Roles of airway epithelial integrins in health and disease. The Parker B. Francis Lectureship

Generation and functional characterization of recombinant Porphyromonas gingivalis W83 FimA

Porphyromonas gingivalis (P. gingivalis) is regarded as a keystone pathogen in destructive periodontal diseases. It expresses a variety of virulence factors, amongst them fimbriae that are involved in colonization, invasion, establishment and persistence of the bacteria inside the host cells. The fimbriae also were demonstrated to affect the host immune-response mechanisms. The major fimbriae are able to bind specifically to different host cells, amongst them peripheral blood monocytes. The interaction of these cells with fimbriae induces release of cytokines such as interleukin-1 (IL-1), IL-6, and tumor necrosis factor-α (TNF-α). The aim of this study was to generate recombinant major FimA protein from P. gingivalis W83 fimbriae and to prove its biological activity. FimA of P. gingivalis W83 was amplified from chromosomal DNA, cloned in a vector and transferred into Listeria innocua. (L. innocua).The expressed protein was harvested and purified using FPLC via a His trap HP column. The identity and purity was demonstrated by gel-electrophoresis and mass-spectrometry. The biological activity was assessed by stimulation of human oral epithelial cells and peripheral blood monocytes with the protein and afterwards cytokines in the supernatants were quantified by enzyme linked immunosorbent assay (ELISA) and cytometric bead array. Recombinant FimA could successfully be generated and purified. Gel-electrophoresis and mass-spectrometry confirmed that the detected sequences are identical with FimA. Stimulation of human monocytes induced the release of high concentrations of IL-1β, IL-6, IL-10 and TNF-α by these cells. In conclusion, a recombinant FimA protein was established and its biological activity was proven. This protein may serve as a promising agent for further investigation of its role in periodontitis and possible new therapeutic approaches.

Novel α(2)β(1) integrin-targeted peptide probes for prostate cancer imaging

Accumulating experimental evidence indicates that overexpression of α(2)β(1) integrin may correlate with progression in human prostate cancer. The objective of this study was to design a novel imaging probe based on the Asp-Gly-Glu-Ala (DGEA) peptide for near-infrared-fluorescent (NIRF) imaging of α(2)β(1) integrin expression in prostate cancer. The peptides were conjugated with appropriate fluorescent dyes, and the binding affinity of these probes was evaluated by flow cytometry in three human prostate cell lines (PC-3, CWR-22, and LNCaP). In vivo NIRF imaging of the α(2)β(1)-positive PC-3 xenograft model was performed to evaluate the α(2)β(1) targeted probe. In vitro immunofluorescence staining was carried out to confirm the α(2)β(1) integrin expression level. Flow cytometry analysis showed that PC-3 had the highest probe uptake, followed by CWR-22 and LNCaP tumor cells. In the subcutaneous PC-3 model, the tumor demonstrated prominent uptake with good tumor to background contrast. Immunohistochemistry staining also supported the in vivo optical imaging results. DGEA-based optical agents have been developed for specific imaging of α(2)β(1) integrin expression. In vitro and in vivo localization demonstrated the potential of this agent to identify tumor subtypes amenable to anti-α(2)β(1) integrin treatment and potentially provide prognostic information regarding tumor progression.

Epithelium-fibroblast interactions in response to airway inflammation

Dramatic changes to the architecture of the airway walls have been commonly described in the airways of patients with asthma, cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD). Much research has focused on how airway inflammation drives these structural changes, particularly in terms of the mechanisms/mediators that are involved, and a number of parallels are observed between the disease phenotypes. For example, the increased deposition of extracellular matrix (ECM) at focal sites in the airway wall is seen in asthma and all interstitial lung diseases that involve fibrosis. In addition, increased expression of a number of well characterized cytokines and growth factors, such as TGF-beta and epidermal growth factor (EGF) have been demonstrated in these diseases. However, the role of the lesser-known cytokines, including the leukaemia inhibitory factor (LIF) and other members of the IL-6 family of cytokines in the pathogenesis of airway remodelling and fibrosis is largely unknown. However, the use of genetic manipulation in vivo and more specific inhibitors/antibodies in vitro has now provided increasing evidence to support the hypothesis that a complex interaction exists between these cytokines, ECM and integrins in regulating the function of both epithelial cells and fibroblasts.

