Agents and actions. Supplements最新文献

In addition to inhibition of platelet function, prostacyclin and its stable analogues are reported to attenuate vascular smooth muscle cell proliferation. However, desensitization of prostacyclin responsiveness is a known phenomenon in platelets. In this study we investigated the time-dependent effects of the prostacyclin-mimetic iloprost and of PGE1, respectively, on PDGF-induced proliferation of cultured coronary artery smooth muscle cells. Proliferation, assessed by [3H]thymidine incorporation was markedly inhibited by coincubation with iloprost (100 nM) and PGE1 (100 nM) for 4 h. In contrast, addition of iloprost (100 nM) for 24 h did not decrease smooth muscle cell proliferation, whereas inhibition by PGE1 or by forskolin was not diminished. These results suggest a homologous desensitization of anti-mitogenic effects of iloprost in coronary artery smooth muscle cells, probably at receptor-level.

L-selectin is a lectin cell adhesion molecule expressed on the cell surfaces of lymphocytes, monocytes and granulocytes. Upon leukocyte activation or L-selectin cross-linking the transmembrane-bound L-selectin is rapidly shed from the cell surface. Based on these observations, it has been proposed that L-selectin is proteolytically cleaved from the cell surface. However a panel of common protease inhibitors have no effect on L-selectin proteolysis. To further define the mechanism of L-selectin down-regulation we have produced reagents to study proteolytic fragments of L-selectin. We have developed a trapping ELISA for the detection of soluble L-selectin. In addition we have produced a high affinity polyclonal antisera against the extracellular domain and against the cytoplasmic domain of L-selectin. Both antisera immunoprecipitate the intact form of L-selectin from metabolically labeled PHA lymphoblasts and peripheral blood neutrophils. We review here our progress in defining a 6 kD L-selectin transmembrane peptide (L-STMP) from PMA activated lymphoblasts and fMLP-activated neutrophils. Radiochemical sequencing data indicate that the cleavage site occurs between Lys321 and Ser322 in a short membrane-proximal region of the extracellular domain.

The addition of a nitric oxide-releasing moiety to a number of common nonsteroidal anti-inflammatory drugs markedly reduces their toxicity in the gastrointestinal tract without interfering with their ability to inhibit prostaglandin synthesis. Moreover, the anti-inflammatory and anti-pyretic activities of the nitric-oxide releasing NSAID were comparable to the parent compound, while the anti-thrombotic activity in vivo was significantly enhanced. Nitric oxide-releasing NSAIDs may represent an alternative to existing anti-inflammatory, anti-pyretic and anti-thrombotic agents with greatly reduced toxicity in the gastrointestinal tract.

Secretory phospholipase A2 (sPLA2) is now clearly considered to be involved in the pathogenesis of both experimental and clinical inflammatory processes. This has led academic and pharmaceutical industry researchers to expend enormous efforts to identify specific sPLA2 inhibitors to better understand the role of this enzyme in biological systems and to enable its clinical use in the treatment of inflammation and related disorders. Presented here is a brief review of the biological activity of sPLA2 inhibitors and diseases that may be postulated as their possible targets. Also discussed are problems associated with the evaluation of sPLA2 inhibitors for their selectivity and specificity.

Using site-directed mutagenesis, we have determined the location and composition of the binding sites in human IL-1 alpha and IL-1 beta for the Type I IL-1 receptor (IL-1R). The binding site in each ligand is a discontinuous epitope made up of at least seven amino acids whose side chains are exposed on a contiguous region of the protein surface. Although human IL-1 alpha and IL-1 beta have similar affinities and cross-compete for binding to the human Type I IL-1R, the binding site residues are not identical in the two ligands. In addition, the residues in the binding site of each ligand contribute differently to binding of the human versus the mouse IL-1R. The structure of the IL-1 binding site has implications for the rational design of IL-1 antagonists.

Thromboxane A2 and prostacyclin are the two prostanoids involved in the regulation of the vascular tone. Their release is controlled by the activity of cyclooxygenase which has made this enzyme a preferred pharmacological target. We here report on the distribution of the two isoforms of cyclooxygenase in cultured mesangial cells and on a selective inhibitor of the cytokine-inducible cyclooxygenase-2. We also comment on the structure of thromboxane and prostacyclin synthase and their regulation under physiological and pathophysiological conditions.

In the present study, we have shown that the protein kinase C (PKC) inhibition by staurosporine augmented fMet-Leu-Phe-(FMLP)-induced arachidonic acid (AA) release in human polymorph neutrophils (PMN). This effect is in contradiction to a recently reported mechanism that besides Ca2+, the phosphorylation of cytosolic phospholipase A2 (cPLA2) is essential for the enzyme activation. In addition, we found that staurosporine elevated the basal concentration of intracellular Ca2+, although initial Ca2+ release was not affected. Since thapsigargin, a blocker of endogenous Ca2+ ATPase, also increased AA release dose-dependently, we believe that the elevation of intracellular Ca2+ is the most essential step and not the phosphorylation of enzyme for the activation of cPLA2.

The study shows that endothelial cells from human umbilical veins have a soluble guanylate cyclase which can be activated by sodium nitroprusside (SNP), SIN-1 (3-morpholinosydnonimine) and S35b (4-methyl-3-phenylsulfonylfuroxan). Cells which were pretreated with these compounds showed an inhibition of thrombin-induced arachidonic acid release, PGI2 formation, PAF synthesis and PMNL adhesion. Endothelial guanylate cyclase can also be activated by nitric oxide (NO) which is generated in endothelial cells upon stimulation with thrombin or ionomycin. It is suggested that endogenously produced NO might control cell activation and endothelial function through a cGMP-dependent mechanism.