BACKGROUND Tibolone is a synthetic steroid used in clinical practice for the treatment of climacteric symptoms and osteoporosis. Active metabolites of tibolone, generated in target tissues, have an affinity for estrogen and androgen receptors. Astrocytes are direct targets for estrogenic compounds and previous studies have shown that tibolone protects brain cortical neurons in association with a reduction in reactive astrogliosis in a mouse model of traumatic brain injury. Since phagocytosis is a crucial component of the neuroprotective function exerted by astrocytes, in the present study, we have assessed whether tibolone regulates phagocytosis in primary astrocytes incubated with brain-derived cellular debris. METHODS Male and female astrocyte cell cultures were obtained from newborn (P0-P2) female and male Wistar rats. Astrocytic phagocytosis was first characterized using carboxylate beads, Escherichia coli particles, or brain-derived cellular debris. Then, the effect of tibolone on the phagocytosis of Cy3-conjugated cellular debris was quantified by measuring the intensity of Cy3 dye-emitted fluorescence in a given GFAP immunoreactive area. Before the phagocytosis assays, astrocytes were incubated with tibolone in the presence or absence of estrogen or androgen receptor antagonists or an inhibitor of the enzyme that synthesizes estradiol. The effect of tibolone on phagocytosis was analyzed under basal conditions and after inflammatory stimulation with lipopolysaccharide. RESULTS Tibolone stimulated phagocytosis of brain-derived cellular debris by male and female astrocytes, with the effect being more pronounced in females. The effect of tibolone in female astrocytes was blocked by a selective estrogen receptor β antagonist and by an androgen receptor antagonist. None of these antagonists affected tibolone-induced phagocytosis in male astrocytes. In addition, the inhibition of estradiol synthesis in the cultures enhanced the stimulatory effect of tibolone on phagocytosis in male astrocytes but blocked the effect of the steroid in female cells under basal conditions. However, after inflammatory stimulation, the inhibition of estradiol synthesis highly potentiated the stimulation of phagocytosis by tibolone, particularly in female astrocytes. CONCLUSIONS Tibolone exerts sex-specific regulation of phagocytosis in astrocytes of both sexes, both under basal conditions and after inflammatory stimulation.

中文翻译：

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合成类固醇替勃龙在基础条件下和炎症激发后对星形胶质细胞的吞噬作用进行性别特异性调节。

背景技术替勃龙是在临床实践中用于治疗更年期症状和骨质疏松症的合成类固醇。靶组织中生成的替勃龙的活性代谢产物对雌激素和雄激素受体具有亲和力。星形胶质细胞是雌激素化合物的直接靶标，先前的研究表明，替勃龙在创伤性脑损伤的小鼠模型中与反应性星形胶质细胞减少症相关联，从而保护了大脑皮层神经元。由于吞噬作用是星形胶质细胞发挥神经保护功能的重要组成部分，因此，在本研究中，我们评估了替勃龙是否调节与脑源性细胞碎片孵育的原代星形胶质细胞的吞噬作用。方法从新生（P0-P2）雌性和雄性Wistar大鼠获得雄性和雌性星形胶质细胞培养物。首先使用羧酸盐珠，大肠杆菌颗粒或脑源性细胞碎片表征星形细胞吞噬作用。然后，通过在给定的GFAP免疫反应区域中测量Cy3染料发射的荧光强度，来定量测定替勃龙对Cy3缀合的细胞碎片吞噬作用的影响。在吞噬作用测定之前，在存在或不存在雌激素或雄激素受体拮抗剂或合成雌二醇的酶抑制剂的情况下，将星形胶质细胞与替勃龙一起孵育。在基础条件下和脂多糖刺激后，分析了替勃龙对吞噬作用的影响。结果替勃龙可刺激雄性和雌性星形胶质细胞吞噬脑源性细胞碎片，在雌性中这种作用更为明显。替勃龙在雌性星形胶质细胞中的作用被选择性雌激素受体β拮抗剂和雄激素受体拮抗剂阻断。这些拮抗剂均未影响替勃龙诱导的雄性星形胶质细胞吞噬作用。此外，培养物中雌二醇合成的抑制增强了替勃龙对雄性星形胶质细胞吞噬作用的刺激作用，但在基础条件下阻断了类固醇在雌性细胞中的作用。然而，在炎症刺激之后，雌二醇合成的抑制高度增强了替勃龙对吞噬作用的刺激，特别是在雌性星形胶质细胞中。结论替勃龙在基础条件下和炎症刺激后均可对性别的星形胶质细胞进行吞噬作用的性别特异性调节。