Up-regulation of miR-335 and miR-674-3p in the rostral ventrolateral medulla contributes to stress-induced hypertension

The rostral ventrolateral medulla (RVLM) is known as the vasomotor center that plays a crucial role in mediating the development of stress-induced hypertension (SIH). MicroRNAs (miRNAs) are involved in many different biological processes and diseases. However, studies that evaluated the roles of miRNAs in the RVLM during SIH do not exist. Here, we performed RNA sequencing to explore the genome-wide miRNA profiles in RVLM in an SIH rat model established by administering electric foot-shocks and noises. The function of miRNAs in blood pressure regulation was determined in vivo via the intra-RVLM microinjection of the agomir or antagomir. Furthermore, the underlying mechanisms of miRNAs on SIH were investigated through in vitro and in vivo experiments, like gain-of-function. We discovered 786 miRNA transcripts among which 4 were differentially expressed. The over-expression of miR-335 and miR-674-3p in RVLM dramatically increased the heart rate (HR), arterial blood pressure (ABP), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) levels of normotensive rats, whereas the knockdown of miR-335 and miR-674-3p in RVLM markedly reduced the HR, ABP, SBP, DBP, and MAP levels of SIH rats. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation revealed that miR-335 and miR-674-3p participated in regulating the development of SIH from different aspects, like apoptosis-multiple species pathway. Sphk1, whose expression was markedly decreased in SIH, was identified as a novel target of miR-335. MiR-335 over-expression substantially reduced the expression of Sphk1 and promoted neural apoptosis, and its inhibition had opposite effects. Re-introduction of Sphk1 dramatically abrogated the apoptosis induced by miR-335. This study provides the first systematic dissection of the RVLM miRNA landscape in SIH. MiR-335 and miR-674-3p act as SIH promoters, and the identified miR-335/Sphk1/apoptosis axis represents one of the possible mechanisms. These miRNAs can be exploited as potential targets for the molecular-based therapy of SIH.