Challenges in the design of clinically useful brain-targeted drug nanocarriers

Nowadays, the delivery of drugs by means of intravenously administered nanosized drug carriers - polymerdrug conjugates, liposomes and micelles, is technically possible. These delivery systems are mainly designed for tumour therapy, and accumulate passively into tumours by means of the well known EPR effect. Targeted nanocarriers, that additionally contain ligands for receptors expressed on cell surfaces, are also widely studied but products of this kind are not marketed, and only a few are in clinical trial. Polymeric nanoparticles (Np) able to deliver drugs to the CNS were pioneered in 1995; a number of papers have been published dealing with brain-targeted drug delivery using polymeric Np able to cross the BBB, mainly for the treatment of brain tumours. At present, however, the translation potential of these Np seems to have been exceeded by targeted liposomes, a platform based on a proven technology. This drug delivery system entered clinical trials soon after its discovery, while the challenges in formulation, characterization and manufacturing of brain-targeted polymeric Np and the cost/benefit ratio could be the factors that have prevented their development. A key issue is that it is virtually impossible to define the in vivo fate of polymers, especially in the brain, which is a regulatory requirement; perhaps this is why no progress has been made. The most advanced Np for brain tumours treatment will be compared here with the published data available for those in clinical trial for tumours outside the CNS, to highlight the knowledge gaps that still penalise these delivery systems. At present, new approaches for brain tumours are emerging, such as lipid Np or the use of monoclonal antibody (mAb)-drug conjugates, which avoid polymers. The success or failure in the approval of the polymeric Np currently in clinical trials will certainly affect the field. At present, the chances of their approval appear to be very low.

Free IL-18 and IL-33 cytokines in chronic spontaneous urticaria

Overproduction of IL-18 has been described in chronic urticaria. To evaluate free IL-18 and IL-33 in chronic spontaneous urticaria (CSU). IL-18, its inhibitor IL-18BP, IL-33 and its soluble receptor ST2 (sST2) were measured (ELISA) in the sera of 73 CSU patients. Free IL-18 was calculated (law of mass action). Autologous serum skin test (ASST) was performed in all patients. Total IL-18, IL-18BP and free IL-18 serum levels were significantly higher in CSU than in controls. IL-18 and IL-18BP increased significantly in both ASST-positive and negative subgroups. Free IL-18 resulted significantly higher in the ASST-negative, but not in the ASST-positive subgroup. No differences in IL-33/sST2 levels were detected between CSU and controls. Increased levels of free IL-18 and IL-18BP, but not IL-33, was detected in CSU. Whether IL-18 up-regulation is a consequence of inflammation or one of the causes of the pathology needs to be addressed.

Sporulation: an alternative way to recover recombinant proteins from Bacillus subtilis

A recombinant strain of Bacillus subtilis engineered for endocellular expression of human interleukin-1 receptor antagonist (IL-Ira) was subjected to sporulation. The recombinant protein was recovered from the sporulation supernatant in quantities, purity, and activity comparable with those obtained from a traditional cell lysate. Thus, exploitation of this natural mechanism of autolysis could overcome problems of intact protein recovery related to the cell disruption step.

Neutrophil apoptosis in autoimmune Fas-defective MRL lpr/lpr mice

The apoptosis-defective lpr (fas) mutation in MRL mice causes the early onset of a lupus-like autoimmune disease with concomitant inflammation. In order to analyse the consequences of the impaired Fas-dependent apoptosis on inflammation, the susceptibility to apoptosis of polymorphonuclear leukocytes (PMN), obtained from MRL lpr/lpr mice, has been studied. Peritoneal PMN from lpr/lpr and control (+/+) mice were recruited with a mild inflammatory stimulus. The number of cells collected from the peritoneal cavity of young lpr/lpr mice was comparable to that obtained from age-matched control mice, indicating that PMN homeostasis is maintained regardless of the loss-of-function Fas mutation. Recruited neutrophils were exposed in culture to apoptosis-inducing stimuli. Treatment with agonist anti-Fas antibody increased apoptosis of +/+ PMN, but did not affect lpr/lpr PMN which do not express Fas on their surface. However, lpr/lpr PMN could undergo both spontaneous and stimulus-induced apoptosis in a fashion comparable to or higher than that of control +/+ mice. Analysis of mRNA expression revealed that lpr/lpr PMN have reduced expression of IL-18, whereas IL-1beta, IFNgamma, caspase 1 and caspase 3 are expressed at levels comparable to those of +/+ cells. However, caspase-3-like activity was higher in PMN from lpr/lpr mice than in +/+ cells, and correlated with enhanced apoptosis. It could be concluded that in young, uncompromised lpr/lpr mice, PMN homeostasis is still fully regulated through the involvement of Fas-independent, compensatory, apoptotic mechanisms. This could include an increased participation of caspase 3 in the apoptotic pathway, consequent to enhanced activation of the enzyme and to the decreased production of IL-18, which acts as a competitive caspase 3 substrate.

Model of interaction of the IL-1 receptor accessory protein IL-1RAcP with the IL-1beta/IL-1R(I) complex

A preliminary model has been calculated for the activating interaction of the interleukin 1 receptor (IL-1R) accessory protein IL-1RAcP with the ligand/receptor complex IL-1beta/IL-1R(I). First, IL-1RAcP was modeled on the crystal structure of IL-1R(I) bound to IL-1beta. Then, the IL-1RAcP model was docked using specific programs to the crystal structure of the IL-1beta/IL-1R(I) complex. Two types of models were predicted, with comparable probability. Experimental data obtained with the use of IL-1beta peptides and antibodies, and with mutated IL-1beta proteins, support the BACK model, in which IL-1RAcP establishes contacts with the back of IL-1R(I) wrapped around IL-1beta.

Lymphocytes from autoimmune MRL lpr/lpr mice are hyperresponsive to IL-18 and overexpress the IL-18 receptor accessory chain

MRL lpr/lpr mice spontaneously develop a severe autoimmune lupus syndrome characterized by strong autoantibody production and massive lymphoproliferation, in which IFN-gamma plays a major pathogenic effect. The role of the IFN-gamma-inducing cytokine IL-18 in the autoimmune syndrome of lpr/lpr mice has been investigated. In response to IL-18, lymph node cells of lpr/lpr mice produce significant amounts of IFN-gamma and proliferate more potently as compared with cells from +/+ mice. Cells likely responsible for such hyperresponsiveness to IL-18 include NK cells and the CD4(+)/CD8(+) self-reactive T lymphocytes characteristically present in lymph nodes of lpr/lpr mice. Analysis of the expression of IL-18R complex revealed that mRNA for the IL-18R alpha-chain is constitutively expressed at similar level both in +/+ and lpr/lpr lymphocytes. In contrast, the expression of the accessory receptor chain IL-18R beta is low in unstimulated +/+ cells but significantly high in lpr/lpr cells. Thus, the abnormally high expression of the IL-18R chain IL-18R beta could be one of the causes of the hyperresponsiveness of lpr/lpr cells to IL-18 at the basis of consequent enhancement of IFN-gamma production and development of IFN-gamma-dependent autoimmune pathology.

