Abstract
Purpose: :
Transforming growth factor (TGF)-β2 is elevated in the aqueous humor of patients with primary open angle glaucoma (POAG), elevates intraocular pressure in perfusion cultured eyes, and may be involved in the pathogenesis of POAG. Toward a better understanding of POAG pathology, we evaluated quantitative proteomic changes in cultured trabecular meshwork (TM) cells following TGF-β2 treatment.
Methods: :
Primary cultures of human TM cells from 2 POAG and 2 non-glaucomatous donors were treated with or without TGF-β2 (5 ng/ml) for 48 h. Protein was extracted in SDS buffer, digested with trypsin, peptides labeled with iTRAQ tags, and TGF-β2-treated TM samples were combined with their corresponding untreated samples. Following strong cation exchange chromatography, peptides were analyzed by LC MS/MS and proteins were identified using the Mascot search engine and the Swiss-Protein database. Relative protein quantification from iTRAQ labeling utilized code written in R. Immunoblotting was used to corroborate differential expression of select proteins.
Results: :
A total of 653 proteins were quantified with 2 or more peptides from TGF-β2-treated TM cells. No definitive proteomic differences were detected between TGF-β2-treated POAG and control TM cells. The expression of over 30 proteins changed significantly following TGF-β2-treatment, including increased expression of SPARC, α-crystallin B, tropomysin α1 and collagen α1(III) and decreased expression of CD9 antigen, guanine nucleotide-binding protein G(i) α-2, and superoxide dismutase [Mn].
Conclusions: :
Almost 3-fold more proteins were significantly increased than decreased following TGF-β2 treatment. Proteins increased in abundance may contribute to ECM and cytoskeletal abnormalities that facilitate outflow resistance in POAG TM. Proteins reduced in abundance may compromise cellular adhesion, signaling and defense mechanisms in the TM. The results provide new insights to possible molecular mechanisms of POAG.CR:
Keywords: trabecular meshwork • proteomics • aqueous