Taurine Alleviates LPS-Induced Acute Lung Injury by Suppressing TLR-4/NF-κB Pathway

Abstract

Taurine has the function of immune regulation, relieving acute and chronic inflammation caused by various agents, and maintaining cell homeostasis. This investigation focused on the protective functions of taurine targeting acute lung injury (ALI) induced by LPS. Sixty male SD rats aged 6-7 weeks were segregated at random: blank control group (C group), taurine control group (T group), ALI model group (LPS group), and taurine prevention groups (LPST1, LPST, LPST3 Groups). C group and LPS group were given normal drinking water, while T group and LPST group were given 2% taurine in drinking water. LPST1 group was given 1% taurine in drinking water while. LPST3 group was given 3% taurine in drinking water. On the 14th and 28th day, LPS group and LPST1, LPST, and LPST3 groups were subjected to injection of LPS (25 mg/kg) into the trachea of rats. Serum, peripheral blood, lung tissue, and bronchoalveolar lavage fluid (BALF) were collected at 6 h post-LPS injection. The wet/dry ratio (W/D) of lung was measured by hot drying method. The population of white blood cells and the abundance of inflammatory-related cells within peripheral blood were counted by an automatic blood cell analyzer. The population of white blood cells within BALF was counted by a white blood cell counting plate combined with Swiss Giemsa staining, while the proportion of related white blood cells was calculated. BCA reagent was used to determine the protein concentration in BALF. The levels of pro-inflammatory factors (IL-1 β, IL-6, IL-18, TNF - α), anti-inflammation factors (IL-10, IL-4), and taurine within serum and lung tissue were detected by ELISA. Lung structural tissue alterations were observed through HE staining techniques. Myeloperoxidase (MPO) activities within lung tissue were detected through colorimetry. Protein expression levels of TLR4, MyD88, NF-κ Bp65, NF-κ Bp-p65, MCP-1, together with CD68 within lung tissue, were analyzed by Western blot (WB) and immunohistochemistry (IHC). The taurine pretreatment group contained significantly reduced W/D, MPO activity, and the number of inflammatory cells in BALF induced by LPS. In addition, compared with ALI model group, the taurine pretreatment group contained significantly reduced levels of pro-inflammatory factors in lung tissue, increased levels of anti-inflammatory factors, and decreased expression levels of key proteins in TLR-4/NF-κ B pathway. Taurine can protect rats from ALI by inhibiting the activation of neutrophils, macrophages, and TLR-4/NF-κ B signaling pathway.

Keywords: ALI; LPS; Prevention; Taurine.