Origin of the kinetic HDAC2-selectivity of an HDAC inhibitor.

A newly synthesized small molecule, KTT-1, exhibits kinetically selective inhibition of histone deacetylase 2, HDAC2, over its homologous enzyme, HDAC1. KTT-1 is hard to be released from the HDAC2/KTT-1 complex, compared to the HDAC1/KTT-1 complex and the residence time of KTT-1 in HDAC2 is longer than that in HDAC1. To explore the physical origin of this kinetic selectivity, we performed replica-exchange umbrella sampling molecular dynamics simulations for formation of both complexes. The calculated potentials of mean force suggest that KTT-1 is stably bound to HDAC2 and that it is easily disassociated from HDAC1. In the direct vicinity of the KTT-1 binding site in both enzymes, there exists a conserved loop consisting of four consecutive glycine residues (Gly304-307 for HDAC2; Gly299-302 for HDA1). The difference between the two enzymes comes from a single un-conserved residue behind this loop, namely, Ala268 in HDAC2 and Ser263 in HDAC1. The Ala268 contributes to the tight binding of KTT-1 to HDAC2 by the linear orientation of Ala268, Gly306, and one carbon atom in KTT-1. On the other hand, Ser263 cannot stabilize the binding of KTT-1 to HDAC1, because it is relatively further away from the glycine loop and because the directions of the two forces are not in line.

An exploratory study of factors associated with long-term, high-dose opioid prescription in cancer patients in Japan based on a medical claims database.

PURPOSE: As the cancer survivors increase, patients using long-term and high-dose opioids are also increasing. Therefore, the promotion of appropriate use is important. This study investigated the actual status of opioid prescriptions in Japan and identified factors associated with long-term, high-dose prescription. METHODS: We conducted a case-control study using a hospital-based administrative claims database. Patients with a diagnosis of cancer and prescriptions of opioids were included. Patients who received continuous opioid for less than 183 days were defined as the "control," and patients who received continuous opioid at higher dose levels (≥ 120 mg/day of oral morphine equivalent) for 183 days or more were defined as the "case." The case was subdivided into two groups: those with the duration of less than 730 days (case I) and 730 days or more (case II). After describing factors possibly associated with long-term, high-dose opioid prescription, ordinal logistic regression analysis was conducted. RESULTS: We included 19,176 patients; of these, 13,517 were in the control, 111 were in the case I, and 682 were in the case II. The analysis showed that distant metastasis, back pain, dose of opioids, non-opioid analgesics, prescription, and chemotherapy during the opioid prescriptions were significantly associated with long-term, high-dose opioid prescription. CONCLUSION: Four percent of the study population were prescribed long-term, high-dose opioids, and several comorbidities and concomitant medications were identified as associated factors. Opioids might be also prescribed for non-cancer chronic pain. It is necessary to properly distinguish the type of pain and to use opioids safely and appropriately.

Involvement of the Peripheral µ-Opioid Receptor in Tramadol-Induced Constipation in Rodents.

Tramadol is a weak opioid that produces analgesic effect via both the µ-opioid receptor (MOR) and non-opioid targets. Constipation is the most common opioid-related side effect in patients with cancer and non-cancer pain. However, the contribution of MOR to tramadol-induced constipation is unclear. Therefore, we used naldemedine, a peripherally acting MOR antagonist, and MOR-knockout mice to investigate the involvement of peripheral MOR in tramadol-induced constipation using a small intestinal transit model. A single dose of tramadol (3-100 mg/kg, per os (p.o.)) inhibited small intestinal transit dose-dependently in rats. Naldemedine (0.01-10 mg/kg, p.o.) blocked the inhibition of small intestinal transit induced by tramadol (30 mg/kg, p.o.) in rats. The transition rate increased dose-dependently over the range of naldemedine 0.01-0.3 mg/kg, and complete recovery was observed at 0.3-10 m/kg. Additionally, tramadol (30 and 100 mg/kg, subcutaneously (s.c.)) inhibited small intestinal transit in wild-type mice but not in MOR-knockout mice. These results suggest that peripheral MOR participates in tramadol-induced constipation.

