Molecular cloning and expression of rat interleukin-1 alpha cDNA

Comparison of the human and canine cytokines IL-1(alpha/beta) and TNF-alpha to orthologous other mammalians

The cytokines interleukin-1 (IL-1alpha and IL-1beta) and the tumor necrosis factor-alpha (TNF-alpha) both play a major role in the initiation and regulation of inflammation and immunity responses. Polymorphisms within the gene sequences of these cytokines IL-1 and TNF-alpha have been proposed to play an important role in the pathogenesis of certain diseases. Affecting nearly every organ, various diseases, including some cancers, are described to be associated with an increased level of IL-1 and TNF-alpha proteins, for example, solid tumors, hematologic malignancies, malignant histiocytosis, autoimmune disorders, Alzheimer's disease, Parkinson's disease, sepsis, and rheumatoid arthritis. Regarding genetic backgrounds and pathways, numerous canine diseases show close similarities to their human counterparts. As a genetic model, the dog could be used to unravel the genetic mechanisms, for example, in particular the predispositions, the development, and progression of cancer and metabolic diseases. The identity comparison of gene and protein sequences of different species could be used to elucidate the structure and function of the genes and proteins by identifying the evolutionary conserved regions and domains. Herein we analyzed in detail the mRNA and protein structures and identities of the present known mammalian (human, canine, murine, rat, ovine, equine, feline, porcine, and bovine) TNF-alpha, IL-1alpha, and IL-1beta mRNAs and proteins. Additionally, based on the canine genome sequence, we derived in silico the complete mRNA structures of the IL-1alpha and IL-1beta mRNAs.

Opposite regulation of connexin33 and connexin43 by LPS and IL-1α in spermatogenesis

The gap junction proteins, connexins (Cxs), are present in the testis, and among them, Cx43 play an essential role in spermatogenesis. In the present study, we investigated the testicular expression and regulation of another Cx, Cx33, previously described as a negative regulator of gap junction communication. Cx33 mRNA was present in testis and undetectable in heart, liver, ovary, and uterus. In the mature testis, Cx33 was specifically immunolocalized in the basal compartment of the seminiferous tubules, whereas Cx43 was present in both seminiferous tubule and interstitial compartments. During stages IX and X of spermatogenesis, characterized by Sertoli cell phagocytosis of residual bodies, Cx43 was poorly expressed within seminiferous tubules, while Cx33 signal was strong. To evaluate the role of phagocytosis in the control of Cx33 and Cx43 expression, the effect of LPS was analyzed in the Sertoli cell line 42GPA9. We show herein that phagocytosis activation by LPS concomitantly stimulated Cx33 and inhibited Cx43 mRNA levels. These effects appear to have been mediated through IL-1α, because the exposure of Sertoli cells to the IL-1 receptor antagonist partly reversed these effects. IL-1α enhanced and reduced, respectively, the levels of Cx33 and Cx43 mRNA in a time- and dose-dependent manner. These data reveal that Cx33 and Cx43 genes are controlled differently within the testis and suggest that these two Cxs may exert opposite and complementary effects on spermatogenesis.

Overexpression of glia maturation factor in astrocytes leads to immune activation of microglia through secretion of granulocyte-macrophage-colony stimulating factor

We infected a mixed culture of primary rat astrocytes and microglia with a replication-defective adenovirus carrying the rat glia maturation factor (GMF) cDNA. Affymetrix microarray analysis showed a big increase in the expression of several major histocompatibility complex (MHC) class II proteins along with interleukin-1beta (IL-1beta). Subsequent study using reverse transcription-polymerase chain reaction (RT-PCR) yielded the same results with the mixed culture, but not with pure astrocytes or pure microglia. We also noticed that the GMF/virus construct infected only astrocytes but not microglia. This led us to suspect that overexpression of GMF in astrocytes resulted in the secretion of an active substance that stimulated the microglia to express MHC II and IL-1beta. We identified this substance as granulocyte-macrophage-colony stimulating factor (GM-CSF). MHC II are unique to antigen-presenting cells such as microglia and monocytes. The results suggest that GMF in astrocytes can initiate a series of events, leading to immune activation in the nervous system, and implicates its involvement in autoimmune diseases such as multiple sclerosis.

Interleukin-1 is a potent growth factor for immature rat sertoli cells

Testes from rats of different maturational ages were explored for presence of paracrine sertoli cell growth factors. Pubertal and adult testes contained a 17 kDa protein, with potent stimulatory effect on immature Sertoli cell multiplication in vitro. The bioactivity of this protein was mimicked by rat interleukin-1 (IL-1) and neutralized by IL-1 receptor antagonist. A receptor-mediated action was further supported by the demonstration of IL-1 receptor type I mRNA and protein expression in the cultured sertoli cells and in intact immature rat testes. IL-1alpha showed higher efficacy in stimulating proliferation than IL-1beta and follicle-stimulating hormone (FSH), and displayed synergistic action in combination with FSH. As IL-1alpha is constitutively produced by the rat testis and IL-1beta readily inducible by proinflammatory stimuli, our results suggest that IL-1 may serve as a growth factor for Sertoli cells under physiological and pathophysiological conditions.

Localization and regulation of IL-1alpha in rat myometrium during late pregnancy and the postpartum period

Interleukin-1 (IL-1) has been implicated as a participant in preterm labor that is induced by bacterial infection. Previously, we showed that serotonin-induced production of IL-1alpha by myometrial smooth muscle cells in vitro is also essential for the synthesis of interstitial collagenase. It is therefore likely that IL-1alpha production in uterine tissues has implications for both the normal physiology of involution and for the pathophysiological mechanisms of preterm labor. The objective of this study was to characterize the serotonin-induced production of IL-1alpha by myometrial cultures in vitro and to assess the production of IL-1alpha and its relationship to collagenase production in vivo during pregnancy and the postpartum period. Immunohistochemistry demonstrated IL-1alpha protein in the nuclei and cytoplasm of serotonin-treated myometrial cells. IL-1alpha levels were decreased by treatment with progesterone or IL-1-receptor antagonist but were unaffected by lipopolysaccharide. Western analysis of myometrium from pregnant rats showed low levels of IL-1alpha during midpregnancy with increased concentrations at days 21 and 22 and postpartum. IL-1alpha mRNA levels also increased from days 15 to 22. Levels of mRNA for IL-1beta also increased, although to a lesser degree than IL-1alpha. Both mRNAs decreased postpartum. Conversely, mRNA for interstitial collagenase was barely detectable at term but increased postpartum. Together, these data show that serotonin stimulates IL-1alpha production in vitro and indicate that normal myometrium from pregnant rats is an identifiable source of IL-1 during late pregnancy. The findings are consistent with the possibility that myometrial IL-1alpha participates in normal labor as well as the postpartum production of interstitial collagenase.

Constitutive production of interleukin-1alpha mRNA and protein in the developing rat testis

Interleukin-1 (IL-1), a multifunctional cytokine produced mainly by activated macrophages, is also produced in the intact testis. Rat testicular IL-1 was found to be identical to IL-1alpha, judged by immunoneutralization of the bioactive protein and sequence comparison of cloned rat testicular and macrophage pro-IL-1alpha cDNA. Testicular IL-1alpha mRNA was first demonstrated on postnatal day 15, and the corresponding bioactive protein from day 20. IL-1alpha mRNA was still low on day 20, but then increased rapidly in parallel with the bioactive protein to establish a plateau level from day 25. In adult testes, IL-1alpha mRNA and immunoreactive protein were low in stage VII of the seminiferous epithelial cycle, whereas other stages showed a clearly detectable expression. In the adult testis, the concentration of IL-1alpha was 75 pg/mg testicular protein (approximately 200 pM). In conclusion, production of testicular IL-1alpha is developmentally and stage-dependently regulated, probably at the transcriptional level, emphasizing an important paracrine role in testicular function.

