Lipopolysaccharide-Neutralizing Peptide Modulates P2X7 Receptor-Mediated Interleukin-1β Release

Lipopolysaccharide (LPS)-neutralizing peptides are emerging as new potential therapeutic modalities to treat sepsis and skin infections. Purinergic ligand-gated ion channels (P2X receptors) play a critical role in various biological processes, including inflammation. Recent drug development efforts have significantly focused on the modulation of P2X receptors. Here, we investigated the effects of the synthetic LPS-neutralizing peptide Pep19–2.5 on human P2X receptors in cells of the innate immune system. Pep19–2.5 concentration-dependently triggered Ca2+ influx, interleukin (IL)-1β, and lactate dehydrogenase (LDH) release in Toll-like receptor-stimulated human macrophages and monocytes. Ca2+ influx was mediated at least partially by P2X7 receptors, and IL-1β and LDH release by P2X7 receptors, respectively. Confocal microscopy confirmed the colocalization of Pep19–2.5 with P2X7 receptors. Pep19–2.5-induced IL-1β release in primed cells was dependent on K+ efflux, caspase-1, and the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing protein 3 inflammasome. In the presence of the P2X7 receptor agonist 2′(3′)-O-(4-benzoylbenzoyl)adenosine-5′-triphosphate, Pep19–2.5 reduced IL-1β and LDH release. In 1321N1, astrocytoma cells stably transfected with human P2X receptors, Pep19–2.5 potently modulated P2X7 and P2X4 receptors (IC50 values of 0.346 and 0.146 μM, respectively) but showed less (P2X1, P2X3) or no activity (P2X2) at other P2X receptor subtypes. Our findings underline the potential of LPS-neutralizing peptides as modulators of P2X receptors, thus expanding their applicability beyond the treatment of sepsis to the treatment of inflammatory diseases.