Functional Characterization of Cholinergic Receptors in Melanoma Cells

Implications of the non-neuronal cholinergic system for therapeutic interventions of inflammatory skin diseases

The pivotal roles of acetylcholine (ACh) in physiological processes encompass both the nervous and non-neuronal cholinergic systems (NNCS). This review delineates the synthesis, release, receptor interactions, and degradation of ACh within the nervous system, and explores the NNCS in depth within skin cells including keratinocytes, endothelial cells, fibroblasts, macrophages, and other immune cells. We highlight the NNCS's essential functions in maintaining epidermal barrier integrity, promoting wound healing, regulating microcirculation, and modulating inflammatory responses. The potential of the NNCS as a therapeutic target for localized ACh regulation in the skin is discussed, though the translation of these findings into clinical practice remains uncertain due to the complexity of cholinergic signalling and the lack of comprehensive human studies. The review progresses to therapeutic modulation strategies of the NNCS, including AChE inhibitors, nicotinic and muscarinic receptor agonists and antagonists, choline uptake enhancers, and botulinum toxin, highlighting their relevance in dermatology. We highlight the impact of the NNCS on prevalent skin diseases such as psoriasis, atopic dermatitis, rosacea, acne, bullous diseases, hyperhidrosis and hypohidrosis, illustrating its significance in disease pathogenesis and therapy. This comprehensive overview aims to enhance understanding of the NNCS's role in skin health and disease, offering a foundation for future research and therapeutic innovation.

α5-nAChR/ADAM10 signaling mediates nicotine-related cutaneous melanoma progression via STAT3 activation

Skin cutaneous melanoma (SKCM) is the skin malignancy with the highest mortality rate, and its morbidity rate is on the rise worldwide. Smoking is an independent marker of poor prognosis in melanoma. The α5-nicotinic acetylcholine receptor (α5-nAChR), one of the receptors for nicotine, is involved in the proliferation, migration and invasion of SKCM cells. Nicotine has been reported to promote the expression of a disintegrin and metalloproteinase 10 (ADAM10), which is the key gene involved in melanoma progression. Here, we explored the link between α5-nAChR and ADAM10 in nicotine-associated cutaneous melanoma. α5-nAChR expression was correlated with ADAM10 expression and lower survival in SKCM. α5-nAChR mediated nicotine-induced ADAM10 expression via STAT3. The α5-nAChR/ADAM10 signaling axis was involved in the stemness and migration of SKCM cells. Furthermore, α5-nAChR expression was associated with ADAM10 expression, EMT marker expression and stemness marker expression in nicotine-related mice homograft tissues. These results suggest the role of the α5-nAChR/ADAM10 signaling pathway in nicotine-induced melanoma progression.

Activation of the High-Affinity Choline Transporter 1 in the Spinal Cord Relieves Stress-Induced Hyperalgesia

BACKGROUND

The mechanism underlying irritable bowel syndrome (IBS), a common disease with hyperalgesia, remains elusive. The spinal cholinergic system is involved in pain modulation, but its role in IBS is unknown.

AIMS

To determine whether high-affinity choline transporter 1 (CHT1, a major determinant of the cholinergic signaling capacity), is implicated in spinal modulation of stress-induced hyperalgesia.

METHODS

A rat IBS model was established by water avoidance stress (WAS). Visceral sensations were detected by abdominal withdrawal reflex (AWR) and visceromotor response (VMR) to colorectal distension (CRD). Abdominal mechanical sensitivity was determined by von Frey filaments (VFFs) test. RT-PCR, Western blot, and immunostaining were performed for spinal CHT1 expression. Spinal acetylcholine (ACh) was measured by ELISA; the influence of spinal CHT1 on hyperalgesia were evaluated by intrathecal administration of MKC-231 (a choline uptake enhancer) and hemicholinium-3 (HC-3, a specific inhibitor of CHT1). Minocycline treatment was used to explore the role of spinal microglia in hyperalgesia.

RESULTS

After 10 days of WAS, AWR scores and VMR magnitude to CRD, and the number of withdrawal events in VFF test were increased. Double-labeling showed that CHT1 in the dorsal horn was expressed in most of the neurons and almost all the microglia. The CHT1 expression and ACh levels in the spinal cord and the density of CHT1-positive cell in the spinal dorsal horn were enhanced in WAS-exposed rats. HC-3 enhanced pain responses in WAS rats; MKC-231 alleviated pain in WAS rats by upregulating CHT1 expression and increasing ACh production in the spinal cord. Furthermore, microglial activation in the spinal dorsal horn promoted the stress-induced hyperalgesia, and MKC-231 achieved analgesic effects by inhibiting the spinal microglial activation.

