Model Of Mesangial Proliferative Glomerulonephritis Research Articles

Th17 Cells Participate in Thy1.1 Glomerulonephritis Which Is Ameliorated by Tacrolimus

Introduction: Thy1.1 glomerulonephritis (Thy1.1 GN) in rats is widely used as an experimental model of mesangial proliferative glomerulonephritis (GN). We previously reported that T-helper (Th) cells were accumulated in glomeruli from the early phase of this model and that not Th2 cells but Th1 cells play an important role in the development of glomerular alterations. Although Th17 is reported to be involved in the pathogenesis of several autoimmune diseases, the role of Th17 cells in the pathogenesis of mesangial alterations in Thy1.1 GN remains unclear. Methods: The kinetics of the infiltration of subsets of Th cells and the expression of IL-17 in Thy1.1 GN were analyzed. Next, the localization and the cell types of IL-17 receptor (IL-17R)-positive cells and IL-6-positive cells were analyzed. Then, the effect of tacrolimus on the expressions of Th17-related cytokines in Thy1.1 GN was analyzed. Results: Not only Th1 cells but also Th17 cells were recruited into glomeruli from the early phase of the disease. mRNA expression of IL-17 in glomeruli was elevated. The increased positive expression of IL-17R was detected in the mesangial area, and some of IL-17R-positive cells were co-stained with IL-6. Tacrolimus treatment ameliorated mesangial alterations by suppressing the expressions of Th17-related cytokines such as IL-17 and IL-6. Conclusion: Th17 cells participate in the development of Thy1.1 GN, a mimic of mesangial proliferative GN, and Th17 cells and their related cytokines are pertinent therapeutic targets.

Ameliorating role of microRNA-378 carried by umbilical cord mesenchymal stem cells-released extracellular vesicles in mesangial proliferative glomerulonephritis

BackgroundMesenchymal stem cells (MSCs) and their released extracellular vesicles (Evs) have shown protective effects against kidney diseases. This study aims to study the functions of umbilical cord MSCs-released Evs (ucMSC-Evs) and their implicated molecules in mesangial proliferative glomerulonephritis (MsPGN).MethodsA rat model of MsPGN was induced by anti-Thy-1.1, and rat mesangial cells (rMCs) HBZY-1 were treated with PDGF-BB/DD to mimic MsPGN condition in vitro. Rats and cells were treated with different doses of ucMSC-Evs, and then the pathological changes in renal tissues and proliferation of rMCs were determined. Differentially expressed microRNAs (miRNAs) after Evs treatment were screened by microarray analysis. The interactions among miR-378, PSMD14, and TGFBR1 were analyzed. Gain- and loss-of function studies of miR-378 and PSMD14 were performed to explore their effects on tissue hyperplasia and rMC proliferation and their interactions with the TGF-β1/Smad2/3 signaling pathway.ResultsThe ucMSC-Evs treatment ameliorated mesangial hyperplasia and fibrosis in rat renal tissues and suppressed the aberrant proliferation of rMCs in a dose-dependent manner. miR-378 was the most upregulated miRNA in tissues and cells after ucMSC-Evs treatment. miR-378 directly targeted PSMD14, and PSMD14 maintained the stability of TGFBR1 through deubiquitination modification, which led to TGF-β1/Smad2/3 activation. Either miR-378 knockdown or PSMD14 overexpression diminished the protective functions of ucMSC-Evs by activating the TGF-β1/Smad2/3 signaling pathway.ConclusionUcMSC-Evs ameliorate pathological process in MsPGN through the delivery of miR-378, which suppresses PSMD14-mediated TGFBR1 stability and inactivates the TGF-β1/Smad2/3 signaling pathway to reduce tissue hyperplasia and rMC proliferation.Graphical 6tcW_AV6VyAYJya28kLbKyVideo abstract

PC-1 NF suppresses high glucose-stimulated inflammation and extracellular matrix accumulation in glomerular mesangial cells via the Wnt/β-catenin signaling.

