(1/1427) Identification of regions in alleles of the flax rust resistance gene L that determine differences in gene-for-gene specificity.
Thirteen alleles (L, L1 to L11, and LH) from the flax L locus, which encode Toll/interleukin-1 receptor homology-nucleotide binding site-leucine-rich repeat (TIR-NBS-LRR) rust resistance proteins, were sequenced and compared to provide insight into their evolution and into the determinants of gene-for-gene resistance specificity. The predicted L6 and L11 proteins differ solely in the LRR region, whereas L6 and L7 differ solely in the TIR region. Thus, specificity differences between alleles can be determined by both the LRR and TIR regions. Functional analysis in transgenic plants of recombinant alleles constructed in vitro provided further information: L10-L2 and L6-L2 recombinants, encoding the LRR of L2, conferred L2 resistance specificity, and an L2-L10 recombinant, encoding the LRR of L10, conferred a novel specificity. The sequence comparisons also indicate that the evolution of L alleles has probably involved reassortment of variation, resulting from accumulated point mutations, by intragenic recombination. In addition, large deletion events have occurred in the LRR-encoding regions of L1 and L8, and duplication events have occurred in the LRR-encoding region of L2. (+info)
(2/1427) Bacterial lipopolysaccharide causes rapid shedding, followed by inhibition of mRNA expression, of the IL-1 type II receptor, with concomitant up-regulation of the type I receptor and induction of incompletely spliced transcripts.
The IL-1 type I receptor (IL-1RI) is part of a signaling complex together with the IL-1R accessory protein, whereas available information is consistent with a "decoy" model of function for the IL-1 type II receptor (IL-1RII). The present study was designed to investigate the effect of bacterial LPS on IL-1R in human monocytes. LPS causes rapid release of the IL-1RII, an effect blocked by a metalloprotease inhibitor. Subsequently, LPS-treated monocytes showed a drastic reduction of IL-1RII mRNA. In contrast, LPS induced IL-1RI and, to a lesser extent, IL-1AcP expression. LPS-induced augmented expression of the canonical 5-kb IL-1RI mRNA was accompanied by the appearance of 2.4-kb IL-1RI transcripts. The use of probes representative of different regions of the IL-1RI mRNA, as well as cDNA cloning, revealed that the 2.4-kb inducible band includes incompletely spliced, polyadenylated transcripts potentially encoding truncated versions of the receptor. The observation that the prototypic proinflammatory molecule LPS has divergent effects on IL-1Rs, with inhibition of IL-1RII and stimulation of IL-1RI and IL-1R accessory protein, is consistent with the view that these molecules subserve opposite functions in the pathophysiology of the IL-1 system. The rapid shedding of IL-1RII by monocytes early in recruitment may serve to buffer the systemic action of IL-1 leaking from sites of inflammation. This early event, followed by prolonged inhibition of IL-1RII expression and up-regulation of IL-1RI, may render monocytes more responsive to IL-1 at sites of inflammation. (+info)
(3/1427) Transforming growth factor-beta1 is a potent inhibitor of interleukin-1beta action in whole ovarian dispersates.
Transforming growth factor beta1 (TGFbeta1) acts as an inhibitor of the actions of interleukin-1beta (IL-1beta) in various organ systems. In order better to understand the inter|P-actions between these polypeptides in the ovary, we evaluated the effect of TGFbeta1 co-treatment on various IL-1beta-mediated actions in cultures of whole ovarian dispersates. Treatment with IL-1beta enhanced media accumulation of nitrites (4.8-fold), prostaglandin E2 (PGE2, 3. 9-fold) and lactate (2.0-fold), and enhanced glucose consumption (2. 1-fold). Treatment with TGFbeta1 alone did not significantly affect any of these parameters. However, the addition of TGFbeta1 inhibited IL-1beta-stimulated nitrite (100%), PGE2 (44%) and lactate (78%) accumulation and inhibited IL-1beta-stimulated glucose consumption (74%) in a dose-dependent manner. The addition of TGFbeta1 also suppressed the steady-state levels of IL-1beta-stimulated IL-1beta, type I IL-1 receptor and IL-1 receptor antagonist transcripts (98, 67 and 83% inhibition respectively). These data suggest that TGFbeta1 is capable of inhibiting several IL-1beta-stimulated endpoints. Since IL-1 has been identified as a possible proinflammatory mediator of ovulation and TGFbeta has been implicated as a promotor of fibrosis and healing, we speculate that IL-1 and TGFbeta might play antagonistic roles in the normal ovulatory sequence. (+info)
(4/1427) Effects of interleukin-1 receptor antagonist overexpression on infection by Listeria monocytogenes.
