Administration Of IL-1beta Research Articles

151. Neuroinflammation: An animal model of fatigue induced through interleukin-1 beta

The immune system, in response to insult or challenge, is able to induce a range of behavioral modifications, collectively known as sickness behavior. These include fatigue, fever, social withdrawal and reduced food intake. Here we describe a recently developed mouse-model of acute fatigue, utilizing the pro-inflammatory cytokine interleukin-1 beta (IL-1 beta). Six month old female C57Bl/6 J mice peripherally administered with 400 ng IL-1 beta show a significant reduction in voluntary wheel running behavior ( p < 0.01) over 24 h. Notably, general locomotor activity, as determined through external motion sensors and abdominally-inserted telemetry probes, shows no significant changes with IL-1 beta administration ( p > 0.05) over this same period. Other symptoms associated with sickness behavior, including fever and weight loss also remain unaffected by IL-1 beta administration ( p > 0.05). Furthermore, we demonstrate dose-dependent effects and age- and sex-related differences in behavioral responses to IL-1 beta treatment. Preliminary data from mice administered with IL-1 beta in the lateral ventricle suggest a centrally mediated fatigue response. We explore these central effects using immunohistochemistry to study changes in central immune responses, specifically microglial activation, in several regions throughout the brain related to the pathways of arousal and motivational responses. This work was supported by the NIH grant R21NR012845.

40. Peripheral administration of d-cycloserine, but not norepinephrine, restores appropriate cognitive function following systemic bacterial endotoxin exposure

Evidence indicates that the ionotropic NMDA and AMPA glutamate neurotransmitter receptors are critically involved in hippocampus-dependent learning and memory processes. Other reports indicate that inflammation attenuates NMDA-dependent LTP, leads to diminished hippocampal NMDAR NR1 subunit and hippocampal BDNF mRNA expression, and results in a decrease in the number of NMDARs within the dentate gyrus. Administration of the NMDA partial agonist d -cycloserine facilitates a faster recovery of recognition memory function and reinstates traumatic brain injury-induced reduction of BDNF in the CA1 subregion of the hippocampus. Affecting a different glutamate receptor, administration of exogenous IL-1beta also down-regulates the surface expression and Ser831 phosphorylation of the AMPAR GluR1. Further, this effect is abrogated via blockade of IL-1R by either anti-IL-1beta antibody or IL-1ra. Norepinephrine, binding beta-adrenergic receptors and subsequently activating the PKA and CaMKII pathways, induces transient phosphorylation of Ser831 sites of the GluR1 subunit containing AMPARs. Therefore, for the current studies, we administered peripheral d -cycloserine, or norepinephrine, to explore potential NMDAR/glycineB-, or AMPAR-mediated restoration of hippocampus-dependent fear conditioning processes following systemic LPS exposure. The results thus far indicate that peripheral administration of d -cycloserine, but not norepinephrine, restores appropriate cognitive function following systemic bacterial endotoxin exposure, though d -cycloserine administration failed to restore hippocampal BDNF expression levels diminished following LPS exposure.

