Tubulointerstitial heparan sulfate proteoglycan changes in human renal diseases correlate with leukocyte influx and proteinuria

Endothelial cell activation and glycocalyx shedding - potential as biomarkers in patients with lupus nephritis

Lupus nephritis (LN) is a common and severe manifestation of systemic lupus erythematosus and an important cause of acute and chronic kidney injury. Early diagnosis of LN and preventing relapses are key to preserving renal reserve. However, due to the complexity and heterogeneity of the disease, clinical management remains challenging. Kidney biopsy remains the gold standard for confirming the diagnosis of LN and subsequent assessment of kidney histopathology, but it is invasive and cannot be repeated frequently. Current clinical indicators of kidney function such as proteinuria and serum creatinine level are non-specific and do not accurately reflect histopathological changes, while anti-dsDNA antibody and C3 levels reflect immunological status but not kidney injury. Identification of novel and specific biomarkers for LN is prerequisite to improve management. Renal function deterioration is associated with changes in the endothelial glycocalyx, a delicate gel-like layer located at the interface between the endothelium and bloodstream. Inflammation induces endothelial cell activation and shedding of glycocalyx constituents into the circulation. This review discusses the potential role of soluble glycocalyx components as biomarkers of active LN, especially in patients in whom conventional serological and biochemical markers do not appear helpful.

Crotamine/siRNA Nanocomplexes for Functional Downregulation of Syndecan-1 in Renal Proximal Tubular Epithelial Cells

Proteinuria drives progressive tubulointerstitial fibrosis in native and transplanted kidneys, mainly through the activation of proximal tubular epithelial cells (PTECs). During proteinuria, PTEC syndecan-1 functions as a docking platform for properdin-mediated alternative complement activation. Non-viral gene delivery vectors to target PTEC syndecan-1 could be useful to slow down alternative complement activation. In this work, we characterize a PTEC-specific non-viral delivery vector composed of the cell-penetrating peptide crotamine complexed with a syndecan-1 targeting siRNA. Cell biological characterization was performed in the human PTEC HK2 cell line, using confocal microscopy, qRT-PCR, and flow cytometry. PTEC targeting in vivo was carried out in healthy mice. Crotamine/siRNA nanocomplexes are positively charged, about 100 nm in size, resistant to nuclease degradation, and showed in vitro and in vivo specificity and internalization into PTECs. The efficient suppression of syndecan-1 expression in PTECs mediated by these nanocomplexes significantly reduced properdin binding (p < 0.001), as well as the subsequent complement activation by the alternative complement pathway (p < 0.001), as observed in either normal or activated tubular conditions. To conclude, crotamine/siRNA-mediated downregulation of PTEC syndecan-1 reduced the activation of the alternative complement pathway. Therefore, we suggest that the present strategy opens new venues for targeted proximal tubular gene therapy in renal diseases.

Omics are Getting Us Closer to Understanding IgA Nephropathy

During the last decade, thanks to omics technologies, new light has been shed on the pathogenesis of many diseases. Genomics, epigenomics, transcriptomics, and proteomics have helped to provide a better understanding of the origin and heterogeneity of several diseases. However, the risk factors for most autoimmune diseases remain unknown. The successes and pitfalls of omics have also been observed in nephrology, including immunoglobulin A nephropathy (IgAN), the most common form of glomerulonephritis and a principal cause of end-stage renal disease worldwide. Unfortunately, the immense progress in basic research has not yet been followed by the satisfactory development of a targeted treatment. Although, most omics studies describe changes in the immune system, there is still insufficient data to apply their results in the constantly evolving multi-hit pathogenesis model and thus do to provide a complete picture of the disease. Here, we describe recent findings regarding the pathophysiology of IgAN and link omics studies with immune system dysregulation. This review provides insights into specific IgAN markers, which may lead to the identification of potential targets for personalised treatment in the future.

Introducing or removing heparan sulfate binding sites does not alter brain uptake of the blood-brain barrier shuttle scFv8D3

The blood-brain barrier (BBB) greatly limits the delivery of protein-based drugs into the brain and is a major obstacle for the treatment of brain disorders. Targeting the transferrin receptor (TfR) is a strategy for transporting protein-based drugs into the brain, which can be utilized by using TfR-binding BBB transporters, such as the TfR-binding antibody 8D3. In this current study, we investigated if binding to heparan sulfate (HS) contributes to the brain uptake of a single chain fragment variable of 8D3 (scFv8D3). We designed and produced a scFv8D3 mutant, engineered with additional HS binding sites, HS(+)scFv8D3, to assess whether increased HS binding would improve brain uptake. Additionally, a mutant with a reduced number of HS binding sites, HS(-)scFv8D3, was also engineered to see if reducing the HS binding sites could also affect brain uptake. Heparin column chromatography showed that only the HS(+)scFv8D3 mutant bound HS in the experimental conditions. Ex vivo results showed that the brain uptake was unaffected by the introduction or removal of HS binding sites, which indicates that scFv8D3 is not dependent on the HS binding sites for brain uptake. Conversely, introducing HS binding sites to scFv8D3 decreased its renal excretion while removing them had the opposite effect.

Serum parabens and its correlations with immunologic and cellular markers in Southern Taiwan industrialized city systemic lupus erythematosus patients

BACKGROUND

Although the immune systems of patients with systemic lupus erythematosus (SLE) are affected by both personal characteristics and environmental factors, the effects of parabens on patients with SLE have not been well studied. We investigated the indirect effects of four parabens-methylparaben (MP), ethylparaben (EP), propylparaben (n-PrP), and butylparaben (n-BuP)-on several immunological markers.

METHODS

We assessed the serum levels of MP, EP, n-PrP, and n-BuP in 25 SLE patients and correlated the concentration of each paraben with available clinical and laboratory markers, including intracellular markers of antiviral immunity and apoptosis.