CONCLUSIONS

CHT1 exerts antinociceptive effects in spinal modulation of chronic stress-induced hyperalgesia by increasing ACh synthesis and suppressing microglial activation. MKC-231 has potential for treating disorders accompanied by hyperalgesia.

When "No-Smoking" is not enough: Hypoxia and nicotine acetylcholine receptor signaling may drive lung adenocarcinoma progression in never-smokers

The question of how lung cancer progresses in never-smokers remains largely unanswered. In our analysis of data from 1727 lung cancer patients, we observed a difference of only 47 days in the overall survival between lung adenocarcinoma patients who were smokers vis-a-vis never-smokers - the disease has a poor prognosis irrespective of the smoking status, or gender. We have investigated the possible collaboration between the nAChR and hypoxia signaling pathway to explicate a mechanism of disease progression in never-smokers using patient-derived tumor cells. We found a previously unidentified increase in both acetylcholine and nAChR-α7 levels in non-small cell lung cancer cells in hypoxia. A similar increase in ubiquitously expressed nAChR-α7 transcripts was also observed in other cancer lines and primary tumor tissues. A direct binding of HIF-1α with the hypoxia-response element (HRE) present at -48 position preceding the transcriptional start site in nAChR-α7 promoter region was established. Crucially, the increased acetylcholine levels in hypoxia drove a feedback loop via modulation of PI3K/AKT pathway to stabilize HIF-1α in hypoxia. Further, hypoxia-mediated metastasis and induction of HIF-1α in these cells was significantly reversed by bungarotoxin, an antagonist of nAChR-α7. The nAChR-AKT-HIF network needs to be further investigated to conclusively prove its mechanism and to explore its therapeutic potential. Our study gives a plausible explanation for the equally worse prognosis of lung adenocarcinoma in never-smokers wherein the nAChR signaling is enhanced in hypoxia by acetylcholine in the absence of nicotine.

CHRNA1 and its correlated-myogenesis/cell cycle genes are prognosis-related markers of metastatic melanoma

Nicotinic acetylcholine receptors (CHRNs) expression and their critical role in various types of cancer have been reported. However, it is still unclear which CHRNs and their associated genes play essential roles in metastasis in melanoma patients. Here, we performed bioinformatics analyses on publicly available bulk RNA sequencing (RNA-seq) data of patients with melanoma to identify the CHRNs highly expressed in metastatic melanoma. We found that CHRNA1 was highly expressed in metastatic melanoma samples compared to primary melanoma samples and was strongly associated with CHRNB1 and CHRNG. These muscle-type CHRNs (CHRNA1, CHRNB1, and CHRNG) were correlated with the ZEB1 and Rho/ROCK pathway-related genes in metastatic melanoma samples. Pairwise correlations and enrichment analyses revealed that CHRNA1 was significantly associated with myogenesis/muscle contraction and cell cycle genes. Kaplan-Meier curves illustrated the involvement of CHRNA1, four of its correlated genes (DES, FLNC, CDK1, and CDC20), and the myogenesis gene signature in the prognosis of melanoma patients. Following the bulk RNA-seq analysis, single-cell RNA-seq (scRNA-seq) analysis showed that the CHRNA1-expressing melanoma cells are primarily metastatic and had high expression levels of CHRNB1, CHRNG, and myogenesis/cell cycle-related genes. Our bioinformatics analyses of the bulk RNA-seq and scRNA-seq data of patients with melanoma revealed that CHRNA1 and its correlated myogenesis/cell-related cycle genes are critical prognosis-related markers of metastatic melanoma.

The activation of M2 muscarinic receptor inhibits cell growth and survival in human epithelial ovarian carcinoma

