New Pathophysiological Insights from Serum Proteome Profiling in Equine Atypical Myopathy

Equine atypical myopathy (AM) is a severe environmental intoxication linked to the ingestion of protoxins contained in seeds and seedlings of the sycamore maple (Acer pseudoplatanus) in Europe. The toxic metabolites cause a frequently fatal rhabdomyolysis syndrome in grazing horses. Since these toxic metabolites can also be present in cograzing horses, it is still unclear as to why, in a similar environmental context, some horses show signs of AM, whereas others remain clinically healthy. Label-free proteomic analyses on the serum of 26 diseased AM, 23 cograzers, and 11 control horses were performed to provide insights into biological processes and pathways. A total of 43 and 44 differentially abundant proteins between "AM vs cograzing horses" and "AM vs control horses" were found. Disease-linked changes in the proteome of different groups were found to correlate with detected amounts of toxins, and principal component analyses were performed to identify the 29 proteins representing a robust AM signature. Among the pathway-specific changes, the glycolysis/gluconeogenesis pathway, the coagulation/complement cascade, and the biosynthesis of amino acids were affected. Sycamore maple poisoning results in a combination of inflammation, oxidative stress, and impaired lipid metabolism, which is trying to be counteracted by enhanced glycolysis.

Validation of a commercially available photometric analytical system for assessment of plasma oxidative status in healthy horses

Reactive oxygen species (ROS) are the end-products of physiologic functions in health. Oxidative stress occurs when endogenous antioxidants are insufficient to neutralize ROS in the system. As a result, ROS can damage DNA, RNA, proteins, lipids, and cell organelles. To obtain accurate measurements of plasma oxidative stress, levels of both oxidants and antioxidants must be measured. This study validates a commercially available, semi-quantitative, photometric analytical system that measures systemic determinants of reactive oxygen metabolites (dROM) and plasma antioxidant capacity (PAC) in stored equine plasma. The objectives of this work were: 1) to validate a photometric analytical system to quantify dROM and PAC in equine plasma; and 2) to determine expected results for these tests in healthy adult horses. We hypothesized that this system would reliably and reproducibly assess dROM and PAC in equine plasma. We observed expected, dose-dependent increases in dROM generated by adding increasing concentrations of H2O2 or ascorbic acid to equine plasma to provide samples containing a known quantity of oxidants or antioxidants respectively. Mean dROM value in healthy horses was 103.3 ±20.7 U. Carr and mean PAC was 2881.0 ± 313.9 U. Cor. This system reliably and reproducibly quantified dROM and PAC in equine plasma samples.

Evaluation of Oxidative Stress Parameters in Healthy Saddle Horses in Relation to Housing Conditions, Presence of Stereotypies, Age, Sex and Breed

Oxidative stress plays an important role in the development of many horse diseases and it has been shown that housing has important implications for the psychophysical well-being of horses. The aim of this study is to determine if there are any differences between the redox status in horses in relation to housing conditions. The four housing conditions analyzed were: single box, without external access and without contact (Cat A), single box with external access and possibility of partial contact (Cat B), group housing with box and large paddock (Cat C), pasture with more than 7 horses and the possibility of green forage for the whole year (Cat D). A group of 117 healthy horses were selected in several private stables in Northern Italy. All subjects treated with any type of drug were excluded. At the end of the enrollment, the 117 selected horses were divided into the four housing categories. Stereotypies were highest in the group of horses in single box, without external access and without contact (Cat A). Oxidative stress was evaluated by testing plasma or serum samples for the following parameters: superoxide anion (WST), nitric oxide (NO), reactive oxygen species (d-ROMs), ferric reducing ability of plasma (FRAP), and the activity of superoxide dismutase (SOD). Simultaneously with the blood sampling, the owners completed a questionnaire with all the management aspects of the horse (signaling, feeding, equestrian activity, vaccinations, foot management etc.). The statistical evaluation was carried out based on the categories previously described, on the presence and absence of stereotypies and on some signaling data obtained from the questionnaire. There were no significant differences in the parameters analyzed between the categories. No significant redox status differences were detected based on the presence or absence of stereotypies. Interestingly, when the age was introduced as selection (<14 and >14 years old) parameter inside the categories, statistical significance was observed for some of the stress markers considered. Finally, independently of the housing conditions, the horses of the most two represented breeds exhibited different values of FRAP. All these aspects are commented in the discussion.

Investigating the Risk of Equine Motor Neuron Disease in a Brazilian Stable and Successful Intervention

We carried out an investigation to identify the factors that predispose to the risk of equine motor neuron disease (EMND) and evaluated the long-term impact of an intervention. Data on several biomarkers, including antioxidants (α-tocopherols, β-carotenes, glutathione peroxidase (GSHPx)), and superoxide dismutase (SOD1), neurofilaments, and other putative risk factors hypothesized to associate with the likelihood of EMND were collected. The data were analyzed for their significance of association with the condition. The EMND outbreak started in 1991 and continued until 1998. A total of 69 EMND cases and 64 control horses met the inclusion criteria and were enrolled in the study. Most cases (74%) occurred in 1996 and 1997. Horses afflicted with EMND had significantly lower plasma levels of vitamin E than control horses (0.381 vs. 1.148 μg/mL). There were no significant differences in the levels of vitamin A, β-carotenes, GSHPx, or the activities of SOD1 between EMND cases and control horses. Horses afflicted with EMND had significantly higher serum levels of phosphorylated neurofilament heavy than controls (2.85 vs. 0.27 ng/mL). The probability of EMND diagnosis increased above 50% when the serum levels of phosphorylated neurofilament heavy increased beyond 2.54 ng/mL. Mixed and Brazilian breeds had a significantly higher risk of EMND in comparison to Standardbred horse among the study population. In 1997, there was a change in the diet where better quality green hay was used. The incidence of EMND dropped to 0 in 1 year after intervention and remained at that level for the past 20 years.

