Light-induced degeneration and microglial response in the retina of an epibenthonic pigmented teleost: age-dependent photoreceptor susceptibility to cell death

Abstract

SUMMARYConstant intense light causes apoptosis of photoreceptors in the retina of albino fish. However, very few studies have been performed on pigmented species. Tench (Tinca tinca) is a teleost inhabiting dimly lit environments that has a predominance of rods within the photoreceptor layer. To test the hypothesis that constant high intensity light can result in retinal damage in such pigmented epibenthonic teleost species, photodegeneration of the retina was investigated in the larvae and in juveniles of tench to assess whether any damage may also be dependent on fish age. We exposed both groups of animals to 5days of constant darkness, followed by 4days of constant 20,000lx light, and then by 6days of recovery in a 14h light:10h dark cycle. The results showed that the retina of the larvae group exhibited abundant photoreceptor cell apoptosis during the time of exposition to intense light, whereas that of juveniles was indifferent to it. Damaged retinas showed a strong TUNEL signal in photoreceptor nuclei, and occasionally a weak cytoplasmic TUNEL signal in Müller glia. Specific labelling of microglial cells with Griffonia simplicifolia lectin (GSL) histochemistry revealed that photoreceptor cell death alerts microglia in the degenerating retina, leading to local proliferation, migration towards the injured outer nuclear layer (ONL), and enhanced phagocytosis of photoreceptor debris. During the first days of intense light treatment, Müller cells phagocytosed dead photoreceptor cells but, once microglial cells became activated, there was a progressive increase in the phagocytic capacity of the microglia.

Changes in Mouse Thymus and Spleen after Return from the STS-135 Mission in Space

“…Density profiles were expressed as mean number of apoptotic cells per square millimeter. Similar procedures have been described in the literature [43,44]. …”

“…Cell density profiles were expressed as mean number of positive cells per square millimeter for the TUNEL assay. Similar procedures have been described in the literature for various tissues that include the thymus [43,44,50]. …”

Ocular tissue changes associated with anterior segment opacity in lumpfish (Cyclopterus lumpus L) eye

“…However, if caused by external physical trauma impacting the posterior pole of the eye, it would be most likely expected to be associated with noticeable corneal or conjunctival damage of the anterior portion of the eye, which we did not observe. Intense levels of light have also been recognized to cause retinal degeneration in teleosts (Allen, Pipes, Deramus, & Hallows, ; Allison, Hallows, Johnson, Hawryshyn, & Allen, ; Bejarano‐Escobar, Blasco, Martín‐Partido, & Francisco‐Morcillo, ). Such light levels are, however, orders of magnitude higher than the light levels of 30–100 lux under which the JBARB lumpfish are cultured.…”

Retinal development in the gilthead seabream Sparus aurata

“…Surprisingly, in more advanced phases, CERN‐922 immunoreactivity is restricted to a few immunoreactive photoreceptor perikarya located in the ventral retina. CERN‐922 has been considered an excellent rod marker in the retina of most of the species of fishes studied, and its expression has been found distributed throughout the entire retina (Candal et al , ; Villar‐Cheda et al , ; Bejarano‐Escobar et al , 2009, 2010, 2012 a , b ; Ferreiro‐Galve et al , 2010 a ). Helvik et al (2001 a , b ) described the mosaic expression patterns for different visual pigments.…”

“…rerio (Jang et al , ), T . tinca (Bejarano‐Escobar et al , 2009, 2012 b ), S . senegalensis (Bejarano‐Escobar et al , ) and S .…”