Stevia extract alleviated spleen inflammatory injury in LPS-stressed mice by inhibiting the TLR4/MYD88/NF-κB signaling pathway.

This study aimed to explore the alleviating effect of different levels of dietary stevia extract on mice challenged with lipopolysaccharide (LPS) and the possible mechanisms were explored. In this experiment, ninety 3-week-old healthy male Kunming mice with comparable body weights were randomly allocated into five groups, namely the control group, LPS group, and LPS + stevia extract groups at doses of 200, 400 and 600 mg/kg, respectively. Each group comprised 18 mice, with 6 replicates per treatment and 3 mice per replicate. The total feeding period was 28 days. On day 14 and day 28, at 9:00 a.m., the mice were intraperitoneally injected with 1 mg/mL LPS at a dosage of 3 mg/kg body weight (BW), whereas the control group was administered an equivalent volume of normal saline. Six hours post-injection on day 28, the body weights of the mice were recorded, and blood samples, liver tissues, and spleen tissues were collected sequentially. In this study, we found that LPS caused oxidative damage in the mouse spleen, led to splenic congestion, increased spleen index, lymphocyte infiltration and pathological lesions. Meanwhile, antioxidant capacity was compromised, as indicated by a decreasing (P < 0.05) in Glutathione peroxidase (GSH-Px) activity and increases (P < 0.05) in malondialdehyde (MDA) content in plasma and spleen. LPS also induced inflammatory response and increased (P < 0.05) levels of pro-inflammatory cytokines Tumor necrosis factor-alpha (TNF-α), Interleukin-1 beta (IL-1β), and Interleukin-6 (IL-6) in spleen. Furthermore, the expression of key proteins involved in Toll-like receptor 4 (TLR4)-initiated signaling pathway, including TLR4, Myeloid differentiation primary response 88 (MYD88), and Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) were increased (P < 0.05). Dietary supplementation with Stevia rebaudiana extract significantly reduced these LPS-induced effects, partially restored splenic tissue damage, and provided a protective effect by inhibiting the TLR4/MYD88/NF-κB signaling pathway through decreasing the expression of key nodal proteins like TLR4, MYD88, and NF-κB.