Discovery of Novel Soluble Epoxide Hydrolase Inhibitors as Potent Vasodilators

Inhibition of soluble epoxide hydrolase by natural isothiocyanates

GOAL

The long-term goal of our research is to develop safe and effective soluble epoxide hydrolase (sEH) inhibitors. The objective of this study is to evaluate the potency and selectivity of six natural isothiocyanates (ITCs) as sEH inhibitors.

METHODS

Molecular docking was used to model likely interactions between the ligands and receptors. The sEH inhibitory activity was tested using a validated fluorescence-based assay and PHOME as a substrate. To evaluate their selectivity as sEH inhibitors, the inhibitory potential of the ITCs was determined on microsomal epoxide hydrolase (mEH) and cytochrome P450 (CYP) enzymes in human liver microsomes. Probe substrates such as styrene oxide (mEH substrate) and established substrates for CYP2A6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4 were used in this study. The metabolites of these substrates were analyzed using validated LC-MS/MS and HPLC-UV assays.

RESULTS

Molecular Docking revealed significant differences in binding site preference among the ITCs in silico and pointed to important interactions between the ligands and the catalytic residues of the sEH enzyme. In vitro, the ITCs showed varying degrees of sEH inhibition, but sulforaphane (SFN) and phenyl isothiocyanate (PITC) were the most potent inhibitors with IC50 values of 3.65 and 7.5 μM, respectively. mEH was not significantly inhibited by any of the ITCs. Erucin and iberin were the only ITCs that did not inhibit the activity of any of the tested CYP enzymes.

CONCLUSION

Our results demonstrate that natural ITCs have the potential to offer safe, selective, and potent sEH inhibition.

Tinospora cordifolia ameliorates paclitaxel-induced neuropathic pain in albino rats

ETHNOPHARMACOLOGICAL RELEVANCE

Tinospora cordifolia (T. cordifolia) (Willd.) Miers, a member of the Menispermaceae, family documented in the ancient textbooks of the Ayurveda System of Medicine, has been used in the management of sciatica pain and diabetic neuropathy.

AIM

The study has been designed to evaluate the antinociceptive potential of various extracts of T. cordifolia stem in Paclitaxel (PT)-generated neuropathic pain model in albino rats and explore its possible mechanism employing molecular docking studies.

METHODS

Stems of T. cordifolia were shade dried, grinded in fine powder, and extracted separately with different solvents viz. ethanol, water & hydro-alcoholic and characterized using LCMS/MS. The antinociceptive property of T. cordifolia stem (200 and 400 mg/kg) was examined in albino rats using a PT-induced neuropathic pain model. Further, the effect of these extracts was also observed using different behavioral assays viz. cold allodynia, mechanical hyperalgesia (pin-prick test), locomotor activity test, walking track test, and Sciatic Functional Index (SFI) in rats. Tissue lysate of the sciatic nerve was used to determine various biochemical markers such as GSH, SOD, TBARS, tissue protein, and nitrite. Further to explore the possible mechanism of action, the most abundant and therapeutically active compounds available in aqueous extract were analyzed for binding affinity towards soluble epoxide hydrolase (sEH) enzyme (PDB ID: 3wk4) employing molecular docking studies.

RESULTS

The results of the LCMS/MS study of different extracts of T. cordifolia indicated presence of alkaloids, glycosides, terpenoids, sterols and sugars such as amritoside A, tinocordin, magnoflorine, N-methylcoclaurine, coridine, 20β-hydroxyecdysone and menaquinone-7 palmatin, cordifolioside A and tinosporine etc. Among all the three extracts, the hydroalcoholic extract (400 mg/kg) showed the highest response followed by aqueous and ethanolic extracts as evident in in vivo behavioral and biochemical evaluations. Furthermore, docking studies also exposed that these compounds viz. N-methylcoclaurine tinosporin, palmatine, tinocordin, 20β-hydroxyecdysone, and coridine exhibited well to excellent affinity towards target sEH protein.

