BACKGROUND: Biliverdin (BV), a heme metabolite, alleviates cerebral ischemia-reperfusion injury (CIRI) by regulating non-coding RNAs. Long non-coding RNA taurine-upregulated gene 1 (lncRNA TUG1) has been implicated in CIRI pathogenesis. This study investigates the mechanism of lncRNA TUG1 in BV-mediated CIRI mitigation in vivo and in vitro.
METHODS: In vivo CIRI was induced in rats via middle cerebral artery occlusion-reperfusion (MCAO/R), while in vitro CIRI was modeled in PC12 cells using oxygen-glucose deprivation/reoxygenation (OGD/R). BV was administered prior to reperfusion (in vivo) or reoxygenation (in vitro). Western blot and transmission electron microscopy (TEM) were used to evaluate BV's neuroprotective effects and its impact on autophagy. Quantitative real-time PCR (qPCR) and dual-luciferase reporter assays were performed to assess the expression levels of lncRNA TUG1, miR-204-5p, and P4HB mRNA, and their interactions. Functional rescue experiments were conducted by plasmid/siRNA transfection to overexpress lncRNA TUG1 or knockdown miR-204-5p. Autophagy and apoptosis were evaluated using MDC staining, Western blot, and flow cytometry.
RESULTS: BV significantly reduced neurological deficit scores and neuronal apoptosis in CIRI rats, decreased the LC3 II/I ratio, Beclin1, and P4HB protein levels, and reversed rapamycin-induced autophagy activation. BV downregulated lncRNA TUG1 and P4HB mRNA while upregulating miR-204-5p. Overexpression of lncRNA TUG1 or inhibition of miR-204-5p exacerbated OGD/R-induced cell damage through enhanced autophagy, thereby abolishing BV's protective effects.
CONCLUSION: BV alleviates CIRI by suppressing excessive autophagy via the lncRNA TUG1/miR-204-5p/P4HB axis.
