Angiotensina II y Gremlin activan la vía Smad durante la transición epitelio-mesenquinal, un mecanismo báisco de progresión de daño renal

espanolLa transicion epitelio-mesenquimal (TEM) es un proceso que contribuye de forma importante a la fibrosis renal. Entre los factores implicados en la progresion del dano renal, destaca Angiotensina II (AngII) como un elemento clave en la fibrosis. De hecho, los farmacos que bloquean AngII son una de las mejores estrategias terapeuticas actuales en patologia renal. El objetivo de esta tesis ha sido investigar los mecanismos moleculares y mediadores implicados en la TEM. Para ello se han realizado estudios in vitro, in vivo y en biopsias de pacientes, utilizando tecnicas de biologia molecular y bioquimica. Los resultados demuestran que AngII induce TEM en el rinon a traves de la activacion directa, independiente de TGF-s, de la via Smad. La regulacion de este proceso es compleja e implica la activacion de otros sistemas de senalizacion intracelular (como MAPK y RhoA/ROCK), y la sintesis endogena de mediadores profibroticos, como TGF-s y CTGF. En conjunto, estos datos sugieren que el bloqueo de la activacion de Smad o de la sintesis endogena de CTGF son dos potenciales dianas terapeuticas en fibrosis renal. Ademas, explican los efectos organo-protectores del bloqueo de AngII. El estudio de biopsias de pacientes con diversas glomerulopatias progresivas mostro sobre-expresion de Gremlin en areas de fibrosis tubulo-intersticial, co-localizado con TGF-s, Smad activado y marcadores de TEM. Factores claves en el dano renal, como AngII y TGF-s, regulan la expresion renal de Gremlin. En estudios in vitro, Gremlin induce cambios tipicos de TEM, a traves de la activacion de la ruta TGF- s/Smad. Estos datos sugieren que Gremlin puede ser considerado como un nuevo mediador profibrotico, y amplian los conocimientos sobre los procesos moleculares implicados en la fibrosis renal y sugieren nuevas dianas terapeuticas para las enfermedades renales cronicas. English_________ __ Summary Epithelial-mesenchymal transition (EMT) is an important process that contributes to renal fibrosis. Among the factors involved in the progression of renal damage, Angiotensin II (AngII) highlights as inducer of fibrosis. Drugs that block AngII actions are one of the best treatments to slow the progression of kidney diseases. The aim of this thesis was to investigate the molecular mechanisms and mediators involved in EMT. For this purpose, different approaches were done: in vitro, in vivo and in biopsies studies, using various techniques of molecular biology and biochemistry. The results presented in this study show that AngII induces EMT in the kidney through direct activation of the Smad pathway, independently of TGF-s. The regulation of this process is complex and involves the activation of other intracellular signaling systems (such as MAPK and RhoA/ROCK), and endogenous synthesis of profibrotic mediators such as TGF-s and CTGF. Taken together, these data show that inhibition of Smad pathway and endogenous synthesis of CTGF could be good therapeutic strategies against renal fibrosis. In addition, these findings explain the renoprotective effect of drugs that block AngII by acting at the cellular level. The study of biopsies from patients with several progressive glomerulopathies showed over-expression of Gremlin in areas of tubulointerstitial fibrosis in co-localization with TGF-s, Smad activation and EMT markers. Gremlin is regulated in the kidney by key factors in renal damage, such as AngII and TGF-s. Our in vitro studies demonstrated that Gremlin induces typical changes of EMT through activation of TGF-s/Smad pathway. These data suggest that Gremlin can be considered as a new mediator of fibrosis. These results extend the knowledge about the molecular processes involved in renal fibrosis and suggest new therapeutic targets for chronic kidney disease.