Skip Navigation
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

National Institute of Environmental Health Sciences

Use this QR code to view the newest version of this document
Use this QR code to view the newest version of this document

Your Environment. Your Health.

Publication Detail

Title: Differential cytotoxicity of Mn(II) and Mn(III): special reference to mitochondrial [Fe-S] containing enzymes.

Authors: Chen, J Y; Tsao, G C; Zhao, Q; Zheng, W

Published In Toxicol Appl Pharmacol, (2001 Sep 01)

Abstract: Manganese (Mn)-induced neurodegenerative toxicity has been associated with a distorted iron (Fe) metabolism at both systemic and cellular levels. In the current study, we examined whether the oxidation states of Mn produced differential effects on certain mitochondrial [Fe-S] containing enzymes in vitro. When mitochondrial aconitase, which possesses a [4Fe-4S] cluster, was incubated with either Mn(II) or Mn(III), both Mn species inhibited the activities of aconitase. However, the IC(10) (concentration to cause a 10% enzyme inhibition) for Mn(III) was ninefold lower than that for Mn(II). Following exposure of mitochondrial fractions with Mn(II) or Mn(III), there was a significant inhibition by either Mn species in activities of Complex I whose active site contains five to eight [Fe-S] clusters. The dose-time response curves reveal that Mn(III) was more effective in blocking Complex I activity than Mn(II). Northern blotting was used to examine the expression of mRNAs encoding transferrin receptor (TfR), which is regulated by cytosolic aconitase. Treatment of cultured PC12 cells with Mn(II) and Mn(III) at 100 microM for 3 days resulted in 21 and 58% increases, respectively, in the expression of TfR mRNA. Further studies on cell growth dynamics after exposure to 25-50 microM Mn in culture media demonstrated that the cell numbers were much reduced in Mn(III)-treated groups compared to Mn(II)-treated groups, suggesting that Mn(III) is more effective than Mn(II) in cell killing. In cells exposed to Mn(II) and Mn(III), mitochondrial DNA (mtDNA) was significantly decreased by 24 and 16%, respectively. In contrast, rotenone and MPP+ did not seem to alter mtDNA levels. These in vitro results suggest that Mn(III) species appears to be more cytotoxic than Mn(II) species, possibly due to higher oxidative reactivity and closer radius resemblance to Fe.

PubMed ID: 11543648 Exiting the NIEHS site

MeSH Terms: Aconitate Hydratase/metabolism*; Animals; Cell Line; DNA, Mitochondrial/drug effects; Manganese Poisoning/metabolism*; Mitochondria/drug effects*; Mitochondria/enzymology; Mitochondria/metabolism; Oxidation-Reduction; Rats; Rotenone/pharmacology; Structure-Activity Relationship; Uncoupling Agents/pharmacology

Back
to Top