Tissue distribution of 125I-labelled bovine superoxide dismutase (SOD) in the rat

Sex-based differences of antioxidant enzyme nanoparticle effects following traumatic brain injury

Following traumatic brain injury (TBI), reactive oxygen species (ROS) are released in excess, causing oxidative stress, carbonyl stress, and cell death, which induce the additional release of ROS. The limited accumulation and retention of small molecule antioxidants commonly used in clinical trials likely limit the target engagement and therapeutic effect in reducing secondary injury. Small molecule drugs also need to be administered every several hours to maintain bioavailability in the brain. Therefore, there is a need for a burst and sustained release system with high accumulation and retention in the injured brain. Here, we utilized Pro-NP™ with a size of 200 nm, which was designed to have a burst and sustained release of encapsulated antioxidants, Cu/Zn superoxide dismutase (SOD1) and catalase (CAT), to scavenge ROS for >24 h post-injection. Here, we utilized a controlled cortical impact (CCI) mouse model of TBI and found the accumulation of Pro-NP™ in the brain lesion was highest when injected immediately after injury, with a reduction in the accumulation with delayed administration of 1 h or more post-injury. Pro-NP™ treatment with 9000 U/kg SOD1 and 9800 U/kg CAT gave the highest reduction in ROS in both male and female mice. We found that Pro-NP™ treatment was effective in reducing carbonyl stress and necrosis at 1 d post-injury in the contralateral hemisphere in male mice, which showed a similar trend to untreated female mice. Although we found that male and female mice similarly benefit from Pro-NP™ treatment in reducing ROS levels 4 h post-injury, Pro-NP™ treatment did not significantly affect markers of post-traumatic oxidative stress in female CCI mice as compared to male CCI mice. These findings of protection by Pro-NP™ in male mice did not extend to 7 d post-injury, which suggests subsequent treatments with Pro-NP™ may be needed to afford protection into the chronic phase of injury. Overall, these different treatment effects of Pro-NP™ between male and female mice suggest important sex-based differences in response to antioxidant nanoparticle delivery and that there may exist a maximal benefit from local antioxidant activity in injured brain.

Hard, Soft, and Hard-and-Soft Drug Delivery Carriers Based on CaCO3 and Alginate Biomaterials: Synthesis, Properties, Pharmaceutical Applications

Because free therapeutic drug molecules often have adverse effects on normal tissues, deliver scanty drug concentrations and exhibit a potentially low efficacy at pathological sites, various drug carriers have been developed for preclinical and clinical trials. Their physicochemical and toxicological properties are the subject of extensive research. Inorganic calcium carbonate particles are promising candidates as drug delivery carriers owning to their hardness, porous internal structure, high surface area, distinctive pH-sensitivity, low degradability, etc, while soft organic alginate hydrogels are also widely used because of their special advantages such as a high hydration, bio-adhesiveness, and non-antigenicity. Here, we review these two distinct substances as well as hybrid structures encompassing both types of carriers. Methods of their synthesis, fundamental properties and mechanisms of formation, and their respective applications are described. Furthermore, we summarize and compare similarities versus differences taking into account unique advantages and disadvantages of these drug delivery carriers. Moreover, rational combination of both carrier types due to their performance complementarity (yin-&yang properties: in general, yin is referred to for definiteness as hard, and yang is broadly taken as soft) is proposed to be used in the so-called hybrid carriers endowing them with even more advanced properties envisioned to be attractive for designing new drug delivery systems.

Scavenging of superoxide anions by lecithinized superoxide dismutase in HL-60 cells

Superoxide dismutase covalently bound to four lecithin molecules (PC-SOD) on plasma membrane has been found to have beneficial therapeutic effects.

Antioxidant-based therapies for angiotensin II-associated cardiovascular diseases

Cardiovascular diseases, including hypertension and heart failure, are associated with activation of the renin-angiotensin system (RAS) and increased circulating and tissue levels of ANG II, a primary effector peptide of the RAS. Through its actions on various cell types and organ systems, ANG II contributes to the pathogenesis of cardiovascular diseases by inducing cardiac and vascular hypertrophy, vasoconstriction, sodium and water reabsorption in kidneys, sympathoexcitation, and activation of the immune system. Cardiovascular research over the past 15-20 years has clearly implicated an important role for elevated levels of reactive oxygen species (ROS) in mediating these pathophysiological actions of ANG II. As such, the use of antioxidants, to reduce the elevated levels of ROS, as potential therapies for various ANG II-associated cardiovascular diseases has been intensely investigated. Although some antioxidant-based therapies have shown therapeutic impact in animal models of cardiovascular disease and in human patients, others have failed. In this review, we discuss the benefits and limitations of recent strategies, including gene therapy, dietary sources, low-molecular-weight free radical scavengers, polyethylene glycol conjugation, and nanomedicine-based technologies, which are designed to deliver antioxidants for the improved treatment of cardiovascular diseases. Although much work has been completed, additional research focusing on developing specific antioxidant molecules or proteins and identifying the ideal in vivo delivery system for such antioxidants is necessary before the use of antioxidant-based therapies for cardiovascular diseases become a clinical reality.

