Intrinsic Coagulation System Research Articles

The Interaction of Complement and Intrinsic Coagulation System: A Comparative Study between COVID-19 and Bacterial Sepsis Patients.

Background/Objectives: Through the past several years, a constant interaction has been implicated between complement and coagulation cascades. SARS-CoV-2 infection and bacterial sepsis are potent activators of both cascades. This study aims to compare the extent of complement and intrinsic coagulation pathway activation (and the interplay between them) among patients with COVID-19 and bacterial sepsis. Methods: Serum and plasma samples were collected from 25 ICU patients (11 patients with COVID-19 and 14 patients with bacterial sepsis) at two time points (on admission and either on improvement or deterioration). The activities of coagulation factors XI and XII and complement factors C3a and C5a were measured at both time points. Results: The activities of factors XI and XII were increased in both groups of patients and at both time points. However, there were no statistically significant differences between SARS-CoV-2 and bacterial sepsis patients. On the other hand, both C3a and C5a were significantly higher in the COVID-19 group on admission. This correlation was preserved on reassessment. Conclusions: Complement activation seems to be more enhanced in COVID-19 than bacterial sepsis. However, the lack of statistical significance in factors XI and XII indicates t the presence of additional pathways for complement activation in SARS-CoV-2 infection.

Exploring the Dynamics of Sleep Deprivation: Insights into Complete Blood Count and Coagulation Parameters in a Case-Control Study.

The lack of preceding research in Sudan emphasizes the importance of this study, which contributes critical data to the global understanding of sleep-related health effects. This study investigates the complex relationship between sleep deprivation and blood-related factors, particularly focusing on full blood count and coagulation parameters. From January to March 2022, a case-control study was conducted in Kosti, Sudan. A control group of 11 healthy 23-33-year-olds (6 men and 5 women) had regular sleep patterns. Six men and five women ages 23-33 were chosen for this sleep-deprived case study. The case group was deprived of sleep from 7:00 p.m. to 7:00 a.m. for three days and allowed to sleep normally during the day. Daily at 7:00 a.m., antecubital vein blood was drawn. The ACL 7000 coagulation analyzer and Sysmex fully automated hematology analyzers were used for coagulation and whole blood count analysis. Data analysis included descriptive and inferential approaches like the Mann-Whitney U test for group comparisons. The study found no significant differences in total white blood cell counts reported between case and control groups (p=0.898). The case group had a substantial drop in lymphocyte counts on day 3 (p=0.016). The third day showed significant differences in neutrophil and eosinophil levels (p=0.003 and 0.000, respectively). The difference in hemoglobin and hematocrit on day 3 was statistically significant (p=0.023). Platelet counts were stable. Both groups' prothrombin times were unaffected. On all three days, groups had significant differences in activated partial thromboplastin time (APTT) (p=0.004). Therefore, the intrinsic coagulation system may have changed. This study demonstrates the complex link between sleep deprivation, coagulation indicators, and complete blood count. Monitoring blood indicators in poor sleep helps explain fundamental mechanisms and medicinal implications.

Asundexian: an oral small moleculefactor XIa inhibitor for the treatment of thrombotic disorders.

Oral anticoagulants, including warfarin and direct oral anticoagulants, are the standard of care for thrombosis prevention and treatment; however, concerns of bleeding often dictate treatment decisions. Inhibition of the intrinsic coagulation system via factor XIa may allow for selective inhibition of the coagulation cascade without significantly impacting hemostasis after injury. Asundexian is an oral small moleculefactor XIa inhibitor that, via this novel mechanism, may prove to be a safe and effective option compared with available anticoagulants. Early clinical data forasundexian was promising as a safer alternative to current therapiesand prompted further analysis incertainpatient populations atincreasedthrombotic risk. Currently, studies areongoing to evaluate thesafety and efficacy in stroke prevention in atrial fibrillation and in patients following an acute noncardioembolic ischemic stroke or high-risk transient ischemic attack.