RESULTS

The expression of aryl hydrocarbon receptor (AhR) was significantly negatively correlated with n-PrP levels (p = 0.03, r = -0.434). In monocytes, APO2.7 was significantly positively correlated with n-BuP levels (p = 0.019, r = 0.467). Glutathione levels were significantly negatively correlated with n-BuP levels (p = 0.019, r = -0.518). Anti- β2 glycoprotein I IgM was significantly positively correlated with both MP (p = 0.011, r = 0.585) and EP levels (p = 0.032, r = 0.506). Anti-cardiolipin IgA was significantly positively correlated with both MP (p = 0.038, r = 0.493) and n-PrP levels (p = 0.031, r = 0.508). On CD8 T cells, the early apoptotic marker annexin V was significantly negatively correlated with both MP (p < 0.05, r = -0.541) and n-BuP levels (p = 0.02, r = -0.616), and L-selectin was significantly positively correlated with both MP (p < 0.05, r = 0.47) and n-PrP levels (p = 0.02, r = 0.556).

CONCLUSION

Our findings suggest that higher parabens levels were associated with lower AhR expression in leukocytes, increased monocyte apoptosis, lower serum glutathione levels, reduced annexin V expression on CD8 T cells, and higher L-selectin levels on leukocytes.

Association of circulating fibroblast growth factor-2 with progression of HIV-chronic kidney diseases in children

BACKGROUND

Children living with HIV frequently show high plasma levels of fibroblast growth factor-2 (FGF-2/bFGF). FGF-2 accelerates the progression of several experimental kidney diseases; however, the role of circulating FGF-2 in childhood HIV-chronic kidney diseases (HIV-CKDs) is unknown. We carried out this study to determine whether high plasma FGF-2 levels were associated with the development of HIV-CKDs in children.

METHODS

The plasma and urine FGF-2 levels were measured in 84 children (< 12 years of age) living with HIV during the pre-modern antiretroviral era, and followed for at least 3 years to determine the prevalence of proteinuria and HIV-CKDs. We also assessed the distribution of the kidney FGF-2 binding sites by autoradiography and Alcian blue staining, and explored potential mechanisms by which circulating FGF-2 may precipitate HIV-CKDs in cultured kidney epithelial and mononuclear cells derived from children with HIV-CKDs.

RESULTS

High plasma FGF-2 levels were associated with a high viral load. Thirteen children (~ 15%) developed HIV-CKDs and showed a large reservoir of FGF-2 low-affinity binding sites in the kidney, which can facilitate the recruitment of circulating FGF-2. Children with high plasma and urine FGF-2 levels had 73-fold increased odds (95% CI 9-791) of having HIV-CKDs relative to those with normal FGF-2 values. FGF-2 induced the proliferation and decreased the expression of APOL-1 mRNA in podocytes, and increased the attachment and survival of infected mononuclear cells cultured from children with HIV-CKDs.

CONCLUSIONS

High plasma FGF-2 levels appear to be an additional risk factor for developing progressive childhood HIV-CKDs.

Hypercholesterolemia in Progressive Renal Failure Is Associated with Changes in Hepatic Heparan Sulfate - PCSK9 Interaction

BACKGROUND

Dyslipidemia is an important risk factor in CKD. The liver clears triglyceride-rich lipoproteins (TRL) via LDL receptor (LDLR), LDLR-related protein-1 (LRP-1), and heparan sulfate proteoglycans (HSPGs), mostly syndecan-1. HSPGs also facilitate LDLR degradation by proprotein convertase subtilisin/kexin type 9 (PCSK9). Progressive renal failure affects the structure and activity of hepatic lipoprotein receptors, PCSK9, and plasma cholesterol.

METHODS

Uninephrectomy- and aging-induced CKD in normotensive Wistar rats and hypertensive Munich-Wistar-Frömter (MWF) rats.

RESULTS

Compared with 22-week-old sex- and strain-matched rats, 48-week-old uninephrectomized Wistar-CKD and MWF-CKD rats showed proteinuria, increased plasma creatinine, and hypercholesterolemia (all P<0.05), which were most apparent in hypertensive MWF-CKD rats. Hepatic PCSK9 expression increased in both CKD groups (P<0.05), with unusual sinusoidal localization, which was not seen in 22-week-old rats. Heparan sulfate (HS) disaccharide analysis, staining with anti-HS mAbs, and mRNA expression of HS polymerase exostosin-1 (Ext-1), revealed elongated HS chains in both CKD groups. Solid-phase competition assays showed that the PCSK9 interaction with heparin-albumin (HS-proteoglycan analogue) was critically dependent on polysaccharide chain length. VLDL binding to HS from CKD livers was reduced (P<0.05). Proteinuria and plasma creatinine strongly associated with plasma cholesterol, PCSK9, and HS changes.

CONCLUSIONS

Progressive CKD induces hepatic HS elongation, leading to increased interaction with PCSK9. This might reduce hepatic lipoprotein uptake and thereby induce dyslipidemia in CKD. Therefore, PCSK9/HS may be a novel target to control dyslipidemia.

Heparan Sulfate Proteoglycans in Diabetes

Diabetes is a complex disorder responsible for the mortality and morbidity of millions of individuals worldwide. Although many approaches have been used to understand and treat diabetes, the role of proteoglycans, in particular heparan sulfate proteoglycans (HSPGs), has only recently received attention. The HSPGs are heterogeneous, highly negatively charged, and are found in all cells primarily attached to the plasma membrane or present in the extracellular matrix (ECM). HSPGs are involved in development, cell migration, signal transduction, hemostasis, inflammation, and antiviral activity, and regulate cytokines, chemokines, growth factors, and enzymes. Hyperglycemia, accompanying diabetes, increases reactive oxygen species and upregulates the enzyme heparanase that degrades HSPGs or affects the synthesis of the HSPGs altering their structure. The modified HSPGs in the endothelium and ECM in the blood vessel wall contribute to the nephropathy, cardiovascular disease, and retinopathy seen in diabetes. Besides the blood vessel, other cells and tissues in the heart, kidney, and eye are affected by diabetes. Although not well understood, the adipose tissue, intestine, and brain also reveal HSPG changes associated with diabetes. Further, HSPGs are significantly involved in protecting the β cells of the pancreas from autoimmune destruction and could be a focus of prevention of type I diabetes. In some circumstances, HSPGs may contribute to the pathology of the disease. Understanding the role of HSPGs and how they are modified by diabetes may lead to new treatments as well as preventative measures to reduce the morbidity and mortality associated with this complex condition.

