Endogenous Receptor Antagonist Research Articles

Expression of Interleukin-1 and temporomandibular disorder: Contemporary review of the literature

Objective: Temporomandibular disorders (TMD) are a group of conditions affecting the temporomandibular joint (TMJ), leading to jaw dysfunction, joint and muscle pain, and a decrease in quality of life. A communication network of pro- and anti-inflammatory mediators called cytokines maintains the homeostasis of the TMJ. This review will focus on the Interleukin (IL) family of cytokines, which have been quantified in TMJ synovial fluids in a variety of studies. IL-1α and IL-1β have pro-inflammatory effects, while the endogenous receptor antagonist (IL-1RA) inhibits the pro-inflammatory effects of IL-1.Methods: A literature search (2006–2016) to identify eligible studies was completed using the PubMed database. Studies identified used saline irrigation to quantify cytokine profiles in synovial fluid of healthy and/or dysfunctional joints.Results: The initial search yielded 111 articles, 5 of which met the inclusion criteria after inter-reviewer discussion.Conclusions: Articles that compared IL-1 concentrations in TMD vs. control groups found significant differences.

Ischemic preconditioning-induced neuroprotection is associated with differential expression of IL-1β and IL-1 receptor antagonist in the ischemic cortex

Ischemic preconditioning (IP) is a phenomenon that organs develop a tolerance toward subsequent lethal ischemic insults. Among the factors that are involved in IP, IL-1β and its endogenous receptor antagonist IL-1ra have been identified as important players in the induction of IP. The present study investigated whether IP affects the levels of these two antagonistic proteins during tolerance and reperfusion periods after ischemic stroke. The IP 24 h prior to ischemic stroke resulted in neuroprotection in the cortex. IP-induced protection is accompanied by increased IL-1β gene and IL-1ra gene and protein levels during the tolerance period. In the post-ischemic cortex, IP resulted in the suppression of IL-1β mRNA and protein levels at 6 h without affecting IL-1ra expression and the up-regulation of IL-1ra protein at 24 h. These findings demonstrate that IP differentially regulates cortical IL-1β and IL-1ra expression before and after ischemic stroke and suggest that the shift toward an anti-inflammatory state in the post-ischemic cortex may contribute to IP-induced neuroprotection.

Humanized MC1R transgenic mice reveal human specific receptor function

The melanocortin receptor, MC1R, is a key regulator of pigmentation in mammals, and is necessary for production of dark eumelanin pigment. Human MC1R variants with reduced or absent function are associated with red hair; mouse mutants result in yellow fur. Previous reports indicate differences between mouse and human receptors in their sensitivity to, and requirement for, alphaMSH agonist. We have generated a transgenic mouse model in which coat pigmentation is mediated solely by human MC1R. Although the hair pigment pattern is superficially normal, we show the human receptor is more sensitive to exogenous ligand than mouse Mc1r. Furthermore, although the endogenous receptor antagonist, agouti signalling protein, blocks activation of human MC1R, its action is unlike that on the mouse receptor in that it does not generate an inverse signal. In transfected cells, both receptors show ligand independent signalling. However, in transgenic mice, the human receptor does not elicit significant eumelanin synthesis in absence of ligand, in contrast to the mouse receptor which gives normal eumelanogenesis without ligand. Thus, the mouse model recapitulates the observation that humans mutated in POMC, the melanocortin precursor gene, lack eumelanin and have red hair. We suggest this apparent paradox can be explained by the much lower receptor number expressed in human versus mouse melanocytes, resulting in a much lower endogenous signalling in vivo.

