Low-dose Lipopolysaccharide Challenge Research Articles

RLS-0071, a novel anti-inflammatory agent, significantly reduced inflammatory biomarkers in a randomised human evaluation of mechanisms and safety study.

This study was a randomised, double-blind, placebo-controlled study intended to establish the translatability of the RLS-0071 mechanisms of action from animal disease models to humans by inhibiting neutrophil-mediated inflammation at the tissue level and major inflammatory biomarkers. We hypothesised that RLS-0071 inhibits a temporary neutrophil-mediated inflammation in the lungs induced by inhalation of low-dose lipopolysaccharide (LPS) in healthy participants. Participants were randomised to one of three arms to receive inhaled LPS followed by three doses of either low-dose (10 mg·kg-1) or high-dose (120 mg·kg-1 loading dose followed by two doses of 40 mg·kg-1) RLS-0071 i.v. or placebo (saline) every 8 h. Biomarkers evaluating inflammatory responses, with absolute neutrophil counts in induced sputum as the primary end-point, were collected before and at 6 and 24 h after LPS challenge. Active treatment with RLS-0071 showed a similar safety profile to participants receiving placebo. RLS-0071 significantly decreased the numbers of neutrophils in sputum at 6 h post LPS by approximately half (p=0.04). Neutrophil effectors myeloperoxidase, neutrophil elastase and interleukin-1β in sputum were also significantly decreased at 6 h for RLS-0071 compared with placebo. Several biomarkers showed trends suggesting sustained decreases for RLS-0071 versus placebo at 24 h. This clinical trial demonstrated that RLS-0071 was safe and well tolerated and modulated neutrophil-mediated inflammation in humans after inhaled LPS challenge, consistent with results from prior animal model studies.

High variation in the response of calves to a low-dose lipopolysaccharide challenge is associated with early-life measurements

Lipopolysaccharide (LPS) challenges are commonly used in animal studies as a model for infection with gram-negative bacteria and innate immune activation. We used a low-dose LPS challenge for evaluating interindividual variation in innate immune responses in calves. This was part of a larger study aimed at predicting interindividual variation in feed efficiency in veal calves by variation in feeding motivation, digestion, metabolism, immunology, and behavioral traits. However, due to unexpected high mortality, this LPS challenge was performed in 32 calves rather than in 130 calves, which was initially intended in that larger study, and the 32 calves subjected to the LPS challenge were removed from that larger study. The objective of this short communication is to report the effects of a low-dose LPS challenge in those 32 calves and to examine whether the high variation in calves' responses to LPS could be explained by parameters related to feeding motivation, digestion, behavior, and immunology measured in early life. Thirty-two male Holstein-Friesian calves of Dutch origin were intravenously injected with LPS (0.05 μg/kg of body weight) at an age of 72 ± 0.6 d. Rectal temperature and respiratory frequency were recorded before injection and every hour after injection up to 6 h. In the 8 wk before the LPS challenge, measurements were performed related to general health, feeding motivation, digestion, behavior, and immunity. Following LPS administration, 3 calves died of shock, a fourth calf was euthanized because of severe symptoms of shock and 3 other calves were treated with corticosteroids to counteract observed symptoms of shock. Within the group of 25 relatively mild-responding calves, large interindividual variation in clinical responses to LPS was observed. The maximum increase in rectal temperature varied from 0.6 to 1.9°C and averaged 1.2 ± 0.39°C (coefficient of variation was 32%). The maximum increase in respiratory frequency varied from 16 to 132 bouts/min and averaged 60 ± 28 bouts/min (coefficient of variation was 48%). Little differences were found in early-life measurements between the 7 heavy and 25 mild responders, although heavy responders tended to have a better umbilical hernia score, and had a lower score in a human approach test (i.e., were less reactive) and lower presence of fecal pathogens. The maximum increase in rectal temperature correlated negatively with blood hemoglobin concentration at arrival of the calves at the facilities (r = −0.59) and in wk 4 (r = −0.53). The maximum increase in respiratory frequency correlated negatively with fecal color score (r = −0.43) and positively with fur score in wk 5 (r = 0.50). Overall, mortality (12.5%) and variation in clinical response was high after a low-dose LPS challenge in clinically healthy calves and some hematological and health measurements in early life were related to the clinical response of calves to LPS.

