Adenosine analogue inhibitors of S-adenosylhomocysteine hydrolase

Bipolar mania and epilepsy pathophysiology and treatment may converge in purine metabolism: A new perspective on available evidence

Decreased ATPergic signaling is an increasingly recognized pathophysiology in bipolar mania disease models. In parallel, adenosine deficit is increasingly recognized in epilepsy pathophysiology. Under-recognized ATP and/or adenosine-increasing mechanisms of several antimanic and antiseizure therapies including lithium, valproate, carbamazepine, and ECT suggest a fundamental pathogenic role of adenosine deficit in bipolar mania to match the established role of adenosine deficit in epilepsy. The depletion of adenosine-derivatives within the purine cycle is expected to result in a compensatory increase in oxopurines (uric acid precursors) and secondarily increased uric acid, observed in both bipolar mania and epilepsy. Cortisol-based inhibition of purine conversion to adenosine-derivatives may be reflected in observed uric acid increases and the well-established contribution of cortisol to both bipolar mania and epilepsy pathology. Cortisol-inhibited conversion from IMP to AMP as precursor of both ATP and adenosine may represent a mechanism for treatment resistance common in both bipolar mania and epilepsy. Anti-cortisol therapies may therefore augment other treatments both in bipolar mania and epilepsy. Evidence linking (i) adenosine deficit with a decreased need for sleep, (ii) IMP/cGMP excess with compulsive hypersexuality, and (iii) guanosine excess with grandiose delusions may converge to suggest a novel theory of bipolar mania as a condition characterized by disrupted purine metabolism. The potential for disease-modification and prevention related to adenosine-mediated epigenetic changes in epilepsy may be mirrored in mania. Evaluating the purinergic effects of existing agents and validating purine dysregulation may improve diagnosis and treatment in bipolar mania and epilepsy and provide specific targets for drug development.

Identification of novel inhibitors of S-adenosyl-L-homocysteine hydrolase via structure-based virtual screening and molecular dynamics simulations

S-adenosyl-L-homocysteine hydrolase (SAHase) is an important regulator in the methylation reactions in many organisms and thus is crucial for numerous cellular functions. In recent years, SAHase has become one of the popular targets for drug design, and SAHase inhibitors have exhibited potent antiviral activity. In this study, we established the complex-based pharmacophore models based on the known crystal complex of SAHase (PDB ID: 1A7A) to screen the drug-likeness compounds of ChEMBL database. Then, three molecular docking programs were used to validate the reliability of compounds, involving Libdock, CDOCKER, and AutoDock Vina programs. The four promising hit compounds (CHEMBL420751, CHEMBL346387, CHEMBL1569958, and CHEMBL4206648) were performed molecular dynamics simulations and MM-PBSA calculations to evaluate their stability and binding-free energy in the binding site of SAHase. After screening and analyzing, the hit compounds CHEMBL420751 and CHEMBL346387 were suggested to further research to obtain novel potential SAHase inhibitors. A series of computer-aided drug design methods, including pharmacophore, molecular docking, molecular dynamics simulation and MM-PBSA calculations, were employed in this study to identity novel inhibitors of S-adenosyl-L-homocysteine hydrolase (SAHase). Some compounds from virtual screening could form various interactions with key residues of SAHase. Among them, compounds CHEMBL346387 and CHEMBL420751 exhibited potent binding affinity from molecular docking and MM-PBSA, and maintained good stability at the binding site during molecular dynamics simulations as well. All these results indicated that the selected compounds might have the potential to be novel SAHase inhibitors.

Synthesis and biological evaluation of novel pentanediamide derivatives as S-adenosyl-l-homocysteine hydrolase inhibitors

A series of novel pentanediamide derivatives were designed, synthesized and evaluated as S-adenosyl-l-homocysteine hydrolase (SAHase) inhibitors in this study. Some compounds showed good inhibitory activity against SAHase. The optimal compound 7i showed good inhibitory activity against SAHase with IC₅₀ value of 3.58 ± 0.19 μM, cytotoxicity with IC₅₀ values ranging from 13.16 ± 1.44 to 21.23 ± 0.73 μM against four tumor cell lines (MCF-7, A549, MGC-803, Hela) and very weak cytotoxicity (IC₅₀ = 84.22 ± 1.89 μM) on normal LO2 cells. In addition, compound 7i showed potency against respiratory syncytial virus with EC₅₀ value of 27.4 μM and selectivity index of 6.84. Further molecular simulation study suggested that compound 7i had good ADMET properties, and strongly binds to the active site of SAHase. In summary, compound 7i could serve as a new lead compound for further screening novel non-adenosine SAHase inhibitors.

Homocysteine-specific fluorescence detection and quantification for evaluating S-adenosylhomocysteine hydrolase activity

The medium Ks value of copper complex contributed to the specific reduction of Cu2+ by homocysteine and the formation of a stable six-membered ring species.

