High altitude training of dogs results in elevated erythropoietin and endothelin-1 serum levels

Evaluation of VEGF-A and CCL2 in dogs with brachycephalic obstructive airway syndrome or canine idiopathic pulmonary fibrosis and in normocephalic dogs

Brachycephalic obstructive airway syndrome (BOAS) and canine idiopathic pulmonary fibrosis (CIPF) of West Highland White Terriers (WHWTs) often cause intermittent or chronic hypoxemia. Our objective was to evaluate serum and bronchoalveolar lavage fluid (BALF) concentrations of hypoxemia-related proinflammatory mediators vascular endothelial growth factor A (VEGF-A) and chemokine (CC motif) ligand 2 (CCL2) in brachycephalic dogs (BDs) and WHWTs with and without CIPF. Additionally, effects of BOAS severity and ageing on these mediators were assessed. 114 BDs (28 English Bulldogs (EBs), 37 French Bulldogs, 49 Pugs), 16 WHWTs with CIPF, 26 healthy WHWTs, and 39 normocephalic control dogs were included. Fifty-four BDs were re-examined after two to three years. Bead-based immunoassay was used for proinflammatory mediator measurements. Compared with controls, significantly higher serum concentrations of VEGF-A were seen in EBs (P = 0.009) and of CCL2 in CIPF and healthy WHWTs (P < 0.001; P = 0.002). BALF samples were available from controls, EBs, and WHWTs. VEGF-A was significantly lower in EBs (P < 0.001) and in CIPF and healthy WHWTs (P = 0.006; P = 0.007) and CCL2 was higher in CIPF WHWTs (P = 0.01) compared with controls. Between visits, only serum VEGF-A significantly decreased in BDs (P < 0.001), but breed, BOAS severity, or its change had no significant effect. In conclusion, in EBs with BOAS proinflammatory changes in VEGF-A were detected in both serum and BALF. Ageing reduced serum VEGF-A in BDs. In WHWTs, our results confirmed earlier findings of CCL2 as an important biomarker for CIPF.

Polycythemia is uncommon in dogs with chronic hypoxic pulmonary disease

Background

Prolonged tissue hypoxia caused by chronic pulmonary disease is commonly regarded as an important mechanism in the development of secondary polycythemia, but little clinical data are available to support this hypothesis.

Objective

To study the prevalence and severity of erythrocytosis accompanying chronic hypoxic pulmonary disease in dogs.

Animals

Forty‐seven dogs with hypoxic chronic pulmonary disease, 27 dogs with nonhypoxic chronic pulmonary disease, and 60 healthy controls.

Methods

Dogs with chronic pulmonary disease and chronic hypoxemia (partial pressure of arterial oxygen [PaO₂] < 80 mm Hg on at least 2 arterial blood gas measurements a minimum of 1 month apart) were identified retrospectively from patient records. Association between arterial oxygen and red blood cell parameters was analyzed using Pearson's correlation coefficients and multivariable linear regression analysis.

Results

Red blood cell parameters measured at the end of the hypoxemia period were within the laboratory reference range in most dogs. In chronically hypoxemic dogs, hematocrit (Hct) was increased in 4/47 (8.5%; 95% confidence interval [CI], 0‐17) dogs, erythrocyte count (Erytr) was increased in 12/47 (26%; 95%CI, 13‐38) dogs and hemoglobin concentration (Hb) was increased in 3/47 (6.4%; 95%CI, 0‐14) dogs. No marked polycythemia (Hct ≥65%) was noted in any of the dogs. Red blood cell parameters were not associated with the severity of hypoxemia (correlation to PaO₂: Erytr, r = −.14; Hb, r = −.21; Hct, r = −.14; P > .05 for all).

Conclusions and Clinical Importance

Polycythemia is uncommon, and usually mild if present, in dogs with chronic hypoxia caused by pulmonary disease.

