Intracerebroventricular injection of tumor necrosis factor-alpha induces thermal hyperalgesia in rats

To investigate the role of tumor necrosis factor-alpha (TNF-alpha) in the brain in nociception, we injected recombinant human TNF-alpha (rhTNF-alpha; 1 pg-10 ng/rat) into the lateral cerebroventricle (LVC) in rats and observed the changes in paw withdrawal latency to radiant heat by using the plantar test for 90 min after injection. LCV injections of TNF-alpha at doses of 10 pg, 100 pg and 1 ng reduced paw withdrawal latency, showing a maximal response at a dose of 10 pg which peaked 60 min after injection. TNF-alpha at doses of 1 pg and 10 ng had no effect on nociception during the test period. The TNF-alpha (10 pg)-induced reduction in paw withdrawal latency was blocked by simultaneous injection of diclofenac (1 ng), a cyclooxygenase inhibitor, or interleukin-1 receptor antagonist (IL-1 ra, 10 ng). LCV injection of neither diclofenac (1 ng) nor IL-1 ra (10 ng) had any effect on nociception by itself. The results suggest that TNF-alpha in the brain induces thermal hyperalgesia and that the brain TNF-alpha-induced hyperalgesia is mediated by the central action of interleukin-1 and activation of the cyclooxygenase pathway of the arachidonate.     

Interleukin-1 beta induced-desArg9bradykinin-mediated thermal hyperalgesia in the rat

The induction of desArg9Bk-mediated thermal hyperalgesia has been studied in the rat. Intraplantar injections of interleukin-1 beta, (IL-1 beta, 1-100 Units, U) produced a 30-40% decrease in withdrawal latency to noxious heat which lasted for up to 24 hr in the treated paw. IL-1 beta-induced thermal hyperalgesia was also present in the contralateral paw for up to 1 hr following IL-1 beta injection. Intraplantar tumour necrosis factor-alpha (TNF alpha, 500 U) also reduced the withdrawal latency in the u.v.-treated paw with recovery by 18 hr but with no contralateral hyperalgesia. Forty-eight hr after IL-1 beta but not after TNF alpha administration, desArg9Bk (10 nmol/kg i.v.) reduced the withdrawal latency in both the ipsi- and contra-lateral paws by 30-49%. In naive animals, desArg9Bk was without effect. These data suggest that, in the rat, IL-1 beta but not TNF alpha can lead to the induction of bradykinin B1 receptors mediating thermal hyperalgesia.     

The effect of central angiotensin II receptor blockade on interleukin-1beta- and prostaglandin E-induced fevers in rats: possible involvement of brain angiotensin II receptor in fever induction

We investigated the role of the brain angiotensin II (Ang II) receptor subtypes AT1 and AT2 in the development of fever induced in freely moving rats by administration of interleukin-1beta (IL-1beta) or prostaglandin E2 (PGE2). Intraperitoneal (i.p.) injection of IL-1beta (2 microg/kg) induced a marked fever of rapid onset. Intracerebroventricular (i.c.v.) administration, immediately before IL-1beta injection, of a selective AT2 receptor antagonist, CGP42112A (5 or 20 microg), reduced the fever in a dose-related manner. Rats given an i.c.v. injection of PGE2 (200 ng) developed a monophasic fever response that was attenuated by i.c.v. treatment with CGP42112A (10 or 20 microg) in a dose-related manner. The IL-1beta (2 microg/kg i.p.)- and PGE2 (200 ng i.c.v.)-induced fevers were unchanged by the selective AT1 receptor antagonist losartan (60 microg i.c.v.). Treatment with exogenous Ang II (100 ng i.c.v.), which itself had no effect on resting body temperature, resulted in an enhancement of the PGE2 (50 ng i.c.v.)-induced fever. The administration of CGP42112A (2 and 5 microg) into the rostral hypothalamus (preoptic/anterior hypothalamic region) reduced fevers induced by IL-1beta (2 microg/kg i.p.) or intrahypothalamic (i.h.) PGE2 (100 ng). Moreover, i.h. injection of Ang II (25 ng) augmented the PGE2 (25 ng i.h.)-induced fever. Finally, the i.h. administration, 15 min before i.h. PGE2 (100 ng), of the angiotensin-converting enzyme (ACE) inhibitor lisinopril (5 and 10 microg) attenuated the PGE2-induced fever. These results suggest that brain AT2 receptors contribute to the induction of such febrile responses in rats.     

