Effects of continuous or intermittent lipopolysaccharide administration for 48 hours on the systemic inflammatory response in horses

The Clinical Pharmacology and Therapeutic Evaluation of Non-Steroidal Anti-Inflammatory Drugs in Adult Horses

This review firstly examines the underlying pathophysiology of pain and inflammation associated with orthopedic disease and endotoxemia. Then, it reviews the clinical pharmacology (pharmacokinetics and pharmacodynamics) of both conventional and non-conventional NSAIDs in the adult horse, and finally provides an overview of different modalities to evaluate the therapeutic efficacy of NSAIDs in research.

TLR4 and MD2 variation among horses with differential TNFα baseline concentrations and response to intravenous lipopolysaccharide infusion

Gram-negative bacterial septicemia is mediated through binding of lipopolysaccharide (LPS) to mammalian toll-like receptor protein 4 (TLR4). TLR4 and its cognate protein, myeloid differentiation factor 2 (MD2) form a heterodimeric complex after binding LPS. This complex induces a cascade of reactions that results in increased proinflammatory cytokine gene expression, including TNFα, which leads to activation of innate immunity. In horses, the immune response to LPS varies widely. To determine if this variation is due to differences in TLR4 or MD2, DNA from 15 healthy adult horses with different TNFα dynamics after experimental intravenous LPS infusion was sequenced across exons of TLR4 and MD2. Haplotypes were constructed for both genes using all identified variants. Four haplotypes were observed for each gene. No significant associations were found between either TNFα baseline concentrations or response to LPS and haplotype; however, there was a significant association (P value = 0.0460) between the baseline TNFα concentration and one MD2 missense variant. Three-dimensional structures of the equine TLR4-MD2-LPS complex were built according to haplotype combinations observed in the study horses, and the implications of missense variants on LPS binding were modeled. Although the sample size was small, there was no evidence that variation in TLR4 or MD2 explains the variability in TNFα response observed after LPS exposure in horses.

Responses of testosterone hormone and important inflammatory cytokines in bucks after challenge with Mannheimia haemolytica A2 and its LPS endotoxin

Previous studies have shown that Mannheimia haemolytica A2 is the principal microorganism causing pneumonic mannheimiosis, a major bacterial respiratory disease among sheep and goats. The effect of this bacteria on the respiratory system is well-established. However, its effect on the reproductive physiology remains unclear. Therefore, this study aimed to determine the alterations in the level of pro-inflammatory cytokines and testosterone hormone post-inoculation with M. haemolytica serotype A2 and its lipopolysaccharide (LPS) endotoxin which were hypothesized to affect the reproductive functions of bucks. Twelve clinically healthy adult male goats were divided equally into three groups. Goats in group 1 were treated with 2 ml of sterile phosphate-buffered saline (PBS) pH 7.0 intranasally (negative control), group 2 with 2 ml of 10⁹ colony-forming unit (CFU) of M. haemolytica serotype A2 intranasally (positive control), and group 3 were treated with 2 ml of lipopolysaccharide extracted from 10⁹ CFU of M. haemolytica serotype A2 intravenously. Following inoculation, blood samples were collected via jugular venipuncture into plain tubes at pre-determined intervals for serum collection to determine the concentration of interleukin (IL)-1β, IL6, tumor necrosis factor (TNF)-α, and testosterone hormone by using commercial ELISA test kits. Results from this study demonstrated that the inoculation of M. haemolytica A2 and its LPS increases the concentration of pro-inflammatory cytokines but decreases the concentration of testosterone hormone in challenged animals at most time points throughout the 56 days experimental period (p < 0.05). This study suggests that the M. haemolytica A2 and its LPS could alter the concentration of pro-inflammatory cytokines and testosterone hormone, which in turn, may negatively affect the reproductive functions of bucks.

Serial measurements of Paraoxonase-1 (PON-1) activity in horses with experimentally induced endotoxemia

Background

Paraoxonase-1 (PON-1) is an antioxidant enzyme, whose activity decreases during the acute phase response in many species. Little is known about PON-1 and its role as a negative acute phase protein during septic inflammation in horses, but promising findings about its utility in diagnosing SIRS and predicting the outcome in diseased horses, were recently highlighted. The objective of the study was to investigate the behaviour of PON-1 in horses after experimentally induced endotoxemia. To this aim, PON-1 activity was measured on 66 plasma samples collected from six clinically healthy mares, previously included in another study, before and at multiple time points between 12 and 240 h after intravenous infusion of Escherichia coli O55:B5 lipopolysaccharide (LPS).

Results

Compared with baseline values, a progressive transient decrease of PON-1 activity was observed starting from 24 h post-infusion, with lowest values observed between 3 to 7 days post-infusion, followed by a normalisation to pre-infusion levels the tenth day.

Conclusions

The results of this study suggest that measurement and monitoring of PON-1 activity might be useful to evaluate progression and recovery from endotoxemia in horses. Further studies in horses with naturally occurring sepsis are warranted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-020-02629-4.

Protective Effect of Silibinin on Lipopolysaccharide-Induced Inflammatory Responses in Equine Peripheral Blood Mononuclear Cells, an In Vitro Study

Simple Summary

Natural compounds are often an important source of biologically active molecules, which can find important applications in the treatment or pharmacological prevention of several pathologies. Silibinin is a natural polyphenolic flavonoid that is extracted from plant milk thistle, Silybum marianum. Silibinin has been reported to have antioxidant and immunomodulatory and anti-inflammatory activities. In horses, in particular, inflammation secondary to bacterial infection or translocation is one of the most frequent causes of morbidity and mortality. The aim of this study was to test the effect of silibinin on lipopolysaccharide (LPS)-induced inflammatory response in equine peripheral blood mononuclear cells (PBMCs). Taken together, our results showed an interesting prospective in therapeutic use of silibinin in equine inflammatory disease. Furthermore, the results from this study support the evidence of use equine PBMCs as an in vitro model to study inflammatory and immune response and for drug screening into the target specie.

