Fig. 2: Elevated levels of oxidative stress in the aged killifish retinotectal system.

a Representative western blot images revealing 4-HNE in the retina and optic tectum of fish of the various age groups. Quantitative analysis discloses a tendency to increased levels in the retina (b), and a significant age-related increase of 4-HNE levels in the optic tectum of fish of 18 weeks and 24 weeks old (c). All blots derive from the same experiment and were processed in parallel. Full-length blots are presented in Supplementary Fig. 3. n = 3. d Microscopic pictures of Ho-1-labeled retinal cryosections show an elevated expression of this enzyme with increasing age, especially visible in the INL. Scale bar = 100 µm. e Quantification of the area occupied by the Ho-1-positive signal in the retina, expressed relative to its measured surface area, reveals a significant age-associated upregulation in the killifish retina. n = 5. All values are shown as mean ± standard error of mean, statistical significance between different conditions is depicted using different letters. 4-HNE 4-hydroxynonenal, Ho-1 heme oxygenase 1, GCL ganglion cell layer, IPL inner plexiform layer, INL inner nuclear layer, OPL outer plexiform layer, ONL outer nuclear layer.