How Do Avalanche Dogs (and Their Handlers) Cope with Physical Exercise? Heart Rate Changes during Endurance in a Snowy Environment

Simple Summary

Search and rescue (SAR) dogs are irreplaceable support in natural disasters. Not only are these animals required to have optimal scenting capabilities, but they are also required to have excellent physical conditions. Implementing protocols to monitor their fitness would help to optimize their performance and welfare. This study evaluated heart rate (HR) changes in avalanche SAR dogs and handlers during a 5.5 km endurance exercise in the snow, at an altitude of approximately 2000 m.a.s.l., reflecting their usual working and workload conditions. Dogs’ and handlers’ HR and activities were monitored by a global positioning satellite (GPS)/HR system. Factors influencing dogs’ and handlers’ HR changes and their possible correlation were investigated. As expected, the dog’s HR changes during the endurance activity were affected by speed, gradient, altitude, and time. The handlers’ HR changes differed and were not correlated with those recorded in the dogs. Thus, SAR handlers may not perceive the physical stress of their dog in real-time. Findings indicate that GPS/HR monitoring systems could be utilized in field conditions for monitoring SAR units’ physical fitness. A “fitness index” could be developed by incorporating HR and velocity measurements in order to target training strategies and indicate risk factors for physical distress in working dogs.

Abstract

This study aimed to assess the heart rate (HR) responses of avalanche SAR dogs and handlers under working field conditions. Thirteen SAR units (dogs and handlers) performed an exercise (Endurance) consisting of approximately 5.5 km of rough tracks through deep snow, at an altitude of 1991–2250 m.a.s.l. The exercise was repeated twice for each of the two different tracks. Both handlers and dogs were equipped with a global positioning satellite/heart rate (GPS/HR) system (Polar^®). Multivariable models were used to evaluate the effects of environmental (i.e., gradient, altitude, track, and time) and intrinsic (i.e., speed, repetition, and breed) factors on changes from baseline HR (Δ%HR). The dog’s Δ%HR was greater in the flat and uphill compared with downhill, and increased progressively as the speed increased (p < 0.001). Moreover, it rose at altitudes above 2100 m.a.s.l. and peaked after 30 min of the Endurance activity (p < 0.01). These findings indicated that HR monitors could be a valuable tool to contribute to the evaluation of avalanche dogs’ fitness in their real working environment. In contrast, the lack of correlation between the dogs’ and handlers’ HR changes suggests that handlers might not perceive the physical conditions of their dog in real-time. Thus, implementing protocols to monitor avalanche SAR dogs’ fitness using a GPS/HR monitoring system could help handlers to tailor the training and workload and to detect the risk factors for physical distress of working dogs.

Erythropoietin promotes hippocampal mitochondrial function and enhances cognition in mice

Erythropoietin (EPO) improves neuronal mitochondrial function and cognition in adults after brain injury and in those afflicted by psychiatric disorders. However, the influence of EPO on mitochondria and cognition during development remains unexplored. We previously observed that EPO stimulates hippocampal-specific neuronal maturation and synaptogenesis early in postnatal development in mice. Here we show that EPO promotes mitochondrial respiration in developing postnatal hippocampus by increasing mitochondrial content and enhancing cellular respiratory potential. Ultrastructurally, mitochondria profiles and total vesicle content were greater in presynaptic axon terminals, suggesting that EPO enhances oxidative metabolism and synaptic transmission capabilities. Behavioural tests of hippocampus-dependent memory at early adulthood, showed that EPO improves spatial and short-term memory. Collectively, we identify a role for EPO in the murine postnatal hippocampus by promoting mitochondrial function throughout early postnatal development, which corresponds to enhanced cognition by early adulthood.

Robert Jacobs, Mostafa Aboouf, et al. examined the effect of erythropoietin (EPO) in hippocampal mitochondrial function and memory in two mouse models: one overexpressing EPO in the brain, and juvenile mice treated during three days with a high dose of intraperitoneal EPO. Their results suggest that erythropoietin in the neonatal brain may impact spatial memory by increasing mitochondrial content.

Erythropoietin mediates brain-vascular-kidney crosstalk and may be a treatment target for pulmonary and resistant essential hypertension

Organ crosstalk pathways represent the next frontier for target-mining in molecular medicine for existing syndromes. Pulmonary hypertension and resistant essential hypertension are syndromes that have been proven elusive in etiology, and frequently refractory to first-line management. Underlying crosstalk mechanisms, not yet considered in these treatments, may hinder outcomes or unlock novel treatments. This review focuses systematically on erythropoietin, a synthesizable molecule, as a mediator of brain-kidney crosstalk. Insights gained from this review will be applied to cardiovascular diseases in a clinician-directed fashion.