Molecular cloning and expression of a functionally different alternative splice variant of prointerleukin-1alpha from the rat testis

We report here the characterization of an alternative splice variant of prointerleukin-1alpha (proIL-1alpha), constitutively expressed by the normal adult rat testis. In addition to the classical 32K proIL-1alpha (32proIL-1alpha) messenger RNA, the testis produced a shorter variant encoding a putative protein of 24K (24proIL-1alpha). In situ hybridization demonstrated constitutive expression of the splice transcript in the seminiferous tubules. This alternative complementary DNA lacked the fifth exon, harboring the calpain cleavage site essential for generation of mature 17K IL-1alpha. This was verified by calpain treatment, producing the expected cleavage products of recombinant 32proIL-1alpha, but not of 24proIL-1alpha. Similarly, expression in COS-7 cells demonstrated processing of 32proIL-1alpha to the mature 17K form and secretion, whereas 24proIL-1alpha remained unprocessed. Both 32proIL-1alpha and 24proIL-1alpha showed a dose-dependent stimulatory effect in a thymocyte proliferation assay, although at lower potency than mature 17K IL-1alpha. In contrast, when tested on hCG-stimulated Leydig cells in vitro, a dose-dependent inhibition of testosterone production was obtained with mature 17K IL-1alpha and at a lower potency with 32proIL-1alpha, whereas 24proIL-1alpha was inactive. In conclusion, the three IL-1 bioactive proteins described here contribute to IL-1 protein heterogeneity and may serve as constitutive paracrine mediators in the testis.

Differential transport of rat and human interleukin-1alpha across the blood-brain barrier and blood-testis barrier in rats

Human interleukin-1alpha is transported across the murine blood-brain barrier (BBB) and blood-testis barrier (BTB) by a saturable transport system. Differences in the biological activity and binding of human IL-1 in mouse and rat brain raise the possibility of species differences in the transport of IL-1 across the BBB and BTB. We measured the transport of recombinant human 125I-IL-1alpha (I-huIL-1alpha) and rat 125I-IL-1alpha (I-ratIL-1alpha) across the rat BBB and BTB after intravenous injection using a sensitive in vivo technique and film autoradiography. I-ratIL-1alpha was found to cross the rat BBB and rat BTB at rates comparable to those reported previously for murine IL-1alpha in mice. Passage across the BBB was inhibited by the addition of unlabeled rat IL-1alpha, demonstrating saturable transport. In contrast, I-huIL-1alpha entered the brain of the rat much more slowly, and its entry was not inhibited by the addition of unlabeled human IL-1alpha. These results show that the rat interleukin-1 transporter, unlike the murine transporter, does not transport human IL-1alpha. This difference highlights the importance of species specificity in IL-1alpha transport and may partly explain the different physiological responses to exogenous human IL-1alpha among rodent species.

Stimulation of prostaglandin E2 and interleukin-1beta production from old rat periodontal ligament cells subjected to mechanical stress

Although the severity of periodontal disease is known to be affected by the age of the host, the pathological role of aging in periodontal disease, especially that attributable to trauma from occlusion, has not been well characterized. Prostaglandin (PG)E2 and interleukin (IL)-1beta are key mediators involved in periodontal diseases, potent stimulators of bone resorption, and are produced by human periodontal ligament (PDL) cells in response to mechanical stress. To investigate age-related changes in the biosynthetic capacity of PGE2 and IL-1beta in PDL cells, we examined the effects of in vivo aging with mechanical tension on PGE2 and IL-1beta expression by rat PDL cells. PDL cells obtained from the incisors of 6-week (young) and 60-week (old) rats were cultured on flexible-bottomed culture plates. The cells were deformed by causing a 9% or 18% increase in surface area at 6 cycles per minute for 1 to 5 days. We found an approximately twofold increase in PGE2 and IL-1beta production by old PDL cells subjected to mechanical tension compared with that by young cells, although the constitutive levels were similar in both. The expression of cyclooxygenase (COX)-2 and IL-1beta mRNA (messenger ribonucleic acid) was enhanced by mechanical tension as determined by use of reverse transcription-polymerase chain reaction (RT-PCR), whereas COX-1 and IL-1beta-converting enzyme mRNA remained unchanged. It is possible that the large amount of PGE2 and IL-1beta produced by PDL cells from an aged host in response to mechanical force may be positively related to the acceleration of alveolar bone resorption.

Molecular cloning and expression analysis of carp (Cyprinus carpio) interleukin-1 beta, high affinity immunoglobulin E Fc receptor gamma subunit and serum amyloid A

Suppression subtractive hybridisation (SSH) is a powerful means to identify genes of cytokines and other genes that express small amount of mRNA. In this study, cDNA of normal fish (carp) head kidney cells (HKC) was subtracted from pooled cDNA of HKC and peritoneal cell (PC) obtained from fish which had been injected with sodium alginate (SA) and scleroglucan (SG) 3-48 h earlier. This subtraction produced 248 clones of cDNA fragments. After sequencing some of the fragments of interest were used as probes, and yielded full-length cDNAs homologous to mammalian interleukin-1 beta (IL-1 beta), the gamma subunit of high affinity Fc receptor for IgE (Fc epsilon RI gamma) and serum amyloid A (SAA); these were cloned and sequenced. Carp IL-1 beta shows 21.8-24.7% amino acid identities to mammalian mature IL-1 beta, and lacks a signal sequence, which is consistent with mammalian IL-1 beta. Carp Fc epsilon RI gamma, which was the first cloned non-mammalian Fc receptor subunit, shows 39.3-40.4% amino acid identities to mammalian Fc epsilon RI gamma, and contains the immunoreceptor tyrosin-based activation motif characteristic of the signal transduction subunit of antigen- and Fc-receptors. Carp SAA is most similar to mammalian acute phase responsive type SAA with 53.0-55.3% amino acid identities. Both SA-elicited and SG-elicited PC expressed higher amounts of IL-1 beta and SAA mRNA compared to saline-injected fish HKC and PC, indicating that these proteins are associated with inflammatory responses, similar to mammalian homologues. Fc epsilon RI gamma was constitutively expressed in leucocytes and not immunopotentiator-responsive, but this indicates that Fc receptor including Fc epsilon RI gamma subunit is likely functional in the carp immune system.

Immunoglobulin in atherosclerotic lesions of human aorta

An augmented expression of mRNA for IgG light chain was demonstrated age-dependently on atheromatous lesions of the aorta in Watanabe heritable hyperlipidemic (WHHL) rabbits. The present study was designed to determine factors related to inflammation in human vessels excised during surgery. We detected IgG mRNAs using RT-PCR in human atherosclerotic lesions but not in human umbilical arteries which have no atheromatous lesions. To determine the clonality of IgGs, cDNAs encoding variable regions of IgG heavy chain were examined using RT-PCR. Atherosclerotic lesions had several subtypes of IgG gene families' suggesting the involvement of polyclonal B-cells. mRNAs of interleukins-6 (IL-6), -1alpha (IL-1alpha), and -1beta (IL-1beta) were also detected in the same samples. In summary, inflammatory reactions were present in the atherosclerosis lesion.

Activity-dependent regulation of interleukin-1 beta immunoreactivity in the developing rat olfactory bulb

Interleukin-1beta is a relatively small and abundant polypeptide that plays diverse roles in the central nervous system. In the present study, patterns of interleukin-1beta expression were observed in the olfactory bulbs of rats that had either undergone unilateral closure of the external naris or sham surgery on postnatal day 1 and then survived until postnatal day 30. Interleukin-1beta-immunoreactive fibers occupied distinct layers of the olfactory bulb. Dense immunostaining was found in the periglomerular and granule cell layers. Odor deprivation resulted in a noticeable reduction in interleukin-1beta immunoreactivity only in the periglomerular layer. The data demonstrate that interleukin-1beta is present abundantly in the bulbs, and that it can be regulated in an activity-dependent manner.

