Effects of tamoxifen on the immune response phenotype in equine peripheral blood mononuclear cells.

Tamoxifen (TAM) is widely utilized in the prevention and treatment of human breast cancer and has demonstrated the potential to modulate the immune response. It has been proposed as a therapeutic tool for immune-mediated diseases. TAM has been investigated as a possible treatment for asthma-like conditions in horses, revealing specific impacts on the innate immune system. While the effects of TAM on equine neutrophils are well-documented, its influence on lymphocytes and the modulation of the immune response polarization remains unclear. This in vitro study employed peripheral blood mononuclear cells (PBMC) from healthy horses, exposing them to varying concentrations of the TAM and assessing the expression of genes involved in the polarization of the immune response (TBX21, IFNG, GATA3, IL4, IL10, FOXP3, and CTLA4) in PBMC stimulated or not with PMA/ionomycin. Additionally, the effect of TAM over the proportion of regulatory T cells (Treg) was also assessed. TAM did not significantly affect the expression of these genes and Treg at low concentrations. However, at the highest concentration, there was an impact on the expression of GATA3, IL4, IL10, and CTLA4 genes. These alterations in genes associated with a Th2 and regulatory response coincided with a noteworthy increase in drug-associated cytotoxicity but only at concentrations far beyond those achieved in pharmacological therapy. These findings suggest that the effects of TAM, as described in preclinical studies on asthmatic horses, may not be attributed to the modification of the adaptive response.

Characterization of extracellular trap production and release by equine neutrophils in response to different stimuli.

This study explores Neutrophil Extracellular Trap (NET) formation in equine neutrophils, which is crucial for eliminating infections and is implicated in various equine inflammatory diseases. We investigated the molecular pathways involved in NET release by equine neutrophils in response to stimuli. We use PMA, A23187, LPS, PAF, OZ, and cytokines, observing NET release in response to PMA, PAF, and A23187. In contrast, LPS, OZ, and the cytokines tested did not induce DNA release or did not consistently induce citrullination of histone 4. Peptidyl-arginine deiminase inhibition completely halted NET release, while NADPH oxidase and mitochondrial reactive oxygen species only played a role in PMA-induced NETs. Neutrophil elastase inhibition modestly affected PAF-induced NET liberation but not in PMA or A23187-induced NET, while myeloperoxidase did not contribute to NET release. We expect to provide a foundation for future investigations into the role of NETs in equine health and disease and the search for potential therapeutic targets.