Haruaki Nakaya

Bio: Haruaki Nakaya is an academic researcher from Chiba University. The author has contributed to research in topics: Antiarrhythmic agent & Guinea pig. The author has an hindex of 32, co-authored 133 publications receiving 7410 citations. Previous affiliations of Haruaki Nakaya include Tokyo Medical and Dental University & Cardiovascular Institute of the South.

The role of autophagy during the early neonatal starvation period

Abstract: At birth the trans-placental nutrient supply is suddenly interrupted, and neonates face severe starvation until supply can be restored through milk nutrients. Here, we show that neonates adapt to this adverse circumstance by inducing autophagy. Autophagy is the primary means for the degradation of cytoplasmic constituents within lysosomes. The level of autophagy in mice remains low during embryogenesis; however, autophagy is immediately upregulated in various tissues after birth and is maintained at high levels for 3-12 h before returning to basal levels within 1-2 days. Mice deficient for Atg5, which is essential for autophagosome formation, appear almost normal at birth but die within 1 day of delivery. The survival time of starved Atg5-deficient neonates (approximately 12 h) is much shorter than that of wild-type mice (approximately 21 h) but can be prolonged by forced milk feeding. Atg5-deficient neonates exhibit reduced amino acid concentrations in plasma and tissues, and display signs of energy depletion. These results suggest that the production of amino acids by autophagic degradation of 'self' proteins, which allows for the maintenance of energy homeostasis, is important for survival during neonatal starvation.

G-CSF prevents cardiac remodeling after myocardial infarction by activating the Jak-Stat pathway in cardiomyocytes

Abstract: Granulocyte colony-stimulating factor (G-CSF) was reported to induce myocardial regeneration by promoting mobilization of bone marrow stem cells to the injured heart after myocardial infarction, but the precise mechanisms of the beneficial effects of G-CSF are not fully understood. Here we show that G-CSF acts directly on cardiomyocytes and promotes their survival after myocardial infarction. G-CSF receptor was expressed on cardiomyocytes and G-CSF activated the Jak/Stat pathway in cardiomyocytes. The G-CSF treatment did not affect initial infarct size at 3 d but improved cardiac function as early as 1 week after myocardial infarction. Moreover, the beneficial effects of G-CSF on cardiac function were reduced by delayed start of the treatment. G-CSF induced antiapoptotic proteins and inhibited apoptotic death of cardiomyocytes in the infarcted hearts. G-CSF also reduced apoptosis of endothelial cells and increased vascularization in the infarcted hearts, further protecting against ischemic injury. All these effects of G-CSF on infarcted hearts were abolished by overexpression of a dominant-negative mutant Stat3 protein in cardiomyocytes. These results suggest that G-CSF promotes survival of cardiac myocytes and prevents left ventricular remodeling after myocardial infarction through the functional communication between cardiomyocytes and noncardiomyocytes.

Role of sarcolemmal KATP channels in cardioprotection against ischemia/reperfusion injury in mice

Abstract: Recently it has been postulated that mitochondrial ATP-sensitive K(+) (mitoK(ATP)) channels rather than sarcolemmal K(ATP) (sarcK(ATP)) channels are important as end effectors and/or triggers of ischemic preconditioning (IPC). To define the pathophysiological significance of sarcK(ATP) channels, we conducted functional experiments using Kir6.2-deficient (KO) mice. Metabolic inhibition with glucose-free, dinitrophenol-containing solution activated sarcK(ATP) current and shortened the action potential duration in ventricular cells isolated from wild-type (WT) but not KO mice. MitoK(ATP) channel function was preserved in KO ventricular cells. In anesthetized mice, IPC reduced the infarct size in WT but not KO mice. Following global ischemia/reperfusion, the increase of left ventricular end-diastolic pressure during ischemia was more marked, and the recovery of contractile function was worse, in KO hearts than in WT hearts. Treatment with HMR1098, a sarcK(ATP) channel blocker, but not 5-hydroxydecanoate, a mitoK(ATP) channel blocker, produced a deterioration of contractile function in WT hearts comparable to that of KO hearts. These findings suggest that sarcKATP channels figures prominently in modulating ischemia/reperfusion injury in the mouse. The rapid heart rate of the mouse (>600 beats per minute) may magnify the relative importance of sarcK(ATP) channels during ischemia, prompting caution in the extrapolation of the conclusions to larger mammals.

