Epi/perineural and Schwann Cells as Well as Perineural Sheath Integrity are Affected Following 2,4-D Exposure.

Abstract

2,4-dicholorophenoxy acetic acid (2,4-D) is a worldwide-known hormone herbicide. However, there are increasing concerns about its exposure and risks of developing pathological conditions for the peripheral nervous system. The aim of this study was to investigate the mechanism(s) involved in the toxicity of 2,4-D on peripheral nerve's cellular components. The epi/perineural and Schwann cells and a total of three cell lines were treated with 2,4-D. The viability of cells at different doses of 2,4-D was measured by MTT assay. The cell cycle analyses, cumulative cell counting, fluorescent staining, antioxidant and caspase enzymes activity were examined on epi/perineural and Schwann cells. The epi/perineural cells were assessed as having biological macromolecular changes. Some tight junction-related genes and proteins were also tested on explants of 2,4-D treated epi/perineural tissue. The viability of 2,4-D treated cells was reduced in a dose-dependent manner. Reduced growth rate and G1 cell cycle arrest were verified in 2,4-D treated epi/perineural and Schwann cells. The use of staining methods (acridine orange/ethidium bromide and DAPI) and caspase 3/7 activity assay along with malondialdehyde, glutathione peroxidase, and superoxide dismutase activity assays indicated the apoptotic and oxidant effects of 2,4-D on epi/perineural and Schwann cells. Data obtained from FTIR revealed changes in epi/perineural proteins and cell membrane lipids. Additionally, claudin-1, occludin, and ZO-1 gene/protein expression profiles were significantly reduced in 2,4-D-treated epi/perineural pieces. Our data indicated that oxidative stress, apoptosis of epi/perineural and Schwann cell and impaired blood-nerve barrier may have contributed to nerve damage following 2,4-D exposure.