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Keywords:

  • body temperature;
  • cytokines;
  • fever;
  • gastrointestinal motility;
  • prostaglandins;
  • sheep

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Animal preparation
  6. Myoelectric and temperature recordings
  7. Experimental procedure
  8. Drugs
  9. Statistical analysis
  10. Results
  11. Effects of LPS and hrTNF-α
  12. Influence of sTNFR and indomethacin
  13. Discussion
  14. Acknowledgments
  15. References

Cytokines are involved in fever and other symptoms of the acute phase response induced by endotoxins. The aim of this work was to study the involvement of central tumour necrosis factor-α (TNF-α) in the changes induced by lipopolysaccharide (LPS) on gastrointestinal (GI) motility in sheep. Body temperature and myoelectric activity of the antrum, duodenum and jejunum was recorded continuously. Intravenous (i.v.) administration of LPS (0.1 μg kg−1)-induced hyperthermia, decreased gastrointestinal myoelectric activity and increased the frequency of the migrating motor complex (MMC). These effects started 40–50 min after LPS and lasted for 6–7 h. TNF-α (50 and 100 ng kg−1) mimicked these effects when injected intracerebroventricularly (i.c.v.) but not i.v. Pretreatment with soluble recombinant TNF receptor (TNFR:Fc, 10 μg kg−1, i.c.v.) abolished the TNF-induced actions and reduced those evoked by LPS. Furthermore, the effects induced by either LPS or TNF were suppressed by prior i.c.v. injection of indomethacin (100 μg kg−1). In contrast, the i.v. injections of TNFR:Fc or indomethacin were ineffective. Our data suggest that LPS disturbs GI motility in sheep through a central pathway that involves TNF-α and prostaglandins sequentially.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Animal preparation
  6. Myoelectric and temperature recordings
  7. Experimental procedure
  8. Drugs
  9. Statistical analysis
  10. Results
  11. Effects of LPS and hrTNF-α
  12. Influence of sTNFR and indomethacin
  13. Discussion
  14. Acknowledgments
  15. References

Lipopolysaccharide (LPS) is a major component of the cell wall of Gram-negative bacteria and an important contributing factor to the changes associated with these infections. It induces circulatory disturbances and causes damage to numerous organs, including the central nervous system (CNS), heart, kidneys, gastrointestinal (GI) tract, lungs and liver. Consequently, exposure to this endotoxin is associated with a high mortality rate. Experimental endotoxaemia induces profound alterations in GI motility. Peripheral administration of LPS in several species inhibits motor activity of the gastric antrum and small intestine1–6 and disturbs the migrating motor complex (MMC) of the small intestine,1,2,4,6–8 whereas in the large intestine it stimulates colonic contractions.9,10 Furthermore, endotoxin inhibits gastric emptying11–13 and accelerates small intestinal and colonic transit, although a delay in intestinal transit has also been reported.7,9,10,12,14,15

Several cytokines are supposed to be implicated in LPS-induced GI motor disturbances as they mimic these alterations when administered peripherally. Intravenous (i.v.) interleukin-1β (IL-1β), central tumour necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) inhibit forestomach contractions in goats16,17 and IL-1β,18 IL-619 and TNF-α20 inhibit gastric emptying in rats. It has been reported that IL-1β can also modify GI motility by acting at CNS level. In rats, central administration of IL-1β inhibits gastric emptying,18 disrupts the postprandial motor profile of the small intestine, restores MMC pattern and stimulates caecocolonic contractions.21 In sheep, intracerebroventricular (i.c.v.) IL-1β decreases forestomach motility in a similar way to LPS, whereas i.c.v. injection of IL-1ra reduces the LPS-induced effect.22

Lipopolysaccharide and cytokines have been reported to alter digestive motility through the release of prostaglandins (PGs). Peripheral administration of the cyclooxygenase inhibitor indomethacin and of other non-steroidal anti-inflammatory drugs (NSAIDs), reduces GI motor alterations evoked by LPS in rats,8 piglets23 and goats24,25 and by IL-1α in goats,26 and completely prevents the inhibition of gastric emptying evoked by intracisternal IL-1β in rats.18 Although these studies do not establish whether PGs are released in the CNS or in the periphery, other results suggest a role for PGs in the CNS. Thus, i.c.v. pretreatment with indomethacin reduces the GI motor changes induced by intravenous (i.v.) LPS in sheep22 and by i.c.v. IL-1β in rats21 and sheep.22

To our knowledge, the only information available on the effects of TNF-α at the central level on GI motility has been carried out in anaesthetized rats and is restricted to the gastric area. Thus, Hermann et al.27 have recently shown that circulating TNF-α, released by LPS and acting within the brain stem dorsal vagal complex (DVC), inhibits the thyrotropin releasing hormone (TRH)-stimulated gastric motility. Thus, the aim of our work was to study the effect of TNF-α at the central level on the GI motility in conscious sheep and to evaluate the role of this cytokine in the digestive motor disturbances induced by endotoxin. We also determined whether central PGs are involved in these actions.

