Specific interactions of polystyrene biomaterials with factor D of human complement

Network pharmacology and experimental validation-based approach to understand the effect and mechanism of Taohong Siwu Decoction against ischemic stroke

ETHNOPHARMACOLOGICAL RELEVANCE

Taohong Siwu Decoction (THSWD) is a classic prescription of traditional Chinese medicine that is mainly used for promoting blood circulation and alleviating blood stasis. THSWD is composed of Prunus persica (L.) Batsch, Carthamus tinctorius L., Ligusticum chuanxiong hort, Angelica sinensis (Oliv.) Diels, Rehmannia glutinosa (Gaertn.) DC, and Paeoniae Radix Alba. This prescription eliminates blood stasis, supplements blood, and dredges the body as an auxiliary treatment.

AIM OF THE STUDY

To investigate the mechanistic effects of THSWD in the treatment of cerebral ischemia.

MATERIALS AND METHODS

we downloaded 39 blood components for THSWD from the PharmMapper database for target prediction studies and identified the targets of cerebral ischemia. We identified the intersection between the components and targets, constructed a protein-protein interaction (PPI) network, carried out GO and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. a rat model of cerebral ischemia was established in rats, and the results of network pharmacology were verified by in vivo experiments.

RESULTS

Established a component-target-pathway network, further transcriptomics analysis identified a total of 11 target genes (Plau, Fabp4, Mmp9, Mmp12, Cfd, Lcn2, Trem1, Lgals3, Hmox1, Selp and Slc6a4), a total of seven pathways (focal adhesion, complement and coagulation cascades, Staphylococcus aureus infection, malaria, transcriptional dysregulation in cancer, progesterone-mediated oocyte maturation, and the PI3K-Akt signaling pathway), because both targets genes and the complement and coagulation cascade signaling pathways mediate inflammatory responses, the signaling pathways associated with the complement and coagulation cascades were selected for experimental verification. We detected inflammatory factors and several key proteins in the complement and coagulation cascade signaling pathway (C1qb, C1qc, C3ar1, C5ar1, and Cfd). Analysis showed that THSWD can reduce the release of inflammatory factors and inhibit activation of the complement signaling pathways, thereby protecting against ischemic stroke disease.

CONCLUSIONS

Our findings provide preliminary clarification of the predominant mechanism of action of THSWD when used to treat ischemic stroke.

Molecular characterization, expression and antimicrobial activity of complement factor D in Megalobrama amblycephala

Complement factor D (Df) is a serine protease, which can activate the alternative pathway by cleaving complement factor B, and involves in the innate defense against pathogens infection in teleost. In this study, we cloned, characterized the Df gene from blunt snout bream (Megalobrama amblycephala) (Mamdf), and examined its expression pattern and antimicrobial activity. The open reading frame (ORF) of Mamdf was 753 bp, encoding 250 amino acids with a molecular mass of 27.2 kDa. Mamdf consisted of a single serine protease trypsin superfamily domain, 3 substrate binding sites and 3 active sites, but no potential N-glycosylation site. Pairwise alignment showed that Mamdf shared the highest identity (94%) with grass carp (Ctenopharyngodon idellus). Phylogenetic analysis indicated that Mamdf and other vertebrate Df had a common ancestral origin. Mamdf structured with 4 introns and 5 exons. The Mamdf mRNA expressed relatively high at the intestine appearance stage during early development and constitutively expressed in various tissues with the highest expression in the kidney in healthy adults. After challenged with Aeromonas hydrophila, significant changes of Mamdf at both mRNA and protein levels in the kidney, spleen, liver and head-kidney were observed. The recombinant Mamdf protein showed antimicrobial activity against both gram-positive bacteria and gram-negative bacteria. The above results suggested the immune function of Mamdf, and would benefit further detailed Df function research in the immune process in teleost.