Kawasaki Disease and Hyponatremia

Refer to the page 507-513 Kawasaki disease (KD) is an acute febrile vasculitis of unknown etiology that predominantly affects children younger than 5 years.1),2) Because KD causes systemic vasculitis, multiple organ involvement may ensue, including coronary artery lesions (CALs), carditis, arthritis, hepatitis, central nervous system disease, kidney and urinary tract abnormalities, muscle involvement and hyponatremia.2),3) Nakamura et al.4) also recently reported that hyponatremia at the patient's first visit to hospital might be a predictor of giant coronary aneurysm (>8 mm), and speculated that the relationship between hyponatremia and giant coronary aneurysms is based on endothelial permeability, severity of the illness, dehydration, duration of febrile period. Although hyponatremia is not uncommon in patients with KD,3) the clinical characteristics of KD patients with hyponatremia remain inadequately understood. Patients with hyponatremia may exhibit more severe inflammatory findings, including longer duration of fever, higher C-reactive protein (CRP) concentrations and alanine aminotransferase levels and increased incidence of CAL, than in patients without hyponatremia.5) Lim et al.6) also reported that serum sodium was inversely correlated with neutrophil, CRP, and N-terminal pro-B-type natriuretic peptide, and speculated that hyponatremia occurs in KD patients with more severe inflammation. Although the pathogenesis of hyponatremia in KD remains inadequately understood, several possible mechanisms have been postulated, including the syndrome of inappropriate antidiuretic hormone secretion (SIADH), hyponatremic dehydration and ingestion of fluid that is hypo-osmolar relative to the fluid lost.3) Recently, the relationship between interleukin (IL)-6 or IL-1 beta and ADH secretion has been suggested.7),8) Mastorakos et al.7) reported that plasma ADH levels were elevated after IL-6 injection in cancer patients, suggesting that IL-6 activated the magnocellular ADH-secreting neurons, and that it might be involved in SIADH. Ohta and Ito8) reported four cases with hyponatremia secondary to SIADH, which seems to be related to inflammation. Plasma Na+ concentrations decreased and plasma CRP level increased when the patients had fever. In such conditions, plasma ADH and IL-6 concentrations were increased and there was significant correlation between them. Intravenous administrations of IL-1 beta increased ADH, atrial natriuretic hormone, and adrenocorticotropic hormone (ACTH). The changes in ADH and ACTH were abolished by pretreatment administration of intravenous indomethacin. Also, intravenous administration of IL-1 beta increased urinary sodium excretion. Based on these findings, they speculated that IL-6 and IL-1 beta play an important role in SIADH development associated with inflammation. These findings suggest that natriuresis in KD might be secondary not only to renal involvement, but also cytokines, such as IL-6 or IL-1 beta. IL-1 beta is also recognized as a mediator of endothelial damage in KD.6),9) Therefore, there is a possibility that these cytokines may involve in the pathogenesis of hyponatremia due to SIADH, rather than cerebral vasculitis in KD.10) Further studies are necessary to elucidate the clinical characteristics of KD patients with hyponatremia, and the pathogenesis of hyponatremia in KD.

88. Effects of in vitro administration of IL-1beta on PC-12 cells

88. Effects of in vitro administration of IL-1beta on PC-12 cells

Expression of Proteinase-Activated Receptor-2 in the Intervertebral Disc

Immunohistochemical and biochemical analyses of proteinase-activated receptor-2 (PAR-2) in rat and human intervertebral discs (IVDs). To examine the expression and function of PAR-2 in rat IVD cells, and to determine if PAR-2 is expressed in human IVDs. PAR-2 is a G protein-coupled receptor that contributes to the regulation of inflammatory reactions and the pathophysiology of inflammatory diseases, including arthritis. The expression of PAR-2 in the IVD has not been determined. PAR-2 expression by rat IVD cells and tissues was examined using immunohistochemistry and western blot. Rat anulus fibrosus cells in monolayer culture were used to examine the biologic role of PAR-2 in vitro. The effect of PAR-2-activating peptide (PAR-2AP) on the catabolic cascade was assessed by western blot and real-time PCR. The expression of PAR-2 by human IVD tissues at different stages of degeneration was determined by immunohistochemical analyses. PAR-2 was expressed by rat IVD cells and in both anulus fibrosus and nucleus pulposus tissues, PAR-2 expression was up-regulated by interleukin-1beta (IL-1beta). PAR-2AP significantly increased the release of IL-1beta into the medium. Although PAR-2AP had no direct effect on matrix metalloproteinase-3 (MMP-3) and MMP-13 mRNA levels, treatment with PAR-2AP significantly up-regulated the mRNA levels of a disintegrin and metalloproteinase with thrombospondin motif-4. The simultaneous administration of PAR-2AP and IL-1beta synergistically up-regulated the mRNA levels of a disintegrin and metalloproteinase with thrombospondin motif-4, MMP-3, and MMP-13. The expression of PAR-2 was identified in human IVD tissues. The number of PAR-2-expressing cells was significantly elevated in advanced stages of IVD degeneration compared with those in early stages of degeneration. Our results demonstrate for the first time that IVD cells express PAR-2. The expression of PAR-2 is regulated by IL-1beta stimulation. PAR-2 activation accelerates the expression of matrix-degrading enzymes. PAR-2 may play an important role in the cytokine-mediated catabolic cascade and consequently may be involved in IVD degeneration.