Modulation of kinin B1 but not B2 receptors-mediated rat paw edema by IL-1beta and TNFalpha

The modulatory effects of IL-1beta and TNF alpha on the rat paw edema induced by B1 agonists have been analyzed. In naive rats, i.d. injection of B1 agonists, des-Arg9-bradykinin and des-Arg10-kallidin (up to 300 nmol), causes a minimal increase in paw volume, while the B2 agonist tyrosine8-bradykinin (0.3-10 nmol) induces graded paw edema. The injection of des-Arg9-bradykinin (10-100) nmol or des-Arg10-kallidin (1-100 nmol), in paws pre-treated with IL-1beta or TNF alpha (both 5 ng/paw; 60 and 30 min prior, respectively), caused a graded edema formation. The edemas induced by des-Arg9-bradykinin (100 nmol) were evident at 15 min, reaching the maximum 60 and 30 min after treatment with IL-1beta (0.64 +/- 0.06 ml) or TNF alpha (0.47 +/- 0.05 ml), respectively, being reduced at 360 min. The B1 antagonist des-Arg9-NPC 17731 (1-30 nmol), but not the B2 antagonist Hoe 140 (10 nmol), produced marked inhibition of des-Arg9-bradykinin-induced paw edema. Dexamethasone (0.5 mg/kg, s.c., 4 h) or cycloheximide (1.5 mg/kg, s.c., 6 h) significantly prevented the edema caused by des-Arg9-bradykinin (100 nmol) in rats treated with IL-1beta (81 +/- 5% and 59 +/- 3%) or TNF alpha (78 +/- 4% and 43 +/- 2%). Indomethacin (2 mg/kg, i.p.) or meloxicam (3 mg/kg, i.p.), 1 h prior, significantly reduced the edema induced by des-Arg9-bradykinin (100 nmol) in IL-1beta (40 +/- 6% and 69 +/- 8%) or TNF alpha (43 +/- 3% and 53 +/- 9%) treated rats. It is suggested that i.d. injection of the IL-1beta or TNF alpha, produced up-regulation of B1 receptor-mediated paw edema, being this effect sensitive to dexamethasone and cycloheximide and to cyclo-oxygenase pathway.     

An electrophysiological study on the autonomic innervation of the mesenteric lymph node in the rat

Splanchnic innervation of the mesenteric lymph node was studied by means of electrophysiological technique in the rat. The effect of intravenous (i.v.) injection of recombinant human interleukin-1beta (rhIL-1beta) on the activity of efferent nerve fibers innervating the mesenteric lymph node was observed in the urethane anesthetized rat. An i.v. injection of 10 ng rhIL-1beta caused a gradual increase in efferent activity which lasted longer than 90 min. Dose related responses were observed at doses of 1, 10 and 100 ng. The least effective dose was about 10 ng. The conduction velocities estimated in mesenteric nerve fibers to the lymph node distributed in the range of 1.9-0.9 m/s, and the mean velocity was 1.39+/-0.34 m/s (n = 5). These observations implicate the involvement in the neural modulation of immune function of the mesenteric lymph node.     

