Role of Nuclear Factor-κB Signaling Pathway in Inflammatory Injury in L02 Cells Exposed to Organic Extracts from Tap Water

Objective To observe the activation of nuclear factor-κB (NF-κB) signaling pathway and its inflammatoryregulating effects in human normal liver cells (L02 cells) exposed to organic extracts from tap water.

Methods Organic pollutants in tap water samples were extracted by solid phase extraction method. L02 cells were divided into seven groups: blank control group (culture medium), solvent control group (0.1% dimethyl sulfoxide, DMSO), and organic pollutant groups (0.312 5, 0.625 0, 1.250 0, 2.500 0, and 5.000 0 L/mL). Each group was treated for 24 h, 48 h, and 72 h. Western blot was used to observe the activation of NF-κB signaling pathway. ELISA assay was used to detect interleukin 8 (IL-8) and tumor necrosis factor α (TNF-α) le vels in supernatant.

Results (1) The activity of L02 cells decreased obviously after treated with all designed dosages of organic extracts and at all designed exposure time blocks (P < 0.05). (2) The protein expression levels of inhibitor of NF-κB decreased obviously after exposure to the dosages at organic extracts of 0.6250L/mL and above for all designed time blocks (P < 0.05). The protein expression levels of p65 were remarkably higher after administered with the 1.2500L/mL organic extracts and above at 24h and 48h or with the 0.625 0 L/mL and above at 72 h (P < 0.05). (3) After 24 h-and 48 h-exposure, the IL-8 level of L02 cells increased significantly in the 0.625 0 L/mL and above groups (P < 0.05); while after 72 h-exposure, the IL-8 level significantly increased in 0.312 5 L/mL group (P < 0.05). After 24 h-exposure, the TNF-α level of L02 cells increased significantly in the 1.250 0 L/mL and above groups (P < 0.05); while after 48 h-and 72 h-exposure, the TNF-α level increased significantly in the 0.625 0 L/mL and above groups (P < 0.05). Compared with 24h-exposure, the IL-8 and TNF-α levels in all exposed groups with 48h-and 72h-exposure significantly increased (P < 0.05). (4) The IL-8 and TNF-α levels were negatively associated with the protein expression level of inhibitor of NF-κB (r=-0.851 0, -0.8180, P < 0.05), and positively associated with the protein expressions level of p65 (r=0.8160, 0.8650, P < 0.05).

Conclusion The study findings suggest that organic pollutants from tap water could dose-dependently and time-dependently activate NF-κB signaling pathway and induce secretion of IL-8 and TNF-α, which might result in inflammatory injury in L02 cells.