Human interleukin 1 beta is not secreted from hamster fibroblasts when expressed constitutively from a transfected cDNA

NF-κB-dependent role for cold-inducible RNA binding protein in regulating interleukin 1β

The cold inducible RNA binding protein (CIRBP) responds to a wide array of cellular stresses, including short wavelength ultraviolet light (UVC), at the transcriptional and post-translational level. CIRBP can bind the 3'untranslated region of specific transcripts to stabilize them and facilitate their transport to ribosomes for translation. Here we used RNA interference and oligonucleotide microarrays to identify potential downstream targets of CIRBP induced in response to UVC. Twenty eight transcripts were statistically increased in response to UVC and these exhibited a typical UVC response. Only 5 of the 28 UVC-induced transcripts exhibited a CIRBP-dependent pattern of expression. Surprisingly, 3 of the 5 transcripts (IL1B, IL8 and TNFAIP6) encoded proteins important in inflammation with IL-1β apparently contributing to IL8 and TNFAIP6 expression in an autocrine fashion. UVC-induced IL1B expression could be inhibited by pharmacological inhibition of NFκB suggesting that CIRBP was affecting NF-κB signaling as opposed to IL1B mRNA stability directly. Bacterial lipopolysaccharide (LPS) was used as an activator of NF-κB to further study the potential link between CIRBP and NFκB. Transfection of siRNAs against CIRBP reduced the extent of the LPS-induced phosphorylation of IκBα, NF-κB DNA binding activity and IL-1β expression. The present work firmly establishes a novel link between CIRBP and NF-κB signaling in response to agents with diverse modes of action. These results have potential implications for disease states associated with inflammation.

In vitro and in vivo evidence for a role of the P2X7 receptor in the release of IL-1 beta in the murine brain

The P2X(7) receptor (P2X(7)R) is a purinoceptor expressed predominantly by cells of immune origin, including microglial cells. P2X(7)R has a role in the release of biologically active proinflammatory cytokines such as IL-1 beta, IL-6 and TNFalpha. Here we demonstrate that when incubated with lipopolysaccharide (LPS), glial cells cultured from brain of P2X(7)R(-/-) mice produce less IL-1 beta compared to glial cells from brains of wild-type mice. This is not the case for TNFalpha and IL-6. Our results indicate a selective effect of the P2X7R gene deletion on release of IL-1 beta release but not of IL-6 and TNFalpha. In addition, we confirm that only microglial cells produce IL-1beta, and this release is dependent on P2X(7)R and ABC1 transporter. Because IL-1 beta is a key regulator of the brain cytokine network and P2X(7)R is an absolute requirement for IL-1 beta release, we further investigated whether response of brain cytokines to LPS in vivo was altered in P2X(7)R(-/-) mice compared to wild-type mice. IL-1 beta and TNFalpha mRNAs were less elevated in the brain of P2X(7)R(-/-) than in the brain of wild-type mice in response to systemic LPS. These results show that P2X7R plays a key role in the brain cytokine response to immune stimuli, which certainly applies also to cytokine-dependent alterations in brain functions including sickness behavior.

Caspase-1 regulates Escherichia coli sepsis and splenic B cell apoptosis independently of interleukin-1beta and interleukin-18

RATIONALE

Caspase-1 processes interleukin 1beta (IL-1beta) and IL-18 but may also contribute to apoptosis. In this context, caspase-1 knockout mice have been shown to be protected from endotoxin-induced mortality, whereas IL-1beta knockout mice are not protected.

OBJECTIVES

We therefore sought to delineate the mechanisms responsible for the differential responses between caspase-1 and IL-1beta knockout mice.

METHODS

Caspase-1 knockout, IL-1beta knockout, and IL-1beta/IL-18 double knockout mice were compared with wild-type mice for survival after intraperitoneal challenge with live Escherichia coli.

MEASUREMENTS AND MAIN RESULTS

Caspase-1 knockout animals were protected from bacterial challenge, whereas wild-type, IL-1beta knockout, and IL-1beta/IL-18 double knockout animals were not. Wild-type animals and both IL-1beta knockout and IL-1beta/IL-18 double knockout mice demonstrated significant splenic B lymphocyte apoptosis, which was absent in the caspase-1 knockout mice. Importantly, IL-1beta/IL-18 double knockout mice were protected from splenic cell apoptosis and sepsis-induced mortality by the caspase inhibitor zVAD-fmk. Furthermore, wild-type but not caspase-1 knockout splenic B lymphocytes induced peritoneal macrophages to assume an inhibitory phenotype.

CONCLUSION

Taken together, these findings suggest that caspase-1 is important in the host response to sepsis at least in part via its ability to regulate sepsis-induced splenic cell apoptosis.

Interleukin-1beta and signaling of interleukin-1 in vascular wall and circulating cells modulates the extent of neointima formation in mice

Interleukin (IL)-1 is an important mediator of inflammation and cardiovascular disease. Here, we examined the role of IL-1 in arterial neointima formation. Carotid artery neointima was induced by ligation, and arteries were harvested 4 weeks after injury. The neointima/media of mice deficient in the IL-1 signaling receptor (IL-1R1(-/-)) was significantly reduced compared to IL-1R1(+/+) controls (P < 0.01). IL-1R1(+/+) mice receiving subcutaneous IL-1ra also had significantly reduced neointima/media compared with placebo (P < 0.05). IL-1beta(-/-) mice had reduced neointima/media compared to wild-type (P < 0.05), whereas IL-1alpha(-/-) mice were no different from controls. Mice deficient in the P2X(7) receptor (involved in IL-1 release) or caspase-1 (involved in IL-1 activation) did not differ in their response to carotid ligation compared to controls. To examine the site of IL-1 signaling, we generated chimeric mice. IL-1R1(+/+) mice receiving IL-1R1(-/-) marrow and IL-1R1(-/-) mice receiving IL-1R1(+/+) marrow both had significantly reduced neointima/media compared with IL-1R1(+/+) to IL-1R1(+/+) (P < 0.05) but had significantly greater neointima/media than IL-1R1(-/-) to IL-1R1(-/-) controls (P < 0.05). These data confirm the importance of IL-1beta signaling in mediating arterial neointima formation and suggest the involvement of IL-1 signaling in both circulating and arterial wall cells. Furthermore, receptor antagonism may be a better therapeutic target than interruption of IL-1beta processing or release.

Tissue kallikrein mK13 is a candidate processing enzyme for the precursor of interleukin-1beta in the submandibular gland of mice

By using Western blot analysis, high levels of 17.5- and 20-kDa interleukin-1beta (IL-1beta) proteins were detected in the submandibular gland (SMG) of mice. Despite this fact, the amount of pro-IL-1beta protein, a precursor of IL-1beta, with a molecular size of 35 kDa in this tissue was below the detectable level, although strong expression of pro-IL-1beta mRNA was observed. A large amount of 17.5-kDa IL-1beta also appeared in the saliva of mice injected with lipopolysaccharide, suggesting that this IL-1beta is a secretory form produced by the SMG. The protein for IL-1beta-converting enzyme, a processing enzyme for pro-IL-1beta, was expressed only at a low level in the SMG as compared with its level in various epithelial tissues or lipopolysaccharide-stimulated macrophages. On the other hand, mK1, mK9, mK13, and mK22, members of the kallikrein family, were detected strongly in the SMG but not in other tissues. By incubation with mK13, but not with mK1, mK9, or mK22, the 35-kDa pro-IL-1beta was cleaved into two major products with molecular masses of 17.5 and 22 kDa, and production was inhibited by phenylmethylsulfonyl fluoride, a serine protease inhibitor, but not by IL-1beta-converting enzyme inhibitors. A peptide segment corresponding to amino acid residues 107-121 of mouse pro-IL-1beta (107WDDDDNLLVCDVPIR) was cleaved by incubation with mK13, generating two peptides, 107WDDDDNL and 114LVCDVPIR. Therefore, kallikrein mK13 would appear to hydrolyze pro-IL-1beta between its Leu113 and Leu114 residues. The results of immunohistochemistry and an autonomic therapy experiment showed that IL-1beta and kallikrein mK13 were co-localized in the secretory granules of granular convoluted tubular cells. Our present results thus suggest kallikrein mK13 is a plausible candidate for the processing enzyme for pro-IL-1beta in the SMG of mice.

