Interleukin 1 receptor antagonist in human epidermis and cultured keratinocytes

Targeting IL-1 controls refractory pityriasis rubra pilaris

Pityriasis rubra pilaris (PRP) is a rare inflammatory skin disease with a poorly understood pathogenesis. Through a molecularly driven precision medicine approach and an extensive mechanistic pathway analysis in PRP skin samples, compared to psoriasis, atopic dermatitis, healed PRP, and healthy controls, we identified IL-1β as a key mediator, orchestrating an NF-κB-mediated IL-1β-CCL20 axis, including activation of CARD14 and NOD2. Treatment of three patients with the IL-1 antagonists anakinra and canakinumab resulted in rapid clinical improvement and reversal of the PRP-associated molecular signature with a 50% improvement in skin lesions after 2 to 3 weeks. This transcriptional signature was consistent with in vitro stimulation of keratinocytes with IL-1β. With the central role of IL-1β underscoring its potential as a therapeutic target, our findings propose a redefinition of PRP as an autoinflammatory keratinization disorder. Further clinical trials are needed to validate the efficacy of IL-1β antagonists in PRP.

Interleukin-1 receptor antagonist: An alternative therapy for cancer treatment

The interleukin-1 receptor antagonist (IL-1Ra) is an anti-inflammatory cytokine and a naturally occurring antagonist of the IL-1 receptor. It effectively counteracts the IL-1 signaling pathway mediated by IL-1α/β. Over the past few decades, accumulating evidence has suggested that IL-1 signaling plays an essential role in tumor formation, growth, and metastasis. Significantly, anakinra, the first United States Food and Drug Administration (FDA)-approved IL-1Ra drug, has demonstrated promising antitumor effects in animal studies. Numerous clinical trials have subsequently incorporated anakinra into their cancer treatment protocols. In this review, we comprehensively discuss the research progress on the role of IL-1 in tumors and summarize the significant contribution of IL-1Ra (anakinra) to tumor immunity. Additionally, we analyze the potential value of IL-1Ra as a biomarker from a clinical perspective. This review is aimed to highlight the important link between inflammation and cancer and provide potential drug targets for future cancer therapy.

Juvenile idiopathic arthritis in Harlequin ichthyosis, a rare combination or the clinical spectrum of the disease? Report of a child treated with etanercept and review of the literature

BACKGROUND

Harlequin ichthyosis (HI) is the most severe phenotype of autosomal recessive congenital ichthyosis. Juvenile Idiopathic Arthritis (JIA) represents a heterogenous group of disorders all sharing the clinical manifestation of chronic arthritis. Association of HI and chronic arthritis has been reported in few cases.

CASE PRESENTATION

We report the case of a child with HI who developed a severe form of chronic polyarthritis during the first years of life, treated with repeated multiple joint injections, methotrexate and etanercept with good response and without any adverse events.

CONCLUSION

The reported case and the literature review highlighted the presence of a peculiar severe seronegative polyarthritis with early onset in a series of patients with HI, suggesting that polyarthritis may be a specific manifestation of HI, rather than a rare combination of two separate conditions.

A critical role of interleukin-1 in preterm labor

Preterm birth (PTB) is a leading cause of neonatal mortality and morbidity worldwide, and represents a heavy economic and social burden. Despite its broad etiology, PTB has been firmly linked to inflammatory processes. Pro-inflammatory cytokines are produced in gestational tissues in response to stressors and can prematurely induce uterine activation, which precedes the onset of preterm labor. Of all cytokines implicated, interleukin (IL)-1 has been largely studied, revealing a central role in preterm labor. However, currently approved IL-1-targeting therapies have failed to show expected efficacy in pre-clinical studies of preterm labor. Herein, we (a) summarize animal and human studies in which IL-1 or IL-1-targeting therapeutics are implicated with preterm labor, (b) focus on novel IL-1-targeting therapies and diagnostic tests, and (c) develop the case for commercialization and translation means to hasten their development.

Interleukin-1 Gene Polymorphisms and their Relation with NFκB Expression and Histopathological Features in Psoriasis

Background:

Psoriasis is a chronic inflammatory disease driven by exaggerated production of pro-inflammatory cytokines and interleukins. Various genetic polymorphisms including IL-1 are implicated in pathogenesis of psoriasis. The exact role of IL-1 gene polymorphisms and their interaction with NFκB is not yet determined. We aimed to study various genetic polymorphisms of IL-1 in psoriasis and their influence on NFκB and histopathological features.

