Anti-apoptotic role for C1 inhibitor in ischemia/reperfusion-induced myocardial cell injury

Mannose binding lectin-associated serine protease-1 is a novel contributor to myocardial ischemia/reperfusion injury

BACKGROUND

The lectin pathway has been demonstrated to play a critical role in the pathological process of myocardial ischemia/reperfusion injury (IRI). Mannose-binding lectin (MBL)-associated serine protease-1 (MASP-1), especially different from other components of the lectin pathway, mediates proinflammatory and procoagulant reactions independent of complement cascades. However, the role of MASP-1 in myocardial IRI remains unknown so far.

METHODS

Myocardial IRI was established with 45 min ischemia and 24 h reperfusion in mice. C1 inhibitor, as the natural inhibitor of MASP-1, was administrated at 20 IU/Kg via tail vein 5 min before surgical operation. Cardiac function and myocardial infarct size were assessed. Myocardial histology and fibrosis were evaluated by H&E and Masson staining, respectively. Deposition of MASP-1, expression of PAR-1/4 and neutrophil extracellular traps (NET) were investigated on myocardium tissue by IHC staining. Cell apoptosis was detected by TUNEL assay. Levels of myocardial enzymes and proinflammatory cytokines were determined by ELISA.

RESULTS

Inhibition of MASP-1 with C1 INH improved cardiac function and alleviated myocardium tissue injury (infarct size, enzymes, histology and fibrosis) after myocardial IRI. Deposition of MASP-1 and expression PAR-1, as well as NET formation in myocardial tissue were suppressed by MASP-1 inhibitor, while PAR-4 was elevated. Levels of apoptosis, HMGB-1 and IL-6 were lower after blocking MASP-1. Yet, IL-8 and TNF-α remained unchanged.

CONCLUSIONS

MASP-1, as a new contributor, played a critical role in myocardial IRI. Inhibition of MASP-1 protected myocardial tissue from IRI probably via regulation of PARs/NET pathway. This may provide a novel target strategy against myocardial IRI.

C1-Inhibitor: Structure, Functional Diversity and Therapeutic Development

Human C1-Inhibitor (C1INH), also known as C1-esterase inhibitor, is an important multifunctional plasma glycoprotein that is uniquely involved in a regulatory network of complement, contact, coagulation, and fibrinolytic systems. C1INH belongs to a superfamily of serine proteinase inhibitor (serpins) and exhibits its inhibitory activities towards several target proteases of plasmatic cascades, operating as a major anti-inflammatory protein in the circulation. In addition to its inhibitory activities, C1INH is also involved in non-inhibitory interactions with some endogenous proteins, polyanions, cells and infectious agents. While C1INH is essential for multiple physiological processes, it is better known for its deficiency with regards to Hereditary Angioedema (HAE), a rare autosomal dominant disease clinically manifested by recurrent acute attacks of increased vascular permeability and edema. Since the link was first established between functional C1INH deficiency in plasma and HAE in the 1960s, tremendous progress has been made in the biochemical characterization of C1INH and its therapeutic development for replacement therapies in patients with C1INH-dependent HAE. Various C1INH biological activities, recent advances in the HAE-targeted therapies, and availability of C1INH commercial products have prompted intensive investigation of the C1INH potential for treatment of clinical conditions other than HAE. This article provides an updated overview of the structure and biological activities of C1INH, its role in HAE pathogenesis, and recent advances in the research and therapeutic development of C1INH; it also considers some trends for using C1INH therapeutic preparations for applications other than angioedema, from sepsis and endotoxin shock to severe thrombotic complications in COVID-19 patients.

Postconditioning attenuates myocardial ischemia-reperfusion injury by inhibiting complement activation and upregulation of miR-499

The complement system plays a vital role in myocardial ischemia/reperfusion (I/R) injury. microRNA (miR)-499 is involved in the cardioprotection of ischemic postconditioning (IPostC). The present study aimed to study the role of the complement system and miR-499 in IPostC. Rat hearts were subjected to coronary ligation for 30 min, followed by reperfusion for 2 h. IPostC was introduced at the onset of reperfusion with three cycles of reperfusion for 30 sec and coronary artery occlusion for 30 sec. To study the role of miR-499 in IPostC, adeno-associated virus (AAV) vectors of miR-499-5p (AAV-miR-499-5p) and miR-499-5p-sponge (AAV-miR-499-5p-sponge) were transfected via tail vein injection, followed by IPostC protocols. Cardiac injury as well as the status of local and systemic complement activation and inflammation were assessed. IPostC significantly attenuated I/R-induced rat cardiomyocyte apoptosis and the myocardial infarct size. These beneficial effects were accompanied by decreased local and circulating complement component (C)3a and C5a levels, decreased inflammatory marker expression, decreased NF-κB signaling and increased cardiac miR-499 expression. AAV-miR-499-5p prevented local and systemic complement activation and inflammation as well as enhanced the cardioprotection of IPostC, whereas AAV-miR-499-5p-sponge produced the opposite effects. In summary, IPostC protected the rat myocardium against I/R injury, by inhibiting local and systemic complement activation; inflammation; NF-κB signaling; and upregulation of miR-499. As such, miR-499 may have a critical role in IPostC-mediated cardioprotection against I/R injury.

