OBJECTIVES: IgA nephropathy (IgAN) is thought to involve an autoimmune process wherein galactose-deficient IgA1 (Gd-IgA1), recognized as autoantigen by autoantibodies, forms pathogenic immune complexes. Mounting evidence has implicated abnormal activation of some protein-tyrosine kinases (PTKs) in IgAN. Furthermore, genome-wide association studies (GWAS) of IgAN provided insight into disease pathobiology and genetics. A GWAS locus on chromosome 22q12 contains genes encoding leukemia inhibitory factor (LIF) and oncostatin M, interleukin (IL)-6-related cytokines implicated in mucosal immunity and inflammation. We have previously shown that IL-6 mediates overproduction of Gd-IgA1 through aberrant STAT3 activation. Here, we show that LIF enhanced production of Gd-IgA1 in IgA1-secreting cells of patients with IgAN and provide initial analyses of LIF signaling. METHODS: We characterized LIF signaling that is involved in the overproduction of Gd-IgA1, using IgA1-secreting cell lines derived from peripheral blood of patients with IgAN and healthy controls (HC). We used global PTK activity profiling, immunoblotting, lectin ELISA, and siRNA knock-down. RESULTS: LIF stimulation did not significantly affect production of total IgA1 in IgA1-secreting cells from patients with IgAN or HC. However, LIF increased production of Gd-IgA1, but only in the cells from patients with IgAN. LIF stimulation enhanced phosphorylation of STAT1 in IgA1-secreting cells from patients with IgAN to a higher degree than in the cells from HC. siRNA knock-down of STAT1 blocked LIF-mediated overproduction of Gd-IgA1. Unexpectedly, this abnormal phosphorylation of STAT1 in IgA1-secreting cells from patients with IgAN was not mediated by JAK, but rather involved activation of Src-family PTKs (SFKs). CONCLUSION: Abnormal LIF/STAT1 signaling represents another pathway potentially leading to overproduction of Gd-IgA1 in IgAN, providing possible explanation for the phenotype associated with chromosome 22q12 GWAS locus. Abnormal LIF/STAT1 signaling and the associated SFKs may represent potential diagnostic and/or therapeutic targets in IgAN.

• Klíčová slova
• Aberrant O-glycosylation, Autoantigen, IgA nephropathy, Leukemia inhibitory factor, O-glycans,
• Publikační typ
• časopisecké články MeSH

BACKGROUND: IgA nephropathy (IgAN), the most common primary glomerulonephritis worldwide, has serious outcomes with end-stage renal disease developing in 30-50% of patients. The diagnosis requires renal biopsy. Due to its inherent risks, non-invasive approaches are needed. METHODS: We evaluated 91 Czech patients with biopsy-proven IgAN who were assessed at time of diagnosis for estimated glomerular filtration rate (eGFR), proteinuria, microscopic hematuria, and hypertension, and then followed prospectively. Serum samples collected at diagnosis were analyzed for galactose-deficient IgA1 (Gd-IgA1) using new native-IgA1 and established neuraminidase-treated-IgA1 tests, Gd-IgA1-specific IgG autoantibodies, discriminant analysis and logistic regression model assessed correlations with renal function and Oxford classification (MEST score). RESULTS: Serum levels of native (P <0.005) and neuraminidase-treated (P <0.005) Gd-IgA1 were associated with the rate of eGFR decline. A higher relative degree of galactose deficiency in native serum IgA1 predicted a faster eGFR decline and poor renal survival (P <0.005). However, Gd-IgA1 has not differentiated patients with low vs. high baseline eGFR. Furthermore, patients with high baseline eGFR that was maintained during follow-up were characterized by low serum levels of Gd-IgA1-specific IgG autoantibodies (P = 0.003). CONCLUSIONS: Including levels of native and neuraminidase-treated Gd-IgA1 and Gd-IgA1-specific autoantibodies at diagnosis may aid in the prognostication of disease progression in Czech patients with IgAN. Future tests will assess utility of these biomarkers in larger patients cohorts from geographically distinct areas.

