beta-Adrenergic blockers: a 50-year historical perspective. Am J Ther. 2008;15:565-576. [PMID: 19127141 DOI: 10.1097/mjt.0b013e318188bdca]

The β2-adrenergic receptor in the apical membrane of intestinal enterocytes senses sugars to stimulate glucose uptake from the gut

The presence of sugar in the gut causes induction of SGLT1, the sodium/glucose cotransporter in intestinal epithelial cells (enterocytes), and this is accompanied by stimulation of sugar absorption. Sugar sensing was suggested to involve a G-protein coupled receptor and cAMP - protein kinase A signalling, but the sugar receptor has remained unknown. We show strong expression and co-localization with SGLT1 of the β2-adrenergic receptor (β ₂-AR) at the enterocyte apical membrane and reveal its role in stimulating glucose uptake from the gut by the sodium/glucose-linked transporter, SGLT1. Upon heterologous expression in different reporter systems, the β ₂-AR responds to multiple sugars in the mM range, consistent with estimated gut sugar levels after a meal. Most adrenergic receptor antagonists inhibit sugar signaling, while some differentially inhibit epinephrine and sugar responses. However, sugars did not inhibit binding of I¹²⁵-cyanopindolol, a β ₂-AR antagonist, to the ligand-binding site in cell-free membrane preparations. This suggests different but interdependent binding sites. Glucose uptake into everted sacs from rat intestine was stimulated by epinephrine and sugars in a β ₂-AR-dependent manner. STD-NMR confirmed direct physical binding of glucose to the β ₂-AR. Oral administration of glucose with a non-bioavailable β ₂-AR antagonist lowered the subsequent increase in blood glucose levels, confirming a role for enterocyte apical β ₂-ARs in stimulating gut glucose uptake, and suggesting enterocyte β ₂-AR as novel drug target in diabetic and obese patients. Future work will have to reveal how glucose sensing by enterocytes and neuroendocrine cells is connected, and whether β ₂-ARs mediate glucose sensing also in other tissues.

Zolpidem use and risk of suicide: A systematic review and meta-analysis

INTRODUCTION

Zolpidem is one of the most commonly prescribed nonbenzodiazepine hypnotic drugs for insomnia. Published epidemiological studies linked zolpidem with the risk of suicide. However, to date, no meta-analysis investigated this association. Hence, we systematically reviewed and meta-analysed the current evidence from real-world studies reporting the risk of suicide with the use of zolpidem.

METHODS

Medline (Ovid), Embase (Ovid), and PsycINFO databases were searched from inception till June 2021 for real-world evidence studies reporting the risk of suicide with the use of zolpidem. The quality assessment of included studies was assessed using the New-Castle Ottawa Scale (NOS). Random-effect meta-analysis was performed using a generic inverse variance method.

RESULTS

This meta-analysis was based on four studies with 344,753 participants, of which 42,279 were zolpidem users. The methodological quality of all the included studies was of high quality. A significantly increased risk of suicide or suicide attempt was found in zolpidem users compared to non-users, with a pooled relative risk of 1.88 (95% CI: 1.54 - 2.30). Furthermore, an increased risk of suicidal death was observed in zolpidem users compared to non-users, with a pooled relative risk of 1.82 (95% CI: 1.43 - 2.30). Dose-response analysis also revealed a significantly increased risk of suicide in patients receiving ≥ 180cDDD (cumulative defined daily doses) of zolpidem (124 times), followed by 90-179cDDD (113 times) and <90cDDD (93 times) of zolpidem compared to non-users.

CONCLUSION

In conclusion, zolpidem use was associated with an increased risk of suicide or suicide attempt and suicidal death. Therefore, careful prescribing practices must be followed by considering the risk-benefit profile.