Glycated albumin modulates the contact system with implications for the kallikrein-kinin and intrinsic coagulation systems

BackgroundHuman serum albumin (HSA) is the most abundant plasma protein and is sensitive to glycation in vivo. The chronic hyperglycemic conditions in patients with diabetes mellitus (DM) induce a nonenzymatic Maillard reaction that denatures plasma proteins and forms advanced glycation end products (AGEs). HSA-AGE is a prevalent misfolded protein in patients with DM and is associated with factor XII activation and downstream proinflammatory kallikrein-kinin system activity without any associated procoagulant activity of the intrinsic pathway. ObjectivesThis study aimed to determine the relevance of HSA-AGE toward diabetic pathophysiology. MethodsThe plasma obtained from patients with DM and euglycemic volunteers was probed for activation of FXII, prekallikrein (PK), and cleaved high-molecular-weight kininogen by immunoblotting. Constitutive plasma kallikrein activity was determined via chromogenic assay. Activation and kinetic modulation of FXII, PK, FXI, FIX, and FX via in vitro–generated HSA-AGE were explored using chromogenic assays, plasma-clotting assays, and an in vitro flow model using whole blood. ResultsPlasma obtained from patients with DM contained increased plasma AGEs, activated FXIIa, and resultant cleaved cleaved high-molecular-weight kininogen. Elevated constitutive plasma kallikrein enzymatic activity was identified, which positively correlated with glycated hemoglobin levels, representing the first evidence of this phenomenon. HSA-AGE, generated in vitro, triggered FXIIa-dependent PK activation but limited the intrinsic coagulation pathway activation by inhibiting FXIa and FIXa-dependent FX activation in plasma. ConclusionThese data indicate a proinflammatory role of HSA-AGEs in the pathophysiology of DM via FXII and kallikrein-kinin system activation. A procoagulant effect of FXII activation was lost through the inhibition of FXIa and FIXa-dependent FX activation by HSA-AGEs.

Enzym konwertujący angiotensynę 2 (ACE2) – główny receptor dla wirusa SARS-CoV-2

The renin-angiotensin-aldosterone system (RAS) plays a significant role in the regulation of the water and electrolyte balance. Renin from the kidneys converts angiotensinogen to angiotensin I. Angiotensin converting enzyme (ACE) catalyzes the conversion of angiotensin I to angiotensin II. The activation of AT1 receptors by angiotensin II causes vasoconstriction, an increase in aldosterone secretion, and an increase in the reabsorption of sodium ions in nephrons, leading to elevation of the blood pressure. Angiotensin II promotes oxidative stress, growth and proliferation of cells, stimulates coagulation, inhibits fibrinolysis, and intensifies inflammatory processes. The ACE-angiotensin II-AT1R pathway is balanced by angiotensin converting enzyme 2 (ACE2), which degrades angiotensin I to angiotensin (1-9) and angiotensin II to angiotensin (1-7). Angiotensin (1-7) and angiotensin (1-9) pathways exert protective effects by activating, respectively Mas and AT2 receptors. ACE and ACE2 also have intimate roles with the plasma kallikrein-kinin system (KKS), a hormonal pathway that modulates the intrinsic blood coagulation system, endothelial cell growth and angiogenesis, the complement pathway and RAS. The appearance in Wuhan, China, of the first cases of SARS-CoV-2 infections at the end of 2019 launched a series of intensive studies, which proved that the virus invades host cells using ACE2 as a specific receptor. This survey presents basic information on the structure and tissue distribution of ACE2 and the role this enzyme plays in pathogenesis of COVID-19. A particular emphasis is given to pathophysiological effects of the functional superiority of the ACE → angiotensin II → AT1 receptor axis over the pathway ACE2 → angiotensin II → angiotensin (1-7) → Mas receptor. Such disharmony is a consequence of SARS-CoV-2 induced ACE2-downregulation. In the era of the expanding COVID-19 pandemic, intensive research is conducted not only on vaccines and antiviral drugs, but also on compounds that can restore the functional balance between angiotensin II and angiotensin (1-7). © 2021 Polish Pharmaceutical Society. All rights reserved.

Update on factor (F) VIII structure and function-related hemostatic coagulation and its regulatory mechanism (s)

Blood coagulation factor VIII (FVIII) functions as a cofactor for activated factor IX on the phospholipid membrane in the coagulation reaction. FVIII deficiency causes hemophilia A, and conversely, the thrombotic patients show high FVIII levels. Therefore, FVIII is a key coagulant factor involved in the contradictory pathology of hemorrhage and thrombosis. From the crystal structure of the FVIII molecule and bispecific antibody that substitutes for FVIII cofactor function, FVIIIa function and role on the FXase complex are drawing attention. It has been also supported that a concept that the extrinsic coagulation system involved in the initial phase of the coagulation process, the intrinsic coagulation system involved in the thrombin burst, the anti-coagulation system by activated protein C pathway, and the fibrinolytic system involved the dissolving fibrin clot intertwine each other and progress during the coagulation reaction process. FVIII-related FVIIa coagulation system and FVIII-related plasmin regulation system have been also elucidated. We greatly expect that the developmental elucidation of thrombus formation mechanism (s) centered on FVIII/FVIIIa could lead to the development of more effective new FVIII product and antithrombotic drugs.