Blockade of central kappa-opioid receptors inhibits the antidipsogenic effect of interleukin-1β

The objective of the present study was to investigate the role of brain kappa-opioid receptors (KOR) in the antidipsogenic effect promoted by third ventricle injections of interleukin-1beta (IL-1beta). Wistar male rats were submitted to three different, thirst-inducing, physiological conditions: dehydration induced by water deprivation, hyperosmolarity induced by salt-load and hypovolemia induced by polyethylene glycol subcutaneous injection. Third ventricle injections of IL-1beta significantly inhibited the increase in water intake observed in those situations. The pharmacological blockade of central KOR by the selective KOR antagonist nor-binaltorphimine (BNI) at different doses significantly inhibited the antidipsogenic effect induced by the central administration of IL-1beta in all conditions tested: dehydration, hypovolemia and hyperosmolarity. The central administration of IL-1beta failed to induce any locomotor deficit, as verified in an open field test. Stimulation of the central interleukinergic component did not result in any general suppression of ingestive behavior since no change in saccharin intake was recorded during a dessert test in animals receiving central injections of IL-1beta. Furthermore, the inhibitory effects of IL-1beta on water intake cannot be attributed to sickness-like effects induced by these compounds, since an aversion test excluded this possibility. In summary, the data shown in the present study clearly show that the antidipsogenic effect observed in rats following third ventricle injections of IL-1beta depend on the functional integrity of a brain kappa-opioid-dependent component.

Il‐1β‐induced post‐transition effect of NF‐kappaB provides time‐dependent wave of signals for initial phase of intrapostatic inflammation

Our previous findings have shown that systemic administration of interleukin (IL)-1 beta induces up-regulation of nuclear factor-kappa B (NF-kappaB) in mouse prostate tissue that may be responsible for leukocyte extravasation into prostate stroma. It has been hypothesized that NF-kappaB plays a role in the development of prostatitis, and that NF-kappaB activation might provide chemoattractive signals for leukocyte extravasation in the prostate. IL-1 beta was administrated intravenously, alone or with dexamethasone (Dex), to separate groups of C57BL/6J mice. Expression of NF-kappaB, chemoattractant receptors, and IL-17F in the prostates of the two groups of mice at various time periods following treatment was evaluated and compared. IL-1 beta administration up-regulated NF-kappaB/p65 activity in the mouse prostate. IL-1 beta administration promoted extravasation and accumulation of CD45+ mononuclear cells but not neutrophils in the mouse prostate stroma. IL-1 beta administration provided earlier (4 hr) CXCR1/IL-8RA receptor expression in mouse prostate as a first signal, inducing capillary homing, adhesion, and initial extravasation of mononuclear cells into the prostate tissue. IL-1 beta administration also induced relatively late (24 hr) up-regulation of VCAM1 in the endothelial cells of microvessels and of IL-17F in prostate epithelium and in stromal infiltrating leukocytes. Concomitant administration of Dex, a known NF-kappaB inhibitor, resulted in significantly down-regulated IL-1 beta-induced NF-kappaB/p65 activity, as well as reduced expression of chemokine receptors and IL-17F in mouse prostate tissue. Systemic IL-1 beta administration induces NF-kappaB-responsive genes to promote aberrant NF-kappaB/p65 activity, which may be critical in the development of prostatitis through its role in the production of chemoattractant signals that promote extravasation and stromal accumulation of mononuclear cells (mainly by CXCR1/IL-8RA), and initiation of a new wave of pro-inflammatory signals favorable to chronic inflammation (mainly by IL-17F).

