Activation and Regulation of NLRP3 Inflammasome by Intrathecal Application of SDF-1a in a Spinal Cord Injury Model

Carvedilol attenuates inflammatory reactions of lipopolysaccharide-stimulated BV2 cells and modulates M1/M2 polarization of microglia via regulating NLRP3, Notch, and PPAR-γ signaling pathways

Microglial cells coordinate immune responses in the central nervous system. Carvedilol (CVL) is a non-selective β-blocker with anti-inflammatory and anti-oxidant effects. This study aims to investigate the anti-inflammatory effects and the underlying mechanisms of CVL on lipopolysaccharide (LPS)-induced inflammation in microglial BV2 cells. BV2 cells were stimulated with LPS, and the protective effects of CVL were investigated via measurement of cell viability, reactive oxygen species (ROS), and interleukin (IL)-1β liberation. The protein levels of some inflammatory cascade, Notch, and peroxisome proliferator-activated receptor (PPAR)-γ pathways and relative markers of M1/M2 microglial phenotypes were assessed. Neuroblastoma SH-SY5Y cells were cultured with a BV2-conditioned medium (CM), and the capacity of CVL to protect cell viability was evaluated. CVL displayed a protective effect against LPS stress through reducing ROS and down-regulating of nuclear factor kappa B (NF-κB) p65, NLR family pyrin domain containing-3 (NLRP3), and IL-1β proteins. LPS treatment significantly increased the levels of the M1 microglial marker inducible nitric oxide synthase (iNOS) and M1-associated cleaved-NOTCH1 and hairy and enhancer of split-1 (HES1) proteins. Conversely, LPS treatment reduced the levels of the M2 marker arginase-1 (Arg-1) and PPAR-γ proteins. CVL pre-treatment reduced the protein levels of iNOS, cleaved-NOTCH1, and HES1, while increased Arg-1 and PPAR-γ. CM of CVL-primed BV2 cells significantly improved SH-SY5Y cell viability as compared with the LPS-induced cells. CVL suppressed ROS production and alleviated the expression of inflammatory markers in LPS-stimulated BV2 cells. Our results demonstrated that targeting Notch and PPAR-γ pathways as well as directing BV2 cell polarization toward the M2 phenotype may provide a therapeutic strategy to suppress neuroinflammation by CVL.

Elevated NLRP3 Inflammasome Activation Is Associated with Motor Neuron Degeneration in ALS

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by motor neuron degeneration in the central nervous system. Recent research has increasingly linked the activation of nucleotide oligomerization domain-like receptor protein 3 (NLRP3) inflammasome to ALS pathogenesis. NLRP3 activation triggers Caspase 1 (CASP 1) auto-activation, leading to the cleavage of Gasdermin D (GSDMD) and pore formation on the cellular membrane. This process facilitates cytokine secretion and ultimately results in pyroptotic cell death, highlighting the complex interplay of inflammation and neurodegeneration in ALS. This study aimed to characterize the NLRP3 inflammasome components and their colocalization with cellular markers using the wobbler mouse as an ALS animal model. Firstly, we checked the levels of miR-223-3p because of its association with NLRP3 inflammasome activity. The wobbler mice showed an increased expression of miR-223-3p in the ventral horn, spinal cord, and cerebellum tissues. Next, increased levels of NLRP3, pro-CASP 1, cleaved CASP 1 (c-CASP 1), full-length GSDMD, and cleaved GDSMD revealed NLRP3 inflammasome activation in wobbler spinal cords, but not in the cerebellum. Furthermore, we investigated the colocalization of the aforementioned proteins with neurons, microglia, and astrocyte markers in the spinal cord tissue. Evidently, the wobbler mice displayed microgliosis, astrogliosis, and motor neuron degeneration in this tissue. Additionally, we showed the upregulation of protein levels and the colocalization of NLRP3, c-CASP1, and GSDMD in neurons, as well as in microglia and astrocytes. Overall, this study demonstrated the involvement of NLRP3 inflammasome activation and pyroptotic cell death in the spinal cord tissue of wobbler mice, which could further exacerbate the motor neuron degeneration and neuroinflammation in this ALS mouse model.

Intrathecal gastrodin alleviates allodynia in a rat spinal nerve ligation model through NLRP3 inflammasome inhibition

BACKGROUND

Gastrodin (GAS), a main bioactive component of the herbal plant, Gastrodia elata Blume, has shown to have beneficial effects on neuroinflammatory diseases such as Alzheimer's disease in animal studies and migraine in clinical studies. Inflammasome is a multimeric protein complex having a core of pattern recognition receptor and has been implicated in the development of neuroinflammatory diseases. Gastrodin has shown to modulate the activation of nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome. This study investigated the effects of GAS on the intensity of mechanical allodynia and associated changes in NLRP3 inflammasome expression at the spinal level using L5/6 spinal nerve ligation model (SNL) in rats.

METHODS

Intrathecal (IT) catheter implantation and SNL were used for drug administration and pain model in male Sprague-Dawley rats. The effect of gastrodin or MCC950 (NLRP3 inflammasome inhibitor) on mechanical allodynia was measured by von Frey test. Changes in NLRP3 inflammasome components and interleukin-1β (IL-1β) and cellular expression were examined in the spinal cord and dorsal root ganglion.

RESULTS

The expression of NLRP3 inflammasome components was found mostly in the neurons in the spinal cord and dorsal root ganglion. The protein and mRNA levels of NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), caspase-1, and IL-1β were upregulated in SNL animals compared to Sham animals. IT administration of GAS significantly attenuated the expression of NLRP3 inflammasome and the intensity of SNL-induced mechanical allodynia. NLRP3 inflammasome inhibitor, MCC950, also attenuated the intensity of allodynia, but the effect is less strong and shorter than that of GAS.

CONCLUSIONS

Expression of NLRP3 inflammasome and IL-1β is greatly increased and mostly found in the neurons at the spinal level in SNL model, and IT gastrodin exerts a significant anti-allodynic effect in SNL model partly through suppressing the expression of NLRP3 inflammasome.

Inflammation biomarkers in acute ischemic stroke according to different etiologies

BACKGROUND

High throughput technologies provide new opportunities to further investigate the pathophysiology of ischemic strokes. The present cross-sectional study aimed to evaluate potential associations between the etiologic subtypes of ischemic stroke and blood-based proteins.

METHODS

We investigated the associations between ischemic stroke subtypes and a panel of circulating inflammation biomarkers in 364 patients included in the Stroke Cohort Augsburg (SCHANA). Stroke etiologies were categorized according to the TOAST (Trial of Org 10172 in Acute Stroke Treatment) classification. Serum concentrations of 52 biomarkers were measured using the Bio-Plex Pro™ Human Cytokine Screening Panel, ICAM-1 set and VCAM-1 set, plus the Pro™ Human TH17 cytokine sCD40L set and IL31 set (all Bio-Rad, USA). Multivariable linear regression models were used to examine associations. Point estimates were calculated as the mean difference inσ -standardized cytokine levels on the log2 -scale.

RESULTS

Stromal-cell-derived-factor 1 alpha (SDF-1a) showed significantly higher serum levels in cardioembolic compared with large vessel atherosclerotic stroke (β = 0.48; 95% CI 0.22; 0.75; Padj  = 0.036). Significantly lower levels of interleukin-6 (IL-6) (β = -0.53; 95% CI -0.84; -0.23; Padj  = 0.036) and macrophage migration inhibitory factor (MIF) (β = -0.52; 95% CI -0.84; -0.21; Padj  = 0.043) were found in the small vessel versus large vessel stroke subtype.

CONCLUSIONS

Immune dysregulations observed in different stroke subtypes might help uncover pathophysiological mechanisms of the disease. Further studies are needed to validate identified biomarkers in diverse study populations before they can potentially be used in clinical practice to further improve stroke management and patient outcomes.

The Comparative Effects of Schwann Cells and Wharton's Jelly Mesenchymal Stem Cells on the AIM2 Inflammasome Activity in an Experimental Model of Spinal Cord Injury

Inflammasome activation and the consequent release of pro-inflammatory cytokines play a crucial role in the development of sensory/motor deficits following spinal cord injury (SCI). Immunomodulatory activities are exhibited by Schwann cells (SCs) and Wharton's jelly mesenchymal stem cells (WJ-MSCs). In this study, we aimed to compare the effectiveness of these two cell sources in modulating the absent in melanoma 2 (AIM2) inflammasome complex in rats with SCI. The Basso, Beattie, Bresnahan (BBB) test, Nissl staining, and Luxol fast blue (LFB) staining were performed to evaluate locomotor function, neuronal survival, and myelination, respectively. Real-time polymerase chain reaction (RT-PCR), Western blotting, and enzyme-linked immunosorbent assay (ELISA) were employed to analyze the gene and protein expressions of inflammasome components, including AIM2, ASC, caspase-1, interleukin-1β (IL-1β), and IL-18. Both gene and protein expressions of all evaluated factors were decreased after SC or WJ-MSC treatment, with a more pronounced effect observed in the SCs group (P < 0.05). Additionally, SCs promoted neuronal survival and myelination. Moreover, the administration of 3 × 105 cells resulted in motor recovery improvement in both treatment groups (P < 0.05). Although not statistically significant, these effects were more prominent in the SC-treated animals. In conclusion, SC therapy demonstrated greater efficacy in targeting AIM2 inflammasome activation and the associated inflammatory pathway in SCI experiments compared to WJ-MSCs.