Combined docking and machine learning identify key molecular determinants of ligand pharmacological activity on β2 adrenoceptor

G protein‐coupled receptors (GPCRs) are valuable therapeutic targets for many diseases. A central question of GPCR drug discovery is to understand what determines the agonism or antagonism of ligands that bind them. Ligands exert their action via the interactions in the ligand binding pocket. We hypothesized that there is a common set of receptor interactions made by ligands of diverse structures that mediate their action and that among a large dataset of different ligands, the functionally important interactions will be over‐represented. We computationally docked ~2700 known β2AR ligands to multiple β2AR structures, generating ca 75 000 docking poses and predicted all atomic interactions between the receptor and the ligand. We used machine learning (ML) techniques to identify specific interactions that correlate with the agonist or antagonist activity of these ligands. We demonstrate with the application of ML methods that it is possible to identify the key interactions associated with agonism or antagonism of ligands. The most representative interactions for agonist ligands involve K97^2.68×67, F194^ECL2, S203^5.42×43, S204^5.43×44, S207^5.46×641, H296^6.58×58, and K305^7.32×31. Meanwhile, the antagonist ligands made interactions with W286^6.48×48 and Y316^7.43×42, both residues considered to be important in GPCR activation. The interpretation of ML analysis in human understandable form allowed us to construct an exquisitely detailed structure‐activity relationship that identifies small changes to the ligands that invert their pharmacological activity and thus helps to guide the drug discovery process. This approach can be readily applied to any drug target.

Alprazolam and lorazepam overdose and the absence of brainstem reflexes

Benzodiazepines (BZDs) rarely cause respiratory depression and death. On the other hand, high-dose BZDs may lead to profound sedation and diminished brainstem functions that mimic other structural brain lesions as described in our case: a 70-year-old unresponsive woman. She was hypothermic and had rapid shallow breathing. Her Glasgow Coma Scale score was E1V1M4, with pinpoint pupils and absent corneal, oculocephalic and oculovestibular reflexes. Other physical exams, laboratory testing and brain imaging were unremarkable. After two doses of 0.4 mg naloxone and intravenous thrombolytics were given, there were no significant responses, and the diagnosis remained a mystery. The cause of her unconsciousness was uncovered when her husband found empty bags of 80 tablets of alprazolam and lorazepam. Her consciousness and brainstem reflexes improved dramatically after 0.25 mg of intravenous flumazenil. The blood for BZDs concentration showed alprazolam 268 ng/mL (20-40 ng/mL), lorazepam 861 ng/mL (20-250 ng/mL) and their metabolites.

Effects of Antihypertensive Drugs on Thyroid Function in Type 2 Diabetes Patients With Euthyroidism

Objective: There is little literature about whether antihypertensive drugs would affect thyroid function in patients with euthyroid type 2 diabetes, which was significant in maintaining a proper balance of thyroid function. A retrospective cohort study was conducted to evaluate the influence of antihypertensive drugs on thyroid function in patients with type 2 diabetes with euthyroidism. Design and Methods: The study involved dividing 698 patients with antihypertensive monotherapy into five groups according to the antihypertensive drugs they were treated with. Antihypertensive drugs included in this study were β-blockers, angiotensin-converting enzyme inhibitors (ACEI), angiotensin receptor blockers (ARB), and calcium channel blockers (CCB). The clinical data and thyroid function level between or within groups were compared. Multiple logistic regression analysis was conducted to evaluate the association of antihypertensive drugs with thyroid function level. Results: Selective β₁- adrenergic receptor blockers treatment was related to thyroid-stimulating hormone (TSH), increasing in patients with diabetes and euthyroidism as shown by multiple logistic regression analysis. The association existed after adjustment for confounding factors. No significant influence on thyroid function was found among other antihypertensive drugs. Conclusion: These data show the TSH-lifting effect of selective β₁-adrenergic receptor blockers in patients with type 2 diabetes with euthyroidism.

Brain death: a clinical overview

Brain death, also commonly referred to as death by neurologic criteria, has been considered a legal definition of death for decades. Its determination involves many considerations and subtleties. In this review, we discuss the philosophy and history of brain death, its clinical determination, and special considerations. We discuss performance of the main clinical components of the brain death exam: assessment of coma, cranial nerves, motor testing, and apnea testing. We also discuss common ancillary tests, including advantages and pitfalls. Special discussion is given to extracorporeal membrane oxygenation, target temperature management, and determination of brain death in pediatric populations. Lastly, we discuss existing controversies and future directions in the field.