Significance of alpha 9 beta 1 and alpha v beta 6 integrin expression in breast carcinoma

BACKGROUND

Both alpha 9 beta 1 and alpha v beta 6 integrins have been newly identified from the tracheal epithelium of guinea pig. It has been pointed out that alpha 9 beta 1 functions as a receptor for tenascin-C and osteopontin. As for the ligands of alpha v beta 6, fibronectin and tenascin-C have been identified. It has not been ascertained whether alpha 9 beta 1 and alpha v beta 6 are expressed in normal breast tissue, benign breast lesion or breast carcinoma.

METHODS

Immunohistochemical staining for alpha 9 beta 1 and alpha v beta 6 was performed in benign breast lesion and breast carcinoma specimens. Western blotting was carried out on 11 breast carcinoma cases.

RESULTS

alpha 9 beta 1 was expressed in the cytoplasm of carcinoma cells in 23 of 90 cases (26%) and alpha v beta 6 in the membrane of carcinoma cells in 16 of 90 cases (18%). However, these findings of alpha 9 beta 1 and alpha v beta 6 did not correlate with any clinicopathological factors including the patients' age, tumor size, histological type of carcinoma, location of carcinoma cells and hormone receptor status. With regard to the histological grade of carcinoma, alpha v beta 6 and alpha 9 beta 1 expression did not statistically correlate, although no expression of alpha v beta 6 was observed in 14 cases of Grade I. On Western-blott analysis strong and weak bands consistent with alpha v beta 6 were noted in the membrane fraction extracted from breast carcinoma cells. On the other hand weak bands consistent with alpha 9 subunit were noted in the whole cell lysates of breast carcinoma cells and very weak or no bands consistent with alpha 9 subunit were noted in the membrane fraction extracted from the breast carcinoma cells.

CONCLUSIONS

Significance of alpha 9 beta 1 and alpha v beta 6 integrins expression in breast carcinoma was still unknown on clinicopathological examination. The findings of Western blot analysis may indicate that the transportation system of glycoproteins such as integrins to the cell membrane of carcinoma cells is disturbed, although these integrins can be produced.

Long-term ambient ozone concentration and the incidence of asthma in nonsmoking adults: the AHSMOG Study

We conducted a prospective study of a cohort of 3091 nonsmokers, ages 27 to 87 years, to evaluate the association between long-term ambient ozone exposure and development of adult-onset asthma. Over a 15-year period, 3.2% of males and 4.3% of females reported new doctor diagnoses of asthma. For males, we observed a significant relationship between report of doctor diagnosis of asthma and 20-year mean 8-h average ambient ozone concentration (relative risk (RR)=2.09 for a 27 ppb increase in ozone concentration, 95% CI=1.03 to 4.16). We observed no such relationship for females. Other variables significantly related to development of asthma were a history of ever-smoking for males (RR=2.37, 95% CI=1.13 to 4.81), and for females, number of years worked with a smoker (RR=1.21 for a 7-year increment, 95% CI=1.04 to 1.39), age (RR=0.61 for a 16-year increment, 95% CI=0.44 to 0.84), and a history of childhood pneumonia or bronchitis (RR=2.96, 95% CI=1.68 to 5.03). Addition of other pollutants (PM10, SO4, NO2, and SO2) to the models did not diminish the relationship between ozone and asthma for males. These data suggest that long-term exposure to ambient ozone is associated with development of asthma in adult males.

The lymphocytic alveolitis in sarcoidosis is associated with increased amounts of soluble and cell-bound adhesion molecules in bronchoalveolar lavage fluid and serum

OBJECTIVES

Pulmonary sarcoidosis is a chronic inflammatory disorder of unknown aetiology accompanied by a lymphocytic alveolitis. It is likely that a selective and temporal expression of adhesion molecules plays a crucial role in the recruitment of cells to the inflammatory site. We investigated the expression of adhesion molecules on alveolar T-lymphocytes and in bronchoalveolar lavage (BAL) fluid and serum to elucidate mechanisms behind the accumulation of cells in the lung in sarcoidosis.

