Table 1.

Antioxidant agents in Graves’ orbitopathy (GO).

Compound	Main finding	Methods	Results	Reference
Nicotinamide and Allopurinol	Clinically significant improvement of GO	A pilot study including 22 consecutive patients with mild or moderately severe, active GO of recent onset (<6 months). They were treated with placebo or allopurinol (200 mg daily) plus nicotinamide (300 mg daily) for 3 months.	After 3 months, a significant improvement of GO was observed in 9 (82%) and 3 (27%) patients who respectively received antioxidant agents or placebo. The inflammation of soft tissue was the feature that responded more, whereas proptosis was little affected.	(42) Bouzas EA. et al.
Pentoxifylline	Inhibition of GAG release and fibroblast proliferation	Primary cultures of OFs from GO patients and control subjects were obtained. Cell proliferation and GAG production were measured after the addition of pentoxifylline (0.1–1,000 mg/L).	The exposure of OFs cultures to pentoxifylline resulted in a dose-dependent inhibition of fibroblast proliferation and GAG synthesis.	(33) Chang C.C et al.
	Clinically significant improvement of GO	A pilot study, neither randomized nor controlled, which involved 10 patients with active, mild or moderate-to-severe GO. Patients were treated with a daily infusion of pentoxifylline (200 mg/die) for 10 days, following which treatment was continued orally (1,800 to 1,200 mg/day) and stopped after 3 months.	At the end of treatment, a significant improvement of GO was observed in 8 of 10 patients. The beneficial effect was more evident on soft tissue inflammation, whereas diplopia and proptosis were less affected.	(43) Balazs C. et al.
	No improvement of GO	A prospective, multicenter, placebo-controlled clinical trial in which 159 patients with mild GO were randomized to receive sodium selenite (100 μg twice daily orally), pentoxifylline (600 mg twice daily orally) or placebo for 6 months.	Unlike selenium, no beneficial effects of pentoxifylline were observed	(44) Marcocci NEJM
Quercetin	Reduction of cell proliferation and HA release in GO fibroblasts	Primary cultures of OFs from GO patients and control subjects were obtained. Cell proliferation, cell necrosis, apoptosis and HA release were measured after incubation with medium without compounds, or containing: i) quercetin, ii) quercitrin, or iii) rutin. (at concentrations ranging between 1 and 150 μMCell).	Beginning at a 30 μM concentration, quercetin reduced cell proliferation and HA release, acting by the induction of necrosis and cell cycle blockade. No difference between GO and control fibroblasts was observed.	(16) Lisi S. et al.
N-acetyl-cysteine, vitamin C and melatonine .	Reduction of proliferation and release of cytokines in GO fibroblasts	Primary cultures of OFs from GO patients and control subjects. Oxidative stress was induced by H2O2. Cells were pretreated with N-acetylcysteine (100 and 200 μM) or vitamin C (250 and 500 μM). Cell proliferation, cell necrosis, apoptosis and HA release were measured	Treatment with H2O2 at low concentrations of H2O2 (3.125–25 μM) increased the survival of GO fibroblasts. 6.25 μM H2O2 led to a significant elevation of TGF β, IL-1 β and superoxide anion in GO fibroblasts, in GO, but not in control OFs. Pretreatment with N-acetylcysteine or vitamin C reversed the enhanced proliferation and the production of TGF-β, IL-1β and superoxide anion of GO fibroblasts in response to 6.25 μM H2O2.	(24) Tsai CC. et al.
	Reduction of cell proliferation and HA release in GO fibroblasts	GSSG, as a measure of oxidative stress, cell proliferation, HA, TNFα, IFNγ, and IL-1β were measured in primary cultures of GO and control OFs treated with H2O2 and incubated with N-acetyl-cysteine, vitamin C and melatonine	Oxidative stress was reduced by all of the three antioxidant agents. Vitamin C reduced proliferation in GO, but not in control fibroblasts. N-acetyl-l-cysteine reduced proliferation and IFNγ in GO, and HA and IL-1β in both GO and control fibroblasts. Melatonin reduced IL-1β and HA in GO and control fibroblasts, and IFNγ only in GO fibroblasts.	(17) Rotondo Dottore G. et al
Enalapril .	Reduction of cell proliferation and HA release in GO fibroblasts	Primary cultures of GO and control fibroblasts were treated with enalapril (2 or 5 mM, for 3 or 5 days) or with a control compound (lisinopril). Cell proliferation assays, lactate dehydrogenase release assays (as a measure of cell necrosis), apoptosis assays, and measurement of HA in the cell media were performed	Enalapril reduced OFs proliferation and HA release in the cell media in both GO and control fibroblasts. Because enalapril did not affect cell necrosis and apoptosis, the effects on proliferation probably reflected an inhibition of cell growth and/or a delay in cell cycle.	(15) Botta R. et al.
Retinol, β-carotene, vitamin E	Reduction of cell proliferation in GO fibroblasts	Primary cultures of GO and control fibroblasts. Oxidative stress was induced by treatment with H2O2. Cells were pre-incubated for 2 days at 37°C with complete medium without compounds, or with medium containing either one of the compounds investigated at various concentrations. GSSG, cell proliferation, HA, TNFα, IFNγ, and IL1β were measured	Retinol, β-carotene and vitamin E significantly reduced the release of GSSG and IL-1β induced by H2O2 in GO, but not in control fibroblasts. β-carotene reduced OFs proliferation in GO, but not in control fibroblasts, whereas retinol and vitamin E had no effect. Retinol reduced IFNγ in GO and control fibroblasts.	(16) Rotondo Dottore G. et al

OFs, orbital fibroblasts; GAG, glycosaminoglycans; HA, hyaluronic acid; H₂O₂, hydrogen peroxide; TGF β, transforming growth factor β; IL-1β, interleukin-1β, IFNγ, interferon γ; GSSG, Glutathione disulfide; TNFα, tumor necrosis factor α.