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

Nanomedicine-Based Therapeutics for Myocardial Ischemic/Reperfusion Injury

Myocardial ischemic/reperfusion (IR) injury is a global cardiovascular disease with high mortality and morbidity. Therapeutic interventions for myocardial ischemia involve restoring the occluded coronary artery. However, reactive oxygen species (ROS) inevitably impair the cardiomyocytes during the ischemic and reperfusion phases. Antioxidant therapy holds great promise against myocardial IR injury. The current therapeutic methodologies for ROS scavenging depend predominantly on administering antioxidants. Nevertheless, the intrinsic drawbacks of antioxidants limit their further clinical transformation. The use of nanoplatforms with versatile characteristics greatly benefits drug delivery in myocardial ischemic therapy. Nanoplatform-mediated drug delivery significantly improves drug bioavailability, increases therapeutic index, and reduces systemic toxicity. Nanoplatforms can be specifically and reasonably designed to enhance molecule accumulation at the myocardial site. The present review initially summarizes the mechanism of ROS generation during the process of myocardial ischemia. The understanding of this phenomenon will facilitate the advancement of innovative therapeutic strategies against myocardial IR injury. The latest developments in nanomedicine for treating myocardial ischemic injury are then discussed. Finally, the current challenges and perspectives in antioxidant therapy for myocardial IR injury are addressed.

Bioorthogonal phase-directed copper-catalyzed azide–alkyne cycloaddition (PDCuAAC) coupling of selectively cross-linked superoxide dismutase dimers produces a fully active bis-dimer

Superoxide dismutase (SOD) is a 32 kDa dimeric enzyme that actively removes a toxic oxygen species within red cells.

Modulation of endothelial targeting by size of antibody-antioxidant enzyme conjugates

Endothelial targeting of antioxidant enzymes attenuates acute vascular oxidative stress in animal studies. Superoxide dismutase (SOD) and catalase conjugated with antibodies to Platelet-Endothelial Cell Adhesion Molecule-1 (anti-PECAM/SOD and anti-PECAM/catalase) bind to endothelium, accumulate in the pulmonary vasculature, and detoxify reactive oxygen species. In order to define the role of conjugate size in the efficacy and specificity of endothelial targeting, we synthesized anti-PECAM/enzyme conjugates of controlled size (40nm-10,000nm). Binding of anti-PECAM/enzymes to endothelial cells increased with conjugate size from 300nm to 2μm (from 2.5 to 8.5% of bound fraction), and was specific, as conjugates did not bind to PECAM-negative cells. Pulmonary uptake of anti-PECAM/enzyme conjugates injected intravenously in mice also increased from 4.5 to 16% of injected dose for particles from 200 to 800nm. However, control conjugates larger than 300nm showed elevated non-specific pulmonary uptake, indicating that the targeting specificity of anti-PECAM/enzyme conjugates in vivo has a bell-shaped curve with a maximum close to 300-nm diameter. These results show that: i) the size of an antibody/enzyme conjugate modulates efficacy and specificity of targeting, and ii) a size optimum should be defined in vivo to account for parameters that are difficult to model in cell culture.

Role of peroxynitrite and recombinant human manganese superoxide dismutase in reducing ischemia-reperfusion renal tissue injury

BACKGROUND

In an acute kidney transplant rejection rat model, we demonstrated that manganese superoxide dismutase (MnSOD) activity was significantly reduced and MnSOD was nitrated by peroxynitrite (ONOO(-)), resulting in tissue injury. We examined whether tissue injury was reduced after external supplementation of recombinant human MnSOD in a rat renal ischemia-reperfusion injury model.

METHODS

Male Brown-Norway rats underwent dissection of the right kidney. The animals were divided into 3 groups. The controls had the left renal blood vessels clamped for 90 minutes to induce ischemia, followed by reperfusion for 16 hours. In the intraperitoneal administration group, MnSOD was administered 30 minutes before ischemia and immediately before reperfusion. In the sham group, neither ischemia nor reperfusion was performed. After reperfusion, blood was collected, the left kidney was dissected and renal function and tissue injury were evaluated.

RESULTS

Serum creatinine and K(+), blood urea nitrogen, and aspartate aminotransferase activity decreased significantly, whereas serum Na(+) and renal function improved in the MnSOD group compared with the control and sham groups. On hematoxylin and eosin staining, the histological score indicated that acute tubular necrosis was significantly reduced by MnSOD administration. Periodic acid-Schiff staining was absent in the nonadministration group, whereas it persisted in the MnSOD group. In the proximal renal tubules a large proportion of anti-nitrotyrosine staining was present before but absent after MnSOD administration.

CONCLUSIONS

MnSOD administration improved renal function and reduced tissue injury. It may also reduce tissue injury in acute kidney transplant rejection and other tissue injuries caused by similar molecular mechanisms.

Lack of association of polymorphisms 239+34A/C in the SOD1 gene and 47C/T in the SOD2 gene with delayed graft function and acute and chronic rejection of kidney allografts

The superoxide dismutases (SODs) seem to be the most important enzymes involved in defense against reactive oxygen species, in particular against superoxide anion radicals. We hypothesized that genetic variability of antioxidant enzymes may have a role in development of these complications. The objective of the present study was to examine the association between polymorphisms 239+34A/C in the SOD1 gene or 47C/T in the SOD2 gene and development of delayed graft function (DGF) and acute or chronic rejection. The study included 187 recipients of first renal transplants. Patient history was analyzed taking into account DGF, acute rejection episodes, and chronic rejection. The polymorphisms were analyzed using the polymerase chain reaction-restriction fragment length polymorphism method. There were no significant associations between the polymorphisms and DGF or acute or chronic rejection. Our findings suggest that polymorphisms in SOD1 and SOD2 are not associated with development of either DGF or acute or chronic rejection.

Novel pharmacological approaches to the treatment of renal ischemia-reperfusion injury: a comprehensive review

Renal ischemia-reperfusion (I-R) contributes to the development of ischemic acute renal failure (ARF). Multi-factorial processes are involved in the development and progression of renal I-R injury with the generation of reactive oxygen species, nitric oxide and peroxynitrite, and the decline of antioxidant protection playing major roles, leading to dysfunction, injury, and death of the cells of the kidney. Renal inflammation, involving cytokine/adhesion molecule cascades with recruitment, activation, and diapedesis of circulating leukocytes is also implicated. Clinically, renal I-R occurs in a variety of medical and surgical settings and is responsible for the development of acute tubular necrosis (a characteristic feature of ischemic ARF), e.g., in renal transplantation where I-R of the kidney directly influences graft and patient survival. The cellular mechanisms involved in the development of renal I-R injury have been targeted by several pharmacological interventions. However, although showing promise in experimental models of renal I-R injury and ischemic ARF, they have not proved successful in the clinical setting (e.g., atrial natriuretic peptide, low-dose dopamine). This review highlights recent pharmacological developments, which have shown particular promise against experimental renal I-R injury and ischemic ARF, including novel antioxidants and antioxidant enzyme mimetics, nitric oxide and nitric oxide synthase inhibitors, erythropoietin, peroxisome-proliferator-activated receptor agonists, inhibitors of poly(ADP-ribose) polymerase, carbon monoxide-releasing molecules, statins, and adenosine. Novel approaches such as recent research involving combination therapies and the potential of non-pharmacological strategies are also considered.

Activity of CuZn-superoxide dismutase, catalase and glutathione peroxidase in erythrocytes in kidney allografts during reperfusion in patients with and without delayed graft function

BACKGROUND

Generation of reactive oxygen species (ROS) is the main mechanism involved in the ischemic/reperfusion damage of the transplanted organ. Oxygen burst is a trigger for complex biochemical events leading to generation of oxygenated lipids and changes in microcirculation. Many markers have been researched to prove the presence of ROS in the transplanted tissue. Some of them, like superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) are considered to play a major role in graft protection against oxygen stress during reperfusion.

METHODS

The aim of this study was to examine the changes of SOD1, CAT and GPx activity in erythrocytes during the first minutes after total graft reperfusion. Forty patients undergoing kidney transplantation at our center were assigned to two groups: with or without delayed graft function (DGF). Before anastomosing kidney vessels with recipient's iliac vessels, the '0' blood sample was taken from the iliac vein. Next blood samples I, II and III were taken from the graft's renal vein. The reperfusion of the transplanted kidney was evaluated precisely with the thermovision camera. Erythrocyte SOD1, CAT and GPx activity was measured with a spectrophotometric method.

RESULTS

We did not observe statistically significant changes in SOD1, CAT and GPx activity in erythrocytes during the early phase of reperfusion in patients with and without DGF.

CONCLUSIONS

Erythrocyte-antioxidative system in graft's vein remain stable during the early phase of reperfusion. The results of the study suggest that further studies on extracellular enzymes are required for the assessment of antioxidant system in the conditions of ischemia/reperfusion.

mRNA study on Cu/Zn superoxide dismutase induction by hemodialysis treatment

BACKGROUND/AIMS

There is little or no controversy about the increased oxidative stress of hemodialysis (HD) patients. Several reports show that the activity of superoxide dismutase (SOD), one of the major endogenous antioxidant enzymes, in plasma is elevated among HD patients. It is still unclear, however, whether this elevation is due to the promotion of SOD production or a decrease in renal excretion of SOD. This study was designed to investigate the cause of the SOD activation in HD patients, and we examined the expression of SOD mRNA levels in leukocytes of patients with chronic renal failure.

METHODS

The total plasma SOD activity was determined by the nitroblue tetrazolium method, plasma SOD contents by ELISA, and SOD mRNA levels in leukocytes by RT-PCR.

RESULTS

Our results demonstrated that contents and mRNA levels of Cu/Zn SOD in HD patients are 4.4 times and 2.0 times, respectively, as large as those in healthy controls. Furthermore, in contrast to nondialyzed chronic renal failure patients, we observed higher concentrations of Cu/Zn SOD in plasma and a more enhanced mRNA expression of Cu/Zn SOD in leukocytes of HD patients.

CONCLUSION

Increased Cu/Zn SOD mRNA reflects enhanced antioxidant capacity of leukocytes and can be a promising oxidative stress marker in HD patients.

Synthesis and anti-inflammatory activity of a chimeric recombinant superoxide dismutase: SOD2/3

External surfaces of cells are normally protected by extracellular superoxide dismutase, SOD3, which binds to polyanions such as heparan sulfate. We constructed a fusion gene encoding a chimeric SOD consisting of the mature human mitochondrial SOD2 plus the COOH-terminal 26-amino acid heparin-binding "tail" from SOD3. This tail is responsible for the enzyme's affinity for endothelial surfaces. The fusion gene was expressed in Escherichia coli, and the fully active enzyme SOD2/3 was purified. Although native SOD2 has no affinity for heparin, SOD2/3 binds to a heparin-agarose column. In a rat model of acute lung injury induced by intratracheal instillation of IL-1, SOD2/3, SOD2, and denatured SOD2/3 showed 92%, 13.8%, and 0% reduction of lung leak, respectively. Only SOD2/3 prevented neutrophil accumulation. In the carrageenan-induced foot edema model in the rat, SOD2/3 reduced edema by 62% (P < 0.003) at a dose in which native SOD2 produced no significant effect. Thus SOD2/3 appears to have properties as a therapeutic anti-inflammatory agent that are greatly superior to other available forms of the enzyme.

