Stimulation of alpha 7 nicotinic acetylcholine receptor (α7nAChR) inhibits atherosclerosis via immunomodulatory effects on myeloid cells

Alpha-7 Nicotinic Receptor Agonist Protects Mice Against Pulmonary Emphysema Induced by Elastase

Pulmonary emphysema is a primary component of chronic obstructive pulmonary disease (COPD), a life-threatening disorder characterized by lung inflammation and restricted airflow, primarily resulting from the destruction of small airways and alveolar walls. Cumulative evidence suggests that nicotinic receptors, especially the α7 subtype (α7nAChR), is required for anti-inflammatory cholinergic responses. We postulated that the stimulation of α7nAChR could offer therapeutic benefits in the context of pulmonary emphysema. To investigate this, we assessed the potential protective effects of PNU-282987, a selective α7nAChR agonist, using an experimental emphysema model. Male mice (C57BL/6) were submitted to a nasal instillation of porcine pancreatic elastase (PPE) (50 µl, 0.667 IU) to induce emphysema. Treatment with PNU-282987 (2.0 mg/kg, ip) was performed pre and post-emphysema induction by measuring anti-inflammatory effects (inflammatory cells, cytokines) as well as anti-remodeling and anti-oxidant effects. Elastase-induced emphysema led to an increase in the number of α7nAChR-positive cells in the lungs. Notably, both groups treated with PNU-282987 (prior to and following emphysema induction) exhibited a significant decrease in the number of α7nAChR-positive cells. Furthermore, both groups treated with PNU-282987 demonstrated decreased levels of macrophages, IL-6, IL-1β, collagen, and elastic fiber deposition. Additionally, both groups exhibited reduced STAT3 phosphorylation and lower levels of SOCS3. Of particular note, in the post-treated group, PNU-282987 successfully attenuated alveolar enlargement, decreased IL-17 and TNF-α levels, and reduced the recruitment of polymorphonuclear cells to the lung parenchyma. Significantly, it is worth noting that MLA, an antagonist of α7nAChR, counteracted the protective effects of PNU-282987 in relation to certain crucial inflammatory parameters. In summary, these findings unequivocally demonstrate the protective abilities of α7nAChR against elastase-induced emphysema, strongly supporting α7nAChR as a pivotal therapeutic target for ameliorating pulmonary emphysema.

Alpha 7 Nicotinic Acetylcholine Receptor Agonist PHA 568487 Reduces Acute Inflammation but Does Not Affect Cardiac Function or Myocardial Infarct Size in the Permanent Occlusion Model

Stimulation of the alpha 7 nicotinic acetylcholine receptor (α7nAChR) has shown beneficial effects in several acute inflammatory disease models. This study aims to examine whether treatment with the selective α7nAChR agonist PHA 568487 can dampen inflammation and thereby improve cardiac function after myocardial infarction in mice. The possible anti-inflammatory properties of α7nAChR agonist PHA 568487 were tested in vivo using the air pouch model and in a permanent occlusion model of acute myocardial infarction in mice. Hematologic parameters and cytokine levels were determined. Infarct size and cardiac function were assessed via echocardiography 24 h and one week after the infarction. Treatment with α7nAChR agonist PHA 568487 decreased 12 (CCL27, CXCL5, IL6, CXCL10, CXCL11, CXCL1, CCL2, MIP1a, MIP2, CXCL16, CXCL12 and CCL25) out of 33 cytokines in the air pouch model of acute inflammation. However, α7nAChR agonist PHA 568487 did not alter infarct size, ejection fraction, cardiac output or stroke volume at 24 h or at 7 days after the myocardial infarction compared with control mice. In conclusion, despite promising immunomodulatory effects in the acute inflammatory air pouch model, α7nAChR agonist PHA 568487 did not affect infarct size or cardiac function after a permanent occlusion model of acute myocardial infarction in mice. Consequently, this study does not strengthen the hypothesis that stimulation of the α7nAChR is a future treatment strategy for acute myocardial infarction when reperfusion is lacking. However, whether other agonists of the α7nAChR can have different effects remains to be investigated.

Elucidating the mechanisms of formononetin in modulating atherosclerotic plaque formation in ApoE-/- mice

BACKGROUND

Atherosclerosis(AS) poses a pressing challenge in contemporary medicine. Formononetin (FMN) plays a crucial role in its prevention and treatment. However, the detailed impact of FMN on the stability of atherosclerotic plaques and its underlying mechanisms remain to be elucidated.

METHODS

An intervention consisting of FMN was given along with a high-fat food regimen in the ApoE-/- mouse model. The investigation included the evaluation of the degree of atherosclerotic lesion, the main components of the plaque, lipid profiles, particular markers indicating M1/M2 macrophage phenotypes, the quantities of factors related to inflammation, the infiltration of macrophages, and the identification of markers linked to the α7nAChR/JAK2/STAT3 axis effect molecules.

