Background and Purpose. Heroin and cocaine users tailor their dosage, frequency, and method of administration, to maximize the drugs’ effects or prevent withdrawal symptoms. Counterintuitively, preclinical self-administration and choice experiments employ fixed unit-doses and timeouts (after doses) largely resulting in uniform drug-taking patterns. The application of these procedures also disregards the distinct pharmacokinetic properties of heroin and cocaine. This uniformity contrasts with the significantly different ways humans tailor their dosage and frequency of heroin and cocaine use. Here, by combining behavioral and pharmacokinetics assessments we revealed that self-administration procedures lacking the timeout may overcomes this limitation. Experimental Approach. We analyzed heroin and cocaine taking- and seeking-patterns and estimated drug-brain levels in the presence or absence of timeout. We further assessed how absence of timeout and the availability of drug or social peer (access time to the two rewards) affect drug preference in choice procedures. Key Results. Removing the timeout had a profound effect on heroin-taking patterns and seeking, promoting the emergence of burst-like intake, yielding higher brain peak concentrations of heroin. Timeout removal had marginal impact on cocaine taking patterns and seeking. Increasing the access time to the drug in the discrete choice procedure resulted in higher drug intake and increased preference for heroin, but it did not alter cocaine preference. Conclusion and Implications. Removing timeout during self-administration revealed distinct heroin and cocaine taking patterns. Self-administration without timeout and access to high heroin doses during choice more closely mimic human heroin taking patterns and related behaviors, including maladaptive choices.

Background and Purpose: Platelet function during inflammation is dependent on activation by endogenous nucleotides acting on purinergic receptors. The P2Y14 receptor (P2Y14R) has been reported to be expressed on platelets and is involved in leukocyte recruitment during inflammation. However, a role for P2Y14R receptors on platelet function has not yet been determined. Experimental Approach: Platelets obtained from healthy human volunteers were incubated with the P2Y14R agonist, UDP-Glucose (UDP-G), and PPTN, a selective P2Y14R antagonist. Platelet activation was quantified using Ca2+ mobilization, aggregation, and chemotaxis assays. Cooperativity with P2Y1 receptor (P2Y1R) activation was also assessed after stimulation with UDP-G in the presence of MRS2500, a selective P2Y1R antagonist. Key Results: Ca2+ mobilization occurred in platelets after incubation with UDP-G in a concentration-dependent manner, and this was suppressed in platelets treated with PPTN. Platelets did not aggregate, or bind to fibrinogen after incubation with UDP-G. However, platelet chemotaxis towards f-MLP was dependent on P2Y14R stimulation with UDP-G and this was reduced by Rho-GTPase inhibitors. Furthermore, UDP-G induced Ca2+ mobilization and chemotaxis were also inhibited when platelets were pretreated with MRS2500. Conversely, ADP induced Ca2+ mobilization, chemotaxis and aggregation were not affected by the incubation with PPTN. Conclusion and Implications: Platelets can be activated via P2Y14R stimulation to induce chemotaxis but not aggregation. Furthermore, this was dependent on concomitant activation of P2Y1R. Activation of P2Y14Rs on platelets may therefore be relevant during inflammation, but cooperation with P2Y1R activation is required.