CONCLUSION

T. cordifolia stem could alleviate neuropathic pain via soluble epoxide hydrolase inhibitory activity.

Anti-inflammatory of disenecionyl cis-khellactone in LPS-stimulated RAW264.7 cells and the its inhibitory activity on soluble epoxide hydrolase

The objective of the present study was to investigate anti-inflammatory effects of disenecionyl cis-khellactone (DK) isolated from Peucedanum japonicum Thunberg, a traditional edible plant, in RAW264.7 cells stimulated with lipopolysaccharide (LPS). Anti-inflammatory effects of DK were analyzed using various techniques, including NO assay, Western blot analysis, enzyme-linked immunosorbent assay (ELISA), real-time PCR, and immunofluorescence staining. It was revealed that DK reduced the production of pro-inflammatory cytokines including Monocyte chemoattractant protein-1 (MCP-1), Tumor necrosis factor-α (TNF-α), Interleukin 1β (IL-1β), and Interleukin 6 (IL-6) in RAW264.7 cells stimulated with LPS. It was revealed that DK effectively downregulated expression levels of iNOS and COX-2 due to inhibition of NF-κB activation and suppressing the phosphorylation of p38 and jun N-terminal kinase (JNK) mitogen-activated protein kinase (MAPK) phosphorylation. Also, soluble epoxide hydrolase activity and expression were decreased by the proinflammatory inhibitor, DK. Finally, findings of this study suggest that DK isolated from P. japonicum might have potential as a therapeutic candidate for inflammatory diseases.

Inhibitory activity of lignanamides isolated from hemp seed hulls(Cannabis sativa L.) against soluble epoxide hydrolase

Soluble epoxide hydrolase (sEH) is a therapeutic target for inflammation. In the present study, we isolated one new (1) and four known (2-5) compounds from the ethyl acetate fraction of hemp seed hulls. Their structures were elucidated as lignanamides via nuclear magnetic resonance and mass spectral analyses. All five compounds inhibited sEH activity, with half-maximal inhibitory concentrations of 2.7 ± 0.3 to 18.3 ± 1.0 μM. These lignanamides showed a competitive mechanism of inhibition via binding to sEH, with ki values below 10 μmol. Molecular simulations revealed that compounds 1-5 fit stably into the active site of sEH, and the key amino acid residues participating in their bonds were identified. It was confirmed that the potential inhibitors 4 and 5 continuously maintained a distance of 3.5 Å from one (Tyr383) and four amino (Asp335, Tyr383, Asn472, tyr516) residues, respectively. These findings provide a framework for the development of naturally derived sEH inhibitors.

New insights on mode of action of vasorelaxant activity of simvastatin

Simvastatin is a semisynthetic inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and is used extensively to treat atherosclerotic cardiovascular disease. Apart from the lipid-lowering effect, simvastatin has been documented to offer impressive vasorelaxant activity. However, the mechanism associated with this vasorelaxant activity has yet not been substantially explored. Thus, the present study has aimed to elucidate the mechanism(s) associated with simvastatin-induced vasorelaxation using an established rat aortic ring model. The results from the study depicted that simvastatin caused significant relaxation in aortic rings pre-contracted with phenylephrine and potassium chloride (KCl). The vasorelaxant effect of simvastatin was attenuated by methylene blue (sGC-dependent cyclic guanosine monophosphate (cGMP) inhibitor), N^G-nitro-L-arginine methyl ester (L-NAME; NO synthase inhibitor), 4-aminopyridine (K_v blocker), glibenclamide (K_ATP blocker), and barium chloride (K_ir blocker). In addition, the vasorelaxant effect of simvastatin was slightly reduced by PD123319 (angiotensin II type 2 receptor (AT₂R) antagonist). However, indomethacin (COX inhibitor), 1H-[1,2,4]Ox adiazolol [4,3-α]quinoxalin-1-one (ODQ; selective soluble guanylate cyclase (sGC) inhibitor), losartan (angiotensin II type 1 receptor (AT₁R) antagonist), atropine (muscarinic receptor blocker), and tetraethyl ammonium (TEA; K_Ca blocker) did not affect the vasorelaxant effect of simvastatin. Furthermore, simvastatin was found to attenuate the release of calcium (Ca²⁺) from intracellular stores in the presence of ruthenium red (ryanodine receptor, RyR inhibitor) and extracellular stores via nifedipine (voltage-operated Ca²⁺ channels, VOCC blocker) and SK&F96365 (receptor-operated Ca²⁺ channel, ROCC blocker). Thus, it can be concluded that the vasorelaxant effect of simvastatin involves NO/cGMP pathways, AT₂R receptors, Ca²⁺ channels, and K⁺ channels.

