Human neutrophil formyl peptide receptor phosphorylation and the mucosal inflammatory response

Abstract

Bacterial/mitochondrial fMLF analogs bind FPR1, driving accumulation/activation of PMN at sites of infection/injury, while promoting wound healing in epithelia. We quantified levels of UFPR1 and TFPR1 in isolated PMN by use of phosphosensitive NFPRb and phosphorylation-independent NFPRa antibodies. UFPR1 and total TFPR were assessed inflamed mucosa, observed in human IBD. In isolated PMN after fMLF stimulation, UFPR1 declined 70% ((fMLF)EC50 = 11 ± 1 nM; t1/2 = 15 s) and was stable for up to 4 h, whereas TFPR1 changed only slightly. Antagonists (tBoc-FLFLF, CsH) and metabolic inhibitor NaF prevented the fMLF-dependent UFPR1 decrease. Annexin A1 fragment Ac2-26 also induced decreases in UFPR1 ((Ac2-26)EC50 ∼ 3 µM). Proinflammatory agents (TNF-α, LPS), phosphatase inhibitor (okadaic acid), and G-protein activator (MST) modestly increased (fMLF)EC50, 2- to 4-fold, whereas PTX, Ca(2+) chelators (EGTA/BAPTA), H2O2, GM-CSF, ENA-78, IL-1RA, and LXA4 had no effect. Aggregation-inducing PAF, however, strongly inhibited fMLF-stimulated UFPR1 decreases. fMLF-driven PMN also demonstrated decreased UFPR1 after traversing monolayers of cultured intestinal epithelial cells, as did PMN in intestinal mucosal samples, demonstrating active inflammation from UC patients. Total TFPR remained high in PMN within inflamed crypts, migrating through crypt epithelium, and in the lamina propria-adjoining crypts, but UFPR1 was only observed at some peripheral sites on crypt aggregates. Loss of UFPR1 in PMN results from C-terminal S/T phosphorylation. Our results suggest G protein-insensitive, fMLF-dependent FPR1 phosphorylation in isolated suspension PMN, which may manifest in fMLF-driven transmigration and potentially, in actively inflamed tissues, except at minor discrete surface locations of PMN-containing crypt aggregates.

Annexin A1‑mediated inhibition of inflammatory cytokines may facilitate the resolution of inflammation in acute radiation‑induced lung injury

“…A similar correlation between ANXA1 and IL-6 was also observed following fibroblastoma irradiation treatment (43). ANXA1 can induce apoptosis in neutrophils (44), and inhibit neutrophil migration and accumulation in the inflammatory area (45). In the present study, the expression of ANXA1 was increased in patients with RILI without an evident reduction of neutrophils in the circulation system, but with a significant reduction in the level of MPO.…”

Neutrophil interactions with epithelial-expressed ICAM-1 enhances intestinal mucosal wound healing

“…We next examined the role of ICAM-1 in epithelial wound healing in-vivo, using a colonic-mucosal, biopsy-based-wound model. 11 , 34 , 35 In this setup, superficial mucosal wounds were introduced to colons of wild type (WT) and ICAM-1-deficient (ICAM-1ko) mice. Immunofluorescence and western blot analyses of extracted mucosal wounds revealed increased expression of ICAM-1 by IECs ( Supplementary Figure S3a,b ).…”

Inflammation and the Intestinal Barrier: Leukocyte–Epithelial Cell Interactions, Cell Junction Remodeling, and Mucosal Repair

“…Recruitment of additional neutrophils stimulates clearance of dead PMNs and microbes by macrophages and promotes repair of the epithelial barrier. 164–166 Resolvin E1 reduces leukocyte infiltration, decreases inflammatory cytokines (Il12 subunit p40 and TNF), and prevents development of colitis in mice given 2,4,6-trinitrobenzene sulfonic acid. 167 Engagement of the chemerin chemokine-like receptor 1 by Resolvin E1 inhibits recruitment of PMNs and mediates clearance of neutrophils, via induction of the anti-adhesion protein CD55.…”