Angiotensin II effect on microtubule dynamics in renal tubular cells

Abstract

Tubular remodeling in response to acute kidney injury (AKI) involvesthe dedifferentiation and regeneration of the remaining epithelial tubular cells. Microtubules (MT) dynamic instability plays a centralrole in renal repair after AKI. Angiotensin II (AGII) has two main receptors, AT1R and AT2R, which mediate dissimilar effects. Duringischemia reperfusion (IR), AT1R mediates a pro-fibrotic response,whereas AT2R facilitates the recovery of the kidney function (ourunpublished data). The aim of this work was to investigate AT1Rand AT2R participation in the regulation of factors associated withMT dynamic instability that could affect the epithelial tubular cell-response to an AKI. MDCK cells were grown in conditions that assurea well-defined epithelial polarity and treated with 0.5 µM AGII (AGII),AGII plus the AT1R antagonist losartan (5 µM) (AGII + los), or 1µM C21, AT2R agonist (C21). EB1 is a central regulator of MT dynamic instability that participates in tubulogenesis. AGII induced anincrease in EB1 levels which was mimicked by C21 (+50%*, n=3)and was not prevented by Los. α-tubulin acetylation is linked to thepresence of stable MT. Our preliminary data showed that activationof AT2R, but not AT1R, decreased the fraction of acetylated α-tubulin (Control (C): 0.55 ± 0.05; AGII: 0.25 ± 0.05; AGII + Los: 0.06 ±0.03; C21: 0.14 ± 0.03, n=2). Primary cilia are organelles of tubularcells that are down-regulated during AKI-tubular remodeling, whoselength directly correlates with the levels of acetylated α-tubulin.Analysis of the primary cilia showed that through AT1R AGII increasees whereas through AT2R it decreases the cilia length (in µm: C: 2.8± 0.1; AGII: 3.1 ± 0.1; AGII + Los: 2.4 ± 0.1 *; C21: 2.3 ± 0.1 *, n>80).Overall, our results indicate that AGII increases MT dynamic instability through AT2R, which would favor tubular remodeling. Our futurestudies will evaluate the relevance of these effects in the responseto IR induced AKI. * p<0.05 vs C.