The Lectin Pathway of Complement in Myocardial Ischemia/Reperfusion Injury-Review of Its Significance and the Potential Impact of Therapeutic Interference by C1 Esterase Inhibitor

Acute myocardial infarction (AMI) remains a leading cause of morbidity and mortality in modern medicine. Early reperfusion accomplished by primary percutaneous coronary intervention is pivotal for reducing myocardial damage in ST elevation AMI. However, restoration of coronary blood flow may paradoxically trigger cardiomyocyte death secondary to a reperfusion-induced inflammatory process, which may account for a significant proportion of the final infarct size. Unfortunately, recent human trials targeting myocardial ischemia/reperfusion (I/R) injury have yielded disappointing results. In experimental models of myocardial I/R injury, the complement system, and in particular the lectin pathway, have been identified as major contributors. In line with this, C1 esterase inhibitor (C1INH), the natural inhibitor of the lectin pathway, was shown to significantly ameliorate myocardial I/R injury. However, the hypothesis of a considerable augmentation of myocardial I/R injury by activation of the lectin pathway has not yet been confirmed in humans, which questions the efficacy of a therapeutic strategy solely aimed at the inhibition of the lectin pathway after human AMI. Thus, as C1INH is a multiple-action inhibitor targeting several pathways and mediators simultaneously in addition to the lectin pathway, such as the contact and coagulation system and tissue leukocyte infiltration, this may be considered as being advantageous over exclusive inhibition of the lectin pathway. In this review, we summarize current concepts and evidence addressing the role of the lectin pathway as a potent mediator/modulator of myocardial I/R injury in animal models and in patients. In addition, we focus on the evidence and the potential advantages of using the natural inhibitor of the lectin pathway, C1INH, as a future therapeutic approach in AMI given its ability to interfere with several plasmatic cascades. Ameliorating myocardial I/R injury by targeting the complement system and other plasmatic cascades remains a valid option for future therapeutic interventions.

Complement inhibition attenuates acute kidney injury after ischemia-reperfusion and limits progression to renal fibrosis in mice

The complement system is an essential component of innate immunity and plays a major role in the pathogenesis of ischemia-reperfusion injury (IRI). In this study, we investigated the impact of human C1-inhibitor (C1INH) on the early inflammatory response to IRI and the subsequent progression to fibrosis in mice. We evaluated structural damage, renal function, acute inflammatory response, progression to fibrosis and overall survival at 90-days post-injury. Animals receiving C1INH prior to reperfusion had a significant improvement in survival rate along with superior renal function when compared to vehicle (PBS) treated counterparts. Pre-treatment with C1INH also prevented acute IL-6, CXCL1 and MCP-1 up-regulation, C5a release, C3b deposition and infiltration by neutrophils and macrophages into renal tissue. This anti-inflammatory effect correlated with a significant reduction in the expression of markers of fibrosis alpha smooth muscle actin, desmin and picrosirius red at 30 and 90 days post-IRI and reduced renal levels of TGF-β1 when compared to untreated controls. Our findings indicate that intravenous delivery of C1INH prior to ischemic injury protects kidneys from inflammatory injury and subsequent progression to fibrosis. We conclude that early complement blockade in the context of IRI constitutes an effective strategy in the prevention of fibrosis after ischemic acute kidney injury.

C1 inhibitor-mediated myocardial protection from chronic intermittent hypoxia-induced injury

The optimal treatment for chronic intermittent hypoxia (CIH)-induced cardiovascular injuries has yet to be determined. The aim of the current study was to explore the potential protective effect and mechanism of a C1 inhibitor in CIH in the myocardium. The present study used a rat model of CIH in which complement regulatory protein, known as C1 inhibitor (C1INH), was administered to the rats in the intervention groups. Cardiomyocyte apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling. The expression of proteins associated with the apoptotic pathway, such as B-cell lymphoma 2 (Bcl-2), Bax and caspase-3 were detected by western blot analysis. The expression of complement C3 protein and RNA were also analyzed. C1INH was observed to improve the cardiac function in rats with CIH. Myocardial myeloperoxidase activity, a marker of neutrophil infiltration, was significantly decreased in the C1INH intervention group compared with the CIH control group, and cardiomyocyte apoptosis was significantly attenuated (P<0.05). Western blotting and reverse transcription-polymerase chain reaction analysis indicated that the protein expression levels of Bcl-2 were decreased and those of Bax were increased in the CIH group compared with the normal control group, but the protein expression levels of Bcl-2 were increased and those of Bax were decreased in the C1INH intervention group, as compared with the CIH group. Furthermore, the CIH-induced expression and synthesis of complement C3 in the myocardium were also reduced in the C1INH intervention group. C1INH, in addition to inhibiting complement activation and inflammation, preserved cardiac function in CIH-mediated myocardial cell injury through an anti-apoptotic mechanism.

Endogenous C1-inhibitor production and expression in the heart after acute myocardial infarction

BACKGROUND

Complement activation contributes significantly to inflammation-related damage in the heart after acute myocardial infarction. Knowledge on factors that regulate postinfraction complement activation is incomplete however. In this study, we investigated whether endogenous C1-inhibitor, a well-known inhibitor of complement activation, is expressed in the heart after acute myocardial infarction.