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The effect of various doses of intraplantar thymulin injection, on nociceptive thresholds, in the hind paw of rats was assessed using different pain tests. As little as 0.5 ng thymulin resulted in localized mechanical hyperalgesia as assessed by the paw pressure test and thermal hyperalgesia as assessed by the paw immersion, hot plate, and tail flick tests. The highest dose of thymulin (10 ng) reduced both paw pressure and paw immersion latencies in the noninjected paw also. Thymulin (5 ng) also resulted in significant elevation in the levels of interleukin-1 beta (IL-1 beta) and nerve growth factor (NGF) levels in the injected paw. Both dexamethasone and indomethacin reversed thymulin-induced hyperalgesia. Also interleukin-1 receptor antagonist (IL-1ra) and a polyclonal anti-NGF antiserum significantly reduced thymulin-induced hyperalgesia. On the other hand, the tripeptide lys-D-pro-val (known to antagonize IL-1 beta and PGE2 induced hyperalgesia) reversed the hyperalgesia due to thymulin. In conclusion, thymulin induces localized hyperalgesia which is mediated by PGE2-dependent mechanisms and this pathway could be either partially dependent on or totally independent of IL-1 beta mechanisms.     

Leukemia inhibitory factor modulates interleukin-1beta-induced activation of the hypothalamo-pituitary-adrenal axis

We have shown that leukemia inhibitory factor (LIF) is expressed in corticotroph cells and stimulates POMC gene expression and ACTH secretion in vivo and in vitro. We therefore examined the regulation of in vitro and in vivo pituitary LIF expression by cytokines known to stimulate the hypothalamo-pituitary-adrenal axis. In the corticotroph cell line AtT-20/D16v-F2, recombinant murine interleukin-1beta (IL-1beta; 0.1-10.0 ng/ml) caused a 5- to 10-fold increase in LIF messenger RNA (mRNA) levels. LIF mRNA expression was induced as early as 1 h, peaked at 2 h, and still persistently elevated above the baseline after 8 h. This effect of IL-1beta on LIF mRNA expression was abolished by preincubation with human IL-1 receptor antagonist (100 ng/ml) or antimurine IL-1beta antibody (10 microg/ml). Tumor necrosis factor-alpha (20 ng/ml) only modestly increased LIF mRNA, but was synergistic with IL-1beta (up to 2.5-fold). In contrast, IL-2 and IL-6 did not alter LIF mRNA. In C57BL/6 mice, i.p. injection of 100 ng IL-1beta increased plasma ACTH and corticosterone levels after 1 h (P < 0.02). In addition, pituitary LIF mRNA content was increased for up to 2 h in response to IL-1beta. In comparison to wild-type (+/+) B6D2F1 mice, LIF knockout mice with a deleted LIF gene (-/-) exhibited decreased plasma ACTH (631 +/- 61 vs. 376 +/- 50 pg/ml; P < 0.01) and corticosterone (783 +/- 85 vs. 433 +/- 51 ng/ml; P < 0.01) levels 1 h after i.p. IL-1beta administration. In conclusion, corticotroph LIF mRNA expression is specifically stimulated by IL-1beta and tumor necrosis factor-alpha. The attenuated hypothalamo-pituitary-adrenal response to IL-1beta in LIF knockout mice indicates that the effect of IL-1beta on ACTH secretion is modulated by LIF. Thus, LIF appears to function as an immune-neuroendocrine modulator signaling the hypothalamo-pituitary-adrenal axis.     

Inhibition of IL-1 induced tissue factor (TF) synthesis and procoagulant activity (PCA) in purified human monocytes by IL-4, IL-10 and IL-13

Exposure of monocytes to pro-inflammatory cytokines or lipopolysaccharide (LPS) may induce synthesis and expression of tissue factor (TF). In this paper we have focused on the induction of TF-activity in human monocytes by the pro-inflammatory cytokines recombinant human interleukin 1 (rhIL-1 alpha) (rhIL-1 beta) (rhIL-6) and human tumour necrosis factor alpha (rhTNF-alpha), measured as procoagulant activity (PCA) in a microtitre plate-based clot assay. In addition we have studied the modulation of IL-1 alpha/beta induced TF-mRNA and PCA by rhIL-4, rhIL-10 and rhIL13. IL-1 alpha and IL-1 beta induced a concentration dependent increase in TF-activity. Neither IL-6 nor TNF-alpha gave rise to procoagulant activity at the concentrations tested (0.2-20 ng/ml). IL-4, IL-10 and IL-13, all effectively diminished IL-1 alpha/beta induced PCA, shown at the protein- and at the mRNA-level, while cell viability was unaffected. These results add to the previously demonstrated role of IL-4 and IL-10 as inhibitors of LPS-induced TF-activity, showing that these anti-inflammatory cytokines are not specific for LPS-activation but interfere with other stimulating substances such as IL-1, which may be involved in diseases where LPS is not present.     