Background and Purpose: No drugs targeting the core social features of autism spectrum disorder (ASD) have been approved. Although clinical trials with oxytocin (OT) and vasopressin (AVP) have yielded mixed results, targeting their receptors remains the most promising pharmacological strategy for addressing social impairments in ASD. This study aims to identify which receptors and signalling pathways within this family can sustainably improve social impairments. Experimental Approach: We used dose-response and kinetic analyses, along with mathematical modelling, to evaluate OT, AVP, their homologs, and novel synthetic ligands on G protein coupling, β-arrestins recruitment, and internalisation of mouse oxytocin (OTR) and vasopressin (V1A, V1B, V2) receptors in Neuro-2a cells. We tested acute and subchronic administration of OTR agonists and the novel V1A receptor antagonist, alongside OT and AVP, for their effects on social interaction in Fmr1 KO mice, a model exhibiting ASD-like features. Key Results: While OT, AVP and most compounds were non-selective across the four receptors, the OTR agonists TGOT or RO6958375 and the V1A antagonist RO6893074 were selective. TGOT or RO6958375, favouring Gαq signalling, enhanced social interactions in Fmr1 KO mice while showing minimal effects in wild-type mice. In contrast, OT, AVP or RO6893074 exhibited limited efficacy in Fmr1 KO mice. Conclusion and Implications: Selective OTR agonists, unlike OT and AVP, effectively improved social impairments in Fmr1 KO mice after acute and subchronic treatment. These findings highlight the necessity for developing highly selective OTR Gαq-biased agonists to achieve clinical outcomes in ASD.

Background and Purpose The molecular mechanisms responsible for atherogenesis have not been fully elucidated. The intraplaque endothelium dysfunction and associated inflammation are believed to contribute to the progression of atherosclerosis. This study aims to uncover molecular drivers of atherosclerotic cardiovascular disease and then develop therapeutic strategies for the disease. Methods The expression of zinc-finger transcription factor Snail in human and mouse atherosclerotic plaques was assessed using immunostaining, LacZ reporter mouse line and single-cell RNA-sequencing. The functional role and underlying mechanisms of endothelium-derived Snail in driving atherosclerosis was determined using the canonical and accelerated models of atherosclerosis developed in the endothelial cell (EC)-specific Snail-inducible deleted mice with the ApoE-/- background. An orally bioavailable small-molecule inhibitor of Snail was developed using the docking algorithm analysis and chemical structural optimization, and the anti-atherosclerotic effects of the compound were evaluated in mice. Results Snail is activated in ECs in both human and mouse atherosclerotic plaques, and its expression is positively correlated with disease severity. EC-specific Snail deletion in ApoE-/- mice reduces intraplaque endothelium dysfunction, inflammation and lipid uptake in tandem with enhanced plaque stability. Mechanistically, Snail deletion decreases histone acetylation on Ccl5 and Cxcl10 promoters, thereby decreases CCL5/CXCL10-driven vascular damage and inflammation. Administration with recombinant CXCL10 protein could efficiently restore atherogenesis in Snail-deleted mice. The orally bioavailable small-molecule inhibitor of Snail exhibits a potent anti-atherosclerotic effect in ApoE-/- mice. Conclusions These results reveal that Snail plays an essential role in atherogenesis and pharmacological targeting of Snail may provide therapeutic benefits against atherosclerotic cardiovascular disease.

In a recent publication in British Journal of Pharmacology, Rakoczy, et al. describe the use of animal tissues and behavioral tests to study the potential of psychedelic compounds to benefit human mental health. However, the research warrants additional context regarding the limitations of these behavioral tests, whether the proposed benefits outweigh the harms experienced by the animals used, and whether this study has translational capacity considering its lack of human specimens and data.

Background and purpose: Hexahydrocannabinol (HHC) is a novel psychoactive substance that has gained attention due to its psychotropic effects and temporary legal status. It is widely abused in several EU and US countries, where it serves as a legal and easily accessible alternative to ∆9-tetrahydrocannabinol (∆9-THC). Despite its widespread use, few studies have examined its in vivo effects and safety profile. Experimental approach: This study investigated the pharmacokinetics, systemic toxicity, and acute behavioural effects of HHC in male Wistar rats. A mixture of (9R)-HHC and (9S)-HHC epimers (in a 1:1 ratio) was administered via intragastric gavage at doses of 1, 5, and 10 mg/kg. Behavioural effects were assessed using the Open field test and the Prepulse inhibition of acoustic startle response. Key results: Two hours after 10 mg/kg administration, concentrations of both HHC epimers peaked in blood serum and brain tissue. According to the OECD 423 toxicity test, HHC was classified as a Category 4 substance, with an estimated lethal dose of 1000 mg/kg. Compared to the control group (administered sunflower oil), the highest dose (10 mg/kg) led to reduced locomotor activity, increased anxiety, and impaired sensorimotor gating. Conclusions & Implications: HHC readily crosses the blood-brain barrier, exhibits mild toxicity, and produces behavioural effects similar to THC-like cannabinoids.