Comparative effectiveness of bisoprolol and carvedilol among patients receiving maintenance hemodialysis

Background

Despite widespread use, there is no trial evidence to inform β-blocker's (BB) relative safety and efficacy among patients undergoing hemodialysis (HD). We herein compare health outcomes associated with carvedilol or bisoprolol use, the most commonly prescribed BBs in these patients.

Methods

We created a cohort study of 9305 HD patients who initiated bisoprolol and 11 171 HD patients who initiated carvedilol treatment between 2004 and 2011. We compared the risk of all-cause mortality and major adverse cardiovascular events (MACEs) between carvedilol and bisoprolol users during a 2-year follow-up.

Results

Bisoprolol initiators were younger, had shorter dialysis vintage, were women, had common comorbidities of hypertension and hyperlipidemia and were receiving statins and antiplatelets, but they had less heart failure and digoxin prescriptions than carvedilol initiators. During our observations, 1555 deaths and 5167 MACEs were recorded. In the multivariable-adjusted Cox model, bisoprolol initiation was associated with a lower all-cause mortality {hazard ratio [HR] 0.66 [95% confidence interval (CI) 0.60-0.73]} compared with carvedilol initiation. After accounting for the competing risk of death, bisoprolol use (versus carvedilol) was associated with a lower risk of MACEs [HR 0.85 (95% CI 0.80-0.91)] and attributed to a lower risk of heart failure [HR 0.83 (95% CI 0.77-0.91)] and ischemic stroke [HR 0.84 (95% CI 0.72-0.97)], but not to differences in the risk of acute myocardial infarction [HR 1.03 (95% CI 0.93-1.15)]. Results were confirmed in propensity score matching analyses, stratified analyses and analyses that considered prescribed dosages or censored patients discontinuing or switching BBs.

Conclusions

Relative to carvedilol, bisoprolol initiation by HD patients was associated with a lower 2-year risk of death and MACEs, mainly attributed to lower heart failure and ischemic stroke risk.

Overdose and Alcohol Sensitive Immediate Release System (OASIS) for Deterring Accidental Overdose or Abuse of Drugs

Death from an accidental or intentional overdose of sleeping tablets has increased exponentially in the USA. Furthermore, the simultaneous consumption of sleeping tablets with alcoholic beverages not only intensifies the effect of sleeping tablets but also leads to blackouts, sleepwalking, and death in many cases. In this article, we proposed a unique and innovative technology to prevent multi-tablet and alcohol-associated abuse of sleeping tablet. Agonist- and antagonist-loaded polymeric filaments of appropriate Eudragit® polymers were prepared using hot melt extrusion. Metoprolol tartrate and hydrochlorothiazide were used as model drugs in place of zolpidem tartrate (agonist-BCS class I) and flumazenil (antagonist-BCS class IV), respectively. Crushed filaments were converted into a tablet with a novel rapidly soluble co-processed alkalizing agent. Dissolution studies of single tablet and multiple tablets (5) in fasted state simulated gastric fluid (FaSSGF) confirmed that the release of the agonist was significantly (p < 0.0001) reduced in multi-tablet dissolution. Furthermore, the release of antagonist was significantly higher when tablet was exposed to FaSSGF+20% ethanol and various alcoholic beverages. Thus, appropriate use of Eudragit® polymer's chemistry could help design a tablet to prevent the release of agonist in case of overdose and simultaneous release of antagonist when consumed with alcohol.

Metoprolol Impairs β1-Adrenergic Receptor-Mediated Vasodilation in Rat Cerebral Arteries: Implications for β-Blocker Therapy

