The pharmacokinetics, distribution and degradation of human recombinant interleukin 1 beta in normal rats

IL-1 receptor activation undermines respiratory motor plasticity after systemic inflammation

Inflammation undermines respiratory motor plasticity, yet we are just beginning to understand the inflammatory signaling involved. Because interleukin-1 (IL-1) signaling promotes or inhibits plasticity in other central nervous system regions, we tested the following hypotheses: 1) IL-1 receptor (IL-1R) activation after systemic inflammation is necessary to undermine phrenic long-term facilitation (pLTF), a model of respiratory motor plasticity induced by acute intermittent hypoxia (AIH), and 2) spinal IL-1β is sufficient to undermine pLTF. pLTF is significantly reduced 24 h after lipopolysaccharide (LPS; 100 μg/kg ip, 12 ± 18%, n = 5) compared with control (57 ± 25%, n = 6) and restored by peripheral IL-1R antagonism (63 ± 13%, n = 5, AF-12198, 0.5 mg/kg ip, 24 h). Furthermore, acute, spinal IL-1R antagonism (1 mM AF-12198, 15 μl it) restored pLTF (53 ± 15%, n = 4) compared with LPS-treated rats (11 ± 10%; n = 5), demonstrating IL-1R activation is necessary to undermine pLTF after systemic inflammation. However, in healthy animals, pLTF persisted after spinal, exogenous recombinant rat IL-1β (rIL-1β) (1 ng ± AIH; 66 ± 26%, n = 3, 10 ng ± AIH; 102 ± 49%, n = 4, 100 ng + AIH; 93 ± 51%, n = 3, 300 ng ± AIH; 37 ± 40%, n = 3; P < 0.05 from baseline). In the absence of AIH, spinal rIL-1β induced progressive, dose-dependent phrenic amplitude facilitation (1 ng; −3 ± 5%, n = 3, 10 ng; 8 ± 22%, n = 3, 100 ng; 31 ± 12%, P < 0.05, n = 4, 300 ng; 51 ± 17%, P < 0.01 from baseline, n = 4). In sum, IL-1R activation, both systemically and spinally, undermines pLTF after LPS-induced systemic inflammation, but IL-1R activation is not sufficient to abolish plasticity. Understanding the inflammatory signaling inhibiting respiratory plasticity is crucial to developing treatment strategies utilizing respiratory plasticity to promote breathing during ventilatory control disorders.

NEW & NOTEWORTHY This study gives novel insights concerning mechanisms by which systemic inflammation undermines respiratory motor plasticity. We demonstrate that interleukin-1 signaling, both peripherally and centrally, undermines respiratory motor plasticity. However, acute, exogenous interleukin-1 signaling is not sufficient to undermine respiratory motor plasticity.

Inflammatory Cytokines as Uremic Toxins: "Ni Son Todos Los Que Estan, Ni Estan Todos Los Que Son"

Chronic kidney disease is among the fastest growing causes of death worldwide. An increased risk of all-cause and cardiovascular death is thought to depend on the accumulation of uremic toxins when glomerular filtration rate falls. In addition, the circulating levels of several markers of inflammation predict mortality in patients with chronic kidney disease. Indeed, a number of cytokines are listed in databases of uremic toxins and uremic retention solutes. They include inflammatory cytokines (IL-1β, IL-18, IL-6, TNFα), chemokines (IL-8), and adipokines (adiponectin, leptin and resistin), as well as anti-inflammatory cytokines (IL-10). We now critically review the cytokines that may be considered uremic toxins. We discuss the rationale to consider them uremic toxins (mechanisms underlying the increased serum levels and evidence supporting their contribution to CKD manifestations), identify gaps in knowledge, discuss potential therapeutic implications to be tested in clinical trials in order to make this knowledge useful for the practicing physician, and identify additional cytokines, cytokine receptors and chemokines that may fulfill the criteria to be considered uremic toxins, such as sIL-6R, sTNFR1, sTNFR2, IL-2, CXCL12, CX3CL1 and others. In addition, we suggest that IL-10, leptin, adiponectin and resistin should not be considered uremic toxins toxins based on insufficient or contradictory evidence of an association with adverse outcomes in humans or preclinical data not consistent with a causal association.

