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Definitive diagnosis of glomerular disease requires a kidney biopsy, an invasive procedure that may not be safe or feasible to perform in all patients. We developed a noninvasive, accurate, and economical diagnostic assay with easy commercial adaptability to detect recurrent focal segmental glomerulosclerosis (rFSGS) after kidney transplant. Since FSGS involves podocyte damage and death, our approach involved mRNA profiling of cultured podocytes treated with plasma from patients with rFSGS to identify upregulated genes involved in podocyte damage. For concept validation, three upregulated pro-apoptotic candidate genes (IL1β, BMF, and IGFBP3) were selected, and their promoter regions were cloned into a luciferase-based reporter vector and transfected into podocytes to generate stable podocyte cell lines. Strikingly, when exposed to rFSGS patient plasma, these cell lines showed increased reporter activity; in contrast, no reporter activity was noted with plasma from patients with non-recurrent FSGS or membranous nephropathy. Area under the receiver operating characteristics curves (AUCs) for models discriminating between rFSGS and other nephropathies (non-recurrent FSGS and membranous nephropathy) and between rFSGS and non-recurrent FSGS ranged from 0.81 to 0.86, respectively. Estimated sensitivities and specificities for the diagnosis of rFSGS were greater than 80% for the IL1β and BMF cell lines, and were slightly lower for the IGFBP3 cell line. Importantly, the novel approach outlined here for the diagnosis of rFSGS is widely applicable to the design of sensitive and specific diagnostic/prognostic assays for other glomerular diseases.

Introduction Tubular dysfunction is characteristic of Dent’s disease; however, focal segmental glomerulosclerosis (FSGS) can also be present. Glomerulosclerosis could be secondary to tubular injury, but it remains uncertain whether the CLCN5 gene, which encodes an endosomal chloride and/or hydrogen exchanger, plays a role in podocyte biology. Here, we implicate a role for CLCN5 in podocyte function and pathophysiology. Methods Whole exome capture and sequencing of the proband and 5 maternally-related family members was conducted to identify X-linked mutations associated with biopsy-proven FSGS. Human podocyte cultures were used to characterize the mutant phenotype on podocyte function. Results We identified a novel mutation (L521F) in CLCN5 in 2 members of a Hispanic family who presented with a histologic diagnosis of FSGS and low-molecular-weight proteinuria without hypercalciuria. Presence of CLCN5 was confirmed in cultured human podocytes. Podocytes transfected with the wild-type or the mutant (L521F) CLCN5 constructs showed differential localization. CLCN5 knockdown in podocytes resulted in defective transferrin endocytosis and was associated with decreased cell proliferation and increased cell migration, which are hallmarks of podocyte injury. Conclusions The CLCN5 mutation, which causes Dent’s disease, may be associated with FSGS without hyercalcuria and nepthrolithiasis. The present findings supported the hypothesis that CLCN5 participates in protein trafficking in podocytes and plays a critical role in organizing the components of the podocyte slit diaphragm to help maintain normal cell physiology and a functional filtration barrier. In addition to tubular dysfunction, mutations in CLCN5 may also lead to podocyte dysfunction, which results in a histologic picture of FSGS that may be a primary event and not a consequence of tubular damage.

Phosphorylation (activation) and dephosphorylation (deactivation) of the slit diaphragm proteins NEPHRIN and NEPH1 are critical for maintaining the kidney epithelial podocyte actin cytoskeleton and, therefore, proper glomerular filtration. However, the mechanisms underlying these events remain largely unknown. Here we show that NEPHRIN and NEPH1 are novel receptor proteins for hepatocyte growth factor (HGF) and can be phosphorylated independently of the mesenchymal epithelial transition receptor in a ligand-dependent fashion through engagement of their extracellular domains by HGF. Furthermore, we demonstrate SH2 domain-containing protein tyrosine phosphatase-2-dependent dephosphorylation of these proteins. To establish HGF as a ligand, purified baculovirus-expressed NEPHRIN and NEPH1 recombinant proteins were used in surface plasma resonance binding experiments. We report high-affinity interactions of NEPHRIN and NEPH1 with HGF, although NEPHRIN binding was 20-fold higher than that of NEPH1. In addition, using molecular modeling we constructed peptides that were used to map specific HGF-binding regions in the extracellular domains of NEPHRIN and NEPH1. Finally, using an in vitro model of cultured podocytes and an ex vivo model of Drosophila nephrocytes, as well as chemically induced injury models, we demonstrated that HGF-induced phosphorylation of NEPHRIN and NEPH1 is centrally involved in podocyte repair. Taken together, this is the first study demonstrating a receptor-based function for NEPHRIN and NEPH1. This has important biological and clinical implications for the repair of injured podocytes and the maintenance of podocyte integrity.

