Acetylcholine protects mesenteric arteries against hypoxia/reoxygenation injury via inhibiting calcium-sensing receptor

The Role of the Acetylcholine System in Common Respiratory Diseases and COVID-19

As an indispensable component in human beings, the acetylcholine system regulates multiple physiological processes not only in neuronal tissues but also in nonneuronal tissues. However, since the concept of the "Nonneuronal cholinergic system (NNCS)" has been proposed, the role of the acetylcholine system in nonneuronal tissues has received increasing attention. A growing body of research shows that the acetylcholine system also participates in modulating inflammatory responses, regulating contraction and mucus secretion of respiratory tracts, and influencing the metastasis and invasion of lung cancer. In addition, the susceptibility and severity of respiratory tract infections caused by pathogens such as Mycobacterium Tuberculosis and the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) can also correlate with the regulation of the acetylcholine system. In this review, we summarized the major roles of the acetylcholine system in respiratory diseases. Despite existing achievements in the field of the acetylcholine system, we hope that more in-depth investigations on this topic will be conducted to unearth more possible pharmaceutical applications for the treatment of diverse respiratory diseases.

The Calcilytic Drug Calhex-231 Ameliorates Vascular Hyporesponsiveness in Traumatic Hemorrhagic Shock by Inhibiting Oxidative Stress and miR-208a-Mediated Mitochondrial Fission

Background

The calcium-sensing receptor (CaSR) plays a fundamental role in extracellular calcium homeostasis in humans. Surprisingly, CaSR is also expressed in nonhomeostatic tissues and is involved in regulating diverse cellular functions. The objective of this study was to determine if Calhex-231 (Cal), a negative modulator of CaSR, may be beneficial in the treatment of traumatic hemorrhagic shock (THS) by improving cardiovascular function and investigated the mechanisms.

Methods

Rats that had been subjected to THS and hypoxia-treated vascular smooth muscle cells (VSMCs) were used in this study. The effects of Cal on cardiovascular function, animal survival, hemodynamics, and vital organ function in THS rats and the relationship to oxidative stress, mitochondrial fusion-fission, and microRNA (miR-208a) were investigated.

Results

Cal significantly improved hemodynamics, elevated blood pressure, increased vital organ blood perfusion and local oxygen supply, and markedly improved the survival outcomes of THS rats. Furthermore, Cal significantly improved vascular reactivity after THS in vivo and in vitro. Cal also restored the THS-induced decrease in myosin light chain (MLC) phosphorylation (the key element for VSMC contraction). Inhibition of MLC phosphorylation antagonized the Cal-induced restoration of vascular reactivity following THS. Cal suppressed oxidative stress in THS rats and hypoxic-VSMCs. Meanwhile, THS induced expression of mitochondrial fission proteins Drp1 and Fis1 and decreased expression of mitochondrial fusion protein Mfn1 in vascular tissues. Cal reduced expression of Drp1 and Fis1. In hypoxic-VSMCs, Cal inhibited mitochondrial fragmentation and preserved mitochondrial morphology. In addition, miR-208a mimic decreased Fis1 expression, and miR-208a inhibitor prevented Cal-induced Fis1 downregulation in hypoxic-VSMCs.

Conclusion

Calhex-231 exhibits outstanding potential for effective therapy of traumatic hemorrhagic shock, and the beneficial effects result from its protection of vascular function via inhibition of oxidative stress and miR-208a-mediated mitochondrial fission.

Calcimimetic R568 improved cardiac remodeling by classic and novel renin-angiotensin system in spontaneously hypertensive rats

One major cause of cardiac mortality is heart disease caused by hypertension. The formation of cyclic adenosine monophosphate (cAMP) is inhibited by calcium-sensitive receptor (CaSR) activation which increases intracellular Ca2+ concentrations and suppresses renin release. As we know, renin-angiotensin system (RAS) is closely related to development of essential hypertension (EH). Therefore, we focused on exploring the roles of NPSR568 (R568)-activated CaSR in cardiac remodeling of spontaneously hypertensive rats (SHRs), as well as the activity of classic and novel RAS. Wistar-Kyoto rats (WKYs) and SHRs were treated by R568 for four and eight weeks, respectively, and their blood pressure (BP), echocardiographic values, heart-to-body weight ratio (HW/BW%), and left ventricle-to-body weight ratio (LVW/BW%) were evaluated. Then Masson’s trichrome staining and hematoxylin and eosin staining as well as RT-qPCR analysis of β-isoform of myosin heavy chain and brain natriuretic peptide mRNA expression were performed. A Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay and analysis of apoptosis marker proteins were used to assess the extent of myocardial apoptosis. The CaSR expression and the activity of classic and novel RAS were examined by immunohistochemistry, western blotting, and enzyme-linked immunosorbent assay. The present study revealed that the development of hypertension was accompanied by increased BP, apoptosis, hypertrophy, and fibrosis, along with decreased expression of CaSR, decreased novel RAS, and increased classic RAS in myocardial tissues. R568 administration for four and eight weeks reduced BP and myocardial remodeling and reversed the low expression of CaSR; moreover, classic RAS was suppressed and novel RAS was activated in the myocardium. Taken together, these data indicate that R568 may effectively inhibit EH myocardial remodeling by inhibiting classic RAS and activating novel RAS in SHRs.