RESULTS

The evaluation of aortic morphology in ApoE-/-mice revealed that FMN significantly improved the plaque area, fibrous cap protrusion, lipid deposition, and structural alterations on the aortic surface, among other markers of atherosclerosis,and there is concentration dependence. Furthermore, the lipid content of mouse serum was assessed, and the results showed that the low-, medium-, and high-dosage FMN groups had significantly lower levels of LDL-C, ox-LDL, TC, and TG. The results of immunohistochemical staining indicated that the low-, medium-, and high-dose FMN therapy groups had enhanced CD206 expression and decreased expression of CD68 and iNOS. According to RT-qPCR data, FMN intervention has the potential to suppress the expression of iNOS, COX-2, miR-155-5p, IL-6, and IL-1β mRNA, while promoting the expression of IL-10, SHIP1, and Arg-1 mRNA levels. However, the degree of inhibition varied among dosage groups. Western blot investigation of JAK/STAT signaling pathway proteins and cholinergic α7nAChR protein showed that p-JAK2 and p-STAT3 protein expression was suppressed at all dosages, whereas α7nAChR protein expression was enhanced.

CONCLUSIONS

According to the aforementioned findings, FMN can reduce inflammation and atherosclerosis by influencing macrophage polarization, blocking the JAK/STAT signaling pathway, and increasing α7nAChR expression.

Cholinergic signaling via the α7 nicotinic acetylcholine receptor regulates the migration of monocyte-derived macrophages during acute inflammation

BACKGROUND

The involvement of the autonomic nervous system in the regulation of inflammation is an emerging concept with significant potential for clinical applications. Recent studies demonstrate that stimulating the vagus nerve activates the cholinergic anti-inflammatory pathway that inhibits pro-inflammatory cytokines and controls inflammation. The α7 nicotinic acetylcholine receptor (α7nAChR) on macrophages plays a key role in mediating cholinergic anti-inflammatory effects through a downstream intracellular mechanism involving inhibition of NF-κB signaling, which results in suppression of pro-inflammatory cytokine production. However, the role of the α7nAChR in the regulation of other aspects of the immune response, including the recruitment of monocytes/macrophages to the site of inflammation remained poorly understood.

RESULTS

We observed an increased mortality in α7nAChR-deficient mice (compared with wild-type controls) in mice with endotoxemia, which was paralleled with a significant reduction in the number of monocyte-derived macrophages in the lungs. Corroborating these results, fluorescently labeled α7nAChR-deficient monocytes adoptively transferred to WT mice showed significantly diminished recruitment to the inflamed tissue. α7nAChR deficiency did not affect monocyte 2D transmigration across an endothelial monolayer, but it significantly decreased the migration of macrophages in a 3D fibrin matrix. In vitro analysis of major adhesive receptors (L-selectin, β1 and β2 integrins) and chemokine receptors (CCR2 and CCR5) revealed reduced expression of integrin αM and αX on α7nAChR-deficient macrophages. Decreased expression of αMβ2 was confirmed on fluorescently labeled, adoptively transferred α7nAChR-deficient macrophages in the lungs of endotoxemic mice, indicating a potential mechanism for α7nAChR-mediated migration.

CONCLUSIONS

We demonstrate a novel role for the α7nAChR in mediating macrophage recruitment to inflamed tissue, which indicates an important new aspect of the cholinergic regulation of immune responses and inflammation.

Cooling Down Inflammation in the Cardiovascular System via the Nicotinic Acetylcholine Receptor

ABSTRACT

Inflammation is a major player in many cardiovascular diseases including hypertension, atherosclerosis, myocardial infarction, and heart failure. In many individuals, these conditions coexist and mutually exacerbate each other's progression. The pathophysiology of these diseases entails the active involvement of both innate and adaptive immune cells. Immune cells that possess the α7 subunit of the nicotinic acetylcholine receptor on their surface have the potential to be targeted through both pharmacological and electrical stimulation of the cholinergic system. The cholinergic system regulates the inflammatory response to various stressors in different organ systems by systematically suppressing spleen-derived monocytes and chemokines and locally improving immune cell function. Research on the cardiovascular system has demonstrated the potential for atheroma plaque stabilization and regression as favorable outcomes. Smaller infarct size and reduced fibrosis have been associated with improved cardiac function and a decrease in adverse cardiac remodeling. Furthermore, enhanced electrical stability of the myocardium can lead to a reduction in the incidence of ventricular tachyarrhythmia. In addition, improving mitochondrial dysfunction and decreasing oxidative stress can result in less myocardial tissue damage caused by reperfusion injury. Restoring baroreflex activity and reduction in renal damage can promote blood pressure regulation and help counteract hypertension. Thus, the present review highlights the potential of nicotinic acetylcholine receptor activation as a natural approach to alleviate the adverse consequences of inflammation in the cardiovascular system.