Background and Purpose: Preclinical studies suggest that highly selective dopamine D3 receptor (D3R) antagonists or partial agonists hold promise for treating substance use disorders (SUD). However, their limited effectiveness in reducing cocaine self-administration is a major drawback. This study investigated whether cariprazine (a D3R-preferring partial agonist) and its analogs ESG-1-60 and ESG-1-61 have enhanced efficacy in reducing cocaine-taking and -seeking behavior. Experimental Approach: In vitro BRET experiments were used to characterize the functional efficacies of cariprazine and its analogs. Intravenous cocaine self-administration and reinstatement models were used to evaluate efficacy in reducing cocaine-taking and -seeking behavior. Optical intracranial self-stimulation (oICSS) procedures assessed effects on DA-dependent behavior. Open-field locomotion, oral sucrose self-administration, and conditioned place-preference were used to evaluate potential unwanted side effects. Key Results: BRET functional assays indicated that cariprazine and ESG-1-60 are D3R-preferring partial agonists, while ESG-1-61 is a D3R-preferring antagonist/inverse agonist. All three compounds inhibited cocaine self-administration under both fixed-ratio and progressive-ratio reinforcement schedules and reduced cocaine-induced reinstatement of drug-seeking behavior in both male and female rats. The compounds did not alter locomotor behavior but suppressed sucrose intake and DA-dependent oICSS. Cariprazine and ESG-1-61 produced significant place aversion, while ESG-1-60 did not. Chronic administration of ESG-1-60 inhibited cocaine self-administration. Conclusions and Implications: Novel D3R-preferring compounds ESG-1-60 and ESG-1-61 are highly effective in reducing cocaine taking and seeking under various reinforcement conditions. ESG-1-60 warrants further investigation as a new pharmacotherapy for treating cocaine use disorder due to its effectiveness in these models and lack of unwanted behavioral effects.

Cystic fibrosis is an autosomal recessive disease in which mutations in the CFTR gene lead to a reduced life expectancy in carriers, partly due to the rapid loss of respiratory functions. CFTR-F508del is the most frequent mutation, leading to a mislocalized and non-functional CFTR protein. The tri-therapy Elexacaftor/Tezacaftor/Ivacaftor is now given to patients carrying CFTR-F508del mutation, but some biological defaults of this mutation are still not addressed. Among CFTR interactors, we have previously identified COMMD1 as a potential therapeutic target, which overexpression favors the plasma membrane expression of CFTR. In 2013, a cell-penetrating peptide named CIGB-552 was discovered as a COMMD1 protein stabilizer. We evaluate the therapeutic potential of CIGB-552 in cystic fibrosis context. FITC Tagged version of CIGB-552 was used to evaluate its uptake on cell models cultured submerged or in air-liquid interface. HS-eYFP assay was performed for measuring CFTR quenching ratio. Short-circuit current was recorded to evaluate specific chloride flux through CFTR channel. Western blot was used to evaluate CFTR maturation and COMMD1 expression. We demonstrate that CIGB-552 is non-toxic and preferentially enters CFTR-F508del expressing cells without modifying COMMD1 expression or localization in our cystic fibrosis cell models. CIGB-552 is not a potentiator nor a corrector but acts synergistically with Elexacaftor/Tezacaftor/Ivacaftor in improving chloride efflux and increasing transepithelial potential difference of CFTR-F508del cells. The mechanism implied by CIGB-552 with the COMMD1 protein in this positive effect are still undeciphered. CIGB-552 synergy with the tri-therapy to modulate CFTR-F508del function is still a promising strategy to improve cystic fibrosis treatment.

