Cell Proliferation and Interleukin-6-Type Cytokine Signaling Are Implicated by Gene Expression Responses in Early Optic Nerve Head Injury in Rat Glaucoma

Kenneth C. Swan Ocular Neurobiology Laboratory, Casey Eye Institute, Oregon Health and Science University, Portland, Oregon 97201, USA.
Investigative ophthalmology & visual science (Impact Factor: 3.4). 01/2011; 52(1):504-18. DOI: 10.1167/iovs.10-5317
Source: PubMed


In glaucoma, the optic nerve head (ONH) is the principal site of initial axonal injury, and elevated intraocular pressure (IOP) is the predominant risk factor. However, the initial responses of the ONH to elevated IOP are unknown. Here the authors use a rat glaucoma model to characterize ONH gene expression changes associated with early optic nerve injury.
Unilateral IOP elevation was produced in rats by episcleral vein injection of hypertonic saline. ONH mRNA was extracted, and retrobulbar optic nerve cross-sections were graded for axonal degeneration. Gene expression was determined by microarray and quantitative PCR (QPCR) analysis. Significantly altered gene expression was determined by multiclass analysis and ANOVA. DAVID gene ontology determined the functional categories of significantly affected genes.
The Early Injury group consisted of ONH from eyes with <15% axon degeneration. By array analysis, 877 genes were significantly regulated in this group. The most significant upregulated gene categories were cell cycle, cytoskeleton, and immune system process, whereas the downregulated categories included glucose and lipid metabolism. QPCR confirmed the upregulation of cell cycle-associated genes and leukemia inhibitory factor (Lif) and revealed alterations in expression of other IL-6-type cytokines and Jak-Stat signaling pathway components, including increased expression of IL-6 (1553%). In contrast, astrocytic glial fibrillary acidic protein (Gfap) message levels were unaltered, and other astrocytic markers were significantly downregulated. Microglial activation and vascular-associated gene responses were identified.
Cell proliferation and IL-6-type cytokine gene expression, rather than astrocyte hypertrophy, characterize early pressure-induced ONH injury.

Download full-text


Available from: Wendi S Lambert,
  • Source
    • "Components of the complement cascade are induced in human and animal models of glaucoma , suggesting a key role for this system in progression of the disease (Ahmed et al. 2004; Kuehn et al. 2006, 2008; Stasi et al. 2006; Steele et al. 2006; Stevens et al. 2007; Ren and Danias 2010; Tezel et al. 2010; Howell et al. 2011a). In experimental models of glaucoma, induction of complement components in the retina and ONH was one of the earliest signaling responses to high IOP (Howell et al. 2011a; Johnson et al. 2011). Up-regulation of C1qa, a member of the C1 complex that triggers activation of the classical pathway, was observed in microglial cells in the ONH before detection of axonal damage in DBA/2J glaucomatous mice (Howell et al. 2011a). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Glaucoma is a multifactorial neurodegenerative disorder affecting 80 million people worldwide. Loss of retinal ganglion cells and degeneration of their axons in the optic nerve are the major pathological hallmarks. Neuroinflammatory processes, inflammatory processes in the central nervous system, have been identified in human glaucoma and in experimental models of the disease. Furthermore, neuroinflammatory responses occur at early stages of experimental glaucoma, and inhibition of certain proinflammatory pathways appears neuroprotective. Here, we summarize the current understanding of neuroinflammation in the central nervous system, with emphasis on events at the optic nerve head during early stages of glaucoma.
    Cold Spring Harbor Perspectives in Medicine 08/2014; 4(8). DOI:10.1101/cshperspect.a017269 · 9.47 Impact Factor
  • Source
    • "Furthermore, in glaucomatous optic nerves, TNF-α expression of astrocytes and microglia increases with disease severity, whereas IL-6 increases retinal ganglion cell survival [33]. In an animal glaucoma model, Johnson and coworkers provided evidence that in early optic nerve head injury expression of IL-6 is increased [34]. Noma and coworkers provided evidence that the aqueous level of IL-6 is strongly correlated with the vitreous level of IL-6 (ρ=0.81, "
    [Show abstract] [Hide abstract]
    ABSTRACT: Various cytokines, including tumor necrosis factor-alpha (TNF-α), Fas ligand (FasL), interleukin-1α (IL-1α), interleukin-1β (IL-1β), and interleukin-6 (IL-6), contribute to the pathogenesis of primary open angle glaucoma (POAG). The present study was set to measure these cytokines in the aqueous humor of patients with POAG and in control subjects using multiplex bead analysis. Twenty-five patients with POAG and 29 control subjects were enrolled in this case-control study. Aqueous humor concentrations of the cytokines (IL-1 α, IL-1 β, IL-6, FasL, and TNF- α) were measured using multiplex bead analysis. Mean aqueous humor levels of IL-6 were significantly lower in patients with POAG compared to the control subjects (9.3±23.7 versus 55.3±94.4 pg/ml; p=0.002). No significant difference in the aqueous humor concentration of IL-1β was found between patients with POAG and control subjects (0.5±0.8 versus 0.4±0.8 pg/ml; p=0.85.) Concentrations of IL-1α, TNF-α, and FasL were below limits of detection. No significant correlation was found between IL-6 concentration and age, duration of disease, cup/disc ratio, or mean deviation. In the present study, we found significantly lower concentrations of IL-6 in the aqueous humor of patients with POAG.
    Molecular vision 11/2013; 19:2306-2311. · 1.99 Impact Factor
  • Source
    • "Furthermore, IL-6 has been reported to be upregulated after retinal ischemia and to protect RGCs from ischemic injury [39,40]. In contrast, however, early IOP-induced injury in the optic nerve head is characterized by increased IL-6 expression [41]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: To investigate whether the P2X7 receptor is involved in retinal ganglion cell (RGC) death after the intraocular pressure (IOP) is elevated in rats. After the IOP was elevated to 90 mmHg for 1 h, the rats were subsequently administered oxidized adenosine triphosphate (OxATP) and brilliant blue G (BBG) as P2X7 antagonists. The rats were euthanized 7 days after IOP elevation for histologic evaluation and at 1, 3, and 7 days after IOP elevation to immunostain for the P2X7 receptor and neuron-specific class III β-tubulin in the retina. Changes in P2X7 receptor expression were measured in total retina extracts using western blot analysis. Quantitative real-time PCR was also performed using the entire retina to determine whether the P2X7 receptor is involved in upregulating tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 at 1, 2, and 3 days after the IOP was elevated. RGC density and the inner plexiform layer thickness significantly decreased 7 days after IOP elevation, but were dose-dependently preserved when treated with OxATP or BBG. P2X7 immunoreactivity in the RGCs increased after IOP elevation, with the peak occurring from day 1 through day 3. Protein levels of P2X7 receptor were significantly increased 1, 2, and 3 days after IOP elevation. The messenger ribonucleic acid expression of the P2X7 receptor, TNF-α, IL-1β, and IL-6 was significantly upregulated in the retina after IOP elevation, and was suppressed by treatment with OxATP. These results suggest the expression of the P2X7 receptor is upregulated in the retina after IOP elevation, leading to RGC death. Upregulation of TNF-α, IL-1β, and IL-6 might be involved in this mechanism of RGC death. Furthermore, P2X7 antagonists may prevent RGC death after IOP elevation.
    Molecular vision 09/2013; 19:2080-91. · 1.99 Impact Factor
Show more