Role of the Complement System in the Response to Orthopedic Biomaterials

Various synthetic biomaterials are used to replace lost or damaged bone tissue that, more or less successfully, osseointegrate into the bone environment. Almost all biomaterials used in orthopedic medicine activate the host-immune system to a certain degree. The complement system, which is a crucial arm of innate immunity, is rapidly activated by an implanted foreign material into the human body, and it is intensely studied regarding blood-contacting medical devices. In contrast, much less is known regarding the role of the complement system in response to implanted bone biomaterials. However, given the increasing knowledge of the complement regulation of bone homeostasis, regeneration, and inflammation, complement involvement in the immune response following biomaterial implantation into bone appears very likely. Moreover, bone cells can produce complement factors and are target cells of activated complement. Therefore, new bone formation or bone resorption around the implant area might be greatly influenced by the complement system. This review aims to summarize the current knowledge on biomaterial-mediated complement activation, with a focus on materials primarily used in orthopedic medicine. In addition, methods to modify the interactions between the complement system and bone biomaterials are discussed, which might favor osseointegration and improve the functionality of the device.

Development of a Novel Cytomedical Treatment that can Protect Entrapped Cells from Host Humoral Immunity

Cell therapy is expected to relieve the shortage of donors needed for organ transplantation. When patients are treated with allogeneic or xenogeneic cells, it is necessary to develop a means by which to isolate administered cells from an immune attack by the host. We have developed “cytomedicine, ” which consists of functional cells entrapped in semipermeable polymer, and previously reported that alginate-poly-l-lysine-alginate microcapsules and agarose microbeads could protect the entrapped cells from injury by cellular immunity. However, their ability to isolate from humoral immunity was insufficient. It is well known that the complement system plays an essential role in rejection of transplanted cells by host humoral immunity. Therefore, the goal of the present study was to develop a novel cytomedical device containing a polymer capable of inactivating complement. In the screening of various polymers, polyvinyl sulfate (PVS) exhibited high anticomplement activity and low cytotoxicity. Murine pancreatic β-cell line (MIN6 cell) entrapped in agarose microbeads containing PVS maintained viability and physiological insulin secretion, replying in response to glucose concentration, and resisted rabbit antisera in vitro. PVS inhibited hemolysis of sensitized sheep erythrocytes (EAs) and rabbit erythrocytes by the complement system. This result suggests that PVS inhibits both the classical and alternative complement pathways of the complement system. Next, the manner in which PVS exerts its effects on complement components was examined. PVS was found to inhibit generation of C4a and Ba generation in activation of the classical and alternative pathways, respectively. Moreover, when the EAC1 cells, which were carrying C1 on the EAs, treated with PVS were exposed to C1-deficient serum, hemolysis decreased in a PVS dose-dependent manner. These results suggest that PVS inhibits C1 in the classical pathway and C3 convertase formation in the alternative pathway. Therefore, PVS may be a useful polymer for developing an anticomplement device for cytomedical therapy.

Materials engineering for immunomodulation

The engineering of materials that can modulate the immune system is an emerging field that is developing alongside immunology. For therapeutic ends such as vaccine development, materials are now being engineered to deliver antigens through specific intracellular pathways, allowing better control of the way in which antigens are presented to one of the key types of immune cell, T cells. Materials are also being designed as adjuvants, to mimic specific 'danger' signals in order to manipulate the resultant cytokine environment, which influences how antigens are interpreted by T cells. In addition to offering the potential for medical advances, immunomodulatory materials can form well-defined model systems, helping to provide new insight into basic immunobiology.