Interleukin-1 receptor antagonist (IL-1ra) is a naturally occurring cytokine whose only known function is the inhibition of interleukin-1 (IL-1). Using a reverse genetic approach in mice, we previously showed that increasing IL-1ra gene dosage leads to reduced survival of a primary listerial infection. In this study, we characterize further the role of endogenously produced IL-1ra and, by inference, IL-1 in murine listeriosis. IL-1ra overexpression inhibits, but does not eliminate, primary immune responses, reducing survival and increasing bacterial loads in the target organs. We demonstrate that IL-1ra functions in the innate immune response to regulate the peak leukocyte levels in the blood, the accumulation of leukocytes at sites of infection, and the activation of macrophages during a primary infection. Reduced macrophage class II major histocompatibility complex expression was observed despite increased gamma interferon (IFN-gamma) levels, suggesting that IL-1 activity is essential along with IFN-gamma for macrophage activation in vivo. We also show that IL-1ra plays a more limited role during secondary listeriosis, blunting the strength of the delayed-type hypersensitivity response to listerial antigen while not significantly altering cellular immunity to a second infectious challenge. When these results are compared to those for other mutant mice, IL-1ra appears to be unique among the cytokines studied to date in its regulation of leukocyte migration during primary listeriosis. (+info)
(5/1427) The interleukin-1 type 2 receptor gene displays immediate early gene responsiveness in glucocorticoid-stimulated human epidermal keratinocytes.
Human epidermal keratinocytes (HEKs) in primary culture (P2-P4) were used to study glucocorticoid (GC)-mediated transcription of the genes encoding the constitutively expressed interleukin-1 type 1 receptor (IL-1R1) and the inducible interleukin-1 type 2 receptor (IL-1R2). Utilizing Northern dot blot analysis and a quantitative reverse transcription-polymerase chain reaction protocol for IL-1R1 and IL-1R2, dexamethasone and, in particular, the budesonide epimer R were shown to effectively and rapidly induce transcription from the IL-IR2 gene when compared with IL-1R1 or beta-actin RNA message levels in the same sample. Southern blot analysis of newly generated IL-1R2 reverse transcription-polymerase chain reaction products using end-labeled IL-1R2 intron probes suggested that GC enhancement of IL-1R2 expression was regulated primarily at the level of de novo transcription. GC-induced IL-1R2 gene transcription displayed features characteristic of a classical immediate early gene response, including a signal transduction function, a relatively low basal abundance, a rapid, transient induction, cycloheximide superinduction, actinomycin D suppression, and a rapid decay of IL-1R2 RNA message. Parallel time course kinetic analysis of IL-1R2 RNA message levels with Western immunoblotting revealed tight coupling of de novo IL-IR2 gene transcription with translation of the IL-1R2 RNA message; a newly synthesized ( approximately 46-kDa) IL-1R2 protein was detected in the HEK growth medium as early as 1 h after budesonide epimer R treatment. These data indicate that different GC compounds can variably up-regulate the IL-1R2 response in HEKs through transcription-mediated mechanisms and, for the first time, suggest that a gene encoding a soluble cytokine receptor can respond like an immediate early gene. (+info)
(6/1427) Efficacy of sustained blood levels of interleukin-1 receptor antagonist in animal models of arthritis: comparison of efficacy in animal models with human clinical data.