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease worldwide with high morbidity and mortality. Glomerular mesangial cell (MC) proliferation, inflammatory cell infiltration and extracellular matrix (ECM) accumulation are the main pathological characteristics of DN. A previous study revealed that polycystin-1 N-terminal fragment (PC-1 NF) fusion protein could inhibit ECM accumulation in a mesangial proliferative glomerulonephritis model. However, the role of PC-1 NF fusion protein in DN remains unknown. The results of the present study indicated that PC-1 NF fusion protein significantly abolished high glucose (HG)-induced glomerular MC viability over three time points measured (24, 48 and 72 h). In addition, PC-1 NF suppressed the levels of monocyte chemotactic peptide-1 and tumor necrosis factor α, as well as the expression of fibronectin and collagen IV, in HG-stimulated MCs. Furthermore, PC-1 NF fusion protein efficiently inhibited the activation of Wnt/β-catenin signaling pathway in HG-stimulated MCs. Taken together, these data indicated that PC-1 NF fusion protein inhibited HG-induced MC proliferation, inflammation, and ECM expression via the modulation of the Wnt signaling pathway. The present study indicated that PC-1 NF fusion protein may be a potential agent in treating DN.

The effectiveness of chitosan-mediated silencing of PDGF-B and PDGFR-β in the mesangial proliferative glomerulonephritis therapy

Platelet-derived growth factor-B (PDGF-B) is a growth factor that plays an important role in the progression of mesangial proliferative glomerulonephritis (MsPGN). PDGF-B may contribute to mesangioproliferative changes and is overexpressed in MsPGN. Recently, small interfering RNAs (siRNAs) have been widely used for gene silencing effects in experimental models of renal diseases. Nanoparticle-based therapeutics are preferred for reasons such as increasing therapeutic efficacy and reducing toxic effects caused by high doses. The distribution of nanoparticles to the kidney is a significant advantage in siRNA delivery. The aim of this study was to investigate the efficacy of chitosan/siRNA nanoplexes in silencing of PDGF-B and PDGFR-β genes in kidney and to decrease mesangial cell proliferation and matrix accumulation in MsPGN model induced by anti-Thy-1.1 antibody. The therapeutic effects of chitosan/siPDGF-B + siPDGFR-β nanoplexes in glomerulonephritic rats were studied by molecular, biochemical, and histopathologic evaluations. Chitosan/siPDGF-B + siPDGFR-β nanoplexes markedly reduced PDGF-B and PDGFR-β mRNA and protein expressions in experimental MsPGN model. Histopathologic examination results showed that the silencing of PDGF-B and its receptor PDGFR-β led to reduction in mesangial cell proliferation and matrix accumulation. The use of chitosan/siPDGF-B + siPDGFR-β nanoplexes for silencing the PDGF-B pathway in MsPGN can be considered as a new effective therapeutic strategy.

CXCL10 expression induced by Mxi1 inactivation induces mesangial cell apoptosis in mouse Habu nephritis

MAX interactor 1 (Mxi1) proteins are c-myc antagonists that primarily exert their biological functions by inhibiting Myc-dependent gene transcription. In this study, Mxi1−/− mice were used to generate a model of mesangial proliferative glomerulonephritis for the first time. In the present study, we demonstrated that Mxi1−/− mice exhibited a more typical and severe pathological phenotype, which was displayed primarily as a noticeable dissolution phenotype with a higher proportion of apoptotic cells and higher chemokine CXCL10 expression during the early days of modeling, compared with wild-type mice. Additionally, we determined that IRF3-mediated TLR4 signaling was likely involved in regulating CXCL10 expression, which might participate in the mesangial dissolution process. We also found increases in CXCL10 expression, caspase 3 activation, and the proportion of apoptotic cells when Mxi1 expression was inhibited in mouse mesangial cells. Furthermore, the proportion of apoptotic cells decreased after inhibiting CXCL10 expression. Therefore, we concluded that the mesangial cell apoptosis observed in this mesangial proliferative glomerulonephritis model was related to CXCL10 expression induced by Mxi1 inactivation. This finding provides a new theoretical basis for the mechanism of mesangial proliferative glomerulonephritis progression and reveals potential intervention targets for the early treatment of this disease.

