Hypoxia-inducible factor 2α attenuates renal ischemia-reperfusion injury by suppressing CD36-mediated lipid accumulation in dendritic cells. Hypoxia-inducible factor 2α attenuates renal ischemia-reperfusion injury by suppressing CD36-mediated lipid accumulation in dendritic cells

Hypoxia is a hallmark of renal ischemia reperfusion injury (IRI) and serves as an essential regulator of innate immune responses during this process, although the mechanisms of this regulation remain unclear. Here, we show that dendritic cell (DC)-specific genetic ablation of hypoxia-inducible factor (HIF) 2α, a transcription factor induced by oxygen shortage, leads to hyperactivation of natural killer T cells (NKTs), ultimately exacerbating renal IRI in mice. HIF-2α deficiency in DCs triggers IFN-γ and IL-4 production in NKTs, along with upregulation of type I interferon (IFN) and chemokine responses critical for NKT activation. Mechanistically, loss of HIF-2α in DCs promotes their expression of CD36, a scavenger receptor for lipid uptake, resulting in increased lipid accumulation. Furthermore, HIF-2α binds directly to a reverse hypoxia-responsive element (rHRE) in the CD36 promoter, supporting its transcriptional regulation of CD36. Importantly, CD36 blockade by sulfo-N-succinimidyl oleate (SSO), reduces NKT activation and abolishes the exacerbation of renal IRI in mice with DC-specific HIF-2α knockout. Taken together, our study reveals a previously unrecognized role of a HIF-2α-CD36 regulatory axis in rewiring DC lipid metabolism under IRI-associated hypoxia, and suggests a potential therapeutic target to resolve long-standing obstacles in clinical treatment of this severe complication. Overall design: To investigate how HIF-2α affected glycolipid priming by DCs at a molecular level, we used RNA sequencing to examine transcriptomic differences between BMDCs isolated from Hif2αfl/fl (WT) and CD11c-Cre;Hif2αfl/fl (KO) mice, which were cultured for 4 hours with α-GalCer following 24 hour-dimethyloxalylglycine (DMOG, a HIF-2α stabilizer) incubation.

缺氧是肾脏缺血再灌注损伤（renal ischemia reperfusion injury, IRI）的标志性特征，亦是该过程中固有免疫应答的关键调控因子，但其具体调控机制尚未阐明。本研究发现，树突状细胞（dendritic cell, DC）特异性敲除缺氧诱导因子（hypoxia-inducible factor, HIF）2α——一种由缺氧诱导的转录因子——会导致自然杀伤T细胞（natural killer T cells, NKTs）过度活化，最终加重小鼠肾脏缺血再灌注损伤。树突状细胞中HIF-2α缺失会诱导自然杀伤T细胞分泌干扰素-γ（interferon-γ, IFN-γ）与白细胞介素-4（interleukin-4, IL-4），同时上调与自然杀伤T细胞活化密切相关的I型干扰素（type I interferon, IFN）应答与趋化因子应答。从机制上看，树突状细胞中HIF-2α的缺失会促进其表达CD36——一种介导脂质摄取的清道夫受体——进而导致细胞内脂质蓄积增加。此外，HIF-2α可直接结合CD36启动子区域的反向缺氧应答元件（reverse hypoxia-responsive element, rHRE），证实其对CD36的转录调控作用。值得注意的是，使用磺基-N-琥珀酰亚胺油酸盐（sulfo-N-succinimidyl oleate, SSO）阻断CD36，可降低自然杀伤T细胞的活化程度，并消除树突状细胞特异性HIF-2α敲除小鼠的肾脏缺血再灌注损伤加重表型。综上，本研究揭示了一条此前未被认知的HIF-2α-CD36调控轴，其可在缺血再灌注损伤相关的缺氧环境下重塑树突状细胞的脂质代谢，并为解决该严重并发症临床治疗中的长期难题提供了潜在的治疗靶点。整体实验设计：为从分子层面探究HIF-2α如何调控树突状细胞对糖脂抗原的致敏作用，本研究采用RNA测序技术，对比经24小时二甲基乙二酰基甘氨酸（dimethyloxalylglycine, DMOG，一种HIF-2α稳定剂）预处理后，再用α-半乳糖神经酰胺（α-GalCer）刺激4小时的骨髓来源树突状细胞（bone marrow-derived dendritic cell, BMDC）的转录组差异，这些骨髓来源树突状细胞分别分离自Hif2αfl/fl（野生型, WT）小鼠与CD11c-Cre;Hif2αfl/fl（敲除型, KO）小鼠。