Role of the nicotinic acetylcholine receptor α3 subtype in vascular inflammation

Involvement of neuronal factors in tumor angiogenesis and the shaping of the cancer microenvironment

Emerging evidence suggests that nerves within the tumor microenvironment play a crucial role in regulating angiogenesis. Neurotransmitters and neuropeptides released by nerves can interact with nearby blood vessels and tumor cells, influencing their behavior and modulating the angiogenic response. Moreover, nerve-derived signals may activate signaling pathways that enhance the production of pro-angiogenic factors within the tumor microenvironment, further supporting blood vessel growth around tumors. The intricate network of communication between neural constituents and the vascular system accentuates the potential of therapeutically targeting neural-mediated pathways as an innovative strategy to modulate tumor angiogenesis and, consequently, neoplastic proliferation. Hereby, we review studies that evaluate the precise molecular interplay and the potential clinical ramifications of manipulating neural elements for the purpose of anti-angiogenic therapeutics within the scope of cancer treatment.

An integral perspective of canonical cigarette and e-cigarette-related cardiovascular toxicity based on the adverse outcome pathway framework

BACKGROUND

Nowadays, cigarette smoking remains the leading cause of chronic disease and premature death, especially cardiovascular disease. As an emerging tobacco product, e-cigarettes have been advocated as alternatives to canonical cigarettes, and thus may be an aid to promote smoking cessation. However, recent studies indicated that e-cigarettes should not be completely harmless to the cardiovascular system.

AIM OF REVIEW

This review aimed to build up an integral perspective of cigarettes and e-cigarettes-related cardiovascular toxicity.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review adopted the adverse outcome pathway (AOP) framework as a pivotal tool and aimed to elucidate the association between the molecular initiating events (MIEs) induced by cigarette and e-cigarette exposure to the cardiovascular adverse outcome. Since the excessive generation of reactive oxygen species (ROS) has been widely approved to play a critical role in cigarette smoke-related CVD and may also be involved in e-cigarette-induced toxic effects, the ROS overproduction and subsequent oxidative stress are regarded as essential parts of this framework. As far as we know, this should be the first AOP framework focusing on cigarette and e-cigarette-related cardiovascular toxicity, and we hope our work to be a guide in exploring the biomarkers and novel therapies for cardiovascular injury.

Astragali Radix-Coptis Rhizoma Herb Pair Attenuates Atherosclerosis in ApoE-/- Mice by Regulating the M1/M2 and Th1/Th2 Immune Balance and Activating the STAT6 Signaling Pathway

OBJECTIVE

Immune imbalance and the inflammatory response are associated with atherosclerosis (AS) progression. Astragali Radix and Coptis Rhizoma (ARCR) are an ancient and classic herb pair that is used in herbal medicines for the treatment of coronary heart disease. We focused on the effects and mechanisms of the ARCR herb pair attenuation of atherosclerosis in apolipoprotein E knockout (ApoE-/-) mice.

METHODS

ApoE-/- mice were fed a high-fat diet for 12 weeks to establish a model of AS. The ApoE-/- mice were randomly divided into a model group, simvastatin group (Simva), Astragali Radix group (AR), Coptis Rhizoma group (CR), Astragali Radix-Coptis Rhizoma group (ARCR), and Astragali Radix-Coptis Rhizoma + signal transducer and activator of transcription factor 6 (STAT6) inhibitor (AS1517499) group (ARCR + AS1517499). C57BL/6 mice were used as controls. Each group was administered the corresponding drugs, and mice in the model and control groups were given the same volume of normal saline once daily for 6 weeks. The body weights of the mice were observed regularly. The effect of the ARCR herb pair on lipid content in peripheral blood was evaluated using blood lipid tests. The levels of serum matrix metalloproteinase-9 (MMP-9), interleukins-12 (IL-12), IL-10, interferon-γ (IFN-γ), and IL-4 were determined to assess inflammation. Oil Red O staining, Sirius Red staining, and immunohistochemistry were used to observe changes in plaque stability. Western blotting was used to assay M1/M2 macrophages, Th1/Th2 cells, and STAT6 signaling pathway protein expression. Flow cytometry and immunofluorescence were used to detect M1/M2 macrophages and Th1/Th2 cells and reflect the immune imbalance.

RESULTS

The ARCR herb pair significantly reduced blood lipids levels and plaque vulnerability and regulated the levels of inflammatory factors and the number of M1/M2 macrophages and Th1/Th2 cells in ApoE-/- AS mice. It also decreased iNOS and T-bet protein levels and increased the Arg-1 and GATA-3 protein levels. The ARCR herb pair also increased STAT6 phosphorylation. A STAT6 inhibitor attenuated the regulation of M1/M2 and Th1/Th2 markers induced by the ARCR herb pair.

CONCLUSION

The ARCR herb pair regulates blood lipid metabolism and attenuates atherosclerosis via regulation of M1/M2 and Th1/Th2 immune balance, which is achieved partially by increasing STAT6 phosphorylation. Our study provides new evidence for the possible use of ARCR herb pair in the prevention and treatment of AS.

