Cross reactivity between human erythropoietin antibody and horse erythropoietin

Doping detection in animals: A review of analytical methodologies published from 1990 to 2019

Despite the impressive innate physical abilities of horses, camels, greyhounds, or pigeons, doping agents might be administered to these animals to improve their performance. To control these illegal practices, anti-doping analytical methodologies have been developed. This review compiles the analytical methods that have been published for the detection of prohibited substances administered to animals involved in sports over 30 years. Relevant papers meeting the search criteria that discussed analytical methods aiming to detect and/or quantify doping substances in animal biological matrices published from 1990 to 2019 were considered. A total of 317 studies were included, of which 298 were related to horses, demonstrating significant advances toward the development of doping detection methods for equine sports. However, analytical methods for the detection of doping agents in sports involving other species are lacking. Due to enhanced accuracy and specificity, chromatographic analysis coupled to mass spectrometry detection is preferred over immunoassays. Regarding biological matrices, blood and urine remain the first choice, although alternative biological matrices, such as hair and feces, have been considered. With the increasing number and type of drugs used as doping agents, the analytes addressed in the published papers are diverse. It is very important to continue to detect and quantify these drugs, recognizing those that are most frequently used, in order to punish the abusers, protect animals' health, and ensure a healthier and genuine competition.

Low dose exogenous erythropoietin elicits an ergogenic effect in Standardbred horses

REASONS FOR PERFORMING STUDY

Recombinant human erythropoietin (rhuEPO) causes an increase in red blood cell production and aerobic capacity in other species; however, data are lacking on effects in the horse.

HYPOTHESIS

This study tested the hypothesis that rhuEPO administration would alter red cell volume (RCV), aerobic capacity (VO2max) and indices of anaerobic power.

METHODS

Eight healthy, unfit mares accustomed to the laboratory and experimental protocols were randomly assigned to either a control (CON, n = 4; 3 ml saline 3 times/week for 3 weeks) or EPO group (EPO, n = 4, 50 iu/kg bwt rhuEPO/3 ml saline 3 times/week for 3 weeks). Exercise tests (GXT) were performed on a treadmill (6% incline), 1 week before and 1 week after treatment. The GXT started at 4 m/sec, with a 1 m/sec increase every 60 sec until the horse reached fatigue. Oxygen uptake was measured via an open flow indirect calorimeter. Blood samples were collected before, during (each step) and 2 and 15 min post GXT to measure packed cell volume (PCV), haemoglobin concentration (Hb), blood lactate concentration (LA) and plasma protein concentration (TP). Plasma volume (PV) was measured using Evans Blue dye. Blood volume (BV) and RCV were calculated using PCV from the 8 m/sec step of the GXT.

RESULTS

There were no alterations (P>0.05) in any parameters in CON horses. By week 3, EPO produced increases (P<0.05) in resting PCV (37 +/- 2 vs. 51 +/- 2) and Hb (37%). RCV (26%) and VO2max (19%) increased, but BV did not change (P>0.05) due to decreased PV (-11%, P<0.05). There was a significant increase in velocity at VO2max and LApeak for horses treated with rhuEPO and substantial decrease (P<0.05) in VO2 recovery time when the pretreatment GXT was compared to the post treatment GXT. No differences (P<0.05) were detected for TP, VLA4, run time or Vmax.

CONCLUSIONS

Low dose rhuEPO administration increases RCV and aerobic capacity without altering anaerobic power.

POTENTIAL RELEVANCE

This study demonstrates that rhuEPO enhances aerobic capacity and exercise performance, a question relevant to racing authorities.

Erythropoietin and analogs

Erythropoietin (EPO), a glycoprotein hormone, stimulates the growth of red blood cells and as a consequence it increases tissue oxygenation. This performance enhancing effect is responsible for the ban of erythropioetin in sports since 1990. Especially its recombinant synthesis led to the abuse of this hormone, predominatly in endurance sports. The analytical differentiation of endogenously produced erythropoietin from its recombinant counterpart by using isoelectric focusing and double blotting is a milestone in the detection of doping with recombinant erythropoietin. However, various analogous of the initial recombinant products, not always easily detectable by the standard IEF-method, necessitate the development of analytical alternatives for the detection of EPO doping. The following chapter summarizes its mode of action, the various forms of recombinant erythropoietin, the main analytical procedures and strategies for the detection of EPO doping as well as a typical case report.

