| 1. |
- Al-Rabadi, Laith Farah, et al.
(författare)
-
Serine Protease HTRA1 as a Novel Target Antigen in Primary Membranous Nephropathy
- 2021
-
Ingår i: Journal of the American Society of Nephrology. - : American Society of Nephrology (ASN). - 1046-6673 .- 1533-3450. ; 32:7, s. 1666-1681
-
Tidskriftsartikel (refereegranskat)abstract
- Background Identification of target antigens PLA2R, THSD7A, NELL1, or Semaphorin-3B can explain the majority of cases of primary membranous nephropathy (MN). However, target antigens remain unidentified in 15%-20% of patients. Methods A multipronged approach, using traditional and modern technologies, converged on a novel target antigen, and capitalized on the temporal variation in autoantibody titer for biomarker discovery. Immunoblotting of human glomerular proteins followed by differential immunoprecipitation and mass spectrometric analysis was complemented by laser-capture microdissection followed by mass spectrometry, elution of immune complexes from renal biopsy specimen tissue, and autoimmune profiling on a protein fragment microarray. Results These approaches identified serine protease HTRA1 as a novel podocyte antigen in a subset of patients with primary MN. Sera from two patients reacted by immunoblotting with a 51-kD protein within glomerular extract and with recombinant human HTRA1, under reducing and nonreducing conditions. Longitudinal serum samples from these patients seemed to correlate with clinical disease activity. As in PLA2R- and THSD7A- associated MN, anti-HTRA1 antibodies were predominantly IgG4, suggesting a primary etiology. Analysis of sera collected during active disease versus remission on protein fragment microarrays detected significantly higher titers of anti-HTRA1 antibody in active disease. HTRA1 was specifically detected within immune deposits of HTRA1-associated MN in 14 patients identified among three cohorts. Screening of 118 "quadruple-negative" (PLA2R-, THSD7A-, NELL1-, EXT2-negative) patients in a large repository of MN biopsy specimens revealed a prevalence of 4.2%. Conclusions Conventional and more modern techniques converged to identify serine protease HTRA1 as a target antigen in MN.
|
|
| 2. |
- Bergling, Karin, et al.
(författare)
-
Phloretin Improves Ultrafiltration and Reduces Glucose Absorption during Peritoneal Dialysis in Rats
- 2022
-
Ingår i: Journal of the American Society of Nephrology. - 1046-6673. ; 33:10, s. 1857-1863
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Harmful glucose exposure and absorption remain major limitations of peritoneal dialysis. We previously showed that inhibition of sodium glucose cotransporter 2 did not affect glucose transport during peritoneal dialysis in rats. However, more recently we found that phlorizin, a dual blocker of sodium glucose co-transporter 1 and 2, reduces glucose diffusion in peritoneal dialysis. Therefore, either inhibiting sodium glucose co-transporter 1 or blocking facilitative glucose channels by phlorizin metabolite phloretin would reduce glucose transport in peritoneal dialysis. Methods: We tested a selective blocker of sodium glucose co-transporter 1, mizagliflozin, as well as phloretin, a non-selective blocker of facilitative glucose channels, in an anesthetized Sprague-Dawley rat model of peritoneal dialysis. Results: Intraperitoneal phloretin treatment reduced glucose absorption by more than 30% and resulted in a more than 50% higher ultrafiltration rate compared to control animals. Sodium removal and sodium clearances were similarly improved, whereas the amount of ultrafiltration per mmol sodium removed did not differ. Mizagliflozin did not influence glucose transport or osmotic water transport. Conclusions: Taken together, our present and previous results indicate that blockers of facilitative glucose channels may be a promising target for reducing glucose absorption and improving ultrafiltration efficiency in peritoneal dialysis.
|
|
| 3. |
- Boi, Roberto, et al.