Materials and Methods:

112 newly diagnosed cases of psoriasis vulgaris were included in this prospective study. Histology was done on sections and genotyping was done for the IL-1β and IL-1 receptor antagonist (IL-1RA) genetic polymorphisms. In addition, NFκB immunostaining was performed on 89 sections and the intensity of staining was evaluated in the epidermis, basal cells, and the lymphocytes.

Results:

A strong association of IL-1β 511 C/T polymorphism was found with both genotypes and alleles in psoriasis. A strong correlation was also detected between the IL-1β genotype and the grade of NFκB immunostaining in the epidermis (P = 0.012). The grade of NFκB lymphocyte staining showed a strong correlation with the IL-1RA genotype (P = 0.025) but not with the IL-1β genotype (P = 0.226). The genetic polymorphisms did not show any correlation with the histological features.

Conclusions:

IL-1 genetic polymorphisms may not play a very direct role in pathogenesis of psoriasis. However, their interaction with NFκB appears to be a significant factor in this direction as NFκB is activated by pro-inflammatory genetic polymorphisms and therefore may influence the severity of psoriasis.

IL-1 receptor antagonist in metabolic diseases: Dr Jekyll or Mr Hyde?

Interleukin-1 receptor antagonist (IL-1ra) has been shown to play a crucial role in the prevention of various inflammatory diseases. There is also convincing evidence that IL-1ra is able to counteract inflammatory effects of IL-1 members implicated in insulin resistance and diabetes. However, the use of knock-out animal models provides evidence to the contrary and the role of IL-1ra in obesity-linked anomalies remains controversial. This minireview gets an insight into recent findings on the implication of IL-1ra and its gene polymorphism in diabetes and obesity, discusses the potential dual effects of IL-1ra observed in different models, and comments on future directions.

Regulation of interleukin-1alpha expression by integrins and epidermal growth factor receptor in keratinocytes from a mouse model of inflammatory skin disease

Transgenic mice expressing beta1 integrins in the suprabasal epidermal layers have sporadic skin hyperproliferation and inflammation correlated with activation of extracellular signal-regulated kinase (Erk) mitogen-activated protein kinase and increased interleukin (IL)-1alpha production. We investigated the link between aberrant integrin expression, Erk activation, and expression of IL-1alpha. Transgenic keratinocytes had higher basal Erk activity and IL-1alpha levels than nontransgenic controls and were more sensitive to stimulation of Erk activity and IL-1alpha production by IL-1alpha, 12-O-tetradecanoylphorbol-13-acetate (TPA), epidermal growth factor (EGF), and serum. Inhibition of Erk in transgenic keratinocytes reduced basal IL-1alpha levels and the stimulation of IL-1alpha production by serum or phorbol ester, demonstrating that Erk could regulate IL-1alpha expression. TPA or IL-1alpha treatment resulted in rapid down-regulation of the EGF receptor in transgenic cells, indicative of transactivation. Inhibition of transactivation blocked basal and TPA or IL-1alpha induced Erk activation, but not IkappaBalpha degradation, and abolished increased IL-1alpha production in transgenic cells. In transgene-negative cells, constitutive activation of IL-1-dependent signaling by wild type or kinase-dead IRAK1 stimulated IL-1alpha production independent of Erk. We conclude that suprabasal integrin expression leads to Erk activation and increased IL-1alpha expression by potentiating activation of the EGF receptor. These results provide a mechanism by which aberrant integrin expression triggers epidermal hyperproliferation and inflammation.

IL-1ra and IL-1 production in human oral mucosal epithelial cells in culture: differential modulation by TGF-beta1 and IL-4

Regulatory cytokines mediate the participation of oral mucosal epithelial cells (OMEC) in local immune responses. The aim of this study was to characterize the isoforms of IL-1 receptor antagonist (IL-1ra) in cultured human primary OMECs and to compare its production with that of IL-1 alpha (IL-1alpha) and IL-1 beta (IL-1beta). Western blot analysis showed that IL-1ra was 22 kDa in size hence slightly smaller than monocyte IL-1ra (25 kDa). A minor form of 20 kDa was also found in unstimulated cell culture lysates. In culture supernatants, IL-1 bioactivity increased after IL-1ra neutralization, indicating that the baseline production of IL-1ra is biologically relevant. Immunohistochemistry showed a relation between IL-1ra and involucrin expressions, suggesting that intracytoplasmic IL-1ra may be involved in cell terminal differentiation. In unstimulated culture lysates, there was far more IL-1ra than IL-1alpha and IL-1beta. TGF-beta1 markedly increased the IL-1ra/IL-1beta ratio from 93.6 : 1 to 300 : 1. IL-4, which is generally described as an anti-inflammatory cytokine, increased IL-1 but not IL-1ra production. TNF-alpha increased intracellular production of the three IL-1 members. IL-1ra levels were lower in supernatants than in lysates of cultured cells. Our results show that human OMECs constitutively produce significant amounts of a biologically active form of IL-1ra. TGF-beta1 mu(p)-regulation points to a positive amplification loop and IL-4 to a down-regulation loop, both including Th2 cells and OMECs. They may be important in oral tolerance and IgA production, respectively.

