Empagliflozin suppressed cardiac fibrogenesis through sodium-hydrogen exchanger inhibition and modulation of the calcium homeostasis.

BACKGROUND: The novel sodium-glucose co-transporter 2 inhibitor (SGLT2i) potentially ameliorates heart failure and reduces cardiac arrhythmia. Cardiac fibrosis plays a pivotal role in the pathophysiology of HF and atrial myopathy, but the effect of SGLT2i on fibrogenesis remains to be elucidated. This study investigated whether SGLT2i directly modulates fibroblast activities and its underlying mechanisms. METHODS AND RESULTS: Migration, proliferation analyses, intracellular pH assay, intracellular inositol triphosphate (IP3) assay, Ca2+ fluorescence imaging, and Western blotting were applied to human atrial fibroblasts. Empagliflozin (an SGLT2i, 1, or 5 µmol/L) reduced migration capability and collagen type I, and III production. Compared with control cells, empagliflozin (1 µmol/L)- treated atrial fibroblasts exhibited lower endoplasmic reticulum (ER) Ca2+ leakage, Ca2+ entry, inositol trisphosphate (IP3), lower expression of phosphorylated phospholipase C (PLC), and lower intracellular pH. In the presence of cariporide (an Na+-H+ exchanger (NHE) inhibitor, 10 µmol/L), control and empagliflozin (1 µmol/L)-treated atrial fibroblasts revealed similar intracellular pH, ER Ca2+ leakage, Ca2+ entry, phosphorylated PLC, pro-collagen type I, type III protein expression, and migration capability. Moreover, empagliflozin (10 mg/kg/day orally for 28 consecutive days) significantly increased left ventricle systolic function, ß-hydroxybutyrate and decreased atrial fibrosis, in isoproterenol (100 mg/kg, subcutaneous injection)-induced HF rats. CONCLUSIONS: By inhibiting NHE, empagliflozin decreases the expression of phosphorylated PLC and IP3 production, thereby reducing ER Ca2+ release, extracellular Ca2+ entry and the profibrotic activities of atrial fibroblasts.

Effect of macrophage migration inhibitory factor on pulmonary vein arrhythmogenesis through late sodium current.

AIMS: Macrophage migration inhibitory factor (MIF), a pleiotropic inflammatory cytokine, is highly expressed in patients with atrial fibrillation (AF). Inflammation increases the risk of AF and is primarily triggered by pulmonary vein (PV) arrhythmogenesis. This study investigated whether MIF can modulate the electrical activity of the PV and examined the underlying mechanisms of MIF. METHODS AND RESULTS: A conventional microelectrode, a whole-cell patch clamp, western blotting, and immunofluorescent confocal microscopy were used to investigate electrical activity, calcium (Ca2+) regulation, protein expression, ionic currents, and cytosolic reactive oxygen species (ROS) in rabbit PV tissue and isolated single cardiomyocytes with and without MIF incubation (100 ng/mL, treated for 6 h). The MIF (100 ng/mL)-treated PV tissue (n = 8) demonstrated a faster beating rate (1.8 ± 0.2 vs. 2.6 ± 0.1 Hz, P < 0.05), higher incidence of triggered activity (12.5 vs. 100%, P < 0.05), and premature atrial beat (0 vs. 100%, P < 0.05) than the control PV tissue (n = 8). Compared with the control PV cardiomyocytes, MIF-treated single PV cardiomyocytes had larger Ca2+ transients (0.6 ± 0.1 vs. 1.0 ± 0.1, ΔF/F0, P < 0.05), sarcoplasmic reticulum Ca2+ content (0.9 ± 0.20 vs. 1.7 ± 0.3 mM of cytosol, P < 0.05), and cytosolic ROS (146.8 ± 5.3 vs. 163.7 ± 3.8, ΔF/F0, P < 0.05). Moreover, MIF-treated PV cardiomyocytes exhibited larger late sodium currents (INa-Late), L-type Ca2+ currents, and Na+/Ca2+ exchanger currents than the control PV cardiomyocytes. KN93 [a selective calcium/calmodulin-dependent protein kinase II (CaMKII) blocker, 1 µM], ranolazine (an INa-Late inhibitor, 10 µM), and N-(mercaptopropionyl) glycine (ROS inhibitor, 10 mM) reduced the beating rates and the incidence of triggered activity and premature captures in the MIF-treated PV tissue. CONCLUSION: Macrophage migration inhibitory factor increased PV arrhythmogenesis through Na+ and Ca2+ dysregulation through the ROS activation of CaMKII signalling, which may contribute to the genesis of AF during inflammation. Anti-CaMKII treatment may reverse PV arrhythmogenesis. Our results clearly reveal a key link between MIF and AF and offer a viable therapeutic target for AF treatment.

Class I HDAC modulates angiotensin II-induced fibroblast migration and mitochondrial overactivity.

