Targeting pyroptosis as a preventive and therapeutic approach for stroke

Overexpression of low-density lipoprotein receptor prevents neurotoxic polarization of astrocytes via inhibiting NLRP3 inflammasome activation in experimental ischemic stroke

JOURNAL/nrgr/04.03/01300535-202502000-00027/figure1/v/2024-05-28T214302Z/r/image-tiff Neurotoxic astrocytes are a promising therapeutic target for the attenuation of cerebral ischemia/reperfusion injury. Low-density lipoprotein receptor, a classic cholesterol regulatory receptor, has been found to inhibit NLR family pyrin domain containing protein 3 (NLRP3) inflammasome activation in neurons following ischemic stroke and to suppress the activation of microglia and astrocytes in individuals with Alzheimer's disease. However, little is known about the effects of low-density lipoprotein receptor on astrocytic activation in ischemic stroke. To address this issue in the present study, we examined the mechanisms by which low-density lipoprotein receptor regulates astrocytic polarization in ischemic stroke models. First, we examined low-density lipoprotein receptor expression in astrocytes via immunofluorescence staining and western blotting analysis. We observed significant downregulation of low-density lipoprotein receptor following middle cerebral artery occlusion reperfusion and oxygen-glucose deprivation/reoxygenation. Second, we induced the astrocyte-specific overexpression of low-density lipoprotein receptor using astrocyte-specific adeno-associated virus. Low-density lipoprotein receptor overexpression in astrocytes improved neurological outcomes in middle cerebral artery occlusion mice and reversed neurotoxic astrocytes to create a neuroprotective phenotype. Finally, we found that the overexpression of low-density lipoprotein receptor inhibited NLRP3 inflammasome activation in oxygen-glucose deprivation/reoxygenation injured astrocytes and that the addition of nigericin, an NLRP3 agonist, restored the neurotoxic astrocyte phenotype. These findings suggest that low-density lipoprotein receptor could inhibit the NLRP3-meidiated neurotoxic polarization of astrocytes and that increasing low-density lipoprotein receptor in astrocytes might represent a novel strategy for treating cerebral ischemic stroke.

Neutrophil extracellular traps mediate neuro-immunothrombosis

Neutrophil extracellular traps are primarily composed of DNA and histones and are released by neutrophils to promote inflammation and thrombosis when stimulated by various inflammatory reactions. Neutrophil extracellular trap formation occurs through lytic and non-lytic pathways that can be further classified by formation mechanisms. Histones, von Willebrand factor, fibrin, and many other factors participate in the interplay between inflammation and thrombosis. Neuro-immunothrombosis summarizes the intricate interplay between inflammation and thrombosis during neural development and the pathogenesis of neurological diseases, providing cutting-edge insights into post-neurotrauma thrombotic events. The blood-brain barrier defends the brain and spinal cord against external assaults, and neutrophil extracellular trap involvement in blood-brain barrier disruption and immunothrombosis contributes substantially to secondary injuries in neurological diseases. Further research is needed to understand how neutrophil extracellular traps promote blood-brain barrier disruption and immunothrombosis, but recent studies have demonstrated that neutrophil extracellular traps play a crucial role in immunothrombosis, and identified modulators of neuro-immunothrombosis. However, these neurological diseases occur in blood vessels, and the mechanisms are unclear by which neutrophil extracellular traps penetrate the blood-brain barrier to participate in immunothrombosis in traumatic brain injury. This review discusses the role of neutrophil extracellular traps in neuro-immunothrombosis and explores potential therapeutic interventions to modulate neutrophil extracellular traps that may reduce immunothrombosis and improve traumatic brain injury outcomes.

