An enzyme-immunoassay for myoglobin in human serum and urine. Method development, normal values and application to acute myocardial infarction

MS Identification of Blood Plasma Proteins Concentrated on a Photocrosslinker-Modified Surface

This work demonstrates the use of a modified mica to concentrate proteins, which is required for proteomic profiling of blood plasma by mass spectrometry (MS). The surface of mica substrates, which are routinely used in atomic force microscopy (AFM), was modified with a photocrosslinker to allow "irreversible" binding of proteins via covalent bond formation. This modified substrate was called the AFM chip. This study aimed to determine the role of the surface and crosslinker in the efficient concentration of various types of proteins in plasma over a wide concentration range. The substrate surface was modified with a 4-benzoylbenzoic acid N-succinimidyl ester (SuccBB) photocrosslinker, activated by UV irradiation. AFM chips were incubated with plasma samples from a healthy volunteer at various dilution ratios (102X, 104X, and 106X). Control experiments were performed without UV irradiation to evaluate the contribution of physical protein adsorption to the concentration efficiency. AFM imaging confirmed the presence of protein layers on the chip surface after incubation with the samples. MS analysis of different samples indicated that the proteomic profile of the AFM-visualized layers contained common and unique proteins. In the working series of experiments, 228 proteins were identified on the chip surface for all samples, and 21 proteins were not identified in the control series. In the control series, a total of 220 proteins were identified on the chip surface, seven of which were not found in the working series. In plasma samples at various dilution ratios, a total of 146 proteins were identified without the concentration step, while 17 proteins were not detected in the series using AFM chips. The introduction of a concentration step using AFM chips allowed us to identify more proteins than in plasma samples without this step. We found that AFM chips with a modified surface facilitate the efficient concentration of proteins owing to the adsorption factor and the formation of covalent bonds between the proteins and the chip surface. The results of our study can be applied in the development of highly sensitive analytical systems for determining the complete composition of the plasma proteome.

Rhabdomyolysis Causing Renal Failure Following Cardiopulmonary Resuscitation, Cardioversion, and Myocardial Infarction: A Case Report and Review of the Literature

Rhabdomyolysis is a condition where there is damage of skeletal muscle, causing myoglobin leak into the circulation. We report a case of a 69-year-old female with a history of hypertension, hyperlipidemia, diabetes mellitus, morbid obesity, paroxysmal atrial fibrillation, and chronic kidney disease stage who underwent cardiopulmonary resuscitation following ventricular fibrillation to restore effective cardiac rhythm. After the third attempt of defibrillation she converted to sinus rhythm. Her echocardiography was suggestive of myocardial infarction (MI). On the second day of her hospitalization, she started becoming oliguric and her creatinine started rising up causing acute kidney injury (AKI). The patient’s creatinine kinase (CK) level peaked at 6380 u/L (normal range 26-192 u/L), myoglobin was >20,000 ng/mL (normal range 9-83 ng/mL), and myocardial bound (MB) isoenzyme of CK was 4.5 ng/mL (normal range 0-3.6 ng/mL). Plasma creatinine increased to 5.71 mg/dL and ultimately developed renal failure. She was started on hemodialysis. Her cardiac catheterization was suggestive of MI.

Our case highlights that MI, cardiopulmonary resuscitation, and cardioversion can be a cause for myoglobinuric renal failure, which has been rarely reported in the literature before.

Miniaturized monolithic disks for immunoadsorption of cardiac biomarkers from serum

Immunoadsorbers based on 2.0 x 6.0 mm i.d., epoxy-bearing, methacrylate-based monolithic disks were developed in order to target myoglobin and N-terminal pro-natriuretic peptide (NT-proBNP), two biomarkers involved in cardiovascular disease. In both cases, antibodies were successfully coupled to the polymeric disk material. The developed immunoadsorbers permitted the selective isolation of myoglobin and NT-proBNP from human serum. Myoglobin was successfully isolated and detected from serum samples at concentrations down to 250 fmol microL(-1). However, the affinity of the antibodies was not sufficient for the analysis of low-concentration clinical samples. Frontal analysis of anti-NT-proBNP disks revealed the ability of the immunoadsorber to bind up to 250 pmol NT-proBNP, which is more than sufficient for the analysis of clinical samples. Anti-NT-proBNP disks showed good stability over more than 18 months and excellent batch-to-batch reproducibility. Moreover, anti-NT-proBNP disks permitted the isolation of NT-proBNP at concentrations down to 750 amol microL(-1) in serum, corresponding to concentrations of strongly diseased patients. Using reversed-phase trapping columns, the detection of NT-proBNP eluted from immunoadsorbers by mass spectrometry was achieved for concentrations down to 7.8 fmol microL(-1).