Balance between autocrine interleukin-1beta and caspases defines life versus death of polymorphonuclear cells

The role of endogenous IL-1beta in regulating spontaneous and Fas-triggered apoptosis of human PMN has been studied in relation to the activity of the IL-1beta-generating enzyme ICE (caspase-1), an enzyme also involved in the mechanism of cell death. Upon in vitro culture, PMN undergo spontaneous apoptosis and express increasing levels of IL-1beta, caspase-1- and caspase-3-like enzymes. Endogenous IL-1beta protects PMN from apoptosis, since inhibition of either IL-1beta or caspase-1 activity can accelerate PMN apoptotic death. Thus, in spontaneous PMN apoptosis caspase-1 essentially plays an anti-apoptotic role by inducing maturation of protective IL-1beta, whereas other molecules are responsible of driving apoptosis. Upon Fas triggering, PMN apoptosis is greatly accelerated, in correlation with increased caspase activity, whereas IL-1beta production is not augmented. Inhibition of IL-1beta activity can increase Fas-induced apoptosis, whereas caspase-1 inhibitors are without significant effect. It is hypothesized that in Fas-induced PMN apoptosis caspase-1 has a double role: it can protect from apoptosis through generation of protective IL-1beta, as in spontaneous apoptosis, and it can also exert pro-apoptotic activity which counterbalances the protective effect and allows accelerated apoptosis.

The membrane form of the type II IL-1 receptor accounts for inhibitory function

IL-1 signaling is mediated by the type I IL-1R (IL-1RI). The nonsignaling type II receptor has a regulatory function, since it reduces IL-1 effects by scavenging free IL-1 molecules. This regulatory function has been demonstrated only for the soluble form, released from the membrane receptor by action of specific proteases, but is still ill-defined for the membrane receptor itself. To assess the function of membrane IL-1RII, a modified IL-1RII cDNA was constructed, in which the cleavable domain was replaced with the corresponding uncleavable sequence of the epidermal growth factor receptor. The human keratinocyte line HaCaT, which does not express wild-type IL-1RII (wtIL-1RII), was stably transfected with this modified cDNA (unconventionally cleavable IL-1RII (uIL-1RII)). Cells transfected with uIL-1RII expressed the membrane form of IL-1RII, but were unable to produce the 60-kDa soluble receptor. Upon analysis of IL-1 responsiveness, parental HaCaT and vector-transfected cells (E27), expressing IL-1RI and the accessory chain IL-1R accessory protein, were responsive to IL-1. Conversely, cells overexpressing wtIL-1RII (811) or uIL-1RII (9D4) showed comparable reduction in responsiveness to both IL-1alpha (bound by membrane and soluble receptors) and IL-1beta (recognized by the membrane receptor only), suggesting that the membrane form of the IL-1RII is mainly responsible for IL-1 inhibition. In contrast with wtIL-1RII, uIL-1RII did not interact with IL-1R accessory protein. Thus, the membrane form of IL-1RII possesses strong IL-1-inhibitory activity, independent of sequestration of the accessory protein and circumscribed to its ligand sink function.

Interleukin-1 and interleukin-1 fragments as vaccine adjuvants

The human interleukin-1beta (IL-1beta) domain in position 163-171, comprising the amino acids VQGEESNDK, has been synthesized as a nine-amino-acid-long peptide and used in vivo as a nontoxic HCl salt. The IL-1beta nonapeptide reproduces the immunostimulatory and adjuvant effects of the whole mature IL-1beta, but does not possess any of the IL-1beta inflammatory, vasoactive, tumor-promoting, and systemically toxic effects, nor it can synergize with tumor necrosis factor alpha or other molecules in inducing toxicity and shock. The IL-1beta fragment is active as adjuvant either when administered together with the antigen or if inoculated separately; it can be physically linked to the antigen or used as a discrete peptide. Moreover, the DNA sequence encoding the IL-1beta domain has been included in an experimental DNA vaccine with positive results. Thus, immunostimulatory sequences can be identified within a pleiotropic cytokine like IL-1 and used in the rational design of novel vaccination strategies.

The type II IL-1 receptor interacts with the IL-1 receptor accessory protein: a novel mechanism of regulation of IL-1 responsiveness

IL-1 binds to two types of receptors on the cell membrane, of which only type I (IL-1RI) transduces signals in concert with the coreceptor IL-1 receptor accessory protein (IL-1RAcP) while type II (IL-1RII) allegedly functions solely as ligand sink and decoy receptor without participating in IL-1 signaling. To investigate the regulatory role of IL-1RII on IL-1 responsiveness, a chimeric receptor encompassing the extracellular and transmembrane portions of IL-1RII and the cytoplasmic signal-transducing domain of IL-1RI was transfected into two murine EL-4-derived sublines that do or do not express IL-1RAcP, respectively. The chimeric receptor was able to transduce the IL-1 signal and induce IL-2 production only in the cell line which expressed IL-1RAcP, suggesting effective interaction between the extracellular domains of IL-1RII and IL-1RAcP in the presence of IL-1. The physical association of ligated IL-1RII with IL-1RAcP was proven by crosslinking experiments with radio-iodinated IL-1 and subsequent immunoprecipitations in normal human B cells and in EL-4 D6/76 cells transiently cotransfected with IL-1RII and IL-1RAcP, respectively. Based on these findings, it is proposed that upon IL-1 binding IL-1RII can recruit IL-1RAcP into a nonfunctional trimeric complex and thus modulate IL-1 signaling by subtracting the coreceptor molecule from the signaling IL-1RI. In this novel mechanism of coreceptor competition, the ratio between IL-1RII and IL-1RI becomes the central factor in determining the IL-1 responsiveness of a cell and the availability of IL-1RAcP becomes limiting for effective IL-1 signaling.

Role of metalloproteases in the release of the IL-1 type II decoy receptor

The IL-1 type II receptor (decoy RII) is a nonsignaling molecule the only established function of which is to capture IL-1 and prevent it from interacting with signaling receptor. The decoy RII is released in a regulated way from the cell surface. Here, we reported that hydroxamic acid inhibitors of matrix metalloproteases inhibit different pathways of decoy RII release, including the following: (a) the slow (18 h) gene expression-dependent release from monocytes and polymorphonuclear cells exposed to dexamethasone; (b) rapid release (minutes) from myelomonocytic cells exposed to tumor necrosis factor, chemoattractants, or phorbol myristate acetate; (c) phorbol myristate acetate-induced release from decoy RII-transfected fibroblasts and B cells. Inhibition of release was associated with increased surface expression of decoy RII. Inhibitors of other protease classes did not substantially affect release. However, serine protease inhibitors increased the molecular mass of the decoy RII released from polymorphonuclear cells from 45 to 60 kDa. Thus, irrespective of the pathway responsible for release and of the cellular context, matrix metalloproteases, rather than differential splicing, play a key role in production of soluble decoy RII.

