Increased expression of interleukin-8 and aminopeptidase N by cell-cell contact: interleukin-8 is resistant to degradation by aminopeptidase N/CD13

In rheumatic joints, high concentrations of interleukin-8 (IL-8) have been measured in synovial fluid and in pannus tissue. In both locations aminopeptidase N (APN)/CD13, an exopeptidase with reported activity towards IL-8 is also present. The surprising stability of IL-8 in the presence of an alleged IL-8-degrading peptidase prompted us to undertake the present study. Cocultivation of fibroblast-like synoviocytes (SFC) with T cells or with T lymphocytic cell membranes, or of T cells with SFC cell membranes, all resulted in increased IL-8 mRNA expression and IL-8 secretion into the medium, and an increase of APN expression on lymphocytes. IL-8 degradation was monitored by Western blots and HPLC. IL-8(72), as a partially processed form, was used throughout this study since it is abundant in tissues and has increased biological activity in comparison to IL-8(77). Thus its degradation/inactivation is considered of high biological significance. Whereas trypsin as a positive control rapidly degraded IL-8, we did not see any IL-8 degradation, either by a variety of soluble APNs, by leucine aminopeptidase or by APN expressed on the surface of SFC, or on ECV304 cells transfected with an APN expression vector. The much more sensitive HPLC technique resulted in negative results as well.     

Identification of interleukin-8 converting enzyme as cathepsin L

IL-8 is produced by various cells, and the NH₂-terminal amino acid sequence of IL-8 displays heterogeneity among cell types. The mature form of IL-8 has 72 amino acids (72IL-8), while a precursor form (77IL-8) of IL-8 has five additional amino acids to the 72IL-8 NH₂-terminal. However, it has been unclear how IL-8 is processed to yield the mature form. In this study, converting enzyme was purified as a single 31-kDa band on silver-stained polyacrylamide gel from 160 l of cultured fibroblast supernatant by sequential chromatography. NH₂-terminal amino acid sequence analysis revealed a sequence, EAPRSVDWRE, which was identified as a partial sequence of cathepsin L. Polyclonal antibodies raised against cathepsin L recognized the purified converting enzyme on Western blot. Moreover, human hepatic cathepsin L cleaved 77IL-8 between Arg⁵ and Ser⁶, which is the same cleavage site as the putative converting enzyme, resulting in 72IL-8 formation. These data indicate that the converting enzyme of the partially purified fraction of the human fibroblast culture supernatant was cathepsin L. Furthermore, 72IL-8 was sevenfold more potent than 77IL-8 in a neutrophil chemotaxis assay. These results show that cathepsin L is secreted from human fibroblasts in response to external stimuli and plays an important role in IL-8 processing in inflammatory sites.     

Granzyme A and thrombin differentially promote the release of interleukin-8 from alveolar epithelial A549 cells

Some of extracellular serine proteases with trypsin-like specificity of cleavage have been known to increase the release of inflammatory mediators from various cell types. For instance, two well-known trypsin-like serine proteases circulating in blood, granzyme A (GrA) and thrombin, have been found to promote interleukin (IL)-8 release from an alveolar epithelial A549 cell line. However, the mechanisms by which the proteases promote IL-8 release from the cells are not fully understood. In the present study, using A549 cells we found that (1) thrombin promoted IL-8 release from the cells via a mechanism partially involving activation of protease-activated receptor-1, a G-protein coupled receptor, whereas a recombinant form of GrA (rGrA) did it via a mechanism that does not involve the receptor activation; that (2) unlike rGrA, thrombin did not cause detachment and microtubule disruption of the cells; and that (3) the release of IL-8 induced by rGrA was inhibited in the presence of taxol, a microtubule-stabilizing reagent, whereas that induced by thrombin was not. These findings suggest that rGrA and thrombin promote the release of IL-8 from A549 cells through distinct mechanisms.     

