Connectivity mapping of glomerular proteins identifies dimethylaminoparthenolide as a new inhibitor of diabetic kidney disease.

While blocking the renin angiotensin aldosterone system (RAAS) has been the main therapeutic strategy to control diabetic kidney disease (DKD) for many years, 25-30% of diabetic patients still develop the disease. In the present work we adopted a systems biology strategy to analyze glomerular protein signatures to identify drugs with potential therapeutic properties in DKD acting through a RAAS-independent mechanism. Glomeruli were isolated from wild type and type 1 diabetic (Ins2Akita) mice treated or not with the angiotensin-converting enzyme inhibitor (ACEi) ramipril. Ramipril efficiently reduced the urinary albumin/creatine ratio (ACR) of Ins2Akita mice without modifying DKD-associated renal-injuries. Large scale quantitative proteomics was used to identify the DKD-associated glomerular proteins (DKD-GPs) that were ramipril-insensitive (RI-DKD-GPs). The raw data are publicly available via ProteomeXchange with identifier PXD018728. We then applied an in silico drug repurposing approach using a pattern-matching algorithm (Connectivity Mapping) to compare the RI-DKD-GPs's signature with a collection of thousands of transcriptional signatures of bioactive compounds. The sesquiterpene lactone parthenolide was identified as one of the top compounds predicted to reverse the RI-DKD-GPs's signature. Oral treatment of 2 months old Ins2Akita mice with dimethylaminoparthenolide (DMAPT, a water-soluble analogue of parthenolide) for two months at 10 mg/kg/d by gavage significantly reduced urinary ACR. However, in contrast to ramipril, DMAPT also significantly reduced glomerulosclerosis and tubulointerstitial fibrosis. Using a system biology approach, we identified DMAPT, as a compound with a potential add-on value to standard-of-care ACEi-treatment in DKD.

Systems biology combining human- and animal-data miRNA and mRNA data identifies new targets in ureteropelvic junction obstruction.

BACKGROUND: Although renal fibrosis and inflammation have shown to be involved in the pathophysiology of obstructive nephropathies, molecular mechanisms underlying evolution of these processes remain undetermined. In an attempt towards improved understanding of obstructive nephropathy and improved translatability of the results to clinical practice we have developed a systems biology approach combining omics data of both human and mouse obstructive nephropathy. RESULTS: We have studied in parallel the urinary miRNome of infants with ureteropelvic junction obstruction and the kidney tissue miRNome and transcriptome of the corresponding neonatal partial unilateral ureteral obstruction (UUO) mouse model. Several hundreds of miRNAs and mRNAs displayed changed abundance during disease. Combination of miRNAs in both species and associated mRNAs let to the prioritization of five miRNAs and 35 mRNAs associated to disease. In vitro and in vivo validation identified consistent dysregulation of let-7a-5p and miR-29-3p and new potential targets, E3 ubiquitin-protein ligase (DTX4) and neuron navigator 1 (NAV1), potentially involved in fibrotic processes, in obstructive nephropathy in both human and mice that would not be identified otherwise. CONCLUSIONS: Our study is the first to correlate a mouse model of neonatal partial UUO with human UPJ obstruction in a comprehensive systems biology analysis. Our data revealed let-7a and miR-29b as molecules potentially involved in the development of fibrosis in UPJ obstruction via the control of DTX4 in both man and mice that would not be identified otherwise.

A capillary electrophoresis coupled to mass spectrometry pipeline for long term comparable assessment of the urinary metabolome.

Although capillary electrophoresis coupled to mass spectrometry (CE-MS) has potential application in the field of metabolite profiling, very few studies actually used CE-MS to identify clinically useful body fluid metabolites. Here we present an optimized CE-MS setup and analysis pipeline to reproducibly explore the metabolite content of urine. We show that the use of a beveled tip capillary improves the sensitivity of detection over a flat tip. We also present a novel normalization procedure based on the use of endogenous stable urinary metabolites identified in the combined metabolome of 75 different urine samples from healthy and diseased individuals. This method allows a highly reproducible comparison of the same sample analyzed nearly 130 times over a range of 4 years. To demonstrate the use of this pipeline in clinical research we compared the urinary metabolome of 34 newborns with ureteropelvic junction (UPJ) obstruction and 15 healthy newborns. We identified 32 features with differential urinary abundance. Combination of the 32 compounds in a SVM classifier predicted with 76% sensitivity and 86% specificity UPJ obstruction in a separate validation cohort of 24 individuals. Thus, this study demonstrates the feasibility to use CE-MS as a tool for the identification of clinically relevant urinary metabolites.

