The role of cationized catalase and cationized glucose oxidase in mucosal oxidative damage induced in the rat jejunum

Polyphenols by Generating H2O2, Affect Cell Redox Signaling, Inhibit PTPs and Activate Nrf2 Axis for Adaptation and Cell Surviving: In Vitro, In Vivo and Human Health

Human health benefits from different polyphenols molecules consumption in the diet, derived mainly by their common activities in the gastrointestinal tract and at the level of blood micro-capillary. In the stomach, intestine and colon, polyphenols act as reducing agents preventing lipid peroxidation, generation and absorption of AGEs/ALEs (advanced glycation end products/advanced lipid oxidation end products) and postprandial oxidative stress. The low absorption of polyphenols in blood does not support their activity as antioxidants and their mechanism of activity is not fully understood. The results are from in vitro, animal and human studies, detected by relevant oxidative stress markers. The review carries evidences that polyphenols, by generating H₂O₂ at nM concentration, exogenous to cells and organs, act as activators of signaling factors increasing cell Eustress. When polyphenols attain high concentration in the blood system, they generate H₂O₂ at µM concentration, acting as cytotoxic agents and Distress. Pre-treatment of cells or organisms with polyphenols, by generating H₂O₂ at low levels, inhibits cellular PTPs (protein tyrosine phosphatases), inducing cell signaling through transcription of the Nrf2 (nuclear factor erythroid 2-related factor 2) axis of adaptation and protection to oxidation stress. Polyphenols ingestion at the right amount and time during the meal acts synergistically at the level of the gastrointestinal tract (GIT) and blood system, for keeping the redox homeostasis in our organism and better balancing human health.

Amination of enzymes to improve biocatalyst performance: coupling genetic modification and physicochemical tools

Improvement of the features of an enzyme is in many instances a pre-requisite for the industrial implementation of these exceedingly interesting biocatalysts.

Exploiting protein cationization techniques in future drug development

The development of a method for the efficient intracellular delivery of inherently non-permeable proteins is needed for manipulation of cellular phenotypes or the discovery of protein-based drugs. It has been demonstrated that proteins artificially cationized by chemical conjugation show efficient intracellular delivery via adsorptive-mediated endocytosis and then can exert their biological activity in cells. Studies have also revealed that cationic peptides known as cell-penetrating peptides (CPPs) provide a means to deliver molecules into mammalian cells. Although the internalization mechanisms remain controversial, it is now becoming clear that the main port of entry into cells by CPPs also involves adsorptive-mediated endocytosis rather than the direct penetration of the plasma membrane. As the mammalian cell membrane possesses an abundance of negatively charged glycoproteins and glycosphingolipids, cationization of proteins is a reasonable choice to endow them with the ability for intracellular delivery. Cationization of proteins is usually accompanied by drastic changes in protein properties, structure and biological activities. Recently developed sophisticated protein chemistry can minimize these side effects. Therefore, protein cationization techniques will hopefully prove to be powerful tools for innovative research and drug discovery. In this review, techniques for cationization of proteins and their intracellular delivery, as well as some of their potential therapeutic applications, are discussed.

Polyphenols activate Nrf2 in astrocytes via H2O2, semiquinones, and quinones

Polyphenols, which occur both in edible plants and in foodstuff, have been reported to exert a wide range of health effects; however, the mechanism of action of these molecules is not fully understood. One important cellular pathway affected by polyphenols is the activation of the transcription factor Nrf2 via the electrophile response element, which mediates generation of phase 2 detoxifying enzymes. Our study found that Nrf2 nuclear translocation and the activity of NAD(P)H quinone oxidoreductase (NQO1) were increased significantly after treatment of astrocytes with tert-butylhydroquinone (tBHQ), resveratrol, or curcumin, at 20-50μM. Incubation of tBHQ, resveratrol, and curcumin in the growth medium in the absence of astrocytes caused the accumulation of H(2)O(2). Treatment of cells with either glutathione or metmyoglobin was found to decrease Nrf2 translocation and NQO1 activity induced by polyphenols by up to 40 and 60%, respectively. Addition of both glutathione and metmyoglobin to growth medium decreased Nrf2 translocation and NQO1 activity by up to 100 and 80%, respectively. In conclusion, because metmyoglobin, in the presence of polyphenols and glutathione, is known to interact with H(2)O(2), semiquinones, and quinones, the up-regulation of the antioxidant defense of the cells through activation of the Nrf2 transcription factor, paradoxically, occurs via the generation of H(2)O(2) and polyphenol-oxidized species generated from the exogenous microenvironment of the cells.

