Abstract
Tumor necrosis factor receptor-associated factor 6 (TRAF6) has been reported to be expressed in spinal astrocytes and is involved in neuropathic pain. In this study, we investigated the role and mechanism of TRAF6 in complete Freund's adjuvant (CFA)-evoked chronic inflammatory hypersensitivity and the effect of docosahexaenoic acid (DHA) on TRAF6 expression and inflammatory pain. We found that TRAF6 was dominantly increased in microglia at the spinal level after intraplantar injection of CFA. Intrathecal TRAF6 siRNA alleviated CFA-triggered allodynia and reversed the upregulation of IBA-1 (microglia marker). In addition, intrathecal administration of DHA inhibited CFA-induced upregulation of TRAF6 and IBA-1 in the spinal cord and attenuated CFA-evoked mechanical allodynia. Furthermore, DHA prevented lipopolysaccharide (LPS)-caused increase of TRAF6 and IBA-1 in both BV2 cell line and primary cultured microglia. Finally, intrathecal DHA reduced LPS-induced upregulation of spinal TRAF6 and IBA-1, and alleviated LPS-induced mechanical allodynia. Our findings indicate that TRAF6 contributes to pain hypersensitivity via regulating microglial activation in the spinal dorsal horn. Direct inhibition of TRAF6 by siRNA or indirect inhibition by DHA may have therapeutic effects on chronic inflammatory pain.
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs10571-021-01045-y/MediaObjects/10571_2021_1045_Fig1_HTML.png)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs10571-021-01045-y/MediaObjects/10571_2021_1045_Fig2_HTML.jpg)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs10571-021-01045-y/MediaObjects/10571_2021_1045_Fig3_HTML.png)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs10571-021-01045-y/MediaObjects/10571_2021_1045_Fig4_HTML.png)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs10571-021-01045-y/MediaObjects/10571_2021_1045_Fig5_HTML.png)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs10571-021-01045-y/MediaObjects/10571_2021_1045_Fig6_HTML.png)
![](http://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs10571-021-01045-y/MediaObjects/10571_2021_1045_Fig7_HTML.png)
Similar content being viewed by others
Data Availability
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.
References
Ajith TA (2018) A recent update on the effects of omega-3 fatty acids in Alzheimer’s disease. Curr Clin Pharmacol 13(4):252–260. https://doi.org/10.2174/1574884713666180807145648
Arch RH, Gedrich RW, Thompson CB (1998) Tumor necrosis factor receptor-associated factors (TRAFs): a family of adapter proteins that regulates life and death. Genes Dev 12(18):2821–2830. https://doi.org/10.1101/gad.12.18.2821
Bazinet RP, Laye S (2014) Polyunsaturated fatty acids and their metabolites in brain function and disease. Nat Rev Neurosci 15(12):771–785. https://doi.org/10.1038/nrn3820
Bedini A, Baiula M, Vincelli G, Formaggio F, Lombardi S, Caprini M, Spampinato S (2017) Nociceptin/orphanin FQ antagonizes lipopolysaccharide-stimulated proliferation, migration and inflammatory signaling in human glioblastoma U87 cells. Biochem Pharmacol 140:89–104. https://doi.org/10.1016/j.bcp.2017.05.021
Bradley JR, Pober JS (2001) Tumor necrosis factor receptor-associated factors (TRAFs). Oncogene 20(44):6482–6491. https://doi.org/10.1038/sj.onc.1204788
Cao H, Zhang YQ (2008) Spinal glial activation contributes to pathological pain states. Neurosci Biobehav Rev 32(5):972–983. https://doi.org/10.1016/j.neubiorev.2008.03.009
Chen J, Wu X, Shao B, Zhao W, Shi W, Zhang S, Ni L, Shen A (2011) Increased expression of TNF receptor-associated factor 6 after rat traumatic brain injury. Cell Mol Neurobiol 31(2):269–275. https://doi.org/10.1007/s10571-010-9617-6
