| 1. |
- Bian, Q., et al.
(författare)
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Mesangioproliferative Kidney Diseases and Platelet-Derived Growth Factor-Mediated AXL Phosphorylation
- 2021
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Ingår i: Kidney Medicine. - : Elsevier BV. - 2590-0595. ; 3:6
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Tidskriftsartikel (refereegranskat)abstract
- Rationale & Objective: Immunoglobulin A nephropathy (IgAN) is a common glomerular disease, with mesangial cell proliferation as a major feature. There is no disease-specific treatment. Platelet-derived growth factor (PDGF) contributes to the pathogenesis of IgAN. To better understand its pathogenic mechanisms, we assessed PDGF-mediated AXL phosphorylation in human mesangial cells and kidney tissue biopsy specimens. Study Design: Immunostaining using human kidney biopsy specimens and in vitro studies using primary human mesangial cells. Setting & Participants: Phosphorylation of AXL was assessed in cultured mesangial cells and 10 kidney-biopsy specimens from 5 patients with IgAN, 3 with minimal change disease, 1 with membranous nephropathy, and 1 with mesangioproliferative glomerulonephritis (GN). Predictor: Glomerular staining for phospho-AXL in kidney biopsy specimens of patients with mesangioproliferative diseases. Outcomes: Phosphorylated AXL detected in biopsy tissues of patients with IgAN and mesangioproliferative GN and in cultured mesangial cells stimulated with PDGF. Analytic Approach: t test, Mann-Whitney test, and analysis of variance were used to assess the significance of mesangial cell proliferative changes. Results: Immunohistochemical staining revealed enhanced phosphorylation of glomerular AXL in IgAN and mesangioproliferative GN, but not in minimal change disease and membranous nephropathy. Confocal-microscopy immunofluorescence analysis indicated that mesangial cells rather than endothelial cells or podocytes expressed phospho-AXL. Kinomic profiling of primary mesangial cells treated with PDGF revealed activation of several protein-tyrosine kinases, including AXL. Immunoprecipitation experiments indicated association of AXL and PDGF receptor proteins. An AXL-specific inhibitor (bemcentinib) partially blocked PDGF-induced cellular proliferation and reduced phosphorylation of AXL and PDGF receptor and the downstream signals (AKT1 and ERK1/2). Limitations: Small number of kidney biopsy specimens to correlate the activation of AXL with disease severity. Conclusions: PDGF-mediated signaling in mesangial cells involves transactivation of AXL. Finding appropriate inhibitors to block PDGF-mediated transactivation of AXL may provide new therapeutic options for mesangioproliferative kidney diseases such as IgAN.
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| 2. |
- Björnson Granqvist, Anna, 1974, et al.
(författare)
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Impaired glomerular and tubular antioxidative defense mechanisms in nephrotic syndrome.
- 2010
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Ingår i: American journal of physiology. Renal physiology. - : American Physiological Society. - 1522-1466 .- 1931-857X. ; 299:4
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Tidskriftsartikel (refereegranskat)abstract
- The molecular mechanisms behind acquired nephrotic syndrome (NS) are still largely unknown. One possible explanation for the development of proteinuria is oxidative damage to the glomerular cells. Our hypothesis was that the oxidative defense is weakened in NS, and we focused on measurements of the oxidative-antioxidative status in the glomerular and tubular parts of the nephron. Gene expression was analyzed in renal biopsies from patients with NS. In addition, to compare the acute and chronic phases of the disease, we studied puromycin-treated rats. In the biopsy material, the expression of enzymes involved in the antioxidative defense was higher in the tubulointerstitial compartment than in the glomerular cells. Real-time PCR analysis revealed a decreased glomerular expression in nephrotic kidneys for the antioxidant enzymes catalase and glutathione peroxidase-3, and -4. The tubular gene expression was downregulated for catalase, glutathione peroxidase-3, and thioredoxin reductase-1 and -2. The altered gene expression was accompanied by increased lipid peroxidation in urine. In rats, serum concentrations of ascorbyl-free radicals, measured with electron spin resonance, were elevated in the acute phase of the disease, suggesting increased oxidative stress in the circulation. In addition, we saw an increase in the plasma antioxidant capacity combined with a decreased oxidation of proteins in sera from nephrotic rats, but not from humans. In conclusion, there is a marked downregulation of several antioxidative enzymes in nephrotic kidneys, especially in glomerular structures. Our data suggest that oxidative damage to glomerular cells may contribute significantly to the course and prognosis of nephrotic syndrome.
