Proteinase 3 Induces Neuronal Cell Death Through Microglial Activation

Association of admission neutrophil serine proteinases levels with the outcomes of acute ischemic stroke: a prospective cohort study

BACKGROUND

Neutrophil serine proteinases (NSPs), released by activated neutrophils, are key proteins involved in the pathophysiologic processes of stroke. NSPs are also implicated in the process and response of thrombolysis. This study aimed to analyze three NSPs (neutrophil elastase, cathepsin G, and proteinase 3) in relation to acute ischemic stroke (AIS) outcomes and in relation to the outcomes of patients treated with intravenous recombinant tissue plasminogen activator (IV-rtPA).

METHODS

Among 736 patients prospectively recruited at the stroke center from 2018 to 2019, 342 patients diagnosed with confirmed AIS were included. Plasma neutrophil elastase (NE), cathepsin G (CTSG), and proteinase 3 (PR3) concentrations were measured on admission. The primary endpoint was unfavorable outcome defined as modified Rankin Scale score 3-6 at 3 months, and the secondary endpoints were symptomatic intracerebral hemorrhage (sICH) within 48 h, and mortality within 3 months. In the subgroup of patients who received IV-rtPA, post-thrombolysis early neurological improvement (ENI) (defined as National Institutes of Health Stroke Scale score = 0 or decrease of ≥ 4 within 24 h after thrombolysis) was also included as the secondary endpoint. Univariate and multivariate logistic regression analyses were performed to evaluate the association between NSPs levels and AIS outcomes.

RESULTS

Higher NE and PR3 plasma levels were associated with the 3-month mortality and 3-month unfavorable outcome. Higher NE plasma levels were also associated with the risk of sICH after AIS. After adjusting for potential confounders, plasma NE level > 229.56 ng/mL (odds ratio [OR] = 4.478 [2.344-8.554]) and PR3 > 388.77 ng/mL (OR = 2.805 [1.504-5.231]) independently predicted the 3-month unfavorable outcome. Regarding rtPA treatment, patients with NE plasma concentration > 177.22 ng/mL (OR = 8.931 [2.330-34.238]) or PR3 > 388.77 ng/mL (OR = 4.275 [1.045-17.491]) were over 4 times more likely to suffer unfavorable outcomes after rtPA treatment. The addition of NE and PR3 to clinical predictors of unfavorable functional outcome after AIS and the outcome after rtPA treatment improved discrimination as well as reclassification (integrated discrimination improvement = 8.2% and 18.1%, continuous net reclassification improvement = 100.0% and 91.8%, respectively).

CONCLUSIONS

Plasma NE and PR3 are novel and independent predictors of 3-month functional outcomes after AIS. Plasma NE and PR3 also possess predictive value to identify patients with unfavorable outcomes after rtPA treatment. NE is probably an important mediator of the effects of neutrophils on stroke outcomes, which worth further investigation.

Increased Neutrophil elastase and proteinase 3 are closely associated with occurrence and severity of stroke and acute myocardial infarction in patients with type 2 diabetes mellitus

AIMS

The role of Neutrophil elastase (NE) and proteinase 3 (PR3) in the occurrence and severity of stroke and acute myocardial infarction (AMI) have not been explored in type 2 diabetes mellitus (T2DM). This study aimed to investigate the relationship and predictive ability of NE and PR3 in the development of stroke and AMI in patients with T2DM, and to explore the pattern of NE and PR3 in atherosclerotic plaques.

METHODS

465 patients with T2DM (stroke or AMI, n = 234; non stroke or AMI, n = 231) were recruited. Clinical characteristics, and NE and PR3 concentration were measured in all subjects. Semi-quantitative analysis of immunohistochemistry staining for NE and PR3 was performed in detached emboli and stable plaques.

RESULTS

Patients with stroke or AMI had a higher level of NE and PR3, with a more pronounced increase in more severe cases (higher mRS score in stroke and Gensini score in AMI) and associated with clinical markers. An increase in NE and PR3 was an independent risk factor for stroke (OR = 4.318, P = 0.017; OR = 2.979, P = 0.048, respectively) and AMI (OR = 8.385, P = 0.015; OR = 5.540, P = 0.047). Finally, immunohistochemistry staining revealed that the NE and PR3 positive area increased significantly in detached emboli compared with stable plaques.

CONCLUSION

Increased NE and PR3 was associated with occurrence and severity of stroke and AMI in patients with T2DM. Enriched NE and PR3 in detached emboli may be associated with plaque vulnerability.