Paracoccidioides brasiliensis induces secretion of IL-6 and IL-8 by lung epithelial cells. Modulation of host cytokine levels by fungal proteases

Paracoccidioides brasiliensis is a pathogenic, dimorphic fungus that causes paracoccidioidomycosis, a systemic human mycosis that is highly prevalent in Latin America. In this study, we demonstrated that P. brasiliensis yeasts induced interleukin (IL)-8 and IL-6 secretion by human lung epithelial A549 cells. However, tumor necrosis factor-α and interferon-γ were undetectable in these cultures. Moreover, P. brasiliensis yeasts induced activation of p38 mitogen-activated protein kinase (MAPK), c-Jun NH(2)-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) 1/2 in A549 cells, and IL-8 and IL-6 secretion promoted by this fungus was dependent on activation of p38 MAPK and ERK 1/2. In addition, IL-8 and IL-6 levels were significantly higher in culture supernatants of A549 cells that were incubated with formaldehyde-fixed P. brasiliensis compared to cultures of cells that were infected with live yeasts. Our results indicate that the observed cytokine level differences were due to protease expression, in live yeasts, that degraded these cytokines. Degradation of human recombinant IL-8 and IL-6 by live P. brasiliensis was inhibited by AEBSF and aprotinin, suggesting that these proteases belong to a family of serine proteases. This is the first report showing that P. brasiliensis may modulate host inflammation by expressing proteases that degrade proinflammatory cytokines.     

Role of interleukin-6 in murine airway responses to ozone

This study sought to examine the role of interleukin-6 (IL-6) in ozone (O(3))-induced airway injury, inflammation, and hyperresponsiveness (AHR). Subacute (72 h) exposure to 0.3 ppm O(3) significantly elevated bronchoalveolar lavage fluid (BALF) protein, neutrophils, and soluble TNF receptors (sTNFR1 and sTNFR2) in wild-type C57BL/6 (IL-6(+/+)) mice; however, all four outcome indicators were significantly reduced in IL-6-deficient (IL-6(-/-)) compared with IL-6(+/+) mice. Acute O(3) exposure (2 ppm for 3 h) increased BALF protein, KC, macrophage inflammatory protein(MIP)-2, eotaxin, sTNFR1, and sTNFR2 in IL-6(+/+) mice. However, MIP-2 and sTNFR2 were not significantly increased following O(3) exposure in IL-6(-/-) mice. Increases in BALF neutrophils induced by O(3) (2 ppm for 3 h) were also significantly reduced in IL-6(-/-) vs. IL-6(+/+) mice. Airway responsiveness to methacholine was measured by whole body plethysmography before and following acute (3 h) or subacute (72 h) exposure to 0.3 ppm O(3). Acute O(3) exposure caused AHR in both groups of mice, but there was no genotype-related difference in the magnitude of O(3)-induced AHR. AHR was absent in mice of either genotype exposed for 72 h. Our results indicate that IL-6 deficiency reduces airway neutrophilia, as well as the levels of BALF sTNFR1 and sTNFR2 following acute high dose and/or subacute low-dose O(3) exposure, but has no effect on O(3)-induced AHR.     

Structure-activity relationships of interleukin-8 determined using chemically synthesized analogs. Critical role of NH2-terminal residues and evidence for uncoupling of neutrophil chemotaxis, exocytosis, and receptor binding activities.

Interleukin-8 (IL-8) is an inflammatory mediator that stimulates neutrophil migration and functional activation. Analogs of human IL-8 were chemically synthesized, purified, and compared with the full-length 72-residue synthetic IL-8 for their ability to stimulate neutrophil chemotaxis and exocytosis as measured by assaying for release of elastase, as well as their binding to specific receptors in competition assays. Analogs corresponding to the less abundant natural forms, 3-72, 4-72, and 77-residue IL-8, were evaluated and the 3-72 and 4-72 had 2-5-fold higher potencies, whereas the 77-residue IL-8 was 2-fold less potent. A major finding was that NH2-terminal residues 4, 5, and 6 were absolutely essential for IL-8 activity and receptor binding. Quantitative dissociation of elastase release and chemotaxis activity was detected with 5-72, which compared with 1-72, was 80-fold less potent in the elastase assay, but was only slightly less potent in stimulating chemotaxis. IL-8 6-72 lacked all the biological activities tested but had detectable receptor binding activity. The NH2-terminal peptide, AVLPRSAKEL, lacked activity and receptor binding, suggesting that the NH2-terminal region alone is not sufficient for function. Comparison of analogs shortened at the COOH terminus showed that potency was progressively reduced as the COOH-terminal residues were excluded. However activity was retained in an analog (1-51) with the entire COOH-terminal alpha helix and beta turn missing. A peptide corresponding to the COOH-terminal 22 residues, although inactive alone, synergized with the 1-51 analog in stimulating elastase release. The results suggest that the NH2-terminal residues 4, 5, and 6, which are disordered in the IL-8 solution structure, are directly involved in receptor binding, but the COOH-terminal alpha helix is probably important for stabilizing the three-dimensional structure. Other regions within residues 7-51 are also functionally important.     

