m6Am Methyltransferase Pcif1 Knockdown Attenuates Mouse Cerebral Ischemia-Reperfusion Injury in Vitro through Inhibiting Pdpk1 mRNA Translation

Abstract

Background: Ischemia-reperfusion (I/R) injury is a key challenge in the treatment of ischemic cerebrovascular diseases. This study aimed to explore whether phosphorylated C-terminal domain (CTD) interacting factor 1 (Pcif1) could attenuate mouse I/R injury and its downstream mechanisms. Methods: An I/R injury cellular model was induced by treating mouse cortical neurons with oxygen-glucose deprivation and reoxygenation (OGD/R). Mouse cortical neurons were normally cultured (control group cells), and all were subjected to OGD/R after transfection. These were categorized into various groups, including OGD/R group (OGD/R model cells), OGD/R+siRNA negative control (siNC) group (cells were transfected with siNC and then underwent OGD/R treatment), OGD/R+siPcif1-1/2/3 group (OGD/R cells were transfected with siPcif1-1/2/3 before OGD/R treatment), siNC+shNC group (siNC and shNC were transfected into cells), siNC+3-phosphoinositide-dependent protein kinase 1 (Pdpk1) short hairpin RNA (shPdpk1) group (siNC and shPdpk1 were transfected into cells), siPcif1+shNC group (cells were transfected with siPcif1 and shNC), and siPcif1+shPdpk1 group (cells were transfected with siPcif1 and shPdpk1). Pcif1 and Pdpk1 expressions were detected by quantitative real-time PCR. The effects of silenced Pcif1 on cell viability, lactate dehydrogenase (LDH) release rate, malondialdehyde (MDA) level, tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6) concentrations, apoptosis, and V-akt murine thymoma viral oncogene homolog (Akt) related proteins were evaluated by cell counting kit-8 assay, LDH activity assay kit, MDA assay kit, enzyme-linked immunosorbent assay (ELISA), flow cytometry, and western blot, respectively. The targeting relationship between Pcif1 and Pdpk1 was analyzed by m6A-RNA immunoprecipitation qPCR. The loss-of-function assays were used to evaluate the function of Pdpk1 knockdown on OGD/R-treated cells. Results: Pcif1 expression was elevated but Pdpk1 expression was reduced in mouse cortical neurons following OGD/R treatment (p < 0.001). Pcif1 silencing reversed the effects of OGD/R treatment on inhibiting cell viability, and on promoting LDH release, MDA level, TNF-α, and IL-6 contents and apoptosis rate (p < 0.001). Pcif1 knockdown also facilitated B-cell chronic lymphocytic leukemia/lymphoma-2 (Bcl-2) expression and Akt signaling pathway activation, and suppressed Bcl-2-associated X protein (Bax) expression (p < 0.05). Pdpk1 was validated as a downstream target of Pcif1, and its knockdown offset the above effects induced by silencing Pcif1 on OGD/R-treated cells (p < 0.05). Conclusions: Pcif1 knockdown alleviates OGD/R-induced neuronal injury in mice by inhibiting Pdpk1 mRNA translation to activate Akt signaling pathway.