Recently, topics related to substance dependence and behavioral addiction have been reported through the media. Therapeutic treatment for substance dependence and behavioral addiction is one of the challenges in a clinical practice. This is because there is no therapeutic treatment for a complete cure, and reuses and repetitive hospitalization occur in patients. Therefore, it is an urgent need to develop new treatments for substance dependence and behavioral addiction. In the present review, we outline associations between dependence and G-protein-activated inwardly rectifying potassium (GIRK) channels which we focus on as therapeutic targets, and introduce ongoing clinical study using an inhibitor of GIRK channels. Previous studies including animals and patients have accumulated the results that GIRK channels have a key role for mediating signals from addictive substances. GIRK channels are expressed in various rodent brain regions including the reward system. The activation of G protein-coupled receptors (GPCRs) that activates GIRK channels through G-protein βγ subunits and activated GIRK channels contribute to control of neuronal excitability. Pretreatment with ifenprodil that is one of the GIRK channel blockers suppressed addictive substance-induced behaviors in animals. Ifenprodil is safe and broadly used as a cerebral circulation/metabolism ameliorator that is covered by medical insurance in Japan. The authors reported that ifenprodil treatment for 3 months decreased alcohol use scores in patients with alcohol dependence compared with patients who received the control medication. We currently conduct a clinical trial to investigate the outcomes of ifenprodil treatment for methamphetamine dependence. In the future, we will expand clinical studies using ifenprodil for patients with other substance dependence and behavioral addiction.

Stress potentiates craving for addictive drugs including cocaine. To elucidate neural mechanisms underlying this effect of stress, we developed an experimental paradigm combining cocaine-induced conditioned place preference (CPP) with a restraint stress. Acute restraint stress exposure immediately before posttest significantly increased cocaine CPP scores. It has been suggested that the extracellular noradrenaline (NA) level is increased by stress in the laterodorsal tegmental nucleus (LDT), which sends cholinergic projections to dopamine (DA) neurons in the ventral tegmental area (VTA), and medial prefrontal cortex (mPFC), which receives DA input from the VTA. Thus, we investigated the roles of NA in these brain regions. Intra-LDT injection of an α2 or a β adrenoceptor antagonist attenuated the stress-induced enhancement of cocaine CPP. In vitro whole-cell recordings revealed that α2 adrenoceptor stimulation reduced GABAergic inputs to LDT cholinergic neurons that were obtained from cocaine-, but not saline-, treated rats. On the other hand, α1, but not α2 or β, adrenoceptor stimulation excited mPFC pyramidal neurons. Intra-mPFC injection of an α1 adrenoceptor antagonist attenuated the stress-induced enhancement of cocaine CPP. Additionally, chemogenetic silencing of mPFC excitatory neurons also reduced the stress-induced enhancement of cocaine CPP. These findings suggest that stress-induced increases in neuronal activity of the LDT and mPFC may contribute to the enhancement of cocaine craving.

Shati/Nat8l and TMEM168 were identified from nucleus accumbens (NAcc), which received continuous methamphetamine treatments. Shati/Nat8l is a synthetic enzyme that produces N-acetylaspartate (NAA) from L-aspartate and acetyl-coenzyme NAA is converted into N-acetylaspartylglutamate (NAAG) by NAAG synthetase (NAAGS). NAAG works as a highly selective endogenous agonist for the metabotropic glutamate type 3 receptor (mGluR3). We attempted to microinjection of adeno associated virus (AAV) including Shati/Nat8l into mice NAcc. These NAcc-Shati/Nat8l mice showed attenuation of the pharmacological effects of methamphetamine. NAcc-Shati or TMEM168 mice were also produced by AAV strategy and these mice also attenuated the methamphetamine-induced hyper locomotion and place preference test. TMEM168 interacts with osteopontin in NAcc of mice and cultured cells. Further, osteopontin it self has suppressive effects of methamphetamine. TMEM168 enhances anxiety in the elevated-plus maze and light-dark box test. The anxiety is recovered by the treatment of antianxiety drug diazepam. There our serial studies demonstrate that investigation of drug dependence-related molecule could lead to new pathway for new target for psychiatric disease.

