June 2013
Volume 54, Issue 15
Free
ARVO Annual Meeting Abstract  |   June 2013
Mechanisms of Retinal Vascular Alteration in Hyperhomocysteinemia
Author Affiliations & Notes
  • Amany Tawfik
    Cellular Biology & Anatomy, Georgia Health Sciences Univ, Augusta, GA
    Vision Discovery Institute, GHSU, Augusta, GA
  • Shanu Markand
    Cellular Biology & Anatomy, Georgia Health Sciences Univ, Augusta, GA
    Vision Discovery Institute, GHSU, Augusta, GA
  • Sylvia Magyerdi
    Vision Discovery Institute, GHSU, Augusta, GA
    Oral Biology/Anatomy, GHSU, Augusta, GA
  • Mohamed Al-Shabrawey
    Vision Discovery Institute, GHSU, Augusta, GA
    Oral Biology/Anatomy, GHSU, Augusta, GA
  • Sylvia Smith
    Cellular Biology & Anatomy, Georgia Health Sciences Univ, Augusta, GA
    Vision Discovery Institute, GHSU, Augusta, GA
  • Footnotes
    Commercial Relationships Amany Tawfik, None; Shanu Markand, None; Sylvia Magyerdi, None; Mohamed Al-Shabrawey, None; Sylvia Smith, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2013, Vol.54, 2463. doi:
  • Views
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to Subscribers Only
      Sign In or Create an Account ×
    • Get Citation

      Amany Tawfik, Shanu Markand, Sylvia Magyerdi, Mohamed Al-Shabrawey, Sylvia Smith; Mechanisms of Retinal Vascular Alteration in Hyperhomocysteinemia. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2463.

      Download citation file:


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

      ×
  • Supplements
Abstract

Purpose: Excess homocysteine (Hcy), a sulfur containing non-proteinogenic amino acid, is implicated in human vascular disorders. Recently, we described the retinal phenotype in hyperhomocysteinemic mice lacking/deficient in the gene encoding cystathionine β−synthase (CBS). These mice have marked disruption of retinal neuronal layers, decreased ERG function & altered retinal vasculature suggestive of ischemic retinopathy. In this study we explored the mechanism of Hcy-induced retinopathy specifically screening markers of ER stress, oxidative stress, inflammation & NMDA receptor (NMDAr) activation.

Methods: Retinas of cbs+/+ (n=21) & cbs-/- (n=22) mice were harvested at ~3 wks. RNA & protein were isolated & subjected to qPCR & western blotting, respectively to analyze expression of ER stress genes & the proteins they encode including BiP, PERK, pPERK, CHOP, ATF6 & RE1α. Retinal cryosections were subjected to immunofluorescence to evaluate BiP, CHOP, NMDAr, TNFα and the oxidative stress marker DACF-2DA. To investigate whether Hcy altered vascular permeability, human retinal endothelial cells (HREC) were exposed to Hcy-thiolactone (20µM, 50µM, 100µM) in the presence/absence of the NMDAr inhibitor MK801 (25µM) or the ER stress inhibitor phenylbutyric acid, PBA (10mM) followed by incubation with FITC-dextran as an indicator of leakage.

Results: Gene & protein analysis revealed ~40% increase in BiP & PERK expression in cbs-/- retinas compared to cbs+/+; there was no significant change in expression of ATF4, ATF6, CHOP, IRE1α . Immunofluorescence studies in retinal cryosections of cbs-/- mice showed a dramatic increase in BiP & CHOP as well as NMDAr, TNFα & DACF-2A. In vitro studies of Hcy-treated HREC showed a 25% increase in FITC-dextran leakage through the HREC monolayer, which was reduced significantly by MK801 and PBA.

Conclusions: Retinal neurovascular alterations observed in severely hyperhomocysteinemic cbs mice are accompanied by increased levels of ER & oxidative stress as well as activation of NMDAr. Importantly, increased vascular permeability may be associated with Hcy-induced leakiness, which can be attenuated by inhibiting ER stress or NMDAr.

Keywords: 436 blood supply • 426 apoptosis/cell death • 562 inner retina dysfunction: biochemistry and cell biology  
×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×