Podocytes have limited ability to recover from injury. Here, we demonstrate that increased mitochondrial biogenesis, to meet the metabolic and energy demand of a cell, accelerates podocyte recovery from injury. Analysis of events induced during podocyte injury and recovery showed marked upregulation of peroxisome proliferator-activated receptor-γ coactivator–1α (PGC-1α), a transcriptional co-activator of mitochondrial biogenesis, and key components of the mitochondrial electron transport chain. To evaluate our hypothesis that increasing mitochondrial biogenesis enhanced podocyte recovery from injury, we treated injured podocytes with formoterol, a potent, specific, and long-acting β2-adrenergic receptor agonist that induces mitochondrial biogenesis in vitro and in vivo. Formoterol increased mitochondrial biogenesis and restored mitochondrial morphology and the injury-induced changes to the organization of the actin cytoskeleton in podocytes. Importantly, β2-adrenergic receptors were found to be present on podocyte membranes. Their knockdown attenuated formoterol-induced mitochondrial biogenesis. To determine the potential clinical relevance of these findings, mouse models of acute nephrotoxic serum nephritis and chronic (Adriamycin [doxorubicin]) glomerulopathy were used. Mice were treated with formoterol post-injury when glomerular dysfunction was established. Strikingly, formoterol accelerated the recovery of glomerular function by reducing proteinuria and ameliorating kidney pathology. Furthermore, formoterol treatment reduced cellular apoptosis and increased the expression of the mitochondrial biogenesis marker PGC-1α and multiple electron transport chain proteins. Thus, our results support β2-adrenergic receptors as novel therapeutic targets and formoterol as a therapeutic compound for treating podocytopathies.

Background Compared with growth factor (G) alone, the combination of G with plerixafor (G + P) increases peripheral blood CD34+ count (PB-CD34+) and improves CD34+ collection yield (yCD34+) in multiple myeloma and lymphoma patients undergoing autologous hematopoietic progenitor cell (AHPC) mobilization. It is unknown whether the improved yCD34+ with G + P results entirely from expansion of PB-CD34+ or also from increased intraapheresis CD34+ recruitment and collection efficiency. Study Design and Methods We retrospectively studied 192 patients who underwent AHPC mobilization and collection with G (n = 73) or G + P (n = 119) to compare the adjusted relative efficiency (aRE), the proportion of the circulating CD34+ pool that is captured for each blood volume processed. Additionally, in a prospective cohort of nine patients mobilizing with G and 11 with G + P, PB-CD34+ after leukapheresis allowed calculation of the recruitment coefficient (RC), proportion of the initial CD34+ pool recruited from the marrow into peripheral blood for each blood volume processed. Results There was no difference in aRE between G and G + P (0.50 vs. 0.46; p = 0.37) and no substantial decline in aRE with higher blood volumes processed in either group. RC was also not different between G and G + P (median, 0.39 and 0.38, respectively; p = 0.7). Prediction of yCD34+ was determined essentially by PB-CD34+ and not affected independently by plerixafor. Conclusion Kinetics of intraapheresis CD34+ recruitment and collection is proportional to PB-CD34+ but not influenced further by plerixafor.

