Zheng Haolin, Mizokami Akiko, Romera-Giner Sergio, Llera-Oyola Jaime, Yamawaki Yosuke, Sano Tomomi, Jimi Eijiro, García-García Francisco, Kanematsu Takashi
Department of Cell Biology, Aging Science, and Pharmacology, Division of Oral Biological Sciences, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-Ku, Fukuoka, 812-8582, Japan.
OBT Research Center, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-Ku, Fukuoka, 812-8582, Japan.
Biol Sex Differ. 2025 Feb 4;16(1):9. doi: 10.1186/s13293-025-00686-8.
Significant sex differences exist in the prevalence and incidence of Alzheimer's disease (AD). Notably, testosterone has been reported to regulate cognitive functions in the brain, with low serum testosterone levels correlating with increased AD risk. However, the specific mechanisms underlying this relationship remain unclear. Recent studies have demonstrated that microglia, the primary innate immune cells in the brain, play a crucial role in AD development. Therefore, this study aimed to explore sex differences in microglial function, specifically focusing on the role of testosterone in miRNA-mediated regulation of microglial gene expression.
Microglia were isolated from pooled hippocampal tissue of five 8-month-old male and female mice. Total RNA was extracted and subjected to miRNA microarray analysis. The mouse microglial cell line MG6 was used for in vitro experiments. Following testosterone treatment, miRNA, gene, and protein expression levels were investigated. An inflammatory response was induced using lipopolysaccharide (LPS) stimulation, and subsequent p65 phosphorylation was assessed.
Sex-dependent differences were observed in miRNA-mediated biological processes, with males exhibiting greater changes. Male-enriched miRNAs were associated with fatty acid synthesis and metabolism pathways. In MG6 cells, testosterone treatment upregulated the expression of several miRNAs enriched in male microglia, particularly those targeting genes related to fatty acid synthesis. Additionally, testosterone significantly reduced the gene expression of fatty acid synthase (FASN). This testosterone-induced inhibition of FASN expression attenuated NF-κB/p65 phosphorylation. Consequently, the suppression of FASN expression led to reduced expression and secretion of tumor necrosis factor-alpha following LPS stimulation in MG6 cells.
These findings suggest that testosterone modulates inflammation in male microglia by regulating fatty acid synthesis, potentially contributing to the observed sex differences in AD pathogenesis.
阿尔茨海默病（AD）的患病率和发病率存在显著的性别差异。值得注意的是，有报道称睾酮可调节大脑的认知功能，血清睾酮水平低与AD风险增加相关。然而，这种关系背后的具体机制仍不清楚。最近的研究表明，小胶质细胞作为大脑中的主要先天性免疫细胞，在AD的发展中起关键作用。因此，本研究旨在探讨小胶质细胞功能的性别差异，特别关注睾酮在miRNA介导的小胶质细胞基因表达调控中的作用。
从小鼠海马组织中分离小胶质细胞，这些海马组织来自5只8月龄雄性和雌性小鼠。提取总RNA并进行miRNA微阵列分析。小鼠小胶质细胞系MG6用于体外实验。在睾酮处理后，研究miRNA、基因和蛋白质表达水平。使用脂多糖（LPS）刺激诱导炎症反应，并评估随后的p65磷酸化。
在miRNA介导的生物学过程中观察到性别依赖性差异，雄性表现出更大的变化。雄性富集的miRNA与脂肪酸合成和代谢途径相关。在MG6细胞中，睾酮处理上调了几种在雄性小胶质细胞中富集的miRNA的表达，特别是那些靶向与脂肪酸合成相关基因的miRNA。此外，睾酮显著降低了脂肪酸合酶（FASN）的基因表达。这种睾酮诱导的FASN表达抑制减弱了NF-κB/p65磷酸化。因此，FASN表达的抑制导致MG6细胞在LPS刺激后肿瘤坏死因子-α的表达和分泌减少。
这些发现表明，睾酮通过调节脂肪酸合成来调节雄性小胶质细胞中的炎症，这可能是AD发病机制中观察到的性别差异的原因。