BACKGROUND: Inhibition of histone deacetylases (HDACs) attenuates cardiac fibrosis. In this study, we evaluated whether the inhibition of class I HDACs can attenuate angiotensin II (ANG II)-induced fibrogenesis and mitochondrial malfunction through its effects on reactive oxygen species (ROS) and calcium dysregulation in human cardiac fibroblasts (CFs). METHODS: Seahorse XF24 extracellular flux analyser, fluorescence staining, Western blotting, HDAC activity assays and Transwell migration assay were used to study mitochondrial respiration, adenosine triphosphate (ATP) production, mitochondrial calcium uptake and ROS, HDAC expression and activity and fibroblast activity in CFs without (control) or with ANG II (100 nM) and/or MS-275 (HDAC class 1 inhibitor, 10 µM) for 24 h. RESULTS: ANG II increased HDAC activity without changing protein expression in CFs. Compared with controls, ANG II-treated CFs had greater migration activity, higher ATP production, maximal respiration and spare capacity with higher mitochondrial Ca2+ uptake and ROS generation, which was attenuated by the administration of MS-275. ANG II activated CFs by increasing mitochondrial calcium content and ATP production, which may be caused by increased HDAC activity. Inhibition of HDAC1 attenuated the effects of ANG II by reducing mitochondrial ROS generation and calcium overload. CONCLUSIONS: Modulating mitochondrial function by regulation of HDAC may be a novel strategy for controlling CF activity.

Ceramide modulates electrophysiological characteristics and oxidative stress of pulmonary vein cardiomyocytes.

BACKGROUND: Ceramide is involved in regulating metabolism and energy expenditure, and its abnormal myocardial accumulation may contribute to heart injury or lipotoxic cardiomyopathy. Whether ceramide can modulate the electrophysiology of pulmonary veins (PVs) remains unknown. MATERIALS AND METHODS: We used conventional microelectrodes to measure the electrical activity of isolated rabbit PV tissue preparations before and after treatment with various concentrations of ceramide with or without H2 O2 (2 mM), MitoQ, wortmannin or 740 YP. A whole-cell patch clamp and fluorescence imaging were used to record the ionic currents, calcium (Ca2+ ) transients, and intracellular reactive oxygen species (ROS) and sodium (Na+ ) in isolated single PV cardiomyocytes before and after ceramide (1 µM) treatment. RESULTS: Ceramide (0.1, 0.3, 1 and 3 µM) reduced the beating rate of PV tissues. Furthermore, ceramide (1 µM) suppressed the 2 mM H2 O2 -induced faster PV beating rate, triggered activities and burst firings, which were further reduced by MitoQ. In the presence of wortmannin, ceramide did not change the PV beating rate. The H2 O2 -induced faster PV beating rate could be counteracted by MitoQ or wortmannin with no additive effect from the ceramide. Ceramide inhibited pPI3K. Ceramide reduced Ca2+ transients, sarcoplasmic reticulum Ca2+ contents, L-type Ca2+ currents, Na+ currents, late Na+ currents, Na+ -hydrogen exchange currents, and intracellular ROS and Na+ in PV cardiomyocytes, but did not change Na+ -Ca2+ exchange currents. CONCLUSION: C2 ceramide may exert the distinctive electrophysiological effect of modulating PV activities, which may be affected by PI3K pathway-mediated oxidative stress, and might play a role in the pathogenesis of PV arrhythmogenesis.

Lithium Treatment Improves Cardiac Dysfunction in Rats Deprived of Rapid Eye Movement Sleep.

Rapid eye movement (REM) sleep deprivation triggers mania and induces cardiac fibrosis. Beyond neuroprotection, lithium has cardioprotective potential and antifibrotic activity. This study investigated whether lithium improved REM sleep deprivation-induced cardiac dysfunction and evaluated the potential mechanisms. Transthoracic echocardiography, histopathological analysis, and Western blot analysis were performed in control and REM sleep-deprived rats with or without lithium treatment (LiCl of 1 mmol/kg/day administered by oral gavage for 4 weeks) in vivo and in isolated ventricular preparations. The results revealed that REM sleep-deprived rats exhibited impaired contractility and greater fibrosis than control and lithium-treated REM sleep-deprived rats. Western blot analysis showed that REM sleep-deprived hearts had higher expression levels of transforming growth factor beta (TGF-ß), phosphorylated Smad 2/3, and alpha-smooth muscle actin than lithium-treated REM sleep-deprived and control hearts. Moreover, lithium-treated REM sleep-deprived hearts had lower expression of angiotensin II type 1 receptor, phosphorylated nuclear factor kappa B p65, calcium release-activated calcium channel protein 1, transient receptor potential canonical (TRPC) 1, and TRPC3 than REM sleep-deprived hearts. The findings suggest that lithium attenuates REM sleep deprivation-induced cardiac fibrogenesis and dysfunction possibly through the downregulation of TGF-ß, angiotensin II, and Ca2+ signaling.