Efficacy of antisense monocyte chemoattractant protein-1 (MCP-1) in a rat model of mesangial proliferative glomerulonephritis

Objective: The effects of inhibition of monocyte chemoattractant protein-1 (MCP-1) on a rat model of mesangial proliferative glomerulonephritis (MsPGN) were evaluated. Methods: The anti-Thy-1 MsPGN model was developed by intravenously injecting anti-Thy-1 monoclonal antibodies into rats, followed by an injection of mesangial cells transfected with antisense MCP-1 into the renal artery. Exogenous cells were detected by in situ hybridization. Rats (40 total) were randomly divided into five groups: SO (sham operation), TG (Thy-1 glomerulonephritis model), MC (non-transfected normal rat mesangial cell), BC (pLXSN empty vector or blank control), and AM (antisense MCP-1 transfection) groups. Effects of exogenous MCP-1 on urinary protein excretion rate, biochemical parameters, and pathological changes were evaluated. Expression of MCP-1 and transforming growth factor-β1 (TGF-β1) were detected by immunohistochemistry. mRNA expression of MCP-1, TGF-β1, and CC chemokine receptor 2 (CCR2) were detected by RT-PCR. Results: Exogenous MCP-1 cDNA was successfully transfected into mesangial cells. Exogenous mesangial cells were detected in glomeruli by in situ hybridization. Glomerular mesangial cell proliferation, 24-h urinary protein excretion rate, mRNA expression of MCP-1, TGF-β1, and CCR2, and protein expression of MCP-1 all decreased in the AM group as compared to the control group (p < 0.05), but there was no significant difference in the expression level of TGF-β1 protein. Conclusions: (1) Mesangial cells can be used as a vector to transfect exogenous genes into kidneys; (2) antisense MCP-1 decreases mesangial cell proliferation and pathological injury in MsPGN model rats by decreasing expression of MCP-1 and CCR2; and (3) antisense MCP-1 suppressed mesangial cell proliferation and matrix accumulation in anti-Thy-1 MsPGN model rats, which did not entirely depend on TGF-β1.

Glomerular Expression of Hydrogen Peroxide-Inducible Clone-5 in Human and Rat Progressive Mesangial Proliferative Glomerulonephritis

Background/Aims: Hydrogen peroxide-inducible clone-5 (Hic-5) is a transforming growth factor-β₁ (TGF-β₁)- and hydrogen peroxide (H₂O₂)-inducible focal adhesion protein that may be necessary for maintaining the myofibroblastic phenotype in pathological scar formation. To investigate the involvement of Hic-5 in the pathogenesis of glomerulonephritis (GN), we examined the glomerular expression of Hic-5 in human and rat GN as well as the regulation of Hic-5 by TGF-β₁ in vitro. Methods and Results: Immunohistochemical analyses showed that the expression of Hic-5 was increased in mesangial cells (MCs) in human mesangial proliferative GN. Hic-5 expression was significantly correlated not only with the levels of α-smooth muscle actin (α-SMA) and TGF-β₁, the accumulation of extracellular matrix, and the number of glomerular cells, but also with the urinary protein level in patients with GN. Glomerular Hic-5 expression increased in parallel with α-SMA expression in a rat model of mesangial proliferative GN. Combined therapy with an angiotensin type I receptor blocker and an antioxidant in this model improved the histology and the expression of Hic-5 and α-SMA. TGF-β₁ upregulated Hic-5 and α-SMA protein levels in human cultured MCs. Conclusion: Our findings suggest that Hic-5 is involved in changes in the MC phenotype to produce abnormal extracellular matrix remodeling in GN.

