A protease-activated receptor 1 antagonist protects against global cerebral ischemia/reperfusion injury after asphyxial cardiac arrest in rabbits

Cerebral ischemia/reperfusion injury is partially mediated by thrombin, which causes brain damage through protease-activated receptor 1（PAR1）. However, the role and mechanisms underlying the effects of PAR1 activation require further elucidation. Therefore, the present study investigated the effects of the PAR1 antagonist SCH79797 in a rabbit model of global cerebral ischemia induced by cardiac arrest. SCH79797 was intravenously administered 10 minutes after the model was established. Forty-eight hours later, compared with those administered saline, rabbits receiving SCH79797 showed markedly decreased neuronal damage as assessed by serum neuron specific enolase levels and less neurological dysfunction as determined using cerebral performance category scores. Additionally, in the hippocampus, cell apoptosis, polymorphonuclear cell infiltration, and c-Jun levels were decreased, whereas extracellular signal-regulated kinase phosphorylation levels were increased. All of these changes were inhibited by the intravenous administration of the phosphoinositide 3-kinase/Akt pathway inhibitor LY29004（3 mg/kg） 10 minutes before the SCH79797 intervention. These findings suggest that SCH79797 mitigates brain injury via anti-inflammatory and anti-apoptotic effects, possibly by modulating the extracellular signal-regulated kinase, c-Jun N-terminal kinase/c-Jun and phosphoinositide 3-kinase/Akt pathways.

Antagonism of Protease-Activated Receptor 4 Protects Against Traumatic Brain Injury by Suppressing Neuroinflammation via Inhibition of Tab2/NF-κB Signaling

Traumatic brain injury(TBI)triggers the activation of the endogenous coagulation mechanism,and a large amount of thrombin is released to curb uncontrollable bleeding through thrombin receptors,also known as protease-activated receptors(PARs).However,thrombin is one of the most critical factors in secondary brain injury.Thus,the PARs may be effective targets against hemorrhagic brain injury.Since the PAR1 antagonist has an increased bleeding risk in clinical practice,PAR4 blockade has been suggested as a more promising treatment.Here,we explored the expression pattern of PAR4 in the brain of mice after TBI,and explored the effect and possible mechanism of BMS-986120(BMS),a novel selective and reversible PAR4 antagonist on secondary brain injury.Treatment with BMS protected against TBI in mice.mRNA-seq analysis,Western blot,and qRT-PCR verification in vitro showed that BMS significantly inhibited thrombin-induced inflammation in astrocytes,and suggested that the Tab2/ERK/NF-κB signaling pathway plays a key role in this process.Our findings provide reliable evidence that blocking PAR4 is a safe and effective intervention for TBI,and suggest that BMS has a potential clinical application in the management of TBI.

Baicalin Attenuates Focal Cerebral Ischemic Reperfusion Injury by Inhibition of Protease-Activated Receptor-1 and Apoptosis

Objective： To investigate the neuro-protective effects of baicaiin in Wistar rats with focal cerebral ischemic reperfusion injury. Methods： Ninety adult male Wistar rats weighing 320-350 g were randomly divided into the following groups （n=5）： （a） sham control group; （b） vehicle group, subjected to middle cerebral artery occlusion and received vehicle intraperitoneally; （c-e） baicalin groups, which were subjected to the middle cerebral artery occlusion and treated with baicalin 25, 50 and 100 mg/kg, respectively. The neurological scores were determined at postoperative 1, 3 and 7 d after the treatment. The expression of protease-activated receptor-1 （PAR-1）, PAR-1 mRNA and Caspase-3 were determined using Western blot, reverse transcription polymerase chain reaction （RT- PCR） analysis and immunohistochemistry, respectively. Results： Significant decrease was noted in the neurological score in the baicalin group compared with that of the vehicle group （P〈0.01）. Additionally, down-regulation of PAR-1 mRNA, PAR-1 and Caspase-3 was observed in the baicalin groups compared with those obtained from the vehicle group （P〈0.01）. Compared with the low-dose baicalin group （25 mg/kg）, remarkable decrease was noted in neurological score, and the expression of PAR-1 mRNA, PAR-1 as well as Caspase-3 in the high-dose group （P〈0.05）. Conclusion： Baicalin showed neuro-protective effects in focal cerebral ischemic reperfusion injury through inhibiting the expression of PAR-1 and apoptosis.

