Proteomic analysis of the differences in orbital protein expression in thyroid orbitopathy

Thyroid orbitopathy (TO) is a multi-system inflammatory disease characterized by orbital congestion, ocular surface disorders, restrictive myopathy, and skin lesions. The molecular and cellular processes of pathogenic formation of TO orbital fat tissues are not fully understood. In this study, a comparative proteomic analysis was conducted to investigate the importance of some differential proteins of orbital fat tissues in TO.

The differential proteins were analyzed by comparing the two-dimensional gel electrophoresis (2-DE) maps of the orbital fat tissues of TO with those of normal orbital fat tissues. The 2-DE results were further verified by Western blot and immunohistochemistry.

Fifteen up-regulated and two down-regulated proteins in TO orbital fat tissues in comparison with the control were exhibited by 2-DE maps. The over-expressed proteins including guanine nucleotide-binding protein, isocitrate dehydrogenase (IDH), annexin A2, heat shock protein 60 (HSP 60), calreticulin (CALR), protein disulfide-isomerase A3 (PDIA3), spectrin, superoxide dismutase (SOD), and transitional endoplasmic reticulum ATPase (TER ATPase) may contribute to increased thyroid-stimulating hormone receptor (TSHR) expression and cell proliferation. The proteomic data of specific proteins are consistent with those determined by Western blot and immunohistochemistry.

Comparison of orbital fat proteins from thyroid orbitopathy with age-matched controls shows significant differences in the proteome, and up-regulations of the specific proteins in orbital fat tissues from TO are associated with biochemical mechanisms or capacities against endoplasmic reticulum stress, mitochondria dysfunction, and cell proliferation as well as apoptosis in TO orbital fat tissues.