Acute Lipopolysaccharide Administration Research Articles

Differential Effect of Transferrin Lobe Iron Occupancy on a Murine Model of Inflammation

Introduction: Iron status is both affected by and a determinant of the inflammatory response. Several lines of evidence support a role for transferrin as a signaling as well as an iron delivery molecule. We previously demonstrated that mice with transferrin mutations that prevent iron binding to the C-lobe of transferrin (C-blocked) have increased red cell production relative to erythropoietin and increased hepcidin expression relative to iron status compared to mice with transferrin mutations that prevent iron binding to the N-lobe of transferrin (N-blocked). Based on these observations, we hypothesize that two forms of transferrin would differentially modulate the hematopoietic and iron distribution changes that occur with inflammation. We explored this hypothesis by comparing the effects of lipopolysaccharide (LPS) administered either acutely or in repeated doses to wild-type, N-lobe blocked, or C-lobe blocked transferrin mutant mice. Methods: For a model of acute inflammation, 14 day old wild-type (wt), N-blocked and C-blocked Tf mutant mice were treated with 1mg/kg LPS or carrier i.p. and sacrificed 6 hours later. Repeated LPS dosing, seven daily i.p. injections of 0.3 mg/kg LPS or carrier beginning at seven days of age, served as a model of chronic inflammation. Results: While wild-type and C-blocked mice had the expected hypoferremia in response to acute LPS administration, there was no effect on serum iron in the N-blocked mice. These mice moreover demonstrated an unanticipated increase in liver iron concentrations with LPS. All strains manifested expected increases in liver hepcidin expression; however, these were attenuated in the N-blocked mice relative to the C-blocked. Moreover, N-blocked mice have higher serum C reactive protein concentrations compared to C-blocked and wt mice following acute LPS administration. The elevated Hamp1 expression was not sustained in the chronic model. Although serum iron returned to baseline in wt and C-blocked mice, it remained elevated in N-blocked mice. Hemoglobin concentrations were decreased in all strains after repeated endotoxin dosing; however, C-blocked mice demonstrated higher neutrophil to lymphocyte ratios than wt or N-blocked mice, and increased circulating RBC count relative to WBCs. Conclusions: We conclude that the specificity of transferrin lobe iron occupancy is an important modulator of the inflammatory response and speculate that this modulation includes an effect on hematopoietic cell lineage determination.

Chronic lipopolysaccharide impairs motivation when delivered to the ventricles, but not when delivered peripherally in male rats

Increased neuroinflammation relative to controls is observed in major depression. Moreover, depressive disorders are significantly elevated in conditions which increase neuroinflammation (e.g., brain injury, Parkinson's disease, Alzheimer's disease). To better understand the relationship between neuroinflammation and depression, additional research is needed. The current set of studies made use of the progressive ratio (PR) task in male rats, a stable measure of motivation which can be evaluated daily and thus is ideally suited for examining a potential role for chronic neuroinflammation in depressive-like behavior. Lipopolysaccharide (LPS) was used to induce an inflammatory response. Experiment 1 confirmed prior acute LPS administration experiments for sensitivity of the PR task, with a large effect at 2 mg/kg, a partial effect at 1 mg/kg, and no effect at 0.5 mg/kg. Experiment 2 evaluated a dose-response of continuous s.c. LPS infusion but found no significant elevation in brain cytokines after 14 days at any doses of 0.1, 0.5, 1, or 2 mg/kg/week. Experiment 3 assessed motivation during continuous s.c. infusion of a large 5 mg/kg/week LPS dose and found no significant impairments in motivation, but transient decreases in rates of lever pressing (i.e., only motoric deficits). Experiment 4 measured motivation during continuous ICV infusion of 10.5 μg/kg/week LPS and found significantly decreased motivation without changes to rates of lever pressing (i.e., only motivational deficits). Together these results suggest that the PR task is efficient for evaluating models of chronic inflammation, and that the adaptive response to chronic LPS exposure, even when delivered centrally, may necessitate alternative strategies for generating long-term neuroinflammation.