Proteinuria converts hepatic heparan sulfate to an effective proprotein convertase subtilisin kexin type 9 enzyme binding partner

Hepatic uptake of triglyceride-rich remnant lipoproteins is mediated by the low-density lipoprotein receptor, a low-density lipoprotein receptor related protein and the heparan sulfate proteoglycan, syndecan-1. Heparan sulfate proteoglycan also mediates low-density lipoprotein receptor degradation by a regulator of cholesterol homeostasis, proprotein convertase subtilisin kexin type 9 (PCSK9), thereby hampering triglyceride-rich remnant lipoproteins uptake. In this study, we investigated the effects of proteinuria on PCSK9, hepatic heparan sulfate proteoglycan and plasma triglyceride-rich remnant lipoproteins. Adriamycin-injected rats developed proteinuria, elevated triglycerides and total cholesterol (all significantly increased). Proteinuria associated with triglycerides and total cholesterol and serum PCSK9 (all significant associations) without loss of the low-density lipoprotein receptor as evidenced by immunofluorescence staining and western blotting. In proteinuric rats, PCSK9 accumulated in sinusoids, whereas in control rats PCSK9 was localized in the cytoplasm of hepatocytes. Molecular profiling revealed that the heparan sulfate side chains of heparan sulfate proteoglycan to be hypersulfated in proteinuric rats. Competition assays revealed sulfation to be a major determinant for PCSK9 binding. PCSK9 partly colocalized with hypersulfated heparan sulfate in proteinuric rats, but not in control rats. Hence, proteinuria induces hypersulfated hepatic heparan sulfate proteoglycans, increasing their affinity to PCSK9. This might impair hepatic triglyceride-rich remnant lipoproteins uptake, causing proteinuria-associated dyslipidemia. Thus, our study reveals PCSK9/heparan sulfate may be a novel target to control dyslipidemia.

The Metalloproteinase ADAMTS5 Is Expressed by Interstitial Inflammatory Cells in IgA Nephropathy and Is Proteolytically Active on the Kidney Matrix

ADAMTS5 is upregulated in human IgA nephropathy lesions.

ADAMTS5 is related to inflammatory infiltrates in affected kidneys.

ADAMTS5 digests kidney matrix proteins and cleaves complement C3 and fibronectin.

In IgA nephropathy (IgAN), IgA immune complexes are deposited in the mesangium and drive inflammation and extracellular matrix (ECM) remodelling. The functional links between IgA deposition, inflammation, and matrix remodelling are not well characterized. We recently performed urine liquid chromatography–tandem mass spectrometry proteomics and identified multiple ECM glycoproteins whose expression and function in IgAN is unclear. None of the urine glycoproteins was regulated in IgAN transcriptomics, indicating that tissue remodelling rather than increased expression might contribute to their presence in urine. To investigate this, we examined the IgAN expression profile of metalloproteinases, enzymes involved in the remodelling of ECM proteins, and noted that the proteoglycanase ADAMTS5 was upregulated in IgAN kidneys. ADAMTS5 accumulated in areas of inflammation, and ADAMTS5⁺ cells were seen in the tubulointerstitium and glomeruli. The enzyme was expressed by CD64⁺ cells and its expression was increased by IL-1 and LPS. Analysis of myeloid cell transcriptomics revealed that ADAMTS5 is enriched in human classical monocytes. ADAMTS5⁺ cells were present in areas of matrix remodelling and associated with ECM proteins lumican, versican, and collagen-4. Liquid chromatography–tandem mass spectrometry proteomics of kidney explants digested with ADAMTS5, identified multiple kidney proteins affected by ADAMTS5 and revealed specific proteolysis of complement C3 and fibronectin associated with IgA on immune complexes. ADAMTS5 processing of immune complex proteins reduced binding to cultured mesangial cells. ADAMTS5 is associated with interstitial inflammatory cells in IgAN and other kidney lesions and fragments relevant extracellular proteins. The proteolytic enzyme might be a new translational target relevant to inflammation and scarring in kidney disease.

MASP-2 Is a Heparin-Binding Protease; Identification of Blocking Oligosaccharides

It is well-known that heparin and other glycosaminoglycans (GAGs) inhibit complement activation. It is however not known whether fractionation and/or modification of GAGs might deliver pathway-specific inhibition of the complement system. Therefore, we evaluated a library of GAGs and their derivatives for their functional pathway specific complement inhibition, including the MASP-specific C4 deposition assay. Interaction of human MASP-2 with heparan sulfate/heparin was evaluated by surface plasmon resonance, ELISA and in renal tissue. In vitro pathway-specific complement assays showed that highly sulfated GAGs inhibited all three pathways of complement. Small heparin- and heparan sulfate-derived oligosaccharides were selective inhibitors of the lectin pathway (LP). These small oligosaccharides showed identical inhibition of the ficolin-3 mediated LP activation, failed to inhibit the binding of MBL to mannan, but inhibited C4 cleavage by MASPs. Hexa- and pentasulfated tetrasaccharides represent the smallest MASP inhibitors both in the functional LP assay as well in the MASP-mediated C4 assay. Surface plasmon resonance showed MASP-2 binding with heparin and heparan sulfate, revealing high Kon and Koff rates resulted in a Kd of ~2 μM and confirmed inhibition by heparin-derived tetrasaccharide. In renal tissue, MASP-2 partially colocalized with agrin and heparan sulfate, but not with activated C3, suggesting docking, storage, and potential inactivation of MASP-2 by heparan sulfate in basement membranes. Our data show that highly sulfated GAGs mediated inhibition of all three complement pathways, whereas short heparin- and heparan sulfate-derived oligosaccharides selectively blocked the lectin pathway via MASP-2 inhibition. Binding of MASP-2 to immobilized heparan sulfate/heparin and partial co-localization of agrin/heparan sulfate with MASP, but not C3b, might suggest that in vivo heparan sulfate proteoglycans act as a docking platform for MASP-2 and possibly prevent the lectin pathway from activation.