De Smedt-Peyrusse V, Sargueil F, Moranis A, Harizi H, Mongrand S, Laye S (2008) Docosahexaenoic acid prevents lipopolysaccharide-induced cytokine production in microglial cells by inhibiting lipopolysaccharide receptor presentation but not its membrane subdomain localization. J Neurochem 105(2):296–307. https://doi.org/10.1111/j.1471-4159.2007.05129.x
Ding D, Zhu M, Liu X, Jiang L, Xu J, Chen L, Liang J, Li L, Zhou T, Wang Y, Shi H, Yuan Y, Song E (2018) Inhibition of TRAF6 alleviates choroidal neovascularization in vivo. Biochem Biophys Res Commun 503(4):2742–2748. https://doi.org/10.1016/j.bbrc.2018.08.034
Dixon WJ (1980) Efficient analysis of experimental observations. Annu Rev Pharmacol Toxicol 20:441–462. https://doi.org/10.1146/annurev.pa.20.040180.002301
Dou Y, Tian X, Zhang J, Wang Z, Chen G (2018) Roles of TRAF6 in central nervous system. Curr Neuropharmacol 16(9):1306–1313. https://doi.org/10.2174/1570159X16666180412094655
Fernandez-Arjona MDM, Grondona JM, Granados-Duran P, Fernandez-Llebrez P, Lopez-Avalos MD (2017) Microglia morphological categorization in a rat model of neuroinflammation by hierarchical cluster and principal components analysis. Front Cell Neurosci 11:235. https://doi.org/10.3389/fncel.2017.00235
Gao YJ, Ji RR (2010) Targeting astrocyte signaling for chronic pain. Neurotherapeutics 7(4):482–493. https://doi.org/10.1016/j.nurt.2010.05.016
Gao YJ, Xu ZZ, Liu YC, Wen YR, Decosterd I, Ji RR (2010) The c-Jun N-terminal kinase 1 (JNK1) in spinal astrocytes is required for the maintenance of bilateral mechanical allodynia under a persistent inflammatory pain condition. Pain 148(2):309–319. https://doi.org/10.1016/j.pain.2009.11.017
Gosselin RD, Suter MR, Ji RR, Decosterd I (2010) Glial cells and chronic pain. Neuroscientist 16(5):519–531. https://doi.org/10.1177/1073858409360822
Hashemi-Monfared A, Firouzi M, Bahrami Z, Zahednasab H, Harirchian MH (2018) Minocycline decreases CD36 and increases CD44 in LPS-induced microglia. J Neuroimmunol 317:95–99. https://doi.org/10.1016/j.jneuroim.2018.01.010
Horvath RJ, Nutile-McMenemy N, Alkaitis MS, Deleo JA (2008) Differential migration, LPS-induced cytokine, chemokine, and NO expression in immortalized BV-2 and HAPI cell lines and primary microglial cultures. J Neurochem 107(2):557–569. https://doi.org/10.1111/j.1471-4159.2008.05633.x
Hsieh CT, Lee YJ, Dai X, Ojeda NB, Lee HJ, Tien LT, Fan LW (2018) Systemic lipopolysaccharide-induced pain sensitivity and spinal inflammation were reduced by minocycline in neonatal rats. Int J Mol Sci 19(10):2947. https://doi.org/10.3390/ijms19102947
Huang CY, Sheu WH, Chiang AN (2015) Docosahexaenoic acid and eicosapentaenoic acid suppress adhesion molecule expression in human aortic endothelial cells via differential mechanisms. Mol Nutr Food Res 59(4):751–762. https://doi.org/10.1002/mnfr.201400687
Hylden JL, Wilcox GL (1980) Intrathecal morphine in mice: a new technique. Eur J Pharmacol 67(2–3):313–316. https://doi.org/10.1016/0014-2999(80)90515-4
Jakus PB, Kalman N, Antus C, Radnai B, Tucsek Z, Gallyas F Jr, Sumegi B, Veres B (2013) TRAF6 is functional in inhibition of TLR4-mediated NF-kappaB activation by resveratrol. J Nutr Biochem 24(5):819–823. https://doi.org/10.1016/j.jnutbio.2012.04.017
Ji RR, Berta T, Nedergaard M (2013) Glia and pain: is chronic pain a gliopathy? Pain 154(Suppl 1):S10-28. https://doi.org/10.1016/j.pain.2013.06.022
Ji RR, Xu ZZ, Gao YJ (2014) Emerging targets in neuroinflammation-driven chronic pain. Nat Rev Drug Discov 13(7):533–548. https://doi.org/10.1038/nrd4334
Ji RR, Donnelly CR, Nedergaard M (2019) Astrocytes in chronic pain and itch. Nat Rev Neurosci 20(11):667–685. https://doi.org/10.1038/s41583-019-0218-1