Inactivation of Caspase‐1 in Rodent Brain: A Novel Anticonvulsive Strategy

Cytokines and related inflammatory mediators are rapidly synthesized in the brain during seizures. We previously found that intracerebral administration of interleukin-1 (IL-1)-beta has proconvulsant effects, whereas its endogenous receptor antagonist (IL-1Ra) mediates potent anticonvulsant actions in various models of limbic seizures. In this study, we investigated whether seizures can be effectively inhibited by blocking the brain production of IL-1beta, by using selective inhibitors of interleukin-converting enzyme (ICE/caspase-1) or through caspase-1 gene deletion. Caspase-1 was selectively blocked by using pralnacasan or VX-765. IL-1beta release was induced in mouse organotypic hippocampal slice cultures by proinflammatory stimuli [lipopolysaccharide (LPS) + adenosine triphosphate (ATP)] and measured with enzyme-linked immunosorbent assay (ELISA). IL-1beta production during seizures was measured in the rat hippocampus by Western blot. Seizures were induced in freely moving mice and rats by intrahippocampal injection of kainic acid and recorded by EEG analysis. Caspase-1 inhibition reduced the release of IL-1beta in organotypic slices exposed to LPS+ATP. Administration of pralnacasan (intracerebroventricular, 50 microg) or VX-765 (intraperitoneal, 25-200 mg/kg) to rats blocked seizure-induced production of IL-1beta in the hippocampus, and resulted in a twofold delay in seizure onset and 50% reduction in seizure duration. Mice with caspase-1 gene deletion showed a 70% reduction in seizures and an approximate fourfold delay in their onset. Inhibition of caspase-1 represents an effective and novel anticonvulsive strategy, which acts by selectively reducing the brain availability of IL-1beta.

Increased risk of noncardia gastric cancer associated with proinflammatory cytokine gene polymorphisms

Background & Aims: Genetic variations in proinflammatory and anti-inflammatory cytokine genes influence individual response to carcinogenic exposures. Polymorphisms in interleukin (IL)-1β and its endogenous receptor antagonist are associated with risk of Helicobacter pylori-related gastric cancer. The aim of this study was to evaluate the role of proinflammatory cytokine gene polymorphisms in gastric and esophageal cancers defined by anatomic subsite. Methods: We assessed polymorphisms of the IL-1 gene cluster and 4 other cytokine genes in a population-based case-control study of upper gastrointestinal cancers, including gastric cardia (n = 126) and noncardia adenocarcinoma (n = 188), esophageal squamous cell carcinoma (n = 53), and adenocarcinoma (n = 108), and frequency-matched controls (n = 212). ORs for the different cancers were computed from logistic regression models adjusted for potential confounding factors. Results: Proinflammatory genotypes of tumor necrosis factor α and IL-10 were each associated with more than doubling of the risk of noncardia gastric cancer. Carriage of multiple proinflammatory polymorphisms of IL-1B o IL-1 receptor antagonist, tumor necrosis factor A, and IL-10 conferred greater risk, with ORs (and 95% confidence intervals) of 2.8 (1.6–5.1) for one, 5.4 (2.7–10.6) for 2, and 27.3 (7.4–99.8) for 3 or 4 high-risk genotypes. In contrast, these polymorphisms were not consistently related to the risks of esophageal or gastric cardia cancers. Polymorphisms in IL-4 and IL-6 were not associated with any of the cancers studied. Conclusions: A proinflammatory cytokine genetic profile increases the risk of noncardia gastric adenocarcinoma but not other upper gastrointestinal cancers, possibly by inducing a hypochlorhydric and atrophic response to gastric H. pylori infection.

Association analysis of polymorphisms at the interleukin-1 locus in essential hypertension.

Infection with microorganisms such as Helicobacter pylori and Chlamydia pneumoniae has been associated with coronary heart disease (CAD) and hypertension (HT). Infection increases the release of pro-inflammatory cytokines, thus facilitating interactions that lead to vascular damage and other effects. We hypothesized that genetically determined differences in activity or responsiveness of cytokine(s) might contribute to HT. The interleukin-1 gene (IL1) cluster on chromosome 2q14 contains three related genes (IL1A, IL1B, and IL1RN) located within a 430-kb region. These encode IL-1alpha and IL-1beta, as well as their endogenous receptor antagonist, IL-1ra. The IL1RN gene has a penta-allelic 86-bp tandem repeat in intron 2. Allele IL1RN* 2 is associated with a wide range of chronic inflammatory and autoimmune conditions, and its combination with the -31T variant of an IL1B C(-31)T polymorphism constitutes a pro-inflammatory haplotype that leads to vigorous IL-1beta production. We therefore tested each of these polymorphisms for association with HT. Subjects were white Anglo-Celtic residents of Sydney, Australia. Frequencies of IL1B C(-31)T genotypes CC, CT, and TT were 0.50, 0.40, and 0.10 in normotensive (NT) and 0.46, 0.46, and 0.08 in HT, respectively (chi(2) = 1.2, P = 0.55). T allele frequency in NT (0.30) was similar to that in HT (0.31). For the IL1RN variant, frequencies of alleles IL1RN* 1 and * 2 and combined minor alleles * 3, * 4, and * 5 were 0.61, 0.36, and 0.03 in NT and 0.54, 0.36, and 0.10 in HT, respectively (chi(2) = 11, P = 0.004). In conclusion, no association of the IL1B C(- 31)T with HT was found, whereas combined frequency of the minor alleles of the IL1RN polymorphism was increased in the HT cohort studied.