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.

Chondroitin sulfate degradation and eicosanoid metabolism pathways are impaired in focal segmental glomerulosclerosis: Experimental confirmation of an in silico prediction

Introduction: Focal segmental glomerulosclerosis (FSGS), the most common primary glomerular disease, is a diverse clinical entity that occurs after podocyte injury. Although numerous studies have suggested molecular pathways responsible for the development of FSGS, many still remain unknown about its pathogenic mechanisms. Two important pathways were predicted as candidates for the pathogenesis of FSGS in our previous in silico analysis, whom we aim to confirm experimentally in the present study. Methods: The expression levels of 4 enzyme genes that are representative of "chondroitin sulfate degradation" and "eicosanoid metabolism" pathways were investigated in the urinary sediments of biopsy-proven FSGS patients and healthy subjects using real-time polymerase chain reaction (RT-PCR). These target genes were arylsulfatase, hexosaminidase, cyclooxygenase-2 (COX-2), and prostaglandin I2 synthase. The patients were sub-divided into 2 groups based on the range of proteinuria and glomerular filtration rate and were compared for variation in the expression of target genes. Correlation of target genes with clinical and pathological characteristics of the disease was calculated and receiver operating characteristic (ROC) analysis was performed. Results: A combined panel of arylsulfatase, hexosaminidase, and COX-2 improved the diagnosis of FSGS by 76%. Hexosaminidase was correlated with the level of proteinuria, while COX-2 was correlated with interstitial inflammation and serum creatinine level in the disease group. Conclusion: Our data supported the implication of these target genes and pathways in the pathogenesis of FSGS. In addition, these genes can be considered as non-invasive biomarkers for FSGS.

Long term safety of targeted internalization of cell penetrating peptide crotamine into renal proximal tubular epithelial cells in vivo

Activated proximal tubular epithelial cells (PTECs) play a crucial role in progressive tubulo-interstitial fibrosis in native and transplanted kidneys. Targeting PTECs by non-viral delivery vectors might be useful to influence the expression of important genes and/or proteins in order to slow down renal function loss. However, no clinical therapies that specifically target PTECs are available at present. We earlier showed that a cationic cell penetrating peptide isolated from South American rattlesnake venom, named crotamine, recognizes cell surface heparan sulfate proteoglycans and accumulates in cells. In healthy mice, crotamine accumulates mainly in kidneys after intraperitoneal (ip) injection. Herein we demonstrate for the first time, the overall safety of acute or long-term treatment with daily ip administrated crotamine for kidneys functions. Accumulation of ip injected crotamine in the kidney brush border zone of PTECs, and its presence inside these cells were observed. In addition, significant lower in vitro crotamine binding, uptake and reporter gene transport and expression could be observed in syndecan-1 deficient HK-2 PTECs compared to wild-type cells, indicating that the absence of syndecan-1 impairs crotamine uptake into PTECs. Taken together, our present data show the safety of in vivo long-term treatment with crotamine, and its preferential uptake into PTECs, which are especially rich in HSPGs such as syndecan-1. In addition to the demonstrated in vitro gene delivery mediated by crotamine in HK-2 cells, the potential applicability of crotamine as prototypic non-viral (gene) delivery nanocarrier to modulate PTEC gene and/or protein expression was confirmed.

Novel Insights Into the Role of Glycans in the Pathophysiology of Glomerular Endotheliosis in Preeclampsia

The polysaccharide heparan sulfate is ubiquitously expressed as a proteoglycan in extracellular matrices and on cell surfaces. In the glomerular filtration barrier, the action of the heparan sulfate is directly related to the function of glomerular filtration, mostly attributed to the sulfated domains that occur along the polysaccharide chain, as evidenced by fact that release of fragments of heparan sulfate by heparanase significantly increases the permeability of albumin passage through the glomerular endothelium, event that originates proteinuria. This review aims to show the importance of the structural domains of heparan sulfate in the process of selective permeability and to demonstrate how these domains may be altered during the glomerular inflammation processes that occur in preeclampsia.

Intrarenal activation of adaptive immune effectors is associated with tubular damage and impaired renal function in lupus nephritis

Objectives

Chronic renal impairment remains a feared complication of lupus nephritis (LN). The present work aimed at identifying mechanisms and markers of disease severity in renal tissue samples from patients with LN.

Methods

We performed high-throughput transcriptomic studies (Illumina HumanHT-12 v4 Expression BeadChip) on archived kidney biopsies from 32 patients with LN and eight controls (pretransplant donors). Histological staging (glomerular and tubular scores) and immunohistochemistry experiments were performed on the same and on a replication set of 37 LN kidney biopsy samples.

Results

A group of LN samples was identified by unsupervised clustering studies based on their gene expression features, that is, the overexpression of transcripts involved in antigen presentation, T and B cell activation. These samples were characterised by a significantly lower estimated glomerular filtration rate (eGFR) at the time of biopsy (T0) compared with the other systemic lupus erythematosus samples. Yet, apparent disease duration at T0, double-stranded DNA antibody titres at T0 and other relevant characteristics (serum C3, proteinuria, histological scores, numbers of previous flares) were not different between groups.

