The cholinergic anti-inflammatory pathway inhibits inflammation without lymphocyte relay

The magnitude of innate inflammatory immune responses is dependent on interactions between peripheral neural and immune cells. In particular, a cholinergic anti-inflammatory pathway (CAP) has been identified in the spleen whereby noradrenaline (NA) released by splenic nerves binds to ß2-adrenergic receptors (β2-AR) on CD4⁺ T cells which, in turn, release acetylcholine (ACh). The binding of ACh to α7 acetylcholine receptors (α7-AChR) expressed by splenic macrophages inhibits the production of inflammatory cytokines, including tumor necrosis factor (TNF). However, the role of ACh-secreting CD4⁺ T-cells in the CAP is still controversial and largely based on the absence of this anti-inflammatory pathway in mice lacking T-cells (nude, FoxN1^-/-). Using four conscious, non-lymphopenic transgenic mouse models, we found that, rather than acting on CD4⁺ T-cells, NA released by splenic nerve terminals acts directly onto β2-AR on splenic myeloid cells to exert this anti-inflammatory effect. We also show that, while larger doses of LPS are needed to trigger CAP in nude mouse strain compared to other strains, TNF production can be inhibited in these animals lacking CD4⁺ T-cell by stimulating either the vagus or the splenic nerve. We demonstrate that CD4+ T-cells are dispensable for the CAP after antibody-mediated CD4+ T-cell depletion in wild type mice. Furthermore, we found that NA-mediated inhibition of in vitro LPS-induced TNF secretion by human or porcine splenocytes does not require α7-AChR signaling. Altogether our data demonstrate that activation of the CAP by stimulation of vagus or splenic nerves in mice is mainly mediated by direct binding of NA to β2-AR on splenic macrophages, and suggest that the same mechanism is at play in larger species.

Survey of allele specific expression in bovine muscle

Allelic imbalance is a common phenomenon in mammals that plays an important role in gene regulation. An Allele Specific Expression (ASE) approach can be used to detect variants with a cis-regulatory effect on gene expression. In cattle, this type of study has only been done once in Holstein. In our study we performed a genome-wide analysis of ASE in 19 Limousine muscle samples. We identified 5,658 ASE SNPs (Single Nucleotide Polymorphisms showing allele specific expression) in 13% of genes with detectable expression in the Longissimus thoraci muscle. Interestingly we found allelic imbalance in AOX1, PALLD and CAST genes. We also found 2,107 ASE SNPs located within genomic regions associated with meat or carcass traits. In order to identify causative cis-regulatory variants explaining ASE we searched for SNPs altering binding sites of transcription factors or microRNAs. We identified one SNP in the 3’UTR region of PRNP that could be a causal regulatory variant modifying binding sites of several miRNAs. We showed that ASE is frequent within our muscle samples. Our data could be used to elucidate the molecular mechanisms underlying gene expression imbalance.

Environmental signals perceived by the brain abate pro-metastatic monocytes by dampening glucocorticoids receptor signaling

While positive social-behavioral factors predict longer survival in cancer patients, the underlying mechanisms are unknown. Since tumor metastasis are the major cancer mortality factor, we investigated how an enriched environment (EE) conductive to enhanced sensory, cognitive and motor stimulation impact metastatic progression in lungs following intravasation in the circulation. We find that mice housed in EE exhibited reduced number of lung metastatic foci compared to control mice housed in a standard environment (SE). Compared to SE mice, EE mice increased lung inflammation as early as 4 days after circulating tumor cells extravasation. The impact of environmental signals on lung metastasis is independent of adrenergic receptors signaling. By contrast, we find that serum corticosterone levels are lower in EE mice and that glucocorticoid receptor (GR) antagonist reduces the number of lung metastasis in SE mice. In addition, the difference of the number of lung metastasis between SE and EE mice is abolished when inflammatory monocytes are rendered deficient in GR signaling. This decreased GR signaling in inflammatory monocytes of SE mice results in an exacerbated inflammatory profile in the lung. Our study shows that not only EE reduces late stages of metastatic progression in lungs but disclose a novel anti-tumor mechanism whereby GR-dependent reprogramming of inflammatory monocytes can inhibit metastatic progression in lungs. Moreover, while inflammatory monocytes have been shown to promote cancer progression, they also have an anti-tumor effect, suggesting that their role is more complex than currently thought.

