Microglial Inflammasome Activation in Penetrating Ballistic-Like Brain Injury

Increased inflammasome protein expression identified in microglia from postmortem brains with schizophrenia

Schizophrenia (SCZ) is a complex psychiatric disorder that involves an inflammatory response thought to be characterized by microglial activation. The inflammasome complex may play critical roles in the pathomechanism of neuroinflammation but how this relates to SCZ remains unclear. In this study, we performed an immunohistochemical (IHC) analysis to compare the expression of inflammasome proteins in brain tissue from donors with SCZ (n = 16) and non-psychiatric donors (NP; n = 13) isolated from the superior frontal cortex (SFC), superior temporal cortex, and anterior cingulate cortex brain regions. To assess changes in the cell populations that express key inflammasome proteins, we performed IHC analyses of apoptosis-associated speck-like protein containing a CARD (ASC), nod-like receptor protein 3 (NLRP3), and interleukin (IL)-18 to determine if these proteins are expressed in microglia, astrocytes, oligodendrocytes, or neurons. Inflammasome proteins were expressed mainly in microglia from SCZ and NP brains. Increased numbers of microglia were present in the SFC of SCZ brains and exhibited higher inflammasome protein expression of ASC, NLRP3, and IL-18 compared to NPs. These findings suggest that increased inflammasome signaling may contribute to the pathology underlying SCZ.

Multiple sclerosis: the NLRP3 inflammasome, gasdermin D, and therapeutics

Multiple sclerosis (MS) stands as a chronic inflammatory disease characterized by its neurodegenerative impacts on the central nervous system. The complexity of MS and the significant challenges it poses to patients have made the exploration of effective treatments a crucial area of research. Among the various mechanisms under investigation, the role of inflammation in MS progression is of particular interest. Inflammatory responses within the body are regulated by various cellular mechanisms, one of which involves the nucleotide-binding oligomerization domain (NOD)-, leucine-rich repeat (LRR)-, and pyrin domains (PYD)-containing protein 3 (NLRP3). NLRP3 acts as a sensor within cells, playing a pivotal role in controlling the inflammatory response. Its activation is a critical step leading to the assembly of the NLRP3 inflammasome complex, a process that has profound implications for inflammatory diseases like MS. The NLRP3 inflammasome's activation is intricately linked to the subsequent activation of caspase 1 and gasdermin D (GsdmD), signaling pathways that are central to the inflammatory process. GsdmD, a prominent member of the Gasdermin protein family, is particularly noteworthy for its role in pyroptotic cell death, a form of programmed cell death that is distinct from apoptosis and is characterized by its inflammatory nature. This pathway's activation contributes significantly to the pathology of MS by exacerbating inflammatory responses within the nervous system. Given the detrimental effects of unregulated inflammation in MS, therapeutics targeting these inflammatory processes offer a promising avenue for alleviating the symptoms experienced by patients. This review delves into the intricacies of the pyroptotic pathways, highlighting how the formation of the NLRP3 inflammasome induces such pathways and the potential intervention points for therapeutic agents. By inhibiting key steps within these pathways, it is possible to mitigate the inflammatory response, thereby offering relief to those suffering from MS. Understanding these mechanisms not only sheds light on the pathophysiology of MS but also paves the way for the development of novel therapeutic strategies aimed at controlling the disease's progression through the modulation of the body's inflammatory response.

An overview of preclinical models of traumatic brain injury (TBI): relevance to pathophysiological mechanisms

Background

Traumatic brain injury (TBI) is a major cause of morbidity and mortality, affecting millions annually worldwide. Although the majority of TBI patients return to premorbid baseline, a subset of patient can develop persistent and often debilitating neurocognitive and behavioral changes. The etiology of TBI within the clinical setting is inherently heterogenous, ranging from sport related injuries, fall related injuries and motor vehicle accidents in the civilian setting, to blast injuries in the military setting.

Objective

Animal models of TBI, offer the distinct advantage of controlling for injury modality, duration and severity. Furthermore, preclinical models of TBI have provided the necessary temporal opportunity to study the chronic neuropathological sequelae of TBI, including neurodegenerative sequelae such as tauopathy and neuroinflammation within the finite experimental timeline. Despite the high prevalence of TBI, there are currently no disease modifying regimen for TBI, and the current clinical treatments remain largely symptom based. The preclinical models have provided the necessary biological substrate to examine the disease modifying effect of various pharmacological agents and have imperative translational value.

Methods

The current review will include a comprehensive survey of well-established preclinical models, including classic preclinical models including weight drop, blast injury, fluid percussion injury, controlled cortical impact injury, as well as more novel injury models including closed-head impact model of engineered rotational acceleration (CHIMERA) models and closed-head projectile concussive impact model (PCI). In addition to rodent preclinical models, the review will include an overview of other species including large animal models and Drosophila.

Results

There are major neuropathological perturbations post TBI captured in various preclinical models, which include neuroinflammation, calcium dysregulation, tauopathy, mitochondrial dysfunction and oxidative stress, axonopathy, as well as glymphatic system disruption.

Conclusion

The preclinical models of TBI continue to offer valuable translational insight, as well as essential neurobiological basis to examine specific disease modifying therapeutic regimen.

Modulation of Inflammatory Response by Electromagnetic Field Stimulation in Traumatic Brain Injury in Yucatan Swine

Traumatic brain injury is a leading cause of disability and death worldwide and represents a high economic burden for families and national health systems. After mechanical impact to the head, the first stage of the damage comprising edema, physical damage, and cell loss gives rise to a second phase characterized by glial activation, increased oxidative stress and excitotoxicity, mitochondrial damage, and exacerbated neuroinflammatory state, among other molecular calamities. Inflammation strongly influences the molecular events involved in the pathogenesis of TBI. Therefore, several components of the inflammatory cascade have been targeted in experimental therapies. Application of Electromagnetic Field (EMF) stimulation has been found to be effective in some inflammatory conditions. However, its effect in the neuronal recovery after TBI is not known. In this pilot study, Yucatan miniswine were subjected to TBI using controlled cortical impact approach. EMF stimulation via a helmet was applied immediately or two days after mechanical impact. Three weeks later, inflammatory markers were assessed in the brain tissues of injured and contralateral non-injured areas of control and EMF-treated animals by histomorphometry, immunohistochemistry, RT-qPCR, Western blot, and ELISA. Our results revealed that EMF stimulation induced beneficial effect with the preservation of neuronal tissue morphology as well as the reduction of inflammatory markers at the transcriptional and translational levels. Immediate EMF application showed better resolution of inflammation. Although further studies are warranted, our findings contribute to the notion that EMF stimulation could be an effective therapeutic approach in TBI patients.

Regulation of microglial responses after pediatric traumatic brain injury: exploring the role of SHIP-1

Introduction

Severe traumatic brain injury (TBI) is the world's leading cause of permanent neurological disability in children. TBI-induced neurological deficits may be driven by neuroinflammation post-injury. Abnormal activity of SH2 domain-containing inositol 5' phosphatase-1 (SHIP-1) has been associated with dysregulated immunological responses, but the role of SHIP-1 in the brain remains unclear. The current study investigated the immunoregulatory role of SHIP-1 in a mouse model of moderate-severe pediatric TBI.

Methods

SHIP-1+/- and SHIP-1-/- mice underwent experimental TBI or sham surgery at post-natal day 21. Brain gene expression was examined across a time course, and immunofluorescence staining was evaluated to determine cellular immune responses, alongside peripheral serum cytokine levels by immunoassays. Brain tissue volume loss was measured using volumetric analysis, and behavior changes both acutely and chronically post-injury.

Results

Acutely, inflammatory gene expression was elevated in the injured cortex alongside increased IBA-1 expression and altered microglial morphology; but to a similar extent in SHIP-1-/- mice and littermate SHIP-1+/- control mice. Similarly, the infiltration and activation of CD68-positive macrophages, and reactivity of GFAP-positive astrocytes, was increased after TBI but comparable between genotypes. TBI increased anxiety-like behavior acutely, whereas SHIP-1 deficiency alone reduced general locomotor activity. Chronically, at 12-weeks post-TBI, SHIP-1-/- mice exhibited reduced body weight and increased circulating cytokines. Pro-inflammatory gene expression in the injured hippocampus was also elevated in SHIP-1-/- mice; however, GFAP immunoreactivity at the injury site in TBI mice was lower. TBI induced a comparable loss of cortical and hippocampal tissue in both genotypes, while SHIP-1-/- mice showed reduced general activity and impaired working memory, independent of TBI.

Conclusion

Together, evidence does not support SHIP-1 as an essential regulator of brain microglial morphology, brain immune responses, or the extent of tissue damage after moderate-severe pediatric TBI in mice. However, our data suggest that reduced SHIP-1 activity induces a greater inflammatory response in the hippocampus chronically post-TBI, warranting further investigation.