Effect of Tranexamic Acid for Traumatic Brain Injury: A Case Report.

Traumatic brain injury (TBI) often results in coagulopathy, which increases mortality risk. The Clinical Randomization of an Antifibrinolytic in Significant Head injury (CRASH)-2 and CRASH-3 trials confirmed that tranexamic acid (TXA) was effective after trauma. Herein, we report a unique coagulation change in a patient with TBI given TXA after point-of-care assessment. Coagulation functions were impaired on admission. At 1 hour after TXA administration, clotting time was further prolonged in the extrinsic coagulation pathway but shortened in the intrinsic coagulation system. The results of a test of the total thrombus-formation analysis system showed improved blood clot formation ability. Intrinsic coagulation and clot formation improved after TXA administration in a TBI patient with coagulopathy.

Nomenclature of factor XI and the contact system

Nomenclature of factor XI and the contact system

Abstract 136: Activated Factor IX - Antithrombin Complex Predicts Outcome After Out-Of-Hospital Cardiac Arrest

Introduction: Sudden cardiac arrest (SCA) and cardiopulmonary resuscitation (CPR) are associated with activated coagulation and impairment of end-organ perfusion. Activated factor IX (FIXa) is part of the intrinsic coagulation system. FIX may also be activated by extrinsic tenase (tissue factor/activated factor VII), as well as through the intrinsic pathway, which may include thrombin-induced activation of factor XI, by which thrombin generation is sustained. Hypothesis: We hypothesized that the level of activated factor IX -antithrombin (FIXa-AT) complex, as a measure of coagulation activation, would be of prognostic value in SCA patients. Methods: From February 2007 until December 2010 blood samples in EDTA tubes were collected during or closely after termination of CPR from patients aged > 18 years with out-of-hospital cardiac arrest (OHCA) of assumed cardiac origin. Survivors had follow-up samples drawn 8-12 hours and 24-48 hours after admission. FIXa-AT was determined by ELISA. Patients were divided into quartiles (Q1-4) by FIXa-AT levels. Cox regression was used for analysis of death within 30 days. Results: A total of 115 OHCA patients were included. Of these, 71 patients (61,7%) died, of whom 35 died on scene and 36 in-hospital. Early-on FIXa-AT complex levels in the higher quartiles as compared to the lowest were significantly associated with increased risk of death (Figure 1). The hazard ratio (HR) for Q4 patients compared to Q1 was 6.79, (95% CI 2.04-22.61); p = 0.002, for Q3 4.48 (95% CI 1.33-15.16); p = 0,016, and for Q2 3.48 (95% CI 1.01-11.95); p = 0.048. Mean log e (FIXa-AT) in hospitalized non-survivors were higher than in survivors; 8-12 hours (p = 0.002) and 24-48 hours (p = 0.008). There was a positive correlation between the duration of advanced CPR and log e (FIXa-AT), r = 0.24, p = 0.012. Conclusion: Early-on FIXa-AT complex predicts 30-day mortality in OHCA-patients. Prolonged resuscitation seems to be associated with increased coagulation activation.

Evaluation of toxicity of functionalized graphene oxide with ginsenoside Rh2, lysine and arginine on blood cancer cells (K562), red blood cells, blood coagulation and cardiovascular tissue: In vitro and in vivo studies

