Regulation Of Mesangial Cell Proliferation Research Articles

YAP mediates the interaction between the Hippo and PI3K/Akt pathways in mesangial cell proliferation in diabetic nephropathy.

Glomerular mesangial cell (MC) proliferation is one of the main pathological changes in diabetic nephropathy (DN), but its mechanism needs further elaboration. The Hippo and PI3K/Akt signalling pathways are involved in the regulation of MC proliferation, but their relationship in hyperglycaemia-induced MC proliferation has not been reported. We used db/db mice and high-glucose-cultured mesangial cells to generate a diabetic nephropathy model. An MST1-knockdown plasmid was used to identify whether the PI3K/Akt pathway is linked to the Hippo pathway through MST1. LY294002 and SC79 were used to verify the role of the PI3K/Akt signalling pathway in MC cells. RNA silencing and overexpression were performed by using YAP and PTEN-expression/knockdown plasmids to investigate the function of YAP and PTEN, respectively, in the Hippo and PI3K/Akt signalling pathways. By examining a potential feedback loop, we found decreased phosphorylation of MST1 and Lats1 and increased PI3K/Akt activation in db/db mice and high glucose-treated MCs, along with increased MC proliferation. The results of our gene silencing experiment proved PI3K/Akt-mediated intervention in the Hippo pathway and the regulatory effect of YAP on PI3K/Akt through PTEN. The Hippo pathway is inhibited under diabetic conditions, leading to YAP activation and promoting MC proliferation. The PI3K/Akt pathway is activated through the inhibitory effect of YAP on its repressor, PTEN. Finally, activation of the PI3K/Akt pathway inhibits the Hippo pathway, resulting in nuclear YAP accumulation and accelerating MC proliferation and DN formation.

SUN-134 CYTOSKELETON-ASSOCIATED PROTEIN 4 (CKAP4), A NEW PLAYER IN THE REGULATION OF MESANGIAL CELL PROLIFERATION

Cytoskeleton-associated protein 4 (CKAP4) has recently attracted attention within cancer research, where its overexpression has been associated with increased lung, pancreatic and kidney cancer cell proliferation and a worsened prognosis. However, the potential role of CKAP4 in mesangioproliferative diseases such as IgA nephropathy (IgAN) and diabetic nephropathy (DN) has not previously been studied. The main growth factor known to induce proliferation in mesangial cells is PDGF, and the mesangial cells are the only glomerular cells known to express PDGF receptor beta (PDGFRβ). PDGF is normally secreted by the glomerular endothelial cells as well as the mesangial cells themselves resulting in a paracrine and autocrine regulation of mesangial cell proliferation. Increased PDGF levels in the glomeruli leads to mesangial proliferation as seen in DN and IgAN. Our hypothesis is that CKAP4 is involved in the regulation of mesangial proliferation. Expression of CKAP4 in glomeruli was investigated using immunofluorescence and immunoEM on human renal sections. CKAP4 was silenced using shRNA in primary human mesangial cells. Westernblot and masspectrometry was used to study protein expression and BrdU proliferation assay to determine proliferation. In order to understand protein interaction co-immunoprecipitation was used. Finally, two different mouse models of DN was used to investigate CKAP4 expression in disease. Immunohistochemistry as well as immunoEM showed expression of CKAP4 in glomerular mesangial cells and in the cell bodies of podocytes. Silencing CKAP4 resulted in an abated mitogenic response to the growth factor PDGF-BB, and further experiments revealed a significantly decreased expression of the PDGF receptor, both on RNA and protein level. Preliminary results from co-immunoprecipitation experiments indicate that PDGFRβ and CKAP4 interact. Analysis of the total protein content in the silenced cells using mass spectrometry showed only small or no changes in expression of other growth factor receptors such as EGFR and TGFbRs. In two different mouse models of DN CKAP4 was found to be significantly upregulated in later stages of disease with established mesangial expansion and other key features of the disease. We here report for the first time that CKAP4 is expressed in mesangial cells and that the expression of CKAP4 influences the cellular proliferative response to PDGF-BB and the expression of PDGFRβ. CKAP4 has previously been reported to interact with the EGF receptor on the cell surface of hepatocellular carcinomas and thereby influencing the growth of these cells. The EGF receptor and the PDGF receptor has several similarities and are tyrosine kinase receptors. We suggest that the interaction between the PDGF receptor and CKAP4 resembles the one of CKAP4 and EGFR. CKAP4 could be a potential mediator and target of mesangial proliferation in glomerular kidney disease.