Enhanced transferrin receptor expression by proinflammatory cytokines in enterocytes as a means for local delivery of drugs to inflamed gut mucosa

Therapeutic intervention in inflammatory bowel diseases (IBDs) is often associated with adverse effects related to drug distribution into non-diseased tissues, a situation which attracts a rational design of a targeted treatment confined to the inflamed mucosa. Upon activation of immune cells, transferrin receptor (TfR) expression increases at their surface. Because TfR is expressed in all cell types we hypothesized that its cell surface levels are regulated also in enterocytes. We, therefore, compared TfR expression in healthy and inflamed human colonic mucosa, as well as healthy and inflamed colonic mucosa of the DNBS-induced rat model. TfR expression was elevated in the colonic mucosa of IBD patients in both the basolateral and apical membranes of the enterocytes. Increased TfR expression was also observed in colonocytes of the induced colitis rats. To explore the underlying mechanism CaCo-2 cells were treated with various proinflammatory cytokines, which increased both TfR expression and transferrin cellular uptake in a mechanism that did not involve hyper proliferation. These findings were then exploited for the design of targetable carrier towards inflamed regions of the colon. Anti-TfR antibodies were conjugated to nano-liposomes. As expected, iron-starved Caco-2 cells internalized anti-TfR immunoliposomes better than controls. Ex vivo binding studies to inflamed mucosa showed that the anti-TfR immunoliposomes accumulated significantly better in the mucosa of DNBS-induced rats than the accumulation of non-specific immunoliposomes. It is concluded that targeting mucosal inflammation can be accomplished by nano-liposomes decorated with anti-TfR due to inflammation-dependent, apical, elevated expression of the receptor.

Catalase delivery for inhibiting ROS-mediated tissue injury and tumor metastasis

Reactive oxygen species (ROS) have been suggested to be involved in a variety of human diseases. Catalase, an enzyme degrading hydrogen peroxide, can be used as a therapeutic agent for such diseases, but its successful application will depend on the distribution of the enzyme to the sites where ROS are generated. Chemical modification techniques have been used to control the tissue distribution of catalase, and delivery to hepatocytes (galactosylation), liver nonparenchymal cells (mannosylation or succinylation), kidney (cationization) and the blood pool (PEGylation) has been achieved. The effectiveness of catalase delivery has been demonstrated in animal models for hepatic ischemia/reperfusion injury, chemical-induced tissue injuries and tumor metastasis to the liver, lung and peritoneal organs. Significant inhibition was observed in the ROS-mediated oxidative tissue damages and ROS-mediated upregulation of expression of genes responsible for recruitment of inflammatory cells and for metastatic growth of tumor cells. Because oxygen plays a fundamental key role in our life and oxidative stress is implicated in a wide variety of human diseases, catalase delivery could have wide application in the near future.

Local treatment of experimental colitis in the rat by negatively charged liposomes of catalase, TMN and SOD

Superoxide dismutase (SOD), 4-amino tempol (tempamine, denoted as TMN) and catalase were encapsulated into negatively charged liposomes. The activity of the antioxidants against dinitrobenzenesulfonic acid (DNBS) induced colitis was tested in the rat and compared to the anti-inflammatory activity of the native enzymes and free TMN. Inflammation severity was assessed by monitoring tissue myeloperoxidase (MPO) activity, thiobarbituric acid reactive species (TBARS) amounts and by comparing the weights of the dissected colons. In all cases, the liposomal preparations of the antioxidants were more effective than the free molecules in the treatment of the experimental colitis, probably due to the attachment of the negatively charged liposomes, and consequently a longer residence time and better uptake of the antioxidants to the inflamed mucosa. This study suggests that low and high molecular weight antioxidants delivered via anionic liposomes can serve as a novel targeted therapy to treat chronic inflammation of the colonic epithelium, such as ulcerative colitis.

