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Novel functional changes during podocyte differentiation: increase of oxidative resistance and H-ferritin expression.

Bányai E, Balogh E, Fagyas M, Arosio P, Hendrik Z, Király G, Nagy G, Tánczos B, Pócsi I, Balla G, Balla J, Bánfalvi G, Jeney V - Oxid Med Cell Longev (2014)

Bottom Line: We observed that differentiated podocytes were highly resistant to oxidants such as H2O2 and heme when applied separately or in combination, whereas undifferentiated cells were prone to such challenges.Elevated oxidative resistance of differentiated podocytes was associated with increased activities of antioxidant enzymes and H-ferritin expression.Immunohistochemical analysis of normal human kidney specimens revealed that podocytes highly express H-ferritin in vivo as well.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Debrecen, Debrecen 4032, Hungary.

ABSTRACT
Podocytes are highly specialized, arborized epithelial cells covering the outer surface of the glomerular tuft in the kidney. Terminally differentiated podocytes are unable to go through cell division and hereby they are lacking a key property for regeneration after a toxic injury. Podocytes are long-lived cells but, to date, little is known about the mechanisms that support their stress resistance. Our aim was to investigate whether the well-known morphological changes during podocyte differentiation are accompanied by changes in oxidative resistance in a manner that could support their long-term survival. We used a conditionally immortalized human podocyte cell line to study the morphological and functional changes during differentiation. We followed the differentiation process for 14 days by time-lapse microscopy. During this period nondifferentiated podocytes gradually transformed into large, nonproliferating, frequently multinucleated cells, with enlarged nuclei and opened chromatin structure. We observed that differentiated podocytes were highly resistant to oxidants such as H2O2 and heme when applied separately or in combination, whereas undifferentiated cells were prone to such challenges. Elevated oxidative resistance of differentiated podocytes was associated with increased activities of antioxidant enzymes and H-ferritin expression. Immunohistochemical analysis of normal human kidney specimens revealed that podocytes highly express H-ferritin in vivo as well.

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TBARS levels are elevated in nondifferentiated podocytes but not in differentiated cells under stress conditions. (a) Nondifferentiated and differentiated podocytes were exposed to H2O2 (0–500 μmol/L in HBSS) for 4 hours, followed by measurement of TBARS levels. (b) Nondifferentiated and differentiated podocytes were subjected to heme treatment (0–5 μmol/L in HBSS) for 4 hours, followed by measurement of TBARS levels. Results are expressed as fold increase over vehicle-treated controls and shown as mean values ± SEM of three independent experiments each performed in triplicates. *P < 0.05, **P < 0.01, and ***P < 0.001.
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fig5: TBARS levels are elevated in nondifferentiated podocytes but not in differentiated cells under stress conditions. (a) Nondifferentiated and differentiated podocytes were exposed to H2O2 (0–500 μmol/L in HBSS) for 4 hours, followed by measurement of TBARS levels. (b) Nondifferentiated and differentiated podocytes were subjected to heme treatment (0–5 μmol/L in HBSS) for 4 hours, followed by measurement of TBARS levels. Results are expressed as fold increase over vehicle-treated controls and shown as mean values ± SEM of three independent experiments each performed in triplicates. *P < 0.05, **P < 0.01, and ***P < 0.001.

Mentions: When challenged with H2O2 or heme nondifferentiated podocytes underwent cell death, whereas mature podocytes showed high resistance. To assess whether this phenomenon was accompanied by differences in oxidative stress, we measured the oxidative stress marker TBARS levels in both nondifferentiated and differentiated podocytes under normal and stress conditions. We found that nondifferentiated podocytes responded by a dose-dependent elevation of TBARS levels to both H2O2 and heme stress, whereas the same triggers did not cause significant increases in TBARS levels in differentiated podocytes (Figures 5(a) and 5(b)). Then we assessed whether the increased oxidative resistance of mature podocytes is associated with elevated activities of major antioxidant enzymes: GPX, catalase, and SOD. We found that activities of all the tested antioxidant enzymes were significantly higher in mature podocytes when compared to nondifferentiated cells (Figures 6(a)–6(c)).


