Research center of Ophthalmology, Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Department of Ophthalmology, Guangxi Academy of Medical Sciences, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China.
Eye Center, Renmin Hospital of Wuhan University, Wuhan, 430060, China.
Mol Biol Rep. 2023 Dec;50(12):10277-10285. doi: 10.1007/s11033-023-08815-5. Epub 2023 Nov 16.
Recent reports suggest that peroxisome proliferator-activated receptor-γ (PPAR-γ) could promote microglial M2 polarization to inhibit inflammation. However, the specific molecular mechanisms that trigger PPAR-γ's anti-inflammatory ability in microglia are yet to be expounded. Thus, in this study, we aimed to explore the molecular mechanisms behind the anti-inflammatory effects of PPAR-γ in hypoxia-stimulated rat retinal microglial cells.
We used shRNA expressing lentivirus to knock down PPAR-γ and CD200 genes, and we assessed hypoxia-induced polarization markers release - M1 (iNOS, IL-1β, IL-6, and TNF-α) and M2 (Arg-1, YM1, IL-4, and IL-10) by RT-PCR. We also monitored PPAR-γ-related signals (PPAR-γ, PPAR-γ in cytoplasm or nucleus, CD200, and CD200Rs) by Western blot and RT-PCR. Our results showed that hypoxia enhanced PPAR-γ and CD200 expressions in microglial cells. Moreover, PPAR-γ agonist 15d-PGJ elevated CD200 and CD200R1 expressions, whereas sh-PPAR-γ had the opposite effect. Following hypoxia, expressions of M1 markers increased significantly, while those of M2 markers decreased, and the above effects were attenuated by 15d-PGJ. Conversely, knocking down PPAR-γ or CD200 inhibited the polarization of microglial cells to M2 phenotype.
Our findings demonstrated that PPAR-γ performed an anti-inflammatory function in hypoxia-stimulated microglial cells by promoting their polarization to M2 phenotype via the CD200-CD200R1 pathway.
最近的报告表明，过氧化物酶体增殖物激活受体-γ（PPAR-γ）可以促进小胶质细胞 M2 极化以抑制炎症。然而，触发 PPAR-γ 在小胶质细胞中发挥抗炎作用的具体分子机制尚待阐明。因此，在这项研究中，我们旨在探讨 PPAR-γ 在缺氧刺激的大鼠视网膜小胶质细胞中抗炎作用的分子机制。
我们使用表达 shRNA 的慢病毒敲低 PPAR-γ 和 CD200 基因，并通过 RT-PCR 评估缺氧诱导的极化标志物释放 - M1（iNOS、IL-1β、IL-6 和 TNF-α）和 M2（Arg-1、YM1、IL-4 和 IL-10）。我们还通过 Western blot 和 RT-PCR 监测与 PPAR-γ 相关的信号（PPAR-γ、细胞质或核内的 PPAR-γ、CD200 和 CD200Rs）。我们的结果表明，缺氧增强了小胶质细胞中 PPAR-γ 和 CD200 的表达。此外，PPAR-γ 激动剂 15d-PGJ 升高了 CD200 和 CD200R1 的表达，而 sh-PPAR-γ 则有相反的作用。缺氧后，M1 标志物的表达明显增加，而 M2 标志物的表达减少，15d-PGJ 可减弱上述作用。相反，敲低 PPAR-γ 或 CD200 抑制了小胶质细胞向 M2 表型的极化。
我们的研究结果表明，PPAR-γ 通过 CD200-CD200R1 途径促进小胶质细胞向 M2 表型极化，从而在缺氧刺激的小胶质细胞中发挥抗炎作用。