Aminopeptidase A (APA) is expressed in glomerular podocytes and tubular epithelia and metabolizes angiotensin II (AngII), a peptide known to promote glomerulosclerosis. In this study, we tested whether APA expression changes in response to progressive nephron loss or whether APA exerts a protective role against glomerular damage and during AngII-mediated hypertensive kidney injury. At advanced stages of FSGS, fawn-hooded hypertensive rat kidneys exhibited distinctly increased APA staining in areas of intact glomerular capillary loops. Moreover, BALB/c APA-knockout (KO) mice injected with a nephrotoxic serum showed persistent glomerular hyalinosis and albuminuria 96 hours after injection, whereas wild-type controls achieved virtually full recovery. We then tested the effect of 4-week infusion of AngII (400 ng/kg per minute) in APA-KO and wild-type mice. Although we observed no significant difference in achieved systolic BP, AngII-treated APA-KO mice developed a significant rise in albuminuria not observed in AngII-treated wild-type mice along with increased segmental and global sclerosis and/or collapse of juxtamedullary glomeruli, microcystic tubular dilation, and tubulointerstitial fibrosis. In parallel, AngII treatment significantly increased the kidney AngII content and attenuated the expression of podocyte nephrin in APA-KO mice but not in wild-type controls. These data show that deficiency of APA increases susceptibility to glomerular injury in BALB/c mice. The augmented AngII-mediated kidney injury observed in association with increased intrarenal AngII accumulation in the absence of APA suggests a protective metabolizing role of APA in AngII-mediated glomerular diseases.

Summary Background and objectives African Americans (AAs) have four times higher prevalence of ESRD than Caucasians. Therefore, long-term effects of kidney donation are of considerable importance in this patient population. Design, setting, participants, & measurements GFR was measured by 125 I-iothalamate clearance, 24-hour urine albumin excretion, and 24-hour BP monitoring in 33 AAs and 11 CAs who donated kidneys for transplantation 5 to 23 years previously. Results Mean GFRs were 76 13 and 78 11 ml/min per 1.73 m 2 for AA and CA donors, respectively. Nine percent of the AA donors and none of the CA donors had GFRs below 60 ml/min per 1.73 m 2 .A A donors had a tendency for lower prevalence of microalbuminuria compared with CA donors (18.1% versus 36.3%) and a tendency for higher prevalence of macroalbuminuria compared with CAs (12.1% versus 0.0%). Twenty-four percent of the AAs, and 45% of the CAs were hypertensive with mean daytime BP 135/85 mmHg. Only 6% of AAs had a decrease in mean nocturnal systolic BP of 10% or more as compared with daytime readings. Older age at time of donation was associated (P 0.046) with lower GFR values compared with younger ages. Conclusion Carefully selected AA kidney donors have well preserved renal function and a low prevalence of hypertension many years after kidney donation. Abnormal albumin excretion and loss of physiologic decrease in nocturnal BP is more prevalent in AA donors than the general AA population. Older age at donation may predict lower GFR after donation. Clin J Am Soc Nephrol 6: 1474–1480, 2011. doi: 10.2215/CJN.08240910

Acute kidney injury (AKI) is an important cause of death among hospitalized patients. The 2 most common causes of AKI are acute tubular necrosis (ATN) and prerenal azotemia (PRA). Appropriate diagnosis of the disease is important but often difficult. We analyzed urine proteins by 2-dimensional gel electrophoresis from 38 patients with AKI. Patients were randomly assigned to a training set, an internal test set, or an external validation set. Spot abundances were analyzed by artificial neural networks to identify biomarkers that differentiate between ATN and PRA. When the trained neural network algorithm was tested against the training data, it identified the diagnosis for 16 of 18 patients in the training set and all 10 patients in the internal test set. The accuracy was validated in the novel external set of patients where conditions of 9 of 10 patients were correctly diagnosed including 5 of 5 with ATN and 4 of 5 with PRA. Plasma retinol-binding protein was identified in 1 spot and a fragment of albumin and plasma retinol-binding protein in the other. These proteins are candidate markers for diagnostic assays of AKI.