Abstract

Although inflammation is an important physiological response, it plays a prominent role in several diseases across the mammalian species. In horses, in particular, inflammation secondary to bacterial infection or translocation is one of the most frequent causes of morbidity and mortality. Research in new molecules with anti-inflammatory and immunomodulatory proprieties and safe use profile is constantly an active field; natural compounds are an important source of molecules with peculiar properties such as antioxidants, anti-inflammatory and immune modulating. Silibinin, a natural polyphenolic flavonoid, extracted from plant milk thistle, Silybum marianum, has been reported to have actions such as antioxidant immunomodulatory and anti-inflammatory. The aim of this study was to test the effect of silibinin on lipopolysaccharide (LPS)-induced inflammatory response in equine peripheral blood mononuclear cells (PBMCs). Our results showed the protective effect of silibinin 10 μM and 50 μM in equine PBMCs stimulated with LPS. Silibilinin was able to prevent the LPS induced increased levels of TNF-α, IL-1β, IL-6 and IL-8. The results from this study on LPS-stimulated equine PBMCs showed that silibinin could be a useful pharmacological approach in treatment or prevention of several inflammatory conditions in horse.

Meloxicam ameliorates the systemic inflammatory response syndrome associated with experimentally induced endotoxemia in adult donkeys

Background

Little information is available about endotoxemia in donkeys. Characterizing the systemic inflammatory response (SIRS) to lipopolysaccharide (LPS) in donkeys would provide valuable clinical and therapeutic information. The effects of meloxicam on endotoxemia have not been studied in this species.

Objectives

To study the pathophysiology and gene expression associated with experimentally induced endotoxemia, and evaluate the effects of meloxicam on experimentally induced endotoxemia in donkeys and in equine monocyte cultures.

Animals

Six healthy adult female donkeys.

Methods

Endotoxemia was induced by an IV infusion of LPS for 30 minutes. Animals either received 20 mL of saline or 0.6 mg/kg of meloxicam IV after LPS infusion. The experiments lasted 6 hours. Blood samples were collected serially for hematology, serum biochemistry, interleukin measurement, and leukocyte gene expression analysis. Vital signs were recorded throughout the study. Monocyte cultures were used to test the effects of meloxicam on LPS‐activated monocytes.

Results

Lipopolysaccharide induced fever, leukopenia, and neutropenia of similar magnitude in both groups, but meloxicam attenuated increases in plasma lactate, tumor necrosis factor‐alpha (TNFα), and interleukin 1β concentrations compared to controls. No differences were detected between groups for cytokine mRNA expression. Furthermore, meloxicam decreased TNFα release in LPS‐activated monocyte cultures.

Conclusions and Clinical Importance

Meloxicam could be a feasible option for the treatment of endotoxemia and SIRS in donkeys. Additional studies are necessary to investigate possible meloxicam‐related posttranscriptional regulation and to compare this drug with other nonsteroidal anti‐inflammatory drugs (NSAIDs) in animals with endotoxemia.

Anti-inflammatory effects of a p38 MAP kinase inhibitor, doramapimod, against bacterial cell wall toxins in equine whole blood

Doramapimod (BIRB-796-BS), is an anti-inflammatory compound, acting through p38 MAPK inhibition, but its anti-inflammatory effects have not previously been studied in the horse. Whole blood aliquots from healthy horses diluted 1:1 with cell culture medium were incubated for 21 h with 1 μg/ml of lipopolysaccharide (LPS), lipoteichoic acid (LTA) or peptidoglycan (PGN) in the presence of increasing concentrations of doramapimod (3 × 10^-8 M to 10^-5 M). Cell bioassays were used to measure TNF-α and IL-1β activity. Doramapimod significantly and potently inhibited TNF-α and IL-1β activity induced by all three bacterial toxins. There was no significant difference in IC₅₀ or maximum inhibition of TNF-α or IL-1β production between any of the toxins. Maximum inhibition of IL-1β was higher than that of TNF-α for all toxins, and this difference was significant for LPS (P = 0.04). Doramapimod was a potent inhibitor of TNF-α and IL-1β for inflammation induced by LPS, LTA and PGN, with potency much greater than that of other drugs previously tested using similar methods.

The Equine Hoof: Laminitis, Progenitor (Stem) Cells, and Therapy Development

The equine hoof capsule, composed of modified epidermis and dermis, is vital for protecting the third phalanx from forces of locomotion. There are descriptions of laminitis, defined as inflammation of sensitive hoof tissues but recognized as pathologic changes with or without inflammatory mediators, in the earliest records of domesticated horses. Laminitis can range from mild to serious, and signs can be acute, chronic, or transition from acute, severe inflammation to permanently abnormal tissue. Damage within the intricate dermal and epidermal connections of the primary and secondary lamellae is often associated with lifelong changes in hoof growth, repair, and conformation. Decades of research contribute to contemporary standards of care that include systemic and local therapies as well as mechanical hoof support. Despite this, consistent mechanisms to restore healthy tissue formation following a laminitic insult are lacking. Endogenous and exogenous progenitor cell contributions to healthy tissue formation is established for most tissues. There is comparably little information about equine hoof progenitor cells. Equine hoof anatomy, laminitis, and progenitor cells are covered in this review. The potential of progenitor cells to advance in vitro equine hoof tissue models and translate to clinical therapies may significantly improve prevention and treatment of a devastating condition that has afflicted equine companions throughout history.

