A rapid and sensitive enzyme immunoassay for Cu/Zn superoxide dismutase with polyclonal and monoclonal antibodies

Оxidative stress and endogenous intoxication in cancer patients

In the blood serum of 93 patients with various localities of the malignant process, the content of nitric oxide (NO), indicators of lipid peroxidation (POL): superoxide dismutase (SOD), malondialdehyde (MDA) and glutathione in red blood cells were determined. 9 patients with ovarian cancer were examined during chemotherapy (6 courses), 40 patients with colon cancer, previously operated, were with malignant liver damage. In 39 patients with anemia, NO indicators were compared with the level of interleukin 6 (IL-6) and hepcidin-25 (GP-25). As a control, 60 practically healthy individuals were examined. It was shown that the NO content was significantly reduced in 69.7% of patients, regardless of the location of the primary tumor. There was a gradual increase in the NO content before each course of chemotherapy. A high concentration of NO (more than 22 µM) was detected in 22 patients with functional iron deficiency (FJ) against the background of anemia of chronic diseases (AHZ), which was accompanied by hyperexpression of IL-6 (27.0±10.5 pg/ml) and GP-25 (25.2±7.1 ng/ml). In contrast, the lowest NO values (less than 22 µM) were observed in 17 patients with IDA. There is no doubt that there is a certain relationship between the development of oxidative stress with the accumulation of highly toxic lipoperoxidation products that affect the overall homeostasis of the body, and the development of anemic syndrome.

Digital Twin Application for Model-Based DoE to Rapidly Identify Ideal Process Conditions for Space-Time Yield Optimization

The fast exploration of a design space and identification of the best process conditions facilitating the highest space-time yield are of great interest for manufacturers. To obtain this information, depending on the design space, a large number of practical experiments must be performed, analyzed, and evaluated. To reduce this experimental effort and increase the process understanding, we evaluated a model-based design of experiments to rapidly identify the optimum process conditions in a design space maximizing space-time yield. From a small initial dataset, hybrid models were implemented and used as digital bioprocess twins, thus obtaining the recommended optimal experiment. In cases where these optimum conditions were not covered by existing data, the experiment was carried out and added to the initial data set, re-training the hybrid model. The procedure was repeated until the model gained certainty about the best process conditions, i.e., no new recommendations. To evaluate this workflow, we utilized different initial data sets and assessed their respective performances. The fastest approach for optimizing the space-time yield in a three-dimensional design space was found with five initial experiments. The digital twin gained certainty after four recommendations, leading to a significantly reduced experimental effort compared to other state-of-the-art approaches. This highlights the benefits of in silico design space exploration for accelerating knowledge-based bioprocess development, and reducing the number of hands-on experiments, time, energy, and raw materials.

Apparent superoxide dismutase-like activity of immunoglobulin

Using various superoxide generating systems and nitroblue tetrazolium or cytochrome c as superoxide detector molecules it is possible to assess the superoxide dismutase activity of proteins. Intact antibodies raised to different antigens, the Fab' fragment of anti-TNF [M632] and well-characterized recombinant Fv fragments of the murine antibody NQ11.7.22 appear to possess superoxide dismutase (SOD)-like activity. Kinetic characteristics of the SOD-like activity of NQ11.7.22-Fv fragments suggest an enzymatic property and these fragments behave in an analogous manner to human erythrocyte Cu-Zn SOD. Furthermore, the SOD-like activity of the NQ11.7.22-Fv fragment is affected by certain single-point mutations in the amino acid composition and has a pH optimum of 6.2-6.6 which is unlike Cu-Zn SOD (pH 7.8-8.2). A change in tyrosine at the 32 position in the heavy chain and histidine at position 27 of the light chain of the NQ11.7.22-Fv fragment results in a profound reduction in SOD-like activity. Tyrosine at the 32 position in the heavy chain is known to play a significant role in antigen binding suggesting that the SOD-like activity occurs at the antigen-binding site itself. Single-point mutations at the periphery of the antigen combining site on the NQ11.7.22-Fv fragment had little or no effect on SOD-like activity. Further studies show that immunoglobin (lgG-1), a commercially available murine monoclonal antibody, can also enhance the generation of hydrogen peroxide, the product of superoxide dismutation, when present in superoxide producing systems. The generation of hydrogen peroxide was increased by low pH (pH 6.25) with lgG-1 but reduced with Cu-Zn SOD.

