Localisation of Formyl-Peptide Receptor 2 in the Rat Central Nervous System and Its Role in Axonal and Dendritic Outgrowth.

Arachidonic acid and docosahexaenoic acid (DHA) released by the action of phospholipases A2 (PLA2) on membrane phospholipids may be metabolized by lipoxygenases to the anti-inflammatory mediators lipoxin A4 (LXA4) and resolvin D1 (RvD1), and these can bind to a common receptor, formyl-peptide receptor 2 (FPR2). The contribution of this receptor to axonal or dendritic outgrowth is unknown. The present study was carried out to elucidate the distribution of FPR2 in the rat CNS and its role in outgrowth of neuronal processes. FPR2 mRNA expression was greatest in the brainstem, followed by the spinal cord, thalamus/hypothalamus, cerebral neocortex, hippocampus, cerebellum and striatum. The brainstem and spinal cord also contained high levels of FPR2 protein. The cerebral neocortex was moderately immunolabelled for FPR2, with staining mostly present as puncta in the neuropil. Dentate granule neurons and their axons (mossy fibres) in the hippocampus were very densely labelled. The cerebellar cortex was lightly stained, but the deep cerebellar nuclei, inferior olivary nucleus, vestibular nuclei, spinal trigeminal nucleus and dorsal horn of the spinal cord were densely labelled. Electron microscopy of the prefrontal cortex showed FPR2 immunolabel mostly in immature axon terminals or 'pre-terminals', that did not form synapses with dendrites. Treatment of primary hippocampal neurons with the FPR2 inhibitors, PBP10 or WRW4, resulted in reduced lengths of axons and dendrites. The CNS distribution of FPR2 suggests important functions in learning and memory, balance and nociception. This might be due to an effect of FPR2 in mediating arachidonic acid/LXA4 or DHA/RvD1-induced axonal or dendritic outgrowth.

Resolution of inflammation is altered in Alzheimer's disease.

BACKGROUND: Resolution is the final stage of the inflammatory response, when restoration of tissue occurs. Failure may lead to chronic inflammation, which is known as part of the pathology in the brain of individuals with Alzheimer's disease (AD). METHODS: Specialized pro-resolving mediators (SPMs), receptors, biosynthetic enzyme, and downstream effectors involved in resolution were analyzed in postmortem hippocampal tissue from AD patients and non-AD subjects. SPMs were analyzed in cerebrospinal fluid (CSF). RESULTS: SPMs and SPM receptors were detected in the human brain. Levels of the SPM lipoxin A4 (LXA4) were reduced in AD, both in the CSF and hippocampus. An enzyme involved in LXA4 synthesis and two SPM receptors were elevated in AD brains. LXA4 and RvD1 levels in CSF correlated with Mini-Mental State Examination (MMSE) scores. CONCLUSIONS: A resolution pathway exists in the brain and the alterations described herein strongly suggest a dysfunction of this pathway in AD. MMSE correlations suggest a connection with cognitive function in AD.

Differential expression of the G-protein-coupled formyl Peptide receptor in melanoma associates with aggressive phenotype.

Melanoma, due to its metastatic rate, is among the most aggressive forms of skin cancer. Human formyl peptide receptor (FPR) and its variant FPR-like 1 (FPRL1) have been associated with cell migration and invasiveness in neoplasms. We have studied the in situ expression of these receptors in a large series of melanocytic lesions and correlated the expression with clinicopathological features and prognosis. Tissue microarray blocks of 141 cases including nevi (31 cases), primary (84 cases), and metastatic melanomas (26 cases) were semiquantitatively evaluated by immunohistochemistry for the expression of FPR and FPRL1 proteins. A significant association was observed regarding diagnosis and percentage of cells showing expression of FPR (P = 0.0311) and FPRL1 (P = 0.0053). A gain of FPR immunoreactivity was observed in the lesions having ulceration (P = 0.0194) and Breslow thickness (P = 0.044). Also, high FPRL1 cytoplasmic immunoreactivity was seen in lesions without tumor regression (P = 0.04). In addition, in patients with increased cytoplasmic staining for FPR, the probability of disease-specific survival was significantly lower (log rank test, P = 0.0089). Our findings reveal that FPR and FPRL1 are overexpressed in primary melanoma and correlate with aggressive tumor characteristics, underscoring them as potential therapeutic targets.