Intraglomerular renin-angiotensin system enzyme activities have been examined previously using glomerular lysates and immune-based assays. However, preparation of glomerular extracts compromises the integrity of their anatomic architecture. In addition, antibody-based assays focus on angiotensin (Ang) II detection, ignoring the generation of other Ang I–derived metabolites, some of which may cross-react with Ang II. Therefore, our aim was to examine the metabolism of Ang I in freshly isolated intact glomeruli using matrix-assisted laser desorption ionization time of flight mass spectrometry as an analytic method. Glomeruli from male Sprague-Dawley rats were isolated by sieving and incubated in Krebs buffer in the presence of 1 μmol/L of Ang I for 15 to 90 minutes, with or without various peptidase inhibitors. Peptide sequences were confirmed by matrix-assisted laser desorption ionization time of flight tandem mass spectrometry or linear-trap-quadrupole mass spectrometry. Peaks were quantified using customized valine- 13 C ·15 N-labeled peptides as standards. The most prominent peaks resulting from Ang I cleavage were 899 and 1181 m/z , corresponding with Ang (1-7) and Ang (2-10), respectively. Smaller peaks for Ang II, Ang (1-9), and Ang (3-10) also were detected. The disappearance of Ang I was significantly reduced during inhibition of aminopeptidase A or neprilysin. In contrast, captopril did not alter Ang I degradation. Furthermore, during simultaneous inhibition of aminopeptidase A and neprilysin, the disappearance of Ang I was markedly attenuated compared with all of the other conditions. These results suggest that there is prominent intraglomerular conversion of Ang I to Ang (2-10) and Ang (1-7), mediated by aminopeptidase A and neprilysin, respectively. Formation of these alternative Ang peptides may be critical to counterbalance the local actions of Ang II. Enhancement of these enzymatic activities may constitute potential therapeutic targets for Ang II–mediated glomerular diseases.

Background. Nephrogenic systemic fibrosis is a debilitating disease occurring exclusively in patients with renal failure. The aetiology of nephrogenic systemic fibrosis is unclear, but recent reports suggest that exposure to gadolinium for enhancement of magnetic resonance imaging may play a role. In the present study, we assessed the association of exposure to gadolinium with the development of nephrogenic systemic fibrosis in patients with various stages of chronic kidney disease. Methods. We analysed the exposure to gadolinium and development of nephrogenic systemic fibrosis in 849 patients on renal replacement therapy over 5 years. We also performed inquiry of development of the nephrogenic systemic fibrosis in 592 patients exposed to gadolinium and estimated to be in stages 3 and 4 of chronic kidney disease. Results. In 849 patients undergoing chronic dialysis from 2001 through 2006 time period, four of the 261 who had received gadolinium (1.5%) and none of the 588 not exposed to gadolinium developed clinically apparent disease. The odds ratio for developing nephrogenic systemic fibrosis was 6.671 [95% confidence interval (CI) 1.537–53.97] in patients with a single gadolinium exposure compared to patients without gadolinium exposure. This ratio increased to 44.5 (95% CI 2.362–2913) in patients with multiple gadolinium exposures compared to patients not receiving gadolinium. None of the 592 patients estimated to be in stage 3 or 4 of chronic kidney disease developed nephrogenic systemic fibrosis after exposure to gadolinium. Conclusion. Gadolinium exposure is associated with nephrogenic systemic fibrosis in patients on chronic renal replacement therapy at a low rate. This association appears to increase with repeated exposure to gadolinium. Since nephrogenic systemic fibrosis may be clinically occult, its prevalence may be higher than reported. Despite this association, it is unclear if gadolinium is the sole or most important factor in the pathogenesis of the disease.

Diagnosis of the type of glomerular disease that causes the nephrotic syndrome is necessary for appropriate treatment and typically requires a renal biopsy. The goal of this study was to identify candidate protein biomarkers to diagnose glomerular diseases. Proteomic methods and informatic analysis were used to identify patterns of urine proteins that are characteristic of the diseases. Urine proteins were separated by two-dimensional electrophoresis in 32 patients with FSGS, lupus nephritis, membranous nephropathy, or diabetic nephropathy. Protein abundances from 16 patients were used to train an artificial neural network to create a prediction algorithm. The remaining 16 patients were used as an external validation set to test the accuracy of the prediction algorithm. In the validation set, the model predicted the presence of the diseases with sensitivities between 75 and 86% and specificities from 92 to 67%. The probability of obtaining these results in the novel set by chance is 5 x 10(-8). Twenty-one gel spots were most important for the differentiation of the diseases. The spots were cut from the gel, and 20 were identified by mass spectrometry as charge forms of 11 plasma proteins: Orosomucoid, transferrin, alpha-1 microglobulin, zinc alpha-2 glycoprotein, alpha-1 antitrypsin, complement factor B, haptoglobin, transthyretin, plasma retinol binding protein, albumin, and hemopexin. These data show that diseases that cause nephrotic syndrome change glomerular protein permeability in characteristic patterns. The fingerprint of urine protein charge forms identifies the glomerular disease. The identified proteins are candidate biomarkers that can be tested in assays that are more amenable to clinical testing.

