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2,3',4,4',5-Pentachlorobiphenyl induced autophagy of the thyrocytes via DAPK2/PKD/VPS34 pathway
Qi Zhou1, Li Wang1, Huanhuan Chen1
1Department of Endocrinology, The First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029, People's Republic of China.
Abstract:
2,3',4,4',5-Pentachlorobiphenyl (PCB118) has been shown to cause thyroidal ultrastructure lesions, but the underlying mechanism remains elusive. This study aimed to elucidate the mechanism by which PCB118 induces the abnormalities of the thyrocytes. Wistar rats were injected intraperitoneally with PCB118 (0, 10, 100 and 1000 μg/kg/d) for 13 weeks, and FRTL-5 cells were treated with PCB118 (0, 0.25, 2.5 and 25 nM). Transmission electron microscopy showed typical autophagosomes in the thyroid of PCB118-treated rats. Immunofluorescence staining showed dose-dependent increase of autophagy in FRTL-5 cells exposed to PCB118. In vivo and vitro studies found that Tubulin beta 3 class III (Tubb3) mRNA and protein levels decreased significantly, while Death-associated protein kinase 2 (DAPK2) increased after PCB118 exposure, and the binding between Tubb3 and DAPK2 was enhanced by PCB118 in a dose-dependent manner. Moreover, PCB118 resulted in the upregulation of Protein kinase D (PKD) and downregulation of Phosphatidylinositol 3-kinase (VPS34) in mRNA levels, and the activation of PKD and VPS34 phosphorylation. Additionally, Tubb3 small interfering RNA (siTubb3) suppressed DAPK2 protein expression and PKD phosphorylation in FRTL-5 cells, while VPS34 phosphorylation was inhibited by siPKD. Furthermore, DAPK2, PKD and VPS34 were upregulated by Tubb3 overexpression following PCB118 exposure. Our results demonstrate that low concentrations of PCB118 could promote thyroid autophagy formation and cause the abnormalities in thyroidal ultrastructure, and these effects are likely to be mediated by DAPK2/PKD/VPS34 dependent pathway.
Insights
2,3
Area of Science:
- Environmental toxicology
- Cell biology
- Molecular biology
Background:
- 2,3',4,4',5-Pentachlorobiphenyl (PCB118) exposure causes thyroid ultrastructure lesions.
- The precise mechanism underlying PCB118-induced thyroid abnormalities is not fully understood.
Purpose of the Study:
- To investigate the mechanism by which PCB118 induces thyrocyte abnormalities.
- To elucidate the role of autophagy and specific molecular pathways in PCB118 toxicity.
Main Methods:
- Wistar rats and FRTL-5 cells were exposed to varying concentrations of PCB118.
- Transmission electron microscopy and immunofluorescence staining were used to assess ultrastructural changes and autophagy.
- mRNA and protein levels of Tubulin beta 3 class III (Tubb3), Death-associated protein kinase 2 (DAPK2), Protein kinase D (PKD), and Phosphatidylinositol 3-kinase (VPS34) were analyzed.
Main Results:
- PCB118 exposure led to increased autophagy and thyroid ultrastructure lesions in rats and cells.
- PCB118 decreased Tubb3 and increased DAPK2, enhancing their binding.
- PCB118 modulated the DAPK2/PKD/VPS34 pathway, with Tubb3 playing a regulatory role.
Conclusions:
- PCB118 promotes thyroid autophagy and causes ultrastructural abnormalities.
- The DAPK2/PKD/VPS34 pathway, influenced by Tubb3, mediates PCB118-induced thyroid toxicity.