Neuroinflammation as secondary damage in head injury

Abstract

Head injury is one of the main disability causes among the working-age population. Stroke energy induces mechanical injury of tissues to launch secondary damage, i.e. neurotransmission, blood-brain barrier disruption, blood infiltration of brain tissues, cytokine and chemokine overexpression, and other processes. Activated by the injury, microglia plays a special part to initially 'protect' intact tissues from the products of necrosis and apoptosis. After the injury, microglia rapidly differentiates to phenotypes М1 and М2. Pro-inflammatory phenotype М1 produces neuronal cytotoxic cytokines including tumor necrosis factor-, interleukins (IL)-6 and IL-1, and NO that induce apoptosis while phenotype М2 secretes IL-4 and IL-13 that may supposedly reduce inflammation and improve recovery of brain tissues. М2 response lasts much less than М1 response, and increasing pro-inflammatory activation leads to further neuronal death, which affects cognitive and physical status of patients with head injury. The review covers main biochemical processes in the injured brain and possible ways of neuroinflammation modulation.