(författare)
-
Podocyte Geranylgeranyl Transferase Type-I Is Essential for Maintenance of the Glomerular Filtration Barrier
- 2023
-
Ingår i: Journal of the American Society of Nephrology. - : Ovid Technologies (Wolters Kluwer Health). - 1046-6673 .- 1533-3450. ; 34:4, s. 641-655
-
Tidskriftsartikel (refereegranskat)abstract
- Significance StatementA tightly regulated actin cytoskeleton attained through balanced activity of RhoGTPases is crucial to maintaining podocyte function. However, how RhoGTPases are regulated by geranylgeranylation, a post-translational modification, has been unexplored. The authors found that loss of the geranylgeranylation enzyme geranylgeranyl transferase type-I (GGTase-I) in podocytes led to progressive albuminuria and foot process effacement in podocyte-specific GGTase-I knockout mice. In cultured podocytes, the absence of geranylgeranylation resulted in altered activity of its downstream substrates Rac1, RhoA, Cdc42, and Rap1, leading to alterations of & beta;1-integrins and actin cytoskeleton structural changes. These findings highlight the importance of geranylgeranylation in the dynamic management of RhoGTPases and Rap1 to control podocyte function, providing new knowledge about podocyte biology and glomerular filtration barrier function.BackgroundImpairment of the glomerular filtration barrier is in part attributed to podocyte foot process effacement (FPE), entailing disruption of the actin cytoskeleton and the slit diaphragm. Maintenance of the actin cytoskeleton, which contains a complex signaling network through its connections to slit diaphragm and focal adhesion proteins, is thus considered crucial to preserving podocyte structure and function. A dynamic yet tightly regulated cytoskeleton is attained through balanced activity of RhoGTPases. Most RhoGTPases are post-translationally modified by the enzyme geranylgeranyl transferase type-I (GGTase-I). Although geranylgeranylation has been shown to regulate activities of RhoGTPases and RasGTPase Rap1, its significance in podocytes is unknown.MethodsWe used immunofluorescence to localize GGTase-I, which was expressed mainly by podocytes in the glomeruli. To define geranylgeranylation's role in podocytes, we generated podocyte-specific GGTase-I knockout mice. We used transmission electron microscopy to evaluate FPE and measurements of urinary albumin excretion to analyze filtration barrier function. Geranylgeranylation's effects on RhoGTPases and Rap1 function were studied in vitro by knockdown or inhibition of GGTase-I. We used immunocytochemistry to study structural modifications of the actin cytoskeleton and & beta;1 integrins.ResultsDepletion of GGTase-I in podocytes in vivo resulted in FPE and concomitant early-onset progressive albuminuria. A reduction of GGTase-I activity in cultured podocytes disrupted RhoGTPase balance by markedly increasing activity of RhoA, Rac1, and Cdc42 together with Rap1, resulting in dysregulation of the actin cytoskeleton and altered distribution of & beta;1 integrins.ConclusionsThese findings indicate that geranylgeranylation is of crucial importance for the maintenance of the delicate equilibrium of RhoGTPases and Rap1 in podocytes and consequently for the maintenance of glomerular integrity and function. A tightly regulated actin cytoskeleton attained through balanced activity of RhoGTPases is crucial to maintaining podocyte function. However, how RhoGTPases are regulated by geranylgeranylation, a post-translational modification, has been unexplored. The authors found that loss of the geranylgeranylation enzyme geranylgeranyl transferase type-I (GGTase-I) in podocytes led to progressive albuminuria and foot process effacement in podocyte-specific GGTase-I knockout mice. In cultured podocytes, the absence of geranylgeranylation resulted in altered activity of its downstream substrates Rac1, RhoA, Cdc42, and Rap1, leading to alterations of & beta;1-integrins and actin cytoskeleton structural changes. These findings highlight the importance of geranylgeranylation in the dynamic management of RhoGTPases and Rap1 to control podocyte function, providing new knowledge about podocyte biology and glomerular filtration barrier function.
|
|
| 4. |
- Butt, Linus, et al.