Interaction of poly(styrene sulfonic acid) with the alternative pathway of the serum complement system

Bioartificial pancreas, in which the islets of Langerhans are enclosed in artificial membrane to be protected from the host immune system, is expected to be a promising medical device to treat patients who suffer from insulin-dependent diabetes. Our strategy for preparation of a bioartificial pancreas involves utilizing a membrane including polymeric materials that can inhibit the complement reaction. In this study, we examined the effects of poly(styrene sulfonic acid) (PSSa) on the alternative pathway of the serum complement system to identify the mechanism(s) involved. PSSa was dissolved in pooled normal human serum (NHS), and the mixtures were incubated at 37 degrees C for 30 min. Complement activities in sera were determined by hemolytic assays. Amounts of complement activation products released were determined by ELISA. Interactions of PSSa with complement components and fragments were examined with electrophoresis and immunoblotting. From these examinations, it appeared that the manner of PSSa effects on the alternative pathway (AP) highly depends on its concentration. PSSa seemingly acted as an activator when its concentration was 0.005 g/dl to 0.05 g/dl, while it acted as an inhibitor when its concentration was more than 0.1 g/dl. In terms of activation or inhibition of the AP, forming complex of PSSa with factor H induced activation, and that with factor D induced inhibition.

Xenotransplantation of pig islets in diabetic dogs with use of a microcapsule composed of agarose and polystyrene sulfonic acid mixed gel

INTRODUCTION

The authors have designed a microcapsule composed of agarose and polystyrene sulfonic acid (PSSa) mixed gel that provides a protective barrier against complement attack. Xenografts of islets, encapsulated in an agarose-PSSa microcapsule, have been shown to normalize blood glucose in rodents with chemically induced diabetes for extended periods of time without immunosuppression.

AIM

To investigate the efficacy of agarose-PSSa microencapsulated pig islets in reversing diabetes in a large animal model.

METHODOLOGY

Diabetes was induced in beagle recipients by total pancreatectomy. Each recipient received three to five intraperitoneal injections of either encapsulated (n = 5) or nonencapsulated pig islets (n = 2).

RESULTS

In all dogs receiving microencapsulated islets, the graft function was achieved for 7.4 +/- 3.1 weeks (mean +/- standard error), as determined by elimination or reduction of exogenous insulin requirement. In three recipients, the fasting blood glucose levels were maintained at < or = 200 mg/dL without any exogenous insulin for a period of 6, 50, and 119 days. Circulating porcine C-peptide was detected in the sera of all dogs after transplantation of encapsulated islets. Immunohistologic examination revealed the presence of insulin-positive cells in the microcapsules. In contrast, in two dogs receiving nonencapsulated islets there was no graft function.

CONCLUSIONS

This preliminary study demonstrates that agarose-PSSa microencapsulated pig islets can survive and function for weeks or months in totally pancreatectomized diabetic dogs without immunosuppression.

Interaction of poly(2-acrylamido 2-methylpropane sulfonate)-grafted polystyrene beads with cationic complement proteins

Influence of various biomaterials on the complement system in serum has been intensively studied by many research groups, since activation of the complement pathway in vivo has been known to give rise to some pathological conditions, such as inflammation and anaphylaxis. Much effort has been devoted to develop new materials that do not activate or deteriorate the complement system. The present work is aimed at revealing the mode of reactions of anionic poly(2-acrylamido 2-methylpropane sulfonate) grafted on polystyrene bead (PAMPS-g-bead) with serum complement. Complement activity assay, determination of complement proteins levels, and immunoblot analysis were carried out for sera pretreated with PAMPS-g-beads. The results clearly showed that, when PAMPS-g-beads were incubated with serum, those beads adsorbed several complement proteins, i.e. C1q, factor D, factor P, C6, and C8, but the generation of activation fragments of complement components was not observed. Especially, factor D was most effectively removed from serum, resulting in potential inhibition of the alternative pathway. A larger amount of PAMPS-g-beads was needed to decrease the serum CH50 level. That may be caused by removal of C6. Although some polyanions, such as dextran sulfate, were reported to activate the complement system, the obtained results indicate that the PAMPS-g-bead is not an activator of the complement pathway, but acts as an adsorbent of complement components. One possible clinical application of the PAMPS-g-beads is adsorption of serum factor D by extracorporeal treatment of patients with renal failure with a high level of factor D, because the increased quantity of factor D in serum may cause consistent activation of the alternative pathway.

