Level of vitreous alpha-B crystallin in eyes with rhegmatogenous retinal detachment

Evidence for Paracrine Protective Role of Exogenous αA-Crystallin in Retinal Ganglion Cells

Expression and secretion of neurotrophic factors have long been known as a key mechanism of neuroglial interaction in the central nervous system. In addition, several other intrinsic neuroprotective pathways have been described, including those involving small heat shock proteins such as α-crystallins. While initially considered as a purely intracellular mechanism, both αA-crystallins and αB-crystallins have been recently reported to be secreted by glial cells. While an anti-apoptotic effect of such secreted αA-crystallin has been suggested, its regulation and protective potential remain unclear. We recently identified residue threonine 148 (T148) and its phosphorylation as a critical regulator of αA-crystallin intrinsic neuroprotective function. In the current study, we explored how mutation of this residue affected αA-crystallin chaperone function, secretion, and paracrine protective function using primary glial and neuronal cells. After demonstrating the paracrine protective effect of αA-crystallins secreted by primary Müller glial cells (MGCs), we purified and characterized recombinant αA-crystallin proteins mutated on the T148 regulatory residue. Characterization of the biochemical properties of these mutants revealed an increased chaperone activity of the phosphomimetic T148D mutant. Consistent with this observation, we also show that exogeneous supplementation of the phosphomimetic T148D mutant protein protected primary retinal neurons from metabolic stress despite similar cellular uptake. In contrast, the nonphosphorylatable mutant was completely ineffective. Altogether, our study demonstrates the paracrine role of αA-crystallin in the central nervous system as well as the therapeutic potential of functionally enhanced αA-crystallin recombinant proteins to prevent metabolic-stress induced neurodegeneration.

Antibody and Protein Profiles in Glaucoma: Screening of Biomarkers and Identification of Signaling Pathways

Simple Summary

Glaucoma is a chronic eye disease that is one of the leading causes of blindness worldwide. Currently, the only therapeutic option is to lower intraocular pressure. The onset of the disease is often delayed because patients do not notice visual impairment until very late, which is why glaucoma is also known as “the silent thief of sight”. Therefore, early detection and definition of specific markers, the so-called biomarkers, are immensely important. For the methodical implementation, high-throughput methods and omic-based methods came more and more into focus. Thus, interesting targets for possible biomarkers were already suggested by clinical research and basic research, respectively. This review article aims to join the findings of the two disciplines by collecting overlaps as well as differences in various clinical studies and to shed light on promising candidates concerning findings from basic research, facilitating conclusions on possible therapy options.

Abstract

Glaucoma represents a group of chronic neurodegenerative diseases, constituting the second leading cause of blindness worldwide. To date, chronically elevated intraocular pressure has been identified as the main risk factor and the only treatable symptom. However, there is increasing evidence in the recent literature that IOP-independent molecular mechanisms also play an important role in the progression of the disease. In recent years, it has become increasingly clear that glaucoma has an autoimmune component. The main focus nowadays is elucidating glaucoma pathogenesis, finding early diagnostic options and new therapeutic approaches. This review article summarizes the impact of different antibodies and proteins associated with glaucoma that can be detected for example by microarray and mass spectrometric analyzes, which (i) provide information about expression profiles and associated molecular signaling pathways, (ii) can possibly be used as a diagnostic tool in future and, (iii) can identify possible targets for therapeutic approaches.

A case of proliferative diabetic retinopathy in which scintillating particles appeared in the intravitreal cavity after laser photocoagulation

BACKGROUND

To report a case of proliferative diabetic retinopathy (PDR) exhibiting the appearance of scintillating particles presumed to be crystallin inside the intravitreal cavity after laser photocoagulation.

CASE PRESENTATION

A 56-year-old male patient presented at our outpatient clinic after becoming aware of decreased vision in his right eye. Ocular examination performed at the patient's initial visit revealed a massive preretinal macular hemorrhage due to PDR in his right eye. Fundus fluorescein angiography revealed extensive retinal non-perfusion areas and neovascularization in both eyes. However, no opacity was observed in the intravitreal cavity of his left eye. Vitreous surgery was performed on the patient's right eye after ultrasonic phacoemulsification aspiration and intraocular lens implantation. Post surgery, the corrected VA in that eye improved from 0.1 to 1.0. In correlation with the treatment performed on the patient's right eye, we began panretinal photocoagulation on his left eye. Examination performed prior to the patient's third session of panretinal photocoagulation revealed a large number of scintillating particles in the posterior vitreous gel in front of the retina. Examination via slit-lamp microscopy revealed that the particles were of varied hues, and closely resembled a 'Christmas tree' cataract. No posterior vitreous detachment was observed, and since these particles were situated as if captured in the posterior vitreous gel, no eye-movement-associated mobility of the particles was observed. Since the cloudiness was not severe enough to interfere with photocoagulation, additional photocoagulation was performed, and the patient is currently under observation. Six months have now passed since the fourth photocoagulation procedure was performed, and there has been no change in the state of the particles. Optical coherence tomography imaging revealed no change before and after the panretinal photocoagulation. The corrected VA in his left eye has remained at 1.0 during the postoperative follow-up period.

CONCLUSIONS

We speculate that the production of crystallin in the retina in this case was triggered by the photocoagulation procedure performed for diabetic retinopathy.

Increased levels of alphaB-crystallin in vitreous fluid of patients with proliferative diabetic retinopathy and correlation with vascular endothelial growth factor

BACKGROUND

AlphaB-crystallin has been shown to have angiogenic properties. The purpose of this study was to determine the levels of alphaB-crystallin in the vitreous fluid of patients with proliferative diabetic retinopathy and to confirm the association between the expression level of alphaB-crystallin and vascular endothelial growth factor.

METHODS

Vitreous samples were collected before vitrectomy from 46 eyes of 46 consecutive patients with proliferative diabetic retinopathy, and 19 patients without diabetes mellitus had vitrectomy for idiopathic macular hole. The concentrations of alphaB-crystallin and vascular endothelial growth factor were measured via enzyme-linked immunosorbent assay.

RESULTS

The vitreous level (mean ± SD) of alphaB-crystallin was significantly higher in patients with proliferative diabetic retinopathy (317.3 ± 151.7 ng/mL) than in control patients (idiopathic macular hole, 8.3 ± 6.1 ng/mL) (P < 0.0001). The vitreous concentration of vascular endothelial growth factor was also significantly higher in patients with proliferative diabetic retinopathy (860.1 ± 566.4 pg/mL) than in control patients (9 pg/mL) (P < 0.0001). Meanwhile, both the expression levels of alphaB-crystallin and vascular endothelial growth factor were significantly higher in eyes with active proliferative diabetic retinopathy than in those with inactive proliferative diabetic retinopathy. Also, the vitreous concentration of alphaB-crystallin correlated significantly with that of vascular endothelial growth factor in vitreous fluid of proliferative diabetic retinopathy ([correlation coefficient], R = 0.78, P < 0.001).

CONCLUSIONS

These results suggest a significant increase of alphaB-crystallin in the vitreous fluid of patients with proliferative diabetic retinopathy and present a crucial association between alphaB-crystallin and vascular endothelial growth factor with angiogenic activity in proliferative diabetic retinopathy.