Interferon-γ attenuates the survival activity of G-CSF through PI3K/Akt signaling pathway in mouse multipotent progenitor cells

Abstract

Apoptosis plays an important role in the injury to stem and progenitor compartments associated with aberrant interferon-gamma (IFN-gamma) in aplastic anemia (AA), which is characterized by the loss of stem cells; however, its molecular mechanism is poorly understood. In this study, we have addressed the mechanism of the apoptotic function of IFN-gamma against hematopoietic stem and/or progenitors. Although granulocyte colony-stimulating factor (G-CSF) augmented survival and proliferative and differentiating activity in 32D cells, mouse multipotent progenitor cells, these effects were abolished by IFN-gamma and were susceptible to apoptosis with IFN-gamma. IFN-gamma attenuated Akt phosphorylated by G-CSF in a dose- and time-dependent manner. Wortmannin, a specific inhibitor of phosphatidylinositol 3-kinase (PI3K), enhanced the inhibitory effect on Akt phosphorylated by G-CSF in collaboration with IFN-gamma, suggesting that the activity of IFN-gamma might converge on the PI3K pathway. We examined the expression of Bcl-2-associated death (Bad), which works downstream of Akt. IFN-gamma increased the Bad protein reduced by G-CSF. IFN-gamma induced apoptosis in 32D cells through the caspase pathway. Taken together, these results suggest that IFN-gamma could exert inhibitory action on stem cells and/or progenitors by interference with the PI3K/Akt signaling pathway. Our findings may contribute to understanding the decreased number of stem cells characteristic of AA.

Pathogenesis of aplastic anemia

“…IFN-γ and TNF-α levels in the bone marrow of AA patients are significantly higher compared to healthy individuals [42][43][44]. IFN-γ plays an important role in both the innate and adaptive immunity and is a negative regulator of stem and precursor cell proliferation and survival [45]. They are produced by activated T cells in the bone marrow and have a profound impact on the hematopoietic system.…”

Inflammatory signals regulate hematopoietic stem cells

“…With regard to HSCs, IFNγ suppresses human bone marrow colony formation 34,35 and inhibits growth of human CD34+ bone marrow cells by inducing differentiation and apoptosis 36-39;40 41. Similarly, IFNγ attenuates survival of the immortalized myeloblast-like 32D cell line 42, and it induces differentiation of a chronic myeloid leukemia (CML) cell line and CD34+ cells from CML clinical samples 43. IFNγ is thought to be a major contributor to some bone marrow failure syndromes such as acquired aplastic anemia in humans 44,45.…”

Effects of IFN-γ on the proliferation of 32D cells expressing Akt after IRF-1 gene silencing

“…Meanwhile, we found that the level of p-Stat5 decreased, but Stat5 did not change, so IFN-γ might induce a specific decrease in the process of Stat5 dephosphorylation. The previous experimental results and the growth-promoting effect of low concentrations of IFN-γ together may be implemented through the Akt signaling pathway ( 20 , 33 ). Furthermore, p-Stat5 is speculated to exert a double modulatory role, and the effect of IFN-γ is closely related to IRF-1 ( 34 - 37 ).…”

“…It is commonly associated with in vivo signal transduction and is closely related to the cellular activity, metabolism regulation, and the inhibition of apoptosis ( 17 - 19 ). Our previous study suggested that Akt is involved in IFN-γ-mediated cell proliferation ( 20 ). To further confirm that the vital role of Akt in the effect of IFN-γ before and after silencing the IRF - 1 gene, the mechanism underlying IFN-γ in the reversal of the effect was explored.…”