On the physics of multidrug efflux through a biomolecular complex.

Insertion and release of a solute into and from a vessel comprising biopolymers is a fundamental function in a biological system. A typical example is found in a multidrug efflux transporter. "Multidrug efflux" signifies that solutes such as drug molecules with diverse properties can be handled. In our view, the mechanism of the multidrug efflux is not chemically specific but rather has to be based on a physical factor. In earlier works, we showed that the spatial distribution of the solute-vessel potential of mean force (PMF) induced by the solvent plays imperative roles in the insertion∕release process. The PMF can be decomposed into the energetic and entropic components. The entropic component, which originates from the translational displacement of solvent molecules, is rather insensitive to the solute-solvent and vessel inner surface-solvent affinities. This feature is not shared with the energetic component. When the vessel inner surface is neither solvophobic nor solvophilic, the solvents within the vessel cavity and in the bulk offer almost the same environment to any solute with solvophobicity or solvophilicity, and the energetic component becomes much smaller than the entropic component (i.e., the latter predominates over the former). Our idea is that the multidrug efflux can be realized if the insertion/release process is accomplished by the entropic component exhibiting the insensitivity to the solute properties. However, we have recently argued that the entropic release of the solute is not feasible as long as the vessel geometry is fixed. Here we consider a model of TolC, a cylindrical vessel possessing an entrance at one end and an exit at the other end for the solute. The spatial distribution of the PMF is calculated by employing the three-dimensional integral equation theory with rigid-body models in which the constituents interact only through hard-body potentials. Since the behavior of these models is purely entropic in origin, our analysis is focused on the entropic component. We show that the entropically inserted solute can be released by a continuous variation of the vessel geometry which forms a time-dependent entropic force continuing to accelerate the solute motion to the exit. Solutes with a wide range of sizes are entropically released using the same vessel-geometry variation. The results obtained are fairly general and also applicable to the efflux pump protein AcrB and ATP-binding cassette transporter.

A Nationwide Hospital Claims Database Analysis of Real-World Patterns of Laxative Use for Opioid-Induced Constipation in Japanese Patients with Cancer.

INTRODUCTION: Opioid-induced constipation (OIC) is one of the most common side effects in patients with cancer treated with opioid analgesics. The actual use of laxatives for OIC in Japan remains unelucidated. This study aimed to investigate the real-world patterns of laxative use for patients with cancer who newly initiated opioid analgesic therapy. METHODS: We used a Japanese nationwide hospital claims database (January 2018-December 2019). Patients with cancer newly receiving opioid analgesic therapy were included and classified on the basis of opioid classes (weak or strong) and route of administration (oral or transdermal) at initiation. The patients were divided into two groups on the basis of whether they received early medication (starting laxatives within 3 days after initiating opioid analgesic therapy), and patterns of laxative use were analyzed. RESULTS: There were 26,939 eligible patients, with 50.7% of them initiated with strong opioids. The proportion of patients who received early medication was 25.0% for weak opioids and 57.3% for strong opioids. Osmotic laxatives were most frequently used as first-line therapy in the early medication group (oral weak opioids: 12.3%, oral strong opioids: 29.4%, transdermal strong opioids: 12.8%). Stimulant laxatives were frequently used as first-line therapy, to the same extent or more than osmotic laxatives in the non-early medication group (oral weak opioids: 13.7%, oral strong opioids: 7.7%, transdermal strong opioids: 15.1%). Peripherally acting µ-opioid receptor antagonists were the second most frequently used in the early medication group for those on oral strong opioids (9.4%). CONCLUSION: This study demonstrated for the first time that the patterns of laxative use for OIC in Japanese patients with cancer were different, depending on the opioid types at initiation and the timing of laxative medication.

A Survey of the Incidence of Constipation in Patients with Chronic Non-cancer Pain Using Opioid Analgesics in Japan.

