RESUMO
Lymphangiogenesis critically contributes to the lymphatic metastasis of colorectal carcinomas (CRCs), but the underlying mechanism of CRC lymphangiogenesis remains largely elusive. We have previously demonstrated that Semaphorin-3F (SEMA3F) is critically involved in CRC metastasis, and the receptor of SEMA3F, neuropilin-2 (NRP2), originally described as an axon guiding chemorepulsant implicated in nerve development, has been suggested in promoting lymphangiogenesis via acting as an obligate co-receptor of VEGFR3 cooperatively enhancing the activity of VEGF-C. Our present study revealed that in colorectal carcinomas, NRP2 expression levels of tumor-associated lymphatic endothelial cells (LECs) are significantly correlated with the density of tumor lymphatic vessels. In vitro, activation of NRP2 in LECs substantially facilitates their migration, sprouting, and tubulogenesis capacity via regulating the rearrangement of cytoskeleton polarity. In vivo model further showed that in the xenografts generated from SEMA3F knockdown CRC cells, NRP2 is substantially activated in tumor-associated LECs, resulting in a significantly increased tumor lymphangiogenesis. Further evidence demonstrated that CRC cell induces the activation of NRP2 in LECs to promote tumor lymphangiogenesis via integrinα9ß1/FAK/Erk pathway independent VEGF-C/VEGFR3 signaling. Our study for the first time revealed the novel molecular mechanism of NRP2-mediated-lymphangiogenesis in CRCs, suggesting NRP2 as a potential therapeutic target in preventing lymphatic metastasis of CRCs.
Assuntos
Neoplasias Colorretais/metabolismo , Neoplasias Colorretais/patologia , Linfangiogênese , Neuropilina-2/metabolismo , Transdução de Sinais , Fator C de Crescimento do Endotélio Vascular/metabolismo , Receptor 3 de Fatores de Crescimento do Endotélio Vascular/metabolismo , Animais , Linhagem Celular Tumoral , Movimento Celular/genética , Neoplasias Colorretais/genética , Modelos Animais de Doenças , Quinase 1 de Adesão Focal/metabolismo , Humanos , Integrina beta1/metabolismo , Integrinas/metabolismo , Linfangiogênese/genética , Camundongos , Neuropilina-2/genética , Proteínas rac1 de Ligação ao GTP/metabolismoRESUMO
α7 Nicotinic acetylcholine receptor (α7 nAChR) has been found in several non-neuronal cells and is described as an important regulator of cellular function. Naturally occurring CD4(+)CD25(+) regulatory T cells (Tregs) are essential for the active suppression of autoimmunity. The present study investigated whether naturally occurring Tregs expressed α7 nAChR and investigated the functionary role of this receptor in controlling suppressive activity of these cells. We found that CD4(+)CD25(+) Tregs from naive C57BL/6J mice positively expressed α7 nAChR, and its activation by nicotine enhanced the suppressive capacity of Tregs. Nicotine stimulation up-regulated the expression of cytotoxic T-lymphocyte-associated antigen (CTLA)-4 and forkhead/winged helix transcription factor p3 (Foxp3) on Tregs but had no effect on the production of interleukin (IL)-10 and transforming growth factor-ß1 by Tregs. In the supernatants of CD4(+)CD25(+) Tregs/CD4(+)CD25(-) T-cell cocultures, we observed a decrease in the concentration of IL-2 in nicotine-stimulated groups, but nicotine stimulation had no effect on the ratio of IL-4/interferon (IFN)-γ, which partially represented T-cell polarization. The above-mentioned effects of nicotine were reversed by a selective α7 nAChR antagonist, α-bungarotoxin. In addition, the ratio of IL-4/IFN-γ was increased by treatment with α-bungarotoxin. We conclude that nicotine might increase Treg-mediated immune suppression of lymphocytes via α7 nAChR. The effect is related to the up-regulation of CTLA-4 as well as Foxp3 expression and decreased IL-2 secretion in CD4(+)CD25(+) Tregs/CD4(+)CD25(-) T-cell coculture supernatants. α7 nAChR seems to be a critical regulator for immunosuppressive function of CD4(+)CD25(+) Tregs.
Assuntos
Tolerância Imunológica/efeitos dos fármacos , Tolerância Imunológica/imunologia , Subunidade alfa de Receptor de Interleucina-2/metabolismo , Nicotina/farmacologia , Receptores Nicotínicos/metabolismo , Linfócitos T Reguladores/efeitos dos fármacos , Linfócitos T Reguladores/imunologia , Animais , Antígenos CD/metabolismo , Bungarotoxinas/metabolismo , Bungarotoxinas/farmacologia , Linfócitos T CD4-Positivos/imunologia , Antígeno CTLA-4 , Proliferação de Células , Técnicas de Cocultura , Fatores de Transcrição Forkhead/metabolismo , Expressão Gênica/efeitos dos fármacos , Expressão Gênica/genética , Interferon gama/metabolismo , Interleucina-10/metabolismo , Interleucina-2/metabolismo , Interleucina-4/metabolismo , Ativação Linfocitária/imunologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Antagonistas Nicotínicos/metabolismo , Antagonistas Nicotínicos/farmacologia , Receptores Nicotínicos/genética , Baço/citologia , Linfócitos T Reguladores/metabolismo , Fator de Crescimento Transformador beta1/metabolismo , Receptor Nicotínico de Acetilcolina alfa7RESUMO
The cholinergic anti-inflammatory pathway (CAP) is a neurophysiological mechanism that regulates the immune system. The CAP inhibits inflammation by suppressing cytokine synthesis via release of acetylcholine in organs of the reticuloendothelial system, including the lungs, spleen, liver, kidneys and gastrointestinal tract. Acetylcholine can interact with alpha7 nicotinic acetylcholine receptors (alpha7 nAchR) expressed by macrophages and other cytokine producing cells, down-regulate pro-inflammatory cytokine synthesis and prevent tissue damage. Herein is a review of the neurophysiological mechanism in which the CAP regulates inflammatory response, as well as its potential interventional strategy for inflammatory diseases.