In situ complement activation by polyethylene wear debris

A frequent long-term complication of total joint arthroplasty is aseptic loosening, the end result of wear debris accumulation, synovitis, and osteolysis about the implant-bone or cement-bone interface. Complement, an effector system in plasma, synovial fluid, and tissue, has powerful chemotactic, inflammatory, and osteoclast-activating potentials. This study explored the complement-activating ability of polyethylene, a material used in joint implants. In vitro hemolytic assays using sheep red blood cells (E(sh)), human serum, and particulate polyethylene suggested alternative pathway complement activation, as well as polyethylene adsorption of activated complement components. These results were confirmed by enzyme-linked immunosorbent assay (ELISA) quantification of activated complement factors Bb and C3b. In situ double antibody immunoperoxidase staining for factors Bb, C3a, iC3b, and SC5-9 in synovial tissue from revision hip specimens showed localized alternative pathway activation and component adsorption. These results introduce a likely role for complement activation in particle-mediated recruitment, proliferation, and activation of macrophages during early events in osteolysis and implant loosening.

Complement activation by model drug carriers for intravenous application: determination by two-dimensional electrophoresis

The interactions of intravenously injected drug carriers with blood proteins are considered as an important factor for the fate of the particles after their administration. Protein adsorption on latex particles applied as model for intravenous drug carriers was analysed using two-dimensional electrophoresis (2-DE). The particles were incubated in citrated plasma, serum and heat-inactivated serum, respectively. Incubation in the various media resulted in clear differences in the protein adsorption patterns. Two characteristic protein spots were determined to be enriched on the 2-DE gels only after incubation of the particles in serum. Employing N-terminal microsequencing these protein spots were identified to be fragments of the complement protein C3. Enrichment of these particular spots was most likely a result of complement activation by the particles. Mechanism of C3 binding to the particle surface and subsequent inactivation by cleavage are discussed in order to explain the results. It could be demonstrated that 2-DE analysis provides the possibility to distinguish between adsorption and covalent attachment of C3 to particulate surfaces. The findings indicate that complement activation was caused by covalent binding of the C3 component C3b to the particles' surface. The influence of the incubation medium on the in vitro protein adsorption of particulate drug carriers has to be considered when a correlation between the protein adsorption pattern and the in vivo behaviour of the particles is approached.

New anionic polyelectrolyte hydrogel for corneal surgery

A new high-water-content (78%) anionic polyelectrolyte hydrogel was obtained by phase inversion (demixion) of a polymer solution containing 9.0% poly(acrylonitrile sodium methallylsulphonate), 85.0% dimethylformamide, and 6.0% saline solution (0.9% NaCl). The hydrogel is permeable to water, saline, urea, creatinine, glucose, human albumin, and saline-dissolved oxygen. Investigation of the interactions between human serum and surfaces prepared with the new yielded hydrogel, compared to serum interaction with silica-free silicone (RTV), regenerated cellulose (Cuprophan), MMA/PVP copolymer (Lidofilcon), PMMA (Perspex), FIFE (Gore-Tex), and poly(acrylonitrile sodium methallylsulphonate) hemodialysis membrane (AN-69), showed the hydrogel and hemodialysis membrane (both prepared with AN-69 copolymer) to be the only materials devoid of complement (C')-activating ability.

Dialysis membrane adsorption during CRRT

Experimental and clinical studies have suggested that dialysis membrane biocompatibility may influence the morbidity and mortality of patients with acute renal failure. Complement activation by dialysis membranes may also prolong the recovery from acute renal failure. In this article, we review the concept of dialysis membrane adsorption, with particular attention to adsorption/inhibition of factor D, a highly specific serine protease of the alternative pathway of complement. The adsorptive properties of some dialysis membranes may be useful during continuous renal replacement therapies (CRRT) in critically ill patients.

