Substance P primes lipoteichoic acid‐ and Pam3CysSerLys4‐mediated activation of human mast cells by up‐regulating Toll‐like receptor 2

Abstract

Summary Substance P (SP) is a neuropeptide with neuroimmunoregulatory activity that may play a role in susceptibility to infection. Human mast cells, which are important in innate immune responses, were analysed for their responses to pathogen‐associated molecules via Toll‐like receptors (TLRs) in the presence of SP. Human cultured mast cells (LAD2) were activated by SP and TLR ligands including lipopolysaccharide (LPS), Pam3CysSerLys4 (Pam3CSK4) and lipoteichoic acid (LTA), and mast cell leukotriene and chemokine production was assessed by enzyme‐linked immunosorbent assay (ELISA) and gene expression by quantitative PCR (qPCR). Mast cell degranulation was determined using a β‐hexosaminidase (β‐hex) assay. SP treatment of LAD2 up‐regulated mRNA for TLR2, TLR4, TLR8 and TLR9 while anti‐immunoglobulin E (IgE) stimulation up‐regulated expression of TLR4 only. Flow cytometry and western blot confirmed up‐regulation of TLR2 and TLR8. Pretreatment of LAD2 with SP followed by stimulation with Pam3CSK4 or LTA increased production of leukotriene C4 (LTC4) and interleukin (IL)‐8 compared with treatment with Pam3CSK4 or LTA alone (> 2‐fold; P < 0·01). SP alone activated 5‐lipoxygenase (5‐LO) nuclear translocation but also augmented Pam3CSK4 and LTA‐mediated 5‐LO translocation. Pam3CSK4, LPS and LTA did not induce LAD2 degranulation. SP primed LTA and Pam3CSK4‐mediated activation of JNK, p38 and extracellular‐signal‐regulated kinase (ERK) and activated the nuclear translocation of c‐Jun, nuclear factor (NF)‐κB, activating transcription factor 2 (ATF‐2) and cyclic‐AMP‐responsive element binding protein (CREB) transcription factors. Pretreatment with SP followed by LTA stimulation synergistically induced production of chemokine (C‐X‐C motif) ligand 8 (CXCL8)/IL‐8, chemokine (C‐C motif) ligand 2 (CCL2)/monocyte chemotactic protein 1 (MCP‐1), tumour necrosis factor (TNF) and IL‐6 protein. SP primes TLR2‐mediated activation of human mast cells by up‐regulating TLR expression and potentiating signalling pathways associated with TLR. These results suggest that neuronal responses may influence innate host defence responses.

Differential Effects of the Toll-like Receptor 2 Agonists, PGN and PAM3CSK4, on Substance P-Induced Human Mast Cell Activation

“…Synergistic release of IL-8 and TNF-a through upregulation of TLR2 expression was observed in a previous study where LAD2 cells were pre-incubated with SP for 24 h prior to being challenged with lipoteichoic acid or Pam3CSK4 (23). In contrast, our data showed that the two commonly employed TLR2 agonists, PGN and Pam3CSK4, differentially modulated SP-induced human mast cell activation via distinct mechanisms when the cells were challenged with SP together or after 24-h pre-incubation with the TLR2 ligands.…”

The Role of Eosinophils and Mast Cells in Intestinal Functional Disease

“…As TLR-3 and TLR-7 recognize viral RNA sequences, these results suggest GM-CSF may have a role in enhancing mast cell responses to viral infection. Substance P primes mast cells by up-regulating TLR-2 expression and potentiating associated downstream signalling pathways [77]. Interestingly, substance Pimmunoreactive nerve fibers were reported to be more prevalent in rectosigmoid biopsies from IBS subjects and associated with low-grade inflammation, compared to controls, therefore neuronal responses may modulate innate immunity in IBS [78].…”

Mast cells in endometriosis: guilty or innocent bystanders?

“…SP is known to provide a positive feedback on MCs by causing degranulation and the release of pro-inflammatory mediators that, in turn, can attract other inflammatory cells [31][32][33].…”