Immunohistochemistry studies confirmed the association between interstitial infiltration by adaptive immune effectors and decreased renal function in the same and in a replication group of LN kidney biopsies. This was associated with transcriptomic, histological and immunohistochemical evidence of renal tubular cell involvement.

Conclusion

Interstitial infiltration of LN kidney biopsies by adaptive immune effectors is associated with impaired renal tubular cell function and decreased eGFR. These results open new perspectives in evaluating and treating patients with LN, focusing on intrarenal mechanisms of immune cell activation.

The bittersweet taste of tubulo-interstitial glycans

Recently, interesting work was published by Farrar et al. [1] showing the interaction of fucosylated glycoproteins on stressed tubular epithelial cells with collectin-11 leading to complement activation via the lectin route of complement. This elegant work stimulated us to evaluate the dark side (bittersweet taste) of tubulo-interstitial glycans in kidney tissue damage. As will be discussed, glycans not only initiate tubular complement activation but also orchestrate tubulo-interstitial leucocyte recruitment and growth factor responses. In this review we restrict ourselves to tubulo-interstitial damage mainly by proteinuria, ischaemia-reperfusion injury and transplantation, and we discuss the involvement of endothelial and tubular glycans in atypical and Escherichia coli-mediated haemolytic uraemic syndrome. As will be seen, fucosylated, mannosylated, galactosylated and sialylated oligosaccharide structures along with glycosaminoglycans comprise the most important glycans related to kidney injury pathways. Up to now, therapeutic interventions in these glycan-mediated injury pathways are underexplored and warrant further research.

Evaluation of TGF-β1 and MCP-1 expression and tubulointerstitial fibrosis in children with Henoch-Schönlein purpura nephritis and IgA nephropathy: A clinical correlation

OBJECTIVES:

Henoch-Schönlein purpura nephritis and immunoglobulin A nephropathy are two diseases with similar clinical presentations but very different prognoses. Transforming growth factor β1 and monocyte chemoattractant protein-1 have been associated with the development of tissue fibrosis. We examined the development of tubulointerstitial fibrosis and its relationship with Transforming growth factor β1 and monocyte chemoattractant protein-1 expression in these patients.

METHODS:

Renal tissue samples were collected by renal biopsy from 50 children with Henoch-Schönlein purpura nephritis and 50 children with immunoglobulin A nephropathy. Hematoxylin and eosin and Masson's trichrome-stained tissues were examined using light microscopy. Tubulointerstitial fibrosis was graded using the method described by Bohle et al. (1). The immunohistochemical detection of Transforming growth factor β1 and monocyte chemoattractant protein-1 expression was correlated with the tubulointerstitial fibrosis grade. Clinical Trial registration number: ZJCH-2012-0105.

RESULTS:

Transforming growth factor β1 and monocyte chemoattractant protein-1 expression in the renal tissues was significantly greater in the patients with immunoglobulin A nephropathy than in the patients with Henoch-Schönlein purpura nephritis (both p<0.001). The immunoglobulin A nephropathy patients had a higher tubulointerstitial fibrosis grade than the Henoch-Schönlein purpura nephritis patients (p<0.001). The tubulointerstitial fibrosis grade was in accordance with the Transforming growth factor β1 and monocyte chemoattractant protein-1 expression levels in both diseases (both p<0.001).

CONCLUSION:

Transforming growth factor β1 and monocyte chemoattractant protein-1 expression was associated with the development of immunoglobulin A nephropathy and Henoch-Schönlein purpura nephritis. Further studies are needed to better evaluate this association.

Toward Noninvasive Diagnosis of IgA Nephropathy: A Pilot Urinary Metabolomic and Proteomic Study

IgA nephropathy is diagnosed by renal biopsy, an invasive procedure with a risk of significant complications. Noninvasive approaches are needed for possible diagnostic purposes and especially for monitoring disease activity or responses to treatment. In this pilot project, we assessed the utility of urine samples as source of biomarkers of IgA nephropathy. We used spot urine specimens from 19 healthy controls, 11 patients with IgA nephropathy, and 8 renal-disease controls collected on day of renal biopsy. Urine samples were analyzed using untargeted metabolomic and targeted proteomic analyses by several experimental techniques: liquid chromatography coupled with mass spectrometry, immunomagnetic isolation of target proteins coupled with quantitation by mass spectrometry, and protein arrays. No single individual biomarker completely differentiated the three groups. Therefore, we tested the utility of several markers combined in a panel. Discriminant analysis revealed that combination of seven markers, three metabolites (dodecanal, 8-hydroxyguanosine, and leukotriene C₄), three proteins (α1-antitrypsin, IgA-uromodulin complex, and galactose-deficient IgA1), and heparan sulfate, differentiated patients with IgA nephropathy from patients with other renal diseases and healthy controls. Future studies are needed to validate these preliminary findings and to determine the power of these urinary markers for assessment of responses to therapy.

ADAM10 mediates the house dust mite-induced release of chemokine ligand CCL20 by airway epithelium

BACKGROUND

House dust mite (HDM) acts on the airway epithelium to induce airway inflammation in asthma. We previously showed that the ability of HDM to induce allergic sensitization in mice is related to airway epithelial CCL20 secretion.

OBJECTIVE

As a disintegrin and metalloprotease (ADAM)s have been implicated in chemokine shedding, we sought to determine their involvement in HDM-induced release of chemokines, including CCL20, by airway epithelial cells.

METHODS

We studied the effects of pharmacological ADAM inhibitors as well as ADAM10 and ADAM17 siRNA downregulation on chemokine release using (multiplex) ELISA in supernatants from HDM-exposed human bronchial epithelial 16HBE cells and primary normal human bronchial epithelial cells (NHBE) at 4-24 h.

