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

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.

The Role of Intestinal Microbial Metabolites in the Immunity of Equine Animals Infected With Horse Botflies

The microbiota and its metabolites play an important role in regulating the host metabolism and immunity. However, the underlying mechanism is still not well studied. Thus, we conducted the LC-MS/MS analysis and RNA-seq analysis on Equus przewalskii with and without horse botfly infestation to determine the metabolites produced by intestinal microbiota in feces and differentially expressed genes (DEGs) related to the immune response in blood and attempted to link them together. The results showed that parasite infection could change the composition of microbial metabolites. These identified metabolites could be divided into six categories, including compounds with biological roles, bioactive peptides, endocrine-disrupting compounds, pesticides, phytochemical compounds, and lipids. The three pathways involving most metabolites were lipid metabolism, amino acid metabolism, and biosynthesis of other secondary metabolites. The significant differences between the host with and without parasites were shown in 31 metabolites with known functions, which were related to physiological activities of the host. For the gene analysis, we found that parasite infection could alarm the host immune response. The gene of “cathepsin W” involved in innate and adaptive immune responses was upregulated. The two genes of the following functions were downregulated: “protein S100-A8” and “protein S100-A9-like isoform X2” involved in chemokine and cytokine production, the toll-like receptor signaling pathway, and immune and inflammatory responses. GO and KEGG analyses showed that immune-related functions of defense response and Th17 cell differentiation had significant differences between the host with and without parasites, respectively. Last, the relationship between metabolites and genes was determined in this study. The purine metabolism and pyrimidine metabolism contained the most altered metabolites and DEGs, which mainly influenced the conversion of ATP, ADP, AMP, GTP, GMP, GDP, UTP, UDP, UMP, dTTP, dTDP, dTMP, and RNA. Thus, it could be concluded that parasitic infection can change the intestinal microbial metabolic activity and enhance immune response of the host through the pathway of purine and pyrimidine metabolism. This results will be a valuable contribution to understanding the bidirectional association of the parasite, intestinal microbiota, and host.

Dynamics of local gene regulations in synovial fluid leukocytes from horses with lipopolysaccharide-induced arthritis

The role of resident cells such a synoviocytes and chondrocytes in intra-articular inflammation is well-characterized, however the in vivo gene expression patterns of cells (predominantly leukocytes) in the synovial fluid (SF) of an inflamed joint have never previously been investigated. The aim of this study was to investigate gene expression in SF leukocytes from the inflamed joint cavity after intra-articular lipopolysaccharide (LPS) injection in horses to improve our understanding of the temporal regulation of the intra-articular inflammatory response. Gene expression was investigated in SF samples available from six horses 2, 4, 8 16 and 24 h after experimental induction of inflammation in the radiocarpal joint by lipopolysaccharide (LPS) injection. Leukocytic expression of 43 inflammation-related genes was studied using microfluidic high throughput qPCR (Fluidigm®). Expression of 26 genes changed significantly over the 24 h study period, including pro- and anti-inflammatory genes such as interleukin (IL)1, IL6, tumor necrosis factor (TNF), cyclooxygenase 2 (COX2), IL1 receptor antagonist (IL1RN), IL10, and superoxide dismutase 2 (SOD2), chemokine genes, apoptosis-related genes, and genes related to cartilage turnover (matrix metalloproteinase 8 and tissue inhibitor of metalloproteinase 1). The inflammatory responses appeared to be regulated, as an early increase (at 2 h) in expression of the pro-inflammatory genes IL1, IL6, TNF and COX2 was rapidly followed by increased expression (at 4 h) of several anti-inflammatory genes (IL10, IL1RN and SOD2). Similarly, both pro- and anti-apoptotic gene expression as well as expression of chondrodegenerative and chondroprotective genes were activated in SF leukocytes. Thus, the inflammatory response in leukocytes infiltrating the joint in the acute stage of arthritis was well orchestrated in this single-hit LPS-induced arthritis model. This study is the first to describe gene expression patterns in SF-derived leukocytes in vivo during severe joint inflammation, and the results thus expand our knowledge of basic inflammatory mechanisms in the early local response in an inflamed joint.