C3G overexpression in glomerular epithelial cells during anti-GBM-induced glomerulonephritis

The guanine nucleotide exchange factor C3G, along with the CrkII adaptor protein, mediates GTP activation of the small GTPase proteins Rap1 and R-Ras, facilitating their activation of downstream signaling pathways, which had been found to be important in the pathogenesis of glomerulonephritis. We found that expression of C3G protein was upregulated in glomerular epithelial cells in an experimental model of accelerated anti-GBM antibody-induced glomerulonephritis expression. To determine the consequence of its increased expression, we transfected C3G (using adenoviral constructs) into cultured glomerular epithelial cells and measured the activated forms (i.e., GTP-bound) forms of Rap1 and R-Ras. Activation of Rap1 was not affected by C3G; however, the basal level of GTP-bound R-Ras was decreased. Further, C3G over-expression enhanced the activation of R-Ras in response to endothelin. Overexpression of C3G also led to a significant reduction in glomerular epithelial cell spreading and decreased the cells' E-cadherin expression and augmented their migration. We found that C3G was overexpressed in accelerated anti-GBM antibody-induced glomerulonephritis and suggest that this modulates glomerular epithelial cell morphology and behavior.

TLR agonists regulate PDGF-B production and cell proliferation through TGF-β/type I IFN crosstalk

Transforming growth factor-beta (TGF-beta) and type I interferon (IFN) autocrine/paracrine loops are recognized as key mediators of signaling cascades that control a variety of cellular functions. Here, we describe a novel mechanism by which Toll-like receptor (TLR) agonists utilize these two autocrine/paracrine loops to differentially regulate the induction of PDGF-B, a growth factor implicated in a number of diseases ranging from tumor metastasis to glomerulonephritis. We demonstrate that CpG-specific induction of PDGF-B requires activation of Smads through TGFbeta1 autocrine/paracrine signaling. In contrast, polyinosinic:polycytidylic acid strongly represses CpG's as well as its own intrinsic ability to induce PDGF-B mRNA through type I IFN-mediated induction of Smad7, a negative regulator of Smad3/4. Furthermore, we have shown that this crosstalk mechanism translates into similar regulation of mesangial cell proliferation. Thus, our results demonstrate the importance of crosstalk between TGF-beta and type I IFNs in determining the specificity of TLR-mediated gene induction.

Inhibition of geranylgeranylation suppresses the proliferation of rat cultured mesangial cells

SUMMARY: Mesangial hypercellularity is a critical early histopathological finding observed in human and experimental glomerular diseases. the regulation of mesangial cell proliferation may be crucial in the treatment of glomerular injury. Ras proteins are guanosine triphosphatases that regulate proliferation and differentiation by transducing biological information from extracellular signals to the nucleus. the blocking of Ras function by inhibitors of prenyltransferase has been shown to suppress the proliferation in several kinds of cell types. the objective of the present study was to examine the effects of selective inhibitors of farnesylation (FTI‐277) and geranylgeranylation (GGTI‐286) on proliferation of cultured rat mesangial cells. the incubation of mesangial cells with FTI‐277 and GGTI‐286 with stimulation by either 10% fetal calf cell (FCS) or platelet‐derived growth factor (PDGF) was performed, and bromo‐deoxyuridine (BrdU) incorporation was measured. Ras processing and mitogen‐active protein (MAP) kinase activation, after the incubation with 10% FCS, were also examined. Geranylgeranylation caused a dose‐dependent reduction of FCS or PDGF‐stimulated BrdU incorporation. Geranylgeranylation also inhibited the activation of MAP kinase, but not Ras processing, stimulated by 10% FCS. However, FTI‐277 had little effect on DNA synthesis and MAP kinase activation induced by FCS or PDGF, despite the inhibition of Ras processing. the present study showed that GGTI‐286 inhibited the proliferation of rat cultured mesangial cells. It appears that the antiproliferative effect of the geranylgeranyl transferase I inhibitor may be useful in preventing mesangial cell proliferation.

