Baseline oxidative stress responses and cytochrome P450 gene expression in Tympanotonos fuscatus from PAH-contaminated ecosystem in the Niger Delta, Nigeria.

The pervasive contamination of aquatic ecosystems by polycyclic aromatic hydrocarbons (PAHs) poses risks to benthic macroinvertebrates. This study investigates Tympanotonos fuscatus biochemical and molecular responses to PAH exposure in Chanomi Creek to assess its biomarker potential. Tissue samples were collected from two stations with varying PAH levels and analyzed for PAH concentrations, oxidative stress biomarkers, and cytochrome P450 (CYP450) gene expression. PAH concentrations were determined using gas chromatography-mass spectrometry (GC-MS), while oxidative stress biomarkers, including superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), guaiacol peroxidase (GPx), ascorbate peroxidase (APx), glutathione reductase (GR), and malondialdehyde (MDA), were quantified spectrophotometrically. CYP450 gene expression was assessed through real-time quantitative PCR (RT-qPCR). Mean PAH concentrations were 0.42 ± 0.63 mg/kg (Station A) and 0.60 ± 1.16 mg/kg (Station B) in the sampling stations. Significant correlations were observed between CAT and MDA (r = 0.64, P < 0.05), suggesting increased oxidative stress due to PAH bioaccumulation. Furthermore, MDA levels correlated positively with CYP450 gene expression (r = 0.89), reinforcing the role of PAH metabolism in oxidative damage. CYP450 expression was upregulated at Station A and downregulated at Station B, though differences were not statistically significant (P > 0.05). The observed biochemical alterations indicate cellular stress responses to PAH exposure, yet the variability in CYP450 expression suggests additional regulatory mechanisms. This study highlights T. fuscatus as a potential bioindicator of PAH contamination, though further validation through controlled exposure experiments and seasonal monitoring is required to establish its biomonitoring efficacy. These findings provide critical insights into PAH-induced biochemical and molecular responses, supporting improved ecosystem assessment and management strategies.