Ciani Elisabetta, Calvanese Vincenzo, Crochemore Christophe, Bartesaghi Renata, Contestabile Antonio
Department of Human and General Physiology, University of Bologna, Piazza di Porta San Donato 2, 40126 Bologna, Italy.
J Cell Sci. 2006 Aug 1;119(Pt 15):3161-70. doi: 10.1242/jcs.03042. Epub 2006 Jul 11.
The diffusible messenger, nitric oxide plays multiple roles in neuroprotection, neurodegeneration and brain plasticity. Its involvement in neurogenesis has been disputed, on the basis of results on models in vivo and in culture. We report here that pharmacological blockade of nitric oxide production in rat pups resulted, during a restricted time window of the first three postnatal days, in increased cerebellar proliferation rate, as assessed through tritiated thymidine or BrdU incorporation into DNA. This was accompanied by increased expression of Myc, a transcription factor essential for cerebellar development, and of the cell cycle regulating gene, cyclin D1. These effects were mediated downstream by the nitric oxide-dependent second messenger, cGMP. Schedules of pharmacological NO deprivation targeted to later developmental stages (from postnatal day 3 to 7), no longer increased proliferation, probably because of partial escape of the cGMP level from nitric oxide control. Though limited to a brief temporal window, the proliferative effect of neonatal nitric oxide deprivation could be traced into adulthood. Indeed, the number of BrdU-labeled surviving cells, most of which were of neuronal phenotype, was larger in the cerebellum of 60-day-old rats that had been subjected to NO deprivation during the first three postnatal days than in control rats. Experiments on cell cultures from neonatal cerebellum confirmed that nitric oxide deprivation stimulated proliferation of cerebellar precursor cells and that this effect was not additive with the proliferative action of sonic hedgehog peptide. The finding that nitric oxide deprivation during early cerebellar neurogenesis, stimulates a brief increase in cell proliferation may contribute to a better understanding of the controversial role of nitric oxide in brain development.
可扩散信使一氧化氮在神经保护、神经退行性变和脑可塑性中发挥多种作用。基于体内和体外模型的研究结果，其在神经发生中的作用一直存在争议。我们在此报告，在出生后前三天的特定时间窗口内，对新生大鼠进行一氧化氮生成的药理学阻断，会导致小脑增殖率增加，这通过将氚标记胸腺嘧啶核苷或溴脱氧尿苷掺入DNA来评估。这伴随着Myc（小脑发育所必需的转录因子）和细胞周期调节基因细胞周期蛋白D1的表达增加。这些效应由一氧化氮依赖性第二信使环磷酸鸟苷（cGMP）介导。针对后期发育阶段（出生后第3天至第7天）的药理学一氧化氮剥夺方案不再增加增殖，可能是因为cGMP水平部分脱离了一氧化氮的控制。尽管仅限于短暂的时间窗口，但新生儿一氧化氮剥夺的增殖效应可追溯至成年期。事实上，在出生后前三天接受一氧化氮剥夺的60日龄大鼠小脑中，溴脱氧尿苷标记的存活细胞数量（其中大多数为神经元表型）比对照大鼠更多。对新生小脑细胞培养物的实验证实，一氧化氮剥夺刺激了小脑前体细胞的增殖，并且这种效应与音猬因子肽的增殖作用不具有叠加性。早期小脑神经发生期间一氧化氮剥夺刺激细胞增殖短暂增加这一发现，可能有助于更好地理解一氧化氮在脑发育中存在争议的作用。
