Inhibition of cytokine production and endothelial expression of adhesion antigens by 5'-methylthioadenosine.

We investigated the activity of endogenous nucleoside 5'-deoxy-5'-methylthioadenosine (MTA) on both the production of inflammatory cytokines and the cytokine-dependent endothelial expression of adhesion molecules. The compound inhibited the production of tumor necrosis factor (but not interleukin-1) in lipopolysaccharide-activated macrophages. In addition, MTA selectively inhibited the expression of intercellular adhesion molecule-1 in endothelial cells activated with interleukin-1. This effect was paralleled by a reduction in endothelial adhesiveness for polymorphonuclear leukocytes. These data suggest that MTA might have anti-inflammatory activity.

Alpha v beta 5 integrin is localized at focal contacts by HT-1080 fibrosarcoma cells and human skin fibroblasts attached to vitronectin.

In this study we characterized alpha v beta 5 integrin on HT-1080 fibrosarcoma cells. First, alpha v beta 5 integrin was immunoprecipitated by 125I-surface labeled HT-1080 cells using a polyclonal antibody specific for beta 5 subunit (cytoplasmic domain). A heterodimer consisting of a beta 5-chain running at 100 kD (reduced) and 90 kD (non-reduced) associated with an alpha-chain 145 kD (non-reduced) and 125 kD (reduced) was obtained by SDS-PAGE and autoradiography. By double-immunofluorescence labeling, we then investigated alpha v beta 5 distribution on HT-1080 cells. Upon staining with anti-beta 5 subunit antibody, alpha v beta 5 was detected in focal contacts on cells attached to vitronectin (vn), co-localizing with vinculin at the end of actin filaments. Comparative analysis of alpha v beta 5 and alpha v beta 3 showed that both receptors can occupy the same focal contact, although on the same cell mostly they are clustered in independent focal contacts. Focal distribution of alpha v beta 5 was also found on normal human fibroblasts attached to vn, suggesting that this is not a specific feature of HT-1080 cells. Finally, we investigated the role of alpha v beta 5 and alpha v beta 3 integrins in mediating HT-1080 cell adhesion to vn. Inhibition studies using antibodies with function-blocking activity to alpha v beta 5 and alpha v beta 3 suggest a primary role of alpha v beta 5 to support cell adhesion, with a weak contribute of alpha v beta 3. Their activity can be modulated by divalent cations. Our results provide the first evidence of focal distribution of alpha v beta 5 integrin on cells attached to vn.

Effect of heparin, dermatan sulfate, and related oligo-derivatives on human polymorphonuclear leukocyte functions.

The in vitro effect of unfractionated heparin and dermatan sulfate, as well as oligo-heparin and oligo-dermatan sulfate, on human PMN function was investigated. Superoxide anion generation in fMLP-stimulated PMN was dose-dependently reduced by heparin and oligo-heparin, while DS and oligo-DS lacked inhibitory activity. FMLP-stimulated PMN adhesion to endothelial cells was reduced to a similar extent by both heparin and oligo-heparin, but not by DS and oligo-DS. On the other hand, none of the compounds affected the adhesion of unstimulated PMN to either IL-1- or PMA-activated endothelial cells. Heparin and oligo-heparin also inhibited the homotypic aggregation of fMLP-stimulated PMN. As reported, coincubation of platelets with fMLP-stimulated PMN resulted in platelet activation, a process mainly mediated by the PMN-derived serine protease cathepsin G. Both heparin and DS, as well as their oligo-derivatives, reduced platelet activation induced by either fMLP-stimulated PMN or purified leukocytic cathepsin G. Finally, besides cathepsin G, also the activity of beta-glucuronidase and lysozyme released by stimulated PMN were reduced by heparin, oligo-heparin and DS. These data support the hypothesis that heparin and other GAGs may exert an antiinflammatory role.