OBJECTIVE: To determine the role of interleukin-1 receptor antagonist (IL-1Ra) in rat adjuvant arthritis and rat type II collagen-induced arthritis, and to compare the efficacy in rat models with that seen in human clinical trials of IL-1Ra. METHODS: Rats with developing adjuvant arthritis or established collagen-induced arthritis were treated with IL-1Ra by continuous infusion in order to determine and maintain efficacious blood levels of this IL-1 inhibitory protein in the rats for comparison with human clinical data. The effects of treatment in the rats were monitored by sequential caliper measurement of the ankle joints, determination of final paw weights, and histologic evaluation with particular emphasis on bone and cartilage lesions. The effects of IL-1Ra on joint swelling and radiographic bone damage in patients with rheumatoid arthritis (RA) in a 6-month trial were compared with the findings in rats. RESULTS: Dramatic differences in the profile of IL-1Ra activity were seen between the 2 groups of rats. Modest antiinflammatory effects were observed in the adjuvant arthritis rats treated with IL-1Ra. However, marked inhibition of bone resorption occurred, even at doses with which antiinflammatory activity was not seen. In contrast, IL-1Ra treatment of rats with established collagen-induced arthritis resulted in nearly complete suppression of all aspects of the disease when adequate blood levels of IL-1Ra were maintained. Treatment of RA patients with IL-1Ra (150 mg daily) resulted in modest inhibition of joint swelling and inhibition of radiographic progression of bone lesions. CONCLUSION: IL-1 appears to be of major importance in mediating the bone resorption that occurs in rat adjuvant arthritis, but is less important in the pathogenesis of periarticular inflammation in this disease. In contrast, IL-1 is of major importance in mediating all aspects of disease progression in rat collagen-induced arthritis. Similar to the response in adjuvant arthritic rats, RA patients treated with IL-1Ra showed only modest antiinflammatory activity, but had evidence of inhibition of progression of bone resorption. However, a comparison of the plasma levels of IL-1Ra in humans and rats suggests that the optimal level of dosing for continuous saturation of IL-1 receptors may not have been achieved in humans, although this was achieved in the rat studies. (+info)
(7/1427) Somnogenic relationships between tumor necrosis factor and interleukin-1.
Both tumor necrosis factor (TNF) and interleukin (IL)-1 are somnogenic cytokines. They also induce each other's production and both induce nuclear factor kappa B activation, which in turn enhances IL-1 and TNF transcription. We hypothesized that TNF and IL-1 could influence each other's somnogenic actions. To test this hypothesis, we determined the effects of blocking both endogenous TNF and IL-1 on spontaneous sleep and on sleep rebound after sleep deprivation in rabbits. Furthermore, the effects of inhibition of TNF on IL-1-induced sleep and the effects of blocking IL-1 on TNF-induced sleep were determined. A TNF receptor fragment (TNFRF), as a TNF inhibitor, and an IL-1 receptor fragment (IL-1RF), as an IL-1 inhibitor, were used. Intracerebroventricular injection of a combination of the TNFRF plus the IL-1RF significantly reduced spontaneous non-rapid eye movement sleep by 87 min over a 22-h recording period. Pretreatment of rabbits with the combination of TNFRF and IL-1RF also significantly attenuated sleep rebound after sleep deprivation. Furthermore, the TNFRF significantly attenuated IL-1-induced sleep but not fever. Finally, the IL-1RF blocked TNF-induced sleep responses but not fever. Results indicate that TNF and IL-1 cooperate to regulate physiological sleep. (+info)
(8/1427) Augmentation of type I IL-1 receptor expression and IL-1 signaling by IL-6 and glucocorticoid in murine hepatocytes.
IL-1 signal is transduced through type I receptor (IL-1RI). We have recently reported that LPS augments IL-1RI mRNA expression in the hepatocytes of mice in vivo, and the augmentation is mediated by the interaction of IL-1, IL-6, and glucocorticoid (GC). In this study, we examined whether IL-1RI mRNA expression level in the hepatocytes reflects those of cell surface molecule and IL-1 signaling. When primary cultured murine hepatocytes were treated with dexamethasone (Dex) or IL-6, these two reagents synergistically up-regulated IL-1RI mRNA expression in the cells. 125I-labeled IL-1 binding experiment showed that the level of binding was also up-regulated by the treatment with Dex and IL-6. Scatchard analysis revealed that the number of IL-1R increased. The increased binding of IL-1 was completely inhibited by an Ab against murine IL-1RI, indicating that Dex and IL-6 augmented the expression of cell surface IL-1RI molecule. When hepatocytes were pretreated with Dex and IL-6, the activation of IL-1R-associated kinase was augmented in response to IL-1, indicating that IL-1 signaling was also augmented. In addition, IL-1 treatment following administration of the combination of Dex and IL-6 into mice markedly increased the serum level of serum amyloid A. These results indicate that GC and IL-6 augment the expression of cell surface IL-1RI in hepatocytes, as well as IL-1 signaling and IL-1R-associated kinase activation, through up-regulation of IL-1RI mRNA level, which represents a novel regulatory network between IL-1, GC, and IL-6. (+info)