The Selective Estrogen Receptor Modulator Raloxifene Inhibits Neutrophil Extracellular Trap Formation

Abstract

Raloxifene is a selective estrogen receptor modulator typically prescribed for the prevention/treatment of osteoporosis in postmenopausal women. Although raloxifene is known to have anti-inflammatory properties, its effects on human neutrophils, the primary phagocytic leukocytes of the immune system, remain poorly understood. Here, through a screen of pharmacologically active small molecules, we find that raloxifene prevents neutrophil cell death in response to the classical activator phorbol 12-myristate 13-acetate (PMA), a compound known to induce formation of DNA-based neutrophil extracellular traps (NETs). Inhibition of PMA-induced NET production by raloxifene was confirmed using quantitative and imaging-based assays. Human neutrophils from both male and female donors express the nuclear estrogen receptors ERα and ERβ, known targets of raloxifene. Similar to raloxifene, selective antagonists of these receptors inhibit PMA-induced NET production. Furthermore, raloxifene inhibited PMA-induced ERK phosphorylation, but not reactive oxygen species production, pathways known to be key modulators of NET production. Finally, we found that raloxifene inhibited PMA-induced, NET-based killing of the leading human bacterial pathogen, methicillin-resistant Staphylococcus aureus. Our results reveal that raloxifene is a potent modulator of neutrophil function and NET production.

Drug Repurposing for the Treatment of Bacterial and Fungal Infections

“…Moreover, tamoxifen can stimulate chemotaxis, phagocytosis, and neutrophil extracellular trap (NET) formation through the modulation of the ceramide pathway upon infection with S. aureus (Corriden et al, 2015). Unlike tamoxifen, its analog raloxifene has been shown to reduce NET formation in human neutrophils, thus resulting in cell death of S. aureus (Flores et al, 2016). In addition, denileukin diftitox has been reported to bind to the IL-2 receptor in T lymphocytes, thereby introducing diphtheria toxin inside these cells to suppress them.…”

Life and death of circulating cell-free DNA

“…155 Moreover, various therapeutics may stimulate NET production differently: an analysis of estrogen receptor modulators showed that Tamoxifen induced 156 and Raloxifene inhibited NET formation. 157 Discussion cfDNA has attracted increasing attention as a promising component of the liquid biopsy. cfDNA carries information about genetic and epigenetic tumor-specific alterations.…”

The immunomodulatory effects of endocrine therapy in breast cancer

“…Corriden et al [ 38 ] revealed a positive effect of tamoxifen on the proinflammatory processes of human neutrophils, including chemotaxis, phagocytosis and ceramide/PKCζ-mediated neutrophil extracellular traps (NETs) formation. Nevertheless, the same group later found raloxifene exerted an inhibitory effect on ceramide expression in neutrophils and phorbol 12-myristate 13-acetate (PMA)-induced NETs, suppressing the NETs-based killing function of neutrophils against bacterial pathogens [ 39 ]. The distinct effects of tamoxifen and raloxifene on NETs formation in neutrophils might be due to their slight differences in molecular structure.…”

“…Similar to tamoxifen, toremifene upregulates intercellular adhesion molecule-1 (ICAM-1) expression on MCF-7 cells, and ICAM-1 is a key factor bridging and forming the immunological synapses between NK and target cells [85]. Moreover, estrogen-induced tumor immune CD8+T cells proliferation↑ [35], cytotoxicity↓ [12] CD4+T cells Treg polarization↑ [12] NK cells cytotoxicity↑ [36] DCs functional differentiation and immunostimulatory capacity↓ [37] neutrophils tamoxifen improves the proinflammatory pathway [38], while raloxifene has the opposite effect [39] Selective estrogen receptor down-regulators (SERDs) fulvestrant CD8+T cells cytotoxicity↓ [12], tumor infiltration↑ [40] CD4+T cells Treg polarization↑ [12], tumor infiltration↑ [40] MDSCs, Tregs tumor infiltration↓ [40] DCs tumor infiltration↑ [40] Aromatase inhibitors (AIs) letrozole, anastrozole, exemestane, formestane…”