MCC950, a selective NLPR3 inflammasome inhibitor, improves neurologic function and survival after cardiac arrest and resuscitation

Novel Targets and Strategies Addressing Residual Cardiovascular Risk in Post-acute Coronary Syndromes Patients

Despite the advancement in secondary cardiovascular prevention strategies for post-acute coronary syndrome (ACS) patients, the development of new drugs addressing dyslipidemia and the personalization of dual antiplatelet therapies (DAPT), these patients continue to suffer a significant incidence of recurrent ischemic events. Therefore, novel targets that can be tackled to reduce cardiovascular risk are needed to improve the outcome of this very high-risk population. The role of chronic inflammation and inflammasome in the development and progression of atherosclerosis has been broadly investigated in patients with established coronary artery disease (CAD) and recent randomized trials have highlighted the possibility to manage these targets with specific drugs such as colchicine and monocolonal antibodies with a significant improvement of cardiovascular outcomes in post-ACS patients. Lipoprotein(a) [Lp(a)] is the most promising non-traditional risk factor and has shown to predict worse outcome in post-ACS patients. Lowering Lp(a) through PCSK9 inhibitors and specific targeted therapies has shown positive results in reducing adverse cardiovascular events in patients with established CAD. The effect of microbiome and its alteration in gut dysbiosis seems to actively participate in residual cardiovascular risk of CAD patients; however, the risk-modifying effect of targeted-microbiome therapies hasn't been yet investigated in large population-based studies. Long-term outcome of post-ACS patients is a complex puzzle of multiple factors. In this minireview, we summarize the emerging risk factors that may interplay in the residual risk of post-ACS patients and their possible prognostic and therapeutic implications.

Neuroprotective Approaches for Brain Injury After Cardiac Arrest: Current Trends and Prospective Avenues

With the implementation of improved bystander cardiopulmonary resuscitation techniques and public-access defibrillation, survival after out-of-hospital cardiac arrest (OHCA) has increased significantly over the years. Nevertheless, OHCA survivors have residual anoxia/reperfusion brain damage and associated neurological impairment resulting in poor quality of life. Extracorporeal membrane oxygenation or targeted temperature management has proven effective in improving post-cardiac arrest (CA) neurological outcomes, yet considering the substantial healthcare costs and resources involved, there is an urgent need for alternative treatment strategies that are crucial to alleviate brain injury and promote recovery of neurological function after CA. In this review, we searched PubMed for the latest preclinical or clinical studies (2016-2023) utilizing gas-mediated, pharmacological, or stem cell-based neuroprotective approaches after CA. Preclinical studies utilizing various gases (nitric oxide, hydrogen, hydrogen sulfide, carbon monoxide, argon, and xenon), pharmacological agents targeting specific CA-related pathophysiology, and stem cells have shown promising results in rodent and porcine models of CA. Although inhaled gases and several pharmacological agents have entered clinical trials, most have failed to demonstrate therapeutic effects in CA patients. To date, stem cell therapies have not been reported in clinical trials for CA. A relatively small number of preclinical stem-cell studies with subtle therapeutic benefits and unelucidated mechanistic explanations warrant the need for further preclinical studies including the improvement of their therapeutic potential. The current state of the field is discussed and the exciting potential of stem-cell therapy to abate neurological dysfunction following CA is highlighted.

Lead inhibits microglial cell migration via suppression of store-operated calcium entry

Lead (Pb) is a non-biodegradable environmental pollutant that can lead to neurotoxicity by inducing neuroinflammation. Microglial activation plays a key role in neuroinflammation, and microglial migration is one of its main features. However, whether Pb affects microglial migration has not yet been elucidated. Herein, the effect of Pb on microglial migration was investigated using BV-2 microglial cells and primary microglial cells. The results showed that cell activation markers (TNF-α and CD206) in BV-2 cells were increased after Pb treatment. The migration ability of microglia was inhibited by Pb. Both store-operated calcium entry (SOCE) and the Ca2+ release-activated Ca2+ (CRAC) current were downregulated by microglia treatment with Pb in a dose-dependent manner. However, there was no statistical difference in the protein levels of stromal interaction molecule (STIM) 1, STIM2, or Ca2+ release-activated Ca2+ channel protein (Orai) 1 in microglia. The external Ca2+ influx and cell migration ability were restored to a certain extent after overexpression of either STIM1 or its CRAC activation domain in microglia. These results indicated that Pb inhibits microglial migration by downregulation of SOCE and impairment of the function of STIM1.

MCC950 reduces autophagy and improves cognitive function by inhibiting NLRP3-dependent neuroinflammation in a rat model of Alzheimer's disease

Alzheimer's disease (AD) is the seventh most common cause of mortality and one of the major causes of disability and vulnerability in the elderly. AD is characterized by gradual cognitive deterioration, the buildup of misfolded amyloid beta (Aβ) peptide, and the generation of neurofibrillary tangles. Despite enormous scientific progress, there is no effective cure for AD. Thus, exploring new treatment options to stop AD or at least slow down its progress is important. In this study, we investigated the potential therapeutic effects of MCC950 on NLRP3-mediated inflammasome-driven inflammation and autophagy in AD. Rats treated with streptozotocin (STZ) exhibited simultaneous activation of the NLRP3 inflammasome and autophagy, as confirmed by Western blot, immunofluorescence, and co-immunoprecipitation analyses. MCC950, a specific NLRP3 inhibitor, was intraperitoneally administered (50 mg/kg body weight) to rats with AD-like symptoms induced by intracerebroventricular STZ injections (3 mg/kg body weight). MCC950 effectively suppressed STZ-induced cognitive impairment and anxiety by inhibiting NLRP3-dependent neuroinflammation. Moreover, our findings indicate that MCC950 exerts neuroprotective effects by attenuating autophagy in neuronal cells. The inhibiting effects of MCC950 on inflammasome activation and autophagy were reproduced in vitro, provding further mechansistic insights into MCC950 therapeutic action. Our findings suggest that MCC950 impedes the progression of AD and may also improve cognitive function through the mitigation of autophagy and NLRP3 inflammasome inhibition.

