嗅球中TET2缺失加重香烟烟雾诱导的鼻息肉小鼠的嗅觉障碍

文献信息

中文摘要

背景： 香烟烟雾（CS）是嗅觉障碍的关键环境风险因素，但其在慢性鼻窦炎伴鼻息肉（CRSwNP）中的潜在机制仍不完全清楚。
目的： 阐明TET2在CS诱导的嗅觉障碍中的发病机制。
方法： 在野生型（WT）和Tet2敲除（Tet2-/-）小鼠中建立鼻息肉（NPs）模型，随后暴露于CS。通过行为学评估嗅觉功能，并检测嗅上皮中嗅觉标记蛋白（OMP）的表达。使用免疫荧光、TUNEL染色、ELISA和Western blot评估嗅球中小胶质细胞活化、神经炎症和神经元损伤。通过Dot blot和羟甲基化DNA免疫沉淀-定量PCR（hMeDIP-qPCR）分析DNA羟甲基化水平。还探讨了尼古丁对TET2、GPX4和SLC7A11表达的影响及其潜在机制。
结果： Tet2敲除显著加重了CS诱导的嗅觉障碍，表现为嗅觉能力更明显的下降以及息肉样改变和杯状细胞增生的发生率增加。然而，嗅上皮中OMP的表达未受影响。与CS刺激的WT小鼠相比，Tet2敲除小鼠嗅球中小胶质细胞活化和神经炎症增加更明显，表现为IL-1β、IL-6和TNF-α水平升高。此外，TET2缺失加重了嗅球中的神经元损伤，表现为神经元凋亡增加和尼古丁积累。机制上，TET2缺失通过下调GPX4表达增强了嗅球中的铁死亡，而SLC7A11表达未受影响。发现尼古丁通过TET2介导的DNA去甲基化下调小胶质细胞和嗅球神经元中GPX4的表达，从而诱导铁死亡。
结论： 嗅球中TET2的缺失加重了CS诱导的GPX4下调，随后诱导的铁死亡可能是CRSwNP中嗅觉障碍加重的关键机制。

英文摘要

BACKGROUND: Cigarette smoke (CS) is a key environmental risk factor for olfactory impairment, yet its underlying mechanisms in chronic rhinosinusitis with nasal polyps (CRSwNP) remain incompletely understood.
OBJECTIVE: To elucidate the pathogenesis involving TET2 in CS-induced olfactory impairment.
METHODS: A mouse model for nasal polyps (NPs) was established in wild-type (WT) and Tet2 knockout (Tet2-/-) mice followed by CS exposure. Olfactory function was assessed behaviorally, and the expression of olfactory marker protein (OMP) in the olfactory epithelium was examined. The activation of microglia, neuroinflammation, and neuronal damage in the olfactory bulb were evaluated using immunofluorescence, TUNEL staining, ELISA, and Western blot. DNA hydroxymethylation levels were analyzed by Dot blot and hydroxymethylated DNA immunoprecipitation-quantitative PCR (hMeDIP-qPCR). The effects of nicotine on TET2, GPX4, and SLC7A11 expression and the underlying mechanisms were also explored.
RESULTS: Tet2 knockout significantly exacerbated CS-induced olfactory impairment, as evidenced by a more pronounced reduction in olfactory ability and increased incidence of polypoid changes and goblet cell hyperplasia. However, the expression of OMP in the olfactory epithelium remained unaffected. Compared with WT mice stimulated by CS, Tet2 knockout mice exhibited more increased microglial activation and neuroinflammation in the olfactory bulb, characterized by elevated levels of IL-1β, IL-6, and TNF-α. Moreover, TET2 deletion aggravated neuronal damage in the olfactory bulb, as evidenced by increased neuronal apoptosis and nicotine accumulation. Mechanistically, TET2 deletion potentiated ferroptosis in the olfactory bulb by downregulating GPX4 expression, while SLC7A11 expression was not affected. Nicotine was found to downregulate GPX4 expression in microglia and olfactory bulb neurons via TET2-mediated DNA demethylation, thereby inducing ferroptosis.
CONCLUSION: Depletion of TET2 in the olfactory bulb aggravates CS-induced downregulation of GPX4, and the subsequent induction of ferroptosis may represent a critical mechanism underlying the exacerbation of olfactory impairment in CRSwNP.