Proteomic Analysis of Retinal Tissue in an S100B Autoimmune Glaucoma Model

Abstract

Glaucoma is a neurodegenerative disease that leads to damage of retinal ganglion cells and the optic nerve. Patients display altered antibody profiles and increased antibody titer, e.g., against S100B. To identify the meaning of these antibodies, animals were immunized with S100B. Retinal ganglion cell loss, optic nerve degeneration, and increased glial cell activity were noted. Here, we aimed to gain more insights into the pathophysiology from a proteomic point of view. Hence, rats were immunized with S100B, while controls received sodium chloride. After 7 and 14 days, retinae were analyzed through mass spectrometry and immunohistology. Using data-independent acquisition-based mass spectrometry, we identified more than 1700 proteins on a high confidence level for both study groups, respectively. Of these 1700, 43 proteins were significantly altered in retinae after 7 days and 67 proteins revealed significant alterations at 14 days. For example, α2-macroglobulin was found significantly increased not only by mass spectrometry analysis, but also with immunohistological staining in S100B retinae at 7 and 14 days. All in all, the identified proteins are often associated with the immune system, such as heat shock protein 60. Once more, these data underline the important role of immunological factors in glaucoma pathogenesis.

Glaucoma Animal Models beyond Chronic IOP Increase

“…Microglia are the macrophages of the CNS, yet it is known that microglia also have the ability of cellular cytotoxicity [122]. Recent proteomic data further confirmed that the immune system plays an important role in the pathology of glaucoma since a shift in the regulation was observed in several immune system-associated proteins after immunization with S100 calcium-binding protein B (S100B), including HSP60 [123]. Altogether, the immune system seems to be a promising target for new therapeutic approaches.…”

Molecular Genomics of Glaucoma: An Update

“…Axon regeneration is inhibited by the suppressor of cytokine signalling (SOCS) suppressing the Jak/STAT signalling [101]. Interestingly, in an immunoreactive male Lewis rats for S100B protein (the antibody which is found in high titre in glaucoma patients) showed 43 proteins were dysregulated in the retina, out of which alpha-2 macroglobulin increase was significantly associated with heat shock protein 60, showcasing the role of immunological factors in glaucoma [102].…”

Mass spectrometry‐based retina proteomics

“…In addition, peptides can be quantified through automated data analyses with consistency and accuracy comparable with that of SRM (Gillette & Carr, 2013; Röst et al, 2017). Therefore, SWATH‐MS has become an emerging methodology introduced into several recent retina proteomics studies focused on oxygen‐induced retinopathy in mouse (Vähätupa et al, 2018; Xu et al, 2022), identification of differentially expressed proteins in the retinal emmetropization process in guinea pig (Shan et al, 2018), creation of spectral library of proteins for the normal C57BL/6 mouse retina (Sze et al, 2021), revealing the significance of lipid metabolism in myopic guinea pig retina (Bian et al, 2021), detecting and quantifying regional changes of retinal protein expressions after optic nerve injury in rats (Kwong et al, 2021), as well as proteomic analysis of retinal tissue in an S100B autoimmune glaucoma model (Reinehr et al, 2021).…”

“…However, the activation of the classical complement pathway and upregulation of cholesterol transport proteins were exclusive for the glaucomatous human retinae. In the most recent proteomics study focused on glaucoma using retinal tissue (Reinehr et al, 2021), DIA‐based LC‐MS/MS measurements showed a complex, time‐dependent regulations of protein expression in an S100B autoimmune model in rats with the TCA cycle and glutamate processing representing the main functional interactions related to the disease one and two weeks after immunization, respectively. The role of microglia in this model of glaucoma‐like degeneration of the retina also was addressed earlier through a label‐free shotgun proteomics study and using minocycline to inhibit inflammatory response (Grotegut et al, 2020).…”