Acute brain injury triggers MyD88-dependent, TLR2/4-independent inflammatory responses

Am J Pathol. 2007 Jul;171(1):200-13. doi: 10.2353/ajpath.2007.060821.

Abstract

Endogenous molecules released from disrupted cells and extracellular matrix degradation products activate Toll-like receptors (TLRs) and, thus, might contribute to immune activation after tissue injury. Here, we show that aseptic, cold-induced cortical injury triggered an acute immune response that involves increased production of multiple cytokines/chemokines accompanied by neutrophil recruitment to the lesion site. We observed selective reductions in injury-induced cytokine/chemokine expression as well as in neutrophil accumulation in mice lacking the common TLR signaling adaptor MyD88 compared with wild-type mice. Notably, attenuation of the immune response was paralleled by a reduction in lesion size. Neutrophil depletion of wild-type mice and transplantation of MyD88-deficient bone marrow into lethally irradiated wild-type recipients had no substantial impact on injury-induced expression of cytokines/chemokines and on lesion development. In contrast to MyD88 deficiency, double deficiency of TLR2 and TLR4 -- despite the two receptors being activated by specific endogenous molecules associated to danger and signal through MyD88 -- altered neither immune response nor extent of tissue lesion size on injury. Our data indicate modulation of the neuroinflammatory response and lesion development after aseptic cortical injury through MyD88-dependent but TLR2/4-independent signaling by central nervous system resident nonmyeloid cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain Injuries / genetics*
  • Brain Injuries / immunology*
  • Chemokines / metabolism
  • Cold Temperature
  • Cytokines / metabolism
  • Immunity, Cellular / genetics*
  • Inflammation / genetics
  • Inflammation / immunology
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Myeloid Differentiation Factor 88 / genetics*
  • Neutrophils / immunology
  • Toll-Like Receptor 2 / physiology*
  • Toll-Like Receptor 4 / physiology*

Substances

  • Chemokines
  • Cytokines
  • Myd88 protein, mouse
  • Myeloid Differentiation Factor 88
  • TLR4 protein, human
  • Tlr2 protein, mouse
  • Toll-Like Receptor 2
  • Toll-Like Receptor 4