We present a case of acute, symptomatic hyponatremia in a young woman that developed after use of 3,4-methylenedioxymethylamphetamine (MDMA), more commonly known as “ecstasy.” The patient was treated with 5% saline and had complete recovery. The pathogenesis of MDMA-associated hyponatremia involves excessive water intake and inappropriately elevated antidiuretic hormone (ADH) levels. It seems that young, premenopausal women are at particularly high risk for the development of severe, symptomatic hyponatremia after use of this drug. Review of the literature revealed 4 fatal outcomes from MDMA-associated hyponatremia. All were women and all died from cerebellar tonsillar herniation. We suggest that acute hyponatremia that develops after MDMA use may be a life-threatening condition. Recent recommendation that MDMA users should drink large volumes of water may not be appropriate.

We evaluated 52 renal grafts transplanted into 41 patients with a pretransplantation diagnosis of Alport's syndrome. Overall 1-, 5-, and 10-year patient and graft survival rates were 95.1%, 90.2%, and 80.5% and 86.8%, 66%, and 45.3%, respectively. Although 14% of renal graft biopsy specimens examined with immunofluorescent microscopy showed linear glomerular basement membrane (GBM) immunoglobulin G deposits, only 1 of 41 patients (2.4%) or 52 grafts (1.9%) developed posttransplantation anti-GBM disease. The incidence of anti-GBM disease was 3.1% (1 of 32 patients) in a subgroup of male transplant recipients. Our analysis suggests that the incidence of anti-GBM disease in transplant recipients with Alport's syndrome is less than previously reported. In addition, it does not appear that HLA-DR alleles, which predispose to the development of anti-GBM disease in native kidneys, have a role in transplant recipients with Alport's syndrome posttransplantation. However, immunosuppression level may have a pathophysiological role in the development of anti-GBM disease. The majority of grafts in transplant recipients with Alport's syndrome failed because of chronic allograft nephropathy (69% of grafts) and acute rejection (22% of grafts). A history of previous acute rejection was the only factor that significantly affected graft outcome.

Compared with growth factor (G) alone, the combination of G with plerixafor (G + P) increases peripheral blood CD34+ count (PB-CD34+) and improves CD34+ collection yield (yCD34+) in multiple myeloma and lymphoma patients undergoing autologous hematopoietic progenitor cell (AHPC) mobilization. It is unknown whether the improved yCD34+ with G + P results entirely from expansion of PB-CD34+ or also from increased intraapheresis CD34+ recruitment and collection efficiency.We retrospectively studied 192 patients who underwent AHPC mobilization and collection with G (n = 73) or G + P (n = 119) to compare the adjusted relative efficiency (aRE), the proportion of the circulating CD34+ pool that is captured for each blood volume processed. Additionally, in a prospective cohort of nine patients mobilizing with G and 11 with G + P, PB-CD34+ after leukapheresis allowed calculation of the recruitment coefficient (RC), proportion of the initial CD34+ pool recruited from the marrow into peripheral blood for each blood volume processed.There was no difference in aRE between G and G + P (0.50 vs. 0.46; p = 0.37) and no substantial decline in aRE with higher blood volumes processed in either group. RC was also not different between G and G + P (median, 0.39 and 0.38, respectively; p = 0.7). Prediction of yCD34+ was determined essentially by PB-CD34+ and not affected independently by plerixafor.Kinetics of intraapheresis CD34+ recruitment and collection is proportional to PB-CD34+ but not influenced further by plerixafor.

Objective: To describe an extreme presentation of the chylomicronemia syndrome resulting in multiorgan system dysfunction. Patient: A 40-year-old African American male with no past medical history presented with multiorgan system dysfunction manifested by acute respiratory failure and acute kidney injury. He was noted to have very-high triglyceride levels (>5000 mg/dL) at admission. Interventions: An echocardiogram showed normal cardiac function. Amylase and lipase were normal. We confirmed the chylomicronemia syndrome with a triglyceride assay. The associated hyperviscosity was treated with plasmapheresis to reduce the plasma triglyceride level. Results: After 3 sessions of plasmapheresis, his triglyceride levels were significantly reduced, his oxygenation improved, and his acute kidney injury resolved. He was successfully extubated on day 7 of the intensive care unit stay. His diabetes and hypertriglyceridemia were newly diagnosed and drug therapy was instituted with home discharge on day 14. Conclusions: Severe chylomicronemia can cause multiorgan system dysfunction related to hyperviscosity. Early institution of plasmapheresis to reduce the triglyceride-rich lipoproteins can improve tissue perfusion and prevent further organ damage.