Pharmacological and Toxicological Advances in PPAR-Related Medicines

Pharmacological and Toxicological Advances in PPAR-Related Medicines

Stem Cell Therapy for the Kidney

Over the past few years, tremendous advances have occurred in stem cell biology. With the development of induced pluripotent stem cell technology, it is now possible to reprogram adult cells to differentiate into multiple cell types, including renal cells.1 Although induced pluripotent stem cells hold great promise for treatment of chronic diseases such as kidney failure in the future, current therapies are limited to readily available endogenous progenitor cell populations that can be isolated or mobilized from the bone marrow. These include hematopoietic stem cells (HSCs), mesenchymal stem cells, and endothelial progenitor cells, collectively known as bone marrow–derived cells (BMDCs). Therapies to enhance mobilization of endogenous BMDCs or infusions of BMDCs have been used in preclinical models of renal disease that include ischemia-reperfusion injury, the Thy1.1 model of mesangial proliferative glomerulonephritis, renovascular disease, and Alport syndrome, to name a few.2–10 Improved renal outcomes were reported in a number of these studies, although it is debated whether this is the result of cytokines or secreted factors produced by the BMDCs or the consequence of transdifferentiation of BMDCs into specific renal cell types. In regard to the latter, studies suggested variable abilities of these cells to transdifferentiate into renal endothelial, tubular, and glomerular epithelial cell lineages. Although it is not uniformly accepted that true transdifferentiation from BMDCs occurs, most agree that if it does occur, then it contributes only a small proportion of cells to the kidney. In the renal clinical …

Genetic predisposition for glomerulonephritis-induced glomerulosclerosis in rats is linked to chromosome 1

Genetic factors influence renal disease progression, and several loci have been linked to the spontaneous development of proteinuria and glomerulosclerosis in animal models. However, the role of genetic susceptibility in glomerulonephritis-induced progressive glomerulosclerosis is unknown. In a rat model of mesangial proliferative glomerulonephritis, anti-Thy-1 glomerulonephritis (antiThy1GN), Lewis/Maastricht (Lew/Maa) rats exhibit progression to glomerulosclerosis, whereas in genetically related Lewis/Møllegard (Lew/Moll) rats, glomerular lesions are repaired within 3 wk. The genetic factors underlying this strain-related difference are not known. To identify novel quantitative trait loci (QTL) involved in progression or repair in Lewis rats, 145 female backcross rats [F1(Lew/Maa x Lew/Moll) x Lew/Maa] were studied. After induction of antiThy1GN proteinuria, we determined mesangial activation, the percentage of microaneurysms, and the glomerular damage score for each animal; a genome scan using 187 microsatellite markers was performed. QTL mapping revealed a significant QTL for glomerular damage score on chromosome 1 with a logarithm of odds (LOD) score of 3.9. Homozygosity for Lew/Maa DNA in this region was associated with a higher percentage of damaged glomeruli on day 21. Furthermore, suggestive linkage was found for the percentage of glomeruli with microaneurysms on day 3 on chromosome 1, 6, and 11; for mesangial activation on day 7 on chromosome 18, while proteinuria was suggestively linked to chromosome 5 (day 0), 4 (day 3), and 6 (day 7). This study identifies a QTL on rat chromosome 1 that is significantly linked to progressive glomerulosclerosis after acute glomerulonephritis.

Microarray and bioinformatic detection of novel and established genes expressed in experimental anti-Thy1 nephritis

Microarray technology is a powerful tool that can probe the molecular pathogenesis of renal injury. In this present study microarray analysis was used to monitor serial changes in the renal transcriptome of a rat model of mesangial proliferative glomerulonephritis. Administration of anti-Thy1 antibody results in phases of acute mesangial injury (day 2), cell proliferation (day 5), matrix expansion (days 5 and 7), and subsequent healing (day 14). Using Affymetrix (RAE230A) microarrays coupled with sequential primary biologic function-focused and secondary "baited" global cluster analysis, a cohort of established and putative novel modulators of mesangial cell turnover was identified. Cluster analysis of proliferative genes identified a number of gene expression profiles. The most striking pattern was increased gene expression at day 5, a cluster that included platelet-derived growth factor (PDGF), cyclins and transforming growth factor-beta (TGF-beta). The gene expression patterns identified by primary focused cluster analysis were used as bioinformatic bait and resulted in the identification of novel families of genes such as the S100 family. The expression of established and novel genes was confirmed using reverse transcription-polymerase chain reaction (RT-PCR). Next, in vivo gene expression was compared to PDGF-stimulated mesangial cells in vitro revealing similar patterns of dysregulation. Transcriptomic analysis defined both known and novel molecules involved in mesangial cell proliferation in vitro and in vivo and defined a panel of molecules that are potential contributors to mesangial cell dysfunction in glomerular disease.