Promoter polymorphisms of the genes encoding tumor necrosis factor-alpha and interleukin-1beta are associated with different subtypes of psoriasis characterized by early and late disease onset

The psoriatic inflammatory process is characterized by an overexpression of pro-inflammatory cytokines such as tumor necrosis factor-alpha and interleukin-1beta compared with a relative deficiency of anti-inflammatory factors such as interleukin-10 and the interleukin-1 receptor antagonist (interleukin-1Ra). Gene polymorphisms that affect cytokine production may contribute to the disease-associated cytokine imbalance and influence susceptibility to psoriasis. Here, we investigated the relationship between polymorphisms in the genes encoding for tumor necrosis factor-alpha (G-238A, G-308A), interleukin-1beta (C-511T, T+3953C), and interleukin-1Ra (intron 2), and cytokine production in peripheral blood mononuclear cells of healthy donors, and analyzed the distribution of these polymorphisms in patients with psoriasis vulgaris (n = 231) and healthy controls (n = 345). Carriage of tumor necrosis factor A-238 allele 2 (-238*A) was associated with increased production of tumor necrosis factor-alpha in response to lipopolysaccharide in vitro, and with early onset disease (< 40 y), especially in male patients with psoriasis [32% vs 7% in male controls; odds ratio = 6.78, 95% confidence interval = (3.18-15.15), p(adjusted) = 2 x 10(-7)]. Carriage of the interleukin-1B-511*1 (-511*C) homozygous genotype was associated with increased production of interleukin-1Ra in response to lipopolysaccharide and interleukin-10, and with late onset psoriasis [> or = 40 y; 61% vs 44% in controls; odds ratio = 2.04, 95% confidence interval = (1.19-3.53), p(adjusted) = 0.0419]. These findings indicate that gene polymorphisms associated with altered cytokine responses in vitro may modify age of onset of psoriasis. They also provide further evidence that patients with early and late onset psoriasis differ in their genetic background.

An increased ratio of interleukin-1 receptor antagonist to interleukin-1alpha in inflammatory skin diseases

IL-1 receptor antagonist (IL-1ra) is a cytokine that competitively binds the IL-1 receptor to antagonize IL-1 activity without any agonist function. Previous experiments indicated that the ratio of IL-1ra to IL-1alpha in the normal stratum corneum (SC) was much higher in the sun-exposed face than in the sun-protected area, upper arms. It was also reported by another laboratory that IL-1ra is increased in the lesional skin of psoriatic patients. This study was designed to measure the contents of IL-1alpha and IL-1ra in non-lesional and pathological SC obtained from inflammatory skin diseases including psoriasis and non-psoriatic dermatoses such as atopic dermatitis. The SC materials were obtained with a non-invasive tape-stripping method. Their soluble fractions were prepared and assayed for IL-1alpha and IL-1ra by enzyme-linked immunosorbent assays. As a result we confirmed the previous findings that the ratio of IL-1ra to IL-1alpha in the normal SC was much higher in the face than in the sun-protected sites, the trunk as well as extremities. Next, we found that IL-1alpha contents were significantly reduced in the SC samples obtained from inflammatory skin regardless of whether their IL-1ra contents increased or unchanged. Moreover, we noted that an increased ratio of IL-1ra to IL-1alpha in the SC was not specific to psoriasis, but was also found in other inflammatory skin diseases including atopic dermatitis. This ratio was found to become lower after successful treatment of these skin lesions with topical glucocorticoids. We conclude from these observations that the increased ratio of IL-1ra to IL-1alpha in the SC is a non-specific phenomenon that can occur in any inflammatory skin diseases regardless of the inflammatory pattern, probably reflecting a skin regulation process against various kinds of inflammation.

Changes of the interleukin-6 levels in skin at different sites after thermal injury

OBJECTIVE

To delineate the regulation of IL-6 production in unburned skin adjacent to a burn in an animal model.

