Formation and use of poly-L-histidine-catalase complexes: protection of cells from hydrogen peroxide-mediated injury

Bacteria Coated by Polyphenols Acquire Potent Oxidant-Scavenging Capacities

Several microbial species, including probiotic lactic acid bacteria, have the ability to irreversibly bind a large variety of polyphenols (flavonoids) and anthocyanidins found in many colored fruits and vegetables and to enhance their total oxidant-scavenging capacities (TOSC). The binding of flavonoids to microbial surfaces was further increased by the cationic polyelectrolytes ligands poly-L-histidine, chlorhexidine and Copaxone®. This phenomenon was confirmed visually, by the FRAP, DPPH, cyclic voltammetry, Folin-Ciocalteu as well as by luminol-dependent chemiluminescence techniques employed to assay TOSC. The possibility is considered that clinically, microbial cells in the oral cavity and in the gastro intestinal tract, complexed with antioxidant polyphenols from nutrients and with cationic ligands, might increase the protection of mammalian cells against damage induced by excessive generation of reactive oxygen species during infections and inflammation.

Hepatocyte-specific distribution of catalase and its inhibitory effect on hepatic ischemia/reperfusion injury in mice

To explore the possibility of using catalase for the treatment of reactive oxygen species (ROS)-mediated injuries, the pharmacokinetics of bovine liver catalase (CAT) labeled with 111In was investigated in mice. At a dose of 0.1 mg/kg, more than 70% of 111In-CAT was recovered in the liver within 10 min after intravenous injection. In addition, 111In-CAT was predominantly recovered from the parenchymal cells (PC) in the liver. Increasing the dose retarded the hepatic uptake of 111In-CAT, suggesting saturation of the uptake process. This cell-specific uptake could not be inhibited by coadministration of various compounds which are known to be taken up by liver PC, indicating that the uptake mechanism of CAT by PC is very specific to this compound. The preventive effect of CAT on a hepatic ischemia/reperfusion injury was examined in mice by measuring the GOT and GPT levels in plasma. A bolus injection of CAT at 5 min prior to the reperfusion attenuated the increase in the levels of these indicators in a dose-dependent manner. These results suggest that catalase can be used for various hepatic injuries caused by ROS.

Histidine-proline-rich glycoprotein as a plasma pH sensor. Modulation of its interaction with glycosaminoglycans by ph and metals

The middle domain of plasma histidine-proline-rich glycoprotein (HPRG) contains unusual tandem pentapeptide repeats (consensus G(H/P)(H/P)PH) and binds heparin and transition metals. Unlike other proteins that interact with heparin via lysine or arginine residues, HPRG relies exclusively on histidine residues for this interaction. To assess the consequences of this unusual requirement, we have studied the interaction between human plasma HPRG and immobilized glycosaminoglycans (GAGs) using resonant mirror biosensor techniques. HPRG binding to immobilized heparin was strikingly pH-sensitive, producing a titration curve with a midpoint at pH 6.8. There was little binding of HPRG to heparin at physiological pH in the absence of metals, but the interaction was promoted by nanomolar concentrations of free zinc and copper, and its pH dependence was shifted toward alkaline pH by zinc. The affinity of HPRG for various GAGs measured in a competition assay decreased in the following order: heparin > dermatan sulfate > heparan sulfate > chondroitin sulfate A. Binding of HPRG to immobilized dermatan sulfate had a midpoint at pH 6.5, was less influenced by zinc, and exhibited cooperativity. Importantly, plasminogen interacted specifically with GAG-bound HPRG. We propose that HPRG is a physiological pH sensor, interacting with negatively charged GAGs on cell surfaces only when it acquires a net positive charge by protonation and/or metal binding. This provides a mechanism to regulate the function of HPRG (the local pH) and rationalizes the role of its unique, conserved histidine-proline-rich domain. Thus, under conditions of local acidosis (e.g. ischemia or hypoxia), HPRG can co-immobilize plasminogen at the cell surface as well as compete for heparin with other proteins such as antithrombin.

Prevention and induction of oxidative damage in E. coli cells by cationized proteins

The successful prevention of oxidative damage in E. coli B cells by cationized catalase (cCAT), and the induction of oxidative stress by cationized glucose oxidase (cGO) and cationized superoxide dismutase (cSOD) is presented in this study. Exposure of E. coli cells to hydrogen peroxide and hydroxyl radical resulted in a rapid killing of the cells. Measurements of biochemical markers: cellular potassium levels and uptake and accumulation of leucin indicated membrane damage in some of the oxidants employed. Following incubation with native CAT or SOD, the cells were washed and exposed to oxidative stress. The results of this procedure did not protect the cells against the oxidative damage. In contrast, incubation of the cells with pretreated CAT with poly-L-histidine, followed by washing of the cells and the subsequent introduction of oxidative stress inducers, resulted in a pronounced protection of the cells against the oxidative stress. Employment of pretreated SOD, and exposure, after washing the cells, to oxidative stress, resulted in an enhancement of the oxidative damage in some cases. Exposure of the cells to cGO resulted in a marked killing of the cells as compared to the untreated enzyme. The use of E. coli cells as a model system for studying the effect of cationized enzymes on cell surfaces is discussed.