The practice of prescribing β-blockers to lower blood pressure and mitigate perioperative cardiovascular events has been questioned because of reports of an increased risk of stroke. The benefit of β-blocker therapy primarily relies on preventing activation of cardiac β1-adrenergic receptors (ARs). However, we reported that β1ARs also mediate vasodilator responses of rat cerebral arteries (CAs), implying that β-blockers may impair cerebral blood flow under some conditions. Here, we defined the impact of metoprolol (MET), a widely prescribed β1AR-selective antagonist, on adrenergic-elicited diameter responses of rat CAs ex vivo and in vivo. MET (1-10 µmol/l) prevented β1AR-mediated increases in diameter elicited by dobutamine in cannulated rat CAs. The β1AR-mediated dilation elicited by the endogenous adrenergic agonist norepinephrine (NE) was reversed to a sustained constriction by MET. Acute oral administration of MET (30 mg/kg) to rats in doses that attenuated resting heart rate and dobutamine-induced tachycardia also blunted β1AR-mediated dilation of CAs. In the same animals, NE-induced dilation of CAs was reversed to sustained constriction. Administration of MET for 2 weeks in drinking water (2 mg/ml) or subcutaneously (15 mg/kg per day) also resulted in NE-induced constriction of CAs in vivo. Thus, doses of MET that protect the heart from adrenergic stimulation also prevent β1AR-mediated dilation of CAs and favor anomalous adrenergic constriction. Our findings raise the possibility that the increased risk of ischemic stroke in patients on β-blockers relates in part to adrenergic dysregulation of cerebrovascular tone. SIGNIFICANCE STATEMENT: β-Blocker therapy using second-generation, cardioselective β-blockers is associated with an increased risk of stroke, but the responsible mechanisms are unclear. Here, we report that either acute or chronic systemic administration of a cardioselective β-blocker, metoprolol, mitigates adrenergic stimulation of the heart as an intended beneficial action. However, metoprolol concomitantly eliminates vasodilator responses to adrenergic stimuli of rat cerebral arteries in vivo as a potential cause of dysregulated cerebral blood flow predisposing to ischemic stroke.

Structural Basis of the Activation of Heterotrimeric Gs-Protein by Isoproterenol-Bound β1-Adrenergic Receptor

Cardiac disease remains the leading cause of morbidity and mortality worldwide. The β₁-adrenergic receptor (β₁-AR) is a major regulator of cardiac functions and is downregulated in the majority of heart failure cases. A key physiological process is the activation of heterotrimeric G-protein Gs by β₁-ARs, leading to increased heart rate and contractility. Here, we use cryo-electron microscopy and functional studies to investigate the molecular mechanism by which β₁-AR activates Gs. We find that the tilting of α5-helix breaks a hydrogen bond between the sidechain of His373 in the C-terminal α5-helix and the backbone carbonyl of Arg38 in the N-terminal αN-helix of Gα_s. Together with the disruption of another interacting network involving Gln59 in the α1-helix, Ala352 in the β6-α5 loop, and Thr355 in the α5-helix, these conformational changes might lead to the deformation of the GDP-binding pocket. Our data provide molecular insights into the activation of G-proteins by G-protein-coupled receptors.

Toxicologic Confounders of Brain Death Determination: A Narrative Review

The aim of this narrative review is to describe the toxicologic confounders of brain death currently reported in the literature to offer guidance for physicians assessing brain death after a toxic exposure. We established an a priori definition of a “brain death mimic” as an unresponsive, intubated patient missing some, but not all brainstem reflexes. We completed a review of the literature utilizing MEDLINE and EMBASE to find case reports of patients of all ages in English, French, and Spanish meeting the criteria and hand searched the references of the results. We recorded xenobiotic dose, duration of physical exam suggesting brain death, and how the cases failed to meet full brain death criteria, when available. Fifty-six cases representing 19 different substances met the a priori definition of brain death mimic. Xenobiotic toxicities included: snake envenomation (13), baclofen (11), tricyclic antidepressants (8), bupropion (7), alcohols (4), antiepileptic agents (3), barbiturates (2), antidysrhythmics (2), organophosphates (2), and one case each of magnesium, succinylcholine, tetrodotoxin, and zolpidem. All patients except one survived to discharge and the majority at their baseline physical health. The most common means by which the cases failed brain death examination prerequisites was via normal neuroimaging. The xenobiotics in this review should be considered in cases of poisoning resulting in loss of brainstem reflexes and addressed before brain death determination. Brain death diagnosis should not be pursued in the setting of normal cerebral imaging or incomplete evaluation of brain death prerequisites.

