Glaucoma related proteomic changes have been documented in cell and animal models. However, proteomic studies investigating on human retina samples are still rare. In the present work, retina samples of glaucoma and non-glaucoma control donors have been examined by a state-of-the-art mass spectrometry (MS) workflow to uncover glaucoma related proteomic changes. More than 600 proteins could be identified with high confidence (FDR < 1%) in human retina samples. Distinct proteomic changes have been observed in 10% of proteins encircling mitochondrial and nucleus species. Numerous proteins showed a significant glaucoma related level change (p < 0.05) or distinct tendency of alteration (p < 0.1). Candidates were documented to be involved in cellular development, stress and cell death. . In 2010, worldwide 60.5 million people suffered from glaucoma and over 70 million people are expected to develop glaucoma by 2020 making glaucoma to one of the leading causes of blindness affecting people of all ages, however with increasing prevalence with age 3 . Inflammatory 4 and autoimmune processes 5,6 implementing oxidative stress 7 and mitochondrial dysfunction 8,9 have been documented for glaucoma so far and underlying molecular mechanisms are shifting in focus of research. Accordingly, numerous studies have demonstrated proteomic changes referring to experimental in-vivo and in-vitro models, regarding rodents 10-12 and primates 13 . Glaucoma related proteomic alterations have also been reported for human sample material, e.g. aqueous humor [14][15][16][17][18][19] , trabecular meshwork 20,21 and tears 22 proposing key proteins and biomarker candidates. Focusing on human glaucomatous retina samples, Tezel et al. documented hemoglobin upregulation using immunohistochemistry 23 , whereas the research groups of Yang and Luo revealed proteomic changes linked to TNF-α /TNFR1 24 and Toll-like receptors (TLRs) 25 using mass spectrometry. However, proteomic investigations on human retinal sample species are rare due to limitation of donors and human sample material. Therefore, the purpose of the present study was to analyze human retinal samples of glaucoma (N = 5) and non-glaucoma subjects (N = 5) by use of a state-of-the-art "bottom-up" high performance liquid chromatography electro spray ionization mass spectrometry (BU LC ESI MS) workflow. Retinal sample exploration should provide an in-depth view to the human retina proteome, reveal glaucomatous proteomic alterations and should contribute to a better understanding of the molecular pathomechanism of glaucoma. Moreover, new molecular candidates linked to glaucomatous neurodegeneration should be proposed giving direction for future glaucoma research projects.

BackgroundElevated intraocular pressure (IOP), as well as fluctuations in IOP, is a main risk factor for glaucoma, but its pathogenic effect has not yet been clarified. Beyond the multifactorial pathology of the disease, autoimmune mechanisms seem to be linked to retinal ganglion cell (RGC) death. This study aimed to identify if intermittent IOP elevations in vivo (i) elicit neurodegeneration, (ii) provokes an immune response and (iii) whether progression of RGC loss can be attenuated by the B lymphocyte inhibitor Belimumab.MethodsUsing an intermittent ocular hypertension model (iOHT), Long Evans rats (n = 21) underwent 27 unilateral simulations of a fluctuating pressure profile. Nine of these animals received Belimumab, and additional seven rats served as normotensive controls. Axonal density was analyzed in PPD-stained optic nerve cross-sections. Retinal cross-sections were immunostained against Brn3a, Iba1, and IgG autoantibody depositions. Serum IgG concentration and IgG reactivities were determined using ELISA and protein microarrays. Data was analyzed using ANOVA and Tukey HSD test (unequal N) or student’s independent t test by groups.ResultsA wavelike IOP profile led to a significant neurodegeneration of optic nerve axons (−10.6 %, p < 0.001) and RGC (−19.5 %, p = 0.02) in iOHT eyes compared with fellow eyes. Belimumab-treated animals only showed slightly higher axonal survival and reduced serum IgG concentration (−29 %) after iOHT. Neuroinflammatory events, indicated by significantly upregulated microglia activation and IgG autoantibody depositions, were shown in all injured retinas. Significantly elevated serum autoantibody immunoreactivities against glutathione-S-transferase, spectrin, and transferrin were observed after iOHT and were negatively correlated to the axon density.ConclusionsIntermittent IOP elevations are sufficient to provoke neurodegeneration in the optic nerve and the retina and elicit changes of IgG autoantibody reactivities. Although the inhibition of B lymphocyte activation failed to ameliorate axonal survival, the correlation between damage and changes in the autoantibody reactivity suggests that autoantibody profiling could be useful as a biomarker for glaucoma.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0542-6) contains supplementary material, which is available to authorized users.

These data suggest that antidepressant treatment is associated with hyponatraemia affecting a subgroup of individuals only. Generalised linear modelling showed that the risk of hyponatraemia increases with increased age, female gender, and particularly the antidepressant agents sertraline and escitalopram. The findings are of clinical significance as they demonstrate that hyponatraemia can occur rapidly with antidepressants, and SSRI/SNRI medications induce more rapid changes. They support the use of electrolyte monitoring early in antidepressant treatment in patients receiving antidepressants.

Purpose of this study was to investigate firstly specific proteomic changes within the retina in the course of an animal glaucoma model and to identify secondly new approaches for neuroprotective, therapeutic options in glaucoma by addressing those specific changes. Intraocular pressure was elevated through cauterization of episcleral veins in adult Sprague Dawley rats. Molecular and morphological changes were surveyed using mass spectrometry, optical coherence tomography as well as immunohistochemical cross section- and flat mount stainings. By quantifying more than 1500 retinal proteins, it was found that the HspB5 protein and numerous beta-crystallins showed a uniform and unique shifting expression pattern as a result of different periods of elevated IOP exposure. Crystallins showed a significant downregulation (p<0.05) after 3 weeks of elevated IOP and an upregulation after 7 weeks. Counteracting those typical changes, an intravitreal injection of β-crystallin B2 at the time of IOP elevation was found to reduce retinal ganglion cell loss (p<0.05), decrease of the retinal nerve fiber layer (p<0.05) and impairment of the optic nerve. Ultimately, proteomic data revealed that β-crystallin B2 might influence calcium-depended cell signaling pathways with severe effect on apoptosis and gene regulation. In this context especially annexin A5, calcium-transporting ATPase 1 and various histone proteins seem to play a major role.

In conclusion, these results provide further lines of evidence that substantial molecular changes occur at the onset of the disease, identifying potential key players, which might be useful as biomarkers for diagnostics and development of medical treatment in the future.