Single-cell transcriptomics reveal a hyperacute cytokine and immune checkpoint axis after cardiac arrest in patients with poor neurological outcome

BACKGROUND

Most patients hospitalized after cardiac arrest (CA) die because of neurological injury. The systemic inflammatory response after CA is associated with neurological injury and mortality but remains poorly defined.

METHODS

We determine the innate immune network induced by clinical CA at single-cell resolution.

FINDINGS

Immune cell states diverge as early as 6 h post-CA between patients with good or poor neurological outcomes 30 days after CA. Nectin-2+ monocyte and Tim-3+ natural killer (NK) cell subpopulations are associated with poor outcomes, and interactome analysis highlights their crosstalk via cytokines and immune checkpoints. Ex vivo studies of peripheral blood cells from CA patients demonstrate that immune checkpoints are a compensatory mechanism against inflammation after CA. Interferon γ (IFNγ)/interleukin-10 (IL-10) induced Nectin-2 on monocytes; in a negative feedback loop, Nectin-2 suppresses IFNγ production by NK cells.

CONCLUSIONS

The initial hours after CA may represent a window for therapeutic intervention in the resolution of inflammation via immune checkpoints.

FUNDING

This work was supported by funding from the American Heart Association, Brigham and Women's Hospital Department of Medicine, the Evergreen Innovation Fund, and the National Institutes of Health.

The Potential of NLRP3 Inflammasome as a Therapeutic Target in Neurological Diseases

NLRP3 (NLRP3: NOD-, LRR-, and pyrin domain-containing protein 3) inflammasome is the best-described inflammasome that plays a crucial role in the innate immune system and a wide range of diseases. The intimate association of NLRP3 with neurological disorders, including neurodegenerative diseases and strokes, further emphasizes its prominence as a clinical target for pharmacological intervention. However, after decades of exploration, the mechanism of NLRP3 activation remains indefinite. This review highlights recent advances and gaps in our insights into the regulation of NLRP3 inflammasome. Furthermore, we present several emerging pharmacological approaches of clinical translational potential targeting the NLRP3 inflammasome in neurological diseases. More importantly, despite small-molecule inhibitors of the NLRP3 inflammasome, we have focused explicitly on Chinese herbal medicine and botanical ingredients, which may be splendid therapeutics by inhibiting NLRP3 inflammasome for central nervous system disorders. We expect that we can contribute new perspectives to the treatment of neurological diseases.

Mouse Cardiac Arrest Model for Brain Imaging and Brain Physiology Monitoring During Ischemia and Resuscitation

Most cardiac arrest (CA) survivors experience varying degrees of neurologic deficits. To understand the mechanisms that underpin CA-induced brain injury and, subsequently, develop effective treatments, experimental CA research is essential. To this end, a few mouse CA models have been established. In most of these models, the mice are placed in the supine position in order to perform chest compression for cardiopulmonary resuscitation (CPR). However, this resuscitation procedure makes the real-time imaging/monitoring of brain physiology during CA and resuscitation challenging. To obtain such critical knowledge, the present protocol presents a mouse asphyxia CA model that does not require the chest compression CPR step. This model allows for the study of dynamic changes in blood flow, vascular structure, electrical potentials, and brain tissue oxygen from the pre-CA baseline to early post-CA reperfusion. Importantly, this model applies to aged mice. Thus, this mouse CA model is expected to be a critical tool for deciphering the impact of CA on brain physiology.

Secondary Cardiovascular Prevention after Acute Coronary Syndrome: Emerging Risk Factors and Novel Therapeutic Targets

The control of cardiovascular risk factors, the promotion of a healthy lifestyle, and antithrombotic therapy are the cornerstones of secondary prevention after acute coronary syndrome (ACS). However, many patients have recurrent ischemic events despite the optimal control of traditional modifiable risk factors and the use of tailored pharmacological therapy, including new-generation antiplatelet and lipid-lowering agents. This evidence emphasizes the importance of identifying novel risk factors and targets to optimize secondary preventive strategies. Lipoprotein(a) (Lp(a)) has emerged as an independent predictor of adverse events after ACS. New molecules such as anti-PCSK9 monoclonal antibodies, small interfering RNAs, and antisense oligonucleotides can reduce plasma Lp(a) levels and are associated with a long-term outcome benefit after the index event. The inflammatory stimulus and the inflammasome, pivotal elements in the development and progression of atherosclerosis, have been widely investigated in patients with coronary artery disease. More recently, randomized clinical trials including post-ACS patients treated with colchicine and monoclonal antibodies targeting cytokines yielded promising results in the reduction in major cardiovascular events after an ACS. Gut dysbiosis has also raised great interest for its potential pathophysiological role in cardiovascular disease. This evidence, albeit preliminary and needing confirmation by larger population-based studies, suggests the possibility of targeting the gut microbiome in particularly high-risk populations. The risk of recurrent ischemic events after ACS is related to the complex interaction between intrinsic predisposing factors and environmental triggers. The identification of novel risk factors and targets is fundamental to customizing patient clinical management with a precision medicine perspective.

NLRP3 activation in microglia contributes to learning and memory impairment induced by chronic lead exposure in mice

Lead (Pb)-induced microglial activation and neuroinflammation has been considered as one of the main pathological events of Pb neurotoxicity. The NLRP3 inflammasome signaling pathway is a major contributor to the neuroinflammatory process in the central nervous system. However, the relationship between chronic Pb exposure and neurogenic NLRP3 inflammasome is unclear. Therefore, the aim of this study was to characterize the role of NLRP3 inflammasome activation during the chronic Pb exposure using in vitro and in vivo models. Our results showed that chronic Pb exposure induce learning and memory impairment in mice, mainly related to the activation of microglia and NLRP3 inflammasome. This phenomenon was reversed in mice by treating with the NLRP3 inhibitor MCC950 and using NLRP3-/- mice. In addition, Pb caused the activation of NLRP3 inflammasome, the production of mitochondrial ROS (mtROS), and mitochondrial Ca2+ overload in BV2 cells. Amelioration of mtROS abolished Pb-induced NLRP3 inflammasome activation. Moreover, after regulation of Ca2+ redistribution, mtROS and NLRP3 inflammasome activation was restored. In conclusion, NLRP3 inflammasome activation in microglia plays a vital role in Pb neurotoxicity, by a novel mechanism of enhancing mtROS production and Ca2+ redistribution.