Importance of MAPK pathways for microglial pro-inflammatory cytokine IL-1 beta production

In Alzheimer's disease (AD), chronically activated glia contribute to neuronal dysfunction through production of neuroinflammatory molecules like interleukin (IL)-1beta. As a first step to address the signaling pathways important for pro-inflammatory cytokine induction, and whether different activators use distinct pathways, we tested the involvement of mitogen-activated protein kinase (MAPK) pathways in microglial IL-1beta production. Microglial cultures stimulated with lipopolysaccharide, S100B, or beta-amyloid showed rapid activation of three different MAPKs (p38, ERK1/2, and JNK) and a later increase in IL-1beta levels, consistent with a possible mechanistic relationship between MAPK and IL-1beta. To more directly test this possibility, we stimulated microglia in the presence of selective MAPK inhibitors, and found that inhibition of each of the three MAPK pathways inhibited IL-1beta production in a concentration-dependent manner. In addition, the relative importance of each MAPK to IL-1beta production depended on the activating stimulus. These data demonstrate that MAPK pathways are important for microglial IL-1beta production, and suggest that different glial activators use distinct sets of signaling pathways to induce the same disease-relevant end-point in microglia.

Plasma membrane disruption in orthodontic tooth movement in rats

Sublethal plasma membrane disruption (PMD) is an established mechanism for signaling in several cell types, including endothelial cells and skeletal muscle. We used a rat model of orthodontic tooth movement to test the hypothesis that periodontal ligament (PDL) cells communicate stretch to changes in bone cell activity in part via PMD. To produce PMD, we used a 50-g load from a spring activated in the buccal direction against the maxillary first molars for 5 min. Uptake of endogenous serum albumin was used as a PMD marker. Immunohistochemistry demonstrates albumin in PDL cells surrounding moved first molar tips. Image analysis shows significantly more albumin in cells of the buccal side (tension) of the moved teeth compared with those of the lingual, distal, and mesial sides, and those of the unmoved control. Albumin localization within cells of the PDL, after only 5 min of mechanical loading, suggests that PMD could promote uptake or release of signaling molecules.

Inhibition of ATP-binding cassette transporter downregulates interleukin-1beta-mediated autocrine activation of human dermal fibroblasts

Fibroblasts constitute an important source of cytokines during inflammatory processes in the skin. Interleukin-1 is a potent, pleiotropic cytokine that is induced in activated human dermal fibroblasts. Interleukin-1 further induces many inflammatory mediators, including the chemokine interleukin-8. As fibroblasts express both interleukin-1 and the interleukin-1 receptor complex, the cellular response may be enhanced by autocrine activation. Interleukin-1alpha and interleukin-1beta lack a signal peptide and are translocated at the plasma membrane using an alternative secretory pathway, which may involve ATP-binding cassette transporter proteins. We hypothesize that inhibition of this pathway prevents secretion of interleukin-1, thereby downregulating interleukin-1-dependent autocrine induction of interleukin-8. We used the ATP-binding cassette 1 transporter inhibitor glybenclamide, which has been previously shown to block interleukin-1beta secretion in human monocytes. Using enzyme-linked immunosorbent assay, we assessed the effect of glybenclamide on interleukin-8 production in human dermal fibroblasts. In interleukin-1beta-transfected human dermal fibroblasts, interleukin-8 was induced through an autocrine activity of interleukin-1beta. Glybenclamide disabled this activation loop and significantly reduced interleukin-8. In human dermal fibroblasts that were stimulated with tumor necrosis factor alpha to reach high interleukin-1 expression levels, glybenclamide similarly suppressed interleukin-8. In contrast, glybenclamide did not affect interleukin-8 production in cells stimulated with interleukin-1 only. Glybenclamide did not affect caspase-1 in fibroblasts, which was expressed as an inactive precursor form, irrespective of treatments with tumor necrosis factor alpha and/or glybenclamide. Using overexpressing, interleukin-1-transfected COS-1 cells, inhibition of interleukin-1alpha and interleukin-1beta secretion was directly demonstrated on Western blots. These results are consistent with glybenclamide preventing externalization of interleukin-1 and subsequent autocrine induction of interleukin-8 in human dermal fibroblasts. Acting through such a mechanism, ATP-binding cassette transporter inhibitors may downregulate inflammation locally.

Intracellular IL-1 Receptor Antagonist Is Elevated in Human Dermal Fibroblasts That Overexpress Intracellular Precursor IL-1α

Cultured dermal fibroblasts from systemic sclerosis patients express higher levels of intracellular IL-1α than fibroblasts from healthy controls. In this study, we found that systemic sclerosis dermal fibroblasts also express higher levels of the intracellular isoform of IL-1 receptor antagonist (icIL-1Ra) than normal fibroblasts after stimulation with IL-1β or TNF-α. A possible relationship between elevated precursor IL-1α (preIL-1α) and elevated icIL-1Ra was investigated by transducing normal dermal fibroblasts to overexpress preIL-1α, preIL-1β, or icIL-1Ra. Fibroblasts that overexpressed icIL-1Ra did not have elevated levels of IL-1α. On the other hand, fibroblasts that overexpressed preIL-1α had at least 4-fold higher basal levels of icIL-1Ra than control fibroblasts and 4-fold higher levels of icIL-1Ra after induction with IL-1β or TNF-α. Fibroblasts overexpressing preIL-1β did not exhibit elevated icIL-1Ra. The differences in icIL-1Ra protein levels were reflected in differences in mRNA. In contrast, IL-1-stimulated levels of MCP-1 and IL-6 were not different in control and preIL-1α-transduced fibroblasts. Addition of neutralizing anti-IL-1α Abs to fibroblast cultures did not diminish basal or stimulated levels of icIL-1Ra in the preIL-1α-transduced cells, supporting an intracellular site of action of preIL-1α. This is the first report of an association between intracellular levels of these IL-1 family members. We hypothesize that intracellular preIL-1α participates in the regulation of icIL-1Ra.

Potent antitumor effects mediated by local expression of the mature form of the interferon-gamma inducing factor, interleukin-18 (IL-18)

IL-18 is produced during the acute immune response by macrophages and immature dendritic cells. IL-18 receptors are induced on T cells and NK cells by IL-12 and together they enhance a cellular immune response. We constructed retroviral and adenoviral vectors encoding the mature bioactive murine IL-18 in order to examine their immune and antitumor effects in murine tumor models. Secretion of bioactive IL-18 from murine tumor cells was facilitated by transfecting them with recombinant viral vectors carrying the prepro leader sequence of human parathyroid hormone fused to the 5' end of the mature murine IL-18 cDNA. Direct injection of the IL-18 recombinant adenoviral vector (Ad.PTH.IL-18) into an established MCA205 murine fibrosarcoma completely eradicated tumor in all animals with concomitant induction of protective systemic immunity. Co-administration of systemic IL-12 provided synergistic antitumor effects when combined with peritumoral injections of Ad.PTH.IL-18 without apparent side-effects as we observed with systemic administration of IL-18. Depletion of asialo GM-1+ cells completely abrogated the antitumor effects of Ad.PTH.IL-18, suggesting a major role for NK cells in mediating the anti-tumor effects of IL-18. Peritumoral injection of Ad.PTH.IL-18 was also associated with reduced numbers of CD8+ cells found within the tumor (HBSS versus Ad.PTH.IL-18, P < 0.0001). This suggests that IL-18 could be utilized as an alternative cancer gene therapy especially when combined with systemic administration of IL-12.

