Thrombolytic Proteases Research Articles

Thrombolytic protease characterization from leaves and fruit flesh of the jernang rattan plant (Daemonorops draco)

Thrombolytic agents are used for thrombolytic therapy to dissolve blood clots that form in a blood vessel. All currently used thrombolytic agents have unfavorable shortcomings, such as gastrointestinal bleeding, allergic reactions, and thrombolytic agent resistance, treatment for some of which can be quite expensive. As a result, the search for thrombolytic agents derived from plants is currently taking place. Some plants have been discovered to contain protease enzymes with thrombolytic activity; pharmaceuticals derived from plants are believed to be safer. Jernang rattan (Daemonorops draco) is a plant of the Arecaceae family and is known to produce resin. Jernang rattan resin is also known to have antioxidant, antiseptic, antitumor, antimicrobial, and cytotoxic activity, but very limited information on proteolytic activity of the protease from this plant. This research aims to isolate proteases from the leaves and fruit flesh of the rattan jernang plant (D. draco) and to investigate the proteolytic activity of the isolated proteases. The protease was isolated from the leaves and the fruit flesh, and then partially purified by ammonium sulfate precipitation. The radial caseinolytic assay showed that protease in a 60% ammonium sulfate fraction gave a clear zone, with diameters of 1.4 cm and 1.8 cm for the protease isolated from leaves and fruit flesh, respectively. A Folin‐Ciocalteau assay showed that the enzymes isolated were able to hydrolyze casein and release L‐tyrosine, with activity of 0.158 U/mL and 0.174 U/mL for the protease from the leaves and fruit flesh, respectively. A fibrinogenolytic assay showed that the protease from the fruit flesh hydrolyzed the A‐α, B‐β and the γ chain of human fibrinogen, while the protease from the leaves hydrolyzed the A‐α and γ chain. Both proteases were inhibited by 56% by phenylmethylsulfonyl fluoride (PMSF), indicating that the enzymes are serine proteases. Based on the assay results obtained, it can be concluded that proteases isolated from the leaves and fruit flesh have potential as thrombolytic proteases.

Optimization of Crude Protease Production from Bacillus thuringiensis HSFI-12 and Thrombolytic Activity Its Enzyme Dialysate

Cardiovascular disease (CVD) is among the leading causes of death in the world caused by thrombosis. Thrombosis is the formation of excessive blood clots on the walls of blood vessels called thrombus. This could lead to fatal blockage of the heart muscle or brain. Thrombosis can be treated using enzyme-type drugs such as thrombolytic proteases. There have been many studies of bacteria producing thrombolytic enzymes isolated from fermented foodstuffs. However, commercial production of bacterial enzymes to fulfill the need of thrombolytic agents is still limited, causing high price of CVD therapy. Bacillus sp. HSFI-12 (Holothuria scabra Fermented Intestine-12) isolated from the fermented intestine of sea cucumber Holothuria scabra had been reported to have a competitive thrombolytic activity to the commercial Nattokinase. This study aimed to determine bacterial optimum incubation time based on enzyme activity after bacterium molecular identification was done. It also aimed to obtain the dialysate of bacterial crude protease and then determine the thrombolytic activity of the obtained dialysate. Thrombolytic activity was tested on 4 different types of blood (A, B, AB and O). Results of molecular identification showed that strain HSFI-12 shared similarity level of 99.80 %, with Bacillus thuringiensis. Activity of crude protease from the incubated cultures peaked at 48 h of incubation with activity of 191.5 U/mL The activity of concentrated protease after precipitation and dialysis process (dialysate) was 2-times higher by 355,7 U/mL. The percentage of lysis of blood clots produced by crude blood groups A, B, AB and O showed a range of values ​​of 66.423 - 67.656 % while those that produce dialysate are 77.564 - 78.861 %. As conclusion, the best (optimized) incubation time to produce crude enzyme from B. thuringiensis HSFI-12 with the highest activity was 48 h. The process of concentrating the crude thrombolytic protease of B. thuringiensis HSFI-12 increases both activity and thrombolytic ability of the bacterial enzyme. HIGHLIGHTS The most optimum incubation time for protease production from Bacillus thuringiensis is 48 h Partial purification on bacterial crude protease through resulted in 86 % increased activity Partial purification on bacterial crude protease resulted in 17 % increased blood clot lysis ability Clot lysis ability of both crude and dialysate proteases are higher than that of Nattokinase (NK) GRAPHICAL ABSTRACT

Serine Proteases and Chemokines in Neurotrauma: New Targets for Immune Modulating Therapeutics in Spinal Cord Injury.