Determination of the secondary structure of interleukin-8 by nuclear magnetic resonance spectroscopy

The solution conformation of interleukin-8 (IL-8), a small protein of 72 residues with a wide range of proinflammatory activities, has been investigated by two-dimensional NMR spectroscopy. The 1H-NMR spectrum of IL-8 is assigned in a sequential manner and regular elements of secondary structure are identified on the basis of a qualitative interpretation of the nuclear Overhauser, coupling constant and amide exchange data. The IL-8 monomer contains a triple stranded anti-parallel beta-sheet arranged in a Greek key and a long C-terminal helix (residues 57-72). It is shown that IL-8 is a dimer in solution in which the interface is principally formed by six backbone hydrogen bonds between residues 25, 27, and 29 of one monomer and residues 29, 27, and 25, respectively, of the other. As a result, the two units of the dimer form a contiguous six-stranded anti-parallel beta-sheet. The secondary structure of IL-8 is similar to that found in the crystal structure of the sequence related protein platelet factor 4.     

Differential synthesis of two interleukin-1 receptor antagonist variants and interleukin-8 by peripheral blood neutrophils

With a short lifespan and containing only few ribosomes and endoplasmic reticulum structures, neutrophils are thought to have a limited capacity for protein synthesis. We here show that peripheral blood polymorphonuclear neutrophils (PMN) are able react to stimulants with differential production of two interleukin (IL)-1 receptor antagonist (IL-1ra) isoforms, secreted IL-1ra (sIL-1ra) and the 16kDa intracellular form of IL-1ra (icIL-1ra3), as well as IL-8. Neutrophils of a high purity and with a low degree of preactivation upregulate mRNA and de novo synthesize protein of both IL-1ra variants and IL-8 in response to granulocyte-macrophage colony-stimulating factor and lipopolysaccharide. The cytokines are differentially regulated and distributed in two intracellular compartments. In comparison with peripheral blood mononuclear cells (PBMC), PMN produce distinctly more sIL-1ra but significantly less IL-8. This may indicate an anti-inflammatory role, enabling PMN to antagonize proinflammatory signals. It is therefore possible that PMN play an important role in immune regulation by counteracting a dysregulation of the inflammatory process.     

Reciprocal regulation of 17β-estradiol, interleukin-6 and interleukin-8 during growth and progression of epithelial ovarian cancer

Estrogens have been associated with risk for epithelial ovarian cancer (OVCA). Both IL-6 and IL-8 are also likely involved in the progression of OVCA. In order to discover the underline molecular mechanism, we investigated the modulation of estrogen and two cytokines in the growth and progression of epithelial OVCA. In these studies, the effect of 17β-estradiol (E₂) on the expression levels of IL-6, IL-8 and their receptors was investigated. The effect of IL-6 and IL-8 on activation of estrogen-responsive promoter as well as estrogen receptor (ER)α and ERβ expression was also analyzed. Gene expression profile analysis revealed that CAOV-3 and OVCAR-3 cells, which express ER, IL-6 and IL-8 receptors, are suitable model for this study. We found that E₂ not only enhanced IL-6 and IL-8 production via NF-κB signaling pathway, but also modulated their respective receptor expression. Tamoxifen (Txf), an ER antagonist, completely abolished E₂-stimulated cell growth and the expression of IL-6 and IL-8. IL-6/IL-8-induced cell proliferation was completely blocked by their specific neutralizing antibodies, which partially inhibited E₂-induced cell growth. In the absence of estrogen, both cytokines activated estrogen-responsive promoter, which was completely blocked by Txf, and caused a dose-dependent ERα increase and ERβ decrease. Pretreatment of OVCAR-3 with p38 MAPK, MEK1/2 or ErbB2 MAPK inhibitors, respectively, blocked IL-6-mediated induction of estrogen-responsive promoter while Src inhibitor blocked IL-8-induced activation of estrogen-responsive promoter. These results provide a novel mechanism that estrogens, IL-6 and IL-8 may form a common amplifying signaling cascade to modulate OVCA growth and progression. Estrogen-induced OVCA proliferation is partially occurring via enhanced IL-6 and IL-8 production and modulated their receptors, and IL-6/IL-8 could also promote OVCA growth through an ERα pathway.     