Involvement of cystic fibrosis transmembrane conductance regulator in infection‐induced edema

Abnormal fluid accumulation in tissues, including the life-threatening cerebral and pulmonary edema, is a severe consequence of bacteria infection. Chlamydia (C.) trachomatis is an obligate intracellular gram-negative human pathogen responsible for a spectrum of diseases, causing tissue fluid accumulation and edema in various organs. However, the underlying mechanism for tissue fluid secretion induced by C. trachomatis and most of other infectious pathogens is not known. Here, we report that in mice C. trachomatis infection models, the expression of cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP activated chloride channel, is up regulated together with increased cytokine release and tissue fluid accumulation that can be reversed by treatment with antibiotic specific for C. trachomatis and CFTR channel blocker. However, C. trachomatis infection cannot induce tissue edema in CFTRtm1Unc mutant mice. Administration of exogenous IL-1beta to mice mimics the C. trachomatis infection-induced CFTR upregulation, enhanced CFTR channel activity and fluid accumulation, further confirming the involvement of CFTR in infection-induced tissue fluid secretion.

Influence of continuous infusion of interleukin-1β on depression-related processes in mice: corticosterone, circulating cytokines, brain monoamines, and cytokine mRNA expression

Activation of the immune system typically occurs on a subchronic or chronic basis (e.g., in response to bacterial or viral insults). However, analyses of the effects of cytokine treatments have typically involved acute treatments, and limited data are available concerning the behavioral and central neurochemical impact of subchronic interleukin-1beta (IL-1beta) administration. Several peripheral and central effects of IL-1beta treatment were assessed following single or repeated bolus injections or after infusion of the cytokine (through Alzet minipumps) over several days. The impact of an acute bolus injection of IL-1beta (1.0 microg) on plasma corticosterone and on circulating IL-1beta, IL-6, and TNF-alpha were diminished following 5-day IL-1beta treatment, although high levels of sickness were still apparent. When IL-1beta (1.0 or 2.0 mug/day) was continuously infused over 3 days, plasma corticosterone and sickness were elevated, but these effects were attenuated after 7 days (subchronic) of treatment. As well, the effects of IL-1beta treatment on diurnal variations of motor activity diminished over days. Despite the diminution of the behavioral and neuroendocrine effects of the cytokine after treatment 7 days, subchronic IL-1beta infusion altered prefrontal cortical and hippocampal serotonin and norepinephrine utilization, and within these regions, the messenger RNA (mRNA) expression of IL-1beta, IL-6, TNF-alpha, and their receptors, as well as that of 5-HT(2C), 5-HT(1B) receptors, and p11, was increased. The findings indicate that peripheral cytokine infusion markedly influences central cytokine mRNA expression and also influences 5-HT turnover, which might contribute to behavioral changes elicited by IL-1beta.

MyD88 signaling in brain endothelial cells is essential for the neuronal activity and glucocorticoid release during systemic inflammation

