Cogolludo Angel, Moreno Laura, Lodi Federica, Tamargo Juan, Perez-Vizcaino Francisco
Department of Pharmacology, School of Medicine, Universidad Complutense, 28040 Madrid, Spain.
Cardiovasc Res. 2005 Apr 1;66(1):84-93. doi: 10.1016/j.cardiores.2004.12.019. Epub 2005 Jan 27.
The neonate is at high risk of developing pulmonary hypertension, which may reflect a misbalance between vasodilator and vasoconstrictor agents. Thromboxane A(2) (TXA(2)) is involved in several forms pulmonary hypertension, but the signaling pathways mediating its pulmonary vasoconstrictor responses during postnatal maturation have not been analyzed. We therefore investigated the role of L-type Ca(2+) channels, protein kinase C (PKC) zeta, voltage-gated K(+) channels (K(V)), and RhoA/Rho kinase in TXA(2)-induced pulmonary vasoconstriction during postnatal maturation.
Changes in contractility and intracellular calcium were analyzed in 1 day (newborn) and 2-week-old piglets' pulmonary arteries (PA). K(V) currents were investigated in freshly isolated smooth muscle cells using the whole-cell configuration of the patch clamp technique.
The contractile responses to the TXA(2) mimetic U46619 were similar at both ages but the L-type Ca(2+) channel blocker nifedipine and a PKCzeta pseudosubstrate inhibitor only attenuated the contraction in newborn PA. K(V) currents were similarly inhibited by U46619, although their density was dramatically reduced in 2-week-old as compared to newborn PA smooth muscle cells. This was consistent with a greater contraction to the K(V) inhibitor, 4-aminopyridine, and with a leftward shift in the increase in intracellular Ca(2+) by U46619 in newborn versus older animals. On the other hand, the Rho kinase inhibitor Y-27632 induced a stronger inhibitory effect on the contraction induced by U46619 in 2-week-old than in newborn PA and this was accompanied with minor effects on intracellular calcium levels.
TXA(2)-induced pulmonary vasoconstriction involves PKCzeta-K(V)-L-type Ca(2+) channel and RhoA/Rho kinase signaling pathways, which are downregulated and upregulated, respectively, during postnatal maturation. The different contribution of these pathways could be of relevant importance for the vasodilator therapy choice in the treatment of pulmonary hypertension.
新生儿患肺动脉高压的风险很高，这可能反映了血管舒张剂和血管收缩剂之间的失衡。血栓素A2（TXA2）与多种形式的肺动脉高压有关，但在出生后成熟过程中介导其肺血管收缩反应的信号通路尚未得到分析。因此，我们研究了L型钙通道、蛋白激酶C（PKC）ζ、电压门控钾通道（Kv）和RhoA/Rho激酶在出生后成熟过程中TXA2诱导的肺血管收缩中的作用。
分析了1日龄（新生）和2周龄仔猪肺动脉（PA）的收缩性和细胞内钙的变化。使用膜片钳技术的全细胞配置，在新鲜分离的平滑肌细胞中研究Kv电流。
对TXA2模拟物U46619的收缩反应在两个年龄段相似，但L型钙通道阻滞剂硝苯地平和PKCζ假底物抑制剂仅减弱新生PA的收缩。U46619同样抑制Kv电流，尽管与新生PA平滑肌细胞相比，其密度在2周龄时显著降低。这与对Kv抑制剂4-氨基吡啶的更大收缩一致，并且与新生动物相比，U46619在新生动物中细胞内钙增加的左移一致。另一方面，Rho激酶抑制剂Y-27632对2周龄PA中U46619诱导的收缩的抑制作用比对新生PA更强，并且这伴随着对细胞内钙水平的轻微影响。
TXA2诱导的肺血管收缩涉及PKCζ-Kv-L型钙通道和RhoA/Rho激酶信号通路，它们在出生后成熟过程中分别下调和上调。这些通路的不同贡献对于肺动脉高压治疗中血管舒张剂治疗的选择可能具有重要意义。