Protection of the rat jejunal mucosa against oxidative injury by cationized superoxide dismutase

The purpose of the present study was to investigate whether local prevention of luminal superoxide-mediated biological damage in the rat jejunal mucosa could be achieved by use of cationized superoxide dismutase (SOD). Mucosal damage was induced in a closed circulating intestinal loop of the rat either by a mixture of xanthine and xanthine oxidase or by a mixture of xanthine, xanthine oxidase, and chelated ferrous sulfate. Thus, superoxide radicals or hydroxyl (OH.) radicals were induced. The mucosal activity of intracellular lactate dehydrogenase and the levels of cellular potassium ions were used to quantitatively characterize the tissue damage. SOD was cationized by reaction with N,N'-dimethyl-1,3-propanediamine to yield a soluble product or with polyhistidine to yield an insoluble product. The cationization yield and the activity of the modified enzymes were assessed, and the ability of the cationized enzymes to protect the rat jejunal mucosa against oxidative stress was studied. It was found that cationized SOD provided significant protection against mucosal damage induced by OH. radicals. The findings indicate the potential role of cationized enzymes in the local protection of the intestinal epithelium against pathological processes associated with oxidative stress.

Killing of endothelial cells and release of arachidonic acid. Synergistic effects among hydrogen peroxide, membrane-damaging agents, cationic substances, and proteinases and their modulation by inhibitors

51Chromium-labeled rat pulmonary artery endothelial cells (EC) cultivated in MEM medium were killed, in a synergistic manner, by mixtures of subtoxic amounts of glucose oxidase-generated H2O2 and subtoxic amounts of the following agents: the cationic substances, nuclear histone, defensins, lysozyme, poly-L-arginine, spermine, pancreatic ribonuclease, polymyxin B, chlorhexidine, cetyltrimethyl ammonium bromide, as well as by the membrane-damaging agents phospholipases A2 (PLA2) and C (PLC), lysolecithin (LL), and by streptolysin S (SLS) of group A streptococci. Cytotoxicity induced by such mixtures was further enhanced by subtoxic amounts either of trypsin or of elastase. Glucose-oxidase cationized by complexing to poly-L-histidine proved an excellent deliverer of membrane-directed H2O2 capable of enhancing EC killing by other agonists. EC treated with rabbit anti-streptococcal IgG were also killed, in a synergistic manner, by H2O2, suggesting the presence in the IgG preparation of cross-reactive antibodies. Killing of EC by the various mixtures of agonists was strongly inhibited by scavengers of hydrogen peroxide (catalase, dimethylthiourea, MnCl2), by soybean trypsin inhibitor, by polyanions, as well as by putative inhibitors of phospholipases. Strong inhibition of cell killing was also observed with tannic acid and by extracts of tea, but less so by serum. On the other hand, neither deferoxamine, HClO, TNF, nor GTP gamma S had any modulating effects on the synergistic cell killing. EC exposed either to 6-deoxyglucose, puromycin, or triflupromazin became highly susceptible to killing by mixtures of hydrogen peroxide with several of the membrane-damaging agents. While maximal synergistic EC killing was achieved by mixtures of H2O2 with either PLA2, PLC, LL, or with SLS, a very substantial release of [3H]arachidonic acid (AA), PGE2, and 6-keto-PGF occurred only if a proteinase was also added to the mixture of agonists. The release of AA from EC was markedly inhibited either by scavengers of H2O2, by proteinase inhibitors, by cationic agents, by HClO, by tannic acid, and by quinacrin. We suggest that cellular injury induced in inflammatory and infectious sites might be the result of synergistic effects among leukocyte-derived oxidants, lysosomal hydrolases, cytotoxic cationic polypeptides, proteinases, and microbial toxins, which might be present in exudates. These "cocktails" not only kill cells, but also solubilize AA and several of its metabolites. However, AA release by the various agonists can be also achieved following attack by leukocyte-derived agonists on dead cells. It is proposed that treatment by "cocktails" of adequate antagonists might be beneficial to protect against cellular injury in vivo.