Effect of lipo-prostaglandin E1 on mesangial proliferative glomerulonephritis in rats.

The antinephritic effect of lipo-prostaglandin E1 prostaglandin E1 incorporated in lipid microspheres was investigated using an experimental model of mesangial proliferative glomerulonephritis (MsPGN). Twenty-two female rats were randomly divided into nephritic group (N, n = 6), lipo-prostaglandin E1 treated group (NL, n = 8) and control group (C, n = 6). Lipo-prostaglandin E1 was given intravenously at 40 microg x kg(-1) x d(-1) from the 6th week to the 8th week. Twenty-four h urinary protein contents and blood creatinine (Cr) were determined and the pathological changes were observed in the experiment. The expression of proliferating cell nuclear antigen (PCNA), extracellular matrix (fibronectin, FN; collagen type IV, Col IV) and transforming growth factor beta1 (TGFbeta1) was detected by using immunohistochemistry. The results showed that lipo-prostaglandin E1 significantly inhibited the glomerular histopathological changes as well as the elevation of plasma Cr (P < 0.05). The overexpression of PCNA, FN, Col IV and TGFbeta1 were also obviously inhibited in group NL as compared with the group N (P < 0.01). It was suggested that lipo-prostaglandin E1 could improve renal function, inhibit the proliferation of glomerular cells and reduce the deposition of extracellular matrix, which may be related to the down-regulation of the TGFbeta1 expression.

Stimulation of soluble guanylyl cyclase inhibits mesangial cell proliferation and matrix accumulation in experimental glomerulonephritis

To date, no specific treatment is established in mesangial proliferative glomerulonephritis in humans. Specific stimulation of soluble guanylyl cyclase (sGC), an enzyme catalyzing the synthesis of cGMP from GTP, can be achieved by the novel pyrazolopyridine derivative BAY 41-2272. The effect of sGC stimulation via BAY 41-2272 on mesangial proliferation was assessed in vivo using a mesangial proliferative glomerulonephritis model in rats (anti-Thy1 model). Renal biopsies, as well as glomerular isolates, urine samples, and blood samples were compared in BAY 41-2272- and placebo-treated groups during anti-Thy1 nephritis. The sGC beta(1)-subunit is upregulated during anti-Thy1 nephritis and mainly confined to mesangial areas by immunohistochemistry. Specific therapeutic sGC stimulation during anti-Thy1 nephritis in vivo was achieved via BAY 41-2272 treatment as demonstrated by increased glomerular cGMP levels causing inhibition of mesangial proliferation, glomerular matrix accumulation, and proteinuria compared with placebo-treated animals. sGC is tightly regulated in glomeruli during experimental glomerulonephritis. Considering its beneficial antiproliferative, antifibrotic, and antiproteinuric effect in experimental glomerulonephritis, the therapeutic stimulation of sGC could become a promising future goal in mesangial proliferative glomerulonephritis in humans.

Inhibition of Interleukin-10 by the Immunomodulator AS101 Reduces Mesangial Cell Proliferation in Experimental Mesangioproliferative Glomerulonephritis: ASSOCIATION WITH DEPHOSPHORYLATION OF STAT3