Neuroadaptive Biochemical Mechanisms of Remote Ischemic Conditioning

This review summarizes the currently known biochemical neuroadaptive mechanisms of remote ischemic conditioning. In particular, it focuses on the significance of the pro-adaptive effects of remote ischemic conditioning which allow for the prevention of the neurological and cognitive impairments associated with hippocampal dysregulation after brain damage. The neuroimmunohumoral pathway transmitting a conditioning stimulus, as well as the molecular basis of the early and delayed phases of neuroprotection, including anti-apoptotic, anti-oxidant, and anti-inflammatory components, are also outlined. Based on the close interplay between the effects of ischemia, especially those mediated by interaction of hypoxia-inducible factors (HIFs) and steroid hormones, the involvement of the hypothalamic-pituitary-adrenocortical system in remote ischemic conditioning is also discussed.

Formononetin ameliorates the LPS-induced inflammatory response and apoptosis of neuronal cells via NF-κB/NLRP3 signaling pathway

The objective of this study was to investigate the impact of formononetin on cellular apoptosis and inflammatory responses following spinal cord injury (SCI), as well as the underlying mechanisms involved. In this study, PC12 cells were treated with lipopolysaccharide (LPS) and different concentrations of Formononetin (FT) (50 μM, 100 μM, 200 μM). To confirm the effect of nuclear factor-κB (NF-κB)/NLR family pyrin domain containing 3 (NLRP3) signaling pathways, the cells in the phorbol-12-myristate-13-acetate (PMA) group were treated with 0.1 μmol/L PMA (NF-κB/NLRP3 signaling pathway activators). The lactate dehydrogenase (LDH) concentration and cell viability, proliferating cell nuclear antigen (PCNA) fluorescence intensity, and cell apoptosis were determined using an LDH kit, Cell Counting Kit-8 (CCK-8), immunofluorescence, and flow cytometry assays, respectively. Tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-16 (IL-6) expression levels were detected by quantitative ELISA assay. The expression of proteins related to the NF-κB/NLRP3 signaling pathway was detected by western blotting. Our results showed that LPS increased LDH levels in PC12 cells, suggesting that inflammation caused PC12 cell damage. However, the PC12 cell damage was decreased by methylprednisolone. Formononetin promotes cell survival and proliferation, and prevents apoptosis in a concentration-dependent manner. Formononetin reduced the TNF-α, IL-1β, and IL-6 levels in the LPS-treated model. Moreover, formononetin decreased the levels of p-p65 NF-κB and NLRP3 in PC12 cells. We conclude that formononetin ameliorated the inflammatory response and apoptosis in LPS-induced inflammatory injury in neuronal cells via the NF-κB/NLRP3 signaling pathway.

Ginkgolide attenuates memory impairment and neuroinflammation by suppressing the NLRP3/caspase-1 pathway in Alzheimer's disease

The NLRP3 inflammasome is involved in the neuroinflammatory pathway of Alzheimer's disease (AD). The aim of this study is to explore the roles and underlying mechanisms of ginkgolide (Baiyu®) on amyloid precursor protein (APP)/presenilin 1 (PS1) transgenic mice and a murine microglial cell line, BV-2. In the present study, the APP/PS1 mice were administered with ginkgolide, followed by a Morris water maze test. The mice were then euthanized to obtain brain tissue for histological and Aβ analysis. Additionally, BV-2 cells were pretreated with ginkgolide and then incubated with Aβ1-42 peptide. NLRP3, ASC, and caspase-1 mRNA and protein expression in brain tissue of mice and BV-2 cells were quantified by real-time PCR and western blotting, as well as reactive oxygen species (ROS) production, interleukin (IL)-1β and IL-18 levels by lucigenin technique and ELISA. Compared with the APP/PS1 mice, ginkgolide-treated mice demonstrated the shortened escape latency, reduced plaques, less inflammatory cell infiltration and neuron loss in the hippocampi of APP/PS1 mice. The levels of NLRP3, ASC, caspase-1, ROS, IL-1β, and IL-18 were also decreased in the brain tissue of APP/PS1 mice or Aβ1-42-treated BV-2 cells following ginkgolide treatment. Ginkgolide exerted protective effects on AD, at least partly by inactivating the NLRP3/caspase-1 pathway.

TGN020 application against aquaporin 4 improved multiple sclerosis by inhibiting astrocytes, microglia, and NLRP3 inflammasome in a cuprizone mouse model

In multiple sclerosis (MS), activation of the astrocytes and microglia induces a cascading inflammatory response. Overexpression of the aquaporin 4 (AQP4) in the glia is a trigger for this reaction. This study aimed to block AQP4 by injecting TGN020 to alleviate the symptoms of MS. Total of 30 male mice were randomly divided into control (intact), cuprizone model of MS (fed with 0.2% cuprizone for 35 days), and TGN020-treated (received daily intraperitoneal injections of 200 mg/kg TGN020 with cuprizone intake) groups. Astrogliosis, M1-M2 microglia polarization, NLRP3 inflammasome activation, and demyelination were investigated in the corpus callosum by immunohistochemistry, real-time PCR, western blot, and luxol fast blue staining. The Rotarod test was performed for a behavior assessment. AQP4 inhibition caused a significant decrease in the expression of the astrocyte-specific marker, GFAP. It also changed the microglia polarization from M1 to M2 indicated by a significant downregulation of iNOS, CD86, MHC-ІІ, and upregulation of arginase1, CD206, and TREM-2. In addition, western blot data showed a significant decrease in the NLRP3, caspase1, and IL-1b proteins in the treatment group, which indicated inflammasome inactivation. The molecular changes following the TGN020 injection resulted in remyelination and motor recovery enhancement in the treatment group. In conclusion, the results draw the attention to the role of AQP4 in the cuprizone model of MS.

Elamipretide reduces pyroptosis and improves functional recovery after spinal cord injury

AIMS

Elamipretide (EPT), a novel mitochondria-targeted peptide, has been shown to be protective in a range of diseases. However, the effect of EPT in spinal cord injury (SCI) has yet to be elucidated. We aimed to investigate whether EPT would inhibit pyroptosis and protect against SCI.

METHODS

After establishing the SCI model, we determined the biochemical and morphological changes associated with pyroptosis, including neuronal cell death, proinflammatory cytokine expression, and signal pathway levels. Furthermore, mitochondrial function was assessed with flow cytometry, quantitative real-time polymerase chain reaction, and western blot.

RESULTS

Here, we demonstrate that EPT improved locomotor functional recovery following SCI as well as reduced neuronal loss. Moreover, EPT inhibited nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) inflammasome activation and pyroptosis occurrence and decreased pro-inflammatory cytokines levels following SCI. Furthermore, EPT alleviated mitochondrial dysfunction and reduced mitochondrial reactive oxygen species level.

CONCLUSION

EPT treatment may protect against SCI via inhibition of pyroptosis.

Mesenchymal stem cells (MSCs) and MSC-derived exosomes in animal models of central nervous system diseases: Targeting the NLRP3 inflammasome

The NLRP3 (NOD-, LRR-, and pyrin domain-containing protein 3) inflammasome is a multimeric protein complex that is engaged in the innate immune system and plays a vital role in inflammatory reactions. Activation of the NLRP3 inflammasome and subsequent release of proinflammatory cytokines can be triggered by microbial infection or cellular injury. The NLRP3 inflammasome has been implicated in the pathogenesis of many disorders affecting the central nervous system (CNS), ranging from stroke, traumatic brain injury, and spinal cord injury to Alzheimer's disease, Parkinson's disease, epilepsy, multiple sclerosis, and depression. Furthermore, emerging evidence has suggested that mesenchymal stem cells (MSCs) and their exosomes may modulate NLRP3 inflammasome activation in a way that might be promising for the therapeutic management of CNS diseases. In the present review, particular focus is placed on highlighting and discussing recent scientific evidence regarding the regulatory effects of MSC-based therapies on the NLRP3 inflammasome activation and their potential to counteract proinflammatory responses and pyroptotic cell death in the CNS, thereby achieving neuroprotective impacts and improvement in behavioral impairments.

Anti-aging mechanism of different age donor-matched adipose-derived stem cells

BACKGROUND

Adipose-derived stem cells (ASCs) have anti-aging and anti-obesity effects in aged animals, but the underlying molecular mechanism remains unknown.

METHODS

In the present study, we evaluated the in vivo transplantation effects of different age donor-matched ASCs on natural aging and leptin knockout mice (ob-/ob- mice). The multi-omics expression profiles of young and aged mouse donor-derived ASCs were also analyzed.

RESULTS

The results revealed that ASCs from young donors induced weight and abdominal fat loss for older recipients but not for young or ob-/ob-mice. The young and aged mouse donor ASCs displayed significant phenotypic differences, contributing to the distinguished weight loss and anti-aging effects in aged mice.

CONCLUSIONS

Our data suggest an underlying molecular mechanism by which young-donor ASCs reduce immune cells and inflammation in aged mice via secreted immune factors. These findings point to a general anti-aging mechanism of stem cells, which may provide new insights into age-related disturbances of stem cell plasticity in healthy aging and age-related diseases.

Acupuncture combined with moxibustion mitigates spinal cord injury-induced motor dysfunction in mice by NLRP3-IL-18 signaling pathway inhibition

BACKGROUND

Spinal cord injury (SCI), which reportedly induces severe motor dysfunction, imposes a significant social and financial burden on affected individuals, families, communities, and nations. Acupuncture combined with moxibustion (AM) therapy has been widely used for motor dysfunction treatment, but the underlying mechanisms remain unknown. In this work, we aimed to determine whether AM therapy could alleviate motor impairment post-SCI and, if so, the potential mechanism.