Background and Purpose: D-amino acid oxidase (DAO) has been developed as a chemogenetic tool to precisely manipulate redox levels in tissues and cells by generating H2O2 in the presence of D-amino acids. The enzyme’s significant oxygen consumption during H2O2 production may influence cellular oxygen levels. We set out to explore if DAO activation results in hypoxia, which in turn alters the activity of the cellular oxygen sensors that are prolyl-4-hydroxylase domain enzymes and thus the hypoxia-inducible factor (HIF) pathway. Experimental Approach: We analyzed oxygen consumption rate (OCR), pericellular oxygen concentration, and HIF-1α stabilization in HEK293 cells stably overexpressing DAO in either the cytoplasm or mitochondrial matrix. The obtained experimental data were used to test whether a simple mathematical model can be used to predict oxygen levels. Key Result: Using HEK293 cells expressing DAO in either the cytoplasm or mitochondrial matrix, we found a dose-dependent increase in OCR upon stimulating the DAO reaction, which resulted in a decreased pericellular O2. Correspondingly, HIF-1α protein levels were stabilized over time, reflecting the biological cellular response to DAO-induced hypoxia. Furthermore, we provide a spreadsheet with a simplified diffusion model that allows users to input experimental parameters and assess the risk of hypoxic conditions in cell cultures. Conclusion and Implications: High DAO activity can induce hypoxia due to increased oxygen consumption. Caution should be taken to prevent hypoxic conditions in cell culture experiments while using DAO. The provided spreadsheet is intended to help control oxygen levels in combination with OCR measurements.

Background and Purpose: Vitiligo, a common depigmenting skin disorder, is characterised by the selective loss of melanocytes, which leads to distinctive non-scaly, chalky-white macules. Galangin (GA), a flavonoid found in galangal and propolis, our previous study highlighted the therapeutic potential of GA. However, the contributions of GA to restoring skin pigmentation and maintaining immune homeostasis, as well as its detailed molecular roles in vitiligo management, have not been fully elucidated. Experimental Approach: We used H2O2-induced vitiligo mice and imiquimod-induced erythema mice to test the anti-vitiligo effects and anti-inflammatory effects of GA. We also revealed the potential mechanism by immunoprecipitation-mass spectrometry, pull-down assays, Autodock and surface plasmon resonance analysis in cells. Key Results: We found that GA exerts anti-inflammatory and antioxidant effects through a dual mechanism: it promotes melanocyte proliferation while inhibiting macrophage proliferation. Using immunoprecipitation-mass spectrometry, pull-down assays, Autodock and surface plasmon resonance analyses, we revealed that GA binds to Annexin A2 (ANXA2) and promotes its degradation in macrophages. This interaction led to the inhibition of macrophage proliferation and activation. In vivo, GA administration significantly improved skin conditions in H2O2-induced vitiligo mice and imiquimod-induced erythema mice. Furthermore, ANXA2 knockout abolished the protective effects of GA in these models. Conclusion and Implications: Our findings provide novel evidence of GA’s dual mechanism in vitiligo treatment, which involves selective binding and degradation of ANXA2 in macrophages. These results support the potential clinical application of GA for vitiligo therapy.