Mesangial cell (MC) proliferation is essential for the pathogenesis and progression of glomerular disease. Using an acute model of mesangial proliferative glomerulonephritis (Thy1 GN), we show that neutralization of interleukin (IL)-10 greatly ameliorated the disease as expressed by both decreased MC expansion and proteinuria. Treatment with the tellurium compound AS101 (ammonium trichloro(dioxoethylene-o,o')tellurate) resulted in favorable effects provided that the compound was administered 24 h before insult, whereas partial effects were obtained when administered after insult. We identified STAT3 as playing a pivotal role in IL-10-induced MC proliferation in vitro and in vivo. IL-10 activates MC STAT3 in vitro as expressed by its phosphorylation and nuclear translocation. The role of STAT3 in MC proliferation induced by IL-10 was deduced from results showing that IL-10-induced proliferation was abrogated if MC transfected with STAT3 antisense oligonucleotides were used or if cells were incubated with inhibitors of STAT3. AS101 deactivates STAT3 in control but not in MC transfected with IL-10 antisense oligonucleotides. Inactivation of STAT3 prevents reduction of MC proliferation by AS101. We further demonstrate the role of STAT3 in the regulation of cell cycle and survival regulatory proteins by AS101 in MC via inhibition of IL-10. IL-10 increased MC expression of Bcl-2 and Bcl-X1 and simultaneously decreased the levels of p27kip1. These survival factors were decreased by AS101 in a STAT3- and IL-10-dependent manner, whereas p27kip1 was similarly increased. In Thy1 GN, phosphorylated STAT3 in glomerular MC peaked at day 6 and correlated with MC expansion. Neutralization of IL-10 or its inhibition by AS101 abolished phosphorylation of STAT3. This effect positively correlated with amelioration of the disease. These in vitro and in vivo studies indicate that the autocrine MC growth factor IL-10 induces MC proliferation via STAT3. We suggest that IL-10 or its downstream target STAT3 might be therapeutic targets for kidney diseases induced by mesangial proliferation.

Thrombospondin-1 is a major activator of TGF-β in fibrotic renal disease in the rat in vivo

Transforming growth factor-beta (TGF-beta), a profibrotic cytokine involved in many scarring processes, has to be activated extracellularly before it can bind to its receptors. Thrombospondin 1 (TSP1), a multifunctional matricellular glycoprotein, has been identified as an activator of TGF-beta in in vitro systems and during mouse postnatal development in vivo. TSP1 is expressed de novo in many inflammatory disease processes, including glomerular disease. In this study we investigated whether peptides specifically interfering with the activation process of TGF-beta by TSP1 may be able to block activation of TGF-beta in an in vivo model of mesangial proliferative glomerulonephritis. Continuous intravenous infusion of blocking peptide by minipumps significantly reduced expression of active TGF-beta in glomeruli on day 7 of disease as indicated by immunohistochemistry, bioassay, and activation of the TGF-beta signal transduction pathway, while total TGF-beta expression was unchanged. Inhibition of glomerular TGF-beta activation was accompanied by a decrease of glomerular extracellular matrix accumulation and proteinuria, but was without effect on mesangial cell proliferation or influx of monocytes/macrophages. TSP1 is a major endogenous activator of TGF-beta in experimental inflammatory glomerular disease. Drugs interfering with the activation of TGF-beta by locally produced TSP1 may be considered as a future specific treatment of scarring kidney disease.

Antisense Oligonucleotides Against Thrombospondin-1 Inhibit Activation of TGF-β in Fibrotic Renal Disease in the Rat in Vivo

Specific treatment of chronic progressive renal disease is very limited. TGF-beta, considered as the major cytokine causing tissue scarring, must be activated extracellularly before it can bind to its receptors. Thrombospondin-1 (TSP1) has been identified as an activator of latent TGF-beta in in vitro systems and in pancreas and lung homeostasis in mouse pups in vivo, but whether this is also true in inflammatory fibrotic disease is unknown. We examined a rat model of mesangial proliferative glomerulonephritis, where TGF-beta has been demonstrated to mediate renal fibrosis. In this study, antisense phosphorothioate oligonucleotides against TSP1 were successfully transferred into almost all glomeruli of perfused diseased kidneys and markedly inhibited de novo synthesis of TSP1. This effect was accompanied by decreased activation but not expression of TGF-beta and by the inhibition of the TGF-beta-dependent smad-signaling pathway, as well as transcription of TGF-beta target genes such as EDA-fibronectin, resulting in a markedly suppressed accumulation of extracellular matrix. In sharp contrast, neither glomerular cell proliferation nor influx of macrophages was affected by this therapy in experimental mesangial proliferative glomerulonephritis. These results demonstrate that TSP1 is the major endogenous activator of TGF-beta in experimental inflammatory kidney disease.

