Post-stroke treatment with 17β-estradiol exerts neuroprotective effects in both normotensive and hypertensive rats

Although ischemic stroke is a major cause of death worldwide and the predominant cause of acquired disability, the only effective drug therapy that has been developed thus far is reperfusion by tissue plasminogen activator. Since most patients do not qualify for this treatment, new methods have to be developed. It is well known that estradiol (E2) exerts neuroprotective effects in different models of cerebral ischemia, but post-stroke treatment after an acute stroke has hardly been investigated. As many patients with an acute ischemic stroke have arterial hypertension, it is also of interest to evaluate the influence of this co-morbidity on the treatment efficacy of E2. The effects of E2 administered 30min after a transient middle cerebral artery occlusion (tMCAO) induced by an intracerebral injection of endothelin-1 were assessed in male normotensive Wistar Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs). Treatment with E2 reduced infarct size in both WKY and SHRs and decreased the number of degenerating neurons, indicating that acute treatment with E2 is indeed neuroprotective. To address the role of glia in neuroprotection, the effects of E2 on the activation of microglia and astrocytes was determined. It appeared that E2 had no effect on microglial activation, but reduced the activation of astrocytes in SHRs but not in the normotensive controls. We conclude that post-stroke E2 treatment in both normotensive and hypertensive rats is neuroprotective. Although the presence of hypertension changed the astrocytic response to E2, it did not affect treatment efficacy.