An inexorable loss of terminally differentiated heart muscle cells is a crucial causal factor for heart failure. Here, we have provided several lines of evidence to demonstrate that mitofusin-2 (Mfn-2; also called hyperplasia suppressor gene), a member of the mitofusin family, is a major determinant of oxidative stress-mediated cardiomyocyte apoptosis. First, oxidative stress with H 2 O 2 led to concurrent increases in Mfn-2 expression and apoptosis in cultured neonatal rat cardiomyocytes. Second, overexpression of Mfn-2 to a level similar to that induced by H 2 O 2 was sufficient to trigger myocyte apoptosis, which is associated with profound inhibition of Akt activation without altering ERK1/2 signaling. Third, Mfn-2 silencing inhibited oxidative stress-induced apoptosis in H9C2 cells, a cardiac muscle cell line. Furthermore, Mfn-2-induced myocyte apoptosis was abrogated by inhibition of caspase-9 (but not caspase-8) and by overexpression of Bcl-x L or enhanced activation of phosphatidylinositol 3-kinase-Akt, suggesting that inhibition of Akt signaling and activation of the mitochondrial death pathway are essentially involved in Mfn-2-induced heart muscle cell apoptosis. These results indicate that increased cardiac Mfn-2 expression is both necessary and sufficient for oxidative stress-induced heart muscle cell apoptosis, suggesting that Mfn-2 deregulation may be a crucial pathogenic element and a potential therapeutic target for heart failure.An imbalance between cell survival and cell death signaling pathways triggers either proliferative or degenerative disorders, diseases in which apoptosis (or programmed cell death) can be either abnormally blocked or undesirably activated. In this regard, Ras plays a central role in the regulation of cell fate, including cell proliferation, differentiation, senescence, and survival or apoptosis. In particular, Ras-mediated activation of Akt has emerged as a focal point for signal transduction pathways promoting cell survival, whereas Ras-activated ERK1/2 4 and Akt signaling cascades drive cell cycle progression (1-3). Thus, dysfunction of Ras signaling pathways has been implicated in a multitude of degenerative and proliferative diseases.Originally, Ras was identified as a viral oncogene because of its causal relationship with various cancers (3). Over the past decade, increasing evidence has, however, placed Ras signaling at the center of pathways for diverse cardiovascular diseases such as congestive heart failure, hypertensive vascular proliferative growth, and endothelial dysfunction (4). We have recently identified a powerful endogenous Ras inhibitor, mitofusin-2 (Mfn-2), also named hyperplasia suppressor gene because of its anti-proliferative effects (5). Although previous studies have shown that human Mfn-2 and its homologs localize to the mitochondrial outer membrane and play an essential role in mitochondrial fusion, thus regulating mitochondrial morphology and function (6 -11), we recently demonstrated that Mfn-2 profoundly suppresses cell growth and proliferat...

Background Magnifying endoscopy with narrow band imaging (M-NBI) has been applied to examine early gastric cancer by observing microvascular architecture and microsurface structure of gastric mucosal lesions. However, the diagnostic efficacy of non-experts in differentiating early gastric cancer from non-cancerous lesions by M-NBI remained far from satisfactory. In this study, we developed a new system based on convolutional neural network (CNN) to analyze gastric mucosal lesions observed by M-NBI. Methods A total of 386 images of non-cancerous lesions and 1702 images of early gastric cancer were collected to train and establish a CNN model (Inception-v3). Then a total of 341 endoscopic images (171 non-cancerous lesions and 170 early gastric cancer) were selected to evaluate the diagnostic capabilities of CNN and endoscopists. Primary outcome measures included diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value. Results The sensitivity, specificity, and accuracy of CNN system in the diagnosis of early gastric cancer were 91.18%, 90.64%, and 90.91%, respectively. No significant difference was spotted in the specificity and accuracy of diagnosis between CNN and experts. However, the diagnostic sensitivity of CNN was significantly higher than that of the experts. Furthermore, the diagnostic sensitivity, specificity and accuracy of CNN were significantly higher than those of the non-experts. Conclusions Our CNN system showed high accuracy, sensitivity and specificity in the diagnosis of early gastric cancer. It is anticipated that more progress will be made in optimization of the CNN diagnostic system and further development of artificial intelligence in the medical field.

Background: Immune inhibitory receptors play an important role in chronic infections. However, little is known about their role in hepatitis B virus (HBV) infection. Here, we analyzed the relationship between programmed death-1 (PD-1) and lymphocyte activation gene-3 (LAG-3) expression on CD4 + T cells and HBV disease progression. Results: PD-1 and LAG-3 expression was significantly higher on CD4 + T cells from HBV patients than on those from the HCs. In addition, a significant positive correlation was found between the PD-1 and LAG-3 expression levels and the ALT(alanine aminotransferase) level. CD4 + T cell function was inhibited by high PD-1 and LAG-3 levels, and CD4 + T cells with high PD-1 and LAG-3 expression lost the ability to secrete IFN-γ, IL-2 and TNF-α. Furthermore, blockade of the PD-1 and LAG-3 pathways reversed the damage to CD4 + T cell proliferation and cytokine secretion. Conclusions: CD4 + T cell exhaustion during chronic HBV had high PD-1 and LAG-3 expression and the absence of helper T cell cytokines, including IFN-γ, IL-2 and TNF-α. After blocking PD-L1 and LAG-3, CD4 + T cell function in chronic hepatitis B patients was partially restored.

