The formation of
glial scar impedes the neurogenesis and neural functional recovery following
cerebral ischemia.
Histamine showed neuroprotection at early stage after
cerebral ischemia, however, its long-term effect, especially on
glial scar formation, hasn't been characterized. With various administration regimens constructed for
histidine, a precursor of
histamine, we found that
histidine treatment at a high dose at early stage and a low dose at late stage demonstrated the most remarkable long-term neuroprotection with decreased
infarct volume and improved neurological function. Notably, this treatment regimen also robustly reduced the
glial scar area and facilitated the astrocyte migration towards the
infarct core. In wound-healing assay and transwell test,
histamine significantly promoted astrocyte migration. H2 receptor antagonists reversed the promotion of astrocyte migration and the neuroprotection provided by
histidine. Moreover,
histamine upregulated the
GTP-bound
small GTPase Rac1, while a Rac1 inhibitor,
NSC23766, abrogated the neuroprotection of
histidine and its promotion of astrocyte migration. Our data indicated that a dose/stage-dependent
histidine treatment, mediated by H2 receptor, promoted astrocyte migration towards the
infarct core, which benefited long-term post-
cerebral ischemia neurological recovery. Therefore, targeting histaminergic system may be an effective therapeutic strategy for long-term
cerebral ischemia injury through its actions on astrocytes.