RESULTS

House dust) mite markedly increased CCL20 levels in both 16HBE and NHBE cells (16-24 h). In 16HBE cells, the HDM-induced increase was observed as early as 4 h upon exposure and the use of specific inhibitors indicated the involvement of ADAM10/17-mediated shedding. siRNA knockdown of ADAM10, but not of ADAM17, significantly reduced the HDM-induced release of CCL20 in both 16HBE and NHBE cells. A similar effect was observed for HDM-induced CCL2, CCL5, and CXCL8 release in NHBE cells. The HDM-induced increase in CCL20 levels was not affected by protein synthesis inhibitor cycloheximide nor protein transport inhibitor monensin, indicating that HDM induces surface shedding of chemokines.

CONCLUSION

Our data show for the first time that ADAM10 activity contributes to HDM-induced shedding of chemokines, including CCL20. The ADAM10/CCL20 axis may be a target for novel therapeutic strategies in asthma.

Incipient renal transplant dysfunction associates with tubular syndecan-1 expression and shedding

Syndecan-1 is a transmembrane heparan sulfate proteoglycan involved in regenerative growth and cellular adhesion. We hypothesized that the induction of tubular syndecan-1 is a repair response to incipient renal damage in apparently stable, uncomplicated renal transplant recipients. We quantified tubular syndecan-1 in unselected renal protocol biopsies taken 1 yr after transplantation. Spearman rank correlation analysis revealed an inverse correlation between tubular syndecan-1 expression and creatinine clearance at the time of biopsy ( r = −0.483, P < 0.03). In a larger panel of protocol and indication biopsies from renal transplant recipients, tubular syndecan-1 correlated with tubular proliferation marker Ki67 ( r = 0.518, P < 0.0001). In a rat renal transplantation model, 2 mo after transplantation, mRNA expression of syndecan-1 and its major sheddase, A disintegrin and metalloproteinase-17, were upregulated (both P < 0.03). Since shed syndecan-1 might end up in the circulation, in a stable cross-sectional human renal transplant population ( n = 510), we measured plasma syndecan-1. By multivariate regression analysis, we showed robust independent associations of plasma syndecan-1 with renal (plasma creatinine and plasma urea) and endothelial function parameters (plasma VEGF-A, all P < 0.01). By various approaches, we were not able to localize syndecan-1 in vessel wall or endothelial cells, which makes shedding of syndecan-1 from the endothelial glycocalyx unlikely. Our data suggest that early damage in transplanted kidneys induces repair mechanisms within the graft, namely, tubular syndecan-1 expression for tubular regeneration and VEGF production for endothelial repair. Elevated plasma syndecan-1 levels in renal transplantation patients might be interpreted as repair/survival factor related to loss of tubular and endothelial function in transplanted kidneys.

Elevated Serum Levels of Syndecan-1 Are Associated with Renal Involvement in Patients with Systemic Lupus Erythematosus

Objective.

Syndecan-1 (SDC-1) is a major constituent of the endothelial glycocalyx, which plays a role in maintaining vascular homeostasis and functions as a glomerular filtration barrier. SDC-1 is readily shed into the blood under various conditions, but the clinical implication of circulating SDC-1 in patients with systemic lupus erythematosus (SLE) remains unclear. We aimed to investigate the association of serum SDC-1 level with certain clinical manifestations of SLE.

Methods.

We measured serum SDC-1 levels by ELISA in 111 patients with SLE, 18 with rheumatoid arthritis (RA), and 20 healthy subjects, and investigated its association with clinical manifestations and laboratory variables.

Results.

Serum SDC-1 levels were higher in patients with SLE than in those with RA and healthy controls (both p < 0.001) and were positively correlated with SLE Disease Activity Index (SLEDAI; r = 0.367, p < 0.001) and anti-dsDNA antibody level (r = 0.259, p = 0.007), but inversely correlated with serum C3 and CH50 levels (r = −0.305, p = 0.001 and r = −0.244, p = 0.012). Patients with active nephritis had higher serum SDC-1 levels than patients with inactive nephritis and those without nephritis (both p < 0.001). In addition, serum SDC-1 levels were correlated with renal SLEDAI score (r = 0.540, p < 0.001) and excretion of proteinuria as measured by spot urine protein/creatinine ratio (r = 0.538, p < 0.001). In 14 patients with lupus nephritis (LN) whose serum samples were obtained at the time of renal biopsy, there was a positive correlation between serum SDC-1 levels and activity index (r = 0.632, p = 0.015).

Conclusion.

Serum SDC-1 levels are increased in SLE patients with nephritis, indicating that SDC-1 might be a useful serum biomarker for active LN.

Serum-free culture of rat proximal tubule cells with enhanced function on chitosan

The proximal tubule performs a variety of important renal functions and is the major site for nutrient reabsorption. The purpose of this study is to culture rat renal proximal tubule cells (PTCs) on chitosan without serum to maintain a transcellular pathway to transport water and ions effectively without loss of highly differentiated cell function. The effect of chitosan, which is structurally similar to glycosaminoglycans, in the absence of serum on the primary cultured PTCs was compared that of collagen with or without serum. Two days after seeding, more tubule fragments and higher PTC viability were observed on chitosan than on collagen with or without serum. Proliferation marker Ki-67 immunostaining and phosphorylated extracellular-regulated kinase (ERK) expression results displayed similar proliferation capability of PTCs established on chitosan without serum and collagen with 2% fetal bovine serum after 4 days of incubation. When grown to confluence, PTCs formed a monolayer with well-organized tight junctions and formation of domes on chitosan without serum. Moreover, evaluation of the transepithelial electrical resistance showed that both chitosan and serum were involved in the modification of water and ion transport in confluent cells. By showing the direct suppression of PTC growth and dome formation treated with heparinase, we demonstrated that the interaction between cell surface heparin sulfate proteoglycan and chitosan played an important role in PTC proliferation and differentiation. A successful primary culture of PTCs has now been produced on chitosan in serum-free culture condition, which offers potential applications for chitosan in renal tissue engineering.