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| 3. |
- Boi, Roberto, et al.
(författare)
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Modified lipid metabolism and cytosolic phospholipase A2 activation in mesangial cells under pro-inflammatory conditions
- 2022
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Diabetic kidney disease is a consequence of hyperglycemia and other complex events driven by early glomerular hemodynamic changes and a progressive expansion of the mesangium. The molecular mechanisms behind the pathophysiological alterations of the mesangium are yet to be elucidated. This study aimed at investigating whether lipid signaling might be the missing link. Stimulation of human mesangial cells with high glucose primed the inflammasome-driven interleukin 1 beta (IL-1 beta) secretion, which in turn stimulated platelet-derived growth factor (PDGF-BB) release. Finally, PDGF-BB increased IL-1 beta secretion synergistically. Both IL-1 beta and PDGF-BB stimulation triggered the formation of phosphorylated sphingoid bases, as shown by lipidomics, and activated cytosolic phospholipase cPLA2, sphingosine kinase 1, cyclooxygenase 2, and autotaxin. This led to the release of arachidonic acid and lysophosphatidylcholine, activating the secretion of vasodilatory prostaglandins and proliferative lysophosphatidic acids. Blocking cPLA2 release of arachidonic acid reduced mesangial cells proliferation and prostaglandin secretion. Validation was performed in silico using the Nephroseq database and a glomerular transcriptomic database. In conclusion, hyperglycemia primes glomerular inflammatory and proliferative stimuli triggering lipid metabolism modifications in human mesangial cells. The upregulation of cPLA2 was critical in this setting. Its inhibition reduced mesangial secretion of prostaglandins and proliferation, making it a potential therapeutical target.
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| 4. |
- Boi, Roberto, et al.
(författare)
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Podocyte Geranylgeranyl Transferase Type-I Is Essential for Maintenance of the Glomerular Filtration Barrier
- 2023
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Ingår i: Journal of the American Society of Nephrology. - : Ovid Technologies (Wolters Kluwer Health). - 1046-6673 .- 1533-3450. ; 34:4, s. 641-655
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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.
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| 5. |
- Boi, Roberto, et al.
(författare)
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The role of the mesangium in glomerular function
- 2023
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Ingår i: Acta Physiologica. - 1748-1708. ; 239:2
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Tidskriftsartikel (refereegranskat)abstract
- When discussing glomerular function, one cell type is often left out, the mesangial cell (MC), probably since it is not a part of the filtration barrier per se. The MCs are instead found between the glomerular capillaries, embedded in their mesangial matrix. They are in direct contact with the endothelial cells and in close contact with the podocytes and together they form the glomerulus. The MCs can produce and react to a multitude of growth factors, cytokines, and other signaling molecules and are in the perfect position to be a central hub for crosstalk communication between the cells in the glomerulus. In certain glomerular diseases, for example, in diabetic kidney disease or IgA nephropathy, the MCs become activated resulting in mesangial expansion. The expansion is normally due to matrix expansion in combination with either proliferation or hypertrophy. With time, this expansion can lead to fibrosis and decreased glomerular function. In addition, signs of complement activation are often seen in biopsies from patients with glomerular disease affecting the mesangium. This review aims to give a better understanding of the MCs in health and disease and their role in glomerular crosstalk and inflammation.
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| 6. |
- Buvall, Lisa, 1976, et al.
