Redox-dependent internalization of the purinergic P2Y6 receptor limits colitis progression

Discovery of a potent, Highly selective, and In vivo anti-inflammatory Efficacious, P2Y6R antagonist with a novel quinoline-pyrazole scaffold

The P2Y6 receptor (P2Y6R), as a crucial member of the purine family, is a potential therapeutic target for the treatment of intestinal inflammation, tracheal inflammation and diabetes. We first discovered the hit compound (5a, IC50 = 168.5 nM against P2Y6R) through our in-house library screening. Then, further medicinal chemistry efforts were made to optimize compound 5a, and a potent P2Y6R antagonist (5 ab) with better antagonistic activity (IC50 = 19.6 nM) was obtained. The molecular docking, CETSA, SPR and pull-down results indicated that compound 5 ab displayed strong binding to P2Y6R. Also, compound 5 ab possessed high selectivity and satisfying oral bioactivity and pharmacokinetic profiles. In experiments with LPS-induced acute lung injury in mice, after treatment with compound 5 ab, the level of inflammatory factors IL-6, TNF-α and IL-β were considerably decreased, the infiltration of immune cells was decreased. Further exploration revealed that 5 ab inhibited the expression and release of chemokines in lung tissue, suppressing the activation of the NLRP3 inflammasome. Compound 5 ab had certain anti-inflammatory abilities in vivo and in vitro. These results demonstrate that compound 5 ab is a potential P2Y6R antagonist and is worthy of further study.

The microglial P2Y6 receptor as a therapeutic target for neurodegenerative diseases

Neurodegenerative diseases are associated with chronic neuroinflammation in the brain, which can result in microglial phagocytosis of live synapses and neurons that may contribute to cognitive deficits and neuronal loss. The microglial P2Y6 receptor (P2Y6R) is a G-protein coupled receptor, which stimulates microglial phagocytosis when activated by extracellular uridine diphosphate, released by stressed neurons. Knockout or inhibition of P2Y6R can prevent neuronal loss in mouse models of Alzheimer's disease (AD), Parkinson's disease, epilepsy, neuroinflammation and aging, and prevent cognitive deficits in models of AD, epilepsy and aging. This review summarises the known roles of P2Y6R in the physiology and pathology of the brain, and its potential as a therapeutic target to prevent neurodegeneration and other brain pathologies.

Functionalized Congeners of 2H-Chromene P2Y6 Receptor Antagonists

The P2Y6 receptor (P2Y6R), a Gq-coupled receptor, is a potential drug discovery target for various inflammatory and degenerative conditions. Antagonists have been shown to attenuate colitis, acute lung injury, etc. In the search for competitive antagonists, we have investigated the SAR of 3-nitro-2-(trifluoromethyl)-2H-chromene derivatives, although high affinity is lacking. We now reveal that long-chain amino-functionalized congeners display greatly enhanced affinity in the antagonism of UDP-induced Ca2+ mobilization in human (h) P2Y6R-transfected 1321N1 astrocytoma cells. A 6-(Boc-amino-n-heptylethynyl) analogue 30 (MRS4940) had an IC50 of 162 nM, which was a 123-fold greater affinity than the corresponding unprotected primary alkylamine, 107-fold greater than the corresponding pivaloyl derivative 30, and 132-fold selective compared to the P2Y14R. However, similar Boc-amino chains attached at the 8-position produced weak µM affinity. Thus, the P2Y6R affinity depended on the chain length, attachment point, and terminal functionality. Off-target activities, at 45 sites, were tested for acylamino derivatives 20, 24, 26, 30, 31, and 37, which showed multiple interactions, particularly at the biogenic amine receptors. The more potent analogues may be suitable for evaluation in inflammation and cancer models, which will be performed in future studies.

Astilbin inhibited neutrophil extracellular traps in gouty arthritis through suppression of purinergic P2Y6 receptor

BACKGROUND

Gouty arthritis (GA), a common inflammatory condition triggered by monosodium urate crystal accumulation, often necessitates safer treatment alternatives due to the limitations of current therapies. Astilbin, a flavonoid from Smilax glabra Roxb, has demonstrated potential in traditional Chinese medicine for its anti-inflammatory properties. However, the anti-GA effect and its underlying mechanism have not been fully elucidated.