Cyclooxygenase inhibitors enhance the production of tissue inhibitor-1 of metalloproteinases (TIMP-1) and pro-matrix metalloproteinase 1 (proMMP-1) in human rheumatoid synovial fibroblasts

OBJECTIVE AND DESIGN: We investigated the influence of cyclooxygenase inhibitors against the production of tissue inhibitor-1 of metalloproteinases (TIMP-1) and pro-matrix metalloproteinase 1 (proMMP-1) in rheumatoid arthritis (RA) synoviocytes. MATERIAL: Synovial fibroblasts from RA patients were used. TREATMENT: The cells were treated with recombinant human interleukin 1 beta (rhIL-1 beta) (100 ng/ml) and/or indomethacin (0.1, 1, 10 microM) and diclofenac (0.1, 1, 10 microM) and/or prostaglandin E2 (PGE2) (1, 10 microM) for 72 h. METHODS: The amounts of TIMP-1, proMMP-1 and PGE2 was measured by enzyme linked immunosorbent assay (ELISA). Statistical significance was tested with Student's t-test and Dunnett test. RESULTS: RhIL-1 beta augments the production of TIMP-1 and proMMP-1 in synovial fibroblasts from RA patients, and this IL-1-induced production of TIMP-1 and proMMP-1 was further enhanced by treatment with the cyclooxygenase inhibitors, indomethacin and diclofenac. Exogenous PGE2 significantly suppresses indomethacin- and diclofenacenhanced TIMP-1 and proMMP-1 production. CONCLUSION: PGE2 down-regulates the production of TIMP-1 and proMMP-1 in RA synoviocytes, and cyclooxygenase inhibitors regulate the production of TIMP-1 and proMMP-1 through the inhibition of PGE2 production in inflammation.     

Interleukin-1 beta induced transient diabetes mellitus in rats. A model of the initial events in the pathogenesis of insulin-dependent diabetes mellitus?

