Linagliptin Suppresses Electrical and Structural Remodeling in the Isoproterenol Induced Myocardial Injury Model.

The effect of DPP-4 inhibitor on the electrical and structural remodeling in myocardial injury has not been evaluated. We hypothesized that linagliptin, DPP-4 inhibitor, suppresses myocardial remodeling in the isoproterenol (ISP)-induced myocardial injury model.Sprague-Dawley rats were assigned to 3 groups: 1) sham group, 2) ISP group (subcutaneous ISP injection of 70 mg/kg), and 3) ISP + linagliptin (ISP + Lin) (5 mg/kg/day, p.o.) group. Serum was sampled on day 1 (acute phase) and day 7 (sub-acute phase) to evaluate derivatives of reactive oxidative metabolites (d-ROMs). The electrophysiological study was performed in sub-acute phase for the evaluation of the ventricular effective refractory period (VERP) and monophasic action potential duration (MAPD). The VERP and MAPD were markedly prolonged in the ISP group in comparison with the sham (MAPD20: 14 ± 6 versus 11 ± 3 ms, MAPD90: 57 ± 8 versus 44 ± 7 ms, VERP: 74 ± 22 versus 38 ± 10 ms, P < 0.05). In contrast in the ISP + Lin group, such prolongations were suppressed, and the parameters were shorter than the ISP group (MAPD20: 9 ± 2 ms, MAPD90: 35 ± 6 ms, VERP: 52 ± 13 ms, P < 0.05). ISP treatment induced myocardial injury. The injured area was reduced in the ISP + Lin group in comparison with the ISP group (P < 0.05). Serum d-ROMs level in acute phase was higher in ISP group than the other 2 groups (sham: 214 ± 55 versus ISP: 404 ± 45 versus ISP + Lin: 337 ± 20 U.CARR, P < 0.05).Linagliptin suppressed structural and electrical changes, possibly through the antioxidative effect, in this myocardial injury model.

Rivaroxaban Inhibits Angiotensin II-Induced Activation in Cultured Mouse Cardiac Fibroblasts Through the Modulation of NF-κB Pathway.

Cell migration, proliferation, and differentiation of cardiac fibroblasts (CFs) play a central role in cardiac fibrosis. Factor Xa (FXa)-dependent protease-activated receptor (PAR)-1 and PAR-2 have been reported as important targets in proinflammatory and fibroproliferative diseases. From this viewpoint, we aimed to investigate whether treatment of rivaroxaban, an approved oral direct FXa inhibitor, attenuates functional changes in angiotensin (Ang) II-induced mouse CFs.Confluent cultured mouse CFs were pretreated with or without rivaroxaban. Ang II-induced cell migration was decreased by 73% in rivaroxaban induced cells. Rivaroxaban inhibited Ang II-induced cell proliferation by 27% at 0.01 µg/ mL, 69% at 0.1 µg/mL, 71% at 1 µg/mL, and 69% at 5 µg/mL. In mouse cytokine array measuring 40 cytokines, the productions of interleukin-16, TIMP-1, and tumor necrosis factor-α (TNF-α) were significantly reduced with 0.1 µg/mL of rivaroxaban pretreatment (all P < 0.05). TIMP-1 levels in the culture supernatant measured by ELISA were also decreased by rivaroxaban pretreatment in Ang II-induced CFs (35% decrease at 0.01 µg/mL, 47% at 0.1 µg/mL, 47% at 1 µg/mL, and 57% at 5 µg/mL). In the dual reporter assay analysis, rivaroxaban inhibited various inflammatory signal pathways, including the nuclear factor-kappa B (NF-κB), active protein-1 (AP-1), and mitogen-activated protein kinase (MAPK) pathways (decreases of 82%, 78%, and 75%, respectively).These data suggest that rivaroxaban inhibits Ang II-induced functional activation in cultured mouse CFs via inhibiting NF-κB and MAPK/AP-1 signaling pathways, which may be a possible target of heart failure, through the antifibrotic and anti-inflammatory efficacy of rivaroxaban in Ang II-stimulated cardiac fibroblasts.

