STAT3 Protein-Protein Interaction Analysis Finds P300 as a Regulator of STAT3 and Histone 3 Lysine 27 Acetylation in Pericytes.

Background: Signal transducer and activator of transcription 3 (STAT3) is a member of the cytoplasmic inducible transcription factors and plays an important role in mediating signals from cytokines, chemokines, and growth factors. We and others have found that STAT3 directly regulates pro-fibrotic signaling in the kidney. The STAT3 protein-protein interaction plays an important role in activating its transcriptional activity.

Mast cells link immune sensing to antigen-avoidance behaviour.

The physiological functions of mast cells remain largely an enigma. In the context of barrier damage, mast cells are integrated in type 2 immunity and, together with immunoglobulin E (IgE), promote allergic diseases. Allergic symptoms may, however, facilitate expulsion of allergens, toxins and parasites and trigger future antigen avoidance.

Indian Hedgehog release from TNF-activated renal epithelia drives local and remote organ fibrosis.

Progressive fibrosis is a feature of aging and chronic tissue injury in multiple organs, including the kidney and heart. Glioma-associated oncogene 1 expressing (Gli1) cells are a major source of activated fibroblasts in multiple organs, but the links between injury, inflammation, and Gli1 cell expansion and tissue fibrosis remain incompletely understood. We demonstrated that leukocyte-derived tumor necrosis factor (TNF) promoted Gli1 cell proliferation and cardiorenal fibrosis through induction and release of Indian Hedgehog (IHH) from renal epithelial cells.

Therapeutic silencing of SMOC2 prevents kidney function loss in mouse model of chronic kidney disease.

Chronic kidney disease (CKD) is associated with substantial morbidity and mortality. We developed a mouse model that mimics human CKD with inflammation, extracellular matrix deposition, tubulointerstitial fibrosis, increased proteinuria, and associated reduction in glomerular filtration rate over time. Using this model, we show that genetic deficiency of SMOC2 or therapeutic silencing of SMOC2 with small interfering RNAs (siRNAs) after disease onset significantly ameliorates inflammation, fibrosis, and kidney function loss.

Dicer1 activity in the stromal compartment regulates nephron differentiation and vascular patterning during mammalian kidney organogenesis.

MicroRNAs, activated by the enzyme Dicer1, control post-transcriptional gene expression. Dicer1 has important roles in the epithelium during nephrogenesis, but its function in stromal cells during kidney development is unknown. To study this, we inactivated Dicer1 in renal stromal cells.

Anti-microRNA-21 oligonucleotides prevent Alport nephropathy progression by stimulating metabolic pathways.

MicroRNA-21 (miR-21) contributes to the pathogenesis of fibrogenic diseases in multiple organs, including the kidneys, potentially by silencing metabolic pathways that are critical for cellular ATP generation, ROS production, and inflammatory signaling. Here, we developed highly specific oligonucleotides that distribute to the kidney and inhibit miR-21 function when administered subcutaneously and evaluated the therapeutic potential of these anti-miR-21 oligonucleotides in chronic kidney disease. In a murine model of Alport nephropathy, miR-21 silencing did not produce any adverse effects and resulted in substantially milder kidney disease, with minimal albuminuria and dysfunction, compared with vehicle-treated mice.

Pericyte TIMP3 and ADAMTS1 modulate vascular stability after kidney injury.

Kidney pericytes are progenitors of scar-forming interstitial myofibroblasts that appear after injury. The function of kidney pericytes as microvascular cells and how these cells detach from peritubular capillaries and migrate to the interstitial space, however, are poorly understood. Here, we used an unbiased approach to identify genes in kidney pericytes relevant to detachment and differentiation in response to injury in vivo, with a particular focus on genes regulating proteolytic activity and angiogenesis.

MicroRNA-21 promotes fibrosis of the kidney by silencing metabolic pathways.

Scarring of the kidney is a major public health concern, directly promoting loss of kidney function. To understand the role of microRNA (miRNA) in the progression of kidney scarring in response to injury, we investigated changes in miRNA expression in two kidney fibrosis models and identified 24 commonly up-regulated miRNAs. Among them, miR-21 was highly elevated in both animal models and in human transplanted kidneys with nephropathy.

Loss of sphingosine kinase-1 in carcinoma cells increases formation of reactive oxygen species and sensitivity to doxorubicin-induced DNA damage.

Background And Purpose: Sphingosine kinases (SK) catalyse the formation of sphingosine 1-phosphate, which is a key lipid mediator regulating cell responses such as proliferation, survival and migration. Here we have investigated the effect of targeted inhibition of SK-1 on cell damage and elucidated the mechanisms involved.

Experimental Approach: Three human carcinoma cell lines (colon HCT-116, breast MDA-MB-231, lung NCI-H358) were used, which were either transduced with shRNA constructs to deplete SK-1, or treated with a SK-1 inhibitor.

A novel mode of action of the putative sphingosine kinase inhibitor 2-(p-hydroxyanilino)-4-(p-chlorophenyl) thiazole (SKI II): induction of lysosomal sphingosine kinase 1 degradation.

Background: Sphingosine kinase 1 (SK1) is a key enzyme in the generation of sphingosine 1-phosphate (S1P) which critically regulates a variety of important cell responses such as proliferation and migration. Therefore, inhibition of SK-1 has been suggested to be an attractive approach to treat tumor growth and metastasis formation.

Results: We show here that the previously developed putative SK-1 inhibitor 2-(p-hydroxyanilino)-4-(p-chlorophenyl) thiazole (SKI II) displays an additional facet of action complementary to the known inhibition of enzymatic SK-1 activity.