PURPOSE

This study aimed to investigate the therapeutic potential of astilbin in GA, focusing on its effects on neutrophil extracellular traps (NETs), as well as the potential molecular target of GA both in vitro and in vivo.

STUDY DESIGN

Firstly, astilbin inhibited the citrullinated histone H3 (Cit h3) protein levels and reduced the NETs formation in neutrophils stimulated by monosodium urate (MSU). Secondly, we wondered the effect of astilbin on migration of neutrophils and dimethyl-sulfoxide (DMSO)-differentiated HL-60 (dHL-60) cells under the stimulation of MSU. Then, the effect of astilbin on suppressing NETs through purinergic P2Y6 receptor (P2Y6R) and Interlukin-8 (IL-8)/ CXC chemokine receptor 2 (CXCR2) pathway was investigated. Also, the relationship between P2Y6R and IL-8/CXCR2 was explored in dHL-60 cells under stimulation of MSU. Finally, we testified the effect of astilbin on reducing NETs in GA through suppressing P2Y6R and then down-regulating IL-8/CXCR2 pathway.

METHODS

MSU was used to induce NETs in neutrophils and dHL-60 cells. Real-time formation of NETs and migration of neutrophils were monitored by cell living imaging with or without MSU. Then, the effect of astilbin on NETs formation, P2Y6R and IL-8/CXCR2 pathway were detected by immunofluorescence (IF) and western blotting. P2Y6R knockdown dHL-60 cells were established by small interfering RNA to investigate the association between P2Y6R and IL-8/CXCR2 pathway. Also, plasmid of P2Y6R was used to overexpress P2Y6R in dHL-60 cells, which was employed to explore the role of P2Y6R in astilbin inhibiting NETs. Within the conditions of knockdown and overexpression of P2Y6R, migration and NETs formation were assessed by transmigration assay and IF staining, respectively. In vivo, MSU-induced GA mice model was established to assess the effect of astilbin on inflammation by haematoxylin-eosin and ELISA. Additionally, the effects of astilbin on neutrophils infiltration, NETs, P2Y6R and IL-8/CXCR2 pathway were analyzed by IF, ELISA, immunohistochemistry (IHC) and western blotting.

RESULTS

Under MSU stimulation, astilbin significantly suppressed the level of Cit h3 and NETs formation including the fluorescent expressions of Cit h3, neutrophils elastase, myeloperoxidase, and intra/extracellular DNA. Also, results showed that MSU caused NETs release in neutrophils as well as a trend towards recruitment of dHL-60 cells to MSU. Astilbin could markedly decrease expressions of P2Y6R and IL-8/CXCR2 pathway which were upregulated by MSU. By silencing P2Y6R, the expression of IL-8/CXCR2 pathway and migration of dHL-60 cells were inhibited, leading to the suppression of NETs. These findings indicated the upstream role of P2Y6R in the IL-8/CXCR2 pathway. Moreover, overexpression of P2Y6R was evidently inhibited by astilbin, causing a downregulation in IL-8/CXCR2 pathway, migration of dHL-60 cells and NETs formation. These results emphasized that astilbin inhibited the IL-8/CXCR2 pathway primarily through P2Y6R. In vivo, astilbin administration led to marked reductions in ankle swelling, inflammatory infiltration as well as neutrophils infiltration. Expressions of P2Y6R and IL-8/CXCR2 pathway were evidently decreased by astilbin and P2Y6R inhibitor MRS2578 either alone or in combination. Also, astilbin and MRS2578 showed notable effect on reducing MSU-induced NETs formation and IL-8/CXCR2 pathway whether used alone or in combination, parallelly demonstrating that astilbin decreased NETs formation mainly through P2Y6R.

CONCLUSION

This study revealed that astilbin suppressed NETs formation via downregulating P2Y6R and subsequently the IL-8/CXCR2 pathway, which evidently mitigated GA induced by MSU. It also highlighted the potential of astilbin as a promising natural therapeutic for GA.

