Abstract: Objective To explore the acute injury effect of formaldehyde on human eosinophils(EOL-1)and the mechanism. Methods EOL-1 cells were cultured in vitro. Eol-1 cells treated with formaldehyde for 2 hours at room temperature were set as the 0 mmol, 5 mmol, 10 mmol, 25 mmol and 50 mmol groups. Cells co-treated with DPI, Tiron and NAC and 25 mmol formaldehyde were divided into control group, formaldehyde group, formaldehyde + DPI group, formaldehyde + Trion group, and formaldehyde + NAC group. According to the different concentrations of NAC, the cells were set as the control group, formaldehyde group, formaldehyde + 0.01 mmol NAC group, formaldehyde + 0.1 mmol NAC group, and formaldehyde +1 mmol NAC group. Cell apoptosis and death were detected with propidium iodide(PI)and Hoechst fluorescent staining. The mitochondrial function damage was detected with rhodamine 123(Rho-123)fluorescent labeling method. The expressions of Bax and Bcl-2 were detected with Western blotting. Results The cell death rates of different concentrations of formaldehyde(0, 5, 10, 25, 50 mmol)were(3.313±2.395)%,(8.205±5.719)%,(20.335±5.167)%,(19.387±6.056)%, and(28.043±8.851)%, respectively. Compared with the 0 mmol group, the 5 mmol group had unchanged cell apoptosis and death(P=1.00), but the 10 mmol(P=0.030), 25 mmol(P=0.033)and 50 mmol groups(P=0.001)had significantly increased cell death, with EC₅₀=25 mmol. The cell mortality rates of formaldehyde group, formaldehyde + DPI group, formaldehyde + Trion group and formaldehyde + NAC group were(61.430±9.885)%,(57.907±13.619)%,(55.700±18.487)% and(21.837±6.674)%, respectively. Formaldehyde + DPI group(P=1.00)and formaldehyde + Trion group(P=1.00)had no effect on formaldehyde-induced cell damage, but formaldehyde + NAC group reversed the formaldehyde-induced cell death(P=0.01). Compared with formaldehyde group(52.853±11.338)%, with different concentrations of NAC, the cell mortality was different ［formaldehyde + 0.01 mmol NAC(10.620±4.483)%, formaldehyde + 0.1 mmol NAC(6.257±6.265)%, formaldehyde + 1 mmol NAC(4.002±2.50)%］, and the reverse effect of formaldehyde on cell death was concentration-dependent. The results of Rho-123 fluorescence labeling showed that compared with the 0 mmol group, the 10 mmol, 25 mmol, and 50 mmol groups had reduced mitochondrial function(P<0.001), while formaldehyde + NAC group reversed the mitochondrial function damage induced by formaldehyde(809.339±163.210 vs 675.552±126.993, P=0.021). Western blotting results showed that, compared with the control group, 25 mmol formaldehyde significantly down-regulated the protein expression of Bcl-2(0.401±0.122, P<0.001)but up-regulated the protein expression of Bax(2.937±1.388, P=0.006); formaldehyde + NAC group significantly reduced the protein expressions of Bax(1.196±0.597, P=0.018)and Bcl-2(0.717±0.246, P=0.018). Conclusion Formaldehyde ≥10 mmol can induce eosinophil EOL-1 damage by inhibiting mitochondrial function and regulating Bcl-2/Bax signal pathway, while antioxidant NAC can reduce the damage and signal pathway of eosinophil EOL-1 caused by formaldehyde.

Key words: Formaldehyde, EOL-1 cells, Cell death, Mitochondrial function, Signal pathway