When aiming at preventing IDDM in man, knowledge of the molecular mechanisms leading to beta cell destruction may facilitate identification of new possible intervention modalities. A model of IDDM pathogenesis in man suggests that cytokines, and IL-1 in particular, are of major importance in the initial events (Nerup et al 1994) (Fig. 1). In vitro rat experiments demonstrated that rhIL-1 beta inhibits beta cell function and induces beta cell death both in isolated islets of Langerhans and in the isolated perfused pancreatic gland. With the long term goal of identifying new modalities capable of preventing IDDM in man, the aim af this review was to investigate the effects of rhIL-1 beta on beta-cell function and viability in normal rats. This review discussed 1) the pharmacokinetics of IL-1 beta in rats as the basis for choice of route of administration and dose of rhIL-1 beta, 2) the effects and molecular mechanisms of IL-1 beta on temperature and food intake used as control parameters for successful injection of rhIL-1 beta in rats, 3) the effects of one or more injection of IL-1 beta on rat beta cell function, 4) the molecular mechanisms leading to IL-1 beta induced beta cell inhibition in vivo, and some possible intervention modalities based on the molecular mechanisms, 5) the effects of IL-1 beta on spontaneous diabetes mellitus in DP BB rats, and 6) the effects and molecular mechanisms of IL-1 beta induced inhibition of thyroid epithelial cell function and aggravated thyroiditis in DP BB rats, compared to the effects of IL-1 beta on rat beta cell function. Finally, this review discussed the effects of IL-1 beta on human beta cells in vitro, and the clinical relevance of these experiments, with special reference to a clinical trial with the aim of preventing IDDM in man. The pharmacokinetic studies suggested that IL-1 beta is distributed according to a two-compartment model with a first-order elimination. Interleukin-1 beta reached all the investigated organs in the rats, was accumulated in kidneys and was excreted in the urine. The data suggested that IL-1 beta also accumulated in the islets of Langerhans. After injection of 4.0 micrograms/kg pathophysiologically relevant concentrations of rhIL-1 beta were reached and intact rhIL-1 beta persisted for up to 5 hrs in plasma. Peripheral injections of IL-1 beta dose-dependently induced fever and anorexia in rats, probably via induction of PGE2 in the brain or in peripheral tissues thereafter passing the blood-brain barrier. Nitric oxide produced by cNOS seems to be a molecular mediator of IL-1 beta induced fever but not of anorexia. Fever and anorexia are well described effects of IL-1 beta in rats, and are as such usefull control parameters of the absorption and biological activity of IL-1 beta after peripheral injection. Injections of rhIL-1 beta to normal, non-diabetes prone rats induced initial beta cell stimulation followed by inhibition, in accordance with in vitro data. Furthermore, induction of peripheral insulin resistance coincided with beta cell inhibition after one daily injection for 5 days, leading to a transient diabetes mellitus-like state, characterized by hyperglycemia and hypoinsulinemia. At this time point, electron-microscopy did not demonstrate beta cell destruction. However, IL-1 beta induced intercellularly edema and microvillous processes on the beta cells, which might be early evidence of apoptosis. The diabetes mellitus-like state was not aggravated if the daily injections were continued beyond 5 days. Daily injections of rhIL-1 beta for 2 to 4 weeks induced formation of blocking IL-1 beta-antibodies in normal rats. Hence, injections exceeding 2 weeks should only be performed using species homologous IL-1 beta. The molecular mechanism of IL-1 beta induced beta cell inhibition in rats in vivo as in vitro, are likely to involve binding of IL-1 beta to the IL-1RtI, since the IL-1RtII is considered to be a decoy receptor. (ABSTRACT TRUNCATED)     

Different receptor mechanisms mediate the effects of endotoxin and interleukin-1 on female sexual behavior

Activation of the immune system by lipopolysaccharide (LPS) produces physiological, neuroendocrine and behavioral effects, some of which are mediated by cytokine production. We have previously shown that the cytokine interleukin-1 (IL-1) inhibits sexual behavior in female, but not male rats, while producing a comparable suppression of locomotion in both sexes. The present study examined the effects of LPS on sexual behavior and locomotion of male and female rats, and the involvement of IL-1 receptors in mediating the effects of IL-1 and LPS on females' behavior. Peripheral (i.p.) administration of LPS (50 or 250 microg/kg) significantly decreased sexual behavior in females, up to 6 h after administration, while it had no effect on male sexual behavior. However, locomotor activity, measured in the open-field test, was similarly reduced by LPS in both males and females. Pretreatment with the IL-1 receptor antagonist (IL-1ra) either i.p. (10 mg/kg) or intracerebroventricularly (i.c.v.) (50 microg/rat) did not prevent the inhibition of female sexual behavior and locomotion induced by either i.p. (50 microg/kg) or i.c.v. (200 or 400 ng/rat) administration of LPS, respectively. However, identical doses of IL-1ra significantly reversed the effects of IL-1beta, administered either i.p. (5 microg/kg) or i.c.v. (50 ng/rat), respectively. These results demonstrate that both LPS and IL-1beta produce marked inhibition of sexual behavior in female, but not in male rats. However, IL-1 receptors are not required for the effects of LPS on sexual behavior in female rats.     