Oxidative stress reduces transintestinal transports and (Na+, K+) -ATPase activity in rat jejunum

Because oxidative stress is a component of gastrointestinal injury, we investigated the effect of H(2)O(2) on transintestinal transport using isolated rat jejunum incubated in vitro. Millimolar concentrations of H(2)O(2) inhibited all the tested parameters without inducing any cytotoxic effect. Electrophysiological experiments indicated that H(2)O(2) decreases significantly both short circuit current and transepithelial electrical potential difference without affecting transepithelial resistance. The possibility that H(2)O(2) could influence (Na+, K+) -ATPase activity was explored using isolated basolateral membranes. Besides H(2)O(2), free radicals (O(2)(*-), HO*) were generated using different iron-dependent and independent systems; (Na+, K+) -ATPase activity was inhibited after membrane exposure to all ROS tested. The inhibition was prevented by allopurinol, superoxide dismutase or desferrioxamine. Western blot analysis showed a decreased expression of the alpha(1)-subunit of (Na+, K+) -ATPase. We conclude that H(2)O(2) may be a modulator of jejunal ion and water transport by multiple mechanisms, among which a significant inhibition of the basolateral (Na+, K+) -ATPase.

Improved anti-oxidant activity of superoxide dismutase by direct chemical modification

Chemically modified derivatives of superoxide dismutase (SOD), i.e., cationized (Cat-SOD) and mannosylated SOD (Man-SOD), were designed to improve an ability of SOD to suppress reactive oxygen species (ROS)-mediated injury in the alveolar epithelium. To evaluate their effectiveness, an in vitro model of paraquat poisoning was developed with primary cultured rabbit alveolar type II cells. Despite a 5.6-fold higher cellular association than native SOD, Man-SOD did not protect cell injury due to paraquat following evaluation by MTT assay. In contrast, Cat-SOD exhibited a 140-fold higher cellular association than native SOD and greatly suppressed paraquat-induced cell injury, as well as lipid peroxidation. Incubation with 300 U/ml Cat-SOD for 2 h increased intracellular SOD activity 5.3-fold. The increase in intracellular SOD activity was significantly inhibited in the presence of cytochalasin B, an endocytosis inhibitor. Internalization of Cat-SOD was also confirmed by confocal laser scanning fluorescein microscopy. In addition, the protective effect of Cat-SOD against paraquat-induced cell injury was completely abolished by the presence of cytochalasin B. In conclusion, this study demonstrated that cationization of SOD greatly enhances its intracellular delivery and, as a consequence, produces a significant protective effect against ROS-mediated injury of the alveolar epithelium.

Liver targeting of catalase by cationization for prevention of acute liver failure in mice

To achieve hepatic delivery of CAT for the prevention of CCl4-induced acute liver failure in mice, two types of cationized CAT derivatives, HMD- and ED-conjugated CAT, were developed. Slight structural changes occurred during cationization and the number of increased free amino groups was 3.1 in HMD-CAT and 13.6 in ED-CAT. 111In-cationized CAT derivatives showed an increased binding to HepG2 cells, and were rapidly taken up by the liver. H2O2-induced cytotoxicity in HepG2 cells was significantly prevented by preincubation of the cells with cationized CAT derivatives. A bolus intravenous injection of the cationized CAT derivatives reduced the hepatotoxicity induced by CCl4 in mice. The ED-CAT, which showed more rapid and greater binding to the liver than the HMD-CAT, exhibited more beneficial effects as far as all the parameters examined (serum GOT, GPT, LDH and hepatic GSH) were concerned, suggesting that a high degree of cationization is effective in delivering CAT to the liver to prevent CCl4-induced hepatotoxicity. These results suggest that cationized CAT derivatives are effective in preventing acute liver failure, and ED-based cationization is a suitable method for developing liver-targetable cationized CAT derivatives, because it provides CAT with a high degree of cationization and a high remaining enzymatic activity.

Targeting normal and neoplastic tissues in the rat jejunum and colon with boronated, cationic acrylamide copolymers