Interleukin-1 Receptor Antagonist as Therapy for Traumatic Brain Injury

Traumatic brain injury is a common type of acquired brain injury of varying severity carrying potentially deleterious consequences for the afflicted individuals, families, and society. Following the initial, traumatically induced insult, cellular injury processes ensue. These are believed to be amenable to treatment. Among such injuries, neuroinflammation has gained interest and has become a specific focus for both experimental and clinical researchers. Neuroinflammation is elicited almost immediately following trauma, and extend for a long time, possibly for years, after the primary injury. In the acute phase, the inflammatory response is characterized by innate mechanisms such as the activation of microglia which among else mediates cytokine production. Among the earliest cytokines to emerge are the interleukin- (IL-) 1 family members, comprising, for example, the agonist IL-1β and its competitive antagonist, IL-1 receptor antagonist (IL-1ra). Because of its early emergence following trauma and its increased concentrations also after human TBI, IL-1 has been hypothesized to be a tractable treatment target following TBI. Ample experimental data supports this, and demonstrates restored neurological behavior, diminished lesion zones, and an attenuated inflammatory response following IL-1 modulation either through IL-1 knock-out experiments, IL-1β inhibition, or IL-1ra treatment. Of these, IL-1ra treatment is likely the most physiological. In addition, recombinant human IL-1ra (anakinra) is already approved for utilization across a few rheumatologic disorders. As of today, one randomized clinical controlled trial has utilized IL-1ra inhibition as an intervention and demonstrated its safety. Further clinical trials powered for patient outcome are needed in order to demonstrate efficacy. In this review, we summarize IL-1 biology in relation to acute neuroinflammatory processes following TBI with a particular focus on current evidence for IL-1ra treatment both in the experimental and clinical context.

Genetic predisposition to Alzheimer's disease alters inflammasome activity after traumatic brain injury

Traumatic Brain Injury (TBI) is a major cause of death and disability in the US and a recognized risk factor for the development of Alzheimer's disease (AD). The relationship between these conditions is not completely understood, but the conditions may share additive or synergistic pathological hallmarks that may serve as novel therapeutic targets. Heightened inflammasome signaling plays a critical role in the pathogenesis of central nervous system injury (CNS) and the release of apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) speck from neurons and activated microglia contribute significantly to TBI and AD pathology. This study investigated whether inflammasome signaling after TBI was augmented in AD and whether this signaling pathway impacted biochemical and neuropathological outcomes and overall cognitive function. Five-month-old, 3xTg mice and respective wild type controls were randomized and underwent moderate controlled cortical impact (CCI) injury or served as sham/uninjured controls. Animals were sacrificed at 1 hour, 1 day, or 1 week after TBI to assess acute pathology or at 12 weeks after assessing cognitive function. The ipsilateral cerebral cortex was processed for inflammasome protein expression by immunoblotting. Mice were evaluated for behavior by open field (3 days), novel object recognition (2 weeks), and Morris water maze (6 weeks) testing after TBI. There was a statistically significant increase in the expression of inflammasome signaling proteins Caspase-1, Caspase-8, ASC, and interleukin (IL)-1β after TBI in both wild type and 3xTg animals. At 1-day post injury, significant increases in ASC and IL-1β protein expression were measured in AD TBI mice compared to WT TBI. Behavioral testing showed that injured AD mice had altered cognitive function when compared to injured WT mice. Elevated Aβ was seen in the ipsilateral cortex and hippocampus of sham and injured AD when compared to respective groups at 12 weeks post injury. Moreover, treatment of injured AD mice with IC100, an anti-ASC monoclonal antibody, inhibited the inflammasome, as evidenced by IL-1β reduction in the injured cortex at 1-week post injury. These findings show that the inflammasome response is heightened in mice genetically predisposed to AD and suggests that AD may exacerbate TBI pathology. Thus, dampening inflammasome signaling may offer a novel approach for the treatment of AD and TBI.

Activation of inflammasomes and their effects on neuroinflammation at the microelectrode-tissue interface in intracortical implants

Invasive neuroprosthetics rely on microelectrodes (MEs) to record or stimulate the activity of large neuron assemblies. However, MEs are subjected to tissue reactivity in the central nervous system (CNS) due to the foreign body response (FBR) that contribute to chronic neuroinflammation and ultimately result in ME failure. An endogenous, acute set of mechanisms responsible for the recognition and targeting of foreign objects, called the innate immune response, immediately follows the ME implant-induced trauma. Inflammasomes are multiprotein structures that play a critical role in the initiation of an innate immune response following CNS injuries. The activation of inflammasomes facilitates a range of innate immune response cascades and results in neuroinflammation and programmed cell death. Despite our current understanding of inflammasomes, their roles in the context of neural device implantation remain unknown. In this study, we implanted a non-functional Utah electrode array (UEA) into the rat somatosensory cortex and studied the inflammasome signaling and the corresponding downstream effects on inflammatory cytokine expression and the inflammasome-mediated cell death mechanism of pyroptosis. Our results not only demonstrate the continuous activation of inflammasomes and their contribution to neuroinflammation at the electrode-tissue interface but also reveal the therapeutic potential of targeting inflammasomes to attenuate the FBR in invasive neuroprosthetics.

Neuroprotective and Immunomodulatory Effects of Probiotics in a Rat Model of Parkinson's Disease

It is now well recognized that a bidirectional relationship between gut microbiota and the brain, referred to as the gut-brain axis, plays a prominent role in maintaining homeostasis and that a disruption in this axis can result in neuroinflammatory response and neurological disorders such as Parkinson's disease (PD). The protective action of probiotics such as Bifidobacterium animalis ssp. lactis Bb12 and Lactobacillus rhamnosus GG in various animal models of PD has been reported. Therefore, in this study, we used an inflammatory model of PD to assess the effects of a combination of these two probiotics (Microbiot^®) on motor behavior as well as on the response of microglia, including microglia morphology, to gain a better understanding of their mechanism of action. Microbiot^® (300 µL) was administered orally once daily for 15 days in a lipopolysaccharide-induced PD model using male Wistar rats. Although LPS-induced motor asymmetry in cylinder test was not affected by Microbiot^®, impairment of motor coordination in the narrow-beam test was significantly reduced by this probiotic. Moreover, Microbiot^® treatment reduced microglial activation suggesting an anti-inflammatory effect. While further mechanistic investigation of Microbiot^® in neurodegenerative diseases is warranted, our results support the potential utility of probiotics in PD.

Inflammasome activation in traumatic brain injury and Alzheimer's disease

Traumatic brain injury (TBI) and Alzheimer's disease (AD) represent 2 of the largest sources of death and disability in the United States. Recent studies have identified TBI as a potential risk factor for AD development, and numerous reports have shown that TBI is linked with AD associated protein expression during the acute phase of injury, suggesting an interplay between the 2 pathologies. The inflammasome is a multi-protein complex that plays a role in both TBI and AD pathologies, and is characterized by inflammatory cytokine release and pyroptotic cell death. Products of inflammasome signaling pathways activate microglia and astrocytes, which attempt to resolve pathological inflammation caused by inflammatory cytokine release and phagocytosis of cellular debris. Although the initial phase of the inflammatory response in the nervous system is beneficial, recent evidence has emerged that the heightened inflammatory response after trauma is self-perpetuating and results in additional damage in the central nervous system. Inflammasome-induced cytokines and inflammasome signaling proteins released from activated microglia interact with AD associated proteins and exacerbate AD pathological progression and cellular damage. Additionally, multiple genetic mutations associated with AD development alter microglia inflammatory activity, increasing and perpetuating inflammatory cell damage. In this review, we discuss the pathologies of TBI and AD and how they are impacted by and potentially interact through inflammasome activity and signaling proteins. We discuss current clinical trials that target the inflammasome to reduce heightened inflammation associated with these disorders.

Antidepressant and Neuroprotective Effects of 3-Hydroxy Paroxetine, an Analog of Paroxetine in Rats

BACKGROUND

Paroxetine (PX) is a widely used antidepressant with side effects such as weakness, dizziness, and trouble sleeping. In search of novel compounds with better efficacy and fewer side effects, we synthesized 3HPX, a hydroxylated analog of PX, and compared the 2 in silico for their pharmacokinetic and binding properties and in vivo for their antidepressant and potential neuroprotective effects.

METHODS

In silico studies compared pharmacological properties as well as interactions of PX and 3HPX with the serotonin transporter. In vivo studies utilized an animal model of comorbid depression-Parkinson disease. Adult male Wistar rats were injected (sterotaxically) with lipopolysaccharide in the striatum (unilaterally), followed by 14 days of once-daily injections (i.p.) of 10 mg/kg PX or 3HPX. Animals were tested for motor asymmetry and locomotor activity as well as indices of anhedonia and helplessness using sucrose preference and forced swim tests, respectively. Brains of these animals were collected after the last test, and tyrosine hydroxylase-positive neurons in substantia nigra pars compacta and Iba-1-positive stained microglia in ipsilateral striatum were measured.

RESULTS

In silico findings indicated that 3HPX could bind stronger to serotonin transporter and also have a better clearance and hence less toxicity compared with PX. In vivo results revealed a more effective reversal of immobility in the swim test, substantial increase in tyrosine hydroxylase-positive cells in the substantia nigra pars compacta, and more ramified Iba-1+ cells by 3HPX compared with PX.

CONCLUSION

The findings suggest superior effectiveness of 3HPX as an antidepressant and neuroprotectant compared with PX and hence potential utility in Parkinson disease depression co-morbidity.

