Effects on plasma endotoxin and eicosanoid concentrations and serum cytokine activities in horses competing in a 48-, 83-, or 159-km endurance ride under similar terrain and weather conditions

Effect of an endothelial regulatory module on plasma proteomics in exercising horses

Elite performing exercise requires an intricate modulation of the blood pressure to support the working muscles with oxygen. We have previously identified a genomic regulatory module that associates with differences in blood pressures of importance for elite performance in racehorses. This study aimed to determine the effect of the regulatory module on the protein repertoire. We sampled plasma from 12 Coldblooded trotters divided into two endothelial regulatory module haplotype groups, a sub-elite performing haplotype (SPH) and an elite performing haplotype (EPH), each at rest and exercise. The haplotype groups and their interaction were interrogated in two analyses, i) individual paired ratio analysis for identifying differentially abundant proteins of exercise (DAPE) and interaction (DAPI) between haplotype and exercise, and ii) unpaired ratio analysis for identifying differentially abundant protein of haplotype (DAPH). The proteomics analyses revealed a widespread change in plasma protein content during exercise, with a decreased tendency in protein abundance that is mainly related to lung function, tissue fluids, metabolism, calcium ion pathway and cellular energy metabolism. Furthermore, we provide the first investigation of the proteome variation due to the interaction between exercise and related blood pressure haplotypes, which this difference was related to a faster switch to the lipoprotein and lipid metabolism during exercise for EPH. The molecular signatures identified in the present study contribute to an improved understanding of exercise-related blood pressure regulation.

Equine Peripheral Gene Expression Changes in Response to Dose-Dependent Lipopolysaccharide-Induced Synovitis

The use of lipopolysaccharide to induce a localized source of inflammation (acute synovitis) and allow for monitoring of changes in systemic mRNA expression has been recently reported. Here, the goal was to maintain a significant systemic mRNA response while limiting the severity of lameness such that this model can be used to examine the effects of various anti-inflammatory treatment modalities on mRNA expression. Three mixed breeds, four-year-old geldings were utilized for this study. One milliliter of phosphate-buffered saline containing 1,000 ng or less of lipopolysaccharide from E. coli O111:B4 was aseptically injected into alternating radiocarpal joints following washout periods. Blood for complete blood cell count, serum amyloid A concentration, and mRNA analysis via RT-qPCR for 23 different genes were collected before each injection, as well as at multiple times post-injection. Lameness severity was also graded at each time point. Two-way, repeated measures analysis of variance was used for statistical analysis (P < .05). Results largely replicated those previously reported, with multiple genes exhibiting significant expression changes during the acute inflammatory period (including increases in CD14, TLR4, IL-1β, IL1RN, MMP1, and MMP9 expression) while some demonstrated dose-dependent changes; significant increases in complete blood cell count parameters and serum amyloid A concentrations were also noted. Attempts to temper the severity of lameness were not successful as nonweight bearing lameness was noted at doses of 10ng or higher, while a dose of 1ng elicited neither a detectable lameness nor a significant change in mRNA expression.

Influence of exhaustive aerobic exercise on some cytokines and serum iron parameters in canine experimental model

The aim of the experiment was to study the effect of exhaustive exercise on some cytokines and iron status parameters. We used 12 male, mongrel dogs divided into two groups – animals from experimental group were submitted to exercise at moderate intensity with exhaustion as the end-point; animals from control group did no exercise. Serum levels of tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6), hepcidin prohormone, serum iron (SI), total iron binding capacity (TIBC) and transferrin saturation (TS) were measured before exercise (BE), right after exercise (0 hour) and on 2, 4, 24, 48 and 72 hours after exercise. SI, TIBC and TS were measured also on day 7 and 14 after exercise. Serum levels of TNF-α increased after the exhaustive exercise. Serum levels of IL-6 demonstrated an increase at 0 hour, but increase was not statistically significant compared to BE level. Serum levels of hepcidin prohormone marked a slight increase 48 hours after the exercise, but change was insignificant. Levels of SI decreased on hour 72 (P<0.01) and on day 7 (P<0.01) and 14 (P<0.05) after the exercise, as compared to BE level. Similar were changes in TS. TIBC decreased on 4, 24 and 72 hours (P<0.05) after exercise, but only compared to control group. In conclusion, exhaustive exercise causes inflammatory response and a significant decrease in SI levels.

The effect of agility exercise on eicosanoid excretion, oxidant status, and plasma lactate in dogs

Background

The objective was to determine the effects of agility exercise on dogs of different skill levels with respect to urinary eicosanoids, urinary 15F_2t-isoprostane (lipid peroxidation marker) and hematological/biochemical changes in plasma. Fifteen adult dogs had blood and urine samples obtained prior to, immediately and 4-hours following an agility exercise.