We present the case of a 19 year-old Caucasian female with history of systemic lupus erythematosus (SLE) and normal baseline kidney function who developed severe acute renal failure following treatment of thrombocytopenia with the thrombopoietic agent romiplostim. Percutaneous kidney biopsy revealed thrombotic microangiopathy (TMA) without immune complex lupus glomerulonephritis. We discuss pathogenesis and differential diagnosis of TMA in patients with SLE and raise concerns regarding the use of thrombopoietic agents in such patients. Based on favorable long-term outcome in our case aggressive treatment and in particular prolonged use of plasma exchange in these patients are advocated.

Calciphylaxis is a rare and life-threatening complication that is estimated to occur in 1% of patients with ESRD each year. Typically, extensive microvascular calcification and occlusion/thrombosis leads to violaceous skin lesions, which progress to nonhealing ulcers and sepsis. Secondary infection of skin lesions is common, often leading to sepsis and death. The lower extremities are predominantly involved (roughly 90% of patients). Patients with skin involvement over the trunk or proximal extremities have a poorer prognosis. Although most calciphylaxis patients have abnormalities of the calcium:phosphate axis or elevated levels of parathyroid hormone, these abnormalities do not appear to be fundamental to the pathophysiology of the disorder, and the etiology of calciphylaxis remains unclear. Recently, functional protein C deficiency has been hypothesized to cause a hypercoagulable state that could induce thrombosis in small vessels, with resulting skin ischemia, necrosis, and gangrene. The lack of understanding of the pathophysiology of the disease results in treatments that are equally unsatisfactory. Patients who undergo parathyroidectomy have a tendency to improve, but the prognosis for the disease is poor and mortality remains high.

Summary Background and objectives In the FSGS Clinical Trial, 22 cyclosporine-treated and 20 mycophenolate/dexamethasone-treated patients experienced a complete or partial remission after 26 weeks, completed 52 weeks of treatment, and were studied through 78 weeks. Herein, changes in the urine protein/creatinine ratio (UP/C) and estimated GFR (eGFR) throughout the entire study period are defined. Design, setting, participants, and measurements The FSGS Clinical Trial, which was conducted from November 2004 to January 2010, enrolled patients aged 2–40 years, with eGFR ≥40 ml/min per 1.73 m2 and UP/C >1 mg/mg after ≥4 weeks of corticosteroid therapy. Both groups received lisinopril or losartan throughout the study. UP/C and eGFR were measured at 0, 26, 52, and 78 weeks. Results The median UP/C in the cyclosporine- and mycophenolate/dexamethasone-responsive patients fell by 89.8% and 82.7% at 52 weeks; the fall was largely sustained at 78 weeks (74.7% and 80.3%, respectively). The mean eGFR fell by 19.4% in the cyclosporine group and rose by 7.0% in the mycophenolate mofetil/dexamethasone group at 52 weeks, but subsequently rose by 16.4% and fell by 2.6%, respectively, in the two groups from 52 to 78 weeks. Conclusions In this subset of responding FSGS patients, the improvement in UP/C after cyclosporine or mycophenolate/dexamethasone treatment was largely sustained for 6 months after therapy. Reduction in eGFR in the cyclosporine group was improved 6 months after cyclosporine was stopped although the levels were lower than baseline in seven patients who entered the study with decreased eGFR.

Publisher Summary Proteomic analysis provides an additional tool to identify novel biomarkers. These novel markers can then be tested to determine their validity. In addition, combinations of biomarkers can be analyzed using statistical or informatic tools. These approaches have been used to attempt to diagnose glomerular diseases and to provide prognostic information. One of the promising techniques is capillary electrophoresis coupled to mass spectrometry (CE/MS). This approach was used to identify patterns of polypeptides that can differentiate between glomerular diseases including differentiating minimal change disease from FSGS. While the approach needs to be further validated, it provides an interesting insight into the potential of such techniques. A number of candidate markers have been identified in glomerular diseases. The most promising are markers for early prediction of flares in patients with lupus nephritis, prediction of outcome in patients with membranous nephropathy, differentiation between children with minimal change disease and FSGS and progression of IgA nephropathy. Some of these markers, such as the use of sCD80 to differentiate between children with FSGS and minimal change disease and the use of NGAL as a predictor of renal flares in lupus, may be validated to the point where they can be used clinically within the next several years. Other markers still require much validation and may ultimately not be sufficiently discriminatory to serve as useful markers. The use of discovery techniques such as proteomics may provide additional new candidate markers. Ultimately, some diseases are likely to require the use of combinations of markers in useful clinical assays.

