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

BACKGROUND: Interferon regulatory factor-1 (IRF-1) plays a critical role in the injury to stem and progenitor regions associated with aberrant interferon-gamma (IFN-γ) in aplastic anemia (AA). The present study aimed to investigate the effects of IFN-γ on murine myeloid precursor cells (32D cells) with wild-type and inactive-type protein kinase B (Akt) after IRF-1 gene silencing. METHODS: With treatment of four concentrations of IFN-γ, the 32D cell viability and inhibition rate were assayed by middle-time-spray (MTS). The apoptosis rate was determined by flow cytometry, and the expression of the phosphorylated signal transducer and activator of transcription 3 (p-Stat3) and the phosphorylated signal transducer and activator of transcription 5 (p-Stat5) was analyzed by Western blot. RESULTS: The results from real time PCR (RT-PCR) assays suggested that the relative expression level of IRF-1-mRNA in the knockdown group (KD) was lower than that of in the negative control (NC) and blank control (Ctrl). In addition, the silencing efficiency was >70%, which was further validated by Western blotting. At 48 h, the rate of proliferation of 32D cells of wild-type Akt was significantly higher than that of inactive-type Akt (0.918±0.005 vs. 0.503±0.003, P=0.008), while the apoptosis rate in wild-type was significantly lower than that of inactive Akt (1.46%±0.41% vs. 2.98%±0.32%, P=0.006). After reducing the expression of IRF-1 gene, the promotion of hematopoiesis was recovered, resulting from the high concentration of IFN-γ achieved by reducing the expression of p-Stat5 via the Akt signaling pathway. CONCLUSIONS: Taken together, these results suggested that IRF-1 plays a critical role in the pro-apoptotic effect of IFN-γ on the proliferation of hematopoietic progenitor cells. These findings could contribute to understanding the mechanisms underlying the conversion from IFN-γ-mediated inhibition to promotion of hematopoiesis.