A series of boronated cationic copolymers, composed of different ratios of acrylamide, N-acryloyl-3-aminophenylboronic acid and N-acryloyl-diaminoethane (the cationic moiety), were prepared with the intention of localizing boron neutron capture therapy (BNCT) in experimentally induced polyps on the luminal side of the gut of the rat. The goals of this study were to: (a) test the effect of cationization of the boronated copolymers on their uptake by polyps and normal adjacent epithelium; (b) compare the whole rat body distribution of aminophenylboronic acid (APB) and polymeric APB after local application; (c) measure the effect of micro-environmental parameters such as pH, the presence of mucin and cations on the interaction between the APB-copolymers and the epithelium of the rat intestines. Direct analysis of tissue boron levels showed that polymeric APB-uptake was higher in the colonic polyps than in the surrounding normal tissues. Free APB, however, was found in similar quantities in both. When tested in the normal jejunum and colon of the rat, polymeric APB uptake was directly proportional to the molar content of the cationic monomer in the copolymers. The presence of magnesium ions, free boron cationic monomer and mucin interfered with this uptake in a concentration-dependent manner. The uptake was pH-independent at pH 5, 7 and 10. APB accumulation in the colon polyps was inversely proportional to the cationic monomer content in the copolymers, suggesting an increased amount of mucus around the polyps, which probably impeded the electrostatic attachment of the polymer to the malignant tissue. The use polymeric APB for targeting BNCT in perioperative treatment of colorectal carcinoma is suggested, especially in the cases of microscopic residual disease after curative resection.

Changes in reducing power profile of gastric juice in patients with active duodenal ulcer

Reactive oxygen species have been postulated to play a role in the pathogenesis of mucosal GI injury and in peptic ulcer disease (PUD). The low molecular weight antioxidants (LMWA) group plays an important role in the defense mechanism of the GI tract against oxidative damage, and is a major component of the reducing capacity of biological tissues and fluids. We hypothesized that altered gastric LMWA anti oxidative status might play a role in the pathogenesis of upper GI disorders such as PUD and could be evaluated by measuring gastric juice reducing power. The aim of the present study was to determine, by cyclic voltammetry, changes in the overall antioxidant activity of the gastric juice in active duodenal ulcer (DU) obtained during upper endoscopy from patients as compared with normal subjects. The results show that in 28/37 (76%) of the control subjects, gastric juice demonstrated a reducing power of at least two anodic waves indicating at least two different LMWA groups. Three or more anodic waves were recorded in 12 normal subject (32%). In contrast, 16/25 (64%) of gastric juice samples obtained from active DU patients exhibited only one anodic wave usually at a high potential (>900 mV). These results imply that gastric juice normally possesses a reducing power profile that can be determined by cyclic voltammetry. This profile is significantly changed in untreated DU disease. These changes in active DU may indicate decreased gastric antioxidant activity reflecting reduced mucosal protection that leading to increased susceptibility of the gastro-duodenum to injury.

Cationic charge-dependent hepatic delivery of amidated serum albumin

To obtain a quantitative correlation between the physicochemical properties of amidated bovine serum albumin (BSA) and their tissue distribution characteristics for the development of targeted delivery of proteins, BSA was amidated with hexamethylenediamine (HMD) or ethylenediamine (ED) to obtain cationized BSAs. Their structural changes were examined by spectroscopic and electrophoretic techniques then their tissue distribution was studied in mice. Circular dichroism (CD) and fluorescence measurements showed that spectroscopic changes occurred as the number of free NH2 groups increased. Capillary electrophoresis revealed a linear relationship between the mobility and the increased number of free NH2 groups. 111In-cationized BSAs were rapidly taken up by liver, but HMD-BSA showed a faster uptake than ED-BSA with a similar number of free NH2 groups, suggesting that the diamine reagent with a longer carboxyl side chain results in more efficient hepatic targeting. The hepatic uptake clearance (CL(liver)) of both derivatives increased significantly with a decrease in electrophoretic mobility (mu(ep)) towards the anode and reached a plateau at low electrophoretic mobility. The electrophoretic mobility is an appropriate indicator of the degree of amidation, which was closely correlated with the hepatic uptake clearance. The correlation between the mobility and the clearance shows that a low degree of amidation is sufficient for efficient hepatic targeting of proteins.

Local prevention of oxidative stress in the intestinal epithelium of the rat by adhesive liposomes of superoxide dismutase and tempamine

The purpose of the present study was to investigate whether the local prevention of luminal superoxide-mediated biological damage in the rat jejunal mucosa could be achieved by liposomal superoxide dismutase (SOD) and the SOD mimic tempamine (TMN). Cationic liposomes loaded with either SOD or TMN were perfused in the rat jejunum prior to the induction of oxidative insult. Reactive hydroxyl radicals were generated in situ in a closed circulating intestinal loop of the rat from the reaction between hypoxanthine and xanthine oxidase in the presence of chelated ferrous sulfate. Mucosal activity of lactate dehydrogenase and levels of potassium ions were used to quantify the tissue damage. Intracellular uptake and locality of SOD were examined in HT-29 cells. The intestinal uptake of SOD and TMN was further measured by using rat colon sacs. Entrapment in cationic liposomes was found to significantly enhance the antioxidant effect of SOD and TMN against the induced oxidative damage in the jejunal mucosa, compared with their free forms. The effect was found to be local and was caused by the increased mucosal adhesion of the liposomes. The cationic liposomes also triggered SOD uptake into the HT-29 cell line. It is concluded that the increased residence time of the cationic liposomes of SOD and TMN in the jejunal mucosa resulted in a local effect against oxidative injury. This local protection may be exploited for drug delivery purposes.