Constitutive expression of interleukin-1alpha messenger ribonucleic acid in rat Sertoli cells is dependent upon interaction with germ cells

Interleukin-1 (IL-1), a proinflammatory cytokine originally isolated as a product of activated mononuclear phagocytes, consists of two distinct agonist proteins, IL-1alpha and IL-1beta, of which IL-1beta is the major inducible IL-1 protein produced by macrophages. We show here that mRNA of IL-1alpha, but not IL-1beta, is constitutively expressed by the intact rat testis and localize the transcript to Sertoli cells as confirmed by a novel squash technique. The expression is developmentally regulated and appears only after postnatal day 20 in the rat testis, corresponding to onset of puberty. IL-1alpha mRNA shows a stage-dependent expression pattern during the cycle of the seminiferous epithelium. It is low or absent in stage VII, but present in all other stages of the cycle. The same stage-dependent distribution was also observed at the protein level when bioactive IL-1 was measured in extracts of accurately defined one millimeter segments of seminiferous tubules. No IL-1alpha mRNA was detected in adult rat testes after germ cell depletion by fetal irradiation or cytostatic drug treatment. Because stage VII is the only segment of the seminiferous tubules lacking DNA replication, we propose that IL-1alpha is involved in this event during mitosis and meiosis of spermatogenesis and that its expression is dependent upon interactions between Sertoli cells and germ cells.

Serotonin-inducible transcription of interleukin-1alpha in uterine smooth muscle cells requires an AP-1 site: cloning and partial characterization of the rat IL-1alpha promoter

Interleukin-1 has been shown to contribute to infection-induced inflammatory processes during pregnancy. Prior work from this laboratory has demonstrated that serotonin-induced IL-1alpha also is required for the in-vitro production of collagenase in uterine smooth muscle cells, a normal, non-inflammatory process that occurs in-vivo during post-partum uterine involution. To understand the molecular mechanisms that regulate transcription of the IL-1alpha gene in these cells, we isolated and characterized 1.6 kilobases of the 5'-flanking region of the rat IL-1alpha gene. Sequencing and primer extension identified a single transcription start site and multiple potential regulatory elements, including a TATA box at - 30 bp, a CAAT box at - 74 bp, and a conserved AP-1 site at - 9 bp. This 5'-flanking DNA exhibited low basal promoter activity that was inducible by serotonin. Serotonin-induced promoter activity was unaffected or induced by either medroxyprogesterone or IL-1 receptor antagonist. This occurred despite the ability of both of these hormones to markedly decrease IL-1alpha mRNA. Deletional analysis revealed a strong repressor in the region between - 147 and - 98 bp; removal of this sequence resulted in a fivefold higher basal promoter activity that was still serotonin responsive. Constitutive promoter activity appeared to reside between - 97 and - 22 bp. Deletion of this promoter region, which contained the TATA and CAAT boxes and an NF-IL-6/PEA-3 site, resulted in decreased basal transcriptional activity to the low level seen in larger constructs. Mutational analysis showed that serotonin-inducible transcriptional activity was mediated, at least in part, by the conserved AP-1 site at - 9 bp. This site is located within a larger extended palindromic region: 5'-AAGCCTGACTCAGACTT-3', that together effects both the basal and serotonin-inducible expression of the IL-1alpha gene.

Enhancement of lipopolysaccharide-stimulated PGE2 and IL-1beta production in gingival fibroblast cells from old rats

The effect of aging on gingival fibroblasts in response to bacterial infection was studied. Rat gingival fibroblast (rGF) cells were cultured from gingival tissue removed from young (6 weeks old) and old (20 months old) rats. Both types of rGF cells were challenged with lipopolysaccharide (LPS) from the periodontal pathogen Campylobacter rectus. The levels of prostaglandin E2 (PGE2) and interleukin 1beta (IL-1beta) released into the cultured medium were measured by a specific radioimmunoassay. LPS stimulated PGE2 and IL-1beta production in a dose-and time-dependent manner in rGF cells from both young and old rats was seen. Production of PGE2 and IL-1beta by rGF cells from the old rats was higher than those from the young in response to LPS. This greater ability from the older rGF cells to produce PGE2 and IL-1beta was due to higher mRNA levels of cyclooxygenase 2 and IL-1beta, respectively. In contrast, cyclooxygenase-1 and IL-1beta converting enzyme gene mRNA levels remained unchanged. Because LPS-stimulated PGE2 and IL-1beta production was enhanced by in vivo cellular aging, aging of GF may affect the severity of inflammation and bone resorption by producing a large amount of PGE2 and IL-1beta in response to bacterial infection.

Cytokine expression in the rat central nervous system following perinatal Borna disease virus infection

Borna disease virus (BDV) causes central nervous system (CNS) disease in several vertebrate species, which is frequently accompanied by behavioral abnormalities. In the adult rat, intracerebral (i.c.) BDV infection leads to immunomediated meningoencephalitis. In contrast, i.c. infection of neonates causes a persistent infection in the absence of overt signs of brain inflammation. These rats (designated PTI-NB) display distinct behavioral and neurodevelopmental abnormalities. However, the molecular mechanisms for these virally induced CNS disturbances are unknown. Cytokines play an important role in CNS function, both under normal physiological and pathological conditions. Astrocytes and microglia are the primary resident cells of the central nervous system with the capacity to produce cytokines. Strong reactive astrocytosis is observed in the PTI-NB rat brain. We have used a ribonuclease protection assay to investigate the mRNA expression levels of proinflammatory cytokines in different brain regions of PTI-NB and control rats. We show here evidence of a chronic upregulation of proinflammatory cytokines interleukin-6, tumor necrosis factor alpha, interleukins-1alpha, and -1beta in the hippocampus and cerebellum of the PTI-NB rat brain. These brain regions exhibited only a very mild and transient immune infiltration. In contrast, in addition to reactive astrocytes, a strong and sustained microgliosis was observed in the PTI-NB rat brains. Our data suggest that CNS resident cells, namely astrocytes and microglia, are the major source of cytokine expression in the PTI-NB rat brain. The possible implications of these findings are discussed.

Induction of Keratinocyte Proliferation and Lymphocytic Infiltration by In Vivo Introduction of the IL-6 Gene into Keratinocytes and Possibility of Keratinocyte Gene Therapy for Inflammatory Skin Diseases Using IL-6 Mutant Genes

To understand biological function of IL-6 in the skin in vivo, we constructed a vector that strongly expressed human IL-6 in keratinocytes and introduced it into rat keratinocytes in vivo by the naked DNA method. The overexpression of IL-6 induced macroscopic erythema and histologically evident keratinocyte proliferation and lymphocytic infiltration in the treated area of rat skin. Since previous studies using IL-6 transgenic mice have not shown skin inflammation of these mice, our result provides the first evidence that IL-6 is related to the pathogenesis of inflammatory skin diseases. ELISA suggested that a certain degree of transgenic IL-6 expression in keratinocytes was required for inducing skin inflammation. Cytokine profile in rat keratinocytes after the gene introduction was examined by reverse transcriptase-PCR assay and revealed that gene expression of rat IL-1α and TNF-α showed no marked change until 24 h, whereas that of rat IL-6 and TGF-α increased with time. We then introduced and expressed the IL-6 mutant genes, which were designed to behave as IL-6Rα antagonists, and found that their ability to induce erythema was lower than that of the wild-type gene. Furthermore, preintroduction of some mutant genes delayed the erythema induced by postintroduction of the wild-type IL-6 gene, suggesting that the mutant forms of IL-6 prevent wild-type IL-6 from binding to IL-6Rα. This result indicates that keratinocyte gene therapy may be possible for inflammatory skin diseases using IL-6 mutant genes.

