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A phosphodiesterase inhibitor is a drug that blocks one or more of the five subtypes of the enzyme phosphodiesterase (PDE), thereby preventing the inactivation of the intracellular second messengers, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) by the respective PDE subtype(s). The ubiquitous presence of this enzyme means that non-specific inhibitors have a wide range of actions, the actions in the heart, and lungs being some of the first to find a therapeutic use.
Adenosine (symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N9-glycosidic bond. Adenosine is one of the four nucleoside building blocks of RNA (and its derivative deoxyadenosine is a building block of DNA), which are essential for all life on Earth. Its derivatives include the energy carriers adenosine mono-, di-, and triphosphate, also known as AMP/ADP/ATP. Cyclic adenosine monophosphate (cAMP) is pervasive in signal transduction. Adenosine is used as an intravenous medication for some cardiac arrhythmias.
The adenosine receptors (or P1 receptors) are a class of purinergic G protein-coupled receptors with adenosine as the endogenous ligand. There are four known types of adenosine receptors in humans: A1, A2A, A2B and A3; each is encoded by a different gene.
The adenosine A1 receptor (A1AR) is one member of the adenosine receptor group of G protein-coupled receptors with adenosine as endogenous ligand.
A muscarinic acetylcholine receptor agonist, also simply known as a muscarinic agonist or as a muscarinic agent, is an agent that activates the activity of the muscarinic acetylcholine receptor. The muscarinic receptor has different subtypes, labelled M1-M5, allowing for further differentiation.
Levonantradol (CP 50,556-1) is a synthetic cannabinoid analog of dronabinol (Marinol) developed by Pfizer in the 1980s. It is around 30 times more potent than THC, and exhibits antiemetic and analgesic effects via activation of CB1 and CB2 cannabinoid receptors. Levonantradol is not currently used in medicine as dronabinol or nabilone are felt to be more useful for most conditions, however it is widely used in research into the potential therapeutic applications of cannabinoids.
Purinergic receptors, also known as purinoceptors, are a family of plasma membrane molecules that are found in almost all mammalian tissues. Within the field of purinergic signalling, these receptors have been implicated in learning and memory, locomotor and feeding behavior, and sleep. More specifically, they are involved in several cellular functions, including proliferation and migration of neural stem cells, vascular reactivity, apoptosis and cytokine secretion. These functions have not been well characterized and the effect of the extracellular microenvironment on their function is also poorly understood.
Magnolol is an organic compound that is classified as lignan. It is a bioactive compound found in the bark of the Houpu magnolia and in M. grandiflora. The compound exists at the level of a few percent in the bark of species of magnolia, the extracts of which have been used in traditional Chinese and Japanese medicine. In addition to magnolol, related lignans occur in the extracts including honokiol, which is an isomer of magnolol.
A heteromer is something that consists of different parts; the antonym of homomeric. Examples are:
The adenosine A2A receptor, also known as ADORA2A, is an adenosine receptor, and also denotes the human gene encoding it.
The adenosine A3 receptor, also known as ADORA3, is an adenosine receptor, but also denotes the human gene encoding it.
The adenosine A2B receptor, also known as ADORA2B, is a G-protein coupled adenosine receptor, and also denotes the human adenosine A2b receptor gene which encodes it.
SCH-58261 is a drug which acts as a potent and selective antagonist for the adenosine receptor A2A, with more than 50x selectivity for A2A over other adenosine receptors. It has been used to investigate the mechanism of action of caffeine, which is a mixed A1 / A2A antagonist, and has shown that the A2A receptor is primarily responsible for the stimulant and ergogenic effects of caffeine, but blockade of both A1 and A2A receptors is required to accurately replicate caffeine's effects in animals. SCH-58261 has also shown antidepressant, nootropic and neuroprotective effects in a variety of animal models, and has been investigated as a possible treatment for Parkinson's disease.