METHODS

A SCI model was established in mice through impact methods. AM treatment was performed in SCI model mice at Dazhui (GV14) and Jiaji points (T7-T12), Mingmen (GV4), Zusanli (ST36), and Ciliao (BL32) on both sides for 30 min once per day for 28 days. The Basso-Beattie-Bresnahan score was used to assess motor function in mice. A series of experiments including astrocytes activation detected by immunofluorescence, the roles of NOD-like receptor pyrin domain-containing-3 (NLRP3)-IL-18 signaling pathway with the application of astrocyte-specific NLRP3 knockout mice, and western blot were performed to explore the specific mechanism of AM treatment in SCI.

RESULTS

Our data indicated that mice with SCI exposure exhibited motor dysfunction, a significant decrease of neuronal cells, a remarkable activation of astrocytes and microglia, an increase of IL-6, TNF-α, IL-18 expression, and an elevation of IL-18 colocalized with astrocytes, while astrocytes-specific NLRP3 knockout heavily reversed these changes. Besides, AM treatment simulated the neuroprotective effects of astrocyte-specific NLRP3 knockout, whereas an activator of NLRP3 nigericin partially reversed the AM neuroprotective effects.

CONCLUSION

AM treatment mitigates SCI-induced motor dysfunction in mice; this protective mechanism may be related to the NLRP3-IL18 signaling pathway inhibition in astrocytes.

Microglial NLRP3 inflammasome activation mediates diabetes-induced depression-like behavior via triggering neuroinflammation

BACKGROUND

Abundant evidence suggests that the prevalence and risk of depression in people with diabetes is high. However, the pathogenesis of diabetes-related depression remains unclear. Since neuroinflammation is associated with the pathophysiology of diabetic complications and depression, this study aims to elucidate the neuroimmune mechanism of diabetes-related depression.

METHODS

Male C57BL/6 mice were injected with streptozotocin to establish a diabetes model. After screening, diabetic mice were treated with the NLRP3 inhibitor MCC950. Then, metabolic indicators and depression-like behaviors were evaluated in these mice, as well as their central and peripheral inflammation. To explore the mechanism of high glucose-induced microglial NLRP3 inflammasome activation, we performed in vitro studies focusing on its canonical upstream signal I (TLR4/MyD88/NF-κB) and signal II (ROS/PKR/P₂X₇R/TXNIP).

RESULTS

Diabetic mice exhibited depression-like behaviors and activation of NLRP3 inflammasome in hippocampus. In vitro high-glucose (50 mM) environment primed microglial NLRP3 inflammasome by promoting NF-κB phosphorylation in a TLR4/MyD88-independent manner. Subsequently, high glucose activated the NLRP3 inflammasome via enhancing intracellular ROS accumulation, upregulating P₂X₇R, as well as promoting PKR phosphorylation and TXNIP expression, thereby facilitating the production and secretion of IL-1β. Inhibition of NLRP3 with MCC950 significantly restored hyperglycemia-induced depression-like behavior and reversed the increase in IL-1β levels in the hippocampus and serum.

CONCLUSION

The activation of NLRP3 inflammasome, probably mainly in hippocampal microglia, mediates the development of depression-like behaviors in STZ-induced diabetic mice. Targeting the microglial inflammasome is a feasible strategy for the treatment of diabetes-related depression.

Lipocalin-2 Deficiency Diminishes Canonical NLRP3 Inflammasome Formation and IL-1β Production in the Subacute Phase of Spinal Cord Injury

Spinal cord injury (SCI) results in the production of proinflammatory cytokines due to inflammasome activation. Lipocalin 2 (LCN2) is a small secretory glycoprotein upregulated by toll-like receptor (TLR) signaling in various cells and tissues. LCN2 secretion is induced by infection, injury, and metabolic disorders. In contrast, LCN2 has been implicated as an anti-inflammatory regulator. However, the role of LCN2 in inflammasome activation during SCI remains unknown. This study examined the role of Lcn2 deficiency in the NLRP3 inflammasome-dependent neuroinflammation in SCI. Lcn2^-/- and wild-type (WT) mice were subjected to SCI, and locomotor function, formation of the inflammasome complex, and neuroinflammation were assessed. Our findings demonstrated that significant activation of the HMGB1/PYCARD/caspase-1 inflammatory axis was accompanied by the overexpression of LCN2 7 days after SCI in WT mice. This signal transduction results in the cleaving of the pyroptosis-inducing protein gasdermin D (GSDMD) and the maturation of the proinflammatory cytokine IL-1β. Furthermore, Lcn2^-/- mice showed considerable downregulation in the HMGB1/NLRP3/PYCARD/caspase-1 axis, IL-1β production, pore formation, and improved locomotor function compared with WT. Our data suggest that LCN2 may play a role as a putative molecule for the induction of inflammasome-related neuroinflammation in SCI.

Immune and inflammatory mechanism of remote ischemic conditioning: A narrative review

The benefits of remote ischemic conditioning (RIC) on multiple organs have been extensively investigated. According to existing research, suppressing the immune inflammatory response is an essential mechanism of RIC. Based on the extensive effects of RIC on cardiovascular and cerebrovascular diseases, this article reviews the immune and inflammatory mechanisms of RIC and summarizes the effects of RIC on immunity and inflammation from three perspectives: (1) the mechanisms of the impact of RIC on inflammation and immunity; (2) evidence of the effects of RIC on immune and inflammatory processes in ischaemic stroke; and (3) possible future applications of this effect, especially in systemic infectious diseases such as sepsis and sepsis-associated encephalopathy. This review explores the possibility of using RIC as a treatment in more inflammation-related diseases, which will provide new ideas for the treatment of this kind of disease.

Clinical Trials Targeting Secondary Damage after Traumatic Spinal Cord Injury

Spinal cord injury (SCI) often causes loss of sensory and motor function resulting in a significant reduction in quality of life for patients. Currently, no therapies are available that can repair spinal cord tissue. After the primary SCI, an acute inflammatory response induces further tissue damage in a process known as secondary injury. Targeting secondary injury to prevent additional tissue damage during the acute and subacute phases of SCI represents a promising strategy to improve patient outcomes. Here, we review clinical trials of neuroprotective therapeutics expected to mitigate secondary injury, focusing primarily on those in the last decade. The strategies discussed are broadly categorized as acute-phase procedural/surgical interventions, systemically delivered pharmacological agents, and cell-based therapies. In addition, we summarize the potential for combinatorial therapies and considerations.

Pyroptosis in Alzheimer's disease: cell type-specific activation in microglia, astrocytes and neurons

The major neuropathological hallmarks of Alzheimer's disease (AD) are amyloid β (Aβ) plaques and neurofibrillary tangles (NFT), accompanied by neuroinflammation and neuronal loss. Increasing evidence is emerging for the activation of the canonical NOD-, LRR- and pyrin domain-containing 3 (NLRP3) inflammasome in AD. However, the mechanisms leading to neuronal loss in AD and the involvement of glial cells in these processes are still not clear. The aim of this study was to investigate the contribution of pyroptosis, a pro-inflammatory mechanism of cell death downstream of the inflammasome, to neurodegeneration in AD. Immunohistochemistry and biochemical analysis of protein levels were performed on human post-mortem brain tissue. We investigated the presence of cleaved gasdermin D (GSDMD), the pyroptosis effector protein, as well as the NLRP3 inflammasome-forming proteins, in the medial temporal lobe of 23 symptomatic AD, 25 pathologically defined preclinical AD (p-preAD) and 21 non-demented control cases. Cleaved GSDMD was detected in microglia, but also in astrocytes and in few pyramidal neurons in the first sector of the cornu ammonis (CA1) of the hippocampus and the temporal cortex of Brodmann area 36. Only microglia expressed all NLRP3 inflammasome-forming proteins (i.e., ASC, NLRP3, caspase-1). Cleaved GSDMD-positive astrocytes and neurons exhibited caspase-8 and non-canonical inflammasome protein caspase-4, respectively, potentially indicating alternative pathways for GSDMD cleavage. Brains of AD patients exhibited increased numbers of cleaved GSDMD-positive cells. Cleaved GSDMD-positive microglia and astrocytes were found in close proximity to Aβ plaques, while cleaved GSDMD-positive neurons were devoid of NFTs. In CA1, NLRP3-positive microglia and cleaved GSDMD-positive neurons were associated with local neuronal loss, indicating a possible contribution of NLRP3 inflammasome and pyroptosis activation to AD-related neurodegeneration. Taken together, our results suggest cell type-specific activation of pyroptosis in AD and extend the current knowledge about the contribution of neuroinflammation to the neurodegenerative process in AD via a direct link to neuron death by pyroptosis.