Progressive neurological damage after brain or spinal cord trauma causes loss of motor function and treatment is very limited. Clotting and hemorrhage occur early after spinal cord (SCI) and traumatic brain injury (TBI), inducing aggressive immune cell activation and progressive neuronal damage. Thrombotic and thrombolytic proteases have direct effects on neurons and glia, both healing and also damaging bidirectional immune cell interactions. Serine proteases in the thrombolytic cascade, tissue- and urokinase-type plasminogen activators (tPA and uPA), as well as the clotting factor thrombin, have varied effects, increasing neuron and glial cell growth and migration (tPA), or conversely causing apoptosis (thrombin) and activating inflammatory cell responses. tPA and uPA activate plasmin and matrix metalloproteinases (MMPs) that break down connective tissue allowing immune cell invasion, promoting neurite outgrowth. Serine proteases also activate chemokines. Chemokines are small proteins that direct immune cell invasion but also mediate neuron and glial cell communication. We are investigating a new class of therapeutics, virus-derived immune modulators; One that targets coagulation pathway serine proteases and a second that inhibits chemokines. We have demonstrated that local infusion of these biologics after SCI reduces inflammation providing early improved motor function. Serp-1 is a Myxomavirus-derived serine protease inhibitor, a serpin, that inhibits both thrombotic and thrombolytic proteases. M-T7 is a virus-derived chemokine modulator.Here we review the roles of thrombotic and thrombolytic serine proteases and chemoattractant proteins, chemokines, as potential therapeutic targets for SCI. We discuss virus-derived immune modulators as treatments to reduce progressive inflammation and ongoing nerve damage after SCI.

Acute Toxicity, Immunotoxicity and Allergenicity of Protease Complex Obtained from Micromycete Sarocladium strictum.

The different effects on animals of the thrombolytic protease complex of the new producer S. strictum 203 were studied. The tests of acute toxicity, immunotoxicity and allergenicity should conclude that the studied proteolytic complex is safe for medical usage. For the intravenous and the intraperitoneal routes of administration, the maximum tolerated dose and the median lethal dose were not determined.

PEGylated Serp-1 Markedly Reduces Pristane-Induced Experimental Diffuse Alveolar Hemorrhage, Altering uPAR Distribution, and Macrophage Invasion.

Diffuse alveolar hemorrhage (DAH) is one of the most serious clinical complications of systemic lupus erythematosus (SLE). The prevalence of DAH is reported to range from 1 to 5%, but while DAH is considered a rare complication there is a reported 50–80% mortality. There is at present no proven effective treatment for DAH and the therapeutics that have been tested have significant side effects. There is a clear necessity to discover new drugs to improve outcomes in DAH. Serine protease inhibitors, serpins, regulate thrombotic and thrombolytic protease cascades. We are investigating a Myxomavirus derived immune modulating serpin, Serp-1, as a new class of immune modulating therapeutics for vasculopathy and lung hemorrhage. Serp-1 has proven efficacy in models of herpes virus-induced arterial inflammation (vasculitis) and lung hemorrhage and has also proved safe in a clinical trial in patients with unstable coronary syndromes and stent implant. Here, we examine Serp-1, both as a native secreted protein expressed by CHO cells and as a polyethylene glycol modified (PEGylated) variant (Serp-1m5), for potential therapy in DAH. DAH was induced by intraperitoneal (IP) injection of pristane in C57BL/6J (B6) mice. Mice were treated with 100 ng/g bodyweight of either Serp-1 as native 55 kDa secreted glycoprotein, or as Serp-1m5, or saline controls after inducing DAH. Treatments were repeated daily for 14 days (6 mice/group). Serp-1 partially and Serp-1m5 significantly reduced pristane-induced DAH when compared with saline as assessed by gross pathology and H&E staining (Serp-1, p = 0.2172; Serp-1m5, p = 0.0252). Both Serp-1m5 and Serp-1 treatment reduced perivascular inflammation and reduced M1 macrophage (Serp-1, p = 0.0350; Serp-1m5, p = 0.0053), hemosiderin-laden macrophage (Serp-1, p = 0.0370; Serp-1m5, p = 0.0424) invasion, and complement C5b/9 staining. Extracellular urokinase-type plasminogen activator receptor positive (uPAR+) clusters were significantly reduced (Serp-1, p = 0.0172; Serp-1m5, p = 0.0025). Serp-1m5 also increased intact uPAR+ alveoli in the lung (p = 0.0091). In conclusion, Serp-1m5 significantly reduces lung damage and hemorrhage in a pristane model of SLE DAH, providing a new potential therapeutic approach.