Therapeutic potential of endothelin inhibitors in canine hemangiosarcoma

AIMS

Hemangiosarcoma (HSA) that originates from vascular endothelial cells is the most common splenic malignant neoplasm in dogs, as it accounts for approximately 20% of all canine soft tissue sarcomas. In this study, inhibitory effects of endothelin receptor antagonists on the growth of HSA cells were examined using cell lines established from canine HSA.

MAIN METHODS

The preproendothelin-1 (PPET-1), endothelin type A receptor (ETA) and endothelin type B receptor (ETB) mRNA expression levels in HSA cell lines (n=5) were analyzed quantitatively by real-time RT-PCR. These levels were compared with those in HSA tissues (n=11) and those in normal splenic tissues (n=6). ETA and ETB protein expression was examined by western blot. The production and secretion of endothelin-1 (ET-1) and big ET-1 by cell lines were analyzed by measuring the levels in the culture medium by ELISA. The inhibitory effects of endothelin receptor antagonists (ambrisentan, BQ788 and bosentan) on cell growth were evaluated by WST-8 assay.

KEY FINDINGS

The PPET1 and ETA mRNA expression levels were elevated in HSA tissues and HSA cell lines compared with normal tissues. In cell lines, the production of ET-1 and big ET-1 peptide as well as the expression of ETA protein were detected, but the levels of ETB were not measured. Ambrisentan and bosentan inhibited growth activity in cell lines. Ambrisentan was more effective than bosentan.

SIGNIFICANCE

These findings demonstrate the importance of the ETA axis in canine HSA as well as the potential of ETA inhibitors in the treatment of canine HSA.

Serum big endothelin-1 as a clinical marker for cardiopulmonary and neoplastic diseases in dogs

AIMS

Many studies of human subjects have demonstrated the utility of assessing serum levels of endothelin-1 (ET-1) and big ET-1 as clinical biomarkers in cardiopulmonary and neoplastic diseases. In this study we explored the feasibility of using serum big ET-1 as a reliable veterinary marker in dogs with various cardiopulmonary and neoplastic diseases.

MAIN METHODS

Serum big ET-1 levels were measured by ELISA in dogs with cardiopulmonary (n=21) and neoplastic diseases (n=57). Dogs exhibiting cardiopulmonary disease were divided into two groups based on the velocity of tricuspid valve regurgitation (3.0>m/s) measured by ultrasound: without and with pulmonary hypertension. Big ET-1 levels for the dogs with the diseases were compared with levels in normal healthy dogs (n=17).

KEY FINDINGS

Dogs with cardiopulmonary disease (4.6±4.6 pmol/l) showed a significantly (P<0.01) higher level of big ET-1 than healthy control dogs (1.1±0.53 pmol/l). Serum levels in the dogs with pulmonary hypertension (6.2±5.3 pmol/l) were significantly (P<0.01) higher than those without pulmonary hypertension (2.0±0.6 pmol/l). Dogs with hemangiosarcoma (5.6±2.2 pmol/l), adenocarcinoma (2.0±1.8 pmol/l), histiocytic sarcoma (3.3±1.9 pmol/l), chondrosarcoma or osteosarcoma (3.0±1.6 pmol/l) and hepatocellular carcinoma (2.7±1.8 pmol/l) showed significantly (P<0.05) higher levels than healthy control dogs.

SIGNIFICANCE

These findings point to the potential of serum big ET-1 as a clinical marker for cardiopulmonary and neoplastic diseases in dogs.

Acute and chronic elevation of erythropoietin in the brain improves exercise performance in mice without inducing erythropoiesis

Application of recombinant human erythropoietin (rhEpo) improves exercise capacity by stimulating red blood cell production that, in turn, enhances oxygen delivery and utilization. Apart from this, when applied at high doses, rhEpo crosses the blood-brain barrier, triggering protective neuronal effects. Here we show a fundamental new role by which the presence of Epo in the brain augments exercise performance without altering red blood cell production. Two different animal models, the transgenic mouse line Tg21, which constitutively overexpresses human Epo exclusively in the brain without affecting erythropoiesis, and wild-type mice treated with a single high dose of rhEpo, demonstrate an unexpected improvement in maximal exercise performance independent of changes in total hemoglobin mass, as well as in whole blood volume and cardiovascular parameters. This novel finding builds a more complete understanding regarding the central effects of endogenously produced and exogenously applied Epo on exercise performance.