Increased Soluble Epoxide Hydrolase Activity Positively Correlates with Mortality in Heart Failure Patients with Preserved Ejection Fraction: Evidence from Metabolomics

Epoxyeicosatrienoic acids (EETs) have pleiotropic endogenous cardiovascular protective effects and can be hydrolyzed to the corresponding dihydroxyeicosatrienoic acids by soluble epoxide hydrolase (sEH). Heart failure with preserved ejection fraction (HFpEF) has shown an increased prevalence and worse prognosis over the decades. However, the role of sEH activity in HFpEF remains unclear. We enrolled 500 patients with HFpEF and 500 healthy controls between February 2010 and March 2016. Eight types of sEH-related eicosanoids were measured according to target metabolomics, and their correlation with clinical endpoints was also analyzed. The primary endpoint was cardiac mortality, and the secondary endpoint was a composite of cardiac events, including heart failure (HF) readmission, cardiogenic hospitalization, and all-cause mortality. Furthermore, the effect of sEH inhibitors on cardiac diastolic function in HFpEF was investigated in vivo and in vitro. Patients with HFpEF showed significantly enhanced EET degradation by the sEH enzyme compared with healthy controls. More importantly, sEH activity was positively correlated with cardiac mortality in patients with HFpEF, especially in older patients with arrhythmia. A consistent result was obtained in the multiple adjusted models. Decreased sEH activity by the sEH inhibitor showed a significant effective effect on the improvement of cardiac diastolic function by ameliorating lipid disorders in cardiomyocytes of HFpEF mouse model. This study demonstrated that increased sEH activity was associated with cardiac mortality in patients with HFpEF and suggested that sEH inhibition could be a promising therapeutic strategy to improve diastolic cardiac function. Clinical trial identifier: NCT03461107 (https://clinicaltrials.gov).

Supplementary Information

The online version contains supplementary material available at 10.1007/s43657-022-00069-8.

Therapeutic Potential of Reserpine in Metabolic Syndrome: An Evidence Based Study

Reserpine is as old as the scientific diagnosis of hypertension. For many years' clinicians have used it for the treatment of high blood pressure, but with the passage of time and introduction of new anti-hypertensive drugs, the usage of reserpine has gone down drastically most probably due to poorly understood mechanism of action and multiple misleading adverse effects precisely due to high dosing of reserpine. With an aim to elucidate the specific mechanism of action, we screened reserpine against various targets associated with regulation of blood pressure. Surprisingly reserpine showed remarkable inhibitory potential for soluble epoxide hydrolase an enzyme responsible for pathophysiology of not only hypertension but also hyperlipidemia, diabetes and inflammation collectively known as metabolic syndrome. The in-silico, in-vitro and in-vivo results showed that reserpine has the ability to treat metabolic syndrome effectively by inhibiting soluble epoxide hydrolase.

Repositioning of tubocurarine as analgesic and anti-inflammatory agent: Exploring beyond myorelaxant activity

BACKGROUND AND PURPOSE

Tubocurarine (d-TC), a non-depolarizing competitive blocker of nicotinic acetylcholine receptors is extensively utilized for the relaxation of skeletal muscles. Drug repositioning is a forthright approach to reduce the cost and speed up drug development process. Herein, we have attempted to evaluate the analgesic and anti-inflammatory activity of d-TC for its possible repurposing in pain and inflammation-related issues.

EXPERIMENTAL APPROACH

We examined the soluble epoxide hydrolase inhibitory (sEHI) activity of d-TC employing in silico high throughput screening protocols, in vitro cell-free sEH inhibitory assay, and in in vivo rodent models for its repositioning in pain and inflammation-related disorders.

KEY RESULTS

In molecular docking study, d-TC displayed impressive hydrogen bonding interactions within the cavity of sEH enzyme with good docking score. d-TC also exhibited notable sEH inhibitory activity (IC₅₀ 3.72 nm) at the in vitro assay. Oral absorption capability of d-TC (0.1 and 0.2 mg/mL) was determined using an in vitro everted intestinal sac model employing rat ileum tissue that revealed significant oral absorption of d-TC. Besides, in vivo studies revealed that oral administration of d-TC (0.1 and 0.2 mg/kg) in rodents significantly attenuated hyperalgesia (cold plate test, tail immersion test and formalin test) and inflammation (estimation of rectal temperature, acetic acid induced pleurisy test and cotton pellet-induced granuloma test) induced in robust preclinical models. Conclusion and implications These findings are novel and warrant immediate efforts to reposition d-TC as a new therapeutic candidate in the management of hyperalgesia, inflammation, and associated conditions.