Dl-3-n-butylphthalide improves stroke outcomes after focal ischemic stroke in mouse model by inhibiting the pyroptosis-regulated cell death and ameliorating neuroinflammation

Recent studies have highlighted the involvement of pyroptosis-mediated cell death and neuroinflammation in ischemic stroke (IS) pathogenesis. DL-3-n-butylphthalide (NBP), a synthesized compound based on an extract from seeds of Apium graveolens, possesses a broad range of biological effects. However, the efficacy and the underlying mechanisms of NBP in IS remain contentious. Herein, we investigated the therapeutic effects of NBP and elucidated its potential mechanisms in neuronal cell pyroptosis and microglia inflammatory responses. Adult male mice underwent permanent distal middle cerebral artery occlusion (dMCAO), followed by daily oral gavage of NBP (80 mg/kg) for 1, 7, or 21 consecutive days. Gene Expression Omnibus (GEO) dataset of IS patients peripheral blood RNA sequencing was analyzed to identify differentially expressed pyroptosis-related genes (PRGs) during the ischemic process. Our results suggested that NBP treatment effectively alleviated brain ischemic damage, resulting in decreased neurological deficit scores, reduced infarct volume, and improved neurological and behavioral functions. RNA sequence data from human unveiled upregulated PRGs in IS. Subsequently, we observed that NBP downregulated pyroptosis-associated markers at days 7 and 21 post-modeling, at both the protein and mRNA levels. Additionally, NBP suppressed the co-localization of pyroptosis markers with neuronal cells to variable degrees and simultaneously mitigated the accumulation of activated microglia. Overall, our data provide novel evidence that NBP treatment significantly attenuates ischemic brain damage and promotes recovery of neurological function in the early and recovery phases after IS, probably by negatively regulating the pyroptosis cell death of neuronal cells and inhibiting toxic neuroinflammation in the central nervous system.

Caspase-1 deletion reveals pyroptosis participates in neural damage induced by cerebral ischemia/reperfusion in tMCAO model mice

Pyroptosis, a form of programmed cell death, drives inflammation in the context of cerebral ischemia/reperfusion. The molecular mechanism of pyroptosis underlying ischemia/reperfusion, however, is not fully understood. The transient middle cerebral artery occlusion was applied to wild-type and caspase-1 knockout mice. 2,3,5-Triphenyltetrazolium chloride-staining and immunohistochemistry were used to identify the ischemic region, and western blot and immunofluorescence for the examination of neuronal pyroptosis. The expression of inflammatory factors and the behavioral function assessments were further conducted to examine the effects of caspase-1 knockout on protection against ischemia/reperfusion injury. Ischemia/reperfusion injury increased pyroptosis-related signals represented by the overexpression of pyroptosis-related proteins including caspase-1 and gasdermin D (GSDMD). Meanwhile, the number of GSDMD positive neurons increased in penumbra by immunofluorescence staining. Compared with wild-type mice, those with caspase-1 knockout exhibited decreased levels of pyroptosis-related proteins following ischemia/reperfusion. Furthermore, ischemia/reperfusion attack-induced brain infarction, cerebral edema, inflammatory factors, and neurological outcomes were partially improved in caspase-1 knockout mice. The data indicate that pyroptosis participates in ischemia/reperfusion induced-damage, and the caspase-1 might be involved, it provides some new insights into the molecular mechanism of ischemia.

Maresin1 alleviates neuroinflammation by inhibiting caspase-3/ GSDME-mediated pyroptosis in mice cerebral ischemia-reperfusion model

OBJECTIVE

To explore the mechanism of Maresin1 in reducing cerebral ischemia-reperfusion injury.

MATERIALS AND METHODS

Male C57BL/6 mice were randomly divided (n = 5 in each group), and focal middle cerebral artery occlusion (MCAO) model was used to simulate cerebral ischemia/reperfusion injury. TTC and the Longa score were used to detect the degree of neurological deficits. Western blot was used to detect the expression levels of GSDME, GSDME-N, caspase-3 and cleaved caspase-3 in cerebral ischemic penumbra tissue, and immunofluorescence was used to detect the expression levels of GSDME-N. The mRNA expression levels of GSDME and pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α) were detected by RT-PCR.

RESULTS

Compared with sham group, GSDME mRNA levels in MCAO group were significantly increased at 12 h and 24 h after reperfusion, and GSDME and GSDME-N significantly increased at 6-48 h after reperfusion. Compared with sham group, the percentage of infarct size, the Longa score, the mRNA expression levels of IL-1β, IL-6 and TNF-α, and GSDME, GSDME-N, caspase-3 and cleaved caspase-3 in MCAO group was significantly increased. Then, the percentage of infarct size and the Longa score significantly decreased after MaR1 administration, the mRNA expression levels of IL-1β and IL-6 downregulated, and GSDME, GSDME-N, caspase-3 and cleaved caspase-3 were also reduced. After administration of Z-DEVD-FMK(ZDF), the expression of caspase-3, cleaved caspase-3 and GSDME-N was decreased, which in MCAO+MaR1+ZDF group was not statistically significant compared with MCAO+ ZDF group.

