentin and fibronectin and the reduced expression of E-cadherin. Our results also revealed that β2-M could induce the EMT in the HK-2 cells without significant affecting cell viability. Excess β2-M in the HK-2 cells led to a decrease in iron and an increase in hypoxia inducible factor-1α (HIF-1α), which induced EMT in the HK-2 cells. Additionally, disrupting the function of the β2-M/hemochromatosis (HFE) complex by HFE knockdown was sufficient to reverse β2-M-mediated EMT in the HK-2 cells.

Conclusion

These findings demonstrate that the activity of β2-M is mediated by the β2-M/HFE complex, which regulates intracellular iron homeostasis and HIF-1α and ultimately induces EMT in HK2 cells.

Toxicological studies of stem bark extract from Schefflera barteri Harms (Araliaceae)

BACKGROUND

The use of herbal medicines as complements or alternatives to orthodox medicines has been on the increase. There has been the erroneous belief that these medicines are free from adverse effects. Schefflera barteri is popularly used in the West region of Cameroon for the treatment of various diseases such as diarrhea, spasm, pneumonia and animals bite. Considering the ethnopharmacological relevance of this plant, this study was designed to investigate the possible toxic effects of the stem bark extract of S. barteri.

METHODS

The extract was prepared by maceration of stem bark dry powder in methylene chloride/methanol mixture. Phytochemical analysis was performed by chemical reaction method. Oral acute toxicity study was carried out by administering single geometric increasing doses (2 to 16 g/kg body weight) of plant extract to Swiss albino mice. For sub-acute toxicity study, repeated doses (100, 200, 400 and 800 mg/kg bw) of plant extract were given to Wistar albino rats for 28 consecutive days by oral route. At the end of the treatment period, hematological and biochemical parameters were assessed, as well as histopathological studies.

RESULTS

Phytochemical analysis of stem bark extract of S. barteri revealed the presence of anthocyanins, anthraquinons and saponins. Acute toxicity results showed that the LD50 was greater than 16000 mg/kg. Sub-acute treatment significantly (P < 0.05) increased the level of serum transaminase, proteins and HDL cholesterol. On the other hand, the extract significantly (P < 0.05) reduced the level of leucocytes as well as neutrophils, basophils and monocytes in female. No significant variation of serum creatinine, LDL cholesterol, serum triglycerides as well as liver, spleen, testicles and ovaries proteins was noted. Histopathological analysis of organs showed vascular congestion, inflammation of peri-portal and vacuolization of hepatocytes at the level of the liver. Leucocytes infiltration of peri-portal veins were noticed on lungs and liver cells as well as inflammatory peri-bronchial and basal membranes seminar tube merely joined on lungs and testis respectively.

CONCLUSION

The results suggest that acute administration of the stem bark extract of S. barteri is associated with signs of toxicity, administration over a long duration provokes hepatotoxicity, testes and lungs toxicities.

Fractional excretion of IgG in idiopathic membranous nephropathy with nephrotic syndrome: a predictive marker of risk and drug responsiveness

Background

Treatment of idiopathic membranous nephropathy with nephrotic syndrome is still controversial. There is currently little known about the clinical use of renal biomarkers which may explain contradictory results obtained from clinical trials. In order to assess whether IgG-uria can predict the outcome in membranous nephropathy, we examined the value of baseline EF-IgG in predicting remission and progression of nephrotic syndrome.

Methods

In a prospective cohort of 84 (34 female) idiopathic membranous nephropathy patients with nephrotic syndrome we validated the ability of the clinically available urine biomarker, IgG, to predict the risk of kidney disease progression and the beneficial effect of immunosuppression with steroids and cyclophosphamide. The fractional excretion of IgG (FE-IgG) and α1-microglobulin (FE-α1m), urine albumin/creatinine ratio, and eGFR were measured at the time of kidney biopsy. Primary outcome was progression to end stage kidney failure or kidney function (eGFR) decline ≥ 50% of baseline. Patients were followed up for 7.2 ± 4.1 years (range 1–16.8).

Results

High FE-IgG (≥0.02) predicted an increased risk of kidney failure (Hazard Ratio, (HR) 8.2, 95%CI 1.0–66.3, p = 0.048) and lower chance of remission (HR 0.18, 95%CI 0.09–0.38, p < 0.001). The ten-year cumulative risk of kidney failure was 51.7% for patients with high FE-IgG compared to only 6.2% for patients with low FE-IgG. During the study, only 24% of patients with high FE-IgG entered remission compared to 90% of patients with low FE-IgG. Combined treatment with steroids and cyclophosphamide decreased the progression rate (–40%) and increased the remission rate (+36%) only in patients with high FE-IgG.

