Cytoprotective activated protein C averts Nlrp3 inflammasome-induced ischemia-reperfusion injury via mTORC1 inhibition

The parmodulin NRD-21 is an allosteric inhibitor of PAR1 Gq signaling with improved anti-inflammatory activity and stability

Novel analogs of the allosteric, biased PAR1 ligand ML161 (parmodulin 2, PM2) were prepared in order to identify potential anti-thrombotic and anti-inflammatory compounds of the parmodulin class with improved properties. Investigations of structure-activity relationships of the western portion of the 1,3-diaminobenzene scaffold were performed using an intracellular calcium mobilization assay with endothelial cells, and several heterocycles were identified that inhibited PAR1 at sub-micromolar concentrations. The oxazole NRD-21 was profiled in additional detail, and it was confirmed to act as a selective, reversible, negative allosteric modulator of PAR1. In addition to inhibiting human platelet aggregation, it showed superior anti-inflammatory activity to ML161 in a qPCR assay measuring the expression of tissue factor in response to the cytokine TNF-alpha in endothelial cells. Additionally, NRD-21 is much more plasma stable than ML161, and is a promising lead compound for the parmodulin class for anti-thrombotic and anti-inflammatory indications.

Activated protein C in neuroprotection and malaria

PURPOSE OF REVIEW

Activated protein C (APC) is a homeostatic coagulation protease with anticoagulant and cytoprotective activities. Focusing on APC's effects in the brain, this review discusses three different scenarios that illustrate how APC functions are intimately affecting the physiology and pathophysiology of the brain.

RECENT FINDINGS

Cytoprotective APC therapy holds promise for the treatment of ischemic stroke, and a recently completed trial suggested that cytoprotective-selective 3K3A-APC reduced bleeding in ischemic stroke patients. In contrast, APC's anticoagulant activity contributes to brain bleeding as shown by the disproportional upregulation of APC generation in cerebral cavernous malformations lesions in mice. However, too little APC generation also contributes to maladies of the brain, such as in case of cerebral malaria where the binding of infected erythrocytes to the endothelial protein C receptor (EPCR) may interfere with the EPCR-dependent functions of the protein C pathway. Furthermore, discoveries of new activities of APC such as the inhibition of the NLRP3-mediated inflammasome and of new applications of APC therapy such as in Alzheimer's disease and graft-versus-host disease continue to advance our knowledge of this important proteolytic regulatory system.

SUMMARY

APC's many activities or lack thereof are intimately involved in multiple neuropathologies, providing abundant opportunities for translational research.

Genetic Deletion or Pharmacological Inhibition of Soluble Epoxide Hydrolase Ameliorates Cardiac Ischemia/Reperfusion Injury by Attenuating NLRP3 Inflammasome Activation

Activation of the nucleotide-binding oligomerization domain-like receptor (NLR) family pyrin domain containing 3 (NLRP3) inflammasome cascade has a role in the pathogenesis of ischemia/reperfusion (IR) injury. There is growing evidence indicating cytochrome p450 (CYP450)-derived metabolites of n-3 and n-6 polyunsaturated fatty acids (PUFAs) possess both adverse and protective effects in the heart. CYP-derived epoxy metabolites are rapidly hydrolyzed by the soluble epoxide hydrolase (sEH). The current study hypothesized that the cardioprotective effects of inhibiting sEH involves limiting activation of the NLRP3 inflammasome. Isolated hearts from young wild-type (WT) and sEH null mice were perfused in the Langendorff mode with either vehicle or the specific sEH inhibitor t-AUCB. Improved post-ischemic functional recovery and better mitochondrial respiration were observed in both sEH null hearts or WT hearts perfused with t-AUCB. Inhibition of sEH markedly attenuated the activation of the NLRP3 inflammasome complex and limited the mitochondrial localization of the fission protein dynamin-related protein-1 (Drp-1) triggered by IR injury. Cardioprotective effects stemming from the inhibition of sEH included preserved activities of both cytosolic thioredoxin (Trx)-1 and mitochondrial Trx-2 antioxidant enzymes. Together, these data demonstrate that inhibiting sEH imparts cardioprotection against IR injury via maintaining post-ischemic mitochondrial function and attenuating a detrimental innate inflammatory response.

