Therapeutic effects of superoxide dismutase derivatives modified with mono- or polysaccharides on hepatic injury induced by ischemia/reperfusion

Artificial Glycoproteins as a Scaffold for Targeted Drug Therapy

Akin to a cellular "fingerprint," the glycocalyx is a glycan-enriched cellular coating that plays a crucial role in mediating cell-to-cell interactions. To gain a better understanding of the factors that govern in vivo recognition, artificial glycoproteins were initially created to probe changes made to the accumulation and biodistribution of specific glycan assemblies through biomimicry. As a result, the organ-specific accumulation for a variety of glycoproteins decorated with simple and/or complex glycans was identified. Additionally, binding trends with regard to cancer cell selectivity were also investigated. To exploit the knowledge gained from these studies, numerous groups thus became engaged in developing targeted drug methodologies based on the use of artificial glycoproteins. This has either been done through adopting the glycoprotein scaffold as a drug carrier, or to directly glycosylate therapeutic proteins/enzymes to localize their biological activity. The principle aim of this Review is to present the foundational research that has driven artificial glycoprotein-based targeting and subsequent adaptations with potential therapeutic applications.

Intrahepatic Delivery of Pegylated Catalase Is Protective in a Rat Ischemia/Reperfusion Injury Model

BACKGROUND

Ischemia/reperfusion injury (IRI) can occur during liver surgery. Endogenous catalase is important to cellular antioxidant defenses and is critical to IRI prevention. Pegylation of catalase (PEG-CAT) improves its therapeutic potential by extending plasma half-life, but systemic administration of exogenous PEG-CAT has been only mildly therapeutic for hepatic IRI. Here, we investigated the protective effects of direct intrahepatic delivery of PEG-CAT during IRI using a rat hilar clamp model.

MATERIALS AND METHODS

PEG-CAT was tested in vitro and in vivo. In vitro, enriched rat liver cell populations were subjected to oxidative stress injury (H₂O₂), and measures of cell health and viability were assessed. In vivo, rats underwent segmental (70%) hepatic warm ischemia for 1 h, followed by 6 h of reperfusion, and plasma alanine aminotransferase and aspartate aminotransferase, tissue malondialdehyde, adenosine triphosphate, and GSH, and histology were assessed.

RESULTS

In vitro, PEG-CAT pretreatment of liver cells showed substantial uptake and protection against oxidative stress injury. In vivo, direct intrahepatic, but not systemic, delivery of PEG-CAT during IRI significantly reduced alanine aminotransferase and aspartate aminotransferase in a time-dependent manner (P < 0.01, P < 0.0001, respectively, for all time points) compared to control. Similarly, tissue malondialdehyde (P = 0.0048), adenosine triphosphate (P = 0.019), and GSH (P = 0.0015), and the degree of centrilobular necrosis, were improved by intrahepatic compared to systemic PEG-CAT delivery.

CONCLUSIONS

Direct intrahepatic administration of PEG-CAT achieved significant protection against IRI by reducing the volume distribution and taking advantage of the substantial hepatic first-pass uptake of this molecule. The mode of delivery was an important factor for protection against hepatic IRI by PEG-CAT.

Mannan-conjugated adenovirus enhanced gene therapy effects on murine hepatocellular carcinoma cells in vitro and in vivo

The incidence of advanced hepatocellular carcinoma (HCC) is increasing worldwide, and its prognosis is extremely poor. For some patients for whom surgical treatments are not appropriate, one can only rely on chemotherapy. In the conventional chemotherapy, side effects usually occurred in most cases due to high toxicity levels. Moreover, the development of drug resistance toward chemotherapeutic agents often prevents the successful long-term use of chemotherapy for HCC. Gene therapy represents the exciting biotechnological advance that may revolutionize the conventional fashion of cancer treatment. Overexpression of phosphatase and tensin homologue (PTEN) in cancer cells carrying deletion/mutant type of it can induce the apoptosis of cancer cells and inhibit cell proliferation. In this work, in order to make full use of the high transfectivity of adenovirus, we managed to conjugate the polysaccharide mannan (polymannose) to the surface of the adenovirus chemically under appropriate oxidizing conditions to prepare the mannan-modified adenovirus (Man-Ad5-PTEN). The cytotoxicity and anticancer activity of Man-Ad5-PTEN were assessed in vitro. Reporter gene expression of LacZ transferred by Man-Ad5-LacZ was verified on mannose receptor-deficient NIH/3T3 cells versus mannose receptor-efficient macrophages. Hepatocellular carcinoma cell lines transduced by mannan-modified adenovirus were assayed for cell cycle, apoptosis, invasion, and migration. Further, we detected the antitumor effect on intraperitoneal H22 tumor-bearing mice treated by Man-Ad5-PTEN alone or combined with chemotherapeutic agent of doxorubicin. The results demonstrated that cell growth suppression was not observed in Chang normal hepatocyte cells and the cell killing by Man-Ad5-PTEN is tumor selective. Further, the results showed that the strategy of mannan conjugation could enhance adenovirus-mediated PTEN gene therapy effects on murine hepatocellular carcinoma cells in vitro and in vivo.

Recent developments in protein and peptide parenteral delivery approaches

Discovery of insulin in the early 1900s initiated the research and development to improve the means of therapeutic protein delivery in patients. In the past decade, great emphasis has been placed on bringing protein and peptide therapeutics to market. Despite tremendous efforts, parenteral delivery still remains the major mode of administration for protein and peptide therapeutics. Other routes such as oral, nasal, pulmonary and buccal are considered more opportunistic rather than routine application. Improving biological half-life, stability and therapeutic efficacy is central to protein and peptide delivery. Several approaches have been tried in the past to improve protein and peptide in vitro/in vivo stability and performance. Approaches may be broadly categorized as chemical modification and colloidal delivery systems. In this review we have discussed various chemical approaches such as PEGylation, hyperglycosylation, mannosylation, and colloidal carriers including microparticles, nanoparticles, liposomes, carbon nanotubes and micelles for improving protein and peptide delivery. Recent developments on in situ thermosensitive gel-based protein and peptide delivery have also been described. This review summarizes recent developments on some currently existing approaches to improve stability, bioavailability and bioactivity of peptide and protein therapeutics following parenteral administration.

