Phosphocholine-Modified Lipooligosaccharides of Haemophilus influenzae Inhibit ATP-Induced IL-1β Release by Pulmonary Epithelial Cells

Abstract

Phosphocholine-modified bacterial cell wall components are virulence factors enabling immune evasion and permanent colonization of the mammalian host, by mechanisms that are poorly understood. Recently, we demonstrated that free phosphocholine (PC) and PC-modified lipooligosaccharides (PC-LOS) from Haemophilus influenzae, an opportunistic pathogen of the upper and lower airways, function as unconventional nicotinic agonists and efficiently inhibit the ATP-induced release of monocytic IL-1β. We hypothesize that H. influenzae PC-LOS exert similar effects on pulmonary epithelial cells and on the complex lung tissue. The human lung carcinoma-derived epithelial cell lines A549 and Calu-3 were primed with lipopolysaccharide from Escherichia coli followed by stimulation with ATP in the presence or absence of PC or PC-LOS or LOS devoid of PC. The involvement of nicotinic acetylcholine receptors was tested using specific antagonists. We demonstrate that PC and PC-LOS efficiently inhibit ATP-mediated IL-1β release by A549 and Calu-3 cells via nicotinic acetylcholine receptors containing subunits α7, α9, and/or α10. Primed precision-cut lung slices behaved similarly. We conclude that H. influenzae hijacked an endogenous anti-inflammatory cholinergic control mechanism of the lung to evade innate immune responses of the host. These findings may pave the way towards a host-centered antibiotic treatment of chronic airway infections with H. influenzae.

Conopeptides [V11L;V16D]ArIB and RgIA4: Powerful Tools for the Identification of Novel Nicotinic Acetylcholine Receptors in Monocytes

“…Whether stimulation of immune cells with nAChR agonists induces ion-channel functions is unclear. In most studies, no ion-currents have been detected in response to nAChR agonists (Peng et al, 2004; Razani-Boroujerdi et al, 2007; Hecker et al, 2009, 2015; Mikulski et al, 2010; Richter et al, 2016, 2018a; Zakrzewicz et al, 2017). However, stimulation of murine intestinal macrophages with agonists of α7 nAChR evoked small Ca 2+ transients (Matteoli et al, 2014).…”

“…Apart from conventional nAChR agonists, phosphocholine stimulates monocytic nAChRs and inhibits ATP-induced IL-1β release (Hecker et al, 2015; Richter et al, 2016, 2018a,b; Figure 1). The response of monocytic cells to free phosphocholine resembles that of choline: IC 50 values are in the range of 10 μM, signaling involves nAChR subunits α7, α9, and α10, both compounds do not elicit ion-currents at U937 cells, but inhibit the ion-channel function of the P2X7R (Hecker et al, 2015; Richter et al, 2016).…”

“…Under physiological conditions, CRP forms Ca 2+ -dependent complexes with phosphocholine and other compounds with a phosphocholine head-group at a stoichiometric proportion of 1:1 per monomer (Pepys and Hirschfield, 2003; Mantovani et al, 2008). Native CRP-ligand complexes are potent nAChR agonists at human monocytic cells that inhibit the ATP-dependent inflammasome assembly (Figure 1) and IL-1β release, whereas CRP devoid of ligands is ineffective (Richter et al, 2018a). The IC 50 of CRP isolated from human bodily fluids is about 40 nM, far below that of phosphocholine (10 μM), suggesting that CRP potentiates the effect of free phosphocholine (Richter et al, 2018a).…”

“…Native CRP-ligand complexes are potent nAChR agonists at human monocytic cells that inhibit the ATP-dependent inflammasome assembly (Figure 1) and IL-1β release, whereas CRP devoid of ligands is ineffective (Richter et al, 2018a). The IC 50 of CRP isolated from human bodily fluids is about 40 nM, far below that of phosphocholine (10 μM), suggesting that CRP potentiates the effect of free phosphocholine (Richter et al, 2018a). The effects of CRP-phosphocholine complexes on monocytic cells are sensitive to [V11L;V16D]ArIB and RgIA4, depend on interaction of nAChR subunits α7, α9, α10, and resemble silent agonists or partial antagonists at canonical α9α10 nAChR (Richter et al, 2018a).…”

Curses or Cures: A Review of the Numerous Benefits Versus the Biosecurity Concerns of Conotoxin Research

“…Lastly, conotoxins are among the most rapidly evolving gene products known in nature and have served as tools in a diverse range of studies on the effects of feeding ecology, prey taxa, dietary breadth, age and geographical heterogeneity on the evolution of venom genes [72][73][74][75][76], and studies on the role of gene duplication and positive selection on venom gene expression and diversification [77][78][79]. Elucidating peptide biosynthesis and folding [68][69][70] α-ImI α7 nAChR Subtype selectivity [56] Targeted drug delivery in cancer [62], engineering D. melanogaster as better human disease model [61], chromaffin cell signaling [57] α-MII nAChR Subtype selective [80] Inflammation [81], reward and addiction [82,83] α-Vc1.1 and α-Rg1A α9α10 nAChR Subtype selective [84,85] Neuropathic pain and inflammation [86][87][88], immunology [89][90][91] Con-ikot-ikot AMPA receptor…”