Repurposing of digoxin in pain and inflammation: An evidence-based study

In recent years, the drug repositioning strategy has gained considerable attention in the drug discovery process that involves establishing new therapeutic uses of already known drugs. In line with this, we have identified digoxin a cardiac glycoside, as a potent inhibitor of soluble epoxide hydrolase (sEH) enzyme employing in silico high throughput screening protocols and further confirmed using in vitro cell-free sEH inhibitory assay and in vivo preclinical studies in rodents for its repurposing in hyperalgesia, inflammation, and related disorders. Oral administration of digoxin at dose 0.2 mg/kg significantly reduced (p < .0001) the allodynia in mice induced by using hot plate (3.6 ± 1.9) and tail-flick test (7.58 ± 0.9). In addition, digoxin at a dose of 0.2 mg/kg showed marked reduction (94%, p < .0001) in acetic acid-induced abdominal contraction in rats. Further, digoxin also demonstrated antipyretic activity (37.04 ± 0.2, p < .0001) and showed notable reduction (0.60 ± 0.06) in carrageenan-induced paw edema in rats. Also, the histopathological evaluation revealed that digoxin treatment attenuated the edema, neutrophil infiltration, and alveolar septal thickening in lung tissue. These findings are novel and highlight the newer insights towards repurposing digoxin as a new lead in the treatment of hyperalgesia, inflammation, and related disorders.

Identifying simultaneous matrix metalloproteinases/soluble epoxide hydrolase inhibitors

Matrix metalloproteinase (MMP) and soluble epoxide hydrolase (sEH) have completely unrelated biological functions; however, their dysregulation produce similar effects on biological systems. Based on the similarity in the reported structural requirements for their inhibition, the current study aimed to identify a simultaneous inhibitor for MMP and sEH. Six compounds were identified as potential simultaneous MMP/sEH inhibitors and tested for their capacity to inhibit MMP and sEH. Inhibition of MMP and sEH activity using their endogenous and exogenous substrates was measured by liquid chromatography/mass spectrometry, spectrophotometry, and zymography. Two compounds, CTK8G1143 and ONO-4817, were identified to inhibit both MMP and sEH activity. CTK8G1143 and ONO-4817 inhibited the recombinant human sEH activity by an average of 67.4% and 55.2%, respectively. The IC₅₀ values for CTK8G1143 and ONO-4817 to inhibit recombinant human sEH were 5.2 and 3.5 µM, respectively, whereas their maximal inhibition values were 71.4% and 42.8%, respectively. Also, MMP and sEH activity of human cardiomyocytes were simultaneously inhibited by CTK8G1143 and ONO-4817. Regarding other compounds, they showed either MMP or sEH inhibitory activity but not both. In conclusion, these two simultaneous inhibitors of MMP and sEH could provide a promising intervention for the prevention and control of several diseases, especially cardiovascular diseases.

Simvastatin ameliorates oxidative stress levels in HepG2 cells and hyperlipidemic rats

Simvastatin is an established anti-hyperlipidemic drug and few studies have indicated its role in the mitigation of oxidative stress. However, a systematic study considering molecular binding/interaction of simvastatin with anti-oxidant enzymes followed by confirmational in vitro and in vivo studies have never been done. We investigated the molecular binding of simvastatin with multiple anti-oxidant enzymes and assessed their levels after the treatment of simvastatin in vitro and in vivo. This study is the first to show the molecular binding of simvastatin to catalase through molecular docking analysis. Moreover, the anti-oxidative properties of simvastatin have not been studied in Lipopolysaccharide (LPS) induced oxidative stress in HepG2 cells. We found that simvastatin effectively attenuated oxidative stress in LPS induced HepG2 cells and high-fat diet (HFD) fed hyperlipidemic rats by increasing the levels of antioxidant enzymes. The activity of catalase and superoxide dismutase (SOD) both increased significantly in oxidatively stressed HepG2 cells after the treatment with simvastatin (10 ​μM, 24 ​h). In addition to this, he original cell morphology of oxidatively stressed cells was restored by simvastatin, and an increase in antioxidant enzymes, catalase (0.08 U/cells to 0.12 U/cells), and SOD (0.57 U/cells to 0.74 U/cells) was also noted in HepG2 cells. Furthermore, a significant increase in the antioxidant enzymes such as Catalase, SOD, and reduced glutathione (GSH) was noted after simvastatin treatment in the HFD model. Moreover, we also observed degradation of by-products of lipid peroxidation thiobarbituric acid reactive substances (TBARs), nitric oxide (NO), and protein carbonyl levels. This indicates that simvastatin enhances anti-oxidant enzyme activities and can be repurposed for the treatment of oxidative stress in liver diseases in humans after extensive clinical trials.

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In silico, molecular docking analysis shows that simvastatin binds to the active site of the catalase enzyme.

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Simvastatin attenuates LPS induced oxidative stress in HepG2 cells by increasing the amount of antioxidant enzymes catalase and SOD.

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Simvastatin significantly reduces triglycerides, cholesterol, LDL, VLDL, and increases HDL level in HFD induced oxidative stress in Wistar rats.