Ovarian cancer is the fifth leading cause of cancer-related deaths in females. Many ovarian tumor cell lines express muscarinic receptors (mAChRs), and their expression is correlated with reduced survival of patients. We have characterized the expression of mAChRs in two human ovarian carcinoma cell lines (SKOV-3, TOV-21G) and two immortalized ovarian surface epithelium cell lines (iOSE-120, iOSE-398). Among the five subtypes of mAChRs (M1-M5 receptors), we focused our attention on the M2 receptor, which is involved in the inhibition of tumor cell proliferation. Western blot analysis and real-time PCR analyses indicated that the levels of M2 are statistically downregulated in cancer cells. Therefore, we investigated the effect of arecaidine propargyl ester hydrobromide (APE), a preferential M2 agonist, on cell growth and survival. APE treatment decreased cell number in a dose and time-dependent manner by decreasing cell proliferation and increasing cell death. FACS and immunocytochemistry analysis have also demonstrated the ability of APE to accumulate the cells in G2/M phase of the cell cycle and to increase the percentage of abnormal mitosis. The higher level of M2 receptors in the iOSE cells rendered these cells more sensitive to APE treatment than cancer cells. The data here reported suggest that M2 has a negative role in cell growth/survival of ovarian cell lines, and its downregulation may favor tumor progression.

Brain-heart communication in health and diseases

Tight connections between the brain and heart have attracted a considerable amount of attention. This review focuses on the anatomical (extrinsic cardiac autonomic nervous system and intrinsic cardiac autonomic nervous system) and functional (neuroendocrine-heart axis and neuroimmune-heart axis) connections between the brain and heart, the linkage between central nervous system diseases and cardiovascular diseases, the harm of sympathetic hyperactivity to the heart, and current neuromodulation therapies. Depression is a comorbidity of cardiovascular diseases, and the two are causally related. This review summarizes the mechanisms and treatment of depression and cardiovascular diseases, providing theoretical evidence for basic research and clinical studies to improve treatment options.

Model-Based Anticancer Effect of Botulinum Neurotoxin Type A1 on Syngeneic Melanoma Mice

In recent, Botulinum Neurotoxin A1 (BoNT/A1) has been suggested as a potential anticancer agent due to neuronal innervation in tumor cells. Although potential BoNT/A1's mechanism of action for the tumor suppression has been gradually revealed so far, there were no reports to figure out the exposure-response relationships because of the difficulty of its quantitation in the biological matrix. The main objectives of this study were to measure the anticancer effect of BoNT/A1 using a syngeneic mouse model transplanted with melanoma cells (B16-F10) and developed a kinetic-pharmacodynamic (K-PD) model for quantitative exposure-response evaluation. To overcome the lack of exposure information, the K-PD model was implemented by the virtual pharmacokinetic compartment link to the pharmacodynamic compartment of Simeoni's tumor growth inhibition model and evaluated using curve-fitting for the tumor growth-time profile after intratumoral injection of BoNT/A1. The final K-PD model was adequately explained for a pattern of tumor growth depending on represented exposure parameters and simulation studies were conducted to determine the optimal dose under various scenarios considering dose strength and frequency. The optimal dose range and regimen of ≥13.8 units kg^-1 once a week or once every 3 days was predicted using the final model in B16-F10 syngeneic model and it was demonstrated with an extra in-vivo experiment. In conclusion, the K-PD model of BoNT/A1 was well developed to optimize the dosing regimen for evaluation of anticancer effect and this approach could be expandable to figure out quantitative interpretation of BoNT/A1's efficacy in various xenograft and/or syngeneic models.

Nicotinic acetylcholine receptors in chemotherapeutic drugs resistance: An emerging targeting candidate

There is no definitive cure for cancer, and most of the current chemotherapy drugs have limited effects due to the development of drug resistance and toxicity at high doses. Therefore, there is an ongoing need for identifying the causes of chemotherapeutic resistance, and it will be possible to develop innovative treatment approaches based on these novel targeting candidates. Cigarette smoking is known to be one of the main causes of resistance to chemotherapeutic agents. Nicotine as a component of cigarette smoke is an exogenous activator of nicotinic acetylcholine receptors (nAChRs). It can inhibit apoptosis, increase cell proliferation and cell survival, reducing the cytotoxic effects of chemotherapy drugs and cause a reduced therapeutic response. Recent studies have demonstrated that nAChRs and their downstream signaling pathways have considerable implications in different cancer's initiation, progression, and chemoresistance. In some previous studies, nAChRs have been targeted to obtain better efficacies for chemotherapeutics. Besides, nAChRs-based therapies have been used in combination with chemotherapy drugs to reduce the side effects. This strategy requires lower doses of chemotherapy drugs compared to the conditions that must be used alone. Here, we discussed the experimental and clinical studies that show the nAChRs involvement in response to chemotherapy agents. Also, controversies relating to the effects of nAChR on chemotherapy-induced apoptosis are in our focus in this review article. Delineating the complex influences of nAChRs would be of great interest in establishing new effective chemotherapy regimens.