Angiotensin‐receptor blocker losartan alleviates atrial fibrillation in rats by downregulating frizzled 8 and inhibiting the activation of WNT‐5A pathway

Abstract Atrial fibrillation (AF) is a common arrhythmia. Angiotensin‐receptor blocker (ARB) is related to AF treatment. This study explored the mechanism of ARB in AF. AF rat models were established by Ach‐CaCl2 mixed solution injection. Rats were treated with ARB by gavage and injected with pcDNA3.1‐based frizzled homolog 8 (FZD8) overexpression plasmids (oe‐FZD8) through the tail vein. The 12‐lead electrocardiogram was recorded by biological signal acquisition and processing system and AF duration was recorded, and atrial effective refractory period (AERP) was monitored by electrophysiology. Atrial fibrosis degree, FZD8 messenger RNA and protein levels, collagen I, collagen III, transforming growth factor β1 (TGF‐β1), fibronectin, α smooth muscle actin (α‐SMA), WBT‐5B, and p‐JNK1/2 levels, interleukin 1 β (IL‐1β) and interleukin 6 (IL‐6) levels were detected by Masson staining, reverse transcription quantitative polymerase chain reaction, western blot assay, immunohistochemistry, and enzyme‐linked immunosorbent assay. ACh‐CaCl2‐induced AF rats showed a large area of fused necrosis, abnormal collagen fibre proliferation, high atrial fibrosis degree, and increased atrial fibrosis area in atrial interstitium, elevated collagen I, collagen III, TGF‐β1, fibronectin, α‐SMA, IL‐1β, and IL‐6 levels, whereas these trends were averted by ARB treatment. FZD8 was highly expressed in AF rat myocardium. ARB repressed FZD8 expression, prolonged AERP and reduced AF incidence. FZD8 overexpression annulled the effects of ARB on improving AF rat myocardial fibrosis. ARB inactivated the WNT‐5A pathway by suppressing FZD8. ARB inactivated the WNT‐5A pathway by silencing FZD8, therefore, alleviating AF rat atrial fibrosis.