Peimine ameliorates LPS-induced acute lung injury by regulating Nrf2 and NF-κB pathways

Objective: To investigate the protective effect of Peimine (PM) against lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice and the underlying mechanisms.

Methods: KM mice were randomly divided into five groups: Control, LPS, Peimine low-dose (PM-L, 0.1 mg/kg), medium-dose (PM-M, 1 mg/kg), and high-dose (PM-H, 10 mg/kg) groups. Mice in the PM treatment groups received intraperitoneal injection of Peimine at different doses, while the mice in control and LPS groups received physiological saline. Afterwards, mice in the LPS and PM groups were subjected to intranasal instillation of LPS to establish the model of acute lung injury. The wet-to-dry (W/D) weight ratio of lung tissues was calculated, and H&E staining was performed to observe pathological changes in the lung tissues. Serum levels of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), and MDA were measured using ELISA kits. Western blot was employed to assess the expression of NF-κB, IκBα, phospho-IκBα, Nrf2, HO-1, and SOD2 in lung tissues. RT-PCR quantified the mRNA levels of Nrf2 and its downstream genes HO-1 and NQO1. Additionally, RAW264.7 cells were treated with various drug concentrations for 24 hours followed by LPS exposure (100 ng/mL) for another 24 hours. Prior to treatment of RAW264.7 cells with PM and LPS, the ML385+PM group was pre-treated with ML385 (3 μM) for 4 hours. ELISA kits were used to measure TNF-α, IL-6, IL-1β, and MDA in cell supernatants, while ROS levels were determined using a ROS assay kit.

Results: Compared with the model group, pretreatment with PM significantly reduced the lung tissue W/D weight ratio, ameliorated lung tissue pathological changes, and inhibited the secretion of TNF-α, IL-6, and IL-1β in bronchoalveolar lavage fluid. PM inhibited the LPS-induced elevation in lung tissue MDA levels, SOD2 consumption, and ROS levels. Furthermore, PM suppressed LPS-induced NF-κB activation and nuclear translocation, while significantly enhancing the protein expression of Nrf2 and HO-1 and increasing the mRNA levels of Nrf2 and its downstream genes, such as HO-1 and NQO1. In RAW264.7 cells, LPS induction led to elevated IL-1β, IL-6, TNF-α, MDA, and ROS levels, which were significantly suppressed by PM treatment. However, the antioxidative and anti-inflammatory effects of PM were effectively blocked by inhibiting the Nrf2 pathway.

Conclusion: PM effectively ameliorates LPS-induced lung injury, primarily through inhibition of the NF-κB pathway, and activation of the Nrf2 pathway, alongside a reduction in the release of inflammatory factors.