Adipose-derived mesenchymal stem cells overexpressing prion improve outcomes via the NLRP3 inflammasome/DAMP signalling after spinal cord injury in rat

Traumatic spinal cord injury (SCI) is a highly destructive disease in human neurological functions. Adipose-derived mesenchymal stem cells (ADMSCs) have tissue regenerations and anti-inflammations, especially with prion protein overexpression (PrPc^OE ). Therefore, this study tested whether PrPc^OE -ADMSCs therapy offered benefits in improving outcomes via regulating nod-like-receptor-protein-3 (NLRP3) inflammasome/DAMP signalling after acute SCI in rats. Compared with ADMSCs only, the capabilities of PrPc^OE -ADMSCs were significantly enhanced in cellular viability, anti-oxidative stress and migration against H₂ O₂ and lipopolysaccharide damages. Similarly, PrPc^OE -ADMSCs significantly inhibited the inflammatory patterns of Raw264.7 cells. The SD rats (n = 32) were categorized into group 1 (Sham-operated-control), group 2 (SCI), group 3 (SCI + ADMSCs) and group 4 (SCI + PrPc^OE -ADMSCs). Compared with SCI group 2, both ADMSCs and PrPc^OE -ADMSCs significantly improved neurological functions. Additionally, the circulatory inflammatory cytokines levels (TNF-α/IL-6) and inflammatory cells (CD11b/c+/MPO+/Ly6G+) were highest in group 2, lowest in group 1, and significantly higher in group 3 than in group 4. By Day 3 after SCI induction, the protein expressions of inflammasome signalling (HGMB1/TLR4/MyD88/TRIF/c-caspase8/FADD/p-NF-κB/NEK7/NRLP3/ASC/c-caspase1/IL-ß) and by Day 42 the protein expressions of DAMP-inflammatory signalling (HGMB1/TLR-4/MyD88/TRIF/TRAF6/p-NF-κB/TNF-α/IL-1ß) in spinal cord tissues displayed an identical pattern as the inflammatory patterns. In conclusion, PrPc^OE -ADMSCs significantly attenuated SCI in rodents that could be through suppressing the inflammatory signalling.

EGCG promotes the sensory function recovery in rats after dorsal root crush injury by upregulating KAT6A and inhibiting pyroptosis

Dorsal root injury usually leads to irreversible sensory function loss and lacks effective treatments. (-)-epigallocatechin-3-gallate (EGCG) is reported to exert neuroprotective roles in the nervous systems. However, the function of EGCG in treating dorsal root injury remains unclear. Hence, we built the dorsal root crush injury (DRCI) rat model to be treated with EGCG, followed by the western blot, Enzyme-linked immunosorbent assay, and sensory behavior tests. We observed that EGCG can upregulate the Lysine acetyltransferase 6A (KAT6A) level and inhibit the pyroptosis, indicated by downregulated gasdermin-D, caspase-1, and interleukin 18 protein levels, and alleviate the neuropathic pain, indicated by the decreased paw withdraw threshold in Plantar test and decreased paw withdraw latency in von Frey test, and downregulated calcitonin gene-related peptide, nerve growth factor, and c-Fos protein levels. But EGCG cannot alleviate the neuropathic pain when the KAT6A was inhibited by CTX-0124143 and pyroptosis was activated by Miltirone. These combined results indicated that EGCG can promote the sensory function recovery in rats after DRCI via upregulating KAT6A and inhibiting pyroptosis, laying the foundation for EGCG to be a novel candidate for the treatment of dorsal root injury.

Secondary White Matter Injury Mediated by Neuroinflammation after Intracerebral Hemorrhage and Promising Therapeutic Strategies of Targeting the NLRP3 Inflammasome

Intracerebral hemorrhage (ICH) is a neurological disease with high mortality and disability. Recent studies showed that white matter injury (WMI) plays an important role in motor dysfunction after ICH. WMI includes WMI proximal to the lesion and WMI distal to the lesion, such as corticospinal tract injury located at the cervical enlargement of the spinal cord after ICH. Previous studies have tended to focus only on gray matter (GM) injury after ICH, and fewer studies have paid attention to WMI, which may be one of the reasons for the poor outcome of previous drug treatments. Microglia and astrocyte-mediated neuroinflammation are significant mechanisms responsible for secondary WMI following ICH. The NOD-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome activation, has been shown to exacerbate neuroinflammation and brain injury after ICH. Moreover, NLRP3 inflammasome is activated in microglia and astrocytes and exerts a vital role in microglia and astrocytes-mediated neuroinflammation. We speculate that NLRP3 inflammasome activation is closely related to the polarization of microglia and astrocytes and that NLRP3 inflammasome activation may exacerbate WMI by polarizing microglia and astrocytes to the pro-inflammatory phenotype after ICH, while NLRP3 inflammasome inhibition may attenuate WMI by polarizing microglia and astrocytes to the anti-inflammatory phenotype following ICH. Therefore, NLRP3 inflammasome may act as leveraged regulatory fulcrums for microglia and astrocytes polarization to modulate WMI and WM repair after ICH. This review summarized the possible mechanisms by which neuroinflammation mediated by NLRP3 inflammasome exacerbates secondary WMI after ICH and discussed the potential therapeutic targets.

Dopamine inhibits pyroptosis and attenuates secondary damage after spinal cord injury in female mice

BACKGROUND

An excessive inflammatory response accompanies the pathogenesis of spinal cord injury (SCI) and has been found to be promoted by inflammasomes in a variety of disease models. Dopamine is a neurotransmitter that also regulates nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) inflammasome-dependent neuroinflammation. However, little is known regarding the effects and molecular mechanisms underlying the role of dopamine in SCI.

METHODS

Functional recovery in mice was assessed with the Basso Mouse Scale (BMS). Neuronal loss was evaluated with immunochemical staining of NeuN. Pyroptosis was assessed with immunofluorescence staining, flow cytometry, western blotting, and cell viability and cytotoxicity assays.

RESULTS

Dopamine was significantly associated with enhanced locomotor recovery after SCI, and with decreased NLRP3 inflammasome activation, pyroptosis, neuronal loss and pro-inflammatory cytokine levels. In vitro data suggested that dopamine suppressed NLRP3 inflammasome activation and pyroptosis, and decreased pro-inflammatory cytokine levels.

CONCLUSIONS

Dopamine may be a novel approach for alleviating secondary damage after SCI.

Review: Myelin clearance is critical for regeneration after peripheral nerve injury

Traumatic peripheral nerve injury occurs frequently and is a major clinical and public health problem that can lead to functional impairment and permanent disability. Despite the availability of modern diagnostic procedures and advanced microsurgical techniques, active recovery after peripheral nerve repair is often unsatisfactory. Peripheral nerve regeneration involves several critical events, including the recreation of the microenvironment and remyelination. Results from previous studies suggest that the peripheral nervous system (PNS) has a greater capacity for repair than the central nervous system. Thus, it will be important to understand myelin and myelination specifically in the PNS. This review provides an update on myelin biology and myelination in the PNS and discusses the mechanisms that promote myelin clearance after injury. The roles of Schwann cells and macrophages are considered at length, together with the possibility of exogenous intervention.

MicroRNA-451 Attenuates the Inflammatory Response of Activated Microglia by Downregulating Nucleotide Binding Oligomerization Domain-Like Receptor Protein 3

BACKGROUND

Spinal cord injury is the most common problem encountered during spinal surgery. After the initial trauma, the disruption of the blood-brain barrier and subsequent microglia activation result in extensive inflammatory responses. Inflammasomes are large protein complexes that are essential during inflammation. One of the most studied inflammasome components, nucleotide binding oligomerization domain-like receptor protein 3 (NLRP; nucleotide binding oligomerization domain-, leucine-rich repeat-, and pyrin domain-containing 3), is widely expressed in the central nervous system. Previous research has shown that microRNA-451 (miR-451) might play a role in regulating inflammatory conditions.

METHODS

Using bioinformatics analysis, we found that NLRP3 is a direct target of miR-451. This in silico prediction was confirmed using dual-luciferase reporter gene assays. To further demonstrate that miR-451 influenced microglial NLRP3 production, we activated microglial cells with lipopolysaccharides.

RESULTS

Activating microglial cells with lipopolysaccharides resulted in the production of NLRP3 inflammasomes and the secretion of the proinflammatory cytokines interleukin-1β and interleukin-18. We were able to demonstrate that overexpression of miR-451 suppressed this NLRP3-induced proinflammatory cascade of events.

CONCLUSIONS

Our findings have highlighted the potential anti-inflammatory role of miR-451 in reducing the secondary neuronal damage after spinal cord injury.

Neuroprotective effect of the Nrf2/ARE/miRNA145-5p signaling pathway in the early phase of spinal cord injury

AIMS

Spinal cord injury (SCI) is a debilitating neurological condition often associated with chronic neuroinflammation and redox imbalance. Oxidative stress is one of the main hallmark of secondary injury of SCI which is tightly regulated by nuclear factor E2-related factor 2/antioxidant response element (Nrf2/ARE) signaling. In this study, we aimed at investigating the interplay between inflammation-related miRNAs and the Nrf2 pathway in animal model of SCI.

MATERIALS AND METHODS

The expression of selected four validated miRNA-target pairs (miRNA223-3p, miRNA155-5p, miRNA145-5p, and miRNA124-3p) was examined at different time points (6 h, 12 h, 1 day, 3 day and 7 day) after SCI. Further, using GFAP-specific kelch-like ECH-associated protein 1 deletion (Keap1-/-) and whole-body Nrf2-/- knockout mice, we investigated the potential interplay between each miRNA and the Keap1/Nrf2 signaling system.

KEY FINDINGS

The expression of all miRNAs except miRNA155-5p significantly increased 24 h after SCI and decreased after 7 days. Interestingly, Keap1-/- mice only showed significant increase in the miRNA145-5p after 24 h SCI compared to the WT group. In addition, Keap1-/- mice showed significant decrease in CXCL10/12 (CXCL12 increased in Nrf2-/- mice), and TNF-α, and an increase in Mn-SOD and NQO-1 (Mn-SOD and NQO-1 decreased in Nrf2-/- mice) compared to WT mice.

