1 Veterans Affairs San Diego Healthcare System, San Diego, California, and University of California San Diego, San Diego, California.
2 Department of Medicine, University of California San Diego, San Diego, California.
Hum Gene Ther. 2019 Jun;30(6):682-692. doi: 10.1089/hum.2018.176. Epub 2019 Mar 8.
A fusion protein (C1C2) constructed by fusing the intracellular C1 and C2 segments of adenylyl cyclase type 6 (AC6) retains beneficial effects of AC6 expression, without increasing cyclic adenosine monophosphate generation. The effects of cardiac-directed expression in pressure overload is unknown. Left ventricular (LV) pressure overload was induced by transverse aortic constriction (TAC) in C1C2 mice and in transgene negative (TG-) mice. Four weeks after TAC, LV systolic function and diastolic function were measured, and Ca2+ handling was assessed. Four weeks after TAC, TG- animals showed reduced LV peak +dP/dt. LV peak +dP/dt in C1C2 mice was statistically indistinguishable from that of normal mice and was higher than that seen in TG- mice 4 weeks after TAC ( = 0.02), despite similar and substantial cardiac hypertrophy. In addition to higher LV peak +dP/dt , cardiac myocytes from C1C2 mice showed shorter time-to-peak Ca2+ transient amplitude ( = 0.002) and a reduced time constant of cytosolic Ca2+ decline (Tau; = 0.003). Sarcomere shortening fraction ( < 0.03) and the rate of sarcomere shortening ( < 0.02) increased in C1C2 cardiac myocytes. Myofilament sensitivity to Ca2+ was increased in systole ( = 0.02) and diastole ( = 0.04) in C1C2 myocytes. These findings indicate enhanced Ca2+ handling associated with expression. Favorable effects on Ca2+ handling and LV function were associated with increased LV SERCA2a protein content ( = 0.015) and reduced LV fibrosis ( = 0.008). Cardiac-directed expression improves Ca2+ handling and increases LV contractile function in pressure overload. These data provide a rationale for further exploration of C1C2 gene transfer as a potential treatment for heart failure.
腺嘌呤核苷酸环化酶 6（AC6）的细胞内 C1 和 C2 片段融合构建的融合蛋白（C1C2）保留了 AC6 表达的有益效果，而不会增加环腺苷酸的产生。其在心脏压力超负荷中的作用尚不清楚。通过横主动脉缩窄（TAC）在 C1C2 小鼠和转基因阴性（TG-）小鼠中诱导左心室（LV）压力超负荷。TAC 后 4 周，测量 LV 收缩功能和舒张功能，并评估 Ca2+处理。TAC 后 4 周，TG-动物的 LV 收缩期峰值+dp/dt 降低。C1C2 小鼠的 LV 收缩期峰值+dp/dt 与正常小鼠无统计学差异，且高于 TAC 后 4 周 TG-小鼠（=0.02），尽管存在相似且显著的心肌肥厚。除了更高的 LV 收缩期峰值+dp/dt 外，C1C2 小鼠的心肌细胞显示 Ca2+瞬变幅度达峰时间更短（=0.002）和胞浆 Ca2+下降的时间常数（Tau；=0.003）降低。C1C2 心肌细胞的肌节缩短分数（<0.03）和肌节缩短率（<0.02）增加。C1C2 心肌细胞收缩期和舒张期肌球蛋白对 Ca2+的敏感性增加（分别为=0.02 和=0.04）。C1C2 小鼠的 LV SERCA2a 蛋白含量增加（=0.015）和 LV 纤维化减少（=0.008）与 Ca2+处理和 LV 功能的有利影响相关。心脏定向表达改善 Ca2+处理并增加压力超负荷下的 LV 收缩功能。这些数据为进一步探索 C1C2 基因转移作为心力衰竭潜在治疗方法提供了依据。