X-ray crystallography and mass spectroscopy reveal that the N-lobe of human transferrin expressed in Pichia pastoris is folded correctly but is glycosylated on serine-32

The ferric form of the N-lobe of human serum transferrin (Fe(III)-hTF/2N) has been expressed at high levels in Pichia pastoris. The Fe(III)-hTF/2N was crystallized in the space group P41212, and X-ray crystallography was used to solve the structure of the recombinant protein at 2.5 A resolution. This represents only the second P. pastoris-derived protein structure determined to date, and allows the comparison of the structures of recombinant Fe(III)-hTF/2N expressed in P. pastoris and mammalian cells with serum-derived transferrin. The polypeptide folding pattern is essentially identical in all of the three proteins. Mass spectroscopic analyses of P. pastoris- hTF/2N and proteolytically derived fragments revealed glycosylation of Ser-32 with a single hexose. This represents the first localization of an O-linked glycan in a P. pastoris-derived protein. Because of its distance from the iron-binding site, glycosylation of Ser-32 should not affect the iron-binding properties of hTF/2N expressed in P. pastoris, making this an excellent expression system for the production of hTF/2N.

Generation of Biologically Active IL-1β by Matrix Metalloproteinases: A Novel Caspase-1-Independent Pathway of IL-1β Processing

Biologic activity of IL-1β requires processing of the inactive precursor, a function generally ascribed to IL-1β-converting enzyme (caspase-1). However, alternative mechanisms of IL-1β activation have been postulated in local inflammatory reactions. Expression of IL-1β and matrix metalloproteinases (MMPs) frequently occurs simultaneously at sites of inflammation. We describe here that stromelysin-1 (MMP-3), as well as the gelatinases A (MMP-2) and B (MMP-9), processes recombinant human IL-1β precursor (pIL-1β) into biologically active forms. Detection of both pIL-1β processing and biologic IL-1β activity demonstrated different processing capacities of the respective MMPs. Conversion of pIL-1β by stromelysin-1 required coincubation for at least 1 h, and biologic activity faded after 8 h to 24 h. Gelatinase A was less effective in processing pIL-1β, requiring at least 24 h of coincubation. In contrast, gelatinase B processed pIL-1β within minutes, resulting in immunoreactive products as well as biologic activity stable for 72 h. In addition, prolonged incubation of mature IL-1β with stromelysin-1, and to a lesser extent also with gelatinases, but not with interstitial collagenase, resulted in the degradation of mature IL-1β. None of the MMPs processed the second isoform of IL-1, IL-1α. The present study indicates a biphasic regulation of IL-1β activity by MMPs: a caspase-1-independent pathway of IL-1β activation and inhibition of IL-1β activity by degrading the mature cytokine. The balance of the respective MMPs and pIL-1β might regulate the long term appearance of IL-1β activity at sites of acute or chronic inflammation.

An interleukin-1 loop is induced in human skin fibroblasts upon stress relaxation in a three-dimensional collagen gel but is not involved in the up-regulation of matrix metalloproteinase 1

The integrin-mediated stress relaxation as it occurs in a retracting three-dimensional collagen gel (RCG) is accompanied by a large up-regulation of the interstitial collagenase, matrix metalloproteinase 1 ((MMP-1), EC 3.4.24.7), regulated notably by interleukin-1 (IL-1), phorbol esters, and cytoskeleton-disrupting drugs as cytochalasin D (CD). The repression of MMP-1 up-regulation in RCG by cycloheximide suggested the participation in the regulation process of a de novo synthesized intermediary component. We demonstrate here that culture of human skin fibroblasts in RCG or in CD- and 12-O-tetradecanoylphorbol-13-acetate (TPA)-treated monolayers resulted in the activation of an IL-1 autocrine feedback loop that was switched off by the naturally occurring IL-1 receptor antagonist (IL-1RA), a blocker of the common IL-1 receptor. The IL-1RA did not suppress the MMP-1 up-regulation induced in RCG nor in CD-treated cells, indicating that the up-regulation of MMP-1 and the IL-1 autocrine loop occurred in an independent way, while the TPA-induced MMP-1 expression was suppressed by the receptor antagonist. The RCG- as well as the TPA-, IL-1-, and CD-induced up-regulation of both MMP-1 and IL-1 was totally suppressed by protein tyrosine kinases inhibitors. In contrast bisindoylmaleimide, at a concentration (5 microM) that inhibits the TPA-induced protein kinase C activity, suppressed the CD-induced MMP-1 expression but did not or barely altered that induced in RCG or by IL-1. None of the other tested inhibitors of a variety of signaling pathways including those used by integrins was able to suppress the RCG or CD-induced MMP-1. These results point to a potent regulation of MMP-1 by mechanical stress relaxation, a process depending on de novo protein synthesis and occurring independently of the activation of an IL-1 autocrine feedback loop.

Expression, distribution, and activity of Na+,K+-ATPase in normal and cholestatic rat liver

Hepatocellular Na+,K+-ATPase is an important driving force for bile secretion and has been localized to the basolateral plasma membrane domain. Cholestasis or impaired bile flow is known to modulate the expression, domain specificity, and activity of various transport systems involved in bile secretion. This study examined Na+, K+-ATPase after ethinylestradiol (EE) treatment and after bile duct ligation (BDL), two rat models of cholestasis. It applied quantitative immunoblotting, biochemical and cytochemical determination of enzyme activity, and immunocytochemistry to the same livers. The data showed a good correlation among the results of the different methods. Neither EE nor BDL induced alterations in the subcellular distribution of Na+,K+-ATPase, which was found in the basolateral but not in the canalicular (apical) plasma membrane domain. Protein expression and enzyme activity showed a small (approximately 10%) decrease after EE treatment and a similar increase after BDL. These modest changes could not be detected by immunofluorescence, immuno EM, or cytochemistry. The data, therefore, demonstrate that Na+,K+-ATPase is only slightly affected by EE and BDL. They suggest that other components of the bile secretory apparatus that take effect downstream of the primary basolateral driving force may play a more prominent role in the pathogenesis of cholestasis.

Characterization of mice deficient in interleukin-1 beta converting enzyme

Interleukin-1 beta converting enzyme (ICE) processes the inactive prolL-1 beta to the proinflammatory mature IL-1 beta. ICE belongs to a family of cysteine proteases that have been implicated in apoptosis. To address the biological functions of ICE, we generated ICE-deficient mice through gene targeting technology. ICE-deficient mice developed normally, appeared healthy, and were fertile. Peritoneal macrophages from ICE-deficient mice underwent apoptosis normally upon ATP treatment. Thymocytes from young ICE-deficient mice also underwent apoptosis when triggered by dexamethasone, gamma irradiation, or aging. ICE-deficient mice had a major defect in the production of mature IL-1 beta and had impaired IL-1 alpha production on LPS stimulation in vitro and in vivo. ICE-deficient mice were resistant to LPS-induced endotoxic shock.

