Lipocalin-2-mediated astrocyte pyroptosis promotes neuroinflammatory injury via NLRP3 inflammasome activation in cerebral ischemia/reperfusion injury

QBT improved cognitive dysfunction in rats with vascular dementia by regulating the Nrf2/xCT/GPX4 and NLRP3/Caspase-1/GSDMD pathways to inhibit ferroptosis and pyroptosis of neurons

BACKGROUND

The novel phthalein component QBT, extracted from Ligusticum chuanxiong, shows promising biological activity against cerebrovascular diseases. This study focused on ferroptosis and pyroptosis to explore the effects of QBT on nerve injury, cognitive dysfunction, and related mechanisms in a rat model of vascular dementia (VaD).

METHODS

We established a rat model of VaD and administered QBT as a treatment. Cognitive dysfunction in VaD rats was evaluated using novel object recognition and Morris water maze tests. Neuronal damage and loss in the brain tissues of VaD rats were assessed with Nissl staining and immunofluorescence. Furthermore, we investigated the neuroprotective mechanisms of QBT by modulating the nuclear factor erythroid 2-related factor 2 (Nrf2)/cystine-glutamate antiporter (xCT)/glutathione peroxidase 4 (GPX4) and Nod-like receptor family pyrin domain-containing 3 (NLRP3)/cysteine-requiring aspartate protease-1 (Caspase-1)/Gasdermin D (GSDMD) pathways to inhibit ferroptosis and pyroptosis both in vivo and in vitro.

RESULTS

Our findings indicated that QBT significantly ameliorated neuronal damage and cognitive dysfunction in VaD rats. Additionally, QBT reversed abnormal changes associated with ferroptosis and pyroptosis in the brains of VaD rats, concurrently up-regulating the Nrf2/xCT/GPX4 pathway and down-regulating the NLRP3/Caspase-1/GSDMD pathway to inhibit ferroptosis and pyroptosis in neuronal cells, thereby exerting a neuroprotective role.

CONCLUSION

In summary, QBT effectively mitigated neuronal damage and cognitive dysfunction in VaD rats, demonstrating a neuroprotective effect by inhibiting ferroptosis and pyroptosis in neuronal cells. This study offers a novel perspective and theoretical foundation for the future development of drugs targeting VaD.

The role of LCN2 in exacerbating ferroptosis levels in acute ischemic stroke injury

Due to the complex pathogenesis of acute ischemic stroke (AIS), further investigation into its underlying mechanisms is necessary. Presently, existing literature indicates a close association between ferroptosis and AIS injury; however, the precise mechanism and molecular target of ferroptosis in AIS injury remain elusive. By RNA sequencing, we found a significant increase in LCN2 expression in the ischemic cortex. In order to investigate the potential role of LCN2 in modulating AIS injury through the regulation of ferroptosis, we utilized RNA interference (RNAi) knockdown and gene overexpression experiments. The findings from experiments conducted both in vitro and in vivo revealed a marked increase in ferroptosis levels within the AIS model group. Suppression of the LCN2 gene resulted in a significant reduction in ferroptosis levels in OGD/R cells. Conversely, upregulation of LCN2 exacerbated ferroptosis levels in OGD/R cells. The results suggest that elevated levels of ferroptosis may result from heightened expression of LCN2, thereby exacerbating ischemia/reperfusion injury. This study indicates the involvement of ferroptosis in the pathogenesis of AIS and highlights LCN2 as a regulator of ferroptosis in AIS-induced injury, suggesting a potential therapeutic target for ischemic stroke.

Pre-electroacupuncture Ameliorates Cerebral Ischemia-reperfusion Injury by Inhibiting Microglial RhoA/pyrin/GSDMD Signaling Pathway

