Irisin attenuates angiotensin II-induced atrial fibrillation and atrial fibrosis via LOXL2 and TGFβ1/Smad2/3 signaling pathways.

Figures

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  Figure 1. Serum irisin levels in AF patients and controls. (a) Serum irisin levels are higher in AF patients (n = 207) than in healthy controls (n = 160) (P<0.001). (b) Serum irisin levels are higher in the PeAF (n = 76) than in the PAF (n = 131). ***P<0.001

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  Figure 2. Irisin expression is decreased in Ang II-induced mice and increased by aerobic exercise. Mice were infused with saline or Ang II (2000 ng/kg/min) using osmotic mini-pumps for four weeks or kept in a sedentary state and subjected to aerobic exercise for four weeks. (a) Irisin protein levels in serum are significantly reduced in Ang-II-induced compared with control mice and are significantly increased in mice with aerobic exercise compared with sedentary mice. (b) mRNA levels of irisin precursor FNDC5 are determined in the atria muscle by RT-qPCR. (c) Representative bands of FNDC5 protein in atria muscle of mice by western blot. (d) Quantification of FNDC5 protein levels. Data are presented as mean ± SD (n=8 in each group). ***P<0.001 vs saline group; ###P<0.001 vs sedentary group

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  Figure 3. Irisin attenuates Ang II-induced susceptibility in AF. (a) For four weeks, representative atrial electrogram recordings of mice infused with saline, irisin, Ang II, and Ang II + irisin. (b) Numbers of AF episodes in mice. (c) Total AF duration. Data are presented as mean ± SD (n=8 in each group). ***P<0.001 vs saline group; ###P<0.001 vs Ang II group

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  Figure 4. Irisin inhibits Ang II-induced atrial apoptosis and inflammation. (a) Representative image of TUNEL staining in atrial tissues of mice. (b) Quantification of TUNEL-positive cells in atrial tissues. RT-qPCR was carried out to determine the mRNA expression of (c) TNF-α and (d) IL-6 in atrial tissues. n = 8 mice per group. ***P<0.001 vs control group; ###P<0.001 vs Ang II group

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  Figure 5. Irisin suppresses Ang II-induced atrial fibrosis. (a) Representative images of atrial fibrosis, which was stained with Masson trichrome. (b) Quantification of collagen volume fraction (%) is used to evaluate the fibrotic area. RT-qPCR analyses show (c) Collagen I and (d) Collagen III mRNA levels in atrial tissues. (e) Representative bands of proteins in atria muscle of mice by western blot. (f) Collagen I and (g) Collagen III proteins were quantified. n = 8 mice per group. ***P<0.001 vs control group; ##P<0.01, ###P<0.001 vs Ang II group

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  Figure 6. Irisin inhibited the fibroblast transdifferentiation of atrial tissue in Ang II-treated mice. (a) Immunohistochemistry image of α-SMA. (b) Quantification of the percentage of α-SMA-positive cells. n = 8 mice per group. ***P<0.001 vs control group; ###P<0.001 vs Ang II group

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  Figure 7. Irisin suppressed the expression of LOXL2 and TGFβ/Smad pathway in Ang II-treated mice. (a) Representative images of LOXL2 by immunohistochemistry. (b) Quantification of the percentage of LOXL2-positive cells. (c) Representative protein bands by western blot. Proteins are quantified for (d) LOXL2 (normalized to GAPDH), (e) TGFβ1 (normalized to GAPDH), (f) p-Smad2 (normalized to Smad2/3), and (g) p-Smad3 (normalized to Smad2/3). n = 8 mice per group. ***P<0.001 vs saline group; ##P<0.01, ###P<0.001 vs Ang II group