Pulmonary hypertension in dogs: diagnosis and therapy

Pulmonary hypertension (PH) has been recognized as a clinical syndrome for many years in veterinary medicine, but routine accurate clinical diagnosis in dogs was greatly enhanced by widespread use of echocardiography and Doppler echocardiography. Most cases of PH in veterinary medicine can be categorized as precapillary or postcapillary. These subsets of patients often differ with regard to clinical presentation, response to therapy, and prognosis. Effective medical therapy is now available to treat this often-devastating clinical complication of common chronic diseases, making accurate diagnosis even more important to patient longevity and quality of life.

Analytical validation of commercial immunoassays for the measurement of cardiovascular peptides in the dog

Immunoassays for the measurement of concentrations of the cardiovascular peptides pro-atrial natriuretic peptide (proANP), brain natriuretic peptide (BNPPen and BNPPhoe), endothelin-1 (ET-1Bio, ET-1IBL and ET-1Phoe) and big endothelin-1 (Big-ETBio and Big-ETIBL) were validated in canine serum by determination of intra-assay variability and dilutional parallelism. Commercial kits that showed good results were further validated by determination of intra- and inter-assay variability, dilutional parallelism and spiking recovery. Assays for proANP, BNPPhoe, ET-1IBL and Big-ETIBL showed acceptable results in the preliminary validation and were fully validated. The intra- and inter-assay variability was acceptable for all four assays, linearity was demonstrated and recovery rates were acceptable. The performances of the different immunoassays varied considerably, underscoring the importance of validation. Of the assays studied, proANP, BNP(Phoe), ET-1IBL and Big-ETIBL produced precise, reproducible and accurate results and can be recommended for clinical application.

Interrelation of directly measured oxygenation levels, erythropoietin and erythropoietin receptor expression in spontaneous canine tumours

The expression of the hypoxia-inducible protein erythropoietin in tumour cells correlates with levels of tumour hypoxia. Our aim was to look for an interrelation of directly measured oxygenation levels, the presence of tissue erythropoietin and its receptor. Data of tumour oxygenation status, plasma and tissue erythropoietin and its receptor in a group of spontaneously occurring tumours in 15 dogs were collected. Polarographic tumour oxygen partial pressure measurements were obtained and data were correlated. Significant positive correlations were found between tissue erythropoietin and the percentages of pO2 values < or = 10 mmHg. Multivariate analysis revealed no parameters influencing plasma erythropoietin levels. Our results show that a co-expression of erythropoietin receptor and its ligand in spontaneous canine tumours exists, that the level of hypoxia in tumour cells correlates with the level of tissue erythropoietin and suggest the need to be quantitatively and functionally tested as novel prognostic biological parameters in neoplastic tissues.

Swimming ability and physiological response to swimming fatigue in whiteleg shrimp, Litopenaeus vannamei

Some penaeids are active swimmers, undertaking migrations of hundreds of nautical miles. At present, however, very little is known of swimming ability in penaeid shrimps. The aim of the present study is to investigate swimming endurance of whiteleg shrimp, Litopenaeus vannamei, against one of five flow velocities (5.41, 6.78, 8.21, 10.11, and 11.47 cm s(-1)) for up to 9000 s at 20 degrees C in a swimming channel. Body mass, hemolymph total protein concentration, and hemolymph glucose level were measured before swimming and immediately following swimming to evaluate physiological effect of swimming in L. vannamei. No shrimp swam the full 9000 s at any of the velocities tested. The swimming endurance decreased as swimming speed was increased. The relationship between swimming endurance (t, in s) and swimming speed (v, in cm s(-1)) can be described by the Curve Estimation: v.t0.38 = 159.64 (R2 = 0.94). The swimming ability index (SAI), defined as SAI = integral 0-9000 vdt x 10(-4) (cm) was found to be 7.28 cm for the shrimp tested. Swimming to fatigue leads to severe loss of body mass, hemolymph total protein concentration, and hemolymph glucose level in L. vannamei (P < 0.05). Furthermore, these decreases and swimming speed showed significantly polynomial relationships (P < 0.05). The results suggest that the power model fits well to the observed endurance estimates and the SAI is a good index to quantitatively describe the overall swimming ability of L. vannamei. Furthermore, hemolymph total protein concentration may be used as a rapid and reliable indicator to assess the penaeid shrimps' swimming speed and hence swimming ability.