Utilizing human blood plasma for proteomic biomarker discovery

Candidate proteomic biomarker discovery from human plasma holds both incredible clinical potential as well as significant challenges. The dynamic range of proteins within plasma is known to exceed 10(10), and many potential biomarkers are likely present at lower protein abundances. At present, proteomic based MS analyses provide a dynamic range typically not exceeding approximately 10(3) in a single spectrum, and approximately 10(4)-10(6) when combined with on-line separations (e.g., reversed-phase gradient liquid chromatography), and thus are generally insufficient for low level biomarker detection directly from human plasma. This limitation is providing an impetus for the development of experimental methodologies and strategies to increase the possible number of detections within this biofluid. Discussed is the diversity of available approaches currently used by our laboratory and others to utilize human plasma as a viable medium for biomarker discovery. Various separation, depletion, enrichment, and quantitative efforts as well as recent improvements in MS capabilities have resulted in measurable improvements in the detection and identification of lower abundance proteins (by approximately 10-10(2)). Despite these improvements, further advances are needed to provide a basis for discovery of candidate biomarkers at very low levels. Continued development of depletion and enrichment techniques, coupled with improved pre-MS separations (both at the protein and peptide level) holds promise in extending the dynamic range of proteomic analysis.

The human plasma proteome: history, character, and diagnostic prospects

The human plasma proteome holds the promise of a revolution in disease diagnosis and therapeutic monitoring provided that major challenges in proteomics and related disciplines can be addressed. Plasma is not only the primary clinical specimen but also represents the largest and deepest version of the human proteome present in any sample: in addition to the classical "plasma proteins," it contains all tissue proteins (as leakage markers) plus very numerous distinct immunoglobulin sequences, and it has an extraordinary dynamic range in that more than 10 orders of magnitude in concentration separate albumin and the rarest proteins now measured clinically. Although the restricted dynamic range of conventional proteomic technology (two-dimensional gels and mass spectrometry) has limited its contribution to the list of 289 proteins (tabulated here) that have been reported in plasma to date, very recent advances in multidimensional survey techniques promise at least double this number in the near future. Abundant scientific evidence, from proteomics and other disciplines, suggests that among these are proteins whose abundances and structures change in ways indicative of many, if not most, human diseases. Nevertheless, only a handful of proteins are currently used in routine clinical diagnosis, and the rate of introduction of new protein tests approved by the United States Food and Drug Administration (FDA) has paradoxically declined over the last decade to less than one new protein diagnostic marker per year. We speculate on the reasons behind this large discrepancy between the expectations arising from proteomics and the realities of clinical diagnostics and suggest approaches by which protein-disease associations may be more effectively translated into diagnostic tools in the future.

Myoglobinuria

Myoglobinuria refers to an abnormal pathologic state in which an excessive amount of myoglobin is found in the urine, imparting a cola-like hue, usually in association with myonecrosis and a clinical picture of weakness, myalgias, and edema. Myoglobinuria is produced by multiple causes: any condition that accelerates the use or interferes with the availability of oxygen or energy substrates to muscle cells can result in myoglobinuria, as can events that produce direct muscle injury, either mechanical or chemical. Acute renal failure is the most serious complication, which can be prevented by prompt, aggressive treatment. In patients surviving acute attacks, recovery of muscle and renal function is usually complete.

Myoglobinuria, malignant hyperthermia, neuroleptic malignant syndrome and serotonin syndrome

This article presents an overview of the causes and manifestations of myoglobinuria and provides criteria for its diagnosis and management. The article also reviews neuroleptic malignant syndrome, malignant hyperthermia, and serotonin syndrome, all of which could cause rhabdomyolysis and myoglobinuria.

The levels of serum myoglobin in cardiac patients with elevated creatine kinase-MB and suspected acute myocardial infarction

A monoclonal antibody enzyme immunoinhibition assay was used to quantitate serial serum myoglobin (Mb) levels in 121 patients who had > or = 5% creatine kinase-MB (CK-MB) and suspected acute myocardial infarction (AMI). Serum Mb levels higher than 0.16 micrograms/ml were considered abnormal. In 94% of these patients who were finally diagnosed with AMI, Mb levels were higher than 0.16 micrograms/ml, whereas all 30 normal control blood donors had lower Mb levels. Patients with anterior or inferior wall infarcts had higher Mb levels (> or = 0.64 micrograms/ml) than patients with lateral or subendocardial infarction. Only 68% (82/121) of patients evaluated by elevated CK-MB alone had a final diagnosis of AMI. In contrast, 94% (77/83) of patients who in addition showed elevated Mb had AMI. It is suggested that analysis of Mb levels allows a more accurate diagnosis of AMI in patients with elevated CK-MB than does reliance on CK-MB values alone.