Activation of neuronal circuits involved in the control of autonomic responses is critical for the host survival to immune threats. The brain vascular system plays a key role in such immune-CNS communication, but the signaling pathway and exact type of cells within the blood-brain barrier (BBB) mediating these functions have yet to be uncovered. To elucidate this issue we used myeloid differentiation factor 88 (MyD88)-deficient mice, because these animals do not show any responses to the cytokine interleukin-1beta (IL-1beta). We created chimeric mice with competent MyD88 signaling in either the BBB endothelium or perivascular microglia of bone marrow origin and challenged them with IL-1beta. Systemic treatment with the cytokine caused a robust transcriptional activation of genes involved in the prostaglandin E(2) (PGE(2)) production by vascular cells of the brain. Upregulation of these genes is dependent on a functional MyD88 signaling in the endothelium, because MyD88-deficient mice that received bone marrow stem cells from wild-type animals (for example, functional perivascular microglia) exhibited no response to systemic IL-1beta administration. MyD88 competent endothelial cells also mediate neuronal activation and plasma release of glucocorticoids, whereas chimeric mice with MyD88-competent perivascular microglia did not show a significant increase of these functions. Moreover, competent endothelial cells for the gene encoding Toll-like receptor 4 (TLR4) are essential for the release of plasma corticosterone in response to low and high doses of lipopolysaccharide. Therefore, BBB endothelial cells and not perivascular microglia are the main target of circulating inflammatory mediators to activate the brain circuits and key autonomic functions during systemic immune challenges.

Molecular imaging of NF‐kappaB in prostate tissue after systemic administration of IL‐1β

Activation of nuclear-factor kappaB (NF-kappaB) influences the transcription of number of genes, many of which participate in inflammatory responses and tumor development. A wide range of human cancers and inflammatory disorders express inappropriate regulation of NF-kappaB. The role of NF-kappaB in intraprostatic inflammation has not been elucidated. Using transgenic NF-kappaB-Luciferase Tag mice coupled to the luciferase reporter gene, we performed serial, noninvasive in vivo and ex vivo molecular imaging of NF-kappaB activation in the mouse body after systemic administration of mouse pro-inflammatory cytokines: TNF-alpha, IL-6, and IL-1 beta at 10 microg/kg body weights. In some experiments, pretreatment with dexamethasone (10 mg/kg) was used to modulate the cytokine-induced NF-kappaB-dependent luminescence in vivo. Treatment of NF-kappaB-Luc mice with cytokines increased luminescence in a time- and organ- specific manner. Highest levels of NF-kappaB-dependent luminescence were observed approximately 3-4 hr after IL-1 beta administration. An important finding was the cumulative effect of IL-1 beta to activate NF-kappaB in the prostate during chronic administration. The molecular imaging of NF-kappaB activity might be an attractive approach to distinguish the role of cytokine-induced NF-kappaB signaling in intraprostatic inflammation and prostate cancer development. Since dexamethasone, a known NF-kappaB inhibitor, could reduce the IL-1 beta-induced NF-kappaB-dependent luminescence in the prostate, NF-kappaB-Luc mice might be useful tool to screen potential candidate drugs for treatment of inflammation and tumor associated with aberrant NF-kappaB activity.

Antigen‐specific suppression of established arthritis in mice by dendritic cells deficient in NF‐κB

NF-kappaB inhibitors applied to animal models of rheumatoid arthritis (RA) demonstrate the important role of NF-kappaB in the production of mediators of inflammation in the joint and their antiinflammatory effects. Because NF-kappaB is involved in the differentiation, activation, and survival of almost all cells, its prolonged inhibition might have unwanted adverse effects. Therefore, we sought to apply NF-kappaB inhibitors more specifically, targeting dendritic cell (DC) differentiation, in order to influence the outcome of the autoimmune response, rather than to produce a broad antiinflammatory effect. We tested whether DCs treated with the NF-kappaB inhibitor BAY 11-7082 and exposed to arthritogenic antigen would suppress established arthritis in C57BL/6 mice. Antigen-induced arthritis was generated in C57BL/6 mice by injection of methylated bovine serum albumin (mBSA). After mBSA challenge, mouse knee joints were injected with antigen-exposed BAY 11-7082-treated DCs or with soluble tumor necrosis factor receptor (sTNFR). Intraarticular injection of interleukin-1 (IL-1) was used to induce disease flare. Inflammation and erosion were suppressed in mice that received mBSA-exposed BAY 11-7082-treated DCs, but not in those that received keyhole limpet hemocyanin-exposed BAY 11-7082-treated DCs. Clinical improvement was dependent on IL-10 and was associated with antigen-specific suppression of the delayed-type hypersensitivity (DTH) reaction and switching of anti-mBSA antibody isotype from IgG2b to IgG1 and IgA. Suppression of the DTH reaction or arthritic disease was not impaired by concomitant administration of sTNFR. Suppression could be reversed with intraarticular administration of IL-1beta and could be restored by a second injection of mBSA-exposed BAY 11-7082-treated DCs. BAY 11-7082-treated DCs induce antigen-specific immune suppression in this model of inflammatory arthritis, even after full clinical expression of the disease. Such DCs have potential as antigen-specific therapy for autoimmune inflammatory arthritis, including RA.