Cerebral ischemia reperfusion injury is a severe neurological impairment that occurs after blood flow reconstruction in stroke, and microglia cell pyroptosis is one of its important mechanisms. Electroacupuncture has been shown to be effective in mitigating and alleviating cerebral ischemia reperfusion injury by inhibiting neuroinflammation, reducing cellular pyroptosis, and improving neurological function. In this experiment, we divided the rats into three groups, including the sham operation (Sham) group, the middle cerebral artery occlusion/reperfusion (MCAO/R) group, and the pre-electroacupuncture (EAC) group. Pre-electroacupuncture group was stimulated with electroacupuncture of a certain intensity on the Baihui (GV 20) and Dazhui (GV 14) of the rat once a day from the 7th day to the 1st day before the MCAO/R operation. The extent of cerebral infarction was detected by TTC staining. A modified Zea-Longa five-point scale scoring system was used to determine neurologic function in MCAO rats. The number of neurons and morphological changes were accessed by Nissl staining and HE staining. The cellular damage was detected by TUNEL staining. In addition, the expression levels of RhoA, pyrin, GSDMD, Caspase1, cleaved-Caspase1, Iba-1, CD206, and ROCK2 were examined by western blotting and immunofluorescence. The results found that pre-electroacupuncture significantly attenuated neurological impairment and cerebral infarction compared to the post-MCAO/R rats. In addition, pre-electroacupuncture therapy promoted polarization of microglia to the neuroprotective (M2) phenotype. In addition, pre-electroacupuncture inhibited microglia pyroptosis by inhibiting RhoA/pyrin/GSDMD signaling pathway, thereby reducing neuronal injury and increasing neuronal survival in the MCAO/R rats. Taken together, these results demonstrated that pre-acupuncture could attenuate cerebral ischemia-reperfusion injury by inhibiting microglial pyroptosis. Therefore, pre-electroacupuncture might be a potential preventive strategy for ischemic stroke patients.

Resveratrol Ameliorates Retinal Ischemia-Reperfusion Injury by Modulating the NLRP3 Inflammasome and Keap1/Nrf2/HO-1 Signaling Pathway

Glaucoma, as an ischemia-reperfusion (I/R) injury disease, leading irreversible blindness through the loss of retinal ganglion cells (RGCs), mediated by various pathways. Resveratrol (Res) is a polyphenolic compound that exerts protective effects against I/R injury in many tissues. This article aimed to expound the underlying mechanisms through which Res protects RGCs and reduces visual dysfunction in vivo. An experimental glaucoma model was created using 6-8-week wild-type male C57BL/6J mice. Res was injected intraperitoneally for 5 days. The mice were then grouped according to the number of days after surgery and whether Res treatment was administered. We applied the Brn3a-labeled immunofluorescence staining and flash electroretinography (ERG) to assess the survival of RGCs and visual function. The expression of components of the NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome, the interleukin-1-beta (IL-1β), and vital indicators of kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2)/heme-oxygenase 1 (HO-1) pathway at the protein and RNA levels were detected respectively. The survival of RGCs was reduced after surgery compared to controls, whereas Res application rescued RGCs and improved visual dysfunction. In conclusion, our results discovered that Res administration showed neuroprotective effects through inhibition of the NLRP3 inflammasome pathway and activation of Keap1/Nrf2/HO-1 pathway. Thus, we further elucidated the potential of Res in glaucoma therapy.

Lipocalin-2-mediated intestinal epithelial cells pyroptosis via NF-κB/NLRP3/GSDMD signaling axis adversely affects inflammation in colitis

Ulcerative colitis (UC) is a major inflammatory bowel disease (IBD) characterized by intestinal epithelium damage. Recently, Lipocalin-2 (LCN2) has been identified as a potential fecal biomarker for patients with UC. However, further investigation is required to explore its pro-inflammatory role in UC and the underlying mechanism. The biological analysis revealed that Lcn2 serves as a putative signature gene in the colon mucosa of patients with UC and its association with the capsase/pyroptosis signaling pathway in UC. In wild-type mice with DSS-induced colitis, LCN2 overexpression in colon mucosa via in vivo administration of Lcn2 overexpression plasmid resulted in exacerbation of colitis symptoms and epithelium damage, as well as increased expression levels of pyroptosis markers (cleaved caspase1, GSDMD, IL-1β, HMGB1 and IL-18). Additionally, we observed downregulation in the expression levels of pyroptosis markers following in vivo silencing of LCN2. However, the pro-inflammatory effect of LCN2 overexpression was effectively restrained in GSDMD-KO mice. Moreover, single-cell RNA-sequencing analysis revealed that Lcn2 was predominantly expressed in the intestinal epithelial cells (IECs) within the colon mucosa of patients with UC. We found that LCN2 effectively regulated pyroptosis events by modulating the NF-κB/NLRP3/GSDMD signaling axis in NCM460 cells stimulated by LPS and ATP. These findings demonstrate the pro-inflammatory role of LCN2 in colon epithelium and provide a potential target for inhibiting pyroptosis in UC.

Lipocalin-2 aggravates blood-brain barrier dysfunction after intravenous thrombolysis by promoting endothelial cell ferroptosis via regulating the HMGB1/Nrf2/HO-1 pathway

BACKGROUND

Disruption of the blood-brain barrier (BBB) is a major contributor to hemorrhagic transformation (HT) in patients with acute ischemic stroke (AIS) following intravenous thrombolysis (IVT). However, the clinical therapies aimed at BBB protection after IVT remain limited.