Abstract In this study, blood- and cardio-toxicity of Rh2–treated graphene oxide (GO-Rh2), lysine-treated graphene oxide (GO-Lys), arginine-treated GO (GO-Arg), Rh2–treated GO-Lys (GO-Lys-Rh2) and Rh2–treated GO-Arg (GO-Arg-Rh2) were evaluated. Two concentrations of each nanostructures (200 and 1000 µg/ml) was injected to rats. After 2 weeks, the effects of agents were evaluated on heart tissue by histopathological assays. Cytotoxicity of all designed nanostructures was investigated on blood cancer cells (K562) by MTT assay. Toxicity of designed nanostructures was also investigated on Red Blood Cells (RBCs), Prothrombin Time (PT) and Partial Thromboplastin Time (PTT). The results demonstrated increase of anticancer activity for GO-Arg-Rh2 and GO-Lys-Rh2 in comparison with free Rh2 and GO. GO, GO-Rh2, GO-Lys, GO-Arg, GO-Lys-Rh2, and GO-Arg-Rh2 had 50% hemolysis at concentrations 250, 360, 420, 435, 500, and 575 µg/ml, respectively. GO led to RBCs aggregation and morphological change at 5–100 µg/ml, but other functionalized nanostructures did not show these changes. All nanostructures had slight effect on intrinsic and extrinsic coagulation system, especially on PTT. GO-Arg-Rh2 and GO-Lys-Rh2 had lower effect on blood coagulation system in comparison with other examined nanosystems. Besides, GO-Rh2, GO-Arg-Rh2, and GO-Lys-Rh2 had lowest toxicity on heart tissue than other synthesized nanostructures. Functionalization of GO with Arg, Lys, and especially, Rh2 led to decrease the destruction of heart tissue. So, modified GO with Rh2 and basic amino acids may be a potential and promising strategy to enhance the therapeutic index for GO because of the reduction of side effects on normal cells.

In Vitro Anticoagulant Activity and Active Components of Safflower Injection

Safflower injection is well-known as a traditional Chinese medicine used to improve the blood circulation. In this study, seven safflower injection samples from different companies were evaluated for their in vitro anticoagulant activity by measuring their activated partial thromboplastin time (APTT) and prothrombin time (PT) against human plasma. The screening results suggested that the safflower injections exhibited a significant prolonging influence on APTT (p < 0.05 vs. the control group), but not on prolonging PT (p > 0.05 vs. the control group). The safflower injection was separated into four fractions, and among them, fraction four demonstrated the most anticoagulant activity, with an APTT of 95.4 ± 1.4 s at a concentration of 4.0 μg/μL (p < 0.01 vs. control group). In addition, three active components, p-hydroxybenzaldehyde, p-hydroxy-cinnamic acid, and (8Z)-decaene-4,6-diyne-1-O-β-d-glucopyranoside were isolated from fraction four with Sephadex LH-20 and C18 column chromatography. All three active components showed significant prolonging of APTT (p < 0.05 vs. control group). Among them, p-hydroxy-cinnamic acid exhibited the most activity (p < 0.01 vs. control group). The results indicated that safflower injection strongly affects the intrinsic coagulation system, and we suggest that this might be the mechanism by which the safflower injection activates and promotes blood circulation.

The Mast Cell, Contact, and Coagulation System Connection in Anaphylaxis.

Anaphylaxis is the most severe form of allergic reaction, resulting from the effect of mediators and chemotactic substances released by activated cells. Mast cells and basophils are considered key players in IgE-mediated human anaphylaxis. Beyond IgE-mediated activation of mast cells/basophils, further mechanisms are involved in the occurrence of anaphylaxis. New insights into the potential relevance of pathways other than mast cell and basophil degranulation have been unraveled, such as the activation of the contact and the coagulation systems. Mast cell heparin released upon activation provides negatively charged surfaces for factor XII (FXII) binding and auto-activation. Activated FXII, the initiating serine protease in both the contact and the intrinsic coagulation system, activates factor XI and prekallikrein, respectively. FXII-mediated bradykinin (BK) formation has been proven in the human plasma of anaphylactic patients as well as in experimental models of anaphylaxis. Moreover, the severity of anaphylaxis is correlated with the increase in plasma heparin, BK formation and the intensity of contact system activation. FXII also activates plasminogen in the fibrinolysis system. Mast cell tryptase has been shown to participate in fibrinolysis through plasmin activation and by facilitating the degradation of fibrinogen. Some usual clinical manifestations in anaphylaxis, such as angioedema or hypotension, or other less common, such as metrorrhagia, may be explained by the direct effect of the activation of the coagulation and contact system driven by mast cell mediators.

