Local proinflammatory effects of repeated skin exposure to warfarin, an anticoagulant rodenticide in rats.

Objective: To evaluate the effects of epicutaneous application of anticoagulant warfarin, by examining the presence of tissue injury and immune/inflammatory activity in exposed skin.

Methods: Rats were exposed to warfarin by applying 10 μg of warfarin-sodium to 10-12 cm(2) skin (range 0.8-1 μg per 1 cm(2)) for 3 consecutive days. Tissue injury was evaluated by lipid peroxidation, histomorphological changes and signs of reparative activity in skin. T cell infiltration and selected aspects of epidermal cell activity were examined as indicators of immune/inflammatory skin response to warfarin application.

Results: Repeated warfarin application exerted no effect on skin metabolic viability, but resulted in tissue injury (increased malondialdehyde, MDA, production, evident histo-morphological changes in epidermis and dermis depicting cell injury and death). Increased numbers of proliferating cell nuclear antigen (PCNA(+)) cells indicated reparative processes in injured skin. Infiltration of CD3(+) cells (T lymphocytes) along with the increased production of tumor necrosis factor-a (TNF-a) by epidermal cells from warfarin-treated skin and their co-stimulatory effect in an in vitro T-cell activation assay demonstrated immunomodulatory effects of epicutaneous warfarin.

Conclusion: Presented data have documented tissue damage associated with immune/inflammatory activity in skin exposed to warfarin. Observed effects are relevant to immunotoxic potential of this anticoagulant in settings of external exposure.