Identification and functional importance of IL-1 receptors on rat parietal cells

We studied the expression of interleukin-1 (IL-1) receptors and the effect of IL-1beta on the function of highly enriched (>97%) rat parietal cells. RT-PCR of parietal cell poly(A)+ RNA with primers specific for the rat IL-1 receptor revealed a single 547-kb PCR product highly homologous to the published sequence of the IL-1 receptor. Northern blot analysis of poly(A)+ RNA of rat parietal cells and brain revealed a single RNA species of 5.7 kb. Cytochemistry of parietal cell IL-1 receptor was performed with biotinylated recombinant human IL-1beta, visualized by avidin-coupled fluorescein. Corresponding to the high degree of parietal cell enrichment, 95% of the cells stained positive. Basal H+ production ([14C]aminopyrine accumulation) was not changed by IL-1beta (0.25-100 pg/ml) nor was the response to histamine or carbachol when added simultaneously with the cytokine. However, when parietal cells were preincubated with IL-1beta (0.5-5 pg/ml) for 10 min before the addition of histamine or carbachol, the response to these secretagogues was reduced by 35 and 67%, respectively. Inhibition by IL-1beta was fully reversed by the human recombinant IL-1 receptor antagonist. Preincubation of parietal cells with IL-1beta failed to alter histamine-stimulated cAMP production but markedly inhibited carbachol-induced formation of D-myo-inositol 1,4, 5-trisphosphate. In fura 2-loaded, purified parietal cells, 10 min preincubation with IL-1beta dramatically reduced the initial transient peak elevation of intracellular Ca2+ concentration in response to carbachol. We conclude that rat parietal cells express IL-1 receptors mediating inhibition of H+ production. The antisecretory effect of IL-1beta may contribute to hypoacidity secondary to acute Helicobacter pylori infection or during chronic colonization by H. pylori preferring the fundic mucosa.

Altered cytokine (receptor) mRNA expression as a tool in immunotoxicology

Molecular immunotoxicology is aimed at analysing exposure effects on the temporal expression of important immunoregulatory genes. Cytokines play key roles in the immune system and thus molecular immunotoxicology has focused on the analysis of cytokine (expression) levels. These targets offer important new avenues to explore both in terms of mechanistic understanding of immunotoxicity and in terms of developing new assays and tests for predicting the immunotoxic potential of novel compounds. Effects on cytokine levels can be analysed on two different levels, these being mRNA and protein. The choice essentially depends on the aim of the study. Proteins comprise the biological activity so they are a more direct measure than mRNA. mRNA on the other hand, measures at a specific point in time within a tissue or organ, whereas protein is measured in a body fluid, possibly as a spill-over from tissue, or in a supernatant as a summation over a culture period. mRNA levels are assayed using Northern or dot blotting that both comprise hybridisation and using reverse transcription-polymerase chain reaction (RT-PCR). Although the latter technique has both enormous sensitivity and relative ease of operation as important advantages, it requires much more effort in terms of quantitation. References to the nucleic acid sequences of human, murine, and rat cytokines and their receptors are presented (with accession numbers). Examples in which molecular techniques were successfully employed to assess immunotoxicity and (in some cases) understand mechanisms of action are also presented.

Borrelia burgdorferi induces the production and release of proinflammatory cytokines in canine synovial explant cultures

Canine synovial membrane explants were exposed to high- or low-passage Borrelia burgdorferi for 3, 6, 12, and 24 h. Spirochetes received no treatment, were UV light irradiated for 16 h, or were sonicated prior to addition to synovial explant cultures. In explant tissues, mRNA levels for the proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha), interleukin-1alpha (IL-1alpha), IL-1beta, and IL-8 were surveyed semiquantitatively by reverse transcription-PCR. Culture supernatants were examined for numbers of total and motile (i.e., viable) spirochetes, TNF-like and IL-1-like activities, polymorphonuclear neutrophil (PMN) chemotaxis-inducing activities, and IL-8. During exposure to synovial explant tissues, the total number of spirochetes in the supernatants decreased gradually by approximately 30%, and the viability also declined. mRNAs for TNF-alpha, IL-1alpha, IL-1beta, and IL-8 were up-regulated in synovial explant tissues within 3 h after infection with untreated or UV light-irradiated B. burgdorferi, and mRNA levels corresponded to the results obtained with bioassays. During 24 h of coincubation, cultures challenged with untreated or UV light-irradiated spirochetes produced similar levels of TNF-like and IL-1-like activities. In contrast, explant tissues exposed to untreated B. burgdorferi generated significantly higher levels of chemotactic factors after 24 h of incubation than did explant tissues exposed to UV light-treated spirochetes. In identical samples, a specific signal for IL-8 was identified by Western blot analysis. High- and low-passage borreliae did not differ in their abilities to induce proinflammatory cytokines. No difference in cytokine induction between untreated and sonicated high-passage spirochetes was observed, suggesting that fractions of the organism can trigger the production and release of inflammatory mediators. The titration of spirochetes revealed a dose-independent cytokine response, where 10(3) to 10(7) B. burgdorferi organisms induced similar TNF-like activities but only 10(7) spirochetes induced measurable IL-1-like activities. The release of chemotactic factors was dose dependent and was initiated when tissues were infected with at least 10(5) organisms. We conclude that intact B. burgdorferi or fractions of the bacterium can induce the local up-regulation of TNF-alpha, IL-1alpha, and IL-1beta in the synovium but that the interaction of viable spirochetes with synovial cells leads to the release of IL-8, which probably is a prime initiator of PMN migration during acute Lyme arthritis.

Interleukin 1 receptor blockade reduces tumor necrosis factor production, tissue injury, and mortality after hepatic ischemia-reperfusion in the rat

The inflammatory cytokines interleukin (IL) 1 and tumor necrosis factor (TNF) may play an important role in hepatic ischemia-reperfusion (I/R) injury. To study the role of IL-1 in hepatic I-R injury, we investigated the effect of pretreatment with IL-1 receptor antagonist (IL-1ra) on the production of IL-1, TNF, histological findings in the liver, and the survival rate for 7 days. Rats were subjected to 90 min of partial liver warm ischemia by clamping the vessels of the left and middle lobes. In the IL-1ra-treated group, IL-1ra was given 5 min before liver ischemia was induced. IL-1alpha and TNF levels were determined in blood and liver at 0, 30, 90, and 180 min after reperfusion. In a second experiment to determine the effect of IL-1ra pretreatment on survival rate, after 90 min of partial liver ischemia, the right lateral and caudate lobes were excised, leaving only the ischemic lobes. In both groups, IL-1alpha was undetectable in blood, but increased in liver tissue. TNF increased in both blood and liver tissue as reperfusion time increased. Histological evidence of tissue injury was minimal in the IL-1ra-treated group. Furthermore, in the IL-1ra-treated group, the production of TNF decreased in both blood and liver tissue compared with the nontreated group. Survival rates in the IL-1ra-treated and nontreated group were 80% and 30%, respectively. The data demonstrated that the production of IL-1 and TNF increases in hepatic I-R injury and that pretreatment with IL-1ra protects the liver from ischemic insult, indicating an important role for IL-1 in I-R injury.

IL-1 is an important mediator for microcirculatory changes in endotoxin-induced intestinal mucosal damage

Although small intestine is frequently injured in endotoxin shock, the exact pathological sequence has not been fully understood. The major objective of this study is to elucidate the role of interleukin (IL)-1 in endotoxin-induced microcirculatory disturbance of rat small intestine. Mucosal and submucosal microvessels of the rat ileum were observed by intravital microscope with a high speed video camera system and the attenuating effect of E5090, an inhibitor of IL-1 generation, on endotoxin-induced intestinal microcirculatory disturbances was investigated. Endotoxin infusion produced significant mucosal damage, but before these morphological changes became significant, microvascular stasis in villi, decreased red blood cell velocity, and increased leukocyte adherence to venular walls were observed in intestinal microcirculatory beds 30 min after endotoxin administration. Intestinal IL-1alpha levels were also significantly increased at that time. Endotoxin treatment enhanced chemiluminescence activity from neurophils and rapidly mobilized CD18 on leukocytes. E5090, which suppressed the IL-1 production in intestinal mucosa, attenuated the microcirculatory disturbances induced by endotoxin, and significantly reduced the subsequent mucosal damage. E5090 also attenuated the increased chemiluminescence activity and CD18 expression on leukocytes. In conclusion, the production of IL-1alpha is enhanced in the intestinal mucosa during endotoxin infusion. IL-1 may be an important mediator of microcirculatory changes, including decreased red blood cell velocity and increased leukocyte sticking and its activation, leading to the mucosal damage.

Interleukin 10 suppresses experimental chronic, granulomatous inflammation induced by bacterial cell wall polymers

BACKGROUND AND AIMS

Interleukin 10 (IL10) inhibits monocyte/macrophage and T lymphocyte effector functions. This study examined the effect of systemically administered IL10 on acute and chronic granulomatous enterocolitis, hepatitis, and arthritis in a rat model.

