Inhibitory effect of activin A on IL-9 production by mouse NK cells through Smad3 signaling

Abstract

Interleukin-9 (IL-9) is a cytokine secreted by T-helper (Th)9 cells, and activin A can enhance Th9 cell differentiation. However, whether activin A affects IL-9 production by natural killer (NK) cells remains unclear. Herein, we found that not only Th cells, but also CD3−CD49b+NKp46+ NK cells of Balb/c mice produced IL-9. Although activin A promoted IL-9 expression in CD4+ Th cells, it inhibited IL-9 production by CD49b+NKp46+ NK cells in mice. Furthermore, the enzyme-linked immunosorbent assay (ELISA) results showed that mouse NK cells could secrete mature IL-9 protein, and activin A inhibited IL-9 release by NK cells. Additionally, activin A inhibited interferon (IFN)-γ production in splenic NK cells in mice, but promoted IL-2 production, and did not alter the production of IL-10. Western blotting results showed that levels of activin type IIA receptor (ActRIIA), Smad3 and phosphorylated-Smad3 (p-SMAD3) protein increased in activin A-treated splenic NK cells, compared with that in control NK cells. The inhibitory effects of activin A on IL-9 production by NK cells were attenuated in the presence of activin antagonist follistatin (FST) or Smad3 knockdown to NK cells. These data suggest that although activin A up-regulates IL-9 expression in Th cells, it inhibits IL-9 production in NK cells through Smad3 signaling.

Activin A, a Novel Chemokine, Induces Mouse NK Cell Migration via AKT and Calcium Signaling

“…In the present study, Western blotting was used to examine the expression of signaling proteins to better understand the signal transduction mechanism of activin A-induced mouse NK cell migration. Activin A significantly increased the p-SMAD3 protein level in mouse NK cells and upregulated the p-SMAD3/SMAD3 ratio, consistent with previous studies [15]. Furthermore, activin A significantly increased the level of p-AKT protein and the p-AKT/AKT ratio in mouse NK cells (Figure 5A).…”

“…The flow cytometry results showed that the ratio of CD49b + NKp46 + NK cells was more than 85% (Figure 1B), indicating that isolated cells were suitable for NK cell experiments. Previous studies have shown that 10 ng/mL of activin A promotes IL-2 production but inhibits IL-9 secretion by NK cells [15]. In this study, the CCK8 assay was used to determine the viability of NK cells treated with 0-10 ng/mL activin A.…”

“…Recent studies have reported that various immune cells can synthesize and secrete activin A, such as monocytes/macrophages, neutrophils, mast cells and NK cells [9,10,13,14]. Additionally, activin A plays a crucial role in regulating the activities of various immune cells, including T cells, B cells, NK cells, monocytes/macrophages, neutrophils and microglia [14][15][16][17][18]. Activin A in the tumor microenvironment may affect tumors' development by regulating immune cells' function.…”

Activin A impairs ActRIIA+ neutrophil recruitment into infected skin of mice

“…Multiple lines of evidence indicate that activin A is a pleiotropic cytokine which plays pivotal roles in regulating immune responses. It exhibits different effects on a wide variety of immune cells, including macrophages, dendritic cells, mast cells, natural killer cells, T cells, and B cells, with both pro-or anti-inflammatory characteristics depending on the cellular context (Morianos et al, 2019;Li et al, 2013;Ma et al, 2020). Although in vitro experiments have uncovered neutrophils as an important source of activin A ll OPEN ACCESS (Chen et al, 2011) and elevated activin A levels occur in diseases characterized by neutrophil activation, which suggest that a relationship between neutrophils and activin A may be anything but coincidental (Sideras et al, 2013), it was only recently that our studies demonstrated an expression of activin signaling components in neutrophils and that activin A can in fact modulate neutrophil function in an autocrine and paracrine manner Xie et al, 2017).…”

Different Immunoregulation Roles of Activin A Compared With TGF-β

“…( 44 ). Moreover, IL-10 expression in NK cells was not altered after activin A administration, while IL-2 expression was up-regulated ( 24 , 48 ).…”