Interaction between interleukin-1 and ciliary neurotrophic factor in the regulation of neuroblastoma cell functions

Human neuroblastoma cells SK-N-SH express significant numbers of IL-1R type I on their surface, as detected by saturation binding and RT-PCR, and are responsive to IL-1beta activation by producing inflammatory cytokines IL-6 and IL-8. IL-1beta can also have an indirect effect on nervous cell functions, since it is able to modulate the stimulus-induced increase of intracellular Ca++ levels, one of the first steps of the cell activation mechanism. In fact, on SK-N-SH neuroblastoma cells, IL-1beta can inhibit the Ca++ increase induced by stimulation of acetylcholine receptors with carbachol. In parallel to IL-1beta, the neurotrophic factor CNTF also shows an inhibitory effect on carbachol-stimulated Ca++ increase in CNTFRalpha-expressing SK-N-SH cells. However, when simultaneously present, the two cytokines cross-inhibit, thus allowing full cell activation in response to the cholinoceptor agonist. The inhibitory effect of CNTF on IL-1beta activities on nervous cells was confirmed in the IL-6 production assay. In fact, while CNTF could not induce IL-6 production, it could strongly inhibit cytokine production in response to IL-1beta in SK-N-SH cells. The down-modulation of IL-1 effects by CNTF could be one of the mechanisms controlling the extent of the inflammatory reaction at the nervous system level.

Interleukin-1 beta primes interleukin-8-stimulated chemotaxis and elastase release in human neutrophils via its type I receptor

Interleukin-1 (IL-1) is a pleiotropic proinflammatory cytokine which binds to human neutrophils (PMN) and can directly or indirectly activate their functions. In this study we show that a brief exposure to IL-1 beta induces a potentiation of both PMN elastase release and chemotactic response to interleukin-8 (IL-8), the prototype of C-X-C chemokines. Priming by IL-1 beta was maximal at 100 ng/ml, was completely blocked in the presence of IL-1 receptor antagonist (IL-1ra) and, in the chemotaxis assay, was best observed at suboptimal (3-6 ng/ml) or inactive (0.75 ng/ml) concentrations of IL-8. Priming of PMN by IL-1 beta was completely blocked by M1, a specific antibody against the type I IL-1 receptor (IL-1RI). On the other hand M22, an antibody directed against the IL-1 decoy type II IL-1 receptor did not affect IL-1 beta action and slightly increased the priming effect. Thus, exclusively via its type I receptor, IL-1 beta can act on PMN at multiple levels, by promoting their accumulation in tissues through the induction of chemotactic factors (e.g. IL-8) and the upregulation of adhesion molecules, and by priming their response to chemotactic agonists.

Functional epitope mapping of human interleukin-1 beta by surface plasmon resonance

A panel of monoclonal antibodies to human IL-1 beta has been used to probe its conformational and functional characteristics. Real time antibody-protein interaction was assessed by surface plasmon resonance with a BIAcore apparatus, in order to determine the kinetic and thermodynamic parameters of the interaction and to map the recognition sites of the antibodies on the IL-1 beta surface. Topological analysis was thus compared to the inhibitory capacity of antibodies for IL-1 beta bioactivity and binding to the activating receptor IL-1RI. This functional mapping analysis allows the following hypothesis. At least two discrete areas of IL-1 beta, located within the sequences 133-147 and 177-186 (as defined by mAbs MhC1 and BRhD2, respectively), are apparently involved in IL-1RI-independent agonist activity, and thus possibly take part in the interaction with the receptor accessory protein IL-1RAcP. Another area in the 133-147 sequence (defined by mAb BRhC3) is involved in agonist binding to its receptor CDw121a (IL-1RI), whereas a site recognized by mAb BRhG5 within the sequence 218-243 is selectively responsible for non-agonist binding to the activating receptor. The loop between the 4th and the 5th beta-strand, at the open end of the IL-1 beta-barrel structure, may possibly take part in both non-agonist binding to IL-1RI and in the interaction with IL-1RAcP.

Inhibitory activity of IL-1 receptor antagonist depends on the balance between binding capacity for IL-1 receptor type 1 and IL-1 receptor type II

A series of mutants of human IL-1 receptor antagonist (IL-1ra) has been designed by comparison of IL-1ra and IL-1beta structures in order to increase receptor antagonist capacity. Upon in vitro and in vivo assay of IL-1 antagonism, the IL-1ra mutants DoB 0039 (N91-->R), DoB 0040 (T109-->A) and DoB 0041 (N91/T109-->R/A) could inhibit IL-1beta effects more efficiently than wild-type IL-1ra, with DoB 0041 being the most active. Analysis of the receptor-binding capacity of the IL-1ra mutants showed that all three mutants could inhibit binding of IL-1alpha or IL-1beta to IL-1RI-bearing cells more efficiently than wild-type IL-1ra. Conversely, binding of IL-1beta to IL-1RII-bearing cells could be inhibited by DoB 0041 much less efficiently than by wild-type IL-1ra. It is known that the two types of IL-1 receptors (IL-1RI and IL-1RII) play different roles in the regulation of IL-1 activity, with IL-1RI being solely responsible for cell triggering upon IL-1 binding, whereas IL-1RII acts as a scavenger of IL-1 and can thus be considered as a natural IL-1 inhibitor. Thus, the enhanced inhibitory capacity of DoB 0041 as compared with wild-type IL-1ra is explained in terms of better binding to the activating receptor IL-1RI and poorer interaction with the inhibitory receptor IL-1RII.

Inhibitory activity of IL-1 receptor antagonist depends on the balance between binding capacity for IL-1 receptor type 1 and IL-1 receptor type II

A series of mutants of human IL-1 receptor antagonist (IL-1ra) has been designed by comparison of IL-1ra and IL-1beta structures in order to increase receptor antagonist capacity. Upon in vitro and in vivo assay of IL-1 antagonism, the IL-1ra mutants DoB 0039 (N91-->R), DoB 0040 (T109-->A) and DoB 0041 (N91/T109-->R/A) could inhibit IL-1beta effects more efficiently than wild-type IL-1ra, with DoB 0041 being the most active. Analysis of the receptor-binding capacity of the IL-1ra mutants showed that all three mutants could inhibit binding of IL-1alpha or IL-1beta to IL-1RI-bearing cells more efficiently than wild-type IL-1ra. Conversely, binding of IL-1beta to IL-1RII-bearing cells could be inhibited by DoB 0041 much less efficiently than by wild-type IL-1ra. It is known that the two types of IL-1 receptors (IL-1RI and IL-1RII) play different roles in the regulation of IL-1 activity, with IL-1RI being solely responsible for cell triggering upon IL-1 binding, whereas IL-1RII acts as a scavenger of IL-1 and can thus be considered as a natural IL-1 inhibitor. Thus, the enhanced inhibitory capacity of DoB 0041 as compared with wild-type IL-1ra is explained in terms of better binding to the activating receptor IL-1RI and poorer interaction with the inhibitory receptor IL-1RII.

Purification of human recombinant interleukin 1 receptor antagonist proteins upon Bacillus subtilis sporulation

Human interleukin 1 receptor antagonist (IL-1ra) and IL-1ra mutants were constitutively expressed in recombinant Bacillus subtilis in endocellular and active form. In order to optimize the purification of the recombinant proteins, a new method has been developed. After bacterial growth in fermenter, release of recombinant protein was achieved by starvation-induced sporulation. The sporulation supernatant was recovered by centrifugation, filtered, and subjected sequentially to cation- and anion-exchange chromatography. Alternatively, the fermenter's contents were directly subjected to expanded bed adsorption on a Streamline cation-exchange column, thus avoiding the centrifugation and filtration steps. Up to 88 mg of biological active purified recombinant protein per liter of culture was obtained, with a 72-79% recovery and 98% purity, depending on the molecule. By using the method described here, it is possible to achieve a spontaneous release of recombinant proteins expressed endocellularly at high levels in B. subtilis without need of a cell breakage step. Thus, this method could allow purification of the endocellular recombinant protein as if it were secreted. Furthermore, when using the expanded bed adsorption, highly purified protein was obtained in only two steps after sporulation. Among the advantages of the method, one of the most relevant is the possibility of keeping the system closed up to completion of the first purification step.