Preclinical characterization and clinical development of ILARIS(®) (canakinumab) for the treatment of autoinflammatory diseases

Interleukin-1beta (IL-1β) is a pro-inflammatory cytokine which is part of the first line innate response in vertebrates and is induced in injury, infection, and immunity. While temporally limited induction of IL-1β is believed to protect the organisms against traumatic or infectious insults, its aberrant expression in chronic inflammation is detrimental. Therefore, pharmacological neutralization of IL-1β in chronic inflammatory diseases is a meaningful strategy to treat inflammation and to alleviate respective clinical symptoms in man. Canakinumab is a high-affinity human monoclonal antibody designed to target human IL-1β in inflammatory diseases. Indeed, canakinumab has shown excellent efficacy in rare genetic autoinflammatory diseases or pathological conditions associated with aberrant production of IL-1β. This review focuses on the molecular and clinical mode of action and pharmaceutical development of canakinumab in (auto)inflammatory diseases.

Lipopolysaccharide stimulates platelets through an IL-1β autocrine loop

LPS activates platelets through TLR4, aiding productive sepsis, with stimulated splicing and translation of stored heteronuclear pro-IL-1β RNA. Although the IL-1R type 1 (IL-1R1) receptor for IL-1 shares downstream components with the TLR4 receptor, platelets are not known to express IL-1R1, nor are they known to respond to this cytokine. We show by flow cytometry and Western blotting that platelets express IL-1R1, and that IL-1β and IL-1α stimulate heteronuclear I-1β splicing and translation of the newly made mRNA in platelets. Platelets also respond to the IL-1β they make, which is exclusively associated with shed microparticles. Specific blockade of IL-1R1 with IL-1R antagonist suppressed platelet stimulation by IL-1, so IL-1β stimulates its own synthesis in an autocrine signaling loop. Strikingly, IL-1R antagonist inhibition, pharmacologic or genetic suppression of pro-IL-1β processing to active cytokine by caspase-1, or blockade of de novo protein synthesis also blocked LPS-induced IL-1β mRNA production. Robust stimulation of platelets by LPS therefore also required IL-1β amplification. Activated platelets made IL-1β in vivo as IL-1β rapidly accumulated in occluded murine carotid arteries by posttranscriptional RNA splicing unique to platelets. We conclude that IL-1β is a platelet agonist, that IL-1β acts through an autocrine stimulatory loop, that an IL-1β autocrine loop is required to amplify platelet activation by LPS, and that platelets immobilized in occlusive thrombi are activated over time to produce IL-1β. IL-1 is a new platelet agonist that promotes its own synthesis, connecting thrombosis with immunity.

Changes in Mobility of the Golden Hamster with Induction of an IL-1-Induced Arthritis

Many studies in animals have examined biochemical, immune and histological changes during arthritis; however, the study of the effects of arthritis on mobility has been largely neglected. Interleukin-1, administered by the intraarticular route into hamster knee joints, resulted in inhibition of spontaneous wheel running activity; however, the effect was transient, lasting only through the evening following IL-1 administration. A further injection of IL-1 2 days later showed still greater inhibition of running. The effect again did not extend beyond the first evening after injection. IL-1alpha and IL-1beta showed equivalent effects on mobility, and no evidence was seen for cooperative interaction between them. A 50% inhibition of running occurred at a dose of approximately 10 ng/knee of IL-1alpha. The effect appeared not to be systemic since intraperitoneal injection required microgram amounts of IL-1 for an equivalent inhibition. At the time mobility had been restored to normal, histological examination showed the continued presence of inflammatory cells, soft tissue swelling and cartilage proteoglycan loss. These results suggest a lack of correlation between inhibition of mobility and histopathological changes in cartilage and soft tissue.

The role of the kidney in the systemic elimination of interleukin 6, platelet-derived growth factor and transforming growth factor beta

STUDY GOAL

The aim of the study was to assess the role of the kidney in systemic elimination of IL-6 and growth factors (PDGF, TGF-β) by comparison of their concentrations in renal arteries and veins, peripheral veins and urine.

MATERIAL AND METHODS

30 brain-dead kidney donors were included in the study. Samples were obtained during the harvesting procedure. 10 healthy volunteers served as controls. A mathematical model of elimination of investigated proteins from systemic circulation was developed. The elimination ratio (ER) formula indicates the predominance of renal synthesis or degradation and also quantifies the renal uptake (UR) and renal pass (PR) of investigated proteins. Serum levels of investigated proteins were estimated using an immunoenzymatic method (ELISA).