DESIGN

In a cross-sectional study in patients with active and inactive sarcoidosis and in healthy volunteers, we examined, in serum and in BAL fluid, the soluble adhesion molecules, VCAM-1, ICAM-1, and P-, E- and L-selectin. In addition, the expressions of alpha4-beta1 (VLA-4) and alpha5-beta1 (VLA-5) integrins on alveolar T-lymphocytes were analysed.

SETTING

The subjects attended the outpatient clinic at the Division of Respiratory Medicine, Karolinska Hospital, Stockholm, Sweden.

SUBJECTS

Nineteen sarcoidosis patients, nine with clinically active disease, and 13 healthy volunteers were included in the study. The sarcoidosis diagnosis was based on a typical histological and/or clinical (symptoms, radiograph, lung function) picture.

RESULTS

In sarcoidosis patients, particularly in those with active disease, an increase of the expressions of beta1-integrins was accompanied by elevated concentrations in BAL fluid of soluble VCAM-1. In serum, the levels of E-selectin and ICAM-1 were significantly higher in patients with active disease than in those with inactive disease and controls.

CONCLUSIONS

The findings offer some mechanistic explanations as to how the cell-rich alveolitis in sarcoidosis occurs, and furthermore suggest additional markers, such as s-ICAM-1, for assessment of disease activity.

A novel peptide, PLAEIDGIELTY, for the targeting of alpha9beta1-integrins

Targeting gene therapy vectors to abundant receptors on airway epithelia may allow a significant enhancement of gene delivery and thereby be of particular importance for the gene therapy of cystic fibrosis. Alpha9beta1-integrins are highly expressed throughout the human airway epithelia in vivo, irrespective of any particular clinical status. Aiming to improve the targeting of our non-viral integrin-mediated gene transfer systems to airway epithelia, we searched for a short tenascin C-derived peptide which would bind to these integrins. By utilizing recombinant bacteriophages that display overlapping regions of the third fibronectin type III repeat of tenascin C (TNfn3), we were able to localize its alpha9beta1-integrin binding site to the B-C loop of TNfn3. A synthetic Pro-Leu-Ala-Glu-Ile-Asp-Gly-Ile-Glu-Leu-Thr-Tyr peptide (PLAEIDGIELTY) was shown to displace alpha9beta1-integrin-expressing cells completely from binding to TNfn3. This peptide, therefore, may prove useful both for the examination of the functional importance of alpha9beta1-integrins in vivo and the development of gene therapy vectors or drugs targeting these integrins.

Identification of the ligand binding site for the integrin alpha9 beta1 in the third fibronectin type III repeat of tenascin-C

The integrin alpha9 subunit forms a single heterodimer, alpha9 beta1 that mediates cell adhesion to a site within the third fibronectin type III repeat of tenascin-C (TNfn3). In contrast to at least 3 other integrins that bind to this region of tenascin-C, alpha9 beta1 does not recognize the common integrin recognition motif, Arg-Gly-Asp (RGD). In this report, we have used substitution mutagenesis to identify a unique ligand recognition sequence in TNfn3. We introduced mutations substituting alanine for each of the acidic residues in or adjacent to each of the exposed loops predicted from the solved crystal structure. Most of these mutations had little or no effect on adhesion of alpha9-transfected SW480 colon carcinoma cells, but mutations of either of two acidic residues in the B-C loop region markedly reduced attachment of these cells. In contrast, cells expressing the integrin alphav beta3, previously reported to bind to the RGD sequence in the adjacent F-G loop, attached to all mutant fragments except one in which the RGD site was mutated to RAA. The peptide, AEIDGIEL, based on the sequence of human tenascin-C in this region blocked the binding of alpha9-transfected cells, but not beta3-transfected cells to wild type TNfn3. This sequence contains a tripeptide, IDG, homologous to the sequences LDV, IDA, and LDA in fibronectin and IDS in VCAM-1 recognized by the closely related integrin alpha4 beta1. These findings support the idea that this tripeptide motif serves as a ligand binding site for the alpha4/alpha9 subfamily of integrins.