Prevention of hepatic ischemia-reperfusion injury by pre-administration of catalase-expressing adenovirus vectors

Liver ischemia/reperfusion (I/R) injury, which is mainly caused by the generation of reactive oxygen species (ROS) during the reperfusion, remains an important clinical problem associated with liver transplantation and major liver surgery. Therefore, ROS should be detoxified to prevent hepatic I/R-induced injury. Delivery of antioxidant genes into liver is considered to be promising for prevention of hepatic I/R injury; however, therapeutic effects of antioxidant gene transfer to the liver have not been fully examined. The aim of this study was to examine whether adenovirus (Ad) vector-mediated catalase gene transfer in the liver is an effective approach for scavenging ROS and preventing hepatic I/R injury. Intravenous administration of Ad vectors expressing catalase, which is an antioxidant enzyme scavenging H(2)O(2), resulted in a significant increase in catalase activity in the liver. Pre-injection of catalase-expressing Ad vectors dramatically prevented I/R-induced elevation in serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, and hepatic necrosis. The livers were also protected in another liver injury model, CCl(4)-induced liver injury, by catalase-expressing Ad vectors. Furthermore, the survival rates of mice subjected to both partial hepatectomy and I/R treatment were improved by pre-injection of catalase-expressing Ad vectors. On the other hand, control Ad vectors expressing beta-galactosidase did not show any significant preventive effects in the liver on the models of I/R-induced or CCl(4)-induced hepatic injury described above. These results indicate that hepatic delivery of the catalase gene by Ad vectors is a promising approach for the prevention of oxidative stress-induced liver injury.

The preventive effects of heparin-superoxide dismutase on carbon tetrachloride-induced acute liver failure and hepatic fibrosis in mice

In this study, the effects of heparin-superoxide dismutase conjugate (heparin-SOD) on carbon tetrachloride (CCl4)-induced acute liver failure and hepatic fibrosis were evaluated. To investigate the effects of heparin-SOD on acute liver failure, heparin-SOD was administered to CCl4-treated mice by intravenous injection. Biochemical indicators, such as glutamic oxaloacetic transaminase/glutamic pyruvic transaminase (GOT/GPT), GSH (glutathione), lactate dehydrogenase (LDH), and malondialdehyde (MDA) were determined 24 h after CCl4 treatment. The development of CCl4-induced acute liver failure altered the redox state with a decreased hepatic GSH and increased formation of lipid peroxidative products, which were partially normalized by treatment with heparin-SOD or heparin + SOD. Compared with other groups, the acute liver injury of heparin-SOD group was significantly lessened (reduced activities of GOT/GPT, MDA, and increased activities of GSH). To investigate the effects of heparin-SOD on hepatic fibrosis, heparin-SOD and CCl4 were co-administered by intraperitoneal injection twice a week for 12 weeks. Histological and hepatic hydroxyproline examination revealed that heparin-SOD could significantly prevent the progression of hepatic fibrosis. Moreover, real-time PCR was used to determine transforming growth factor-beta1 (TGF-beta1), metalloproteinase-2 (MMP-2), fibronectin, and collagen-I expression. Significantly, greater fibrosis and TGF-beta1, MMP-2, fibronectin, and collagen-I expression were found in the liver of CCl4-induced mice at the end of 12th week. Heparin-SOD could markedly attenuate the mRNA expression of TGF-beta1, MMP-2, and collagen-I. Western blots of tissue homogenates revealed that the protein expression of TGF-beta1 was substantially reduce also by heparin-SOD treatment. These results demonstrate that administration of heparin-SOD may be useful in the treatment and prevention of acute liver failure and hepatic fibrosis.

[Development of cell-selective targeting systems of NFkappaB decoy for inflammation therapy]

NFkappaB regulate several inflammatory related molecules and evoke immune and inflammatory response by several stimuli, therefore inhibition of NFkappaB activation would be a novel therapeutic strategy. To date, there are many conventional drugs including nonsteroldal or steroldal anti-inflammatory drugs or immune suppressors etc. were known to inhibit NFkappaB activation, however, several side effects were also reported. Recently, double stranded oligonucleotide including NFkappaB binding sequence, called NFkappaB decoy, was developed to prevent NFkappaB activation, which is powerful tool in a new class of anti-gene strategy for molecular therapy with low side effect. However, NFkappaB decoy is easily degraded by nuclease and rapidly excreted to urine, therefore it is necessary to develop carrier for NFkappaB decoy therapy. Here, we shall review delivery system for NFkappaB decoy and introduce our cell-selective delivery system for NFkappaB decoy using sugar decorated cationic liposomes.

Analysis of the molecular interaction of glycosylated proteins with rabbit liver asialoglycoprotein receptors using surface plasmon resonance spectroscopy

A sensitive, accurate, and efficient biosensor analysis using surface plasmon resonance (SPR) spectroscopy was used for delineating the molecular interaction between rabbit liver asialoglycoprotein receptors (ASGPR) and glycosylated proteins. Isolated rabbit liver ASGPR obtained by affinity column chromatography was dissolved in buffer solution containing TritonX-100 and immobilized on the SPR sensor chip by amine coupling. The SPR study demonstrated that the association rate constants (ka) of galactosylated proteins with ASGPR are dependent on the number of galactose residues, while the dissociation rate constants (kd) are influenced not only by the surface density of the galactose moieties but also by their steric configuration. In addition, it was demonstrated that D-fucosylated BSA had a higher binding affinity to ASGPR than Gal-BSA, when the degree of sugar modification was equivalent.