Mechanism of action of IC 100, a humanized IgG4 monoclonal antibody targeting apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC)

Inflammasomes are multiprotein complexes of the innate immune response that recognize a diverse range of intracellular sensors of infection or cell damage and recruit the adaptor protein apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) into an inflammasome signaling complex. The recruitment, polymerization and cross-linking of ASC is upstream of caspase-1 activation and interleukin-1β release. Here we provide evidence that IC 100, a humanized IgG4κ monoclonal antibody against ASC, is internalized into the cell and localizes with endosomes, while another part is recycled and redistributed out of the cell. IC 100 binds intracellular ASC and blocks interleukin-1β release in a human whole blood cell inflammasome assay. In vitro studies demonstrate that IC 100 interferes with ASC polymerization and assembly of ASC specks. In vivo bioluminescence imaging showed that IC 100 has broad tissue distribution, crosses the blood brain barrier, and readily penetrates the brain and spinal cord parenchyma. Confocal microscopy of fluorescent-labeled IC 100 revealed that IC 100 is rapidly taken up by macrophages via a mechanism utilizing the Fc region of IC 100. Coimmunoprecipitation experiments and confocal immunohistochemistry showed that IC 100 binds to ASC and to the atypical antibody receptor Tripartite motif-containing protein-21 (TRIM21). In A549 WT and TRIM21 KO cells treated with either IC 100 or IgG4κ isotype control, the levels of intracellular IC 100 were higher than in the IgG4κ-treated controls at 2 hours, 1 day and 3 days after administration, indicating that IC 100 escapes degradation by the proteasome. Lastly, electron microscopy studies demonstrate that IC 100 binds to ASC filaments and alters the architecture of ASC filaments. Thus, IC 100 readily penetrates a variety of cell types, and it binds to intracellular ASC, but it is not degraded by the TRIM21 antibody-dependent intracellular neutralization pathway.

Inflammasomes as biomarkers and therapeutic targets in traumatic brain injury and related-neurodegenerative diseases: A comprehensive overview

Given the ambiguity surrounding traumatic brain injury (TBI) pathophysiology and the lack of any Food and Drug Administration (FDA)-approved neurotherapeutic drugs, there is an increasing need to better understand the mechanisms of TBI. Recently, the roles of inflammasomes have been highlighted as both potential therapeutic targets and diagnostic markers in different neurodegenerative disorders. Indeed, inflammasome activation plays a pivotal function in the central nervous system (CNS) response to many neurological conditions, as well as to several neurodegenerative disorders, specifically, TBI. This comprehensive review summarizes and critically discusses the mechanisms that govern the activation and assembly of inflammasome complexes and the major methods used to study inflammasome activation in TBI and its implication for other neurodegenerative disorders. Also, we will review how inflammasome activation is critical in CNS homeostasis and pathogenesis, and how it can impact chronic TBI sequalae and increase the risk of developing neurodegenerative diseases. Additionally, we discuss the recent updates on inflammasome-related biomarkers and the potential to utilize inflammasomes as putative therapeutic targets that hold the potential to better diagnose and treat subjects with TBI.

Dose-dependent modulation of microglia activation in rats after penetrating traumatic brain injury (pTBI) by transplanted human neural stem cells

Traumatic brain injury (TBI) often results in long-lasting patterns of neurological deficits including motor, sensory, and cognitive abnormalities. Cranial gunshot survivors are among the most disabled TBI patients and face a lifetime of disability with no approved strategies to protect or repair the brain after injury. Recent studies using a model of penetrating TBI (pTBI) have reported that human neural stem cells (hNSCs) transplantation can lead to dose and location-dependent neuroprotection. Evidence for regional patterns of microglial activation has also been reported after pTBI with evidence for microglial cell death by pyroptosis. Because of the importance of injury-induced microglial activation in the pathogenesis of TBI, we tested the hypothesis that dose-dependent hNSC mediated neuroprotection after pTBI was associated with reduced microglial activation in pericontusional cortical areas. To test this hypothesis, quantitative microglial/macrophage Iba1 immunohistochemistry and Sholl analysis was conducted to investigate the arborization patterns using four experimental groups including, (i) Sham operated (no injury) + low dose (0.16 million cells/rat), (ii) pTBI + vehicle (no cells), (iii) pTBI + low dose hNSCs (0.16 million/rat), and (iv) pTBI + high dose hNSCs (1.6 million cells/rat). At 3 months post-transplantation (transplants at one week after pTBI), the total number of intersections was significantly reduced in vehicle treated pTBI animals versus sham operated controls indicating increased microglia/macrophage activation. In contrast, hNSC transplantation led to a dose-dependent increase in the number of intersections compared to pTBI vehicle indicating less microglia/macrophage activation. The peak of Sholl intersections at 1 μm from the center of the microglia/macrophages ranged from ~6,500-14,000 intersections for sham operated, ~250-500 intersections for pTBI vehicle, ~550-1,000 intersections for pTBI low dose, and ~2,500-7,500 intersections for pTBI high dose. Plotting data along the rostrocaudal axis also showed that pericontusional cortical areas protected by hNSC transplantation had increased intersections compared to nontreated pTBI animals. These studies using a non-biased Sholl analysis demonstrated a dose-dependent reduction in inflammatory cell activation that may be associated with a neuroprotective effect driven by the cellular transplant in perilesional regions after pTBI.

Injury-Transplantation Interval-Dependent Amelioration of Axonal Degeneration and Motor Deficit in Rats with Penetrating Traumatic Brain Injury

Penetrating traumatic brain injury (pTBI) is increasingly survivable, but permanently disabling as adult mammalian nervous system does not regenerate. Recently, our group demonstrated transplant location-dependent neuroprotection and safety of clinical trial-grade human neural stem cell (hNSC) transplantation in a rodent model of acute pTBI. To evaluate whether longer injury-transplantation intervals marked by chronic inflammation impede engraftment, 60 male Sprague-Dawley rats were randomized to three sets. Each set was divided equally into two groups: 1) with no injury (sham) or 2) pTBI. After either 1 week (groups 1 and 2), 2 weeks (groups 3 and 4), or 4 weeks after injury (groups 5 and 6), each animal received 0.5 million hNSCs perilesionally. A seventh group of pTBI animals treated with vehicle served as the negative control. All animals were allowed to survive 12 weeks with standard chemical immunosuppression. Motor capacity was assessed pre-transplant to establish injury-induced deficit and followed by testing at 8 and 12 weeks after transplantation. Animals were euthanized, perfused, and examined for lesion size, axonal degeneration, and engraftment. Compared to vehicle, transplanted groups showed a trend for reduced lesion size and axonal injury across intervals. Remote secondary axonal injury was significantly reduced in groups 2 and 4, but not in group 6. The majority of animals showed robust engraftment independent of the injury-transplant time interval. Modest amelioration of motor deficit paralleled the axonal injury trend. In aggregate, pTBI-induced remote secondary axonal injury was resolved by early, but not delayed, hNSC transplantation.

Methods to Study Inflammasome Activation in the Central Nervous System: Immunoblotting and Immunohistochemistry

The inflammasome is a multiprotein complex that is responsible for mounting an innate immune response through the activation of caspase-1 and the cleavage of interleukin-1β. This multiprotein complex plays an important role in a variety of central nervous system (CNS) diseases and conditions such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, stroke, and traumatic brain injury, among others. Here we describe methodological procedures to carry out immunoblotting and immunohistochemical techniques used to study inflammasome signaling in CNS tissues (brain and spinal cord).

LncRNA Tug1 Contributes Post-stroke NLRP3 Inflammasome-Dependent Pyroptosis via miR-145a-5p/Tlr4 Axis

Pyroptosis, a type of programmed cell death illuminated by inflammasomes and active caspases, is implicated in post-stroke inflammation. Our previous study showed that lncRNA taurine upregulated gene 1 (Tug1) sponging miR-145a-5p modulated microglial activation after oxygen-glucose deprivation (OGD). However, the role and mechanism of Tug1 on post-stroke pyroptosis is not fully clear. Photo-thrombosis stroke mice and OGD-treated BV-2 microglia were established respectively. Tug1 knockdown or overexpression was achieved by intraventricular infusion of AAV-shTug1 in vivo, or transfection of siTug1 and pcDNA3.1-Tug1 in vitro. Neurological function and infarction volume were evaluated. Meanwhile, pyroptosis-associated proteins (IL-1β, IL-18, NLRP3, ASC, cleaved-caspase-1, and GSDMD-N), TLR4, and p-p65/p65 as well as Tug1 and miR-145a-5p were detected 24 h after photo-thrombosis or 4 h after OGD by qRT-PCR, western blot, and ELISA. The correlation between Tug1/miR-145a-5p/Tlr4 axis and pyroptosis was explored by dual-luciferase reporter assay and functional gain-and-loss experiments. Photo-thrombosis or OGD caused neural injury and upregulated pyroptosis-associated proteins, Tug1, TLR4, and p-p65 as well as downregulated miR-145a-5p, which was prevented by Tug1 knockdown in vivo and in vitro. Tlr4 gene, putatively binding with miR-145a-5p by bioinformatics analysis, was found to be a direct target of miR-145a-5p with negative interactions. Furthermore, miR-145a-5p inhibitor abolished the inhibitive effects of siTug1 on TLR4 and p-p65 as well as pyroptosis-associated proteins, whereas miR-145a-5p mimics abrogated the enhanced effects of pcDNA3.1-Tug1 on that, suggesting an involvement of Tug1/miR-145a-5p/Tlr4 axis on pyroptosis. Tug1 contributes NLRP3 inflammasome-dependent pyroptosis through miR-145a-5p/Tlr4 axis post-stroke, providing a promising therapeutic strategy against inflammatory injury.

