<i>Let-7i</i> inhibition enhances progesterone-induced functional recovery in a mouse model of ischemia.

Abstract

Progesterone (P4) is a potent neuroprotectant and a promising therapeutic for stroke treatment. However, the underlying mechanism(s) remain unclear. Our laboratory recently reported that brain-derived neurotrophic factor (BDNF) is a critical mediator of P4's protective actions and that P4-induced BDNF release from cortical astrocytes is mediated by a membrane-associated progesterone receptor, Pgrmc1. Here, we report that the microRNA (miRNA) <i>let-7i</i> is a negative regulator of Pgrmc1 and BDNF in glia and that <i>let-7i</i> disrupts P4-induced BDNF release and P4's beneficial effects on cell viability and markers of synaptogenesis. Using an in vivo model of ischemia, we demonstrate that inhibiting <i>let-7i</i> enhances P4-induced neuroprotection and facilitates functional recovery following stroke. The discovery of such factors that regulate the cytoprotective effects of P4 may lead to the development of biomarkers to differentiate/predict those likely to respond favorably to P4 versus those that do not.