4-Methylumbelliferone suppresses hyaluronan and adipogenesis in primary cultured orbital fibroblasts from Graves' orbitopathy

TMEM2 inhibits the development of Graves' orbitopathy through the JAK-STAT signaling pathway

A mouse model was used to investigate the role of the hyaluronidase, transmembrane protein 2 (TMEM2), on the progression of Graves' orbital (GO) disease. We established a GO mouse model through immunization with a plasmid expressing the thyroid stimulating hormone receptor. Orbital fibroblasts (OFs) were subsequently isolated from both GO and non-GO mice for comprehensive in vitro analyses. The expression of TMEM2 was assessed using qRT-PCR, Western blot and immunohistochemistry in vivo. Disease pathology was evaluated by H&E staining and Masson's trichrome staining in GO mouse tissues. Our investigation revealed a notable reduction in TMEM2 expression in GO mouse orbital tissues. Through overexpression and knockdown assays, we demonstrated that TMEM2 suppresses inflammatory cytokines and reactive oxygen species production. TMEM2 also inhibits the formation of lipid droplets in OFs and the expression of adipogenic factors. Further incorporating Gene Set Enrichment Analysis of relevant GEO datasets and subsequent in vitro cell experiments, robustly confirmed that TMEM2 overexpression was associated with a pronounced upregulation of the JAK/STAT signaling pathway. In vivo, TMEM2 overexpression reduced inflammatory cell infiltration, adipogenesis, and fibrosis in orbital tissues. These findings highlight the varied regulatory role of TMEM2 in GO pathogenesis. Our study reveals that TMEM2 plays a crucial role in mitigating inflammation, suppressing adipogenesis, and reducing fibrosis in GO. TMEM2 has potential as a therapeutic target and biomarker for treating or alleviating GO. These findings advance our understanding of GO pathophysiology and provide opportunities for targeted interventions to modulate TMEM2 for therapeutic purposes.

Autophagy in graves' ophthalmopathy

Graves' ophthalmopathy (GO) is an inflammatory autoimmune disease that affects the eyes. It can significantly alter the quality of life in patients because of its distinctive pathological appearance and the effect on vision. To date, the exact pathological mechanism of GO has not been explicitly discovered. However, several studies have associated autophagy with this disease. Autophagy is a catabolic process that helps maintain homeostasis in all organisms by protecting the cells and tissues from various endogenous and exogenous stress factors. Based on our results, patients affected with GO have comparatively elevated levels of autophagy, which critically affects the pathological mechanism of the GO. In this review, we have summarized the autophagy mechanism in the pathogenesis of GO.

Therapeutic effect of ibrutinib, a selective Bruton's tyrosine kinase inhibitor, in orbital fibroblasts from patients with Graves' orbitopathy

PURPOSE

Bruton's tyrosine kinase (BTK) is an essential protein in B-cell antigen receptor (BCR) signaling pathway and is known to be related to pathogenetic effect on B-cell related malignancies and various autoimmune diseases. In this study, we investigated the therapeutic effect of ibrutinib, an orally bioavailable BTK inhibitor in the pathogenesis of Graves' orbitopathy (GO) in in vitro model.

METHODS

Expression of BTK in orbital tissues from GO and normal control subjects were evaluated by real-time polymerase chain reaction (PCR). Primary cultured orbital fibroblasts from each subject were exposed to ibrutinib and stimulated with interleukin (IL)-1β or insulin like growth factor (IGF)-1. Production of inflammatory cytokines was evaluated by real time PCR and enzyme-linked immunosorbent assays (ELISA). The downstream transcription factors were also determined by western blot assays.

RESULTS

The expression of BTK in GO tissues were significantly higher than in healthy controls. After stimulation of GO orbital fibroblasts with IL-1β or IGF-1, BTK mRNA and phosphorylated (p)- BTK protein expression was also enhanced. Ibrutinib reduced the expression of BTK mRNA and proteins of p-BTK, and inhibited the IL-1β- and IGF-1-induced production of proinflammatory cytokines including IL-6, IL-8 and COX-2 in both GO and normal cells. Ibrutinib also significantly attenuated phosphorylation of Akt, p38, c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), and nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-κB) in IL-1β stimulated GO cells and Akt, JNK, and NF-κB in IL-1ß stimulated normal cells.

CONCLUSIONS

BTK expression is enhanced in GO tissue and orbital fibroblasts. Ibrutinib, a BTK inhibitor suppresses proinflammatory cytokine production as well as phosphorylation of Akt and NF-κB protein. Our results suggest the potential role of BTK in GO inflammatory pathogenesis and possibility of a novel therapeutic target of GO.