Inhibition of proteinase 3 by ANCA and its correlation with disease activity in Wegener's granulomatosis

Inhibition of proteinase 3 by ANCA and its correlation with disease activity in Wegener's granulomatosis. Detection of circulating antineutrophil cytoplasmic antibodies (ANCA) to the neutrophil serine proteinase, proteinase 3 (PR3), has proven valuable for the diagnosis of Wegener's granulomatosis (WG). However, the importance of these autoantibodies in the pathogenesis of WG remains unknown. It was recently reported that anti-PR3 autoantibodies (PR3-ANCA) from some patients with WG inhibit the proteolytic activity of PR3 and interfere with the inactivation of PR3 by the physiologic inhibitor, α1-proteinase inhibitor (α1-PI). We have studied the effect of PR3-ANCA on the enzymatic activity of PR3 and its correlation with disease activity in patients with WG. We purified IgG from 21 PR3-ANCA positive sera obtained from 17 patients with WG, and determined its effect on the esterolytic and proteolytic activity of purified human PR3 using Boc-Ala-O-Nitrophenyl ester and fluoresceinated-elastin as enzyme substrates. Controls included seven sera containing anti-MPO autoantibodies (MPO-ANCA) from patients with systemic vasculitis and seven ANCA-negative sera obtained from healthy individuals. We found that PR3-ANCA from 9 of the 17 patients significantly inhibited the activity of PR3. There was no correlation between the titers of PR3-ANCA and their inhibitory activity. For one extensively characterized autoantibody, the inhibition reached 70 to 95% at 20-fold molar excess of IgG to enzyme, with an apparent Kiapp of 56.5 µM. This inhibition was non-competitive in nature, and was additive to that produced by α1-PI. A review of the clinical histories of the patients revealed a strong association between active WG and inhibitory autoantibodies. PR3-ANCA from eight of 10 patients with active disease showed significant inhibition of PR3 activity, whereas only one of seven patients in remission had inhibitory PR3-ANCA. These results suggest that the inhibitory profile of PR3-ANCA may be more reflective of disease activity in patients with WG than the absolute titer, and suggest possible alternative mechanisms for the role of these autoantibodies in the pathogenesis of WG

Exome Sequencing Discerns Syndromes in Patients from Consanguineous Families with Congenital Anomalies of the Kidneys and Urinary Tract

Congenital anomalies of the kidneys and urinary tract (CAKUT) are the leading cause of CKD in children, featuring a broad variety of malformations. A monogenic cause can be detected in around 12% of patients. However, the morphologic clinical phenotype of CAKUT frequently does not indicate specific genes to be examined. To determine the likelihood of detecting causative recessive mutations by whole-exome sequencing (WES), we analyzed individuals with CAKUT from 33 different consanguineous families. Using homozygosity mapping and WES, we identified the causative mutations in nine of the 33 families studied (27%). We detected recessive mutations in nine known disease-causing genes: ZBTB24, WFS1, HPSE2, ATRX, ASPH, AGXT, AQP2, CTNS, and PKHD1. Notably, when mutated, these genes cause multiorgan syndromes that may include CAKUT as a feature (syndromic CAKUT) or cause renal diseases that may manifest as phenocopies of CAKUT. None of the above monogenic disease-causing genes were suspected on clinical grounds before this study. Follow-up clinical characterization of those patients allowed us to revise and detect relevant new clinical features in a more appropriate pathogenetic context. Thus, applying WES to the diagnostic approach in CAKUT provides opportunities for an accurate and early etiology-based diagnosis and improved clinical management

Beyond the tubule: pathological variants of LRP2, encoding the megalin receptor, result in glomerular loss and early progressive chronic kidney disease.

