Low-dose cadmium induces lymphangiogenesis through activation of the STAT3 signaling pathway

Cadmium (Cd) is a widespread environmental toxicant that poses significant threat to public health. After intake, Cd is distributed throughout the body via blood and lymphatic circulation. However, the effect of Cd on lymphatic vessels has not been revealed. In this study, mice were exposed to 10 mu M cadmium chloride through drinking water immediately after corneal alkali burn. In vivo analyses showed that Cd treatment enhances the alkali burn-induced corneal lymphangiogenesis, which is characterized by increased expression of lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1), prospero-related homeobox 1 (PROX-1) and vascular endothelial growth factor receptor 3 (VEGFR3). In vitro, the proliferation and migration of human dermal lymphatic endothelial cells (HDLECs) are increased by 1 mu M Cd treatment, while inhibited by 10 mu M Cd treatment. At a concentration of 1 mu M, Cd specifically induces phosphorylation of signal transducer and activator of transcription 3 (STAT3), but has no effect on the MAPK, AKT, or NF-xB signaling pathway. In the presence of the STAT3 inhibitor STATTIC, Cd fails to induce HDLECs proliferation and migration. In addition, Cd upregulates VEGFR3 expression and its gene promoter activity in a STAT3-dependent manner. Our study suggests that lowdose Cd promotes lymphangiogenesis through activation of the STAT3 signaling pathway.