PSV-5 The Effect of a Prenatal Immune Challenge on Offspring Skeletal Muscle Characteristics in the Longissimus Muscle of Weaned Pigs

Abstract An insult to the health status of an animal is associated with decreased skeletal muscle growth. Furthermore, an immune challenge to a gestating dam may inhibit pre- and postnatal muscle growth of the offspring. The objective of this study was to determine if the administration of low-dose lipopolysaccharide (LPS) to gestating sows would alter muscle characteristics of the longissimus muscle (LM) in weaned pigs exposed to LPS. Pregnant Camborough sows were randomly assigned to receive LPS (LPS; n = 7) at a dose of 2.5 μg/kg BW or saline (CON; n= 7) on 78 ± 1.8 d of gestation. At weaning (21 ± 1.3 d of age), barrows (CON n = 17; LPS n = 17) from each sow received a secondary LPS challenge. Following the postnatal challenge, barrows were euthanized (31 ± 1.3 d of age), and both LM were collected. The left LM was weighed, measured for length, and measured for circumference at the cranial, middle, and caudal portion of the muscle. Two samples from the right LM were preserved for histological analyses. Morphometric, fiber type count, primary myofiber clustering, and satellite cell counts were analyzed using the MIXED procedure of SAS 9.4 with a main effect of prenatal treatment and covariate of body weight. There were no differences (P > 0.248) between any morphometric measures. The average diameter for myosin heavy chain (MHC) type I and IIB/X fibers was increased (P < 0.048) 8.6 and 5.9% respectively in LPS offspring compared with CON offspring. Average cross-sectional area (CSA) was increased 10.6% (P = 0.030) in MHC IIB/X fibers and tended to be increased 14.9% (P = 0.080) in MHC 1 fibers of LPS offspring. Number of myofibers within the LM was increased 16.1% (P = 0.032) in CON compared with LPS offspring. Diameter, CSA, and total CSA of oxidative myofibers (MHC type I and IIA) clusters was increased (P < 0.001) 13.8, 27.6, and 22.3% respectively in LPS compared with CON offspring. There were no differences (P > 0.186) between treatment groups for total nuclei or nuclei positive for MYF5, PAX7, or MYF5 and PAX7 nuclei. Based on the timing of the maternal challenge, it can be theorized that LPS hinders hyperplasia during secondary myogenesis following an immune challenge to the dam, with a rescue response of increased hypertrophy of MHC I and IIB/X myofibers post-weaning and glycolytic myofiber profile. However, due to the reduction in total myofibers, the impact of LPS on parameters such as average daily gain, feed efficiency, and lean skeletal muscle accretion should be studied further.

Dextromethorphan reduces prenatal lipopolysaccharide exposure-induced dopaminergic neuronal loss and cytokine changes in offspring.

Maternal infection during pregnancy may affect fetal brain development and increase the risk of developing neurological and mental disorders later in life in offspring. In this study, we used low-dose lipopolysaccharide (LPS) injection to mimic mild maternal infection at a critical time window for fetal dopamine (DA) and serotonin (5-HT) neuron development. The affected offspring exhibited reduction of dopaminergic and serotonergic neurons and anxiety- and depression-related behaviors in adulthood. In the current study, we evaluated whether dextromethorphan (DM, 30 mg/kg), an over-the-counter antitussive drug with anti-inflammatory and neuroprotective properties, could reduce the adverse effects of maternal infection mimicked by LPS exposure. We discovered that DM application did not change the baseline serum interleukin-6 (IL-6) and tumor necrosis factor α (TNFα) levels in the LPS-exposed offspring. However, DM treatment could reduce the heightened immune responses induced by a postnatal LPS challenge test in prenatal LPS-exposed offspring. The neuroprotective effect of DM was only seen in DA neurons but not in 5-HT neurons. We concluded that DM treatment can partially protect the offspring against the adverse effects of LPS-induced maternal immune activation. The reduction in heightened immune responses and dopaminergic neuronal loss in LPS-exposed offspring could potentially reduce the risk of DA-related neurological and psychiatric disorders later in life.

