The interleukin-1 receptor in Raji human B-lymphoma cells. Molecular characterization and evidence for receptor-mediated activation of gene expression

Toxicity of silver nanoparticles on Endometrial Receptivity in Female Mice

Nanoparticles (NPs) have many toxic effects on fertility and can prevent successful implantation by affecting the maternal uterine tissue. Herein, by deploying thirty female NMRI mice, the effect of silver nanoparticles on the endometrium and implantation has been investigated. Using spherical silver nanoparticles of a diameter of 18-30 nm at doses of 2 and 4 mg/kg, mice in both groups were treated. Then, female mice mated with male mice. Endometrial tissue was extracted 4.5 days later. On the fourth day of pregnancy, the mice were anesthetized and blood samples were taken from the heart; furthermore, endometrial tissue was isolated and used for molecular tests, ICP, and examination of pinopods. The results revealed that the levels of IL6 and IL1β and the accumulation of nanoparticles in endometrial tissue in the group receiving nanoparticles at a dose of 4 mg/kg had a major increase relative to the other two groups (p<0.05); group receiving a dose of 4 mg/kg, exhibited a decrease in pinopods and microvillus compared to the other two groups. According to the results, NPs can reach the endometrium, suggesting that caution should be exercised due to serious exposure to nanoparticles throughout pregnancy.

Endocytosis of pro-inflammatory cytokine receptors and its relevance for signal transduction

The pro-inflammatory cytokines tumor necrosis factor (TNF), interleukin-1 (IL-1) and interleukin-6 (IL-6) are key players of the innate and adaptive immunity. Their activity needs to be tightly controlled to allow the initiation of an appropriate immune response as defense mechanism against pathogens or tissue injury. Excessive or sustained signaling of either of these cytokines leads to severe diseases, including rheumatoid arthritis, inflammatory bowel diseases (Crohn's disease, ulcerative colitis), steatohepatitis, periodic fevers and even cancer. Studies carried out in the last 30 years have emphasized that an elaborate control system for each of these cytokines exists. Here, we summarize what is currently known about the involvement of receptor endocytosis in the regulation of these pro-inflammatory cytokines' signaling cascades. Particularly in the last few years it was shown that this cellular process is far more than a mere feedback mechanism to clear cytokines from the circulation and to shut off their signal transduction.

Interleukin-1 receptor antagonist mediates toll-like receptor 3-induced inhibition of trophoblast adhesion to endometrial cells in vitro

STUDY QUESTION

Is interleukin-1 receptor antagonist (IL-1RA) involved in the toll-like receptor 3 (TLR 3)-induced inhibition of trophoblast cells' adhesion to endometrial cells in vitro?

SUMMARY ANSWER

IL-1RA mediates the TLR 3-induced inhibition of trophoblast cells' adhesion to endometrial cells in vitro.

WHAT IS KNOWN ALREADY

It is well documented that endometrial TLR 3 activation leads to impairment of trophoblast binding to endometrial cells in vitro. IL-1RA is known as an anti-implantation factor, as its injection significantly reduced implantation rates in mice by an effect on endometrial receptivity.

STUDY DESIGN, SIZE, DURATION

Poly I:C was used as a TLR3 specific ligand and endometrial cells were either treated or not with Poly I:C (treated versus control) in vitro. IL-1RA was applied to block IL-1 signal transduction. IL-1RA was knocked down by Accell Human IL1RN siRNA. Flagellin was used to stimulate TLR 5. SP600125 (JNK) was applied to inhibit the mitogen-activated protein kinases (MAPK) pathway. BAY11 -7082 was used to inhibit the nuclear factor-κB (NF-κB) pathway. The experiments were performed in three replicates on three separate days.

PARTICIPANTS/MATERIALS, SETTING, METHODS

An in vitro assay was developed using RL95-2 (an endometrial cell line) and JAr (a trophoblast cell line) cells. Initially, the production of IL-1RA in RL95-2 cells in response to TLR 3 activation was measured. To determine whether the TLR 3-induced inhibition of trophoblast binding was mediated through IL-1RA: (i) we evaluated the effect of IL-1RA on the attachment of trophoblast cells to endometrial cells; (ii) we knocked down TLR3-induced IL-1RA gene expression by IL-1RA Small interfering RNA (siRNA) and evaluated trophoblast attachment to endometrial cells. Finally, to clarify through which pathway TLR 3-induced inhibition of trophoblast binding occurs: (i) activation of NF-κB and MAPK was detected by transfecting the cells with secreted placental alkaline phosphatase reporter plasmids bearing promoter sequences for each transcription factor; (ii) the inhibitors for NF-κB and MAPK were used to block signaling; (iii) it was then investigated whether addition of these inhibitors could restore the TLR 3-induced impairment of trophoblast attachment to the endometrial cells.

MAIN RESULTS AND THE ROLE OF CHANCE

Our results showed that addition of polyinosinic:polycytidylic acid (Poly I:C) to RL95-2 cells significantly increased the production of IL-1RA (P < 0.05). Addition of human recombinant IL-1RA to RL95-2 cells remarkably decreased the adhesion rate of trophoblast cells to endometrial cells (P < 0.05). In addition, suppression of TLR3-induced IL-1RA gene expression in RL95-2 cells significantly restored trophoblast cells attachment to endometrial cells in the presence of Poly I:C (P < 0.05). Only TLR3 and not TLR5 induced MAPK activation (P < 0.05). TLR3 ligation did not affect NF-κB activation. Of NF-kB and MAPK inhibitors, only MAPK's inhibitor could achieve restoration of spheroid adhesion to endometrial cells (P < 0.05).

LIMITATIONS, REASONS FOR CAUTION

This study has been only done in vitro. Future in vivo studies will confirm our data.