Conclusion

In idiopathic membranous nephropathy patients with nephrotic syndrome, FE-IgG could be useful for predicting kidney disease progression, remission, and response to treatment.

Urinary concentration of monocyte chemoattractant protein-1 in idiopathic glomerulonephritis: a long-term follow-up study

Background

Monocyte chemoattractant protein-1 (MCP-1), which is up regulated in kidney diseases, is considered a marker of kidney inflammation. We examined the value of urine MCP-1 in predicting the outcome in idiopathic glomerulonephritis.

Methods

Between 1993 and 2004, 165 patients (68 females) diagnosed with idiopathic proteinuric glomerulopathy and with serum creatinine <150 µmol/L at diagnosis were selected for the study. Urine concentrations of MCP-1 were analyzed by ELISA in early morning spot urine samples collected on the day of the diagnostic kidney biopsy. The patients were followed until 2009. The progression rate to end-stage kidney disease was calculated using Kaplan–Meier survival analysis. End-stage kidney disease (ESKD) was defined as the start of kidney replacement therapy during the study follow-up time.

Results

Patients with proliferative glomerulonephritis had significantly higher urinary MCP-1 excretion levels than those with non-proliferative glomerulonephritis (p<0.001). The percentage of patients whose kidney function deteriorated significantly was 39.0% in the high MCP-1 excretion group and 29.9% in the low MCP-1 excretion group. However, after adjustment for confounding variables such as glomerular filtration rate (GFR) and proteinuria, there was no significant association between urine MCP-1 concentration and progression to ESKD, (HR = 1.75, 95% CI = 0.64–4.75, p = 0.27).

Conclusion

Our findings indicate that progression to end-stage kidney disease in patients with idiopathic glomerulopathies is not associated with urine MCP-1 concentrations at the time of diagnosis.

Urinary protein patterns in patients with Balkan endemic nephropathy

PURPOSE

Urinary excretion of beta2-microglobulin (beta2-MG), albumin, immunoglobulin G (IgG) and protein was examined in patients with Balkan endemic nephropathy (BEN), glomerulonephritis (GN) and healthy controls.

METHODS

The proteins were measured in morning urine samples from 74 patients with BEN, 50 healthy persons and 22 patients with GN.

RESULTS

In BEN patients, median values for albumin, beta2-MG and protein were above upper normal limits, but median IgG was inside normal range. All patients with GN had microalbuminuria (MAU) and half of them had increased urinary beta2-MG, which was also found in eleven patients with increased urinary IgG. In BEN patients, there were significant negative correlations between eGFR and all measured urinary proteins, the composition of which changed during the course of BEN. In patients with eGFR > 60 ml/min/1.73 m(2) isolated beta2-MG was the most frequent finding (10/12 patients), but MAU was present in 4/12 patients. In BEN patients with eGFR between 30 and 59 ml/min/1.73 m(2), beta2-MG appeared as often as the combination of beta2-MG and albumin and isolated MAU. Out of 49 BEN patients with eGFR > 30 ml/min/1.73 m(2) 15 had increased urinary IgG either alone (1) or together with beta2-MG (3) or albumin (3) or beta2-MG and albumin (8). In BEN patients with GFR < 30 ml/min/1.73 m(2) only 1/25 had isolated beta2-MG but increased urinary IgG with increased beta2-MG, and albumin was the most frequent.

CONCLUSION

Although low-molecular weight proteinuria was the most frequent urinary finding in BEN patients, MAU was frequently detected in advanced stages of BEN but also in some patients with eGFR > 60 ml/min/1.73 m(2). IgG was increasingly found as eGFR decreased.

Associations between urinary excretion of cadmium and proteins in a nonsmoking population: renal toxicity or normal physiology?

BACKGROUND

Associations between cadmium (Cd) and kidney function have been reported even at low levels of exposure in the general population. Recently, the causality of these associations has been questioned.

OBJECTIVES

We examined associations between urinary Cd (U-Cd; a biomarker of exposure) and urinary proteins that are used as biomarkers of kidney effects, based on repeated short-term sampling in healthy subjects.