Novel carbon quantum dots from egg yolk oil and their haemostatic effects

In this study, the properties of egg yolk oil (EYO) were investigated. Water extraction, dialysis, and ultrafiltration were used to extract and purify EYO, and microscopy, spectrophotometry, and chromatography were used to identify carbon dots (CDs) present in EYO (EYO CDs). Morphology analyses demonstrated that CDs were almost spherical, with an average size of <10 nm, a lattice spacing of 0.267 nm, and a composition of mainly C, O, and Fe. The solution showed bright blue fluorescence at 365 nm. Tail haemorrhaging and liver haemorrhaging experiments showed that CD-treated mice had significantly shorter bleeding times than did control mice. Coagulation assays suggested that EYO CDs stimulate the intrinsic blood coagulation system and activate the fibrinogen system. Thus, EYO CDs possess the ability to activate haemostasis, which may lead to further investigations of this ingredient of traditional Chinese medicine.

Factor XI deficiency enhances the pulmonary allergic response to house dust mite in mice independent of factor XII.

Asthma is associated with activation of coagulation in the airways. The coagulation system can be initiated via the extrinsic tissue factor-dependent pathway or via the intrinsic pathway, in which the central player factor XI (FXI) can be either activated via active factor XII (FXIIa) or via thrombin. We aimed to determine the role of the intrinsic coagulation system and its possible route of activation in allergic lung inflammation induced by the clinically relevant human allergen house dust mite (HDM). Wild-type (WT), FXI knockout (KO), and FXII KO mice were subjected to repeated exposure to HDM via the airways, and inflammatory responses were compared. FXI KO mice showed increased influx of eosinophils into lung tissue, accompanied by elevated local levels of the main eosinophil chemoattractant eotaxin. Although gross lung pathology and airway mucus production did not differ between groups, FXI KO mice displayed an impaired endothelial/epithelial barrier function, as reflected by elevated levels of total protein and IgM in bronchoalveolar lavage fluid. FXI KO mice had a stronger systemic IgE response with an almost completely absent HDM-specific IgG1 response. The phenotype of FXII KO mice was, except for a higher HDM-specific IgG1 response, similar to that of WT mice. In conclusion, FXI attenuates part of the allergic response to repeated administration of HDM in the airways by a mechanism that is independent of activation via FXII.

Should We Replace the Terms Intrinsic and Extrinsic Coagulation Pathways With Tissue Factor Pathway?

Present review highlights some new aspects of the role of individual components of blood coagulation process and proposes a modified concept of hemocoagulation cascade. The role of FXII in the initiation of the so-called intrinsic coagulation system is currently questioned. Its role has been recently demonstrated mainly in the thrombus propagation and final stabilization together with factors XI and XIII. The edited concept underlines the common part of the tissue factor (TF) in the initiation of both the intrinsic and extrinsic pathways of the coagulation system and therefore may make it not improperly be called the TF coagulation pathway. The search for new antithrombotic agents shows that the level of the coagulation system blockade depends on which step in the coagulation cascade is targeted and results in different degrees of the antithrombotic efficiency and the risk of bleeding complications.

Improving blood-compatibility via surface heparin-immobilization based on a liquid crystalline matrix

Blood compatibility is of considerable importance in developing medical materials and devices that are in contact with blood. In this work, we successfully developed a novel liquid crystalline heparin-immobilized material (Hep-OPPC) by two-step modification for further improvement of hydrophilicity and hemocompatibility of the liquid crystalline hydroxypropyl cellulose ester (OPCL). The results showed that Hep-immobilization on the OPCL led to dramatic changes in the surface morphology and crystallinity, whereas, the Hep-OPPCs also maintained the liquid crystalline feature at room temperature after heparinization. Furthermore, the hemocompatibility of the Hep-OPPCs was markedly enhanced at low levels of hemolysis assay (HR) with unimpaired erythrocytomorphology, significantly lower concentrations of C3a in blood plasma and remarkable increases in plasma re-calcification time (PRT). This suggests that the heparinized surface could restrict the transformation of fibrinogen with less activation of the intrinsic coagulation system. Moreover, the activated partial thromboplastin time (APTT) and prothrombin time (PT) values of the Hep-OPPCs with low heparin density could also be prolonged in this study suggesting that the liquid crystal feature of the matrix might be blocking the clotting factors. We concluded that the heparin-immobilized liquid crystalline material has the potential to be used in blood-contact materials.

Complex history of the discovery and characterization of congenital factor X deficiency.

