Crystallization of human interleukin-8. A protein chemotactic for neutrophils and T-lymphocytes

Thirty-five years since the discovery of chemotactic cytokines, interleukin-8 and MCAF: A historical overview

Inflammation is a host defense response to various invading stimuli, but an excessive and persistent inflammatory response can cause tissue injury, which can lead to irreversible organ damage and dysfunction. Excessive inflammatory responses are believed to link to most human diseases. A specific type of leukocyte infiltration into invaded tissues is required for inflammation. Historically, the underlying molecular mechanisms of this process during inflammation were an enigma, compromising research in the fields of inflammation, immunology, and pathology. However, the pioneering discovery of chemotactic cytokines (chemokines), monocyte-derived neutrophil chemotactic factor (MDNCF; interleukin [IL]-8, CXCL8) and monocyte chemotactic and activating factor (MCAF; monocyte chemotactic factor 1 [MCP-1], CCL2) in the late 1980s finally enabled us to address this issue. In this review, we provide a historical overview of chemokine research over the last 35 years.

Overview of protein structural and functional folds

This overview provides an illustrated, comprehensive survey of some commonly observed protein‐fold families and structural motifs, chosen for their functional significance. It opens with descriptions and definitions of the various elements of protein structure and associated terminology. Following is an introduction into web‐based structural bioinformatics that includes surveys of interactive web servers for protein fold or domain annotation, protein‐structure databases, protein‐structure‐classification databases, structural alignments of proteins, and molecular graphics programs available for personal computers. The rest of the overview describes selected families of protein folds in terms of their secondary, tertiary, and quaternary structural arrangements, including ribbon‐diagram examples, tables of representative structures with references, and brief explanations pointing out their respective biological and functional significance.

Design and characterization of a membrane permeable N-methyl amino acid-containing peptide that inhibits Abeta1-40 fibrillogenesis

Alzheimer's disease, Huntington's disease and prion diseases are part of a growing list of diseases associated with formation of beta-sheet containing fibrils. In a previous publication, we demonstrated that the self-association of the Alzheimer's beta-amyloid (Abeta) peptide is inhibited by peptides homologous to the central core domain of Abeta, but containing N-methyl amino acids at alternate positions. When these inhibitor peptides are arrayed in an extended, beta-strand conformation, the alternating position of N-methyl amino acids gives the peptide two distinct faces, one exhibiting a normal pattern of peptide backbone hydrogen bonds, but the other face having limited hydrogen-bonding capabilities due to the replacement of the amide protons by N-methyl groups. Here, we demonstrate, through two-dimensional NMR and circular dichroic spectroscopy, that a pentapeptide with two N-methyl amino acids, Abeta16-20m or Ac-K(Me)LV(Me)FF-NH2, does indeed have the intended structure of an extended beta-strand. This structure is remarkably stable to changes in solvent conditions and resists denaturation by heating, changes in pH (from 2.5 to 10.5), and addition of denaturants such as urea and guanindine-HCl. We also show that this peptide, despite its hydrophobic composition, is highly water soluble, to concentrations > 30 mm, in contrast to the nonmethylated congener, Abeta16-20 (Ac-KLVFF-NH2). The striking water solubility, in combination with the hydrophobic composition of the peptide, suggested that the peptide might be able to pass spontaneously through cell membranes and model phospholipid bilayers such as unilamellar vesicles. Thus, we also demonstrate that this peptide is indeed able to pass spontaneously through both synthetic phospholipid bilayer vesicles and cell membranes. Characterization of the biophysical properties of the Abeta16-20m peptide may facilitate the application of this strategy to other systems as diverse as the HIV protease and chemokines, in which there is dimerization through beta-strand domains.

Cloning of BRAK, a novel divergent CXC chemokine preferentially expressed in normal versus malignant cells

Chemokines are a family of related proteins that regulate leukocyte infiltration into inflamed tissue and play important roles in many disease processes. Chemokines are divided into two major groups, CC or CXC, based on their sequence around the amino terminal cysteines. We report the PCR cloning of a novel human chemokine termed BRAK for its initial isolation from breast and kidney cells. This novel chemokine is distantly related to other CXC chemokines (30% identity with MIP-2alpha and beta) and shares several biological activities. BRAK is expressed ubiquitously and highly in normal tissue. However, it was expressed in only 2 of 18 cancer cell lines. BRAK is located on human chromosome 5q31.

Relationship between interleukin-8 levels and myeloperoxidase activity in human gastric mucosa

Although interleukin (IL)-8 is well known as a chemotactic agent for neutrophil migration in vitro, the relationship between IL-8 activity and the degree of neutrophil infiltration in gastric mucosa is still unclear. In the present study, we investigated IL-8 and myeloperoxidase activity, a marker of neutrophil infiltration, in gastric antral mucosa using biopsy samples in 23 patients with no gastric lesions. The results indicate that there is a good correlation between IL-8 and myeloperoxidase activity (y = 0.173x + 13.9; r = 0.49, P < 0.01). Furthermore, IL-8 and myeloperoxidase activity are significantly higher in Helicobacter pylori-positive patients than in H. pylori-negative patients. In conclusion, an increase of IL-8 activity in the gastric mucosa causes increased neutrophil infiltration in human gastric mucosa and H. pylori infection accelerates these reactions in the mucosa.