WIDER IMPLICATIONS OF THE FINDINGS

The findings of this study have a potential clinical application in introducing IL-1RA as one of the diagnostic infertility markers in the endometrium, which can affect the process of embryo adhesion at the time of implantation. Moreover, based on the novel data obtained in the current study, blocking and regulating the MAPK pathway by its inhibitors can be used as a new strategy to prevent and treat virus-induced infertility cases in ART techniques.

STUDY FUNDING/COMPETING INTEREST

This study was partially funded by a Marie Curie IIF-253948 grant to I.C. and was partially funded by the author's institutions. The authors have no conflict of interest to declare.

The role of interleukins in the ovary

A brief look at the history of cytokine research shows that the term ‘lymphokine’ was first described in 1969 as the product of sensitized lymphocytes exposed to specific antigens. To eliminate the incorrect notion that such proteins can be produced only by lymphocytes, Cohenet al.(1974) proposed the term ‘cytokines’ to indicate their production also by nonlymphoid cells.2After a long-persisting reluctance, it seems that ‘cytokine’ is becoming the prevalent term for these proteins. Meanwhile, a group of participants at the Second International Lymphokine Workshop held in 1979 proposed the term ‘interleukin’ in order to develop, ‘a system of nomenclature based on the protein's ability to act as communication signals between different populations of leukocytes’.3They introduced the names IL-I and IL-2 for two important cytokines. Since then the number of described interleukins reached 16 and this number may increase. Furthermore, notwithstanding this previous notion, interleukins are now known to be produced in a variety of tissues other than leucocytes and affect the functions of many and diverse somatic cell types (e.g. IL-1 or IL-6). Therefore, while many cytokines are now termed as interleukins, others continue to be known by their old names [e.g. tumour necrosis factor-alpha (TNF-α)], suggesting that they had been recognized earlier, but all of them are included under the generic name of cytokines.

Endometrial receptivity markers, the journey to successful embryo implantation

Human embryo implantation is a three-stage process (apposition, adhesion and invasion) involving synchronized crosstalk between a receptive endometrium and a functional blastocyst. This ovarian steroid-dependent phenomenon can only take place during the window of implantation, a self-limited period of endometrial receptivity spanning between days 20 and 24 of the menstrual cycle. Implantation involves a complex sequence of signalling events, consisting in the acquisition of adhesion ligands together with the loss of inhibitory components, which are crucial to the establishment of pregnancy. Histological evaluation, now considered to add little clinically significant information, should be replaced by functional assessment of endometrial receptivity. A large number of molecular mediators have been identified to date, including adhesion molecules, cytokines, growth factors, lipids and others. Thus, endometrial biopsy samples can be used to identify molecules associated with uterine receptivity to obtain a better insight into human implantation. In addition, development of functional in vitro systems to study embryo-uterine interactions will lead to better definition of the interactions existing between the molecules involved in this process. The purpose of this review was not only to describe the different players of the implantation process but also to try to portray the relationship between these factors and their timing in the process of uterine receptivity.

Interleukin-1 system messenger ribonucleic acid and protein expression in human fallopian tube may be associated with ectopic pregnancy

OBJECTIVE

To investigate the interleukin-1 (IL-1) system mRNA and protein expression in human fallopian tubes with ectopic pregnancies.

DESIGN

A controlled study.

SETTING

Clinical and academic research setting in a university medical center.

PATIENT(S)

Women undergoing salpingectomy for fallopian tube with ectopic pregnancy and women undergoing tubal ligation.

INTERVENTION(S)

Paired segments of human fallopian tubes containing an ectopic pregnancy and parafallopian tube segments adjacent to the ectopic pregnancy were collected from five women undergoing laparoscopic salpingectomy. Segments of fallopian tubes from four women undergoing tubal ligation were used as control tissues. Quantitative competitive polymerase chain reaction (QC-PCR) and immunohistochemistry were performed.

MAIN OUTCOME MEASURE(S)

The differences of IL-1 system mRNA and the ratio of IL-1beta to IL-1 receptor antagonist (IL-1ra) in both fallopian tubes with ectopic pregnancies and normal controls were analyzed.

RESULT(S)

A complete IL-1 system mRNA and protein expression was identified in both fallopian tubes with ectopic pregnancies and normal controls. As QC-PCR demonstrated, IL-1beta mRNA expression was decreased, and IL-1ra and IL-1 receptor type 1 were increased in fallopian tubes with ectopic pregnancies in comparison with normal control tubes. In para-ectopic tubes, IL-1 receptor type 1 mRNA was statistically significantly increased in comparison with normal controls. There was a lower ratio of IL-1beta to IL-1ra at mRNA in fallopian tubes with ectopic pregnancies.

CONCLUSION(S)

These results suggest that an inappropriate ratio of IL-1beta to IL-1ra and a higher expression of its receptor in fallopian tubes may possibly be implicated to the implantation of an ectopic pregnancy in the oviduct.

Interleukin-1beta-induced expression of IL-6 and production of human chorionic gonadotropin in human trophoblast cells via nuclear factor-kappaB activation

PROBLEM

The cytokine, interleukin-6 (IL-6), stimulates the production of human chorionic gonadotropine (hCG) in chorionic cells. The purpose of this study was to examine the role of nuclear factor-kappaB (NF-kappaB) during the induction of IL-6 by IL-1beta in human trophoblast cells.

METHOD OF STUDY

Reverse transcription-polymerase chain reaction was used to determine the gene expressions of IL-1, IL-1 receptor (IL-1R), IL-6R and gp130 in a human choriocarcinoma cell line, BeWo. The BeWo cells were cultured for 24 hr with IL-1beta (0-10 ng/mL), IL-1beta (10 ng/mL) together with IL-1 receptor antagonist (IL-1Ra) or NF-kappaB inhibitor, N-tocyl-l-phenylalanine chloromethyl ketone (TPCK). The concentrations of IL-6 in culture supernatants were measured by enzyme-linked immunosorbent assay.