Antioxidant and prooxidant effects of phenolics on pancreatic beta-cells in vitro

A number of natural phenolic compounds display antioxidant and cell protective effects in cell culture models, yet in some studies show prooxidant and cytotoxic effects. Pancreatic beta-cells have been reported to exhibit particular sensitivity to oxidative stress, a factor that may contribute to the impaired beta-cell function characteristic of diabetes. The aim of this study was to examine the potential of natural phenolics to protect cultured pancreatic beta-cells (betaTC1 and HIT) from H(2)O(2) oxidative stress. Exposure of cells to H(2)O(2) led to significant proliferation inhibition. Contrary to what one should expect, simultaneous exposure to H(2)O(2) and the phenolics, quercetin (10-100 microM), catechin (50-500 microM), or ascorbic acid (100-1000 microM), led to amplification of proliferation inhibition. At higher concentrations, these compounds inhibited proliferation, even in the absence of added H(2)O(2). This prooxidant effect is attributable to the generation of H(2)O(2) through interaction of the added phenolic compounds with as yet undefined componenets of the culture media. On the other hand, inclusion of metmyoglobin (30 microM) in the culture medium significantly reduced the prooxidant impact of the phenolics. Under these conditions, quercetin and catechin significantly protected the cells against oxidative stress when these components were present during the stress period. Furthermore, significant cell protection was observed upon preincubation of cells with chrysin, quercetin, catechin, or caffeic acid (50 microM, each) prior to application of oxidative stress. It is concluded that provided artifactual prooxidant effects are avoided, preincubation of beta-cells with relatively hydrophobic natural phenolics can confer protection against oxidative stress.

Oxidation of biological systems: oxidative stress phenomena, antioxidants, redox reactions, and methods for their quantification

Reactive oxygen species (ROS) and other radicals are involved in a variety of biological phenomena, such as mutation, carcinogenesis, degenerative and other diseases, inflammation, aging, and development. ROS are well recognized for playing a dual role as deleterious and beneficial species. The objectives of this review are to describe oxidative stress phenomena, terminology, definitions, and basic chemical characteristics of the species involved; examine the biological targets susceptible to oxidation and the defense mechanisms of the organism against these reactive metabolites; and analyze methodologies, including immunohistochemical markers, used in toxicological pathology in the visualization of oxidative stress phenomena. Direct detection of ROS and other free radicals is difficult, because these molecules are short-lived and highly reactive in a nonspecific manner. Ongoing oxidative damage is, thus, generally analyzed by measurement of secondary products including derivatives of amino acids, nuclei acids, and lipid peroxidation. Attention has been focused on electrochemical methods based on voltammetry measurements for evaluating the total reducing power of biological fluids and tissues. This approach can function as a tool to assess the antioxidant-reducing profile of a biological site and follow changes in pathological situations. This review thus includes different topics essential for understanding oxidative stress phenomena and provides tools for those intending to conduct study and research in this field.

Electrical charge on protein regulates its absorption from the rat small intestine

The effect of the electrical charge on the intestinal absorption of a protein was studied in normal adult rats. Chicken egg lysozyme (Lyz), a basic protein with a molecular weight of 14,300, was selected and several techniques for chemical modification were applied. Then the intestinal absorption of Lyz derivatives was evaluated by measuring the radioactivity in plasma and tissues, after the administration of an (111)In-labeled derivative to an in situ closed loop of the jejunum. After the administration of (111)In-Lyz, the level of radioactivity in plasma was comparable with the lytic activity of Lyz, supporting the fact that the radioactivity represents intact Lyz. (111)In-cationized Lyz showed a 2-3 times higher level of radioactivity in plasma, whereas the radioactivity of (111)In-anionized Lyz was much lower. The absorption rate of (111)In-Lyz derivatives calculated by a deconvolution method was correlated for the strength of their positive net charge. A similar relationship was observed using superoxide dismutase. These findings indicate that the intestinal absorption of a protein is, at least partially, determined by its electrical charge.

