OBJECTIVETo investigate the regulatory effects of lanthanum chloride (LaCl3) on the activation of nuclear factor kappa B inhibitor (IκB) kinase beta (IKKβ) induced by tumor necrosis factor alpha (TNF-α).

METHODS(1) Hela cells were cultured routinely in vitro. One portion of cells were collected and divided into TNF-α group (cultured with serum-free RMPI 1640 medium containing 20 ng/mL TNF-α for 30 min), low-dose LaCl3 + TNF-α group, moderate-dose LaCl3 + TNF-α group, high-dose LaCl3 + TNF-α group, LaCl3 group (cultured with serum-free RMPI 1640 medium containing 100 µmol/L LaCl3 for 30 min), and control group (cultured with serum-free RMPI 1640 medium for 30 min) according to the random number table. Cells in low-dose LaCl3 + TNF-α group, moderate-dose LaCl3 + TNF-α group, high-dose LaCl3 + TNF-α group were first cultured with serum-free RMPI 1640 medium containing 5, 25, 100 µmol/L LaCl3 for 4 h, and then stimulated with serum-free RMPI 1640 medium containing 20 ng/mL TNF-α for 30 min. There were 3 samples in each group. Cells were collected for detection of intracellular location of NF-κB/p65 protein by immunofluorescence staining. (2) Another portion of cells were collected and divided into TNF-α group, low-dose LaCl3 + TNF-α group, moderate-dose LaCl3 + TNF-α group, high-dose LaCl3 + TNF-α group, and control group with the same treatment as above. There were 3 samples in each group. The protein levels of NF-κB/p65 in nuclei, and the protein levels of IκBα, phosphorylated IκBα (p-IκBα) as well as IKKβ and phosphorylated IKKβ (p-IKKβ) in cytoplasm were determined by Western blotting. The binding activity between NF-κB/p65 in the nuclear and target gene was determined by NF-κB/p65 transcription factor kit (denoted as absorption value). Data were processed with analysis of variance or LSD-t test.

RESULTS(1) High expression of NF-κB/p65 was observed in cytoplasm of control group. High expression of NF-κB/p65 was observed in nuclei of TNF-α group. The expression of NF-κB/p65 in cytoplasm of LaCl3 group was lower than that of control group. In groups treated with LaCl3 and TNF-α, NF-κB/p65 expression levels in nuclei and cytoplasm were decreased along with the increase in the concentration of LaCl3, which were all lower than those in TNF-α group. (2) There was certain amount of NF-κB/p65 protein expressed in nuclei of control group. The expression of NF-κB/p65 protein in nuclei of TNF-α group was higher than that of control group. In groups treated with LaCl3 and TNF-α, the expressions of NF-κB/p65 protein in nuclei were decreased along with an increase in the concentration of LaCl3. The level of IκBα in TNF-α group was significantly decreased but that of p-IκBα increased as compared with those in control group. Along with the increase in the concentration of LaCl3, the levels of IκBα gradually increased and the levels of p-IκBα gradually decreased in groups treated with LaCl3 and TNF-α. There were no statistical differences in expression levels of IKKβ among the 5 groups. The expression of p-IKKβ could be hardly observed in control group, but it was obviously increased in TNF-α group. The expression levels of p-IKKβ in groups treated with LaCl3 and TNF-α were gradually decreased along with the increase in the concentration of LaCl3. The absorption value in TNF-α group was 0.39 ± 0.03, which was higher than that in control group (0, t = -7.23, P<0.01). The absorption values in low-dose LaCl3 +TNF-α group, moderate-dose LaCl3 + TNF-α group, and high-dose LaCl3 +TNF-α group were respectively 0.17 ± 0.03, 0.15 ± 0.03, and 0, which were obviously lower than that in TNF-α group (with t values respectively -6.54, -5.92, -7.23, P values all below 0.01).

CONCLUSIONSLaCl3 can block the activation of NF-κB signaling pathway by blocking the phosphorylation of IKKβ of Hela cells.