Metabolomic, Lipidomic and Proteomic Characterisation of Lipopolysaccharide-induced Inflammation Mouse Model

Neuroinflammation is an important feature in the pathogenesis and progression of central nervous system (CNS) diseases including Alzheimer’s disease (AD). One of the widely used animal models of peripherally induced neuroinflammation and neurodegeneration is a lipopolysaccharide (LPS)-induced inflammation mouse model. An acute LPS administration has been widely used for investigation of inflammation-associated disease and testing inflammation-targeting drug candidates. In the present metabolomic, lipidomic and proteomic study, we investigated short-term effects of systemic inflammation induced by LPS administration on the mouse plasma and brain cortical and hippocampal metabolome, lipidome as well as expression of the brain cortical proteins which were shown to be involved in inflammation-associated CNS diseases. From a global perspective, the hippocampus was more vulnerable to the effects of LPS-induced systemic inflammation than the cortex. In addition, the study revealed several brain region-specific changes in metabolic pathways and lipids, such as statistically significant increase in several cortical and hippocampal phosphatidylcholines/phosphatidylethanolamines, and significantly decreased levels of brain cortical betaine after LPS treatment in mice. Moreover, LPS treatment in mice caused significantly increased protein expression of GluN1 receptor in the brain cortex. The revealed perturbations in the LPS-induced inflammation mouse model may give insight into the mechanisms underlying inflammation-associated CNS diseases. In addition, the finding of the study provide important information about the appropriate use of the model during target validation and drug candidate testing.

Exposure to in utero inflammation increases locomotor activity, alters cognitive performance and drives vulnerability to cognitive performance deficits after acute immune activation

Fetal exposure to intrauterine inflammation (IUI) affects brain development. Using intrauterine lipopolysaccharide (LPS) administration to induce a localized, rather than a systemic, inflammation, we have previously shown that IUI increases cytokine expression and microglia number, and reduces white matter in the brains of exposed offspring. Clinical data suggest that IUI may increase the risk for cognitive and neurodevelopmental disorders, however, IUI is often found in the context of preterm birth, making it difficult to disentangle the adverse effects of inflammation from those related to prematurity. Therefore, using a mouse model of IUI that does not involve preterm birth, operant tasks were used to evaluate motivation, attention, impulsivity, and locomotion. IUI-exposed offspring were found to have increased locomotion and increased motivation (females only), and testing in the 5-choice serial reaction time task (5-CSRTT) showed that IUI-exposed offspring performed more trials and could respond accurately at a shorter stimulus length. We have previously shown that IUI animals have a potentiated cytokine response to a “second hit” (acute LPS injection) in adulthood, so animals’ performance in the 5CSRTT was evaluated following an acute injection of LPS. As opposed to the improved performance observed under baseline conditions, IUI exposed animals demonstrated a greater decrease in performance after an acute LPS administration. To identify putative molecular mechanisms underlying this potentiated decline in cognitive performance, PFC samples were collected immediately after post-LPS cognitive testing and targeted gene expression analysis was correlated with specific measures of cognitive performance. Three receptors important for neuron-microglia crosstalk were found to correlate with task performance in the males following acute LPS administration. These data demonstrate that early life exposure to localized inflammation of the uterus, in the absence of prematurity, increases locomotor activity and improves some aspects of cognitive performance, but drives a vulnerability for adult cognitive performance deficits in response to acute infection.

Effects of melatonin on low-dose lipopolysaccharide-induced oxidative stress in mouse liver, muscle, and kidney.

Lipopolysaccharide (LPS) administration in an in vivo experimental mice model causes oxidative damage in the liver, muscle, and kidney. We aimed to determine specific mechanisms underlying melatonin's antioxidant protective role. Assays were carried out in quadruplicate in the control, melatonin (10 mg/kg, 10 days), acute LPS administration (once 150 μg), and LPS + melatonin groups. LPS stimulated lipid peroxidation processes (dienes and malondialdehyde) and antioxidant enzyme concentrations (superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase) were assessed in all investigated tissues. Protein oxidation processes (measured as aldehyde and kenotic carbonyl protein derivatives) were enhanced by LPS in the kidney and liver but not in muscle. Melatonin reversed LPS-induced changes, with the exception of muscle protein oxidation. LPS-induced oxidative stress resulted in augmented early-stage diene conjugated and end-stage malondialdehyde lipid peroxidation processes and affected antioxidant activity in liver, kidney, and muscle tissues. LPS activated protein oxidation processes in the kidney and liver. Melatonin ameliorated oxidative damage in the liver, kidney, and partially in the muscle. Melatonin modulates oxidative stress-induced states. Potential synergism between melatonin and systemic inflammation in terms of oxidative modification of muscle proteins needs to be clarified in further studies.