Preventing T7 RNA polymerase read-through transcription-A synthetic termination signal capable of improving bioprocess stability

The phage-derived T7 RNA polymerase is the most prominent orthogonal transcriptions system used in the field of synthetic biology. However, gene expression driven by T7 RNA polymerase is prone to read-through transcription due to contextuality of the T7 terminator. The native T7 terminator has a termination efficiency of approximately 80% and therefore provides insufficient insulation of the expression unit. By using a combination of a synthetic T7 termination signal with two well-known transcriptional terminators (rrnBT1 and T7), we have been able to increase the termination efficiency to 99%. To characterize putative effects of an enhanced termination signal on product yield and process stability, industrial-relevant fed batch cultivations have been performed. Fermentation of a E. coli HMS174(DE3) strain carrying a pET30a derivative containing the improved termination signal showed a significant decrease of plasmid copy number (PCN) and an increase in total protein yield under standard conditions.

Evaluation of three industrial Escherichia coli strains in fed-batch cultivations during high-level SOD protein production

BACKGROUND

In the biopharmaceutical industry, Escherichia coli (E. coli) strains are among the most frequently used bacterial hosts for producing recombinant proteins because they allow a simple process set-up and they are Food and Drug Administration (FDA)-approved for human applications. Widespread use of E. coli in biotechnology has led to the development of many different strains, and selecting an ideal host to produce a specific protein of interest is an important step in developing a production process. E. coli B and K-12 strains are frequently employed in large-scale production processes, and therefore are of particular interest. We previously evaluated the individual cultivation characteristics of E. coli BL21 and the K-12 hosts RV308 and HMS174. To our knowledge, there has not yet been a detailed comparison of the individual performances of these production strains in terms of recombinant protein production and system stability. The present study directly compared the T7-based expression hosts E. coli BL21(DE3), RV308(DE3), and HMS174(DE3), focusing on evaluating the specific attributes of these strains in relation to high-level protein production of the model protein recombinant human superoxide dismutase (SOD). The experimental setup was an exponential carbon-limited fed-batch cultivation with minimal media and single-pulse induction.

RESULTS

The host strain BL21(DE3) produced the highest amounts of specific protein, followed by HMS174(DE3) and RV308(DE3). The expression system HMS174(DE3) exhibited system stability by retaining the expression vector over the entire process time; however, it entirely stopped growing shortly after induction. In contrast, BL21(DE3) and RV308(DE3) encountered plasmid loss but maintained growth. RV308(DE3) exhibited the lowest ppGpp concentration, which is correlated with the metabolic stress level and lowest degradation of soluble protein fraction compared to both other strains.

CONCLUSIONS

Overall, this study provides novel data regarding the individual strain properties and production capabilities, which will enable targeted strain selection for producing a specific protein of interest. This information can be used to accelerate future process design and implementation.

An advanced monitoring platform for rational design of recombinant processes

Bioprocess engineering is an application-oriented science in an interdisciplinary environment, and a meaningful combination of different scientific disciplines is the only way to meet the challenges of bioprocess complexity. Setting up a reasoned process monitoring platform is the first step in an iterative procedure aiming at process and systems understanding, being the key to rational and innovative bioprocess design. This chapter describes a comprehensive process monitoring platform and how the resulting knowledge is translated into new strategies in process and/or host cell design.

Plasmid-free T7-based Escherichia coli expression systems

In order to release host cells from plasmid-mediated increases in metabolic load and high gene dosages, we developed a plasmid-free, T7-based E. coli expression system in which the target gene is site-specifically integrated into the genome of the host. With this system, plasmid-loss, a source of instability for conventional expression systems, was eliminated. At the same time, system leakiness, a challenging problem with recombinant systems, was minimized. The efficiency of the T7 RNA polymerase compensates for low gene dosage and provides high rates of recombinant gene expression without fatal consequences to host metabolism. Relative to conventional pET systems, this system permits improved process stability and increases the host cell's capacity for recombinant gene expression, resulting in higher product yields. The stability of the plasmid-free system was proven in chemostat cultivation for 40 generations in a non-induced and for 10 generations in a fully induced state. For this reason plasmid-free systems benefit the development of continuous production processes with E. coli. However, time and effort of the more complex cloning procedure have to be considered in relation to the advantages of plasmid-free systems in upstream-processing.