Regulation of mesangial cell proliferation

Regardless of the source of injury, an imbalance in the control of mesangial cell proliferation appears to play a direct role in the degree of progressive renal injury and glomerulosclerosis. Some of the regulatory mechanisms include specific soluble or non-soluble extracellular factors and a complex array of receptor-mediated signals that control the progression of the cell cycle or cell death. Understanding these regulatory processes could lead to novel therapeutic strategies to alleviate or arrest proliferative glomerular disease.

Effect of simvastatin on proliferative nephritis and cell-cycle protein expression

Mesangial cell proliferation is important in subsequent mesangial matrix expansion in glomerular injury. Therefore, the regulation of mesangial cell proliferation may be critical in the treatment of glomerulonephritis. Inhibition of 3-hydro-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibits the production of mevalonate and has been shown to suppress proliferation in many cell types, including mesangial cells in vitro. It is expected that HMG-CoA reductase inhibitor may suppress mesangial cell proliferation and subsequent progression of glomerulonephritis. Recently, the tight relationship between cell-cycle regulatory protein expression and mesangial cell proliferation in experimental glomerulonephritis was demonstrated. The aim of the present study is to examine the effect of simvastatin, one of the HMG-CoA reductase inhibitors, on the glomerular cell proliferation and on the expression of CDK2 or p27Kip1 in mesangial cells in experimental glomerulonephritis in vivo. The effect of simvastatin on a rat mesangial proliferative glomerulonephritis induced by antithymocyte antibody (anti-Thy 1.1 GN) was studied. Administration of simvastatin or vehicle (for control GN) were started from two days before disease induction, and was continued to the day of nephrectomy. Nephrectomy was done at days 0, 2, 4, 7, 12 and 20 after disease induction. Immunohistochemistry for proliferating cells, macrophages, alpha-smooth muscle actin, type IV collagen and PDGF-B chain was performed, respectively, in addition to conventional periodic-acid Schiff staining. Double immunostaining for CDK2/OX-7 or p27Kip1/OX-7 was also done, respectively. There was no difference in the degree of the initial injuries between simvastatin-treated and control GN rats. The most pronounced feature of simvastatin-treated GN was the suppression of the early glomerular cell proliferation (about 70% of proliferation was suppressed at day 4). At day 4, alpha-smooth muscle actin expression was also decreased in simvastatin-treated GN rats. Inhibition of macrophage recruitment into glomeruli by simvastatin was also a prominent feature (about 30% decrease in the number of glomerular macrophages at day 2). Simvastatin significantly suppressed subsequent mesangial matrix expansion and type IV collagen accumulation in glomeruli. Although it might simply reflect the reduction in mesangial cells, glomerular PDGF-B chain expression was reduced. There was no significant difference in plasma lipids levels at day 2 and day 4. In vehicle-treated GN rats, the number of CDK2+/OX-7+ cells (CDK2-expressed mesangial cells) in glomeruli increased significantly from day 4 to day 7. Although simvastatin suppressed mesangial cell proliferation, the increase in the number of glomerular CDK2+/OX-7+ cells was also attenuated by simvastatin treatment. There was no difference in the number of p27Kip1+/OX-7+ cells (p27Kip1-expressed mesangial cells) in the glomerulus between vehicle-treated and simvastatin-treated GN rats. Simvastatin suppressed mesangial cell proliferation and subsequent matrix expansion, and macrophage infiltration into glomeruli in anti-Thy 1.1 GN rats. The antiproliferative effect of simvastatin in this model was also associated with the reduction of CDK2 expression in mesangial cells.