Mesenchymal stem cells protect against TBI-induced pyroptosis in vivo and in vitro through TSG-6

Background

Pyroptosis, especially microglial pyroptosis, may play an important role in central nervous system pathologies, including traumatic brain injury (TBI). Transplantation of mesenchymal stem cells (MSCs), such as human umbilical cord MSCs (hUMSCs), has been a focus of brain injury treatment. Recently, MSCs have been found to play a role in many diseases by regulating the pyroptosis pathway. However, the effect of MSC transplantation on pyroptosis following TBI remains unknown. Tumor necrosis factor α stimulated gene 6/protein (TSG-6), a potent anti-inflammatory factor expressed in many cell types including MSCs, plays an anti-inflammatory role in many diseases; however, the effect of TSG-6 secreted by MSCs on pyroptosis remains unclear.

Methods

Mice were subjected to controlled cortical impact injury in vivo. To assess the time course of pyroptosis after TBI, brains of TBI mice were collected at different time points. To study the effect of TSG-6 secreted by hUMSCs in regulating pyroptosis, normal hUMSCs, sh-TSG-6 hUMSCs, or different concentrations of rmTSG-6 were injected intracerebroventricularly into mice 4 h after TBI. Neurological deficits, double immunofluorescence staining, presence of inflammatory factors, cell apoptosis, and pyroptosis were assessed. In vitro, we investigated the anti-pyroptosis effects of hUMSCs and TSG-6 in a lipopolysaccharide/ATP-induced BV2 microglial pyroptosis model.

Results

In TBI mice, the co-localization of Iba-1 (marking microglia/macrophages) with NLRP3/Caspase-1 p20/GSDMD was distinctly observed at 48 h. In vivo, hUMSC transplantation or treatment with rmTSG-6 in TBI mice significantly improved neurological deficits, reduced inflammatory cytokine expression, and inhibited both NLRP3/Caspase-1 p20/GSDMD expression and microglial pyroptosis in the cerebral cortices of TBI mice. However, the therapeutic effect of hUMSCs on TBI mice was reduced by the inhibition of TSG-6 expression in hUMSCs. In vitro, lipopolysaccharide/ATP-induced BV2 microglial pyroptosis was inhibited by co-culture with hUMSCs or with rmTSG-6. However, the inhibitory effect of hUMSCs on BV2 microglial pyroptosis was significantly reduced by TSG-6-shRNA transfection.

Conclusion

In TBI mice, microglial pyroptosis was observed. Both in vivo and in vitro, hUMSCs inhibited pyroptosis, particularly microglial pyroptosis, by regulating the NLRP3/Caspase-1/GSDMD signaling pathway via TSG-6.

Assessing fetal human neural stem cells tumorigenicity potential in athymic rats with penetrating traumatic brain injury (pTBI)

Traumatic brain injuries (TBI) often produce disability in survivors due to unresolved inflammation and progressive neurodegeneration. The central nervous system in mammals is incapable of self-repair. Two decades of preclinical studies and clinical trials have provided insights into TBI pathophysiology that could be utilized to develop clinically relevant therapy. Our laboratory recently reported efficacy of clinical trial grade fetal human neural stem cells (hNSCs) in immunosuppressed rats with penetrating traumatic brain injury (pTBI). Next, in compliance with the United States Food and Drug Administration (USFDA) guidance, this study explores safety by assessing the tumorigenicity potential of intracranial hNSC transplants in athymic rats with pTBI. First, the maximum tolerated dose (MTD) was determined. Then, forty athymic pTBI rats were randomized to either: Group A. pTBI + vehicle or Group B. pTBI + hNSCs at MTD one week after injury with 6-months survival, sufficient time to uncover transplant associated tumorigenicity. A board-certified Pathologist examined hematoxylin-eosin (H&E), Ki67 immunostained brain and spinal cord, serial sections along with several abnormal peripheral masses for evidence of lesion, transplant, and oncogenesis. There was no evidence of transplant derived tumors or oncogenic tissue necrosis. Consistent with athymic literature, the lesion remained unchanged even after robust hNSC engraftment. This safety study supports the conclusion that hNSCs are safe for transplantation in pTBI. The differences in lesion expansion between immunosuppressed and athymic rats in the presence of hNSCs suggests an unexpected role for thymus derived cells in resolution of trauma induced inflammation.

Paeonol regulates NLRP3 inflammasomes and pyroptosis to alleviate spinal cord injury of rat

Background

Spinal cord injury (SCI) is a life-threatening traumatic disorder. Paeonol has been confirmed to be involved in a variety of diseases. The purpose of this study is to investigate the role of paeonol on SCI progression.

Methods

Sprague Dawley (SD) rat was used for the establishment of SCI model to explore the anti-inflammation, anti-oxidation, and neuroprotective effects of paeonol (60 mg/kg) on SCI in vivo. For in vitro study, mouse primary microglial cells (BV-2) were induced by lipopolysaccharide (LPS)/adenosine triphosphate (ATP) treatment. The effect of paeonol on the polarization of LPS/ATP-induced BV-2 cells was determined by detection the expression inducible nitric oxide synthase (iNOS), tumour necrosis factor alpha (TNF-α), arginase-1 (Arg-1), and interleukin (IL)-10 using qRT-PCR. ELISA was used to assess the levels of IL-1β, IL-18, TNF-α, malondialdehyde (MDA), and glutathione (GSH). Western blotting was conducted to determine the levels of NLRP3 inflammasomes and TLR4/MyD88/NF-κB (p65) pathway proteins.

Results

Paeonol promoted the recovery of locomotion function and spinal cord structure, and decreased spinal cord water content in rats following SCI. Meanwhile, paeonol reduced the levels of apoptosis-associated speck-like protein (ASC), NLRP3, active caspase 1 and N-gasdermin D (N-GSDMD), repressed the contents of IL-1β, IL-18, TNF-α and MDA, and elevated GSH level. In vitro, paeonol exerted similarly inhibiting effects on pyroptosis and inflammation. Meanwhile, paeonol promoted BV-2 cells M2 polarization. In addition, paeonol also inactivated the expression of TLR4/MyD88/NF-κB (p65) pathway.

Conclusion

Paeonol may regulate NLRP3 inflammasomes and pyroptosis to alleviate SCI, pointing out the potential for treating SCI in clinic.

Targeting NLRP3 signaling by a novel-designed sulfonylurea compound for inhibition of microglial inflammation

The nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome plays an important role in microglia-mediated inflammation. Dysregulation of NLRP3 signaling results in microglial activation and triggers inflammatory responses contributing to the development of neurological disorders including ischemic stroke, schizophrenia, Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). Inhibition of the NLRP3-linked inflammatory pathways reduces microglia-induced inflammation and is considered as a promising therapeutic approach for neuro-inflammatory diseases. In the present study, we report the development of AMS-17, a rationally-designed tertiary sulfonylurea compound for inhibition of inflammation in microglia. AMS-17 inhibited expression of the NLRP3, and its downstream components and cytokines such as caspase-1, tumor necrosis factor-α (TNF-α), IL-1β and inducible nitric oxide synthase (iNOS). It also suppressed lipopolysaccharide (LPS)-induced N9 microglial cell phagocytosis in vitro and activation of the microglia in mouse brain in vivo. Together, these results provide promising evidences for the inhibitory effects of AMS-17 in inflammation. This proof-of-concept study provides a new chemical scaffold, designed with the aid of pharmacophore modeling, with NLRP3 inhibitory activity which can be further developed for the treatment of inflammation-associated neurological disorders.

The Role of Non-canonical and Canonical Inflammasomes in Inflammaging

Neurodegenerative diseases currently affect millions of people worldwide and continues to increase in the expanding elderly population. Neurodegenerative diseases usually involve cognitive decline and are among the top causes of death. Thus, there is a critical need for the development of treatments and preventive strategies for neurodegenerative diseases. One of the risk factors of neurodegeneration is inflammaging, a low level of chronic inflammation due to old age. We have previously shown that the inflammasome contributes to inflammaging in the central nervous system (CNS). The inflammasome is a multiprotein complex of the innate immune response consisting of a sensor protein, apoptosis speck-like protein containing a CARD (ASC), and caspase-1. Our lab has developed a humanized monoclonal antibody against ASC (anti-ASC). Here, we analyzed cortical lysates from young (3 months old), aged (18 months old), and aged anti-ASC treated mice for the expression of canonical and non-canonical inflammasome proteins. We show that the protein levels of NLRP1, ASC, caspase-1, and caspase-8 were elevated in the cortex of aged mice, and that anti-ASC decreased the expression of these proteins, consistent with lower levels of the pro-inflammatory cytokine interleukin (IL)-1β. Additionally, we show that these proteins form a novel NLRP1-caspase-8 non-canonical inflammasome comprised of NLRP1, caspase-8 and ASC. Moreover, these inflammasome proteins were present in neurons in young and aged mice. Together, these results indicate that a novel NLRP1-caspase-8 non-canonical inflammasome is present in the cortex of mice and that anti-ASC is a potential therapeutic to decrease inflammasome-mediated inflammaging in the CNS.

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.

Crosstalk between Neuron and Glial Cells in Oxidative Injury and Neuroprotection

To counteract oxidative stress and associated brain diseases, antioxidant systems rescue neuronal cells from oxidative stress by neutralizing reactive oxygen species and preserving gene regulation. It is necessary to understand the communication and interactions between brain cells, including neurons, astrocytes and microglia, to understand oxidative stress and antioxidant mechanisms. Here, the role of glia in the protection of neurons against oxidative injury and glia–neuron crosstalk to maintain antioxidant defense mechanisms and brain protection are reviewed. The first part of this review focuses on the role of glia in the morphological and physiological changes required for brain homeostasis under oxidative stress and antioxidant defense mechanisms. The second part focuses on the essential crosstalk between neurons and glia for redox balance in the brain for protection against oxidative stress.

