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 6

T3 administration induces cell proliferation and restores cell size and normal cell cycle distribution in damaged podocytes.

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T3 administration induces cell proliferation and restores cell size and ...
(A) Percentage of standard or large treated and untreated podocytes analyzed with FACS by plotting FSC (as dimension of cells) versus SSC (as granularity of cells). Both high levels of glucose and H2O2 increased the large cell population and T3 restored the standard cell size. (B) Quantification of hypertrophy expressed as total protein content per cell number. Diabetic stimuli induced cell hypertrophy and T3 reversed this effect. (C) Quantification of cell number in treated and untreated podocytes by manual cell counting. T3 strongly increased proliferation in podocytes exposed to high levels of glucose or H2O2. (D) A representative graph of the percentage of podocytes in the cell cycle phases evaluated by FACS. Diabetic stimuli induced a marked G2/M accumulation, while T3 administration reduced G2/M phase arrest and increased S phase cells. T3 treatment had no effect on cell size, hypertrophy, proliferation, and cell cycle distribution in control podocytes. Data from 3 independent experiments are expressed as mean ± SEM. (E) Representative images of senescence-associated β-galactosidase (SA-β-Gal) staining in cultured human podocytes. Scale bar: 100 μm. (F) Quantification of senescent podocytes expressed as SA-β-Gal–positive cells per cell number. Both stress stimuli increased the numbers of SA-β-Gal–positive cells (blue) compared with control, while T3 administration strongly reduced the amount of senescent cells. SA-β-Gal activity did not differ between control groups. To quantify the number of positive cells, representative images were taken randomly from diverse areas of cell cultures. Number of fields analyzed: n = 17 for ctr, n = 20 for ctr+T3, n = 17 for glucose, n = 20 for glucose+T3, n = 19 for H2O2, n = 20 for H2O2+T3. Data 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.