(författare)
-
Super-Resolution Imaging of the Filtration Barrier Suggests a Role for Podocin R229Q in Genetic Predisposition to Glomerular Disease
- 2021
-
Ingår i: Journal of the American Society of Nephrology. - : Wolters Kluwer. - 1046-6673 .- 1533-3450. ; 33:1, s. 138-154
-
Tidskriftsartikel (refereegranskat)abstract
- Significance Statement Podocin R229Q results from the most frequent missense variant in NPHS2, and its association with FSGS when podocin R229Q is transassociated with a second mutation in NPHS2 is well recognized. However, because results from observational studies are ambiguous and appropriate animal studies are lacking, its isolated pathogenic potency is not entirely clear. In this study, the authors introduced this genetic alteration in mice and assessed the phenotype using super-resolution microscopy and albuminuria measurements. They demonstrated a deleterious effect of the variant on podocyte morphology and on the integrity of the glomerular filtration barrier under basal conditions and after external glomerular injury. Because this finding suggests that this mutation confers a genetic predisposition to glomerular disease, it has implications for a large number of carriers worldwide.Background Diseases of the kidney’s glomerular filtration barrier are a leading cause of end stage renal failure. Despite a growing understanding of genes involved in glomerular disorders in children, the vast majority of adult patients lack a clear genetic diagnosis. The protein podocin p.R229Q, which results from the most common missense variant in NPHS2, is enriched in cohorts of patients with FSGS. However, p.R229Q has been proposed to cause disease only when transassociated with specific additional genetic alterations, and population-based epidemiologic studies on its association with albuminuria yielded ambiguous results.Methods To test whether podocin p.R229Q may also predispose to the complex disease pathogenesis in adults, we introduced the exact genetic alteration in mice using CRISPR/Cas9-based genome editing (PodR231Q). We assessed the phenotype using super-resolution microscopy and albuminuria measurements and evaluated the stability of the mutant protein in cell culture experiments.Results Heterozygous PodR231Q/wild-type mice did not present any overt kidney disease or proteinuria. However, homozygous PodR231Q/R231Q mice developed increased levels of albuminuria with age, and super-resolution microscopy revealed preceding ultrastructural morphologic alterations that were recently linked to disease predisposition. When injected with nephrotoxic serum to induce glomerular injury, heterozygous PodR231Q/wild-type mice showed a more severe course of disease compared with Podwild-type/wild-type mice. Podocin protein levels were decreased in PodR231Q/wild-type and PodR231Q/R231Q mice as well as in human cultured podocytes expressing the podocinR231Q variant. Our in vitro experiments indicate an underlying increased proteasomal degradation.Conclusions Our findings demonstrate that podocin R231Q exerts a pathogenic effect on its own, supporting the concept of podocin R229Q contributing to genetic predisposition in adult patients.
|
|
| 5. |
- Hu, Chunyan, et al.
(författare)
-
Renomedullary Interstitial Cell Endothelin A Receptors Regulate BP and Renal Function
- 2020
-
Ingår i: Journal of the American Society of Nephrology. - : American Society of Nephrology (ASN). - 1046-6673 .- 1533-3450. ; 31:7, s. 1555-1568
-
Tidskriftsartikel (refereegranskat)abstract
- Significance Statement The functional significance of renomedullary interstitial cells, which are uniquely and abundantly expressed in the renal inner medulla, is largely unknown. In vitro studies have demonstrated that endothelin A receptors regulate multiple aspects of renomedullary interstitial cell function. Using a novel mouse model with inducible renomedullary interstitial cell?specific endothelin A receptor gene targeting, the authors found that compared with control mice, mice lacking endothelin A receptors in renomedullary interstitial cells exhibited reduced BP, enhanced natriuresis and diuresis, increased endogenous natriuretic and diuretic factor production, and reduced medullary transporter expression. These studies identify a role