CONCLUSION

Maresin1 alleviates cerebral ischemia/reperfusion injury by inhibiting pyroptosis mediated by caspase-3/GSDME pathway and alleviating neuroinflammation.

Molecular probes for monitoring pyroptosis: design, imaging and theranostic application

Pyroptosis is a recently discovered process of programmed cell death that is linked with tumor progression and potential treatment strategies. Unlike other forms of programmed cell death, such as apoptosis or necrosis, pyroptosis is associated with pore-forming proteins gasdermin D (GSDMD), which are cleaved by caspase enzymes to form oligomers. These oligomers are then inserted into the cell surface membrane, causing pores to consequently result in rapid cell death. Pyroptosis, in conjunction with immunotherapy, represents a promising avenue for prognostication and antitumor therapy, providing a more precise direction for disease treatment. To gain deeper insight into the mechanisms underlying pyroptosis in real-time, non-invasive and live cell imaging techniques are urgently needed. Non-invasive imaging techniques can enhance future diagnostic and therapeutic approaches for inflammatory diseases, including different types of tumors. This review article discusses various non-invasive molecular probes for detecting pyroptosis, including genetic reporters and nanomaterials. These strategies can enhance scientists' understanding of pyroptosis and help discover personalized and effective ways to treat inflammatory diseases, particularly tumors.

T cell-mediated skin-brain axis: Bridging the gap between psoriasis and psychiatric comorbidities

Psoriasis, a chronic inflammatory skin condition, is often accompanied by psychiatric comorbidities such as anxiety, depression, suicidal ideation, and other mental disorders. Psychological disorders may also play a role in the development and progression of psoriasis. The intricate interplay between the skin diseases and the psychiatric comorbidities is mediated by the 'skin-brain axis'. Understanding the mechanisms underlying psoriasis and psychiatric comorbidities can help improve the efficacy of treatment by breaking the vicious cycle of diseases. T cells and related cytokines play a key role in the pathogenesis of psoriasis and psychiatric diseases, and are crucial components of the 'skin-brain axis'. Apart from damaging the blood-brain barrier (BBB) directly, T cells and secreted cytokines could interact with the hypothalamic-pituitary-adrenal axis (HPA axis) and the sympathetic nervous system (SNS) to exacerbate skin diseases or mental disorders. However, few reviews have systematically summarized the roles and mechanisms of T cells in the interaction between psoriasis and psychiatric comorbidities. In this review, we discussed several key T cells and their roles in the 'skin-brain axis', with a focus on the mechanisms underlying the interplay between psoriasis and mental commodities, to provide data that might help develop effective strategies for the treatment of both psoriasis and psychiatric comorbidities.

Therapeutic strategies targeting the NLRP3‑mediated inflammatory response and pyroptosis in cerebral ischemia/reperfusion injury (Review)

Ischemic stroke poses a major threat to human health. Therefore, the molecular mechanisms of cerebral ischemia/reperfusion injury (CIRI) need to be further clarified, and the associated treatment approaches require exploration. The NOD‑like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome serves an important role in causing CIRI, and its activation exacerbates the underlying injury. Activation of the NLRP3 inflammasome triggers the maturation and production of the inflammatory molecules IL‑1β and IL‑18, as well as gasdermin‑D‑mediated pyroptosis and CIRI damage. Thus, the NLRP3 inflammasome may be a viable target for the treatment of CIRI. In the present review, the mechanisms of the NLRP3 inflammasome in the intense inflammatory response and pyroptosis induced by CIRI are discussed, and the therapeutic strategies that target the NLRP3‑mediated inflammatory response and pyroptosis in CIRI are summarized. At present, certain drugs have already been studied, highlighting future therapeutic perspectives.

