Tamoxifen induces apoptotic neutrophil efferocytosis in horses

Abstract

Macrophages and neutrophils are important cellular components in the process of acute inflammation and its subsequent resolution, and evidence increasingly suggests that they play important functions during the resolution of chronic, adaptive inflammatory processes. Exacerbated neutrophil activity can be harmful to surrounding tissues; this is important in a range of diseases, including allergic asthma and chronic obstructive pulmonary disease in humans, and equine asthma (also known as recurrent airway obstruction (RAO). Tamoxifen (TX) is a non-steroidal estrogen receptor modulator with effects on cell growth and survival. Previous studies showed that TX treatment in horses with induced acute pulmonary inflammation promoted early apoptosis of blood and BALF neutrophils, reduction of BALF neutrophils, and improvement in animals' clinical status. The aim of this study was to describe if TX induces in vitro efferocytosis of neutrophils by alveolar macrophages. Efferocytosis assay, myeloperoxidase (MPO) detection and translocation phosphatidylserine (PS) were performed on neutrophils isolated from peripheral blood samples from five healthy horses. In in vitro samples from heathy horses, TX treatment increases the phenomenon of efferocytosis of peripheral neutrophils by alveolar macrophages. Similar increases in supernatant MPO concentration and PS translocation were observed in TX-treated neutrophils, compared to control cells. In conclusion, these results confirm that tamoxifen has a direct effect on equine peripheral blood neutrophils, through stimulation of the engulfment of apoptotic neutrophils by alveolar macrophages.

Tamoxifen and its metabolites induce mitochondrial membrane depolarization and caspase‐3 activation in equine neutrophils

“…Our group has previously demonstrated in vitro that TX exerts its effect via a mechanism that is independent of its interaction with oestrogen receptors (ER) (Olave, Morales, et al, 2018). It has been shown that TX exerts many off‐target effects, and ultimately, it is possible that as a whole, these off‐target effects mediate the therapeutic effect of the drug (Mandlekar & Kong, 2001).…”

Tamoxifen inhibits chemokinesis in equine neutrophils

“…TX also dampens chemotactic index and respiratory burst production in equine peripheral blood neutrophils [ 16 ]; and this study shows that TX inhibits the chemokinetic effects of IL-8 in equine neutrophils. Furthermore, recent results show that incubation of neutrophils with 5 μm of tamoxifen induces their efferocytosis by macrophages [ 27 ]. All of the above could partially explain the anti-inflammatory effect of TX in horses with airway inflammation described by our group [ 17 ].…”

Tamoxifen in horses: pharmacokinetics and safety study

“…The few clinical studies that have looked into the potential use of TAM for equine airway inflammation have been based on a single dosage (approximately 0,25 mg/kg) extrapolated from human medicine, with conflicting results regarding clinical efficacy based on that single empirical dose [15,16]. However, there is robust pre-clinical information on modulation of inflammation, which warrants the pharmacokinetic and safety data presented here [17][18][19][20][21]. Oral TAM absorption was similar to findings in other species, since plasma concentration of TAM was maximum 3 h after oral administration, comparably to reports in humans and mice, where maximum concentration is also reached between 4 and 9 h postadministration [1].…”