Animal preparation

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Animal preparation
  6. Myoelectric and temperature recordings
  7. Experimental procedure
  8. Drugs
  9. Statistical analysis
  10. Results
  11. Effects of LPS and hrTNF-α
  12. Influence of sTNFR and indomethacin
  13. Discussion
  14. Acknowledgments
  15. References

Animals were handled in accordance with the European Council Legislation 86/609/EEC on experimental animal protection. All experimental protocols were approved by the Ethical Committee of the University of Zaragoza. We used ewes that were 3–4 years old and weighed 40–50 kg. They were fasted for 24 h before surgical preparation for electromyography, according to a previously described technique.28 Under general anaesthesia with i.v. thiopentone sodium (20 mg kg−1; Pentothal, Abbott, Madrid, Spain), a right flank laparotomy was performed. Eight triplets of 120 μm nickel/chrome electrodes (Microfil Industries, Renens, Switzerland) were implanted in the muscular wall of the abomasal antrum (−5 cm from the pylorus), duodenum (40 cm from the pylorus) and proximal jejunum (0, 1, 2, 3, 4 and 5 m from the ligament of Treitz). In order to measure the body temperature, a thermistor probe (NTC type, code 10K3A1, Farnell, Barcelona, Spain) was placed into the peritoneal cavity. In addition, a stainless-steel cannula (length, 24 mm; diameter 2 mm) was inserted into the right lateral ventricle of the brain to perform i.c.v. administrations, using a previously described technique.29 For analgesia, flunixin meglumine (5 mg kg−1; Finadyne, Schering-Plough, Madrid, Spain) was administered intramuscularly for 3 days after surgery. The animals were housed in metabolism cages at controlled room temperature (15–20 °C) on a 12 h light–dark cycle and fed ad libitum with pelleted lucerne hay.

Myoelectric and temperature recordings

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Animal preparation
  6. Myoelectric and temperature recordings
  7. Experimental procedure
  8. Drugs
  9. Statistical analysis
  10. Results
  11. Effects of LPS and hrTNF-α
  12. Influence of sTNFR and indomethacin
  13. Discussion
  14. Acknowledgments
  15. References

Recording sessions began 1 week after surgery. Electrodes were connected to high-gain amplifiers (MT 8P; Lectromed, St Peter Jersey Channel Islands, UK). The amplified spiking activity was filtered by low-pass (50 Hz) and high-pass filters (10 Hz), to select net spike bursts. Simultaneously, a computer-based method (Datasystem EMG 4.0; Panlab, Barcelona, Spain) converted the analogue signal into digital values and stored them onto a computer hard disk with a sampling frequency of 100 samples per second per channel. The myoelectric activity was integrated as the sum of the absolute values of the signal amplitude minus the background value (5–10% of the maximal signal amplitude) over 1-min intervals as described previously.30 In order to simplify the presentation of the results, data for the jejunum are only shown at 2 m from the ligament of Treitz. Recordings were reproduced by a printer at an equivalent paper speed of 0.9 cm min−1. However, to analyse specific myoelectric events, the computer program allowed a recording expansion of up to 1.75 cm s−1. Intraperitoneal temperature was measured with a thermistor-based electronic thermometer. It was calibrated to give an initial output of 0 V at 35 °C with a sensitivity of 400 mV °C−1. Temperature was then recorded continuously on a potentiometric recorder (L6514; Linseis, Selb, Germany) at a paper speed of 6 cm h−1.

Experimental procedure

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Animal preparation
  6. Myoelectric and temperature recordings
  7. Experimental procedure
  8. Drugs
  9. Statistical analysis
  10. Results
  11. Effects of LPS and hrTNF-α
  12. Influence of sTNFR and indomethacin
  13. Discussion
  14. Acknowledgments
  15. References

Myoelectric activity and body temperature were monitored during a control period of at least 3 h. After this control period, injections began 20–30 min after a spontaneous duodenal phase III (i.e. the cyclic period of intense and regular spike activity).31 Recordings were continued for 24 h. In the first series of experiments, one of the following drugs was administered in a randomized order: LPS (0.1 μg kg−1, i.v.), human recombinant TNF-α (hrTNF-α, 25, 50 and 100 ng kg−1, i.c.v.) or hrTNF-α (100 ng kg−1, i.v.). During the second series of experiments, sheep received saline, LPS (0.1 μg kg−1, i.v.) or hrTNF-α (100 ng kg−1, i.c.v.), 15 min after an i.c.v. or i.v. administration of soluble TNF receptor (sTNFR) at a dose of 10 μg kg−1. In the third series of experiments, indomethacin (an inhibitor of cyclooxygenase) was injected i.c.v. or i.v. twice, 30 min before (100 μg kg−1) and 90 min after (100 μg kg−1) administration of saline, LPS (0.1 μg kg−1, i.v.) or hrTNF-α (100 ng kg−1, i.c.v.).

This dose of indomethacin i.c.v. was chosen because it blocked the inhibition of forestomach motility evoked by LPS (0.1 μg kg−1) in sheep.22 The dose of sTNFR was chosen according to its efficacy in preventing LPS-induced delayed rectal allodynia in rats.32 Each treatment was carried out in five sheep. In order to exclude diurnal variations in the studied parameters, all recordings started at 9:00 am. To minimize tachyphylaxis, injections of LPS or hrTNF-α were performed in each sheep at 1-week intervals.