Background and Purpose Hydrogen sulphide (H2S) is synthesised endogenously through cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3-MST). Although exogenous H2S is known to produce vasodilatation, the vascular effect of H2S produced through 3-MST is unknown. In this study we demonstrate the effect of a novel inhibitor of 3-MST, DPHE, and determined the effect of this compound on contractile responses in porcine coronary artery. Experimental Approach Synthesis of H2S through 3-MST, and CBS/CSE was determined in rat liver cytosols. Effects of 3-MST inhibitors DPHE, 3-PAB, or I3MT-3, or CBS/CSE inhibitors AOAA and PPG on contractile responses in porcine coronary arteries were determined using isolated tissue baths. Key Results DPHE inhibited the production of H2S from 3-meraptopyruvate (IC50 ~8 µM). The 3-MST inhibitors DPHE, I3MT-3, and 3-PAB all inhibited contractions to U46619 in porcine coronary artery segments through an endothelium-independent mechanism. DPHE and 3MT-3 reduced the U46619 contractions in the absence of extracellular calcium and inhibited the contraction to the L-type calcium channel opener BAY K8644. The combination of AOAA (100 µM) and PPG (10 µM) had no effect on the U46619 contractions. The inhibitory effect of the 3-MST inhibitors does not appear to involve Rho kinase, ERK-MAP kinase, or the mitochondrial electron transport chain. Conclusions and Implications Inhibition of 3-MST in coronary arteries leads to an inhibition of both calcium-dependent and -independent contractions, whereas CBS/CSE inhibitors had no effect on receptor mediated contractions. These data suggest that 3-MST, not CBS/CSE, regulates vascular tone in porcine coronary artery.

Background and Purpose: Pharmacokinetics have traditionally been assessed using concentration measurements from methods with low temporal resolution, such as blood draws, leading to profiles being estimated from sparse or blended data. Recent advances in in vivo sensors, however, now enable the collection of hundreds of observations over a few-hours for each individual drug administration. Previous analyses of such data for the antibiotic tobramycin have identified significant (several-fold), hours-scale changes in the efficiency with which this renally cleared drug is eliminated. Here we apply similar analyses to study the pharmacokinetics of another renally cleared drug, the antibiotic vancomycin. Experimental Approach: We estimate vancomycin pharmacokinetic profiles using previously collected time-dense plasma concentration measurements within six anesthetized rats. Specifically, we fit standard one- and two-compartment models, as well as time-varying one-compartment models (in which the proportionality relating concentration to elimination rate is time-varying), to these data to investigate if the time-varying models are statistically preferred for describing individual-level vancomycin pharmacokinetics, over standard one- and two-compartment models. Key Results: One-compartment models incorporating time-varying elimination proportionalities are statistically preferred over standard one- and two- compartment models for 5 of our 6 vancomycin time courses. When the initial impact of the distribution phase is removed from these data, a reciprocally time-varying one-compartment model is preferred over the standard-one compartment model in 4 of 5 considered datasets. Conclusion and Implications: These results provide further animal-model evidence that the pharmacokinetics of renally cleared drugs can vary significantly over timescales as short as a few hours.

Background and Purpose Neuroinflammation is increasingly recognized to contribute to drug-resistant epilepsy. Activation of the ATP-gated P2X7 receptor (P2X7R) has emerged as an important upstream mechanism and increased P2X7R expression is present in the seizure focus in rodent models and patients. Pharmacologic antagonism of the P2X7R can attenuate seizures in rodents but this has not been explored in human neuronal networks. Experimental Approach Human neurons were differentiated from two induced pluripotent stem cell (hiPSC) lines. P2X7R function on neurons was assessed via P2X7R agonist BzATP-evoked calcium transients. Acute or chronic in vitro models of epileptiform-like events were generated by exposure of hiPSC cultures to the GABAA receptor antagonist picrotoxin or a cocktail of picrotoxin and neuroinflammatory agents with or without the presence of P2X7R antagonists. Epileptiform-like activity was measured via single cell patch-clamp recordings. Key Results BzATP application (300 µM) resulted in increased calcium influx in hiPSC-derived neurons which was blocked by the P2X7R antagonists JNJ-47965567 (100 nM) and AFC-5128 (30 nM). Single-cell patch-clamp recordings showed that, while treatment with AFC-5128 did not reduce epileptiform-like activity triggered by picrotoxin alone, AFC-5128 reduced the severity of epileptiform-like activity under inflammatory conditions. Notably, epileptiform-like events in the inflammation-primed picrotoxin model were refractory to the anti-seizure medication carbamazepine alone but were reduced by the co-application of carbamazepine with AFC-5128. Conclusion and Implications Our findings demonstrate anti-seizure effects of targeting the P2X7R in a human neuronal network model of epilepsy and suggest P2X7R-based treatments may be an effective add-on therapy for controlling drug-resistant seizures.

