慢性肾脏病循环中FGF23对心房纤维化的促进作用

Promoting effect of circulating FGF23 on atrial fibrosis in chronic kidney disease

目的探究慢性肾脏疾病(CKD)循环中成纤维细胞生长因子(FGF)23通过与心房组织成纤维细胞生长因子受体(FGFR)4结合促进心房纤维化的可能机制。方法选择健康雄性SD大鼠22只,随机数字表法抽取14只行5/6肾切除手术并且喂养15周建立CKD模型,剩余8只作为假手术(Sham)组。观察2组体质量、血压、肾功能、超声心动图、心外膜电标测以及病理指标。酶联免疫吸附试验测定2组大鼠循环中的FGF23水平,左心房组织转录组测序寻找差异表达基因。大鼠心房成纤维细胞分为对照组、FGFR抑制剂组、转化生长因子-β(TGF-β)组及TGF-β+FGFR抑制剂组,采用Western blot法检测α-平滑肌肌动蛋白(α-SMA)、胶原蛋白Ⅰ(ColⅠ)以及磷酸化蛋白激酶B(p-AKT)蛋白的表达。结果CKD组大鼠收缩压、肌酐以及血尿素氮水平升高。心脏电生理检查显示CKD可促进心房颤动及房室传导阻滞的发生。心脏超声提示CKD组左心房内径明显增大,病理染色显示CKD组左心房发生明显纤维化,心外膜电标测提示CKD组大鼠左心房电传导速度明显减慢并且传导异质性明显增加。CKD大鼠循环中的FGF23水平明显增加。Western blot检测发现CKD组大鼠FGFR4表达上调。阻断心房成纤维细胞FGF23/FGFR4信号通路后,纤维化相关蛋白α-SMA、ColⅠ及p-AKT/AKT降低。结论CKD可能通过诱导心房结构重构及电重构促进房颤的发生,循环中增加的FGF23可能通过与心房组织中FGFR4结合启动下游AKT通路,进而促进心房纤维化。

Objective To explore the possible mechanisms by which fibroblast growth factor(FGF)23 promoted atrial fibrosis in circulation of chronic kidney disease(CKD)by binding to atrial tissue fibroblast growth factor receptor(FGFR)4.Methods Twenty-two healthy male Sprague-Dawley(SD)rats were selected.Rats were randomly selected to undergo 5/6 nephrectomy and fed for 15 weeks to establish a CKD model(n=14).The remaining 8 rats were used as the sham group.The sham group(n=8)underwent the same surgery without removing renal tissue.Body weight,blood pressure,renal function,cardiac ultrasound,epicardial electrocardiography and pathological indices were monitored in both groups.Enzyme-linked immunosorbent assay(ELISA)method was used to determine the circulating levels of FGF23 in the two groups of rats.Transcriptomic analysis of left atrial tissue was performed to search for differentially expressed genes.Rat atrial fibroblasts were divided into the control group,the FGFR inhibitor group,the transforming growth factor-β(TGF-β)group and the TGF-β+FGFR inhibitor group.The expression levels ofα-smooth muscle actin(α-SMA),collagenⅠ(ColⅠ)and phosphorylated protein kinase B(p-AKT)protein were detected by Western blot assay.Results Systolic blood pressure,blood urea nitrogen and creatinine were elevated in the CKD group of rats.Cardiac electrophysiological study showed that CKD could promote the occurrence of atrial fibrillation(AF)and atrioventricular block.Cardiac ultrasound suggested that the internal diameter of the left atrium was significantly increased in rats of the CKD group.Pathological findings showed that the left atrium in the CKD group underwent significant fibrosis,and epicardial electrical markers showed that left atrial electrical conduction velocity was significantly slower and conduction heterogeneity was significantly increased in the CKD group.These changes were accompanied by higher circulating FGF23.Western blot results showed that FGFR4 expression was upregulated in the CKD group.After blocking the FGF23/FGFR4 signaling pathway in atrial fibroblasts,the fibrosis-related proteinsα-SMA,ColⅠand p-AKT/AKT were decreased.Conclusion CKD promotes the occurrence of AF by inducing both structural and electrical remodeling.Increased circulating FGF23 promotes atrial fibrosis by activating the downstream AKT pathway binding to FGFR4 in atrial tissue.