A Virus-Derived Immune Modulating Serpin Accelerates Wound Closure with Improved Collagen Remodeling.

Numerous treatments have been developed to promote wound healing based on current understandings of the healing process. Hemorrhaging, clotting, and associated inflammation regulate early wound healing. We investigated treatment with a virus-derived immune modulating serine protease inhibitor (SERPIN), Serp-1, which inhibits thrombolytic proteases and inflammation, in a mouse excisional wound model. Saline or recombinant Serp-1 were applied directly to wounds as single doses of 1 μg or 2 µg or as two 1 µg boluses. A chitosan-collagen hydrogel was also tested for Serp-1 delivery. Wound size was measured daily for 15 days and scarring assessed by Masson’s trichrome, Herovici’s staining, and immune cell dynamics and angiogenesis by immunohistochemistry. Serp-1 treatment significantly accelerated wound healing, but was blocked by urokinase-type plasminogen activator (uPAR) antibody. Repeated dosing at a lower concentration was more effective than single high-dose serpin. A single application of Serp-1-loaded chitosan-collagen hydrogel was as effective as repeated aqueous Serp-1 dosing. Serp-1 treatment of wounds increased arginase-1-expressing M2-polarized macrophage counts and periwound angiogenesis in the wound bed. Collagen staining also demonstrated that Serp-1 improves collagen maturation and organization at the wound site. Serp-1 has potential as a safe and effective immune modulating treatment that targets thrombolytic proteases, accelerating healing and reducing scar in deep cutaneous wounds.

In vitro Thrombolytic Potential of Actinoprotease from Marine Streptomyces violaceus VITYGM.

The main aim of the study was to isolate, screen, characterize and produce an extracellular thrombolytic protease from marine actinomycetes. Marine actinomycete was isolated and characterized on the basis of morphological, biochemical, and molecular characterization. The primary screening for protease activity was done by casein hydrolysis method followed by radial caseinolytic assay. The actinoprotease was partially purified using ammonium sulfate precipitation technique followed by dialysis and Sephadex G-50 gel permeation chromatography. 16srDNA sequencing and BLAST search analysis of the sequence revealed close affiliation with Streptomyces genera and identified as Streptomyces violaceus VITYGM with 99% similarity. The specific activity of purified protease was found to be 1437 units/mg along with purification fold up to 1.5 times. The blood clot lysis activity was compared with the standard and found to lyse the blood clot with 97.43%. Till now very less evidences have been reported on actinoprotease. A single peak at retention time 0.9 min observed on high performance liquid chromatography (HPLC) confirmed the homogeneity of the preparation. This is the first study to report on actinoprotease from Streptomyces violaceus VITYGM. This study emphasizes the potency of novel actinoproteases as active compound in drugs for the treatment of cardiovascular diseases.

Reactive Center Loop (RCL) Peptides Derived from Serpins Display Independent Coagulation and Immune Modulating Activities

