Overexpression of the short endoglin isoform reduces renal fibrosis and inflammation after unilateral ureteral obstruction

Abstract

Transforming growth factor beta 1 (TGF-β1) is one of the most studied cytokines involved in renal tubulo-interstitial fibrosis, which is characterized by myofibroblast abundance and proliferation, and high buildup of extracellular matrix in the tubular interstitium leading to organ failure. Endoglin (Eng) is a 180-kDa homodimeric transmembrane protein that regulates a great number of TGF-β1 actions in different biological processes, including ECM synthesis. High levels of Eng have been observed in experimental models of renal fibrosis or in biopsies from patients with chronic kidney disease. In humans and mice, two Eng isoforms are generated by alternative splicing, L-Eng and S-Eng that differ in the length and composition of their cytoplasmic domains. We have previously described that L-Eng overexpression promotes renal fibrosis after unilateral ureteral obstruction (UUO). However, the role of S-Eng in renal fibrosis is unknown and its study would let us analyze the possible function of the cytoplasmic domain of Eng in this process. For this purpose, we have generated a mice strain that overexpresses S-Eng (S-ENG(+)) and we have performed an UUO in S-ENG(+) and their wild type (WT) control mice. Our results indicate that obstructed kidney of S-ENG(+) mice shows lower levels of tubulo-interstitial fibrosis, less inflammation and less interstitial cell proliferation than WT littermates. Moreover, S-ENG(+) mice show less activation of Smad1 and Smad2/3 pathways. Thus, S-Eng overexpression reduces UUO-induced renal fibrosis and some associated mechanisms. As L-Eng overexpression provokes renal fibrosis we conclude that Eng-mediated induction of renal fibrosis in this model is dependent on its cytoplasmic domain.

TWEAK promotes migration and invasion in MEFs through a mechanism dependent on ERKs activation and Fibulin 3 down‐regulation

“…Previously, it was demonstrated that TWEAK‐induced ERKs activation in renal fibroblasts mediated proliferation, which might contribute to promote renal fibrosis (Ucero et al, ). Here, we additionally show that ERKs activation by TWEAK promotes migration and invasion of MEFs under non‐proliferative conditions, which agrees with the pro‐migratory function of ERKs in MEFs (Muñoz‐Félix et al, ). Moreover, MMP9 activity is increased by TWEAK in MEFs, as previously described in neonatal rat cardiac fibroblasts, where this increase together with the enhanced expression of collagen contributed to induce myocardial fibrosis (Chen et al, ).…”

Endoglin in human liver disease and murine models of liver fibrosis—A protective factor against liver fibrosis

“…This is pivotal for evaluating Endoglin function since both isoforms show opposing effects in vitro and in vivo and underscore the critical role of the intracellular domain which differs in both splice variants. 11,36 RT-PCR analysis shows that both splice variants are co-expressed in all tissues tested and that the L-variant is the predominantly expressed form. This finding is in line with a previous report confirming the high organ expression of the L-form compared to the varying but low expression of the S-form.…”

“…These findings show a differential regulation of both isoforms. This is pivotal for evaluating Endoglin function since both isoforms show opposing effects in vitro and in vivo and underscore the critical role of the intracellular domain which differs in both splice variants . RT‐PCR analysis shows that both splice variants are co‐expressed in all tissues tested and that the L‐variant is the predominantly expressed form.…”

La endoglina de membrana y la endoglina soluble modulan la respuesta inflamatoria

“…Además, los niveles de marcadores inflamatorios como CD68, COX-2, iNOS, y moléculas de adhesión como VCAM-1 e ICAM-1, eran menores en los ratones S-ENG+ que en los WT(Muñoz-Félix et al, 2016). Estos resultados indican que, mientras que la sobreexpresión de L-endoglina aumenta la fibrosis inducida por OUU, la sobreexpresión de S-endoglina la disminuye, lo que pone de manifiesto que el dominio citoplasmático de endoglina tiene un papel en la regulación de la fibrosis, un componente clave en la inflamación crónica.A la vista de nuestros resultados, no se observan diferencias significativas en condiciones control a nivel de infiltrado inflamatorio entre los ratones WT, L-ENG+ y S-ENG+, corroborando los resultados deOujo et al y Muñoz-Félix et al (Oujo et al, 2014;Muñoz-Félix et al, 2016).Esto nos lleva a concluir que la sobreexpresión de las distintas isoformas de endoglina, por sí sola, no altera el reclutamiento leucocitario. Además, podemos observar que, tras inducción inflamatoria, ya sea por nebulización de LPS, carragenina o isquemiareperfusión, no se observan diferencias a nivel de infiltrado leucocitario entre los ratonesWT y los L-ENG+.…”

“…Los únicos estudios que hay al respecto se centran en inflamación crónica, valorándose la fibrosis tubulointersticial en modelos de daño renal agudo. Estas publicaciones han demostrado que mientras que la sobreexpresión de L-endoglina aumenta la fibrosis inducida por obstrucción ureteral unilateral (OUU)(Oujo et al, 2014), la sobreexpresión de S-endoglina la disminuye(Muñoz-Félix et al, 2016), lo que pone de manifiesto que el dominio citoplasmático de endoglina tiene un papel en la regulación de la fibrosis, la cual está estrechamente relacionada con la inflamación crónica.El hecho de que las isoformas L-endoglina y S-endoglina presenten funciones antagónicas es de gran interés, ya que, dado que solo se diferencian en el dominio intracelular, cualquier diferencia que observemos se debe a que dicho proceso se controla por ese dominio. Esto, junto con que S-endoglina aumente en senescencia…”