Neurotrophin and Trk expression by cells of the human lamina cribrosa following oxygen-glucose deprivation

BACKGROUND: Ischemia within the optic nerve head (ONH) may contribute to retinal ganglion cell (RGC) loss in primary open angle glaucoma (POAG). Ischemia has been reported to increase neurotrophin and high affinity Trk receptor expression by CNS neurons and glial cells. We have previously demonstrated neurotrophin and Trk expression within the lamina cribrosa (LC) region of the ONH. To determine if ischemia alters neurotrophin and Trk protein expression in cells from the human LC, cultured LC cells and ONH astrocytes were exposed to 48 hours of oxygen-glucose deprivation (OGD). Also cells were exposed to 48 hours of OGD followed by 24 hours of recovery in normal growth conditions. Cell number, neurotrophin and Trk receptor protein expression, neurotrophin secretion, and Trk receptor activation were examined. RESULTS: Cell number was estimated using an assay for cell metabolism following 24, 48 and 72 hours of OGD. A statistically significant decrease in LC and ONH astrocyte cell number did not occur until 72 hours of OGD, therefore cellular protein and conditioned media were collected at 48 hours OGD. Protein expression of NGF, BDNF and NT-3 by LC cells and ONH astrocytes increased following OGD, as did NGF secretion. Recovery from OGD increased BDNF protein expression in LC cells. In ONH astrocytes, recovery from OGD increased NGF protein expression, and decreased BDNF secretion. Trk A expression and activation in LC cells was increased following OGD while expression and activation of all other Trk receptors was decreased. A similar increase in Trk A expression and activation was observed in ONH astrocytes following recovery from OGD. CONCLUSIONS: In vitro conditions that mimic ischemia increase the expression and secretion of neurotrophins by cells from the ONH. Increased Trk A expression and activation in LC cells following OGD and in ONH astrocytes following recovery from OGD suggest autocrine/paracrine neurotrophin signaling could be a response to ONH ischemia in POAG. Also, the increase in NGF, BDNF and NT-3 protein expression and NGF secretion following OGD also suggest LC cells and ONH astrocytes may be a paracrine source of neurotrophins for RGCs

Caspase-7: a critical mediator of optic nerve injury-induced retinal ganglion cell death

Reduction in caspase-7 expression in the retina of Casp7 −/− mice. Representative western blot images of pro-caspase-7 in protein extracts from retinas from WT and Casp7 −/− mice. (TIFF 42 kb

Anterior Chamber-Associated Immune Deviation Induced by Soluble Antigens

Immune responses to cellular antigens placed in the anterior chamber of the eye are deviant: antibodies and cytotoxic T cells are generated, but delayed hypersensitivity is impaired. To determine whether a similar pattern of unusual reactivity would be induced by soluble antigens placed in this privileged site, we have examined the systemic immune responses of mice to anterior chamber injections of bovine serum albumin and bovine retinal S antigen-both soluble molecules. Recipients of intraocular injections of these antigens without adjuvant developed no detectable systemic immune response. When BSA was mixed with complete or incomplete Freund's adjuvant and injected into the anterior chamber, recipients produced serum specific antibodies; however, they displayed impaired delayed hypersensitivity. Anterior chamber recipients of soluble antigens subsequently proved refractory to the development of delayed hypersensitivity when immunogenic doses of the same antigens were placed subcutaneously. Moreover, the inability to mount delayed hypersensitivity could be adoptively transferred with spleen cells from animals that had previously received intraocular injections of bovine albumin or S antigen. It is concluded that soluble antigens, as well as surface membrane-bound antigens, are capable of inducing anterior chamber-associated immune deviation (ACAID). The possibility is discussed that the capacity of soluble retinal S antigen to induce ACAID may be pertinent to the maintenance of self-tolerance to this autologous, intraocular molecule. Invest Ophthalmol Vis Sc

Optic nerve crush induces spatial and temporal gene expression patterns in retina and optic nerve of BALB/cJ mice

BACKGROUND: Central nervous system (CNS) trauma and neurodegenerative disorders trigger a cascade of cellular and molecular events resulting in neuronal apoptosis and regenerative failure. The pathogenic mechanisms and gene expression changes associated with these detrimental events can be effectively studied using a rodent optic nerve crush (ONC) model. The purpose of this study was to use a mouse ONC model to: (a) evaluate changes in retina and optic nerve (ON) gene expression, (b) identify neurodegenerative pathogenic pathways and (c) discover potential new therapeutic targets. RESULTS: Only 54% of total neurons survived in the ganglion cell layer (GCL) 28 days post crush. Using Bayesian Estimation of Temporal Regulation (BETR) gene expression analysis, we identified significantly altered expression of 1,723 and 2,110 genes in the retina and ON, respectively. Meta-analysis of altered gene expression (≥1.5, ≤-1.5, p < 0.05) using Partek and DAVID demonstrated 28 up and 20 down-regulated retinal gene clusters and 57 up and 41 down-regulated optic nerve clusters. Regulated gene clusters included regenerative change, synaptic plasticity, axonogenesis, neuron projection, and neuron differentiation. Expression of selected genes (Vsnl1, Syt1, Synpr and Nrn1) from retinal and ON neuronal clusters were quantitatively and qualitatively examined for their relation to axonal neurodegeneration by immunohistochemistry and qRT-PCR. CONCLUSION: A number of detrimental gene expression changes occur that contribute to trauma-induced neurodegeneration after injury to ON axons. Nrn1 (synaptic plasticity gene), Synpr and Syt1 (synaptic vesicle fusion genes), and Vsnl1 (neuron differentiation associated gene) were a few of the potentially unique genes identified that were down-regulated spatially and temporally in our rodent ONC model. Bioinformatic meta-analysis identified significant tissue-specific and time-dependent gene clusters associated with regenerative changes, synaptic plasticity, axonogenesis, neuron projection, and neuron differentiation. These ONC induced neuronal loss and regenerative failure associated clusters can be extrapolated to changes occurring in other forms of CNS trauma or in clinical neurodegenerative pathological settings. In conclusion, this study identified potential therapeutic targets to address two key mechanisms of CNS trauma and neurodegeneration: neuronal loss and regenerative failure