Characterization and stability investigation of Cu,Zn-superoxide dismutase covalently modified by low molecular weight heparin

Cu,Zn-superoxide dismutase (SOD) was chemically modified with low molecular weight heparin (LMWH). To characterize the conjugate, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and native polyacrylamide gel electrophoresis (native PAGE) with protein staining and polysaccharide staining were employed. The stabilities of the modified enzyme to heat, acid, alkali, and trypsin treatment were also investigated. SDS-PAGE of the conjugate presented two major bands, and native PAGE of the conjugate showed similar banding position with protein staining and polysaccharide staining, which was different from that of the unmodified SOD and LMWH/SOD mixture. Moreover, the conjugate migrated faster with increasing extent of the modification. Enhanced heat stability, acid resistance, alkali resistance, and anti-trypsin stability of the modified enzyme were observed compared with those of the unmodified enzyme. Results of the study suggest that covalent linkage in LMWH-SOD can be effectively characterized by electrophoretic techniques and the chemical modification of SOD with LMWH can enhance the stabilities of the enzyme. In addition, native PAGE with protein staining can be used to evaluate the extent of the modification.

The contemporary role of antioxidant therapy in attenuating liver ischemia-reperfusion injury: a review

Oxidative stress is an important factor in many pathological conditions such as inflammation, cancer, ageing and organ response to ischemia-reperfusion. Humans have developed a complex antioxidant system to eliminate or attenuate oxidative stress. Liver ischemia-reperfusion injury occurs in a number of clinical settings, including liver surgery, transplantation, and hemorrhagic shock with subsequent fluid resuscitation, leading to significant morbidity and mortality. It is characterized by significant oxidative stress but accompanied with depletion of endogenous antioxidants. This review has 2 aims: firstly, to highlight the clinical significance of liver ischemia-reperfusion injury, the underlying mechanisms and the main pathways by which the antioxidants function, and secondly, to describe the new developments that are ongoing in antioxidant therapy and to present the experimental and clinical evidence about the role of antioxidants in modulating hepatic ischemia-reperfusion injury.

Uptake characteristics of mannosylated and fucosylated bovine serum albumin in primary cultured rat sinusoidal endothelial cells and Kupffer cells

The purpose of this study is to delineate uptake characteristics of mannosylated and fucosylated proteins in primary cultured sinusoidal endothelial cells and Kupffer cells. In cultured sinusoidal endothelial cells, uptake of mannosylated and fucosylated bovine serum albumin (BSA) was significantly inhibited by excess mannosylated and fucosylated BSAs but not by galactosylated BSA, suggesting that both glycosylated proteins might be primarily taken up via mannose receptors. In cultured Kupffer cells, uptake of fucosylated BSA was significantly inhibited by excess galactosylated BSA as well as mannosylated and fucosylated BSAs, although that of mannosylated BSA was inhibited only by mannosylated and fucosylated BSAs. This suggests that uptake of fucosylated BSA by Kupffer cells might be mediated by both Kupffer cell lectin (fucose receptor) and mannose receptor. On the other hand, in vivo hepatic uptake of fucosylated BSA was inhibited to a greater extent by GdCl3 pretreatment than that of mannosylated BSA. Based on in vitro and in vivo experiments, it was concluded that fucosylated BSA is more Kupffer cell-selective because it exhibited a lower sinusoidal endothelial cell uptake than mannosylated BSA.

Development of cell-specific targeting systems for drugs and genes

Cell-specific targeting systems for drugs and genes have been developed by using glycosylated macromolecule as a vehicle that can be selectively recognized by carbohydrate receptors. Pharmacokinetic analyses of the tissue distribution of glycosylated proteins came to the conclusion that the surface density of the sugar moiety on the protein derivative largely determines the binding affinity for the receptors and plasma lectin. Many glycosylated delivery systems have been developed and their usefulness investigated in various settings. Galactosylated polymers, when properly designed, were found to be effective in delivering prostaglandin E1 and other low-molecular-weight drugs selectively to hepatocytes. In addition, glycosylated superoxide dismutase and catalase were successfully developed with minimal loss of enzymatic activity. A simultaneous targeting of these two enzymes to liver nonparenchymal cells significantly prevented hepatic ischemia/reperfusion injury. On the other hand, galactosylated catalase, a derivative selectively delivered to hepatocytes, effectively inhibited hepatic metastasis of colon carcinoma cells in mice. Finally, hepatocyte-targeted in vivo gene transfer was achieved by synthesizing a multi-functional carrier molecule, which condenses plasmid DNA, delivering DNA to hepatocytes through recognition by asialoglycoprotein receptors, and releasing DNA from endosomes/lysosomes into cytoplasm.

Inhibition of experimental hepatic metastasis by targeted delivery of catalase in mice

Bovine liver catalase derivatives possessing diverse tissue distribution properties were synthesized, and their effects on hepatic metastasis of colon carcinoma cells were examined in mice. An intraportal injection of 1 x 10(5) colon 26 cells resulted in the formation of more than 50 metastatic colonies on the surface of the liver at 14 days after injection. An intravenous injection of catalase (CAT; 35000 units/kg of body weight) significantly (P < 0.001) reduced the number of the colonies in the liver. Galactosylated (Gal-), mannosylated (Man-) and succinylated (Suc-) CAT were also tested in the same system. Of these derivatives, Gal-CAT showed the greatest inhibitory effect on hepatic metastasis, and the number of colonies was significantly (P < 0.001) smaller than following treatment with catalase. High activities of matrix metalloproteinases (MMPs), especially MMP-9, were detected in the liver of mice bearing metastatic tumor tissues, which was significantly (P < 0.05) reduced by Gal-CAT. These results, combined with our previous finding that Gal-CAT can be efficiently delivered to hepatocytes, indicate that the targeted delivery of catalase to the liver by galactosylation is a promising approach to suppress hepatic metastasis. Decreased MMP activity by catalase delivery seems to be involved in its anti-metastatic effect.