Progression of ventricular remodeling and arrhythmia in the primary hyperoxidative state of glutathione-depleted rats.

BACKGROUND: Although oxidative stress is considered to promote arrhythmogenic substrates in diseased model animals, it is difficult to evaluate its primary role. In this study, we evaluated the promotion of arrhythmogenic substrates in the primary hyperoxidative state. METHODS AND RESULTS: Sprague-Dawley rats were treated with L-buthionine-sulfoximine (BSO, 30 mmol · L(-1) · day(-1)) for 14 days. On day 7 or 14, the serum levels of derivatives of reactive oxygen metabolites (d-ROM) were measured, and immune staining of 8-hydroxy-2'-deoxyguanosine (8O HdG) was performed to assess oxidative stress. The ventricular effective refractory period (ERP), monophasic action potential duration (MAPD), and the inducibility of ventricular arrhythmia were also evaluated. BSO rats exhibited higher serum d-ROM and clearer 8OHdG staining than the controls. The inducibility of ventricular arrhythmia was higher in the BSO rats than in the controls. The ERP was shorter in the BSO rats than the control (day 14, 32 ± 1 vs. 36 ± 1 ms, P<0.05), whereas the MAPD(90) was longer in the BSO rats (day 14, 76 ± 5 vs. 55 ± 4 ms, P<0.05). The mRNA levels of Kv4.2, erg, and SERCA2a were downregulated in the BSO rats (P < 0.05), and Western blot analysis exhibited the downregulation of erg and SERCA2 expression in the BSO rats (P < 0.05). CONCLUSIONS: Systemic oxidative stress might be one of the primary factors promoting cardiac electrophysiological remodeling and increasing the inducibility of arrhythmia independently of major organ disorders.

N-acetylcysteine suppresses the progression of ventricular remodeling in acute myocarditis: studies in an experimental autoimmune myocarditis (EAM) model.

BACKGROUND: Electrical and structural remodeling, characterized by prolonged action potential duration (APD), Kv4.2 downregulation and cellular infiltration were studied in rat experimental autoimmune myocarditis (EAM). Because the reactive oxygen species (ROS) has been speculated to play a role in the promotion of such remodeling, the effect of N-acetylcysteine (NAC) on the progression of ventricular remodeling was evaluated. METHODS AND RESULTS: Six-week-old Lewis rats were immunized with porcine cardiac myosin. On Days 10-11 after the immunization, NAC (0, 1, 10, or 100mg) was injected intraperitoneally to EAM and control rats. On Day 14, the electrophysiological parameters were evaluated and the expression levels of the mRNA were examined by quantitative real-time reverse-transcription polymerase chain reaction (RT-PCR).The EAM rats exhibited a typical acute myocarditis with prolonged APD and reduced Kv4.2 expression as previously reported. The myocarditis and electrical changes were significantly suppressed by NAC-treatment in a dose-dependent manner (P<0.05). In rats with 100mg NAC, the myocarditis was almost totally negated although the mortality increased. In rats with 1mg NAC, the suppression of myocarditis was not obvious, but APD prolongation and Kv4.2 reduction was attenuated (P<0.05). CONCLUSIONS: The NAC treatment suppressed ventricular remodeling in the EAM rats. This may indicate the role of oxidative stress in causing remodeling and myocarditis itself in the acute phase of myocarditis.

Tumor necrosis factor-alpha downregulates the voltage gated outward K+ current in cultured neonatal rat cardiomyocytes: a possible cause of electrical remodeling in diseased hearts.

