Mizushima T, Obata K, Katsura H, Yamanaka H, Kobayashi K, Dai Y, Fukuoka T, Tokunaga A, Mashimo T, Noguchi K
Department of Anatomy and Neuroscience, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan.
Neuroscience. 2006 Jul 21;140(4):1337-48. doi: 10.1016/j.neuroscience.2006.03.024. Epub 2006 May 3.
Two cold-sensitive transient receptor potential (TRP) channels, TRPA1 and TRPM8, have been identified and considered interesting because of their possible roles in thermosensation, nociception and other functions. Recently, we have reported that the phosphorylation of extracellular signal-regulated protein kinase and p38 mitogen-activated protein kinase occurred in primary afferent neurons in response to noxious heat stimulation of the peripheral tissue, i.e. activity-dependent activation of extracellular signal-regulated protein kinase and p38 in dorsal root ganglion neurons. In the present study, we investigated the phosphorylation of extracellular signal-regulated protein kinase, p38, and c-Jun N-terminal kinase in the rat dorsal root ganglion by cold stimulation using immunohistochemistry. Cold stimuli (28-4 degrees C) were applied by immersion of the hind paw into a water bath (six times of 10 s stimulation and 10 s interval, total 2 min). Noxious cold stimulation induced phosphorylated-extracellular signal-regulated protein kinase and phosphorylated-p38, but not phosphorylated-c-Jun N-terminal kinase, in small to medium diameter sensory neurons with a peak at 2 min after stimulation. We found that a cold stimulation at 4 degrees C showed a marked increase in the number of activated neurons. Furthermore, double staining for phosphorylated-extracellular signal-regulated protein kinase and phosphorylated-p38 showed no colocalization in the dorsal root ganglion neurons. We then performed double-labeling experiments for TRPA1 and TRPM8 mRNA and phosphorylation of mitogen-activated protein kinase. The majority of phosphorylated-extracellular signal-regulated protein kinase-positive neurons also expressed TRPM8 mRNA, whereas phosphorylated-p38 heavily colocalized with TRPA1 mRNA after noxious cold stimulation. Our data suggest that the noxious, but not innocuous, cold stimulation in vivo induced differential activation of extracellular signal-regulated protein kinase and p38 pathways in each subpopulation containing TRPA1 or TRPM8 in dorsal root ganglion.
两种冷敏瞬时受体电位（TRP）通道，即TRPA1和TRPM8，已被识别并因其在温度感觉、伤害感受及其他功能中可能发挥的作用而备受关注。最近，我们报道了外周组织受到有害热刺激时，初级传入神经元中细胞外信号调节蛋白激酶（ERK）和p38丝裂原活化蛋白激酶（p38 MAPK）会发生磷酸化，即背根神经节神经元中ERK和p38的活性依赖性激活。在本研究中，我们采用免疫组织化学方法，通过冷刺激研究大鼠背根神经节中ERK、p38和c-Jun氨基末端激酶（JNK）的磷酸化情况。将后爪浸入水浴中施加冷刺激（28 - 4℃）（每次刺激10秒，共6次，间隔10秒，总计2分钟）。有害冷刺激在中小直径感觉神经元中诱导了磷酸化ERK和磷酸化p38，但未诱导磷酸化JNK，刺激后2分钟达到峰值。我们发现4℃的冷刺激使激活神经元数量显著增加。此外，磷酸化ERK和磷酸化p38的双重染色显示在背根神经节神经元中无共定位。然后，我们进行了TRPA1和TRPM8 mRNA与丝裂原活化蛋白激酶磷酸化的双重标记实验。大多数磷酸化ERK阳性神经元也表达TRPM8 mRNA，而有害冷刺激后，磷酸化p38与TRPA1 mRNA大量共定位。我们的数据表明，体内有害而非无害的冷刺激在背根神经节中含有TRPA1或TRPM8的每个亚群中诱导了ERK和p38通路的差异激活。