Serpins regulate coagulation and inflammation, binding serine proteases in suicide-inhibitory complexes. Target proteases cleave the serpin reactive center loop scissile P1-P1' bond, resulting in serpin-protease suicide-inhibitory complexes. This inhibition requires a near full-length serpin sequence. Myxomavirus Serp-1 inhibits thrombolytic and thrombotic proteases, whereas mammalian neuroserpin (NSP) inhibits only thrombolytic proteases. Both serpins markedly reduce arterial inflammation and plaque in rodent models after single dose infusion. In contrast, Serp-1 but not NSP improves survival in a lethal murine gammaherpesvirus68 (MHV68) infection in interferon γ-receptor-deficient mice (IFNγR(-/-)). Serp-1 has also been successfully tested in a Phase 2a clinical trial. We postulated that proteolytic cleavage of the reactive center loop produces active peptide derivatives with expanded function. Eight peptides encompassing predicted protease cleavage sites for Serp-1 and NSP were synthesized and tested for inhibitory function in vitro and in vivo. In engrafted aorta, selected peptides containing Arg or Arg-Asn, not Arg-Met, with a 0 or +1 charge, significantly reduced plaque. Conversely, S-6 a hydrophobic peptide of NSP, lacking Arg or Arg-Asn with -4 charge, induced early thrombosis and mortality. S-1 and S-6 also significantly reduced CD11b(+) monocyte counts in mouse splenocytes. S-1 peptide had increased efficacy in plasminogen activator inhibitor-1 serpin-deficient transplants. Plaque reduction correlated with mononuclear cell activation. In a separate study, Serp-1 peptide S-7 improved survival in the MHV68 vasculitis model, whereas an inverse S-7 peptide was inactive. Reactive center peptides derived from Serp-1 and NSP with suitable charge and hydrophobicity have the potential to extend immunomodulatory functions of serpins.

Abstract 16279: Serine Protease Inhibitor (serpin) Reactive Site Loop Peptides Prevent Transplant Vasculopathy and Inflammatory Vasculitis

Aim: Ser ine p rotease in hibitors ( Serpins ) regulate key clotting and inflammatory pathways. Two anti-inflammatory Serpins , neuroserpin (NSP) and Serp-1 markedly reduce arterial inflammation and plaque growth in a rodent aortic transplant vasculitis model after single dose infusion. NSP is a mammalian serpin that inhibits thrombolytic proteases and Serp-1 is a virus-derived serpin that inhibits both thrombotic and thrombolytic proteases. We postulated that proteolytic cleavage of the reactive site loop (RSL) produces active peptide derivatives with expanded functions. 8 peptide sequences encompassing predicted cleavage sites for Serp-1 and NSP were synthesized and tested in mouse aortic allograft transplant and herpesvirus (MHV68) vasculitis models. The main aim was to assess therapeutic potential for RSL peptides derived from NSP and Serp-1 in vascular inflammation. Methods: We assessed the capacity of 8 predicted serpin RSL peptides, 4 from Serp-1 and 4 from NSP to reduce vascular inflammation. 40 C57BL/6 mice had aortic allograft transplant with a single IV injection of each single peptide. 29 IFN-γR KO mice had MHV-68 infection and were treated for 10 days with S-2 (ISRMAV), S-7 (GTTASSDTAITLIPR), Inverse S-7 (RPILTIATDSSATTG), S-8 (MAVLYPQVIVDHPFFFLIRNR) peptides, or Saline control. Results: RSL peptides with R or RN sequences, but not RM, and with 0-+1 charge significantly reduced vascular inflammatory cell invasion and plaque growth after aortic transplant from C57Bl/6 donor to BALB/c recipient transplant mice (5-6 transplants/peptide) (P < 0.01). S-1, S-3, S-7 & S-8 peptides reduced inflammation and plaque in aortic transplant. Hydrophobicity and negative charge in S-6 peptide increased thrombosis. S-7 peptide also significantly improved survival in a lethal MHV68 infection vasculitic model (150 days survival; P < 0.043), while inactive S-2 peptide, Inverse S-7 and S-8 had no effect (P = NS; 40 days) (P< 0.043). Conclusions: In conclusion, a series of serpin RSL peptides were synthesized based upon natural protease cleavage sites. RSL peptides have demonstrated significant efficacy in reducing inflammatory vasculitis after transplant or after lethal mouse herpesviral (MHV) infections, extending serpin regulatory activity.

