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Neuroinflammation is closely associated with the poor prognosis in subarachnoid hemorrhage (SAH) patients. This study was aimed to determine the role of stimulator of IFN genes (STING), an essential regulator to innate immunity, in the context of SAH. A total of 344 male C57BL/6 J mice were subjected to endovascular perforation to develop a model of SAH. Selective STING antagonist C-176 and STING agonist CMA were administered at 30 min or 1 h post-modeling separately. To investigate the underlying mechanism, the AMPK inhibitor compound C was administered intracerebroventricularly at 30 min before surgery. Post-SAH assessments included SAH grade, neurological test, brain water content, western blotting, RT-PCR, and immunofluorescence. Oxygenated hemoglobin was introduced into BV2 cells to establish a SAH model in vitro. STING was mainly distributed in microglia, and microglial STING expression was significantly increased after SAH. Administration of C-176 substantially attenuated SAH-induced brain edema and neuronal injury. More importantly, C-176 significantly alleviated both short-term and persistent neurological dysfunction after SAH. Meanwhile, STING agonist CMA remarkably exacerbated neuronal injury and deteriorated neurological impairments. Mechanically, STING activation aggravated neuroinflammation via promoting microglial activation and polarizing into M1 phenotype, evidenced by microglial morphological changes, as well as the increased level of microglial M1 markers including IL-1β, iNOS, IL-6, TNF-α, MCP-1, and NLRP3 inflammasome, while C-176 conferred a robust anti-inflammatory effect. However, all the mentioned beneficial effects of C-176 including alleviated neuroinflammation, attenuated neuronal injury and the improved neurological function were reversed by AMPK inhibitor compound C. Meanwhile, the critical role of AMPK signal in C-176 mediated anti-inflammatory effect was also confirmed in vitro. Microglial STING yielded neuroinflammation after SAH, while pharmacologic inhibition of STING could attenuate SAH-induced inflammatory injury at least partly by activating AMPK signal. These data supported the notion that STING might be a potential therapeutic target for SAH.

Intracerebral hemorrhage (ICH) is a devastating cerebrovascular disease resulting from blood extravasating into the brain parenchyma. Escalation of erythrophagocytosis (a form of efferocytosis), avoiding the consequent release of the detrimental erythrocyte lysates, may be a promising target of ICH management. The ADAM17 inhibitor and liver X receptor (LXR) agonist could promote efficient efferocytosis and injury repair. Nevertheless, the poor bioavailability and restriction of the blood-brain barrier (BBB) hinder their application. Therefore, it is needed that biocompatible and smart nanoplatforms were designed and synthesized to realize effective therapy targeting erythrophagocytosis. We first assessed the synergistic effect of therapeutic GW280264X (an ADAM17 inhibitor) and desmosterol (an LXR agonist) on erythrophagocytosis . Then a pH-responsive neutrophil membrane-based nanoplatform (NPEOz) served as a carrier to accurately deliver therapeutic GW280264X and desmosterol to the damaged brain was prepared via co-extrusion. Afterwards, their pH-responsive performance was valued and targeting ability was assessed through fluorescence image Finally, the pro-erythrophagocytic and anti-neuroinflammatory ability of the nanomedicine and related mechanisms were investigated. After the synergistical effect of the above two drugs on erythrophagocytosis was confirmed, we successfully developed neutrophil-disguised pH-responsive nanoparticles to efficiently co-deliver them. The nanoparticles could responsively release therapeutic agents under acidic environments, and elicit favorable biocompatibility and ability of targeting injury sites. D&G@NPEOz nanoparticles enhanced erythrophagocytosis through inhibiting shedding of the efferocytotic receptors MERTK/AXL mediated by ADAM17 and accelerating ABCA-1/ABCG-1-mediated cholesterol efflux regulated by LXR respectively. In addition, the nano-formulation was able to modulate the inflammatory microenvironment by transforming efferocytes towards a therapeutic phenotype with reducing the release of proinflammatory cytokines while increasing the secretion of anti-inflammatory factors, and improve neurological function. This biomimetic nanomedicine is envisaged to offer an encouraging strategy to effectively promote hematoma and inflammation resolution, consequently alleviate ICH progression.