MATERIALS AND METHODS

C1-inhibitor and complement activation products C3d and C4d were analyzed immunohistochemically in the hearts of patients who died at different time intervals after acute myocardial infarction (n=28) and of control patients (n=8). To determine putative local C1-inhibitor production, cardiac transcript levels of the C1-inhibitor-encoding gene serping1 were determined in rats after induction of acute myocardial infarction (microarray). Additionally, C1-inhibitor expression was analyzed (fluorescence microscopy) in human endothelial cells and rat cardiomyoblasts in vitro.

RESULTS

C1-inhibitor was found predominantly in and on jeopardized cardiomyocytes in necrotic infarct cores between 12h and 5days old. C1-inhibitor protein expression coincided in time and colocalized with C3d and C4d. In the rat heart, serping1 transcript levels were increased from 2h up until 7days after acute myocardial infarction. Both endothelial cells and cardiomyoblasts showed increased intracellular expression of C1-inhibitor in response to ischemia in vitro (n=4).

CONCLUSIONS

These observations suggest that endogenous C1-inhibitor is likely involved in the regulation of complement activity in the myocardium following acute myocardial infarction. Observations in rat and in vitro suggest that C1-inhibitor is produced locally in the heart after acute myocardial infarction.

ESC working group cellular biology of the heart: position paper: improving the preclinical assessment of novel cardioprotective therapies

Ischaemic heart disease (IHD) remains the leading cause of death and disability worldwide. As a result, novel therapies are still needed to protect the heart from the detrimental effects of acute ischaemia–reperfusion injury, in order to improve clinical outcomes in IHD patients. In this regard, although a large number of novel cardioprotective therapies discovered in the research laboratory have been investigated in the clinical setting, only a few of these have been demonstrated to improve clinical outcomes. One potential reason for this lack of success may have been the failure to thoroughly assess the cardioprotective efficacy of these novel therapies in suitably designed preclinical experimental animal models. Therefore, the aim of this Position Paper by the European Society of Cardiology Working Group Cellular Biology of the Heart is to provide recommendations for improving the preclinical assessment of novel cardioprotective therapies discovered in the research laboratory, with the aim of increasing the likelihood of success in translating these new treatments into improved clinical outcomes.

Protective role of retinoid X receptor in H9c2 cardiomyocytes from hypoxia/reoxygenation injury in rats

BACKGROUND

Retinoid X receptor (RXR) plays a central role in the regulation of intracellular receptor signaling pathways. The activation of RXR has protective effect on H2O2-induced apoptosis of H9c2 ventricular cells in rats. But the protective effect and mechanism of activating RXR in cardiomyocytes against hypoxia/reoxygenation (H/R)-induced oxidative iniury are still unclear.

METHODS

The model of H/R injury was established through hypoxia for 2 hours and reoxygenation for 4 hours in H9c2 cardiomyocytes of rats. 9-cis-retinoic acid (9-cis RA) was obtained as an RXR agonist, and HX531 as an RXR antagonist. Cultured cardiomyocytes were randomly divided into four groups: sham group, H/R group, H/R+9-cis RA -pretreated group (100 nmol/L 9-cis RA), and H/R+9-cis RA+HX531-pretreated group (2.5 μmol/L HX531). The cell viability was measured by MTT, apoptosis rate of cardiomyocytes by flow cytometry analysis, and mitochondrial membrane potential (ΔΨm) by JC-1 fluorescent probe, and protein expressions of Bcl-2, Bax and cleaved caspase-9 with Western blotting. All measurement data were expressed as mean±standard deviation, and analyzed using one-way ANOVA and the Dunnett test. Differences were considered significant when P was <0.05.

RESULTS

Pretreatment with RXR agonist enhanced cell viability, reduced apoptosis ratio, and stabled ΔΨm. Dot blotting experiments showed that under H/R stress conditions, Bcl-2 protein level decreased, while Bax and cleaved caspase-9 were increased. 9-cis RA administration before H/R stress prevented these effects, but the protective effects of activating RXR on cardiomyocytes against H/R induced oxidative injury were abolished when pretreated with RXR pan-antagonist HX531.

CONCLUSION

The activation of RXR has protective effects against H/R injury in H9c2 cardiomyocytes of rats through attenuating signaling pathway of mitochondria apoptosis.

C1-esterase-inhibitor for primary graft dysfunction in lung transplantation

BACKGROUND

Primary graft dysfunction (PGD) is the most important cause of early morbidity and mortality in lung transplantation (LTX) with an incidence of 8% to 20%. We hypothesized that application of C1-esterase-inhibitor (C1-INH) in LTX-recipients showing early signs of severe PGD would attenuate the condition.

METHODS

Starting as of May 2010, all recipients showing a PaO2/FiO2 ratio of less than 100 as early sign of PGD at first measurement in the OR were immediately treated with C1-INH. Postoperative courses of C1-INH-treated recipients were compared with a subgroup of recipients that developed severe PGD (PGD3-group) within 72 hours after LTX but did not receive C1-INH. Additionally, a third group consisting of all remaining recipients was assembled.

