RESUMEN
The Wnt/ß-catenin signaling pathway plays an important role in renal development and is reexpressed in the injured kidney and other organs. ß-Catenin signaling is protective in acute kidney injury (AKI) through actions on the proximal tubule, but the current dogma is that Wnt/ß-catenin signaling promotes fibrosis and development of chronic kidney disease (CKD). As the role of proximal tubular ß-catenin signaling in CKD remains unclear, we genetically stabilized (i.e., activated) ß-catenin specifically in murine proximal tubules. Mice with increased tubular ß-catenin signaling were protected in 2 murine models of AKI to CKD progression. Oxidative stress, a common feature of CKD, reduced the conventional T cell factor/lymphoid enhancer factor-dependent ß-catenin signaling and augmented FoxO3-dependent activity in proximal tubule cells in vitro and in vivo. The protective effect of proximal tubular ß-catenin in renal injury required the presence of FoxO3 in vivo. Furthermore, we identified cystathionine γ-lyase as a potentially novel transcriptional target of ß-catenin/FoxO3 interactions in the proximal tubule. Thus, our studies overturned the conventional dogma about ß-catenin signaling and CKD by showing a protective effect of proximal tubule ß-catenin in CKD and identified a potentially new transcriptional target of ß-catenin/FoxO3 signaling that has therapeutic potential for CKD.
Asunto(s)
Proteína Forkhead Box O3/metabolismo , Túbulos Renales Proximales/metabolismo , Insuficiencia Renal Crónica/metabolismo , Transducción de Señal , beta Catenina/metabolismo , Lesión Renal Aguda/genética , Lesión Renal Aguda/metabolismo , Lesión Renal Aguda/patología , Animales , Proteína Forkhead Box O3/genética , Túbulos Renales Proximales/patología , Masculino , Ratones , Ratones Transgénicos , Insuficiencia Renal Crónica/genética , Insuficiencia Renal Crónica/patología , beta Catenina/genéticaRESUMEN
Tuberous sclerosis complex 2 (TSC2), or tuberin, is a pivotal regulator of the mechanistic target of rapamycin signaling pathway that controls cell survival, proliferation, growth, and migration. Loss of Tsc2 function manifests in organ-specific consequences, the mechanisms of which remain incompletely understood. Recent single cell analysis of the kidney has identified ATP-binding cassette G2 (Abcg2) expression in renal proximal tubules of adult mice as well as a in a novel cell population. The impact in adult kidney of Tsc2 knockdown in the Abcg2-expressing lineage has not been evaluated. We engineered an inducible system in which expression of truncated Tsc2, lacking exons 36-37 with an intact 3' region and polycystin 1, is driven by Abcg2. Here, we demonstrate that selective expression of Tsc2fl36-37 in the Abcg2pos lineage drives recombination in proximal tubule epithelial and rare perivascular mesenchymal cells, which results in progressive proximal tubule injury, impaired kidney function, formation of cystic lesions, and fibrosis in adult mice. These data illustrate the critical importance of Tsc2 function in the Abcg2-expressing proximal tubule epithelium and mesenchyme during the development of cystic lesions and remodeling of kidney parenchyma.
Asunto(s)
Transportador de Casetes de Unión a ATP, Subfamilia G, Miembro 2/metabolismo , Fibrosis/patología , Enfermedades Renales Poliquísticas/patología , Transportador de Casetes de Unión a ATP, Subfamilia G, Miembro 2/genética , Animales , Linaje de la Célula , Femenino , Fibrosis/genética , Túbulos Renales Proximales/patología , Masculino , Ratones , Miofibroblastos/fisiología , Enfermedades Renales Poliquísticas/metabolismo , Moduladores Selectivos de los Receptores de Estrógeno/farmacología , Tamoxifeno/farmacología , Proteína 2 del Complejo de la Esclerosis Tuberosa/genética , Proteína 2 del Complejo de la Esclerosis Tuberosa/metabolismoRESUMEN
The TGF-ß and Wnt/ß-catenin pathways have important roles in modulating CKD, but how these growth factors affect the epithelial response to CKD is not well studied. TGF-ß has strong profibrotic effects, but this pleiotropic factor has many different cellular effects depending on the target cell type. To investigate how TGF-ß signaling in the proximal tubule, a key target and mediator of CKD, alters the response to CKD, we injured mice lacking the TGF-ß type 2 receptor specifically in this epithelial segment. Compared with littermate controls, mice lacking the proximal tubular TGF-ß receptor had significantly increased tubular injury and tubulointerstitial fibrosis in two different models of CKD. RNA sequencing indicated that deleting the TGF-ß receptor in proximal tubule cells modulated many growth factor pathways, but Wnt/ß-catenin signaling was the pathway most affected. We validated that deleting the proximal tubular TGF-ß receptor impaired ß-catenin activity in vitro and in vivo Genetically restoring ß-catenin activity in proximal tubules lacking the TGF-ß receptor dramatically improved the tubular response to CKD in mice. Deleting the TGF-ß receptor alters many growth factors, and therefore, this ameliorated response may be a direct effect of ß-catenin activity or an indirect effect of ß-catenin interacting with other growth factors. In conclusion, blocking TGF-ß and ß-catenin crosstalk in proximal tubules exacerbates tubular injury in two models of CKD.