• MeSH
• autoprotilátky krev   imunologie   MeSH
• biologické markery krev   MeSH
• dospělí MeSH
• galaktosa krev   imunologie   MeSH
• IgA nefropatie krev   diagnóza   imunologie   mortalita   MeSH
• imunoglobulin A krev   imunologie   MeSH
• lidé MeSH
• následné studie MeSH
• progrese nemoci MeSH
• prospektivní studie MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• klinické zkoušky MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• autoprotilátky MeSH
• biologické markery MeSH
• galaktosa MeSH
• imunoglobulin A MeSH

INTRODUCTION: IgA nephropathy is a chronic renal disease characterized by mesangial immunodeposits that contain autoantigen, which is aberrantly glycosylated IgA1 with some hinge-region O-glycans deficient in galactose. Macroscopic hematuria during an upper respiratory tract infection is common among patients with IgA nephropathy, which suggests a connection between inflammation and disease activity. Interleukin-6 (IL-6) is an inflammatory cytokine involved in IgA immune response. We previously showed that IL-6 selectively increases production of galactose-deficient IgA1 in IgA1-secreting cells from patients with IgA nephropathy. METHODS: We characterized IL-6 signaling pathways involved in the overproduction of galactose-deficient IgA1. To understand molecular mechanisms, IL-6 signaling was analyzed by kinomic activity profiling and Western blotting, followed by confirmation assays using siRNA knock-down and small-molecule inhibitors. RESULTS: STAT3 was differentially activated by IL-6 in IgA1-secreting cells from patients with IgA nephropathy compared with those from healthy control subjects. Specifically, IL-6 induced enhanced and prolonged phosphorylation of STAT3 in the cells from patients with IgA nephropathy, which resulted in overproduction of galactose-deficient IgA1. This IL-6-mediated overproduction of galactose-deficient IgA1 could be blocked by small molecule inhibitors of JAK/STAT signaling. DISCUSSION: Our results revealed that IL-6-induced aberrant activation of STAT3-mediated overproduction of galactose-deficient IgA1. STAT3 signaling pathway may thus represent a new target for disease-specific therapy of IgA nephropathy.

• Klíčová slova
• IgA nephropathy, IgA1, O-glycans, aberrant glycosylation, autoantigen,
• Publikační typ
• časopisecké články MeSH

Autoantibodies against galactose-deficient IgA1 drive formation of pathogenic immune complexes in IgA nephropathy. IgG autoantibodies against galactose-deficient IgA1 in patients with IgA nephropathy have a specific amino-acid sequence, Y1CS3, in the complementarity-determining region 3 of the heavy chain variable region compared with a Y1CA3 sequence in similar isotype-matched IgG from healthy controls. We previously found that the S3 residue is critical for binding galactose-deficient IgA1. To determine whether this difference is due to a rare germline sequence, we amplified and sequenced the corresponding germline variable region genes from peripheral blood mononuclear cells of seven patients with IgA nephropathy and six healthy controls from whom we had cloned single-cell lines secreting monoclonal IgG specific for galactose-deficient IgA1. Sanger DNA sequencing revealed that complementarity-determining region 3 in the variable region of the germline genes encoded the Y1C(A/V)3 amino-acid sequence. Thus, the A/V>S substitution in the complementarity-determining region 3 of anti-galactose-deficient-IgA1 autoantibodies of the patients with IgA nephropathy is not a rare germline gene variant. Modeling analyses indicated that the S3 hydroxyl group spans the complementarity-determining region 3 loop stem, stabilizing the adjacent β-sheet and stem structure, important features for effective binding to galactose-deficient IgA1. Understanding processes leading to production of the autoantibodies may offer new approaches to treat IgA nephropathy.

• Klíčová slova
• IgA nephropathy, immune complexes, immunology,
• MeSH
• autoprotilátky genetika   MeSH
• galaktosa nedostatek   MeSH
• IgA nefropatie enzymologie   genetika   imunologie   MeSH
• imunoglobulin A * MeSH
• lidé MeSH
• mutace * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• autoprotilátky MeSH
• galaktosa MeSH
• imunoglobulin A * MeSH

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.