Circulating blood cells and extracellular vesicles in acute cardioprotection

During an ST-elevation myocardial infarction (STEMI), the myocardium undergoes a prolonged period of ischaemia. Reperfusion therapy is essential to minimize cardiac injury but can paradoxically cause further damage. Experimental procedures to limit ischaemia and reperfusion (IR) injury have tended to focus on the cardiomyocytes since they are crucial for cardiac function. However, there is increasing evidence that non-cardiomyocyte resident cells in the heart (as discussed in a separate review in this Spotlight series) as well as circulating cells and factors play important roles in this pathology. For example, erythrocytes, in addition to their main oxygen-ferrying role, can protect the heart from IR injury via the export of nitric oxide bioactivity. Platelets are well-known to be involved in haemostasis and thrombosis, but beyond these roles, they secrete numerous factors including sphingosine-1 phosphate (S1P), platelet activating factor, and cytokines that can all strongly influence the development of IR injury. This is particularly relevant given that most STEMI patients receive at least one type of platelet inhibitor. Moreover, there are large numbers of circulating vesicles in the blood, including microvesicles and exosomes, which can exert both beneficial and detrimental effects on IR injury. Some of these effects are mediated by the transfer of microRNA (miRNA) to the heart. Synthetic miRNA molecules may offer an alternative approach to limiting the response to IR injury. We discuss these and other circulating factors, focussing on potential therapeutic targets relevant to IR injury. Given the prevalence of comorbidities such as diabetes in the target patient population, their influence will also be discussed. This article is part of a Cardiovascular Research Spotlight Issue entitled 'Cardioprotection Beyond the Cardiomyocyte', and emerged as part of the discussions of the European Union (EU)-CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225.

Cardiac arrhythmias after renal I/R depend on IL-1β

AIMS

Cardiac arrhythmias are one of the most important remote complications after kidney injury. Renal ischemia reperfusion (I/R) is a major cause of acute renal injury predisposing to several remote dysfunctions, including cardiac electrical disturbance. Since IL-1β production dependent on NLRP3 represents a link between tissue malfunctioning and cardiac arrhythmias, here we tested the hypothesis that longer ventricular repolarization and arrhythmias after renal I/R depend on this innate immunity sensor.

METHODS AND RESULTS

Nlrp3^-/- and Casp1^-/- mice reacted to renal I/R with no increase in plasma IL-1β, different from WT (wild-type) I/R. A prolonged QJ interval and an increased susceptibility to ventricular arrhythmias were found after I/R compared to Sham controls in wild-type mice at 15 days post-perfusion, but not in Nlrp3^-/- or CASP1^-/- I/R, indicating that the absence of NLRP3 or CASP1 totally prevented longer QJ interval after renal I/R. In contrast with WT mice, we found no renal atrophy and no renal dysfunction in Nlrp3^-/- and Casp1^-/- mice after renal I/R. Depletion of macrophages in vivo after I/R and a day before IL-1β peak (at 7 days post-perfusion) totally prevented prolongation of QJ interval, suggesting that macrophages might participate as sensors of tissue injury. Moreover, treatment of I/R-WT mice with IL-1r antagonist (IL-1ra) from 8 to 15 days post perfusion did not interfere with renal function, but reversed QJ prolongation, prevented the increase in susceptibility to ventricular arrhythmias and rescued a close to normal duration and amplitude of calcium transient.

CONCLUSION

Taken together, these results corroborate the hypothesis that IL-1β is produced after sensing renal injury through NRLP3-CASP1, and IL-1β on its turn triggers longer ventricular repolarization and increase susceptibility to cardiac arrhythmias. Still, they offer a therapeutic approach to treat cardiac arrhythmias that arise after renal I/R.

