Role of miR-124 and miR-141 in the regulation of vascular reactivity and the relationship to RhoA and Rac1 after hemorrhage and hypoxia

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Recent studies show that hypoxia can alter expression levels of microRNAs (miRNAs). Whether hypoxia or hemorrhage-induced vascular hyporeactivity is related to miRNAs and the underlying mechanisms of this process is not clear. Using hypoxia-treated superior mesenteric arteries (SMAs) and vascular smooth muscle cells (VSMCs) of rats that underwent hemorrhage, we observed the regulatory effects of miR-124/miR-141 on vascular reactivity, the relationship of these miRNAs to RhoA and Rac1, and the mutual regulation of miR-124 and miR-141. The contractile responses of SMAs and VSMCs showed an increase in early stages and a decrease in late stages of hypoxia and hemorrhage. Forty-five miRNAs appeared to have been significantly changed in SMAs after hypoxia, and miR-124 and miR-141 underwent the most change. Overexpressed miR-124 or miR-141 and their antisenses appeared to alter both vascular reactivity and expression of the proteins RhoA and Rac1 after hypoxia. miR-124 inhibited Rac1 by acting at the Rac1 mRNA 3'-untranslated region (UTR), but it led to an increase in RhoA by inhibiting miR-141. miR-141 inhibited RhoA by acting at the RhoA mRNA 3'-UTR, but it led to an increase in Rac1 by inhibiting miR-124. Further study found that miR-124 inhibited miR-141 via transcription factor early growth response gene-1 (Egr-1), whereas miR-141 inhibited miR-124 via transcription of nuclear factor erythroid 2-related factor 2 (Nrf-2). These results suggest that miR-124 and miR-141 participate in the regulation of vascular reactivity after hypoxia and hemorrhage by regulating expression of the RhoA and Rac1 proteins, and in doing so, miR-124 and miR-141 are mutually regulated. These findings provide potential targets for restoring vascular function as part of the treatment protocol for hemorrhagic shock and some other critical illness.