SIGNIFICANCE

Our results suggest that astrocytic hyperactivation of Nrf2 exert neuroprotective effects at least in part through the upregulation of miRNA145-5p, a negative regulator of astrocyte proliferation, and induction of ARE in early phase of SCI. Further studies are needed to investigate the potential interplay between Nrf2 and miRNA145-5p in neuroinflammatory condition.

Inflammation: A Target for Treatment in Spinal Cord Injury

Spinal cord injury (SCI) is a significant cause of disability, and treatment alternatives that generate beneficial outcomes and have no side effects are urgently needed. SCI may be treatable if intervention is initiated promptly. Therefore, several treatment proposals are currently being evaluated. Inflammation is part of a complex physiological response to injury or harmful stimuli induced by mechanical, chemical, or immunological agents. Neuroinflammation is one of the principal secondary changes following SCI and plays a crucial role in modulating the pathological progression of acute and chronic SCI. This review describes the main inflammatory events occurring after SCI and discusses recently proposed potential treatments and therapeutic agents that regulate inflammation after insult in animal models.

Targeting NLRP3-Mediated Neuroinflammation in Alzheimer’s Disease Treatment

Alzheimer’s disease (AD) is the most common cause of dementia in the general population and, to date, constitutes a major therapeutic challenge. In the pathogenesis of AD, aggregates of amyloid β (Aβ) and neurofibrillary tangles (NFTs) containing Tau-microtubule-associated protein (tau) are known to trigger a neuroinflammatory response with subsequent formation of an inflammasome. In particular, the NOD-like receptor pyrin domain-containing 3 (NLRP3) inflammasome is thought to play a crucial role in AD-related pathology. While the mechanisms for NLRP3 activation are not fully understood, it has been demonstrated that, after detection of protein aggregates, NLRP3 induces pro-inflammatory cytokines, such as interleukin 18 (IL-18) or interleukin 1β (IL-1β), that further potentiate AD progression. Specific inhibitors of NLRP3 that exhibit various mechanisms to attenuate the activity of NLRP3 have been tested in in vivo studies and have yielded promising results, as shown by the reduced level of tau and Aβ aggregates and diminished cognitive impairment. Herein, we would like to summarize the current state of knowledge on NLRP3 inflammasome priming, activation, and its actual role in AD pathogenesis, and to characterize the NLRP3 inhibitors that have been studied most and their impact on AD-related pathology.

Glial Cells and Brain Diseases: Inflammasomes as Relevant Pathological Entities

Inflammation mediated by the innate immune system is a physiopathological response to diverse detrimental circumstances such as microbe infections or tissular damage. The molecular events that underlie this response involve the assembly of multiprotein complexes known as inflammasomes. These assemblages are essentially formed by a stressor-sensing protein, an adapter protein and a non-apoptotic caspase (1 or 11). The coordinated aggregation of these components mediates the processing and release of pro-inflammatory interleukins (IL-β and IL-18) and cellular death by pyroptosis induction. The inflammatory response is essential for the defense of the organism; for example, it triggers tissue repair and the destruction of pathogen microbe infections. However, when inflammation is activated chronically, it promotes diverse pathologies in the lung, liver, brain and other organs. The nervous system is one of the main tissues where the inflammatory process has been characterized, and its implications in health and disease are starting to be understood. Thus, the regulation of inflammasomes in specific cellular types of the central nervous system needs to be thoroughly understood to innovate treatments for diverse pathologies. In this review, the presence and participation of inflammasomes in pathological conditions in different types of glial cells will be discussed.

Topoisomerase 1 inhibition modulates pyroptosis to improve recovery after spinal cord injury

Excessive neuroinflammation and neuronal loss contribute to mechanisms of spinal cord injury (SCI). Accumulating evidence has suggested that topoisomerase 1 (Top1) inhibition can suppress exacerbated immune responses and protect against lethal inflammation. Pyroptosis is a recently identified pro-inflammatory programmed mode of cell death. However, the effects and underlying mechanisms of Top1 inhibition in SCI remains unclear. Locomotor functional recovery in mice was evaluated through Basso Mouse Scale (BMS). Neuronal loss was evaluated by immunochemistry staining of NeuN. Pyroptosis was determined by immunofluorescence staining, western blot, flow cytometry, cell viability, and cytotoxicity assays. In the present study, we estimated the effects of chemical inhibition of Top1 in an SCI model. Administration of Top1 inhibitor camptothecin (CPT) to mice significantly improved locomotor functional recovery after SCI. Moreover, CPT reduced Top1 level, inhibited nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) inflammasome activation and pyroptosis, attenuated proinflammatory cytokines levels, diminished the number of neutrophil and neuronal loss in mice. Furthermore, CPT in oxygen-glucose deprivation neurons down-regulated Top1 level, attenuated NLRP3 inflammasome activation, and suppressed pyroptosis and inflammatory response. Together, our findings indicate that inhibition of Top1 with CPT can inhibit pyroptosis, control neuroinflammation, and improve functional recovery after SCI.

Novel Small-Molecule Inhibitor of NLRP3 Inflammasome Reverses Cognitive Impairment in an Alzheimer's Disease Model

Aberrant activation of the Nod-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome plays an essential role in multiple diseases, including Alzheimer's disease (AD) and psoriasis. We report a novel small-molecule inhibitor, NLRP3-inhibitory compound 7 (NIC7), and its derivative, which inhibit NLRP3-mediated activation of caspase 1 along with the secretion of interleukin (IL)-1β, IL-18, and lactate dehydrogenase. We examined the therapeutic potential of NIC7 in a disease model of AD by analyzing its effect on cognitive impairment as well as the expression of dopamine receptors and neuronal markers. NIC7 significantly reversed the associated disease symptoms in the mice model. On the other hand, NIC7 did not reverse the disease symptoms in the imiquimod (IMQ)-induced disease model of psoriasis. This indicates that IMQ-based psoriasis is independent of NLRP3. Overall, NIC7 and its derivative have therapeutic prospects to treat AD or NLRP3-mediated diseases.

Combined Effect of Co-administration of Stromal Cell-Derived Factor-1 and Granulocyte-Colony Stimulating Factor on Rat Model of Alzheimer’s Disease

Introduction

Alzheimer’s disease (AD) is a neurodegenerative disease that is characterized by amyloid plaque deposits, neuronal cell loss, and memory impairment. Granulocyte-colony stimulating factor (G-CSF) is a growth factor associated with AD improvement. Stromal cell-derived factor-1 (SDF-1) mediates therapeutic effects of G-CSF. This study investigated the effect of combination treatment of G-CSF and SDF-1 on amyloid plaque deposits, apoptosis, and behavior of AD rats.

Methods

Intracerebroventricular amyloid-beta [Aβ(1-42)] peptide was used to induce AD in Aβ rats. There were six groups including naive control, sham-operated, Aβ, Aβ + G-CSF, Aβ + SDF-1, and Aβ + G-CSF + SDF-1. SDF-1 intra-cerebroventricular (ICV), G-CSF Subcutaneous (SC), or a combination of them were administered to Aβ rats weekly for 2 months. The cognition and memory were assessed using the novel object recognition, passive avoidance, and Morris water maze tests. Next, rat brains were removed and the amyloid plaque and apoptosis were detected in the brain and hippocampus using immunohistochemistry and TUNEL assay, respectively.

Results

The amyloid-beta and apoptotic cell levels dropped in groups receiving SDF-1 and G-CSF combination compared to the Aβ group. Also, number of microglial cells increased significantly in the combination group compared to other treatment groups. Moreover, learning and memory were significantly improved in the combination group compared to the Aβ groups (P < 0.05).

Conclusion

SDF-1 and G-CSF combination therapy can offer a promising strategy for AD.

All-Trans Retinoic Acid-Preconditioned Mesenchymal Stem Cells Improve Motor Function and Alleviate Tissue Damage After Spinal Cord Injury by Inhibition of HMGB1/NF-κB/NLRP3 Pathway Through Autophagy Activation

Spinal cord injury (SCI) is a significant public health issue that imposes numerous burdens on patients and society. Uncontrolled excessive inflammation in the second pathological phase of SCI can aggravate the injury. In this paper, we hypothesized that suppressing inflammatory pathways via autophagy could aid functional recovery, and prevent spinal cord tissue degeneration following SCI. To this end, we examined the effects of intrathecal injection of all-trans retinoic acid (ATRA)-preconditioned bone marrow mesenchymal stem cells (BM-MSCs) (ATRA-MSCs) on autophagy activity and the HMGB1/NF-κB/NLRP3 inflammatory pathway in an SCI rat model. This study demonstrated that SCI increased the expression of Beclin-1 (an autophagy-related gene) and NLRP3 inflammasome components such as NLRP3, ASC, Caspase-1, and pro-inflammatory cytokines IL-1β, IL-18, IL-6, and TNF-α. Additionally, following SCI, the protein levels of key autophagy factors (Beclin-1 and LC3-II) and HMGB1/NF-κB/NLRP3 pathway factors (HMGB1, p-NF-κB, NLRP3, IL-1β, and TNF-α) increased. Our findings indicated that ATRA-MSCs enhanced Beclin-1 and LC3-II levels, regulated the HMGB1/NF-κB/NLRP3 pathway, and inhibited pro-inflammatory cytokines. These factors improved hind limb motor activity and aided in the survival of neurons. Furthermore, ATRA-MSCs demonstrated greater beneficial effects than MSCs in treating spinal cord injury. Overall, ATRA-MSC treatment revealed beneficial effects on the damaged spinal cord by suppressing excessive inflammation and activating autophagy. Further research and investigation of the pathways involved in SCI and the use of amplified stem cells may be beneficial for future clinical use.

