Correction: Microsomal prostaglandin E synthase-1 gene deletion impairs neuro-immune circuitry of the cholinergic anti-inflammatory pathway in endotoxaemic mouse spleen.

[This corrects the article DOI: 10.1371/journal.pone.0193210.]

Acute and subchronic treatments with selective serotonin reuptake inhibitors increase Nociceptin/Orphanin FQ (NOP) receptor density in the rat dorsal raphe nucleus; interactions between nociceptin/NOP system and serotonin

International audienceNociceptin/Orphanin FQ is the endogenous ligand of NOP receptor, formerly referred to as the Opioid Receptor-Like 1 receptor. We have previously shown that NOP receptors were located on serotonergic neurons in the rat dorsal raphe nucleus, suggesting possible direct interactions between nociceptin and serotonin in this region, which is a target for antidepressant action. In the present study, we investigated further the link between Selective Serotonin Reuptake Inhibitor (SSRI) antidepressant treatments and the nociceptin/NOP receptor system. Intraperitoneal administration of the SSRI citalopram induced an increase in NOP-receptor density, measured by autoradiographic [3H] nociceptin binding, in the rat dorsal raphe nucleus, from the first to the 21st day of treatment. This effect was also observed with other SSRIs (sertraline, fluoxetine), but not with two tricyclic antidepressants (imipramine, clomipramine) and was abolished by pre-treatment with para-chlorophenylalanine, an inhibitor of serotonin synthesis. Using microdialysis experiments, we demonstrated that NOP-receptor activation by infusion of nociceptin 10−6 M or 10−5 M increased the level of extracellular serotonin in the dorsal raphe nucleus. This effect was abolished by co-infusion of the NOP-receptor antagonist UFP 101. These results confirm the existence of reciprocal interactions between serotonin and nociceptin/NOP transmissions in the dorsal raphe nucleus

Evidence of different mediators of central inflammation in dysfunctional and inflammatory pain — Interleukin-8 in fibromyalgia and interleukin-1 β in rheumatoid arthritis

AbstractThe purpose of this study was to relate central inflammation to autonomic activity (heart rate variability (HRV)) in patients with rheumatoid arthritis (RA) and fibromyalgia (FM). RA patients had reduced parasympathetic activity and FM patients had increased sympathetic activity compared to healthy controls. Comparisons between RA and FM showed higher cerebrospinal fluid (CSF) interleukin (IL)-1β inversely correlated to parasympathetic activity in RA. The FM patients had higher concentrations of CSF IL-8, IL-1Ra, IL-4 and IL-10, but none of these cytokines correlated with HRV. In conclusion, we found different profiles of central cytokines, i.e., elevated IL-1β in inflammatory pain (RA) and elevated IL-8 in dysfunctional pain (FM)

Microsomal prostaglandin E synthase-1 gene deletion impairs neuro-immune circuitry of the cholinergic anti-inflammatory pathway in endotoxaemic mouse spleen

<div><p>The cholinergic anti-inflammatory pathway (CAP) is an innate neural reflex where parasympathetic and sympathetic nerves work jointly to control inflammation. Activation of CAP by vagus nerve stimulation (VNS) has paved way for novel therapeutic strategies in treating inflammatory diseases. Recently, we discovered that VNS mediated splenic acetylcholine (ACh) release and subsequent immunosuppression in response to LPS associated inflammation is impaired in mice lacking microsomal prostaglandin E synthase-1 (mPGES-1) expression, a key enzyme responsible for prostaglandin E2 synthesis. Here, we have further investigated the consequences of mPGES-1 deficiency on various molecular/cellular events in the spleen which is critical for the optimal functioning of VNS in endotoxaemic mice. First, VNS induced splenic norepinephrine (NE) release in both mPGES-1 (+/+) and (-/-) mice. Compared to mPGES-1 (+/+), immunomodulatory effects of NE on cytokines were strongly compromised in mPGES-1 (-/-) splenocytes. Interestingly, while LPS increased choline acetyltransferase (ChAT) protein level in mPGES-1 (+/+) splenocytes, it failed to exert similar effects in mPGES-1 (-/-) splenocytes despite unaltered β₂ AR protein expression. In addition, nicotine inhibited TNFα release by LPS activated mPGES-1 (+/+) splenocytes <i>in vitro</i>. However, such immunosuppressive effects of nicotine were reversed both in mPGES-1 (-/-) mouse splenocytes and human PBMC treated with mPGES-1 inhibitor. In summary, our data implicate PGE2 as an important mediator of ACh synthesis and noradrenergic/cholinergic molecular events in the spleen that constitute a crucial part of the CAP immune regulation. Our results suggest a possible link between cholinergic and PG system of CAP that may be of clinical significance in VNS treatment.</p></div

Cytokine profiling of activated mPGES-1 (-/-) splenocytes in response to NE stimulation.

