Sammut I A, Foresti R, Clark J E, Exon D J, Vesely M J, Sarathchandra P, Green C J, Motterlini R
Department of Surgical Research, Northwick Park Institute for Medical Research, Harrow, Middlesex.
Br J Pharmacol. 1998 Dec;125(7):1437-44. doi: 10.1038/sj.bjp.0702212.
The contribution of haeme oxygenase-derived carbon monoxide (CO) to the regulation of vascular tone in thoracic aorta was investigated following induction of the inducible isoform of haeme oxygenase (HO-1). Isometric smooth muscle contractions were recorded in isolated rat aortic ring preparations. Rings were incubated in the presence of the nitric oxide (NO) donor S-nitroso-N-acetyl penicillamine (SNAP, 500 microM) for 1 h, then repetitively washed and maintained for a further 4 h prior to producing a concentration-response curve to phenylephrine (PE, 1-3000 nM). Treatment with SNAP resulted in increased mRNA and protein expression of aortic HO-1 and was associated with a significant suppression of the contractile response to PE (P<0.05 vs control). Immunohistochemical staining procedures revealed marked HO-1 expression in the endothelial layer and, to a lesser extent, in smooth muscle cells. Induction of HO-1 in SNAP-treated rings was associated with a higher 14CO release compared to control, as measured by scintillation counting after incubation of aortas with [2-14C]-L-glycine, the precursor of haeme. Guanosine 3',5'-monophosphate (cyclic GMP) content was also greatly enhanced in aortas expressing high levels of HO-1. Incubation of aortic rings with the NO synthase inhibitor, NG-monomethyl-L-arginine (100 microM), significantly (P<0.05) increased the contractile response to PE in controls but failed to restore PE-mediated contractility in SNAP-treated rings. In contrast, the selective inhibitor of haeme oxygenase, tin protoporphyrin IX (SnPP-IX, 10 microM), restored the pressor response to PE in SNAP-treated rings whilst markedly reducing CO and cyclic GMP production. We conclude that up-regulation of the HO-1/CO pathway significantly contributes to the suppression of aortic contractility to PE. This effect appears to be mediated by the elevation of cyclic GMP levels and can be reversed by inhibition of the haeme oxygenase pathway.
在诱导血红素加氧酶（HO-1）的可诱导同工型后，研究了血红素加氧酶衍生的一氧化碳（CO）对胸主动脉血管张力调节的作用。在分离的大鼠主动脉环标本中记录等长平滑肌收缩。将主动脉环在一氧化氮（NO）供体S-亚硝基-N-乙酰青霉胺（SNAP，500μM）存在下孵育1小时，然后反复冲洗并再维持4小时，之后绘制对去氧肾上腺素（PE，1-3000 nM）的浓度-反应曲线。用SNAP处理导致主动脉HO-1的mRNA和蛋白表达增加，并与对PE的收缩反应显著抑制相关（与对照组相比，P<0.05）。免疫组织化学染色程序显示在内皮层中有明显的HO-1表达，在平滑肌细胞中的表达程度较低。与对照组相比，SNAP处理的主动脉环中HO-1的诱导与更高的14CO释放相关，这是在用[2-14C]-L-甘氨酸（血红素的前体）孵育主动脉后通过闪烁计数测量的。在表达高水平HO-1的主动脉中，鸟苷3',5'-单磷酸（环磷酸鸟苷）含量也大大增加。用NO合酶抑制剂NG-单甲基-L-精氨酸（100μM）孵育主动脉环，在对照组中显著（P<0.05）增加了对PE的收缩反应，但未能恢复SNAP处理的主动脉环中PE介导的收缩性。相反，血红素加氧酶的选择性抑制剂锡原卟啉IX（SnPP-IX，10μM）恢复了SNAP处理的主动脉环中对PE的升压反应，同时显著降低了CO和环磷酸鸟苷的产生。我们得出结论，HO-1/CO途径的上调显著有助于抑制主动脉对PE的收缩性。这种作用似乎是由环磷酸鸟苷水平的升高介导的，并且可以通过抑制血红素加氧酶途径来逆转。
