Circ_TLK1 knockdown alleviates oxygen-glucose deprivation/reoxygenation-induced PC12 cell injury by regulating microRNA-136-5p/follistatin like-1 axis.

Abstract

Circular RNAs (circRNAs) are aberrantly expressed in the central nervous system (CNS) and are involved in diverse CNS diseases. However, the functions of circRNAs in ischemic stroke (IS) are largely unknown. In this study, we aimed to explore the effect of circ_TLK1 in oxygen-glucose deprivation/reoxygenation (OGD/R)-induced PC12 cell injury. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed for the levels of circ_TLK1, TLK1, microRNA-136-5p (miR-136-5p), and follistatin like-1 (FSTL1). RNase R and Actinomycin D assays were conducted to analyze the features of circ_TLK1. 3-(4, 5-ethynyl-2'-deoxyuridine [EdU] assay and 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) assay were adopted to analyze cell proliferation capacity. Flow cytometry analysis was applied to determine cell death. Western blot assay was employed to measure protein levels. The release of lactate dehydrogenase (LDH) was measured with specific kits. The interaction between circ_TLK1 and miR-136-5p, as well as miR-136-5p and FSTL1, was verified by Dual-luciferase reporter assay. Circ_TLK1 was upregulated in OGD/R-injured PC12 cells. OGD/R treatment inhibited cell proliferation, promoted cell death, and increased LDH release in PC12 cells, while circ_TLK1 knockdown partially alleviated OGD/R-induced PC12 cell injury. Circ_TLK1 directly bound to miR-136-5p and miR-136-5p inhibition reversed the effect of circ_TLK1 knockdown on OGD/R-induced PC12 cell damage. Moreover, FSTL1 was targeted by miR-136-5p. MiR-136-5p upregulation inhibited PC12 cell injury induced by OGD/R, while FSTL1 overexpression partially reversed the effect. Circ_TLK1 knockdown ameliorated OGD/R-induced PC12 cell injury by modulating miR-136-5p and FSTL1, which might provide a new understanding of IS treatment.