Effects of a blend of green tea and curcuma extract supplementation on lipopolysaccharide-induced inflammation in horses and ponies

Background

In horses and ponies numerous medical conditions are known to be linked with inflammation in different tissues, especially in the liver. Besides affecting other metabolic pathways such as the expression of certain interleukins (IL), inflammation is associated with stress of the endoplasmic reticulum (ER). In particular, ER stress leads to adaptive stress response and can be measured by several markers of inflammatory and stress signalling pathways, like nuclear factor κB (NF-kB).

Objectives

To investigate lipopolysaccharide (LPS)-induced inflammatory reactions and their modulation in horses and ponies by feeding a polyphenol-rich supplement consisting of green tea and curcuma.

Methods

In a cross-over study, 11 animals were allocated to either a placebo or a supplement group and supplemented with 10 g of a blend of green tea and curcuma extract (GCE) or a placebo (calcium carbonate) once daily. After 21 days of supplementation, all animals underwent a LPS challenge to induce moderate systemic inflammation. Blood samples and liver biopsies were taken at standardized time points: 24 hours before and 12 hours after LPS challenge. Inflammatory blood parameters such as serum amyloid A (SAA), haptoglobin and retinol binding protein 4 (RBP4) were measured in serum. Hepatic mRNA levels of selected markers of inflammation such as haptoglobin, tumor necrosis factor α (TNF-α), IL-1β, IL-6, cluster of differentiation 68 (CD68), fibroblast growth factor 21 (FGF-21), NF-κB, activating transcription factor 4 (ATF4) were quantified by RT-qPCR. In addition, liver biopsies were examined histologically for inflammatory alterations.

Results

Blood markers of acute inflammatory response increased after LPS challenge. In the liver, the proinflammatory cytokine IL-1β showed significantly lower mRNA levels after LPS challenge in the supplemented group (P = 0.04) compared to the placebo group. Levels of the hepatic CD68 mRNA increased significantly in the placebo group (P = 0.04). There were no significant differences between supplemented and placebo groups concerning other markers of inflammation and markers of ER stress within the liver. The number of hepatic macrophages were not different after LPS challenge in both feeding groups.

Conclusion

LPS was able to induce inflammation but seemed less suitable to induce ER stress in the horses and ponies. The polyphenol-rich supplement showed some potential to reduce inflammatory responses. Nevertheless, the supplementation did not exert an overall anti-inflammatory effect in horses and ponies.

Comparative Anti-inflammatory Effects of Insulin and Flunixin on Acute-Phase Responses and Cardiovascular Biomarkers During Inflammatory Phase in Miniature Donkeys

The objective of this study was to comparatively evaluate the anti-inflammatory effects of intravenous administration of insulin (in different doses) and flunixin on physiological variables, acute-phase responses, and cardiovascular biomarkers during inflammatory phase which was induced by Escherichia coli lipopolysaccharide (LPS) serotype O55:B5 in miniature donkeys. A total of twenty-four clinically healthy male adult miniature donkeys aged 5 ± 1 year and weighing 120 ± 10 kg were studied. The animals were assigned randomly to four experimental groups (three treatment and one positive control groups). Six hours after induction of inflammatory phase (by 20 ng kg^-1 LPS), donkeys in groups Insln 1.5, Insln 3, and Flnx received insulin at 1.5 IU kg^-1, insulin at 3 IU kg^-1, and flunixin at 2.2 mg kg^-1, respectively. Animals in the positive control group were assigned to receive LPS without any anti-inflammatory drugs. We have shown that serum concentrations of cardiovascular, acute-phase proteins and cytokines were increased during inflammatory phase in miniature donkeys. Our results revealed that insulin at 3 IU kg^-1 as well as flunixin at 2.2 mg kg^-1 can improve almost all of the physiological variables and hematobiochemical variables (including serum concentrations of tumor necrosis factor-alpha, interferon-gamma, haptoglobin, serum amyloid A, cardiac troponin I, hemocysteine, white blood cell, and packed cell volume) after 24 hours. Unlike insulin at 1.5 IU kg^-1, insulin at 3 IU kg^-1 may be considered useful for inflammatory conditions in miniature donkeys.

A Comparative Review of Equine SIRS, Sepsis, and Neutrophils

The most recent definition of sepsis in human medicine can be summarized as organ dysfunction caused by a dysregulated host response to infection. In equine medicine, although no consensus definition is available, sepsis is commonly described as a dysregulated host systemic inflammatory response to infection. Defense against host infection is the primary role of innate immune cells known as neutrophils. Neutrophils also contribute to host injury during sepsis, making them important potential targets for sepsis prevention, diagnosis, and treatment. This review will present both historical and updated perspectives on the systemic inflammatory response (SIRS) and sepsis; it will also discuss the impact of sepsis on neutrophils, and the impact of neutrophils during sepsis. Future identification of clinically relevant sepsis diagnosis and therapy depends on a more thorough understanding of disease pathogenesis across species. To gain this understanding, there is a critical need for research that utilizes a clearly defined, and consistently applied, classification system for patients diagnosed with, and at risk of developing, sepsis.