Structure and function of interleukin-1 beta converting enzyme

An overwhelming body of evidence has shown that IL-1 beta is a major mediator of inflammatory disease (Tocci and Schmidt, 1996). The discovery of ICE, a unique processing enzyme involved in the production of active IL-1 beta, has provided a new approach to specifically block the production of this potent cytokine. Consequently, the discovery and development of inhibitors against the enzyme could hold great promise therapeutically. Potent inhibitors of the enzyme would be useful in the treatment of a number of important inflammatory diseases and potentially in the management of leukemia (Arend, 1993b; Estrov and Talpaz, 1996). A number of key questions must be answered before the therapeutic potential of such inhibitors can be realized. The development of a pharmaceutically acceptable cysteine proteinase inhibitor will almost certainly involve new chemical strategies gauged at safely inactivating the enzyme. For such inhibitors, it will be necessary to achieve selectivity for ICE from among the growing number of ICE family members while retaining potency. It will also be important to establish the level of inhibition of IL-1 beta required to achieve therapeutic efficacy. The studies comparing IL-1 beta- and ICE-deficient mice suggest that complete abrogation of IL-1 beta is required to achieve efficacy in models of inflammation. It is not known if this is the case in humans. Understanding the source of the residual IL-1 beta produced in ICE-deficient mice will be important in order to ascertain if a similar mechanism could generate active IL-1 beta in patients receiving if a ICE inhibitor. As for ICE itself, a number of formidable questions remain regarding its regulation and mechanism of activation. Answering these questions experimentally will present a major challenge due to the extremely low levels of enzyme present in cells. Studies on other family members may provide easier access to some of these questions and provide clues that can be applied to ICE. The components of the pathway involved in IL-1 trafficking and secretion are unknown, as are the mechanisms of ICE activation and regulation. Clearly other cellular proteins that have yet to be discovered will be involved in each of these processes, opening up new avenues of research in this field.

Factors affecting IL-1-mediated collagen metabolism by fibroblasts and the pathogenesis of periodontal disease: a review of the literature

Fibroblasts have been studied extensively for their contribution to connective tissue destruction in diseases where the metabolism of extracellular matrix components plays an essential part in their pathogenesis. A considerable dissolution, especially of collagen fibrils, is a well-known characteristic of the periodontal ligament and the gingival connective tissue in microbial-induced periodontal disease. Fibroblasts, responsible for the assembly of the extracellular matrix, are capable of responding directly to oral microbial challenges or indirectly, following activation of the host immune response, and can alter the composition of connective tissue in several ways: synthesis of inflammatory mediators, their receptors and antagonists; fibroblast proliferation; collagen synthesis; phagocytosis of collagen fibrils; and synthesis of proteolytic enzymes, including matrix metalloproteinases and their corresponding inhibitors. The contributions of these cellular fibroblastic properties to the pathogenesis of periodontal disease are reviewed in the context of the cytokine, interleukin-1, as the inflammatory regulator.

Tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-1 receptor antagonist in dialysate and serum from patients on continuous ambulatory peritoneal dialysis

Dialysate and serum levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and IL-1-ra were investigated in 20 patients on continuous ambulatory peritoneal dialysis (CAPD), who altogether had 30 episodes of peritonitis. Bacterial growth was found in 25 (83%) of the dialysate samples. Staphylococcus epidermidis was the single most common microorganism, found in 44% of the culture-verified peritonitis. Samples from dialysate bags were obtained during the first month of dialysis and during peritonitis from the first three bags on day 1 (the day of admittance) and from night bags on days 3 and 10. Serum samples were drawn on days 1 and 10. The peak concentrations of cytokines occurred on the first day of infection. In dialysates, TNF-alpha was elevated in 96% of the patients, with a peak median concentration of 160 pg/mL (range, <15 to 4,400 pg/mL). Seventy-five percent of the dialysates had elevated IL-1-beta, with the highest median level of 52 pg/mL (range, <10 to 940 pg/mL), whereas all patients had elevated IL-1 ra, with a peak median value of 10,300 pg/mL (range, 470 to 79,000 pg/mL). TNF-alpha, IL-1 beta, and IL-Ira were significantly higher than in corresponding noninfected samples (TNF-alpha median value, <15 pg/mL; IL-1 beta, <10 pg/mL; and IL-1-ra, 150 pg/mL; P < 0.0001, P < 0.002, and P < 0.001, respectively). In serum, elevated TNF-alpha levels were found in 92% of the episodes, but the median levels were less than one third of the corresponding lavage levels. IL-1-beta was detected in 8% of the episodes and, although IL-1-ra was found in 92% of the patients, the dialysate levels were more than 15 times higher. In dialysate, a correlation was observed for TNF-alpha and IL-Ira and also between IL-1-beta and IL-Ira. IL-1 beta and IL-1-ra also correlated with the previously analyzed IL-6, and IL-1-beta correlated with the previously analyzed IL-8. Patients infected with high virulent strains had higher cytokine levels as compared with those infected with low virulent strains. In conclusion, our study shows markedly elevated TNF-alpha, IL-1 beta, and IL-1-ra levels in the acute stage in CAPD patients with peritonitis.

Mechanisms of cytokine production by fibroblasts-implications for normal connective tissue homeostasis and pathological conditions

Fibroblasts actively participate in cellular immune responses in connective tissues, when activated by signals abundant at inflammatory sites, i.e. cytokines and bacterial products. This is manifested by the generation of proinflammatory cytokines and by presenting antigens to proliferating T cells. The array of cytokines generated by immune-activated fibroblasts is determined by the stimulant and is controlled at multiple regulatory levels, such as transcription, translation, posttranslational modifications, the signal transduction pathways which are activated, the timing of expression as well as compartmentation within the producing cell. In general, cytokines with potential of tissue damage, i.e. IL-1 alpha and, to a lesser extent, IL-6, are more tightly regulated than cytokines with restricted target cell specificity (i.e. CSFs). Deviations in the pattern of expression of IL-1 alpha in pathological conditions affecting connective tissues are described; a long-lasting suppression of IL-1 alpha production was observed in dermal fibroblasts of mice suffering from chronic graft-vs.-host disease (cGVHD), while some oncogene-transformed fibroblastoid cell lines were shown to generate this cytokine in a constitutive manner and as a result expressed reduced tumorigenicity. The latter is due to the adjuvant effects of IL-1 alpha, expressed by the malignant cells, which induce potent antitumor specific immune responses which ultimately lead to its eradication. Understanding the molecular mechanisms which control cytokine production in fibroblasts may enrich our knowledge of connective tissue homeostasis and deviations from it in pathological states. The latter may also lead to the development of novel therapeutical means for controlling chronic inflammatory diseases or malignancies.

Reduction of inflammation and pyrexia in the rat by oral administration of SDZ 224-015, an inhibitor of the interleukin-1 beta converting enzyme

1. The aim of this study was to determine whether a synthetic inhibitor of the interleukin-1 beta converting enzyme (ICE) displays oral activity in models of inflammation. 2. To this end, the ICE inhibitor, SDZ 224-015, was examined in rat paw oedema, pyrexia and nociception tests. 3. SDZ 224-015 (0.3-300 micrograms kg-1) potently reduced carrageenin-induced paw oedema, with an oral ED50 of approximately 25 micrograms kg-1. This effect was independent of endogenous glucocorticoid, as shown by retention of activity upon adrenalectomy. 4. Pyrexia induced by lipopolysaccharide (0.1 mg kg-1 s.c.) or by interleukin-1 beta (100 ng i.v.) was also reduced, over a similar dose-range to oedema (oral ED50s 11 micrograms kg-1 and 4 micrograms kg-1 respectively). 5. SDZ 224-015 (0.2-5 mg kg-1, p.o.) displayed analgesic activity in the Randall-Selitto yeast-inflamed paw pressure test, significant at a dose of 1 mg kg-1, p.o. 6. Thus, SDZ 224-015 has potent oral activity in several acute models for inflammation, suggesting that ICE inhibitors may constitute a novel type of anti-inflammatory agent.