A2B adenosine receptor signaling and regulation

The A2B adenosine receptor (A2BR) is one of the four adenosine-activated G protein-coupled receptors. In addition to adenosine, protein kinase C (PKC) was recently found to activate the A2BR. The A2BR is coupled to both Gs and Gi, as well as Gq proteins in some cell types. Many primary cells and cell lines, such as bladder and breast cancer, bronchial smooth muscle, skeletal muscle, and fat cells, express the A2BR endogenously at high levels, suggesting its potentially important role in asthma, cancer, diabetes, and other conditions. The A2BR has been characterized as both pro- and anti-inflammatory, inducing cell type-dependent secretion of IL-6, IL-8, and IL-10. Theophylline and enprofylline have long been used for asthma treatment, although it is still not entirely clear if their A2BR antagonism contributes to their therapeutic effects or side effects. The A2BR is required in ischemic cardiac preconditioning by adenosine. Both A2BR and protein kinase C (PKC) contribute to cardioprotection, and both modes of A2BR signaling can be blocked by A2BR antagonists. Inhibitors of PKC and A2BR are in clinical cancer trials. Sulforaphane and other isothiocyanates from cruciferous vegetables such as broccoli and cauliflower have been reported to inhibit A2BR signaling via reaction with an intracellular A2BR cysteine residue (C210). A full, A2BR-selective agonist, critical to elucidate many controversial roles of the A2BR, is still not available, although agonist-bound A2BR structures have recently been reported.

Comprehensive insights into potential roles of purinergic P2 receptors on diseases: Signaling pathways involved and potential therapeutics

BACKGROUND

Purinergic P2 receptors, which can be divided into ionotropic P2X receptors and metabotropic P2Y receptors, mediate cellular signal transduction of purine or pyrimidine nucleoside triphosphates and diphosphate. Based on the wide expression of purinergic P2 receptors in tissues and organs, their significance in homeostatic maintenance, metabolism, nociceptive transmission, and other physiological processes is becoming increasingly evident, suggesting that targeting purinergic P2 receptors to regulate biological functions and signal transmission holds significant promise for disease treatment.

AIM OF REVIEW

This review highlights the detailed mechanisms by which purinergic P2 receptors engage in physiological and pathological progress, as well as providing prospective strategies for discovering clinical drug candidates.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The purinergic P2 receptors regulate complex signaling and molecular mechanisms in nervous system, digestive system, immune system and as a result, controlling physical health states and disease progression. There has been a significant rise in research and development focused on purinergic P2 receptors, contributing to an increased number of drug candidates in clinical trials. A few influential pioneers have laid the foundation for advancements in the evaluation, development, and of novel purinergic P2 receptors modulators, including agonists, antagonists, pharmaceutical compositions and combination strategies, despite the different scaffolds of these drug candidates. These advancements hold great potential for improving therapeutic outcomes by specifically targeting purinergic P2 receptors.

Machine learning-aided search for ligands of P2Y6 and other P2Y receptors

The P2Y6 receptor, activated by uridine diphosphate (UDP), is a target for antagonists in inflammatory, neurodegenerative, and metabolic disorders, yet few potent and selective antagonists are known to date. This prompted us to use machine learning as a novel approach to aid ligand discovery, with pharmacological evaluation at three P2YR subtypes: initially P2Y6 and subsequently P2Y1 and P2Y14. Relying on extensive published data for P2Y6R agonists, we generated and validated an array of classification machine learning model using the algorithms deep learning (DL), adaboost classifier (ada), Bernoulli NB (bnb), k-nearest neighbors (kNN) classifier, logistic regression (lreg), random forest classifier (rf), support vector classification (SVC), and XGBoost (XGB) classifier models, and the common consensus was applied to molecular selection of 21 diverse structures. Compounds were screened using human P2Y6R-induced functional calcium transients in transfected 1321N1 astrocytoma cells and fluorescent binding inhibition at closely related hP2Y14R expressed in CHO cells. The hit compound ABBV-744, an experimental anticancer drug with a 6-methyl-7-oxo-6,7-dihydro-1H-pyrrolo[2,3-c]pyridine scaffold, had multifaceted interactions with the P2YR family: hP2Y6R inhibition in a non-surmountable fashion, suggesting that noncompetitive antagonism, and hP2Y1R enhancement, but not hP2Y14R binding inhibition. Other machine learning-selected compounds were either weak (experimental anti-asthmatic drug AZD5423 with a phenyl-1H-indazole scaffold) or inactive in inhibiting the hP2Y6R. Experimental drugs TAK-593 and GSK1070916 (100 µM) inhibited P2Y14R fluorescent binding by 50% and 38%, respectively, and all other compounds by < 20%. Thus, machine learning has led the way toward revealing previously unknown modulators of several P2YR subtypes that have varied effects.