RESULTS

The gene expressions of IL-1R, IL-6R and gp130, but not IL-1beta, were observed. The concentration of IL-6 was enhanced by IL-1beta in a dose-dependent fashion. The addition of IL-1Ra neutralized the effects of IL-1beta on IL-6 secretion. IL-1beta induced expression of phosphorylated IkappaB and the activation of NF-kappaB. The addition of TPCK reduced the IL-1beta-induced IL-6 expression. Adding IL-1beta increased beta-hCG production in a dose-dependent manner, and the addition of TPCK neutralized the effect of IL-1beta.

CONCLUSION

IL-1beta may induce the IL-6 expression and hCG production in human BeWo cells via NF-kappaB.

Interleukin-1beta regulation of gonadotropin-releasing hormone messenger ribonucleic acid in cultured human endometrial stromal cells

OBJECTIVE

To investigate the role of interleukin-1beta (IL-1beta) in regulating GnRH mRNA expression in cultured human endometrial stromal cells using a modified semiquantitative competitive reverse transcription and polymerase chain reaction (PCR).

DESIGN

A controlled study.

SETTING

Clinical and academic research setting in a university medical center.

PATIENT(S)

Women undergoing hysterectomy for nonmalignant indications.

INTERVENTION(S)

Confluent stromal cell cultures treated with steroid hormones were stimulated with IL-1beta and attenuated by anti-IL-1beta antibody or IL-1 receptor antagonist.

MAIN OUTCOME MEASURE(S)

The human endometrial stromal cell expression of GnRH and its receptor were determined by PCR. Interleukin-1beta-mediated regulation of stromal cell GnRH mRNA expression was determined by quantitative competitive PCR.

RESULT(S)

The GnRH and GnRH receptor mRNA expression were amplified in cultured stromal cells by PCR and two rounds of nested PCR, respectively. Treatment with IL-1beta stimulated stromal cell GnRH mRNA expression at concentrations of IL-1beta above 10 IU/mL. Recombinant IL-1 receptor antagonist and anti-IL-1beta antibody attenuated the increase of gene expression of GnRH initiated by IL-1beta.

CONCLUSION(S)

These results provide indirect evidence that IL-1beta may play a crucial role at the level of embryo-maternal interaction by regulating stromal cell expression of GnRH and its receptor, both known to be important in mediating trophoblast invasion and placental hormone regulation.

Interleukin (IL)-1beta regulation of IL-1beta and IL-1 receptor antagonist expression in cultured human endometrial stromal cells

The interleukin (IL)-1 system is a major regulator of local cellular interactions during embryonic implantation. Because IL-1beta and IL receptor antagonist (IL-1ra) are both expressed in human endometrium, we hypothesized that an appropriate ratio of IL-1beta to IL-1ra might favor the process of embryo implantation. Therefore, we investigated IL-1 regulation of the quantitative ratio of IL-1beta/IL-1ra messenger RNA (mRNA) expression in human endometrial stromal cells using quantitative competitive PCR, as well as intracellular protein expression after stromal cell solubilization. Confluent stromal cell cultures were stimulated with human IL-1beta (0-1000 IU/mL) for 24 h. After 24 h, total RNA was extracted, reverse transcribed, and coamplified by PCR with a defined amount of internal standard. The quantitative ratio was determined by the density of target to the internal standard. After culture with IL-1beta for 24 and 48 h, stromal cells were solubilized, and the intracellular protein levels of IL-1beta and IL-1ra were measured by enzyme-linked immunosorbent assay. The IL-1beta and IL-1ra mRNA were both up-regulated, and IL-1R tI mRNA was down-regulated, by IL-1beta in a dose-dependent manner. The quantitative ratio of IL-1beta to IL-1ra mRNA was constant with the presence of increasing concentrations of IL-1beta (1-1000 IU/mL). IL-1beta and IL-1ra protein was not detected in conditioned media of cultures before addition of IL-1beta. IL-1beta and IL-1ra protein levels increased with increasing amounts of IL-1beta after solubilization of stromal cells. The IL-1beta was detectable after 12 h of culture, in comparison with IL-1ra, which was detectable after 24 h of IL-1beta stimulation. These results suggest that IL-1 may play a crucial role in embryo-maternal interaction by regulating stromal cell expression of IL-1beta and IL-1ra, resulting in an appropriate ratio during the process of embryonic implantation.

Triphasic expression of interleukin-1 receptor type I in human endometrium throughout the menstrual cycle of fertile women and women with unexplained infertility

OBJECTIVE

To evaluate expression of interleukin-1 receptor type I in the endometrium of fertile women throughout the menstrual cycle and to investigate whether unexplained infertility may be associated with abnormal expression of IL-1 receptor type I.

DESIGN

Retrospective study using immunohistochemical technique, Western blot assay, and reverse transcription polymerase chain reaction.

SETTING

Gynecology clinic and human reproduction research laboratory.

PATIENT(S)

39 fertile women and 25 women with unexplained infertility.

INTERVENTION(S)

Endometrial biopsy of samples obtained at laparoscopy.

MAIN OUTCOME MEASURE(S)

Immunostaining intensity, molecular weight, and messenger RNA levels of IL-1 receptor type I.

RESULT(S)

Immunostaining showed that two threshold days (13 and 22) separate the menstrual cycle into three distinct periods of IL-1 receptor type I expression, both in epithelial and stromal cells. Results of Western blot assay and reverse transcription polymerase chain reaction confirmed the immunohistochemical data. Statistical analyses showed that the pattern of IL-1 receptor type I expression was similar in women with unexplained infertility and fertile women.

CONCLUSION(S)

IL-1 receptor type I exhibits three distinct levels of expression throughout the menstrual cycle in the endometrium of fertile women, suggesting different physiologic roles of the receptor within the cycle. However, IL-1 receptor type I does not seem to be involved in unexplained infertility.

