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. 2021 Mar 31;22(7):3641. doi: 10.3390/ijms22073641

Figure 4.

Figure 4

The effects of caffeic acid phenethyl ester (CAPE) on saliva-induced interleukin-8 (IL-8) expression in THP-1 cells and potential underlying molecular mechanisms. (A) Structure of CAPE. (B) Effects of CAPE (20 μM) and tin-protoporphyrin (SnPP, heme oxygenase-1 (HO-1) inhibitor; 20 μM) on HO-1 mRNA and protein expression in THP-1 cells. Data represent the mean ± standard error of the mean (SEM; n = 3). *** p < 0.001 compared to control group; ### p < 0.01 compared to CAPE-treated group (Student’s t-test). (C) Effects of CAPE and SnPP on saliva-induced IL-8 mRNA expression in THP-1 cells. (D) Levels of phosphorylated IKK2, IκBα, and NF-κB (p65) proteins in THP-1 cells stimulated with 5% saliva alone or pretreated with 20 μM CAPE or CAPE combined with SnPP before saliva treatment. Data represent the mean ± SEM (n = 3). * p < 0.05, *** p < 0.001 compared to control group; # p <0.05 compared to saliva-treated group; ++ p < 0.01, +++ p < 0.001 compared to CAPE-treated group (Student’s t-test). (E) Working model for saliva-induced IL-8 expression via the IKK2/IκBα/NF-κB pathway in periodontal disease. Blue arrow = stimulation; red line with an end bar = inhibition; black arrow = direction or flow.