Background and Purpose- Sex differences in the incidence and outcome of
stroke have been well documented. The severity of
stroke in women is, in general, significantly lower than that in men, which is mediated, at least in part, by the protective effects of β-
estradiol. However, the detailed mechanisms underlying the neuroprotection by β-
estradiol are still elusive. Recent studies have demonstrated that activation of ASIC1a (
acid-sensing ion channel 1a) by tissue
acidosis, a common feature of
brain ischemia, plays an important role in ischemic
brain injury. In the present study, we assessed the effects of β-
estradiol on
acidosis-mediated and ischemic neuronal injury both in vitro and in vivo and explored the involvement of ASIC1a and underlying mechanism. Methods- Cultured neurons and NS20Y cells were subjected to
acidosis-mediated injury in vitro. Cell viability and cytotoxicity were measured by methylthiazolyldiphenyl-tetrazolium
bromide and
lactate dehydrogenase assays, respectively. Transient (60 minutes) focal
ischemia in mice was induced by
suture occlusion of the middle cerebral artery in vivo. ASIC currents were recorded using whole-cell patch-clamp technique while intracellular Ca2+ concentration was measured with fluorescence imaging using
Fura-2. ASIC1a expression was detected by Western blotting and quantitative real-time polymerase chain reaction. Results- Treatment of neuronal cells with β-
estradiol decreased
acidosis-induced cytotoxicity. ASIC currents and
acid-induced elevation of intracellular Ca2+ were all attenuated by β-
estradiol treatment. In addition, we showed that β-
estradiol treatment reduced ASIC1a
protein expression, which was mediated by increased protein degradation, and that
estrogen receptor α was involved. Finally, we showed that the level of ASIC1a
protein expression in brain tissues and the degree of neuroprotection by ASIC1a blockade were lower in female mice, which could be attenuated by
ovariectomy. Conclusions- β-
estradiol can protect neurons against
acidosis-mediated neurotoxicity and ischemic
brain injury by suppressing ASIC1a
protein expression and channel function. Visual Overview- An online visual overview is available for this article.