Endotoxin-induced changes of type VII collagen- cleaving matrix metalloproteinases in lamellar tissue of extracorporeally perfused equine limbs

OBJECTIVE To investigate the effect of lipopolysaccharide (LPS) on type VII collagen- cleaving matrix metalloproteinases (MMPs) in the lamellar tissue of extracorporeally perfused equine limbs. SAMPLE 10 right forelimbs and 3 left forelimbs collected from 10 adult horses after slaughter at a licensed abattoir. PROCEDURES Extracorporeal perfusion of the isolated equine limbs was performed for 10 hours under physiologic conditions (control-perfused limbs; n = 5) and with the addition of 80 ng of LPS/L of perfusate (LPS-perfused limbs; 5). Lamellar tissue specimens were then collected from the dorsal aspect of the hooves. Additionally, corresponding control specimens were collected from the 3 nonperfused left forelimbs. Immunohistochemical analysis was performed on paraffin-embedded tissue blocks with antibodies against total (latent and active) MMP-1, MMP-2, MMP-8, and MMP-9 as well as antibody against active MMP-9. Intensity of immunohistochemical staining was scored, and stain distribution in the lamellar tissue was noted. RESULTS Staining intensity of total and active MMP-9 was significantly increased in LPS-perfused versus control-perfused limbs. No such difference was identified for MMP-1, MMP-2, and MMP-8. CONCLUSIONS AND CLINICAL RELEVANCE Of the 4 MMPs that are capable of degrading type VII collagen, MMP-9 was the only one for which production increased in the lamellar tissue of isolated equine limbs perfused with versus without a clinically relevant concentration of LPS. These results suggested that MMP-9 may be involved in initiation of pathological changes in lamellar tissue in endotoxin-induced laminitis, whereas MMP-1, MMP-2, and MMP-8 may be less relevant.

Misoprostol Inhibits Lipopolysaccharide-Induced Pro-inflammatory Cytokine Production by Equine Leukocytes

Pro-inflammatory cytokines including tumor necrosis factor α (TNFα), IL-1β, IL-6, and IL-8 are potent immune mediators that exacerbate multiple equine diseases such as sepsis and laminitis. Unfortunately, safe and effective cytokine-targeting therapies are lacking in horses; therefore, novel mechanisms of inhibiting cytokine production are critically needed. One potential mechanism for inhibiting cytokine synthesis is elevation of intracellular cyclic AMP (cAMP). In human leukocytes, intracellular cAMP production is induced by activation of E-prostanoid (EP) receptors 2 and 4. These receptors can be targeted by the EP2/4 agonist and prostaglandin E1 analog, misoprostol. Misoprostol is currently used as a gastroprotectant in horses but has not been evaluated as a cytokine-targeting therapeutic. Thus, we hypothesized that misoprostol treatment would inhibit pro-inflammatory cytokine production by lipopolysaccharide (LPS)-stimulated equine leukocytes in an in vitro inflammation model. To test this hypothesis, equine leukocyte-rich plasma (LRP) was collected from 12 healthy adult horses and used to model LPS-mediated inflammatory signaling. LRP was treated with varying concentrations of misoprostol either before (pretreated) or following (posttreated) LPS stimulation. LRP supernatants were assayed for 23 cytokines using an equine-specific multiplex bead immunoassay. Leukocytes were isolated from LRP, and leukocyte mRNA levels of four important cytokines were evaluated via RT-PCR. Statistical differences between treatments were determined using one-way RM ANOVA (Holm-Sidak post hoc testing) or Friedman's RM ANOVA on Ranks (SNK post hoc testing), where appropriate (p < 0.05, n = 3-6 horses). These studies revealed that misoprostol pre- and posttreatment inhibited LPS-induced TNFα and IL-6 protein production in equine leukocytes but had no effect on IL-8 protein. Interestingly, misoprostol pretreatment enhanced IL-1β protein synthesis following 6 h of LPS stimulation, while misoprostol posttreatment inhibited IL-1β protein production after 24 h of LPS stimulation. At the mRNA level, misoprostol pre- and posttreatment inhibited LPS-induced TNFα, IL-1β, and IL-6 mRNA production but did not affect IL-8 mRNA. These results indicate that misoprostol exerts anti-inflammatory effects on equine leukocytes when applied before or after a pro-inflammatory stimulus. However, the effects we observed were cytokine-specific and sometimes differed at the mRNA and protein levels. Further studies are warranted to establish the inhibitory effects of misoprostol on equine cytokine production in vivo.

Changes in concentrations of haemostatic and inflammatory biomarkers in synovial fluid after intra-articular injection of lipopolysaccharide in horses

Background

Septic arthritis is a common and potentially devastating disease characterized by severe intra-articular (IA) inflammation and fibrin deposition. Research into equine joint pathologies has focused on inflammation, but recent research in humans suggests that both haemostatic and inflammatory pathways are activated in the joint compartment in arthritic conditions. The aim of this study was to characterize the IA haemostatic and inflammatory responses in horses with experimental lipopolysaccharide (LPS)-induced joint inflammation. Inflammation was induced by IA injection of LPS into one antebrachiocarpal joint of six horses. Horses were evaluated clinically with subjective grading of lameness, and blood and synovial fluid (SF) samples were collected at post injection hours (PIH) -120, −96, −24, 0, 2, 4, 8, 16, 24, 36, 48, 72 and 144. Total protein (TP), white blood cell counts (WBC), serum amyloid A (SAA), haptoglobin, iron, fibrinogen, thrombin-antithrombin (TAT) and d-dimer concentrations were assessed in blood and SF.

