Curcumin, an antioxidant and anti-inflammatory agent, induces heme oxygenase-1 and protects endothelial cells against oxidative stress

Curcumin, a widely used spice and coloring agent in food, has been shown to possess potent antioxidant, antitumor promoting and anti-inflammatory properties in vitro and in vivo. The mechanism(s) of such pleiotropic action by this yellow pigment is unknown; whether induction of distinct antioxidant genes contributes to the beneficial activities mediated by curcumin remains to be investigated. In the present study we examined the effect of curcumin on endothelial heme oxygenase-1 (HO-1 or HSP32), an inducible stress protein that degrades heme to the vasoactive molecule carbon monoxide and the antioxidant biliverdin. Exposure of bovine aortic endothelial cells to curcumin (5-15 microM) resulted in both a concentration- and time-dependent increase in HO-1 mRNA, protein expression and heme oxygenase activity. Hypoxia (18 h) also caused a significant (P < 0.05) increase in heme oxygenase activity which was markedly potentiated by the presence of low concentrations of curcumin (5 microM). Interestingly, prolonged incubation (18 h) with curcumin in normoxic or hypoxic conditions resulted in enhanced cellular resistance to oxidative damage; this cytoprotective effect was considerably attenuated by tin protoporphyrin IX, an inhibitor of heme oxygenase activity. In contrast, exposure of cells to curcumin for a period of time insufficient to up-regulate HO-1 (1.5 h) did not prevent oxidant-mediated injury. These data indicate that curcumin is a potent inducer of HO-1 in vascular endothelial cells and that increased heme oxygenase activity is an important component in curcumin-mediated cytoprotection against oxidative stress.

In vivo damage of rat lungs by oxygen metabolites

The intrapulmonary instillation into rat lung of enzymes that generate oxygen metabolites results in acute lung injury. The injection of xanthine oxidase and xanthine produces acute lung injury that, in the presence of superoxide dismutase, but not in the presence of catalase, can be significantly diminished, suggesting that O2- has the capacity to injure the lung. Instillation of a generator of H2O2, namely glucose oxidase, will, in sufficient quantities, produce acute injury that is not neutrophil-dependent. When either a low dose of glucose oxidase alone or lactoperoxidase alone is employed, little lung injury occurs. However, instilling the combination of the two enzymes produces severe, acute injury that can be blocked in a dose-dependent manner by catalase, but not by superoxide dismutase. Purified human leukocytic myeloperoxidase, but not horseradish peroxidase, will substitute for lactoperoxidase in the model of lung injury. The lung damaging effects of these enzymes cannot be attributed to the presence of contaminating proteases. Acute lung injury produced by the instillation of glucose oxidase and lactoperioxidase progresses to interstitial fibrosis. These studies represent a direct application of generators of oxygen metabolites to the in vivo induction of lung injury. The data suggest that rat lung is susceptible to injury by a variety of oxygen metabolites, including O2-, H2O2 and its lactoperoxidase or myeloperoxidase-produced derivatives. The studies also indicate that lung injury produced by oxygen metabolites can result in interstitial pulmonary fibrosis.

Acetylcarnitine induces heme oxygenase in rat astrocytes and protects against oxidative stress: involvement of the transcription factor Nrf2

Efficient functioning of maintenance and repair processes seem to be crucial for both survival and physical quality of life. This is accomplished by a complex network of the so-called longevity assurance processes, under control of several genes termed vitagenes. These include members of the heat shock protein system, and there is now evidence that the heat shock response contributes to establishing a cytoprotective state in a wide variety of human conditions, including inflammation, neurodegenerative disorders, and aging. Among the various heat shock proteins, heme oxygenase-1 has received considerable attention; it has been recently demonstrated that heme oxygenase-1 induction, by generating the vasoactive molecule carbon monoxide and the potent antioxidant bilirubin, could represent a protective system potentially active against brain oxidative injury. Acetyl-L-carnitine is proposed as a therapeutic agent for several neurodegenerative disorders. Accordingly, we report here that treatment of astrocytes with acetyl-L-carnitine induces heme oxygenase-1 in a dose- and time-dependent manner and that this effect was associated with up-regulation of heat shock protein 60 as well as high expression of the redox-sensitive transcription factor Nrf2 in the nuclear fraction of treated cells. In addition, we show that addition of acetyl-L-carnitine to astrocytes, prior to proinflammatory lipopolysaccharide- and interferon-gamma-induced nitrosative stress, prevents changes in mitochondrial respiratory chain complex activity, protein nitrosation and antioxidant status induced by inflammatory cytokine insult. Given the broad cytoprotective properties of the heat shock response, molecules inducing this defense mechanism appear to be possible candidates for novel cytoprotective strategies. Particularly, manipulation of endogenous cellular defense mechanisms via acetyl-L-carnitine may represent an innovative approach to therapeutic intervention in diseases causing tissue damage, such as neurodegeneration. We hypothesize that maintenance or recovery of the activity of vitagenes may delay the aging process and decrease the risk of age-related diseases.

