Naringin activates semaphorin 3A to ameliorate TGF-ß-induced endothelial-to-mesenchymal transition related to atrial fibrillation.

The loss of semaphorin 3A (Sema3A), which is related to endothelial-to-mesenchymal transition (EndMT) in atrial fibrosis, is implicated in the pathogenesis of atrial fibrillation (AF). To explore the mechanisms by which EndMT affects atrial fibrosis and assess the potential of a Sema3A activator (naringin) to prevent atrial fibrosis by targeting transforming growth factor-beta (TGF-ß)-induced EndMT, we used human atria, isolated human atrial endocardial endothelial cells (AEECs), and used transgenic mice expressing TGF-ß specifically in cardiac tissues (TGF-ß transgenic mice). We evaluated an EndMT marker (Twist), a proliferation marker (proliferating cell nuclear antigen; PCNA), and an endothelial cell (EC) marker (CD31) through triple immunohistochemistry and confirmed that both EndMT and EC proliferation contribute to atrial endocardial fibrosis during AF in TGF-ß transgenic mice and AF patient tissue sections. Additionally, we investigated the impact of naringin on EndMT and EC proliferation in AEECs and atrial fibroblasts. Naringin exhibited an antiproliferative effect, to which AEECs were more responsive. Subsequently, we downregulated Sema3A in AEECs using small interfering RNA to clarify a correlation between the reduction in Sema3A and the elevation of EndMT markers. Naringin treatment induced the expression of Sema3A and a concurrent decrease in EndMT markers. Furthermore, naringin administration ameliorated AF and endocardial fibrosis in TGF-ß transgenic mice by stimulating Sema3A expression, inhibiting EndMT markers, reducing atrial fibrosis, and lowering AF vulnerability. This suggests therapeutic potential for naringin in AF treatment.

Aldehyde Dehydrogenase 2 (ALDH2) Deficiency, Obesity, and Atrial Fibrillation Susceptibility: Unraveling the Connection.

Atrial fibrillation (AF), characterized by structural remodeling involving atrial myocardial degradation and fibrosis, is linked with obesity and transforming growth factor beta 1 (TGF-ß1). Aldehyde dehydrogenase 2 (ALDH2) deficiency, highly prevalent in East Asian people, is paradoxically associated with a lower AF risk. This study investigated the impact of ALDH2 deficiency on diet-induced obesity and AF vulnerability in mice, exploring potential compensatory upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme-oxygenase 1 (HO-1). Wild-type (WT) and ALDH2*2 knock-in (KI) mice were administered a high-fat diet (HFD) for 16 weeks. Despite heightened levels of reactive oxygen species (ROS) post HFD, the ALDH2*2 KI mice did not exhibit a greater propensity for AF compared to the WT controls. The ALDH2*2 KI mice showed equivalent myofibril degradation in cardiomyocytes compared to WT after chronic HFD consumption, indicating suppressed ALDH2 production in the WT mice. Atrial fibrosis did not proportionally increase with TGF-ß1 expression in ALDH2*2 KI mice, suggesting compensatory upregulation of the Nrf2 and HO-1 pathway, attenuating fibrosis. In summary, ALDH2 deficiency did not heighten AF susceptibility in obesity, highlighting Nrf2/HO-1 pathway activation as an adaptive mechanism. Despite limitations, these findings reveal a complex molecular interplay, providing insights into the paradoxical AF-ALDH2 relationship in the setting of obesity.

CD44 regulates Epac1-mediated ß-adrenergic-receptor-induced Ca2+-handling abnormalities: implication in cardiac arrhythmias.