Caspase 1 deficiency reduces inflammation-induced brain transcription.

The systemic inflammatory response syndrome (SIRS) is a life-threatening medical condition characterized by a severe and generalized inflammatory state that can lead to multiple organ failure and shock. The CNS regulates many features of SIRS such as fever, cardiovascular, and neuroendocrine responses. Central and systemic manifestations of SIRS can be induced by LPS or IL-1beta administration. The crucial role of IL-1beta in inflammation has been further highlighted by studies of mice lacking caspase 1 (casp1, also known as IL-1beta convertase), a protease that cleaves pro-IL-1beta into mature IL-1beta. Indeed, casp1 knockout (casp1(-/-)) mice survive lethal doses of LPS. The key role of IL-1beta in sickness behavior and its de novo expression in the CNS during inflammation led us to test the hypothesis that IL-1beta plays a major role modulating the brain transcriptome during SIRS. We show a gene-environment effect caused by LPS administration in casp1(-/-) mice. During SIRS, the expression of several genes, such as chemokines, GTPases, the metalloprotease ADAMTS1, IL-1RA, the inducible nitric oxide synthase, and cyclooxygenase-2, was differentially increased in casp1(-/-) mice. Our findings may contribute to the understanding of the molecular changes that take place within the CNS during sepsis and SIRS and the development of new therapies for these serious conditions. Our results indicate that those genes may also play a role in several neuropsychiatric conditions in which inflammation has been implicated and indicate that casp1 might be a potential therapeutic target for such disorders.

Airway nociceptors activated by pro-inflammatory cytokines

The present studies evaluate whether the vagus nerves link the lungs' immune and neural systems by transmitting information through pulmonary nociceptors. Single unit activities from pulmonary nociceptors [C fiber receptors (CFRs) and high threshold Adelta fiber receptors (HTARs)] were recorded from the cervical vagus nerve in anesthetized, open-chest, and mechanically ventilated rabbits. Interleukin1beta was then injected into the nociceptor field (IL-1beta, 10 microg/ml, 20 microl). Both CFRs and HTARs were stimulated by the local injection; their activities increased from 0.2+/-0.1 to 1.8+/-0.5 imp/s (n=10; p<0.01), and from 0.2+/-0.1 to 1.1+/-0.1 imp/s, respectively (n=6; p<0.01). These increases were greatly attenuated by simultaneous administration of IL-1beta with IL-1 ra, a natural IL-1 receptor antagonist. The nociceptors were not stimulated by local injection of normal saline. Our data demonstrate that nociceptors can be activated by pro-inflammatory cytokines and support the hypothesis that airway nociceptors transmit immune signals from the lung to the brain.