Oxidative stress: A bridge between Down's syndrome and Alzheimer's disease

Besides the genetic, biochemical and neuropathological analogies between Down's syndrome (DS) and Alzheimer's disease (AD), there is ample evidence of the involvement of oxidative stress (OS) in the pathogenesis of both disorders. The present paper reviews the publications on DS and AD in the past 10 years in light of the "gene dosage" and "two-hit" hypotheses, with regard to the alterations caused by OS in both the central nervous system and the periphery, and the main pipeline of antioxidant therapeutic strategies. OS occurs decades prior to the signature pathology and manifests as lipid, protein and DNA oxidation, and mitochondrial abnormalities. In clinical settings, the assessment of OS has traditionally been hampered by the use of assays that suffer from inherent problems related to specificity and/or sensitivity, which explains some of the conflicting results presented in this work. For DS, no scientifically proven diet or drug is yet available, and AD trials have not provided a satisfactory approach for the prevention of and therapy against OS, although most of them still need evidence-based confirmation. In the future, a balanced up-regulation of endogenous antioxidants, together with multiple exogenous antioxidant supplementation, may be expected to be one of the most promising treatment methods.

Establishment of anti-rat-Cu,Zn-superoxide dismutase monoclonal antibodies applied to a highly sensitive immunoassay and immunohistochemistry system

The superoxide anion has been implicated in a wide range of diseases. The major protector against superoxide anion in the cell cytosol is Cu,Zn-superoxide dismutase (Cu,Zn-SOD). In this study, anti rat Cu,Zn-SOD was established in murine monoclonal antibodies for the first time. These antibodies were applied to both a highly sensitive EIA system in serum and immunohistochemical methods for detection in gastric mucosa tissues. The proposed EIA method had a high sensitivity within the assay range, 10-300 pg/mL, good percentage, 96.9 +/- 5.60%, and good reproducibility; within-day assay CV = 8.6-10.2%, between-day assay CV = 6.5-11.7%. Inmmunohistochemically, Cu,Zn-SOD localized in the esophagus epithelial cells, gastric oxyntic cells, surface of the gastric lumen side in the small intestine and colonic epithelial cells. The establishment of anti-rat CuZn-SOD monoclonal antibody allows both specific analysis of immunoquantitation in rat Cu,Zn-SOD and highly specific detection of Cu,Zn-SOD location by immunohistochemical methods.

Optimization of recombinant protein expression level in Escherichia coli by flow cytometry and cell sorting

Overexpression of recombinant proteins in Escherichia coli often leads to a severe growth retardation of the host cells. The phage T7 promoter phi10 in a pET vector was utilized to express human superoxide dismutase. Induction with IPTG lead to an increase in protein content and cell size and a termination of cell division, due to the deviation of the general metabolic fluxes from all cellular processes to plasmid maintenance and foreign protein synthesis. To generate promoter mutants which are better tolerated by the host cells we constructed a random mutation library by PCR with degenerated primers in a part of the promoter involved in the binding to the RNA polymerase and the initiation of transcription. This library was sorted by flow cytometry for cells with a lower total protein content as an indicator for continued cell replication and hence a less severe stress situation. The clones obtained had a similar SOD production compared to the original strain, but were able to reach higher densities in a batch culture, which resulted in a higher total yield.