Gentiopicroside abrogates lipopolysaccharide-induced depressive-like behavior in mice through tryptophan-degrading pathway.

Targeting neuroinflammatory disturbances has been acknowledged as a potential strategy for treatment of depressive disorder in humans. Over-activation of tryptophan-degrading pathway by pro-inflammatory cytokines resulted in N-methyl-d-aspartate (NMDA)-mediated excitotoxicity, which is implicated in pathophysiology of depression. Gentiopicroside (Gent) has powerful anti-inflammatory property and exhibits promising antidepressant effect in an animal model of pain/depression dyad by down-regulating GluN2B-containing NMDA receptors. Therefore, the present study aimed to investigate the ability of Gent to abolish depressive-like behavior induced by lipopolysaccharide (LPS) in mice. Acute administration of LPS (0.5mg/kg, i.p.) increased immobility time in both forced swimming test (FST) and tail suspension test (TST) without affecting spontaneous locomotor activity, indicative of depressive-like behavior. Gent (50mg/kg, i.p.) administered once a day for three consecutive days prevented the development of depressive-like behavior induced by LPS. The antidepressant-like effect was paralleled with restoration of LPS-induced alterations in brain inflammatory mediators (i.e. IL-1β and TNF-α). In addition, Gent prevented over-activation of indoleamine 2,3-double oxygen enzyme (IDO) and recovered GluN2B subunit expression in the PFC challenged by LPS. In conclusion, our results suggested that Gent pretreatment provided protection against LPS-induced depressive-like behavior and the effect appeared to be demonstrated, at least partially, by blocking various steps of tryptophan-degrading pathway.

Histone demethylase LSD1 regulates hematopoietic stem cells homeostasis and protects from death by endotoxic shock

Hematopoietic stem cells (HSCs) maintain a quiescent state during homeostasis, but with acute infection, they exit the quiescent state to increase the output of immune cells, the so-called "emergency hematopoiesis." However, HSCs' response to severe infection during septic shock and the pathological impact remain poorly elucidated. Here, we report that the histone demethylase KDM1A/LSD1, serving as a critical regulator of mammalian hematopoiesis, is a negative regulator of the response to inflammation in HSCs during endotoxic shock typically observed during acute bacterial or viral infection. Inflammation-induced LSD1 deficiency results in an acute expansion of a pathological population of hyperproliferative and hyperinflammatory myeloid progenitors, resulting in a septic shock phenotype and acute death. Unexpectedly, in vivo administration of bacterial lipopolysaccharide (LPS) to wild-type mice results in acute suppression of LSD1 in HSCs with a septic shock phenotype that resembles that observed following induced deletion of LSD1 The suppression of LSD1 in HSCs is caused, at least in large part, by a cohort of inflammation-induced microRNAs. Significantly, reconstitution of mice with bone marrow progenitor cells expressing inhibitors of these inflammation-induced microRNAs blocked the suppression of LSD1 in vivo following acute LPS administration and prevented mortality from endotoxic shock. Our results indicate that LSD1 activators or miRNA antagonists could serve as a therapeutic approach for life-threatening septic shock characterized by dysfunction of HSCs.

Differential activation of neuronal and glial STAT3 in the spinal cord of the SOD1G93A mouse model of amyotrophic lateral sclerosis