Results

Intra-articular injection of LPS caused local and systemic signs of inflammation including increased rectal temperature, lameness and increased joint circumference and skin temperature. Most of the biomarkers (TP, WBC, haptoglobin, fibrinogen and TAT) measured in SF increased quickly after LPS injection (at PIH 2–4), whereas SAA and d-dimer levels increased more slowly (at PIH 16 and 144, respectively). SF iron concentrations did not change statistically significantly. Blood WBC, SAA, haptoglobin and fibrinogen increased and iron decreased significantly in response to the IA LPS injection, while TAT and d-dimer concentrations did not change. Repeated pre-injection arthrocenteses caused significant changes in SF concentrations of TP, WBC and haptoglobin.

Conclusion

Similar to inflammatory joint disease in humans, joint inflammation in horses was accompanied by an IA haemostatic response with changes in fibrinogen, TAT and d-dimer concentrations. Inflammatory and haemostatic responses were induced simultaneously and may likely interact. Further studies of interactions between the two responses are needed for a better understanding of pathogenesis of joint disease in horses. Knowledge of effects of repeated arthrocenteses on levels of SF biomarkers may be of value when markers are used for diagnostic purposes.

Kinetics of plasma procalcitonin, soluble CD14, CCL2 and IL-10 after a sublethal infusion of lipopolysaccharide in horses

Endotoxemia represents a significant clinical and economic problem for the equine industry. This study assesses the kinetics of soluble CD14 (sCD14), chemokine (CC motif) ligand 2 (CCL2), interleukin 10 (IL-10) and plasma procalcitonin (PCT) in healthy horses after the intravenous infusion of lipopolysaccharide (LPS). The aim was to contribute to the basic understanding of the equine species-specific kinetics of these molecules in response to LPS exposure, which could support further findings in clinical studies and identify valuable inflammatory biomarkers for equine practice. Eleven healthy horses were involved in this experimental in vivo study. Horses were classified as healthy before the LPS infusion. After the pre-infusion blood collection (T0), all horses received an infusion of E. coli endotoxin (30ng/kg over 30min). Data and samples were collected 1h (T1), 2 (T2), 3 (T3) and 24h (T24) after infusion. Plasma sCD14, CCL2 and IL-10 were evaluated with a fluorescent bead-based assay, while PCT was evaluated with an equine PCT ELISA assay. A one-way ANOVA test was performed between each blood-sampling time for PCT, sCD14 and IL-10, and a Friedman test was performed for CCL2. Plasma PCT, IL-10 and CCL2 concentrations increased statistically significantly at T1, T2 and T3 compared to T0. No statistically significant differences were found between plasma IL-10 and CCL2 concentrations between T0 vs T24, although plasma PCT values remained high 24h after LPS infusion. Plasma sCD14 concentration showed no statistically significant differences for any of sampling times. Our results demonstrate that LPS injection into healthy horses results in PCT, CCL2 and IL-10 increases in plasma without an increase in sCD14. The increases in PCT, CCL2 and IL-10 are related to the inflammatory response induced by circulating lipopolysaccharide.

Laminar lesions in horses with systemic oxidative stress, committed by experimentally induced or naturally occurring gastrointestinal disorders

Abstract: Laminitis in horses can be associated with lesions in multiple organs secondary to sepsis. Twenty-one horses suffering from gastrointestinal disorders were used in the experiment; 7 horses with experimentally induced endotoxemia and intestinal ischaemia, and 14 horses suffering from naturally occurring colic syndrome. Tissue samples of lungs, liver, heart, brain, cerebellum and hoof laminar tissue were collected for histopathological and oxidative stress evaluation using nitrotyrosine and superoxide dismutase (SOD2) immunostaining. The horses were divided into two groups: the non-oxidative lesions group (NOLG), with 7 horses showing weak immunostaining in lungs, liver and kidney, and the oxidative lesions group (OLG), with 14 horses showing immunostaining indicating systemic oxidative stress in multiple organs. The horses from OLG showed increase of laminar lesions and SOD2 immunostaining in multiple organs when compared to the horses from the NOLG. No differences were found ln regard to laminar immunostaining by nitrotyrosine and SOD2 between experimental groups. It was concluded that systemic oxidative stress can be associated with the development of laminar lesions, and that the laminar tissue does not respond to oxidative stress with increase of SOD as occurs in other organs.

Characterization and differentiation of equine experimental local and early systemic inflammation by expression responses of inflammation-related genes in peripheral blood leukocytes

Background

Local inflammation may progress into systemic inflammation. To increase our understanding of the basic immunological processes during transition of equine local inflammation into a systemic state, investigation into the equine systemic immune response to local inflammation is warranted. Therefore, the aim of this study was to investigate the innate peripheral blood leukocyte (PBL) immune response to local inflammation in horses, and to compare this response with the PBL immune response during the early phase of acute systemic inflammation. Expression of 22 selected inflammation-related genes was measured in whole blood leukocytes from 6 horses in an experimental cross-over model of lipopolysaccharide- (LPS-) induced acute synovitis (3 μg LPS intraarticularly; locally inflamed [LI] horses) and endotoxemia (1 μg LPS/kg intravenously; systemically inflamed [SI] horses). Multiple clinical and hematological/biochemical examinations were performed, and serial blood samples were analyzed by reverse transcription quantitative real-time PCR. Post-induction expression profiles of all genes were compared between study groups using principal component analysis (PCA) and hierarchical clustering.

Results

Moderate synovitis and mild systemic inflammation of approximately 24 h duration was confirmed by clinical and paraclinical observations in LI and SI horses, respectively. In the LI group, samples obtained 3–16 h post-injection showed distinct clustering in the PCA compared with baseline levels, indicating a transcriptional response to local inflammation in PBLs in this time interval. There was no clinical or hematological indication of actual systemic inflammation. There was a clear separation of all LI samples from all SI samples in two distinct clusters, indicating that expression profiles in the two study groups were different, independent of time since LPS injection. Co-regulated genes formed four clusters across study groups which were distinctly differently regulated. Only few of individual genes displayed different expression between the study groups at all times after LPS injection.