RESULTS

Renal IL-6 uptake ratio (UR) amounted to 6.6%, elimination ratio (ER) amounted to 6.4% and pass ratio (PR) amounted to 0.2%. PDGF ratios amounted to 5.1%, 5.0% and 0.1% and TGF-β ratios amounted to -9%, -9% and 0%, respectively.

CONCLUSIONS

The kidney takes part in the elimination of IL-6 and PDGF from systemic circulation. The kidney does not take part in the elimination of TGF-β.

Amino acid and protein metabolism in the human kidney and in patients with chronic kidney disease

The progressive loss of kidney function in patients with chronic kidney disease (CKD) is associated with a number of complications, including cardiovascular diseases, anemia, hyperparathyroidism, inflammation, metabolic acidosis, malnutrition and protein-energy wasting. The excess cardiovascular risk related to CKD is due in part to a higher prevalence of traditional atherosclerotic risk factors, in part to non-traditional, emerging risk factors peculiar to CKD. While even minor renal dysfunction is an independent predictor of adverse cardiovascular prognosis, nutritional changes are more often observed in an advanced setting. In addition, factors related to renal-replacement treatment may be implicated in the pathogenesis of heart disease and protein-energy wasting in dialysis-treated patients. Progressive alterations in kidney metabolism may cause progressive effects on cardiovascular status and nutrition. Altered kidney amino acid/protein metabolism and or excretion may be a key factor in the homeostasis of several vasoactive compounds and hormones in patients with more advanced disease. In this discussion recent research regarding the kidney handling of amino acids and protein turnover and their potential link with cardiovascular disease, progressive kidney dysfunction and nutritional status are reviewed.

Differential involvement of trigeminal transition zone and laminated subnucleus caudalis in orofacial deep and cutaneous hyperalgesia: the effects of interleukin-10 and glial inhibitors

Background

In addition to caudal subnucleus caudalis (Vc) of the spinal trigeminal complex, recent studies indicate that the subnuclei interpolaris/caudalis (Vi/Vc) transition zone plays a unique role in processing deep orofacial nociceptive input. Studies also suggest that glia and inflammatory cytokines contribute to the development of persistent pain. By systematically comparing the effects of microinjection of the antiinflammatory cytokine interleukin (IL)-10 and two glial inhibitors, fluorocitrate and minocycline, we tested the hypothesis that there was a differential involvement of Vi/Vc and caudal Vc structures in deep and cutaneous orofacial pain.

Results

Deep or cutaneous inflammatory hyperalgesia, assessed with von Frey filaments, was induced in rats by injecting complete Freund's adjuvant (CFA) into the masseter muscle or skin overlying the masseter, respectively. A unilateral injection of CFA into the masseter or skin induced ipsilateral hyperalgesia that started at 30 min, peaked at 1 d and lasted for 1-2 weeks. Secondary hyperalgesia on the contralateral site also developed in masseter-, but not skin-inflamed rats. Focal microinjection of IL-10 (0.006-1 ng), fluorocitrate (1 μg), and minocycline (0.1-1 μg) into the ventral Vi/Vc significantly attenuated masseter hyperalgesia bilaterally but without an effect on hyperalgesia after cutaneous inflammation. Injection of the same doses of these agents into the caudal Vc attenuated ipsilateral hyperalgesia after masseter and skin inflammation, but had no effect on contralateral hyperalgesia after masseter inflammation. Injection of CFA into the masseter produced significant increases in N-methyl-D-aspartate (NMDA) receptor NR1 serine 896 phosphorylation and glial fibrillary acidic protein (GFAP) levels, a marker of reactive astrocytes, in Vi/Vc and caudal Vc. In contrast, cutaneous inflammation only produced similar increases in the Vc.

Conclusion

These results support the hypothesis that the Vi/Vc transition zone is involved in deep orofacial injury and suggest that glial inhibition and interruption of the cytokine cascade after inflammation may provide pain relief.

Renal cytokine profile in an endotoxemic porcine model

INTRODUCTION

In animals exposed to acute endotoxemia with lipopolysaccharide (LPS), high levels of cytokines are found in the kidney. The objective of this study is to determine whether the high renal content of TNF-alpha, IL-1beta, IL-10 and IL-1 receptor antagonist (IL-1ra) is due to glomerular filtration and reabsorption, or whether the cytokines are produced locally in the kidney.

