Modulation of chemokine secretion and oxidative stress in vitro in thyroid cells after exposure to thiocyanate, nitrate, or perchlorate

Background: Perchlorate, nitrate, and thiocyanate are thyroid disruptors. Emerging evidence suggests they may exert further effects independent of iodide uptake inhibition, influencing oxidative stress and thyroid tumour development. This study aimed to assess their effects on cell viability, proliferation, reactive oxygen species (ROS) production, and chemokine expression in normal human thyroid cells and thyroid cancer cell lines. Methods: Thyroid cells, both normal (NHT, in primary cultures) and cancer (TPC-1 and 8505C), were exposed to increasing concentrations of perchlorate, nitrate, or thiocyanate for 24 hours. Cell viability and proliferation were assessed in each cell type. Intracellular ROS production was measured using H2DCFDA. CXCL8 and CXCL10 expression was evaluated at both mRNA (RT-PCR) and protein levels (ELISA in cell supernatants). Results: None of the three anions significantly affected viability in NHT or 8505C cells, whereas high-dose thiocyanate reduced viability in TPC-1 cells. Proliferative responses were modest and cell-type specific, occurring mainly at the highest concentrations tested. Perchlorate induced a biphasic increase in ROS production in NHT, while thiocyanate slightly reduced ROS levels in TPC-1 cells; no consistent effects were observed in 8505C cells. Thiocyanate consistently increased CXCL8 secretion in NHT and TPC-1 cells, with a concentration-dependent but non-monotonic pattern, whereas nitrate and perchlorate had minimal effects. CXCL10 protein was undetectable in all conditions, despite significant and cell-specific modulation of CXCL10 mRNA expression. Conclusions: Beyond their role as NIS inhibitors, perchlorate, nitrate and thiocyanate modulate oxidative stress and chemokine secretion in human thyroid cells. Thiocyanate promotes a pro-inflammatory phenotype, potentially favouring a tumour-promoting thyroid microenvironment.