Das M, Bouchey D M, Moore M J, Hopkins D C, Nemenoff R A, Stenmark K R
Cardiovascular Pulmonary and Developmental Lung Biology Research Labs and the Department of Renal Medicine, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
J Biol Chem. 2001 May 11;276(19):15631-40. doi: 10.1074/jbc.M010690200. Epub 2001 Feb 22.
Hypoxia has been shown to act as a proliferative stimulus for adventitial fibroblasts of the pulmonary artery. The signaling pathways involved in this growth response, however, remain unclear. We tested the hypothesis that hypoxia-induced proliferation of fibroblasts would be dependent on distinct (compared with serum) activation and utilization patterns of mitogen-activated protein (MAP) kinases initiated by Galpha(i/o) proteins. We found that hypoxia stimulated increases in DNA synthesis and growth of quiescent fibroblasts in the absence of exogenous mitogens and also markedly augmented serum-stimulated growth responses. Hypoxia caused a transient activation of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK), the time course and pattern of which was somewhat similar to that induced by serum but which was of lesser magnitude. On the other hand, hypoxia-induced activation of p38 MAP kinase was biphasic, whereas serum-stimulated activation of p38 MAP kinase was transient, and the magnitude of activation was greater for hypoxia compared with that of serum stimulation. ERK1/2, JNK1, and p38 MAP kinase but not JNK2 were necessary for hypoxia-induced proliferation because PD98059, SB202190, and JNK1 antisense oligonucleotides nearly ablated the growth response. JNK2 appeared to act as a negative modulator of hypoxia-induced growth because JNK2 antisense oligonucleotides led to an increase in DNA synthesis. In serum-stimulated cells, antisense JNK1 oligonucleotides and PD98059 had inhibitory effects on proliferation, whereas SB202190 led to an increase in DNA synthesis. Pertussis toxin, which blocks Galpha(i/o)-mediated signaling, markedly attenuated hypoxia-induced DNA synthesis and activation of ERK and JNK but not p38 MAP kinase. We conclude that hypoxia itself can act as a growth promoting stimulus for subsets of bovine neonatal adventitial fibroblasts largely through Galpha(i/o)-mediated activation of a complex network of MAP kinases whose specific contributions to hypoxia-induced proliferation differ from traditional serum-induced growth signals.
缺氧已被证明可作为肺动脉外膜成纤维细胞的增殖刺激因素。然而，参与这种生长反应的信号通路仍不清楚。我们检验了以下假设：缺氧诱导的成纤维细胞增殖将依赖于由Gα（i/o）蛋白引发的有丝分裂原激活蛋白（MAP）激酶独特的（与血清相比）激活和利用模式。我们发现，在没有外源性有丝分裂原的情况下，缺氧刺激静止成纤维细胞的DNA合成增加和生长，并且还显著增强血清刺激的生长反应。缺氧导致细胞外信号调节激酶（ERK）和c-Jun氨基末端激酶（JNK）的短暂激活，其时间进程和模式与血清诱导的情况有些相似，但程度较小。另一方面，缺氧诱导的p38 MAP激酶激活是双相的，而血清刺激的p38 MAP激酶激活是短暂的，并且与血清刺激相比，缺氧诱导的激活程度更大。ERK1/2、JNK1和p38 MAP激酶而非JNK2是缺氧诱导增殖所必需的，因为PD98059、SB202190和JNK1反义寡核苷酸几乎消除了生长反应。JNK2似乎作为缺氧诱导生长的负调节因子起作用，因为JNK2反义寡核苷酸导致DNA合成增加。在血清刺激的细胞中，反义JNK1寡核苷酸和PD98059对增殖有抑制作用，而SB202190导致DNA合成增加。百日咳毒素可阻断Gα（i/o）介导的信号传导，显著减弱缺氧诱导的DNA合成以及ERK和JNK的激活，但不影响p38 MAP激酶。我们得出结论，缺氧本身可作为牛新生外膜成纤维细胞亚群的生长促进刺激因素，主要通过Gα（i/o）介导激活一个复杂的MAP激酶网络，其对缺氧诱导增殖的具体作用不同于传统的血清诱导生长信号。
