Elsevier

Brain Research

Volume 1109, Issue 1, 13 September 2006, Pages 14-21
Brain Research

Research Report
Cortical expression of nuclear factor κB after human brain contusion

https://doi.org/10.1016/j.brainres.2006.06.045Get rights and content

Abstract

The aim of current study was to analyze the binding activity and the temporal and cellular expression of nuclear factor kappa B (NF-κB) in human contused brain. Eighteen contused brain samples were obtained from 17 patients undergoing surgery for brain contusions 5–80 h after trauma. NF-κB binding activity was detected by electrophoretic mobility shift assay (EMSA), and temporal and cellular expression of NF-κB subunits p65 and p50 was analyzed by immunohistochemistry. The results showed that a progressive upregulation of NF-κB activity occurred in the area surrounding the injured brain with the time from brain trauma to operation. The maximal expression of NF-κB was detected after 48 h postinjury. The expression of NF-κB p65 was mainly located at glial and vascular endothelial cells without expression at neurons. The expression of NF-κB p50 was mainly located at glial cells, a little at neurons and no expression at vascular endothelial cells. Within 24 h postinjury, both NF-κB p65 and p50 immunoreactivity was mainly observed in the nucleus of cells. After 24 h postinjury, NF-κB p65 labeling was found in the both nucleus and cytoplasm of glial and endothelial cells; otherwise, p50 labeling was primarily found in the nucleus of glial cells and in the nucleus, cytoplasm and process of neurons. It is concluded that NF-κB could be highly upregulated at human contused brain and the cellular pattern of p65 and p50 expression might be closely associated with the cell functions.

Introduction

Focal traumatic brain injury (TBI) induces primary neuronal degeneration in the site of injury and initiates a series of cellular and molecular events that lead to protracted secondary damage in the surrounding tissue and distally connected areas (Knoblach et al., 1999, Holmin et al., 1997, Holmin et al., 1998). In base to experimental studies performed in rodents, it is now known that secondary damage is exacerbated by the inflammatory response, commonly mediated and magnified by the upregulation or de novo expression of different genes (Yang et al., 1994, Yang et al., 1995, Hang et al., 2005, Arvin et al., 1995, Isaksson et al., 1997). Several studies have shown that the nuclear factor kappa B (NF-κB) family (cRel, RelA/p65, Rel B, p50 and p52) of transcription factor is one of the most important modulators of inflammatory gene expression in the nervous system as well as in non-neural tissues (Grilli and Memo, 1999, Baeuerle and Baltimore, 1996). NF-κB is one of the most important modulators of stress and inflammatory gene expression in the nervous system (CNS) and may be important determinants of cell death and disease of the CNS (Baeuerle and Baltimore, 1996, Salminen et al., 1995). NF-κB upregulation has been demonstrated in neurons and glial cells in response to experimental injury and neuropathological disorders, where it has been related to both neurodegenerative and neuroprotective activities (Yang et al., 1995, Hang et al., 2005, O'Neill and Kaltschmidt, 1997, Mattson et al., 2000, Kaltschmidt et al., 1994a, Bales et al., 1998, Nonaka et al., 1999). Activation of NF-κB in neurons has been generally involved in synaptic plasticity, neuronal function, development and survival (O'Neill and Kaltschmidt, 1997, Mattson et al., 2000), and in glial cells it has been mainly related to the inflammatory response (Kaltschmidt et al., 1994a, Bales et al., 1998) through induction of expression of proinflammatory genes such as TNF-α, IL-1β, IL-6, cyclooxygenase-2 (Cox-2), iNOS and adhesion molecules (VCAM-1 and ICAM-1) (Grilli and Memo, 1999).

Prototypical NF-κB heterodimers contain p50 and p65 subunits complexed with an IκB inhibitory protein to maintain an inactive cytosolic complex. Appropriate intracellular signals induce phosphorylation of IκB by an IκB kinase (IKK)-containing signalsome, dissociation of the inhibitory protein and its consequent degradation. The resulting nuclear migration of p65 and p50 modulates target gene expression by binding cognate GGGRNNYYCC DNA promoter sequences. Among the inducible transcription factors, members of the NF-κB family have been shown to play a role in the regulation of genes in the glial cells and neurons (Lipton, 1997). Some experiments have shown that p50 is involved in an adaptive response of neurons that survive injury (Meberg et al., 1996, Pennypacker et al., 2001). Selective activation of distinct subunits intrinsic to particular models of neurodegeneration may indeed promote cell death, with alternative dimer combinations conferring neuroprotection. However, till now it is unclear about the cellular localization of NF-κB subunits p65 and p50 in the different cell types and whether it changes among time in the human brain after TBI.