Effect of castration on renal glycosaminoglycans and their urinary excretion in male and female rats with chronic renal failure

Glycosaminoglycans (GAGs) participate in a variety of processes in the kidney, and evidence suggests that gender-related hormones participate in renal function. The aim of this study was to analyze the relationship of GAGs, gender, and proteinuria in male and female rats with chronic renal failure (CRF). GAGs were analyzed in total kidney tissue and 24-h urine of castrated (c), male (M), and female (F) Wistar control (C) rats (CM, CMc, CF, CFc) and after 30 days of CRF induced by 5/6 nephrectomy (CRFM, CRFMc, CRFF, CRFFc). Total GAG quantification and composition were determined using agarose and polyacrylamide gel electrophoresis, respectively. Renal GAGs were higher in CF compared to CM. CRFM presented an increase in renal GAGs, heparan sulfate (HS), and proteinuria, while castration reduced these parameters. However, CRFF and CRFFc groups showed a decrease in renal GAGs concomitant with an increase in proteinuria. Our results suggest that, in CRFM, sex hormones quantitatively alter GAGs, mainly HS, and possibly the glomerular filtration barrier, leading to proteinuria. The lack of this response in CRFMc, where HS did not increase, corroborates this theory. This pattern was not observed in females. Further studies of CRF are needed to clarify gender-dependent differences in HS synthesis.

Reduced sulfation of chondroitin sulfate but not heparan sulfate in kidneys of diabetic db/db mice

Heparan sulfate proteoglycans are hypothesized to contribute to the filtration barrier in kidney glomeruli and the glycocalyx of endothelial cells. To investigate potential changes in proteoglycans in diabetic kidney, we isolated glycosaminoglycans from kidney cortex from healthy db/+ and diabetic db/db mice. Disaccharide analysis of chondroitin sulfate revealed a significant decrease in the 4-O-sulfated disaccharides (D0a4) from 65% to 40%, whereas 6-O-sulfated disaccharides (D0a6) were reduced from 11% to 6%, with a corresponding increase in unsulfated disaccharides. In contrast, no structural differences were observed in heparan sulfate. Furthermore, no difference was found in the molar amount of glycosaminoglycans, or in the ratio of hyaluronan/heparan sulfate/chondroitin sulfate. Immunohistochemical staining for the heparan sulfate proteoglycan perlecan was similar in both types of material but reduced staining of 4-O-sulfated chondroitin and dermatan was observed in kidney sections from diabetic mice. In support of this, using qRT-PCR, a 53.5% decrease in the expression level of Chst-11 (chondroitin 4-O sulfotransferase) was demonstrated in diabetic kidney. These results suggest that changes in the sulfation of chondroitin need to be addressed in future studies on proteoglycans and kidney function in diabetes.

Heparan sulfate proteoglycans in the control of B cell development and the pathogenesis of multiple myeloma

Heparan sulfate proteoglycans (HSPGs) have essential functions during embryonic development and throughout postnatal life. To exert these functions, they undergo a series of processing reactions by heparan-sulfate-modifying enzymes (HSMEs), which endows them with highly modified heparan sulfate (HS) domains that provide specific docking sites for a large number of bioactive molecules. The development and antigen-dependent differentiation of normal B lymphocytes, as well as the growth and progression of B-lineage malignancies, are orchestrated by an array of growth factors, cytokines and chemokines many of which display HS binding. As discussed in this review, tightly regulated HSPG expression is a requirement for normal B cell maturation, differentiation and function. In addition, the HSPG syndecan-1 functions as a versatile co-receptor for signals from the bone marrow microenvironment, essential for the survival of long-lived plasma cells and multiple myeloma (MM) plasma cells. Targeting of HSMEs or HS chains on MM cells increases their sensitivity to drugs currently used in MM treatment, including bortezomib, lenalidomide or dexamethasone. Taken together, these findings render the HS biosynthetic machinery a promising target for MM treatment.

Role of glomerular proteoglycans in IgA nephropathy

Mesangial matrix expansion is a prominent feature of the most common form of glomerulonephritis, IgA nephropathy (IgAN). To find molecular markers and improve the understanding of the disease, the gene and protein expression of proteoglycans were investigated in biopsies from IgAN patients and correlated to clinical and morphological data. We collected and microdissected renal biopsies from IgAN patients (n = 19) and from healthy kidney donors (n = 14). Patients were followed for an average time of 4 years and blood pressure was according to target guidelines. Distinct patterns of gene expression were seen in glomerular and tubulo-interstitial cells. Three of the proteoglycans investigated were found to be of special interest and upregulated in glomeruli: perlecan, decorin and biglycan. Perlecan gene expression negatively correlated to albumin excretion and progress of the disease. Abundant decorin protein expression was found in sclerotic glomeruli, but not in unaffected glomeruli from IgAN patients or in controls. Transforming growth factor beta (TGF-β), known to interact with perlecan, decorin and biglycan, were upregulated both on gene and protein level in the glomeruli. This study provides further insight into the molecular mechanisms involved in mesangial matrix expansion in IgAN. We conclude that perlecan is a possible prognostic marker for patients with IgAN. In addition, the up-regulation of biglycan and decorin, as well as TGF-β itself, indicate that regulation of TGF-β, and other profibrotic markers plays a role in IgAN pathology.

