Optic nerve dynein motor protein distribution changes with intraocular pressure elevation in a rat model of glaucoma

Keith R G Martin, Harry A Quigley, Danielle Valenta, Jennifer Kielczewski, Mary Ellen Pease

Research output: Contribution to journalArticle

Abstract

Acute intraocular pressure (IOP) elevation causes accumulation of retrogradely-transported brain derived neurotrophic factor and its receptor at the optic nerve head (ONH) in rats and monkeys. Obstruction of axonal transport may therefore be involved in glaucoma pathogenesis, but it is unknown if obstruction is specific to certain transported factors or represents a generalized failure of retrograde axonal transport. The dynein motor complex mediates retrograde axonal transport in retinal ganglion cells (RGC). Our hypothesis was that elevated IOP interferes with dynein-mediated axonal transport. We studied the distribution of dynein subunits in the retina and optic nerve after acute and chronic experimental IOP elevation in the rat. IOP was elevated unilaterally in 54 rats. Dynein subunit distribution was compared in treated and control eyes by immunohistochemistry and Western blotting at 1 day (n = 12), 3 days (n = 4), 1 week (n = 15), 2 weeks (n = 12) and 4 weeks (n = 11). For immunohistochemistry, sections through the ONH were probed with an anti-dynein heavy chain (HC) antibody and graded semi-quantitatively by masked observers. Other freshly enucleated eyes were microdissected for separate Western blot quantification of dynein intermediate complex (IC) in myelinated and unmyelinated optic nerve, ONH and retina. Immunohistochemistry showed accumulation of dynein HC at the ONH in IOP elevation eyes compared to controls (P <0.001, Wilcoxon paired sign-rank test, n = 29). ONH dynein IC was elevated by 46.5% in chronic IOP elevation eyes compared to controls by Western blotting (P <0.001, 95% CI = 25.9% to 67.8%, n = 17). The maximum increase in ONH dynein IC was 78.7% after 1 week (P <0.05, n = 5), but significant increases were also detected after 4 h and 4 weeks of IOP elevation (P <0.05, n = 4 rats per group). Total retinal dynein IC was increased by 8.7% in chronic IOP elevation eyes compared to controls (P <0.03, 95% CI 1.4% to 16.1%, n = 24). In the retina, IOP elevation particularly affected the 72 kD subunit of dynein IC, which was 100.7% higher in chronic IOP elevation eyes compared to controls (P <0.00001, 95% CI 71.0% to 130.4%, n = 21). Dynein IC changes in myelinated and unmyelinated optic nerve were not significant (P > 0.05). We conclude that dynein accumulates at the ONH with experimental IOP elevation in the rat, supporting the hypothesis that disrupted axonal transport in RGC may be involved in the pathogenesis of glaucoma. The effect of IOP elevation on other motor proteins deserves further investigation in the future.

Original languageEnglish (US)
Pages (from-to)255-262
Number of pages8
JournalExperimental Eye Research
Volume83
Issue number2
DOIs
StatePublished - Aug 2006

Fingerprint

Dyneins
Optic Nerve
Intraocular Pressure
Glaucoma
Axonal Transport
Optic Disk
Proteins
Retinal Ganglion Cells
Immunohistochemistry
Retina
Western Blotting
trkB Receptor
Haplorhini
Antibodies

Keywords

  • dynein
  • glaucoma
  • optic nerve
  • rat

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems

Cite this

Optic nerve dynein motor protein distribution changes with intraocular pressure elevation in a rat model of glaucoma. / Martin, Keith R G; Quigley, Harry A; Valenta, Danielle; Kielczewski, Jennifer; Pease, Mary Ellen.

In: Experimental Eye Research, Vol. 83, No. 2, 08.2006, p. 255-262.

