Hormetic effect induced by depleted uranium in zebrafish embryos

Area of Science:

• Environmental Toxicology
• Developmental Biology
• Biochemistry

Background:

• Hormesis describes a biphasic dose-response: low-dose stimulation and high-dose inhibition.
• Uranium (U) is a toxic heavy metal with potential environmental and health impacts.
• Apoptosis, or programmed cell death, is a key biological endpoint for assessing toxicity.

Purpose of the Study:

• To investigate the hormetic effect of uranium exposure in zebrafish embryos.
• To use apoptosis as a sensitive biomarker for uranium-induced toxicity and hormesis.
• To determine the concentration- and time-dependent nature of uranium's effects on zebrafish development.

Main Methods:

• Zebrafish embryos were dechorionated at 4 hours post fertilization (hpf).
• Embryos were exposed to 10 or 100 μg/l depleted uranium (DU) from 5 to 6 hpf.
• Apoptotic signals in embryos were quantified at 20, 24, and 30 hpf.

Main Results:

• Exposure to 10 μg/l DU resulted in increased apoptosis at 20 hpf and decreased apoptosis at 24 hpf, demonstrating hormesis.
• Exposure to 100 μg/l DU led to increased apoptosis at 20, 24, and 30 hpf.
• Hormesis was not definitively shown at 100 μg/l DU, but its occurrence between 30 and 48 hpf could not be excluded.

Conclusions:

• Uranium can induce a hormetic effect in zebrafish embryos.
• The observed hormesis is dependent on both uranium concentration and exposure time.
• Apoptosis serves as a reliable indicator for studying uranium-induced hormesis in developmental toxicity.