METHODS

Eighteen anesthetized and mechanically ventilated pigs (35-43 kg) were randomized into two groups: Group 1 (n=12) LPS infusion for 360 min and Group 2 (n=6) control pigs, no treatment. At 360 min, the pigs were euthanized and tissue samples from the kidneys were obtained. Localization of the cytokines was determined by immunohistochemistry and double immunofluorescence (dIF).

RESULTS

Pigs exposed to endotoxemia showed increased accumulation of leukocytes and increased protein expression of TNF-alpha and IL-1beta when compared with controls. dIF showed that TNF-alpha-positive cells co-localized with both endothelial and mesangial cells in the glomeruli. Furthermore, the endothelial cells of the cortical arterioles were positive for IL-1beta. TNF-alpha and IL-1beta staining were absent in renal tubular cells. A positive signal for IL-10 was detected at the tubular brush border while IL-1ra was detected in the glomerulus and in the tubular cells.

CONCLUSION

LPS-induced endotoxemia increased TNF-alpha and IL-1beta protein expression and leukocyte accumulation in the kidneys. The results indicate that the increased levels of the pro-inflammatory cytokines TNF-alpha and IL-1beta are caused by a local production in the kidneys while the anti-inflammatory cytokines IL-10 and IL-1ra are filtrated and reabsorbed in the tubuli.

Kidney and splanchnic handling of Interleukin-6 in humans

Chronic elevation of circulating Interleukin-6 (IL-6) is observed in elderly individuals as well as in several illnesses, including chronic kidney diseases. A number of cells and tissues possess the ability to metabolize significant amounts of IL-6 in vitro. However, information on signals and mechanisms by which IL-6 is removed from blood in humans is still incomplete. To assess the individual role of splanchnic organs and kidney on IL-6 inter-organ exchange we used the IL-6 mass-balance technique across the hepato-splanchnic bed and kidney in six subjects with normal renal and liver function undergoing diagnostic venous catheterizations. Both in the hepatic and renal veins IL-6 levels were significantly lower (p=0.041 and 0.038, respectively), than in the artery. The fractional extraction of IL-6, i.e., the percentage of arterial IL-6 extracted after a single pass, was greater across the splanchnic organs (18%) than across the kidney (8%). Accordingly, IL-6 plasma clearance across splanchnic organs was greater than across the kidney and the sum of kidney and splanchnic removal accounted for as much as 63% of the estimated adipocyte IL-6 release. Our data demonstrate that, although the individual contribution to removal is different, both splanchnic organs and kidneys affect in a significant way the disposal of IL-6 in humans. According, both liver and kidney dysfunction could affect the handling of this proinflammatory cytokine and favour a chronic inflammatory response.

Interleukin-1 beta contributes to the upregulation of kappa opioid receptor mrna in dorsal root ganglia in response to peripheral inflammation

During local painful inflammation, axonal transport of opioid receptors from dorsal root ganglia toward the periphery is increased, associated with a higher receptor density and enhanced efficacy of opioid analgesics at the injured site. To examine whether this increase is related to transcription, mRNA of the kappa opioid receptor in lumbar dorsal root ganglia was quantified by real time light cycler polymerase chain reaction. In dorsal root ganglia of naive rats, kappa opioid receptor mRNA expression was three-fold higher than previously shown for delta opioid receptor and two times lower than mu opioid receptor mRNA, respectively. After induction of unilateral paw inflammation by Freund's complete adjuvant, kappa opioid receptor mRNA was significantly upregulated with a peak at 12 h in ipsilateral dorsal root ganglia. This effect could be mimicked by intraplantar injection of the proinflammatory cytokine interleukin-1 beta. Kappa opioid receptor mRNA upregulation lasted longer in interleukin-1 beta-treated rats compared with Freund's complete adjuvant-treated rats. Furthermore, a significant increase in kappa opioid receptor positive neurons was detected by immunohistochemistry 24 h after local injection of Freund's complete adjuvant or interleukin-1 beta. In Freund's complete adjuvant-induced inflammation, kappa opioid receptor upregulation was blocked by treatment with interleukin-1 receptor antagonist without changing the leukocyte infiltration in the paw. In conclusion, kappa opioid receptor mRNA and protein in dorsal root ganglia are upregulated in response to peripheral inflammation. This effect can be mimicked by a single local injection of interleukin-1 beta, and Freund's complete adjuvant-induced upregulation in kappa opioid receptor mRNA and protein can be prevented by treatment with interleukin-1 receptor antagonist. These data suggest that the peripheral production of the proinflammatory cytokine interleukin-1 beta is a specific inducer of kappa opioid receptor expression in the dorsal root ganglia.