Cyclooxygenase-2 and synthesis of PGE2 in human bronchial smooth-muscle cells

The purpose of this study was to determine the mechanism of enhanced prostaglandin synthesis in cultured human bronchial smooth-muscle cells challenged with interleukin-1 beta (IL-1 beta). Cells were incubated with IL-1 beta (10 to 50 U/ml) for 0 to 24 h. Prostaglandin E2 (PGE2) production was evaluated through the conversion of exogenous (14C)-arachidonic acid and specific enzyme immunoassay of endogenous products. IL-1 beta enhanced PGE2 formation in a concentration- and time-dependent manner, reaching its peak at 6 to 8 h and fading at 18 to 24 h. Immunoblot analysis showed that the inducible cyclooxygenase enzyme (COX-2) was expressed only in IL-1 beta treated cells, whereas the constitutive isoform of cyclooxygenase (COX-1) remained unaltered. COX-2 expression and PGE2 formation were inhibited by dexamethasone (2 microM), cycloheximide (10 microM), and IL-1-receptor antagonist (IL-1 ra) (250 ng/ml), independently. PGE2 synthesis was significantly reduced by compound SC-58125, a specific COX-2 inhibitor. The close parallelism between the kinetics of COX-2 protein expression and PGE2 accumulation, as well as the constitutive nature of COX-1 isoform, indicate that IL-1 beta-driven PGE2 formation in human bronchial smooth-muscle cells is mediated by de novo expression of COX-2 enzyme.

Structure-function relationship in the IL-1 family

The interleukin 1 (IL-1) family is a group of related cytokines including two agonist proteins (IL-1alpha and IL-1beta), each derived by enzymatic cleavage of precursor proteins (pro-IL-1alpha and pro-IL-1beta), and three forms of an antagonist protein (IL-1ra, icIL-1raI, icIL-1raII). IL-1 plays a key role in the onset and development of the host reaction to invasion, being an important factor in the initiation of the inflammatory response and in the triggering of immune functions. Due to its pleiotropic activity and to the high potency of its inflammatory effects, IL-1 activity is tightly regulated in the body by a complex network of control systems. These include the presence of two types of inhibitors, the receptor antagonist IL-1ra and the second type of IL-1 receptor (IL-1RI), which is a natural scavenger of IL-1. Furthermore, regulation of IL-1 activity is attained by a strict hierarchy of binding affinity of the two receptors (the activating IL-1RI and the inhibitory IL-1RII) for the various members of the IL-1 family. Additional levels of control are represented by the presence of soluble forms of both receptors and of immature pro-IL-1 forms with different characteristics of activity and receptor binding capacity. To clarify the features of reciprocal interaction among ligands and receptors, in the attempt to understand the rules regulating the IL-1 system and its effectiveness, a deep analysis of the relationship between structure and function in the proteins of the IL-1 family becomes of key importance. Information on this line has been provided by several groups mainly with studies of mutagenesis of IL-1alpha, IL-1beta and IL-1ra in parallel with biological assays of activity. In this review, a survey of the available data is provided, in order to construct a hypothetical model of the functional structure of IL-1 proteins as a basis for future therapeutic interventions based on genetic and protein engineering.

Mapping of receptor binding sites on IL-1 beta by reconstruction of IL-1ra-like domains

Upon structure comparison between IL-1 beta and its antagonist IL-1ra, single or multiple residues along the IL-1 beta sequence were replaced with the corresponding amino acids present in the IL-1ra protein, in the attempt to identify sites important for receptor binding and for biologic activity on the two molecules. Ten of fifteen mutant proteins had activity comparable to that of wild-type IL-1 beta in three different biologic assays and in receptor binding, indicating that the introduced changes did not influence the functional structure of the protein. Conversely, three mutants (SMIL-9: 127/263 R/T-->W/Y; SMIL-10: 125/127/263/265 T/R/T/Q-->R/W/Y/E; SMIL-15:222/227 I/E-->S/S) showed an increased binding capacity for IL-1RI, not paralleled by increased agonist activity, indicating that the introduced IL-1ra residues could be involved in the nonagonist IL-1RI binding site. On the other hand, two mutants showed diminished binding capacity with concomitant decrease in biologic activity. Both mutants (SMIL-1, five substitutions in the loop 202-214; and SMIL-3, total replacement of the loop 164-173 with the IL-1ra stretch 52-55) included substitutions of residues allegedly important for agonist binding to IL-1RI. Mutant SMIL-3 showed the most profound reduction in binding capacity for IL-1RI (CDw121a) and a more than 1,000-fold reduced biologic activity both in vitro and in vivo, but it retained full capacity of binding to IL-1RII (CDw121b) and acted as a selective antagonist of IL-1RII. From these results the following conclusions can be drawn. IL-1 beta binds to IL-1RI and to IL-1RII through different sites, and the loop 164-173 appears as one of the areas involved in the selective interaction with IL-1RI. Agonist (IL-1 beta) and nonagonist (IL-1ra) binding to IL-1RI occur through distinct sites, with loops 164-173 and 202-214 of IL-1 beta identified as two of the sites selectively involved in agonist binding to the activating receptor.

Mapping of receptor binding sites on IL-1 beta by reconstruction of IL-1ra-like domains

Upon structure comparison between IL-1 beta and its antagonist IL-1ra, single or multiple residues along the IL-1 beta sequence were replaced with the corresponding amino acids present in the IL-1ra protein, in the attempt to identify sites important for receptor binding and for biologic activity on the two molecules. Ten of fifteen mutant proteins had activity comparable to that of wild-type IL-1 beta in three different biologic assays and in receptor binding, indicating that the introduced changes did not influence the functional structure of the protein. Conversely, three mutants (SMIL-9: 127/263 R/T-->W/Y; SMIL-10: 125/127/263/265 T/R/T/Q-->R/W/Y/E; SMIL-15:222/227 I/E-->S/S) showed an increased binding capacity for IL-1RI, not paralleled by increased agonist activity, indicating that the introduced IL-1ra residues could be involved in the nonagonist IL-1RI binding site. On the other hand, two mutants showed diminished binding capacity with concomitant decrease in biologic activity. Both mutants (SMIL-1, five substitutions in the loop 202-214; and SMIL-3, total replacement of the loop 164-173 with the IL-1ra stretch 52-55) included substitutions of residues allegedly important for agonist binding to IL-1RI. Mutant SMIL-3 showed the most profound reduction in binding capacity for IL-1RI (CDw121a) and a more than 1,000-fold reduced biologic activity both in vitro and in vivo, but it retained full capacity of binding to IL-1RII (CDw121b) and acted as a selective antagonist of IL-1RII. From these results the following conclusions can be drawn. IL-1 beta binds to IL-1RI and to IL-1RII through different sites, and the loop 164-173 appears as one of the areas involved in the selective interaction with IL-1RI. Agonist (IL-1 beta) and nonagonist (IL-1ra) binding to IL-1RI occur through distinct sites, with loops 164-173 and 202-214 of IL-1 beta identified as two of the sites selectively involved in agonist binding to the activating receptor.