Pyruvate kinase M2 (PKM2) interacts with activating transcription factor 2 (ATF2) to bridge glycolysis and pyroptosis in microglia

Pyruvate kinase M2 (PKM2), a glycolytic rate-limiting enzyme, reportedly plays an important role in tumorigenesis and the inflammatory response by regulating the metabolic reprogramming. However, its contribution to microglial activation during neuroinflammation is still unknown. In this study, we observed an enhanced glycolysis level in the lipopolysaccharide (LPS)-activated microglia. Utilizing the glycolysis inhibitor 2-DG, we proved that LPS requires glycolysis to induce microglial pyroptosis. Moreover, the protein expression, dimer/monomer formation, phosphorylation and nuclear translocation of PKM2 were all increased by LPS. Silencing PKM2 or preventing its nuclear translocation by TEPP-46 significantly alleviated the LPS-induced inflammatory response and pyroptosis in microglia. Employing biological mass spectrometry combined with immunoprecipitation technology, we identified for the first time that PKM2 interacts with activating transcription factor 2 (ATF2) in microglia. Inhibition of glycolysis or preventing PKM2 nuclear aggregation significantly reduced the phosphorylation and activation of ATF2. Furthermore, knocking down ATF2 reduced the LPS-induced pyroptosis of microglia. In vivo, we showed the LPS-induced pyroptosis in the cerebral cortex tissues of mice, and first found that an increased PKM2 expression was co-localized with ATF2 in the inflamed mice brain. Collectively, our data suggested for the first time that PKM2, a key rate-limiting enzyme of the Warburg effect, directly interacts with the pro-inflammatory transcription factor ATF2 to bridge glycolysis and pyroptosis in microglia, which might be a pivotal crosstalk between metabolic reprogramming and neuroinflammation in the CNS.

Pyroptosis, and its Role in Central Nervous System Disease

Pyroptosis is an inflammatory form of cell death executed by transmembrane pore-forming proteins known as gasdermins and can be activated in an inflammasome-dependent or -independent manner. Inflammasome-dependent pyroptosis is triggered in response to pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs) and has emerged as an important player in the pathogenesis of multiple inflammatory diseases, mainly by releasing inflammatory contents. More recently, numerous studies have revealed the intricate mechanisms of pyroptosis and its role in the development of neuroinflammation in central nervous system (CNS) diseases. In this review, we summarize current understandings of the molecular and regulatory mechanisms of pyroptosis. In addition, we discuss how pyroptosis can drive different forms of neurological diseases and new promising therapeutic strategies targeting pyroptosis that can be leveraged to treat neuroinflammation.

Traumatic Brain Injury: Mechanisms of Glial Response

Traumatic brain injury (TBI) is a heterogeneous disorder that involves brain damage due to external forces. TBI is the main factor of death and morbidity in young males with a high incidence worldwide. TBI causes central nervous system (CNS) damage under a variety of mechanisms, including synaptic dysfunction, protein aggregation, mitochondrial dysfunction, oxidative stress, and neuroinflammation. Glial cells comprise most cells in CNS, which are mediators in the brain’s response to TBI. In the CNS are present astrocytes, microglia, oligodendrocytes, and polydendrocytes (NG2 cells). Astrocytes play critical roles in brain’s ion and water homeostasis, energy metabolism, blood-brain barrier, and immune response. In response to TBI, astrocytes change their morphology and protein expression. Microglia are the primary immune cells in the CNS with phagocytic activity. After TBI, microglia also change their morphology and release both pro and anti-inflammatory mediators. Oligodendrocytes are the myelin producers of the CNS, promoting axonal support. TBI causes oligodendrocyte apoptosis, demyelination, and axonal transport disruption. There are also various interactions between these glial cells and neurons in response to TBI that contribute to the pathophysiology of TBI. In this review, we summarize several glial hallmarks relevant for understanding the brain injury and neuronal damage under TBI conditions.

Penetrating Ballistic Brain Injury Produces Acute Alterations in Sleep and Circadian-Related Genes in the Rodent Cortex: A Preliminary Study

Traumatic brain injury (TBI) affects millions of Americans each year, with extremely high prevalence in the Veteran community, and sleep disturbance is one of the most commonly reported symptoms. Reduction in the quality and amount of sleep can negatively impact recovery and result in a wide range of behavioral and physiological symptoms, such as impaired cognition, mood and anxiety disorders, and cardiovascular effects. Thus, to improve long-term patient outcomes and develop novel treatments, it is essential to understand the molecular mechanisms involved in sleep disturbance following TBI. In this effort, we performed transcriptional profiling in an established rodent model of penetrating ballistic brain injury (PBBI) in conjunction with continuous sleep/wake EEG/EMG recording of the first 24 h after injury. Rats subjected to PBBI showed profound differences in sleep architecture. Injured animals spent significantly more time in slow wave sleep and less time in REM sleep compared to sham control animals. To identify PBBI-related transcriptional differences, we then performed transcriptome-wide gene expression profiling at 24 h post-injury, which identified a vast array of immune- related genes differentially expressed in the injured cortex as well as sleep-related genes. Further, transcriptional changes associated with total time spent in various sleep stages were identified. Such molecular changes may underlie the pathology and symptoms that emerge following TBI, including neurodegeneration, sleep disturbance, and mood disorders.

The immunological influence of physical exercise on TBI-induced pathophysiology: Crosstalk between the spleen, gut, and brain

Traumatic brain injury (TBI) is a non-degenerative and non-congenital insult to the brain and is recognized as a global public health problem, with a high incidence of neurological disorders. Despite the causal relationship not being entirely known, it has been suggested that multiorgan inflammatory response involving the autonomic nervous system and the spleen-gut brain axis dysfunction exacerbate the TBI pathogenesis in the brain. Thus, applying new therapeutic tools, such as physical exercise, have been described in the literature to act on the immune modulation induced by brain injuries. However, there are caveats to consider when interpreting the effects of physical exercise on this neurological injury. Given the above, this review will highlight the main findings of the literature involving peripheral immune responses in TBI-induced neurological damage and how changes in the cellular metabolism of the spleen-gut brain axis elicited by different protocols of physical exercise alter the pathophysiology induced by this neurological injury.

HIF-1α aggravated traumatic brain injury by NLRP3 inflammasome-mediated pyroptosis and activation of microglia

Hypoxia inducible factor 1 alpha (HIF-1α) is involved in regulating the biological functions of neuronal death after traumatic brain injury (TBI), and attaches importance in the inflammatory response, but its potential mechanism is still unknown. Our study aimed to explore the regulatory mechanism between HIF-1α and NLRP3 inflammasome after TBI. Male mice underwent controlled cortical impact (CCI) or sham-operated procedures. Brain water content and blood-brain barrier permeability were measured at the indicated time after TBI. The behavioral performance, ELISA, immunofluorescence, and western blot analysis were used to determine whether HIF-1α specifically targeted TBI-induced pyroptosis. We discovered that TBI-induced brain injury caused by external mechanical forces is characterized by edema and blood-brain barrier disorder, and the release of IL-1β, IL-18, and LDH and upregulation of HIF-1α expression, reaching the peak on the third day post-TBI. In addition, HIF-1α accumulated NLRP3 inflammasome-mediated pyroptosis and activation of microglia. The protein expressions of NLRP3, GSDMD, GSDMD-N, pro-caspase 1, and cleaved caspase 1 were markedly increased in the injured cortex, which were restored to normal levels by the interference of HIF-1α. The inactivation of HIF-1α conferred neuroprotection and alleviated brain injury after TBI. HIF-1α was implicated in TBI-induced brain injury, aggravated NLRP3 inflammasome -mediated pyroptosis, and the activation of microglia, which provided a potential target for treating TBI.

Pretreatment with kaempferol attenuates microglia-mediate neuroinflammation by inhibiting MAPKs-NF-κB signaling pathway and pyroptosis after secondary spinal cord injury

Spinal cord injury (SCI) is a devastating injury that characterized by oxidative stress and inflammatory response. Kaempferol is reported to be an anti-neuroinflammation in neurologic disorders. Nevertheless, the role and mechanism of kaempferol in SCI remains unclear. The present study aims to investigate effects of kaempferol on SCI and its possible underlying mechanisms in in vivo and in vitro models. A C5 hemi-contusion injury was induced in Sprague-Dawley rats to investigate the neuroprotective effects of kaempferol after SCI. For in vitro study, the BV2 microglia cell lines were pretreated with or without kaempferol. A combination of molecular and histological methods was used to clarify the mechanism and explore the signaling pathway both in vivo and in vitro. One-way analysis of variance (ANOVA) was conducted with Bonferroni post hoc tests to examine the differences between groups. The in vivo studies showed that kaempferol could improve the recovery of hindlimb motor function and ameliorate tissue damage in the spinal cord after SCI. Moreover, administration of kaempferol reduced microglia activation and oxidative stress level in the spinal cord. The in vitro studies showed that kaempferol suppressed the microglia activation resulting from the administration of LPS with ATP to BV-2 cells. Pretreated BV2 cells with kaempferol reduced the generation of reactive oxygen species (ROS) by inhibiting NADPH oxidase 4, and then, suppressed the phosphorylation of p38 MAPK and JNK, which subsequently inhibited nuclear translocation of NF-κB p65 to express pro-inflammatory factors. We also observed that kaempferol could inhibite the pyroptosis related proteins (NLRP3 Caspase-1 p10 ASC N-GSDMD) and reduce the release of IL-18 and IL-1β. In conclusion, kaempferol was able to reduce oxidative stress and inflammatory response through down-regulation of ROS dependent MAPKs- NF-κB and pyroptosis signaling pathway, which suggested that kaempferol might be a novel promising therapeutic agent for SCI.