Acute neuroinflammation, sickness behavior and working memory responses to acute systemic LPS challenge following noradrenergic lesion in mice

Locus coeruleus (LC)-derived noradrenaline is important in cognition and decreases with age, but the impact of prior noradrenaline deficiency on vulnerability to inflammation-induced acute cognitive dysfunction is unclear. Here we assessed whether noradrenergic depletion, in female mice, impacted upon inflammation, locomotor activity and working memory directly after acute systemic immune challenge with bacterial lipopolysaccharide (LPS), a paradigm we have previously used to capture delirium-like acute cognitive deficits. Mice received 2 doses of the LC-selective noradrenergic toxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4; 50 mg/kg i.p.) and were challenged, 2 weeks later, with LPS (100 μg/kg i.p.). DSP-4 dramatically reduced noradrenaline concentrations and tyrosine hydroxylase-positive afferents in the frontal cortex and hippocampus. This did not significantly alter numbers of Pu.1-positive microglia, Iba1-positive microglial morphology or mRNA expression of microglia-associated gene transcripts (Tyrobp, Sall1, Cd68, Sra2, Clec7a) in the hippocampus or frontal cortex and produced modest reductions in Cx3cr1 and P2ry12. LPS induced blood and brain cytokine levels, cFOS activation and locomotor responses that were highly similar in DSP-4- and vehicle-treated mice, although LPS-induced plasma TNF-α was significantly reduced in those treated with DSP-4. Importantly, prior noradrenergic depletion did not predispose to LPS-induced T-maze working memory deficits. The data demonstrate that significant depletion of noradrenaline in the hippocampus and frontal cortex does not prompt acutely exaggerated neuroinflammation or leave the brain vulnerable to acute, transient working memory deficits upon low dose LPS challenge. These findings have implications for our understanding of the impact of systemic inflammation on the aging and vulnerable brain during septic encephalopathy and delirium.

Role of Gate-16 and Gabarap in Prevention of Caspase-11-Dependent Excess Inflammation and Lethal Endotoxic Shock.

Sepsis is a life-threating multi-organ disease induced by host innate immunity to pathogen-derived endotoxins including lipopolysaccharide (LPS). Direct sensing of LPS by caspase-11 activates inflammasomes and causes lethal sepsis in mice. Inhibition of caspase-11 inflammasomes is important for the prevention of LPS-induced septic shock; however, whether a caspase-11 inflammasome-specific suppressive mechanism exists is unclear. Here we show that deficiency of GABARAP autophagy-related proteins results in over-activation of caspase-11 inflammasomes but not of canonical inflammasomes. Gate-16−/−Gabarap−/− macrophages exhibited elevated guanylate binding protein 2 (GBP2)-dependent caspase-11 activation and inflammatory responses. Deficiency of GABARAPs resulted in formation of GBP2-containing aggregates that promote IL-1β production. High mortality after low dose LPS challenge in Gate-16−/−Gabarap−/− mice primed with poly(I:C) or polymicrobial sepsis was ameliorated by compound GBP2 deficiency. These results reveal a critical function of Gate-16 and Gabarap to suppress GBP2-dependent caspase-11-induced inflammation and septic shock.

Circadian desynchronization alters metabolic and immune responses following lipopolysaccharide inoculation in male mice

Metabolism and inflammation are linked at many levels. Sickness behaviors are elicited by the immune system’s response to antigenic stimuli, and include changes in feeding and metabolism. The immune system is also regulated by the circadian (daily) clock, which generates endogenous rhythms, and synchronizes these rhythms to the light-dark cycle. Modern society has resulted in chronic misalignment or desynchronization of the circadian clock and the external environment. We have demonstrated that circadian desynchronization (CD) in mice alters metabolic function, and also affects both peripheral and central immune responses following a low-dose lipopolysaccharide (LPS) challenge. However, it is unclear how this altered immune response impacts sickness behaviors and metabolism following challenge. To test this, we housed male mice in circadian desynchronized (10-hours light:10-hours dark) or control (12-hours light:12-hours dark) conditions for 5–6 weeks. We then challenged mice with LPS (i.p., 0.4 mg/kg) or PBS and measured changes in body mass, feeding, drinking and locomotion using a comprehensive phenotyping system. Plasma, liver, and brain were collected 36 h post-inoculation (hpi) and inflammatory messengers were measured via multiplex cytokine/chemokine array and qPCR. We find that recovery of locomotion and body mass is prolonged in CD mice following LPS challenge. Additionally, at 36 hpi the expression of several proinflammatory cytokines differ depending on pre-inoculation lighting conditions. Our findings add to the growing literature which documents how desynchronization of circadian rhythms can lead to disrupted immune responses and changes in metabolic function.