METHODS

Twenty-four hour urine samples were collected on 2 separate days at six fixed times from 30 healthy nonsmoking men and women (median age 39 years). We analyzed the samples (N = 354) for Cd (i.e., U-Cd) and two proteins used as kidney function biomarkers: urinary albumin (U-Alb) and alpha-1-microglobulin (U-A1M). Concentrations were adjusted for creatinine concentration or for specific gravity, and excretion rates (mass per hour) were calculated. Possible associations were assessed within each individual participant, and mean correlations and regressions were evaluated.

RESULTS

We found clear positive mean associations within individuals between the excretion of U-Cd [mean, 0.11 µg/g creatinine (range, 0.01-0.52 µg/g creatinine)] and both U-Alb and U-A1M. The associations were stronger for excretion rates and concentrations adjusted for specific gravity than for concentrations adjusted for creatinine. We also found significant positive associations of urinary flow with excretion of U-Cd, U-Alb, and U-A1M.

CONCLUSIONS

Associations between short-term changes in U-Cd and markers of kidney function within individual nonsmoking study participants are unlikely to reflect effects of Cd toxicity. A more likely explanation is that these associations result from normal variation in renal function, including changes in urinary flow, that influence the urinary excretion of both Cd and proteins in the same direction. These effects of normal variability may result in overestimation of the adverse effects of Cd on kidney function at low-level Cd exposure.

Persistent decline in estimated but not measured glomerular filtration rate on tenofovir may reflect tubular rather than glomerular toxicity

BACKGROUND

Tenofovir disoproxil fumarate (TDF) has been associated with proximal renal tubulopathy and reduction in estimated glomerular filtration rate (eGFR), without accounting for the tubular secretion of creatinine.

METHODS

A substudy was performed among 19 participants of a randomized 48-week trial, comparing continuing first-line zidovudine/lamivudine (ZDV/3TC) with switching to TDF/emtricitabine (FTC). GFR was measured with [(125)I]-iothalamate (mGFR) and effective renal plasma flow (ERPF) with [(131)I]-hippuran. eGFR and tubular effects were assessed using plasma and urine samples.

RESULTS

Of the 19 patients, 18 were men, 15 whites, mean (SD) age 46.0 (8.9) years, plasma HIV-1 RNA less than 50 copies/ml in all. After 48 weeks, eGFR using Cockcroft-Gault equation and ERPF, but not mGFR, had significantly decreased, and urinary α1-microglobulin/creatinine and microalbumin/creatinine significantly increased in patients on TDF. Although phosphate metabolism on TDF was affected at week 4, differences between groups disappeared during follow-up.

CONCLUSION

Replacing ZDV/3TC with TDF/FTC in this limited sample of virologically suppressed HIV-1-infected adults was associated with mild persistent tubular but not glomerular dysfunction over 48 weeks. The observed persistent decrease in Cockcroft-Gault-based eGFR, but not mGFR, rather than being indicative of glomerular dysfunction may be explained by TDF inhibiting tubular creatinine excretion.

Podocyte injury damages other podocytes

Loss of podocytes promotes glomerulosclerosis, but whether this results from a continued primary insult or a secondary mechanism triggered by the initial loss of podocytes is unknown. We generated chimeric mice in which only a subpopulation of podocytes expressed hCD25, which is the receptor for the immunotoxin LMB2. In addition, genetic labeling of hCD25-negative cells with human placental alkaline phosphatase allowed the study of these two distinct podocyte populations. Administration of LMB2 did not cause podocyte injury in hCD25-negative control mice. In contrast, LMB2 severely damaged or sloughed off the subpopulation of hCD25-positive podocytes within the chimeric glomeruli. Moreover, hCD25-negative podocytes, which were immune to the initial toxin injury, developed injury as early as 4 d after LMB2 injection, evidenced by foot process effacement, upregulation of desmin, and downregulation of nephrin, podocin, and podocalyxin. Furthermore, the magnitude of secondary injury correlated with the magnitude of primary injury, supporting the concept of an amplified cascade of podocyte injury. In conclusion, podocyte damage can propagate injury by triggering secondary damage of "remnant" intact podocytes, even when the primary insult is short-lived. This transmission of podocyte injury may form a vicious cycle leading to accelerated podocyte deterioration and glomerulosclerosis.

