Inhibition of Src kinase activity reduces heart rate without significant alteration of heart rate variability

藉由抑制Src激酶的活性來談討對心率之調控及心率變異之影響

張博鳴(Po-Ming Chang) ； 李貫綸(Kun-Lun Li) ； 林彥昌(Yen-Chang Lin)

《華岡農科學報》 35期 (2015/06) Pp. 123-134

摘要

Heart rate variability (HRV) is the cardiac index representing the oscillation of the intervals between consecutive heartbeats (RR intervals in the ECG). It reflects the influences of the autonomic nervous system (ANS) on the sinus node. In order to investigate the involvement of tyrosine phosphorylation in cardiac function of the whole rat system and its effect on HRV, we employed a potent selective inhibitor of Src family kinases, PP2 (4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyramidine), to inhibit the activity of Src kinases that include Src, Fyn, and Yes. Heart rate was decreased 20% by PP2 at the dose of 0.2 mg/kg. PP3, a negative control compound of PP2, which does not inhibit the activity of Src kinases decreased heart rate by 8% (when at the identical dose of 0.2 mg/kg) when compared with the basal. Interestingly, HRV was not significantly altered at a relatively low dose of PP2 (0.2 mg/kg) when compared with that of PP3 or the basal. Unlike that of PP2, HRV was significantly decreased after application of 0.4 μg/kg isoproterenol. Similar to that of PP2, ZD7288, a specific inhibitor of HCN channels, when at the low dose of 0.2 mg/kg, was able to decrease the heart rate without significant change of HRV in comparison to isoproterenol. Furthermore, atrial ventricular block (AV block) can be induced at the higher dose of PP2 (0.3 mg/kg) whereas in ZD7288, higher dose application (0.7 mg/kg) can elicit both premature ventricular contraction (PVC) and AV block. Although PP2 and ZD7288 slightly increased the short-term (SD1) and the long-term (SD2) HRV, larger degree of increase in SD1 or SD2 was observed in isoproterenol. The fractal scaling exponent alpha 1 (α1) in basal level was 0.640, which was comparable to that of PP3 (0.605), but slightly decreased in PP2 (0.328) and ZD7288 (0.144) at the low dose of 0.2 mg/kg. Overall, PP2, like ZD7288, can serve as a potential candidate in the treatment of tachycardia-induced arrhythmias via inhibition of Src-mediated tyrosine phosphorylation.

關鍵字

HRV ； tyrosine phosphorylation ； atrial ventricular block ； premature ventricular contraction

並列摘要

心率變異（heart rate variability, HRV）是代表連續心跳間的時間間隔（ECG 的RR interval）振盪的心臟指數。它反映了自主神經系統（autonomic nervous system, ANS）對竇房結的影響。為了研究酪氨酸磷酸化（tyrosine phosphorylation ） 對大鼠心臟功能及其心率變異的影響， 我們利用Src 家族激酶的強效抑製劑PP2(4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyramidine)來抑制包括Src，Fyn 和Yes 等Src 激酶的活性。通過給予0.2 mg/kg 劑量的PP2 能減少20％的心跳速率。PP3，是一種PP2 的陰性對照化合物，不會抑制Src 激酶的活性。給予相同劑量（0.2 mg/ kg）時，與正常狀態相比心臟速率會下降8％。有趣的是，當與PP3或正常狀態相比，在相對較低劑量的PP2（0.2mg/kg）時，HRV 沒有顯著的改變。與PP2 不同的是，給予0.4 μg/kg的isoproterenol 後，HRV 有顯著的下降。對HCN通道（Hyperpolarization-activated and cyclic nucleotide-gated channels）具特異性的抑製劑ZD7288（類似PP2），在0.2 mg/ kg（低劑量）下，與isoproterenol 相比能降低心臟速率，但HRV 變化則不顯著。此外，在給予高劑量PP2（0.3 mg/kg）房室傳導阻滯（atrial ventricular block, AV block）會被誘導，而高劑量（0.7 mg/kg）的ZD7288，會引起心室性早搏（premature ventricular contraction, PVC）和AV block。雖然PP2 和ZD7288 能略為增加短期（SD1）和長期（SD2）的HRV，在給予isoproterenol 時，則可觀察到SD1 或SD2 增加的幅度較大。在0.2 mg/kg 的低劑量下，分形標度指數（fractal scaling exponent）的alpha 1 （α1）在正常值為0.640，PP3 為0.605，但在PP2 和ZD7288 則略微下降（分別為0.328 和0.144）。整體來說，PP2 和ZD7288，對通過抑制由Src 誘導酪氨酸磷酸化的心動過速性心律失常，可被視為具有潛力的治療方法。

並列關鍵字

心率變異 ； 酪氨酸磷酸化 ； 房室傳導阻滯 ； 心室性早搏