Protection of Ang1-7 througth MKK/P38MAPKs inflammatory signal pathway on TNF-α stimulated mouse HL-1 cells

Background to explore the effect of Ang1-7 througth MKK/P38MAPKs inflammatory signaling pathway on TNF-α-stimulated mouse HL-1 cells. Methods Using TNF-α (100 µg/ml) to establish an inflammatory atrial fibrillation model in HL-1 cell, which derived from mouse atrial myocyte. treated HL-1 cells with different concentrations of Ang 1-7 (0.1, 1 and 10 mmol/L) and divided into 5 groups, namely A group(control group), B group(TNF ), C group(TNF + Ang 1-7 0.1 mmol/L), D group(TNF + Ang 1-7 1 mmol/L ) and E group(TNF + Ang 1-7 10 mmol/L ). Firstly, different concentrations of Ang 1-7 (0.1 mmol/L, 1 mmol/L and 10 mmol/L) were used to stimulate for half an hour, and then TNF-α (100 µg/ml) was added to stimulate for four hours. Both the cells and supernatant were collected. Cells were collected for Western Blotting to detect the protein expression of MKK3, MKK4, MKK6, PMMK4 and PP38. The supernatant was subjected to flow cytometry for detecting multi-inflammatory factors. Results Compared with the A group, the protein expression of MKK3, MKK4, MKK6, PMMK4 and PP38 was statistically significant increased after stimulation with inflammatory factors (TNF-α) (P < 0.05). After intervention with Ang 1-7, the protein expression of MKK3, MKK4, MKK6, PMMK4 and PP38 was statistically significant lower than that of B group (P < 0.05). There is no significant difference of the protein expression of P38 after stimulation with inflammatory factor (TNF-α). Compared with the A group, there was no significant difference in the protein expression of MAS after the stimulation of inflammatory factor (TNF-α). After the intervention of Ang 1-7, the protein expression of MAS was higher than that of the A group and B group, but there was no significant difference (P > 0.05). The expression of MAS protein had an increasing trend, but there was no significant difference (P > 0.05). TGF-β, TNF-α was significantly increased after stimulating factor (TNF-α) was given, but was decreased after the intervention of Ang 1-7, both there were statistically significant (P < 0.05). IL-6 also had the same trend, but there was no significant difference. Conclusion Ang1-7 througth MKK/P38MAPKs inflammatory signal pathway protected on TNF-α stimulated mouse HL-1 cells

Low-Level Vagus Nerve Stimulation Reverses Obstructive Sleep Apnea-Related Atrial Fibrillation by Ameliorating Sympathetic Hyperactivity and Atrial Myocyte Injury

Background: Previous studies have proved that low-level vagus nerve stimulation (LLVS) could suppress acute obstructive sleep apnea (OSA), which is associated with atrial fibrillation (AF).Objective: This study investigates the underlying electrophysiological, neural, and cardiomyocyte injury mechanisms on acute OSA-induced AF, examining whether LLVS can attenuate or reverse this remodeling.Methods and Results: Eighteen mongrel dogs received endotracheal intubation under general anesthesia and were randomly divided into three groups: the OSA group (simulated OSA with clamping of the trachea cannula at the end of expiration for 2min followed ventilation 8min, lasting 6h, n=6), the OSA+LLVS group (simulated OSA plus LLVS, n=6), and a control group (sham clamping the trachea cannula without stimulation, n=6). In the OSA+LLVS group, the atrial effective refractory period was significantly lengthened while the sinus node recovery time and AF duration decreased after the 4th hour, and the expression level of Cx40 and Cx43 was significantly increased compared to the OSA group. Norepinephrine, TH, and ChAT were significantly decreased in the OSA+LLVS group compared with the OSA group. Mitochondrial swelling, cardiomyocyte apoptosis, and glycogen deposition, along with a higher concentration of TNF-α, IL-6 were observed in the OSA group, and the LLVS inhibited the structural remodeling and expression of inflammatory cytokines.Conclusion: LLVS decreased the inducibility of AF partly by ameliorating sympathetic hyperactivity and atrial myocyte injury after acute OSA-induced AF.

The selective late sodium current inhibitor eleclazine reduces atrial fibrillation dominant frequency and facilitates the suppression of arrhythmia in HL-1 cells

Background The cardiac late sodium current (INaL) has been increasingly implicated in the initiation of atrial fibrillation (AF). In fact, it has been reported that the augmentation of INaL in pathophysiological conditions prolongs repolarization and facilitates the appearance of afterdepolarizations, which can act as triggers of arrhythmic activity. Eleclazine is a novel selective inhibitor of INaL and is undergoing clinical testing for the treatment of cardiac arrhythmias. Purpose The aim of this study was to investigate the effects of eleclazine on spectral characteristics of atrial fibrillation in cultured atrial myocyte monolayer in order to assess whether this inhibitor could protect against cardiac arrhythmias. Methods Confluent HL-1 murine atrial myocyte monolayer with spontaneous fibrillatory activity was cultured in 1.5 cm diameter petri dishes (n=10). A high-resolution optical mapping system was used to record fibrillatory activity under basal conditions (without drug), and under eleclazine at increasing concentrations (1, 3 and 5 μM). Power spectra of optical signals were estimated by using Welch periodogram and dominant frequency (frequency with the largest peak in the spectrum between 0.05 and 30 Hz) was determined. The incidence of spontaneous defibrillation was analyzed under control and drug conditions. An ANOVA and a chi-squared test were used. Significance was reached when p&lt;0.05. Results Eleclazine at 1, 3 and 5 μM significantly decreased dominant frequency with respect to basal conditions (basal: 4.74±1.31 Hz; 1μM: 3.59±1.17 Hz, p&lt;0.001; 3μM: 3.19±0.64 Hz, p&lt;0.01; 5μM: 2.58±0.40 Hz, p&lt;0.01). The magnitude of drug-induced decrease in AF activation frequency was enhanced by increasing concentrations (1μM: 27%, 3μM: 42%; 5μM: 46%; p&lt;0.05). After the analysis of optical signals, we observed that the incidence of spontaneous defibrillation in atrial monolayers was significantly greater under eleclazine 5μM action than under control conditions (chi-square=5.00, p=0.025). In fact, under the action of eleclazine 5μM, fibrillatory activity was suppressed in 4 of the 10 monolayers, phenomenon that did not occur in any case of control situation. Conclusions Selective late INa inhibition with eleclazine reduced dominant frequency of atrial fibrillation and facilitates the termination of arrhythmia in cultured atrial myocyte monolayer. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Instituto de Salud Carlos III, Ministerio de Innovaciόn y Ciencia, Spain; Generalitat Valenciana, Spain