The value of IgG-uria in predicting renal failure in idiopathic glomerular diseases. A long-term follow-up study

BACKGROUND

Proteinuria is the hallmark of glomerular disease and non-selective proteinuria is often associated with progression to renal failure. The predictive value of urine IgG excretion was studied comprehensively in patients with nephrotic syndrome. In the present follow-up study, we examine the predictive value of IgG-uria in patients with idiopathic glomerular diseases with a wide range of proteinuia.

METHODS

A total of 189 (113 males and 76 females) patients with idiopathic glomerulonephritis and serum creatinine of less than 150 μmol/L diagnosed between 1993 and 2004 were followed up to their last visit in 2009. Measurement of urine excretion of albumin, IgG, and protein HC were performed in the early morning of spot urine samples collected at the time of the diagnostic renal biopsy. Patients were stratified according to urine protein concentrations and the progression rate to end-stage renal disease (ESRD) calculated using Kaplan-Meier survival analysis. ESRD was defined as the start of renal replacement therapy.

RESULTS

During the study follow-up time of 1429 person-years; 26 (13.8%) patients reached ESRD. The overall mean kidney survival time of studied patients with serum creatinine less than 150 were 13.4 years. The incidence rate of ESRD was ∼18 per 1000 person-years. Stratified analysis identified urinary excretion of IgG, but not albuminuria, as predictor of ESRD. The progression rate to ESRD was 36 per 1000 person-years in patients with urine IgG concentration exceeding 5 mg/mmol urine creatinine, compared to a progression rate of 6/1000 person-years for patients with lower levels of urine IgG.

CONCLUSION

The findings of the study suggest that at early stages, the level of IgG-uria is useful to be used in risk stratification of patients with proteinuric glomerular diseases.

Proteomics and detection of uromodulin in first-time renal calculi patients and recurrent renal calculi patients

Renal calculi disease or known as kidney stone disease is the most common urological disorder in both men and women, although it is more prevalent in men. The lifetime chance for an individual to develop renal calculi is approximately 10% whereas the risk of recurrence in a 10-year period is 74%. Therefore, a diagnostic tool for screening or detecting renal calculi is greatly needed. In this study, we analyze urinary protein profiles from patients with renal calculi for the first time (RC), healthy subjects (HS), and patients with recurrent renal calculi (RRC) to identify a biomarker for detecting the disease. Urinary proteins were isolated by salt precipitation and the proteins resolved by SDS-PAGE. Target proteins were analyzed with LC/MS/MS. Thirty-two proteins were identified from healthy subjects and patients. Uromodulin was the most abundant urinary protein in HS but was a very faint band if detected at all from those that formed renal calculi for the first time (p < 0.05). Yet the excreted levels of urinary uromodulin in RRC were similar to those of the HS suggesting that uromodulin is a reliable biomarker for only RC. In addition, a few immunoglobulins that were commonly found in the urine of both RC and RRC, which include Ig alpha heavy chain 1, Ig gamma-2 c region, Ig gamma-3 heavy chain disease protein, Ig heavy chain variable region, Ig heavy constant region gamma 4, and Ig heavy chain. Ig heavy chain Fab frag and antibody a5b7 chain B may serve as potential biomarkers for renal calculi disease.

Megalin contributes to the early injury of proximal tubule cells during nonselective proteinuria

Megalin, a member of the LDL receptor family, is expressed on the apical membrane of proximal tubules and serves as an endocytic scavenger of filtered proteins and hence might contribute to the tubule injury as a consequence of glomerular disease. To study its role, we crossed megalin knockout mosaic mice (lacking megalin expression in 60% of proximal tubule cells) with NEP25 mice (a transgenic line expressing human CD25 in the podocyte). Treatment of this transgenic mouse with the immunotoxin causes nephrotic syndrome, focal segmental glomerulosclerosis and tubule-interstitial injury. Following this treatment, the double transgenic mice had massive non-selective proteinuria and mild glomerular and tubular injury. Comparison of megalin-containing to megalin-deficient proximal tubule cells within each kidney showed that albumin, immunoglobulin light chain, IgA and IgG were preferentially accumulated in proximal tubule cells expressing megalin. Tubule injury markers such as heme-oxygenase-1, monocyte chemoattractant protein-1 and cellular apoptosis were also preferentially found in these megalin-expressing cells. These results show that megalin plays a pivotal role in the reabsorption of small to large molecular size proteins and provides direct in vivo evidence that reabsorption of filtered proteins triggers events leading to tubule injury.