Vascular endothelial growth factor on Runt-related transcript factor-2 in aortic valve cells.

BACKGROUND: Calcific aortic valve disease is associated with ageing and high mortality. However, no effective pharmacological treatment has been developed. Vascular endothelial growth factor (VEGF) and its receptor are overexpressed in the calcified aortic valve tissue. However, the role of VEGF in calcific aortic valve disease pathogenesis and its underlying mechanisms remain unclear. MATERIALS AND METHODS: Runt-related transcription factor 2 expression and calcium-related signalling were investigated in porcine valvular interstitial cells with or without human VEGF-A recombinant protein (VEGF165 , 1-100 ng/mL) treatment and/or calmodulin-dependent kinase II (CaMKII) inhibitor (KN93, 10 µmol/L) and inositol triphosphate receptor inhibitor (2-aminoethyldiphenyl borate, 30 µmol/L) for 5 days. RESULTS: VEGF165 -treated cells had higher Runt-related transcription factor 2 expression and CaMKII/ adenosine 3',5'-monophosphate response element-binding protein (CREB) signalling activation than did control cells. KN93 reduced Runt-related transcription factor 2 expression and CREB phosphorylation in VEGF165 -treated cells. The 2-aminoethyldiphenyl borate also reduced Runt-related transcription factor 2 expression in VICs treated with VEGF165 . CONCLUSION: VEGF upregulated Runt-related transcription factor 2 expression in VICs by activating the IP3R/CaMKII/CREB signalling pathway.

Physiological testosterone attenuates profibrotic activities of rat cardiac fibroblasts through modulation of nitric oxide and calcium homeostasis.

Testosterone deficiency is associated with poor prognosis among patients with chronic heart failure (HF). Physiological testosterone improves the exercise capacity of patients with HF. In this study, we evaluated whether treatment with physiological testosterone contributes to anti-fibrogenesis by modifying calcium homeostasis in cardiac fibroblasts and we studied the underlying mechanisms. Nitric oxide (NO) analyses, calcium (Ca2+) fluorescence, and Western blotting were performed in primary isolated rat cardiac fibroblasts with or without (control cells) testosterone (10, 100, 1,000 nmol/L) treatment for 48 hours. Physiological testosterone (10 nmol/L) increased NO production and phosphorylation at the inhibitory site of the inositol trisphosphate (IP3) receptor, thereby reducing Ca2+ entry, phosphorylated Ca2+/calmodulin-dependent protein kinase II (CaMKII) expression, type I and type III pro-collagen production. Non-physiological testosterone-treated fibroblasts exhibited similar NO and collagen production capabilities as compared to control (testosterone deficient) fibroblasts. These effects were blocked by co-treatment with NO inhibitor (L-NG-nitro arginine methyl ester [L-NAME], 100 µmol/L). In the presence of the IP3 receptor inhibitor (2-aminoethyl diphenylborinate [2-APB], 50 µmol/L), testosterone-deficient and physiological testosterone-treated fibroblasts exhibited similar phosphorylated CaMKII expression. When treated with 2-APB or CaMKII inhibitor (KN93, 10 µmol/L), testosterone-deficient and physiological testosterone-treated fibroblasts exhibited similar type I, and type III collagen production. In conclusion, physiological testosterone activates NO production, and attenuates the IP3 receptor/Ca2+ entry/CaMKII signaling pathway, thereby inhibiting the collagen production capability of cardiac fibroblasts.

Lithium Reduces Migration and Collagen Synthesis Activity in Human Cardiac Fibroblasts by Inhibiting Store-Operated Ca2+ Entry.

Cardiac fibrosis plays a vital role in the pathogenesis of heart failure. Fibroblast activity is enhanced by increases in store-operated Ca2+ entry (SOCE) and calcium release-activated calcium channel protein 1 (Orai1) levels. Lithium regulates SOCE; however, whether therapeutic concentrations of lithium can be used to inhibit cardiac fibrogenesis is unknown. Migration and proliferation assays, Western blotting, real-time reverse-transcription polymerase chain reaction analysis, and calcium fluorescence imaging were performed in human cardiac fibroblasts treated with or without LiCl at 1.0 mM (i.e., therapeutic peak level) or 0.1 mM (i.e., therapeutic trough level) for 24 h. Results showed that LiCl (0.1 mM, but not 1.0 mM) inhibited the migration and collagen synthesis ability of cardiac fibroblasts. Additionally, thapsigargin-induced SOCE was reduced in fibroblasts treated with LiCl (0.1 mM). The expression level of Orai1 was lower in LiCl (0.1 mM)-treated fibroblasts relative to the fibroblasts without LiCl treatment. Fibroblasts treated with a combination of LiCl (0.1 mM) and 2-APB (10 µM, an Orai1 inhibitor) demonstrated similar migration and collagen synthesis abilities as those in LiCl (0.1 mM)-treated fibroblasts. Altogether, lithium at therapeutic trough levels reduced the migration and collagen synthesis abilities of human cardiac fibroblasts by inhibiting SOCE and Orai1 expression.

