Astrocyte-targeted expression of IL-6 protects the CNS against a focal brain injury

Exp Neurol. 2003 Jun;181(2):130-48. doi: 10.1016/s0014-4886(02)00051-1.

Abstract

The effect of CNS-targeted IL-6 gene expression has been thoroughly investigated in the otherwise nonperturbed brain but not following brain injury. Here we examined the impact of astrocyte-targeted IL-6 production in a traumatic brain injury (cryolesion) model using GFAP-IL6 transgenic mice. This study demonstrated that transgenic IL-6 production significantly increased wound healing following the cryolesion. Thus, at 20 days postlesion (dpl) the GFAP-IL6 mice showed almost complete wound healing compared to litter mate nontransgenic controls. It seems likely that a reduced inflammatory response in the long term could be responsible for this IL-6-related effect. Thus, while in the acute phase following cryolesion (1-6 dpl) the recruitment of macrophages and T lymphocytes was higher in GFAP-IL6 mice, at 10-20 dpl it was significantly reduced compared to controls. Reactive astrogliosis was also significantly increased up to but not including 20 dpl in the GFAP-IL6 mice. Oxidative stress as well as apoptotic cell death was significantly decreased throughout the time period studied in the GFAP-IL6 mice compared to controls. This could be linked to the altered inflammatory response as well as to the transgenic IL-6-induced increase of the antioxidant, neuroprotective proteins metallothionein-I + II. These results indicate that although in the brain the chronic astrocyte-targeted expression of IL-6 spontaneously induces an inflammatory response causing significant damage, during an acute neuropathological insult such as following traumatic injury, a clear neuroprotective role is evident.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antioxidants / metabolism
  • Apoptosis
  • Astrocytes / metabolism*
  • Astrocytes / pathology
  • Brain Injuries / metabolism*
  • Brain Injuries / pathology
  • Central Nervous System / injuries
  • Central Nervous System / metabolism*
  • Central Nervous System / pathology
  • Cerebral Cortex / injuries
  • Cerebral Cortex / metabolism
  • Cerebral Cortex / pathology
  • Disease Models, Animal
  • Female
  • Freezing
  • Gene Targeting
  • Gliosis / pathology
  • Interleukin-6 / biosynthesis*
  • Interleukin-6 / genetics
  • Lymphocytes / pathology
  • Macrophages / pathology
  • Mice
  • Mice, Transgenic
  • Microglia / pathology
  • Oxidative Stress / genetics
  • Wound Healing / genetics*

Substances

  • Antioxidants
  • Interleukin-6