Poly(vinylpyrrolidone-co-dimethyl maleic acid) as a novel renal targeting carrier

Poly(vinylpyrrolidone-co-dimethyl maleic acid) (PVD) was found to have high renal-targeting capability and safety as a drug carrier. To optimize the renal drug delivery system using PVD, the relationship between the molecular weight of PVD and its renal accumulation were evaluated in mice by their intravenous injection. It was found that the molecular size of 6-8 kDa was associated with the highest renal accumulation. The specific bioactivity of PVD-conjugated superoxide dismutase (SOD) relative to that of unmodified SOD gradually decreased with an increase in the degree of modification to SOD with PVD6K. The conjugated SOD (L-PVD-SOD) with the molecular size of 73 kDa, which had comparable specific bioactivity with native SOD, showed longer plasma half-life than native SOD. About sixfold more L-PVD-SOD was distributed to the kidneys than native SOD 3 h after intravenous injection, whereas extensive PVD modification did not enhance the renal accumulation of SOD. This L-PVD-SOD effectively accelerated recovery from mercuric chloride-induced acute renal failure in vivo. These results suggest that L-PVD-SOD may be the optimal derivative as a potential therapeutic agent to various renal diseases.

Efficient scavenger receptor-mediated hepatic targeting of proteins by introduction of negative charges on the proteins by aconitylation: the influence of charge density and size of the proteins molecules

The in vivo disposition characteristics of some aconitylated proteins in mice were studied after intravenous injection in relation to their molecular properties such as overall negative charge and size of the molecules. Superoxide dismutase (SOD, M(w)=32000) and bovine serum albumin (BSA, M(w)=67000) were used to produce aconitylated derivatives with a different extent of modification. Aconitylated SOD (Aco-SOD) was only moderately taken up by the liver in spite of its negative charge density, whereas aconitylated BSA (Aco-BSA) with a smaller charge density was taken up by the liver very efficiently. Aco-BSA was more rapidly cleared by the liver than succinylated BSA due to the introduction of more anionic groups, especially when the degree of modification was low. Interestingly, highly aconitylated BSAs exhibited significant accumulation in the kidney at higher doses, especially when the hepatic uptake was saturated. Further analysis that was based on a physiological pharmacokinetic model including a saturable hepatic uptake process revealed that the higher the number of negative charges on the proteins, the higher was the apparent affinity of aconitylated proteins for the hepatic SRs. In general, the affinity of aconitylated proteins was higher than that of succinylated proteins when the degree of acylation was the same. Thus, the present study indicates that apart from charge density on the proteins the molecular size of the proteins is important for SR-mediated uptake in the liver. Aconitylation of proteins seems more suitable than succinylation for targeting of proteins to the liver nonparenchymal cells, in particular, at a low degree of acylation of the proteins at which the enzymatic activity is better retained for sufficient negative charges introduced.

Pharmacokinetics and preventive effects of targeted catalase derivatives on hydrogen peroxide-induced injury in perfused rat liver

PURPOSE

To investigate the pharmacokinetics and preventive effects of liver-targeted catalase (CAT) derivatives on hepatic injury caused by reactive oxygen species.

METHODS

The hepatic uptake of 111In-CAT, galactosylated (Gal-), mannosylated (Man-) and succinylated (Suc-) CAT was investigated in isolated perfused rat livers in a single-pass constant infusion mode. Then, pharmacokinetic parameters were obtained by fitting equations derived from a one-organ pharmacokinetic model to the outflow profile. Their effects in preventing hydrogen peroxide-induced injury were determined by lactate dehydrogenase (LDH) release from the perfused liver.

RESULTS

The extraction of CAT derivatives by the liver was dose-dependent, and increased by the chemical modifications described. After being bound to the cell surface, chemically modified CAT derivatives were internalized by the liver faster than CAT. Preperfusion of a CAT derivative significantly reduced LDH release by hydrogen peroxide at least for 30 min, and Man-CAT and Suc-CAT effectively inhibited this release.

CONCLUSIONS

Internalized CAT derivatives are also effective in degrading hydrogen peroxide and targeted delivery of CAT to liver nonparenchymal cells by mannosylation or succinylation is a useful method for the prevention of hepatic injury caused by reactive oxygen species.

Polyethylene glycol-superoxide dismutase, a conjugate in search of exploitation

Without a doubt PEG-SOD has been the enzyme most studied in PEGylation. One can say that it represents the preferred model to assess chemistries for PEG activation, analytical procedures suitable for conjugate characterization, the influence of PEG size in conjugate removal from circulation and elimination of immunogenicity and antigenicity, and the effect of route of administration. The effect of PEG conjugation was studied in vitro and in vivo models in comparison with the free enzyme and the following conclusions may be drawn: (1) At the blood vessel level, PEG-SOD has been shown to provide a greater resistance to oxidant stress, to improve endothelium relaxation and inhibit lipid oxidation. (2) In the heart, PEG-SOD proved to be at least as effective as native SOD in treatment of reperfusion-induced arrhythmias and myocardial ischemia. (3) In the lung, PEG-SOD appeared to be able to reduce oxygen toxicity and E. coli-induced lung injury, but not in the treatment of lung physiopathology associated with endotoxin-induced acute respiratory failure and in the reduction of asbestos-induced cell damage. (4) On cerebral ischemia/reperfusion injuries the effect of PEG-SOD was uncertain, also due to the difficulty of cerebral cell penetration. (5) In kidney and liver ischemia both enzyme forms were found to ameliorate reperfusion damage. In view of so much positive research on PEG-SOD, it is surprising that no approved application in human therapy has been established and approved.