Monoclonal antibody-based immunoassays for serum myoglobin quantification in acute myocardial infarction

We have developed a monoclonal antibody-based enzyme immunoassay and a solid-phase radioimmunoassay for human myoglobin. Both assays are based on competition for the monoclonal antibody between the free myoglobin present in the standards or serum samples and the myoglobin coated to the wells of microtiter plates. Consequently, the absorbance at 630 nm and the radioactivity are inversely related to the concentrations of free myoglobin. The sensitivity of both assays was 10 micrograms/L with linearity up to 1,000 micrograms/L. There was no interference with other serum proteins, as judged from analysis of specimens with high concentrations of lactate dehydrogenase, creatine kinase, or hemoglobin. The average serum myoglobin concentration in 30 normal individuals was 67 micrograms/L. Five patients with cardiac arrhythmias had normal values (average, 63 micrograms/L) while four patients with myocardial infarction had abnormally high concentrations of myoglobin (300-1,000 + micrograms/L). In a typical case of myocardial infarction, serum myoglobin rose 21 hr earlier and peaked 12 hr earlier than creatine kinase and its cardiac isoenzyme. These rapid immunoassays appear to be useful for the early detection of increased serum myoglobin indicative of myocardial infarction.

Rapid, simple and sensitive antigen capture ELISA for the quantitation of myoglobin using monoclonal antibodies

A rapid ELISA method has been developed to quantitate myoglobin in serum. An antigen capture enzyme-linked immunoassay with IgG1 mouse monoclonal antibodies produced by cell clones MGB20-4A1.1 and MGB20-3C1.2 were used for myoglobin detection. These monoclonal antibodies are specific for different epitopes of the myoglobin molecule. Monoclonal antibodies from the hybridoma clone MGB20-4A1.1 were adsorbed to microtiter plate wells. The plates were washed with PBS containing 0.05% Tween 20 and then 20 microliter of standard serum or serum of patients and 200 microliter of peroxidase labeled monoclonal antibodies MGB20-3C1.2 were added to each well. Plates were incubated for 90 min at 37 degrees C and enzyme activity was determined using o-phenylenediamine as a substrate. The ELISA assay described is a rapid and sensitive procedure to assess the quantity of myoglobin within the range 2-1000 ng/ml serum. 120 samples can be tested in 3 h.

A sensitive sandwich enzyme immunoassay for human myoglobin using Fab'-horseradish peroxidase conjugate: methods and results in normal subjects and patients with various diseases

A sensitive sandwich enzyme immunoassay (EIA) for human myoglobin (Mb) was developed. Serum Mb was assayed by incubation with an anti-Mb rabbit IgG-coated polystyrene ball and then with affinity-purified anti-Mb Fab'-horseradish peroxidase (HRP) conjugate. The HRP activity bound to the polystyrene ball was assayed fluorimetrically. The sensitivity was 3.1 pg/tube and serum Mb levels of 0.4-1000 micrograms/l could be determined. The recoveries of Mb added to human sera at 3 concentrations were 92.8-99.8%. The within- and between-assay coefficients of variations (CV values) were both below 10%. The regression equation of values determined by EIA and radioimmunoassay (RIA) was y(EIA) = 0.964x (RIA)--2.30 and the correlation coefficient was 0.984. The mean normal serum concentration of Mb was 21.5 +/- 6.0 micrograms/l (mean +/- SD) in males and 16.9 +/- 5.8 micrograms/l in females. The significance of serum Mb determination by the EIA in various diseases was confirmed. The present EIA for Mb is more sensitive and economical than RIA and should be useful for determining Mb in biological materials.

Monoclonal antibodies directed against human myoglobin: characterization and application in a bideterminant radioimmunoassay

Monoclonal hybridoma cell lines secreting antibodies directed against human myoglobin were selected. Two of these cell lines were grown in mouse ascitic fluid resulting in the production of large quantities of antibody. Antimyoglobin antibodies isolated from the ascitic fluids were employed in the development of the sensitive solid-phase, bideterminant radioimmunoassay for human myoglobin that uniquely recognizes two different epitopes on the same molecule.

Comparison of serum myoglobin and creatine kinase MB isoenzyme in early diagnosis of acute myocardial infarction

We compared the clinical usefulness of serum myoglobin and creatine kinase MB (CK MB) isoenzyme determinations in the early diagnosis of acute myocardial infarction in 109 consecutive patients admitted to a coronary care unit. Of these, 37 patients were diagnosed as having definite infarction, three possible infarction, and 69 no infarction, using World Heath Organisation criteria. Blood samples were taken on admission and two to four hours later, Both CK MB and myoglobin were raised in the initial serum samples in 24 of the 37 patients with definite infarction. In an additional seven patients both CK MB and myoglobin were negative in the first specimen though both were detected in the second sample. In five patients CK MB preceded the appearance of myoglobin while in the remaining patient myoglobin appeared before CK MB. We conclude that the detection of serum myoglobin does not offer any clinical advantage over CK MG as an early indicator of myocardial infarction.