Size-dependent intracellular immunotargeting of therapeutic cargoes into endothelial cells

Cell-selective intracellular targeting is a key element of more specific and safe enzyme, toxin, and gene therapies. Endothelium poorly internalizes certain candidate carriers for vascular immunotargeting, such as antibodies to platelet endothelial cell adhesion molecule 1 (PECAM-1). Conjugation of poorly internalizable antibodies with streptavidin (SA) facilitates the intracellular uptake. Although both small and large (100-nm versus 1000-nm diameter) anti-PECAM/SA-beta galactosidase (SA-beta-gal) conjugates bound selectively to PECAM-expressing cells, only small conjugates showed intracellular accumulation of active beta-gal. To study whether size of the conjugates controls the uptake, a series of anti-PECAM/SA and anti-PECAM/bead conjugates ranging from 80 nm to 5 microm in diameter were produced. Human umbilical vein endothelial cells and PECAM-transfected mesothelioma cells internalized 80- to 350-nm anti-PECAM conjugates, but not conjugates larger than 500 nm. Further, size controls intracellular targeting of active therapeutic cargoes in vitro and in vivo. Small anti-PECAM/DNA conjugates transfected target cells in culture 5-fold more effectively than their large counterpart (350- versus 4200-nm diameter). To evaluate the practical significance of the size-controlled subcellular addressing, we coupled glucose oxidase (GOX) to anti-PECAM and antithrombomodulin. Both types of conjugates had equally high pulmonary uptake after intravenous injection in mice, yet only small (200- to 250-nm), not large (600- to 700-nm), GOX conjugates caused profound oxidative vascular injury in the lungs, presumably owing to intracellular generation of H(2)O(2). Thus, engineering of affinity carriers of specific size permits intracellular delivery of active cargoes to endothelium in vitro and in vivo, a paradigm useful for the targeting of drugs, genes, and toxins.

O2 metabolites and neutrophil elastase synergistically cause edematous injury in isolated rat lungs

Addition of glucose oxidase (GO) increased H2O2 concentrations and decreased antielastolytic activities of beta-D-glucose containing perfusates of isolated rat lungs. Pretreatment with GO also caused acute edematous injury (increased lung weight gains, increased recovery of Ficoll in lung lavages, and increased pulmonary arterial pressures) in isolated lungs perfused with purified human neutrophil elastase (NE). Acute edematous injury in isolated lungs pretreated with GO and then NE exceeded levels found in lungs following addition of GO or NE alone or NE before GO. Simultaneous addition of catalase (an H2O2 scavenger) or methoxy-succinyl-L-alanyl-L-alanyl-prolyl-L-valine-chloromethyl ketone (an NE inhibitor, but not aminotriazole-inactivated catalase, N-tosyl-L-phenyl-alanine chloromethyl ketone (a chymotrypsin inhibitor) or N-alpha-p-tosyl-L-lysine chloromethyl ketone (a trypsin inhibitor), prevented acute edematous injury in isolated lungs perfused with both GO and NE. This observation indicated that injury was dependent on both H2O2 and NE, especially since the relative inactivating specificities of the inhibitors for H2O2 or NE, respectively, were confirmed under similar conditions in vitro. The synergistic nature of the interaction between H2O2 and NE-mediated injury was further clarified when GO- and NE-induced lung injury was prevented by addition of an oxidant-resistant NE inhibitor (Eglin-C), but not an oxidant-sensitive NE inhibitor (human alpha 1-protease inhibitor, alpha 1PI). Moreover, treatment with H2O2 also decreased the ability of alpha 1PI but not Eglin-C to decrease NE activity in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Injurious effect of the eosinophil peroxide-hydrogen peroxide-halide system and major basic protein on human nasal epithelium in vitro