A Point Mutation in Suppressor of Cytokine Signalling 2 (Socs2) Increases the Susceptibility to Inflammation of the Mammary Gland while Associated with Higher Body Weight and Size and Higher Milk Production in a Sheep Model.

Mastitis is an infectious disease mainly caused by bacteria invading the mammary gland. Genetic control of susceptibility to mastitis has been widely evidenced in dairy ruminants, but the genetic basis and underlying mechanisms are still largely unknown. We describe the discovery, fine mapping and functional characterization of a genetic variant associated with elevated milk leukocytes count, or SCC, as a proxy for mastitis. After implementing genome-wide association studies, we identified a major QTL associated with SCC on ovine chromosome 3. Fine mapping of the region, using full sequencing with 12X coverage in three animals, provided one strong candidate SNP that mapped to the coding sequence of a highly conserved gene, suppressor of cytokine signalling 2 (Socs2). The frequency of the SNP associated with increased SCC was 21.7% and the Socs2 genotype explained 12% of the variance of the trait. The point mutation induces the p.R96C substitution in the SH2 functional domain of SOCS2 i.e. the binding site of the protein to various ligands, as well-established for the growth hormone receptor GHR. Using surface plasmon resonance we showed that the p.R96C point mutation completely abrogates SOCS2 binding affinity for the phosphopeptide of GHR. Additionally, the size, weight and milk production in p.R96C homozygote sheep, were significantly increased by 24%, 18%, and 4.4%, respectively, when compared to wild type sheep, supporting the view that the point mutation causes a loss of SOCS2 functional activity. Altogether these results provide strong evidence for a causal mutation controlling SCC in sheep and highlight the major role of SOCS2 as a tradeoff between the host's inflammatory response to mammary infections, and body growth and milk production, which are all mediated by the JAK/STAT signaling pathway.

Shear Stress-Induced Alteration of Epithelial Organization in Human Renal Tubular Cells.

Tubular epithelial cells in the kidney are continuously exposed to urinary fluid shear stress (FSS) generated by urine movement and recent in vitro studies suggest that changes of FSS could contribute to kidney injury. However it is unclear whether FSS alters the epithelial characteristics of the renal tubule. Here, we evaluated in vitro and in vivo the influence of FSS on epithelial characteristics of renal proximal tubular cells taking the organization of junctional complexes and the presence of the primary cilium as markers of epithelial phenotype. Human tubular cells (HK-2) were subjected to FSS (0.5 Pa) for 48 h. Control cells were maintained under static conditions. Markers of tight junctions (Claudin-2, ZO-1), Par polarity complex (Pard6), adherens junctions (E-Cadherin, ß-Catenin) and the primary cilium (α-acetylated Tubulin) were analysed by quantitative PCR, Western blot or immunocytochemistry. In response to FSS, Claudin-2 disappeared and ZO-1 displayed punctuated and discontinuous staining in the plasma membrane. Expression of Pard6 was also decreased. Moreover, E-Cadherin abundance was decreased, while its major repressors Snail1 and Snail2 were overexpressed, and ß-Catenin staining was disrupted along the cell periphery. Finally, FSS subjected-cells exhibited disappeared primary cilium. Results were confirmed in vivo in a uninephrectomy (8 months) mouse model where increased FSS induced by adaptive hyperfiltration in remnant kidney was accompanied by both decreased epithelial gene expression including ZO-1, E-cadherin and ß-Catenin and disappearance of tubular cilia. In conclusion, these results show that proximal tubular cells lose an important number of their epithelial characteristics after long term exposure to FSS both in vitro and in vivo. Thus, the changes in urinary FSS associated with nephropathies should be considered as potential insults for tubular cells leading to disorganization of the tubular epithelium.