Flufenamic acid improves survival and neurologic outcome after successful cardiopulmonary resuscitation in mice

Background

Brain injury is the main cause of high mortality and disability after successful cardiopulmonary resuscitation (CPR) from sudden cardiac arrest (CA). The transient receptor potential M4 (TRPM4) channel is a novel target for ameliorating blood–brain barrier (BBB) disruption and neuroinflammation. Herein, we tested whether flufenamic acid (FFA), which is reported to block TRPM4 with high potency, could confer neuroprotection against brain injury secondary to CA/CPR and whether its action was exerted by blocking the TRPM4 channel.

Methods

Wild-type (WT) and Trpm4 knockout (Trpm4^−/−) mice subjected to 10-min CA/CPR were randomized to receive FFA or vehicle once daily. Post-CA/CPR brain injuries including neurologic deficits, survival rate, histological damage, edema formation, BBB destabilization and neuroinflammation were assessed.

Results

In WT mice subjected to CA/CPR, FFA was effective in improving survival and neurologic outcome, reducing neuropathological injuries, attenuating brain edema, lessening the leakage of IgG and Evans blue dye, restoring tight junction protein expression and promoting microglia/macrophages from the pro-inflammatory subtype toward the anti-inflammatory subtype. In comparison to WT mice, Trpm4^−/− mice exhibited less neurologic deficiency, milder histological impairment, more BBB integrity and more anti-inflammatory microglia/macrophage polarization. As expected, FFA did not provide a benefit of superposition compared with vehicle in the Trpm4^−/− mice after CA/CPR.

Conclusions

FFA mitigates BBB breach and modifies the functional status of microglia/macrophages, thereby improving survival and neurologic deficits following CA/CPR. The neuroprotective effects occur at least partially by interfering with the TRPM4 channel in the neurovascular unit. These results indicate the significant clinical potential of FFA to improve the prognosis for CA victims who are successfully resuscitated.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02571-2.

Chrysophanol postconditioning attenuated cerebral ischemia-reperfusion injury induced NLRP3-related pyroptosis in a TRAF6-dependent manner

Individuals who suffer from post-CA (cardiac arrest) brain injury experience higher mortality and more severe functional disability. Neuroinflammation has been identified as a vital factor in cerebral ischemia-reperfusion injury (CIRI) following CA. Pyroptosis induces neuronal death by triggering an excessive inflammatory injury. Chrysophanol possesses robust anti-inflammatory features, and it is protective against CIRI. The purpose of this research was to assess the effect of Chrysophanol postconditioning on CIRI-induced pyroptotic cell death, and to explore its underlying mechanisms. CIRI was induced in rats by CA and subsequent cardiopulmonary resuscitation, and PC12 cells were exposed to oxygen-glucose deprivation/reoxygenation (OGD/R) to imitate CIRI in vitro. It was found that post-CA brain injury led to a notable cerebral damage revealed by histopathological changes and neurological outcomes. The existence of pyroptosis was also confirmed in in vivo and in vitro CIRI models. Moreover, we further confirmed that Chrysophanol, the main bioactive ingredient of Rhubarb, significantly suppressed expressions of pyroptosis-associated proteins, e.g., NLRP3, ASC, cleaved-caspase-1 and N-terminal GSDMD, and inhibited the expression of tumor necrosis factor receptor-associated factor 6 (TRAF6). Furthermore, NLRP3 overexpression neutralized the neuroprotection of Chrysophanol postconditioning, suggesting that pyroptosis was the major neuronal death pathway modulated by Chrysophanol postconditioning in OGD/R. Additionally, the neuroprotection of Chrysophanol postconditioning was also abolished by gain-of-function analyses of TRAF6. Finally, the results demonstrated that Chrysophanol postconditioning suppressed the interaction between TRAF6 and NLRP3. Taken together, our findings revealed that Chrysophanol postconditioning was protective against CIRI by inhibiting NLRP3-related pyroptosis in a TRAF6-dependent manner.

The protective effect of MiR-27a on the neonatal hypoxic-ischemic encephalopathy by targeting FOXO1 in rats

BACKGROUND

Neonatal hypoxic-ischemic encephalopathy (HIE), a kind of hypoxic-ischemic brain damage caused by perinatal asphyxia, is the most crucial cause of neonatal death and long-term neurological dysfunction in children. We aimed to investigate the protective effects of micro (mi)R-27a on HIE in neonatal rats.

METHODS

A rat model of neonatal HIE was constructed by modification of the Rice-Vannucci model. Real-time quantitative polymerase chain reaction (RT-qPCR) was used to test the expressions of miR-27a, FOXO1 messenger RNA (mRNA), interleukin-1β (IL-1β) mRNA, and tumor necrosis factor-α (TNF-α) mRNA, and western blot was applied to test the expression of FOXO1. In order to overexpress miR-27a, an intracerebroventricular injection (i.c.v) of miR-27a mimic was administered. We adopted 2,3,5-triphenytetrazolium chloride (TTC) staining and brain water content measurement to test the effects of miR-27a on the infarcted volume and edema in brain after HIE. Flow cytometry (FCM) analysis was applied to test the effects of miR-27a on the infiltrated peripheral immune cells in the rat brains after HIE.

RESULTS

We successfully established a rat model of neonatal HIE. It was revealed that the expressions of miR-27a decreased gradually after HIE, however, the expressions of FOXO1 mRNA increased. After injection of the miR-27a mimic, the expression of miR-27a in the rat HIE model brains was significantly upregulated, however, the expression of FOXO1 was robustly downregulated. Both TTC staining and brain water content showed that the infarcted volume and brain edema was markedly increased after HIE. Interestingly, the overexpression of miR-27a reduced the infarcted volume and edema induced by HIE. Additionally, RT-qPCR and FCM analysis showed that HIE lead to increases of IL-1β, TNF-α, and infiltrated immune cells. Overexpression of miR-27a could reduce the expressions of IL-1β mRNA and TNF-α mRNA, and the cell numbers of infiltrated peripheral macrophages and neutrophils in the brain.

