Endothelial nitric oxide synthase uncoupling as a key mediator of melanocyte malignant transformation associated with sustained stress conditions.

Abstract

Melanoma cell lines and cells corresponding to premalignant melanocytes were established by our group after subjecting a nontumorigenic murine melanocyte lineage, melan-a, to sequential cycles of anchorage blockade. Previous results showed that in melan-a cells the superoxide level increases after such procedure. Superoxide production during melanocyte de-adhesion was inhibited by L-sepiapterin, the precursor of eNOS cofactor BH4, and increased by the inhibitor of BH4 synthesis, DAHP, hence indicating a partial uncoupling state of eNOS. The eNOS uncoupling seems to be maintained in cells derived from melan-a, because they present decreased nitric oxide and increased superoxide levels. The inhibition of superoxide production in Tm5 melanoma cells with L-sepiapterin reinforces their eNOS-uncoupled state. The maintenance of oxidative stress seems to be important in melanoma apoptosis resistance because Mn(III)TBAP, a superoxide scavenger, or L-sepiapterin renders Tm5 cells more sensitive to anoikis and chemotherapy. More importantly, eNOS uncoupling seems to play a pivotal role in melanocyte malignant transformation induced by sustained anchorage impediment, because no malignant transformation was observed when L-NAME-treated melanocytes were subjected to sequential cycles of de-adhesion. Our results show that uncoupled eNOS contributes to superoxide production during melanocyte anchorage impediment, contributing to anoikis resistance and malignant transformation.

• Authors: Fabiana H M Melo, Fernanda Molognoni, Alice S Morais, Mariana Toricelli, Margareth G Mouro, Elisa M S Higa, José D Lopes, Miriam G Jasiulionis
• Journal: Free radical biology & medicine (Free Radic Biol Med) Vol. 50 Issue 10 Pg. 1263-73 (May 15 2011) ISSN: 1873-4596 [Electronic] United States
• PMID: 21362470 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2011 Elsevier Inc. All rights reserved.

Chemical References

• Superoxides
• Nitric Oxide Synthase Type III
• NG-Nitroarginine Methyl Ester

Topics

• Animals
• Melanocytes (drug effects, metabolism, pathology)
• Mice
• NG-Nitroarginine Methyl Ester (pharmacology)
• Nitric Oxide Synthase Type III (metabolism)
• Oxidative Stress (drug effects)
• Superoxides (metabolism)
• Tumor Cells, Cultured