Antioxidant Actions of Selenium in Orbital Fibroblasts: A Basis for the Effects of Selenium in Graves' Orbitopathy
Giovanna Rotondo Dottore1, Marenza Leo1, Giamberto Casini2
11 Department of Clinical and Experimental Medicine, Endocrinology Units, University of Pisa and University Hospital of Pisa , Pisa, Italy .
Background:
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.
Methods:
Primary cultures of orbital fibroblasts from six GO patients and six control subjects were established. Cells were treated with H2O2 to 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.
Results:
H2O2 induced 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), H2O2 did not significantly affect HA release, but it was reduced by SeMCys. H2O2 determined 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.
Conclusions:
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.
Insights
Selenium supplementation, specifically methylselenocysteine (SeMCys), mitigates oxidative stress effects in Graves' orbitopathy (GO) fibroblasts. SeMCys reduces fibroblast proliferation and pro-inflammatory cytokine release, offering insights into selenium
Area of Science:
- Ophthalmology
- Endocrinology
- Cell Biology
Background:
- Graves' orbitopathy (GO) is an autoimmune condition affecting the eye socket.
- Oxidative stress plays a role in GO pathogenesis.
- Selenium has shown potential benefits in clinical trials for GO.
Purpose of the Study:
- To investigate the cellular mechanisms of selenium's beneficial effects in Graves' orbitopathy.
- To examine the impact of selenium on orbital fibroblasts under oxidative stress.
Main Methods:
- Orbital fibroblasts from GO patients and controls were cultured.
- Cells were exposed to hydrogen peroxide (H2O2) to induce oxidative stress.
- Selenium-(methyl)selenocysteine (SeMCys) was used for pre-incubation.
- Assays measured glutathione disulfide (GSSG), glutathione peroxidase (GPX) activity, cell proliferation, hyaluronic acid (HA) release, and pro-inflammatory cytokines.
Main Results:
- SeMCys reduced H2O2-induced increases in GSSG and fibroblast proliferation.
- SeMCys enhanced glutathione peroxidase (GPX) activity.
- SeMCys decreased hyaluronic acid (HA) release in GO fibroblasts.
- SeMCys blocked H2O2-induced increases in tumor necrosis factor alpha and interferon gamma.
Conclusions:
- Selenium, as SeMCys, counteracts oxidative stress effects in orbital fibroblasts.
- SeMCys inhibits proliferation and pro-inflammatory cytokine secretion.
- SeMCys demonstrates specific effects on GO fibroblasts, including reduced HA release.
- These findings elucidate cellular mechanisms for selenium's therapeutic potential in GO.