Label-free quantitative urinary proteomics identifies the arginase pathway as a new player in congenital obstructive nephropathy.

Obstructive nephropathy is a frequently encountered situation in newborns. In previous studies, the urinary peptidome has been analyzed for the identification of clinically useful biomarkers of obstructive nephropathy. However, the urinary proteome has not been explored yet and should allow additional insight into the pathophysiology of the disease. We have analyzed the urinary proteome of newborns (n = 5/group) with obstructive nephropathy using label free quantitative nanoLC-MS/MS allowing the identification and quantification of 970 urinary proteins. We next focused on proteins exclusively regulated in severe obstructive nephropathy and identified Arginase 1 as a potential candidate molecule involved in the development of obstructive nephropathy, located at the crossroad of pro- and antifibrotic pathways. The reduced urinary abundance of Arginase 1 in obstructive nephropathy was verified in independent clinical samples using both Western blot and MRM analysis. These data were confirmed in situ in kidneys obtained from a mouse obstructive nephropathy model. In addition, we also observed increased expression of Arginase 2 and increased total arginase activity in obstructed mouse kidneys. mRNA expression analysis of the related arginase pathways indicated that the pro-fibrotic arginase-related pathway is activated during obstructive nephropathy. Taken together we have identified a new actor in the development of obstructive nephropathy in newborns using quantitative urinary proteomics and shown its involvement in an in vivo model of disease. The present study demonstrates the relevance of such a quantitative urinary proteomics approach with clinical samples for a better understanding of the pathophysiology and for the discovery of potential therapeutic targets.

Long term metabolic syndrome induced by a high fat high fructose diet leads to minimal renal injury in C57BL/6 mice.

Metabolic syndrome can induce chronic kidney disease in humans. Genetically engineered mice on a C57BL/6 background are highly used for mechanistic studies. Although it has been shown that metabolic syndrome induces cardiovascular lesions in C57BL/6 mice, in depth renal phenotyping has never been performed. Therefore in this study we characterized renal function and injury in C57BL/6 mice with long-term metabolic syndrome induced by a high fat and fructose diet (HFFD). C57BL/6 mice received an 8 months HFFD diet enriched with fat (45% energy from fat) and drinking water enriched with fructose (30%). Body weight, food/water consumption, energy intake, fat/lean mass ratio, plasma glucose, HDL, LDL, triglycerides and cholesterol levels were monitored. At 3, 6 and 8 months, renal function was determined by inulin clearance and measure of albuminuria. At sacrifice, kidneys and liver were collected. Metabolic syndrome in C57BL/6 mice fed a HFFD was observed as early 4 weeks with development of type 2 diabetes at 8 weeks after initiation of diet. However, detailed analysis of kidney structure and function showed only minimal renal injury after 8 months of HFFD. HFFD induced moderate glomerular hyperfiltration (436,4 µL/min vs 289,8 µL/min; p-value=0.0418) together with a 2-fold increase in albuminuria only after 8 months of HFFD. This was accompanied by a 2-fold increase in renal inflammation (p-value=0.0217) but without renal fibrosis or mesangial matrix expansion. In addition, electron microscopy did not show alterations in glomeruli such as basal membrane thickening and foot process effacement. Finally, comparison of the urinary peptidome of these mice with the urinary peptidome from humans with diabetic nephropathy also suggested absence of diabetic nephropathy in this model. This study provides evidence that the HFFD C57BL/6 model is not the optimal model to study the effects of metabolic syndrome on the development of diabetic kidney disease.

Fetal urinary peptides to predict postnatal outcome of renal disease in fetuses with posterior urethral valves (PUV).