Four cases of equine motor neuron disease in Japan

In this study, fasciculation of the limbs and tongue was observed in four horses kept by a riding club. Neurogenic muscle atrophy was also observed in biopsy of pathological tissues. In addition, in two cases that subjected to autopsy, Bunina-like bodies of inclusion in the cell bodies of neurons in the spinal cord ventral horn were confirmed, leading to a diagnosis of equine motor neuron disease (EMND). Serum vitamin E concentrations varied between 0.3 and 0.4µg/ml, which is significantly lower than the levels in normal horses. Although lack of vitamin E is speculated to be a contributory factor for development of EMND, no significant improvement was observed following administration of vitamin E.

Biomarkers for differentiation of causes of respiratory distress in dogs and cats: Part 2--Lower airway, thromboembolic, and inflammatory diseases

OBJECTIVES

To review the current veterinary and relevant human literature regarding biomarkers of respiratory diseases leading to dyspnea and to summarize the availability, feasibility, and practicality of using respiratory biomarkers in the veterinary setting.

DATA SOURCES

Veterinary and human medical literature: original research articles, scientific reviews, consensus statements, and recent textbooks.

HUMAN DATA SYNTHESIS

Numerous biomarkers have been evaluated in people for discriminating respiratory disease processes with varying degrees of success.

VETERINARY DATA SYNTHESIS

Although biomarkers should not dictate clinical decisions in lieu of gold standard diagnostics, their use may be useful in directing care in the stabilization process. Serum immunoglobulins have shown promise as an indicator of asthma in cats. A group of biomarkers has also been evaluated in exhaled breath. Of these, hydrogen peroxide has shown the most potential as a marker of inflammation in asthma and potentially aspiration pneumonia, but methods for measurement are not standardized. D-dimers may be useful in screening for thromboembolic disease in dogs. There are a variety of markers of inflammation and oxidative stress, which are being evaluated for their ability to assess the severity and type of underlying disease process. Of these, amino terminal pro-C-type natriuretic peptide may be the most useful in determining if antibiotic therapy is warranted. Although critically evaluated for their use in respiratory disorders, many of the biomarkers which have been evaluated have been found to be affected by more than one type of respiratory or systemic disease.

CONCLUSION

At this time, there are point-of-care biomarkers that have been shown to reliably differentiate between causes of dyspnea in dogs and cats. Future clinical research is warranted to understand of how various diseases affect the biomarkers and more bedside tests for their utilization.

Eosinophilic Enteritis in Horses with Motor Neuron Disease

BACKGROUND

Equine motor neuron disease (EMND) is a neuromuscular disorder that affects adult horses. Although EMND has been linked to vitamin E deficiency, its etiopathogenesis is poorly understood.

OBJECTIVES

To describe clinical features, laboratory results, and postmortem findings in a series of young horses with motor neuron disease (MND).

ANIMALS

A herd of 15 young Andalusian horses with weakness, weight loss, muscle atrophy, and muscle fasciculations related to restricted intake of green forage.

METHODS

A case series is presented in which horses were subjected to a clinical examination and plasma vitamin E measurement. Five severely affected horses were euthanized for detailed postmortem examination. Muscle specimens were taken from the M. sacrocaudalis dorsalis medialis and the M. gluteus medius for histopathologic and morphometric evaluation.

RESULTS

MND was diagnosed in 5 horses based on clinical signs, low serum levels of vitamin E (0.11 ± 0.05 mg/dL; normal range,: 0.3-1.5 mg/dL), changes in muscle histopathology (neurogenic atrophy), and spinal cord lesions (neuronal chromatolysis in ventral horns). An unexpected postmortem finding was the presence of intestinal inflammation (catarrhal enteritis, edema, and eosinophilic infiltrate) associated with the presence of giant ciliated protozoa in all of the horses.

CONCLUSIONS

Although a mechanistic link could not be established, it is hypothesized that intestinal inflammation may have been involved in the decreased absorption of vitamin E, thus favoring the development of MND.

Generation of functional neurons from feeder-free, keratinocyte-derived equine induced pluripotent stem cells

Pluripotent stem cells (PSCs) offer unprecedented biomedical potential not only in relation to humans but also companion animals, particularly the horse. Despite this, attempts to generate bona fide equine embryonic stem cells have been unsuccessful. A very limited number of induced PSC lines have so far been generated from equine fibroblasts but their potential for directed differentiation into clinically relevant tissues has not been explored. In this study, we used retroviral vectors to generate induced pluripotent stem cells (iPSCs) with comparatively high efficiency from equine keratinocytes. Expression of endogenous PSC markers (OCT4, SOX2, LIN28, NANOG, DNMT3B, and REX1) was effectively restored in these cells, which could also form in vivo several tissue derivatives of the three germ layers, including functional neurons, keratinized epithelium, cartilage, bone, muscle, and respiratory and gastric epithelia. Comparative analysis of different reprogrammed cell lines revealed an association between the ability of iPSCs to form well-differentiated teratomas and the distinct endogenous expression of OCT4 and REX1 and reduced expression of viral transgenes. Importantly, unlike in previous studies, equine iPSCs were successfully expanded using simplified feeder-free culture conditions, constituting significant progress toward future biomedical applications. Further, under appropriate conditions equine iPSCs generated cells with features of cholinergic motor neurons including the ability to generate action potentials, providing the first report of functional cells derived from equine iPSCs. The ability to derive electrically active neurons in vitro from a large animal reveals highly conserved pathways of differentiation across species and opens the way for new and exciting applications in veterinary regenerative medicine.