BACKGROUND: Sustained, chronic activation of ß-adrenergic receptor (ß-AR) signaling leads to cardiac arrhythmias, with exchange proteins directly activated by cAMP (Epac1 and Epac2) as key mediators. This study aimed to evaluate whether CD44, a transmembrane receptor mediating various cellular responses, participates in Epac-dependent arrhythmias. METHODS: The heart tissue from CD44 knockout (CD44-/-) mice, cultured HL-1 myocytes and the tissue of human ventricle were used for western blot, co-immunoprecipitaiton and confocal studies. Line-scanning confocal imaging was used for the study of cellular Ca2+ sparks on myocytes. Optical mapping and intra-cardiac pacing were applied for arrhythmia studies on mice's hearts. RESULTS: In mice, isoproterenol, a ß-AR agonist, upregulated CD44 and Epac1 and increased the association between CD44 and Epac1. Isoproterenol upregulated the expression of phospho-CaMKII (p-CaMKII), phospho-ryanodine receptor (p-RyR), and phospho-phospholamban (p-PLN) in mice and cultured myocytes; these effects were attenuated in CD44-/- mice compared with wild-type controls. In vitro, isoproterenol, 8-CPT-cAMP (an Epac agonist), and osteopontin (a ligand of CD44) significantly upregulated the expression of p-CaMKII, p-RyR, and p-PLN; this effect was attenuated by CD44 small interfering RNA (siRNA). In myocytes, resting Ca2+ sparks were induced by isoproterenol and overexpressed CD44, which were prevented by inhibiting CD44. Ex vivo optical mapping and in vivo intra-cardiac pacing studies showed isoproterenol-induced triggered events and arrhythmias in ventricles were prevented in CD44-/- mice. The inducibility of ventricular arrhythmias (VAs) was attenuated in CD44-/- HF mice compared with wild-type HF controls. In patients, CD44 were upregulated, and the association between CD44 and Epac1 were increased in ventricles with reduced contractility. CONCLUSION: CD44 regulates ß-AR- and Epac1-mediated Ca2+-handling abnormalities and VAs. Inhibition of CD44 is effective in reducing VAs in HF, which is potentially a novel therapeutic target for preventing the arrhythmias and sudden cardiac death in patients with diseased hearts.

Ubiquitin Pathway Is Associated with Worsening Left Ventricle Function after Mitral Valve Repair: A Global Gene Expression Study.

The molecular mechanism for worsening left ventricular (LV) function after mitral valve (MV) repair for chronic mitral regurgitation remains unknown. We wished to assess the LV transcriptome and identify determinants associated with worsening LV function post-MV repair. A total of 13 patients who underwent MV repair for chronic primary mitral regurgitation were divided into two groups, preserved LV function (N = 8) and worsening LV function (N = 5), for the study. Specimens of LV from the patients taken during surgery were used for the gene microarray study. Cardiomyocyte cell line HL-1 cells were transfected with gene-containing plasmids and further evaluated for mRNA and protein expression, apoptosis, and contractile protein degradation. Of 67,258 expressed sequence tags, microarrays identified 718 genes to be differentially expressed between preserved-LVF and worsening-LVF, including genes related to the protein ubiquitination pathway, bone morphogenetic protein (BMP) receptors, and regulation of eIF4 and p70S6K signaling. In addition, worsening-LVF was associated with altered expressions of genes pathologically relevant to heart failure, such asdownregulated apelin receptors and upregulated peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1A). HL-1 cardiomyocyte cells transfected with ubiquitination-related genes demonstrated activation of the protein ubiquitination pathwaywith an increase in the ubiquitin activating enzyme E1 (UAE-E1). It also led to increased apoptosis, downregulated and ubiquitinated X-linked inhibitor of apoptosis protein (XIAP), and reduced cell viability. Overexpression of ubiquitination-related genes also resulted in degradation and increased ubiquitination of α-smooth muscle actin (SMA). In conclusion, worsening-LVF presented differential gene expression profiles from preserved-LVF after MV repair. Upregulation of protein ubiquitination-related genes associated with worsening-LVF after MV repair may exert adverse effects on LV through increased apoptosis and contractile protein degradation.

Aldehyde Dehydrogenase 2 Ameliorates Chronic Alcohol Consumption-Induced Atrial Fibrillation through Detoxification of 4-HNE.

Aldehyde dehydrogenase 2 (ALDH2) is an enzyme that detoxifies reactive oxygen species (ROS)-generated aldehyde adducts such as 4-hydroxy-trans-2-nonenal (4-HNE). Previous meta-analyses have shown an increase in the risk of atrial fibrillation (AF) in patients with chronic alcohol consumption. ALDH2*2, a common dysfunctional polymorphism in the ALDH2 gene, has been linked to an increased risk of cancer and heart disease. We tested the effect of ALDH2 deficiency on alcohol-induced AF in a murine model of chronic-binge ethanol feeding, with ALDH2*2 knock-in (KI) mice generated by a CRISPR/CAS9 system. In addition, right atrial appendages were obtained from eight patients with AF undergoing open heart surgery. The results showed that burst atrial pacing induced a greater susceptibility to AF in ALDH2*2 KI mice exposed to chronic ethanol intoxication than in wild-type mice, resulting from a higher degree of 4-HNE accumulation and collagen deposition in their atria. Alda-1 attenuated transforming growth factor beta 1 (TGF-ß1) expression and collagen deposition in the atria and reduced AF inducibility. Patients with AF and the ALDH2*2 allele exhibited greater oxidative stress and substrate remodeling in their atria than non-carriers. In conclusion, ALDH2 deficiency may increase the risk of chronic alcohol and tachypacing-induced AF through the accumulation of 4-HNE and increased ROS production.