Bilateral congenital abnormalities of the kidney and urinary tract (CAKUT), although are individually rare diseases, remain the main cause of chronic kidney disease in infants worldwide. Bilateral CAKUT display a wide spectrum of pre- and postnatal outcomes ranging from death in utero to normal postnatal renal function. Methods to predict these outcomes in utero are controversial and, in several cases, lead to unjustified termination of pregnancy. Using capillary electrophoresis coupled with mass spectrometry, we have analyzed the urinary proteome of fetuses with posterior urethral valves (PUV), the prototypic bilateral CAKUT, for the presence of biomarkers predicting postnatal renal function. Among more than 4000 fetal urinary peptide candidates, 26 peptides were identified that were specifically associated with PUV in 13 patients with early end-stage renal disease (ESRD) compared to 15 patients with absence of ESRD before the age of 2. A classifier based on these peptides correctly predicted postnatal renal function with 88% sensitivity and 95% specificity in an independent blinded validation cohort of 38 PUV patients, outperforming classical methods, including fetal urine biochemistry and fetal ultrasound. This study demonstrates that fetal urine is an important pool of peptides that can predict postnatal renal function and thus be used to make clinical decisions regarding pregnancy.

[Renal urinary shear stress: a novel actor in nephropathies]. / Quand l'urine cisaille les cellules rénales - Un nouveau rôle pour le shear stress dans les néphropathies.

The role of fluid shear stress is well established in vascular pathophysiology. However, urinary shear stress now also appears as a key mechanism in the regulation of renal function. In addition, there is a growing body of evidence showing that modified urinary shear stress is involved in the development of nephropathies. Therefore we review here the state-of-the-art on the pathophysiological roles of urinary shear stress.

Renal tubular fluid shear stress facilitates monocyte activation toward inflammatory macrophages.

Modified urinary fluid shear stress (FSS) induced by variations of urinary fluid flow and composition is observed in early phases of most kidney diseases. Recently, we reported that renal tubular FSS promotes endothelial cell activation and subsequent adhesion of human monocytes, thereby suggesting that changes in urinary FSS can induce the development of inflammation (Miravète M, Klein J, Besse-Patin A, Gonzalez J, Pecher C, Bascands JL, Mercier-Bonin M, Schanstra JP, Buffin-Meyer B, BBRC 407: 813-817, 2011). Here, we evaluated the influence of tubular FSS on monocytes as they play an important role in the progression of inflammation in nephropathies. Human renal tubular cells (HK-2) were exposed to FSS 0.01 Pa for 30 min or 5 h. Treatment of human THP-1 monocytes with the resulting conditioned medium (FSS-CM) modified the expression of macrophage differentiation markers, suggesting differentiation toward the inflammatory M1-type macrophage. The effect was confirmed in freshly isolated human monocytes. In contrast to endothelial cells, the activation of monocytes by FSS-CM did not require TNF-α. Cytokine array analysis of FSS-CM showed that FSS modified secretion of cytokines by HK-2 cells, particularly by increasing secretion of TGF-ß and by decreasing secretion of C-C chemokine ligand 2 (CCL2). Neutralization of TGF-ß or CCL2 supplementation attenuated the effect of FSS-CM on macrophage differentiation. Finally, FSS-injured HK-2 cells expressed and secreted early biomarkers of tubular damage such as kidney injury molecule 1 and neutrophil gelatinase-associated lipocalin. In conclusion, changes in urinary FSS should now also be considered as potential insults for tubular cells that initiate/perpetuate interstitial inflammation.

Alloantibodies against MHC class I: a novel mechanism of neonatal pancytopenia linked to vaccination.

Fetal/neonatal alloimmune thrombocytopenia is a frequent disease in humans where alloantibodies against platelet Ags lead to platelet destruction and hemorrhage. Although a role in the disease for Abs against MHC has been suspected, this has not been formally demonstrated. Since 2007, a hemorrhagic syndrome due to thrombocytopenia and designated as bovine neonatal pancytopenia (BNP) has been recognized in calves in several European countries. An inactivated antiviral vaccine is strongly suspected to be involved in this syndrome because of its highly frequent use in the dams of affected calves. In this study, we show that BNP is an alloimmune disease, as we reproduced the signs by transferring serum Abs from vaccinated BNP dams into healthy neonatal calves. Ab specificity was strongly associated with the presence of allogeneic MHC class I Abs in the dams. MHC class I staining was also observed on Madin-Darby bovine kidney cells, a cell line related to the one used to produce the vaccine Ag. Our report emphatically demonstrates that alloimmunization against MHC class I is associated with a substantial risk of developing cytopenia-associated syndromes in neonates when a cell line of the same species is used to produce an inactivated vaccine injected into the mother.