Evaluation of Treatment With Respiratory Gene Technology and Serum in a Group of Standard Bred Racehorses With Cytological Evidence of Mild Equine Asthma

Alternative treatment options to glucocorticoids for equine asthma is desirable due to withdrawal time. The objective was to evaluate if serum and Respiratory Gene Technology (RGT), a commercial kit to produce autologous conditioned serum, was effective in reducing bronchoalveolar lavage (BAL) neutrophils and mast cells in racehorses with cytological evidence of mild equine asthma . Thirty-six Standardbred trotters in active training were enrolled in this randomized clinical trial; a healthy control group (n=11), a RGT group (n=12) and a serum group (n=13). Endoscopy including tracheal wash (TW) and BAL was performed before (T0), after a 6-week treatment period including 12 intramuscular injections of RGT or serum (T6) and as a follow-up 10 weeks after treatment (T16). A significant decrease in BAL neutrophils for the RGT group was found between T0 and T6 (P = .002, d=-1.51, CI: -2.43;-0.59) and for the serum group between T0-T6 (P = .002, d=-1.36, CI: -2.26;-0.46). Further, a significant decrease in BAL mast cells between T0-T6 for the both the RGT group (P = .019, d=-1.23, CI: -1.22;-0.34) and the serum group (P= .004, d=-0.81, CI: -1.65;0.04), and further between T0-T16 (RGT P= .011, d=-1.55, CI: -2.62;-0.48; serum P= .044, d=-0.65, CI: -1.68;-0.37). No significant difference in TW cytology was found for any of the time-points. Pro- and anti-inflammatory cytokines were regulated according to treatment. The control group showed no cytological differences between any time-point. Study results showed that intramuscular treatment with both RGT and serum was effective associated with reduction of BAL neutrophils and mast cells in horses with cytological evidence of mild equine asthma. Further large-scale studies are necessary.

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.

Hematologic, prostaglandin F2α -metabolite, serum amyloid A, and serum iron changes in horses with experimentally induced endotoxemia

BACKGROUND

Endotoxemia is a common and severe disease of horses. Most previous studies have monitored changes caused by a bolus dose of endotoxin over short time periods.

OBJECTIVES

We aimed to describe inflammatory responses to endotoxin with inflammatory and hematologic markers monitored over a longer time than has been performed in the past using more prolonged endotoxin exposures.

METHODS

Escherichia coli O55:B5 endotoxin was administered as a 6-hour continuous intravenous infusion of lipopolysaccharide (LPS) to eight horses. Blood cell counts, and prostaglandin F_2α -metabolite (PGM), serum amyloid A (SAA), and serum total iron concentrations were monitored for up to 3 or 6 days.

RESULTS

An immediate and severe decrease in neutrophils and monocytes occurred in all horses, which subsequently changed to a moderate to strong neutrophilia and monocytosis that persisted for more than 78 hours postinfusion (PI) of LPS. Lymphocyte and eosinophil numbers decreased gradually and then normalized after 66- and 78-hours PI, respectively. Mild to moderate, biphasic thrombocytopenia occurred. A pronounced, transient increase in PGM occurred between 1 and 7 hours, peaking at 2 hours. Serum amyloid A began to increase after 6 hours PI and remained elevated after 72 hours PI. Serum iron was decreased between 6 and 48 hours. The clinical signs were most prominent during the first 24 hours PI and subsided within 48 hours PI.

CONCLUSIONS

Neutrophilia, monocytoses, and high SAA concentrations were present in horses even after the clinical signs had subsided. Serum iron normalized before SAA. Knowledge of these findings is imperative when interpreting laboratory results in horses with possible endotoxin exposure.

Bronchoalveolar lavage fluid cytokine, cytology and IgE allergen in horses with equine asthma

The pathophysiology of equine asthma (EA) is still not fully described, but the involvement of an allergic reaction is strongly suspected. This theory has led to the use of allergen-specific immunoglobulin (Ig)E tests to support a diagnosis of asthma. The objective of this descriptive study was to evaluate the correlation between four subgroups of EA (mastocytic mild equine asthma [MEA], neutrophilic MEA, mixed MEA, and severe equine asthma [SEA]), allergen specific IgE (measured in both serum and BALF) and mRNA expression of selected genes in bronchoalveolar lavage fluid (BALF). Serum and BALF were collected from 64 horses with a history of lower airway problems with or without poor performance. Differential cell counts from BALF were used to assign horses to one of four groups (mastocytic MEA; neutrophilic MEA, mixed MEA, and SEA). The expression of messenger RNA (mRNA) coding for IL4, IL5, IL8, IL10, TGFB, TNFA, toll-like receptor (TLR)4, IL1RA, IL1B, matrix metalloproteinase 8 (MMP8), TLR9, chemokine ligand 5 (CCL5) and cluster of differentiation (CD)14 in BALF were measured using reverse transcriptase (RT) quantitative PCR (qPCR). Allergen-specific IgE was measured in serum and BALF using an allergen-specific IgE ELISA test with the screening panel: house mites, storage mites, mould and pollen. As expected, the BALF neutrophil differential count correlated with mRNA expression of MMP-8 (r = 0.611, p < 0.001), TLR-4 (r = 0.540, p < 0.001), IL-1RA (r = 0.490, p < 0.001), IL-1β (r = 0.463, p < 0.001) and IL-8 (r = 0.302, p = 0.015). Cytokine expression of IL-1β (p = 0.014), MMP8 (p = 0.028) and IL-1RA (p = 0.037) was significantly higher in the SEA group compared to the MEA subgroups. The BALF mast cell count was correlated with allergen-specific IgE for insects (r = 0.370, p = 0.002) and pollen (r = 0.313, p = 0.011). Eosinophils in BALF were correlated with BALF mRNA expression of IL-4 (r = 0.340, p = 0.006) together with a significant correlation between BALF eosinophils and allergen-specific IgE for mites (r = 0.930, p < 0.001) and pollen in BALF (r = 0.837, p < 0.001). No correlation was found between allergen-specific IgE in serum and BALF for any of the allergen in the screening panel. Based on these results from allergen-specific IgE in horses with EA is not found in systemic circulation, and only the mastocytic and mixed subgroups of horses with EA had allergen-specific IgE in BALF. Further studies are needed to clarify the relationships identified here.