Tachycardia-induced CD44/NOX4 signaling is involved in the development of atrial remodeling.

Atrial fibrillation (AF) is associated with oxidative stress and Ca2+-handling abnormalities in atrial myocytes. Our prior study has demonstrated the involvement of CD44, a membrane receptor for hyaluronan (HA), in the pathogenesis of AF. This study further evaluated whether CD44 and its related signaling mediate atrial tachycardia-induced oxidative stress and Ca2+-handling abnormalities. Tachypacing in atrium-derived myocytes (HL-1 cell line) induced the activation of CD44-related signaling, including HA and HA synthase (HAS) expression. Blocking HAS/HA/CD44 signaling attenuated tachypacing-induced oxidative stress (NADPH oxidase [NOX] 2/4 expression) and Ca2+-handling abnormalities (oxidized Ca2+/calmodulin-dependent protein kinase II [ox-CaMKII] and phospho-ryanodine receptor type 2 [p-RyR2] expression) in HL-1 myocytes. Furthermore, a direct association between CD44 and NOX4 was documented in tachy-paced HL-1 myocytes and atrial tissues from AF patients. In vitro, Ca2+ spark frequencies in atrial myocytes isolated from CD44-/- mice were lower than those from wild-type mice. Furthermore, administration of an anti-CD44 blocking antibody in atrial myocytes isolated from wild-type mice diminished the frequency of Ca2+ spark. Ex vivo tachypacing models of CD44-/- mice exhibited a lower degree of oxidative stress and expression of ox-CaMKII/p-RyR2 in their atria than those of wild-type mice. In vivo, burst atrial pacing stimulated a less inducibility of AF in CD44-/-mice than in wild-type mice. In conclusion, atrial tachypacing-induced Ca2+-handling abnormalities are mediated via CD44/NOX4 signaling, which provides a possible explanation for the development of AF.

Cathepsin S promotes the development of pulmonary arterial hypertension.

Cysteine cathepsin proteases play critical roles in cardiovascular disease progression and are implicated in extracellular matrix (ECM) degradation. Patients with pulmonary arterial hypertension (PAH) exhibit increased elastase production by pulmonary arterial smooth muscle cells (PASMCs), which is related to the degradation of elastic fibers and pulmonary vascular remodeling. However, the mechanism by which cathepsins regulate the ECM and PASMC proliferation in PAH remains unclear. We hypothesized that cathepsin proteases in PASMCs promote the development of PAH. Here, we show overexpression of cathepsin S (Cat S) and degradation of elastic laminae in the lungs of patients with idiopathic PAH and in the PASMCs of monocrotaline-induced PAH model (MCT-PAH) rats. In addition, pulmonary hypertension can be treated in MCT-PAH rats by administering a selective Cat S inhibitor, Millipore-219393, which stimulates peroxisome proliferator-activated receptor-γ (PPARγ) to inhibit the expression of Cat S, thus suppressing the proliferation and migration of MCT-PAH PASMCs. We then reduced Cat S or PPARγ expression by using small interfering RNA in human PASMCs to demonstrate a mechanistic link between Cat S signaling and PPARγ protein, and the results suggest that PPARγ is upstream of Cat S signaling. In conclusion, the activity of Cat S in pulmonary vascular remodeling and degradation of elastin fibers through the disruption of PPARγ is pathophysiologically significant in PAH.

Inhibition of Advanced Glycation End Products Formation Attenuates Cardiac Electrical and Mechanical Remodeling and Vulnerability to Tachyarrhythmias in Diabetic Rats.