Single-cell analysis of macrophage chemotactic protein-1-regulated cytosolic Ca2+ increase in human adherent monocytes

The increase in intracellular free Ca2+ ([Ca2+]i) associated with interaction of monocyte chemotactic protein-1 (MCP-1) and related chemokines beta with adherent human blood monocytes was investigated at the single-cell level. We used f-MLP as reference chemotactic agent. MCP-1 caused an increase in [Ca2+]i in individual adherent monocytes, with 95% of cells responding to the chemokine at 20 ng/mL. Response to MCP-1 was already detectable at 1 pg/mL, whereas at least 5 ng/mL were required for significant chemotactic response. The kinetics of the increase in [Ca2+]i were considerably different for MCP-1 compared with f-MLP. MCP-1 produced a slow increase of [Ca2+]i that reached a plateau in 5 to 7 minutes. On the other hand, the increase of [Ca2+]i induced by f-MLP appeared to be biphasic, with a fast phase peaking after 5 to 40 seconds followed by a slower wave. Blocking of Ca2+ channels by Ni2+ or Cd2+ and/or chelation of extracellular free Ca2+ considerably reduced but did not abolish response to MCP-1, had no effect on the first wave of [Ca2+]i induced by f-MLP, and completely abrogated the second, slower wave. Thapsigargin, which empties intracellular Ca2+ stores, inhibited f-MLP-induced [Ca2+]i increase but fully blocked the action of MCP-1 only when combined with Ni2+. Thus, increase of [Ca2+]i induced by MCP-1 is apparently due to independent opening of a channel and mobilization from intracellular stores, whereas f-MLP-induced mobilization of Ca2+ from stores causes subsequent opening of a channel. At variance with MCP-1, the related chemokine MCP-2 induced only a low increase of [Ca2+]i in about 40% of adherent monocytes. Inhibition of chemokine-induced increase of [Ca2+]i by cholera or pertussis toxin indicated that MCP-1 and MCP-2 activate monocytes through different intracellular pathways. These results demonstrate at the single-cell level that the mechanisms and dynamics of increased [Ca2+]i are considerably different for f-MLP and chemokines beta. In addition, the [Ca2+]i increase induced by the two related chemokines beta MCP-1 and MCP-2 appears to be differently regulated, suggesting interaction with distinct receptors.

Identification of MIP-1 alpha/LD78 as a monocyte chemoattractant released by the HTLV-I-transformed cell line MT4

It is known that the HTLV-I-transformed cell line MT4 releases chemotactic activity for monocytes spontaneously. The MT4 monocyte chemoattractant was purified to homogeneity and sequencing of 25 amino acids revealed identity with the C-C chemokine macrophage inflammatory protein-1 alpha (MIP-1 alpha/LD78). An anti-MIP-1 alpha/LD78 rabbit antiserum substantially inhibited chemotaxis of the MT4 chemoattractant. MT4 cells constitutively expressed MIP-1 alpha/LD78 but not the C-C chemokines MCP-1, RANTES, and MIP-1 beta/Act2 and the C-X-C chemokines IL-8, gro alpha, and gro beta. MT4-derived MIP-1 alpha/LD78 was active on monocytes but was a weak chemoattractant for polymorphonuclear leukocytes. Thus, MIP-1 alpha/LD78 is a major monocyte chemoattractant released by HTLV-I-transformed T cells. Expression of MIP-1 alpha/LD78, a leukocyte chemotactic and myelosuppressive molecule, may play an important role in the manifestations of HTLV-I-related diseases.

Cytokines as vaccine adjuvants: interleukin 1 and its synthetic peptide 163-171

The possibility of preventing infectious diseases by employing efficacious vaccine is rapidly growing as a consequence of the new technologies in recombinant DNA and protein chemistry. However, the increasing number of synthetic and recombinant antigens further stresses the role of appropriate adjuvants to ensure maximal vaccine activity and the protection of all vaccinees. Several approaches can be applied to develop safe and effective agents capable of enhancing specific immune responses which can then protect the host from the pathogen. Among others, the direct use as adjuvant of those cytokines which are induced in animals by the classical Freund's adjuvants has recently become a matter of investigation. In particular, interleukin 1 (IL-1) has been shown to possess adjuvant activity for a variety of infectious and tumour antigens. However, the numerous side effects associated with the proinflammatory action of IL-1 represent a serious disadvantage for its use as a vaccine adjuvant. It was therefore of great interest that a nonpeptide contained in the IL-1 beta sequence (residues 163-171 corresponding to the sequence VQGEESNDK) is devoid of all proinflammatory activities but maintains the immunostimulating activity of the whole IL-1 beta. Thus, peptide 163-171 was successfully employed in animals to potentiate the specific immune response against T-helper-dependent cellular antigens, T helper-independent polysaccharidic antigens and recombinant as well as synthetic antigenic preparations derived from human pathogens. Furthermore, IL-1 and peptide 163-171 have been successfully used in tumour vaccines in experimental systems. It can therefore be concluded that peptide 163-171 is potentially a good candidate as vaccine adjuvant for human use.

Type II interleukin-1 receptor is not expressed in cultured endothelial cells and is not involved in endothelial cell activation

Interleukin-1 (IL-1) profoundly affects a number of functions of endothelial cells (EC). It was previously shown that EC express the type I 80-Kd IL-1 receptor (IL-1 RI). In this study we define the expression and functional significance of the type II IL-1R (IL-1 RII) in EC. Human umbilical vein EC did not express appreciable levels of IL-1 RII mRNA as assessed by Northern analysis or reverse transcription and polymerase chain reaction. Exposure to various cytokines (including IL-4, which augments IL-1 RII in neutrophils) failed to induce IL-1 RII mRNA. The binding of radiolabeled IL-1 beta to EC was blocked by antitype I (M4) but not by antitype II (M22) monoclonal antibodies (MoAbs). MoAbs directed against the IL-1 RI (M1 and M4) inhibited the induction of IL-6 and adhesion molecules in EC by IL-1, whereas an anti-IL-1 RII (M22) was inactive. The human IL-1 receptor antagonist (IL-1ra) preferentially interacts with IL-1 RI versus IL-1 RII in the mouse. IL-1 ra inhibited the response of mouse endothelial cells to IL-1. We conclude that EC selectively express the IL-1 RI and that this is involved in the response of this cell type to IL-1.

Human peritoneal mesothelial cells produce many cytokines (granulocyte colony-stimulating factor [CSF], granulocyte-monocyte-CSF, macrophage-CSF, interleukin-1 [IL-1], and IL-6) and are activated and stimulated to grow by IL-1

To investigate the role of peritoneal mesothelial cells in regulating hematopoiesis, as well as inflammation, healing, and tissue regeneration processes, long-term cultures of peritoneal mesothelial cells from human endocavitarian fluids were established. The purity of the cell population was assessed by morphologic and immunocytochemical criteria. Five peritoneal mesothelial cell cultures were analyzed for cytokine expression. Macrophage colony-stimulating factor (M-CSF), granulocyte-CSF (G-CSF), interleukin-1 alpha (IL-1 alpha), IL-1 beta, and IL-6 transcripts were constantly but variably detected throughout the culture period, while granulocyte-monocyte-CSF (GM-CSF) expression started as the cell culture aged. No IL-2, IL-3, IL-4, IL-5, or IL-7 transcripts were detected in the same samples. Corresponding cytokine activities were detected in the supernatants of the cultures. Peritoneal mesothelial cells proliferated after the addition of exogenous IL-1 beta or IL-1 alpha, whereas the addition of recombinant GM-CSF, G-CSF, M-CSF, or IL-6 failed to trigger proliferation. IL-1 receptor type I transcripts were detected in peritoneal mesothelial cells. Moreover, IL-1 was able to upregulate the expression of the genes that code for G-CSF, GM-CSF, IL-1 alpha, and IL-1 beta in these cells. These data indicate that peritoneal mesothelial cells produce many cytokines and suggest that IL-1 is a regulatory molecule for peritoneal mesothelial cells.