Novel thrombolytic protease from edible and medicinal plant Aster yomena (Kitam.) Honda with anticoagulant activity: Purification and partial characterization

A thrombolytic protease named kitamase possessing anticoagulant property was purified from edible and medicinal plant Aster yomena (Kitam.) Honda. Kitamase showed a molecular weight of 50kDa by SDS-PAGE and displayed a strong fibrin zymogram lysis band corresponding to the similar molecular mass. The enzyme was active at high temperatures (50°C). The fibrinolytic activity of kitamase was strongly inhibited by EDTA, EGTA, TPCK and PMSF, inhibited by Zn(2+). The Km and Vmax values for substrate S-2251 were determined as 4.31mM and 23.81mM/mg respectively. It dissolved fibrin clot directly and specifically cleaved the α, Aα and γ-γ chains of fibrin and fibrinogen. In addition, kitamase delayed the coagulation time and increased activated partial thromboplastin time and prothrombin time. Kitamase exerted a significant protective effect against collagen and epinephrine induced pulmonary thromboembolism in mice. These results suggest that kitamase may have the property of metallo-protease like enzyme, novel fibrino(geno)lytic enzyme and a potential to be a therapeutic agent for thrombosis.

Viral Anti-Inflammatory Proteins Target Diverging Immune Pathways with Converging Effects on Arterial Dilatation, Plaque and Apoptosis

Abdominal aortic aneurysms are often fatal due to atherosclerosis, thromboembolism, rupture, and hemorrhage, however, treatment is limited to expectant monitoring and surgical intervention. Inflammation is detected in aneurysms and in plaque with associated increased apoptosis, chemokines, cytokines, hemorrhage, and thrombosis. We compared treatment with three different myxomavirus-derived anti-inflammatory proteins targeting apoptosis, thrombosis, and chemokine pathways. The effect of each protein on aortic dilatation and plaque growth was assessed after angioplasty in Apolipoprotein Enull mice. Four myxomavirus-derived proteins were studied; Serp-1 a serine protease inhibitor (serpin) targeting thrombotic and thrombolytic proteases, Serp-2 a cross-class serpin inhibiting granzyme B and caspases 1 and 8, M-T7 a broad spectrum C, CC, and CXC chemokine inhibitor, and R171E, an inactive M-T7 mutant. Cell invasion, elastin breaks, plaque progression, and aortic dilatation were significantly reduced by Serp-1, Serp-2, or M-T7 protein treatment, but not by R171E. PCR array analysis detected altered expression of a group of shared 40 apoptotic genes in monocytes after treatment with each active protein, but not R171E. Interference with inflammatory cell responses, through highly divergent inflammatory response pathways, produces similar reductions in monocyte invasion, arterial dilatation, and plaque growth potentially through modified expression of apoptotic genes.

Abstract 524: Myxomaviral Anti-angiogenesis Protein Serp-1 Inhibits Pancreatic Cancer Growth in Mice

Modification of the tumor microenvironment by inflammatory cells represents a newly recognized driving force in cancer with a critical role in tumor invasion, growth, angiogenesis, and metastasis. Increased serine proteases in the thrombolytic cascade, specifically urokinase-type plasminogen activator and its receptor, correlate with inflammatory cell invasion, angiogenesis, cancer growth and invasion. Inflammation in pancreatic cancer is linked with myeloid-derived suppressor cell activity and cancer progression. Myxomavirus is a complex DNA virus encoding highly potent immune modulators such as Serp-1, which inhibits uPA, tPA, plasmin and coagulation factor X. Serp-1 has also been demonstrated to inhibit angiogenesis in a chicken chorioallantoic membrane (CAM) model. To explore the potential use of anti-inflammatory, anti-angiogenesis proteins that target thrombotic and thrombolytic as well as inflammatory pathways, for cancer treatment, severe combined immunodeficient (SCID) mice engrafted with human cancer cells were treated with Serp-1 and neuroserpin, a selective mammalian inhibitor of thrombolytic proteases or control saline. Proteins were tested for efficacy in preventing human pancreatic and breast cancer cell growth in NOD/SCID mice (n=67 total) at 4 weeks after implantation. Serp-1 and neuroserpin inhibited pancreatic cancer Hs766t (n=27; P=0.03 and P=0.01, respectively), but not breast cancer MDA231 growth (n=11) when compared to saline controls (N =5). Serpin inhibition of pancreatic tumor growth was associated with decreased MDSC as shown by flow cytometry analysis of splenocyte (P=0.009). Serpin-mediated anti-inflammatory activity in pancreatic tumor growth was also demonstrated by reduced macrophage infiltration in tumors (P=0.001). Furthermore, RT-PCR array analysis revealed a five-fold decrease in the expression of inducible nitric oxide synthase (iNOS), which has been shown to play important role in tumor angiogenesis. Conclusions Anti-inflammatory protease inhibitors, virus-derived Serp-1 and mammalian neuroserpin, may provide new treatment approaches by targeting the angiogenesis and inflammatory responses that support cancer cell growth.