RESULTS

A total of 275 LTX were performed between May 2010 and September 2012 at our center. Among these, 24 patients (8.7%) revealed a first PaO2/FiO2 ratio less than 100 and were treated with C1-INH (C1-INH-group). The PGD3-group consisted of 14 patients; the control cohort consisted of 237 patients. PGD scores were significantly higher in the C1-INH-group and PGD3-group as compared with the control group at all times postoperatively. ICU stay was longest in the PGD3 cohort and prolonged in C1-INH patients compared with the control group (29 [2-70] vs. 9 [2-83] vs. 3 [1-166] days, P=0.002). One-year survival in the PGD3-cohort was 71.4%, the C1-INH-treated-group had a one-year-survival of 82.5%, the control group had the best outcome (95%) (P=0.001).

CONCLUSION

Treatment of PGD with C1-INH led to acceptable outcome. Although survival in the C1-INH treated patients was lower than in the remaining collective, it was as good or better, compared with the PGD3 group and as what is internationally regarded as reasonable after LTX.

Mannan-binding lectin in cardiovascular disease

Cardiovascular disease remains the leading cause of mortality and morbidity worldwide so research continues into underlying mechanisms. Since innate immunity and its potent component mannan-binding lectin have been proven to play an important role in the inflammatory response during infection and ischaemia-reperfusion injury, attention has been paid to its role in the development of cardiovascular complications as well. This review provides a general outline of the structure and genetic polymorphism of MBL and its role in inflammation/tissue injury with emphasis on associations with cardiovascular disease. MBL appears to be involved in the pathogenesis of atherosclerosis and, in consequence, coronary artery disease and also inflammation and tissue injury after myocardial infarction and heart transplantation. The relationship between MBL and disease is rather complex and depends on different genetic and environmental factors. That could be why the data obtained from animal and clinical studies are sometimes contradictory proving not for the first time that innate immunity is a "double-edge sword," sometimes beneficial and, at other times disastrous for the host.

Anti-inflammatory strategies for ventricular remodeling following ST-segment elevation acute myocardial infarction

Acute myocardial infarction (AMI) leads to molecular, structural, geometric, and functional changes in the heart in a process known as ventricular remodeling. An intense organized inflammatory response is triggered after myocardial ischemia and necrosis and involves all components of the innate immunity, affecting both cardiomyocytes and noncardiomyocyte cells. Inflammation is triggered by tissue injury; it mediates wound healing and scar formation and affects ventricular remodeling. Many therapeutic attempts aimed at reducing inflammation in AMI during the past 3 decades presented issues of impaired healing or increased risk of cardiac rupture or failed to show any additional benefit in addition to standard therapies. More recent strategies aimed at selectively blocking one of the key factors upstream rather than globally suppressing the response downstream have shown some promising results in pilot trials. We herein review the pathophysiological mechanisms of inflammation and ventricular remodeling after AMI and the results of clinical trials with anti-inflammatory strategies.

Human C1 inhibitor attenuates liver ischemia-reperfusion injury and promotes liver regeneration

Liver ischemia-reperfusion injury (IRI) is a well-known cause of morbidity and mortality after liver transplantation (LT). Activation of the complement system contributes to the pathogenesis of IRI. Effective treatment strategies aimed at reducing hepatic IRI and accelerating liver regeneration could offer major benefits in LT. Herein, we investigated the effect of C1-esterase inhibitor (human) [C1-INH] on IRI and liver regeneration. Mice were subjected to 60-min partial IRI, with or without 70% partial hepatectomy, or CCl4-induced acute liver failure. Before liver injury, the animals were pretreated with intravenous C1-INH or normal saline. Liver IRI was evaluated using serum levels of alanine aminotransferase, serum interleukin-6, and histopathology. Liver samples were stained for specific markers of regeneration (5-bromo-2'-deoxyuridine [BrdU] staining and proliferating cell nuclear antigen [PCNA]). Histology, serum interleukin-6, and alanine aminotransferase release revealed that C1-INH treatment attenuated liver injury compared with controls. Improved animal survival and increased number of BrdU- and PCNA-positive cells were observed in C1-INH-treated animals which underwent IRI + partial hepatectomy or CCl4 injection compared with control group. These data indicate that complement plays a key role in IRI and liver regeneration. C1-INH represents a potential therapeutic strategy to reduce IRI and promote regeneration in LT.

C1 esterase inhibitor reduces lower extremity ischemia/reperfusion injury and associated lung damage

Background

Ischemia/reperfusion injury of lower extremities and associated lung damage may result from thrombotic occlusion, embolism, trauma, or surgical intervention with prolonged ischemia and subsequent restoration of blood flow. This clinical entity is characterized by high morbidity and mortality. Deprivation of blood supply leads to molecular and structural changes in the affected tissue. Upon reperfusion inflammatory cascades are activated causing tissue injury. We therefore tested preoperative treatment for prevention of reperfusion injury by using C1 esterase inhibitor (C1 INH).

