顧曉明,張淑苗,張 圓
第四軍醫(yī)大學(xué),陜西西安 7100321基礎(chǔ)部生理學(xué)教研室;2航空航天醫(yī)學(xué)系
神經(jīng)系統(tǒng)對炎癥反應(yīng)的調(diào)節(jié)
顧曉明1,張淑苗1,張 圓2
第四軍醫(yī)大學(xué),陜西西安 7100321基礎(chǔ)部生理學(xué)教研室;2航空航天醫(yī)學(xué)系
神經(jīng)系統(tǒng)和免疫系統(tǒng)之間存在著直接的相互作用,尤其是神經(jīng)對炎癥反應(yīng)的調(diào)控作用是與多種疾病相關(guān)具有重要臨床意義的研究內(nèi)容。炎癥反射和膽堿能抗炎通路的發(fā)現(xiàn),為這一領(lǐng)域的研究提供了新的機(jī)遇和挑戰(zhàn)。
神經(jīng)系統(tǒng);免疫系統(tǒng);膽堿能抗炎通路
神經(jīng)、內(nèi)分泌、免疫是體內(nèi)3大調(diào)控系統(tǒng),它們之間互相協(xié)調(diào)、相互制約,使機(jī)體處于自穩(wěn)的狀態(tài)。1977年Besedovsky提出“神經(jīng)-內(nèi)分泌-免疫網(wǎng)絡(luò)”的概念,提出神經(jīng)遞質(zhì)、激素和細(xì)胞因子介導(dǎo)了這3大系統(tǒng)的穩(wěn)態(tài)和平衡。傳統(tǒng)觀念認(rèn)為,神經(jīng)可以通過兩條途徑影響免疫功能,一條是通過釋放神經(jīng)遞質(zhì)來發(fā)揮作用,比如外周神經(jīng)分泌神經(jīng)肽類物質(zhì)(P物質(zhì)、降鈣素基因相關(guān)肽),誘導(dǎo)巨噬細(xì)胞和肥大細(xì)胞產(chǎn)生炎癥因子;另一條則是通過改變內(nèi)分泌活動進(jìn)而影響免疫功能。而新近的研究發(fā)現(xiàn),神經(jīng)系統(tǒng)和免疫系統(tǒng)可能存在著直接的聯(lián)系,隨之應(yīng)運(yùn)而生的是一門新興的交叉學(xué)科,神經(jīng)免疫學(xué)。本文就相關(guān)的進(jìn)展進(jìn)行綜述,以期為生理學(xué)和免疫學(xué)的教學(xué)提供參考。
淋巴組織和淋巴器官具有神經(jīng)支配作用是久已周知的事實(shí),神經(jīng)纖維伴隨血管穿過被膜而進(jìn)入淋巴組織,其性質(zhì)為交感或副交感神經(jīng)纖維。例如胸腺的結(jié)構(gòu)和功能可受交感和副交感神經(jīng)活動的影響[1]。一般認(rèn)為,交感神經(jīng)興奮可減弱免疫功能,而副交感神經(jīng)興奮則作用相反。同時(shí),自主神經(jīng)功能的紊亂與炎癥的發(fā)生發(fā)展也有內(nèi)在的聯(lián)系。研究證實(shí),自主神經(jīng)可以影響淋巴組織和器官的功能、調(diào)節(jié)免疫反應(yīng)[2-3]。此外,多種免疫細(xì)胞可以表達(dá)神經(jīng)遞質(zhì)受體,包括乙酰膽堿(acetylcholine,ACh)受體、多巴胺受體、5-羥色胺受體、組胺受體和腎上腺素受體,進(jìn)而調(diào)節(jié)免疫細(xì)胞的分化和活性。例如人外周血淋巴細(xì)胞、單核細(xì)胞、巨噬細(xì)胞及血小板上均有腎上腺素能受體;小鼠和大鼠淋巴細(xì)胞表面有多巴胺受體,其中小鼠B淋巴細(xì)胞上的受體密度為60 000個(gè)/細(xì)胞,且多種抗多巴胺藥物可抑制放射性配基與多巴胺受體的結(jié)合。有些T細(xì)胞表達(dá)膽堿乙酰轉(zhuǎn)移酶(choline acetyltransferase,ChAT),可以在細(xì)胞內(nèi)合成ACh,因此被稱為ChAT+T細(xì)胞。在脾中,腎上腺能神經(jīng)末梢附近亦有T細(xì)胞分布,這些都說明脾中存在神經(jīng)和T細(xì)胞直接發(fā)生作用的物質(zhì)基礎(chǔ)。過繼回輸ChAT+T細(xì)胞至裸鼠體內(nèi),可以重建迷走神經(jīng)對腫瘤壞死因子(tumor necrosis factor,TNF)-α釋放的抑制作用[4]。