Results

Hematocrit, red blood cells (RBC), albumin, and hemoglobin increased following exercise, with greatest increases correlating to increased skill group (novice, intermediate, masters); at 4-hours post-exercise, hematocrit, RBC, and hemoglobin were decreased. Phosphorus increased following exercise with the greatest increase in novice and intermediates. Plasma lactate increased 3.6-fold in masters, 3.2-fold in intermediates, and 1.2-fold in novice dogs. Urine thromboxane B₂ (TXB2) more than tripled 4-hours post-exercise while 6-keto prostaglandin F_1α (PGF1α, prostacyclin metabolite), prostaglandin E₂ metabolites (13,14-dihydro-15-keto-prostaglandin A₂ and 13,14-dihydro-15-keto-prostaglandin E₂), and 13,14-dihydro-15-keto prostaglandin F_2α were unaffected as determined by a competitive enzyme immunoassay and standardized by division with urine creatinine. Urine 15F_2t-isoprostane increased insignificantly.

Conclusions

Alterations in the plasma post-exercise were likely due to hemoconcentration from insensible water loss, splenic contraction and sympathetic stimulation while 4-hours later autohemodilution reduced RBC parameters. Elevations in plasma lactate and urinary TXB2 correlated with advanced skill level/speed of the dogs.

Pattern recognition receptors in equine endotoxaemia and sepsis

Pattern recognition receptors (PRRs) on host cells detect pathogens to activate innate immunity which, in turn, initiates inflammatory and adaptive immune responses. Successful activation of PRRs is, therefore, critical to controlling infections and driving pathogen‐specific adaptive immunity, but overactivity of PRRs causes systemic inflammation, which is detrimental to the host. Here we review the PRR literature as it relates to horses and speculate on the role PRRs may play in sepsis and endotoxaemia.

The effects of prolonged endurance exercise on the neurological system in horses

Horses compete routinely in endurance-type activities. Many of the various pathophysiological mechanisms which arise during endurance exercise have implications for the health and function of the neurological system. The development of centrally-mediated fatigue is a normal homeostatic physiological event with several possible mechanisms. Development of pathophysiological phenomena such as cerebral oedema may be near-terminal events during or after endurance exhaustion. Cellular damage resulting in cytotoxic cerebral oedema may result from decreases in circulating blood volume (dehydration), blood pressure, oxygen, and glucose, or increases in brain temperature. Vasogenic cerebral oedema arises from changes in cerebral vascular perfusion, tone, and permeability. Increased vascular permeability results from increased brain temperature, poor vascular integrity due to severe dehydration, disseminated intravascular coagulation due to hemoconcentration or endotoxemia, and iatrogenic overhydration during therapy. Clinical signs of intracranial disease after endurance exercise include staggering, shaking, ataxia, paresis, poor tongue tone, facial twitching, collapse, recumbency, seizures, and death. Treatment should include active and aggressive cooling, intravenous polyionic fluids, acid-base imbalance correction, intravenous glucose and calcium supplementation, non-steroidal anti-inflammatory agents once the patient is better hydrated, intra-nasal oxygen therapy if practicable, and achievement of a non-dependent head posture to prevent jugular venous hypertension and further increases in intracranial pressure. The prognosis for central fatigue is good with appropriate supportive care, but the prognosis for successful treatment of cerebral oedema must be considered guarded at best. Prevention is critical and must be through incorporation of mandatory rest stops with sufficient length and veterinary monitoring to allow prevention and detection of exhaustion, excessive dehydration, and neurological signs. Management flexibility in shortening or postponing rides in hot and humid conditions, mandated use of aggressive cooling techniques, and more restrictive entry criteria for upper level Fédération Equestre Internationale races should all be considered as viable options for optimising the safety of endurance horses.

Relationship between exercise-induced systemic inflammatory like reaction and racing performance in endurance horses

Endurance race induces a rise of serum creatine kinase (CK) activity and a systemic inflammatory like response characterised by an increase of neutrophil counts, plasma and muscle myeloperoxidase (MPO) and elastase (ELT) concentrations in horses. Horses performing the same standardised exercise test do not respond with the same magnitude of inflammatory reaction. The aim of the present study was to measure the total neutrophil count, the ratio neutrophil:lymphocyte, the MPO and ELT plasma concentrations and concomitant increases of serum CK activities in competing endurance horse and to relate these results to their race performance. Twenty one horses participating in a 120 km 4 star endurance race recruited on a voluntary basis finished the race with a mean speed ranging from 13.1 to 19.8 km/h. Blood was taken the day before the race and two hours after the race. Mean values of neutrophil counts, ratio neutrophil:lymphocyte, plasma MPO and ELT concentrations and serum CK activities after the race were significantly higher than the pre-race values. There was no correlation between neutrophil counts, MPO, ELT or CK and the mean speed of the horses during the race except for the ratio neutrophil:lymphocyte where a significant negative correlation was observed. These results showed that systemic responses induced by strenuous exercise such as an endurance race is not clearly related to performance but also to horse-related factors, such as intrinsic capacity or training.