Nodular scleroderma: focally increased tenascin expression differing from that in the surrounding scleroderma skin

Nodular scleroderma is a rare variant of the disease, whose pathogenesis is uncertain. Tenascin is a recently cloned extracellular matrix protein which is thought to be a marker for tissue remodelling. To further investigate the pathogenesis of nodular scleroderma, we have followed up a case of this disease and studied tenascin expression in the nodular lesions and surrounding progressive systemic sclerosis skin. Previously, we demonstrated a long-lasting intermediate level of dermal tenascin expression in progressive systemic sclerosis; morphea and hypertrophic scar lesions showed strong but short-lived tenascin expression. In our current patient, high levels of tenascin were found in the nodules, which rapidly resolved. Thus, the time course of the clinical and histopathological findings together with the tenascin expression were more suggestive of hypertrophic scar than progressive systemic sclerosis. These findings imply that nodular scleroderma has a supplementary pathogenesis, such as itching, in addition to the proceeding systemic sclerosis.

Construction and expression in tumor cells of a recombinant vaccinia virus encoding human interleukin-1 beta

BACKGROUND

Human interleukin-1 beta (hIL-1 beta) injected intratumorally has demonstrated growth inhibition of transplanted subcutaneous tumors in mice, regression of metastatic lesions, resistance to tumor rechallenge, and increased survival. Vaccinia virus (VV) can be genetically engineered to produce cytokines and may be an effective vector for gene therapy of cancer. This study was designed to (a) construct a VV expressing hIL-1 beta, (b) assess tumor cell infection in vitro with this construct, (c) measure hIL-1 beta production, and (d) assess the bioactivity of the secreted cytokine.

METHODS

The hIL-1 beta gene was amplified from a plasmid clone using polymerase chain reaction (PCR) and then cloned into a homologous recombination (HR) and expression vector, which was used to insert the hIL-1 beta gene into the VV genome. Selection of the recombinant VV (vMJ601hIL-1 beta) was based on inactivation of viral TK and expression of beta-galactosidase. vMJ601hIL-1 beta infectivity and cytokine production was assessed by infecting tumor cell lines and analyzing culture supernatants for hIL-1 beta. Bioactivity of the hIL-1 beta produced was demonstrated using an IL-1 dependent T helper cell line.

RESULTS

The hIL-1 beta gene was successfully cloned into the VV genome by HR, which was confirmed by PCR. vMJ601hIL-1 beta efficiently infected tumor cells, as shown by increased hIL-1 beta secretion (0 to > 500 ng/ml) and morphologic evidence of viral cytopathic effect. vMJ601hIL-1 beta-infected cells secreted large amounts of hIL-1 beta (mean 772 ng/10(6) cells/24 h). The secreted hIL-1 beta was bioactive (mean bioactivity 6.8 x 10(8) U/mg of hIL-1 beta).

CONCLUSIONS

(a) hIL-1 beta can be cloned into VV, (b) vMJ601hIL-1 beta retains its infectivity, (c) a large amount of hIL-1 beta is secreted, and (d) the secreted hIL-1 beta is bioactive. Recombinant VV may allow in situ cytokine gene delivery and expression in established tumors.

Mice deficient in IL-1 beta-converting enzyme are defective in production of mature IL-1 beta and resistant to endotoxic shock

IL-1 beta-converting enzyme (ICE) cleaves pro-IL-1 beta to generate mature IL-1 beta. ICE is homologous to other proteins that have been implicated in apoptosis, including CED-3 and Nedd-2/lch-1. We generated ICE-deficient mice and observed that they are overtly normal but have a major defect in the production of mature IL-1 beta after stimulation with lipopolysaccharide. IL-1 alpha production is also impaired. ICE-deficient mice are resistant to endotoxic shock. Thymocytes and macrophages from the ICE-deficient animals undergo apoptosis normally. ICE therefore plays a dominant role in the generation of mature IL-1 beta, a previously unsuspected role in production of IL-1 alpha, but has no autonomous function in apoptosis.

Polarity and nucleation of microtubules in polarized epithelial cells

Microtubules oriented in the apicobasal axis of columnar epithelial cells are arranged with a uniform polarity with minus ends toward the apical surface, suggesting that these cytoskeletal filaments might serve as a substrate for polarized movement of membrane vesicles within the cell. It is not known whether hepatocytes, a cuboidal epithelium in which transcellular transport is a requisite step in normal apical membrane biogenesis, contain microtubules arranged with a similar polarity. In the present study, we explore the question of microtubule polarity and possible mechanisms for nucleation in the epithelial cell lines WIF-B (hepatocyte), Caco-2 (intestine), and Madin-Darby canine kidney (MDCK). Caco-2 microtubules in the apicobasal axis had uniform polarity with minus ends nearest the apical surface. After cold and nocodazole-induced depolymerization, microtubule regrowth initiated in the apical region in all three cell types. The apex of WIF-B and Caco-2 cells contained two pools of gamma-tubulin: one associated with centrosomes and the other delocalized under the apical membrane. Non-centrosomal gamma-tubulin was present in complexes that sedimented between 10S and 29S; both forms could bind microtubules. The presence of both centrosomal and noncentrosomal gamma-tubulin in apical cytoplasm suggest multiple mechanisms by which microtubule nucleation might occur in epithelial cells.

Crystal structure of the cysteine protease interleukin-1 beta-converting enzyme: a (p20/p10)2 homodimer

Interleukin-1 beta-converting enzyme (ICE) proteolytically cleaves pro-IL-1 beta to its mature, active form. The crystal structure at 2.5 A resolution of a recombinant human ICE-tetrapeptide chloromethylketone complex reveals that the holoenzyme is a homodimer of catalytic domains, each of which contains a p20 and a p10 subunit. The spatial separation of the C-terminus of p20 and the N-terminus of p10 in each domain suggests two alternative pathways of assembly and activation in vivo. ICE is homologous to the C. elegans cell death gene product, CED-3, and these may represent a novel class of cytoplasmic cysteine proteases that are important in programmed cell death (apoptosis). Conservation among members of the ICE/CED-3 family of the amino acids that form the active site region of ICE supports the hypothesis that they share functional similarities.

Endogenous interleukin 1 alpha must be transported to the nucleus to exert its activity in human endothelial cells

We have previously shown that the signal peptideless cytokine interleukin 1 alpha (IL-1 alpha) may play a role as an intracellular regulator of human endothelial cell senescence (J. A. M. Maier, P. Voulalas, D. Roeder, and T. Maciag, Science 249:1570-1574, 1990). To investigate the potential intracellular function of IL-1 alpha, transformed endothelial cells were transfected with the human cDNAs that code for the two forms of IL-1 alpha, the precursor molecule IL-1(1-271) and the mature protein IL-1(113-271). The subcellular localization of the two different polypeptides was investigated directly or by using chimeric genes constructed by fusion of different fragments of the IL-1 alpha gene and the beta-galactosidase open reading frames. The IL-1(113-271) protein was cytoplasmic, while IL-1(1-271) was nuclear. The basic cluster at the NH2 terminus of IL-1, KVLKKRR, has been shown to mediate IL-1 alpha nuclear targeting. Moreover, nuclear localization of IL-1 alpha correlates with impaired cell growth and expression of some IL-1 alpha-inducible genes. These results suggest that transport of endogenous IL-1(1-271) into the nucleus is required for it to modulate endothelial cell function.