Drugs

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Animal preparation
  6. Myoelectric and temperature recordings
  7. Experimental procedure
  8. Drugs
  9. Statistical analysis
  10. Results
  11. Effects of LPS and hrTNF-α
  12. Influence of sTNFR and indomethacin
  13. Discussion
  14. Acknowledgments
  15. References

Lipopolysaccharide (obtained from Escherichia coli serotype 0111:B4) and indomethacin were purchased from Sigma-Aldrich (Madrid, Spain), whereas hrTNF-α was obtained from Amersham Biosciences (Barcelona, Spain). Recombinant human dimeric TNF soluble receptor (rhTNF:Fc molecule p75, linked to the Fc portion of the human IgG1, sTNFR) was kindly provided by Dr Mickael B. Widmer (Immunex, Seattle, WA, USA).

Lipopolysaccharide and hrTNF-α were dissolved in water. sTNFR was initially dissolved in 25 mmol L−1 Tris/150 mmol L−1 NaCl pH 7.4 (1.45 mg mL−1) and indomethacin in a solution of 5% sodium bicarbonate (25 mg mL−1). They were then dissolved in water. Indomethacin was freshly prepared daily, stock solutions of LPS were stored at −20 °C, and hrTNF-α and sTNFR were stored at −80 °C. For i.v. or i.c.v. administrations, the stock solutions were finally dissolved in sterile saline (2 mL) or water (200 μL), respectively. They were injected as a bolus in the jugular vein or in the right lateral ventricle of the brain. Equivalent volumes of these vehicles were also injected in control experiments. Previous administration of these vehicles did not modify GI myoelectric activity.

Statistical analysis

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Animal preparation
  6. Myoelectric and temperature recordings
  7. Experimental procedure
  8. Drugs
  9. Statistical analysis
  10. Results
  11. Effects of LPS and hrTNF-α
  12. Influence of sTNFR and indomethacin
  13. Discussion
  14. Acknowledgments
  15. References

Data of integrated myoelectric activity were expressed as a percentage relative to the mean value of the phase II from the control period (3 h before drug administration). In order to simplify statistical comparisons, the mean of the data corresponding with phases I and II of the MMC in the control period was compared with the mean obtained in the equivalent phases after treatment (analysed in periods of 3 h). Changes in body temperature were expressed as the difference with the mean of the control period. The results are expressed as mean ± standard error of the mean (SEM) from five animals. A one-way analysis of variance (anova) was used to determine the significance of the overall variation in the data. A posterior SchefféF-test was used to analyse multiple comparisons between mean values. Differences with P < 0.05 were considered statistically significant.

Effects of LPS and hrTNF-α

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Animal preparation
  6. Myoelectric and temperature recordings
  7. Experimental procedure
  8. Drugs
  9. Statistical analysis
  10. Results
  11. Effects of LPS and hrTNF-α
  12. Influence of sTNFR and indomethacin
  13. Discussion
  14. Acknowledgments
  15. References

The i.v. injection of LPS (0.1 μg kg−1) induced a biphasic rise of body temperature for 6 h with peaks at 100 min (0.8 ± 0.2 °C) and 240 min (1.9 ± 0.2 °C). Simultaneously, the myoelectric activity of antrum was strongly reduced for 7 h, starting 47.8 ± 4.6 min after LPS administration. In addition, several periods of intense activity appeared in the duodenum and migrated down to the jejunum. Their duration and integrated activity were similar to those of phase III of the MMC recorded in the control period but they recurred at a higher rate. Duodenal and jejunal myoelectric activity was also smaller between these activity fronts than in the control period. Intestinal motility was restored 6 h after LPS (Figs 1 and 2).

On the other hand, the administration of i.c.v. hrTNF-α at 50 and 100 ng kg−1 mimicked the effects of i.v. LPS in a dose-dependent manner (Figs 3 and 4). The dose of 25 ng kg−1 did not modify any of the studied parameters while the highest doses of hrTNF-α (50 and 100 ng kg−1) caused fever, decreased GI myoelectric activity and increased MMC frequency. Compared with the actions induced by endotoxin, those evoked by hrTNF-α began later (80–90 min after injection) and were longer-lasting (12–13 h) (Fig. 3). At 100 ng kg−1, the cytokine-evoked responses in body temperature were monophasic, with a peak at 360 min (1.7 ± 0.1 °C). In contrast to i.c.v. administration, hrTNF-α injected i.v. at the highest dose (100 ng kg−1) did not alter body temperature or the GI motility (Fig. 4).