Inhibition of IL-1 beta-induced peripheral inflammation by peripheral and central administration of analogs of the neuropeptide alpha-MSH

Interleukin-1 (IL-1) is a proinflammatory cytokine, alpha-MSH(1-13) molecules inhibit inflammation induced by cytokines, other mediators of inflammation, and by peripheral irritants. D-valine substitution in the antiinflammatory/antipyretic message sequence [alpha-MSH(11-13), Lys-Pro-Val] of alpha-MSH(1-13) increases the activity of the tripeptide. Our aim was to learn if D-valine substitution also enhances the antiinflammatory activity of the entire alpha-MSH(1-13) molecule and to determine if an antipyretic D-valine-substituted alpha-MSH(8-13) molecule is also antiinflammatory. Intraperitoneal injection of alpha-MSH(1-13) and of (D-Val13)alpha-MSH(1-13) caused dose-related suppression of ear edema induced in mice by intradermal injection of IL-1 beta; the two molecules were equipotent. (D-Val13)alpha-MSH(8-13) likewise inhibited inflammation, but the potency was less than that of the larger molecules. Intracerebroventricular injections of (D-Val13)alpha-MSH(1-13) and of the unsubstituted molecule were equipotent in reducing inflammation; the (D-Val13)alpha-MSH(8-13) molecule was less effective. The results support the idea that the alpha-MSH(1-13) molecule inhibits inflammation and suggest that the L-conformation of alpha-MSH(1-13) is maximally effective with regard to its antiinflammatory activity. The results with alpha-MSH(8-13) are consistent with previous findings of lesser antihost response activity of alpha-MSH fragments that contain the COOH-terminal tripeptide Lys-Pro-Val.     

Cytokines and cognitive behavior

Proinflammatory cytokines help orchestrate host responses to infection and are a major communication link between peripheral immunity and the CNS. These cytokines initiate a number of CNS events that culminate in both physiological and behavioral changes. Peripheral IL-1beta also affects information processing. A series of experiments examining the effect of learning intensity, motivation, and cytokine dose are reported. Using a well-established Morris water maze (MWM) system with female C57BL/6 mice, we report that (1) IL-1 (100 ng/mouse, i.p.) has no effect on MWM learning when mice are subjected to a spaced as opposed to a massed learning protocol; (2) water temperature is critical to the IL-1 effect on learning insofar as IL-1 interferes with learning in a warm-water but not a cold-water maze, and (3) higher doses (1,000 ng/mouse, i.p.) of IL-1 in experimental systems known to produce the IL-1-induced learning deficit with lower doses (100 ng/mouse, i.p.) show consistent facilitation, not impairment, of learning.     

The intracerebroventricular injection of interleukin-1beta blunts the testosterone response to human chorionic gonadotropin: role of prostaglandin- and adrenergic-dependent pathways

The present work extends our previous report that the intracerebroventricular (i.c.v.) injection of interleukin-1beta(IL-1beta, 80 ng) significantly blunted the testosterone response to 1 U/kg human CG (hCG), an effect that we attributed to the stimulation of inhibitory pathways connecting the hypothalamus to the testes. Systemic blockade of prostaglandin-dependent pathways with ibuprofen (alpha-methyl-4-[2-methylpropyl]benzeneacetic acid; sodium salt), which did not, in itself, alter the stimulatory effect of hCG on testosterone release in control rats, modestly, but significantly (P < 0.05) reversed the inhibitory influence of IL-1beta. In contrast, blockade of brain receptors for CRF was unable to alter the effect of IL-1beta, as were lesions of the ventromedial hypothalamic nucleus, a brain area implicated in the control of ovarian function. Blockade of beta-adrenergic receptors significantly prevented the decrease in testicular responsiveness induced by the i.c.v. injection of IL-1beta. Finally, the central injection of the beta-adrenergic agonist isoproterenol, as well as that of norepinephrine, mimicked the ability of icv IL-1beta to blunt testicular secretory activity and produced a marked (P < 0.01) decrease in the response to hCG within 5 min of their administration. We propose that the explanation that best fits our findings is that the i.c.v. injection of IL-1beta activates a neural, catecholamine-dependent pathway that connects the brain and the testes independently of the pituitary.     