Endogenous interleukin 1 alpha must be transported to the nucleus to exert its activity in human endothelial cells

We have previously shown that the signal peptideless cytokine interleukin 1 alpha (IL-1 alpha) may play a role as an intracellular regulator of human endothelial cell senescence (J. A. M. Maier, P. Voulalas, D. Roeder, and T. Maciag, Science 249:1570-1574, 1990). To investigate the potential intracellular function of IL-1 alpha, transformed endothelial cells were transfected with the human cDNAs that code for the two forms of IL-1 alpha, the precursor molecule IL-1(1-271) and the mature protein IL-1(113-271). The subcellular localization of the two different polypeptides was investigated directly or by using chimeric genes constructed by fusion of different fragments of the IL-1 alpha gene and the beta-galactosidase open reading frames. The IL-1(113-271) protein was cytoplasmic, while IL-1(1-271) was nuclear. The basic cluster at the NH2 terminus of IL-1, KVLKKRR, has been shown to mediate IL-1 alpha nuclear targeting. Moreover, nuclear localization of IL-1 alpha correlates with impaired cell growth and expression of some IL-1 alpha-inducible genes. These results suggest that transport of endogenous IL-1(1-271) into the nucleus is required for it to modulate endothelial cell function.

Biosynthesis and intracellular transport of a bile canalicular plasma membrane protein: studies in vivo and in the perfused rat liver

B10 is an integral glycoprotein of the plasma membrane that is exclusively localized to the canalicular (apical) domain in normal rat hepatocytes but may be expressed on the basolateral (sinusoidal and lateral) membrane in pathophysiological situations. To understand how B10 may be localized to the basolateral surface, we studied the biosynthesis and transport of this apical protein. In vivo pulse-chase experiments, followed by subcellular fractionation of the liver and immunoprecipitation, showed that B10 is first synthesized as a high-mannose form of 123 kD and then matured to a complex glycosylated form of 130 kD, which peaks in the Golgi apparatus after 15 min of chase and reaches the plasma membrane with a half-time of 30 to 45 min. Analysis of the protein in plasma membrane domain fractions showed that most of the newly synthesized molecule was localized in basolateral fractions after 30 min of chase and subsequently appeared in apical fractions. After 90 min of chase, most of the radiolabeled protein had reached its steady-state apical distribution. The same experiments performed in the perfused rat liver, in which the chase can be improved, gave similar results, except that the apical distribution of the radioactive molecule was attained more quickly. Thus B10, like all apical plasma membrane proteins studied so far in hepatocytes, is first transported to the basolateral surface and then reaches the membrane of the bile canaliculi. Alterations of the transcytotic step from the basolateral to the apical surfaces may result in abnormal basolateral localization.

Pyridinyl imidazoles inhibit IL-1 and TNF production at the protein level

The mechanism by which SK&F 86002 and other pyridinyl imidazoles inhibit the production of IL-1 and TNF from LPS-stimulated human monocytes was examined. Inhibition of IL-1 and TNF production was found to depend on the time of addition of SK&F 86002, with diminishing effect when added more than 2 h after LPS stimulation. Analysis of Western blots confirmed that both intracellular IL-1 beta and extracellular TNF were significantly reduced in response to SK&F 86002, but these reductions were not paralleled by changes in IL-1 and TNF mRNA. 35S methionine pulse and pulse-chase studies on IL-1 biosynthesis suggest that significant inhibition by SK&F 86002 and related compounds occurs at the translational level.

Development and application of a radioimmunoassay to detect interleukin-1 in rat peripheral circulation

We describe the development and application of a radioimmunoassay to detect circulating interleukin (IL)-1 beta concentrations in the rat. No IL-1 immunoreactivity above the detection limit of the assay (100 pg/ml) could be detected in plasma of control rats. In contrast, immunoreactive IL-1 was detected after intravenous administration of rat recombinant IL-1 beta (rrIL-1 beta) or bacterial lipopolysaccharide (LPS) to rats. The effect of LPS on plasma immunoreactive IL-1 concentrations was time and dose dependent. The immunoreactive IL-1 response to LPS was prevented by in vivo macrophage depletion induced by liposome-directed macrophage suicide technique. Gel filtration of plasma from LPS-treated rats revealed the presence of a high and a smaller molecular form of immunoreactive IL-1. The small molecular immunoreactive IL-1 peak coeluted with rrIL-1 beta and probably represents the 17-kDa form of IL-1 beta. In conclusion, our data support the hypothesis that IL-1 secreted by macrophages can act as a humoral signal molecule to induce the immunological, metabolic, and neuroendocrine changes in response to bacterial LPS.

Transthyretin is an inhibitor of monocyte and endothelial cell interleukin-1 production

Human serum was found to contain an inhibitor of constitutive interleukin-1 (IL-1) production by human umbilical vein endothelial cells (ECs). Purification of the serum activity by anion exchange chromatography, molecular sieve HPLC, and hydroxyl apatite chromatography yielded material 82% pure with a molecular weight of 17 kDa by SDS-PAGE. Amino acid sequencing revealed the purified inhibitor to be transthyretin (TTR), a liver-derived protein. There was a 42.6% reduction in the production of spontaneous IL-1 activity in EC supernatants after coculture with 10 micrograms/ml TTR. TTR was subsequently found by ELISA to inhibit LPS-stimulated IL-1 production by cells of the human monocytic leukemia line THP-1 by 47.1 +/- 9.4%, whereas a less striking but still significant inhibition of monocyte-derived IL-1 beta production was also observed. Inhibition of IL-1 secretion correlated with increased IL-1 mRNA synthesis in both THP-1 cells and monocytes. Furthermore, TTR was associated with increased intracellular concentrations of IL-1 beta. These data suggest that TTR functions by inhibiting processing of newly synthesized peptide for secretion. This novel inhibitory effect of TTR on the production of IL-1 activity suggests a previously unrecognized endogenous antiinflammatory mediator.

Expression of interleukin-1 alpha, interleukin-1 beta, and an interleukin-1 receptor antagonist in human retinal pigment epithelial cells

mRNA expression and protein production of interleukin-1 alpha, interleukin-1 beta and intracellular and secreted forms of an interleukin-1 receptor antagonist were measured in visually confluent monolayers of unstimulated cultured human retinal pigment epithelial cells and after cells were stimulated with recombinant cytokines. Using reverse transcription polymerase chain reaction, transcripts for interleukin-1 alpha and interleukin-1 beta were not detected in unstimulated cells from any of six donors whereas mRNA expression for both interleukin-1 alpha and interleukin-1 beta was readily induced in all six cell lines after cells were stimulated with recombinant IL-1 (alpha or beta), tumor necrosis factor alpha, or lipopolysaccharide. The combination of cycloheximide and recombinant interleukin-1 caused a 14-fold enhancement of interleukin-1 alpha and interleukin-1 beta mRNA expression above that observed after cells were stimulated with interleukin-1 alone. After stimulation by interleukin-1, cells produced intracellular interleukin-1 alpha protein, but did not secrete it into medium. In contrast, interleukin-1 beta protein was not detected in cell lysates or conditioned-medium after stimulation with interleukin-1. An intracellular interleukin-1 receptor antagonist was expressed constitutively by human retinal pigment epithelial cells; mRNA transcripts were enhanced in a dose and time dependent manner after cells were exposed to recombinant interleukin-1 or tumor necrosis factor alpha. In contrast, mRNA for a secreted form of the interleukin-1 receptor antagonist was not detected under basal conditions or after cells were stimulated by recombinant cytokines. Interleukin-1 receptor antagonist protein was found primarily in cell lysates; little interleukin-1 receptor antagonist protein was secreted by the cells. The presence of cell-associated interleukin-1 receptor antagonist was confirmed by immunocytochemistry. Levels of cell-associated IL-1 receptor antagonist protein were not significantly influenced by recombinant interleukin-1 or tumor necrosis factor alpha. Endogenous expression of interleukin-1 receptor antagonist may attenuate the effect of exogenous or endogenous interleukin-1, thus providing the RPE cell a means of maintaining interleukin-1 homeostasis in ocular inflammatory disease.

