Reactive astrogliosis is a common response to insults to the central nervous system, but the mechanism remains unknown. In this study, we found the temporal and spatial differential expression of glial fibrillary acidic protein (GFAP) and Vimentin in the intracerebral hemorrhage (ICH) mouse brain, indicating that the de-differentiation and astroglial-mesenchymal transition (AMT) of astrocytes might be an early event in reactive astrogliosis. Further we verified the AMT finding in purified astrocyte cultures exposed to hemoglobin (Hb). Additionally, Connexin 43 (Cx43) downregulation and YAP nuclear translocation were observed in Hb-activated astrocytes. Knocking down Cx43 by siRNA triggered YAP nuclear translocation. Cx43 and YAP were physically associated as determined by immunofluorescence and co-immunoprecipitation. We propose that astrocytes undergo AMT during Hb-induced activation where Cx43 downregulation facilitates YAP nuclear translocation is a novel mechanism involved in this process. Cx43-YAP interaction may represent a potential therapeutic target for modulating astrocyte activation.

Brain metastases (BrMs) are the leading cause of death in patients with solid cancers. BrMs exhibit a highly immunosuppressive milieu and poor response to immunotherapies; however, the underlying mechanism remains largely unclear. Here, we show that upregulation of HSP47 in tumor cells drives metastatic colonization and outgrowth in the brain by creating an immunosuppressive microenvironment. HSP47-mediated collagen deposition in the metastatic niche promotes microglial polarization to the M2 phenotype via the α2β1 integrin/nuclear factor κB pathway, which upregulates the anti-inflammatory cytokines and represses CD8⁺ T cell anti-tumor responses. Depletion of microglia reverses HSP47-induced inactivation of CD8⁺ T cells and abolishes BrM. Col003, an inhibitor disrupting HSP47-collagen association restores an anti-tumor immunity and enhances the efficacy of anti-PD-L1 immunotherapy in BrM-bearing mice. Our study supports that HSP47 is a critical determinant of M2 microglial polarization and immunosuppression and that blocking the HSP47-collagen axis represents a promising therapeutic strategy against brain metastatic tumors.

Background: Intracerebral hemorrhage (ICH) is a common neurological crisis leading to high mortality and morbidity. Oxidative stress-induced secondary injury plays a critical role in neurological deterioration. Previously, we synthesized a porous [email protected]₂ nanocomposite and identified their therapeutic role in osteonecrosis of the femoral head. Whether this nanocomposite is neuroprotective remains to be elucidated. Methods: A porous [email protected]₂ nanocomposite was synthesized, and its biosafety was determined using a CCK-8 assay. The neuroprotective effect was evaluated by TUNEL staining, and intracellular ROS were detected with a DCFH-DA probe in SH-SY5Y cells exposed to hemin. Furthermore, the effect of the nanocomposite on cell apoptosis, brain edema and blood–brain barrier permeability were evaluated in a collagenase-induced ICH mouse model. The potential mechanism was also explored. Results: The results demonstrated that [email protected]₂ treatment significantly improved neurological function, increased glutathione peroxidase activity and downregulated malonaldehyde levels. The proportion of apoptotic cells, brain edema and blood–brain barrier permeability were reduced significantly in ICH mice treated with [email protected]₂ compared to vehicle-treated mice. In vitro, [email protected]₂ protected SH-SY5Y cells from hemin-induced apoptosis by preventing intracellular reactive oxygen species accumulation. Conclusion: These results suggested that the porous [email protected]₂ nanocomposite exerted neuroprotection by suppressing oxidative stress. [email protected]₂ may be a potential candidate for the clinical treatment of ICH and oxidative stress-related brain injuries.