Influence of sTNFR and indomethacin

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Animal preparation
  6. Myoelectric and temperature recordings
  7. Experimental procedure
  8. Drugs
  9. Statistical analysis
  10. Results
  11. Effects of LPS and hrTNF-α
  12. Influence of sTNFR and indomethacin
  13. Discussion
  14. Acknowledgments
  15. References

The i.c.v. or i.v. administration of sTNFR (10 μg kg−1) or indomethacin (two doses of 100 μg kg−1 separated by 120 min) did not modify per se any of the studied parameters. When sTNFR (10 μg kg−1) was injected i.c.v. 15 min before hrTNF-α (100 ng kg−1, i.c.v.) it completely blocked the overall effects induced by the cytokine (Fig. 5). In addition, when injected i.c.v. 15 min before LPS (0.1 μg kg−1, i.v.), sTNFR (10 μg kg−1) reduced the mean increase in body temperature by 34% and the increase in the MMC frequency by 40%. Similarly, it also reverted the inhibition of myoelectric activity by 57% in the antrum, by 29% in the duodenum and by 42% in the jejunum (Figs 6 and 7). On the other hand, indomethacin injected i.c.v. twice, 30 min before (100 μg kg−1) and 90 min after (100 μg kg−1) administration of LPS (0.1 μg kg−1, i.v.) or hrTNF-α (100 ng kg−1, i.c.v.) suppressed both the endotoxin- and the cytokine-induced actions (Figs 5 and 7). In contrast to their i.c.v. administration, sTNFR or indomethacin injected i.v., using the same protocol than i.c.v., did not modify the response to either LPS (0.1 μg kg−1, i.v.) or hrTNF-α (100 ng kg−1, i.c.v.) (Figs 5 and 7).

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Animal preparation
  6. Myoelectric and temperature recordings
  7. Experimental procedure
  8. Drugs
  9. Statistical analysis
  10. Results
  11. Effects of LPS and hrTNF-α
  12. Influence of sTNFR and indomethacin
  13. Discussion
  14. Acknowledgments
  15. References

Our results show that i.c.v. administration of TNF-α-induced hyperthermia, decreased GI myoelectric activity and increased MMC frequency in sheep, alterations that closely resemble those evoked by the i.v. injection of LPS. In addition, the endotoxin-induced effects were reduced by the central administration of the soluble TNF receptor p75. Similarly, the actions evoked by both LPS or TNF-α were suppressed by indomethacin, a cyclooxygenase inhibitor. These data suggest that LPS induces fever and disturbs GI motor activity, at least in part, through the central release of TNF-α and the subsequent production of PGs.

Proinflammatory cytokines such as IL-1β, IL-6 and TNF-α have already been suggested to participate to the deleterious effects of LPS. Indeed, peripheral injection of LPS increases IL-1, TNF-α, and IL-6 concentrations in plasma and in the hypothalamus.33–36 In rabbits, LPS induces expression of IL-1β mRNA in macrophages of the organum vasculosum laminae terminalis (OVLT), a circumventricular organ that lacks a blood–brain barrier, located in the anterior wall of the third ventricle, in the centre of the preoptic-anterior hypothalamus (POA).37 Cytokines can modify body temperature by exerting their effects on the CNS. In fact, IL-1α, IL-1β, IL-6, TNF and IFN causes dose-dependent increases in body temperature when injected into the POA, the brain region that contains the primary thermoregulatory controller38 and the probable site of action of endogenous pyrogens.39 It has been proposed that LPS induces fever by the production of IL-6 in the anterior hypothalamus in response to a local increase in IL-1β.35

The role of TNF in LPS-induced hyperthermia is more complex. Systemic administration of LPS induces TNF-α mRNA in perivascular cells and neurones in circumventricular organs including the OVLT, median eminence and area postrema.40 The i.c.v. administration of TNF-α induces fever in rats41 and in rabbits42 and i.v. injection of monoclonal antibody to TNF in rabbits reduces the LPS-induced biphasic fever.43 These results suggest that LPS induces fever through the release of TNF-α at the central level. In contrast, intraperitoneal administration of non-pyrogenic doses of TNF in rats abolishes fever induced by LPS whereas i.c.v. or intrahypothalamic infusion is ineffective.44 In addition, i.v. TNF antiserum45 or intraperitonial (i.p.) sTNFR44 increases the LPS thermogenic response. Thus, it has also been proposed that, at physiological levels, TNF acts outside the CNS as an endogenous antipyretic.44,45

In our study, fever and GI motor alterations induced by i.v. LPS were reproduced by i.c.v. administration of TNF-α at doses that were ineffective when administered i.v. In addition, the LPS-evoked effects were reduced by prior i.c.v. but not i.v. injection of sTNFR, suggesting a central rather than a peripheral site of action for TNF-α. However, a dose of sTNFR:Fc that completely blocked the effects of i.c.v. administration of TNF-α, only partially reduced those evoked by LPS. This result suggests that other cytokines might be involved. Indeed, the i.c.v. injection of IL-1β in sheep also mimics fever and GI motor disturbances evoked by LPS.22,46 Furthermore, these LPS-provoked alterations are reduced but not suppressed by i.c.v. injection of IL-1 receptor antagonist (IL-1ra).22 Thus, among cytokines, at least both IL-1β and TNF-α could mediate the digestive motor disturbances induced by LPS in this species. Furthermore, the fact that the effects evoked by IL-1β are not modified by i.c.v. sTNFR:Fc46 indicates that IL-1β does not act through the release of central TNF and supports the view that these cytokines are acting in the CNS through different pathways to mediate fever and digestive motor disturbances induced by LPS in sheep.