Hyperthermia increases interleukin-6 in mouse skeletal muscle

Skeletal muscles produce and contribute to circulating levels of IL-6 during exercise. However, when core temperature is reduced, the response is attenuated. Therefore, we hypothesized that hyperthermia may be an important and independent stimulus for muscle IL-6. In cultured C2C12 myotubes, hyperthermia (42°C) increased IL-6 gene expression 14-fold after 1 h and 35-fold after 5 h of 37°C recovery; whereas exposure to 41°C resulted in a 2.6-fold elevation at 1 h. IL-6 protein was secreted and significantly elevated in the cell supernatant. Similar but reduced responses to heat were seen in C2C12 myoblasts. Isolated soleus muscles from mice, exposed ex vivo to 41°C for 1 h, yielded similar IL-6 gene responses (>3-fold) but without a significant effect on protein release. When whole animals were exposed to passive hyperthermia, such that core temperature increased to 42.4°C, IL-6 mRNA in soleus increased 5.4-fold compared with time matched controls. Interestingly, TNF-α gene expression was routinely suppressed at all levels of hyperthermia (40.5-42°C) in the isolated models, but TNF-α was elevated (4.2-fold) in the soleus taken from intact mice exposed, in vivo, to hyperthermia. Muscle HSP72 mRNA increased as a function of the level of hyperthermia, and IL-6 mRNA responses increased proportionally with HSP72. In cultured C2C12 myotubes, when heat shock factor was pharmacologically blocked with KNK437, both HSP72 and IL-6 mRNA elevations, induced by heat, were suppressed. These findings implicate skeletal muscle as a "heat stress sensor" at physiologically relevant hyperthermia, responding with a programmed cytokine expression pattern characterized by elevated IL-6.     

Endothelial and leukocyte forms of IL-8. Conversion by thrombin and interactions with neutrophils

We have recently shown that endothelial cell-derived IL-8 inhibits neutrophil adhesion to IL1-beta-activated human umbilical vein endothelial cell monolayers. IL-8 secreted by T lymphocytes or monocytes has been characterized as a promoter of neutrophil degranulation and chemotaxis. The IL-8 isolated from each of these cell types is a mixture of two IL-8 polypeptides, one consisting of 72 amino acids (herein called [ser-IL-8]72) and the other 77 amino acids (an N-terminal extended form herein called [ala-IL-8]77). IL-8 derived from T lymphocytes and monocytes is predominantly [ser-IL-8]72, whereas endothelial-derived IL-8 is highly enriched (greater than 80%) in [ala-IL-8]77. We address the relationship and activities of these two forms of IL-8 using recombinant proteins expressed by both mammalian cells and Escherichia coli. Thrombin was found to efficiently convert [ala-IL-8]77 to [ser-IL-8]72. In contrast, urokinase and tissue-type plasminogen activator were unable to cleave [ala-IL-8]77, and trypsin generated multiple IL-8 cleavage fragments. In competitive binding assays using 125I[ala-IL-8]77 neutrophils exhibited a twofold preference for [ser-IL-8]72 over [ala-IL-8]77. Both forms of IL-8 inhibited neutrophil adhesion to IL-1-beta-activated HUVEC monolayers by up to 90%. However, [ser-IL-8]72 was approximately 10-fold more potent than [ala-IL-8]77 in these assays (ED50 approximately 0.3 nM for [ser-IL-8]72 vs approximately 3 nM for [ala-IL-8]77. Both forms of IL-8 promoted degranulation of cytochalasin B-treated neutrophils [[ser-IL-8]72 (ED50 greater than 10 nM) was two- to three-fold more potent than [ala-IL-8]77], although in this regard they were less active than FMLP. Our data suggest that [ala-IL-8]77 and [ser-IL-8]72 have qualitatively similar and potentially complex biological activities, and that full activation of IL-8 requires cleavage to the [ser-IL-8]72 form. In the case of inflamed endothelial cells this activation could be mediated by thrombin generated in the procoagulant environment associated with these cells.     

Serum and urine levels of interleukin-6 and interleukin-8 in children with acute pyelonephritis

Urinary tract infection (UTI) is a common clinical disorder in younger infants and children and may result in permanent renal damage. The inflammatory cytokines interleukin (IL)-6 and IL-8 play an important role in response to bacterial infection. This prospective study investigated the association between serum and urine IL-6 and IL-8 levels and acute pyelonephritis confirmed by (99m)Tc-dimercaptosuccinic acid (DMSA) scan. A total of 78 children aged 1-121 months with a diagnosis of first-time febrile UTI were included. The following inflammatory markers were assessed: fever; white blood cells count (WBC); C-reactive protein (CRP); and serum and urine IL-6 and IL-8. The patients were divided into the acute pyelonephritis group (n=42) and the lower UTI group (n=36) according to the results of DMSA scan. Fever, WBC and CRP levels were significantly higher in children with acute pyelonephritis than in those with lower UTI (all p <0.001). Significantly, higher initial serum and urine IL-6 and IL-8 levels were found in children with acute pyelonephritis than in those with lower UTI (all p <0.001). Serum and urine IL-6 in children with acute pyelonephritis were positively correlated with fever, CRP and leucocyturia. These results indicate that both serum and urine IL-6 and IL-8 levels, particularly IL-6, are useful diagnostic tools for early recognition of acute pyelonephritis in febrile children.     