Pharmacological Activation of TRPC6 Channel Prevents Colitis Progression

We recently reported that transient receptor potential canonical (TRPC) 6 channel activity contributes to intracellular Zn2+ homeostasis in the heart. Zn2+ has also been implicated in the regulation of intestinal redox and microbial homeostasis. This study aims to investigate the role of TRPC6-mediated Zn2+ influx in the stress resistance of the intestine. The expression profile of TRPC1-C7 mRNAs in the actively inflamed mucosa from inflammatory bowel disease (IBD) patients was analyzed using the GEO database. Systemic TRPC3 knockout (KO) and TRPC6 KO mice were treated with dextran sulfate sodium (DSS) to induce colitis. The Zn2+ concentration and the mRNA expression levels of oxidative/inflammatory markers in colon tissues were quantitatively analyzed, and gut microbiota profiles were compared. TRPC6 mRNA expression level was increased in IBD patients and DSS-treated mouse colon tissues. DSS-treated TRPC6 KO mice, but not TRPC3 KO mice, showed severe weight loss and increased disease activity index compared with DSS-treated WT mice. The mRNA abundances of antioxidant proteins were basically increased in the TRPC6 KO colon, with changes in gut microbiota profiles. Treatment with TRPC6 activator prevented the DSS-induced colitis progression accompanied by increasing Zn2+ concentration. We suggest that TRPC6-mediated Zn2+ influx activity plays a key role in stress resistance against IBD, providing a new strategy for treating colitis.

GPCR kinases differentially modulate biased signaling downstream of CXCR3 depending on their subcellular localization

Some G protein-coupled receptors (GPCRs) demonstrate biased signaling such that ligands of the same receptor exclusively or preferentially activate certain downstream signaling pathways over others. This phenomenon may result from ligand-specific receptor phosphorylation by GPCR kinases (GRKs). GPCR signaling can also exhibit location bias because GPCRs traffic to and signal from subcellular compartments in addition to the plasma membrane. Here, we investigated whether GRKs contributed to location bias in GPCR signaling. GRKs translocated to endosomes after stimulation of the chemokine receptor CXCR3 or other GPCRs in cultured cells. GRK2, GRK3, GRK5, and GRK6 showed distinct patterns of recruitment to the plasma membrane and to endosomes depending on the identity of the biased ligand used to activate CXCR3. Analysis of engineered forms of GRKs that localized to either the plasma membrane or endosomes demonstrated that biased CXCR3 ligands elicited different signaling profiles that depended on the subcellular location of the GRK. Each GRK exerted a distinct effect on the regulation of CXCR3 engagement of β-arrestin, internalization, and activation of the downstream effector kinase ERK. Our work highlights a role for GRKs in location-biased GPCR signaling and demonstrates the complex interactions between ligands, GRKs, and cellular location that contribute to biased signaling.