Absence of Increased α1-Microglobulin in IgA Nephropathy Proteinuria

To search for biomarkers of IgA nephropathy, protein profiles of urine samples from patients with IgA nephropathy and normal volunteers were compared using two-dimensional DIGE. Most of the 172 spots identified in the urine were serum proteins, and their amounts in IgA nephropathy urine were much higher than those in normal urine; this can be explained as proteinuria caused by glomerular dysfunction. However, only alpha(1)-microglobulin, also one of the major serum proteins, in IgA nephropathy urine was not higher in amount than that in normal urine. We confirmed using ELISA analysis that the amounts of transferrin and albumin in IgA nephropathy and diabetic nephropathy urine were much higher than those in normal urine, whereas the amount of alpha(1)-microglobulin in IgA nephropathy urine was not higher than that in normal urine and was much lower than that in diabetic nephropathy urine. Approximately 50% of alpha(1)-microglobulin forms a complex with IgA in serum. These results suggest that alpha(1)-microglobulin in IgA nephropathy urine is a characteristic protein and might be a biomarker for IgA nephropathy and that alpha(1)-microglobulin might have a relationship with IgA nephropathy pathology.

Rapid and simultaneous quantification of 4 urinary proteins by piezoelectric quartz crystal microbalance immunosensor array

BACKGROUND

Urinary proteins are predictive and prognostic markers for diabetes nephropathy. Conventional methods for the quantification of urinary proteins, however, are time-consuming, and most require radioactive labeling. We designed a label-free piezoelectric quartz crystal microbalance (QCM) immunosensor array to simultaneously quantify 4 urinary proteins.

METHODS

We constructed a 2 x 5 model piezoelectric immunosensor array fabricated with disposable quartz crystals for quantification of microalbumin, alpha1-microglobulin, beta2-microglobulin, and IgG in urine. We made calibration curves after immobilization of antibodies at an optimal concentration and then evaluated the performance characteristics of the immunosensor with a series of tests. In addition, we measured 124 urine samples with both QCM immunosensor array and immunonephelometry to assess the correlation between the 2 methods.

RESULTS

With the QCM immunosensor array, we were able to quantify 4 urinary proteins within 15 min. This method had an analytical interval of 0.01-60 mg/L. The intraassay and interassay imprecisions (CVs) were <10%, and the relative recovery rates were 90.3%-109.1%. Nonspecificity of the immunosensor was insignificant (frequency shifts <20 Hz). ROC analyses indicated sensitivities were > or =95.8% and, specificities were > or =76.3%. Bland-Altman difference plots showed the immunosensor array to be highly comparable to immunonephelometry.

CONCLUSIONS

The QCM system we designed has the advantages of being rapid, label free, and highly sensitive and thus can be a useful supplement to commercial assay methods in clinical chemistry.

Urine IgM excretion predicts outcome in ANCA-associated renal vasculitis

BACKGROUND

Renal function at diagnosis is a strong predictor not only of renal survival but also of patient survival of those with anti-neutrophil cytoplasmic antibody (ANCA)-associated small vessel vasculitis (ASVV). Apart from the renal function at diagnosis, there are no other established risk factors for renal outcome in ASVV. We have previously reported that in other forms of glomerular diseases, an increased urine excretion of IgM is an early marker of poor renal outcome.

METHODS

In this single-centre observational study, the prognostic significance of urine IgM excretion and other selected prognostic markers was studied in 83 consecutive patients (49 males, 34 females) with ASVV with renal involvement.

RESULTS

Patient survival at 1 and 5 years was 93 and 77%, respectively, and the corresponding figures for renal survival censored for death were 84 and 76%. Univariate analysis indicated that patient survival was inversely associated with age, male sex, serum creatinine, low serum albumin and high urine IgM excretion. Renal survival was inversely associated with serum creatinine, albuminuria and urine IgM. Multivariate analysis determined that only old age and high urine IgM excretion were independent predictors of patient survival [odds ratio (OR) = 11.2 and 4.4, respectively, P<0.01]. Urine excretion of IgM was the only independent predictor of end-stage renal disease (OR = 19.8, P = 0.004). Overall, 35% of the patients reached the composite end-point of either death or renal replacement therapy. Urine IgM excretion was the most potent single predictor of such an outcome (OR = 7.7, P = 0.000).