有趣的是,反過來感覺神經(jīng)元也可以表達(dá)模式識別受體[5-6]。那么是否說明中樞神經(jīng)系統(tǒng)(central nervous system,CNS)可以通過這些受體感知外周的炎癥反應(yīng)呢?最近,Chiu等[7]的實(shí)驗(yàn)證實(shí),獨(dú)立于免疫系統(tǒng)之外,感覺神經(jīng)確實(shí)可以直接對外來病原菌產(chǎn)生反應(yīng)。而且越來越多的研究證實(shí),神經(jīng)系統(tǒng)可以表達(dá)細(xì)胞因子及其受體,如腦內(nèi)神經(jīng)元、星形細(xì)胞和小膠質(zhì)細(xì)胞均能合成和分泌多種細(xì)胞因子[8];中樞或外周神經(jīng)系統(tǒng)內(nèi)注射脂多糖(lipopolysacchride,LPS)可以誘導(dǎo)皮層、下丘腦和小腦等部位表達(dá)白細(xì)胞介素(interleukin,IL)-1等細(xì)胞因子及其受體[9]。這些共用的細(xì)胞因子等介質(zhì)為神經(jīng)系統(tǒng)和免疫系統(tǒng)的信息交流提供了物質(zhì)基礎(chǔ)。
當(dāng)病原菌入侵機(jī)體以后,首先通過表達(dá)于固有免疫細(xì)胞表面的模式識別受體激活固有免疫系統(tǒng)。機(jī)體早期的防御反應(yīng)通過募集白細(xì)胞、釋放細(xì)胞因子等方式最終清除病原菌,重建機(jī)體穩(wěn)態(tài)。早期反應(yīng)中還有一個(gè)關(guān)鍵的步驟就是炎癥反應(yīng),包括局部的紅腫、進(jìn)而可能發(fā)展為影響CNS的全身反應(yīng),例如發(fā)熱、厭食和疲勞。而過度的炎癥反應(yīng)本身也會導(dǎo)致組織損傷或者炎性疾病,甚至死亡[10]。那么,炎癥反應(yīng)信號是如何傳入CNS,而CNS又是如何來傳出信號,調(diào)控機(jī)體使炎癥能夠維持在適度的范圍內(nèi)呢?
有一種看法認(rèn)為,免疫信號主要通過體液途徑進(jìn)入腦,即血液中的細(xì)胞因子穿過血腦屏障作用于腦內(nèi)神經(jīng)元,并且有證據(jù)顯示腦內(nèi)確實(shí)存在細(xì)胞因子受體[11]。另一種看法則認(rèn)為,免疫信號可以通過神經(jīng)來介導(dǎo)。免疫反應(yīng)的許多發(fā)生部位如肝、脾和淋巴結(jié)等都有廣泛的迷走神經(jīng)分布?!把装Y反射”是指信號通過迷走神經(jīng)傳入CNS,經(jīng)過處理后興奮迷走神經(jīng)傳出纖維,調(diào)控炎癥反應(yīng),例如炎癥反射可以調(diào)節(jié)脾中巨噬細(xì)胞因子的釋放[12]。切斷膈下迷走神經(jīng)使細(xì)胞因子誘導(dǎo)的急性期反應(yīng)、腦內(nèi)去甲腎上腺素以及糖皮質(zhì)激素增高等消失,顯著抑制LPS誘導(dǎo)的血漿促腎上腺皮質(zhì)激素ACTH水平升高[13]。大鼠實(shí)驗(yàn)發(fā)現(xiàn),腹腔注射L-1β刺激產(chǎn)生發(fā)熱反應(yīng)需要完整迷走神經(jīng)的存在,如果切斷膈下迷走神經(jīng)則不能引起發(fā)熱。通過門靜脈給大鼠輸入IL-1β可以增加迷走傳入神經(jīng)和脾神經(jīng)的興奮性,但是如果切斷迷走神經(jīng)肝分支的話,該反應(yīng)消失[14]。因此,迷走神經(jīng)參與了機(jī)體炎癥反應(yīng)向CNS傳入的過程。