• MeSH
• aldehydy moč   MeSH
• alfa-1-antitrypsin moč   MeSH
• biologické markery moč   MeSH
• dospělí MeSH
• guanosin analogy a deriváty   moč   MeSH
• heparitinsulfát moč   MeSH
• IgA nefropatie patologie   moč   MeSH
• imunoglobulin A moč   MeSH
• leukotrien C4 moč   MeSH
• lidé středního věku MeSH
• lidé MeSH
• metabolom * MeSH
• proteom * MeSH
• senioři MeSH
• studie případů a kontrol MeSH
• uromodulin moč   MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• 8-hydroxyguanosine MeSH Prohlížeč
• aldehydy MeSH
• alfa-1-antitrypsin MeSH
• biologické markery MeSH
• guanosin MeSH
• heparitinsulfát MeSH
• imunoglobulin A MeSH
• leukotrien C4 MeSH
• proteom * MeSH
• uromodulin MeSH

We have summarized the latest findings on markers for progression of immunoglobulin A (IgA) nephropathy (IgAN), the most common primary glomerulonephritis with a high prevalence among end-stage renal disease (ESRD) patients. The clinical predictors of renal outcome in IgAN nephropathy, such as proteinuria, hypertension, and decreased estimated glomerular filtration rate (eGFR) at the time of the diagnosis, are well known. The Oxford classification of IgAN identified four types of histological lesions (known as the MEST score) associated with the development of ESRD and/or a 50 % reduction in eGFR. In addition, the role of genetic risk factors associated with IgAN is being elucidated by genome-wide association studies, with multiple risk alleles described. Recently, biomarkers in serum (galactose-deficient IgA1, IgA/IgG autoantibodies against galactose-deficient IgA1, and soluble CD 89-IgA complexes) and urine (soluble transferrin receptor, interleukin-6/epidermal growth factor ratio, fractalkine, laminin G-like 3 peptide, κ light chains, and mannan-binding lectin) have been identified. Some of these biomarkers may represent candidates for the development of noninvasive diagnostic tests, that would be useful for detection of subclinical disease activity, monitoring disease progression, assessment of treatment, and at the same time circumventing the complications associated with renal biopsies. These advances, along with future disease-specific therapy, will be helpful in improving the treatment effectiveness, prognosis, and the quality of life in connection with IgAN.

• Klíčová slova
• Biomarkers, End-stage renal disease, IgA nephropathy, Renal biopsy,
• MeSH
• biologické markery analýza   MeSH
• biopsie MeSH
• chronické selhání ledvin etiologie   MeSH
• IgA nefropatie komplikace   diagnóza   MeSH
• ledviny metabolismus   MeSH
• lidé MeSH
• prognóza MeSH
• progrese nemoci MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• biologické markery MeSH

IgA nephropathy (IgAN) is the most common primary glomerulonephritis, frequently leading to end-stage renal disease, as there is no disease-specific therapy. IgAN is diagnosed from pathological assessment of a renal biopsy specimen based on predominant or codominant IgA-containing immunodeposits, usually with complement C3 co-deposits and with variable presence of IgG and/or IgM. The IgA in these renal deposits is galactose-deficient IgA1, with less than a full complement of galactose residues on the O-glycans in the hinge region of the heavy chains. Research from the past decade led to the definition of IgAN as an autoimmune disease with a multi-hit pathogenetic process with contributing genetic and environmental components. In this process, circulating galactose-deficient IgA1 (autoantigen) is bound by antiglycan IgG or IgA (autoantibodies) to form immune complexes. Some of these circulating complexes deposit in glomeruli, and thereby activate mesangial cells and induce renal injury through cellular proliferation and overproduction of extracellular matrix components and cytokines/chemokines. Glycosylation pathways associated with production of the autoantigen and the unique characteristics of the corresponding autoantibodies in patients with IgAN have been uncovered. Complement likely plays a significant role in the formation and the nephritogenic activities of these complexes. Complement activation is mediated through the alternative and lectin pathways and probably occurs systemically on IgA1-containing circulating immune complexes as well as locally in glomeruli. Incidence of IgAN varies greatly by geographical location; the disease is rare in central Africa but accounts for up to 40% of native-kidney biopsies in eastern Asia. Some of this variation may be explained by genetically determined influences on the pathogenesis of the disease. Genome-wide association studies to date have identified several loci associated with IgAN. Some of these loci are associated with the increased prevalence of IgAN, whereas others, such as deletion of complement factor H-related genes 1 and 3, are protective against the disease. Understanding the molecular mechanisms and genetic and biochemical factors involved in formation and activities of pathogenic IgA1-containing immune complexes will enable the development of future disease-specific therapies as well as identification of non-invasive disease-specific biomarkers.

• Klíčová slova
• IgA, autoantibodies, complement C3, immune complexes, nephropathy,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH