Dussor Gregory O, Leong Anthony S, Gracia Nicholas B, Kilo Sonja, Price Theodore J, Hargreaves Kenneth M, Flores Christopher M
Department of Pharmacology, The University of Texas Health Science Center, San Antonio, TX, USA.
Eur J Neurosci. 2003 Nov;18(9):2515-26. doi: 10.1046/j.1460-9568.2003.02935.x.
Inflammation of the buccal mucosa, gingiva and periodontal tissues is a significant problem in users of nicotine-containing tobacco products; however, the potential role of nicotine in the development of this inflammation is unclear. In many tissues, nicotine, acting through nicotinic acetylcholine receptors (nAChRs), has been shown to increase the release of the pro-inflammatory mediator calcitonin gene-related peptide (CGRP) thereby potentially contributing to neurogenic inflammation. The purpose of the present studies was to determine the effects of nicotine and other nAChR agonists on capsaicin-evoked immunoreactive CGRP (iCGRP) release from rat buccal mucosa and to identify a potential cellular basis for these effects. Using a previously validated model of in vitro superfusion, we show that the nAChR agonists nicotine (EC50 557 micro m), epibatidine (EC50 317 pm) and cytisine (EC50 4.83 nm) potentiated capsaicin-evoked iCGRP release in a concentration-dependent manner by 123, 70 and 76%, respectively. The expression and distribution patterns of the mRNA transcripts encoding the alpha3, alpha4 and alpha6 nAChR subunits and their colocalization with CGRP and the capsaicin receptor VR1 were examined in rat trigeminal ganglion using combined in situ hybridization and immunohistofluorescence. Of all trigeminal neurons counted, mRNA encoding the alpha3, alpha4 and alpha6 subunits was found, respectively, in 14.45, 9.2 and 19.21% of neurons. The cell body diameter of most neurons containing any nAChR subunit was in the 30-40 micro m range with slightly fewer in the 20-30 micro m range. Co-localization of these alpha subunit transcripts with either CGRP or VR1 immunoreactivity ranged from approximately 5 to 7% for alpha4 and over 8% for alpha3 to 18% for alpha6. These data support the hypothesis that nicotinic agents, acting at nAChRs contained on primary sensory neurons, are capable of directly modulating the stimulated release of iCGRP. In the case of users of nicotine-containing tobacco products, this modulation could contribute to inflammatory processes within the oral cavity.
颊黏膜、牙龈和牙周组织的炎症是含尼古丁烟草制品使用者面临的一个重大问题；然而，尼古丁在这种炎症发展过程中的潜在作用尚不清楚。在许多组织中，尼古丁通过烟碱型乙酰胆碱受体（nAChRs）发挥作用，已被证明会增加促炎介质降钙素基因相关肽（CGRP）的释放，从而可能导致神经源性炎症。本研究的目的是确定尼古丁和其他nAChR激动剂对辣椒素诱发的大鼠颊黏膜免疫反应性CGRP（iCGRP）释放的影响，并确定这些作用的潜在细胞基础。使用先前验证的体外灌流模型，我们发现nAChR激动剂尼古丁（EC50 557 μM）、埃博霉素（EC50 317 pm）和金雀花碱（EC50 4.83 nM）分别以浓度依赖性方式使辣椒素诱发的iCGRP释放增强了123%、70%和76%。使用原位杂交和免疫荧光相结合的方法，在大鼠三叉神经节中检测了编码α3、α4和α6 nAChR亚基的mRNA转录本的表达和分布模式，以及它们与CGRP和辣椒素受体VR1的共定位情况。在所有计数的三叉神经元中，分别有14.45%、9.2%和19.21%的神经元发现了编码α3、α4和α6亚基的mRNA。大多数含有任何nAChR亚基的神经元的细胞体直径在30 - 40μm范围内，在20 - 30μm范围内的略少。这些α亚基转录本与CGRP或VR1免疫反应性的共定位，α4约为5%至7%，α3超过8%，α6为18%。这些数据支持这样一种假设，即作用于初级感觉神经元上的nAChRs的烟碱类药物能够直接调节iCGRP的刺激释放。对于含尼古丁烟草制品的使用者来说，这种调节可能会导致口腔内的炎症过程。