Structural analysis and modeling of a synthetic interleukin-2 mimetic and its interleukin-2Rbeta2 receptor

Peptide p1-30, which is composed of the 30 amino-terminal residues (alpha-helix A) of human interleukin-2 (IL-2), binds as a tetramer to the dimeric IL-2Rbeta2 receptor, whereas the entire IL-2 recognizes the tricomponent receptor IL-2Ralphabetagamma. p1-30 is an IL-2 mimetic that activates CD8 low lymphocytes and natural killer cells, because these cells produce IL-2Rbeta constitutively. It also induces a strong lymphokine-activated killer cell response. A series of truncated peptides were analyzed by circular dichroism and analytical centrifugation to elucidate the role of p1-30 residues. We propose a model where residues 10-30 of the p1-30 peptide form an alpha-helix with eight hydrophobic side chains on the same surface buried in a hydrophobic core when four anti-parallel helices combine to form a bundle. IL-2Rbeta dimerization was further studied, and three-dimensional models of the free IL-2Rbeta2 receptor and the p1-304.IL-2Rbeta2 complex were built by comparative modeling based on the crystal structure of the erythropoietin receptor complex, because this belongs to the same hematopoietin family as IL-2. These models suggest that binding of the p1-30 tetramer rotates the COOH-terminal domains and brings both transmembrane regions 50 A closer together, driving the association of the two intracytoplasmic domains that would transduce the signal into the cytoplasm.     

Effect of heat acclimation on heat shock protein 72 and interleukin-10 in humans.

Heat acclimation (HA) results in whole body adaptations that increase heat tolerance, and in addition, HA may also result in protective cellular adaptations. We hypothesized that, after HA, basal intracellular heat shock protein (HSP) 72 and extracellular IL-10 levels would increase, while extracellular HSP72 levels decrease. Ten male and two female subjects completed a 10-day exercise/HA protocol (100-min exercise bout at 56% of maximum O(2) uptake in a 42.5 degrees C DB, 27.9% RH environment); subjects exhibited classic adaptations that accompany HA. Peripheral blood mononuclear cells (PBMCs) were isolated before and after each acclimation session on days 1, 6, and 10; plasma and serum were collected before and after exercise on the 1st and 10th day of HA. SDS-PAGE was used to determine PBMC HSP72 levels during HA, and ELISA was used to measure plasma IL-10 and serum HSP72 concentrations. The increase in PBMC HSP72 from pre- to postexercise on the 1st day of HA was not significant (mean +/- SD, 1.0 +/- 0 vs. 1.6 +/- 0.6 density units). Preexercise HSP72 levels on day 1 were significantly lower compared with the pre- and postexercise samples on days 6 and 10 (mean +/- SD, day 6: 2.1 +/- 1.0 and 2.2 +/- 1.0, day 10: 2.0 +/- 1.3 and 2.2 +/- 1.0 density units, respectively, P < 0.05). There were no differences in plasma IL-10 and serum HSP72 postexercise or after 10 days of HA. The sustained elevation of HSP72 from days 6 to 10 may be evidence of a cellular adaptation to HA that contributes to improved heat tolerance and reduced heat illness risk.     

Synergistic upregulation of interleukin-8 secretion from pulmonary epithelial cells by direct and monocyte-dependent effects of respiratory syncytial virus infection

