Role of the central opioid system in the inhibition of water and salt intake induced by central administration of IL-1beta in rats.

In the present study we investigated, the effect of third ventricle injections of IL-1beta on water and salt intake in fluid-deprived and sodium-depleted rats. Central administration of IL-1beta significantly reduced water and salt intake in fluid-deprived animals and decreased salt intake in sodium-depleted rats. The antidipsogenic and antinatriorexic effects elicited by the central administration of IL-1beta were suppressed by pretreatment with central injections of the non-selective opioid antagonist naloxone (10 mug) in the two different experimental protocols used here (water deprivation and sodium depletion). In addition, central administration of IL-1beta failed to modify the intake of a 0.1% saccharin solution when the animals were submitted to a "dessert test" or to induce any significant locomotor deficit in the open-field test. The present results suggest that the activation of the central interleukinergic component by IL-1beta impairs the increase in water and salt intake induced by water deprivation and the enhancement in sodium appetite that follows sodium depletion. The data also support the conclusion that the antidipsogenic and antinatriorexic effects resulting from the activation of the central interleukinergic component rely on an opioid-dependent, naloxone-blockable system.

Inhibition of water intake by the central administration of IL-1beta in rats: role of the central opioid system.

In the present study we investigated, the effect of third ventricle injections of IL-1beta on water intake, in rats, induced by three different physiological stimuli: dehydration induced by water deprivation, hypernatremia associated with hyperosmolarity induced by intragastric salt load, and hypovolemia produced by subcutaneous polytethyleneglycol administration. Central administration of IL-1beta at the doses of 4 and 8 ng reduced water intake in all three conditions studied. Third ventricle injections of IL-1beta (8 ng) were unable to diminish water intake in the groups of rats pretreated with central injections of the non-selective opioid antagonist naloxone (10 microg) in the three different conditions studied. Furthermore, the central administration of IL-1beta was neither able to modify the intake of a 0.1% saccharin solution when the animals were submitted to a "dessert test" nor to induce any significant locomotor deficit in the open-field test. These results suggest that the central activation of interleukin-1 receptors by IL-1beta is able to impair the thirst-inducing mechanisms triggered by the physiological stimuli represented by dehydration, hyperosmolarity and hypovolemia. These results lead us to conclude that the antidipsogenic effects observed following central administration of IL-1beta require the functional integrity of the brain opiatergic system.

alpha-MSH and gamma-MSH inhibit IL-1beta induced activation of the hypothalamic-pituitary-adrenal axis through central melanocortin receptors.

Alpha-melanocyte-stimulating hormone (alpha-MSH) is a neuroimmunomodulatory peptide that is involved in the control of host responses trough modulation of production and action of proinflammatory cytokines in inflammatory cells in the periphery and within the central nervous system (CNS). However, little is known about the receptors that mediate the modulatory effects of alpha-MSH in the CNS. The objective of the present study was to establish the specific melanocortin receptors involved in the inhibition by MSH peptides of IL-1beta-induced activation of the HPA. i.c.v. injection of 12.5 ng of IL-1beta caused significant changes in plasma corticosterone, as compared to basal levels. The treatment with gamma-MSH (1 microg), an MC3 receptor agonist, resulted in significant reduction of the IL-1beta-induced plasma corticosterone levels. Administration of the MC3/MC4 receptor antagonist SHU9119 blocked this effect. Besides, treatment with a high dose of alpha-MSH (1 microg) increased plasma corticosterone. When alpha-MSH was given at a lower dose (0.1 microg), it did not modify corticosterone levels but caused an inhibitory effect on the corticosterone release induced by IL-1beta. The administration of SHU9119 or a more selective MC4 receptor antagonist like HS014 blocked the effects of alpha-MSH. In conclusion, our results suggest that both alpha-MSH and gamma-MSH are capable of inhibiting the effect of the IL-1beta on the activation of HPA axis acting at the CNS, and that this effect is mediated by specific central melanocortin receptors.

Interleukin-1beta increases spinal cord wind-up activity in normal but not in monoarthritic rats.

Cytokines produced by spinal cord glia after peripheral inflammation, infection or trauma have a relevant role in the maintenance of pain states. The effect of intrathecally administered interleukin-1beta (IL-1beta) on spinal cord nociceptive transmission was studied in normal and monoarthritic rats by assessing wind-up activity in a C-fiber-mediated reflex paradigm evoked by repetitive (1 Hz) electric stimulation. Low i.t. doses of IL-1beta (0.03, 0.12, 0.5 and 2.0 ng) dose-dependently enhanced wind-up activity in normal rats, while higher doses (8.0 ng) only produced a marginal unsignificant effect. IL-1beta administration to monoarthritic rats did not significantly change wind-up scores at any dose. Adaptive changes developed in the spinal cord during chronic pain may underlie the ineffectiveness of exogenous IL-1beta to up-regulate nociceptive transmission.