Diabetic patients with cardiomyopathy show a higher incidence of arrhythmias and sudden death. Chronic hyperglycemia induces the formation of advanced glycation end products (AGEs), which contribute to the pathogenesis of diabetic cardiomyopathy. This study investigated whether inhibition of AGEs formation by aminoguanidine (AG) could prevent cardiac electromechanical and arrhythmogenic remodeling in diabetes mellitus. Streptozotocin-induced diabetic rats received AG (100 mg/kg daily, i.p.) or vehicle (normal saline, i.p.) for 5 weeks. The rats underwent hemodynamic recording to evaluate cardiac function, and heart preparations were used to determine the electrical, mechanical, and biochemical functions. In vitro high glucose-induced AGEs formation, reactive oxygen species (ROS) generation, and action potential changes were examined in HL-1 atrial cells. AG treatment improved the diabetes-induced depression in left ventricular pressure and the relaxation rate, and normalized the prolongation of QTc intervals in anesthetized rats. AG reduced the vulnerabilities to atrial and ventricular tachyarrhythmias in perfused diabetic hearts. AG normalized the prolonged action potential duration in diabetic atrial and ventricular muscles, which was correlated with the restoration of both transient outward (I to) and steady-state outward (I SS) K+ current densities in cardiomyocytes. The abnormal kinetics of Ca2+ transients and contraction were reversed in cardiomyocytes from AG-treated diabetic rats, along with parallel preservation of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA2a) expression. Furthermore, ex vivo and in vitro studies showed AG attenuated AGEs and ROS formation. Thus, long-term administration of AG ameliorated cardiac electromechanical remodeling and arrhythmogenicity in diabetic rats and may present an effective strategy for the prevention of diabetes-associated arrhythmias.

Atrial fibrillation and its arrhythmogenesis associated with insulin resistance.

BACKGROUND: Insulin resistance (IR) is considered as a risk factor for atrial fibrillation (AF) even before diabetes develops. The pathophysiology and underlying mechanism are largely unclear. METHODS: We investigated the corresponding mechanism in two IR models of rats fed 15-week high-fat (HFa) and high-fructose/cholesterol (HFr) diets. AF was evaluated and induced by burst atrial pacing. Isolated atrial myocytes were used for whole-cell patch clamp and calcium assessment. Ex vivo whole heart was used for optical mapping. Western blot and immunofluorescence were used for quantitative protein evaluation. RESULTS: Both HFa and HFr rat atria were vulnerable to AF evaluated by burst atrial pacing. Isolated atrial myocytes from HFa and HFr rats revealed significantly increased sarcoplasmic reticulum calcium content and diastolic calcium sparks. Whole-heart mapping showed prolonged calcium transient duration, conduction velocity reduction, and repetitive ectopic focal discharge in HFa and HFr atria. Protein analysis revealed increased TGF-ß1 and collagen expression; increased superoxide production; abnormal upregulation of calcium-homeostasis-related proteins, including oxidized CaMKIIδ, phosphorylated-phospholamban, phosphorylated-RyR-2, and sodium-calcium exchanger; and increased Rac1 activity in both HFa and HFr atria. We observed that inhibition of CaMKII suppressed AF in both HF and HFr diet-fed rats. In vitro palmitate-induced IR neonatal cardiomyocytes and atrial fibroblasts expressed significantly more TGF-ß1 than did controls, suggesting paracrine and autocrine effects on both myocytes and fibroblasts. CONCLUSIONS: IR engenders both atrial structural remodeling and abnormal intracellular calcium homeostasis, contributing to increased AF susceptibility. The inhibition of CaMKII may be a potential therapeutic target for AF in insulin resistance.

Prostanoid EP4 agonist L-902,688 activates PPARγ and attenuates pulmonary arterial hypertension.

Prostacyclin agonists that bind the prostacyclin receptor (IP) to stimulate cAMP synthesis are effective vasodilators for the treatment of idiopathic pulmonary arterial hypertension (IPAH), but this signaling may occur through nuclear peroxisome proliferator-activated receptor-γ (PPARγ). There is evidence of scant IP and PPARγ expression but stable prostanoid EP4 receptor (EP4) expression in IPAH patients. Both IP and EP4 functionally couple with stimulatory G protein (Gs), which activates signal transduction. We investigated the effect of an EP4-specific agonist on pulmonary arterial remodeling and its regulatory mechanisms in pulmonary arterial smooth muscle cells (PASMCs). Immunoblotting evealed IP, EP4, and PPARγ expression in human pulmonary arterial hypertension (PAH) and monocrotaline (MCT)-induced PAH rat lung tissue. Isolated PASMCs from MCT-induced PAH rats (MCT-PASMCs) were treated with L-902,688, a selective EP4 agonist, to investigate the anti-vascular remodeling effect. Scant expression of IP and PPARγ but stable expression of EP4 was observed in IPAH patient lung tissues and MCT-PASMCs. L-902,688 inhibited IP-insufficient MCT-PASMC proliferation and migration by activating PPARγ in a time- and dose-dependent manner, but these effects were reversed by AH-23848 (an EP4 antagonist) and H-89 [a protein kinase A (PKA) inhibitor], highlighting the crucial role of PPARγ in the activity of this EP4 agonist. L-902,688 attenuated pulmonary arterial remodeling in hypoxic PAH mice and MCT-induced PAH rats; therefore, we conclude that the selective EP4 agonist L-902,688 reverses vascular remodeling by activating PPARγ. This study identified a novel EP4-PKA-PPARγ pathway, and we propose EP4 as a potential therapeutic target for PAH.