CONCLUSIONS

MiR-27a plays protective roles by reducing infarct volume and brain edema, and inhibiting inflammatory factors and infiltrated peripheral immune cells by targeting FOXO1 in neonatal HIE rats.

Macrophage-NLRP3 Activation Promotes Right Ventricle Failure in Pulmonary Arterial Hypertension

RATIONALE

Pulmonary arterial hypertension (PAH) often results in death from right ventricular failure (RVF). NLRP3-macrophage activation may promote RVF in PAH.

OBJECTIVES

Evaluating the contribution of the NLRP3 inflammasome in RV-macrophages to PAH-RVF.

METHODS

Rats with decompensated RV hypertrophy (RVH) [monocrotaline (MCT) and Sugen-5416 hypoxia (SuHx)] were compared with compensated RVH rats [pulmonary artery banding (PAB)]. Echocardiography and right heart catheterization were performed. Macrophages, atrial natriuretic peptide (ANP) and fibrosis were evaluated by microscopy or flow cytometry. NLRP3 inflammasome activation and cardiotoxicity were confirmed by immunoblot and in vitro strategies. MCT-rats were treated with SC-144 (a GP130 antagonist) and MCC950 (an NLRP3 inhibitor). Macrophage-NLRP3 activity was evaluated in PAH-RVF patients.

MEASUREMENTS AND MAIN RESULTS

Macrophages, fibrosis, and ANP were increased in MCT and SuHx-RVs but not LVs or PAB rats. While MCT-RV macrophages were inflammatory, lung macrophages were anti-inflammatory. CCR2+ macrophages (monocyte-derived) were increased in MCT- and SuHx-RVs and highly expressed NLRP3. The macrophage-NLRP3 pathway was upregulated in PAH patients' decompensated RVs. Cultured MCT-monocytes showed NLRP3 activation, and in co-culture experiments resulted in cardiomyocyte mitochondrial damage, which MCC950 prevented. In vivo, MCC950 reduced NLRP3 activation and regressed pulmonary vascular disease and RVF. SC-144 reduced RV-macrophages and NLRP3 content, prevented STAT3 activation, and improved RV function without regressing pulmonary vascular disease.

CONCLUSION

NLRP3-macrophage activation occurs in the decompensated RV in preclinical PAH models and PAH patients. Inhibiting GP130 or NLRP3 signaling improves RV function. The concept that PAH-RVF results from RV inflammation rather than solely from elevated RV afterload suggest a new therapeutic paradigm. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/).

The Inflammasome NLR Family Pyrin Domain-Containing Protein 3 (NLRP3) as a Novel Therapeutic Target for Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a dramatic disease without cure. The US Food and Drug Administration-approved drugs, pirfenidone and nintedanib, only slow disease progression. The clinical investigation of novel therapeutic approaches for IPF is an unmet clinical need. Nucleotide-binding oligomerization domain-like receptor or NOD-like receptors are pattern recognition receptors capable of binding a large variety of stress factors. NLR family pyrin domain-containing protein 3 (NLRP3), once activated, promotes IL-1β, IL-18 production, and innate immune responses. Multiple reports indicate that the inflammasome NLRP3 is overactivated in IPF patients, leading to increased production of class I IL and collagens. Similarly, data from animal models of pulmonary fibrosis confirm the role of NLRP3 in the development of chronic lung injury and pulmonary fibrosis. This report provides a review of the evidence of NLRP3 activation in IPF and of NLRP3 inhibition in different animal models of fibrosis, and highlights the recent advances in direct and indirect NLRP3 inhibitors.

Baclofen attenuates cognitive deficits in post-cardiac arrest brain injury

Between 30% and 50% of survivors of cardiac arrest (CA) suffer from cognitive deficits. However, no effective medical intervention is available to alleviate cognitive deficits. Baclofen is known to protect damaged neurons, but researchers have still not clearly whether baclofen alleviates CA-induced cognitive deficits. The present study aimed to investigate whether baclofen protects against post-CA cognitive deficits and to reveal the protective mechanism of baclofen. Rats underwent 10 min of asphyxia to establish CA models. Intriguingly, our results indicated that baclofen improved spatial memory 72 h after CA. Baclofen increased plasticity-related protein (PSD95, and GAP43) expression in the brain after CA. Baclofen reduced microglial number and the release of inflammatory factors (IL-1β and IL-18). Furthermore, baclofen significantly reduced the expression of pyroptosis-related molecules after CA. Notably, activation of NLRP3 abolished the anti-pyroptosis effect of baclofen and reduced the expression of synaptic plasticity-related proteins after CA. Taken together, this study first shows that baclofen attenuates cognitive deficits induced by brain injury after CA. The mechanism is at least partially attributed to baclofen regulating pyroptosis by inhibition of NLRP3 activation.

Cervical Vagus Nerve Stimulation Improves Neurologic Outcome After Cardiac Arrest in Mice by Attenuating Oxidative Stress and Excessive Autophagy

BACKGROUND

Cerebral ischemia and reperfusion (I/R) induces oxidative stress and activates autophagy, leading to brain injury and neurologic deficits. Cervical vagus nerve stimulation (VNS) increases cerebral blood flow (CBF). In this study, we investigate the effect of VNS-induced CBF increase on neurologic outcomes after cardiac arrest (CA).

MATERIALS AND METHODS

A total of 40 male C57Bl/6 mice were subjected to ten minutes of asphyxia CA and randomized to vagus nerve isolation (VNI) or VNS treatment group. Eight mice received sham surgery and VNI. Immediately after resuscitation, 20 minutes of electrical stimulation (1 mA, 1 ms, and 10 Hz) was started in the VNS group. Electrocardiogram, blood pressure, and CBF were monitored. Neurologic and histologic outcomes were evaluated at 72 hours. Oxidative stress and autophagy were assessed at 3 hours and 24 hours after CA.