Nontranscriptional Regulation of Cardiac Repolarization Currents by Testosterone

Abstract: Background— Women have longer QTc intervals than men and are at greater risk for arrhythmias associated with long QTc intervals, such as drug-induced torsade de pointes. Recent clinical and experimental data suggest an important role of testosterone in sex-related differences in ventricular repolarization. However, studies on effects of testosterone on ionic currents in cardiac myocytes are limited. Methods and Results— We examined effects of testosterone on action potential duration (APD) and membrane currents in isolated guinea pig ventricular myocytes using patch-clamp techniques. Testosterone rapidly shortened APD, with an EC50 of 2.1 to 8.7 nmol/L, which is within the limits of physiological testosterone levels in men. APD shortening by testosterone was mainly due to enhancement of slowly activating delayed rectifier K+ currents (IKs) and suppression of L-type Ca2+ currents (ICa,L), because testosterone failed to shorten APD in the presence of an IKs inhibitor, chromanol 293B, and an ICa,L inhibitor,...

Autophagy fights disease through cellular self-digestion

Abstract: Autophagy, or cellular self-digestion, is a cellular pathway involved in protein and organelle degradation, with an astonishing number of connections to human disease and physiology. For example, autophagic dysfunction is associated with cancer, neurodegeneration, microbial infection and ageing. Paradoxically, although autophagy is primarily a protective process for the cell, it can also play a role in cell death. Understanding autophagy may ultimately allow scientists and clinicians to harness this process for the purpose of improving human health.

Guidelines for the management of atrial fibrillation The Task Force for the Management of Atrial Fibrillation of the European Society of Cardiology (ESC)

Abstract: Guidelines summarize and evaluate all currently available evidence on a particular issue with the aim of assisting physicians in selecting the best management strategy for an individual patient suffering from a given condition, taking into account the impact on outcome, as well as the risk–benefit ratio of particular diagnostic or therapeutic means. Guidelines are no substitutes for textbooks. The legal implications of medical guidelines have been discussed previously. A large number of Guidelines have been issued in recent years by the European Society of Cardiology (ESC) as well as by other societies and organizations. Because of the impact on clinical practice, quality criteria for development of guidelines have been established in order to make all decisions transparent to the user. The recommendations for formulating and issuing ESC Guidelines can be found on the ESC Web Site (http://www.escardio.org/guidelines-surveys/esc-guidelines/about/Pages/rules-writing.aspx). In brief, experts in the field are selected and undertake a comprehensive review of the published evidence for management and/or prevention of a given condition. A critical evaluation of diagnostic and therapeutic procedures is performed, including assessment of the risk–benefit ratio. Estimates of expected health outcomes for larger societies are included, where data exist. The level of evidence and the strength of recommendation of particular treatment options are weighed and graded according to pre-defined scales, as outlined in Tables 1 and 2 . View this table: Table 1 Classes of recommendations View this table: Table 2 Levels of evidence The experts of the writing panels have provided disclosure statements of all relationships they may have that might be perceived as real or potential sources of conflicts of interest. These disclosure forms are kept on file at the European Heart House, headquarters of the ESC. Any changes in conflict of interest that arise during the writing period must be notified to the ESC. The Task Force report received its entire financial support from …

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

Abstract: In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure flux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation, it is imperative to target by gene knockout or RNA interference more than one autophagy-related protein. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways implying that not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular assays, we hope to encourage technical innovation in the field.