The role of P2Y6 receptor in the pathogenesis of cardiovascular and inflammatory diseases

The purinergic receptor P2Y6 receptor (P2Y6R) is a member of the G protein-coupled receptors (GPCR) family. P2Y6R is widely expressed in various cell types and plays a critical role in physiological processes, where it is activated by extracellular uridine diphosphate (UDP) and mobilizes Ca2+ via the Gαq/11 protein pathway. We have recently discovered the pathophysiological role of P2Y6R in cardiovascular and inflammatory diseases, including inflammatory bowel disease and non-alcoholic fatty liver disease. Furthermore, we uncovered the redox-dependent internalization of P2Y6R. In this review, we provide a comprehensive overview of the pathophysiological activity of P2Y6R in cardiovascular and inflammatory diseases. Additionally, we discuss the concept of atypical internalization control of GPCRs, which may be applied in the prevention and treatment of intestinal inflammation and cardiovascular remodeling.

β-Glucan alleviates mice with ulcerative colitis through interactions between gut microbes and amino acids metabolism

BACKGROUND

Food polysaccharide 1,3-β-d-glucan (OBG) has been shown to alleviate ulcerative colitis (UC) in a mouse model, but the underlying mechanisms remain unclear. Here, we aimed to investigate potential mechanisms involving interactions among gut microbiota, microbial metabolites and host metabolic function.

RESULTS

OBG alleviated colonic inflammation, barrier dysfunction and intestinal concentrations of short-chain fatty acids in mice with UC. In addition, the relative abundance of Muribaculaceae, Alistipes, Erysipelatoclostridium and Blautia increased, whereas the abundance of Proteus, Lachnospiraceae and Ruminococcus decreased within the gut microbiota upon OBG treatment. Kyoto Encyclopedia of Genes and Genomes analyses showed that intestinal enzymes altered upon OBG treatment were mainly enriched in sub-pathways of amino acid biosynthesis. Metabolomics analyses showed that l-tryptophan, l-tyrosine, l-phenylalanine and l-alanine increased, which is consistent with the predictive metabolism of gut microbiota. Correlation analysis and interaction networks highlighted gut microbiota (especially Lactobacillus, Parabacteroides, Proteus and Blautia), metabolites (especially l-phenylalanine, l-tryptophan, l-tyrosine and acetic acid) and metabolism (phenylalanine, tyrosine and tryptophan biosynthesis) that may be key targets of OBG.

CONCLUSION

OBG is beneficial to the gut microecological balance in mice with colitis, mainly becaue of its impact on the interactions between gut microbes and amino acids metabolism (especially tyrosine and tryptophan metabolism). © 2022 Society of Chemical Industry.

New paradigms in purinergic receptor ligand discovery

The discovery and clinical implementation of modulators of adenosine, P2Y and P2X receptors (comprising nineteen subtypes) have progressed dramatically in ∼50 years since Burnstock's definition of purinergic signaling. Although most clinical trials of selective ligands (agonists and antagonists) of certain purinergic receptors failed, there is a renewed impetus to redirect efforts to new disease conditions and the discovery of more selective or targeted compounds with potentially reduced side effects, such as biased GPCR agonists. The elucidation of new receptor and enzyme structures is steering rational design of potent and selective agonists, antagonists, allosteric modulators and inhibitors. A2A adenosine receptor (AR) antagonists are being applied to neurodegenerative conditions and cancer immunotherapy. A3AR agonists have potential for treating chronic inflammation (e.g. psoriasis), stroke and pain, as well as cancer. P2YR modulators are being considered for treating inflammation, metabolic disorders, acute kidney injury, cancer, pain and other conditions, often with an immune mechanism. ADP-activated P2Y12R antagonists are widely used as antithrombotic drugs, while their repurposing toward neuroinflammation is considered. P2X3 antagonists have been in clinical trials for chronic cough. P2X7 antagonists have been in clinical trials for inflammatory diseases and depression (compounds that penetrate the blood-brain barrier). Thus, purinergic signaling is now recognized as an immense regulatory system in the body for rebalancing tissues and organs under stress, which can be adjusted by drug intervention for therapeutic purposes. The lack of success of many previous clinical trials can be overcome given more advanced pharmacokinetic and pharmacodynamic approaches, including structure-based drug design, prodrugs and biased signaling. This article is part of the Special Issue on "Purinergic Signaling: 50 years".

