No abstract

Intraepithelial lymphocytes (IEL) utilize the integrin alphaebeta7 on their surface to bind to E-cadherin on epithelial cells in the gut and breast. In oral mucosa and skin IEL express alphaebeta7 and the cutaneous lymphocyte-associated antigen (CLA) but the mechanisms of adhesion of these subsets to keratinocytes are unknown. Levels of alphaebeta7 and CLA were up-regulated on peripheral blood lymphocytes (PBL) by transforming growth factor-beta (TGF-beta) and interleukin-12 (IL-12), respectively, and both groups of lymphocytes adhered onto oral and skin keratinocytes. Adhesion of IL-12-activated PBL was totally abolished by anti-lymphocyte-associated function antigen type 1 (anti-LFA-1) antibodies but was unaffected by anti-alphaebeta7 antibodies indicating that adhesion of the CLA-positive subset is mediated via LFA-1 interaction with intercellular adhesion molecule-1 (ICAM-1). Adhesion of TGF-beta-activated PBL to E-cadherin-positive oral and skin keratinocytes was partially inhibited by anti-alphaebeta7 antibodies but was unaffected by the blocking antibody E4.6 against E-cadherin which detects the binding site for alphaebeta7-positive lymphocytes in breast and gut epithelium. TGF-beta-activated PBL also bound to an E-cadherin-negative oral keratinocyte cell line and adhesion was inhibited by anti-alphaebeta7 antibodies. These results strongly suggest that in oral epithelium and epidermis alphaebeta7-positive lymphocytes do not bind to E-cadherin and there may be a novel second ligand for the alphaebeta7 integrin.

Matrix metalloproteinases (MMPs) are Zn2+ dependent proteases produced by a variety of cell types. They have a fundamental role in tissue remodelling, tumour invasion and metastasis. Scatter factor (SF), secreted by fibroblasts, has a paracrine action on epithelial cells and binds the trans-membrane c-met receptor inducing loss of adhesion, cell motility and invasiveness in vitro. The purpose of this study was to test if SF can regulate the production of MMPs by epithelial cells. Supernatants from oral squamous cell carcinoma-derived cells (H375 and H376), a human keratinocyte line (UP), and primary cultures of oral mucosal keratinocytes, grown in the presence or absence of SF, were analysed using 0.1% gelatin zymography. MMPs were characterised by comparison with human recombinant enzymes and by the use of specific inhibitors. Oral mucosal keratinocytes, UP, and H357 cells expressed MMP-2 and MMP-9, whilst H376 cells only expressed MMP-2. SF increased the expression of MMP-9 in UP and MMP-2 in H376 supernatants. Both MMP-2 and MMP-9 activity were increased in H357 and normal keratinocyte supernatants. This could be blocked using a human recombinant anti-SF antibody. In all epithelial lines tested, c-Met, the cell surface receptor for SF, could be detected. The results indicate that SF stimulates MMP expression in UP, H376, H357, and normal oral mucosal cells and points to a role for SF in the regulation of oral keratinocyte behaviour in wound healing and neoplasia.

The development of the CNS is associated with an increasing use of the 30-bp variable alternative, spliced exon (VASE) in neural cell adhesion molecule (NCAM). We have assessed the relative usage of VASE by reverse transcriptase-linked polymerase chain reaction in the developing cerebellum and hippocampus at times when neurons isolated from these tissues can respond to substrate-associated NCAM by increased axonal growth and also at later developmental stages, when they are no longer responsive to substrate-associated NCAM. Neurons isolated from the developing cerebellum at postnatal day 6 respond to NCAM with increased neurite growth. NCAM transcripts from these cells were found to have negligible levels of VASE usage. In contrast, neurons that are isolated at later stages of development (postnatal days 8, 10, and 11) and do not respond to NCAM were found to synthesise a much higher proportion of NCAM transcripts containing VASE. In the hippocampus, embryonic day 18 neurons, which are responsive to NCAM, express low levels of VASE, whereas postnatal days 4 and 5 neurons, which are not responsive to NCAM, have a greater proportion of transcripts containing VASE. Thus, the level of NCAM VASE exon usage by neurons appears to be a good indicator of the ability of these cells to respond to non-VASE-containing NCAM (expressed in a cellular substratum) by increased neurite outgrowth.