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.本研究旨在验证如下假说：疾病状态的产生并非源于单一诱因，而是源自生物网络中具有协同显著效应的微小改变。此前我们已证实，在模拟人类原发性高血压（essential hypertension）的自发性高血压大鼠（spontaneously hypertensive rat, SHR）模型中，高血压（hypertension, HTN）的发生过程伴随脑干内微小RNA（microRNA）表达水平的变化，且该变化与HTN的病程进展同步1,2。这一发现催生了如下假说：阻断微小RNA表达水平的异常变化，可阻止HTN的发生发展。本研究提出，高血压的发生源于某一生物网络被从正常血压稳态中推离，进入代偿性病理状态。我们证实，通过选择性阻断此前研究结果中凸显的两种微小RNA——miR-135a与miR-376a，对脑干内基因调控网络（gene regulatory networks）施加微小扰动，即可有效阻止SHR模型中HTN的发生：给药一周后大鼠血压降低38%，该效果持续至两周时仍维持29%的降幅；而同期WKY对照组的血压无任何变化。该效应似乎仅由包括IL1a、IL1b、Agtr1a及Dbh等在内的限速基因（rate-limiting genes）表达的适度（但有时具有显著性）变化所驱动。上述基因中有许多均为这两种微小RNA的直接靶标，这表明网络中被靶向的基因组合是该效应的核心成因。高血压作为底层调控网络的涌现特性这一结论，提示我们亟需开发全新的高血压治疗范式。