Chronic environmental caffeine exposure induces gut transcriptomic reprogramming in zebrafish.

Area of Science:

• Environmental toxicology
• Aquatic toxicology
• Molecular toxicology

Background:

• Aquatic contaminants pose risks to ecosystems.
• Caffeine is a common emerging contaminant in water bodies.
• Previous research on caffeine's aquatic effects often used short-term exposures.

Purpose of the Study:

• To investigate the physiological and transcriptomic effects of acute and chronic caffeine exposure in zebrafish (Danio rerio).
• To understand caffeine's impact across a range of concentrations, from acute high doses to chronic environmentally relevant levels.

Main Methods:

• Zebrafish were exposed to varying concentrations of caffeine.
• Physiological responses including mortality and heart rate were monitored.
• Transcriptomic analysis (RNA-seq) and quantitative PCR (RT-qPCR) were used to assess gene expression changes in various tissues.

Main Results:

• Acute high-dose caffeine exposure induced bradycardia and mortality with complex dose-time-response relationships.
• Chronic low-dose exposure led to tissue-specific gene expression changes, notably in the gut.
• Significant dysregulation of retinol metabolism, lysosomal function, and immune processes was observed in the gut at higher chronic doses.
• Systemic effects included altered dopamine and adenosine receptor expression in the brain and potential suppression of antioxidant pathways in the liver.

Conclusions:

• Caffeine causes significant cardiac toxicity and mortality in zebrafish at high concentrations.
• Chronic exposure to environmentally relevant caffeine concentrations induces molecular reprogramming across multiple organ systems.
• Caffeine disrupts key metabolic, neurological, and oxidative stress pathways in aquatic organisms, indicating a potential risk to aquatic ecosystems.