Gene expression profiling of dendritic cells reveals important mechanisms associated with predisposition to Staphylococcus infections.

BACKGROUND: Staphylococcus aureus is a major pathogen of humans and animals and emerging antibiotic-resistant strains have further increased the concern of this health issue. Host genetics influence susceptibility to S. aureus infections, and the genes determining the outcome of infections should be identified to find alternative therapies to treatment with antibiotics. Here, we used outbred animals from a divergent selection based on susceptibility towards Staphylococcus infection to explore host immunogenetics. METHODOLOGY/PRINCIPAL FINDINGS: We investigated how dendritic cells respond to heat-inactivated S. aureus and whether dendritic cells from animals showing different degrees of susceptibility had distinct gene expression profiles. We measured gene expression levels of in vitro S. aureus-stimulated bone marrow-derived dendritic cells at three different time points (0, 3 and 8 hrs) by using 15 k ovine Agilent microarrays. Furthermore, differential expression of a selected number of genes was confirmed by RT-qPCR. Gene signatures of stimulated DCs were obtained and showed that genes involved in the inflammatory process and T helper cell polarization were highly up-regulated upon stimulation. Moreover, a set of 204 genes were statistically differentially expressed between susceptible and resistant animals, and grouped them according to their predisposition to staphylococcal infection. Interestingly, over-expression of the C1q and Ido1 genes was observed in the resistant line and suggested a role of classical pathway of complement and early regulation of inflammation pathways, respectively. On the contrary, over expression of genes involved in the IL1R pathway was observed in susceptible animals. Furthermore, the leucocyte extravasation pathway was also found to be dominant in the susceptible line. CONCLUSION/SIGNIFICANCE: We successfully obtained Staphylococcus aureus associated gene expression of ovine BM-DC in an 8-hour kinetics experiment. The distinct transcriptional profiles of dendritic cells obtained from resistant and susceptible animals may explain susceptibility towards S. aureus infections in a broader context.

Corneodesmosomes and corneodesmosin: from the stratum corneum cohesion to the pathophysiology of genodermatoses.

Corneodesmosin (CDSN) was identified 20 years ago by raising monoclonal antibodies against human plantar stratum corneum. The protein is specific to corneodesmosomes, cell-junction structures that, in humans, are found in the epidermis, the hard palate epithelium, and the inner root sheath of the hair follicles. Synthesized by the granular keratinocytes and secreted via the lamellar bodies, CDSN is incorporated into the desmoglea of the desmosomes, shortly before their transformation into corneodesmosomes during cornification. CDSN displays adhesive properties, mostly attributable to its N-terminal glycine-rich domain, and is sequentially proteolyzed as corneocytes migrate towards the skin surface prior to desquamation. The recent inactivation of Cdsn in mice induced a lethal epidermal barrier disruption and hair follicle degeneration, related to corneodesmosome dysfunction. That confirmed the essential role of the protein in maintaining integrity of the epidermis and the hair follicle. The CDSN gene is located in PSORS1, the major psoriasis susceptibility locus on the chromosome 6, but to date its involvement in the disease pathophysiology is not clear. By contrast, two different monogenic diseases associated with nonsense mutations in CDSN, were recently identified. First, hypotrichosis simplex of the scalp in which mutated CDSN accumulates in the dermis and forms amyloid deposits; then, peeling skin disease in which the genetic defect induces dyscohesion of the stratum corneum, responsible for abnormal desquamation and increased skin penetration of allergens.

Transcriptomic analysis of milk somatic cells in mastitis resistant and susceptible sheep upon challenge with Staphylococcus epidermidis and Staphylococcus aureus.