Exogenous Administration of Low-Dose Lipopolysaccharide Potentiates Liver Fibrosis in a Choline-Deficient l-Amino-Acid-Defined Diet-Induced Murine Steatohepatitis Model

Various rodent models have been proposed for basic research; however, the pathogenesis of human nonalcoholic steatohepatitis (NASH) is difficult to closely mimic. Lipopolysaccharide (LPS) has been reported to play a pivotal role in fibrosis development during NASH progression via activation of toll-like receptor 4 (TLR4) signaling. This study aimed to clarify the impact of low-dose LPS challenge on NASH pathological progression and to establish a novel murine NASH model. C57BL/6J mice were fed a choline-deficient l-amino-acid-defined (CDAA) diet to induce NASH, and low-dose LPS (0.5 mg/kg) was intraperitoneally injected thrice a week. CDAA-fed mice showed hepatic CD14 overexpression, and low-dose LPS challenge enhanced TLR4/NF-κB signaling activation in the liver of CDAA-fed mice. LPS challenge potentiated CDAA-diet-mediated insulin resistance, hepatic steatosis with upregulated lipogenic genes, and F4/80-positive macrophage infiltration with increased proinflammatory cytokines. It is noteworthy that LPS administration extensively boosted pericellular fibrosis with the activation of hepatic stellate cells in CDAA-fed mice. Exogenous LPS administration exacerbated pericellular fibrosis in CDAA-mediated steatohepatitis in mice. These findings suggest a key role for LPS/TLR4 signaling in NASH progression, and the authors therefore propose this as a suitable model to mimic human NASH.

Early life stress induces immune priming in kidneys of adult male rats.

Early life stress (ELS) in humans is associated with elevated proinflammatory markers. We hypothesized that ELS induces activation of the immune response in a rat model of ELS, maternal separation (MatSep), in adulthood. MatSep involves separating pups from the dam from postnatal day 2 to postnatal day 14 for 3 h/day. Control rats are nonseparated littermates. We determined circulating and renal immune cell numbers, renal immune cell activation markers, renal cytokine levels, and the renal inflammatory gene expression response to low-dose lipopolysaccharide (LPS) in male MatSep and control rats. We observed that MatSep did not change the percentage of gated events for circulating CD3+, CD4+, CD8+, and CD4+/Foxp3+ cells or absolute numbers of mononuclear and T cells in the circulation and kidneys; however, MatSep led to an increase in activation of renal neutrophils as well as CD44+ cells. Renal toll-like receptor 4 (TLR4) and interleukin 1 beta (IL-1β) was significantly increased in MatSep rats, specifically in the outer and inner medulla and distal nephron, respectively. Evaluation of renal inflammatory genes showed that in response to a low-dose LPS challenge (2 mg/kg iv) a total of 20 genes were significantly altered in kidneys from MatSep rats (17 genes were upregulated and 3 were downregulated), as opposed to no significant differences in gene expression in control vs. control + LPS groups. Taken together, these findings indicate that MatSep induces priming of the immune response in the kidney.

Low-dose lipopolysaccharide (LPS) inhibits aggressive and augments depressive behaviours in a chronic mild stress model in mice.