Respiratory syncytial virus (RSV) infection is the major cause of severe bronchiolitis in infants. Pathology of this infection is partly due to excessive proinflammatory leukocyte influx mediated by chemokines. Although direct infection of the respiratory epithelium by RSV may induce chemokine secretion, little is known about the role of cytokine networks. We investigated the effects of conditioned medium (CM) from RSV-infected monocytes (RSV-CM) on respiratory epithelial (A549) cell chemokine release. RSV-CM, but not control CM (both at a 1:5 dilution), stimulated interleukin-8 (IL-8) secretion from A549 cells within 2 h, and secretion increased over 72 h to 11,360 +/- 1,090 pg/ml without affecting cell viability. In contrast, RSV-CM had only a small effect on RANTES secretion. RSV-CM interacted with direct RSV infection to synergistically amplify IL-8 secretion from respiratory epithelial cells (levels of secretion at 48 h were as follows: RSV-CM alone, 8,140 +/- 2,160 pg/ml; RSV alone, 12,170 +/- 300 pg/ml; RSV-CM plus RSV, 27,040 +/- 5,260 pg/ml; P < 0.05). RSV-CM induced degradation of IkappaBalpha within 5 min but did not affect IkappaBbeta. RSV-CM activated transient nuclear binding of NF-kappaB within 1 h, while activation of NF-IL6 was delayed until 8 h and was still detectable at 24 h. Promoter-reporter analysis demonstrated that NF-kappaB binding was essential and that NF-IL6 was important for IL-8 promoter activity in RSV-CM-activated cells. Blocking experiments revealed that the effects of RSV-CM depended on monocyte-derived IL-1 but that tumor necrosis factor alpha was not involved in this network. In summary, RSV infection of monocytes results in and amplifies direct RSV-mediated IL-8 secretion from respiratory epithelial cells by an NF-kappaB-dependent, NF-IL6-requiring mechanism.     

High altitude increases circulating interleukin-6, interleukin-1 receptor antagonist and C-reactive protein

Hypoxic pulmonary vasoconstriction is associated with but may not be sufficient for the development of high-altitude pulmonary oedema (HAPO). Hypoxia is known to induce an inflammatory response in immune cells and endothelial cells. It has been speculated that hypoxia-induced inflammatory cytokines at high altitude may contribute to the development of HAPO by causing capillary leakage in the lung. We were interested if such an inflammatory response, possibly involved in a later development of HAPO, is detectable at high altitude in individuals without HAPO. We examined the plasma levels of interleukin 6 (IL-6), interleukin 1 receptor antagonist (IL-1ra) and C-reactive protein (CRP) in two independent studies: study A, Jungfraujoch, Switzerland, three overnight stays at 3458 m, n=12; study B: Capanna Regina Margherita, Italy, 3 overnight stays at 3647 m and one overnight stay at 4559 m, n=10. In both studies, probands showed symptoms of acute mountain sickness but no signs of HAPO. At the Jungfraujoch, IL-6 increased from 0.1+/-0.03 pg/ml to 2. 0+/-0.5 pg/ml (day 2, P=0.03), IL-1ra from 101+/-21 to 284+/-73 pg/ml (day 2, P=0.01), and CRP from 1.0+/-0.4 to 5.8+/-1.5 micrograms/ml (day 4, P=0.01). At the Capanna Margherita, IL-6 increased from 0. 5+/-0.2 pg/ml to 2.0+/-0.8 pg/ml (P=0.02), IL-1ra from 118+/-25 to 213+/-28 pg/ml (P=0.02), and CRP from 0.4+/-0.03 to 3.5+/-1.1 micrograms/ml (P=0.03). IL-8 was below the detection limit of the ELISA (<25 pg/ml) in both studies. The increase of IL-6 and IL-1ra in response to high altitude was delayed and preceded the increase of CRP. We conclude that: (1) circulating IL-6, IL-1ra and CRP are upregulated in response to hypobaric hypoxic conditions at high altitude, and (2) the moderate systemic increase of these inflammatory markers may reflect considerable local inflammation. The existence and the kinetics of high altitude-induced cytokines found in this study support the hypothesis that inflammation is involved in the development of HAPO.     

The GroEL-like protein from Campylobacter rectus: immunological characterization and interleukin-6 and -8 induction in human gingival fibroblast

The native GroEL-like protein was purified from Campylobacter rectus, a putative periodontal pathogen, by affinity chromatography on ATP-agarose followed by high performance liquid chromatography on Superose 6. The purified 64-kDa protein (denatured form of GroEL-like protein) was immunoreactive by SDS-PAGE and Western immunoblotting with the monoclonal antibody directed against heat shock protein 60 of human origin. The native GroEL-like protein stimulated both interleukin-6 (IL-6) and IL-8 secretion by a confluent monolayer of human gingival fibroblast in their culture supernatant. During the 22-h incubation, the amounts of IL-6 and IL-8 were increased by 5.4- and 3.5-fold, respectively. These data suggested that the GroEL-like protein might be considered to be a virulence factor of C. rectus in periodontal disease.