Conclusions

Local inflammation in horses initiated an innate transcriptional response in PBLs, which differed from the transcriptional response during the early phase of systemic inflammation. This study may provide new insights into the immunobiology of PBLs during the transition of local inflammation into a systemic state.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0706-8) contains supplementary material, which is available to authorized users.

Duration of in vivo endotoxin tolerance in horses

Endotoxemia models are used to study mechanisms and treatments of early sepsis. Repeated endotoxin exposures induce periods of endotoxin tolerance, characterized by diminished proinflammatory responses to lipopolysaccharide (LPS) and modulated production of proinflammatory cytokines. Repeated measure designs using equine endotoxemia models are rarely performed, despite the advantages associated with reduced variability, because the altered responsiveness would confound study results and because the duration of equine endotoxin tolerance is unknown. We determined the interval of endotoxin tolerance, in vivo, in horses based on physical, clinicopathologic, and proinflammatory gene expression responses to repeated endotoxin exposures. Six horses received 30 ng/kg LPS in saline infused over 30 min. Behavior pain scores, physical examination parameters, and blood for complete blood count and proinflammatory gene expression were obtained at predetermined intervals for 24h. Horses received a total of 3 endotoxin exposures. The first exposure was LPS 1, followed 7 days later by LPS 7 or 14-21 days later by LPS 14-21. Lipopolysaccharide exposures were allocated in a randomized, crossover design. Lipopolysaccharide produced clinical and clinicopathologic signs of endotoxemia and increased expression of tumor necrosis factor alpha (TNFα), interleukin (IL)-6 and IL-8, P<0.001. Horses exhibited evidence of endotoxin tolerance following LPS 7 but not following LPS 14-21. Horses had significantly lower pain scores, heart rates, respiratory rates and duration of fever, after LPS 7 compared to LPS 1 and LPS 14-21, P<0.001, and expression of TNFα was lower in the whole blood of horses after LPS 7, P=0.05. Clinical parameters and TNFα gene expression were similar or slightly increased in horses following LPS 14-21 compared to measurements made in horses following LPS 1, suggesting that endotoxin tolerance had subsided. A minimum of 3 weeks between experiments is warranted if repeated measures designs are used to assess in vivo response to endotoxin in horses.

Plasma HMGB-1 and Nucleosome Concentrations in Horses with Colic and Healthy Horses

Background

Acute gastrointestinal disease occurs commonly in horses. Novel biomarkers might improve the understanding of SIRS and aid diagnosis and determination of prognosis.

Hypotheses

Increased plasma concentrations of the biomarkers HMGB‐1 and nucleosomes are associated with severity of gastrointestinal lesions in horses; concentrations of these biomarkers will be greater in horses with lesions more likely to cause SIRS; and will provide additional information compared with standard biomarkers fibrinogen and SAA.

Animals

Thirty horses with gastrointestinal disease, 22 healthy horses.

Methods

Prospective study. Plasma samples taken on admission were used for measurement of HMGB‐1, nucleosomes, fibrinogen, and SAA. Values were compared between healthy horses and those with gastrointestinal disease, and between horses with gastrointestinal disease grouped by lesion type (inflammatory, strangulating, and nonstrangulating). Correlations between biomarkers were assessed.

Results

Plasma concentrations of all biomarkers were significantly higher in horses with gastrointestinal disease compared to healthy horses (P ≤ .001). HMGB‐1 and nucleosomes were significantly higher in inflammatory and strangulating groups compared to healthy horses (3.5‐fold and 5.4‐fold increases, respectively, for HMGB‐1 (P < .05) and 4.8‐fold and 5.6‐fold increases for nucleosomes (P < .05)), but concentrations in the group with nonstrangulating disease did not differ from healthy horses. There was significant correlation between HMGB‐1 and nucleosomes (Spearman's r = 0.623; P < .001), and fibrinogen and SAA (Spearman's r = 0.801; P < .001) but not between other biomarkers.

Conclusions and Clinical Importance

High mobility group box‐1 and nucleosomes might have use as biomarkers for horses with gastrointestinal disease. Further studies are required to determine kinetics and prognostic value of serial measurements of these biomarkers in horses.

Concentrations of serum amyloid A and plasma fibrinogen in horses undergoing emergency abdominal surgery

OBJECTIVE

To compare the perioperative response of serum amyloid A (SAA) to fibrinogen in horses requiring exploratory celiotomy for colic and to determine if SAA could be used to predict complications and outcome.

DESIGN

Prospective observational clinical study.

SETTING

University teaching hospital.

ANIMALS

Eighteen horses undergoing exploratory celiotomy for colic. Inclusion criteria for the study included survival and anesthetic recovery from exploratory celiotomy, no history of surgery within the past year.

INTERVENTIONS

Blood was obtained via jugular venipuncture before surgery (time 0) and at 24, 48, 72, and 96 hours after recovery from anesthesia.

MEASUREMENTS AND MAIN RESULTS

Quantitative and semiquantitative fibrinogen, SAA, total nucleated cell counts, and total protein were evaluated at each time point. Multivariable linear regression was used to assess differences at each time point and after grouping horses according to duration of colic prior to surgery, strangulating surgical lesion or not, presence of systemic inflammatory response syndrome (SIRS) on admission, and postsurgical complications. Significant (P < 0.05) increases in SAA concentrations occurred in all cases after surgery compared to fibrinogen concentration, which only demonstrated a mild, clinically insignificant increase postsurgery. SAA concentrations were also significantly increased (P < 0.05) in cases identified with SIRS prior to surgery and postoperatively at 48 (P = 0.05) and 72 hours (P = 0.02) in horses that developed complications.

