Stigmasterol ameliorates neurological deficits and neuroinflammation in rats with traumatic brain injury by suppressing STAT3/NF-κB/LCN-2.

PURPOSE: TBI triggers intricate inflammatory processes that lead to secondary damage. Stig, a compound known for its cholesterol-lowering effects, demonstrates significant therapeutic potential, encompassing anti-cancer, antioxidant, and anti-atherosclerotic properties. It possesses an ability to penetrate the blood-brain barrier and accumulate in the brain, where it exerts potent anti-inflammatory, anti-apoptotic, and anti-oxidative stress properties, specifically in conditions impacting the central nervous system.

METHODS: This study is a basic research combining in vitro and in vivo experiments. The experimental subjects include BV2 microglia (a murine-derived microglial cell line) and HT22 neurons (a murine-derived hippocampal neuronal cell line), with 3 samples of Sprague-Dawley rats in each group. In vitro experiments involved stimulating BV2 mouse microglial cells with LPS and HT22 mouse neuronal cells with H2O2, followed by treatment with varying concentrations of Stig to assess its impact on pro-inflammatory cytokines, oxidative stress mediators, and LCN-2. In vivo, a TBI rat model was developed, and rats were arbitrarily split into Sham, TBI, TBI + normal saline, and TBI + Stig cohorts. Neurological function was evaluated using the modified neurological severity score for acute phase assessment, while cognitive abilities and spatial learning were assessed via the Morris water maze test. HE staining and Nissl staining were employed to observe neuronal death, and the wet-dry method was utilized to quantify brain water content. Levels of LCN-2, microglial polarization markers, and apoptotic markers were quantified by Western blot and immunofluorescence. Data were examined utilizing GraphPad Prism 9.0 and SPSS 26.0 software. Continuous variables were expressed as mean ± SD. Normality of the data was evaluated utilizing the Shapiro-Wilk test. For normally distributed continuous variables between 2 cohorts, an independent samples t-test was employed. When comparing more than 2 cohorts, a one-way ANOVA was performed. Non-normally distributed data were denoted by the median (Q1, Q3). The Mann-Whitney U test was applied to compare variables not following a normal distribution. The Spearman correlation test was utilized to assess links between variables. Statistical significance was set as p < 0.05.

RESULTS: In vivo treatment with Stig ameliorated neurological dysfunction, brain edema, and neuronal apoptosis in TBI rats while enhancing both memory and learning performance. Stig reduced microglial activation and inflammatory responses in TBI by inhibiting the STAT3/NF-κB pathway and downregulating LCN-2 expression. Additionally, Stig markedly attenuated inflammation in LPS-stimulated microglial cells and reduced neuronal apoptosis and oxidative stress in H₂O₂-treated HT22 cells. Moreover, it effectively suppressed the activation of the STAT3/NF-κB/LCN-2 signaling cascade induced by LPS or H₂O₂.

CONCLUSION: Stig mitigates neuroinflammation and neuronal cell death by suppressing the STAT3/NF-κB/LCN-2 signaling cascade, offering neuroprotective effects in a rat TBI model.