Methods and Findings

Wistar rats systemically pretreated with C1 INH (n = 6), APT070 (a membrane-targeted myristoylated peptidyl construct derived from human complement receptor 1, n = 4), vehicle (n = 7), or NaCl (n = 8) were subjected to 3h hind limb ischemia and 24h reperfusion. The femoral artery was clamped and a tourniquet placed under maintenance of a venous return. C1 INH treated rats showed significantly less edema in muscle (P<0.001) and lung and improved muscle viability (P<0.001) compared to controls and APT070. C1 INH prevented up-regulation of bradykinin receptor b1 (P<0.05) and VE-cadherin (P<0.01), reduced apoptosis (P<0.001) and fibrin deposition (P<0.01) and decreased plasma levels of pro-inflammatory cytokines, whereas deposition of complement components was not significantly reduced in the reperfused muscle.

Conclusions

C1 INH reduced edema formation locally in reperfused muscle as well as in lung, and improved muscle viability. C1 INH did not primarily act via inhibition of the complement system, but via the kinin and coagulation cascade. APT070 did not show beneficial effects in this model, despite potent inhibition of complement activation. Taken together, C1 INH might be a promising therapy to reduce peripheral ischemia/reperfusion injury and distant lung damage in complex and prolonged surgical interventions requiring tourniquet application.

Hepatitis B virus X protein modulates apoptosis in human renal proximal tubular epithelial cells by activating the JAK2/STAT3 signaling pathway

Hepatitis B virus X protein (HBx) is a multifunctional protein, and it activates multiple signal transduction pathways in multiple types of cells and regulates the process of cell apoptosis. In the present study, we mainly investigated the correlation between HBx and renal tubular epithelial cell apoptosis in hepatitis B virus-associated glomerulonephritis (HBVGN) and the possible signaling mechanism. Cell apoptosis in nephridial tissues of patients with HBVGN were determined by the TUNEL method. HBx, p-STAT3 and STAT3 levels in nephridial tissues were determined by immunohistochemical assay, and a correlation analysis between HBx expression levels and apoptosis index in nephridial tissues was conducted. The activation of the JAK2/STAT3 signaling pathway in HK-2 cells and the expression of the apoptosis-related proteins Bax and Bcl-2 were determined by western blot analysis following transfection with the HBx eukaryotic expression vector. Cellular proliferation activity was determined by the CCK-8 method, and cell apoptosis was determined with HO33342 staining using transmission electron microscopy and Annexin V/PI double staining flow cytometry. The results revealed that the apoptosis index in nephridial tissues of patients with HBVGN was significantly higher when compared to that of the control group, and p-STAT3 expression levels in HBVGN nephridial tissues were significantly increased. In the control group, no HBx expression was observed in the nephridial tissues, whereas HBx expression was found in the nephridial tissues of 86% of the patients with HBVGN. The HBx expression levels had a linear correlation with the apoptosis index in the nephridial tissues. After target gene HBx infection, expression levels of both p-JAK2 and p-STAT3 in human proximal HK-2 cells were significantly increased, and the Bax/Bcl-2 ratio was also significantly increased. At the same time, cellular proliferation of HK-2 cells was significantly inhibited, and the rate of apoptosis was increased. After incubation with AG490, the JAK2/STAT3 signaling pathway was partially blocked, which caused a decrease in the Bax/Bcl-2 ratio and reduced cell apoptosis caused by HBx. In conclusion, HBx upregulates the Bax/Bcl-2 ratio by activating the JAK2/STAT3 signaling pathway to cause renal tubular epithelial cell apoptosis, and it is possibly involved in the pathogenic mechanism of nephridial tissue damage caused by HBV.

Role of complement in multiorgan failure

Multiorgan failure (MOF) represents the leading cause of death in patients with sepsis and systemic inflammatory response syndrome (SIRS) following severe trauma. The underlying immune response is highly complex and involves activation of the complement system as a crucial entity of innate immunity. Uncontrolled activation of the complement system during sepsis and SIRS with in excessive generation of complement activation products contributes to an ensuing dysfunction of various organ systems. In the present review, mechanisms of the inflammatory response in the development of MOF in sepsis and SIRS with particular focus on the complement system are discussed.

C1-esterase inhibitor protects against early vein graft remodeling under arterial blood pressure

OBJECTIVES

Arterial pressure induced vein graft injury can result in endothelial loss, accelerated atherosclerosis and vein graft failure. Inflammation, including complement activation, is assumed to play a pivotal role herein. Here, we analyzed the effects of C1-esterase inhibitor (C1inh) on early vein graft remodeling.

METHODS

Human saphenous vein graft segments (n=8) were perfused in vitro with autologous blood either supplemented or not with purified human C1inh at arterial pressure for 6h. The vein segments and perfusion blood were analyzed for cell damage and complement activation. In addition, the effect of purified C1inh on vein graft remodeling was analyzed in vivo in atherosclerotic C57Bl6/ApoE3 Leiden mice, wherein donor caval veins were interpositioned in the common carotid artery.

RESULTS

Application of C1inh in the in vitro perfusion model resulted in significantly higher blood levels and significantly more depositions of C1inh in the vein wall. This coincided with a significant reduction in endothelial loss and deposition of C3d and C4d in the vein wall, especially in the circular layer, compared to vein segments perfused without supplemented C1inh. Administration of purified C1inh significantly inhibited vein graft intimal thickening in vivo in atherosclerotic C57Bl6/ApoE3 Leiden mice, wherein donor caval veins were interpositioned in the common carotid artery.

