Anti-inflammatory effects of Eucommia ulmoides Oliv. male flower extract on lipopolysaccharide-induced inflammation

BACKGROUND: Eucommia ulmoides Oliv. is a medicinal plant native to China, with its bark (Eucommiae Cortex) traditionally being used for medicinal purposes. Previous research has shown that Eucommia male flowers can exert anti-inflammatory, analgesic, antibacterial, and other pharmacological effects, including immune regulation. This study explored the anti-inflammatory effects of the 70% ethanol extract of male flowers (EF) of E. ulmoides in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells and LPS-administered mice. METHODS: Cytotoxicity of EF for RAW 264.7 cells was investigated using Cell Counting Kit-8. The production of proinflammatory mediators, nitric oxide (NO), tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 was determined using enzyme-linked immunosorbent assays. IL-17, IL-23, and IL-10 mRNA levels were determined using quantitative real-time polymerase chain reaction. Activation of the nuclear factor (NF)-κB pathway in RAW 264.7 cells was investigated via Western blotting. In vivo anti-inflammatory effects of EF were studied in an LPS-induced acute inflammation mouse model by analyzing lung tissue histopathology, serum TNF-α and IL-6 levels, and myeloperoxidase (MPO) activity in lung tissue. RESULTS: EF showed no significant cytotoxicity at concentrations from 10 to 60 μg/mL (cell viability > 80%) in the CCK-8 cell viability assay. EF inhibited the RAW 264.7 cell proliferation (EF 60 μg/mL, 120 μg/mL, and 250 μg/mL vs. negative control: 87.31 ± 2.39% vs. 100.00 ± 2.50%, P = 0.001; 79.01 ± 2.56 vs. 100.00 ± 2.50%, P < 0.001; and 64.83 ± 2.50 vs. 100.00 ± 2.50%, P < 0.001), suppressed NO (EF 20 μg/mL and 30 μg/mL vs. LPS only, 288.81 ± 38.01 vs. 447.68 ± 19.07 μmol/L, P = 0.004; and 158.80 ± 45.14 vs. 447.68 ± 19.07 μmol/L, P < 0.001), TNF-α (LPS+EF vs. LPS only, 210.20 ± 13.85 vs. 577.70 ± 5.35 pg/mL, P < 0.001), IL-1β (LPS+EF vs. LPS only, 193.30 ± 10.80 vs. 411.03 ± 42.28 pg/mL, P < 0.001), and IL-6 (LPS+EF vs. LPS only, 149.67 ± 11.60 vs. 524.80 ± 6.24 pg/mL, P < 0.001) secretion, and downregulated the mRNA expression of IL-17 (LPS+EF vs. LPS only, 0.23 ± 0.02 vs. 0.43 ± 0.12, P < 0.001), IL-23 (LPS+EF vs. LPS only, 0.29 ± 0.01 vs. 0.42 ± 0.06, P=0.002), and IL-10 (LPS+EF vs. LPS only, 0.30 ± 0.01 vs. 0.47 ± 0.01, P=0.008) in LPS-stimulated RAW 264.7 cells. EF inhibited the LPS-induced NF-κB p65 (LPS+EF 20 μg/mL and 30 μg/mL vs. LPS only: 0.78 ± 0.06 vs. 1.17 ± 0.08, P < 0.001; and 0.90 ± 0.06 vs. 1.17 ± 0.08, P =0.002) and inhibitor of kappa B (IκBα) phosphorylation (LPS+EF 20 μg/mL and 30 μg/mL vs. LPS only: 0.25 ± 0.01 vs. 0.63 ± 0.03, P < 0.001; and 0.31 ± 0.01 vs. 0.63 ± 0.03, P < 0.001), LPS+EF 30 μg/mL inhibited IκB kinase (IKKα/β) phosphorylation (LPS+EF 30 μg/mL vs. LPS only, 1.12 ± 0.14 vs. 1.71 ± 0.25, P = 0.002) in RAW 264.7 cells. Furthermore, EF 10 mg/kg and EF 20 mg/kg inhibited lung tissue inflammation in vivo and suppressed the serum TNF-α (LPS+EF 10 mg/kg and 20 mg/kg vs. LPS only, 199.99 ± 186.49 vs. 527.90 ± 263.93 pg/mL, P=0.001; and 260.56 ± 175.83 vs. 527.90 ± 263.93 pg/mL, P = 0.005), and IL-6 (LPS+EF 10 mg/kg and 20 mg/kg vs. LPS only, 41.26 ± 30.42 vs. 79.45 ± 14.16 pg/ ml, P = 0.011; and 42.01 ± 26.26 vs. 79.45 ± 14.16 pg/mL, P = 0.012) levels and MPO (LPS+EF 10 mg/kg and 20 mg/kg vs. LPS only, 3.19 ± 1.78 vs. 5.39 ± 1.51 U/g, P = 0.004; and 3.32 ± 1.57 vs. 5.39 ± 1.51 U/g, P = 0.006) activity in lung tissue. CONCLUSIONS: EF could effectively inhibit the expression of inflammatory factors and overactivation of neutrophils. Further investigation is needed to evaluate its potential for anti-inflammation therapy.