LC−MS/MS Method for Confirmation of Recombinant Human Erythropoietin and Darbepoetin α in Equine Plasma

Recombinant human erythropoietin (rhEPO) and darbepoetin alpha (DPO) are protein-based drugs for the treatment of anemia by stimulating red blood cell production. Consequently, they are abused in human and equine sports. To deter their abuse in the horse racing industry, a sensitive and reliable method for confirmation of these agents in equine plasma has been in urgent need. Such a method by LC-MS/MS is described in this paper. The method involved analyte enrichment by immunoaffinity separation using anti-rhEPO antibody linked to magnetic beads, digestion by trypsin, and analysis by LC-MS/MS. Two specific proteotypic peptides, 46VNFYAWK52 and 144VYSNFLR150 from rhEPO and DPO were employed for confirmation of the analytes based on chromatographic retention times and major product ions. The limit of confirmation of this method was 0.2 ng/mL, and the limit of detection was 0.1 ng/mL for rhEPO and DPO in equine plasma. This method was successful in confirming the presence of rhEPO and DPO in plasma samples collected from research horses to which rhEPO or DPO was administered and from racehorses following competition and in noncompetition samples in North America. To our knowledge, this is the first LC-MS method with adequate sensitivity and specificity in providing unequivocal confirmation of rhEPO and DPO in equine plasma samples. This method provides a powerful enforcement tool that was lacking in the fight against the abuse of rhEPO and DPO in the horse racing industry.

Reticulocyte changes after experimental anemia and erythropoietin treatment of horses

Availability of recombinant human erythropoietin (EPO) has facilitated use to enhance red blood cell production, and therefore aerobic performance, in human and equine athletes. Recombinant human EPO promotes growth and differentiation of equine erythroid precursor cells, but in some horses repeat administration induces immune interference with endogenous EPO resulting in fatal anemia. Although blood reticulocyte parameters acquire unique changes in humans treated with EPO, with manual enumeration methods, horses were not considered to release reticulocytes from the bone marrow into circulation, even under severe erythropoietic stress. The goals of this study were to determine whether reticulocytes could be detected and characterized in horses that are anemic or have been treated with EPO using a modern hematology analyzer. Anemia was induced in six horses by removal of 30 ml of blood/kg of body wt over 24 h. After 28 days, the horses were treated twice with 55 U/kg of EPO (Eprex), and after 65 days they were treated thrice with 73 U/kg of EPO. Blood samples were analyzed with the ADVIA120 instrument every 3–5 days and bone marrow samples 7 days after anemia and EPO treatments. Analysis of blood reticulocyte parameters by ANOVA in a randomized complete block design determined that anemia and EPO induced significant ( P ≤ 0.05) increases in red cell distribution width and reticulocyte mean cell volume. Parameters changed only after EPO treatment were cellular hemoglobin concentration mean, mean cell volume, reticulocyte concentration, proportion of macrocytic reticulocytes, and reticulocyte cellular hemoglobin. These findings indicate that horses under erythropoietic stress and after EPO treatment release reticulocytes with unique characteristics into circulation.

Postnatal ontogeny of erythropoietin and hematology in free-ranging Steller sea lions (Eumetopias jubatus)

The hormone erythropoietin (EPO) is responsible for the increased production of red blood cells (RBC) in response to tissue hypoxia. While the role of EPO in hematological development has been established in humans and terrestrial mammals, this relationship has never been examined in marine mammals that rely heavily on stored oxygen to maintain aerobic metabolism while diving. Since blood is the major oxygen storage site in marine mammals, it was hypothesized that EPO may have a significant influence on the development of hematology parameters associated with the expansion of blood oxygen stores during development. To explore this hypothesis, serum EPO concentrations were determined by radioimmunoassay in 235 free-ranging Steller sea lions (Eumetopias jubatus), throughout their Alaskan range. Hematocrit (Hct), hemoglobin (Hb), and red blood cell (RBC) counts were also measured, and mean corpuscular hemoglobin content (MCHC), mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCV) values determined. Erythropoietin and most hematological parameters varied with age. Hematocrit, Hb, RBC, and MCHC decreased after birth, reached their lowest values at two to three months of age, and then increased to values similar to those of adults by five months of age. Since changes in Hct and Hb account for the majority of the changes in blood oxygen stores and EPO was negatively correlated with both, it appears that EPO may play an important role in blood development of Steller sea lions, similar to previous studies on terrestrial mammals.

Nucleotide sequence of equine erythropoietin and characterization of region-specific antibodies

OBJECTIVE

To determine the full-length complementary DNA (cDNA) sequence of equine erythropoietin (EPO) and to develop region-specific antibodies to differentiate equine EPO (eEPO) and human EPO (hEPO).