The Cardioprotective Signaling Activity of Activated Protein C in Heart Failure and Ischemic Heart Diseases

Activated protein C (APC) is a vitamin-K dependent plasma serine protease, which functions as a natural anticoagulant to downregulate thrombin generation in the clotting cascade. APC also modulates cellular homeostasis by exhibiting potent cytoprotective and anti-inflammatory signaling activities. The beneficial cytoprotective effects of APC have been extensively studied and confirmed in a number of preclinical disease and injury models including sepsis, type-1 diabetes and various ischemia/reperfusion diseases. It is now well-known that APC modulates downstream cell signaling networks and transcriptome profiles when it binds to the endothelial protein C receptor (EPCR) to activate protease-activated receptor 1 (PAR1) on various cell types. However, despite much progress, details of the downstream signaling mechanism of APC and its crosstalk with other signaling networks are far from being fully understood. In this review, we focus on the cardioprotective properties of APC in ischemic heart disease and heart failure with a special emphasis on recent discoveries related to the modulatory effect of APC on AMP-activated protein kinase (AMPK), PI3K/AKT, and mTORC1 signaling pathways. The cytoprotective properties of APC might provide a novel strategy for future therapies in cardiac diseases.

Novel Antiplatelet Therapies for Atherothrombotic Diseases

Antiplatelet therapies are an essential tool to reduce the risk of developing clinically apparent atherothrombotic disease and are a mainstay in the therapy of patients who have established cardiovascular, cerebrovascular, and peripheral artery disease. Strategies to intensify antiplatelet regimens are limited by concomitant increases in clinically significant bleeding. The development of novel antiplatelet therapies targeting additional receptor and signaling pathways, with a focus on maintaining antiplatelet efficacy while preserving hemostasis, holds tremendous potential to improve outcomes among patients with atherothrombotic diseases.

Activated Protein C in Cutaneous Wound Healing: From Bench to Bedside

Independent of its well-known anticoagulation effects, activated protein C (APC) exhibits pleiotropic cytoprotective properties. These include anti-inflammatory actions, anti-apoptosis, and endothelial and epithelial barrier stabilisation. Such beneficial effects have made APC an attractive target of research in a plethora of physiological and pathophysiological processes. Of note, the past decade or so has seen the emergence of its roles in cutaneous wound healing-a complex process involving inflammation, proliferation and remodelling. This review will highlight APC's functions and mechanisms, and detail its pre-clinical and clinical studies on cutaneous wound healing.

3K3A-activated protein C blocks amyloidogenic BACE1 pathway and improves functional outcome in mice

3K3A-activated protein C (APC), a cell-signaling analogue of endogenous blood serine protease APC, exerts vasculoprotective, neuroprotective, and anti-inflammatory activities in rodent models of stroke, brain injury, and neurodegenerative disorders. 3K3A-APC is currently in development as a neuroprotectant in patients with ischemic stroke. Here, we report that 3K3A-APC inhibits BACE1 amyloidogenic pathway in a mouse model of Alzheimer's disease (AD). We show that a 4-mo daily treatment of 3-mo-old 5XFAD mice with murine recombinant 3K3A-APC (100 µg/kg/d i.p.) prevents development of parenchymal and cerebrovascular amyloid-β (Aβ) deposits by 40-50%, which is mediated through NFκB-dependent transcriptional inhibition of BACE1, resulting in blockade of Aβ generation in neurons overexpressing human Aβ-precursor protein. Consistent with reduced Aβ deposition, 3K3A-APC normalized hippocampus-dependent behavioral deficits and cerebral blood flow responses, improved cerebrovascular integrity, and diminished neuroinflammatory responses. Our data suggest that 3K3A-APC holds potential as an effective anti-Aβ prevention therapy for early-stage AD.

