Assessing the toxicological effects of synthetic musk ketone using the Caenorhabditis elegans model

Synthetic musk ketone (MK) is extensively used in perfumes, cosmetics, and detergents. Due to its high lipophilicity, persistence, and limited removal efficiency in wastewater treatment, MK has been detected in various environmental matrices and human tissues. However, the ecotoxicity of MK remains poorly characterized. This study aimed to systematically evaluate the toxicological effects of MK and elucidate its underlying mechanisms using Caenorhabditis elegans (C. elegans) as a model organism.

Wild-type C. elegans (strain N2) were exposed to MK at concentrations ranging from 0.4 to 20 mg/L for 24 h. Physiological endpoints including body size, locomotor activity, lifespan, and brood size were assessed. Biochemical markers comprising reactive oxygen species (ROS) levels and lipofuscin accumulation were quantified. Acute heat-stress tolerance was evaluated to assess stress resistance. Transcriptome sequencing (RNA-seq) and quantitative real-time PCR (qRT-PCR) were employed to investigate molecular mechanisms. Differential gene expression analysis was performed using DESeq2, and functional enrichment analyses were conducted for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways.

MK exposure significantly and concentration-dependently reduced body length and width, locomotor activity (head thrash and body bend frequencies), brood size, and lifespan. Lipofuscin accumulation and intracellular ROS levels were markedly elevated. Acute heat-stress tolerance was significantly impaired. Transcriptomic analysis identified 159 differentially expressed genes (DEGs) at 2 mg/L MK (19 up-regulated, 140 down-regulated) and 136 DEGs at 20 mg/L MK (30 up-regulated, 106 down-regulated). Key DEGs included ugt-30 (detoxification), Y9C9A.16 (oxidation-reduction), msp-59 (spermatogenesis), and acdh-8 (lipid metabolism). GO enrichment revealed significant alterations in spermatogenesis, protein catabolism, and kinase activity. KEGG pathway analysis identified perturbations in sulfur metabolism, branched-chain amino acid metabolism, fatty acid metabolism, and apoptosis. Protein-protein interaction network analysis identified cyc-2.2 and acdh-8 as hub genes.

MK exposure induces multi-faceted toxicity in C. elegans, including developmental impairment, neurotoxicity, reproductive toxicity, accelerated aging, and diminished stress resilience. These adverse outcomes are strongly associated with oxidative stress, germline impairment, and disrupted lipid metabolism, suggesting that these pathways play central roles in MK-induced toxicity. Our findings indicate that environmental exposure to MK may pose significant toxicological risks to living organisms and warrant further assessment of its ecological and health impacts.