Background: Previous research demonstrated that emodin inhibits cardiac fibrosis through metastasisasspcoated protein 3 (MTA3), but its limited bioavailability hinders clinical application. Aim: To enhance emodin clinical potential, a new derivative, emodin succinyl ethyl ester, was synthesized by modifying the 3’-OH position. This study assessed its drug-likeness, anti-fibrotic properties, and molecular mechanisms involving MTA3. Methods: Drug-likeness properties of the emodin derivative were evaluated using computational-aided drug design (CADD) approaches. An animal model of transverse aortic constriction (TAC)-induced cardiac fibrosis and Angiotensin II (AngII) stimulated cardiac fibroblasts were used in vivo and ex vivo, respectively, to determine the effects of emodin derivative on cardiac fibrosis and fibroblast transdifferentiation. Bioinformatics analysis of the PROMO database, CADD, chromatin immunoprecipitation (ChIP), luciferase reporter assays, and functional experiments were employed to predict, identify and validate the relationship between MTA3 and its upstream transcription factors. Results: Emodin derivative exhibited superior drug-likeness and anti-fibrotic effects compared to emodin by effectively inhibiting cardiac fibroblast transdifferentiation and restored MTA3 expression. E2F1 was identified and validated as a transcriptional regulator, promoting α-SMA and COL1A2 expression, and directly reducing MTA3 expression in cardiac fibroblasts. The emodin derivative demonstrated stronger binding to E2F1 transcription site than emodin, reducing E2F1 expression and enhancing anti-fibrotic action via MTA3. Conclusion: The emodin derivative shows improved drug-likeness and potent inhibition of cardiac fibrosis by targeting E2F1, disrupting its pro-fibrotic function, restoring MTA3 expression, and halting fibrosis progression. This advances emodin’s potential as a clinical therapy for cardiac fibrosis and provides insights into its anti-fibrotic mechanisms.

Background & Purpose: Reactive oxygen species (ROS) play pivotal roles in cellular signaling. Nrf2 is a key transcription factor that regulates redox homeostasis. However, the relationship between Nrf2 and H2O2 is controversially discussed in the literature. Thus, we aimed to investigate how varying intracellular H2O2 levels, manipulated through different methods, influence Nrf2 regulation in brain endothelial cells under physiological normoxia (5 kPa O₂), contrasting with typical hyperoxic cell culture conditions. Experimental Approach: In this study, we developed and validated a novel oxygen-independent Nrf2 biosensor, Pericellular Oxygen-Insensitive Nrf2 Total LEvel Reporter (POINTER), using human cerebral microvascular endothelial cells (hCMEC/D3). We investigated the relationship between intracellular H2O2 and Nrf2 levels under varying oxygen conditions, employing exogenous H₂O₂ application, chemogenetic production of H2O2 via modified D-amino acid oxidase (mDAAO), and pharmacological induction of H2O2 with Auranofin. Key Results: POINTER confirmed significantly lower Nrf2 levels in hCMEC/D3 cells under physiological normoxia (5 kPa) compared to hyperoxia (room air). Auranofin demonstrated efficacy in modulating intracellular H2O2 increase comparable to exogenous administration of H₂O₂, yet H₂O₂ levels recovered to the baseline 24 hours after this treatment. Moreover, only chemogenetically produced H2O2 remained significantly elevated in cells after 24 hours. More importantly, only Auranofin, but not exogenous provision of H2O2 and chemogenetically induced oxidative stress robustly increased Nrf2 levels under physiological oxygen conditions demonstrated by the POINTER biosensor. Conclusion and Implications: These findings reveal the intricate regulation of Nrf2, indicating that both antioxidant inhibition and the elevation of H₂O₂ are crucial for modulating Nrf2 levels under physioxia.

