Low Molecular Weight CXCR2 Antagonists as Promising Therapeutics

Abstract

The chemokine receptor CXCR2 recognizes endogenous chemokines that possess a N-terminal Glu-Leu-Arg (ELR) þ amino acid sequence immediately adjacent to their CXC motif. CXCR2 and the closely related receptor CXCR1 are expressed on the cellular surface of leukocytes, notably neutrophils, endothelial cells and a range of other cell types throughout the human body. It has been firmly established now that CXCR2 plays a critical role in the development of numerous inflammatory disorders, wound healing and tumor progression [1-5]. As classically defined for chemokine receptors, CXCR2 mediates cell migration but has also been recognized as a key angiogenic factor [6,7]. These multifunctional roles have drawn increased attention to CXCR2 as a potentially successful drug target for therapeutic intervention in a range of diseases. The first half of this chapter summarizes the biological role of CXCR2 and its involvement, particularly in inflammatory disorders, in order to illuminate the potential clinical impact and relevance of CXCR2 blocking strategies. A review of all currently known low molecular weight (LMW) CXCR2 antagonists is addressed in the second half of this chapter. CXCR2 Ligands and Signal TransductionCXCR2, which shows 78% overall amino acid identity with CXCR1, was first cloned in 1991 out of human promyelocytic leukemia HL60 cells [8]. Subsequent research demonstrated that CXCR2 is the cognate receptor for at least seven structurally related (ELR) þ chemokines, which are growth-related protein (Gro)-a, -b and -c (CXCL1-CXCL3), epithelium-derived neutrophil attractant-78 (ENA-78; CXCL5), granulocyte chemotactic protein-2 (GCP-2; CXCL6), neutrophil-activating peptide-2 (NAP-2; CXCL7) and interleukin-8 (IL-8; CXCL8) [9, 10]. In contrast,