(författare)
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Orellanine specifically targets renal clear cell carcinoma
- 2017
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Ingår i: Oncotarget. - : Impact Journals, LLC. - 1949-2553. ; 8:53, s. 91085-91098
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Tidskriftsartikel (refereegranskat)abstract
- Renal cell carcinoma (RCC), arising from the proximal tubule in the kidney, accounts for approximately 85% of kidney cancers and causes over 140,000 annual deaths worldwide. In the last decade, several new therapies have been identified for treatment of metastatic RCC. Although these therapies increase survival time compared to standard care, none of them has curative properties. The nephrotoxin orellanine specifically targets proximal tubular epithelial cells, leaving other organs unaffected. We therefore hypothesized that the selective toxicity of orellanine extends to clear cell RCC (ccRCC) cells since they emanate from proximal tubular cells. Orellanine would thus target both primary and metastatic ccRCC in vitro and in vivo. We found that orellanine induces dose-dependent cell death in proximal tubular cells and in all ccRCC cells tested, both primary and cell lines, with no toxicity detected in control cells. The toxic action of orellanine involve decreased protein synthesis, disrupted cell metabolism and induction of apoptosis. In nude rats carrying human ccRCC xenografts, brief orellanine treatment eliminated more than 90% of viable tumor mass compared to control rats. This identifies orellanine as a potential treatment concept for ccRCC patients on dialysis, due to its unique selective toxicity towards ccRCC.
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| 7. |
- Ebefors, Kerstin, 1977, et al.
(författare)
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Endothelin receptor-A mediates degradation of the glomerular endothelial surface layer via pathologic crosstalk between activated podocytes and glomerular endothelial cells
- 2019
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Ingår i: Kidney International. - : Elsevier BV. - 0085-2538. ; 96:4, s. 957-970
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Tidskriftsartikel (refereegranskat)abstract
- Emerging evidence of crosstalk between glomerular cells in pathological settings provides opportunities for novel therapeutic discovery. Here we investigated underlying mechanisms of early events leading to filtration barrier defects of podocyte and glomerular endothelial cell crosstalk in the mouse models of primary podocytopathy (podocyte specific transforming growth factor-beta receptor 1 signaling activation) or Adriamycin nephropathy. We found that glomerular endothelial surface layer degradation and albuminuria preceded podocyte foot process effacement. These abnormalities were prevented by endothelin receptor-A antagonism and mitochondria! reactive oxygen species scavenging. Additional studies confirmed increased heparanase and hyaluronoglucosaminidase gene expression in glomerular endothelial cells in response to podocyte-released factors and to endothelin-1. Atomic force microscopy measurements showed a significant reduction in the endothelial surface layer by endothelin-1 and podocyte-released factors, which could be prevented by endothelin receptor-A but not endothelin receptor-B antagonism. Thus, our studies provide evidence of early crosstalk between activated podocytes and glomerular endothelial cells resulting in loss of endothelial surface layer, glomerular endothelial cell injury and albuminuria. Hence, activation of endothelin-1-endothelin receptor-A and mitochondrial reactive oxygen species contribute to the pathogenesis of primary podocytopathies in experimental focal segmental glomerulosclerosis.
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| 8. |
- Ebefors, Kerstin, 1977, et al.
(författare)
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Mesangial cells from patients with IgA nephropathy have increased susceptibility to galactose-deficient IgA1
- 2016
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Ingår i: Bmc Nephrology. - : Springer Science and Business Media LLC. - 1471-2369. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- Background: IgA nephropathy (IgAN) is the most common glomerulonephritis in the world, affecting close to a million people. Circulating galactose-deficient IgA (gd-IgA), present in patients with IgAN, form immune complex deposits in the glomerular mesangium causing local proliferation and matrix expansion. Intriguing though, individuals having gd-IgA deposits in the kidneys do not necessarily have signs of glomerular disease. Recurrence of IgAN only occurs in less than half of transplanted patients with IgAN, indicating that gd-IgA is not the only factor driving the disease. We hypothesize that, in addition to IgA complexes, patients with IgAN possess a subtype of mesangial cells highly susceptible to gd-IgA induced cell proliferation. Methods: To test the hypothesis, we designed a technique to culture primary mesangial cells from renal biopsies obtained from IgAN patients and controls. The cell response to gd-IgA treatment was then measured both on gene and protein level and the proliferation rate of the cells in response to PDGF was investigated. Results: When treated with gd-IgA, mesangial cells from patients with IgAN express and release more PDGF compared to controls. In addition, the mesangial cells from patients with IgAN were more responsive to treatment with PDGF resulting in an increased proliferation rate of the cells compared to control. Mesangial cells cultured from patients with IgAN expressed and released more IL-6 than controls and had a higher expression of matrix genes. Both mesangial cells derived from patients with IgAN and controls increased their expressed TGF beta 1 and CCL5 when treated with gd-IgA. Conclusion: We conclude that mesangial cells derived from IgAN patients have a mesangioproliferative phenotype with increased reactivity to IgA and that these cellular intrinsic properties may be important for the development of IgA nephropathy.