Signal transducer and activator of transcription (STAT) proteins are activated by phosphorylation in the spinal cord of patients suffering from amyotrophic lateral sclerosis (ALS). The major scope of our study is a comprehensive histological characterization of the mechanisms underlying neuronal and glial STAT3 activation in the pathogenesis of ALS using SOD1G93A mice. We calculated the fold changes (FCs, ratios vs. appropriate controls) of the numerical densities of the following phosphorylated STAT3-positive (pSTAT3)+ cells - choline acetyltransferase (ChAT)+ α-motoneurons, ionized calcium-binding adapter molecule 1 (Iba1)+ microglia, and S100β+ astrocytes in SOD1G93A mice. The FCs of pSTAT3+ microglia and pSTAT3+ astrocytes were increased from 9 to 15weeks of age and then plateaued until 21weeks. In contrast, the FCs of pSTAT3+ α-motoneurons peaked at 9weeks and then decreased until 21weeks. The immunoreactivity for nonphosphorylated neurofilament protein (SMI-32), a marker of axonal impairment, was decreased in pSTAT3+ α-motoneurons compared with pSTAT3- α-motoneurons at 9weeks of age. We then compared the following pharmacological models - the chronic administration of 3,3'-iminodipropionitrile (IDPN), which models axonal impairment, and the acute administration of lipopolysaccharide (LPS), which is a model of neuroinflammation. The FCs of pSTAT3+ α-motoneurons were increased in IDPN-treated mice, while those of pSTAT3+ microglia were increased in LPS-treated mice. The FCs of pSTAT3+ astrocytes were higher in SOD1G93A mice at 9weeks compared with IDPN- and LPS-treated mice. Our results indicate that axonopathy and neuroinflammation may trigger the respective activation of neuronal and glial STAT3, which is observed during ALS pathogenesis.

Microglial depletion and activation: A [11C]PBR28 PET study in nonhuman primates

BackgroundThe 18-kDa translocator protein (TSPO) is an important target for assessing neuroimmune function in brain with positron-emission tomography (PET) imaging. The goal of this work was to assess two [11C]PBR28 imaging paradigms for measuring dynamic microglia changes in Macaca mulatta.MethodsDynamic [11C]PBR28 PET imaging data with arterial blood sampling were acquired to quantify TSPO levels as [11C]PBR28 VT. Scans were acquired at three timepoints: baseline, immediately post-drug, and prolonged post-drug.ResultsIn one animal, a colony-stimulating factor 1 receptor kinase inhibitor, previously shown to deplete brain microglia, reduced [11C]PBR28 VT in brain by 46 ± 3% from baseline, which recovered after 12 days to 7 ± 5% from baseline. In a different animal, acute lipopolysaccharide administration, shown to activate brain microglia, increased [11C]PBR28 VT in brain by 39 ± 9% from baseline, which recovered after 14 days to −11 ± 3% from baseline.ConclusionsThese studies provide preliminary evidence of complementary paradigms to assess microglia dynamics via in vivo TSPO imaging.

Increase in hypothalamic AMPK phosphorylation induced by prolonged exposure to LPS involves ghrelin and CB1R signaling

Acute administration of lipopolysaccharide (LPS) from Gram-negative bacteria induces hypophagia. However, the repeated administration of LPS leads to desensitization of hypophagia, which is associated with increased hypothalamic p-AMPK expression. Because ghrelin and endocannabinoids modulate AMPK activity in the hypothalamus, we hypothesized that these neuromodulators play a role in the reversal of tolerance to hypophagia in rats under long-term exposure to LPS. Male Wistar rats were treated with single (1 LPS, 100μg/kg body weight, ip) or repeated injections of LPS over 6days (6 LPS). Food intake was reduced in the 1 LPS, but not in the 6 LPS group. 6 LPS rats showed an increased serum concentration of acylated ghrelin and reduced ghrelin receptor mRNA expression in the hypothalamus. Ghrelin injection (40μg/kg body weight, ip) increased food intake, body weight gain, p-AMPK hypothalamic expression, neuropeptide Y (NPY) and Agouti related peptide (AgRP) mRNA expression in control animals (Saline). However, in 6 LPS rats, ghrelin did not alter these parameters. Central administration of a CB1R antagonist (AM251, 200ng/μl in 5μl/rat) induced hypophagia in 6 LPS animals, suggesting that the endocannabinoid system contributes to preserved food intake during LPS tolerance. In the presence of AM251, the ability of ghrelin to phosphorylate AMPK in the hypothalamus of 6 LPS group was restored, but not its orexigenic effect. Our data highlight that the orexigenic effects of ghrelin require CB1R signaling downstream of AMPK activation. Moreover, CB1R-mediated pathways contribute to the absence of hypophagia during repeated exposure to endotoxin.