Nicotine Administration Augments Abdominal Aortic Aneurysm Progression in Rats

Inflammation and elastin degradation are key hallmarks in the pathogenesis of abdominal aortic aneurysms (AAAs). It has been acknowledged that activation of alpha7 nicotinic acetylcholine receptors (α7nAChRs) attenuates inflammation, termed the cholinergic anti-inflammatory pathway (CAP). Thus, we hypothesize that low-dose nicotine impairs the progression of elastase-induced AAAs in rats by exerting anti-inflammatory and anti-oxidative stress properties. Male Sprague-Dawley rats underwent surgical AAA induction with intraluminal elastase infusion. We compared vehicle rats with rats treated with nicotine (1.25 mg/kg/day), and aneurysm progression was monitored by weekly ultrasound images for 28 days. Nicotine treatment significantly promoted AAA progression (p = 0.031). Additionally, gelatin zymography demonstrated that nicotine significantly reduced pro-matrix metalloproteinase (pro-MMP) 2 (p = 0.029) and MMP9 (p = 0.030) activity in aneurysmal tissue. No significant difference was found in the elastin content or the score of elastin degradation between the groups. Neither infiltrating neutrophils nor macrophages, nor aneurysmal messenger RNA (mRNA) levels of pro- or anti-inflammatory cytokines, differed between the vehicle and nicotine groups. Finally, no difference in mRNA levels of markers for anti-oxidative stress or the vascular smooth muscle cells' contractile phenotype was observed. However, proteomics analyses of non-aneurysmal abdominal aortas revealed that nicotine decreased myristoylated alanine-rich C-kinase substrate and proteins, in ontology terms, inflammatory response and reactive oxygen species, and in contradiction to augmented AAAs. In conclusion, nicotine at a dose of 1.25 mg/kg/day augments AAA expansion in this elastase AAA model. These results do not support the use of low-dose nicotine administration for the prevention of AAA progression.

Nicotinic acetylcholine receptors: Key targets for attenuating neurodegenerative diseases

Nicotinic acetylcholine receptors (nAChRs) are master regulators of immune functions via the cholinergic anti-inflammatory pathway and are expressed in microglia, the brain's resident immune cells. There is an extensive dialogue between the neurons and the glial cells around them from which microglia are tasked with monitoring, nurturing, and defending their microenvironment. Dysregulation of any of these processes can have devastating and long-lasting consequences involving microglia-mediated neuroinflammation associated with neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and Huntington's disease, amongst others. Disease-associated microglia acquire a distinguishing phenotype that emphasizes scavenging and defence functions while nurturing and repairing functions become muted. Attempts to resolve this critical imbalance remain a key focus of research. Furthermore, cholinergic modulation of neuroinflammation represents a promising avenue for treatment.

Neuroimmune nexus in the pathophysiology and therapy of inflammatory disorders: role of α7 nicotinic acetylcholine receptors

The α7-nicotinic acetylcholine receptor (α7nAChR) is a key protein in the cholinergic anti-inflammatory pathway (CAP) that links the nervous and immune systems. Initially, the pathway was discovered based on the observation that vagal nerve stimulation (VNS) reduced the systemic inflammatory response in septic animals. Subsequent studies form a foundation for the leading hypothesis about the central role of the spleen in CAP activation. VNS evokes noradrenergic stimulation of ACh release from T cells in the spleen, which in turn activates α7nAChRs on the surface of macrophages. α7nAChR-mediated signaling in macrophages reduces inflammatory cytokine secretion and modifies apoptosis, proliferation, and macrophage polarization, eventually reducing the systemic inflammatory response. A protective role of the CAP has been demonstrated in preclinical studies for multiple diseases including sepsis, metabolic disease, cardiovascular diseases, arthritis, Crohn's disease, ulcerative colitis, endometriosis, and potentially COVID-19, sparking interest in using bioelectronic and pharmacological approaches to target α7nAChRs for treating inflammatory conditions in patients. Despite a keen interest, many aspects of the cholinergic pathway are still unknown. α7nAChRs are expressed on many other subsets of immune cells that can affect the development of inflammation differently. There are also other sources of ACh that modify immune cell functions. How the interplay of ACh and α7nAChR on different cells and in various tissues contributes to the anti-inflammatory responses requires additional study. This review provides an update on basic and translational studies of the CAP in inflammatory diseases, the relevant pharmacology of α7nAChR-activated drugs and raises some questions that require further investigation.