Pharmacokinetic analysis of lectin-dependent biodistribution of fucosylated bovine serum albumin: a possible carrier for Kupffer cells

To examine the potential utility of fucosylation of drug carriers for targeted drug delivery to Kupffer cells, the pharmacokinetics of (111)In-labeled fucosylated bovine serum albumin (Fuc-BSA) with different numbers of fucose residues (11, 16, 25, 31 or 41) was studied. After intravenous injection in mice, all (111)In-Fuc-BSAs were mainly delivered to the liver and their hepatic uptake became saturated when the dose was increased. Of these derivatives, only (111)In-Fuc41-BSA showed a slow plasma elimination at low doses, suggesting an interaction with blood components. Examination of binding conditions as well as electrophoretic analysis of the binding components indicated that the serum-type mannan binding protein (MBP) is responsible. Kupffer cells, which possess fucose receptors, showed the highest uptake of (111)In-Fuc41-BSA, followed by endothelial cells and hepatocytes. The hepatic uptake of (111)In-Fuc41-BSA was inhibited by co-injection of Gal42-BSA, but not by Man46-BSA. On the other hand, excess Fuc41-BSA inhibited the hepatic uptake of (111)In-Man46-BSA, while (111)In-Gal42-BSA did not: These findings suggest that not only the fucose receptors on Kupffer cells but also other lectins are involved in the biodistribution of Fuc-BSAs. To understand how the degree of fucose modification affects the binding affinity of Fuc-BSA with hepatic lectins and serum MBP, a pharmacokinetic analysis was performed based on a physiological model. The Michaelis constant of the hepatic uptake of (111)In-Fuc-BSA decreased with an increasing number of fucose units, and the intrinsic hepatic clearance of (111)In-Fuc25-, (111)In-Fuc31- and (111)In-Fuc41-BSAs was close to, or much greater than, the hepatic plasma flow rate, indicating efficient hepatic uptake of these derivatives. These results suggest that fucosylation is a potentially useful method making drug carriers selective for Kupffer cells, although extensive modification might result in retarded delivery due to binding to other lectins like MBP.

Synthesis and pharmacological activity of a novel water-soluble hepatocyte-specific polymeric prodrug of prostaglandin E(1) using lactosylated poly(L-glutamic hydrazide) as a carrier

A novel polymeric prodrug of prostaglandin E(1) (PGE(1)) was synthesized using lactosylated poly(L-glutamic hydrazide) (Lac-NH-PLGA) as a targetable carrier to hepatocytes. Poly(L-glutamic hydrazide) (PLGA-HZ) was prepared by reacting poly(gamma-benzyl-L-glutamate) with hydrazine monohydrate, followed by coupling with lactose via a hydrazone linkage. Then the lactosylated PLGA-HZ was reduced by sodium cyanoborohydride (NaBH(3)CN) in order to make the linkage irreversible (Lac-NH-PLGA). Finally, PGE(1) was bound to hydrazide moieties remaining in Lac-NH-PLGA without any condensing agent under weakly acidic conditions (pH 5) where PGE(1) would be chemically most stable at room temperature (PGE(1) conjugate). The PGE(1) conjugate prepared was sufficiently water-soluble in spite of the hydrophobic nature of its backbone (-NH-CH-CO-) and PGE(1) itself. After intravenous injection in mice, the [111In]PGE(1) conjugate rapidly accumulated in the liver, whereas [111In]PLGA-HZ did not, suggesting the involvement of a galactose-specific mechanism in the uptake of the [111In]PGE(1) conjugate. Fractionation of liver cells revealed that the [111In]PGE(1) conjugate was preferentially taken up by liver parenchymal cells. The pharmacological activity was examined in mice with fulminant hepatitis induced by intraperitoneal injection of carbon tetrachloride. Intravenous injection of the PGE(1) conjugate at a dose of 1 mg (0.065 mg PGE(1))/kg effectively inhibited the increase in plasma glutamic pyruvic transaminase (GPT) activity compared with that of free PGE(1) at a dose of 0.065 or 0.65 mg/kg. These results suggest that the PGE(1) conjugate is an excellent prodrug for the treatment of fulminant hepatitis.

A novel glycosylated Cu/Zn-containing superoxide dismutase: production and potential therapeutic effect

The fungal strain Humicola lutea 103 produces a naturally glycosylated Cu/Zn SOD. To improve its yield, the effect of an increased concentration of dissolved oxygen (DO) on growth and enzyme biosynthesis by the producer, cultivated in a 3 l bioreactor, was examined. Exposure to a 20% DO level caused a 1.7-fold increase of SOD activity compared to the DO-uncontrolled culture. Maximum enzyme productivity of SOD was approximately 300 x 10(3) U (kg wet biomass)(-1). The novel enzyme was purified to electrophoretic homogeneity. The presence of Cu and Zn were confirmed by atomic absorption spectrometry. The molecular mass of H. lutea Cu/Zn SOD was calculated to be 31870 Da for the whole molecule and 15936 Da for the structural subunits. The N-terminal sequence revealed a high degree of structural homology with Cu/Zn SOD from other prokaryotic and eukaryotic sources. H. lutea Cu/Zn SOD was used in an in vivo model for the demonstration of its protective effect against myeloid Graffi tumour in hamsters. Comparative studies revealed that the enzyme (i) elongated the latent time for tumour appearance, (ii) inhibited tumour growth in the early stage of tumour progression (73-75% at day 10) and (iii) increased the mean survival time of Graffi-tumour-bearing hamsters. Moreover, the fungal Cu/Zn SOD exhibited a strong protective effect on experimental influenza virus infection in mice. The survival rate increased markedly, the time of survival rose by 5.2 d and the protective index reached 86%. The H. lutea SOD protected mice from mortality more efficiently compared to the selective antiviral drug ribavirin and to commercial bovine SOD. In conclusion, our results suggest that appropriate use of the novel fungal SOD, applied as such or in combination with selective inhibitors, could outline a promising strategy for the treatment of myeloid Graffi tumour and influenza virus infection.