Background Neuroinflammation and oxidative stress plays an important role in the pathogenesis of early brain injury (EBI) after subarachnoid hemorrhage (SAH). This study is the first to show that activation of autophagy protein nuclear receptor binding factor 2 (NRBF2) could reduce endoplasmic reticulum stress (ERS)-associated inflammation and oxidative stress after SAH. Methods Male C57BL/6J mice were subjected to endovascular perforation to establish a model of SAH. NRBF2 overexpression adeno-associated virus (AAV), NRBF2 small interfering RNAs (siRNA), lysosomal inhibitor-chloroquine (CQ), and late endosome GTPase Rab7 receptor antagonist-CID1067700 (CID) were used to investigate the role of NRBF2 in EBI after SAH. Neurological tests, brain water content, western blotting and immunofluorescence staining were evaluated. Results Our study found that the level of NRBF2 was increased after SAH and peaked at 24 h after SAH. In addition, we found that the overexpression of NRBF2 significantly improved neurobehavioral scores and reduced ERS, oxidative stress, and neuroinflammation in SAH, whereas the inhibition of NRBF2 exacerbated these phenotypes. In terms of mechanism, NRBF2 overexpression significantly promoted autophagosome maturation, with the downregulation of CHOP, Romo-1, TXNIP, NLRP3, TNF-α, and IL-1β expression through interaction with Rab7. The protective effect of NRBF2 on ERS-associated neuroinflammation and oxidative stress after SAH was eliminated by treatment with CQ. Meanwhile, it was also reversed by intraperitoneal injection of CID. Moreover, the MIT domain of NRBF2 was identified as a critical binding site that interacts with Rab7 and thereby promotes autophagosome maturation. Conclusion Our data provide evidence that the autophagy protein NRBF2 has a protective effect on endoplasmic reticulum stress-associated neuroinflammation and oxidative stress by promoting autophagosome maturation through interactions with Rab7 after SAH.

Neuroinflammation is a key process in the pathogenesis of subarachnoid hemorrhage (SAH) and contributes to poor outcome in patients. The purpose of this study is to explore the effect of triggering receptor expressed on myeloid cells 1 (TREM1) in the SAH, as well as its potential mechanism. In our study, plasma levels of soluble TREM1 was increased significantly after SAH and correlated to SAH severity and serum C-reactiveprotein. TREM1 inhibitory peptide LP17 alleviated the neurological deficits, attenuated brain water content, and reduced neuronal damage after SAH. Meanwhile, TREM1 inhibitory peptide decreased neuroinflammation (evidenced by the decreased levels of markers including IL-6, IL-1β, TNF-α) by attenuating proinflammatory subtype transition of microglia (evidenced by the decreased levels of markers including CD68, CD16, CD86) and decreasing the formation of neutrophil extracellular traps (evidenced by the decreased levels of markers including CitH3, MPO, and NE). Further mechanistic study identified that TREM1 can activate downstream proinflammatory pathways through interacting with spleen tyrosine kinase (SYK). In conclusion, inhibition of TREM1 alleviates neuroinflammation by attenuating proinflammatory subtype transition of microglia and decreasing the formation of neutrophil extracellular traps through interacting with SYK after SAH. TREM1 may be a a promising therapeutic target for SAH.