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| 9. |
- Ebefors, Kerstin, 1977, et al.
(författare)
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Modeling the Glomerular Filtration Barrier and Intercellular Crosstalk
- 2021
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Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- The glomerulus is a compact cluster of capillaries responsible for blood filtration and initiating urine production in the renal nephrons. A trilaminar structure in the capillary wall forms the glomerular filtration barrier (GFB), composed of glycocalyx-enriched and fenestrated endothelial cells adhering to the glomerular basement membrane and specialized visceral epithelial cells, podocytes, forming the outermost layer with a molecular slit diaphragm between their interdigitating foot processes. The unique dynamic and selective nature of blood filtration to produce urine requires the functionality of each of the GFB components, and hence, mimicking the glomerular filter in vitro has been challenging, though critical for various research applications and drug screening. Research efforts in the past few years have transformed our understanding of the structure and multifaceted roles of the cells and their intricate crosstalk in development and disease pathogenesis. In this review, we present a new wave of technologies that include glomerulus-on-a-chip, three-dimensional microfluidic models, and organoids all promising to improve our understanding of glomerular biology and to enable the development of GFB-targeted therapies. Here, we also outline the challenges and the opportunities of these emerging biomimetic systems that aim to recapitulate the complex glomerular filter, and the evolving perspectives on the sophisticated repertoire of cellular signaling that comprise the glomerular milieu.
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| 10. |
- Ebefors, Kerstin, 1977
(författare)
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Molecular mechanisms of the kidney in health and disease
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In 2010, 307 Swedish patients received a new kidney through transplantation, and the first of April 2011, 603 patients were on the kidney transplant waiting list. In Sweden over 8000 patients are presently in active uremic care with about half in dialysis and the other half with a functional kidney graft. The numbers of patients in need of active uremic care are escalating and so are the costs for renal health care, in Sweden as in most of the western world. For patients with end stage renal disease active uremic care is the last option for survival since there is no cure or specific treatment for most renal diseases. The lack of treatment options often leaves steroids and chemotherapy as the only available choices. In order to find more specific treatment and to cure or delay the progress of renal disease we need to learn more about the molecular background of these diseases. To increase our understanding of the molecular mechanisms behind renal disease we have studied the gene expression in both an animal model of the nephrotic syndrome in rat as well as in human material in form of renal biopsies and cell cultures. The most common renal diseases all start in the glomerulus, the capillary tuft in the nephron where the ultrafiltration of blood takes place, and therefore we have focused on gene expression in the glomerulus. When investigating the gene expression in glomeruli from healthy kidney donors and from mice we found a core cluster of conserved, highly glomerulus-specific genes. Normal function of some of these genes in the glomerulus is already known to be of importance to the filtration barrier and mutations in certain of them are tightly connected to proteinuria. The discovered core cluster also contained genes that so far has not been coupled to renal function and disease, and can therefore be used as a new source of kidney glomerular-specific genes and biomarkers. By studying gene expression in rats with nephrotic syndrome and in patients with renal disease we found that expression of a special family of extracellular matrix proteins, called proteoglycans, was changed in renal disease compared to healthy controls. Proteoglycans are multifunctional proteins with functions ranging from holding and releasing signal molecules to making up part of the extracellular matrix structure. In patients with IgA nephropathy we found that the proteoglycan perlecan had an increased gene expression compared to control, and that the gene expression correlated to the excretion of protein in the urine and even to the progress rate of the disease. This suggests that perlecan could likely be used as a molecular marker for IgA nephropathy and as such help us to further understand the progression of the disease. In addition we have developed a unique method of culturing cells from patients with renal disease and we believe that this will give us new information about the molecular mechanism of this disorder and help us develop more specific and individualized treatment for patients with kidney failure.
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