Nutr Res Pract.  2014 Jun;8(3):249-256.

Effects of plant-based Korean food extracts on lipopolysaccharide-stimulated production of inflammatory mediators in vitro

• Lee SY
• Kim YS
• Lim JY
• Chang N
• Kang MH
• Oh SY
• Lee HJ
• Kim H
• Kim Y

Abstract

BACKGROUND/OBJECTIVES
The traditional Korean diet is plant-based and rich in antioxidants. Previous studies have investigated the potential health benefits of individual nutrients of Korean foods. However, the cumulative effects of a Korean diet on inflammation remain poorly understood. Therefore, the aim of this study was to investigate the anti-inflammatory effects of a plant-based Korean diet.
MATERIALS/METHODS
Using data from the Fifth Korean National Health and Nutrition Examination Survey, 75 individual plant food items were selected which represent over 1% of the total diet intake of the Korean diet. These items were classified into ten different food groups, and the vegetable (Veg) and fruit (Fruit) groups were studied based on their high antioxidant capacity. For comparison, a mixture of all ten groups (Mix) was prepared. To produce a model of inflammation with which to test these Veg, Fruit, and Mix plant-based Korean food extracts (PKE), RAW264.7 macrophages were treated with lipopolysaccharide (LPS).
RESULTS
Levels of nitric oxide (NO) and prostaglandin E2 (PGE2), as well as protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) were found to be lower following PKE treatment. Furthermore, PKE treatment was found to suppress tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) via the nuclear transcription factor kappa-B (NF-kappaB) signaling pathway. Overall, the Mix group exhibited the greatest anti-inflammatory effects compared with Veg and Fruit PKE group.
CONCLUSIONS
Inhibition of LPS-induced pro-inflammatory mediators by the PKE tested was found to involve an inhibition of NF-kB activation. Moreover, PKE tested have the potential to ameliorate various inflammation-related diseases by limiting the excessive production of pro-inflammatory mediators.

Keyword

Plant-based Korean food extracts; Inflammation; NO; TNF-alpha; NF-kB

MeSH Terms

Antioxidants
Cyclooxygenase 2
Diet
Dinoprostone
Fruit
Inflammation
Insurance Benefits
Interleukin-6
Macrophages
NF-kappa B
Nitric Oxide
Nitric Oxide Synthase Type II
Nutrition Surveys
Plants
Transcription Factors
Tumor Necrosis Factor-alpha
Vegetables
Antioxidants
Cyclooxygenase 2
Dinoprostone
Interleukin-6
NF-kappa B
Nitric Oxide
Nitric Oxide Synthase Type II
Transcription Factors
Tumor Necrosis Factor-alpha

Figure

• 

  Fig. 1 PKE inhibits production of NO in LPS-induced RAW264.7 macrophages. Cells were pretreated with each PKE for 30 min, then were incubated with LPS. After 24 h, the culture medium was collected and analyzed for NO using Griess reagent. Three independent experiments were performed and the data shown represent the mean ± SEM for absrobances recorded at 560 nm. One-way ANOVA was implemented using Tukey's post-hoc test (α = 0.05). Data for Mix PKE (A), Veg PKE (B), Fruit PKE (C), and all three PKE at 8 mg/ml (D) are shown. Mix, an extract containing all ten food groups; Veg, vegetable PKE; Fruit, fruit PKE.

• 

  Fig. 2 PKE down-regulates iNOS expression in LPS-induced RAW264.7 macrophages. Cells were treated with various doses of each PKE for 24 h and were incubated with LPS for 30 min. Expression of iNOS in RAW264.7 cells was assayed using western blotting with α-tubulin used as a loading control. Data for Mix PKE (A), Veg PKE (B), Fruit PKE (C) are shown. Mix, an extract containing all ten food groups; Veg, vegetable PKE; Fruit, fruit PKE.