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Simvastatin can be repurposed for the treatment of oxidative stress in liver diseases.

Salt-Sensitive Hypertension in GR+/- Rats Is Accompanied with Dysregulation in Adrenal Soluble Epoxide Hydrolase and Polyunsaturated Fatty Acid Pathways

Mutations within the glucocorticoid receptor (GR) gene locus lead to glucocorticoid resistance which is characterized by several clinical symptoms such as adrenal gland hyperplasia and salt-sensitive hypertension, although the underlying mechanisms are still unknown. We studied GR haploinsufficient (GR^+/−) Sprague Dawley rats which, on a standard diet, showed significantly increased plasma aldosterone and corticosterone levels and an adrenocortex hyperplasia accompanied by a normal systolic blood pressure. Following a high salt diet, these rats developed salt-sensitive hypertension and maintained elevated enzyme-soluble epoxide hydrolase (sEH) in adrenal glands, while sEH was significantly decreased in wild-type rats. Furthermore, GR^+/− rats showed dysregulation of the equilibrated linoleic and arachidonic acid pathways, with a significant increase of less active metabolites such as 8,9-DiHETrE. In Sprague Dawley rats, GR haploinsufficiency induced steroid disturbances, which provoked hypertension only in combination with high salt intake, which was accompanied by disturbances in sEH and fatty acid metabolism. Our results suggest that sEH inhibition could be a potential target to treat hypertension in patients with GR haploinsufficiency.

Molecular modeling in cardiovascular pharmacology: Current state of the art and perspectives

Molecular modeling in pharmacology is a promising emerging tool for exploring drug interactions with cellular components. Recent advances in molecular simulations, big data analysis, and artificial intelligence (AI) have opened new opportunities for rationalizing drug interactions with their pharmacological targets. Despite the obvious utility and increasing impact of computational approaches, their development is not progressing at the same speed in different fields of pharmacology. Here, we review current in silico techniques used in cardiovascular diseases (CVDs), cardiological drug discovery, and assessment of cardiotoxicity. In silico techniques are paving the way to a new era in cardiovascular medicine, but their use somewhat lags behind that in other fields.

Heme-oxygenase and lipid mediators in obesity and associated cardiometabolic diseases: Therapeutic implications

Obesity-mediated metabolic syndrome remains the leading cause of death worldwide. Among many potential targets for pharmacological intervention, a promising strategy involves the heme oxygenase (HO) system, specifically its inducible form, HO-1. This review collects and updates much of the current knowledge relevant to pharmacology and clinical medicine concerning HO-1 in metabolic diseases and its effect on lipid metabolism. HO-1 has pleotropic effects that collectively reduce inflammation, while increasing vasodilation and insulin and leptin sensitivity. Recent reports indicate that HO-1 with its antioxidants via the effect of bilirubin increases formation of biologically active lipid metabolites such as epoxyeicosatrienoic acid (EET), omega-3 and other polyunsaturated fatty acids (PUFAs). Similarly, HO-1and bilirubin are potential therapeutic targets in the treatment of fat-induced liver diseases. HO-1-mediated upregulation of EET is capable not only of reversing endothelial dysfunction and hypertension, but also of reversing cardiac remodeling, a hallmark of the metabolic syndrome. This process involves browning of white fat tissue (i.e. formation of healthy adipocytes) and reduced lipotoxicity, which otherwise will be toxic to the heart. More importantly, this review examines the activity of EET in biological systems and a series of pathways that explain its mechanism of action and discusses how these might be exploited for potential therapeutic use. We also discuss the link between cardiac ectopic fat deposition and cardiac function in humans, which is similar to that described in obese mice and is regulated by HO-1-EET-PGC1α signaling, a potent negative regulator of the inflammatory adipokine NOV.

Computational insights into the known inhibitors of human soluble epoxide hydrolase

Human soluble epoxide hydrolase (hsEH) is involved in the hydrolysis of epoxyeicosatrienoic acids (EETs), which have potent anti-inflammatory properties. Given that EET conversion generates nonbioactive molecules, inhibition of this enzyme would be beneficial. Past decades of work on hsEH inhibitors resulted in numerous potential compounds, of which a hundred hsEH-ligand complexes were crystallized and deposited in the Protein Data Bank (PDB). We analyzed all deposited hsEH-ligand complexes to gain insight into the binding of inhibitors and to provide feedback on the future drug design processes. We also reviewed computationally driven strategies that were used to propose novel hsEH inhibitors.

