Lipopolysaccharide infusion up-regulates hepcidin mRNA expression in equine liver

Hepcidin, ferritin and iron homeostasis in pregnant Spanish Purebred mares

During pregnancy, maternal erythropoietic expansion and fetal development require greater mobilization of available iron (Fe) stores. These adjustments in Fe metabolism in humans and rodents are largely mediated by the hormone hepcidin (Hepc), which controls the expression of ferroportin (Fpn), a transporter responsible for exporting Fe from stores to extracellular fluid and plasma. These mechanisms based on the regulation of Hepc on the availability of Fe during gestation in healthy mares remain unknown. The objective of this study was to determine the existence of interrelationships among concentrations of Hepc, ferritin (Ferr), Fe, and estrone (E₁) and progesterone (P₄) in Spanish Purebred mares along the whole gestation. Blood samples were taken from 31 Spanish Purebred mares each month, during 11 months of pregnancy. Fe and Ferr significantly increased and Hepc decreased during pregnancy (P < 0.05). The secretion peak of estrone (E₁) was reached in the 5th month and progesterone (P₄) between the 2nd and 3rd months of gestation (P < 0.05). Fe and Ferr were weakly positively correlated (r = 0.57; P < 0.05). Fe and Ferr were negatively correlated with Hepc (r = -0.80 and r = -0.67, respectively) (P < 0.05). P₄ was positively correlated with Hepc (r = 0.53; P < 0.05). Pregnancy in the Spanish Purebred mare was characterized by a progressive increase in Fe and Ferr and a reduction in Hepc concentrations. E₁ was partially responsible for the suppression of Hepc; on the other hand, P₄ induced its stimulation during pregnancy in the mare.

Changes of Hepcidin, Ferritin and Iron Levels in Cycling Purebred Spanish Mares

Several studies have demonstrated that in woman the sex hormones such as estrogen (E2) and progesterone (P4) influence iron (Fe) regulation, contributing to variations in Fe parameters along the menstrual cycle. These mechanisms based on the regulation of hepcidin (Hepc) which limits Fe availability during the cycle, remain poorly characterized in healthy mares. The objective of this study was to establish the relationship between Hepc, Fe, ferritin (Ferr), and the primary ovarian hormones E2 and P4 in cycling Purebred Spanish mares. Blood samples were taken from 31 Purebred Spanish mares day −5, on day 0, day +5 and day +16 of the cycle. Fe and Ferr significantly increased and Hepc decreased during pre- and ovulatory periods. The secretion peak of estradiol-17β (E2) was reached on day 0 and progesterone (P4) between days +5 and +16. Fe and Ferr were positively correlated (r = 0.57). Fe and Ferr were negatively correlated with Hepc (r = −0.72 and r = −0.02, respectively). E2 and P4 were negatively and positively correlated with Hepc (r = −0.753 and r = 0.54, respectively). In cycling Purebred Spanish mares there is a measurable relationship between steroid hormones and systemic Fe metabolism. Estrogenic dominance in the pre- and ovulatory period allows for a more effective iron status, mediated by hepcidin inhibition. However, P4 during the luteal phase substantially reduces serum Fe and iron stores, possibly related to Hepc stimulation. Future research is required to clarify the relationship between steroid hormones and iron metabolism at the molecular level in equids.

Central Nervous System Inflammation Induced by Lipopolysaccharide Up-Regulates Hepatic Hepcidin Expression by Activating the IL-6/JAK2/STAT3 Pathway in Mice

It is known that lipopolysaccharide (LPS) triggers inflammatory response after intracerebroventricular (ICV) injection and elevates the expression of hepcidin through the interleukin 6/janus kinase 2/transducer and activator of the transcription 3 (IL-6/JAK2/STAT3) signaling pathway in the brain. This study was conducted to determine whether LPS ICV injection can regulate peripheral hepatic hepcidin expression and iron metabolism. Here, we studied the hepcidin expression in the liver, as well as serum iron and transferrin saturation, after LPS ICV injection. We also demonstrated the role of the IL-6/JAK2/STAT3 pathway in hepcidin expression in the livers of IL-6 knockout (IL-6–/– mice) and IL-6+/+ mice. AG490 was used to verify the effect of the IL-6/JAK2/STAT3 pathway on hepatic hepcidin expression. Our present study demonstrated that LPS ICV injection up-regulated hepatic hepcidin expression. This finding provides further evidence for highlighting the importance of the central inflammation on hepatic hepcidin expression and peripheral iron metabolism.