Coordinated regulation of ceruloplasmin and metallothionein mRNA by interleukin-1 and copper in HepG2 cells

During the acute phase response, cytokines induce hepatic metallothionein and ceruloplasmin synthesis and the uptake of metals. We have investigated how copper and cytokines may interact in controlling ceruloplasmin (CP) and metallothionein mRNA in liver cells. We found that IL-1alpha, IL-1beta and IL-6 increased both metallothionein-1 (MT-1) and metallothionein-2 (MT-2) mRNA in HepG2 cells. The time and pattern of induction was different, both IL-1alpha and IL-1beta inducing two peaks of MT-1 and MT-2, with that of MT-2 being much larger. IL-6 induced only low levels of both MT-1 and MT-2 mRNA. CP mRNA was also increased after 16 h by IL-1beta, whereas IL-1alpha induced two CP peaks at 8 and 20 h, while IL-6 had little effect. Copper administration gave rise to substantially increased MT-1 mRNA, a slightly lower increase in MT-2 and also a significant increase in CP mRNA with similar kinetics. These parallel increases in MT and CP mRNA suggest that the coordinated expression of these proteins may be important for their synthesis during the acute phase response.

Gene transfer of type 1 interleukin-1 receptor extracellular-domain complementary DNA into rabbit synovial cell line HIG-82 results in cellular blockade of interleukin-1 signal transduction

OBJECTIVE

To produce, by means of expression cloning, a soluble type 1 interleukin-1 receptor (sIL-1R), and to assess its inhibitory properties on the IL-1 pathway.

METHODS

High-affinity IL-1R sites were identified in a human chondrosarcoma cell line by means of 125I-IL-1beta binding. A 1-kilobase complementary DNA (cDNA) encoding the ligand-binding domain of the type 1 IL-1R was cloned by using polymerase chain reaction, and the cDNA was inserted into a mammalian expression vector pRc/CMV. The sIL-1R expression vector was transfected into a rabbit synovial cell line (HIG-82) and a stably transfected cell population was selected. The production of sIL-1R was confirmed in the medium of transfected cells using 125I-IL-1beta binding. 35S labeling of transfected cultures, followed by immunoprecipitation and gel electrophoresis, was used to characterize the size of the recombinant sIL-1R. Stromelysin and IL-1alpha steady-state messenger RNA (mRNA) levels were assessed by Northern blotting. Prostaglandin E2 (PGE2) release was measured by enzyme-linked immunosorbent assay.

RESULTS

IL-1R on the surface of HIG-82 cells bound 125I-IL-1beta with an equilibrium dissociation constant (Kd) of 67.3 +/- 7.8 pM (mean +/- SD). Transfection of the sIL-1R expression vector into a synovial cell line in vitro resulted in the appearance of an sIL-1R protein that bound 125I-IL-1beta with high affinity in the medium (Kd = 108 +/- 5 pM). Two protein bands (Mr 42 kd and 47 kd) were immunoprecipitated with an antibody against type 1 T cell-derived sIL-1R. Expression of sIL-1R was accompanied by a marked decrease in both stromelysin and IL-1alpha steady-state mRNA levels. In conjunction, there was a significant inhibition of basal and IL-1-stimulated PGE2 released by sIL-1R-producing cells.

CONCLUSION

The data suggest that gene transfer of type 1 sIL-1R into the synovium may be an effective means of inhibiting IL-1-induced metalloproteinase expression and inflammatory responses.

Preferential localization of systemically administered radiolabeled interleukin 1alpha in experimental inflammation in mice by binding to the type II receptor

Previously, we have shown that systemically administered radiolabeled interleukin 1alpha (IL-1alpha) accumulates preferentially in inflammatory foci in mice. Since inflammation is characterized by influx of leukocytes, which represent IL-1 receptor (IL-1R) positive cells, radiolabeled IL-1 may specifically localize in inflammation by binding to its receptors on infiltrated leukocytes. This hypothesis was tested in a series of studies in mice with acute focal inflammations. Evidence for specific IL-1-IL-1R interaction in induced inflammation was found: microscopic autoradiography revealed that 125I-IL-1alpha localized at the site of inflammatory cells with time; 125I-myoglobin, a similar-sized protein with no known interactions in vivo, was not retained in the inflammation. Furthermore, the uptake 125I-IL-1alpha in inflammatory tissue was significantly lower in neutropenic mice than in immunocompetent mice (0.05+/-0.004 vs. 0.65+/-0.06% ID/g at 48 h after injection, P < 0.0007). Moreover, the uptake of 125I-IL-1alpha at the inflammatory site could be blocked with the anti-IL-1R type II antibody 4E2. At 48 h after injection, the uptake with and without blocking the type II IL-1R was 0.13+/-0.01 and 0. 65+/-0.05% ID/g, respectively (P < 0.0001). These in vivo studies provide evidence that systemically administered radiolabeled IL-1alpha localizes in inflammatory tissue by specific receptor binding, predominantly by binding to the type II IL-1R.

The interleukin-1 system and human implantation

PROBLEM

Cytokines and growth factors are increasingly implicated in embryonic implantation. In the present study, we focus on the interleukin-1 system as an example of local regulator in human implantation.

METHOD

Three different approaches are considered. First, we present evidence demonstrating its presence, regulation, and relevance on the human endometrium. Second, we demonstrate the presence of IL-1 system in the human embryo and the selective IL-1 release only when embryos were co-cultured with human endometrial epithelial cells (EEC) or EEC-conditioned media, indicating an obligate role of the endometrium in the regulation of the embryonic IL-1 system. Finally, we show data regarding the presence, hormonal regulation, and endometrial origin of IL-1 alpha, IL-beta, and IL-1ra levels in the endometrial fluid inside the endometrial cavity. Specifically, we present the IL-1 intracavitary microenvironment surrounding the human embryo at the apposition phase.