The Alpha 7 Nicotinic Acetylcholine Receptor Does Not Affect Neonatal Brain Injury

Inflammation plays a central role in the development of neonatal brain injury. The alpha 7 nicotinic acetylcholine receptor (α7nAChR) can modulate inflammation and has shown promising results as a treatment target in rodent models of adult brain injury. However, little is known about the role of the α7nAChR in neonatal brain injury. Hypoxic-ischemic (HI) brain injury was induced in male and female C57BL/6 mice, α7nAChR knock-out (KO) mice and their littermate controls on postnatal day (PND) 9–10. C57BL/6 pups received i.p. injections of α7nAChR agonist PHA 568487 (8 mg/kg) or saline once daily, with the first dose given directly after HI. Caspase-3 activity and cytokine mRNA expression in the brain was analyzed 24 h after HI. Motor function was assessed 24 and 48 h after HI, and immunohistochemistry was used to assess tissue loss at 24 h and 7 days after HI and microglial activation 7 days after HI. Activation of α7nAChR with the agonist PHA 568487 significantly decreased CCL2/MCP-1, CCL5/RANTES and IL-6 gene expression in the injured brain hemisphere 24 h after HI compared with saline controls in male, but not female, pups. However, α7nAChR activation did not alter caspase-3 activity and TNFα, IL-1β and CD68 mRNA expression. Furthermore, agonist treatment did not affect motor function (24 or 48 h), neuronal tissue loss (24 h or 7 days) or microglia activation (7 days) after HI in either sex. Knock-out of α7nAChR did not influence neuronal tissue loss 7 days after HI. In conclusion, targeting the α7nAChR in neonatal brain injury shows some effect on dampening acute inflammatory responses in male pups. However, this does not lead to an effect on overall injury outcome.

Interactions between the Autonomic Nervous System and the Immune System after Stroke

Acute stroke is one of the leading causes of morbidity and mortality worldwide. Stroke-induced immune-inflammatory response occurs in the perilesion areas and the periphery. Although stroke-induced immunosuppression may alleviate brain injury, it hinders brain repair as the immune-inflammatory response plays a bidirectional role after acute stroke. Furthermore, suppression of the systemic immune-inflammatory response increases the risk of life-threatening systemic bacterial infections after acute stroke. Therefore, it is essential to explore the mechanisms that underlie the stroke-induced immune-inflammatory response. Autonomic nervous system (ANS) activation is critical for regulating the local and systemic immune-inflammatory responses and may influence the prognosis of acute stroke. We review the changes in the sympathetic and parasympathetic nervous systems and their influence on the immune-inflammatory response after stroke. Importantly, this article summarizes the mechanisms on how ANS regulates the immune-inflammatory response through neurotransmitters and their receptors in immunocytes and immune organs after stroke. To facilitate translational research, we also discuss the promising therapeutic approaches modulating the activation of the ANS or the immune-inflammatory response to promote neurologic recovery after stroke. © 2022 American Physiological Society. Compr Physiol 12:3665-3704, 2022.

Cardiovagal Function Measured by the Deep Breathing Test: Relationships With Coronary Atherosclerosis

Background

The cardiovagal function can be assessed by quantification of respiratory sinus arrhythmia (RSA) during a deep breathing test. However, population studies of RSA and coronary atherosclerosis are lacking. This population‐based study examined the relationship between RSA during deep breathing and coronary atherosclerosis, assessed by coronary artery calcium score (CACS).

Methods and Results

SCAPIS (Swedish Cardiopulmonary Bioimage Study) randomly invited men and women aged 50 to 64 years from the general population. CACS was obtained from computed tomography scanning, and deep breathing tests were performed in 4654 individuals. Expiration–inspiration differences (E‐Is) of heart rates were calculated, and reduced RSA was defined as E‐I in the lowest decile of the population. The relationship between reduced RSA and CACS (CACS≥100 or CACS≥300) was calculated using multivariable‐adjusted logistic regression. The proportion of CACS≥100 was 24% in the lowest decile of E‐I and 12% in individuals with E‐I above the lowest decile (P<0.001), and the proportion of CACS≥300 was 12% and 4.8%, respectively (P<0.001). The adjusted odds ratio (OR) for CACS≥100 was 1.42 (95% CI, 1.10–1.84) and the adjusted OR for CACS≥300 was 1.62 (95% CI, 1.15–2.28), when comparing the lowest E‐I decile with deciles 2 to 10. Adjusted ORs per 1 SD lower E‐I were 1.17 (P=0.001) for CACS≥100 and 1.28 (P=0.001) for CACS≥300.

Conclusions

Low RSA during deep breathing is associated with increased coronary atherosclerosis as assessed by CACS, independently of traditional cardiovascular risk factors. Cardiovagal dysfunction could be a prevalent and modifiable risk factor for coronary atherosclerosis in the general population.