In this sense, in the last decade several studies have proposed a role of NF-κB activation in the degenerative and inflammatory response occurring after TBI in the rat brain (Yang et al., 1995, Nonaka et al., 1999, Nomoto et al., 2001). Till now, no study was found in the literature to investigate the NF-κB expression in the human brain after TBI. Therefore, little is known about the involvement of this transcription factor in the evolution of TBI-induced inflammatory response in the human brain contusion. Our previous studies have demonstrated that cortical brain damage is associated with increased activity of NF-κB and proinflammatory cytokine (Hang et al., 2004, Hang et al., 2005); therefore, the study of NF-κB along the evolution of TBI in the human brain may provide some insights into the importance of this signal transduction pathway in the degenerative/regenerative events that underlie poor brain lesion outcome. In this regard, the aim of the present study was to evaluate the binding activity and temporal and cellular expression pattern of NF-κB following a lesion biopsy in the human brain contusion.

Section snippets

EMSA autoradiography of NF-κB DNA binding activity

EMSA autoradiography of NF-κB DNA binding activity of 18 injured brain samples in 17 patients was shown in Fig. 1. Low NF-κB binding activity (weak EMSA autoradiography) was found in the patients who were early operated (≤ 6 h). NF-κB binding activity was progressively upregulated with the time from initial brain injury to operation. As compared with ≤ 6 h group, NF-κB binding activity measured by EMSA was significantly increased in the late operated patients (12–48 h, P < 0.05; ≥ 48 h, P < 0.01). In

Discussion

In this clinical study, we have first reported that upregulation of NF-κB occurred at human contused brain. The NF-κB binding activity was time dependent, showing progressively increased after brain injury. A weak expression of NF-κB was observed in the early stage of trauma, and the maximal expression occurred after 48 h postinjury. Immunohistochemical study showed that NF-κB subunits were localized in different cells. p65 was expressed at both neuroglial cells and vascular epithelial cells,

Patients

This study was approved by Najing University's Medical Institutional Review Board. Eighteen contused brain tissue biopsies were obtained from 17 consecutive patients undergoing surgery for brain contusions 5–80 h after trauma (Table 1). One patient underwent 2 operations at 12 h and 26 h postinjury, respectively (cases 10 and 14). No anti-inflammatory drugs, hypotension/hypovolemia or hypoxia either before hospital admission or during surgery was used in all patients. During surgery, following

Acknowledgments

We would like to thank Dr. Genbao Feng and Bo Wu for their technical assistance.

References (32)

  • L.A.J. O'Neill et al.

    NF-κB: a crucial transcription factor for glial and neuronal cell function

    Trends Neurosci.

    (1997)
  • K.R. Pennypacker et al.

    NF-kappaB p50 is increased in neurons surviving hippocampal injury

    Exp. Neurol.

    (2001)
  • A. Salminen et al.

    Alteration of transcription factor binding activities in the ischemic rat brain

    Biochem. Biophys. Res. Commun.

    (1995)
  • K. Yang et al.

    Increased expression of c-fos gene and AP-1 transcription factor after cortical impact injury in rodent model

    Brain Res.

    (1994)
  • K. Yang et al.

    Increased cortical nuclear factor-κB (NFκB) DNA binding activity after traumatic brain injury in rats

    Neurosci. Lett.

    (1995)
  • B. Arvin et al.

    Brain injury and inflammation: a putative role of TNF alpha

    Ann. N. Y. Acad. Sci.

    (1995)
  • Cited by (68)

    • Inhibition of leukotriene B4 synthesis protects against early brain injury possibly via reducing the neutrophil-generated inflammatory response and oxidative stress after subarachnoid hemorrhage in rats

      2018, Behavioural Brain Research
      Citation Excerpt :

      The shifted bands were visualized after exposure to film. All protocols of EMSA were performed according to our previous study [24]. The relative levels of reactive oxygen species (ROS) and malondialdehyde (MDA) and the activities of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) in the brain cortex were investigated by corresponding detection kits (Nanjing Jiancheng Bioengineering Institute, Nanjing, JS, China) according to the manufacturers’ instructions as described [25].

    • Common biochemical defects linkage between post-traumatic stress disorders, mild traumatic brain injury (TBI) and penetrating TBI

      2015, Brain Research
      Citation Excerpt :

      The levels of pro-inflammatory cytokine interleukin-6 (IL-6) were elevated in patients with acute TBI, and a significant relationship existed between the severity of TBI and the transcranial IL-6 gradient (Minambres et al., 2003). In addition, activation of nuclear factor-kappa B (NF-kappaB) occurred after TBI in both animals and humans (Xiao and Wei, 2005; Hang et al., 2006). Treatment with beta-aescin (a natural triterpenoid isolated from the seed of Chinese horse chestnut) inhibited activation of NF-kappaB and expression of TNF-alpha (Xiao and Wei, 2005).

    View all citing articles on Scopus
    View full text