CONCLUSIONS

Measurement of SAA is a more sensitive indicator of inflammation than fibrinogen in the perioperative period of horses requiring exploratory celiotomy for colic. Serial measurement of SAA at 48, 72, and 96 hours after surgery may be helpful to determine risk of complications and guide postoperative management. Measurement of SAA on admission also allows for quantification of SIRS when it is detected clinically.

Dynamic expression of leukocyte innate immune genes in whole blood from horses with lipopolysaccharide-induced acute systemic inflammation

Background

In horses, insights into the innate immune processes in acute systemic inflammation are limited even though these processes may be highly important for future diagnostic and therapeutic advances in high-mortality disease conditions as the systemic inflammatory response syndrome (SIRS) and sepsis. Therefore, the aim of this study was to investigate the expression of 31 selected blood leukocyte immune genes in an equine model of acute systemic inflammation to identify significantly regulated genes and to describe their expression dynamics during a 24-h experimental period. Systemic inflammation was induced in 6 adult horses by the intravenous injection of 1 μg lipopolysaccharide (LPS) per kg btw. Sixteen blood samples were collected for each horse at predetermined intervals and analyzed by reverse transcription quantitative real-time PCR. Post-induction expression levels for each gene were compared with baseline levels.

Results

Systemic inflammation was confirmed by the presence of clinical and hematological changes which were consistent with SIRS. The clinical response to LPS was transient and brief as all horses except one showed unaltered general demeanor after 24 h. Twenty-two leukocyte genes were significantly regulated at at least one time point during the experimental period. By close inspection of the temporal responses the dynamic changes in mRNA abundance revealed a very rapid onset of both pro- and anti-inflammatory mediators and a substantial variation in both expression magnitudes and duration of changes between genes. A majority of the 22 significantly regulated genes peaked within the first 8 h after induction, and an on-going, albeit tightly controlled, regulation was seen after 24 h despite approximate clinical recovery.

Conclusions

This first broad study of gene expressions in blood leukocytes during equine acute LPS-induced systemic inflammation thoroughly characterized a highly regulated and dynamic innate immune response. These results provide new insights into the molecular mechanisms of equine systemic inflammation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0450-5) contains supplementary material, which is available to authorized users.

A review of equine sepsis

Sepsis is defined as an exaggerated, systemic inflammatory response to infection and is a common condition in horses. Systemic inflammatory response syndrome (SIRS) associated with bacterial infection is a hallmark of sepsis. Sepsis in neonatal foals is a common sequela of failure of passive transfer and, in addition to development of SIRS, may be characterised by bacteraemia, pneumonia, enterocolitis, omphalophlebitis, meningoencephalitis or arthritis. Sepsis in mature horses is most commonly observed secondary to gastrointestinal lesions that result in disrupted mucosa and bacterial translocation into circulation (endotoxaemia). Pleuropneumonia and metritis may also cause sepsis in mature horses. Diagnosis of sepsis is based on SIRS criteria as well as suspected or confirmed infection. Due to the relatively low sensitivity of microbial culture and the subjectivity of sepsis scoring, many sepsis biomarkers are being studied for their usefulness in diagnosis and prognostication of sepsis in horses. Treatment of sepsis requires an intensive care approach that includes antimicrobial drug administration, fluid resuscitation and pressure support, and treatment for inflammation, endotoxaemia and coagulopathy. Early recognition of sepsis and prompt antimicrobial drug treatment are critical for a successful outcome. Multiple organ dysfunction syndrome may occur in severe cases of sepsis, with common manifestations including laminitis and coagulopathies. Although prognosis for septic mature horses depends highly on the primary disease process, the overall survival rate in septic neonatal foals ranges from 26 to 86%, with most studies indicating a survival rate of 45-60%.

Effects of clopidogrel on horses with experimentally induced endotoxemia

OBJECTIVE

To evaluate the effects of clopidogrel on clinical and clinicopathologic variables in healthy horses with experimentally induced endotoxemia.

ANIMALS

12 adult mares. Procedures-Horses were assigned with a randomization procedure to receive clopidogrel (4 mg/kg, once, then 2 mg/kg, q 24 h; n = 6) or a placebo (6) through a nasogastric tube. After 72 hours of treatment, horses received lipopolysaccharide (LPS; 30 ng/kg, IV). Heart rate, respiratory rate, rectal temperature, CBC variables, plasma fibrinogen concentration, serum tumor necrosis factor-α concentration, plasma von Willebrand factor concentration, and measures of platelet activation (including ADP- and collagen-induced platelet aggregation and closure times, thrombelastography variables, and results of flow cytometric detection of platelet membrane P-selectin, phosphatidylserine, and microparticles) were determined at various times before and after LPS administration by investigators unaware of the treatment groups. Statistical analyses were performed with repeated-measures ANOVA.

RESULTS

4 of 6 clopidogrel-treated horses had significant decreases in ADP-induced platelet aggregation before and after LPS administration. Heart rate increased significantly after LPS administration only for the placebo group. No significant differences were detected between groups for CBC variables, closure time, and plasma concentration of fibrinogen or serum concentration of tumor necrosis factor-α, and no clinically relevant differences were detected for other hemostatic variables.

CONCLUSIONS AND CLINICAL RELEVANCE

In this study, administration of LPS did not induce platelet hyperreactivity in horses on the basis of measures of platelet adhesion, aggregation, degranulation, and procoagulant activity. Administration of clopidogrel was associated with variable platelet antiaggregatory activity and attenuated some clinical signs of endotoxemia.