BACKGROUND: The existence of a genetic basis for host responses to bacterial intramammary infections has been widely documented, but the underlying mechanisms and the genes are still largely unknown. Previously, two divergent lines of sheep selected for high/low milk somatic cell scores have been shown to be respectively susceptible and resistant to intramammary infections by Staphylococcus spp. Transcriptional profiling with an 15K ovine-specific microarray of the milk somatic cells of susceptible and resistant sheep infected successively by S. epidermidis and S. aureus was performed in order to enhance our understanding of the molecular and cellular events associated with mastitis resistance. RESULTS: The bacteriological titre was lower in the resistant than in the susceptible animals in the 48 hours following inoculation, although milk somatic cell concentration was similar. Gene expression was analysed in milk somatic cells, mainly represented by neutrophils, collected 12 hours post-challenge. A high number of differentially expressed genes between the two challenges indicated that more T cells are recruited upon inoculation by S. aureus than S. epidermidis. A total of 52 genes were significantly differentially expressed between the resistant and susceptible animals. Further Gene Ontology analysis indicated that differentially expressed genes were associated with immune and inflammatory responses, leukocyte adhesion, cell migration, and signal transduction. Close biological relationships could be established between most genes using gene network analysis. Furthermore, gene expression suggests that the cell turn-over, as a consequence of apoptosis/granulopoiesis, may be enhanced in the resistant line when compared to the susceptible line. CONCLUSIONS: Gene profiling in resistant and susceptible lines has provided good candidates for mapping the biological pathways and genes underlying genetically determined resistance and susceptibility towards Staphylococcus infections, and opens new fields for further investigation.

Congenital ureteropelvic junction obstruction: human disease and animal models.

Ureteropelvic junction (UPJ) obstruction is the most frequently observed cause of obstructive nephropathy in children. Neonatal and foetal animal models have been developed that mimic closely what is observed in human disease. The purpose of this review is to discuss how obstructive nephropathy alters kidney histology and function and describe the molecular mechanisms involved in the progression of the lesions, including inflammation, proliferation/apoptosis, renin-angiotensin system activation and fibrosis, based on both human and animal data. Also we propose that during obstructive nephropathy, hydrodynamic modifications are early inducers of the tubular lesions, which are potentially at the origin of the pathology. Finally, an important observation in animal models is that relief of obstruction during kidney development has important effects on renal function later in adult life. A major short-coming is the absence of data on the impact of UPJ obstruction on long-term adult renal function to elucidate whether these animal data are also valid in humans.

Simultaneous inactivation of espB and tir abrogates the strong, but non-protective, inflammatory response induced by EPEC.

Enteropathogenic Escherichia coli (EPEC) belong to the attaching and effacing (A/E) family of bacterial pathogens that represent a worldwide health concern. These non-invasive bacteria attach to intestinal enterocytes through a type III secretion system (T3SS), leading to intestinal inflammation and severe diarrhea. To dissect the signals leading to the induction of the inflammatory response and to understand its role in the pathogenesis of infection, we used the rabbit model, which represents a close model of human infections. Rabbits were orally inoculated with either the wild type O103:K-:H2 E22 EPEC strain or with the E22Δtir/espB strain, which bears mutations in two genes involved in the injectisome structure and function. To monitor the development of the inflammatory response, we developed a quantitative real-time RT-PCR (qPCR) assay specific for a panel of rabbit genes. Using combined immunohistochemistry and qPCR, we show here that the inflammatory response triggered by wild type EPEC occurs very early, preceding the bacterial colonization of the epithelium. However, this early response is unable to prevent bacterial attachment on enterocytes. Moreover, our results show that expression of a complete bacterial injectisome is required for the development of inflammation. Finally, infection by the virulent strain, but not by the doubly mutated strain, rapidly induces the development of a specific immune response in the mesenteric lymph nodes, which is not associated with protection. Our findings suggest that the induction of a strong inflammatory response by T3SS dependent components represents a selective advantage for T3SS+ bacteria, thereby facilitating their colonization.

A new amyloidosis caused by fibrillar aggregates of mutated corneodesmosin.

