Alteration of thyroid hormone signaling triggers the diabetes-induced pathological growth, remodeling, and dedifferentiation of podocytes
Valentina Benedetti, Angelo Michele Lavecchia, Monica Locatelli, Valerio Brizi, Daniela Corna, Marta Todeschini, Rubina Novelli, Ariela Benigni, Carlamaria Zoja, Giuseppe Remuzzi, Christodoulos Xinaris
Valentina Benedetti, Angelo Michele Lavecchia, Monica Locatelli, Valerio Brizi, Daniela Corna, Marta Todeschini, Rubina Novelli, Ariela Benigni, Carlamaria Zoja, Giuseppe Remuzzi, Christodoulos Xinaris
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Research Article Cell biology

Alteration of thyroid hormone signaling triggers the diabetes-induced pathological growth, remodeling, and dedifferentiation of podocytes

Abstract

Thyroid hormone (TH) signaling is a universal regulator of metabolism, growth, and development. Here, we show that TH-TH receptor (TH-TR) axis alterations are critically involved in diabetic nephropathy–associated (DN-associated) podocyte pathology, and we identify TRα1 as a key regulator of the pathogenesis of DN. In ZSF1 diabetic rats, T3 levels progressively decreased during DN, and this was inversely correlated with metabolic and renal disease worsening. These phenomena were associated with the reexpression of the fetal isoform TRα1 in podocytes and parietal cells of both rats and patients with DN and with the increased glomerular expression of the TH-inactivating enzyme deiodinase 3 (DIO3). In diabetic rats, TRα1-positive cells also reexpressed several fetal mesenchymal and damage-related podocyte markers, while glomerular and podocyte hypertrophy was evident. In vitro, exposing human podocytes to diabetes milieu typical components markedly increased TRα1 and DIO3 expression and induced cytoskeleton rearrangements, adult podocyte marker downregulation and fetal kidney marker upregulation, the maladaptive cell cycle induction/arrest, and TRα1-ERK1/2–mediated hypertrophy. Strikingly, T3 treatment reduced TRα1 and DIO3 expression and completely reversed all these alterations. Our data show that diabetic stress induces the TH-TRα1 axis to adopt a fetal ligand/receptor relationship pattern that triggers the recapitulation of the fetal podocyte phenotype and subsequent pathological alterations.

Authors

Valentina Benedetti, Angelo Michele Lavecchia, Monica Locatelli, Valerio Brizi, Daniela Corna, Marta Todeschini, Rubina Novelli, Ariela Benigni, Carlamaria Zoja, Giuseppe Remuzzi, Christodoulos Xinaris

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Figure 7

TRα1 regulates glucose-induced hypertrophy through downstream activation of ERK1/2.

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TRα1 regulates glucose-induced hypertrophy through downstream activation...
(A and B) Densitometric analysis of (A) ERK1/2 and (B) pERK1/2 protein in podocytes by Western blot. (A) Podocyte total ERK1/2 protein expression was not changed either by glucose or T3 treatment. (B) Glucose induced an increase in pERK1/2 protein levels, which were significantly reduced by T3 treatment. (C) Quantification of hypertrophy expressed as protein content per cell number. Glucose induced podocyte hypertrophy, which was prevented by UO126 and DBD. Neither UO126 nor DBD had any effect on untreated cells. (D) Densitometric analysis of pERK1/2 protein in podocytes by Western blot. The increase in pERK1/2 protein levels in glucose-stimulated podocytes was prevented by administering UO126 or DBD. Tubulin protein expression was used as sample loading control (A, B, and D). Data from 3 independent experiments are expressed as mean ± SEM. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001, 1-way ANOVA with Tukey’s post hoc test. n = 3–6. pERK1/2, phospho-ERK1/2.