Kawasaki Y, Zhang L, Cheng JK, Ji RR (2008) Cytokine mechanisms of central sensitization: distinct and overlap** role of interleukin-1beta, interleukin-6, and tumor necrosis factor-alpha in regulating synaptic and neuronal activity in the superficial spinal cord. J Neurosci 28(20):5189–5194. https://doi.org/10.1523/JNEUROSCI.3338-07.2008
Konigs A, Kiliaan AJ (2016) Critical appraisal of omega-3 fatty acids in attention-deficit/hyperactivity disorder treatment. Neuropsychiatr Dis Treat 12:1869–1882. https://doi.org/10.2147/NDT.S68652
Landa-Juarez AY, Perez-Severiano F, Castaneda-Hernandez G, Ortiz MI, Chavez-Pina AE (2019) The antihyperalgesic effect of docosahexaenoic acid in streptozotocin-induced neuropathic pain in the rat involves the opioidergic system. Eur J Pharmacol 845:32–39. https://doi.org/10.1016/j.ejphar.2018.12.029
Li Z, Wei H, Piirainen S, Chen Z, Kalso E, Pertovaara A, Tian L (2016) Spinal versus brain microglial and macrophage activation traits determine the differential neuroinflammatory responses and analgesic effect of minocycline in chronic neuropathic pain. Brain Behav Immun 58:107–117. https://doi.org/10.1016/j.bbi.2016.05.021
Li M, Zhang D, Ge X, Zhu X, Zhou Y, Zhang Y, Peng X, Shen A (2019) TRAF6-p38/JNK-ATF2 axis promotes microglial inflammatory activation. Exp Cell Res 376(2):133–148. https://doi.org/10.1016/j.yexcr.2019.02.005
Lu Y, Zhao LX, Cao DL, Gao YJ (2013) Spinal injection of docosahexaenoic acid attenuates carrageenan-induced inflammatory pain through inhibition of microglia-mediated neuroinflammation in the spinal cord. Neuroscience 241:22–31. https://doi.org/10.1016/j.neuroscience.2013.03.003
Lu Y, Jiang BC, Cao DL, Zhang ZJ, Zhang X, Ji RR, Gao YJ (2014) TRAF6 upregulation in spinal astrocytes maintains neuropathic pain by integrating TNF-alpha and IL-1beta signaling. Pain 155(12):2618–2629. https://doi.org/10.1016/j.pain.2014.09.027
Lu Y, Cao DL, Jiang BC, Yang T, Gao YJ (2015) MicroRNA-146a-5p attenuates neuropathic pain via suppressing TRAF6 signaling in the spinal cord. Brain Behav Immun 49:119–129. https://doi.org/10.1016/j.bbi.2015.04.018
Manzhulo IV, Ogurtsova OS, Lamash NE, Latyshev NA, Kasyanov SP, Dyuizen IV (2015) Analgetic effect of docosahexaenoic acid is mediated by modulating the microglia activity in the dorsal root ganglia in a rat model of neuropathic pain. Acta Histochem 117(7):659–666. https://doi.org/10.1016/j.acthis.2015.07.001
Manzhulo IV, Ogurtsova OS, Kipryushina YO, Latyshev NA, Kasyanov SP, Dyuizen IV, Tyrtyshnaia AA (2016) Neuron-astrocyte interactions in spinal cord dorsal horn in neuropathic pain development and docosahexaenoic acid therapy. J Neuroimmunol 298:90–97. https://doi.org/10.1016/j.jneuroim.2016.07.015
Marret E, Kurdi O, Zufferey P, Bonnet F (2005) Effects of nonsteroidal antiinflammatory drugs on patient-controlled analgesia morphine side effects: meta-analysis of randomized controlled trials. Anesthesiology 102(6):1249–1260. https://doi.org/10.1097/00000542-200506000-00027
Mohammadi M, Manaheji H, Maghsoudi N, Danyali S, Baniasadi M, Zaringhalam J (2020) Microglia dependent BDNF and proBDNF can impair spatial memory performance during persistent inflammatory pain. Behav Brain Res 390:112683. https://doi.org/10.1016/j.bbr.2020.112683
Nakamoto K, Nishinaka T, Mankura M, Fujita-Hamabe W, Tokuyama S (2010) Antinociceptive effects of docosahexaenoic acid against various pain stimuli in mice. Biol Pharm Bull 33(6):1070–1072. https://doi.org/10.1248/bpb.33.1070
Nakamoto K, Nishinaka T, Sato N, Mankura M, Koyama Y, Kasuya F, Tokuyama S (2013) Hypothalamic GPR40 signaling activated by free long chain fatty acids suppresses CFA-induced inflammatory chronic pain. PLoS ONE 8(12):e81563. https://doi.org/10.1371/journal.pone.0081563
