Assessment of microplastic-contaminated liver through gene expression profiling of four commercial fish species in the Lagos Lagoon, Nigeria

Microplastic (MP) occurrence in the Lagos Lagoon has been on a progressive increase in recent years. The potential impacts and hazards of MPs on commercially available fish species from the Lagoon have been understudied. This study aims to assess molecular damage due to microplastic accumulation in the liver of four commercial fish species (Oreochromis niloticus, Chrysichthys nigrodigitatus, Clarias gariepinus, and Gymnarchus niloticus) sourced directly from the Lagoon. The results revealed that MP load in the liver of the fish species ranged between 7.2 ± 1.9 and 9.5 ± 4.4 particles/individual, with G. niloticus recording the maximum concentration. The observed extracted MPs are predominantly black and blue fibres while the Fourier Transform Infrared spectroscopy revealed polyethylene dominance in the plastic polymers. Relative gene expression results revealed statistically significant downregulation of the CYP 1a gene and upregulation of the HSP 70 gene in all the microplastic-laden liver samples except in G. niloticus. The findings from this study suggest that microplastic contamination in fish tissues may exacerbate cellular toxicity in commercially available biota in the Lagos Lagoon, thereby calling for urgent measures to curb microplastic and ultimately plastic pollution. However, there's a need for in-depth research on the effects of environmentally relevant microplastics on edible fish tissues to further elucidate their molecular impact.