Polymorphisms in alpha 7 nicotinic acetylcholine receptor gene, CHRNA7, and its partially duplicated gene, CHRFAM7A, associate with increased inflammatory response in human peripheral mononuclear cells

The vagus nerve can, via the alpha 7 nicotinic acetylcholine receptor (α7nAChR), regulate inflammation. The gene coding for the α7nAChR, CHRNA7, can be partially duplicated, that is, CHRFAM7A, which is reported to impair the anti-inflammatory effect mediated via the α7nAChR. Several single nucleotide polymorphisms (SNPs) have been described in both CHRNA7 and CHRFAM7A, however, the functional role of these SNPs for immune responses remains to be investigated. In the current study, we set out to investigate whether genetic variants of CHRNA7 and CHRFAM7A can influence immune responses. By investigating data available from the Swedish SciLifeLab SCAPIS Wellness Profiling (S3WP) study, in combination with droplet digital PCR and freshly isolated PBMCs from the S3WP participants, challenged with lipopolysaccharide (LPS), we show that CHRNA7 and CHRFAM7A are expressed in human PBMCs, with approximately four times higher expression of CHRFAM7A compared with CHRNA7. One SNP in CHRFAM7A, rs34007223, is positively associated with hsCRP in healthy individuals. Furthermore, gene ontology (GO)-terms analysis of plasma proteins associated with gene expression of CHRNA7 and CHRFAM7A demonstrated an involvement for these genes in immune responses. This was further supported by in vitro data showing that several SNPs in both CHRNA7 and CHRFAM7A are significantly associated with cytokine response. In conclusion, genetic variants of CHRNA7 and CHRFAM7A alters cytokine responses. Furthermore, given that CHRFAM7A SNP rs34007223 is associated with inflammatory marker hsCRP in healthy individuals suggests that CHRFAM7A may have a more pronounced role in regulating inflammatory processes in humans than previously been recognized.

Inflammation Regulation via an Agonist and Antagonists of α7 Nicotinic Acetylcholine Receptors in RAW264.7 Macrophages

The α7 nicotinic acetylcholine receptor (nAChR) is widely distributed in the central and peripheral nervous systems and is closely related to a variety of nervous system diseases and inflammatory responses. The α7 nAChR subtype plays a vital role in the cholinergic anti-inflammatory pathway. In vivo, ACh released from nerve endings stimulates α7 nAChR on macrophages to regulate the NF-κB and JAK2/STAT3 signaling pathways, thereby inhibiting the production and release of downstream proinflammatory cytokines and chemokines. Despite a considerable level of recent research on α7 nAChR-mediated immune responses, much is still unknown. In this study, we used an agonist (PNU282987) and antagonists (MLA and α-conotoxin [A10L]PnIA) of α7 nAChR as pharmacological tools to identify the molecular mechanism of the α7 nAChR-mediated cholinergic anti-inflammatory pathway in RAW264.7 mouse macrophages. The results of quantitative PCR, ELISAs, and transcriptome analysis were combined to clarify the function of α7 nAChR regulation in the inflammatory response. Our findings indicate that the agonist PNU282987 significantly reduced the expression of the IL-6 gene and protein in inflammatory macrophages to attenuate the inflammatory response, but the antagonists MLA and α-conotoxin [A10L]PnIA had the opposite effects. Neither the agonist nor antagonists of α7 nAChR changed the expression level of the α7 nAChR subunit gene; they only regulated receptor function. This study provides a reference and scientific basis for the discovery of novel α7 nAChR agonists and their anti-inflammatory applications in the future.

Therapeutic Effect of Combining Anisodamine With Neostigmine on Local Scar Formation Following Roux-en-Y Choledochojejunostomy in a Novel Rat Model

Background: The present study aimed to explore the potential effect of combining anisodamine with neostigmine on local scar formation following Roux-en-Y choledochojejunostomy (RCJS) in a novel rat model.

Methods: The biliary obstruction model of Sprague Dawley (SD) rats was established in advance, and 54 rats were divided into nine groups randomly (sham operation group, anisodamine group, neostigmine group, combination group, and control group). Anisodamine (25 mg/kg) and neostigmine (50 μg/kg) were injected to the abdominal cavity separately or simultaneously for 1 week since the first day after surgery according to their allocated intervention, while the same amount of saline (0.5 ml) was injected intraperitoneally in the control group. Indexes including body weight, the diameter of the common bile duct, liver function, inflammatory indexes, and the condition of scar formation in different groups at certain time were evaluated in our study.

Results: Recovery of liver function (ALT, AST, TB, DB, and GGT) and systematic inflammation indexes (CRP, TNF-α, and IL-1β) in the combination group was prior to that in the control group (p < 0.05), while no statistical difference in the serum level of IL-10 was observed among groups. Rats in the combination group represented a wider anastomotic diameter and lower expression of α-SMA and TGF-β1 at anastomotic stoma compared to the control group (p < 0.05). Histopathological staining showed slighter proliferation of collagen and smooth muscle fibers in rats’ bile duct wall and less local scar formation at anastomotic stoma compared to the control group.

Conclusion: The combination of anisodamine and neostigmine can alleviate local and systemic inflammatory response, promote the recovery of liver function, and reduce scar formation in rats after the RCJS procedure.