Activation of oxytocin neurons in the paraventricular nucleus drives cardiac sympathetic nerve activation following myocardial infarction in rats

Myocardial infarction (MI) initiates an increase in cardiac sympathetic nerve activity (SNA) that facilitates potentially fatal arrhythmias. The mechanism(s) underpinning sympathetic activation remain unclear. Some neuronal populations within the hypothalamic paraventricular nucleus (PVN) have been implicated in SNA. This study elucidated the role of the PVN in triggering cardiac SNA following MI (left anterior descending coronary artery ligation). By means of c-Fos, oxytocin, and vasopressin immunohistochemistry accompanied by retrograde tracing we showed that MI activates parvocellular oxytocin neurons projecting to the rostral ventral lateral medulla. Central inhibition of oxytocin receptors using atosiban (4.5 µg in 5 µl, i.c.v.), or retosiban (3 mg/kg, i.v.), prevented the MI-induced increase in SNA and reduced the incidence of ventricular arrhythmias and mortality. In conclusion, pre-autonomic oxytocin neurons can drive the increase in cardiac SNA following MI and peripheral administration of an oxytocin receptor blocker could be a plausible therapeutic strategy to improve outcomes for MI patients.

Roy et al. showed that activation of parvocellular pre-autonomic oxytocin neurons increased sympathetic nerve activity following myocardial infarction. This and other aberrant physiological changes induced by acute myocardial infarction were decreased by oxytocin receptor antagonists, hinting to their potential therapeutic role.

Ivabradine in the treatment of systolic heart failure - A systematic review and meta-analysis

AIM

To perform a systematic-review and meta-analysis to compare outcomes of ivabradine combined with beta-blocker to beta-blocker alone in heart failure with reduced ejection fraction (HFrEF).

METHODS

We searched PubMed, Cochrane, EMBASE, CINAHL and Web of Science for trials comparing ivabradine + beta-blocker to beta-blocker alone in HFrEF. We performed a systematic-review and meta-analysis of published literature. Primary end-point was combined end point of cardiac death and hospitalization for heart failure.

RESULTS

Six studies with 17671 patients were included. Mean follow-up was 8.7 ± 7.9 mo. Combined end-point of heart failure readmission and cardiovascular death was better in ivabradine + beta-blocker group compared to beta-blocker alone (RR: 0.93, 95%CI: 0.79-1.09, P = 0.354). Mean difference (MD) in heart rate was higher in the ivabradine + beta-blocker group (MD: 6.14, 95%CI: 3.80-8.48, P < 0.001). There was no difference in all cause mortality (RR: 0.98, 95%CI: 0.89-1.07, P = 0.609), cardiovascular mortality (RR: 0.99, 95%CI: 0.86-1.15, P = 0.908) or heart failure hospitalization (RR: 0.87, 95%CI: 0.68-1.11, P = 0.271).

CONCLUSION

From the available clinical trials, ivabradine + beta-blocker resulted in a significantly greater reduction in HR coupled with improvement in combined end-point of heart failure readmission and cardiovascular death but with no improvement in all cause or cardiovascular mortality. Given the limited evidence, further randomized controlled trials are essential before widespread clinical application of ivabradine + beta-blocker is advocated for HFrEF.

Quantifying Effects of Pharmacological Blockers of Cardiac Autonomous Control Using Variability Parameters

Objective: The aim of this study was to identify the most sensitive heart rate and blood pressure variability (HRV and BPV) parameters from a given set of well-known methods for the quantification of cardiovascular autonomic function after several autonomic blockades.

Methods: Cardiovascular sympathetic and parasympathetic functions were studied in freely moving rats following peripheral muscarinic (methylatropine), β1-adrenergic (metoprolol), muscarinic + β1-adrenergic, α1-adrenergic (prazosin), and ganglionic (hexamethonium) blockades. Time domain, frequency domain and symbolic dynamics measures for each of HRV and BPV were classified through paired Wilcoxon test for all autonomic drugs separately. In order to select those variables that have a high relevance to, and stable influence on our target measurements (HRV, BPV) we used Fisher's Method to combine the p-value of multiple tests.

