Mechanism of MicroRNA-146a/Notch2 Signaling Regulating IL-6 in Graves Ophthalmopathy

Background/Aims: We intended to investigate the significance of microRNA-146a, Notch2 and IL-6 on Graves ophthalmopathy (GO) and the relationships among them. Methods: About 27 GO patients were incorporated in this study, including 13 patients with inactive GO and14 patients with active GO. Another 15 patients who had previously received strabismus orthopedics or ophthalmectomy due to trauma were selected as the control population. QRT-PCR assay was used to detect microRNA-146a and Notch2 expression levels in plasma. MTT assay and flow cytometry were respectively used to assess the viability and mitosis of the fibroblasts isolated from orbital connective tissue. Double antibody sandwich enzyme-linked immunosorbent assay (ELISA) was employed to detect serum IL-6 levels. The dual luciferase reporter gene assay was used to verify the targeting relationship between microRNA-146a and Notch2. Results: Compared with the control group, the relative expression of miR-146a was significantly increased whereas the relative expression of Notch2 was significantly decreased (all P < 0.05) in GO patients compare with the control. Notch2 can be directly targeted by microRNA-146a. The over-expression of miR-146a markedly facilitated Orbital Fibroblasts (OFs) viability and mitosis whereas markedly suppressed cell apoptosis (all P < 0.05). Exogenous microRNA-146a mimics could down-regulat the expression of Notch2 and up-regulate IL-6 (P < 0.05). The inhibition of microRNA-146 resulted in the elevated expression of Notch2 and decreased expression of IL-6 (P < 0.05). Conclusion: MicroRNA-146a may increase the IL-6 levels and exacerbate GO by directly targeting Notch2.

Graves' ophthalmopathy: eye muscle involvement in patients with diplopia

BACKGROUND: Diplopia identifies patients with eye muscle involvement in Graves' ophthalmopathy (GO). OBJECTIVE: To identify clinical parameters that could eliminate the need for magnetic resonance imaging (MRI) to assess the activity of inflammation in the eye muscles of GO patients with diplopia. METHODS: In 43 patients with GO with recently developed diplopia, orbital ultrasound and MRI were performed. Muscle diameters and MRI T2 relaxation times were measured, and the amount of orbital connective tissue was calculated from MRI scans and compared with ultrasound readings, diplopia grades, degree of protrusion, ocular pressure, tear production, antibody levels and hormonal parameters of thyroid function. RESULTS: No correlation was found between diameters of 233 extraocular muscles measured by MRI and by ultrasound. For each of the four muscles, there was a diameter above which ultrasound was always unreliable. MRI data were used in further analysis. Of the muscles examined, the inferior rectuses were the most frequently enlarged - at least one, in 93% of cases. Medial, lateral and superior rectuses were enlarged in 59%, 37% and 34% of the orbits respectively. The pattern of muscle involvement of the two orbits tended to be symmetric (r=0.49, P=0.003), particularly for the medial rectuses (r=0.90, P=0.000). Proptosis correlated with the sum of the muscle diameters for a given eye (right eye: r=0.54, P=0.003; left eye: r=0.57, P=0.001), but it failed to correlate with the amount of orbital connective tissue. In 53% of the patients, normal T2 relaxation times were found in all eight muscles. There was only a weak correlation between muscle thickness and T2 relaxation time (r=0.49, P=0.003), indicating that muscle enlargement alone is not a sign of disease activity. The severity of diplopia was independent of T2 relaxation time. The amount of orbital connective tissue showed a negative correlation with the greatest T2 relaxation time for a given eye (r= -0.52, P=0.004); this suggests that disease types exist that have predominant muscle involvement and predominant connective tissue expansion. No correlation between connective tissue expansion and proptosis, diplopia grade, muscle thickness or disease duration was found - that is, connective tissue expansion is not a major factor in diplopia. Both muscle and connective tissue findings were independent of thyroid function. CONCLUSION: Ultrasound and MRI eye muscle diameter readings do not correlate, because of the inherent inaccuracy of orbital ultrasound. Muscle enlargement alone does not mean oedematous swelling and active disease. Neither ultrasound, nor any combination of 11 clinical and laboratory parameters provided the degree of information on muscles and connective tissue that was obtainable by MRI. In unclear cases of recently developed diplopia, before orbital decompression surgery, in the case of treatment failure or if, for any other reason, imaging is needed in GO, MRI is the method of choice.

Expression of Hyaluronan Synthase Messenger Ribonucleic Acids and Their Induction by Interleukin-1β in Human Orbital Fibroblasts: Potential Insight into the Molecular Pathogenesis of Thyroid-Associated Ophthalmopathy1

The disordered accumulation of hyaluronan, a nonsulfated glycosaminoglycan, is a hallmark feature of the tissue remodeling observed in thyroid-associated ophthalmopathy (TAO). Orbital fibroblasts have been shown to exhibit substantial up-regulation of hyaluronan synthesis when activated with proinflammatory cytokines such as interleukin-1β (IL-1β). Recently, three members of the hyaluronan synthase (HAS) gene family were cloned. Here we report that IL-1β can dramatically and consistently induce in orbital fibroblasts the expression of HAS2 in the five orbital strains examined. HAS3 messenger ribonucleic acid (mRNA) was also detectable in all these strains by RT-PCR under both control and IL-1β-treated conditions. In contrast, HAS1 mRNA was detected by Northern blot analysis in only one of the strains treated with IL-1β, but in three of five strains examined by RT-PCR. These HAS inductions by the cytokine were time dependent and could be attenuated with dexamethasone and cycloheximide. They were accompanied by an increased incorporation of[ 3H]glucosamine into hyaluronan, and dexamethasone could attenuate induction of macromolecular synthesis as well. Our observations suggest that the cytokine-dependent induction of the HAS genes in orbital fibroblasts may be the molecular basis at least in part for the increased accumulation of hyaluronan, driven by immunocompetent cells, in orbital connective tissue and the extraocular muscles in TAO.