Natacci L, D MM, A CG, Nunes MA, A BM, L OC, Giatti L, MDC BM, I SS, Brunoni AR, P AL, I MB (2018) Omega 3 Consumption and anxiety disorders: a cross-sectional analysis of the Brazilian longitudinal study of adult health (ELSA-Brasil). Nutrients 10 (6). https://doi.org/10.3390/nu10060663
Oh DY, Talukdar S, Bae EJ, Imamura T, Morinaga H, Fan W, Li P, Lu WJ, Watkins SM, Olefsky JM (2010) GPR120 is an omega-3 fatty acid receptor mediating potent anti-inflammatory and insulin-sensitizing effects. Cell 142(5):687–698. https://doi.org/10.1016/j.cell.2010.07.041
Orr SK, Palumbo S, Bosetti F, Mount HT, Kang JX, Greenwood CE, Ma DW, Serhan CN, Bazinet RP (2013) Unesterified docosahexaenoic acid is protective in neuroinflammation. J Neurochem 127(3):378–393. https://doi.org/10.1111/jnc.12392
Pimentel GD, Lira FS, Rosa JC, Oller do Nascimento CM, Oyama LM, Harumi Watanabe RL, Ribeiro EB, (2013) High-fat fish oil diet prevents hypothalamic inflammatory profile in rats. ISRN Inflam 2013:419823. https://doi.org/10.1155/2013/419823
Qian B, Li F, Zhao LX, Dong YL, Gao YJ, Zhang ZJ (2016) Ligustilide ameliorates inflammatory pain and inhibits TLR4 upregulation in spinal astrocytes following complete Freund’s adjuvant peripheral injection. Cell Mol Neurobiol 36(1):143–149. https://doi.org/10.1007/s10571-015-0228-0
Saunders EF, Ramsden CE, Sherazy MS, Gelenberg AJ, Davis JM, Rapoport SI (2016) Omega-3 and omega-6 polyunsaturated fatty acids in bipolar disorder: a review of biomarker and treatment studies. J Clin Psychiatry 77(10):e1301–e1308. https://doi.org/10.4088/JCP.15r09925
Selvam C, Mutisya D, Prakash S, Ranganna K, Thilagavathi R (2017) Therapeutic potential of chemically modified siRNA: recent trends. Chem Biol Drug Des 90(5):665–678. https://doi.org/10.1111/cbdd.12993
Song ZP, **ong BR, Guan XH, Cao F, Manyande A, Zhou YQ, Zheng H, Tian YK (2016) Minocycline attenuates bone cancer pain in rats by inhibiting NF-kappaB in spinal astrocytes. Acta Pharmacol Sin 37(6):753–762. https://doi.org/10.1038/aps.2016.1
Starobova H, Mueller A, Allavena R, Lohman RJ, Sweet MJ, Vetter I (2019) Minocycline prevents the development of mechanical allodynia in mouse models of vincristine-induced peripheral neuropathy. Front Neurosci 13:653. https://doi.org/10.3389/fnins.2019.00653
Sukhotnik I, Haj B, Pollak Y, Dorfman T, Bejar J, Matter I (2016) Effect of bowel resection on TLR signaling during intestinal adaptation in a rat model. Surg Endosc 30(10):4416–4424. https://doi.org/10.1007/s00464-016-4760-x
Sun GY, Simonyi A, Fritsche KL, Chuang DY, Hannink M, Gu Z, Greenlief CM, Yao JK, Lee JC, Beversdorf DQ (2018) Docosahexaenoic acid (DHA): an essential nutrient and a nutraceutical for brain health and diseases. Prostaglandins Leukot Essent Fatty Acids 136:3–13. https://doi.org/10.1016/j.plefa.2017.03.006
Svensson CI, Zattoni M, Serhan CN (2007) Lipoxins and aspirin-triggered lipoxin inhibit inflammatory pain processing. J Exp Med 204(2):245–252. https://doi.org/10.1084/jem.20061826
Walsh MC, Lee J, Choi Y (2015) Tumor necrosis factor receptor- associated factor 6 (TRAF6) regulation of development, function, and homeostasis of the immune system. Immunol Rev 266(1):72–92. https://doi.org/10.1111/imr.12302
Wang C, Kong X, Zhu C, Liu C, Sun D, Xu Q, Mao Z, Qin Q, Su H, Wang D, Zhao X, Lin N (2017) Wu-tou decoction attenuates neuropathic pain via suppressing spinal astrocytic IL-1R1/TRAF6/JNK signaling. Oncotarget 8(54):92864–92879. https://doi.org/10.18632/oncotarget.21638
Wang Y, Chen H, Chen Q, Jiao FZ, Zhang WB, Gong ZJ (2018a) The protective mechanism of CAY10683 on intestinal mucosal barrier in acute liver failure through LPS/TLR4/MyD88 pathway. Mediators Inflamm 2018:7859601. https://doi.org/10.1155/2018/7859601