In addition to their role at the central level, TNF-α and IL-1β acting outside the CNS may also mediate the LPS-evoked effects. Thus, i.v. administration of IL-1β and TNF-α in goats inhibits forestomach motility and increases body temperature in a similar way to LPS,16,17 although the doses required to evoke these effects are 20–40 times higher than the i.c.v. doses used in our studies in sheep. On the other hand, LPS given in vivo, in addition to activating the intestinal muscularis macrophage network,47 it causes a decrease in the intestinal smooth muscle contractility measured in vitro,47–49 an effect that is prevented by peripheral injection of sTNFR type I (p55) plus IL-1ra.48

The effects induced by central TNF-α in our study lasted longer than those evoked by LPS. Similar findings were observed with IL-1β in sheep.22 Because LPS also releases endogenous antipyretics,44 they could limit the duration of the endotoxin-induced actions. In sheep, the effects induced by LPS or cytokines on body temperature and GI motility were simultaneous, suggesting a common pathway. The inhibition of forestomach motility induced by LPS in goats is not primarily due to hyperthermia because it also occurs while LPS-induced fever is completely suppressed by NSAID flurbiprofen.24 Similarly, we observed in some cases after LPS or TNF-α, myoelectric antral activity remained inhibited for a variable time when body temperature had returned to control values.

Among the mediators implicated in the brain pathways stimulated by endotoxin and cytokines, PGs have been reported to play a key role. In this way, forestomach hypomotility induced by LPS or IL-1β in sheep is mediated through central release of PGs.22 Our results show that the effects induced by either systemic LPS or central TNF-α are suppressed by i.c.v. but not i.v. administration of indomethacin (an agent that inhibits PG synthesis). These results suggest that systemic administration of LPS increases body temperature and disturbs GI motility in sheep through a central pathway involving IL-1β and TNF-α, that in turn act through a release of PGs in the CNS.

Central or peripheral injection of cyclooxygenase inhibitors almost completely abolishes the thermogenic and pyrogenic actions of exogenously administered IL-1α, IL-1β, IL-6, TNF-α and IFN.50,51 Thus, fever has been ascribed to the synthesis of eicosanoids within the brain, and particularly to the release of PGE2.52–54 The OVLT seems to mediate the LPS-induced fever because it is reduced when this area is ablated.55 Similarly, it has been suggested that the release of PGE2 in the interstitial fluid of the OVLT-medial POA may be important to transduce a systemic immune signal, such as elevations of circulating IL-1β, into activated CNS events as induction of fever.56

Prostaglandins may also participate in GI motor disturbances induced by endotoxin or its mediators. The i.v. pretreatment with NSAID reduces hyperthermia and ruminal stasis induced by i.v. administrations of LPS24,25 and IL-1α26 in goats. Similarly, the disruption of the intestinal MMC cycle induced by i.v. LPS or i.p. platelet activating factor (PAF) in fasted rats is reduced by peripheral administration of both indomethacin or the selective PGE2 EP1 receptor antagonist SC 19220.8 In the same way, i.p. indomethacin completely prevents the inhibition of gastric emptying evoked by intracisternal IL-1β in rats.18 In piglets, i.v. pretreatment with indomethacin reduces fever and GI hypomotility evoked by i.v. LPS.23 As PGs act as local regulatory agents that modulate GI motility, these results could be because LPS-induced GI alterations are mediated at least in part through the release of PGs at the peripheral level. However a role for PGs in the CNS has also been proposed because the i.c.v. administration of indomethacin, at doses 25–50-fold lower than peripherally, reduces the reappearance of the MMC pattern in the small intestine elicited by i.c.v. IL-1β in fed rats.21 In our study in sheep indomethacin, i.c.v. injected at these low doses, completely prevented fever and GI motor alterations induced by i.v. LPS and i.c.v. TNF-α in a similar way to previously reported for IL-1β.22 However, the i.v. administration of indomethacin is ineffective, probably because its concentration is not high enough to supress PG synthesis at the central level. Similarly, i.c.v. administration of PGE2 alters GI motility at doses that are ineffective when given peripherally. Thus, it restores the MMC pattern in fed rats and reduces the duration of jejunal postprandial motor state in fed dogs.57 In ruminants, i.c.v. injection of PGE2 mimics the LPS- and the cytokine-induced actions. It inhibits extrinsic ruminal contractions in goats58 whereas in sheep it decreases myoelectric activity of gastric antrum and small intestine and increases MMC frequency.46 All of the results suggest that LPS and its mediators alter digestive motility through the release of PGs at the central level.

The central site of action of cytokines and PGs in the LPS-induced GI motor alterations in sheep is unknown. One possibility is that these cytokines could act in the brain stem dorsal vagal complex (DVC). Thus, it has been shown that microinjections of IL-1β59 and TNF-α60 into the DVC inhibit vagally stimulated gastric motility in rats. Another possibility is that IL-1β and TNF-α, produced in structures of the brain such as the hypothalamus or surroundings (e.g., OVLT) could stimulate the release of PGs in these areas. These PGs in turn activate different pathways in the hypothalamus to induce fever and to disturb GI motility. In this way, IL-1β microinjected into the medial preoptic area, anterior hypothalamus and paraventricular nucleus inhibits gastric acid secretion in rats, an effect that is mimicked by microinjection of PGE2 into the preoptic area.61 Thus, it has been suggested that IL-1β could also inhibit gastric emptying acting at hypothalamic sites and through the release of PGs.18

In conclusion, LPS induces fever, decreases GI myoelectric activity and increases MMC frequency in sheep through a central pathway that involves TNF-α and the subsequent release of PGs.