CONCLUSION

C1inh significantly protects against early vein graft remodeling, including loss of endothelium and intimal thickening. These data suggest that it may be worth considering its use in patients undergoing coronary artery bypass grafting.

San-Huang-Xie-Xin-Tang protects cardiomyocytes against hypoxia/reoxygenation injury via inhibition of oxidative stress-induced apoptosis

Oxidative stress has been widely implicated in the pathogenesis of hypoxia/reoxygenation (H/R) injury. San-Huang-Xie-Xin-Tang (SHXT), a widely used traditional Chinese medication, has been shown to possess antioxidant effects. Here, we investigated whether SHXT and its main component baicalin can attenuate oxidative stress induced by H/R injury. H9c2 rat ventricular cells were exposed to SHXT or baicalin followed by hypoxia for 24 h and/or reoxygenation for 8 h. Pretreatment with SHXT and baicalin both significantly prevented cell death and production of reactive oxygen species induced by hypoxia or H/R in H9c2 cardiomyoctes. In addition, SHXT and baicalin also inhibited hypoxia- or H/R-induced apoptosis, with associated decreased Bax protein, increased Bcl-2 protein, and decreased caspase-3 activity. Furthermore, we found that hypoxia and H/R decreased endothelial nitric oxide synthase (eNOS) expression and nitrite production, and these effects were counteracted by SHXT and baicalein. Finally, SHXT inhibited H/R-induced activation of p38 mitogen activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK) phosphorylation in H9c2 rat ventricular cells. The present study demonstrates for the first time that SHXT can protect cardiomyocytes from H/R injury via inhibition of oxidative stress-induced apoptosis. These cardioprotective effects are possibly mediated through eNOS enhancement and p38 MAPK and JNK-dependent signaling pathways.

Fucoidan, a sulfated polysaccharide from brown algae, against myocardial ischemia-reperfusion injury in rats via regulating the inflammation response

The aim of the study was to determine the effects of fucoidan on rat myocardial ischemia-reperfusion (I/R) model and elucidate the potential mechanisms. Myocardial I/R injury was induced by the occlusion of left anterior descending coronary artery for 30 min followed by reperfusion for 2h. After 2h reperfusion, hemodynamics parameters were detected. Blood samples were collected to determine serum levels of tumor necrosis factor-α (TNF-α) and interleukin 6, 10 (IL-6, 10). Hearts were harvested to assess histopathological changes, infarct size (IS), and the content of myeloperoxidase (MPO). The expression of high-mobility group box 1 (HMGB1), phosphor-IκB-α and phosphor-nuclear factor kappa B (NF-κB) were assayed by western blot. Compared with control group, treatment with fucoidan improved left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP) and the contractility index (P<0.05, P<0.01). Fucoidan reduced the myocardial IS, the levels of TNF-α and IL-6, and the activity of MPO (P<0.05, P<0.01). Fucoidan down-regulated the expression of HMGB1, phosphor-IκB-α and NF-κB, but increased the content of IL-10 when compared with control (P<0.05, P<0.01). Besides, the infiltration of polymorph nuclear leukocytes (PMNs) and histopathological damages in myocardium were decreased in fucoidan treated groups (PMNs, P<0.05, P<0.01). These findings revealed that the administration of fucoidan could regulate the inflammation response via HMGB1 and NF-κB inactivation in I/R-induced myocardial damage.

Anticomplement therapy

The complement system is an important part of innate immunity; however, as with other parts of the immune system, the complement system can become pathologically activated and create or worsen disease. Anticomplement reagents have been studied for several years, but only recently have they emerged as a viable therapeutic tool. Here, we describe the role of the complement system in a wide array of diseases, as well as the use of anticomplement therapy as treatment for these diseases in animal models and in human clinical trials. Specifically, we will discuss the role of anticomplement therapy in paroxysmal nocturnal hemoglobinuria, glomerulonephritis, and heart disease, including coronary artery disease, myocardial infarction, and coronary revascularization procedures such as percutaneous coronary angioplasty and coronary artery bypass graft surgery.

San-Huang-Xie-Xin-Tang Prevents Rat Hearts from Ischemia/Reperfusion-Induced Apoptosis through eNOS and MAPK Pathways