Roles of Coagulation Proteases and PARs (Protease-Activated Receptors) in Mouse Models of Inflammatory Diseases

Activation of the blood coagulation cascade leads to fibrin deposition and platelet activation that are required for hemostasis. However, aberrant activation of coagulation can lead to thrombosis. Thrombi can cause tissue ischemia, and fibrin degradation products and activated platelets can enhance inflammation. In addition, coagulation proteases activate cells by cleavage of PARs (protease-activated receptors), including PAR1 and PAR2. Direct oral anticoagulants have recently been developed to specifically inhibit the coagulation proteases FXa (factor Xa) and thrombin. Administration of these inhibitors to wild-type mice can be used to determine the roles of FXa and thrombin in different inflammatory diseases. These results can be compared with the phenotypes of mice with deficiencies of either Par1 (F2r) or Par2 (F2rl1). However, inhibition of coagulation proteases will have effects beyond reducing PAR signaling, and a deficiency of PARs will abolish signaling from all proteases that activate these receptors. We will summarize studies that examine the roles of coagulation proteases, particularly FXa and thrombin, and PARs in different mouse models of inflammatory disease. Targeting FXa and thrombin or PARs may reduce inflammatory diseases in humans.

Rapamycin ameliorates lipopolysaccharide-induced acute lung injury by inhibiting IL-1β and IL-18 production

Interleukin (IL)-1β and IL-18 play central and detrimental roles in the development of acute lung injury (ALI), and mammalian target of rapamycin (mTOR) is involved in regulating IL-1β and IL-18 production. However, it is not clear whether the mTOR specific inhibitor rapamycin can attenuate lipopolysaccharide (LPS)-induced ALI by modulating IL-1β and IL-18 production. In this study, we found that rapamycin ameliorated LPS-induced ALI by inhibiting NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome-mediated IL-1β and IL-18 secretion. Mechanistically, elevated autophagy and decreased nuclear factor (NF)-κB activation were associated with downregulated IL-1β and IL-18. Moreover, rapamycin reduced leukocyte infiltration in the lung tissue and bronchoalveolar lavage fluid (BALF), and contributed to the alleviation of LPS-induced ALI. Consistently, rapamycin also significantly inhibited IL-1β and IL-18 production by RAW264.7 cells via increased autophagy and decreased NF-κB signaling in vitro. Our results demonstrated that rapamycin protects mice against LPS-induced ALI partly by inhibiting the production and secretion of IL-1β and IL-18. mTOR and rapamycin might represent an appropriate therapeutic target and strategy for preventing ALI induced by LPS.

Role of pyroptosis in cardiovascular disease

Cardiac function is determined by the dynamic equilibrium of various cell types and the extracellular matrix that composes the heart. Cardiovascular diseases (CVDs), especially atherosclerosis and myocardial infarction, are often accompanied by cell death and acute/chronic inflammatory reactions. Caspase‐dependent pyroptosis is characterized by the activation of pathways leading to the activation of NOD‐like receptors, especially the NLRP3 inflammasome and its downstream effector inflammatory factors interleukin (IL)‐1β and IL‐18. Many studies in the past decade have investigated the role of pyroptosis in CVDs. The findings of these studies have led to the development of therapeutic approaches based on the regulation of pyroptosis, and some of these approaches are in clinical trials. This review summarizes the molecular mechanisms, regulation and cellular effects of pyroptosis briefly and then discusses the current pyroptosis studies in CVD research.

Delayed oseltamivir plus sirolimus treatment attenuates H1N1 virus-induced severe lung injury correlated with repressed NLRP3 inflammasome activation and inflammatory cell infiltration

Severe influenza A virus infection causes high mortality and morbidity worldwide due to delayed antiviral treatment and inducing overwhelming immune responses, which contribute to immunopathological lung injury. Sirolimus, an inhibitor of mammalian target of rapamycin (mTOR), was effective in improving clinical outcomes in patients with severe H1N1 infection; however, the mechanisms by which it attenuates acute lung injury have not been elucidated. Here, delayed oseltamivir treatment was used to mimic clinical settings on lethal influenza A (H1N1) pdm09 virus (pH1N1) infection mice model. We revealed that delayed oseltamivir plus sirolimus treatment protects mice against lethal pH1N1 infection by attenuating severe lung damage. Mechanistically, the combined treatment reduced viral titer and pH1N1-induced mTOR activation. Subsequently, it suppressed the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome-mediated secretion of interleukin (IL)-1β and IL-18. It was noted that decreased NLRP3 inflammasome activation was associated with inhibited nuclear factor (NF)-κB activation, reduced reactive oxygen species production and increased autophagy. Additionally, the combined treatment reduced the expression of other proinflammatory cytokines and chemokines, and decreased inflammatory cell infiltration in lung tissue and bronchioalveolar lavage fluid. Consistently, it inhibited the mTOR-NF-κB-NLRP3 inflammasome-IL-1β axis in a lung epithelial cell line. These results demonstrated that combined treatment with sirolimus and oseltamivir attenuates pH1N1-induced severe lung injury, which is correlated with suppressed mTOR-NLRP3-IL-1β axis and reduced viral titer. Therefore, treatment with sirolimus as an adjuvant along with oseltamivir may be a promising immunomodulatory strategy for managing severe influenza.

