Maharani Nani, Ting Ya Kuang, Cheng Jidong, Hasegawa Akira, Kurata Yasutaka, Li Peili, Nakayama Yuji, Ninomiya Haruaki, Ikeda Nobuhito, Morikawa Kumi, Yamamoto Kazuhiro, Makita Naomasa, Yamashita Takeshi, Shirayoshi Yasuaki, Hisatome Ichiro
Division of Regenerative Medicine and Therapeutics, Department of Genetic Medicine and Regenerative Therapeutics, Institute of Regenerative Medicine and Biofunction, Tottori University Graduate School of Medical Science.
Circ J. 2015;79(12):2659-68. doi: 10.1253/circj.CJ-15-0416. Epub 2015 Oct 16.
Hyperuricemia induces endothelial dysfunction, oxidative stress and inflammation, increasing cardiovascular morbidities. It also raises the incidence of atrial fibrillation; however, underlying mechanisms are unknown.
The effects of urate on expression of Kv1.5 in cultured mouse atrial myocytes (HL-1 cells) using reverse transcriptase-PCR, immunoblots, flow cytometry and patch-clamp experiments were studied. Treatment with urate at 7 mg/dl for 24 h increased the Kv1.5 protein level, enhanced ultra-rapid delayed-rectifier K(+)channel currents and shortened action potential duration in HL-1 cells. HL-1 cells expressed the influx uric acid transporter (UAT), URATv1, and the efflux UATs, ABCG2 and MRP4. An inhibitor against URATv1, benzbromarone, abolished the urate effects, whereas an inhibitor against ABCG2, KO143, augmented them. Flow cytometry showed that urate induced an increase in reactive oxygen species, which was abolished by the antioxidant, N-acetylcysteine (NAC), and the NADPH-oxidase inhibitor, apocynin. Both NAC and apocynin abolished the enhancing effects of urate on Kv1.5 expression. A urate-induced increase in the Kv1.5 proteins was accompanied by phosphorylation of extracellular signal-regulated kinase (ERK), and was abolished by an ERK inhibitor, PD98059. NAC abolished phosphorylation of ERK by urate.
Intracellular urate taken up by UATs enhanced Kv1.5 protein expression and function in HL-1 atrial myocytes, which could be attributable to ERK phosphorylation and oxidative stress derived from nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase.
高尿酸血症可导致内皮功能障碍、氧化应激和炎症，增加心血管疾病的发病率。它还会提高心房颤动的发生率；然而，其潜在机制尚不清楚。
利用逆转录-聚合酶链反应、免疫印迹、流式细胞术和膜片钳实验，研究了尿酸盐对培养的小鼠心房肌细胞（HL-1细胞）中Kv1.5表达的影响。用7mg/dl尿酸盐处理24小时可增加HL-1细胞中Kv1.5蛋白水平，增强超快速延迟整流钾通道电流并缩短动作电位时程。HL-1细胞表达尿酸盐流入转运体（UAT）、尿酸盐转运体1（URATv1）以及尿酸盐流出转运体ABCG2和多药耐药相关蛋白4（MRP4）。URATv1抑制剂苯溴马隆可消除尿酸盐的作用，而ABCG2抑制剂KO143则增强其作用。流式细胞术显示尿酸盐可诱导活性氧增加，抗氧化剂N-乙酰半胱氨酸（NAC）和烟酰胺腺嘌呤二核苷酸磷酸（NADPH）氧化酶抑制剂夹竹桃麻素可消除这种增加。NAC和夹竹桃麻素均消除了尿酸盐对Kv1.5表达的增强作用。尿酸盐诱导的Kv1.5蛋白增加伴随着细胞外信号调节激酶（ERK）的磷酸化，ERK抑制剂PD98059可消除这种作用。NAC可消除尿酸盐引起的ERK磷酸化。
UAT摄取细胞内尿酸盐可增强HL-1心房肌细胞中Kv1.5蛋白的表达和功能，这可能归因于ERK磷酸化以及NADPH氧化酶产生的氧化应激。
