Jimenez-Gonzalez, A., García-Concejo, A., López-Benito, S., Gonzalez-Nunez, V., Arévalo, J.C., Rodriguez, R.E. (2016) Role of morphine, miR-212/132 and mu opioid receptor in the regulation of bdnf in zebrafish embryos. Biochimica et biophysica acta. General subjects. 1860(6):1308-16.
Background Morphine is one of the first-line therapies for the treatment of pain despite its secondary effects. It modifies the expression of epigenetic factors like miRNAs. In the present study, we analyzed miR-212 and miR-132 and their implication in morphine effects in the zebrafish Central Nervous System (CNS) through the regulation of Bdnf expression.
Methods We used control and knock-down zebrafish embryos to assess the effects of morphine in miRNAs 212/132 and mitotic or apoptotic cells by qPCR, immunohistochemistry and TUNEL assay, respectively. Bdnf and TrkB were studied by western blot and through a primary neuron culture. A luciferase assay was performed to confirm the binding of miRNAs 212/132 to mecp2.
Results Morphine exposure decreases miR-212 but upregulates miR-132, as wells as Bdnf and TrkB, and changes the localization of proliferative cells. However, Bdnf expression was downregulated when miRNAs 212/132 and oprm1 were knocked-down. Furthermore, we proved that these miRNAs inhibit mecp2 expression by binding to its mRNA sequence. The described effects were corroborated in a primary neuron culture from zebrafish embryos.
Conclusions We propose a mechanism in which morphine alters the levels of miRNAs 212/132 increasing Bdnf expression through mecp2 inhibition. oprm1 is also directly involved in this regulation. The present work confirms a relationship between the opioid system and neurotrophins and shows a key role of miR-212 and miR-132 on morphine effects through the regulation of Bdnf pathway.
General significance miRNAs 212/132 are novel regulators of morphine effects on CNS. Oprm1 controls the normal expression of Bdnf.