Transforming growth factor-beta2 upregulates sphingosine kinase-1 activity, which in turn attenuates the fibrotic response to TGF-beta2 by impeding CTGF expression.

Transforming growth factor-beta2 (TGF-beta2) stimulates the expression of pro-fibrotic connective tissue growth factor (CTGF) during the course of renal disease. Because sphingosine kinase-1 (SK-1) activity is also upregulated by TGF-beta, we studied its effect on CTGF expression and on the development of renal fibrosis. When TGF-beta2 was added to an immortalized human podocyte cell line we found that it activated the promoter of SK-1, resulting in upregulation of its mRNA and protein expression.

Sphingosylphosphorylcholine acts in an anti-inflammatory manner in renal mesangial cells by reducing interleukin-1beta-induced prostaglandin E2 formation.

Sphingosylphosphorylcholine (SPC) is a bioactive lipid that binds to G protein-coupled-receptors and activates various signaling cascades. Here, we show that in renal mesangial cells, SPC not only activates various protein kinase cascades but also activates Smad proteins, which are classical members of the transforming growth factor-beta (TGFbeta) signaling pathway. Consequently, SPC is able to mimic TGFbeta-mediated cell responses, such as an anti-inflammatory and a profibrotic response.

The immunomodulator FTY720 and its phosphorylated derivative activate the Smad signalling cascade and upregulate connective tissue growth factor and collagen type IV expression in renal mesangial cells.

1.--The immunomodulating agent FTY720 is a substrate for the sphingosine kinase and the phosphorylated form is able to bind to sphingosine 1-phosphate (S1P) receptors. In this study, we show that exposure of renal mesangial cells to phospho-FTY720 leads to a rapid and transient activation of several protein kinase cascades, including the mitogen- and stress-activated protein kinases.

PPARalpha activation upregulates nephrin expression in human embryonic kidney epithelial cells and podocytes by a dual mechanism.

Nephrin is an important member of the glomerular ultrafiltration complex and changes in its expression are associated with severe proteinuria. In this study, we show that synthetic PPARalpha agonists, but not PPARgamma agonists, stimulate an increased nephrin mRNA and protein expression in cultures of human podocytes and A293 human embryonic kidney epithelial cells which are blocked by the PPARalpha antagonist Ru486. Furthermore, the PPARalpha agonists have an additive effect on the interleukin-1beta (IL-1beta)-induced nephrin upregulation.

Nitric oxide induces TIMP-1 expression by activating the transforming growth factor beta-Smad signaling pathway.

Excessive accumulation of the extracellular matrix is a hallmark of many inflammatory and fibrotic diseases, including those of the kidney. This study addresses the question whether NO, in addition to inhibiting the expression of MMP-9, a prominent metalloprotease expressed by mesangial cells, additionally modulates expression of its endogenous inhibitor TIMP-1. We demonstrate that exogenous NO has no modulatory effect on the extracellular TIMP-1 content but strongly amplifies the early increase in cytokine-induced TIMP-1 mRNA and protein levels.

Heterologous desensitization of the sphingosine-1-phosphate receptors by purinoceptor activation in renal mesangial cells.

1 Sphingosine-1-phosphate (S1P) is considered a potent mitogen for mesangial cells and activates the classical mitogen-activated protein kinase (MAPK) cascade via S1P receptors. In this study, we show that S1P signalling is rapidly desensitized upon S1P receptor activation. A complete loss of S1P sensitivity occurs after 10 min of S1P pretreatment and remains for at least 8 h.

Sphingosine 1-phosphate cross-activates the Smad signaling cascade and mimics transforming growth factor-beta-induced cell responses.

Exposure of renal mesangial cells to sphingosine 1-phosphate (S1P) leads to a rapid and transient activation of the mitogen- and stress-activated protein kinases but also the protein kinase B. Here, we show that S1P also induces phosphorylation of Smad proteins, which are members of the transforming growth factor-beta (TGF-beta) signaling device. However, Smad phosphorylation occurred more slowly with a maximal effect after 20-30 min of S1P stimulation when compared with the rapid activation of the MAPKs.

Differential binding of ceramide to MEKK1 in glomerular endothelial and mesangial cells.

Previously, we have shown that ceramide is able to directly bind to and activate c-Raf and to trigger the downstream classical mitogen-activated protein kinase (MAPK/ERK) cascade in glomerular mesangial cells [Proc. Natl. Acad.

Interleukin-1beta inhibits ATP-induced protein kinase B activation in renal mesangial cells by two different mechanisms: the involvement of nitric oxide and ceramide.

1 Extracellular nucleotides, like ATP and UTP, have been shown to activate the protein kinase B (PKB) pathway in mesangial cells. In this study we report that the pro-inflammatory cytokine interleukin-1beta (IL-1beta) inhibits ATP-induced PKB activation. 2 Pretreatment of mesangial cells with IL-1beta leads to a time-dependent decrease of ATP-induced PKB phosphorylation.

Interleukin-1 inhibits angiotensin II-stimulated protein kinase B pathway in renal mesangial cells via the inducible nitric oxide synthase.

Exposure of rat renal mesangial cells to angiotensin II and angiotensin III leads to a rapid phosphorylation and activation of the protein kinase B (PKB) pathway. The angiotensin II analogs angiotensin-(1-7), angiotensin-(1-6) and angiotensin-(3-8) were unable to activate PKB. The angiotensin II and III effects are mediated by the angiotensin type 1 receptor as documented by the inhibitory action of valsartan.