Nerve-macrophage interactions in cardiovascular disease

The heart is highly innervated by autonomic neurons, and dynamic autonomic regulation of the heart and blood vessels is essential for animals to carry out the normal activities of life. Cardiovascular diseases, including heart failure and myocardial infarction, are often characterized in part by an imbalance in autonomic nervous system activation, with excess sympathetic and diminished parasympathetic activation. Notably, however, this is often accompanied by chronic inflammation within the cardiovascular tissues, which suggests there are interactions between autonomic dysregulation and inflammation. Recent studies have been unraveling the mechanistic links between autonomic nerves and immune cells within cardiovascular disease. The autonomic nervous system and immune system also act in concert to coordinate the actions of multiple organs that not only maintain homeostasis but also likely play key roles in disease-disease interactions, such as cardiorenal syndrome and multimorbidity. In this review, we summarize the physiological and pathological interactions between autonomic nerves and macrophages in the context of cardiovascular disease.

The selective alpha7 nicotinic acetylcholine receptor agonist AR-R17779 does not affect ischemia-reperfusion brain injury in mice

Inflammation plays a central role in stroke-induced brain injury. The alpha7 nicotinic acetylcholine receptor (α7nAChR) can modulate immune responses in both the periphery and the brain. The aims of the present study were to investigate α7nAChR expression in different brain regions and evaluate the potential effect of the selective α7nAChR agonist AR-R17779 on ischemia-reperfusion brain injury in mice. Droplet digital PCR (ddPCR) was used to evaluate the absolute expression of the gene encoding α7nAChR (Chrna7) in hippocampus, striatum, thalamus and cortex in adult, naïve mice. Mice subjected to transient middle cerebral artery occlusion (tMCAO) or sham surgery were treated with α7nAChR agonist AR-R17779 (12 mg/kg) or saline once daily for 5 days. Infarct size and microglial activation 7 days after tMCAO were analyzed using immunohistochemistry. Chrna7 expression was found in all analyzed brain regions in naïve mice with the highest expression in cortex and hippocampus. At sacrifice, white blood cell count was significantly decreased in AR-R17779 treated mice compared with saline controls in the sham groups, although, no effect was seen in the tMCAO groups. Brain injury and microglial activation were evident 7 days after tMCAO. However, no difference was found between mice treated with saline or AR-R17779. In conclusion, α7nAChR expression varies in different brain regions and, despite a decrease in white blood cells in sham mice receiving AR-R17779, this compound does not affect stroke-induced brain injury.

Stable desensitization of α7 nicotinic acetylcholine receptors by NS6740 requires interaction with S36 in the orthosteric agonist binding site

NS6740 is an α₇ nicotinic acetylcholine receptor-selective partial agonist with low efficacy for channel activation, capable of promoting the stable conversion of the receptors to nonconducting (desensitized) states that can be reactivated with the application of positive allosteric modulators (PAMs). In spite of its low efficacy for channel activation, NS6740 is an effective activator of the cholinergic anti-inflammatory pathway. We observed that the concentration-response relationships for channel activation, both when applied alone and when co-applied with the PAM PNU-120596 are inverted-U shaped with inhibitory/desensitizing activities dominant at high concentrations. We evaluated the potential importance of recently identified binding sites for allosteric activators and tested the hypotheses that the stable desensitization produced by NS6740 may be due to binding to these sites. Our experiments were guided by molecular modeling of NS6740 binding to both the allosteric and orthosteric activation sites on the receptor. Our results indicate that with α₇C190A mutants, which have compromised orthosteric activation sites, NS6740 may work at the allosteric activation sites to promote transient PAM-dependent currents but not the stable desensitization seen with wild-type α₇ receptors. Modeling NS6740 in the orthosteric binding sites identified S36 as an important residue for NS6740 binding and predicted that an S36V mutation would limit NS6740 activity. The efficacy of NS6740 for α₇S36V receptors was reduced to zero, and applications of the compound to α₇S36V receptors failed to induce the desensitization observed with wild-type receptors. The results indicate that the unique properties of NS6740 are due primarily to binding at the sites for orthosteric agonists.

Weight gain and neuroadaptations elicited by high fat diet depend on fatty acid composition

Overconsumption of food is a major health concern in the western world. Palatable food has been shown to alter the activity of neural circuits, and obesity has been linked to alterations in the connectivity between the hypothalamus and cortical regions involved in decision-making and reward processing, putatively modulating the incentive value of food. Outlining neurophysiological adaptations induced by dietary intake of high fat diets (HFD) is thus valuable to establish how the diet by itself may promote overeating. To this end, C57BL/6 mice were fed HFD rich in either saturated fatty acids (HFD-S) or polyunsaturated fatty acids (HFD-P), or a low-fat control diet (LFD) for four weeks. Food and energy intake were monitored and ex vivo electrophysiology was employed to assess neuroadaptations in lateral hypothalamus (LH) and corticostriatal circuits, previously associated with food intake. In addition, the effects of dietary saturated and polyunsaturated fatty acids on the gene expression of NMDA, AMPA and GABA_A receptor subunits in the hypothalamus were investigated. Our data shows that mice fed HFD-P had increased daily food and energy intake compared with mice fed HFD-S or LFD. However, this increase in energy intake had no obesogenic effects. Electrophysiological recordings demonstrated that HFD-P had a selective effect on glutamatergic neurotransmission in the LH, which was concomitant with a change in mRNA expression of AMPA receptor subtypes Gria1, Gria3 and Gria4, with no effect on the mRNA expression of NMDA receptor subtypes or GABA_A receptor subtypes. Furthermore, while synaptic output from corticostriatal subregions was not significantly modulated by diet, synaptic plasticity in the form of long-term depression (LTD) was impaired in the dorsomedial striatum of mice fed HFD-S. In conclusion, this study suggests that the composition of fatty acids in the diet not only affects weight gain, but may also modulate neuronal function and plasticity in brain regions involved in food intake.