Acknowledgments

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Animal preparation
  6. Myoelectric and temperature recordings
  7. Experimental procedure
  8. Drugs
  9. Statistical analysis
  10. Results
  11. Effects of LPS and hrTNF-α
  12. Influence of sTNFR and indomethacin
  13. Discussion
  14. Acknowledgments
  15. References

The authors are grateful to Dr J. I. Bonafonte for technical assistance. This research was supported by grants from Dirección General de Investigación (DGI, AGL2000-1228), Comisión Interministerial de Ciencia y Tecnología (CICYT, AGF97-0922) and University of Zaragoza (UZ00-BIO-02). We are also grateful to Ministerio de Educación y Cultura (MEC) and Diputación General de Aragón (DGA) for the fellowships for of E. Guerrero-Lindner and M. Castro, respectively.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Animal preparation
  6. Myoelectric and temperature recordings
  7. Experimental procedure
  8. Drugs
  9. Statistical analysis
  10. Results
  11. Effects of LPS and hrTNF-α
  12. Influence of sTNFR and indomethacin
  13. Discussion
  14. Acknowledgments
  15. References
  • 1
    Cullen JJ, Caropreso DK, Hemann LL, Hinkhouse M, Conklin JL, Ephgrave KS. Pathophysiology of adynamic ileus. Dig Dis Sci 1997; 42: 7317.
  • 2
    Fioramonti J, Buéno L, Du C. Alterations of digestive motility by Escherichia coli endotoxin in rabbits mediated through central opiate receptors. In: RomanC, ed. Gastrointestinal Motility. Lancaster: MTP Press, 1984: 54956.
  • 3
    De Saedeleer V, Wechsung E, Houvenaghel A. Endotoxin in the conscious piglet: its effects on some general and gastrointestinal myoelectrical parameters. Vet Res Commun 1991; 15: 22738.
  • 4
    Li JX, Oliver JR, Philips JB III. Endotoxin induces biphasic alterations in small intestinal myoelectric activity in fasted newborn piglets. Pediatr Res 1996; 40: 8226.
  • 5
    Wechsung E, Houvenaghel A. Involvement of platelet activating factor in the endotoxin-induced effects on gastrointestinal electrical activity and some haematological parameters in the conscious miniature pig. J Vet Pharmacol Ther 2000; 23: 3237.
  • 6
    King JN, Gerring EL. The action of low dose endotoxin on equine bowel motility. Equine Vet J 1991; 23: 1117.
  • 7
    Hellström PM, Al-Saffar A, Ljung T, Theodorsson E. Endotoxin actions on myoelectric activity, transit, and neuropeptides in the gut. Role of nitric oxide. Dig Dis Sci 1997; 42: 164051.
  • 8
    Pons L, Droy-Lefaix MT, Braquet P, Buéno L. Involvement of platelet-activating factor (PAF) in endotoxin-induced intestinal motor disturbances in rats. Life Sci 1989; 45: 53341.
  • 9
    Pons L, Droy-Lefaix MT, Buéno L. Role of platelet-activating factor (PAF) and prostaglandins in colonic motor and secretory disturbances induced by Escherichia coli endotoxin in conscious rats. Prostaglandins 1994; 47: 12336.
  • 10
    Spates ST, Cullen JJ, Ephgrave KS, Hinkhouse MM. Effect of endotoxin on canine colonic motility and transit. J Gastrointest Surg 1998; 2: 3918.
  • 11
    van Miert ASJPAM, van Duin CTM. Endotoxin-induced inhibition of gastric emptying rate in the rat. The effect of repeated administration and the influence of some antipyretic agents. Arch Int Pharmacodyn Ther 1980; 246: 1927.
  • 12
    Wirthlin DJ, Cullen JJ, Spates ST et al. Gastrointestinal transit during endotoxemia: the role of nitric oxide. J Surg Res 1996; 60: 30711.
  • 13
    Cullen JJ, Caropreso DK, Ephgrave KS. Effect of endotoxin on canine gastrointestinal motility and transit. J Surg Res 1995; 58: 9095.
  • 14
    Ceregrzyn M, Kamata T, Yajima T, Kuwahara A. Biphasic alterations in gastrointestinal transit following endotoxaemia in mice. Neurogastroenterol Motil 2001; 13: 60513.
  • 15
    De Winter BY, Bredenoord AJ, De Man JG, Moreels TG, Herman AG, Pelckmans PA. Effect of inhibition of inducible nitric oxide synthase and guanylyl cyclase on endotoxin-induced delay in gastric emptying and intestinal transit in mice. Shock 2002; 18: 12531.
  • 16
    van Miert ASJPAM, Kaya F, van Duin CTM. Changes in food intake and forestomach motility of dwarf goats by recombinant bovine cytokines (IL-1ß, IL-2) and IFN-γ. Physiol Behav 1992; 52: 85964.