Role of pyroptosis in the pathogenesis of various neurological diseases

Pyroptosis, an inflammatory programmed cell death process, has recently garnered significant attention due to its pivotal role in various neurological diseases. This review delves into the intricate molecular signaling pathways governing pyroptosis, encompassing both caspase-1 dependent and caspase-1 independent routes, while emphasizing the critical role played by the inflammasome machinery in initiating cell death. Notably, we explore the Nucleotide-binding domain leucine-rich repeat (NLR) containing protein family, the Absent in melanoma 2-like receptor family, and the Pyrin receptor family as essential activators of pyroptosis. Additionally, we comprehensively examine the Gasdermin family, renowned for their role as executioner proteins in pyroptosis. Central to our review is the interplay between pyroptosis and various central nervous system (CNS) cell types, including astrocytes, microglia, neurons, and the blood-brain barrier (BBB). Pyroptosis emerges as a significant factor in the pathophysiology of each cell type, highlighting its far-reaching impact on neurological diseases. This review also thoroughly addresses the involvement of pyroptosis in specific neurological conditions, such as HIV infection, drug abuse-mediated pathologies, Alzheimer's disease, and Parkinson's disease. These discussions illuminate the intricate connections between pyroptosis, chronic inflammation, and cell death in the development of these disorders. We also conducted a comparative analysis, contrasting pyroptosis with other cell death mechanisms, thereby shedding light on their unique aspects. This approach helps clarify the distinct contributions of pyroptosis to neuroinflammatory processes. In conclusion, this review offers a comprehensive exploration of the role of pyroptosis in various neurological diseases, emphasizing its multifaceted molecular mechanisms within various CNS cell types. By elucidating the link between pyroptosis and chronic inflammation in the context of neurodegenerative disorders and infections, it provides valuable insights into potential therapeutic targets for mitigating these conditions.

Neutrophil extracellular traps in bacterial infections and evasion strategies

Neutrophils are innate immune cells that have a vital role in host defense systems. Neutrophil extracellular traps (NETs) are one of neutrophils' defense mechanisms against pathogens. NETs comprise an ejected lattice of chromatin associated with histones, granular proteins, and cytosolic proteins. They are thought to be an efficient strategy to capture and/or kill bacteria and received intensive research interest in the recent years. However, soon after NETs were identified, it was observed that certain bacteria were able to evade NET entrapment through many different mechanisms. Here, we outline the recent progress of NETs in bacterial infections and the strategies employed by bacteria to evade or withstand NETs. Identifying the molecules and mechanisms that modulate NET release will improve our understanding of the functions of NETs in infections and provide new avenues for the prevention and treatment of bacterial diseases.

Gasdermin D triggers cardiolipin-driven mitochondrial damage and pyroptosis

In a remarkable recent study, Miao et al. reveal that gasdermin D N-terminal (GSDMD-NT) instigates mitochondrial damage in pyroptosis by forming pores in inner and outer mitochondrial membranes (OMMs). The authors highlight the key role of mitochondrial cardiolipin in the action of GSDMD-NT, and significantly advance our understanding of this inflammatory cell death mechanism.

Discovery of a novel pyroptosis inhibitor acting though modulating glutathionylation to suppress NLRP3-related signal pathway

Pyroptosis is a proinflammatory type of regulated cell death and has been involved in many pathological processes. Inhibition of pyroptosis is thought to be a promising strategy for the treatment of related diseases. Here, we performed a phenotypic screening against NLRP3-dependent pyroptosis and obtained the novel compound N77 after structure optimization. N77 showed a half-maximal effective concentration (EC50) of 0.070 ± 0.008 μM against cell pyroptosis induced by nigericin, and exhibited a remarkable ability to prevent NLRP3-dependent inflammasome activation and the release of IL-1β. Chemical proteomics revealed the biological target of N77 to be glutathione-S-transferase Mu 1 (GSTM1); our mechanism of action studies indicated that GSTM1 might act as a negative regulator of NLRP3 inflammasome activation by modulating the glutathionylation of caspase-1. In vivo, N77 substantially alleviated the inflammatory reaction in a pyroptosis-related acute keratitis model. Overall, we identified a novel pyroptosis inhibitor and revealed a new regulatory mechanism of pyroptosis. Our findings suggest an alternative potential therapeutic strategy for pyroptosis-related diseases.