METHODS

In C57BL/6 mice, at 15, 30, and 60 minutes after a 20% full-thickness burn, skin was removed from various sites. Control samples were obtained from unburned mice. Normal skins were incubated with tumor necrosis factor-alpha (TNF-alpha), interleukin-1 alpha (IL-1alpha), IL-1 beta, and IL-6. Unburned skin specimens were incubated with anti-TNF-alpha and IL-1alpha antibodies. Cytokine levels were measured by enzyme-linked immunosorbent assay.

RESULTS

The burn increased the IL-6 levels at 30 minutes (p < 0.05) and the IL-1alpha levels at 15 and 60 minutes in the unburned skin. TNF-alpha, IL-1alpha, and IL-1beta increased IL-6 production in normal skin (p < 0.05). Anti-IL-1alpha antibody decreased IL-6 production in the unburned skin (p < 0.05).

CONCLUSIONS

IL-1alpha modulates IL-6 production in unburned skin after injury. IL-6 and IL-1alpha might contribute to the alterations after a burn.

Characterization of an interleukin 1 receptor antagonist protein released from ultraviolet-irradiated epidermal sheet

An interleukin 1 (IL-1) inhibitor was detected in the culture supernatant of mouse epidermal sheet which had been irradiated with middle-wavelength ultraviolet (UVB) either in vitro or in vivo. Properties of the IL-1 inhibitor were consistent with those of IL-1 receptor antagonist (IL-1ra), i.e., approximate molecular size of 17 kDa by gel filtration, specific inhibition of IL-1-induced thymocyte proliferation, inhibition of binding of IL-1 to IL-1 receptor on the T-cell surface, and reactivity to anti-mouse IL-1ra antibody shown by immunoblotting and enzyme-linked immunosorbent assay (ELISA). These results indicate that this IL-1 inhibitor, which appears to be identical with IL-1ra, was released from the epidermis upon UVB irradiation, and that the inhibitor may participate in the regulation of inflammation mediated by IL-1, as well as in the pathogenesis of ultraviolet (UV)-induced immunosuppression.

Differences in responses of interleukin-1 and tumor necrosis factor alpha production and secretion to cyclosporin-A and ultraviolet B-irradiation by normal and transformed keratinocyte cultures

Among epidermal cytokines, IL-1 and TNF alpha are involved in inflammatory skin reactions and suspected of modulation by immunosuppressive treatment (e.g., cyclosporin A, CsA) or UVB-irradiation, 2 mediators probably being involved in epithelial carcinogenesis. We evaluated the effects of 8 micrograms/ml CsA and 100 J/m2 UVB-irradiation on the production and secretion of IL-1 and TNF alpha on normal human epidermal keratinocytes (NHK) and epidermal keratinocyte cell lines either spontaneously transformed (HaCaT) or transformed by human papillomavirus (HPV) type 16 or 18 (EK 16 and EK18), by using ELISA test. Normal and immortalized keratinocytes constitutively produced and released IL-1 alpha, IL-1 beta and IL-1 receptor antagonist (IL-1RA) but IL-1 synthesis by NHK was significantly higher than by cell lines. All the cells spontaneously excreted low amounts of TNF alpha. Different responses to treatments were evidenced between NHK and cell lines. CsA modified significantly the production and secretion of IL1 in most cells whereas slight changes were observed with TNF alpha secretion. UVB irradiation had no effect on the intracellular IL1 pool of any cells but increased the release of IL1 and TNF alpha. The association CsA-UVB did not result in additive effects on synthesis and secretion of IL1; the release of TNF alpha by the cells remained poor except for EK18 cells. Taken together, these results show that, in immortalized keratinocytes, the IL-1 and TNF alpha expression was differently affected by treatments with CsA and/or UVB-irradiation as compared to NHK. In addition, spontaneously transformed keratinocytes, HaCaT, reacted differently from HPV-transformed keratinocytes, EK16 and EK18.

Human chorionic gonadotrophin-induced testicular inflammation may be related to increased sensitivity to interleukin-1

Treatment of adult male rats with human chorionic gonadotrophin (hCG) results in an inflammation-like response in the testicular microcirculation. Polymorphonuclear (PMN) leukocytes accumulate in venules and vascular permeability is increased. The mechanism behind this response was studied. Treatment with an interleukin-1 receptor antagonist partly prevented the hCG induced accumulation of PMN leukocytes 4 h after treatment. Human recombinant interleukin-1 alpha (IL-1 alpha) and beta (IL-1 beta), serotonin, and histamine were injected intratesticularly on one side and saline injected on the contralateral side in both intact and hCG-pretreated adult rats. A low dose of IL-alpha (a dose that did not increase vascular permeability in unstimulated testes) increased vascular permeability in the testes of animals treated with hCG 4, 6 or 8 h earlier, but it was without effect in testes from rats treated with hCG 0,1, 2, 16 or 32 h prior to IL-1 injection. The sensitivity to the pro-inflammatory effect of locally injected IL-1 beta was also increased by hCG treatment. There was no increase in vascular permeability after local injection of a large dose of histamine or serotonin in either saline- or in hCG-pretreated animals. Hypothetically, the hCG-induced inflammation-like increase in testicular vascular permeability could be related to increased sensitivity to constitutively produced mediators such as IL-1.

