The cholinergic anti-inflammatory pathway: towards innovative treatment of rheumatoid arthritis

The efferent vagus nerve can regulate inflammation via its principal neurotransmitter acetylcholine (Ach), a concept referred to as the 'cholinergic anti-inflammatory pathway'. Ach interacts with members of the nicotinic acetylcholine receptor (nAchr) family, in particular with the alpha 7 subunit (alpha 7nAchr), which is expressed not only by neurons but also macrophages and other cells involved in the inflammatory response. in these inflammatory cells, the stimulation of alpha 7nAchr by Ach and other alpha 7nAchr-specific agonists suppresses the release of proinflammatory cytokines. recent work has suggested that alpha 7nAchr could represent a new target for the treatment of rheumatic diseases. in this perspective, we describe the cholinergic anti-inflammatory pathway and the therapeutic potential of modulating this pathway in rheumatoid arthriti

Role of the cholinergic nervous system in rheumatoid arthritis: aggravation of arthritis in nicotinic acetylcholine receptor alpha7 subunit gene knockout mice

BACKGROUND: The alpha7 subunit of nicotinic acetylcholine receptors (alpha7nAChR) can negatively regulate the synthesis and release of proinflammatory cytokines by macrophages and fibroblast-like synoviocytes in vitro. In addition, stimulation of the alpha7nAChR can reduce the severity of arthritis in murine collagen-induced arthritis (CIA). OBJECTIVE: To provide more insight into the role of the alpha7nAChR in the pathogenesis of arthritis by investigating the effect of the absence of alpha7nAChR in CIA in alpha7-deficient (alpha7nAChR(-/-)) compared with wild-type (WT) mice. METHODS: CIA was induced in alpha7nAChR(-/-) and WT littermate mice at day 0 by immunisation with chicken collagen type II (cCII) followed by a booster injection with cCII on day 20. Mice were killed on day 44 or day 63 and arthritis activity as well as radiological and histological damage were scored. The effects on the immune response were evaluated by measurement of antigen-specific antibodies and cytokines, and evaluation of the effects on antigen-specific stimulated spleen cells. RESULTS: In alpha7nAChR(-/-) mice a significant increase in the incidence and severity of arthritis as well as increased synovial inflammation and joint destruction were seen. Exacerbation of CIA was associated with elevated systemic proinflammatory cytokines and enhanced T-helper cell 1 (Th1)-cytokine and tumour necrosis factor alpha production by spleen cells. Moreover, a specific decrease in the collagen-specific 'Th1-associated' IgG2a response was seen, whereas IgG1 titres were unaffected. CONCLUSIONS: The results presented here indicate that immune cell function in a model of rheumatoid arthritis is regulated by the cholinergic system and, at least in part, mediated by the alpha7nACh

Stimulation of nicotinic acetylcholine receptors attenuates collagen-induced arthritis in mice

OBJECTIVE: The parasympathetic nervous system, through the vagus nerve, can down-regulate inflammation in vivo by decreasing the release of cytokines, including tumor necrosis factor alpha (TNFalpha), by activated macrophages. The vagus nerve may exert antiinflammatory actions via a specific effect of its principal neurotransmitter, acetylcholine, on the alpha7 subunit of nicotinic acetylcholine receptors (alpha7nAChR) on macrophages. The present study was undertaken to obtain insight into the role of the cholinergic antiinflammatory pathway in arthritis. METHODS: To inhibit the cholinergic antiinflammatory pathway, mice were subjected to unilateral cervical vagotomy or sham surgery, after which arthritis was induced with type II collagen. In a separate study, nicotine was added to the drinking water of mice with collagen-induced arthritis (CIA). In addition, we investigated the effects of intraperitoneally (IP)-injected nicotine and the specific alpha7nAChR agonist AR-R17779. RESULTS: Clinical arthritis was exacerbated by vagotomy and ameliorated by oral nicotine administration. Moreover, oral nicotine inhibited bone degradation and reduced TNFalpha expression in synovial tissue. Both IP-injected nicotine and AR-R17779 ameliorated clinical arthritis and reduced synovial inflammation. This was accompanied by a reduction of TNFalpha levels in both plasma and synovial tissue. The effect of AR-R17779 was more potent compared with that of nicotine and was associated with delayed onset of the disease as well as with protection against joint destruction. CONCLUSION: These data provide the first evidence of a role of the cholinergic antiinflammatory pathway in the murine CIA model of rheumatoid arthriti