San-Huang-Xie-Xin-Tang (SHXT) is a traditional Chinese medication consisting of three herbs, namely Coptidis rhizome, Scutellariae radix and Rhei rhizome. This study aimed to examine the cardioprotective effects of SHXT in a rat model of acute myocardial apoptosis induced by ischemia/reperfusion (I/R). Vehicle (intravenous saline) or SHXT (intravenous or oral) was administered prior to I/R (occlusion of left coronary artery for 45 min followed by reperfusion for 2 h). In the vehicle group, myocardial I/R caused myocardial infarction with increased plasma cardiac enzymes, severe arrhythmia and mortality. Myocardial apoptosis was induced by I/R as evidenced by DNA ladder and Bcl-2/Bax ratio. In the SHXT group, we found that SHXT significantly reduced plasma levels of cardiac enzymes, arrhythmia scores (from 5 ± 1 to 2 ± 1, P < .01) and mortality rate (from 53 to 0%, P < .01). In addition, pretreatment with intravenous SHXT reduced the infarct size dose-dependently when compared with the vehicle group (10 mg kg(-1): 14.0 ± 0.2 versus 44.5 ± 5.0%, and 30 mg kg(-1): 6.2 ± 1.2% versus 44.5 ± 5.0%, both P < .01). Similarly, oral administration of SHXT reduced the infarct size dose-dependently. Furthermore, SHXT markedly decreased the apoptosis induced by I/R with increased Bcl-2/Bax ratio. Finally, we found that SHXT counteracted the I/R-induced downstream signaling, resulting in increased myocardial eNOS expression and plasma nitrite, and decreased activation of ERK1/2, p38 and JNK. These data suggest that SHXT has cardioprotective effects against I/R-induced apoptosis, and that these effects are mediated, at least in part, by eNOS and MAPK pathways.

Proteomic analysis of serum proteins in acute ischemic stroke patients treated with acupuncture

In the present study, we have investigated the effects of acupuncture on (1) serum protein expression that might have a beneficial effect on stroke patients and (2) the strength of limb muscles in stroke patients. A total of 35 acute ischemic stroke (IS) patients were divided into two groups, one receiving drug treatment alone and the other receiving electroacupuncture (EA) and drug treatment. EA treatment was performed on eight acupuncture points once a day for 10 consecutive days. Serum proteins were detected using a proteomics method based on two-dimensional gel electrophoresis, and the specificity of proteins was confirmed by Western blotting. Changes of limb muscle strength were measured using a modified Medical Research Council grading scale. After EA, SerpinG1 protein expression in serum was down-regulated while the expressions of gelsolin, complement component I, C3, C4B and beta-2-glycoprotein I proteins were up-regulated in patients. The changes of serum protein expression were further confirmed by Western blotting in a majority of the cases. The muscle strength of limbs was increased after EA in 18 patients. EA appears to be effective in regulating differential expression of multiple serum proteins involved in stroke, and also in enhancement of muscle strength recovery in acute IS patients despite an individual variation.

Bench-to-bedside review: the role of C1-esterase inhibitor in sepsis and other critical illnesses

The purpose of this bench-to-bedside review is to summarize the literature relating to complement activation in sepsis and other critical illnesses and the role of C1-esterase inhibitor (C1 INH) as a potential therapy.

Role of NADPH oxidase in H9c2 cardiac muscle cells exposed to simulated ischaemia-reperfusion

Oxidative stress is associated with several cardiovascular pathologies, including hypertension, cardiac hypertrophy and heart failure. Although oxidative stress is also increased after ischaemia-reperfusion (I/R), little is known about the role and the activation mechanisms, in cardiac myocytes under these conditions, of NADPH oxidase, a superoxide-producing enzyme. We found that rat cardiac muscle cells (H9c2) subjected to an in vitro simulated ischaemia (substrate-free medium plus hypoxia) followed by 'reperfusion', displayed increased reactive oxygen species (ROS) production attributable to a parallel increase of NADPH oxidase activity. Our investigation on mechanisms responsible for NADPH oxidase activation showed a contribution of both the increase of NOX2 expression and p47(phox) translocation to the membrane. We also found that the increase of NADPH oxidase activity was associated with higher levels of lipid peroxidation, the activation of redox-sensitive kinases, in particular ERK and JNK, and with cell death. Diphenyleneiodonium (DPI), a flavoprotein inhibitor used as NADPH oxidase inhibitor, prevented I/R-induced ROS formation in treated cells, together with the related lipoperoxidative damage, and JNK phosphorylation without affecting ERK activation, resulting in protection against cell death. Our results provide evidence that NADPH oxidase is a key enzyme involved in I/R-induced oxidant generation and suggest it can be a possible target in cardioprotective strategies against I/R injury, a condition of great importance in human pathology.

Complement-mediated ischemia-reperfusion injury: lessons learned from animal and clinical studies

Ischemia-reperfusion (I/R) injury provides a substantial limitation to further improvements in the development of therapeutic strategies for ischemia-related diseases. Studies in animal I/R models, including intestinal, hindlimb, kidney, and myocardial I/R models, have established a key role of the complement system in mediation of I/R injury using complement inhibitors and knock-out animal models. As complement activation has been shown to be an early event in I/R injury, inhibiting its activation or its components may offer tissue protection after reperfusion. However, clinical study results using complement inhibitors have largely been disappointing. Therefore, identification of a more specific pathogenic target for therapeutic intervention seems to be warranted. For this purpose more detailed knowledge of the responsible pathway of complement activation in I/R injury is required. Recent evidence from in vitro and in vivo models suggests involvement of both the classic and the lectin pathways in I/R injury via exposition of neo-epitopes in ischemic membranes. However, most of these findings have been obtained in knock-out murine models and have for a large part remained unconfirmed in the human setting. The observation that the relative role of each pathway seems to differ among organs complicates matters further. Whether a defective complement system protects from I/R injury in humans remains largely unknown. Most importantly, involvement of mannose-binding lectin as the main initiator of the lectin pathway has not been demonstrated at tissue level in human I/R injury to date. Thus, conclusions drawn from animal I/R studies should be extrapolated to the human setting with caution.