Elevation of inactive cleaved annexin A1 in the neocortex is associated with amyloid, inflammatory and apoptotic markers in neurodegenerative dementias

Inflammation is usually a tightly regulated process whose termination by mediators including Annexin A1 (AnxA1) results in the resolution of inflammatory responses. In neurodegenerative dementias, chronic neuroinflammation, along with accumulation of aggregated β-amyloid (Aβ) peptides and apoptosis, has long been recognized to be a pathological hallmark; but it is unclear whether a failure of inflammation resolution contributes to this pathophysiological process. In this study, we measured AnxA1 immunoreactivities in postmortem neocortex (Brodmann areas BA9 and BA40) of well characterized Alzheimer's disease (AD), Parkinson disease dementia (PDD) and dementia with Lewy bodies (DLB) patients as well as aged controls. Inactive cleaved AnxA1 was found to be elevated in AD and DLB in BA40. Levels of cleaved AnxA1 also positively correlated with amyloidogenic brain Aβ, anti-inflammatory markers such as IL10 and IL13, as well as with the pro-apoptotic marker cleaved caspase-3 in BA40. Our findings suggest that elevated cleaved AnxA1 in neurodegenerative dementias may reflect a failure of inflammation resolution in certain regions of the diseased brain, and also support a mechanistic link between AnxA1 and amyloid pathology, neuroinflammation and apoptosis.

Neutrophil, Extracellular Matrix Components, and Their Interlinked Action in Promoting Secondary Pathogenesis After Spinal Cord Injury

Secondary pathogenesis following primary mechanical damage to the spinal cord is believed to be the ultimate reason for the limitation of currently available therapies. Precisely, the complex cascade of secondary events-mediated scar formation is the sole hurdle in the recovery process due to its inhibitory effect on axonal regeneration, plasticity, and remyelination. Neutrophils initiate this secondary injury along with other extracellular matrix components such as matrix metalloproteinase (MMPs), and chondroitin sulfate proteoglycans (CSPGs). Together, they mediate inflammation, necrosis, apoptosis, lesion, and scar formation at the injury site. Activated neutrophil releases several proteases, cytokines, and chemokines that cause complete tissue destruction. Thus, neutrophil activation and infiltration in the acute phase of injury act as a roadmap for inducing tissue destruction. MMPs, are extracellular proteolytic enzymes that degrade the ECM proteins, increases vascular permeability, and are predominantly released by neutrophils. These MMPs, in turn, cleave NG2 proteoglycan, a subtype of CSPG, into the active form. This active or shed form is involved in both the fibrotic as well as glial scar formation. Since neutrophils and ECM components are closely associated with each other in pathological conditions. Herein, we emphasize the interaction of neutrophils and their influence on ECM protein expression during the acute and chronic phases to identify a promising targets for designing a therapeutic approach in spinal cord injury.

Immune Response in Neurological Pathology: Emerging Role of Central and Peripheral Immune Crosstalk

Neuroinflammation is a key component of neurological disorders and is an important therapeutic target; however, immunotherapies have been largely unsuccessful. In cases where these therapies have succeeded, particularly multiple sclerosis, they have primarily focused on one aspect of the disease and leave room for improvement. More recently, the impact of the peripheral immune system is being recognized, since it has become evident that the central nervous system is not immune-privileged, as once thought. In this review, we highlight key interactions between central and peripheral immune cells in neurological disorders. While traditional approaches have examined these systems separately, the immune responses and processes in neurological disorders consist of substantial crosstalk between cells of the central and peripheral immune systems. Here, we provide an overview of major immune effector cells and the role of the blood-brain barrier in regard to neurological disorders and provide examples of this crosstalk in various disorders, including stroke and traumatic brain injury, multiple sclerosis, neurodegenerative diseases, and brain cancer. Finally, we propose targeting central-peripheral immune interactions as a potential improved therapeutic strategy to overcome failures in clinical translation.

PGC-1α-Mediated Mitochondrial Biogenesis is Involved in Cannabinoid Receptor 2 Agonist AM1241-Induced Microglial Phenotype Amelioration

Cannabinoid type 2 receptor (CB2R) agonist AM1241 induces anti-inflammation by ameliorating microglial phenotypes, the mechanism, however, is still unknown. Peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) is a transcription protein which can regulate mitochondrial biogenesis, and the aim of this study is to investigate whether PGC-1α is involved in AM1241-induced anti-inflammation in N9 microglial cells. We used 10 ng/ml lipopolysaccharide (LPS) plus 10 U/ml interferon γ (IFNγ) to activate microglia into classic activated phenotype (M1 phenotype), and found that co-administration of 10 µM AM1241 increased the expressions of mitochondria biogenesis-associated proteins, including nuclear respiratory factor 1 (NRF-1), mitochondrial transcription factor A (TFAM) and COX IV, and up-regulated the biomarker levels of microglial M2 phenotype, including arginase 1 (Arg-1) and brain-derived neurotrophic factor (BDNF), and down-regulated biomarker levels of M1 phenotype, including inducible nitric oxide synthase (iNOS) and tumor necrosis factor α (TNF-α), compared to the cells treated with LPS plus IFNγ only (P < 0.05). By using PGC-1α-siRNA, however, we found that down-regulation of PGC-1α significantly reversed the AM1241-induced effects above (P < 0.05). According to the results in this study, we found that PGC-1α may mediate CB2R agonist AM1241-induced anti-inflammation in N9 microglial cells, and the mechanism might be associated with the enhancement of mitochondria biogenesis.