Results: This analysis led to the following best set of cardiovascular variability parameters: The mean normal beat-to-beat-interval/value (HRV/BPV: meanNN), the coefficient of variation (cvNN = standard deviation over meanNN) and the root mean square differences of successive (RMSSD) of the time domain analysis. In frequency domain analysis the very-low-frequency (VLF) component was selected. From symbolic dynamics Shannon entropy of the word distribution (FWSHANNON) as well as POLVAR3, the non-linear parameter to detect intermittently decreased variability, showed the best ability to discriminate between the different autonomic blockades.

Conclusion: Throughout a complex comparative analysis of HRV and BPV measures altered by a set of autonomic drugs, we identified the most sensitive set of informative cardiovascular variability indexes able to pick up the modifications imposed by the autonomic challenges. These indexes may help to increase our understanding of cardiovascular sympathetic and parasympathetic functions in translational studies of experimental diseases.

Non-Benzodiazepine Receptor Agonists for Insomnia

Because of proven efficacy, reduced side effects, and less concern about addiction, non-benzodiazepine receptor agonists (non-BzRA) have become the most commonly prescribed hypnotic agents to treat onset and maintenance insomnia. First-line treatment is cognitive-behavioral therapy. When pharmacologic treatment is indicated, non-BzRA are first-line agents for the short-term and long-term management of transient and chronic insomnia related to adjustment, psychophysiologic, primary, and secondary causation. In this article, the benefits and risks of non-BzRA are reviewed, and the selection of a hypnotic agent is defined, based on efficacy, pharmacologic profile, and adverse events.

Clinical utility of fixed-dose combinations in hypertension: evidence for the potential of nebivolol/valsartan

Despite significant advances in pharmacologic approaches to treat hypertension during the last decades, hypertension- and hypertension-related organ damage are still a high health and economic burden because a large proportion of patients with hypertension do not achieve optimal blood pressure control. There is now general agreement that combination therapy with two or more antihypertensive drugs is required for targeted blood pressure accomplishment and reduction of global cardiovascular risk. The goals of combination therapies are to reduce long-term cardiovascular events by targeting different mechanism underlying hypertension and target organ disease, to block the counterregulatory pathways activated by monotherapies, to improve tolerability and decrease the adverse effects of up-titrated single agents, and to increase persistence and adherence with antihypertensive therapy. Multiple clinical trials provide evidence that fixed-dose combinations in a single pill offer several advantages when compared with loose-dose combinations. This review discusses the advances in hypertension control and associated cardiovascular disease as they relate to the prospect of combination therapy targeting a third-generation beta (β) 1-adrenergic receptor (nebivolol) and an angiotensin II receptor blocker (valsartan) in fixed-dose single-pill formulations.

The clinical and forensic toxicology of Z-drugs

The Z-drugs zolpidem, zopiclone, and zaleplon were hailed as the innovative hypnotics of the new millennium, an improvement to traditional benzodiazepines in the management of insomnia. Increasing reports of adverse events including bizarre behavior and falls in the elderly have prompted calls for caution and regulation. Z-drugs have significant hypnotic effects by reducing sleep latency and improving sleep quality, though duration of sleep may not be significantly increased. Z-drugs exert their effects through increased γ-aminobutyric acid (GABA) transmission at the same GABA-type A receptor as benzodiazepines. Their pharmacokinetics approach those of the ideal hypnotic with rapid onset within 30 min and short half-life (1-7 h). Zopiclone with the longest duration of action has the greatest residual effect, similar to short-acting benzodiazepines. Neuropsychiatric adverse events have been reported with zolpidem including hallucinations, amnesia, and parasomnia. Poisoning with Z-drugs involves predominantly sedation and coma with supportive management being adequate in the majority. Flumazenil has been reported to reverse sedation from all three Z-drugs. Deaths from Z-drugs are rare and more likely to occur with polydrug overdose. Z-drugs can be detected in blood, urine, oral fluid, and postmortem specimens, predominantly with liquid chromatography-mass spectrometry techniques. Zolpidem and zaleplon exhibit significant postmortem redistribution. Zaleplon with its ultra-short half-life has been detected in few clinical or forensic cases possibly due to assay unavailability, low frequency of use, and short window of detection. Though Z-drugs have improved pharmacokinetic profiles, their adverse effects, neuropsychiatric sequelae, and incidence of poisoning and death may prove to be similar to older hypnotics.

