Transcriptional impact of organophosphate and metal mixtures on olfaction: Copper dominates the chlorpyrifos-induced response in adult zebrafish

Abstract

Chemical exposures in fish have been linked to loss of olfaction leading to an inability to detect predators and prey and decreased survival. However, the mechanisms underlying olfactory neurotoxicity are not well characterized, especially in environmental exposures which involve chemical mixtures. We used zebrafish to characterize olfactory transcriptional responses by two model olfactory inhibitors, the pesticide chlorpyrifos (CPF) and mixtures of CPF with the neurotoxic metal copper (Cu). Microarray analysis was performed on RNA from olfactory tissues of zebrafish exposed to CPF alone or to a mixture of CPF and Cu. Gene expression profiles were analyzed using Principal Component Analysis and hierarchical clustering, whereas gene set analysis was used to identify biological themes in the microarray data. Microarray results were confirmed by real-time PCR on genes serving as potential biomarkers of olfactory injury. In addition, we mined our previously published Cu-induced zebrafish olfactory transcriptional response database (Tilton et al., 2008) for the purposes of discriminating pathways of olfaction impacted by either the individual agents or the CPF-Cu mixture transcriptional signatures. CPF exposure altered the expression of gene pathways associated with cellular morphogenesis and odorant binding, but not olfactory signal transduction, a known olfactory pathway for Cu. The mixture profiles shared genes from the Cu and CPF datasets, whereas some genes were altered only by the mixtures. The transcriptional signature of the mixtures was more similar to that in zebrafish exposed to Cu alone then for CPF. In conclusion, exposure to a mixture containing a common environmental metal and pesticide causes a unique transcriptional signature that is heavily influenced by the metal, even when organophosphate predominates. Our findings support using zebrafish microarray analysis to elucidate mechanisms of olfactory loss and to identify the components of mixtures which most strongly contribute to olfactory injury.

Sublethal toxicity of chlorpyrifos to salmonid olfaction after hypersaline acclimation

“…in differential regulation as was seen in Tilton et al (2011) and microarray data mining (Maryoung et al, 2014, in review).…”

“…Transcripts expressed during salinity acclimation were compared with gene expression profiles in zebrafish treated with chlorpyrifos (Tilton et al, 2011). Primers were designed using Primer3 software for G protein zgc:101761 (GNA11B) and adrenergic alpha 2C receptor (ADRA2C).…”

In vivo changes in carbonic anhydrase activity and histopathology of gill and liver tissues after acute exposure to chlorpyrifos in rainbow trout

“…Numerous environmental issues have arisen so far due to the excessive use of this chemical compound (3), as it, among other consequences, causes toxic effects in non-target aquatic organisms, especially fish (4). Fish are used to assess the health of aquatic environments and physiological changes occurring as a result of pollution and multiple studies have already established that chlorpyrifos has various detrimental effects on t h e m ( 5 -1 0 ) , s u c h a s n e u r o t o x i c i t y v i a acetylcholinesterase inhibition (11), biochemical and histopathological alterations (12, 13), oxidative stress (12, 14), genotoxicity (15), and olfactory and neurobehavioral injuries (16). It therefore poses a serious threat to aquatic organisms as well as to human health (17).…”

Dietary sodium protects fish against copper-induced olfactory impairment

“…Tilton et al (2008Tilton et al ( , 2011),) exposed zebrafish (Danio rerio) to low concentrations of copper and/or chlorpyrifos. Tilton et al (2008) exposed zebrafish to increasing concentrations of copper (6.3, 16, and 40 g/L) for 24 h and found that the transcription of many genes was altered in response to copper exposure, with the largest number of genes having altered transcription at the highest tested concentrations.…”

“…Tilton et al (2008) exposed zebrafish to increasing concentrations of copper (6.3, 16, and 40 g/L) for 24 h and found that the transcription of many genes was altered in response to copper exposure, with the largest number of genes having altered transcription at the highest tested concentrations. Tilton et al (2011) exposed zebrafish to copper and/or chlorpyrifos (an organophosphate pesticide) for 24 h and both contaminants showed unique transcriptional signatures. However, when they used a mixture of copper and chlorpyrifos, the transcriptional signature was closer to that of copper, even at high concentrations of chlorpyrifos.…”