Tissue injury is observed in allergic and nonallergic eosinophilic rhinitis, but the mechanism of this injury is unclear. Because eosinophils are prominent in biopsy specimens in these conditions, we hypothesized that they may participate in the injury process. Initially, we developed techniques to isolate and purify human nasal epithelial cells from turbinate biopsies to use as target cells for eosinophil granule products. Primary cultures from explants were characterized by electron microscopy and indirect immunofluorescence with a panel of primary monoclonal and polyclonal antibodies. These studies revealed the homogeneity of the cells and confirmed their epithelial nature. Cultured nasal epithelial cells were then exposed to either purified human eosinophil peroxidase, bromide, and glucose plus glucose oxidase, as a continuous source of hydrogen peroxide, or eosinophil major basic protein. Neither eosinophil peroxidase alone nor glucose plus glucose oxidase in the absence of eosinophil peroxidase were injurious, but the combined addition of eosinophil peroxidase, glucose/glucose oxidase, and bromide produced marked target cell lysis. This effect was time- and eosinophil peroxidase dose-dependent. Catalase and azide significantly inhibited the lysis of these cells, suggesting the eosinophil peroxidase-catalyzed products of halide oxidation mediated this form of injury. The addition of purified human eosinophil major basic protein also caused dose- and time-dependent lysis of the nasal epithelial cells but required longer incubation periods to effect injury. We hypothesize that the eosinophil peroxidase-hydrogen peroxide-halide system and major basic protein may injure the nasal epithelium in inflammatory conditions such as allergic and nonallergic eosinophilic rhinitis.

Vascular immunotargeting of glucose oxidase to the endothelial antigens induces distinct forms of oxidant acute lung injury: targeting to thrombomodulin, but not to PECAM-1, causes pulmonary thrombosis and neutrophil transmigration

Oxidative endothelial stress, leukocyte transmigration, and pulmonary thrombosis are important pathological factors in acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Vascular immunotargeting of the H(2)O(2)-generating enzyme glucose oxidase (GOX) to the pulmonary endothelium causes an acute oxidative lung injury in mice.(1) In the present study we compared the pulmonary thrombosis and leukocyte transmigration caused by GOX targeting to the endothelial antigens platelet-endothelial cell adhesion molecule (PECAM) and thrombomodulin (TM). Both anti-PECAM and anti-TM delivered similar amounts of (125)I-GOX to the lungs and caused a dose-dependent, tissue-selective lung injury manifested within 2 to 4 hours by high lethality, vascular congestion, polymorphonuclear neutrophil (PMN) sequestration in the pulmonary vasculature, severe pulmonary edema, and tissue oxidation, yet at an equal dose, anti-TM/GOX inflicted more severe lung injury than anti-PECAM/GOX. Moreover, anti-TM/GOX-induced injury was accompanied by PMN transmigration in the alveolar space, whereas anti-PECAM/GOX-induced injury was accompanied by PMN degranulation within vascular lumen without PMN transmigration, likely because of PECAM blockage. Anti-TM/GOX caused markedly more severe pulmonary thrombosis than anti-PECAM/GOX, likely because of TM inhibition. These results indicate that blocking of specific endothelial antigens by GOX immunotargeting modulates important pathological features of the lung injury initiated by local generation of H(2)O(2) and that this approach provides specific and robust models of diverse variants of human ALI/ARDS in mice. In particular, anti-TM/GOX causes lung injury combining oxidative, prothrombotic, and inflammatory components characteristic of the complex pathological picture seen in human ALI/ARDS.

Hydrogen peroxide-induced cell and tissue injury: protective effects of Mn2+

Recent evidence indicates that under in vitro conditions, superoxide anion and hydrogen peroxide (H2O2) are unstable in the presence of manganese ion (Mn2+). The current studies show that in the presence of Mn2+, H2O2-mediated injury of endothelial cells is greatly attenuated. A source of bicarbonate ion and amino acid is required for Mn2+ to exert its protective effects. Injury by phorbol ester-activated neutrophils is also attenuated under the same conditions. EDTA reverses the protective effects. Acute lung injury produced in vivo in rats by intratracheal instillation of glucose-glucose oxidase is almost completely blocked in rats treated with Mn2+ and glycine. Conversely, treatment of rats with EDTA, a chelator of Mn2+, markedly accentuates lung injury caused by glucose-glucose oxidase. These data are consistent with the findings of others that Mn2+ can facilitate direct oxidation of amino acids with concomitant H2O2 disproportionation. This could form the basis of a new therapeutic approach against oxygen radical-mediated tissue injury.