Expression of protease-activated receptors on platelets in healthy individuals

This study aimed to investigate the expression of protease-activated receptors(PARs)on platelets in healthy individuals and preliminarily elucidate physiolo-gical functions of PARs.Thirty healthy volunteers,who did not take any anticoagulants and antiplatelet agents within 10 days before the examination,were recruited.Fasting venous blood(5 mL)was taken from the medial cubital vein in each individual and platelet-rich plasma(PRP)was prepared.The expression of PAR1 mRNA and PAR4 mRNA in PRP was determined by RT-PCR analysis.The results showed that the average levels of PAR1 mRNA and PAR4 mRNA on platelets in healthy individuals were 0.1601�0.0269 and 0.1073�0.0194 respectively.In combination with literature analysis,it was concluded that the thrombin signaling pathway plays a vital role in the development of hemostasis and thrombosis,and the selective PARs antagonist has the potential for extensive application in clinical practice.

Argatroban promotes recovery of spinal cord injury by inhibiting the PAR1/JAK2/STAT3 signaling pathway

Argatroban is a synthetic thrombin inhibitor approved by U.S.Food and Drug Administration for the treatment of thrombosis.However,whether it plays a role in the repair of spinal cord injury is unknown.In this study,we established a rat model of T10 moderate spinal cord injury using an NYU Impactor ModerⅢand performed intraperitoneal injection of argatroban for 3 consecutive days.Our results showed that argatroban effectively promoted neurological function recovery after spinal cord injury and decreased thrombin expression and activity in the local injured spinal cord.RNA sequencing transcriptomic analysis revealed that the differentially expressed genes in the argatroban-treated group were enriched in the JAK2/STAT3 pathway,which is involved in astrogliosis and glial scar formation.Western blotting and immunofluorescence results showed that argatroban downregulated the expression of the thrombin receptor PAR1 in the injured spinal cord and the JAK2/STAT3 signal pathway.Argatroban also inhibited the activation and proliferation of astrocytes and reduced glial scar formation in the spinal cord.Taken together,these findings suggest that argatroban may inhibit astrogliosis by inhibiting the thrombin-mediated PAR1/JAK2/STAT3 signal pathway,thereby promoting the recovery of neurological function after spinal cord injury.

Liver myofibroblasts activate protein C and respond to activated protein C

AIM:To study the protein C activation system in human liver myofibroblasts,and the effects of activated protein C(APC)on these cells.METHODS:Human liver myofibroblasts were obtained by outgrowth.Expression of protease activated receptor 1(PAR-1),endothelial protein C receptor(EPCR) and thrombomodulin(TM)was analyzed by flow cytometry.Extracellular signal-regulated kinase(ERK)1/2 activation was assessed by Western blotting using anti-phospho-ERK antibodies.Collagen synthesis was studied with real-time reverse transcription-polymerase chain reaction(RT-PCR).Activation of protein C was studied by incubating liver myofibroblasts with zymogen protein C in the presence of thrombin and detecting the generation of APC with a colorimetric assay using a peptide substrate. RESULTS:Primary cultures of human liver myofibroblasts expressed EPCR on their surface,together with PAR-1 and TM.This receptor system was functional since exposure of myofibroblasts to APC inducedERK1/2 phosphorylation in a dose-and time-dependent manner.Furthermore,APC significantly upregulated the expression of collagen mRNA,as shown by real-time RT-PCR.Collagen upregulation was controlled through the ERK pathway as it was inhibited when using the mitogen-activated protein/extracellular signal-regulated kinase kinase inhibitor PD98059.Finally,using a cell-based colorimetric assay,we showed that intact myofibroblasts converted protein C into APC in the presence of thrombin.CONCLUSION:These data suggest that APC is a new modulator of liver myofibroblast activity and contributes to the pathophysiology of chronic liver diseases.