Research output: Contribution to journalArticle

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abstract = "Acute intraocular pressure (IOP) elevation causes accumulation of retrogradely-transported brain derived neurotrophic factor and its receptor at the optic nerve head (ONH) in rats and monkeys. Obstruction of axonal transport may therefore be involved in glaucoma pathogenesis, but it is unknown if obstruction is specific to certain transported factors or represents a generalized failure of retrograde axonal transport. The dynein motor complex mediates retrograde axonal transport in retinal ganglion cells (RGC). Our hypothesis was that elevated IOP interferes with dynein-mediated axonal transport. We studied the distribution of dynein subunits in the retina and optic nerve after acute and chronic experimental IOP elevation in the rat. IOP was elevated unilaterally in 54 rats. Dynein subunit distribution was compared in treated and control eyes by immunohistochemistry and Western blotting at 1 day (n = 12), 3 days (n = 4), 1 week (n = 15), 2 weeks (n = 12) and 4 weeks (n = 11). For immunohistochemistry, sections through the ONH were probed with an anti-dynein heavy chain (HC) antibody and graded semi-quantitatively by masked observers. Other freshly enucleated eyes were microdissected for separate Western blot quantification of dynein intermediate complex (IC) in myelinated and unmyelinated optic nerve, ONH and retina. Immunohistochemistry showed accumulation of dynein HC at the ONH in IOP elevation eyes compared to controls (P <0.001, Wilcoxon paired sign-rank test, n = 29). ONH dynein IC was elevated by 46.5{\%} in chronic IOP elevation eyes compared to controls by Western blotting (P <0.001, 95{\%} CI = 25.9{\%} to 67.8{\%}, n = 17). The maximum increase in ONH dynein IC was 78.7{\%} after 1 week (P <0.05, n = 5), but significant increases were also detected after 4 h and 4 weeks of IOP elevation (P <0.05, n = 4 rats per group). Total retinal dynein IC was increased by 8.7{\%} in chronic IOP elevation eyes compared to controls (P <0.03, 95{\%} CI 1.4{\%} to 16.1{\%}, n = 24). In the retina, IOP elevation particularly affected the 72 kD subunit of dynein IC, which was 100.7{\%} higher in chronic IOP elevation eyes compared to controls (P <0.00001, 95{\%} CI 71.0{\%} to 130.4{\%}, n = 21). Dynein IC changes in myelinated and unmyelinated optic nerve were not significant (P > 0.05). We conclude that dynein accumulates at the ONH with experimental IOP elevation in the rat, supporting the hypothesis that disrupted axonal transport in RGC may be involved in the pathogenesis of glaucoma. The effect of IOP elevation on other motor proteins deserves further investigation in the future.",
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AB - Acute intraocular pressure (IOP) elevation causes accumulation of retrogradely-transported brain derived neurotrophic factor and its receptor at the optic nerve head (ONH) in rats and monkeys. Obstruction of axonal transport may therefore be involved in glaucoma pathogenesis, but it is unknown if obstruction is specific to certain transported factors or represents a generalized failure of retrograde axonal transport. The dynein motor complex mediates retrograde axonal transport in retinal ganglion cells (RGC). Our hypothesis was that elevated IOP interferes with dynein-mediated axonal transport. We studied the distribution of dynein subunits in the retina and optic nerve after acute and chronic experimental IOP elevation in the rat. IOP was elevated unilaterally in 54 rats. Dynein subunit distribution was compared in treated and control eyes by immunohistochemistry and Western blotting at 1 day (n = 12), 3 days (n = 4), 1 week (n = 15), 2 weeks (n = 12) and 4 weeks (n = 11). For immunohistochemistry, sections through the ONH were probed with an anti-dynein heavy chain (HC) antibody and graded semi-quantitatively by masked observers. Other freshly enucleated eyes were microdissected for separate Western blot quantification of dynein intermediate complex (IC) in myelinated and unmyelinated optic nerve, ONH and retina. Immunohistochemistry showed accumulation of dynein HC at the ONH in IOP elevation eyes compared to controls (P <0.001, Wilcoxon paired sign-rank test, n = 29). ONH dynein IC was elevated by 46.5% in chronic IOP elevation eyes compared to controls by Western blotting (P <0.001, 95% CI = 25.9% to 67.8%, n = 17). The maximum increase in ONH dynein IC was 78.7% after 1 week (P <0.05, n = 5), but significant increases were also detected after 4 h and 4 weeks of IOP elevation (P <0.05, n = 4 rats per group). Total retinal dynein IC was increased by 8.7% in chronic IOP elevation eyes compared to controls (P <0.03, 95% CI 1.4% to 16.1%, n = 24). In the retina, IOP elevation particularly affected the 72 kD subunit of dynein IC, which was 100.7% higher in chronic IOP elevation eyes compared to controls (P <0.00001, 95% CI 71.0% to 130.4%, n = 21). Dynein IC changes in myelinated and unmyelinated optic nerve were not significant (P > 0.05). We conclude that dynein accumulates at the ONH with experimental IOP elevation in the rat, supporting the hypothesis that disrupted axonal transport in RGC may be involved in the pathogenesis of glaucoma. The effect of IOP elevation on other motor proteins deserves further investigation in the future.

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