INTRODUCTION: Although opioids have potent analgesic properties, their use is associated with side effects, including opioid-induced constipation (OIC). This study investigated the incidence of OIC based on the Rome IV diagnostic criteria in patients using opioid analgesics for chronic non-cancer pain and to explore and compare the risk factors for the development of OIC in opioid analgesic users. METHODS: We surveyed patients aged 20 years or more living in Japan via the internet; who had been using opioid or non-opioid analgesics (N = 500 each) for at least 3 months for relief from chronic non-cancer musculoskeletal pain (low back pain or osteoarthritis); and who provided electronic consent to participate in and complete the survey. The groups were matched for age and sex. RESULTS: Of the patients using opioid analgesics, 89% were taking weak opioids. The proportion of patients perceiving constipation was comparable between the opioid and non-opioid analgesic groups (34% vs 29%, respectively); however, a significantly higher proportion of patients in the opioid group, compared to the non-opioid group, reported self-assessed constipation (40% vs 18%, respectively) after using an analgesic and fulfilled two or more symptoms of the Rome IV diagnostic criteria for constipation (28% vs 19%, respectively). A higher proportion of patients were taking prescribed medicine for constipation in the opioid group compared with the non-opioid group (33% vs 18%, respectively). Low back pain, but not opioid strength and scheduled dosing, was identified as a risk factor for OIC among various covariates assessed in the logistic regression analysis in 81 patients with OIC and Rome IV diagnosis vs 419 patients without OIC in the opioid group. CONCLUSION: Use of opioid analgesics, including weak opioids, for treating chronic non-cancer musculoskeletal pain is associated with OIC. This finding highlights the need for appropriate treatment of constipation in patients with chronic non-cancer pain in Japan. TRIAL REGISTRATION: UMIN000043985.

Evaluation of the Effect of Patient Education and Strengthening Exercise Therapy Using a Mobile Messaging App on Work Productivity in Japanese Patients With Chronic Low Back Pain: Open-Label, Randomized, Parallel-Group Trial.

BACKGROUND: Artificial intelligence-assisted interactive health promotion systems are useful tools for the management of musculoskeletal conditions. OBJECTIVE: This study aimed to explore the effects of web-based video patient education and strengthening exercise therapy, using a mobile messaging app, on work productivity and pain in patients with chronic low back pain (CLBP) receiving pharmacological treatment. METHODS: Patients with CLBP were randomly allocated to either the exercise group, who received education and exercise therapy using a mobile messaging app, or the conventional group. For patient education, a web-based video program was used to provide evidence-based thinking regarding the importance of a cognitive behavioral approach for CLBP. The exercise therapy was developed in accordance with the recommendations for alignment, core muscles, and endogenous activation, including improvement of posture and mobility for proper alignment, stimulation and/or strengthening of deep muscles for spinal stability, and operation of intrinsic pain for the activation of endogenous substances by aerobic exercise. Both groups continued to receive the usual medical care with pharmacological treatment. The end points were changes in work productivity, pain intensity, quality of life, fear of movement, and depression. The observation period for this study was 12 weeks. An analysis adjusted for baseline values, age at the time of consent acquisition, sex, and willingness to strengthen the exercise therapy was performed. RESULTS: The exercise and conventional groups included 48 and 51 patients, with a mean age of 47.9 years (SD 10.2 years; n=27, 56.3% male patients) and 46.9 years (SD 12.3 years; n=28, 54.9% male patients) in the full analysis set, respectively. No significant impact of these interventions on work productivity was observed in the exercise group compared with the conventional group (primary end point: Quantity and Quality method; 0.062 vs 0.114; difference between groups -0.053, 95% CI -0.184 to 0.079; P=.43). However, the exercise group showed consistently better trends for the other end points than did the conventional group. Compared with the conventional group, the exercise group showed a significant improvement in the symptoms of low back pain (3.2 vs 3.8; difference between groups -0.5, 95% CI -1.1 to 0.0; P=.04), quality of life (EuroQoL 5 Dimensions 5 Level: 0.068 vs 0.006; difference between groups 0.061, 95% CI 0.008 to 0.114; P=.03), and fear of movement at week 12 (-2.3 vs 0.5; difference between groups -2.8, 95% CI -5.5 to -0.1; P=.04). CONCLUSIONS: This study suggests that patient education and strengthening exercise therapy using a mobile messaging app may be useful for treating CLBP. This study does not reveal the effect of therapeutic interventions on CLBP on work productivity. Thus, further research is required to assess work productivity with therapeutic interventions. TRIAL REGISTRATION: University Hospital Medical Information Network Clinical Trials Registry UMIN000041037; https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000046866.

