Sulphur dioxide and fluoride co-exposure cause enamel damage by disrupting the Cl-/HCO3- ion transport

Objective: Although there is growing evidence linking the exposure to sulphur dioxide (SO₂) and fluoride to human diseases, there is little data on the co-exposure of SO₂ and fluoride. Moreover, literature on SO₂ and fluoride co-exposure to enamel damage is insufficient. In this work, we concentrate on the concurrent environmental issues of excessive SO₂ and fluoride in several coal-consuming regions.

Method: To identify the toxicity of SO₂ and fluoride exposure either separately or together, we used both ICR mice and LS8 cells, and factorial design was employed to assess the type of potential combined action.

Result: In this study, co-exposure to SO₂ and fluoride exacerbated enamel damage, resulting in more severe enamel defects of incisor and the damage occurred earlier. Cl^-/HCO₃^- exchanger expression is increased by SO₂ and fluoride in mouse incisor. Consistent with in vivo results, co-exposure of SO₂ and fluoride decreased pHi and increased [Cl^-]i level by increasing the expression of the Cl^-/HCO₃^- exchanger in LS8 cells. Furthermore, SO₂ and F may increase merlin protein expression, and merlin deficiency causes AE2 expression to decrease in vitro.

Conclusion: Overall, these results indicate that co-exposure to SO₂ and fluoride may result in more toxicity both in vitro and in vivo than a single exposure to SO₂ and fluoride, suggesting that residents in areas contaminated with SO₂ and fluoride may be more likely to suffer enamel damage.

AE2; Cl(-)/HCO(3)(-); Fluoride; Merlin; Sulphur dioxide.