학술논문
El receptor del factor de crecimiento epidérmico (EGFR): Nueva diana terapéutica en la patología renal
Document Type
Dissertation/Thesis
Author
Source
Subject
Language
Spanish; Castilian
Abstract
La mayor parte de las enfermedades renales crónicas (ERC) se caracterizan por una inflamación crónica y una fibrosis progresiva, que conduce a una insuficiencia renal terminal. Existen diferentes factores/mediadores que participan en la progresión de la ERC, entre los que destacan CCN2, PTHrP y TWEAK. El EGFR es un receptor de membrana de tipo tirosina quinasa que se expresa en glomérulo y túbulointersticio renal. Estudios previos han descrito el papel clave del EGFR en la progresión de la fibrosis renal. Sin embargo, no existen apenas datos concluyentes sobre su papel en el proceso inflamatorio. El objetivo general de esta tesis es determinar la contribución de la vía del EGFR en el daño renal experimental, investigando sus efectos en los procesos de inflamación y fibrosis, y evaluando los mecanismos intracelulares implicados, con el fin de mejorar las estrategias terapéuticas actuales empleadas en pacientes con ERC. La activación del EGFR se puede producir mediante activación directa o mediante “transactivación”, esta última dependiente de MMPs/ADAMs. Los resultados de esta tesis han demostrado que CCN2 es un nuevo ligando del EGFR que se une directamente a este receptor y lo activa, de forma independiente de MMPs/ADAMs. Por otro lado, diversos factores implicados en el daño renal, tales como PTHrP y TWEAK, desencadenan la transactivación del EGFR en el riñón. Los mecanismos implicados en la transactivación del EGFR inducida por PTHrP, vía el receptor acoplado a proteínas G PTH1R, incluyen MMPs, PKC y Src. Por otro lado, TWEAK, mediante su interacción con su receptor Fn14, transactiva el EGFR por activación de ADAM17 y liberación de los ligandos HB-EGF y TGF-α. Estudios experimentales previos sugieren que el bloqueo de la vía del EGFR podría ser una diana antifibrótica en la patología renal. En estudios in vitro hemos observado que la activación directa del EGFR por CCN2, y la transactivación de esta ruta por PTHrP es capaz de regular los eventos asociados a la transición epitelio mesenquimal, proceso que contribuye a la fibrogénesis renal. Los resultados obtenidos en esta tesis estudiando los modelos experimentales de daño renal por administración sistémica de CCN2(IV) o de TWEAK en ratón, demuestran que la activación de la vía del EGFR se asocia a un proceso inflamatorio que se previene con el bloqueo farmacológico de esta ruta. El bloqueo de la transactivación del EGFR inducida por TWEAK modulando el eje ADAM17/EGFR, disminuyó la respuesta inflamatoria, sugiriendo que el bloqueo de este eje podría ser una buena opción terapéutica para enfermedades inflamatorias renales. La enfermedad renal crónica se caracteriza por una deficiencia en los niveles de vitamina D. Diversos datos experimentales demuestran que los agonistas del receptor de vitamina D (VDRAs) ejercen efectos antinflamatorios beneficiosos en ERC. En esta tesis hemos observado que el tratamiento con el VDRA Paricalcitol inhibió la transactivación del EGFR inducida por TWEAK así como la activación de mecanismos intracelulares posteriores, incluyendo la sobreexpresión de factores proinflamatorios y la presencia de células infiltrantes en el riñón. El factor de trascripción NF-κB juega un papel clave en la regulación de la respuesta inflamatoria renal. TWEAK es una de las pocas citoquinas que activa la vía canónica y la no canónica de NF-κB. El bloqueo de la trasactivación de EGFR inducido por TWEAK mediante diferentes abordajes farmacológicos, como Paricalcitol, no inhibió la activación de la vía canónica de NF-κB1 mientras que si bloqueó la activación de la vía no canónica NF-κB2 y la inducción de quimioquinas específicas de esta ruta. Estos resultados muestran un nuevo mecanismo antinflamatorio de los VDRAs mediante la modulación de la vía del EGFR y de la ruta no canónica de NF-κB. En resumen, estos datos sugieren que la vía de señalización de EGFR podría ser considerada como una nueva diana terapéutica en el daño renal debido a su participación recurrente en el proceso inflamatorio y fibrótico en respuesta a diferentes estímulos en el riñón. El uso de bloqueantes de esta vía de señalización podría tener un alto valor terapéutico para el tratamiento de pacientes con ECR.