for renomedullary interstitial cells in vivo in regulating renal function under physiologic conditions. Background The physiologic role of renomedullary interstitial cells, which are uniquely and abundantly found in the renal inner medulla, is largely unknown. Endothelin A receptors regulate multiple aspects of renomedullary interstitial cell function in vitro. Methods To assess the effect of targeting renomedullary interstitial cell endothelin A receptors in vivo, we generated a mouse knockout model with inducible disruption of renomedullary interstitial cell endothelin A receptors at 3 months of age. Results BP and renal function were similar between endothelin A receptor knockout and control mice during normal and reduced sodium or water intake. In contrast, on a high-salt diet, compared with control mice, the knockout mice had reduced BP; increased urinary sodium, potassium, water, and endothelin-1 excretion; increased urinary nitrite/nitrate excretion associated with increased noncollecting duct nitric oxide synthase-1 expression; increased PGE(2) excretion associated with increased collecting duct cyclooxygenase-1 expression; and reduced inner medullary epithelial sodium channel expression. Water-loaded endothelin A receptor knockout mice, compared with control mice, had markedly enhanced urine volume and reduced urine osmolality associated with increased urinary endothelin-1 and PGE(2) excretion, increased cyclooxygenase-2 protein expression, and decreased inner medullary aquaporin-2 protein content. No evidence of endothelin-1?induced renomedullary interstitial cell contraction was observed. Conclusions Disruption of renomedullary interstitial cell endothelin A receptors reduces BP and increases salt and water excretion associated with enhanced production of intrinsic renal natriuretic and diuretic factors. These studies indicate that renomedullary interstitial cells can modulate BP and renal function under physiologic conditions.
|
|
| 6. |
- Inker, Lesley A., et al.
(författare)
-
CKD-EPI and EKFC GFR Estimating Equations: Performance and Other Considerations for Selecting Equations for Implementation in Adults
- 2023
-
Ingår i: Journal of the American Society of Nephrology. - 1046-6673. ; 34:12, s. 1953-1964
-
Tidskriftsartikel (refereegranskat)abstract
- Background: New CKD-EPI and EKFC estimated GFR (eGFR) equations usingcreatinine (eGFRcr), cystatin C (eGFRcys) and both (eGFRcr-cys) have sufficientaccuracy for use in clinical practice. A better understanding of the equations, includingtheir performance in race, sex and age subgroups, is important for selection of eGFRequations for global implementation.Methods: We evaluated performance (bias and P30) of equations and methods usedfor equation development in an independent study population comprising 4050participants pooled from 12 studies. The mean (SD) mGFR was 76.4 (29.6)ml/min/1.73 m2, age 57.0 (17.4) years, with 1557 (38%) women and 579 (14%) Blackparticipants.Results: Coefficients for creatinine, cystatin C, age and sex in the CKD-EPI and EKFCequations are similar. Performance of the eGFRcr-cys equations in the overallpopulation (bias 90%) was better than the eGFRcr oreGFRcys equations, with fewer differences among race, sex and age subgroups.Differences in performance across subgroups reflected differences in diversity ofsource populations and use of variables for race and sex for equation development.Larger differences among eGFRcr equations reflected regional population differencesin non-GFR determinants of creatinine.Conclusion: CKD-EPI and EKFC equations are approaching convergence. It is notpossible to maximize both accuracy and uniformity in selecting one of the currentlyavailable eGFRcr equations for implementation across regions. Decisions shouldconsider methods for equation development in addition to performance. Wider use ofcystatin C with creatinine could maximize both accuracy and uniformity of GFRestimation using currently available equations.
|
|
| 7. |
- Niroula, Abhishek, et al.
(författare)
-
Clonal Hematopoiesis and CKD Progression
- 2022
-
Ingår i: Journal of the American Society of Nephrology. - 1046-6673. ; 33:5, s. 878-879
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 8. |
- Rehnberg, Johanna, 1982-, et al.