The severity and lethality of influenza A virus infection are frequently aggravated by virus-induced tissue destruction and overwhelming immune responses. Combined therapy with antiviral medications and immunomodulators, which not only inhibit viral replication, but also reduce the damaging consequences of host immune responses, will be beneficial in the treatment of severe influenza. In the present study, we revealed that pH1N1-induced activation of mTOR promotes lung immunopathological injury, which is correlated with upregulated NF-κB activity and increased reactive oxygen species production. Subsequently, it induces NLRP3 inflammasome activation and the secretion of IL-1β and IL-18. Combined treatment with oseltamivir and the mTOR inhibitor sirolimus (as an adjuvant) not only blocks viral replication, but also suppresses mTOR-NLRP3-IL-1β axis-mediated immune damage, thus protecting mice against lethal pH1N1 infection. Our findings provide the theoretical and experimental basis for the clinical investigation of sirolimus as an adjunct treatment for severe influenza.

The role of mitochondria in NLRP3 inflammasome activation

The NLRP3 inflammasome is a multiprotein platform which is activated upon cellular infection or stress. Its activation leads to caspase-1-dependent secretion of proinflammatory cytokines like interleukin-1β (IL-1β) and IL-18, and an inflammatory form of cell death termed as pyroptosis. Recent studies have unveiled the pivotal roles of mitochondria in initiation and regulation of the NLRP3 (nucleotide-binding domain, leucine-rich-repeat containing family, pyrin domain-containing 3) inflammasome. NLRP3 activators induce mitochondrial destabilization, NLRP3 deubiquitination, linear ubiquitination of ASC, and externalization or release of mitochondria-derived molecules such as cardiolipin and mitochondrial DNA. These molecules bind to NLRP3 that is translocated on mitochondria and activate the NLRP3 inflammasome. Here we review recently described mechanisms by which mitochondria regulate NLRP3 inflammasome activation.

Inflammasome, pyroptosis, and cytokines in myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion injury induces a sterile inflammatory response, leading to further injury that contributes to the final infarct size. Locally released danger-associated molecular patterns lead to priming and triggering of the NOD-like receptor protein 3 inflammasome and amplification of the inflammatory response and cell death by activation of caspase-1. We review strategies inhibiting priming, triggering, or caspase-1 activity or blockade of the inflammasome-related cytokines interleukin-1β and interleukin-18, focusing on the beneficial effects in experimental models of acute myocardial infarction in animals and the initial results of clinical translational research trials.

Activated protein C reverses epigenetically sustained p66Shc expression in plaque-associated macrophages in diabetes

Impaired activated protein C (aPC) generation is associated with atherosclerosis and diabetes mellitus. Diabetes-associated atherosclerosis is characterized by the hyperglycaemic memory, e.g., failure of disease improvement despite attenuation of hyperglycaemia. Therapies reversing the hyperglycaemic memory are lacking. Here we demonstrate that hyperglycaemia, but not hyperlipidaemia, induces the redox-regulator p66Shc and reactive oxygen species (ROS) in macrophages. p66Shc expression, ROS generation, and a pro-atherogenic phenotype are sustained despite restoring normoglycemic conditions. Inhibition of p66Shc abolishes this sustained pro-atherogenic phenotype, identifying p66Shc-dependent ROS in macrophages as a key mechanism conveying the hyperglycaemic memory. The p66Shc-associated hyperglycaemic memory can be reversed by aPC via protease-activated receptor-1 signalling. aPC reverses glucose-induced CpG hypomethylation within the p66Shc promoter by induction of the DNA methyltransferase-1 (DNMT1). Thus, epigenetically sustained p66Shc expression in plaque macrophages drives the hyperglycaemic memory, which-however-can be reversed by aPC. This establishes that reversal of the hyperglycaemic memory in diabetic atherosclerosis is feasible.

