Following treatment with ALA in HCE cells, which were stimulated with LPS complex, a significant decrease was demonstrated in the protein content of TNF-α to 23.81% (
P < 0.001), IL-6 to 46.71% (
P < 0.001), IL-1β to 20.86% (
P < 0.05), and IL-8 to 52.21% (
P < 0.001) compared with the corresponding protein contents of HCE cells incubated with LPS complex only (
Figs. 1A–D).
These anti-inflammatory effects of ALA were comparable with the effects of the DM. Incubation of HCE cells with DM (which served as a positive control to ALA) resulted in decreased TNF-α protein content to 33.6% (
P < 0.001), IL-6 to 48.02% (
P < 0.001), IL-1β to 33.7% (
P < 0.05), and IL-8 to 52.44% (
P < 0.001), compared with the protein contents of these cytokines after incubation of HCE cells with LPS complex only (
Figs. 1A–D).
Interestingly, there were no significant differences between the amount of decrease of the cytokines after treatment with either ALA or DM in HCE cells after stimulation with LPS complex (
Figs. 1A–D). This observation suggests a similar efficacy of ALA and DM as potent anti-inflammatory agents on cultured HCE cells.
GLA and LA achieved only minor anti-inflammatory effects compared with ALA and DM (
Fig. 1). As expected, OA did not achieve a similar anti-inflammatory effect and, therefore, served as negative control (
Fig. 1). This finding was expected based on previous studies that used OA as a control fatty acid in dietary PUFA intervention trials due to its lack of effect on eiconasoid biosynthesis.
25,26
In order to evaluate another type of inflammatory stimulus, the authors have repeated this set of experiments with stimulation with poly I:C, a stimulus that mimics viral antigens. Similarly, a significant increase of cytokine production was evident following stimulation with poly I:C, as demonstrated for the LPS complex. ALA treatment significantly decreased TNF-α protein secretion to 25.87% (
P < 0.05), IL-6 to 43.53% (
P < 0.001), IL-1β to 33.11% (
P < 0.05), and IL-8 to 49.66% (
P < 0.001), compared with poly I:C stimulus alone (
Figs. 2A–D). OA, which served as a negative control, did not cause a significant decrease in cytokines protein contents. These anti-inflammatory effects of ALA were comparable with that of DM, which decreased TNF-α protein secretion to 22.41% (
P < 0.05), IL-6 to 38.03% (
P < 0.001), IL-1β to 18.0% (
P < 0.05), and IL-8 to 50.53% (
P < 0.001), compared with incubation of HCE cells with poly I:C only. There was no significant difference between the decrease in cytokines after treatments with either DM or ALA in HCE cells after stimulated with poly I:C (
Fig. 2), suggesting again a similar anti-inflammatory effects of ALA and DM.
Similar to what was noted for the LPS complex stimulation, GLA and LA induced only minor anti-inflammatory effects compared with ALA and DM after stimulation with poly I:C.