Fibroblast Growth Factor 23 Stimulates Cardiac Fibroblast Activity through Phospholipase C-Mediated Calcium Signaling.

Fibroblast growth factor (FGF)-23 induces hypertrophy and calcium (Ca2+) dysregulation in cardiomyocytes, leading to cardiac arrhythmia and heart failure. However, knowledge regarding the effects of FGF-23 on cardiac fibrogenesis remains limited. This study investigated whether FGF-23 modulates cardiac fibroblast activity and explored its underlying mechanisms. We performed MTS analysis, 5-ethynyl-2'-deoxyuridine assay, and wound-healing assay in cultured human atrial fibroblasts without and with FGF-23 (1, 5 and 25 ng/mL for 48 h) to analyze cell proliferation and migration. We found that FGF-23 (25 ng/mL, but not 1 or 5 ng/mL) increased proliferative and migratory abilities of human atrial fibroblasts. Compared to control cells, FGF-23 (25 ng/mL)-treated fibroblasts had a significantly higher Ca2+ entry and intracellular inositol 1,4,5-trisphosphate (IP3) level (assessed by fura-2 ratiometric Ca2+ imaging and enzyme-linked immunosorbent assay). Western blot analysis showed that FGF-23 (25 ng/mL)-treated cardiac fibroblasts had higher expression levels of calcium release-activated calcium channel protein 1 (Orai1) and transient receptor potential canonical (TRPC) 1 channel, but similar expression levels of α-smooth muscle actin, collagen type IA1, collagen type Ⅲ, stromal interaction molecule 1, TRPC 3, TRPC6 and phosphorylated-calcium/calmodulin-dependent protein kinase II when compared with control fibroblasts. In the presence of ethylene glycol tetra-acetic acid (a free Ca2+ chelator, 1 mM) or U73122 (an inhibitor of phospholipase C, 1 µM), control and FGF-23-treated fibroblasts exhibited similar proliferative and migratory abilities. Moreover, polymerase chain reaction analysis revealed that atrial fibroblasts abundantly expressed FGF receptor 1 but lacked expressions of FGF receptors 2-4. FGF-23 significantly increased the phosphorylation of FGF receptor 1. Treatment with PD166866 (an antagonist of FGF receptor 1, 1 µM) attenuated the effects of FGF-23 on cardiac fibroblast activity. In conclusion, FGF-23 may activate FGF receptor 1 and subsequently phospholipase C/IP3 signaling pathway, leading to an upregulation of Orai1 and/or TRPC1-mediated Ca2+ entry and thus enhancing human atrial fibroblast activity.

Empagliflozin and Liraglutide Differentially Modulate Cardiac Metabolism in Diabetic Cardiomyopathy in Rats.

Glucagon-like peptide 1 receptor agonists (GLP-1RAs) and sodium-glucose cotransporter-2 inhibitors (SGLT2is) are antihyperglycemic agents with cardioprotective properties against diabetic cardiomyopathy (DCM). However, the distinctive mechanisms underlying GLP-1RAs and SGLT2is in DCM are not fully elucidated. The purpose of this study was to investigate the impacts of GLP1RAs and/or SGLT2is on myocardial energy metabolism, cardiac function, and apoptosis signaling in DCM. Biochemistry and echocardiograms were studied before and after treatment with empagliflozin (10 mg/kg/day, oral gavage), and/or liraglutide (200 µg/kg every 12 h, subcutaneously) for 4 weeks in male Wistar rats with streptozotocin (65 mg/kg intraperitoneally)-induced diabetes. Cardiac fibrosis, apoptosis, and protein expression of metabolic and inflammatory signaling molecules were evaluated by histopathology and Western blotting in ventricular cardiomyocytes of different groups. Empagliflozin and liraglutide normalized myocardial dysfunction in diabetic rats. Upregulation of phosphorylated-acetyl coenzyme A carboxylase, carnitine palmitoyltransferase 1ß, cluster of differentiation 36, and peroxisome proliferator-activated receptor-gamma coactivator, and downregulation of glucose transporter 4, the ratio of phosphorylated adenosine monophosphate-activated protein kinase α2 to adenosine monophosphate-activated protein kinase α2, and the ratio of phosphorylated protein kinase B to protein kinase B in diabetic cardiomyocytes were restored by treatment with empagliflozin or liraglutide. Nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing 3, interleukin-1ß, tumor necrosis factor-α, and cleaved caspase-1 were significantly downregulated in empagliflozin-treated and liraglutide-treated diabetic rats. Both empagliflozin-treated and liraglutide-treated diabetic rats exhibited attenuated myocardial fibrosis and apoptosis. Empagliflozin modulated fatty acid and glucose metabolism, while liraglutide regulated inflammation and apoptosis in DCM. The better effects of combined treatment with GLP-1RAs and SGLT2is may lead to a potential strategy targeting DCM.

