S1P1-mediated metabolic reprogramming promotes astrocytic mitochondrial dysfunction via histone lactylation in subarachnoid hemorrhage

Abstract Background Mitochondrial dysfunction is a central event in the pathophysiology of subarachnoid hemorrhage (SAH). Accumulating evidence has demonstrated that mitochondrial function is vulnerable to metabolic alterations. While the role of neuronal mitochondrial dysfunction in SAH pathology is firmly established, less is known about mitochondrial dysfunction in astrocytes, the key regulators of brain homeostasis, especially its potential regulation by metabolic reprogramming after SAH. Hence, we aimed to define the metabolic reprogramming and its potential role in mitochondrial dysfunction in astrocytes post SAH. Methods We established in vivo and in vitro models of SAH. Glucose uptake, lactate production, and extracellular acidification rate (ECAR) measurement were employed to profile the metabolic alterations in astrocytes after SAH. ATP level, mitochondrial membrane potential, mitochondrial reactive oxygen species (ROS) production, oxygen consumption rate (OCR), and transmission electron microscopy (TEM) were applied to assess the structural and functional integrity of astrocytic mitochondria. Lentivirus carrying short hairpin RNA (shRNA) and adeno-associated virus (AAV) were used to knockdown sphingosine-1-phosphate receptor 1 (S1P1) to explore the role of S1P1 in astrocytic metabolism switch. Additionally, ChIP-qPCR was utilized to elucidate the epigenetic mechanism of S1P1-mediated metabolic reprogramming in regulating the mitochondrial function of astrocytes post SAH. Results We provided new evidence that astrocytes underwent metabolic switch with enhanced glycolysis in the early stage of SAH which was mediated by S1P1 through mammalian target of rapamycin/hypoxia-inducible factor 1ɑ (mTOR/HIF1ɑ) activation. Notably, enhanced glycolysis-derived lactate accumulation in astrocytes promoted mitochondrial dysfunction. Mechanistically, we found that the enhanced glycolysis facilitated mitochondrial fission factor (MFF) transcription by elevated H3K9la, resulting in excessive mitochondrial fission and subsequent mitochondrial dysfunction in the early stage of SAH. Conclusion Our findings demonstrate that S1P1-driven glycolysis enhancement promotes astrocytic mitochondrial dysfunction via histone lactylation and provide a potential therapeutic strategy for SAH.