Elevation of interleukin 1 receptor antagonist in the stratum corneum of sun-exposed and ultraviolet B-irradiated human skin

Keratinocytes produce not only interleukin 1 (IL-1) but also IL-1 receptor antagonist (IL-1ra), a competitive inhibitor of IL-1. Because little is known about the presence of IL-1ra in the stratum corneum, we examined the content of IL-1ra in the stratum corneum, especially the balance between IL-1 and IL-1ra. IL-1 alpha and IL-1ra, but not IL-1 beta, were detected in the tape-stripped stratum corneum of healthy volunteers by enzyme-linked immunosorbent assays. IL-1 alpha and IL-1ra were bioactive as determined by thymocyte co-stimulation assay, and their molecular masses were 17 and 20 kDa, respectively, suggesting that the stratum corneum contains active forms of IL-1 alpha and IL-1ra produced by keratinocytes. The stratum corneum of an unexposed area, the inner side of the upper arm. contained more IL-1 alpha than a sun-exposed area, the face. In contrast, the stratum corneum of the sun-exposed area contained a markedly higher amount of IL-1ra than that of the unexposed area. The ratio of IL-1ra to IL-1 alpha was 8 in the unexposed area, and over 100 in the sun-exposed area. Therefore, IL-1 alpha activity was dominant in the unexposed area, and in contrast, IL-1ra activity was dominant in the sun-exposed area. An elevated level of IL-1ra was detected in the stratum corneum of the sun-exposed area independently of age. In the unexposed area, however, IL-1a increased, but IL-1ra decreased, with age, resulting in a significant decline of the ratio of IL-1ra to IL-1a with increasing age. Irradiation of 2 MED of ultraviolet B to the back skin, an unexposed area, resulted in striking elevation of IL-1ra in the stratum corneum in desquamating scales. These data suggest that IL-1ra in the epidermis may be inducible by chronic UV irradiation, although IL-1ra production in the epidermis may decrease with aging in the absence of any stimulus. IL-1ra in the epidermis may play a role in the regulation of IL-1-induced inflammatory responses, and an appropriate balance between IL-1 and IL-1ra may help to maintain homeostasis of the skin.

Effect of smokeless tobacco extract on human gingival keratinocyte levels of prostaglandin E2 and interleukin-1

Gingival recession and white mucosal lesions frequently occur at sites of smokeless tobacco (ST) placement. The etiology of these alterations is presumably related to the irritating effects of tobacco components. The purpose of this study was to examine the effect of an aqueous ST extract (STE) on gingival keratinocyte production of prostaglandin E2 (PGE2) and interleukin-1 (IL-1), mediators involved in periodontal destruction and keratinocyte proliferation. Keratinocyte cultures were established from healthy tissues discarded from 8 subjects undergoing crown lengthening procedures. Cells (passage 2-3) were seeded at 2.5 x 10(4) cells/well into 48 well tissue culture plates and maintained in serum-free media at 37 degrees C. On day 4 or 5, the wells were divided into 4 groups receiving either 10%, 5%, 2.5%, or 0% STE for time periods ranging from 30 to 240 minutes. PGE2 levels (pg/10(4) cells), as measured by enzyme immunoassay, were significantly (P < 0.05) increased in the 10% (215.66 +/- 34.58) and 5% STE (151.82 +/- 27.97) treated cultures compared to untreated cells (46.16 +/- 9.58). IL-1 alpha and IL-1 beta proteins were elevated (P < 0.05) in cell lysates (299.45 +/- 38.69 and 28.45 +/- 5.18, respectively) from 5% STE exposed cultures compared to control wells. At 10% STE, secreted IL-1 alpha was decreased (P < 0.05) relative to 2.5% STE. This may reflect a toxic effect, as 10% STE significantly (P < 0.05) depressed cell numbers and viability. Lower tobacco concentrations did not affect cell numbers or viability, but significantly (P < 0.05) increased PGE2 and IL-1 levels. Tobacco-induced synthesis of these mediators may play a role in the development of tobacco-related oral disease.