The Long Non-Coding RNA MIR503HG Enhances Proliferation of Human ALK-Negative Anaplastic Large-Cell Lymphoma.

Anaplastic lymphoma kinase (ALK)-negative anaplastic large-cell lymphoma (ALCL) is a rare type of highly malignant, non-Hodgkin lymphoma. Currently, only a few gene rearrangements have been linked to ALK-negative ALCL progression. However, the specific molecular mechanisms underlying the growth of ALK-negative ALCL tumors remain unclear. Here, we investigated aberrantly expressed, long non-coding RNAs (lncRNAs) in ALK-negative ALCL and assessed their potential biological function. MIR503HG (miR-503 host gene) was highly expressed in ALK-negative cell lines and was significantly upregulated in tumors in mice formed from ALK-negative ALCL cell lines. Depletion of MIR503HG suppressed tumor cell proliferation in vivo and in vitro; conversely, its overexpression enhanced tumor cell growth. MIR503HG-induced proliferation was mediated by the induction of microRNA-503 (miR-503) and suppression of Smurf2, resulting in stabilization of the tumor growth factor-ß receptor (TGFBR) and enhanced tumor cell growth. Collectively, these findings support a potential role for MIR503HG in cancer cell proliferation through the miR-503/Smurf2/TGFBR axis and indicate that MIR503HG is a potential marker in ALK-negative ALCL.

Hepatoma cell functions modulated by NEK2 are associated with liver cancer progression.

NEK2 (NIMA-related expressed kinase 2) is a serine/threonine centrosomal kinase that acts as a critical regulator of centrosome structure and function. Aberrant NEK2 activities lead to failure in regulating centrosome duplication. NEK2 overexpression promotes tumorigenesis and is associated with poor prognosis in several cancers. Increased NEK2 expression during the late pathological stage has been detected in the Oncomine liver dataset and hepatocellular carcinoma (HCC) specimens. Elevated NEK2 protein is associated with poor overall survival in patients with HCC. However, the precise roles and mechanisms of NEK2 in liver cancer progression remain largely unknown. An earlier functional study revealed that NEK2 mediates drug resistance (cisplatin or lipo-doxorubicin) via expression of an ABCC10 transporter. Active angiogenesis and metastasis underlie the rapid recurrence and poor survival of HCC. Results from the current study showed that NEK2 mediates tumor growth, metastasis and angiogenesis in vivo. NEK2-mediated drug resistance was blocked by a specific PI3K or AKT inhibitor. Moreover, NEK2 mediated liver cancer cell migration via pAKT/NF-κB signaling and matrix metalloproteinase (MMP) activation. Angiogenesis was induced via the same signaling pathway and IL-8 stimulation. Our findings collectively indicate that NEK2 modulates hepatoma cell functions, including growth, drug resistance, metastasis and angiogenesis via downstream genes activation.

Transforming growth factor-ß-mediated CD44/STAT3 signaling contributes to the development of atrial fibrosis and fibrillation.