TI: NLRP3 Inflammasome-Dependent Pyroptosis in CNS Trauma: A Potential Therapeutic Target

Central nervous system (CNS) trauma, including traumatic brain injury (TBI) and traumatic spinal cord injury (SCI), is characterized by high morbidity, disability, and mortality. TBI and SCI have similar pathophysiological mechanisms and are often accompanied by serious inflammatory responses. Pyroptosis, an inflammation-dependent programmed cell death, is becoming a major problem in CNS post-traumatic injury. Notably, the pyrin domain containing 3 (NLRP3) inflammasome is a key protein in the pyroptosis signaling pathway. Therefore, underlying mechanism of the NLRP3 inflammasome in the development of CNS trauma has attracted much attention. In this review, we briefly summarize the molecular mechanisms of NLRP3 inflammasome in pyroptosis signaling pathway, including its prime and activation. Moreover, the dynamic expression pattern, and roles of the NLRP3 inflammasome in CNS post-traumatic injury are summarized. The therapeutic applications of NLRP3 inflammasome activation inhibitors are also discussed.

Melatonin ameliorates bupivacaine-induced spinal neurotoxicity in rats by suppressing neuronal NLRP3 inflammasome activation

Bupivacaine is a common local anesthetic that causes neurotoxicity when used at clinical concentrations. Melatonin (MT), is a potent neuroprotective molecule. The study aimed to characterize the neuroprotective effects of MT on spinal neurotoxicity induced by bupivacaine in rats. It showed that bupivacaine, by intrathecal injection, induced spinal injury, and that the protein levels of Nod-like receptor protein 3 (NLRP3), cleaved caspase-1, and the N-terminal region of gasdermin D (GSDMD-N) were significantly increased. NLRP3 was expressed mainly in neurons and microglia. MT treatment ameliorated bupivacaine-induced spinal cord injury in rats by suppressing activation of neuronal NLRP3 inflammasomes.

Tibolone restrains neuroinflammation in mouse experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an immune-mediated and degenerating disease in which myelin sheaths are damaged as a result of chronic progressive inflammation of the central nervous system. Tibolone [(7α,17α)-17-hydroxy-7-methyl-19-norpregn-5(10)-en-20-in-3-one], a synthetic estrogenic compound with tissue-specific actions and used for menopausal hormone therapy, shows neuroprotective and antioxidant properties both in vivo and in vitro. In the present study, we analyzed whether tibolone plays a therapeutic role in experimental autoimmune encephalomyelitis (EAE) mice, a commonly used model of MS. Female C57BL/6 mice were induced with the myelin oligodendrocyte glycoprotein MOG_35-55 and received s.c. tibolone (0.08 mg kg^-1 ) injection every other day from the day of induction until death on the acute phase of the disease. Reactive gliosis, Toll like receptor 4 (TLR4), high mobility group box protein 1 (HMGB1), inflammasome parameters, activated Akt levels and myelin were assessed by a real-time polymerase chain reaction, immunohistochemistry, and western blot analysis. Our findings indicated that, in the EAE spinal cord, tibolone reversed the astrocytic and microglial reaction, and reduced the hyperexpression of TLR4 and HMGB1, as well as NLR family pyrin domain containing 3-caspase 1-interleukin-1β inflammasome activation. At the same time, tibolone attenuated the Akt/nuclear factor kappa B pathway and limited the white matter demyelination area. Estrogen receptor expression was unaltered with tibolone treatment. Clinically, tibolone improved neurological symptoms without uterine compromise. Overall, our data suggest that tibolone may serve as a promising agent for the attenuation of MS-related inflammation.

Bruton's tyrosine kinase drives neuroinflammation and anxiogenic behavior in mouse models of stress

BACKGROUND

Current therapies targeting several neurotransmitter systems are only able to partially mitigate the symptoms of stress- and trauma-related disorder. Stress and trauma-related disorders lead to a prominent inflammatory response in humans, and in pre-clinical models. However, mechanisms underlying the induction of neuroinflammatory response in PTSD and anxiety disorders are not clearly understood. The present study investigated the mechanism underlying the activation of proinflammatory NLRP3 inflammasome and IL1β in mouse models of stress.

METHODS

We used two mouse models of stress, i.e., mice subjected to physical restraint stress with brief underwater submersion, and predator odor stress. Mice were injected with MCC950, a small molecule specific inhibitor of NLRP3 activation. To pharmacologically inhibit BTK, a specific inhibitor ibrutinib was used. To validate the observation from ibrutinib studies, a separate group of mice was injected with another BTK-specific inhibitor LFM-A13. Seven days after the induction of stress, mice were examined for anxious behavior using open field test (OFT), light-dark test (LDT), and elevated plus maze test (EPM). Following the behavior tests, hippocampus and amygdale were extracted and analyzed for various components of NLRP3-caspase 1-IL1β pathway. Plasma and peripheral blood mononuclear cells were also used to assess the induction of NLRP3-Caspase 1-IL-1β pathway in stressed mice.

RESULTS

Using two different pre-clinical models of stress, we demonstrate heightened anxious behavior in female mice as compared to their male counterparts. Stressed animals exhibited upregulation of proinflammatory IL1β, IL-6, Caspase 1 activity and NLRP3 inflammasome activation in brain, which were significantly higher in female mice. Pharmacological inhibition of NLRP3 inflammasome activation led to anxiolysis as well as attenuated neuroinflammatory response. Further, we observed induction of activated Bruton's tyrosine kinase (BTK), an upstream positive-regulator of NLRP3 inflammasome activation, in hippocampus and amygdala of stressed mice. Next, we conducted proof-of-concept pharmacological BTK inhibitor studies with ibrutinib and LFM-A13. In both sets of experiments, we found BTK inhibition led to anxiolysis and attenuated neuroinflammation, as indicated by significant reduction of NLRP3 inflammasome and proinflammatory IL-1β in hippocampus and amygdala. Analysis of plasma and peripheral blood mononuclear cells indicated peripheral induction of NLRP3-caspase 1-IL1β pathway in stressed mice.

CONCLUSION

Our study identified BTK as a key upstream regulator of neuroinflammation, which drives anxiogenic behavior in mouse model of stress. Further, we demonstrated the sexually divergent activation of BTK, providing a clue to heightened neuroinflammation and anxiogenic response to stress in females as compared to their male counterparts. Our data from the pharmacological inhibition studies suggest BTK as a novel target for the development of potential clinical treatment of PTSD and anxiety disorders. Induction of pBTK and NLRP3 in peripheral blood mononuclear cells of stressed mice suggest the potential effect of stress on systemic inflammation.

Methylation Status of the miR-141-3p Promoter Regulates miR-141-3p Expression, Inflammasome Formation, and the Invasiveness of HTR-8/SVneo Cells

MicroRNA-141 (miR-141-3p) is upregulated in preeclampsia. This study investigated the effect of methylation of the miR-141-3p promoter on cell viability, invasion capability, and inflammasomes in vitro. The expression of miR-141-3p and methylation status of the miR-141-3p promoter were examined by RT-qPCR and pyrosequencing in villus tissues of women with spontaneous delivery (VTsd), villus tissues of women with preeclampsia (VTpe), and also in HTR-8/SVneo cells treated with a miR-141-3p inhibitor and 20 μmol/L 5-aza-2'-deoxycytidine (5-Aza), a DNA methyltransferase inhibitor. Cell viability and invasion were evaluated by CCK-8 and transwell assays. In addition, the levels of CXCL12, CXCR4, CXCR2, MMPs, NLRP3, and ASC expression were assessed by western blotting, and IL-1β and IL-18 concentrations were assayed by ELISA. miR-141-3p expression was upregulated, and the levels of miR-141-3p promoter methylation and CXCL12, CXCR4, and CXCR2 expression were decreased in VTpe relative to VTsd. In HTR-8/SVneo cells, hypomethylation caused by 5-Aza treatment increased miR-141-3p expression, while DNA methyltransferase 3 (DNMT3) transfection decreased miR-141-3p expression. miRNA-141-3p induced NLRP3, IL-1β, and IL-18 production, decreased CXCR4, MMP, and MMP2 production, and suppressed cell growth and invasion. Furthermore, we observed that NLRP3 plays an important mediatory role in the effects of miR-141-3p described above. Decreased methylation of the miR-141-3p promoter increases miR-141-3p expression, which in turn increases NLRP3 expression, resulting in higher IL-1β and IL-18 levels and lower levels of MMP2/9 and CXCR4. We conclude that modification of the miR-141-3p promoter might be a curial mediator in preeclampsia.