Novel functional changes during podocyte differentiation: increase of oxidative resistance and H-ferritin expression.

Bányai E, Balogh E, Fagyas M, Arosio P, Hendrik Z, Király G, Nagy G, Tánczos B, Pócsi I, Balla G, Balla J, Bánfalvi G, Jeney V - Oxid Med Cell Longev (2014)

TBARS levels are elevated in nondifferentiated podocytes but not in differentiated cells under stress conditions. (a) Nondifferentiated and differentiated podocytes were exposed to H2O2 (0–500 μmol/L in HBSS) for 4 hours, followed by measurement of TBARS levels. (b) Nondifferentiated and differentiated podocytes were subjected to heme treatment (0–5 μmol/L in HBSS) for 4 hours, followed by measurement of TBARS levels. Results are expressed as fold increase over vehicle-treated controls and shown as mean values ± SEM of three independent experiments each performed in triplicates. *P < 0.05, **P < 0.01, and ***P < 0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4109136&req=5

fig5: TBARS levels are elevated in nondifferentiated podocytes but not in differentiated cells under stress conditions. (a) Nondifferentiated and differentiated podocytes were exposed to H2O2 (0–500 μmol/L in HBSS) for 4 hours, followed by measurement of TBARS levels. (b) Nondifferentiated and differentiated podocytes were subjected to heme treatment (0–5 μmol/L in HBSS) for 4 hours, followed by measurement of TBARS levels. Results are expressed as fold increase over vehicle-treated controls and shown as mean values ± SEM of three independent experiments each performed in triplicates. *P < 0.05, **P < 0.01, and ***P < 0.001.
Mentions: When challenged with H2O2 or heme nondifferentiated podocytes underwent cell death, whereas mature podocytes showed high resistance. To assess whether this phenomenon was accompanied by differences in oxidative stress, we measured the oxidative stress marker TBARS levels in both nondifferentiated and differentiated podocytes under normal and stress conditions. We found that nondifferentiated podocytes responded by a dose-dependent elevation of TBARS levels to both H2O2 and heme stress, whereas the same triggers did not cause significant increases in TBARS levels in differentiated podocytes (Figures 5(a) and 5(b)). Then we assessed whether the increased oxidative resistance of mature podocytes is associated with elevated activities of major antioxidant enzymes: GPX, catalase, and SOD. We found that activities of all the tested antioxidant enzymes were significantly higher in mature podocytes when compared to nondifferentiated cells (Figures 6(a)–6(c)).

Bottom Line: We observed that differentiated podocytes were highly resistant to oxidants such as H2O2 and heme when applied separately or in combination, whereas undifferentiated cells were prone to such challenges.Elevated oxidative resistance of differentiated podocytes was associated with increased activities of antioxidant enzymes and H-ferritin expression.Immunohistochemical analysis of normal human kidney specimens revealed that podocytes highly express H-ferritin in vivo as well.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Debrecen, Debrecen 4032, Hungary.

ABSTRACT
Podocytes are highly specialized, arborized epithelial cells covering the outer surface of the glomerular tuft in the kidney. Terminally differentiated podocytes are unable to go through cell division and hereby they are lacking a key property for regeneration after a toxic injury. Podocytes are long-lived cells but, to date, little is known about the mechanisms that support their stress resistance. Our aim was to investigate whether the well-known morphological changes during podocyte differentiation are accompanied by changes in oxidative resistance in a manner that could support their long-term survival. We used a conditionally immortalized human podocyte cell line to study the morphological and functional changes during differentiation. We followed the differentiation process for 14 days by time-lapse microscopy. During this period nondifferentiated podocytes gradually transformed into large, nonproliferating, frequently multinucleated cells, with enlarged nuclei and opened chromatin structure. We observed that differentiated podocytes were highly resistant to oxidants such as H2O2 and heme when applied separately or in combination, whereas undifferentiated cells were prone to such challenges. Elevated oxidative resistance of differentiated podocytes was associated with increased activities of antioxidant enzymes and H-ferritin expression. Immunohistochemical analysis of normal human kidney specimens revealed that podocytes highly express H-ferritin in vivo as well.

Show MeSH
Related in: MedlinePlus