RESULTS

Baseline characteristics were not different among groups. VNS mice had better behavioral performance (ie, open field, rotarod, and neurologic score) and less neuronal death (p < 0.05, vs VNI) in the hippocampus. CBF was significantly increased in VNS-treated mice at 20 minutes after return of spontaneous circulation (ROSC) (p < 0.05). Furthermore, levels of 8-hydroxy-2'-deoxyguanosine in the blood and autophagy-related proteins (ie, LC-3Ⅱ/Ⅰ, Beclin-1, and p62) in the brain were significantly decreased in VNS mice. Aconitase activity was also reduced, and the p-mTOR/mTOR ratio was increased in VNS mice.

CONCLUSIONS

Oxidative stress induced by global brain I/R following CA/ROSC leads to early excessive autophagy and impaired autophagic flux. VNS promoted CBF recovery, ameliorating these changes. Neurologic and histologic outcomes were also improved.

Neurological complications associated with Covid-19; molecular mechanisms and therapeutic approaches

With the progression of investigations on the pathogenesis of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), neurological complications have emerged as a critical aspect of the ongoing coronavirus disease 2019 (Covid‐19) pandemic. Besides the well‐known respiratory symptoms, many neurological manifestations such as anosmia/ageusia, headaches, dizziness, seizures, and strokes have been documented in hospitalised patients. The neurotropism background of coronaviruses has led to speculation that the neurological complications are caused by the direct invasion of SARS‐CoV‐2 into the nervous system. This invasion is proposed to occur through the infection of peripheral nerves or via systemic blood circulation, termed neuronal and haematogenous routes of invasion, respectively. On the other hand, aberrant immune responses and respiratory insufficiency associated with Covid‐19 are suggested to affect the nervous system indirectly. Deleterious roles of cytokine storm and hypoxic conditions in blood‐brain barrier disruption, coagulation abnormalities, and autoimmune neuropathies are well investigated in coronavirus infections, as well as Covid‐19. Here, we review the latest discoveries focussing on possible molecular mechanisms of direct and indirect impacts of SARS‐CoV‐2 on the nervous system and try to elucidate the link between some potential therapeutic strategies and the molecular pathways.

Dying by fire: noncanonical functions of autophagy proteins in neuroinflammation and neurodegeneration

Neuroinflammation and neurodegeneration are key components in the establishment and progression of neurodegenerative diseases including Alzheimer's Disease (AD). Over the past decade increasing evidence is emerging for the use of components of the canonical autophagy machinery in pathways that are characterized by LC3 lipidation yet are distinct from traditional macro-autophagy. One such pathway that utilizes components of the autophagy machinery to target LC3 to endosomes, a process termed LC3-associated endocytosis (LANDO), has recently been identified and regulates neuroinflammation. Abrogation of LANDO in microglia cells results in a propensity for elevated neuroinflammatory cytokine production. Using the well-established 5xFAD model of AD to interrogate neuroinflammatory regulation, impairment of LANDO through deletion of a key upstream regulator Rubicon or other downstream autophagy components, exacerbated disease onset and severity, while deletion of microglial autophagy alone had no measurable effect. Mice presented with robust deposition of the neurotoxic AD protein β-amyloid (Aβ), microglial activation and inflammatory cytokine production, tau phosphorylation, and aggressive neurodegeneration culminating in severe memory impairment. LANDO-deficiency impaired recycling of receptors that recognize Aβ, including TLR4 and TREM2. LANDO-deficiency alone through deletion of the WD-domain of the autophagy protein ATG16L, revealed a role for LANDO in the spontaneous establishment of age-associated AD. LANDO-deficient mice aged to 2 years presented with advanced AD-like disease and pathology correlative to that observed in human AD patients. Together, these studies illustrate an important role for microglial LANDO in regulating CNS immune activation and protection against neurodegeneration. New evidence is emerging that demonstrates a putative linkage between pathways such as LANDO and cell death regulation via apoptosis and possibly necroptosis. Herein, we provide a review of the use of the autophagy machinery in non-canonical mechanisms that alter immune regulation and could have significant impact in furthering our understanding of not only CNS diseases like AD, but likely beyond.

LncRNA GAS5/miR-137 Is a Hypoxia-Responsive Axis Involved in Cardiac Arrest and Cardiopulmonary Cerebral Resuscitation

Background

Cardiac arrest/cardiopulmonary resuscitation (CA/CPR) represents one of the devastating medical emergencies and is associated with high mortality and neuro-disability. Post-cardiac arrest syndrome (PCAS) is mechanistically ascribed to acute systemic ischemia/reperfusion(I/R) injury. The lncRNA/microRNA/mRNA networks have been found to play crucial roles in the pathogenesis of the hypoxia-responsive diseases. Nonetheless, the precise molecular mechanisms by which lncRNA/miRNA/mRNA axes are involved in the astrocyte-microglia crosstalk in CA/CPR have not been fully elucidated.

Methods

We collected and purified the exosomes from the blood of CA/CPR patients and supernatant of OGD/R-stimulated astrocytes. On the basis of microarray analysis, bioinformatic study, and luciferase activity determination, we speculated that lncRNA GAS5/miR-137 is implicated in the astrocyte-microglia crosstalk under the insult of systemic I/R injury. The regulation of lncRNA GAS5/miR-137 on INPP4B was examined by cellular transfection in OGD/R cell culture and by lateral ventricle injection with miR-137 agomir in CA/CPR mice model. Flow cytometry and immunofluorescence staining were performed to detect the microglial apoptosis, M1/M2 phenotype transformation, and neuroinflammation. Neurological scoring and behavior tests were conducted in CA/CPR group, with miR-137 agomir lateral-ventricle infusion and in their controls.