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.

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.

Training Program Intensity Induces an Acute Phase Response in Clinically Healthy Horses

Physiological and hematochemical changes associated with exercise have been extensively investigated in equine species. It is known that stress elevates circulating levels of acute phase proteins (APPs). This survey evaluated whether horses trained with different training programs exhibit changes in APP levels after exercise event. Twenty Saddle Italian horses (11 geldings and 9 females, 9 ± 1 years old, body weight of 425 ± 35 kg) were divided into two equal groups according to the intensity of training programs they were subjected: group A was subjected to an intense training program, group B was subjected to a moderate training program. At the end of the training period, horses were subjected to a simulated exercise event (show jumping course of 400 m length with 12 obstacles). From horses, blood samples were collected at rest conditions (T_REST) and after 12 and 24 hour from the end of exercise (T_{12 h} and T_{24 h}); the concentration of serum amyloid A (SAA), haptoglobin, albumin, total proteins, iron, and fibrinogen was assessed. The circulating levels of SAA, fibrinogen, and iron were influenced by simulated exercise event (P < .01), starting from 12 hour after the end of exercise, suggesting the onset of an acute phase-like response, and it would seem that training program intensity the horses underwent also affected the degree of response, although only SAA values were significantly different between groups (P < .001). The findings obtained suggest that jumping exercise induces an acute phase response; however, further studies are advocated to better evaluate mechanisms by which exercise activates this response in the athletic horse.

Description of the D4/D4 genotype in Miniature horses with dwarfism

Four causative mutations (D1, D2, D3*, and D4) of chondrodysplastic dwarfism have been described in the equine aggrecan (ACAN) gene. Homozygotes for one of these mutations and heterozygotes for any combination of these mutations exhibit the disproportionate dwarfism phenotype. However, no case description of homozygotes for D4 (D4/D4) has been reported in the literature, to our knowledge. We report 2 Miniature horses with the genotype D4/D4 in the ACAN gene. Clinically, the 2 dwarfs had a domed head that was large compared to the rest of the body, mandibular prognathism, and short and bowed limbs, mainly in the proximal region of the metatarsal bones. Radiographic examination revealed contour irregularities of the subchondral bone in the long bones and confirmed mandibular prognathism; histopathology revealed irregular chondrocyte organization. To determine the genotypes of the horses, we performed DNA extraction from white blood cells, PCR, and Sanger sequencing. Genotyping demonstrated that these 2 animals had the D4/D4 genotype in the ACAN gene. The D4/D4 dwarfs were clinically similar to animals with the other ACAN genotypes reported for this disease. Identification of heterozygous animals makes mating selection possible and is the most important control measure to minimize economic losses and casualties.

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.

Pathological Role and Diagnostic Value of Endogenous Host Defense Peptides in Adult and Neonatal Sepsis: A Systematic Review

BACKGROUND

Sepsis is a systemic host response to an infection leading to organ failure. This is associated with dynamic expression of endogenous host defense peptides. Dysregulation of these peptides is associated with septic morbidity and mortality.

METHODS

We performed a systematic search of articles indexed in PubMed, ISI Web of Knowledge, EmBase, and Scopus database from inception to October 2016. Both preclinical and clinical studies investigating the role of host defense peptides in pathogenesis and as biomarkers for sepsis were included.

RESULTS

Of the available literature, cathelicidin, defensin, and hepcidin are among the best-characterized peptides. These regulate immune response, and crosstalk with pyroptosis and coagulation cascades. The applicability of these peptides as septic biomarkers has been investigated in vitro and in vivo studies. However, numerous studies were based on endotoxemia without an infection, jeopardizing interpretation of the outcomes. Cathelicidin and defensin were frequently reported in adult sepsis while hepcidin in neonatal sepsis. The expression level of these peptides is significantly associated with septic condition. Most of the studies employed a cross-sectional design, precluding the establishment of a temporal relationship between candidate peptide biomarkers and sepsis.

CONCLUSIONS

Innate defense peptides have been insufficiently evaluated as either diagnostic or prognostic biomarkers. In the future, evaluation of host defense peptides as septic biomarkers may employ a longitudinal design and consider a panel of multiple peptides.

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.