METHODS

One hundred patients with AIS who underwent IVT were enrolled (42 with HT and 58 without HT 24 h after IVT). Based on the cytokine chip, the serum levels of several AIS-related proteins, including LCN2, ferritin, matrix metalloproteinase-3, vascular endothelial-derived growth factor, and X-linked inhibitor of apoptosis, were detected upon admission, and their associations with HT were analyzed. After finding that LCN2 was related to HT in patients with IVT, we clarified whether the modulation of LCN2 influenced BBB dysfunction and HT after thrombolysis and investigated the potential mechanism.

RESULTS

In patients with AIS following IVT, logistic regression analysis showed that baseline serum LCN2 (p = 0.023) and ferritin (p = 0.046) levels were independently associated with HT. A positive correlation between serum LCN2 and ferritin levels was identified in patients with HT. In experimental studies, recombinant LCN2 (rLCN2) significantly aggravated BBB dysfunction and HT in the thromboembolic stroke rats after thrombolysis, whereas LCN2 inhibition by ZINC006440089 exerted opposite effects. Further mechanistic studies showed that, LCN2 promoted endothelial cell ferroptosis, accompanied by the induction of high mobility group box 1 (HMGB1) and the inhibition of nuclear translocation of nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) proteins. Ferroptosis inhibitor ferrostatin-1 (fer-1) significantly restricted the LCN2-mediated BBB disruption. Transfection of LCN2 and HMGB1 siRNA inhibited the endothelial cell ferroptosis, and this effects was reversed by Nrf2 siRNA.

CONCLUSION

LCN2 aggravated BBB disruption after thrombolysis by promoting endothelial cell ferroptosis via regulating the HMGB1/Nrf2/HO-1 pathway, this may provide a promising therapeutic target for the prevention of HT after IVT.

SIRT6 modulates lesion microenvironment in LPC induced demyelination by targeting astrocytic CHI3L1

Demyelination occurs widely in the central nervous system (CNS) neurodegenerative diseases, especially the multiple sclerosis (MS), which with a complex and inflammatory lesion microenvironment inhibiting remyelination. Sirtuin6 (SIRT6), a histone/protein deacetylase is of interest for its promising effect in transcriptional regulation, cell cycling, inflammation, metabolism and longevity. Here we show that SIRT6 participates in the remyelination process in mice subjected to LPC-induced demyelination. Using pharmacological SIRT6 inhibitor or activator, we found that SIRT6 modulated LPC-induced damage in motor or cognitive function. Inhibition of SIRT6 impaired myelin regeneration, exacerbated neurological deficits, and decreased oligodendrocyte precursor cells (OPCs) proliferation and differentiation, whereas activation of SIRT6 reversed behavioral performance in mice, demonstrating a beneficial effect of SIRT6. Importantly, based on RNA sequencing analysis of the corpus callosum tissues, it was further revealed that SIRT6 took charge in regulation of glial activation during remyelination, and significant alterations in CHI3L1 were obtained, a glycoprotein specifically secreted by astrocytes. Impaired proliferation and differentiation of OPCs could be induced in vitro using supernatants from reactive astrocyte, especially when SIRT6 was inhibited. Mechanistically, SIRT6 regulates the secretion of CHI3L1 from reactive astrocytes by histone-H3-lysine-9 acetylation (H3K9Ac). Adeno-associated virus-overexpression of SIRT6 (AAV-SIRT6-OE) in astrocytes improved remyelination and functional recovery after LPC-induced demyelination, whereas together with AAV-CHI3L1-OE inhibits this therapeutic effect. Collectively, our data elucidate the role of SIRT6 in remyelination and further reveal astrocytic SIRT6/CHI3L1 as the key regulator for improving the remyelination environment, which may be a potential target for MS therapy.

MCC950 as a promising candidate for blocking NLRP3 inflammasome activation: A review of preclinical research and future directions

The NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome is a key component of the innate immune system that triggers inflammation and pyroptosis and contributes to the development of several diseases. Therefore, blocking the activation of the NLRP3 inflammasome has therapeutic potential for the treatment of these diseases. MCC950, a selective small molecule inhibitor, has emerged as a promising candidate for blocking NLRP3 inflammasome activation. Ongoing research is focused on elucidating the specific targets of MCC950 as well as assessfing its metabolism and safety profile. This review discusses the diseases that have been studied in relation to MCC950, with a focus on stroke, Alzheimer's disease, liver injury, atherosclerosis, diabetes mellitus, and sepsis, using bibliometric analysis. It then summarizes the potential pharmacological targets of MCC950 and discusses its toxicity. Furthermore, it traces the progression from preclinical to clinical research for the treatment of these diseases. Overall, this review provides a solid foundation for the clinical therapeutic potential of MCC950 and offers insights for future research and therapeutic approaches.