Change in Antidepressant Use After Initiation of ADHD Medication in Japanese Adults with Comorbid Depression: A Real-World Database Analysis.

PURPOSE: To better understand the treatment of comorbid depression in adults with attention-deficit/hyperactivity disorder (ADHD) by investigating the prescription patterns of antidepressants, anxiolytics, and hypnotics after commencing ADHD medication. PATIENTS AND METHODS: In this retrospective observational study in Japan, the data of patients initiating ADHD medication while already receiving antidepressants (ADHD group) and of patients prescribed antidepressants but not diagnosed with ADHD (control group) were extracted from an electronic medical record database. Additionally, one-to-one matching for patients in both groups was performed using sex, age, baseline dosage of antidepressants, and any comorbid psychiatric disorders as covariates. The observation period included a 1-month baseline period and a 6-month follow-up period. The percentage of patients prescribed antidepressants and the mean prescribed dosages were compared between matched-cohort groups. Prescriptions for anxiolytics and hypnotics were also assessed. RESULTS: In the matched cohorts, consisting of 239 patients in the ADHD group and 239 patients from the unmatched control cohort of 10,485, the percentage of patients prescribed antidepressants decreased from baseline in both groups to 94.1% in the ADHD group and 89.5% in the control group during the first month of follow-up, and 77.0% and 78.7%, respectively, during the last month. There were no significant differences between groups in the percentages of patients prescribed antidepressants or in the mean prescribed dosages of antidepressants at any time point over the follow-up period. Prescribed dosages of anxiolytics and hypnotics tended to be lower in the ADHD group. CONCLUSION: The two groups were medicated similarly with respect to their depressive symptoms over 6 months. Our results suggest that in patients with ADHD and comorbid depression, which is more likely to be more severe than in depression without ADHD, depressive symptoms are managed following initiation of add-on ADHD medication, without requiring higher antidepressant dosages than in patients with depression only.

Efficacy and Safety of Medication for Attention-Deficit Hyperactivity Disorder in Children and Adolescents with Common Comorbidities: A Systematic Review.

INTRODUCTION: Comorbid psychiatric conditions in children and adolescents with attention-deficit hyperactivity disorder (ADHD) occur frequently, complicate management, and are associated with substantial burden on patients and caregivers. Very few systematic reviews have assessed the efficacy and safety of medications for ADHD in children and adolescents with comorbidities. Of those that were conducted, most focused on a particular comorbidity or medication. In this systematic literature review, we summarize the efficacy and safety of treatments for children and adolescents with ADHD and comorbid autism spectrum disorders, oppositional defiant disorder, Tourette's disorder and other tic disorders, generalized anxiety disorder, and major depressive disorder. METHODS: We searched MEDLINE, Embase, and ClinicalTrials.gov (to October 2019) for studies of patients (aged < 18 years) with an ADHD diagnosis and the specified comorbidities treated with amphetamines, methylphenidate and derivatives, atomoxetine (ATX), and guanfacine extended-release (GXR). For efficacy, placebo-controlled randomized controlled trials (RCTs) or meta-analyses of RCTs were eligible for inclusion; for safety, all study types were eligible. The primary efficacy outcome measure was ADHD Rating Scale IV (ADHD-RS-IV) total score. RESULTS: Of 2177 publications/trials retrieved, 69 were included in this systematic literature review (5 meta-analyses, 37 placebo-controlled RCTs, 16 cohort studies, 11 case reports). A systematic narrative synthesis is provided because insufficient data were retrieved to combine ADHD-RS-IV total scores or effect sizes. Effect sizes for ADHD-RS-IV total scores were available for ten RCTs and ranged from 0.46 to 1.0 for ATX and from 0.92 to 2.0 for GXR across comorbidities. The numbers and types of adverse events in children with comorbidities were consistent with those in children without comorbidities, but treatment should be individualized to ensure children can tolerate the lowest effective dose. CONCLUSION: Limited information is available from placebo-controlled RCTs on the efficacy (by ADHD-RS-IV) or safety of medication in children with ADHD and psychiatric comorbidities. Further studies are required to support evidence-based drug selection for these populations.