Exercise-induced increases in inflammatory cytokines in muscle and blood of horses

REASONS FOR PERFORMING STUDY

Studies have demonstrated increases in mRNA expression for inflammatory cytokines following exercise in horses and have suggested those markers of inflammation may play a role in delayed onset muscle soreness. However, measurement of mRNA expression in white blood cells is an indirect method. No studies to date have documented the cytokine response to exercise directly in muscle in horses.

HYPOTHESIS

This study tested the hypothesis that exercise increases cytokine markers of inflammation in blood and muscle.

METHODS

Blood and muscle biopsies were obtained from 4 healthy, unfit Standardbred mares (∼ 500 kg). The randomised crossover experiment was performed with the investigators performing the analysis blind to the treatment. Each horse underwent either incremental exercise test (GXT) or standing parallel control with the trials performed one month apart. During the GXT horses ran on a treadmill (1 m/s increases each min until fatigue, 6% grade). Blood and muscle biopsies were obtained 30 min before exercise, immediately after exercise and at 0.5, 1, 2, 6 and 24 h post GXT or at matched time points during the parallel control trials. Samples were analysed using real time-PCR for measurement of mRNA expression of interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and interleukin-1 (IL-1). Data were analysed using t tests with the null hypothesis rejected when P < 0.10.

RESULTS

There were no changes (P > 0.10) in IL-1, IL-6, IFN-gamma or TNF-alpha during control. Exercise induced significant increases in IFN-gamma, IL1 and TNF-alpha in blood and significant increases in IFN-gamma, IL-6 and TNF-alpha in muscle. There were no significant changes in mRNA expression of IL-1 in muscle or IL-6 in blood following the GXT. These cytokine markers of inflammation all returned to preGXT levels by 24 h post GXT.

CONCLUSION

High intensity exercise results in a transient increase in the expression of inflammatory cytokines in muscle and blood.

Neuroendocrine and non-neuroendocrine markers of inflammation associated with performance in endurance horses

REASONS FOR PERFORMING STUDY

The inflammatory and neuroendocrine response to endurance exercise and relationship of these parameters to performance is not well documented in horses. HYPOTHESES OR OBJECTIVES: Evidence of systemic inflammation is associated with poor performance in horses competing in endurance events.

METHODS

Blood was collected prior to and at the finish or elimination point from horses competing in both the 80 and 160 km American Endurance Ride National Championship competitions in 2006. Immunoreactive alpha-melanocyte stimulating hormone (α-MSH) and tumour necrosis factor-alpha (TNF-α) were quantified utilising radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) techniques, respectively. The concentration of total thiobarbituric acid reactive substances (TBARS) was measured fluorometrically.

RESULTS

Thirty horses were included in the study. Endurance exercise was associated with a significant increase in TBARS in the 80 km group but not the 160 km group. TNF-α and α-MSH did not significantly change as a result of exercise in either distance group. Precompetition TBARS was significantly higher in horses that failed to finish the 80 km race, as well as when distances were combined. In addition, precompetition α-MSH was significantly lower in nonfinishers in the 160 km group. Furthermore, competition speed was positively correlated with precompetition α-MSH in the 80 km and negatively correlated with precompetition TNF-α when distances were combined.

CONCLUSIONS

Our results suggest that basal oxidative stress markers, circulating cytokines and anti-inflammatory neuroendocrine hormones appear to correlate with endurance performance in horses.

POTENTIAL RELEVANCE

Basal oxidative stress markers, circulating cytokines and anti-inflammatory neuroendocrine hormones may be predictive of athletic performance in endurance horses. Future studies evaluating the effect of training on these markers in endurance horses are warranted.

Prevalence of gastric ulcer syndrome in high-level endurance horses

REASONS FOR PERFORMING THE STUDY

Equine gastric ulcers syndrome (EGUS) prevalence studies are rare in the endurance horse and none has been carried out to date in horses competing at high level.

OBJECTIVES

To determine the prevalence of EGUS in high-level endurance horses.

