Targeted inhibition of two specific microRNAs in the brainstem prevents the development of hypertension through the cumulative effect of gene network changes [Fig3]

We here test the concept that disease states may result not from a single cause but from small changes in a network that are collectively significant. We recently showed that development of hypertension (HTN) in the spontaneously hypertensive rat (SHR) model of human essential hypertension is accompanied by changes in microRNA expression levels in the brainstem tracking the development of HTN 1,2. This led to the hypothesis that preventing the change in microRNA levels could prevent the development of HTN. We propose that hypertension emerges from a network that has been pushed out of a normotensive equilibrium into a compensatory, pathological state. We show that small perturbations in the gene regulatory networks in the brainstem by selectively blocking two microRNAs highlighted in our previous results, miR-135a and miR-376a, is sufficient to prevent development of hypertension in the SHR model with a 38% reduction in blood pressure after one week persisting to 29% reduction after two weeks with no change in blood pressure in WKY controls at either timepoint. This effect appears driven by only modest, yet sometimes significant, changes in the expression of rate-limiting genes including IL1a, IL1b, Agtr1a, and Dbh among others. Many of these genes are direct targets of these miRNAs, suggesting that the combination of genes that are targeted in the network is responsible for the effect. The demonstration that hypertension is an emergent property of an underlying regulatory network suggests that a new treatment paradigm altogether is needed. Combined assay of miRNA and mRNA of single neurons in the NTS of age-matched SHR and WKY rats (4-5 animals per group).