Stabilizing plasmid copy number to improve recombinant protein production

The key objective for recombinant protein production in bacteria is the maximum exploitation of the cell factory's potential, whereby often strong expression vectors are used to increase product yield. If the metabolic load caused by recombinant expression exceeds the host's capacity, the system exhausts itself, resulting in a loss of protein yield. Excessive plasmid replication is observed after inducing recombinant gene expression, which greatly contributes to metabolic overload of the host cell. The transcriptional and translational machineries are extremely overstrained. By abolishing sequence homology between ColE1 RNA I/RNA II and tRNAs, we were able to restore the plasmid's replication control mechanisms and to keep the plasmid copy number constant throughout the culture process, thereby prolonging metabolic activity and productivity of the bacterial expression system. Because the bacterial host cell is not being exploited beyond its tolerable potential with this method, the constancy of the plasmid copy number level throughout the whole period of the bioprocess provides novel strategies for bioprocess optimization.

Cu/Zn-SOD in human pancreatic tissue and pancreatic juice

CONCLUSION

Cu/Zn-SOD is present in pancreatic juice and tissue. Immunohistochemical studies reveal a localization of this enzyme in islet, duct, and centroacinar cells, but to a much lower extent in pancreatic acinar cells.

BACKGROUND

It is generally accepted that oxygen radicals are involved in the pathogenesis of acute and chronic pancreatitis. An imbalance of radical-generating and radical-scavenging processes is thought to lead to the damage of pancreatic acinar cells that initiate the autodigestion of the whole organ.

METHODS

We investigated the distribution pattern of the cytosolic radical-scavenging enzyme, copper/zinc-superoxide dismutase (Cu/Zn-SOD), in pancreatic juice and tissue. In patients with chronic pancreatitis or pancreatic malignancies, Cu-Zn-SOD was quantitated in different fractions of pancreatic juice by means of an enzyme immunoassay using two Cu/Zn-SOD-specific monoclonal antibodies. Cryostat or paraffin sections of pancreatic tissue were analyzed by immunohistochemical techniques.

RESULTS

We found this enzyme to be present in the first secretin-triggered fraction of endoscopically obtained pancreatic juice in concentrations similar to serum. In contrast, after cholecystokinin stimulation, only low levels could be found in pancreatic juice, indicating that this enzyme is not actively secreted. Interestingly, pancreatic juice of patients with chronic pancreatitis or pancreas tumor contained higher levels (25-29 ng/mL) of Cu/Zn-SOD than juice of controls without pancreatic diseases (15 ng/mL). Immunohistochemical studies of Cu/Zn-SOD in pancreatic tissue revealed a more intense staining of duct cells, islet cells, and centroacinar cells, whereas acinar cells showed almost no staining for Cu/Zn-SOD.

Optimization of recombinant gene expression in Escherichia coli

The major targets for improvement of recombinant expression efficiency in Escherichia coli are gene dosage, transcription and, to some extent, translation. In order to evaluate the relative importance of these factors, the kinetics of specific mRNA compared to product formation was studied for different widely used expression systems, producing recombinant human superoxide dismutase. For a system employing phage T7 RNA polymerase, where a high level of recombinant protein expression puts a high metabolic burden on the cells, it was shown that transcription is not the limiting factor. To improve the translation rate of a common vector based on the tac promoter, the Shine-Dalgarno (SD) sequence was mutated towards stronger homology to the anti-SD sequence of the E. coli 16S rRNA. A 12.2-fold increase in protein yield was accompanied by a 4.3-fold increase in specific mRNA, indicating that transcription of the recombinant gene is coupled to translation. As this coupling amplifies the detrimental effect of a low-efficiency ribosomal binding site, much attention should be paid to translation initiation when optimizing a recombinant protein production system. Finally, reasons for the high expression level before induction are discussed, and first results towards reducing it are presented.