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.

The adjuvant G3 promotes a Th1 polarizing innate immune response in equine PBMC

The immunomodulatory effect of a new particulate adjuvant, G3, alone or in combination with agonists to TLR2/1 or TLR5 was evaluated in cultures of equine PBMC. Exposure to the G3 adjuvant up-regulated genes encoding IFN-γ, IL-1β, IL-6, IL-8, IL-12p40 and IL-23p19 in the majority of the horses tested, indicating that the G3 adjuvant induced a pro-inflammatory and Th1 dominated profile. In accordance, genes encoding IL-13, IL-4, IL-10 and TGF-β remained unaffected and genes encoding IFN-α, IL-17A and TNF-α were only occasionally and weakly induced. The two TLR agonists Pam3CSK4 (TLR2/1) and FliC (TLR5) induced cytokine profiles characterized by a clear induction of IL-10 as well as up-regulation of the genes encoding IL-1β, IL-6 and IL-8. The presence of G3 modified this response, in particular by reducing the FliC and Pam3CSK4 induced production of IL-10. Furthermore, G3 acted in synergy with Pam3CSK4 in enhancing the production of IFN-γ whereas G3 combined with FliC increased the gene expression of IL-8. Thus, the G3 adjuvant seems to have the capacity to promote a Th1 polarizing innate immune response in eqPBMC, both by favouring IFN-γ production and by reducing production of IL-10 induced by co-delivered molecules. These features make G3 an interesting candidate to further evaluate for its potential as an adjuvant in equine vaccines.

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.

Activation of innate immune genes in caprine blood leukocytes after systemic endotoxin challenge

Background

Sepsis is a serious health problem associated with a range of infectious diseases in animals and humans. Early events of this syndrome can be mimicked by experimental administration of lipopolysaccharides (LPS). Compared with mice, small ruminants and humans are highly sensitive to LPS, making goats valuable in inflammatory models. We performed a longitudinal study in eight Norwegian dairy goats that received LPS (0.1 μg/kg, Escherichia coli O26:B6) intravenously. A control group of five goats received corresponding volumes of sterile saline. Clinical examinations were performed continuously, and blood samples were collected throughout the trial.

Results

Characteristic signs of acute sepsis, such as sickness behavior, fever, and leukopenia were observed within 1 h of LPS administration. A high-throughput longitudinal gene expression analysis of circulating leukocytes was performed, and genes associated with the acute phase response, type I interferon signaling, LPS cascade and apoptosis, in addition to cytokines and chemokines were targeted. Pro-inflammatory genes, such as IL1B, CCL3 and IL8, were significantly up-regulated. Interestingly, increased mRNA levels of seven interferon stimulated genes (ISGs) were observed peaking at 2 h, corroborating the increasing evidence that ISGs respond immediately to bacterial endotoxins. A slower response was manifested by four extrahepatic acute phase proteins (APP) (SAA3, HP, LF and LCN2) reaching maximum levels at 5 h.

Conclusions

We report an immediate induction of ISGs in leukocytes in response to LPS supporting a link between the interferon system and defense against bacterial infections. The extrahepatic expression of APPs suggests that leukocytes contribute to synthesis of these proteins at the beginning of a systemic inflammation. Taken together, these findings provide insights into the dynamic regulation of innate immune genes, as well as raising new questions regarding the importance of ISGs and extrahepatic APPs in leukocytes after systemic endotoxin challenge.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0870-x) contains supplementary material, which is available to authorized users.

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.