Cu/Zn-superoxide dismutase gene attenuates ischemia-reperfusion injury in the rat kidney

Evidence has accumulated for a role of toxic oxygen radicals in the pathogenesis of ischemia-reperfusion injury in the kidney. The aim of this study was to evaluate the hypothesis that reducing postischemic renal injury is possible by delivery of the gene for the antioxidant enzyme superoxide dismutase (SOD). Female Sprague-Dawley rats received intravenous injections of recombinant adenovirus (1 x 10(9) pfu) containing the transgenes for Escherichia coli beta-galactosidase (Ad-LacZ, as control) or human Cu/Zn-SOD (Ad-SOD). Three days later, renal ischemia was produced by cross-clamping the left renal vessels for 60 min. The right kidney was removed before reperfusion and processed for the transgene. Renal SOD protein and activity in rats given Ad-SOD was 2.5-fold higher than from the animals receiving Ad-LACZ: Urinary lactate dehydrogenase concentrations were elevated by ischemia-reperfusion in the Ad-LacZ group (1403 +/- 112 U/L), yet values were 50% lower in Ad-SOD-treated rats. Free radical production was elevated by ischemia-reperfusion but was significantly lower in SOD-treated animals. Importantly, on postischemic day 1, glomerular filtration rates were reduced to 0.21 ml/min per 100 g in the Ad-LacZ group, whereas values remained significantly higher (0.39) in the Ad-SOD group. Two weeks after ischemia-reperfusion, inflammation, interstitial fibrosis, tubular atrophy and tissue levels of tumor necrosis factor alpha and interleukin-1 were significantly higher in the Ad-LacZ-treated than in Ad-SOD-treated rats. In conclusion, these results indicate that SOD expression can be increased by delivery of the sod gene to the kidney by intravenous injection and that sod gene transduction minimized ischemia-reperfusion-induced acute renal failure.

Targeting of superoxide dismutase to the liver results in anti-inflammatory effects in rats with fibrotic livers

BACKGROUND/AIMS

The rapid clearance from plasma and the limited uptake of superoxide dismutase (SOD) in the liver hampers the effectiveness of this enzyme in liver diseases. We therefore compared the pharmacokinetics and in vivo efficacy of SOD with two modified forms of this protein: SOD coupled to the copolymer DIVEMA and mannosylated-SOD.

METHODS

Reactive oxygen scavenging activity of SOD conjugates was tested in livers of bile duct ligated rats. Intrahepatic production of reactive oxygen species (ROS) and neutrophil infiltration were studied immunohistochemically and related to the organ and cellular distribution of radiolabeled SOD conjugates.

RESULTS

Native SOD was rapidly cleared from the circulation and accumulated in renal tubuli. The enzyme had no effect on the intrahepatic ROS production. Covalent attachment of SOD to DIVEMA yielded a polyanionic conjugate with a prolonged elimination half-life compared to native SOD. In contrast to native SOD, DIVEMA-SOD was taken up by the liver via scavenger receptors. Mannosylation of SOD (Man-SOD) resulted in a conjugate that was rapidly cleared from the blood. This Man-SOD was taken up by non-parenchymal liver cells. The pharmacokinetics of SOD and its derivatives were similar in normal and bile duct ligated rats. Efficacy studies with Man-SOD revealed only a slight decrease in intrahepatic ROS production. However, DIVEMA-SOD exhibited a potent inhibitory effect on ROS production in the liver. Nearly complete ROS-scavenging activity was observed in the portal areas.

CONCLUSIONS

Considering the prolonged half-life, the increased delivery of SOD to the target cells, and the concomitant increased effectiveness, application of DIVEMA-SOD seems a promising new approach to attenuate intrahepatic inflammatory processes.