反過來,神經(jīng)系統(tǒng)同樣可以直接向免疫系統(tǒng)傳出信號。Wan等證實(shí),應(yīng)激反應(yīng)對大鼠脾體液免疫和細(xì)胞免疫的抑制效應(yīng)主要由腎上腺能神經(jīng)纖維介導(dǎo)[15]。腦還可以通過迷走神經(jīng)調(diào)節(jié)胸腺淋巴細(xì)胞生成和向外周淋巴器官的遷移。Tracey[16]發(fā)現(xiàn),CNI-1493(一種具有抗炎作用的四價(jià)丙咪腙)直接作用于腦比靜脈輸注更有效,而且該反應(yīng)是依賴于完整迷走神經(jīng)的存在。進(jìn)一步的實(shí)驗(yàn)證實(shí),電刺激迷走神經(jīng)可以顯著降低體內(nèi)TNF-α的水平,減少實(shí)驗(yàn)性內(nèi)毒素休克的發(fā)生,如果切斷迷走神經(jīng)則效果相反。說明起源于CNS的信號可以通過迷走神經(jīng)傳遞來調(diào)節(jié)外周的炎癥反應(yīng)。
脾是外周最大的免疫器官,脾中的巨噬細(xì)胞是內(nèi)毒素休克時(shí)TNF-α一個(gè)主要的來源,研究證實(shí)電刺激迷走神經(jīng)可以減少脾細(xì)胞因子的釋放[17]。因此,推測迷走神經(jīng)在神經(jīng)系統(tǒng)和免疫系統(tǒng)之間的聯(lián)系中有重要作用。2000年,Borovikova等[18]提出“膽堿能抗炎通路”的概念,即迷走神經(jīng)及其遞質(zhì)可抑制巨噬細(xì)胞的活化,在抗炎反應(yīng)中有重要作用。膽堿能抗炎通路是以迷走神經(jīng)、乙酰膽堿及其特異性受體為基礎(chǔ),高效、直接、迅速的一條抗炎通路。它可以被看作是一種內(nèi)源性的神經(jīng)反饋調(diào)節(jié)機(jī)制,膽堿能抗炎通路功能的下降也可能參與了炎癥水平升高[19-20]。但是迷走神經(jīng)并不直接支配脾,而是先到腹腔神經(jīng)節(jié)換元,再由節(jié)后神經(jīng)纖維發(fā)揮作用。
單核細(xì)胞和巨噬細(xì)胞均表達(dá)膽堿能受體,使用膽堿能受體激動劑可以減少炎癥因子的釋放[21]。Tracy等研究發(fā)現(xiàn),ACh在體外可以有效抑制LPS刺激外周巨噬細(xì)胞釋放TNF-α;刺激傳出迷走神經(jīng)可抑制大鼠內(nèi)毒素血癥時(shí)的全身炎癥反應(yīng)[22]。尤其是α7-煙堿型乙酰膽堿受體的表達(dá)(cholinergic α7-nicotinic ACh receptor,α7nAChR),是介導(dǎo)迷走神經(jīng)抑制TNF-α釋放的重要因素,也是參與炎癥反射的重要“效應(yīng)器”[23]。使用骨髓移植α7nAChR缺陷的嵌合鼠發(fā)現(xiàn),非骨髓來源細(xì)胞可以保留迷走神經(jīng)抑制內(nèi)毒素休克細(xì)胞因子產(chǎn)生的能力,而骨髓來源的α7nAChR缺陷的白細(xì)胞,迷走神經(jīng)抑制TNF-α的能力消失[24]。
當(dāng)中樞收到免疫刺激的信息,然后將信號投射到各迷走神經(jīng)核團(tuán),傳出迷走神經(jīng)纖維被激活,從而引起外周神經(jīng)末梢釋放ACh,通過結(jié)合免疫細(xì)胞上的α7nAChR而激活,經(jīng)過一系列的細(xì)胞內(nèi)信號途徑而減少免疫細(xì)胞多種促炎因子的釋放,達(dá)到抑制炎癥反應(yīng)、減少炎癥造成的損傷和抗毒、抗休克的作用。其機(jī)制可能與細(xì)胞內(nèi)的NF-кB[25]、ERK[26]和JAK2/STAT3[27]信號轉(zhuǎn)導(dǎo)途徑有關(guān),例如大鼠內(nèi)毒素血癥中,迷走神經(jīng)通過激活α7nAChR來抑制NF-кB通路,減少TNF-α產(chǎn)生。
隨著對膽堿能抗炎通路研究的深入,也發(fā)現(xiàn)了其他的靶細(xì)胞。例如在關(guān)節(jié)炎病人體內(nèi)分離出的滑膜成纖維細(xì)胞,在加入ACh后可以劑量依賴性地降低由IL-1刺激而釋放的IL-6;而α7nAChR特異性激動劑PNU-282987可以劑量依賴性地抑制這種反應(yīng);α7nAChR特異性拮抗劑或小干擾RNA(small interfering RNA,siRNA)可以消除ACh對IL-6的作用[28]。說明滑膜成纖維細(xì)胞也是該通路的靶細(xì)胞之一[29]。此外,α7nAChR還表達(dá)于CNS和自主神經(jīng)節(jié)等器官,所以很可能還存在獨(dú)立于免疫系統(tǒng)和脾巨噬細(xì)胞之外的膽堿能信號通路參與炎癥反射[30-31]。
