Heme oxygenase (HO) exists as two isoenzymes designated heme oxygenase
-1 (HO-1) and heme oxygenase-2 (HO-2), HO-1 has been identified as a h
eat shock or stress protein and is inducible whereas HO-2 is largely r
efractory to induction. HO-2 is the predominant isoenzyme in normal br
ain and appears to have a predominantly neuronal distribution in cereb
ral cortex. Cortical stab wound injury resulted in HO-1 induction as d
etermined by Western blot analysis. Immunohistochemical analysis sugge
sted that induced HO-1 was largely restricted to reactive astrocytes a
nd macrophage-like cells. Enhanced HO-1 immunoreactivity was observed
in hypertrophied, GFAP(+) reactive astrocytes near the wound margin as
early as 12 h after injury, Very rarely were HO-1(+) neurons observed
and then only up to 6 h after stabbing. Maximal numbers of HO-1(+) as
trocytes were found 3 days after stabbing, Their numbers declined ther
eafter. By 5 days after stab injury few HO-1(+) reactive astrocytes we
re observed although GFAP(+) reactive astrocytes were still prominent
near the wound margin, HO-1(+) macrophage-like cells were initially ob
served between 1 and 3 days after injury and they persisted in the mar
gin of the wound for at least 14 days, The proximity of HO-1(+) cells
to the wound margin suggests that factors associated with injury contr
ibute to the regulation of HO-1 in injured cortex.