RESULTS

This work suggests that the IL-1 system seems to be relevant for human endometrial and embryonic physiology. Furthermore, this family of molecules must be considered as a relevant paracrine language displayed by both partners that may be important to endometrial and embryonic crosstalk during embryonic implantation.

Hormonal regulation of serum and endometrial IL-1 alpha, IL-1 beta and IL-1ra: IL-1 endometrial microenvironment of the human embryo at the apposition phase under physiological and supraphysiological steroid level conditions

We have investigated serum and intracavitary levels of IL-1 alpha, IL-1 beta and IL-1ra from agonadal women undergoing mock cycles (n = 20) of oocyte donation as a clinical model of controlled hormonal stimulation. Further, we compared the intracavitary IL-1 alpha, IL-1 beta and IL-1ra levels in the microenvironment of the human embryo at the apposition phase, day 5 after progesterone (P) administration using two different clinical models: oocyte donation (n = 20) which provides physiological steroid levels and a higher implantation rate per embryo, and in vitro fertilization (n = 6) with supraphysiological hormonal levels and a lower implantation rate.

High affinity type I interleukin 1 receptor antagonists discovered by screening recombinant peptide libraries

Two families of peptides that specifically bind the extracellular domain of the human type I interleukin I (IL-1) receptor were identified from recombinant peptide display libraries. Peptides from one of these families blocked binding of IL-lalpha to the type I IL-1 receptor with IC50 values of 45-140 microM. Affinity-selective screening of variants of these peptides produced ligands of much higher affinity (IC50 approximately 2 nM). These peptides block IL-1-driven responses in human and monkey cells; they do not bind the human type II IL-1 receptor or the murine type I IL-1 receptor. This is the first example (that we know of) of a high affinity peptide that binds to a cytokine receptor and acts as a cytokine antagonist.

Synthetic alleles at position 121 define a functional domain of human interleukin-1 beta

The non-conservative substitution of the tyrosine residue at position 121 of human interleukin-1 beta (IL-1 beta) generates protein mutants showing strong reduction of the capacity to induce (a) prostaglandin E2 (PGE2) release from fibroblasts and smooth muscle cells, (b) murine T-cells proliferation and (c) activation of interleukin-6 (IL-6) gene expression. It is generally accepted that these functions are mediated by the type-I interleukin-1 receptor (IL-1RI). However, the mutant proteins maintain the binding affinity to the types-I and II IL-1 receptors, which is the same as the control IL-1 beta, suggesting that this amino acid substitution does not alter the structure of the molecule, except locally. Thus we have identified a new functional site of IL-1 beta different from the known receptor binding region, responsible for fundamental IL-1 beta functions. Moreover, we show that the same mutants maintain at least two hypothalamic functions, that is, the in vitro short-term PGE2 release from rat hypothalamus and the induction of fever in rabbits. This result suggests that there is yet another site of the molecule responsible for the hypothalamic functions, implying that multiple active sites on the IL-1 beta molecule, possibly binding to more than one receptor chain, trigger different signals.

The superficial layer of human articular cartilage is more susceptible to interleukin-1-induced damage than the deeper layers

OBJECTIVE

To compare the responses of chondrocytes from superficial and deep layers of normal human articular cartilage to interleukin-1 (IL-1) and IL-1 receptor antagonist protein (IRAP), and to evaluate the binding sites for IL-1 on these cells.

METHODS

Cartilage and chondrocytes from superficial and deeper layers of human femoral condyles were cultured with and without IL-1 in the presence and absence of IRAP. The effect of these agents on 35S- proteoglycan synthesis and catabolism and production of stromelysin and tissue inhibitor of metalloproteinases 1 (TIMP-1) were measured by biochemical and immunologic assays. Receptor binding was evaluated using 125I-labeled IL-1.

RESULTS

IL-1 induced more severe inhibition of proteoglycan synthesis and a lower ratio of secreted TIMP-l:stromelysin in chondrocytes from superficial cartilage than those from deeper cartilage. IRAP blocked responses to IL-1 more effectively in chondrocytes from deep cartilage than those from superficial cartilage. Chondrocytes from the articular surface showed approximately twice the number of high-affinity b!nding sites for IL-1 as did cells from deep cartilage.

CONCLUSION

Chondrocytes from the surface of articular cartilage show a greater vulnerability to the harmful effects of IL-1 and are less responsive to the potential therapeutic effects of IRAP than cells in the deeper layers of the tissue.

A role for interleukin-1 in epidermal differentiation: regulation by expression of functional versus decoy receptors

Although human epidermis contains levels of interleukin-1 (IL-1) up to 100 times higher than other tissues, the role of this cytokine in epidermal biology is unknown. Here, we show that interleukin-1 regulates the expression of mRNAs for two proteins associated with the differentiated phenotype of human keratinocytes, cellular retinoic acid-binding protein type II (CRABP II) and small, proline rich protein 1 (SPRR1). The ability of IL-1 to induce these transcripts correlates directly with keratinocyte expression of the IL-1 receptor type I (IL-1 RI) during differentiation and inversely with the expression of the type II IL-1 receptor (IL-1 RII), shown in other cell types to be a nonfunctional, decoy receptor. Furthermore, addition to keratinocyte cultures of an IL-1 RI-blocking, but not an IL-1 RII-blocking, antibody reduces the levels of CRABP II and SPRR1 mRNAs in these cells. These data suggest that epidermal IL-1 functions to promote keratinocyte differentiation and that a change in the IL-1 receptor profile of these cells initiates this IL-1 response through a relative enhanced expression of functional IL-1 receptors.