Effects of intraperitoneal recombinant interleukin-1 beta in intraperitoneal human ovarian cancer xenograft models: comparison with the effects of tumour necrosis factor

The effect of intraperitoneal (i.p.) injection of recombinant human interleukin-1 beta (rhIL-1 beta) was studied in three i.p. nude mouse xenograft models of human ovarian cancer (HU, OS, and LA). Intraperitoneal rhIL-1 beta administration led to a dose dependent replacement of peritoneal ascitic tumour with solid tumours attached to the peritoneum and intraabdominal viscera in two (HU and LA) out of the three xenograft models. In the third xenograft model (OS), low doses of rhIL-1 beta (10 ng day) promoted micrometastatic peritoneal implants of tumour, but higher doses of rhIL-1 beta (1 microgram day) had a marked antitumour effect. This was due to direct cytotoxicity for tumour cells and was not related to peritoneal neutrophil influx induced by rhIL-1 beta. Recombinant human TNF (rhTNF) also promoted tumour implantation in all three xenograft models, but its antitumour effects differed from rhIL-1 beta. TNF increased the survival of HU and LA bearing mice, but had no antitumour effect in the OS xenograft model. Analysis of peritoneal fluid and tumour xenografts showed that TNF induced murine IL-1 in the tumour bearing mice. The magnitude of IL-1 induction indicated that TNF induced IL-1 did not contribute significantly to its effects.

Binding and internalization of the 163-171 fragment of human IL-1 beta

The mechanisms of cell association of the human interleukin (IL-1 beta) immunostimulatory fragment 163-171 have been studied. The fragment was able to associate abundantly to both IL-1R- and IL-1R+ cells. Binding was strictly temperature dependent, was not saturable and could be inhibited by excess amounts of unlabelled 163-171 peptide but not by IL-1 beta, suggesting that the 163-171 fragment is not an IL-1R-binding domain of IL-1 beta. The fragment is readily internalized by cells by a cytochalasin-insensitive mechanism and it localizes mainly in the cytoplasm. It is concluded that the active domain 163-171 of IL-1 beta can be taken up by cells through a receptor-independent, temperature-dependent mechanisms and that its ability to activate cellular functions is based on IL-1R-independent intracellular pathways.

Immunohistochemical localization of IL-1 alpha and IL-1 beta in normal human placenta

Many reports show that interleukin 1 (IL-1) is produced by mouse and human placenta but the cell type that is responsible for this production has yet to be identified. For this reason we attempted to localize IL-1 alpha and IL-1 beta directly on formalin-fixed paraffin-embedded normal human placentae at different stages of pregnancy using immunohistochemical techniques and specific antibodies. The results obtained show that both IL-1 forms are localized to villous syncytiotrophoblast and to extravillous trophoblast, while villous cytotrophoblast and cytotrophoblast columns are unreactive. A gradual decrease of reactivity was observed with increasing gestation age for both IL-1 forms, but the staining for IL-1 beta was in all sections higher than for IL-1 alpha. Although the physiological role of IL-1 in pregnancy has yet to be established, the presence of this cytokine in the cells facing maternal blood and tissues suggests a possible involvement in the immunoregulation of fetal acceptance.

Cytokine-associated tissue injury and lethality in mice: a comparative study

A comparative study was performed to examine the lethal effects of several cytokines injected into mice sensitized with actinomycin D (Act-D). Consistent with published data, human tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) (0.2-5 micrograms) caused the death of the animals within 8-12 hr after injection. Human interleukin-6 (IL-6) and interleukin-8 (IL-8) (0.6-6 micrograms) known to be induced by TNF-alpha did not show any lethal effects, indicating that TNF-alpha-associated lethality is not mediated by IL-6 or IL-8. Human tumor necrosis factor-beta (TNF-beta) (also called lymphotoxin), which shares structural and functional properties with TNF-alpha, was as potent as TNF-alpha in its lethal effects. Murine interferon-gamma (IFN-gamma) (0.04-5 micrograms) was also tested and showed no lethal effects in this model. In addition, a synthetic peptide corresponding to amino acid residues 163-171 of IL-1 beta, and which has been shown to lack the inflammatory effects of IL-1 beta, also caused no lethality among Act-D sensitized mice. The pretreatment of mice with IL-6, IL-8, or IFN-gamma had no protective effects on TNF-alpha or IL-1 beta-induced lethality in contrast to the protection observed by a pretreatment with TNF-alpha/IL-1 beta themselves or with endotoxin. Histopathologic data showed that severe tissue injury in vital organs is associated with the rapid lethality among sensitized mice.

Differential inhibition of IL-1 beta activities and receptor binding by monoclonal antibodies mapping within a discrete region of the protein

The importance of the region in position 148-192 for the biological activities and receptor-binding capacity of the human IL-1 beta protein has been assessed by the use of mAbs. Four mAbs have been used, which recognize different epitopes within the 148-192 region. None of the mAbs could inhibit binding of IL-1 beta to IL-1RI (expressed on T cells and fibroblasts), suggesting that the 148-192 region does not contain IL-1RI binding sites. Conversely, mAbs Vhp20 (recognizing the fragment 166-169) and BRhD2 (directed to an epitope in the sequence 177-186) recognize sites partially involved in binding to IL-1RII (expressed on B cells, macrophages, and PMN). Only mAbs BRhD2 and FIB 1 (which recognizes an epitope in the sequence 174-186) can inhibit IL-1 beta-induced thymocyte proliferation, whereas all four can inhibit the adjuvant capacity of IL-1 beta in vivo. It is concluded that the region 148-192 encompasses domains important for T cell activation but not for binding to the IL-1RI on T cells, others involved in immunostimulation in vivo, and others important for binding to IL-1RII, although not directly involved in it.

Radiation protection and restoration by the synthetic 163-171 nonapeptide of human interleukin 1 beta

We have previously reported that the synthetic nonapeptide VQGEESNDK, position 163-171 of human interleukin 1 (IL-1 beta), when injected in immunodepressed mice, shows immunorestorative activity similar to that of the whole protein, but with no IL-1-like inflammatory effects [Frasca et al., J. Immunol. 141, 2651-2655 (1988)]. In the present study we have compared the protective and restorative activities of the nonapeptide and human recombinant (hur) IL-1 beta on the survival of lethally irradiated mice. When mice were given a single injection of different doses of the nonapeptide or hurIL-1 beta 20 h before total-body irradiation, both molecules increased the percentage survival of mice exposed to 750 or 850 cGy, but not to 950 cGy. The nonapeptide, however, is less effective than hurIL-1 beta and displays a different dose-response relationship, suggesting that the two molecules act through different radioprotective pathways. When mice were injected with the nonapeptide or hurIL-1 beta immediately after exposure to 850 cGy, the percentage survival was also increased but restoration was lower than protection in both cases. The nonapeptide was also less effective than hurIL-1 beta in restoration, but the two molecules displayed a comparable dose-response relationship as if they shared similar mechanisms. These findings indicate that the 163-171 nonapeptide is able to protect from lethal radiation injury and to restore viability. The nonapeptide appears less effective than hurIL-1 beta but does not exhibit the IL-1-like side effects of the whole molecule.