(författare)
-
Inflammatory Bowel Disease Is More Common in Patients with IgA Nephropathy and Predicts Progression of ESKD : A Swedish Population-Based Cohort Study
- 2021
-
Ingår i: Journal of the American Society of Nephrology. - : American Society of Nephrology. - 1046-6673 .- 1533-3450. ; 32:2, s. 411-423
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Case reports suggest an association between inflammatory bowel disease, a chronic autoimmune condition linked to increased circulating IgA levels, and IgA nephropathy, the most common form of primary GN and a leading cause of ESKD.METHODS: In a Swedish population-based cohort study, we compared 3963 biopsy-verified IgA nephropathy patients with 19,978 matched controls between 1974 and 2011, following up participants until 2015. Inflammatory bowel disease data and ESKD status were obtained through national medical registers. We applied Cox regression to estimate hazard ratios (HRs) for future inflammatory bowel disease in IgA nephropathy and conditional logistic regression to assess risk of earlier inflammatory bowel disease in IgA nephropathy. We also explored whether inflammatory bowel disease affects development of ESKD in IgA nephropathy.RESULTS: During a median follow-up of 12.6 years, 196 (4.95%) patients with IgA nephropathy and 330 (1.65%) matched controls developed inflammatory bowel disease (adjusted HR, 3.29; 95% confidence interval [95% CI], 2.73 to 3.96). Inflammatory bowel disease also was more common before a confirmed IgA nephropathy diagnosis. Some 103 (2.53%) IgA nephropathy patients had an earlier inflammatory bowel disease diagnosis compared with 220 (1.09%) controls (odds ratio [OR], 2.37; 95% CI, 1.87 to 3.01). Both logistic regression (OR, 2.60; 95% CI, 2.02 to 3.35) and time-varying Cox regression (HR, 1.84; 95% CI, 1.33 to 2.55) demonstrated that inflammatory bowel disease was associated with increased ESKD risk in patients with IgA nephropathy.CONCLUSIONS: Patients with IgA nephropathy have an increased risk of inflammatory bowel disease both before and after their nephropathy diagnosis. In addition, among patients with IgA nephropathy, comorbid inflammatory bowel disease elevates the risk of progression to ESKD.
|
|
| 9. |
|
|
| 10. |
- Uhlin, Fredrik, et al.
(författare)
-
Endopeptidase Cleavage of Anti-Glomerular Basement Membrane Antibodies in vivo in Severe Kidney Disease : An Open-Label Phase 2a Study
- 2022
-
Ingår i: Journal of the American Society of Nephrology. - : AMER SOC NEPHROLOGY. - 1046-6673 .- 1533-3450. ; 33:4, s. 829-838
-
Tidskriftsartikel (refereegranskat)abstract
- Background The prognosis for kidney survival is poor in patients presenting with circulating anti-glomerular basement membrane (GBM) antibodies and severe kidney injury. It is unknown if treat-ment with an endopeptidase that cleaves circulating and kidney bound IgG can alter the prognosis.& nbsp;Methods An investigator-driven phase 2a one-arm study (EudraCT 2016-004082-39) was performed in 17 hospitals in five European countries. A single dose of 0.25 mg/kg of imlifidase was given to 15 adults with circulating anti-GBM antibodies and an eGFR < 15 ml/min per 1.73m(2). All patients received standard treatment with cyclophosphamide and corticosteroids, but plasma exchange only if autoantibodies rebounded. The primary outcomes were safety and dialysis independency at 6 months.& nbsp;Results At inclusion, ten patients were dialysis dependent and the other five had eGFR levels between 7 and 14 ml/min per 1.73m(2). The median age was 61 years (range 19-77), six were women, and six were also positive for anti-neutrophil cytoplasmic antibodies. Then 6 hours after imlifidase infusion, all patients had anti-GBM antibodies levels below the reference range of a prespecified assay. At 6 months 67% (ten out of 15) were dialysis independent. This is significantly higher compared with 18% (nine out of 50) in a historical control cohort (P < 0.001, Fisher's exact test). Eight serious adverse events (including one death) were reported, none assessed as probably or possibly related to the study drug.& nbsp;Conclusions In this pilot study, the use of imlifidase was associated with a better outcome compared with earlier publications, without major safety issues, but the findings need to be confirmed in a randomized controlled trial.
|
|