Wang Z, Liu F, Wei M, Qiu Y, Ma C, Shen L, Huang Y (2018b) Chronic constriction injury-induced microRNA-146a-5p alleviates neuropathic pain through suppression of IRAK1/TRAF6 signaling pathway. J Neuroinflamm 15(1):179. https://doi.org/10.1186/s12974-018-1215-4
Watkins LR, Hutchinson MR, Milligan ED, Maier SF (2007) “Listening” and “talking” to neurons: implications of immune activation for pain control and increasing the efficacy of opioids. Brain Res Rev 56(1):148–169. https://doi.org/10.1016/j.brainresrev.2007.06.006
Weng RX, Chen W, Tang JN, Sun Q, Li M, Xu X, Zhang PA, Zhang Y, Hu CY, Xu GY (2020) Targeting spinal TRAF6 expression attenuates chronic visceral pain in adult rats with neonatal colonic inflammation. Mol Pain 16:1744806920918059. https://doi.org/10.1177/1744806920918059
**ang X, Wang S, Shao F, Fang J, Xu Y, Wang W, Sun H, Liu X, Du J (2019) Electroacupuncture stimulation alleviates CFA-induced inflammatory pain via suppressing P2X3 expression. Int J Mol Sci 20(13):3248. https://doi.org/10.3390/ijms20133248
**ng Y, Yao X, Li H, Xue G, Guo Q, Yang G, An L, Zhang Y, Meng G (2017) Cutting edge: TRAF6 mediates TLR/IL-1R signaling-induced nontranscriptional priming of the NLRP3 inflammasome. J Immunol 199(5):1561–1566. https://doi.org/10.4049/jimmunol.1700175
Yan W, Sun W, Fan J, Wang H, Han S, Li J, Yin Y (2020) Sirt1-ROS-TRAF6 signaling-induced pyroptosis contributes to early injury in ischemic mice. Neurosci Bull 36(8):845–859. https://doi.org/10.1007/s12264-020-00489-4
Yang C, Gao J, Wu B, Yan N, Li H, Ren Y, Kan Y, Liang J, Jiao Y, Yu Y (2017) Minocycline attenuates the development of diabetic neuropathy by inhibiting spinal cord Notch signaling in rat. Biomed Pharm 94:380–385. https://doi.org/10.1016/j.biopha.2017.07.078
Young K, Morrison H (2018) Quantifying microglia morphology from photomicrographs of immunohistochemistry prepared tissue using ImageJ. JoVE. https://doi.org/10.3791/57648
Zhang L, Terrando N, Xu ZZ, Bang S, Jordt SE, Maixner W, Serhan CN, Ji RR (2018) Distinct analgesic actions of DHA and DHA-derived specialized pro-resolving mediators on post-operative pain after bone fracture in mice. Front Pharmacol 9:412. https://doi.org/10.3389/fphar.2018.00412
Zhao XH, Zhang T, Li YQ (2015) The up-regulation of spinal Toll-like receptor 4 in rats with inflammatory pain induced by complete Freund’s adjuvant. Brain Res Bull 111:97–103. https://doi.org/10.1016/j.brainresbull.2015.01.002
Zhou J, Deng Y, Li F, Yin C, Shi J, Gong Q (2019) Icariside II attenuates lipopolysaccharide-induced neuroinflammation through inhibiting TLR4/MyD88/NF-kappaB pathway in rats. Biomed Pharm 111:315–324. https://doi.org/10.1016/j.biopha.2018.10.201
Zhu MD, Zhao LX, Wang XT, Gao YJ, Zhang ZJ (2014) Ligustilide inhibits microglia-mediated proinflammatory cytokines production and inflammatory pain. Brain Res Bull 109:54–60. https://doi.org/10.1016/j.brainresbull.2014.10.002
Acknowledgements
This work was supported by grants from the National Natural Science Foundation of China (Nos. 31871064, 32030048, and 31700899) and Nantong Science and Technology Planning Project (Nos. JC2020073 and JC2020038).
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflict of interest
No conflicts of interest, financial or otherwise, are declared by the authors.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Lu, Y., Cao, DL., Ma, LJ. et al. TRAF6 Contributes to CFA-Induced Spinal Microglial Activation and Chronic Inflammatory Pain in Mice. Cell Mol Neurobiol 42, 1543–1555 (2022). https://doi.org/10.1007/s10571-021-01045-y
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10571-021-01045-y