IL-1-driven endogenous IL-10 production protects against the systemic and local acute inflammatory response following intestinal reperfusion injury.

TNF-alpha release and action are central in the pathogenesis of the local and systemic inflammatory responses that occur after intestinal reperfusion. In this study we examined whether IL-1 participated in the cascade of events leading to TNF-alpha production and TNF-alpha-mediated injury following reperfusion of the ischemic superior mesenteric artery in rats. Blockade of the action of IL-1 by the use of anti-IL-1 antiserum or administration of IL-1R antagonist (IL-1ra), a natural antagonist of IL-1Rs, resulted in marked enhancement of reperfusion-associated tissue injury, TNF-alpha expression, and lethality. In contrast, there was marked decrease in IL-10 production. Facilitation of IL-1 action by administration of anti-IL-1ra, which antagonizes endogenous IL-1ra, or exogenous administration of rIL-1beta suppressed reperfusion-induced tissue pathology, TNF-alpha production, and lethality, but increased IL-10 production. Exogenous administration of IL-10 was effective in preventing the increase in tissue or plasma levels of TNF-alpha, the exacerbated tissue injury, and lethality. An opposite effect was observed after treatment with anti-IL-10, demonstrating a role for endogenous production of IL-10 in modulating exacerbated reperfusion-associated tissue pathology and lethality. Finally, pretreatment with anti-IL-10 reversed the protective effect of IL-1beta on reperfusion-associated lethality. Thus, IL-1 plays a major role in driving endogenous IL-10 production and protects against the TNF-alpha-dependent systemic and local acute inflammatory response following intestinal reperfusion injury.

Pretreatment of mice with lipopolysaccharide (LPS) or IL-1beta exerts dose-dependent opposite effects on Shiga toxin-2 lethality.

Haemolytic uraemic syndrome (HUS) has been closely associated with infection with a group of Shiga toxin-producing enterohaemorrhagic Eschericchia coli in young children. Shiga toxins (Stx) have been implicated as pathogenic agents of HUS by binding to the surface receptor of endothelial cells. LPS is a central product of the Gram-negative bacteria and several reports have documented that both LPS and Stx are important for disease development. In this study the reciprocal interactions between LPS and Stx2 are analysed in a mouse model. The results demonstrated that LPS was able to reduce or enhance Stx2 toxicity, depending on the dose and the timing of the injection. The involvement of the main early cytokines induced by LPS, tumour necrosis factor alpha (TNF-alpha) and IL-1beta, in those LPS opposite effects on Stx2 toxicity was evaluated. Stx2 toxicity was enhanced by in vivo injection of murine TNF-alpha and low doses of murine IL-1beta. However, at higher doses of IL-1beta which induced corticosteroid increase in serum, Stx2 lethality was decreased. Considering that dexamethasone and IL-1beta reproduce the LPS protective effects, it is suggested that endogenous corticosteroids secondary to the inflammatory response induced by LPS, mediate the protection against Stx2. It can be concluded that the fine equilibrium between proinflammatory and anti-inflammatory activities strongly influences Stx2 toxicity.

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.

Indomethacin blocks the febrile response induced by interleukin-8 in rabbits.

Interleukin (IL)-8 induces fever in rats by a mechanism independent of the release of cyclooxygenase products. The purpose of this study was to investigate whether a similar mechanism is responsible for the pyrogenic effect of IL-8 in rabbits. Intravenous (0.31-5.0 ng/kg) or intracerebroventricular (15.6-250 pg) injections of IL-8 induced a dose-dependent increase in body temperature. The correlations between the doses of recombinant human IL-8 and the fever index were 0.98 and 0.99 for the intravenous and intracerebroventricular injections, respectively. The pyrogenic activity of IL-8 was not due to contamination with lipopolysaccharide (LPS), inasmuch as the Limulus amoebocyte lysate test showed < 10 pg endotoxin/micrograms IL-8, and boiled IL-8 lost its pyrogenic activity. Indomethacin (2 and 5 mg/kg i.p.) abolished the febrile response induced by the intravenous injection of LPS (5.0 ng/kg), IL-1 beta (5 ng/kg), and IL-8 (5 ng/kg). Indomethacin also abolished the fever induced by the intracerebroventricular injection of IL-8 (62.5 pg) but only partially reduced the response induced by the injection of IL-1 beta (25 pg icv). These results show that, different from rats, indomethacin blocks the febrile response induced by the central or peripheral administration of IL-8 in rabbits.

Cytokine-mediated inflammatory hyperalgesia limited by interleukin-10.

