Activation of MAPK and FoxO by Manganese (Mn) in rat neonatal primary astrocyte cultures

Vernat Exil, Li Ping, Yingchun Yu, Sudipta Chakraborty, Samuel W. Caito, K. Sam Wells, Pratap Karki, Eunsook Lee, Michael Aschner

Research output: Contribution to journalArticle

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Abstract

Environmental exposure to manganese (Mn) leads to a neurodegenerative disease that has shared clinical characteristics with Parkinson's disease (PD). Mn-induced neurotoxicity is time- and dose-dependent, due in part to oxidative stress. We ascertained the molecular targets involved in Mn-induced neurodegeneration using astrocyte culture as: (1) Astrocytes are vital for information processing within the brain, (2) their redox potential is essential in mitigating reactive oxygen species (ROS) levels, and (3) they are targeted early in the course of Mn toxicity. We first tested protein levels of Mn superoxide dismutase -2 (SOD-2) and glutathione peroxidase (GPx-1) as surrogates of astrocytic oxidative stress response. We assessed levels of the forkhead winged-helix transcription factor O (FoxO) in response to Mn exposure. FoxO is highly regulated by the insulin-signaling pathway. FoxO mediates cellular responses to toxic stress and modulates adaptive responses. We hypothesized that FoxO is fundamental in mediating oxidative stress response upon Mn treatment, and may be a biomarker of Mn-induced neurodegeneration. Our results indicate that 100 or 500 μM of MnCl2 led to increased levels of FoxO (dephosphorylated and phosphorylated) compared with control cells (P,0.01). p-FoxO disappeared from the cytosol upon Mn exposure. Pre-treatment of cultured cells with (R)-(-)-2-oxothiazolidine-4-carboxylic acid (OTC), a cysteine analog rescued the cytosolic FoxO. At these concentrations, MAPK phosphorylation, in particular p38 and ERK, and PPAR gamma coactivator-1 (PGC-1) levels were increased, while AKT phosphorylation remained unchanged. FoxO phosphorylation level was markedly reduced with the use of SB203580 (a p38 MAPK inhibitor) and PD98059 (an ERK inhibitor). We conclude that FoxO phosphorylation after Mn exposure occurs in parallel with, and independent of the insulin-signaling pathway. FoxO levels and its translocation into the nucleus are part of early events compensating for Mn-induced neurotoxicity and may serve as valuable targets for neuroprotection in the setting of Mn-induced neurodegeneration.

Original languageEnglish (US)
Article numbere94753
JournalPLoS One
Volume9
Issue number5
DOIs
StatePublished - May 2 2014
Externally publishedYes

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astrocytes
Manganese
Astrocytes
manganese
Rats
neonates
Chemical activation
Phosphorylation
Oxidative stress
phosphorylation
mitogen-activated protein kinase
Oxidative Stress
neurotoxicity
oxidative stress
Winged-Helix Transcription Factors
stress response
insulin
Insulin
Neurodegenerative diseases
Forkhead Transcription Factors

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

Activation of MAPK and FoxO by Manganese (Mn) in rat neonatal primary astrocyte cultures. / Exil, Vernat; Ping, Li; Yu, Yingchun; Chakraborty, Sudipta; Caito, Samuel W.; Wells, K. Sam; Karki, Pratap; Lee, Eunsook; Aschner, Michael.

In: PLoS One, Vol. 9, No. 5, e94753, 02.05.2014.

Research output: Contribution to journalArticle

Exil, V, Ping, L, Yu, Y, Chakraborty, S, Caito, SW, Wells, KS, Karki, P, Lee, E & Aschner, M 2014, 'Activation of MAPK and FoxO by Manganese (Mn) in rat neonatal primary astrocyte cultures', PLoS One, vol. 9, no. 5, e94753. https://doi.org/10.1371/journal.pone.0094753
Exil, Vernat ; Ping, Li ; Yu, Yingchun ; Chakraborty, Sudipta ; Caito, Samuel W. ; Wells, K. Sam ; Karki, Pratap ; Lee, Eunsook ; Aschner, Michael. / Activation of MAPK and FoxO by Manganese (Mn) in rat neonatal primary astrocyte cultures. In: PLoS One. 2014 ; Vol. 9, No. 5.
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AU - Ping, Li

AU - Yu, Yingchun

AU - Chakraborty, Sudipta

AU - Caito, Samuel W.

AU - Wells, K. Sam

AU - Karki, Pratap

AU - Lee, Eunsook

AU - Aschner, Michael

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