Interleukin-1 alpha-stimulated fibroblast eicosanoid synthesis is not mediated by interleukin-6

Adherent human dermal fibroblasts secreted interleukin-6, prostaglandin E2, prostaglandin I2 and 15-hydroxyeicosatetraenoic acid (assayed by radioimmunoassay) during a 3 h incubation period. Although human dermal fibroblasts did not secrete interleukin-1 alpha or interleukin-1 beta, human recombinant interleukin-1 alpha stimulated arachidonic acid metabolism and interleukin-6 synthesis. This effect was, at least partly, dependent on de novo protein synthesis. In contrast, human recombinant interleukin-6 had no effect on the synthesis and release of the eicosanoids measured. Human recombinant interleukin-1 alpha also stimulated the metabolism of [14C]arachidonic acid, but only if fibroblast were pre-incubated with the cytokine for three hours. Our data indicate that (a) fibroblasts secrete interleukin-6 but not interleukin-1, (b) interleukin-1 alpha, but not interleukin-6, stimulates fibroblast arachidonic acid metabolism and (c) the mechanisms involved in the metabolism of endogenous arachidonic acid are more sensitive to human recombinant interleukin-1 alpha than those involved in metabolism of the exogenous substrate.

Processing of interleukin-1 in cells of monocytic lineage is differentiation-dependent

The interleukin-1 (IL-1) alpha and beta precursor proteins are processed and released from several cell types in the absence of a canonical signal peptide. To gain some insight into the mechanisms that allow the production of IL-1 alpha and beta, we have investigated by immunoprecipitation the synthesis, their release and processing in a promyeloblastic cell line of tumoral origin, U937, and in peripheral blood monocytes. We show that U937 monocytic cells, on induction with a tumor-promoting agent, synthesize and release into the culture medium proIL-1 beta but do not process it. Similarly, peripheral blood monocytes left in adherence for 24 h or longer, prior to addition of lipopolysaccharide, synthesize and release proIL-1 alpha and beta without detectable processing of either cytokine. Processing and release of IL-1 alpha and beta by peripheral blood monocytes can be observed when monocytes are left to adhere for periods less than 15 h before lipopolysaccharide addition. IL-1 alpha and beta show similar kinetics of release from the cells, suggesting the existence of a common mechanism regulating their secretion. Since peripheral blood monocytes left in adherence in the presence of lipopolysaccharide differentiate into macrophages, we conclude that release and processing of IL-1 can occur independently and that processing depends on the stage of differentiation of monocytes, i.e. only the monocytes at an early stage of differentiation produce 17-kDa IL-1 alpha and beta.

Articular chondrocytes secrete IL-1, express membrane IL-1, and have IL-1 inhibitory activity

Previous work from our laboratory has shown that rabbit articular chondrocytes, like macrophages, produce reactive oxygen intermediates, express Ia antigen, and can mediate immunologic functions such as antigen presentation and induction of mixed and autologous lymphocyte reactions. We were interested in seeing if these cells could secrete interleukin-1 (IL-1) or express membrane form of IL-1 (mIL-1). Using the standard C3H/HeJ thymocyte assay, neither secreted IL-1 nor mIL-1 activity was detected in untreated or LPS-treated chondrocytes. However, the D10.G4.1 proliferation assay showed that chondrocytes, stimulated with LPS, secrete IL-1 and express the mIL-1 in a dose- and time-dependent manner. The IL-1 activity in LPS-stimulated chondrocyte supernatant and on fixed cells could be inhibited by anti-IL-1 antibodies. Sephadex G-75 chromatography of pooled, concentrated LPS culture supernatant resolved into two peaks of IL-1 activity at 13-17 and at 45-70 kDa, respectively. The bioactivity of chromatographic fractions were similar using both the thymocyte and D10.G4.1 bioassays. Western blot analysis of chondrocyte supernatant detects 17-kDa IL-1 beta; no processed 17-kDa IL-1 alpha was seen but IL-1 alpha-specific reactivity was observed at 64 kDa. Immunoblot analysis of chondrocyte lysates shows that cell-associated IL-1 is IL-1 alpha and is 37 kDa in size. PCR analysis shows the presence of mRNA for IL-1 beta and IL-1 alpha in LPS-treated cells; IL-1 beta mRNA was detected in untreated chondrocytes. The inability to detect IL-1 by the thymocyte assay is due to the presence of a chondrocyte inhibitor of IL-1 that can be demonstrated in cell sonicates, supernatants, and on paraformaldehyde-fixed chondrocytes. Chromatography of LPS-stimulated supernatant showed a peak of IL-1 inhibitory activity at 21-45 kDa. Chondrocytes which secrete IL-1 and express mIL-1 could play a critical role in maintaining chronic inflammation in rheumatoid arthritis. Therefore, the ability of chondrocytes to produce both IL-1 and an inhibitor to IL-1 is important in interpreting the mechanism of cartilage matrix maintenance and degradation.

High-level secretion of correctly processed recombinant human interleukin-1 beta in Kluyveromyces lactis

The lactose-assimilating yeast, Kluyveromyces lactis, has been developed as a microbial host for the synthesis and secretion of human proteins. Here, we report the use of multi-copy vectors based on the 2 mu-like plasmid pKD1 from Kluyveromyces drosophilarum [Chen et al., Nucleic Acids Res. 14 (1986) 4471-4481] for the secretion of recombinant human interleukin-1 beta (reIL-1 beta). High levels of reIL-1 beta were secreted into the growth medium when the structural gene was fused in-frame to a synthetic secretion signal derived from the 'pre'-region of the K. lactis killer toxin. N-terminal sequencing of the excreted protein showed highly efficient (greater than 95%) maturation of the signal sequence. Synthesis as prepro-IL-1 beta, the 'pro'-sequence being derived from the human serum albumin-encoding gene, resulted in equally efficient secretion of mature IL-1 beta. Cytoplasmic production of Met-IL-1 beta, without a secretion signal, was found to be toxic to K. lactis. As in Saccharomyces cerevisiae [Baldari et al., EMBO J. 6 (1987) 229-234], but unlike native human IL-1 beta, K. lactis reIL-1 beta is glycosylated. This glycosylation led to a 95% loss of its biological activity. Removal of the carbohydrate chains by endo-beta-N-acetyl-glucosamidase H treatment fully restored the biological activity. A modified form of IL-1 beta (Asn7----Gln7), in which the unique site for Asn-linked glycosylation was deleted, exhibited the same biological activity as native IL-1 beta. The level of secretion of mature recombinant IL-1 beta ws glycosylation-independent.

