1. Calmodulin inhibition as a mode of action of antifungal imidazole pharmaceuticals in non-target organisms
- Author
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Magnus Breitholtz, Elena Gorokhova, Pavel Ivanov, and Karin Ek
- Subjects
Drug ,Paper ,calmodulin ,Calmodulin ,Health, Toxicology and Mutagenesis ,NOS1 ,media_common.quotation_subject ,Daphnia magna ,010501 environmental sciences ,Toxicology ,01 natural sciences ,Nitric oxide ,03 medical and health sciences ,chemistry.chemical_compound ,Gene expression ,medicine ,Mode of action ,030304 developmental biology ,0105 earth and related environmental sciences ,media_common ,postabdominal organ ,0303 health sciences ,immunostaining ,biology ,nitric oxide synthase ,Nitric oxide synthase ,Biochemistry ,chemistry ,biology.protein ,gene expression ,Miconazole ,medicine.drug - Abstract
To improve assessment of risks associated with pharmaceutical contamination of the environment, it is crucial to understand effects and mode of action of drugs in non-target species. The evidence is accumulating that species with well-conserved drug targets are prone to be at risk when exposed to pharmaceuticals. An interesting group of pharmaceuticals released into the environment is imidazoles, antifungal agents with inhibition of ergosterol synthesis as a primary mode of action in fungi. However, imidazoles have also been identified as competitive antagonists of calmodulin (CaM), a calcium-binding protein with phylogenetically conserved structure and function. Therefore, imidazoles would act as CaM inhibitors in various organisms, including those with limited capacity to synthesize sterols, such as arthropods. We hypothesized that effects observed in crustaceans exposed to imidazoles are related to the CaM inhibition and CaM-dependent nitric oxide (NO) synthesis. To test this hypothesis, we measured (i) CaM levels and its gene expression, (ii) NO accumulation and (iii) gene expression of NO synthase (NOS1 and NOS2), in the cladoceran Daphnia magna exposed to miconazole, a model imidazole drug. Whereas significantly increased CaM gene expression and its cellular allocation were observed, supporting the hypothesized mode of action, no changes occurred in either NO synthase expression or NO levels in the exposed animals. These findings suggest that CaM inhibition by miconazole leads to protein overexpression that compensates for the loss in the protein activity, with no measurable downstream effects on NO pathways. The inhibition of CaM in D. magna may have implications for effect assessment of exposure to mixtures of imidazoles in aquatic non-target species.
- Published
- 2020