Knockout of Purinergic P2Y6 Receptor Fails to Improve Liver Injury and Inflammation in Non-Alcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a disease that progresses from nonalcoholic fatty liver (NAFL) and which is characterized by inflammation and fibrosis. The purinergic P2Y₆ receptor (P2Y₆R) is a pro-inflammatory G_q/G₁₂ family protein-coupled receptor and reportedly contributes to intestinal inflammation and cardiovascular fibrosis, but its role in liver pathogenesis is unknown. Human genomics data analysis revealed that the liver P2Y₆R mRNA expression level is increased during the progression from NAFL to NASH, which positively correlates with inductions of C-C motif chemokine 2 (CCL2) and collagen type I α1 chain (Col1a1) mRNAs. Therefore, we examined the impact of P2Y₆R functional deficiency in mice crossed with a NASH model using a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD). Feeding CDAHFD for 6 weeks markedly increased P2Y₆R expression level in mouse liver, which was positively correlated with CCL2 mRNA induction. Unexpectedly, the CDAHFD treatment for 6 weeks increased liver weights with severe steatosis in both wild-type (WT) and P2Y₆R knockout (KO) mice, while the disease marker levels such as serum AST and liver CCL2 mRNA in CDAHFD-treated P2Y₆R KO mice were rather aggravated compared with those of CDAHFD-treated WT mice. Thus, P2Y₆R may not contribute to the progression of liver injury, despite increased expression in NASH liver.

Echinochrome Prevents Sulfide Catabolism-Associated Chronic Heart Failure after Myocardial Infarction in Mice

Abnormal sulfide catabolism, especially the accumulation of hydrogen sulfide (H2S) during hypoxic or inflammatory stresses, is a major cause of redox imbalance-associated cardiac dysfunction. Polyhydroxynaphtoquinone echinochrome A (Ech-A), a natural pigment of marine origin found in the shells and needles of many species of sea urchins, is a potent antioxidant and inhibits acute myocardial ferroptosis after ischemia/reperfusion, but the chronic effect of Ech-A on heart failure is unknown. Reactive sulfur species (RSS), which include catenated sulfur atoms, have been revealed as true biomolecules with high redox reactivity required for intracellular energy metabolism and signal transduction. Here, we report that continuous intraperitoneal administration of Ech-A (2.0 mg/kg/day) prevents RSS catabolism-associated chronic heart failure after myocardial infarction (MI) in mice. Ech-A prevented left ventricular (LV) systolic dysfunction and structural remodeling after MI. Fluorescence imaging revealed that intracellular RSS level was reduced after MI, while H2S/HS- level was increased in LV myocardium, which was attenuated by Ech-A. This result indicates that Ech-A suppresses RSS catabolism to H2S/HS- in LV myocardium after MI. In addition, Ech-A reduced oxidative stress formation by MI. Ech-A suppressed RSS catabolism caused by hypoxia in neonatal rat cardiomyocytes and human iPS cell-derived cardiomyocytes. Ech-A also suppressed RSS catabolism caused by lipopolysaccharide stimulation in macrophages. Thus, Ech-A has the potential to improve chronic heart failure after MI, in part by preventing sulfide catabolism.

Synthesis and pharmacological characterization of multiply substituted 2H-chromene derivatives as P2Y6 receptor antagonists

P2Y6 receptor (P2Y6R) antagonists represent potential drugs for treating cancer, pain, neurodegeneration, asthma, diabetes, colitis and other disorders. However, there are few chemical classes of known competitive antagonists. We recently explored the structure activity relationship (SAR) of 2H-chromene derivatives as P2Y6R antagonists of moderate affinity. New analogues in this series modified at five positions were synthesized and shown to antagonize Ca2+ transients induced by the native agonist UDP in human (h) P2Y6R-expressing (but not turkey P2Y1R-, hP2Y2R- or hP2Y4R-expressing) astrocytoma cells. Alternatives to the reported 2-(trifluoromethyl)- and 3-nitro- substitutions of this scaffold were not identified. However, 6‑fluoro 11 and 6‑chloro 12 analogues displayed enhanced potency compared to other halogens, although still in the 1 - 2 µM range. Similar halogen substitution at 5, 7 or 8 positions reduced affinity. 5- or 8‑Triethylsilylethynyl extension maintained hP2Y6R affinity, with IC50 0.46 µM for 26 (MRS4853). The 6,8‑difluoro analogue 27 (IC50 2.99 µM) lacked off-target activities among 45 sites examined, unlike earlier analogues that bound to biogenic amine receptors. 11 displayed only one weak off-target activity (σ2). Mouse P2Y6R IC50s of 5, 25, 26 and 27 were 4.94, 17.6, 6.15 and 17.8 µM, respectively, but most other analogues had reduced affinity (>20 µM) compared to the hP2Y6R. These analogues are suitable for evaluation in in vivo inflammation and cancer models, which will be performed in the future studies.

