Antioxidant Actions of Selenium in Orbital Fibroblasts: A Basis for the Effects of Selenium in Graves' Orbitopathy.
A recent clinical trial has shown a beneficial effect of the antioxidant agent selenium in Graves' orbitopathy (GO). In order to shed light on the cellular mechanisms on which selenium may act, this study investigated its effects in cultured orbital fibroblasts.



Primary cultures of orbital fibroblasts from six GO patients and six control subjects were established. Cells were treated with H2O2to induce oxidative stress, after pre-incubation with selenium-(methyl)selenocysteine (SeMCys). The following assays were performed: glutathione disulfide (GSSG), as a measure of oxidative stress, glutathione peroxidase (GPX) activity, cell proliferation, hyaluronic acid (HA), and pro-inflammatory cytokines.



H2O2induced an increase in cell GSSG and fibroblast proliferation, which were reduced by SeMCys. Incubation of H2O2-treated cells with SeMCys was followed by an increase in glutathione peroxidase activity, one of the antioxidant enzymes into which selenium is incorporated. At the concentrations used (5 μM), H2O2did not significantly affect HA release, but it was reduced by SeMCys. H2O2determined an increase in endogenous cytokines involved in the response to oxidative stress and GO pathogenesis, namely tumor necrosis factor alpha, interleukin 1 beta, and interferon gamma. The increases in tumor necrosis factor alpha and interferon gamma were blocked by SeMCys. While the effects of SeMCys on oxidative stress and cytokines were similar in GO and control fibroblasts, they were exclusive to GO fibroblasts in terms of inhibiting proliferation and HA secretion.



Selenium, in the form of SeMCys, abolishes some of the effects of oxidative stress in orbital fibroblasts, namely increased proliferation and secretion of pro-inflammatory cytokines. SeMCys reduces HA release in GO fibroblasts in a manner that seems at least in part independent from H2O2-induced oxidative stress. Some effects of SeMCys are specific for GO fibroblasts. These findings reveal some cellular mechanisms by which selenium may act in patients with GO.
1 Department of Clinical and Experimental Medicine, Endocrinology Units, University of Pisa and University Hospital of Pisa , Pisa, Italy .
Giovanna
G
Rotondo Dottore
1 Department of Clinical and Experimental Medicine, Endocrinology Units, University of Pisa and University Hospital of Pisa , Pisa, Italy .
Marenza
M
Leo
2 Department of Surgical, Medical and Molecular Pathology, Ophthalmopathy Unit I, University of Pisa and University Hospital of Pisa , Pisa, Italy .
Giamberto
G
Casini
1 Department of Clinical and Experimental Medicine, Endocrinology Units, University of Pisa and University Hospital of Pisa , Pisa, Italy .
Francesco
F
Latrofa
2 Department of Surgical, Medical and Molecular Pathology, Ophthalmopathy Unit I, University of Pisa and University Hospital of Pisa , Pisa, Italy .
Luca
L
Cestari
3 Department of Surgical, Medical and Molecular Pathology, ENT Unit I, University of Pisa and University Hospital of Pisa , Pisa, Italy .
Stefano
S
Sellari-Franceschini
2 Department of Surgical, Medical and Molecular Pathology, Ophthalmopathy Unit I, University of Pisa and University Hospital of Pisa , Pisa, Italy .
Marco
M
Nardi
1 Department of Clinical and Experimental Medicine, Endocrinology Units, University of Pisa and University Hospital of Pisa , Pisa, Italy .
Paolo
P
Vitti
1 Department of Clinical and Experimental Medicine, Endocrinology Units, University of Pisa and University Hospital of Pisa , Pisa, Italy .
Claudio
C
Marcocci
1 Department of Clinical and Experimental Medicine, Endocrinology Units, University of Pisa and University Hospital of Pisa , Pisa, Italy .
Michele
M
Marinò
D000368:Aged; D000975:Antioxidants / Q000494:pharmacology*; D016022:Case-Control Studies; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D016207:Cytokines / Q000187:drug effects / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000187:drug effects*; D019803:Glutathione Disulfide / Q000187:drug effects / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000187:drug effects / Q000378:metabolism; D049970:Graves Ophthalmopathy / Q000188:drug therapy* / Q000378:metabolism; D006801:Humans; D006820:Hyaluronic Acid / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D009915:Orbit / Q000166:cytology; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects*; D012643:Selenium / Q000494:pharmacology*; D017279:Selenocysteine / Q000031:analogs & derivatives* / Q000494:pharmacology
D000975:Antioxidants; D016207:Cytokines; D016877:Oxidants; D017279:Selenocysteine; D006820:Hyaluronic Acid; D006861:Hydrogen Peroxide; D005979:Glutathione Peroxidase; D012643:Selenium; C002979:selenomethylselenocysteine; D019803:Glutathione Disulfide
Graves'; fibroblast; ophthalmopathy; orbitopathy; selenium