Cellular and Molecular Biology


Immunohistochemical characterization of Fas (CD95) and Fas Ligand (FasL/CD95L) expression in the injured brain: Relationship with neuronal cell death and inflammatory mediators

M.B. Grosjean1, P.M. Lenzlinger2, P.F. Stahel3, I. Yatsiv4, E. Shohami5, O. Trentz2, T. Kossmann6 and M.C. Morganti-Kossmann6

1Center for Dental and Oral Medicine and Cranio-Maxillofacial Surgery, University of Zurich, Zurich, Switzerland, 2Divisions of Surgical Research and Trauma Surgery, University Hospital, Zurich, Switzerland, 3Department of Trauma and Reconstructive Surgery, Charité University Medical School, Campus Benjamin Franklin, Berlin, Germany, 4Pediatric Critical Care Medicine, Hadassah University Hospitals and 5Department of Pharmacology, The Hebrew University, Hadassah Medical School, Jerusalem, Israel and 6Department of Trauma Surgery, National Trauma Research Institute, The Alfred Hospital, Monash University, Melbourne, Australia

Offprint requests to: Maria Cristina Morganti-Kossmann, Ph.D., Department of Trauma Surgery, National Trauma Research Institute, The Alfred Hospital, Monash University, Commercial Road, Melbourne, Victoria 3004, Australia. e-mail: cristina.morganti-kossmann@med.monash.edu.au

Summary. Traumatic brain injury causes progressive tissue atrophy and consequent neurological dysfunction, resulting from neuronal cell death in both animal models and patients. Fas (CD95) and Fas ligand (FasL/CD95L) are important mediators of apoptosis. However, little is known about the relationship between Fas and FasL and neuronal cell death in mice lacking the genes for inflammatory cytokines. In the present study, double tumor necrosis factor/lymphotoxin-alpha knockout (–/–) and interleukin-6–/– mice were subjected to closed head injury (CHI) and sacrificed at 24 hours or 7 days post-injury. Consecutive brain sections were evaluated for Fas and FasL expression, in situ DNA fragmentation (terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling; TUNEL), morphologic characteristics of apoptotic cell death and leukocyte infiltration. A peak incidence of TUNEL positive cells was found in the injured cortex at 24 hours which remained slightly elevated at 7 days and coincided with maximum Fas expression. FasL was only moderately increased at 24 hours and showed maximum expression at 7 days. A few TUNEL positive cells were also found in the ipsilateral hippocampus at 24 hours. Apoptotic, TUNEL positive cells mostly co-localized with neurons and Fas and FasL immunoreactivity. The amount of accumulated polymorphonuclear leukocytes and CD11b positive cells was maximal in the injured hemispheres at 24 hours. We show strong evidence that Fas and FasL might be involved in neuronal apoptosis after CHI. Furthermore, Fas and FasL upregulation seems to be independent of neuroinflammation since no differences were found between cytokine–/– and wild-type mice. Histol Histopathol 22, 235-250 (2007)

Key words: Apoptosis, Fas, Cytokines, Closed head injury, TUNEL, Neurodegeneration, Traumatic brain injury

DOI: 10.14670/HH-22.235