Effect of Thrombin on the Apoptosis of Hippocampal Neurons in vitro

Hippocampal neurons were treated by thrombin and thrombin receptor activatingpeptides (TRAP). Cell survival rate was decreased in a dose-dependent manner by MTT assay. Thenumbers of apoptotic cell and apoptotic rate of hippocampal neurons treated bydifferentconcentrations of thrombin were increased in a dose-dependent manner by terminal deoxynucleotidyltransferase (TdT) mediated dUTP-biotin nick end-labeling (TUNED method and Flow Cytometry. When theconcentration of thrombin is 40 U/mL, TUNEL positive cells and apoptotic rate of hippocampal neuronsreached peak value, were 27. 3 +- 4. 0 and (29. 333 +- 4. 633 ) % , respectively.Immunocytochemistry assay show that Bcl-2 protein expression was down- regulated and Bax proteinexpression was up-regulated with the concentration of thrombin increased. TRAP can mimic the effectof thrombin to induce apoptosis on hippocampal neurons. These data demonstrated that thrombininduced hippocampal neuron apoptosis in a dose-dependent manner through activatingprotease-acti-vated protein-1 (PAR-1). The change in expression of Bcl-2 and Bax was related withthe effect of high concentration thrombin induced apoptosis on hippocampal neurons.

Activated protein C: A regulator of human skin epidermal keratinocyte function

Activated protein C(APC) is a physiological anticoagulant, derived from its precursor protein C(PC). Independent of its anticoagulation, APC possesses strong anti-inflammatory, anti-apoptotic and barrier protective properties which appear to be protective in a number of disorders including chronic wound healing. The epidermis is the outermost skin layer and provides the first line of defence against the external environment. Keratinocytes are the most predominant cells in the epidermis and play a critical role in maintaining epidermal barrier function. PC/APC and its receptor, endothelial protein C receptor(EPCR), once thought to be restricted to the endothelium, are abundantly expressed by skin epidermal keratinocytes. These cells respond to APC by upregulating proliferation, migration and matrix metalloproteinase-2 activity and inhibiting apoptosis/inflammation leading to a wound healing phenotype. APC also increases barrier function of keratinocyte monolayers by promoting the expression of tight junction proteins and re-distributing them to cell-cell contacts. These cytoprotective properties of APC are mediated through EPCR, protease-activated receptors, epidermal growth factor receptor or Tie2. Future preventive and therapeutic uses of APC in skin disorders associated with disruption of barrier function and inflammation look promising. This review will focus on APC's function in skin epidermis/keratinocytes and its therapeutical potential in skin inflammatory conditions.

Expressions of Connexin and Par-3 in the Distal Margin of Rectal Cancer after Ultra-low Anterior Resection