GPCRs in NLRP3 Inflammasome Activation, Regulation, and Therapeutics

The NLRP3 inflammasome is an intracellular multimeric protein complex which plays an important role in the pathogenesis of various human inflammatory diseases, such as diabetes, Alzheimer's disease and atherosclerosis. Recently, various G protein-coupled receptors (GPCRs) have been reported to be involved in the activation and regulation of the NLRP3 inflammasome by sensing multiple ions, metabolites, and neurotransmitters, suggesting GPCR signaling is an important regulator for NLRP3 inflammasome. Here, we will review how various GPCRs promote or inhibit NLRP3 inflammasome activation and discuss the implications of GPCRs as drug targets for the therapy of NLRP3-driven diseases.

Blood coagulation dissected

Hemostasis is the physiological control of bleeding and is initiated by subendothelial exposure. Platelets form the primary vascular seal in three stages (localization, stimulation and aggregation), which are triggered by specific interactions between platelet surface receptors and constituents of the subendothelial matrix. As a secondary hemostatic plug, fibrin clot formation is initiated and feedback-amplified to advance the seal and stabilize platelet aggregates comprising the primary plug. Once blood leakage has been halted, the fibrinolytic pathway is initiated to dissolve the clot and restore normal blood flow. Constitutive and induced anticoagulant and antifibrinolytic pathways create a physiological balance between too much and too little clot production. Hemostatic imbalance is a major burden to global healthcare, resulting in thrombosis or hemorrhage.

Activated protein C, protease activated receptor 1, and neuroprotection

Protein C is a plasma serine protease zymogen whose active form, activated protein C (APC), exerts potent anticoagulant activity. In addition to its antithrombotic role as a plasma protease, pharmacologic APC is a pleiotropic protease that activates diverse homeostatic cell signaling pathways via multiple receptors on many cells. Engineering of APC by site-directed mutagenesis provided a signaling selective APC mutant with 3 Lys residues replaced by 3 Ala residues, 3K3A-APC, that lacks >90% anticoagulant activity but retains normal cell signaling activities. This 3K3A-APC mutant exerts multiple potent neuroprotective activities, which require the G-protein-coupled receptor, protease activated receptor 1. Potent neuroprotection in murine ischemic stroke models is linked to 3K3A-APC-induced signaling that arises due to APC's cleavage in protease activated receptor 1 at a noncanonical Arg46 site. This cleavage causes biased signaling that provides a major explanation for APC's in vivo mechanism of action for neuroprotective activities. 3K3A-APC appeared to be safe in ischemic stroke patients and reduced bleeding in the brain after tissue plasminogen activator therapy in a recent phase 2 clinical trial. Hence, it merits further clinical testing for its efficacy in ischemic stroke patients. Recent studies using human fetal neural stem and progenitor cells show that 3K3A-APC promotes neurogenesis in vitro as well as in vivo in the murine middle cerebral artery occlusion stroke model. These recent advances should encourage translational research centered on signaling selective APC's for both single-agent therapies and multiagent combination therapies for ischemic stroke and other neuropathologies.

