Characterization of antithrombotic activity of lumbrokinase-immobilized polyurethane valves in the total artificial heart

Maggot Kinase and Natural Thrombolytic Proteins

Thrombolytic enzymes constitute a class of proteases with antithrombotic functions. Derived from natural products and abundant in nature, certain thrombolytic enzymes, such as urokinase, earthworm kinase, and streptokinase, have been widely used in the clinical treatment of vascular embolic diseases. Fly maggots, characterized by their easy growth and low cost, are a traditional Chinese medicine recorded in the Compendium of Materia Medica. These maggots can also be used as raw material for the extraction and preparation of thrombolytic enzymes (maggot kinase). In this review, we assembled global research reports on natural thrombolytic enzymes through a literature search and reviewed the functions and structures of natural thrombolytic enzymes to provide a reference for natural thrombophilic drug screening and development.

Effect of enrofloxacin on the proteome of earthworms

The environmental and human health risks of veterinary drugs are becoming public health issues. Enrofloxacin (EF) is an extensively used animal-specific antibacterial agent that leaves drug residues in the environment. This study investigated the proteomic response of the earthworm Eisenia fetida to EF exposure. Earthworms were exposed to EF in soil at 1-500mg·kg^-1, and samples were collected at intervals during a 28 day period. The extracted proteins were separated by two dimensional electrophoresis to detect differentially expressed proteins (DEPs) in EF-exposed earthworms. In total, 35 unique DEPs were found. These proteins were subjected to MALDI-TOF/TOF-MS analysis and identified through comparison of their mass spectra with those in protein databases. The DEPs were grouped on the basis of their function, into metabolism, stress-related, transport, transcription, and predicted/hypothetical protein categories. Knowledge of proteins that are induced or repressed by EF in earthworms could provide insight into mechanisms of sub-clinical physiological effects of xenobiotic residues in the environment, and may also help understand synergy between pollutants. As several DEPs in E. fetida showed similarity to human protein sequences, E. fetida has potential as an indicator species to assess the environmental and biological risks of drug residues.

Lumbrokinase attenuates diabetic nephropathy through regulating extracellular matrix degradation in Streptozotocin-induced diabetic rats

OBJECTIVE

The present study was undertaken to investigate the therapeutic effect and underlying mechanisms of lumbrokinase on diabetic nephropathy.

METHODS

Type I diabetes was induced in male Sprague-Dawley rats via intraperitoneal injection of Streptozotocin (STZ). Lumbrokinase was administered to the diabetic rats at a dose of 600,000 U/kg body weight by gavage. As a positive control, perindopril, an angiotensin-converting enzyme inhibitor (ACEI), was given to diabetic rats at a dose of 4 mg/kg body weight. Following 12 weeks treatment, we measured the creatinine clearance rate (Ccr), urinary albumin excretion (UAE) and kidney injury scores. In addition, the expression of collagen IV, MMP-2 and MMP-9 in renal tissue was evaluated.

RESULTS

The diabetic rats developed proteinuria, glomerulosclerosis, tubulointerstitial fibrosis and a marked increase of renal cortical collagen IV. In contrast, MMP-2 and MMP-9 were significantly reduced in the renal cortex of diabetic rats. Interestingly, lumbrokinase treatment markedly reduced the proteinuria and improved the glomerulosclerosis and tubulointerstitial fibrosis in diabetic rats. The induction of collagen IV and the down-regulation of MMP-2 and MMP-9 was significantly attenuated by lumbrokinase. All these beneficial effects of lumbrokinase were comparable to the ACEI group.

CONCLUSION

Lumbrokinase treatment attenuated diabetic nephropathy in rats, possibly through increasing the activity of MMPs and the subsequent degradation of extracellular matrix.