Alcohol dependence is one of the psychiatric disorders affecting over 1 million people in Japan. Mesolimbic dopamine neuron projecting from ventral tegmental area to nucleus accumbens (Reward system) plays important roles in alcohol dependence including other dependence. Accumulating evidence indicates that the endogenous opioid system regulate this reward system. That is, alcohol stimulates the release of endogenous opioid peptides such as β-endorphin and dynorphin in the brain. β-endorphin activates μ-opioid receptor leading to euphoric mood and positive reinforcement, while dynorphin activates κ-opioid receptor leading to dysphoric mood and negative reinforcement. These euphoric/dysphoric mood and reinforcement effects via endogenous opioid systems are suggested to be implicated in repeated alcohol intake in patients with alcohol dependence. Nalmefene acts as an antagonist at μ- and δ-opioid receptor and a partial agonist at κ-opioid receptor. Preclinical studies have shown that nalmefene reduced the alcohol intake in alcohol preference rats. In clinical trials, as-needed use of nalmefene with psychosocial support reduced the number of heavy-drinking days and total alcohol consumption. These results suggest that nalmefene modulates the alcohol-induced euphoric/dysphoric mood via opioid system and thereby contribute to reduction in alcohol consumption in patients with alcohol dependence. Here, we summarize the implications of opioid system in alcohol dependence and pharmacological profiles of nalmefene in preclinical and clinical studies.

Many strategies have been tried to produce monoclonal antibodies (mAbs); however, there have been several problems about focusing on molecular targets and screening methods. For instance, the high tumor/normal ratio of antigen expression using DNA microarray has been thought to be important when we determine the molecular targets for antibody-drug. Although many antigens are expressed highly in tumors, those antigens have been removed from the candidates of antibody-drug targets because they were also expressed in normal tissues. We recently established a novel technology to produce a cancer-specific monoclonal antibody (CasMab). The post-translational difference such as glycans can be utilized to produce the CasMab, although the protein possesses the same amino acid sequence in both cancer and normal cells. We have already produced CasMabs against several glycoproteins such as podoplanin, which is expressed in both cancer and normal cells. Those CasMabs possess antibody-dependent cellular cytotoxicity (ADCC) or complement-dependent cytotoxicity (CDC) in vitro and anti-tumor effect in xenograft models in vivo. In conclusion, the CasMab technology is the platform to develop cancer-specific mAbs, which could attack only cancer cells without side effects.

Histidine-rich glycoprotein (HRG) is a 75 kDa plasma glycoprotein synthesized in liver mainly, which exists at approximately 60–100 μg/ml in human plasma. HRG is known to bind to several ligands and cells, leading to exert coagulation, fibrinolysis, immune and inflammation regulatory activity in septic condition. Thus, decreased plasma HRG level induces the dysregulations of coagulation, fibrinolysis and immune system, resulting in disseminated intravascular coagulation and multiple organ failure. This article focuses on the physiological activity of HRG and the potential of HRG as the biomarker and therapeutic drug for sepsis.

Positron emission tomography (PET) is a molecular imaging technique that visualizes pathophysiology in the body using radiotracers at tracer doses (~μg). PET would provide the information regarding not only pharmacokinetics of radiolabeled compounds, but also target engagements, patient selection, and biomarkers. Previously small molecules are widely used as radiotracers, but recently biopharmaceuticals are launched, providing a novel type radiotracer. In general, antibodies are radiolabeled by long physiological half-lives radionuclides such as Cu-64 and Zr-89 because of their slow pharmacokinetics. However, shorter half-lives radiolabeled tracers (C-11 and F-18) might be suitable on the point view of radiation. Now small protein ligands such as affibodies (~7 kDa) are developed as a radiotracer. We are trying to develop a novel approach to label proteins for PET imaging, which are based on radiolabeled amino acids and cell-free protein synthesis system. In this review, we introduced the topics of protein-based PET tracers.

Cardiovascular disorders in cancer patients with cachexia have recently become a great concern. However, the relationship between cancer cachexia and cardiac dysfunction remains unclear, due to lack of suitable models. We established a novel murine model of cancer cachexia by implantation of 85As2 cells, a cell line derived from human gastric cancer cells, presenting anorexia, weight loss and low fat-free mass similar to those observed in patients. Moreover, cardiac dysfunction is expected in this model, which has not been yet examined. In the present study, we firstly evaluated cardiac functions with the model. Secondly, we investigated effects of voluntary wheel running (VWR) on cachexia-induced cardiac dysfunction using this model, as the exercise is considered to be one of therapies for chronic heart failure. 85As2 cells were transplanted subcutaneously into mice, which observed a symptomatic cachexia; decrease in body, skeletal muscle weight, and food intake. In addition, this cachexia mouse developed severe cardiac atrophy and left ventricular ejection fraction (LVEF) also markedly reduced with cachexia progression. Moreover, VWR suppressed the decrease in food intake and skeletal muscle weight loss in this model, and improved LVEF with suppression of heart weight loss. These results imply that our 85As2-cachexia mice models show cardiac dysfunction and VWR may improve not only cachexia symptoms but also cardiac dysfunction. As exercise therapy is generally introduced for the purpose of improving heart failure symptoms, this study suggests a possible therapeutic effect of exercise on cardiac dysfunction induced by cancer cachexia.