Oxidant-induced endothelial leak correlates with decreased cellular energy levels

A common finding in oxidant-induced organ injury is loss of vascular endothelial cell (EC) integrity and subsequent leak. The mechanisms involved are unclear, but maintenance of EC structure and functional integrity is highly dependent on the EC energy level. This study investigates whether oxidant-induced EC injury and concomitant increased monolayer permeability correlate with decreased energy levels. Rabbit pulmonary microvascular EC in vitro were exposed to varying levels of glucose oxidase as an oxidant-generating source for 2 h. Permeability changes were determined by albumin-Evans blue dye exclusion by monolayers of EC. ATP (nm/10(6) cells) and energy charge [ATP + 1/2ADP/(ATP + ADP + AMP)] were determined by HPLC. ATP and energy charge were found to decrease as permeability increased in response to increasing glucose oxidase concentration. ATP levels were a significantly more sensitive predictor of increased permeability than was energy charge. At 24 h, both permeability and ATP levels returned toward baseline. It appears that cell energy charge is preserved despite significant increases in monolayer permeability.

A study on antioxidant, free radical scavenging, anti-inflammatory and hepatoprotective actions of Aegiceras corniculatum (stem) extracts

AIM OF THE STUDY

The present study was conducted to evaluate the antioxidant, anti-inflammatory and hepatoprotective potential of Aegiceras corniculatum Linn. Blanco (Aegicerataceae).

METHODS AND RESULTS

The n-hexane, ethyl acetate and methanol extracts, derived from Aegiceras corniculatum stems, scavenged superoxide anions (O2*) and hydroxyl radicals (*OH) in nitro blue tetrazolium reduction and deoxyribose degradation assays, respectively. All the extracts inhibited the process of lipid peroxidation at its initiation step. Additionally, in rat liver microsomes n-hexane and ethyl acetate extracts also caused termination of radical chain reaction supporting their scavenging action towards lipid peroxy radicals (LOO*). Moreover, increased production of O2* in human neutrophils, stimulated by phorbol-12-myristate-13-acetate (PMA) and/or opsonized zymosan were also suppressed (IC50 approximately 3-20 microg/mL). Thereby, revealing the ability of plant extracts to antagonize the oxidative stress via interference with NADPH oxidase metabolic pathway. These in vitro results coincide with the reduction in the glucose oxidase-induced paw edema in mice in the presence of ethyl acetate and methanol extracts (10, 50, and 100mg/kg, i.p.). Plant extracts (250, 500 and 1000 mg/kg, p.o.) also significantly protected the carbon tetrachloride (CCl4)-induced oxidative tissue injury in rat liver. This was reflected by a approximately 60% decline in the levels of serum aminotransferase enzymes.

CONCLUSION

Aegiceras corniculatum extracts found to possess pronounced antioxidant effect that may be at least in part related to its anti-inflammatory and hepatoprotective activities. This study provides a scientific basis for the ethnomedical claims that Aegiceras corniculatum is effective against inflammation and liver injury.

Potency, selectivity and cell cycle dependence of catechols in human tumour cells in vitro