Molecular cloning and characterization of a second subunit of the interleukin 1 receptor complex

A monoclonal antibody (mAb) was isolated that blocked the binding and bioactivity of both human and murine interleukin 1 beta (IL-1 beta) on murine IL-1 receptor-bearing cells. This mAb recognized a protein that was distinct from the Type I and Type II IL-1 receptors, suggesting that an additional protein exists that is involved in IL-1 biological responses. By expression cloning in COS-7 cells, we have isolated a cDNA from mouse 3T3-LI cells encoding this putative auxiliary molecule, which we term the IL-1 receptor accessory protein (IL-1R AcP). Sequence analysis of the cDNA predicts an open reading frame that encodes a 570-amino acid protein with a molecular mass of approximately 66 kDa. The IL-1R AcP is a member of the Ig superfamily by analysis of its putative extracellular domain and also bears limited homology throughout the protein to both Type I and Type II IL-1 receptors. Northern analysis reveals that murine IL-1R AcP mRNA is expressed in many tissues and appears to be regulated by IL-1. In mammalian cells expressing natural or recombinant Type I IL-1R and IL-1R AcP, the accessory protein forms a complex with the Type I IL-1R and either IL-1 alpha or IL-1 beta but not IL-1ra. The recombinant accessory protein also increases the binding affinity of the recombinant Type I IL-1R for IL-1 beta when the two receptor proteins are coexpressed. Therefore, the functional IL-1 receptor appears to be a complex composed of at least two subunits.

Expression of type I and type II interleukin-1 receptors in mouse brain

Although binding sites for IL-1 have been identified in the mouse brain, it is still unknown whether these binding sites correspond to the type I or type II IL-1 receptor. Quantitative autoradiography was used to confirm the presence of specific binding sites for radiolabelled recombinant human IL-1 alpha (125I-HuIL-1 alpha) in the brain of DBA/2 mice. IL-1 binding was highest in the dentate gyrus, consisting of a single class of high affinity binding sites with a Kd of 0.1 nM and a Bmax of 57 fmol/mg protein. A similar Kd of 0.2 nM was obtained using isolated membranes from the whole hippocampus, although the number of binding sites was lower (2 fmol/mg protein). Affinity cross-linking of 125I-Hu-IL-1 alpha to hippocampal membranes revealed the existence of two types of IL-1 receptor proteins, consistent with the sizes of the type I (85 kD) and type II (60 kD) IL-1 receptor. Oligonucleotide probes were then synthesized and used in RT-PCR followed by Southern blotting to show that the whole brain expresses transcripts for both the type I and type II IL-1 receptors. The murine neuroblastoma cell line, C1300, expresses type I rather than type II IL-1 receptor mRNA. The type I receptor protein can be identified by flow cytometry on the membrane of the C1300 neuronal cell line using indirect immunofluorescence with a rat anti-mouse type I IL-1 receptor MoAb. These data show that mouse brain expresses both type I and type II IL-1 receptor mRNA and proteins and offer further support to the idea that type I IL-1 receptors are synthesized and expressed by neurons.

Cytokines and reproduction

Cytokines are important in reproduction. Interleukin-1, an established immune mediator, is one of the best-characterized members of the cytokine family. We describe what is known about the interactions between the interleukin-1 system and the hypothalamic-pituitary-gonadal, the hypothalamic pituitary-adrenal, and the hypothalamic-pituitary-thyroid axes. We also review the ovarian role of the interleukin-1 system. This cytokine has an immense and, as yet, imperfectly understood effect on the human reproductive tract. Clearly the immune system has a potential autocrine, paracrine, and endocrine role in regulating human reproductive events such as ovulation, luteinization, and implantation.

Species differences in [125I]interleukin-1 binding in brain, endocrine and immune tissues

There were dramatic species differences in the level of [125I]recombinant human interleukin-1 alpha ([125I]hIL-1 alpha) binding with high levels of binding present in mouse and rabbit tissues, while no specific binding was present in rat and guinea pig tissues. Utilizing [125I]hIL-1 alpha, moderate to high levels of specific binding were observed in EL-4 6.1 cells (representative of Type I IL-1 receptors) and in mouse hippocampus, spleen and testis; however, no specific [125I]hIL-1 alpha binding was present in Raji cells (representative of Type II IL-1 receptors) and in rat tissues. On the other hand, utilizing [125I]hIL-1 beta, high specific IL-1 binding was present in EL-4 6.1 and Raji cells and moderate binding was evident in mouse tissues, whereas specific [125I]hIL-1 beta binding to rat tissues was not detectable. Moreover, no IL-1 binding in rat tissues was observed using [125I]hIL-1 receptor antagonist, [125I]mouse IL-1 beta or the homologous radioligands [125I]rat IL-1 beta or [125I]rat IL-1 receptor antagonist. These data demonstrate that under optimal conditions for labeling Type I or Type II IL-1 receptors, no specific binding is observed in rat tissues suggesting the presence of novel IL-1 receptor(s) in rat tissues.

Interleukin 1 signaling occurs exclusively via the type I receptor

Two receptors for the proinflammatory cytokine interleukin 1 (IL-1) have been cloned and characterized biochemically. While it has been well established that the type I (80-kDa) IL-1 receptor can mediate responses to IL-1, the function of the type II (60-kDa) IL-1 receptor has been unknown. In this manuscript we describe experiments designed to ask whether the type II receptor is capable of delivering a biological signal. We have examined two types of experimental situation: responses to IL-1 in cells which express predominantly the type II receptor, and responses to IL-1 which have been suggested previously in the literature to be mediated by type II receptors. In both situations we find that the responses instead are mediated via type I receptors. A blocking antibody against the type II receptor never inhibits, and in fact sometimes enhances, the responses. We conclude that a very small number of type I receptors is sufficient to mediate all of the actions of IL-1 which we have examined here and that the function of the type II receptor may not be to transduce signals.