No COVID-19 in Patients With Sudden Sensorineural Hearing Loss (SSNHL)

Background: Various case reports have described sudden sensorineural hearing loss (SSNHL) in patients with the 2019 novel coronavirus disease (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARSCoV-2). Our aim was to determine the incidence of COVID-19 in patients with SSNHL. Methods: All consecutive patients with audiometric confirmed SSNHL between November 2020 and March 2021 in a Dutch large inner city teaching hospital were included. All patients were tested for COVID-19 by polymerase-chain-reaction (PCR) and awaited the results in quarantine. Results: Out of 25 patients, zero (0%) tested positive for COVID-19. Two patients had previously tested positive for COVID-19: at three and eight months prior to the onset of hearing loss. Conclusions: This is the largest series to date investigating COVID-19 in SSNHL patients. In this series there is no apparent relationship between SSNHL and COVID-19

No COVID-19 in patients with sudden sensorineural hearing loss (SSNHL)

Background: Various case reports have described sudden sensorineural hearing loss (SSNHL) in patients with the 2019 novel coronavirus disease (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARSCoV-2). Our aim was to determine the incidence of COVID-19 in patients with SSNHL. Methods: All consecutive patients with audiometric confirmed SSNHL between November 2020 and March 2021 in a Dutch large inner city teaching hospital were included. All patients were tested for COVID-19 by polymerase-chain-reaction (PCR) and awaited the results in quarantine. Results: Out of 25 patients, zero (0%) tested positive for COVID-19. Two patients had previously tested positive for COVID-19: at three and eight months prior to the onset of hearing loss. Conclusions: This is the largest series to date investigating COVID-19 in SSNHL patients. In this series there is no apparent relationship between SSNHL and COVID-19

Two novel α7 nicotinic acetylcholine receptor ligands: in vitro properties and their efficacy in collagen-induced arthritis in mice.

INTRODUCTION:The cholinergic anti-inflammatory pathway can downregulate inflammation via the release of acetylcholine (ACh) by the vagus nerve. This neurotransmitter binds to the α7 subunit of nicotinic acetylcholine receptors (α7nAChR), expressed on macrophages and other immune cells. We tested the pharmacological and functional profile of two novel compounds, PMP-311 and PMP-072 and investigated their role in modulating collagen-induced arthritis (CIA) in mice. METHODS:Both compounds were characterized with binding, electrophysiological, and pharmacokinetic studies. For in vivo efficacy studies in the CIA model the compounds were administered daily by oral gavage from day 20 till sacrifice at day 34. Disease progression was monitored by visual clinical scoring and measurement of paw swelling. Inflammation and joint destruction were examined by histology and radiology. RESULTS:Treatment with PMP-311 was effective in preventing disease onset, reducing clinical signs of arthritis, and reducing synovial inflammation and bone destruction. PMP-072 also showed a trend in arthritis reduction at all concentrations tested. The data showed that while both compounds bind to α7nAChR with high affinity, PMP-311 acts like a classical agonist of ion channel activity, and PMP-072 can actually act as an ion channel antagonist. Moreover, PMP-072 was clearly distinct from typical competitive antagonists, since it was able to act as a silent agonist. It synergizes with the allosteric modulator PNU-120596, and subsequently activates desensitized α7nAChR. However, PMP-072 was less efficacious than PMP-311 at both channel activation and desensitization, suggesting that both conducting and non-conducting states maybe of importance in driving an anti-inflammatory response. Finally, we found that the anti-arthritic effect can be observed despite limited penetration of the central nervous system. CONCLUSIONS:These data provide direct evidence that the α7nAChR in immune cells does not require typical ion channel activation to exert its antiinflammatory effects

Two novel α7 nicotinic acetylcholine receptor ligands: in vitro properties and their efficacy in collagen-induced arthritis in mice