Lipopolysaccharide administration induces sex-dependent behavioural and serotonergic neurochemical signatures in mice

Challenging the innate immune machinery with the pro-inflammatory agent lipopolysaccharide (LPS) results in the development of a sickness syndrome characterized by numerous depressive-like behavioural and physiological manifestations, most of which overlap with the clinical symptoms of major depression. Although women are known to mount stronger pro-inflammatory responses during infections and being at higher risk to develop depressive disorders compared to men, the vast majority of experimental studies investigating the neurobiological effects of LPS administration have been conducted in males. Herein, we investigated the behavioural effects of LPS administration (0.83mg/kg) in male and female C57BL/6J mice subjected to tests screening for alterations in locomotor activity (open field test), anorexia (food consumption), anhedonia (sucrose preference test), behavioural despair (forced swim test) and grooming behaviour (splash-test). We further mapped the brain's serotonergic and dopaminergic activity in five limbic brain regions implicated in the pathophysiology of major depression (i.e., prefrontal cortex, hippocampus, striatum, amygdala, and hypothalamus) at two critical time-points post-LPS treatment; at 6h when depression of behavioural activity is maximal, and at 24h when depressive-like symptoms develop independently of obvious locomotor performance impairments associated with acute LPS administration. Our findings indicate that the two sexes present with differential behavioural sensitivity to this immune stressor, as impairment of grooming behaviour in the splash test was more persistent in female mice, and anorexia lasted longer in their male counterparts. Notably, LPS affects the brain's serotonergic neurochemistry in a sex-specific manner, as it induced sustained serotonergic hyperactivity in females at 24h post-LPS administration in all the brain regions examined. Moreover, the kinetics of dopaminergic activation appeared to be sex-differentiated upon LPS challenge. Given the higher prevalence of affective disorders in women, a focus of basic science on sex differences that underlie neuroinflammatory processes is imperative in order to elucidate the neuroimmunological substrate of major depression.

Effects of nicotinic acetylcholine receptor positive allosteric modulator on microglia activation following lipopolysaccharide‐induced neuropathic pain

Neuropathic pain is a chronic neurological disorder characterized by hyperalgesia and allodynia. Recent studies indicate that microglia activation as measured by microglia marker-Iba-1 and microglia morphological changes plays a critical role in pathophysiology of neuropathic pain phenotypes. The objectives of the present study was to determine the effect of TQS, an alpha7 nAChR positive allosteric modulator, on lipopolysaccharide (LPS)-induced neuropathic pain using hot plate, a widely used technique for hyperalgesia assessment and von Frey hair test, a widely used method for the quantification of mechanical allodynia in male mice. In addition, we investigated the effect of TQS (1 or 4 mg.kg, i.p.) on Iba-1 expression using Western blot analysis and on microglia morphology using immunohistochemistry. Acute administration of LPS (1 mg/kg, i.p.) increased (p<0.05) the sensitivity to pain (allodynia and hyperalgesia) after 6 hours. Pretreatment of TQS (1 or 4 mg/kg, i.p.) decreased the LPS induced allodynic or hyperalgesic respose (p<0.05). TQS (1 or 4 mg/kg, i.p.) also reduced Iba-1 expression in the hippocampus (p<0.05). Moreover, TQS decreased the LPS-induced microglia morphological changes. These results suggest that TQS reduces LPS-induced neuropathic pain by decreasing microglia activation through targeting alpha-7 nAChR allosteric site. (Supported by Fulbright Foundation USA)

Hypoxia-Inducible Factor and Target Gene Expression Are Decreased in Patients With Sepsis