Interleukin-1 type I receptor messenger ribonucleic acid expression in human endometrium throughout the menstrual cycle

OBJECTIVE

To investigate the messenger ribonucleic acid (mRNA) expression of interleukin-1 (IL-1) type I receptor in the endometrial tissue of normal patients during the menstrual cycle.

DESIGN

Prospective longitudinal study.

SETTING

Department of Obstetrics and Gynecology, Stanford University Medical Center, Stanford, California.

PATIENTS

Twenty fertile women between 19 and 41 years of age underwent hysterectomy for benign reasons (n = 9) and laparoscopy for tubal ligation (n = 11). In all cases, endometriosis was not visualized.

INTERVENTIONS

Endometrial biopsy using the Novak curette was obtained at the time of surgery.

MAIN OUTCOME MEASURE

Total RNA extracted from unfractioned endometrial tissue was analyzed on Northern blots by using specific complementary deoxyribonucleic acid probes.

RESULTS

We found IL-1 type I receptor mRNA expression in endometrial tissue throughout the entire menstrual cycle. However, IL-1 type I receptor mRNA levels were significantly higher during both early and late luteal phases than follicular and midluteal phases.

CONCLUSIONS

Our results demonstrate the presence of the IL-1 system in the human endometrium and that the receptor is regulated throughout the menstrual cycle with a 4.1-fold increased expression of the IL-1 receptor gene in the early luteal phase compared with preovulatory endometrium.

Human aortic endothelial cells express the type I but not the type II receptor for interleukin-1 (IL-1)

Endothelial cells (EC) are very responsive to the proinflammatory cytokine interleukin-1 (IL-1). EC are induced by IL-1 to secrete chemotactic factors and to increase expression of cell surface adhesion molecules leading to increased leukocyte adhesion. Activated EC further contribute to the inflammatory response by secreting additional cytokines. IL-1 interacts with EC through high-affinity cell-surface receptors. However, the low number of receptors present on EC has made characterization difficult. Further, recent evidence has suggested diversity in the responses of EC from different regions of the vascular system. Interested in the effect of IL-1 on early atherosclerotic lesion formation, we have characterized the IL-1 receptors on human aortic endothelial cells (HAEC). Using a direct binding assay, we found that HAEC have 1,000-3,000 IL-1 receptors per cell and bind IL-1 alpha with a Kd of 3.5 x 10(-10) M. We found that a monoclonal antibody specific for the type I receptor completely blocks IL-1 alpha binding. The blocking antibody also completely inhibits the IL-1 induced increase in intracellular adhesion molecule 1 (ICAM-1) expression by HAEC. Using solution hybridization and ribonuclease protection with an antisense probe, a sensitive method for detection of low abundance mRNA species we found that HAEC as well as human umbilical vein EC (HUVEC) have significant levels of mRNA for the type I IL-1 receptor. To test whether HAEC might also contain transcripts for the type II IL-1 receptor, we compared levels of mRNAs by polymerase chain reaction (PCR) amplification of cDNAs reverse-transcribed from total RNA. We found only transcripts for the type I receptor and not the type II receptor in HAEC. Based on this data, we conclude that aortic endothelial cells respond to IL-1 through the type I receptor.

Type I interleukin-1 receptors in the mouse brain-endocrine-immune axis labelled with [125I]recombinant human interleukin-1 receptor antagonist

Iodine-125-labelled recombinant human interleukin-1 (IL-1) receptor antagonist ([125I]IL-1ra) was utilized to further determine the characteristics of IL-1 receptors in the brain-endocrine-immune axis. The binding of [125I]IL-1ra in homogenates of mouse hippocampus, spleen and testis was linear over a broad range of membrane protein concentrations, saturable, reversible, and of high affinity (KD, 20-30 pM). In competition studies, IL-1ra, recombinant human IL-1 alpha, IL-1 beta and a weak IL-1 beta analog inhibited [125I]IL-1ra binding to mouse tissues in parallel with their biological activities. In autoradiographic studies, [125I]IL-1ra and [125I]IL-1 alpha binding showed comparable distribution patterns with highest densities of binding sites present in the dentate gyrus of the hippocampus, choroid plexus, anterior pituitary, marginal zones and red pulp regions of the spleen, epididymis and interstitial area of the testis. The binding characteristics and distribution of [125I]IL-1ra are comparable to those of previously characterized Type I IL-1 receptors. These data provide further support for a role for IL-1 in coordinating brain-endocrine-immune responses to physiological and pharmacological stimuli.

Blocking IL-1: interleukin 1 receptor antagonist in vivo and in vitro

Clinical and experimental evidence suggests that shock, arthritis, osteoporosis, colitis, leukemia, diabetes, wasting and atherosclerosis are mediated, in part, by interleukin 1 (IL-1). Inhibition of this cytokine has been a strategy for studying disease and for new drug development. A naturally-occurring IL-1 inhibitor (IL-1 receptor antagonist, IL-1ra) that blocks binding of IL-1 to its receptors has been cloned and produced in recombinant organisms. IL-1ra reduces the severity of sepsis, colitis, arthritis and diabetes in animals and is presently being tested in humans with arthritis, shock and myelogenous leukemia.

A novel IL-1 receptor, cloned from B cells by mammalian expression, is expressed in many cell types

cDNA clones corresponding to an Mr approximately 80,000 receptor (type I receptor) for interleukin-1 (IL-1) have been isolated previously by mammalian expression. Here, we report the use of an improved expression cloning method to isolate human and murine cDNA clones encoding a second type (Mr approximately 60,000) of IL-1 receptor (type II receptor). The mature type II IL-1 receptor consists of (i) a ligand binding portion comprised of three immunoglobulin-like domains; (ii) a single transmembrane region; and (iii) a short cytoplasmic domain of 29 amino acids. This last contrasts with the approximately 215 amino acid cytoplasmic domain of the type I receptor, and suggests that the two IL-1 receptors may interact with different signal transduction pathways. The type II receptor is expressed in a number of different tissues, including both B and T lymphocytes, and can be induced in several cell types by treatment with phorbol ester. Both IL-1 receptors appear to be well conserved in evolution, and map to the same chromosomal location. Like the type I receptor, the human type II IL-1 receptor can bind all three forms of IL-1 (IL-1 alpha, IL-1 beta and IL-1ra). Vaccinia virus contains an open reading frame bearing strong resemblance to the type II IL-1 receptor.