Molecular Mechanisms in Pathophysiology of Mucopolysaccharidosis and Prospects for Innovative Therapy

Mucopolysaccharidoses (MPSs) are a group of inborn errors of the metabolism caused by a deficiency in the lysosomal enzymes required to break down molecules called glycosaminoglycans (GAGs). These GAGs accumulate over time in various tissues and disrupt multiple biological systems, including catabolism of other substances, autophagy, and mitochondrial function. These pathological changes ultimately increase oxidative stress and activate innate immunity and inflammation. We have described the pathophysiology of MPS and activated inflammation in this paper, starting with accumulating the primary storage materials, GAGs. At the initial stage of GAG accumulation, affected tissues/cells are reversibly affected but progress irreversibly to: (1) disruption of substrate degradation with pathogenic changes in lysosomal function, (2) cellular dysfunction, secondary/tertiary accumulation (toxins such as GM2 or GM3 ganglioside, etc.), and inflammatory process, and (3) progressive tissue/organ damage and cell death (e.g., skeletal dysplasia, CNS impairment, etc.). For current and future treatment, several potential treatments for MPS that can penetrate the blood-brain barrier and bone have been proposed and/or are in clinical trials, including targeting peptides and molecular Trojan horses such as monoclonal antibodies attached to enzymes via receptor-mediated transport. Gene therapy trials with AAV, ex vivo LV, and Sleeping Beauty transposon system for MPS are proposed and/or underway as innovative therapeutic options. In addition, possible immunomodulatory reagents that can suppress MPS symptoms have been summarized in this review.

Mechanisms of immune response and cell death in ischemic stroke and their regulation by natural compounds

Ischemic stroke (IS), which is the third foremost cause of disability and death worldwide, has inflammation and cell death as its main pathological features. IS can lead to neuronal cell death and release factors such as damage-related molecular patterns, stimulating the immune system to release inflammatory mediators, thereby resulting in inflammation and exacerbating brain damage. Currently, there are a limited number of treatment methods for IS, which is a fact necessitating the discovery of new treatment targets. For this review, current research on inflammation and cell death in ischemic stroke was summarized. The complex roles and pathways of the principal immune cells (microglia, astrocyte, neutrophils, T lymphocytes, and monocytes/macrophage) in the immune system after IS in inflammation are discussed. The mechanisms of immune cell interactions and the cytokines involved in these interactions are summarized. Moreover, the cell death mechanisms (pyroptosis, apoptosis, necroptosis, PANoptosis, and ferroptosis) and pathways after IS are explored. Finally, a summary is provided of the mechanism of action of natural pharmacological active ingredients in the treatment of IS. Despite significant recent progress in research on IS, there remain many challenges that need to be overcome.

Neuroprotective effects of Jie-du-huo-xue decoction on microglia pyroptosis after cerebral ischemia and reperfusion--From the perspective of glial-vascular unit

ETHNOPHARMACOLOGICAL RELEVANCE

Ischemic stroke poses a serious risk to public health and quality of life. Jie-Du-Huo-Xue decoction (JDHXD) is a classical and well-known Chinese formula for stroke treatment, but the pharmacological mechanism is still unclear.

AIM OF THE STUDY

This study aims to investigate the mechanism underlying microglial pyroptosis and polarization, as well as the potential efficacy of JDHXD against cerebral ischemia-reperfusion injury (CIRI).

MATERIALS AND METHODS

Models of CIRI were established by the middle cerebral artery occlusion/reperfusion (MCAO/R) method in rats. In the first stage, 36 SD rats were randomly divided into sham group, I/R group, JDHXD-L group (5.36 g/kg/day), JDHXD-M group (10.71 g/kg/day), JDHXD-H group (21.42 g/kg/day), and positive drug edaravone group. The effectiveness of JDHXD on CIRI was confirmed by neurological function testing and cerebral infarct measuring. The best dose (JDXHD-M) was subsequently chosen to perform the tests that followed. In the second stage, 36 SD rats were randomly divided into the sham group, the I/R group, and the JDHXD-M group. Detection of nerve damage using Nissl staining, proteins of pyroptosis, Iba-1, and NeuN expressions were detected by western blotting, and proteins of microglial pyroptosis and M1/M2 phenotypic polarization were detected by immunofluorescence.

