heparitin-sulfate and Hypersensitivity

Glycosaminoglycans (GAGs) are large, polyanionic molecules expressed throughout the body. The GAG heparin, co-released with histamine, is synthesised by and stored exclusively in mast cells, whereas the closely related molecule heparan sulphate is expressed, as part of a proteoglycan, on cell surfaces and throughout tissue matrices. These molecules are increasingly thought to play a role in regulation of the inflammatory response and heparin like molecules are now being seriously considered to hold potential in the treatment of inflammatory diseases such as asthma. Heparin and related molecules have been found to exert anti-inflammatory effects in a wide range of in vitro assays, animal models and in human disease. The anti-inflammatory activities of heparin are independent of the well-established anticoagulant activity of heparin, suggesting that the separation of these properties could yield novel anti-inflammatory drugs, which may be useful in the future treatment of inflammatory diseases.

Topics: Animals; Anti-Inflammatory Agents; Glucuronidase; Glycosaminoglycans; Heparin; Heparitin Sulfate; Humans; Hypersensitivity; Inflammation; Mast Cells

Heparan sulfate proteoglycans (HSPGs) are glycoproteins consisting of a core protein to which linear heparan sulfate (HS) side chains are covalently attached. These HS side chains mediate a variety of biologic functions involved in inflammation. Radionuclide imaging of HS side chains in tissues with inflammation may be used for the stratification of patients who would most likely benefit from HSPG-targeting therapy. The goal of this study was to evaluate the feasibility of in vivo radionuclide imaging of HS side chain expression in a mouse model of asthma using the recombinant eosinophil cationic protein (rECP).. rECP was radioiodinated with (125)I or (123)I using the Chloramine-T method. The 50% inhibitory concentration value for (125)I-labeled rECP was determined in a competitive cell-binding assay using Beas-2B cells. The binding of radiolabeled rECP to HS side chains was evaluated both in vitro and in vivo. The biodistribution of radiolabeled rECP was assessed in asthma mice or in control mice using SPECT imaging, ex vivo biodistribution measurements, and microautoradiography.. The 50% inhibitory concentration value for (125)I-rECP was 7.4 ± 0.1 nM. The loss of HS side chains substantially inhibited the cellular and tissue uptake of (125)I- or (123)I-rECP, indicating that HS side chains of HSPGs are required for (125)I- or (123)I-eosinophil cationic protein binding and uptake both in vitro and in vivo. SPECT imaging demonstrated an appreciably higher accumulation of radioactivity in the lungs of asthma mice than in those of control mice. Ex vivo biodistribution studies also confirmed that there was at least a 4-fold increase in the lung-to-muscle ratio of asthma mice, compared with control mice. The accumulation of radiolabeled rECP was linearly correlated with leukocyte infiltration.. This study illustrates the feasibility of using radiolabeled rECP for the visualization of HS side chains of HSPGs and the evaluation of allergic lung inflammation in living subjects. Our data indicate that radiolabeled rECP is a novel imaging agent for HS side chains of HSPGs in predicting allergic lung inflammation in living mice.

Topics: Allergens; Animals; Asthma; Biological Transport; Cell Line, Tumor; Disease Models, Animal; Drug Stability; Eosinophil Cationic Protein; Female; Gene Expression Regulation; Heparitin Sulfate; Humans; Hypersensitivity; Inflammation; Iodine Radioisotopes; Isotope Labeling; Leukocytes; Mice; Molecular Imaging; Multimodal Imaging; Positron-Emission Tomography; Radiochemistry; Recombinant Proteins; Tomography, X-Ray Computed