Characterization of a neuronal interleukin-1 receptor and the corresponding mRNA in the mouse anterior pituitary cell line AtT-20

Interleukin-1 (IL-1) mediates numerous responses on the mouse anterior pituitary cell line AtT-20. We have studied the ligand binding properties of the IL-1 receptors (IL-1R) of the AtT-20 cells and found that they possess 1.5 x 10(3) receptors/cell with a Kd of 0.15 nM for [125I]IL-1 alpha. Using oligonucleotide primers, which define a 236 bp region of the cDNA coding for the cytosolic part of the mouse T-cell IL-1R, and cDNA prepared from AtT-20 cells, we obtained by polymerase chain reaction (PCR) a DNA fragment which was shown to possess an identical sequence to that of the corresponding region of the mouse T-cell IL-1R. Thus the AtT-20 pituitary cell line IL-1 receptor appears to be similar to those found on mouse T-cells and fibroblasts.

Differences in internalization and intracellular processing of interleukin-1 associated with the two forms of interleukin-1 receptor found in B-cells and T-cells

There are at least two classes of interleukin-1 (IL-1) receptor, namely p80, and 80 kDa single-chain protein found in T-cells, fibroblasts and many other cell types, and p68, a 68 kDa protein expressed in B-cells and macrophages. The to classes of IL-1 receptor show distinct differences in their substrate-binding site and molecular properties. In this study we show that the kinetics of IL-1 internalization and the consequences of ligand processing in the two subtypes of IL-1 receptor are also very different. The Raji cell line was used as a source of the p68 form of the IL-1 receptor, whereas the YT cell line was used as a source of p80 receptor. Under conditions of steady-state binding the IL-1 was equally distributed between cell-surface and intracellular sites in YT cells, compared with predominantly cell-surface binding (85%) in Raji cells. The mechanism of IL-1 processing was also different in the two cell types. In Raji cells 60% of internalized IL-1 was released from the cells in an intact form, whereas the remainder was degraded. All of the IL-1 extruded from YT cells was intact. The kinetics of IL-1 release was faster in Raji cells, with a half-time of 4.5 h compared with over 15 h in YT cells. SDS/PAGE analysis of internalized IL-1 in Raji cells revealed that the ligand was sequentially processed to trichloroacetic acid-soluble products. The YT receptor-ligand complex was resistant to dissociation at pH 5, whereas that in Raji cells rapidly dissociated at this pH. Treatment of Raji cells with the lysosomotropic agent chloroquine inhibited the degradation of IL-1 without having any effect on the amount of intact IL-1 in the intracellular compartments. From these data we conclude that the pathways of internalization, intracellular trafficking and overall processing of IL-1 are different for p68 IL-1 receptors compared with p80. This could have direct consequences for IL-1 action and IL-1 receptor regulation in the cell.

Chromosomal location of murine and human IL-1 receptor genes

The gene for the type I interleukin-1 (IL-1) receptor has been mapped in both mouse and human. In the human genome, a combination of segregation analysis of rodent-human hybrid cells and chromosomal in situ hybridization has placed the gene on the long arm of chromosome 2, at band 2q12. This is near the reported map position of the loci for IL-1 alpha and IL-1 beta (2q13----2q21). The murine gene has been mapped by analysis of restriction fragment length polymorphisms in interspecific backcrosses to the centromeric end of chromosome 1, in a region that is syntenic to a portion of human chromosome 2. The murine Il-1r1 gene has thus been separated from the IL-1 genes, which lie on murine chromosome 2.

A soluble form of the interleukin-1 receptor produced by a human B cell line

A soluble protein that binds specifically to interleukin-1 (IL-1)beta was released from a B cell line (Raji). The covalently cross-linked binding protein/[125I]IL-1 beta migrated at 60 kDa by SDS-PAGE. The IL-1 receptor (IL-1R) on Raji cells had the same ligand specificity. Stimulation of Raji with dexamethasone increased surface expression of the IL-1R and the rate of release of soluble binding protein. A serine protease inhibitor prevented release of the binding protein and increased IL-1R expression on the cells. These results suggest that the soluble IL-1 beta binding protein is a proteolytically cleaved form of the novel B cell IL-1R.

Interleukin 1 responsiveness and receptor expression by murine TH1 and TH2 clones

Murine Th1 and Th2 T cell lines differ in their responses to interleukin 1 (IL 1). Therefore, we examined two T-cell lines, D10.G4.1 (Th2) and MTg12B (Th1) in an attempt to correlate IL 1 receptor (IL 1R) expression with their IL 1 responsiveness. D10.G4.1 cells, which respond to IL 1, expressed two forms of the IL 1R, with molecular masses of approximately 80 kDa and approximately 60 kDa. In contrast, MTg12B cells failed to respond to IL 1 and only expressed the approximately 60 kDa receptor form. This suggests that the approximately 80 kDa receptor is essential for signaling. Expression of both IL 1R forms on D10.G4.1 cells could be inhibited by the anti-IL 4 antibody, 11B11. Antigen presentation reversibly upregulated both forms of the IL 1R, whereas stimulation with concanavalin A (ConA) and anti-CD3 only upregulated the approximately 60 kDa moiety. Upregulation of the approximately 80-kDa IL 1R by repeated antigenic stimulation resulted in a marked increase in sensitivity of D10.G4.1 cells to IL 1.