ABSTRACT
As a neonicotinoid pesticide, imidacloprid is widely used to control sucking insects on agricultural planting and fleas on domestic animals. However, the extent to which imidacloprid exposure has an influence on cardiogensis in early embryogenesis is still poorly understood. In vertebrates, the heart is the first organ to be formed. In this study, to address whether imidacloprid exposure affects early heart development, the early chick embryo has been used as an experimental model because of its accessibility at its early developmental stage. The results demonstrate that exposure of the early chick embryo to imidacloprid caused malformation of heart tube. Furthermore, the data reveal that down-regulation of GATA4, NKX2.5, and BMP4 and up-regulation of Wnt3a led to aberrant cardiomyocyte differentiation. In addition, imidacloprid exposure interfered with basement membrane breakdown, E-cadherin/laminin expression, and mesoderm formation during the epithelial-mesenchymal transition (EMT) in gastrula chick embryos. Finally, the DiI-labeled cell migration trajectory indicated that imidacloprid restricted the cell migration of cardiac progenitors to primary heart field in gastrula chick embryos. A similar observation was also obtained from the cell migration assay of scratch wounds in vitro. Additionally, imidacloprid exposure negatively affected the cytoskeleton structure and expression of corresponding adhesion molecules. Taken together, these results reveal that the improper EMT, cardiac progenitor migration, and differentiation are responsible for imidacloprid exposure-induced malformation of heart tube during chick embryo development.
Subject(s)
Gene Expression Regulation, Developmental , Heart Valve Diseases/pathology , Heart/drug effects , Heart/embryology , Imidazoles/toxicity , Insecticides/toxicity , Nitro Compounds/toxicity , Animals , Bone Morphogenetic Protein 4/genetics , Bone Morphogenetic Protein 4/metabolism , Cadherins/metabolism , Cell Differentiation/drug effects , Cell Line , Cell Movement/drug effects , Chick Embryo , Down-Regulation , Epithelial-Mesenchymal Transition/drug effects , GATA4 Transcription Factor/genetics , GATA4 Transcription Factor/metabolism , Heart Valve Diseases/chemically induced , Homeobox Protein Nkx-2.5/genetics , Homeobox Protein Nkx-2.5/metabolism , Laminin/genetics , Laminin/metabolism , Myocytes, Cardiac/drug effects , Myocytes, Cardiac/metabolism , Neonicotinoids , Rats , Up-Regulation , Wnt3A Protein/genetics , Wnt3A Protein/metabolismABSTRACT
Cyclooxygenase-2 (COX-2)-catalysed synthesis of prostaglandin E2 plays a key role in inflammation and its associated diseases, such as cancer and cardiovascular disease. There are numerous reports demonstrating that flavonoids inhibit COX-2 activity. However, transcriptional regulation of COX-2 can also be important. Nobiletin, amentoflavone, quercetin, quercetin penta-acetate, flavone, resveratrol, apigenin, chrysin, kaempferol, galangin, and genistein have been reported to modulate COX-2 transcription in a wide variety of systems. Here, we briefly review the literature on regulation of COX-2 transcription by flavonoids, and report some new preliminary data on Vitamin E and quercetin conjugates. Quercetin, quercetin 3-glucuronide, quercetin 3'-sulfate and 3'methylquercetin 3-glucuronide reduced COX-2 mRNA expression in both unstimulated and interleukin-1beta stimulated colon cancer (Caco2) cells. Quercetin and quercetin 3'-sulfate, unlike quercetin 3-glucuronide and 3'methylquercetin 3-glucuronide, also inhibited COX-2 activity. In contrast, tocopherols (alpha-tocopherol, alpha-tocopherol acetate, and gamma-tocopherol at 10microM) did not affect COX-2 mRNA expression in unstimulated Caco2 cells. However, the tocopherols inhibited COX-2 activity showing that the tocopherols act post-transcriptionally on activity, whereas quercetin and some quercetin conjugates affect both the transcription and activity of COX-2. Flavonoid modulation of COX-2 transcription may therefore be an important mechanism in anti-carcinogenesis.