Involvement of central beta-adrenoceptors in the induction of hypothalamic interleukin-1 beta mRNA by methamphetamine

Methamphetamine (2-15 mg/kg, i.p.) has been shown to induce interleukin-1 beta (IL-1 beta) mRNA in the rat hypothalamus. The induction of IL-1 beta mRNA was blocked by intraperitoneal pretreatment with beta-blockers propranolol (0.1-1 mg/kg, but not 0.01 mg/kg) and pindolol (0.3 and 1 mg/kg). Prazosin (1 and 5 mg/kg) and yohimbine (1 and 5 mg/kg), alpha-blockers and haloperidol (1 mg/kg), a dopamine antagonist, produced partial and little suppression, respectively. When injected intracerebroventricularly (i.c.v.), propranolol, but neither prazosin nor yohimbine, significantly suppressed the methamphetamine-induced expression of IL-1 beta mRNA at a dose of 1 nmol/rat. An i.c.v. injection of the beta-adrenoceptor agonist isoproterenol (1 and 3 micrograms/rat) dose-dependently increased the hypothalamic level of IL-1 beta mRNA. The present results suggest that the induction of hypothalamic IL-1 beta mRNA by methamphetamine is mediated by beta-adrenoceptors in the brain.

Induction of interleukin-1 beta production in human dermal fibroblasts by interleukin-1 alpha and tumor necrosis factor-alpha. Involvement of protein kinase-dependent and adenylate cyclase-dependent regulatory pathways

It has previously been demonstrated that interleukin-1 (IL-1) is expressed in a variety of fibroblast cell lines. In this study, we investigated the mechanisms involved in the regulation of IL-1 beta production by cultured human dermal fibroblasts. We have shown that IL-1 beta is constitutively expressed as a cell-associated form, with no soluble form detectable in control cell or in stimulated cell supernatants. IL-1 alpha and tumor necrosis factor-alpha (TNF-alpha) exerted a dose-dependent stimulation on the production of the cell-associated IL-1 beta, as estimated using a specific enzyme linked immunosorbent assay (ELISA). As expected, this effect was accompanied by a huge release of prostaglandin E2 (PGE2) and a transient rise in intracellular cyclic AMP. Furthermore, IL-1 beta production was elevated to a lesser extent by the addition of increasing concentrations of the protein kinase C activator phorbol myristate acetate or by low concentration (0.001 microgram/ml) of PGE2. In contrast, higher concentrations (0.1 and 1 micrograms/ml) of PGE2, as well as exogenous dibutyryl-cyclic AMP, were clearly inhibitory. H7, an inhibitor of protein kinases also reduced the stimulatory effect of IL-1 alpha and TNF-alpha. Together with the results obtained with phorbol myristate acetate, these data suggest that protein kinase C may play a role in the upregulation of IL-1 beta expression in normal skin fibroblasts. The addition of indomethacin not only suppressed prostaglandin synthesis, but also dramatically reduced cyclic AMP formation, probably because the PGE2-induced stimulation of adenylate cyclase was abolished. This resulted in a strong potentiation of the stimulatory effect of IL-1 alpha and TNF-alpha, supporting the role of both the cyclooxygenase and adenylate cyclase pathways in the endogenous downregulation of IL-1 beta induction by the two cytokines studied.

Interleukin 1 is processed and released during apoptosis

Interleukin (IL-) 1 alpha and 1 beta are synthesized as 31- to 34-kDa pro molecules. They are released from monocytes and macrophages as proteolytically processed 17-kDa mature molecules that bind with high affinity to specific receptors on target cells. IL-1 is not released via the classic secretory pathway. The pro molecules are synthesized as cytosolic proteins without signal peptides. Although the proteases that convert the pro molecules to the mature forms are cytosolic enzymes, processed IL-1 is not detected associated with the cell but is found only in culture supernatants. We demonstrate here that release of IL-1 is efficiently induced by cell injury. When the injury causes cellular necrosis, IL-1 alpha is released as a mixture of unprocessed and processed molecules but IL-1 beta is released exclusively as the biologically inactive pro form. In contrast, when cells undergo apoptosis, maturation of both IL-1 alpha and IL-1 beta is efficient. When apoptosis is rapid, as in macrophages that are targets for allospecific cytotoxic T lymphocytes, processing is observed to occur intracellularly. These findings suggest that cell injury is an important physiologic stimulus for release of IL-1. The nature of the injury profoundly affects the forms of IL-1 that are released.

Basic fibroblast growth factor is efficiently released from a cytolsolic storage site through plasma membrane disruptions of endothelial cells

Cells of gut and skin frequently suffer mechanically-induced plasma membrane disruptions in vivo, and bioactive molecules, including basic fibroblast growth factor (bFGF), could enter and leave cytoplasm through these disruptions. We here provide three lines of evidence that bFGF is released with surprising efficiency through plasma membrane disruptions, resembling those known to occur in vivo, produced by scraping endothelial cells from their culturing substratum. First, 41% of the total of bFGF extractable in 1 M NaCl by freeze-thaw and sonication was released simply by scraping the endothelial cells. Second, relative to release of lactate dehydrogenase, cells wounded by scraping under conditions promoting greater than 60% cell survival released a significantly larger amount (up to twofold more) of growth promoting activity than did cells uniformly killed and irreversibly permeabilized by scraping in the cold or by freezing and thawing. Last, cells that survived membrane disruptions released, and contained, less bFGF on each subsequent wounding, consistent with release of bFGF through transient (i.e., survivable) membrane disruptions. A polyclonal antibody against bFGF completely neutralized the growth promoting activity released by scraping, confirming that bFGF is released through endothelial cell plasma membrane disruptions. Cell fractionation and immunolocalization, including a novel permeabilization technique for electron microscope immunolocalization, demonstrated a cytosolic location of bFGF. We conclude that many characteristics of bFGF--its broad spectrum of producing and target cell types, cytosolic location, efficient release through biologically and pathologically relevant plasma membrane wounds, and its release from cells that survive membrane wounds--make it a strong candidate as a "wound hormone" for rapidly initiating the cell growth required for routine maintenance of tissue integrity and/or repair after injury.

Elevated 32-kDa LBP and low laminin mRNA expression in developing mouse cerebrum

Several laminin receptors have been identified, originally a high-affinity 67-kDa laminin binding protein ('LBP-67'), and later galactosyltransferase and the low-affinity but functionally potent integrin receptors. Attempts at obtaining cDNA for LBP-67, although unsuccessful, have given rise to a full-length cDNA coding for an interesting 32-kDa protein, tentatively referred to as '32-kDa LBP', whose relationship to LBP-67 is unclear. Since no information is available on the in vivo expression of 32-kDa LBP mRNA nor of the three laminin chains during CNS development, appropriate 35S-antisense and -sense RNA probes were applied to developing mouse cerebral wall at embryonic day (E)10-16, birth and 1-3 weeks after birth. Expression was examined using Northern blot analysis and in situ hybridization. The 32-kDa LBP mRNA was found to be elevated during the embryonic and perinatal period, and then rapidly declined. At the cellular level, 32-kDa LBP mRNA was distributed throughout the embryonic cerebral wall and became concentrated during the perinatal period in the proliferative ventricular zone and in the cortical plate. By comparison, laminin B1, B2, and A chain mRNA expression was relatively low at all times examined, in keeping with the punctate distribution of laminin antigenicity previously observed by others in developing brain parenchyma. Whereas the functional characterization of 32-kDa LBP and the nature of its laminin and proposed nonlaminin ligands is incomplete, the elevated and unique distribution of 32-kDa LBP mRNA raises interesting questions of the role of 32-kDa LBP mRNA in CNS development.