Dynamics of Central Remyelination and Treatment Evolution in a Model of Multiple Sclerosis with Optic Coherence Tomography

The need for remyelinating drugs is essential for healing disabling diseases such as multiple sclerosis (MS). One of the reasons for the lack of this class of therapies is the impossibility to monitor remyelination in vivo, which is of utmost importance to perform effective clinical trials. Here, we show how optical coherence tomography (OCT), a cheap and non-invasive technique commonly used in ophthalmology, may be used to assess remyelination in vivo in MS patients. Our pioneer approach validates OCT as a technique to study remyelination of the optic nerve and reflects what is occurring in non-accessible central nervous system (CNS) structures, like the spinal cord. In this study we used the orally bioavailable small molecule VP3.15, confirming its therapeutical potential as a neuroprotective, anti-inflammatory, and probably remyelinating drug for MS. Altogether, our results confirm the usefulness of OCT to monitor the efficacy of remyelinating therapies in vivo and underscore the relevance of VP3.15 as a potential disease modifying drug for MS therapy.

Ac-FLTD-CMK inhibits pyroptosis and exerts neuroprotective effect in a mice model of traumatic brain injury

Pyroptosis has been reported to contribute to the traumatic brain injury (TBI) process. Ac-FLTD-CMK is a newly synthesized pyroptosis inhibitor. However, whether Ac-FLTD-CMK inhibits pyroptosis and plays a neuroprotective role after TBI is unknown. The present study aimed to determine the effects of Ac-FLTD-CMK on TBI in a mouse model. Male C57BL/6 mice were randomly divided into sham, TBI + vehicle, and TBI + Ac-FLTD-CMK groups. TBI was induced using a weight-drop apparatus. Intraventricular injection of Ac-FLTD-CMK was performed 30 min after TBI. Caspase-1, caspase-11, gasdermin-D (GSDMD), and caspase-3 expression in the peri-contusional cortex were assessed by western blotting. Interleukin-1β (IL-1β) and interleukin-18 (IL-18) expression in the peri-contusional cortex were measured using ELISA. Behavioral experiments, brain water content, Evans blue extravasation, lactate dehydrogenase (LDH) release, and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling staining were also performed. The results showed that Ac-FLTD-CMK administration significantly downregulated caspase-1 p20, caspase-11 p20, GSDMD N-terminal, IL-1β, and IL-18 expression; reduced LDH release; alleviated neuronal death; attenuated brain edema and blood-brain barrier damage; and improved neurobehavioral function. These findings indicate that Ac-FLTD-CMK treatment suppresses pyroptosis and protects mice against TBI.

The NLRP3 inflammasome: a potential therapeutic target for traumatic brain injury

Although the precise mechanisms contributing to secondary brain injury following traumatic brain injury are complex and obscure, a number of studies have demonstrated that inflammatory responses are an obvious and early feature in the pathogenesis of traumatic brain injury. Inflammasomes are multiprotein complexes that prompt the stimulation of caspase-1 and subsequently induce the maturation and secretion of proinflammatory cytokines, such as interleukin-1β and interleukin-18. These cytokines play a pivotal role in facilitating innate immune responses and inflammation. Among various inflammasome complexes, the NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is the best characterized, a crucial role for NLRP3 has been demonstrated in various brain diseases, including traumatic brain injury. Several recent studies have revealed the contribution of NLRP3 inflammasome in identifying cellular damage and stimulating inflammatory responses to aseptic tissue injury after traumatic brain injury. Even more important, blocking or inhibiting the activation of the NLRP3 inflammasome may have substantial potential to salvage tissue damage during traumatic brain injury. In this review, we summarize recently described mechanisms that are involved in the activation and regulation of the NLRP3 inflammasome. Moreover, we review the recent investigations on the contribution of the NLRP3 inflammasome in the pathophysiology of TBI, and current advances and challenges in potential NLRP3-targeted therapies. A significant contribution of NLRP3 inflammasome activation to traumatic brain injury implies that therapeutic approaches focused on targeting specific inflammasome components could significantly improve the traumatic brain injury outcomes.

Ablation of GSDMD Improves Outcome of Ischemic Stroke Through Blocking Canonical and Non-canonical Inflammasomes Dependent Pyroptosis in Microglia

Ischemia/reperfusion (I/R) injury is a significant cause of mortality and long-term disability worldwide. Recent evidence has proved that pyroptosis, a novel cell death form, contributes to inflammation-induced neuron death and neurological function impairment following ischemic stroke. Gasdermin D (GSDMD) is a newly discovered key molecule of cell pyroptosis, but its biological function and precise role in ischemic stroke are still unclear. The present study investigates the cleavage activity of GSDMD, localization of pyroptotic cells, and global neuroinflammation in gsdmd ^-/- mice after I/R. The level of cell pyroptosis around the infarcted area was significantly increased in the acute phase of cerebral I/R injury. The ablation of GSDMD reduced the infraction volume and improved neurological function against cerebral I/R injury. Furthermore, we confirmed I/R injury induced cell pyroptosis mainly in microglia. Knockdown of GSDMD effectively inhibited the secretion of mature IL-1β and IL-18 from microglia cells but did not affect the expression of caspase-1/11 in vitro and in vivo. In summary, blocking GSDMD expression might serve as a potential therapeutic strategy for ischemic stroke.

Penetrating Ballistic-Like Brain Injury Leads to MicroRNA Dysregulation, BACE1 Upregulation, and Amyloid Precursor Protein Loss in Lesioned Rat Brain Tissues

Severe traumatic brain injury (TBI) is a risk factor for neurodegenerative diseases. Yet, the molecular events involving dysregulated miRNAs that may be associated with protein degradation in the brain remains elusive. Quantitation of more than 800 miRNAs was conducted using rat ipsilateral coronal brain tissues collected 1, 3, or 7 days after penetrating ballistic-like brain injury (PBBI). As a control for each time-point, Sham-operated animals received craniotomy alone. Microarray and systems biology analysis indicated that the amplitude and complexity of miRNAs affected were greatest 7 day after PBBI. Arrays and Q-PCR inferred that dysregulation of miR-135a, miR-328, miR-29c, and miR-21 were associated with altered levels of beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), PSEN1, PSEN2, and amyloid precursor protein (APP) genes. These events were followed by increased levels of mature BACE1 protein and concomitant loss of full length APP within 3–7 days, then elevation of amyloid beta (Aβ)-40 7 days after PBBI. This study indicates that miRNA arrays, coupled with systems biology, may be used to guide study design prior validation of miRNA dysregulation. Associative analysis of miRNAs, mRNAs, and proteins within a proposed pathway are poised for further validation as biomarkers and therapeutic targets relevant to TBI-induced APP loss and subsequent Aβ peptide generation during neurodegeneration.

Role of inflammasomes in multiple sclerosis and their potential as therapeutic targets

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS), and it remains the most common immune-mediated disorder affecting the CNS. While the cause of MS is unclear, the underlying pathomechanisms are thought to be either destruction by autoimmune T cells or dysfunction of myelin-producing cells. Recent advances have indicated that inflammasomes contribute the etiology of MS. Inflammasomes are multiprotein complexes of the innate immune response involved in the processing of caspase-1, the activation of pro-inflammatory cytokines interleukin (IL)-1β and IL-18 as well as the cell death-mediated mechanism of pyroptosis and the activation of the adaptive immune response. Here we review the literature to date on the role of different inflammasome signaling pathways in the pathogenesis of MS and how these pathways may be targeted to reduce deleterious inflammatory processes and improve outcomes in this patient population.

Activation of the executioner caspases-3 and -7 promotes microglial pyroptosis in models of multiple sclerosis

BACKGROUND

Pyroptosis is a type of proinflammatory regulated cell death (RCD) in which caspase-1 proteolytically cleaves gasdermin D (GSDMD) to yield a cytotoxic pore-forming protein. Recent studies have suggested that additional cell death pathways may interact with GSDMD under certain circumstances to execute pyroptosis. Microglia/macrophages in the central nervous system (CNS) undergo GSDMD-associated pyroptosis in multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE) but the contribution of other cell death pathways to this phenomenon is unknown. Herein, we tested the hypothesis that multiple RCD pathways underlie microglial pyroptosis in the context of neuroinflammation.

METHODS

A siRNA screen of genes with known RCD functions was performed in primary human microglia to evaluate their role in nigericin-induced pyroptosis using supernatant lactate dehydrogenase activity as a read-out of cell lysis. Activation of apoptotic executioner proteins and their contribution to pyroptosis was assessed using semi-quantitative confocal microscopy, high-sensitivity ELISA, immunoblot, cell lysis assays, and activity-based fluorescent probes. Quantification of pyroptosis-related protein expression was performed in CNS lesions from patients with progressive MS and mice with MOG_35-55-induced EAE, and in matched controls.