Modulation of the IL-1 cytokine network in keratinocytes by intracellular IL-1 alpha and IL-1 receptor antagonist

The IL-1 cytokine network in epidermal cells was studied in vitro, using the spontaneously transformed HaCAT human keratinocyte line. Intracellular (ic) IL-1 alpha and IL-1 receptor antagonist protein (IL-1Ra) following cell lysis were readily identified assayed using a capture ELISA; whereas in culture supernatants IL-1Ra was not detected, and IL-1 alpha was present at only very low levels. Confluent cultures of HaCAT cells were shown to provide optimal conditions for the study, since confluence increased the icIL-1Ra:IL-1 alpha ratio to a level as seen in vivo, which was independent of Ca2+ concentration in the culture medium. The IL-1Ra extracted from HaCAT cell lysates was functionally active, as demonstrated in the mouse thymocyte co-proliferation assay which could be blocked using a rabbit anti-IL-1Ra antibody. Transforming growth factor-beta (TGF-beta 1) stimulated a dose-dependent increase in HaCAT cell IL-1 alpha without changing IL-1Ra concentration, with a resultant reduction in the icIL-1Ra: IL-1 alpha ratio from 320:1 to 100:1. Similarly, TGF-alpha, interferon-gamma (IFN-gamma), IL-6, and tumour necrosis factor-alpha (TNF-alpha) substantially increased HaCAT cell IL-1 alpha, but had no effect on the IL-1Ra, with a concomitant reduction in the icIL-1Ra:IL-1 alpha ratio. In contrast to their effects on monocytes, IL-4 and IL-10 at biologically active levels had no effect on IL-1 alpha, IL-1Ra or the icIL-1Ra: IL-1 alpha ratio in confluent HaCAT cells. Hydrocortisone reduced IL-1 alpha to below the limit of sensitivity of the ELISA, and induced a small increase in IL-1Ra of questionable biological significance. Thus, regulation of the IL-1 cytokine network in keratinocytes involves modulation of icIL-1 alpha rather than of icIL-1Ra levels, and is markedly different from that noted in monocytes.

In vitro modulation of keratinocyte-derived interleukin-1 alpha (IL-1 alpha) and peripheral blood mononuclear cell-derived IL-1 beta release in response to cutaneous commensal microorganisms

The ability of a range of skin commensal microorganisms to modulate interleukin-1 (IL-1) release by cultured human keratinocytes and peripheral blood mononuclear cells (PBMCs) was investigated by a combination of enzyme-linked immunosorbent assays and bioassays. Three fractions (formaldehyde-treated whole cells, culture supernatants, and cellular fractions) were prepared from Propionibacterium acnes, Propionibacterium granulosum, Staphylococcus epidermidis, Staphylococcus capitis, Staphylococcus hominis, and Malassezia furfur serovar B. The levels of immunochemical IL-1 alpha released by cultured keratinocytes during coincubations with these microbial fractions ranged from 0 to 136 pg/ml and were maximal after 72 h. No microbial fraction consistently upregulated immunochemical IL-1 alpha release by freshly isolated keratinocytes from two donors and a transformed cell line, all of which produced the cytokine constitutively to various extents. Bioassays revealed that most of the IL-1 released was biologically inactive. In contrast, whole cells of formaldehyde-treated P. granulosum and S. epidermidis significantly stimulated release of IL-1 beta by PBMCs from three donors compared with the negative control (culture medium). Release was maximal at 24 h. Coincubation with intact cells of the yeast M. furfur significantly decreased levels of IL-1 beta below the values for the negative control by PBMCs from all three donors. There was good correlation between bioassay data and immunoassay data for IL-1 beta, and the depressive effect of M. furfur cells on cytokine production by all three cultures of PBMCs was mirrored in the levels of bioactive cytokine. This reduction in IL-1 beta release by PBMCs by M. furfur may provide an explanation why dermatoses thought to be caused by this yeast are essentially noninflammatory or only mildly inflammatory.

Expression of interleukin-1 alpha and interleukin-1 receptor type I genes in murine brown adipose tissue

At thermoneutral conditions, high steady-state levels of transcripts for both IL-1 alpha and its receptor IL-1RtI were found in specialized thermogenic organ, brown adipose tissue (BAT) of adult mice, as compared with the levels in lymph nodes, brain and spleen. A pronounced decrease of IL-1 alpha mRNA level in BAT was observed after lipopolysaccharide (LPS) administration and after exposure to cold. Likewise, LPS decreased the IL-1RtI mRNA level and depressed also the expression of cold-inducible genes for the BAT-specific heat-producing uncoupling protein and for lipoprotein lipase. It is concluded that, besides the centrally-mediated effects, there exists a direct peripheral interaction of IL-1 cytokines with BAT cells.