Differential expression of genes in the earthworm Eisenia fetida following exposure to Escherichia coli O157:H7

In this study, suppression subtractive hybridization was used to construct forward and reverse cDNA libraries to identify genes involved in the response of Eisenia fetida after exposure to Escherichia coli O157:H7. We cloned 1428 cDNAs or expressed sequence tags (ESTs), of which 738 were confirmed to be differentially expressed on dot blotting analysis. A total of 394 good-quality ESTs (GenBank dbEST accession numbers HO001170-HO001563) were obtained from the raw clone sequences after cleaning. The genes were associated with metabolism (10%), transport (10%), translation (5%), immunity (2%), and the cytoskeleton (1%). Thirteen candidates were selected to assess expression levels in earthworms exposed to artificially contaminated soil by real-time PCR. The translated amino acid sequences of clones were similar to fibrinolytic protease 1, extracellular globin-3, myosin essential light chain, lumbrokinase, lysozyme, ferritin, ATP synthase F0 subunit 6, and hsp 70. Characterization of differential gene expression in the earthworm E. fetida on exposure to E. coli O157:H7 expands our understanding of the molecular mechanisms of interactions at the earthworm-pathogen interface.

Tailored Synthesis of Nitric Oxide-Releasing Polyurethanes Using O-Protected Diazeniumdiolated Chain Extenders

Nitric oxide (NO) has been shown to exhibit significant anti-platelet activity and its release from polymer matrices has been already utilized to increase the biocompatibility of various blood-contacting devices. Herein, details of a new synthetic approach for preparing NO-releasing diazeniumdiolated polyurethanes (PU) are described. The method's utility is demonstrated by the incorporation of methoxymethyl- or sugar-protected pre-formed diazeniumdiolate moieties directly into chain extender diols which are then incorporated into the polyurethane backbone. This approach provides the ability to control the number of diazeniumdiolate groups incorporated into the polymer backbone, and hence the surface flux of NO that can ultimately be liberated from polymeric films prepared from the new PU materials. The method provides a means of covalently attaching diazeniumdiolate groups to polyurethanes in a form that resists dissociation of NO during processing but can be activated for spontaneous NO release via hydrolysis of the carbohydrate or methoxymethyl moieties under basic and acidic conditions, respectively.

Expression, purification, and characterization of recombinant lumbrokinase PI239 in Escherichia coli

Lumbrokinase (LK) is an important fibrinolytic enzyme derived from earthworms. It has been found that LK is composed of a group of isoenzymes. To construct and express the mature peptide of LK PI239 in Escherichia coli, we amplified and optimized the gene of LK which was then cloned into the prokaryotic expression vector pET-22b(-). The recombinant LK (rLK) protein was expressed as inclusion bodies and we have developed a purification process of rLK from these inclusion bodies. A step-down urea concentration strategy was applied to the rLK renaturation process. The purified and renatured rLK apparently ameliorated the conditions of the model thrombosis rats used, and may be developed into a therapeutic agent for thrombotic-associated diseases.

Antithrombotic effects by oral administration of novel proteinase fraction from earthworm Eisenia andrei on venous thrombosis model in rats

A novel proteinase fraction, SPP-501, was purified from the earthworm, Eisenia andrei, and its antithrombotic effects compared with those of urokinase and t-PA (tissue type-plasminogen activator) in a thrombosis model, induced by the insertion of a stainless wire coil into the inferior vena cava. SPP-501, urokinase and t-PA were administrated once a day for 14 days. On the oral administration of SPP-501, as well as urokinase and t-PA, the thrombus weight was dramatically decreased. The euglobulin lysis time (ELT) was also shortened by SPP-501, but urokinase and t-PA failed to dissolve the euglobulin clot. Conversely, urokinase and t-PA produced detectable fibrinogen/fibrin degradation products (FDP), but SPP-501 did not. Thrombin induced platelet aggregation was desensitized in the SPP-501 treatment groups. With a high dose of SPP-501 (45 mg/kg), the APTT (activated partial thromboplastin time) was prolonged. These results suggest that SPP-501 shows both antithrombotic and fibrinolytic activities when orally administered.