Background Hypoxia-inducible factor-1 (HIF-1) is a molecular key player in response to hypoxemic/inflammatory conditions prevailing in sepsis. In a prospective observational study, we tested the hypotheses that sepsis affects HIF-1α messenger ribonucleic acid (mRNA) expression (primary hypothesis) and also (secondary hypotheses) the expression of the HIF-1α target genes adrenomedullin and β2-integrins. Furthermore, we tested that lipopolysaccharide administration increases HIF-1α mRNA and protein in naive and endotoxin-tolerant monocytes. Methods In 99 patients with sepsis and 48 healthy volunteers, leukocyte HIF-1α mRNA expression (real-time polymerase chain reaction), cytokine concentrations (enzymelinked immunosorbent assay), and intracellular distribution of HIF-1α protein (immunofluorescence staining) were assessed. In vitro, HIF-1α mRNA expression and protein were measured in naive or endotoxin-tolerant (48 h; 0.05 ng/ml lipopolysaccharide) monocytes, with/without additional lipopolysaccharide (6h; 1 μg/ml). Results In comparison to healthy volunteers, HIF-1α mRNA expression (-67%; P = 0.0001) and HIF-1α protein positive cells (-66.7%; P = 0.01) were decreased in sepsis. mRNA expression of adrenomedullin (-75%), CD11a (-85%), and CD11b (-86%; all P = 0.0001) was also decreased. In contrast, interleukin 6 (P = 0.0001), interleukin 10 (P = 0.0001), and tumor necrosis factor-α (P = 0.0002) concentrations were increased. Of note, HIF-1α mRNA expression was inversely associated with illness severity (Simplified Acute Physiology Score II; r = -0.29; P = 0.0001). In vitro, acute lipopolysaccharide administration of naive monocytic cells increased HIF-1α mRNA expression, whereas HIF-1α mRNA and protein (-60%; P = 0.001) were decreased in endotoxin-tolerant cells, which still up regulated cytokines. Conclusions In sepsis, HIF-1α mRNA expression was suppressed and inversely associated with illness severity. While acute lipopolysaccharide administration increased HIF-1α mRNA expression, prolonged stimulation suppressed HIF-1α expression. The clinical implications of decreased HIF-1α may include maladaption to tissue hypoxia or depressed immune function.

T4 Mutations in BMPR-II Promote Inflammation Via Altered Superoxide Signalling: Insights into the Mechanisms Underlying Pulmonary Arterial Hypertension

IntroductionAlthough the presence of inflammation is well recognised in pulmonary arterial hypertension (PAH), the underlying mechanisms remain poorly understood. Mutations in the bone morphogenetic protein type II receptor gene, BMPR2,...

Differential sensitivity to endotoxin exposure in young and middle-age mice

Aging can have a profound effect on the neurobehavioral response to immune activation; aged subjects are predisposed to greater deficits in performance and cognitive function in conjunction with an exaggerated neuroinflammatory response. While increased reactivity to an immune insult has been well characterized in aged subjects, the alterations that may exist by middle-age have not been thoroughly investigated. The present study compared the reactions of young (4-month) and middle-age (12-month) male BALB/c mice to an acute or repeated lipopolysaccharide (LPS) challenge(s). The data suggest that in some respects middle-aged mice are more sensitive to endotoxin exposure, as they show enhanced weight loss, splenic cytokine levels, and c-fos expression in the brain following acute LPS administration compared to younger mice. However, acute LPS exposure led to comparable decreases in locomotor activity in young and middle-aged mice. Following repeated LPS administration both age groups showed diminished behavioral and neural reactions to the final LPS challenge, indicating tolerance development. However, the immune system of the middle-aged mice was still mildly responsive to the final LPS exposure, as splenic levels of IL-1β were significantly elevated. Collectively, the data suggest that middle-age subjects are more sensitive to an immune insult.