Excess cellular iron increases reactive oxygen species (ROS) production and causes cellular damage. Mitochondria are the major site of iron metabolism and ROS production; however, few studies have investigated the role of mitochondrial iron in the development of cardiac disorders, such as ischemic heart disease or cardiomyopathy (CM). We observe increased mitochondrial iron in mice after ischemia/reperfusion (I/R) and in human hearts with ischemic CM, and hypothesize that decreasing mitochondrial iron protects against I/R damage and the development of CM. Reducing mitochondrial iron genetically through cardiac-specific overexpression of a mitochondrial iron export protein or pharmacologically using a mitochondria-permeable iron chelator protects mice against I/R injury. Furthermore, decreasing mitochondrial iron protects the murine hearts in a model of spontaneous CM with mitochondrial iron accumulation. Reduced mitochondrial ROS that is independent of alterations in the electron transport chain's ROS producing capacity contributes to the protective effects. Overall, our findings suggest that mitochondrial iron contributes to cardiac ischemic damage, and may be a novel therapeutic target against ischemic heart disease.

Rationale: Rad (Ras associated with diabetes) GTPase, a monomeric small G protein, binds to Ca v ␤ subunit of the L-type Ca 2؉ channel (LCC) and thereby regulates LCC trafficking and activity. Emerging evidence suggests that Rad is an important player in cardiac arrhythmogenesis and hypertrophic remodeling. However, whether and how Rad involves in the regulation of excitation-contraction (EC) coupling is unknown. Objective: This study aimed to investigate possible role of Rad in cardiac EC coupling and ␤-adrenergic receptor (␤AR) inotropic mechanism. Methods and Results: Adenoviral overexpression of Rad by 3-fold in rat cardiomyocytes suppressed LCC current (I Ca ), [Ca 2؉ ] i transients, and contractility by 60%, 42%, and 38%, respectively, whereas the "gain" function of EC coupling was significantly increased, due perhaps to reduced "redundancy" of LCC in triggering sarcoplasmic reticulum release. Conversely, Ϸ70% Rad knockdown by RNA interference increased I Ca (50%), [Ca 2؉ ] i transients (52%) and contractility (58%) without altering EC coupling efficiency; and the dominant negative mutant RadS105N exerted a similar effect on I Ca . Rad upregulation caused depolarizing shift of LCC activation and hastened time-dependent LCC inactivation; Rad downregulation, however, failed to alter these attributes. Key Words: Rad Ⅲ GTPase Ⅲ Ca 2ϩ signaling Ⅲ excitation-contraction coupling Ⅲ ␤-adrenergic signaling C ardiac excitation-contraction (EC) coupling is mainly mediated by intermolecular signaling between two types of Ca 2ϩ channels, the voltage-gated L-type Ca 2ϩ channel (LCC), and the ryanodine receptor (RyR) Ca 2ϩ release channel that reside in the plasma membrane and the sarcoplasmic reticulum (SR), respectively. During EC coupling, LCC Ca 2ϩ influx activates a large number of "Ca 2ϩ sparks" 1 from clusters of RyRs, via the Ca 2ϩ -induced Ca 2ϩ release mechanism. 2 Summation of Ca 2ϩ sparks across the cell gives rise to an intracellular Ca 2ϩ transient that signals contractile myofilaments to generate force and movement. Return to the diastolic Ca 2ϩ level, to relax the muscle, is controlled by Ca 2ϩ cycling via the SR Ca 2ϩ -ATPase (SERCA) and, to a lesser extent, the sarcolemmal Na ϩ /Ca 2ϩ exchanger (NCX). Albeit controversial, recurrent evidence also suggests the involvement of trigger mechanism other than LCC. In particular, it has been suggested that reverse NCX allosterically activated by LCC current augments the trigger Ca 2ϩ at high membrane voltage. 3 Rad (Ras associated with diabetes), a monomeric small G protein that was initially identified by subtractive cloning as genes overexpressed in the skeletal muscle of a subset of patients with type 2 diabetes, is expressed most abundantly in the heart, 4 along with its cousin Rem, but not Gem/Kir 5 in the RGK family. At the molecular level, Rad comprises multiple functional domains including calmodulin binding and 14-3-3 protein-binding domains, as well as regulatory phosphorylation sites. 6,7 A common feature of Rad and other RGK proteins is to bin...