Chronic kidney diseases (CKD) are characterized by persistent inflammation and progressive fibrosis leading to end stage renal disease. Several studies have demonstrated that CCN2, PTHrP and TWEAK, are key factors involved in the progression of CKD. EGFR is a membrane tyrosine kinase receptor expressed in the kidney. Previous data have described the role of EGFR in experimental renal fibrosis, but information about its potential role in the inflammatory process is scarce. The main aim of this thesis was to investigate the contribution of the EGFR pathway in experimental kidney damage, evaluating its role on inflammation and fibrosis, and the intracellular mechanisms involved in EGFR signalling. An additional goal was to increase the actual knowledge of renal pathology and improve the current therapeutic strategies. EGFR activation may occur by direct binding or by "transactivation", the latter process mediated by MMPs/ADAMs. The results of this study have shown that CCN2 is a new EGFR ligand that directly binds to this receptor and activates its signalling pathway, by an MMPs/ADAMs independent process. Furthermore, EGFR can be transactivated in the kidney by several factors involved in renal damage such as PTHrP and TWEAK, as described here for the first time. PTHrP, by its binding to the G coupled receptor PTH1R, can transactivate EGFR by 2 different mechanisms; PKC/MMPs activation or Src activation. TWEAK, through interaction with its receptor Fn14, activates ADAM17 that release HB-EGF and TGF-α ligands, leading to EGFR transactivation. Previous experimental studies suggest that EGFR pathway blockade could be an antifibrotic target for renal disease. In vitro studies showed that direct activation of EGFR by CCN2, and EGFR transactivation by PTHrP, could regulate epithelial mesenchymal transition, a process that contributes to renal fibrogenesis. In vivo studies, including the experimental models of renal damage mediated caused by systemic administration of CCN2 (IV) or TWEAK in mice, have demonstrated that activation of the EGFR pathway is associated with an inflammatory process in the kidney, which it is prevented by EGFR pharmacological blockade. In particular, TWEAK-induced EGFR transactivation and renal inflammation was blocked by ADAM17/EGFR inhibition, suggesting that the blockade of this axis could be a good therapeutic option for renal inflammatory diseases. Chronic renal disease is characterized by vitamin D deficiency. Several experimental data have shown that vitamin D receptor agonists (VDRAs) exert beneficial antinflammatory effects in CKD. In this thesis we have described that treatment with the VDRA Paricalcitol inhibited TWEAK-mediated EGFR transactivation and subsequent activation of intracellular mechanisms, including overexpression of proinflammatory factors and the infiltration of inflammatory cells into the kidney. The NF-κB plays a key role in the regulation of the inflammatory response. TWEAK is one of the few cytokines that activates both the canonical and non-canonical NF-κB pathway. Blockade of TWEAK-induced EGFR transactivation by different approaches, including Paricalcitol, inhibited the non canonical, but not the canonical, NF-κB pathway. These results described a novel antinflammatory mechanism of VDRAs that includes the modulation of the EGFR pathway and the inhibition of the noncanonical NF-κB2 pathway. In summary, all these data show that EGFR signalling pathway activation is involved in the modulation of inflammatory and fibrotic process in the kidney in response to different stimuli, and suggest that the blockade of EGFR signalling pathway could be considered as a new therapeutic target in renal diseases. Blockers of this signalling pathway could have a relevant therapeutic value for the treatment of CKD patients.
Chronic kidney diseases (CKD) are characterized by persistent inflammation and progressive fibrosis leading to end stage renal disease. Several studies have demonstrated that CCN2, PTHrP and TWEAK, are key factors involved in the progression of CKD. EGFR is a membrane tyrosine kinase receptor expressed in the kidney. Previous data have described the role of EGFR in experimental renal fibrosis, but information about its potential role in the inflammatory process is scarce. The main aim of this thesis was to investigate the contribution of the EGFR pathway in experimental kidney damage, evaluating its role on inflammation and fibrosis, and the intracellular mechanisms involved in EGFR signalling. An additional goal was to increase the actual knowledge of renal pathology and improve the current therapeutic strategies. EGFR activation may occur by direct binding or by "transactivation", the latter process mediated by MMPs/ADAMs. The results of this study have shown that CCN2 is a new EGFR ligand that directly binds to this receptor and activates its signalling pathway, by an MMPs/ADAMs independent process. Furthermore, EGFR can be transactivated in the kidney by several factors involved in renal damage such as PTHrP and TWEAK, as described here for the first time. PTHrP, by its binding to the G coupled receptor PTH1R, can transactivate EGFR by 2 different mechanisms; PKC/MMPs activation or Src activation. TWEAK, through interaction with its receptor Fn14, activates ADAM17 that release HB-EGF and TGF-α ligands, leading to EGFR transactivation. Previous experimental studies suggest that EGFR pathway blockade could be an antifibrotic target for renal disease. In vitro studies showed that direct activation of EGFR by CCN2, and EGFR transactivation by PTHrP, could regulate epithelial mesenchymal transition, a process that contributes to renal fibrogenesis. In vivo studies, including the experimental models of renal damage mediated caused by systemic administration of CCN2 (IV) or TWEAK in mice, have demonstrated that activation of the EGFR pathway is associated with an inflammatory process in the kidney, which it is prevented by EGFR pharmacological blockade. In particular, TWEAK-induced EGFR transactivation and renal inflammation was blocked by ADAM17/EGFR inhibition, suggesting that the blockade of this axis could be a good therapeutic option for renal inflammatory diseases. Chronic renal disease is characterized by vitamin D deficiency. Several experimental data have shown that vitamin D receptor agonists (VDRAs) exert beneficial antinflammatory effects in CKD. In this thesis we have described that treatment with the VDRA Paricalcitol inhibited TWEAK-mediated EGFR transactivation and subsequent activation of intracellular mechanisms, including overexpression of proinflammatory factors and the infiltration of inflammatory cells into the kidney. The NF-κB plays a key role in the regulation of the inflammatory response. TWEAK is one of the few cytokines that activates both the canonical and non-canonical NF-κB pathway. Blockade of TWEAK-induced EGFR transactivation by different approaches, including Paricalcitol, inhibited the non canonical, but not the canonical, NF-κB pathway. These results described a novel antinflammatory mechanism of VDRAs that includes the modulation of the EGFR pathway and the inhibition of the noncanonical NF-κB2 pathway. In summary, all these data show that EGFR signalling pathway activation is involved in the modulation of inflammatory and fibrotic process in the kidney in response to different stimuli, and suggest that the blockade of EGFR signalling pathway could be considered as a new therapeutic target in renal diseases. Blockers of this signalling pathway could have a relevant therapeutic value for the treatment of CKD patients.