Bacterial lipopolysaccharide induces apoptosis in the trout ovary

BackgroundIn mammals it is well known that infections can lead to alterations in reproductive function. As part of the innate immune response, a number of cytokines and other immune factors is produced during bacterial infection or after treatment with lipopolysaccharide (LPS) and acts on the reproductive system. In fish, LPS can also induce an innate immune response but little is known about the activation of the immune system by LPS on reproduction in fish. Therefore, we conducted studies to examine the in vivo and in vitro effects of lipopolysaccharide (LPS) on the reproductive function of sexually mature female trout.MethodsIn saline- and LPS -injected brook trout, we measured the concentration of plasma steroids as well as the in vitro steroidogenic response (testosterone and 17alpha-hydroxyprogesterone) of ovarian follicles to luteinizing hormone (LH), the ability of 17alpha,20beta-dihydroxy-4-pregnen-3-one to induce germinal vesicle breakdown (GVBD) in vitro, and that of epinephrine to stimulate follicular contraction in vitro. We also examined the direct effects of LPS in vitro on steroid production, GVBD and contraction in brook trout ovarian follicles. The incidence of apoptosis was evaluated by TUNEL analysis. Furthermore, we examined the gene expression pattern in the ovary of saline- and LPS-injected rainbow trout by microarray analysis.ResultsLPS treatment in vivo did not affect plasma testosterone concentration or the basal in vitro production of steroids, although a small but significant potentiation of the effects of LH on testosterone production in vitro was observed in ovarian follicles from LPS-treated fish. In addition, LPS increased the plasma concentration of cortisol. LPS treatment in vitro did not affect the basal or LH-stimulated steroid production in brook trout ovarian follicles. In addition, we did not observe any effects of LPS in vivo or in vitro on GVBD or follicular contraction. Therefore, LPS did not appear to impair ovarian steroid production, oocyte final maturation or follicular contraction under the present experimental conditions. Interestingly, LPS administration in vivo induced apoptosis in follicular cells, an observation that correlated with changes in the expression of genes involved in apoptosis, as evidenced by microarray analysis.ConclusionThese results indicate that female trout are particularly resistant to an acute administration of LPS in terms of ovarian hormone responsiveness. However, LPS caused a marked increase in apoptosis in follicular cells, suggesting that the trout ovary could be sensitive to the pro-apoptotic effects of LPS-induced inflammatory cytokines.

Protracted increases in core body temperature and interleukin-1 following acute administration of lipopolysaccharide: Implications for the stress response

Administration of lipopolysaccharide (LPS) produces a fever response often precipitated by the production of pro-inflammatory cytokines in the CNS. This pro-inflammatory cascade has traditionally been regarded as a transitory event that, with a non-replicating antigen such as LPS, would subside within a few hours. We present data showing that central and peripheral levels of IL-1 were substantially elevated as much as 48 h after LPS in some structures. In order to explore other aspects of the sickness response that might follow a similarly protracted time course, rats were implanted with telemetry probes and injected (i.p.) with 0, 10 or 100 μg/kg of LPS and left undisturbed for 96 h. Rats injected with LPS evinced a polyphasic fever with intermediate temperature peaks at approximately 5 and 8 h. Although the fever appeared to subside during the first night cycle, more detailed analysis confirmed that it was masked by the circadian rise in core temperature during the dark cycle and actually persisted for approximately 36 h following LPS. In contrast, LPS produced a transient suppression of social interaction that was no longer evident 24 h after LPS. Finally, we report that prior LPS produced a sensitized fever response to social conflict 48 h later. Taken together, these results suggest that acute administration of LPS results in a protracted fever response and increased IL-1 that persist for at least 24–48 h, and that LPS may render certain aspects of the stress response to a sensitized state.

Modulatory role of cyclooxygenase inhibitors in aging- and scopolamine or lipopolysaccharide-induced cognitive dysfunction in mice

Inflammation processes may play a critical role in the pathogenesis of the degenerative changes and cognitive impairments associated with Alzheimer's disease (AD). Non-steroidal anti-inflammatory drugs are reported to be effective in reducing the risk of developing AD or cognitive impairments. Present experiments were performed to study the possible effect of various NSAIDs on cognitive performance of young, aged and scopolamine or lipopolysaccharide (LPS) treated mice (an animal model of AD) using one trial step through type of passive avoidance and in elevated plus maze task. Chronic administration of NSAIDs at the ED 50 doses (nimesulide, rofecoxib and naproxen for 15 days) significantly reversed the age or scopolamine-induced retention deficits in both test paradigms. However, in both the memory paradigms chronic administration of NSAIDs failed to modulate the retention performance of young mice. Acute administration of LPS (50 mcg/mouse, i.p.) significantly exhibited retention deficits after 24 h and seventh day of its administration in both test paradigms. Chronic administration (7 days) of rofecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor (1.92 mg/kg, p.o.) significantly reversed the LPS-induced retention deficits in both tests. The results of this study showed chronic treatment of NSAIDs reverses the cognitive deficits in age and scopolamine or LPS treated mice. These findings establish a link between the central nervous system expression of various pro-inflammatory cytokines and learning impairment in mice.