Pathogenic variants in the LRP2 gene, encoding the multiligand receptor megalin, cause a rare autosomal recessive syndrome: Donnai-Barrow/Facio-Oculo-Acoustico-Renal (DB/FOAR) syndrome. Because of the rarity of the syndrome, the long-term consequences of the tubulopathy on human renal health have been difficult to ascertain, and the human clinical condition has hitherto been characterized as a benign tubular condition with asymptomatic low-molecular-weight proteinuria. We investigated renal function and morphology in a murine model of DB/FOAR syndrome and in patients with DB/FOAR. We analyzed glomerular filtration rate in mice by FITC-inulin clearance and clinically characterized six families, including nine patients with DB/FOAR and nine family members. Urine samples from patients were analyzed by Western blot analysis and biopsy materials were analyzed by histology. In the mouse model, we used histological methods to assess nephrogenesis and postnatal renal structure and contrast-enhanced magnetic resonance imaging to assess glomerular number. In megalin-deficient mice, we found a lower glomerular filtration rate and an increase in the abundance of injury markers, such as kidney injury molecule-1 and N-acetyl-β-d-glucosaminidase. Renal injury was validated in patients, who presented with increased urinary kidney injury molecule-1, classical markers of chronic kidney disease, and glomerular proteinuria early in life. Megalin-deficient mice had normal nephrogenesis, but they had 19% fewer nephrons in early adulthood and an increased fraction of nephrons with disconnected glomerulotubular junction. In conclusion, megalin dysfunction, as present in DB/FOAR syndrome, confers an increased risk of progression into chronic kidney disease.Peer reviewe

Beyond the tubule: pathological variants of <i>LRP2</i>, encoding the megalin receptor, result in glomerular loss and early progressive chronic kidney disease

Pathogenic variants in the LRP2 gene, encoding the multiligand receptor megalin, cause a rare autosomal recessive syndrome: Donnai-Barrow/Facio-Oculo-Acoustico-Renal (DB/FOAR) syndrome. Because of the rarity of the syndrome, the long-term consequences of the tubulopathy on human renal health have been difficult to ascertain, and the human clinical condition has hitherto been characterized as a benign tubular condition with asymptomatic low-molecular-weight proteinuria. We investigated renal function and morphology in a murine model of DB/FOAR syndrome and in patients with DB/FOAR. We analyzed glomerular filtration rate in mice by FITC-inulin clearance and clinically characterized six families, including nine patients with DB/FOAR and nine family members. Urine samples from patients were analyzed by Western blot analysis and biopsy materials were analyzed by histology. In the mouse model, we used histological methods to assess nephrogenesis and postnatal renal structure and contrast-enhanced magnetic resonance imaging to assess glomerular number. In megalin-deficient mice, we found a lower glomerular filtration rate and an increase in the abundance of injury markers, such as kidney injury molecule-1 and N-acetyl-β-d-glucosaminidase. Renal injury was validated in patients, who presented with increased urinary kidney injury molecule-1, classical markers of chronic kidney disease, and glomerular proteinuria early in life. Megalin-deficient mice had normal nephrogenesis, but they had 19% fewer nephrons in early adulthood and an increased fraction of nephrons with disconnected glomerulotubular junction. In conclusion, megalin dysfunction, as present in DB/FOAR syndrome, confers an increased risk of progression into chronic kidney disease. </jats:p

Genetic variants in the LAMA5 gene in pediatric nephrotic syndrome.

Nephrotic syndrome (NS), a chronic kidney disease, is characterized by significant loss of protein in the urine causing hypoalbuminemia and edema. In general, ∼15% of childhood-onset cases do not respond to steroid therapy and are classified as steroid-resistant NS (SRNS). In ∼30% of cases with SRNS, a causative mutation can be detected in one of 44 monogenic SRNS genes. The gene LAMA5 encodes laminin-α5, an essential component of the glomerular basement membrane. Mice with a hypomorphic mutation in the orthologous gene Lama5 develop proteinuria and hematuria

アジア各国・地域 経済統計

Damage to and loss of glomerular podocytes has been identified as the culprit lesion in progressive kidney diseases. Here, we combine mass spectrometry-based proteomics with mRNA sequencing, bioinformatics, and hypothesis-driven studies to provide a comprehensive and quantitative map of mammalian podocytes that identifies unanticipated signaling pathways. Comparison of the in vivo datasets with proteomics data from podocyte cell cultures showed a limited value of available cell culture models. Moreover, in vivo stable isotope labeling by amino acids uncovered surprisingly rapid synthesis of mitochondrial proteins under steady-state conditions that was perturbed under autophagy-deficient, disease-susceptible conditions. Integration of acquired omics dimensions suggested FARP1 as a candidate essential for podocyte function, which could be substantiated by genetic analysis in humans and knock-down experiments in zebrafish. This work exemplifies how the integration of multi-omics datasets can identify a framework of cell-type-specific features relevant for organ health and disease