Myxomaviral Anti-Inflammatory Serpin Reduces Myeloid-Derived Suppressor Cells and Human Pancreatic Cancer Cell Growth in Mice.

Modification of the tumor microenvironment by inflammatory cells represents a newly recognized driving force in cancer with critical roles in tumor invasion, growth, angiogenesis, and metastasis. Increased thrombolytic cascade serine proteases, specifically urokinase-type plasminogen activator and its receptor, correlate with inflammatory cell migration, pancreatic cancer growth, invasion and unfavorable outcomes. Inflammation in pancreatic cancer is linked with myeloid-derived suppressor cell (MDSC) activity and cancer progression. Myxomavirus is a complex DNA virus encoding highly potent immune modulators. Serp-1 and M-T7 are two such secreted anti-inflammatory myxomaviral proteins. Serp-1 inhibits uPA, plasmin and coagulation factor X while M-T7 inhibits C, CC, and CXC chemokines. We have explored the potential use of these viral proteins for treatment of a range of human cancer isolates engrafted in severe combined immunodeficient (SCID) mice. Engrafted tumors were treated with either Serp-1, neuroserpin, a related mammalian serpin that inhibits thrombolytic proteases, or M-T7. Serp-1 and neuroserpin inhibited growth of the pancreatic cancer cell line Hs766t (P=0.03 and P=0.01, respectively) at 4 weeks after implantation. Serp-1 also inhibited growth of a second pancreatic cancer cell line MIA PaCa-2 in mice (P=0.02). Growth of the human breast cancer line MDA231 was not inhibited by Serp-1. M-T7, in contrast, did not alter growth of any of the cancer cell lines tested after implant into SCID mice. Serpin inhibition of pancreatic tumor growth was associated with a significant decrease in splenocyte MDSC counts by flow cytometry (P=0.009), without detected change in other splenocyte subpopulations. Serp-1 and NSP treatment also significantly reduced macrophage infiltration in tumors (P=0.001). In summary two anti-inflammatory serpins reduced inflammatory macrophage invasion and pancreatic tumor cell growth, suggesting potential therapeutic efficacy.

Abstract 18589: Virus-Derived Serpin Prolongs Survival and Reduces Vasculitis in Lethal Viral Sepsis in Unrelated Infections

Lethal viral infections produce a cytokine storm with disseminated vascular leak, clotting, bleeding, organ failure and high mortality, but treatment remains limited. With this cytokine storm there is a massive influx of inflammatory macrophage and T lymphocytes into the arterial wall and affected organs. Serine proteases in clot-forming and clot-dissolving cascades are regulated by inhibitors termed serpins. Serpins such as anti-thrombin III have been used to reduce DIC and improve outcomes but with limited success. Myxomavirus secretes a potent anti-inflammatory serpin, Serp-1, that inhibits thrombotic factor Xa (fXa) and thrombolytic tissue and urokinase-type plasminogen activators (tPA, uPA). Serp-1 treatment was tested in mouse models of lethal gammaHerpesvirus68 and Ebola virus infections. Serp-1 significantly increased survival in both infections, whereas mammalian neuroserpin, that targets only tPA and uPA, did not. Fator Xa levels were reduced in aortic tissues after Serp-1 treatment. Serp-1 reduced virus load, hemorrhage, inflammation, and organ damage. NSP treatment allowed for a marked suppression of normal spleen cell responses during infections on flow cytometry analysis, while Serp-1 did not. RT-PCR array analysis of aortic sections from infected mice demonstrated significantly altered thrombotic and thrombolytic pathway proteases and serpins as well as addressin gene expression changes with Serp-1 treatment but not with NSP treatment. Treatments with other myxomaviral anti-inflammatory proteins, Serp-2 targeting apoptosis, and M-T7 a chemokine modulator showed trends toward reduced inflammation in the MHV68 infected mice. Conclusions: Myxomaviral Serp-1 modulates thrombotic and thrombolytic proteases, markedly improving survival in unrelated lethal viral infections, whereas a mammalian serpin targeting only thrombolysis was ineffective. Treatment targeting both thrombotic and the thrombolytic cascades may improve outcomes in severe viral septic states with vascular inflammation and DIC.