The cholinergic anti-inflammatory pathway can downregulate inflammation via the release of acetylcholine (ACh) by the vagus nerve. This neurotransmitter binds to the α7 subunit of nicotinic acetylcholine receptors (α7nAChR), expressed on macrophages and other immune cells. We tested the pharmacological and functional profile of two novel compounds, PMP-311 and PMP-072 and investigated their role in modulating collagen-induced arthritis (CIA) in mice. Both compounds were characterized with binding, electrophysiological, and pharmacokinetic studies. For in vivo efficacy studies in the CIA model the compounds were administered daily by oral gavage from day 20 till sacrifice at day 34. Disease progression was monitored by visual clinical scoring and measurement of paw swelling. Inflammation and joint destruction were examined by histology and radiology. Treatment with PMP-311 was effective in preventing disease onset, reducing clinical signs of arthritis, and reducing synovial inflammation and bone destruction. PMP-072 also showed a trend in arthritis reduction at all concentrations tested. The data showed that while both compounds bind to α7nAChR with high affinity, PMP-311 acts like a classical agonist of ion channel activity, and PMP-072 can actually act as an ion channel antagonist. Moreover, PMP-072 was clearly distinct from typical competitive antagonists, since it was able to act as a silent agonist. It synergizes with the allosteric modulator PNU-120596, and subsequently activates desensitized α7nAChR. However, PMP-072 was less efficacious than PMP-311 at both channel activation and desensitization, suggesting that both conducting and non-conducting states maybe of importance in driving an anti-inflammatory response. Finally, we found that the anti-arthritic effect can be observed despite limited penetration of the central nervous system. These data provide direct evidence that the α7nAChR in immune cells does not require typical ion channel activation to exert its antiinflammatory effect

CD62L Is a Functional and Phenotypic Marker for Circulating Innate Lymphoid Cell Precursors

Innate lymphoid cells (ILCs) guard epithelial tissue integrity during homeostasis, but can be potent immune effector cells during inflammation. Precursors to all ILC subsets (ILC precursors [ILCP]) have been identified in human peripheral blood (PB). We found that during homeostasis, ILCP in PB of mouse and human expressed homing receptors for secondary lymphoid organs, mainly CD62L. These ILCP entered mouse lymph nodes in a CD62L-dependent way and relied on S1P receptors for their exit. Importantly, CD62L expression was absent on human ILCs expressing NKp44 in tonsils and PB of Crohn disease patients, and relatively fewer CD62L+ ILCP were present in PB of Crohn disease patients. These data are in agreement with selective expression of CD62L on nonactivated ILCP. As such, we conclude that CD62L not only serves as a functional marker of ILCP, but has potential to be used in the clinic as a diagnostic marker in inflammatory disorders

Inhibition of bone degradation and reduction of synovial inflammation in murine collagen-induced arthritis by PMP-311 (n = 15, 5 mg/kg).

<p><b>A</b>, Semiquantitative scores of joint destruction. Joint destruction was decreased in mice treated with PMP-311. ** <i>P</i> < 0.01 compared to saline-treated mice <b>B</b>, Semiquantitative scores for synovial inflammation, assessed by hematoxylin and eosin staining of the knee joints, showed a decrease of synovitis in PMP-311-treated mice. * <i>P</i> < 0.05 compared to the control group.</p

Dose-response study of PMP-311 and PMP-072 on clinical arthritis and paw swelling in murine collagen-induced arthritis.

<p>Mice were treated daily with PMP-311 (2, 5, 10 mg/kg, n = 15), PMP-072 (5, 10, 20 mg/kg, n = 15) or saline (n = 15) by oral gavage from day 20 until day 34. Percentages of areas under the curve (AUC) are shown. <b>A</b>, AUC of the clinical score was decreased more pronounced in PMP-311-treated mice versus control mice than in mice treated with PMP-072. <b>B</b>, Paw swelling was decreased in mice treated with PMP-311 at doses of 2 and 5 mg/kg and in mice treated with PMP-072 at 10 mg/kg. * <i>P</i> < 0.05 and ** <i>P</i> < 0.01 compared to saline treated mice.</p