PTPRQ is a novel phosphatidylinositol phosphatase that can be expressed as a cytoplasmic protein or as a subcellularly localized receptor-like protein

PTPRQ (rPTP-GMC1) is a member of the type III receptor-like protein tyrosine phosphatase family. PTPRQ has very low activity against phosphotyrosine but is active against phosphatidylinositol phosphates that are involved in regulation of survival, proliferation, and subcellular architecture. Here, we report that PTPRQ can be expressed as a cytosolic or a receptor-like protein and that the form, subcellular localization, and cell types in which it is expressed are regulated by alternative promoter use and by alternative splicing. The first promoter drives expression of transcripts encoding a transmembrane protein in human podocytes and lung. PTPRQ protein is localized to the basal membrane of human podocytes, beginning when podocyte progenitors can first be identified in the embryonic kidney. A second promoter drives expression of a transcript that can encode a cytoplasmic protein containing the catalytic site. This is the major PTPRQ transcript in rat mesangial cells and human testis and is upregulated in mesangial cells in a rat model of mesangial proliferative glomerulonephritis. Differential regulation of expression of the transmembrane vs cytosolic forms, in different cell types during development or response to injury, may be a mechanism through which PTPRQ, with its activities against membrane phospholipids and against phosphotyrosine, can target specific substrates under different conditions.

Differential effects of low-dose docosahexaenoic acid and eicosapentaenoic acid on the regulation of mitogenic signaling pathways in mesangial cells

Although dietary fish oil supplementation has been used to prevent the progression of kidney disease in patients with IgA nephropathy, relatively few studies provide a mechanistic rationale for its use. Using an antithymocyte (ATS) model of mesangial proliferative glomerulonephritis, we recently demonstrated that fish oil inhibits mesangial cell (MC) activation and proliferation, reduces proteinuria, and decreases histologic evidence of glomerular damage. We therefore sought to define potential mechanisms underlying the antiproliferative effect of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), the predominant &omega;-3 polyunsaturated fatty acids found in fish oil, in cultured MC. DHA and EPA were administered to MC as bovine serum albumin fatty-acid complexes. Low-dose (10-50 &mu;mol/L) DHA, but not EPA, inhibited basal and epidermal growth factor (EGF)&ndash;stimulated [ 3H]-thymidine incorporation in MCs. At higher doses (100 &mu;mol/L), EPA and DHA were equally effective in suppressing basal and EGF-stimulated MC mitogenesis. Low-dose DHA, but not EPA, decreased ERK activation by 30% ( P &lt; .01), as assessed with Western-blot analysis using phosphospecific antibodies. JNK activity was increased by low-dose DHA but not by EPA. p38 activity was not significantly altered by DHA or EPA. Cyclin E activity, as assessed with a histone H1 kinase assay, was inhibited by low-dose DHA but not by EPA. DHA increased expression of the cell cycle inhibitor p21 but not p27; EPA had no effect on p21 or p27. We propose that the differential effect of low-dose DHA vs EPA in suppressing MC mitogenesis is related to down-regulation of ERK and cyclin E activity and to induction of p21.