Viral cross-class serpin inhibits vascular inflammation and T lymphocyte fratricide; a study in rodent models in vivo and human cell lines in vitro.

Poxviruses express highly active inhibitors, including serine proteinase inhibitors (serpins), designed to target host immune defense pathways. Recent work has demonstrated clinical efficacy for a secreted, myxomaviral serpin, Serp-1, which targets the thrombotic and thrombolytic proteases, suggesting that other viral serpins may have therapeutic application. Serp-2 and CrmA are intracellular cross-class poxviral serpins, with entirely distinct functions from the Serp-1 protein. Serp-2 and CrmA block the serine protease granzyme B (GzmB) and cysteine proteases, caspases 1 and 8, in apoptotic pathways, but have not been examined for extracellular anti-inflammatory activity. We examined the ability of these cross-class serpins to inhibit plaque growth after arterial damage or transplant and to reduce leukocyte apoptosis. We observed that purified Serp-2, but not CrmA, given as a systemic infusion after angioplasty, transplant, or cuff-compression injury markedly reduced plaque growth in mouse and rat models in vivo. Plaque growth was inhibited both locally at sites of surgical trauma, angioplasty or transplant, and systemically at non-injured sites in ApoE-deficient hyperlipidemic mice. With analysis in vitro of human cells in culture, Serp-2 selectively inhibited T cell caspase activity and blocked cytotoxic T cell (CTL) mediated killing of T lymphocytes (termed fratricide). Conversely, both Serp-2 and CrmA inhibited monocyte apoptosis. Serp-2 inhibitory activity was significantly compromised either in vitro with GzmB antibody or in vivo in ApoE/GzmB double knockout mice. Conclusions The viral cross-class serpin, Serp-2, that targets both apoptotic and inflammatory pathways, reduces vascular inflammation in a GzmB-dependent fashion in vivo, and inhibits human T cell apoptosis in vitro. These findings indicate that therapies targeting Granzyme B and/or T cell apoptosis may be used to inhibit T lymphocyte apoptosis and inflammation in response to arterial injury.

Abstract 17956: Serpin Treatment Reduces Inflammation in Transplanted Temporal Artery Biopsy Specimens from Patients with Suspected Giant Cell Arteritis in Immunodeficient Mice

Background - Giant cell / temporal arteritis (GCTA) is a severe inflammatory vasculitic syndrome (IVS), which causes arterial occlusion and sudden loss of vision. Treatment for IVS remains limited. Intra-aortic full thickness implants of human TA biopsy and left internal mammary artery (LIMA) specimens were surgically engrafted into the abdominal aorta of immunodeficient SCID mice as a new model for analyzing development of vascular inflammation, as well as response to new treatments. Serp-1 is a myxomaviral-derived serine protease inhibitor (serpin) that blocks thrombotic and thrombolytic protease pathways, arterial inflammation, and plaque growth. Serp-1 was recently tested in acute coronary syndromes (ACS), where reduced markers of myocardial damage were detected after stent implant. Objective - We assessed the effects of Serp-1 or saline treatment on inflammatory cell invasion and plaque growth after TA and LIMA engraftment in NOD-SCID mice. Results - Normal arterial (LIMA) specimens were harvested during bypass surgery and implanted into 24 SCID mice. Half the mice had saline (N=12) and half had Serp-1 treatment (N=12). In each group 6 mice had 5x106 peripheral blood mononuclear cells (PBMCs) infusions from the same patient as the donor LIMA graft, given immediately postop by tail vein and 6 had no cell infusion. TA grafts from patients with suspected GCA were implanted into a separate group of 24 SCID mice - 12 mice had saline (100µl) and 12 Serp-1 (100ng/g/100µl) treatment (one i.v. injection followed by daily i.p. injection for 10 days). in each treatment group 4 mice had infusion of non-matched PBMCs. At 4 weeks LIMA (P < 0.034) or TA (P < 0.0001) grafts, had significantly reduced plaque growth with Serp-1 treatment when human PBMC were also infused (p<0.05). In the absence of PBMC, Serp-1 had minimal effect. Mononuclear cell invasion was reduced in Serp-1 treated mice with PBMCs. Flow cytometry did not detect significant changes in splenocytes. Conclusions - Aortic implant of human LIMA or TA xenografts in SCID mice provides a physiological model for investigating inflammatory vasculitis. With PBMC infusion, treatment with the myxomaviral Serp-1, reduced inflammatory cell invasion and plaque growth in arterial xenografts.