Results

In all the micRNAs, miR-137 was among the top 10 micRNAs that experienced greatest changes, in both the blood of CA/CPR patients and supernatant of OGD/R-stimulated astrocytes. Bioinformatic analysis revealed that miR-137 was sponged by lncRNA GAS5, targeting INPP4B, and the result was confirmed by Luciferase activity assay. qRT-PCR and Western blotting showed that lncRNA GAS5 and INPP4B were over-expressed whereas miR-137 was downregulated in the blood of CA/CPR patients, OGD/R-stimulated astrocytes, and brain tissue of CA/CPR mice. Silencing lncRNA GAS5 suppressed INPP4B expression, but over-expression of miR-137 negatively modulated its expression. Western blotting exhibited that PI3K and Akt phosphorylation was increased when lncRNA GAS5 was silenced or miR-137 was over-expressed. However, PI3K and Akt phosphorylation was notably suppressed in the absence of miR-137, almost reversing their phosphorylation in the silencing lncRNA GAS5 group. Then we found that GAS5 siRNA or miR-137 mimic significantly increased cell viability and alleviated apoptosis after OGD/R injury. Furthermore, over-expression of miR-137 attenuated microglial apoptosis and neuroinflammation in CA/CPR mice model, exhibiting significantly better behavioral tests after CA/CPR.

Conclusion

LncRNA GAS5/miR-137 may be involved in the astrocyte-microglia communication that inhibits PI3K/Akt signaling activation via regulation of INPP4B during CA/CPR.

The Influence of Mitochondrial-DNA-Driven Inflammation Pathways on Macrophage Polarization: A New Perspective for Targeted Immunometabolic Therapy in Cerebral Ischemia-Reperfusion Injury

Cerebral ischemia-reperfusion injury is related to inflammation driven by free mitochondrial DNA. At the same time, the pro-inflammatory activation of macrophages, that is, polarization in the M1 direction, aggravates the cycle of inflammatory damage. They promote each other and eventually transform macrophages/microglia into neurotoxic macrophages by improving macrophage glycolysis, transforming arginine metabolism, and controlling fatty acid synthesis. Therefore, we propose targeting the mtDNA-driven inflammatory response while controlling the metabolic state of macrophages in brain tissue to reduce the possibility of cerebral ischemia-reperfusion injury.

Activation of the XBP1s/O-GlcNAcylation Pathway Improves Functional Outcome After Cardiac Arrest and Resuscitation in Young and Aged Mice

ABSTRACT

After cardiac arrest (CA) and resuscitation, the unfolded protein response (UPR) is activated in various organs including the brain. However, the role of the UPR in CA outcome remains largely unknown. One UPR branch involves spliced X-box-binding protein-1 (XBP1s). Notably, XBP1s, a transcriptional factor, can upregulate expression of specific enzymes related to glucose metabolism, and subsequently boost O-linked β-N-acetylglucosamine modification (O-GlcNAcylation). The current study is focused on effects of the XBP1 UPR branch and its downstream O-GlcNAcylation on CA outcome. Using both loss-of-function and gain-of-function mouse genetic tools, we provide the first evidence that activation of the XBP1 UPR branch in the post-CA brain is neuroprotective. Specifically, neuron-specific Xbp1 knockout mice had worse CA outcome, while mice with neuron-specific expression of Xbp1s in the brain had better CA outcome. Since it has been shown that the protective role of the XBP1s signaling pathway under ischemic conditions is mediated by increasing O-GlcNAcylation, we then treated young mice with glucosamine, and found that functional deficits were mitigated on day 3 post CA. Finally, after confirming that glucosamine can boost O-GlcNAcylation in the aged brain, we subjected aged mice to 8 min CA, and then treated them with glucosamine. We found that glucosamine-treated aged mice performed significantly better in behavioral tests. Together, our data indicate that the XBP1s/O-GlcNAc pathway is a promising target for CA therapy.

Mitochondria as a Cellular Hub in Infection and Inflammation

Mitochondria are the energy center of the cell. They are found in the cell cytoplasm as dynamic networks where they adapt energy production based on the cell’s needs. They are also at the center of the proinflammatory response and have essential roles in the response against pathogenic infections. Mitochondria are a major site for production of Reactive Oxygen Species (ROS; or free radicals), which are essential to fight infection. However, excessive and uncontrolled production can become deleterious to the cell, leading to mitochondrial and tissue damage. Pathogens exploit the role of mitochondria during infection by affecting the oxidative phosphorylation mechanism (OXPHOS), mitochondrial network and disrupting the communication between the nucleus and the mitochondria. The role of mitochondria in these biological processes makes these organelle good targets for the development of therapeutic strategies. In this review, we presented a summary of the endosymbiotic origin of mitochondria and their involvement in the pathogen response, as well as the potential promising mitochondrial targets for the fight against infectious diseases and chronic inflammatory diseases.

The role of Interleukin-18 in recurrent early pregnancy loss

BACKGROUND

A successful pregnancy is a unique and complex immunological state. Cytokines seem to be crucial for the implementation of a tolerogenic environment at the feto-maternal interphase towards the semi-allogenic fetus. Importantly, the switch from a Th1- to a Th2 cytokine profile might play a key role. Interestingly, Interleukin-18 (IL-18) can induce either Th1 or Th2 immune response depending on the local cytokine environment. Therefore, this study investigates the expression of IL-18 in early pregnancy loss.

PATIENTS AND METHODS

The TaqMan® Human Cytokine Network Array was carried out with placental tissue of patients with healthy pregnancies (n = 15) and recurrent miscarriage (n = 15) in order to investigate differences in IL-18 mRNA expression. Immunohistochemical staining was applied to examine the IL-18 protein expression in the syncytiotrophoblast and decidua of healthy pregnancies (n = 15), spontaneous (n = 12) and recurrent miscarriage (n = 9). The characterization of IL-18 expressing cells in the decidua was evaluated by double-immunofluorescence. Correlation analysis between IL-18 protein expression and clinical data of the study population was performed via spearman correlation coefficient.

RESULTS

Gene expression analysis revealed a 4,9-times higher expression of IL-18 in recurrent miscarriage patients. IL-18 protein expression was significantly upregulated only in the decidua in the recurrent miscarriage group (p = 0.031). We did not observe significant changes of IL-18 protein expression in spontaneous miscarriage specimens when compared to healthy controls (p = 0.172). Double-immunofluorescence identified decidual stroma cells as IL-18 expressing cells. Correlation analysis showed a significant negative correlation of IL-18 protein expression and gestational age in healthy controls (r = -,745, p = 0.034). Also, a positive correlation of IL-18 and maternal age was observed in patients suffering from recurrent pregnancy loss (r =, 894, p = 0.041).

