Cathepsin B as a key regulator of ferroptosis in microglia following intracerebral hemorrhage.

Intracerebral hemorrhage (ICH) is a subtype of stroke marked by elevated mortality and disability rates. Recently, mounting evidence suggests a significant role of ferroptosis in the pathogenesis of ICH. Through a combination of bioinformatics analysis and basic experiments, our goal is to identify the primary cell types and key molecules implicated in ferroptosis post-ICH. This aims to propel the advancement of ferroptosis research, offering potential therapeutic targets for ICH treatment. Our study reveals pronounced ferroptosis in microglia and identifies the target gene, cathepsin B (Ctsb), by analyzing differentially expressed genes following ICH. Ctsb, a cysteine protease primarily located in lysosomes, becomes a focal point in our investigation. Utilizing in vitro and in vivo models, we explore the correlation between Ctsb and ferroptosis in microglia post-ICH. Results demonstrate that ICH and hemin-induced ferroptosis in microglia coincide with elevated levels and activity of Ctsb protein. Effective alleviation of ferroptosis in microglia after ICH is achieved through the inhibition of Ctsb protease activity and protein levels using inhibitors and shRNA. Additionally, a notable increase in m6A methylation levels of Ctsb mRNA post-ICH is observed, suggesting a pivotal role of m6A methylation in regulating Ctsb translation. These research insights deepen our comprehension of the molecular pathways involved in ferroptosis after ICH, underscoring the potential of Ctsb as a promising target for mitigating brain damage resulting from ICH.

Oestrogen ameliorates blood-brain barrier damage after experimental subarachnoid haemorrhage via the SHH pathway in male rats.

BACKGROUND: Sex differences affect the occurrence, progression and regression of subarachnoid haemorrhage (SAH). Oestrogen plays a protective role in alleviating the vasospasm and neuronal apoptosis induced by SAH. However, whether oestrogen affects blood‒brain barrier (BBB) integrity has not been fully studied. Oestrogen has been found to regulate the sonic hedgehog (SHH) signalling pathway through the oestrogen receptor in gastric cancer and adrenal glands, and the SHH signalling pathway has an important role in maintaining the BBB by upregulating the expression of tight junction proteins. In this study, we investigated the relationship between oestrogen and the SHH signalling pathway using clinical data and established an experimental SAH model to explore whether oestrogen could ameliorate BBB damage after SAH through the SHH pathway. METHODS: Correlations between oestrogen and the SHH pathway were analysed by patients' cerebrospinal fluid (CSF) samples and the Genotype-Tissue Expression database (GTEx). Then, an experimental rat SAH model was established using the endovascular perforation method and treated with oestrogen, oestrogen inhibitors and SHH signalling pathway inhibitors. Then, the effects of oestrogen on BBB damage were analysed by western blot, immunofluorescence and neurobehavioural experiments. RESULTS: ESLIA detection and correlation analysis showed that oestrogen levels in patients' CSF were positively correlated with the SHH pathway, which was further verified by GTEx gene-correlation analysis. SHH was found to be mainly expressed in neurons and astrocytes in rats under physiological conditions and was upregulated by oestrogen pretreatment. In the SAH model, oestrogen pretreatment was found to reverse SAH-induced decreases in the SHH pathway, which were counteracted by oestrogen receptor inhibitors. Furthermore, oestrogen pretreatment reduced SAH-induced BBB damage, brain oedema and neurological dysfunction, which were eliminated by SHH pathway inhibitors. CONCLUSION: In conclusion, we demonstrate here that oestrogen pretreatment ameliorates brain injury after SAH, at least in part through SHH pathway-mediated BBB protection.

Galectin-9 Promotes Neuronal Restoration via Binding TLR-4 in a Rat Intracerebral Hemorrhage Model.

Intracerebral hemorrhage (ICH) is a devastating disease with high rates of mortality and morbidity. Galactose lectin-9 (Gal-9) belongs to the family of ß-galactoside-binding lectins, which has been shown to play a vital role in immune tolerance and inflammation. However, the function of Gal-9 in ICH has not been fully studied in details. Several experiments were carried out to explore the role of Gal-9 in the late period of ICH. Primarily, ICH models were established in male adult Sprague Dawley (SD) rats. Next, the relative protein levels of Gal-9 at different time points after ICH were examined and the result showed that the level of Gal-9 increased and peaked at the 7th day after ICH. Then we found that when the content of Gal-9 increased, both the number of M2-type microglia and the corresponding anti-inflammatory factors also increased. Through co-immunoprecipitation (CO-IP) analysis, it was found that Gal-9 combines with Toll-like receptor-4 (TLR-4) during the period of the recovery after ICH. TUNEL staining and Fluoro-Jade B staining (FJB) proved that the amount of cell death decreased with the increase of Gal-9 content. Additionally, several behavioral experiments also demonstrated that when the level of Gal-9 increased, the motor, sensory, learning, and memory abilities of the rats recovered better compared to the ICH group. In short, this study illustrated that Gal-9 takes a crucial role after ICH. Enhancing Gal-9 could alleviate brain injury and promote the recovery of ICH-induced injury, so that Gal-9 may exploit a new pathway for clinical treatment of ICH.

Sex-Specific Associations of Smoking with Spontaneous Subarachnoid Hemorrhage: Findings from Observational Studies.

BACKGROUND: Some studies have reported that women are at higher risk for spontaneous subarachnoid hemorrhage (SAH) compared with men, and smoking is the most important lifestyle risk factor for spontaneous SAH. However, it is still unknown whether the risk of SAH from smoking and smoking status is differential for women and men. We performed a meta-analysis to estimate the effect of smoking on SAH in women compared with men. METHODS: PubMed (January 1, 1966 to February 19, 2020) and EMBASE (January 1, 1980 to February 19, 2020) were systematically searched. Studies that estimated sex-specific relative risks (RRs) of SAH were selected. We pooled sex-specific RRs, comparing women with men using random-effects meta-analysis. RESULTS: Data from 20 observational studies that included 1,387,204 participants (563,898 women) and 7,838 SAHs (3,977 women) were analyzed. The combined women-to-men RRs of former smokers versus never smokers for SAH were 1.08 (95% confidence interval [CI] 0.62-1.89, p = 0.78). The pooled women-to-men RRs of current smokers versus never smokers were 1.39 (95% CI 1.05-1.83, p = 0.02). The combined women-to-men RRs of total smokers versus never smokers RRs were 1.15 (95% CI 0.88-1.52, p = 0.30). CONCLUSIONS: Our study shows there is not enough evidence to suggest that women who smoke have a greater risk for SAH than men; however, women who persistently smoke have a greater risk. Smoking seems to be more susceptible in the increased SAH risk in women.