RESULTS

Among progressive MS patients, activated caspase-3 was detected in GSDMD immunopositive pyroptotic microglia/macrophages within demyelinating lesions. In the siRNA screen, suppression of caspase-3/7, caspase-1, or GSDMD expression prevented plasma membrane rupture during pyroptosis. Upon exposure to pyroptotic stimuli (ATP or nigericin), human microglia displayed caspase-3/7 activation and cleavage of caspase-3/7-specific substrates (e.g., DFF45, ROCK1, and PARP), with accompanying features of pyroptosis including GSDMD immunopositive pyroptotic bodies, IL-1β release, and membrane rupture. Pyroptosis-associated nuclear condensation and pyroptotic body formation were suppressed by caspase-3/7 inhibition. Pharmacological and siRNA-mediated inhibition of caspase-1 diminished caspase-3/7 activation during pyroptosis. In mice with EAE-associated neurological deficits, activated caspase-3 colocalized with GSDMD immunopositivity in lesion-associated macrophages/microglia.

CONCLUSIONS

Activation of executioner caspases-3/7, widely considered key mediators of apoptosis, contributed to GSDMD-associated microglial pyroptosis under neuroinflammatory conditions. Collectively, these observations highlight the convergence of different cell death pathways during neuroinflammation and offer new therapeutic opportunities in neuroinflammatory disease.

Oxidative Stress-Mediated Blood-Brain Barrier (BBB) Disruption in Neurological Diseases

The blood-brain barrier (BBB), as a crucial gate of brain-blood molecular exchange, is involved in the pathogenesis of multiple neurological diseases. Oxidative stress is caused by an imbalance between the production of reactive oxygen species (ROS) and the scavenger system. Since oxidative stress plays a significant role in the production and maintenance of the BBB, the cerebrovascular system is especially vulnerable to it. The pathways that initiate BBB dysfunction include, but are not limited to, mitochondrial dysfunction, excitotoxicity, iron metabolism, cytokines, pyroptosis, and necroptosis, all converging on the generation of ROS. Interestingly, ROS also provide common triggers that directly regulate BBB damage, parameters including tight junction (TJ) modifications, transporters, matrix metalloproteinase (MMP) activation, inflammatory responses, and autophagy. We will discuss the role of oxidative stress-mediated BBB disruption in neurological diseases, such as hemorrhagic stroke, ischemic stroke (IS), Alzheimer’s disease (AD), Parkinson’s disease (PD), traumatic brain injury (TBI), amyotrophic lateral sclerosis (ALS), and cerebral small vessel disease (CSVD). This review will also discuss the latest clinical evidence of potential biomarkers and antioxidant drugs towards oxidative stress in neurological diseases. A deeper understanding of how oxidative stress damages BBB may open up more therapeutic options for the treatment of neurological diseases.

IC100: a novel anti-ASC monoclonal antibody improves functional outcomes in an animal model of multiple sclerosis

BACKGROUND

The inflammasome adaptor apoptosis-associated speck-like protein containing a CARD (ASC) is involved in immune signaling by bridging the interactions between inflammasome sensors and caspase-1. Strong experimental evidence has shown that ASC-/- mice are protected from disease progression in animal models of multiple sclerosis (MS), suggesting that targeting inflammasome activation via ASC inhibition may be a promising therapeutic strategy in MS. Thus, the goal of our study is to test the efficacy of IC100, a novel humanized antibody targeting ASC, in preventing and/or suppressing disease in the experimental autoimmune encephalomyelitis (EAE) model of MS.

METHODS

We employed the EAE model of MS where disease was induced by immunization of C57BL/6 mice with myelin oligodendrocyte glycoprotein peptide 35-55 (MOG35-55). Mice were treated with vehicle or increasing doses of IC100 (10, 30, and 45 mg/kg) and clinical disease course was evaluated up to 35 days post EAE induction. Immune cell infiltration into the spinal cord and microglia responses were assessed.

RESULTS

We show that IC100 treatment reduced the severity of EAE when compared to vehicle-treated controls. At a dose of 30 mg/kg, IC100 significantly reduced the number of CD4+ and CD8+ T cells and CD11b+MHCII+ activated myeloid cells entering the spinal cord from the periphery, and reduced the number of total and activated microglia.

CONCLUSIONS

These data indicate that IC100 suppresses the immune-inflammatory response that drives EAE development and progression, thereby identifying ASC as a promising target for the treatment of MS as well as other neurological diseases with a neuroinflammatory component.

Microglial and Astrocytic Function in Physiological and Pathological Conditions: Estrogenic Modulation

There are sexual differences in the onset, prevalence, and outcome of numerous neurological diseases. Thus, in Alzheimer’s disease, multiple sclerosis, and major depression disorder, the incidence in women is higher than in men. In contrast, men are more likely to present other pathologies, such as amyotrophic lateral sclerosis, Parkinson’s disease, and autism spectrum. Although the neurological contribution to these diseases has classically always been studied, the truth is that neurons are not the only cells to be affected, and there are other cells, such as glial cells, that are also involved and could be key to understanding the development of these pathologies. Sexual differences exist not only in pathology but also in physiological processes, which shows how cells are differentially regulated in males and females. One of the reasons these sexual differences may occur could be due to the different action of sex hormones. Many studies have shown an increase in aromatase levels in the brain, which could indicate the main role of estrogens in modulating proinflammatory processes. This review will highlight data about sex differences in glial physiology and how estrogenic compounds, such as estradiol and tibolone, could be used as treatment in neurological diseases due to their anti-inflammatory effects and the ability to modulate glial cell functions.

VX765 Attenuates Pyroptosis and HMGB1/TLR4/NF-κB Pathways to Improve Functional Outcomes in TBI Mice

Background

Traumatic brain injury (TBI) refers to temporary or permanent damage to brain function caused by penetrating objects or blunt force trauma. TBI activates inflammasome-mediated pathways and other cell death pathways to remove inactive and damaged cells, however, they are also harmful to the central nervous system. The newly discovered cell death pattern termed pyroptosis has become an area of interest. It mainly relies on caspase-1-mediated pathways, leading to cell death.

Methods

Our research focus is VX765, a known caspase-1 inhibitor which may offer neuroprotection after the process of TBI. We established a controlled cortical impact (CCI) mouse model and then controlled the degree of pyroptosis in TBI with VX765. The effects of caspase-1 inhibition on inflammatory response, pyroptosis, blood-brain barrier (BBB), apoptosis, and microglia activation, in addition to neurological deficits, were investigated.

Results

We found that TBI led to NOD-like receptors (NLRs) as well as absent in melanoma 2 (AIM2) inflammasome-mediated pyroptosis in the damaged cerebral cortex. VX765 curbed the expressions of indispensable inflammatory subunits (caspase-1 as well as key downstream proinflammatory cytokines such as interleukin- (IL-) 1β and IL-18). It also inhibited gasdermin D (GSDMD) cleavage and apoptosis-associated spot-like protein (ASC) oligomerization in the injured cortex. In addition to the above, VX765 also inhibited the inflammatory activity of the high-mobility cassette -1/Toll-like receptor 4/nuclear factor-kappa B (HMGB1/TLR4/NF-kappa B) pathway. By inhibiting pyroptosis and inflammatory mediator expression, we demonstrated that VX765 can decrease blood-brain barrier (BBB) leakage, apoptosis, and microglia polarization to exhibit its neuroprotective effects.

Conclusion

In conclusion, VX765 can counteract neurological damage after TBI by reducing pyroptosis and HMGB1/TLR4/NF-κB pathway activities. VX765 may have a good therapeutic effect on TBI.

Human neural stem cell transplant location-dependent neuroprotection and motor deficit amelioration in rats with penetrating traumatic brain injury

BACKGROUND

Penetrating traumatic brain injury induces chronic inflammation that drives persistent tissue loss long after injury. Absence of endogenous reparative neurogenesis and effective neuroprotective therapies render injury-induced disability an unmet need. Cell replacement via neural stem cell transplantation could potentially rebuild the tissue and alleviate penetrating traumatic brain injury disability. The optimal transplant location remains to be determined.

METHODS

To test if subacute human neural stem cell (hNSC) transplant location influences engraftment, lesion expansion, and motor deficits, rats (n = 10/group) were randomized to the following four groups (uninjured and three injured): group 1 (Gr1), uninjured with cell transplants (sham+hNSCs), 1-week postunilateral penetrating traumatic brain injury, after establishing motor deficit; group 2 (Gr2), treated with vehicle (media, no cells); group 3 (Gr3), hNSCs transplanted into lesion core (intra); and group 4 (Gr4), hNSCs transplanted into tissue surrounding the lesion (peri). All animals were immunosuppressed for 12 weeks and euthanized following motor assessment.

RESULTS

In Gr2, penetrating traumatic brain injury effect manifests as porencephalic cyst, 22.53 ± 2.87 (% of intact hemisphere), with p value of <0.0001 compared with uninjured Gr1. Group 3 lesion volume at 17.44 ± 2.11 did not differ significantly from Gr2 (p = 0.36), while Gr4 value, 9.17 ± 1.53, differed significantly (p = 0.0001). Engraftment and neuronal differentiation were significantly lower in the uninjured Gr1 (p < 0.05), compared with injured groups. However, there were no differences between Gr3 and Gr4. Significant increase in cortical tissue sparing (p = 0.03), including motor cortex (p = 0.005) was observed in Gr4 but not Gr3. Presence of transplant within lesion or in penumbra attenuated motor deficit development (p < 0.05) compared with Gr2.

CONCLUSION

In aggregate, injury milieu supports transplanted cell proliferation and differentiation independent of location. Unexpectedly, cortical sparing is transplant location dependent. Thus, apart from cell replacement and transplant mediated deficit amelioration, transplant location-dependent neuroprotection may be key to delaying onset or preventing development of injury-induced disability.