Heterozygous nonsense mutations in the CDSN gene encoding corneodesmosin (CDSN), an adhesive protein expressed in cornified epithelia and hair follicles, cause hypotrichosis simplex of the scalp (HSS), a nonsyndromic form of alopecia. Truncated mutants of CDSN ((mut)CDSN), which bear the N-terminal adhesive Gly/Ser-rich domain (GS domain) of the protein, abnormally accumulate as amorphous deposits at the periphery of hair follicles and in the papillary dermis of the patient skin. Here, we present evidence that the (mut)CDSN deposits display an affinity for amyloidophilic dyes, namely Congo red and thioflavin T. We also detected the serum amyloid protein component in the dermis of HSS patients. We demonstrated that recombinant forms of (mut)CDSN and of the GS domain assemble in vitro into ring-shaped oligomeric structures and fibrils. The amyloid-like nature of the fibrils was demonstrated by dye binding and Fourier transform infrared spectrometry measurements. We showed that the ring-shaped oligomers of (mut)CDSN, but not the fibrillar forms, are toxic to cultured keratinocytes. Finally, online algorithms predicted the GS domain to be a particularly disordered region of CDSN in agreement with circular dichroism measurements. This identifies HSS as a human amyloidosis related to the aggregation of natively unfolded (mut)CDSN polypeptides into amyloid fibrils.

Advances in urinary proteome analysis and biomarker discovery in pediatric renal disease.

Recent progress in proteomic analysis and strategies for the identification of clinically useful biomarkers in biofluids has led to the identification of urine as an excellent non-invasive reservoir for biomarkers of disease. Urinary biomarkers have been identified and validated on independent cohorts in different high-incidence adult renal diseases, including diabetic nephropathy, chronic kidney disease and immunoglobulin A-nephropathy, but also in extrarenal disease, such as coronary artery disease. Unfortunately, this type of research is underrepresented in the pediatric population. Here, we present the rare studies in the pediatric population that identified potential clinically useful urinary biomarkers in ureteropelvic junction (UPJ) obstruction and renal Fanconi syndrome. These studies, although limited in number, clearly show the potential of urinary proteomics, especially in the pediatric population. It is anticipated that the advances made in the adult population, the lessons learned on the use of appropriate statistics and the inclusion of independent blinded validation cohorts in these types of studies will rapidly lead to clinical useful urinary biomarkers for other pediatric (renal) disease in a population where non-invasive analysis is particularly appreciated.

Secretory IgA-mediated neutralization of Shigella flexneri prevents intestinal tissue destruction by down-regulating inflammatory circuits.

Shigella, a Gram-negative invasive enteropathogenic bacterium responsible for bacillary dysentery, causes the rupture, invasion, and inflammatory destruction of the human colonic mucosa. We explored the mechanisms of protection mediated by Shigella LPS-specific secretory IgA (SIgA), the major mucosal Ab induced upon natural infection. Bacteria, SIgA, or SIgA-S. flexneri immune complexes were administered into rabbit ligated intestinal loops containing a Peyer's patch. After 8 h, localizations of bacteria, SIgA, and SIgA-S. flexneri immune complexes were examined by immunohistochemistry and confocal microscopy imaging. We found that anti-Shigella LPS SIgA, mainly via immune exclusion, prevented Shigella-induced inflammation responsible for the destruction of the intestinal barrier. Besides this luminal trapping, a small proportion of SIgA-S. flexneri immune complexes were shown to enter the rabbit Peyer's patch and were internalized by dendritic cells of the subepithelial dome region. Local inflammatory status was analyzed by quantitative RT-PCR using newly designed primers for rabbit pro- and anti-inflammatory mediator genes. In Peyer's patches exposed to immune complexes, limited up-regulation of the expression of proinflammatory genes, including TNF-alpha, IL-6, Cox-2, and IFN-gamma, was observed, consistent with preserved morphology. In contrast, in Peyer's patches exposed to Shigella alone, high expression of the same mediators was measured, indicating that neutralizing SIgA dampens the proinflammatory properties of Shigella. These results show that in the form of immune complexes, SIgA guarantees both immune exclusion and neutralization of translocated bacteria, thus preserving the intestinal barrier integrity by preventing bacterial-induced inflammation. These findings add to the multiple facets of the noninflammatory properties of SIgA.