Enhancement of the potency and melanoma-selectivity of redox agents was sought by two different approaches. In screening a series of catechols, derivatives of moderate half-life (dopa, dopamine, noradrenaline, 3,4-dihydroxybenzylamine, 3,4-dihydroxyphenylacetic acid; t1/2 12-33 hr) had significant toxicity (D37 20-30 microM) and selectivity for melanoma cells compared with HeLa. Less stable catechols (5-hydroxy- and 6-hydroxydopamine; t1/2 4 and 5 hr respectively) were toxic but lacked selectivity whereas more stable derivatives (4-hydroxyanisole, 2,3-dihydroxybenzoic acid; t1/2 greater than 72 hr) were less potent (D37 greater than 100 microM) and had poor selectivity. Gossypol, a complex catechol derivative, exhibited significant toxicity (D37 7.7 microM) but little selectivity. Enzymes capable of reacting with components of the culture medium and known to continuously generate hydrogen peroxide (glucose-6-oxidase) or superoxide ion (xanthine oxidase) exhibited a similar degree of selectivity as dopa, indicating that active oxygen species are more important mediators of catechol toxicity than quinones. Rhodamine 123, a cationic dye preferentially taken up by some tumour cells, was accumulated equally by melanoma and HeLa yet had a similar selectivity to that of dopa. In the second approach, the potency of dopa was found to be greatly enhanced during early S phase. This phenomenon, found with cells synchronised both by mitotic shake off and by 24 hr accumulation in G1S in the presence of 5 mM hydroxyurea, occurred during a period in which the proportion of cells in S phase cells was low. These results indicate that human cells are extremely sensitive to extracellular active oxygen species during a relatively short period in early S phase, and selective killing of asynchronous melanoma cells therefore requires agents capable of sustaining a redox effect for at least one cell cycle.

Cell death and lipid peroxidation in isolated hepatocytes incubated in the presence of hydrogen peroxide and iron salts

The incubation of isolated hepatocytes in the presence of glucose plus glucose oxidase, a H2O2-generating system, resulted in extensive loss of cell viability, as expressed by the release of lactate dehydrogenase (LDH). Disturbance of metabolic functions such as glycogen and protein synthesis was also caused by H2O2, but in no case was malondialdehyde (MDA)-like products detected. The lytic effect of H2O2 was significantly enhanced by incubating hepatocytes in the presence of iron salts. Under these conditions, MDA-like products were detected, but lipid peroxidation and cell injury did not correlate. Iron chelators modulated the cytotoxicity of H2O2 in different (and opposite) ways: when iron was complexed with ADP, increased cell lysis was observed compared to uncomplexed iron plus H2O2. Iron-DTPA, on the contrary, decreased such a lytic effect. The preincubation of hepatocytes with desferrioxamine mesylate (Desferal; a strong iron chelator) abolished the cytolytic effects produced by the association of iron salts and H2O2, as well as the membrane oxidative injury due to H2O2 alone, thus suggesting the existence of an intracellular source of iron. This kind of mechanism (metal chelation rather than radical scavenging) is supported by the absence of any protective effect by some free radical scavengers against the oxidative injury induced by the association iron H2O2. Nevertheless, the glycogenolytic effects observed in the presence of H2O2 were not modified by Desferal. In our opinion, the cytotoxicity of the association H2O2 plus iron salts involves at least two different and independent mechanisms.

Time-dependent inhibition of oxygen radical induced lung injury

Experimental acute lung injury mediated by reactive metabolites of oxygen can be inhibited by the antioxidant enzymes catalase and superoxide dismutase (SOD). However, the specific time interval during which these enzymes must be present in order to cause protection is not well defined. Using two experimental models of oxidant-dependent acute lung injury, one involving the intratracheal injection of glucose, glucose oxidase, and lactoperoxidase and the other involving the intravenous injection of cobra venom factor (CVF), we investigated the effects of delaying antioxidant administration on the outcome of the inflammatory response. In both cases, the protective effects of catalase and SOD were rapidly attenuated when their administration was delayed for a short period of time. For example, intratracheal catalase resulted in 98% protection when given simultaneously with the glucose oxidase and lactoperoxidase, but only 13% protection when the catalase was delayed 4 min. Likewise, in the CVF-induced lung injury model, intravenous catalase resulted in 40% protection when given simultaneously with the CVF, but only 2% protection when the catalase was delayed 20 min, even though the peak of the injury occurred hours after the initiation of the injury. A similar time dependence was seen with SOD. These results indicate that antioxidant therapy is required early in the course of oxygen radical-mediated acute lung injury for effective protection.