Gandouling Regulates Ferroptosis and Improves Neuroinflammation in Wilson's Disease Through the LCN2/NLRP3 Signaling Pathway

Purpose

Neuroinflammation is a main cause of neurological damage in Wilson's disease (WD). Ferroptosis is present in the WD pathological process, which is also closely related to the neuroinflammation. LCN2, a ferroptosis-related gene in WD, is linked with the activation of NLRP3 inflammasome. Our group has previously demonstrated that Gandouling (GDL) can effectively improve neuroinflammation in WD. This study aims to investigate the protective effect of GDL on neuroinflammation in animal and cell models of WD, and whether the pharmacological mechanism is related to the LCN2/NLRP3 signaling pathway.

Methods

Toxic milk (TX) mice and HT22 cells stimulated by copper ions were selected as models. The pathology of hippocampal tissues in TX mice were observed by HE staining and transmission electron microscopy. High-throughput sequencing analysis was conducted to screen ferroptosis-related genes in WD. The expression of LCN2 and GPX4 in hippocampus of TX mice were detected by immunohistochemical. The expression of LCN2, NLRP3, GPX4, and SLC7A11 was determined in TX mice and HT22 cells by Western blotting and RT-qPCR. The levels of Fe2+, inflammatory factor indicators TNF-α, IL-1β and IL-6 and oxidative stress indicators 4-HNE, MAD, SOD, GSH and ROS were detected in each group by ELISA.

Results

The results showed that GDL ameliorated pathological and mitochondrial damages in hippocampus of TX mice. The analysis of bioinformatics showed that LCN2 was a differential gene associated with ferroptosis in WD. The results of Western blotting and RT-qPCR indicated that GDL reduced the expression of LCN2 and NLRP3, and enhanced the expression of GPX4 and SLC711 in TX mice and HT22 cells. The ELISA results showed that GDL decreased the expression of Fe2+ and inflammatory factors TNF-α, IL-1β and IL-6 in TX mice with ferroptosis inducer intervention and copper ion-loaded HT22 cells. GDL decreased the expression of oxidative stress indicators ROS, 4-HNE and MDA, and increased the expression of oxidative stress indicators GSH and SOD in TX mice and copper ion-loaded HT22 cells.

Conclusion

GDL has anti-inflammatory and antioxidant effects. LCN2 is a differential gene associated with ferroptosis in WD. GDL may alleviate ferroptosis by inhibiting the LCN2/NLPR3 signaling pathway, thereby improving neuroinflammatory responses and exerting neuroprotective effects in WD.

Lipocalin-2 promotes breast cancer brain metastasis by enhancing tumor invasion and modulating brain microenvironment

Breast cancer is the leading cancer diagnosed in women globally, with brain metastasis emerging as a major cause of death, particularly in human epidermal growth factor receptor 2 positive and triple-negative breast cancer subtypes. Comprehensive understanding of the molecular foundations of central nervous system metastases is imperative for the evolution of efficacious treatment strategies. Lipocalin-2 (LCN2), a secreted iron transport protein with multiple functions, has been linked to the progression of breast cancer brain metastasis (BCBM). In primary tumors, LCN2 promotes the proliferation and angiogenesis of breast cancer cells, triggers the epithelial-mesenchymal transition, interacts with matrix metalloproteinase-9, thereby facilitating the reorganization of the extracellular matrix and enhancing cancer cell invasion and migration. In brain microenvironment, LCN2 undermines the blood-brain barrier and facilitates tumor seeding in the brain by modulating the behavior of key cellular components. In summary, this review meticulously examines the fuel role of LCN2 in BCBM cascade, and investigates the potential mechanisms involved. It highlights the potential of LCN2 as both a therapeutic target and biomarker, indicating that interventions targeting LCN2 may offer improved outcomes for patients afflicted with BCBM.