Endothelial cells express the interleukin-1 receptor type I

Interleukin-1 (IL-1) profoundly affects a number of functions of vascular cells. Two distinct IL-1 receptors (IL-1R) are expressed on different cell types: the 80 Kd IL-1RI on T cells and fibroblasts, and the 68 Kd IL-1RII on B cells and myelomonocytic cells. The presence and functionality of IL-1R on vascular cells has been investigated by using polyomatransformed mouse endothelial cell (EC) lines (sEnd.1 and tEnd.1). These cells expressed specific and saturable binding sites for IL-1 (1,273 sites per cell with kd 9.5 x 10(-11) mol/L for sEnd.1, and 771 sites per cell with kd 8.5 x 10(-11) mol/L for tEnd.1, with radioiodinated IL-1 alpha as ligand). Binding of IL-1 was also evident at single cell level by autoradiography. By cross-linking studies, the molecular weight of the IL-1 binding protein on EC was approximately 80 Kd. This was confirmed by the presence in EC of mRNA for the 80 Kd IL-1RI. The IL-1RI on EC was apparently functional, since EC responded to IL-1 with IL-6 mRNA expression and IL-6 bioactivity production. These results were extended to human EC and vascular smooth muscle cells, which were also found to express mRNA for IL-1RI.

Binding of IL-1 beta to IL-1R type II at single cell level

To gain information on the possible biologic role of IL-1R type II (IL-1RII), expression of the 68-kDa IL-1 binding protein on human lymphoblastoid B cells was investigated at single cell level. Binding of iodinated IL-1 beta was evaluated by autoradiography on cytosmears of IL-1RII positive B cell lines RAJI, the RAJI clone 1H7, and STS 25. Results obtained suggest an heterogeneity of IL-1RII expression within the B cell population, with only 5 to 16% of the cells able to bind IL-1 beta. Up-regulation of IL-1RII expression by dexamethasone, evident in conventional binding assays, was achieved through both increase in the number of IL-1 binding cells (14-30%) and augmentation of receptor density on positive cells, By combining autoradiography with immunocytochemical staining, it could be shown that about 80% of IL-1RII + cells were negative for Ki67, a nuclear antigen expressed from late G1 to M phase. Cell cycle dependent expression of IL-1RII was confirmed on cells enriched in different phases of the cell cycle by counterflow centrifugal elutriation. It is thus proposed that IL-1RII is associated to the cell cycle.

Binding of IL-1 beta to IL-1R type II at single cell level

To gain information on the possible biologic role of IL-1R type II (IL-1RII), expression of the 68-kDa IL-1 binding protein on human lymphoblastoid B cells was investigated at single cell level. Binding of iodinated IL-1 beta was evaluated by autoradiography on cytosmears of IL-1RII positive B cell lines RAJI, the RAJI clone 1H7, and STS 25. Results obtained suggest an heterogeneity of IL-1RII expression within the B cell population, with only 5 to 16% of the cells able to bind IL-1 beta. Up-regulation of IL-1RII expression by dexamethasone, evident in conventional binding assays, was achieved through both increase in the number of IL-1 binding cells (14-30%) and augmentation of receptor density on positive cells, By combining autoradiography with immunocytochemical staining, it could be shown that about 80% of IL-1RII + cells were negative for Ki67, a nuclear antigen expressed from late G1 to M phase. Cell cycle dependent expression of IL-1RII was confirmed on cells enriched in different phases of the cell cycle by counterflow centrifugal elutriation. It is thus proposed that IL-1RII is associated to the cell cycle.

Quantitation of biologically active IL-1 by a sensitive assay based on immobilized human IL-1 receptor type II (IL-1RII)

A rapid and sensitive solid-phase radioassay is described for the quantitative detection of human interleukin-1 (IL-1) based on its capability to bind the nitrocellulose-immobilized IL-1 receptor solubilized from plasma membranes of a subclone of the human B cell lymphoma Raji. The assay can detect human IL-1 beta levels as low as 1 X 10(-11) M, both in physiological buffers and in human plasma. Much lower sensitivity was observed for human IL-1 alpha (3.7 X 10(-9) M) and murine IL-1 beta (2 X 10(-9) M). This assay has the advantage to specifically detect only the correctly folded biologically active IL-1. Simple pretreatment procedure that selectively removes IL-1 beta from samples has been devised so that the ratio of the two IL-1s isoforms in the sample can be precisely determined. This assay represents a fast method for the simultaneous-testing of large numbers of biological samples.

Murine interferon-gamma/interleukin-1 fusion proteins used as antigens for the generation of hybridomas producing monoclonal anti-interleukin-1 antibodies

In several biological systems interferon-gamma (IFN-gamma) and interleukin-1 (IL-1) act synergistically. We therefore examined whether it would be possible to construct IFN-gamma/IL-1 hybrid proteins that would be more active than the individual components. Hybrid proteins were examined that consisted of the amino-terminal 118 residues of mouse IFN-gamma and the 156 or 152 carboxyl-terminal residues of mouse IL-1 alpha or IL-1 beta, respectively. They were obtained by ligation of the respective coding sequences and expression of the fused genes under control of the PL promotor in Escherichia coli. Both the IFN-gamma/IL-1 alpha and the IFN-gamma/IL-1 beta fusion proteins were purified by affinity chromatography on an anti-IFN-gamma monoclonal antibody column. Analysis of biological activities showed that these fusion proteins were less active than the individual cytokines. Specific antiviral activity of the IFN-gamma/IL-1 beta hybrids was less than 0.1% that of IFN-gamma and D10.G4.1 T-cell proliferative (IL-1) activity amounted to 0.1% that of mouse IL-1. Affinity-purified preparations of the IFN-gamma/IL-1 alpha hybrid were found to contain variable proportions of a Mr 14,000 degradation product possessing IFN-gamma activity, whereas the undegraded Mr 30,000 fusion protein, while being devoid of detectable IFN-gamma activity, did possess IL-1 activity (1%). Serum from rats immunized with the IFN-gamma/IL-1 alpha hybrid contained high levels of IL-1 alpha-binding and -neutralizing antibodies and IFN-gamma-binding antibodies, but no detectable levels of IFN-gamma-neutralizing antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of human interleukin-1 beta and its 163-171 peptide in bone resorption and the immune response

Human interleukin-1 beta (IL-1 beta) caused a dose- and time-dependent enhancement of the release of 45Ca from prelabeled mouse calvaria in organ culture. In addition, IL-1 beta dose-dependently stimulated the formation of prostaglandin E2 (PGE2) and 6-keto-PGF1 alpha in the calvarial bones. However, IL-1 beta-induced 45Ca release was only partially inhibited by blocking the PGE2 response with indomethacin, suggesting that enhanced PGE2 formation in response to IL-1 beta is not necessary to obtain a bone resorptive effect, but that prostaglandins potentiate the action of IL-1 beta. The synthetic nonapeptide VQGEESNDK, corresponding to the fragment 163-171 of human IL-1 beta, administered simultaneously with antigen (SRBC) to C3H/HeN male mice, induced a dose-dependent enhancement of specific antibody-producing cells in the spleen (PFC). The degree of PFC stimulation was comparable to that caused by native human IL-1 beta. In mouse bone cultures, neither 45Ca release nor prostanoid formation was stimulated by fragment 163-171. These data indicate that (1) IL-1 beta-induced stimulation of bone resorption is dissociable from IL-1 beta-induced increase of prostanoid biosynthesis and (2) the epitope of the IL-1 beta molecule involved in the immunostimulatory effects may be different from that involved in the stimulatory effects on bone resorption.