NLRP3 inflammasome-driven pathways in depression: Clinical and preclinical findings

Over the past three decades, an intricate interaction between immune activation, release of pro-inflammatory cytokines and changes in brain circuits related to mood and behavior has been described. Despite extensive efforts, questions regarding when inflammation becomes detrimental or how we can target the immune system to develop new therapeutic strategies for the treatment of psychiatric disorders remain unresolved. In this context, novel aspects of the neuroinflammatory process activated in response to stressful challenges have recently been documented in major depressive disorder (MDD). The Nod-like receptor pyrin containing 3 inflammasome (NLRP3) is an intracellular multiprotein complex responsible for a number of innate immune processes associated with infection, inflammation and autoimmunity. Recent data have demonstrated that NLRP3 activation appears to bridge the gap between immune activation and metabolic danger signals or stress exposure, which are key factors in the pathogenesis of psychiatric disorders. In this review, we discuss both preclinical and clinical evidence that links the assembly of the NLRP3 complex and the subsequent proteolysis and release of the pro-inflammatory cytokines interleukin-1β (IL-1β) and interleukin-18 (IL-18) in chronic stress models and patients with MDD. Importantly, we also focus on the therapeutic potential of targeting the NLRP3 inflammasome complex to improve stress resilience and depressive symptoms.

Identification of Sphingosine 1-Phosphate Receptor Subtype 1 (S1P1) as a Pathogenic Factor in Transient Focal Cerebral Ischemia

Medically relevant roles of receptor-mediated sphingosine 1-phosphate (S1P) signaling have become a successful or promising target for multiple sclerosis or cerebral ischemia. Animal-based proof-of-concept validation for the latter is particularly through the neuroprotective efficacy of FTY720, a non-selective S1P receptor modulator, presumably via activation of S1P₁. In spite of a clear link between S1P signaling and cerebral ischemia, it remains unknown whether the role of S1P₁ is pathogenic or neuroprotective. Here, we investigated the involvement of S1P₁ along with its role in cerebral ischemia using a transient middle cerebral artery occlusion ("tMCAO") model. Brain damage following tMCAO, as assessed by brain infarction, neurological deficit score, and neural cell death, was reduced by oral administration of AUY954, a selective S1P₁ modulator as a functional antagonist, in a therapeutic paradigm, indicating that S1P₁ is a pathogenic mediator rather than a neuroprotective mediator. This pathogenic role of S1P₁ in cerebral ischemia was reaffirmed because tMCAO-induced brain damage was reduced by genetic knockdown with an intracerebroventricular microinjection of S1P₁ shRNA lentivirus into the brain. Genetic knockdown of S1P₁ or AUY954 exposure reduced microglial activation, as assessed by reduction in the number of activated microglia and reversed morphology from amoeboid to ramified, and microglial proliferation in ischemic brain. Its role in microglial activation was recapitulated in lipopolysaccharide-stimulated primary mouse microglia, in which the mRNA expression level of TNF-α and IL-1β, well-known markers for microglial activation, was reduced in microglia transfected with S1P₁ siRNA. These data suggest that the pathogenic role of S1P₁ is associated with microglial activation in ischemic brain. Additionally, the pathogenic role of S1P₁ in cerebral ischemia appears to be associated with the blood-brain barrier disruption and brain-derived neurotrophic factor (BDNF) downregulation. Overall, findings from the current study clearly identify S1P₁ signaling as a pathogenic factor in transient focal cerebral ischemia, further implicating S1P₁ antagonists including functional antagonists as plausible therapeutic agents for human stroke.

Neutrophil granulocytes in cerebral ischemia - Evolution from killers to key players

Neutrophil granulocytes (or polymorphonuclear cells, PMNs) have long been considered as crude killing machines, particularly trained to attack bacterial or fungal pathogens in wounds or infected tissues. That perspective has fundamentally changed over the last decades, as PMNs have been shown to exert a livery exchange between other cells of the innate and adaptive immune system. PMNs do provide major immunomodulatory contribution during acute inflammation and subsequent clearance. Following sterile inflammation like cerebral ischemia, PMNs are among the first hematogenous cells attracted to the ischemic tissue. As inflammation is a crucial component within stroke pathophysiology, several studies regarding the role of PMNs following cerebral ischemia have been carried out. And indeed, recent research suggests a direct connection between PMNs' influx and brain damage severity. This review highlights the latest research regarding the close interconnection between PMNs and co-working cells following cerebral ischemia. We describe how PMNs are attracted to the site of injury and their tasks within the inflamed brain tissue and the periphery. We further report of new findings regarding the interaction of PMNs with resident microglia, immigrating macrophages and T cells after stroke. Finally, we discuss recent research results from experimental studies in the context with current clinical trials and point out potential new therapeutic applications that could emerge from this new knowledge on the action and interaction of PMNs following cerebral ischemia.