Serine protease inhibitor nafamostat given before reperfusion reduces inflammatory myocardial injury by complement and neutrophil inhibition

Animal data strongly support a role for inflammation in myocardial ischemia reperfusion injury. Attempts at cardioprotection by immunomodulation (such as with the specific C5 antibody pexelizumab) in humans have been disappointing. We hypothesized that a broader spectrum antiinflammatory agent might yield successful cardioprotection. The serine protease inhibitor nafamostat (FUT-175), which is already in clinical use, is a potent antiinflammatory synthetic serine protease inhibitor with anticomplement activity that we tested in a well-established rabbit model of 1 hour of myocardial ischemia followed by 3 hours of reperfusion. Compared to vehicle-treated animals, nafamostat (1 mg/kg of body weight) administered 5 minutes before reperfusion significantly reduced myocardial injury assessed by plasma creatine kinase activity (38.1 +/- 6.0 versus 57.9 +/- 3.7I U/g protein; P < 0.05) and myocardial necrosis (23.6 +/- 3.1% versus 35.7 +/- 1.0%; P < 0.05) as well as myocardial leukocyte accumulation (P < 0.05). In parallel in vitro studies, Nafamostat was a significantly more potent broad spectrum complement suppressor than C1 inhibitor. Nafamostat appears to have capability as an inhibitor of both complement pathways and as a broad-spectrum antiinflammatory agent by virtue of its serine protease inhibition. Administration of nafamostat before myocardial reperfusion after ischemia produced significant, dose-dependent cardioprotection. Reduced leukocyte accumulation and complement activity seem involved in the mechanism of this cardioprotective effect.

Biological activities of C1 inhibitor

Broadly speaking, C1 inhibitor plays important roles in the regulation of vascular permeability and in the suppression of inflammation. Vascular permeability control is exerted largely through inhibition of two of the proteases involved in the generation of bradykinin, factor XIIa and plasma kallikrein (the plasma kallikrein-kinin system). Anti-inflammatory functions, however, are exerted via several activities including inhibition of complement system proteases (C1r, C1s, MASP2) and the plasma kallikrein-kinin system proteases, in addition to interactions with a number of different proteins, cells and infectious agents. These more recently described, as yet incompletely characterized, activities serve several potential functions, including concentration of C1 inhibitor at sites of inflammation, inhibition of alternative complement pathway activation, inhibition of the biologic activities of gram negative endotoxin, enhancement of bacterial phagocytosis and killing, and suppression of the influx of leukocytes into a site of inflammation. C1 inhibitor has been shown to be therapeutically useful in a variety of animal models of inflammatory diseases, including gram negative bacterial sepsis and endotoxin shock, suppression of hyperacute transplant rejection, and treatment of a variety of ischemia-reperfusion injuries (heart, intestine, skeletal muscle, liver, brain). In humans, early data appear particularly promising in myocardial reperfusion injury. The mechanism (or mechanisms) of the effect of C1 inhibitor in these conditions is (are) not completely clear, but involve inhibition of complement and contact system activation, in addition to variable contributions from other C1 inhibitor activities that do not involve protease inhibition.

C1 inhibitor: just a serine protease inhibitor? New and old considerations on therapeutic applications of C1 inhibitor

C1 inhibitor is a potent anti-inflammatory protein as it is the major inhibitor of proteases of the contact and the complement systems. C1-inhibitor administration is an effective therapy in the treatment of patients with hereditary angioedema (HAE) who are genetically deficient in C1 inhibitor. Owing to its ability to modulate the contact and complement systems and the convincing safety profile, plasma-derived C1 inhibitor is an attractive therapeutic protein to treat inflammatory diseases other than HAE. In the present review we give an overview of the biology of C1 inhibitor and its use in HAE. Furthermore, we discuss C1 inhibitor as an experimental therapy in diseases such as sepsis and myocardial infarction.

Soluble complement receptor 1 protects the peripheral nerve from early axon loss after injury

Complement activation is a crucial early event in Wallerian degeneration. In this study we show that treatment of rats with soluble complement receptor 1 (sCR1), an inhibitor of all complement pathways, blocked both systemic and local complement activation after crush injury of the sciatic nerve. Deposition of membrane attack complex (MAC) in the nerve was inhibited, the nerve was protected from axonal and myelin breakdown at 3 days after injury, and macrophage infiltration and activation was strongly reduced. We show that both classical and alternative complement pathways are activated after acute nerve trauma. Inhibition of the classical pathway by C1 inhibitor (Cetor) diminished, but did not completely block, MAC deposition in the injured nerve, blocked myelin breakdown, inhibited macrophage infiltration, and prevented macrophage activation at 3 days after injury. However, in contrast to sCR1 treatment, early signs of axonal degradation were visible in the nerve, linking MAC deposition to axonal damage. We conclude that sCR1 protects the nerve from early axon loss after injury and propose complement inhibition as a potential therapy for the treatment of diseases in which axon loss is the main cause of disabilities.