  • 17
    van Miert ASJPAM, van Duin CTM, Wensing T. Fever and acute phase response induced in dwarf goats by endotoxin and bovine and human recombinant tumour necrosis factor alpha. J vet Pharmacol Ther 1992; 15: 33242.
  • 18
    Süto G, Király A, Taché Y. Interleukin 1ß inhibits gastric emptying in rats: mediation through prostaglandin and corticotropin-releasing factor. Gastroenterology 1994; 106: 156875.
  • 19
    McCarthy DO. Tumor necrosis factor alpha and interleukin-6 have differential effects on food intake and gastric emptying in fasted rats. Res Nurs Health 2000; 23: 2228.
  • 20
    Arbós J, López-Soriano FJ, Carbó N, Argilés JM. Effects of tumour necrosis factor-alpha (cachectin) on glucose metabolism in the rat. Intestinal absorption and isolated enterocyte metabolism. Mol Cell Biochem 1992; 112: 5359.
  • 21
    Fargeas MJ, Fioramonti J, Buéno L. Central action of interleukin 1ß on intestinal motility in rats: mediation by two mechanisms. Gastroenterology 1993; 104: 37783.
  • 22
    Plaza MA, Fioramonti J, Buéno L. Role of central interleukin-1ß in gastrointestinal motor disturbances induced by lipopolysaccharide in sheep. Dig Dis Sci 1997; 42: 24250.
  • 23
    De Saedeleer V, Wechsung E, Houvenaghel A. Influence of indomethacin on endotoxin-induced changes in gastrointestinal myoelectrical activity and some haematological and clinical parameters in the conscious piglet. Vet Res Commun 1992; 16: 5967.
  • 24
    van Miert ASJPAM, van der Wal-Komproe LE, van Duin CTM. Effects of antipyretic agents on fever and ruminal stasis induced by endotoxins in conscious goats. Arch Int Pharmacodyn Ther 1977; 225: 3950.
  • 25
    Veenendaal GH, Woutersen-van Nijnanten FMA, van Duin CTM, van Miert ASJPAM. Role of circulating prostaglandins in the genesis of pyrogen (endotoxin)-induced ruminal stasis in conscious goats. J Vet Pharmacol Ther 1980; 3: 5968.
  • 26
    van Miert ASJPAM, van Duin CTM, Wensing T. Effects of flurbiprofen on recombinant human IL-1α-induced fever and associated clinical, haematological and blood biochemical changes in the dwarf goat. Vet Q 1994; 16: 16.
  • 27
    Hermann GE, Tovar CA, Rogers RC. LPS-induced suppression of gastric motility relieved by TNFR:Fc construct in dorsal vagal complex. Am J Physiol 2002; 283: G6349.
  • 28
    Ruckebusch Y. The electrical activity of the digestive tract of the sheep as an indication of the mechanical events in various regions. J Physiol 1970; 210: 85782.
  • 29
    Buéno L, Sorraing JM, Fioramonti J. Influence of dopamine on rumino-reticular motility and rumination in sheep. J Vet Pharmacol Ther 1983; 6: 9398.
  • 30
    Plaza MA, Arruebo MP, Sopena J, Bonafonte JI, Murillo MD. Myoelectrical activity of the gastrointestinal tract in sheep analysed by computer. Res Vet Sci 1996; 60: 5560.
  • 31
    Szurszewski JH. A migrating electric complex of the canine small intestine. Am J Physiol 1969; 217: 175763.
  • 32
    Coelho AM, Fioramonti J, Buéno L. Brain interleukin-1ß and tumor necrosis factor-α are involved in lipopolysaccharide-induced delayed rectal allodinia in awake rats. Brain Res Bull 2000; 52: 22328.
  • 33
    Jansky L, Vybíral S, Pospísilová D et al. Production of systemic and hypothalamic cytokines during the early phase of endotoxin fever. Neuroendocrinology 1995; 62: 5561.
  • 34
    Klir JJ, Roth J, Szelényi Z, McClellan JL, Kluger MJ. Role of hypothalamic interleukin-6 and tumor necrosis factor-α in LPS fever in rat. Am J Physiol 1993; 265: R51217.
  • 35
    Klir JJ, McClellan JL, Kluger MJ. Interleukin-1ß causes the increase in anterior hypothalamic interleukin-6 during LPS-induced fever in rats. Am J Physiol 1994; 266: R18458.
  • 36
    Del Rey A, Randolf A, Pitossi F, Rogausch H, Besedovsky HO. Not all peripheral immune stimuli that activate the HPA axis induce proinflammatory cytokine gene expression in the hypothalamus. Ann N Y Acad Sci 2000; 917: 16974.
  • 37
    Nakamori T, Morimoto A, Yamaguchi K, Watanabe T, Murakami N. Interleukin-1ß production in the rabbit brain during endotoxin-induced fever. J Physiol 1994; 476: 17786.
  • 38