Mechanism of acute toxicity of IL-1 beta in mice

Human recombinant IL-1 beta was able to kill C3H/HeJ mice only when inoculated intravenously at very high doses. IL-1 beta, inoculated at 100 mg/kg i.v. as a bolus, induced a shock-like state characterized by anorexia, severe hypothermia and hypoglycemia and persistent neutrophilia, leading to death in 55% of animals generally between 24 and 48 h. In contrast, the noninflammatory adjuvant IL-1 beta peptide VQGEESNDK (position 163-171) did not induce any toxic effect in vivo, when administered following the same schedule. At variance with what was previously observed in endotoxin induced shock, IL-1 beta induced death was not preceded by appearance of circulating TNF. On the other hand, very high and persistent levels of circulating IL-6 could be detected after lethal IL-1 beta administration. Treatment of mice with ibuprofen or with chlorpromazine, both known to counteract some of the toxic effects of IL-1 in vivo, could protect from IL-1 beta induced mortality. Both drugs, at doses protecting from IL-1 beta induced death, were able to abolish IL-1 beta-induced rise of circulating phospholipase A2 (PLA2) activity, and the subsequent generation of toxic PLA2-derived metabolites.

Cytokine production (IL-1 alpha, IL-1 beta, and TNF alpha) and endothelial cell activation (ELAM-1 and HLA-DR) in reactive lymphadenitis, Hodgkin's disease, and in non-Hodgkin's lymphomas. An immunocytochemical study

Cryostat sections of 58 lymph nodes were immunostained with a polyclonal rabbit serum against IL-1 alpha, and with monoclonal antibodies directed to IL-1 alpha (Vmp18), IL-1 beta (Vhp20 and BRhC3), and tumor necrosis factor alpha (TNF alpha) (B154.7). Furthermore the presence of cytokine-containing cells was correlated with the expression of endothelial leukocyte adhesion molecule (ELAM-1; 29F2) and of human leukocyte antigen (HLA-DR) (OKIa-1) by endothelial cells. Cells containing IL-1 and/or TNF alpha were detected mainly in pathologic conditions characterized by reactive or neoplastic expansion of the lymph node paracortex. Cells positive for IL-1 were detected in 16 of 21 cases of Hodgkin's disease, in 4 of 4 cases of T-NHL, and in 5 cases of diffuse or mixed lymphadenitis. Interleukin-1 alpha was detected in macrophages, interdigitating reticulum cells (IDRCs), endothelial cells, and neoplastic Hodgkin's and Reed-Sternberg (H-RS) cells. Cells positive for IL-1 beta were much fewer and consisted mainly of macrophages. Hodgkin's Reed-Sternberg cells were negative for IL-1 beta even after in vitro stimulation with bacterial endotoxin. Tumor necrosis factor alpha (TNF alpha) was present in macrophages and H-RS cells. Endothelial leukocyte adhesion molecule-1 expression by endothelial venules was detected in 17 of 20 cases of Hodgkin's disease, in 2 of 4 cases of T-NHL, and in 5 of 5 cases of diffuse lymphadenitis. In these pathologic conditions, HLA-DR antigens also were expressed frequently by endothelial cells. Cytokine-containing cells and ELAM-1-positive high endothelial venules (HEV) were extremely rare in lymph nodes involved by follicular lymphadenitis (12 cases) or B-NHL (16 cases). In cases of reactive or neoplastic B-cell proliferations, HLA-DR-positive HEVs still were present often. Our results indicate that IL-1/TNF alpha production at tissue level is often associated with ELAM-1 expression by HEVs, but is less well correlated with expression of HLA-DR antigens by endothelial cells.

Macrophages and interdigitating reticulum cells in normal human thymus and thymomas: immunoreactivity for interleukin-1 alpha, interleukin-1 beta and tumour necrosis factor alpha

Pairs of monoclonal/polyclonal antibodies directed against interleukin-1 (IL-1) alpha, IL-1 beta and tumour necrosis factor (TNF) alpha were used for immunocytochemical identification of cytokine-containing cells in cryostat sections of human fetal thymuses and thymomas. In the fetal thymus immunoreactivity for IL-1 alpha was mainly confined to the medulla and was detected in S-100 positive interdigitating reticulum cells. The pattern of immunoreactivity for IL-1 beta was similar to that for IL-1 alpha, but the number of positive cells was much lower. Cells positive for TNF alpha were extremely rare in the fetal thymus. In 11 thymomas macrophages were constantly present and were regularly distributed throughout the tumour, whereas S-100 positive interdigitating reticulum cells were fewer and were characterized by a zonal distribution. Thymoma-associated macrophages were negative for IL-1 beta and were poorly reactive for IL-1 alpha, only a few positive cells being detected in five of the cases. Some macrophages with immunoreactivity for TNF alpha were detected in seven cases; they formed rosettes with surrounding lymphocytes or were located in a perivascular position. A marked immunoreactivity for TNF alpha was constantly detected in mast cell granules, which were observed in nine thymomas but not in fetal thymus. Positive immunoreactivity of interdigitating reticulum cells for IL-1 alpha was confirmed in five reactive lymph nodes and was also observed in Langerhans' cells in dermatopathic lymphadenitis. Our findings suggest that IL-1 alpha is a crucial molecule for interdigitating reticulum cell and Langerhans' cell function.(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin 1-induced augmentation of experimental metastases from a human melanoma in nude mice

This study has examined the effect of the cytokine interleukin 1 (IL-1) on metastasis formation by the human melanoma A375M in nude mice. We have found that human recombinant IL-1 beta (a single injection greater than 0.01 micrograms per mouse i.v. given before tumor cells) induced an augmentation of experimental lung metastases from the A375M tumor cells in nude mice. This effect was rapidly induced and reversible within 24 h after IL-1 injection. A similar effect was induced by human recombinant IL-1 alpha and human recombinant tumor necrosis factor, but not by human recombinant interleukin 6. 5-[125I]odo-2'-deoxyuridine-radiolabeled A375M tumor cells injected i.v. remained at a higher level in the lungs of nude mice receiving IL-1 than in control mice. In addition, IL-1 injected 1 h, but not 24 h, after tumor cells enhanced lung colonization as well, thus suggesting an effect of IL-1 on the vascular transit of tumor cells. These findings may explain the observation of enhanced secondary localization of tumor cells at inflammatory sites and suggest that modulation of secondary spread should be carefully considered when assessing the ability of this cytokine to complement cytoreductive therapies.