S-nitrosylation is required for β2AR desensitization and experimental asthma

The β2-adrenergic receptor (β2AR), a prototypic G-protein-coupled receptor (GPCR), is a powerful driver of bronchorelaxation, but the effectiveness of β-agonist drugs in asthma is limited by desensitization and tachyphylaxis. We find that during activation, the β2AR is modified by S-nitrosylation, which is essential for both classic desensitization by PKA as well as desensitization of NO-based signaling that mediates bronchorelaxation. Strikingly, S-nitrosylation alone can drive β2AR internalization in the absence of traditional agonist. Mutant β2AR refractory to S-nitrosylation (Cys265Ser) exhibits reduced desensitization and internalization, thereby amplifying NO-based signaling, and mice with Cys265Ser mutation are resistant to bronchoconstriction, inflammation, and the development of asthma. S-nitrosylation is thus a central mechanism in β2AR signaling that may be operative widely among GPCRs and targeted for therapeutic gain.

Drug repurposing for the treatment of COVID-19

Coronavirus disease 2019 (COVID-19) remains prevalent worldwide since its onset was confirmed in Wuhan, China in 2019. Vaccines against the causative virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), have shown a preventive effect against the onset and severity of COVID-19, and social and economic activities are gradually recovering. However, the presence of vaccine-resistant variants has been reported, and the development of therapeutic agents for patients with severe COVID-19 and related sequelae remains urgent. Drug repurposing, also called drug repositioning or eco-pharma, is the strategy of using previously approved and safe drugs for a therapeutic indication that is different from their original indication. The risk of severe COVID-19 and mortality increases with advancing age, cardiovascular disease, hypertension, diabetes, and cancer. We have reported three protein-protein interactions that are related to heart failure, and recently identified that one mechanism increases the risk of SARS-CoV-2 infection in mammalian cells. This review outlines the global efforts and outcomes of drug repurposing research for the treatment of severe COVID-19. It also discusses our recent finding of a new protein-protein interaction that is common to COVID-19 aggravation and heart failure.

6-(Methylsulfinyl) Hexyl Isothiocyanate Inhibits IL-6 and CXCL10 Production in TNF-α-Stimulated Human Oral Epithelial Cells

6-(Methylsulfinyl) hexyl isothiocyanate (6-MSITC) is a bioactive substance found in wasabi (Wasabia japonica) and has been reported to have some bioactive effects including anticancer and antioxidant effects. However, there are no reports on its effects on periodontal resident cells, and many points remain unclear. In this study, we aimed to investigate whether 6-MSITC exerts anti-inflammatory effects on human oral epithelial cells, including effects on signal transduction pathway activation. 6-MSITC inhibited interleukin (IL)-6 and C-X-C motif chemokine ligand 10 (CXCL10) production in TNF-α-stimulated TR146 cells, which are a human oral epithelial cell line. Moreover, we found that 6-MSITC could suppress signal transducer and activator of transcription (STAT)3, nuclear factor (NF)-κB, and p70S6 kinase (p70S6K)-S6 ribosomal protein (S6) pathways activation in TNF-α-stimulated TR146 cells. Furthermore, STAT3 and NF-κB inhibitors could suppress IL-6 and CXCL10 production in TNF-α-treated TR146 cells. In summary, 6-MSITC could decrease IL-6 and CXCL10 production in human oral epithelial cell by inhibiting STAT3 and NF-κB activation.