與體液抗炎通路相比,神經(jīng)反饋機(jī)制在某些方面更有優(yōu)勢,比如神經(jīng)抗炎通路反應(yīng)更快速、更局限化,也更容易控制。膽堿能抗炎通路活化后,可以同時(shí)抑制多種炎癥因子的釋放,包括TNF-α、IL-1β、IL-6和高遷移率族蛋白1等。利用電刺激迷走神經(jīng)或者使用α7nAChR特異性激動劑可以抑制局部或者全身的炎癥反應(yīng)[32-33],目前已有相關(guān)研究成果應(yīng)用于阿爾茨海默病[34]、類風(fēng)濕關(guān)節(jié)炎[35]、內(nèi)毒素血癥[36-37]和心血管等疾病的1期或2期臨床試驗(yàn)[19,38-39]。進(jìn)一步闡明神經(jīng)反射的機(jī)制,尋找特異性的增強(qiáng)內(nèi)源性膽堿能抗炎通路的治療靶點(diǎn)具有十分重要的臨床意義。
1 Niijima A, Hori T, Katafuchi T, et al. The effect of interleukin-1 beta on the efferent activity of the vagus nerve to the thymus[J]. J Auton Nerv Syst, 1995, 54(2): 137-144.
2 Grebe KM, Hickman HD, Irvine KR, et al. Sympathetic nervous system control of anti-influenza CD8+ T cell responses[J]. Proc Natl Acad Sci U S A, 2009, 106(13): 5300-5305.
3 Kees MG, Pongratz G, Kees F, et al. Via beta-adrenoceptors,stimulation of extrasplenic sympathetic nerve fibers inhibits lipopolysaccharide-induced TNF secretion in perfused rat spleen[J]. J Neuroimmunol, 2003, 145(1/2): 77-85.
4 Rosas-Ballina M, Olofsson PS, Ochani M, et al. Acetylcholinesynthesizing T cells relay neural signals in a vagus nerve circuit[J].Science, 2011, 334(652): 98-101.
5 Chiu IM, Von Hehn CA, Woolf CJ. Neurogenic inflammation and the peripheral nervous system in host defense and immunopathology[J]. Nat Neurosci, 2012, 15(8): 1063-1067.
6 Liu J, Buisman-Pijlman F, Hutchinson MR. Toll-like receptor 4: innate immune regulator of neuroimmune and neuroendocrine interactions in stress and major depressive disorder[J]. Front Neurosci, 2014, 8: 309.
7 Chiu IM, Heesters BA, Ghasemlou N, et al. Bacteria activate sensory neurons that modulate pain and inflammation[J]. Nature, 2013,501(7465): 52-57.