<p>Primary splenocyte cultures established from mPGES-1 (+/+) and (-/-) mice were pretreated with norepinephrine (NE) at 1μM concentration for 30 mins and then activated with the endotoxin, LPS (100ng/ml). Cell supernatants were analyzed for cytokine production following 3 hours of treatment. (*p<0.05; LPS versus LPS+NE). (^# p<0.05; mPGES-1(+/+) versus (-/-) within LPS+NE treatment; student’s T-test). Each sample was run as duplicates during the assay and values are represented as mean ±SEM from 3 independent experiments. Statistical analysis was done using One-way ANOVA unless otherwise indicated.</p

<i>In vitro</i> mPGES-1 blockade impairs nicotine’s limiting effects on TNFα production by LPS activated human peripheral blood mononuclear cells (PBMCs).

<p>Human PBMC cultures were freshly prepared from healthy blood donors using ficoll density gradient separation. (a) TNFα levels measured by ELISA in culture supernatants after treatment with endotoxin, LPS (100ng/ml) for 6, 14 and 20 hours respectively. Untreated cells served as control. TNFα levels in the culture supernatants were measured by ELISA (*p>0.05, **p<0.01; control versus LPS; One-way ANOVA, *p>0.05; LPS versus LPS+mPGES-1 inhibitor; One-way ANOVA). (b) TNFα levels measured by ELISA in culture supernatants after treatment with nicotine (100 μM) for 14 hours. (*p>0.05; LPS versus LPS+ Nicotine; One-way ANOVA, **p>0.05; LPS+ Nicotine versus LPS+Nicotine+mPGES-1 inhibitor; One-way ANOVA). Each sample was run as duplicates during ELISA and values are represented as mean ±SEM from (a) 3 and (b) 4 independent experiments.</p

Immunomodulatory effects of α7nAChR agonist nicotine on LPS activated mouse splenocytes is reversed by mPGES-1 gene deletion.

<p>Primary splenocyte cultures of mPGES-1(+/+) and (-/-) mice were pretreated with nicotine (100 μM) for 30 mins and later activated with the endotoxin, LPS (10ng/ml). Cell supernatants were analyzed for LPS induced cytokine production following 3 hour incubation. (a) TNFα as measured in cell culture supernatants by ELISA. (*p<0.05; LPS versus LPS+Nicotine within WT; One-way ANOVA, n.s. p>0.05; WT versus KO within LPS+Nicotine treatment group; One-way ANOVA). (b) Fold change of TNFα, KC Gro and IL-1β as measured in cell culture supernatants by Multiplex assay (*p<0.05; LPS versus LPS+Nicotine within WT; One-way ANOVA). Each sample was run as duplicates during ELISA and values are represented as mean ±SEM from 3 independent experiments. Due to high variations between individual experiments, cytokine production in each group was normalized to TNF α level induced by LPS and represented as % fold change.</p

Lipopolysaccharide activated splenocytes lacking mPGES-1 gene expression display an altered response to NE stimulation.

<p>Primary splenocyte cultures established from mPGES-1 (+/+) and (-/-) mice were pretreated with norepinephrine (NE) at 1, 10 and 100 μM concentration for 30 mins and then activated with the endotoxin, LPS (100ng/ml). Cell supernatants were analyzed for cytokine production following 3 hours of treatment. ^a,b p<0.0001; LPS versus LPS+NE within WT or KO; One-way ANOVA. ^# p<0.05; mPGES-1(+/+) versus mPGES-1 (-/-) within LPS+NE treatment; student’s T-test. Each sample was run as duplicates during the assay and values are represented as mean ±SEM from 3 independent experiments.</p

LPS fails to increase choline acetyltransferase (ChAT) expression in the absence of mPGES-1 expression.

<p>Primary splenocyte cultures from mPGES-1(+/+) and (-/-) mice were grown on chamber slides and treated with the endotoxin, LPS (10ng/ml). Following 20 hour treatment, cells were paraformaldehyde fixed and stained for ChAT protein expression. (a) Representative microscope images showing ChAT staining (green) and nuclear staining with DAPI (blue). (b) Microscopic analysis of unstimulated and LPS treated mPGES-1(+/+) and (-/-) splenocytes. (* p<0.05; LPS versus control within mPGES-1(+/+); Mann-Whitney Test). (*p<0.05; mPGES-1(+/+) versus (-/-) within the LPS treatment group; Mann-Whitney Test). Each treatment condition was performed in duplicates on the chamber slides and values are represented as mean ±SEM. Quantitative analysis for ChAT positive cells includes measurement of 7 different fields obtained from two independent experiments.</p