Distribution of oncodevelopmental markers in neoplastic cells: therapeutic implications

When the subcellular distribution of secretory component (SC) and carcinoembryonic antigen (CEA) were determined immunoelectronmicroscopically, SC was found on the baso-lateral surface and CEA on the apical surface of the normal gastrointestinal epithelium. In contrast, on the neoplastic cells SC and/or CEA were found all around the cell surface. Taking the change in the distribution of CEA on the neoplastic cells as an advantage, an attempt was made to develop an immunotherapeutic method for adenocarcinoma. The method was based upon an assumption that intravenously injected anti-CEA is not accessible to normal epithelial cells, since the tight junction will act as a barrier for the diffusion of antibodies from the interstitium to the apical cell surface, but the anti-CEA will form immunecomplexes with the CEA on the baso-lateral surface of neoplastic cells. Specifically, CEA-producing human gall bladder carcinoma were transplanted into nude mice. To the tumor-bearing mice, glucose oxidase-labeled anti-CEA was intravenously injected. As a control, glucose oxidase-labeled normal rabbit IgG was injected. This was followed with an injection of NaI. It was found that in those mice injected with the labeled anti-CEA, the size of tumor was reduced as much as 30% within three days. In the controls, the tumor continued to grow. In those injected with the labeled anti-CEA, CEA-anti-CEA immunecomplexes were deposited on the glomerular basement membrane, consequently a search for an insoluble apical antigen is currently made.

Platelets attenuate oxidant-induced permeability in endothelial monolayers: glutathione-dependent mechanisms

We studied the effects of adding washed human platelets or platelets with nonintact glutathione redox cycles to endothelial cell monolayers treated with glucose oxidase to initiate oxidant stress and increase permeability. Changes in 125I-labeled albumin transmonolayer movement were used as the index of monolayer permeability. Washed human platelets attenuated oxidant-induced increases in albumin flux. Platelets treated with 1,3-bis(2-chloroethyl)-1-nitrosurea, 1-chloro-2,4-dinitrobenzene, or buthionine sulfoximine to inhibit selective enzymatic steps in the glutathione redox cycle decreased permeability to a lesser degree. We conclude that 1) washed human platelets attenuate monolayer permeability defects in aortic endothelial monolayers exposed to glucose oxidase and 2) the protective effects of platelets are partially dependent on an intact platelet glutathione redox cycle.

Local tissue injury induced by glucose oxidase conjugated with anti-collagen antibody

The conjugation of glucose oxidase with anti-collagen antibody using periodate oxidation of the enzyme carbohydrate moiety is described. After conjugation, the antibody retained its antigen-binding capacity and the enzyme retained hydrogen peroxide-generating activity. Intradermal administration of the immune conjugate into rats induced local tissue injury at doses 10-100 micrograms. Pronounced damage (local hyperemia and edema) occurred 24 h after injection and necrosis developed 1 week later. The enzyme was tightly bound to the fibrillar components of the extracellular matrix and retained its activity in vivo for a prolonged period of time. In contrast, non-immune IgG-conjugated glucose oxidase was removed rapidly from the site of injection and did not induce tissue damage. Pure native anti-collagen antibody was retained at the site of injection for 8 days, but caused no tissue injury. These results suggest that active glucose oxidase conjugated with antibodies to tissue antigen can be accumulated and retained in the tissues. At the site of accumulation local 'proinflammatory' damage develops even in the absence of the halide-peroxidase system. Similar conjugates could be potential agents for local modulation of inflammation.

A new enzymatic assay for evaluating the clearance of immune complexes from the circulation of mice

A new photometric in vivo enzymatic immune complex clearance (EIC) assay was developed in a homologous system using glucose oxidase-anti-glucose oxidase complexes (GAG) as a model of immune complexes. Chromatographically purified GAG was injected into mouse tail veins and at intervals thereafter the enzyme activities of GAG remaining in the circulation were estimated. The GAG were cleared in a size dependent manner and were stable, being eluted as the same discrete peaks on HPLC size-exclusion chromatography both before and after injection into mice. The complement consuming activity of the GAG was weak, and depletion of complement components with cobra-venom factor did not alter clearance of the GAG from the circulation, whereas pretreatment of aggregated mouse gamma globulin suppressed the clearance rate. These results suggested that most of the GAG were not cleared via complement receptors but via FcR. Normal clearance rates were significantly changed by administration of immunomodulators such as carrageenan or LPS. Intravenous administration of GAG at a dose 50 times higher than normal caused no deaths suggesting that the complexes were of low toxicity. The enzymatic method presented should be of value for measuring the function of the mononuclear phagocytic system with respect to immune complex clearance. It provides a rapid and sensitive alternative assay which avoids using radioisotopes.