Intracerebral hemorrhage (ICH), a severe stroke subtype common in the elderly, often results in high morbidity and mortality, with limited treatment options for long-term recovery. While glial scar formation is increasingly recognized as key to central nervous system (CNS) repair, its role and characteristics in the aging brain post-ICH remain unclear. This study investigated glial scar formation after ICH (100 μL autologous blood injected into the right basal ganglia model) in aged Fischer 344 rats and assessed the effects of deferoxamine (DFX) treatment. Histological and immunohistochemical analyses were conducted on days 7, 28, and 60 post-ICH using cell-specific and iron-related markers, with DFX administered at 100 mg/kg daily for 14 days in separate groups. Over time, the lesion core showed increased hemosiderin accumulation and astrogliosis. By day 60, the area of astrogliosis corresponded to an area with persistent neuronal loss (DARPP-32-negative). Glial composition shifted from microglia dominance on day 28 to astrocyte predominance by day 60. DFX treatment reduced iron deposition, astrogliosis, and DARPP-32-negative regions while enhancing oligodendrocyte presence. Iron-related markers (HO-1, ferritin, Perls’ staining) and PDGFRβ-positive fibrotic cells were concentrated in the scar core. These findings provide novel insights into scar formation after ICH in aged rats and suggest DFX as a potential therapy to improve outcomes in elderly stroke patients.

Background White matter injury (WMI) is a major neuropathological event associated with intracerebral hemorrhage (ICH). P2X purinoreceptor 4 (P2X4R) is a member of the P2X purine receptor family, which plays a crucial role in regulating WMI and neuroinflammation in central nervous system (CNS) diseases. Our study investigated the role of P2X4R in the WMI and the inflammatory response in mice, as well as the possible mechanism of action after ICH. Methods ICH was induced in mice via collagenase injection. Mice were treated with 5-BDBD and ANA-12 to inhibit P2X4R and tropomyosin-related kinase receptor B (TrkB), respectively. Immunostaining and quantitative polymerase chain reaction (qPCR) were performed to detect microglial phenotypes after the inhibition of P2X4R. Western blots (WB) and immunostaining were used to examine WMI and the underlying molecular mechanisms. Cylinder, corner turn, wire hanging, and forelimb placement tests were conducted to evaluate neurobehavioral function. Results After ICH, the protein levels of P2X4R were upregulated, especially on day 7 after ICH, and were mainly located in the microglia. The inhibition of P2X4R via 5-BDBD promoted neurofunctional recovery after ICH as well as the transformation of the pro-inflammatory microglia induced by ICH into an anti-inflammatory phenotype, and attenuated ICH-induced WMI. Furthermore, we found that TrkB blockage can reverse the protective effects of WMI as well as neuroprotection after 5-BDBD treatment. This result indicates that P2X4R plays a crucial role in regulating WMI and neuroinflammation and that P2X4R inhibition may benefit patients with ICH. Conclusions Our results demonstrated that P2X4R contributes to WMI by polarizing microglia into a pro-inflammatory phenotype after ICH. Furthermore, the inhibition of P2X4R promoted pro-inflammatory microglia polarization into an anti-inflammatory phenotype, enhanced brain-derived neurotrophic factor (BDNF) production, and through the BDNF/TrkB pathway, attenuated WMI and improved neurological function. Therefore, the regulation of P2X4R activation may be beneficial for the reducing of ICH-induced brain injury.