This study examined the expression of connexin and protease-activated receptor 3 （par-3） in the distal resection margin of rectal cancer and the correlation of the expression of the two proteins with tumor relapse. A total of 40 patients with rectal cancer underwent ultra-low anterior resection with curved cutter stapler. The pathological specimens were divided into 3 groups in terms of sampling sites： tumor group, 2.0-cm group （in which the tissues were harvested 2.0 cm distal to the tumor tissues）, 3.0-cm group （in which the tissues were taken 3.0 cm away from the tumor tissues）. All the samples were pathologically observed and then measured for the expression of connexin and par-3 by employing immunohistochemistry and Western blotting. The operations in this series went uneventfully. No anastomotic stoma bleeding, stenosis and death occurred postoperatively. Histopathologically, in the tumor group, epithelial cells lost normal pattern of arrangement and polarity, and were loosely connected and even detached. In the 3.0-cm group, the epithelia had normal appearance, obvious cell polarity and essentially intact cell junction. Immunohistochemistry and Western blotting indicated that the 3.0-cm group had the strongest expression of connexin and par-3, and the expression in the 2.0-cm group and the tumor group was relatively weak. There existed significant difference in the expression of the two proteins among the three groups （P〈0.05 for all）. It was concluded that the down-regulated connexin and par-3 in the distal margin of rectal cancer tissues may indicate the progression of the disease and high likelihood of recurrence and metastasis. Although no tumor cells were found in the sections of the 2.0cm group, the decreased expression of connexin and par-3 may suggest the development of anaplasia and the increased odds of tumor relapse. Therefore, we are led to speculate that tumor resection only including 2.0 cm of unaffected rectum could not completely avoid the distant metastasis and local relapse.

Genome editing of PAR2 through targeted delivery of CRISPR-Cas9 system for alleviating acute lung inflammation via ERK/NLRP3/IL-1β and NO/iNOS signalling

Excessive and uncontrollable inflammatory responses in alveoli can dramatically exacerbate pulmonary disease progressions through vigorous cytokine releases,immune cell infiltration and protease-driven tissue damages.It is an urgent need to explore potential drug strategies for mitigating lung inflammation.Protease-activated receptor 2(PAR2)as a vital molecular target principally participates in various inflammatory diseases via intracellular signal transduction.However,it has been rarely reported about the role of PAR2 in lung inflammation.This study applied CRISPR-Cas9 system encoding Cas9 and sg RNA(p Cas9-PAR2)for PAR2 knockout and fabricated an anionic human serum albuminbased nanoparticles to deliver p Cas9-PAR2 with superior inflammation-targeting efficiency and stability(TAP/p Cas9-PAR2).TAP/p Cas9-PAR2 robustly facilitated p Cas9-PAR2 to enter and transfect inflammatory cells,eliciting precise gene editing of PAR2 in vitro and in vivo.Importantly,PAR2 deficiency by TAP/p Cas9-PAR2 effectively and safely promoted macrophage polarization,suppressed proinflammatory cytokine releases and alleviated acute lung inflammation,uncovering a novel value of PAR2.It also revealed that PAR2-mediated pulmonary inflammation prevented by TAP/p Cas9-PAR2was mainly dependent on ERK-mediated NLRP3/IL-1β and NO/i NOS signalling.Therefore,this work indicated PAR2 as a novel target for lung inflammation and provided a potential nanodrug strategy for PAR2 deficiency in treating inflammatory diseases.

Chemical constituents from heartwoods of Caesalpinia sappan with antiplatelet aggregation activities

Objective:To clarify the active constituents of the heartwoods of Caesalpinia sappan,a traditional Chinese medicine with the functions of promoting blood circulation(Huoxue in Chinese)and removing blood stasis(Quyu in Chinese).Methods:The chemical constituents were isolated and purified by combination of silica gel and Sephadex LH-20 column chromatography,along with semipreparative HPLC.Their chemical structures were established by multiple spectroscopic methods and comparison with literature data.The in vitro antiplatelet aggregation activities were evaluated using mouse platelet induced by AYPGKF-NH2,a gold agonist of protease-activated receptor 4(PAR4).Results:Two new phenols,methyl 2-(4,4’,5’-trihydroxy-2’-(methoxymethyl)biphenyl-2-yloxy)acetate(1)and 1’-methylcaesalpin J(2),together with 24 known compounds(3-26),were isolated from the heartwoods of C.sappan.Among them,sappanchalcone(16)and brazilin(20)showed inhibitory activities against mouse platelet aggregation with IC50 values of 114.8μmol/L and 100.8μmol/L,respectively.Conclusion:Antiplatelet compounds from C.sappan targeting at PAR4 are reported for the first time.