ABSTRACT
Trace concentrations of a number of pharmaceutically active compounds have been detected in the aquatic environment in many countries, where they are thought to have the potential to exert adverse effects on non-target organisms. Amiodarone (AMD) is one such high-risk compound commonly used in general hospitals. AMD is known to alter normal thyroid hormone (TH) function, although little information is available regarding the specific mechanism by which this disruption occurs. Anuran tadpole metamorphosis is a TH-controlled developmental process and has proven to be useful as a screening tool for environmental pollutants suspected of disrupting TH functions. In the present study, our objective was to clarify the effects of AMD on Xenopus metamorphosis as well as to assess the bioconcentration of this pharmaceutical in the liver. We found that AMD suppressed spontaneous metamorphosis, including tail regression and hindlimb elongation in pro-metamorphic stage tadpoles, which is controlled by endogenous circulating TH, indicating that AMD is a TH antagonist. In transgenic X. laevis tadpoles carrying plasmid DNA containing TH-responsive element (TRE) and a 5'-upstream promoter region of the TH receptor (TR) ßA1 gene linked to a green fluorescent protein (EGFP) gene, triiodothyronine (T3) exposure induced a strong EGFP expression in the hind limbs, whereas the addition of AMD to T3 suppressed EGFP expression, suggesting that this drug interferes with the binding of T3 to TR, leading to the inhibition of TR-mediated gene expression. We also found AMD to be highly bioconcentrated in the liver of pro-metamorphic X. tropicalis tadpoles, and we monitored hepatic accumulation of this drug using mass spectrometry imaging (MSI). Our findings suggest that AMD imposes potential risk to aquatic wildlife by disrupting TH homeostasis, with further possibility of accumulating in organisms higher up in the food chain.
Subject(s)
Amiodarone/toxicity , Bioaccumulation , Endocrine Disruptors/toxicity , Gene Expression Regulation, Developmental/drug effects , Larva/drug effects , Water Pollutants, Chemical/toxicity , Amiodarone/metabolism , Animals , Endocrine Disruptors/metabolism , Hindlimb/drug effects , Larva/genetics , Larva/metabolism , Receptors, Thyroid Hormone/genetics , Receptors, Thyroid Hormone/metabolism , Triiodothyronine/genetics , Triiodothyronine/metabolism , Water Pollutants, Chemical/metabolism , Xenopus laevisABSTRACT
A large number of chemicals are routinely detected in aquatic environments, and these chemicals may adversely affect aquatic organisms. Accurate risk assessment requires understanding drug-metabolizing systems in aquatic organisms because metabolism of these chemicals is a critical determinant of chemical bioaccumulation and related toxicity. In this study, we evaluated mRNA expression levels of nuclear receptors and drug-metabolizing enzymes as well as cytochrome P450 (CYP) activities in pro-metamorphic tadpoles, froglets, and adult frogs to determine how drug-metabolizing systems are altered at different life stages. We found that drug-metabolizing systems in tadpoles were entirely immature, and therefore, tadpoles appeared to be more susceptible to chemicals compared with metamorphosed frogs. On the other hand, cyp1a mRNA expression and CYP1A-like activity were higher in tadpoles. We found that thyroid hormone (TH), which increases during metamorphosis, induced CYP1A-like activity. Because endogenous TH concentration is significantly increased during metamorphosis, endogenous TH would induce CYP1A-like activity in tadpoles.
Subject(s)
Cytochrome P-450 Enzyme System/genetics , Cytochrome P-450 Enzyme System/metabolism , Gene Expression Regulation, Developmental/genetics , Gene Expression/genetics , Metamorphosis, Biological/genetics , Thyroid Hormones/metabolism , Thyroid Hormones/physiology , Xenopus/genetics , Xenopus/physiology , Animals , Cytochrome P-450 CYP1A1/genetics , Cytochrome P-450 CYP1A1/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , Receptors, Cytoplasmic and Nuclear/genetics , Receptors, Cytoplasmic and Nuclear/metabolismABSTRACT
BACKGROUND: The adoption of pathogen reduction technology (PRT) is considered for the implementation of safer platelet (PLT) transfusion. However, the effects of PRT treatment on PLT thrombus formation under blood flow have not yet been fully clarified. STUDY DESIGN AND METHODS: Leukoreduced PLT concentrates (PCs) obtained by plateletpheresis were treated with riboflavin and ultraviolet light (Mirasol PRT). PC samples were passed through a column filled with collagen-coated beads at a fixed shear rate after 1, 3, and 5 days of storage. The thrombus formation ability was evaluated by measuring collagen column retention rate. The change in the activation state of integrin αIIbß3 on PLTs during storage was examined by flow cytometry. RESULTS: The retention rate of the PRT-treated PLTs was significantly higher than that of the control PLTs on the day of treatment and decreased with storage but remained higher than those of the control during storage. This modification did not correlate with the total αIIbß3 or fibrinogen binding on the PLTs but correlated significantly with PAC-1 binding. Mn(2+) -induced αIIbß3 activation also fully restored the retention rate in the Day 5 PRT-treated PLTs along with the increase in PAC-1 binding. CONCLUSION: Riboflavin-based PRT treatment of PCs leads to the enhancement of thrombus formation on collagen, which is related to the activation status of αIIbß3, which does not bind to fibrinogen but binds to PAC-1. The impact of this finding on the hemostatic or even thrombogenic potential in vivo must await clinical evaluation.