Acute kidney injury (AKI) is an important cause of death among hospitalized patients. The 2 most common causes of AKI are acute tubular necrosis (ATN) and prerenal azotemia (PRA). Appropriate diagnosis of the disease is important but often difficult. We analyzed urine proteins by 2-dimensional gel electrophoresis from 38 patients with AKI. Patients were randomly assigned to a training set, an internal test set, or an external validation set. Spot abundances were analyzed by artificial neural networks to identify biomarkers that differentiate between ATN and PRA. When the trained neural network algorithm was tested against the training data, it identified the diagnosis for 16 of 18 patients in the training set and all 10 patients in the internal test set. The accuracy was validated in the novel external set of patients where conditions of 9 of 10 patients were correctly diagnosed including 5 of 5 with ATN and 4 of 5 with PRA. Plasma retinol-binding protein was identified in 1 spot and a fragment of albumin and plasma retinol-binding protein in the other. These proteins are candidate markers for diagnostic assays of AKI.

Better characterization of the molecular mechanisms underlying glomerular cell proliferation may improve our understanding of the pathogenesis of glomerulonephritis and yield disease-specific markers. We used two-dimensional gel electrophoresis (2DE) and mass spectrometry (MS) to generate expression profiles of glomerular proteins in the course of anti-Thy-1 nephritis. Glomeruli were isolated from Wistar rats by sieving, and proteins were separated by 2DE. In preliminary studies using normal rats, we identified known glomerular proteins from microfilaments [tropomyosin (Tm)] and intermediate filaments (vimentin and lamin A), proteins involved in assembly (α-actinin-4, F-actin capping protein) and membrane cytoskeletal linking (ezrin), as well as several enzymes (protein disulfide isomerase, ATP synthase, and aldehyde dehydrogenase). Comparison of glomerular protein abundance between normal rats and rats in the early phase of anti-Thy-1 nephritis yielded 28 differentially expressed protein spots. MS analysis identified 16 differentially expressed proteins including Tm. Altered Tm abundance in the course of anti-Thy-1 nephritis was confirmed, and specific isoforms were characterized by Western blotting. We demonstrated a complex change in Tm isoform abundance in the course of anti-Thy-1 nephritis. The early mesangiolytic phase of the disease was characterized by decreased abundance of low-molecular-weight isoforms Tm5a/5b and increased abundance of high-molecular-weight isoforms Tm6, Tm1, Tm2, and Tm3. The late proliferative phase of the disease was associated with increased abundance of isoforms Tm5a/5b, Tm6, and Tm1 and decreased abundance of Tm3. Isoforms Tm4 and Tm5 remained unchanged in the course of this model of experimental glomerulonephritis. Characterization of Tm isoform abundance in the course of clinical glomerulonephritis may identify disease-specific markers.

Reactive oxygen species (ROS) are increasingly believed to be important intracellular signaling molecules in mitogenic pathways involved in the pathogenesis of glomerulonephritis (GN). We explored the effects of the antioxidants α-lipoic acid and N-acetyl-l-cysteine on ERK activation in cultured mesangial cells and the role of ERK activation in the severity of glomerular injury in a rat model of anti-Thy 1 GN. In cultured mesangial cells, growth factors stimulated ERK phosphorylation by 150–450%. Antioxidants reduced this increase by 50–60%. Induction of anti-Thy 1 nephritis in rats led to a 210% increase in glomerular ERK phosphorylation. This increase in phosphorylated ERK was reduced by 50% in animals treated with α-lipoic acid. Treatment with α-lipoic acid resulted in significant improvement of glomerular injury. Cellular proliferation was reduced by 100%, and the number of proliferating cell nuclear antigen-positive cells was reduced by 64%. The increased expression of glomerular transforming growth factor-β1protein and mRNA in rats with anti-Thy 1 nephritis was significantly attenuated and mesangial cell transformation into myofibroblasts was completely prevented by treatment with α-lipoic acid. The effects of α-lipoic acid were at least partially due to inhibition of oxidative stress. In rats with anti-Thy 1 nephritis, ROS production was increased 400–500%, and this increase was inhibited by 55% by treatment with α-lipoic acid. We suggest that ROS may mediate glomerular injury by inducing ERK phosphorylation. α-Lipoic acid should be considered a potential therapeutic agent in certain types of human GN.