CONCLUSION

The occurrence of an increased amount of IgM in urine at presentation is a strong marker of poor prognosis for patients with ANCA-associated renal vasculitis.

Why is proteinuria an ominous biomarker of progressive kidney disease?

Progressive tubule injury and interstitial fibrosis frequently accompany glomerulopathies associated with proteinuria. Clinical experience indicates that higher levels of proteinuria prior to, as well as after initiation of treatment predict more rapid decline in renal function and more pronounced tubulointerstitial injury. It has been proposed that filtration of potentially tubulotoxic plasma proteins is responsible for the observed correlations between proteinuria and progression (i.e., proteinuria is a cause and not only a consequence of progressive renal injury). Numerous attempts have been made to identify the species of putative tubulotoxic proteins in this progressive injury process, but much uncertainty persists. These uncertainties stem from nonphysiologic exposure of apical cell surfaces to proteins in vitro, the extremely high concentrations of various proteins tested in vitro, and the nonuniformity of end points measured. Furthermore, there is often a lack of correlation between in vitro and in vivo findings, and a lack of uniformity of results even for seemingly similar in vitro experiments. Less controversy is evident in the potential pathways whereby injured tubules evoke a tubulointerstitial inflammatory and fibrotic response, with many in vivo models serving to incriminate excessive cytokine and chemokine production, infiltration of various inflammatory cells, and the balance between apoptosis and cell proliferation. Despite many years of concerted efforts, we believe it is still unclear whether proteinuria is a cause (and if so, which species of protein), or only a consequence of progressive renal injury. Nevertheless, pending the resolution of these uncertainties by more decisive and unambiguous experimentation, the strongly predictive inverse relationship between level of proteinuria and long-term renal survival currently justifies aggressive antiproteinuric treatment strategies, with a goal of reducing protein excretion rate to the lowest level possible without the induction of symptoms or undue risk.

Henoch Schönlein nephritis: clinical findings related to renal function and morphology

We evaluated the renal hemodynamics and the urine protein excretion rates of 73 children with Henoch-Schonlein nephritis (HSN). In 40 children we also performed a renal biopsy. The glomerular filtration rate (GFR) and effective renal plasma flow were determined by the clearances of inulin and para-aminohippurate during water diuresis. Urine albumin and IgG excretion were assessed in short-term timed samples. The mean GFR at the first examination was reduced in the HSN patients and most reduced in those with nephrotic proteinuria. There was an inverse correlation between the GFR at the first examination and the amount of albuminuria and urinary IgG excretion. Among the 40 patients with some degree of proteinuria who underwent a renal biopsy, 9 of 13 patients with mild to moderate proteinuria had severe morphological changes. GFR correlated inversely and fractional albumin and IgG excretion directly with the severity of the pathological findings on the biopsy, and with segmental and global sclerosis, the grade of mesangial proliferation, and interstitial inflammation. In conclusion, GFR is moderately reduced early in HSN and more reduced in patients with more proteinuria and in those with more advanced morphological changes. Moreover, even mild to moderate proteinuria may indicate severe morphological changes, which increase the indications for early renal biopsy in these patients.

High molecular weight plasma proteins induce apoptosis and Fas/FasL expression in human proximal tubular cells

BACKGROUND

In proteinuria, proximal tubular epithelial cells (PTECs) are exposed to abnormally high protein concentrations, eventually leading to tubular atrophy and end-stage renal disease. The mode of cell death leading to tubular atrophy in proteinuria has not been fully established. This study examines the role of protein overload on apoptosis, necrosis and cell proliferation in primary cultures of human PTECs using plasma protein fractions representative of selective and non-selective proteinuria. The involvement of the Fas/Fas ligand (FasL) system was also investigated.

METHODS

Plasma was collected from healthy volunteers and fractionated into albumin-rich (30-100 kDa), high molecular weight (100-440 kDa) and combined (30-440 kDa) fractions. PTECs were exposed to 10 mg/ml of the protein fractions for 24, 48 and 72 h. Apoptosis was measured using fluorescein isothiocyanate (FITC)-annexinV and TUNEL. Necrosis was measured using propidium iodide, metabolic activity by MTT and cell proliferation by bromodeoxyuridine incorporation. Fas and FasL expression was analysed by western blotting.