An immuno-isolative membrane capable of consuming cytolytic complement proteins

In an earlier article we demonstrated that xenogeneic islets of Langerhans in an agarose/poly(styrenesulfonic acid) (PSSa) microcapsule were protected from the host's immune rejection and that diabetic animals maintained a normal glucose level for a long period of time after their transplantation. In this study, we attempted to make clear the immuno-isolative mechanisms of the agarose-PSSa microcapsule from the standpoint of permeability of antibodies and complement proteins through this microcapsule membrane. It was found that the microcapsule was unable to prevent the permeation of IgG for longer than a few days, but protect the encapsulated cells from cytolytic complement attack. This strongly suggests that the cytolytic complement activity was lost during permeation through the microcapsule, probably because of the strong interaction of PSSa in the membrane with complement proteins. Based on these findings we proposed the minimum requirement for the immuno-isolative membrane to be applicable to xenotransplantation.

Inhibition of degranulation of human polymorphonuclear leukocytes by complement factor D

A degranulation inhibiting protein could be isolated from human plasma ultrafiltrate by a three-step purification method including ion-exchange chromatography, gelfiltration and affinity-chromatography. The protein was identified as complement factor D by means of sequence analysis. Its degranulation inhibiting activity was determined with regard to its effect on the FNLPNTL-induced lactoferrin secretion of human polymorphonuclear leukocytes. Complement factor D caused a dose-dependent decrease of the FNLPNTL-stimulated lactoferrin degranulation down to 34% of stimulated controls.

Relationship between reduction of complement activation by polysaccharide surfaces bearing diethylaminoethyl groups and their degree of substitution

The relationships between substitution of hydroxyl (OH) by diethylaminoethyl (DEAE) groups on cellulose membranes and the resulting reduction of complement activation are not clear. As a model, Sephadex has been randomly substituted with DEAE groups. Modification of 10% of the glucose units, i.e. about 3% of the groups, had no noticeable effect on the complement activating capacity of the polymer surface, whereas 20% substitution dramatically reduced it. This result could be explained in part by the fact that Sephadex-specific antibodies are not adsorbed by this modified surface. Thus, they cannot enhance complement activation as they do on Sephadex or cellulose. Comparison of our results with those published on Hemophan led us to the conclusion that a similar effect could occur. However, the degree of substitution of the membrane surface is probably greater than that of the membrane core due to the preparation process. Comparison with Sephadex substituted with other groups, or with other polymers bearing a variable density of OH groups, led us to the conclusion that, as hypothesized by Chenoweth (Artif Organs 1984; 8: 281-287), reduction of the availability of OH groups decreases complement activation, but the relationship is probably not linear. Moreover, replacement by other groups results in additional modulations due to (i) interactions between the groups and proteins responsible for formation or decay of the amplifying C3 convertase and/or (ii) decrease in recognition of the modified surface by antibodies which enhance complement activation on polysaccharides.

Activation of the complement system by polysaccharidic surfaces bearing carboxymethyl, carboxymethylbenzylamide and carboxymethylbenzylamide sulphonate groups

Substituted Sephadex derivatives bearing carboxymethyl (CM), CM-benzylamide (CMB), CM-propylamide (CMP) and CMB-sulphonate (CMBS) groups are used as models of polysaccharidic surfaces to measure the effects of substituting OH groups on the complement activating capacity (CAC) of the modified surfaces in normal human serum. CM substitution decreases and can suppress the CAC of Sephadex. Low CMB substitution also decreases the CAC, whereas high CMB or CMP substitutions increase it again after a minimum. In addition to C3 cleavage occurring at high substitution with CMB or CMP groups, the presence of CMB induces consumption of a protein, limiting CH50 measurements. The CAC variations could be due to rearrangements of the polymer surfaces at the aqueous interface with proteins. Highly substituted CMB-bearing surfaces could activate complement-like polystyrene surfaces. The presence of CMBS groups does not reduce the CAC of the surface. Such polymer surfaces, which are heparin-like concerning coagulation, are not heparin-like concerning complement inhibition.