Synergism among oxidants, proteinases, phospholipases, microbial hemolysins, cationic proteins, and cytokines

A striking similarity exists between the pathogenetic properties of group A streptococci and those of activated mammalian professional phagocytes (neutrophils, macrophages). Both types of cells are endowed by the ability to adhere to target cells; to elaborate oxidants, hydrolases, and membrane-active agents (hemolysins, phospholipases); and to freely invade tissues and destroy cells. From the evolutionary point of view, streptococci might justifiably be considered the forefathers of "modern" leukocytes. Our earlier findings that synergy between a streptococcal hemolysin (streptolysin S, SLS) and a streptococcal thiol-dependent proteinase and between cytotoxic antibodies+complement and streptokinase-activated plasmin readily killed tumor cells, led us to hypothesize that by analogy to the pathogenetic mechanisms of streptococci, the mechanisms of tissue destruction initiated by activated leukocytes in inflammatory sites, as well as in tissues undergoing episodes of ischemia and reperfusion, might also be the result of the synergistic effects among leukocyte-derived oxidants, phospholipases, proteinases, cytokines, and cationic proteins. The current report extends our previous synergy studies with endothelial cells to two additional cell types--monkey kidney epithelial cells and rat beating heart cells. Monolayers of 51Cr-labeled cells that had been treated by combinations of sublytic amounts of hydrogen peroxide (generated either by glucose oxidase, xanthine-xanthine oxidase, or by paraquat) and with sublytic amounts of a variety of membrane-active agents (streptolysin S, phospholipases A2 and C, lysophosphatides, histone, chlorhexidine) were killed in a synergistic manner (double synergy). Crystalline trypsin markedly enhanced cell killing by combinations of oxidant and the membrane-active agents (triple synergy). Injury to the cells was characterized by the appearance of large membrane blebs that detached from the cells and floated freely in the media, looking like lipid droplets. Cytotoxicity induced by the various combinations of agonists was depressed, to a large extent, by scavengers of hydrogen peroxide (catalase, dimethyl thiourea, and by Mn2+) but not by SOD or by deferoxamine. When cationic agents were employed together with hydrogen peroxide, polyanions (heparin, polyanethole sulfonate) were also found to inhibit cell killing. It is proposed that in order to effectively combat the deleterious toxic effects of leukocyte-derived agonists on cells and tissues, antagonistic "cocktails" comprised of cationized catalase, cationized SOD, dimethylthiourea, Mn(2+)+glycine, proteinase inhibitors, putative inhibitors of phospholipases, and polyanions might be concocted. The current literature on synergistic phenomena pertaining to mechanisms of cell and tissue injury in inflammation is selectively reviewed.

Cationic polyelectrolytes: potent opsonic agents which activate the respiratory burst in leukocytes

Bacteria and yeasts which are "opsonized" with cationic polyelectrolytes (poly-L-arginine, poly-L-histidine and arginine-rich histone) are avidly endocytosed by both "professional" and "non-professional" phagocytes. The cationized particles also strongly activate the respiratory burst in neutrophils and in macrophages leading to the generation of chemiluminescence, superoxide and hydrogen peroxide. On the other hand, lysine and ornithine-rich polymers are poor opsonic agents. Poly L-arginine is unique in its capacity to act synergistically with lectins, with chemotactic peptides and with cytochalasin B to generate large amounts of chemiluminescence and superoxide in human neutrophils. Unlike polyarginine, polyhistidine, in the absence of carrier particles, is one of the most potent stimulators of superoxide generations, known. Neutrophils treated with cetyltrimethylammonium bromide fail to generate superoxide, but generate strong luminol-dependent chemiluminescence which is totally inhibited by sodium azide and by thiourea. Neutrophils injured by cytolytic agents (saponin, digitonin, lysolecithin) lose their chemiluminescence and superoxide-generating capacities upon stimulation by a variety of ligands. These activities are however regained by the addition of NADPH. Lysolecithin can replace polyarginine in a "cocktail" also containing lectins and cytochalasin B, which strongly activate the respiratory burst. This suggests that polyarginine acts both as a cytolytic agent and as a ligand. Arginine and histidine-rich polyelectrolytes enhance the pathogenic effects of immune complexes in vivo (reversed Arthus phenomenon) presumably by "glueing" them to tissues. Polyhistidine complexed to catalase or to superoxide dismutase, markedly enhances their efficiency as antioxidants. On the other hand polyhistidine complexed to glucose oxidase markedly enhances injury to endothelial cells suggesting that the close association of the cationized enzyme with the plasma membrane facilitates the interaction of hydrogen peroxide with the targets. A variety of cationic agents (histone, polyarginine, polyhistidine, polymyxin B) and membrane-active agents (lysophosphatides, microbial hemolysins) act synergistically with glucose oxidase or with reagent hydrogen peroxide to kill target cells. The mechanisms by which arginine- and histidine-rich polyelectrolytes activate the respiratory burst in neutrophils might involve interaction with G-proteins, the activation of arachidonic acid metabolism and phospholipase A2, or the interaction with myeloperoxidase. Naturally-occurring cationic proteins might modulate several important functions of leukocytes and the course and outcome of the inflammatory process.