METHODS

Lewis rats were injected intramurally with streptococcal peptidoglycan-polysaccharide (PG-APS) polymers. Beginning 12 hours before PG-APS injection, rats were treated daily with subcutaneous murine recombinant IL10 or vehicle for three or 17 days.

RESULTS

IL10 attenuated acute enterocolitis in a dose dependent fashion (p < 0.01). Protective effects were more profound in the chronic granulomatous phase with decreased enterocolitis and markedly inhibited leucocytosis, hepatic granulomas, and chronic erosive arthritis (p < 0.001). IL10 downregulated tissue IL1, IL6, tumour necrosis factor alpha, and interferon gamma gene expression, consistent with the in vitro effects of IL10 on PG-APS-stimulated splenocytes. Caecal IL1 protein concentrations and IL2 and interferon gamma secretion by in vitro stimulated mesenteric lymph nodes were downregulated in IL10 treated animals.

CONCLUSIONS

These results indicate that exogenous IL10 can inhibit experimental granulomatous inflammatory responses and suggest that IL10 treatment could be an effective new therapeutic approach in human disorders such as Crohn's disease, rheumatoid arthritis, and sarcoidosis.

Induction of interleukin-1 and interleukin-8 mRNAs and proteins by TGF beta 1 in rat lung alveolar epithelial cells

The transforming growth factor-beta (TGF-beta) has been shown to increase in lung injury and in fibrotic states of the lung. In the current study, we sought to investigate whether TGF beta 1 induced the expression of IL-1 alpha and IL-8 in rat alveolar epithelial cells. We evaluated TGF beta 1, IL-1 alpha, and IL-8 expression by immunofluorescence in silica-injured and saline-treated control rat lungs. Antibodies to IL-1 alpha, IL-8, and TGF beta 1 showed intense staining in silica-injured lungs as compared to saline-instilled lungs. Primary isolated type II cells from silica-injured lungs showed increased expression of IL-1 alpha as compared to saline-instilled lungs. To evaluate the effects of TGF beta 1, we treated an immortalized rat type II cell-derived cell line (LM5) with 100 pg/ml of TGF beta 1 in serum-free medium for 0-24 hours and analyzed the expression of IL-1 alpha and IL-8 mRNAs and proteins using semiquantitative RT-PCR, Northern blot analysis, Western blot analysis, and immunohistochemistry. Densitometric analysis of Northern blots showed modest constitutive expression of IL-1 alpha gene in untreated control LM5 cells. TGF beta 1 treatment resulted in an increase in IL-1 alpha mRNA, that reached maximum levels (4-fold) by 2 hours and remained elevated for 4-16 hours, with a subsequent decline by 24 hours. Similarly, Northern blot and RT-PCR analysis demonstrated that TGF beta 1 treatment resulted in maximum induction of IL-8 mRNA (6- 8.5-fold) within 1-4 hours. The levels remained elevated for up to 24 hours afterwards. Western blot analysis results further confirmed the expression of both IL-1 alpha and IL-8 proteins by LM5 cells. TGF beta 1 treatment resulted in increased expression of both IL-1 alpha and IL-8 proteins. Immunofluorescence studies demonstrated increased staining of IL-1 alpha by TGF beta 1 as compared to untreated cells. These results suggest that TGF beta 1 may regulate IL-1 alpha and IL-8 expression in alveolar epithelial cells and contribute to polymorphonuclear leukocyte recruitment and lung injury in clinical states with increased TGF beta 1.

Enhanced expression of interleukin (IL)-1 and IL-6 messenger RNA and bioactive protein after hypoxia-ischemia in neonatal rats

The effect of hypoxia-ischemia (HI) on IL-1, and IL-6 bioactivity in relation to expression of IL-1 alpha, IL-1 beta, and IL-6 mRNA was studied, and the neuroprotective efficacy of IL-1 receptor antagonist (IL-1ra) was evaluated in neonatal rats. HI was induced in 7-d-old rats by unilateral carotid artery ligation and hypoxia for 70-100 min. Animals were killed at different time points up to 14 d after HI, and brains were analyzed for IL-1 and IL-6 bioactivity using bioassays and for mRNA for IL-1 alpha, IL-1 beta, and IL-6 with reverse transcription followed by a polymerase chain reaction. In separate animals, IL-1ra was administered intracerebrally before or after HI, and the extent of brain injury was assessed 14 d after HI. A transient increase of IL-1 bioactivity occurred after HI, reaching a peak at 6 h of recovery. IL-1 beta mRNA followed a similar time course but attained maximum expression at 3 h. IL-6 bioactivity and mRNA were also stimulated by HI and followed a similar time course as IL-1. Pretreatment with IL-1ra reduced HI brain damage from 54.4 +/- 9.3 to 41.4 +/- 10.0% (p < or = 0.01), and IL-1ra posttreatment increased the proportion of animals devoid of brain injury (40%) compared with vehicle-treated controls (13%) (p < or = 0.05). In conclusion, a transient activation of IL-1 and IL-6 occurred after HI, and IL-1ra reduced HI brain injury to a moderate degree.

The immune response following small bowel transplantation: I. An unusual pattern of cytokine expression

Acute cell mediated graft rejection is frequently associated with an immune response dominated by cytokines like IL-2 and IFNgamma. While small bowel grafts are rejected acutely, there is little information on the type of immune response generated following transplantation and, in particular, whether the cytokine profile resembles that seen during the rejection of other solid organ grafts. In this paper we compare the expression of cytokines in isolated gut tissue following experimental small bowel transplantation with that in heart grafts. Heterotopic small bowel (n=32) and cardiac (n=32) transplants were performed using the following rat strain combinations: syngeneic Lewis (Lew) > Lew (n=8), blood group D Agouti (DA) > Lew (n=8) and allogeneic Lew > DA (n=8), DA > Lew (n=8). Two rats from each group were sacrificed at 1, 3, 5, or 7 days after transplantation. RNA was prepared separately from gut wall, after removing the Peyer's patches (PPs) and mesenteric lymph nodes (MLNs) and from heart. Cytokine (IL-1alpha, IL-2, IL-4, IL-6, IL-10 and IFNgamma) transcripts were analyzed using semiquantitative RT-PCR. Most notably, transcripts of only a single cytokine, IFNgamma, became progressively elevated with time in the rejecting small bowel grafts. This is in marked contrast to the findings presented here for rat cardiac grafts in which transcripts of all cytokines tested show an increase with rejection. This significant and steady increase in IFNgamma expression occurred before there was any clinical or histological evidence of rejection. These data demonstrate that the mechanisms of rejection in small bowel and other solid organ grafts are likely to be different. Further, the unique rise in IFNgamma expression in the gut wall may be a valuable and early indicator of graft rejection.

Normal luminal bacteria, especially Bacteroides species, mediate chronic colitis, gastritis, and arthritis in HLA-B27/human beta2 microglobulin transgenic rats

Genetic and environmental factors are important in the pathogenesis of clinical and experimental chronic intestinal inflammation. We investigated the influence of normal luminal bacteria and several groups of selected bacterial strains on spontaneous gastrointestinal and systemic inflammation in HLA-B27 transgenic rats. Rats maintained germfree for 3-9 mo were compared with littermates conventionalized with specific pathogen-free bacteria. Subsequently, germfree transgenic rats were colonized with groups of five to eight bacteria that were either facultative or strictly anaerobic. Transgenic germfree rats had no gastroduodenitis, colitis, or arthritis, but developed epididymitis and dermatitis to the same degree as conventionalized rats. Colonic proinflammatory cytokine expression was increased in transgenic conventionalized rats but was undetectable in germfree and nontransgenic rats. Colitis progressively increased over the first 4 wk of bacterial exposure, then plateaued. Only transgenic rats colonized with defined bacterial cocktails which contained Bacteroides spp. had colitis and gastritis. Normal luminal bacteria predictably and uniformly induce chronic colonic, gastric and systemic inflammation in B27 transgenic F344 rats, but all bacterial species do not have equal activities.

Osteoclast activation in inflammatory periodontal diseases

OBJECTIVE

In this paper, we review the mechanisms thought to be involved in the activation of osteoclasts in periodontitis.