Tumor necrosis factor-alpha induces interleukin-1 alpha and interleukin-1 receptor antagonist production by cultured human keratinocytes

Interleukin-1 (IL-1) may have a significant pro-inflammatory effect in the skin; an imbalance in its production has been linked to cutaneous disease processes. IL-1 receptor antagonist (IL-1ra) is a recently described competitive inhibitor of IL-1 alpha and IL-1 beta that binds to human types I and II IL-1 receptors without apparent cell activation. Human keratinocytes synthesize IL-1ra, IL-1 alpha, and IL-1 beta but fail to secrete these cytokines. This study investigated IL-1ra and IL-1 alpha accumulation by cultured keratinocytes stimulated by tumor necrosis factor-alpha (TNF-alpha), IL-3, IL-4, IL-6, IL-10, interferon-gamma, granulocyte-macrophage colony-stimulating factor, granulocyte colony-stimulating factor, and macrophage colony-stimulating factor and by various extracellular matrix proteins, conditions that these cells may encounter in normal or inflamed skin in vivo. IL-1ra and IL-1 alpha proteins were measured by specific enzyme-linked immunosorbent assay in keratinocyte supernatants and lysates. Only TNF-alpha induced IL-1ra and IL-1 alpha production. TNF-alpha added to culture in amounts of 10 ng/ml or higher, induced a twofold increase in intracellular levels of both IL-ra and IL-1 alpha without secretion at 48 h. The IL-1ra concentration in keratinocyte lysates increased from 9.6 to 17.6 ng/ml after TNF-alpha stimulation, and the IL-1 alpha concentration increased from 1.0 to 3.3 ng/ml. Keratinocytes also exhibited comparable increases in IL-1 alpha and IL-1ra mRNA levels after 12 h in culture with TNF-alpha, as determined by in vitro hybridization to specific cDNA probes. The IL-1 alpha and IL-1ra response to TNF-alpha stimulation showed a varied pattern among different keratinocyte strains over 72 h of culture on plain plastic. In contrast, extracellular matrix proteins (laminin, fibronectin, collagen I and IV, and vitronectin) did not stimulate keratinocyte accumulation of IL-1 alpha or IL-1ra proteins after 72 h in culture. When TNF-alpha was added to cells cultured on these matrices, no change in IL-1 alpha or IL-1ra production was observed above that which could be attributed to TNF-alpha alone. In conclusion, TNF-alpha, but not the extracellular matrix proteins tested, stimulated production of intracellular IL-1 alpha and IL-1ra by keratinocytes. The ratio of IL-1ra to IL-1 alpha after TNF-alpha stimulation of keratinocytes may influence the inflammatory profile in the epidermis.

Regulation of interleukin-1ra, interleukin-1 alpha, and interleukin-1 beta production by human alveolar macrophages with phorbol myristate acetate, lipopolysaccharide, and interleukin-4

Human alveolar macrophages (AM) are antigen-presenting cells that have an important immune effector function in the lung. We have previously shown that AM produce a specific interleukin-1 (IL-1) inhibitor of 20 to 25 kD that blocks biologic activities of IL-1 alpha and IL-1 beta such as prostaglandin E2 production by fibroblasts. This inhibitor acts as a receptor antagonist (IL-1ra) by binding to the IL-1 receptor. We are now presenting evidence that the natural AM-derived IL-1ra is immunologically identical to IL-1ra cloned from human peripheral blood monocytes and shows a band at 20 kD compatible with the natural glycosylated IL-1ra. No constitutive expression of IL-1 mRNA was detected when analyzed by Northern blot immediately after bronchoalveolar lavage from six control patients. Comparison of in vitro kinetics of IL-1ra, IL-1 alpha, and IL-1 beta analyzed during culture in the presence or absence of phorbol myristate acetate revealed that their mRNA expression was asynchronous. IL-1 alpha and IL-1 beta mRNA were expressed after as little as 15 min, whereas IL-1ra mRNA was detectable only after 3 h in culture. The production of IL-1ra was measured by enzyme-linked immunosorbent assay and compared with that of IL-1 alpha and IL-1 beta. In freshly isolated AM (10(6)/ml), cell-associated IL-1ra was present in an average amount of 2.0 +/- 0.5 ng/ml, i.e., 25 and 100 times more than IL-1 alpha and IL-1 beta, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin-1 receptor antagonist