BACKGROUND: Inflammatory cytokines have been reported to contribute to the progression of cardiac remodeling in various heart diseases and a remarkable prolongation of the monophasic action potential duration and reductions in the expression of Kv4.2 and K+ channel-interacting protein-2 (KChIP-2) in a rat autoimmune myocarditis model have been documented. In this study, the effect of tumor necrosis factor-alpha (TNF-alpha) on cultured cardiomyocytes was evaluated, focusing on the change in the voltage-gated outward K+ current and expression of related molecules. METHODS AND RESULTS: Cardiomyocytes isolated from 1-day-old Lewis rats were cultured for 72 h and treated with TNF-alpha (50 ng/ml) for an additional 48 h. The myocytes treated with TNF-alpha showed a 22% reduction in the peak K+ current, which consisted of a transient outward K+ current (Ito) and 1.4-fold enhancement of the cell-capacitance in comparison with the control. Among the cardiac ion channel related molecules evaluated in this study, Kv4.2 and KChIP-2 mRNA exhibited remarkable reductions (p < 0.05). CONCLUSIONS: Treatment with TNF-alpha induced reductions in Ito as well as cellular hypertrophy in neonatal cultured myocytes, which indicates that TNF-alpha might play a role in promoting electrical remodeling of cardiomyocytes under inflammatory conditions.

In vitro effect of cyclosporin A, mitomycin C and prednisolone on cell kinetics in cultured human umbilical vein endothelial cells.

INTRODUCTION: Vascular endothelial cell damage plays an important role in microvascular thrombogenesis. In vivo administration of cyclosporin A or mitomycin C sometimes results in thrombotic microangiopathy in patients. MATERIALS AND METHODS: The effects of cyclosporin A, mitomycin C and/or prednisolone on the cell cycle in cultured human umbilical vein endothelial cells were investigated to evaluate drug-induced endothelial cell damage and the protective effect of prednisolone on endothelial cells against the damage by cyclosporin A or mitomycin C in vitro. RESULTS: The addition of cyclosporin A to cultures caused proliferation arrest in the G1-phase in a dose-dependent manner, while mitomycin C inhibited DNA synthesis, which resulted in cell cycle arrest and inhibition of BrdUrd incorporation in the S-phase. The administration of prednisolone also caused cell cycle arrest in the G1 by itself, and protected the cells from the damage caused by mitomycin C. The inhibitory effects of cyclosporin A and prednisolone on the cell cycle were reversible, while mitomycin C was not. The highly phosphorylated retinoblastoma protein expressed in human umbilical vein endothelial cells decreased in the presence of mitomycin C. Soluble thrombomodulin levels in the culture supernatant were elevated by the addition of cyclosporin A. CONCLUSION: These effects of the drugs may cause the cell cycle arrest and the prolonged repair of damaged endothelial cells in patients.

Immunomodulatory effect of pentoxifylline in suppressing experimental autoimmune myocarditis.

Although a recent clinical study reported the beneficial effects of pentoxifylline (PTX), a phosphodiesterase inhibitor, on both symptoms and cardiac function in dilated cardiomyopathy (DCM), the precise mechanism of the drug has not been delineated. This study examined the efficacy of PTX in the treatment of experimental autoimmune myocarditis (EAM), as a model of the autoimmune mechanism involved in DCM. Oral PTX, or saline as control, was administered to Lewis rats at 150mg/kg body weight per day bid daily from 5 days before immunization with cardiac myosin until death on Day 21. Histological examination of the hearts showed PTX significantly reduced the severity of EAM. mRNA expression of tumor necrosis factor (TNF)-alpha, interleukin (IL)-4, IL-6, and IL-10 was significantly reduced in peripheral blood mononuclear cells, but expression of IL-4 and IL-6 was upregulated in heart tissue. PTX in vitro could suppress T cell proliferation and inhibit TNF-alpha and interferon-gamma production. In conclusion, the immunomodulatory effects of PTX had a significant therapeutic result in EAM. This is the first report to describe such an effect of PTX in a specific animal model for DCM.