Annexin 1 exerts anti-nociceptive effects after peripheral inflammatory pain through formyl-peptide-receptor-like 1 in rat dorsal root ganglion.

BACKGROUND: Annexin 1 (ANXA1) has analgesic effects in inflammatory pain. We aimed to investigate the anti-nociceptive role of ANXA1, at the dorsal root ganglion (DRG) level, through an interaction with formyl-peptide-receptor-like 1 (FPR2/ALX). METHODS: Inflammatory pain was evoked by injecting complete Freund's adjuvant (CFA, 50 µl) into the hindpaw of male Sprague-Dawley rats. The distribution of ANXA1 and FPR2/ALX in L4/5 DRGs was evaluated by immunofluorescence. The expression of ANXA1 was measured by western blot. The involvement of FPR2/ALX in the anti-nociception of ANXA1 was investigated by thermal (irradiant heat) and mechanical (von Frey filament) pain tests with intrathecal (i.t.) ANXA1-derived peptide (Anxa1(2-26)), FPR2/ALX agonist 5(S)-6(R)-7-trihydroxyheptanoic-acid-methyl-ester (BML-111), and antagonist N-t-Boc-Phe-Leu-Phe-Leu-Phe (Boc1). RESULTS: ANXA1 and FPR2/ALX localized in the satellite glial cells and neurones in L4/5 DRGs. CFA treatment (n=20) increased ANXA1 expression in L4/5 DRGs within 7 days (P<0.01). I.T. Anxa1(2-26) (20 and 100 µg µl(-1)) and BML-111 (10 and 100 nmol) reduced CFA-induced thermal and mechanical nociception within 48 h (n=40) (P<0.05). However, i.t. Boc1 10 µg intensified inflammatory pain (P<0.05) and reversed the anti-nociceptive effect of Anxa1(2-26) (n=25) (P<0.05). Moreover, ANXA1 expression increased in L4/5 DRGs after i.t. Anxa1(2-26) (20 µg µl(-1)) (P<0.05) and BML-111 (10 nmol) (P<0.01) but decreased after i.t. Boc1 (10 and 100 µg) alone (P<0.01) or Boc1 (10 µg) co-injection with Anxa1(2-26) (20 µg µl(-1)) (P<0.05). CONCLUSIONS: Endogenous ANXA1 expression at the DRG level is involved in CFA-induced inflammatory pain, and i.t. ANXA1 20 µg µl(-1) produces its anti-nociceptive effect through FPR2/ALX.

Theranostic systems assembled in situ on demand by host-guest chemistry.

Theranostic systems have been explored extensively for a diagnostic therapy in the forms of polymer conjugates, implantable devices, and inorganic nanoparticles. In this work, we report theranostic systems in situ assembled by host-guest chemistry responding to a request. As a model theranostic system on demand, cucurbit[6]uril-conjugated hyaluronate (CB[6]-HA) was synthesized and decorated with FITC-spermidine (spmd) and/or formyl peptide receptor like 1 (FPRL1) specific peptide-spmd by simple mixing in aqueous solution. The resulting (FITC-spmd and/or peptide-spmd)@CB[6]-HA was successfully applied to the bioimaging of its target-specific delivery to B16F1 cells with HA receptors and its therapeutic signal transduction with elevated Ca(2+) and phosphor-extracellular signal-regulated kinase (pERK) levels in FPRL1-expressing human breast adenocarcinoma (FPRL1/MCF-7) cells. Finally, we could confirm in vitro and in vivo stability of the highly specific host-guest interaction. The on-demand theranostic platform technology using host-guest chemistry can be exploited for various bioimaging, biosensing, drug delivery, and tissue engineering applications.