IL-1ra is the first described naturally occurring receptor antagonist of any cytokine or hormone-like molecule. IL-1ra is a member of the IL-1 family by three criteria: amino acid sequence homology of 26 to 30% to IL-1 beta and 19% to IL-1 alpha; similarities in gene structure; and common gene localization to human chromosome 2q14. Two structural variants of IL-1ra exist: sIL-1ra, a secretory molecule produced by monocytes, macrophages, neutrophils, fibroblasts, and other cells; and icIL-1ra, an intracellular molecule produced by keratinocytes and other epithelial cells, macrophages, and fibroblasts. IL-1ra production by monocytes, macrophages, and neutrophils may be regulated in a differential fashion with IL-1 beta. Human IL-1ra binds to both human IL-1RIs and IL-1RIIs on cell surfaces, although with 100-fold greater avidity to IL-1RIs. IL-1ra may bind preferentially to soluble IL-1RIs and not at all to soluble IL-1RIIs. IL-1ra competitively inhibits binding of both IL-1 alpha and IL-1 beta to cell surface receptors without inducing any discernible intracellular responses. All three forms of IL-1 may bind to IL-1 receptors in a similar fashion but IL-1ra may lack the secondary interactions necessary to trigger cell responses. A 100-fold or greater excess of IL-1ra over IL-1 may be necessary to inhibit biological responses to IL-1 both in vitro and in vivo. The roles of sIL-1ra and icIL-1ra in normal physiology or in host defense mechanisms remain unclear. The administration of IL-1ra blocks the effects of IL-1 in some animal models of septic shock, inflammatory arthritis, graft-versus-host disease, and inflammatory bowel disease. The preliminary results of clinical trials in humans indicate possible efficacy of IL-1ra in sepsis syndrome, rheumatoid arthritis, and GVHD.

Synergistic induction of interleukin-6 by tumor necrosis factor and lithium chloride in mice: possible role in the triggering and exacerbation of psoriasis by lithium treatment

One of the side effects of treatment of manic depressive disease with lithium salts is the triggering or aggravation of psoriasis. In a murine model, subcutaneous (s.c.) injection of a combination of tumor necrosis factor (TNF) and lithium chloride (LiCl) induces a psoriasiform inflammatory reaction. Recent studies suggest that interleukin (IL)-6 and its inducer TNF may play an important role in the pathophysiology of psoriasis. To understand the mechanism involved in the exacerbation of psoriasis by lithium salts, the IL-1, IL-6 and granulocyte-macrophage colony-stimulating factor (GM-CSF) levels in murine skin injected with TNF in combination with LiCl were studied. IL-6 levels in skin extracts of mice treated s.c. with a combination of TNF and LiCl were considerably increased as compared to the levels found in skin extracts from mice treated with TNF or LiCl alone. In contrast, in the same skin extracts IL-1 levels were not changed and GM-CSF was even not detectable. Although less pronounced, increased IL-6 levels could also be found in the sera of mice treated s.c. with TNF and LiCl. Injection with IL-1, interferon-gamma, lipopolysaccharide, or phorbol 12-myristate 13-acetate also induced IL-6 in murine skin. However, these IL-6 levels were not enhanced by co-treatment with LiCl. Likewise, on inflammatory reaction could be seen in mice treated with these agents. These results suggest a role for endogenous TNF and IL-6 in the triggering or aggravation of psoriasis in lithium-treated patients.

The role of cytokines and their inhibitors in arthritis

The role of cytokines in inflammatory joint diseases is well documented, especially with regard to tissue destruction and remodelling. In these processes, IL-1 and TNF alpha play a prominent part by stimulating protease production. The regulation of their production, their release and their effects on target cells (e.g. synovial cells, chondrocytes and bone-derived cells) has therefore been the subject of intensive investigations. In this context a new dimension has emerged recently due to the observation of the existence of natural specific cytokine inhibitors. IL-1-ra and the soluble fragments of both TNF receptors--inhibitory by binding to TNF alpha--are natural products. These appear to be the molecules best suited for controlling the imbalance between pro- and anti-inflammatory processes. The use of the recombinant forms of these inhibitors may open new perspectives for therapeutic intervention. The fact that the respective mechanisms of action of receptor antagonists and inhibitory binding proteins differ does not rule out their complementarity. Preliminary experiments with animal models have yielded promising results which should be followed up by clinical trials.