RESULTS

In rats after CIRI, JDHXD significantly reduced neurological impairment and cerebral infarction. In addition, JDHXD facilitated the M1-to-M2 transition of microglia in order to minimize neuroinflammation and improve anti-inflammatory repair. In addition, JDXHD inhibited microglial pyroptosis by blocking the cleavage of caspase-1 P10 and gasdermin D, hence reducing neuronal damage and enhancing neuronal survival following reperfusion. Interestingly, JDHXD also demonstrated a protective effect on the glial-vascular unit (GVU).

CONCLUSIONS

Our investigation demonstrated that JDHXD exerted a GVU-protective effect on CIRI rats by decreasing neuroinflammation-associated microglial pyroptosis, suppressing microglial M1 activation, and promoting microglial M2 activation.

Immunological dimensions of neuroinflammation and microglial activation: exploring innovative immunomodulatory approaches to mitigate neuroinflammatory progression

The increasing life expectancy has led to a higher incidence of age-related neurodegenerative conditions. Within this framework, neuroinflammation emerges as a significant contributing factor. It involves the activation of microglia and astrocytes, leading to the release of pro-inflammatory cytokines and chemokines and the infiltration of peripheral leukocytes into the central nervous system (CNS). These instances result in neuronal damage and neurodegeneration through activated nucleotide-binding domain and leucine-rich repeat containing (NLR) family pyrin domain containing protein 3 (NLRP3) and nuclear factor kappa B (NF-kB) pathways and decreased nuclear factor erythroid 2-related factor 2 (Nrf2) activity. Due to limited effectiveness regarding the inhibition of neuroinflammatory targets using conventional drugs, there is challenging growth in the search for innovative therapies for alleviating neuroinflammation in CNS diseases or even before their onset. Our results indicate that interventions focusing on Interleukin-Driven Immunomodulation, Chemokine (CXC) Receptor Signaling and Expression, Cold Exposure, and Fibrin-Targeted strategies significantly promise to mitigate neuroinflammatory processes. These approaches demonstrate potential anti-neuroinflammatory effects, addressing conditions such as Multiple Sclerosis, Experimental autoimmune encephalomyelitis, Parkinson's Disease, and Alzheimer's Disease. While the findings are promising, immunomodulatory therapies often face limitations due to Immune-Related Adverse Events. Therefore, the conduction of randomized clinical trials in this matter is mandatory, and will pave the way for a promising future in the development of new medicines with specific therapeutic targets.

Role of calpain-5 in cerebral ischemia and reperfusion injury

BACKGROUND

Ischemia and reperfusion (I/R) injury exacerbate the prognosis of ischemic diseases. The cause of this exacerbation is partly a mitochondrial cell death pathway. Mitochondrial calpain-5 is proteolyzed/autolyzed under endoplasmic reticulum stress, resulting in inflammatory caspase-4 activation. However, the role of calpain-5 in I/R injury remains unclear. We hypothesized that calpain-5 is involved in ischemic brain disease.

METHODS

Mitochondria from C57BL/6J mice were extracted via centrifugation with/without proteinase K treatment. The expression and proteolysis/autolysis of calpain-5 were determined using western blotting. The mouse and human brains with I/R injury were analyzed using hematoxylin and eosin staining and immunohistochemistry. HT22 cells were treated with tunicamycin and CAPN5 siRNA.

RESULTS

Calpain-5 was expressed in the mitochondria of mouse tissues. Mitochondrial calpain-5 in mouse brains was responsive to calcium earlier than cytosolic calpain-5 in vitro calcium assays and in vivo bilateral common carotid artery occlusion model mice. Immunohistochemistry revealed that neurons were positive for calpain-5 in the normal brains of mice and humans. The expression of calpain-5 was increased in reactive astrocytes at human infarction sites. The knockdown of calpain-5 suppressed of cleaved caspase-11.