Intra-amniotic injection of IL-1 induces inflammation and maturation in fetal sheep lung

Antenatal inflammation may be an important triggering event in the pathogenesis of bronchopulmonary dysplasia but may also accelerate fetal lung maturation. We examined the effects of intra-amniotic (IA) interleukin (IL)-1 alpha and IL-1 beta on maturation of the fetal sheep lung. These cytokine effects were compared with IA endotoxin, a potent proinflammatory stimulus that accelerated lung maturation. Date-bred ewes received 15 or 150 microg recombinant ovine IL-1 alpha or IL-1 beta or 10 mg Escherichia coli endotoxin by IA injection at 118 days gestation (term = 150 days), and fetuses were delivered at 125 days. IL-1 alpha and IL-1 beta improved lung function and increased alveolar saturated phosphatidylcholine (Sat PC) and surfactant protein mRNA expression at the higher dose. The maturation response to IL-1 alpha was greater than that to IL-1 beta, which was similar to endotoxin response. Inflammation was also more pronounced after IL-1 alpha treatment. Only endotoxin animals had residual inflammation of the fetal membranes at 7 days. Lung compliance, lung volume, and alveolar Sat PC were positively correlated with residual alveolar wash leukocyte numbers 7 days after IL-1 treatment, suggesting a link between lung inflammation and maturation.

The central nucleus of the amygdala; a conduit for modulation of HPA axis responses to an immune challenge?

Physical stressors such as infection, inflammation and tissue injury elicit activation of the hypothalamic-pituitary-adrenal (HPA) axis. This response has significant implications for both immune and central nervous system function. Investigations in rats into the neural substrates responsible for HPA axis activation to an immune challenge have predominantly utilized an experimental paradigm involving the acute administration of the pro-inflammatory cytokine interleukin- 1β (IL-1β). It is well recognized that medial parvocellular corticotrophin-releasing factor cells of the paraventricular nucleus (mPVN CRF) are critical in generating HPA axis responses to an immune challenge but little is known about how peripheral immune signals can activate and/or modulate the mPVN CRF cells. Studies that have examined the afferent control of the mPVN CRF cell response to systemic IL-1β have centred largely on the inputs from brainstem catecholamine cells. However, other regulatory neuronal populations also merit attention and one such region is a component of the limbic system, the central nucleus of the amygdala (CeA). A large number of CeA cells are recruited following systemic IL-lβ administration and there is a significant body of work indicating that the CeA can influence HPA axis function. However, the contribution of the CeA to HPA axis responses to an immune challenge is only just beginning to be addressed. This review examines three aspects of HPA axis control by systemic IL-1β: (i) whether the CeA has a role in generating HPA axis responses to systemic IL-1β, (ii) the identity of the neural connections between the CeA and mPVN CRF cells that might be important to HPA axis responses and(iii) the mechanisms by which systemic IL-Iβ triggers the recruitment of CeA cells.

Interleukin-1 beta alters brown adipose tissue but not renal sympathetic nerve responses to hypothermia

Proinflammatory cytokines and acute physical stress influence sympathetic nerve discharge (SND). Because interleukin-1 beta (IL-1 beta) produces physiological responses that require central neural integration and because the sympathetic nervous system mediates physiological responses to environmental stress, we hypothesized that IL-1 beta modulates SND responses to acute physical stress. Therefore, this study examined the effects of IL-1 beta (290 ng/kg iv) and mild hypothermia on renal and interscapular brown adipose tissue (IBAT) SND regulation in chloralose-anesthetized rats. IBAT SND did not change after IL-1 beta administration but was significantly increased during acute mild hypothermia, which was induced 60 min after IL-1 beta treatment. Renal SND was unchanged after IL-1 beta administration and during hypothermia. Acute hypothermia, without prior IL-1 beta administration, did not alter IBAT and renal SND. Increases in IBAT SND during sustained (120 min) hypothermia were significantly higher in IL-1 beta-treated rats compared with saline-treated rats, whereas renal SND responses to sustained hypothermia did not differ among groups. Exposure to acute cold stress after sustained hypothermia produced greater increases in IBAT SND in IL-1 beta-treated rats compared with saline-treated controls. These data suggest that IL-1 beta alters IBAT SND responses to acute and sustained hypothermia.