Vascular endothelial growth factor enhances profibrotic activities through modulation of calcium homeostasis in human atrial fibroblasts.

Vascular endothelial growth factor (VEGF), a pivotal activator of angiogenesis and calcium (Ca2+) signaling in endothelial cells, was shown to increase collagen production in atrial fibroblasts. In this study, we evaluated whether VEGF may regulate Ca2+ homeostasis in atrial fibroblasts and contribute to its profibrogenesis. Migration, and proliferation analyses, patch-clamp assay, Ca2+ fluorescence imaging, and western blotting were performed using VEGF-treated (300 pg/mL or 1000 pg/mL) human atrial fibroblasts with or without coadministration of Ethylene glycol tetra-acetic acid (EGTA, 1 mmol/L), or KN93 (a Ca2+/calmodulin-dependent protein kinase II [CaMKII] inhibitor, 10 µmol/L). VEGF (1000 pg/mL) increased migration, myofibroblast differentiation, pro-collagen type I, pro-collagen type III production, and phosphorylated VEGF receptor 1 expression of fibroblasts. VEGF (1000 pg/mL) increased the nonselective cation current (INSC) of transient receptor potential (TRP) channels and potassium current of intermediate-conductance Ca2+-activated K+ (KCa3.1) channels thereby upregulating Ca2+ entry. VEGF upregulated phosphorylated ERK expression. An ERK inhibitor (PD98059, 50 µmol/L) attenuated VEGF-activated INSC of TRP channels. The presence of EGTA attenuated the profibrotic effects of VEGF on pro-collagen type I, pro-collagen type III production, myofibroblast differentiation, and migratory capabilities of fibroblasts. VEGF upregulated the expression of phosphorylated CaMKII in fibroblasts, which was attenuated by EGTA. In addition, KN93 reduced VEGF-increased pro-collagen type I, pro-collagen type III production, myofibroblast differentiation, and the migratory capabilities of fibroblasts. In conclusion, we found that VEGF increases atrial fibroblast activity through CaMKII signaling by enhancing Ca2+ entry. Our findings provide benchside evidence leading to a potential novel strategy targeting atrial myopathy and arrhythmofibrosis.

Pitx2c inhibition increases atrial fibroblast activity: Implications in atrial arrhythmogenesis.

BACKGROUND: A Pitx2c deficiency increases the risk of atrial fibrillation (AF). Atrial structural remodelling with fibrosis blocks electrical conduction and leads to arrhythmogenesis. A Pitx2c deficiency enhances profibrotic transforming growth factor (TGF)-ß expression and calcium dysregulation, suggesting that Pitx2c may play a role in atrial fibrosis. The purposes of this study were to evaluate whether a Pitx2c deficiency modulates cardiac fibroblast activity and study the underlying mechanisms. MATERIALS AND METHODS: A migration assay, proliferation analysis, Western blot analysis and calcium fluorescence imaging were conducted in Pitx2c-knockdown human atrial fibroblasts (HAFs) using short hairpin (sh)RNA or small interfering (si)RNA. RESULTS: Compared to control HAFs, Pitx2c-knockdown HAFs had a greater migration but a similar proliferative ability. Pitx2c-knockdown HAFs had a higher calcium influx with enhanced phosphorylation of calmodulin kinase II (CaMKII), α-smooth muscle actin and matrix metalloproteinase-2. In the presence of a CaMKII inhibitor (KN-93, 0.5 µmol/L), control and Pitx2c-knockdown HAFs exhibited similar migratory abilities. CONCLUSION: These findings suggest that downregulation of Pitx2c may regulate atrial fibrosis through modulating calcium homeostasis, which may contribute to its role in anti-atrial fibrosis, and Pitx2c downregulation may change the atrial electrophysiology and AF occurrence through modulating fibroblast activity.

Empagliflozin Attenuates Myocardial Sodium and Calcium Dysregulation and Reverses Cardiac Remodeling in Streptozotocin-Induced Diabetic Rats.

