PERMANENT FOCAL AND TRANSIENT GLOBAL CEREBRAL-ISCHEMIA INCREASE GLIALAND NEURONAL EXPRESSION OF HEME OXYGENASE-1, BUT NOT HEME OXYGENASE-2, PROTEIN IN RAT-BRAIN
Jw. Geddes et al., PERMANENT FOCAL AND TRANSIENT GLOBAL CEREBRAL-ISCHEMIA INCREASE GLIALAND NEURONAL EXPRESSION OF HEME OXYGENASE-1, BUT NOT HEME OXYGENASE-2, PROTEIN IN RAT-BRAIN, Neuroscience letters, 210(3), 1996, pp. 205-208
Two heme oxygenase (HO) proteins have been identified to date; HO-1, a
stress-induced protein, and HO-2, a constitutively ex pressed isoform
. Recently, it was demonstrated that HO-1 mRNA expression is increased
following transient global ischemia. The present study examined the e
ffects of global and focal ischemia on HO-I and HO-2 protein, using im
munocytochemistry. Following 20 min of ischemia (rat 4 vessel occlusio
n model with hypotension) and 6 h of recirculation, increased HO immun
oreactivity was evident in hippocampal neurons. After 24 h of recircul
ation, HO-1 was observed in both hippocampal neurons and astroglial ce
lls. By 72 h, expression was primarily glial and restricted to CAI and
CA3c, In addition to hippocampus, HO-1 I was also evident in both neu
rons and glia in cerebral cortex and thalamus, and in striatal glial c
ells. Twenty-four hours following permanent focal ischemia, HO-1 immun
oreactivity was observed in astroglial cells in the penumbra region su
rrounding the infarct. In contrast to HO-1, the pattern of HO-2 immuno
reactivity was not altered following transient global or permanent foc
al ischemia: The increased expression of HO-1 following ischemia may c
onfer protection against oxidative stress, but might also contribute t
o the subsequent neuronal degeneration.