Effect of dexmedetomidine on ncRNA and mRNA profiles of cerebral ischemia-reperfusion injury in transient middle cerebral artery occlusion rats model

Ischemic stroke poses a significant global health burden, with rapid revascularization treatments being crucial but often insufficient to mitigate ischemia-reperfusion (I/R) injury. Dexmedetomidine (DEX) has shown promise in reducing cerebral I/R injury, but its potential molecular mechanism, particularly its interaction with non-coding RNAs (ncRNAs), remains unclear. This study investigates DEX's therapeutic effect and potential molecular mechanisms in reducing cerebral I/R injury. A transient middle cerebral artery obstruction (tMACO) model was established to simulate cerebral I/R injury in adult rats. DEX was administered pre-ischemia and post-reperfusion. RNA sequencing and bioinformatic analyses were performed on the ischemic cerebral cortex to identify differentially expressed non-coding RNAs (ncRNAs) and mRNAs. The sequencing results showed 6,494 differentially expressed (DE) mRNA and 2698 DE circRNA between the sham and tMCAO (I/R) groups. Additionally, 1809 DE lncRNA, 763 DE mRNA, and 2795 DE circRNA were identified between the I/R group and tMCAO + DEX (I/R + DEX) groups. Gene ontology (GO) analysis indicated significant enrichment in multicellular biogenesis, plasma membrane components, and protein binding. KEGG analysis further highlighted the potential mechanism of DEX action in reducing cerebral I/R injury, with hub genes involved in inflammatory pathways. This study demonstrates DEX's efficacy in reducing cerebral I/R injury and offers insights into its brain-protective effects, especially in ischemic stroke. Further research is warranted to fully understand DEX's neuroprotective mechanisms and its clinical applications.

Astrocyte modulation in cerebral ischemia-reperfusion injury: A promising therapeutic strategy

Cerebral ischemia-reperfusion injury (CIRI) poses significant challenges for drug development due to its complex pathogenesis. Astrocyte involvement in CIRI pathogenesis has led to the development of novel astrocyte-targeting drug strategies. To comprehensively review the current literature, we conducted a thorough analysis from January 2012 to December 2023, identifying 82 drugs aimed at preventing and treating CIRI. These drugs target astrocytes to exert potential benefits in CIRI, and their primary actions include modulation of relevant signaling pathways to inhibit neuroinflammation and oxidative stress, reduce cerebral edema, restore blood-brain barrier integrity, suppress excitotoxicity, and regulate autophagy. Notably, active components from traditional Chinese medicines (TCM) such as Salvia miltiorrhiza, Ginkgo, and Ginseng exhibit these important pharmacological properties and show promise in the treatment of CIRI. This review highlights the potential of astrocyte-targeted drugs to ameliorate CIRI and categorizes them based on their mechanisms of action, underscoring their therapeutic potential in targeting astrocytes.

A2 reactive astrocyte-derived exosomes alleviate cerebral ischemia-reperfusion injury by delivering miR-628

Ischemia and hypoxia activate astrocytes into reactive types A1 and A2, which play roles in damage and protection, respectively. However, the function and mechanism of A1 and A2 astrocyte exosomes are unknown. After astrocyte exosomes were injected into the lateral ventricle, infarct volume, damage to the blood-brain barrier (BBB), apoptosis and the expression of microglia-related proteins were measured. The dual luciferase reporter assay was used to detect the target genes of miR-628, and overexpressing A2-Exos overexpressed and knocked down miR-628 were constructed. qRT-PCR, western blotting and immunofluorescence staining were subsequently performed. A2-Exos obviously reduced the infarct volume, damage to the BBB and apoptosis and promoted M2 microglial polarization. RT-PCR showed that miR-628 was highly expressed in A2-Exos. Dual luciferase reporter assays revealed that NLRP3, S1PR3 and IRF5 are target genes of miR-628. After miR-628 was overexpressed or knocked down, the protective effects of A2-Exos increased or decreased, respectively. A2-Exos reduced pyroptosis and BBB damage and promoted M2 microglial polarization through the inhibition of NLRP3, S1PR3 and IRF5 via the delivery of miR-628. This study explored the mechanism of action of A2-Exos and provided new therapeutic targets and concepts for treating cerebral ischemia.

Lipocalin-2 as a mediator of neuroimmune communication

Lipocalin-2, a neutrophil gelatinase-associated lipocalin, is a 25-kDa secreted protein implicated in a broad range of inflammatory diseases affecting the brain and periphery. It is a pleotropic protein expressed by various immune and nonimmune cells throughout the body. Importantly, the surge in lipocalin-2 levels in disease states has been associated with a myriad of undesirable effects, further exacerbating the ongoing pathological processes. In the brain, glial cells are the principal source of lipocalin-2, which plays a definitive role in determining their functional phenotypes. In different central nervous system pathologies, an increased expression of glial lipocalin-2 has been linked to neurotoxicity. Lipocalin-2 mediates a crosstalk between central and peripheral immune cells under neuroinflammatory conditions. One intriguing aspect is that elevated lipocalin-2 levels in peripheral disorders, such as cancer, metabolic conditions, and liver diseases, potentially incite an inflammatory activation of glial cells while disrupting neuronal functions. This review comprehensively summarizes the influence of lipocalin-2 on the exacerbation of neuroinflammation by regulating various cellular processes. Additionally, this review explores lipocalin-2 as a mediator of neuroimmune crosstalk in various central nervous system pathologies and highlights the role of lipocalin-2 in carrying inflammatory signals along the neuroimmune axis.

