Cadmium-induced ectopic apoptosis in zebrafish embryos

Area of Science:

• Developmental toxicology
• Cell biology
• Zebrafish models

Background:

• Cadmium is a toxic heavy metal with known adverse effects on development.
• The mechanisms underlying cadmium-induced developmental toxicity, specifically apoptosis, require further elucidation.

Purpose of the Study:

• To investigate if cadmium-induced developmental toxicity in zebrafish embryos is mediated by ectopic apoptosis.
• To determine the spatial and temporal distribution of apoptosis during embryonic development following cadmium exposure.

Main Methods:

• Confocal microscopy and 3D reconstruction of whole-mount stained zebrafish embryos.
• Terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) assay on sectioned embryos.
• Flow cytometry to assess apoptosis dynamics and cell-cycle progression.

Main Results:

• Cadmium exposure led to significantly higher numbers of apoptotic cells in malformed zebrafish embryos.
• Apoptotic cells were localized in the degenerating neural tube of cadmium-treated embryos, but not in controls.
• Cadmium did not induce cell-cycle arrest, and apoptosis percentages were similar until 19 hours post-fertilization (hpf).
• A significant increase in apoptotic cells was observed at 28 hpf in cadmium-exposed embryos.

Conclusions:

• Cadmium induces ectopic apoptosis during zebrafish embryonic development, primarily affecting the neural tube.
• This apoptosis occurs at later developmental stages (28 hpf) and is not associated with cell-cycle arrest.
• The findings highlight apoptosis as a key mechanism in cadmium-induced developmental toxicity.