CYP3A4 and CYP2C19 genetic polymorphisms and zolpidem metabolism in the Chinese Han population: a pilot study

Zolpidem (ZPD) is an imidazopyridine hypnotic and little is known about the pharmacogenetics of ZPD. Our objective was to evaluate inter-individual genetic variation in conjunction with metabolic ratios of ZPD found in a toxicological analysis. Healthy individuals (n=300) were genotyped for CYP2D6, CYP2C19, CYP2C9, CYP3A4 and CYP1A2 by allele-specific primer extension followed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS). Twenty-four Chinese volunteers were chosen and divided into the following four groups (n=6/group): group 1: CYP3A4*18 (wild-type, W), CYP2C19*2 (W); group 2: CYP3A4*18 (mutant, M), CYP2C19*2 (W); group 3: CYP3A4*18 (W), CYP2C19*2 (M); and group 4: CYP3A4*18 (M), CYP2C19*2 (M). ZPD and its major metabolites zolpidem 6-carboxylic acid (ZCA) and zolpidem phenyl-4-carboxylic acid (ZPCA) were determined after oral administration of ZPD (10mg), using an UPLC-MS/MS method. Positive correlations between CYP3A4 and CYP2C19 alleles and ZPD metabolism were found. The results of this study show that CYP3A4*18 increases CYP3A4 activity while CYP2C19*2 reduces CYP2C19 activity; the latter mutation is associated with the poor metabolism of ZPD in the Chinese Han population. The results also suggest that genetic factors play a major role in the metabolism of individual drugs with implications for both forensic science and clinical pharmacogenetics.

Conducting the G-protein Coupled Receptor (GPCR) Signaling Symphony in Cardiovascular Diseases: New Therapeutic Approaches

G protein-coupled receptors (GPCRs) are a virtually ubiquitous class of membrane-bound receptors, which functionally couple hormone or neurotransmitter signals to physiological responses. Dysregulation of GPCR signaling contributes to the pathophysiology of a host of cardiovascular disorders. Pharmacological agents targeting GPCRs have been established as therapeutic options for decades. Nevertheless, the persistent burden of cardiovascular diseases necessitates improved treatments. To that end, exciting drug development efforts have begun to focus on novel compounds that discriminately activate particular GPCR signaling pathways.

β2-Adrenergic ion-channel coupled receptors as conformational motion detectors

Ion Channel-Coupled Receptors (ICCRs) are artificial proteins comprised of a G protein-coupled receptor and a fused ion channel, engineered to couple channel gating to ligand binding. These novel biological objects have potential use in drug screening and functional characterization, in addition to providing new tools in the synthetic biology repertoire as synthetic K⁺-selective ligand-gated channels. The ICCR concept was previously validated with fusion proteins between the K⁺ channel Kir6.2 and muscarinic M₂ or dopaminergic D₂ receptors. Here, we extend the concept to the distinct, longer β₂-adrenergic receptor which, unlike M₂ and D₂ receptors, displayed barely detectable surface expression in our Xenopus oocyte expression system and did not couple to Kir6.2 when unmodified. Here, we show that a Kir6.2-binding protein, the N-terminal transmembrane domain of the sulfonylurea receptor, can greatly increase plasma membrane expression of β₂ constructs. We then demonstrate how engineering of both receptor and channel can produce β₂-Kir6.2 ICCRs. Specifically, removal of 62–72 residues from the cytoplasmic C-terminus of the receptor was required to enable coupling, suggesting that ligand-dependent conformational changes do not efficiently propagate to the distal C-terminus. Characterization of the β₂ ICCRs demonstrated that full and partial agonists had the same coupling efficacy, that an inverse agonist had no effect and that the stabilizing mutation E122 W reduced agonist-induced coupling efficacy without affecting affinity. Because the ICCRs are expected to report motions of the receptor C-terminus, these results provide novel insights into the conformational dynamics of the β₂ receptor.