Interleukin-1 beta differentially affects interleukin-6 and soluble interleukin-6 receptor in the blood and central nervous system of the monkey

Two studies were conducted to investigate whether behavioral and physiological responses induced by administration of interleukin-1 beta (IL-1 beta) were also associated with changes in interleukin-6 (IL-6) and soluble IL-6 receptor levels (sIL-6R). Following intravenous injection of rhIL-1 beta, blood and cerebrospinal fluid (CSF) samples were collected from juvenile rhesus monkeys. Marked increases in IL-6 levels were evident at 1 h in both blood and intrathecal compartments. IL-1 beta also induced significant elevations in the release of ACTH and cortisol into the blood stream, and following high doses, the monkeys evinced signs of sickness behavior. The second study characterized the IL-beta dose-response relationship showing that these physiological changes were most evident at doses between 0.5 microgram and 1.0 microgram IL-1/kg body weight. Soluble IL-6 receptor concentration was also increased, but only in plasma. There was no detectable sIL-6R in CSF. The large release of IL-6 into CSF suggests that some behavioral symptoms may be due to intrinsic changes in central nervous system activity concomitant with the alterations in peripheral physiology.     

Interleukin-10 inhibits activation of coagulation and fibrinolysis during human endotoxemia

Interleukin-10 (IL-10) has been found to inhibit lipopolysaccharide (LPS)-induced tissue factor expression by monocytes in vitro. To determine the effects of IL-10 on LPS-induced activation of the hemostatic mechanisms in vivo, we performed a placebo-controlled, cross-over study of human endotoxemia. Two groups of eight volunteers were challenged with LPS (4 ng/kg) on two occasions: once in conjunction with placebo, and once with recombinant human IL-10 (rhIL-10; 25 microg/kg). In group 1, placebo or rhIL-10 was given 2 minutes before LPS challenge, group 2 received placebo or rhIL-10 1 hour after LPS administration. Pretreatment with rhIL-10 reduced both LPS-induced activation of the fibrinolytic system (plasma concentrations of tissue type plasminogen activator, plasmin-alpha2-antiplasmin complexes, and D-dimer), and inhibition of fibrinolysis (plasma levels of plasminogen activator inhibitor 1), whereas posttreatment only inhibited the latter response. Both IL-10 pre- and posttreatment attenuated activation of the coagulation system (plasma levels of prothrombin fragment F1 + 2 and thrombin-antithrombin complexes). These results indicate that rhIL-10, besides its well-described inhibitory effects on cytokine release, potently modulates the fibrinolytic system and inhibits the coagulant responses during endotoxemia.     

Role of central interleukin-1 beta in gastrointestinal motor disturbances induced by lipopolysaccharide in sheep

Cytokines are involved in the symptoms of the acute phase response induced by infectious diseases in humans as well as in animals, and interleukin-1 beta (IL-1 beta) has a pivotal role in these changes. The role of central IL-1 beta in the gastrointestinal hypomotility and fever evoked by intravenous administration of lipopolysaccharide (LPS) and the mechanisms involved, were investigated in sheep as an experimental model. LPS (0.1 microgram/kg, intravenously) induced gastrointestinal hypomotility and fever that were significantly reduced by prior intracerebroventricular administration of IL-1 receptor antagonist protein (IL-1ra, 2 micrograms/kg). The effects of LPS were mimicked by intracerebroventricular IL-1 beta (50 ng/kg), whereas IL-1 beta injected intravenously at the same dose only caused a slight and transient fever without modifying the gastrointestinal motility. Prior intracerebroventricular administration of the cyclooxygenase inhibitor indomethacin (100 micrograms/kg) but not the corticotropin-releasing factor (CRF) receptor antagonist alpha-helical CRF9-41 (5 micrograms/kg) blocked all effects by both LPS and IL-1 beta. These results suggest that in sheep, LPS induces digestive motor disturbances through a central release of IL-1 beta and prostaglandins.