Association of rs11780592 Polymorphism in the Human Soluble Epoxide Hydrolase Gene (EPHX2) with Oxidized LDL and Mortality in Patients with Diabetic Chronic Kidney Disease

Soluble epoxide hydrolase 2 (EPHX2) is an enzyme promoting increased cellular apoptosis through induction of oxidative stress (OS) and inflammation. The EPHX2 gene which encodes soluble EPHX2 might be implicated in the pathogenesis and development of OS and atherosclerosis. We aimed to assess the possible association between two functional polymorphisms of the EPHX2 gene (rs2741335 and rs11780592) with oxidized LDL (ox-LDL), carotid atherosclerosis, mortality, and cardiovascular (CV) disease in 118 patients with diabetic chronic kidney disease (CKD). At baseline, ox-LDL and carotid intima-media thickness (cIMT) were evaluated and all patients were followed for seven years with outcomes all-cause mortality and CV events. rs11780592 EPHX2 polymorphism was associated with ox-LDL, cIMT, albuminuria, and hypertension. Compared to AG and GG, AA homozygotes had higher values of albuminuria, ox-LDL, and cIMT (p = 0.046, p = 0.003, and p = 0.038, respectively). These associations remained significant, even after grouping for the G allele. After the follow-up period, 42/118 patients died (30/60 with AA genotype, 11/42 with AG genotype, and 1/12 with GG genotype) and 49/118 experienced a new CV event (fatal or nonfatal). The Kaplan-Meier analysis revealed that patients with the AA genotype exhibited a significantly higher mortality risk, compared to patients with AG and GG genotypes (p = 0.006). This association became even stronger, when AG and GG genotypes were grouped (AA vs. AG/GG, p = 0.002). AA homozygotes were strongly associated with all-cause mortality in both univariate (hazard ratio (HR) = 2.74, confidence interval (CI) = 1.40-5.35, p = 0.003) and multivariate Cox regression analysis (HR = 2.61, CI = 1.32-5.17, p = 0.006). In conclusion, our study demonstrated that genetic variations of EPHX2 gene were associated with increased circulating ox-LDL, increased cIMT, and all-cause mortality in diabetic CKD. Since EPHX2 regulates the cholesterol efflux and the oxidation of LDL in foam cells and macrophages, our study suggests that a genetic basis to endothelial dysfunction and OS might be present in diabetic CKD.

Discovery of novel heterocyclic amide-based inhibitors: an integrative in-silico approach to targeting soluble epoxide hydrolase

Inhibition of soluble epoxide hydrolase (sEH) is considered as an emerging druggable target to reduce blood pressure, improve insulin sensitivity, and decrease inflammation. Despite the availability of different classes of sEH small molecule inhibitors for the potential treatment of hypertension, only a few candidates have reached clinical trials, making the optimal control of blood pressure presently unattainable. This necessity motivated us to explore a series of novel quinazoline-4(3H)-one and 4,6-disubstituted pyridin-2(1H)-one derivatives targeting sEH enzyme. Herein, comprehensive computational investigations were performed to probe the inhibition efficacy of these potent compounds in terms of inhibitor-enzyme interactions against sEH. In this study, the 39 in-house with a focused library comprising 39 in-house synthesized compounds were selected. The structure-based pharmacophore modeling was developed based on the crystal structure of sEH with its co-crystallized biologically active inhibitor. The generated hypotheses were applied for virtual screening-based PHASE fitness scores. Docking-based virtual screening workflows were used to generate lead compounds using HTVS, SP and XP based GLIDE G-score values. The candidate leads were filtered using ADMET pharmacological and physicochemical properties screening. A 100-ns of molecular dynamics simulations with Molecular dynamics simulations (100 ns) were performed to explore the binding affinities of the considered compounds. Our study identified four best candidates from quinazoline-4(3H)-one derivatives, which indicated that a quinazolinone ring serves as a suitable scaffold to develop novel small molecule sEH inhibitors.

Targeting arachidonic acid-related metabolites in COVID-19 patients: potential use of drug-loaded nanoparticles

In March 2020, The World Health Organization (WHO) has declared that the coronavirus disease 2019 (COVID-19) is characterized as a global pandemic. As of September 2020, infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread to 213 countries and territories around the world, affected more than 31.5 million people, and caused more than 970,000 deaths worldwide. Although COVID-19 is a respiratory illness that mainly targets the lungs, it is currently well established that it is a multifactorial disease that affects other extra-pulmonary systems and strongly associated with a detrimental inflammatory response. Evidence has shown that SARS-CoV-2 causes perturbation in the arachidonic acid (AA) metabolic pathways; this disruption could lead to an imbalance between the pro-inflammatory metabolites of AA including mid-chain HETEs and terminal HETE (20-HETE) and the anti-inflammatory metabolites such as EETs and subterminal HETEs. Therefore, we propose novel therapeutic strategies to modulate the level of endogenous anti-inflammatory metabolites of AA and induce the patient's endogenous resolution mechanisms that will ameliorate the virus-associated systemic inflammation and enhance the primary outcomes in COVID-19 patients. Also, we propose that using nanoencapsulation of AA and its associated metabolites will contribute to the development of safer and more efficacious treatments for the management of COVID-19.