1. The effect of interleukin-10 (IL-10) upon the hyperalgesic activities in rats of bradykinin, tumor necrosis factor alpha (TNF alpha), interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), interleukin-8 (IL-8), prostaglandin E2 (PGE2) and carrageenin were investigated in a model of mechanical hyperalgesia. 2. Hyperalgesic responses to bradykinin (1 micrograms) were inhibited in a dose-dependent manner by prior treatment with IL-10 (1-100 ng). 3. Hyperalgesic responses to TNF alpha (2.5 pg), IL-1 beta (0.5 pg) and IL-6 (1.0 ng) but not to IL-8 (0.1 ng) and PGE2 (50 ng and 100 ng) were inhibited by prior treatment with IL-10 (10 ng). 4. Hyperalgesic responses to carrageenin (100 micrograms) were inhibited by IL-10 (10 ng) when this cytokine was injected before but not after the carrageenin. 5. A monoclonal antibody to mouse IL-10 potentiated the hyperalgesic responses to carrageenin (10 micrograms) and TNF alpha (0.025 pg) but not that to IL-8 (0.01 ng). 6. In in vitro experiments in human peripheral blood mononuclear cells (MNCs), IL-10 (0.25-4.0 ng ml-1) inhibited in a dose-dependent manner PGE2 production by MNCs stimulated with IL-1 beta (1-64 ng ml-1) or endotoxin (lipopolysaccharide, LPS, 1 iu = 143 pg ml-1) but evoked only small increases in IL-1ra production. 7. These data suggest that IL-10 limits the inflammatory hyperalgesia evoked by carrageenin and bradykinin by two mechanisms: inhibition of cytokine production and inhibition of IL-1 beta evoked PGE2 production. Our data suggest that the latter effect is not mediated via IL-10 induced IL-Ira and may result from suppression by IL-10 of prostaglandin H synthase-2 (COX-2).

Intratracheal but not intravascular interleukin-1 causes acute edematous injury in isolated neutrophil-perfused rat lungs through an oxygen radical-mediated mechanism.

Our goal was to determine whether administration of interleukin-1 (IL-1) intratracheally causes acute edematous injury in isolated rat lungs perfused only with neutrophils and physiologic buffer. We found that administration of native (50 ng) but not heated IL-1 intratracheally rapidly (60 minutes) increased (p < 0.05) lung weights and lung lavage Ficoll concentrations in isolated rat lungs perfused only with purified human neutrophils as compared with lungs given IL-1 intratracheally alone, lungs perfused with neutrophils alone, or untreated control lungs. In contrast, lung weights or lavage Ficoll concentrations did not increase (p > 0.05) when as much as 1 microgram of IL-1 was administered intravascularly with neutrophils. The mechanism of injury appeared to involve neutrophil-derived oxygen radicals, because acute edematous injury did not occur in isolated lungs given IL-1 intratracheally and then perfused with neutrophils previously heated at 48 degrees C for 10 minutes. The latter procedure decreased superoxide anion (O2-.) production but did not alter the adhesion or chemotactic properties of neutrophils in vitro. In parallel, incubation with IL-1 and human neutrophils did not lyse (as measured by chromium 51 release) cultured purified bovine pulmonary artery endothelial cells in vitro. Our results indicate that increased alveolar but not intravascular concentrations of IL-1 initiate a neutrophil-dependent, oxidant-mediated acute edematous lung injury.

Interleukin-1 and tumor necrosis factor-alpha as radio- and chemoprotectors of bone marrow.

Administration of interleukin 1 (IL-1) or tumor necrosis factor-alpha (TNF alpha) protects bone marrow precursor cells (BMPC) from ionizing radiation and antineoplastic drugs. The time of injection is critical: the best protective results being obtained when cytokines are given around 24h prior to the induced injury. Multiple daily cytokine injections that precede irradiation or drug administration are more effective than single ones although single doses are quite effective at increasing survival in mice. Protection is positively correlated with both rapid granulocyte recovery and BMPC survival. Mechanisms involved in BMPC radioprotection include: (1) push to the S/G2 + M or arrest in the G0 phases of the cell cycle by IL-1 or TNF alpha, respectively, and (2) induction of mitochondrial manganous superoxide dismutase synthesis. For BMPC chemoprotection, proposed mechanisms are: (1) increase of aldehyde dehydrogenase synthesis, and (2) modulation of multiple-drug resistant gene expression. Stimulation of glutathione synthesis in BMPC could be operating in both radio- and chemoprotection. These findings point to the relevance of IL-1 or TNF alpha in cancer therapy as a means of reducing BMPC sensitivity to cytoreductive drugs or irradiation (including radioimmunotherapy) as well as in in vitro tumor cell purging with drugs in autologous BMT. Prior administration of these cytokines should be also considered for people in imminent danger of exposure to radiation.