BackgroundAggression, hyperactivity, impulsivity, helplessness and anhedonia are all signs of depressive-like disorders in humans and are often reported to be present in animal models of depression induced by stress or by inflammatory challenges. However, chronic mild stress (CMS) and clinically silent inflammation, during the recovery period after an infection, for example, are often coincident, but comparison of the behavioural and molecular changes that underpin CMS vs a mild inflammatory challenge and impact of the combined challenge is largely unexplored. Here, we examined whether stress-induced behavioural and molecular responses are analogous to lipopolysaccharide (LPS)-induced behavioural and molecular effects and whether their combination is adaptive or maladaptive.MethodsChanges in measures of hedonic sensitivity, helplessness, aggression, impulsivity and CNS and systemic cytokine and 5-HT-system-related gene expression were investigated in C57BL/6J male mice exposed to chronic stress alone, low-dose LPS alone or a combination of LPS and stress.ResultsWhen combined with a low dose of LPS, chronic stress resulted in an enhanced depressive-like phenotype but significantly reduced manifestations of aggression and hyperactivity. At the molecular level, LPS was a strong inducer of TNFα, IL-1β and region-specific 5-HT2A mRNA expression in the brain. There was also increased serum corticosterone as well as increased TNFα expression in the liver. Stress did not induce comparable levels of cytokine expression to an LPS challenge, but the combination of stress with LPS reduced the stress-induced changes in 5-HT genes and the LPS-induced elevated IL-1β levels.ConclusionsIt is evident that when administered independently, both stress and LPS challenges induced distinct molecular and behavioural changes. However, at a time when LPS alone does not induce any overt behavioural changes per se, the combination with stress exacerbates depressive and inhibits aggressive behaviours.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0572-0) contains supplementary material, which is available to authorized users.

Characterization of inflammation and immune cell modulation induced by low-dose LPS administration to healthy volunteers

Human in vivo models of systemic inflammation are used to study the physiological mechanisms of inflammation and the effect of drugs and nutrition on the immune response. Although in vivo lipopolysaccharide (LPS) challenges have been applied as methodological tool in clinical pharmacology studies, detailed information is desired on dose-response relationships, especially regarding LPS hyporesponsiveness observed after low-dose in vivo LPS administration. A study was performed to assess the in vivo inflammatory effects of low intravenous LPS doses, and to explore the duration of the induced LPS hyporesponsiveness assessed by subsequent ex vivo LPS challenges. This was a randomized, double-blind, placebo-controlled study with single ascending low doses of LPS (0.5, 1 and 2 ng/kg body weight) administered to healthy male volunteers (3 cohorts of 8 subjects, LPS:placebo 6:2). The in vivo inflammatory response was assessed by measurement of cytokines and CRP. Ex vivo LPS challenges were performed (at −2, 6, 12, 24, 48 and 72 hours relative to in vivo LPS administration) to estimate the duration and magnitude of LPS hyporesponsiveness by assessment of cytokine release (TNF-α, IL-1β, IL-6, IL-8). LPS administration dose-dependently increased body temperature (+1.5°C for 2 ng/kg LPS), heart rate (+28 bpm for 2 ng/kg LPS), CRP and circulating cytokines which showed clearly distinctive increases from placebo already at the lowest LPS dose level tested (0.5 ng/kg, contrast for timeframe 0–6 hours: TNF-α +413%, IL-6 +288%, IL-8 +254%; all p ≤ 0.0001). In vivo LPS administration dose-dependently induced a period of hyporesponsiveness in the ex vivo LPS-induced cytokine release (IL-1β, IL-6 and TNF-α), with maximal hyporesponsiveness observed at 6 hours, lasting no longer than 12 hours. For IL-6 and IL-8, indications for immune cell priming were observed. We demonstrated that an in vivo LPS challenge, with LPS doses as low as 0.5 ng/kg, elicits a cytokine response that is clearly distinctive from baseline cytokine levels. This study expanded the knowledge about the dose-effect relationship of LPS-induced hyporesponsiveness. As such, the low-dose LPS challenge has been demonstrated to be a feasible methodological tool for future clinical studies exploring pharmacological or nutritional immune-modulating effects.

Pro-inflammatory cytokine and acute phase protein responses to low-dose lipopolysaccharide (LPS) challenge in pigs