Background Subarachnoid hemorrhage (SAH) is an uncommon type of potentially fatal stroke. The pathophysiological mechanisms of brain injury remain unclear, which hinders the development of drugs for SAH. We aimed to investigate the pathophysiological mechanisms of SAH and to elucidate the cellular and molecular biological response to SAH-induced injury. Methods A cross-species (human and mouse) multiomics approach combining high-throughput data and bioinformatic analysis was used to explore the key pathophysiological processes and cells involved in SAH-induced brain injury. Patient data were collected from the hospital (n = 712). SAH was established in adult male mice via endovascular perforation, and flow cytometry, a bone marrow chimera model, qPCR, and microglial depletion experiments were conducted to explore the origin and chemotaxis mechanism of the immune cells. To investigate cell effects on SAH prognosis, murine neurological function was evaluated based on a modified Garcia score, pole test, and rotarod test. Results The bioinformatics analysis confirmed that inflammatory and immune responses were the key pathophysiological processes after SAH. Significant increases in the monocyte levels were observed in both the mouse brains and the peripheral blood of patients after SAH. Ly6C-high monocytes originated in the bone marrow, and the skull bone marrow contribute a higher proportion of these monocytes than neutrophils. The mRNA level of Ccl2 was significantly upregulated after SAH and was greater in CD11b-positive than CD11b-negative cells. Microglial depletion, microglial inhibition, and CCL2 blockade reduced the numbers of Ly6C-high monocytes after SAH. With CCR2 antagonization, the neurological function of the mice exhibited a slow recovery. Three days post-SAH, the monocyte-derived dendritic cell (moDC) population had a higher proportion of TNF-α-positive cells and a lower proportion of IL-10-positive cells than the macrophage population. The ratio of moDCs to macrophages was higher on day 3 than on day 5 post-SAH. Conclusions Inflammatory and immune responses are significantly involved in SAH-induced brain injury. Ly6C-high monocytes derived from the bone marrow, including the skull bone marrow, infiltrated into mouse brains via CCL2 secreted from microglia. Moreover, Ly6C-high monocytes alleviated neurological dysfunction after SAH.

AimThe complement cascade is activated and may play an important pathophysiologic role in brain injury after experimental intracerebral hemorrhage (ICH). However, the exact mechanism of specific complement components has not been well studied. This study determined the role of complement C1q/C3-CR3 signaling in brain injury after ICH in mice. The effect of minocycline on C1q/C3-CR3 signaling-induced brain damage was also examined.MethodsThere were three parts to the study. First, the natural time course of C1q and CR3 expression was determined within 7 days after ICH. Second, mice had an ICH with CR3 agonists, LA-1 or vehicle. Behavioral score, neuronal cell death, hematoma volume, and oxidative stress response were assessed at 7 days after ICH. Third, the effect of minocycline on C1q/C3-CR3 signaling and brain damage was examined.ResultsThere were increased numbers of C1q-positive and CR3-positive cells after ICH. Almost all perihematomal C1q-positive and CR3-positive cells were microglia/macrophages. CR3 agonist LA-1 aggravated neurological dysfunction, neuronal cell death, and oxidative stress response on day 7 after ICH, as well as enhancing the expression of the CD163/HO-1 pathway and accelerating hematoma resolution. Minocycline treatment exerted neuroprotective effects on brain injury following ICH, partly due to the inhibition of C1q/C3-CR3 signaling, and that could be reversed by LA-1.ConclusionsThe complement C1q/C3-CR3 signaling is upregulated after ICH. The activation of C1q/C3-CR3 signaling by LA-1 aggravates brain injury following ICH. The neuroprotection of minocycline, at least partly, is involved with the repression of the C1q/C3-CR3 signaling pathway.

Neurovascular units (NVUs) are basic functional units in the central nervous system and include neurons, astrocytes and vascular compartments. Ischemic stroke triggers not only neuronal damage, but also dissonance of intercellular crosstalk within the NVU. Stroke is sexually dimorphic, but the sex-associated differences involved in stroke-induced neurovascular dysfunction are studied in a limited extend. Preclinical studies have found that in rodent models of stroke, females have less neuronal loss, stronger repairing potential of astrocytes and more stable vascular conjunction; these properties are highly related to the cerebroprotective effects of female hormones. However, in humans, these research findings may be applicable only to premenopausal stroke patients. Women who have had a stroke usually have poorer outcomes compared to men, and because stoke is age-related, hormone replacement therapy for postmenopausal women may exacerbate stroke symptoms, which contradicts the findings of most preclinical studies. This stark contrast between clinical and laboratory findings suggests that understanding of neurovascular differences between the sexes is limited. Actually, apart from gonadal hormones, differences in neuroinflammation as well as genetics and epigenetics promote the sexual dimorphism of NVU functions. In this review, we summarize the confirmed sex-associated differences in NVUs during ischemic stroke and the possible contributing mechanisms. We also describe the gap between clinical and preclinical studies in terms of sexual dimorphism.