Rh-CXCL-12 Attenuates Neuronal Pyroptosis after Subarachnoid Hemorrhage in Rats via Regulating the CXCR4/NLRP1 Pathway

Subarachnoid hemorrhage (SAH) is a cerebrovascular disease associated with high morbidity and mortality. CXCR4 provides neuroprotective effects, which can alleviate brain injury and inflammation induced by stroke. Previous studies have suggested that CXCR4 reduces the pyroptosis of LPS-stimulated BV2 cells. The purpose of this study was to evaluate the antipyroptosis effects and mechanisms of CXCR4 after SAH. SAH animal model was induced via endovascular perforation. A total of 136 male Sprague-Dawley rats were used. Recombinant human cysteine-X-cysteine chemokine ligand 12 (rh-CXCL-12) was administered intranasally at 1 h after SAH induction. To investigate the underlying mechanism, the inhibitor of CXCR4, AMD3100, was administered intraperitoneally at 1 h before SAH. The neurobehavior tests were assessed, followed by performing Western blot and immunofluorescence staining. The Western blot results suggested that the expressions of endogenous CXCL-12, CXCR4, and NLRP1 were increased and peaked at 24 h following SAH. Immunofluorescence staining showed that CXCR4 was expressed on neurons, microglia, and astrocytes. Rh-CXCL-12 treatment improved the neurological deficits and reduced the number of FJC-positive cells, IL-18-positive neurons, and cleaved caspase-1(CC-1)-positive neurons after SAH. Meanwhile, rh-CXCL-12 treatment increased the levels of CXCL-12 and CXCR4, and reduced the levels of NLRP1, IL-18, IL-1β, and CC-1. Moreover, the administration of AMD3100 abolished antipyroptosis effects of CXCL-12 and its regulation of CXCR4 post-SAH. The CXCR4/NLRP1 signaling pathway may be involved in CXCL-12-mediated neuronal pyroptosis after SAH. Early administration of CXCL-12 may be a preventive and therapeutic strategy against brain injury after SAH.

Regulation of Inflammasomes by Application of Omega-3 Polyunsaturated Fatty Acids in a Spinal Cord Injury Model

Omega-3 polyunsaturated fatty acids (PUFA n3) ameliorate inflammation in different diseases and potentially improve neurological function after neuronal injury. Following spinal cord injury (SCI), inflammatory events result in caspase-1 mediated activation of interleukin-1 beta (IL-1b) and 18. We aim to evaluate the neuroprotective potency of PUFA n3 in suppressing the formation and activation of inflammasomes following SCI. Male Wistar rats were divided into four groups: control, SCI, SCI+PUFA n3, and SCI+Lipofundin MCT (medium-chain triglyceride; vehicle). PUFA n3 or vehicle was intravenously administered immediately after SCI and every 24 h for the next three days. We analyzed the expression of NLRP3, NLRP1, ASC, caspase-1, IL-1b, and 18 in the spinal cord. The distribution of microglia, oligodendrocytes, and astrocytes was assessed by immunohistochemistry analysis. Behavioral testing showed significantly improved locomotor recovery in PUFA n3-treated animals and the SCI-induced upregulation of inflammasome components was reduced. Histopathological evaluation confirmed the suppression of microgliosis, increased numbers of oligodendrocytes, and the prevention of demyelination by PUFA n3. Our data support the neuroprotective role of PUFA n3 by targeting the NLRP3 inflammasome. These findings provide evidence that PUFA n3 has therapeutic effects which potentially attenuate neuronal damage in SCI and possibly also in other neuronal injuries.

Advances in the Relationship Between Pyroptosis and Diabetic Neuropathy

Pyroptosis is a novel programmed cell death process that promotes the release of interleukin-1β (IL-1β) and interleukin-18 (IL-18) by activating inflammasomes and gasdermin D (GSDMD), leading to cell swelling and rupture. Pyroptosis is involved in the regulation of the occurrence and development of cardiovascular and cerebrovascular diseases, tumors, and nerve injury. Diabetes is a metabolic disorder characterized by long-term hyperglycemia, insulin resistance, and chronic inflammation. The people have paid more and more attention to the relationship between pyroptosis, diabetes, and its complications, especially its important regulatory significance in diabetic neurological diseases, such as diabetic encephalopathy (DE) and diabetic peripheral neuropathy (DPN). This article will give an in-depth overview of the relationship between pyroptosis, diabetes, and its related neuropathy, and discuss the regulatory pathway and significance of pyroptosis in diabetes-associated neuropathy.

GDF-11 Protects the Traumatically Injured Spinal Cord by Suppressing Pyroptosis and Necroptosis via TFE3-Mediated Autophagy Augmentation

Spinal cord injury (SCI) refers to a major worldwide cause of accidental death and disability. However, the complexity of the pathophysiological mechanism can result in less-effective clinical treatment. Growth differentiation factor 11 (GDF-11), an antiageing factor, was reported to affect the development of neurogenesis and exert a neuroprotective effect after cerebral ischaemic injury. The present work is aimed at investigating the influence of GDF-11 on functional recovery following SCI, in addition to the potential mechanisms involved. We employed a mouse model of spinal cord contusion injury and assessed functional outcomes via the Basso Mouse Scale and footprint analysis following SCI. Using western blot assays and immunofluorescence, we analysed the levels of pyroptosis, autophagy, necroptosis, and molecules related to the AMPK-TRPML1-calcineurin signalling pathway. The results showed that GDF-11 noticeably optimized function-related recovery, increased autophagy, inhibited pyroptosis, and alleviated necroptosis following SCI. Furthermore, the conducive influences exerted by GDF-11 were reversed with the application of 3-methyladenine (3MA), an autophagy suppressor, indicating that autophagy critically impacted the therapeutically related benefits of GDF-11 on recovery after SCI. In the mechanistic study described herein, GDF-11 stimulated autophagy improvement and subsequently inhibited pyroptosis and necroptosis, which were suggested to be mediated by TFE3; this effect resulted from the activity of TFE3 through the AMPK-TRPML1-calcineurin signalling cascade. Together, GDF-11 protects the injured spinal cord by suppressing pyroptosis and necroptosis via TFE3-mediated autophagy augmentation and is a potential agent for SCI therapy.

Salidroside Alleviates Chronic Constriction Injury-Induced Neuropathic Pain and Inhibits of TXNIP/NLRP3 Pathway

Neuropathic pain is one of the most common conditions requiring treatment worldwide. Salidroside (SAL), a phenylpropanoid glucoside extracted from Rhodiola, has been suggested to produce an analgesic effect in chronic pain. However, whether SAL could alleviate pain hypersensitivity after peripheral nerve injury and its mode of action remains unclear. Several studies suggest that activation of the spinal NOD-like receptor protein 3 (NLRP3) inflammasome and its related proteins contribute to neuropathic pain's pathogenesis. This study investigates the time course of activation of spinal NLRP3 inflammasome axis in the development of neuropathic pain and also whether SAL could be an effective treatment for this type of pain by modulating NLRP3 inflammasome. In the chronic constriction injury (CCI) mice model, spinal NLRP3 inflammasome-related proteins and TXNIP, the mediator of NLRP3, were upregulated from the 14th to the 28th day after injury. The TXNIP and NLRP3 inflammasome-related proteins were mainly present in neurons and microglial cells in the spinal dorsal horn after CCI. Intraperitoneal injection of SAL at 200 mg/kg for 14 consecutive days starting from the 7th day of CCI injury could ameliorate mechanical and thermal hypersensitivity in the CCI model. Moreover, SAL inhibited the activation of the TXNIP/NLRP3 inflammasome axis and mitigated the neuronal loss of spinal dorsal horn induced by nerve injury. These results indicate that SAL could produce analgesic and neuroprotective effects in the CCI model of neuropathic pain.

Inhibition of the NLRP3 inflammasome by OLT1177 induces functional protection and myelin preservation after spinal cord injury

Spinal cord injury (SCI) leads to irreversible functional deficits due to the disruption of axons and the death of neurons and glial cells. The inflammatory response that occurs in the injured spinal cord results in tissue degeneration; thus, targeting inflammation after acute SCI is expected to ameliorate histopathological evidence indicative of damage and, consequently, reduce functional disabilities. Interleukin 1 beta (IL-1β) and interleukin 18 (IL-18) are pro-inflammatory cytokines members of the IL-1 family that initiate and propagate inflammation. Here, we report that protein levels of IL-1β and IL-18 were increased in spinal cord parenchyma after SCI, but with different expression profiles. Whereas levels of IL-1β were rapidly increased reaching peak levels at 12 h after the injury, levels of IL-18 did not increase until 7 days after the injury. Since activation of the NLRP3 inflammasome is required for the processing and release of IL-1β and IL-18, we intraperitoneally administered OLT1177, a selective inhibitor of the NLRP3 inflammasome, to reduce the contribution of these cytokines to SCI. At a dose of 200 mg/kg, OLT1177 protected against neurological deficits and histological evidence of damage. OLT1177 also reduced the levels of IL-1β in the spinal cord after contusion injury and diminished the accumulation of neutrophils and macrophages at later time points. These data suggest that targeting the NLRP3 inflammasome with OLT1177 could be a novel therapeutic strategy to arrest neuroinflammation and reduce functional impairments after acute SCI in humans.

Inhibition of heat shock protein family A member 8 attenuates spinal cord ischemia-reperfusion injury via astrocyte NF-κB/NLRP3 inflammasome pathway : HSPA8 inhibition protects spinal ischemia-reperfusion injury

Background

Astrocyte over-activation and extensive neuron loss are the main characteristic pathological features of spinal cord ischemia–reperfusion injury (SCII). Prior studies have placed substantial emphasis on the role of heat shock protein family A member 8 (HSPA8) on postischemic myocardial inflammation and cardiac dysfunction. However, it has never been determined whether HSPA8 participates in astrocyte activation and thus mediated neuroinflammation associated with SCII.