• 

  Fig. 3 PKE inhibits NO production in LPS/IFN-γ-induced RAW264.7 macrophages. Cells were pretreated with each PKE for 30 min and were incubated with LPS + IFN-γ. After 24 h, the culture medium was collected and assayed for NO production using Griess reagent. Three independent experiments were performed and the data shown represent the mean ± SEM for absorbances recorded at 560 nm. One-way ANOVA was implemented using Tukey's post-hoc test (α = 0.05). Data for Mix PKE (A), Veg PKE (B), Fruit PKE (C), and all three PKE at 8 mg/ml (D) are shown. Mix, an extract containing all ten food groups; Veg, vegetable PKE; Fruit, fruit PKE.

• 

  Fig. 4 PKE inhibits PGE2 production in LPS-induced RAW264.7 macrophages. Cells were treated with each PKE (2, 4, or 8 mg/ml) in 24-well plates for 30 min, then were stimulated with LPS. After 24 h, cell-free culture medium was collected and analyzed for levels of PGE2. Absorbance values were measured at 450 nm and three independent experiments were performed. Data represent the mean ± SEM, and different letters indicate significant differences (n = 3). One-way ANOVA was implemented using Tukey's post-hoc test (α = 0.05). Mix PKE (A), Veg PKE (B), Fruit PKE (C), and all three PKEs at 8 mg/ml (D) are shown. Mix, an extract containing all ten food groups; Veg, vegetable PKE; Fruit, fruit PKE.

• 

  Fig. 5 PKE down-regulates expression of COX-2 in LPS-induced RAW264.7 macrophages. Cells were pretreated with various doses of each PKE for 30 min and were incubated with LPS. After 24 h, levels of COX-2 were analyzed using western blotting with α-tubulin used as a loading control. Mix PKE (A), Veg PKE (B), and Fruit PKE (C) are shown. Mix, an extract containing all ten food groups; Veg, vegetable PKE; Fruit, fruit PKE.

• 

  Fig. 6 PKE inhibits IL-6 production in LPS-induced RAW264.7 macrophages. Cells were pretreated with each PKE (2, 4, or 8 mg/ml) in 24-well plates for 30 min, then were stimulated with LPS. After 24 h, cell-free culture medium was collected and analyzed using an IL-6 ELISA kit. Absorbances were measured at 450 nm, and three independent experiments were performed. Data represent the mean ± SEM. One-way ANOVA was implemented using Tukey's post-hoc test (α = 0.05). Mix PKE (A), Veg PKE (B), Fruit PKE (C), and all three PKEs at 8 mg/ml (D) are shown. Mix, an extract containing all ten food groups; Veg, vegetable PKE; Fruit, fruit PKE.

• 

  Fig. 7 PKE inhibits TNF-α production in LPS-induced RAW264.7 macrophages. Cells were pretreated with each PKE (2, 4, or 8 mg/ml) in 24-well plates for 30 min, then stimulated with LPS. After 24 h, cell-free culture medium was collected and analyzed using a TNF-α ELISA kit. Absorbance values were at 450 nm recorded for three independent experiments. Data represent the mean ± SEM. One-way ANOVA was implemented using Tukey's post-hoc test (α = 0.05). Mix PKE (A), Veg PKE (B), Fruit PKE (C), and all three PKE at 8 mg/ml (D) are shown. Mix, an extract containing all ten food groups; Veg, vegetable PKE; Fruit, fruit PKE.

• 

  Fig. 8 PKE inhibits IκBα phosphorylation and translocation of the NF-κB p65 subunit in LPS-induced RAW264.7 macrophages. Cells were treated with various doses of each PKE for 30 min and were incubated with LPS for 24 h. Levels of cytosolic p-IκBα and nuclear NF-κB p65 were analyzed using western blotting. Lamin A/C and α-tubulin were used as loading controls for nuclear and cytosolic proteins, respectively. Mix PKE (A), Veg PKE (B), Fruit PKE (C), and all three PKE at 8 mg/ml (D) are shown. Mix, an extract containing all ten food groups; Veg, vegetable PKE; Fruit, fruit PKE.

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