Small Molecule Soluble Epoxide Hydrolase Inhibitors in Multitarget and Combination Therapies for Inflammation and Cancer

The enzyme soluble epoxide hydrolase (sEH) plays a central role in metabolism of bioactive lipid signaling molecules. The substrate-specific hydrolase activity of sEH converts epoxyeicosatrienoic acids (EETs) to less bioactive dihydroxyeicosatrienoic acids. EETs exhibit anti-inflammatory, analgesic, antihypertensive, cardio-protective and organ-protective properties. Accordingly, sEH inhibition is a promising therapeutic strategy for addressing a variety of diseases. In this review, we describe small molecule architectures that have been commonly deployed as sEH inhibitors with respect to angiogenesis, inflammation and cancer. We juxtapose commonly used synthetic scaffolds and natural products within the paradigm of a multitarget approach for addressing inflammation and inflammation induced carcinogenesis. Structural insights from the inhibitor complexes and novel strategies for development of sEH-based multitarget inhibitors are also presented. While sEH inhibition is likely to suppress inflammation-induced carcinogenesis, it can also lead to enhanced angiogenesis via increased EET concentrations. In this regard, sEH inhibitors in combination chemotherapy are described. Urea and amide-based architectures feature prominently across multitarget inhibition and combination chemotherapy applications of sEH inhibitors.

A Random Forest Model to Predict the Activity of a Large Set of Soluble Epoxide Hydrolase Inhibitors Solely Based on a Set of Simple Fragmental Descriptors

BACKGROUND

The Soluble Epoxide Hydrolase (sEH) is a ubiquitously expressed enzyme in various tissues. The inhibition of the sEH has shown promising results to treat hypertension, alleviate pain and inflammation.

OBJECTIVE

In this study, the power of machine learning has been employed to develop a predictive QSAR model for a large set of sEH inhibitors.

METHODS

In this study, the random forest method was employed to make a valid model for the prediction of sEH inhibition. Besides, two new methods (Treeinterpreter python package and LIME, Local Interpretable Model-agnostic Explanations) have been exploited to explain and interpret the model.

RESULTS

The performance metrics of the model were as follows: R2=0.831, Q2=0.565, RMSE=0.552 and R2 pred=0.595. The model also demonstrated good predictability on the two extra external test sets at least in terms of ranking. The Spearman's rank correlation coefficients for external test set 1 and 2 were 0.872 and 0.673, respectively. The external test set 2 was a diverse one compared to the training set. Therefore, the model could be used for virtual screening to enrich potential sEH inhibitors among a diverse compound library.

CONCLUSION

As the model was solely developed based on a set of simple fragmental descriptors, the model was explained by two local interpretation algorithms, and this could guide medicinal chemists to design new sEH inhibitors. Moreover, the most important general descriptors (fragments) suggested by the model were consistent with the available crystallographic data. The model is available as an executable binary at http://www.pharm-sbg.com and https://github.com/shamsaraj.

Pharmacophore-driven identification of N-methyl-D-receptor antagonists as potent neuroprotective agents validated using in vivo studies

Alzheimer's disease (AD), apparently the most widespread reason behind dementia, is delineated by a continuous cognitive weakening in the aged. During its progression, N-methyl-D-aspartate receptor (NMDAR) antagonists are known to play a pivotal part in the mechanisms of learning and memory. Since there is an unmet medical need for the treatment of AD, we aim to identify possible chemical compounds targeted toward N-methyl-D-aspartate receptors. Three-dimensional models are developed to unveil some of the essential characteristics of the N-methyl-D-aspartate receptors by using a collection of already discovered N-methyl-D-aspartate receptor inhibitors. This is followed by virtual screening, which results in novel chemical compounds having the potential to inhibit N-methyl-D-aspartate receptors. Molecular docking studies and analysis promulgated two lead compounds with a high LibDock score. The compounds are shortlisted based on high estimated activity, fit values, LibDock score, no violation of Lipinski's, and availability for procuring. Finally, the shortlisted compounds are tested by employing in vivo studies, which we further propose as potential NMDA inhibitors for treating AD.