The Role of α7nAChR-Mediated Cholinergic Anti-inflammatory Pathway in Immune Cells

Alpha 7 nicotinic acetylcholine receptor (α7nAChR) is widely distributed in the nervous and non-cholinergic immune systems. It is necessary for the cholinergic transmitter to participate in the regulation of inflammatory response and is the key element of cholinergic anti-inflammatory pathway (CAP). Because of the profound impact of CAP on the immune system, α7nAChR is considered as a potential therapeutic target for the treatment of inflammatory diseases. Available evidences confirmed that manipulation of CAP by activating α7nAChR with either endogenous acetylcholine (ACh) or cholinergic agonists can substantially alleviate inflammatory responses both in vivo and in vitro. However, the mechanism through which CAP curbs the excessive pro-inflammatory responses and maintains immune homeostasis is not fully understood. Obtained clues suggest that the crosstalk between CAP and classical inflammatory pathways is the key to elucidate the anti-inflammatory mechanism, and the impacts of CAP activation in α7nAChR-expressing immune cells are the foundation of the immunoregulatory property. In this article, we review and update the knowledge concerning the progresses of α7nAChR-based CAP, including α7nAChR properties, signal transductions, interactions with classic immune pathways, and immunoregulatory functions in different immune cells. Certain critical issues to be addressed are also highlighted. By providing a panoramic view of α7nAChR, the summarized evidences will pave the way for the development of novel anti-inflammatory reagents and strategy and inspire further researches.

Role of the α7 Nicotinic Acetylcholine Receptor in the Pathophysiology of Atherosclerosis

Atherosclerosis constitutes a major risk factor for cardiovascular diseases, the leading cause of morbidity and mortality worldwide. This slowly progressing, chronic inflammatory disorder of large- and medium-sized arteries involves complex recruitment of immune cells, lipid accumulation, and vascular structural remodeling. The α7 nicotinic acetylcholine receptor (α7nAChR) is expressed in several cell types involved in the genesis and progression of atherosclerosis, including macrophages, dendritic cells, T and B cells, vascular endothelial and smooth muscle cells (VSMCs). Recently, the α7nAChR has been described as an essential regulator of inflammation as this receptor mediates the inhibition of cytokine synthesis through the cholinergic anti-inflammatory pathway, a mechanism involved in the attenuation of atherosclerotic disease. Aside from the neuronal cholinergic control of inflammation, the non-neuronal cholinergic system similarly regulates the immune function. Acetylcholine released from T cells acts in an autocrine/paracrine fashion at the α7nAChR of various immune cells to modulate immune function. This mechanism additionally has potential implications in reducing atherosclerotic plaque formation. In contrast, the activation of α7nAChR is linked to the induction of angiogenesis and VSMC proliferation, which may contribute to the progression of atherosclerosis. Therefore, both atheroprotective and pro-atherogenic roles are attributed to the stimulation of α7nAChRs, and their role in the genesis and progression of atheromatous plaque is still under debate. This minireview highlights the current knowledge on the involvement of the α7nAChR in the pathophysiology of atherosclerosis.

Chinese Herbal Formula Ermiao Powder () Regulates Cholinergic Anti-inflammatory Pathway in Rats with Rheumatoid Arthritis

OBJECTIVE

To investigate the effect of Chinese herbal formula Ermiao Powder (, EMP) on the expression of cholinergic anti-inflammatory pathway in rats with rheumatoid arthritis (RA).

METHODS

Seventy-two rats were randomly divided into 6 groups according to body weight, including normal control group, collageninduced arthritis (CIA) group, three doses EMP groups, and methotrexate (MTX) group (n=12 per group). All of the rats except for those in the normal control group were given multipoint subcutaneous injection of bovine type II collagen to establish a CIA model. Three EMP groups received a high- (4.5 g/kg), medium- (3.0 g/kg), and low- (1.5 g/kg) doses of EMP by intragavage, respectively. MTX group was injected intraperitoneally MTX at 0.9 mg/kg once a week as the positive control. The administration was 3 consecutive weeks. Joint swelling, arthritis index, and body weight changes in different experimental groups of rats were tested. The joint damage was evaluated by masson staining. Quantitative real-time polymerase chain reaction, Western blot, and immunohistochemistry (IHC) were performed to evaluate the expression of CHRNA7, encoding α7 nicotinic acetylcholine receptor in the cholinergic anti-inflammatory pathway, in different tissues and their localization in the spleen and joints.