A photo-activated, protein-based, NO/H2O2 generating system with tumoricidal activity composed of the nitric oxide derivative of apo-metallothionein (thionein-NO) and glucose oxidase

The S-nitroso derivative of apo-metallothionein (thionein) was prepared by transnitrosation with S-nitrosoglutathione. The thionein-NO thus formed has an absorption maximum at 334 nm. Light-induced NO release from thionein-NO was demonstrated by flash photolysis. This system produces peroxynitrite at neutral pH as evidenced by nitrotyrosine formation. The cytotoxic potential of this protein-based, light-activated NO/H2O2 generating system was demonstrated by exposing human colon adenocarcinoma cells (SW 948) in culture to thionein-NO and glucose oxidase in the presence and absence of light. The cell density of the samples, 72 h subsequent to receiving 1 h of light exposure, decreased by approximately 98%, relative to controls. In comparison, cell density of the samples that were incubated in the presence of catalase and did not receive light treatment, decreased by only approximately 22% after 72 h.

Multi-drug delivery system using streptavidin-transforming growth factor-alpha chimeric protein

Tissue-specific delivery of a variety of molecules has been a valuable technique for biological and medical research. Therefore, we have constructed a recombinant plasmid containing the coding regions for streptavidin core and mature human transforming growth factor-alpha (TGF-alpha). The recombinant plasmid has been expressed in Escherichia coli to produce a chimeric protein with both streptavidin and TGF-alpha activity. The streptavidin-TGF-alpha chimeric protein (ST-TGF-alpha) could efficiently transfer biotinylated beta-galactosidase into A431 cells via the epidermal growth factor receptor. More than 99% of the cells contained the enzyme transferred. Furthermore, ST-TGF-alpha complexed with biotinylated-glucose oxidase had a significant cytotoxic effect when incubated with A431 cells. These findings suggest that the ST-TGF-alpha chimeric protein could be used to deliver proteins of interest into target cells without the need for chemical linkage or genetic construction. Essentially, ST-TGF-alpha serves as a high-modular "molecular bridge" for the passage of a wide variety of effector molecules into target cells.

Construction of glucose oxidase-loaded human erythrocytes: a model of oxidative cytotoxicity

Human red blood cells were loaded with Glucose oxidase from Aspergillus niger by a standardized procedure of encapsulation involving transient hypotonic hemolysis followed by isotonic resealing. The amount of loaded enzyme activity, as evaluated by O2 consumption at 5 mM glucose, ranged from 40 to 75 mumoles O2/hr/ml of packed red cells at 37 degrees C. The red cells loaded with Glucose oxidase were found to behave as efficient glucose-consuming bioreactors. Moreover, at 5 mM glucose, no clear mechanism of H2O2-induced damage was apparent, with the exception of a significantly increased formation of methemoglobin (10% approximately) and of a several-fold stimulated intracellular rate of hexose monophosphate shunt activity, indicating glutathione peroxidase-mediated draining of reduced glutathione for removal of bursts of H2O2. The Glucose oxidase-loaded red cells represent a convenient model system for cytotoxicity studies aiming at clarifying the effects of intracellularly formed H2O2.

Preclinical safety studies of glucose oxidase

The purpose of this study was to develop preclinical safety data regarding the toxicologic and pharmacokinetic properties of glucose oxidase. Groups of adult BALB/c mice were injected with four doses of the enzyme ranging from 0.125 U of glucose oxidase/g b.wt. to 1 U/g b.wt., and the following responses were measured: survival, methemoglobin, glucose, blood urea nitrogen, creatine phosphokinase, erythrocyte count and body weight. We also compared the biodistribution of the enzyme in mice to the biodistribution of glucose oxidase conjugated to a monoclonal antibody. Finally, we assessed the histopathologic changes produced in mice by glucose oxidase and the binding of the enzyme to snap-frozen, human autopsy tissues. As expected, the acute toxicity of glucose oxidase was primarily due to methemoglobinemia (mean concentration 36% at the highest dose) and transient hypoglycemia (as low as 35 mg/dl). Furthermore, conjugated and unconjugated glucose oxidase had a blood half-life of less than 2 hr and concentrated in the liver and spleen. On the basis of our studies, we conclude that glucose oxidase has reasonably predictable toxicities and is, therefore, safe for human trials. The rapid uptake of conjugated and unconjugated glucose oxidase by the liver and spleen, however, may significantly limit the therapeutic targeting of glucose oxidase.