SAT0018 THE THERAPEUTIC EFFECT OF STIMULATION OF THE SPLENIC NEUROVASCULAR BUNDLE IN MICE WITH COLLAGEN-INDUCED ARTHRITIS IS ENHANCED BY CONCOMITANT ANTI-TNF TREATMENT

Background:

Vagus nerve (VN) stimulation has shown the potential to improve the disease development in animal models of arthritis and in patients with RA. However, the VN can affect respiratory, cardiovascular, endocrine and gastro-intestinal physiology. The splenic nerve (SpN) has been confirmed to be the principal effector nerve for the VN-mediated immune control. Previous studies have shown that stimulating the splenic nerve resulted in an increase of norephiniphrine in the spleen, as well as a significant reduction in LPS-induced TNF (1).

Objectives:

To test the therapeutic efficiency of splenic nerve stimulation (SNS) in collagen-induced arthritis (CIA) in mice alone or in combination with anti-TNF treatment.

Methods:

CIA was induced in DBA1/J mice by immunization with bovine type II collagen at days 0 and 21. At day 11, mice were implanted with micro-cuff electrode (CorTec) onto the SpN or VN. From day 16 to day 45, SNS were applied as rectangular charged-balanced biphasic pulses with 650 μA pulse amplitude, 200 µs pulse width at 10 Hz frequency for 2 min 1 or 6 times a day using a Plexon stimulator. In order to investigatedthe mechanism of action in more detail, propranolol, a beta-adrenergic receptor (β-AR) antagonist, was added to the drinking water of mice receiving SNS. In addition, a control group was treated with anti-TNF (etanercept, 3 times/week; 10mg/kg i.p.). In curative settings, SNS and/or anti-TNF treatment was applied starting when mice scored positive for 3 consecutive days. Clinical arthritis was determined by visual examination of swelling and redness of the paws and measurement of paw thickness. Sham mice were undergoing the same procedure but did not receive stimulation.

Results:

In CIA in mice all sham animals developed arthritis, compared to only 14% following six times per day SNS (p <0.001) in a prophylactic setting. In contrast, 85% of the animals developed arthritis (p = 0.35) when SNS was applied only once a day. In both stimulated groups a significant decrease in clinical scores and paw thickness was observed compared to unstimulated group (p < 0.01 and p < 0.05, respectively). While etanercept treatment reduced clinical scores (p <0.001) an immediate rebound in clinical score was seen following treatment arrest, while mice with SNS were still partially protected 35 days after treatment discontinuation (p = 0.013, compared to sham). Propranolol inverted the effect of SNS in CIA mice. Finally, when SNS was applied as a curative treatment, clinical scores were significantly reduced (p < 0.001). Importantly, these clinical scores even further decreased when anti-TNF treatment was given to mice receiving SNS.

Conclusion:

These studies demonstrate that SNS suppresses pro-inflammatory cytokine production, and reduces clinical symptoms in mice with CIA which is at least partially mediated by the β-AR. The additive effect of anti-TNF in reducing the clinical scores demonstrates that that mechanism of action of SNS is not primarilys mediated by reducing TNF levels. Moreover, anti-TNF potentiating the inhibitory effect of SNS is supporting a combined use of these treatments, or even a combination of SNS with other biologicals, to treat RA, potentially getting more patients closer to remission. In conclusion, the data is providing compelling scientific rationale and pre-clinical evidence that splenic neuromodulation might be a new treatment modality for RA.

References:

[1] Guyot M et al, Brain Behav Immun. 2019;80:238.

Disclosure of Interests:

Thomas Simon Grant/research support from: research grant from Galvani Bioelectronics, Clara Panzolini Grant/research support from: Working on research grant Galvani bioelectronics, Julien Lavergne Grant/research support from: working on research grant Galvani Bioelectrocnics, Nicolas Hypolite Grant/research support from: Working on research grant Galvani Bioelectronics, Nicolas Glaichenhaus: None declared, Margriet Vervoordeldonk Employee of: I am an employee of Galvani Bioelectronics, Philippe Blancou Grant/research support from: Received research grant from Galvani Bioelectronics