Neuroprotective effect of transcorneal electrical stimulation on light-induced photoreceptor degeneration

Exp Neurol. 2009 Oct;219(2):439-52. doi: 10.1016/j.expneurol.2009.06.016. Epub 2009 Jul 2.

Abstract

Direct electrical stimulation of neural tissues is a strategic approach to treat injured axons by accelerating their outgrowth [Al-Majed, A.A., Neumann, C.M., Brushart, T.M., Gordon, T., 2000. Brief electrical stimulation promotes the speed and accuracy of motor axonal regeneration. J. Neurosci. 20, 2602-2608] and promoting their regeneration [Geremia, N.M., Gordon, T., Brushart, T.M., Al-Majed, A.A., Verge, V.M.K., 2007. Electrical stimulation promotes sensory neuron regeneration and growth-associated gene expression. Exp. Neurol. 205, 347-359]. Recently, transcorneal electrical stimulation (TCES), a novel less invasive method, has been shown to rescue axotomized and damaged retinal ganglion cells [Morimoto, T., Miyoshi, T., Matsuda, S., Tano, Y., Fujikado, T., Fukuda, Y., 2005. Transcorneal electrical stimulation rescues axotomized retinal ganglion cells by activating endogenous retinal IGF-1 system. Invest. Ophthalmol. Vis. Sci. 46(6), 2147-2155]. Here, we investigated the neuroprotection of TCES on light-induced photoreceptor degeneration and the underlying mechanism. Adult male Sprague-Dawley (SD) rats received TCES before (pre-TCES) or after (post-TCES) intense light exposure. After fourteen days of light exposure, retinal histology and electroretinography were performed to evaluate the neuroprotective effect of TCES. The mRNA and protein levels of apoptotic-associated genes including Bcl-2, Bax, Caspase-3 as well as ciliary neurotrophic factor (CNTF) and brain-derived neurotrophic factor (BDNF) in the retinas were determined by real-time PCR and Western blot analysis. The localization of these gene products in the retinas was examined by immunohistochemistry. Both pre- and post-TCES ameliorated the progressive photoreceptor degeneration. The degree of rescue depended on the strength of the electric charge. Post-TCES showed a relatively better and longer-term protective effect than pre-TCES. Real-time PCR and Western blot analysis revealed an upregulation of Bcl-2, CNTF, and BDNF and a downregulation of Bax in the retinas after TCES. Immunohistochemical studies showed that Bcl-2 and CNTF were selectively upregulated in Müller cells. These findings provide a new therapeutic method to prevent or delay photoreceptor degeneration through activating the intrinsic survival system.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Animals
  • Biophysics
  • Brain-Derived Neurotrophic Factor / genetics
  • Brain-Derived Neurotrophic Factor / metabolism
  • Caspase 3 / genetics
  • Caspase 3 / metabolism
  • Ciliary Neurotrophic Factor / genetics
  • Ciliary Neurotrophic Factor / metabolism
  • Cornea / physiology
  • Disease Models, Animal
  • Electric Stimulation Therapy / methods*
  • Electroretinography
  • Gene Expression Regulation / physiology*
  • Light / adverse effects
  • Male
  • Photoreceptor Cells, Vertebrate / pathology*
  • Proto-Oncogene Proteins c-bcl-2 / genetics
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Retina / pathology
  • Retina / physiopathology
  • Retinal Degeneration / etiology
  • Retinal Degeneration / pathology*
  • Retinal Degeneration / physiopathology
  • Retinal Degeneration / therapy*
  • Time Factors
  • bcl-2-Associated X Protein / genetics
  • bcl-2-Associated X Protein / metabolism

Substances

  • Brain-Derived Neurotrophic Factor
  • Ciliary Neurotrophic Factor
  • Proto-Oncogene Proteins c-bcl-2
  • bcl-2-Associated X Protein
  • Caspase 3