Chemical modification of hyaluronidase regulates its inhibition by heparin

Chemical modification of surface amino groups of bovine testicular hyaluronidase with aldehyde dextran was conducted. It was found that with the increase of modification degree of hyaluronidase amino groups the value of residual enzymatic catalytic activity is decreased rather monotonously. It turned out that the value of inhibition of enzyme activity by heparin considerably depends on modification degree of enzyme. This dependence is of a threshold character. Sharp conformational changes in the enzyme occurring at 70-90% degree of its modification considerably lowers heparin inhibition. The higher the degree of hyaluronidase modification, the weaker its inhibition by heparin. More completely/deeply modified derivatives of hyaluronidase (modification degree 96-100%) are practically not inhibited by heparin. Thus, chemical conjugation of hyaluronidase with aldehyde dextran regulates the value of enzyme inhibition by heparin. Hyaluronidase modification becomes an informative tool to study the mechanism of inhibition of its enzyme activity and an efficient means for the development of new therapeutic preparations improving tissue permeability during cardiovascular injuries.

Biodistribution characteristics of mannosylated, fucosylated, and galactosylated liposomes in mice

The in vivo disposition behavior and pharmacokinetic characteristics of galactosylated (Gal), mannosylated (Man) and fucosylated (Fuc) liposomes were compared in this study. For the preparation of the glycosylated liposomes, cholesten-5-yloxy-N-(4-((1-imino-2-beta-D-thiogalactosyle thyl)amino)a lkyl)formamide (Gal-C4-Chol) (Kawakami et al., Biochem. Biophys. Res. Commun. 252 (1998) 78-83) and its mannosylated and fucosylated derivatives (Man-C4-Chol and Fuc-C4-Chol, respectively) were synthesized. The glycosylated liposomes are composed of distearoylphosphatidylcholine (DSPC), cholesterol (Chol), and Gal-C4-Chol (or Man-C4-Chol or Fuc-C4-Chol) with the molar ratio of 60:35:5. After intravenous injection in mice, these three types of [(3)H]cholesteryl hexadecyl ether-labeled glycosylated liposomes were rapidly eliminated from the circulating blood and preferentially recovered in the liver. In contrast, DSPC/Chol (60:40) liposomes without glycosylation were retained for a long time in the circulating blood. The uptake ratios by parenchymal cells (PC) and nonparenchymal cells (NPC) (PC/NPC ratios) for 0.5% Gal, Man and Fuc liposomes were found to be 15.1, 0.6 and 0.2, respectively. The effect of predosing glycosylated proteins and liposomes on the hepatic uptake of 0.5% (3)H-labeled Gal, Man, and Fuc liposomes was investigated and the results support the conclusion that Gal, Man, and Fuc liposomes are taken up by the liver via asialoglycoprotein receptors in PC, mannose receptors in NPC, and fucose receptors in NPC, respectively. Interestingly, Gal liposomes were taken up by NPC rather than by PC at a high dose (5%). Together with the finding that 5% Gal liposomes inhibit the hepatic uptake of (3)H-labeled Fuc liposomes, this suggests that Gal-liposomes administered at a high dose will also be taken up by fucose receptors in NPC, that are considered to act as galactose particle receptors.

Dextrans for targeted and sustained delivery of therapeutic and imaging agents

Dextrans are glucose polymers which have been used for more than 50 years as plasma volume expanders. Recently, however, dextrans have been investigated for delivery of drugs, proteins/enzymes, and imaging agents. These highly water soluble polymers are available commercially as different molecular weights (M(W)) with a relatively narrow M(W) distribution. Additionally, dextrans contain a large number of hydroxyl groups which can be easily conjugated to drugs and proteins by either direct attachment or through a linker. In terms of pharmacokinetics, the intact polymer is not absorbed to a significant degree after oral administration. Therefore, most of the applications of dextrans as macromolecular carriers are through injectable routes. However, a few studies have reported the potential of dextrans for site (colon)-specific delivery of drugs via the oral route. After the systemic administration, the pharmacokinetics of the conjugates of dextran with therapeutic/imaging agents are significantly affected by the kinetics of the dextran carrier. Animal and human studies have shown that both the distribution and elimination of dextrans are dependent on the M(W) and charge of these polymers. Pharmacodynamically, conjugation with dextrans has resulted in prolongation of the effect, alteration of toxicity profile, and a reduction in the immunogenicity of drugs and/or proteins. A substantial number of studies on dextran conjugates of therapeutic/imaging agents have reported favorable alteration of pharmacokinetics and pharmacodynamics of these agents. However, most of these studies have been carried out in animals, with only a few being extended to humans. Future studies should concentrate on barriers for the clinical use of dextrans as macromolecular carriers for delivery of drugs, proteins, and imaging agents.

Mannose receptor-mediated gene transfer into macrophages using novel mannosylated cationic liposomes

A novel mannosylated cholesterol derivative, cholesten-5-yloxy-N-(4-((1-imino-2-beta-D-thiomannosyl -ethyl)amino)bu tyl) formamide (Man-C4-Chol), was synthesized in order to perform mannose receptor-mediated gene transfer with liposomes. Plasmid DNA encoding luciferase gene (pCMV-Luc) complexed with liposomes, consisting of a 6:4 mixture of Man-C4-Chol and dioleoylphosphatidylethanolamine (DOPE), showed higher transfection activity than that complexed with 3beta[N-(N', N'-dimethylaminoethane)-carbamoyl]cholesterol (DC-Chol)/DOPE(6:4) and N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA)/DOPE(1:1) liposomes in mouse peritoneal macrophages. The presence of 20 mM mannose significantly inhibited the transfection efficiency of pCMV-Luc complexed with Man-C4-Chol/DC- Chol/DOPE(3:3:4) and Man-C4-Chol/DOPE(6:4) liposomes. High gene expression of pCMV-Luc was observed in the liver after intravenously injecting mice with Man-C4-Chol/DOPE(6:4) liposomes, whereas DC-Chol/DOPE(6:4) liposomes only showed marked expression in the lung. The gene expression with Man-C4-Chol/DOPE(6:4) liposome/ DNA complexes in the liver was observed preferentially in the non-parenchymal cells and was significantly reduced by predosing with mannosylated bovine serum albumin. The gene expression in the liver was greater following intraportal injection. These results suggest that plasmid DNA complexed with mannosylated liposomes exhibits high transfection activity due to recognition by mannose receptors both in vitro and in vivo. Gene Therapy (2000) 7, 292-299.