Measurement of cytokines in clinical samples using immunoassays: problems and pitfalls

With the explosion in interest in cytokines and an increasing understanding of their possible involvement in the pathogenesis of many diseases, the number of studies measuring cytokines in body fluids has increased markedly over the last 5 to 10 years. However, it is readily apparent from the literature that the level of awareness of the many factors that can potentially influence the results obtained is very low. Such factors are likely to contribute considerably to the disparities seen among similar types of study. These include assay properties such as standardization and specificity, type of sample and sample handling, and many biological influences such as age, sex, ethnic background, and diurnal rhythmicity. Clearly, it is not possible to control for all these factors, but a minimum evaluation of assays should be carried out as described, including recovery and parallelity studies using relevant samples and the establishment of reproducibility and normal healthy population levels. An awareness of these factors, which is the purpose of this review, may hopefully lead to an improvement in the quality of studies incorporating the measurement of cytokines in clinical samples and should aid in the interpretation of the data.

Evidence for an intramedullary prostaglandin-dependent mechanism in the activation of stress-related neuroendocrine circuitry by intravenous interleukin-1

We have provided evidence that the stimulatory effects of intravenous interleukin-1 (IL-1) on neurosecretory neurons in the paraventricular nucleus (PVH) that express corticotropin-releasing factor (CRF) depend specifically on the integrity of catecholaminergic projections originating in caudal medulla. Here we report on experiments designed to test alternative means by which circulating IL-1 might access medullary aminergic neurons, including mechanisms involving sensory components of the vagus, the area postrema, or perivascular cells bearing IL-1 receptors. Neither abdominal vagotomy nor area postrema lesions reliably altered Fos expression induced in the medulla or PVH in response to a moderately suprathreshold dose of IL-1beta. Cytokine-stimulated increases in CRF mRNA in the PVH were also unaffected by either ablation. By contrast, systemic administration of the cyclooxygenase inhibitor indomethacin resulted in parallel dose-related attenuations of IL-1 effects in hypothalamus and medulla. Microinjections of prostaglandin E2 (PGE2; >/=10 ng) in rostral ventrolateral medulla, the principal seat of IL-1-sensitive neurons that project to the PVH, provoked discrete patterns of cellular activation in hypothalamus and medulla that mimicked those seen in response to intravenous IL-1. We interpret these findings as supporting the hypothesis that paracrine effects of PGE2 released from perivascular cells in the medulla as a consequence of IL-1 stimulation and, acting through prostanoid receptors on or near local aminergic neurons that project to the PVH, contribute to the stimulatory effects of increased circulating IL-1 on neurons constituting the central limb of the hypothalamo-pituitary-adrenal axis.

Type 1 interleukin-1 receptor in the rat brain: distribution, regulation, and relationship to sites of IL-1-induced cellular activation

Systemic interleukin-1 (IL-1) activates the hypothalamo-pituitary-adrenal (HPA) axis, an effect exerted through increased synthesis and secretion of corticotropin-releasing factor (CRF) by parvicellular neurosecretory neurons. The site(s) and mechanism(s) through which circulating IL-1 may access central systems governing HPA axis output remain obscure. To identify potential cellular targets for blood-borne IL-1, we analyzed the distribution of mRNA encoding the rat type 1 IL-1 receptor (IL-1R1) in rat brain. Regional ribonuclease protection assays detected a single protected fragment corresponding to the membrane-bound form of the IL-1R1 mRNA in all areas analyzed. In situ hybridization revealed labeling predominantly over barrier-related cells, including the leptomeninges, non-tanycytic portions of the ependyma, the choroid plexus, and vascular endothelium. Low to moderate levels of the IL-1R1 mRNA were detected in just a few neuronal cell groups, including the basolateral nucleus of the amygdala, the arcuate nucleus of the hypothalamus, the trigeminal and hypoglossal motor nuclei, and the area postrema. No specific labeling for IL-1R1 mRNA was detected over neurons that respond to intravenous IL-1 beta by induction of transcription factor Fos, including hypophysiotropic CRF cells and brainstem catecholamine neurons. Injection of IL-1 beta did, however, provoke induction of mRNA encoding the immediate-early gene, NGFI-B, but not c-fos, in two major loci of IL-1R1 expression, vascular endothelial cells, and the area postrema. Intravenous injection of IL-1 beta acutely down-regulated IL-1R1 mRNA in perivascular cells, but not in neuronal cell groups. These results suggest the parenchymal sites of IL-1R1 expression in rat to be distinct from those reported previously in mouse. The common expression in both species of an IL-1R in non-neuronal elements highlights the possibility that IL-1-mediated activation of CRF neurons may result from cytokine-receptor interaction at vascular, and/or other barrier-related, sites to trigger release of secondary signalling molecules in a position to interact with components of HPA control circuitry.