Diabetes mellitus (DM) has significant effects on cardiac calcium (Ca2+) and sodium (Na⁺) regulation. Clinical studies have shown that empagliflozin (Jardiance™) has cardiovascular benefits, however the mechanisms have not been fully elucidated. This study aimed to investigate whether empagliflozin modulates cardiac electrical activity as well as Ca2+/Na⁺ homeostasis in DM cardiomyopathy. Electrocardiography, echocardiography, whole-cell patch-clamp, confocal microscopic examinations, and Western blot, were performed in the ventricular myocytes of control and streptozotocin-induced DM rats, with or without empagliflozin (10 mg/kg for 4 weeks). The results showed that the control and empagliflozin-treated DM rats had smaller left ventricular end-diastolic diameters and shorter QT intervals than the DM rats. In addition, the prolonged action potential duration in the DM rats was attenuated in the empagliflozin-treated DM rats. Moreover, the DM rats had smaller sarcoplasmic reticular Ca2+ contents, intracellular Ca2+ transients, L-type Ca2+, reverse mode Na⁺-Ca2+exchanger currents, lower protein expressions of sarcoplasmic reticulum ATPase, ryanodine receptor 2 (RyR2), but higher protein expressions of phosphorylated RyR2 at serine 2808 than the control and empagliflozin-treated DM rats. The incidence and frequency of Ca2+ sparks, cytosolic and mitochondrial reactive oxygen species, and late Na⁺ current and Na⁺/hydrogen-exchanger currents were greater in the DM rats than in the control and empagliflozin-treated DM rats. Empagliflozin significantly changed Ca2+ regulation, late Na⁺ and Na⁺/hydrogen-exchanger currents and electrophysiological characteristics in DM cardiomyopathy, which may contribute to its cardioprotective benefits in DM patients.

Factor Xa inhibition by rivaroxaban regulates fibrogenesis in human atrial fibroblasts with modulation of nitric oxide synthesis and calcium homeostasis.

BACKGROUND: Rivaroxaban, a widely used factor Xa inhibitor in reducing stroke in atrial fibrillation (AF) patients has multiple biological effects with activation of protease-activated receptor (PAR) signaling. Atrial fibrosis plays a critical role in the pathophysiology of AF. In this study, we evaluated whether rivaroxaban regulates atrial fibroblast activity and its underlying mechanisms. METHODS AND RESULTS: Migration, proliferation analyses, nitric oxide (NO) production assay, calcium fluorescence imaging, and western blots were conducted in human atrial fibroblasts with or without rivaroxaban (100 nmol/L or 300 nmol/L) and co-administration of L-NAME (L-NG-nitro arginine methyl ester, 100 µmol/L), EGTA (Ethylene glycol tetra-acetic acid, 1 mmol/L), thrombin (0.5 U/mL), PAR1 agonist peptide (TFLLR-NH2, 100 µmol/L), PAR1 inhibitor (SCH79797, 0.5 µmol/L) and PAR2 inhibitor (GB83, 10 µmol/L). Atrial fibrosis was examined in isoproterenol (100 mg/kg, subcutaneous injection)-treated rats with or without rivaroxaban (10 mg/kg/day orally for 14 consecutive days). Rivaroxaban reduced the migration, pro-collagen type I production, and proliferation of atrial fibroblasts. Rivaroxaban decreased phosphorylated endothelial NO synthase (eNOS) (Thr 495, an inhibitory phosphorylated site of eNOS), and calcium (Ca2+) entry, and increased NO production. Moreover, L-NAME blocked the effects of rivaroxaban on fibroblast collagen and NO production. In the presence of EGTA, the migratory capability was similarly decreased in atrial fibroblasts with and without treatment with rivaroxaban (100 nmol/L), which suggests that rivaroxaban decreases migratory capability of atrial fibroblasts by inhibiting Ca2+ entry. Additionally, rivaroxaban significantly attenuated the effects of thrombin, and TFLLR-NH2 on migratory, proliferative, and pro-collagen type I production capability in atrial fibroblasts. SCH79797 or GB83 decreased pro-collagen type I production, migration, and proliferation capability in fibroblasts, but combined SCH79797 or GB83 with and without rivaroxaban had similar fibroblast activity. Moreover, rivaroxaban significantly decreased atrial fibrosis in isoproterenol-treated rats. CONCLUSIONS: Rivaroxaban (100-300 nmol/L) regulates atrial fibroblast activity and atrial fibrosis by increasing NO production and decreasing Ca2+ entry through inhibition of PAR signaling.

Novel Histone Deacetylase Inhibitor Modulates Cardiac Peroxisome Proliferator-Activated Receptors and Inflammatory Cytokines in Heart Failure.

BACKGROUND: Heart failure (HF) affects cardiac metabolism and inflammation. Histone deacetylases (HDACs) play a critical role in cardiac pathophysiology. This study investigated whether HDAC inhibition can regulate HF by modifying cardiac inflammation and peroxisome proliferator-activated receptor (PPAR) isoforms. METHODS: Echocardiography, electrocardiography, ELISA and Western blot were performed in rats with isoproterenol-induced HF, with and without orally administered MPT0E014 (a novel HDAC inhibitor, 50 mg/kg for 7 consecutive days). RESULTS: The left ventricles (LVs) of HF rats expressed significantly higher levels of HDAC1, HDAC2, HDAC3, HDAC4 and HDAC6 than the healthy LVs did. HF rats treated with MPT0E014 exhibited improved cardiac fraction shortening with reducing chamber size. The MPT0E014-treated HF LVs exhibited a smaller increase in the expression of interleukin (IL)-6, p22, SMAD2/3, extracellular signal-regulated kinase 1/2, PPAR isoforms and circulatory tumor growth factor-ß1 than the untreated HF LVs did. Moreover, MPT0E014-treated HF LVs expressed less fibroblast growth factor receptor than untreated HF LVs did. CONCLUSIONS: HDAC inhibition can improve cardiac function and attenuate the effects of HF on cardiac metabolism and inflammation, which might contribute to the beneficial effects of HDAC inhibition in HF.