SAMPLE POPULATION

RNA and lysate extracted from renal tissues of an adult Thoroughbred.

PROCEDURE

Full-length cDNA was determined by use of a reverse transcriptase-polymerase chain reaction assay and a rapid amplification of cDNA ends method. The deduced amino acid sequence was compared with sequences of EPO reported for other species. Furthermore, 4 synthetic peptides were designed in 2 distinctive parts of the eEPO and hEPO amino acid sequences to obtain antibodies specific for eEPO and hEPO. Specificity of the antibodies was tested against supernatant of homogenized equine kidney and recombinant hEPO (rhEPO) by use of western immunoblotting techniques.

RESULTS

Analysis of the 1,181 bp in the nucleotide sequence revealed that eEPO was a residue of 192 amino acids. Similarity of eEPO with amino acid sequences of EPO from other species was 81.0% to 90.6%. Antibodies were specifically recognized by eEPO or rhEPO molecules. Anti-hEPO (161 to 165) antibody specifically recognized rhEPO. In contrast, anti-eEPO (133 to 144) antibody reacted with the equine kidney lysate.

CONCLUSIONS AND CLINICAL RELEVANCE

We determined the cDNA and amino acid sequence of eEPO and developed region-specific antibodies that specifically recognized eEPO or rhEPO. These antibodies may be useful in distinguishing rhEPO from eEPO in a test to detect the misuse of rhEPO in racehorses.

The endocrine system and the challenge of exercise

Fine-tuning of the response to exercise that lasts longer than a few seconds is reliant on the regulation of several key variables governing the cardiopulmonary, vascular, and metabolic response to exercise. This type of integrative response requires communication between organ systems that relies on the secretion of endocrine and paracrine substances by one tissue or organ that are transported remotely to other tissues or organs to evoke a response to adjust to the disturbance.

17Beta-estradiol decreases hypoxic induction of erythropoietin gene expression

Exposure to chronic hypoxia induces erythropoietin (EPO) production to facilitate oxygen delivery to hypoxic tissues. Previous studies from our laboratory found that ovariectomy (OVX) exacerbates the polycythemic response to hypoxia and treatment with 17beta-estradiol (E2-beta) inhibits this effect. We hypothesized that E2-beta decreases EPO gene expression during hypoxia. Because E2-beta can induce nitric oxide (NO) production and NO can attenuate EPO synthesis, we further hypothesized that E2-beta inhibition of EPO gene expression is mediated by NO. These hypotheses were tested in OVX catheterized rats treated with E2-beta (20 microg/day) or vehicle for 14 days and exposed to 8 or 12 h of hypoxia (12% O(2)) or normoxia. We found that E2-beta treatment significantly decreased EPO synthesis and gene expression during hypoxia. E2-beta treatment did not induce endothelial NO synthase (eNOS) expression in the kidney but potentiated hypoxia-induced increases in plasma nitrates. We conclude that E2-beta decreases hypoxic induction of EPO. However, this effect does not appear to be related to changes in renal eNOS expression.

Endothelin response during and after exercise in horses

The objective of the present study was to measure plasma endothelin-1 (ET-1) at rest and during exercise in the horse. Six healthy, Standardbred and Thoroughbred mares (5.3+/-0.8 years; 445.2+/-13.1 kg) which were unfit, but otherwise accustomed to running on the treadmill, were used in the study. Plasma ET-1 concentrations were measured using a commercially available radioimmunoassay kit. Horses performed three trials: a standing control (CON) trial where blood was collected from the jugular vein every minute for 5 min; a graded exercise test (GXT) where blood samples were collected at the end of each 1 min step of an incremental exercise test; and a 15 min submaximal (60% VO(2max)) steady-state exercise test (SST) where blood samples were collected 1 min before, immediately after, and at 2 min, 10 min and 20 min post-exercise. Plasma ET-1 concentration did not change (P>0.05) during the CON trial where it averaged 0.18+/- 0.03 pg/mL (mean+/-SE). Surprisingly, plasma ET-1 concentration did not change during the GXT trial where it averaged 0.20+/-0.03 pg/mL. There were no differences between the mean concentrations obtained in either trial (P>0.05). Plasma ET-1 concentrations were, however, significantly elevated (P<0.05) immediately following exercise and at 2 min post-exercise in the SST. Post-exercise plasma ET-1 concentrations returned to baseline (P>0.05) by 10 min of recovery. Together, these data may suggest that ET-1 concentrations are altered in response to an exercise challenge.