Molecular movie of nucleotide binding to a motor protein.

BACKGROUND: The SecA DEAD (Asp-Glu-Ala-Asp) motor protein uses binding and hydrolysis of adenosine triphosphate (ATP) to push secretory proteins across the plasma membrane of bacteria. The reaction coordinate of nucleotide exchange is unclear at the atomic level of detail. METHODS: We performed multiple atomistic computations of the DEAD motor domain of SecA with different occupancies of the nucleotide and magnesium ion sites, for a total of ~1.7 µs simulation time. To characterize dynamics at the active site we analyzed hydrogen-bond networks. RESULTS: ATP and ADP can bind spontaneously at the interface between the nucleotide binding domains, albeit at an intermediate binding site distinct from the native site. Binding of the nucleotide is facilitated by the presence of a magnesium ion close to the glutamic group of the conserved DEAD motif. In the absence of the magnesium ion, protein interactions of the ADP molecule are perturbed. CONCLUSIONS: A protein hydrogen-bond network whose dynamics couples to the occupancy of the magnesium ion site helps guide the nucleotide along the nucleotide exchange path. In SecA, release of magnesium might be required to destabilize the ADP binding site prior to release of the nucleotide. GENERAL SIGNIFICANCE: We identified dynamic hydrogen-bond networks that help control nucleotide exchange in SecA, and stabilize ADP at an intermediate site that could explain slow release. The reaction coordinate of the protein motor involves complex rearrangements of a hydrogen-bond network at the active site, with perturbation of the magnesium ion site likely occurring prior to the release of ADP.

Statistical thermodynamics for functionally rotating mechanism of the multidrug efflux transporter AcrB.

AcrB, a homotrimer, is the pivotal part of a multidrug efflux pump. A "functionally rotating" picture has been proposed for the drug transport by AcrB, but its mechanism remains unresolved. Here, we investigate the energetics of the whole functional rotation cycle using our theoretical methods. We find that the packing efficiency of AcrB is ununiform, and this ununiformity plays imperative roles primarily through the solvent-entropy effect. When a proton binds to or dissociates from a protomer, the packing properties of this protomer and its two interfaces are perturbed overall in the direction that the solvent translational entropy is lowered. The packing properties of the other two protomers are then reorganized with the recovery or maintenance of closely packed interfaces, so that the solvent-entropy loss can be compensated. The functional structural change by an isolated protomer would cause a seriously large free-energy increase. By forming a trimer, any free-energy increase caused by a protomer is always canceled out by the free-energy decrease brought by the other two protomers via the mechanism mentioned above. The functional structural rotation is thus accomplished using the free-energy decrease arising from the transfer of only a single proton per cycle. The similarities to F1-ATPase are also discussed.

Characterization of experimentally determined native-structure models of a protein using energetic and entropic components of free-energy function.

We show how to characterize the native-structure models of a protein using our free-energy function F which is based on hydration thermodynamics. Ubiquitin is adopted as an example protein. We consider models determined by the X-ray crystallography and two types of NMR model sets. A model set of type 1 comprises candidate models for a fixed native structure, and that of type 2 forms an ensemble of structures representing the structural variability of the native state. In general, the X-ray models give lower F than the NMR models. There is a trend that, as a model deviates more from the model with the lowest F among the X-ray models, its F becomes higher. Model sets of type 1 and those of type 2, respectively, exhibit two different characteristics with respect to the correlation between the deviation and F. It is argued that the total amount of constraints such as NOEs effectively taken into account in constructing the NMR models can be examined by analyzing the behavior of F. We investigate structural characteristics of the models in terms of the energetic and entropic components of F which are relevant to intramolecular hydrogen bonding and to backbone and side-chain packing, respectively.