PUBLICATION

Phosphodiesterase Inhibitors Sildenafil and Vardenafil Reduce Zebrafish Rod Photoreceptor Outer Segment Shedding

Authors
Campbell, L.J., Jensen, A.M.
ID
ZDB-PUB-171103-6
Date
2017
Source
Investigative ophthalmology & visual science   58: 5604-5615 (Journal)
Registered Authors
Jensen, Abigail
Keywords
none
MeSH Terms
  • Animals
  • Animals, Genetically Modified
  • Cell Line
  • Cyclic GMP/metabolism*
  • Dark Adaptation/drug effects
  • Dark Adaptation/physiology*
  • Models, Animal
  • Phosphodiesterase 5 Inhibitors/pharmacology
  • Rod Cell Outer Segment/drug effects*
  • Rod Cell Outer Segment/metabolism
  • Sildenafil Citrate/pharmacology*
  • Vardenafil Dihydrochloride/pharmacology*
  • Zebrafish
PubMed
29094165 Full text @ Invest. Ophthalmol. Vis. Sci.
Abstract
The vertebrate rod photoreceptor undergoes daily growth and shedding to renew the rod outer segment (ROS), a modified cilium that contains the phototransduction machinery. It has been demonstrated that ROS shedding is regulated by the light-dark cycle; however, we do not yet have a satisfactory understanding of the molecular mechanisms that underlie this regulation. Given that phototransduction relies on the hydrolysis of cGMP via phosphodiesterase 6 (PDE6), we examined ROS growth and shedding in zebrafish treated with cGMP-specific PDE inhibitors.
We used transgenic zebrafish that express an inducible, transmembrane-bound mCherry protein, which forms a stripe in the ROS following a heat shock pulse and serves as a marker of ROS renewal. Zebrafish were reared in constant darkness or treated with PDE inhibitors following heat shock. Measurements of growth and shedding were analyzed in confocal z-stacks collected from treated retinas.
As in dark-reared zebrafish, shedding was reduced in larvae and adults treated with the PDE5/6 inhibitors sildenafil and vardenafil but not with the PDE5 inhibitor tadalafil. In addition, vardenafil noticeably affected rod inner segment morphology. The inhibitory effect of sildenafil on shedding was reversible with drug removal. Finally, cones were more sensitive than rods to the toxic effects of sildenafil and vardenafil.
We show that pharmacologic inhibition of PDE6 mimics the inhibition of shedding by prolonged constant darkness. The data show that the influence of the light-dark cycle on ROS renewal is regulated, in part, by initiating the shedding process through activation of the phototransduction machinery.
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