Interleukin (IL)-8 immunoreactivity of injured axons and surrounding oligodendrocytes in traumatic head injury

摘要

Interleukin (IL)-8 has been suggested to be a positive regulator of myelination in the central nervous system, in addition to its principal role as a chemokine for neutrophils. Immunostaining for beta-amyloid precursor protein (A beta PP) is an effective tool for detecting traumatic axonal injury, although AbPP immunoreactivity can also indicate axonal injury due to hypoxic causes. In this study, we examined IL-8 and A beta PP immunoreactivity in sections of corpus callosum obtained from deceased patients with blunt head injury and from equivalent control tissue. A beta PP immunoreactivity was detected in injured axons, such as axonal bulbs and varicose axons, in 24 of 44 head injury cases. These A beta PP immunoreactive cases had survived for more than 3 h. The A beta PP immunostaining pattern can be classified into two types: traumatic (Pattern 1) and non-traumatic (Pattern 2) axonal injuries, which we described previously [Hayashi et al. Int. J. Legal Med. 129 (2015) 1085-1090]. Three of 44 control cases also showed A beta PP immunoreactive injured axons as Pattern 2. In contrast, IL-8 immunoreactivity was detected in 7 A beta PP immunoreactive and in 2 non-A beta PP immunoreactive head injury cases, but was not detected in any of the 44 control cases, including the 3 A beta PP immunoreactive control cases. The IL-8 immunoreactive cases had survived from 3 to 24 days, whereas those cases who survived less than 3 days (n = 29) and who survived 90 days (n = 1) were not IL-8 immunoreactive. Moreover, IL-8 was detected as Pattern 1 axons only. In addition, double immunofluorescence analysis showed that IL-8 is expressed by oligodendrocytes surrounding injured axons. In conclusion, our results suggest that immunohistochemical detection of IL-8 may be useful as a complementary diagnostic marker of traumatic axonal injury. (C) 2016 Elsevier Ireland Ltd. All rights reserved.