Kawasaki disease and hyponatremia

Sirs, We read with great interest the recent contribution by Watanabe et al. in Pediatric Nephrology [1]. They reported that hyponatremia in Kawasaki disease (KD) is a common finding, which suggests severe inflammation. They suggested that renal salt wasting due to renal involvement might underlie the development of hyponatremia in their patients with KD. They also cited that the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) in KD has sometimes been reported, and cerebral vasculitis is thought to be the etiology of SIADH in KD. Nakamura et al. [2] also recently reported that hyponatremia at the patient’s first visit to hospital might be a predictor of giant coronary aneurysm (>8 mm), which was not mentioned in Watanabe et al.’s study. Nakamura et al. speculated that the relationship between hyponatremia and giant coronary aneurysms is based on the permeability of the endothelium, severity of the illness, dehydration, duration of period with fever, and so forth [2]. Although the exact mechanism for the development of hyponatremia in KD remains unknown, the relationship between interleukin (IL)-6 or IL-1 beta and ADH secretion has been suggested [3, 4]. Mastorakos et al. [3] reported that plasma ADH levels were elevated after IL-6 injection in cancer patients, suggesting that IL-6 activated the magnocellular ADH-secreting neurons and that it might be involved in SIADH. Ohta et al. [4] reported four cases with hyponatremia due to SIADH, which seems to be related to inflammation. The plasma Na concentration decreased when the patients had fever and increased plasma C-reactive protein (CRP) level. In such conditions, plasma ADH and IL-6 concentrations were increased and there was a significant correlation between them. Therefore, they performed animal experiments to investigate the role of IL in the development of SIADH. Intravenous administrations of IL-1 beta increased ADH, atrial natriuretic hormone (ANH), and adrenocorticotropic hormone (ACTH). The changes in ADH and ACTH were abolished by the pretreatment with an intravenous administration of indomethacin. Also, the intravenous administration of IL-1 beta increased the urinary sodium excretion. The pretreatment of HS142-1, an ANH antagonist, abolished the increase in urinary sodium excretion induced by IL-1 beta. Based on these findings, they speculated that IL-6 and IL-1 beta play an important role in the development of SIADH associated with inflammation. These findings suggest that natriuresis in KD might be due to not only renal involvement but also cytokines, such as IL-6 or IL-1 beta. One of our authors reported that serum IL-6 was markedly elevated in the acute stage of KD and serum IL-6 positively correlated with the serum CRP level [5]. IL-1 beta is also recognized as a mediator of endothelial damage in KD [6]. Therefore, there is a possibility that these cytokines might involve the pathogenesis of hyponatremia due to SIADH rather than cerebral vasculitis in KD, although they did not measure serum and urinary osmolarity and urinary electrolytes. Further studies are necessary to elucidate the possible relationship between these cytokines and hyponatremia due to SIADH in KD. Pediatr Nephrol (2006) 21:1490–1491 DOI 10.1007/s00467-006-0242-z

Interleukin‐1β induces the expression of aquaporin‐4 through a nuclear factor‐κB pathway in rat astrocytes

Interleukin (IL)-1beta is known to play a role in the formation of brain edema after various types of injury. Aquaporin (AQP)4 is also reported to be involved in the progression of brain edema. We tested the hypothesis that AQP4 is induced in response to IL-1beta. We found that expression of AQP4 mRNA and protein was significantly up-regulated by IL-1beta in cultured rat astrocytes, and that intracerebroventricular administration of IL-1beta increased the expression of AQP4 protein in rat brain. The effects of IL-1beta on induction of AQP4 were concentration and time dependent. The effects of IL-1beta on AQP4 were mediated through IL-1beta receptors because they were abolished by co-incubation with IL-1 receptor antagonist. It appeared that IL-1beta increased the level of AQP4 mRNA without involvement of de novo protein synthesis because cycloheximide, a protein synthesis inhibitor, did not inhibit the effects of IL-1beta. Inhibition of the nuclear factor-kappaB (NF-kappaB) pathway blocked the induction of AQP4 by IL-1beta in a concentration-dependent manner. These findings show that IL-1beta induces expression of AQP4 through a NF-kappaB pathway without involvement of de novo protein synthesis in rat astrocytes.