Atrial fibrillation (AF) is associated with atrial fibrosis. Inhibition of atrial fibrosis might be a plausible approach for AF prevention and therapy. This study is designed to evaluate the potential role of CD44, a membrane receptor known to regulate fibrosis, and its related signaling in the pathogenesis of atrial fibrosis and AF. Treatment of cultured rat atrial fibroblasts with transforming growth factor-ß (TGF-ß, a key mediator of atrial fibrosis) led to a higher expression of hyaluronan (HA), CD44, STAT3, and collagen (a principal marker of fibrosis) than that of ventricular fibroblasts. In vivo, TGF-ß transgenic mice and AF patients exhibited a greater expression of HA, CD44, STAT3, and collagen in their atria than wild-type mice and sinus rhythm subjects, respectively. Treating TGF-ß transgenic mice with an anti-CD44 blocking antibody resulted in a lower expression of STAT3 and collagen in their atria than those with control IgG antibody. Programmed stimulation triggered less AF episodes in TGF-ß transgenic mice treated with anti-CD44 blocking antibody than in those with control IgG. Blocking CD44 signaling with anti-CD44 antibody and mutated CD44 plasmids attenuated TGF-ß-induced STAT3 activation and collagen expression in cultured atrial fibroblasts. Deletion and mutational analysis of the collagen promoter along with chromatin immunoprecipitation demonstrated that STAT3 served as a vital transcription factor in collagen expression. TGF-ß-mediated HA/CD44/STAT3 pathway plays a crucial role in the development of atrial fibrosis and AF. Blocking CD44-dependent signaling may be a feasible way for AF management.

Protective role of heme oxygenase-1 in atrial remodeling.

Structural and electrical remodeling in the atrium constitutes the main feature of atrial fibrillation (AF), which is characterized by increased oxidative stress. Heme oxygenase-1 (HO-1) is a potent anti-oxidant system that may provide protection against various oxidative stress-related diseases. The aim of this study is to investigate whether HO-1 has a protective effect on AF-related remodeling. Cultured atrium-derived myocytes (HL-1 cell line) were used to evaluate tachypacing-induced oxidative stress, structural, and electrical remodeling. Transforming growth factor-ß (TGF-ß) was utilized to assess collagen (a main fibrosis-related protein) expression in atrial fibroblasts. Tachypacing in HL-1 myocytes and treatment of atrial fibroblasts with TGF-ß enhanced the expression of HO-1, both of which were mediated by the activation of nuclear factor erythroid-2-related factor 2. Over-expression of HO-1 in HL-1 cells attenuated tachypacing-induced oxidative stress, myofibril degradation, down-regulation of L-type calcium channel, and shortening of action potential duration. Furthermore, HO-1 over-expression in atrial fibroblasts blocked the up-regulation of collagen by TGF-ß, implicating a protective role of HO-1 in structural and electrical remodeling in the atrium. In vivo, HO-1(-/-) mice exhibited a higher degree of oxidative stress, myofibril degradation, and collagen deposit in their atria than wild-type mice. Moreover, burst atrial pacing induced a greater susceptibility to AF in HO-1(-/-) mice than in wild-type mice. In conclusion, a negative-feedback regulation of HO-1 in activated atrial myocytes and fibroblasts may provide protection against AF-related remodeling and AF development.

A comparison between angiotensin converting enzyme inhibitors and angiotensin receptor blockers on end stage renal disease and major adverse cardiovascular events in diabetic patients: a population-based dynamic cohort study in Taiwan.

BACKGROUND: Contemporary guidelines recommend angiotensin-converting-enzyme inhibitors (ACEi) or angiotensin-receptor blockers (ARB) for hypertensive patients with diabetes. However, there is limited data to evaluate the comparison between ACEi and ARB on end stage renal disease (ESRD) and major adverse cardiovascular events (MACE), in Asian diabetic patients. METHODS: We used the Taiwan Longitudinal Cohort of Diabetes Patients Database to perform a population-based dynamic cohort study. The comparison between ACEi and ARB on ESRD and MACE in diabetic patients was examined using the propensity score weighting method. We followed these patients until the occurrence of first study outcomes or end date of the study, whichever came first. RESULTS: There were 6898 and 12,758 patients in ACEi and ARB groups, respectively. The mean follow-up period was about 3.5 years in ESRD and 2.5 years in MACE. The incidence of ESRD was 0.44 % and 0.63 % per person-years in the ACEi and ARB group, respectively. The risk of ESRD was lower in the ACEi group than the ARB group [hazard ratio (HR) 0.69; 95 % confidence interval (CI) 0.54-0.88, P = 0.0025]. Among those without chronic kidney disease (CKD), the incidence of ESRD was 0.30 % and 0.37 % per person-years in the ACEi and ARB group, respectively. ACEi was similar to ARB in preventing ESRD for those without CKD (P = 0.11). Among those with CKD, the incidence of ESRD was 1.39 % and 2.34 % per person-years in the ACEi and ARB group, respectively. The ACEi group had a lower risk of ESRD than the ARB group (HR 0.61; 95 % CI 0.42-0.88, P = 0.008). The incidence of MACE was 9.33 % and 9.62 % per person-years in the ACEi and ARB group, respectively. There was no significant difference in the composite MACE outcome between the two groups (P = 0.42), but the ACEi group was associated with a higher risk of stroke than the ARB group (HR 1.12; 95 % CI 1.02-1.24, P = 0.02). CONCLUSIONS: ACEi compared with ARB was associated with a lower incidence of ESRD, especially in those with CKD. Though ACEi and ARB had a similar risk of composite MACE outcome, ACEi had a slightly higher incidence of stroke than ARB, among the Asian diabetic patients.