Methods

The left renal artery ligation-induced SCII rat models and oxygen–glucose deprivation and reoxygenation (OGD/R)-induced rat primary cultured astrocytes were established. The lentiviral vector encoding short hairpin RNA targeting HSPA8 was delivered to the spinal cord by intrathecal administration or to culture astrocytes. Then, the spinal neuron survival, gliosis, and nod-like receptor pyrin domain-containing 3 (NLRP3) inflammasome and its related pro-inflammatory cytokines were analyzed.

Results

SCII significantly enhanced the GFAP and HSPA8 expression in the spinal cord, resulting in blood–brain barrier breakdown and the dramatical loss of spinal neuron and motor function. Moreover, injury also increased spinal nuclear factor-kappa B (NF-κB) p65 phosphorylation, NLRP3 inflammasome-mediated caspase-1 activation, and subsequent interleukin (IL)-1β as well as IL-18 secretion. Silencing the HSPA8 expression efficiently ameliorated the spinal cord tissue damage and promoted motor function recovery after SCII, through blockade of the astrocyte activation and levels of phosphorylated NF-κB, NLRP3, caspase-1, IL-1β, and IL-18. Further in vitro studies confirmed that HSPA8 knockdown protected astrocytes from OGD/R-induced injury via the blockade of NF-κB and NLRP3 inflammasome activation.

Conclusion

Our findings indicate that knockdown of HSPA8 inhibits spinal astrocytic damage after SCII, which may provide a promising therapeutic strategy for SCII treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02220-0.

Ameliorative effects of miR-423-5p against polarization of microglial cells of the M1 phenotype by targeting a NLRP3 inflammasome signaling pathway

Spinal cord injury (SCI) causes sensation and motion dysfunction. Activation of microglial cells (MCs) in the central nervous system (CNS) is heterogeneous. Heterogeneous types of MCs can produce cytotoxic or neuroprotective effects, secrete proinflammatory or anti-inflammatory factors. The cytotoxic effect of MCs is one of the reasons for secondary damage after SCI. The NLR family pyrin domain containing 3 (NLRP3) inflammasome is a protein that can recognize pathogen-related molecular patterns or host-derived danger signal molecules, responses to microbial infection, and sterile stressors. SCI triggers activation of the NLRP3 inflammasome in the CNS. We investigated the interaction between miR-423-5p and NLRP3 in MCs polarization after SCI. A rat model of SCI was established by a modified version of Allen's method. Spinal samples were adopted for preparation and sequencing of RNA. We screenedapromising microRNA (miR-423-5p) according to the results. Then, we found that NLRP3 was one of the prediction targets of miR-423-5p. By intervening in expression of miR-423-5p and NLRP3, we observed the different polarization of MCs. We employeda dual-luciferase reporter study, proteomics, and transcriptomicsto ascertain the direct targeting relationship between miR-423-5p and NLRP3. MiR-423-5p expression was decreased significantly after SCI in vivo and in vitro. Upregulation of miR-423-5p expression could prevent MCs from lipopolysaccharide-induced M1 polarization. Knockdown of NLRP3 expression could prevent MCs from lipopolysaccharide-induced M1 polarization. MiR-423-5p inhibited MCs polarization to the M1 phenotype by targeting NLRP3.

Exogenous stromal cell-derived factor-1 (SDF-1) suppresses the NLRP3 inflammasome and inhibits pyroptosis in synoviocytes from osteoarthritic joints via activation of the AMPK signaling pathway

Objective

NLRP3 inflammasome may play a key role in OA pathogenesis. Stromal cell-derived factor-1 (SDF-1) is a homeostatic CXC chemokine. Since the role of SDF-1 in OA has not been explored, this study aimed to examine the effect of SDF-1 on NLRP3 inflammasome and pyroptosis in synoviocytes from OA joints.

Materials and methods

Human synovium was obtained from OA patients for isolation of primary synoviocytes and a murine model of collagenase-induced OA was established for testing intra-articular injections of SDF-1. Immunoblotting assays were used to examine the effects and underlying mechanism of action of SDF-1 on NLRP3 inflammasome and synoviocyte pyroptosis in synoviocytes. Inhibitors of AMPK and PI3K–mTOR were utilized to investigate the key signaling pathways involved in SDF-1-mediated OA inflammasome formation and pyroptosis.

Results

Synoviocytes from OA joints exhibited significantly higher expression of NLRP3 inflammasome and biomarkers of synoviocyte pyroptosis relative to healthy individuals. This was confirmed in the collagenase-induced OA model, where OA synoviocytes had a significantly lower SDF-1 expression than healthy ones. SDF-1 treatment in synoviocytes of OA patients and collagenase-induced OA led to significant downregulation in the expression of NLRP3 inflammasome and synoviocyte pyroptosis biomarkers. Inhibition of the AMPK signaling pathway significantly suppressed the inhibitory effect of SDF-1 on NLRP3 inflammasome expression of OA synoviocytes. However, blocking the SDF-1-activated PI3K–mTOR signaling pathway could still suppress the expression of NLRP3 inflammasome and synoviocyte pyroptosis biomarkers.

Conclusions

SDF-1 ameliorates NLRP3 inflammasome and pyroptosis in OA synoviocytes through activation of the AMPK signaling pathway. Therefore, SDF-1 may be a novel therapeutic target for OA.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10787-021-00814-x.

Involvement of Asc and Nlrp3 inflammasomes in the testes following spinal cord injury

OBJECTIVE

The exact mechanism, by which spinal cord injury (SCI) leads to a male subfertility is not well-known. Present study was conducted to determine the mechanisms that lead to the elevated end-product cytokines and inflammasomes in the testes of an SCI rat model. Moreover, we evaluated the inflammasome components following SCI in testis over a defined time periods.

METHODS

Weight drop technique was used to induce SCI at the level of the T10 vertebra in male Wistar rats. The animals were sacrificed at specific time intervals (3, 7, 14, 21, and 28 day's post-SCI). mRNA levels of inflammasomes and cytokines were measured by real-time PCR, germ cells apoptosis was evaluated by TUNEL staining, and the epithelium of seminiferous tubules by Miller's and Johnsen's scores.

RESULTS

The results showed activation of Nlrp3 in the testes of SCI animals at different time points. Expression of Nlrp3 and IL-1β sharply increased 14 days after the SCI. Upregulation of IL-1β and IL-18 at days 14 and 21 post-SCI might disintegrate the epithelium of seminiferous tubules at day 14 and induce germ cells apoptosis, increase abnormal sperm cells, and attenuate motility and viability at 21 days post-SCI.

CONCLUSION

This study provided further evidence of innate immunity activation in testes that could lead to more disruption of spermatogenesis in SCI patients at specific times.

Expression and Cell Type-specific Localization of Inflammasome Sensors in the Spinal Cord of SOD1(G93A) Mice and Sporadic Amyotrophic lateral sclerosis Patients

Inflammasomes are key components of the innate immune system and activation of these multiprotein platforms is a crucial event in the etiopathology of amyotrophic lateral sclerosis (ALS). Inflammasomes consist of a pattern recognition receptor (PRR), the adaptor protein apoptosis-associated speck-like protein containing a CARD (ASC) and caspase 1. Exogenous or endogenous "danger signals" can trigger inflammasome assembly and promote maturation and release of pro-inflammatory cytokines, including interleukin 1β. Previous studies have demonstrated presence and activation of NLRP3 in spinal cord tissue from SOD1^(G93A) mice and human sporadic ALS (sALS) patients. However, regulation and cell type-specific localization of other well-known PRRs has not yet been analysed in ALS. Here, we explored gene expression, protein concentration and cell type-specific localization of the NLRP1, NLRC4 and AIM2 inflammasomes in spinal cord samples from SOD1^(G93A) mice and sALS patients. Transcription levels of NLRP1 and NLRC4, but not AIM2, were elevated in symptomatic SOD1^(G93A) animals. Immunoblotting revealed elevated protein levels of NLRC4, which were significantly increased in sALS vs. control patients. Immunofluorescence studies revealed neuronal labelling of all investigated PRRs. Staining of AIM2 was detected in all types of glia, whereas glial type-specific labelling was observed for NLRP1 and NLRC4. Our findings revealed pathology-related and cell type-specific differences in the expression of subsets of PRRs. Besides NLRP3, NLRC4 appears to be linked more closely to ALS pathogenesis.

CXCL12 inhibits inflammasome activation in LPS-stimulated BV2 cells

The activation of the CXCL12-CXCR4 signaling axis is implicated in the regulation of cell survival, proliferation, and mobilization of bone marrow stem cells into the injured site. We have shown in a previous study that intrathecal administration of CXCL12 reduces spinal cord tissue damage and neuroinflammation and provides functional improvement by reducing inflammasome activity and local inflammatory processes in an experimental spinal cord injury (SCI) rat model. Here, we aimed at investigating whether these neuroprotective effects rely on the control of CXCL12 signaling on microglial activation as microglia cells are known to be the primary immune cells of the brain. LPS induced the expression of the inflammasome components NLRP3, NLRC4 and ASC, the secretion of the cytokines IL-1b and IL-18 and the activation of caspase-1 protease in BV2 cells. Pre-treatment with CXCL12 significantly reduced LPS-induced IL-1b/IL-18 secretion and inflammasome induction. Our results also showed that CXCL12 can suppress caspase-1 activity, which leads to a decrease of SCI-related induction of active IL-1b.