Right Ventricle Mass Induced Coronary Artery Steal Phenomenon: A Rare Clinical Manifestation on One Leiomyosarcoma Patient.

UNLABELLED: We report a 43-year-old female with the underlying disease of retroperitoneal leiomyosarcoma and initial presentation of ST elevation myocardial infarction. Coronary angiography showed an absence of coronary artery stenosis and a huge, ill-defined cardiac mass which was fed by both the left anterior descending artery and the right coronary artery. Coronary blood flow was obviously shunted by the neovascularized cardiac tumor. Right ventricle metastatic leiomyosarcoma was diagnosed according to her clinical course, images of echocardiography and computed tomography. In conclusion, we speculated that ST-segment elevation in electrocardiogram and typical anginal symptoms can provide significant evidence for myocardial ischemia caused by coronary steal phenomenon due to a right ventricular metastatic leiomyosarcoma. KEY WORDS: Coronary steal phenomenon; Leiomyosarcoma; Myocardial infarction.

Curcumin Suppress Cardiac Fibroblasts Activities by Regulating Proliferation, Migration, and the Extracellular Matrix.

BACKGROUND: Cardiac fibrosis plays a critical role in the pathophysiology of cardiovascular disease. It has been observed that curcumin has several cardiovascular effects. The purpose of this study was to evaluate whether curcumin can attenuate cardiac fibroblasts activity. METHODS AND RESULTS: We evaluated the migration, proliferation, collagen production, and transcription signaling in rat cardiac fibroblasts isolated from Sprague-Dawley rats (males, weighing 300-350 g) that were or were not incubated with curcumin (25 µM) and the co-administration of transforming growth factor (TGF)- ß1 (10 ng/ml) or angiotensin (Ang) II (100 nM) by a cell migration analysis, proliferation assay, and Western blot analysis. Compared to those without curcumin, curcumin-treated cardiac fibroblasts exhibited lower migratory, proliferative abilities and collagen production at the baseline and after the co-administration of TGF-ß1 or Ang II. Curcumin-treated cardiac fibroblasts had increased matrix metalloproteinase (MMP)-2 activity in the presence of Ang II treatment. Curcumin-treated cardiac fibroblasts down-regulated phosphorylated protein kinase B (Akt) and phosphorylated Smad2/3 expression irrespective of TGF-ß1 treatment. Curcumin also decreased phosphorylated extracellular signal-regulated kinase (ERK)1/2 levels in the presence of Ang II. CONCLUSIONS: Curcumin attenuated Akt, Smad2/3, and ERK1/2 phosphorylation which were mediated by TGF-ß1 and angiotensin II. This resulted in decreased cardiac fibroblast activation and supports the assertion that curcumin is an effective antifibrotic agent which can be used to treat heart failure. KEY WORDS: Angiotensin; Curcumin; Fibroblasts; Heart failure; Transforming growth factor.

Lithium downregulates phosphorylated acetyl­CoA carboxylase 2 and attenuates mitochondrial fatty acid utilization and oxidative stress in cardiomyocytes.

Acetyl-CoA carboxylase 2 plays a crucial role in regulating mitochondrial fatty acid oxidation in cardiomyocytes. Lithium, a monovalent cation known for its cardioprotective potential, has been investigated for its influence on mitochondrial bioenergetics. The present study explored whether lithium modulated acetyl-CoA carboxylase 2 and mitochondrial fatty acid metabolism in cardiomyocytes and the potential therapeutic applications of lithium in alleviating metabolic stress. Mitochondrial bioenergetic function, fatty acid oxidation, reactive oxygen species production, membrane potential and the expression of proteins involved in fatty acid metabolism in H9c2 cardiomyocytes treated with LiCl for 48 h was measured by using a Seahorse extracellular flux analyzer, fluorescence microscopy and western blotting. Small interfering RNA against glucose transporter type 4 was transfected into H9c2 cardiomyocytes for 48 h to induce metabolic stress mimicking insulin resistance. The results revealed that LiCl at a concentration of 0.3 mM (but not at a concentration of 0.1 or 1.0 mM) upregulated the expression of phosphorylated (p-)glycogen synthase kinase-3 beta and downregulated the expression of p-acetyl-CoA carboxylase 2 but did not affect the expression of adenosine monophosphate-activated protein kinase or calcineurin. Cotreatment with TWS119 (8 µM) and LiCl (0.3 mM) downregulated p-acetyl-CoA carboxylase 2 expression to a similar extent as did treatment with TWS119 (8 µM) alone. Moreover, LiCl (0.3 mM) inhibited mitochondrial fatty acid oxidation, improved coupling efficiency and the cellular respiratory control ratio, hindered reactive oxygen species production and proton leakage and restored mitochondrial membrane potential in glucose transporter type 4 knockdown-H9c2 cardiomyocytes. These findings suggested that low therapeutic levels of lithium can downregulate p-acetyl-CoA carboxylase 2, thus reducing mitochondrial fatty acid oxidation and oxidative stress in cardiomyocytes.