AbstractThe objective of this study was to establish the pro-inflammatory cytokine and acute phase protein responses to low-dose lipopolysaccharide (LPS) challenge in pigs and to determine whether these immune parameters could also be measured in saliva. Possible gender differences in the acute phase reaction were also assessed. At 6 weeks of age, 24 male and 24 female pigs were injected intraperitoneally with a single dose of 0 or 5 μg/kg live weight (LW) of LPS fromEscherichia coli(treatment). Matched saliva and blood samples were taken at 0, 2, 4, 8, 12 or 24 h after treatment administration. Samples were analysed for concentrations of the pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin-1beta (IL-1β), the acute phase proteins C-reactive protein (CRP), serum amyloid A (SAA), haptoglobin (Hp), and cortisol. Low-dose LPS administration increased plasma levels of TNF-α (P<0·001), CRP (P<0·05) and SAA (P<0·05) but did not affect plasma concentrations of IL-1β or Hp (P>0·1). Treatment by time interactions showed that plasma levels of TNF-α and CRP in LPS-treated pigs peaked at 2 h (P<0·001) and 12 h (P<0·01), respectively. Low-dose LPS injection tended to increase plasma concentrations of cortisol (P=0·056) and the response to LPS differed between genders (P<0·05), with females showing higher cortisol responsiveness to the challenge (P<0·01). Males showed higher levels of both cytokines regardless of the treatment (P<0·05), probably due to the inhibition of cytokine synthesis by cortisol. Concentrations of both pro-inflammatory cytokines were consistently detectable in saliva and were present in higher concentrations than in plasma (P<0·001). Hence, plasma TNF-α, CRP and SAA are useful indicators of sub-acute inflammation/infection in pigs as simulated by a low-dose LPS challenge and gender differences exist in the pro-inflammatory cytokine response after a low dose of LPS.

Effects of surgical castration on the behavioural and physiological responses of weaned pigs

Surgical castration is an acute stressor that can affect the behaviour, endocrine and immune responses of pigs [1,2]. Therefore, it may impair the health and welfare of these animals. This could be of particular concern at weaning, which constitutes a severe nutritional, physical and psychological stressor often associated with increased disease susceptibility [3]. Thus, an experiment was carried out to evaluate the effect of surgical castration on postweaning behaviour and on the behavioural, endocrine and immune responses elicited by a low-dose lipopolysaccharide (LPS) challenge after weaning. At 5 days-ofage, 64 male piglets were randomly assigned to undergo surgical castration or were left untreated. Pigs were weaned at 28 days-of-age. Behaviour post-weaning and mixing was assessed during a 1-h period, during which agonistic interactions were recorded. One day post-weaning, pigs were injected with a single dose of 0 or 5 μg/kg of body weight (BW) of LPS from Escherichia coli. Sickness behaviour was studied by scan sampling every 5 minutes for 45 minutes at 0, 1, 2, 3, 4, 6 and 8 h after the challenge was initiated. Blood samples were taken at 0, 2, 12 and 24 h after injection and were analysed for plasma concentrations of tumor necrosis factor-alpha (TNF-α), interleukin 1-beta (IL-1β), C-reactive protein (CRP), serum amyloid A (SAA) and cortisol. Saliva samples were also taken when pigs were 3, 4, 5, 6 and 8 weeks-of-age for subsequent determination of salivary testosterone concentrations. Results showed that entire males were more aggressive than castrated pigs immediately after weaning (P < 0.05). Administration of LPS provoked behaviours characteristic of sickness including a reduction in general activity, as well as decreased eating and exploratory behaviours (P < 0.05). Significant treatment by challenge interactions showed that castration reduced the occurrence of sickness behaviours induced by LPS, such as depressed general activity (P < 0.01), anorexia (P < 0.01) and reduced exploratory behaviours (P < 0.05). LPS administration increased TNF-α levels (P < 0.05), with peak concentrations 2 h after injection (P < 0.01). CRP levels of LPStreated pigs were higher that saline-treated animals at 12 h (P < 0.05). LPS administration tended to increase plasma SAA levels (P < 0.1), but did not increase cortisol levels. Nonetheless, castration did not affect the response of pro-inflammatory cytokines, acute phase proteins and cortisol to the challenge. Concentrations of testosterone in saliva were higher in entire males (P < 0.001). Furthermore, salivary testosterone levels in entire males varied with age and were markedly elevated at 4 weeks-of-age (P < 0.001), which coincided with weaning. These results show that surgical castration reduces aggressiveness at weaning. It is likely that peak levels of testosterone are in part responsible for the higher frequency of agonistic encounters among entire male pigs [4]. In addition, castration affects the coping mechanisms of weaned pigs against a low-dose LPS challenge. It is also possible that entire males may be more efficient in overcoming the bacterial endotoxin challenge, taking into consideration the beneficial effects of sickness behaviour in the recovery from infection [5]. In conclusion, surgical castration reduces aggressiveness at weaning and also impairs the behavioural, but not the endocrine and immune responses elicited by low-dose LPS challenge in pigs. from Prevention of Boar Taint in Pig Production: The 19th Symposium of the Nordic Committee for Veterinary Scientific Cooperation Gardermoen, Norway. 21–22 November 2005