8 Gadient RA, Otten U. Postnatal expression of interleukin-6 (IL-6)and IL-6 receptor (IL-6R) mRNAs in rat sympathetic and sensory ganglia[J]. Brain Res, 1996, 724(1): 41-46.
9 Quan N, Sundar SK, Weiss JM. Induction of interleukin-1 in various brain regions after peripheral and central injections of lipopolysaccharide[J]. J Neuroimmunol, 1994, 49(1/2): 125-134.
10 Nathan C, Ding A. Nonresolving inflammation[J]. Cell, 2010,140(6): 871-882.
11 Rothwell NJ, Hopkins SJ. Cytokines and the nervous system II:Actions and mechanisms of action[J]. Trends Neurosci, 1995, 18(3):130-136.
12 Borovikova LV, Ivanova S, Nardi D, et al. Role of vagus nerve signaling in CNI-1493-mediated suppression of acute inflammation[J]. Auton Neurosci, 2000, 85(1/3): 141-147.
13 Gaykema RP, Dijkstra I, Tilders FJ. Subdiaphragmatic vagotomy suppresses endotoxin-induced activation of hypothalamic corticotropin-releasing hormone neurons and ACTH secretion[J]. Endocrinology, 1995, 136(10): 4717-4720.
14 Niijima A. The afferent discharges from sensors for interleukin 1 beta in the hepatoportal system in the anesthetized rat[J]. J Auton Nerv Syst, 1996, 61(3): 287-291.
15 Haas HS, Schauenstein K. Neuroimmunomodulation via limbic structures--the neuroanatomy of psychoimmunology[J]. Prog Neurobiol, 1997, 51(2): 195-222.
16 Tracey KJ. The inflammatory reflex[J]. Nature, 2002, 19-26;420(6917):853-859.
17 Huston JM, Ochani M, Rosas-Ballina M, et al. Splenectomy inactivates the cholinergic antiinflammatory pathway during lethal endotoxemia and polymicrobial sepsis[J]. J Exp Med, 2006, 203(7):1623-1628.
18 Borovikova LV, Ivanova S, Zhang M, et al. Vagus nerve stimulation attenuates the systemic inflammatory response to endotoxin[J]. Nature, 2000, 405(6785): 458-462.
19 Li DJ, Evans RG, Yang ZW, et al. Dysfunction of the cholinergic anti-inflammatory pathway mediates organ damage in hypertension[J]. Hypertension, 2011, 57(2): 298-307.
20 Gallowitsch-Puerta M, Pavlov VA. Neuro-immune interactions via the cholinergic anti-inflammatory pathway[J]. Life Sci, 2007, 80(24/25): 2325-2329.
21 Bencherif M, Lippiello PM, Lucas R, et al. Alpha7 nicotinic receptors as novel therapeutic targets for inflammation-based diseases[J]. Cell Mol Life Sci, 2011, 68(6): 931-949.
22 Wang H, Yu M, Ochani M, et al. Nicotinic acetylcholine receptor alpha7 subunit is an essential regulator of inflammation[J]. Nature,2003, 421(6921): 384-388.
23 Li Q, Zhou XD, Kolosov VP, et al. Nicotine reduces TNF-α expression through a α7 nAChR/MyD88/NF-?B pathway in HBE16 airway epithelial cells[J]. Cell Physiol Biochem, 2011, 27(5):605-612.
24 Olofsson PS, Katz DA, Rosas-Ballina M, et al. α7 nicotinic acetylcholine receptor (α7nAChR) expression in bone marrowderived non-T cells is required for the inflammatory reflex[J]. Mol Med, 2012, 18:539-543.
25 Han Z, Shen F, He Y, et al. Activation of α-7 nicotinic acetylcholine receptor reduces ischemic stroke injury through reduction of pro-inflammatory macrophages and oxidative stress[J]. PLoS One, 2014, 9(8): e105711.
26 El Kouhen R, Hu M, Anderson DJ, et al. Pharmacology of alpha7 nicotinic acetylcholine receptor mediated extracellular signalregulated kinase signalling in PC12 cells[J]. Br J Pharmacol,2009, 156(4): 638-648.
27 De Jonge WJ, Van Der Zanden EP, The FO, et al. Stimulation of the vagus nerve attenuates macrophage activation by activating the Jak2-STAT3 signaling pathway[J]. Nat Immunol, 2005, 6(8): 844-851.