Exercise capacity-hemodynamics mismatch in elderly patients with pulmonary hypertension: A nationwide multicenter study from Taiwan Society of Cardiology Pulmonary Hypertension Registry (TAIPANS).

Background: Demographics of pulmonary hypertension (PH) has changed a lot over the past forty years. Several recent registries noted an increase in mean age of PH but only a few of them investigated the characteristics of elderly patients. Thus, we aimed to analyze the characteristics of PH in such a population in this study. Methods: This multicenter study enrolled patients diagnosed with PH in group 1, 3, 4, and 5 consecutively from January 1, 2019 to December 31, 2020. A total of 490 patients was included, and patients were divided into three groups by age (≤45 years, 45-65 years, and >65 years). Results: The mean age of PH patients diagnosed with PH was 55.3 ± 16.3 years of age. There was higher proportion of elderly patients classified as group 3 PH (≤45: 1.3, 45-65: 4.5, >65: 8.1 %; p = 0.0206) and group 4 PH (≤45: 8.4, 45-65: 14.5, >65: 31.6 %; p < 0.0001) than young patients. Elderly patients had shorter 6-min walking distance (6 MWD) (≤45 vs. >65, mean difference, 77.8 m [95% confidence interval (CI), 2.1-153.6 m]), lower mean pulmonary arterial pressure (mPAP) (≤45 vs. >65, mean difference, 10.8 mmHg [95% CI, 6.37-15.2 mmHg]), and higher pulmonary arterial wedge pressure (PAWP) (≤45 vs. 45-65, mean difference, -2.1 mmHg [95% CI, -3.9 to -0.3 mmHg]) compared to young patients. Elderly patients had a poorer exercise capacity despite lower mPAP level compared to young population, but they received combination therapy less frequently compared to young patients (triple therapy in group 1 PH, ≤45: 16.7, 45-65: 11.3, >65: 3.8 %; p = 0.0005). Age older than 65 years was an independent predictor of high mortality for PH patients. Conclusions: Elderly PH patients possess unique hemodynamic profiles and epidemiologic patterns. They had higher PAWP, lower mPAP, and received combination therapy less frequently. Moreover, ageing is a predictor of high mortality for PH patients. Exercise capacity-hemodynamics mismatch and inadequate treatment are noteworthy in the approach of elderly population with PH.

An iTRAQ proteomic study reveals an association between diet-induced enhanced fatty acid metabolism and the development of glucose intolerance in prediabetic mice.

High-fat diet (HFD)-induced glucose intolerance and insulin resistance increases the chances of developing type-2 diabetes and cardiovascular disease. To study the mechanism(s) by which a HFD impairs glucose tolerance, we used a quantitative proteomic platform that integrated pI-based OFFGEL fractionation and iTRAQ labeling to profile the temporal changes in adipose membrane protein expression in mice fed a HFD for up to 8 months. Within 2 months of starting the diet, the mice adipose and liver tissues accumulated fat droplets, which contributed to subsequent insulin resistance and glucose intolerance within 6 months. The membrane proteomic delineation of such phenotypic expression resulted in quantification of 1713 proteins with 266, 343, and 125 differentially expressed proteins in 2-, 6-, and 8-month HFD-fed versus control mice, respectively. Pathway analysis of these differentially expressed proteins revealed the interplay between upregulation of fatty acid metabolism and downregulation of glucose metabolism. Substantial upregulation of adipose and liver carnitine palmitoyltransferase (Cpt) 1, the rate-limiting enzyme in the transport of long-chain fatty acids into mitochondria, occurred by 2 months. The increase in hepatic Cpt 1a expression was associated with a progressive decrease in glucose uptake as evidenced by downregulation of the liver glucose transporter protein (Glut) 2. Loss of glycogen storage was found in those hepatocytes full of fat droplets. Intriguingly, skeletal muscle Cpt 1b expression was unaltered by the HFD, whereas skeletal muscle Glut 4 and tyrosine phosphoryated insulin receptor substrate 1 (p-IRS1) were substantially upregulated at the same time as abnormal glucose metabolism developed in adipose and liver tissues. This study defines some of the molecular mechanisms as well as the relationship among adipose tissue, liver and skeletal muscle during development of HFD-induced glucose intolerance in vivo and identifies Cpt 1 as a potential drug target for the control or prevention of diabetes.