MMP9 Rs3918242 Polymorphism Affects Tachycardia-Induced MMP9 Expression in Cultured Atrial-Derived Myocytes but Is Not a Risk Factor for Atrial Fibrillation among the Taiwanese.

Matrix metalloproteinase (MMP) plays an important role in the pathogenesis of atrial fibrillation (AF). The MMP9 promoter has a functional polymorphism rs3918242 that can regulate the level of gene transcription. This study recruited 200 AF patients and 240 controls. The MMP9 rs3918242 was examined by polymerase chain reactions. HL-1 atrial myocytes were cultured and electrically stimulated. Right atrial appendages were obtained from six patients with AF and three controls with sinus rhythm undergoing open heart surgery. The MMP9 expression and activity were determined using immunohistochemical analysis and gelatin zymography, respectively. Rapid pacing induces MMP9 secretion from HL-1 myocytes in a time- and dose-dependent manner. The responsiveness of MMP9 transcriptional activity to tachypacing was significantly enhanced by rs3918242. The expression of MMP9 was increased in fibrillating atrial tissue than in sinus rhythm. However, the distribution of rs3918242 genotypes and allele frequencies did not significantly differ between the control and AF groups. HL-1 myocyte may secrete MMP9 in response to rapid pacing, and the secretion could be modulated by rs3918242. Although the MMP9 expression of human atrial myocyte is associated with AF, our study did not support the association of susceptibility to AF among Taiwanese subjects with the MMP9 rs3918242 polymorphism.

Rosuvastatin suppresses atrial tachycardia-induced cellular remodeling via Akt/Nrf2/heme oxygenase-1 pathway.

Atrial fibrillation (AF) is associated with structural remodeling in atrial myocytes. Emerging evidence suggests that statin has a protective effect on AF through cholesterol-independent mechanisms. The aim of this study is to investigate whether heme oxygenase-1 (HO-1), a potent antioxidant system, mediates the suppressive effect of statin on atrial tachycardia-induced structural remodeling. Treatment of cultured atrium-derived myocytes (HL-1 cell line) with rosuvastatin enhanced HO-1 expression/activity and attenuated tachypacing-induced oxidative stress and myofibril degradation. Heme oxygenase-1 inhibitors and small-interfering RNA for HO-1 blocked the inhibitory effect of rosuvastatin on tachypacing-stimulated changes, suggesting the crucial role of HO-1 in mediating the effect of rosuvastatin. Time-dependent experiments and loss-of-function study demonstrated that Akt/Nrf2 pathways lay to the up-stream of HO-1 in this signaling cascade. Furthermore, the involvement of Akt/Nrf2/HO-1 pathway in the antioxidant effect of rosuvastatin was documented in an ex vivo tachypacing model. The suppressive effect of statin on atrial tachypacing-induced cellular remodeling is mediated via the activation of Akt/Nrf2/HO-1 signaling, which provides a possible explanation for the protective effect of statin on AF.

Negative modulation of the epigenetic regulator, UHRF1, by thyroid hormone receptors suppresses liver cancer cell growth.