Betalains--a new class of dietary cationized antioxidants

Antioxidant nutrients from fruits and vegetables are believed to be a class of compounds that exert their effects in humans by preventing oxidative processes which contribute to the onset of several degenerative diseases. This study found a new class of dietary cationized antioxidants in red beets (Beta vulgaris L.). These antioxidants are betalains, and the major one, betanin, is a betanidin 5-O-beta-glucoside. Linoleate peroxidation by cytochrome c was inhibited by betanin, betanidin, catechin, and alpha-tocopherol with IC(50) values of 0.4, 0.8, 1.2, and 5 microM, respectively. In addition, a relatively low concentration of betanin was found to inhibit lipid peroxidation of membranes or linoleate emulsion catalyzed by the "free iron" redox cycle, H(2)O(2)-activated metmyoglobin, or lipoxygenase. The IC(50) inhibition of H(2)O(2)-activated metmyoglobin catalysis of low-density lipoprotein oxidation by betanin was <2.5 microM and better than that of catechin. Betanin and betanidin at very small concentrations were found to inhibit lipid peroxidation and heme decomposition. During this reaction, betanidin was bleached completely, but betanin remained unchanged in its absorption. This difference seems to derive from differing mechanisms of protection by these two compounds. The high affinity of betanin and betanidin for membranes was demonstrated by determining the rate of migration of the compounds through a dialysis tube. Betanin bioavailability in humans was demonstrated with four volunteers who consumed 300 mL of red beet juice, containing 120 mg of the antioxidant. The betacyanins were absorbed from the gut and identified in urine after 2-4 h. The calculated amount of betacyanins found in the urine was 0.5-0.9% of that ingested. Red beet products used regularly in the diet may provide protection against certain oxidative stress-related disorders in humans.

Preparation of potent cytotoxic ribonucleases by cationization: enhanced cellular uptake and decreased interaction with ribonuclease inhibitor by chemical modification of carboxyl groups

Carboxyl groups of bovine RNase A were amidated with ethylenediamine (to convert negative charges of carboxylate anions to positive ones), 2-aminoethanol (to eliminate negative charges), and taurine (to keep negative charges), respectively, by a carbodiimide reaction. Human RNase 1 was also modified with ethylenediamine. Surprisingly, the modified RNases were all cytotoxic toward 3T3-SV-40 cells despite their decreased ribonucleolytic activity. However, their enzymatic activity was not completely eliminated by the presence of excess cytosolic RNase inhibitor (RI). As for native RNase A and RNase 1 which were not cytotoxic, they were completely inactivated by RI. More interestingly, within the cytotoxic RNase derivatives, cytotoxicity correlated well with the net positive charge. RNase 1 and RNase A modified with ethylenediamine were more cytotoxic than naturally occurring cytotoxic bovine seminal RNase. An experiment using the fluorescence-labeled RNase derivatives indicated that the more cationic RNases were more efficiently adsorbed to the cells. Thus, it is suggested that the modification of carboxyl groups could change complementarity of RNase to RI and as a result endow RNase cytotoxicity and that cationization enhances the efficiency of cellular uptake of RNase so as to strengthen its cytotoxicity. The finding that an extracellular human enzyme such as RNase 1 could be effectively internalized into the cell by cationization suggests that cationization is a simple strategy for efficient delivery of a protein into cells and may open the way of the development of new therapeutics.

Skin antioxidants: their role in aging and in oxidative stress--new approaches for their evaluation

Skin is a highly metabolic tissue which possesses the largest surface area in the body and serves as the protective layer for internal organs [1]. Skin is also a major candidate and target of oxidative stress. It is designed to give both physical and biochemical protection, and is equipped with a large number of defense mechanisms. The skin tissue is exposed to a variety of damaging species which originate in the outer environment, in the skin itself, and in various endogenous sources [2, 3]. The structure of skin is quite complex being composed of several layers, each of which plays a specific role and carries out different functions [4]. Each layer is equipped with its own arsenal of defense molecules, and the various systems differ from each other based on the layer's susceptibility to oxidative stress and its function. It is generally agreed that one of the major and important contributions to skin aging, skin disorders and skin diseases results from reactive oxygen species (ROS) [1, 5]. Due to the high occurrence of potential biological targets for oxidative damage, skin is very susceptible to such reactions. For example, skin is rich in lipids, proteins, and DNA, all of which are extremely sensitive to the oxidation process [6-8]. Elucidation of the mechanisms involved in skin oxidation and the examination of the defense systems may contribute to the understanding of skin aging and of the mechanisms involved in the various pathological processes of skin. This review addresses the antioxidant defense mechanism of the skin, the role it plays during the aging process, and the role skin has following exposure to oxidative stresses.