Powerful anticonvulsant action of IL-1 receptor antagonist on intracerebral injection and astrocytic overexpression in mice.

IL-1beta and its endogenous receptor antagonist (IL-1Ra) are rapidly induced by seizures in the rodent hippocampus. Exogenously applied IL-1beta prolongs seizures in an IL-1R type I-mediated manner. This effect depends on N-methyl-d-aspartate receptor activation. We report here that intrahippocampal application of recombinant IL-1Ra or its selective endogenous overexpression in astrocytes under the control of glial acidic fibrillary protein promoter potently inhibits motor and electroencephalographic seizures induced by bicuculline methiodide in mice. Accordingly, transgenic mice show a reduced seizure-related c-fos mRNA expression in various forebrain areas compared with their wild-type littermates. Recombinant IL-1Ra was ineffective in mice deficient in IL-1R type I, having per se a delayed onset to generalized convulsions. These results demonstrate that IL-1Ra mediates potent anticonvulsant effects acting on IL-1R type I and suggest that the balance between brain IL-1beta and IL-1Ra represents a crucial mechanism to control seizure generalization.

Screening of receptor antagonists using agonist-activated patch clamp detection in chemical separations.

We present a capillary electrophoresis-patch clamp detection system optimized for screening of antagonists and inhibitors of ligand-gated ion channels. In this system, highly selective receptor agonists are delivered through the electrophoresis capillary to the cell surface where they continuously activate a receptor, resulting in increased steady-state transmembrane currents. Thus, receptor selection and biosensor functionality is simply achieved by selection of an appropriate agonist. The antagonists are fractionated in the same electrophoresis capillary and inhibit the agonist-evoked response, resulting in transiently decreased steady-state transmembrane currents. Specifically, a mixture containing 6-cyano-7-nitroquinoxaline-2,3-dione, that reversibly blocks alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate and kainate receptors, and 6,7-dichloro-3-hydroxy-2-quinoxaline-carboxylate, a broad-spectrum glutamate receptor antagonist, were separated and detected by kainate-activated patch-clamped interneurons freshly dissociated from rat brain olfactory bulb. In addition, Mg2+ that reversibly blocks the N-methyl-D-aspartate receptor in a voltage-dependent way was detected using the same cell detector system when activated by N-methyl-D-aspartate and the co-agonist glycine. The presented method offers new possibilities for drug screening and for identifying endogenous receptor antagonists and to determine their mode of action on any ionotropic receptor system of interest.

Interleukin-1β Inhibits Glutamate Release in Hippocampus of Young, But Not Aged, Rats

The proinflammatory cytokine, interleukin-1, is synthesized in neuronal and glial cells and is released in response to stress/injury. IL-1 exerts profound effects on the central nervous system, which include an inhibitory effect on synaptic activity in hippocampus, a brain area expressing a high density of IL-1 receptors. We report that IL-1β has an inhibitory effect on KCl-stimulated release of glutamate and KCl-stimulated [ 45Ca] influx in synaptosomes prepared from hippocampus of 4-month-old rats. These effects were inhibited by the endogenous receptor antagonist, IL-1ra, and by the phospholipase A 2 (PLA 2) inhibitor, quinacrine, suggesting that IL-1 receptor activation is coupled to PLA 2. An inhibitory effect of IL-1β on protein kinase C activity was also observed. KCl-induced calcium-dependent release and calcium influx, and protein kinase C activity were significantly decreased in hippocampal synaptosomes prepared from 22-month-old compared to 4-month-old animals. In contrast to the inhibitory effect of IL-1β in synaptosomes prepared from young adult animals, no effect was observed on release, calcium influx, or protein kinase C activity in synaptosomes prepared from aged animals. We report that there is an age-related increase in expression of IL-1β in hippocampus and propose that this change may underlie the attenuated responses to IL-1β in hippocampus of aged animals.