Gas6 Induces Mesangial Cell Proliferation via Latent Transcription Factor STAT3

Mesangial cell proliferation is essential for the pathogenesis and progression of glomerular disease. Previously, we showed that Gas6 plays a pivotal role in mesangial cell proliferation in vitro and in vivo. In the present study, we identified downstream targets of Gas6 signaling to examine the role in mesangial cell proliferation in vitro and in vivo. We found that Gas6 tyrosine phosphorylates STAT3 (signal transducers and activators of transcription) with concomitant translocation to the nucleus and induces STAT3-dependent transcriptional activation in cultured mesangial cells. Expressing dominant negative STAT3 inhibited Gas6-mediated transcriptional activation of STAT3 and abolished Gas6-induced mesangial cell proliferation. In a model of mesangial proliferative glomerulonephritis, STAT3 is phosphorylated in mesangial cells, and its phosphorylation peaks at day 8 after the injection of anti-Thy1.1 antibody. Inhibition of Gas6 by warfarin and the extracellular domain of its receptor, Axl, abolished phosphorylation of STAT3 in vivo. Thus, our in vitro and in vivo findings indicate that autocrine growth factor Gas6 induces mesangial cell proliferation via latent transcription factor STAT3. Therefore, STAT3 might be a new therapeutic target for kidney disease induced by mesangial proliferation.

Effects of 1,25(OH)2D3 in experimental mesangial proliferative nephritis in rats

1,25-Dihydroxyvitamin D3 [1,25(OH)2D3], the active form of vitamin D3, is a potent immunomodulatory agent on several cell types such as monocytes and mesangial cells. Recruitment of inflammatory cells, as well as stimulation of resident cells and mesangial matrix accumulation are key features of various experimental and human glomerular diseases. Here we show that 1,25(OH)2D3 attenuates the morphologic and functional alterations in anti-Thy-1.1. nephritis, an experimental model of mesangial proliferative glomerulonephritis. The anti-Thy-1.1 group (group I) comprised 24 rats that at day 0 received 0.5 mL of saline containing 400 microg of monoclonal antibodies (mAb) anti-Thy-1.1 IgG. The anti-Thy-1.1 treated with 1,25(OH)2D3 group (group II) were 24 rats given 1,25(OH)2D3 at the dose of 25 ng/100 g body wt/day, from day -3 to day 14. At day 0, the rats received 400 microg of anti-Thy-1.1 monoclonal IgG. The control group (group III) comprised 12 rats injected with vehicle alone; the control group treated with 1,25(OH)2D3 (group IV)-12 rats were given 1,25(OH)2D3 as in group II without mAb administration. Proteinuria and urinary interleukin-6 excretion were measured daily. Blood urea nitrogen and creatinine, creatinine clearance, calcium, and phosphate were measured at days 0, 4, 7, and 14. In addition to conventional periodic acid-Schiff staining, binding of anti-Thy-1.1 IgG and C3b complement fraction, His48- and ED1-positive cells were studied by immunofluorescence. Mesangial proliferation was studied by the proliferating cell nuclear antigen (PCNA) technique. Apoptosis was evaluated by the TUNEL assay. The anti-Thy-1.1 treated with 1,25(OH)2D3 group versus the anti-Thy-1.1 alone group showed a significant reduction in urinary protein (at day 7, 424 +/- 228 vs. 66 +/- 30 mg/mg urinary creatinine, P = 0.02) and interleukin-6 excretion (at day 3, 537 +/- 360 pg/mL vs. 110 +/- 34 pg/mg urinary creatinine, P = 0.015), reduced glomerular diameters (at day 7, 283 +/- 38 vs. 261 +/- 48 microm, P < 0.01), decreased neutrophil (at day 4, 20 +/- 12 His48-positive cells/glomerulus vs. 3.7 +/- 1.3 His48-positive cells/glomerulus, P < 0.001), and monocyte accumulation (day 7, 4.9 +/- 2.9 ED1-positive cells/glomerulus vs. 2.8 +/- 2.9 ED1-positive cells/glomerulus, P < 0.05), and attenuated glomerular cells proliferation (day 7, 13 +/- 3.2 PCNA-positive cells/glomerulus vs. 9.4 +/- 3 PCNA-positive cells/glomerulus, P < 0.01). Apoptosis showed a biphasic behavior with an early peak at day 4 in the anti-Thy-1.1 group (2.3 +/- 2.2 TUNEL-positive cells/glom) related to cellular lysis and a late peak at day 14 related to the recovery phase. 1,25(OH)2D3 can reduce glomerular hypercellularity, inflammatory infiltration in anti-Thy-1.1 nephritis, preserving the apoptotic response of the reparative phase.