Lipopolysaccharide induces biochemical alterations in chicks trained on the passive avoidance learning task

The effect of intraperitoneal injection of Glycyrrhizin on central regulation of food intake in broilers injected with LPS

1. Poultry farming faces challenges regarding correct hygiene and nutrition. One of the challenges is gram-negative bacteria that stimulate pro-inflammatory reactions through lipopolysaccharide (LPS) and cause disease and anorexia. Liquorice, a medicinal plant containing glycyrrhizin (Glz; a saponin and emulsifier compound) as its main active ingredient, was injected into broilers to investigate any beneficial effects on feed intake in LPS-injected broilers.2. The study involved three experiments using 72 male broiler chickens in each, to examine the impact of Glz on feed intake, especially when challenged with lipopolysaccharide (LPS) by intra-peritoneal (IP) injection to cause inflammation (n = 24). Experiment 1 was conducted to examine the effects of intraperitoneal injection of Glz (12.5, 25 and 50 mg) on feed intake in chickens. In experiment 2, the effects of intracerebroventricular injections of LPS (6.25, 12.5 and 25 ng) were examined. The third experiment investigated the impact of IP injection of Glz on inflammation induced by LPS.3. Injection of Glz significantly increased feed intake in a dose-dependent manner. Whereas LPS significantly reduced the feed intake in feed-deprived chickens (p < 0.05).4. In conclusion, Glz can neutralise the feed intake reduction caused by inflammation in broilers, highlighting its potential role in modulating feed intake in broilers.

Lipopolysaccharide-Induced Immunological Tolerance in Monocyte-Derived Dendritic Cells

Bacterial lipopolysaccharides (LPS), also referred to as endotoxins, are major outer surface membrane components present on almost all Gram-negative bacteria and are major determinants of sepsis-related clinical complications including septic shock. LPS acts as a strong stimulator of innate or natural immunity in a wide variety of eukaryotic species ranging from insects to humans including specific effects on the adaptive immune system. However, following immune stimulation, lipopolysaccharide can induce tolerance which is an essential immune-homeostatic response that prevents overactivation of the inflammatory response. The tolerance induced by LPS is a state of reduced immune responsiveness due to persistent and repeated challenges, resulting in decreased expression of pro-inflammatory modulators and up-regulation of antimicrobials and other mediators that promote a reduction of inflammation. The presence of environmental-derived LPS may play a key role in decreasing autoimmune diseases and gut tolerance to the plethora of ingested antigens. The use of LPS may be an important immune adjuvant as demonstrated by the promotion of IDO1 increase when present in the fusion protein complex of CTB-INS (a chimera of the cholera toxin B subunit linked to proinsulin) that inhibits human monocyte-derived DC (moDC) activation, which may act through an IDO1-dependent pathway. The resultant state of DC tolerance can be further enhanced by the presence of residual E. coli lipopolysaccharide (LPS) which is almost always present in partially purified CTB-INS preparations. The approach to using an adjuvant with an autoantigen in immunotherapy promises effective treatment for devastating tissue-specific autoimmune diseases like multiple sclerosis (MS) and type 1 diabetes (T1D).

Sickness behaviors across vertebrate taxa: proximate and ultimate mechanisms

There is nothing like a pandemic to get the world thinking about how infectious diseases affect individual behavior. In this respect, sick animals can behave in ways that are dramatically different from healthy animals: altered social interactions and changes to patterns of eating and drinking are all hallmarks of sickness. As a result, behavioral changes associated with inflammatory responses (i.e. sickness behaviors) have important implications for disease spread by affecting contacts with others and with common resources, including water and/or sleeping sites. In this Review, we summarize the behavioral modifications, including changes to thermoregulatory behaviors, known to occur in vertebrates during infection, with an emphasis on non-mammalian taxa, which have historically received less attention. We then outline and discuss our current understanding of the changes in physiology associated with the production of these behaviors and highlight areas where more research is needed, including an exploration of individual and sex differences in the acute phase response and a greater understanding of the ecophysiological implications of sickness behaviors for disease at the population level.

Central histaminergic system interplay with suppressive effects of immune challenge on food intake in chicken

The aim of the current study was to investigate the interaction of the lipopolysaccharide (LPS) and histaminergic systems on appetite regulation in broilers. Effects of intracerebroventricular (ICV) injection of α-fluoromethylhistidine (α-FMH, histidine decarboxylase inhibitor), chlorpheniramine (histamine H1 receptor antagonist), famotidine (histamine H2 receptor antagonist) and thioperamide (histamine H3 receptor antagonist) on LPS-induced hypophagia in broilers were studied. A total of 128 broilers were randomly allocated into 4 experiments (4 groups and 8 replications in each experiment). A cannula was surgically implanted into the lateral ventricle. In Experiment 1, broilers were ICV injected with LPS (20 ng) prior to α-FMH (250 nmol). In Experiment 2, chickens were ICV injected with LPS followed by chlorpheniramine (300 nmol). In Experiment 3, broilers were ICV injected with famotidine (82 nmol) after LPS (20 ng). In Experiment 4, ICV injection of LPS was followed by thioperamide (300 nmol). Then, cumulative food intake was recorded until 4 h post-injection. According to the results, LPS significantly decreased food intake. Chlorpheniramine significantly amplified food intake, and LPS-induced hypophagia was lessened by injection of chlorpheniramine. α-FMH, famotidine and thioperamide had no effect on LPS-induced hypophagia. These results suggest that there is an interaction between central LPS and the histaminergic system where LPS-induced hypophagia is mediated by H1 histamine receptors in 3 h food-deprived broilers.