SUMMARY

Osteoclasts are regulated by both microbial and host factors. Some factors act directly on cells of the osteoclast lineage, whereas others act indirectly through other cell types in the bone environment. The proinflammatory cytokines (interleukins 1 and 6, tumor necrosis factors) have been implicated in the stimulation of osteoclastic resorption. The roles of the immunoregulatory cytoknes (interleukins 2 and 4, interferon gamma) are less clear, but decreased levels of these factors may contribute to periodontitis. A number of lipid mediators may be involved in stimulation of bone resorption. These include bacterial lipopolysaccharide and host-derived platelet-activating factor and prostaglandins. More recently, reactive oxygen intermediates and extracellular nucleotides, both present at sites of inflammation, have been investigated as possible modulators of osteoclast activity. The potential use of antiresorptive therapies in periodontitis is reviewed.

CONCLUSIONS

A wide range of host and bacterial factors contribute to the loss of alveolar bone in periodontitis. However, much remains to be understood about the complex mechanisms through which these factors regulate osteoclast activity. Further studies at the cellular and molecular level will lead to a better understanding of these processes and perhaps suggest new approaches for periodontal therapy.

Constitutive in vivo mRNA expression by osteocytes of beta-actin, osteocalcin, connexin-43, IGF-I, c-fos and c-jun, but not TNF-alpha nor tartrate-resistant acid phosphatase

Osteocytes have been proposed to be the cells primarily responsible for sensing the effects of mechanical loading in bone. Osteocytes respond to loading in vivo, and have been shown to express osteotropic agents and their receptors, and cell/matrix adhesion molecules in vitro, but the functional significance of such findings is not clear. One obstacle to increased understanding of the role of osteocytes in the regulation of bone mass is that the cells are not easily accessible for study. In situ studies are difficult, and although it is possible to extract and culture osteocytes from neonatal bones, the responses of such cells might be very different from those in older bones in situ. We have developed a technique to investigate osteocyte gene expression in vivo, using the reverse transcriptase linked polymerase chain reaction (PCR), and have shown that they express mRNA for beta-actin (beta-ACT), osteocalcin (OC), connexin-43 (Cx43), insulin-like growth factor I (IGF-I), c-fos and c-jun, but not tumor necrosis factor alpha (TNF-alpha) or tartrate-resistant acid phosphatase (TRAP). The principle behind the method is that after removal of the periosteum, tangential cryostat sections of a tubular bone contain RNA only from osteocytes and a very small number of endothelial cells as long as the marrow cavity is not broached. Using this method, we have investigated gene expression in cells from rat ulnar cortical bone under forming and resorbing bone surfaces. In addition, we have investigated the effect on gene expression of mechanical loading which, if repeated daily, initiates new bone formation on quiescent or resorbing surfaces. Although the expression of the genes we have studied in osteocytes is different from those expressed by the periosteal surfaces overlying the cortex, we have not detected loading-related changes in osteocyte gene expression in any cortical bones. This may be because of the extreme sensitivity of the PCR technique which can only resolve large differences in expression. The use of quantitative methods in the future may allow demonstration of regulated gene expression in osteocytes.

A factor derived from polymorphonuclear leukocytes enhances interleukin-1-induced synovial cell collagenase and prostaglandin E2 production in rats

We found that short-term culture medium and homogenate of casein-induced rat peritoneal polymorphonuclear leukocytes (PMN) markedly induced collagenase and prostaglandin E2 (PGE2) production by normal rat synovial cells and these effects were abrogated by anti-(rat interleukin-1 alpha) (IL-1 alpha) polyclonal antibodies. However, collagenase activity and PGE2 induced by recombinant rat IL-1 alpha were less than those induced by rat PMN culture medium. It was also proved by radioimmunoassay that rat PMN culture medium contains a relatively small amount of IL-1 alpha. The introduction of IL-1 alpha-deleted PMN culture medium and recombinant rat IL-1 alpha together into the synovial cell culture system revealed that IL-1 alpha deleted PMN culture medium has a significant enhancing activity on IL-1 alpha-induced synovial cell collagenase and PGE2 production. This new factor, which was shown to be a negatively charged protein of about 80 kDa, may have important roles in connective tissue destruction and chronic inflammation in diseases such as rheumatoid arthritis.

Release of interleukin-1 beta by dermatan sulfate suppresses hepatocyte growth

Among glycosaminoglycans, dermatan sulfate (DS) is the strongest inhibitor of DNA synthesis in adult rat hepatocytes in primary culture stimulated with insulin and epidermal growth factor. Hyaluronate also inhibited DNA synthesis, whereas chondroitin-6 sulfate, 4-sulfate or heparin had no effect on DNA synthesis in hepatocytes. Analysis of growth regulatory factors in hepatocyte culture medium treated with DS revealed that interleukin-1 (IL-1) was released into the medium. IL-1 beta mRNA was detected in DS-treated hepatocytes by reverse transcriptase-polymerase chain reaction, but not in untreated hepatocytes. For a marked inhibition of DNA synthesis, more than 10 hr of exposure to DS before cultured hepatocytes started DNA synthesis, was required. Similarly, more than 10 hr was required after the addition of DS before IL-1 beta mRNA was detected. These findings suggest that DS in the medium induced the production of IL-1 beta which, in turn, reduced DNA synthesis in hepatocytes.

Expression of mRNAs of multiple growth factors and receptors by neuronal cell lines: detection with RT-PCR

Neurons and glia are capable of both secreting and responding to a large variety of growth factors. However, information on multiple expression of growth factors and their receptors was usually obtained from uncorrelated observations, using cells from various animals of origin, developmental stages, growth phases, culture ages and culture conditions. Because of its specificity and extreme sensitivity, reverse transcription-polymerase chain reaction (RT-PCR) is uniquely suitable to study a large panel of growth factors and their receptors from a limited cell sample, free of these intervening variables. In this paper we evaluate the expression of mRNA of a total of 35 growth factor-related proteins by conducting RT-PCR on three neuronal cell lines: the PC12 rat pheochromocytoma line, the MAH rat sympathoadrenal progenitor line, and the N18 mouse neuroblastoma line. Three types of results are presented. The first confirms the existing knowledge such as the presence of Trk-A (NFG receptor) in PC12. The second consists of new information that expands and extends earlier observations, such as the presence of CNTF receptor complex in PC12, which explains our previous report that CNTF enhances the biological effects of NGF on these cells. The third consists of novel information that leads the way to further experimentation by the more conventional methods. These include the strong expression of Trk-B by MAH, predicting the biological responsiveness of MAH to BDNF and NT-4, and the expression of CNTF receptor in N18. Our results also suggest that CNTF is an autocrine factor for PC12 and MAH, since both lines express the growth factor as well as the receptor. Thus, RT-PCR is a valuable tool in growth factor research that can be used in complement to, and interactively with, other approaches such as bioassay, receptor binding, and immunochemical determination. It will be particularly useful for screening a large number of growth factors in minute areas of the brain in patients suffering from neurodegenerative diseases such as Parkinson's and Alzheimer's.

Molecular cloning of equine interleukin-1 alpha and -beta cDNAs

Equine interleukin-1 alpha (IL-1 alpha) and IL-1 beta were molecularly cloned to establish a basis for research on inflammatory and immune responses in the horse. Equine peripheral blood mononuclear cells (PBMC) were stimulated with lipopolysaccharide (LPS), and cDNA clones of equine IL-1 alpha and IL-1 beta covering the whole coding sequences were isolated from them. These equine IL-1 alpha and IL-1 beta clones contained open reading frames encoding 271 and 269 amino acids, respectively. The deduced amino acid sequence of equine IL-1 alpha showed 71.6% and 60.2% similarity with that of human and murine IL-1 alpha, respectively. Similarly, the amino acid sequence of equine IL-1 beta showed 66.7% and 61.8% similarity with that of human and murine IL-1 beta, respectively. In both equine IL-1 alpha and IL-1 beta, amino acids at miristoylation sites were well conserved. Dot blot analysis indicated that the expression of IL-1 beta was predominant to that of IL-1 alpha in equine PBMC stimulated with LPS or phorbol myristate acetate.