Pharmacokinetic evaluation of mannosylated bovine serum albumin as a liver cell-specific carrier: quantitative comparison with other hepatotropic ligands

To assess the feasibility of mannosylated macromolecules as a liver-specific carrier system, hepatic uptake characteristics of mannosylated bovine serum albumin (Man-BSA) were pharmacokinetically investigated. After intravenous injection, 111In-Man18-BSA accumulated in the liver up to 70% of dose at 2h; the endothelial cells and Kupffer cells contributed about 66% and 21% of the uptake, respectively. In single-pass perfusion experiments using rat liver at varying inflow concentrations (0.1-2.0 microg/ml), 111In-Man18-BSA and 111In-Man33-BSA were continuously extracted by the liver and their extraction ratios decreased with the increasing inflow concentrations. The outflow curves of each 111In-Man-BSA at three concentrations were simultaneously fitted to a pharmacokinetic model including a binding to the cell surface and an internalization, by using a nonlinear regression program MULTI(RUNGE). The binding constant augmented with the increase in the number of mannose per BSA, whereas the internalization rate constant was quite comparable for both derivatives. The pharmacokinetic analysis has demonstrated that the uptake process of 111In-Man-BSA is characterized to possess fewer binding sites and a greater internalization rate in comparison with other liver-specific carriers such as galactosylated, succinylated and cationized BSAs. These results will provide useful information in designing drug targeting systems to the liver nonparenchymal cells via mannose receptors.

Liver uptake and hepato-biliary transfer of galactosylated proteins in rats are determined by the extent of galactosylation

The effect of molecular mass and surface density of galactose residues on hepatic uptake and subsequent biliary excretion of galactosylated proteins was investigated in rats. Several proteins with different molecular weights (15-70 kDa) and different numbers of galactose units were synthesized and radiolabeled with 111In. Galactosylated proteins were administered i.v. to anaesthetized rats and samples of plasma and bile were collected for 3 h. Liver was harvested at the end of the experiments and the radioactivity of all samples was measured. Galactosylated proteins accumulated primarily in the liver and 2-10% of the administered dose appeared in the bile, mainly in undegraded form. The hepatic uptake clearance (Cl liver) and biliary excretion rate constant (kbile) of galactosylated proteins were calculated. No direct effect of molecular weight was observed, however, on increasing the galactose density, Cl liver increased from about 4 to 400 ml/h whereas kbile gradually decreased from about 0.057 to 0.007 (h-1). In conclusion, both hepatic uptake and biliary excretion of galactosylated proteins were found to be affected by the extent of galactosylation.

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.

Development of glycosylated human interleukin-1alpha, neoglyco IL-1alpha, coupled with D-galactose monosaccharide: biological activities in vivo

In our previous study, a galactose monosaccharide with C9 spacer was chemically coupled to recombinant human interleukin 1alpha (rhIL-1alpha) in order to study the effect of glycosylation on its activities, and to develop IL-1 with less deleterious effects. The glycosylated IL-la exhibited reduced activities in vitro by 10 to 10000-fold depending upon different aspects of activities addressed. The affinity to type I and II IL-1 receptors were also reduced. In this study we examined a variety of IL-1 activities in vivo, including upregulation of serum levels of IL-6, alpha1-acid glycoprotein, NOx, corticosterone, downregulation of serum level of glucose, and recovery of peripheral white blood cells (WBCs) from myelosuppression in 5-fluorouracil-treated mice. In contrast to the biological activities in vitro, these activities in vivo were uniformly reduced by only about 10 to 20-fold compared to untreated IL-1alpha.

Development of glycosylated human interleukin-1alpha, neoglyco IL-1alpha, by coupling with D-galactose monosaccharide: biological activities in vitro

In the previous study, galactose with C9 spacer was chemically coupled to human recombinant (rh) IL-1alpha in order to study the effect of glycosylation on its activities, and to develop IL-1 with less deleterious effects. In this study we examined a variety of IL-1 activities in vitro, including proliferative effect on T cells, antiproliferative effect on myeloid leukemic cells and melanoma cells, stimulatory effects on IL-6 synthesis by melanoma cells and PGE2 synthesis by fibroblast cells Galactose-introduced IL-1alpha (Gal-IL-1alpha) exhibited reduced activities from 10 to 10000 times compared with unmodified IL-1alpha in all the activities performed in vitro. The competitive binding of 125I-IL-1alpha to mouse T cells and pre-B cells with unlabeled IL-1alpha s suggests a decrease in binding affinities of Gal-IL-1alpha to both type I and type II IL-1 receptors. Therefore, reduced activities of Gal-IL-1alpha are due, at least partially, to the decrease in their receptor binding affinities.