C-type natriuretic peptide inhibits mesangial cell proliferation and matrix accumulation in vivo

Local C-type natriuretic peptide (CNP) production and CNP receptor expression have been demonstrated in glomeruli. However, the glomerular (patho-)physiological functions of CNP are largely unknown. We therefore investigated the effects of CNP on mesangial cell proliferation and matrix accumulation in the rat mesangioproliferative anti-Thy 1.1 model. Over seven days rats received a continuous infusion (1 microgram/kg/min) of either CNP (N = 6), an irrelevant control peptide (N = 3) or buffer alone (N = 6). Kidney biopsies were performed on days 2, 4 and 8. Few significant differences between the groups were noted on days 2 and 4. Compared to buffer treated rats on day 8, those receiving CNP showed a 35% reduction of glomerular mitoses, a 62% reduction of glomerular uptake of the thymidine analogue BrdU and a significant reduction in glomerular expression of PDGF B-chain. Double immunoperoxidase staining also revealed blunting of proliferating, activated mesangial cells (515 reduction of alpha-smooth muscle actin-/BrdU-positive cells) and macrophage influx. Moreover, there was a marked reduction of mesangial collagen IV and fibronectin accumulation at the protein and mRNA level. Rats receiving the control peptide were indistinguishable from buffer treated rats. Systemic blood pressure was reduced by 10 to 20% in both CNP and control peptide treated rats on day 8, excluding that the findings were due to hemodynamic effects of CNP. Our findings demonstrate that CNP is involved in the regulation of mesangial cell proliferation and matrix production in vivo. The data suggest the existence of a glomerular natriuretic peptide system that may regulate tissue homeostasis and contribute to resolution of mesangioproliferative diseases.

Regulation of mesangial cell proliferation by the mevalonate pathway.

Regulation of mesangial cell proliferation by the mevalonate pathway.

Lipids and the kidney

Part 1 Lipids as a risk factor for renal disease: lipid abnormalities in progressive renal insufficiency hypertension, hyperlipidemia and microalbuminuria apolipoprotein E phenotype and renal disease lipoprotein glomerulopathy and its pathogenesis cholesterol as a predictor of progression in diabetic renal disease cholesterol as a predictor of progression in nondiabetic chronic renal disease role of lipids in chronic renal allograft rejection. Part 2 Treatment of dyslipidemia in patients with renal disease: effect of lipid-lowering therapy on the progression of renal disease in nondiabetic nephrotic patients treatment of hyperlipidemia in patients with non-insulin-dependent diabetes mellitus with progressive nephropathy effect of antiproteinuric treatment on the lipid profile in nondiabetic renal disease the effect of HMG-CoA reductase inhibitors on chronic allograft rejection long-term low-density lipoprotein immunoapheresis in renal disease. Part 3 Mechanisms of lipid-induced renal injury - experimental insights: role of lipids in progressive renal disease - insights from the analbuminemic rat hyperlipidemia and tissue contents of N-sigma-(carboxymethyl)lysine in streptozotocin diabetes effects of lipids on glomerular fibrinolysis in vitro effects of lipoprotein (a) on mesangial cell biology HMG-CoA reductase inhibitor suppression of glomerular cell proliferation in rats with anti-thy-1.1 nephritis the role of oxidatively modified lipoproteins in lipid nephropathy effect of low-density lipoproteins on mesangial cell expression of monocyte chemoattractant peptides. Part 4 New insights into effects of antilipemic therapy: regulation of mesangial cell proliferation by the mevalonate pathway hypercholesterolemia and progressive kidney disease - the role of macrophages and macrophage-derived products central role of the transcription factor nuclear factor-kB in mesangial cell production of chemokines isoprenoids, ras and proliferative glomerular disease.