RESULTS

Exposure to the 100-440 and 30-440 kDa fractions produced significant increases in apoptosis at all time points, whereas PTECs exposed to the 30-100 kDa fraction were not significantly different from control cells. There were no changes in the rates of necrosis as a result of protein loading. A significant reduction in metabolic activity was observed in PTECs exposed to the 100-440 and 30-440 kDa fractions, but not to the 30-100 kDa fraction. Cell proliferation was significantly reduced by 24 h in cells exposed to the 100-440 and 30-440 kDa fractions. By 48 and 72 h, all the three fractions had inhibited cell proliferation. PTECs exposed to the 100-440 and the 30-440 kDa fractions showed a significant upregulation in the expression of Fas and FasL. Overall, the high molecular weight fraction was more 'toxic' than the albumin-rich or combined fraction.

CONCLUSION

Increased apoptosis and decreased cell proliferation are the major mechanisms of cell death in human PTECs in response to protein overload. These effects may be mediated at least in part by overexpression of the Fas/FasL system. The severity of such changes is largely determined by the high molecular weight fraction (100-440 kDa) rather than the albumin-rich fraction.

Detection of anti-Leishmania immunoglobulin G antibodies in urine specimens of dogs with leishmaniasis

For years, anti-Leishmania immunoglobulin G (IgG) antibodies have been detected in the sera of dogs living in areas of leishmaniasis endemicity. They have also been found in the aqueous humor and cerebrospinal fluid. In contrast, a review of the literature failed to identify the detection of anti-Leishmania antibodies in urine samples from dogs with leishmaniasis. Ninety-five dog urine samples were examined for the presence of anti-Leishmania antibodies by using a protein A enzyme-linked immunosorbent assay (ELISA). Twenty additional urine samples were collected from healthy dogs as controls. An IgG2 ELISA was performed on 26 urine samples found positive by the protein A ELISA. Twenty-three urine samples found positive to anti-Leishmania antibodies were tested for the local production of anti-Leishmania antibodies in the urinary tract by means of the urine antibody coefficient. Ten urine samples (and the corresponding serum samples) were compared by Western blot (WB) analysis. Thirty-five out of the 95 urine samples were found positive, 57 were found negative, and 3 were found inconclusive for antibody detection by the protein A ELISA. A high correlation between protein A and IgG2 levels was found in positive urine samples. Anti-Leishmania antibodies were present in the urine of dogs that had leishmaniasis, urinary protein/creatinine (U P/C) ratios of greater than one, and normal urinary sediment. A statistically significant correlation was observed between the U P/C ratios and the levels of anti-Leishmania antibodies in positive urine samples. In general, WB analysis and the urine antibody coefficient suggested that the presence of anti-Leishmania antibodies in urine was the consequence of an impairment of filtration of the glomerular barrier. However, in some dogs, WB analysis could be interpreted as suggesting that the presence of anti-Leishmania antibodies was caused, to a lesser extent, by local antibody production in the urinary tract. Antibody detection in urine could be a noninvasive method for leishmaniasis diagnosis and prognosis in dogs with glomerulonephropathies.

Pathophysiology of proteinuria

Proteinuria is consequence of two mechanisms: the abnormal transglomerular passage of proteins due to increased permeability of glomerular capillary wall and their subsequent impaired reabsorption by the epithelial cells of the proximal tubuli. In the various glomerular diseases, the severity of disruption of the structural integrity of the glomerular capillary wall correlates with the area of the glomerular barrier being permeated by "large" pores, permitting the passage in the tubular lumen of high-molecular-weight (HMW) proteins, to which the barrier is normally impermeable. The increased load of such proteins in the tubular lumen leads to the saturation of the reabsorptive mechanism by the tubular cells, and, in the most severe or chronic conditions, to their toxic damage, that favors the increased urinary excretion of all proteins, including low-molecular-weight (LMW) proteins, which are completely reabsorbed in physiologic conditions. Recent clinical studies showed that in patients with glomerular diseases the urinary excretion of some HMW proteins [immunoglobulins G and M (IgG and IgM)] and of some LMW proteins, alpha1-microglobulin, beta2-microglobulin, correlates with the severity of the histologic lesions, and may predict, better than the quantity of proteinuria, the natural course, the outcome, and the response to treatment. It is suggested that some patients have already, at the time of clinical presentation, a structural damage of the glomerular capillary wall (injury of podocytes) and of the tubulointerstitium, the severity and scarce reversibility of which are reliably indicated by an elevated urinary excretion of HMW and LMW proteins.