Dopamine induces ERK activation in renal epithelial cells through H2O2 produced by monoamine oxidase.
BACKGROUND
The rat renal proximal tubule cells contain a large amount of monoamine oxidase, which catalyzes the oxidative deamination of catecholamines such as dopamine (DA). The aim of this study is to investigate the potential role of hydrogen peroxide (H2O2) produced by monoamine oxidase (MAO) isoform on regulation of cell signaling and function.


METHODS
Primary rat proximal tubular cells, which contain almost exclusively MAO-A, and human embryonic kidney 293 (HEK 293) cells stably transfected with human MAO-B cDNA were treated with DA or tyramine in the presence or the absence of some inhibitors. Then, Shc protein tyrosine phosphorylation and extracellular-regulated kinase (ERK) activation were evaluated by immunoprecipitation/immunoblot analysis and cell proliferation by [3H]thymidine incorporation or cell counting.


RESULTS
In rat proximal tubule cells, DA induced tyrosine phosphorylation of Shc, ERK activation, and a significant increase in DNA synthesis. The involvement of MAO-dependent H2O2 generation induced by DA (5 micromol/L) was supported by the demonstration that the DA effects were (1) fully prevented by cell pretreatment with the MAO inhibitor pargyline, the antioxydant N-acetylcysteine (NAC), and the DA uptake inhibitor GBR 12909; (2) not abrogated by the D1 and D2 receptor antagonists; (3) observed in HEK 293 MAO-B cells but not in HEK 293 wild-type cells, which do not express MAO; and (4) similar to those induced by another MAO substrate, tyramine.


CONCLUSIONS
Taken together, these results show that in addition to the effects related to receptor stimulation, DA, and probably the other catecholamines, may induce some of its effects through the MAO-dependent H2O2 production.
Vindis
C
C
INSERM U388, Institut Louis Bugnard, CHU Rangueil, Toulouse, France.
Séguélas
M H
MH
Lanier
S
S
Parini
A
A
Cambon
C
C
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D004298:Dopamine / Q000494:pharmacology*; D004789:Enzyme Activation; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008995:Monoamine Oxidase / Q000378:metabolism*; D010766:Phosphorylation; D011506:Proteins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D013379:Substrate Specificity; D013936:Thymidine / Q000378:metabolism; D014439:Tyramine / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D011506:Proteins; C528024:SHC1 protein, human; D055765:Shc Signaling Adaptor Proteins; C528035:Shc1 protein, rat; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D014443:Tyrosine; D006861:Hydrogen Peroxide; D008995:Monoamine Oxidase; D020928:Mitogen-Activated Protein Kinases; D013936:Thymidine; D004298:Dopamine; D014439:Tyramine