Western blot patterns of serum autoantibodies against optic nerve antigens in dogs with goniodysgenesis-related glaucoma

Abstract

Objective To investigate whether differences existed between clinically normal dogs and dogs with goniodysgenesis-related glaucoma (GDRG) in serum autoantibodies against optic nerve antigens. Animals 16 dogs with GDRG, 17 healthy dogs with unremarkable pectinate ligament and iridocorneal angle morphology, and 13 euthanized dogs with no major ocular abnormalities or underlying diseases. Procedures Western blotting was performed with optic nerve extracts from the euthanized dogs as an antigen source and serum from clinically normal dogs and dogs with GDRG as a primary antibody (autoantibody) source. Blots were evaluated for presence and density of bands. Results Multiple bands were identified on western blots from all dogs with GDRG and all clinically normal dogs, with a high degree of variability among individual dogs. Dogs with GDRG were significantly more likely than healthy dogs to have bands present at 38, 40, and 68 kDa. Dogs with GDRG had significant increases in autoreactivity at 40 and 53 kDa and a significant decrease in autoreactivity at 48 kDa. Conclusions and Clinical Relevance Significant differences in serum autoantibodies against optic nerve antigens were found in dogs with versus without GDRG. Although it remains unclear whether these differences were part of the pathogenesis of disease or were sequelae to glaucomatous changes, these findings provide support for the hypothesis that immune-mediated mechanisms play a role in the development or progression of GDRG. However, the high degree of variability among individual dogs and the considerable overlap between groups suggest that the clinical usefulness of this technique for distinguishing dogs with GDRG from clinically normal dogs is likely limited.

Prophylactic anti‐glaucoma therapy in dogs with primary glaucoma: A practitioner survey of current medical protocols

“…There is no doubt that IOP is an important risk factor for the development of optic nerve damage at the level of the lamina cribrosa, but other factors may act in combination to cause or exacerbate changes to the outflow apparatus and atrophy and loss of RGCs 1,2,20,32‐34,38‐43,50‐52 . In goniodysgenesis‐related canine glaucoma, neutrophilic (acute) and lymphoplasmacytic (chronic) inflammation and pigment dispersion that are the result of segmental loss from the posterior iris epithelium, clumping of the posterior iris pigment epithelium, pigmented cells within the trabecular meshwork or anterior chamber, and preferential settling of pigmented cells in the ventral iridocorneal angle, are regularly observed 36 .…”

“…While IOP remains the target of mainstay treatment of glaucoma and most drugs employed for prophylactic anti‐glaucoma therapy aim to directly lower the IOP, other medications with alternative targets and mechanisms are sometimes used, including anti‐inflammatory agents and a variety of alleged neuroprotectant preparations 1,3,9,10,20‐31 . The role of inflammation and auto‐immunity before, during, and with prolonged periods of elevated IOP (<50 mm Hg) in primary glaucomas is poorly understood 32‐34 . Clinical observations suggest anterior and posterior segment inflammation occurs with many primary forms of canine glaucoma, especially when IOP is markedly elevated (>50 mm Hg) 1‐3,35‐37 .…”

The future of canine glaucoma therapy

“…Considerable effort has been put into the study of IOP-independent disease mechanisms responsible for RGC death in animal models and human patients, so that neuroprotective treatments can be developed. Some of these disease pathways, which may or may not be triggered by IOP, include: excitotoxicity caused by excessive excitatory amino acid release, such as glutamate and aspartate 107,108 ; neurotrophin deprivation from blockage of retrograde axonal transport [109][110][111][112] ; excessive intracellular calcium 113 ; compromised blood flow to the ONH and retina [114][115][116][117][118][119][120] ; oxidative stress 121,122 ; inflammation and autoimmunity against retinal and optic nerve antigens [123][124][125] ; and reactive gliosis. [126][127][128][129] Unfortunately, most of these mechanisms have not yet been investigated in dogs, and there may be profound species differences.…”

Genetic and Biochemical Biomarkers in Canine Glaucoma

“…97,98 Autoantibodies Against Optic Nerve Antigens Significant differences in the levels of autoreactivity at certain bands (increased autoreactivity at 40 and 53 kDa and decreased autoreactivity at 48 kDa) were identified in serum autoantibodies against optic nerve antigens between dogs with and without goniodysgenesis-related glaucoma. 76 However, the study did not address whether immune-mediated mechanisms are involved in the initial pathogenesis or are a consequence of the disease that may in turn accelerate or intensify the disease process. 76 Further studies are required given the population studied (advanced glaucoma vs healthy dogs), the high variability in autoantibodies among individual dogs, and the considerable overlap between groups.…”

“…76 However, the study did not address whether immune-mediated mechanisms are involved in the initial pathogenesis or are a consequence of the disease that may in turn accelerate or intensify the disease process. 76 Further studies are required given the population studied (advanced glaucoma vs healthy dogs), the high variability in autoantibodies among individual dogs, and the considerable overlap between groups.…”