The thyroid hormone, 3,3',5-triiodo-l-thyronine (T3 ), mediates several physiological processes, including embryonic development, cellular differentiation, metabolism and regulation of cell proliferation. Thyroid hormone (T3 ) and its receptor (TR) are involved in metabolism and growth. In addition to their developmental and metabolic functions, TRs play a tumor suppressor role, and therefore, their aberrant expression can lead to tumor transformation. Aberrant epigenetic silencing of tumor suppressor genes promotes cancer progression. The epigenetic regulator, Ubiquitin-like with PHD and ring finger domains 1 (UHRF1), is overexpressed in various cancers. In our study, we demonstrated that T3 negatively regulates UHRF1 expression, both in vitro and in vivo. Our results further indicate that UHRF1 regulation by T3 is indirect and mediated by Sp1. Sp1-binding elements of UHRF1 were identified at positions -664/-505 of the promoter region using the luciferase and chromatin immunoprecipitation assays. Notably, UHRF1 and Sp1 levels were elevated in subgroups of hepatocellular carcinoma patients and inversely correlated with TRα1 expression. Knockdown of UHRF1 expression should therefore provide a means to inhibit hepatoma cell proliferation. Expression of UHRF1 was downregulated by TRs, in turn, relieving silencing of the UHRF1 target gene, p21. Based on the collective findings, we propose that T3 /TR signaling induces hepatoma cell growth inhibition via UHRF1 repression.

Repression of microRNA-130b by thyroid hormone enhances cell motility.

BACKGROUND & AIMS: Thyroid hormone (T3) and its receptor (TR) are involved in cell growth and cancer progression. Although deregulation of microRNA (miRNA) expression has been detected in many tumor types, the mechanisms underlying functional impairment and specific involvement of miRNAs in tumor metastasis remain unclear. In the current study, we aimed to elucidate the involvement of deregulated miRNA-130b (miR-130b) and its target genes mediated by T3/TR in cancer progression. METHODS: Quantitative reverse transcription-PCR, luciferase and chromatin immunoprecipitation assays were performed to identify the miR-130b transcript and the mechanisms implicated in its regulation. The effects of miR-130b on hepatocellular carcinoma (HCC) invasion were further examined in vitro and in vivo. Clinical correlations among miR-130b, TRs and interferon regulatory factor 1 (IRF1) were examined in HCC samples using Spearman correlation analysis. RESULTS: Our experiments disclosed negative regulation of miR-130b expression by T3/TR. Overexpression of miR-130b led to marked inhibition of cell migration and invasion, which was mediated via suppression of IRF1. Cell migration ability was promoted by T3, but partially suppressed upon miR-130b overexpression. Furthermore, miR-130b suppressed expression of epithelial-mesenchymal transition (EMT)-related genes, matrix metalloproteinase-9, phosphorylated mammalian target of rapamycin (mTOR), p-ERK1/2, p-AKT and p-signal transducer and activator of transcription (STAT)-3. Notably, miR-130b was downregulated in hepatoma samples and its expression patterns were inversely correlated with those of TRα1 and IRF1. CONCLUSIONS: Our data collectively highlight a novel pathway interlinking T3/TR, miR-130b, IRF1, the EMT-related genes, p-mTOR, p-STAT3 and the p-AKT cascade, which regulates the motility and invasion of hepatoma cells.

Association of metformin with lower atrial fibrillation risk among patients with type 2 diabetes mellitus: a population-based dynamic cohort and in vitro studies.

BACKGROUND: Atrial fibrillation (AF), an inflammatory process involving arrhythmia, is associated with severe morbidity and mortality and commonly seen in patients with diabetes mellitus (DM). The effect of metformin, the most commonly used medication for patients with DM, on AF has not been investigated. The primary aim of this study was to examine whether metformin prevented the occurrence of AF in type 2 DM patients by analyzing a nationwide, population-based dynamic cohort. Additionally, we investigated the effect of metformin on tachycardia-induced myolysis and oxidative stress in atrial cells. METHODS: The study population included 645,710 patients with type 2 diabetes and not using other anti-diabetic medication from a subset of the Taiwan National Health Insurance Research Database. Of these patients, those who used metformin were categorized as the user group, and the remaining were classified as the non-user group. The time-dependent Cox's proportional hazard model was used to examine the effect of metformin on AF and the status of metformin use was treated as a time-dependent covariate. HL-1 atrial cells were paced with or without metformin, and then troponin and heavy-chain-myosin were measured as markers of myolysis. RESULTS: After 13 years of follow-up, 9,983 patients developed AF with an incidence rate of 1.5% (287 per 100,000 person-years). After adjusting for co-morbidities and medications, metformin independently protected the diabetic patients from new-onset AF with a hazard ratio of .81 (95% confidence interval 0.76-0.86, p < 0.0001). Metformin significantly decreased the extent of pacing-induced myolysis and the production of reactive oxygen species. CONCLUSION: Metformin use was associated with a decreased risk of AF in patients with type 2 DM who were not using other anti-diabetic medication, probably via attenuation of atrial cell tachycardia-induced myolysis and oxidative stress.