Background and Purpose Adenosine, through the A1 receptor (A1R), is an endogenous anticonvulsant. Development of adenosine receptor agonists as antiseizure medications has been hampered by their cardiac side effects. A moderately A1R-selective agonist, MRS5474, has been reported to suppress seizures without considerable cardiac action. Hypothesizing that this drug could act through other than A1R and/or through a disease specific mechanism, we assessed the effect of MRS5474 on the hippocampus. Experimental Approach Excitatory synaptic currents, field potentials, spontaneous activity, [3H]GABA uptake and GABAergic currents were recorded from rodent or human hippocampal tissue. Alterations in adenosine A3 receptor (A3R) density in human tissue were assessed by Western Blot. Key Results MRS5474 (50-500nM) was devoid of effect upon rodent excitatory synaptic signals in hippocampal slices, except when hyperexcitability was previously induced in vivo or ex vivo. This contrasted with the effect of other A1R agonists. MRS5474 inhibited GAT-1 mediated GABA uptake, an action not blocked by an A1R antagonist but blocked by an A3R antagonist and mimicked by an A3R agonist. A3R was overexpressed in human hippocampal tissue samples from patients with epilepsy that had focal resection from surgery. MRS5474 induced a concentration-dependent potentiation of GABA-evoked currents in oocytes micro-transplanted with human hippocampal membranes prepared from epileptic hippocampal tissue but not from non-epileptic tissue, an action blocked by an A3R antagonist. Conclusion and Implications We identified a drug that activates A3R and has selective actions on epileptic hippocampal tissue. This underscores A3R as a promising target for the development of antiseizure medications.

Background and Purpose: Many structurally and therapeutically diverse drugs block the human ether-à-go-go related gene (HERG) potassium channel, predisposing patients to an increased risk of arrythmias and sudden cardiac death. Many drugs show state-dependence of block, exhibiting a greater preference for block of the inactivated state. Five key residues within the central pore cavity of HERG have been implicated in drug binding. However, whether drugs bind differently to these key residues to dictate preference for the inactivated over the open state is not known. Experimental Approach: We used the SyncroPatch 384PE, automated patch clamp platform to measure how drug block was impacted by point mutations at residues T623, S624, Y652, and F656 when introduced into wild-type HERG (preferentially occupies the inactivated state) and N588K-HERG (preferentially occupies the open state) channels at depolarised potentials. Key Results: Mutations to Y652 and F656, that abolished aromatic and hydrophobic characteristics respectively, reduced drug binding in both WT and N588K backgrounds. The S624A mutation attenuated block by cisapride, astemizole, and quinidine in the WT background but not in the N588K background. Conclusion and Implications: We suggest that relative movements between the polar S624 sidechain and the aromatic Y652 and F656 sidechains in WT (inactivated) compared to N588K (open) channels can explain preferential binding to the inactivated state. An improved understanding of the structural basis of where and how drugs bind to HERG channels should facilitate efforts to reduce inadvertent HERG drug block during the drug development process.

High-altitude hypoxia affects respiratory, central nervous, cardiovascular, and endocrine systems. These outcomes affect the expression of cytochrome P450 (CYP), the most important family of metabolic enzymes in the body involved in the metabolism of both exogenous and endogenous substances. Hypoxia influences CYP expression and activity, mediating changes in drug and endogenous substance metabolism, with endogenous substance metabolites playing a substantial role in controlling high-altitude diseases. However, the mechanisms that regulate CYP changes under hypoxic conditions and the effects of CYP changes on drug and endogenous metabolism remain unclear. We examined how CYP expression and function change during hypoxia and how they are controlled by nuclear receptors, epigenetic modifications, cytokines, and gut microbiota during hypoxia. This was done to understand how CYP affects the metabolism of drugs and endogenous substances, such as arachidonic acid, vitamins, and steroid hormones during hypoxia, and to determine how CYP and its metabolites are involved in the pathophysiology of diseases linked to high-altitude hypoxia.