The role of central 5-HT(2C) and NMDA receptors on LPS-induced feeding behavior in chickens

In mammals, LPS regulate feeding primarily through the 5-HT(1A) and 5-HT(2c) receptors within the brain. However, the central effect of 5-HT(1A) and 5-HT(2c) on LPS-induced feeding behavior has not been studied in non-mammalian species. Also, the role of glutamatergic system in LPS-induced anorexia has never been examined in either mammalian or non-mammalian species. Therefore, in this study, we examined the role of serotonergic and glutamatergic systems on LPS-induced anorexia in chickens. Food intake was measured in chickens after centrally administered lipopolysaccharide (LPS) (20 ng) (0 h), followed by intracerebroventricular (ICV) injection of the 5-HT(1A) autoreceptor agonist (8-OH-DPAT, 61 nmol), 5-HT(2c) receptor antagonist (SB 242084, 30 nm), and NMDA receptor antagonist (DL-AP5, 5 nm) at the onset of anorexia (4 h). In the following experiments, we used DL-AP5 before 5-HT (10 μg) and SB242084 before glutamate (300 nm) for evaluation of the interaction between 5-HTergic and glutamatergic systems on food intake. The results of this study showed that SB 242084 and DL-AP5 significantly attenuated food intake reduction caused by LPS (P < 0.05) but 8-OH-DPAT had no effect. In addition, 5-HT-induced anorexia was significantly attenuated by DL-AP5 pretreatment (P < 0.05), while SB 242084 had no effect on glutamate-induced hypophagia. These results indicated that 5-HT and glutamate (via 5-HT(2c) and NMDA receptor, respectively) dependently regulate LPS-induced hypophagia in chickens.

Polyinosinic:polycytidylic acid induces memory processing deficits in the day-old chick

Anecdotal and experimental evidence has demonstrated that humans and animals exhibit physiological and cognitive alterations in response to sickness and injury. It is now clear that these changes are due to the actions of proinflammatory cytokines. The current study examined the effects of peripheral administration of polyinosinic:polycytidylic acid, a synthetic double-stranded viral RNA, on the memory processes of day-old chicks trained on a single trial passive avoidance task. Polyinosinic:polycytidylic acid impaired performance on the passive avoidance task in a dose-dependent manner. Maximal deficits were observed when 5 g/kg polyinosinic:polycytidylic acid was administered 120 min before training. Tests for retention revealed that interference in memory consolidation appeared between 30 and 40 min after training. These results indicate an inhibitory effect of polyinosinic:polycytidylic acid on the processes of memory formation at the transition from intermediate-term memory phase (A) to intermediate-term memory phase (B) of the Gibbs and Ng model of memory formation. The study also investigated the pyrogenic actions of polyinosinic:polycytidylic acid, and examined the effect of pretreatment with ketoprofen, a cyclooxygenase inhibitor. Significant rises in body temperature were observed 30 min after injection of polyinosinic:polycytidylic acid. Inhibition of cyclooxygenase by ketoprofen ameliorated the polyinosinic:polycytidylic acid-induced deficits in retention and attenuated the increase in body temperature. These results demonstrate that polyinosinic:polycytidylic acid induces memory processing deficits and is pyrogenic in the day-old chick and that these effects are cyclooxygenase-dependent.

A model for predicting feed intake of growing animals during exposure to pathogens