METHODS

Thirty endurance horses competing at high level were selected and submitted to 2 gastroscopic examinations. The first gastroscopy was performed during the interseason period, and the second during the competition season within 2-3 days following a ride of 90-160 km. Data related to housing, feeding, training system as well as age, breed and gender were recorded for each horse.

RESULTS

The prevalence of squamous gastric ulcers was 48% during the interseason period (mean score 0.85 ± 0.13 on a scale from 0-4) and 93% during the competition season (mean score 1.60 ± 1.15) with a highly significant difference between the seasons (P = 0.001). Most of the lesions were situated in the squamous portion of the stomach but 33.3% of horses showed also glandular lesions. Significant influence of training and performance level on the gastric score (according to the distance of the ride preceding the second gastroscopy) was shown (P = 0.038). There was also a significant influence of housing on the gastric score (P = 0.002) showing higher scores in the horses kept totally on pasture (mean score: 2.14 ± 0.14) vs. horses housed in a mixed environment (stable + pasture, mean score: 1.43 ± 0.17). Both the pastured and (stabled + pastured) groups were receiving a grain supplement but the pastured group received a higher daily starch intake, which might explain the higher ulcer prevalence. There was no influence of age, breed or gender on the gastric scores.

CONCLUSIONS

The high prevalence of gastric lesions observed in this study is probably related to the high level of training and performance of the horses examined compared to the population of horses included in the prior study.

POTENTIAL RELEVANCE

This prevalence of EGUS in high-level endurance horses is comparable to the prevalence established in racing horses. The equine veterinarians may take into consideration EGUS as a potential cause of poor performance.

Exercise-induced alterations in pro-inflammatory cytokines and prostaglandin F2α in horses

Using an established standardized exercise test on a high-speed treadmill, thirteen Thoroughbred racehorses were exercised to fatigue (failure); blood samples were obtained before exercise, at failure, and at 2, 6, 24, 48, and 72 h after exercise. The exercise test induced a systemic inflammatory response characterized by a mild transient endotoxemia, leukocytosis, increased leukocyte expression of mRNA for tumor necrosis factor-alpha (TNF-alpha), IL-1 beta, and IL-6, and increased circulating concentrations of TNF-alpha and prostaglandin F2 alpha (PGF 2 alpha), with the most pronounced changes being evident at failure and 2h after exercise. Expression of mRNA for IL-6, TNF-alpha, and IL-1 beta was increased by 120-fold, three-fold, and four-fold, respectively, when compared to pre-exercise values. Plasma concentrations of 6-keto-PGF1alpha and PGE2 did not change in response to the exercise test. Collectively, these findings indicate that brief, strenuous exercise induces endotoxemia and a systemic pro-inflammatory response in horses that persists for at least 2h.

Gene expression profiling in blood cells of endurance horses completing competition or disqualified due to metabolic disorder

REASONS FOR PERFORMING STUDY

Genomics using cDNA microarrays could provide useful information about physiological adaptations and metabolic disorders in endurance horses.

OBJECTIVES

In order to show that genes are modulated in leucocytes in relationship with performance and clinical status of the horses, gene expression in leucocytes, haematological and biochemical parameters were compared between successful and disqualified endurance horses.

METHODS

Blood samples were collected at rest (TO) and just after a 140-160 km endurance race (T1) in 2 groups of horses: 10 continuing successful (S) and 10 disqualified horses stopped at a vet-gate for metabolic disorders (D). Total RNA was extracted from the blood cells (leucocytes), checked for purity, amplified and hybridised using mouse cDNA microarrays including 15,264 unique genes. Differential gene expressions were studied by hybridisation of each sample T1 vs. a control sample collected at TO (pool of 20 sound horses).

RESULTS

Some significant differences were observed in the haematology and biochemistry of the 2 groups (S vs. D). In Group D, rhadomyolysis was confirmed with CK 13,124 u/l and AST 1242 u/l. The list of 726 (including 603 annotated genes) significant genes was filtered according to a high P-value cut-off (P<0.00001). Among them, 130 were upregulated (expression ratio>1.5) and 288 were down-regulated (<1/1.5). Analysis of variance revealed 62 genes differentially expressed (P<0.05) in Groups D and S. The expression levels of 28 and 50 genes were significantly correlated (r>0.75) with CK and AST level in Group D, respectively. The gene ontology classification showed that more genes were up-regulated in S than in the D. More genes were down-regulated in the disqualified horses.

CONCLUSIONS

Long exercise induced many significant gene modulations in leucocytes. Some genes were expressed in relationship with the clinical phenotype observed in Group D: rhabdomyolysis and haemolysis.

POTENTIAL RELEVANCE

Some of these genes could be candidates to explain poor performance or pathologies. Further association studies with a greater number of genes should be conducted.