Molecular cloning, sequencing, and expression of a fibrinolytic serine-protease gene from the earthworm Lumbricus rubellus

The full-length cDNA of the lumbrokinase fraction 6 (F6) protease gene of Lumbricus rubellus was amplified using an mRNA template, sequenced and expressed in E. coli cells. The F6 protease gene consisted of pro- and mature sequences by gene sequence analysis, and the protease was translated and modified into active mature polypeptide by N-terminal amino acid sequence analysis of the F6 protease. The pro-region of F6 protease consisted of the 44 residues from methionine-1 to lysine-44, and the mature polypeptide sequence (239 amino acid residues and one stop codon; 720 bp) started from isoleucine-45 and continued to the terminal residue. F6 protease gene clones having pro-mature sequence and mature sequence produced inclusion bodies in E. coli cells. When inclusion bodies were orally administrated rats, generated thrombus weight in the rat's venous was reduced by approximately 60 % versus controls. When the inclusion bodies were solubilized in pepsin and/or trypsin solutions, the solubilized enzymes showed hemolytic activity in vitro. It was concluded the F6 protease has hemolytic activity, and that it is composed of pro- and mature regions.

Codon optimization, expression, and characterization of recombinant lumbrokinase in goat milk

Lumbrokinase is an important fibrinolytic enzyme derived from earthworm. Although its cDNA has been isolated and sequenced, there is still no report on expression of the lumbrokinase due to unknown reasons. To determine the elements affecting the expression of lumbrokinase, two copies of a lumbrokinase cDNA(w) obtained by RT-PCR and a synthesized lumbrokinase cDNA(m) with optimized codons were cloned into a mammary-gland-specific expression vector pIbCP. The pIbCP-LK-LK vector preparations were directly injected in the lactating goat mammary glands. Results showed that both LK-w and LK-m were successfully expressed in goat milk. The fibrinolytic activity of the LK-w in milk was 225,000 +/- 13,200 tPA units/L, while that of the LK-m was 550,000 +/- 21,600 tPA units/L, indicating that the codon optimization plays an important role in improving the lumbrokinase expression. The molecular weight of the recombinant lumbrokinase is 31.8 kDa. The main physiochemical features of the recombinant lumbrokinase, including temperature stability, pH resistance, and sensitivity to pepsin, were also clarified. This is the first report on expression and characterization of a genetically engineered lumbrokinase.

Purification and Characterization of Six Fibrinolytic Serine-Proteases from Earthworm Lumbricus rubellus

The six lumbrokinase fractions (F1 to F6) with fibrinolytic activities were purified from earthworm Lumbricus rubellus lysates using the procedures of autolysis, ammonium sulfate fractionation, and column chromatography. The proteolytic activities on the casein substrate of the six iso-enzymes ranged from 11.3 to 167.5 unit/mg with the rank activity orders of F2 > F1 > F5 > F6 > F3 > F4. The fibrinolytic activities of the six fractions on the fibrin plates ranged from 20.8 to 207.2 unit/mg with rank orders of F6 > F2 > F5 > F3 > F1 > F4. The molecular weights of each iso-enzyme, as estimated by SDS-PAGE, were 24.6 (F1), 26.8 (F2), 28.2 (F3), 25.4 (F4), 33.1 (F5), and 33.0 kDa (F6), respectively. The plasminogen was activated into plasmin by the enzymes. The optimal temperature of the six iso-enzymes was 50 degrees C, and the optimal pH ranged from pH 4-12. The four iso-enzymes (F1-F4) were completely inhibited by PMSF. The two enzymes (F5 and F6) were completely inhibited by aprotinin, TLCK, TPCK, SBTI, LBTI, and leupeptin. The N-terminal amino acid (aa) sequences of the first 20 to 22 residues of each fraction had high homology. All six iso-enzymes had identical aa residues 2-3 and 13-15. The N-terminal 21-22 aa sequences of the F2, F3, and F4 iso-enzymes were almost the same. The N-terminal aa sequences of F5 and F6 were identical.

