June 2020
Volume 61, Issue 7
Open Access
ARVO Annual Meeting Abstract  |   June 2020
Systemic Rho kinase inhibition protects optic nerve axons against acute intraocular pressure elevation through stabilization of astrocyte cytoskeleton and connexin43 gap junctions
Author Affiliations & Notes
  • Shandiz Tehrani
    Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, United States
  • Katherine Delf
    Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, United States
  • William O. Cepurna
    Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, United States
  • Diana C Lozano
    Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, United States
  • Elaine C. Johnson
    Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, United States
  • John C Morrison
    Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, United States
  • Footnotes
    Commercial Relationships   Shandiz Tehrani, None; Katherine Delf, None; William Cepurna, None; Diana Lozano, None; Elaine Johnson, None; John Morrison, None
  • Footnotes
    Support  NIH Grant K08EY024025; Research to Prevent Blindness CDA and Unrestrictred Grants
Investigative Ophthalmology & Visual Science June 2020, Vol.61, 1165. doi:
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      Shandiz Tehrani, Katherine Delf, William O. Cepurna, Diana C Lozano, Elaine C. Johnson, John C Morrison; Systemic Rho kinase inhibition protects optic nerve axons against acute intraocular pressure elevation through stabilization of astrocyte cytoskeleton and connexin43 gap junctions. Invest. Ophthalmol. Vis. Sci. 2020;61(7):1165.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : The role of intraocular pressure (IOP)-dependent optic nerve head (ONH) astrocyte reactivity in subsequent axon degeneration is poorly understood. Fasudil (a Rho kinase inhibitor) stabilizes astrocyte stellate morphology in vitro. Here, we investigate the effects of systemic fasudil administration on astrocyte reactivity and axon injury post controlled elevation of IOP (CEI) in vivo.

Methods : Brown Norway rats received intraperitoneal fasudil (10mg/kg/day; n=22) or vehicle (water; n=22) 1 day pre- and up to 2 weeks post-CEI (IOP elevation under 2.25% isoflurane anesthesia at 60 mmHg for 8 hours using anterior chamber cannulation). Eyes were fixed at various times post-CEI. ONH sections were labeled with phalloidin (actin marker) and antibodies against connexin43 (gap junction protein), followed by actin bundle length & antibody label intensity quantification. Retrobulbar optic nerve axon injury was graded on a scale of 1 (uninjured) to 5 (>50% degeneration) by 6 masked observers. Means ± SEM were calculated and statistical analysis was performed using ANOVA.

Results : ONH astrocyte actin bundle lengths were significantly reduced immediately post-CEI relative to controls (8.51 ± 0.21 [n=6] vs 13.21 ± 0.33 µm [n=6], p=0.03). However, in fasudil-treated animals, ONH astrocyte actin bundle lengths were not significantly different in post-CEI vs control ONHs (p=0.21). ONH connexin43 labeling was significantly lower immediately post-CEI relative to controls (3.99 ± 0.86 [n=6] vs 8.65 ± 0.55 AU [n=6], p=0.02). However, in fasudil-treated animals, ONH connexin43 labeling was not significantly different post-CEI vs. controls (p=0.29). Two weeks post-CEI, optic nerve axon injury was significantly higher relative to controls (1.53 ± 0.11 [n=16] vs 1.02 ± 0.01 [n=16], p<0.0001). By contrast, axonal injury post-CEI in fasudil-treated animals was significantly reduced compared to post-CEI eyes in vehicle-treated animals (injury grade 1.19 ± 0.05 [n=16] vs 1.53 ± 0.11 [n=16], p=0.0006). Systemic fasudil had no effects on awake IOP or systemic blood pressure.

Conclusions : ONH astrocyte process retraction in response to elevated IOP is temporally correlated with loss of ONH connexin43 labeling. Gap junction stability through actin cytoskeletal stabilization may be an important mechanism in protecting axons against elevated IOP.

This is a 2020 ARVO Annual Meeting abstract.

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