Low-Molecular-Weight Versus Protein Inhibitors for the CXCL8/Glycosaminoglycan Interaction: Biophysical Characterization and Cellular Activity

CXCL8, a pro-inflammatory chemokine, which can be induced by TNF-α or IL-1, is responsible for the recruitment and activation of neutrophils. Chemokines interact with glycosaminoglycans on endothelial cells and are thus protected from degradation and sequestration, holding them in an optimal position for recruiting immune cells. Inhibiting the interaction of chemokines with their glycosaminoglycan co-receptors represents an attractive approach for the treatment of chemokine-mediated diseases. Two polyketide-pyrone compounds, PA501 and PA502 were synthesized, which bind to CXCL8 with affinities higher than the natural glycosaminoglycan ligand heparan sulfate, and in a similar range as heparin. Significant structural changes were induced in the chemokine by interacting with the two compounds, as expressed in fluorescence and far-UV CD experiments. In filter binding assays, both compounds were found to displace heparan sulfate efficiently from CXCL8, with PA501 displaying the highest competition efficacy. Using a C-terminally truncated form of the chemokine, CXCL81-58, which lacks the main glycosaminoglycan-binding α-helical domain, the two compounds are suggested to use—to a varying degree—different binding sites on the protein, which have also been proposed for the natural heparan sulfate ligand. In a transmigration assay, PA501 and PA502 exhibited dose-dependent modulation of CXCL8-induced neutrophil mobilization and migration. The compounds PA501 and PA502 may thus be regarded as early novel lead compounds in the quest for anti-inflammatory, chemokine-targeting drugs.