Downregulation of Circular RNA Gla Reduced Astrocyte Inflammatory Status by Regulating miR-488/MEKK1 Levels and Promoted Functional Recovery After Spinal Cord Injury

Qiang Shao,1,2,* Ying Zhang,2,* Zhiyuan Zhang,2 Wei Jiang,2 Yongcheng Yin,3 Yuepeng Fang,1 Ce Zhang,1 Qingfa Chen,2 Bin Ning1,2 1Cheeloo College of Medicine, Jinan Central Hospital, Shandong University, Jinan, People’s Republic of China; 2Central Hospital Affiliated to Shandong First Medical University, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, Shandong, People’s Republic of China; 3School of Clinical Medicine, Shandong Second Medical University, Weifang, People’s Republic of China*These authors contributed equally to this workCorrespondence: Bin Ning; Qingfa Chen, Central Hospital Affiliated to Shandong First Medical University, No. 105, Jiefang Road, Jinan, Shandong, 250013, People’s Republic of China, Tel +86-18866510349, Email [email protected]; [email protected]: Post-spinal cord injury (SCI) inflammation correlates with neurologic recovery. Through sequencing, we explored the roles of a differentially expressed circRNA in mice after SCI, circGla, on inflammation and recovery of SCI.Methods: The T8–T10 SCI model was established in C57BL6 mice. HE staining and RT-qPCR verified circGla upregulation results after injury obtained through sequencing. RNase R digestion and primer amplification experiments confirmed the circular properties of circGla. Nucleus and cytoplasm isolation experiments and FISH confirmed circGla expression in the astrocyte cytoplasm. AAV was used to establish a circGla knockdown mouse model. Behavioral tests were conducted to assess the recovery of the neurological function. The key inflammatory molecules after SCI were evaluated through MRI, RT-qPCR, and ELISA. For in vitro experiments, circGla was upregulated or knocked down in mouse astrocytes to detect its effect. The binding between miR-488 and circGla was confirmed through RIP and the dual luciferase experiment. RT-qPCR and ELISA confirmed the content correlation of the two molecules and the in vitro inflammatory function of miR-488. The binding experiment in astrocytes confirmed the binding between miR-488 and MEKK1 mRNA. Western blotting of MAPK pathway-related proteins confirmed that MEKK1 is a downstream effector for circGla and miR-488 in astrocytes.Results: Following SCI, the circular RNA circGla levels increased and it existed in the astrocyte cytoplasm. circGla knockdown reduced inflammation and improved neurological recovery in vivo. The correlation between circGla and proinflammatory factors was confirmed in vitro. circGla bound to miR-488, and the high miR-488 level was associated with the low astrocyte inflammatory state. miR-488 bound to MEKK1 mRNA, and upregulation or knockdown of circGla or miR-488 affected MAPK pathway-related protein expression.Conclusion: Following SCI, downregulation of circGla expression in astrocytes can reduce inflammatory manifestations and stimulate long-term functional recovery in mice through miR-488 and MEKK1. Keywords: non-coding RNAs, inflammation, competing endogenous RNAs, traumatic spinal cord injury, secondary injury