CONCLUSIONS

The neurons of human and mouse brains express calpain-5, which is proteolyzed/autolyzed in the mitochondria in the early stage of I/R injury and upregulated in reactive astrocytes in the end-stage.

GENERAL SIGNIFICANCE

Our results provide a comprehensive understanding of the mechanisms underlying I/R injury. Targeting the expression or activity of mitochondrial calpain-5 may suppress the inflammation during I/R injuries such as cerebrovascular diseases.

To re-examine the intersection of microglial activation and neuroinflammation in neurodegenerative diseases from the perspective of pyroptosis

Neurodegenerative diseases (NDs), such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and motor neuron disease, are diseases characterized by neuronal damage and dysfunction. NDs are considered to be a multifactorial disease with diverse etiologies (immune, inflammatory, aging, genetic, etc.) and complex pathophysiological processes. Previous studies have found that neuroinflammation and typical microglial activation are important mechanisms of NDs, leading to neurological dysfunction and disease progression. Pyroptosis is a new mode involved in this process. As a form of programmed cell death, pyroptosis is characterized by the expansion of cells until the cell membrane bursts, resulting in the release of cell contents that activates a strong inflammatory response that promotes NDs by accelerating neuronal dysfunction and abnormal microglial activation. In this case, abnormally activated microglia release various pro-inflammatory factors, leading to the occurrence of neuroinflammation and exacerbating both microglial and neuronal pyroptosis, thus forming a vicious cycle. The recognition of the association between pyroptosis and microglia activation, as well as neuroinflammation, is of significant importance in understanding the pathogenesis of NDs and providing new targets and strategies for their prevention and treatment.

Ursolic Acid Alleviates Neuroinflammation after Intracerebral Hemorrhage by Mediating Microglial Pyroptosis via the NF-κB/NLRP3/GSDMD Pathway

The neuroinflammatory response after intracerebral hemorrhage (ICH) causes a large amount of neuronal loss, and inhibiting the inflammatory response can improve the prognosis. In previous laboratory studies and clinical trials, ursolic acid (UA) inhibited the inflammatory response, but whether it can be administered to inhibit the neuroinflammatory response after cerebral hemorrhage is unknown. The aim of this study was to investigate the effects of ursolic acid after cerebral hemorrhage. Online databases were used to obtain potential therapeutic targets of ursolic acid for the treatment of cerebral hemorrhage, and possible mechanisms were analyzed by KEGG, GO, and molecular docking. A rat model of cerebral hemorrhage was established using collagenase, and an in vitro cerebral hemorrhage model was constructed by adding hemin to BV2 cell culture medium. Enzyme-linked immunosorbent assay (ELISA), Western blotting (WB), immunofluorescence, TUNEL staining, and calcein/PI staining were used to investigate the degree of microglial M1 polarization, changes in the levels of inflammatory factors, activation of the NF-κB pathway, and changes in the indicators of cellular death after ursolic acid treatment. In addition, phorbol 12-myristate 13-acetate (PMA) was used to activate the NF-κB pathway to verify that ursolic acid exerts its anti-neuroinflammatory effects by regulating the NF-κB/NLRP3/GSDMD pathway. Network pharmacology and bioinformatics analyses revealed that ursolic acid may exert its therapeutic effects on cerebral hemorrhage through multiple pathways. Together, in vivo and in vitro experiments showed that ursolic acid inhibited microglial M1 polarization and significantly reduced the levels of p-NF-κB, GSDMD-N, cleaved caspase-1, TNF-α, IL-6, and IL-1β, which were significantly inhibited by the use of PMA. Ursolic acid inhibits microglial pyroptosis via the NF-κB/NLRP3/GSDMD pathway to alleviate neuroinflammatory responses after cerebral hemorrhage.

The NLRP3 inflammasome in viral infection (Review)

The interplay between pathogen and host determines the immune response during viral infection. The Nod‑like receptor (NLR) protein 3 inflammasome is a multiprotein complex that induces the activation of inflammatory caspases and the release of IL‑1β, which play an important role in the innate immune responses. In the present review, the mechanisms of the NLR family pyrin domain containing 3 inflammasome activation and its dysregulation in viral infection were addressed.