RESUMO
Injury to the central nervous system initiates an uncontrolled inflammatory response that results in both tissue repair and destruction. Here, we showed that, in rodents and humans, injury to the spinal cord triggered surface expression of CD95 ligand (CD95L, FasL) on peripheral blood myeloid cells. CD95L stimulation of CD95 on these cells activated phosphoinositide 3-kinase (PI3K) and metalloproteinase-9 (MMP-9) via recruitment and activation of Syk kinase, ultimately leading to increased migration. Exclusive CD95L deletion in myeloid cells greatly decreased the number of neutrophils and macrophages infiltrating the injured spinal cord or the inflamed peritoneum after thioglycollate injection. Importantly, deletion of myeloid CD95L, but not of CD95 on neural cells, led to functional recovery of spinal injured animals. Our results indicate that CD95L acts on peripheral myeloid cells to induce tissue damage. Thus, neutralization of CD95L should be considered as a means to create a controlled beneficial inflammatory response.
Assuntos
Movimento Celular , Proteína Ligante Fas/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Células Mieloides/metabolismo , Peritonite/imunologia , Proteínas Tirosina Quinases/metabolismo , Animais , Células Cultivadas , Proteína Ligante Fas/genética , Proteína Ligante Fas/imunologia , Humanos , Inflamação , Metaloproteinase 9 da Matriz/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Células Mieloides/imunologia , Células Mieloides/patologia , Peritônio/imunologia , Peritônio/patologia , Peritonite/induzido quimicamente , Fosfatidilinositol 3-Quinases/metabolismo , Transdução de Sinais , Medula Espinal/imunologia , Medula Espinal/patologia , Quinase Syk , Tioglicolatos/administração & dosagemRESUMO
Adult neurogenesis persists in the subventricular zone and the dentate gyrus and can be induced upon central nervous system injury. However, the final contribution of newborn neurons to neuronal networks is limited. Here we show that in neural stem cells, stimulation of the "death receptor" CD95 does not trigger apoptosis but unexpectedly leads to increased stem cell survival and neuronal specification. These effects are mediated via activation of the Src/PI3K/AKT/mTOR signaling pathway, ultimately leading to a global increase in protein translation. Induction of neurogenesis by CD95 was further confirmed in the ischemic CA1 region, in the naive dentate gyrus, and after forced expression of CD95L in the adult subventricular zone. Lack of hippocampal CD95 resulted in a reduction in neurogenesis and working memory deficits. Following global ischemia, CD95-mediated brain repair rescued behavioral impairment. Thus, we identify the CD95/CD95L system as an instructive signal for ongoing and injury-induced neurogenesis.