Amphiphilic cholic-acid-modified dextran sulfate and its application for the controlled delivery of superoxide dismutase

A novel amphiphilic and biodegradable polyelectrolyte DS-CA is prepared by the esterification of DS with CA. DS-CA can self-assemble into stable nanoparticles in water. SOD can effectively associate with DS-CA at pH = 5.0 by virtue of electrostatic and hydrophobic interactions. SOD release from the complex nanoparticles is slow at pH = 1.2. The release at pH = 7.4 PBS shows an extended behavior and is tunable by changing the weight ratio of SOD to DS-CA as well as the CA substitution degree. Increasing the CA substitution degree of DS-CA can significantly enhance the cellular uptake of the loaded SOD. This study demonstrates that the amphiphilic DS-CA provides a promising strategy for oral delivery of protein/peptide drugs.

The attenuation of central angiotensin II-dependent pressor response and intra-neuronal signaling by intracarotid injection of nanoformulated copper/zinc superoxide dismutase

Adenoviral-mediated overexpression of the intracellular superoxide (O(2)(*-)) scavenging enzyme copper/zinc superoxide dismutase (CuZnSOD) in the brain attenuates central angiotensin II (AngII)-induced cardiovascular responses. However, the therapeutic potential for adenoviral vectors is weakened by toxicity and the inability of adenoviral vectors to target the brain following peripheral administration. Therefore, we developed a non-viral delivery system in which CuZnSOD protein is electrostatically bound to a synthetic poly(ethyleneimine)-poly(ethyleneglycol) (PEI-PEG) polymer to form a polyion complex (CuZnSOD nanozyme). We hypothesized that PEI-PEG polymer increases transport of functional CuZnSOD to neurons, which inhibits AngII intra-neuronal signaling. The AngII-induced increase in O(2)(*-), as measured by dihydroethidium fluorescence and electron paramagnetic resonance spectroscopy, was significantly inhibited in CuZnSOD nanozyme-treated neurons compared to free CuZnSOD- and non-treated neurons. CuZnSOD nanozyme also attenuated the AngII-induced inhibition of K(+) current in neurons. Intracarotid injection of CuZnSOD nanozyme into rabbits significantly inhibited the pressor response of intracerebroventricular-delivered AngII; however, intracarotid injection of free CuZnSOD or PEI-PEG polymer alone failed to inhibit this response. Importantly, neither the PEI-PEG polymer alone nor the CuZnSOD nanozyme induced neuronal toxicity. These findings indicate that CuZnSOD nanozyme inhibits AngII intra-neuronal signaling in vitro and in vivo.

Importance of calcitonin gene-related peptide, adenosine and reactive oxygen species in cerebral autoregulation under normal and diseased conditions

1. Mechanisms regulating cerebral circulation, including autoregulation of cerebral blood flow (CBF), have been widely investigated. Vasodilators such as nitric oxide, prostacyclin, calcitonin gene-related peptide (CGRP) and K+ channel openers are well known to have important roles in the physiological and pathophysiological control of CBF autoregulation. In the present review, the focus is on the mechanism(s) of altered CBF autoregulation after traumatic brain injury and subarachnoid haemorrhage (SAH) and on the effect of adenovirus-mediated transfer of Cu/Zn superoxide dismutase (SOD)-1 in amelioration of impaired CBF autoregulation. 2. The roles of CGRP and adenosine are particularly emphasized, both being implicated in the autoregulatory vasodilation of the pial artery in response to hypotension. 3. After fluid percussion injury, production of NADPH oxidase-derived superoxide anion and activation of tyrosine kinase links the inhibition of K+ channels to impaired autoregulatory vasodilation in response to acute hypotension and alterations in CBF autoregulation in rat pial artery. 4. Subarachnoid haemorrhage during the acute stage causes an increase in NADPH oxidase-dependent superoxide formation in cerebral vessels in association with activated tyrosine phosphorylation-coupled increased expression of gp91phox mRNA and membrane translocation of Rac protein, thereby resulting in a significant reduction of autoregulatory vasodilation. 5. Fluid percussion injury and SAH-induced overproduction of superoxide anion in cerebral vessels contributes to the impairment of CBF autoregulation and administration of recombinant adenovirus-mediated transfer of the Cu/Zn SOD-1 gene effectively ameliorates the impairment of CBF autoregulation of the pial artery.

Prevention of impairment of cerebral blood flow autoregulation during acute stage of subarachnoid hemorrhage by gene transfer of Cu/Zn SOD-1 to cerebral vessels

The present study determined whether gene transfer of human copper/zinc superoxide dismutase-1 (Cu/Zn SOD-1) prevented the autoregulatory impairment of CBF induced by subarachnoid hemorrhage (SAH). After application of recombinant adenovirus (100 microL of 1 x 10(10) pfu/mL, intracisternally) encoding human Cu/Zn SOD-1 3 days before experiments, Cu/Zn SOD-1 activity significantly increased in association with increase in Cu/Zn SOD-1 mRNA and protein expression in the cerebral vasculature of both sham-operated and SAH rats as determined by reverse transcriptase-polymerase chain reaction, Western blotting, and immunohistochemistry, and SAH-induced increase in superoxide anion was markedly reduced in accordance with increased nitric oxide production. In line with these findings, rats that received human Cu/Zn SOD-1 therapy showed the prominent restoration of blunted vasodilation of the pial artery in response to calcitonin gene-related peptide and levcromakalim, and the recovery of impaired autoregulatory vasodilation in response to acute hypotension, thereby leading to significant restoration of CBF autoregulation. These results provide a rational basis for application of Cu/Zn SOD-1 gene therapy for protection of the impairment of autoregulatory CBF during the acute stage of SAH.

Gene transfer of Cu/Zn SOD to cerebral vessels prevents FPI-induced CBF autoregulatory dysfunction

The goal of this study was to determine whether gene transfer of human copper-zinc (Cu/Zn) superoxide dismutase (SOD) has preventive effects on cerebral blood flow (CBF) autoregulatory dysfunction after fluid percussion injury (FPI). Rats subjected to FPI (2-2.5 atm) exhibited enhanced activity of reduced NADP (NADPH) oxidase in the cerebral vasculature. In line with these findings, the rats showed not only reduced vasodilation of the pial artery in response to calcitonin gene-related peptide and levcromakalim but also impaired autoregulatory vasodilation in response to acute hypotension. The FPI-induced hemodynamic alterations were significantly prevented by pretreatment with diphenyleneiodonium (10 micromol/l), an NAD(P)H oxidase inhibitor. Intracisternal application of recombinant adenovirus (100 microl of 1 x 10(10) pfu/ml)-encoding human Cu/Zn SOD 3 days before FPI prevented the impairment of vasodilation to hypotension and vasorelaxants, resulting in the restoration of CBF autoregulation. Our findings demonstrate that FPI-induced impairment of CBF autoregulation is closely related with NAD(P)H oxidase-derived superoxide anion, and these alterations can be prevented by the recombinant adenovirus-mediated transfer of human Cu/Zn SOD gene to the cerebral vasculature.

Targeting of superoxide dismutase and catalase to vascular endothelium

Reactive oxygen species, such as superoxide anion (O2(-)) and H2O2, cause oxidative stress in endothelial cells, a condition implicated in the pathogenesis of many cardiovascular and pulmonary diseases. Antioxidant enzymes, superoxide dismutases (SOD, converting superoxide anion into H2O2) and catalase (converting H2O2 into water), are candidate drugs for augmentation of antioxidant defenses in endothelium. However, SOD and catalase undergo fast elimination from the bloodstream, which compromises delivery and permits rather modest, if any, protection against vascular oxidative stress. Coupling of polyethylene glycol (PEG) to the enzymes and encapsulating them in liposomes increases their bioavailability and enhances their protective effect. Chemical modifications and genetic manipulations of SOD and catalase have been proposed in order to provide more effective delivery to endothelium. For example, chimeric protein constructs consisting of SOD and heparin-binding peptides have an affinity for charged components of the endothelial glycocalix. However, the problem of developing a more effective and precise delivery of the drugs to endothelial cells persists. Endothelial surface antigens may be employed to provide targeting and subcellular addressing of drugs (vascular immunotargeting strategy). Thus, SOD and catalase conjugated to antibodies directed against the constitutively expressed endothelial antigens, angiotensin-converting enzyme (ACE) and adhesion molecules (ICAM-1 or PECAM-1), bind to endothelium in intact animals after intravascular administration, accumulate in the pulmonary vasculature, enter endothelial cells and augment their antioxidant defenses. Such immunotargeting strategies may provide secondary therapeutic benefits by inhibiting the function of target antigens. For example, blocking of ICAM-1 and PECAM-1 by carrier antibodies may attenuate inflammation and leukocyte-mediated vascular damage. Additional studies in animal models of vascular oxidative stress are necessary in order to more fully characterize potential therapeutic effects and limitations of targeting of antioxidant enzymes to endothelial cells.

Delivery of antioxidant enzyme proteins to the lung

Protection of alveolar epithelial cells (alveolocytes) and vascular endothelial cells against pulmonary oxidative stress is an important problem. An inadequate delivery to the target cells limits the protective utility of the antioxidant enzymes, superoxide dismutase (SOD) and catalase. SOD and catalase modifications, such as coupling with polyethylene glycol and encapsulation in liposomes, prolong the life span of the active enzymes in vivo. The airway administration of SOD and catalase protects alveolocytes against hyperoxic oxidative stress. Although pulmonary endothelium is poorly accessible from the airways, it is accessible from circulation. However, antioxidant enzymes and their derivatives display poor targeting to pulmonary endothelium. To improve the targeting and provide intracellular delivery to endothelium, the enzymes can be conjugated with antibodies against endothelial antigens, such as angiotensin-converting enzyme and adhesion molecules [intercellular adhesion molecule-1 (ICAM-1) or platelet-endothelial cell adhesion molecule-1 (PECAM-1)]. These immunoconjugates accumulate in the pulmonary vasculature in intact animals, enter endothelium, and augment the antioxidant defenses. The immunoconjugates directed against ICAM-1 and PECAM-1 may also provide a secondary therapeutic benefit by blocking of sequestration and infiltration of leukocytes in the lungs. Further investigations are necessary to evaluate the therapeutic effectiveness of the vascular immunotargeting of antioxidant enzymes and solve technical problems associated with production of safe, clinically useful conjugates.

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.

Preventive effects of superoxide dismutase derivatives modified with monosaccharides on reperfusion injury in rat liver transplantation

BACKGROUND

Superoxide dismutase (SOD) derivatives modified with monosaccharides such as mannosylated SOD (Man-SOD) and galactosylated SOD (Gal-SOD) are taken up by parenchymal and nonparenchymal cells of the liver, respectively, via receptor-mediated endocytosis. We examined the preventive effects of Man- or Gal-SOD on cold ischemia-reperfusion injury in orthotopic liver transplantation (OLT) in rats.

METHODS

Male Lewis rats underwent OLT. Native SOD and modified SOD with mannose (Man-SOD) or galactose (Gal-SOD) were intravenously given just prior to reperfusion of the grafted liver.

RESULTS

After OLT, no significant changes in serum levels of aspartate aminotransferase or lactate dehydrogenase were evident among rats, with or without various types of SOD. However, tissue levels of Na+,K+-ATPase, an indicator of tissue viability, were significantly higher in rats treated with Man- and Gal-SODs compared with that in untreated OLT rats. When comparisons were made between Gal-SOD and Man-SOD, higher levels of Na+,K+-ATPase were evident in rats treated with Gal-SOD. Elevations of tissue levels of lipid peroxides were significantly inhibited by modified SODs. The survival rates of rats following OLT after prolonged cold preservation correlated with results of graft viability.

CONCLUSIONS

SOD derivatives, particularly Gal-SOD, have protective effects on cold ischemia-reperfusion injury during OLT in rats.

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.

L-arginine and superoxide dismutase prevent or reverse cerebral hypoperfusion after fluid-percussion traumatic brain injury

To determine whether treatment with L-arginine or superoxide dismutase (SOD) would prove effective in reducing cerebral hypoperfusion after traumatic brain injury (TBI), we measured cerebral blood flow (CBF) using laser Doppler flowmetry (LDF) in rats treated before or after moderate (2.2 atm) fluid-percussion (FP) TBI. Rats were anesthetized with isoflurane and prepared for midline FP TBI and then for LDF by thinning the calvaria using an air-cooled drill. Rats were then randomly assigned to receive sham injury, sham injury plus L-arginine (100 mg/kg, 5 min after sham TBI), TBI plus 0.9% NaCl, TBI plus L-arginine (100 mg/kg, 5 min post-TBI), TBI plus SOD (24,000 U/kg pre-TBI + 1600 units/kg/min for 15 min after TBI), or TBI plus SOD and L-arginine. A second group of rats received TBI plus saline, L-, or D-arginine (100 mg/kg, 5 min after-TBI). After treatment and TBI or sham injury, CBF was measured continuously using LDF for 2 h and CBF was expressed as a percent of the preinjury baseline for 2 h after TBI. Rats treated with saline or D-arginine exhibited significant reductions in CBF that persisted throughout the monitoring period. Rats treated with L-arginine alone or in combination with SOD exhibited no decreases in CBF after TBI. CBF in the SOD-treated group decreased significantly within 15 min after TBI but returned to baseline levels by 45 min after TBI. These studies indicate that L-arginine but not D-arginine administered after TBI prevents posttraumatic hypoperfusion and that pretreatment with SOD will restore CBF after a brief period of hypoperfusion.

Antioxidants attenuate endotoxin-induced acute renal failure in rats

Acute kidney dysfunction, manifested by a reduction in renal blood flow and in the glomerular filtration rate, is a common finding in septic shock. The pathogenetic mechanisms responsible for the renal dysfunction observed in the endotoxemic murine model are not completely understood. In this study, an attempt was made to halt the progressive renal dysfunction in the rats by administration of the antioxidants dimethylthiourea (DMTU) (50 mg/100 g) and superoxide dismutase (SOD) (0.4 mg/100 g) before endotoxin infusion (0.5 mg/100 g), or by inducing endotoxin tolerance. Renal function, assessed by creatinine, inulin, and p-aminohippuric acid clearance, nicotinamide adenine dinucleotide, and electrolyte reabsorption, was measured 4 hours after the endotoxin infusion. Renal function declined in all rats throughout the study period. However, the reduction in renal function was markedly slower in endotoxemic rats administered DMTU and SOD compared with untreated rats. Similar results were found following induction of endotoxin tolerance. These data suggest that DMTU, SOD, and endotoxin tolerance may be potentially beneficial in halting progressive renal damage associated with endotoxemia.

Targeted delivery of superoxide dismutase to macrophages via mannose receptor-mediated mechanism

Human recombinant superoxide dismutase (SOD) was modified into a mannosylated form (Man-SOD), and its cellular uptake and inhibitory effect on superoxide anion release were studied in vitro, using cultured mouse peritoneal macrophages. [111In]Man-SOD was taken up by the macrophages to a great extent, whereas no significant uptake was observed for native and galactosylated SOD. The uptake of Man-SOD was inhibited significantly at a low temperature and by the presence of mannan, mannose and colchicine, demonstrating the targeted delivery of Man-SOD via mannose receptor-mediated endocytosis. Man-SOD exhibited a superior inhibitory effect on superoxide anion release from inflammatory macrophages stimulated by phorbol-myristate acetate. The present study suggested the potential of Man-SOD as a therapeutic agent for the inflammatory disease mediated by superoxide anions generated by macrophages.

Improvement of therapeutic effect of human recombinant superoxide dismutase on ischemic acute renal failure in the rat via cationization and conjugation with polyethylene glycol

Therapeutic effect of superoxide dismutase (SOD) and three derivatives: a conjugate with polyethylene glycol (SOD-PEG2), a cationized derivative (cSOD), and a mannosylated derivative (Man-SOD), on acute renal failure induced by ischemia/reperfusion was studied in rats. SOD and derivatives were administered intravenously to the rat after nephrectomy of the right kidney and before and after 60 min occlusion of the left renal artery. At 48 hr after reperfusion, the renal function was evaluated by determining the urinary excretion rate of 14C-inulin injected intravenously. No therapeutic effect on the impaired renal function was shown in the case of low dose SOD (2600 unit/kg) treatment. In contrast, administration of cSOD which was shown to be taken up by the isolated perfused kidney from its capillary side and SOD-PEG2 which maintained high plasma concentration exhibited significant therapeutic effect, as did SOD at ten-fold higher dose (26,000 unit/kg). On the other hand, renal damage was promoted by Man-SOD. Thus, the present study demonstrated that chemical modification may improve the therapeutic effect of SOD on the ischemic acute renal failure and increased SOD concentration in the renal vascular space is an important factor for the improved effect.

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

Therapeutic effects of four types of recombinant superoxide dismutase (SOD) derivatives, conjugates with polysaccharides, carboxymethyl (SOD-CMD) and diethylaminoethyl (SOD-DEAED) dextrans and galactosylated (Gal-SOD) and mannosylated (Man-SOD) derivatives, on hepatic ischemia/reperfusion injury were studied in rats. Hepatic injury induced by transient occlusion and subsequent reflow of hepatic blood was evaluated by the analysis of biliary excretion of bromosulfophthalein (BSP) injected intravenously. At a dose of 10000 units/kg, native SOD and SOD-DEAE did not show any significant effect and SOD-CMD showed slight effect. On the other hand, Gal-SOD and Man-SOD, targeted to the liver parenchymal and nonparenchymal cells, respectively, by a receptor-mediated endocytosis, exhibited superior inhibitory effects. These results demonstrated that these glycosylated SOD derivatives were useful for the prevention of hepatic ischemia/reperfusion injury.

Brain and tissue distribution of polyethylene glycol-conjugated superoxide dismutase in rats

BACKGROUND AND PURPOSE

The purpose of this study was to determine the distribution of polyethylene glycol-conjugated superoxide dismutase in the brain, cerebrospinal fluid, and various organs.

METHODS

Distribution of iodine-125-labeled polyethylene glycol-conjugated superoxide dismutase was determined in three groups of male Sprague-Dawley rats: a normotensive sham control group (n = 9) and groups given 125I-labeled polyethylene glycol-conjugated superoxide dismutase either 30 minutes before (n = 10) or 30 minutes after (n = 7) norepinephrine-induced hypertensive injury.

RESULTS

In the first 30 minutes after intravenous administration, polyethylene glycol-conjugated superoxide dismutase plasma activity declined to 70% of the initial value and then decreased negligibly between 30 and 90 minutes. Levels of 125I-labeled polyethylene glycol-conjugated superoxide dismutase in normotensive animals were low in the brain and cerebrospinal fluid and highest in kidney. Brain levels of polyethylene glycol-conjugated superoxide dismutase were elevated only in those rats that received it before hypertensive injury; however, cerebrospinal fluid levels were elevated in animals receiving the drug either before or after hypertensive injury.

CONCLUSION

Our results suggest that the blood-brain barrier becomes more permeable to polyethylene glycol-conjugated superoxide dismutase only during the hypertensive period but that the blood-cerebrospinal fluid barrier sustains more permanent injury. We suggest that the therapeutic effectiveness of polyethylene glycol-conjugated superoxide dismutase in hypertensive brain injury is due to its action in the vascular wall or to its extracellular activity in the cerebrospinal fluid.

Extracellular-superoxide dismutase type C (EC-SOD C) reduces myocardial damage in rats subjected to coronary occlusion and 24 hours of reperfusion

Extracellular-superoxide dismutase type C (EC-SOD C) is a secretory SOD isoenzyme which, in contrast to the intracellular CuZn SOD, has affinity to the endothelium and a long vascular half-life. In the present study, the effects of EC-SOD C and CuZn SOD on reperfusion-induced myocardial damage were determined in rats subjected to 10 min of left coronary artery ligation followed by 24 h of reperfusion. Recombinant human EC-SOD C (rh-EC-SOD C) or the corresponding volume of the vehicle was administered after completion of the coronary ligation. CuZn SOD was given in two equal doses, the first dose directly after ligation and the second one 6 h later. At the end of the reperfusion period the myocardial damage was quantified by measuring the creatine kinase concentration (CK) in the reperfused part of the left ventricular free wall (LVFW), and expressed as a percentage of the concentration in the non-ischemic septum. In the group given the vehicle, 47 +/- 10 (mean +/- SD) of the CK remained in the reperfused LVFW. In the rats receiving rh-EC-SOD C the corresponding values for each dose: 1.4, 4.2 and 12.6 mg/kg were 55 +/- 12 (ns), 55 +/- 12 (ns) and 65 +/- 12% (p less than 0.05, vs. vehicle, Dunnett's multiple comparison test), respectively. Administration of CuZn SOD (2 x 10 mg/kg) resulted in 58 +/- 16% (ns) CK remaining in the LVFW.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain levels of polyethylene glycol-conjugated superoxide dismutase following fluid percussion brain injury in rats

Polyethylene glycol-conjugated superoxide dismutase (PEG-SOD) is being explored as an agent to reduce oxygen radical-mediated damage following brain injury. Yet little is known concerning the site of action of IV-administered PEG-SOD or the capacity of this conjugated enzyme to enter the brain. The purpose of this study was to determine the brain content of PEG-SOD in normal and fluid percussion injured rats. The fluid percussion device was attached over the right parietal cortex and a moderate (2.0 atm) intensity injury was produced. PEG-SOD was conjugated with 125I and given (2000 U/kg, 5 microCi/kg) to rats either 30 min before or 30 min after brain injury. Another group received [125I]PEG-SOD but was not injured. Plasma and left and right brain hemispheres were counted for [125I]PEG-SOD. Plasma levels of [125I]PEG-SOD declined similarly in all three groups during the 90-min period after IV administration. Brain [125I]PEG-SOD was low in control animals (0.034 U/g wet wt). In animals given PEG-SOD after injury the brain level was elevated sixfold in both the left and right hemispheres, compared to control. In rats given the drug before injury, [125I]PEG-SOD was 10 times control level in the right hemisphere, which is the side on which the injury device is attached, and 6 times control level in the left hemisphere. We conclude that traumatic brain injury produces an increase in brain PEG-SOD. The exact cellular site of the increased brain PEG-SOD remains to be clarified.

Superoxide dismutase as an inhibitor of erythroid progenitor cell cycling

C57Bl/6 (B6) mice and mice of a congeneic strain, B6S, differ in the proportions of erythroid progenitor cells (BFU-E) typically seen in DNA synthesis in in vivo cell suicide assays, and bone marrow supernatants (MS) prepared from B6 mice can inhibit BFU-E cycling in vitro. Using in vitro BFU-E DNA synthesis assays and a model system of BFU-E in culture (DA-1 cells) as screening methods for the detection of inhibitors of BFU-E cycling, we have purified the protein that is apparently responsible for the inhibitory effects of MS on progenitor cells and that is also an antagonist of the stimulatory effects of interleukin-3 (IL-3) on DA-1 cell proliferation in culture. We have identified this protein as the Cu,Zn-containing form of the antioxidant enzyme superoxide dismutase (SOD), which is normally present in large amounts in erythrocytes. MS from B6S mice does not inhibit BFU-E DNA synthesis. However, measurements of SOD activity showed no differences between B6 and B6S mice; thus the difference between the effects of B6S-MS and B6-MS is not due to differences in the levels of SOD present. The inhibitory effects of SOD on BFU-E in vitro are opposed by the stimulatory effects of IL-3 in a dose-dependent manner, and similar interactions between stimulatory and inhibitory factors also appear to determine the effects of mouse-derived preparations on erythroid cells. If the interactions seen in vitro are applicable to the state in vivo, SOD may be a constitutive inhibitor of erythroid progenitor cell cycling in mice, acting in opposition to stimulatory factors whose expression varies in response to genetic and physiological influences.

Transport kinetics for superoxide dismutase and catalase between plasma and interstitial fluid in the rat small intestine

The purpose of these studies was to determine the initial rates (first 5 h) of plasma-to-interstitial fluid transport for superoxide dismutase, catalase, and albumin in the rat small intestine. In all experiments, the renal vascular pedicles were ligated to prevent the renal excretion of these macromolecules. Plasma and intestinal interstitial fluid (lymph) samples were collected at timed intervals after bolus intravenous administration of SOD, catalase, or 125I-labeled albumin. Before injection of the proteins, the plasma concentrations (43.8 +/- 16.9 and 7.6 +/- 1.2 U/mL, respectively), interstitial fluid (lymph) concentrations (28.8 +/- 7.6 and 1.6 +/- 0.8 U/mL, respectively), and the lymph-to-plasma (L/P) protein concentration ratios (0.59 +/- 0.13 and 0.22 +/- 0.09, respectively) for endogenous SOD and catalase were determined. The plasma disappearance rate for exogenously administered catalase far exceeded the rates for SOD or albumin. However, the rate of catalase disappearance from the plasma was markedly reduced in animals in which the circulation through the liver was eliminated, suggesting that the hepatic route may be important for elimination of exogenously administered catalase. Maximal interstitial fluid catalase concentrations were achieved within 30 min while SOD and albumin required 45-90 min. The L/P ratios for exogenously administered SOD and albumin increased to 0.22 +/- 0.06 and 0.19 +/- 0.03 within 60 and 120 min of injection, respectively, and remained at these levels for the remainder of the experimental protocol. The catalase L/P ratio increased to 0.24 +/- 0.07 within 90 min of injection and subsequently declined to levels measured for endogenous catalase over the remaining 3.5 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Polymers of Cu/Zn superoxide dismutase produced by cross-linking with glutaraldehyde

Soluble polymers of bovine Cu/Zn superoxide dismutase (EC 1.15.1.1) have been prepared using the homobifunctional cross-linking reagent, glutaraldehyde. A form of the enzyme, a tetramer, with a molecular weight of 64,000 has been purified by gel filtration. The functional properties of the tetramer have been investigated. Reconstitution with copper and zinc was required for full activity. After metal reconstitution, the specific activity of the tetramer was shown to be close to 90% that of the native dimeric enzyme. The serum half-life of the tetramer in rats was found to be increased by a factor of six when compared with native superoxide dismutase. The tissue distribution of the two forms was also found to be different with the tetramer accumulating predominantly in the liver.

Reactive oxygen metabolites in endotoxin-induced acute renal failure in rats

Based on recent reports that reactive oxygen metabolites may play a role in endotoxin-induced injury in other tissues, we postulated that reactive oxygen metabolites may be important mediators of endotoxin-induced acute renal failure. Superoxide dismutase, a scavenger of superoxide, or catalase, which destroys hydrogen peroxide, did not protect against endotoxin-induced renal failure. Similarly, neither the hydroxyl radical scavenger dimethylthiourea nor the iron chelator deferoxamine (which presumably would act by preventing the generation of hydroxyl radical via the iron-catalyzed Haber-Weiss reaction) prevented the endotoxin-induced fall in renal function. In separate experiments, we found no increase in renal cortical lipid peroxidation (a marker of reactive oxygen metabolite-mediated tissue injury) in endotoxin-treated rats, providing further evidence against a role for reactive oxygen metabolites in endotoxin-induced renal injury. Finally, using the aminotriazole-induced inhibition of catalase (a measure of in vivo changes in the hydrogen peroxide generation) we found no evidence of enhanced hydrogen peroxide generation in the renal cortex in endotoxin-treated rats. Taken together, the data from these three separate experimental approaches suggest that reactive oxygen metabolites are not important mediators of endotoxin-induced acute renal failure.

Tissue distribution of 125I-labelled carbonic anhydrase isozymes I, II and III in the rat

Carbonic anhydrase (CA) isozymes CA I and CA II were isolated from rat erythrocytes, and CA III from rat skeletal muscle. They were purified to homogeneity and labelled with 125I using the Bolton-Hunter method. The tissue distribution of these [125I]CA isozymes was studied in rats with whole-body autoradiography at various times after an intravenous injection. The distribution pattern showed a remarkable organ specificity. CA I and CA III were to a great extent localized to the renal cortex. This is compatible with renal uptake, secondary to glomerular filtration, of these isozymes. This would be expected from the renal handling of proteins with the following characteristics: molecular weight of 29,000; iso-electric points, pI, around 7.2 and 6.5 respectively. However, CA II of similar molecular shape and size, with a pI of 6.8, remained in the blood and was preferentially localized to the liver. Further studies are needed to clarify why such similar proteins are targeted to different organs.

Plasma elimination kinetics and renal handling of copper/zinc superoxide dismutase in the rat

The renal handling of bovine and human superoxide dismutase (SOD) was investigated in Sprague-Dawley and Munich-Wistar rats. Under normal physiological conditions the half-time of the major rapid component of the plasma elimination curve was estimated at 6.0 +/- 0.5 min, the volume of distribution at 35.7 +/- 3.3 ml kg-1, i.e. the plasma volume and the corresponding plasma clearance at 4 ml min-1 kg-1. After a single intravenous dose, most of the enzyme was distributed to and eliminated by the two kidneys, whereas the non-renal clearance was low, 0.5 ml min-1 kg-1. The single nephron filtration of SOD, as assessed from micropuncture of Bowman's space, was 10.4 +/- 1.0 nl min-1, which was 26 +/- 2% of that for inulin. The total elimination of SOD by glomerular filtration would thereby be 2.5 ml min-1 kg-1, i.e. the glomerular ultrafiltration process would account for the largest part of the elimination of SOD from circulating plasma. After the dosage of 20 mg kg-1, about two-thirds of the injected SOD was excreted as the intact molecule into the urine, whereas one-third was found to be reabsorbed and metabolized by the proximal tubular epithelial cells. In animals suffering from unilateral post-ischaemic acute renal failure, the elimination half-time was 13 +/- 1.9 min, a value which increased by 55 +/- 5 min after bilateral functional nephrectomy. By contrast, the distribution volume remained essentially unchanged.