PET imaging of soluble epoxide hydrolase in non-human primate brain with [18F]FNDP

Purpose

Soluble epoxide hydrolase (sEH) is a promising candidate positron emission tomography (PET) imaging biomarker altered in various disorders, including vascular cognitive impairment (VCI), Alzheimer’s disease (AD), Parkinson’s disease (PD), stroke, and depression, known to regulate levels of epoxyeicosatrienoic acids (EETs) and play an important role in neurovascular coupling. [¹⁸F]FNDP, a PET radiotracer for imaging sEH, was evaluated through quantitative PET imaging in the baboon brain, radiometabolite analysis, and radiation dosimetry estimate.

Methods

Baboon [¹⁸F]FNDP dynamic PET studies were performed at baseline and with blocking doses of the selective sEH inhibitor AR-9281 to evaluate sEH binding specificity. Radiometabolites of [¹⁸F]FNDP in mice and baboons were measured by high-performance liquid chromatography. Regional brain distribution volume (V_T) of [¹⁸F]FNDP was computed from PET using radiometabolite-corrected arterial input functions. Full body distribution of [¹⁸F]FNDP was studied in CD-1 mice, and the human effective dose was estimated using OLINDA/EXM software.

Results

[¹⁸F]FNDP exhibited high and rapid brain uptake in baboons. AR-9281 blocked [¹⁸F]FNDP uptake dose-dependently with a baseline V_T of 10.9 ± 2.4 mL/mL and a high-dose blocking V_T of 1.0 ± 0.09 mL/mL, indicating substantial binding specificity (91.70 ± 1.74%). The V_ND was estimated as 0.865 ± 0.066 mL/mL. The estimated occupancy values of AR-9281 were 99.2 ± 1.1% for 1 mg/kg, 88.6 ± 1.3% for 0.1 mg/kg, and 33.8 ± 3.8% for 0.02 mg/kg. Murine biodistribution of [¹⁸F]FNDP enabled an effective dose estimate for humans (0.032 mSv/MBq). [¹⁸F]FNDP forms hydrophilic radiometabolites in murine and non-human primate plasma. However, only minute amounts of the radiometabolites entered the animal brain (< 2% in mice).

Conclusions

[¹⁸F]FNDP is a highly sEH-specific radiotracer that is suitable for quantitative PET imaging in the baboon brain. [¹⁸F]FNDP holds promise for translation to human subjects.

Discovery of phthalimide derivatives as novel inhibitors of a soluble epoxide hydrolase

Soluble epoxide hydrolase (sEH) inhibitors are effective in reducing blood pressure, inflammation, and pain in a number of mammalian disease models. As most classical urea-based sEH inhibitors suffer from poor solubility and pharmacokinetic properties, the development of novel sEH inhibitors with an improved pharmacokinetic specification has received a great deal of attention. In this study, a series of amide-based sEH inhibitors bearing a phthalimide ring as the novel secondary pharmacophore (P₂ ) was designed, synthesized, and evaluated. Docking results illustrated that the amide group as the primary pharmacophore (P₁ ) was placed at a suitable distance from the three key amino acids (Tyr383, Tyr466, and Asp335) for an effective hydrogen bonding. In agreement with these findings, most of the newly synthesized compounds demonstrated moderate to high sEH inhibitory activities, relative to 12-(3-adamantan-1-yl-ureido)dodecanoic acid as the reference standard. Compound 12e with a 4-methoxybenzoyl substituent exhibited the highest sEH inhibitory activity, with an IC₅₀ value of 1.06 nM. Moreover, the ADME properties of the compounds were evaluated in silico, and the results revealed appropriate predictions.

Subnormothermic Machine Perfusion of Steatotic Livers Results in Increased Energy Charge at the Cost of Anti-Oxidant Capacity Compared to Normothermic Perfusion

There continues to be significant debate regarding the most effective mode of ex situ machine perfusion of livers for transplantation. Subnormothermic (SNMP) and normothermic machine perfusion (NMP) are two methods with different benefits. We examined the metabolomic profiles of discarded steatotic human livers during three hours of subnormothermic or normothermic machine perfusion. Steatotic livers regenerate higher stores of ATP during SNMP than NMP. However, there is a significant depletion of available glutathione during SNMP, likely due to an inability to overcome the high energy threshold needed to synthesize glutathione. This highlights the increased oxidative stress apparent in steatotic livers. Rescue of discarded steatotic livers with machine perfusion may require the optimization of redox status through repletion or supplementation of reducing agents.