Interleukin-1 receptor antagonist protein and mRNA in the rat adrenal gland

The occurrence of the endogenous receptor antagonist for the cytokine interleukin-1 in the rat adrenal gland was analyzed y polymerase chain reaction and by immunohistochemistry using a rabbit polyclonal antiserum. Expression of interleukin-1 receptor antagonist mRNA was demonstrated in both adrenal medulla and cortex, and a marked increase in the transcription was observed after systemic administration of lipopolysaccharides. Interleukin-1 receptor antagonist immunoreactivity was seen in the adrenal medulla, and the immunofluorescence intensity was stronger in the adrenergic, phenylethanolamine N-methyltransferase-positive cells than in the noradrenergic chromaffin cells. The distribution of interleukin-1 receptor antagonist protein is complementary to that of interleukin-1 alpha-like immunoreactivity found in phenylethanolamine N-methyltransferase-negative cells and overlaps with and resembles the distribution of interleukin-1 beta-immunoreactive material. The expression of the interleukin-1 receptor antagonist in the adrenal gland complements previous findings of large constitutive pools of interleukin-1 alpha and interleukin-1 beta in this neuroendocrine organ and also suggests participation of adrenal interleukin-1 receptor antagonist in neuroimmune modulation.

Interleukin-1 alpha and vasoactive intestinal peptide: enigmatic regulation of neuronal survival

A neurotrophic role for interleukin-1 alpha (IL-1 alpha) was investigated in dissociated spinal cord-dorsal root ganglion cultures. Three observations suggested a survival-promoting action for IL-1 alpha in nine-day-old cultures: (1) neutralizing antiserum to murine IL-1 alpha decreased neuronal survival; (2) treatment with IL-1 alpha in electrically blocked cultures increased neuronal survival; and (3) antiserum to the type I IL-1 receptor decreased neuronal survival. Treatment with VIP prevented neuronal cell death associated with the antiserum to IL-1 alpha. In contrast, treatment of one-month-old cultures with IL-1 alpha produced neuronal cell death and neutralizing antiserum to the IL-1 receptor had no effect on neuronal survival in these cultures. These experiments suggested that an IL-1-like substance was necessary for neuronal survival during a specific stage in development and that a relationship between VIP and IL-1 alpha might account in part for the neurotrophic properties of VIP. To test if VIP might be a secretagogue for IL-1, a neuron-free model system was utilized: astroglial cultures derived from cerebral cortex. VIP treatment produced a concentration-dependent (EC50: 50 pM) increase in the amount of IL-1 alpha in the medium and a decrease in cellular IL-1 alpha. Interleukin-1 beta (IL-1 beta) was also increased (EC 50: 1 nM) in the medium by VIP but without depleting IL-1 beta in the cytosol. Semi-quantitative measurements of the IL-1 alpha mRNA after VIP treatment indicated a significant but transient decrease. These data indicate that VIP produced an increase in the secretion of IL-1 alpha while depleting IL-1 alpha mRNA.

Neutrophil-independent myocardial dysfunction during an early stage of global ischemia and reperfusion of isolated hearts

The effect of global ischemia and reperfusion on the expression of cytokine genes and cell adhesion molecules by myocardial tissues and neutrophils was studied by using the Langendorff model. Although cardiac function deteriorated after reperfusion of ischemic hearts, there was no evidence of inflammation and myocardial degeneration, which is in contrast to previous findings that neutrophil-mediated inflammation is a critical step in post-ischemic reperfusion injury in regional ischemia. Flow cytometry analysis demonstrated that the global ischemia and reperfusion did not affect the expression of adhesion molecules on neutrophils. We also examined the expression of various cytokines which are involved in inflammatory responses. Only interleukin 1 alpha was induced after the reperfusion of the ischemic hearts. These results suggest that neutrophils barely contribute to the myocardial dysfunction and IL-1 alpha may play a role in post-ischemic myocardial dysfunction during the early stage of reperfusion.

Expression of mRNAs of multiple growth factors and receptors by astrocytes and glioma cells: detection with reverse transcription-polymerase chain reaction

1. Although glial cells in culture are known to secrete growth factors and are also known to be responsive to some of them, detailed comparisons are difficult because the bulk of information was based on various animals of origin, developmental stages, growth properties, culture age, and culture conditions. 2. To present a unified picture of the growth factors and their receptors found in glial cells, we surveyed the expression of messenger RNAs of a panel of growth factors and receptors, using reverse transcription-polymerase chain reaction (RT-PCR), in three common glial cell types: rat astrocytes in primary culture, rat glioma line C6, and human glioma line A172. 3. We observed that normal and neoplastic glial cells in culture express multiple growth factors and also possess most of the receptors to the factors, suggesting multiple autocrine functions. In addition, glia produce growth factors known to be capable of acting on neurons, implicating paracrine function involving glia-neuron interaction. Glial cells also produce growth factors and receptors that are capable of communicating with hematopoietic cells, suggesting neuroimmunologic interaction. What is most interesting is that glial cells express receptors for growth factors previously thought to be acting on neurons only. 4. The current study demonstrates the feasibility of screening from a small sample a large number of growth factors and receptors. The method portends future clinical application to biopsy or necropsy samples from brain tumors or pathologic brains suffering from degenerative diseases such as Alzheimer's or Parkinson's disease.

Cytokine gene expression in intact anagen rat hair follicles

Substantial cellular proliferative activity is necessary to produce a mature hair follicle. Therefore, it is likely that cytokines and their receptors play an important controlling role. To provide an understanding of the mechanisms involved during hair growth, we investigated the expression of cytokines in rat anagen hair follicles. A new technique was developed that allowed the rapid isolation of large numbers of intact, viable, anagen, rat pelage hair follicles. Total RNA was isolated from these follicles using an acid-phenol-chloroform extraction and analyzed for cytokine expression. Using the conventional technique of Northern blotting, it was only possible to detect transcripts for transforming growth factor beta (TGF beta) and insulin-like growth factor I (IGFI). Polymerase chain reaction amplification of reverse-transcribed mRNA detected cDNA fragments for TGF beta, IGF I, IGF II, nerve growth factor beta (NGF beta), and interleukin-1 alpha (IL-1 alpha). The amplified products were confirmed by digestion with restriction endonucleases. The proteins themselves for TGF beta and IGF I have been shown to be present within the anagen hair follicle using immunogold antibody labeling. This study has provided the first reported cytokine expression profile of rat anagen hair follicles. It is likely that the analysis of the pattern and timing of expression of these cytokines in the follicle will provide valuable insights into hair growth regulation.

Developmental expression of cytokine genes in the cortex and hippocampus of the rat central nervous system

Cytokines are now considered as constitutive factors of the brain. Some of them are involved in the mechanism regulating lineage commitment and cellular differentiation of the central nervous system (CNS). We describe here the analysis of gene expression in cortex and hippocampus, of interleukin-1 alpha (IL1), interleukin-2 (IL2), interleukin-6 (IL6), macrophage-colony stimulating factor-1 (MCSF) and monocyte chemoattractant protein-1 (MCP1) in fetal (day 18 of gestation; G18), newborn (postnatal day 2; P2), young (postnatal day 21; P21) and adult rat using the reverse transcriptase-polymerase chain reaction (RT-PCR). IL6 and MCP1 mRNA presented distinct patterns of expression levels: IL6 mRNA level is most highly expressed in the embryonic cortex, whereas MCP1 is expressed at a maximal level in the postnatal day 2 cortical area. In the hippocampus, IL6 is most expressed at the adult stage and MCP1 exhibits an equal level of expression from day two to the adult stage. However, under our experimental conditions, IL1 alpha, IL2 and MCSF mRNA were not observed. Thus, certain cytokine genes, each with a specific pattern, are expressed in the rat CNS in adult and during ontogenesis. These observations suggest that cytokines might be involved as regulating factors promoting CNS development.

