Premarin stimulates estrogen receptor-α to protect against traumatic brain injury in male rats*

Objectives: To establish mechanisms of neuroprotective actions induced by Premarin (an estrogen sulfate) during traumatic brain injury. Design: Chi Mei Medical Center research laboratory. Subjects: Male Sprague-Dawley rats 244 to 268 g. Interventions: Anesthetized rats, immediately after the onset of fluid percussion injury, were divided into three major groups and given the vehicle solution (1 mL/kg of body weight), Premarin (1 mg/kg of body weight), or Premarin (1 mg/kg of body weight) plus the nonselective estrogen receptor-α antagonist ICI 182, 780 (0.25 mg/kg of body weight) intravenously and immediately after fluid percussion injury. Measurements and Main Results: Premarin, in addition to inducing pharmacologic levels of estradiol, causes attenuation of fluid percussion injury-induced cerebral infarction and motor and cognitive function deficits. Fluid percussion injury-induced apoptosis (e.g., increased numbers of both terminal deoxynucleotidyl transferase dUTP nick-end labeling-positive and caspase-3-positive cells) as well as activated inflammation (e.g., increased levels of tumor necrosis factor-α) was also significantly Premarin-reduced. In peri-ischemic areas of hippocampus, both angiogenesis (e.g., increased numbers of both 5-bromodeoxyuridine-positive endothelial and vascular endothelial growth factor-positive cells) and neurogenesis (e.g., increased numbers of both 5-bromodeoxyuridine/neuronal-specific nuclear protein double-positive and glial cell line-derived neurotrophic factor-positive cells) were Premarin therapy-promoted. In estrogen receptor-α blockade rats, Premarin therapy had less or no effect on fluid percussion injury-induced behavioral deficits, cerebral infarction and apoptosis, and activated inflammation. Furthermore, Premarin-induced angiogenesis and neurogenesis were estrogen receptor-α blockade-reduced. Conclusions: Our results indicate that pharmacologic levels of Premarin therapy-induced estradiol protect against cortical and hippocampal programmed cell death after fluid percussion injury through mechanisms stimulating estrogen receptor-α in the male rats.