Renal handling and plasma elimination kinetics of carbonic anhydrase isoenzymes I, II and III in the rat

Using a radio-immunosorbent technique, the levels of the carbonic anhydrase (CA) isoenzymes CA I, II and III in plasma (1-3 micrograms ml-1), lymph (0.5-1.6 micrograms ml-1) and urine (0.03-0.06 micrograms ml-1), were determined in the rat. The renal clearances of CA I, II and III were 11 +/- 3, 42 +/- 11 and 35 +/- 4 nl min-1 (g kidney wet wt)-1 (n = 4-5), respectively. After a single i.v. injection of purified native or 125I-labelled isoenzymes, the elimination of CA I, and CA III from plasma followed a bi-exponential decline, with half-times of 7 and 9 min for the rapid phase and 112 min for the slow phase, respectively. Nephrectomy decreased the rapid phase and the build-up of catabolites. Therefore, the rapid phase of CA I and III elimination is probably explained by filtration of unbound isoenzyme at the glomeruli and subsequent degradation by the proximal tubules. The plasma elimination curve for CA II was different and followed a mono-exponential decline, with a half-time of 210 min both in normal and nephrectomized animals. This indicates that CA II is not filtered at the glomeruli. However, in acute renal failure, with leaking tubular cells, CA II was excreted into the urine. The slow elimination of the major part of the isoenzymes from plasma is explained by the binding of CA I, II and III to a plasma protein, immunochemically similar to transferrin, forming a macromolecular complex with a mol wt of 114 +/- 2 kDa.

ESR-measurement of oxygen radicals in vivo after renal ischaemia in the rabbit. Effects of pre-treatment with superoxide dismutase and heparin

The effects of intracellular and extracellular superoxide dismutase and heparin administration on oxygen radical formation after ischaemia in the rabbit kidney were studied. Radicals were measured with ESR and spin trapping. At reperfusion after 60 min of renal ischaemia there was a significant increase in the production of free radicals in the venous effluent from the kidney. Administration of either intracellular superoxide dismutase or extracellular superoxide dismutase before ischaemia and before reperfusion prevented approximately 85% of the radical formation seen in the untreated control group. Administration of heparin 5 min before recirculation resulted in a 65% decrease in radical production compared to the control group.

Reactive oxygen and ischemia/reperfusion injury of the liver

Pharmacological experiments suggested that reactive oxygen species contribute to ischemia-reperfusion injury of the liver. Since there is no evidence that quantitatively sufficient amounts of reactive oxygen are generated intracellularly to overwhelm the strong antioxidant defense mechanisms in the liver and cause parenchymal cell injury, the role of reactive oxygen in the pathogenesis remains controversial. This paper reviews the data and conclusions obtained with pharmacological intervention studies in vivo, the sources of reactive oxygen in the liver as well as the growing evidence for the importance of liver macrophages (Kupffer cells) and infiltrating neutrophils in the pathogenesis. A comprehensive hypothesis is presented that focuses on the extracellular generation of reactive oxygen in the hepatic sinusoids, where Kupffer cell-derived reactive oxygen species seem to be involved in the initial vascular and parenchymal cell injury and indirectly also in the recruitment of neutrophils into the liver. Reactive oxygen species may also contribute to the subsequent neutrophil-dependent injury phase as one of the toxic mediators released by these inflammatory cells.

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)

The long-term outcome of post-ischaemic acute renal failure in the rat. I. A functional study after treatment with SOD and sucrose

The long-term outcome in rat kidneys subjected to 45 min of warm ischaemia with no treatment and after administration of 20 mg superoxide dismutase (SOD) and of SOD combined with 2 ml of a 12% sucrose solution was studied by the micropuncture technique. It was found that, although in the acute phase SOD prevented trapping of erythrocytes in the medullary vasculature and that SOD + sucrose also prevented the formation of tubular obstruction, the long-term results as studied 1 week and 1 month after the primary ischaemic insult were virtually identical. This was due to the formation of new obstructions, during the first week, mainly in the thick ascending limb of Henle's loop. After 1 month the proximal tubular free-flow pressure and the single-nephron filtration rate had returned to normal. However, since the total glomerular filtration was only one-third of that under normal conditions, it would seem that two-thirds of the nephrons had undergone complete degeneration. This degeneration was probably the result of persistent tubular obstruction. The tubular degeneration was also accompanied by a reduction in urine osmolality and potassium secretion.

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.