Impact statement

Our study reveals that low calcium-sensitive receptor (CaSR) expression is associated with the occurrence and development of essential hypertension-mediated myocardial remodeling. The activation of CaSR can reverse adverse myocardia remodeling by inhibiting local classical renin-angiotensin system (RAS) and activating novel RAS in cardiac tissues. CaSR is closely related to many cardiovascular diseases, but its specific mechanism remains not to be elucidated. To date, CaSR has not been investigated with regard to cardiovascular treatment; however, given the important relationship between CaSR and cardiovascular disease, CaSR regulators can be potential drugs for the treatment of cardiovascular disease.

Antagonism of Ca2+-sensing receptors by NPS 2143 is transiently masked by p38 activation in mouse brain bEND.3 endothelial cells

Ca²⁺-sensing receptors (CaSR) are G protein-coupled receptors which are activated by a rise in extracellular Ca²⁺. CaSR activation has been known to inhibit parathyroid hormone release and stimulate calcitonin release from parathyroid glands and thyroid parafollicular C cells, respectively. The roles of CaSR in other cell types including endothelial cells (EC) are much less understood. In this work, we demonstrated protein and functional expression of CaSR in mouse cerebral EC (bEND.3). Unexpectedly, CaSR response (high Ca²⁺-elicited cytosolic [Ca²⁺] elevation) was unaffected by edelfosine or U73122 but strongly suppressed by SK&F 96365, ruthenium red, and 2-aminoethoxydiphenyl borate (2-APB), suggesting involvement of TRPV and TRPC channels but not Gq-phospholipase C. Acute application of NPS2143, a negative allosteric modulator of CaSR, suppressed CaSR response. However, a 40-min NPS2143 pre-treatment surprisingly enhanced CaSR response. After 4-24 h of application, this enhancement faded away and suppression of CaSR response was observed again. Similar results were obtained when La³⁺ and Sr²⁺ were used as CaSR agonists. The transient NPS 2143 enhancement effect was abolished by SB203580, a p38 inhibitor. Consistently, NPS 2143 triggered a transient p38 activation. Taken together, results suggest that in bEND.3 cells, NPS 2143 caused acute suppression of CaSR response, but then elicited a transient enhancement of CaSR response in a p38-dependent manner. NPS 2143 effects on CaSR in bEND.3 cells therefore depended on drug exposure time. These findings warrant cautious use of this agent as a CaSR modulator and potential cardiovascular drug.

Acetylcholine signaling system in progression of lung cancers

The neurotransmitter acetylcholine (ACh) acts as an autocrine growth factor for human lung cancer. Several lines of evidence show that lung cancer cells express all of the proteins required for the uptake of choline (choline transporter 1, choline transporter-like proteins) synthesis of ACh (choline acetyltransferase, carnitine acetyltransferase), transport of ACh (vesicular acetylcholine transport, OCTs, OCTNs) and degradation of ACh (acetylcholinesterase, butyrylcholinesterase). The released ACh binds back to nicotinic (nAChRs) and muscarinic receptors on lung cancer cells to accelerate their proliferation, migration and invasion. Out of all components of the cholinergic pathway, the nAChR-signaling has been studied the most intensely. The reason for this trend is due to genome-wide data studies showing that nicotinic receptor subtypes are involved in lung cancer risk, the relationship between cigarette smoke and lung cancer risk as well as the rising popularity of electronic cigarettes considered by many as a "safe" alternative to smoking. There are a small number of articles which review the contribution of the other cholinergic proteins in the pathophysiology of lung cancer. The primary objective of this review article is to discuss the function of the acetylcholine-signaling proteins in the progression of lung cancer. The investigation of the role of cholinergic network in lung cancer will pave the way to novel molecular targets and drugs in this lethal malignancy.