CONCLUSION

Our results indicate that IL-18 expression might be necessary in early gestation but requires a tight regulation for a successful ongoing pregnancy. In the present study we observed that a significant upregulation of IL-18 in the decidua was restricted to patients with recurrent miscarriage and therefore might be interesting as a diagnostic marker. Further studies need to evaluate the exact pathophysiological mechanisms.

The ERK/CREB/PTN/syndecan-3 pathway involves in heparin-mediated neuro-protection and neuro-regeneration against cerebral ischemia-reperfusion injury following cardiac arrest

BACKGROUND

Heparin, a commonly used anticoagulant, has been found to improve cerebral ischemia-reperfusion injury (CIR-CA) following cardiopulmonary resuscitation (CPR). Here, we aimed to explore the role of pleiotrophin (PTN)/syndecan-3 pathway in heparin therapy for CIR-CA.

MATERIALS AND METHODS

The CA-CPR model was constructed in Sprague-Dawley (SD) rats, which were treated with low molecular weight heparin, and the neurological changes and brain histopathological changes were evaluated. For in-vitro experiments, the ischemic injury model of primary neurons was established by oxygen and glucose deprivation (OGD), and the neuron regeneration was detected via the Cell counting Kit-8 (CCK8) method, flow cytometry and microscopy. CREB antagonist (KG-501), ERK antagonist (PD98059) and si-PTN were used respectively to inhibit the expression of CREB, ERK and PTN in cells, so as to explore the role of heparin in regulating neuronal regeneration.

RESULTS

Compared with the sham rats, the neurological deficits and cerebral edema of CA-CPR rats were significantly improved after heparin treatment. Heparin also attenuated OGD-mediated neuronal apoptosis and promoted neurite outgrowth in vitro. Moreover, heparin attenuated CA-CPR-mediated neuronal apoptosis and microglial neuroinflammation. In terms of the mechanism, heparin upregulated the expression of ERK, CREB, NF200, BDNF, NGF, PTN and syndecan-3 in the rat brains. Inhibition of ERK, CREB and interference with PTN expression notably weakened the heparin-mediated neuroprotective effects and restrained the expression of ERK/CREB and PTN/syndecan-3 pathway.

CONCLUSION

Heparin attenuates the secondary brain injury induced by CA-CPR through regulating the ERK/CREB-mediated PTN/syndecan-3 pathway.

Protective effect of andrographolide against STZ induced Alzheimer's disease in experimental rats: possible neuromodulation and Aβ(1-42) analysis

STZ is a glucosamine-nitrosourea compound, causes dysfunctioning of insulin receptors in the brain and disrupts glucose metabolism, produces cognitive decline and AD-like symptoms. ICV injection of STZ causes accumulation of Aβ and cognitive dysfunctions. Andrographolide (ANDRO) is a major bioactive constituent of Andrographis paniculata, has various biological activities such as antioxidant, anti-inflammatory, anti-cholinesterase, and neuroprotective properties. The study aimed to evaluate the neuroprotective effect of ANDRO against ICV-STZ induced AD-like symptoms in rats. To conduct the study, the Wistar rat received two injections of STZ (3 mg/kg) through the ICV route. Rats were treated with three different doses of ANDRO (15, 30, and 60 mg/kg, p.o.) and donepezil (5 mg/kg, p.o.) for 14 days. The behavioral impairments were analyzed on weekly basis. Subsequently, rats were sacrificed for the assessment of biochemical (MDA, Nitrite, GSH, SOD, Catalase and AChE), neuroinflammatory markers (IL-1β, IL-16, and TNF-α), neurotransmitters (glutamate and GABA), level of Aβ_1-42 and p tau in the hippocampus on day 21st. Our result indicated that ANDRO treatment provided a protective effect against STZ induced behavioral deficits and changes in the biochemical, neuroinflammatory mediators, and neurotransmitters of the hippocampus. Further, ANDRO also reduced the level of Aβ_1-42 and p tau in the rat hippocampus. These findings suggested that the antioxidant, anti-inflammatory, anti-cholinesterase potential of ANDRO contributed to its neuroprotective effect as well as promising therapeutic candidate for the treatment of cognitive impairment and AD-like symptoms.

Pharmacological Inhibition of the Nod-Like Receptor Family Pyrin Domain Containing 3 Inflammasome with MCC950

Activation of the Nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome drives release of the proinflammatory cytokines interleukin (IL)-1β and IL-18 and induces pyroptosis (lytic cell death). These events drive chronic inflammation, and as such, NLRP3 has been implicated in a large number of human diseases. These range from autoimmune conditions, the simplest of which is NLRP3 gain-of-function mutations leading to an orphan disease, cryopyrin-associated period syndrome, to large disease burden indications, such as atherosclerosis, heart failure, stroke, neurodegeneration, asthma, ulcerative colitis, and arthritis. The potential clinical utility of NLRP3 inhibitors is substantiated by an expanding list of indications in which NLRP3 activation has been shown to play a detrimental role. Studies of pharmacological inhibition of NLRP3 in nonclinical models of disease using MCC950 in combination with human genetics, epigenetics, and analyses of the efficacy of biologic inhibitors of IL-1β, such as anakinra and canakinumab, can help to prioritize clinical trials of NLRP3-directed therapeutics. Although MCC950 shows excellent (nanomolar) potency and high target selectivity, its pharmacokinetic and toxicokinetic properties limited its therapeutic development in the clinic. Several improved, next-generation inhibitors are now in clinical trials. Hence the body of research in a plethora of conditions reviewed herein may inform analysis of the potential translational value of NLRP3 inhibition in diseases with significant unmet medical need. SIGNIFICANCE STATEMENT: The nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is one of the most widely studied and best validated biological targets in innate immunity. Activation of NLRP3 can be inhibited with MCC950, resulting in efficacy in more than 100 nonclinical models of inflammatory diseases. As several next-generation NLRP3 inhibitors are entering proof-of-concept clinical trials in 2020, a review of the pharmacology of MCC950 is timely and significant.