Serum copper/zinc superoxide dismutase levels in patients with rheumatoid arthritis

Rheumatoid arthritis is characterized by a chronic hypertrophic synovitis leading to destruction of connective tissue and functional damage of cartilage and bone structures. Reactive oxygen species play an important role in tissue injury in this disease. To clarify the role of the cellular antioxidant system in the protection against oxygen free radicals, we examined the levels of copper/zinc superoxide dismutase in the sera of patients with rheumatoid arthritis. We used an enzyme-linked immunosorbent assay which determines the concentration of copper/zinc superoxide dismutase independently from its enzymatic activity. We found that patients with rheumatoid arthritis have higher serum copper/zinc superoxide dismutase levels than control subjects. Copper/zinc superoxide dismutase also correlated positively with serum levels of both neopterin and rheumatoid factor, sensitive markers for disease activity in rheumatoid arthritis. These results support the hypothesis that the increased amount of copper/zinc superoxide dismutase is probably inadequate to exert an effective antioxidant protection but can result in a pro-inflammatory, pathogenic effect enhancing tissue damage. Furthermore, copper/zinc superoxide dismutase might be used as a marker of inflammatory activity in rheumatoid arthritis.

Cu,Zn SOD in German families with ALS

We studied the gene for Cu,Zn SOD in 15 German patients with familial ALS and did not find any mutation. Activity of the enzyme and its expression at the protein level was also normal in each patient and in 18 patients suffering from the sporadic form of ALS.

Determination of immune complexes by high-performance gel chromatography (positive cooperativity of antibody-antigen reaction)

Positive cooperativity of antibody-antigen complex formation using human Cu/Zn superoxide dismutase and a murine monoclonal antibody as model is demonstrated by high-performance gel chromatography using TSK G3000sw and TSK G4000sw columns. Three different antibody-antigen complexes named Type I, II and III composed from two antigen molecules+two antibody molecules, two antigen molecules+one antibody molecule and one antigen molecule+one antibody molecule could be separated. The degree and ratio of complexes present in solution depends mainly on the ratios of antibody and antigen.

Scale-up of recombinant protein purification by hydrophobic interaction chromatography

The scale-up of hydrophobic interaction chromatography is described. Human recombinant superoxide dismutase was used as a model. The scale-up was performed by keeping the height to diameter (H/D) ratio of the column constant. The success of scale-up was evaluated by reversed-phase high-performance liquid chromatography of the eluted material. The wrong H/D ratio causes decreased resolution.

Copper,zinc superoxide dismutase is primarily a cytosolic protein in human cells

The intracellular localization of human copper,zinc superoxide dismutase (Cu,Zn-SOD; superoxide:superoxide oxidoreductase, EC 1.15.1.1) was evaluated by using EM immunocytochemistry and both isolated human cell lines and human tissues. Eight monoclonal antibodies raised against either native or recombinant human Cu,Zn-SOD and two polyclonal antibodies raised against either native or recombinant human Cu,Zn-SOD were used. Fixation with 2% paraformaldehyde/0.2% glutaraldehyde was found necessary to preserve normal distribution of the protein. Monoclonal antibodies were less effective than polyclonal antibodies in recognizing the antigen after adequate fixation of tissue. Cu,Zn-SOD was found widely distributed in the cell cytosol and in the cell nucleus, consistent with it being a soluble cytosolic protein. Mitochondria and secretory compartments did not label for this protein. In human cells, peroxisomes showed a labeling density slightly less than that of cytoplasm.

Cu/Zn superoxide dismutase quantification from fetal erythrocytes--an efficient confirmatory test for Down's syndrome after maternal serum screening and sonographic investigations

An enzyme immunoassay especially designed for the quantification of Cu/Zn superoxide dismutase (SOD) in erythrocytes has been applied to measure the SOD of outcomes with high risk for Down's syndrome. From 148 fetuses SOD was quantified from erythrocytes of umbilical vein blood and related to the number of cells, the content of haemoglobin (Hb), and to the haematocrit (Hc). Comparative studies between the SOD content of erythrocytes from the fetuses and their mothers resulted in similar SOD levels (14.09 +/- 1.20 for fetal and 14.48 +/- 1.63 for maternal cells) with a 1.84-fold smaller variance for fetal cells. The best differentiation between normal fetuses and fetuses with Down's syndrome resulted from the SOD/cell ratio followed by the SOD/Hb ratio. Fixing a cut-off value from the probability density functions that the method results in a specificity of 99.99 per cent, the sensitivity to detect cases of Down's syndrome was 99.71 per cent for the SOD/cell ratio, 70.92 per cent for the SOD/Hb ratio, and 60.21 per cent for the SOD/He ratio. Nine cases with Down's syndrome were correctly diagnosed by the SOD/cell ratio determination. Eight of these were confirmed as free trisomy 21 by karyotype analysis and one was found to be a triploidy. The latter was not detected by the SOD/Hb and SOD/Hc ratios because of the one-third higher content of haemoglobin and the larger volume of the erythrocytes which resulted in ratios within the normal range.

