Benchtop Mass Spectrometry Imaging of Eisenia Hortensis Exposed to Statins

Pharmaceuticals are contaminants of emerging concern due to their ineffective removal in wastewater treatment plants and largely unknown effects on the ecosystem. Specifically, statins are a class of blood-lipid lowering agents that are the most prescribed drug class in the United States. High concentrations of statins have been reported in water systems ranging from fresh water to wastewater. Exposure studies are frequently conducted on aquatic organisms; however, terrestrial organisms must also be assessed for accumulation of pharmaceuticals as treated wastewater is frequently used to irrigate farm fields, introducing contaminants to a greater number of species. Earthworms, specifically Eisenia hortensis, are frequently used as bioindicators of soil contamination. However, they have not been assessed as a bioindicator of pharmaceuticals in the environment, which this work seeks to address. Benchtop matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) was optimized and employed to visualize statin localization in longitudinal sections of Eisenia hortensis following an exposure period to atorvastatin, lovastatin, or simvastatin. All three statins were detected successfully by MSI. Lovastatin and simvastatin were ubiquitously distributed, providing evidence for both dermal absorption and ingestion of contaminated soil. Atorvastatin localized to the intestinal wall, differing from the other two analytes likely due to differences in logP values. This work suggests that Eisenia hortensis is a suitable bioindicator of statins in the environment.