Molecular Changes in the Ischemic Brain as Non-Invasive Brain Stimulation Targets-TMS and tDCS Mechanisms, Therapeutic Challenges, and Combination Therapies

Ischemic stroke is one of the leading causes of death and disability. As the currently used neurorehabilitation methods present several limitations, the ongoing research focuses on the use of non-invasive brain stimulation (NIBS) techniques such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS). NIBS methods were demonstrated to modulate neural excitability and improve motor and cognitive functioning in neurodegenerative diseases. However, their mechanisms of action are not fully elucidated, and the clinical outcomes are often unpredictable. This review explores the molecular processes underlying the effects of TMS and tDCS in stroke rehabilitation, including oxidative stress reduction, cell death, stimulation of neurogenesis, and neuroprotective phenotypes of glial cells. A highlight is put on the newly emerging therapeutic targets, such as ferroptotic and pyroptotic pathways. In addition, the issue of interindividual variability is discussed, and the role of neuroimaging techniques is investigated to get closer to personalized medicine. Furthermore, translational challenges of NIBS techniques are analyzed, and limitations of current clinical trials are investigated. The paper concludes with suggestions for further neurorehabilitation stroke treatment, putting the focus on combination and personalized therapies, as well as novel protocols of brain stimulation techniques.

Aberrant activation of hippocampal astrocytes causes neuroinflammation and cognitive decline in mice

Reactive astrocytes are associated with neuroinflammation and cognitive decline in diverse neuropathologies; however, the underlying mechanisms are unclear. We used optogenetic and chemogenetic tools to identify the crucial roles of the hippocampal CA1 astrocytes in cognitive decline. Our results showed that repeated optogenetic stimulation of the hippocampal CA1 astrocytes induced cognitive impairment in mice and decreased synaptic long-term potentiation (LTP), which was accompanied by the appearance of inflammatory astrocytes. Mechanistic studies conducted using knockout animal models and hippocampal neuronal cultures showed that lipocalin-2 (LCN2), derived from reactive astrocytes, mediated neuroinflammation and induced cognitive impairment by decreasing the LTP through the reduction of neuronal NMDA receptors. Sustained chemogenetic stimulation of hippocampal astrocytes provided similar results. Conversely, these phenomena were attenuated by a metabolic inhibitor of astrocytes. Fiber photometry using GCaMP revealed a high level of hippocampal astrocyte activation in the neuroinflammation model. Our findings suggest that reactive astrocytes in the hippocampus are sufficient and required to induce cognitive decline through LCN2 release and synaptic modulation. This abnormal glial-neuron interaction may contribute to the pathogenesis of cognitive disturbances in neuroinflammation-associated brain conditions.

Toll-Like Receptor 9 Aggravates Pulmonary Fibrosis by Promoting NLRP3-Mediated Pyroptosis of Alveolar Epithelial Cells

The apoptosis-prone property of alveolar epithelial cells plays a crucial role in pulmonary fibrosis(PF), but the role of pyroptosis in it is still unclear. Toll-like receptor 9(TLR9) has been reported to play a vital role in the pathogenesis of many diseases. However, the effect of TLR9 on alveolar epithelial cells in PF has not been fully elucidated. Gene expression microarray related to Idiopathic pulmonary fibrosis(IPF) was obtained from the Gene Expression Omnibus(GEO) database. In the mouse model of bleomycin-induced PF, adeno-associated virus(AAV6) was used to interfere with TLR9 to construct TLR9 knockdown mice to study the role of TLR9 in PF, and the specific mechanism was studied by intratracheal instillation of NLR family pyrin domain containing 3(NLRP3) activator. In vitro experiments were performed using A549 cells. Bleomycin-induced pyroptosis in the lung tissue of PF mice increased, and TLR9 protein levels also increased, especially in alveolar epithelial cells. The levels of fibrosis and pyroptosis in lung tissue of TLR9 knockdown mice were improved. We found that TLR9 can bind to the NLRP3, thereby increasing the activation of the NLRP3/caspase-1 inflammasome pathway. When we use the NLRP3 activator, the levels of fibrosis and pyroptosis in lung tissue of TLR9 knockout mice can be counteracted. Pyroptosis of alveolar epithelial cells plays a vital role in PF, and TLR9 can promote NLRP3-mediated pyroptosis of alveolar epithelial cells to aggravate the progression of PF and may become a feasible target for the prevention and treatment of PF.

