Research On The Hormesis Effect Of FA And The Underlying Molecular Mechanisms

As the main indoor air pollutant,formaldehyde(FA)can cause neurotoxicity,reproductive toxicity,hematopoietic toxicity,genotoxicity and so on and it is defined as"A1 carcinogen".The Hormesis effect refers to the negative effects of high-dose chemicals on the body but a beneficial effect at low doses.Studies have shown that high concentrations of FA can cause cell death or cell apoptosis,while low concentrations of FA can promote cell proliferation,but the molecular mechanisms are rarely reported.In this study,different types of cells were chosen to treat by various levels of FA.By analyzing the FA-treated cells viability,we established the dose range of the levels of FA-induced cell proliferation,and by testing the expression of biomolecules related to cell proliferation,we explored the molecular mechanisms of the Hormesis effect of FA.The cell viability of cells of human normal epithelial(the 16HBE line)and cells of human leukemia(the K562 line)who were treated with different concentrations of FA was measured by CCK-8 method and MTT method.The results showed that for K562 cells and 16HBE cells,the safe dose range of FA was between 0-125?inol/L and 0-60?mol/L,respectively.As the dose of FA increased,cell viability decreased,indicating that FA did have the Hormesis effect.Notably,75 ?mol/L and 40 ?mol/L FA could promote cell proliferation significantly for K562 cells and 16HBE cells.Next,cells were divided into four groups:the control group,the FA exposure group,the combination of FA and inhibitor group and the inhibitor group.The FA treatment concentrations were 75?mol/L and 40?mol/L,respectively,lasting for 2 h.On the one hand,combined with the antioxidant vitamin E(VE),we found that low concentrations of FA also induced intracellular oxidative damage while increasing cell viability,including reactive oxygen species(ROS)content increased and the levels of glutathione(GSH)decreased.At the same time,low levels of FA increased the expression of CyclinD-cdk4 and transcription factor E2F1 in cell division,and Pyruvate kinase M2 isoenzyme(PKM2),glucose,Glucose transporter 1(GLUT1),Lactate dehydrogenase A(LDHA),and lactic acid levels in carbohydrate metabolism.However,the addition of VE resulted in a decrease above molecules content compared with the FA group.On the other hand,in combination with C-4-(3-bromophenylamino)-6,7-bismethoxyquinazoline(PD153035),the specific inhibitor of EGFR,we found that low levels of FA made Epithelial growth factor receptor(EGFR)and Proliferating cell nuclear antigen(PCNA)levels having a increasing trendy in protein and gene expression levels,but their content reduced in the FA group compared with the FA+PD153035 group.The results of this study indicate that the effect of FA on cell proliferation in a dose-dependent manner:relatively speaking,low concentrations of FA can promote cell proliferation while high concentrations of FA can inhibit cell proliferation,showing that it is consistent with the characteristics of the Hormsesis effect.The related molecular mechanisms are that low concentrations of FA can promote cell proliferation by promoting key factors in cell division or carbohydrate metabolism mediated by oxidative stress or directly affecting growth signal transduction molecules.Once the cell proliferation is out of control,cancer is onset.Our study contributes to the objective evaluation of FA,laying the foundation of the comprehensive disclosure of the relationship between formaldehyde-promoted cell proliferation and FA-caused cancer or other diseases.