Istradefylline, sold under the brand name Nourianz, is a medication used as an add-on treatment to levodopa/carbidopa in adults with Parkinson's disease (PD) experiencing "off" episodes. Istradefylline reduces "off" periods resulting from long-term treatment with the antiparkinson drug levodopa. An "off" episode is a time when a patient's medications are not working well, causing an increase in PD symptoms, such as tremor and difficulty walking.
CP-532,903 is a selective adenosine A3 subtype receptor agonist. It has antiinflammatory effects and has been shown to reduce superoxide generation in damaged tissues, and protects against tissue damage following myocardial ischemia, mediated via an interaction with ATP-sensitive potassium channels.
PSB-10 is a drug which acts as a selective antagonist for the adenosine A3 receptor (ki value at human A3 receptor is 0.44 nM), with high selectivity over the other three adenosine receptor subtypes (ki values at human A1, A2A and A2B receptors are 4.1, 3.3 and 30 μM). Further pharmacological experiments in a [35S]GTPγS binding assay using hA3-CHO-cells indicated that PSB-10 acts as an inverse agonist (IC50 = 4 nM). It has been shown to produce antiinflammatory effects in animal studies. Simple xanthine derivatives such as caffeine and DPCPX have generally low affinity for the A3 subtype and must be extended by expanding the ring system and adding an aromatic group to give high A3 affinity and selectivity. The affinity towards adenosine A3 subtype was measured against the radioligand PSB-11.
Cartazolate (SQ-65,396) is a drug of the pyrazolopyridine class. It acts as a GABAA receptor positive allosteric modulator at the barbiturate binding site of the complex and has anxiolytic effects in animals. It is also known to act as an adenosine antagonist at the A1 and A2 subtypes and as a phosphodiesterase inhibitor. Cartazolate was tested in human clinical trials and was found to be efficacious for anxiety but was never marketed. It was developed by a team at E.R. Squibb and Sons in the 1970s.
Purinergic signalling is a form of extracellular signalling mediated by purine nucleotides and nucleosides such as adenosine and ATP. It involves the activation of purinergic receptors in the cell and/or in nearby cells, thereby regulating cellular functions.
An adenosine receptor agonist is a drug which acts as an agonist of one or more of the adenosine receptors. Examples include the neurotransmitter adenosine, its phosphates, adenosine monophosphate (AMP), adenosine diphosphate (ADP), and adenosine triphosphate (ATP), and the pharmaceutical drug regadenoson.
Namodenoson is a small molecule A3 adenosine receptor (A3AR) agonist. It is developed by Can-Fite for non-alcoholic fatty liver disease, liver cancer, and pancreatic cancer.
References
- ↑ Jayanetti, Viran; Sandhu, Sartaj; Lusthaus, Jed A. (20 November 2020). "The Latest Drugs in Development That Reduce Intraocular Pressure in Ocular Hypertension and Glaucoma". Journal of Experimental Pharmacology. 12: 539–548. doi: 10.2147/JEP.S281187 . PMC 7685378 . PMID 33244278.
- ↑ Park, JeongSu; Choi, Su-Yeon; Wang, Feng; Park, Chong-Woo; Lee, Jiyoun; Lee, Hyuk-Woo; Roh, Yoon-Seok (April 2020). "Imbalance Between α1-Antitrypsin and Neutrophil Elastase in Simple Steatosis Promotes Inflammation and Fibrosis Through Regulation of Adenosine a3 Receptor Signaling in Non-alcoholic Steatohepatitis". The FASEB Journal. 34 (S1): 1. doi: 10.1096/fasebj.2020.34.s1.03837 . S2CID 219099467.
- ↑ Park, Chong-Woo; Han, Chung-Tack; Sakaguchi, Yasue; Lee, Jiyoun; Youn, Hwa-young (12 February 2020). "Safety evaluation of FM101, an A3 adenosine receptor modulator, in rat, for developing as therapeutics of glaucoma and hepatitis". EXCLI Journal. 19: 187–200. doi:10.17179/excli2019-2058. ISSN 1611-2156. PMC 7105940 . PMID 32256265.
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