Cardiac safety assessments play a key role in drug development. New non-clinical cardiac safety risk assessments, such as the use of iPSC-derived cardiomyocytes, have been validated by several consortiums both in Japan and abroad. The emerging multidisciplinary field of cardio-oncology has been recognized more important. The success of new cancer therapies has improved life expectancy of cancer patients, hence more attention has been paid to cardiotoxicities associated with existing and new anti-cancer therapies, such as cardiomyocyte injury and heart failure, vascular injury and hypertension or thrombosis, which accelerated coronary artery disease. In addition to the well-studied proarrhythmia risk, some cardiotoxicities, such as contractility impairment, are expected to be evaluated by iPSC-derived cardiomyocytes. Here we developed a novel imaging-based in vitro contractility assay using iPSC-derived cardiomyocytes. In the review, we would like to discuss the current status and future perspectives in the assessment of cardiac contractile function by anti-cancer agents.

Genomic DNA, which contains all of the genetic information, is damaged by a variety of endogenous and environmental factors such as genotoxic chemicals, ionizing radiation and UV light. Consequently, the DNA repair process is constantly active as it responds to damage in the DNA structure. Not only cardiotoxicity of anticancer drug treatment but also ischemic heart disease and heart failure associated with overloaded pressure interfere with DNA damage response and DNA repair regulation in cardiomyocytes. DNA methylation, catalyzed by the DNMTs, plays an important role in maintaining genome stability, but the molecular mechanism is not clear. In this study, we examine and outline the links between DNA methylation and the DNA damage repair systems and discuss the possible mechanisms of how they are orchestrated, with a focus on cardiotoxicity of anticancer drugs.

Advances in cancer treatment have led to dramatic increase in cancer survivors. In addition to cardiotoxicity resulting from anthracyclines and radiation therapy, the emergence of novel cancer treatment-related cardiovascular disease (CTRCD) with molecularly targeted therapies and immune checkpoint inhibitors has been recognized as an unmet medical need. Cardio-oncology is a new interdisciplinary research opportunity at the intersection of cardiovascular disease and cancer. Research priorities need to be identified for diagnosis, treatment, and prevention of previously unknown CTRCD(s), including (a) cardiac dysfunction and heart failure, (b) coronary artery disease, (c) valvular disease, (d) arrhythmias and QT-prolongation, (e) arterial hypertension, (f) thromboembolic disease, and (g) other cardiovascular disorders. In particular, understanding the fundamental mechanisms underlying CTRCD is essential for developing new methods. Applying more appropriate disease models and more effective methods for toxicity screening will help to better understand CTRCD. Although animal models have been used to predict potential problems, more advanced predictive models are also needed. Biobanks and other specimens with patient registries are expected to facilitate the validation of new biomarkers, genomic analysis, and imaging methods.

Parkinson’s disease is a neurodegenerative disorder that manifests as motor deficits, tremors, rigidity, and postural instability. The most prominent pathological feature of this disease is reduced striatal dopamine concentration due to the loss of nigrodopaminergic neurons. Symptomatic dopamine replacement therapy is the standard management approach for Parkinson’s disease. Treatment with monoamine oxidase B (MAO-B) inhibitors also improves Parkinson’s disease symptoms by inhibiting the striatal dopamine metabolism and increasing the intracerebral dopamine concentration. Rasagiline is a potent and specific MAO-B inhibitor and is currently approved as an antiparkinsonian drug in more than 50 countries, including the United States and European countries. Clinical trials conducted in Japan to evaluate the efficacy of rasagiline monotherapy in patients with early-stage Parkinson’s disease using the Movement Disorder Society-Unified Parkinson’s Disease Rating Scale Part II (patient motor experience of daily living) and Part III (clinician motor examination) have demonstrated the antiparkinsonian action of rasagiline. Furthermore, in patients with advanced Parkinson’s disease receiving levodopa, concomitant rasagiline administration reduced the duration of “wearing–off”. Based on these favorable results, rasagiline mesilate (Azilect^® tablets) was approved for manufacture and sales in Japan in March 2018. Here, we provide a comprehensive overview of the pharmacological properties and clinical effects of rasagiline based on the results of domestic trials, with the aim of increasing the understanding of rasagiline use in Japan.