The Journal of Neuroscience, January 1, 1999, 19(1):133-146
Heparin-Binding Epidermal Growth Factor-Like Growth Factor in
Hippocampus: Modulation of Expression by Seizures and Anti-Excitotoxic
Action
Lisa A.
Opanashuk1,
Robert J.
Mark1, 2,
Julie
Porter1,
Deborah
Damm3,
Mark P.
Mattson1, 2, and
Kim B.
Seroogy1
1 Department of Anatomy and Neurobiology and
2 Sanders-Brown Research Center on Aging, University of
Kentucky, Lexington, Kentucky 40536, and 3 Scios
Inc., Mountain View, California 94043
The expression of heparin-binding epidermal growth factor-like
growth factor (HB-EGF), an EGF receptor ligand, was investigated in rat
forebrain under basal conditions and after kainate-induced excitotoxic
seizures. In addition, a potential neuroprotective role for HB-EGF was
assessed in hippocampal cultures. In situ hybridization
analysis of HB-EGF mRNA in developing rat hippocampus revealed its
expression in all principle cell layers of hippocampus from birth to
postnatal day (P) 7, whereas from P14 through adulthood, expression
decreased in the pyramidal cell layer versus the dentate gyrus granule
cells. After kainate-induced excitotoxic seizures, levels of HB-EGF
mRNA increased markedly in the hippocampus, as well as in several other
cortical and limbic forebrain regions. In the hippocampus, HB-EGF mRNA
expression increased within 3 hr after kainate treatment, continued to
increase until 24 hr, and then decreased; increases occurred in the
dentate gyrus granule cells, in the molecular layer of the dentate
gyrus, and in and around hippocampal pyramidal CA3 and CA1 neurons. At
48 hr after kainate treatment, HB-EGF mRNA remained elevated in
vulnerable brain regions of the hippocampus and amygdaloid complex.
Western blot analysis revealed increased levels of HB-EGF protein in
the hippocampus after kainate administration, with a peak at 24 hr. Pretreatment of embryonic hippocampal cell cultures with HB-EGF protected neurons against kainate toxicity. The kainate-induced elevation of [Ca2+]i in hippocampal
neurons was not altered in cultures pretreated with HB-EGF, suggesting
an excitoprotective mechanism different from that of previously
characterized excitoprotective growth factors. Taken together, these
results suggest that HB-EGF may function as an endogenous
neuroprotective agent after seizure-induced neural activity/injury.
Key words:
HB-EGF; hippocampus; neuroprotection; epilepsy; excitotoxicity; in situ hybridization; kainic acid; calcium
Copyright © 1999 Society for Neuroscience 0270-6474/99/191133-14$05.00/0