Acute endotoxin tolerance downregulates superoxide anion release by the perfused liver and isolated hepatic nonparenchymal cells

This work is based on the hypothesis that low-dose lipopolysaccharide (LPS) suppresses the stimulatory and priming effects of a subsequent high-dose endotoxin on the formation of toxic oxygen-derived radicals by the perfused liver and isolated hepatic nonparenchymal cells. Such effects may in turn contribute to hyposensitivity to the lethal effect of large doses of endotoxin. Male Sprague-Dawley rats received a nonlethal ("low-dose") intravenous injection of Escherichia coli LPS (0.5 mg/kg body weight) 12 to 120 hours before they were challenged by a "large dose" of endotoxin (10 mg/kg). Three hours after LPS challenge, the livers were perfused, and superoxide release was determined. Nonparenchymal cells were also isolated for the determination of superoxide anion formation in vitro. There was a low rate (0.14 +/- 0.1 nmol/min/g liver weight) of superoxide generated by the perfused livers from rats that received the low-dose LPS 1 to 5 days previously. Control livers generated less than 0.08 nmol superoxide. A high rate (1.3 +/- 0.1 nmol/min/g) of superoxide release was measured in the perfused liver 4 hours after treatment of previously untreated control rats with large-dose LPS. This was attenuated to 0.7 +/- 0.04 nmol/min/g by an injection of low-dose LPS before challenge. This attenuation was time dependent; it failed to manifest at 12, 24, or 120 hours after low-dose LPS. Isolated endothelial cells, Kupffer cells, and sequestered hepatic neutrophils from rats given a high-dose LPS also generated significant amounts of superoxide both in the presence or absence of agonists, i.e., phorbol myristate acetate or opsonized zymosan.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute endotoxin tolerance downregulates superoxide anion release by the perfused liver and isolated hepatic nonparenchymal cells

This work is based on the hypothesis that low-dose lipopolysaccharide (LPS) suppresses the stimulatory and priming effects of a subsequent high-dose endotoxin on the formation of toxic oxygen-derived radicals by the perfused liver and isolated hepatic nonparenchymal cells. Such effects may in turn contribute to hyposensitivity to the lethal effect of large doses of endotoxin. Male Sprague-Dawley rats received a nonlethal (“low-dose”) intravenous injection of Escherichia coli LPS (0.5 mg/kg body weight) 12 to 120 hours before they were challenged by a “large dose” of endotoxin (10 mg/kg). Three hours after LPS challenge, the livers were perfused, and superoxide release was determined. Nonparenchymal cells were also isolated for the determination of superoxide anion formation in vitro. There was a low rate (0.14 ± 0.1 nmol/min/g liver weight) of superoxide generated by the perfused livers from rats that received the low-dose LPS 1 to 5 days previously. Control livers generated less than 0.08 nmol superoxide. A high rate (1.3 ± 0.1 nmol/min/g) of superoxide release was measured in the perfused liver 4 hours after treatment of previously untreated control rats with large-dose LPS. This was attenuated to 0.7 ± 0.04 nmol/min/g by an injection of low-dose LPS before challenge. This attenuation was time dependent; it failed to manifest at 12, 24, or 120 hours after low-dose LPS. Isolated endothelial cells, Kupffer cells, and sequestered hepatic neutrophils from rats given a high-dose LPS also generated significant amounts of superoxide both in the presence or absence of agonists, i.e., phorbol myristate acetate or opsonized zymosan. Pretreatment of rats with the low dose of LPS 48 hours before the large dose attenuated the spontaneous and primed release of superoxide by isolated nonparenchymal cells. Serum transaminase activities were also reduced in these LPS-tolerant rats. The suppressed oxygen-derived radical formation by the liver and nonparenchymal cells during acute LPS tolerance was associated with down-regulation of tumor necrosis factor (TNF) release in vivo. TNF has been shown to stimulate and prime neutrophils and Kupffer cells for increased respiratory burst. These results suggest that suppression of free radical formation may contribute to the amelioration of hepatic injury during acute endotoxin tolerance.