Interleukin-1 beta induces long-term increase of axonally transported opiate receptors and substance P

Interleukin-1 is known to exert pleiotropic effects in host defence mechanisms and in inflammation. Chronic pain, inflammation and interleukin-1 beta enhance the production of substance P. Recently, axonal transport of opiate receptors was found to increase in rat sciatic nerves in the model of Freund's adjuvant-induced arthritis. Here we show that a single intraplantar injection of interleukin-1 beta is able to enhance the axonal transport of mu and kappa opiate receptors and substance P. Indeed, their accumulation was markedly increased in the proximal part of ligated sciatic nerves, but only in the paw injected with interleukin-1. The time course revealed a delayed onset and, more importantly, a long-term increase lasting at least six days, which is in contrast with the short-term pyrogenic effect of interleukin-1. Pretreatment of rats with capsaicin or administration of dexamethasone completely prevented the interleukin-1 beta effect. The present results suggest that interleukin-1 beta may serve as a mediator to sensitize nociceptors in chronic inflammation and possibly in hyperalgesia through long-term changes in neuronal plasticity.

Interleukin 1 beta inhibits gastric emptying in rats: mediation through prostaglandin and corticotropin-releasing factor

BACKGROUND/AIMS

Interleukin 1 beta (IL-1 beta) increases the release of corticotropin-releasing factor (CRF) in the brain through prostaglandin pathways. Because central CRF inhibits gastric motor function, the influence and mechanism of action of intracisternal injection of IL-1 beta on gastric emptying were investigated.

METHODS

The 20-minute rate of gastric emptying of a nonnutrient test meal was assessed by the phenol red methylcellulose method 30 minutes after injection of human recombinant IL-1 beta in conscious rats.

RESULTS

IL-1 beta injected intracisternally (0.01-1 ng) or intravenously (0.01-10 ng) dose-dependently decreased gastric emptying by 10%-82% and 0%-89%, respectively. The median effective dose (ED50) was 30-fold lower when IL-1 beta was injected intracisternally (0.1 ng) than intravenously (3 ng). The inhibitory effect of intracisternal IL-1 beta had a rapid onset (within 20 minutes) and was long-lasting (6 hours). Indomethacin (5 mg/kg, intraperitoneally) completely prevented the 61% inhibition induced by intracisternal IL-1 beta (0.1 ng) but had no effect on CRF-induced (600 ng) 72% inhibition of gastric emptying. The intracisternal injection of the IL-1 receptor antagonist (100 ng) or the CRF antagonist [DPhe12, [DPhe12,Nle21,38,C alpha MeLeu37]CRF12-41 (20 micrograms) prevented by 100% and 52%, respectively, the inhibition of gastric emptying evoked by intracisternal IL-1 beta (0.1 ng). The antagonists alone had no effect on basal gastric emptying.

CONCLUSIONS

IL-1 beta acts in the brain to induce a long-lasting inhibition of gastric emptying; IL-1 beta action is mediated through central IL-1 receptors and prostaglandin- and CRF-dependent mechanisms.

Interleukin-1 beta (IL-1) does not reduce the diabetes incidence in diabetes-prone BB rats