LEVEL OF EVIDENCE

Preclinical study evaluation of therapeutic intervention, level VI.

Minocycline alleviates NLRP3 inflammasome-dependent pyroptosis in monosodium glutamate-induced depressive rats

BACKGROUND

Inflammasome activation and followed by the release of proinflammatory cytokines play a pivotal role in the development and progression of depression. However, the involvement of gasdermin D (GSDMD)-mediated pyroptosis in inflammasome-associated depression has not been studied. The present study aimed to determine the involvement of pyroptosis in the development of depression.

METHODS

The rat depressive model was established by the administration of monosodium glutamate (MSG) in postnatal rats. Minocycline (an anti-inflammatory agent) and VX-765 (a specific inhibitor of caspase-1) were given as intervention treatments when rats were two-month-old. Rat depressive behaviors were evaluated by behavioral tests, including open field test, sucrose preference test, and forced swim test. Rat hippocampi were collected for western blotting and immunofluorescence examination.

RESULTS

MSG administration induced depressive-like behavior in rats. MSG upregulated protein presences of caspase-1, GSDMD, interleukin-1β (IL-1β), interleukin-18 (IL-18), NLR pyrin domain-containing 3 (NLRP3), apoptosis-associated speck-like protein (ASC), high mobility group box 1 protein (HMGB1), and the receptor for advanced glycation end products (RAGE) in the hippocampus. Protein presences of HMGB1, NLRP3 and GSDMD were upregulated in Olig2+ oligodendrocytes in the hippocampus. The data suggest that both HMGB1/RAGE/NLRP3 signalings and GSDMD-dependent pyroptosis were activated. Both minocycline and VX-765 treatments improved depressive-like behaviors. Minocycline treatment significantly reduced both HMGB1/RAGE/NLRP3 inflammasome signalings and GSDMD-dependent pyroptosis. VX-765 downregulated GSDMD-dependent pyroptosis, but not HMGB1/RAGE signalings, indicating that GSDMD-dependent pyroptosis is a key player in the progress of depression.

CONCLUSION

In rats hippocampus, NLRP3 inflammasome activates GSDMD mediated-pyroptosis in the hippocampus of MSG-induced depressive rats.

Platelet regulates neuroinflammation and restores blood-brain barrier integrity in a mouse model of traumatic brain injury

Neuroinflammation accompanied by microglial activation triggers multiple cell death after traumatic brain injury (TBI). The secondary injury caused by inflammation may persist for a long time. Recently, platelet C-type lectin-like 2 receptor (CLEC-2) has been shown to regulate inflammation in certain diseases. However, its possible effects on TBI remain poorly understood. Here, we aimed to investigate the role of platelet CLEC-2 in the pathological process of neuroinflammation after TBI. In this study, mice were subjected to sham or controlled cortical impact injury, and arbitrarily received recombinant platelet CLEC-2. In parallel, BV2 cells were treated with lipopolysaccharide (LPS) to mimic microglial activation after TBI. Primary endothelial cells were also subjected to LPS in order to replicate the inflammatory damage caused by TBI. We used western blot analysis, reverse transcription polymerase chain reaction (RT-PCR), and immunostaining to evaluate the role of platelet CLEC-2 in TBI. In conditional knock out platelet CLEC-2 mice, trauma worsened the integrity of the blood-brain barrier and amplified the release of inflammatory cytokines. In wild type mice subjected to controlled cortical impact injury, recombinant platelet CLEC-2 administration altered the secretion of inflammatory cytokines, reduced brain edema, and improved neurological function. In vitro, the polarization phenotype of microglia induced by LPS was transformed by recombinant platelet CLEC-2, and this conversion depended on the mammalian target of rapamycin (mTOR) pathway. Endothelial cell injury by LPS was ameliorated when microglia expressed mostly M2 phenotype markers. In conclusion, platelet CLEC-2 regulates trauma-induced neuroinflammation and restores blood-brain barrier integrity.

Suppression of miR-193a alleviates neuroinflammation and improves neurological function recovery after traumatic brain injury (TBI) in mice

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality in the world, and is tightly associated with microglia-regulated neuroinflammation. However, the activation profile of microglia during the pathophysiological responses is still not fully understood. Micro-RNAs (miRs), as noncoding RNAs, are involved in the progression of TBI. In this study, we attempted to explore the effects of miR-193a on TBI using the in vivo and in vitro studies. Following experimental TBI in mice, we found that miR-193a expression was significantly up-regulated in ipsilateral cortical tissues and in the microglia/macrophages isolated from the ipsilateral cortical tissues, which was accompanied with markedly enhanced expression of pro-inflammatory factors. We then found that miR-193a hairpin inhibitor (antagomir) markedly reduced lesion volume, brain water contents and neuron death in TBI mice induced by the controlled cortical impact (CCI). In addition, cognitive dysfunction in TBI mice was markedly improved after miR-193a antagomir injection. Of note, CCI-induced activation of microglia was repressed by miR-193a inhibition, along with significantly reduced expression of neuroinflammatory markers, which were associated with the blockage of nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome. The anti-neuroinflammation effects of miR-193a suppression were verified in lipopolysaccharide (LPS)-incubated microglial cells transfected with miR-193a inhibitor. In contrast, LPS-induced activation of microglial cells and the expression of pro-inflammatory factors was markedly further accelerated by the transfection of miR-193a mimic. Taken together, TBI resulted in a robust neuroinflammatory response that was closely associated with the up-regulated miR-193a expression mainly in microglia/macrophages; however, miR-193a suppression significantly alleviated post-traumatic neuroinflammation and cognitive dysfunction. Therefore, miR-193a might be a promising therapeutic target for the treatment of TBI-associated neuroinflammation.

Fiery Cell Death: Pyroptosis in the Central Nervous System

Pyroptosis ('fiery death') is an inflammatory type of regulated cell death (RCD), which occurs downstream of inflammasome activation. Pyroptosis is mediated directly by the recently identified family of pore-forming proteins known as gasdermins, the best characterized of which is gasdermin D (GSDMD). Recent investigations implicate pyroptosis in the pathogenesis of multiple neurological diseases. In this review, we discuss molecular mechanisms that drive pyroptosis, evidence for pyroptosis within the CNS, and emerging therapeutic strategies for its inhibition in the context of neurological disease.

Neural-respiratory inflammasome axis in traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality. Approximately 20-25% of TBI subjects develop Acute Lung Injury (ALI), but the pathomechanisms of TBI-induced ALI remain poorly defined. Currently, mechanical ventilation is the only therapeutic intervention for TBI-induced lung injury. Our recent studies have shown that the inflammasome plays an important role in the systemic inflammatory response leading to lung injury-post TBI. Here, we outline the role of the extracellular vesicle (EV)-mediated inflammasome signaling in the etiology of TBI-induced ALI. Furthermore, we evaluate the efficacy of a low molecular weight heparin (Enoxaparin, a blocker of EV uptake) and a monoclonal antibody against apoptosis speck-like staining protein containing a caspase recruitment domain (anti-ASC) as therapeutics for TBI-induced lung injury. We demonstate that activation of an EV-mediated Neural-Respiratory Inflammasome Axis plays an essential role in TBI-induced lung injury and disruption of this axis has therapeutic potential as a treatment strategy.

Differential Effects of LPS and 6-OHDA on Microglia's Morphology in Rats: Implications for Inflammatory Model of Parkinson's Disease

Parkinson's disease (PD) is an idiopathic and progressive neurodegenerative disease characterized by the loss of ~ 80% of dopaminergic neurons in substantia nigra pars compacta (SNpc). Because activation of the innate cellular immune response, mediated by microglia, has been linked to the neurodegeneration in PD, in the present study, we evaluated the effects of lipopolysaccharide (LPS) and 6-hydroxydopamine (6-OHDA) on microglia's morphology, reflective of their activity, as well as tyrosine hydroxylase (TH)-positive neurons in SNpc and motor behavior. Adult male Wistar rats were stereotactically injected with LPS or 6-OHDA into the left dorsolateral striatum. Control groups received appropriate vehicle. The morphological changes of microglial cells and neurotoxic effects were examined at 1, 7, and 14 post-injection days. Both LPS and 6-OHDA caused activation and morphological changes in microglial cells as well as loss of dopaminergic neurons in SNpc. These effects were maximal at 14 days post-injection where motor impairments were also evident. However, our findings indicate that 6-OHDA causes a low degree of microglia activation compared to LPS. Hence, it may be concluded that LPS model of PD might be a better representation of inflammatory involvement in this devastating disease.

Antioxidant and Anti-inflammatory Mechanisms of Neuroprotection by Ursolic Acid: Addressing Brain Injury, Cerebral Ischemia, Cognition Deficit, Anxiety, and Depression

Ursolic acid (UA) is a pentacyclic triterpene which is found in common herbs and medicinal plants that are reputed for a variety of pharmacological effects. Both as an active principle of these plants and as a nutraceutical ingredient, the pharmacology of UA in the CNS and other organs and systems has been extensively reported in recent years. In this communication, the antioxidant and anti-inflammatory axis of UA's pharmacology is appraised for its therapeutic potential in some common CNS disorders. Classic examples include the traumatic brain injury (TBI), cerebral ischemia, cognition deficit, anxiety, and depression. The pharmacological efficacy for UA is demonstrated through the therapeutic principle of one drug → multitargets → one/many disease(s). Both specific enzymes and receptor targets along with diverse pharmacological effects associated with oxidative stress and inflammatory signalling are scrutinised.