Identification of IL-5 and RANTES as the major eosinophil chemoattractants in the asthmatic lung

The study was carried out to identify those molecules that are important in vivo in the attraction of eosinophil granulocytes to the lungs of patients with asthma. Asthmatic patients with birch pollen allergy had lavages performed before and during the pollen season, and the chemotactic activity of the bronchoalveolar lavage fluid was tested against normal eosinophils. The activity was significantly increased during the pollen season as compared with the activity before the pollen season (p less than 0.01). Neutralizing antibodies to IL-2, IL-5 and IL-8, leukemia inhibitory factor, and to RANTES were added to the bronchoalveolar lavage fluid. Antibodies to IL-5 and RANTES, but not to IL-2 and IL-8 or leukemia inhibitory factor, significantly inhibited the chemotactic activity for eosinophils (p less than 0.001). It is concluded that IL-5 and RANTES are important chemoattractants in the lungs of patients with allergic asthma. The effect of IL-5 may be that of a cofactor to the chemotactic molecules, of which RANTES may be one of the most important in allergic asthma.

Isolation and characterization of an interleukin-8-like peptide in the bovine species

Human interleukin-8 (IL-8) is a biologically active peptide which displays chemo-attractive activity for neutrophils and T-cells. The molecule is produced by a variety of cell types upon exposure to lipopolysaccharide, interleukin-1 and tumor necrosis factor. Recombinant human IL-8 also stimulates chemotaxis of bovine cells in a dose dependent manner. The purpose of this series of studies was to investigate the ability of bovine cells to produce an active IL-8-like molecule and to determine if bovine cells respond to human recombinant IL-8. Stimulation of purified peripheral blood mononuclear cells results in the time dependent production of an IL-8-like molecule as determined using an anti-human IL-8 ELISA assay and a bovine neutrophil chemotactic assay. Physical characterization indicates that the biological activity of the molecule was significantly reduced by heat inactivation at 56 degrees C for 30 min or exposure to extreme acidic or basic conditions. The peptide was affinity purified using an anti-human IL-8 antibody produced from ATCC hybridoma HB9647. SDS-PAGE analysis yields a distinct band at 7.8 kDa. The isoelectric point of the purified protein was determined to be 8.65. Biological activity of the purified protein was confirmed and the anti-human IL-8 antibody was capable of partially neutralizing the chemotactic activity.

Purification, crystallization and preliminary X-ray diffraction analysis of recombinant human neutrophil-activating peptide 2 (rhNAP-2)

The potent activator and chemoattractant for human neutrophils, neutrophil-activating peptide 2 (NAP-2), has been cloned and expressed in Escherichia coli. The protein has been purified to homogeneity (> 98%) by a series of chromatographic techniques, including reversed phase HPLC. The biological activity of recombinant human NAP-2 (rhNAP-2), characterized by the induction of elastase release from human neutrophils, was found to be comparable to natural NAP-2. rhNAP-2 has been crystallized by the hanging drop vapor diffusion method. The crystals belong to space group P222 with unit cell dimensions of a = 30.8 A, b = 39.5 A and c = 95.3 A. A packing density of 3.8 A3/Da with a solvent content of approximately 68% is obtained when one molecule per asymmetric unit is assumed. The crystals were shown to diffract to beyond 2.0 A on a conventional X-ray source. They are stable to X-rays for several days and are thus suitable for high resolution structure determination.

Chemoattractants for neutrophils in lipopolysaccharide-induced inflammatory exudate from rats are not interleukin-8 counterparts but gro-gene-product/melanoma-growth-stimulating-activity-related factors

Potent chemotactic activity for neutrophils was detected in rat inflammatory exudate induced by a subcutaneous injection of lipopolysaccharide in a carboxymethyl-cellulose suspension. We purified and characterized chemoattractants from the exudate by the following procedures: carboxymethyl-Sephadex C-25 ion-exchange chromatography; G3000SW gel-filtration chromatography; preparative reverse-phase high-pressure liquid chromatography; rechromatography on reverse-phase HPLC. Two chemotactic factors were purified and their N-terminal amino acid sequences were determined. One factor was a protein in which the first 20 N-terminal amino acids were identical to those of rat cytokine-induced neutrophil chemoattractant (CINC), a counterpart of human gro/melanoma growth-stimulating activity (MGSA). The other factor was highly similar to mouse macrophage inflammatory protein 2 (MIP-2). Mouse MIP-2, a chemotactic factor for neutrophils, is a member of the interleukin-8 family; however the protein we purified had higher similarity to human gro/MGSA than to human interleukin-8. These results indicate that, in rats, chemotactic factors for neutrophils induced by lipopolysaccharide stimulation are not counterparts of interleukin-8, but are gro/CINC-related peptides.

Small cytokine superfamily

Proteins comprising a newly described superfamily of small inducible cytokines (tentatively designated 'scy') exhibit considerable similarity with respect to activity, regulation and genomic structure. Recent observations, however, have identified specific biological activities and contexts in which these cytokines differ and which may allow fine tuning of immune and inflammatory responses.