Neat1 regulates oxidized low-density lipoprotein-induced inflammation and lipid uptake in macrophages via paraspeckle formation

Oxidized low-density lipoprotein (oxLDL) induces macrophage inflammation and lipid uptake, and serves important roles in the development of atherosclerosis. The long non-coding RNA (lncRNA) nuclear paraspeckle assembly transcript 1 (neat1) has two isoforms; the longer isoform, neat1_2, mediates the formation of subnuclear structures called paraspeckles. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR), western blotting and RNA protein immunoprecipitation (RIP), revealed that oxLDL induced paraspeckle formation in the THP-1 cell line. Additionally, the nuclear factor-kappa B and p38 pathways were observed to be involved in neat1 transcription. To investigate the role of paraspeckles in oxLDL-induced macrophage inflammation and lipid uptake, macrophages were transfected with small interfering RNAs against NEAT1, NEAT1_2, non-POU domain-containing octamer-binding (NONO) and splicing factor proline and glutamine rich prior to oxLDL incubation. In addition, inflammation-associated pathways and scavenger receptors were analyzed by performing western blotting and RT-qPCR. p65 phosphorylation and cluster of differentiation 36 (CD36) were demonstrated to serve roles in paraspeckle-mediated inflammation and lipid uptake, respectively. To determine the underlying mechanism, RIP was preformed, which revealed that NONO binds CD36 mRNA to decrease its expression. In conclusion, oxLDL induced neat1_2-mediated paraspeckle formation. Paraspeckles participate in oxLDL-induced macrophage inflammation and lipid uptake by regulating p65 phosphorylation and CD36 mRNA.