کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5040628 | 1473903 | 2017 | 16 صفحه PDF | دانلود رایگان |
- Repeated concussion is linked to the later development of neurodegenerative diseases.
- The effect of immune activation on later neurodegeneration is not yet known.
- TLR4 activation at 1D post-injury was neuroprotective.
- TLR4 activation at 5D post-injury exacerbated deficits.
- Immune activation after rmTBI can influence long-term outcome.
A history of repeated concussion has been linked to the later development of neurodegeneration, which is associated with the accumulation of hyperphosphorylated tau and the development of behavioral deficits. However, the role that exogenous factors, such as immune activation, may play in the development of neurodegeneration following repeated mild traumatic brain injury (rmTBI) has not yet been explored. To investigate, male Sprague-Dawley rats were administered three mTBIs 5Â days apart using the diffuse impact-acceleration model to generate â¼100Â G. Sham animals underwent surgery only. At 1 or 5Â days following the last injury rats were given the TLR4 agonist, lipopolysaccharide (LPS, 0.1Â mg/kg), or saline. TLR4 activation had differential effects following rmTBI depending on the timing of activation. When given at 1Â day post-injury, LPS acutely activated microglia, but decreased production of pro-inflammatory cytokines like IL-6. This was associated with a reduction in neuronal injury, both acutely, with a restoration of levels of myelin basic protein (MBP), and chronically, preventing a loss of both MBP and PSD-95. Furthermore, these animals did not develop behavioral deficits with no changes in locomotion, anxiety, depressive-like behavior or cognition at 3Â months post-injury. Conversely, when LPS was given at 5Â days post-injury, it was associated acutely with an increase in pro-inflammatory cytokine production, with an exacerbation of neuronal damage and increased levels of aggregated and phosphorylated tau. At 3Â months post-injury, there was a slight exacerbation of functional deficits, particularly in cognition and depressive-like behavior. This highlights the complexity of the immune response following rmTBI and the need to understand how a history of rmTBI interacts with environmental factors to influence the potential to develop later neurodegeneration.
Journal: Brain, Behavior, and Immunity - Volume 64, August 2017, Pages 124-139