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Master's Dissertation
DOI
10.11606/D.17.2018.tde-28052018-152655
Document
Author
Full name
David Wilson Ferreira
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Ribeirão Preto, 2013
Supervisor
Committee
Cunha, Thiago Mattar (President)
Cury, Yara
Prado, Wiliam Alves do
Title in Portuguese
Mecanismos nociceptivos desencadeados pela ativação espinal dos receptores NOD2 (CARD15) na gênese da dor crônica
Keywords in Portuguese
Astrócito
Células da glia
Dor crônica
Hipersensibilidade
Micróglia
Muramil dipeptídeo
NOD2
Receptor do tipo NOD
Receptores de reconhecimento padrão
Abstract in Portuguese
Entre os PRRs (receptores de reconhecimento padrão), NOD-like receptors (NLRs), tal como NOD2, são responsáveis pela detecção intracelular de muramil dipeptídeo (MDP); padrão molecular associado a patógeno (PAMP), encontrado no peptidoglicano (PGN) de praticamente todas bactérias GRAM positiva e negativa. Após o reconhecimento e estimulação por MDP, NOD2 recruta diretamente a serina-treonina quinase RIPK2, uma proteína adaptadora importante na ativação de NF?B mediada por NOD2. A expressão de NOD2 foi descrita em macrófagos e em outras células. Além disso, trabalhos anteriores indicaram que PRRs desempenham papel crucial na ativação de células gliais da medula espinal, na indução e manutenção da dor inflamatória crônica e dor neuropática. No presente estudo, avaliamos o papel de NOD2 na modulação da sensibilidade à dor, focando sua importância na ativação de células da glia da medula espinal, bem como a sua via de sinalização (RIPK2) e liberação de citocinas pró-nociceptivas, como o fator de necrose tumoral alfa (TNF-?), interleucina-6 (IL-6) e interleucina-1 beta (IL-1?). Os resultados demonstram que camundongos selvagens tratados com MDP, apresentaram diminuição no limiar nociceptivo mecânico (pico entre 3 e 5 horas) comparado com o grupo controle (veículo), retornando ao basal após 48 horas. Além disso, camundongos NOD2-/- , RIPK2-/- , TNFR1/2-/- e IL-6 -/- tratados com MDP não diferiram o limiar nociceptivo mecânico, comparado com seus respectivos grupos controle (veículo). Entretanto, camundongos TNFR1- /- , CCR2-/- , TLR4-/- , MyD88-/- e TRIF-/- tratados com MDP, apresentaram diminuição no limiar nociceptivo mecânico similar aos camundongos selvagens tratados com MDP. Adicionalmente, o pré-tratamento de camundongos selvagens com IL-1ra, propentofilina, minociclina, fluorocitrato e SB 203580 inibiu o desenvolvimento da hipersensibilidade mecânica induzida por MDP. Estes dados sugerem que a ativação do sensor intracellular NOD2 esta presente em células da glia da medula espinal e estimula a ativação das vias de sinalização RIPK2 e p38 MAPK com subsequente produção de IL-1?, IL-6 e TNF?, por uma via de sinalização independente de TLR4, MyD88 e TRIF. Finalmente, estes mecanismos contribuem para o processo de hipersensibilidade mecânica durante a neuropatia periférica e representam uma nova abordagem para elucidar os mecanismos envolvidos na fisiopatologia da dor crônica.
Title in English
Nociceptive mechanisms triggered by spinal activation of NOD2 (CARD15) in the genesis of chronic pain
Keywords in English
Astrocytes
Chronic pain
Glial cells
Hypersensitivity
Microglia
Muramyl dipeptide
NOD-like receptors
NOD2
Pattern recognition receptors
Abstract in English
Among PRRs (pattern recognition receptors), NOD-like receptors (NLRs), such as NOD2 are responsible by intracellular detection of muramyl dipeptide (MDP); pathogen-associated molecular pattern (PAMP) found in the peptidoglycan (PGN) from virtually all gram positive and gram negative bacteria. Upon recognition and stimulation by MDP, NOD2 recruits directly the receptor-interacting serine/threonine-protein kinase 2 (RIPK2), an adaptor protein important in the NOD2-mediated NF?B activation. The expression of NOD2 has been described in macrophages and other cells. Moreover, previous work has indicated that PRRs play a crucial role in the activation of spinal cord glial cells, in the induction and maintenance of chronic inflammatory and neuropathic pain. In the present study, we aimed to evaluate the role of NOD2 in the modulation of pain sensitivity, focusing on its importance in the activation of spinal cord glial cells, as well as its signaling pathway (RIPK2) and release of pro-nociceptive cytokines, such as tumour necrosis factor-alpha (TNF-?), interleukin-6 (IL-6) and interleukin-1beta (IL-1?). The results demonstrate that WT mice treated with MDP showed a decrease in mechanical nociceptive threshold (peak 3 to 5 hours) compared with the control group (vehicle), returning to the base line after 48 hours. Furthermore, NOD2-/- , RIPK2-/- , TNFR1/2-/- and IL-6 -/- mice treated with MDP did not differ the mechanical nociceptive threshold compared with their respective control groups (vehicle). However, TNFR1-/- , CCR2-/- , TLR4-/- , MyD88-/- and TRIF-/- mice treated MDP, showed a decrease in mechanical nociceptive threshold similar to WT mice treated with MDP. In addition, the pretreatment of WT mice with IL-1ra, propentofylline, minocycline, fluorocitrate and SB 203580 inhibited the development of mechanical hypersensitivity induced by MDP. These data suggest that activation of the intracellular sensor NOD2 present in spinal cord glial cells stimulates the activation of RIPK2 and p38 MAPK signaling pathways and subsequent production of IL-1?, IL-6 and TNF?, in a TLR4-, MyD88- and TRIF-independent signaling pathway. Finally, these mechanisms contribute to the process of mechanical hypersensitivity during peripheral neuropathy and represent a novel approach for elucidating the mechanisms underlying pathophysiology of chronic pain.
 
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Publishing Date
2018-07-16
 
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