Ocular malformations are observed in embryos and adults of aquatic species after exposure to toxicants. In this study, cadmium, a chemical stressor, was used to determine the toxic effects on the retinal development and visual ability of adult zebrafish (Danio rerio). Our results demonstrated that Cd-exposure (100 μM)from sphere (4 hpf) to gastrula stage (8hpf) led to the up-regulation of the expression of lambda1-crystallin and Retinoblastoma Binding Protein 6 transcripts in embryos. Cryl1 is a lens protein that acts as a molecular chaperone; Rbbp6 is a protein regulating cellular proliferation. In situ hybridization demonstrated that Cd induced the up-regulation of these genes also in adult retina, in the inner and outer nuclear layers. The Cd-induced over-expression was dose-dependent and reversible. Interestingly, metallothionein, the cysteine-rich, low molecular mass metal-binding protein considered a key molecule involved in cellular protection against toxic metals, did not seem to be up-regulated. Adult retinal morpho-cytological alterations were investigated by light and electron microscopy, while the functionality of Cd-exposed retina was assessed by re-illumination behavioral tests. After Cd-treatment, dose-dependent alterations were clearly observed. The nerve fiber layer was clearly thickened and vacuolated, several ganglion cells had compact pycnotic nuclei. Changes occurred in the thickness of the pigmented epithelium and at the level of the cones inner segments. TEM observations oCd-treated retina showed ganglion cells with highly vacuolated cytoplasm and cells with ultrastructural apoptotic features. Apoptotic cells were also evident in the inner nuclear and in the photoreceptor layers. Many polymorphic Müller cells were observed both in inner and outer nuclear layers. Behavioral tests demonstrated that re-illumination with white or colored light induced a significant escape response after Cd-treatment, not observed in untreated animals. All together, data demonstrated that Cd toxicity caused: 1) dysregulation of gene expression; 2) degeneration and loss of organization at both macro and microscopic levels; 3) impairment of the functional response, particularly through increased light sensitivity. The increased amount of Müller cells with irregular shape suggested that the recovery of visual acuity is due to a regenerative process involving these retinal macroglial cells, that are able to dedifferentiate and function as neural stem cells.

Morpho-functional and transcriptional response of zebrafish retinal cells to cadmium stress / Scudiero, Rosaria; Panzuto, Raffaele; Esposito, ; Simoniello, Palma; Avallone, Bice; Motta, CHIARA MARIA. - (2015), pp. 174-174. (Intervento presentato al convegno SETAC Europe 25th Annual Meeting tenutosi a Barcelona, Spain nel 3-7 May 2015).

Morpho-functional and transcriptional response of zebrafish retinal cells to cadmium stress

Rosaria scudiero
Data Curation
;
Bice Avallone
Data Curation
;
chiara maria motta
Data Curation
2015

Abstract

Ocular malformations are observed in embryos and adults of aquatic species after exposure to toxicants. In this study, cadmium, a chemical stressor, was used to determine the toxic effects on the retinal development and visual ability of adult zebrafish (Danio rerio). Our results demonstrated that Cd-exposure (100 μM)from sphere (4 hpf) to gastrula stage (8hpf) led to the up-regulation of the expression of lambda1-crystallin and Retinoblastoma Binding Protein 6 transcripts in embryos. Cryl1 is a lens protein that acts as a molecular chaperone; Rbbp6 is a protein regulating cellular proliferation. In situ hybridization demonstrated that Cd induced the up-regulation of these genes also in adult retina, in the inner and outer nuclear layers. The Cd-induced over-expression was dose-dependent and reversible. Interestingly, metallothionein, the cysteine-rich, low molecular mass metal-binding protein considered a key molecule involved in cellular protection against toxic metals, did not seem to be up-regulated. Adult retinal morpho-cytological alterations were investigated by light and electron microscopy, while the functionality of Cd-exposed retina was assessed by re-illumination behavioral tests. After Cd-treatment, dose-dependent alterations were clearly observed. The nerve fiber layer was clearly thickened and vacuolated, several ganglion cells had compact pycnotic nuclei. Changes occurred in the thickness of the pigmented epithelium and at the level of the cones inner segments. TEM observations oCd-treated retina showed ganglion cells with highly vacuolated cytoplasm and cells with ultrastructural apoptotic features. Apoptotic cells were also evident in the inner nuclear and in the photoreceptor layers. Many polymorphic Müller cells were observed both in inner and outer nuclear layers. Behavioral tests demonstrated that re-illumination with white or colored light induced a significant escape response after Cd-treatment, not observed in untreated animals. All together, data demonstrated that Cd toxicity caused: 1) dysregulation of gene expression; 2) degeneration and loss of organization at both macro and microscopic levels; 3) impairment of the functional response, particularly through increased light sensitivity. The increased amount of Müller cells with irregular shape suggested that the recovery of visual acuity is due to a regenerative process involving these retinal macroglial cells, that are able to dedifferentiate and function as neural stem cells.
2015
Morpho-functional and transcriptional response of zebrafish retinal cells to cadmium stress / Scudiero, Rosaria; Panzuto, Raffaele; Esposito, ; Simoniello, Palma; Avallone, Bice; Motta, CHIARA MARIA. - (2015), pp. 174-174. (Intervento presentato al convegno SETAC Europe 25th Annual Meeting tenutosi a Barcelona, Spain nel 3-7 May 2015).
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11588/719563
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