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.

Migration of adhesive and nonadhesive particles in the rat intestine under altered mucus secretion conditions

The migration rate of adhesive (polycarbophil) and nonadhesive (Eudragit RL-100) particles was studied in the small and large intestine of the anesthetized rat under altered mucus secretion conditions accomplished by cholinergic stimulation (a previously developed in situ model which distinctly accounts for the effect of regional changes in mucus turnover rate on mucoadhesion in the digestive tube of the rat). It was found that in the proximal jejunum the relative recovery time (RRT) of adhesive particles, but not nonadhesive particles, was decreased by carbachol stimulation. However, adhesive particles agglomerated a short while after their administration into this organ. In the colon RRT of both adhesive and nonadhesive particles decreased in a similar manner as the mucus secretion increased. It is concluded that, in the rat, interactions between intestinal mucus layer and adhesive and nonadhesive particles are similar. The corresponding similarity in the intestinal transit time for both types of particles raises doubts about the advantage of nonspecific adherence in the design of oral prolonged-release dosage forms.

Protection against oxidative injury and permeability alteration in cultured alveolar epithelium by transferrin-catalase conjugate

The successful prevention of hydrogen peroxide-induced alveolar permeability alterations and cell injury by transferrin-catalase conjugate is described in this study. Permeability alterations and cell injury were induced in cultured alveolar epithelial monolayers by hydrogen peroxide. Transepithelial transport of a permeability marker, [14C] mannitol, and cellular nuclear fluorescence of a membrane integrity indicator, propidium iodide, were used to quantitate epithelial permeability and damage respectively. Hydrogen peroxide (0.1 - 10 mM) induced a dose-dependent increase in both alveolar permeability and cellular damage; however, the oxidant effect on monolayer permeability did not require prior cell damage. Electron spin resonance measurements using the spin trap 5,5-dimethyl-l-pyrroline-N-oxide indicated the formation of hydroxyl radicals in hydrogen peroxide-treated cells. Chelation of the cellular pool of iron by deferoxamine inhibited radical formation and helped protect the cells from oxidative changes. Prior treatment of the cells with catalase (0.1 U-10 U/ml) had minimal protective effects on cell injury and permeability alterations. In contrast, transferrin-catalase conjugate, at the same concentration range, exhibited much improved protective effects on the cells in response to oxidant stress. This enhanced protection was found to correlate well with an increase in cellular uptake of the enzyme conjugate via the transferrin receptor endocytosis pathway. Effective protection by the enzyme conjugate was shown to require both the antioxidant enzyme moiety and the cognate moiety for the cell surface receptor. These findings indicate the potential therapeutic merit of transferrin-catalase conjugate for the treatment of pathological processes in the lung, whenever oxidative stress is involved.

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.

The use of cyclic voltammetry for the evaluation of oxidative damage in biological samples

A method using cyclic voltammetry to evaluate oxidative damage in biological systems is presented. Three biological systems were tested: Escherichia coli cells, the rat jejunal mucosa, and the enzyme, lactate dehydrogenase. Exposure of E. coli cells to oxidative stress resulted in a rapid decrease in their survival and a decrease in their ability to accumulate 14C-leucine. This was accompanied by a significant increase in the oxidation potential of the cells. Similar results were obtained when the rat jejunal mucosa was exposed in a perfusion system to oxidative stress induced by the hydroxyl radical produced by either hydrogen peroxide and ferrous ions or the combination of ascorbic acid and copper ions. Loss of cellular potassium was taken as an indication of damage to the rat jejunum. Exposure of lactate dehydrogenase to oxidative stress induced by hydroxyl and peroxyl radicals also resulted in a significant loss of enzyme activity along with a pronounced change in the cyclic voltammogram of the enzyme. It was concluded that measurement of the oxidation potentials of these biological systems can give an indication of the occurrence of oxidative damage.