Angiogenesis effects of 4-methoxy benzyl alcohol on cerebral ischemia-reperfusion injury via regulation of VEGF-Ang/Tie2 balance

Angiogenesis facilitates the formation of microvascular networks and promotes neurological deficit recovery after cerebral ischemia-reperfusion injury (CIRI). This study investigated the angiogenesis effects of 4-methoxy benzyl alcohol (4-MA) on CIRI. The angiogenesis effects of 4-MA and the potential underlying mechanisms were assessed based on a middle cerebral artery occlusion/reperfusion (MCAO/R) rat model and a hind limb ischemic (HLI) mouse model. Immunofluorescence was conducted to detect microvessel density, and Western blotting and polymerase chain reaction were performed to determine the expression of angiogenesis-promoting factors. In addition, we investigated whether the angiogenesis effects of 4-MA caused damage to the blood-brain barrier (BBB). After treatment with 4-MA (20 mg/kg) for 7 days, the neurological deficits recovered and microvessel density in the cerebral cortex increased in the MCAO/R rats. Additionally, 4-MA also regulated the expression of angiogenesis factors, with an increase in vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor 2 (VEGFR-2) expression and a decrease in angiopoietin 1 (Ang-1), Ang-2, and Tie-2 expression in both MCAO/R rats and HLI mice. Moreover, 4-MA increased the expression of angiogenesis-promoting factors without exacerbating BBB cascade damage in MCAO/R rats. Our results indicated that 4-MA may contribute to the formation of microvascular networks, thus promoting neurological deficit recovery after CIRI.

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.

Ion-Selective Carbon Nanotube Field-Effect Transistors for Monitoring Drug Effects on Nicotinic Acetylcholine Receptor Activation in Live Cells

We developed ion-selective field-effect transistor (FET) sensors with floating electrodes for the monitoring of the potassium ion release by the stimulation of nicotinic acetylcholine receptors (nAChRs) on PC12 cells. Here, ion-selective valinomycin-polyvinyl chloride (PVC) membranes were coated on the floating electrode-based carbon nanotube (CNT) FETs to build the sensors. The sensors could selectively measure potassium ions with a minimum detection limit of 1 nM. We utilized the sensor for the real-time monitoring of the potassium ion released from a live cell stimulated by nicotine. Notably, this method also allowed us to quantitatively monitor the cell responses by agonists and antagonists of nAChRs. These results suggest that our ion-selective CNT-FET sensor has potential uses in biological and medical researches such as the monitoring of ion-channel activity and the screening of drugs.

α-Conotoxins active at α3-containing nicotinic acetylcholine receptors and their molecular determinants for selective inhibition

Neuronal α3-containing nicotinic acetylcholine receptors (nAChRs) in the peripheral nervous system (PNS) and non-neuronal tissues are implicated in a number of severe disease conditions ranging from cancer to cardiovascular diseases and chronic pain. However, despite the physiological characterization of mouse models and cell lines, the precise pathophysiology of nAChRs outside the CNS remains not well understood, in part because there is a lack of subtype-selective antagonists. α-Conotoxins isolated from cone snail venom exhibit characteristic individual selectivity profiles for nAChRs and, therefore, are excellent tools to study the determinants for nAChR-antagonist interactions. Given that human α3β4 subtype selective α-conotoxins are scarce and this is a major nAChR subtype in the PNS, the design of new peptides targeting this nAChR subtype is desirable. Recent studies using α-conotoxins RegIIA and AuIB, in combination with nAChR site-directed mutagenesis and computational modelling, have shed light onto specific nAChR residues, which determine the selectivity of the α-conotoxins for the human α3β2 and α3β4 subtypes. Publications describing the selectivity profile and binding sites of other α-conotoxins confirm that subtype-selective nAChR antagonists often work through common mechanisms by interacting with the same structural components and sites on the receptor.

LINKED ARTICLES

This article is part of a themed section on Nicotinic Acetylcholine Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.11/issuetoc.

Role of the nicotinic acetylcholine receptor α3 subtype in vascular inflammation

BACKGROUND AND PURPOSE

Vascular inflammation is a major factor contributing to the development of vascular diseases. The aim of this study was to investigate the role of the nicotinic acetylcholine receptor α3 subtype (α3-nAChR) in vascular inflammation.

EXPERIMENTAL APPROACH

Vascular inflammation was studied in apolipoprotein E knockout (ApoE^-/- ) mice fed a high-fat diet. Inflammatory markers were measured in mouse aortic endothelial cells (MAECs) and macrophages after α3-nAChRs were antagonized pharmacologically, or after the gene of α3-nAChRs was silenced.

KEY RESULTS

Treatment with α-conotoxin MII (MII; an α3-nAChR antagonist) increased the number of inflammatory cells infiltrating the aortic walls and further impaired the endothelium-dependent vasodilatations in the aorta of ApoE^-/- mice. MII also increased the plasma levels of inflammatory cytokines. Furthermore, the infiltration of classical activated macrophages into the arterial wall of ApoE^-/- mice was markedly elevated by MII but that of alternative activated macrophages was reduced. In MAECs, the lipopolysaccharide-stimulated secretion of adhesion molecules and inflammatory cytokines was enhanced by MII, or by silencing the gene of α3-nAChRs. This effect was reversed by inhibitors of the PI3K-Akt-IκKα/β-IκBα-NFκB pathways. In macrophages, the classical activation was enhanced, but the alternative activation was reduced when the gene of α3-nACh receptors was silenced. These effects were prevented by inhibitors of the IκKα/β-IκBα-NFκB and JAK2-STAT6-PPARγ pathways respectively.

CONCLUSIONS AND IMPLICATIONS

α3-nAChRs play a pivotal role in regulating the inflammatory responses in endothelial cells and macrophages. The mechanisms involve the modulations of multiple cell signalling pathways.