Transfection of rat dermal papilla cells with a gene encoding a temperature-sensitive polyomavirus large T antigen generates cell lines retaining a differentiated phenotype

The dermal papilla is a discrete group of cells at the base of the hair follicle and is implicated in controlling the hair growth cycle. Early passage dermal papilla cells can induce hair growth in vivo, but, upon further culturing, this property is lost. In order to study the events occurring in hair induction, a representative dermal papilla cell line was required. We have transfected passage 1 rat vibrissa dermal papilla cells with a polyomavirus large T gene encoding a temperature-sensitive T antigen, and generated permanent cell lines in which the immortalizing function can be switched off by temperature shift. The cells established without crisis, resembled cells in the starting population, and retained the aggregative properties of early passage dermal papilla cells. Growth studies were performed on the immortalized cell lines, which showed that transferring the cells to the restrictive temperature for the large T gene product resulted in cell senescence or quiescence, and changes in morphology. Implantation of cell pellets into the ears of immunologically compatible rats showed that the immortal cells retained hair-inductive ability. Cytokines are believed to have an important role in the control of hair growth. The pattern of cytokine gene expression in the immortal cell lines was compared with early passage dermal papilla cells and a non-hair-inducing dermal papilla cell line, using reverse transcriptase-polymerase chain reaction. Epidermal growth factor, tumour necrosis factor, and interleukin-1a were detected in the immortalized and non-hair-inducing dermal papilla cell lines, but were absent in passage 2 dermal papilla cells. All other cytokines examined were detected in all the cell types under study. These results demonstrate that the polyomavirus large Ttsa-immortalized dermal papilla cell lines are very similar to passage 2 dermal papilla cells and thus provide a good model for hair growth studies. Cytokine expression profiles indicate that the expression of several cytokines may be implicated in hair induction. Further studies are under way to investigate the relationship between cytokine expression and the hair growth cycle.

Effect of IL-1 receptor antagonist and antiserum to TNF-alpha on LPS-induced plasma ACTH and corticosterone rise in rats

Using an antiserum against tumor necrosis factor (TNF)-alpha and an interleukin (IL-1) receptor antagonist, we studied putative roles of these cytokines in mediating the endotoxin-induced elevation of plasma adrenocorticotropic hormone (ACTH) and corticosterone levels in freely moving rats. Intravenous administration of Escherichia coli lipopolysaccharide (LPS) increased plasma ACTH and corticosterone levels in a dose-dependent manner. The plasma corticosterone reached to its highest level among a series of experiments after the administration of even the smallest dose (0.03 microgram/kg) tested. Plasma ACTH and corticosterone levels in these rats were completely inhibited by the intravenous administration of anti-murine TNF-alpha-rabbit antiserum (anti-TNFAS) after the administration of LPS but not by the intravenous administration of IL-1 receptor antagonist (IL-1RA). On the other hand, both recombinant human IL-1RA and anti-TNFAS significantly inhibited plasma ACTH increase stimulated with 10 micrograms/kg LPS. These findings indicate that 1) when the plasma corticosterone increase induced by intravenous LPS remains below its maximum, the effect is exclusively mediated by TNF-alpha, and 2) when a larger amount of LPS is administered, both IL-1 beta and TNF-alpha participate at least in part in the hypothalamic-pituitary-adrenal axis activation.

Differential effects of indomethacin and dexamethasone on cytokine production in carrageenin-induced rat pleurisy

The effect of anti-inflammatory drugs on cytokine production at local inflammatory sites was investigated in a carrageenin-induced rat pleurisy model. Exudate volume and leukocyte number in the pleural cavity at 3 h after the carrageenin injection were significantly reduced by the pretreatment with indomethacin or dexamethasone. Both drugs also reduced the prostaglandin E2 level in the exudate. However, production of tumor necrosis factor (TNF) and interleukin-1 in the pleural exudate was significantly enhanced by the pretreatment with indomethacin, whereas the interleukin-6 level was reduced. Pretreatment with dexamethasone markedly suppressed all these cytokine levels. When resident pleural cells were stimulated with lipopolysaccharide in vitro, the presence of exogenous prostaglandin E2 reduced the production of TNF and interleukin-1, while it increased that of interleukin-6 in a dose-dependent manner. These results suggest that prostaglandin E2 could be a regulating factor involved in cytokine production at the inflammatory site. Dexamethasone may express a direct suppressive action on cytokine production rather than an indirect regulatory action through prostaglandin E2 level.

Induction of interleukin-1 in various brain regions after peripheral and central injections of lipopolysaccharide

The presence of bioactive interleukin-1 (IL-1) in various brain regions (cerebellum, cortex, brainstem, diencephalon or hippocampus) after either intraperitoneal (i.p.) or intraventricular (i.c.v.) injection of lipopolysaccharide (LPS) was studied in the rat. To detect IL-1, extracellular fluid and cell lysate were fractionated by gel exclusion chromatography and fractions tested for thymocyte stimulation; presence of IL-1 was confirmed by blockade of stimulation by addition to the assay of a monoclonal antibody (mAb) to IL-1 receptor. When LPS was infused i.c.v., IL-1 was detected in the brainstem and diencephalon 2 h after injection, and in all the brain regions except cerebellum 6 h after injection; IL-1 was not detected in the plasma of these animals. When LPS was injected i.p., IL-1 was detected in the plasma but not in the brain 2 h after the injection, and in all brain regions but not in the plasma 6 h after the injection. In all of these cases, IL-1 was found in extracellular fluid; in some cases (cortex, cerebellum) cell lysate of the region did not produce detectable bioactivity, thereby indicating that IL-1 in these brain regions is processed to active peptide during release, as has been reported in the periphery. In those cases where bioactivity was detected in cell lysate (brainstem, diencephalon), bioactivity was not blocked by IL-1 receptor mAb, indicating presence of a non-IL-1 stimulating factor. These results further support the idea that IL-1 is secreted by cells in the brain, and indicate that it is found in the extracellular fluid of many brain regions following an appropriate stimulus in the periphery as well as in the brain.

An examination of the generation-time effect on molecular evolution

By using DNA sequences of 17 mammalian genes, the generation-time effect is estimated separately for synonymous substitutions and nonsynonymous substitutions. Star phylogenies composed of rodentia, artiodactyla, and primates are examined. The generation-time effect is found to be more conspicuous for synonymous substitutions than for non-synonymous substitutions, by using the methods of (i) Nei and Gojobori, (ii) Li, and (iii) Ina. The proportion of accepted amino acid substitutions in evolution is estimated to be about twice as large in the primate lineage as in the rodent lineage. This result is in accord with the nearly neutral theory of molecular evolution.

Cytokines in neuronal cell types

Cytokines are signals in the immune system, and may have effects on cells distant from the cells of origin. These proteins have been suggested as messengers in the communication between the immune system and the nervous system, in which signals travel only short distances. Neuroimmune interactions have been discussed in view of findings that nervous signals are important for the immune response. The occurrence of neurotransmitter receptors on lymphocytes and cytokine receptors on nerve cells or glia has initiated further studies e.g. on the localization of different cytokines in the nervous system and on long and short term actions of cytokines in the nervous system. Interleukin-1 has been studied extensively along these lines, and found to occur in the nervous and endocrine system, for example in the adrenal chromaffin cells, and to have effects such as induction of slow-wave sleep and stimulation of adrenocortical and gonadotropic hormones. Other cytokines implicated as signals in neuroimmune interactions are IL-2, IL-6, IFN-gamma and TNF-alpha. The functional studies suggest the occurrence of cytokine receptors in the brain, and experiments using 125iodine-labelled IL-1 alpha demonstrate differential distribution of binding sites in the mouse brain. Recently, evidence emerged of an endogenous receptor antagonist for IL-1, which may prove useful for the understanding of the mechanisms of IL-1's actions in the nervous system. A role for cytokines in regulation of the immune response but also in adjusting the organism to the host reaction is implicated. Furthermore, several findings indicate their role as growth promoting factors, and for example the induction of NGF production by IL-1 suggests involvement of this cytokine in regeneration and development in the nervous system. The significance of neuronally produced cytokines may be based upon the anatomically distinct releasing sites that the specific synaptic organization of the nervous system offer and future studies should determine whether cytokines act as neurotransmitters.