The interaction of lipocalin-2 and astrocytes in neuroinflammation: mechanisms and therapeutic application

Neuroinflammation is a common pathological process in various neurological disorders, including stroke, Alzheimer's disease, Parkinson's disease, and others. It involves the activation of glial cells, particularly astrocytes, and the release of inflammatory mediators. Lipocalin-2 (Lcn-2) is a secretory protein mainly secreted by activated astrocytes, which can affect neuroinflammation through various pathways. It can also act as a pro-inflammatory factor by modulating astrocyte activation and polarization through different signaling pathways, such as NF-κB, and JAK-STAT, amplifying the inflammatory response and aggravating neural injury. Consequently, Lcn-2 and astrocytes may be potential therapeutic targets for neuroinflammation and related diseases. This review summarizes the current knowledge on the role mechanisms, interactions, and therapeutic implications of Lcn-2 and astrocytes in neuroinflammation.

Influence of the brain‑gut axis on neuroinflammation in cerebral ischemia‑reperfusion injury (Review)

Stroke, a debilitating cerebrovascular ailment, poses significant threats to human life and health. The intricate interplay between the gut‑brain‑microbiota axis (GBMA) and cerebral ischemia‑reperfusion has increasingly become a focal point of scientific exploration, emerging as a pivotal research avenue in stroke pathophysiology. In the present review, the authors delved into the nexus between the GBMA and neuroinflammation observed post‑stroke. The analysis underscored the pivotal roles of histone deacetylase 3 and neutrophil extracellular traps subsequent to stroke incidents. The influence of gut microbial compositions and their metabolites, notably short‑chain fatty acids and trimethylamine N‑oxide, on neuroinflammatory processes, was further elucidated. The involvement of immune cells, especially regulatory T‑cells, and the intricate signaling cascades including cyclic GMP‑AMP synthase/stimulator of interferon genes/Toll‑like receptor, further emphasized the complex regulatory mechanisms of GBMA in cerebral ischemia/reperfusion injury (CI/RI). Collectively, the present review offered a comprehensive perspective on the metabolic, immune and inflammatory modulations orchestrated by GBMA, augmenting the understanding of its role in neuroinflammation following CI/RI.

Therapeutic gene delivery by mesenchymal stem cell for brain ischemia damage: Focus on molecular mechanisms in ischemic stroke

Cerebral ischemic damage is prevalent and the second highest cause of death globally across patient populations; it is as a substantial reason of morbidity and mortality. Mesenchymal stromal cells (MSCs) have garnered significant interest as a potential treatment for cerebral ischemic damage, as shown in ischemic stroke, because of their potent intrinsic features, which include self-regeneration, immunomodulation, and multi-potency. Additionally, MSCs are easily obtained, isolated, and cultured. Despite this, there are a number of obstacles that hinder the effectiveness of MSC-based treatment, such as adverse microenvironmental conditions both in vivo and in vitro. To overcome these obstacles, the naïve MSC has undergone a number of modification processes to enhance its innate therapeutic qualities. Genetic modification and preconditioning modification (with medications, growth factors, and other substances) are the two main categories into which these modification techniques can be separated. This field has advanced significantly and is still attracting attention and innovation. We examine these cutting-edge methods for preserving and even improving the natural biological functions and therapeutic potential of MSCs in relation to adhesion, migration, homing to the target site, survival, and delayed premature senescence. We address the use of genetically altered MSC in stroke-induced damage. Future strategies for improving the therapeutic result and addressing the difficulties associated with MSC modification are also discussed.

AIM2 inflammasome: A potential therapeutic target in ischemic stroke

Ischemic stroke (IS) is a significant global public health issue with a high incidence, disability, and mortality rate. A robust inflammatory cascade with complex and wide-ranging mechanisms occurs following ischemic brain injury. Inflammasomes are multiprotein complexes in the cytoplasm that modulate the inflammatory response by releasing pro-inflammatory cytokines and inducing cellular pyroptosis. Among these inflammasomes, the Absent in Melanoma 2 (AIM2) inflammasome shows the ability to detect a wide range of pathogen DNAs, thereby triggering an inflammatory response. Recent studies have indicated that the aberrant expression of AIM2 inflammasome in various cells is closely associated with the pathological processes of ischemic brain injury. This paper summarizes the expression and regulatory role of AIM2 in CNS and peripheral immune cells and discusses current therapeutic approaches targeting AIM2 inflammasome. These findings aim to serve as a reference for future research in this field.