Insulin dysregulation

Abnormalities of insulin metabolism include hyperinsulinaemia and insulin resistance, and these problems are collectively referred to as insulin dysregulation in this review. Insulin dysregulation is a key component of equine metabolic syndrome: a collection of endocrine and metabolic abnormalities associated with the development of laminitis in horses, ponies and donkeys. Insulin dysregulation can also accompany prematurity and systemic illness in foals. Causes of insulin resistance are discussed, including pathological conditions of obesity, systemic inflammation and pituitary pars intermedia dysfunction, as well as the physiological responses to stress and pregnancy. Most of the discussion of insulin dysregulation to date has focused on insulin resistance, but there is increasing interest in hyperinsulinaemia itself and insulin responses to feeding. An oral sugar test or in-feed oral glucose tolerance test can be performed to assess insulin responses to dietary carbohydrates, and these tests are now recommended for use in clinical practice. Incretin hormones are likely to play an important role in postprandial hyperinsulinaemia and are the subject of current research. Insulin resistance exacerbates hyperinsulinaemia, and insulin sensitivity can be measured by performing a combined glucose-insulin test or i.v. insulin tolerance test. In both of these tests, exogenous insulin is administered and the rate of glucose uptake into tissues measured. Diagnosis and management of hyperinsulinaemia is recommended to reduce the risk of laminitis. The term insulin dysregulation is introduced here to refer collectively to excessive insulin responses to sugars, fasting hyperinsulinaemia and insulin resistance, which are all components of equine metabolic syndrome.

Effects of equine metabolic syndrome on inflammatory responses of horses to intravenous lipopolysaccharide infusion

OBJECTIVE

To test the hypothesis that inflammatory responses to endotoxemia differ between healthy horses and horses with equine metabolic syndrome (EMS). Animals-6 healthy horses and 6 horses with EMS.

PROCEDURES

Each horse randomly received an IV infusion of lipopolysaccharide (20 ng/kg [in 60 mL of sterile saline {0.9% NaCl} solution]) or saline solution, followed by the other treatment after a 7-day washout period. Baseline data were obtained 30 minutes before each infusion. After infusion, a physical examination was performed hourly for 9 hours and at 15 and 21 hours; a whole blood sample was collected at 30, 60, 90, 120, 180, and 240 minutes for assessment of inflammatory cytokine gene expression. Liver biopsy was performed between 240 and 360 minutes after infusion. Results-Following lipopolysaccharide infusion in healthy horses and horses with EMS, mean rectal temperature, heart rate, and respiratory rate increased, compared with baseline findings, as did whole blood gene expression of interleukin (IL)-1β, IL-6, IL-8, IL-10, and tumor necrosis factor-α. The magnitude of blood cytokine responses did not differ between groups, but increased expression of IL-6, IL-8, IL-10, and tumor necrosis factor-α persisted for longer periods in EMS-affected horses. Lipopolysaccharide infusion increased liver tissue gene expressions of IL-6 in healthy horses and IL-8 in both healthy and EMS-affected horses, but these gene expressions did not differ between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Results supported the hypothesis that EMS affects horses' inflammatory responses to endotoxin by prolonging cytokine expression in circulating leukocytes. These findings are relevant to the association between obesity and laminitis in horses with EMS.

Effects of a "two-hit" model of organ damage on the systemic inflammatory response and development of laminitis in horses

The role of endotoxemia in the development of laminitis remains unclear. Although systemic inflammation is a risk factor for laminitis in hospitalized horses, experimental endotoxin administration fails to induce the disease. While not sufficient to cause laminitis by itself, endotoxemia might predispose laminar tissue to damage from other mediators during systemic inflammation. In "two-hit" models of organ damage, sequential exposure to inflammatory stimuli primes the immune system and causes exaggerated inflammatory responses during sepsis. Acute laminitis shares many characteristics with sepsis-associated organ failure, therefore an equine "two-hit" sepsis model was employed to test the hypothesis that laminitis develops with increased frequency and severity when repeated inflammatory events exacerbate systemic inflammation and organ damage. Twenty-four light breed mares (10) and geldings (14) with chronic disease conditions or behavioral abnormalities unrelated to laminitis that warranted euthanasia were obtained for the study. Horses were randomly assigned to receive an 8-h intravenous infusion of either lipopolysaccharide (5 ng/kg/h) or saline beginning at -24h, followed by oligofructose (OF; 5 g/kg) via nasogastric tube at 0 h. Euthanasia and tissue collection occurred at Obel grade 2 laminitis, or at 48 h if laminitis had not developed. Liver biopsies were performed at 24h in laminitis non-responders. Blood cytokine gene expression was measured throughout the study period. Lipopolysaccharide and OF administration independently increased mean rectal temperature (P<0.001), heart rate (P=0.003), respiratory rate (P<0.001), and blood interleukin (IL)-1β gene expression (P<0.0016), but responses to OF were not exaggerated in endotoxin-pretreated horses. The laminitis induction rate did not differ between treatment groups and was 63% overall. When horses were classified as laminitis responders and non-responders, area under the blood IL-1β expression curve (P=0.010) and liver and lung gene expression of IL-1β, IL-6, IL-8, IL-10, and tumor necrosis factor-α (P<0.05) were higher in responders following OF administration. The results indicate that endotoxin pretreatment did not enhance responses to OF. However, systemic inflammation was more pronounced in laminitis responders compared to non-responders, and tissue-generated inflammatory mediators could pose a greater risk than those produced by circulating leukocytes.