Effect of acute lipopolysaccharide administration on (±)-1-(2,5-dimethoxy-4-iodophenyl)-2 aminopropane-induced wet dog shake behavior in rats: comparison with body weight change and locomotor activity

1. Several reports have shown that serotonin (5-HT) 2A receptor density and its function are altered after physiological or pharmacological stress. To examine whether an acute administration of lipopolysaccharide (LPS), a bacterial endotoxin, affected 5-HT 2A receptor function, wet dog shakes of male Wistar rats were observed after a subcutaneous injection of DOI, a 5-HT 2A receptor agonist following LPS treatment. Body weight change and locomotor activity were also observed. 2. DOI (1 mg/kg)-induced WDS significantly decreased after 400 or 1000 μg/kg LPS treatment compared with that of control rats 1 and 3 hr after injection, and WDS completely recovered 8 hr after LPS treatment. Treatment with 10 mg/kg indomethacin (IND) or 1 mg/kg naltrexone (NLTX) canceled the effect of 400 μg/kg LPS on DOI-induced WDS. 3. Body weight decrease was significantly greater in LPS-treated rats compared with control rats 3, 5 and 8 hr after treatment. Treatment with IND (10 mg/kg) significantly recovered the reduction in body weight induced by 400 μg/kg LPS. Treatment with NLTX (1 mg/kg) also prevented the LPS effect on body weight decrease. 4. Eight hr after treatment with LPS (400 μg/kg), the rats showed significant attenuation of locomotor activity. IND (10mg/kg) treatment abolished the inhibitory effect of LPS on locomotor activity, and NLTX (1 mg/kg) also improved the decrease in locomotion 8 hr after LPS treatment. 5. Plasma tumor necrosis factor (TNF)-α concentration dramatically increased 1 hr after the injection of 400 μg/kg LPS, and returned almost to the basal level 3 hr later. Next, rats were injected with 50 μg/kg TNF-α intraperitoneally, and body weight change and DOI-induced WDS was determined 3 hr after TNF-α injection. Body weight loss was significantly greater in rats treated with TNF-α. On the other hand, DOI-induced WDS was not altered when rats were treated with TNF-α. 6. These results suggest that acute treatment with LPS inhibited 5-HT 2A receptor-mediated behavior via cyclooxygenase and opioid receptor activation, but that the inhibition of the WDS by LPS appears to be independent of TNF-α production.

Regulation of interleukin-1 receptors and hypothalamic-pituitary-adrenal axis by lipopolysaccharide treatment in the mouse

We measured iodine-125-labeled recombinant human interleukin-1α ( 125I-IL-1α) binding in the hippocampus, pituitary, liver, spleen and testis, and plasma adrenocorticotropic hormone (ACTH) and corticosterone levels after i.p. injection of various dose and treatment regimens of the bacterial endotoxin, lipopolysaccharide (LPS) Plasma ACTH and corticosterone levels were significantly increased at 2 h after acute administration of LPS (60 or 300 μg/mouse). 125I-IL-1α binding in all peripheral tissues examined was significantly and comparably decreased at 2 h after a single injection of 30 μg or 300 μg LPS/mouse. On the other hand, 125I-IL-1α binding in hippocampus was significantly decreased only after high dose administration of LPS (300 μg/mouse). In order to evaluate if activation of IL-1 in brain resulting in the observed decrease in 125I-IL-1α binding may require more sustained exposure to endotoxin, we compared the effects of a single injection (60 μg/mouse) and two injections of LPS (30 μg/mouse each at 0 and 12 h). A single injection of LPS (60 μg/mouse) decreased 125I-IL-1α binding in the testis but not in the hippocampus, while two LPS injections (30 μg/mouse each at 0 and 12 h) caused dramatic reductions in 125I-IL-1α binding in both the hippocampus and testis. These data demonstrating differential effects of LPS treatment on the regulation of IL-1 receptors in the brain versus peripheral tissues and on ACTH and corticosterone secretion suggest that sites of action outside the blood-brain barrier may be important in regulating the effects of IL-1 on the hypothalamic-pituitary-adrenal axis.