Cenicriviroc prevents dysregulation of astrocyte/endothelial cross talk induced by ischemia and HIV-1 via inhibiting the NLRP3 inflammasome and pyroptosis

Blood-brain barrier (BBB) breakdown is one of the pathophysiological characteristics of ischemic stroke, which may contribute to the progression of brain tissue damage and subsequent neurological impairment. Human immunodeficiency virus (HIV)-infected individuals are at greater risk for ischemic stroke due to diminished immune function and HIV-associated vasculopathy. Studies have shown that astrocytes are involved in maintaining BBB integrity and facilitating HIV-1 infection in the brain. The present study investigated whether targeting astrocyte-endothelial cell signaling with cenicriviroc (CVC), a dual chemokine receptor (CCR)2 and CCR5 antagonist, may protect against dysregulation of cross talk between these cells after oxygen-glucose deprivation/reoxygenation (OGD/R) combined with HIV-1 infection. Permeability assay with 10 kDa fluorescein isothiocyanate (FITC)-dextran demonstrated that CVC alleviated endothelial barrier disruption in noncontact coculture of human brain microvascular endothelial cells (HBMECs) with HIV-1-infected human astrocytes, and reversed downregulation of tight junction protein claudin-5 induced by OGD/R- and HIV-1. Moreover, CVC attenuated OGD/R- and HIV-1-triggered upregulation of the NOD-like receptor protein-3 (NLRP3) inflammasome and IL-1β secretion. Treatment with CVC also suppressed astrocyte pyroptosis by attenuating cleaved caspase-1 levels and the formation of cleaved N-terminal GSDMD (N-GSDMD). Secretome profiling revealed that CVC ameliorated secretion levels of chemokine CC chemokine ligand 17 (CCL17), adhesion molecule intercellular adhesion molecule-1 (ICAM-1), and T cell activation modulator T cell immunoglobulin and mucin domain 3 (TIM-3) by astrocytes synergistically induced by OGD/R and HIV-1. Overall, these results suggest that CVC contributes to restoring astrocyte-endothelial cross interactions in an astrocyte-dependent manner via protection against NLRP3 activation and pyroptosis.NEW & NOTEWORTHY The present study reveals the role of astrocytic NOD-like receptor protein-3 (NLRP3) inflammasome in dysfunctional astrocyte-endothelial cross interactions triggered in response to oxygen/glucose deprivation injury associated with human immunodeficiency virus type 1 (HIV-1) infection. Our results suggest that blocking NLRP3 inflammasome activation and pyroptosis-mediated inflammation with cenicriviroc (CVC) may constitute a potentially effective therapeutic strategy for blood-brain barrier (BBB) protection during HIV-1-associated ischemic stroke.

Knockdown of LCN2 Attenuates Brain Injury After Intracerebral Hemorrhage via Suppressing Pyroptosis

Objective

The aims of this study are to screen novel differentially expressed genes (DEGs) for intracerebral hemorrhage (ICH) and reveal the role of Lipocalin-2 (LCN2) in ICH.

Methods

We constructed the ICH model by injection of autologous whole blood into the right basal ganglia in rats. RNA-sequencing and bioinformatics analyses were performed to identify the DEGs between ICH and sham rats, and some important ones were confirmed using quantitative real-time PCR (qRT-PCR). LCN shRNA was used to knockdown of LCN2 in ICH rats. Pathological examination was carried out using 2,3,5-triphenyltetrazolium chloride (TTC) staining and Hematoxylin-eosin (HE) staining. Immunohistochemistry detected Caspase-3, and co-staining of Terminal dUTP nick end labeling (TUNEL) and NEUN staining were performed for neuron apoptosis assessment. Western blot analysis was performed to quantify pyroptosis-related proteins. Enzyme-linked immunosorbent assay (ELISA) was used to measure inflammatory cytokine levels.

Results

ICH rats exhibited significant hematomas, higher brain water content, obvious interstitial edema, and inflammatory infiltration, as well as more apoptotic cells in brain tissues. RNA-seq analysis identified 103 upregulated and 81 downregulated DEGs. The expression of LCN2, HSPB1, CXCL10, and MEF2B were upregulated in ICH rats. ICH triggered the release of interleukin (IL)-1β, tumor necrosis factor-α (TNF-α), and IL-18, and promoted the expression of pyroptosis-related proteins Caspase-1, GSDMD, NLRP3, and ASC. LCN2 knockdown attenuated the pathological characteristics of ICH, and also reduced pyroptosis in brain tissues.

Conclusion

Inhibition of LCN2 attenuates brain injury after ICH via suppressing pyroptosis, which provide guidance for ICH management.