A Dual Effect of Somatostatin on the Proliferation of Cultured Rat Mesangial Cells

The present experiments were designed to analyze the ability of somatostatin to modulate the proliferation of cultured rat mesangial cells. In the absence of fetal calf serum, somatostatin stimulated cell proliferation in a dose-dependent manner. In contrast, in proliferating cells, somatostatin inhibited cell proliferation, also in a dose-dependent fashion. Zaprinast, a rather specific cyclic GMP phosphodiesterase blocker, inhibited the somatostatin-dependent proliferation in the absence of growth factors. However, it potentiated the inhibitory effect on proliferating cells. These results support a dual role for somatostatin in the regulation of mesangial cell proliferation. The inhibitory effect of the peptide may be mediated by cyclic GMP.

Mesangial cells in the pathogenesis of progressive glomerular disease in animal models.

Increasing evidence supports a role for glomerular mesangial cell proliferation and over-production of extracellular matrix by mesangial cells in the development of focal or diffuse glomerulosclerosis. Experimental data obtained mainly in the chronic progressive remnant kidney model and in the acute mesangioproliferative anti-Thy 1.1 glomerulonephritis in rats have shed some insights into the factors governing mesangial cell proliferation and matrix synthesis in vivo. In these experimental models, mesangial cell activation can be demonstrated early in the course of disease as exemplified by the de novo expression by the mesangial cell of a smooth muscle "specific" actin isotype (i.e., alpha-smooth muscle actin). Following mesangial cell activation, cellular proliferation ensues both in the acute anti-Thy 1.1 model and, to a lesser degree, in the chronic remnant kidney model. While a multitude of mitogens for mesangial cells has been proposed on the basis of in vitro experiments, the factors involved in the regulation of mesangial cell proliferation in vivo remain largely undefined. Three growth factors which may have important roles in the in vivo mesangioproliferative response are platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), and transforming growth factor-beta (TGF-beta). All three cytokine growth factors are present in various inflammatory cells as well as in mesangial cells themselves, thereby allowing these factors to mediate cell proliferation by either paracrine and/or autocrine pathways. In vivo studies show that PDGF, bFGF, and TGF-beta participate in the mesangial cell proliferation and/or the mesangial matrix expansion that follows mesangial cell injury with anti-Thy 1.1 antibody.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of Mesangial Cell Proliferation

Mesangial cell proliferation constitutes a frequent finding in a number of glomerular diseases that progress to glomerular sclerosis. The factors responsible for mesangial cell growth regulation in vivo are ill defined. However, cell culture data indicate that an array of mediators may have mitogenic or antimitogenic effects on these cells. This brief review discusses the relevance of selected factors such as platelet-derived growth factor (PDGF) in this context. In vitro data indicate that PDGF is one of the most potent mesangial cell mitogens, that it may have autoregulatory properties, and that it may represent the final common pathway for a number of other mitogenic peptides. In contrast to PDGF, the relevance of inflammatory cytokines such as interleukin-1 (IL-1), tumor necrosis factor (TNF) or interleukin-6 (IL-6) for mesangial cell proliferation is less evident, with growth-inhibitory to weakly growth-promoting effects on mesangial cells. Transforming growth factor beta (TGF beta) appears to be unique in that it has a concentration-dependent mitogenic or antimitogenic effect on mesangial cells. Prostaglandins may also have variable effects, ranging from mitogenic (PGE2 alpha) to growth inhibitory (PGI2, PGF2, TxA2). These data support the notion that mesangial cell growth in vivo is regulated by a complex network of synergistic or antagonistic growth factors. The relative importance of each of these growth factors in the in vivo situation will have to be elucidated by future studies using specific receptor antagonists or neutralizing antibodies.