Interleukin-1 Receptor Antagonist Protein and mRNA in the Rat Adrenal Gland

The occurrence of the endogenous receptor antagonist for the cytokine interleukin-1 in the rat adrenal gland was analyzed y polymerase chain reaction and by immunohistochemistry using a rabbit polyclonal antiserum. Expression of interleukin-1 receptor antagonist mRNA was demonstrated in both adrenal medulla and cortex, and a marked increase in the transcription was observed after systemic administration of lipopolysaccharides. Interleukin-1 receptor antagonist immunoreactivity was seen in the adrenal medulla, and the immunofluorescence intensity was stronger in the adrenergic, phenylethanolamine N-methyltransferase-positive cells than in the noradrenergic chromaffin cells. The distribution of interleukin-1 receptor antagonist protein is complementary to that of interleukin-1 alpha-like immunoreactivity found in phenylethanolamine N-methyltransferase-negative cells and overlaps with and resembles the distribution of interleukin-1 beta-immunoreactive material. The expression of the interleukin-1 receptor antagonist in the adrenal gland complements previous findings of large constitutive pools of interleukin-1 alpha and interleukin-1 beta in this neuroendocrine organ and also suggests participation of adrenal interleukin-1 receptor antagonist in neuroimmune modulation.

Biologic control of the tumor necrosis factor and interleukin-1 signaling cascade

It is clear that activation of the proinflammatory cytokine cascade is both the cause and the consequence of renal injury. Recently, it has been appreciated that a rich network of signaling pathways contributes to modulation of tumor necrosis factor-alpha (TNF) and interleukin-1 (IL-1) bioactivity, both in vitro and in vivo. Insight into the checks and balances that intervene or temper endogenous cytokine effector mechanisms has arisen from an explosion of new information on the cell biology of proinflammatory cytokines. Novel mechanisms of cytokine regulation are currently being described and hold promise for therapeutic potential: soluble cytokine receptors, endogenous receptor antagonists, and anti-inflammatory cytokines such as IL-4, IL-10, and IL-13.

Cytokines in neuronal cell types

Cytokines are signals in the immune system, and may have effects on cells distant from the cells of origin. These proteins have been suggested as messengers in the communication between the immune system and the nervous system, in which signals travel only short distances. Neuroimmune interactions have been discussed in view of findings that nervous signals are important for the immune response. The occurrence of neurotransmitter receptors on lymphocytes and cytokine receptors on nerve cells or glia has initiated further studies e.g. on the localization of different cytokines in the nervous system and on long and short term actions of cytokines in the nervous system. Interleukin-1 has been studied extensively along these lines, and found to occur in the nervous and endocrine system, for example in the adrenal chromaffin cells, and to have effects such as induction of slow-wave sleep and stimulation of adrenocortical and gonadotropic hormones. Other cytokines implicated as signals in neuroimmune interactions are IL-2, IL-6, IFN-γ and TNF-α. The functional studies suggest the occurrence of cytokine receptors in the brain, and experiments using 125iodine-labelled IL-1α demonstrate differential distribution of binding sites in the mouse brain. Recently, evidence emerged of an endogenous receptor antagonist for IL-1, which may prove useful for the understanding of the mechanisms of IL-1's actions in the nervous system. A role for cytokines in regulation of the immune response but also in adjusting the organism to the host reaction is implicated. Furthermore, several findings indicate their role as growth promoting factors, and for example the induction of NGF production by IL-1 suggests involvement of this cytokine in regeneration and development in the nervous system. The significance of neuronally produced cytokines may be based upon the anatomically distinct releasing sites that the specific synaptic organization of the nervous system offer and future studies should determine whether cytokines act as neurotransmitters.

9 - Native cytokine antagonists

Cytokines orchestrate the complex homeostasis of cells and tissues by acting in both an autocrine and paracrine fashion. The processes responsible for regulation of cytokines is not well understood. This chapter has summarized what is known about antagonism and inhibition of the action of cytokines. Several concepts have emerged from work in this area. At least two cytokines (IL-1 alpha and IL-1 beta) have an endogenous receptor antagonist, the IL-1 receptor antagonist. This is the first example of one endogenous molecule directly blocking the binding of another molecule to its receptor: most forms of regulation occur through independent receptors. Several cytokines, including TNF, IFN-gamma, IL-2 and IL-4, are inhibited by soluble receptors. Several cytokines, including IL-10, TGF-beta and MDF, act to inhibit other cytokines. It is likely that these inhibitors will be found to have pleiotropic actions in vivo. Finally, we describe antibody inhibition of cytokines. Detailed studies will be required to understand the complex interplay of the aforementioned cytokine inhibitors and the processes they regulate.