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Immune response after intermittent minimally invasive intraocular pressure elevations in an experimental animal model of glaucoma.

Gramlich OW, Teister J, Neumann M, Tao X, Beck S, von Pein HD, Pfeiffer N, Grus FH - J Neuroinflammation (2016)

Bottom Line: A 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.

View Article: PubMed Central - PubMed

Affiliation: Experimental Ophthalmology, Department of Ophthalmology, University Medical Center of the Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131, Mainz, Germany.

ABSTRACT

Background: Elevated 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.

Methods: Using 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.

Results: A 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.

Conclusions: Intermittent 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.

No MeSH data available.


Related in: MedlinePlus

Retinal ganglion cell analysis. a The survival of retinal ganglion cells was analyzed as the number of Brn3a-positive cells per mm retina in naso-temporal cross-sections of the eye. A significant loss of retinal ganglion cells was observed in injured eyes of iOHT group and iOHT + Belimumab group (both p < 0.01, horizontal lines) compared with control eyes (black). Furthermore, a significant difference in damage was observed between fellow and injured eye of iOHT group (p < 0.05), but not between both eyes of iOHT + Belimumab group (p = 0.8). Significant values are indicated as follows: *p < 0.05, **p < 0.01. b–f Representative images of retinal cross-sections (×20 magnification) show different densities of Brn3a-positive cells (arrows) in controls (CTRL, b), fellow and injured eyes of iOHT group (c and d, respectively), and fellow and injured eyes of iOHT + Belimumab group (e and f, respectively). Images were taken at the same eccentricity to the optic nerve head to ensure comparability. Note the low number of retinal ganglion cells in injured eyes. Abbreviations: GCL ganglion cell layer, INL inner nuclear layer, ONL outer nuclear layer, CHO choroid. Scale bar represents 100 μm. Significant values are indicated as follows: *p < 0.05, **p < 0.01
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Fig3: Retinal ganglion cell analysis. a The survival of retinal ganglion cells was analyzed as the number of Brn3a-positive cells per mm retina in naso-temporal cross-sections of the eye. A significant loss of retinal ganglion cells was observed in injured eyes of iOHT group and iOHT + Belimumab group (both p < 0.01, horizontal lines) compared with control eyes (black). Furthermore, a significant difference in damage was observed between fellow and injured eye of iOHT group (p < 0.05), but not between both eyes of iOHT + Belimumab group (p = 0.8). Significant values are indicated as follows: *p < 0.05, **p < 0.01. b–f Representative images of retinal cross-sections (×20 magnification) show different densities of Brn3a-positive cells (arrows) in controls (CTRL, b), fellow and injured eyes of iOHT group (c and d, respectively), and fellow and injured eyes of iOHT + Belimumab group (e and f, respectively). Images were taken at the same eccentricity to the optic nerve head to ensure comparability. Note the low number of retinal ganglion cells in injured eyes. Abbreviations: GCL ganglion cell layer, INL inner nuclear layer, ONL outer nuclear layer, CHO choroid. Scale bar represents 100 μm. Significant values are indicated as follows: *p < 0.05, **p < 0.01

Mentions: Examination of the RGC density recapitulated the results of the optic nerve axon analysis. Eyes of control animals (Fig. 3b) and those exposed to iOHT displayed normal retinal morphology (Fig. 3c–f), but a significant loss of −19 % of RGC compared with the RGC density of their fellow uninjured eyes (p = 0.02), or to RGC numbers of control animals (−30.5 %, p = 0.0001, Fig. 3a, Table 1). Additionally, contralateral eyes of the iOHT group showed a slight, but not significant, loss of RGC compared with controls. Belimumab-treated animals displayed decreased RGC density in eyes after iOHT. As was the case for axonal density, the RGC loss was not statistically significant in comparison to the fellow eyes (p = 0.76).Fig. 3


Immune response after intermittent minimally invasive intraocular pressure elevations in an experimental animal model of glaucoma.

Gramlich OW, Teister J, Neumann M, Tao X, Beck S, von Pein HD, Pfeiffer N, Grus FH - J Neuroinflammation (2016)

Retinal ganglion cell analysis. a The survival of retinal ganglion cells was analyzed as the number of Brn3a-positive cells per mm retina in naso-temporal cross-sections of the eye. A significant loss of retinal ganglion cells was observed in injured eyes of iOHT group and iOHT + Belimumab group (both p < 0.01, horizontal lines) compared with control eyes (black). Furthermore, a significant difference in damage was observed between fellow and injured eye of iOHT group (p < 0.05), but not between both eyes of iOHT + Belimumab group (p = 0.8). Significant values are indicated as follows: *p < 0.05, **p < 0.01. b–f Representative images of retinal cross-sections (×20 magnification) show different densities of Brn3a-positive cells (arrows) in controls (CTRL, b), fellow and injured eyes of iOHT group (c and d, respectively), and fellow and injured eyes of iOHT + Belimumab group (e and f, respectively). Images were taken at the same eccentricity to the optic nerve head to ensure comparability. Note the low number of retinal ganglion cells in injured eyes. Abbreviations: GCL ganglion cell layer, INL inner nuclear layer, ONL outer nuclear layer, CHO choroid. Scale bar represents 100 μm. Significant values are indicated as follows: *p < 0.05, **p < 0.01
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Fig3: Retinal ganglion cell analysis. a The survival of retinal ganglion cells was analyzed as the number of Brn3a-positive cells per mm retina in naso-temporal cross-sections of the eye. A significant loss of retinal ganglion cells was observed in injured eyes of iOHT group and iOHT + Belimumab group (both p < 0.01, horizontal lines) compared with control eyes (black). Furthermore, a significant difference in damage was observed between fellow and injured eye of iOHT group (p < 0.05), but not between both eyes of iOHT + Belimumab group (p = 0.8). Significant values are indicated as follows: *p < 0.05, **p < 0.01. b–f Representative images of retinal cross-sections (×20 magnification) show different densities of Brn3a-positive cells (arrows) in controls (CTRL, b), fellow and injured eyes of iOHT group (c and d, respectively), and fellow and injured eyes of iOHT + Belimumab group (e and f, respectively). Images were taken at the same eccentricity to the optic nerve head to ensure comparability. Note the low number of retinal ganglion cells in injured eyes. Abbreviations: GCL ganglion cell layer, INL inner nuclear layer, ONL outer nuclear layer, CHO choroid. Scale bar represents 100 μm. Significant values are indicated as follows: *p < 0.05, **p < 0.01
Mentions: Examination of the RGC density recapitulated the results of the optic nerve axon analysis. Eyes of control animals (Fig. 3b) and those exposed to iOHT displayed normal retinal morphology (Fig. 3c–f), but a significant loss of −19 % of RGC compared with the RGC density of their fellow uninjured eyes (p = 0.02), or to RGC numbers of control animals (−30.5 %, p = 0.0001, Fig. 3a, Table 1). Additionally, contralateral eyes of the iOHT group showed a slight, but not significant, loss of RGC compared with controls. Belimumab-treated animals displayed decreased RGC density in eyes after iOHT. As was the case for axonal density, the RGC loss was not statistically significant in comparison to the fellow eyes (p = 0.76).Fig. 3

Bottom Line: A 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.

View Article: PubMed Central - PubMed

Affiliation: Experimental Ophthalmology, Department of Ophthalmology, University Medical Center of the Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131, Mainz, Germany.

ABSTRACT

Background: Elevated 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.

Methods: Using 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.

Results: A 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.

Conclusions: Intermittent 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.

No MeSH data available.


Related in: MedlinePlus