28 Waldburger JM, Boyle DL, Pavlov VA, et al. Acetylcholine regulation of synoviocyte cytokine expression by the alpha7 nicotinic receptor[J]. Arthritis Rheum, 2008, 58(11): 3439-3449.
29 Li T, Wu S, Zhang H, et al. Activation of Nicotinic Receptors Inhibits TNF-α-Induced Production of Pro-inflammatory Mediators Through the JAK2/STAT3 Signaling Pathway in Fibroblast-Like Synoviocytes[J/OL]. http://link.springer.com/article/10.1007%2Fs10753-015-0117-1.
30 Pinheiro NM, Miranda CJ, Perini A, et al. Pulmonary inflammation is regulated by the levels of the vesicular acetylcholine transporter[J]. PLoS One, 2015, 10(3): e0120441.
31 Downs AM, Bond CE, Hoover DB. Localization of α7 nicotinic acetylcholine receptor mRNA and protein within the cholinergic antiinflammatory pathway[J]. Neuroscience, 2014, 266:178-185.
32 Zhang R, Wugeti N, Sun J, et al. Effects of vagus nerve stimulation via cholinergic anti-inflammatory pathway activation on myocardial ischemia/reperfusion injury in canine[J]. Int J Clin Exp Med,2014, 7(9): 2615-2623.
33 Ulloa L. The anti-inflammatory potential of selective cholinergic agonists[J]. Shock, 2011, 36(1): 97-98.
34 Vicens P, Ribes D, Heredia L, et al. Motor and anxiety effects of PNU-282987, an alpha7 nicotinic receptor agonist, and stress in an animal model of Alzheimer’s disease[J]. Curr Alzheimer Res,2013, 10(5): 516-523.
35 Koopman FA, Schuurman PR, Vervoordeldonk MJ, et al. Vagus nerve stimulation: a new bioelectronics approach to treat rheumatoid arthritis?[J]. Best Pract Res Clin Rheumatol, 2014, 28(4):625-635.
36 Mazloom R, Eftekhari G, Rahimi M, et al. The role of α7 nicotinic acetylcholine receptor in modulation of heart rate dynamics in endotoxemic rats[J]. PLoS One, 2013, 8(12): e82251.
37 Kim TH, Kim SJ, Lee SM. Stimulation of the α7 nicotinic acetylcholine receptor protects against sepsis by inhibiting Toll-like receptor via phosphoinositide 3-kinase activation[J]. J Infect Dis,2014, 209(10): 1668-1677.
38 Xiong J, Yuan YJ, Xue FS, et al. Postconditioning with α7nAChR agonist attenuates systemic inflammatory response to myocardial ischemia--reperfusion injury in rats[J]. Inflammation, 2012, 35(4): 1357-1364.
39 Liu C, Su D. Nicotinic acetylcholine receptor α7 subunit: a novel therapeutic target for cardiovascular diseases[J]. Front Med,2012, 6(1): 35-40.
Regulation of infammation by nervous system
GU Xiaoming1, ZHANG Shumiao1, ZHANG Yuan21Department of Physiology;2Department of Aerospace Medicine Fourth Military Medical University, Xi'an 710032, Shaanxi Province, China
ZHANG Yuan. Email: zhangyuan@fmmu.edu.cn
Recent researches have found that there are direct interaction between nervous system and immune system. The regulation of immune responses is associated with diseases, and it has signifcance in clinical research. The discoveries of infammatory refect and cholinergic anti-infammatory pathway provides new opportunity and challenge in this feld.
nervous system; immune system; cholinergic anti-infammatory pathway
R 392.12
A
2095-5227(2015)09-0963-03
10.3969/j.issn.2095-5227.2015.09.029
時(shí)間:2015-05-25 09:50
http://www.cnki.net/kcms/detail/11.3275.R.20150525.0950.001.html
2015-04-09
國家自然科學(xué)基金項(xiàng)目(81370388)
Supported by the National Natural Science Foundation of China(81370388)
顧曉明,女,碩士,助理實(shí)驗(yàn)師。研究方向:心血管生理學(xué)。Email: gxm5683@qq.com
張圓,女,博士,講師。Email: zhangyuan@fmmu.edu.cn