Hepcidin and its potential clinical utility

A number of pathophysiological conditions are related to iron metabolism disturbances. Some of them are well known, others are newly discovered or special. Hepcidin is a newly identified iron metabolism regulating hormone, which could be a promising biomarker for many disorders. In this review, we provide background information about mammalian iron metabolism, cellular iron trafficking, and the regulation of expression of hepcidin. Beside these molecular biological processes, we summarize the methods that have been used to determine blood and urine hepcidin levels and present those pathological conditions (cancer, inflammation, neurological disorders) when hepcidin measurement may have clinical relevance.

Lipopolysaccharides upregulate hepcidin in neuron via microglia and the IL-6/STAT3 signaling pathway

Neuroinflammation is closely related to brain iron homeostasis. Our previous study demonstrated that lipopolysaccharides (LPS) can regulate expression of iron-regulatory peptide hepcidin; however, the mechanism is undefined. Here, we demonstrated that intracerebroventricular injection of LPS in rat brain upregulated hepcidin and downregulated ferroportin 1 in the cortex and substantia nigra. LPS increased hepcidin expression in neurons only when they were co-cultured with BV-2 microglia, and the upregulation was suppressed by IL-6 neutralizing antibody in vitro. In addition, IL-6 but not IL-1α, IL-1β, or tumor necrosis factor-alpha increased hepcidin expression and signal transducer and activator of transcription 3 (STAT3) phosphorylation in cortical neurons and MES23.5 dopaminergic neurons. These effects were blocked by the STAT3 inhibitor, stattic. Our results show that neurons are the major source of increased hepcidin expression in response to LPS challenge but microglia play a key mediator role by releasing IL-6 and recruiting the STAT3 pathway. We conclude that LPS upregulates hepcidin expression in neurons via microglia and the IL-6/STAT3 signaling pathway.

Freund's adjuvant-induced inflammation: clinical findings and its effect on hepcidin mRNA expression in horses

Hypoferremia observed during systemic inflammatory disorders is regulated by hepcidin. Hepcidin up-regulation is particularly important during acute inflammation, as it restricts the availability of iron, which is necessary for pathogenic microorganism growth before adaptive immunity occurs. The aim of this study was to evaluate the clinical findings and hepatic hepcidin mRNA expression in horses using a Freund's complete adjuvant (FCA) model of inflammation. The expression of hepcidin mRNA in the liver was determined in healthy horses following two intramuscular injections of FCA at 0 h and 12 h. Plasma iron and fibrinogen concentrations were measured at multiple time points between 0 h and 240 h post-FCA injection (PI). Hepcidin mRNA expression was determined by RT-qPCR using liver biopsy samples performed at 0 h (control), 6 h and 18 h PI. The mean plasma fibrinogen level was significantly different from the control values only between 120 and 216 h PI. The mean plasma iron level was significantly lower than the control between 16 and 72 h PI, reaching the lowest levels at 30 h PI (33 % of the initial value), and returned to the reference value from 96 h PI to the end of the experiment. Hepcidin mRNA expression increased at 6 h PI and remained high at 18 h PI. The iron plasma concentration was an earlier indicator of inflammatory processes in horses when compared with fibrinogen and might be useful for the early detection of inflammation in the horse. FCA administration caused the rapid onset of hypoferremia, and this effect was likely the result of up-regulated hepatic hepcidin gene expression. This study emphasizes the importance of hepcidin and iron metabolism during inflammation in horses.

Equine poisoning by coffee husk (Coffea arabica L.)

Background

In Brazil, coffee (Coffea arabica) husks are reused in several ways due to their abundance, including as stall bedding. However, field veterinarians have reported that horses become intoxicated after ingesting the coffee husks that are used as bedding. The objective of this study was to evaluate whether coffee husk consumption causes intoxication in horses.

Results

Six horses fed coast cross hay ad libitum were given access to coffee husks and excitability, restlessness, involuntary muscle tremors, chewing movements and constant tremors of the lips and tongue, excessive sweating and increased respiration and heart rates were the most evident clinical signs. Caffeine levels were measured in the plasma and urine of these horses on two occasions: immediately before the coffee husks were made available to the animals (T0) and at the time of the clinical presentation of intoxication, 56 h after the animals started to consume the husks (T56). The concentrations of caffeine in the plasma (p < 0.001) and urine (p < 0.001) of these animals were significantly greater at T56 than at T0.

Conclusions

It was concluded that consumption of coffee husks was toxic to horses due to the high levels of caffeine present in their composition. Therefore, coffee husks pose a risk when used as bedding or as feed for horses.