Immunoquantitation of rat erythrocyte superoxide dismutase: its use in copper deficiency

Two immunoassays have been developed for the determination of rat erythrocyte dismutase (Cu,Zn-SOD). An enzyme-linked immunosorbent assay (ELISA) was very sensitive down to 4 ng/ml with a coefficient of variation (CV) of 18% while the single radial immunodiffusion assay (SRID) permitted an adequate detection level (5 micrograms/ml) with far better accuracy (CV = 4.2%). The latter was thus selected for the determination of Cu,Zn-SOD in the red blood cells of normal and copper-depleted rats. The average value of Cu,Zn-SOD in normal adult rat erythrocytes was 1142 +/- 120 ng/mg hemoglobin. When compared to activity measurements, good correlation was obtained between enzyme content and enzyme activity (r = 0.803, P less than .001). In an experimental copper deficiency followed by supplementation, good correlation was observed in the course of depletion (r = 0.848, P less than .001) and repletion (r = 0.896, P less than .001). During depletion, the loss of enzyme activity was mainly related to a loss of enzyme. However, enzymatically inactive protein was formed which would be activated when copper was added. These results indicate the importance of a combined use of Cu,Zn-SOD immunoquantitation and activity measurements to enable a better understanding of changes occurring with respect to enzyme activity.

Enhancement of S-100 beta protein in blood of patients with Down's syndrome

The human gene encoding the beta subunit of S-100 protein (S-100 beta) was mapped on chromosome 21. In order to confirm the expression of gene-dosage effect of S-100 beta in patients with Down's syndrome (DS), concentrations of immunoreactive S-100 alpha and S-100 beta proteins were determined in the blood plasma and lymphocytes fraction of the patients and control subjects. Cu/Zn-superoxide dismutase (SOD), a protein that is known to show the gene-dosage effect on the trisomy of chromosome 21, also was immunoassayed in the same blood samples as control proteins. In blood plasma, S-100 beta protein as well as Cu/Zn SOD was enhanced (P less than 0.001) in the patients (160 +/- 70 pg S-100 beta/ml and 87 +/- 83 ng SOD/ml, N = 44) as compared with control individuals (76 +/- 25 pg/ml, and 18 +/- 11 ng/ml, respectively, N = 28). However, concentrations of S-100 alpha in blood plasma of DS patients were similar to those of normal subjects. Concentrations of S-100 beta in lymphocyte fractions of DS patients (24.7 +/- 10.9 ng/mg protein) were also higher (P less than 0.001) than those of control subjects (10.1 +/- 5.8 ng/mg protein). These results indicate that gene-dosage effect of S-100 beta levels are expressed in DS patients.

Sensitive enzyme immunoassay for human Cu/Zn superoxide dismutase

A highly sensitive enzyme immunoassay method for measurement of human Cu/Zn superoxide dismutase (SOD) was established. Antisera were raised in rabbits by injecting SOD purified from human erythrocytes, and antibodies to SOD were purified by the use of Cu/Zn SOD-coupled Sepharose 4B. The assay system consisted of polystyrene balls with immobilized monospecific antibody F(ab')2 fragments and the same antibody Fab' fragments labeled with beta-D-galactosidase from Escherichia coli. The assay was highly sensitive, and the minimum detection limit was 3 pg or 0.1 fmol/assay tube. Serum Cu/Zn SOD levels of normal healthy subjects (36.3 +/- 15.6, n = 120, 16-64 years old) were not related to age and sex. It was confirmed that Cu/Zn SOD levels in erythrocytes and blood plasma were significantly enhanced in patients with Down syndrome. Immunoreactive Cu/Zn SOD was detectable in all the tissues examined and was present at high concentrations in brain, adrenal gland, liver, heart and kidney.