Epigenetics and epilepsy prevention: The therapeutic potential of adenosine and metabolic therapies

Prevention of epilepsy and its progression remains the most urgent need for epilepsy research and therapy development. Novel conceptual advances are required to meaningfully address this fundamental challenge. Maladaptive epigenetic changes, which include methylation of DNA and acetylation of histones - among other mechanisms, are now well recognized to play a functional role in the development of epilepsy and its progression. The methylation hypothesis of epileptogenesis suggests that changes in DNA methylation are implicated in the progression of the disease. In this context, global DNA hypermethylation is particularly associated with chronic epilepsy. Likewise, acetylation changes of histones have been linked to epilepsy development. Clinical as well as experimental evidence demonstrate that epilepsy and its progression can be prevented by metabolic and biochemical manipulations that target previously unrecognized epigenetic functions contributing to epilepsy development and maintenance of the epileptic state. This review will discuss epigenetic mechanisms implicated in epilepsy development as well as metabolic and biochemical interactions thought to drive epileptogenesis. Therefore, metabolic and biochemical mechanisms are identified as novel targets for epilepsy prevention. We will specifically discuss adenosine biochemistry as a novel therapeutic strategy to reconstruct the DNA methylome as antiepileptogenic strategy as well as metabolic mediators, such as beta-hydroxybutyrate, which affect histone acetylation. Finally, metabolic dietary interventions (such as the ketogenic diet) which have the unique potential to prevent epileptogenesis through recently identified epigenetic mechanisms will be reviewed. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

Inhibition of juvenile hormone synthesis in mosquitoes by the methylation inhibitor 3-deazaneplanocin A (DZNep)

Juvenile hormone (JH), synthesized by the corpora allata (CA), controls development and reproduction in mosquitoes through its action on thousands of JH-responsive genes. These JH-dependent processes can be studied using tools that increase or decrease JH titers in vitro and in vivo. Juvenile hormone acid methyl transferase (JHAMT) is a critical JH biosynthetic enzyme. JHAMT utilizes the methyl donor S-adenosyl-methionine (SAM) to methylate farnesoic acid (FA) into methyl farnesoate (MF), releasing the product S-adenosyl-L-homocysteine (AdoHcy), which inhibits JHAMT. S-adenosyl-homocysteine hydrolase (SAHH) catalyzes AdoHcy hydrolysis to adenosine and homocysteine, alleviating AdoHcy inhibition of JHAMT. 3-deazaneplanocin A (DZNep), an analog of adenosine, is an inhibitor of SAHH, and an epigenetic drug for cancer therapy. We tested the effect of DZNep on in vitro JH synthesis by CA of mosquitoes. DZNep inhibited JH synthesis in a dose-response fashion. Addition of MF, but not of FA relieved the inhibition, demonstrating a direct effect on JHAMT. In vivo experiments, with addition of DZNep to the sugar ingested by mosquitoes, resulted in a dose-response decrease in JH synthesis and JH hemolymphatic titers, as well as expression of early trypsin, a JH-dependent gene. Our studies suggest that DZNep can be employed to lower JH synthesis and titer in experiments evaluating JH-controlled processes in mosquitoes.

Characterization of human S-adenosyl-homocysteine hydrolase in vitro and identification of its potential inhibitors

Human S-adenosyl-homocysteine hydrolase (SAHH, E.C.3.3.1.1) has been considered to be an attractive target for the design of medicines to treat human disease, because of its important role in regulating biological methylation reactions to catalyse the reversible hydrolysis of S-adenosylhomocysteine (SAH) to adenosine (Ado) and l-homocysteine (Hcy). In this study, SAHH protein was successfully cloned and purified with optimized, Pichia pastoris (P. pastoris) expression system. The biological activity results revealed that, among the tested compounds screened by ChemMapper and SciFinder Scholar, 4-(3-hydroxyprop-1-en-1-yl)-2-methoxyphenol (coniferyl alcohol, CAS: 458-35-5, ZINC: 12359045) exhibited the highest inhibition against rSAHH (IC₅₀= 34 nM). Molecular docking studies showed that coniferyl alcohol was well docked into the active cavity of SAHH. And several H-bonds formed between them, which stabilized coniferyl alcohol in the active site of rSAHH with a proper conformation.

Discovery and structural analyses of S-adenosyl-L-homocysteine hydrolase inhibitors based on non-adenosine analogs

Optimization of a new series of S-adenosyl-L-homocysteine hydrolase (AdoHcyase) inhibitors based on non-adenosine analogs led to very potent compounds 14n, 18a, and 18b with IC50 values of 13 ± 3, 5.0 ± 2.0, and 8.5 ± 3.1 nM, respectively. An X-ray crystal structure of AdoHcyase with NAD(+) and 18a showed a novel open form co-crystal structure. 18a in the co-crystals formed intramolecular eight membered ring hydrogen bond formations. A single crystal X-ray structure of 14n also showed an intramolecular eight-membered ring hydrogen bond interaction.

Discovery of S-adenosyl-L-homocysteine hydrolase inhibitors based on non-adenosine analogs

High throughput screening using Automated Ligand Identification System (ALIS) resulted in the discovery of a new series of S-adenosyl-L-homocysteine hydrolase inhibitors based on non-adenosine analogs. The optimization campaign led to very potent and competitive compound 39 with a Ki value of 1.5 nM. Compound 39 could be a promising lead compound for research to reduce elevated homocysteine levels.