Hydrolysis of fibrinogen and plasminogen by immobilized earthworm fibrinolytic enzyme II from Eisenia fetida

Earthworm fibrinolytic enzyme II (EFE-II) from Eisenia fetida has a broad hydrolytic specificity for peptide bonds. Our experiments show that EFE-II can hydrolyze the specific chromogenic substrates of thrombin (Chromozym TH), trypsin (Chromozym TRY) and elastase (Chromozym ELA). The Michaelis-Menten constant (K(m)) for Chromozym ELA (approximately 245 microM) is much higher than those for the thrombin (approximately 90 microM) and trypsin (approximately 60 microM) substrates. On the other hand, EFE-II is inhibited most strongly by soybean trypsin inhibitor (SBTI), and weakly inhibited by elastinal, suggesting that EFE-II has a trypsin-like activity. Degradation of plasminogen (PLg) and fibrinogen by EFE-II was investigated after EFE-II had been immobilized onto 1,1'-carboryl-diimidazole (CDI)-activated Sepharose CL-6B. The immobilized EFE-II has 55-60% activity of the native enzyme with a higher thermal and pH resistance. EFE-II cleaves PLg at four hydrolytic sites: Lys(77)-Arg(78), Arg(342)-Met(343), Ala(444)-Ala(445) and Arg(557)-Ile(558). The site Arg(557)-Ile(558) is also recognized and cleaved by tissue plasminogen activator (t-PA) and urokinase (UK), producing active plasmin. Cleaving Ala(444)-Ala(445) released mini-plasmin with secondary activity to hydrolyze fibrin. Immobilized EFE-II degrades not only the Aalpha chain of fibrinogen in the C-terminal region (like human neutrophil elastase, HNE), but also in the N-terminal region at the Val(21)-Glu(22) site.

Bisphosphonate derivatized polyurethanes resist calcification

Calcification of polyurethane cardiovascular implants is an important disease process that has the potential to compromise the long-term function of devices such as polymer heart valves and ventricular assist systems. In this study we report the successful formulation and characterization of bisphosphonate-derivatized polyurethanes, hypothesized to resist implant calcification based on the pharmacologic activity of the immobilized bisphosphonate. Fully polymerized polyurethanes (a polyurea-polyurethane and a polycarbonate polyurethane) were modified (post-polymerization) with bromoalkylation of the hard segments followed by attachment of a bisphosphonate group at the bromine site. These bisphosphonate-polyurethanes resisted calcification in rat 60 day subdermal implants compared to nonmodified control polyurethane implants, that calcify. Bisphosphonates-modified polyurethanes were also studied in circulatory implants using a pulmonary valve cusp replacement model in sheep. Polyurethane cusps modified with bisphosphonate did not calcify in 90 day implants. compared to control polyurethane cusps implants, that demonstrated nodular surface oriented calcific deposits. It is concluded that bisphosphonate modified polyurethanes resist calcification both in subdermal implants and in the circulation. This novel biomaterial approach offers great promise for long-term blood stream implantation with calcification resistance.

Bioencapsulation within synthetic polymers (Part 2): non-sol-gel protein-polymer biocomposites

Since the introduction of sol-gel bioencapsulation and the demonstration that biological function can be incorporated into, and preserved within, polymer matrices, a number of alternative polymers have been used to immobilize proteins. Various enzymes have been trapped in such diverse polymers as epoxy-amine resins, polyvinyl plastics, polyurethane foams and silicone elastomers. Together with sol-gel encapsulates, these biocomposites represent a powerful approach for immobilizing biological materials for applications as biosensors and biocatalysts, and hold promise as bioactive, fouling-resistant polymers for environmental, food and medical uses. Although still at the developmental stage, these biocomposites promise to revolutionize the whole arena of high-performance bioimmobilization.