literature regarding the effects of smoking on the kidney is rather abundant. However, data assessing the singular effects of nicotine on the kidney are sparse. There are more than 100 substances in tobacco, and nicotine is not a direct cause of most of the tobacco-related diseases ([2][1]).

Abstract 4638 Thrombotic thrombocytopenic purpura (TTP), a syndrome characterized by thrombocytopenia and microangiopathic hemolytic anemia due to deficiency of the von Willebrand factor cleaving protease ADAMTS13, was once a highly fatal condition, but therapeutic plasma exchange (PEX) has dramatically improved outcomes. We report the results of a retrospective chart review of TTP patients treated with PEX at our institution from September 2006 through December 2011. Complete demographic, clinical, laboratory, treatment, and response data were collected to examine the influence of race on clinical outcomes. A total of 49 patients were treated for TTP. This cohort was predominantly female (71%) and African American (61%). Three patients were of Hispanic ethnicity. The median age was 50 years (14–81), and the median number of comorbidities at presentation was 4 (range 0–14). Assays for ADAMTS13 activity with reflex to ADAMTS13 inhibitor were performed by the Blood Center of Wisconsin. All patients were treated with PEX (1–1.5 plasma volume using fresh frozen plasma as replacement fluid) once daily until plateau in the platelet count, and then PEX frequency was tapered over 2 weeks in remitting patients. The median number of PEX procedures for the first episode was 8 (1–22). The median total PEX for all episodes was 9 (1–56). The majority of patients, 37 (75.5%), received corticosteroids, and rituximab was administered to 19 (38.8%) of patients at some point during their treatment, usually for slow response or relapse. An initial response to PEX, defined by normalization of platelet count (above 140×109/L) and resolution of signs of hemolysis, was achieved in 36/49 (73.5%) patients. The response rate was not significantly different between African Americans (73.3%) and Caucasians (68.8%, p=0.742), and all 3 Hispanic patients responded to initial treatment. Pre-treatment ADAMTS13 activity was severely deficient (0.4 Inhibitor Units) in 19/23 (82.6%) patients tested. African Americans were more likely to have severely deficient ADAMTS13 activity (16/25, 64%) than Caucasians (2/13, 15.4%; p=0.004). The initial response rate was higher in patients with severely deficient ADAMTS 13 activity (90.0%) in comparison to those with >10% activity (68.4%), however the difference did not reach statistical significance (p=0.067). Of the patients with severely deficient ADAMTS 13 activity and detectable inhibitor levels, 89.5% had an initial response to PEX. All four patients with severely deficient ADAMTS 13 activity but undetectable inhibitor levels also responded to PEX. The total number of relapse events was 16 (32.7%), and the median time to relapse was 19.4 months. All three Hispanic patients, 4 (25%) Caucasians, and 9 (30%) African Americans relapsed. One-year relapse free survival was similar among Caucasians and African Americans at 72% and 75% respectively (p=0.852). All three Hispanic patients relapsed within the first year. One-year overall survival was similar for Caucasians and African Americans at 81.3% and 83.3% respectively (p=0.968). A total of 10 deaths were documented. The causes of death were relapse of TTP (3/10), sepsis (4/10), GI bleeding (2/10), and unknown etiology (1/10). In this unusual TTP cohort with 61% African Americans, we found that African Americans were more likely to have severely deficient ADAMTS13 activity than Caucasians, but response to PEX, relapse, and survival for Caucasian and African Americans were very similar. This study also supports pre-treatment assays for ADAMTS13 activity and its inhibitor, not only for the diagnosis of TTP, but also for predicting response to PEX therapy. Disclosures: No relevant conflicts of interest to declare.