A potent superoxide dismutase mimic: manganese beta-octabromo-meso-tetrakis-(N-methylpyridinium-4-yl) porphyrin

Variously modified metalloporphyrins offer a promising route to stable and active mimics of superoxide dismutase (SOD). Here we explore bromination on the pyrroles as a means of increasing the redox potentials and the catalytic activities of the copper and manganese complexes of a cationic porphyrin. Mn(II) and Cu(II) octabrominated 5,10,15,20-tetrakis-(N-methylpyridinium-4-yl) porphyrin, Mn(II)OBTMPyP4+, and Cu(II)OBTMPyP4+ were prepared and characterized. The rate constants for the porphyrin-catalyzed dismutation of O2.- as determined from the inhibition of the cytochrome c reduction are k(cat) = 2.2 x 10(8) and 2.9 x 10(6) M(-1) s(-1), i.e., IC50 was calculated to be 12 nM and 0.88 microM, respectively. The metal-centered half-wave potential was E(1/2) = +0.48 V vs NHE for the manganese compound. Cu(II)OBTMPyP4+ proved to be extremely stable, while its Mn(II) analog has a moderate stability, log K = 8.08. Nevertheless, slow manganese dissociation from Mn(II)OBTMPyP4+ enabled the complex to persist and exhibit catalytic activity even at the nanomolar concentration level and at biological pH. The corresponding Mn(III)OBTMPyP5+ complex exhibited significantly increased stability, i.e., demetallation was not detected in the presence of a 400-fold molar excess of EDTA at micromolar porphyrin concentration and at pH 7.8. The beta-substituted manganese porphyrin facilitated the growth of a SOD-deficient strain of Escherichia coli when present at 0.05 microM but was toxic at 1.0 microM. The synthetic approach used in the case of manganese and copper compounds offers numerous possibilities whereby the interplay of the type and of the number of beta substituents on the porphyrin ring would hopefully lead to porphyrin compounds of increased stability, catalytic activity, and decreased toxicity.

CD4(+) T-lymphocytes mediate ischemia/reperfusion-induced inflammatory responses in mouse liver

The success of orthotopic liver transplantation is dependent on multiple factors including MHC tissue compatibility and ischemic/reperfusion injury. Ischemic/reperfusion (I/R) injury in the liver occurs in a biphasic pattern consisting of both acute phase (oxygen free radical mediated) and subacute phase (neutrophil-mediated) damage. Although numerous studies have given insights into the process of neutrophil recruitment after I/R injury to the liver, the exact mechanism that initiates this subacute response remains undefined. Using a T cell-deficient mouse model, we present data that suggests that T-lymphocytes are key mediators of subacute neutrophil inflammatory responses in the liver after ischemia and reperfusion. To this end, using a partial lobar liver ischemia model, we compared the extent of reperfusion injury between immune competent BALB/c and athymic nu/nu mice. Studies evaluating the extent of liver damage as measured by serum transaminases (GPT) demonstrate similar acute (3-6 h) post-I/R responses in these two mouse models. In contrast, the subacute phase (16-20 h) of liver injury, as measured by both serum GPT levels and percent hepatocellular necrosis, was dramatically reduced in T cell-deficient mice as compared with those with an intact immune system. This reduction in liver injury seen in nu/nu mice was associated with a 10-fold reduction in hepatic neutrophil infiltration. Adoptive transfer of T cell-enriched splenocytes from immune competent mice was capable of reconstituting the neutrophil-mediated subacute inflammatory response within T cell-deficient nu/nu mice. Furthermore, in vivo antibody depletion of CD4(+) T-lymphocytes in immune competent mice resulted in a reduction of subacute phase injury and inflammation as measured by serum GPT levels and neutrophil infiltration. In contrast, depletion of CD8(+) T-lymphocytes had no effect on these indexes of subacute inflammation. Kinetic analysis of T cell infiltration in the livers of BALB/c mice demonstrated a fivefold increase in the number of hepatic CD4(+) T-lymphocytes within the first hour of reperfusion with no significant change in the number of CD8(+) T-lymphocytes. In summary, these results implicate CD4(+) T-lymphocytes as key regulators in initiating I/R-induced inflammatory responses in the liver. Such findings have implications for therapy directed at the early events in this inflammatory cascade that may prove useful in liver transplantation.

Augmented inhibitory effect of superoxide dismutase on superoxide anion release from macrophages by direct cationization

Superoxide dismutase (SOD) was modified into cationized form (Cat-SOD) in order to enhance its pharmacological efficacy based on an electrostatic interaction. The inhibitory effect of Cat-SOD on superoxide anion release from inflammatory macrophages and its cellular interaction were studied in vitro. Cat-SOD exhibited an excellent inhibitory effect on superoxide anion release from the macrophages, and this effect surpassed those of native SOD and SOD modified with mannose (Man-SOD) which is taken up via mannose receptor-mediated endocytosis by macrophages. In the presence of colchicine, a microtubule-disruptive agent, the inhibitory effect of Cat-SOD was slightly impaired, whereas the effect of Man-SOD completely disappeared. The intracellular localization of fluorescein isothiocyanate-labeled SOD, Cat-SOD and Man-SOD observed by confocal laser microscopy supported the difference in their abilities to eliminate superoxide anions. The different sensitivities of Cat-SOD and Man-SOD to colchicine were also confirmed by the confocal laser microscopic images, suggesting their distinct intracellular trafficking pathways in the macrophages. In conclusion, Cat-SOD is desirable for its pharmacological activity, which is probably the result of its ability to be delivered to the vicinity of NADPH-oxidase which locates in the cell membrane and generates superoxide anions.

Non-polarized secretion of mouse interferon-beta from gene-transferred human intestinal Caco-2 cells

PURPOSE

The intestinal epithelium is considered to be a feasible target for somatic gene therapy. To this end, Caco-2 cells derived from human colon carcinoma were transfected with a mouse interferon-beta (IFN-beta) expression vector and several stable sublines were established; this hetero-specific cytokine allows unexpected cellular effects to be avoided. Using the highest mouse IFN-beta-producing sublines, the mode of IFN secretion was examined.

METHODS

The secretion polarity of mouse IFN-beta in its gene-transduced Caco-2 sublines was studied in a bicameral culture system in which the chambers were separated by microporous filters.

RESULTS

Mouse IFN-beta was secreted to the same extent from both apical and basolateral surfaces of the transduced cells regardless of cell aging.

CONCLUSIONS

These results suggest that in the intestinal epithelium exogenous gene products such as IFNs can be delivered to both the luminal and blood sides in vivo. Thus, the intestinal epithelium may be suitable for systemic and local delivery of therapeutic proteins by gene transfer.