title: Early activation, motility, and homing of neonatal microglia to injured neurons does not require protein synthesis.
abstract: Neuronal injury in CNS tissues induces a rapid activation and mobilization of resident microglia (MG). It is widely assumed that changes in gene expression drive the morphological transformation of MG and regulate their mobilization during activation. Here, we used acutely excised neonatal rat brain slices to test whether the morphological transformation and homing of MG to injured neurons requires gene expression and de novo protein synthesis. Traumatic injury during excision of live brain tissue slices induces a rapid and transient translocation of a transcription factor, NF-kappaB, to nuclei in MG. This is followed within 4-8 h by an increase in immunolabeling for cell adhesion molecules and lysosomal proteins, accompanied by changes in cell morphology. Application of anisomycin, a protein synthesis inhibitor, prevents the increase in immunolabeling for markers of MG activation but not the morphological transformation. Confocal time-lapse imaging in live tissue slices indicates that MG cell motility (branch extension and retraction) and locomotion are unaffected by anisomycin at early postinjury time-points (<4 h), while at later time-points (4-8 h postinjury) MG locomotion but not motility is inhibited. Thus, activated MG rapidly localize to injured pyramidal neuron cell bodies by 4-h postinjury, even in the presence of anisomycin. Moreover, this early MG activation and homing to injured neurons is unaffected in tissue slices from beta2 integrin deficient mice. These results indicate that gene activation and new protein synthesis coincide with, but are not necessary for, the rapid morphological transformation and early migration-dependent homing of activated MG to injured neurons in CNS tissues.
authors.affiliation: Department of Biological Sciences, The University of Iowa, Iowa City, 52242, USA.
authors.forename: Dana
authors.initials: D
authors.lastname: Kurpius
authors.forename: Nicholas
authors.initials: N
authors.lastname: Wilson
authors.forename: Leah
authors.initials: L
authors.lastname: Fuller
authors.forename: Amara
authors.initials: A
authors.lastname: Hoffman
authors.forename: Michael E
authors.initials: ME
authors.lastname: Dailey
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000166:cytology / Q000378:metabolism* / Q000503:physiopathology; D001930:Brain Injuries / Q000378:metabolism / Q000503:physiopathology; D018821:CD18 Antigens / Q000235:genetics / Q000378:metabolism; D002450:Cell Communication / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D004195:Disease Models, Animal; D005911:Gliosis / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology; D016169:Lymphocyte Function-Associated Antigen-1 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D017628:Microglia / Q000166:cytology / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D009474:Neurons / Q000378:metabolism*; D009924:Organ Culture Techniques; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D015533:Transcriptional Activation / Q000187:drug effects / Q000502:physiology*
chemical_list: D018821:CD18 Antigens; D016169:Lymphocyte Function-Associated Antigen-1; D016328:NF-kappa B; D009419:Nerve Tissue Proteins; D011500:Protein Synthesis Inhibitors