RESULTS

CHRNA7 expression levels were significantly higher in the joints and spleens of CIA group than those in normal control group (both P<0.05). Moreover, the CHRNA7 mRNA and protein levels in the spleen and joints of MTX and three doses of EMP groups were significantly lower than CIA group (all P<0.05). Compared with the MTX group, treatment with low-dose EMP resulted in significant reduction of CHRNA7 mRNA and protein expression levels (P<0.05 or P<0.01). IHC showed positive signals of CHRNA7 in the white pulp and red pulp of the spleens of rats; CHRNA7 was expressed on fibroblast-like synoviocytes, macrophages, and endothelial cells in the joints of rats, and the expression in the joints of low-dose EMP group was significantly lower than that in the CIA group (P<0.01).

CONCLUSIONS

Cholinergic anti-inflammatory pathway was involved in the generation of the inflammatory reaction in CIA rats, and EMP exerted therapeutic effect on RA through cholinergic anti-inflammatory pathway.

Smoking and COVID-19: Similar bronchial ACE2 and TMPRSS2 expression and higher TMPRSS4 expression in current versus never smokers

Uncertainties remain concerning the pathophysiology, epidemiology, and potential therapeutics for COVID-19. Among unsettled controversies is whether tobacco smoking increases or protects from severe COVID-19. Several epidemiological studies reported reduced COVID-19 hospitalizations among smokers, while other studies reported the opposite trend. Some authors assumed that smokers have elevated airway expression of ACE2, the cell recognition site of the SARS-Cov-2 spike protein, but this suggestion remains unverified. We therefore performed data mining of two independent NCBI GEO genome-wide RNA expression files (GSE7894 and GSE994) and report that in both data sets, current smokers and never smokers have, on average, closely similar bronchial epithelial cell mRNA levels of ACE2, as well as TMPRSS2, coding for a serine protease priming SARS-Cov-2 for cell entry, and ADAM17, coding for a protease implicated in ACE2 membrane shedding. In contrast, the expression levels of TMPRSS4, coding for a protease that primes SARS-CoV-2 for cell entry similarly to TMPRSS2, were elevated in bronchial epithelial cells from current smokers compared with never smokers, suggesting that higher bronchial TMPRSS4 levels in smokers might put them at higher SARS-Cov-2 infection risk. The effects of smoking on COVID-19 severity need clarification with larger studies. Additionally, the postulated protective effects of nicotine and nitric oxide, which may presumably reduce the risk of a "cytokine storm" in infected individuals, deserve assessment by controlled clinical trials.

Advancing continuous subcutaneous insulin infusion in vivo: New insights into tissue challenges

Continuous Subcutaneous Insulin Infusion (CSII) is superior to conventional insulin therapy as it improves glycemic control thus reducing the probability of diabetic complications. Notwithstanding CSII's benefits, insulin dependent diabetic patients rarely achieve optimal glucose control. Moreover, CSII is only FDA approved for 3 days and often fails prematurely for reasons that have not been fully elucidated. We hypothesize that phenolic compounds, such as m-cresol and phenol, which are present in all commercial insulin formulations are responsible for the tissue reaction occurring at the insulin infusion site. This hypothesis was examined with in vitro cell cultures and a mouse air-pouch model to determine cellular and tissue reactions following infusions with saline, phenolic compounds, (i.e., commercial diluent), and insulin. We demonstrated that diluent and insulin were cytotoxic to cells in culture at sub-clinical concentrations (e.g., >1:10 of commercial insulin). Air pouch studies demonstrated that infusion of either diluted insulin or diluent itself induced three to five-fold level of recruited leukocytes as compared to saline. At both 3- and 7-days post infusion, these were predominantly neutrophils and macrophages. We conclude that phenolic compounds in commercial insulin preparations are cell and tissue toxic, which contributes to the failure of effective insulin infusion therapy.

RNA sequencing data describing transcriptional changes in aorta of ApoE-/- mice after alpha 7 nicotinic acetylcholine receptor (α7nAChR) stimulation

This manuscript is a companion paper to Ulleryd M.U. et al., “Stimulation of alpha 7 nicotinic acetylcholine receptor (α7nAChR) inhibits atherosclerosis via immunomodulatory effects on myeloid cells” Atherosclerosis, 2019 [1]. Data shown here include RNA sequencing data from whole aorta of ApoE-/- mice fed high fat diet and treated with the alpha 7 nicotinic acetylcholine receptor (α7nAChR) agonist AZ6983 for 8 weeks using subcutaneously implanted osmotic minipumps. Here we present the top gene networks affected by treatment with AZ6983, as well as the up- and down-regulated genes in aorta after treatment. Further, a URL link to the RNA sequencing datasets submitted to GEO is included.