Role Played by Brainstem Neurons in Regulating Testosterone Secretion via a Direct Neural Pathway between the Hypothalamus and the Testes

We previously reported anatomical and functional evidence for a direct, inhibitory neural pathway that regulates testosterone (T) secretion independently of the pituitary. This pathway is activated by the intracerebroventricular (icv) administration of agents that stimulate stress responses, such as IL-1beta, corticotropin-releasing factor (CRF), and norepinephrine (NE), which results in a blunted T response to the administration of human chorionic gonadotropin (hCG). Blunting of the T response is mediated by central beta-adrenergic receptor stimulation. CRF, but not ethanol (EtOH) or IL-1beta, acts directly on the paraventricular nucleus of the hypothalamus to activate the pathway. Here we explored the role played by brain areas hypothesized to be part of this pathway, such as neurons in the dorsal pons [including the locus coeruleus (LC) of the brainstem], where NE is produced. Microinfusion of EtOH or IL-1beta, but not CRF, into these neurons activated the pathway. Electrolytic lesions of this region significantly reversed the inhibitory effect of icv-administered EtOH on hCG-induced T release, while having no effect on the ability of IL-1beta or CRF to do so. However, the icv administration of IL-1beta, EtOH, or CRF, in doses that rapidly inhibit the T response to hCG, all caused a significant depletion of NE from the LC. Collectively, these results indicate that in addition to the paraventricular nucleus, the brainstem area containing the LC is part of a neural pathway that connects the brain to the testes independently of the pituitary. We also speculate that EtOH may stimulate this pathway through NE-dependent activation of the dorsal pons.

Development and application of a radioimmunoassay to detect interleukin-1 in rat peripheral circulation.

We describe the development and application of a radioimmunoassay to detect circulating interleukin (IL)-1 beta concentrations in the rat. No IL-1 immunoreactivity above the detection limit of the assay (100 pg/ml) could be detected in plasma of control rats. In contrast, immunoreactive IL-1 was detected after intravenous administration of rat recombinant IL-1 beta (rrIL-1 beta) or bacterial lipopolysaccharide (LPS) to rats. The effect of LPS on plasma immunoreactive IL-1 concentrations was time and dose dependent. The immunoreactive IL-1 response to LPS was prevented by in vivo macrophage depletion induced by liposome-directed macrophage suicide technique. Gel filtration of plasma from LPS-treated rats revealed the presence of a high and a smaller molecular form of immunoreactive IL-1. The small molecular immunoreactive IL-1 peak coeluted with rrIL-1 beta and probably represents the 17-kDa form of IL-1 beta. In conclusion, our data support the hypothesis that IL-1 secreted by macrophages can act as a humoral signal molecule to induce the immunological, metabolic, and neuroendocrine changes in response to bacterial LPS.

Inhibition of water intake by the central administration of IL-1β 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.

Interleukin‐1 beta‐induced expression of the prostaglandin E2‐receptor subtype EP3 in U373 astrocytoma cells depends on protein kinase C and nuclear factor‐kappaB

Both interleukin-1beta (IL-1beta) and prostaglandins (PGs) are important mediators of physiological and pathophysiological processes in the brain. PGE2 exerts its effects by binding to four different types of PGE2 receptors named EP1-EP4. EP3 has found to be expressed in neurons, whereas expression of EP3 in glial cells has not been reported in the brain yet. Here we describe IL-1beta-induced EP3 receptor expression in human astrocytoma cells, primary astrocytes of rat and human origin and in rat brain. Using western blot, we found a marked up-regulation of EP3 receptor synthesis in human and rat primary glial cells. Intracerebroventricular administration of IL-1beta stimulated EP3 receptor synthesis in rat hippocampus. The analysis of involved signal transduction pathways by pathway-specific inhibitors revealed an essential role of protein kinase C and nuclear factor-kappaB in astrocytic IL-1beta-induced EP3 synthesis. Our data suggest that PGE2 signaling in the brain may be altered after IL-1beta release due to up-regulation of EP3 receptors. This might play an important role in acute and chronic conditions such as cerebral ischemia, traumatic brain injury, HIV-encephalitis, Alzheimer's disease and prion diseases in which a marked up-regulation of IL-1beta is followed by a prolonged increase of PGE2 levels in the brain.