Characterization of Protease-Activated Receptor (PAR) ligands: Parmodulins are reversible allosteric inhibitors of PAR1-driven calcium mobilization in endothelial cells

Several classes of ligands for Protease-Activated Receptors (PARs) have shown impressive anti-inflammatory and cytoprotective activities, including PAR2 antagonists and the PAR1-targeting parmodulins. In order to support medicinal chemistry studies with hundreds of compounds and to perform detailed mode-of-action studies, it became important to develop a reliable PAR assay that is operational with endothelial cells, which mediate the cytoprotective effects of interest. We report a detailed protocol for an intracellular calcium mobilization assay with adherent endothelial cells in multiwell plates that was used to study a number of known and new PAR1 and PAR2 ligands, including an alkynylated version of the PAR1 antagonist RWJ-58259 that is suitable for the preparation of tagged or conjugate compounds. Using the cell line EA.hy926, it was necessary to perform media exchanges with automated liquid handling equipment in order to obtain optimal and reproducible antagonist concentration-response curves. The assay is also suitable for study of PAR2 ligands; a peptide antagonist reported by Fairlie was synthesized and found to inhibit PAR2 in a manner consistent with reports using epithelial cells. The assay was used to confirm that vorapaxar acts as an irreversible antagonist of PAR1 in endothelium, and parmodulin 2 (ML161) and the related parmodulin RR-90 were found to inhibit PAR1 reversibly, in a manner consistent with negative allosteric modulation.

Regulation of immune cell signaling by activated protein C

Innate immune cells are an essential part of the host defense response, promoting inflammation through release of proinflammatory cytokines or formation of neutrophil extracellular traps. While these processes are important for defense against infectious agents or injury, aberrant activation potentiates pathologic inflammatory disease. Thus, understanding regulatory mechanisms that limit neutrophil extracellular traps formation and cytokine release is of therapeutic interest for targeting pathologic diseases. Activated protein C is an endogenous serine protease with anticoagulant activity as well as anti-inflammatory and cytoprotective functions, the latter of which are mediated through binding cell surface receptors and inducing intracellular signaling. In this review, we discuss certain leukocyte functions, namely neutrophil extracellular traps formation and cytokine release, and the inhibition of these processes by activated protein C.

shRNA interference of NLRP3 inflammasome alleviate ischemia reperfusion-induced myocardial damage through autophagy activation

Myocardial ischemia-reperfusion (I/R) injury always occur during the recovery of myocardial blood supply with high morbidity and mortality. Although, various therapeutic schedules were applied in clinic, there are real problems that have to be resolved on curative effect. Nod-like receptor protein 3 (NLRP3) inflammasome has moderation effects on cellular damage and inflammatory reaction after I/R injury. Our research aims to investigate a more effective approach to restrain the activation of NLRP3 inflammasome in treating myocardial I/R injury. Results indicated that cell viability, Bax/Bcl-2 expression were affected hardly by sh-NLRP3 transfection in normal cells. However, the decreased cell viability and increased Bax/Bcl-2 expression level caused by I/R were remarkably suppressed through sh-NLRP3 transfection. Besides that, the reduced levels of pro-autophagy proteins (Beclin1, Agt7, LC3II/LC3I) while enhanced level of anti-autophagy protein (p62) and apoptosis-related proteins (Bax/Bcl-2) were significantly repressed via sh-NLRP3 transfection. Nevertheless, the autophagy inhibitor 3 MA could reverse the results. Moreover, in vivo experiment suggested that NLRP3 was up-regulated in wild type (WT) rats with I/R injury. The expansion of infarct size induced by ischemia was tremendously constricted in NLRP3 knockout (KO) rats. NLRP3 silence had nearly no impact on myocardial enzymes (AST, LDH and CK) expressions, inflammatory factors (TNF-α and IL-1β) expressions and cell apoptosis in rats without I/R injury. Nonetheless, the elevated levels of myocardial enzymes, inflammatory factors and cell apoptosis caused by I/R injury were vastly inhibited in NLRP3 KO rats. Furthermore, NLRP3 KO itself would lead to higher level of pro-autophagy proteins (Beclin1, Agt7, LC3II/LC3I) while lower level of anti-autophagy protein (p62) in vivo. The decreased expressions of pro-autophagy proteins while increased expressions of anti-autophagy protein induced by I/R injury were remarkably suppressed by NLRP3 KO. Taken together, our study indicated that shRNA interference of NLRP3 inflammasome attenuated myocardial I/R injury via autophagy activation. These findings demonstrated that NLRP3 KO may a promising therapy in myocardial I/R injury.