Astrocytes in glaucomatous optic neuropathy

Mechanism of Aqueous Humor Secretion, Its Regulation and Relevance to Glaucoma

“…Other hypothesis includes oxidative or nitrative stress, both at the level of trabecular meshwork (Sacca et al, 2007) and 21 retinal ganglion cells (Aslan et al, 2008;Tezel, 2006); autoimmune reactions in which an individual's immune system facilitate somatic/axonal degeneration of retinal ganglion cells (Wax and Tezel, 2009); glutamate toxicity (Vorwerk et al, 1999); loss of neurotrophic factors (Pease et al, 2000), etc. However, a various combination of these factors may be involved.The glial cells in the optic nerve head region (lamina cribrosa cells) (Quill et al, 2011), and in particular the astrocytes, the principal glial cells, have been proposed to play an important role in the glaucomatous change in the extracellular matrix in around the ganglion cells (Hernandez, 2000;Hernandez et al, 2008). In primates, alterations in the expression of metalloproteinases (MMPs) and their inhibitors (TIMPs) occur in the optic nerve head of experimental glaucoma (Agapova et al, 2003a).…”

“…Thus, future research should be directed towards exploring the exact causes of optic nerve damage or ganglion cell death. Recent studies have suggested some role of the glial cells, such as, lamina cribrosa cells (Quill et al, 2011) and astrocytes (Hernandez, 2000;Hernandez et al, 2008), in the remodeling of the extracellular matrix in the optic nerve head. How these cells and remodeling of the region plays role in causing ganglion cell death is unclear.…”

Neurovascular Interactions in the Retina: Physiological and Pathological Roles

“…This phenomenon may be, at least in part, the result of an abnormal response in retinal blood vessels due to endothelial dysfunction and an imbalance between endothelial-derived contracting and relaxing factors (3). Reduced neural activity and altered glial cell function (40,41) may also contribute to the diminished vasodilation. A decrease in the number of capillaries in the optic nerve head and atrophy of the peripapillary capillaries supplying the retinal nerve fiber layer have been reported as well (42).…”

Retinal Ganglion Cell Death

“…In addition, a growing body of evidence suggests that, under glaucomatous stress conditions, glial cells may even become neurodestructive, releasing increased amounts of neurotoxic substances including TNF-α and nitric oxide (NO) [Tezel, 2006]. Astrocytes become reactive in response to various stimuli, including elevated intraocular pressure, excitotoxicity, and retinal ischemia [Neufeld & Liu 2003, Hernandez et al, 2008. Reactive astrocytes in glaucomatous optic nerve heads apparently play important roles in the development of local neurotoxicity, confined to the retinal ganglion cell axons, by producing excessive levels of NO in patients with glaucomatous optic neuropathy [Liu & Neufeld 2000].…”