A general model is proposed for predicting the effects of subclinical pathogen challenges of different doses and virulence on the relative feed intake (RFI) of animals. The RFI is defined as the feed intake (FI, kg/d) of the animal challenged by a pathogen divided by its FI in the same state had it not been challenged. Actual FI can be predicted from the RFI and the animal's state. The RFI was assumed to be affected only when animals were naïve to a particular pathogen (i.e., had not previously experienced it) and when the challenge dose was above a predetermined threshold. The model is for the period from recognition of a pathogen through acquisition and subsequent expression of immunity. The way in which RFI changes with time is described by 5 main parameters and is based on data for RFI during different pathogen challenges of a range of hosts. Lag time (L, d) is the delay from a pathogen challenge until any effects on RFI are seen. Reduction time (R, d) describes the time it takes for the lowest value of RFI (lambda) to be achieved. The duration time (D, d) describes the time that lambda is maintained for, and rho (RFI/d) describes the rate of recovery of RFI until RFI = 1. There is no compensatory intake, and RFI is always < or = 1. The effects of host resistance on the values of the model parameters are proposed. Attempts were made to parameterize the model; when data were scarce, initial parameter values were derived on conceptual grounds. Predictions of the effects of pathogen dose, virulence, and host resistance are described and discussed. When comparing the responses in RFI for different genotypes, it is crucial to define the pathogen challenge (in terms of dose and virulence) and the degree of resistance of different hosts. Possible interactions between dose, virulence, and resistance were explored. Feed intake of healthy and challenged animals, at a time, may be different once the challenged animal has recovered (RFI = 1). The issue of reductions in FI during pathogen challenges is important for nutritionist and animal breeders. The large variation that has been observed for reductions in FI during pathogen challenges may be a viable point of selection. The points highlighted will aid selection strategies by quantifying the effects of pathogen dose and virulence, and time, on the FI of challenged animals. The proposed model may be integrated with other models of growth to predict animal performance during exposure to pathogens.

Interleukin-10 (IL-10) but not Lipopolysaccharide (LPS) produces increased motor activity and abnormal exploratory patterns while impairing spatial learning in Balb/c mice

Lipopolysaccharide (LPS) is a potent endotoxin, which produces "sickness behaviours" including loss of weight, loss of interest in food and decreased exploration. LPS has also been shown in some studies to cause deficits in various learning and memory abilities, while in others these LPS-induced learning impairments have been attributed to performance-related deficits rather than learning deficits per se. Here, we use the novelty-preference paradigm, a task that minimises performance-related factors such as motivation, in an attempt to extract and examine the effects of LPS on spatial learning. In addition, some studies have indicated that the anti-inflammatory cytokine Interleukin-10 (IL-10) can alleviate some of the symptoms induced by LPS. Here, we also examine the effect of IL-10 on feeding, motor and learning behaviours. We demonstrate that a single injection of LPS does produce a lack of interest in food and weight loss; LPS, however, does not impair habituation in the novelty-preference paradigm. Furthermore, co-injection of IL-10 with LPS does not attenuate the LPS-induced effects of weight loss and lack of food intake. Interestingly, a single injection of IL-10 produces abnormal patterns of exploration, a general increase in activity and abnormal patterns of habituation.

Minocycline reduces lipopolysaccharide-induced neurological dysfunction and brain injury in the neonatal rat

Preferential brain white matter injury and hypomyelination induced by intracerebral administration of the endotoxin lipopolysaccharide (LPS) in the neonatal rat brain has been characterized as associated with the activation of microglia. To examine whether inhibition of microglial activation might provide protection against LPS-induced brain injury and behavioral deficits, minocycline (45 mg/kg) was administered intraperitoneally 12 hr before and immediately after an LPS (1 mg/kg) intracerebral injection in postnatal day 5 (P5) Sprague-Dawley rats and then every 24 hr for 3 days. Brain injury and myelination were examined on postnatal day 21 and the tests for neurobehavioral toxicity were carried out from P3 to P21. LPS administration resulted in severe white matter injury, enlarged ventricles, deficits in the hippocampus, loss of oligodendrocytes and tyrosine hydroxylase neurons, damage to axons and dendrites, and impaired myelination as indicated by the decrease in myelin basic protein immunostaining in the P21 rat brain. LPS administration also significantly affected physical development (body weight) and neurobehavioral performance, such as righting reflex, wire hanging maneuver, cliff avoidance, locomotor activity, gait analysis, and responses in the elevated plus-maze and passive avoidance task. Treatment with minocycline significantly attenuated the LPS-induced brain injury and improved neurobehavioral performance. The protective effect of minocycline was associated with its ability to attenuate LPS-induced microglial activation. These results suggest that inhibition of microglial activation by minocycline may have long-term protective effects in the neonatal brain on infection-induced brain injury and associated neurologic dysfunction in the rat.

The effect of prenatal morphine exposure on memory consolidation in the chick

The central nervous system exhibits remarkable plasticity in early life and can be altered significantly by prenatal morphine exposure. Previous studies show that prenatal morphine exposure may alter the capacity for learning and memory in post-partum chicks. The one-trial passive avoidance learning paradigm with 1-day-old chicks is an excellent model to study several mechanisms of memory formation, including STM, ITM, and LTM. The following represents our investigation of the effect of prenatal morphine exposure on learning and memory deficits in the chick. In these experiments, morphine was injected into the airspace of eggs (20 mg/kg) and the one-trial passive avoidance learning paradigm was used to test the effect of prenatal morphine exposure on memory consolidation. The data suggest that chicks injected with morphine daily from E12 to E16 had significantly impaired long-term memory at 120 min after training (p<0.001) but not intermediate-term memory at 30 min after training.