Identification of tubular heparan sulfate as a docking platform for the alternative complement component properdin in proteinuric renal disease

Properdin binds to proximal tubular epithelial cells (PTEC) and activates the complement system via the alternative pathway in vitro. Cellular ligands for properdin in the kidney have not yet been identified. Because properdin interacts with solid-phase heparin, we investigated whether heparan sulfate proteoglycans (HSPG) could be the physiological ligands of properdin. Kidneys from proteinuric rats showed colocalization of syndecan-1, a major epithelial HSPG, and properdin in the apical membranes of PTEC, which was not seen in control renal tissue. In vitro, PTEC did not constitutively express properdin. However, exogenous properdin binds to these cells in a dose-dependent fashion. Properdin binding was prevented by heparitinase pretreatment of the cells and was dose-dependently inhibited by exogenous heparin. ELISA and surface plasmon resonance spectroscopy (BIAcore) showed a strong dose-dependent interaction between heparan sulfate (HS) and properdin (K(d) = 128 nm). Pretreatment of HSPG with heparitinase abolished this interaction in ELISA. Competition assays, using a library of HS-like polysaccharides, showed that sulfation pattern, chain length, and backbone composition determine the interaction of properdin with glycosaminoglycans. Interestingly, two nonanticoagulant heparin derivatives inhibited properdin-HS interaction in ELISA and BIAcore. Incubation of PTEC with human serum as complement source led to complement activation and deposition of C3 on the cells. This C3 deposition is dependent on the binding of properdin to HS as shown by heparitinase pretreatment of the cells. Our data identify tubular HS as a novel docking platform for alternative pathway activation via properdin, which might play a role in proteinuric renal damage. Our study also suggests nonanticoagulant heparinoids may provide renoprotection in complement-dependent renal diseases.

Preclinical and clinical evidence of nephro- and cardiovascular protective effects of glycosaminoglycans

Despite advances in pharmacological treatment, diabetic nephropathy is still the leading cause of end-stage renal disease and an important cause of morbidity and mortality in diabetics. Glycosaminoglycans are long, unbranched mucopolysaccharides that play an important role in establishing a charge-selective barrier that restricts the passage of negatively charged molecules, such as albumin and other proteins, at the level of the glomerular basal membrane. Their loss is associated with loss of selectivity and proteinuria. Extensive preclinical evidence and some clinical trials suggest that glycosaminoglycans replacement is associated with improvement of glomerular selectivity and of proteinuria. Sulodexide could also have some other effects, potentially useful to reduce the renal damage and the cardiovascular disease associated with proteinuria, such as improvement of haemorheological and blood lipid parameters, an endothelium protective effect and anti-inflammatory action. This review will discuss the evidence supporting the potential nephroprotective effects of sulodexide and other glycosaminoglycans.

Nephroprotective action of glycosaminoglycans: why the pharmacological properties of sulodexide might be reconsidered

A relatively large body of evidence supports the notion that glomerular capillary wall and mesangial alterations in diabetic nephropathy involve biochemical alterations of glycoproteins in these structures. Evidence in experimental animals rendered diabetic reveals that the administration of heparin and other anionic glycoproteins can effectively prevent the biochemical alterations that promote albuminuria. Moreover, angiotensin II inhibits heparan sulfate synthesis, while heparins modulate angiotensin II signaling in glomerular cells, inhibiting aldosterone synthesis and lowering proteinuria in diabetes patients. Sulodexide, a mixture of heparin and dermatan sulfate, appears to be a promising treatment for diabetic proteinuria partially resistant to renin-angiotensin system blocking agents. Sulodexide prevents heparan sulfate degradation, thus allowing reconstruction of heparan sulfate content and restoration of glomerular basement membrane ionic permselectivity. The antiproteinuric effect appears to be mainly related to the basal proteinuria and consequently to the duration of treatment in a relatively large number of small clinical trials. On the other hand, several sulodexide pharmacodynamic properties could improve the prognosis of chronic kidney disease patients, also independently from its antiproteinuric effect. However, sulodexide development as an antiproteinuric drug needs to be continued, in order to define which kind of patients could better respond to this treatment.

Differential expression of proteoglycans in tissue remodeling and lymphangiogenesis after experimental renal transplantation in rats

Background

Chronic transplant dysfunction explains the majority of late renal allograft loss and is accompanied by extensive tissue remodeling leading to transplant vasculopathy, glomerulosclerosis and interstitial fibrosis. Matrix proteoglycans mediate cell-cell and cell-matrix interactions and play key roles in tissue remodeling. The aim of this study was to characterize differential heparan sulfate proteoglycan and chondroitin sulfate proteoglycan expression in transplant vasculopathy, glomerulosclerosis and interstitial fibrosis in renal allografts with chronic transplant dysfunction.

Methods

Renal allografts were transplanted in the Dark Agouti-to-Wistar Furth rat strain combination. Dark Agouti-to-Dark Agouti isografts and non-transplanted Dark Agouti kidneys served as controls. Allograft and isograft recipients were sacrificed 66 and 81 days (mean) after transplantation, respectively. Heparan sulfate proteoglycan (collXVIII, perlecan and agrin) and chondroitin sulfate proteoglycan (versican) expression, as well as CD31 and LYVE-1 (vascular and lymphatic endothelium, respectively) expression were (semi-) quantitatively analyzed using immunofluorescence.

Findings

Arteries with transplant vasculopathy and sclerotic glomeruli in allografts displayed pronounced neo-expression of collXVIII and perlecan. In contrast, in interstitial fibrosis expression of the chondroitin sulfate proteoglycan versican dominated. In the cortical tubular basement membranes in both iso- and allografts, induction of collXVIII was detected. Allografts presented extensive lymphangiogenesis (p<0.01 compared to isografts and non-transplanted controls), which was associated with induced perlecan expression underneath the lymphatic endothelium (p<0.05 and p<0.01 compared to isografts and non-transplanted controls, respectively). Both the magnitude of lymphangiogenesis and perlecan expression correlated with severity of interstitial fibrosis and impaired graft function.

Interpretation

Our results reveal that changes in the extent of expression and the type of proteoglycans being expressed are tightly associated with tissue remodeling after renal transplantation. Therefore, proteoglycans might be potential targets for clinical intervention in renal chronic transplant dysfunction.