Neuroserpin, a thrombolytic serine protease inhibitor (serpin), blocks transplant vasculopathy with associated modification of T-helper cell subsets

Thrombolytic serine proteases not only initiate fibrinolysis, but also are up-regulated in vascular disease and acute inflammatory responses. Although the serine protease inhibitor (serpin) plasminogen activator inhibitor-1 (PAI-1) is considered a main regulator of thrombolysis, PAI-1 is also associated with vascular inflammation. The role of other serpins that target thrombolytic proteases, PAI-2, PAI-3, and neuroserpin (NSP), in vascular inflammation is, however, less well defined. NSP is a mammalian serpin that, similar to PAI-1, inhibits urokinase- and tissue-type plasminogen activators (uPA and tPA, respectively) and has been most closely associated with the nervous system, with a demonstrated protective role after cerebral infarction in mouse models. However, the role of NSP in systemic arterial inflammation and plaque growth is not known. Serp-1 is a myxoma viral serpin that also inhibits tPA and uPA, as well as additionally inhibiting plasmin and factor Xa (fXa). Serp-1 has proven highly potent anti-inflammatory and anti-atherogenic activity. Here we assess the effects of NSP treatment on plaque growth and T-helper (Th) lymphocyte activity in a mouse aortic allograft transplant model, with comparison to Serp-1. NSP and Serp-1 both significantly reduced plaque growth and T-cell invasion. T-bet (a Th1 differentiation marker) was significantly reduced in transplanted aorta with associated reductions in Th1 and Th17, but not Th2, in splenocytes. NSP had additional Th modifying activity in non-transplanted mice. In summary, this is the first report that NSP possesses anti-inflammatory activity in systemic arteries, modifying Th cell responses and significantly reducing plaque growth in mouse aortic allografts.

Serpins, the vasculature, and viral therapeutics

Serine protease inhibitors, termed serpins, are key regulators of numerous biological pathways that initiate inflammation, coagulation, angiogenesis, apoptosis, extra-cellular matrix composition and complement activation responses. Viruses have encoded serpins to guard themselves from host immune attack. The myxoma virus which infects rabbits secretes a highly potent anti-inflammatory serpin, Serp-1, which targets thrombolytic and thrombotic proteases as a means to fend off coagulation and inflammatory reactions to viral infection. These reactions act as a defense, produced by the host, to counter viral infection and invasion. When infused in animals after vascular injury, Serp-1 elicits exceptional anti-inflammatory activity, whereas the mammalian serpin, plasminogen activator inhibitor-1 (PAI-1), which also targets thrombotic and thrombolytic proteases can induce a pro-thrombotic response. During arterial injury, PAI-1 is highly expressed and increased PAI-1 concentration can result in acute thrombosis after aortic transplant in mouse models. The reactive center loop amino acid sequence is a fingerprint for serpin function and this function is highly sequence specific such that modification in this sequence can markedly alter activity. For instance, the alteration of the serpin reactive site loop P1-P1I amino acid sequence nullified the anti-inflammatory activity of Serp-1 and modification of P2-P7 initiated a pro-inflammatory response with vascular remodeling with aneurysm formation. Furthermore Serp-1 has demonstrated the capacity to utilize a mammalian serine protease receptor, the urokinase-type plasminogen activator receptor (uPAR), to alter cellular signaling in part through the actin binding protein cytoskeletal system (via filamin B). In this review, the molecular mechanisms relating inflammation and coagulation pathways to atherosclerosis and how the viral serpin, Serp-1, modifies these pathways in order to exhibit this profound anti-inflammatory activity without associated adverse thrombosis are discussed. Viral and vascular serpins targeting the thrombolytic cascade represent a potential new and untapped therapeutic resource.