    Blatteis CM. The pyrogenic action of cytokines. In: RothwellNJ, DantzerRD, eds. Interleukin-1 in the Brain. Oxford: Pergamon Press, 1992: 2749.
  • 39
    Cooper KE, Cranston WI, Honour AM. Observation on the site and mode of action of pyrogens in the rabbit brain. J Physiol 1967; 191: 32537.
  • 40
    Breder CD, Hazuka C, Ghayur T et al. Regional induction of tumor necrosis factor α expression in the mouse brain after systemic lipopolysaccharide administration. Proc Natl Acad Sci USA 1994; 91: 113937.
  • 41
    Rothwell NJ. Central effects of TNFα on thermogenesis and fever in the rat. Biosci Rep 1988; 8: 34552.
  • 42
    Watanabe M. Characteristics of TNFα - and TNFß -induced fever in the rabbit. Jpn J Physiol 1992; 42: 10116.
  • 43
    Kawasaki H, Moriyama M, Ohtani Y, Naitoh M, Tanaka A, Nariuchi H. Analysis of endotoxin fever in rabbits by using a monoclonal antibody to tumor necrosis factor (cachectin). Infect Immun 1989; 57: 31315.
  • 44
    Klir JJ, McClellan JL, Kozak W, Szelényi Z, Wong GHW, Kluger MJ. Systemic but not central administration of tumor necrosis factor-α attenuates LPS-induced fever in rats. Am J Physiol 1995; 268: R4806.
  • 45
    Long NC, Otterness I, Kunkel SL, Vander AJ, Kluger MJ. Roles of interleukin 1ß and tumor necrosis factor in lipopolysaccharide fever in rats. Am J Physiol 1990; 259: R7248.
  • 46
    Guerrero-Lindner E, Castro M, Muñoz JM et al. Role of central TNF alpha in the gastrointestinal motor disturbances evoked by lipopolisaccharide (LPS) in sheep. Neurogastroenterol Motil 2002; 14: 594 (Abstract).
  • 47
    Eskandari MK, Kalff JC, Billiar TR, Lee KKW, Bauer AJ. Lipopolysaccharide activates the muscularis macrophage network and suppresses circular smooth muscle activity. Am J Physiol 1997; 273: G72734.
  • 48
    Lodato RF, Khan AR, Zembowicz MJ et al. Roles of IL-1 and TNF in the decreased ileal muscle contractility induced by lipopolysaccharide. Am J Physiol 1999; 276: G135662.
  • 49
    Rebollar E, Arruebo MP, Plaza MA, Murillo MD. Effect of lipopolysaccharide on rabbit small intestine muscle contractility in vitro: role of prostaglandins. Neurogastroenterol Motil 2002; 14: 63342.
  • 50
    Rothwell NJ. Functions and mechanisms of interleukin 1 in the brain. Trends Pharmacol Sci 1991; 12: 4306.
  • 51
    Rothwell NJ. Mechanisms of the pyrogenic actions of cytokines. Eur Cytokine Netw 1990; 1: 21113.
  • 52
    Blatteis CM. Neural mechanisms in the pyrogenic and acute-phase responses to interleukin-1. Int J Neurosci 1988; 38: 22332.
  • 53
    Coceani F, Lees J, Bishai I. Further evidence implicating prostaglandin E2 in the genesis of pyrogen fever. Am J Physiol 1988; 254: R4639.
  • 54
    Yamagata K, Matsumura K, Inoue W et al. Coexpression of microsomal-type prostaglandin E synthase with cyclooxygenase-2 in brain endothelial cells of rats during endotoxin-induced fever. J Neurosci 2001; 21: 266977.
  • 55
    Blatteis CM, Hales JR, McKinley MJ, Fawcett AA. Role of the anteroventral third ventricle region in fever in sheep. Can J Physiol Pharmacol 1987; 65: 125560.
  • 56
    Gottschall PE, Komaki G, Arimura A. Interleukin-1ß activation of the central nervous system. In: RothwellNJ, DantzerRD, eds. Interleukin-1 in the Brain. Oxford: Pergamon Press, 1992: 2749.
  • 57
    Buéno L, Fargeas MJ, Fioramonti J, Primi MP. Central control of intestinal motility by prostaglandins: a mediator of the actions of several peptides in rats and dogs. Gastroenterology 1985; 88: 188894.
  • 58
    van Miert ASJPAM , van Duin CTM , Woutersen-van Nijnanten FMA. Effect of intracerebroventricular injection of PGE2 and 5HT on body temperature, heart rate and rumen motility of conscious goats. Eur J Pharmacol 1983; 92: 1436.
  • 59
    Morrow NS, Quinonez G, Weiner H, Taché Y, Garrick T. Interleukin-1ß in the dorsal vagal complex inhibits TRH analogue-induced stimulation of gastric contractility. Am J Physiol 1995; 269: G196202.
  • 60
    Hermann GE, Rogers RC. Tumor necrosis factor-alpha in the dorsal vagal complex suppresses gastric motility. Neuroimmunomodulation 1995; 2: 7481.
  • 61
    Saperas E, Yang H, Taché Y. Interleukin-1ß acts at hypothalamic sites to inhibit gastric acid secretion in rats. Am J Physiol 1992; 263: G41418.