Factor X (FX) plays a pivotal role in blood coagulation. FX represents the point where all coagulation systems converge and, once activated, it converts prothrombin into thrombin. The discovery and definition of FX are based on the description between 1956 and 1957 about three patients and their families with a peculiar defect later demonstrated to be almost identical. These patients were an American (Mr. Stuart), a British (Ms. Prower), and a Swiss with Italian background (infant Delia B). We stated "almost identical" because immunological and molecular biology studies subsequently revealed that even though the basic clotting defect was identical, the FX protein level and the mutation were different in each case. Mr. Stuart had no FX protein in his plasma and the mutation was Val298Met (homozygote). Ms. Prower instead had a normal level of FX protein and the mutation was Arg287Trp + Asp282Asn (compound heterozygote). Unfortunately, the status of the Swiss patient in this regard is not known. Subsequent studies described a few major variants (FX Friuli, FX Melbourne, FX Padua, and other similar patients), which showed peculiar activation patterns (FX Friuli had a normal Russell viper venom clotting time; FX Melbourne was defective only in the intrinsic coagulation system; FX Padua, on the contrary, was defective only in the extrinsic coagulation system). All these studies have informed on the great heterogeneity and complexity of the FX defect. The story of the discovery and classification of FX deficiency has contributed considerably to our understanding of blood coagulation. The three original families and the families of the major variants, together with the researchers that discovered them, should be remembered with deep respect and gratitude.

Diffuse alveolar hemorrhage due to valproic acid: Case report and review of the literature.

Valproic acid (VPA) is one of the most frequently used antiepileptic drugs for the treatment of focal and generalized epilepsies, absence seizures, and Lennox-Gastaut syndrome (LGS). VPA has been demonstrated to have a negative effect on both the intrinsic and extrinsic coagulation systems and controversy exists about the clinical relevance of such hematological abnormalities. We describe a case of reversible lung hemorrage due to VPA. In English-language literature only two other similar cases (one of which fatal) have been described so far.

Study on the antithrombotic activity of Umbilicaria esculenta polysaccharide

Umbilicaria esculenta as a traditional food is known to have many pharmacological activities, such as cholesterol synthesis inhibition, anti-inflammation and anti-tumor. The antithrombotic activities of UEP isolated from the lichen were examined in vitro and in vivo for the first time. The in vitro anticoagulant activity of UEP was tested by its PT, APTT and TT. The more prolongation of APTT suggested a more obvious inhibition of the intrinsic coagulation systems than the extrinsic. Its antithrombotic properties were evaluated using an arteriovenous shunt thrombosis model in rats, and its inhibition of thrombus formation increased in a dose-dependent manner. It also caused a dose-dependent increase in tail transection bleeding time. Oral administration of UEP also showed a significant dose dependent preventive effect against thrombotic death or paralysis. UEP has a potent antithrombotic effect in vitro and in vivo, which may be used as a novel, effective and promising antithrombotic agent.

Ellagic acid-induced thrombotic focal cerebral ischemic model in rats

IntroductionIschemic stroke is a common cause of human disability and death. Animal models of focal cerebral ischemia are widely utilized to mimic human ischemic stroke. Although models of focal cerebral ischemia have been well established, very few evidence is based on triggering the intrinsic coagulation system to induce focal cerebral ischemia. Ellagic acid (EA) has been identified to trigger the intrinsic coagulation system via activating coagulation factor XII. However, it remains unknown whether EA can serve as a novel pharmacological approach to induce a new model of focal cerebral ischemia in rats. MethodsEA was used for inducing focal cerebral ischemia in adult rats. The dose- and time-dependent effects of EA were characterized. The cerebral infarction ratio was determined with triphenyltetrazolium chloride staining, and the histopathological analysis of the brain tissue was performed under light microscopy. The neurological deficit score was evaluated by a modified method of Bederson. Malondialdehyde (MDA) level and lactate dehydrogenase (LDH) and superoxide dismutase (SOD) activities in serum were determined by spectrophotometry. ResultsInjection of EA into the middle cerebral artery of rats was able to generate focal cerebral infarction and increased the neurological deficit score and the brain weight to body weight ratio in dose- and time-dependent manners. Furthermore, EA raised serum LDH activity and MDA level and decreased serum SOD activity in a dose-related fashion. DiscussionThis is the first evidence to show that EA induces focal cerebral ischemia in rats, which is similar to human ischemia stroke in pathogenesis. This model holds promise for pathological, pharmacological and clinical studies of ischemic stroke.