Development and Evaluation of a Novel Mouse Model of Asphyxial Cardiac Arrest Revealed Severely Impaired Lymphopoiesis After Resuscitation

Background Animal disease models represent the cornerstone in basic cardiac arrest (CA) research. However, current experimental models of CA and resuscitation in mice are limited. In this study, we aimed to develop a mouse model of asphyxial CA followed by cardiopulmonary resuscitation (CPR), and to characterize the immune response after asphyxial CA/CPR. Methods and Results CA was induced in mice by switching from an O2/N2 mixture to 100% N2 gas for mechanical ventilation under anesthesia. Real-time measurements of blood pressure, brain tissue oxygen, cerebral blood flow, and ECG confirmed asphyxia and ensuing CA. After a defined CA period, mice were resuscitated with intravenous epinephrine administration and chest compression. We subjected young adult and aged mice to this model, and found that after CA/CPR, mice from both groups exhibited significant neurologic deficits compared with sham mice. Analysis of post-CA brain confirmed neuroinflammation. Detailed characterization of the post-CA immune response in the peripheral organs of both young adult and aged mice revealed that at the subacute phase following asphyxial CA/CPR, the immune system was markedly suppressed as manifested by drastic atrophy of the spleen and thymus, and profound lymphopenia. Finally, our data showed that post-CA systemic lymphopenia was accompanied with impaired T and B lymphopoiesis in the thymus and bone marrow, respectively. Conclusions In this study, we established a novel validated asphyxial CA model in mice. Using this new model, we further demonstrated that asphyxial CA/CPR markedly affects both the nervous and immune systems, and notably impairs lymphopoiesis of T and B cells.

Neuroinflammation in Alzheimer's Disease

Alzheimer’s disease (AD) is a neurodegenerative disease associated with human aging. Ten percent of individuals over 65 years have AD and its prevalence continues to rise with increasing age. There are currently no effective disease modifying treatments for AD, resulting in increasingly large socioeconomic and personal costs. Increasing age is associated with an increase in low-grade chronic inflammation (inflammaging) that may contribute to the neurodegenerative process in AD. Although the exact mechanisms remain unclear, aberrant elevation of reactive oxygen and nitrogen species (RONS) levels from several endogenous and exogenous processes in the brain may not only affect cell signaling, but also trigger cellular senescence, inflammation, and pyroptosis. Moreover, a compromised immune privilege of the brain that allows the infiltration of peripheral immune cells and infectious agents may play a role. Additionally, meta-inflammation as well as gut microbiota dysbiosis may drive the neuroinflammatory process. Considering that inflammatory/immune pathways are dysregulated in parallel with cognitive dysfunction in AD, elucidating the relationship between the central nervous system and the immune system may facilitate the development of a safe and effective therapy for AD. We discuss some current ideas on processes in inflammaging that appear to drive the neurodegenerative process in AD and summarize details on a few immunomodulatory strategies being developed to selectively target the detrimental aspects of neuroinflammation without affecting defense mechanisms against pathogens and tissue damage.

A selective NLRP3 inflammasome inhibitor attenuates behavioral deficits and neuroinflammation in a mouse model of Parkinson's disease

Nod-like receptor pyrin containing (NLRP)3 inflammasome-mediated neuroinflammation is involved in the pathology of Parkinson's disease (PD), but the roles of other inflammasomes in PD remain unclear. The NLRP3 inhibitor MCC950 exerts neuroprotective effects in several neurological diseases. Using a 1-methyl-4-phenyl-1,2,3,6-tetrahydro pyridine (MPTP)-induced mouse model with or without intraperitoneal MCC950 administration, we assessed whether specifically the NLRP3 inflammasome is activated in the nigrostriatal system and whether MCC950 has therapeutic potential in this PD model. Western blots were used to determine the nigrostriatal expression of inflammasome-specific proteins, including NLRP1, NLRP2, NLRP3, nod-like receptor CARD containing 4 (NLRC4), and absent in melanoma 2 (AIM2). The pole, hanging, and swimming tests were used to assess functional deficits, western blots and immunostainings were used to analyze dopaminergic neuronal degeneration, as well as activation of glial cells and the NLRP3 inflammasome. NLRP3 expression in the nigrostriatal system of MPTP-induced mice was significantly increased compared to control, whereas NLRP1, NLRP2, NLRC4, and AIM2 expression in the nigrostriatal system, as well as NLRP3 expression in the cerebral cortex and hippocampus, were similar in the two groups. Furthermore, MPTP-induced mice exhibited behavioral dysfunctions, dopaminergic neuronal degeneration, and activation of glial cells and the NLRP3 inflammasome. MCC950 treatment of MPTP-induced mice improved behavioral dysfunctions, reduced dopaminergic neuronal degeneration, and inhibited the activation of glial cells and the NLRP3 inflammasome. In conclusion, these findings indicated that NLRP3, not NLRP1, NLRP2, NLRC4, and AIM2, may be the key inflammasome that promotes MPTP-induced pathogenesis. MCC950 protects against MPTP-induced nigrostriatal damage and may be a novel promising therapeutic approach in treating MPTP-induced PD.

NLRP3 Inflammasome Inhibitors in Cardiovascular Diseases

Virtually all types of cardiovascular diseases are associated with pathological activation of the innate immune system. The NACHT, leucine-rich repeat (LRR), and pyrin domain (PYD)-containing protein 3 (NLRP3) inflammasome is a protein complex that functions as a platform for rapid induction of the inflammatory response to infection or sterile injury. NLRP3 is an intracellular sensor that is sensitive to danger signals, such as ischemia and extracellular or intracellular alarmins during tissue injury. The NLRP3 inflammasome is regulated by the presence of damage-associated molecular patterns and initiates or amplifies inflammatory response through the production of interleukin-1β (IL-1β) and/or IL-18. NLRP3 activation regulates cell survival through the activity of caspase-1 and gasdermin-D. The development of NLRP3 inflammasome inhibitors has opened the possibility to targeting the deleterious effects of NLRP3. Here, we examine the scientific evidence supporting a role for NLRP3 and the effects of inhibitors in cardiovascular diseases.