The cytokine interleukin 1 beta (IL-1) has been implicated as a pathogenetic factor in the initial events leading to insulin-dependent diabetes mellitus. Previous studies investigating the impact of IL-1 on diabetes incidence in spontaneously diabetic rodent models have been conflicting. IL-1 induces anorexia and previous studies are hampered by the lack of pair-fed controls to the IL-1 treated animals. We report that daily injections of 4.0 micrograms/kg/day of recombinant human IL-1 (rhIL-1) for 13 weeks from 25-30 days of age did not alter the incidence of diabetes in the diabetes-prone (DP) BB rats (75%) when compared to pair-fed, vehicle treated controls (55%, p = 0.18), or to unhandled DP BB rats (80%, p = 0.71). However, IL-1 induced significantly higher blood glucose concentrations in the prediabetic period (p < 0.00005) and at diabetes onset (p < 0.00005) in the DP BB rats and caused episodes of blood glucose concentrations > 11 mmol/l in the prediabetic period in 11/20 DP BB rats compared to 4/27 diabetes-resistant (DR) BB rats and 4/28 Wistar Furth (WF) rats (both p < 0.004), compared to DP BB). Further, rhIL-1 induced fever in 11 weeks in the DP BB rats compared to 3 weeks in the DR BB and 6 weeks in the WF rats. Using high performance size exclusion chromatography specific anti-rhIL-1-antibodies were demonstrated in DR BB and WF, but not in DP BB rats. These antibodies neutralized the inhibitory effect of rhIL-1 on insulin secretion from isolated islets of Langerhans in vitro. The reduced pyrogenic and endocrine effect of rhIL-1 in the DR BB and WF rats compared to the DP BB rats could be explained by the impaired ability of the DP BB rats to produce anti-rhIL-1-antibodies. In conclusion, administration of rhIL-1 modulated the prediabetic period, and produced higher blood glucose concentrations at diagnosis, but did not change the diabetes incidence in DP BB rats. The results are not in conflict with the hypothesis that IL-1 is a pathogenetic factor in IDDM, caused by high local concentrations of rat IL-1 in the islets during early insulitis. The results also show the necessity of pair-feeding of the control group to the rhIL-1 group when interpreting data from experiments investigating rhIL-1 effects on diabetes development in animal models.

Differential effects of human recombinant interleukin-1 beta and dexamethasone on hepatic drug-metabolizing enzymes in male and female rats

Interleukin-1 beta (IL-1) is one of the major inflammation mediators, commonly reported to be an inhibitor of hepatic drug metabolism. We studied the effect of IL-1 treatment on various drug-metabolizing enzymes in male and female rats. IL-1 induced both cytochrome P450 (P450) 3A1 activity and protein in females, but in males, IL-1 repressed P450 3A2 activity, without decreasing the protein. P450 1A1 was impaired in males, but was retained after dexamethasone pretreatment. IL-1 did not change P450 2B1/2 activity and protein, but counteracted their induction by dexamethasone. Uridine diphospho-glucuronosyltransferase (UGT) 1A2 (bilirubin) activity and its induction by dexamethasone were not affected by IL-1 treatment. Both P450 2C11 and epoxide hydrolase activities were repressed by IL-1 treatment, and both activities were impaired after dexamethasone treatment. These results clearly demonstrate that IL-1 acts at different steps of protein synthesis and gene expression. The effect of IL-1 on P450 was isoform-dependent, indicating that IL-1 can act on pretranscriptional events. The discrepancy between the variations of the activities and the protein of P450 3A2 suggests a post-translational regulation. For P450 2C11, 3A1, and for microsomal epoxide hydrolase, but not for P450 1A1 and 2B1/2, IL-1 mimics the glucocorticoid effects. These differential effects can affect the kinetics and the bioavailability of drugs used in pathologies in which IL-1 is increased.

Potent inhibition of gastric acid secretion and ulcer formation by centrally and peripherally administered interleukin-1

IL-1 beta is one of the most potent centrally acting inhibitors of gastric acid secretion in rats. Sites of action have been located in the anterior/preoptic area and paraventricular nucleus of the hypothalamus where other biological activities of IL-1 have also been described. IL-1 beta action is, so far, quite unique to this cytokine and its action is not reproduced by IL-2 or TNF alpha. The IL-1 effect involves prostaglandin pathways and is unrelated to CRF. Similarly, systemic injection of IL-1 induces a long lasting inhibition of acid secretion through prostaglandin-dependent mechanisms. Several findings support the possibility that the effect of systemic IL-1 can be CNS-mediated and/or exerted at the periphery through local release of PG in the stomach. Exogenous IL-1 given into either the circulation or the cerebrospinal fluid also inhibits gastric injury induced by a variety of experimental models (stress, aspirin, ethanol). Such a protective effect is mediated through the inhibition of acid secretion and prostaglandin release, although other mechanisms may also contribute. Whether endogenously released IL-1 beta exerts a protective role in the gastric mucosa is still to be investigated.