Asunto(s)
Fallo Renal Crónico/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Receptores de Factores de Crecimiento Transformadores beta/metabolismo , Factor de Crecimiento Transformador beta1/metabolismo , beta Catenina/metabolismo , Animales , Ácidos Aristolóquicos/química , Núcleo Celular/metabolismo , Colágeno/química , Cruzamientos Genéticos , Epitelio/metabolismo , Femenino , Eliminación de Gen , Túbulos Renales Proximales/metabolismo , Masculino , Ratones , Ratones Endogámicos BALB C , Ratones Noqueados , Ratones Transgénicos , Receptor Tipo II de Factor de Crecimiento Transformador beta , Transducción de Señal , Factor de Crecimiento Transformador beta1/antagonistas & inhibidores , Proteínas Wnt/metabolismo , beta Catenina/antagonistas & inhibidoresRESUMEN
Transforming growth factor-ß (TGF-ß) and hepatocyte growth factor (HGF) play key roles in regulating the response to renal injury but are thought to mediate divergent effects on cell behavior. However, how TGF-ß signaling alters the response to HGF in epithelia, the key site of HGF signaling in the injured kidney, is not well studied. Contrary to our expectation, we showed that deletion of the TGF-ß type II receptor in conditionally immortalized proximal tubule (PT) cells impaired HGF-dependent signaling. This reduced signaling was due to decreased transcription of c-Met, the HGF receptor, and the TGF-ß-dependent c-Met transcription and increased response to HGF in PT cells were mediated by the Notch pathway. The interactions of TGF-ß, HGF, and Notch pathways had biologically significant effects on branching morphogenesis, cell morphology, migration, and proliferation. In conclusion, epithelial TGF-ß signaling promotes HGF signaling in a Notch-dependent pathway. These findings suggest that TGF-ß modulates PT responses not only by direct effects, but also by affecting other growth factor signaling pathways.
Asunto(s)
Factor de Crecimiento de Hepatocito/metabolismo , Túbulos Renales Proximales/metabolismo , Proteínas Proto-Oncogénicas c-met/metabolismo , Receptores Notch/metabolismo , Factor de Crecimiento Transformador beta/metabolismo , Secretasas de la Proteína Precursora del Amiloide/antagonistas & inhibidores , Animales , Células Cultivadas , Ratones , Proteínas Serina-Treonina Quinasas/deficiencia , Receptor Tipo II de Factor de Crecimiento Transformador beta , Receptores de Factores de Crecimiento Transformadores beta/deficiencia , Transducción de Señal , Factor de Crecimiento Transformador beta/antagonistas & inhibidoresRESUMEN
Transforming growth factor-ß (TGF-ß) strongly promotes renal tubulointerstitial fibrosis, but the cellular target that mediates its profibrotic actions has not been clearly identified. While in vitro data suggest that TGF-ß-induced matrix production is mediated by renal fibroblasts, the role of these cells in TGF-ß-dependent tubulointerstitial fibrosis following renal injury is not well defined. To address this, we deleted the TGF-ß type II receptor in matrix-producing interstitial cells using two different inducible Cre models: COL1A2-Cre with a mesenchymal enhancer element and tenascin-Cre that targets medullary interstitial cells, and either the mouse unilateral ureteral obstruction or the aristolochic acid renal injury model. Renal interstitial cells lacking the TGF-ß receptor had significantly impaired collagen I production, but, unexpectedly, overall tissue fibrosis was unchanged in the conditional knockouts after renal injury. Thus, abrogating TGF-ß signaling in matrix-producing interstitial cells is not sufficient to reduce fibrosis after renal injury.
Asunto(s)
Matriz Extracelular/metabolismo , Enfermedades Renales/metabolismo , Riñón/metabolismo , Transducción de Señal , Factor de Crecimiento Transformador beta/metabolismo , Actinas/metabolismo , Animales , Ácidos Aristolóquicos , Células Cultivadas , Colágeno Tipo I/metabolismo , Modelos Animales de Enfermedad , Matriz Extracelular/genética , Fibrosis , Riñón/patología , Enfermedades Renales/etiología , Enfermedades Renales/genética , Enfermedades Renales/patología , Enfermedades Renales/prevención & control , Ratones Endogámicos C57BL , Ratones Noqueados , Proteínas Serina-Treonina Quinasas/genética , Proteínas Serina-Treonina Quinasas/metabolismo , Receptor beta de Factor de Crecimiento Derivado de Plaquetas/metabolismo , Receptor Tipo II de Factor de Crecimiento Transformador beta , Receptores de Factores de Crecimiento Transformadores beta/genética , Receptores de Factores de Crecimiento Transformadores beta/metabolismo , Factores de Tiempo , Obstrucción Ureteral/complicacionesRESUMEN
TGF-ß is a profibrotic growth factor in CKD, but its role in modulating the kidney's response to AKI is not well understood. The proximal tubule epithelial cell, which is the main cellular target of AKI, expresses high levels of both TGF-ß and its receptors. To determine how TGF-ß signaling in this tubular segment affects the response to AKI, we selectively deleted the TGF-ß type II receptor in the proximal tubules of mice. This deletion attenuated renal impairment and reduced tubular apoptosis in mercuric chloride-induced injury. In vitro, deficiency of the TGF-ß type II receptor protected proximal tubule epithelial cells from hydrogen peroxide-induced apoptosis, which was mediated in part by Smad-dependent signaling. Taken together, these results suggest that TGF-ß signaling in the proximal tubule has a detrimental effect on the response to AKI as a result of its proapoptotic effects.